Yogesh Gupta, P.S. Sundararaghavan and Mesbah U. Ahmed
This paper deals with finding economic order quantity, number of orders to be placed and/or the time to place each order for four different special types of problems that may be…
Abstract
This paper deals with finding economic order quantity, number of orders to be placed and/or the time to place each order for four different special types of problems that may be encountered in practice. The first problem (Problem 1a) assumes a fixed planning horizon and a perishable product such as Christmas trees or fashion merchandise whose value deteriorates as the item gets aged. Under constant demand assumption, solution for this type of problem is worked out by capturing the deterioration in value by increasing holding cost. The second problem (Problem 2) has the same assumption as the first, except that the demand is assumed to increase as we move forward in time. The third problem (Problem 2a) is a restricted version of the second, which allows a specific number of integer orders during the planning horizon. The fourth problem (Problem 3) allows the ordering cost to increase as time progresses. All formulae derived can be easily applied to find numerical answers. The answers may have to be adjusted to reflect container size, minimum order quantity and any other restriction not modeled, or to take into account any violation of the model assumptions.
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Mesbah Fathy Sharaf and Ahmed Shoukry Rashad
This study aims to analyze whether precarious employment is associated with youth mental health, self-rated health and happiness in marriage and whether this association differs…
Abstract
Purpose
This study aims to analyze whether precarious employment is associated with youth mental health, self-rated health and happiness in marriage and whether this association differs by sex.
Design/methodology/approach
This paper uses longitudinal data from the Survey of Young People in Egypt conducted in 2009 and 2014 and estimates a fixed-effects model to control for time-invariant unobserved individual heterogeneity. The analysis is segregated by sex.
Findings
The results indicate that precarious employment is significantly associated with poor mental health and less happiness in marriage for males and is positively associated with poor self-reported health for females. The adverse impact of precarious work is likely to be mediated through poor working conditions such as low salary, maltreatment at work, job insecurity and harassment from colleagues.
Social implications
Governmental policies that tackle job precariousness are expected to improve population health and marital welfare.
Originality/value
Egypt has witnessed a significant increase in the prevalence of precarious employment, particularly among youth, in recent decades, yet the evidence on its effect on the health and well-being of youth workers is sparse. This paper adds to the extant literature by providing new evidence on the social and health repercussions of job precariousness from an understudied region.
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Mesbah Fathy Sharaf and Abdelhalem Mahmoud Shahen
This study aims to examine the symmetric and asymmetric impact of external debt on inflation in Sudan from 1970 to 2020 within a multivariate framework by including money supply…
Abstract
Purpose
This study aims to examine the symmetric and asymmetric impact of external debt on inflation in Sudan from 1970 to 2020 within a multivariate framework by including money supply and the nominal effective exchange rate as additional inflation determinants.
Design/methodology/approach
The authors utilize an Auto Regressive Distributed Lag (ARDL) model to examine the symmetric impact of external debt on inflation, while the asymmetric impact is examined using a Nonlinear ARDL (NARDL) model. The existence of a long-run relationship between inflation and external debt is tested using the bounds-testing approach to cointegration, and a vector error-correction model is estimated to determine the short parameters of equilibrium dynamics.
Findings
The linear ARDL model results show that external debt has no statistically significant impact on inflation in the long run. On the contrary, the results of the NARDL model show that positive and negative external debt shocks statistically affect inflation in the long run. The estimated long-run elasticity coefficients of the linear and nonlinear ARDL models reveal that the domestic money supply has a statistically significant positive impact on inflation. In contrast, the nominal effective exchange rate has a statistically significant negative impact on inflation.
Practical implications
The reliance on symmetric analysis may not be sufficient to uncover the existence of a linkage between external debt and inflation. Proper external debt management is crucial to control inflation rates in Sudan.
Originality/value
To date, no empirical study has assessed the external debt-inflation nexus and its potential asymmetry in Sudan, and the current study aims to fill this gap in the literature.
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The purpose of this paper is to present numerical simulations for magnetohydrodynamics natural convection of a nanofluid flow inside a cavity with an H-shaped obstacle based on…
Abstract
Purpose
The purpose of this paper is to present numerical simulations for magnetohydrodynamics natural convection of a nanofluid flow inside a cavity with an H-shaped obstacle based on combining artificial neural network (ANN) with the finite element method (FEM), and predict the heat transfer rate and system entropy.
Design/methodology/approach
The enclosure is assumed to be inclined. Changing the inclination angle results in a different obstacle shape, which affects the buoyancy force. Hence, different configurations of the contours of the fluid flow, isotherms and the entropy of the system are obtained. The outer walls of the cavity as well as the central part of the obstacle are kept adiabatic. The left vertical portion of the hindrance is cooled, whereas the right vertical part of the obstacle is a heated wall. Using dimensionless variables allows obtaining a dimensionless version of the governing system of equations that is solved via the consistency FEM. The coupled problem of pressure and velocity is overcome via the Increment Pressure Correction Scheme, which is known for its accuracy and stability for similar simple problems. A numerical computation is performed across a broad range of the governing parameters. A total of 304 data sets were used in the development of an ANN model. That data set was conducted from the numerical simulations. The data set underwent optimization, with 70% sets used for training the model, 15% for validation and another 15% for the testing phase. The training of the network model used the Levenberg–Marquardt training algorithm.
