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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.
441

Representative Environments for Reduced Estimation Time of Wide Area Acoustic Performance

Fabre, Josette 14 May 2010 (has links)
Advances in ocean modeling (Barron et al., 2006) have improved such that ocean forecasts and even ensembles (e.g., Coelho et al., 2009) representing ocean uncertainty are becoming more widely available. This facilitates nowcasts (current time ocean fields / analyses) and forecasts (predicted ocean fields) of acoustic propagation conditions in the ocean which can greatly improve the planning of acoustic experiments. Modeling of acoustic transmission loss (TL) provides information about how the environment impacts acoustic performance for various systems and system configurations of interest. It is, however, very time consuming to compute acoustic propagation to and from many potential source and receiver locations for multiple locations on an area-wide grid for multiple analysis / forecast times, ensembles and scenarios of interest. Currently, to make such wide area predictions, an area is gridded and acoustic predictions for multiple directions (or radials) at each grid point for a single time period or ensemble, are computed to estimate performance on the grid. This grid generally does not consider the environment and can neglect important environmental acoustic features or can overcompute in areas of environmental acoustic isotropy. This effort develops two methods to pre-examine the area and time frame in terms of the environmental acoustics in order to prescribe an environmentally optimized computational grid that takes advantage of environmental-acoustic similarities and differences to characterize an area, time frame and ensemble with fewer acoustic model predictions and thus less computation time. Such improvement allows for a more thorough characterization of the time frame and area of interest. The first method is based on critical factors in the environment that typically indicate acoustic response, and the second method is based on a more robust full waveguide mode-based description of the environment. Results are shown for the critical factors method and show that this proves to be a viable solution for most cases studied. Limitations are at areas of high loss, which may not be of concern for exercise planning. The mode-based method is developed for range independent environments and shows significant promise for future development.
442

Computation of a Virtual Tide Corrector to Support Vertical Adjustment of Autonomous Underwater Vehicle Multibeam Sonar Data

Haselmaier, Lawrence H 18 December 2015 (has links)
One challenge for Autonomous Underwater Vehicle (AUV) multibeam surveying is the limited ability to assess internal vertical agreement rapidly and reliably. Applying an external ellipsoid reference to AUV multibeam data would allow for field comparisons. A method is established to merge ellipsoid height (EH) data collected by a surface vessel in close proximity to the AUV. The method is demonstrated over multiple collection missions in two separate areas. Virtual tide corrector values are derived using EH data collected by a boat and a measured ellipsoid to chart datum separation distance. Those values are compared to measurements by a traditional tide gauge installed nearby. Results from the method had a mean difference of 6 centimeters with respect to conventional data and had a mean total propagated uncertainty of 15 centimeters at the 95% confidence interval. Methodologies are examined to characterize their accuracies and uncertainty contribution to overall vertical correction.
443

Reductionist and integrative research approaches to complex water security policy challenges

Zeitoun, Mark, Lankford, Bruce, Krueger, Tobias, Forsyth, Tim, Carter, Richard, Hoekstra, Arjen Y., Taylor, Richard, Varis, Olli, Cleaver, Frances, Boelens, Rutgerd, Swatuk, Larry, Tickner, David, Scott, Christopher A., Mirumachi, Naho, Matthews, Nathanial 07 1900 (has links)
This article reviews and contrasts two approaches that water security researchers employ to advance understanding of the complexity of water-society policy challenges. A prevailing reductionist approach seeks to represent uncertainty through calculable risk, links national GDP tightly to hydro-climatological causes, and underplays diversity and politics in society. When adopted uncritically, this approach limits policy-makers to interventions that may reproduce inequalities, and that are too rigid to deal with future changes in society and climate. A second, more integrative, approach is found to address a range of uncertainties, explicitly recognise diversity in society and the environment, incorporate water resources that are less-easily controlled, and consider adaptive approaches to move beyond conventional supply-side prescriptions. The resultant policy recommendations are diverse, inclusive, and more likely to reach the marginalised in society, though they often encounter policy-uptake obstacles. The article concludes by defining a route towards more effective water security research and policy, which stresses analysis that matches the state of knowledge possessed, an expanded research agenda, and explicitly addresses inequities.
444

