Archives-June...  

This paper presents the solution to the problem of grid voltage instability during occurrence of fault, on a system connected with wind turbine - driven doubly-fed induction generator (DFIG) which supplies alternating current (AC) power to the utility grid. Here, two pulse width modulated voltage source converters are connected back to back between the rotor terminals and utility grid via common direct current (DC) link. The grid side converter controls the power flow between the DC bus and the AC side. It allows the system to be operated in sub-synchronous and super synchronous mode of operation. The rotor excitation is provided by the machine side converter. The model makes use of d-q rotor reference frame using dynamic vector approach for machine model. The controller was implemented by the orientation of the generator stator flux vector along a synchronous reference axis. In this way, constant voltage and frequency was obtained and the generator would supply the active and reactive power demanded for the voltage correction by the load, while the wind turbine will be responsible for achieving power balance in the system. The system is modelled and simulated in the Matlab Simulink environment in such a way that it can be suited for modelling of all types of induction generator configurations. The results of the simulations show that DFIG wind turbines improved the voltage stability of the system through its ability to control reactive power and decouple control of active and reactive power by independently controlling the rotor excitation current especially during fault.

Studies were undertaken on the zooplankton communities of the Androth Island. Major planktonic groups were copepods, decapods, amphipods, chaetognaths, mysids, fish eggs and larvae. Besides these foraminiferans, ciliates, cladocerans, ostracods, polychaete larvae, gastopod larvae, crustacean larvae and echinoderm larvae were also encountered during the present study. Copepoda was found to be the most abundant group. The study provides baseline information on the Zooplankton community structure, which could give new insight to the future ecological assessment of Androth waters.

The banking industry has undergone a sea change after the first phase of economic liberalization in 1991 and hence credit management. While the primary function of banks is to lend funds as loans to various sectors such as agriculture, industry, personal loans, housing loans etc., in recent times the banks have become very cautious in extending loans. The reason being mounting non-performing assets (NPAs). NPA account not only reduces profitability of banks by provisioning in the profit and loss account, but their carrying cost is also increased which results in excess & avoidable management attention. Apart from this, a high level of NPA also puts strain on a banks net worth because banks are under pressure to maintain a desired level of Capital Adequacy and in the absence of comfortable to assess the health of various categories of loan assets in various categories of banks.

This research work is nominated for an image protection technique in the area of spatial domain based digital watermarking and steganography. The proposed work has evolved a hybrid algorithm, Namely, MP-1. In this paper, a new data hiding and digital watermarking algorithm basedonimage matrix vectorization is provided. Experimental results show that the research work has achievedfew of targeted goal such as good concealment ability, large embedding capacity. The proposed algorithm can be widely used in area of spatial domain based digital watermarking and steganography.

The association between atrial fibrillation and left atrial thrombus had been widely described; on the contrary, the relation between atrial fibrillation and right atrial thrombus hasn’t been demonstrated. We always thought that right atrial thrombus originated from deep venous thrombosis and named as “emboli in transit”. We report the case of a 91 year-old male patient, presenting with a permanent atrial fibrillation, his echocardiography showed a huge floating right atrial thrombus complicated with a bilateral pulmonary embolism. Our aim is to demonstrate through this case the association between atrial fibrillation and right atrial thrombus, using our findings in the literature, and comparing between the prevalence of right and left atrial thrombi in association with atrial fibrillation, explaining the difference between the both, and discussing therapeutic options.

In the latest development of Orthogonal Frequency Division Multiplexing (OFDM) communication system, the system performance can be distracted by the frequency offsets (FOs) which can demolish the orthogonality of the subcarriers, and hence leads to a number of impairments in the received signal, thereby making its detection incorrect. In this paper, a new threshold-based frequency offset estimation algorithm for orthogonal frequency division multiplexing (OFDM) systems is proposed. Through a detailed analysis and simulation over AWGN channel, it has been shown that the proposed method shows good performance i.e. it offers low error variance as the SNR (signal to noise ratio) increases.

In view of the place of biological parameters in defining soil health, many scientists of repute have developed methods of assessing environmental parameters one of which is soil health. Soil health is assessed from several angles: biological, chemical, physical, bearing in mind that the top and sub soils are the zones of plant growth and active flora and fauna activities. Biological parameters of the soil cannot do without reference to enzyme, humic acid and microbial activities. A lot of methods have been developed for their assessment and a lot of scientists have adopted and modified the methods with varying results. Each of them have additional benefits. There may be limitations but that is the basis of science. A big thank you to all the scientists living and dead who have shaped the scientific community and the world from their research and findings. All of them have been recognized globally directly as nobel laureates and indirectly through other honours by peer groups. This paper presents enzyme and microbial activities methods of assessment and their pros and cons.

Environmental and Ecological issues call for the reduction in usage of cutting fluids in metal cutting industry. New techniques are being inquired to achieve this objective. Hard turning with minimum quantity lubrication is one such technique which can alleviate the pollution problems associated with cutting fluids. In the present work, vegetable oil based cutting fluids like castor oil, palm oil and ground nut oil is made to drop at tool-work interface using over-head system. The present paper deals with experimental investigation carried out for machinability study of hardened AISI D3 steel in combination with CVD coated cemented carbide inserts of different styles and to obtain optimum process parameters using Deng’s similarity approach. An orthogonal array, overall performance index and analysis of variance ( ANOVA) are applied to study the performance of process parameters such as insert style, cutting fluid cutting speed, feed and depth of cut with consideration of quality characteristics i.e., surface roughness, material removal rate and specific energy. Finally a clear presentation is made for Deng’s approach

The aim of the present study is to investigate the rectal dose during three different radiotherapy techniques of cervical cancer. The study was carried out using a Anderson Rando female phantom. The thermo-luminescent dosimeter (TLD) capsules and detectors of rainbow dosimeter were employed for rectal and target volume dose determination. Several techniques of external beam radiation therapy such as two-field (AP-PA), three-field and four-field with equal applied dose were planned. During application of different radiotherapy techniques, the maximum dose received by rectum is due to the two-field technique. The results of two dosimetry types were compared with each other, In three-field, four-field equal applied dose, rectal dose was lower than tumor dose. This study showed that using TLD and rainbow dosimetry during radiotherapy could have a useful role as a predictor of choosing appropriate technique for preventing future rectal complications. Dose limitation to the rectum could possibly be achieved by using three-field and four-field techniques with equal tumor dose while maintaining a high dose to the tumor.

The aim of this study is to investigate, identify and compare Human Resource Management (HRM) practices in private hospital in Tiruchirappalli, Tamil Nadu India. Self developed survey; based on literature reviews are an instrument used for data collection. The findings of this study such as social characteristics sex, ages religion, community, nativity etc., are important for understanding the needs of human resource management practices in hospitals. This study also deals with the contributions of different factors towards quality care of patients and work culture among the staff.