rizal - school

Saccharides, Lignin and Lipids

2012-01-27T02:46:00.000-08:00

Monosaccharides are the simplest form of carbohydrates with only one simple sugar. They essentially contain an aldehyde or ketone group in their structure. The presence of an aldehyde group in a monosaccharide is indicated by the prefix aldo-. Similarly, a ketone group is denoted by the prefix keto-. Examples of monosaccharides are the hexoses glucose, fructose, and galactose and pentoses, ribose, and deoxyribose Consumed fructose and glucose have different rates of gastric emptying, are differentially absorbed and have different metabolic fates, providing multiple opportunities for 2 different saccharides to differentially affect food intake. Disaccharides are formed when two monosaccharides, or two single simple sugars, form a bond with removal of water. They can be hydrolyzed to yield their saccharin building blocks by boiling with dilute acid or reacting them with appropriate enzymes. Examples of disaccharides include sucrose, maltose, and lactose. Polysaccharides are polymerized monosaccharides, complex, carbohydrates. They have multiple simple sugars. Examples are starch, cellulose, and glycogen. They are generally large and often have a complex branched connectivity. Because of their size, polysaccharides are not water-soluble, but their many hydroxy groups become hydrated individually when exposed to water, and some polysaccharides form thick colloidal dispersions when heated in water. Shorter polysaccharides, with 3 - 10 monomers, are called oligosaccharides. A fluorescent indicator-displacement molecular imprinting sensor was developed for discriminating saccharides. It successfully discriminated three brands of orange juice beverage. The change in fluorescence intensity of the sensing films resulting is directly related to the saccharide concentration.

Lignin is a complex polyphenolic macromolecule composed mainly of beta-O4-aryl linkages. After cellulose, lignin is the second most abundant biopolymer and is one of the primary structural components of most plants. It contains subunits derived from p-coumaryl alcohol, coniferyl alcohol, and sinapyl alcohol and is unusual among biomolecules in that it is racemic. The lack of optical activity is due to the polymerization of lignin which occurs via free radical coupling reactions in which there is no preference for either configuration at a chiral center.

Lipids are chiefly fatty acid esters, and are the basic building blocks of biological membranes. Another biological role is energy storage (e.g., triglycerides). Most lipids consist of a polar or hydrophilic head (typically glycerol) and one to three nonpolar or hydrophobic fatty acid tails, and therefore they are amphiphilic. Fatty acids consist of unbranched chains of carbon atoms that are connected by single bonds alone (saturated fatty acids) or by both single and double bonds (unsaturated fatty acids). The chains are usually 14-24 carbon groups long, but it is always an even number. (wikipdedia)

E-Business: SCM, SCE and SCP

2012-01-26T15:22:00.000-08:00

Oracle offers four Supply Chain Management (SCM) product lines that address requirements across procurement, order management, manufacturing, product lifecycle management, maintenance, logistics, and supply chain planning and execution. Regardless of your industry focus or individual supply chain model, Oracle provides SCM solutions with the flexibility to streamline all supply chain processes, then adopt industry and business best practices and leverage information for continuous improvement.

E-Business Suite Supply Chain Execution family of applications supports the complete order to cash business process, capturing demand from any channel, providing inbound and outbound transportation management, and supporting large, complex distribution operations. A unified data model provides a single, accurate view of the entire supply chain execution process, so you can plan, manage, and control the flow and storage of goods, services, and related information from the point of origin to the point of consumption in order to meet customer requirements. And when Oracle Supply Chain Execution runs on Oracle technology, you speed implementation, optimize performance, streamline support, and maximize return on your investment.

E-Business Suite Supply Chain Planning family of applications provides holistic planning capabilities, from long-range aggregate planning to short-term detail scheduling. A unified data model provides a single, accurate view of the entire planning process, so you can optimize the flow of materials, cash, and information. And when Oracle Supply Chain Planning runs on Oracle technology, you speed implementation, optimize performance, streamline support, and maximize return on your investment. (oracle)

antimatter

2009-08-10T03:42:00.000-07:00

In particle physics, antimatter is the extension of the concept of the antiparticle to matter, where antimatter is composed of antiparticles in the same way that normal matter is composed of particles. For example, an antielectron (a positron, an electron with a positive charge) and an antiproton (a proton with a negative charge) could form an antihydrogen atom in the same way that an electron and a proton form a normal matter hydrogen atom. Furthermore, mixing matter and antimatter would lead to the annihilation of both in the same way that mixing antiparticles and particles does, thus giving rise to high-energy photons (gamma rays) or other particle–antiparticle pairs.

There is considerable speculation as to why the observable universe is apparently almost entirely matter, whether there exist other places that are almost entirely antimatter instead, and what might be possible if antimatter could be harnessed, but at this time the apparent asymmetry of matter and antimatter in the visible universe is one of the greatest unsolved problems in physics. The process by which this asymmetry between particles and antiparticles developed is called baryogenesis.

Almost every object observable from the Earth seems to be made of matter rather than antimatter. Many scientists believe that this preponderance of matter over antimatter (known as baryon asymmetry) is the result of an imbalance in the production of matter and antimatter particles in the early universe, in a process called baryogenesis. The amount of matter presently observable in the universe only requires an imbalance in the early universe on the order of one extra matter particle per billion matter-antimatter particle pairs.

Antiparticles are created everywhere in the universe where high-energy particle collisions take place. High-energy cosmic rays impacting Earth's atmosphere (or any other matter in the solar system) produce minute quantities of antimatter in the resulting particle jets, which are immediately annihilated by contact with nearby matter. It may similarly be produced in regions like the center of the Milky Way Galaxy and other galaxies, where very energetic celestial events occur (principally the interaction of relativistic jets with the interstellar medium). The presence of the resulting antimatter is detectable by the gamma rays produced when positrons annihilate with nearby matter.

Recent observations by the European Space Agency's INTEGRAL (International Gamma-Ray Astrophysics Laboratory) satellite may explain the origin of a giant cloud of antimatter surrounding the galactic center. The observations show that the cloud is asymmetrical and matches the pattern of X-ray binaries, binary star systems containing black holes or neutron stars, mostly on one side of the galactic center. While the mechanism is not fully understood, it is likely to involve the production of electron-positron pairs, as ordinary matter gains tremendous energy while falling into a stellar remnant.

(source: wikipedia)

nuclear fusion

2009-06-17T05:31:00.000-07:00

In nuclear physics and nuclear chemistry, nuclear fusion is the process by which multiple like-charged atomic nuclei join together to form a heavier nucleus. It is accompanied by the release or absorption of energy, which allows matter to enter a plasma state.

The fusion of two nuclei with lower mass than iron (which, along with nickel, has the largest binding energy per nucleon) generally releases energy while the fusion of nuclei heavier than iron absorbs energy; vice-versa for the reverse process, nuclear fission. In the simplest case of hydrogen fusion, two protons have to be brought close enough for their mutual electric repulsion to be overcome by the nuclear force and the subsequent release of energy.

Nuclear fusion occurs naturally in stars. Artificial fusion in human enterprises has also been achieved, although has not yet been completely controlled. Building upon the nuclear transmutation experiments of Ernest Rutherford done a few years earlier, fusion of light nuclei (hydrogen isotopes) was first observed by Mark Oliphant in 1932; the steps of the main cycle of nuclear fusion in stars were subsequently worked out by Hans Bethe throughout the remainder of that decade. Research into fusion for military purposes began in the early 1940s as part of the Manhattan Project, but was not successful until 1952. Research into controlled fusion for civilian purposes began in the 1950s, and continues to this day.

Fusion reactions power the stars and produce all but the lightest elements in a process called nucleosynthesis. Although the fusion of lighter elements in stars releases energy, production of the heavier elements absorbs energy.

When the fusion reaction is a sustained uncontrolled chain, it can result in a thermonuclear explosion, such as that generated by a hydrogen bomb. Reactions which are not self-sustaining can still release considerable energy, as well as large numbers of neutrons.

Research into controlled fusion, with the aim of producing fusion power for the production of electricity, has been conducted for over 50 years. It has been accompanied by extreme scientific and technological difficulties, but has resulted in steady progress. At present, break-even (self-sustaining) controlled fusion reactions have been demonstrated in a few tokamak-type reactors around the world. These have enabled the creation of workable designs for a reactor which will deliver ten times more fusion energy than the amount needed to heat up plasma to required temperatures (see ITER which is scheduled to be operational in 2018).

