Postponement implementation in integrated production and inventory plan under deterioration effects: a case study of a juice producer with limited storage capacity

Abstract

The aim of this study is to develop a production and inventory plan for a fresh apple juice producer. During harvest season, the producer extracts premium juice from freshly picked apples and keeps an inventory of these premium apples in his temperature-controlled storage facility. The producer extracts also regular juice from regular apples purchased from third-party storages. To satisfy future demand, the producer carries inventories of juice and apple. The levels of apple inventories are constrained by the producer’s limited storage space, but he can replenish regular apples. To assist the producer in facing demand uncertainty and deterioration of apples, we develop a production and inventory plan that incorporates postponement to mitigate demand uncertainty. As postponement decisions are shaped by the cost structure of inventories, we integrate in one model the postponement decisions and the deterioration mitigation decisions that can alter the inventory costs. We build multi-period stochastic programming with recourse model to determine juice batch sizes and apple inventories that maximize the producer’s expected profit. The optimal solution illustrates the use of time and form postponements. We discuss the interactions between postponement implementation and decisions to mitigate apples deterioration. We compare the production and inventory plans with and without postponement and with and without apple deterioration. We also present sensitivity analyses for the plan under varying inventory cost and storage space.     

Welfare gains of the poor: An endogenous Bayesian approach with spatial random effects

We introduce a Bayesian instrumental variable procedure with spatial random effects that handles endogeneity, and spatial dependence with unobserved heterogeneity. We find through a limited Monte Carlo experiment that our proposal works well in terms of point estimates and prediction. We apply our method to analyze the welfare effects generated by a process of electricity tariff unification on the poorest households. In particular, we deduce an Equivalent Variation measure where there is a budget constraint for a two-tiered pricing scheme, and find that 10% of the poorest municipalities attained welfare gains above 2% of their initial income.     

Focused estimation for noisy and small data sets: a Bayesian minimum expected loss estimator approach

Central to many inferential situations is the estimation of rational functions of parameters. The mainstream in statistics and econometrics estimates these quantities based on the plug‐in approach without consideration of the main objective of the inferential situation. We propose the Bayesian Minimum Expected Loss (MELO) approach focusing explicitly on the function of interest, and calculating its frequentist variability. Asymptotic properties of the MELO estimator are similar to the plug‐in approach. Nevertheless, simulation exercises show that our proposal is better in situations characterised by small sample sizes and/or noisy data sets. In addition, we observe in the applications that our approach gives lower standard errors than frequently used alternatives when data sets are not very informative.     

Sexual Dysfunction among Male Patients with Tramadol abuse: A Case-Control Study

Objective: Here we have investigated the association between tramadol abuse and male sexual function. Methods: Eighty-two male tramadol abuse patients and 55 healthy controls (20- to 45-years-old) were included in the study. Data from a sociodemographic questionnaire and the International Index of Erectile Function Questionnaire were collected and analyzed. Results: The tramadol abuse patients were 5 times more likely than their healthy counterparts to have erectile dysfunction. The tramadol abuse patients also had worse scores in the orgasmic, sexual desire, intercourse satisfaction, and overall satisfaction domains compared to the controls. Conclusion: Sexual dysfunctions are common among tramadol abuse patients.     

A generalized binomial exponential 2 distribution: modeling and applications to hydrologic events

Developing statistical methods to model hydrologic events is always interesting for both statisticians and hydrologists, because of its importance in hydraulic structures design and water resource planning. Because of this, a flexible 3-parameter generalization of the exponential distribution is introduced based on the binomial exponential 2 (BE2) distribution [2 H.S. Bakouch, M. Aghababaei Jazi, S. Nadarajah, A. Dolati, and R. Roozegar, A lifetime model with increasing failure rate, Appl. Math. Model. 38 (2014), pp. 5392–5406. doi: 10.1016/j.apm.2014.04.028[Crossref], [Web of Science ®] , [Google Scholar]]. The proposed distribution involving the exponential, gamma and BE2 distributions as submodels; and it exhibits decreasing, increasing and bathtub-shaped hazard rates, so it turns out to be quite flexible for analyzing non-negative real life data. Some statistical properties, parameters estimation and information matrix of the distribution are investigated. The proposed distribution, Gumbel, generalized Logistic and other distributions are utilized to model and fit two hydrologic data sets. The distribution is shown to be more appropriate to the data than the compared distributions using the selection criteria: average scaled absolute error, Akaike information criterion, Bayesian information criterion and Kolmogorov–Smirnov statistics. As a result, some hydrologic parameters of the data are obtained such as return level, conditional mean, mean deviation about the return level and the rth moments of order statistics.     

Social acceleration and the network effect: a defence of social ‘science fiction’ and network determinism

This essay is a response to Judy Wajcman's essay ‘Life in the fast lane? Towards a sociology of technology and time’ (2008: 59–77). In that article Wajcman argued that recent developments in the sociology of temporal change had been marked by a tendency in social theory towards a form of ‘science fiction’– a sociological theorizing, she maintains, that bears no real relation to actual, empirically provable developments in the field and should therefore be viewed as not contributing to ‘a richer analysis of the relationship between technology and time’ (2008: 61). This reply argues that as Wajcman suggests in her essay, there is indeed an ‘urgent need for increased dialogue to connect social theory with detailed empirical studies’ (2008: 59) but that the most fruitful way to proceed would not be through a constraining of ‘science fiction’ social theorizing but, rather, through its expansion – and more, that ‘science fiction’ should take the lead in the process. This essay suggests that the connection between social theory and empirical studies would be strengthened by a wider understanding of the function of knowledge and research in the context of what is termed ‘true originality’ and ‘routine originality’. The former is the domain of social theory and the latter resides within traditional sociological disciplines. It is argued that both need each other to advance our understanding of society, especially in the context of the fast‐changing processes of technological development. The example of ‘technological determinism’ is discussed as illustrative of how ‘routine originality’ can harden into dogma without the application of ‘true originality’ to continually question (sometimes through ideas that may appear to border on ‘science fiction’) comfortable assumptions that may have become ‘routine’ and shorn of their initial ‘originality’.     

Financial development and economic growth: The Egyptian experience

This paper examines the causal relationship between financial development and economic growth in Egypt during the period 1960–2001 within a trivariate vector autoregressive (VAR) framework (investment being the additional variable). We employ four different measures of financial development and apply Granger causality tests using the cointegration and vector error-correction (VEC) methodology. Our results strongly support the view that financial development and economic growth are mutually causal, that is, causality is bi-directional. Furthermore, we find that financial development causes economic growth through both increasing resources for investment and enhancing efficiency. These findings suggest the need to accelerate the financial reforms that the Egyptian government launched in 1991 and to improve the efficiency of the financial system to stimulate saving/investment and, consequently, long-term economic growth.     

Numerical solution of likelihood equations for a first-order response surface model for mixture paired comparisons

Summary A simple procedure for numerical solution of the likelihood equations for estimating the regression parameters of a first-order response surface model for the treatment parameters of mixture paired comparison experiments is developed. It is demonstrated that, for defined rotatable designs, those regression parameters are simple functions of the main effect parameters of a corresponding factorial model with no interactions. The maximum likelihood estimators of those main effect parameters, and hence of their corresponding regression parameters, are obtained through using procedures of treatment contrasts, factorial and iterations. A numerical example is given to illustrate applications of the procedures developed in this paper.