The effect of soil Ph on olsen bicarbonate phosphate values

The effect of increases in soil pH by liming on Olsen bicarbonate phosphate (P) test values was investigated using two contrasting New Zealand soils: a highly P retentive Egmont soil and a Tokomaru soil with a low P retention capacity. After incubation with three rates of Ca(OH)₂, soil pH was increased, and a reduction in the Olsen P values was observed. The amounts of ³²P-exchangeable P, however, increased with increasing soil pH, and there was very little change in water-extractable P. The addition of lime had no significant effect on either the yield or uptake of P by ryegrass grown on the same soils in the glasshouse. It appears that the decline in Olsen P values in soils following liming is a result of an artefact in the Olsen procedure. High concentrations of Ca are involved in the decrease in Olsen P values in limed soils. It is suggested that the precipitation of calcium phosphates in the Olsen extracts of limed soils is responsible for the decrease in the Olsen P values. In a field experiment, increasing soil pH by lime addition also resulted in a decrease in the Olsen P values.     

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.     

Optimal Reliability of a Complex System

In a complex system where the redundant units cannot be reduced to a purely parallel or series configuration, the reliability is obtained by using Bayes' theorem. A mathematical model is formulated for the reliability of a system with nonlinear constraints. The system reliability is optimized based on the model and the solution is obtained by using the sequential unconstrained minimization technique (SUMT). This method is an efficient method for solving this type of problem. Two life support systems, one is the communication system of a two-man space capsule and another is a high-pressure oxygen supply system in a space capsule, have been identified to have the complex system configuration treated in this work.     

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.     

Optimization of System Reliability by the Sequential Unconstrained Minimization Technique

The reliability of a complex system was optimized by a new approach for implementing the sequential unconstrained minimization technique (SUMT) with the aid of Hooke and Jeeves pattern search and heuristic programming. Two optimization problems were considered. In the first, the system reliability was maximized subject to a nonlinear weight constraint. In the second, the weight of the system was minimized without violating the requirements of the minimal system reliability and the minimum reliability for each component. The sensitivities of the system reliability and that of the system weight to the reliability of each component were determined under optimal conditions.     

Optimization of Systems Reliability

The purpose of this paper is to obtain an optimum redundancy of the parallel system by a variational technique. The objective function is to maximize the system profit. A simple computational procedure is obtained for the optimum design of the multistage parallel systems by this method. Two numerical examples are given in detail.     

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.     

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.     

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.     

The effects of connector spacing and distribution on the buckling behaviour of some single-cell and twin-cell box columns

Results are presented from a series of compression tests carried out on geometrically similar single-cell and twin-cell thin-walled box columns made by joining thin flat sheets together with rivet connectors. In particular a study has been made of the effect of changing the connectors' spacing and distribution on a column's initial buckling stress.The results show that the single-cell columns responded least to the changes and this appeared to be related to the geometry of the constituent plates. Significant differences were observed, however, with the twin-cell columns. Higher initial buckling loads were obtained from columns that had been made by using a ‘staggered’ connector distribution pattern as compared with those made by using a more ‘regular’ pattern. This result appeared to depend on the development of a skewed local buckling mode between the connectors.