bluuebunny/crossref_metadata_2025_split huggingface dataset:
An M/M/1 queue with delayed feedback
Authors: Hannibalsson Ingjaldur , Disney Ralph L. 
Published: May 2007

AbstractWe present some results for M/M/1 queues with finite capacities with delayed feedback. The delay in the feedback to an M/M/1 queue is modelled as another M‐server queue with a finite capacity. The steady state probabilities for the two dimensional Markov process {N(t), M(t)} are solved when N(t) = queue length at server 1 at t and M(t) = queue length at server 2 at t. It is shown that a matrix operation can be performed to obtain the steady state probabilities. The eigenvalues of the operator and its eigenvectors are found. The problem is solved by fitting boundary conditions to the general solution and by normalizing. A sample problem is run to show that the solution methods can be programmed and meaningful results obtained numerically.
Solving multicommodity transportation problems using a primal partitioning simplex technique
Authors: Kennington Jeff L. 
Published: May 2007

AbstractThis paper presents the details for applying and specializing the work of Saigal [28] and Hartman and Lasdon [16] to develop a primal partitioning code for the multicommodity transportation problem. The emphasis of the paper is in presenting efficient data structure techniques for exploiting the underlying network structure of this class of problems. Computational experience with test problems whose corresponding linear programming formulation has over 400 rows and 2,000 columns is presented.
Stochastic transportation problems and other newtork related convex problems
Authors: Cooper Leon , Leblanc Larry J. 
Published: May 2007

AbstractA class of convex programming problems with network type constraints is addressed and an algorithm for obtaining the optimal solution is described. The stochastic transportation problem (minimize shipping costs plus expected holding and shortage costs at demand points subject to limitations on supply) is shown to be amenable to the solution technique presented. Network problems whose objective function is non‐separable and network problems with side constraints are also shown to be solvable by the algorithm. Several large stochastic transportation problems with up to 15,000 variables and non‐negativity constraints and 50 supply constraints are solved.
A note on the strategy of restriction and degenerate linear programming problems
Authors: Holloway Charles A. 
Published: May 2007

AbstractUsing the general computational strategy of restriction, necessary conditions for optimality provide an alternative criterion for entering variables when degeneracies arises in linear programming problems. Although cycling may still occur, it is shown that if it is possible to make progress at the next iteration, the criterion is guaranteed to identify a non‐basic variable which increases the value of the basic solution, thereby reducing stalling. An alternative method for determining variables to exit the basis when degeneracies occur is also suggested.
Relation between continuous and discrete time markovian decision problems
Authors: Kakumanu Prasadarao 
Published: May 2007

AbstractAn associated discrete (continuous) time Markovian decision problem for any given continuous (discrete) time Markovian decision model is formulated. A relationship between the continuous and associated discrete time discounted returns is obtained. This result is used to show the existence of a deterministic stationary policy that optimizes both discounted return functions. It is also proved that the same policy optimizes the average expected return for both continuous and the associated discrete time processes. The results obtained in this paper can be used to solve the continuous time Markovian decision problem by using the discrete time algorithms or vice versa.
Queueing models for spares provisioning
Authors: Gross Donald , Kahn Henry D. , Marsh Joseph D. 
Published: May 2007

AbstractA population of items which break down at random times and require repair is studied (the classic “machine repair problem with spares”). It is desired to determine the number of repair channels and spares required over a multiyear planning horizon in which population size and component reliability varies, and a service level constraint is imposed. When an item fails, a spare (if available) is immediately dispatched to replace the failed item. The failed item is removed, transported to the repair depot, repaired, and then placed in the spares pool (which is constrained to be empty not more than 10% of the time) unless there is a backlog of requests for spares, in which case it is dispatched immediately. The first model considered treats removal, transportation, and repair as one service operation. The second model is a series queue which allows for the separate treatment of removal, transportation, and repair. Breakdowns are assumed Poisson and repair times exponential.
Optimal investment, pricing and replacement of computer resources
Authors: Kriebel Charles H. , Atkinson Anthony A. , Zia Huntley W. H. 
Published: May 2007

