bluuebunny/crossref_metadata_2025_split huggingface dataset:
Minimizing Total Cost in Scheduling Outpatient Appointments
Authors: Ho Chrwan-Jyh , Lau Hon-Shiang 
Published: November 2008

This paper considers various rules for scheduling appointments for medical clinic outpatients and investigates their ability to minimize a weighted sum of medical personnel's and patients' idle-time costs. It is shown that the idle times incurred by any given rule are affected by the following three “environmental factors” (in decreasing order of importance): the probability of no-show, the coefficient of variation of service times, and the number of patients per clinical session. Theoretically, an appropriate scheduling rule can be identified only if one knows the values of these parameters and the ratio between the medical personnel's and patients' idle-time costs. Under environments characterized by 27 different combinations of the three environmental factors, the performance of nine scheduling rules are evaluated using simulation. Some of the rules evaluated are original to this study. The results are presented in the form of “efficient frontiers,” together with a simple procedure for identifying the best scheduling rule for given environmental-parameter values. This rule-identification procedure is shown to be easily adaptable for circumstances with limited knowledge about the environmental factors; it also reveals that the simple Bailey-Welch individual-appointment rules are surprisingly robust.
Dynamic Pricing and Ordering Decisions by a Monopolist
Authors: Rajan Arvind , Rakesh  , Steinberg Richard 
Published: November 2008

This paper considers the relationship between pricing and ordering decisions for a monopolistic retailer facing a known demand function where, over the inventory cycle, the product may exhibit: (i) physical decay or deterioration of inventory called wastage; and (ii) decrease in market value called value drop associated with each unit of inventory on hand. The retailer is allowed to continuously vary the selling price of the product over the cycle. We introduce a notion of instantaneous margin, and use it to derive profit maximizing conditions for the retailer. The model explains the markdown of retail goods subject to decay. It also provides guidance in determining when price changes during the cycle are worthwhile due to product aging, how often such changes should be made, and how such changes affect ordering intervals and quantities.
A Nonlinear Heuristic Short-Term Model for Hydroelectric Energy Production: The Case of the Hazbani-Dan Water System
Authors: Rabinowitz Gad , Mehrez Abraham , Rabina Avi 
Published: November 2008

A two-stage decision and control model for the operation of the power station in the Hazbani-Dan Water System (Israel) was developed and implemented. In this system, river water is stored and then either consumed by agricultural farms or released to a hydroelectric power station. Under management policy, agricultural consumption is taken as a constraint. The problem was solved via a two-stage procedure consisting of a long-term model (LTM) and a short-term model (STM). The LTM was presented by Rabinowitz et al. (1988). This paper reports on the development and analysis of the STM, in which operational flexibilities of the power station are taken into consideration, thereby improving the LTM solution. Our main contributions are aimed at: (1) describing the (nontraditional) systematic thinking process which transformed the mathematically expressed problem into an efficiently solvable model; (2) presenting the analysis of the model; and (3) reporting on a practical application of the model in a unique system.
A Min-Max-Max-Min Approach to Solving a Stochastic Programming Problem with Simple Recourse
Authors: White D. J. 
Published: November 2008

This paper studies a problem of determining the level of certain decisions, taken prior to certain events taking place, and the subsequent additional resource procurement decisions needed to implement the initial program once these events have materialised. The problem is formulated first of all as a max-min problem, and then as an equivalent min-max problem. The min-max problem is easier to solve than the max-min problem. The information provided in solving the min-max problem may be used to facilitate the solution of the max-min problem.
Optimal Acquisition of Pollution Control Equipment Under Uncertainty
Authors: Hartl Richard F. 
Published: November 2008

This paper considers a firm, which has to acquire a certain amount of pollution control equipment in order to comply with government pollution standards. Due to political battles and lobbying efforts, the compliance date and the date when it is announced are not known in advance. Furthermore, the target stock of pollution control equipment is also unknown. This amounts to an optimal control problem, in which the terminal time and the terminal state are random variables for which certain probability distributions can be estimated. The model explicitly considers technological progress in the production of abatement equipment, which leads to decreasing installation costs over time. Furthermore it is assumed that having a high stock of abatement equipment at early stages improves the firm's public image and thus its revenue. Tax deductions and other benefits for health conscious firms are also taken into account. Using optimal control theory the optimal investment in pollution control equipment is obtained, and the sensitivity with respect to discounting, wear out, technological progress and with respect to the parameters of the probability distributions is investigated.
Risk, Return, Skewness and Preference
Authors: Brockett Patrick L. , Kahane Yehuda 
Published: November 2008

