Distributed Finite-Time Cooperative Localization for Three-Dimensional Sensor Networks

This paper addresses the distributed localization problem for a network of sensors placed in a three-dimensional space, in which sensors are able to perform range measurements, i.e., measure the relative distance between them, and exchange information on a network structure. First, we derive a necessary and sufficient condition for node localizability using barycentric coordinates. Then, building on this theoretical result, we design a distributed localizability verification algorithm, in which we propose and employ a novel distributed finite-time algorithm for sum consensus. Finally, we develop a distributed localization algorithm based on conjugate gradient method, and we derive a theoretical guarantee on its performance, which ensures finite-time convergence to the exact position for all localizable nodes. The efficiency of our algorithm compared to the existing ones from the state-of-the-art literature is further demonstrated through numerical simulations.Comment: 39 pages, 7 figures, under revie

Prediction of Leakage in Elastomeric Seals for High Pressure Applications

Elastomeric seals are mechanical devices that are used to prevent the leakage of fluids across a boundary. Most commonly, a leak is driven by differential pressure acting across a seal, and failure occurs due to elastic leak, fracture, or a combination thereof. A pure elastic leak occurs when fluid bypasses a seal without imparting mechanical damage, so when the differential pressure is reduced sufficiently, the device recovers some or all of its sealing capability. When seal fracture occurs, it may be followed by elastic leak of the damaged seal, nearly always with a reduction in the maximum sealing ability. When severe enough, fracture can render a seal completely useless. It is important to understand both failure modes, but rubber fracture has received much more attention in the literature than elastic leak. Hence, this thesis focuses strictly on elastic leak failures. To reduce cost and development time, it is advantageous to predict elastic leaks during the design process. Some reasonably accurate analytical models to assess sealing performance exist for simple geometries such as O-rings, but non-standard seal configurations are notoriously difficult to design and model. Although the basic operating principles of rubber seals are simple, complexities arise due to many factors such as the tribological conditions, finite deformations, time-dependent mechanical properties, and thermal effects. Thus, custom seal design remains an empirical and iterative process. Some challenges are partially mitigated with numerical techniques such as finite-element analysis (FEA), but the subtleties to accurately simulate fluid leakage are neither well-described nor resolved in the literature. FEA has been used to simulate seal leakage for at least two decades, but no systematic, comprehensive study of the modelling parameters that affect leak simulations has been disclosed. This thesis closes this gap with numerical sensitivity analyses that consider the following: the hyperelastic material model and its validation; stress relaxation; volumetric compressibility; friction models; mesh sensitivity; contact interactions; static versus dynamic solvers; discretisation of pressures into nodal forces; the fluid pressure penetration algorithm; and the leak criterion. This latter parameter which tells the solver when to propagate fluid pressure from one node to the next is of primary importance in this thesis. Two leak criteria that were previously proposed in the literature are studied. Researchers have attempted to experimentally validate simulated leak pressures, but there is no comprehensive discussion of the variables that affect test measurements and model predictions. The present work addresses this gap by conducting experimental tests on bonded rubber seals to validate leak simulation studies and provides the following details: the materials tested including their formulations; manufacturing and material model validation tests; justification for critical settings in finite-element models; and potential sources of error in the experimental tests and numerical models. Poor correlations are found between the laboratory and numerically simulated leak pressures. It is argued that the primary source of error is the leak criterion, and it should be the focal point for future validation attempts. An alternative leak criterion, which is yet to be numerically implemented, is proposed for further investigation

The size anomaly in the London Stock Exchange: an empirical investigation

This study tests the size effect in the London Stock Exchange, using data for all nonfinancial listed firms from January 1985 to December 1995. The initial tests indicate that average stock returns are negatively related to firm size and that small firm portfolios earn returns in excess of the market risk. Further, the study tests whether the size effect is a proxy for variables such as the Book-to- Market Value and the Borrowing Ratio, as well as the impact of the dividend and the Bid- Ask spread on the return of the extreme size portfolios. The originality of this study is in the application of the Markov Chain Model to testing the Random Walk and Bubbles hypotheses, and the Vector Autoregression (VAR) framework for testing the relationship of macroeconomic variables with size portfolio returns

Low Cost Point Focus Solar Concentrator. Phase 1: Preliminary Design

The preliminary design of a low cost point focus solar concentrator is presented. The analysis, design, testing, and manufacturing assessments are described

Idaho Dairymen\u27s Ass\u27n v. Gooding County Clerk\u27s Record v. 6 Dckt. 35980

https://digitalcommons.law.uidaho.edu/idaho_supreme_court_record_briefs/3302/thumbnail.jp

The impact of knowledge management processes on organizational resilience: data mining as an instrument of measurement.

