A Primal Simplex Specialization for the Equal Flow Problem

This paper presents a primal simplex specialization for the equal flow problem. This approach is motivated by a desire to exploit the special structure of the side constraints and to maintain as much of the characteristics of pure network problems as possible. The simplex computations are discussed and a starting solution based on the subgradient optimization technique is presented. Our implementation is tested on problems with up to 1500 nodes, 6600 arcs and 600 equal flow pairs. These problems are also solved using MPSX and another specialized code for the equal flow problem. We present Computational experience which indicates that our approach is well suited for problems with up to 150 side constraints. As the number of pairs increased, MPSX with an advanced start procedure, performed better than our specialized code.     

Allocating Items to an Automated Storage and Retrieval System

To reduce material handling costs, distribution centers purchase automated storage and retrieval systems (AS/RS). It is often the case that the capacity of the AS/RS is insufficient to store all items. The distribution center must then decide which items to assign to the AS/RS and in what quantities they will be stored. In this paper, we develop a heuristic procedure to solve this problem. A priori and a posteriori tests of the data for the optimality of this heuristic procedure are provided. The proposed procedure is testedwith data gathered fr oma naval supply center.     

A Study of an Automatic Transfer Line System with a Sub-Line

The purpose of this paper is to investigate the behaviour of an automatic transfer line system with a sub-line in which each stage has one machine using a Markov model. In the system each machine has an unequal operation cycle time, so we observe the system state at intervals of the greatest common measure of the unequal operation cycle times. From the numerical analysis we present a split interference between main- and sub-lines which decreases the production rate. This interference is different from one presented in a series line. Furthermore, we present the effects of buffer and split probability on the production rate.     

Monotonicity in Optimal Policy of a Flexible Manufacturing Cell Feeding Several Production Lines

This paper deals with an optimal part selection problem tominimize the expected cost, in an automated manufacturing system in which a flexible manufacturing cell produces different parts for several production lines. The optimal control problem is formulated as an undiscounted semi-Markov decision process. Properties of the optimal policy are analyzed. Moreover, sufficiency conditions are derived for the optimal policy to be of control iimit type.     

The interaction of location and inventory in designing distribution systems

Many companies face the strategic decision of deciding on the number of Distribution Centers (DCs), their location, and which customers they serve. One objective for a company facing this decision is to maintain acceptable service while minimizing the fixed costs of operating the DCs, inventory holding costs at the DCs, and transportation costs between plants and DCs, and DCs and customers. For insight into this problem, we develop an analytical model for a stylized version of it. However, since the general version of the problem is NP-Hard, we also develop heuristic procedures. We solve a variety of example problems to test the performance of these heuristics relative to optimal solutions and a lower bound based on a relaxation of the original problem. Managerial insight based on our computational studies is provided. We also present a small case-study example motivated by our interaction with Frito-Lay, Inc     

Optimal Depreciation Policy Under the Tax Reform Act of 1986

Mathematical expressions for allowable depreciation are developed for the Modified Accelerated Cost Recovery System (MACRS) as well as the allowed alternate method (AMACRS), two capital recovery methods permitted under the Tax Reform Act of 1986. The choice between MACRS or AMACRS is rigorously analyzed with respect to normal asset disposition, premature asset disposition, monotone decreasing tax rates and monotone increasing tax rates. Conditions under which either MACRS or AMACRS is optimal are specified, and the economic value of the optimal policy is determined. Numerical illustrations are provided throughout the paper to demonstrate the underlying methodology.     

Degradation of tobramycin in aqueous solution

The kinetics of degradation of tobramycin (Ne-De-Ka) in aqueous solution was studied as a function of pH. Tobramycin hydrolyzes in acidic solution to yield kanosamine (Ka-OH) and nebramine (Ne-De-OH) with a pseudo first-order rate constant of 2.7 × 10^-6 s^-1 in 1 N HCl at 80°C. The activation energy for the acid catalyzed hydrolysis is 32 kcal mol^-1. In basic solution, the hydrolysis products are deoxystreptamine (De-OH), nebramine (Ne-De-OH) and deoxystreptamine-kanosaminide (HO-De-Ka). The pseudo first-order rate constant for the hydrolysis in 1 N KOH is 1 × 10^-8 s^-1 at 80°C. The activation energy for the base catalyzed hydrolysis is 15 kcal mol^-1. Tobramycin is very stable towards hydrolysis at neutral pH; however, it rapidly oxidizes giving several products including De-OH, Ne-De-OH, and HO-De-Ka. In pH 7 phosphate buffer (0.01 M), the t₉₀ value is 70 hr at 80°C.     

