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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.
11

Examining the use of Simarouba glauca Seed Oil as a Feedstock for the Production of Biodiesel using a Small Scale Model Developed in India

Jungman, Andrew Aaron 06 November 2012 (has links)
Simarouba glauca, a non-edible oilseed crop native to South Florida, is gaining popularity as a feedstock for the production of biodiesel. The University of Agriculture Sciences in Bangalore, India has developed a biodiesel production model based on the principles of decentralization, small scales, and multiple fuel sources. Success of such a program depends on conversion efficiencies at multiple stages. The conversion efficiency of the field-level, decentralized production model was compared with the in-laboratory conversion efficiency benchmark. The study indicated that the field-level model conversion efficiency was less than that of the lab-scale set up. The fuel qualities and characteristics of the Simarouba glauca biodiesel were tested and found to be the standards required for fuel designation. However, this research suggests that for Simarouba glauca to be widely accepted as a biodiesel feedstock further investigation is still required.
12

Improving Helicopter Yarding with Onboard GPS

Horcher, Andy 29 April 2008 (has links)
Despite its relatively high cost, helicopter yarding has become a common means of timber extraction where site sensitivity, access, or regulations limit the use of less costly alternatives. The high costs associated with helicopter yarding, as well as the desire to expand the application of this system to extract lower value timber, increases the need for innovation to improve the operations. The cost or benefit of a particular harvest prescription or innovative technique is commonly assessed with a time and motion study. Capturing time study data require additional personnel or an imposition on the operator to record additional information. Onboard GPS can reduce or eliminate the need for additional personnel and/or operator input providing a rapid means of assessing and improving helicopter operations. This research employed onboard GPS in helicopter yarding to assess the potential of developing time studies using GPS data. Three helicopter models were sampled on a total of nine sites. Three of the sites have both experienced and inexperienced pilot data. Hemispherical canopy images were sampled at three sites. This complement of data permitted the following analysis: assessment of differences between experienced and inexperienced pilots, assessment of canopy cover on hook time, and the development of production models. The results indicate onboard GPS and the automated processing methods are suitable for creating time study data. Specifically, in all three case studies quantitative results were obtained, analyzed and opportunities for improvement identified. The time penalty suffered from using inexperienced pilots created 64 to 94% additional turn time. Increasing canopy cover correlated with increased hook time at two sites for the zenith angle segment 0 – 15°. Regressions assessing production show distance, slope, and choker delivery to be significant. This research shows the combination of onboard GPS, the automation process, and commonly collected turn information presents a number of opportunities, enabling the assessment of a wide range of helicopter yarding conditions. / Ph. D.
13

Three Essays on Price Analysis of Summer Flounder and China's Soybean Imports

Chen, Wei 07 August 2009 (has links)
This dissertation contains three papers from two projects. The first two papers (Chapter Two and Chapter Three) are from a project entitled “Managing Flounder Openings for Maximum Revenue.” The objective of this project is to (1) estimate the monthly dockside price of summer flounder and identify seasonality in this price; and (2) set up a mathematical programming model to maximize the landing revenue by allocating the federal government quota on summer flounder across twelve months. In the first paper (Chapter Two), various forms of inverse demand equations are used to estimate the dockside price of summer flounder. These models are evaluated based on their out-of-sample forecasting performance. A structural functional form is selected. In the second paper (Chapter Three), the selected price equation for summer flounder is applied into a revenue maximization model with both the federal government quota constraint and biological constraints from twelve months. The model is solved using CONPOT Solver of GAMS 21.5. The results of the scenarios indicate that the industry should move the landing effort from the period of October – February to the period of March – August. Comparing with historical data, this method can increase $44.73 million for the industry of landing summer flounder from 1991 to 2005. The third paper (Chapter Four) investigates how China's soybean import prices and domestic prices of soybeans and soybean products affect China's soybean imports. Since 2000, soybeans have been the U.S. leading agricultural exports for bulk commodities. China is the largest importer of U.S. soybean exports. For China's soybean crushing industry, imported soybeans are inputs rather than final products and used to produce soybean meal and oil. A differential production model, which is derived from a two-stage profit maximization model in producer theory, is adopted in this research. Estimates are used to calculate conditional and unconditional price elasticities for China's soybean imports from its major source countries – the United States, Argentina, and Brazil. In addition, the Divisia index and unconditional output price elasticities are obtained for China's soybean imports. Estimation results support the hypothesis that China's soybean imports are determined by its domestic demand for soybean meal, rather than soybean oil. This implies that U.S. agribusinesses should pay attention to the dominant role of China's demand for soybean meal and animal feed. U.S. agribusinesses can also use results in this research to evaluate how China's soybean imports from different source countries will change when either international market prices or China's domestic market prices change. / Ph. D.
14

