A Sequential Simplex Pattern Search Solution to Production Planning Problems

There are several efficient search procedures which have been developed recently for finding the minimum or maximum of a function of several variables. The search techniques are contrasted, as alternate ways of solving problems, to the usual algorithmic techniques of operations research such as linear and dynamic programming. Among these search procedures are Powell's method (7), Fletcher and Powell's method (3), Hooke and Jeeves' pattern search (5), and the sequential simplex pattern search (1), (2), (6), and (8). Of these, the sequential pattern search is probably the simplest and most efficient. It is the purpose of this article to expose the reader to this method and to illustrate how this method can be used to solve problems arising in production planning and inventory control.     

Optimization Techniques for System Reliability with Redundancy?A Review

This paper is a state-of-art review of the literature related to optimal system reliability with redundancy. The literature is classified as follows. Optimal system reliability models with redundancy Series Parallel Series-parallel Parallel-series Standby Complex (nonseries, nonparallel) Optimization techniques for obtaining optimal system configuration Integer programming Dynamic programming Maximum principle Linear programming Geometric programming Sequential unconstrained minimization technique (SUMT) Modified sequential simplex pattern search Lagrange multipliers and Kuhn-Tucker conditions Generalized Lagrangian function Generalized reduced gradient (GRG) Heuristic approaches Parametric approaches Pseudo-Boolean programming Miscellaneous     

One pot,two step sequence converting atom transfer radical polymerization directly to radical trap-assisted atom transfer radical coupling

Monobrominated polystyrene (PStBr) chains were prepared using standard atom transfer radical polymerization (ATRP) procedures at 80 °C in THF, with monomer conversions allowed to proceed to approximately 40%. At this time, additional copper catalyst, reducing agent, and ligand were added to the unpurified reaction mixture, and the reaction was allowed to proceed at 50 °C in an atom transfer radical coupling (ATRC) phase. During this phase, polymerization continued to occur as well as coupling; expected due to the substantial amount of residual monomer remaining. This was confirmed using gel permeation chromatography (GPC), which showed increases in molecular weight not matching a simple doubling of the PStBr formed during ATRP, and an increase in monomer conversion after the second phase. When the radical trap 2-methyl-2-nitrosopropane (MNP) was added to the ATRC phase, no further monomer conversion occurred and the resulting product showed a doubling of peak molecular weight (M_p), consistent with a radical trap-assisted ATRC (RTA-ATRC) reaction.     

Bax is an important determinant of chemosensitivity in pediatric tumor cell lines independent of Bcl-2 expression and p53 status

Susceptibility of a tumor cell to undergo chemotherapy-induced apoptosis appears to be dependent upon the balance of proapoptotic and survival factors that are expressed within any given cell. We have chosen to evaluate how expression of several of these proteins influences chemosensitivity of a panel of 10 pediatric tumor cell lines chosen from three tumor histiotypes: neuroblastoma, rhabdomyosarcoma, and pediatric glial tumors. The proteins evaluated were p53 and six members of the Bax/Bcl-2 family: three proapoptotic proteins (Bax, Bak, and Bcl-xS) and three survival factors (Bcl-2, Bcl-xL, and Mcl-1). We investigated whether there was any relationship between endogenous expression of these proteins and chemosensitivity (or resistance) to three chemotherapeutic agents that directly damage DNA (doxorubicin, actinomycin D, and topotecan) and a mitotic spindle poison (vincristine). Even though exogenous overexpression of wild-type p53 has been associated with a chemosensitive phenotype in several model systems we demonstrated no such relationship in these studies. In addition, expression levels of Bcl-2, Bcl-xL, Bcl-xS, Bak, or Mcl-1 did not correlate with sensitivity or resistance to the four drugs. However, there was a statistically significant correlation between endogenous levels of Bax protein and sensitivity to both doxorubicin and actinomycin D. We conclude that even though many proteins such as p53 and Bcl-2 have been shown to influence drug response when exogenously overexpressed in model systems, in unmodified cell lines endogenous protein levels may not generate the same results. We have demonstrated that endogenous Bax expression was the only protein found to be associated with chemosensitivity across the three different tumor histiotypes and propose that analysis of Bax may be a more useful prognostic indicator for tumor response to therapy than either p53 or Bcl-2.     

