Bayes Estimation of Reliability for Special k-out-of-m:G Systems

Component lifetimes of a k-out-of-m: G system are s-independent and exponentially distributed. The Bayes-quadratic-loss estimator of reliability for the system is obtained using a conjugate (1-parameter case) or a noninformative (2-parameter case) prior when data are type-II censored. A simple approximation formula for the mean square error of the Bayes estimator is proposed. Based on the mean square-error criterion, the performance of the Bayes estimator under a noninformative prior is compared with that of the maximum likelihood and minimum variance s-unbiased estimators.     

Reception of Nonhomogeneous Signal Fields in the Presence of Homogeneous Noise Fields

The reception of a nonhomogeneous signal field embedded in a homogeneous noise field, using a simple two-element subtractive array, is studied. For element spacing which is small compared to both the distance to the source and to the center-frequency-wavelength, the signal-to-noise improvement over a single element is shown to be independent of element spacing d, relatively independent of bandwidth and the noise spatial distribution, and to depend only on the distance to the signal source in wavelengths and on the signal ground-wave attenuation rate.     

Mixed mode stress intensity distributions for part circular surface flaws

Using the frozen stress method, mixed mode stress intensity factor (SIF) distributions were obtained for a series of low aspect ratio part circular surface flaws in flat plates over a depth to plate thickness range of 0.20–0.70. Mode I results were compared with Mode I solutions in order to sense the influence of the crack surface inclination to the free boundary. It was found that maximum SIF values did not necessarily occur at maximum flaw depth. A rationale is offered to explain this observation. It was also found that the effect of the boundary inclination was to reverse the relative magnitudes of $\text{K}{}_1\text{K}\text{?}{}_1$ and $\text{K}{}_2\text{K}\text{?}{}_2$ in going from a 30° to a 60° crack surface inclination with the boundary.     

The effect of wastewater phosphorus removal on shagawa lake, Minnesota: phosphorus supplies, lake phosphorus and chlorophyll a

In early 1973, the phosphorus supply to Shagawa Lake, Minnesota, was reduced by about 80% when a tertiary wastewater treatment plant began operating. Significant reductions in total and soluble reactive phosphorus concentrations have occurred in the lake since that time. By 1976 the average (volume weighted over the entire lake) total and soluble reactive phosphorus concentrations had declined from about 51 and 21 μg l⁻¹ to about 30 and 4.5 μg l⁻¹, respectively, corresponding to 40 and 80% reductions. During 1975 and 1976, chlorophyll a (averaged over the top 5 m) had decreased to less than 50% of the pretreatment level during May-June but during July-August little change had occurred.

A phosphorus residence time model projected equilibrium total phosphorus concentrations of about 12 μg l⁻¹ within 1.5 years. The fact that this level was not reached is attributed to a feedback of phosphorus from the sediments, primarily during summer. This phenomenon has been incorporated into a modified total phosphorus mass balance model which projects the phosphorus pattern through 1976 quite accurately. The close fit of the modified mass balance model implies that the phosphorus supply from the sediments has not diminished since treatment since treatment began, and that further recovery of the lake will depend upon how long this feedback of phosphorus from the sediments continues.     

Power company fuel supply — Problems and solutions

A power company in the business of supplying electricity to its customers faces numerous problems associated with power production. One of its major problems is to supply its power plants with fuel and to use that fuel as economically as possible.The purpose of this paper is to discuss the difficulties that a power company has in supplying itself with fuel and to propose a technique that will produce a more prudent and economical use of fuel. The technique utilizes a multistage computer algorithm, which takes into consideration the power company's complete fuel supply process from coal mine to busbar. It requires a mathematical modeling of this process and allows for as much modeling flexibility as possible.