Papers

Since the advent of semiconductor devices, a continuous improvement in size, losses, operation, application etc are the areas of studies for researchers. The process control instrumentation did not remained untouched with the advancement in technology. We have worked out to find suitable device for the construction of inverter for induction motor V/Hz control operation in industries. A comparative study has been made to find out the best operational advantages between MOSFET and IGBT based inverter. A suitable gate parameters of IGBTs has also been found out for its smooth conducting. FPGA as gate driver controller has been employed for controlling the ON-OFF operation of inverter to produce three phase at 120^o. IGBT and MOSFET have been tested at 1000V to find out the on state resistance and load current bearing capacity.
 

In extraction process of soyabean, soyameal obtained as a by-product. In this process n-Hexane has vital role, n-Hexane separates the complete oil contents of soya. Despite this vital function of n-Hexane, it is also known as health hazard compound. From the meal n-Hexane is metabolized into gamma diketone 2,5-hexanedione (2,5 HD), which binds with the lysine residues of neurophilament protein causing toxicological implication . The solvents n-hexane exposure, the following four metabolites, 2-hexanol, 2,5-hexanedione, 2,5-dimethylfuran and g-valerolactone, were identified. 2,5-Hexanedione was the main n-hexane metabolite found in previous study. n-Hexane in animals is a neurotoxic agent, also seems to be responsible for the neuropathies. Results suggest that the feeding of soybean containing up to 120 ppm n-Hexane and inhalation of n-Hexane is toxic from 30 ppm to120 ppm.
 

We theoretically investigated photon excited K_a x-ray satellite spectra of Si and SiO₂ using plasmon theory. The KaL¹/ KaL⁰ and KaL² / KaL⁰ intensity ratio are found to be agreed well with experimentally observed values. In the calculation of relative intensity; intrinsic, extrinsic and their relative contributions have been discussed.
 

A mathematical analysis for oxygen transport in capillary and tissue is presented for the case of first order consumption by the tissue in presence of magnetic field .This model consist of a single capillary from which substrate diffuses into a surrounding co-axial tissue. The oxygen transport is appreciably influenced by the application of the magnetic field. Analytical results are obtained by using a series solution method and Picard's type iterative procedure .We have obtained the results for oxygen concentration in capillary and tissue region. This description has a complete view on effects of different parameter on the oxygen concentration in both regions.
 

Curcuma xanthorrhiza, a well-known traditional medicinal plant used in Malaysia and Indonesia, is commonly known with the local name 'temu lawak' or 'temu raya'. Phytochemical studies on Curcuma xanthorrhiza have afforded five compounds, namely a-curcumene (1), germacrone (2), zedorone (3), xanthorrhizol (4) and curcumin (5). The structures of these compounds were established using spectroscopic techniques. The cytotoxicity and antimicrobial tests were carried out on the crude extracts of Curcuma xanthorrhiza as well as isolated pure compounds. Ethyl acetate and methanol extracts showed very strong cytotoxic activity against T-Acute Lymphoblastic Leukemia cells (CEM-SS) with IC₅₀ values of 2.8 and 3.7 µg/mL, respectively. All the extracts of Curcuma xanthorrhiza also exhibited strong and moderate activity against all the bacteria tested, while isolated compound curcumin showed moderate activity against Staphylococcus aureus.
 

The essential oils of Kaempferia angustifolia and Kaempferia rotunda were obtained by hydrodistillation of the rhizomes of the plants. The constituents of the oil were identified by using GC- MS and retention indices. The oils of K. angustifolia was found to be rich in sesquiterpenoids. The major constituents were camphor (21.1%), together with borneol, borneol formate, b- Maaliene, a-guaiene, caryophyllene oxide, vellerdiol and ledol. Essential oils of K. rotunda consisted of monoterpenoids (22.5%) and sesquiiterenoids (6.8%). However the major constituent was identified as an aromatic ester, benzyl benzoate (49.8%).
 

Development and pollution are two interrelated processes that have been causing great concern to the planners with the increasing population in the country. The quality of waste water generated has been increasing beyond treatment capacities, as a result of huge quantity of waste water finds its way into natural water bodies like river, streams, canal, ponds etc. and finally into sea causing alarmingly high rate of pollution and environmental hazards. A survey and the analytical work on waste water especially sewage characteristics of a sewage fed fisheries at Varanasi were due to assess the sewage treatment capabilities of aquaculture and production potentialities of sewage. It was observed that aquaculture itself could remove BOD, COD, nitrogen, phosphorus, heavy metal, suspended solids and bacteria to the extent of 85%, 72%, 70%, 51%, 98-100%, 97% and 93% respectively at the end of its operation and thus to save the environmental pollution. Fish production observed at the rate of 4-5 t/ha/year without conventional feed and fertilizer. It is desirable to remove off flavour and bacterial load, fishes should be kept in fresh water containing marketing pond atleast for 10-15 days before sending it to market.

Modification in Darlington pair amplifier is proposed by adding an extra biasing resistance R_D in the conventional circuit. This simultaneously produces high voltage gain and wide bandwidth. Proposed modification also removes the consequences of conventional Darlington pair amplifier at higher frequencies. Proposed amplifier may be useful for amplification of small signals in mid frequency range and beneficial for various analog communication applications.
 

Many insecticides are available in market. Carbofuran is one of them. Carbofuran was inhibitory to the growth and yield of soyabean and got accumulated in different parts of plant. Vegetative growth and yield of plant indicate a linear decrease. But application of Neem Seed Kernel Extract (NSKE) 10mg/l alone with Carbofuram (5mg/l) significantly reversed the inhibitory effect. NSKE possesses natural insecticide- Azadirachtin. The advantages associated with the use of NSKE are that it has a rapid knock down effect, possess low mammalian toxicity and do not persist in the environment for long.
 

The reactions of hexabutylditin with bifunctional tri dentate Schiff bases in molar ratios of 1:2 were studied in the medium of anhydrous benzene. Complexes of the type R₃Sn-SBH (where R= -C₆H₅ and SBH is Schiff base) have been synthesized. All the reactions were not so facile and tin-tin bond was cleaved in preference to the tin -carbon bond. The resulting derivatives of tin (IV) were isolated in the form of brown or yellow solids. They are soluble in common organic solvents and are highly sensitive to the atmospheric moisture. These complexes are monomers. In these complexes, the tin atom may be in hexacoordination state and structures may be octahedral.