Biometrics

The biometric technology is closely bonded via computer and optics, acoustics, biosensors and bio-statistical principles and other high-tech means, using the body's natural physiological characteristics (such as fingerprints, face, like, iris, etc.) and behavioral characteristics (such as handwriting , voice, gait, etc.) to identify personal identity.

According to IBG (International Biometric Group) statistics in 2009, the market has a variety of features for different physiological and behavioral characteristics of the application. Among them, the highest share is the fingerprint of.
Identification methods

The traditional identification methods include the identity of objects (such as keys, certificates, ATM card, etc.) and knowledge of identity (such as a user name and password), but as the main means of in vitro matter, once proof of identity and identification knowledge to identify items stolen or forgotten, their identity impersonate or are likely to be substituted by others.

Biometric technology is more secure than the traditional identification methods, privacy and convenience. Biometrics has easy to forget, good security performance, easy forgery or theft, carry "portable" and other advantages available anywhere.

Biometric technology mainly refers to a technology for authentication through human biological characteristics, unique to humans generally can be measured or automatic identification and verification, genetic or other characteristics constant for life, thus biometric authentication technology there is a big advantage compared with traditional authentication techniques.

Biometric systems biometric sampling, extracting its unique features and converted into digital code and code composition further feature template. Since the microprocessor and the declining cost of various electronic components, precision gradually improve, biometric systems increasingly used in authorized commercial control such as access control, time and attendance management system enterprise security certification and other fields. Biometric Biometrics has a hand, fingerprint, face, iris, retina, pulse, ear and other behavioral characteristics a signature sound, key efforts and so on.
Based on these characteristics, people have developed a hand shape recognition, fingerprint recognition, face recognition, pronunciation recognition, iris recognition, signature recognition and other biometric technology.

Chinese biometric industry is the first development of fingerprint identification technology, basic and foreign synchronization, back in the early 1980s began the research, and mastered the core technology, industrial development is relatively mature. The China Research for biometric vein recognition, face recognition, iris recognition is carried out after 1996. In 1996, the current deputy secretary-general Tan Tieniu Chinese Academy of Sciences, National Laboratory of Pattern Recognition, director of the Chinese Academy of Sciences named "Hundred Talents Program", resigned lifelong teaching positions at the University of Reading, UK home, opened a biometric-based identification of other international human the new frontier of research disciplines, China began research in the field of biometric vein, face, iris, etc.

The fuel cell

The fuel cell is main oxygen or other oxidizing agent via a redox reaction, the chemical energy in the fuel cell is converted into electrical energy. The most common fuel is hydrogen a number of hydrocarbons such as natural gas, alcohols, and methane as fuel may also be used. Unlike primary cells of the fuel cell, because of the need of oxygen and fuel When set of sources to ensure the operation of the power supply. The advantage of this battery is that it can provide uninterrupted and stable power, until the fuel runs out.

In 1839, British physicist William Grove produced the first fuel cell. The first fuel cell applications in which NASA space missions in the 1960s to provide electricity for the detectors, satellites and space capsule. Since then, the fuel cell began to be widely used in industrial, housing, transportation and other aspects, as a basic or back-up power supply unit.

Today life in the presence of a variety of fuel cells, but they are basically about the same principle of operation, must contain an anode, a cathode and an electrolyte to make a charge through the battery poles. DC transmitted electrons from the anode cathode, to form a complete circuit. The fuel cell is based on using a variety of different electrolytes and battery size classification, and therefore become more diversified type of battery, also use more extensive. Due to the individual fuel cell count, a single cell can only be a relatively small output voltage, about 0.7V, so fuel cells in series or fractional multiple manufacturing a group, in order to increase the voltage to meet the application requirements.

On the other hand, will produce a fuel cell producing electricity and hot water, based on different fuels, it is possible to produce a very small amount of nitrogen dioxide and other substances, pollution of the environment is less than the original battery, is a green energy source. Energy efficiency of the fuel cell is usually between 40-60%; if the use of waste heat is captured, the energy efficiency of its cogeneration up to 85%.

