bluuebunny/crossref_metadata_2025 huggingface dataset:
Learning and costs in airframe production: A multiple‐output production function approach
Authors: Gulledge Thomas R. , Worner Norman K. , Dorroh James R.
Published: May 2007

This article examines the influence of both production rate and learning on airframe program costs. A dynamic multiple‐output production model is developed and is used to observe the cost impact of changes in production rate and learning. Several simulations are performed to demonstrate the sensitivity of the optimal time path of cost to changes in the model parameters. The model is applied by estimating parameters from the F102 airframe program.
A note on the constrained shortest‐path problem
Authors: Pujari Arun K. , Agarwal Suneeta , Gulati V. P.
Published: May 2007

The subject of this note is the validity of the algorithm described by Aneja and Nair to solve the constrained shortest‐path problem.
A model in which component failure rates depend on the working set
Authors: Ross Sheldon M.
Published: May 2007

We consider a multicomponent system in which the failure rate of a given component at any time depends on the set of working components at that time. Sufficient conditions are presented under which such a system has a life distribution of specified type. The Laplace transform of the time until all components are down is derived. When repair is allowed, conditions under which the resulting process is time reversible are presented.
Distribution of number of point targets killed and higher moments of coverage of area targets
Authors: Schroeter Gerhard
Published: May 2007

The coverage C of area targets by salvos of weapons generally varies randomly, because of random target location and weapon impact point fluctuations. A third source of variation appears when, instead of an area target, a multiple‐element target is considered, consisting of m point targets distributed randomly and independently of one another around the target center. A multiple‐integral expression is derived for the probability pk of killing exactly k target elements. It is shown that pk is a linear function of the higher moments, of the order k to m, of the area coverage C. More explicit expressions are derived for the case of two weapons and for circular‐symmetric functions. Similar to well‐known results for the expectation and variance of coverage of area targets, these expressions can be evaluated by numerical quadrature. Furthermore, the coverage problem in which all underlying functions are Gaussian can be completely solved in closed form. For such a problem, with two weapons, numerical results are presented. They show that the distribution of k can be approximated by a binomial distribution only if the target center and weapon impact point fluctuations are small.
Evaluation of costs of ordering policies in large machine repair problems
Authors: Albright S. Christian , Soni A.
Published: May 2007

This article examines a version of the machine repair problem where failures may be irreparable. Since the number of machines in the system keeps decreasing, we impose a fixed state‐dependent ordering policy of the type often encountered in inventory models. Although the system is Markovian, the number of states becomes very large. The emphasis of the article, therefore, is on deriving computationally tractable formulas for the steady‐state probabilities, the long‐run average cost per unit time, and the vector of expected discounted costs. When the state space is so large that exact computations may be infeasible, we propose approximations which are relatively quick and simple to compute and which yield very accurate results for the test problems examined.
An inventory model with finite‐range stochastic lead times
Authors: Sphicas Georghios P. , Nasri Farrokh
Published: May 2007

This article considers an inventory model with constant demand and stochastic lead times distributed over a finite range. A generalization of the EOQ formula with backorders is derived and ranges for the decision variables are obtained. The results are illustrated with the case of uniformly distributed lead time.
Testing goodness of fit to the increasing failure rate family
Authors: Tenga Robert , Santner Thomas J.
Published: May 2007

One branch of the reliability literature is concerned with devising statistical procedures with various nonparametric “restricted family” model assumptions because of the potential improved operating characteristics of such procedures over totally nonparametric ones. In the single‐sample problem with unknown increasing failure rate (IFR) distribution F, (1) maximum‐likelihood estimators of F have been calculated, (2) upper or lower tolerance limits for F have been determined, and (3) tests of the null hypothesis that F is exponential have been constructed. Barlow and Campo proposed graphical methods for assessing goodness of fit to the IFR model when the validity of this assumption is unknown. This article proposes several analytic tests of the IFR null hypothesis based on the maximum distance and area between the cumulative hazard function and its greatest convex minorant (GCM), and the maximum distance and area between the total time on test statistic and its GCM. A table of critical points is provided to implement a specific test having good overall power properties.
Inequalities involving the lifetime of series and parallel systems
Authors: Stein William E. , Dattero Ronald , Pfaffenberger Roger C.
Published: May 2007

Let {Xi} be independent HNBUE (Harmonic New Better Than Used in Expectation) random variables and let {Yi} be independent exponential random variables such that E{Xi}=E{Yi} It is shown that \documentclass{article}\pagestyle{empty}\begin{document}$ E\left[{u\left({\mathop {\min \,X_i}\limits_{l \le i \le n}} \right)} \right] \ge E\left[{u\left({\mathop {\min \,Y_i}\limits_{l \le i \le n}} \right)} \right] $\end{document} for all increasing and concave u. This generalizes a result of Kubat. When comparing two series systems with components of equal cost, one with lifetimes {Xi} and the other with lifetimes {Yi}, it is shown that a risk‐averse decision‐maker will prefer the HNBUE system. Similar results are obtained for parallel systems.
Present practices and future plans for MIL‐STD‐781
Authors: Wallace W. E.
Published: May 2007

