Acoustic point-source reflection from an unperturbed seabed with a continuously varying density and sound speed profile in a fluid-like sediment layer overlying an elastic basement is considered in this paper. This fundamental problem has illuminated many interesting phenomena about the effects of sediment stratification on acoustic wave interactions with the seabeds. The analysis employs the analytical solutions for the Helmholtz equation in the sediment layer, in which the density and the sound speed are, respectively, described by three kinds of geological models. The results have demonstrated that the effects of sediment stratifacation are confined in a region in range, where the reflection field is dominated by the reflected ray bundles containing ray components with the grazing angles which are neither too steep nor too shallow. The effects of many other factors, such as frequency, sediment thickness, basement elasticity, on the reflection fields are investigated, in particular, the interface wave component may become important in the region close to the seabed, if the sediment thickness is relatively thin in comparison with the acoustic wave length.

This report estimates the steady-state, non-point source bacteria pollution along the international river system of the Lower Rio Grande / Río Bravo between Falcón Reservoir and the Gulf of Mexico. The results from this report may be used by environmental agencies in the United States and México in order to develop a steady-state water quality model of the bacterial load in this river system. This report creates a GIS-based estimation of the steady-state, non-point source pollution from sources such as failing septic tanks, untreated sewage, grazing animals, and wildlife in the watershed. This report also provides recommendations for environmental agencies when developing the water quality model. The results and methodology developed for this report may be used as part of the Lower Rio Grande / Río Bravo Watershed Initiative, a binational pilot project to develop a plan to restore and protect the quality of the Rio Grande/Río Bravo. / text

The agricultural industry in the United States has seen unprecedented growth in productivity and changes in industry structure. However, some negative environmental effects have emerged related to nitrogen, phosphorous, and sediment runoff. This study developed a novel, community economic systems methodology called the Biophysical and Economic Simulation of Agricultural Production (BESAP) model. This analyzed the economic tradeoff between farm and community level impacts associated with potential water quality standards for mitigating runoff in Mississippi. Key findings include: 1) farm-level net returns decrease with more stringent conservation practices to reduce nutrient runoff; 2) reductions in farm-level net returns have greater indirect cost effects on input suppliers and households than at the farm-level; and 3) farm-level net returns vary significantly depending on the conservation practices used, and the greater the change in farm-level net returns, the greater the net economic effect on the local food system in terms of employment, and valueded.

In the field of aeronautics (Aircraft, helicopters, space launchers...), as in the field of the automobile, reducing the harmful effects of acoustics constitutes a major concern at the international level and justifies the call for further research. With these challenges in mind, the manufacturers have expressed the need for simple models immediately available as early as the stage of preliminary drafts. This Master's Thesis presents the study and the validation of three different approaches to meet this industrial need. The first approach is based on the propagation of waves in the structure; the second approach uses the technique of SEA by calculating the equivalent damping; and the last approach uses the modal technique.In the three approaches, the transfer matrix method has been used to study the succession of layers. Applying these approaches to some aircraft structures confirm their relevance in relation to more exact and costly methods, such as the finite elements method.

