Effects of financial development and capital accumulation on labor productivity in sub‑Saharan Africa:new insight from cross sectional autoregressive lag approach

This study aims to shed light on the effects of financial development and accumula-tion of capital on the productivity of labor in the sub-Sahara African region within the period of 1990–2018.In this work,we used the(dynamic)common correlated effects estimator-mean group and additional techniques such as cross-section autoregressive distributed lag to calibrate the sample into the African subregion to ensure robustness.The findings reveal that financial progress in the region over time leads to an increase in productivity of labor and also the accumulation of capital.Furthermore,financial markets have a progressive impact on the productivity of labor within sub-Saharan African regions.We extend the very limited literature on the nexus between financial development and labor productivity by incorporating capital accumulation into our model which has not been previously studied.

The Effects of Job Insecurity, Emotional Exhaustion, and Met Expectations on Hotel Employees’ Pro-Environmental Behaviors: Test of a Serial Mediation Model

There are a plethora of empirical pieces about employees’pro-environmental behaviors.However,the extant literature has either ignored or not fully examined various factors(e.g.,negative or positive non-green workplace factors)that might affect employees’pro-environmental behaviors.Realizing these voids,the present paper proposes and tests a serial mediation model that examines the interrelationships of job insecurity,emotional exhaustion,met expectations,and proactive pro-environmental behavior.We used data gathered from hotel customer-contact employees with a time lag of one week and their direct supervisors in China.After presenting support for the psychometric properties of the measures via confirmatory analysis in LISREL 8.30,the abovementioned linkages were gauged using the PROCESS plug-in for statistical package for social sciences.The findings delineated support for the hypothesized associations.Specifically,emotional exhaustion and met expectations partly mediated the effect of job insecurity on proactive pro-environmental behavior.More importantly,emotional exhaustion and met expectations serially mediated the influence of job insecurity on proactive pro-environmental behavior.These findings have important theoretical implications as well as significant implications for diminishing job insecurity,managing emotional exhaustion,increasing met expectations,and enhancing ecofriendly behaviors.

Toward a sustainable growth path in Arab economies:an extension of classical growth model

Background/Objectives:Many economies are on the trajectory of alternative growth drivers other than conventional capital and labor.Access to credit facilities is a pertinent indicator of economic growth.In line with the United Nations Sustainable Development Goals(UNSDGs-8)agenda,the national goal for sustainable development for most economies and Arab economies is no exception.Therefore,the current study adopts a traditional growth model by exploring the relationship between gross domestic product(GDP)per capita,credit for private sectors,ratio of exports,real GDP,and per labor force participants for selected Arab economies annually from 2001 to 2020.Research design:This study leverages the Fourier Kwiatkowski–Phillips–Schmidt–Shin(KPSS)unit root test and second-generation panel econometrics as estimation techniques,such as Westerlund and Edgerton panel cointegration test,and the use of two estimators,namely the augmented mean group(AMG)and common correlated error mean group(CCEMG),to obtain robust results.Findings:Empirical findings from Westerlund and Edgerton panel cointegration tests validate the long-run equilibrium relationship among the outlined variables.Further empirical results indicate that the share of exports is negatively significant with economic growth in countries such as Kuwait,Lebanon,Tunisia,and Jordan.Additionally,savings and labor force participation have a positive relationship with economic growth in individual countries such as Algeria and Bahrain.As per the panel,there is no significant relationship between labor force participation and economic growth.This indicates that the skilled labor force enhanced economic growth.Conclusions:These findings come with inherent far-reaching policy suggestions for economies and panels.Further details on country-specific policy actions are presented in the concluding section.

