Presentation on theme: "Electrical and Computer Engineering Science & Engineering Saturday Seminar 23 January, 2010 Marinos N. Vouvakis Special Thanks to:"— Presentation transcript:
Electrical and Computer Engineering Science & Engineering Saturday Seminar 23 January, 2010 Marinos N. Vouvakis firstname.lastname@example.org Special Thanks to: Baird Soules, Kris Hollot, Maciej Ciesielski, Wayne Burleson, Pat Kelly, Sandip Kundu, Russ Tessier What Electrical & Computer Engineering Can Do for You?
2 Electrical and Computer Engineering Who Am I? Professional: Assistant Professor in ECE (5 years at UMass) Teaching: Electromagnetics, Mathematics, Antennas Research: Computational Electromagnetics & Antennas Education: PhD 2005, The Ohio State University MS 2002, Arizona State University Dipl. Ing 1999, Democritus University of Thrace, Greece Personal: Hellenic National, Crete 33 years old (single) Favorite Music: Velvet Underground, Slint, Fugazi Favorite Sport: Basketball Hobbies: Traditional Greek music, politics, history, play with my cats.
3 Electrical and Computer Engineering Seminar Objectives Why am I doing this? Science vs. Engineering? What is Electrical & Computer Engineering? What are major ECE sub-areas? What are the trends? A Closer look at some basic concepts ECE: Analog CKTs (sensing & signals) Digital (entering the Digital world) Wireless (the communications revolution) Demos Sensing & Transducers (Chris) Sampling & Bits (Baird, Marinos)
4 Electrical and Computer Engineering Why am I participation on this Seminar Series? The Vision I want to make impact on society. Engineering is key to a better future for humans and our environment. The Problem Low engineering enrolments nationwide. Alarming enrolment trends. Most teachers do not have engineering background. A Possible solution When incoming students are aware about engineering is, they are likely to choose it. Educate teachers about engineering.
5 Electrical and Computer Engineering Science and Engineering
6 Electrical and Computer Engineering Science vs. Engineering Science: Why things happen the way they happen? Example: Movement of objects (force, friction, etc) Engineering: Creative problem solving. More formally: engineering is the discipline, art and profession of acquiring and applying knowledge to design and implement materials, structures, machines, devices, systems, and processes that realize a desired objective. Example: Wheel!! Engineering = applied science
7 Electrical and Computer Engineering Science vs. Engineering (contd) Remember Apply Analyze Evaluate Understand Create The Taxonomy of Learning Engineering Q: Can we have engineering without science (or vise-versa)?
8 Electrical and Computer Engineering Science and Engineering Observation Instrumentation First Principles Intuition Science Engineering Mathematics
9 Electrical and Computer Engineering Science and Engineering (contd) Science Engineering Technology Society Technology logic = (art/craft)+ (knowledge/logic) Beliefs/behaviors
10 Electrical and Computer Engineering Engineering Grand Challenges* 1.Make solar energy economical 2.Provide energy from fusion 3.Provide access to clean water 4.Reverse-engineer the brain 5.Advance personalized learning 6.Develop carbon sequestration methods 7.Engineer the tools of scientific discovery 8.Restore and improve urban infrastructure 9.Advance health informatics 10.Prevent nuclear terror 11.Engineer better medicines 12.Enhance virtual reality 13.Manage the nitrogen cycle 14.Secure cyberspace *Source: US. National Academy of Engineering
11 Electrical and Computer Engineering Electrical & Computer Engineering
12 Electrical and Computer Engineering What do Electrical and Computer Engineers do?
13 Electrical and Computer Engineering What do Electrical and Computer Engineers do? Any sufficiently advanced technology is indistinguishable from magic. http://en.wikipedia.org/wiki/Arthur_C._Clarke
14 Electrical and Computer Engineering Inside the iPhone 3G Any sufficiently advanced technology is indistinguishable from magic. http://en.wikipedia.org/wiki/Arthur_C._Clarke
