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[en] DETERMINISTIC PROPAGATION MODEL IN MILLIMETER WAVES OVER URBAN ENVIRONMENTS WITH HIGH DENSITY OF SCATTERERS / [pt] MODELO DETERMINÍSTICO DE PROPAGAÇÃO DE ONDAS MILIMÉTRICAS EM AMBIENTES URBANOS COM ALTA DENSIDADE DE ESPALHADORESJEAN CARNEIRO DA SILVA 29 June 2020 (has links)
[pt] A futura saturação do espectro eletromagnético atualmente alocado para as comunicações móveis tem levado a comunidade científica a considerar o uso das vastas faixas de frequência disponíveis em ondas milimétricas. Esta contribuição se insere no esforço de pesquisa para caracterização dos canais urbanos em ambientes exteriores. O modelo desenvolvido utiliza o traçado de raios 2.5D, com base nos conceitos da ótica geométrica e teoria uniforme da difração. Foram implementadas diversas técnicas consideradas em um futuro padrão de comunicações móveis 5G para a transmissão de sinais de banda ultra larga em canais com e sem visada e consideradas várias classes de espalhadores, como árvores, postes e paredes rugosas com espalhamento difuso. Adicionalmente, foram feitas simulações e comparações em ambientes onde foram realizadas campanhas de medições, nas métricas de: potência recebida, retardo médio, desvio RMS e XPD. Os resultados comparativos mostraram boa concordância geral e foram investigadas possíveis causas de erro em previsões nas métricas adotadas. / [en] The future saturation of the electromagnetic spectrum currently allocated for mobile communications has led the scientific community to consider the use of the vast frequency bands available in millimeter waves. There are some technical obstacles limiting the immediate use of this band. In the radio propagation area, there is a research effort to characterize the outdoor urban channels. The developed model uses a 2.5D ray tracing algorithm based on geometrical optics and UTD concepts in outdoor environments. The model implements several techniques considered in a future standard of 5G mobile communications for the transmission of ultra wide band signals in LOS and NLOS channels with a high density of scatterers: trees, poles and diffuse scattering by rough building walls. In addition, simulations and comparisons were performed in environments where measurement campaigns were carried out, considering the following metrics: received power, mean delay, RMS deviation and XPD. The comparative results showed a good agreement. Possible model impairments were investigated.
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[pt] ANÁLISE DOS EFEITOS DA PROPAGAÇÃO EM CANAIS COM MÚLTIPLAS ENTRADAS E MÚLTIPLAS SAÍDAS (MIMO) COM BASE NO TRAÇADO DE RAIOS / [en] RAY TRACING ANALYSIS OF THE EFFECTS OF PROPAGATION ON MULTIPLE-INPUT MULTIPLE-OUTPUT (MIMO) CHANNELSLUCIANA FERREIRA VIEIRA 16 December 2005 (has links)
[pt] Um modelo de traçado de raios baseado no método das
imagens será
aplicado para estudar a propagação de ondas de rádio nas
regiões de
Copacabana e Ipanema no Rio de Janeiro. Nesses ambientes
altamente
urbanizados, pode-se assumir que a propagação é restrita à
seção horizontal
dos vales nas ruas que são formados pelos blocos de
edificações. Várias
classes de raios, caracterizados pelo número, tipo
(reflexão ou difração), e
ordem de ocorrência de interação com as faces laterais dos
blocos são
considerados no modelo. As direções de partida e chegada,
assim como a
amplitude e o atraso no tempo, caracterizam cada raio,
considerando seu
comprimento total, além dos produtos dos coeficientes
associados com cada
interação com o ambiente. Neste trabalho, demonstra-se o
aumento na
capacidade do canal com múltiplas entradas e múltiplas
saídas (MIMO), usando
conjunto de antenas na transmissão e na recepção para um
sistema faixa
estreita, operando a 1.9 GHZ, estudando situações com
linha de visada (LOS) e
sem linha de visada (NLOS). Sistemas de comunicações
wireless com múltiplas
entradas e múltiplas saídas (MIMO), utilizando conjunto de
antenas na
transmissão e na recepção apresentam grande interesse
atualmente, devido a
grande eficiência espectral apresentada e ao aumento na
capacidade do canal.
