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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.
281

AIS-vektorer i antikollision - En relativ sanning / AIS-vectors in collision avoidance - A relative truth

Lewander, Gunnar, Måspers, Ola January 2010 (has links)
Intervjuer med kunniga på AIS-området har utförts parallellt med en enkät riktad till aktiva befäl ute till sjöss. Detta i syfte att ta reda på dels hur detta hjälpmedel bör användas vad avser antikollision, dels hur det faktiskt används i praktiken. AIS, Automatic Identification System, är ett informationsdelningssystem som hjälper fartyg att navigera säkert genom att sända ut egen navigationsdata och samtidigt ta emot motsvarande information från andra fartyg. Systemet nyttjas även som informationssystem för landbaserade stationer såsom VTS-centraler och kustbevakning. Undersökningen har engagerat och visat att expertisen anser att AIS, i många avseenden, är ett bra och användbart hjälpmedel som bör komplettera övrig utrustning vid bedömning om kollisionsrisk. Vidare visar enkäten att ARPA-systemet, trots vissa inneboende brister, tillmäts större förtroende än AIS och AIS-vektorer används därför sparsamt. Enkäten visar även att en stor del av de aktiva inte är främmande för att göra avsteg från sjövägsreglerna emedan expertisen i huvudsak avråder från sådant. / Interviews with experts, in the field of AIS, have been conducted alongside a quantitative survey aimed at certified seagoing officers. The purpose of the survey was to investigate how this navigational aid preferably should be used in collision avoidance, in contrast to how it is used in reality. AIS, Automatic Identification System, is an information sharing system to assist in safe navigation by transmitting the own vessels navigational data while, at the same time, receiving corresponding information from other ships. The system is also utilized by land based stations such as VTS-centers and coast guards. The investigation shows that experts conclude AIS to be, in many aspects, a good and useful aid which should be used in collaboration with other equipment when assessing risk of collision. Furthermore, the survey show that the ARPA-system, in spite of some internal shortcomings, is awarded more trust than AIS and AIS vectors are therefore rarely used. The survey also shows that a large number of officers are open to deviating from the COLREGs while the experts, in general, advise against it.
282

Optimisation-based verification process of obstacle avoidance systems for unmanned vehicles

Thedchanamoorthy, Sivaranjini January 2014 (has links)
This thesis deals with safety verification analysis of collision avoidance systems for unmanned vehicles. The safety of the vehicle is dependent on collision avoidance algorithms and associated control laws, and it must be proven that the collision avoidance algorithms and controllers are functioning correctly in all nominal conditions, various failure conditions and in the presence of possible variations in the vehicle and operational environment. The current widely used exhaustive search based approaches are not suitable for safety analysis of autonomous vehicles due to the large number of possible variations and the complexity of algorithms and the systems. To address this topic, a new optimisation-based verification method is developed to verify the safety of collision avoidance systems. The proposed verification method formulates the worst case analysis problem arising the verification of collision avoidance systems into an optimisation problem and employs optimisation algorithms to automatically search the worst cases. Minimum distance to the obstacle during the collision avoidance manoeuvre is defined as the objective function of the optimisation problem, and realistic simulation consisting of the detailed vehicle dynamics, the operational environment, the collision avoidance algorithm and low level control laws is embedded in the optimisation process. This enables the verification process to take into account the parameters variations in the vehicle, the change of the environment, the uncertainties in sensors, and in particular the mismatching between model used for developing the collision avoidance algorithms and the real vehicle. It is shown that the resultant simulation based optimisation problem is non-convex and there might be many local optima. To illustrate and investigate the proposed optimisation based verification process, the potential field method and decision making collision avoidance method are chosen as an obstacle avoidance candidate technique for verification study. Five benchmark case studies are investigated in this thesis: static obstacle avoidance system of a simple unicycle robot, moving obstacle avoidance system for a Pioneer 3DX robot, and a 6 Degrees of Freedom fixed wing Unmanned Aerial Vehicle with static and moving collision avoidance algorithms. It is proven that although a local optimisation method for nonlinear optimisation is quite efficient, it is not able to find the most dangerous situation. Results in this thesis show that, among all the global optimisation methods that have been investigated, the DIviding RECTangle method provides most promising performance for verification of collision avoidance functions in terms of guaranteed capability in searching worst scenarios.
283

Ion mobility-mass spectrometry studies of organic and organometallic complexes and reaction monitoring