This paper considers choice between individual projects and shows that when the choice set includes arbitrary distributions, then any assumed relationship between expected utility theory and general moment preferences for individual decision makers is theoretically unsound. In particular, a risk averse investor with any common utility function may, when choosing between two positive return opportunities, prefer the project simultaneously having a lower mean, higher variance, and lower positive skewness. Moreover, the decision maker can prefer opportunities with higher variance even when the opportunities are continuous, unimodal, and arbitrarily visually and statistically close to the normal distribution in shape. Our conclusions hold for any decision maker with a utility function whose derivatives alternate in sign being strictly positive or negative (i.e., we exclude the uninteresting cases of quadratic and cubic utilities). The method of analysis is based upon the theory of Tchebychev systems of functions which deals with the expected value of [utility] functions of stochastic variables with known moments. Although we focus on the first three moments, the results, as presented here, apply to all higher moments as well. It is also shown that there can be extremely large deviations between the certainty equivalents of distributions having the same moments, so this result is also pertinent to practical decision analysts as well. The paper demonstrates that the properties of utility functions have implications which are much more subtle than previously recognized for evaluating distributions in terms of their moments.
Service by a Queue and a Cart
Authors: Coffman E. G. , Gilbert E. N. 
Published: November 2008

Items arrive randomly at a production facility that functions as a single-server queueing system. The items might represent parts, raw material, etc. and the server might be a factory worker or a machine in a production line. Following service, items are placed in a buffer where they are accumulated before delivery to a customer or some downstream activity in a production line. In practice, the buffer might be called a hopper; it may take the form of a cart or a pallet moved by a forklift. For simplicity the discussion here keeps with the cart terminology. The cart is delivered at times to be determined; during its absence the queue will in general grow by new arrivals. An item's average time in system, from arrival to delivery, is to be made small. The system must compromise between infrequent deliveries to avoid long delays in the queue and frequent deliveries to avoid long waits in the cart. This problem has a simple relation with standard batch-sizing problems in production scheduling. The cart delivery (batch-sizing) strategy considered here depends on two integers M and N. Delivery begins when N are in the cart or when the queue is empty and at least M are in the cart (M ≤ N). Items are assumed to arrive by a Poisson process, and their service times have a general distribution. Generating functions are derived which determine probability distributions for the numbers k in the cart, q in the queue, and k + q in the system. Numerical results are given for special cases M = N, N = ∞, and M = 0.
Note: Microcomputer Performance of “FABLE” on Hoffmann's Data Sets
Authors: Johnson Roger V. 
Published: November 2008

Some of the legitimacy of Hoffmann's (1992) Eureka is gained from his statement that “Eureka … would seem to be approximately six times as fast (as Johnson's (1988) FABLE on the literature set). However, Eureka had one problem for which its solution was one station over the optimal, whereas FABLE's solutions were all optimal.”
Maximum Likelihood, Consistency and Data Envelopment Analysis: A Statistical Foundation
Authors: Banker Rajiv D. 
Published: November 2008

This paper provides a formal statistical basis for the efficiency evaluation techniques of data envelopment analysis (DEA). DEA estimators of the best practice monotone increasing and concave production function are shown to be also maximum likelihood estimators if the deviation of actual output from the efficient output is regarded as a stochastic variable with a monotone decreasing probability density function. While the best practice frontier estimator is biased below the theoretical frontier for a finite sample size, the bias approaches zero for large samples. The DEA estimators exhibit the desirable asymptotic property of consistency, and the asymptotic distribution of the DEA estimators of inefficiency deviations is identical to the true distribution of these deviations. This result is then employed to suggest possible statistical tests of hypotheses based on asymptotic distributions.
A Multistage Screening Model for Evaluation and Control of Misclassification Error in the Detection of Hypertension
Authors: Moskowitz Herbert , Plante Robert , Tsai Hsien-Tang 
Published: November 2008

