1,596 research outputs found
Balancing reliability and cost to choose the best power subsystem
A mathematical model is presented for computing total (spacecraft) subsystem cost including both the basic subsystem cost and the expected cost due to the failure of the subsystem. This model is then used to determine power subsystem cost as a function of reliability and redundancy. Minimum cost and maximum reliability and/or redundancy are not generally equivalent. Two example cases are presented. One is a small satellite, and the other is an interplanetary spacecraft
How much redundancy: Some cost considerations, including examples for spacecraft systems
How much redundancy should be built into a subsystem such as a space power subsystem. How does a reliability or design engineer choose between a power subsystem with 0.990 reliability and a more costly subsystem with 0.995 reliability. How does the engineer designing a power subsystem for a satellite decide between one power subsystem and a more reliable but heavier power subsystem. High reliability is not necessarily an end in itself. High reliability may be desirable in order to reduce the statistically expected loss due to a subsystem failure. However, this may not be the wisest use of funds since the expected loss due to subsystem failure is not the only cost involved. The subsystem itself may be very costly. The cost of the subsystem or the expected loss due to subsystem failure may not be considered separately. Therefore, the total of the two costs is minimized, i.e., the total of the cost of the subsystem plus the expected loss due to subsystem failure. A specific type of redundant system is considered, called a k-out-of-n: G subsystem. Such a subsystem has n modules, of which k are required to be good for the subsystem to be good. Five models are discussed which can be applied in the design of a power subsystem to select the unique redundancy method which will minimize the total of the cost of the power subsystem plus the expected loss due to the power subsystem failure. A BASIC computer program is available
Reliability and cost: A sensitivity analysis
In the design phase of a system, how a design engineer or manager choose between a subsystem with .990 reliability and a more costly subsystem with .995 reliability is examined, along with the justification of the increased cost. High reliability is not necessarily an end in itself but may be desirable in order to reduce the expected cost due to subsystem failure. However, this may not be the wisest use of funds since the expected cost due to subsystem failure is not the only cost involved. The subsystem itself may be very costly. The cost of the subsystem nor the expected cost due to subsystem failure should not be considered separately but the total of the two costs should be maximized, i.e., the total of the cost of the subsystem plus the expected cost due to subsystem failure
Beneficial True Bugs: Minute Pirate Bugs
This fact sheet describes beneficial true bugs: minute pirate bugs. It includes their life cycle and tips for promoting beneficial insects such as conservation and enhancement, predator release, and the predator release process
What is Science?
We give a brief discussion of issues related to the nature of science. Our formulation is such that it applies to all scientific domains. We also present an argument which illustrates why mathematics is of fundamental importance to scientific methodology. Finally, a summary is provided of the pre-conditions which must be satisfied, in the physical universe, such that science is possible
Systems Exhibiting Alternative Futures
We construct an explicit example of a physical system having alternative futures (AFs). Several other such systems are also introduced and characterized, but not discussed in detail. Our major goal is to use these results to demonstrate the existence and meaning of the concept of counterfactual histories (CFHs). We find that any system having AFs will also exhibit the phenomenon of CFHs
Gardening Basics
This fact sheet provides basics for gardening, including location, sunlight, spacing, growing season, soil, water, and planting seeds versus plants
Small Acreage Low Flow (Micro or Drip) Irrigation System Design and Installation
Irrigation has been an essential part of Utah’s agriculture since pioneer days. Over half of Utah’s 1.3 million irrigated acres are watered using surface methods such as flood, furrow, border, or basin irrigation
Effects of Sulfates in Water on Performance of Steers Grazing Rangeland
Surface and subsurface water in South Dakota often contains high concentrations of total dissolved solids (TDS) and sulfates, which, in severe cases, can cause livestock deaths. Data from our laboratory have demonstrated that sulfate concentrations of 3,000 ppm in water consumed by steers in dry-lot decreased ADG, feed intake, and water consumption. Little information is available on the effects of water sulfate concentrations on grazing livestock. This study evaluated the effects of water quality and two vegetation communities on the performance of steers grazing rangeland. Eight native pastures at the SDSU Cottonwood Research Station were used. Four pastures were dominated by warm-season shortgrasses (SG) and four by cool-season midgrasses (MG). Yearling steers (105/year) were allotted to pastures in 2001 and in 2002 to attain a moderate stocking rate of 0.50 AUM/acre during a 4-month grazing season. In 2002, cattle were removed after two months due to drought, resulting in a stocking rate of 0.25 AUM/acre. Number of cattle per pasture varied from 7 to 30, depending on pasture size. Cattle in two of the SG and two of the MG pastures received high sulfate water (HS, 2001: average = 3,947 ppm sulfates; 2002: average = 4,654 ppm sulfates) with low sulfate water (LS, 2001: average = 404 ppm sulfates; 2002: average = 441 ppm sulfates) provided in the remaining pastures. Average daily gain was greater for the LS steers than HS steers in 2001 (P = 0.003; 1.85 and 1.65 lb/d, respectively) and in 2002 (P = 0.001; 2.43 and 1.79 lb/d, respectively). An interaction between sulfate concentration in water and vegetation community in 2002 (P = 0.078) resulted from similar ADG for steers on SG (1.83 lb/d) and MG (1.74 lb/d) pastures for HS water, but greater ADG for steers on MG (2.54 lb/d) than SG (2.32 lb/d) pastures for LS water. During the two-year study, only one steer had health problems related to sulfur, with no deaths. Our study showed water with sulfate concentrations of 3,947 ppm and greater reduced ADG of grazing steers, and that the response was influenced by vegetation
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