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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.
661

Utilization Of Fluidized Bed Combustion Ashes As Raw Material In The Production Of A Special Cement

Soner, Ilker 01 June 2009 (has links) (PDF)
Fluidized bed combustion (FBC) ashes containing significant amount of free CaO and CaSO4 in addition to valuable inorganic acidic oxide ingredients such as SiO2, Fe2O3 and Al2O3 can be utilized as potential raw materials in the production of nonexpansive belite-rich calcium sulfoaluminate cement which is one of the special cement type of sulfoaluminate-belite cements having performance characteristics similar to those of ordinary portland cement besides lower energy requirements and CO2 emissions during manufacturing. Therefore, in this thesis study, possibility of producing non-expansive belite-rich calcium sulfoaluminate cement by adding FBC ashes in various proportions to the raw meal was investigated. For this purpose, a raw meal composed a mixture of limestone, bauxite, gypsum together with 10 wt % bottom ash and 15 wt % baghouse filter ash was prepared. It was sintered in a laboratory scale muffle furnace at temperatures of 1200, 1250 and 1300 &deg / C for various holding times. The results of chemical and mineralogical analysis as well as microscopic examination reveal that FBC ashes have the potential to be used in the raw meal due to the presence of characteristic mineral phases of this type of cements, i.e. yeelimite, larnite, ferrite and anhydrite, in the sample obtained at optimum sintering temperature of 1250 &deg / C for 60 min.
662

A Preemptive Channel Allocation Mechanism for GSM/GPRS Cellular Networks

Yang, Wei-Chun 23 August 2001 (has links)
In the near future, the integration of GSM and GPRS services will bring the wireless personal communication networks into a new era. With the extreme growth in the number of users for contending limited resources, an efficient channel allocation scheme for GSM/GPRS users become very important. Currently, existing channel allocation schemes do not consider the various characteristics of traffic classes. Consequently, users can not obtain their optimal channel resources in delivering different types of traffic. In this thesis, a preemptive channel allocation mechanism is introduced for GSM/GPRS cellular networks. Based on the call requests, for different types of services, we classify the traffic into GSM, real-time GPRS and non-real-time GPRS. Two channel thresholds are defined. TGSM/GPRS is used to separate the channels between GSM and GPRS users, while TGPRS_rt is used to separate the channels between real-time and non-real-time GPRS users. Since the two thresholds can be dynamically adjusted based on the number of call requests, the channel utilization is increased and less resources are wasted. Note that in our proposed scheme, high-priority users¡]i.e., GSM handoff calls¡^can preempt the channels being used by low-priority users¡]i.e., non-real-time GPRS calls¡^. Hence, the call blocking probability of high-priority calls can be significantly reduced and their quality of services can be guaranteed as well. We build a 3-D Markov Chain mathematical model to analyze our proposed channel allocation schemes. The parameters of our interests include the call blocking probability, the average number of active calls, the average call completion rate and the overall channel utilization. To verify our mathematical results, we employ OPNET simulator to simulate the proposed schemes. Through the mathematical and simulation results, we have observed that with the preemptive channel allocation, the high-priority calls¡]i.e., GSM and real-time GPRS¡^can achieve relatively low blocking probability while slightly increasing the blocking probability of non-real-time GPRS calls. Besides, the overall channel utilization is greatly improved due to the appropriate channel allocation.
663

Extending and formalizing the energy signature method for calibrating simulations and illustrating with application for three California climates

Bensouda, Nabil 15 November 2004 (has links)
This thesis extends and formalizes the energy signature method developed by Wei et al. (1998) for the rapid calibration of cooling and heating energy consumption simulations for commercial buildings. This method is based on the use of "calibration signatures" which characterize the difference between measured and simulated performance. By creating a library of shapes for certain known errors, clues can be provided to the analyst to use in identifying what simulation input errors may be causing the discrepancies. These are referred to as "characteristic signatures". In this thesis, sets of characteristic signatures are produced for the climates typified by Pasadena, Sacramento and Oakland, California for each of the four major system types: single-duct variable-air-volume, single-duct constant-volume, dual-duct variable-air-volume and dual-duct constant-volume. A detailed step-by-step description is given for the proposed methodology, and two examples and a real-world case study serve to illustrate the use of the signature method.
664

General schedulability bound analysis and its applications in real-time systems

Wu, Jianjia 17 September 2007 (has links)
Real-time system refers to the computing, communication, and information system with deadline requirements. To meet these deadline requirements, most systems use a mechanism known as the schedulability test which determines whether each of the admitted tasks can meet its deadline. A new task will not be admitted unless it passes the schedulability test. Schedulability tests can be either direct or indirect. The utilization based schedulability test is the most common schedulability test approach, in which a task can be admitted only if the total system utilization is lower than a pre-derived bound. While the utilization bound based schedulability test is simple and effective, it is often difficult to derive the bound. For its analytical complexity, utilization bound results are usually obtained on a case-by-case basis. In this dissertation, we develop a general framework that allows effective derivation of schedulability bounds for different workload patterns and schedulers. We introduce an analytical model that is capable of describing a wide range of tasks' and schedulers'€™ behaviors. We propose a new definition of utilization, called workload rate. While similar to utilization, workload rate enables flexible representation of different scheduling and workload scenarios and leads to uniform proof of schedulability bounds. We introduce two types of workload constraint functions, s-shaped and r-shaped, for flexible and accurate characterization of the task workloads. We derive parameterized schedulability bounds for arbitrary static priority schedulers, weighted round robin schedulers, and timed token ring schedulers. Existing utilization bounds for these schedulers are obtained from the closed-form formula by direct assignment of proper parameters. Some of these results are applied to a cluster computing environment. The results developed in this dissertation will help future schedulability bound analysis by supplying a unified modeling framework and will ease the implementation practical real-time systems by providing a set of ready to use bound results.
665

