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  • American Society of Mechanical Engineers  (10)
  • American Institute of Physics (AIP)  (3)
  • Periodicals Archive Online (PAO)  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 150-157 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The pairing of solute atoms in solution-hardened binary and ternary face-centered cubic (fcc) binary and ternary Cu alloys has been investigated with the EXAFS (extended x-ray-absorption fine structure) technique using synchrotron radiation. Two binary Cu alloys, one containing 6 at. % Ni and the other 6 at. % Pd and a ternary Cu alloy containing 3 at. % Ni and 3 at. % Pd alloy were studied. The solute concentration in each system was chosen below that (8.33 at. %) required for finding one solute-solute pair in the first coordination sphere in the fcc structure. Detailed simulations of the experimental EXAFS signal arising from the first coordination shell of the Ni and Pd solute atoms in these alloys give the following results: (i) In both binary and ternary alloys, Ni is coordinated by 12 Cu host atoms at a distance equal to sum of the Goldschmidt radii. There is little evidence for Ni-Ni pairing. (ii) On the other hand, Pd-Pd pairing is found in both the binary and ternary systems. In addition, chemical interaction with the Cu matrix is evident from the Pd-Cu separation of 2.60 A(ring) which is ∼0.05 A(ring) shorter than the sum of their Goldschmidt radii. (iii) Finally, there is no pairing of Ni-Pd solute atoms in the ternary alloy.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: GaAs metal-semiconductor field-effect transistors (MESFETs) and other integrated-circuit elements were characterized by including extensive process test sites on wafers with digital logic and memory circuits. A self-aligned, refractory-gate enhancement/depletion (E/D) process was employed which included 47SiF+ channel and source/drain implants, capless arsenic overpressure furnace annealing, WSi0.11 gate metal with in situ sputter cleaning, Ni-Au-Ge ohmic contacts, Si3N4 or SiO2 insulation, and Ni-Au wiring. On-water threshold voltage standard deviations as low as 31 mV for 1-μm E-FETs and 49 mV for 1-μm D-FETs were measured using 51-mm standard semi-insulating liquid-encapsulated Czochralski GaAs substrates. Threshold voltage control from wafer to wafer was of order 100 mV. Schottky diode barrier height was about 0.73 eV with an ideality of 1.2, although small self-aligned Schottky gates often showed excess conduction believed to occur at the gate edges. FET square-law coefficient, subthreshold leakage, gate capacitance, backgating, contact resistance, and wiring and insulation characteristics were also measured and found satisfactory. Fully functional 1-μm gate E/D MESFET circuits including a 4×4 bit multiplier, a 4×4 crosspoint switch, a 448-bit static RAM, and an integrated photodiode amplifier were demonstrated.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The use, transportation, and storage of the hazardous gas, arsine, raise serious safety issues. Consequently, there is considerable interest in the generation of arsine on demand from less hazardous substances. We report the first use of in situ generated arsine for III-V epitaxy. The gas has been generated electrochemically at an arsenic cathode in an aqueous electrolyte and used to supply a hydride vapor phase epitaxy reactor. InGaAs/InP test structures were grown on InP substrates and were similar to comparison structures grown using tank arsine. Recessed-gate enhanced Schottky metal-semiconductor field-effect transistors were fabricated and exhibited well-behaved current-voltage characteristics.
    Type of Medium: Electronic Resource
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  • 4
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    Canberra : Periodicals Archive Online (PAO)
    Quarterly review of the rural economy. 10:1 (1957:Jan.) 6 
    ISSN: 0156-7446
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 5
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    Canberra : Periodicals Archive Online (PAO)
    Quarterly review of the rural economy. 8:4 (1955:Oct.) 179 
    ISSN: 0156-7446
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 6
    Publication Date: 1981-05-01
    Description: A general design procedure is presented for solar-assisted series heat pump systems used for space and process water heating. The procedure accounts for the variable efficiency and rate of energy delivery by the heat pump. The fraction of the required energy supplied by solar and the fractions supplied by work and auxiliary are determined. The performance results from this design procedure are compared against detailed computer simulations on a monthly and seasonal basis. For low temperature space heating applications, the maximum difference between the design procedure and computer simulations is three percent on a seasonal basis and 12 percent on a monthly basis. For high temperature process water heating systems, the maximum differences are three to six percent on a seasonal basis and six to 12 percent on a monthly basis, with the accuracy dependent upon the control strategy used. This design procedure is used to investigate high temperature series heat pump systems for providing hot water for industrial processes. Various system parameters are evaluated in terms of the overall effect that each has on system performance and design. Recommendations are given for high temperature series heat pump system design.