It takes considerable energy to force nuclei to fuse, even those of the lightest element, hydrogen. This is because all nuclei have a positive charge (due to their protons), and as like charges repel, nuclei strongly resist being put too close together. Accelerated to high speeds (that is, heated to thermonuclear temperatures), they can overcome this electromagnetic repulsion and get close enough for the attractive nuclear force to be sufficiently strong to achieve fusion. The fusion of lighter nuclei, which creates a heavier nucleus and a free neutron, generally releases more energy than it takes to force the nuclei together; this is an exothermic process that can produce self-sustaining reactions.

The energy released in most nuclear reactions is much larger than that in chemical reactions, because the binding energy that holds a nucleus together is far greater than the energy that holds electrons to a nucleus. For example, the ionization energy gained by adding an electron to a hydrogen nucleus is 13.6 electron volts—less than one-millionth of the 17 MeV released in the D-T (deuterium-tritium) reaction shown in the diagram to the right. Fusion reactions have an energy density many times greater than nuclear fission; i.e., the reactions produce far greater energies per unit of mass even though individual fission reactions are generally much more energetic than individual ones, which are themselves millions of times more energetic than chemical reactions. Only direct conversion of mass into energy, such as that caused by the collision of matter and antimatter, is more energetic per unit of mass than nuclear fusion.

(source: wikipedia)

The laws of thermodynamics

2009-05-30T21:49:00.000-07:00

In thermodynamics, there are four laws that do not depend on the details of the systems under study or how they interact. Hence these laws are very generally valid, can be applied to systems about which one knows nothing other than the balance of energy and matter transfer. Examples of such systems include Einstein's prediction, around the turn of the 20th century, of spontaneous emission, and ongoing research into the thermodynamics of black holes.

These four laws are:
Zeroth law of thermodynamics, about thermal equilibrium:
If two thermodynamic systems are separately in thermal equilibrium with a third, they are also in thermal equilibrium with each other.
If we grant that all systems are (trivially) in thermal equilibrium with themselves, the Zeroth law implies that thermal equilibrium is an equivalence relation on the set of thermodynamic systems. This law is tacitly assumed in every measurement of temperature. Thus, if we want to know if two bodies are at the same temperature, it is not necessary to bring them into contact and to watch whether their observable properties change with time.

First law of thermodynamics, about the conservation of energy:
The change in the internal energy of a closed thermodynamic system is equal to the sum of the amount of heat energy supplied to the system and the work done on the system.

Second law of thermodynamics, about entropy:
The total entropy of any isolated thermodynamic system tends to increase over time, approaching a maximum value.

Third law of thermodynamics, about the absolute zero of temperature:
As a system asymptotically approaches absolute zero of temperature all processes virtually cease and the entropy of the system asymptotically approaches a minimum value; also stated as: "the entropy of all systems and of all states of a system is zero at absolute zero" or equivalently "it is impossible to reach the absolute zero of temperature by any finite number of processes".

The following has sometimes been called the "Fourth Law of Thermodynamics", about the transfer of heat energy between systems.

Onsager reciprocal relations:
In connected thermodynamic systems which are in equilibrium neither for pressure nor temperature, heat flow between is caused by forces proportional with unit of pressure difference, and equal to the proportional density flow caused per unit of temperature difference.

(source: wikipedia)

Security Proofs and Quantum Attack

2009-05-26T01:15:00.000-07:00

The above is just a simple example of an attack. If Eve is assumed to have unlimited resources, for example classical and quantum computing power, there are many more attacks possible. BB84 has been proven secure against any attacks allowed by quantum mechanics, both for sending information using an ideal photon source which only ever emits a single photon at a time[12], and also using practical photon sources which sometimes emit multiphoton pulses. These proofs are unconditionally secure in the sense that no conditions are imposed on the resources available to the Eavesdropper, however there are other conditions required:
Eve cannot access Alice and Bob's encoding and decoding devices.
The random number generators used by Alice and Bob must be trusted and truly random (for example a Quantum random number generator).
The classical communication channel must be authenticated using an unconditionally secure authentication scheme.

Quantum cryptography is vulnerable to a man-in-the-middle attack when used without authentication to the same extent as any classical protocol, since no principle of quantum mechanics can distinguish friend from foe. As in the classical case, Alice and Bob cannot authenticate each other and establish a secure connection without some means of verifying each other's identities (such as an initial shared secret). If Alice and Bob have an initial shared secret then they can use an unconditionally secure authentication scheme (such as Carter-Wegman) along with quantum key distribution to exponentially expand this key, using a small amount of the new key to authenticate the next session. Several methods to create this initial shared secret have been proposed, for example using a 3rd party or chaos theory.

In the BB84 protocol Alice sends quantum states to Bob using single photons. In practice many implementations use laser pulses attenuated to a very low level to send the quantum states. These laser pulses contain a very small number of photons, for example 0.2 photons per pulse, which are distributed according to a Poissonian distribution. This means most pulses actually contain no photons (no pulse is sent), some pulses contain 1 photon (which is desired) and a few pulses contain 2 or more photons. If the pulse contains more than one photon, then Eve can split off the extra photons and transmit the remaining single photon to Bob. This is the basis of the photon number splitting attack, where Eve stores these extra photons in a quantum memory until Bob detects the remaining single photon and Alice reveals the encoding basis. Eve can then measure her photons in the correct basis and obtain information on the key without introducing detectable errors.

Even with the possibility of a PNS attack a secure key can still be generated, as shown in the GLLP security proof, however a much higher amount of privacy amplification is needed reducing the secure key rate significantly (with PNS the rate scales as t2 as compared to t for a single photon sources, where t is the transmittance of the quantum channel).

There are several solutions to this problem. The most obvious is to use a true single photon source instead of an attenuated laser. While such sources are still at a developmental stage QKD has been carried out successfully with them. However as current sources operate at a low efficiency and frequency key rates and transmission distances are limited. Another solution is to modify the BB84 protocol, as is done for example in the SARG04 protocol, in which the secure key rate scales as t3 / 2. The most promising solution is the decoy state idea[21], in which Alice randomly sends some of her laser pulses with a lower average photon number. These decoy states can be used to detect a PNS attack, as Eve has no way to tell which pulses are signal and which decoy. Using this idea the secure key rate scales as t, the same as for a single photon source. This idea has been implemented successfully in several QKD experiments, allowing for high key rates secure against all known attacks.

Hacking attacks target imperfections in the implementation of the protocol instead of the protocol directly. If the equipment used in quantum cryptography can be tampered with, it could be made to generate keys that were not secure using a random number generator attack. Another common class of attacks is the Trojan horse attack which does not require physical access to the endpoints: rather than attempt to read Alice and Bob's single photons, Mallory sends a large pulse of light back to Alice in between transmitted photons. Alice's equipment reflects some of Mallory's light, revealing the state of Alice's polarizer. This attack is easy to avoid, for example using an optical isolator to prevent light from entering Alice's system, and all other hacking attacks can similarly be defeated by modifying the implementation. Apart from Trojan horse there are several other known attacks including faked state attacks, phase remapping attacks and time-shift attacks. The time-shift attack has even been successfully demonstrated on a commercial quantum crypto-system. This demonstration is the first successful demonstration of quantum hacking against a non-homemade quantum key distribution system.

Because currently a dedicated fibre optic line (or line of sight in free space) is required between the two points linked by quantum cryptography, a denial of service attack can be mounted by simply cutting or blocking the line or, perhaps more surreptitiously, by attempting to tap it.

(wikipedia)

Quantum Cryptography

2009-05-17T18:25:00.000-07:00

Or quantum key distribution (QKD), uses quantum mechanics to guarantee secure communication. It enables two parties to produce a shared random bit string known only to them, which can be used as a key to encrypt and decrypt messages.

An important and unique property of quantum cryptography is the ability of the two communicating users to detect the presence of any third party trying to gain knowledge of the key. This results from a fundamental aspect of quantum mechanics: the process of measuring a quantum system in general disturbs the system. A third party trying to eavesdrop on the key must in some way measure it, thus introducing detectable anomalies. By using quantum superpositions or quantum entanglement and transmitting information in quantum states, a communication system can be implemented which detects eavesdropping. If the level of eavesdropping is below a certain threshold a key can be produced that is guaranteed to be secure (i.e. the eavesdropper has no information about), otherwise no secure key is possible and communication is aborted.

The security of quantum cryptography relies on the foundations of quantum mechanics, in contrast to traditional public key cryptography which relies on the computational difficulty of certain mathematical functions, and cannot provide any indication of eavesdropping or guarantee of key security.