The aim of the research conducted for this thesis is to test the feasibility of using data mining (DM) to assess the relationship between and the impact of knowledge management (KM) on organizational resilience (OR). The emphasis currently placed on the value of intangible assets by private sector organizations and the recent increase in the use of data mining technologies are the key drivers in this evaluation of the use of data mining tools as an alternative to classical statistics when measuring intangibles. Data was collected using a questionnaire that was sent to the senior executives of a number of mid-sized companies located in the mid-west of the USA. Using Microsoft's SQL Server's Analytical Services (MSSAS) and the data provided by the respondents, five predictive models are built to test the suitability of the MSSAS' DM tool for assessing the relationships between and the impact of KM on OR. Of the five models constructed as part of this research, four classification models (two Naïve Bayes models, one neural network model, and one decision tree model) and one clustering model were found to be suitable tools for capturing the intricate relationships that exist between KM and OR. These models made it possible to evaluate the strengths of the relationships between KM and OR and to identify which KM processes contribute, and to what extent, to OR. In addition, the models enabled the collation of predicted OR scores, based on the responses given in the questionnaire. Finally, this research identifies some of the key challenges associated with using DM as a measurement instrument for assessing the relationship between and the impact of KM on OR. This research makes a number of significant contributions to the existing body of knowledge. It contributes to the understanding of the impact of KM on OR, to the understanding of the methods used to measure such impact and to the processes involved in measuring such impact using DM. From a practitioner perspective, this research contributes to the understanding of OR and provides a framework for achieving OR within an organizational context

Kabul Times, May 1975

Kabul Times, May 1975 *This is a large file and may take a couple of minutes to download

Building Future Security: Strategies for Restructuring the Defense Technology and Industrial Base

This report elaborates on the findings of the earlier OTA publications and examines in greater detail the specific policy choices involved in restructuring the defense technology and industrial base (DTIB) over the next decade

Mediterranean Soils with Particular Reference to Archaeology

Following a review ofthe Mediterranean environment and its development during the late Quaternary, eleven published papers, one paper in preparation, a book (which accompanies the thesis volume) and as yet unpublished data are presented on seven areas of the Mediterranean (in s Portugal, Sicily and Greece). The aims of the research are to consider methodologies in the study of .soils in relation to archaeology (including the relationships between soils, geomorphology and archaeology), and to consider questions of relevance to such research, including a number which have been raised, but not satisfactorily answered, in the wider literature on the Mediterranean. The research comes within the area of geoarchaeology. The studies presented cover a range of spatial scales: single soil profile and archaeological excavation context - the hillslope - river catchmentand broader region. General conclusions in respect of the questions raised include the following. 1. Significant differences in environment and soils occur between the Mediterranean and neighbouring regions arising particularly from climate, but also from other aspects of the environment and human history. Distinctively Mediterranean soils began forming in the Pleistocene or earlier; Holocene soils tend to be weakly de~eloped and similar to soils of cool temperate regions. 2. Geomorphological changes in the physical landscape during the Holocene are generally well defined, if not always well dated. 3. Evidence from much of the Mediterranean points to environmental resilience (an ability to recover from disturbance) rather than 'degradation', though some 20th and 21 st century land use pressures have caused changes that are probably significantly faster and possibly more severe than any during the Holocene. 4. The 'paradox' ofthe Mediterranean - much diversity within elements of strong regional conformity - may result in local factors in environmental change overriding major regional. In many cases, data are not available to permit more than speculation as to the relative importance of anthropogenic versus natural triggers of change during the last five millennia. Intensive, local studies are required to test assertions about major regional effects. 5. For its impact on the archaeological record, 'erosion' must be defined in terms of precise processes and their potential effects in the context of detailed conditions on the hillslope; analysis of valley alluvial sediments, though invaluable in the study of erosion history, cannot fully address these questions. 6. Geoarchaeological analysis requires close integration of archaeological, geomorphological and pedological analyses. Research applying soil information to archaeological diagnosis of excavation contexts also requires a closely integrated, multidisciplinary approach to sampling and analysis, and to intensive computer processing and advanced statistical methods of data analysis