Yahoo奇摩 網頁搜尋

  1. MediaTek - Wikipedia

    en.wikipedia.org/wiki/MediaTek

    MediaTek Inc. (Chinese: 聯發科技股份有限公司; pinyin: Liánfā Kējì Gǔfèn Yǒuxiàn Gōngsī) is a Taiwanese fabless semiconductor company that provides chips for wireless communications, high-definition television, handheld mobile devices like ...

    • May 28, 1997; 24 years ago
    • Hsinchu, Taiwan
    • 17,554 (2019)
    • NT$322.15 billion (2020)
  2. Cisco Systems - Wikipedia

    en.wikipedia.org/wiki/Cisco_Systems

    Cisco Systems, Inc. is an American multinational technology conglomerate headquartered in San Jose, California, in the center of Silicon Valley.Cisco develops, manufactures and sells networking hardware, software, telecommunications equipment ...

  3. Internet of things - Wikipedia

    en.wikipedia.org/wiki/Internet_of_Things

    The Internet of things ( IoT) describes the network of physical objects—a.k.a. "things"—that are embedded with sensors, software, and other technologies for the purpose of connecting and exchanging data with other devices and systems ...

  4. Set-top box - Wikipedia

    en.wikipedia.org/wiki/Set-top_box
    • TV Signal Sources
    • Features
    • Ambiguities in The Definition
    • Energy Use
    • See Also

    The signal source might be an Ethernet cable, a satellite dish, a coaxial cable (see cable television), a telephone line (including DSL connections), broadband over power lines (BPL), or even an ordinary VHF or UHF antenna. Content, in this context, could mean any or all of video, audio, Internet web pages, interactive video games, or other possibilities. Satellite and microwave-based services also require specific external receiver hardware, so the use of set-top boxes of various formats has never completely disappeared. Set-top boxes can also enhance source signal quality.

    Software alternatives

    As complexity and potential programming faults of the set-top box increase, software such as MythTV, Select-TV and Microsoft's Media Center have developed features comparable to those of set-top boxes, ranging from basic DVR-like functionality to DVD copying, home automation, and housewide music or video playback.

    Firmware update features

    Almost all modern set-top boxes feature automatic firmware updateprocesses. The firmware update is typically provided by the service provider.

    With the advent of flat-panel televisions, set-top boxes are now deeper in profile than the tops of most modern TV sets. Because of this, set-top boxes are often placed beneath televisions, and the term set-top box has become something of a misnomer, possibly helping the adoption of the term digibox. Additionally, newer set-top boxes that sit at the edge of IP-based distribution networks are often called net-top boxes or NTBs, to differentiate between IP and RF inputs. The Roku LT is around the size of a pack of cards and delivers Smart TV to conventional sets. The distinction between external tuner or demodulator boxes (traditionally considered to be "set-top boxes") and storage devices (such as VCR, DVD, or disc-based PVR units) is also blurred by the increasing deployment of satellite and cable tuner boxes with hard disk, network or USBinterfaces built-in. Devices with the capabilities of computer terminals, such as the WebTV thin client, also fall into the grey area that could i...

    In June 2011 a report from the American National Resources Defense Council brought attention to the energy efficiency of set-top boxes, and the US Department of Energy announced plans to consider the adoption of energy efficiency standards for set-top boxes. In November 2011, the National Cable & Telecommunications Association announced a new energy efficiency initiative that commits the largest American cable operators to the purchase of set-top boxes that meet Energy Star standards and the development of sleep modesthat will use less energy when the set-top box is not being used to watch or record video.

  5. Application-specific integrated circuit - Wikipedia

    en.wikipedia.org/wiki/Application-specific_integrated_circuit
    • History
    • Standard-Cell Designs
    • Gate-Array and Semi-Custom Design
    • Full-Custom Design
    • Structured Design
    • Cell Libraries, Ip-Based Design, Hard and Soft Macros
    • Multi-Project Wafers
    • Application-Specific Standard Product
    • Sources

