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There is worldwide concern that the availability of oil will diminish within 20 or 30 years. (See, for example, Frank Kreith et al., Ground Transportation for the 21st Century, ASME Press, 2000.) In an effort to maintain the availability of a convenient fuel while at the same time reducing adverse environmental impact, some have suggested that in the future there will be a paradigm shift from oil to hydrogen as the primary fuel. Hydrogen, however, is not available in nature as is oil. Consequently, it must be produced by splitting water electrically or by producing it from a hydrogen-rich fuel. Moreover, to transport hydrogen, it has to be liquified and transported through pipelines to the location where it is needed. Prepare a preliminary assessment for the feasibility of a hydrogen fuel supply system. As a first step, it is necessary to split water into hydrogen and oxygen. To do this, wind turbines will be used to generate electricity for the electrolytic separation of hydrogen and oxygen. This can be accomplished at a cost of $0.06/kWh in parts of the country that have adequate wind resources, such as, for example, North Dakota. Begin your thermal analysis by calculating the energy required to cool the gaseous hydrogen from a temperature of 30°C to a temperature at which it will become a liquid. Assume, for this estimate, that refrigeration can be achieved with a COP of approximately 50% of Carnot efficiency between appropriate temperature limits. Now that hydrogen is available as a liquid, estimate the heat loss from a pipe laid at a reasonable distance underground and insulated with cryogenic insulation in transporting the hydrogen from North Dakota to Chicago. Also estimate the pumping requirements of moving the hydrogen, assuming that suitable pumps with an overall efficiency of 65% are available. Once the liquified hydrogen has reached its destination, it must be stored in a suitable spherical container. Estimate the size of the container sufficient to supply approximately 100 MW of electric power in Chicago by means of a fuel cell that has an efficiency of 60%. The cost of the fuel cell is estimated to be about $5,000/kW. After having completed these estimates, prepare a brief analysis on whether or not a hydrogen economy appears to be technically and economically feasible. For some additional background on this problem,

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Electrical resistance heaters are usually made from coils of nichrome wire. The coiled wire can be supported between insulators and backed with a reflector, for example, as in a supplemental room heater. In other applications, however, it is often necessary to protect the nichrome wire from its environment. An example of such an application is a process heater where a flowing fluid is to be heated. In such a case, the nichrome wire is embedded in an electrical insulator and covered by a metal sheath. Sketch (a) shows the construction details. Since the sheathed heater is often used to heat a fluid flowing over its outside surface, it may be necessary to increase the surface area of the heater sheath. A proposed design for such an application is shown in sketch (b) The preliminary design of a fast-response hot-water heater using this proposed heater element design is shown in sketch (c) The heating element is located inside a pipe carrying the water to be heated. The heating element dissipates 4800 watts per meter length and has a maximum temperature limit of 200°C. Water is to be heated to 65°C by the device and the surface of the heating element should not exceed 100°C to avoid boiling. For simplicity, assume that the heat dissipated by the nichrome wire is distributed uniformly over the cross section of the heating element shown in sketch (b) and that the thermal conductivity of the MgO insulation is 2 W/m K. You may also assume that the metal sheath is very thin. First, perform an order-of-magnitude analysis to estimate the required convective heat transfer coefficient and to determine whether the temperature constraints given above can be met. Next, use analytical tools developed in this chapter to refine your answer.

Q:

Dielectric heating, also known as RF or high frequency heating, is a process in which a high-frequency alternating electric field or microwave electromagnetic radiation heats a dielectric material. An important application of this phenomenon is in the heating of food in a microwave oven. Microwave ovens heat food by bombarding it with electromagnetic radiation in the microwave spectral range, causing polarized molecules in the field to rotate and build up thermal energy, thus cooking or heating the food. However, when the food is initially frozen, because the molecules in the solid do not rotate readily, volumetric heat generation is an order of magnitude less than if the material were in the liquid form. Microwave power not absorbed in the food is dissipated to the microwave generator in the form of heat. Estimate the time it takes to heat a 1 kg roast, initially at a temperature of – 20°C, after it is placed in a 1-kW total power micros-wave oven with an interior temperature of 30°C. Assume the meat has a spherical shape and a heat transfer coefficient of 12 W/m 2 •K from its surface. First estimate the time required to reach a uniform temperature of 0°C when the water in the meat is in the form of ice. Assume that 4% of the oven power is absorbed in the food. After the meat thaws (all ice is melted), the meat increases in temperature. Now estimate the time required for the meat to reach 75°C if 90% of the microwave oven power is absorbed in the meat. Assume that the physical properties of meat are the same as those of liquid water.