Microstructural evolution during semisolid state strain induced melt activation process of aluminum 7075 alloy

7075 艾尔合金由导致的紧张生产了的半固体的微观结构进化上的压缩比率的效果融化激活(SIMA ) 过程被调查。样品是压缩使变形进不同高度直到 40% 减小的寒冷。等温的成立处理在 625 猠畬牲 ? 慷 ? 牰摯 ' 讚瓚?湩敪瑣湩 ? 楦敮朠獡戠 'T 汢獥椠瑮 ? 桴 ? 被执行敭瑬琠牨畯桧愠朠慲桰瑩 ? 楤晦獵牥搠牵湩 ?

On modeling with multiplicative differential equations

This work is aimed to show that various problems from different fields can be modeled more efficiently using multiplicative calculus, in place of Newtonian calculus. Since multiplicative calculus is still in its infancy, some effort is put to explain its basic principles such as exponential arithmetic, multiplicative calculus, and multiplicative differential equations. Examples from finance, actuarial science, economics, and social sciences are presented with solutions using multiplicative calculus concepts. Based on the encouraging results obtained it is recommended that further research into this field be vested to exploit the applicability of multiplicative calculus in different fields as well as the development of multiplicative calculus concepts.

搅拌摩擦焊含铜嵌入板的6061-T6铝合金(Al/Cu/Al)的显微组织和力学性能（英文）

将两块6061-T6板中间嵌入一块纯铜板(Al/Cu/Al),利用搅拌摩擦焊(FSW)技术焊合,研究铜板插入对焊接接头性能的影响,并与无铜板的搅拌摩擦焊AA 6061(Al/Al)的研究结果进行比较。用光学显微镜和扫描电镜观察焊接样品的显微组织,用X射线衍射分析Al/Cu/Al样品的相组成。在转速为1000 r/min和焊接速度为25 mm/min条件下观察到Al/Cu/Al焊接接头无缺陷。焊核区的显微组织观察结果显示类似复合物结构的形成促进了铝和铜的冶金结合。XRD结果显示形成了金属间化合物(IMCs),如Al_4Cu_9和Al_2Cu。由于其更高的位错密度,有Cu板的焊接样品的硬度较高,且IMCs存在的区域其硬度值明显更高。由于铝和铜之间更强的冶金结合,有铜板的焊接接头的极限抗拉强度比无铜板的接头更高。

Size-dependent shear buckling response of FGM skew nanoplates modeled via different homogenization schemes

The size effects on the shear buckling behaviors of skew nanoplates made of functionally graded materials(FGMs)are presented.The material properties are supposed to be changed uniformly from the ceramic phase to the metal one along the plate thickness.To estimate the associated effective material properties,various homogenization schemes including the Reuss model,the Voigt model,the Mori-Tanaka model,and the Hashin-Shtrikman bound model are used.The nonlocal elasticity theory together with the oblique coordinate system is applied to the higher-order shear deformation plate theory to develop a size-dependent plate model for the shear buckling analysis of FGM skew nanoplates.The Ritz method using Gram-Schmidt shape functions is used to solve the size-dependent problem.It is found that the significance of the nonlocality in the reduction of the shear buckling load of an FGM skew nanoplate increases for a higher value of the material property gradient index.Also,by increasing the skew angle,the critical shear buckling load of an FGM skew nanoplate enhances.This pattern becomes a bit less significant for a higher value of the material property gradient index.Furthermore,among various homogenization models,the Voigt and Reuss models in order estimate the overestimated and underestimated shear buckling loads,and the difference between them reduces by increasing the aspect ratio of the skew nanoplate.

渐进成形圆柱孔翻边的有限元和实验分析（英文）

研究单点渐进成形中坯料预切孔尺寸对圆柱孔翻边的可成形性的影响。翻边制造从45°到90°分为4个阶段,采用铝作为实验材料。孔尺寸对圆柱翻边的应力/应变分布有显著影响。随着孔尺寸的增大周向应变增大,翻边的壁厚增厚。同样地,随着孔尺寸的增大von Mises应力降低。而且,孔尺寸存在一个临界值(80 mm),当低于这个值时会产生严重的应力,从而导致板材断裂,圆柱翻边成形失败。随着孔尺寸的减小,且大于临界尺寸时,可成形性降低。结果表明,孔的临界尺寸为80 mm能使铝板在渐进孔成形中的可成形性能最大化。