Designing a Cellular Manufacturing System: A Materials Flow Approach Based on Operation Sequences

This paper presents a cell formation method which integrates the issues of cell formation and with in-cell material flows. A coefficient which assesses the similarity of two parts in terms of their operation sequences is proposed and used to form part families and cells. Further, the within-cell machine sequence and machine loads are explicitly considered in the design process. The methodology has been operationalized through several computer programs )written in FORTRAN 77) and implemented on an IBM/PC, An application of the design methodology to a hypothetical cell formation problem is provided.     

Parallel time scales and two-dimensional manufacturer and individual customer warranties

We deal with a system whose failures depend on several parallel effects, such as the time in use L and the mileage H. Manufacturer warranties are typically described by a two-dimensional region in the (L, H)-plane. A proper determination of the warranty limits must be based on a two-dimensional distribution of time to failure on this plane. The aim of this paper is to demonstrate the possibility of designing individual warranties for a “nontypical” customer who has a very low or very high usage rate b = H/L, and to show a simple way to calculate warranty limits by minimizing the lifetime coefficient of variation. The latter is carried out by introducing the “best” combined time scale in the form K = (1-ε)L+εH which provides the minimal lifetime coefficient of variation.     

Reacting to Scheduling Exceptions in FMS Environments

Uncertainties in the production environment and modelling limitations inevitably result in operational deviations from schedules generated using predictive models. A production control mechanism monitors the environment for exceptions, and takes corrective actions, with the objective of adhering closely to planned objectives. This paper proposes a knowledge based (KB) methodology to perform such control in FMS environments. Use of KB techniques is motivated by the observation that control knowledge has a high heuristic content. A PROLOG implementation of this methodology, that generates automatic response to machine failures, dynamic introduction of new jobs, and dynamic increase in job priority, is presented. Experimental results appear to show that simple and generic design strategies for the KB can provide the basis for effective and robust control behavior.     

Effect of hydroxypropyl-beta-cyclodextrin on the solubility of an antibacterial isoxazolyl-naphthoquinone

The complexation of 2-hydroxy-N-(3,4-dimethyl-5-isoxazolyl)-1,4-naphthoquinone-4-imine (I) with a highly soluble cyclodextrin, hydroxypropyl-β-cyclodextrin (HP-β-CD) was studied in aqueous media by solubility methods. I is an antibacterial and trypanocidal agent that is undergoing preclinical testing. Unfortunately, I exhibits low water solubility, and it is therefore difficult to prepare the solutions for biological tests. I inclusion took place with 1:1 stoichiometry. The stability constants of the I complexes calculated from the slope and the intercept of the phase solubility diagrams are larger in the less ionized form, whereas greater overall solubility is obtained in basic media.     

Analysis of the Prediction Problem with Errors in the Variables

In engineering and other scientific works variables are frequently measured with error, resulting in so-called errors-in-variables situations. The problem of estimating unknown parameters in an errors-in-variables model (EVM)has been extensively discussed in the literature while relatively little has been concerned with the prediction problem in the EVM context. In this paper the integrated mean square, error of prediction (TMSE) is developed for a multiple functional relationship model as a measure of the effect of errors in the variables on the predicted values. The IMSE may be used for assessing the severeness of measurement errors as well as for discriminating competing estimators. Relative performances of various estimation methods for a simple functional relationship are compared in terms of the IMSB, Proposed methods are illustrated with two examples, one from business forecasting and the other from work measurement.     

Variance Reduction in the Presence of Initial-Condition Bias

We consider the application of antithetic variates and control variates variance reduction techniques (VRTs) in the context of steady-state simulation experiments when initial-condition bias is present. We show that, by appropriately modifying the experiment design, incorporating a VRT can improve both point and interval-estimator performance. Guidelines for modifying the experiment design are given.     

Control Charts Applied as Filtering Devices Within a Feedback Control Loop

A set of statistical process control filters and the procedures for their employment as filters in a feedback control loop are designed. These filters are similar to the control charts applied to continuous flow processes. The statistical process control filters are evaluated for the quality of the process output given that a particular filter is used and compared to the results that are achieved if conventional filtering devices are used. The performance measure employed is developed within the research.     

Human Physiological Capabilities for Prolonged Manual Lifting Tasks

The objective of this study was to determine human physiological capabilities for prolonged lifting tasks performed from the floor to table height. Frequency and weight of load were the independent variables. Oxygen consumption, minute ventilation, and heart rate were the dependent variables. Physiological responses were monitored continuously for each frequency-load combination. Eleven male subjects participated in the experiments. The duration of each experimental session was controlled by the subject. Each subject was instructed to perform the lifting task continuously until he could not maintain it any longer due to complete physical exhaustion. Each subject was given 10 minutes of rest every 50 minutes of work and 1 hour for lunch after the fourth hour of work. The upper limit of lifting duration was set to 8 hours. One of the main findings obtained from this study was that a physiological fatigue limit (PFL) is a function of lifting task parameters (frequency, weight of load, and task duration). Thus, one cannot recommend a single PFL value such as 1 liter/min for lifting tasks of varied work durations.     

