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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

An analysis of the impact of reliability and maintainability on the operating and support (O & S) costs and operational availability (Ao) of the RAH-66 Comanche Helicopter

Dellert, Gregg M. 12 1900 (has links)
S costs and Ao is significant if the predicted reliability goals are not met. / US Army (USA) author
2

Measuring availability of healthful foods in two rural Texas counties

Bustillos, Brenda Diane 15 May 2009 (has links)
A comprehensive in-store survey may capture the availability of healthful food alternatives in different store types in two rural counties. The purpose of this study was to: (1) compare the availability of healthful foods in two rural Texas counties; and (2) compare the variety of healthful foods in two rural Texas counties. This study also acts as a pilot test for further food availability research in four other rural counties of the Brazos Valley. An unobtrusive, observational survey was used to measure availability of healthful food in all (100%) grocery, convenience, and discount stores (n=44) in two rural counties in the Brazos Valley of Texas. Results from the surveys indicated that availability of healthful food alternatives varied greatly among the three different store types and two counties surveyed. Grocery stores (n=7) were more likely than convenience (n=31) and discount (n=6) stores to offer fresh fruits and vegetables, leanmeat options, and low-fat/skim milk products. Fresh fruits and vegetables were available in 100% of grocery stores. Only 16.1% of convenience stores, compared with 0.0% in discount stores, offered fresh fruits and vegetables. Variety of fruits and vegetables varied greatly among the three different store types and the two counties surveyed. Findings suggest that the survey utilized was feasible in determining the availability of healthful food items in two rural counties. Implications of this study include the need for knowledge and awareness of rural consumers and rural food supply. Furthermore, nutrition education for rural consumers and those purchasing foods provided to rural areas is desired. This study provided that further investigation into the availability of healthful foods in rural areas is needed.
3

Assessment of server location on system availability by computer simulation /

Weissmann, Eric. January 1994 (has links)
Report (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Includes bibliographical references (leaf 40). Also available via the Internet
4

An analysis of the impact of reliability and maintainability on the operating and support (O&S) costs and operational availability (Ao) of the RAH-66 Comanche Helicopter/

Dellert, Gregg M. January 2001 (has links) (PDF)
Thesis (M.S. in Management) Naval Postgraduate School, Dec. 2001. / "December 2001." Thesis advisor(s): Thom W. Crouch, Keebom Kang. Includes bibliographical references (p. 121-123). Also available online.
5

Analysis of glucosinolates in oilseed rape

Wright, Alan January 1995 (has links)
Four methods of analysis for the determination of total and individual glucosinolates in Brassica napus cultivars (ie Gas Chromatography (GC), High Pressure Liquid Chromatography (HPLQ, Glucose Release, and X-ray Fluorescence Spectrometry (XRF)) were developed, refined, validated and applied. These were used to investigate both high and low glucosinolate cultivars of rapeseed (oilseed rape, Brassica napus), and reproducibility (between replicates) and repeatability (between analysis days) of these methods was assessed. From these studies, an indirect method of glucosinolate determination, involving X-Ray Fluorescence analysis, proved to give the least variable results. Furthermore, this was markedly more rapid than the other methods of analysis. Of the methods assessed for the determination of individual glucosinolates, High Pressure Liquid Chromatography (HPLC) gave less variable results than Gas Chromatography (the European Community (EC) recommended method for glucosinolate determination in oilseed rape at the time of study). Thus, BPLC and XRF analysis were selected as methods for subsequent glucosinolate analysis in the remainder of the study. Effects of geographicallo cation in relation to atmospherics ulphur depositiona nd plant sulphur uptake in Brassica napus cv Ariana grown throughout the UK were determinedin two consecutivey ears. An initial study comparedg lucosinolatele vels in rapeseed samples from 211 sites. A second more detailed study involved determinationo f foliar sulphurl evels (by XRF analysis)a t three stagesd uring plant developmenftr om selecteds itest hroughoutt he UK, and comparisono f thesew ith glucosinolate levels in the harvested seed from these sites. The results of these investigations proved comparable between years, with final glucosinolate levels generally corresponding to atmospheric sulphur deposition levels. Furthermore, high glucosinolatele vels in harvesteds eedg enerallyc orrespondewd ith high sulphur levelsi n foliage ast he plantse ntereds eed-podd evelopment.A series of controlled environment and glasshouse experiments were developed to investigate the effects of sulphur nutrition on glucosinolate development in rape plants during growth. These highlighted that glucosinolate levels in plant material could be manipulated with variation in supplied nutrients. Furthermore, plants initially propagated with sulphur-complete nutrient in hydroponic media, then transferred to sulphur-free nutrient mid-development, were found to give good seed yields with substantially lower glucosinolate levels. In conclusion, attention must be given to choosing the appropriate method for analysis of glucosinolates. Secondly, sulphur availability and sulphur status are critical factors in the determination of glucosinolatelevels, and the relationship between these factors merits further study
6

