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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.
581

Assessing the impact of feral hog populations on the natural resources of Big Thicket National Preserve

Chavarria, Pedro Mazier 15 May 2009 (has links)
The Big Thicket National Preserve (BTNP) is a unit of the National Park Service whose mission prioritizes conservation of its wildlands in the United States. One threat to natural resources of the BTNP has been impacts associated with feral hog (Sus scrofa) activities. Population numbers of this non-native game species have increased throughout Texas, including areas within the preserve. Recreational hunting permitted by the BTNP has served as a means of controlling hog numbers, although the reported amounts of hog damage to park resources appear to have increased in recent years. Population reduction of feral hogs and mitigation of their impacts require research that documents and validates feral hog impacts on park resources. Here, I evaluated (1) population trends of feral hogs for the past 20 years via data from hunter-card surveys and track-counts, and (2) feral hog impacts on native vegetation for 3 management units of the BTNP. Results from my analysis suggest a nearly 3-fold increase in hog numbers throughout the preserve since 1981. The overall damage to vegetation from hog rooting or wallowing averaged to 28% among the 3 units of the BTNP. Landscape features such as topography, soil moisture, soil type, and dominant vegetative cover types were used to predict hog damage. Floodplains had the most damage in the Big Sandy unit (45%), while flatlands were mostly impacted in the Turkey Creek unit (46%), and uplands in the Lance Rosier unit (32%). Vegetative cover was an important variable in explaining variation in hog damage throughout the 3 units of the preserve. Impacts were more widespread across different vegetative strata than previously believed. Study results also support the premise that hog damage in the BTNP parallels the increase in hog abundance over the past 20 years. A more aggressive program for population reduction of feral hogs and mitigation of their impacts is recommended for the BTNP to continue to meet its legal mandates for conservation.
582

Damage assessment and sampling of the rice stink bug, Oebalus pugnax (Fabricius) (Hemiptera: Pentatomidae), in rice, Oryza sativa L., in Texas

Vargas, Luis Espino 02 June 2009 (has links)
Field and greenhouse experiments were conducted from 2003 to 2006 at the Texas A&M University Agricultural Research and Extension Center at Beaumont and commercial rice fields throughout the Texas Rice Belt with the objectives of characterizing the nature of rice stink bug, Oebalus pugnax (Fabricius), damage to rice, Oryza sativa L., and developing visual sampling methods and sequential sampling plans. During 2005 and 2006, in greenhouse and field experiments, rice plants were caged and infested with adult or nymph O. pugnax during the heading, milk or soft dough stage. No differences were found in the weight of rough, brown or milled rice infested with O. pugnax during different stages. More peck was found in grain from plants infested during milk and soft dough than heading. Adult O. pugnax caused more peck than nymphs in all stages. In field experiments conducted during 2005 and 2006, single rice panicles were caged at the onset of heading and infested with one male or female O. pugnax for 48 h during the heading, milk, soft or hard dough stage. No differences were found in the weight of rough rice per panicle infested with O. pugnax. No differences were detected in percentage peck caused by male and female O. pugnax. Infestation during all stages of panicle development produced significantly more peck than no infestation In greenhouse experiments conducted during 2004 and 2005, rice plants at the pre-heading, heading, milk and soft dough stages were caged together and infested with male and female O. pugnax. Insects were observed for a period of five days and their preferences recorded. More insects were observed on milk and soft dough than on pre-heading or heading plants.Commercial rice fields throughout the Texas Rice Belt were sampled during 2003 and 2004 and visual sampling methods were compared to the sweep net method of sampling. Analysis of covariance showed that one sweep of the “long stick” or two sweeps of the “sweep stick” compared favorably to 10 sweep net sweeps. Analyses revealed that visual sampling using the long stick is more cost-reliable than sweep net sampling for O. pugnax in Texas rice fields.
583

Using Genetic Algorithms to Optimize Bathymetric Surveys for Hydrodynamic Model Input

Manian, Dinesh 2009 December 1900 (has links)
The first part of this thesis deals with studying the effect of the specified bathymetric resolution and ideal bathymetric form parameters on the output from the wave and hydrodynamic modules of Delft-3D. This thesis then describes the use of an optimization to effectively reduce the required bathymetric sampling for input to a numerical forecast model, by using the model’s sensitivity to this input. A genetic algorithm is developed to gradually evolve the survey path for a ship, AUV, or other measurement platform to an optimum, with the resulting effect of the corresponding measured bathymetry on the model, used as a metric. Starting from an initial simulated set of possible random or heuristic sampling paths over the given bathymetry using certain constraints like limited length of track, the algorithm can be used to arrive at the path that would provide the best possible input to the model under those constraints. This suitability is tested by a comparison of the model results obtained by using these new simulated observations, with the results obtained using the best available bathymetry. Two test study areas were considered, and the algorithm was found to consistently converge to a sampling pattern that best captured the bathymetric variability critical to the model prediction.
584

A Study on Medical Claim Payments Auditing Procedure in Taiwan National Health Insurance

