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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

Tracking Short-range Ballistic Targets

Acar, Recep Serdar 01 September 2011 (has links) (PDF)
The trajectories of ballistic targets are determined significantly by the characteristics that are specific to them. In this thesis, these characteristics are presented and a set of algorithms in order to track short-range ballistic targets are given. Firstly, motion and measurement models for the ballistic targets are formed and then four different filtering techniques are built on these models which are the extended Kalman filter, the unscented Kalman filter, the particle filter and the marginalized particle filter. The performances of these filters are evaluated by making Monte Carlo simulation. The simulations are run using target scenarios obtained according to six degrees-of-freedom trajectory for ballistic targets. Apart from the tracking errors of the filters, drag parameter estimations and the effect of drift calculation on the filter performances are investigated. The estimation results obtained by each filter are discussed in detail by making various simulations.
22

Signal Processing for mmWave MIMO Radar

Faus García, Óscar January 2015 (has links)
This thesis addresses the design study, implementation and analysis of signal processing algorithms for a 79 GHz millimeter-wave Phase Modulated Continuous Wave (PMCW) Multi Input Multi Output (MIMO) short range radar; performed in IMEC research institute (Leuven, Belgium). The radar system targets high resolution performance with low power consumption in order to integrate a full MIMO radar transceiver with digital processor and antennas in a compact package featuring a size of 1 cm2. Achieving such radar system characteristics requires the exploitation of a highly demanding digital architecture with signal processing gain and high range, speed and angle resolutions. The improved resolution and detection capabilities will be achieved by performing signal processing algorithms on the reflected waveform. The digital front-end implements parallel range gate processing with a bank of correlators that perform: pulse compression, coherent accumulation to further increase Signal to Noise Ratio (SNR) and N-point FFT to extract the Doppler information. The use of MIMO is proposed implementing a code domain technique in the PMCW waveform, the Outer Hadamard Code MIMO. This concept makes use of a unique sequence for all the transmitting antennas that is rendered by an outer sequence to ensure the orthogonality of the transmitted waveforms. The outer code makes use of the good cross-correlation properties of the Hadamard sequences and the waveform uses sequences that exhibit perfect auto-correlation profile, the Almost Perfect Autocorrelation Sequences (APAS). The MIMO implementation results in higher angular resolution and extra processing gain. The use of beamforming techniques in the radar allows the angle estimation of the detected targets; using rough and fine beamforming that provides with coarse and precise Angle of Arrival (AoA) estimation in an early and late stage respectively. A Constant False Alarm Rate (CFAR) processing stage is implemented in the stage of the system where higher signal processing gain is achieved. This algorithm allows the variation of the CFAR parameters and analyzes the detections in order to improve the probability of detection (Pd) while decreasing the probability of false alarm (Pfa). A series of simulations with different scenarios and variable parameters are set in order to analyze the performance of the system. The simulations analyze the gain achieved in each stage and their outcomes show an impressive processing gain that can reach SNR improvements as high as 77 dB for a small virtual array while keeping the Pfa low with the CFAR adjustment. The use of bigger arrays demonstrates the possibility to enable clear detections for low Radar Cross Section (RCS) targets in far distances of the unambiguous range. The use of beamforming shows interference reduction improvement as the beam widths narrow with the increasing number of virtual array antennas. These results have been achieved while keeping the system design parameters to a range resolution of 7.5 cm for a maximum range of 37.5 meters with speed resolution of 0.2 m/s and a maximum detectable speed of 12.66 m/s. The outcomes support the good performance of the signal processing techniques implemented and the benefits in applying them in a SoC mmWave MIMO radar.
23

Hållbara inköpsresor : Stads- och handelsutveckling i samverkan / Sustainable Shopping Journeys : Developing Cities and Retail in collaboration