VLSI highly integrated circuits

VLSI Very Large Scale Integrated Circuit is a combination of a large number of transistors to a single integrated circuit chip, which is larger than the degree of LSI integration. The number of transistors integrated different in different standards. Starting in the 1970s, with the development of complex semiconductor and communication technology, integrated research, development has gradually expanded. The computer control core microprocessor is the most typical examples of ultra large scale integrated circuit, VLSI Design, especially digital integrated circuits, electronic design automation usually the way, has become an important branch of computer engineering one.

IC according to the level of integration can be divided into small-scale integrated circuits, the size of integrated circuits, LSI, VLSI, VLSI and huge integrated circuits.

Small-scale integrated circuit in 1960 appeared on a silicon wafer containing 10-100 1-10 element or logic gates. Such as logic gates and flip-flops and so on. If small-scale digital integrated circuits (SSI) design combinational logic circuit, it is the gate as the basic unit of the circuit, so simplifying logic function of the number of gates should be used at least, and also the number of inputs of the gate at least.

Modulation

Modulation is a cyclical one or more carriers want to transfer the mixed signal technology, commonly used in radio wave propagation and communications, the use of all aspects of data communication telephone lines and the like. Depending on the modulation signal can be divided into several bits modulation and analog modulation, these different modulation, in a different way, the signal and the carrier synthesis technology. The reverse process is called modulation demodulation for the solution of the original signal.

Significance of modulation

Spectrum signals can be move to any position, thus contributing to the transmitted signal, and the spectrum resources are fully utilized. For example, the antenna size is one tenth or larger signal, the signal can be effectively radiated.  For speech signals, corresponding antenna size to be in the tens of kilometers or more, it is virtually impossible to achieve. This requires that the signal spectrum modulation process move to a higher frequency range. If you do not put the signal directly modulated radiation out, then the frequency of the radio signal emitted by each will be the same. Modulation of the substance is to make the same frequency range signals are relying on a different carrier frequency, the receiver can be isolated frequency signal required, will not interfere with each other. This is the basis to achieve multiplexed on the same channel.

Universal Mobile Telecommunications System

Universal Mobile Telecommunications System, called UMTS (Universal Mobile Telecommunications System), UMTS as a complete 3G mobile communication technology standards, UMTS is not limited to define an air interface. In addition to WCDMA air interface technology as the preferred continuous improvement get outside, UMTS also have been introduced in the TD-SCDMA and HSDPA technology.

One kind of third-generation (3G) mobile phone technology. It uses WCDMA as the underlying standard by the 3GPP, and represents the European response to ITUIMT-2000 for 3G Cellular radio systems. UMTS is also sometimes called 3GSM, emphasizing the combination of 3G technology and the GSM standard follow-up criteria. UMTS packet switching system is being evolved by the GPRS system, so the architecture of the system is quite similar.

UMTS supports transfer rates of 1920 kbps (not often seen 2Mbps), but typically the highest rate of 384Kbps in reality only about high-load systems. Even so the data rate has been higher than the GSM error correcting data channel 14.4kbps or more consisting of 14.4 kbps HSCSD channel can really achieve price acceptable mobile WWW access and MMS. UMTS premise implementation is now widely used in GSM mobile telephone system, belonging to 2G technology. There is also a way evolution from 2G GPRS called. (Can be seen as 2.5G) GPRS support better data rate (theoretical maximum 140.8kbps, can actually achieve close 56Kbps), better than the connection-oriented data encapsulation. GPRS has been deployed in many GSM networks.

China Unicom's UMTS network upgrade to HSDPA, sometimes also called 3.5G. It can make a downlink transmission speed of 10Mbps.

UMTS has emphasized the possibility in the market for mobile video conference call to achieve, despite the fact that there are many promising service has not been tested to verify.
Other possible uses for UMTS music downloads and video telephony.

Lathe

Lathe is the main vehicles for rotating the workpiece knife turning machine.
In 1797, the British created the modern mechanical inventor Maudslay lathe turret with a screw drive, and in 1800 the use of change gears, you can change the feed rate and the processing thread pitch. In 1817, another Englishman Roberts uses four wheels and rear wheel mechanism to change the spindle speed.

In order to improve the degree of mechanization and automation, in 1845, the US Fitch invention turret lathe.

Early 20th century by a single motor-driven lathe with a gear transmission.
After World War I, due to the need of arms, vehicles and other machinery industry, a variety of efficient automatic lathes,  and specialized rapid development. In order to improve the productivity of small quantities of the workpiece, the late 1940s, lathes with hydraulic copying device be promoted at the same time, multi-tool lathes have also been developed. In the 1950s, the development of the program control lathe with a punch card, latch plate and thumbwheels like. CNC technology in the 1960s for turning, after 70 years of rapid development.

