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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.
11

Multiscale electro-thermal modeling of AlGaN/GaN heterostructure field effect transistors

Donmezer, Fatma 12 1900 (has links)
Understanding the magnitude of the temperature in AlGaN/GaN heterostructure fi eld e ffect transistors(HFETs) is a critical aspect of understanding their reliability and providing proper thermal management. At present, most models used to determine the temperature rise in these devices are based on continuum based heat conduction. However, in such devices, the heat generation region can be on the order of or smaller than the phonon mean free path of the heat carriers, and thus, such models may under predict the temperature. The aim of this work is towards building a multiscale thermal model that will allow for the prediction of heat transport from ballistic-diffusive phonon transport near the heat generation region and diffusive transport outside of this zone. First, a study was performed to determine the appropriate numerical solution to the phonon Boltzmann transport equation followed by its integration into a multiscale thermal scheme. The model, which utilizes a Discrete Ordinates Solver, was developed for both gray and non-gray phonon transport. The scheme was applied to the solution of speci fic test problems and then finally to the electrothermal modeling of AlGaN/GaN HFETs under various electrical bias conditions.
12

The origin and evolution of North American kimberlites

Zurevinski, Shannon 11 1900 (has links)
Recent discoveries of kimberlites in North America have revealed that different processes are involved in the generation of kimberlite magma. A multi-disciplinary approach combining mineralogical, petrological, geochemical, and geochronological methods is used to classify the kimberlites, investigate possible sources of magma and evaluate current tectonic models proposed for the generation of kimberlite magma. The two main study areas are 1) the diamond-poor Churchill kimberlite field (Nunavut); and 2) the highly diamondiferous Lac de Gras kimberlite field (NWT). The Attawapiskat kimberlite field, the Kirkland Lake kimberlite field and the Timiskaming kimberlite field (Ontario) are also included in this study. The 55-56 Ma Diavik kimberlite cluster (NWT) have been classified as resedimented volcaniclastic > olivine-bearing volcaniclastic > mud-bearing volcaniclastic > macrocrystic oxide-bearing hypabyssal kimberlite > calcite oxide hypabyssal kimberlite > tuffisitic kimberlite breccia. Geochemical features of Diavik kimberlites include: 1) LREE enrichment, 2) large intra-field range in REE content, and 3) highly diamondiferous kimberlites at Diavik with primitive geochemical signatures. The Churchill kimberlites are classified as sparsely macrocrystic, oxide-rich calcite evolved hypabyssal kimberlite and macrocrystic oxide-rich monticellite phlogopite hypabyssal kimberlite. Electron microprobe analyses of olivine, phlogopite, spinel and perovskite support this petrographical classification. Twenty-seven precise U-Pb perovskite and Rb-Sr phlogopite emplacement ages indicate that magmatism spans ~45 million years (225-170 Ma). The crystallization ages and the Sr and Nd isotopic compositions of groundmass perovskite from a well-established, SE-trending Triassic-Jurassic corridor of kimberlite magmatism in Eastern North America (ENA) were determined to investigate the origin of this magmatism. The Sr isotopic results indicate that the Churchill (0.7032-0.7036) and Attawapiskat kimberlites (0.7049-0.7042) have unique isotopic compositions, while Kirkland Lake/Timiskaming perovskite have a larger range of 87Sr/86Sr ratios. This implies the derivation of kimberlite magma from two distinct sources in the mantle, a depleted MORB mantle source and a kimberlite magma with a Bulk Silicate Earth signature. The pattern of increasing 87Sr/86Srinitial with younging of kimberlite magmatism along the ~2000 km corridor of continuous Triassic/Jurassic magmatism could be explained from either a single or multiple hotspot track(s), responsible for the addition of heat required to generate small volume mantle melting of a kimberlite source.
13

Efficient Use of Force: Evaluating Police Tactics in Reducing Gun Violence

Cockerham, Meredith 01 January 2016 (has links)
This evaluation strives to determine what is the best police tactic in reducing gun violence. There are four approaches that are discussed are the pulling levers approach, the use of increased sentencing, hotspot identification, and the focus on reducing gun trafficking and illegal gun use. In addition to examining other evaluations, data from the FBI UCR database of specific case-study cities are included to determine to what extent each approach had. The study includes the analysis of programs such as Operation Ceasefire and Project Exile, but also includes analyses of smaller lesser known programs. Though many of the cities used a combination of these four approaches, overall, hotspot identification had great success in reducing gun violence. However with the preliminary research, it is difficult to come to any greater conclusions; more research is necessary.
14