O efeito dos sistemas MIMO na capacidade do canal é
estudado para situações
LOS e NLOS, visando compreender sua relação em função do
ambiente de
propagação. Apresenta-se a relação da capacidade do canal
em função do
crescimento da relação sinal-ruído (SNR), da potência de
transmissão, da
distância, do atraso e do espalhamento angular para pontos
de recepção em
LOS e NLOS. Além disso, resultados simulando um canal
Rayleigh também são
comparados com os resultados obtidos. / [en] A ray tracing model based on the method of images has been
applied to
study the propagation of radio waves in the regions of
Copacabana and Ipanema
in Rio de Janeiro. In such highly urbanized environments,
it can be realistically
assumed that propagation is restricted to a horizontal
section of the street
canyons characterized by the blocks of buildings. Several
classes of rays,
characterized by the number, type (reflection and
diffraction), and order of
occurrence of interaction with the lateral faces of the
blocks are considered by the
model. The directions of departure and arrival, as well as
the amplitude and the
time delay characterize each ray, considering its total
length, as well as product of
the coefficients associated with each interaction with the
environment. In addition
to analyzing the behaviors of the ray parameters
considering both line-of-sight
(LOS) and non line-of-sight (NLOS) situations, the
capacity growth of multipleelement
antenna arrays (MEAs) will be demonstrated for a
narrowband system
operating at 1.9 GHz. Indeed, multiple-input, multiple-
output (MIMO) wireless
communications systems, making use of smart antenna arrays
at both ends of
the communications link, has been receiving increased
interest due to their high
spectral efficiency and channel capacity. The effect of
MIMO systems in the
channel capacity will be studied for representative LOS
and NLOS situations to
understand how the results change as a function of the
environment. It will be
seen how the capacity scales with increasing signal-to-
noise ratio (SNR) for a
large but practical number of antenna elements at both
transmitter and receiver.
The increase in capacity with transmitter power, distance,
delay and angular
spreads for LOS and NLOS cases will also be presented, as
well as a
comparison of the results with those corresponding to a
Rayleigh channel.
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Den svenska nolltoleransens baksida : En kvalitativ fallstudie om den svenska nolltoleransen mot narkotika samt dess följderBrag, Julia January 2022 (has links)
The Swedish death rate related to narcotics is amongst the highest within the EU. The purpose of this study is to use process tracing while investigating and understanding the high death rate among people who use narcotics in Sweden. The focus is on whether the Swedish drug policy is driven by morals instead of scientific proof and asks whether morals are the main cause of the high death rate in Sweden. The study utilizes the “threshold theory” and the theory of “symbolic politics.” To do this the following questions are being answered: “How has the Swedish zero tolerance towards narcotics looked like since the 1970s until present day?” and “are there any signs to proof that the Swedish drug policy is driven more by morals than by scientific evidence, and if so, what are they?” The study also tests the hypothesis that the high death rate is related to the restrictive drug policy in Sweden. In order to answer this the study collects data and regulations from different time periods in Sweden thru a qualitative method. The study confirms that the Swedish drug policy is driven by moral while overlooking scientific proof and it is also likely that the hypothesis of the study is true.
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Norms and non-governmental advocacy on conventional arms control : dynamics and governance.Anders, Nils H. January 2009 (has links)
Clear changes occurred in the field of conventional arms control in the last two
decades. States adopted a multitude of norms on especially small arms control in
various multilateral control instruments. In addition, non-governmental advocacy actors
often established themselves as active participants in control debates with governments.
