a. Explain why filtering of an X-ray beam causes a simultaneous decrease in beam quantity and increase in quality [a diagram may be useful]

b. The two main mechanisms by which X-rays interact with matter are via Compton scattering and absorption by the photoelectric effect. By referring to the dependence of these effects on X-ray energy, explain what happens to X-ray image quality when using excessively high tube voltages

a) Plot the structure of p-channel MOS-FET (Show semiconductor structure, gate, drain, source and voltage polarities) and summarize the working principle. b) Explain what happens if you change drain source voltage polarity. c) Plot the band diagram, approximate distributions of charge, electric field, and electrostatic potential in the ideal MOS capacitor in inversion for the p-channel case.

1.  An insulated container contains 1.20kg of water with 0.73kg of ice floating in it.  You place a block of iron with mass of 4.60kg in this ice bath.  The iron is initially at a temperature of 400 ºC.  What is the composition and temperature of the final mixture?

For ice L_f=33.5x10⁴J/kg.

For water c=4186J/(kg•K).

For iron c=448 J/(kg•K).

2. A heat transfer of 9.5 x 10⁵ J is needed to convert a block of ice at -15°C to water at 15°C.  What was the mass of the block of ice?

For ice L_f=33.5x10⁴J/kg.

For ice c=2090 J/(kg•K).

For water c=4186J/(kg•K).

Nikola Tesla y Thomas Edison are well known for their inventions even though they both had an idealistic war between them. One of them promoted the continuous current (DC) while the other one was more inclined towards the alternating current. Each technique had their pros and cons.

What is the AC current and the DC current? Name the pros and cons of each and which one has the minimal loss of transmission of energy and why?

1- An electron moving in a metal nanowire is a reasonable approximation of a particle in a one-dimensional infinite well. Suppose the electron is in a wire 10nm long. (a) Compute the ground-state energy for the electron. (b) The electron moves freely inside in metal nanowire. Find the electron’s velocity in ground state. c) If the electron’s energy is equal to 10 eV, what is the electron’s quantum number n?

2- Briefly explain the differences between quantum and classical thermodynamical approximation of electron energy.

3- Think about the electron where it is in first energy state in metal with length of L. (a) What would be the probability of finding it somewhere in the region 0< x< 3L/2? Find energy level corresponding energy state of the electron.

4- Find the second state electron energy (E2) by substituting the radial wave function R that corresponds to n=2 l=0 and mı=0

Write an 8051-assembly language program for the interfacing of ADC0804 and LM35 to display the room temperature on 16x2 LCD (10marks)

please note that the program should be interfacing with ADC0804.

Consider 3 typical MRI systems of 0.5T, 1.5T and 3.0T for proton imaging (given the proton’s gyromagnetic ratio γ/2π = 42.48 MHz/Tesla) (a) What are the RF frequencies at which these systems operate? (b) Briefly discuss the main physics factors affecting the MR signal strength and rank the MR signal strengths among these three MRI systems

Consider collision problems. Real-world collisions are rather complicated to capture in full and we approximate them by special cases. Name the two basic collision types we use to describe and idealize real-world collisions. What distinguishes both? In most collision problems we know a) the masses and initial velocities of objects involved in the collision and ask for their final velocities, or b) we know the objects’ masses and aftercollision (final) velocities and ask what their initial velocities were (forensic engineering). Which conservation laws help to mathematically describe collision situations? Name and state them in form of (ansatz) equations. Looking at your answer, explain whether or not these conservation laws are valid for each of the previously named types of collisions.

A communications satellite is in a synchronous orbit that is 3.61×107 m directly above the equator. The satellite is located midway between Quito, Equador, and Belem, Brazil, two cities almost on the equator that are separated by a distance of 3.87×106 m. Calculate the time it takes for a telephone call to go by way of satellite between these cities. Ignore the curvature of the earth.

A 64 pound weight is attached to the lower end of a coiled spring suspended from the ceiling. The weight comes to rest at its equilibrium position, thereby stretching the spring 1/2 foot. At time t = 0, the weight is positioned 1 /√3 feet below equilibrium and given a downward velocity of 8 feet per second.

(a) Determine the equation of motion of the weight as a function of time.

(b) Find the amplitude of the motion.

(c) Find the period of the motion.

(d) Find the phase angle.

(e) Determine the times that the weight passes through equilibrium.

(f) Determine the third time the weight passes through equilibrium moving upward.

(g) Determine the second time the weight passes through equilibrium moving downward.

(h) Determine the times the weight is 1 foot below equilibrium.

(i) Determine the second time the weight is 1 foot below equilibrium moving upward.

(j) Determine the second time the weight is 1 foot below equilibrium moving downward

The plant H(s)=40/(S^2+4) is now put in a unity-feedback connection with a proportionalderivative compensator

Cpd(s) = K(1 + sT), where K and T are real constants to be determined. The closed-loop is stable with a constant step-response error of +20% in steady state. Ignore implementation issues arising from the improperness of the compensator. (a)Determine K.

(b)What range of values can T take?

(c) What is the gain margin?

(d) If the gain cross-over frequency is 10 rad/s, determine the phase margin in radians.

(e) Assuming gain cross-over at 10 rad/s, sketch the Bode diagrams for the open-loop transfer function. Indicate and evaluate all relevant features: asymptotes, asymptotic slopes, any breakpoints, and the exact magnitude and phase at each breakpoint.

(f) Suppose there is a delay ∆ > 0 (s) in the plant, in series with H(s). i. Briefly explain whether or not this this would change the gain cross-over frequency. ii. What range of ∆ could be tolerated? What would happen to the closed-loop system for ∆ values outside this range?

(g) A colleague of yours decides to instead use an alternative compensator of form Ca(s) = k(1 + sτ )(s 2 + 4) (1 + sτ0) 3 in a unity-feedback configuration with H(s). He claims this effectively ‘removes’ the plant dynamics, and simplifies his controller design. He chooses positive constants k, τ and τ0 that ensure stability of the transfer function from the reference r to output y, and implements his design on the physical plant. However, the physical system does not behave as he anticipated. Explain what he observes, and why.

Suppose you have an electric hot water heater for your house which is an aluminum cylinder which has a 0.56 m radius and is 2 m high. The walls are 1.0 cm thick. The thermal conductivity of Aluminum is 217 W/(m K). Assume that the temperature of the hot water inside the hot water heater is kept at a constant 90 C, and the external temperature is 27 C.

Part A:

What is the surface area of the cylinder?

Part B:

How much energy is lost through the walls of the hot water heater in one week? (Assume thinner surface of the heater is 90 C and the outer surface is 27 C.)

Part C:

Assume you pay $0.10 per kW-hour for electricity. How much would it cost just to keep the hot water inside the heater for one week?

Part D:

Suppose that you wrap the hot water heater on all sides with a 10 cm thick blanket of fiberglass insulation which has a thermal conductivity of 0.04 W/(m K). Assume the inner surface of the fiberglass insulation is at 90 C and the outer surface is at 27 C, and the total surface area is still what you calculated in part A.

Part E:

Assume you pay $0.10 per kW-hour for electricity. How much would it cost just to keep the hot water inside the fiberglass-wrapped heater for one week?