Quantum cryptography is only used to produce and distribute a key, not to transmit any message data. This key can then be used with any chosen encryption algorithm to encrypt (and decrypt) a message, which can then be transmitted over a standard communication channel. The algorithm most commonly associated with QKD is the one-time pad, as it is provably secure when used with a secret, random key.

Quantum communication involves encoding information in quantum states, or qubits, as opposed to classical communications use of bits. Usually, photons are used for these quantum states. Quantum cryptography exploits certain properties of these quantum states to ensure its security. There are several different approaches to quantum key distribution, but they can be divided into two main categories depending on which property they exploit.

In contrast to classical physics, the act of measurement is an integral part of quantum mechanics. In general, measuring an unknown quantum state will change that state in some way. This is known as quantum indeterminacy, and underlies results such as the Heisenberg uncertainty principle, information-disturbance theorem and no cloning theorem. This can be exploited in order to detect any eavesdropping on communication (which necessarily involves measurement) and, more importantly, to calculate the amount of information that has been intercepted. The quantum states of two (or more) separate objects can become linked together in such a way that they must be described by a combined quantum state, not as individual objects. This is known as entanglement and means that, for example, performing a measurement on one object will affect the other. If an entangled pair of objects is shared between two parties, anyone intercepting either object will alter the overall system, allowing the presence of the third party (and the amount of information they have gained) to be determined.

These two approaches can each be further divided into three families of protocols; discrete variable, continuous variable and distributed phase reference coding. Discrete variable protocols were the first to be invented, and they remain the most widely implemented. The other two families are mainly concerned with overcoming practical limitations of experiments. The two protocols described below both use discrete variable coding.

(source: wikipedia)

Other Microcontroller Features

2009-05-10T22:39:00.000-07:00

Since embedded processors are usually used to control devices, they sometimes need to accept input from the device they are controlling. This is the purpose of the analog to digital converter. Since processors are built to interpret and process digital data, i.e. 1s and 0s, they won't be able to do anything with the analog signals that may be being sent to it by a device. So the analog to digital converter is used to convert the incoming data into a form that the processor can recognize. There is also a digital to analog converter that allows the processor to send data to the device it is controlling.

In addition to the converters, many embedded microprocessors include a variety of timers as well. One of the most common types of timers is the Programmable Interval Timer, or PIT for short. A PIT just counts down from some value to zero. Once it reaches zero, it sends an interrupt to the processor indicating that it has finished counting. This is useful for devices such as thermostats, which periodically test the temperature around them to see if they need to turn the air conditioner on, the heater on, etc.

Time Processing Unit or TPU for short is a sophisticated timer. In addition to counting down, the TPU can detect input events, generate output events, and perform other useful operations. Dedicated Pulse Width Modulation (PWM) block makes it possible for the CPU to control power converters, resistive loads, motors, etc., without using lots of CPU resources in tight timer loops.

Universal Asynchronous Receiver/Transmitter (UART) block makes it possible to receive and transmit data over a serial line with very little load on the CPU. For those wanting ethernet one can use an external chip like Crystal Semiconductor CS8900A, Realtek RTL8019, or Microchip ENC 28J60. All of them allow easy interfacing with low pin count.

Some microcontrollers use a Harvard architecture: separate memory buses for instructions and data, allowing accesses to take place concurrently. Where a Harvard architecture is used, instruction words for the processor may be a different bit size than the length of internal memory and registers; for example: 12-bit instructions used with 8-bit data registers.

The decision of which peripheral to integrate is often difficult. The microcontroller vendors often trade operating frequencies and system design flexibility against time-to-market requirements from their customers and overall lower system cost. Manufacturers have to balance the need to minimize the chip size against additional functionality.

Microcontroller architectures vary widely. Some designs include general-purpose microprocessor cores, with one or more ROM, RAM, or I/O functions integrated onto the package. Other designs are purpose built for control applications. A microcontroller instruction set usually has many instructions intended for bit-wise operations to make control programs more compact.For example, a general purpose processor might require several instructions to test a bit in a register and branch if the bit is set, where a microcontroller could have a single instruction to provide that commonly-required function.

Microcontrollers typically do not have a math coprocessor, so fixed point or floating point arithmetic are performed by program code. Microcontrollers were originally programmed only in assembly language, but various high-level programming languages are now also in common use to target microcontrollers. These languages are either designed specially for the purpose, or versions of general purpose languages such as the C programming language. Compilers for general purpose languages will typically have some restrictions as well as enhancements to better support the unique characteristics of microcontrollers. Some microcontrollers have environments to aid developing certain types of applications. Microcontroller vendors often make tools freely available to make it easier to adopt their hardware.

Many microcontrollers are so quirky that they effectively require their own non-standard dialects of C, such as SDCC for the 8051, which prevent using standard tools (such as code libraries or static analysis tools) even for code unrelated to hardware features. Interpreters are often used to hide such low level quirks.

Interpreter firmware is also available for some microcontrollers. For example, BASIC on the early microcontrollers Intel 8052; BASIC and FORTH on the Zilog Z8 as well as some modern devices. Typically these interpreters support interactive programming.

Simulators are available for some microcontrollers, such as in Microchip's MPLAB environment. These allow a developer to analyze what the behavior of the microcontroller and their program should be if they were using the actual part. A simulator will show the internal processor state and also that of the outputs, as well as allowing input signals to be generated. While on the one hand most simulators will be limited from being unable to simulate much other hardware in a system, they can exercise conditions that may otherwise be hard to reproduce at will in the physical implementation, and can be the quickest way to debug and analyze problems. Recent microcontrollers are often integrated with on-chip debug circuitry that when accessed by an In-circuit emulator via JTAG, allow debugging of the firmware with a debugger.

(source: wikipedia)

Microcontroller

2009-04-29T23:17:00.000-07:00

also called microcontroller unit, MCU or µC is a small computer on a single integrated circuit consisting of a relatively simple CPU combined with support functions such as a crystal oscillator, timers, watchdog, serial and analog I/O etc. Program memory in the form of NOR flash or OTP ROM is also often included on chip, as well as a, typically small, read/write memory. Microcontrollers are designed for small applications. Thus, in contrast to the microprocessors used in personal computers and other high-performance applications, simplicity is emphasized. Some microcontrollers may operate at clock frequencies as low as 32KHz, as this is adequate for many typical applications, enabling low power consumption (milliwatts or microwatts). They will generally have the ability to retain functionality while waiting for an event such as a button press or other interrupt; power consumption while sleeping (CPU clock and most peripherals off) may be just nanowatts, making many of them well suited for long lasting battery applications.

Microcontrollers are used in automatically controlled products and devices, such as automobile engine control systems, remote controls, office machines, appliances, power tools, and toys. By reducing the size and cost compared to a design that uses a separate microprocessor, memory, and input/output devices, microcontrollers make it economical to digitally control even more devices and processes.The majority of computer systems in use today are embedded in other machinery, such as automobiles, telephones, appliances, and peripherals for computer systems. These are called embedded systems. While some embedded systems are very sophisticated, many have minimal requirements for memory and program length, with no operating system, and low software complexity. Typical input and output devices include switches, relays, solenoids, LEDs, small or custom LCD displays, radio frequency devices, and sensors for data such as temperature, humidity, light level etc. Embedded systems usually have no keyboard, screen, disks, printers, or other recognizable I/O devices of a personal computer, and may lack human interaction devices of any kind. It is mandatory that microcontrollers provide real time response to events in the embedded system they are controlling. When certain events occur, an interrupt system can signal the processor to suspend processing the current instruction sequence and to begin an interrupt service routine (ISR). The ISR will perform any processing required based on the source of the interrupt before returning to the original instruction sequence. Possible interrupt sources are device dependent, and often include events such as an internal timer overflow, completing an analog to digital conversion, a logic level change on an input such as from a button being pressed, and data received on a communication link. Where power consumption is important as in battery operated devices, interrupts may also wake a microcontroller from a low power sleep state where the processor is halted until required to do something by a peripheral event.

Microcontroller programs must fit in the available on-chip program memory, since it would be costly to provide a system with external, expandable, memory. Compilers and assembly language are used to turn high-level language programs into a compact machine code for storage in the microcontroller's memory. Depending on the device, the program memory may be permanent, read-only memory that can only be programmed at the factory, or program memory may be field-alterable flash or erasable read-only memory.

(source: wikipedia)

User View of Operating Systems

2009-04-22T05:48:00.000-07:00

User Interface: Help the user use the computer system productively, Provide consistent user interface services to application programs to lower learning curves and increase productivity, Choice of user interface depends on the kind of user.