AbstractThe problem of multiple‐resource capacity planning under an infinite time horizon is analyzed using a nonlinear programming model. The analysis generalizes to the long term the short‐run pricing model for computer networks developed in Kriebel and Mikhail [5]. The environment assumes heterogeneous resource capacities by age (vingate), which service a heterogeneous and relatively captive market of users with known demand functions in each time period. Total variable operating costs are given by a continuous psuedoconcave function of system load, capacity, and resource age. Optimal investment, pricing, and replacement decision rules are derived in the presence of economies of scale and exogenous technological progress. Myopic properties of the decision rules which define natural (finite) planning subhorizons are discussed.
The one‐period, N‐location distribution problem
Authors: Karmarkar Uday S. , Patel Nitin R. 
Published: May 2007

AbstractThis paper studies the one‐period, general network distribution problem with linear costs. The approach is to decompose the problem into a transportation problem that represents a stocking decision, and into decoupled newsboy problems that represent the realization of demand with the usual associated holding and shortage costs. This approach leads to a characterization of optimal policies in terms of the dual of the transportation problem. This method is not directly suitable for the solution for large problems, but the exact solution for small problems can be obtained. For the numerical solutions of large problems, the problem has been formulated as a linear program with column generation. This latter approach is quite robust in the sense that it is easily extended to incorporate capacity constraints and the multiproduct case.
Monotone failure rates for multivariate distributions
Authors: Block Henry W. 
Published: May 2007

AbstractIt is shown that the monotone multivariate failure rates of Brindley and Thompson have no natural analog involving the multivariate failure rate function of Basu for absolutely continuous distributions. Quantities related to the multivariate failure rate function are used to define monotone failure rates. It is shown that these are equivalent to the monotone failure rates of Brindley and Thompson. Based on these quantities, the loss of memory property of Marshall and Olkin is characterized.
Confidence intervals in discrete event simulation: A comparison of replication and batch means
Authors: Law Averill M. 
Published: May 2007

AbstractSuppose that we have enough computer time to make n observations of a stochastic process by means of simulation and would like to construct a confidence interval for the steady‐state mean. We can make k independent runs of m observations each (n=k.m) or, alternatively, one run of n observations which we then divide into k batches of length m. These methods are known as replication and batch means, respectively. In this paper, using the probability of coverage and the half length of a confidence interval as criteria for comparison, we empirically show that batch means is superior to replication, but that neither method works well if n is too small. We also show that if m is chosen too small for replication, then the coverage may decrease dramatically as the total sample size n is increased.
The search for an intelligent evader: Strategies for searcher and evader in the two‐region problem
Authors: Roberts D. M. , Gittins J. C. 
Published: May 2007

AbstractThis paper considers the search for an evader concealed in one of two regions, each of which is characterized by its detection probability. The single‐sided problem, in which the searcher is told the probability of the evader being located in a particular region, has been examined previously. We shall be concerned with the double‐sided problem in which the evader chooses this probability secretly, although he may not subsequently move: his optimal strategy consists of that probability distribution which maximizes the expected time to detection, while the searcher's optimal strategy is the sequence of searches which limits the evader to this expected time. It transpires for this problem that optimal strategies for both searcher and evader may generally be obtained to a surprisingly good degree of approximation by using the optimal strategies for the closely related (but far more easily solved) problem in which the evader is completely free to move between searches.
Determining confidence bounds for highly reliable coherent systems based on a paucity of component failures
Authors: Myhre Janet M. , Rosenfeld Andrew M. , Saunders Sam C. 
Published: May 2007