The changes are surprising because they took place in the security sphere and therewith
in an area traditionally understood to be the exclusive domain of governments. This
research project investigates the significance of the changes for the traditional
understanding of security governance. Specifically, it investigates the emergence of
control norms and the role and policy impact of non-governmental actors in the
promotion of the norms. It asks whether the normative changes and significance of nongovernmental
actors therein challenge the understanding of security governance that
underpins many established approaches to international relations theory.
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Sensorimotor Neuroplasticity after ACL Reconstruction: Insights into Neuromodulationin Orthopedic Clinical RehabilitationSherman, David Alexander 28 July 2022 (has links)
No description available.
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Sequential Knowledge Tracing with Transformer ModelsSegala, Nino Yan-Nick Lucien January 2022 (has links)
Transformer models, delivering big improvement in AI text-models (NLP), are now being applied in Knowledge Tracing to track the knowledge of students over time. One of the first, SAINT, showed quite some improvement over the then SOTA results on the public EdNet dataset and caused an increase in research based on transformer-based models. In this paper, we firstly aim to reproduce the SAINT results on the EdNet dataset but are unable to report a similar performance as the original paper. This might be due to implementation details, which we were not able to completely reconstruct. We hope to pave the road for further reproducibility, as an increasingly important part of AI research. Furthermore, we apply the model to a company dataset much larger than any public dataset (more interactions, more exercises and more skills). Such a dataset is on the one hand more challenging (more skills mixed), and on the other hand, provides much more data (which should help our models). We compare the SAINT model and the seminal IRT model, and find that the SAINT model performance is 4% better in AUC but 1.7% worse in RMSE. Our experiments on window size suggest that transformer models still struggle with modelling beyond recent performance, and do not yet deliver the step-change observed in NLP. / Transformermodeller, som ger stora förbättringar av AI-textmodeller (NLP), används nu i Knowledge Tracing för att spåra elevernas kunskaper över tid. En av de första, SAINT, visade en hel del förbättring jämfört med de dåvarande SOTA-resultaten på den offentliga EdNet-datauppsättningen och orsakade en ökning av forskning baserad på transformerbaserade modeller. I denna artikeln siktar vi först efter att återskapa SAINT-resultaten på EdNet-datauppsättningen, men vi kan inte rapportera liknande prestanda som den ursprungliga uppsatsen. Detta kan bero på implementeringsdetaljer som vi inte kunde rekonstruera helt. Vi hoppas kunna bana väg för ytterligare reproduktioner, som en allt viktigare del av AI-forskningen. Dessutom tillämpar vi modellen på en företagsdatauppsättning som är mycket större än någon offentlig datauppsättning (fler interaktioner, fler övningar och fler färdigheter). En sådan datauppsättning är å ena sidan mer utmanande (mer blandad kompetens), men å andra sidan ger den mycket mer data (vilket borde hjälpa våra modeller). Vi jämför SAINT-modellen och den framträdande IRT-modellen och finner att SAINT-modellens prestanda är 4% bättre i AUC men 1,7% sämre i RMSE. Våra experiment på fönsterstorlek tyder på att transformermodeller fortfarande kämpar med modellering utöver de senaste prestanda och ännu inte levererar den stegförändring som observerats i NLP.
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Laser-mediated osteoblast ablation triggers a pro-osteogenic inflammatory response regulated by reactive oxygen species and glucocorticoid signaling in zebrafishGeurtzen, Karina, López-Delgado, Alejandra Cristina, Duseja, Ankita, Kurzyukova, Anastasia, Knopf, Franziska 26 February 2024 (has links)
In zebrafish, transgenic labeling approaches, robust regenerative responses and excellent in vivo imaging conditions enable precise characterization of immune cell behavior in response to injury. Here, we monitored osteoblast-immune cell interactions in bone, a tissue which is particularly difficult to in vivo image in tetrapod species. Ablation of individual osteoblasts leads to recruitment of neutrophils and macrophages in varying numbers, depending on the extent of the initial insult, and initiates generation of cathepsin K+ osteoclasts from macrophages. Osteoblast ablation triggers the production of pro-inflammatory cytokines and reactive oxygen species, which are needed for successful macrophage recruitment. Excess glucocorticoid signaling as it occurs during the stress response inhibits macrophage recruitment, maximum speed and changes the macrophage phenotype. Although osteoblast loss is compensated for within a day by contribution of committed osteoblasts, macrophages continue to populate the region. Their presence is required for osteoblasts to fill the lesion site. Our model enables visualization of bone repair after microlesions at single-cell resolution and demonstrates a pro-osteogenic function of tissue-resident macrophages in non-mammalian vertebrates.