User Functions: Program execution, File commands, Mount and unmount devices, Printer spooling, Security, Inter-user communication, System Status, Program Services.

Interface Design: CLI - Command Line Interface, Batch System Commands, Menu-Driven Interfaces, GUI - Graphical User Interface.

Command Languages: Provide a mechanism to combine sequences of commands together. These pseudo-programs are known as scripts or batch files. Startup files – OS configuration, user preferences.
Features of Command Languages: Can accept input from the user and can output messages to I/O devices, Provide ability to create and manipulate variables, Include the ability to branch and loop, Ability to specify arguments to the program command and to transfer those arguments to variables within the program, Provide error detection and recovery.

Menu-Driven Interface: No need to memorize commands, All available commands are listed, Menus can be nested, Low data requirements.

Duocentric Interface: Focus on the document rather than the application being executed, Expand role of OS by moving capabilities from the application to system services. Example: click on document to run program, Effort to assure that every application program responds in similar ways to user actions.

(source: John Wiley & Sons - Wilson Wong, Linda Senne, Bentley College)

WANs (Wide Area Networks)

2009-04-12T19:42:00.000-07:00

The term Wide Area Network (WAN) usually refers to a network which covers a large geographical area, and use communications circuits to connect the intermediate nodes. A major factor impacting WAN design and performance is a requirement that they lease communications circuits from telephone companies or other communications carriers. Transmission rates are typically 2 Mbps, 34 Mbps, 45 Mbps, 155 Mbps, 625 Mbps (or sometimes considerably more).

Numerous WANs have been constructed, including public packet networks, large corporate networks, military networks, banking networks, stock brokerage networks, and airline reservation networks. Some WANs are very extensive, spanning the globe, but most do not provide true global coverage. Organisations supporting WANs using the Internet Protocol are known as Network Service Providers (NSPs). These form the core of the Internet.

By connecting the NSP WANs together using links at Internet Packet Interchanges (sometimes called "peering points") a global communication infrastructure is formed. NSPs do not generally handle individual customer accounts (except for the major corporate customers), but instead deal with intermediate organisations whom they can charge for high capacity communications. They generally have an agreement to exchange certain volumes of data at a certain "quality of service" with other NSPs. So practically any NSP can reach any other NSP, but may require the use of one or more other NSP networks to reach the required destination. NSPs vary in terms of the transit delay, transmission rate, and connectivity offered.

A typical network is shown in the figure above. This connects a number of End Systems (ES) (e.g. A, C, H, K) and a number of Intermediate Systems (IS) (e.g. B, D, E, F, G, I, J) to form a network over which data may be communicated between the End Systems (ES).

The characteristics of the transmission facilities lead to an emphasis on efficiency of communications techniques in the design of WANs. Controlling the volume of traffic and avoiding excessive delays is important. Since the topologies of WANs are likely to be more complex than those of LANs, routing algorithms also receive more emphasis. Many WANs also implement sophisticated monitoring procedures to account for which users consume the network resources. This is, in some cases, used to generate billing information to charge individual users.

(source: erg.abdn.ac.uk)

Secure BGP Project

2009-03-16T01:28:00.000-07:00

Internet routing is based on a distributed system composed of many routers, grouped into management domains called Autonomous Systems (ASes). Routing information is exchanged between ASes in Border Gateway Protocol (BGP) UPDATE messages. BGP is a critical component of the Internet's routing infrastructure. However, it is highly vulnerable to a variety of attacks due to the lack of a scalable means of verifying the authenticity and authorization of BGP control traffic. Secure BGP (S-BGP) addresses these vulnerabilities. The S-BGP architecture employs three security mechanisms. First, a Public Key Infrastructure (PKI) is used to support the authentication of ownership of IP address blocks, ownership of Autonomous System (AS) numbers, an AS's identity, and a BGP router's identity and its authorization to represent an AS. This PKI parallels the IP address and AS number assignment system and takes advantage of the existing infrastructure (Internet registries, etc.) Second, a new, optional, BGP transitive path attribute is employed to carry digital signatures (in "attestations") covering the routing information in a BGP UPDATE. These signatures along with certificates from the S-BGP PKI enable the receiver of a BGP routing UPDATE to verify the address prefixes and path information that it contains. Third, IPsec is used to provide data and partial sequence integrity, and to enable BGP routers to authenticate each other for exchanges of BGP control traffic. Under a previous contract with DARPA, a proof-of-concept prototype of S-BGP was developed and used to demonstrate the effectiveness and feasibility of deploying S-BGP. However, a major obstacle to the deployment of S-BGP is that it requires the participation of several distinct organizations -- the Internet registries, router vendors, and Internet service providers (ISPs). Because there will be no security benefits unless a few of each type of the organizations participate, each organization cannot justify the expense of investing in this new technology unless the others have also done so -- a classic chicken-and-egg problem. The goal of this project is to overcome these obstacles and promote deployment of S-BGP into the Internet. Deploying S-BGP will require working with the Internet registries and ISPs to set up the PKI; working with router vendors to implement the S-BGP enhancements (new path attribute, IPsec, etc.) on COTS routers; and convincing ISPs to buy and use these routers.

(source: www.ir.bbn.com)

Software Engineering

2009-03-11T18:18:00.000-07:00

Software Engineering is an approach to developing software that attempts to treat it as a formal process more like traditional engineering than the craft that many programmers believe it is. We talk of crafting an application, refining and polishing it, as if it were a wooden sculpture, not a series of logic instructions. The problem here is that you cannot engineer art. Programming falls somewhere between an art and a science.
Programming - Art or Engineering?
There has always been considerable debate about the nature of programming. If bridges were designed like software then there would be a lot of ferries operating. You can't have a second go if a bridge fails. That's the argument that the Software Engineering proponents put forward.

How do I Stop my Software Killing Someone?
Manufacturers cannot build complex life-critical systems like aircraft, nuclear reactor controls, medical systems and expect the software to be thrown together. They require the whole process to be thoroughly managed, so that budgets can be estimated, staff recruited, and to minimize the risk of failure or expensive mistakes.

In safety critical areas such as aviation,space, nuclear power plants,medicine, fire detection systems, and roller coaster rides the cost of failure can be enormous as lives are at risk. A divide by zero error that brings down an aircraft is just not acceptable.
So It Never Goes Wrong?
In spite of this there have been a few high profile disasters. Ariane 5, a rocket system for delivering satellites into orbit blew up in June 1996, 40 seconds after takeoff due to an arithmetic overflow bug. The system had used specifications from an earlier rocket Ariane 4 without having been fully tested.

What Is Computer Aided Software Engineering?
The whole design process has to be formally managed long before the first line of code is written. Enormous design documents- hundreds or thousands of pages long are produced using C.A.S.E. (Computer Aided Software Engineering) tools then converted into Design Specification documents which are used to design code.

C.A.S.E suffers from the "not quite there yet" syndrome. There are no systems that can take a set of design constraints and requirements then generate code that satisfies all the requirements and constraints. Its far too complex a process. So the available C.A.S.E. systems manage parts of the lifecycle process but not all of it.
So it is Paper Work?
One distinguishing feature of Software Engineering is the paper trail that it produces. Designs have to be signed off by Managers and Technical Authorities all the way from top to bottom and the role of Quality Assurance is to check the paper trail. Many Software Engineers would admit that their job is around 70% paperwork and 30% code. It's a costly way to write software and this is why avionics in modern aircraft are so expensive.

(source: cplus.about.com)

Knowledge Management

2009-03-04T18:10:00.000-08:00

Knowledge Management (KM) comprises a range of practices used in an organisation to identify, create, represent, distribute and enable adoption of insights and experiences. Such insights and experiences comprise knowledge, either embodied in individuals or embedded in organisational processes or practice. An established discipline since 1995, KM includes courses taught in the fields of business administration, information systems, management, and library and information sciences (Alavi & Leidner 1999). More recently, other fields, to include those focused on information and media, computer science, public health, and public policy, also have started contributing to KM research. Many large companies and non-profit organisations have resources dedicated to internal KM efforts, often as a part of their 'Business Strategy', 'Information Technology', or 'Human Resource Management' departments (Addicott, McGivern & Ferlie 2006). Several consulting companies also exist that provide strategy and advice regarding KM to these organisations.

