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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.
301

Geometria da informação quântica: uma abordagem geral acerca do tempo de evolução / Quantum information geometry: a general framework to approach time evolution

Pires, Diego Paiva 20 February 2017 (has links)
As últimas décadas testemunharam intensa atividade de pesquisa teórica e experimental visando compreender o conceito do tempo na mecânica quântica. Este tema desencadeou significante progresso na busca por dispositivos mais rápidos e eficientes no processamento de informação e implementação de tecnologias de comunicação. Motivados pela pergunta quão rápido um sistema quântico evolui sob uma dada dinâmica?, tais avanços levaram a formulação do chamado limite quântico de velocidade ou quantum speed limit, (QSL), i.e., um limite inferior definindo o tempo mínimo de evolução entre estados quânticos distintos. Diversos resultados reportaram QSLs obtidos via tratamentos diferentes e aparentemente desconexos, muitas vezes sob configurações específicas, que deixaram uma lacuna fundamental à resposta da questão geral colocada anteriormente. Neste projeto investigamos como a não-unicidade de uma medida de distinguibilidade de operadores densidade definida no espaço de estados quânticos influencia o QSL e pode ser explorada no intuito de obter limites inferiores mais robustos no tempo de evolução de estados arbitrários. Em particular, baseando-nos no formalismo da geometria da informação, estabelecemos uma família infinita de QSLs válidos para evoluções unitárias e não-unitárias. Este trabalho se propõe unificar e generalizar resultados existentes sobre QSLs na literatura, além de fornecer exemplos de limites mais precisos do que aqueles baseados na informação de Fisher convencional. Em termos físicos, esta investigação é a primeira a destacar o papel das populações e coerências quânticas no cálculo e saturação dos QSLs. Nossos resultados podem encontrar aplicações na otimização de protocolos em computação quântica e metrologia, além de fornecer novos pontos de vista em investigações fundamentais da termodinâmica quântica. / The last decades witnessed intense theoretical and experimental research activity in order to understand the concept of time in quantum mechanics. This subject triggered significant progress in the search for faster and efficient schemes in the implementation of quantum information and communication technologies. Starting from the puzzle How fast can a quantum state evolve under a given dynamics?, such advances have led to the establishment of quantum speed limits (QSLs), i.e., a lower bound setting the minimum time evolution between two distinct quantum states. Past results have included different, apparently unrelated approaches to quantum speed limits, and sometimes tailored to specific settings, which therefore left a fundamental gap in obtaining a satisfactory answer to the general question posed above. In this work we provide a breakthrough for the study and applications of quantum speed limits. We approach the problem from a general information theoretic point of view and we adopt an elegant geometric formalism to construct an infinite family of quantum speed limits valid for closed and open system evolutions. Our description is based on the geometrization of the quantum state space by introducing an information metric which defines a non-unique measure of distinguishability on the state space. We show in particular how our approach incorporates and unifies the previous specialized results, interpreting them under a new comprehensive framework, and allowing us to reach significantly beyond. From the physical point of view, our investigation is the first to highlight the role of populations versus quantum coherences in the determination and saturation of the speed limits. Our results can find applications in the optimization of quantum protocols in quantum computation and metrology, and might provide new insights in fundamental investigations of quantum thermodynamics.
302