Comparison and Prediction of Temporal Hotspot Maps

Arnesson, Andreas, Lewenhagen, Kenneth January 2018 (has links)
Context. To aid law enforcement agencies when coordinating and planningtheir efforts to prevent crime, there is a need to investigate methods usedin such areas. With the help of crime analysis methods, law enforcementare more efficient and pro-active in their work. One analysis method istemporal hotspot maps. The temporal hotspot map is often represented asa matrix with a certain resolution such as hours and days, if the aim is toshow occurrences of hour in correlation to weekday. This thesis includes asoftware prototype that allows for the comparison, visualization and predic-tion of temporal data. Objectives. This thesis explores if multiprocessing can be utilized to im-prove execution time for the following two temporal analysis methods, Aoris-tic and Getis-Ord*. Furthermore, to what extent two temporal hotspotmaps can be compared and visualized is researched. Additionally it wasinvestigated if a naive method could be used to predict temporal hotspotmaps accurately. Lastly this thesis explores how different software packag-ing methods compare to certain aspects defined in this thesis. Methods. An experiment was performed, to answer if multiprocessingcould improve execution time of Getis-Ord* or Aoristic. To explore howhotspot maps can be compared, a case study was carried out. Another ex-periment was used to answer if a naive forecasting method can be used topredict temporal hotspot maps. Lastly a theoretical analysis was executedto extract how different packaging methods work in relation to defined as-pects. Results. For both Getis-Ord* and Aoristic, the sequential implementationsachieved the shortest execution time. The Jaccard measure calculated thesimilarity most accurately. The naive forecasting method created, provednot adequate and a more advanced method is preferred. Forecasting Swedishburglaries with three previous months produced a mean of only 12.1% over-lap between hotspots. The Python package method accumulated the highestscore of the investigated packaging methods. Conclusions. The results showed that multiprocessing, in the languagePython, is not beneficial to use for Aoristic and Getis-Ord* due to thehigh level of overhead. Further, the naive forecasting method did not provepractically useful in predicting temporal hotspot maps.
15