Wärnhjelm, Mathias January 2015 (has links)
This thesis is focused on the objective: How can the city's transport system and land use be coordinated and stakeholder collaboration be developed, to make the proportion of environmentally sustainable shopping trips increase? Trading and transportation in the town has been developed so that consumer’s traffic dependence has increased and the elderly, children and people without cars have got poorer accessibility to basic services. The consequences in terms of increased car use is negative for environmentally sustainable development. The premise of this thesis is three questions; What knowledge is there in Sweden and internationally on travel and shopping habits? What is the individual's behavior and what determines the choice of travel mode when doing purchasing trips? How does corporations and national, regional and local public agencies coordinate their decision-making? The aim of the thesis is to analyze and discuss how trade and the transportation system can be coordinated and developed to contribute to attractive and environmentally sustainable trade structures. Given this aim it was an important focus of the thesis to study and analyze how the forms of collaboration between stakeholders can be developed A review and analysis is made of the theoretical and practical aspects of individuals' behavior and how collaboration in decision-making can be developed and enhanced. The driving forces behind the emergence of today's trading structures are analyzed as well as their ability to influence society's conditions for increased durability. The state of knowledge is reported when it comes to travel- and purchasing-habits in Sweden and internationally, as well as the observed and projected impacts on traffic and the development of sustainability. Case studies from semi-central business establishments in Nacka, Falun and Umeå with 578 interviews of consumers and nine interviews with stakeholders handling trade in the case study locations, is reported. Results from a Web Panel with 1 839 web interviews with the same issues as in the case studies, but across the country, is described. The final chapters discusses the three questions and the objective and in the final discussion is the most important points highlighted regarding the development of trade in a sustainable and attractive city. A methodology for creating a sustainable trade policy in a municipality as well as a detailed account of the current state description, case studies and web-based survey is reported in the appendices. / <p>QC 20151002</p>
24

Hard QCD Processes in the Nuclear Medium

Freese, Adam 29 March 2016 (has links)
The environment inside the atomic nucleus is one of the most fascinating arenas for the study of quantum chromodynamics (QCD). The strongly-interacting nature of the nuclear medium affects the nature of both QCD processes and the quark-gluon structure of hadrons, allowing several unique aspects of the strong nuclear force to be investigated in reactions involving nuclear targets. The research presented in this dissertation explores two aspects of nuclear QCD: firstly, the partonic structure of the nucleus itself; and secondly, the use of the nucleus as a micro-laboratory in which QCD processes can be studied. The partonic structure of the nucleus is calculated in this work by deriving and utilizing a convolution formula. The hadronic structure of the nucleus and the quark-gluon structure of its constituent nucleons are taken together to determine the nuclear partonic structure. Light cone descriptions of short range correlations, in terms of both hadronic and partonic structure, are derived and taken into account. Medium modifications of the bound nucleons are accounted for using the color screening model, and QCD evolution is used to connect nuclear partonic structure at vastly different energy scales. The formalism developed for calculating nuclear partonic structure is applied to inclusive dijet production from proton-nucleus collisions at LHC kinematics, and novel predictions are calculated and presented for the dijet cross section. The nucleus is investigated as a micro-laboratory in vector meson photoproduction reactions. In particular, the deuteron is studied in the break-up reaction γd → Vpn, for both the ϕ(1020) and J/ψ vector mesons. The generalized eikonal approximation is utilized, allowing unambiguous separation of the impulse approximation and final state interactions (FSIs). Two peaks or valleys are seen in the angular distribution of the reaction cross section, each of which is due to an FSI between either the proton and neutron, or the produced vector meson and the spectator nucleon. The presence and size of the latter FSI valley/peak contains information about the meson-nucleon interaction, and it is shown that several models of this interaction can be distinguished by measuring the angular distribution for the deuteron breakup reaction.
25

Price models with weakly correlated processes

Richter, Matthias, Starkloff, Hans-Jörg, Wunderlich, Ralf 31 August 2004 (has links)
Empirical autocorrelation functions of returns of stochastic price processes show phenomena of correlation on small intervals of time, which decay to zero after a short time. The paper deals with the concept of weakly correlated random processes to describe a mathematical model which takes into account this behaviour of statistical data. Weakly correlated functions have been applied to model numerous problems of physics and engineering. The main idea is, that the values of the functions at two points are uncorrelated if the distance between the points exceeds a certain quantity epsilon > 0. In contrast to the white noise model, for distances smaller than epsilon a correlation between the values is permitted.
26

Automated Enforcement Using Dedicated Short Range Communication

Kim, Gilbert 01 January 2012 (has links) (PDF)
This thesis presents a set of system algorithms and a feasibility analysis of an automated enforcement system that uses dedicated short-range communication with an emphasis on seatbelt and speed enforcement. The current seatbelt and speed enforcement limitations and disadvantages can be overcome because future vehicles will be equipped with devices that can be used to communicate with other vehicles or the traffic infrastructure. One limitation of the current seatbelt enforcement system is that it relies only on human vision. Today’s automated photo speed enforcement also has the following major limitations and disadvantages: fixed position enforcement, system installation and maintenance costs, enforcement based only on spot speed, sensitivity to lighting conditions, and vulnerability to sprays and obstructions that might block the license plates. This thesis proposes an automated enforcement system that uses wireless communication (IEEE 802.11p protocol), which can resolve all of the above-mentioned problems and is also more efficient, accurate, and cost effective.
27