AbstractA computationally simple method for obtaining confidence bounds for highly reliable coherent systems, based on component tests which experience few or no failures, is given. Binomial and Type I censored exponential failure data are considered. Here unknown component unreliabilities are ordered by weighting factors, which are firstly presumed known then sensitivity of the confidence bounds to these assumed weights is examined and shown to be low.
Approximations to the reliability of phased missions
Authors: Ziehms Harald 
Published: May 2007

AbstractA system whose configuration (block diagram or fault tree) changes during consecutive time periods (phases) performs a “phased mission.” Recently, Esary and Ziehms have shown that any multiphase mission can be transformed into an equivalent, synthetic, single‐phase system, and thus that the phased mission problem can in principle be solved by standard reliability methods. We employ these ideas here to study approximations to mission reliability and to develop an algorithm which may be of practical interest. In addition, we extend the reliability calculus of Rubinstein, and Esary and Hayne, based on an approximate hazard transform, to phased missions, and we show how this extended calculus can be used in situations where phases are not of known fixed duration.
Inspection policies for deteriorating equipment characterized by n quality levels
Authors: Kander Z. 
Published: May 2007

AbstractInspection models deal with operating systems whose stochastic failure is detected by observations carried out intermittently. The current communication deals with systems in which N + 1 levels of quality can be diagnosed. Optimal policies leading to minimal loss are developed, while the system's distribution is represented by an (N + 1)‐state semi‐markov process. Based on previous studies of the authors, relative efficiencies of the proposed checking policies are ascertained, by comparison with the loss sustained if discrimination of quality by intermediate levels is disregarded and by viewing the system as one which is either good or failed. Various models are treated where checking, truncated checking, and monitoring policies optimize loss per cycle, per unit of time and per unit of good time. Numerical examples are given.
The error in the normal approximation to the multinomial with an increasing number of classes
Authors: Weiss Lionel 
Published: May 2007

AbstractIn an earlier paper, it was shown that under certain conditions, if the number of classes in a multinomial distribution increases as the number of trials increases, the probabilities assigned to arbitrary regions by the multinomial distribution are close to the probabilities assigned by the distribution of slightly rounded‐off normal random variables. A different method of studying the approximation of the multinomial distribution by a normal distribution is to use the multivariate Berry‐Esseen bound. In this paper, these two methods are compared, particularly with respect to the class of multinomial distributions for which the bounds on the error remain useful.
A probability model for initial crack size and fatigue life of gun barrels
Authors: Proschan F. , Sethuraman J. 
Published: May 2007

AbstractWith constant firing, metal fatigue produces cracks in a gun barrel. The useful life of the barrel comes to an end when a crack develops to a critical size. The theory of Fracture Mechanics suggests a formula for crack size growth rate. This formula can be used to determine the life of a barrel, depending on the initial and critical crack sizes and other factors. The initial crack size turns out to be a dominant factor. Unfortunately, accurate measurements are not generally available on the initial crack size. In this paper, we propose a simple probability model for the initial crack size and this, in turn, leads to a probability distribution of the life of the barrel. This last distribution is the well‐known exponential distribution with a location shift. The simplicity of this final result is one of the factors that make the model appealing.
A heuristic network procedure for the assembly line balancing problem
Authors: Pinto Peter A. , Dannenbring David G. , Khumawala Basheer M. 
Published: May 2007

AbstractProposed is a Heuristic Network (HN) Procedure for balancing assembly lines. The procedure uses simple heuristic rules to generate a network which is then traversed using a shortest route algorithm to obtain a heuristic solution. The advantages of the HN Procedure are: a) it generally yields better solutions than those obtained by application of the heuristics, and b) sensitivity analysis with different values of cycle time is possible without having to regenerate the network. The rationale for its effectiveness and its application to problems with paralleling are presented. Computational experience with the procedure on up to 50 task test problems is provided.
A targeting model that minimizes collateral damage
Authors: Grotte Jeffrey H. 
Published: May 2007