Identification of pulse-like ground motions using artificial neural network

For more than 20 years,the concept of near-fault pulse-like ground motion has been a topic of great interest due to its distinct characteristics,particularly due to directivity or fling effects,which are hugely influenced by the rupture mechanism.These unexpected characteristics,along with their effective frequency,energy rate,and damage indices,create a near-fault,pulse-like ground motion capable of causing severe damage to structures.One of the most common approaches for identifying these ground motions is done by conducting wavelet decomposition of the ground motion time history to extract a pulse signal and eventually categorize an earthquake by comparing the original signal to the residual one.However,to overcome the intensive calculations required in this approach,this study proposes using artificial neural networks to identify pulse-like ground motions through classification to predict their pulse period by means of regression analysis.Furthermore,the study is intended to evaluate the reliability and accuracy of various artificial neural networks in identifying pulse-like ground motions and predicting their pulse periods.In general,the results of the study have shown that the artificial neural network can identify pulse-like earthquakes and reliably predict their pulse period.

Prediction of seismic collapse risk of steel moment frame mid-rise structures by meta-heuristic algorithms

Different performance levels may be obtained for sideway collapse evaluation of steel moment frames depending on the evaluation procedure used to handle uncertainties. In this article, the process of representing modelling uncertainties, record to record （RTR） variations and cognitive uncertainties for moment resisting steel frames of various heights is discussed in detail. RTR uncertainty is used by incremental dynamic analysis （IDA）, modelling uncertainties are considered through backbone curves and hysteresis loops of component, and cognitive uncertainty is presented in three levels of material quality. IDA is used to evaluate RTR uncertainty based on strong ground motion records selected by the k-means algorithm, which is favoured over Monte Carlo selection due to its time saving appeal. Analytical equations of the Response Surface Method are obtained through IDA results by the Cuckoo algorithm, which predicts the mean and standard deviation of the collapse fragility curve. The Takagi-Sugeno-Kang model is used to represent material quality based on the response surface coefficients. Finally, collapse fragility curves with the various sources of uncertainties mentioned are derived through a large number of material quality values and meta variables inferred by the Takagi-Sugeno-Kang fuzzy model based on response surface method coefficients. It is concluded that a better risk management strategy in countries where material quality control is weak, is to account for cognitive uncertainties in fragility curves and the mean annual frequency.

Synthesis and characterization of salt-impregnated anodic aluminum oxide composites for low-grade heat storage

Thermochemical heat storage(THS)systems have recently attracted a lot of attention in research and development.In this study,an anodic aluminum oxide(AAO)template,fabricated by a two-step anodization method,was used for the first time as the matrix material for a THS system.Different salts were studied as thermochemical materials for their suitability in low-grade heat storage application driven by solar energy for an open system.Compositions were prepared by absorbing CaCl2,MgCl2,LiCl,LiNO3 and mixtures of these salts under a vacuum in an AAO matrix.Field Emission Scanning Electron Microscopy was used to examine the morphology of the produced AAO composites.Thermal energy storage capacities of the composites were characterized using a differential scanning calorimeter.Characterization analysis showed that anodized Al plates were suitable matrix materials for THS systems,and composite sorbent prepared with a 1:1 ratio LiCl/LiNO3 salt mixture had the highest energy value among all composites,with an energy density of 468.1 k J·kg-1.

