Synthesis and single crystal growth of gallium phosphide by the liquid encapsulated vertical Bridgman technique

Gallium phosphide is a typical III–V compound semiconductor and is also an important electronic material. The synthesis and single crystal growth of this compound by melt methods is rendered very difficult because of the large phosphorus vapour pressure. A high pressure vessel with internal heating and a quartz reactor was first developed for the direct synthesis of gallium phosphide. The crystal growth was carried out in a second high pressure chamber rated for 100 bars gas pressure and equipped with the paraphernalia for crystal growth. Single crystals of gallium phosphide were grown from the polycrystalline starting material by the vertical Bridgman method and the vapour pressure problem was overcome by encapsulating the melt in a column of molten boric oxide. Both boron nitride and silica were employed as crucibles, and with the former, single crystal rods of 8–10 mm diameter and 10–15 mm length were obtained.     

Prospects for wind energy utilisation in Karnataka State

An examination of the data available at 22 meteorological stations in Karnataka State shows that wind velocities in the State as a whole are neither spectacularly high nor negligibly low. The highest winds (annual mean of around 13 km/hr) are experienced in parts of the northern maidan region of the State (Gulbarga, Raichur and Bidar districts) and in Bangalore. The winds are strongly seasonal: typically, the five monsoon months May-September account for about 80% of the annual wind energy flux. Although the data available are inadequate to make precise estimates, they indicate that the total wind energy potential of the State is about an order of magnitude higher than the current electrical energy consumption. The possible exploitation of wind energy for applications in rural areas therefore requires serious consideration, but it is argued that to be successful it is essential to formulate an integrated and carefully planned programme. The output of current windpumps needs to be increased; a doubling should be feasible by the design of suitable load-matching devices. The first cost has to be reduced by careful design, by the use of local materials and skills and by employing a labour-intensive technology. A consideration of the agricultural factors in the northern maidan region of the State shows that there is likely to be a strong need for mechanical assistance in supplemental and life-saving irrigation for the dry crops characteristic of the area. A technological target for a windmill that could find applications in this area would be one with a rotor diameter of about 10 m that can lift about 10,000 litres of water per hour in winds of 10 km/hr (2.8 m/s) hourly average speed and costs less than about Rs 10,000. Although no such windmills exist as of today, the authors believe that achievement of this target is feasible. An examination of various possible scenarios for the use of windmills in this area suggests that with a windpump costing about Rs 12,000, a three hectare farm growing two dry crops a year can expect an annual return of about 150% from an initial investment of about Rs 15,000. It is concluded that it should be highly worthwhile to undertake a coordinated programme for wind energy development that will include more detailed wind surveys in the northern maidan area (as well as some others, such as the Western Ghats), the development of suitable windmill designs and a study of their applications to agriculture as well as to other fields.     

Financing solar thermal technologies under DSM programs: an innovative approach to promote renewable energy

A wide range of demand side management (DSM) options has been practiced so far in developed as well as in developing countries. However, solar thermal technologies have been left out from DSM programs considering them as supply side options. This study argues that a number of solar thermal technologies, which provide the same services as electric appliances, can be considered as DSM options and examines the possibility of promoting solar water heaters (SWH) under DSM programs in Thailand. The study found that installation of SWH in place of conventional electric water heaters (EWH) to meet hot water demand in the residential sector would be economically beneficial to the country as a whole. However, switching to SWH from EWH would be unlikely without having government interventions as there would be no incentives to individual consumers in doing so. If the government or state electric utilities provide funding to residential consumers through DSM programs for replacing their EWH by SWH, the total electricity generation in Thailand during the 2000–2015 period would decrease by 3.8 per cent. Moreover, promotion of SWH under DSM programs would cause 3.35 and 1.41 per cent reductions of total power sector CO₂‐ and NO_x‐emissions respectively, during the same period. This study also reveals that solar thermal technologies, especially the SWH, could be better options for DSM programs compared to the end‐use efficiency improvement options in Thailand. Copyright © 2000 John Wiley & Sons, Ltd.     

