Sharif Digital Repository

This paper addresses the multiple allocation hub set-covering problem considering backup coverage and mandatory dispersion of hubs. In the context of this paper, it has been assumed that a flow is covered if there are at least Q possible routes to satisfy its demand within a time bound. Moreover, there is a lower limit for the distance between hubs in order to provide a degree of dispersion in the solution. Mathematical formulation of this problem is given, which has O( n2) variables and constraints. Computational experiments carried out on the well-known CAB dataset give useful insights concerning model behavior and its sensitivity to parameters  

The maximal covering location problem (MCLP) is a challenging problem with numerous applications in practice. Previous publications in the area of MCLP proposed models and presented solution methodologies to solve this problem with up to 900 nodes. Due to the fact that in real-life applications, the number of nodes could be much higher, this paper presents a customized Genetic Algorithm (GA) to solve MCLP instances, with up to 2500 nodes. Results show that the proposed approach is capable of solving problems with a fair amount of exactness. In order to fine-tune the algorithm, Tukey's Least Significant Difference (LSD) tests are employed on a set of test problems  

A Hub Location Problem (HLP) deals with finding the locations of hub facilities and assignment of demand nodes to established facilities. Hubs play a central role in many networks such as telecommunication networks and their unavailability may lead to network breakdown or poor service levels. An objective in design of a hub-and-spoke network is maximization of reliability to transfer flows. This paper puts forward design of a reliable single-allocation hub-and-spoke network using an interactive fuzzy goal programming. To model and solve the problem, a fuzzy goal programming approach was developed for design of network in an interactive manner between decision maker and the model. To validate... 

Most of the publications regarding the maxim covering location problem (MCLP) address the case where the decision is to be made for one period. In this paper, we deal with a rather untouched version of MCLP which is called dynamic MCLP (DMCLP). In order to solve this problem, a simulated annealing (SA) has been presented. The proposed solution algorithm is capable of solving problems with up to 2500 demand nodes and 200 potential facilities with a fair amount of exactness. Our experiments showed that the proposed approach finds solutions with errors less than one percent  

In the framework of a household’s collective decision processes, this study presents a structural empirical model to test the hypothesis that child labour is compelled by household’s poverty and parent’s bargaining power against one another. To this end, a measure for mother’s intra-household bargaining power is developed. I use Iranian Household’s Income and Expenditures Surveys (2005 and 2010). Estimation method used in this study is multinomial logit. Findings indicate that household’s poverty is not the sole cause of child’s work incidence. Instead, given the other factors such as poverty, being the first born, local labour market prospect and gender fixed, mother’s bargaining power is... 

Muscle fatigue affects the underlying EMG-force relationship on which EMG-assisted biomechanical models rely. The aim of this study was to evaluate the impact of short duration muscle fatigue on the muscle gain value. Participants performed controlled, isometric trunk extension exertions at 10, 20, and 30 degrees of trunk flexion and controlled isokinetic trunk extension exertions at 5 and 15°/sec on five separate days. Fatigue of the lumbar extensors was generated by moderate-intensity, trunk extension exertions. Participants performed controlled test contractions at defined intervals throughout the fatiguing bout and the EMG activities of trunk muscles were collected. These EMG data were... 

This paper provides an empirical investigation on the individual labor supply of Iranian spouses in an intra-household collective decision framework in which gender ratio and divorce rate play a central role for resource allocation of household. The dataset is taken from the Households’ Expenditures Survey (2008) and the Annual Statistical Yearbook (2008) of Iran. I have conducted the parameters estimation and hypothesis testing using switching regression technique to catch the presence of the widespread non-participation of spouses across Iranian households. Reduced forms of labor supply are estimated considering the endogeneity of wage rates. The findings show that the unitary model of... 

Purpose: The purpose of this paper is to estimate the wage difference between overeducated and adequately educated workers in a sample of semi-skilled and low-skill occupations in Iran’s labor market. The objective is to see if overeducated employees in these occupations enjoy higher wages in comparison to their adequately educated co-workers. Design/methodology/approach: The authors use the propensity score matching (PSM) model to estimate the wage difference between overeducated and adequately educated workers in a sample of semi-skilled and low-skill occupations in Iran’s labor market. The PSM method allows the authors to prevent selection bias by comparing each group of overeducated... 

Circuit breakers, like price limits and trading suspensions, are used to reduce price volatility in security markets. When returns hit price limits or missed, observed returns deviate from equilibrium returns. This creates a challenge for predicting stock returns and modelling value at risk (VaR). In Tehran Stock Exchange (TSE), the circuit breakers are applied to control for the excess price volatilities. This paper intend to address which models and what methodology should be applied by risk analysts to calculate the VaR when the returns are unobservable. To this end, we extend Wei’s (2002) model, in the framework of Bayesian Censored and Missing-GARCH approach, to estimate VaR for a share... 

The recent researches show that value-at-risk (VaR) estimations are biased and is calculated conservatively. Bao and Ullah (2004) proved the bias of an ARCH(1) model for VaR can be decomposed in to two parts: bias due to the returns' misspecification distributional assumption for GARCH(1,1), i.e., (Bias1) and bias due to estimation error, i.e., (Bias2). Using quasi maximum likelihood estimation method this paper intends to find an analytical framework for the two sources of bias. We generate returns from Normal and t-student distributions, then estimate the GARCH(1,1) under Normal and t-student assumptions. Our findings reveal that Bias1 equals to zero for the Normal likelihood function, but... 

Market practitioners and speculators attempt to make benefits from the existence of market price gaps and profit opportunities by arbitrage strategies. Although some investors trade stocks based on the available financial and fundamental information of a particular share, there are others who make profits by risk hedging and swing trading opportunities. One of these strategies is pairs trading, which is a sub-category of statistical arbitrage. Pairs trading can assure reasonably a risk-free profit gaining. This paper aims to make a hypothetical portfolio composed of pairs of stocks by exploring a significant association between their prices in the Toronto Stock Exchange, TSX. We compare the... 

Market practitioners and speculators attempt to make benefits from the existence of market price gaps and profit opportunities by arbitrage strategies. Although some investors trade stocks based on the available financial and fundamental information of a particular share, there are others who make profits by risk hedging and swing trading opportunities. One of these strategies is pairs trading, which is a sub-category of statistical arbitrage. Pairs trading can assure reasonably a risk-free profit gaining. This paper aims to make a hypothetical portfolio composed of pairs of stocks by exploring a significant association between their prices in the Toronto Stock Exchange, TSX. We compare the... 

The raising trend both in violent and property crime are of major concern in Iran. Using a panel data modeling (province wide), the paper provides an econometrics assessment of the relationship between crime against properties and violent crimes as functions of deterrent, social, economic and demographic factors in Iran, in the framework of Becker-Ehrlich crime supply theory. The findings indicate that, although deterrence hypothesis is not confirmed for burglary and assault, it explains the variations of murders and threats. Economic factors play key role in burglary and threat explanation, but they do not affect willful murders, however, Literacy explains both murders and threats. Average... 

This paper aims to estimate a demand model for health insurance and medical care in Iran, in the presence of heterogeneous and latent health status of individuals; moreover it tests the asymmetry of information in the health insurance market. Our data set have been taken from the Households expenditures survey (2006) of Iran. Parameters of the model are estimated by the Generalized Method of Moments (GMM) and the presence of asymmetric information (adverse selection and moral hazard) is tested by a non-parametric econometric method. The analytical model is specified under minimal assumptions on the selection process of different insurance categories and the statistical distribution of...