Optimization of Abrasive Water Jet Cutting of Ductile Materials

Full factorial design of experiments was developed in order to investigate the effects of jet pressure, abrasive mixing rate, cutting feed, and plate thickness upon three response variables, surface finish of cutting wear zone, percentage proportion of striation free area, and maximum width of cut. The set of sixteen experiments was performed on each of the following two ductile materials： AISI 4340 （high strength low alloy steel, hardened to 49HRc） and Aluminum 2219. Analysis of Variance （ANOVA） was performed on experimental data in order to determine the significance of effects of different parameters on the performance measures. It was found that cutting feed and thickness were highly influential parameters, while abrasive mixing rate is influential upon surface roughness only. Strong interaction was found between jet pressure and workpiece material. Multi-criteria numerical optimization was performed in order to simultaneously maximize/minimize different combinations of performance measures.

Solidification, microstructure, and mechanical properties of the as-cast ZRE1 magnesium alloy with different praseodymium contents

The influence of praseodymium(Pr) content on the solidification characteristics, microstructure, and mechanical properties of ZRE1 magnesium(Mg) cast alloy was investigated. The obtained solidification parameters showed that Pr strongly affected the solidification time, leading to refinement of the microstructure of the alloys. When the freezing time was reduced to approximately 52 s, the grain size decreased by 12%. Mg_(12)Zn(Ce,Pr) was formed as a new phase upon the addition of Pr and was detected via X-ray diffraction analysis. The addition of Pr led to a substantial improvement in mechanical properties, which was attributed to the formation of intermetallic compounds; the ultimate tensile strength and yield strength increased by approximately 10% and 13%, respectively. Pr addition also refined the microstructure, and the hardness was recovered. The results herein demonstrate that the mechanical properties of Mg alloys are strongly influenced by their microstructure characteristics, including the grain size, volume fraction, and distribution of intermetallic phases.

Application of Ceramic Film as Means of Lubrication for Forming of TiSheet in a Highly Localized Deformation Process

Incremental forming is a novel die-less sheet forming process. There is a need for special means to retain lubricant at the tool/sheet interface during forming. To fulfillthe stated aim, a porous ceramic film was developed on pure Ti substrate, and it was done through an electrochemical depsition process known as plasma electrolytic oxidation. The film with preferred pore size could be realized after several attempts by varying the processing parameters. In order to characterize the film, a variety of tests including rnicrostructure, film-substrate bond strength and tribological properties tests were conducted. On-job performance of the film was also examined by forming Ti components employing a range of forming conditions. It was found that the proposed method of lubrication was effective, and the plasma eletrolytic oxidation process can be employed to fabricate films on pure Ti sheet to provide means of lubrication during incremental forming.

Couple stress-based nonlinear primary resonant dynamics of FGM composite truncated conical microshells integrated with magnetostrictive layers

The size-dependent geometrically nonlinear harmonically soft excited oscillation of composite truncated conical microshells(CTCMs)made of functionally graded materials(FGMs)integrated with magnetostrictive layers is analyzed.It is supposed that the FGM CTCMs are subjected to mechanical soft excitations together with external magnetic fields.An analytical framework is created by a microstructuredependent shell model having the 3rd-order distribution of shear deformation based on the modified couple stress(MCS)continuum elasticity.With the aid of the discretized form of differential operators developed via the generalized differential quadrature technique,a numerical solution methodology is introduced for obtaining the couple stress-based amplitude and frequency responses related to the primary resonant dynamics of the FGM CTCMs.Jump phenomena due to the loss of the first stability branch and falling down to the lower stable branch can be seen in the nonlinear primary resonance of the FGM CTCMs.It is demonstrated that the hardening type of nonlinearity results in bending the frequency response to the right side,and the MCS type of size effect weakens this pattern.Moreover,for higher material gradient indexes,the hardening type of nonlinearity is enhanced,and the MCS-based frequency response bends more considerably to the right side.