Evaluation of hospital readmission among elderly patient with Asthma and COPD

Chiu, Hsiao-wen 18 June 2008 (has links)
Abstract Objective: Readmission is a big part of health care expenditure and recent studies suggested that hospital readmissions can be applied as an important indicator of quality of care within health care system. Furthermore elderly population usually costs the large amount health care expenses and is the main group in readmission. Moreover readmission is usually attributed to chronic diseases. Nevertheless, evaluations of hospital readmissions under universal health care coverage areas were not well-studied in Taiwan. Therefore this study aims to explore the associations between initial hospitalizations and probability of hospital readmissions in details. Research method: Patients aged 65 or older with primary clinical diagnosis of asthma or COPD based on ICD-9-CM for hospital admissions and readmissions in Taiwan.National claims of these two diseases were collected and analyzed from year 2000 to 2004. Population-based descriptive analyses of related health care utilizations were estimated. Multivariate logistic regressions were conducted to predict the probability of hospital readmissions. Controlled variables included patient factors, medical institutions¡¦ characteristics, urbanizations, and air quality indicators. Result: Among asthma and COPD elderly patients, more health care utilizations were observed in the hospital readmissions than initial admissions. Multivariate logistic regressions indicated that age, gender, disease severity, hospital characteristics, and air quality were significant predictors of the probability of hospital readmission. Meanwhile, age, disease severity, and hospital characteristics also significantly affected the time interval between initial admission and readmission. In addition, longer length of stay in the initial admission will significantly shorten the time interval between initial admission and readmission (P<0.001). Conclusion: For Asthma and COPD elderly patients, longer length of stay in the initial admission will significantly shorten the time interval between initial admission and readmission and have higher probability of hospital readmission. This study provides the evidence of reducing the health care expenditure by controlling readmission rate. With more understandings of factors affecting hospital readmissions, we can improve the health care delivery and reduce unplanned readmissions in the future. Key words: Asthma, COPD, hospital readmission, health care utilization, length of stay, admission fees
666

Bedeutende Planungshilfe für den Bibliotheks- und Archivbau. Der neue DIN-Fachbericht 13

Rabe, Roman 22 December 2009 (has links) (PDF)
Der DIN-Fachbericht 13 „Bau- und Nutzungsplanung von wissenschaftlichen Bibliotheken“ zählt seit 1988 zu den wichtigsten Planungsinstrumenten für den Bibliotheksbau. Ein DIN-Fachbericht stellt keine verbindliche Norm dar. Seine Aussagen besitzen lediglich empfehlenden Charakter. Trotzdem wurden vor allem die quantitativen Kernaussagen zum Flächenbedarf von Beständen, Nutzerarbeitsplätzen und speziellen Funktionen im DIN-Fachbericht 13 von Trägern, Bauherren und Architekten als Grundlage für die Planung konkreter Projekte weitgehend anerkannt. Die Aussagen des DIN-Fachberichtes haben schon deshalb erheblichen Einfluss auf Bibliotheksplanungen in Deutschland – und sogar darüber hinaus, denn sie werden wegen ihrer Detailliertheit und Vollständigkeit in der internationalen Normenentwicklung geschätzt und als Vorbild betrachtet. Als ambitioniertes Ziel nahm sich das DIN diesmal nicht nur eine Aktualisierung, sondern auch eine Erweiterung um Belange von Öffentlichen Bibliotheken und Archiven vor.
667

Maintenance of a 3D Visualization System

Wang, Cishen January 2008 (has links)
<p>Vizz3D is a powerful 3D visualization system. The current version is neither perfect nor up-to-date. Furthermore, some important features are missing. In order to keep the tool valuable it needs to be maintained. I implemented a new feature allowing to save and load the view port in the graph to control the camera position. I also improved the CPU utilization and the navigation system to solve the limitations in Vizz3D and to improve the overall performance.</p>
668

Understanding causes of hospitalization and access to care among newly diagnosed HIV patients in Houston, TX.