Wright, Victoria E. January 2013 (has links)
Ion mobility (IM) spectrometry is a gas-phase electrophoretic technique in which ions are separated on the basis of their relative mobility in the presence of a weak electric field gradient and a buffer gas. Ion mobility-mass spectrometry (IM-MS) has the capability of separating ions based on m/z, size and shape, providing additional structural information compared to using mass spectrometry on its own. In this thesis, IM-MS has been used to investigate organic and organometallic complexes and identify reactants, intermediates and products in reaction mixtures. Collision cross sections (CCS) have been measured for three salen ligands, and their complexes with copper and zinc using travelling-wave ion mobility-mass spectrometry (TWIMS) and drift tube ion mobility-mass spectrometry (DTIMS), allowing a comparative size evaluation of the ligands and complexes. CCS measurements using TWIMS were determined using peptide and TAAH calibration standards with good intra-day and inter-day reproducibility. TWIMS measurements gave significantly larger CCS than DTIMS derived data in helium, indicating that the choice of calibration standards is important in ensuring the accuracy of TWIMS derived CCS measurements. The CCS data obtained from IM-MS measurements have been compared to CCS values obtained from X-ray coordinates and modelled structures. The analysis of small organic and organometallic molecules has been extended to investigations of the potential of IM-MS for reaction monitoring and structural studies of the components of catalytic cycles. Reaction mixtures of an organocatalysed Diels-Alder cycloaddition reaction have been monitored using IM-MS and high-field asymmetric waveform ion mobility-mass spectrometry (FAIMS-MS). Reactant, product, catalyst and reaction intermediates, including an intermediate not previously detected, were identified and the catalyst and intermediates monitored over time. An organometallic catalytic cycle using a palladium catalyst has been analysed using IM-MS and the CCS of reactants, intermediates and products have been measured and compared to theoretical CCS calculations. Good agreement was observed between measured and calculated data. Species not amenable to electrospray ionisation were covalently bound to an ionisable tag containing a quaternary ammonium ion allowing the tagged molecules to be detected by IM-MS.
284

Development of an integrated decision analysis framework for selecting ICT-based logistics systems in the construction industry

Fadiya, Olusanjo Olaniran January 2012 (has links)
The current application of logistics in the construction industry is relatively inefficient when compared with other industries such as retail and manufacturing. The factors attributed to this inefficiency include the fragmented and short-term nature of construction process and inadequate tracking facilities on site. The inefficiency of construction logistics creates inter alia loss of materials and equipment, waste, construction delay, excessive cost and collision accident on site. Meanwhile, several information and communication technologies (ICT) have been proposed and developed by researchers to improve logistics functions such as tracking and monitoring of resources through the supply chain to the construction site. Such technologies include global positioning system (GPS), radio frequency identification devices (RFID), wireless sensors network (WSN) and geographical information system (GIS). While considerable research has been undertaken to develop the aforementioned systems, limited work has so far been done on investment justification prior to implementation. In this research, a framework has been developed to assess the extent of construction logistics problems, measure the significances of the problems, match the problems with existing ICT-based solutions and develop a robust ready-to-use multi-criteria analysis tool that can quantify the costs and benefits of implementing several ICT-based construction logistics systems. The tool is an integrated platform of related evaluation techniques such as Fault Tree Analysis, Decision Tree Analysis, Life Cycle Cost Analysis and Multi-Attribute Utility Theory. Prior to the development of this tool, data was collected through questionnaire survey and analysed by means of statistical analysis in order to derive some foundational parameters of the tool. Quantitative research method was adopted for data collection because the processes of the tool for which the data was required are quantitative. The implementation of this tool is novel given the integration of the analytical techniques mentioned above and the application of the tool for selecting ICT-based construction logistics systems. The tool takes in data such as cost and quantities of materials for a building project and quantifies the cost and benefits of alternative ICT-based tracking systems that can improve the logistics functions of the project. The application of the tool will eliminate guesswork on the benefits of ICT-based tracking systems by providing an objective platform for the quantification of cost and benefits of the systems prior to implementation.
285

Collision-induced absorption in the rototranslational band of H2-H2 and in the fundamental band and first and second overtone of H2 in dense hydrogen gas