Virus Fate and Transport in Groundwater : Organic matter, uncertainty, and cold climate

Mayotte, Jean-Marc January 2016 (has links)
Water managers must balance the need for clean and safe drinking water with ever-increasing amounts of waste-water. A technique for treating and storing surface water called “managed aquifer recharge” (MAR) is frequently used to help maintain this balance. When MAR is used to produce drinking water, water managers must ensure that disease-causing microbial contaminants are removed from the water prior to its distribution. This thesis examined the processes responsible for removing a specific class of microbial contaminants called “enteric viruses” during MAR. Viruses are naturally removed in groundwater through adsorption and inactivation mechanisms. This thesis investigated how these virus removal mechanisms were affected by ionic strength (IS), dissolved organic carbon (DOC), and the age of the sand used in a MAR infiltration basin. This was done using batch and flow-through column experiments designed to mimic conditions characteristic of a basin infiltration MAR scheme in Uppsala, Sweden. Bacteriophage MS2 was used as a proxy for enteric viruses. All of the experiments were conducted at 4°C. Experimental data were modeled to describe the fate and transport of viruses in the infiltrated groundwater. Conventional least-squares optimization and generalized likelihood uncertainty estimation (GLUE) were compared as model fitting-approaches in order to determine how data uncertainty affects parameter estimates and model predictions. Results showed that the sand used in the infiltration basins accumulates adsorbed organic matter as it is exposed to infiltrating surface waters. This reduced the amount of MS2 that was removed due to adsorption and inactivation. Results from GLUE indicated that MS2 is more likely to inactivate in a time-dependent manner when in the presence of sand with high concentrations of organic matter. Both model fitting techniques indicated that virus attachment rates were significantly lower for sand with high organic carbon content. Neither methodology was capable of adequately capturing the kinetics of virus adsorption. Uncertainties in the experimental data had a large effect on the conclusions that could be drawn from fitted models. This study showed that the presence of natural organic matter reduces the value of the infiltration basin as a microbial barrier.
445

Lze považovat produkční mezeru za vhodný ukazatel inflace? / Can We Consider Inflation as a Suitable Indicator of Inflation?

Kloudová, Dana January 2011 (has links)
Output gap belongs to standard indicators of inflationary pressures used in central banks. The aim of this paper is to find the answer to the question, whether we can consider output gap as a suitable indicator of inflation for the Czech economy. First hypothesis, which we analysed is that we can estimate output gap only with uncertainty. For confirmation or refutation of this hypothesis we used ten models of estimation of output gap. The second hypothesis is that output gap can be used as suitable indicator of inflation. For testing of this hypothesis we chose gap model from Coe, McDetmott (1997) -- with the level of output gap and the change (difference) of output gap. All tests confirmed, that central bank can use inflation as a useful indicator of inflation.
446

RELATIONSHIP BETWEEN TOLERANCE OF AMBIGUITY, TOLERANCE OF UNCERTAINTY, AND COPING WITH ACADEMIC STRESS

Paralkar, Urvi Pradeep 01 May 2019 (has links)
Researchers point to the fact that stress and anxiety among college students are a
447

Political Risk & Earnings Quality : An analysis of political effects on earnings management

Hawborn Dahlstedt, Simon January 2019 (has links)
The high level of political risk might enhance the information asymmetry between managers and stakeholders, therefore leading to increased opportunity for earnings management activities, which depress the usefulness of financial information. On the other hand, times of high political uncertainty possibly increase the demand for information among stakeholders, consequently leading to enhanced scrutiny and fewer earnings management activities. By examine 625 firms listed in the United States between 20022016, I make use of a firm-level measurement of political risk to identify the possible impact on earnings quality. I identify that political risk exposure measured on a firm-level is negatively associated with earnings management. Therefore I can conclude that firm-level political risk increases earnings quality. I further show how firm-level political risk better predicts earnings management activities than an aggregated measurement of political risk. Finally, I provide evidence that suggests that accrual-based earnings management is affected by the past level of political risk exposure. Real earnings management activities show no such indications.
448

