Chapter 9, Exercises 5, page 199 Doãn Hà Tiên

jet engine, any of a class of internal-combustion engines that propel aircraft by means of the rearward discharge of a jet of fluid, usually hot exhaust gases generated by burning fuel with air drawn in from the atmosphere.

The prime mover of virtually all jet engines is a gas turbine. Variously called the core, gas producer, gasified, or gas generator, the gas turbine converts the energy derived from the combustion of a liquid hydrocarbon fuel to mechanical in the form of a high-pressure, high-temperature airstream. This energy is then harnessed by what is termed the propulsion (e.g., airplane propeller and helicopter rotor) to generate a thrust with which to propel the aircraft.

Basic engine types

Achieving a high propulsive efficiency for a jet engine is dependent on designing it so that the exiting jet velocity is not greatly in excess of the flight speed. At the same time, the amount of thrust generated is proportional to that very same velocity excess that must be minimized. This set of restrictive requirements has led to the evolution of a large number of specialized variations of the basic turbojet engine, each tailored to achieve a balance of good fuel efficiency, low weight, and compact size for duty in some band of the flight speed–altitude–mission spectrum. There are two features characteristic of all the different engine types, however. First, in order to achieve a high propulsive efficiency, the jet velocity, or the velocity of the gas stream exiting the propulsor, is matched to the flight speed of the aircraft—slow aircraft have engines with low jet velocities and fast aircraft have engines with high jet velocities. Second, as a result of designing the jet velocity to match the flight speed, the size of the propulsor varies inversely with the flight speed of the aircraft—slow aircraft have very large propulsors, as, for example, the helicopter rotor—and the relative size of the propulsor decreases with increasing design flight speed—turboprop propellers are relatively small and turbofan fans even smaller.

 + Turboshaft engines

The helicopter is designed to operate for substantial periods of time hovering at zero flight speed. Even in forward flight, helicopters rarely exceed 240 kilometers per hour or a Mach number of 0.22. (The Mach number is the ratio of the velocity of the aircraft to the speed of sound.) The principal propulsor is the helicopter rotor, which is driven by one or more turboshaft engines

                                   

in all modern helicopters of large size. As was previously noted, the propulsor is designed to give a very low discharge or jet velocity and is by the same token very large for a given size aircraft when compared to the propulsors of higher-speed aircraft. The prime mover of a helicopter is a core engine whose gas horsepower is extracted by a power turbine, which then drives the helicopter rotor via a speed-reducing (and combining) gearbox. The power turbine is usually located on a spool separate from the gas generator; thus its rotative speed and that of the helicopter rotor which it drives are independent of the rotative speed of the gas generator. This allows the rotor speed to be varied or kept constant independently of the gas-generator speed, which must be varied to modulate the amount of power generated.

 + Turboprops, propfans, and unducted fan engines

The turboprop is the power plant that occupies the next band of flight speeds in the flight spectrum, from a Mach number of 0.2 to 0.7. The propulsor is propeller with a somewhat higher discharge, or jet velocity, than that of the helicopter rotor to match the flight speed, and it has a proportionately smaller area than the latter for a similarly sized aircraft. The prime mover is a turbo shaft engine. It’s very similar to the one that drives a helicopter rotor except for a different gearbox 

              

designed to provide a somewhat higher rotative speed for the propeller, which turns faster than the helicopter rotor having a much larger diameter. The control mode of the turboprop also is somewhat different from that of a helicopter’s turboshaft engine. In a helicopter the pilot calls for power by manipulating the pitch of the rotor blades (a greater pitch taking a bigger “bite” of air and so demanding more power to maintain rotative speed). The engine’s control responds by increasing fuel to the engine to maintain output shaft speed. In a turboprop the pilot calls for power by selecting fuel flow to the prime mover. The propeller control responds by varying propeller pitch to attain a greater “pull” while maintaining a preselected propeller rotative speed.

 + Medium-bypass turbofans, high-bypass turbofans, and ultrahigh-bypass engines

Moving up in the spectrum of flight speeds to the transonic regime—Mach numbers from 0.75 to 0.9—the most common engine configurations are turbofan engines, such as those shown in

  

                                       .