Abel, Martin Andreas 2009 August 1900 (has links)
The absorption due to pairs of H2 molecules is an important opacity source in the atmospheres of various types of planets and cool stars, such as late stars, low-mass stars, brown dwarfs, certain white dwarfs, etc., and therefore of special astronomical interest [13]. The emission spectra of cool white dwarf stars differ signicantly from the expected blackbody spectra of the cores, due to collision-induced absorption by collisional complexes of hydrogen and helium in the stellar atmospheres. In order to model the radiative processes in these atmospheres, which have temperatures of several thousand kelvin, one needs accurate knowledge of the induced dipole and potential energy surfaces of collisional complexes such as H2-H2. These come from quantum-chemical calculations with the H2 bonds stretched or compressed far from equilibrium length. Since no measurements of the collision-induced absorption for these high temperatures exist, one has to undertake ab initio calculations which take into account the high vibrational excitations of the hydrogen molecules. However, before one attempts to proceed to higher temperatures where no laboratory measurements exist it is good to know that the formalism is correct and reproduces the results at temperatures where measurements exist. Therefore, in order to make sure that the calculations are reliable one compares the results of the calculations with existing laboratory measurements where possible before proceeding to higher temperatures. Molecular hydrogen has always played a special role in the collision-induced spectroscopies. The rotational transition frequencies of H2 are widely separated so that translational, rotational and vibrational induced spectral bands can be studied separately. Moreover, the H2 molecule has a small anisotropy of the intermolecular interactions which may often be ignored in first order approximations. In general hydrogen gas is a mixture of para- and ortho-hydrogen. Para-hydrogen at sufficiently low temperature is not rotationally excited and is therefore an isotropic system. However, the anisotropy can be turned on and of by raising and lowering the temperature, because the ratio of para- to ortho-hydrogen depends on the temperature. What is even more, roughly 90% of all the known matter in the universe is hydrogen, in the ionized, atomic or molecular states, which makes hydrogen one of the most important species in astrophysics. The hydrogen molecule is non-polar, and some of the most important spectra in the near and far infrared and microwave region are collision-induced, due to H2-H2 complexes. At the temperature of 297.5K measurements of the collision-induced absorption spectra of H2-H2 gas are reported in the frequency range from 1900 to 2260cm^{-1} [9]. The gas densities for these measurements ranged from 51 to 610 amagat. These measurements were compared with ab initio calculations of the absorption. For these calculations the isotropic potential approximation was used. In contrast to previous ab initio calculations [9] agreement between calculations and measured spectra is now observed over the full frequency range considered. A major difference to the earlier calculations is that in this work new dipole and potential energy surfaces were used. Furthermore, measurements exist of the fundamental band and first and second overtone of H2 in dense hydrogen gas. They have been compared with ab initio calculations based on the new method. Over the full range of frequencies considered the agreement between calculations and measurements is remarkable. This work demonstrates that the new method is capable of reproducing the measured spectra where those exist with high accuracy, and predicts reliable opacities where no laboratory measurements exist. / text
286

Environmental characteristics around hotspots of pedestrian-automobile collision in the city of Austin

Geng, Sunxiao 12 September 2014 (has links)
The increasingly serious pedestrian safety issue in the City of Austin aroused the concern. Other than conducting quantitative analysis at aggregate level via collecting and examining the secondary data extracted from the existing datasets, the authors shifted towards the disaggregate level analysis, focusing on twenty-six hotspots of pedestrian collisions via mixed method research. Qualitative data was collected in the field survey to precisely capture the contextual features of collision locations, and was interpreted and coded as explanatory variables for the quantitative analysis. Instead of the frequency of pedestrian collision, crash rate measured by incident count per million pedestrians was the dependent variable to identify the factors truly influencing the pedestrian safety issue, not just the total number of walkers. The stepwise bivariate analysis and negative binomial regression examined the association between pedestrian collision rate and independent variables. Finally, the average block length, speed limit posted, sidewalk condition, and the degree of proximity to major pedestrian attractors were statistically significant factors correlating with the pedestrian collision risk. / text
287

DATA MINING OF PEPTIDE MS/MS SPECTRA TO ELUCIDATE GAS-PHASE PEPTIDE DISSOCIATION MECHANISMS AND IMPROVE PROTEIN IDENTIFICATION