MIL‐STD‐781 specifies reliability acceptance test procedures based on both fixed‐length tests and probability ratio sequential tests. The assumption underlying MIL‐STD‐781 is a constant mean time between failures (MTBF) and typical practice applies MIL‐STD‐781 to electrical, electronic, and mechanical equipment. This article discusses some of the difficulties that have prompted the C and D revisions of MIL‐STD‐781. In addition, it discusses the relationship of MIL‐STD‐781 with MIL‐STD‐1635(EC) which deals with reliability growth testing. The article concludes with a discussion of needed research in reliability growth testing, in support of MIL‐STD‐781, and in the area of stress and its impact of MTBF.
Some distributions arising as a consequence of errors in inspection
Authors: Johnson Norman L. , Kotz Samuel
Published: May 2007

In this article, the authors survey and consolidate their investigations during the years 1980‐1983 dealing with consequences of errors in inspection sampling models. Some indication of the current and future research is given.
Application of renewal theory to continuous sampling plans
Authors: Yang Grace L.
Published: May 2007

Renewal theory is used to study the effectiveness of a class of continuous sampling plans first introduced by Dodge. This approach provides a simple way of viewing and computing the long‐run Average Outgoing Quality (AOQ) and its maximum AOQL. More importantly, it is used to study the average outgoing quality in a short production run through an approximation formula AOQ*(t). Formulas for AOQ and AOQ*(t) are provided. By simulation, it is found that AOQ*(t) is sufficiently accurate in situations corresponding to actual practice.
Toward a determination of optimal multilevel sampling plans
Authors: Sackrowitz Harold
Published: May 2007

Traditionally continuous sampling plans have been evaluated according to relatively few criteria. These typically include the OC curve (on which AQL systems are based), the ASN, and the AOQ curve. These characteristics are all calculated under the assumption that the process is “in control” so that mathematically they are derived as long‐term averages. Thus, any two plans which (long term) spend the same proportion of time on each type of sampling inspection will be identical relative to these criteria. This is true whether sampling from lots or doing unit‐by‐unit inspection. The goal is to first establish desirable additional criteria and then to develop methods to determine which procedure (of those which satisfy the standard criteria) is optimal relative to the new criteria. To be considered will be measures of a plan's ability to detect a sudden drop in quality (such as ARL).
Qmp/USP: A modern alternative to MIL‐STD‐105D
Authors: Buswell George , Hoadley Bruce
Published: May 2007

The Quality Measurement Plan (QMP) and the Universal Sampling Plan (USP) are the data analysis and sampling plans for the AT&T Technologies quality audit. This article describes QMP/USP, an acceptance sampling plan based on QMP and USP principles. QMPIUSP is a complete acceptance sampling system. It combines the elements of classical rectification inspection plans with those of MIL‐STD‐IOSD. There is no switching between plans, no tables of numbers to look through, and no discontinue state. QMP/USP is a computerized, self‐contained system that features:

Acceptance decisions based on the QMP Bayes empirical Bayes analysis of current and past sampling result

Sample size selection based on USP, i.e., lot size, AQL, a cost ratio, the QMP analysis, and a budget constraint

Guaranteed AOQ

A complete statistical analysis of the quality process.

In this article, we describe the operation of QMP/USP and compare its performance with that of MIL‐STD‐IOSD. The comparison is made under many different quality environments with many metrics. Our results show that QMP/USP and MIL/STD/IOSD perform similarly for the environments where quality could be described as “in control”; and that QMPlUSP is superior in the environments where quality is “out of control”.
Heuristic modeling of supply availabilities in large networks
Authors: Patterson W. M. , Olson A. E. , Mitchell C. R.
Published: May 2007

The objective of this article is to describe heuristic solutions to the problem of modeling inventories at each node of a large network in the context of a computer simulation model of that network. The heuristic solutions are compared with the mathematical solution which is too unwieldy for use in a simulation model. The Weibull cumulative distribution is used as an approximation for the heuristic models. We question whether the good performance of the Weibull is coincidence or perhaps mathematically justifiable.
Closure properties of the relevation transform*
Authors: Shanthikumar J. G. , Baxter Laurence A.
Published: May 2007

Sufficient conditions under which the relevation of two probability distributions is (i) NBU, (ii) IFRA, (iii) IFR are derived. The result for case (iii) corrects an error in a previous article by Baxter.
Attack and defense of ICBMs deceptively based in a number of identical areas
Authors: Bracken Jerome , Brooks Peter S.
Published: May 2007