Hypertension is one of the most important risk factors with respect to coronary heart disease and stroke. The benefits of early detection of hypertension and the subsequent design of follow-up treatment programs are well documented. Consequently, screening programs have been designed to identify subjects as normotensive (normal) or hypertensive (abnormal). In order for these programs to be effective, full participation of the subject population is required. However, such classification programs can incur massive risks of incorrectly classifying subjects as normotensive who are truly hypertensive and incorrectly classifying subjects as hypertensive who are truly normotensive. To date, the only means to reduce these risks of misclassification is to require subjects to make numerous visits for blood pressure measurement before they can be classified. Such requirements reduce the level of participation in screening programs and also delay the identification of subjects who are truly hypertensive, thereby depriving them of the benefits of early detection and immediate follow-up treatment. We propose a multiple-stage screening model that controls for maximum as well as average misclassification error which is used to design and/or evaluate screening programs for hypertension. A multiple-stage screening model not only permits the early detection of subjects who are truly hypertensive, but also requires a much smaller level of participation of subjects, while retaining control of misclassification risks that are comparable to those of screening programs based on numerous visits. We then design multiple-stage screening programs for several different subject populations.
A Dual Ascent and Column Generation Heuristic for the Discrete Lotsizing and Scheduling Problem with Setup Times
Authors: Cattrysse Dirk , Salomon Marc , Kuik Roelof , Van Wassenhove Luk N. 
Published: November 2008

In this paper the Discrete Lotsizing and Scheduling Problem (DLSP) with setup times is considered. DLSP is the problem of determining the sequence and size of production batches for multiple items on a single machine. The objective is to find a minimal cost production schedule such that dynamic demand is fulfilled without backlogging. DLSP is formulated as a Set Partitioning Problem (SPP). We present a dual ascent and column generation heuristic to solve SPP. The quality of the solutions can be measured, since the heuristic generates lower and upper bounds. Computational results on a personal computer show that the heuristic is rather effective, both in terms of quality of the solutions as well as in terms of required memory and computation time.
Effects of Ambiguity in Market Experiments
Authors: Sarin Rakesh K. , Weber Martin 
Published: November 2008

Prior studies have shown that individuals are averse to ambiguity in probability. Many decisions are, however, made in market settings where an individual's decision is influenced by decisions of others participating in the market. In this paper, we extend the previous research to evaluate the effect of ambiguity on individual decisions and the resulting market price in market settings. We therefore examine an important issue: whether ambiguity effects persist in the face of market incentives and feedback. Two different market organizations, the sealed bid auction and the double oral auction, were employed. The subjects in the experiments were graduate business students and bank executives. Our results show that the individual bids and market prices for lotteries with ambiguous probabilities are consistently lower than the corresponding bids and market prices for equivalent lotteries with well-defined probabilities. The aversion to ambiguity therefore does not vanish in market settings. Our results provide insights into what a manager can expect in bidding situations where the object of the sale (oil leases, mineral rights) involves ambiguity in probability due to, for example, lack of information or prior experience. The results may also be useful in understanding some phenomena in insurance and equity markets.
Were the Returns from Stocks and Bonds of Different Countries Really Different in the 1980s?
Authors: Turner Andrew L. , Hensel Chris R. 
Published: November 2008

We analyzed the total equity returns of indexes from Australia, Canada, Germany, Japan, the UK, and the US and total fixed income returns of indexes from all but Australia (excluded due to lack of data) to see if the returns of stocks and bonds were statistically different across markets during the 1980s. At the end of 1989, these countries represented over 87% of the market capitalization of the Morgan Stanley Capital International (MSCI) World Equity Index and over 88% of the Salomon Brothers World Bond Index. This study used monthly observations from January 1980 through December 1989 and examined returns based in local currency and hedged and unhedged US dollars. We found that sample mean stock and bond returns during the 1980s were statistically indistinguishable across countries. However, because the sample variances were so large relative to the sample means, it would have been difficult to detect differences in population means by any test. We found evidence of variance heterogeneity, which may be explainable by other economic factors. We also found that intercountry stock and bond correlations were not significantly different. Thus, we confirmed the results of other researchers, such as Jobson and Korkie (1981), but in a broader global context using more asset types and different statistical tests. Our work suggests reducing the number of input estimates to a MV global asset allocation problem. For practitioners trying to put MV analysis to use, these findings could have a significant effect on the practice of asset allocation.
Weighted Batch Means for Confidence Intervals in Steady-State Simulations
Authors: Bischak Diane P. , Kelton W. David , Pollock Stephen M. 
Published: November 2008