Huang, Yingying January 2005 (has links)
Mining of datasets obtained from proteomics experiments was performed to investigate the dissociation pathways of protonated peptides activated in the gas phase under low energy collision-induced dissociation (CID). Intensity patterns in ion trap tandem mass spectra were exploited and different statistical approaches were employed to elucidate the dissociation mechanisms.Chapter 2 describes a study of 506 doubly-protonated tryptic peptides that shows the presence of an internal basic residue can increase the preferential fragmentation C-terminal to aspartic acid (Asp-Xxx) significantly. The degree of enhancement varies with the identity of the basic residues. The result corroborates a previously published mechanism based on studies from model peptides, and was incorporated into an existing peptide sequencing algorithm. A preliminary test on a separate dataset of 119 spectra shows that implementing rules to predict enhanced cleavages at Asp-Xxx improves the ability of the algorithm to identify the correct sequence from a list of candidates.Chapters 3-4 describe much more elaborate analyses on 28,330 peptides of different sequences and charge states. Extensive sorting based on prior knowledge was first performed to probe the correlation of fragmentation patterns with structural features. Pair-wise fragmentation maps reveal that the difference in basicity between Arg and Lys results in different dissociation patterns among singly-protonated tryptic peptides. While one dominant protonation form (proton localized) exists for Arg-ending peptides, a heterogeneous population of two or more protonated forms (proton partially-mobile) exist for Lys-ending peptides. Asp/Glu-Xxx dominates spectra from peptides that have a localized proton(s) and Xxx-Pro dominates those that have a mobile or partially mobile proton(s). When Pro is absent from peptides that have a mobile or partially mobile proton(s), cleavage at each peptide bond becomes more prominent. A fundamental dependence of gas phase peptide fragmentation on conformational constraints was found.A knowledge mining scheme was proposed in Chapter 5 to bypass the prior knowledge constraints and cluster the dissociation behaviors of 28,330 peptides into four distinct categories. The most influential factors in the fragmentation process are: the mobility of the proton(s), the presence and the location of Pro and Arg. Structural motifs responsible for each dissociation behavior are also elucidated.
288

Tectonic evolution of the Yarlung suture zone, Lopu Range region, southern Tibet

Laskowski, Andrew K., Kapp, Paul, Ding, Lin, Campbell, Clay, Liu, XiaoHui 01 1900 (has links)
The Lopu Range, located similar to 600km west of Lhasa, exposes a continental high-pressure metamorphic complex beneath India-Asia (Yarlung) suture zone assemblages. Geologic mapping, 14 detrital U-Pb zircon (n=1895 ages), 11 igneous U-Pb zircon, and nine zircon (U-Th)/He samples reveal the structure, age, provenance, and time-temperature histories of Lopu Range rocks. A hornblende-plagioclase-epidote paragneiss block in ophiolitic melange, deposited during Middle Jurassic time, records Late Jurassic or Early Cretaceous subduction initiation followed by Early Cretaceous fore-arc extension. A depositional contact between fore-arc strata (maximum depositional age 971Ma) and ophiolitic melange indicates that the ophiolites were in a suprasubduction zone position prior to Late Cretaceous time. Five Gangdese arc granitoids that intrude subduction-accretion melange yield U-Pb ages between 49 and 37Ma, recording Eocene southward trench migration after collision initiation. The south dipping Great Counter Thrust system cuts older suture zone structures, placing fore-arc strata on the Kailas Formation, and sedimentary-matrix melange on fore-arc strata during early Miocene time. The north-south, range-bounding Lopukangri and Rujiao faults comprise a horst that cuts the Great Counter Thrust system, recording the early Miocene (similar to 16Ma) transition from north-south contraction to orogen-parallel (E-W) extension. Five early Miocene (17-15Ma) U-Pb ages from leucogranite dikes and plutons record crustal melting during extension onset. Seven zircon (U-Th)/He ages from the horst block record 12-6Ma tectonic exhumation. JurassicEocene Yarlung suture zone tectonics, characterized by alternating episodes of contraction and extension, can be explained by cycles of slab rollback, breakoff, and shallow underthrustingsuggesting that subduction dynamics controlled deformation.
289

STUDY OF REQUIREMENTS FOR POST-CONSTRUCTION AUTOMATED BIRD MITIGATION SYSTEMS FROM STAKEHOLDER’S PERSPECTIVE

Crasilşcic, Veaceslav January 2016 (has links)
The expansion of wind power comes with additional risks for bird populations, one of which is the collision with wind turbine components, mainly the rotating blades. In order to mitigate this risk, few systems on the market propose solutions with modules that deter the birds from the wind turbine or trigger the temporary shutdown of the turbines.The thesis seeks to obtain a common view from different stakeholders in order to create a list of requirements that the bird protection systems must have so as to be accepted by all the parties involved in the wind industry in Sweden. In order to meet this objective, interviews were conducted with interested stakeholders. Consequently, the interviews were summarized and common points were extracted to create a list of requirements and additional suggestions.Firstly, a comprehensive literature review was done that has pointed out issues like impacts of wind farms on bird species, especially raptors, causes of bird mortality, environmental legislation in European Union and Sweden, and current solutions on mitigating the risk of collisions with wind turbines onshore. Additionally, the author looked up into the most efficient ways to engage the stakeholders in constructive discussions and develop an easy framework for presenting the requirements.The primary data was collected through interviews with stakeholders representing 12 organizations. In the next steps, the data was analyzed by summarizing each interview and identifying the common and differentiating points in respondents’ views and suggestions over automated bird mitigation systems. The identified points laid the basis for a list of requirements considered important for safe and efficient bird mitigation systems in Sweden. Among others, stakeholders identified that the most crucial issues regarding bird mitigation systems are the response time to shutdown of the turbine, distance from the birds’ species living areas, need of species identification in bad weather conditions and night time and overall financial feasibility of such technologies.
290

