The optimal number of suppliers considering the costs of individual supplier failures

This paper utilizes the decision tree approach to determine the optimal number of suppliers in the presence of supplier failure risks. Previous proposed models have considered only two states of nature: all suppliers fail to deliver and not all suppliers fail to deliver. In practice, however, there is clearly a partial loss associated with the failure of any individual supplier. We present models that allow a more realistic decision-making process by taking into consideration the independent risks of individual supplier failures when the probability of failure for each of the suppliers is equal as well as the case where the probability of failure from each of the suppliers is not equal. We also consider various levels of supplier failure probability and possible procurement or operating cost savings gained from using less reliable suppliers. The results indicate that when suppliers are highly reliable, sole sourcing is the lowest cost approach under all experimental conditions. However, as the suppliers become less reliable, additional suppliers may be required to obtain the lowest cost. Finally, it was shown that only in the extreme conditions of unreliable suppliers, high loss to operational cost per supplier, and low ability to mitigate the failure from a partial set of suppliers, having a large number of suppliers is an effective strategy.     

Approximate sorting of data streams with limited storage

We consider the problem of approximate sorting of a data stream (in one pass) with limited internal storage where the goal is not to rearrange data but to output a permutation that reflects the ordering of the elements of the data stream as closely as possible. Our main objective is to study the relationship between the quality of the sorting and the amount of available storage. To measure quality, we use permutation distortion metrics, namely the Kendall tau, Chebyshev, and weighted Kendall metrics, as well as mutual information, between the output permutation and the true ordering of data elements. We provide bounds on the performance of algorithms with limited storage and present a simple algorithm that asymptotically requires a constant factor as much storage as an optimal algorithm in terms of mutual information and average Kendall tau distortion. We also study the case in which only information about the most recent elements of the stream is available. This setting has applications to learning user preference rankings in services such as Netflix, where items are presented to the user one at a time.     

Non-mixture cure correlated frailty models in Bayesian approach

In this article, we develop a Bayesian approach for the estimation of two cure correlated frailty models that have been extended to the cure frailty models introduced by Yin [34]. We used the two different type of frailty with bivariate log-normal distribution instead of gamma distribution. A likelihood function was constructed based on a piecewise exponential distribution function. The model parameters were estimated by the Markov chain Monte Carlo method. The comparison of models is based on the Cox correlated frailty model with log-normal distribution. A real data set of bilateral corneal graft rejection was used to compare these models. The results of this data, based on deviance information criteria, showed the advantage of the proposed models.     

Tandem Configuration Automated Guided Vehicle Systems: A Comparative Study*

Automated guided vehicle (AGV) systems provide the flexibility and integration required for flexible manufacturing systems. Previous AGV system studies have attempted to reduce the controlling complexities commonly encountered in these systems. However, this has not been accomplished without additional resources (e.g., automated guided vehicles) and lower system flexibility. The primary objective of this study is to compare the performance of AGV system configurations that reduce controlling and modification complexities (i.e., tandem configurations) to traditional AGV system configuration. Three AGV system configurations were tested under 16 experimental conditions. Performance metrics considered were AGV utilization, mean flowtime, mean tardiness, and percent tardy. The results of this study extend the findings of the previous studies in demonstrating the viability of tandem configurations, in that the tandem configurations match the performance of traditional configuration across all performance metrics, without sacrificing ease of control and system flexibility. Finally, the cost tradeoffs inherent in selecting a particular configuration are discussed.     

Variable selection in finite mixture of semi-parametric regression models

Abstract

In this paper we are concerned with variable selection in finite mixture of semiparametric regression models. This task consists of model selection for non parametric component and variable selection for parametric part. Thus, we encountered separate model selections for every non parametric component of each sub model. To overcome this computational burden, we introduced a class of variable selection procedures for finite mixture of semiparametric regression models using penalized approach for variable selection. It is shown that the new method is consistent for variable selection. Simulations show that the performance of proposed method is good, and it consequently improves pervious works in this area and also requires much less computing power than existing methods.     

Life here beyond now: Chronotopes of the ideal life among Iranian transnationals

I address how U.S.‐based Iranian transnationals’ migration paths affect their (re)‐construction of chronotopes of the ideal life. Adopting an ethnographically grounded, discourse‐analytic approach, I illustrate how participants with student visas and U.S. Green Cards position themselves differently relative to images of success here [in the U.S.] and lack of success there [in Iran]. I argue that the chronotopes of success here and lack of success there (re)‐constructed by non‐resident Iranian students are prompted by a large‐scale cultural chronotope which pertains to their aspiration to stay in the U.S. This chronotope of ‘life beyond’ is less about a ‘remove from homeland’ and more about an ideal future in the host country. Migrants’ desires and anxieties, I argue, can determine what receives topical prominence in migration chronotopes – as in the case of Iranian educational migrants whose future positionings make temporality topically more prominent than spatiality.

     

Estimating total and specific process capability indices in three-stage processes with measurement errors

In multistage processes, two kinds of process capability indices (specific and total process capability indices) are defined in each stage. The total process capability index calculates the capability of each stage when it is affected by the previous stages and the specific process capability index calculates the capability of the stage when the effects of the previous stages are eliminated. Process capability indices in multistage processes are proposed under the assumption of no measurement errors. However, sometimes this assumption may be violated and leads to misleading interpretations. In this paper, the effects of measurement errors on the specific and total process capability indices in the second and third stages of the three-stage processes are statistically analysed. In addition, the effects of the measurement errors on the bias and the mean square error value of the total and specific process capability indices in the second and third stages are studied. Finally, the effects of the measurement errors on the specific and total process capability indices are shown through a numerical example.     

Nonverbal communication of pharmacists during counseling leading to patient satisfaction: evidence from Iranian retail market

The purpose of this study was to investigate the impact of nonverbal communication of community pharmacists on patients’ satisfaction throughout the counseling process. Eight dimensions of nonverbal communication have been taken into account: vocalics, kinesics, proxemics, haptics, oculesics, olfactics, chronemics, and atmospherics. To gather data relevant to the aim of this study, a survey was conducted among the pharmacies in the city of Tehran (Iran). A questionnaire was offered to patients waiting to receive their medicine asking them about the nonverbal communication of the pharmacists and the degree of their satisfaction of service encounters. Proposed hypotheses were tested with a structural equation modeling approach using the Smart PLS software package. The results strongly support the theoretical model and suggest that there is a significant correlation between all components of nonverbal communication (excluding proxemics and haptics) and consumers’ satisfaction. The originality of this article is that it is the first empirical research to evaluate all aspects of the nonverbal cues of pharmacists and their effects on patient satisfaction. Considering the relatively high growth rate of the Iran retail market, this study has profound implications for academia and the practice of pharmacy.     

Inference of R=P[X<Y] for generalized logistic distribution

This paper deals with the estimation of R=P[X<Y] when X and Y come from two independent generalized logistic distributions with different parameters. The maximum-likelihood estimator (MLE) and its asymptotic distribution are proposed. The asymptotic distribution is used to construct an asymptotic confidence interval of R. Assuming that the common scale parameter is known, the MLE, uniformly minimum variance unbiased estimator, Bayes estimation and confidence interval of R are obtained. The MLE of R, asymptotic distribution of R in the general case, is also discussed. Monte Carlo simulations are performed to compare the different proposed methods. Analysis of a real data set has also been presented for illustrative purposes.