Browsing by Author "Iqra Javed"

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    Mixture Regression Ratio Product Estimator under Stratified Random Sampling
    (UMT.Lahore, 2019-03-28) Iqra Javed
    In this study, Mixture Regression Ratio Product Estimators for single phase sampling under stratified random sampling have been proposed, by incorporating the simultaneous use of information on auxiliary variables and attributes. The estimators have been proposed for two different cases and their mean square errors have been derived mathematically. A Simulation study has been done by using simulated data, to check the distribution of proposed estimators. This study shows that proposed estimators, seems to follow the normal distribution. An empirical study has also been done by considering two natural data sets. Mean square errors (MSE’s) for the proposed estimators have also been computed and Efficiency comparisons made with single phase mixture regression estimators proposed by Moeen et al. (2012). On the basis of MSE’s computed through simulation and empirical studies, it is to be concluded that proposed estimators are more efficient than that of estimators proposed by Moeen et al. (2012) for simple random sampling.
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    Short Circuit Stress Calculation in Power Transformer Using Finite Element Method on High Voltage Winding Displaced Vertically
    (2013) Ashfaq Ahmad; Iqra Javed; Waseem Nazar
    The objective of this research is to compute the mechanical stresses in power transformer resulting from the currents more than rated value during its operation. Due to this high fault current, mechanical stresses are produced indifferent directions which may cause the damage of winding insulation. Various techniques have been adopted to analyze the stresses on transformer windings. For the accomplishment of research, FEM (Finite Element Method) is utilized for the calculation of short circuit forces. All mechanical generated in transformers are calculated mathematically and verified through software. For the verification of results, real time measurements on 20MVA 132 /11.5KV power transformer are made. Various failure mechanisms due to these forces have been discussed. Moreover, design parameters which determine the maximum stresses in different parts of the transformer are also the part of research. Effects of asymmetrical current and forces in various parts of transformer have also been narrated. Moreover, Different properties of materials have been studied and the usage of proper material for withstanding the dynamic effects of short circuits is discussed. Workmanship errors on short circuit withstand capability have also been elucidated. Finally, a complete model for the study of dynamic effects of short-circuits in a power transformer and comparison with forces calculated with FEMM soft ware [13].