In a turbofan, only a part of the gas horsepower generated by the core is extracted to drive a propulsor, which usually consists of a single low-pressure-ratio, shrouded turbocompression stage. The fan is generally placed in front of the core inlet so that the air entering the core first passes through the fan and is partially compressed by it. Most of the air, however, bypasses the core (hence the designation bypass stream) and goes directly to an exhaust nozzle. The core stream, with some modest fraction of the gas horsepower remaining (not extracted to drive the fan) proceeds directly to its own exhaust nozzle.

Exercise 6 , chapter 9 , page 199 (Ho Hai Nam , 09ece)

How a Nuclear Power Plant Works

Nuclear power plants run on uranium fuel. In the reactor, uranium atoms are split through a process known as fission. When atoms are spilt, they produce a large amount of energy that is then converted to heat. The heat boils water, creating steam that is used to turn turbines, which spins the shaft of a generator. Inside the generator, coils of wire spin in a magnetic field and electricity is produced. Nuclear power plants in the United States use two types of reactors to achieve this process: boiling water reactors and pressurized water reactors.

The Pressurized Water Reactor (PWR)

Pressurized Water Reactors (PWR) keep water under pressure, so the water heats but does not boil. The heated pressurized water is run through pipes, which heat a separate water line to create steam. The water to generate steam is never mixed with the pressurized water used to heat it.

Boiling Water Reactor (BWR)

 Boiling Water Reactors (BWR) heat water by generating heat from fission in the reactor vessel to boil water and create steam, which turns the generator. In both types of plants, the steam is turned back into water and can be used again in the process. Animation courtesy of the Nuclear Regulatory Commission (NRC) “Students’ Corner”

 Fukushima power plant after tsunami

The water in the reactor also serves as a coolant for the radioactive material, preventing it from overheating and melting down. In March 2011, viewers around the world became well acquainted with this reality as Japanese citizens fled by the tens of thousands from the area surrounding the Fukushima-Daiichi nuclear facility after the most powerful earthquake on record and the ensuing tsunami inflicted serious damage on the plant and several of its reactor units. Among other events, water drained from the reactor core, which in turn made it impossible to control core temperatures. This resulted in overheating and a partial nuclear meltdown.

As of March 1, 2011, there were 443 operating nuclear power reactors spread across the planet in 47 different countries [source: WNA]. In 2009 alone, atomic energy accounted for 14 percent of the world's electrical production. Break that down to the individual country and the percentage skyrockets as high as 76.2 percent for Lithuania and 75.2 for France [source: NEI]. In the United States, 104 nuclear power plants supply 20 percent of the electricity overall, with some states benefiting more than others.

Chapter 9, Exercises 6, page 199 Doãn Hà Tiên

The nuclear power plant stands on the border between humanity's greatest hopes and its deepest fears for the future.

On one hand, atomic energy offers a clean alternative that frees us from the shackles of fossil fuel dependence. On the other, it summons images of disaster: quake-ruptured Japanese belching radioactive steam, the dead zone surrounding Chernobyl's concrete sarcophagus.

But what happens inside a nuclear power plant to bring such marvel and misery into being? Imagine following a volt of electricity back through the wall socket, all the way through miles of power lines to the nuclear reactor that generated it. You'd encounter the generator that produces the spark and the turbine that turns it. Next, you'd find the jet of steam that turns the turbine and finally the radioactive uranium bundle that heats water into steam. Welcome to the nuclear reactor core

The water in the reactor also serves as a coolant for the radioactive material, preventing it from overheating and melting down. In March 2011, viewers around the world became well acquainted with this reality as Japanese citizens fled by the tens of thousands from the area surrounding the Fukushima-Daiichi nuclear facility after the most powerful earthquake on record and the ensuing tsunami inflicted serious damage on the plant and several of its reactor units. Among other events, water drained from the reactor core, which in turn made it impossible to control core temperatures. This resulted in overheating and a partial nuclear meltdown.