Fu, Hwai-hui 03 June 2004 (has links)
Abstract National Health Insurance (NHI) has been implemented in Taiwan for nearly eight years; since then, over 96% of 23 million residents of Taiwan have benefited from this program, and 70% of them are satisfied. Recently, the growth rate of healthcare expenditure, however, has been phenomenally rapid, owing to the ageing population, the economic development, the expansion of health insurance, the increased supply of healthcare resources, and the innovation of medical technology. Under the circumstance that the bill of raising the insurance premium rate could not be passed by the legislative congress, the Bureau of NHI (BNHI) was forced to economize on expense to achieve the financial balance. Currently, the BNHI implements ¡§total amount control¡¨ to control the total medical claimed payments of each medical healthcare provider. Facing the increasing volume of documentary auditing, the BNHI has to make its efforts on how to improve its auditing efficiency. This is also one of the purposes of this thesis. This study aimed to establish a reasonable and fair auditing procedure of medical claim payment, termed ¡§medical claim payments auditing (MCPA) procedure¡¨. At the stage of professional auditing, adopted the ¡§MIL-STD-105E sampling plan¡¨ to select data for professional audit and used the auditing results as a payment criterion. To verify the adaptability of the MCPA procedure, the researcher used the data provided by the institutes of Kaohsiung and Pintong as simulation objects. Further, the estimated cost model was adopted to increase the possibility of using this procedure. The MCPA procedure consists of the following characteristics: 1) The number of sampling is much lower than that of the current system used by the NHI, thus the audit labor-force and time can be reduced significantly. 2) The incentive mechanism design encourages the healthcare providers to honestly apply their medical claim payments and avoids inappropriate healthcare services. 3) Adopting international standards of sampling technology makes the MCPA procedure trustworthy and simultaneously can reduce the implementing obstructs. Keywords: National Health Insurance; Sampling plan; Incentive mechanism design
585

Gibbs sampling's application in censored regression model and unit root test

Wu, Wei-Lun 02 September 2005 (has links)
Abstract Generally speaking, when dealing with some data, our analysis will be limited because of the given data was incompletely or hidden. And these kinds of errors in calculation will arrive at a statistics answer. This thesis adopts an analysis based on the Gibbs sampling trying to recover the part of hidden data. Since we found out whether time series is unit root or not, the effects of the simulated series will be similar to the true value. After observing the differences between the hidden data and the recovered data in unit root, we noticed that the hidden data has a bigger size and a weakened power over the recovered data. Finally, as an example, we give the unsecured loans at the Japanese money market to prove our issues by analyzing the data from January, 1999 to July, 2004. Since we found out that the numerical value of loan is zero at several months these past several years. In order to observe the Japanese money market, if we substitute the data of zero loan and use the traditional way to inspect unit root without taking model of average value into account, the result will be I(0). And if we simulate the hidden data with Gibbs sampling and substitute the data to inspect the Japanese money market without taking model of average value into account, the result will be I(0) also. But if we take model of average value into account, the of the Japanese Money Market will be I(1). And if we simulate the hidden data with Gibbs sampling and substitute the data to inspect the Japanese money market, the result will be I(I) also.
586

Stochastic modeling of vehicle trajectory during lane-changing

Nishiwaki, Yoshihiro, Miyajima, Chiyomi, Kitaoka, Hidenori, Takeda, Kazuya 19 April 2009 (has links)
No description available.
587

Methodology to quantify leaks in aerosol sampling system components

Vijayaraghavan, Vishnu Karthik 15 November 2004 (has links)
Filter holders and continuous air monitors (CAMs) are used extensively in the nuclear industry. It is important to minimize leakage in these devices and in recognition of this consideration, a limit on leakage for sampling systems is specified in ANSI/HPS N13.1-1999; however the protocol given in the standard is really germane to measurement of significant leakage, e.g., several percent of the sampling flow rate. In the present study, a technique for quantifying leakage was developed and that approach was used to measure the sealing integrity of a CAM and two kinds of filter holders. The methodology involves use of sulfur hexafluoride as a tracer gas with the device being tested operated under dynamic flow conditions. The leak rates in these devices were determined in the pressure range from 2.49 kPa (10 In. H2O) vacuum to 2.49 kPa (10 In. H2O) pressure at a typical flow rate of 56.6 L/min (2 cfm). For the two filter holders, the leak rates were less than 0.007% of the nominal flow rate. The leak rate in the CAM was less than 0.2% of the nominal flow rate. These values are well within the limit prescribed in the ANSI standard, which is 5% of the nominal flow rate. Therefore the limit listed in the ANSI standard should be reconsidered as lower values can be achieved, and the methodology presented herein can be used to quantify lower leakage values in sample collectors and analyzers. A theoretical analysis was also done to determine the nature of flow through the leaks and the amount of flow contribution by the different possible mechanisms of flow through leaks.
588

Diversity, abundance, seasonality and interactions of ants (Hymenoptera: Formicidae) in pecans in Mumford, Robertson Co., Texas