O Complexo Geoidal Leste Brasileiro: características geológicas e geofísicas

Ivo Bruno Machado Pessanha 19 December 2003 (has links)
Agência Nacional do Petróleo / A margem continental leste brasileira apresenta uma fisiografia típica de margens continentais do tipo passiva derivada de processo de rifteamento, que foi posteriormente modificada por um conjunto de feições, aqui denominado Província Magmática de Abrolhos (PMA), em que se destacam a plataforma de Abrolhos, o banco Royal Charlotte, os montes submarinos da Bahia e a Cadeia Vitória/Trindade, além de montes submarinos isolados e corpos magmáticos intercalados aos sedimentos. O presente estudo concentrou-se na investigação da correlação espacial e temporal entre PMA e anomalias gravimétricas, anteriormente nomeadas Complexo Geoidal Leste Brasileiro (CGLB), entre elas o Alto Geoidal de Abrolhos (AGA). Para tanto foram utilizados dados de batimetria derivada da altimetria de satélites, gravimetria e sísmica multicanal. A partir da interpretação dos perfis de sísmica multicanal e dos mapas e blocos diagramas elaborados, pôde-se observar as distintas características do embasamento e coluna sedimentar, bem como das anomalias gravimétricas correspondentes ao longo de diferentes setores da Província Magmática de Abrolhos. As anomalias gravimétricas puderam ser primariamente diferenciadas em rasas (crustais) e outras mais profundas.. As mais profundas podem ser separadas em dois setores, norte e sul. O setor norte de alinhamento NW-SE apresenta um menor valor de altura do geóide, está diretamente relacionado com os montes submarinos da Bahia e se estende até a Z.F. Bragation. Diferentemente, o setor sul é constituído de um proeminente alto geoidal alinhado na direção WSW-ENE e não está justaposto a nenhuma feição topográfica proeminente. Estas anomalias gravimétricas aparentemente estão relacionadas a duas diferentes fontes mantélicas de idades e profundidades diferentes, o que é sugerido pelas diferenças de amplitude e alinhamentos, respectivamente. Entretanto, não se pode eliminar por completo a hipótese de serem estas anomalias de diferentes setores de uma única pluma, e que tiveram suas fases de atividade em diferentes épocas, sendo 80 Ma para o setor norte, enquanto o setor sul pode ser considerado ainda em atividade. A isso associa-se ainda a existência pretérita de zonas de fraquezas com direções de alinhamento distintos, NW-SE e W-E para as regiões norte e sul respectivamente. As evidências de que toda a região de estudos vêm sendo constantemente influenciada por eventos magmáticos desde o Terciário sugerem que, independente da gênese destes eventos estar relacionada a apenas uma ou a várias fontes, é fundamental levá-las em consideração no estabelecimento de modelos geológicos e na aplicação destes seja em pesquisa acadêmica, seja na indústria de Óleo e Gás. Haja vista a importância do conhecimento da evolução destas anomalias térmicas, considerando-se a influência destas no processo de geração (maturação da matéria orgânica) e acumulação (modificações estruturais) nas bacias sedimentares da região. Evidenciou-se neste trabalho a necessidade de continuidade do estudo destas feições, de forma a permitir o desenvolvimento de modelos geofísicos e geofísicos capazes de estimar a natureza, origem e os efeitos destas anomalias térmicas nos ambientes deposicionais da margem continental leste brasileira. / The Eastern Brazilian continental margin is a typical passive continental margin derived from a rifting process that has been modified by a set of features, here named Abrolhos Magmatic Province (AMP). Abrolhos continental shelf, Royal Charlotte bank, Bahia seamounts, and Vitória/Trindade ridge, along with isolated seamounts, and igneous bodies interbedded within the sedimentary sequences are the main components of such Province. This study is based on satellite altimetry derived bathymetric data as well as gravity and multichannel seismic data in order to investigate the spatial and temporal relationship between AMP and a group of gravity anomalies formerly designated as East Brazilian Geoidal Complex. Among these anomalies is the Geoid High of Abrolhos. The interpretation of seismic profiles and bathymetric, gravity, and isopach maps allowed to unravel distinct characteristics of the oceanic basement and sedimentary sequences so as related gravity anomalies along the different sectors of the Abrolhos Magmatic Province. Gravity anomalies could be primarily classified as shallow (crustal) and deeper ones. Deeper anomalies can be separated into a northern and a southern sector. Northern sector strikes NW-SE with a smaller geoid high, can be directly related to Bahia seamounts and extends southeasterly up to Bragation fracture zone. Contrarily southern sector is a prominent WSWENE striking geoid high, which is not related to any important topographic feature. So apparently these two anomalies are related to distinct mantle sources differing in age and in depth as suggested by amplitude and strike, respectively. Nevertheless it can not be discarded the hypothesis that these two anomalies come from different parts of a single plume that have been actives in different times; 80 Ma. for the northern sector while the southern sector can be considered still in activity nowadays. It has to be added that there existed yet weakness zones striking NW-SE and W-E in northern and southern regions, respectively. Evidences that the whole study area has been constantly influenced by magmatic events since the Tertiary suggest that it is of fundamental importance to take them into account while establishing geological models and in the application of such models either in academic research or in oil and gas industry no matter the origin of such events to be related to a single or multiple sources. Knowledge of the evolution of these thermal anomalies is important since it is considered their influence in the process of oil and gas origin and accumulation (structural changes) in the sedimentary basins of the region. It became evident in this work the need of continuing the study of these features in order to allow the development of geological and geophysical models capable to estimate the nature, origin, and effects of these thermal anomalies in depositional environments of the eastern Brazilian continental margin.
16

Autentiseringsmetoder i trådlösa nätverk : Jämförelse av autentiseringsportaler i öppna trådlösa nätverk

Modig, Dennis January 2011 (has links)
Trådlösa nätverk finns idag överallt och behovet av ständig internetaccess ökar för varje dag. Behovet av bra mjukvaror för att erbjuda säker trådlös internetaccess och samtidigt kunna ta betalt för det är ett problem. Denna rapport är en funktionsjämförelse av produkter som gör det möjligt att introducera spårbarhet och säkerhet för användarna i ett trådlöst nätverk. Mikrotik RouterOS jämfördes emot Zeroshell där funktionaliteten sedan sattes i en verklighetsbaserad kontext och möjliga implementationer presenterades. Resultatet påvisade att Mikrotik RouterOS passade bättre för de flesta scenarier än exempelvis Zeroshell. Men att Zeroshell istället har mycket bra stöd för katalogtjänster.
17