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Interleaved Prefetching Ray Traversal on CPUsMeyer, Viktor January 2021 (has links)
Ray tracing is used in computer graphics to generate images. The process of rendering images using ray tracing includes testing large counts of rays for intersection against geometry. Testing for ray-geometry intersection is more formally known as the Ray Shooting Problem (RSP) and has broad applications across multiple communities. Hierarchical acceleration structures are frequently employed to index geometry and increase processing speed. Such hierarchical structures make it almost impossible for central processing units to predict memory access and branching patterns. This project focuses on the Bounding Volume Hierarchy (BVH) structure and improving its performance when querying large batches of first hit ray-geometry intersections. The core contribution is an Interleaved Prefetching Ray Traversal (IPRT) algorithm that addresses memory and branching issues. Five standardized test scenarios with varying geometric complexity provide evaluation data. The experimental evaluation suggests that for incoherent rays, IPRT achieves 6:1 - 41:8% faster performance compared to Stackless Traversal. However, for fully coherent rays, performance is 68:8 - 149:1% slower. These results suggest that for select ray tracing workloads that elicit low coherence, the IPRT algorithm is likely to outperform Stackless Traversal. A microarchitectural analysis affirms previous research; memory accesses and branching behavior are critical for performance. Surprisingly, addressing each component in isolation yields no significant performance improvement. It is paramount to address the two simultaneously, as the IPRT algorithm does successfully. / Ray tracing används inom datorgrafik för att generera bilder. Att rendera bilder med ray tracing kräver att datorer simulerar stora mängder ljusstrålar i en virtuell miljö. Problemet att beräkna om en stråle träffar geometri är mer formellt känt som Ray Shooting Problem (RSP) och har breda applikationer inom flera områden. Hierarkiska accelerationsstrukturer används ofta för att indexera geometri och öka beräkningshastighet. Sådana hierarkiska strukturer gör det nästan omöjligt för centrala processorenheter att förutsäga minnesåtkomst och förgreningsmönster. Detta projekt fokuserar på Bounding Volume Hierarchy (BVH) strukturen och dess prestanda. En ny algoritm tas fram för att behandla dessa identifierade problem: Interleaved Prefetching Ray Traversal (IPRT). Fem standardiserade testscener med varierande geometrisk komplexitet används för experimentell utvärdering. Den experimentella utvärderingen antyder i jämförelse med Stackless Traversal så uppnår IPRT-algoritmen 6:1 - 41:8% bättre prestanda för osammanhängande strålar. När det gäller helt sammanhängande strålar är prestandan dock 68:8 - 149:1% långsammare. En mikroarkitektisk analys bekräftar tidigare forskning; minnesåtkomst och förgreningsbeteende är mycket viktigt för prestanda. Isolerad optimering av faktorerna ger dessvärre ingen signifikant prestandaförbättring. Det är därför ytterst viktigt att optimera båda komponenter samtidigt, vilket IPRT-algoritmen lyckas med.
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TRACKING FLUID-BORNE ODORS IN DIVERSE AND DYNAMIC ENVIRONMENTS USING MULTIPLE SENSORY MECHANISMSTaylor, Brian Kyle 27 August 2012 (has links)
No description available.
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Non-equilibrium Models for High Temperature Gas FlowsAndrienko, Daniil 07 August 2014 (has links)
No description available.
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