http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Abdus Samad(Abdus Samad ) People&Global Business Association 2023 Global Business and Finance Review Vol.28 No.1
Purpose: This paper retested the Okun’s Law established in the 1960s and the subsequent research on Okun’s findings that a 1% increase in unemployment would lead to a 3 % decrease in GDP), i.e. Okun’s coefficient (β)=-3 in diverse economies of sixteen South and Southeast Asia, sixteen countries. Design/methodology/approach: Using panel data in two models, the first difference model: (Yt -Yt-1) = α - β(Ut-Ut-1) and the gap model: (Yt -Y,) = α - β(Ut -U)were estimated. Findings: Results of pool ordinary least square (POLS), Fixed Effect Model (FEM), and Random Effects Model(REM) supports Okun’s Law and shows that the coefficient, β, is (-4.4) suggesting that every 1 percent unemployment rate leads to 4.4 decrease in GDP. The Okun’s coefficient varies with country. The validity of Okun’ coefficient, β= -2 percent, is found only in four. Findings of negative coefficient and its significance provides important policy prescriptions for nine countries. Research limitations/implications: This paper suffers from limitations. First data limitation. This paper used annual data of 30 years. Future research may include quarterly data or annual data with more observations. Second, as Hodrick and Prescott [1997] filtering approach suffers from criticism, Cobb-Douglas production function estimate may be applied for estimating full-employment GDP and natural rate of unemployment. Originality/value: All studies of Okun’s law studies derived its coefficient focused on the economically developed countries, this study is an exception. The survey of literature shows that there is no research of Okun’s for sixteen South and Southeast Asian countries with diverse level of economic growth. So, the result of this study is an important contribution in the literature of Okun’s law. Second, as the policy makers of these countries are facing mounting pressure of unemployment, finding the value of Okun’s coefficient is a contribution of this paper for them.
Multi-Objective Shape Optimization of an Axial Fan Blade
Abdus Samad,Ki-Sang Lee,Kwang-Yong Kim 대한설비공학회 2008 International Journal Of Air-Conditioning and Refr Vol.16 No.1
Numerical optimization for design of a blade stacking line of a low speed axial flow fan with a fast and elitist Non-Dominated Sorting of Genetic Algorithm (NSGA-Ⅱ) of multi-objective optimization using three-dimensional Navier-Stokes analysis is presented in this work. Reynolds-averaged Navier-Stokes (RANS) equations with k-ε turbulence model are discretized with fmite volume approximations and solved on unstructured grids. Regression analysis is performed to get second order polynomial response which is used to generate Pareto optimal front with help of NSGA-Ⅱ and local search strategy with weighted sum approach to refine the result obtained by NSGA-Ⅱ to get better Pareto optimal front. Four geometric variables related to spanwise distributions of sweep and lean of blade stacking line are chosen as design variables to find higher performed fan blade. The performance is measured in terms of the objectives; total efficiency, total pressure and torque. Hence the motive of the optimization is to enhance total efficiency and total pressure and to reduce torque.
Performance of Surrogate Models in Optimizing Heat Transfer Augmentation Devices
Abdus Samad(압두스 사마드),Kwang-Yong Kim(김광용) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-
A three dimensional channel with oblique rib attached on both walls has been optimized to enhance turbulent heat transfer using multiple surrogate models. Objective functions values are evaluated at design points by Reynolds-averaged Navier-Stokes analysis, and surrogates models are constructed for optimization. It is found that the turbulent heat transfer rates increased reasonably by shape optimization and the multiple surrogate methods performed well since these models protect the designer from using any individual basic surrogate poor in prediction. The present approach can help to address the multi-objective designs on a rational basis with quantifiable cost-benefit analysis of system design.
Flow Analyses Inside Jet Pumps Used for Oil Wells
Abdus Samad,Mohammad Nizamuddin 한국유체기계학회 2013 International journal of fluid machinery and syste Vol.6 No.1
Jet pump is one type of artificial lifts and is used when depth and deviation of producing wells increases and pressure depletion occurs. In the present study, numerical analysis has been carried out to analyze the flow behavior and find the performance of the jet pump. Reynolds-averaged Navier Stokes equations were solved and k-ε turbulence model was used for simulations. Water and light oil as primary fluids were used to pump water, light oil and heavy oil. The ratios of area and length to diameter of the mixing tube were considered as design parameters. The pump efficiency was considered to maximize for the downhole conditions. It was found that the increase in viscosity and density of the secondary fluid reduced efficiency of the system. Water as primary fluid produced better efficiency than the light oil. It was also found that the longer throat length increased efficiency upto 40% if light oil was used as primary fluid and secondary fluid viscosity was 350 cSt.
Evaluation of Surrogate Models for Shape Optimization of Compressor Blades
Abdus Samad,Kwang-Yong Kim 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-
Performances of multiple surrogate models are evaluated in a turbomachinery blade shape optimization. The basic models, i.e., Response Surface Approximation, Kriging and Radial Basis Neural Network models as well as weighted average models are tested for shape optimization. Global data based errors for each surrogates are used to calculate the weights. These weights are multiplied with the respective surrogates to get the final weighted average models. The design points are selected using three level fractional factorial D-optimal designs. The present approach can help address the multi-objective design on a rational basis with quantifiable cost-benefit analysis.
Numerical Analysis of Centrifugal Impeller for Different Viscous Liquids
Abdus Samad,Sayed Ahmed Imran Bellary 한국유체기계학회 2015 International journal of fluid machinery and syste Vol.8 No.1
Oil and gas industry pumps viscous fluids and investigation of flow physics is important to understand the machine behavior to deliver such fluids. 3D numerical flow simulation and analysis for different viscous fluids at different rotational speeds of a centrifugal impeller have been reported in this paper. Reynolds-averaged Navier Stokes (RANS) equations were solved and the performance analysis was made. Standard two equation k-ε model was used for the turbulence closure of steady incompressible flow. An inlet recirculation and reverse flow in impeller passage was observed at low impeller speeds. It was also found that the higher viscosity fluids have higher recirculation which hinders the impeller performance.