Investigating the performance of process-observation-error-estimator and robust estimators in surplus production model: a simulation study

He, Qing 15 September 2010 (has links)
This study investigated the performance of the three estimators of surplus production model including process-observation-error-estimator with normal distribution (POE_N), observation-error-estimator with normal distribution (OE_N), and process-error-estimator with normal distribution (PE_N). The estimators with fat-tailed distributions including Student's t distribution and Cauchy distribution were also proposed and their performances were compared with the estimators with normal distribution. This study used Bayesian method, revised Metropolis Hastings within Gibbs sampling algorithm (MHGS) that was previously used to solve POE_N (Millar and Meyer, 2000), developed the MHGS for the other estimators, and developed the methodologies which enabled all the estimators to deal with data containing multiple indices based on catch-per-unit-effort (CPUE). Simulation study was conducted based on parameter estimation from two example fisheries: the Atlantic weakfish (Cynoscion regalis) and the black sea bass (Centropristis striata) southern stock. Our results indicated that POE_N is the estimator with best performance among all six estimators with regard to both accuracy and precision for most of the cases. POE_N is also the robust estimator to outliers, atypical values, and autocorrelated errors. OE_N is the second best estimator. PE_N is often imprecise. Estimators with fat-tailed distribution usually result in some estimates more biased than estimators with normal distribution. The performance of POE_N and OE_N can be improved by fitting multiple indices. Our study suggested that POE_N be used for population dynamic models in future stock assessment. Multiple indices from valid surveys should be incorporated into stock assessment models. OE_N can be considered when multiple indices are available. / Master of Science
15

Investigating single and multiple species fisheries management: stock status evaluation of hammerhead (Sphyrna spp.) sharks in the western North Atlantic Ocean and Gulf of Mexico

Hayes, Christopher Glenn 07 February 2008 (has links)
Three hammerhead sharks (Sphyrna spp.) are currently managed as part of the large coastal shark complex in the United States. Including multiple species in an assessment ignores the different stock dynamics of each individual species within the complex due to different life histories. This study completed individual assessments of scalloped (S. lewini), great (S. mokarran), and smooth (S. zygaena) hammerhead sharks in the U.S. Atlantic Ocean and Gulf of Mexico. Combined data for all three species and unclassified hammerhead sharks were also used to produce a stock assessment of the hammerhead shark complex. Depletions of 83%, 96%, and 91% were estimated for scalloped, great, and smooth hammerhead sharks, respectively, between 1981 and 2005. When modeled as a single stock, the hammerhead shark complex experienced a 90% decline over the same time period. All three stocks, and the complex were overfished (below population size associated with maximum sustainable yield (MSY)), and overfishing (fishing level above that associated with MSY) occurred in 2005. We found that scalloped hammerhead shark population recovery is likely to occur within 10 years if catch remains at or below 2005 levels. Great and smooth hammerhead sharks will likely still be overfished in 30 years unless catches are reduced. It appears that the species composition could be changing in this hammerhead shark complex. The faster-growing scalloped hammerhead sharks are able to withstand fishing pressure better than great or smooth hammerhead sharks. However, it is difficult to target any single large coastal shark species while fishing; hence they are subject to similar fishing pressure. The result is a greater decline in great and smooth hammerhead sharks than experienced by scalloped hammerhead sharks. Therefore, the proportion of scalloped hammerhead sharks increased between 1981 and 2005. Species-specific stock assessments, such as those presented here, allow managers to more closely monitor populations of slower-growing species and reduce the risk of overexploitation of those species. / Master of Science
16