KM efforts typically focus on organisational objectives such as improved performance, competitive advantage, innovation, the sharing of lessons learned, and continuous improvement of the organisation. KM efforts overlap with Organisational Learning, and may be distinguished from by a greater focus on the management of knowledge as a strategic asset and a focus on encouraging the exchange of knowledge. KM efforts can help individuals and groups to share valuable organisational insights, to reduce redundant work, to avoid reinventing the wheel per se, to reduce training time for new employees, to retain intellectual capital as employees turnover in an organisation, and to adapt to changing environments and markets (McAdam & McCreedy 2000)(Thompson & Walsham 2004).

KM efforts have a long history, to include on-the-job discussions, formal apprenticeship, discussion forums, corporate libraries, professional training and mentoring programs. More recently, with increased use of computers in the second half of the 20th century, specific adaptations of technologies such as knowledge bases, expert systems, knowledge repositories, group decision support systems, and computer supported cooperative work have been introduced to further enhance the such efforts.

In 1999, the term personal knowledge management was introduced which refers to the management of knowledge at the individual level (Wright 2005).Different frameworks for distinguishing between knowledge exist. One proposed framework for categorising the dimensions of knowledge distinguishes between tacit knowledge and explicit knowledge. Tacit knowledge represents internalised knowledge that an individual may not be consciously aware of how he or she accomplishes particular tasks. At the opposite end of the spectrum, explicit knowledge represents knowledge that the individual holds consciously in mental focus, in a form that can easily be communicated to others.(Alavi & Leidner 2001).

Early research suggested that a successful KM effort needs to convert internalised tacit knowledge into explicit knowledge in order to share it, but the same effort must also permit individuals to internalise and make personally meaningful any codified knowledge retrieved from the KM effort. Subsequent research into KM suggested that a distinction between tacit knowledge and explicit knowledge represented an oversimplification and that the notion of explicit knowledge is self-contradictory. Specifically, for knowledge to be made explicit, it must be translated into information (i.e., symbols outside of our heads) (Serenko & Bontis 2004).

A second proposed framework for categorising the dimensions of knowledge distinguishes between embedded knowledge of a system outside of a human individual (e.g., an information system may have knowledge embedded into its design) and embodied knowledge representing a learned capability of a human body’s nervous and endocrine systems.

A third proposed framework for categorising the dimensions of knowledge distinguishes between the exploratory creation of "new knowledge" (i.e., innovation) vs. the transfer or exploitation of "established knowledge" within a group, organisation, or community. Collaborative environments such as communities of practice or the use of social computing tools can be used for both knowledge creation and transfer.

Knowledge may be accessed at three stages: before, during, or after KM-related activities. Different organisations have tried various knowledge capture incentives, including making content submission mandatory and incorporating rewards into performance measurement plans. Considerable controversy exists over whether incentives work or not in this field and no consensus has emerged.

One strategy to KM involves actively managing knowledge. In such an instance, individuals strive to explicitly encode their knowledge into a shared knowledge repository, such as a database, as well as retrieving knowledge they need that other individuals have provided to the repository. Another strategy to KM involves individuals making knowledge requests of experts associated with a particular subject on an ad hoc basis. In such an instance, expert individual(s) can provide their insights to the particular person or people needing this (Snowden 2002)

(source: en.wikipedia.org)

Software Design

2009-02-22T20:53:00.000-08:00

Designing software is an exercise in managing complexity. The complexity exits within the software design itself, within the software organization of the company, and within the industry as a whole. Software design is very similar to systems design. It can span multiple technologies and often involves multiple sub-disciplines. Software specifications tend to be fluid, and change rapidly and often, usually while the design process is still going on. Software development teams also tend to be fluid, likewise often changing in the middle of the design process. In many ways, software bears more resemblance to complex social or organic systems than to hardware. All of this makes software design a difficult and error prone process. None of this is original thinking, but almost 30 years after the software engineering revolution began, software development is still seen as an undisciplined art compared to other engineering professions.

The general consensus is that when real engineers get through with a design, no matter how complex, they are pretty sure it will work. They are also pretty sure it can be built using accepted construction techniques. In order for this to happen, hardware engineers spend a considerable amount of time validating and refining their designs. Consider a bridge design, for example. Before such a design is actually built the engineers do structural analysis; they build computer models and run simulations; they build scale models and test them in wind tunnels or other ways. In short, the designers do everything they could think of to make sure the design is a good design before it is built. The design of new airliner is even worse; for those, full scale prototypes must be built and test flown to validate the design predictions.

It seems obvious to most people that software designs do not go through the same rigorous engineering as hardware designs. However, if we consider source code as design, we see that software designers actually do a considerable amount of validating and refining their designs. Software designers do not call it engineering, however, we call it testing and debugging. Most people do not consider testing and debugging as real "engineering"; certainly not in the software business. The reason has more to do with the refusal of the software industry to accept code as design than with any real engineering difference. Mock-ups, prototypes, and bread-boards are actually an accepted part of other engineering disciplines. Software designers do not have or use more formal methods of validating their designs because of the simple economics of the software build cycle.

it is cheaper and simpler to just build the design and test it than to do anything else. We do not care how many builds we do -- they cost next to nothing in terms of time and the resources used can be completely reclaimed later if we discard the build. Note that testing is not just concerned with getting the current design correct, it is part of the process of refining the design. Hardware engineers of complex systems often build models (or at least they visually render their designs using computer graphics). This allows them to get a "feel" for the design that is not possible by just reviewing the design itself. Building such a model is both impossible and unnecessary with a software design. We just build the product itself. Even if formal software proofs were as automatic as a compiler, we would still do build/test cycles. Ergo, formal proofs have never been of much practical interest to the software industry.

This is the reality of the software development process today. Ever more complex software designs are being created by an ever increasing number of people and organizations. These designs will be coded in some programming language and then validated and refined via the build/test cycle. The process is error prone and not particularly rigorous to begin with. The fact that a great many software developers do not want to believe that this is the way it works compounds the problem enormously.

Most current software development processes try to segregate the different phases of software design into separate pigeon-holes. The top level design must be completed and frozen before any code is written. Testing and debugging are necessary just to weed out the construction mistakes. In between are the programmers, the construction workers of the software industry. Many believe that if we could just get programmers to quit "hacking" and "build" the designs as given to them (and in the process, make fewer errors) then software development might mature into a true engineering discipline. Not likely to happen as long as the process ignores the engineering and economic realities.

(source: bleading-edge.com)

Domain Name System and DNS Server

2009-02-14T14:39:00.000-08:00

Definition: The DNS translates Internet domain and host names to IP addresses. DNS automatically converts the names we type in our Web browser address bar to the IP addresses of Web servers hosting those sites.

DNS implements a distributed database to store this name and address information for all public hosts on the Internet. DNS assumes IP addresses do not change (are statically assigned rather than dynamically assigned).

The DNS database resides on a hierarchy of special database servers. When clients like Web browsers issue requests involving Internet host names, a piece of software called the DNS resolver (usually built into the network operating system) first contacts a DNS server to determine the server's IP address. If the DNS server does not contain the needed mapping, it will in turn forward the request to a different DNS server at the next higher level in the hierarchy. After potentially several forwarding and delegation messages are sent within the DNS hierarchy, the IP address for the given host eventually arrives at the resolver, that in turn completes the request over Internet Protocol.

DNS additionally includes support for caching requests and for redundancy. Most network operating systems support configuration of primary, secondary, and tertiary DNS servers, each of which can service initial requests from clients. ISPs maintain their own DNS servers and use DHCP to automatically configure clients, relieving most home users of the burden of DNS configuration.
Also Known As: Domain Name System, Domain Name Service, Domain Name Server

A DNS server is any computer registered to join the Domain Name System. A DNS server runs special-purpose networking software, features a public IP address,and contains a database of network names and addresses for other Internet hosts.
DNS Root Servers
DNS servers communicate with each other using private network protocols. All DNS servers are organized in a hierarchy. At the top level of the hierarchy, so-called root servers store the complete database of Internet domain names and their corresponding IP addresses. The Internet employs 13 root servers that have become somewhat famous for their special role. Maintained by various independent agencies, the servers are aptly named A, B, C and so on up to M. Ten of these servers reside in the United States, one in Japan, one in London, UK and one in Stockholm, Sweden.
DNS Server Hierarchy
The DNS is a distributed system, meaning that only the 13 root servers contain the complete database of domain names and IP addresses. All other DNS servers are installed at lower levels of the hierarchy and maintain only certain pieces of the overall database.

Most lower level DNS servers are owned by businesses or Internet Service Providers (ISPs). For example, Google maintains various DNS servers around the world that manage the google.com, google.co.uk, and other domains. Your ISP also maintains DNS servers as part of your Internet connection setup.