    Print ISSN: 0199-6231
    Electronic ISSN: 1528-8986
    Topics: Energy, Environment Protection, Nuclear Power Engineering
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  • 7
    Publication Date: 1982-08-01
    Description: A comparative study of the thermal and economic performance of the parallel and series solar-heat pump systems, stand-alone solar, and stand-alone heat pump systems for residential space and domestic hot water heating has been undertaken for the United States using FCHART 4.0 [1]. The results are useful for a regional assessment of the viability of the different systems, and for assessing policies that will encourage the implementation of the most energy efficient system. The magnitude of the potential energy savings was determined for each system on the basis of an equal total system cost in the case of the series, parallel, and solar systems. The cost was governed by current federal tax credits, and found to be 10,000 dollars. The size and cost of the heat pump are the same in the series, parallel, and stand-alone heat pump systems. A line can be drawn across the United States north of which the parallel heat pump system saves the most energy, and south of which the solar system saves the most. The better of either the solar or the parallel systems consistently used less energy than either stand-alone heat pump or series systems for all locations. The conventional oil or gas furnace seasonal efficiency which would be required to save as much primary energy as the better alternative system was identified regionally. In all but the northern portions of the United States, conventional furnaces would use more primary energy than the better alternative system. The price that the solar collector in the series heat pump system would have to be so that a larger collection system could be installed and the series system would match the energy savings of the preferred system, whether solar or parallel heat pump, was calculated. This price was one-half to two-thirds of current collector prices. The break-even electricity price was determined which is the price below which the life cycle savings of the alternative system are positive. The better alternative was found to be economic against oil furnaces in all regions of the U.S., but economic against gas furnaces only in the Southwest.
    Print ISSN: 0199-6231
    Electronic ISSN: 1528-8986
    Topics: Energy, Environment Protection, Nuclear Power Engineering
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  • 8
    Publication Date: 1988-02-01
    Description: This paper presents a second law analysis of solid desiccant rotary dehumidifiers. The equations for entropy generation for adiabatic flow of humid air over a solid desiccant are developed. The generation of entropy during operation of a rotary dehumidifier with infinite transfer coefficients is investigated and the various sources of irreversibility are identified and quantified. As they pass through the dehumidifier, both the process and regeneration air streams acquire nonuniform outlet states, and mixing both of these air streams to deliver homogeneous outlet streams is irreversible. Transfer of mass and energy between the regeneration air stream and the desiccant matrix occurs across finite differences in vapor pressure and temperature and these transfer processes generate entropy. The second law efficiency of the dehumidifier is given as a function of operating conditions and the effect of finite transfer coefficients for an actual dehumidifier is discussed. It is shown that operating the rotary dehumidifier at conditions that minimize regeneration energy also yields a local maximum for the second law efficiency.
    Print ISSN: 0199-6231
    Electronic ISSN: 1528-8986
    Topics: Energy, Environment Protection, Nuclear Power Engineering
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  • 9
    Publication Date: 1992-11-01
    Description: Previous investigators have shown that an internally reversible Carnot cycle, operating with heat transfer limitations between the heat source and heat sink at temperatures TH and TL, achieves maximum power at an efficiency equal to 1−TL/TH independent of the heat exchanger transfer coefficients. In this paper, optimization of the power output of an internally irreversible heat engine is considered for finite capacitance rates of the external fluid streams. The method of Lagrange multipliers is used to solve for working fluid temperatures which yield maximum power. Analytical expressions for the maximum power and the cycle efficiency at maximum power are obtained. The effects of irreversibility and economics on the performance of a heat engine are investigated. A relationship between the maximum power point and economically optimum design is identified. It is demonstrated that, with certain reasonable economic assumptions, the maximum power point of a heat engine corresponds to a point of minimum life-cycle costs.
    Print ISSN: 0199-6231
    Electronic ISSN: 1528-8986
    Topics: Energy, Environment Protection, Nuclear Power Engineering
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  • 10
    Publication Date: 1992-08-01
    Description: Many previously studied natural convection enclosure problems in the literature have the bounding walls of the enclosure responsible for driving the flow. A number of relevant applications contain sources within the enclosure which drive the fluid flow and heat transfer. The motivation for this work is found in solar thermal storage tanks with immersed coil heat exchangers. The heat exchangers provide a means to charge and discharge the thermal energy in the tank. The enclosure is cylindrical and well insulated. Initially the interior fluid is isothermal and quiescent. At time zero, a step change in the source temperature begins to influence the flow. The final condition is a quiescent isothermal fluid field at the source temperature. The governing time-dependent Navier-Stokes and energy equations for this configuration are solved by a finite element method. Solutions are obtained for 103≤RaD≤106. Scale analysis is used to obtain time duration estimates of three distinct heat transfer regimes. The transient heat transfer during these regimes are compared with limiting cases. Correlations are presented for the three regimes.
    Print ISSN: 0199-6231
    Electronic ISSN: 1528-8986
    Topics: Energy, Environment Protection, Nuclear Power Engineering
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