On‐site verification of ICBMs in the context of an arms control agreement might involve a situation where an inspector would choose one or more of a number of identical areas to inspect and would have confidence that the other areas had the same characteristics. This article considers optimal attack and defense of missiles deceptively based in a number of identical areas. The attacker may allocate warheads across areas as he desires and uniformly within areas. The defender may allocate interceptors across areas as he desires and either uniformly or preferentially within areas. The effect of restricting the defender to uniform allocation across areas is explored for various assumptions. Robustness of surviving missiles with respect to the number of attacking warheads is studied. Results are presented for a wide range of cases.
The theory of combined‐arms lanchester‐type models of warfare
Authors: Maybee John S.
Published: May 2007

The mathematical theory necessary to solve combined arms models of military combat is presented here. We show how to apply the theory of positive operators to such models. Most of the results are purely qualitative in character showing that many properties of such systems are independent of the actual numerical values of the coefficients. Finally, we discuss in some detail an example of such a system.
Optimizing search with positive information feedback
Authors: Stewart Theodor J.
Published: May 2007

A search model is formulated in which positive information may be obtained, through the detection of trails, as to the target's earlier whereabouts. The corresponding Bayesian update formulas for target location probabilities are derived. The model does not appear to be amenable to rigorous optimization. A moving‐horizon rule, and a heuristic simplification thereof, are, however, derived. In two numerical examples it is demonstrated that actively designing for detecting trail information, through use of these moving‐horizon rules, has substantial potential advantage over using, for example, myopic rules even if the positive information is adaptively incorporated into location probabilities before applying the latter rules in each time period.
Control of entry to a nonstationary queuing system
Authors: Nozari Ardavan
Published: May 2007

In this article the control of entry of customers to a queuing system with s servers is considered. It is assumed that the arrivals form a nonstationary Poisson process with a periodic rate. The service times are assumed to be exponentially distributed with a parameter independent of time. The cost structure considered is the same as that of Naor. It is demonstrated numerically that, like the stationary cases, the average expected benefit of customers per unit of time is a unimodal function of the critical point. And, also, the social critical point is smaller than the individual critical point. These suggest the use of a search technique for finding the social critical point. The results show successful application of the discrete version of the Fibonacci search.
Acceleration of the HAP approach for the multifacility location problem
Authors: Charalambous Christakis
Published: May 2007

This article considers the problem of locating multiple new facilities to minimize the cost function consisting of the sum of weighted distances among new facilities and between new and existing facilities. The hyperboloid approximate procedure (HAP) is probably the most widely used approach for solving this problem. In this article, an optimality condition for this problem is derived and a method to accelerate the convergence rate of the HAP for the case of Euclidean distances is presented. From the numerical results presented in this article, it can be concluded that the performance of the new algorithm is superior to the performance of the original HAP.
One‐facility location with rectilinear tour distances
Authors: Drezner Z. , Steiner G. , Wesolowsky G. O.
Published: May 2007

This article concerns the location of a facility among n points where the points are serviced by “tours” taken from the facility. Tours include m points at a time and each group of m points may become active (may need a tour) with some known probability. Distances are assumed to be rectilinear. For m ≤ 3, it is proved that the objective function is separable in each dimension and an exact solution method is given that involves finding the median of numbers appropriately generated from the problem data. It is shown that the objective function becomes multimodal when some tours pass through four or more points. A bounded heuristic procedure is suggested for this latter case. This heuristic involves solving an auxiliary three‐point tour location problem.
A finite descent theory for linear programming, piecewise linear convex minimization, and the linear complementarity problem
Authors: Solow Daniel , Sengupta Partha
Published: May 2007

A descent algorithm simultaneously capable of solving linear programming, piecewise linear convex minimization, and the linear complementarity problem is developed. Conditions are given under which a solution can be found in a finite number of iterations using the geometry of the problem. A computer algorithm is developed and test problems are solved by both this method and Lemke's algorithm. Current results indicate a decrease in the number of cells visited but an increase in the total number of pivots needed to solve the problem.
State information lag markov decision process with control limit rule
Authors: Kim Soung H.
Published: May 2007

In the framework of a discrete Markov decision process with state information lag, this article suggests a way for selecting an optimal policy using the control limit rule. The properties sufficient for an optimal decision rule to be contained in the class of control limit rules are also studied. The degradation in expected reward from that of the perfect information process provides a measure of the potential value of improving the information system.
Single‐period inventory models with demand uncertainty and quantity discounts: Behavioral implications and a new solution procedure
Authors: Jucker James V. , Rosenblatt Meir J.
Published: May 2007

