Does Okun’s Law and its Coefficient value, β exist? Evidence from Sixteenth South and Southeast Asian Countries during 1991-2020

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.

Flow Analyses Inside Jet Pumps Used for Oil Wells

Samad, Abdus,Nizamuddin, Mohammad Korean Society for Fluid machinery 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-${\varepsilon}$ 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.

MoS₂@VS₂ Nanocomposite as a Superior Hybrid Anode Material

Samad, Abdus,Shin, Young-Han American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.35

<P>Using density functional theory, MoS2@VS2 nanocomposite is reported as a hybrid anode with upgraded electronic conductivity and Li/Na storage capacity. The chemically active monolayer VS2 can be stabilized in energy and phonon vibrations by using the monolayer MoS2 as a substrate. The stability of the chemically active monolayer VS2 is attributed to the interfacial charge accumulation between the monolayer MoS2 and VS2. The maximum specific capacity of the nanocomposite has been enhanced to 584 mAh/g both for Li and for Na storage. We attribute the high enhancement in the Li/Na storage capacity of MoS2@VS2 nanocomposite to the charge redistribution in the formation of the nanocomposite. The lithiation/sodiation open-circuit voltage range of the nanocomposite is quite feasible to be used as anode. Diffusion barriers of Li/Na ions on the surfaces of the nanocomposite are comparable to the barriers on corresponding monolayers, while at the interface the barriers are lower than that for bulk MoS2. This study utilizes different aspects of the two different materials in a hybrid anode with highly enhanced electrochemical performance.</P>

First principles study of a SnS2/graphene heterostructure: a promising anode material for rechargeable Na ion batteries

Samad, Abdus,Noor-A-Alam, Mohammad,Shin, Young-Han The Royal Society of Chemistry 2016 Journal of materials chemistry. A, Materials for e Vol.4 No.37

<P>Properties such as the high binding energy of the Na adatom, high charge storage capacity, low half-cell voltage, and low activation energy barrier for Na diffusion render monolayer SnS2a suitable anode material for rechargeable sodium ion batteries. However, the large expansion of the pristine monolayer SnS2during sodiation and its high band gap, which is a barrier to the free flow of electrons, limit its practical use in batteries. These limitations can be adequately overcome by making a SnS2/graphene heterostructure. The graphene layer of the heterostructure prevents the SnS2layer from expanding during sodiation and enhances its electrical conductivity, while the SnS2monolayer makes Na atoms bind tightly. Even though the energy barrier for Na diffusion is increased by the heterostructure, it still competes with popular anode materials for Li and Na ion batteries. The combination of abundant and low-cost carbon, SnS2, and Na has high potential as an efficient commercial anode material for non-toxic rechargeable Na ion batteries.</P>

Superionic and electronic conductivity in monolayer W2C: ab initio predictions

Samad, Abdus,Shafique, Aamir,Kim, Hye Jung,Shin, Young-Han Royal Society of Chemistry 2017 Journal of Materials Chemistry A Vol.5 No.22

<P>Using density functional theory calculations, a freestanding monolayer of W2C in the 2H phase is explored to find its stability in terms of formation energy and phonon vibrations. In addition, the monolayer has a high in-plane stiffness of 278 N m<SUP>−1</SUP>. Its intrinsic metallic nature, high mechanical stability, and high adsorption capability for Li/Na ions make it an appealing anode material for rechargeable Li/Na ion batteries. The anode open circuit voltages of 0.84-0.55 V for Li and 0.88-0.38 V for Na are within the voltage range of commercial anode materials. The low diffusion energy barrier for a Li (0.035 eV) or Na (0.019 eV) ion leads to superionic mobility, which causes ultrafast charge/discharge cycles. The area expansion of the fully loaded anode is negligible. Its high mechanical stiffness, superb ionic and electronic conductivity, and suitable charging voltage range are the indications of a long-life anode having a high recyclability with full recovery and fast charge/discharge processes.</P>

Surrogate Based Optimization Techniques for Aerodynamic Design of Turbomachinery

Samad, Abdus,Kim, Kwang-Yong Korean Society for Fluid machinery 2009 International journal of fluid machinery and syste Vol.2 No.2