In the general: Nuclear power plants works : 

·         First, uranium fuel is loaded up into the reactor—a giant concrete dome that's reinforced in case it explodes. In the heart of the reactor (the core), atoms split apart and release heat energy, producing neutrons and splitting other atoms in a chain reaction.

·         Control rods made of materials such as cadmium and boron can be raised or lowered into the reactor to soak up neutrons and slow down or speed up the chain reaction.

·         Water is pumped through the reactor to collect the heat energy that the chain reaction produces. It constantly flows around a closed loop linking the reactor with a heat exchanger.

·         Inside the heat exchanger, the water from the reactor gives up its energy to cooler water flowing in another closed loop, turning it into steam. Using two unconnected loops of water and the heat exchanger helps to keep water contaminated with radioactivity safely contained in one place and well away from most of the equipment in the plant.

·         The steam from the heat exchanger is piped to a turbine. As the steam blows past the turbine's vanes, they spin around at high speed.

·         The spinning turbine is connected to an electricity generator and makes that spin too.

·         The generator produces electricity that flows out to the power grid—and to our homes, shops, offices, and factories.

Chapter 9, Exercises 4, page 199 Doãn Hà Tiên

Robotics extended defintion:

Roboticists develop man-made mechanical devices that can move by themselves, whose motion must be modelled, planned, sensed, actuated and controlled, and whose motion behaviour can be influenced by “programming”. Robots are called “intelligent” if they succeed in moving in safe interaction with an unstructured environment, while autonomously achieving their specified tasks.

This definition implies that a device can only be called a “robot” if it contains a movable mechanism, influenced by sensing, planning, and actuation and control components. It does not imply that a minimum number of these components must be implemented in software, or be changeable by the “consumer” who uses the device; for example, the motion behavior can have been hard-wired into the device by the manufacturer.

So, the presented definition covers not just “pure” robotics or only “intelligent” robots, but rather the somewhat broader domain of robotics and automation. This includes “dumb” robots such as: metal and woodworking machines, “intelligent” washing machines, dish washers and pool cleaning robots, etc. These examples all have sensing, planning and control, but often not in individually separated components. For example, the sensing and planning behavior of the pool cleaning robot have been integrated into the mechanical design of the device, by the intelligence of the human developer.

Robotics is, to a very large extent, all about system integration, achieving a task by an actuated mechanical device, via an “intelligent” integration of components, many of which it shares with other domains, such as systems and control, computer science, character animation, machine design, computer vision, artificial intelligence, cognitive science, biomechanics, etc. In addition, the boundaries of robotics cannot be clearly defined, since also its “core” ideas, concepts and algorithms are being applied in an ever increasing number of “external” applications, and, vice versa, core technology from other domains (vision, biology, cognitive science or biomechanics, for example) are becoming crucial components in more and more modern robotic systems.

 Types of robots by application

Nowadays, robots do a lot of different tasks in many fields. And this number of jobs entrusted to robots is growing steadily. That's why one of the best ways how to divide robots into types is a division by their application.

There are:

*Industrial robots

*Domestic or household robots

*Medical robots

*Service robots

*Military robots

*Entertainment robots 

Chapter 9, Exercises 1-3, page 199 Doãn Hà Tiên

1.   Add a parenthetical definition for each italicized term in the following term in the following sentences:

a.       Reluctantly, he decides to drop (give up something) the physics course.

b.      Last week the computer was down (being broken).

c.       The department is using shareware (software that is distributed free on a trial basis with the understanding that the user may need or want to pay for it later) in its drafting course.

d.      The tire plant’s managers hope they do not have to lay off (terminate the employment) any more employees.

e.      Please submit your assignments electronically (carried on by or making use of electronic equipment).