Quantity discounts are considered in the context of the single‐period inventory model known as “the newsboy problem.” It is argued that the behavioral implications of the all‐units discount schedule are more complex and interesting than the literature has suggested. Consideration of this behavior and the use of marginal analysis lead to a new method for solving this problem that is both conceptually simpler and more efficient than the traditional approach. This marginal‐cost solution procedure is described graphically, an algorithm is presented, and an example is used to demonstrate that this solution procedure can be extended easily to handle complex discount schedules, such as some combined (simultaneously applied) purchasing and transportation cost discount schedules.
An optimum multiechelon repair policy and stockage model
Authors: Kaplan A. , Orr D.
Published: May 2007

Currently, sophisticated multiechelon models compute stockage quantities for spares and repair parts that will minimize total inventory investment while achieving a target level of weapon system operational availability. The maintenance policies to be followed are input to the stockage models. The Optimum Allocation of Test Equipment/Manpower Evaluated Against Logistics (OATMEAL) model will determine optimum maintenance as well as stockage policies for a weapon system. Specifically, it will determine at which echelon each maintenance function should be performed, including an option for component or module throwaway. Test equipment requirements to handle work load at each echelon are simultaneously optimized. Mixed‐integer programming (MIP) combined with a Lagrangian approach are used to do the constrained cost minimization, that is, to minimize all costs dependent on maintenance and stockage policies while achieving a target weapons system operational availability. Real‐life test cases are included.
A heuristic with tie breaking for certain 0–1 integer programming models
Authors: Fox G. Edward , Scudder Gary D.
Published: May 2007

A heuristic for 0–1 integer programming is proposed that features a specific rule for breaking ties that occur when attempting to determine a variable to set to 1 during a given iteration. It is tested on a large number of small‐ to moderate‐sized randomly generated generalized set‐packing models. Solutions are compared to those obtained using an existing well‐regarded heuristic and to solutions to the linear programming relaxations. Results indicate that the proposed heuristic outperforms the existing heuristic except for models in which the number of constraints is large relative to the number of variables. In this case, it performs on par with the existing heuristic. Results also indicate that use of a specific rule for tie breaking can be very effective, especially for low‐density models in which the number of variables is large relative to the number of constraints.
Production‐location problems with demand considerations
Authors: Venta Enrique R. , Hurter Arthur P.
Published: May 2007

The production‐location problem of a profit maximizing firm is considered. A model is developed for a single firm, facing the joint problems of determining the optimal plant location, the optimal input mix, and the optimal plant size. A homothetic production function is used as the model of the production technologies, and the existence of a sequential “separability” between the production, or input mix, problem and the location problem is demonstrated.
Causative matrix technique for deriving interim period transition probabilities in nonstationary markov process
Authors: Kim Soung H.
Published: May 2007

The Markov assumption that transition probabilities are assumed to be constant over entire periods has been applied in economic and social structures, for example, in the analysis of income and wage distributions. In many cases, however, nonstationary transition probabilities exist over different periods. Based on causative matrix technique, this study shows a binomial approximation for obtaining nonstationary interim transition probabilities under undisturbance when the first and the last transition matrices are known.
Aggregating assignment constraints
Authors: Fishburn Peter C. , Kochenberger Gary A.
Published: May 2007

This article shows how simple systems of linear equations with {0,1} variables can be aggregated into a single linear equation whose {0,1} solutions are identical to the solutions of the original system. Structures of the original systems are exploited to keep the aggregator's integer coefficients from becoming unnecessarily large. The results have potential application in integer programming and information theory, especially for problems that contain assignment‐type constraints along with other constraints. Several unresolved questions of a number‐theoretic nature are mentioned at the conclusion of the article.
On the use of a structural equation for determining inventory order quantities
Authors: Das Chandrasekhar
Published: May 2007

This article considers a structural equation useful for characterizing the order quantity of several inventory models. A correct interpretation of this equation is provided and it is stressed that the equation should be used in conjunction with another equation for the reorder point. Failure to do so may give rise to improper interpretations and invalid conclusions. A specific case like this is cited for the sake of illustration.
Optimal stocking policies for low usage items in multi‐echelon inventory systems
Authors: Cohen Morris A. , Kleindorfer Paul R. , Lee Hau Leung
Published: May 2007

Multi‐echelon logistic systems are essential parts of the service support function of high technology firms. The combination of technological developments and competitive pressures has led to the development of services systems with a unique set of characteristics. These characteristics include (1) low demand probabilities: (2) high cost items; (3) complex echelon structures; (4) existence of pooling mechanisms among stocking locations at the same echelon level; (5) high priority for service, which is often expressed in terms of response time service levels for product groups of items: (6) scrapping of failed parts; and (7) recycling of issued stock due to diagnostic use. This article develops a comprehensive model of a stochastic, multi‐echelon inventory system that takes account of the above characteristics. Solutions to the constrained optimization problem are found using a branch and bound procedure. The results of applying this procedure to a spare parts inventory system for a computer manufacturer have led to a number of important policy conclusions.
A lagrangean relaxation algorithm for the constrained matrix problem
Authors: Cottle Richard W. , Duvall Steven G. , Zikan Karel
Published: May 2007