15 Electrical and Computer Engineering What do Electrical and Computer Engineers do?
16 Electrical and Computer Engineering Electrical engineering is an engineering discipline that deals with the study and/or application of electricity, electronics and electro-magnetism. Computer engineering is a discipline that combines elements of both electrical engineering and computer science. Computer engineers are involved in many aspects of computing, from the design of individual microprocessors, personal computers, and supercomputers, to circuit design. Easier to understand by exploring example systems
17 Electrical and Computer Engineering Electrical Engineering Fields & Waves Electromagnetics Microwaves/RF Optics/Photonics Antennas/Remote Sensing Electronics Circuit Analysis Electronics Control Control Theory Power Systems Power Electronics
18 Electrical and Computer Engineering Electrical Engineering Communications Communication Systems Wireless Comm. Antennas/Radio Wave Propagation Microwaves and RF Signal Processing Signals and Systems Signal Processing & Communications Image Processing
19 Electrical and Computer Engineering Electrical Engineering Semiconductor Technologies Solid State Physics Nano-electronics First Transistor: 1947 32nm TRIGATE Transistor: 2005 Microelectronics VLSI Ckts Embedded Ckts Fabrication Technologies Pentium processor
20 Electrical and Computer Engineering Computer Engineering Computer Design Hardware Organization & Design Embedded Systems Systems Computer Architecture Computer Programming Software Algorithms Computer Graphics
21 Electrical and Computer Engineering Computer Engineering Networking Computer Networks & Internet Cryptography Trustworthy Computing Bioengineering Bio-informatics Bio-sensors Bio-electronics
22 Electrical and Computer Engineering EE/CE Salary In Electrical Engineering salary rises fast with experience Mobility, Flexibility, Job Satisfaction among highest Do not focus just on starting salaries EETIMES salary survey 2006
23 Electrical and Computer Engineering Job Satisfaction: EETIMES Survey
24 Electrical and Computer Engineering Future ECE Job Prospects* Computer hardware engineers are expected to have employment growth of 4 percent over the projections decade, for all occupations. Although the use of information technology continues to expand rapidly, the manufacture of computer hardware is expected to be adversely affected by intense foreign competition. As computer and semiconductor manufacturers contract out more of their engineering needs to both domestic and foreign design firms, much of the growth in employment of hardware engineers is expected to take place in the computer systems design and related services industry. Electrical engineers are expected to have employment growth of 2 percent over the projections decade. Although strong demand for electrical devices including electric power generators, wireless phone transmitters, high-density batteries, and navigation systems should spur job growth, international competition and the use of engineering services performed in other countries will limit employment growth. Electrical engineers working in firms providing engineering expertise and design services to manufacturers should have better job prospects. Electronics engineers, are expected to experience little to no employment change over the projections decade. Although rising demand for electronic goods including communications equipment, defense-related equipment, medical electronics, and consumer products should continue to increase demand for electronics engineers, foreign competition in electronic products development and the use of engineering services performed in other countries will limit employment growth. Growth is expected to be fastest in service-providing industries particularly in firms that provide engineering and design services.little to no employment change *Bureau of Labor & Statistics
25 Electrical and Computer Engineering An advanced engineering system React Electrical & Computer Engineering Systems
26 Electrical and Computer Engineering Analog Electrical CKTs (Sensing & Power) React
27 Electrical and Computer Engineering Charge & Electric Current Each electron carries an electrical charge, q of –1.602x10 -19 coulombs [C] 1 [C] = the charge of 6.242x10 18 electrons Current, I or i flow rate of electrical charge through a conductor or a circuit element Unit: ampere [A]. 1A=1C/s Current-charge relationship:
28 Electrical and Computer Engineering Direct Current (DC) & Alternating Current (AC) DC Current that is constant with time For examples, I=3A or V=12V AC Current that varies with time and reverses its direction periodically (sinusoidal) For example, Nikola Tesla (1856 – 1943) Thomas Edison (1847 – 1931)
29 Electrical and Computer Engineering Water-Model Analogy We cannot see electric current flowing in a wire Water-model or fluid-flow analogy helps us visualize the behaviors of electrical circuits and elements Electric Current = flow of electrical charges (Water) Current = flow of water molecules Assumptions Frictionless pipes No gravity effect Incompressible water i(t) wire / pipe cross section
30 Electrical and Computer Engineering Material Types Conductors Electric currents flow easily. Examples: copper, gold, aluminum… Insulators Do not conduct electricity. Examples: ceramics, plastic, glass, air… Semiconductors Sometimes conductors, sometimes insulators Examples: silicon, germanium Applications: transistors Superconductors Perfect conductors when cooled Applications: MRI, astronomy
31 Electrical and Computer Engineering Voltage Measured between two points (terminals) Energy transferred per unit of charge that flows from one terminal to the other Intuitive interpretations: potential difference, water pressure in water model Variable: Unit: volt [V] Water models For constant voltage sources Constant-pressure water pump Constant-torque motor Alessandro Volta (1745 – 1827)
32 Electrical and Computer Engineering Rules of Current Flow - Kirchhoffs Current Law Kirchhoffs current law (KCL) Conservation of electrical currents The sum of all the currents into a node is zero The sum of the currents entering a node equals the sum of the currents leaving a node node Gustav Kirchhoff (1824 – 1887)
33 Electrical and Computer Engineering Rules of Current Flow - Kirchhoffs Voltage Law Kirchhoffs voltage law (KVL) Conservation of energy The sum of the voltages around any closed path (loop) is zero Example loop 1loop 2 1 5 3 9 + _ + + + _ _ 3 12 4 + + + _ _ __ loop 3
34 Electrical and Computer Engineering CKT Components - The Resistor Resistor Electrical component that resists the current flow Variable: R [ohm] or Water models for a resistor constriction RR sponge R = ~
35 Electrical and Computer Engineering Resistors in Practice Power Supplies Resistive Touch-screen Incandescent Light Bulb
36 Electrical and Computer Engineering Rules of Current Flow - Ohms Law Ohms Law Power dissipated in a resistor R + _ v(t) i(t) Georg Ohm (1789 – 1854)
37 Electrical and Computer Engineering Resistors in Series + _ + + + _ _ _ + _ + _ =
38 Electrical and Computer Engineering Resistors in Parallel + _ + _ = + _
39 Electrical and Computer Engineering Capacitor CKT Components - The Capacitor Capacitor & Capacitance Stores energy through storing charge Construction: separating two sheets of conductor by a thin layer of insulator Variable: C Unit: Farad [F]. 1F=1 coulomb per volt capacitor C Michael Faraday (1791-1867)
40 Electrical and Computer Engineering Capacitor (contd) CKT Components - The Capacitor (contd) + + + + + + _ _ _ _ _ _ i(t) electron flow + _ pistonspring Water Model: CKT Model:
41 Electrical and Computer Engineering Capacitor Equations Current: Voltage: Energy Stored: C + _ MATH (Integration) = CKT (capacitor) !!!
43 Electrical and Computer Engineering Inductor CKT Components - The Inductor Stores energy through storing magnetic field Construction: coiling a wire around some type of form Variable: L [Henry] or [H]. When the electric current changes in the coil, it creates a magnetic field around the wire which induces voltage across the coil + _ L Joseph Henry (1797-1878)
44 Electrical and Computer Engineering Inductor (contd) CKT Components - The Inductor (contd) Operation When the electric current changes in the coil, it creates a magnetic field around the wire which induces voltage across the coil Water model analogy Bi-directional turbine driving a flywheel Passive, driven by current; no motor Momentum
45 Electrical and Computer Engineering Inductor Equations Current: Voltage: Energy Stored: + _ L MATH (differentiation) = CKT (inductor) !!!
47 Electrical and Computer Engineering CKT Components - The Transistor Transistor is active component (generates energy) Controls the flow of currents Construction: combine semiconductor materials (many different implementations) The key element in any ECE application B (base) C (collector) E (emitter) John Bareen Walter Brattain William Shockley (1947) *Julius Edgar Lilienfield (1925)!!