Q:

Light-emitting diodes or LEDs are currently perhaps the most energy-efficient lighting systems. Finned surface heat sinks are used to cool high-intensity LED lighting that are used for spot and/or track lighting systems. A typical circular pin-fin heat sink is shown in the figure, and it is desirable that the fin-base temperature be less than 115°C to ensure efficient performance and longer life of the LED lamp. The fins are made of cold-forged, high-conductivity aluminum (k = 210 W/m K). Each pin has a diameter of 4 mm and a length of 40 mm. If the surrounding air is at 22°C, and it has a convection heat transfer coefficient of h̅ c = 10 W/m 2 K, determine the temperature distribution in the fin, considering convection from the fin tip and the heat transfer rate from the fin. Model it as a one-dimensional system, use a minimum of 9 nodes (including the ones at the base and tip) or more in your numerical scheme, and determine the effect of extra nodes. Compare the results with the one-dimensional fin analysis of Chapter 2. Also, if 90 such fins are evenly distributed on a 50-mm- diameter circular base, what is the maximum heat transfer rate that is dissipated by this heat sink so that the base temperature is less than 115°C? In a typical LED lamp, approximately 70% of the electric power (or wattage) is dissipated as heat (the remainder 30% is useful light). Determine the maximum power of the lamp, in watts, for which this heat sink is used. Ts e e 2 3 P№ e 4 e 5 L e 6 e 7 Too, hc 00, e 00 do X

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In Design Problem 1.3, you calculated the heat loss from a small industrial building in the winter. In the initial calculations, you estimated the convection heat transfer coefficient from Table 1.3. Repeat the heat loss calculations, but now calculate the external heat transfer coefficient from material presented in this chapter. To estimate the forced convection conditions on the building, assume that winds in Denver, Colorado, reach as high as 115 km/h, but under normal conditions do not exceed 30 km/h. Discuss the effect of lighting on the heat load and estimate what the effect of electric lights is if 20 150-W incandescent bulbs are needed to provide adequate lighting for this industrial building. Can you suggest an improved lighting method? Data from in Problem 1.3 A furnace wall is to be constructed of brick having standard dimensions of 22.5 cm × 11 cm × 7.5 cm Two kinds of material are available. One has a maximum usable temperature of 1040°C and a thermal conductivity of 1.7 W/(m K), and the other has a maximum temperature limit of 870°C and a thermal conductivity of 0.85 W/(m K). The bricks have the same cost and are laid in any manner, but we wish to design the most economical wall for a furnace with a temperature of 1040°C on the hot side and 200°C on the cold side. If the maximum amount of heat transfer permissible is 950 W/m 2 , determine the most economical arrangement using the available bricks. Data from in Table 1.3 TABLE 1.3 Thermal conductivities of some metals, nonmetallic solids, liquids, and gases Material Copper Aluminum Carbon steel, 1% C Glass Plastics Water Ethylene glycol Engine oil Freon (Liquid) Hydrogen Air Thermal Conductivity at 300 K (540 °R) W/m K 399 237 43 0.81 0.2-0.3 0.6 0.26 0.15 0.07 0.18 0.026 Btu/h ft °F 231 137 25 0.47 0.12-0.17 0.35 0.15 0.09 0.04 0.10 0.02

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Estimate the heat loss from the surface of a swimming pool with a 3-m × 10-m surface area and an average depth of 1.5 m and then design a solar heating system for it. Previously, the pool had been heated by an electric heater that is used as a backup when there is insufficient solar radiation to maintain the pool’s temperature, but which is shut down when there is enough radiation for the collectors to heat the pool. The collector panels are oriented toward the south at a slope equal to the latitude minus ten degrees, as recommended by solar experts (see, e.g., J. F. Kreider, C. J. Hoogendoorn, and F. Kreith, Solar Design: Component, Systems, Economics, Hemisphere Publishing, 1989). The pool is located in San Diego, California, where wind speeds average 15 km/h, and is to be maintained at a temperature of 28°C yearround. The solar-heating system is a closed water loop with a piping arrangement that permits flow to the existing heater alone, flow through the electric heater and solar panels, and to the solar panels only as shown in the schematic diagram. The solar collector is to be made of a black plastic extrusion without a cover to minimize cost. The heat transfer coefficient for the water in the rectangular-flow passages of the collector is estimated from Table 1.3. Suggest ways to reduce the heat loss from the pool at night and estimate the cost-effectiveness of the system. Data from in Table 1.3 Retrofit Solar Swimming Pool Heating System Collector panels 111111 Pool Incident solar radiation Water Pump Filter Solar Panel Detail Heater Valve