We propose a new procedure for providing confidence-interval estimators of the mean of a covariance-stationary process. The procedure, a modification of the method of batch means, is an improvement over existing methods when the process displays strong correlation and a comparatively small number of observations is available. We assign weights to the observations within a batch. The weights are determined by the order of the time-series model fit to the process and by its estimated parameters. For a given model and its parameters, the weights minimize the variance of the weighted point estimator of the mean; the point and variance estimators formed when these optimal weights are applied are unbiased. The time-series identification procedure and estimation of the parameters and weights bring in bias. Formulas for optimal weights are given for AR(p) and MA(1) processes. Experiments were conducted on AR(1), AR(2), and MA(2) processes as well as on the M/M/1 queue delay process and a periodic inventory system cost process. Results show that for processes with strong correlation over many lags, as is typical in queue-delay processes and inventory processes, the achieved coverage of the constructed interval is closer to nominal levels than for the unweighted-batch-means method. The coverage and average half-length is not as greatly affected by the number of batches, and nonnormality of the weighted batch means is not as severe.
A Linear Programming Model of Integrated Iron and Steel Production
Authors: Fabian Tibor 
Published: November 2008

Integrated steel mills usually have a choice over the use of various materials and production processes. Different ores may be used in the production of iron; steel scrap and iron can be used in different proportions in the production of steel. The economical usage rate of all materials is a function of numerous variables, among which the market price of some materials, notably of various grades of steel scrap, fluctuates and therefore requires a periodic determination of the economical usage rate. This is a typical problem for programming. The paper presents a mathematical formulation of the stages of iron and steel production to determine the optimal (least cost) rate of input of materials. The models of the various stages of production are connected to form a “master model” of an integrated steel mill.
Information Asymmetry, Participation, and Long-Term Contracts
Authors: Sivaramakrishnan K. 
Published: November 2008

This paper examines the economic value of participative processes in the setting of long-term incentives. When informational asymmetries arise between employers (supervisors) and employees (subordinates) about future states, questions arise as to whether and when resolving these informational asymmetries produces economic gains. To address these questions, I use a two-period principal agent contracting framework in which the agent (employee) receives imperfect private information about the second period state in the first period, and make a welfare comparison between two alternative communication regimes. In the “delayed communication regime,” a report from the agent is considered only for second period contract. In the “early communication regime,” the report is considered for first period contracting as well. This regime can therefore be viewed as encouraging participation in long-term contracts. I identify conditions under which the early communication regime is strictly preferable to the delayed communication regime. Further, given some additional structure on the agent's preferences, this result obtains even if the agent can access capital markets to smooth inter-temporal consumption. Finally, I examine the setting in which the principal, at the time of contracting, has the option of whether or not to install an information system that provides the agent with private information about the future period state. I identify conditions under which installing the information system, and resolving the consequent information asymmetry through participation, is strictly preferable to not installing the information system.
Approximation Procedures for the One-Warehouse Multi-Retailer System
Authors: Lu Lu , Posner Marc E. 
Published: November 2008

Two heuristic procedures for a one-warehouse multi-retailer system are developed. Based on the accuracy desired, the first heuristic evaluates a specified number of points. The relative error is within a bound that approaches 1/(√2 ln 2) − 1 ≈ 2.014%. The complexity of the heuristic is O(n) for a fixed number of evaluations. Although our bound only approaches the one of Roundy (1985), when only a small number of points are evaluated, our method is faster. We show that the bound for our procedure and two bounds proposed by Roundy (1985) are tight. The second heuristic pertains to a class of polities called stationary interval policies. For this class of policies, we develop a fully polynomial-time approximation scheme where the relative error is within ε > 0, and the computational effort increases as a linear function of 1/√ε. Computational experiments show that these heuristics perform well in practice.
The Strategic Use of Capacity Slack in the Economic Lot Scheduling Problem with Random Demand
Authors: Bourland Karla E. , Yano Candace A. 
Published: November 2008

Growing interest in designing systems with capacity slack as one form of flexibility raises many questions about its use and its usefulness. In the framework of the economic lot scheduling problem with stochastic demand, we develop on optimization-based model that considers capacity slack, safety stock, and overtime explicitly, and has the objective of minimizing the expected cost per unit time of inventory, overtime, and, where applicable, setup costs. The solution is a continuous-time production plan that consists of a time-dependent inventory trajectory for each of the parts, including the placement of planned idle time in the schedule. We consider schedule stability to be desirable because of potential effects on upstream and downstream operations in multistage production settings. Thus, the plan also has certain characteristics that contribute to achieving stability. Our results on the relative merits of capacity slack and safety stock indicate that capacity slack in the form of planned idle time is not a cost-effective hedge against demand uncertainty in this context. Thus, it is essential that management carefully identify and evaluate other reasons for including idle time in a plan, and use the idle time effectively. For managers who face situations not fully represented by our model, this paper provides analytic results that will guide them in the placement of planned idle time and the choice of safety stock levels.