System Effectiveness Models: An Annotated Bibliography

A state-of-the-art survey on system effectiveness models is presented. A variety of system effectiveness models dealing with military and space systems have been developed by the US Air Force, Army, and Navy. Each model has different attributes in its definition of system effectiveness. This survey classifies these attributes and definitions and presents their relationship to system effectiveness. Attributes included are reliability, availability, operational readiness, repairability, maintainability, serviceability, design adequacy, capability, dependability, human performance, and environmental effects. The system effectiveness models and their computer codes are also classified and reviewed.     

Optimization of Life Support Systems Reliability by an Integer Programming Method

The problem considered is to minimize the weight of the subsystems of a life support system subject to several separable nonlinear constraints while maintaining an acceptable level of reliability of the system. Zero-one integer programming is used to solve this problem. The subsystems of the life support system designed by the Space Division of the North American Rockwell Corporation are studied examples. They are the refrigerant circuit, the cryogenic oxygen circuit, the carbonization cell, and the water reclamation unit. The results obtained are compared with the original design proposed by the North American Rockwell Corporation. The comparison indicates that the use of the integer programming for determining the optimization reliability would result in an improved arrangement of the standby units.     

Simulation Model of Mission Effectiveness for Military Systems

Mission effectiveness, the probability of successfully accomplishing the mission, is a practical measure of a unit's usefulness. Each unit has 2 s-independent components (hardware and operator) in series. Mission effectiveness for a particular sortie and unit is determined by finding the joint probability measure of the following 4 factors: the availability of the unit at the beginning of a sortie; the sortie-reliability of the unit; the conditional probability of successful performance of the unit in a given environment; and the conditional probability of the successful operator performance during a sortie as a function of time since last retraining. A computer simulation model is developed. It is more general and practical than Markov models, since the simulation model can directly handle any empirical probability distributions for the random variables whereas the Markov approach is limited to the exponential distribution. The simulation model appears to be a semi-Markov model where each transition is a regeneration point.     

Optimal Scheduled-Maintenance Policy Based on Multiple-Criteria Decision-Making

Usually, more than one independent (conflicting) criterion is important in determining the replacement age of a critical item for a maintained system. In this study, mathematical models have been developed for three such criteria: 1) minimum replacement cost-rate, 2) maximum availability, and 3) lower-bound on mission reliability. The solutions are obtained using four methods for multiple criteria decision making: 1) strictest-selection, 2) lexicographic, 3) Waltz lexicographic, and 4) sequential multiple-objective problem-solving technique (SEMOPS). Using an aircraft engine as an example, the optimal replacement age has been found by the four different methods. The results and the implications of the methods are discussed.     

An evaluation of water extraction as a soil-testing procedure for phosphorus II. Factors affecting the amounts of water-extractable phosphorus in field soils

The effects of seasonal variation, sampling depth, and fertilizer P addition on water-extractable P values were investigated in two field experiments, involving soils of contrasting P retention capacity (Ramiha and Tokomaru) under permanent pasture over 12 months. The effects of the same parameters on Olsen-extractable P were also evaluated. The amounts of water-extractable P in soil were always lower than those of Olsen-extractable P. Over the 12-month period, the average value of water-extractable P in the unfertilized Ramiha soil (0–7.5 cm depth) was 1.8µg g^–1 soil compared to an Olsen-extractable P value of 12.6µg g^–1. The variability associated with water-extractable P at each sampling time was comparable with that for Olsen-extractable P. However, the relative seasonal variation over 12 months was larger for water-extractable P than for Olsen-extractable P. The results obtained with both extractants showed a seasonal fluctuation which was closely related to the pattern of pasture P uptake. The amounts of water- and Olsen-extractable P were higher in samples taken from the 0–4.0 cm than the 0–7.5 cm sampling depth. Fertilizer P addition resulted in larger increases in water-extractable P in the 0–4.0 cm sampling depth than in the 0–7.5 cm depth. The relative increase in water-extractable P following fertilizer P addition was larger than that of Olsen-extractable P. Seasonal changes in the soil microbial biomass P were not related to changes in either water-extractable P or plant uptake of P. Microbial biomass P may be a less sensitive index of soil P availability than is commonly thought.     

A literature survey of the human reliability component in aman-machine system

The body of literature addressing human errors and their effect on system performance is listed and categorized. The following factors were considered in classifying the literature: (1) applicability-human performance prediction, performance analysis of man-machine system, man-machine reliability allocation, human-error data collection, or human-error overview, (2) system under consideration-human component only or both human and hardware and (3) type of task being performed-operational or maintenance work, continuous or discrete tasks, and full range of human behaviour or single functions like decision-making or signal detection