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Which encryption protocol does Wi-Fi Protected Access 2 (WPA2) implement? Transport Layer Security(TLS) Encryption Advanced Encryption Standard AES Rivest Cipher 4 (RC4) encryption Data encryption standard DES What is required to leverage Wi-Fi protected access (WPA) enterprise? Directory server RADIUS server EAP-TLS implementation EAP-TTLS implementation Which protocol is designed to protect data in motion on home and small business networks without an authentication server? Wi-fi protected Access (WPA) Personal Wi-fi protected Access (WPA) Enterprise Internet Key Exchange IKE Diffie-Hellmann DH An administrator needs to restrict a subordinate certificate authority CA from issuing certificates. Where should those restrictions be stored? Within the private key of the subordinate CA that issues certificates Within the certificate of the parent CA of the subordinate CA Within the certificate of the subordinate CA of the parent CA Within the public key of the subordinate CA that issues certificates How does a certificate authority CA guarantee the authenticity of the certificates that it issues? By creating a hash and signing with its private key By encrypting a serial number with its public key By encrypting a serial number with its private key By creating a hash and signing with its public key Which standard describes the format for World Wide Web WWW certificates? International organization for standardization (ISO) 27001 National institute of standard and technology NIST 800-53 Rev 4 Institute of electrical and electronics engineers (IEEE) 1394 Internet engineering task force IETF X.509v3 What makes virtual private network VPN end-to-end communications different from a local area network LAN environment? Password salting Hashing Port blocking Tunneling Which computer process verifies the correct protocol to use to establish a layer 2 Tunneling Protocol L2TP with an internet protocol security IPsec virtual private network VPN connection? Network basic input/output system (netBIOS) Security Association SA Secure Socket Layer SSL File transfer protocol/ secure FTP/S Which virtual private network(VPN) architecture relies on standard web ports and therefore does not require firewall changes? Layer 2 tunneling protocol L2TP Point-to-point tunneling protocol PPTP Internet protocol Security IPsec Secure sockets layer/ transport layer security (SSL/TLS) Protocol An organization needs to secure an e-commerce website that external users must be able to trust. Which type of certificate should this organization provide for the website? Self signed root certificate Trusted third party signed server certificate Self signed server certificate Trusted third party signed not certificate A user encrypts a document with a key stored on the user’s laptop. What should this user do to ensure the document can be decrypted even if the laptop is stolen or becomes corrupted? Choose a 256 bit key Password-protect the key stored on the laptop Archive a copy of the key to secure location Change the key regularly Which cipher converts the first character of the alphabet to the last character of the alphabet? Vinegere atbash Caesar Affine Which ciphertext would be produced if ‘candy’ were encrypted three times using the ROT13 cipher? xwpzy sivxy pnaql fdqgb Which type of substitution cipher has been proven to be unbreakable if constructed, secured and used properly? Rossignols' great cipher One-time pad cipher caesar cipher Which technique does frequency analysis use? Comparing ciphertext corresponding to a set of known values Attempting every possible key in the range Deducing the length of the keyword used in the polyalphabetic substitution cipher Looking at how often letters appear against the target ciphertext Which attack method exploits common pairs of letters in classical ciphers? Frequency analysis Social engineering Brute force attack Side channel attack Which attack method is the most resource intensive? Ciphertext-only Known-plaintext chosen -plaintext Chosen-ciphertext Which method of breaking a hash digest includes pre-calculating all possible values of the hash digest? Brute force Differential cryptanalysis Linear cryptanalysis Rainbow table What are statically analyzed to determine if alteration has occurred, indicating an image contains a steganography message? The least significant bit of some pixels The pixels’ parity bits The file header bits The most significant bit of some pixels What is the plaintext that will be hidden in a steganographic message? Carrier Payload Channel Bit Which key is used to verify the digital signature of a message or message digest? Sender's public key Sender’s private key Recipient’s public key Recipient’s private key Which combination is used to encrypt and digitally sign a message ? Recipient’s public key to encrypt and sender’s private key to digitally sign Sender’s private key to encrypt and recipient’s public key to digitally sign recipient’s private key to encrypt and sender’s public key to digitally sign sender’s public key to encrypt and recipient’s private key to digitally sign Which scheme reduces the number of keys required to be secured and distributed for secure communications with multiple senders? Asymmetric encryption Hashing function S-box Symmetric encryption Which certificate is used to decrypt a hash from a file that has been digitally signed? Sender’s private key Recipient’s private key Sender’s public key Recipient’s public key

Q:

Hal and Stu have started a small fund, investing $10 thousands of their own capital. Their quantitative strategy has identified 10 stocks to buy, and they plan to use their $10 thousands buy equal dollar amounts of each stock, that is, $1000 in each stock. They would like to short sell a hedging portfolio constructed with the S&P 500 portfolio and the risk-free asset to make their overall portfolio market-neutral. Assume there is no initial/maintenance margin requirement or any kind of restrictions on short-selling. For each stock, the two partners have estimated the single market index model of the form, where it is a stock's excess return in month t, and Rt is the excess return on the S&P 500 index in month t. Across the 10 stocks that Hal and Stu want to buy, the partners estimate that the average a equals 0.02, and the average ß; equals 0.75. Based on historical estimates, they are also assuming that: the standard deviation of Eit equals 0.10 for the 10 stocks that Hal and Stu plan to buy. The correlation between Eit and Ejt equals 0 for every possible pair for stocks that Hal and Stu want to buy. ● * Terminology: ● Rit ai + BiRmt + Eit ● ●. the expected excess monthly return on the S&P 500 equals 0.005 the standard deviation of the monthly market return is 0.06 A hedging portfolio here describes a position to be shorted to make the overall portfolio market neutral Overall portfolio describes the overall position combining the buy position and the short-sell position Market-neutral in the market index model indicates having zero beta on the market index (a) What is the dollar amount of the hedging portfolio should they short sell? (5%) (b) What is the expected dollar profit on the overall position over the next month? (5%) (c) What is the variance of the return on the overall position over the next month? (5%)

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