Full-field vibrometry by high-speed digital holography for middle-ear mechanics

Dobrev, Ivo Tsvetanov 21 July 2014 (has links)
"Hearing loss affects approximately 1 in 10 people in the world and this percentage is increasing every year. Some of the most common causes of hearing loss are disorders of the middle-ear. Early detection and diagnosis of hearing loss as well as research to understand the hearing processes depend on medical and research tools for quantification of hearing capabilities and the function of the middle-ear in the complex acousto-mechanical transformation of environmental sounds into vibrations of the middle-ear, particular of the human tympanic membrane (TM or eardrum). Current ear exams assess the state of a patient’s hearing capabilities mainly based on qualitative evaluation of the healthiness of the TM. Existing quantitative clinical methods for description of the motion of the TM are limited to either average acoustic estimates (admittance or reflectance) or single-point displacement measurements. Such methods could leave examiners and researchers blind to the complex spatio-temporal response of the nanometer scale displacements of the entire TM. Current state-of-the-art medical research tools provide full-field nanometer displacement measurements of the surface of the human TM excited by steady state (tonal) stimuli. However, to fully understand the mechanics of hearing, and the complex acousto-mechanical characteristics of TM in particular, new tools are needed for full-field high-speed characterization of the nanometer scale displacements of the human TM subjected to impulse (wideband) acoustic excitation. This Dissertation reports the development of a new high-speed holographic system (HHS) for full-field nanometer transient (i.e., > 10 kHz) displacement measurement of the human middle-ear and the tympanic membrane, in particular. The HHS allows spatial (i.e., >500k data points) and temporal (i.e., > 40 kHz) resolutions that enable the study of the acoustical and mechanical characteristics of the middle-ear at a level of detail that have never been reached before. The realization of the HHS includes the development and implementation of novel phase sampling and acquisition approaches that allow the use of state-of-the-art high-resolution (i.e., >5 MP) and high-speed (> 80,000 fps) cameras through modular and expandable control architectures. The development of novel acquisition approaches allows the use of conventional speed (i.e., <20 fps) cameras to realize high-temporal resolutions (i.e., <15 us) at equivalent sampling rates of > 50,000 fps with minimum hardware cost and modifications. The design and implementation of novel spatio-temporal phase sampling methods utilize the high temporal resolution (i.e., < 5 us exposure) and frame rate (i.e., >80,000 fps) of high-speed cameras without imposing constraints on their spatial resolution (i.e., >20 um pixel size). Additionally, the research and in-vivo applications capabilities of the HHS are extended through the development and implementation of a holographic otoscope head (OH) and a mechatronic otoscope positioner (MOP). The large (i.e., > 1 GB with > 8x10^9 parameters) spatio-temporal data sets of the HHS measurements are automatically processed by custom parallel data mining and interpretation (PDMI) methods, which allow automatic quantification of medically relevant motion parameters (MRMPs), such as modal frequencies, time constants, and acoustic delays. Such capabilities could allow inferring local material properties across the surface of the TM. The HHS is a new medical tool that enables otologists to improve the quality of diagnosis and treatments as well as provides researchers with spatio-temporal information of the hearing process at a level of detail never reached before. "
303

Análise da velocidade incremental em morros : comparação entre procedimentos normativos e estudo experimental em túnel de vento / Analysis of speed-up in hills : comparison between standards procedures and experimental study in wind tunnel