2.   Write a sentence definition for each of the following terms:

a.       Catalyst          

 à          On chemistry, it is a substance that modifies and increases the rate of a reaction without being consumed in the process.

b.      MP3 player    

à           A digital music player that supports the MP3 audio format.

c.       Job interview

è       An interview to determine whether an applicant is suitable for a position of employment.

d.      Web site       

è         A set of interconnected webpages, usually including a homepage, generally located on the same server, and prepared and maintained as a collection of information by a person, group, or organization.

e.      Automatic teller machine

à           An unattended electronic machine in a public place, connected to a data system and related equipment and activated by a bank customer to obtain cash withdrawals and other banking services.

f.        Fax machine

à            A device that sends and receives printed pages or images over telephone lines by converting them to and from electronic signals.

g.       Intranet

à           A privately maintained computer network that can be accessed only by authorized persons, especially members or employees of the organization that owns it.

3.   Revise any of the following sentence definitions that need revision:

a.       A thermometer measures temperature.

è       A thermometer evaluates temperature.

b.    The spark plugs are the things that ignite the air-gas mixture in a cylinder.

c.     à           The spark plugs are the things that burn the air-gas mixture in a cylinder.

d.      Parallel parking is where you park next to the curb.

à           Parallel parking is where you park next to the wayside.

e.      A strike is when the employees stop working

à            No need to revise.

f.        Multitasking is when you do two things at once while you’re on the computer.

à            Multitasking is when you do two things at once while you’re on the computer. Computer is a device that processes data according to a set of instructions.

Exercise 4 , chapter 9 ,page 199 (Ho Hai Nam, 09ece)

Computer Software

Computer software, or just software, is a collection of computer programs and related data that provide the instructions for telling a computer what to do and how to do it. In other words, software is a conceptual entity which is a set of computer programs, procedures, and associated documentation concerned with the operation of a data processing system. We can also say software refers to one or more computer programs and data held in the storage of the computer for some purposes. In other words software is a set of programs, procedures, algorithms and its documentation. Program software performs the function of the program it implements, either by directly providing instructions to the computer hardware or by serving as input to another piece of software. The term was coined to contrast to the old term hardware (meaning physical devices). In contrast to hardware, software is intangible, meaning it "cannot be touched". Software is also sometimes used in a more narrow sense, meaning application software only. Sometimes the term includes data that has not traditionally been associated with computers, such as film, tapes, and records.

The first theory about software was proposed by Alan Turing in his 1935 essay Computable numbers with an application to the Entscheidungsproblem (Decision problem). The term "software" was first used in print by John W. Tukey in 1958. Colloquially, the term is often used to mean application software. In computer science and software engineering, software is all information processed by computer system, programs and data. The academic fields studying software are computer science and software engineering.

Practical computer systems divide software systems into three major classes[citation needed]: system software, programming software and application software, although the distinction is arbitrary, and often blurred.

System software

Window Vista

System software provides the basic functions for computer usage and helps run the computer hardware and system. It includes a combination of the following:

• Device drivers
• Operating systems
• Servers
• Utilities
• Window systems

System software is responsible for managing a variety of independent hardware components, so that they can work together harmoniously. Its purpose is to unburden the application software programmer from the often complex details of the particular computer being used, including such accessories as communications devices, printers, device readers, displays and keyboards, and also to partition the computer's resources such as memory and processor time in a safe and stable manner.

Programming software

A popular programming language

Programming software usually provides tools to assist a programmer in writing computer programs, and software using different programming languages in a more convenient way. The tools include:

• Compilers
• Debuggers
• Interpreters
• Linkers
• Text editors

An Integrated development environment (IDE) is a single application that attempts to manage all these functions..

Application software

A game software

Application software is developed to aid in any task that benefits from computation. It is a broad category, and encompasses software of many kinds, including the internet browser being used to display this page. This category includes: 

• Business software
• Computer-aided design
• Databases
• Decision making software
• Educational software
• Image editing
• Industrial automation
• Mathematical software
• Medical software
• Molecular modeling software
• Quantum chemistry and solid state physics software
• Simulation software
• Spreadsheets
• Telecommunications (i.e., the Internet and everything that flows on it)
• Video editing software
• Video games
• Word processing

Bill Gate and his company

A great variety of software companies and programmers in the world comprise a software industry. Software can be quite a profitable industry: Bill Gates, the founder of Microsoft was the richest person in the world in 2009 largely by selling the Microsoft Windows and Microsoft Office software products. 