Thermal-aware and uniform priority with scaled routing for high-performance network-on-chip

Okeke, Stanley 01 September 2017 (has links)
3D-NoC architectures are the amalgamation of the 3D integration (Die stacking of 3D-IC Technology) with the increased scalability found in NoC. Originally, it was proposed to tackle the problem of increasing the number of cores in the 2D plane which seems incompetent due to long distance interconnects. This architecture is aimed to optimize performance, power consumption, achieve low latency and increase the network bandwidth. Nevertheless, as more dies were being stacked vertically, IC operating frequency increases and this leads to some thermal issues which include high power density which increases average temperature. In addition to that, longer heat dissipation path results in different heat dissipation in each layer of the NoC which worsen the situation. An increase in the overall power consumption increases the average temperature, reduces performance and reliability. In this paper, an adaptive thermal-aware management scheme was proposed for 3D-NoCs, concentrating more on the hotspot regions in the network. This proposed protocol employs the thermal state of intermediate nodes and flits properties in a random uniform distributive way for packet routing. The proposed algorithm increases network availability and tends to distribute the temperature of the system evenly and uniformly within the network and making sure that packets are not forwarded to the hotspot node(s) and only flits with certain properties in the distribution are forwarded to the hotspot node(s). Before or during transmission, these two distributions must be calculated alongside the current node temperature to knowing which state of the distribution that node and flit belong to. The simulation shows this gave better performance in throughput and reliability of the network by reducing the number of hotspot nodes in the NoC. The proposed algorithm also reduces power consumption which is a function of temperature. Simulations show that our proposed algorithm reduces the total power/energy consumed by more than 59\% and throughput is improved by 69\% compared to a traditional XYZ routing. / Graduate
18

Spatial Statistical Analysis of Bicycle Crashes in Ohio

Rizwan, Modabbir January 2020 (has links)
No description available.
19

Utformning av ett seniorboende i byn Kalvsvik / Designing of a senior housing in the village Kalvsvik

Strömberg, Matilda, Olsson, Noah, Bengtsson Glans, Ebba January 2020 (has links)
Studien presenterar ett förslag på hur ett alternativt seniorboende som riktar sig till personer över 55 i Kalvsvik kan utformas. Studien är inriktad på hur den yttre miljön och exteriören kan utformas på ett lämpligt sätt. Eftersom det råder en bostadsbrist i byn resulterar det i att äldre personer med gårdar i byn endast har möjligheten att flytta in till Växjö när de inte längre har energi att ta hand om sina gårdar. Ett önskemål från byborna har varit att ta fram funktionella lägenheter till äldre personer och med gemensamma utrymmen för att skapa en samhörighet.  Studien baseras på intervjuer med representanter från invånare i Kalvsvik, arkitekter och en landsbygdsutvecklare från Växjö kommun. En komparativ studie har genomförts där fem olika seniorboenden har studerats. Det slutgiltiga resultatet av studien redovisar ett seniorboende som består av två våningar med faluröd träfasad som innehar 16 lägenheter. Det finns även en yttre miljö med stora gemensamhetsytor som är tillgänglighetsanpassade.
20

Investigation into the molecular mechanisms underlying circadian rhythm disruption and human cancer

Janoski, Jesse Ryan 22 August 2023 (has links)
Doctor of Philosophy / Humans and all mammals have an internal timekeeping mechanism named the circadian clock that enables anticipation and response to the approximately 24-hour solar day and other environmental conditions. The circadian clock is self-sustained and coordinates rhythmic physiological functions such as the sleep/wake cycle, body temperature, hormone production, and metabolism, together forming the organism's "circadian rhythm." Chronic disruption of the circadian rhythm is known to be carcinogenic , but the molecular explanation for this phenomenon remains elusive. The purpose of my dissertation work was to investigate the role of mutations commonly associated with cancer as a potential molecular mechanism of circadian clock dysfunction. The PER2 gene produces the PER2 protein, which our laboratory has previously shown to interact with p53, a key "tumor suppressor" that responds to DNA damage. When not functional, these tumor suppressors can lead to uncontrolled cell division and eventually cancer. We focused on a mutation in p53 that changes p53's function and its interaction with PER2 in a manner that also prevents PER2 from functioning normally within the circadian clock. This dual dysregulation leads to the loss of rhythmic clock gene expression, and in turn, changes to cellular fitness, metabolism, and proliferation.

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