We present variants of a convergent Lagrangean relaxation algorithm for minimizing a strictly convex separable quadratic function over a transportation polytope. The algorithm alternately solves two “subproblems,” each of which has an objective function that is defined by using Lagrange multipliers derived from the other. Motivated by the natural separation of the subproblems into independent and very easily solved “subsubproblems,” the algorithm can be interpreted as the cyclic coordinate ascent method applied to the dual problem. We exhibit our computational results for different implementations of the algorithm applied to a set of large constrained matrix problems.
Minimizing mean absolute deviation of completion times about a common due date
Authors: Bagchi Uttarayan , Sullivan Robert S. , Chang Y. L.
Published: May 2007

We consider a single machine scheduling problem in which the objective is to minimize the mean absolute deviation of job completion times about a common due date. We present an algorithm for determining multiple optimal schedules under restrictive assumptions about the due date, and an implicit enumeration procedure when the assumptions do not hold. We also establish the similarity of this problem to the two parallel machines mean flow time problem.
Hybrid heuristics for minimum cardinality set covering problems
Authors: Vasko Francis J. , Wilson George R.
Published: May 2007

Minimum cardinality set covering problems (MCSCP) tend to be more difficult to solve than weighted set covering problems because the cost or weight associated with each variable is the same. Since MCSCP is NP‐complete, large problem instances are commonly solved using some form of a greedy heuristic. In this paper hybrid algorithms are developed and tested against two common forms of the greedy heuristic. Although all the algorithms tested have the same worst case bounds provided by Ho [7], empirical results for 60 large randomly generated problems indicate that one algorithm performed better than the others.
End effects in capacity expansion models with finite horizons
Authors: Murphy F. H. , Soyster A. L.
Published: May 2007

Capacity expansion models are typically formulated in the context of some finite horizon. Because the firm lasts longer than the horizon, a bias can enter into the optimal solution from the model horizon chosen. Recently, Grinold [8] has proposed a “dual‐equilibrium method” for ameliorating possible distortions. Although the dual‐equilibrium method has superior analytical properties to other methods, it is conceptually more complex. In this paper it is shown that there are situations where the “primal‐equilibrium” approach of Manne [15] provides equivalent results and that the use of annualized capital costs in the objective function, although somewhat less efficient, results in a similar model.
Computational aspects in multistage bayesian acceptance sampling
Authors: Waldmann K.‐H.
Published: May 2007

Simple criteria are found for reducing the computational effort in multistage Bayesian acceptance sampling. Regions of optimality are given for both terminal actions accept and reject. Also, criteria are presented for detecting nonoptimality of sets of sample sizes. Finally, nearly optimal (z,c−,c+)‐sampling plans are constructed by restricting attention to a small subset of sample sizes.
Test for the extreme value and weibull distributions based on normalized spacings
Authors: Lockhart R. A. , O'Reilly F. , Stephens M. A.
Published: May 2007

Discussed in this article are tests for the extreme‐value distribution, or, equivalently, for the two‐parameter Weibull distribution when parameters are unknown and the sample may be censored. The three tests investigated are based on the median, the mean, and the Anderson‐DarlingA2statistic calculated from a setziof values derived from the spacings of the sample. The median and the mean have previously been discussed by Mann, Scheuer, and Fertig [10] and by Tiku and Singh [14]. Asymptotic distributions and points are given for the test statistics, based on recently developed theory, and power studies are conducted to compare them with each other and with two other statistics suitable for the test. Of the normalized spacings tests,A2is recommended overall; the mean also gives good power in many situations, but can be nonconsistent.
Geometric programming with multiplicative slack variables
Authors: McNamara John R.
Published: May 2007

A posynomial geometric programming problem formulated so that the number of objective function terms is equal to the number of primal variables will have a zero degree of difficulty when augmented by multiplying each constraint term by a slack variable and including a surrogate constraint composed of the product of the slack variables, each raised to an undetermined negative exponent or surrogate multiplier. It is assumed that the original problem is canonical. The exponents in the constraint on the product of the slack variables must be estimated so that the associated solution to the augmented problem, obtained immediately, also solves the original problem. An iterative search procedure for finding the required exponents, thus solving the original problem, is described. The search procedure has proven quite efficient, often requiring only two or three iterations per degree of difficulty of the original problem. At each iteration the well‐known procedure for solving a geometric programming problem with a zero degree of difficulty is used and so computations are simple. The solution generated at each iteration is optimal for a problem which differs from the original problem only in the values of some of the constraint coefficients, so intermediate solutions provide useful information.
Location of regional facilities
Authors: Drezner Zvi
Published: May 2007