Calixto Sanchez, Alejandro Antonio 17 February 2005 (has links)
Alpha diversity, population dynamics and interactions of ant assemblages were studied in a pecan orchard located in Mumford, Texas. The assemblages included the invasive species Solenopsis invicta Buren, known as the red imported fire ant (RIFA). The study addressed the major question of what is the response of the ant assemblage to the reduction of RIFA following insecticide applications (bait and contact insecticide) and the impact of these on individual species. To address this question three treatments were established in a 16 hectare area in the orchard. The treatments were randomly assigned in 1.33 hectare blocks with four replications and periodically monitored. Treatments were: 1) insect growth regulator (IGR) bait treatment (ExtinguishTM, active compound is 0.5% s-methoprene) applied twice in 2000 and once in 2001; 2) the contact insecticide chlorpyrifos (LorsbanTM) applied on tree trunks four times in 2000 and once in 2001; and 3) untreated Control. Blocks were sampled using pitfall traps, baited vials, direct sampling, and colony counts. Data were analyzed by using ANOVA-GLM with the LSD multiple comparison test to compare the effect of treatment on the ant assemblage (using the Shannon index) and the effect on individual species. Additionally, data obtained from Control plots were used to compare sampling techniques and to determine what method is most efficient for collecting ants in this agroecosystem. Shannon indices were estimated for each method and compared. The ant assemblage consisted of 16 ant species. S. invicta was the most abundant followed by Paratrechina sp. and Monomorium minimum. The IGR treatment consistently reduced RIFA (77%). Native ants were found to coexist with RIFA in the Control and chlorpyrifos plots at lower densities and maintained higher densities in IGR plots. Chlorpyrifos trunk treatment did not have a significant impact on RIFA or native ant densities. The native ant, Dorymyrmex flavus, was greater in IGR plots following RIFA reduction and higher densities were found to persist for more than two years after the last IGR treatment. During this period, D. flavus was observed carrying large numbers of dead RIFA, some taken inside the nest, and some disarticulated RIFA taken out of the nest. RIFA remains were accumulated in D. flavus middens, further indication of an important interaction between these two species. These results indicate D. flavus resisted reinvasion by RIFA.
589

Site-specific strategies for cotton management

Stabile, Marcelo de Castro Chaves 29 August 2005 (has links)
The use of site-specific data can enhance management decisions in the field. Three different uses of site-specific data were evaluated and their outcomes are promising. Historical yield data from yield monitors and height data from the HMAP (plant height mapping) system were used to select representative areas within the field, and areas of average conditions were used as sampling sites for COTMAN, a cotton management expert system. This proved to be effective, with predicted cutout dates and date of peak nodal development similar to the standard COTMAN approach. The HMAP system was combined with historical height data for variable rate application of mepiquat chloride, based on the plant growth rate. The system performance was evaluated, but weather conditions in 2004 did not allow a true evaluation of varying mepiquat chloride. A series of multi-spectral images were normalized utilizing the soil line transformation (SLT) technique and normalized difference vegetation index (NDVI) was calculated from the transformed images, from the raw image and for the true reflectance images. The SLT technique was effective in tracking the change in true reflectance NDVI in some images, but not all. Changes to the soil line extraction program are suggested so that it more effectively determines soil lines.
590

Numerical modeling of species transport in turbulent flow and experimental study on aerosol sampling

Vijayaraghavan, Vishnu Karthik 25 April 2007 (has links)
Numerical simulations were performed to study the turbulent mixing of a scalar species in straight tube, single and double elbow flow configurations. Different Reynolds Averaged Navier Stokes (RANS) and Large Eddy Simulation (LES) models were used to model the turbulence in the flow. Conventional and dynamic Smagorinsky sub-grid scale models were used for the LES simulations. Wall functions were used to resolve the near wall boundary layer. These simulations were run with both two-dimensional and three-dimensional geometries. The velocity and tracer gas concentration Coefficient of Variations were compared with experimental results. The results from the LES simulations compared better with experimental results than the results from the RANS simulations. The level of mixing downstream of a S-shaped double elbow was higher than either the single elbow or the U-shaped double elbow due to the presence of counter rotating vortices. Penetration of neutralized and non-neutralized aerosol particles through three different types of tubing was studied. The tubing used included standard PVC pipes, aluminum conduit and flexible vacuum hose. Penetration through the aluminum conduit was unaffected by the presence or absence of charge neutralization, whereas particle penetrations through the PVC pipe and the flexible hosing were affected by the amount of particle charge. The electric field in a space enclosed by a solid conductor is zero. Therefore charged particles within the conducting aluminum conduit do not experience any force due to ambient electric fields, whereas the charged particles within the non-conducting PVC pipe and flexible hose experience forces due to the ambient electric fields. This increases the deposition of charged particles compared to neutralized particles within the 1.5” PVC tube and 1.5” flexible hose. Deposition 2001a (McFarland et al. 2001) software was used to predict the penetration through transport lines. The prediction from the software compared well with experiments for all cases except when charged particles were transported through non-conducting materials. A Stairmand cyclone was designed for filtering out large particles at the entrance of the transport section.

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