Scotton, Josiane Anderle January 2016 (has links)
A formação do perfil de velocidades do vento é influenciada pela rugosidade e topografia do terreno; em um terreno plano, por exemplo, as velocidades são diminuídas conforme a sua proximidade com a superfície terrestre, determinando a constituição da camada limite atmosférica (C.L.A.). O escoamento do vento em terrenos complexos, ou seja, terrenos que possuem morros e taludes, sejam isolados ou múltiplos, possui o perfil de velocidades modificado, fazendo com que para cotas mais próximas da superfície se observe um aumento das velocidades. A este incremento de velocidades dá-se o nome de speed-up. Esta pesquisa tem como foco a investigação da estrutura do escoamento do vento, analisando minuciosamente o perfil de velocidades em um escoamento turbulento, para topografias isoladas e complexas. Para tanto, foram utilizados dois métodos para obtenção do perfil de velocidades: ensaios experimentais em túnel de vento e aplicação de normas e modelos analítcos de carregamento do vento. O plano experimental engloba nove topografias dentre as quais estão: quatro morros bidimensionais (2D) isolados, quatro morros tridimensionais (3D) isolados e um morro 3D de uma topografia complexa. Os modelos foram ensaiados para duas categorias de terreno, conforme a Norma Brasileira NBR 6123 (ABNT, 1988): I – superfícies lisas de grandes dimensões e III-IV – terreno coberto por obstáculos, no túnel de vento Prof° Joaquim Blessmann. Após a execução do plano experimental aplicou-se modelos analíticos com as mesmas parametrizações do modelo experimental e por fim foram comparados entre si. Os modelos analíticos estudados foram: Jackson e Hunt (1975, Lemelin, Surry e Davenport (1988) e as normas estudadas são: NBR 6123 (ABNT, 1988), Eurocode 1 (CEN-TC, 2010), AIJ (AIJ, 2004), NBCC (NRCC, 2010), AS/NZS (AS/NZS, 2011), ASCE (ASCE, 2010). O estudo comparativo entre os modelos analíticos e normas revela a inexistência de uma homogeneidade entre os modelos, visto que a formulação de cálculo é distinta, quando temos uma topografia em análise. Além disso, os modelos analíticos, quando comparados com os ensaios experimentais, tendem a ser mais conservadores tanto para modelos 2D ou 3D, para pontos à barlavento, no cume e à sotavento do morro. A NBR 6123 apresentou os maiores incrementos de velocidades em comparação com os demais modelos e com os dados experimentais. / The formation of the wind speed profile is influenced by the roughness and topography of the ground; on a flat ground, for example, the speeds are reduced according to their proximity to the earth’s surface, determining the constitution of the atmospheric boundary layer (C.L.A.). The wind flow in complex terrain, in other words, whether single or multiples, has the modified wind speed profile, causing closest to the surface dimensions is observed increased speeds. To this increase speeds gives the name of speed-up. This research focuses on the investigation of the wind flow structure, thoroughly analyzing the speeds profile in turbulent flow, for isolated and complex topographies. For this purpose, two methods for obtaining the speed profile were used: experimental tests in a wind tunnel and application standards or wind loading codes. The experimental plan includes nine topographies among which are: four 2D hills (2D) isolates, four 3D hills (3D) isolates and a complex topography hill. The models were tested for two roughness according to the Brazilian standard NBR 6123 (ABNT, 1988): I – smooth surfaces large dimensions and III-IV – ground covered by obstacles, in the wind tunnel Prof° Joaquim Blessmann. After the execution of the experimental tests were applied analytical models with the same parametrization of the experimental model and finally were compared. The analytical models studied were: Jackson e Hunt (1975, Lemelin, Surry e Davenport (1988), NBR 6123 (ABNT, 1988), Eurocode 1 (CEN-TC, 2010), AIJ (AIJ, 2004), NBCC (NRCC, 2010), AS/NZS (AS/NZS, 2011), ASCE (ASCE, 2010. The compararative study between the analytical models and standards reveals the lack of homogeneity between the models, since the calculation formulation is different when we have a topography analysis. Furthermore, analytical models, compared with the experimental tests tend to be more conservative for both 2D and 3D models, points to the windward, top of the hill and leeward. The NBR 6123 showed the largest increases in speed compared to the other models and experimental data.
304

Development of a programmable load

Minnaar, Ulrich John 14 November 2006 (has links)
Student Number : 0400486V - MSc (Eng) dissertation - School of Electrical and Information Engineering - Faculty of Engineering and the Built Environment / The Voltage Dip Test Facility at the University of the Witwatersrand utilises a resistive load during testing of variable speed drives. This method produces valuable results regarding the performance of drives under dip conditions. It has been shown that load type does influence the performance of drives and this variation cannot be tested under current conditions as only linear loading is attainable with resistive loads. This thesis proposes a programmable load based on the concept of field-oriented control of an induction motor. The concepts involved with field-oriented control are discussed and shown to be suitable for this application. An implementation strategy utilising custom-designed software and an off-the-shelf VSD is developed and executed. The performance of the programmable load is analysed under both steady-state and dynamic conditions.
305

Investigation of the Validity of the ASTM Standard for Computation of International Friction Index

