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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.
21

Detection of defects and thermal distortions in large-size gravitational-wave interferometer test masses

Yan, Zewu January 2008 (has links)
Advanced Laser Interferometric Gravitational Wave Detectors, based on current infrastructure (in particular, the Advanced LIGO detectors), are being planned to significantly increase the sensitivity to gravitational wave strain in the near future. To upgrade the existing detectors requests implementing very high optical power, as well as very high circulating power in the arm cavities; these measures will increase the sensitivity at the shot noise floor by one order of magnitude. However, such extremely high power circulation in the cavities will cause optical distortions in the test masses. Thermal distortions arise from the optical power absorption by defects or inhomogeneities in test masses, resulting in wavefront deformations, which have important consequences for the power buildup of the Radio-Frequency (RF) sidebands in the recycling cavities, thus degrading the performance of the detectors. The degree of this sensitivity degradation in the shot noise floor, due to optical distortions induced by defects or inhomogeneities (i.e. imperfections) in test masses in Advanced Laser Interferometric Gravitational-wave Detectors, is dependent on the test mass optical quality; while the sensitivity degradation in the thermal noise floor is dependent on the test mass mechanical properties. For this reason, it is compulsory to use high optical and mechanical quality test mass materials in the advanced interferometer detectors. Fused silica has been used for test masses in detectors, while sapphire has been planned to be used for test mass substrates in the proposed Large-scale Cryogenic Gravitational-wave Telescope (LCGT) project. Other materials, such as calcium fluoride (CaF2), are also attractive, especially for cryogenic detectors. However, for the state-of-theAbstract II art facilities, it is difficult to manufacture very uniform, defect-free, inhomogeneity-free, high-quality, and large-size samples. Thus, the qualities of sapphire and calcium fluoride single crystal samples were investigated and evaluated, to ensure that they have suitable properties for use in interferometer detectors, i.e. with an adequately low level of imperfections, but also with high mechanical quality factor (Q-factor). This thesis describes research done in the endeavour to investigate bulk defects or inhomogeneities in test masses, as well as their induced thermal distortions, which appear at a high optical power in Laser Interferometric Gravitational-wave Detectors. An Automatic Rayleigh Scattering Mapping System (ARSMS) to examine the optical property of large-size test masses is described. This ARSMS enables quantitative high-resolution 3D mapping of defects or inhomogeneities in optical materials. The measured 3D defect distribution mapping of optical materials can assist in the design of suitable configurations of test masses in high optical power interferometers. In addition, a very sensitive Hartmann wavefront sensor was used to actively monitor the thermal distortions due to bulk and coating absorption in test masses. A very strong thermal distortion in these test masses was observed in the Gingin facility, demonstrating that thermal distortions could be a critical issue in advanced interferometer detectors. A negative thermo-optical coefficient material, to be used in a thermal distortion compensation method, was investigated for the compensation of very localised distortions due to imperfections. This thesis also includes experimental and theoretical studies of the scattering, absorption, and birefringence mechanisms, thermal distortion effects, and optimal compensation methods for test masses.
22

Development of an Atmospheric Pressure Laser Induced Fluorimeter (AP-LIF) for NO₂ and Application of AP-LIF for Study of Heterogeneous NO₂ Chemistry