In this paper we consider the single‐facility and multifacility problems of the minisum type of locating facilities on the plane. Both demand locations and the facilities to be located are assumed to have circular shapes, and demand and service is assumed to have a uniform probability density inside each shape. The expected distance between two facilities is calculated. Euclidean and squared‐Euclidean distances are discussed.
A branch and bound algorithm for solving a class of nonlinear integer programming problems
Authors: Victor Cabot A. , Selcuk Erenguc S.
Published: May 2007

This article presents a branch and bound method for solving the problem of minimizing a separable concave function over a convex polyhedral set where the variables are restricted to be integer valued. Computational results are reported.
An analysis of degeneracy
Authors: Greenberg Harvey J.
Published: May 2007

Degeneracy in linear programming models has been analyzed for its impacts on algorithmic properties. A complementary analysis here is on what the solutions mean. The framework presented is couched in marginal sensitivity analysis, introducing concepts of “compatible bases” and “transition graphs”.
Warranty design under buyer and seller risk aversion
Authors: Ritchken Peter H. , Tapiero Charles S.
Published: May 2007

This paper provides a framework in which warranty policies for non‐repairable items can be evaluated according to risk preferences of both buyers and sellers. In particular, a warranty price schedule is established such that sellers are indifferent among the policies. Given this schedule, a buyer's response is expressed by selecting the price‐warranty combination that minimizes disutility. Within this framework, a warranty can be viewed as an instrumet of risk management that can induce more sales and greater profitability. For given utility functions, analytical results for the development of a price schedule are developed. Numerical results illustrate the substitution effects between warranty terms, prices, and risk parameters.
Stochastic leadtimes in continuous‐time inventory models
Authors: Zipkin Paul
Published: May 2007

This paper shows that one of the fundamental results of inventory theory is valid under conditions much broader than those treated previously. The result characterizes the distributions of inventory level and inventory position in the standard, continuous‐time model with backorders, and leads to the relatively easy calculation of key performance measures. We treat both fixed and random leadtimes, and we examine both stationary and limiting distributions under different assumptions. We consider demand processes described by several general classes of compound‐counting processes and a variety of order policies. For the stochastic‐leadtime case we provide the first explicit proof of the result, assuming the leadtimes are generated according to a specific, but plausible, scenario.
Routing in computer networks
Authors: Frank H. , Chou W.
Published: May 2007

The problem of routing flow in a network of computers is extremely complex. This is especially formidable when routing is to be incorporated in iterative analysis and design. Among the properties of desirable flow patterns is low average delay from message inception to arrival. In this paper, we discuss procedures for minimizing average delay subject to a set of flow constraints. Heuristic routing procedures are presented and compared to optimum routing procedures. Computational experience is given.
Steiner's problem in graphs and its implications
Authors: Hakimi S. L.
Published: May 2007

A graph theoretic version of Steiner's problem in plane geometry is described. An approach for solving this problem, related to Melzak's solution to Steiner's problem, is presented. The problems of finding “shortest route” and “minimal spanning tree” in graphs become special cases of the Steiner's problem in graphs. It is shown that a solution to this problem also provides us with a solution to the problems of finding a minimum externally stable set and a maximum internally stable set in a graph.
Minimum cost routing for static network models
Authors: Yaged B.
Published: May 2007

This paper develops techniques which can be applied to long range planning studies for the domestic long haul communications network. The problem studied is how to select a path through the network for each point‐to‐point demand for communications channels, so that the total network cost is minimized. The problem is to minimize total network cost, subject to multicommodity flow requirements and concave link cost functions. Finding an exact solution is difficult because of the concavity of the cost functions and the complexity (100 to 200 nodes and 200 to 300 links) of the network structure. A specialized technique is developed to provide locally optimal solutions to the problem, one of minimizing a concave function over a convex constraint set. When the link cost displays a fixed charge, a modification of the iterative algorithm provides acceptable a modification of the iterative algorithm provides acceptable solutions. Even though the global optimum cannot be found amidst the immense number of local optima, several sample problems demonstrate the value of the techniques developed.