Kavuri, Kranthi 06 November 2008 (has links)
Runway friction testing is performed in order to enhance the safety of aircraft operation on runways. Preventative maintenance friction surveys are performed to determine if there is any deterioration of the frictional resistance on the surface over a period of time and to determine if there is a need for corrective maintenance. In addition operational performance friction surveys are performed to determine frictional properties of a pavement surface in order to provide corrective action information in maintaining safe take-off or landing performance limits. A major issue encountered in both types of friction evaluation on runways is the standardization of the friction measurements from different Continuous Friction Measuring Equipment (CFME). The International Friction Index (IFI) has been formulated to address the above issue and determine the friction condition of a given runway is a standardized format. The ASTM recommended standard procedure to compute the IFI of a runway surface employs two distinct parameters to express the IFI; F60 is the friction value adjusted to a slip speed of 60 km/h and correlated to the standard Dynamic Friction Tester (DFT) measurement. And Sp is the speed constant which is governed by the mean profile depth of that surface. The primary objective of this thesis is to investigate the reliability of the current ASTM procedure to standardize runway friction measurements in terms of IFI. Based on the ASTM standard procedure, two equipment specific calibration constants (A and B) are assigned for each CFME during calibration. Then, in subsequent testing those calibrations constants can be used to adjust the equipment measurements to reliable IFI values. Just as much as A and B are presumed to be characteristic of any given CFME, they are also expected to be independent of the operational speed. The main objective of the annual NASA Runway Friction Workshop held in Wallops Island, Virginia, is to calibrate commonly used CFMEs such that all calibrated equipment would provide a standard reading (i.e. IFI) on a particular surface. During validation of the existing ASTM procedure using the NASA Runway Friction Workshop data it was observed that the single value-based IFI predictions of the calibrated CFMEs were inaccurate resulting in low correlations with DFT measured values. Therefore, a landing pilot should not be left to make a safe decision with such an uncertain single standard friction value because the actual standard friction value could very well be much less than this value. Hence a modified procedure was formulated to treat the calibration constants A and B as normally distributed random variables even for the same CFME. The new procedure can be used to predict the IFI (F60) of a given runway surface within a desired confidence interval. Since the modified procedure predicts a range of IFI for a given runway surface within two bounds, a landing pilot's decision would be made easier based on his/her experience on critical IFI values. However, even the validation of the modified procedure presented some difficulties since the DFT measurements on a few validated surfaces plotted completely outside the range of F60 predicted by the modified method. Furthermore, although the ASTM standard stipulates the IFI (F60) predictions to be independent of the testing speed, data from the NASA Runway Friction Workshop indicates a significant difference in the predictions from the two testing speeds of 65 km/hr and 95 km/hr, with the results from the 65 km/hr tests yielding better correlations with the corresponding DFT measurements. The above anomaly could be attributed to the significantly different FR60 values obtained when the 65 km/hr data (FR65) and 95 km/hr data (FR95) are adjusted to a slip speed of 60 km/hr. Extended analytical investigations revealed that the expected testing speed independency of the FR60 for a particular CFME cannot be supported by the ASTM defined general linear relationship between Sp and the mean profile depth which probably has been formulated to satisfy a multitude of CFMEs operating on a number of selected test surfaces. This very reason can also be attributed to the above mentioned outliers observed during the validation of the modified procedure.
306

Efekti eksperimentalnog tretmana na razvoj brzinske izdržljivosti kod devojčica / The Effects of Experimental Treatment on Development of Girls' Speed Endurance