The Extent of Reliability for Vehicle-to-Vehicle Communication in Safety Critical Applications: An Experimental Study

Hoque, Mohammad A., Rios-Torres, Jackeline, Arvin, Ramin, Khattak, Asad, Ahmed, Salman 03 May 2020 (has links)
Vehicle-to-vehicle (V2V) communication using Dedicated Short Range Communications (DSRC) technology promises to help drastically reduce vehicle collisions. DSRC allows vehicles in a highly mobile and complex network to send and receive safety messages with more reliability and lower latency compared with other wireless technologies used for automotive communications. However, there are many factors that could cause a safety-critical automotive application to become unreliable due to communication failures. While the reliability of V2V communication has been a subject of study by several researchers, there are still open questions regarding how the placement of the DSRC devices (inside or outside the host vehicle), the vehicle’s interior elements and the differences in altitude can affect the V2V communications. This article provides experimental testing data and analyses in order to quantify the impacts of relative vehicle speeds, altitude differences between vehicles, and interior obstacles on V2V communication range and reliability for opposite traffic, in both city and highway environments. We discuss how these results can adversely affect the design parameters of safety critical applications by considering the V2V application “Safe Pass Advisory” on two-lane rural highways.
28

Analysis of Using V2X DSRC Equipped Snowplows to Request Signal Preemption

Lau, Samantha Kathleen 04 August 2022 (has links)
Dedicated short-range communication (DSRC) systems, a form of vehicle-to-everything (V2X) systems, were placed on Utah Department of Transportation (UDOT) snowplows to request signal preemption. The study took place along five state routes in the Salt Lake City metropolitan area. Snowplows and intersections were equipped with the technology to communicate and process requests for signal preemption. Signal performance and vehicle performance analysis were performed to understand the impacts that snowplows requesting signal preemption had. Signal performance analysis was done to determine how snowplows with V2X systems using DSRC affected signals. Vehicle performance analysis was done to see if plowing and traffic efficiency and performance were improved, as well as evaluating safety implications of signal preemption. To perform the signal performance analysis, V2X data were collected to understand how often signal preemption was requested by snowplows, how often it was granted by signal controllers, and how long preemption requests affected signal controller timing. Snowplows requested preemption over 50 percent of the time they approached a signalized intersection. Of messages that requested signal preemption, over 80 percent were granted. On average, signal controllers are affected by preemption processing for less than 5 minutes. This shows that the system works as designed, is used often, and does not have adverse effects on signal controller. Data for vehicle performance analysis included analysis of snowplow speed data, general travel speed data, and crash data. These were collected to analyze the effects of snowplows requesting signal preemption on vehicle performance. The analysis showed that snowplow speeds are not changed due to the signal preemption system, but the number of times snowplows stopped was reduced. General travel speeds on equipped routes were more consistently closer to the speed limits than not equipped routes. Crash data showed a greater negative decrease on equipped routes than on not equipped routes. These findings showed minimal changes or impacts to vehicle performance, but anecdotal evidence from snowplow drivers indicates benefits from the system overall. There were various limitations in the analysis. Data granularity differed among datasets, making comparison between the different datasets difficult without reducing data integrity. Some datasets did not have much data, making statistical significance unclear. With these data limitations, conclusions were drawn, but do not fully describe all the potential benefits and impacts of snowplows with V2X systems that use DSRC to request signal preemption. Additional research is needed to better understand the impacts that snowplows requesting signal preemption has on different maintenance metrics, such as fuel usage and time spent plowing. It is also recommended that data used is explored for ways to improve the granularity.
29

Deformation mechanisms of the equiatomic Cr-Co-Ni medium-entropy alloy / 等原子量Cr-Co-Niミディアムエントロピ-合金の塑性変形機構

LI, Le 26 September 2022 (has links)
京都大学 / 新制・課程博士 / 博士(工学) / 甲第24231号 / 工博第5059号 / 新制||工||1790(附属図書館) / 京都大学大学院工学研究科材料工学専攻 / (主査)教授 乾 晴行, 教授 田中 功, 教授 安田 秀幸 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM
30