Recent development of high speed computers and use of optimization techniques have given a big momentum of turbomachinery design replacing expensive experimental cost as well as trial and error approaches. The surrogate based optimization techniques being used for aerodynamic turbomachinery designs coupled with Reynolds-averaged Navier-Stokes equations analysis involve single- and multi-objective optimization methods. The objectives commonly tried to improve were adiabatic efficiency, pressure ratio, weight etc. Presently coupling the fluid flow and structural analysis is being tried to find better design in terms of weight, flutter and vibration, and turbine life. The present article reviews the surrogate based optimization techniques used recently in turbomachinery shape optimizations.

Application of Surrogate Modeling to Design of A Compressor Blade to Optimize Stacking and Thickness

Samad, Abdus,Kim, Kwang-Yong Korean Society for Fluid machinery 2009 International journal of fluid machinery and syste Vol.2 No.1

Surrogate modeling is applied to a compressor blade shape optimization to modify its stacking line and thickness to enhance adiabatic efficiency and total pressure ratio. Six design variables are defined by parametric curves and three objectives; efficiency, total pressure and a combined objective of efficiency and total pressure are considered to enhance the performance of compressor blade. Latin hypercube sampling of design of experiments is used to generate 55 designs within design space constituted by the lower and upper limits of variables. Optimum designs are found by formulating a PRESS (predicted error sum of squares) based averaging (PBA) surrogate model with the help of a gradient based optimization algorithm. The optimum designs using the current variables show that, to optimize the performance of turbomachinery blade, the adiabatic efficiency objective is improved substantially while total pressure ratio objective is increased a very small amount. The multi-objective optimization shows that the efficiency can be increased with the less compensation of total pressure reduction or both objectives can be increased simultaneously.

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.

Multi-Objective Shape Optimization of an Axial Fan Blade

Samad, Abdus,Lee, Ki-Sang,Kim, Kwang-Yong The Society of Air-Conditioning and Refrigerating 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 ${\kappa}-{\varepsilon}$ turbulence model are discretized with finite 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.

Stability, spontaneous and induced polarization in monolayer MoC, WC, WS, and WSe

Samad, Abdus,Kim, Hye Jung,Shin, Young-Han IOP 2019 Journal of physics, an Institute of Physics journa Vol.31 No.4

<P> <I>Ferroelectricity</I> in the ultra-low thin films of the <I>ferroelectric</I> materials is a rare phenomenon due to the depolarization electric field established by the uncompensated surface charge. Using density functional theory based calculations, we design buckled honeycomb binary monolayer MoC, WC, WS, and WSe. The feasibility of their experimental synthesis is evident from their low formation energies, stable lattice vibrations, and high elastic stiffnesses. The difference in <I>electronegativity</I> of the building atoms and lack of inversion symmetry results in high spontaneous out-of-plane polarization whereas all the in-plane components cancel out. The existence of the mirror plane along the armchair direction vanishes the in-plane <I>piezoelectric</I> stress effects for a strain applied along the zigzag direction. However, a strain along the armchair direction on MoC and WC results in a high <I>piezoelectric</I> coefficient up to 10 <img ALIGN='MIDDLE' ALT='' SRC='http://ej.iop.org/images/0953-8984/31/4/045301/cmaaf14dieqn001.gif'/> 10<img ALIGN='MIDDLE' ALT='' SRC='http://ej.iop.org/images/0953-8984/31/4/045301/cmaaf14dieqn002.gif'/> C m<img ALIGN='MIDDLE' ALT='' SRC='http://ej.iop.org/images/0953-8984/31/4/045301/cmaaf14dieqn003.gif'/>, about three times larger than that reported for monolayer MoS<img ALIGN='MIDDLE' ALT='' SRC='http://ej.iop.org/images/0953-8984/31/4/045301/cmaaf14dieqn004.gif'/>. The polarization switching barriers for the out-of-plane components range from 0.55 to 2.70 eV per formula unit.</P>