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

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.

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>

Structure stability and high Li storage capacity of the unzipped graphene oxide monolayer

Samad, Abdus,Kim, Hye Jung,Shin, Young-Han Elsevier 2019 APPLIED SURFACE SCIENCE - Vol.475 No.-

<P><B>Abstract</B></P> <P>Density functional theory based calculations are used to investigate the energetically and dynamically most stable structure for a crystalline unzipped graphene oxide (UGO) monolayer by considering parallel or antiparallel dipolar structures. The O atom in the UGO monolayer induces electron excessive and deficient regions, which makes Li-ions selectively trapped in the electron deficient region. Apart from this, the periodic injection of O in graphene (C<SUB>4</SUB>O) opens a small band gap (0.6 eV) while keeps the Dirac cone. The adsorption of Li-ions makes it metallic by donating an extra electron to the UGO monolayer. The UGO monolayer can have a high Li storage capacity of 419 mAh/g and a typical anodic open circuit voltage range of 0.94–0.19 V. The energy barrier for Li migration is almost double of the pristine graphene, which results from the localized positive charge regions in the UGO monolayer.</P> <P><B>Highlights</B></P> <P> <UL> <LI> First-principles calculations on monolayer unzipped graphene oxide. </LI> <LI> Stable Li adsorption on the OC site due to the lone pair electrons from oxygen. </LI> <LI> The open circuit voltage of C<SUB>4</SUB>O is in the range of 0.94 to 0.19 V. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

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.

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.

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.

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>