AbstractThis paper considers the problem of allocating weapons to achieve targeting objectives while simultaneously minimizing aggregate damage to surrounding nonmilitary facilities, each of which has an upper limit to the damage it is permitted to incur. A model is formulated which assumes only that damage to individual targets or associated facilities does not decrease as the number of allocated weapons increases. An implicit enumeration algorithm, based on that of Lawler and Bell is described that yields optimal integer solutions. An example is presented.
On the manipulation of transfer prices in a static environment
Authors: Bonin John P. 
Published: May 2007

AbstractIn a static environment, J. Hirschleifer's marginal cost solution to the transfer pricing problem is commonly accepted as analytically correct. However, actual pricing practice within Western corporations and socialist‐planned economies generally deviates from marginal cost pricing. Some form of average cost pricing is more commonly chosen. Recently in this journal, H. Enzer has claimed to show that some form of average cost pricing is indeed the analytically correct solution to the transfer pricing problem when choice of technique and manipulation are allowed. Enzer claims that optimal decisions made by each of two divisions according to their individual self‐interests are made compatible with overall firm optimization when the transfer price assigned to the internally‐transferred commodity is any form of average cost.We show that the marginal cost solution is correct for Enzer's problem in the absence of manipulation by either division. Indeed, this was all that Hirschleifer claimed. In the process, we uncover a fundamental mathematical error in Enzer's argument. When manipulation of the transfer price by divisions is allowed, we demonstrate the faults with Enzer's average cost solution and conclude Hirschleifer's original statements on manipulation to be correct even in Enzer's environment. A final section briefly indicates the importance to the transfer pricing problem of a growing body of economic literature on incentive structures.
Techniques for establishing ergodic and recurrence properties of continuous‐valued markov chains
Authors: Laslett G. M. , Pollard D. B. , Tweedie R. L. 
Published: May 2007

AbstractWe present techniques for classifying Markov chains with a continuous state space as either ergodic or recurrent. These methods are analogous to those of Foster for countable space chains. The theory is presented in the first half of the paper, while the second half consists of examples illustrating these techniques. The technique for proving ergodicity involves, in practice, three steps: showing that the chain is irreducible in a suitable sense; verifying that the mean hitting times on certain (usually bounded) sets are bounded, by using a “mean drift” criterion analogous to that of Foster; and finally, checking that the chain is such that bounded mean hitting times for these sets does actually imply ergodicity.The examples comprise a number of known and new results: using our techniques we investigate random walks, queues with waiting‐time‐dependent service times, dams with general and random‐release rules, the s‐S inventory model, and feedback models.
User satisfaction, community participation and quality of life among Chinese wheelchair users with spinal cord injury: a preliminary study
Authors: Chan Sam C , Chan Alice P 
Published: May 2007

AbstractThe purpose of the present study was to investigate the relationships between spinal cord injury (SCI), wheelchair users' satisfaction, perceptions of their community participation and quality of life (QoL).Thirty‐one community wheelchair users with SCI were administered the Chinese version of the Quebec User Evaluation of Satisfaction with assistive Technology (C‐QUEST), the abbreviated Hong Kong version of the World Health Organization Quality of Life Questionnaire (WHO QoL‐BREF (HK)) and selected items of ‘Participation Restrictions’ and ‘Environmental Factors’ of the International Classification of Functioning Disability and Health (ICF). Only a weak correlation was found between the C‐QUEST services sub‐scores and one ICF environmental factor, that is, health‐related professionals (Spearman's r = 0.453; p < 0.05). The C‐QUEST device sub‐scores were also weakly correlated with four domain scores of the WHO QoL‐BREF (HK) (Spearman's r = 0.412–0.567; p < 0.05). Social relationship, participation in leisure and driving activities had a moderate association with scores of the WHO QoL‐BREF (HK) (−0.405 > Spearman's r > −0.583; p < 0.05). It is concluded that community participation (e.g. use of transportation) and human environment (e.g. friends and peers) were more related to QoL, than to users' satisfaction with a wheelchair. Further research with a larger sample is recommended to examine the variables related to SCI and QoL. Copyright © 2007 John Wiley & Sons, Ltd.
Synthesis and characterization of painted epoxy nanocomposites
Authors: Chang Ming‐Jen , Chang Lin‐Fen , Jiang George J. 
Published: May 2007

