Production Scheduling with Sequence Dependent Setup Costs

The problem of scheduling products, with constant demand rates, on a single facility is difficult. This difficulty is compounded if the setup costs are not constant for each product but depend on the sequence in which the products are made. A heuristic that iterates between solving the scheduling problem with constant setup costs and solving a “traveling salesman” formulation with sequence dependent setup costs is presented. The heuristic works well in practice and always provides a feasible solution if one exists. Some computational experience is also given.     

A Quadratic Facility Location Problem

This article treats the problem of locating multiple new facilities with respect to multiple existing facilities when there is an interchange of materials between new facilities and between new and existing ones. The “cost” of a solution to the location problem is given as a weighted sum of the square of the Euclidian distances traveled in the interchange of materials. Necessary and sufficient conditions for an optimum location are developed, resulting in the simultaneous solution of a set of linear equations in order to obtain the optimum location. The solution procedure is demonstrated with an example problem.     

The Optimal Sight Angle Problem

We introduce the following problem in this paper. There are n points on the plane that are to be observed from some point on a circle of given radius that encloses all of the points. We wish to find the observation point that has the best possible view of the n points in the sense that if we draw lines of sight from the observation point to the given points, the smallest angle between the lines is maximized. Applications could include the planning of photographs or displays. This is a “maximin problem” in which the function to be maximized has many local optima. We present two methods for solving the problem, one more efficient in computer time, and the other in storage. We also present a simplified procedure for the case where the observation point is “infinitely” distant from the given points.     

A Directly-Coupled Two-Stage Unpaced Line

For a directly-coupled two-stage production system whose stochastic processing times may follow any distribution form, we present a simple procedure for estimating its average cycle time. We then demonstrate systematically the effect of the skewness and kurtosis of processing times on this average cycle time. Finally, we consider a version of the “unbalancing” problem that is more realistic than the classical Hillier-Boling version; we found that for a two-stage directly-coupled system, one should perfectly balance the mean and the skewness of the stages' processing times, but the variance and the fourth moment need not be balanced. Also, if the stages have unequal mean processing times, the station with larger mean should also have larger skewness.     

Epistemic Communities and Cluster Dynamics: On the Role of Knowledge in Industrial Districts

This paper questions the prevailing notions that firms within industrial clusters have privileged access to “tacit knowledge” that is unavailable—or available only at high cost—to firms located elsewhere, and that such access provides competitive advantages that cause the growth and development of both firms and regions. It outlines a model of cluster dynamics emphasizing two mutually interdependent processes: the concentration of specialized and complementary epistemic communities, on the one hand, and entrepreneurship and a high rate of new firm formation on the other.     

Mechanical behaviour of a two-phase material from the behaviour of its components: Interface modelling by finite element method

In this paper, the principle of a solution for “thermal” connection between two solids is analyzed. We shows results given by the solution applied to the mechanical behaviour of a γ/γ′ two-phase material and to “artificial” structures obtained from modern techniques for epitaxial deposit. It appears that the use of a true or fictitious thermal loading constitutes a simple “connection” procedure, but is particularly coherent with the mechanics of two-phase crystalline materials with different lattice parameters. It would be interesting to apply the model to real structures, with misfit and interfacial dislocations.     

HPGe detectors for low-temperature nuclear orientation

Using the Low-Temperature Nuclear Orientation (LTNO) technique one can study various interesting properties of atomic nuclei and nuclear decay which can be deduced from the measurements of the angular distributions of charged particles emitted during the decay. However, the use of particle detectors working in conditions of LTNO devices (which are generally not available commercially) is a necessary precondition for the realization of these experiments.

Planar HPGe detectors for detection of charged particles at “liquid helium” temperatures were developed and produced at NPI e . Relatively simple technology using vacuum evaporation and diffusion was employed. The performance of detectors at low temperatures was tested and their characteristics measured in a testing cryostat before using them in real experiments.

The HPGe detectors were extensively used in a whole range of LTNO experiments with various physical objectives — in offline (IKS Leuven) as well as online (CERN-ISOLDE, Louvain-la-Neuve — LISOL) experiments. In frame of the project “Meson-Exchange Enhancement of First-Forbidden Beta Transitions in the Lead Region”, the measurements of angular distribution of emitted β-particles allowed to determine experimentally the “meson-exchange currents” contribution to the β-decay. In the project “Isospin Mixing in NZ nuclei”, the isospin-forbidden β-transitions of the nuclei in region (A=50–100) were studied in order to obtain information on the isospin structure of the nuclear states. A new project looking for the possible presence of the tensor currents contribution to the β-decay is being prepared for the CERN-ISOLDE facility.     

The calibration of slow neutron polarised beam instruments

A new procedure for calibrating the efficiencies of the polarisation sensitive components in slow neutron polarised beam instruments is described. The measurement of one “flipping ratio” and two “shim ratios” allows the effective polarisation, the spin flipping efficiency, and a depolarising shim efficiency to be determined unambiguously. Results of its application to the calibration of a neutron time-of-flight polarised beam reflectometer are presented.     