48 Electrical and Computer Engineering Transistor Operation Use base voltage to control current flow on collector Amplification (analog CKTs) Switching (digital CKTs) B (base) C (collector) E (emitter) amplifier switch 0 1
49 Electrical and Computer Engineering Circuit Schematics connectionno connection R resistor + battery + _ voltage source current source terminals capacitor V VI C inductor L ground transistor wires
50 Electrical and Computer Engineering An Analog CKT System High-End Sound Amplifier CKT design Hardware Implementation
51 Electrical and Computer Engineering Digital Electrical CKTs (Process) React
53 Electrical and Computer Engineering The Digital World Biological Systems: Electrical Systems:
54 Electrical and Computer Engineering Binary in History Yin-Yang Emblem Pa Kua: Eight Trigrams Binary exists for thousand of years in ancient Chinese history: yin-yang 8 trigrams 64 hexagrams G. Leibniz, 1679: formal development of the system of binary arithmetic G. Leibniz (1646-1716)
55 Electrical and Computer Engineering Signal, Signals, Signals Continuous-AmplitudeDiscrete-Amplitude Continuous -Time (Space) Local telephone, cassette- tape recording,photographtelegraph Discrete -Time (Space) Switched capacitor filter, speech storage chip, half- tone photography CD, DVD, cellular phones, digital camera & camcorder t x(t) t n x[n] n
56 Electrical and Computer Engineering Why Digital? Robust (less susceptible to noise) Simple (deals with 0s & 1s)
57 Electrical and Computer Engineering Entering and Exiting the Digital World…
58 Electrical and Computer Engineering Entering and Exiting the Digital World… (contd)
59 Electrical and Computer Engineering Sampling t x(t) t Increases the sampling rate and the amplitude resolution by a factor of 2 t x(t) ^ ^ t
60 Electrical and Computer Engineering 700Hz Sampling (contd) Sampling rate: How fast should we sample? Fewer samples are needed for a slowly-changing signal. More samples are required for fast-changing signals What is the critical sampling rate? Consider the sampling of a simple sinusoid 300Hz Sampling rate: 1000Hz
61 Electrical and Computer Engineering Sampling (contd) Aliasing Ambiguity in the reconstruction: 700Hz sinusoid can be mistakenly identified as a 300Hz sinusoid in example Generally, aliasing error results from not having enough samples for fast-changing signals To avoid aliasing, sample fast enough! 700Hz Sampling rate increases to: 1400Hz
62 Electrical and Computer Engineering Sampling & Aliasing in Digital Images
63 Electrical and Computer Engineering Example: Digital Audio processing or storage of digital signal (e.g., MP3)
64 Electrical and Computer Engineering Analog to Digital Recording Chain Microphone converts acoustic waves to electrical energy. Its a transducer. Analog signal: continuously varying electrical energy of the sound pressure wave. ADC (Analog to Digital Converter) converts analog to digital electrical signal. Digital signal: digital representation of signal in binary numbers. DAC (Digital to Analog Converter) converts digital signal in computer to analog for your headphones. ADC
65 Electrical and Computer Engineering Digital Quantization 3-bit quantization: use 3 bits to represent values 0,1,…7 0 1 2 3 4 5 6 7 Amplitude Measure amplitude at each tick of sample clock Time 5 6 7 7 5 4 3 1 2 5 7 5 7 4
66 Electrical and Computer Engineering Decimal-Binary Conversion Divide the decimal number repeatedly until the quotient is zero. The remainders in reverse order give the numbers equivalent binary form 343/21711 171/2851 85/2421 42/2210 21/2101 10/250 5/221 2/210 1/201 QuotientRemainder 343 = 101010111 102 1 x 2 + 0 x 2 + 1 x 2 + 0 x 2 + 1 x 2 + 0 x 2 + 1 x 2 + 1 x 2 + 1 x 2 = 343 87654 321 0
67 Electrical and Computer Engineering The Digital Audio Stream This is what appears in a sound file, along with a header that indicates the sampling rate, bit depth and other things Each number is then converted to binary and stored in a register 5 6 7 7 5 4 3 1 2 5 7 5 7 4 101 110 111 111 101 100 101 001 010 101 111 101 111 100 A series of sample numbers, to be interpreted as instantaneous amplitudes one number for every tick of the sample clock From previous example:
69 Electrical and Computer Engineering Digital Technology: DVD Digital Versatile Disc or Digital Video Disc First appeared in the US market in March 1997 Employ the same red laser as in CDs Higher-density multi-layer discs to improve storage capacity DVD Audio: 192-kHz 24-bit sampling rate!
70 Electrical and Computer Engineering Digital Technology: DVD SpecificationCDDVD Track Pitch1600 nm740 nm Min. Pit Length830 nm400/440 nm Storage Capacity780 MB4.38-15.9 GB
73 Electrical and Computer Engineering Binary Arithmetic - Addition (contd) InputsOutputs ABSumCarry 0000 0110 1010 1101 Truth Table of Half-Adder XORAND A B Sum Carry What about n-bit inputs?