L'objectif de cette thèse est la recherche des neutrinos cosmiques de haute énergie émis par des sources ponctuelles avec le télescope à neutrino ANTARES. La détection des neutrinos cosmiques de haute énergie peut apporter des réponses à des problèmes importants comme l'origine des rayons cosmiques et les procédures d'émission des rayons gamma. Dans la première partie de la thèse, le flux des neutrinos émis par des sources galactiques et extragalactiques et le nombre des évènements qui peut être détecté par ANTARES sont estimés. Cette étude utilise les spectres des rayons gamma des sources connues en tenant compte de l'absorption de ces rayons par la lumière extragalactique diffuse. Dans la deuxième partie de la thèse, le pointage absolu du télescope ANTARES est étudié. Étant situé à une profondeur de 2475 m dans l'eau de mer, l'orientation du détecteur est déterminée par un système de positionnement acoustique qui utilise des ondes de basse et haute fréquences entre la surface de la mer et le fond. La troisième partie de la thèse est la recherche des sources ponctuelles de neutrinos avec les données d'ANTARES. L'algorithme de recherche est basé sur une méthode de maximisation du rapport de vraisemblance. Il est utilisé dans deux stratégies de recherche; "la stratégie de recherche avec des sources candidates" et "la stratégie de recherche dans tout le ciel". L'analyse des données de 2007+2008 n'a pas marqué une découverte. Les meilleures limites supérieures au monde sur les flux de neutrinos provenant des différentes sources dans l'Hémisphère Sud sont établies. / The aim of this thesis is the search for high energy cosmic neutrinos emitted by point sources with the ANTARES neutrino telescope. The detection of high energy cosmic neutrinos can bring answers to important questions such as the origin of cosmic rays and the gamma rays emission processes. In the first part of the thesis, the neutrino flux emitted by galactic and extragalactic sources and the number of events which can be detected by ANTARES are estimated. This study uses the measured gamma ray spectra of known sources taking into account the gamma ray absorption by the extragalactic background light. In the second part of the thesis, the absolute pointing of the ANTARES telescope is evaluated. Being located at a depth of 2475 m in sea water, the orientation of the detector is determined by an acoustic positioning system which relies on low and high frequency acoustic waves measurements between the sea surface and the bottom. The third part of the thesis is a search for neutrino point sources in the ANTARES data. The search algorithm is based on a likelihood ratio maximization method. It is used in two search strategies; "the candidate sources list strategy" and "the all sky search strategy". Analysing 2007+2008 data, no discovery is made and the world's best upper limits on neutrino fluxes from various sources in the Southern sky are established.

In Taiwan increasing importance has recently been attached to non-point source pollution(NPS), primarily because of the deteriorated water quality and eutrophication of reservoir watershed that it can result in non-point source pollution. This study aims to understand the non-point source pollution load resulting from a large rain storm event in the Mu-dan Reservoir watershed. Most of the upper catchment of the Mu-dan Reservoir watershed is used for agricultural activities. This study established a database for the Mu-dan Reservoir watershed by using IWMM (Integrated Watershed Management Model), delineated for sub-watershed, and investigate the serious NPS pollution in the Mu-dan Reservoir watershed. Mu-dan Creek watershed and Ru-Reng Creek watershed, two the major sub-watersheds of the Mu-dan Reservoir watershed. A Geographic Information System (GIS) that was established in the watershed to (monitor OR gather) geographic parameter data was used IWMM to simulate the impact of NPS pollution on river water quality in the Mu-dan Creek and Ru-Reng Creek watersheds in 2003 and 2006. The simulation results by IWMM were applied to examine the potential of NPS pollution management plans in the Mu-dan Reservoir watershed. The simulation results for the Mu-dan Reservoir watershed during 2003 were as follows: the total pollutant load of ammonia-nitrogen (NH3-N) nearly 65699.4 kg/year, and the total pollutant load of nitrate ¡Vnitrogen (NO3-N) nearly 91100.5 kg/year. Meanwhile, the results for 2006 were as follows: the total pollutant load of ammonia-nitrogen (NH3-N) nearly 48168.1 kg/year, and the total pollutant load of nitrate ¡Vnitrogen (NO3-N) nearly43962.7kg/year. The simulation results addressed remedial strategies adopted to reduce the impact of NPS pollution on water quality, apply natural treatment systems for stormwater runoff treatment, and apply best management practice to control NPS pollutants. Finally, this study hopes make progress towards effective management of watersheds. KEYWORDS: Integrated watershed management model; non-point source pollution; BMPs

The Kaoping River basin is the largest and the most intensively used river basin in Taiwan. It is 171-km long, drains a catchment of more than 3,250 km2. Based on the current water quality analysis, the Kaoping River is heavily polluted. Concern about the deteriorating condition of the river led the Government of Taiwan to amend the relevance legislations and strengthen the enforcement of the discharge regulations to effectively manage the river and control the pollution. Investigation results demonstrate that both point and non-point source pollutants are now the causes of biochemical oxygen demand (BOD), nutrients, and pathogens in the river. The main water pollution sources are livestock wastewater from hog farms, municipal wastewater, industrial wastewater, non-point source (NPS) pollutants from agricultural areas, and leachate from riverbank landfills. The current daily BOD, NH3-N, and TP loadings to Kaoping River are 74,700, 39,400, and 5,100 kg, respectively. However, the calculated BOD, NH3-N, and TP carrying capacities are 27,700, 4,200, and 600 kg per day. To protect public health and improve the river water quality, the comprehensive management and construction strategy is proposed. The proposed strategy includes the following measures to meet the calculated river carrying capacity: (1) hog ban in the entire Kaoping River basin, (2) sewer system construction to achieve 30% of connection in the basin within 10 years, (3) removal of 10 riverbank landfills, and (4) enforcement of the industrial wastewater discharge standards. After the implementation of the proposed measures, the water quality should be significantly improved and the BOD and nutrient loadings can be reduced to below the calculated carrying capacities.