L'échange informationnel : un outil de prise de décision au sein de l'industrie du capital risque : mise en évidence du rôle des réseaux des investisseurs et des syndications / The informational exchange : a tool for decision making in the venture capital industry : highlighting the role of networks of investors and syndications

Nasr, Zeineb 22 March 2013 (has links)
Malgré une impressionnante revue de la littérature consacrée au rôle de l’information pendant le processus de décision d’investissement en capital-risque, l’échange informationnel au sein des syndications et des réseaux des investisseurs n’était pas suffisamment abordé.Pour cette raison, nous avons dirigé notre recherche, dans un premier temps, vers l’exploration des données existantes sur notre thématique de recherche qui est l’industrie du capital-risque, et plus particulièrement les données traitant les problématiques de l’échange informationnel dans ce domaine. Dans un deuxième temps, l’objectif est d’éclaircir le rôle des réseaux et des syndications dans la limitation de l’ampleur de l’incertain au sein de l’industrie du capital-risque. En effet, l’analyse de la littérature existante sur le capital-risque nous permet de constater l’importance des réseaux des investisseurs et les syndications comme un vecteur d’échange informationnel au sein de cette industrie. Cependant, rares sont les études qui prennent en considération cette dimension au cours de la décision du financement. L’investissement capital-risque présume une évaluation de l’incertain dans un contexte d’asymétrie informationnel. La décision d’investissement s’appuie sur des informations du type formel et informel (Ferrary ; 2004). La relation contractuelle se transforme, en permettant la création des liens sociaux entre les investisseurs et les entrepreneurs, à un cadre formel d’un échange informationnel informel. Un autre échange informationnel entre les investisseurs, s’établit au sein des syndications qui se transforment à un lieu légal d’échange informel, réciproque et différé des informations.D’où l’appellation de notre travail : « L’échange informationnel : un outil de prise de décision au sein de l’industrie du capital-risque ; mise en évidence du rôle des réseaux des investisseurs et des syndications ».Et d’où la problématique suivante : « Quel est le rôle de l’échange informationnel au sein de l’industrie du capital-risque ? ».Apres avoir positionné notre problématique dans le contexte managérial approprie et la définition des concepts utilises dans l’étude (partie 1, chapitre 1), nous procédons ensuite à une tentative d’identification des besoins informationnels à l’intérieur de l’industrie du capital-risque en faisant appel à la littérature au deuxième chapitre au cours duquel nous émettons l’hypothèse suivante : les réseaux d’investisseurs et les syndications jouent un rôle très important dans le processus informationnel. Ces deux vecteurs d’échange informationnel influencent le processus de décision au sein de l’industrie du capital-risque (Partie 1, chapitre 2). / Despite an impressive review of the literature on the role of information during the process of investment decision in venture capital, informational exchange within networks and syndicated investors were not sufficiently addressed.For this reason, we conducted our research; a first step towards the exploration of existing data on our research topic is the venture capital industry, and more specifically data processing issues of informational exchange in this area.In a second step, the goal is to clarify the role of networks and syndicates in limiting the extent of uncertainty in the venture capital industry. Indeed, the analysis of the existing literature on venture capital, we can see the importance of networks of investors and syndications as a vector of informational exchange within the industry. However, there are few studies that take into account this dimension in the funding decision. The venture capital investment assumes an assessment of uncertainty in the context of informational asymmetry. The investment decision is based on information from both formal and informal (Ferrary, 2004). The contractual relationship is transformed, allowing the creation of social ties between investors and entrepreneurs, a formal framework for informal informational exchange. Another informational exchange between investors, stood in the syndications that convert to a legal place for informal exchange, reciprocal and delayed information.Hence the name of our work: "The informational exchange: a tool for decision making in the venture capital industry, highlighting the role of networks of investors and syndications."And where the following problem: "What is the role of informational exchange within the venture capital industry? ".After having set our problem in the managerial context and appropriate definition of the concepts used in the study (Part 1, Chapter 1), we then proceed to attempt to identify information needs within the venture capital industry venture involving literature in the second chapter, in which we put forward the following hypothesis: the networks of investors and syndications play a very important role in the information process. These two vectors informational exchange influence the decision-making process within the venture capital industry (Part 1, Chapter 2).
449