廣播節目數位化產製模式與流程研究 / A Study of the Digitalized Production Model & Process for Radio Broadcasting

李婉琳, Lee, Woan Leng Unknown Date (has links)
本研究為探討數位化後台灣廣播電台的節目產製模式與流程之改變,依據生產流程管理與廣播節目產製理論觀點,析論廣播節目邁向數位化產製模式之可能性,並依據分析所得描繪可能之模式與流程。 透過對台灣廣播產業的現況分析,指出目前台灣廣播電台的節目產製模式大多偏向「需求導向」產製模式的描述;少數電台則是比較偏向「創意導向」產製模式。雖然自動播出系統已經普遍使用,但只是簡化了播出作業。在節目數位化產製程度上,仍在建立資料庫階段,還未扭轉過去的製播經驗,對於進入數位化產製抱持傳統的心態,減低了邁入數位化的可能性。 因此,研究建議首先廣播電台繼續豐富資料庫的資源,還要提升資料庫的功能性。其次,結合聯播網的產製經驗,擴大資料庫網絡,與其它傳播媒介合作,形成一個「需求與資料庫導向」的產製模式,作為達到數位化產製模式與流程的基礎。 / This research aims to understand the digitizing influence the production model & process for broadcast program. Based on the viewpoint of production management theory and the broadcast programming theory, analyze the current broadcast program production model & process and evaluate the possibility of digitization. According to the result, describe the possible digitalized production model & process for broadcast program. By the current situation analysis of Taiwan broadcast industry, point out their production model is mostly inclined to “effect-to-cause” model, and few are inclined to “cause-to-effect” model. Although the “Radio Computing Service” is generally used, but only simplified the program broadcasting stage. On broadcast program production’s digitization level, Taiwan radio stations are still in establishment database stage, but also retain the traditional production experience. This result showed that reduces the advance possibility of the digitization. Therefore, the research suggests the broadcasting continue enrich the database resource; also enhance the functions of database for strategy-planning. Then, by combining the experience of radio network, expand the database network and cooperate with other mass media. The broadcast production will shift to the "effect-database" model which is the relative concept of digitalized production model.
17

Filtro de Kalman Ensemble: uma análise da estimação conjunta dos estados e dos parâmetros / Ensemble Kalman filter: an analysis of the joint estimation of states and parameters

Silva, Rafael Oliveira 08 April 2019 (has links)
O Filtro de Kalman Ensemble (EnKF) é um algoritmo de Monte Carlo sequencial para inferência em modelos de espaço de estados lineares e não lineares. Este filtro combinado com alguns outros métodos propaga a distribuição a posteriori conjunta dos estados e dos parâmetros ao longo do tempo. Existem poucos trabalhos que consideram o problema da estimação simultânea dos estados e parâmetros, e os métodos existentes possuem limitações. Nesta dissertação analisamos a eficiência desses métodos por meio de estudos de simulação em modelos de espaço de estados lineares e não lineares. O problema de estimação não linear aqui tratado refere-se ao modelo de produção excedente logístico, para o qual o EnKF pode ser considerado uma possível alternativa aos algoritmos MCMC. Os resultados da simulação revelam que a acurácia das estimativas aumenta quando a série temporal cresce, mas alguns parâmetros apresentam problemas na estimação. / The Ensemble Kalman Filter (EnKF) is a sequential Monte Carlo algorithm for inference in linear and nonlinear state-space models. This filter combined with some other methods propagates the joint posterior distribution of states and parameters over time. There are fewer papers that consider the problem of simultaneous state-parameter estimation and existing methods have limitations. The purpose of this dissertation is to analyze the efficiency of these methods by means of simulation studies in linear and nonlinear state-space models. The nonlinear estimation problem addressed here refers to the logistic surplus-production model, for which the EnKF can be considered as a possible alternative to MCMC algorithms. The simulation results reveal that the accuracy of the estimates increases when the time series grows, but some parameters present problems in the estimation.
18