Shahani, Lokesh. Giordano, Thomas Peter, Hewett-Emmett, David, Kapadia, Asha Seth, January 2009 (has links)
Source: Masters Abstracts International, Volume: 47-06, page: 3554. Adviser: Thomas Giordano. Includes bibliographical references.
669

Using analytical and numerical modeling to assess deep groundwater monitoring parameters at carbon capture, utilization, and storage sites

Porse, Sean Laurids 09 April 2014 (has links)
Carbon Dioxide (CO₂) Enhanced Oil Recovery (EOR) is becoming an important bridge to commercialize geologic sequestration (GS) in order to help reduce anthropogenic CO₂ emissions. Current U.S. environmental regulations require operators to monitor operational and groundwater aquifer changes within permitted bounds, depending on the injection activity type. We view one goal of monitoring as maximizing the chances of detecting adverse fluid migration signals into overlying aquifers. To maximize these chances, it is important to: (1) understand the limitations of monitoring pressure versus geochemistry in deep aquifers (i.e., >450 m) using analytical and numerical models, (2) conduct sensitivity analyses of specific model parameters to support monitoring design conclusions, and (3) compare the breakthrough time (in years) for pressure and geochemistry signals. Pressure response was assessed using an analytical model, derived from Darcy's law, which solves for diffusivity in radial coordinates and the fluid migration rate. Aqueous geochemistry response was assessed using the numerical, single-phase, reactive solute transport program PHAST that solves the advection-reaction-dispersion equation for 2-D transport. The conceptual modeling domain for both approaches included a fault that allows vertical fluid migration and one monitoring well, completed through a series of alternating confining units and distinct (brine) aquifers overlying a depleted oil reservoir, as observed in the Texas Gulf Coast, USA. Physical and operational data, including lithology, formation hydraulic parameters, and water chemistry obtained from field samples were used as input data. Uncertainty evaluation was conducted with a Monte Carlo approach by sampling the fault width (normal distribution) via Latin Hypercube and the hydraulic conductivity of each formation from a beta distribution of field data. Each model ran for 100 realizations over a 100 year modeling period. Monitoring well location was varied spatially and vertically with respect to the fault to assess arrival times of pressure signals and changes in geochemical parameters. Results indicate that the pressure-based, subsurface monitoring system provided higher probabilities of fluid migration detection in all candidate monitoring formations, especially those closest (i.e., 1300 m depth) to the possible fluid migration source. For aqueous geochemistry monitoring, formations with higher permeabilities (i.e., greater than 4 x 10⁻¹³ m²) provided better spatial distributions of chemical changes, but these changes never preceded pressure signal breakthrough, and in some cases were delayed by decades when compared to pressure. Differences in signal breakthrough indicate that pressure monitoring is a better choice for early migration signal detection. However, both pressure and geochemical parameters should be considered as part of an integrated monitoring program on a site-specific basis, depending on regulatory requirements for longer term (i.e., >50 years) monitoring. By assessing the probability of fluid migration detection using these monitoring techniques at this field site, it may be possible to extrapolate the results (or observations) to other CCUS fields with different geological environments. / text
670

Evaluation of the relationship between Body Mass Index (BMI) and healthcare cost, utilization and health-related quality of life in adult diabetic patients

Adeyemi, Ayoade Olayemi 24 June 2014 (has links)
The present study assessed the relationship between Body Mass Index (BMI) and healthcare cost, utilization and health-related quality of life (HRQoL) of type 2 diabetes patients using the Medical Expenditure Panel Survey (MEPS) database. Study subjects were at least 18 years of age, diagnosed with diabetes and taking ≥1 oral antidiabetic medication. Data were extracted over a 5-year period (01/01/2006-12/31/2010). The main study outcomes were healthcare costs and utilization and HRQoL. The study covariates were age, gender, race, smoking status, census region of residence, marital status, insurance status, Charlson comorbidity index score and additional bed days. Study objectives were addressed using generalized linear model, negative binomial and multivariate regression analyses. A final un-weighted sample size of 7,003 patients was obtained. Mean age (±SE) was 61.2 (±0.24) years, mean BMI (±SE) was 32.2 (±0.12), and 50.4% were males. The majority was white (77.4%), did not smoke (84.5%), and were married (60.4%). Based on BMI categories, 12.6% had normal weight (BMI: 18.0-24.9); 29.2% were overweight (BMI: 25.0-29.9); 45.6% were obese (BMI: 30.0-39.9), and 12.6% were morbidly obese (BMI≥ 40.0). Compared to normal-weight patients; overweight, obese or morbidly obese patients had significantly higher (p<0.05) diabetes-related direct medical costs. However, overweight patients had significantly lower (p=0.021) all-cause direct medical costs. Furthermore, compared to normal weight patients, obese patients had a significantly higher (p=0.009) number of ambulatory care visits, while overweight patients had a significantly lower (p=0.035) number of emergency department visits. In addition, being obese or morbidly obese was associated with a significantly higher (p<0.0001) number of prescribed medicines compared to normal-weight patients. Compared to normal-weight patients; being obese or morbidly obese was also significantly (p<0.0001) associated with lower physical component summary (PCS-12) scores (i.e., worse quality of life) while being overweight was significantly (p=0.038) associated with higher mental component summary (MCS-12) scores (i.e., better quality of life). In conclusion, the present study suggests that among type 2 diabetes patients, being obese may be associated with negative consequences (in terms of healthcare costs, utilization and outcomes). Hence, there is the need to address obesity among type 2 diabetes patients in order to improve their health outcomes and significantly reduce healthcare costs and resource utilization. / text

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