Collisions réactives dans les gaz d'intérêt énergétique / Reactive collisions in gases of energetic interest

Niyonzima, Sébastien 16 September 2013 (has links)
Cette thèse consacrée à l'étude de collisions réactives dans les gaz d'intérêt énergétique a porté sur deux aspects. D'une part, la théorie du défaut quantique multi-voies (Multichannel Quantum Defect Theory : MQDT) [Giusti 1980, Nakashima 1987]a été utilisée pour étudier la recombinaison dissociative (RD), l'excitation vibrationnelle (EV) et la désexcitation vibrationnelle (dEV) de l'ion BeH+ et ses isotopomères dans leurs quatre plus bas niveaux vibrationnels initiaux (X1Σ+,v i+ =0,1,2,3). Les données moléculaires récemment calculées par nos collaborateurs [Roos 2009] ont été utilisées pour calculer les sections efficaces et taux de RD, EV et dEV en considérant les états des trois symétries moléculaires de BeH (2Π, 2Σ+ et 2∆ ). La dépendance vibrationnelle et l'effet isotopique sur les taux de processus collisionnels compétitifs ont été mis en évidence (Fig. V. 7). Une comparaison avec les résultats théoriques de Roos et al. 2009 obtenus à l'aide de la méthode des paquets d'ondes (Wave packets : WP) est effectuée. De cette comparaison, il ressort qu'il y a un bon accord entre les deux méthodes aux énergies intermédiaires. Ainsi, ce travail de thèse est en partie une extension de travail précédent de [Ross 2009]. L'approcheMQDT, capable de traiter complètement les capture temporaires d'électrons dans les éttats de Rydberg liés, ainsi que le couplage vibronique entre les voies d'ionisation, permet d'obtenir les premiers résultats (fiables) à basses énergies [Niyonzima 2013]. Ces taux de processus collisionnels sont utiles dans la modélisation du plasma de bord des machines à fusion [Celiberto 2012]. D'autres parts, nous avons fourni une formulation analytique approximative des sections efficaces de RD, EV, et dEV, utile pour la prédiction et l'interprétation des résultats du calcul numérique. Elle nous permet de comprendre les différentes interactions intramoléculaires et la sensibilité des taux de réaction par rapport aux interactions dominantes. / This thesis devoted to the study of reactive collisions in gases of energetic interest concerns two aspects. Firstly, a Multichannel-Quantum-Defect-Theory-type approach [Giusti 1980, Nakashima 1987] is used in the treatment of the dissociative recombination (DR), vibrational excitation (VE), and vibrational de-excitation (VdE) of BeH+ in their four lowest vibrational states (X1Σ+,v i+ =0,1,2,3). The molecular structure data previously computed [Roos 2009] have been employed in the calculations of cross sections and rate coefficients of DR, VE and VdE including three electronic symmetries of BeH (2Π, 2Σ+ et 2∆ ). The vibrational dependence [Niyonzima 2013] and the isotopic effects in these collisional processes are highlighted – Figure (V.7) – in order to be used in the modeling of the edge fusion plasma [Celiberto 2012]. Satisfactory agreement with results computed with the wave packet method [Roos 2009] is reached at intermediate energies [Niyonzima 2013]. Thereby, this part of the thesis work extends the previous study of [Roos 2009]. The MQDT-based approach, able to fully account for the temporary captures of electrons in Rydberg bound states, as well as the vibronic coupling between ionization channels, provides the first results (reliable) at low energies [Niyonzima 2013]. Lastly, an approximate analytical formulation of DR, VE and VdE cross section for the prediction and interpretation of results of numerical calculations has been provided. This formulation is usefull in the understanding of different intramolecular interactions and explains the sensibility of rate coefficients with respect to dominant interactions.

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