Domesticating the wild type : a historical investigation of the role of the domestic-wild divide in scientific knowledge production

Holmes, Tarquin January 2015 (has links)
This thesis focuses on the role and historical development of strategies of experimental domestication in scientific knowledge production, with a particular focus on the function of the laboratory strains known as 'wild types' in the model organism systems of classical genetics, where they play the role of standing in for the 'natural' instance of the species so that variation may be measured. As part of establishing how lab wild types came to assume this role, I have situated them within a much longer historical trajectory that tracks how changes in the manner that European intellectual traditions conceptualised the domestic-wild divide were linked to the development of new forms of scientific domestication and knowledge production. These new developments required that existing domesticating practices be intensified, expanded and analogised in order to better control, capture and comprehend 'wild' nature. My first two chapters introduce the domestic-wild divide by discussing both contemporary and ancient interpretations of it. In my third and fourth chapter, I explore the roots of the knowledge regime of European scientific domestication. I highlight Francis Bacon's campaign to use knowledge of domesticating practices to restore human dominion, before showing how Linnaeus later re-conceptualised the natural economy as an autonomous order and original order, with domestication reinterpreted as an artful transformation of nature requiring human maintenance to prevent reversion to its wild 'natural state'. I identify this idea of the wild as original and the domestic as derivative and artificially maintained as the basis of the original wild type concept. In my fifth chapter, I discuss Darwin's attempt to unite the domestic and wild under common laws of variation and selection, including his argument that reversion was simply a product of a return to ancestral conditions of existence. I observe that Darwin's theory of variation was problematic for the effort to bring wild nature under controlled conditions for study, so in my sixth and seventh chapters discuss how this difficulty was resolved, first by experimental naturalists both before and after Darwin who utilised vivaria and microscopes to bring pieces of nature indoors, and then by Weismann and Galton's sequestration of heredity, which helped persuade scientists that domestication was not in itself a cause of germinal variation. In my eighth and ninth chapter, I detail how sequestration led the early Mendelians de Vries and Bateson to assume that wild types could be brought into the lab from nature and purified into true-breeding strains. I discuss their differing atomist and interactionist perspectives on wild type, with de Vries favouring 'elementary species' as units of nature, whereas Bateson held wild types and mutants to represent normal and abnormal forms of the species respectively. In my last chapter, I cover the replacement of Bateson's interactionist genetics by the reductionist genetics of the Morgan group and argue that this led to a disintegration of wild types into their component genes. I conclude with a discussion of what wild type strains in classical genetics were meant to be representative of, and end by establishing that whilst these strains may not wholly be representative of their species, they are nonetheless useful tools for scientific knowledge production.
19

Från modellering till dimensionering : Att modifiera produktionsmodeller till analysmodeller / From modelling to dimensioning : To modify production models to analysis models