STRUCTURE AND PHYSICAL PROPERTIES OF TRANSITION METAL BASED COMPOUNDS

Ahmed, Sheikh Jamil January 2018 (has links)
Crystalline systems formed with transition metal elements tend to exhibit strong magneto-structural coupling that gives rise to unusual but exciting physical phenomena in these materials. In this dissertation, we present our findings from the studies of structural and physical properties of single phase compounds Co2MnSi, Ni16Mn6Si7 and Mn(Ni0.6Si0.4)2. In addition, the stability of a Ni2MnSi composition in a multiphase system is discussed by both theoretical and experimental approaches. All the works have been conducted with a focus on explaining the fundamental behaviors of these systems that have not been adequately addressed by other studies in the literature. We present an experimental and theoretical investigation of the half-metallic Heusler compound, Co2MnSi to address disorder occupancies and magnetic interactions in the material. Contrary to previous studies, our neutron diffraction refinement of the polycrystalline sample reveals almost identical amount of Mn and Co antisite disorders of ~6.5% and ~7.6%, respectively which is also supported explicitly by our first-principles calculations on the system with defects. A reduction of the net moment of Co2MnSi due to an antiferromagnetic interaction introduced by disordered Mn is observed by our theoretical study. The neutron refinements at 298 K, 100 K, and 4 K further supports such reduction of moments. The work also reports the growth of single crystal by the Czochralski method and determination of a Curie temperature of ~1014 K measured by both the electrical resistivity and dilatometry measurement. Studies of a Ni2MnSi Heusler system reveal two new systems i.e., the Ni16Mn6Si7 G-phase and the Mn(Ni0.6Si0.4)2 based Laves phase with complex crystal structures. These systems exhibit strong magneto-structural coupling that could lead to interesting physical behaviors. The lack of thorough understanding of the properties of these materials inspired us to undertake the present studies. We address the geometrically frustrated two-dimensional magnetic structure and spin canted weak ferromagnetic behavior of Ni16Mn6Si7. Our magnetization and specific heat measurements on a Czochralski grown single crystal sample depicts the paramagnetic to antiferromagnetic transition at 197 K, and a second phase change at 50 K. Furthermore, a gradual drop of zero field cooled magnetic susceptibility is observed below 6 K that is associated with the spin freezing effect. The neutron diffraction on the polycrystalline powder samples at the temperatures of interest reveals that the antiferromagnetism is governed by the magnetic ordering of the Mn ions in the octahedral network. Below the Néel temperature of 197 K, the 2/3 of Mn atom moments form a two-dimensional magnetic arrangement, while the 1/3 moments remain geometrically frustrated. The phase transition at 50 K is found to be associated with the reorientation of the 2D moments to a canted antiferromagnetic state and development of ordering of the frustrated paramagnetic ions. Magnetization measurements as a function of temperature and magnetic field in principal directions, permit to determine the anisotropic magnetic behavior of Ni16Mn6Si7 in terms of the magnetic structure obtained by the neutron diffraction measurements. We also report an irreversible smeared spin-flop type transition for the system at a higher magnetic field. The diffuse scattering due to the short-range ordering is a commonly occurring phenomenon in Laves phase materials. The occurrence of such distinct atomic arrangement can considerably influence the physical behavior of the material. Nevertheless, no structural reconstruction of such atomic distribution in Laves phase has ever been reported in the literature. In this work, we present the structural ordering, and the associated physical behavior of an antiferromagnetic Ni-Mn-Si Laves phase with a composition Mn(Ni0.6Si0.4)2. The possibility of unique short-range ordering in the material is first concluded based on our single crystal diffraction analysis. With the high-resolution transmission electron microscopy and electron energy loss spectroscopy analysis, our work resolves the distinct atomic ordering of the Laves phase system. The investigations reveal the origin of the short-range ordering to arise from a unique arrangement between Ni and Si. The study also presents the atomic resolution mapping of the Si atoms which has never been reported by any previous studies. With further electrical conductivity measurement, we find one of the consequences of the unique ordering reflected in a semiconducting like temperature dependence of the compound. The neutron diffraction at 298 K suggests Mn(Ni0.6Si0.4)2 to be a strong antiferromagnetic system, which is further supported by the successive magnetic susceptibility measurement. The Néel temperature is determined to be 550 K. We also address the stability of the hypothetical ferromagnetic Heusler compound Ni2MnSi which has been proposed to be a stable system by numerous theoretical studies. Our first-principles work corroborates those studies with a negative formation enthalpy of -1.46 eV/formula unit. However, after numerous attempts to synthesize the composition, we conclude that a single phase Heusler Ni2MnSi compound cannot form under ambient conditions. Our results show that the system crystallizes as a mixture of the two Ni-Mn-Si compounds, i.e., the Ni16Mn6Si7 type G-phase and Mn(Ni0.6Si0.4)2 based Laves phase. Our work provides a possible explanation for the unstable Ni2MnSi Heusler compound with the calculation of formation enthalpy of the hypothetical Heusler system in terms of the computed energies of the neighboring phases Ni16Mn6Si7 and Mn(Ni0.6Si0.4)2. / Thesis / Doctor of Philosophy (PhD)

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