AbstractEpoxy/SWN nanocomposites, based on the diglycidyl ether of bisphenol A (Epon 828) cured by polyoxypropylene triamine (T‐430), were prepared by in situ polymerization. The effect of SWN content on the nanocomposites was investigated, and the morphology and properties were elucidated. The degree of dispersion of SWN loading in the nanocomposites was demonstrated by using X‐ray diffraction and transmission electron microscope. The thermal and mechanical properties of the composite tended to become better, as the SWN content increased. Furthermore, we will also discuss the barrier properties and chemical resistance of the epoxy/SWN nanocomposites observed by scanning electron microscope. POLYM. COMPOS., 28:392–396, 2007. © 2007 Society of Plastics Engineers
Study on superabsorbent composite. XI. Effect of thermal treatment and acid activation of attapulgite on water absorbency of poly(acrylic acid)/attapulgite superabsorbent composite
Authors: Wang Wenji , Li An , Zhang Junping , Wang Aiqin 
Published: May 2007

AbstractThe effect of acid activation and thermal treatment of attapulgite on water absorbency of superabsorbent composite were investigated. Under the same preparation conditions, superabsorbent composite prepared with natural attapulgite exhibited a water absorbency of 639 g/g and it merely kept 71% of its initial water absorbency after 5 times of swelling–deswelling–reswelling test. However, superabsorbent composites prepared with 2–10 M hydrochloric acid acidified attapulgite and 100–400°C thermal treated attapulgite respectively exhibited the water absorbency of 884–1,241 g/g and 701–1,515 g/g. Also, those superabsorbent composites can keep 87% and 85% of their initial water absorbency after 5 times of swelling–deswelling–reswelling test, respectively. These results showed that, compared with superabsorbent composite prepared with natural attapulgite, the comprehensive water‐absorbing properties of poly(acrylic acid)/ attapulgite superabsorbent composites were improved effectively by acid activation and thermal treatment of attapulgite. This improvement of water absorbencies and gel strength of superabsorbent composite may be due to synthetical factors such as changes in the crystalline structure and the specific surface area and improvement of the number and the activity of hydroxyl groups of attapulgite, which in turn influence the grafting efficiency of monomer, crosslinking density, and the structure of superabsorbent composite network. POLYM. COMPOS., 28:397–404, 2007. © 2007 Society of Plastics Engineers
Preparative isolation and purification of dicaffeoylquinic acids from the Ainsliaea fragrans champ by high‐speed counter‐current chromatography
Authors: Wang Yingfeng , Liu Bo 
Published: May 2007

AbstractTwo dicaffeoylquinic acids, namely 3,5‐dicaffeoylquinic acid and 4,5‐dicaffeoylquinic acid, have been successfully separated by high‐speed counter‐current chromatography (HSCCC) from an extract of Ainsliaea fragrans Champ, followed by an initial clean‐up step using AB‐8 resin. A two‐phase solvent system composed of chloroform:methanol:water (8:8:4) was selected for the isolation with the aqueous‐rich phase as the stationary phase and the organic‐rich phase as the mobile phase. The developed HSCCC method yielded 34 mg of 3,5‐dicaffeoylquinic acid and 17 mg of 4,5‐dicaffeoylquinic acid from 150 mg of the crude sample in a one‐step separation with purities of 98 and 95%, respectively, as determined by HPLC. The structures of the two compounds were identified from ESI/MS, 1H‐ and 13C‐NMR spectroscopic data. Copyright © 2007 John Wiley & Sons, Ltd.