A Relational Approach to Organization Design

The paper criticizes the currently dominant view of organization forms as “discrete alternatives” and “coherent” set attributes, and proposes a more refined and micro-analytic view of organization forms as particular combinations of coordination mechanisms and rights allocations. This view is relevant for understanding and devising “new” forms and proposing solutions for governing the composite and fast changing systems of today. The view is “relational” as it offers a procedure for devising “superior” configurations as combinations—relations between organizational components—in a quasi-continuous space of possibilities. The approach is sustained by the quantitative methods of network analysis as applied to relations among firm's resources and activities. Theoretically, the approach revisits organization design, integrating classic organization theory tenets with the new inputs provided by organizational economics. Substantively, it is argued that a mix of much differentiated coordination mechanisms is usually superior to the codified, “packaged”, allegedly “coherent”, forms of organization. The procedure presented in the paper is applied to a field experiment in a medium size firm.1     

Data acquisition system for a hypervelocity-microparticle-impacts laboratory

A Hypervelocity Microparticle Impacts (HMI) laboratory has been established at Los Alamos National Laboratory (LANL) capable of producing high velocity (1 to 100 km/s) highly charged (0.5 to 10 GV/m surface electric field) microparticles (20 to 1000 nm dia). The particles are charged in a “cosmic dust” source and accelerated in either an 80 kV test stand or the 6 MV Van de Graaff facility. A capacitive pick-off particle detection system is used to measure the charge and velocity of individual particles which can be selected to hit the target or deflected away using real-time analog decision circuitry. A NIM/CAMAC/PC based data acquisition system analyzes and displays individual particle events at rates up to 30 events/second. The system setup is data driven from user editable text files so that users can easily reconfigure the system for different types and numbers of data channels or different analysis calculations.     

The Single Period Stochastic Plant Layout Problem

In this paper we present an optimal solution procedure for the single period stochastic plant layout problem. The procedure only requires solving a “deterministic” from-to flow matrix. This “deterministic” matrix is a weighted-average of all from-to flow matrices. Since it may be difficult to estimate the probabilities of occurrence of the various states of nature, we developed a simulation model to test the robustness of our approach. For over 26,000 problems examined, the average error of using our approach was very small, only about one-sixth of one percent.     

Influence of the Parameters Molecular Structure and Granularity on the Compactibility of a Powder

The aim of this study was to determine whether it is possible to obtain better characterization of materials in order to find out if these one are suitable in Quality Assurance for direct tableting. We tried to show that a methodological approach combining chemical, physical and technological aspects could control the direct compression process. We chose orthoboric acid as a study model for the direct compression. From a chemical point of view, our findings show only one crystalline molecular structure (RX, DSC and Pycnometry) which means an homogeneous chemical system. Concerning the particular state (Sieving and Microscopic approach), granularity is very different between the two forms, “crystalline” ABC and “powder” ABP.

Technological studies show a rheological and mechanical difference, as it is demonstrated, on the one hand by the behaviour of the bulk powder (Volumenometer), on the other hand by the feasibility on the machine (Alternative EKO). We explain this difference of behaviour by only the granularity aspect. Consequently, we think that in this case, controling the granularity means controling this direct tableting process.     

Effect of learning and forgetting on economic lot size scheduling problem

The paper determines the sequence of set-ups and quantity to produce in each setup if two products are to be produced on a single facility, considering the effects of learning and forgetting. The cost expression which is to be minimized, consists of three factors: set-up cost, carrying cost and the cost of idle facility. A solution procedure is developed and the analysis is extended for the n-product system.     

A New Approach to Aggregate Production Planning

This paper proposes a new framework for modelling aggregate production planning problems in which emphasis is placed upon offering the user the flexibility to specify (1) the production options to be employed, (2) the relationships among those options (some of which may be highly situation-specific), and (3) the relevant cost structure. The procedure offered for solving the problem embeds Bowmann's “transportation” approach to aggregate production planning into a large mixed integer programming framework.     

A Flow-Through Dissolution Approach to In Vivo/In Vitro Correlation of Adinazolam Release from Sustained Release Formulations

A Copley^TM fraction collector and a Disotest^TM flow-through system were coupled to provide an automatic discrete sampling flow-through dissolution system for use both in the “open-loop” and “closed-loop” mode. The system was used to investigate the release characteristics of adinazolam in sustained release formulations using a pH 1.2 simulated gastric fluid (without enzymes) dissolution medium (USP XXI). These experimental formulations are designed to provide relatively slow to rapid drug release. The dissolution effluent was analysed off-line by reverse phase HPLC to determine the adinazolam concentration at programmed timed intervals. The differential dissolution profiles produced when the system is used in the “open-loop” configuration are more discriminating in describing the release characteristics of the formulations according to the relative release rates than the “closed-loop” cumulative profiles. Using the characteristic dissolution time parameter from the Weibull function, a better correlation with in vivo bioavailability data was achieved for the data from the system in the “open-loop” mode than when it was used in the “closed-loop” mode. In the “open-loop” mode the Weibull function characteristic dissolution time parameter yielded the best quantitative correlation with a correlation coefficient of 0.92 compared to a value of 0.85 for the “closed-loop” configuration     