With the gain in momentum of the structural health monitoring field in the last two decades, the popularity of ultrasonic nondestructive testing (NDT) has grown. However, ultrasonic NDT requires an expert to perform the testing and can be time consuming and costly when measured wave patterns in testing become extremely complex. A computer simulation of these tests can be utilized as a guide during actual evaluations or as a tool to train technicians. Presented in this dissertation is the development of models which simulate such acoustic phenomena as may arise in NDT. These models were developed using the distributed point source method (DPSM) for its proven capability to represent ultrasonic fields.Four sets of boundary conditions that arise from different types of commonly used acoustic transducers are modeled, enabling the visualization of the ultrasonic fields produced by the transducers. The transducer models exhibit good agreement with existing analytical solutions.In addition, the effect of a small cavity located at or near the focal point of an acoustic microscope is discussed. For this application the DPSM technique is modified so that inversion of a large global matrix is avoided, significantly improving the computational efficiency. The model shows that, as the pressure goes to zero, the velocity increases at the location of a cavity. Simulations demonstrate that the microscope is able to sense changes in position of the cavity by variations in the measured ratio of reflected to incident acoustic force.The field generated by an interferometric acoustic microscope is also presented. Qualitative agreement between the DPSM model and the experimental results of fields generated in a homogeneous fluid are obtained for a three-element lens. In the presence of a solid interface, the pressure on the edges of a converging beam near the fluid-solid interface is greater for a three-element lens than for single-element lens. A multi-element lens is also shown to exhibit oscillations in the pressure slightly above the interface.

In order to understand the impact from a point source of pollution a comprehensive air quality monitoring programme must be in place. Measurement stations are at fixed locations and can only measure the relevant concentration if the wind is blowing in a particular direction. With changing wind direction, a measurement station needs to be coupled with a dispersion model to predict the impact from a point source, such as the BCL Limited smelter. The smelter produces 55 500 tonnes per annum of nickel/copper granules; in the process emitting waste gases to the atmosphere through a 153 m stack. The EEGAIR-BCL1. dispersion model was developed for BCL Limited to complement the air quality monitoring programme in the Selebi-Phikwe area. The model was developed for the smelter specifically, using local meteorological data at Selebi-Phikwe and smelter specific emission data. Results from the model were tested against data obtained from existing measurements stations at Selebi-Phikwe for May 2002, using statistical analyses. The average index of agreement indicates that the model predictions were more accurate for Kopano (0,44) and SPSS (0,25) stations than for WUC (0,08) station. Yearly averaged emission data was used for model input and better correlation can be expected when using actual hourly and/or monthly emission data. Based on the EEGAIR-BCl1 dispersion model results, it was found that the highest impact from the smelter stack was at a distance of 4 km to 7 km west from the stack. The model results indicate that, on average, the impact from the smelter stack in residential areas of Selebi-Phikwe was between 0 and 50 µ/m3 for May 2002. / Dissertation (MEng(Environmental Engineering))--University of Pretoria, 2006. / Chemical Engineering / unrestricted

The distributed point source method, or DPSM, developed in the last decade has been used for solving various engineering problems-such as elastic and electromagnetic wave propagation, electrostatic, and fluid flow problems. Based on a semi-analytical formulation, the DPSM solution is generally built by superimposing the point source solutions or Green's functions. However, the DPSM solution can be also obtained by superimposing elemental solutions of volume sources having some source density called the equivalent source density (ESD). In earlier works mostly point sources were used. In this paper the DPSM formulation is modified to introduce a new kind of ESD, replacing the classical single point source by a family of point sources that are referred to as quantum sources. The proposed formulation with these quantum sources do not change the dimension of the global matrix to be inverted to solve the problem when compared with the classical point source-based DPSM formulation. To assess the performance of this new formulation, the ultrasonic field generated by a circular planer transducer was compared with the classical DPSM formulation and analytical solution. The results show a significant improvement in the near field computation.