DNS networking is based on the client / server architecture. Your Web browser functions as a DNS client (also called DNS resolver) and issues requests to your Internet provider's DNS servers when navigating between Web sites.

When a DNS server receives a request not in its database (such as a geographically far away or rarely visited Web site), it temporarily transforms from a server to a DNS client. The server automatically passes that request to another DNS server or up to the next higher level in the DNS hierarchy as needed. Eventually the request arrives at a server that has the matching name and IP address in its database (all the way to the root level if necessary), and the response flows back through the chain of DNS servers to your client.
DNS Servers and Home Networking

Computers on your home network locate a DNS server through the Internet connection setup properties. Providers give their customers the public IP address(es) of primary and backup DNS servers. You can find the current IP addresses of your DNS server configuration via several methods:
on the configuration screens of a home network router.
on the TCP/IP connection properties screens in Windows Control Panel (if configured via that method).
from ipconfig or similar command line utility.

(source: compnetworking.about.com)

Expert System

2009-02-08T19:04:00.000-08:00

The expert system approach is essentially looking for patterns in complex dynamic phenomena that have proved to be beyond standard quantification techniques. For example 'ship decoration' cannot be quantified. The outcome of the expert system is a probability statement concerning the tool type or function that is most consistent with the observations. The interpretations are made according to the balance of indications given by the expert system rules and based on the observation of all features.

Expert systems are not intended to replace human experts. For example, the recognition of retouch on stone tools as opposed to edge damage (from spontaneous retouch, trampling, post depositional movement, etc.), is dependent on the analyst's experience and in particular on experimentation, involving not only observation of experimental and archaeological tools , but also an appreciation of the mechanics of making and using stone tools.

The use of expert systems has a number of advantages over other techniques. Increased consistency and standardisation. The development of an expert system means that the observational techniques have to be systematised and the rules provide a base from which results can be assessed.

Different analysts using the same program will obtain the same results. This has been repeatedly confirmed during instruction in use-wear analysis when several students have independently analysed the same experimental tools and all interpreted the correct function of the tool using FAST. Often students enter different observations, due to inexperience, but the flexibility of the program (in particular the 'fuzzy logic' aspects) allows for this so that some variations in observations can be accommodated.

The use of rule based expert systems is a practical approach to lithic studies that bridges the gap between processual and post processual archaeology. The key here is rules; not laws which are inviolate, but rules that can be changed and indeed are always changing in a reflexive relationship allowing the expert system to accommodate new information.
The rules of the expert system are subjective, but they are explicit in that they are written down and incorporated into the computer program. The observations are defined and the rules are explicit therefore anyone can produce the same results, so that though the system is subjective it is consistent when different subjectivities (i.e. different individuals) use it. The acceptance of the assumptions on which the program is based leads to consistency, and direct comparability between results produced by different people; this fulfills the basic requirements of objective data within the consensus reality of mutual users of the program. Therefore expert systems can extract objective-like data, but the complexity of the dynamic process is retained and the data is produced in the form of probabilities that can be compared as if they are objective data within a defined consensus reality.

Expert systems are so called because they are designed to model the behaviour of a human expert. So they are modeling human behaviour, in fact an individuals behaviour. By extension expert systems can be used to model the more complex behaviour of societies. A series of programs that input the results of each individual program into another program further up the hierarchy is being developed. Not only must the interpretations be consistent with use-wear analysis and lithic programs, but non-lithic material such as the faunal assemblage, environmental evidence and spatial information from the site and any chronological evidence.
Alternative interpretations can be modeled with expert systems so rather than postulating a theory and then testing it, a number of alternatives can be tested and matched against the data simultaneously.

(source: hf.uio.no/iakh/forskning/sarc/iakh/lithic)

Fibonacci and Golden Ratio

2009-02-05T15:05:00.000-08:00

The golden ratio 1·618034 is also called the golden section or the golden mean or just the golden number. It is often represented by a Greek letter Phi . The closely related value which we write as phi with a small "p" is just the decimal part of Phi, namely 0·618034.
We can make another picture showing the Fibonacci numbers 1,1,2,3,5,8,13,21,.. if we start with two small squares of size 1 next to each other. On top of both of these draw a square of size 2 (=1+1). We can now draw a new square - touching both a unit square and the latest square of side 2 - so having sides 3 units long; and then another touching both the 2-square and the 3-square (which has sides of 5 units). We can continue adding squares around the picture, each new square having a side which is as long as the sum of the latest two square's sides. This set of rectangles whose sides are two successive Fibonacci numbers in length and which are composed of squares with sides which are Fibonacci numbers, we will call the Fibonacci Rectangles.
Here is a spiral drawn in the squares, a quarter of a circle in each square. The spiral is not a true mathematical spiral (since it is made up of fragments which are parts of circles and does not go on getting smaller and smaller) but it is a good approximation to a kind of spiral that does appear often in nature. Such spirals are seen in the shape of shells of snails and sea shells and, as we see later, in the arrangement of seeds on flowering plants too. The spiral-in-the-squares makes a line from the centre of the spiral increase by a factor of the golden number in each square. So points on the spiral are 1.618 times as far from the centre after a quarter-turn. In a whole turn the points on a radius out from the centre are 1.618⁴ = 6.854 times further out than when the curve last crossed the same radial line.

Cundy and Rollett (Mathematical Models, second edition 1961, page 70) say that this spiral occurs in snail-shells and flower-heads referring to D'Arcy Thompson's On Growth and Form probably meaning chapter 6 "The Equiangular Spiral". Here Thompson is talking about a class of spiral with a constant expansion factor along a central line and not just shells with a Phi expansion factor.

Below are images of cross-sections of a Nautilus sea shell. They show the spiral curve of the shell and the internal chambers that the animal using it adds on as it grows. The chambers provide buoyancy in the water. Draw a line from the centre out in any direction and find two places where the shell crosses it so that the shell spiral has gone round just once between them. The outer crossing point will be about 1.6 times as far from the centre as the next inner point on the line where the shell crosses it. This shows that the shell has grown by a factor of the golden ratio in one turn.
On the poster shown here, this factor varies from 1.6 to 1.9 and may be due to the shell not being cut exactly along a central plane to produce the cross-section. Several organisations and companies have a logo based on this design, using the spiral of Fibonacci squares and sometime with the Nautilus shell superimposed. It is incorrect to say this is a Phi-spiral. Firstly the "spiral" is only an approximation as it is made up of separate and distinct quarter-circles; secondly the (true) spiral increases by a factor Phi every quarter-turn so it is more correct to call it a Phi⁴ spiral.

(source: mcs.surrey.ac.uk)

Fingerprint Identification: Classification&Image Enhancement

2009-02-02T10:23:00.000-08:00

Large volumes of fingerprints are collected and stored everyday in a wide range of applications including forensics, access control, and driver license registration. An automatic recognition of people based on fingerprints requires that the input fingerprint be matched with a large number of fingerprints in a database (FBI database contains approximately 70 million fingerprints!). To reduce the search time and computational complexity, it is desirable to classify these fingerprints in an accurate and consistent manner so that the input fingerprint is required to be matched only with a subset of the fingerprints in the database.Fingerprint classification is a technique to assign a fingerprint into one of the several pre-specified types already established in the literature which can provide an indexing mechanism. Fingerprint classification can be viewed as a coarse level matching of the fingerprints. An input fingerprint is first matched at a coarse level to one of the pre-specified types and then, at a finer level, it is compared to the subset of the database containing that type of fingerprints only. We have developed an algorithm to classify fingerprints into five classes, namely, whorl, right loop, left loop, arch, and tented arch. The algorithm separates the number of ridges present in four directions (0 degree, 45 degree, 90 degree, and 135 degree) by filtering the central part of a fingerprint with a bank of Gabor filters. This information is quantized to generate a FingerCode which is used for classification. Our classification is based on a two-stage classifier which uses a K-nearest neighbor classifier in the first stage and a set of neural networks in the second stage. The classifier is tested on 4,000 images in the NIST-4 database. For the five-class problem, classification accuracy of 90% is achieved. For the four-class problem (arch and tented arch combined into one class), we are able to achieve a classification accuracy of 94.8%. By incorporating a reject option, the classification accuracy can be increased to 96% for the five-class classification and to 97.8% for the four-class classification when 30.8% of the images are rejected.