Zinc Application and its Availability to Plants

30075885@student.murdoch.edu.au, Ross F. Brennan January 2005 (has links)
Globally, low zinc (Zn) soils are widespread, but one of the largest expanses of such soils is in south west Australia (WA). Early Zn research in the region determined how much fertiliser Zn was required for profitable production of spring wheat (Triticium aestivum L.) and subterranean clover (Trifolium subterraneanum L), the major crop and pasture species at the time. The research showed that Zn sulfate and ZnO were equally effective Zn fertilisers, but ZnO was cheaper and so was widely used. The research indicated that in the year of application, depending on soil type, between 0.5-1.5 kg Zn/ha provided adequate Zn for the production of wheat and subterranean clover. The length of time that a single application of Zn fertiliser remains fully effective in maintaining the production of crops and pasture in future years (residual value; (RV)) had not been determined. This knowledge of the RV of Zn fertilisers is required for soils of WA. The experiments that measured the RV of fertiliser Zn for spring wheat and subterranean clover form the bulk of this thesis. The soils in the region were also initially acutely phosphorus (P) deficient requiring the application of fertiliser P for profitable production. Single superphosphate was the P fertiliser initially used. It was manufactured locally using phosphate rock imported from Nauru and Christmas Islands. This phosphate rock also contained much Zn, and the single superphosphate manufactured from it contained 400-600 mg Zn/kg. At amounts of application needed to provide adequate P, the Zn-contaminated superphosphate also supplied about 90 g Zn/ha. Therefore, early field experiments measured the RV of ZnO applied to soil when single superphosphate was applied annually at >150 kg/ha. In these experiments, the RV of Zn was measured when different amounts of fertiliser nitrogen (N) was applied. This was because it has recently been very profitable to apply fertiliser N to wheat crops, which greatly increased grain yields and so may have increased the demand for Zn, thereby probably decreasing the RV of the original ZnO application. In these experiments, there were many nil-Zn plots. In subsequent years, freshly-applied ZnO amounts were applied to measure the RV of the original ZnO treatments relative to the fresh Zn treatment. No Zn deficiency was detected for up to 23 years after applying ZnO while applying superphosphate at >150 kg/ha per year and for all amounts of N applied. Subsequently cheap imported DAP fertiliser was used for wheat crops instead of locally produced Zn-contaminated single superphosphate and urea. The imported DAP contained about 50 mg Zn/kg (1/12 that of single superphosphate). This new fertiliser strategy induced Zn deficiency in many wheat crops. This led to further field studies to determine the RV of ZnO fertiliser when DAP was applied. The experiments also included 2 Zn-contaminated single superphosphate treatments. In one, no ZnO was applied, and superphosphate was applied at >150 kg/ha per year to match the amount of P applied as DAP to the other treatments. The other treatment was the same, except 1.5 kg/ha Zn as ZnO was applied in the first year only. In subsequent years, freshly-applied ZnO amounts were applied to measure the RV of the original ZnO treatments relative to the fresh Zn treatment. Relative to freshly-applied Zn in each year, the RV of the original ZnO treatments decreased as the length of time that the Zn was in contact with soil increased. However, the rate of decline in the RV was also found to differ with soil type, and was affected by soil pH, clay and organic carbon content of soil, and in alkaline soils with the calcium carbonate content of soil. Parallel glasshouse studies measured the RV of Zn, as Zn sulfate, for wheat and subterranean clover, using many soils from WA and other Australian States. The glasshouse studies also showed that the rate of decline in the RV of the original Zn application varied markedly with soil type and was strongly influenced by soil pH, clay and organic carbon content of soil, and in the alkaline soils, the amount of calcium carbonate in soil. In the above studies, the RV of fertiliser Zn was measured relative to freshly-applied Zn using yield of plants (shoots and grain for wheat, shoots for clover), Zn content in shoots and grain, and soil test Zn using the ammonium oxalate and DTPA procedures. In addition, Zn concentration in young tissue and rest of shoots (glasshouse studies) and young tissue and whole shoots (field studies) was measured, and Zn concentration related to 90 % of the maximum yield (critical Zn in plant parts) was determined. The studies showed that the DTPA soil test procedure, together with soil pH, and clay and organic matter content of soil, was an accurate prognostic test for indicating when Zn deficiency was likely in the next clover or wheat crop. The study confirmed that young tissue (youngest fully expanded leaves) provided critical plant test values for diagnosing Zn deficiency in plants. The plant and soil tests for Zn are now used by commercial soil and tissue testing laboratories. When Zn deficiency was diagnosed early in field grown wheat, Zn sprays can be applied to the crop foliage to prevent or minimise decreases in grain yields at the end of the growing season. Zn sulfate and Zn chelate are the most widely used compounds. This thesis reports the results of a field study to compare the effectiveness of the two compounds when the spray was applied at two growth stages of wheat (Gs14; seedling growth and Gs24; tillering). In addition, Zn applied with the seed while sowing the wheat crop was also included. Zinc applied to the soil while sowing was the most effective treatment. Zn chelate was more effective as a spray than Zn sulfate when applied at the earlier growth stage, but Zn sulfate was cheaper, and both sprays were equally effective when applied at the later growth stage. Recently in the region, durum wheat (T. durum L.), narrow-leafed lupin (Lupinus angustifolius L.), yellow lupin (L. luteus L.), white lupin (L. albus L.), canola (Brassica napus L.), chickpea (Cicer arietinum L.), faba bean (Vicia faba L.) and lentil (Lens culinaris Medik) were all increasingly grown in rotation with spring wheat. Consequently, the Zn requirement of the new crops was compared with the Zn requirements of spring wheat. Species requiring less Zn than spring wheat to produce the same relative yield were faba bean, chickpea, albus lupin and canola; species requiring more Zn were lentil and durum wheat. Spreadsheet models were developed to determine when re-application of fertiliser Zn was required for low and high production systems. Relative to freshly-applied Zn, the rate of decline in the RV of Zn applied in a previous year varied depending on the amount of Zn applied, time the Zn was in contact with soil since application, properties of the soil (soil pH, % clay, % organic carbon, % free calcium carbonate), plant species, and the amount of Zn removed in harvested grain or hay. The thesis has culminated in a better understanding of Zn in the agricultural production systems of WA. The distribution and correction of Zn deficiency is now predictable for the many soil types and cropping systems of WA. Accurate identification of Zn deficiency for a range of crop and pasture species by plant analyses, typically the youngest mature leaf, is now possible for local conditions. With the calibration of the DTPA Zn soil test for soils of WA, particularly for wheat the major crop species grown in WA, prognosis of potential Zn deficiency can now be predicted before the appearance of Zn deficiency or loss in plant production.
7