Parra, Jeremy 01 January 2012 (has links)
Nitrogen dioxide (NO₂) is a pollutant of interest for study both because of its controlling role in the oxidant capacity of the atmosphere and the health risks it poses. Concerns about the health effects of NO₂ and its role in forming deleterious atmospheric species have made it desirable to have low-cost, sensitive ambient measurements of NO₂. A continuous-wave laser-diode laser-induced fluorescence (LIF) system for NO₂ was developed here which operates at ambient pressure, thereby eliminating the need for an expensive pumping system. The current prototype system has achieved sensitivity several orders of magnitude beyond previous efforts at ambient pressure (limit of detection of 2 ppb, 60 s averaging time). Ambient measurements of NO₂ were made in Portland, Oregon using both the standard NO₂ chemiluminescence method and the LIF instrument and showed good agreement (r² = 0.92). In addition, investigations into surface mediated chemistry involving oxides of nitrogen (namely, NO₂) have stimulated new inquiry into potential heterogeneous sources of NO₂ as well as challenged the stability of permanent sinks for NO₂. The possibility that surface mediated chemistry plays a significant role in NOy chemistry in urban air has for the past few decades received considerable attention. The AP-LIF NO₂ instrument is uniquely suited to measure surface chemistry under near ambient conditions. The so called 'renoxification' reaction of gaseous NO with surface bound HNO₃ yielding NO₂ (2HNO₃(surface) + NO--> 3NO₂ +H₂O(surface)) was suggested as a potentially important source of NO₂ which also degraded the stability of nitric acid as a sink of active oxides of nitrogen. Yet, there is disagreement in the literature as to the importance of this reaction. The disagreement stems from differing measurements of the rate for the renoxification reaction. Because there are differences in experimental setups no one research group has studied the renoxification reaction under ambient conditions, i.e., at moderate concentrations of NOy and in a static cell held at 1 atm. In this work, the production of NO₂ was measured using a novel AP-LIF. This setup made it possible to measure the rate of production of NO₂ due to the heterogeneous reaction of NO with HNO₃ under ambient conditions. Under these conditions it was found that renoxification due to gas-phase NO on surface HNO₃ is not a significant source of NO₂. However, this study did show the importance of water vapor in the renoxification of surface HNO₃.
23

Promethean Framework and Measurement Instrument: Career Development, Maintenance and Transitions in Convulsive Economic Cycles

Straub, Larry G. January 2014 (has links)
No description available.
24

Improving Objectivity and Reliability of Observational Risk Assessment Tools by using Technical Instruments / Observationsmetoder för ergonomisk riskbedömning – ökad objektivitet och tillförlitlighet med hjälp av tekniska mätningar

Charsmar-Etor, Cephas January 2023 (has links)
Ergonomic assessments to determine risks of work-related musculoskeletal disorders as well as to compare designs of work-tasks and workstations, are imperative for high sustainability and productivity in any given industry. Hence, assessment tools that can objectively and reliably capture postures, joint angles and muscle activities play very important role in properly determining risks relating to work and various tasks. The introduction of direct measurement instruments/tools has been helping and continue to help improve upon observational assessment methods to attain objectivity and reliability. This project aimed at contributing to future improvements of industrial risk assessment measures in ergonomics by identifying and testing direct measurement instruments/tools that can enhance observational risk assessment methods and introduce a new way of signal processing, hence, reducing assessment time while increasing objectivity and reliability. Several candidate instruments were identified and out of the identified, ten were selected as potential candidates. Two out of the ten, Wergonic and ErgoHandMeter were then selected and tested on common observation risk assessment factors that could be measured and answers provided directly or by analyses. The Wergonic instrument was modified to enhance its measuring capability from one fully and partially two factors to six factors. New algorithms were also employed to analyse measurements of the ErgoHandMeter in order to answer questions regarding repetitive movements. The two instruments tested, are able to measure and provide results for six commonly and one rarely assessed biomechanical risk factors. By combining selected potential candidates, many of the commonly targeted biomechanical risk factors in observational instruments can be measured by the selected direct measurement instruments. However, some factors especially force measurement remain a challenge for measuring by direct wearable sensor instruments.
25

High frequency water vapor density measurements using the beat frequency method

Elorriaga Montenegro, Estefania 15 June 2012 (has links)
This document describes the design and deployment of a first generation water vapor density sensing unit, the HumiSense. This device is based on an open, air-filled capacitor which is part of a resonant circuit. The frequency of the resonant circuit mixed with a fixed frequency oscillator is the basis of the method to generate a signal that is associated to the change in water vapor density within the open capacitor with time. The physical testing results were inconclusive given that there were many unresolved artifacts in the data. Several suggestions for improving the device for future device generations were provided. / Graduation date: 2013
26