Findings
From the numerical simulations, it is concluded that the H-shaped obstacle boosts heat transfer rate in comparison with the I-shaped case. Also, raising the value of the inclination angle improves the entropy of the system presented by the Bejen number. Furthermore, strength heat transfer rate is obtained via decreasing the Hartmann number while this decrease decays the values of the Bejen number for both positive and negative amounts of the nonlinear Boussinesq parameter. Slower velocity and a better heat transfer rate characterize nanofluid compared with pure fluid. Leveraging the capabilities of the ANN, the developed model adeptly forecasts the values of both the average Nusselt and Bejen numbers with a high degree of accuracy.
Originality/value
A novel fusion of FEM and ANN has been tailored to forecast the heat transfer rate and system entropy of MHD natural convective flow within an inclined cavity containing an H-shaped obstacle, amid various physical influences.
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Mohamed Dhia Massoudi, Mohamed Bechir Ben Hamida, Mohammed A. Almeshaal, Yahya Ali Rothan and Khalil Hajlaoui
The purpose of this paper is to examine numerically the magnetohydrodynamic (MHD) free convection and thermal radiation heat transfer of single walled carbon nanotubes-water…
Abstract
Purpose
The purpose of this paper is to examine numerically the magnetohydrodynamic (MHD) free convection and thermal radiation heat transfer of single walled carbon nanotubes-water nanofluid within T-inverted shaped corrugated cavity comprising porous media including uniform heat source/sink for solar energy power plants applications.
Design/methodology/approach
The two-dimensional numerical simulation is performed by drawing on Comsol Multiphysics program, based on the finite element process.
Findings
The important results obtained show that increasing numbers of Rayleigh and Darcy and the parameter of radiation enhance the flow of convection heat. Furthermore, by increasing the corrugation height, the convection flow increases, but it decreases with the multiplication of the corrugation height. The use of a flat cavity provides better output than a corrugated cavity.
Originality/value
The role of surface corrugation parameters on the efficiency of free convection and heat transfer of thermal radiation within the porous media containing the T-inverted corrugated cavity including uniform heat source/sink under the impact of Lorentz forces has never been explored. A contrast is also established between a flat cavity and a corrugated one.
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Alireza Rahimi, Hesam Bakhshi, Ali Dehghan Saee, Abbas Kasaeipoor and Emad Hasani Malekshah
The study aims to study the nanofluid flow and heat transfer in a T-shaped heat exchanger. For the numerical simulations, the lattice Boltzmann method is used.
Abstract
Purpose
The study aims to study the nanofluid flow and heat transfer in a T-shaped heat exchanger. For the numerical simulations, the lattice Boltzmann method is used.
Design/methodology/approach
The end of each branch of the heat exchanger is considered a curve wall that requires special thermal and physical boundary conditions. To improve the thermal performance of the heat exchanger, the CuO–water nanofluid, which has better heat transfer performance with respect to pure water, is used. The dynamic viscosity of nanofluid is estimated by means of KKL model. Several active fins and solid bodies are implanted within the heat exchanger with different thermal arrangements.
Findings
In the present work, different approaches such as heatline visualization, local and total entropy generation analysis, local and total Nusselt variation are used to detect the impact of different considered parameters such as Rayleigh number (103 < Ra < 106), solid volume fraction of nanofluid (φ = 0,0.01,0.02,0.03 and 0.04 vol. per cent) and thermal arrangements of internal bodies (Case A, Case B, Case C and Case D) on the fluid flow and heat transfer performance.
Originality/value
The originality of this work is to analyze the two-dimensional natural convection and entropy generation using lattice Boltzmann method.
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Mahmoud Salari, Emad Hasani Malekshah, Mohammad Reza Sarlak, Masoud Hasani Malekshah and Mohammad Pilfoush
The purpose of this paper is to investigate the three-dimensional natural convection and entropy generation in a cuboid enclosure filled with two immiscible fluids of nanofluid…
Abstract
Purpose
The purpose of this paper is to investigate the three-dimensional natural convection and entropy generation in a cuboid enclosure filled with two immiscible fluids of nanofluid and air.
Design/methodology/approach
One surface of the enclosure is jagged and another one is smooth. The finite volume approach is applied for computation. There are two partially side heaters. Furthermore, the Navier–Stokes equations and entropy generation formulation are solved in the 3D form.
