Use of chalcopyrite semiconductors CuXSe2 (X=Al,Ga and In) in solar cells: a theoretical study

The energy of sunlight falling on surface of the earth can be directly converted into electricity by means of the solar cells. Among the various materials used for photovoltaics, the chalcopyrite compounds CuXSe₂ (X=Al, Ga, In) are very promising as semiconductors and have received much attention in the recent years. To check the applicability of these materials in solar cells, we have computed the energy bands, density of states, optical dielectric tensors, reflectivity, refraction and absorption coefficients using the full potential linearized augmented plane wave method. It is seen that the energy bandgap reduces from X=Al→In. The dielectric property of these materials is discussed in terms of interband transitions. The absorption coefficients of these materials in the region of solar radiation (0–5 eV energy) are discussed to explore their use in the fabrication of solar cells.     

A student project for layered network protocol development

A student project to accompany a course on computer interfacing and local area networks is described. The audience at which the course is aimed consists of beginning graduate students and seniors. The course addresses fundamental concepts in computer networks in general, and local networks in particular. Students are given the specification of a simple sliding window protocol that provides sequence control and error recovery over an unreliable data link. The task is to implement this protocol on the Apple Macintosh computer as a Layer-3 protocol using the services of the link access protocol (Layer 2) already existent on the machine as part of the Appletalk network. Typical implementations and the cost of benefits of utilizing inexpensive microcomputers for projects in the field of computer networks are discussed     

Protonic polymer gel electrolytes based on carboxylic acids: ortho and inductive effects

The conductivity of polymer gel electrolytes containing three aromatic and three aliphatic carboxylic acids has been studied, viz. (i) ortho-, meta- and para-hydroxybenzoic acids and (ii) oxalic, malonic and succinic acids. Polymeric gels were prepared by adding different wt% of polymer poly(methylmethacrylate) (PMMA) in solutions of respective acids in high dielectric constant organic solvent mixtures of propylene carbonate, ethylene carbonate and dimethylformamide. The highest conductivity in the first of the above group of acids is for o-hydroxy benzoic acid and oxalic acid in the second group of acids. Results have been explained on the basis of ortho and/or inductive effects which depend upon the relative positions of the substituted hydroxyl (–OH) and carboxyl (–COOH) group or that of the two carboxylic groups.     

Modeling the anomalous threshold voltage behavior of submicrometerMOSFET's

A simple yet accurate semi-empirical analytical model for simulating the anomalous threshold voltage behavior in submicrometer MOSFETs is reported. The increase in the threshold voltage with decreasing channel length has been modeled by assuming a bias-independent, but channel-length-dependent, fixed charge at the source and drain ends. The new model requires two extra parameters in addition to the usual short-channel threshold voltage model parameters. These two parameters represent the magnitude of the fixed charge and the length over which the charge is spread at the source and drain ends. The model shows excellent agreement with the experimental threshold voltage data (within 2%) for submicrometer devices with varying oxide thickness, junction depth, and channel doping concentration     

HYDROZEN TRANSFER HYDROCRAKING OF C.PROCERA UNDER AMBIENT PRESSURE CONDITIONS TO GET VALUE ADDED CHEMICALS AND FUELS

Biomass is renewable source of energy while the reserves of petroleum arc being depleted. The latex of a potential petrocrop, Colotropis procera, a lalicifcr, arid-plant which is rich in hydrocarbon type triterpene compounds etc. was found lo be a better feed slock for thermal hydrocracking as compared to whole plant biomass inlcrms of liquid product yield. Studies of chemical reaction dynamics of the thermal cracking of latex at 200-400°C showed that the process should be termed as hydrogen-tranfer (H-T) hydrocracking of latex under ambient pressure conditions. The hydrogen rich cracked trilcrpenoids act as the H-donors in this process, where nascent hydrogen atoms and free radicals chemically plug the cracked moities to stabilise these. Latex was also coagulated and the H-T hydrocracking of the feedstock coagulum gave a higher yield of cracked oil in comparision lo that from the dried latex. A model triterpene compound, ursolic acid has been subjected to H-T hydrocracking to understand the process of hydrocracking of latex under similar conditions and it was found that triterpencs on H-T hydrocracking produced only liquid and gaseous products and no solid char. The temperature for hydrocracking of latex has been optimized to 350°C and molecular sieve was round to catalyse the H-T Hytrocraking process to yield more liquid product The distillation range of cracked latex on(CLO)Obtained from H.T Hytrocracking of C procera Latex indicated that it can be used as fuel. Moreover CLO resembled diesel fuels and was predominantly paraffinic in nature as characterised by NMR and FTIR spectral analysis. A process has been recommended for gelling value added fuels and chemicals from C. procera latex.     

Characterization of information improvement due to N revisions and its generalization by a functional equation

The idea of information improvement was introduced by Thiel [3]. This idea was further extended by the first author to information improvement due to 2 and N revisions and specifically states that different experimenters (a finite number) are required to proceed with given distributions P and U and are permitted to choose a suitable revision. We attempted to provide a measure of information corresponding to Theil's measure which reflected the effect of all revisions. In this paper, the authors have studied a joint characterization of information improvement of N revisions and its generalization by considering a suitable functional equation.     

Phase transformations at −175 °C in polytypic crystals of cadmium iodide

Solid-state phase transformations have been observed to occur in polytypic crystals of cadmium iodide, grown from solution, upon cooling them down to — 175 °C. In addition, structural changes with respect to streaking, arcing, and diffuseness of diffraction spots and the background intensity on the x-ray photographs have been observed. The results have been interpreted on the basis of movement of unit and partial edge dislocations generated during crystal growth. The movement of dislocations is possibly caused by internal strains produced upon cooling.     

Reliability of a 2-Unit Standby Redundant System with Constrained Repair Time

This paper considers a 2-unit warm-standby redundant system with repair. The repair of a failed unit is constrained as follows: Associated with each failure of a unit is a random variable termed the Maximum-Repair-Time (MRT) of the failure. If the repair of a failed unit is not completed within the MRT, the unit is rejected for further use. Two types of failure stituations for the system are considered: 1) No allowed down time, and 2) Some allowed down time. Expressions for the Cdf of the Time to System Failure (TSF) and the mean TSF are derived by using Markov renewal processes.     

Specialized supply firms, property rights and firm boundaries

The proper specification of intellectual property rights (IPRs)is a delicate and controversial matter. In this paper, we considerone specialized context in which IPRs can add to efficiency.We build on contributions of both ‘firm capabilities’scholars (e.g. Teece, Pisano et al.) and ‘property rights’economists (e.g. Hart) to show that IPRs can affect efficiencyby influencing the location of technological innovation. Usinga simple set up, where the key choice is whether a technology-intensiveinput will be supplied by an independent firm or produced in-house,we analyze how the choice is affected by the strength of IPRsand by the existence (and nature) of information spillovers.Specifically, we show that when the supply relationship is likelyto produce new information of value to the supplier, strongerproperty rights favor independent suppliers over vertical integration.An important implication of our model (backed by empirical casestudies) is that strong IPRs therefore encourage investmentsin specialized firms with strong ‘firm capabilities’in the area of innovative input supply. IPRs therefore may playa role—along with multiple other factors—in thelocation of firm boundaries in some cases. This contributionto the viability of small, specialized firms, with their superiorability to innovate in some cases, must be taken into accountin evaluating recent criticisms of over-fragmented IPR ownership(i.e. the ‘anticommons’ problem). It also contributesto an understanding of IPRs in the ‘post-Chandlerian’economy, where smaller, specialized firms play a prominent role.