74 Electrical and Computer Engineering Principle of Binary Addition Binary addition Very similar to decimal addition Starting from least significant bit (LSB), keep track of partial sum & carry until reaching most significant bit (MSB) Simpler than decimal addition: only 0 and 1 are involved Example 1101100 1011101 + carry 1 0 0 0 0 1 1 1 0 1 0 1 1 1 1 LSBMSB Binary Addition 108 93 + carry Decimal Addition 201 11
75 Electrical and Computer Engineering Binary Arithmetic - Addition the Full Adder We need to add three bits (A, B, and Carry), not two as in the half- adder This is called a full adder InputsOutputs 00000 00110 01010 01101 10010 10101 11001 11111 Carry-in Carry-out Sum FA
76 Electrical and Computer Engineering Binary Arithmetic - the N-bit Full Adder Ci A0B0 S0 A1B1 S1 A2B2 S2 A3B3 S3 A4B4 S4 A5B5 S5 A6B6 S6 A7B7 S7 Co S8 first carry in, set to 0 here last carry out, overflow bit 8-bit Full Adder CKT = MATH (= $$$$$)
77 Electrical and Computer Engineering The Systems Approach (divide and conquer)
78 Electrical and Computer Engineering System - An external view Inputs System (Perform Function) Outputs System: A collection of interacting elements that form an integrated whole
79 Electrical and Computer Engineering Digital Hardware Building Block Hierarchy Digital system (1) Circuit board (1-4) Chip (5-100) Logic gate (1k-500k) Transistor (1M-10M)
80 Electrical and Computer Engineering PC Motherboard Level Processor I/O bus slots Graphics Processor interface Memory Disk & USB interfaces
83 Electrical and Computer Engineering Transistor Level Uses Polysilicon-Diffusion Capacitance Cross-section Layout M 1 word line Diffused bit line Polysilicon gate Polysilicon plate Capacitor Metal word line Poly SiO 2 Field Oxide n + n + Inversion layer induced by plate bias Poly
84 Electrical and Computer Engineering Software Contains instructions for the computer to accomplish certain tasks Flexible, easy to modify, copy, and transport Data manipulations Arithmetic operations: additions, multiplications, logarithms, trigonometric functions… Logic operations: from OR, AND, NOT to complex logic functions… Conditional operations: if then else… For ECE research and development Matlab, Mathematica, Maple, Mathcad, Labview, Cadence, develop our own software using programming languages such as C++, Java, FORTRAN…
85 Electrical and Computer Engineering Software Building Block Hierarchy Assembly code Most basic low-level programming codes Different and need to be optimize per processor type Operating System (OS) Set of basic instructions for I/O, file system, resource sharing, security, graphical user interface (GUI) UNIX/Linux, Windows, MS-DOS, MacOS… High-level programming language Provide more general, more powerful, more abstract instructions for the computer Visual BASIC, FORTRAN, C, C++, Java… Application User-friendly software package for popular applications Word processors, email & web browser, games… C++: x++ Fortran: x=x+1 UNIX: ls –l rm *.* DOS: dir del *.* MOV 520 R0 ADD R0 R1 Word Explorer Sims
86 Electrical and Computer Engineering Communication CKTs (Sense/React) React
87 Electrical and Computer Engineering Cell Phone A cell phone is a very complex system that can receive input signals in various forms (electromagnetic waves from base station, sound from microphone, text from key pad) and convert them to several desired types of output signals (sound through speaker, electromagnetic waves to base station, graphics to screen)
88 Electrical and Computer Engineering Cell Phones: Inside front back LCD & keypad microprocessorflash memory speaker, microphone
89 Electrical and Computer Engineering Cell Phone System
90 Electrical and Computer Engineering Sound Fundamentals Sound waves: vibrations of air particles Fluctuations in air pressure are picked up by the eardrums Vibrations from the eardrums are then interpreted by the brain as sounds
91 Electrical and Computer Engineering Harmonics in Music Signals The spectrum of a single note from a musical instrument usually has a set of peaks at harmonic ratios If the fundamental frequency is f, there are peaks at f, and also at (about) 2f, 3f, 4f… Best basis functions to capture speech & music: cosines & sines
92 Electrical and Computer Engineering Frequency How fast a vibration happens High frequency -> fast vibration (voice/music: soprano) Low frequency -> slow vibration (voice/music: baritone) The frequency f is the inverse of the period T Sinusoidal frequency Units Period: second (unit of time) Frequency: 1/sec or hertz [Hz] Phase: radians