Šolaja Milan 21 September 2016 (has links)
<p>U na&scaron;oj zemlji je malo objavljenih istraživanja iz oblasti kako brzinske izdržljivosti kod devojčica, tako i eksperimentalnih tretmana koji bi doveli do povećanja ove motoričke sposobnosti. U samoj atletici ova tema nije dovoljno istraživana s&rsquo; obzirom da je veoma puno prisutna u praksi. Osnovni cilj studije bio je da se utvrdi efekat eksperimentalnog tretmana na brzinsku izdržljivost devojčica.<br />Uzorak ispitanika ovog istraživanja činilo je 100 devojčica, uzrasta između 13 i 15 godina iz&nbsp; Novog Sada, koje su uključene u trenažni proces u sportskim klubovima. Uzorak ispitanika je bio podeljen na eksperimentalnu grupu, koju je činilo 50 devojčica i koja je realizovala eksperimentalni plan i program i kontrolnu grupu, sa takođe, 50 devojčica, koja je realizovala treninge po programu Evropske atletske federacije &ldquo;Kid&rsquo;s athletics&rdquo;, u trajanju od 15 nedelja. Testirane su razlike u antropolo&scaron;kim karakteristikama i u motoričkim sposobnostima, koje su se ogledale u efikasnosti primenjenog eksperimentalnog tretmana grupa.<br />U istraživanju je primenjeno 18 varijabli: 6 antropometrijskih, 10 motoričkih i 2 varijable za procenu specifičnih motoričkih sposobnosti. Razlike u antropolo&scaron;kim karakteristikama, motoričkim sposobnostima i brzinskoj izdržljivosti između eksperimentalne i kontrolne grupe analizirane su multivarijatnom analizom varijanse, univarijatnom analizom varijanse i diskriminativnom analizom, dok su sami efekti eksperimentalnog tretmana utvrđeni na osnovu multivarijatne analize kovarijanse.<br />Program rada eksperimentalne i kontrolne grupe realizovan je u okviru redovnih treninga u sportskim klubovima. Trenažni plan i program je sprovođen tri puna nedeljno, za obe testirane grupe. Eksperimentalna grupa je realizovala trenažne jedinice po modelovanom eksperimentalnom tretmanu, koji je sačinjen u skladu sa osnovnim principima trenažnog procesa i periodizacijom istog, i na osnovu bogatog vi&scaron;egodi&scaron;njeg iskustva autora i adekvatne literature najboljih svetskih autora aktuelne oblasti. Kontrolna grupa je realizovala trenažne jedinice po programu Evropske atletske federacije &ldquo;Kid&rsquo;s athletics&rdquo;.<br />Dobijeni rezutati u pogledu antropometrijskih karakteristika ukazuju da je primenjeni eksperimentalni tretman uticao na postojanje statistički značajnih razlika u sistemu pojedinih primenjenih antropometrijskih varijabli. U prostoru motoričkih sposobnosti takođe su utvrđene statistički značajne razlike između grupa nakon primenjenih različitih tretmana.<br />Kada su u pitanju specifične motoričke sposobnosti, odnosno varijable za procenu brzinske izdržljivosti devojčica, analiza kovarijanse je takođe ukazala na statističku značajnost razlika u sistemu primenjenih varijabli. Eksperimentalna grupa je statistički značajno napredovala u obe varijable kojima je testirana brzinska izdržljivost devojčica.<br />Osnovni cilj studije bio je da se utvrdi efekat eksperimentalnog tretmana na brzinsku izdržljivost devojčica, a rezultati univarijantne analize kovarijanse i multivarijatne analize kovarijanse su potvrdili statistički značajnu razliku u korist eksperimentalne grupe.<br />Na osnovu dobijenih rezultata može se zaključiti da je predloženi eksperimentalni tretman u eksperimentalnoj grupi doprineo značajnim razlikama u brzinskoj izdržljivosti. Rezultati koji su dobijeni u finalnom merenju i upoređivanjem motoričkih sposobnosti između eksperimentalne i kontrolne grupe, potvrdili su dosada&scaron;nja naučna i teorijska znanja, da prostor specifične izdržljivosti u brzini egzistira kao posebna sposobnost na koju se adekvatnim tretmanom može pozitivno uticati i doći do napretka koji je statistički značajan. Značaj ove studije je u direktnoj i neposrednoj primeni, ovog tretmana, gde se bolji rezultati postižu usmeravanjem tretmana na ciljane distance koje su po strukturi i vremenskom trajanju slične onim koje su testirane kao kriterijske varijable.