    Early ASICs used gate array technology. By 1967, Ferranti and Interdesign were manufacturing early bipolar gate arrays. In 1967, Fairchild Semiconductor introduced the Micromatrix family of bipolar diode–transistor logic (DTL) and transistor–transistor logic(TTL) arrays. Complementary metal-oxide-semiconductor (CMOS) technology opened the door to the broad commercialization of gate arrays. The first CMOS gate arrays were developed by Robert Lipp,in 1974 for International Microcircuits, Inc. (IMI). Metal-oxide-semiconductor (MOS) standard cell technology was introduced by Fairchild and Motorola, under the trade names Micromosaic and Polycell, in the 1970s. This technology was later successfully commercialized by VLSI Technology (founded 1979) and LSI Logic(1981). A successful commercial application of gate array circuitry was found in the low-end 8-bit ZX81 and ZX Spectrum personal computers, introduced in 1981 and 1982. These were used by Sinclair Research (UK) essentially as a low-...

    In the mid-1980s, a designer would choose an ASIC manufacturer and implement their design using the design tools available from the manufacturer. While third-party design tools were available, there was not an effective link from the third-party design tools to the layout and actual semiconductor process performance characteristics of the various ASIC manufacturers. Most designers used factory-specific tools to complete the implementation of their designs. A solution to this problem, which also yielded a much higher density device, was the implementation of standard cells. Every ASIC manufacturer could create functional blocks with known electrical characteristics, such as propagation delay, capacitance and inductance, that could also be represented in third-party tools. Standard-cell design is the utilization of these functional blocks to achieve very high gate density and good electrical performance. Standard-cell design is intermediate between § Gate-array and semi-custom design...

    Gate array design is a manufacturing method in which diffused layers, each consisting of transistors and other active devices, are predefined and electronics wafers containing such devices are "held in stock" or unconnected prior to the metallization stage of the fabrication process. The physical design process defines the interconnections of these layers for the final device. For most ASIC manufacturers, this consists of between two and nine metal layers with each layer running perpendicular to the one below it. Non-recurring engineering costs are much lower than full custom designs, as photolithographic masks are required only for the metal layers. Production cycles are much shorter, as metallization is a comparatively quick process; thereby accelerating time to market. Gate-array ASICs are always a compromise between rapid design and performance as mapping a given design onto what a manufacturer held as a stock wafer never gives 100% circuit utilization. Often difficulties in rou...

    By contrast, full-custom ASIC design defines all the photolithographic layers of the device.Full-custom design is used for both ASIC design and for standard product design. The benefits of full-custom design include reduced area (and therefore recurring component cost), performance improvements, and also the ability to integrate analog components and other pre-designed—and thus fully verified—components, such as microprocessor cores, that form a system on a chip. The disadvantages of full-custom design can include increased manufacturing and design time, increased non-recurring engineering costs, more complexity in the computer-aided design (CAD) and electronic design automationsystems, and a much higher skill requirement on the part of the design team. For digital-only designs, however, "standard-cell" cell libraries, together with modern CAD systems, can offer considerable performance/cost benefits with low risk. Automated layout tools are quick and easy to use and also offer the...

    Structured ASIC design (also referred to as "platform ASIC design") is a relatively new trend in the semiconductor industry, resulting in some variation in its definition. However, the basic premise of a structured ASIC is that both manufacturing cycle time and design cycle time are reduced compared to cell-based ASIC, by virtue of there being pre-defined metal layers (thus reducing manufacturing time) and pre-characterization of what is on the silicon (thus reducing design cycle time). Definition from Foundations of Embedded Systems states that: This is effectively the same definition as a gate array. What distinguishes a structured ASIC from a gate array is that in a gate array, the predefined metal layers serve to make manufacturing turnaround faster. In a structured ASIC, the use of predefined metallization is primarily to reduce cost of the mask sets as well as making the design cycle time significantly shorter. For example, in a cell-based or gate-array design the user must of...

    Cell libraries of logical primitives are usually provided by the device manufacturer as part of the service. Although they will incur no additional cost, their release will be covered by the terms of a non-disclosure agreement(NDA) and they will be regarded as intellectual property by the manufacturer. Usually, their physical design will be pre-defined so they could be termed "hard macros". What most engineers understand as "intellectual property" are IP cores, designs purchased from a third-party as sub-components of a larger ASIC. They may be provided in the form of a hardware description language (often termed a "soft macro"), or as a fully routed design that could be printed directly onto an ASIC's mask (often termed a "hard macro"). Many organizations now sell such pre-designed cores – CPUs, Ethernet, USB or telephone interfaces – and larger organizations may have an entire department or division to produce cores for the rest of the organization. The company ARM (Advanced RISC...

