Influence of surface treatments on CdSe thin films in photoelectro-chemical solar energy conversion

Photovoltaic performance of semiconductor-liquid junction solar cell using electro-codeposited thin filmn-CdSe is found to improve significantly by proper surface treatments. The solid state parameters of annealed films are calculated and compared with those of unannealed film-based cells. Chemical etching is found to improve short circuit current and fill factor whereas photoelectrochemical etching technique improves the stability of photoanode in polysulphide electrolyte. Annealing promotes incipient fusion of small crystallites, thus reducing the grain boundaries which are known to act as recombination centres for minority carriers and trapping centre for majority carriers. The conversion efficiency and stability are found to improve by chemical etching of the semiconductor layer because chemical etching pins Fermi level of CdSe photoanode and promotes exchange current density.     

Use of waste hot water in double basin solar still

A periodic analysis of a double basin solar still is presented in this paper. In this still waste hot water is fed into the lower basin at a constant rate such as is available from power stations or other industries. The effect of various parameters on the distillate output of the still is also investigated.     

p-channel quantum-well heterostructure MI3SFET

A p-channel heterostructure MISFET-like device based on a quantum well with an underlying impurity layer is discussed. The device is based on an AlGaAs/GaAs heterostructure with a recessed-gate geometry and uses Zn-diffused refractory-metal contacts. The 4100 cm²/V-s hole mobility obtained in this inverted-interface structure at 77 K is comparable to that achieved in normal-interface AlGaAs/GaAs heterostructures. Transconductance and K-factor values as high as 52 mS/mm and 140 mS/V-mm, respectively, are obtained at 77 K in p-channel FETs with 2.0-μm gate lengths and 6.0-μm source-drain spacings, representing state-of-the-art values for p-HFETs at similar dimensions     

Six-phase (multiphase) power transmission systems: A generalized investigation of the load flow problem

This paper deals with the generalized investigation of load flow problems of six-phase (multiphase) power transmission systems and presents several schemes for power flow calculations covering balanced and unbalanced network situations. Initially, the system models and algorithm for the assembly of the multi-phase bus admittance matrix are described. Equivalent single- and three-phase load flow studies are carried out employing the equivalent single- and three-phase representations of a six-phase transmission system. The procedure for phase coordinate load flow retaining the physical identities of the three-phase and six-phase elements is developed to investigate the problem of unbalances existing both in a three-phase and a six-phase portion of a composite power transmission network.The problem of obtaining effective starting solutions is also investigated and the computational requirements for various cases are quantified. The procedures developed in the paper are implemented on a sample system. Finally, the paper concludes with a discussion of the major findings and a future line of investigation.     

Structure and Properties of (Ba,Ca)TiO3 Ceramics Prepared Using (Ba,Ca)CO3 Precursors: II, Diffuse Phase Transition Behavior

Ferroelectric phase transition in (Ba,Ca)TiO₃ ceramics has been investigated using dielectric measurements. It is shown that samples prepared using (Ba,Ca)CO₃, precursors exhibit diffuse phase transition (DPT) while those prepared by the conventional route show BaTiO₃-type sharp transition. The diffuseness of the phase transition is found to increase with increasing calcium content. The critical exponent for the dielectric stiffness (1/ε') departs significantly from the mean field value of unity and is shown to increase from 1.21 to 1.86 with increasing calcium content. Arguments are advanced to show that the DPT behavior in these ceramics is inexplicable in terms of either the internal stress model due to the absence of 90° domains in fine-grain ceramics or the compositional inhomogeneity model. It is proposed that DPT behavidr is intrinsic to the system and is intimately linked with the appearance of polar phase in the critical regime whose width is shown to increase with increasing Ca content.     

Heating effects of clock drivers in bulk, SOI, and 3-D CMOS

Steady-state and transient thermal behavior of the highest power density element in systems and chips-the clock driver-in bulk, silicon-on-insulator (SOI), and three-dimensional (3-D) CMOS is examined. Despite significant metal wiring, a majority of the heat conducts through the buried oxide (BOX) in SOI and the buried interconnect layer in 3-D CMOS. 3-D CMOS has the potential to improve substantially over SOI CMOS in thermal behavior by increasing the wiring density directly beneath the clock driver. Temperature mismatch (important for analog applications) between device planes in 3-D CMOS occurs within a characteristic length, which is as large as 13 /spl mu/m for clock drivers. These results suggest advantages and architectural options for the design of high-power devices in 3-D integration.     

A class of tests for testing an increasing failure-rate-averagedistribution with randomly right-censored data

For testing exponentiality versus (nonexponential) increasing failure rate average (IFRA) alternatives (which are nonexponential) using the randomly right censored data, a class of test statistics based on a functional of the Kaplan-Meier estimator is proposed. The asymptotic relative efficiencies of tests from this class with respect to other test statistics are derived. The efficiency loss due to censoring is studied. The proposed tests are applied to published survival data     

Evaluating alternative controllers for an electric power system

The effectiveness of optimal, suboptimal and modal controllers is examined for their suitability of implementation to electric power systems. The techniques for synthesizing the controllers are discussed at length and their performances for small signal disturbance are illustrated for the test system under study. The merits and disadvantages of the different controllers are examined so that definite recommendations may be made on the basis of system specifications and performance requirements.     

Testing constant failure rate against NBAFR alternatives withrandomly right-censored data

Reliability analysts and biometricians have found it useful to categorize life distributions by the properties of the failure rate. This paper considers the problem of testing exponentiality vs (nonexponential) new better than average failure rate (NBAFR) alternatives. Often, in practice, the data are incomplete because of: (a) withdrawals from the study; and (b) survivors at the time the data are analyzed. The authors propose a test statistic based on a function of the Kaplan-Meier estimator to accommodate randomly right censored data. The asymptotic efficacy of the test is derived and the efficiency loss due to censoring is studied. This test is applied to published survival data, and to simulated data