</p> / <p>There is little published research in our country in girls&rsquo; speed endurance and experimental treatments which would&nbsp; increase this motor ability. This issue is not sufficiently investigated in the athletics, despite the fact that it is very much present in practice. The main objective of the study was to determine the effect of experimental treatment on girls&rsquo; speed endurance.<br />The sample of this study consisted of 100 girls, aged between 13 and 15 years old, from Novi Sad, who are involved in the training process in sports clubs. The sample was divided into an experimental group, which consisted of 50 girls and implemented experimental plan and program and the control group with 50 girls as well, which&nbsp; conducted trainings according to the program of the European Association of Athletics Federations&#39; &ldquo;Kid&#39;s athletics&rdquo;, in a&nbsp; 15 weeks period. The differences in the anthropological characteristics and motor skills were tested, which were reflected in the efficiency of the applied experimental treatment of the groups.<br />18 variables were&nbsp; applied in the study: 6 anthropometric, 10 motor variables and 2 motor variables for assessment of specific motor abilities. Differences in anthropological characteristics, motor skills and speed endurance between the experimental and control groups were analyzed by multivariate analysis of variance, univariate analysis of variance and discriminant analysis, while the actual effects of the experimental treatment were determined on the basis of multivariate analysis of covariance.<br />The working program of the experimental and control groups was carried out in the framework of regular training in sports clubs. The training plan and program was executed three times per week, for both tested groups. The experimental group has implemented the training units by modeled experimental treatment, which is made in accordance with the basic principles of the training process and its periodization, and based on author&#39;s extensive experience and adequate literature of the world&#39;s best authors of the current field. The control group&nbsp; implemented the training units of the program of the European Athletics Federation &quot;Kid&#39;s athletics.&quot;<br />The obtained results of anthropometric characteristics indicate that the applied experimental treatment influenced the existence of statistically significant differences in the system of individual anthropometric variables which were applied. Statistically significant differences were determined between groups in the area of motor abilities, after applaying different treatments.<br />As to the specific motor skills, variables for evaluation of girls&#39; speed endurance, covariance analysis also indicated statistically significant differences in the system of applied variables. The experimental group significantly progressed in both variables by which&nbsp; girls&#39; speed endurance had been tested.<br />The main objective of the study was to determine the effect of experimental treatment on girls&#39; speed endurance, and the results of the univariate analysis of covariance and multivariate analysis of covariance confirmed a statistically significant difference in favor of the experimental group.<br />Based on these results, it can be concluded that the proposed experimental treatment in an experimental group contributed to the significant differences in the speed endurance. The final measuring results obtained by comparison of&nbsp; motor abilities between the experimental and control group, confirmed the recent scientific and theoretical knowledge that specific endurance space in speed exists as a special skill on which the appropriate treatment can positively influence and the statistically significant progress can be reached. The significance of this study is in a direct and immediate application of this treatment, where better results are achieved by focusing the treatment on the target distances which are similar by the structure and duration to those that have been tested as a criterion variable.</p>
307