Barikan, Mohammed, Ehsanzamir, Siavash January 2013 (has links)
Allt fler aktörer inom byggbranschen övergår från att använda gamla och traditionella verktyg i sin projektering till mer avancerade och moderna BIM-verktyg. Däremot sker denna utveckling långsamt på grund av skeptisk och konservativt inställning i byggbranschen. Idag finns analysprogram som har förmågan att beräkna och analysera komplexa strukturer, men trots detta är det väldigt vanligt med handberäkningar. I branschen börjar modellering av produktionsmodeller i moderna 3D BIM-verktyg få fotfäste. Det är praktiskt möjligt att modifiera en produktionsmodell till en analysmodell för att sedan beräknas i ett analysverktyg och det är detta som kommer bland annat undersökas. I denna rapport utreds även skillnaderna mellan handberäkningar och beräkningar i analysverktyg samt undersöks lönsamheten i en arbetsmetod där produktionsmodell och analysmodell integreras. Målet med denna rapport var att skapa ett tillvägagångssätt för en  fungerande överföring mellan produktionsmodell och analysmodell. Vilket enligt denna undersökning resulterar i en effektivare och lönsammare projektering. / Many businesses operating in the construction industry are nowadays substituting traditional tools in their project designing process with more modern and advanced BIM tools. However, this transition is taking place at a rather languid pace due to a skeptical and conservative attitude in the construction industry. Today, analysis software that has the ability to calculate and analyze complex structures is available. Yet, despite of this fact, manual calculations are still very common. The use of modern 3D-BIM tools has just started to gain a foothold, and a slight increase in both use and popularity in the construction branch. It is virtually possible to modify a production model into an analysis model using this technology, and that is one of the many aspects that will be investigated in this report. The differences between manual calculation and calculations made with analysis tools will be outlined, as well as the profitability of working with a production model where an analysis model has been integrated. The main objective of the following study was to provide a functioning approach for the effective transfer from a production model to an analysis model, which this investigation have eventuated to a more efficient and profitable project.
20

Multiscale Modelling as an Aid to Decision Making in the Dairy Industry

Hutchinson, Craig Alan January 2006 (has links)
This work presents the first known attempt to model the dairy business from a multiscale modelling perspective. The multiscale nature of the dairy industry is examined with emphasis on those key decision making and process scales involved in production. Decision making scales identified range from the investor level to the plant operator level, and encompass business, production, plant, and operational levels. The model considers scales from the production manager to the unit operation scale. The cheese making process is used to demonstrate scale identification in the context of the important phenomena and other natural levels of scrutiny of interest to decision makers. This work was a first step in the establishment of a multiscale system model capable of delivering information for process troubleshooting, scheduling, process and business optimization, and process control decision-making for the dairy industry. Here, only material transfer throughout a process, use of raw materials, and production of manufactured product is modelled. However, an implementation pathway for adding other models (such as the precipitation of milk protein which forms curd) to the system model is proposed. The software implementation of the dairy industry multiscale model presented here tests the validity of the proposed: • object model (object and collection classes) used to model unit operations and integrate them into a process, • mechanisms for modelling material and energy streams, • method to create simulations over variable time horizons. The model was implemented using object oriented programming (OOP) methods in conjunction with technologies such as Visual Basic .NET and CAPE-OPEN. An OOP object model is presented which successfully enabled the construction of a multiscale model of the cheese making process. Material content, unit operation, and raw milk supply models were integrated into the multiscale model. The model is capable of performing simulations over variable time horizons, from 1 second, to multiple years. Mechanisms for modelling material streams, connecting unit operations, and controlling unit operation behaviour were implemented. Simple unit operations such as pumps and storage silos along with more complex unit operations, such as a cheese vat batch, were modelled. Despite some simplifications to the model of the cheese making process, the simulations successfully reproduced the major features expected from the process and its constituent unit operations. Decision making information for process operators, plant managers, production managers, and the dairy business manager can be produced from the data generated. The multiscale model can be made more sophisticated by extending the functionality of existing objects, and incorporating other scale partial models. However, increasing the number of reported variables by even a small number can quickly increase the data processing and storage demands of the model. A unit operation’s operational state of existence at any point of time was proposed as a mechanism for integrating and recalculating lower scale partial models. This mechanism was successfully tested using a unit operation’s material content model and is presented here as a new concept in multiscale modelling. The proposed modelling structure can be extended to include any number of partial models and any number of scales.

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