A critical step in automatic fingerprint matching is to automatically and reliably extract minutiae from the input fingerprint images. However, the performance of a minutiae extraction algorithm relies heavily on the quality of the input fingerprint images. In order to ensure that the performance of an automatic fingerprint identification/verification system will be robust with respect to the quality of the fingerprint images, it is essential to incorporate a fingerprint enhancement algorithm in the minutiae extraction module. We have developed a fast fingerprint enhancement algorithm, which can adaptively improve the clarity of ridge and furrow structures of input fingerprint images based on the estimated local ridge orientation and frequency. We have evaluated the performance of the image enhancement algorithm using the goodness index of the extracted minutiae and the accuracy of an online fingerprint verification system. Experimental results show that incorporating the enhancement algorithms improves both the goodness index and the verification accuracy.

(source: Salil Prabhakar, Anil Jain)

Fingerprint Identification: Matching

2009-01-27T23:48:00.000-08:00

Among all the biometric techniques, fingerprint-based identification is the oldest method which has been successfully used in numerous applications. Everyone is known to have unique, immutable fingerprints. A fingerprint is made of a series of ridges and furrows on the surface of the finger. The uniqueness of a fingerprint can be determined by the pattern of ridges and furrows as well as the minutiae points. Minutiae points are local ridge characteristics that occur at either a ridge bifurcation or a ridge ending.

Fingerprint matching techniques can be placed into two categories: minutae-based and correlation based. Minutiae-based techniques first find minutiae points and then map their relative placement on the finger. However, there are some difficulties when using this approach. It is difficult to extract the minutiae points accurately when the fingerprint is of low quality. Also this method does not take into account the global pattern of ridges and furrows. The correlation-based method is able to overcome some of the difficulties of the minutiae-based approach. However, it has some of its own shortcomings. Correlation-based techniques require the precise location of a registration point and are affected by image translation and rotation.

Fingerprint matching based on minutiae has problems in matching different sized (unregistered) minutiae patterns. Local ridge structures can not be completely characterized by minutiae. We are trying an alternate representation of fingerprints which will capture more local information and yield a fixed length code for the fingerprint. The matching will then hopefully become a relatively simple task of calculating the Euclidean distance will between the two codes.

We are developing algorithms which are more robust to noise in fingerprint images and deliver increased accuracy in real-time. A commercial fingerprint-based authentication system requires a very low False Reject Rate (FAR) for a given False Accept Rate (FAR). This is very difficult to achieve with any one technique. We are investigating methods to pool evidence from various matching techniques to increase the overall accuracy of the system. In a real application, the sensor, the acquisition system and the variation in performance of the system over time is very critical. We are also field testing our system on a limited number of users to evaluate the system performance over a period of time.

Concept of Registers

2009-01-21T04:08:00.000-08:00

Small, permanent storage locations within the CPU used for a particular purpose
Manipulated directly by the Control Unit
Wired for specific function
Size in bits or bytes (not MB like memory)
Can hold data, an address or an instruction
How many registers does the LMC have?

Use of Registers;
Scratchpad for currently executing program
Holds data needed quickly or frequently
Stores information about status of CPU and currently executing program
Address of next program instruction
Signals from external devices

General Purpose Registers;
User-visible registers
Hold intermediate results or data values, e.g., loop counters
Equivalent to LMC’s calculator
Typically several dozen in current CPUs

Special-Purpose Registers
Program Count Register (PC)
Also called instruction pointer
Instruction Register (IR)
Stores instruction fetched from memory
Memory Address Register (MAR)
Memory Data Register (MDR)
Status Registers
Status of CPU and currently executing program
Flags (one bit Boolean variable) to track condition like arithmetic carry and overflow, power failure, internal computer error

Register Operations
Stores values from other locations (registers and memory)
Addition and subtraction
Shift or rotate data
Test contents for conditions such as zero or positive

(source: handbook 3rd edition Wilson Wong, Linda Senne, Bentley College)

Instruction Cycle

2009-01-18T10:06:00.000-08:00

Fetch: Little Man finds out what instruction he is to execute
read the address from the location counter
walk over to the mailbox that corresponds to the location counter
And reads the number on the slip of paper (puts the slip back in case he needs to read it again later)

Execute: Little Man performs the work.
goes to the mailbox address specified in the instruction he just fetched.
reads the number in that mailbox (remember to replace it in case he needs it later).
walks over to the calculator and punches the number in and walk over to the location counter and clicks it, which gets him ready to fetch the next instruction.

(source: handbook 2003 John Wiley & Sons)

History of Early Computer

2009-01-17T03:53:00.000-08:00

1642: Blaise Pascal invents a calculating machine
1801: Joseph Marie Jacquard invents a loom that uses punch cards
1800’s:
Charles Babbage attempts to build an analytical engine (mechanical computer)
Augusta Ada Byron develops many of the fundamental concepts of programming
George Boole invents Boolean logic.
1937: Mark I is built (Aiken, Harvard University, IBM).
First electronic computer using relays.
1939: ABC is built
First fully electronic digital computer. Used vacuum tubes.
1943-46: ENIAC (Mauchly, Eckert, University of Pennsylvania).
First general purpose digital computer.
1945: Von Neumann architecture proposed.
Still the standard for present day computers.
1947: Creation of transistor
(Bardeen, Shockley, Brattain, Bell Labs).
1951: UNIVAC.
First commercially available computer.

(source: An Information Technology Approach 3rd Edition, Irv Englander)

The context of structure of Chinese language

2009-01-15T04:47:00.000-08:00

Needham (1959) says that the mental mechanism for the building and the recognition of ideograms by association is a "mental equation". " More primitive elements of Chinese language were generally pictograms, that is pictures reduced to the essential, made conventional, at the end very stylised. Naturally, concrete objects as the heavenly bodies, animals, plants, implements and instruments could be easier pictured. We reported some in the first part of the list two, having them origins in a Haluon's short popular leader. You will note, the most part of them, in the course of the time, have been included in radicals, (you can see later); but, it isn't always like that: hsiang (elephant) isn't a radical, but it has been classified under the radical number 152 (shih, pig) on the other hand, hu (wine's recipe) has been classified under the radical 33 (shid, studious). This depended on decisions made by lexicographers of successive ages.

In this way, the writing's fan extended and includes indirect symbols by different types of metaphoric substitution, like the part for the whole, the attribute for thing, the effect for the cause, the instrument for the activity, the gesture for the action, and so on. The list shows as the word chin, go up, derives from the picture of two footprints turning up; and as the word fù, that means "summit" derives from the ancient pot's picture.

A third characters class has composed of semantic combinations of two or more than two pictograms, making those called compound by association. In this way fu, wife, has composed by women's signs, hand and broom, fu, father, by the ancient signs of hand and stick; hao, to love, or good, combines signs of women and child.
A particularly interesting example, is the word that means male or man, nan, that includes the radicals of plough and field, indicates " who uses his force in the fields". Obviously, the sounds of the different elements lose themselves in the sound " that result", because this sign existed before that, to represent it, the scribes associated signs having other sounds, So, we have a sort of equation: li + thine = nan. These equations make up a mental half-conscious foundation for people acquiring familiarity with the language" (Needham, 1981).

(source: dlibrary.acu.edu.au)

Hardware Components

2009-01-14T02:06:00.000-08:00

Input/Output devices and Storage Devices

CPU
ALU: arithmetic/logic unit
Performs arithmetic and Boolean logical calculations
CU: control unit
Controls processing of instructions
Controls movement of data within the CPU
Interface unit
Moves instructions and data between the CPU and other hardware components
Bus: bundle of wires that carry signals and power between different components

Memory
Short-term storage for CPU calculations
Also known as primary storage, working storage, and RAM (random access memory)
Consists of bits, each of which hold a value of either 0 or 1 (8 bits = 1 byte)
Holds both instructions and data of a computer program (stored program concept)

(source: An Information Technology Approach 3rd Edition)

Computer Architecture

2009-01-14T02:01:00.000-08:00

advantages for User
Understand system capabilities and limitations
Make informed decisions
Improve communications with information technology professionals
Systems Analyst
Conduct surveys, determine feasibility and define and document user requirements
Specify computer systems to meet application requirements

advantages to Programmer
Create efficient application software for specific processing needs

advantages to System Administrator / Manager
Install, configure, maintain, and upgrade computer systems
Maximize system availability
Optimize system performance
Ensure system security

advantages for Web Designer
Optimize customer accessibility to Web services
System administration of Web servers
Select appropriate data formats
Design efficient Web pages

Architecture Components
Software: Instructions executed by the system
Data: Fundamental representation of facts and observations
Communications: Sharing data and processing among different systems
Hardware: Processes data by executing instructions and Provides input and output

(source: An Information Technology Approach 3rd Edition)

SPAM Control: Success or Failure ?