    Some manufacturers and IC design houses offer multi-project wafer service(MPW) as a method of obtaining low cost prototypes. Often called shuttles, these MPWs, containing several designs, run at regular, scheduled intervals on a "cut and go" basis, usually with limited liability on the part of the manufacturer. The contract involves delivery of bare dies or the assembly and packaging of a handful of devices. The service usually involves the supply of a physical design database (i.e. masking information or pattern generation (PG) tape). The manufacturer is often referred to as a "silicon foundry" due to the low involvement it has in the process.

    An application-specific standard product or ASSP is an integrated circuit that implements a specific function that appeals to a wide market. As opposed to ASICs that combine a collection of functions and are designed by or for one customer, ASSPs are available as off-the-shelf components. ASSPs are used in all industries, from automotive to communications.[citation needed] As a general rule, if you can find a design in a data book, then it is probably not an ASIC, but there are some exceptions.[clarification needed] For example, two ICs that might or might not be considered ASICs are a controller chip for a PC and a chip for a modem. Both of these examples are specific to an application (which is typical of an ASIC) but are sold to many different system vendors (which is typical of standard parts). ASICs such as these are sometimes called application-specific standard products (ASSPs). Examples of ASSPs are encoding/decoding chip, standalone USB interface chip, etc. IEEE used to pub...

    Barr, Keith (2007). ASIC Design in the Silicon Sandbox: A Complete Guide to Building Mixed-Signal Integrated Circuits. McGraw Hill Professional. ISBN 978-0-07-148161-8.
    Anthony Cataldo (26 March 2002). "Xilinx looks to ease path to custom FPGAs". EE Times. CMP Media, LLC.
    Golshan, K. (2007). Physical design essentials: an ASIC design implementation perspective. New York: Springer. ISBN 978-0-387-36642-5.
  6. RP-3 - Wikipedia

    en.wikipedia.org/wiki/RP-3
    • History
    • Design
    • Service History
    • Variants
    • Aircraft Using The RP-3 in The Second World War
    • Post Second World War
    • See Also

    The first use of rockets fired from aircraft was during World War I. The "unrotated projectiles" (UPs) were Le Prieur rockets which were mounted on the interplane struts of Nieuport fighters. These were used to attack observation balloons and were reasonably successful. Sopwith Baby and Pup and Home Defence B.E.2 fighters also carried rockets.[page needed]With the war ended the Royal Air Force, intent on retrenching, forgot about firing rockets from aircraft. The British Army, however, did see a use for rockets against low-flying aircraft; from late 1940 parts of Britain were defended by increasing numbers of "Z-Batteries" 2-inch (51 mm) rockets supplementing the conventional anti-aircraft guns.[page needed] When German forces under the command of Rommel intervened in the Western Desert from early 1941, it became clear that the Desert Air Force lacked weapons capable of damaging or destroying the large numbers of armoured fighting vehicles, particularly the heavier Panzer III and Pa...

    The rocket body was a steel tube 3 inches (76 mm) in diameter filled with 11 lb (5.0 kg) of cordite propellant, fired electrically. The warhead was screwed into the forward end, and was initially a solid 25-pound (11 kg), 3.44-inch (87 mm) diameter armour-piercing warhead which was quickly supplemented by a 6-inch-diameter (150 mm), 60-pound (27 kg) high explosivehead. Another type of head was a 25-pound (11 kg) mild steel (later concrete) practice head. Once the rocket had been mounted on the rails, an electrical lead (or "pigtail") connected the rocket to the firing controls. Four large tailfins induced enough spin to stabilize the rocket, but as it was unguided, aiming was a matter of judgment and experience. Approach to the target needed to be precise, with no sideslip or yaw, which could throw the RP off line. Aircraft speed had to be precise at the moment of launch, and the angle of attack required precision. Trajectory drop was also a problem, especially at longer ranges.[not...