A companion paper will extend this work to the dynamic routing problem, of deciding how to route future demands and install transmission facilities so as to minimize the present worth of expenditures during the study interval. The methods and goals of these modeling efforts will be discussed in the companion paper.
On some techniques useful for solution of transportation network problems
Authors: Tomizawa N.
Published: May 2007

This paper presents an efficient algorithm for solving transportation problems. The improvement over the existing algorithms of the “primal‐dual” type [3], [5] consists in modifying the “potential‐raising” stages of the solution process in such a way that negative‐cost arcs are removed so that the Dijkstra's algorithm may be applied. Especially, the algorithm requires at most n3 additions and comparisons when applied to an n‐by‐n assignment problem, as compared with the theoretical upper bound proportional to n4 for the number of such operations required by currently available methods. Furthermore, auxiliary techniques of simplifying the original network by means of “reduction” and “induction” are also introduced as useful tools to treat large‐scale problems and specially‐structured problems with.
A simple derivation of edmonds' algorithm for optimum branchings
Authors: Karp R. M.
Published: May 2007

Edmonds [1] has given an algorithm for constructing a maximum‐weight branching in a weighted directed graph. His proof that the algorithm is correct is based on linear programming theory, and establishes as a by‐product that a certain polyhedron has integer vertices. Here we give a direct combinatorial proof of the correctness of the algorithm.
Two‐way traffic in loop service systems
Authors: Konheim A. G. , Meister B.
Published: May 2007

A model for a communication system which consists of a computer and a number of buffered terminals connected by means of a loop channel is analyzed. Data flows in two directions: from the computer to the terminals and from the terminals to the computer. The channel is alternately available to the computer and the terminals to effect these data transfers. The transient behavior of the system is determined and the stationary or limiting expected queue lengths at all terminals are calculated.
A generalized upper bounding algorithm for multicommodity network flow problems
Authors: Hartman J. K. , Lasdon L. S.
Published: May 2007

An algorithm for solving min‐cost or max‐flow multicommodity flow problems is described. It is a specialization of the simplex method, which takes advantage of the special structure of the multicommodity problem. The only nongraph or nonadditive operations in a cycle involve the inverse of a working basis, whose dimension is the number of currently saturated arcs. Efficient relations for updating this inverse are derived.
Stability of networks with distributed and nonlinear elements. I
Authors: Schwyn P. J. , Bickart T. A.
Published: May 2007

This paper, in two parts, considers the stability of electrical networks consisting of transmission lines interconnected with lumped linear and memoryless nonlinear elements. Let xt be the state of such a network represented as a point in the space C([‐∞, 0], En) of bounded continuous functions mapping the interval [‐∞, 0] into En and let x(t) = xt (0). Then large classes of such networks may be described by an integro‐differential equation of the form

magnified image

where A is a real n × n matrix, G(τ) is a real n x n matrix‐valued function of bounded variation on [‐∞,0], and E is a nonlinear function mapping En into En. The integral is of the Riemann‐Stieltjes type.

A functional is defined on a subset of C and used to obtain stability theorems for the integro‐differential equation using Liapunov stability theory as extended to functional differential equations. Then, these theorems are applied to networks with transmission lines, with the result being stability criteria which depend only on the lumped elements and the total variation of the step response of the transmission lines with suitably chosen terminations. The total variations associated with uniform, distortionless LC lines and nonuniform RC lines are presented. For networks with RC lines the stability criteria are simplified such that they are functions only of the lumped elements and the total resistances of the RC lines.
Computer‐aided interconnection routing: General survey of the state‐of‐the‐art
Authors: Nakahara H.
Published: May 2007

This paper is a brief survey of the computer‐aided interconnection routing techniques currently in use at various facilities as part of their software packages. It summarizes the pros and cons of the techniques available and also indicates further research areas in the future.

Excellent review papers similar to the one presented here have been published previously [26,55,56], which cover a wider range of subjects on design automation in general. Many of the subjects mentioned in the above references are deliberately repeated here since the current paper is intended for tutorial purposes. Those who are interested in the present and related topics are urged to read the aforementioned references.
Dynamic transshipment networks: An algorithm and its application to the distribution of empty containers
Authors: White W. W.
Published: May 2007

The movement of vehicles and goods in a transportation system can be represented as flows through a time‐dependent transshipment network. An inductive out‐of‐kilter type of algorithm is presented which utilizes the basic underlying properties of the dynamic transshipment network to optimize the flow of a homogeneous commodity through the network, given a linear cost function. The algorithm is illustrated by its application to the problem of distributing empty containers from locations at which they are available to locations at which they are required.
Decoupling joint and elastic accelerations in deformable mechanical systems using non‐linear recursive formulations
Authors: Hwang Yunn‐Lin
Published: May 2007