Component

The main components include: headstock, exchange gear box, feed box, apron, turret, tailstock, light bars, screw, bed, foot of the bed and cooling means.

Headstock: its main task is to rotate the main motor sport came after a series of the transmission mechanism of the spindle to give the pros and cons of two different speeds required for steering, while the separation of part of the power headstock the motion to feed me. Headstock spindle lathes are key parts. Processing quality spindle bearing directly affect the smooth functioning of the workpiece, once the rotation accuracy of the spindle is reduced, the machine will reduce the use value.

Feed me: it is also known as pass me, feed tank containing the feed movement of the transmission mechanism, adjust its transmission mechanism, will achieve the desired feed rate or pitch, through light bars or screw motion is transmitted to the knife frame for cutting.

Screw and light bars: to connect the feed box and apron, and the feed box of sports and power to the apron, make apron obtain longitudinal linear motion. Is devoted to turning the screw threads and a variety of settings, other surface during turning of the workpiece, only light bar without screw. Students who want to combine the contents of the apron distinguish between light bars and screw.

Apron: a lathe feed motion control box, built with the rotary motion of the light bar and screw into linear motion mechanism turret, turret achieve transmission via light bars longitudinal feed motion, infeed movement and fast-moving, driven toolholder for longitudinal linear motion by the screw for threading.

Turret: There are two skateboard (medium, small slide), a common component saddle and tool holder body. And promote the tools used to install tools for vertical, horizontal or diagonal movement. Tailstock: mounted on the rail bed, and longitudinal movement along the rail to adjust its working position. After tailstock mainly used to install the top, in order to support long workpieces can also be mounted drills, reamers, etc. hole machining.

Bed: It is turning a large infrastructure component with high precision rail. For supporting and connecting the various components of a lathe, and ensure that all members at work have an accurate relative position.

Cooling system: cooling device mainly by the cooling water pump in the tank pressurized jet cutting fluid to the cutting area, reduce the cutting temperature, away chips, lubricate the machined surface to improve the surface quality tool life and workpiece.

Electric power

Electricity is electricity powered energy. Invented in the 1870s, the invention and application of power set off a second industrial climax. The history of mankind since the 18th century, one of the world's scientific and technological revolution occurred three times, since technology is changing people's lives. Large-scale power system in the 20th century is one of the most important achievements in the history of human engineering science, electricity production and consumption system consists of power generation, transmission, substation, distribution, electricity and other aspects of the composition. It nature of primary energy by means of mechanical energy into electricity, and then by transmission, transformation and distribution of electric power supply to the consumers.

Today is the era of the Internet, we still have a growing demand for electricity, because we invented computers, home appliances and other products use more power. Admittedly continual emergence of new technologies makes electricity become a necessity.

Information produced are: thermal power (coal and other combustible material), solar power, large-capacity wind power technology, nuclear power, hydrogen power, hydroelectric power and other energy science for the 21st century and create greater glories of civilization. The fuel cell is the chemical hydrogen fuel cells, natural gas, coal gas, methanol, hydrazine fuel energy directly into electrical energy of a class of chemical power. Biomass energy efficient and clean use of biomass energy technologies based on biomass as an energy carrier.

Electric current

Current refers to the flow of electric charge of a group . Called the current size of the current strength, is the unit of time lead to a cross-section through the charge per second by the amount of charge is called a Coulomb 1 amp. Ampere is one of the seven basic units of the international system of units. Ampere meter is designed to measure the current instruments.

Nature has a variety of carrier charge carriers, for example, the conductive body can move electrons, ions within the electrolyte, electrons and ion plasma within the quarks inside hadrons. These mobile carriers to form a current. There are some effects and current relevant, such as heating effect of current, according to Ampere's law, current will produce a magnetic field, motors, inductors and generators and effects associated with this.

I will use the current symbol indicates that the origin of the French intensité de courant (current intensity, current strength). Symbol I first used by French scientist Andre - Marie Ampere use, and therefore the current unit Ampere to name. Later this symbol spread from France to England, beginning becomes standard usage, but in 1896 still represents current journals with C, instead of the now common.