    Air-to-ground use

    Before the new weapon was released for service extensive tests were carried out by the Instrument, Armament and Defence Flight (IADF) at Royal Aircraft Establishment, Farnborough. Hawker Hurricanes were fitted with rockets and rails and flown during June and July 1942. Further tests were undertaken from 28 September to 30 November to develop rocket firing tactics. Other aircraft used were a Lockheed Hudson, a Fairey Swordfish biplane torpedo bomber, a Douglas Boston II medium bomber and a Sea...

    Anti-submarine

    Soon after some encouraging results from the initial deployment, trials of the weapon were conducted against targets representing U-boats. It was discovered that if the rockets were fired at a shallow angle, near misses resulted in the rockets curving upwards in seawater and piercing the targets below the waterline. Soon Coastal Command and the Royal Navy's Fleet Air Armaircraft were using the rockets extensively. The first U-boat destroyed with the assistance of a rocket attack was U-752 (co...

    Ground-to-ground use

    In 1945, some British M4 Sherman tanks were fitted with two or four rails – one or two either side of the turret – to carry 60-pound headed rockets. These were used at the Rhine Crossing by tanks of the 1st Coldstream Guards. The tanks were called "Sherman Tulips". The tanks fitted included both conventional Shermans and the more heavily armed Sherman Fireflies. The modifications were first tried out by two officers of the 1st Armoured Battalion, Coldstream Guards, 5th Guards Armoured Brigade...

    Warheads

    Shell, 18 lb, HE 1. 8 kg (17.6 lb) "high-explosive" warhead.[citation needed] Shot, 25 lb, AP, No. 1, Mk. I 1. Armour-piercing (anti-submarine) warhead made out of hardened steel. Shot, 25 lb, AP, No. 2, Mk. I 1. Improved design over the Shot, 25 lb, AP, No. 2, Mk. I warhead made longer and pointier to increase penetration. Shot, 25 lb, SAP, Mk. I 1. Semi-armour-piercing" warhead; same design as the "Shot, 25 lb, AP, No. 2, Mk. I" but made out of mild steel and having the spigot fuzed togethe...

    Rocket engines

    The RP-3 rocket engine was updated a number of times during its lifespan, which gave rise to a number of variants. For example, it was necessary to modify the rocket engine's propellant charge in order to be able to use several types of warheads. Initially the rocket engine was only designed to use warheads up to 25 lb (11 kg), but when warheads up to 60 lb (27 kg) were introduced the propellant charge had to be modified in order to use them. Variants capable of carrying warheads up to 60 lb...

    These are aircraft that used the RP-3 operationally, a number of aircraft types were fitted with RP-3s on an experimental basis.

    The 3-inch RP continued to be used on RAF and RN aircraft in the ground attack role until replaced by the SNEB podded rocket (RAF) and the 2-inch podded RP (RN).[citation needed] 1. Aircraft types included: 2. Royal Navy: Hawker Sea Fury and Sea Hawk; Supermarine Attacker; Scimitar and De Havilland Sea Vixen(24 rockets total on 4 pylons, six per pylon); 3. RAF: Bristol Brigand, de Havilland Hornet, de Havilland Vampire and de Havilland Venom, Gloster Meteor, and the Hawker Hunter. 4. Operational use included the Malayan emergency, the Korean War, the Suez crisis, and the Radfan campaign.[citation needed]

  7. Communications system - Wikipedia

    en.wikipedia.org/wiki/Communications_system

    This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Communications system" – news · ...

  8. CORDIC - Wikipedia

    en.wikipedia.org/wiki/CORDIC
    • History
    • Applications
    • Modes of Operation
    • Implementation
    • Double Iterations CORDIC
    • Related Algorithms
    • See Also
    • Further Reading
    • External Links

    Similar mathematical techniques were published by Henry Briggs as early as 1624 and Robert Flower in 1771,but CORDIC is better optimized for low-complexity finite-state CPUs. CORDIC was conceived in 1956 by Jack E. Volder at the aeroelectronics department of Convair out of necessity to replace the analog resolver in the B-58 bomber's navigation computer with a more accurate and performant real-time digital solution. Therefore, CORDIC is sometimes referred to as a digital resolver. In his research Volder was inspired by a formula in the 1946 edition of the CRC Handbook of Chemistry and Physics: 1. K n R sin ⁡ ( θ ± φ ) = R sin ⁡ ( θ ) ± 2 − n R cos ⁡ ( θ ) , K n R cos ⁡ ( θ ± φ ) = R cos ⁡ ( θ ) ∓ 2 − n R sin ⁡ ( θ ) , {\\displaystyle {\\begin{aligned}K_{n}R\\sin(\\theta \\pm \\varphi )&=R\\sin(\\theta )\\pm 2^{-n}R\\cos(\\theta ),\\\\K_{n}R\\cos(\\theta \\pm \\varphi )&=R\\cos(\\theta )\\mp 2^{-n}R\\sin(\\theta ),\\\\\\end{aligned}}} with K n = 1 + 2 − 2 n {\\displaystyle K_{n}={\\sqrt {1+2^{-2n}}}} , tan ⁡ (...