An Investigation of the Measurements Systems Analysis “Analytic Method” for Attribute Gages

Three automotive corporations have developed and sanctioned the recently revised reference manual entitled Measurement Systems Analysis. This “standard” contains a procedure, called the “analytic method,” whose purpose is to estimate the gage bias and gage repeatability of an attribute gage. An improved estimation procedure for this standard is presented. The improved estimation procedure yields more accurate estimates than those obtained using the procedures currently presented in the standard. In addition, the improved procedure allows more flexibility in data collection than the current test protocol. A simulation study that evaluates the estimation procedure of the current standard and compares it with the improved estimation procedure is presented. Errors that are contained in the present standard are also noted.     

Scheduling with multiple-job-on-one-processor pattern

Most scheduling literature considers a “one-job-on-one-processor” pattern, which assumes that a processor processes exactly one job at a time. In this paper we consider a new scheduling problem with a “multiple-job-on-one-processor” pattern, where several jobs can be processed by a single processor simultaneously, provided that the total size of the jobs being processed does not exceed the capacity of the processor at any point in time. This problem is motivated by the operation of berth allocation, which is to allocate vessels (jobs) to a berth (processor), where the vessels, if small in dimension, may share the berth with some other vessels for loading/unloading the goods. We consider the problem to minimize the makespan of the schedule. The well-known First-Fit Decreasing heuristic is generalized and applied to several variations of the problem, and the worst-case behavior of the generalized heuristics is studied. Worst-case error bounds are obtained for those models. Computational experiments are conducted to test the heuristics. The results suggest that the heuristics are effective in producing near-optimal solutions.     

A dynamic measure of order in structural glasses

Although some patterns of physical behavior are common in the glass transition and in the properties of supercooled liquids and glasses (characteristic viscoelasticity, temperature dependence of viscosity and relaxation times, property evolution through “physical aging”, difficulties in performing equilibrium measurements or simulations, etc.), it is difficult to arrive at a definition of the glass transition which distinguishes it from other phenomena exhibiting similar features. The present paper addresses this problem by defining a dynamical measure of order involving the average “shape” of particle trajectories in supercooled liquids. This dynamic order parameter should provide a measure of “closeness” to the glass transition and some indirect insights into the physical nature of supercooled liquids and glasses. Arguments are given that the proposed dynamic measure of order [“generalized capacity”, C(T)] is related to the temperature-dependent “effective hydrodynamic radius” R_H(T) measured in supercooled liquids and model numerical calculations are given to support this view. Some consequences of the intermittent particle motion at low temperatures for stress relaxation are also discussed.     

A typology for drinking driving offenders: Methods for classification and policy implications

Comprehensive arrest histories were obtained for 353 DUI offenders who were referred to a probation and rehabilitation demonstration program. The average number of total offenses was 7.9, with 89% of all tracked offenders having more than one offense. Approximately 63% of all recorded offenses were other types of offenses besides DUI. The overall arrest history profile of the group suggested that many DUI offenders are habitual violators of other laws as well. To identify distinctive arrest profiles within the referral sample, a Q mode factor analysis followed by a discriminant function analysis was used to classify offenders into profile subgroups. Five distinctive subgroups emerged. A “low offense” group was characterized by the lowest average number of overall arrests and also contained all offenders with no arrest besides the index DUI arrest. A “mixed” group had a higher average number of total arrests than the “low offense” group and diverse types of offenses. A young “traffic” group was distinguished by many hazardous moving violations other than DUI. Two smaller and older groups—a “public drunkenness” group and a “license” group—had the highest average number of arrests including DUI, public drunkenness, license violations, equipment violations, disturbance arrests and assault arrests. These subgroups were found to differ on demographic variables and drinker status variables. The “public drunkenness” group was found to have the highest accident rate. Groups were compared to groups found in other cluster analyses. Also, treatment implications were discussed. It was suggested that treatment programs focusing exclusively on changing alcohol consumption behavior are not likely to reduce accident risk for some of the offender groups. For example, it was suggested that effective intervention for the “traffic” group should target driving behavior, whether drunk or sober, rather than focus exclusively on consumption behavior. Other alternatives are also discussed.     

The Dynamic Lot-Sizing Problem for Multiple Items Under Limited Capacity

This paper addresses the problem of scheduling the timing and quantities of production of n different products over m periods for a single production facility with a prespecified capacity. We assume that the demand is deterministic and can vary from one period to another and from one product to another. The objective is to minimize the sum of production setup and inventory holding costs. For medium-size problems, optimal solution algorithms do not yet exist and therefore heuristic solution algorithms are of interest. Most of the existing heuristics make use of the “forward-pass” concept in one way or the other. Forward pass means we begin by determining the lot sizes for earlier periods before moving to study the later periods. In this paper we study the forward-pass approach as well as a different solution approach which we call the four-step algorithm. We develop the feasibility conditions for pure forward-pass algorithms. Finally, we perform a comparative evaluation study.