Development and application of a new passive sampling device : the lipid-free tube (LFT) sampler

Quarles, Lucas W. 29 September 2009 (has links)
Contaminants can exist in a wide range of states in aqueous environments, especially in surface waters. They can be freely dissolved or associated with dissolved or particulate organic matter depending on their chemical and physical characteristics. The freely dissolved fraction represents the most bioavailable fraction to an organism. These freely dissolved contaminants can cross biomembranes, potentially exerting toxic effects. Passive sampling devices (PSDs) have been developed to aid in sampling many of these contaminants by having the ability to distinguish between the freely dissolved and bound fraction of a contaminant. A new PSD, the Lipid-Free Tube (LFT) sampler was developed in response to some of the shortcomings of other current PSD that sample hydrophobic organic contaminants (HOCs). The device and laboratory methods were original modeled after a widely utilized PSD, the semipermeable membrane device (SPMD), and then improved upon. The effectiveness, efficiency, and sensitivity of not only the PSD itself, but also the laboratory methods were investigated. One requirement during LFT development was to ensure LFTs could be coupled with biological analyses without deleterious results. In an embryonic zebrafish developmental toxicity assay, embryos exposed to un-fortified LFT extracts did not show significant adverse biological response as compared to controls. Also, LFT technology lends itself to easy application in monitoring pesticides at remote sampling sites. LFTs were utilized during a series of training exchanges between Oregon State University and the Centre de Recherches en Ecotoxicologie pour le Sahel (CERES)/LOCUSTOX laboratory in Dakar, Senegal that sought to build "in country" analytical capacity. Application of LFTs as biological surrogates for predicting potential human health risk endpoints, such as those in a public health assessment was also investigated. LFT mass and accumulated contaminant masses were used directly, representing the amount of contaminants an organism would be exposed to through partitioning assuming steady state without metabolism. These exposure concentrations allow for calculating potential health risks in a human health risk model. LFT prove to be a robust tool not only for assessing bioavailable water concentrations of HOCs, but also potentially providing many insights into the toxicological significance of aquatic contaminants and mixtures. / Graduation date: 2010
27

The characterization and temporal distribution of cosmological gravitational wave treatments

Howell, Eric John January 2009 (has links)
[Truncated abstract] As gravitational wave detectors approach sensitivities that will allow observations to become routine, astrophysics lies on the cusp of an exciting new era. Potential sources will include transients such as merging neutron stars and black holes, supernova explosions or the engines that power gamma-ray bursts. This thesis will be devoted to the astrophysical gravitational wave background signal produced by cosmological populations of such transient signals. Particular attention will be devoted to the observation-time dependence imposed on the individual sources that accumulate to produce a gravitational wave background signal. The ultimate aim is to determine what information is encoded in the temporal evolution of such a signal. To lay the foundations for further investigation, the stochastic gravitational wave background signal from neutron star birth throughout the Universe has been calculated. In view of the uncertainties in both the single-source emissions and source rate histories, several models of each are employed. The results show that that the resulting signals are only weakly dependent on the source-rate evolution model and that prominent features in the single-source spectra can be related to the background spectra. In comparison with previous studies, the use of relativistic single-source gravitational wave waveforms rather than Newtonian models and a more slowly evolving source-rate density results in a 1 { 2 order of magnitude reduction in signal. ... A comparison with the more commonly used brightness distribution of events shows that when applying both methods to a data stream containing a background of Gaussian distributed false alarms, the brightness distribution yielded lower standard errors, but was biased by the false alarms. In comparison, a fitting procedure based on the time evolution of events was less prone to errors resulting from false alarms, but as fewer events contributed to the data, had a lower resolution. In further support of the time dependent signature of transient events, an alternative technique is fiapplied to the same source population. In this case, the local rate density is probed by measuring the statistical compatibility of the filtered data against synthetic time dependent data. Although this method is not as compact as the fitting procedure, the rate estimates are compatible. To further investigate how the observation time dependence of transient populations can be used to constrain global parameters, the method is applied to Swift long gamma-ray burst data. By considering a distribution in peak °ux rather than a gravitational wave amplitude, gamma-ray bursts can be considered as a surrogate for resolved gravitational wave transients. For this application a peak °ux{observation time relation is described that takes the form of a power law that is invariant to the luminosity distribution of the sources. Additionally, the method is enhanced by invoking time reversal invariance and the temporal cosmological principle. Results are presented to show that the peak °ux{observation time relation is in good agreement with recent estimates of source parameters. Additionally, to show that the intrinsic time dependence allows the method to be used as a predictive tool, projections are made to determine the upper limits in peak °ux of future gamma-ray burst detections for Swift.
28