    CORDIC uses simple shift-add operations for several computing tasks such as the calculation of trigonometric, hyperbolic and logarithmic functions, real and complex multiplications, division, square-root calculation, solution of linear systems, eigenvalue estimation, singular value decomposition, QR factorization and many others. As a consequence, CORDIC has been used for applications in diverse areas such as signal and image processing, communication systems, robotics and 3D graphicsapart from general scientific and technical computation.

    Rotation mode

    CORDIC can be used to calculate a number of different functions. This explanation shows how to use CORDIC in rotation mode to calculate the sine and cosine of an angle, assuming that the desired angle is given in radians and represented in a fixed-point format. To determine the sine or cosine for an angle β {\\displaystyle \\beta } , the y or x coordinate of a point on the unit circle corresponding to the desired angle must be found. Using CORDIC, one would start with the vector v 0 {\\displayst...

    Vectoring mode

    The rotation-mode algorithm described above can rotate any vector (not only a unit vector aligned along the x axis) by an angle between −90° and +90°. Decisions on the direction of the rotation depend on β i {\\displaystyle \\beta _{i}} being positive or negative. The vectoring-mode of operation requires a slight modification of the algorithm. It starts with a vector the x coordinate of which is positive and the y coordinate is arbitrary. Successive rotations have the goal of rotating the vecto...

    Software example

    The following is a MATLAB/GNU Octave implementation of CORDIC that does not rely on any transcendental functions except in the precomputation of tables. If the number of iterations n is predetermined, then the second table can be replaced by a single constant. With MATLAB's standard double-precision arithmetic and "format long" printout, the results increase in accuracy for nup to about 48. The two-by-two matrix multiplicationcan be carried out by a pair of simple shifts and adds. In Java the...

    Hardware example

    The number of logic gates for the implementation of a CORDIC is roughly comparable to the number required for a multiplier as both require combinations of shifts and additions. The choice for a multiplier-based or CORDIC-based implementation will depend on the context. The multiplication of two complex numbers represented by their real and imaginary components (rectangular coordinates), for example, requires 4 multiplications, but could be realized by a single CORDIC operating on complex numb...

    In the publications: http://baykov.de/CORDIC1972.htm and http://baykov.de/CORDIC1975.htm it was proposed to use the double iterations method for the implementation of the functions: arcsinX, arccosX, lnX, expX, as well as for calculation of the hyperbolic functions. Double iterations method consists in the fact that unlike the classical CORDIC method, where the iteration step value changes EVERY time, i.e. on each iteration, in the double iteration method, the iteration step value is repeated twice and changes only through one iteration. Hence the designation for the degree indicator for double iterations appeared: i = 1,1,2,2,3,3... Whereas with ordinary iterations: i= 1,2,3... The double iteration method guarantees the convergence of the method throughout the valid range of argument changes. The generalization of the CORDIC convergence problems for the arbitrary positional number system http://baykov.de/CORDIC1985.htmwith Radix R were showed that for the functions sin, cos, arctg,...

    CORDIC is part of the class of "shift-and-add" algorithms, as are the logarithm and exponential algorithms derived from Henry Briggs' work. Another shift-and-add algorithm which can be used for computing many elementary functions is the BKM algorithm, which is a generalization of the logarithm and exponential algorithms to the complex plane. For instance, BKM can be used to compute the sine and cosine of a real angle x {\\displaystyle x} (in radians) by computing the exponential of 0 + i x {\\displaystyle 0+ix} , which is cis ⁡ ( x ) = cos ⁡ ( x ) + i sin ⁡ ( x ) {\\displaystyle \\operatorname {cis} (x)=\\cos(x)+i\\sin(x)} . The BKM algorithm is slightly more complex than CORDIC, but has the advantage that it does not need a scaling factor (K).

