An optimization framework for solving capacitated multi-level lot-sizing problems with backlogging

This paper proposes two new mixed integer programming models for capacitated multi-level lot-sizing problems with backlogging, whose linear programming relaxations provide good lower bounds on the optimal solution value. We show that both of these strong formulations yield the same lower bounds. In addition to these theoretical results, we propose a new, effective optimization framework that achieves high quality solutions in reasonable computational time. Computational results show that the proposed optimization framework is superior to other well-known approaches on several important performance dimensions

Measuring The User Experience And Its Importance To Customer Satisfaction: An Empirical Stusy For Telecom e-Service Websites

In telecom settings, using e-service website has become an increasingly common activity among mobile users. As an important channel, website users experience that quality plays a key role for e-service or business successes. With the use of an online structured questionnaire, a total of 20,040 were surveyed to answer the questions in thirty-one provinces in China. With methods of Principal Component Analysis, a five-factor e-service website user experience questionnaire was examined, and the factors of perceived functional completion, perceived websites performance, quality of interface and interaction, quality of content and information, and quality of online customer support or service were found effectively to measure e-service website user experience quality. In addition, all of these five aspects in e-service website user experience were found to be significant in predicting overall customer satisfaction

Designing Temporal Controls

Traditional control systems have been designed to exercise control at regularly spaced time instants. When a discrete version of the system dynamics is used, a constant sampling interval is assumed and a new control value is calculated and exercised at each time instant. In this paper we formulate a new control scheme, {\it temporal control}, in which we not only calculate the control value but also decide the time instants when the new values are to be used. Taking a discrete, linear, time-invariant system, and a cost function which reflects a cost for computation of the control values, as an example, we show the feasibility of using this scheme. We formulate the temporal control scheme as a feedback scheme and, through a numerical example, demonstrate the significant reduction in cost through the use of temporal control. (Also cross-referenced as UMIACS-TR-95-81

On the equivalence of strong formulations for capacitated multi-level lot sizing problems with setup times

Several mixed integer programming formulations have been proposed for modeling capacitated multi-level lot sizing problems with setup times. These formulations include the so-called facility location formulation, the shortest route formulation, and the inventory and lot sizing formulation with (l,S) inequalities. In this paper, we demonstrate the equivalence of these formulations when the integrality requirement is relaxed for any subset of binary setup decision variables. This equivalence has significant implications for decomposition-based methods since same optimal solution values are obtained no matter which formulation is used. In particular, we discuss the relax-and-fix method, a decomposition-based heuristic used for the efficient solution of hard lot sizing problems. Computational tests allow us to compare the effectiveness of different formulations using benchmark problems. The choice of formulation directly affects the required computational effort, and our results therefore provide guidelines on choosing an effective formulation during the development of heuristic-based solution procedures

Mixed integer programming in production planning with backlogging and setup carryover : modeling and algorithms

This paper proposes a mixed integer programming formulation for modeling the capacitated multi-level lot sizing problem with both backlogging and setup carryover. Based on the model formulation, a progressive time-oriented decomposition heuristic framework is then proposed, where improvement and construction heuristics are effectively combined, therefore efficiently avoiding the weaknesses associated with the one-time decisions made by other classical time-oriented decomposition algorithms. Computational results show that the proposed optimization framework provides competitive solutions within a reasonable time

17th IEEE Real-Time Systems Symposium: Work in Progress Sessions

The Table of Contents for the workshop is contained in 1996-027-00main.pdfDear Colleagues: This year marks the beginning of a new tradition within the Real-Time Systems Symposium, that of holding special sessions for the presentation of new and on-going projects in real-time systems. The prime purpose of these Work In Progress (WIP) sessions is to provide researchers in Academia and Industry an opportunity to discuss their evolving ideas and gather feedback thereon from the real-time community at large. The idea of holding these sessions is timely, and I am pleased to report that this year RTSS'96 WIP received 22 submissions, of which 14 have been accepted for presentation during the symposium and for inclusion in RTSS'96 WIP proceedings. Many people worked hard to make the idea of holding the WIP sessions a reality. In particular, I would like to thank Sang Son for his hard work in accommodating the WIP sessions within the busy schedule of RTSS'96. Also, I would like to thank all members of the RTSS'96 Program Committee, Al Mok and Doug Locke in particular, for their encouragement and constructive feedback regarding the organization of these sessions. Finally, I would like to thank all those who submitted their work to RTSS'96 WIP and those from RTSS'96 program committee who helped review these submissions. I hope these sessions will prove beneficial, both to the WIP presenters and to RTSS'96 attendees. Azer Bestavros RTSS'96 WIP Chair December 1996.IEEE-CS TC-RT

Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition)

In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. For example, a key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process versus those that measure fl ux through the autophagy pathway (i.e., the complete process including the amount and rate of cargo sequestered and degraded). In particular, a block in macroautophagy that results in autophagosome accumulation must be differentiated from stimuli that increase autophagic activity, defi ned as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (inmost higher eukaryotes and some protists such as Dictyostelium ) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the fi eld understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. It is worth emphasizing here that lysosomal digestion is a stage of autophagy and evaluating its competence is a crucial part of the evaluation of autophagic flux, or complete autophagy. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. Along these lines, because of the potential for pleiotropic effects due to blocking autophagy through genetic manipulation it is imperative to delete or knock down more than one autophagy-related gene. In addition, some individual Atg proteins, or groups of proteins, are involved in other cellular pathways so not all Atg proteins can be used as a specific marker for an autophagic process. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field

Discontinuous perturbation analysis of discrete-event dynamic systems

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Hybrid Equipartitioning Job Scheduling Policies for Parallel Computer Systems

We propose a new family of job scheduling policies for parallel computer systems that can be optimized to adapt to changes in the workload. Simulation optimization is used to reveal important properties of optimal job scheduling policies. For this optimization a new approach is suggested that combines two recent stochastic optimization methods: the nested partitions method and ordinal optimization. 1 Introduction Parallel computer systems are discrete event dynamic systems (DEDS) that, in recent years, have been increasingly used to solve problems that are intractable on conventional sequential systems. An integral part of realizing the full benefits of such parallel systems is the availability of a job scheduler that can efficiently allocate the available resources under a diverse workload. When seeking the optimal job scheduling policy two approaches may be adapted. The first is that of comparing different scheduling policies over a limited range of workload conditions and selecting..