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811.
The electrical effects of dislocations has been studied by modeling zero-bias resistance-area product (R0A) of long wavelength infrared diodes fabricated in molecular beam epitaxy (MBE)-grown HgCdTe-Si epitaxial films. Results
show that dislocations influence both 40 K and 78 K R0A products in high dislocation density (HgCdTe/Si) material. In low dislocation density samples (HgCdTe/CdZnTe), the variations
in 78 K R0A are limited by the composition (x) variations in Hg1-xCdxTe material, whereas dislocation contribution dominates the variations at 40 K. The origin of relatively large spread in 40
K R0A in both types of samples is traced to the statistical variations in the core charges of dislocations. It is concluded that
additional alternatives besides the reduction of dislocation density (such as control of core charges), may also need attention
in order to make Si a viable substrate material for the growth of HgCdTe epitaxial layers suitable for devices operating at
40 K. 相似文献
812.
Ashok Kumar Singh Puja Saxena Sameena Mehtab Barkha Gupta 《Analytical sciences》2006,22(10):1339-1344
We have developed a highly La(III)-selective PVC membrane electrode based on a hexaaza macrocycle, 8,16-dimethyl-6,14-diphenyl-2,3,4:10,11,12-dipyridine-1,3,5,9,11,13-hexaazacyclohexadeca-3,5,8,11,13,16-hexaene [Bzo2Me2Pyo2(16)-hexaeneN6] (I) as membrane carrier, dibutylbutyl phosphonate (DBBP) as solvent mediator and sodium tetraphenylborate (NaTPB) as lipophilic additive. The best performance was given by the membrane of macrocycle I having a composition 10:260:5:120 (I:DBBP:NaTPB:PVC). The electrode exhibits a Nernstian response to La(III) ion in the concentration range 1.0x10(-1)-7.94x10(-7) M with a slope of 19.8+/-0.2 mV/decade of concentration and a detection limit of 5.62x10(-7) M. The response time of the sensor is 12 s and it can be used over a period of 4 months with good reproducibility. The electrode works well over a pH range of 2.5-10.0 and in partially non-aqueous medium with up to 30% organic content. The sensor was also used as an indicator electrode in potentiometric titration of La(III) ions with EDTA and for determining La(III) concentration in real samples. 相似文献
813.
Gupta P. Prabhakar B. Boyd S. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2004,50(12):3294-3298
This note considers an n-letter alphabet in which the ith letter is accessed with probability p/sub i/. The problem is to design efficient algorithms for constructing near-optimal, depth-constrained Huffman and alphabetic codes. We recast the problem as one of determining a probability vector q/sup */=(q/sup *//sub 1/,...,q/sup *//sub n/) in an appropriate convex set, S, so as to minimize the relative entropy D(p/spl par/q) over all q/spl isin/S. Methods from convex optimization give an explicit solution for q/sup */ in terms of p. We show that the Huffman and alphabetic codes so constructed are within 1 and 2 bits of the corresponding optimal depth-constrained codes. 相似文献
814.
We study the first-order definable, Diophantine, and algebraic subsets in the set of all ordered sets generating a group or generating a group as a normal subgroup for some relatively free solvable groups. 相似文献
815.
RF SQUID behaviour has been observed at 77 K in YBaCuO thick films prepared by screen printing technique. A hole shunted with
a microbridge type of geometry is patterned manually for observing rf SQUID behaviour. Flux noise spectrum is also studied
and it is found to depend on the quality of the film. The spectral density of the flux noise in the white noise region is
1.7×10−3 Φ0/√Hz at 77 K. 相似文献
816.
R. K. Arora
V. K. Gupta
《Microelectronics Reliability》1990,30(6):1081-1084Node location, topological optimization, capacity assignments, optimal cost determination using regression analysis, delay cost trade-offs and routing algorithm of a computer communication network in India are discussed.
The min-max criterion is used, which minimizes the time delay on every link. The optimum cost is calculated on the basis of a shortest-path algorithm, as length is found to be the only significant factor in determination of the cost as a result of regression analysis. As the traffic is low for the communication network under study, fixed routing strategy is found to be most appropriate. 相似文献
817.
Gupta S. Najm F.N. 《Very Large Scale Integration (VLSI) Systems, IEEE Transactions on》2003,11(4):525-537
We present novel macromodeling techniques for estimating the energy dissipated and peak-current drawn in a logic circuit for every input vector pair (we call this the energy-per-cycle and peak-current-per-cycle, respectively). The macromodels are based on classifying the input vector pairs on the basis of their Hamming distances and using a different equation-based macromodel for every Hamming distance. The variables of our macromodel are the zero-delay transition counts at three logic levels inside the circuit. We present an automatic characterization process by which such macromodels can be constructed. The energy-per-cycle macromodel provides a transient energy waveform, and can also be used to estimate the moving average energy over any time window, whereas peak-current-per-cycle macromodel provides peak-current which can be used for studying IR drop problems. Some key features of this technique are: 1) the models are compact (linear in the number of inputs); 2) they can be used for any input sequence; and 3) the characterization is automatic and requires no user intervention. These approaches have been implemented and models have been built and tested for many circuits. The average errors observed in estimating the energy-per-cycle and peak-current-per-cycle are under 20%. The energy-per-cycle model can also be used to measure the long-term average power, with an observed error of under 10% on average. 相似文献
818.
Lester L.F. Hwang K.C. Ho P. Mazurowski J. Ballingall J.M. Sutliff J. Gupta S. Whitaker J. Williamson S.L. 《Photonics Technology Letters, IEEE》1993,5(5):511-514
The authors report the first successful demonstration of a metal-semiconductor-metal photodetector (MSMPD) fabricated on low-temperature InGaAs grown on GaAs by molecular beam epitaxy (MBE) for long-wavelength fiber optic applications. Interdigitated MSMPDs with finger widths and spacings of 0.2, 0.5, 1.0, and 2.0 μm were tested using a femtosecond pulsed laser and high-speed electrooptic sampling. A FWHM pulsed response of 2 and 1.3 ps was measured for low-temperature In 0.25Ga0.75As and In0.35Ga0.65As, respectively. The latter is the fastest response reported to data for a photodetector capable of detection to wavelengths as long as 1.3 μm 相似文献
819.
We consider the problem of designing quality-of-service (QoS)-constrained routes for a set of multicast groups in an all-optical network. We present an integer goal programming formulation with the objectives of minimizing the cost of the multicast solution and minimizing the maximum link load of the network. Based on the structural properties of the problem, we develop a variable-fixing heuristic which is easy to implement, requires a modest amount of CPU time, and provides high-quality solutions. An extensive computational study is presented to justify our claims 相似文献
820.
A bidirectional electromagnetic screen is proposed and demonstrated with properties that can be switched between high reflection, absorption and transmission over /spl sim/10 ns. The screen comprises frequency selective surfaces loaded with pin diodes, which under partial biasing conditions provide the loss mechanism for the absorption state of the screen. 相似文献