Smärta och dess olika samband i livets slutskede

Magnusson Carlsson, Therése, Larsson, Elin January 2015 (has links)
Bakgrund: Palliativ vård syftar bland annat till att lindra lidande och symtom som smärta och ångest. För att kunna bedöma, utvärdera samt lindra symtomen behövs smärtskattningsinstument användas. Att lindra dessa symtom främjar livskvaliteten hos patienter i en palliativ fas. Genom det Svenska palliativregistret finns möjlighet att sammanställa och utvärdera information som kan främja forskning och därmed bidra till ett minskat lidande. Syfte: Syftet är att undersöka förekomst av smärta och smärtlindring i livets slutskede samt se i vilken utsträckning validerade instrument används. Syftet är också att undersöka om det finns någon skillnad mellan smärta och olika bakgrundsvariabler. Metod: Denna studie är en deskriptiv studie av kvantitativ design och är utformad med hjälp av retrospektiv registerdata. Datan insamlades genom det Svenska palliativregistrets dödsfallsenkät. 1435 patienter inkluderades som hade vårdats på olika palliativa vårdformer inom Uppsala och Enköping.   Resultat: Resultatet visar att smärtskattningsinstrument används i en bristande utsträckning inom den palliativa vården, då endast 56 % utav de som hade smärta också smärtskattades. När det gäller smärtlindring så blev 69 % utav patienterna helt och 30 % delvis smärtlindrade. Vid analysen utav samband mellan smärtlindring och vissa dödsplatser så visade resultatet att det fanns en signifikant skillnad. Samma resultat framkom även gällande analysen utav samband mellan vissa grundsjukdomar och upplevelsen utav smärta. Upplevelsen utav smärta samtidigt som upplevd ångest visade sig ha ett samband. Slutsats: Detta område är relativt outforskat, vilket gör att mer forskning behövs. Resultatet från denna studie kan användas som ett underlag för framtida forskning. / Background: Palliative care is intended to alleviate suffering such as pain and anxiety. By using pain measurements instruments these symptoms can be assessed, evaluated and alleviated. The patients life quality is promoted by alleviating these symptoms. Through the Swedish Register of palliative care there is a possibility to compile and evaluate information that can promote research and thereby contribute to a reduced suffering. Aim: The aim is to investigate the presence of pain and pain treatment in end of life care and also to learn in which extent validated pain measurements instruments are used. The aim is also to investigate whether there is a difference between pain and different background variables. Method: This is a descriptive study of a quantitative design and is shaped with retrospective registry data. The data was collected through the Swedish register of palliative cares’ death questionnaire. 1435 patients were included who had been cared in different forms of palliative care in Uppsala and Enköping. Result: The result shows that pain measurement instruments are used in a lacking extent in palliative care, where 56 % of those who experienced pain were pain estimated. When it comes to pain estimation this study shows that 69 % of the patients were completely relieved of their pain and 30 % were partly relieved. The analysis of the connection between pain treatment and some death places showed that there is a significant difference. The same result also appeared in the analyze of the connection between some background diseases and the experience of pain. The experience of pain was shown to have a connection with the experience of anxiety. Conclusion: This area is relatively unexplored, which means more research is required. The results of this study could be used as a basis for future research.
29