The aim of this paper is to develop non‐linear recursive formulations for decoupling joint and elastic accelerations, while maintaining the non‐linear inertia coupling between rigid body motion and elastic deformation in deformable mechanical systems. The inertia projection schemes used in most existing recursive formulations for the dynamic analysis of deformable mechanisms lead to dense coefficient matrices in the equations of motion. Consequently, there are strong dynamic couplings between the joint and elastic coordinates. When the number of elastic degrees of freedom increases, the size of the coefficient matrix in the equations of motion becomes large. Consequently, the use of these recursive formulations for solving the joint and elastic accelerations becomes less efficient. In this paper, the non‐linear recursive formulations have been used to decouple the elastic and joint accelerations in deformable mechanical systems. The relationships between the absolute, elastic and joint variables and generalized Newton–Euler equations are used to develop systems of loosely coupled equations that have sparse matrix structure. By using the inertia matrix structure of deformable mechanical systems and the fact that joint reaction forces associated with elastic coordinates do represent independent variables, a reduced system of equations whose dimension is dependent of the number of elastic degrees of freedom is obtained. This system can be solved for the joint accelerations as well as for the joint reaction forces. The use of the approaches developed in this investigation is illustrated using deformable open‐loop serial robot and closed‐loop four‐bar mechanical systems. Copyright © 2007 John Wiley & Sons, Ltd.
Analysis, design, and optimization of structures with integral compliant mechanisms for mid‐frequency response
Authors: Dede Ercan M. , Hulbert Gregory M.
Published: May 2007

A multi‐scale paradigm is proposed that utilizes periodic, small‐scale, integral compliant mechanisms within larger‐scale structures for the attenuation of vibro‐acoustic response. Amplification principles serve as the basis for the design of these mechanisms in achieving reduced energy transmission. The spectral finite element method is exploited for a force–velocity and energy flow analysis of the resultant truss‐like structures. A genetic algorithm is employed to optimize structure size for greatest effectiveness in the frequency range of interest. This study demonstrates that a significant decrease in structural vibration is achievable and suggests promising applications including the design of acoustic isolation panels for broadband vehicle noise reduction. Copyright © 2007 John Wiley & Sons, Ltd.
Evaluation of elastic modulus of polymer matrix nanocomposites
Authors: Saber‐Samandari Saeed , Afaghi‐Khatibi Akbar
Published: May 2007

A new model to evaluate the elastic modulus of polymer nanocomposites is developed with emphasising on the role of inclusion/matrix interphase. The new model can be applied to polymer nanocomposites reinforced by inclusions with different shapes including spherical, cylindrical, and platelet. After validating the new model using experimental and FEA results, the effects of several parameters such as inclusion shape and modulus, d‐spacing, and matrix properties on the elastic modulus of nanocomposites are investigated. POLYM. COMPOS., 28:405–411, 2007. © 2007 Society of Plastics Engineers
Determination of atom displacement distribution in YBCO superconductors induced by gamma radiation
Authors: Piñera I. , Cruz C. M. , Abreu Y. , Leyva A.
Published: May 2007

The calculation results of the atom displacement distribution induced by gamma radiation in the superconducting material YBa2Cu3O7–xare presented. Firstly, a direct calculation procedure for the atom displacement distribution inside a given material is introduced, starting from the application of the energy flux distribution values of secondary electrons, formerly calculated using the Monte Carlo method based code system MCNP‐4C. Finally, calculation results of the atom displacement distribution, regarding the occupied oxygen crystalline sites, are presented for different incident gamma radiation energies, where an atom displacement threshold energy value of 20 eV was assigned to O(1–3) sites, while a value of 3.45 eV was used for the copper–oxygen chain sites at the basal plane. According to the present calculations, a predominating atom displacement rate at copper‐oxygen chain sites was obtained. On the other hand, nearly linear correlations among atom displacements and energy deposition profiles were also found. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Gate‐lag and drain‐lag effects in (GaN)/InAlN/GaN and InAlN/AlN/GaN HEMTs
Authors: Kuzmik J. , Carlin J.‐F. , Gonschorek M. , Kostopoulos A. , Konstantinidis G. , Pozzovivo G. , Golka S. , Georgakilas A. , Grandjean N. , Strasser G. , Pogany D.
Published: May 2007

Gate and drain‐lag effects are studied in (GaN)/InAlN/GaN and InAlN/AlN/GaN HEMTs grown on sapphire. Electron trapping on the surface states between the gate and the drain forming the net negative charge up‐to ∼2 × 1013 cm–2 is found to be responsible for the gate‐lag effect in the (GaN)/InAlN/GaN HEMTs. If the polarization charge at the device surface is decreased by GaN capping, then density of the trapped charge is not changed, however the electron de‐trapping process becomes faster. The drain‐lag effect is caused by electron injection and trapping in the source‐gate area reaching ∼1 × 1013 cm–2 of the trapped charge in the steady state. In the studied voltage range the InAlN/AlN/GaN HEMT is shown to be gate‐lag‐free suggesting that this parasitic transient can be avoided if thin AlN is used in the epi‐layer growth sequence. It is assumed that this breakthrough quality relates to the decreased or even reverted electric field in the InAlN layer if AlN is inserted. Surface states need not to be generated in this case. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)