Minimum Cost Design of Lined Canal Sections

Though the minimum area section isgenerally adopted for lined canals, it is not the bestsection as it does not involve lining cost, and thecost of earthwork which varies with the excavationdepth. On account of complexities of analysis, theminimum cost design of lined canal sections has notbeen attempted as yet. In this investigation, explicitequations and section shape coefficients for thedesign variables of minimum cost lined canal sectionsfor triangular, rectangular, trapezoidal, and circularshapes have been obtained by applying the nonlinearoptimization technique. Application of the proposeddesign equations along with the tabulated sectionshape coefficients results directly in the optimaldimensions of a lined canal without going through theconventional trial and error method of canal design.The optimal cost equation along with the correspondingsection shape coefficients is useful during theplanning of a canal project.     

Electrical resistance behaviour of Fe-24 wt.%Mn alloy under high pressure

Electrical resistance behaviour of Fe-24 wt.%Mn SMA was studied up to a pressure of ∼6 GPa by using an opposed anvil high pressure device. The system shows a steep rise in resistance up to ∼1 GPa and thereafter a monotonic decrease up to ∼6 GPa during the forward cycle, whereas it shows a monotonic increase during the return cycle. XRD studies of the as-prepared and pressure quenched samples show a mixed α, γ and ε phase in the former and a predominantly ε phase in the latter, indicative of a possible structural transition at ∼1 GPa, as evidenced from the resistance maximum. The decrease in the transition pressure, when compared with alloys of lower Mn concentration, provides a clue that it should be possible to further reduce the transition pressure to the predominantly ε phase by alloying with suitable elements, which may have positive effect on the shape memory of the alloy.     

Laser-Heated Diamond-Anvil Cell （LHDAC） in Materials Science Research

Laser-heated diamond-anvil cell (LHDAC) is emerging as the most suitable, economical and versatile tool for the measurement of a large spectrum of physical properties of materials under extreme pressure and temperature conditions.In this review, the recent developments in the instrumentation, pressure and temperature measurement techniques,results of experimental investigations from the literature were discussed. Also, the future scope of the technique in various avenues of science was explored.     

Design of Minimum Seepage Loss Canal Sections with Drainage Layer at Shallow Depth

This paper presents an analytical solution for the quantity of seepage from a rectangular canal underlain by a drainage layer at shallow depth. The solution has been obtained using inverse hodograph and conformal mapping. Using the solution for the rectangular canal and the existing analytical solutions for triangular and trapezoidal canals, simplified algebraic equations for computation of seepage loss from these canals, when the drainage layer lies at finite depth, have been presented, which replace the cumbersome evaluation of complex integrals. Using these seepage loss equations and a general uniform flow equation, simplified equations for the design variables of minimum seepage loss sections have been obtained for each of the three canal shapes by applying a nonlinear optimization technique. The optimal design equations along with the tabulated section shape coefficients provide a convenient method for design of the minimum seepage loss section. A step-by-step design procedure for rectangular and trapezoidal canal sections has been presented.     

Aflatoxins and food pathogens: impact of biologically active aflatoxins and their control strategies

Globally disease outbreaks as a result of the consumption of contaminated food and feedstuffs are a regular primary problem. The foremost elements contributing to contamination are microorganisms, particularly fungi, which produce low‐molecular weight secondary metabolites, with demonstrated toxic properties that are referred to as mycotoxins. Aflatoxins contaminate agricultural commodities and may cause sickness or fatality in humans and animals. Moreover, poor conditions of storage and a deficiency in regulatory measures in food quality control aggravate the main issue. For that reason, mycotoxin‐related illness of nutrition represents a major health hazard for local populations. Government policies should make regulations aiming to avoid the entry of aflatoxins into food stuffs. For consumer safety, control and management strategies should be developed and implemented by regulatory authorities. There is the need for attention from farmers, scientists, government and collaborative minds throughout the country to ensure aflatoxin‐free food. The present review is informative not only for health‐conscious consumers, but also for relevant authorities with respect to paving the way for future research aiming to fill the existing gaps in our knowledge with regard to mycotoxins and food security. © 2016 Society of Chemical Industry     

Towards an integrated management information system: A case of the University of Mauritius

The University of Mauritius completed the setting up of a modern Local area network in September 1996. Having successfully implemented traditional services such as e-mail, Internet browsing and sharing of resources, the University developed and implemented an Integrated Management Information System in order to support an increasingly dynamic academic and administrative environment. This paper describes the various processes involved in the building of an Integrated MIS for a University in a small developing country that faces serious economic challenges. A background of the motivations for introducing a computerized MIS is provided followed by the decision-making process of whether to build an in-house MIS or to procure one. The paper also explains the methodology used and the systems that have been developed and integrated in a prioritized and phased manner using economic principles.