Performance evaluation of a transportation-type bulk queue with generally distributed inter-arrival times

This paper is motivated by the performance evaluation of circulating vertical conveyor systems (CVCSs). CVCSs are bulk queues of transportation type. These material handling systems feature generally distributed inter-arrival times, which can be longer than the bulk service time. This leads to interdependencies between the number of arrivals in consecutive service intervals and the number of loads in the queue. We propose a new discrete-time approach for the steady-state analysis of such bulk service queues of transportation type with general arrival and service processes and finite server and limited queue capacities. The approach is based on a finite Markov chain that generates complete probability distributions for the key performance measures, including the queue length, waiting time and departing batch size. The proposed approach is exact in the cases of discrete-time slots, e.g. as in communication systems. We investigate the discretisation error that arises if the approach is used as an approximation for the continuous time using a numerical comparison to a discrete-event simulation. Moreover, we examine the impact of arrival stream variability on the system performance and compare the positive effects of a higher frequency of server visits with the effects arising from larger pickup capacities.     

Industrial aspects and literature survey: Fleet composition and routing

The purpose of this paper is to describe industrial aspects of combined fleet composition and routing in maritime and road-based transportation, and to present the current status of research in the form of a comprehensive literature review. First, presents a classification of problems, and then focuses on a basic definition of combined fleet composition and routing: the fleet size and mix vehicle routing problem. A basic mathematical formulation from the literature is presented. Further, the literature of extended and related problems is described and categorized. Surveys of application oriented research in road-based and maritime transportation conclude the review. Finally, we contrast the literature with aspects of industrial applications from a critical, but constructive stance. Major issues for future work are suggested.     

Composite beam–columns with interlayer slip—Approximate analysis

An approximate second order analysis procedure for composite beam–columns with interlayer slip subjected to transverse loading and axial compressive loads is developed. The magnification factors to be applied to the first order solutions in order to estimate the deflections and internal forces obtained by the second order analysis approach are presented. The method of applying magnification factors to internal axial forces is discussed. The approximate second order analysis procedure is developed for the four Euler cases with various transverse load conditions. The procedure is applied to and the accuracy is illustrated for simply supported partially beam–columns of steel and concrete, and timber and concrete with different bending stiffness and interlayer slip properties. The deflections and internal forces obtained by the approximate method compared extremely well, except for slip forces in case of very flexible shear connectors, with those obtained by the more rigorous second order analysis approach for different composite action (partial interaction) parameters (shear connector stiffness values). The study also shows that the magnification factor associated with the deflections can be utilized to estimate also the internal actions, except shear forces in case of very flexible shear connectors, in the second order case with minimal error for simply supported beam–columns. Thus, for members with shear connector stiffness of structural significance the proposed approximate method can be used in general for simply supported beam–columns. For other boundary and loading conditions, the approximate method needs to be re-evaluated. The approach of using one magnification factor greatly simplifies the analysis task for those components.     

Orienting and schizophrenia: Stimulus significance, attention, and distraction in a signaled reaction time task.

Tested the hypothesis that poor performance among schizophrenics (SCZs) is associated with less orienting to task-relevant stimuli and more orienting to task-irrelevant stimuli, interpreting the orienting response as a call for controlled processing resources. 32 SCZs (aged 20–65 yrs) and 32 age- and sex-matched controls were exposed to a signaled reaction time (RT) task in which one tone was followed by an imperative noise stimulus and a different tone signaled nothing. During one phase of the experiment, distracting visual stimuli were presented both between and during RT trials. Controls differentiated between the signal and nonsignal tones in all measures and showed rapid habituation to the distracting visual stimuli. The SCZs showed slow RTs, less overall responding than controls, and limited differential responses to signal and nonsignal stimuli. For the responses to visual distractors, however, the SCZs showed significantly slower habituation than the controls, confirming their inefficient orienting style. (38 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Zerstörungsfreie Bestimmung elastischer Eigenschaften quadratischer 3-schichtiger Brettsperrholzplatten mit symmetrischem Aufbau

Some of the most important material properties of engineered wood products, like cross-laminated solid wood panels, are the elastic properties. Regarding panels, the two in plane MOEs (E_ii) and three shear moduli (G_ij) are of particular interest. In order to determine these parameters with an economically and non-destructive technique, a method was developed which allows to determine all five parameters in one experiment only. This method was approved on 24 square-shaped cross-laminated solid wood panels with side-length of 2.5 m, thickness of 70 mm and two different layer sizes. The panels were produced by two plants applying different technologies. The determined elastic parameters were verified by bending tests and compared with stiffness parameters calculated on basis of the elastic compound theory. Four elastic parameters could be determined and proven to be correct. The results did neither depend on the different production technologies of the panels nor on the two different compositions of layers. The determinability of the elastic parameter G₂₃ depends on the geometry of the panels. Noteworthy is the fact that stiffness parameters calculated assuming that the raw material of the single layers corresponds to strength class C24, can be on the ‘‘unsafe side’’.     

Adaptive memory search for multidemand multidimensional knapsack problems

We describe a simple adaptive memory search method for the 0/1 Multidemand Multidimensional Knapsack Problem (0/1 MDMKP). The search balances the level of infeasibility against the quality of the solution, and uses a simple dynamic tabu search mechanism. A weighting scheme to balance out the differences in the tightness of the constraints is also implemented. Computational results on a portfolio of test problems taken from the literature are reported, showing very favorable results, both in terms of solution quality and the ability of the search to find feasible solutions.     

Mechanisms of weight maintenance under high- and low-protein, low-glycaemic index diets

Scope: Weight maintenance after intended weight loss is a challenge in an obesogenic environment. In a large multicentre dietary intervention study (DiOGenes), it has recently been demonstrated that a high‐protein/low‐glycaemic index (HP/LGI) diet was slightly more efficient in maintaining weight loss than low‐protein/LGI or high‐GI (LP/LGI or HGI) diets. Here, we use a proteomic approach to assess the molecular mechanisms behind this positive effect. Methods and results: A subset of the most successful (weight loser, n=12) and unsuccessful (weight re‐gainer, n=12) individuals consuming the LGI diets with either high‐ or low‐protein content (HP or LP/LGI), following an initial calorie deficit run‐in weight loss phase, were analyzed at the plasma protein level. Proteomic analysis revealed 18 proteins regulated after 6 months of the dietary weight maintenance phase. Furthermore, 12 proteins were significantly regulated as a function of success rate under an HP diet, arising as candidate biomarkers of mechanisms of successful weight maintenance under an HP/LGI diet. Pregnancy‐zone protein (PZP) and protein S (PROS1) were revealed as novel biomarkers of weight maintenance showing opposite effects. Conclusion: Semantic network analysis of the 12 regulated proteins revealed that under an HP/LGI an anti‐atherogenic effect and alterations of fat metabolism were associated with the success of maintaining the initial weight loss.