Synthesis, Photophysical and Photovoltaic Properties of New [60]Fullerene Pyrrolidine Derivatives

Two new [60]fullerene pyrrolidine derivatives 2 and 3 were synthesized and characterized by ¹H NMR, ¹³C NMR and MS. Their photophysical processes have been investigated by using laser flash photolysis. The experiments show quenching of oligomer singlet excited state and the evidence of the fullerene singlet excited emission. And the intramolecular of electron transfer and also energy transfer of 2 and 3 occurred and the triplet excited state of fullerene moiety in 2 and 3 have different lifetime due to their different structures. A photovoltaic device using compound 2 as the only photoactive material has also been investigated which showed the energy conversion efficiency is 0.011%.     

Mixed-model assembly line scheduling using the Lagrangian relaxation technique

The increasing market demand for product variety forces manufacturers to design mixed-model assembly lines on which different product models can be switched back and forth and mixed together with little changeover costs. This paper describes the design and implementation of an optimization-based scheduling algorithm for mixed-model compressor assembly lines at Toshiba with complicated component supply requirements. A separable integer optimization formulation is obtained by treating compressor lots going through a properly balanced line as undergoing a single operation, and the scheduling goal is to delivery products just in time while avoiding possible component shortage. The problem is solved b y using Lagrangian Relaxation (LR). Several generic defects of LR leading to slow algorithm convergence are identified based on geometrical insights, and are overcome by perturbing/ changing problem parameters. Numerical testing shows that near-optimal schedules are efficiently obtained, convergence is significantly improved, and the method is effective for practical problems. The system is currently under deployment at Toshiba     

Policy mechanisms for supply chain coordination

The problem is to determine a review period and stocking policy that are mutually beneficial to a producer and a retailer. In our model, the retailer uses a periodic review, base stock policy for ordering the item from the producer's Distribution Center (DC). Excess customer demand is assumed to be lost. A make-to-order production system supplies to the DC. We show that given a review period, unless the manufacturer agrees to share the cost of carrying a fraction of the safety stocks at the retailer, the two will not agree upon the level of stocks to be carried in the store. We prove that there is an equilibrium value for this fraction, such that the retailer and the manufacturer are always in agreement with regard to the stocking level. We then show that complete coordination on the stocking level as well as the review period can be achieved solely through carrying out negotiations on credit terms. These theoretical results are used to construct an algorithm for calculating the optimal policy parameters for a supply chain. As part of the analysis we suggest a modification of the base stock policy for the positive lag lost sales case of periodic review inventory models that consistently outperforms the base stock policy in our numerical studies.     

Degradation products of mycophenolate mofetil in aqueous solution

The thermal and peroxide-catalyzed degradation products of mycophenolate mofetil (1) were studied in aqueous solution at pH 2.0, 3.5, 6.0, and 8.2. The major thermal degradation product observed was mycophenolic acid (2). At pH 6.0 and 8.2, 2 was the only product observed in the absence of peroxide, while at pH 2.0 and 3.5, the lactone analogue of mycophenolic acid (5), a hydroxylactone due to oxygenation of the double bond (6), and an unidentified product were formed. Compound 6 degraded to 4-hydroxy-6-methoxy-7-methyl-3-oxo-1,3-dihydro-isobenzofuran-5-carbaldehyde (9) on prolonged storage and was present in the sample stressed at pH 2. Mycophenolic acid (2), the N-oxide of mycophenolate mofetil (3), the hydroxylactone of mycophenolic acid (6), and the erythro form of 4-methoxy-5-methyl- 2-(2-methyl-5-oxo-tetrahydro-furan-2-yl)-3,6-dihydro-2H-1,7-dioxa-as-indacen-8- one (8) were observed in the presence of hydrogen peroxide at pH 3.5, 6.0, and 8.2. In addition, at pH 8.2, 4-hydroxy-4-(4-methoxy-5-methyl-8-oxo-2,3,6,8-tetrahydro-1,7-dioxa-as-indacen-2-yl)-pentanoic acid (7) was seen. Peroxide-stressed samples at pH 2.0 gave no major degradation peaks, but a small amount of the hydroxylactone of mycophenolic acid (6) was formed.     

Prediction and optimization of a ceramic casting process using a hierarchical hybrid system of neural networks and fuzzy logic

This paper is a case study that describes a hybrid system integrating fuzzy logic, neural networks and algorithmic optimization for use in the ceramics industry. A prediction module estimates two quality metrics of slip-cast pieces through the simultaneous execution of two neural networks. A process improvement algorithm optimizes controllable process settings using the neural network prediction module in the objective function. An expert system module contains a hierarchy of two fuzzy logic rule bases. The rule bases prescribe processing times customized to individual production lines given ambient conditions, mold characteristics and the neural network predictions. This paper demonstrates the applicability of newer computational techniques to a very traditional manufacturing process and the system has been implemented at a major US plant.