Archives-December  

This paper presents a digital method to develop the three phase voltage source inverter control unit using field programmable gate array (FPGA) based digital Space Vector Pulse Width Modulation (SVPWM) algorithm. In this paper the complicate equations of SVPWM algorithm are simplified to effortless instructions such as shift, addition and subtraction operands in the proposed digital design. Furthermore low power digital circuit to make FPGA based SVPWM control is implemented. The achieved dynamic power consumption is about 63 mW in FPGA clock frequency of 100 MHz. The proposed digital SVPWM was synthesized and implemented using Xilinx ISE and Virtex IV FPGA, with target device XC4VFX100. Also power is analyzed using XPower analyzer. The simulation results demonstrate that proposed method has reduced power consumption.

FUSARIUM WILT is a common disease exploded in the Eastern region , central region and western region of forests of Nepal as well as in the Himalayan and Sub Himalayan region of India and other Asian countries . 6-8 % loss is estimated in the previously reported, MISHRA (2016) especially eastern zone of Nepal and adjoining area of Bihar, while PAVITRA et. al (2018) reported molecular investigation of genes expression analysis in to contrasting genotypes of banana during FUSARIUM WILT ( Foc1) infection .

Graft copolymerization of acrylamide (AAm) on Gum Karaya GK using diode laser (532 nm) was investigated. The results showed that, the optimum conditions to achieve efficient graft copolymerization were: 60 minutes laser irradiation time and 0.5 gm of GK, 0.142 gm of acrylamide (monomer). The percentage of graft efficiency and percentage of graft yield were 28.00%, and 98.59%, respectively. The graft copolymers were characterized using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Thermogravimetric analysis (TGA) and Scanning Electron Microscope (SEM) which proved a successful production of GK-g-AAm. Thus, Laser irradiation was found to be effective and clean method for producing GK-g-AAm.

Glass fiber reinforced polymer composites are finding its increased applications in variety of engineering applications such as aerospace, automobile, electronics and other industries. The main objective of this study is to optimize the process parameters with multiple machinability characteristics. The performance characteristics considered were surface roughness (Ra), Cutting force (Fz) and cutting power (P). Optimal combination of process parameters can then be determined by Taguchi method using the grey relational grade as performance index. The process parameters considered were cutting speed, feed, depth of cut and fiber orientation angle (work piece). Experiments are planned according to Taguchi’s L25 orthogonal array in the design of experiments and were carried out on an all geared lathe using carbide (K20) cutting tool insert. The experimental results reveal that the feed is the most significant process parameter on the multiple machinability characteristics, this proposed method can be effectively used to improve the machining characteristics of GFRP composites.

Single crystals of pure and Glycine-doped Zinc Thiourea Chloride (ZTC) were grown by slow evaporation technique. 1 molar percent of Glycine was added in saturated ZTC solution. The chemical composition of the crystals were determined by Fourier transform infrared (FTIR) analysis. The unit cell parameters and crystal structure were determined by single crystal X-ray diffraction. The UV-visible absorption spectra of pure and Glycine-doped ZTC showed excellent transmittance from 300 nm to 1100 nm. The thermal stability of the grown crystals was studied by thermo-gravimetric analysis (TGA). The second-harmonic generation efficiencies were studied by Kurtz and Perry powder SHG test and observed an enhancement in the SHG efficiency of Glycine-doped ZTC. Micro hardness study was also carried out on the samples to study the mechanical stability of the grown crystals.

ABSTRACT A series of anthracene-based microporous polymers (AMPs) bridged by imide links were successfully prepared by conventional nucleophilic substitution reaction between several 9,10-dihydro-9,10-ethanoanthracenes and cheaper 2,3,5,6-tetrachlorophalonitrile (instead of fluoro-monomer)1. AMPs display a BET surface area in the range of 811-988 m2 g–1, and reversibly adsorb 1.59 wt. % H2 at 1.09 bar/77 K. The enhanced microporosity, in comparison to other organic microporous polymers prepared from (5,5’,6,6’-tetrahydroxy-3,3,3’,3’-tetramethylspirobisindane)2 originates from the macromolecular shape of framework, as dictated by the anthracene units, which helps to reduce intermolecular contact between the extended planar struts of the rigid framework. The impressive hydrogen adsorption capture of these materials verified by Horvath?Kawazoe (HK) and NLDFT analyses of low-pressure nitrogen adsorption data.

In this study, histological examination of the testicles and cellular tissue changes of sperm cells in the spermatogenesis phase of zebrafish are aimed. In this respect; the microscopic structure of the testicles, the position and form of the cells belonging to spermatogenic string, tissue-generating structural cells, and these organisms are examined with the light microscope. All the phases of spermatogenesis are classified as spermatocytogenesis, meiosis and spermiogenesis taking all the phases and histological development of the cells into consideration. All the cells belonging to these phases are seen in separate groups in seminiferous tubules. It is found out that there are somatic cells around spermagony. And spermatogenic cells return into spermatogenic string cells respectively (primer spermatocyte, secondary spermatocyte, spermatide and sperm organisms) by meiosis.

The aim of this paper is to investigate the linkage between macroeconomic variables (inflation rate, exchange rate and interest rate) on stock market returns in Pakistan. We used the Pakistan Karachi stock exchange 100 index as a proxy to represent the stock market returns and the interest rate, inflation rate, and exchange rate were used as the macroeconomic variables. Secondary data was collected from the period of January 2007 to December 2012. A Multiple Linear Regression was performed for the purpose of data analysis. The study showed that there is weak connection between macroeconomic variables and stock market returns. The research validates the findings of earlier studies as well as conclusions and recommendations are discussed.

This paper focuses on anti-reflective coatings on monocrystalline silicon solar cells and the impact of thickness and refractive index on reflectivity. The reference wavelength of silicon is 700nm, with its optimum refractive index (n = 3.7838) and a surface reflectivity of 33%. The calculations were based on values of layer thickness and refractive indices that meet the chosen phase and amplitude conditions, namely (HfO2), (MgF2); (SiOxNy), (SiOx), (Si3N4) and (SiNx:H). Numerical simulations have shown that low reflectivities at the surface of the single-layer coated planar cell can be obtained (3% with Si3N4) and (2% with HfO2). Multilayers such as MgF2/SiNx:H/Si, give a very low reflectivity of around 1%.

Adders are the most vital part of any digital system. Providing an efficient adder design which satisfies the tradeoff between speed and space aides in increasing the performance of the system. parallel prefix adders are the ones widely used in digital design. This is primarily because of the flexibility in designing the adders. Brent kung adder is low power adder, as it uses minimum circuitry and also decrease the speed and memory to obtain the result. The 16-bit design is extended to 32-bit, implemented in the physical level.