2009-01-12T12:31:00.000-08:00

The Bad News
First, the bad news. In a year-end analysis, email-security solutions provider SoftScan announced that less than 3 percent of all of the email it scanned in December was legitimate. "Once again, the rapid increase of spam throughout 2007 demonstrates that there is not enough deterrent for spammers to give up their highly lucrative enterprise," commented Diego d'Ambra, SoftScan's CTO, in a company statement.

Anti-malware software vendor CA painted an equally gloomy picture in a January 2008 Internet-security report. The company observed that spam is now the preferred distribution method for malware, with 80 percent of spam containing links to malicious sites or malware.

Spam's quality is also improving, warned CA. The typical spam message is no longer riddled with grammatical errors and typos, giving the bogus email an increased aura of legitimacy. As always, CA observed, spam attachments such as documents, spreadsheets, graphics and videos typically contain malware or links to malicious Web sites.

The Good News
The good news about spam is not that the onslaught is receding - it isn't - but that spammers are not causing as much mayhem as many experts were predicting just a few years ago. So far, spam's biggest impact on businesses - at least those with adequate safeguards in place - has been the cost of transporting and filtering junk email.

People also seem to be feeling slightly better about spam. According to a study released in May 2007 by the Pew Internet & American Life Project, the percentage of email users who believe spam is "a big problem" fell from 25 percent in 2003 to 18 percent in 2007 - a small but significant decline. Additionally, users who believe spam is "not at all a problem," rose from 16 percent to 28 percent over the same time period.

There is also growing hope that fresh spam-fighting breakthroughs will soon give ISPs, businesses and other email defenders access to new and more powerful tools. Over the past few months, research teams at Carnegie Mellon University, Georgia Institute of Technology, IBM Research and a variety of other institutions have announced methodologies designed to tackle image spam, phishing and a variety of other email threats. More breakthroughs are likely to be announced in March at the MIT Spam Conference.

The Score
In light of all these facts and trends, who's winning the spam war: the spammers or legitimate email users? An objective look at the email battlefield shows that neither side is "winning" in any true sense of the word, despite the rapid rise in spam volume and the steady arrival of anti-spam tools and practices.

Spammers are devious, continuously experimenting with new technologies and shifting tactics. Spam defenders, on the other hand, are also moving quickly and are adopting enhanced protection technologies that effectively neutralize new spam threats almost as soon as they appear. The result of both sides' unflagging efforts has been a giant stalemate, with spammers failing to deliver a crippling blow to Internet email and defenders unable to stifle the flow of spam.

This situation is neither good nor bad news for businesses; it is simply a fact of life. For now, companies can rest assured that a combination of spam filtering, anti-malware technologies and user education will make their email environments generally safe and reliable. This situation may eventually improve or deteriorate over the next few months or years. For the moment, however, spam control has many of the characteristics of a virtual chess game.

(source: networksecurityjournal.com)

Administrasi WinGate

2009-01-12T08:22:00.000-08:00

Konfigurasi LAN/Jaringan
Kita akan mencoba melakukan konfigurasi untuk workstation yang berbasis sistem operasi Windows. Sebelum melakukan konfigurasi, pastikan dulu driver yang diperlukan (misalnya driver ethernet card) telah terinstal dengan baik.
Kita akan menggunakan LAN dengan IP network 10.1.1.0 dan netmask 255.255.255.240. Semua workstation menggunakan IP Private. Gateway akan disetting mempunyai dua buah IP, satu private IP misalnya 10.1.1.1 dan satunya lagi adalah IP internet yang diberikan oleh ISP.
Konfigurasi yang akan kita lakukan pada dasarnya hanya berkisar pada fasilitas internet sharing dan network pada setting control panel.
Buka window Control Panel dengan meng-click tombol start -> setting -> control panel.
Kemudian click dua kali icon Network untuk membuka window Network.
Tambahkan fasilitas-fasilitas yang dibutuhkan (meliputi Client, Adapter, Protocol, dan Service), misalnya
Service -> File and printer sharing for Microsoft Networks (untuk sharing file dan printer vi Network Neighborhood)
Protocol -> NetBEUI
Konfigurasikan untuk protokol IP : IP Address, Gateway, dan DNS Configuration.
Settinglah gateway denagn IP 10.1.1.1 untuk semua komputer yang ada (10.1.1.1 adalah nomor IP private dari Gateway).
Kemudian settinglah DNS server sesuai dengan DNS Server yang ada, misalkan 10.1.1.1.
Kemudian konfigurasi Internet Option (dari Control Panel)
Dan gunakan proxy server dengan IP 10.1.1.1.
Kemudian tekan tombol advanced untuk konfigurasi yang lebih kompleks.

Internet Sharing dengan WinGate
Konfigurasi komputer Gateway.
Pada komputer Gateway pastikan juga sudah dikonfigurasi. Dengan IP Address Gateway untuk ethernet card yang terhubung ke LAN menggunakan IP private 10.1.1. 1 dan IP satunya berasal dari ISP.
Periksa gateway yang digunakan yaitu menunjuk ke IP 10.1.1.1 karena PC Gateway akan mengkoneksikan diri ke internet melalui dirinya sendiri. Juga periksa DNS Server yang dipakai.

Pengaktifan GateKeeper :
Start -> Programs -> WinGate -> GateKeeper,
Pada waktu pertama kali dipakai, Password untuk Adminstrator adalah kosong (tidak diisi apapun), jadi tekan enter saja. Baru setelah masuk kita ubah passwordnya.
Accounting jumlah byte yang telah ditransfer oleh user tertentu.
Banyak fasilitas yang ditawarkan oleh WinGate dan semuanya bersifat user friendly dan mudah dipelajari. Penggunaan WinGate yang dibahas di sini hanyalah dasar-dasarnya saja karena cukup mudah digunakan. Gunakan Fasilitas manual dan help yang ada untuk mendalami fasilitas-fasilitas pada WinGate.

Membongkar PC

2009-01-12T06:57:00.000-08:00

Pastikan PC anda dalam keadaan mati serta matikan sumber tegangan komputer anda.
Lepaskan semua kabel yang mengghubungkan casing dengan komponen luar seperti monitor, speaker, printer (jika ada), scanner (jika ada), mouse, keyboard, joystick (jika ada).
Buka casing dan rebahkan diatas permukaan datar.
Lepaskan semua kabel power dan kabel data dari drive (FDD, HDD, CD-ROM Drive) dan Motherboard anda kemudian lepaskan semua drive (FDD, HDD, CD-ROM) letakkan secara hati-hati (khususnya Harddisk dan CD-ROM).
Melepaskan kabel pada Motherboard :
kabel power motherboard, kabel IDE (kabel data pada harddisk 40 pin), kabel data floppy (34pin), kabel power kipas.
kabel penghubung motherboard dengan komponen casing(tombol on/off, reset, LED.
kabel serial dan paralel.
Lepaskan penyangga (tempat memasang motherboard) dan mur dari komponen motherboard dengan casing.L etakkan pada permukaan datar sehingga memudahkan pelepasan komponen motherboard. Hindari memegang bagian belakang dari Motherboard karena dikhawatirkan adanya listrik statis.
Lepaskan komponen motherboard dari slotnya :
VGA card (slot PCI atau AGP)
Sound card (slot ISA atau PCI)
RAM (slot memory)
Card lainnya jika ada (TV tuner, Ethernet card, Modem internal)
Tahap terakhir adalah tahap pelepasan processor (lakukan dengan hati-hati, mintalah bantuan orang lain jika merasa tidak mampu) :
Socket 7
Buka pengunci tempat processor dengan memindahkan tiand kecil dari posisi horizontal sampai posisi vertikal hingga tegak lurus motherboard.
Lepaskan processor tempatnya hati-hati. Jika pengunci tidak terbuka dengan baik akan dapat menyebab kerusakan pada kaki processor.
Slot 1
Tekan pengunci processor pada bagian kanan dan kiri sesuai posisi slot processor.
Jika telah terlepas maka angkat processor keatas.

Tips Membongkar PC
Siapkan peralatan yang dibutuhkan spperti obeng kembang (+) serta obeng minus(-).
Buatlah diri anda senyaman mungkin dalam membedah PC.
Hindarkan/jangan membedah PC dalam keadaan menyala karena dapat membahayakan diri anda serta komponen dari komputer anda.
Hilangkan muatan statis dari tubuh kita dengan menyalurkan ke bumi, (dinding, lantai) atau memakai gelang anti statis.

(source: handbook tim training SMK TI)