    Parini, Joseph A. (1966-09-05). "DIVIC Gives Answer to Complex Navigation Questions". Electronics: 105–111. ISSN 0013-5070. (NB. DIVIC stands for DIgital Variable Increments Computer. Some sources...
    Anderson, Stanley F.; Earle, John G.; Goldschmidt, Robert Elliott; Powers, Don M. (1965-11-01). "The IBM System/360 Model 91: Floating-Point Execution Unit" (PDF). IBM Journal of Research and Devel...
    Liccardo, Michael A. (September 1968). An Interconnect Processor with Emphasis on CORDIC Mode Operation (MSc thesis). Berkeley, CA, USA: University of California, Berkeley, Department of Electrical...
    US patent 3576983A, Cochran, David S., "Digital calculator system for computing square roots", published 1971-05-04, issued 1971-05-04, assigned to Hewlett-Packard Co. ()
  9. SWOT analysis - Wikipedia

    en.wikipedia.org/wiki/SWOT_analysis
    • Overview
    • Use
    • in Community Organizations
    • Limitations and Alternatives
    • SWOT Analysis in Popular Culture
    • Bibliography

    SWOT assumes that strengths and weaknesses are frequently internal, while opportunities and threats are more commonly external.The name is an acronym for the four parameters the technique examines: 1. Strengths: characteristics of the business or project that give it an advantage over others. 2. Weaknesses: characteristics that place the business or project at a disadvantage relative to others. 3. Opportunities: elements in the environment that the business or project could exploit to its advantage. 4. Threats: elements in the environment that could cause trouble for the business or project. The degree to which the internal environment of the firm matches with the external environment is expressed by the concept of strategic fit. Identification of SWOTs is important because they can inform later steps in planning to achieve the objective. First, decision-makers should consider whether the objective is attainable, given the SWOTs. If the objective is notattainable, they must select a...

    SWOT analysis can be used in any decision-making situation when a desired end-state (objective) is defined, not just profit-seeking organizations. Examples include non-profit organizations, governmental units, and individuals. SWOT analysis may also be used in pre-crisis planning and preventive crisis management. SWOT analysis may also be used in creating a recommendation during a viability study/survey.

    The SWOT analysis has been used in community work as a tool to identify positive and negative factors within organizations, communities, and the broader society that promote or inhibit successful implementation of social services and social change efforts.It is used as a preliminary resource, assessing strengths, weaknesses, opportunities, and threats in a community served by a nonprofit or community organization. Although SWOT analysis is a part of the planning, it will not provide a strategic plan if used by itself, but a SWOT list can becomes a series of recommendations. Strengths and weaknesses (internal factors within an organization): 1. Human resources—staff, volunteers, board members, target population 2. Physical resources—your location, building, equipment 3. Financial—grants, funding agencies, other sources of income 4. Activities and processes—programs you run, systems you employ 5. Past experiences—building blocks for learning and success, your reputation in the communi...

    SWOT is intended as a starting point for discussion and cannot, in itself, show managers how to achieve a competitive advantage,particularly in a rapidly changing environment. Menon et al. (1999) and Hill and Westbrook (1997) suggested "no-one subsequently used the outputs within the later stages of the strategy". Others have critiqued hastily designed SWOT lists. Preoccupation with a single strength, such as cost control, they can neglect their weaknesses, such as product quality.Domineering by one or two community workers devalues the possible contributions of community members. Michael Porter developed the five forces framework as a reaction to SWOT, which he found lacking in rigor and ad hoc. Other names include WOTS-UP (Gray and Smeltzer, 1989) and TOWS(reversing the emphasis, with external first).

    Ads: Coca-Cola has used SWOT analysisin targeting television ads
    Television shows: In the Silicon Valley episode "Homicide" (Season 2, Episode 6), Jared Dunn (Zach Woods) introduces the Pied Piper team to SWOT analysis. Later in that episode Dinesh (Kumail Nanji...

    Dag Øivind Madsen, "SWOT Analysis: A Management Fashion Perspective", International Journal of Business Research 16:1:39–56 (2016) full text