Inductor

Inductors  is a circuit element, because of change in the current generated by the electromotive force, which resist change in the current. This property is called inductance.

inductance element many forms, according to the appearance and function of different, but have different names. In enameled wire multiturn like, often use as an electromagnet in the inductor and transformer used according to the appearance, also known as coil (coil). In order to provide greater resistance to high frequency by a DC or low frequency, depending on the function often referred to choke (choke), also known as choke. Often with a ferromagnetic material, used in the installation of high inductance transformers, motors and generators, also known as the windings (Winding). Wire through the magnetic substance, no coil shape, often acts as a high-frequency filter small inductor acting, according to the appearance often referred to as magnetic beads (Bead).

Inductors term usually used to refer to the self-inductance or effect as the main work of the element. To self-inductance-based non-customarily mostly call it other names do not usually call to the inductor, for example: transformers, motors, etc. in the electromagnetic coil windings.

In Chinese, the word inductor also colloquially referred to as inductance, but the situation To rigorous expressed as physical objects, and still should be called inductors.

Transformer

Transformers  is the use of the principle of electromagnetic induction to change the AC voltage apparatus, the main component is the primary coil, the secondary coil and the core (core). In electrical equipment and radio circuits, commonly used for the lifting voltage, impedance matching, safety isolation. The main features are: voltage conversion, the current conversion, impedance transformation, isolation, voltage regulator (magnetic saturation transformer) and the like. It can be divided according to purpose: distribution transformers, power transformers, sealed transformers, modular transformers, dry-type transformers, oil-immersed transformers, single-phase transformers, electric furnace transformer, rectifier transformers.

With the continued health of China's rapid economic development, electricity demand continues to grow rapidly. In 2011, production in the country amounted to 1.43 billion kVA transformer, an increase of 6.86%. 2011, China's transformer manufacturing industries above designated size (the main business income of 2,000 yuan or more) companies have 1461, it achieved sales of 290.14 billion yuan, total profit of 16.608 billion yuan, the asset size of 263.84 billion yuan, sales profit of 339.72 billion.

Transformers in the electrical equipment and the radio circuit, the transformer used as lifting voltage, impedance matching, safety isolation. In the generator, either the coil moves through the magnetic field or magnetic field moves through the stationary coil, can EMF in the coil, in both cases, the value of the magnetic flux are the same, The most basic form of the transformer, includes two sets of wound coil wire, and another said inductively close together. With the continuous development of transformer industry, more and more enterprises to enter the transformer industry, there are many companies come to the fore, such as Ming Yuan transformer was founded in the early 2000s set up by the joint stock company specializing in dedicated transformers, reactors, filters and other research and development, manufacturers, after nearly a decade of development has now become one of the few advanced technology industry leader and pioneer.

Global System for Mobile Communications

Global System for Mobile Communications (Global System for Mobile Communications), namely GSM, is currently the most widely used mobile phone standard. Worldwide more than 200 countries and regions more than 1 billion people are using GSM phone. Widely used GSM standard makes between mobile phone operators sign international roaming user's "roaming agreement" become commonplace. GSM compared to its previous standard biggest difference is his signaling and speech channels are digital, and thus GSM is considered a second generation (2G) mobile phone system. GSM standard is currently used by 3GPP organization responsible for the development and maintenance.

From the user point of view, the main advantage is that the new GSM choose to provide a higher digital voice quality and low-cost alternative to the call (eg SMS). From the network operator point of view, the advantage is the ability to deploy equipment from different vendors, because GSM as an open standard provides easier interoperability. Moreover, the standard allows network operators to provide roaming services, users can use their mobile phones in the world of.

In the development of the GSM standard (such as packet data capabilities in Release '97 version of the standard was joined by GPRS), maintain backward compatibility with the original GSM phones. Higher speed data transmission with EDGE introduced in Release '99 version of the standard.

Communications satellite

Communication satellites in Earth orbit as a means of artificial earth satellite radio communication relay stations. Communications satellite in geostationary orbit in general use, this track is located 35,786 kilometers above the Earth at the equator. Space communications satellite is part of a satellite communication system.