Nonlinear free vibrations of porous composite microplates incorporating various microstructural-dependent strain gradient tensors

The main objective of the present numerical analysis is to predict the nonlinear frequency ratios associated with the nonlinear free vibration response of porous composite plates at microscale in the presence of different microstructural gradient tensors.To achieve this end,by taking cubic-type elements into account,isogeometric models of porous composite microplates are obtained with and without a central cutout and relevant to various porosity patterns of distribution along the plate thickness.The established unconventional models have the capability to capture the effects of various unconventional gradient tensors continuity on the basis of a refined shear deformable plate formulation.For the simply supported microsized uniform porous functionally graded material(UPFGM)plate having the oscillation amplitude equal to the plate thickness,it is revealed that the rotation gradient tensor causes to reduce the frequency ratio about 0.73%,the dilatation gradient tensor causes to reduce it about 1.93%,and the deviatoric stretch gradient tensor leads to a decrease of it about 5.19%.On the other hand,for the clamped microsized U-PFGM plate having the oscillation amplitude equal to the plate thickness,these percentages are equal to 0.62%,1.64%,and 4.40%,respectively.Accordingly,it is found that by changing the boundary conditions from clamped to simply supported,the effect of microsize on the reduction of frequency ratio decreases a bit.

△_(h)-GOULD-HOPPER APPELL POLYNOMIALS

In this paper,we introduce the △_(h)-Gould-Hopper Appell polynomials An(x,y;h)via h-Gould-Hopper polynomials G_(n)^(h)(x,y).These polynomials reduces to △_(h)-Appell polynomials in the case y=0,△-Appell polynomials in the case y=0 and h=2D-Appell polynomials in the case h→0,2D △-Appell polynomials in the case h=1 and Appell polynomials in the case h→0 and y=0.We obtain some well known main properties and an explicit form,determinant representation,recurrence relation,shift operators,difference equation,integro-difFerence equation and partial difference equation satisfied by them.Determinants satisfied by △_(h)-Gould-Hopper Appell polynomials reduce to determinant of all subclass of the usual polynomials.Recurrence,shift operators and difference equation satisfied by these polynomials reduce to recurrence,shift operators and difference equation of △_(h)-Appell polynomials,△-Appell polynomials;recurrence,shift operators,differential and integro-differential equation of 2D-Appell polynomials,recurrence,shift operators,integrodifference equation of 2D △-Appell polynomials,recurrence,shift operators,differential equation of Appell polynomials in the corresponding cases.In the special cases of the determining functions,we present the explicit forms,determinants,recurrences,difference equations satisfied by the degenerate Gould-Hopper Carlitz Bernoulli polynomials,degenerate Gould-Hopper Carlitz Euler polynomials,degenerate Gould-Hopper Genocchi polynomials,△_(h)-Gould-Hopper Boole polynomials and △_(h)-Gould-Hopper Bernoulli polynomials of the second kind.In particular cases of the degenerate Gould-Hopper Carlitz Bernoulli polynomials,degenerate Gould-Hopper Genocchi polynomials,△_(h)-Gould-Hopper Boole polynomials and △_(h)-Gould-Hopper Bernoulli polynomials of the second kind,corresponding determinants,recurrences,shift operators and difference equations reduce to all subclass of degenerate so-called families except for Genocchi polynomials recurrence,shift operators,and differential equation.Degenerate Gould-Hopper Carlitz Euler polynomials do not satisfy the recurrences and differential equations of 2D-Euler and Euler polynomials.

Identifying Periodical Activities Independent of Video Content

In this research, a completely new and accurate method has been presented for detecting periodic activities with the help of machine vision. The proposed method is independent of motion tracking complex algorithms unlike the previous strategies and it is fully independent of contents and types of activities by performing low level calculation. Not using of heavy computations while improving the ability of periodicity detection is regarded as the unique feature of this method. The use of general and flexible framework in this method causes to facilitate the machine vision periodic activities identification process.

Chaos in Kundt Type-Ⅲ Spacetimes

We consider geodesic motion in a particular Kundt type-Ⅲ spacetime in which the Einstein–Yang–Mills equations admit the solutions.On a particular surface as constraint,we project the geodesics into the(x,y)plane and treat the problem as a two-dimensional one.Our numerical study shows that chaotic behavior emerges under reasonable conditions.