Parametric examination of the destruction of availability due to combustion for a range of conditions and fuels

Chavannavar, Praveen Shivshankar 01 November 2005 (has links)
A comprehensive second law analysis of combustion for a range of conditions and fuels was completed. Constant pressure, constant volume and constant temperature combustion processes were examined. The parameters studied were reactant temperature, reactant pressure, equivalence ratio and the fuels themselves. In addition, the contribution and relative significance of the various components (thermo-mechanical, reactive and diffusion) to the mixture availability was examined. Also, the effect of reactant mixture dissociation was incorporated into the combustion analysis. It was found that for similar initial conditions, constant pressure combustion and constant volume combustion exhibited similar trends. For constant temperature combustion, the trend is significantly different from the constant pressure and constant volume combustion, with almost the entire reactant availability being destroyed due to combustion at lower temperatures. Amongst the parameters examined, reactant mixture temperature had the most significant effect on the fraction of availability destroyed during combustion. The percentage availability destroyed reduced from 25 to 30% at 300 K to about 5% at 6000 K for constant pressure and constant volume combustion processes. The effect of the reactant mixture pressure on the fraction of availability destroyed was more modest. The values for the percentage availability destroyed for pressures ranging from 50 kPa to 5000 kPa were found to lie within a range of 5%. The effect of equivalence ratio on the fraction of reactant mixture availability destroyed was also documented. In general, it was found that the destruction of availability decreased with increasing equivalence ratios. This value, however, accounts for the availability due to fuel like species in the product mixture. Therefore, for practical applications, combustion of the stoichiometric mixture would be preferred over the rich equivalence ratios. It was found that the fraction of reactant availability destroyed increased with increasing complexity of the fuel??s molecular structure. In addition, it was shown that the diffusion availability terms is small and may be neglected, while the reactive availability and thermo-mechanical availability are more significant.
8

Evaluation of an in vitro lipid digestion model : testing poorly soluble drug substances and lipid-based formulations /

Ørskov Christensen, Janne. January 2004 (has links)
Ph.D.
9

Database High Availability using SHADOW Systems

Pan, Xin January 2014 (has links)
Various High Availability DataBase systems (HADB) are used to provide high availability. Pairing an active database system with a standby system is one commonly used HADB techniques. The active system serves read/write workloads. One or more standby systems replicate the active and serve read-only workloads. Though widely used, this technique has some significant drawbacks: The active system becomes the bottleneck under heavy write workloads. Replicating changes synchronously from the active to the standbys further reduces the performance of the active system. Asynchronous replication, however, risk the loss of updates during failover. The shared-nothing architecture of active-standby systems is unnecessarily complex and cost inefficient. In this thesis we present SHADOW systems, a new technique for database high availability. In a SHADOW system, the responsibility for database replication is pushed from the database systems into a shared, reliable, storage system. The active and standby systems share access to a single logical copy of the database, which resides in shared storage. SHADOW introduces write offloading, which frees the active system from the need to update the persistent database, placing that responsibility on the underutilized standby system instead. By exploiting shared storage, SHADOW systems avoid the overhead of database-managed synchronized replication, while ensuring that no updates will be lost during a failover. We have implemented a SHADOW system using PostgreSQL, and we present the results of a performance evaluation that shows that the SHADOW system can outperform both traditional synchronous replication and standalone PostgreSQL systems.
10

A reliability, maintainability, supportability and availability analysis of a submarine sonar system /

O'Keefe, John Daniel. January 1990 (has links)
Project report (M.S.)--Virginia Polytechnic Institute and State University, 1990. / Includes bibliographical references (leaves 164-166). Also available via the Internet.

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