A geostationary orbit communications satellites can cover about 40 percent of Earth's surface, so that any ground, sea and air communications station coverage area can simultaneously communicate with each other. In three geostationary communications satellites equally spaced above the equator can achieve global communications except the poles in some areas. Communications satellite is the world's first application, one of the most widely used satellites, in many countries the United States, the former Soviet Union, Russia and China have launched a communications satellite. The following describes the knowledge of communication satellites.

Before communications satellites appeared on Earth between two distant places to communicate in two ways; one is to use the cable, and the other is to use ground radio equipment. The late 1950s after Sputnik into space, people soon think, can be used in long-distance communications satellites. In August 1960 the United States launched its first such satellite. The satellite is 30 meters in diameter, called "echo on the 1st."

Electric generator

Generators are other forms of energy into electrical energy machinery and equipment, first produced in the second industrial revolution, made by German engineer Siemens in 1866, which consists of turbine, steam turbine, diesel or other power-driven machinery, the water energy airflow, fuel combustion or nuclear fission into mechanical energy produced by the generator to pass, then converted to electricity by the generator. Generating a wide range of uses in industrial and agricultural production, national defense, science and technology and everyday life.

No-load characteristics:

When the generator is not connected to the load, the armature current is zero, called no-load operation. At this point of the three-phase stator windings only the magnetizing current If the load is induced electromotive force E0 (three phase), its size increases with the increase of If. However, since the motor magnetic circuit core saturated phenomenon, so the two are not proportional. Reflect Load EMF E0 and excitation current If the relationship is called load characteristic curve for synchronous generator.

Armature reaction:

When the generator connected to the symmetrical load, the armature windings of the three-phase current generates a rotating magnetic field to another, said armature reaction magnetic field. Its rotational speed coincides with the speed of the rotor is equal to two synchronous rotation. Armature reaction magnetic field and the magnetic field rotor synchronous generator excitation can be approximated by sinusoidal distribution are considered. The space between them depending on the time phase retardation load emf and the armature current I E0 between. Armature reaction magnetic field also load status. When the generator load is inductive, armature reaction from the field demagnetization effect, will cause the voltage of the generator is reduced; when the load was capacitive, the armature reaction magnetic field plays the role of aid will make the generator output voltage increased.

Load operating characteristics:

Mainly refers to the external characteristics and tuning features. The external characteristics of the rated speed when the excitation current and load power factor is constant, the relationship between the generator terminal voltage and load current I U between. Adjustment feature is the speed and terminal voltage rating, the load power factor is constant, the relationship between the excitation current If the load current I.
"China's power generators and power generator unit manufacturing industry sales forecast demand and investment analysis report Prospects" The data show the rate of change in voltage synchronous generator is about 20 to 40 percent. General industrial and household loads are required voltage remains substantially unchanged. To this end, as the load current increases, magnetizing current must be adjusted accordingly. Although the trends and external characteristics adjustment feature on the contrary, for purely resistive and inductive loads, it is rising, while the capacitive load, generally declining.

Circuit breaker

Circuit breakers is the ability to closing, carrying and breaking current under normal circuit conditions and can closing, carrying and breaking current under abnormal circuit conditions within the prescribed time switch means. Divided according to their use of circuit breakers and low voltage circuit breakers high voltage circuit breakers, high and low Delimitation vague, generally referred to as high-voltage electrical 3kV above.

Breaker can be used to distribute electricity, no frequent start asynchronous motor, the implementation of the protection of power lines and motors, etc., when they are severe overload or short circuit, and undervoltage fault can automatically cut off the circuit, its function is equivalent fuse switch and through a combination of relays, etc. due to heat. And after breaking the fault current is generally no need to change components. At present, it has been widely used.
Electricity generation, transport, use, and distribution is an extremely important part. Distribution system including transformers and a variety of high and low voltage electrical equipment, low-voltage circuit breaker is widely used as a surface using large appliances.
Breakers are generally composed of a contact system, arc system, operating mechanism, trip, housing and so on.

When a short circuit, the magnetic field high-current (typically 10-12 times) to produce a reaction force overcomes spring release mechanism is operated pulling operation, switch the instantaneous trip. When the overload current becomes large, the heat intensifies, bimetal deformed to a certain extent promote institutional action (the larger the current, the shorter the operation time).
Electronic type, the use of transformers each phase current collection size, compared with the set value, the microprocessor when the current abnormal signals, the electronic trip unit driven operating mechanism action.