93 Electrical and Computer Engineering Music Signals: Piano
94 Electrical and Computer Engineering Frequency Spectrum - Audio f (Hz) 0 20k10k Human Auditory System 20Hz-20kHz f (Hz) 0 20k10k FM Radio Signals 100Hz-12kHz f (Hz) 0 20k10k AM Radio Signals 100Hz-5kHz f (Hz) 0 20k10k Telephone Speech 300Hz-3.5kHz
95 Electrical and Computer Engineering Frequency Spectrum - Music Signals
96 Electrical and Computer Engineering Large size devices Small bandwidth Small antenna gain Large penetration Small resolution Small size devices Large Bandwidth Large antenna gain Small penetration Large resolution Aeronautical comm 120 - 130 MHz Maritime comm 157 - 162 MHz VHF wireless, TV 169 - 600 MHz Cellular phones 900, 1800, 2400 MHz Detection of buried land mines (900 - 2000 MHz) Microwave imaging of tumors 1100 - 1200 MHz Radio astronomy 1413 MHz Microwave ovens 2400 MHz Bluetooth wireless 2400 MHz Global position sat 1600, 1200 MHz Airport appr. radar 2700 MHz Satellite weather 12 GHz Satellite TV 14 GHz Satellite comm 20 - 22 GHz Adv. environ. radars 37, 98, 220 GHz Transmitting & Receiving Information via Electromagnetic c : speed of light f : frequency
97 Electrical and Computer Engineering Modulation
98 Electrical and Computer Engineering Modulation Using higher-frequency sinusoids to carry signals More efficient transmission & allow multi-user sharing Pulse modulation Amplitude modulation Frequency modulation Modulation (contd) Morse code, infrared remote control… AM radio stations, video part of TV signals… FM radio stations, Cell phones, cordless phones…
99 Electrical and Computer Engineering An advanced RF /microwave system T/R switch Antenna PAMixer LNA LO VCO DSP/ Processor A/D Power Supply waveguide Radio Frequency Systems
100 Electrical and Computer Engineering Modem Transmission Frequency-shift keying (FSK) Uses analog sinusoids of different frequencies to carry digital signals 01001 300 3300 frequency 1070127020252225 ReceiveTransmit 0101
101 Electrical and Computer Engineering Cell Phones Motorola RazrBlackBerry Apple iPhone Google G1 Frst cell phone 1973 DynaTAC 1983 Sony Ericsson Xperia X1 Nokia N96
102 Electrical and Computer Engineering The Cell Approach Cellular telephone system is based on the principle of radio communication Coverage area is divided into hexagonal cells (each covers around 10 square miles) Non-adjacent cells can reuse the same frequencies Low-power transmitters: both phones & base stations Each city has a Mobile Telephone Switching Office (MTSO) Each carrier: 832 radio frequencies Duplex system: 395 voice channels & 42 control channels Each cell: 56 voice channels
103 Electrical and Computer Engineering From Cell to Cell System Identification (SID) code to check for available service MTSO uses the control channels to identify where the user is & assign frequencies MTSO handles the hand- off switching between cells based on signal strengths Everything happens within seconds or even less!
104 Electrical and Computer Engineering Cell Phone Tower Antenna Array Switching, RF and Power Electronics
105 Electrical and Computer Engineering What Next? 1.Connect & collaborate with UMass Amherst ECE faculty 1.Teacher development grants 2.Summer research experience for teachers 2.Recommend exceptional high-school juniors/seniors summer research at UMass. 3.Invite UMass Profs to High-school student seminars. 4.M5 Open house for students and Teachers. 5.Spread the word to students & colleagues. 6.Participate on upcoming ECE SESS(more in-depth). Marinos N. Vouvakis email@example.com
106 Electrical and Computer Engineering Disclaimer Some materials (drawings, figures, text) presented in these slides was obtained from the following web resources: 1.http://images.google.com/imghp?hl=en&tab=wihttp://images.google.com/imghp?hl=en&tab=wi 2.http://www.ecs.umass.edu/ece/engin112/http://www.ecs.umass.edu/ece/engin112/ 3.http://thanglong.ece.jhu.edu/Course/137/Lectures/http://thanglong.ece.jhu.edu/Course/137/Lectures/ 4.http://www.ecs.umass.edu/public/ece_docs/ECE_303_ syllabus_S09.pdfhttp://www.ecs.umass.edu/public/ece_docs/ECE_303_ syllabus_S09.pdf 5.http://www.nae.edu/http://www.nae.edu/ 6.http://www.bls.gov/oco/ocos027.htm#outlookhttp://www.bls.gov/oco/ocos027.htm#outlook 7.http://www.engtrends.com/IEE/0806D.phphttp://www.engtrends.com/IEE/0806D.php 8.http://www.eetimes.com/news/latest/showArticle.jhtml ?articleID=206903802