Optimal sensor placement for measuring operating speeds through curves on rural two-lane highways

Mecham, Megan E. 29 May 2012 (has links)
Operating speed is one of the best performance measures that can tell transportation agencies how well or how poorly the transportation system is functioning. Fluctuating operating speeds often mean there is a design flaw or something about the physical road design that violates drivers' expectations. A primary example of this is a horizontal curve on a highway that had a reduced recommended advisory speed. Traditionally, researchers and transportation agencies measure operating speeds along the approach tangent to a horizontal curve and at the midpoint of the curve. This thesis looks at the significance of alternate measuring locations within the curve. It also analyzes the difference between the 85th percentile maximum speed reduction and the more traditional measure of the reduction in 85th percentile speeds, which is used as an indicator of safety. / Graduation date: 2012
308

Development of Improved Traveler Survey Methods for High-Speed Intercity Passenger Rail Planning

Sperry, Benjamin 2012 May 1900 (has links)
High-speed passenger rail is seen by many in the U.S. transportation policy and planning communities as an ideal solution for fast, safe, and resource-efficient mobility in high-demand intercity corridors. To expand the body of knowledge for high-speed intercity passenger rail in the U.S., the overall goal of this dissertation was to better understand the demand for high-speed intercity passenger rail services in small- or medium-sized intermediate communities and improve planners' ability to estimate such demand through traveler surveys; specifically, the use of different experimental designs for stated preference questions and the use of images to describe hypothetical travel alternatives in traveler surveys. In pursuit of this goal, an Internet-based survey was distributed to residents of Waco and Temple, two communities located along the federally-designated South Central High-Speed Rail Corridor in Central Texas. A total of 1,160 surveys were obtained from residents of the two communities. Mixed logit travel mode choice models developed from the survey data revealed valuable findings that can inform demand estimates and the design of traveler surveys for high-speed intercity passenger rail planning activities. Based on the analysis presented in this dissertation, ridership estimates for new high-speed intercity passenger rail lines that are planned to serve intermediate communities should not assume that residents of these communities have similar characteristics and values. The d-efficient stated preference experimental design was found to provide a mode choice model with a better fit and greater significance on key policy variables than the adaptive design and therefore is recommended for use in future surveys. Finally, it is recommended that surveys should consider the use of images of proposed train services to aid respondent decision-making for stated preference questions, but only if the images used in the survey depict equipment that could be realistically deployed in the corridor.
309

Review of the effectiveness of vehicle activated signs

Jomaa, Diala, Yella, Siril, Dougherty, Mark January 2013 (has links)
This paper reviews the effectiveness of vehicle activated signs. Vehicle activated signs are being reportedly used in recent years to display dynamic information to road users on an individual basis in order to give a warning or inform about a specific event. Vehicle activated signs are triggered individually by vehicles when a certain criteria is met. An example of such criteria is to trigger a speed limit sign when the driver exceeds a pre-set threshold speed. The preset threshold is usually set to a constant value which is often equal, or relative, to the speed limit on a particular road segment. This review examines in detail the basis for the configuration of the existing sign types in previous studies and explores the relation between the configuration of the sign and their impact on driver behavior and sign efficiency. Most of previous studies showed that these signs have significant impact on driver behavior, traffic safety and traffic efficiency. In most cases the signs deployed have yielded reductions in mean speeds, in speed variation and in longer headways. However most experiments reported within the area were performed with the signs set to a certain static configuration within applicable conditions. Since some of the aforementioned factors are dynamic in nature, it is felt that the configurations of these signs were thus not carefully considered by previous researchers and there is no clear statement in the previous studies describing the relationship between the trigger value and its consequences under different conditions. Bearing in mind that different designs of vehicle activated signs can give a different impact under certain conditions of road, traffic and weather conditions the current work suggests that variable speed thresholds should be considered instead.
310

Timing Variables in Reading and Language: The Relation of Naming Speed and Motor Speed to Auditory Temporal Processing

Zettler, Cynthia M. 28 November 2007 (has links)
Naming speed, motor skill, and auditory temporal processing (ATP) are constructs that are important to reading and language. These variables require processing timing information inherent in the stimulus or processing stimuli rapidly. ATP deficits are found in individuals with reading impairments, but studies are conflicting regarding the relationship between reading and ATP. This study examined relationships between naming speed, motor speed, and ATP, and centered on possible factors why inconsistencies have occurred across studies examining the association between reading and ATP. If the timing element of naming speed (rapid automatized naming-RAN) and of motor speed is common to ATP, then RAN and motor speed should predict thresholds for three auditory tasks (CMR, backward masking, and the precedence effect with TOJ) known to require temporal processing. Tasks were administered to adult participants in order to examine the effects with skilled readers. Many of the variables were skewed and there were multiple outliers that altered the analyses. Ultimately, 75 participants were included in the final data set. Results indicated that RAN did not predict thresholds for any of the masking tasks given. However, motor speed predicted thresholds for one CMR and two backward masking tasks, suggesting that motor speed should be controlled for in research assessing the contribution of ATP to reading or language. Neither naming speed nor motor speed predicted localization performance. Non-verbal intelligence predicted performance on several of the masking tasks, consistent with previous research. Performance on all three auditory tasks was similar to that reported in the literature assessing smaller samples of participants. Although the suggestion of a general timing component is not supported, the relationships found between motor speed and several auditory temporal measures indicate that the underlying timing elements are not independent.

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