Design and construction of a contactless excitation and response measurement system

Westlund, Johan January 2019 (has links)
Manufacturing industry works on Overall Equipment Effectiveness (OEE) to increase the yield and speed of machining. A good knowledge of the machine properties is important to increase the speed while still maintaining stable cutting with low tool usage.To make models of the machine is therefore important and in machining a common way to extract the dynamic properties is frequency response measurement. One way is to use an impact hammer to excite the machine tool and measure the response. The problem is that a hammer can only be used on a non running machine. At Manufacturing and Metrology Systems division at KTH (MMS) a test method for contactless excitation has been developed that uses electromagnets to excite the machine tool. By using contactless testing it can be used on rotating machine tools without real cutting in materials. In this thesis a new test system for the contact less testing method has been designed and constructed to test if it is possible to do test on a bigger variety of rotating cutting machine tools. The results for the prototype is presented and evaluated. / Dagens tillverkningsindustri arbetar för att utrsutningens totala effiktivitet ska höjas genomatt öka hastigheten och minska material- och verktygsanvändningen vid bearbetningen utan att minska kvalitén på slutprodukten. För att öka hastigheten krävs en god kännedom om maskinens egenskaper för att maskinen ska arbeta under stabila förhållanden där också verktygets slitage minskas. Att ta fram modeller över maskinen är därför viktigt och inom skärande bearbetning är frekvensresponsmätning ett sätt att få ut de dynamiska egenskaperna av det skärandeverktyget. En vanlig testmetod är att med en hammare exitera verktyget och mäta responsen. Problemet är dock att hammaren bara kan mäta vid stillastående maskin. Vid MMS har en testmetod för kontaktlös exitering tagits fram där elektromagneter användsför exiteringen. På så sätt kan testet utföras på roterande verktyg utan att man behöver förbruka material. I detta arbete har ett nytt testsystem för denna testmetod designats och konstruerats för att testa om det är möjligt med testning på flera storlekar på maskiner för skärandebearbetning. Resultaten för prototypen presenteras och utvärderas.
30

Alternative measurement instruments for the evaluation of learner achievement in business management in the Technikon S A

Van Koller, Johan Frans. 11 1900 (has links)
Thesis / This research is mainly concerned with determining whether the existing evaluation methods/measurement instruments used in Business Management at Technikon SA, are still suitable, adequate and acceptable enough for continued use, or whether there is a need for the introduction of alternative methods. The first objective in this research was to determine what the exact role and function of evaluation in the education process is. On the basis of literature, it was determined that evaluation, and by implication measurement, is a crucial component of the education process and that no real teaching or learning can occur without it. Second, an attempt was made to determine what the nature and extent of the shortcomings of the existing measurement instruments were. Also on the basis of literature it was found that there are numerous and serious disadvantages in the existing measurement instruments. Third, the researcher also attempted to determine whether any other (alternative) measurement instruments, in addition to the existing ones, were available. It was discovered that there are a variety of alternative evaluation/measurement instruments available. Fourth, the measurement instruments used in Business Management were analysed and compared to the Business Management curriculum objectives to determine whether they were indeed suitable for the subject. It was found that, although a positive correlation seems to exist between the measurement instruments and the curriculum objectives, there were certain definite shortcomings in the existing measurement instruments in terms of the realization of some of the curriculum objectives. Fifth, focus group interviews were used as a research method to get an understanding of the views of TSA learners on the aspect of evaluation and the methods/instruments currently used. Most of the participants expressed a need for more practical types of measurement/evaluation. However, many participants felt the written examination should not be abolished entirely, but be used in conjunction with other more practical methods. The research concluded with a number of recommendations based on the findings in this research. / Curriculum and Instructional Studies / D. Ed. (Didactics)

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