The same goes for Larry Ellison, largely through his Oracle database software. Through time the software industry has become increasingly specialized.

Non-profit software organizations include the Free Software Foundation, GNU Project and Mozilla Foundation. Software standard organizations like the W3C, IETF develop software standards so that most software can interoperate through standards such as XML, HTML, HTTP or FTP.

Other well-known large software companies include Kapersky, Norton, Symantec, Adobe Systems, and Avira, while small companies often provide innovation.

Exercise 5 chapter 9 page 199(Ho Hai Nam, 09ece)

TRANSISTOR

The transistor, invented by three scientists at the Bell Laboratories in 1947, rapidly replaced the vacuum tube as an electronic signal regulator. A transistor regulates current or voltage flow and acts as a switch or gate for electronic signals. A transistor consists of three layers of a semiconductor material, each capable of carrying a current. A semiconductor is a material such as germanium and silicon that conducts electricity in a "semi-enthusiastic" way. It's somewhere between a real conductor such as copper and an insulator (like the plastic wrapped around wires).

The semiconductor material is given special properties by a chemical process called doping. The doping results in a material that either adds extra electrons to the material (which is then called N-type for the extra negative charge carriers) or creates "holes" in the material's crystal structure (which is then called P-type because it results in more positive charge carriers). The transistor's three-layer structure contains an N-type semiconductor layer sandwiched between P-type layers (a PNP configuration) or a P-type layer between N-type layers (an NPN configuration).

A small change in the current or voltage at the inner semiconductor layer (which acts as the control electrode) produces a large, rapid change in the current passing through the entire component. The component can thus act as a switch, opening and closing an electronic gate many times per second. Today's computers use circuitry made with complementary metal oxide semiconductor (CMOS) technology. CMOS uses two complementary transistors per gate (one with N-type material; the other with P-type material). When one transistor is maintaining a logic state, it requires almost no power.

Transistors are categorized by

·         Semiconductor material: graphene, germanium, silicon, gallium arsenide, silicon carbide, etc.

·         Structure: BJT, JFET, IGFET (MOSFET), IGBT, "other types"

·         Polarity: NPN, PNP (BJTs); N-channel, P-channel (FETs)

·         Maximum power rating: low, medium, high

·         Maximum operating frequency: low, medium, high, radio frequency (RF), microwave (The maximum effective frequency of a transistor is denoted by the term fT, an abbreviation for "frequency of transition". The frequency of transition is the frequency at which the transistor yields unity gain).

·         Application: switch, general purpose, audio, high voltage, super-beta, matched pair

·         Physical packaging: through hole metal, through hole plastic, surface mount, ball grid array, power modules

·         Amplification factor h_fe (transistor beta)                                                         

Thus, a particular transistor may be described as silicon, surface mount, BJT, NPN, low power, high frequency switch.

The transistor is the key active component in practically all modern electronics, and is considered by many to be one of the greatest inventions of the 20th century. Its importance in today's society rests on its ability to be mass produced using a highly automated process (semiconductor device fabrication) that achieves astonishingly low per-transistor costs.

Although several companies each produce over a billion individually packaged (known as discrete) transistors every year, the vast majority of transistors now are produced in integrated circuits (often shortened to IC, microchips or simply chips), along with diodes, resistors, capacitors and other electronic components, to produce complete electronic circuits. A logic gate consists of up to about twenty transistors whereas an advanced microprocessor, as of 2011, can use as many as 3 billion transistors (MOSFETs). "About 60 million transistors were built this year [2002] ... for [each] man, woman, and child on Earth."

The transistor's low cost, flexibility, and reliability have made it a ubiquitous device. Transistorized mechatronic circuits have replaced electromechanical devices in controlling appliances and machinery. It is often easier and cheaper to use a standard microcontroller and write a computer program to carry out a control function than to design an equivalent mechanical control function.