Findings
The effects of different governing parameters, such as the jagged surface (JR=0, 0.02, 0.04, 0.08, 0.12 and 0.16), Rayleigh number (103⩽Ra⩽106) and solid volume fraction of nanofluid (φ=1, 1.5, 2 vol%), on the fluid flow, temperature field, Nusselt number, volumetric entropy generation and Bejan number are presented, comprehensively. The results indicate that the average Nusselt number increases with the increase in the Rayleigh number and solid volume fraction of nanofluid. Moreover, the flow structure is significantly affected by the jagged surface.
Originality/value
The originality of this work is to analyze the natural-convection fluid flow and heat transfer under the influence of jagged surfaces of electrodes in high-current lead–acid batteries.
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Jia-Bao Liu, Morteza Bayati, Mazhar Abbas, Alireza Rahimi and Mohammad Naderi
The lattice Boltzmann method is used to simulate the nanofluid flow and heat transfer inside a finned multi-pipe heat exchanger.
Abstract
Purpose
The lattice Boltzmann method is used to simulate the nanofluid flow and heat transfer inside a finned multi-pipe heat exchanger.
Design/methodology/approach
The heat exchanger is filled with CuO-water nanofluid. The Koo–Kleinstreuer–Li (KKL) model is used to estimate the dynamic viscosity and considering the Brownian motion in the simulation. On the other hand, the influence of nanoparticles’ shapes on the heat transfer rate is considered, and the best efficient shape is selected to be used in the investigation.
Findings
The Rayleigh number, nanoparticle concentration and the thermal arrangements of internal active fins and bodies are the governing parameters. In addition, the impacts of these two parameters on the nanofluid flow, heat transfer rate, local and total entropy generation and heatline visualization are analyzed, comprehensively.
Originality/value
The originality of this work is using of lattice Boltzmann method for simulation of nanofluid flow and heat transfer during natural convection in a heat exchanger. Furthermore, influence of the shape of nanoparticles on the thermo-physical properties of nanofluid is analyzed using Koo–Kleinstreuer–Li correlation.
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Emad Hasani Malekshah and Lioua Kolsi
The purpose of this study is the hydrothermal analysis of the natural convection phenomenon within the heat exchanger containing nanofluids using the lattice Boltzmann method…
Abstract
Purpose
The purpose of this study is the hydrothermal analysis of the natural convection phenomenon within the heat exchanger containing nanofluids using the lattice Boltzmann method (LBM).
Design/methodology/approach
The thermal conductivity as well as dynamic viscosity of the CuO–water nanofluid is estimated using the Koo-Kleinstreuer-Li model. The LBM has been used with unique modifications to make it flexible with the curved boundaries. The local as well as total entropy generation assessment, local Nusselt variation, as well as heatline visualization are used.
Findings
The solid volume percentage of the CuO–water nanofluid, a range of Rayleigh numbers (Ra) and thermal settings of internal operational fins and bodies are all factors that have been thoroughly researched to determine their effects on entropy production, heat transfer efficiency and nanofluid flow.
Originality/value
The originality of this work is using a novel numerical method (i.e. curved boundary LBM) as well as the local/volumetric second law analysis for the application of heat exchanger hydrothermal analysis.
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Loretta Bortey, David J. Edwards, Chris Roberts and Iain Rillie
Safety research has focused on drivers, pedestrians and vehicles, with scarce attention given to highway traffic officers (HTOs). This paper develops a robust prediction model…
Abstract
Purpose
Safety research has focused on drivers, pedestrians and vehicles, with scarce attention given to highway traffic officers (HTOs). This paper develops a robust prediction model which enables highway safety authorities to predict exclusive incidents occurring on the highway such as incursions and environmental hazards, respond effectively to diverse safety risk incident scenarios and aid in timely safety precautions to minimise HTO incidents.
Design/methodology/approach
Using data from a highway incident database, a supervised machine learning method that employs three algorithms [namely Support Vector Machine (SVM), Random Forests (RF) and Naïve Bayes (NB)] was applied, and their performances were comparatively analysed. Three data balancing algorithms were also applied to handle the class imbalance challenge. A five-phase sequential method, which includes (1) data collection, (2) data pre-processing, (3) model selection, (4) data balancing and (5) model evaluation, was implemented.
Findings
The findings indicate that SVM with a polynomial kernel combined with the Synthetic Minority Over-sampling Technique (SMOTE) algorithm is the best model to predict the various incidents, and the Random Under-sampling (RU) algorithm was the most inefficient in improving model accuracy. Weather/visibility, age range and location were the most significant factors in predicting highway incidents.
Originality/value
This is the first study to develop a prediction model for HTOs and utilise an incident database solely dedicated to HTOs to forecast various incident outcomes in highway operations. The prediction model will provide evidence-based information to safety officers to train HTOs on impending risks predicted by the model thereby equipping workers with resilient shocks such as awareness, anticipation and flexibility.