On the Existence of a Behavioral Component to the Business Cycle

He, Zhaochen January 2014 (has links)
Thesis advisor: Donald Cox / This dissertation consists of two essays which address the origins of the business cycle. In particular, it asks: to what extent do behavioral or psychological effects, famously termed "animal spirits" by John Maynard Keynes, contribute to the amplification of business cycle fluctuations. The first essay, titled "The Labor Market Effects of Bad Economic News", examines the effects of economically pessimistic newspaper articles on hiring and employment patterns. Combining information on newspaper subscriptions with automated content analysis of newspaper articles, the paper reconstructs the flow of pessimistic news across the United States during the past recession on a county-by-county, quarter-by-quarter basis. This high resolution map of pessimistic news delivery is then used to estimate the causal impact of media pessimism on labor market outcomes. Exposure to negative news is found to suppress hiring and total employment during the early stages of the recession by up to 40% compared to pre-recession levels; overall, media pessimism can account for some 7% of jobs lost between 2007 and 2010. Further analysis of Google search data suggests that this contractionary effect is mediated by changes in public attitude caused by exposure to pessimistic stories in the media. Importantly, this study considers only articles which report negative news about the state of the national economy, rather than stories which focus on local events. It argues that the prevalence of such news stories affects local labor market conditions, but is unlikely to be affected by such conditions. This approach helps to address the simultaneity issues which have dogged previous research on the topic. The second essay, titled "Uncertainty and Risk Averse Firms in DSGE" a develops theoretical framework to rationalize the previous paper's empirical results. This paper solves a simple general equilibrium model in which firms are risk averse over future profits in a manner analogous to household risk aversion. It shows that response to increased economic uncertainty - particularly uncertainty with regards to future consumer demand, economies with risk averse firms are likely to undergo a business cycle contraction. This result also addresses a long standing problem in the RBC literature; namely, how to generate a contraction with a Keynesian demand side shock. In most models with risk averse utility-maximizing households, a reduction in aggregate demand due to consumer-side changes is expansionary. The paper argues that by introducing firm-side risk aversion into the model, this counter-intuitive behavior can be corrected in a realistic and parsimonious manner. / Thesis (PhD) — Boston College, 2014. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Economics.
450

Uncertainties in Bloodstain Pattern Analysis : An interview and questionnaire-based study

Herrera Velasquez, Mateo January 2019 (has links)
Forensic science is the field of study that studies crimes and crime scenes. One of the major sub-areas of forensic science is crime scene investigations (CSI). Bloodstain pattern analysis (BPA) is a part of CSI and refers to the study of bloodstain patterns. The purpose of this project is to investigate the needs of those involved in the judicial chain when using a laser scanner to reconstruct a crime scene and how to represent any uncertainties. An additional purpose is to look into what expectations bloodstain pattern analysts have on their work situation. Interviews were held with nine persons involved in the judicial chain and an online questionnaire was distributed to the bloodstain pattern analysts across Sweden. To analyze the interviews a thematic analysis was used which led to three themes being identified (benefit, desires, obstacles) with eleven sub-themes. For the questionnaire two types of data were presented, numeric and written. The numeric result displayed results such as how confident they felt doing work or if the amount of cases was too much or too little. The written result displayed results showing that BPA is cumbersome, not because it is hard to use but rather because each case is unique, and many factors have to be considered. The conclusion of this study is that needs can be met using the framework that combined uncertainties and visualization, and the questionnaire showed that the bloodstain pattern analyst are a group of people who seek knowledge and welcome new technology.

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