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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.
381

Laboratory and field trials of the ability of vegetated porous paving to remediate pollutants

Mayer, M. January 2013 (has links)
Flooding is impossible to prevent completely, consequences of excess water can however, be reduced and often avoided via flood risk management. With the increase in impermeable surfaces, approaches that have the intention of imitating natural drainage to manage storm-water are known as Sustainable (Urban) Drainage Systems (SUDS). Pollutants from vehicles have been identified as a concern in the urban environment, with origins including exhaust emissions, engine oil leakage and erosion of vehicle components. Investigation of vegetated parking surfaces (VPS) to limit the impact of pollutants are scarce, therefore this study aims to determine pollution tolerance of grass species for use in VPSs, prior to investigating the effects that vehicles have on a vegetated surfaces and alternative methods in which to analyse them. A pot trial investigated effects of increasing oil concentrations on the growth of four grass species. F. rubra L. was found to tolerate contamination to a higher degree than the other species and L. perenne L. produced more cumulative biomass throughout the investigation. A parallel study determined that Ca, Cu, K, Mg, Mo, P and Zn accumulated in grass shoots, indicating that F. rubra L. and L. perenne L. may be suitable for further analysis. field trial focused on a regularly-used L. perenne L.-covered VPS at a local school, analysing the influence of vehicles on vegetated parking bays. Compaction and mean element concentrations increased across the VPS, with distance from the roadside. Use of mineral magnetism as a proxy for geochemical detection did not prove successful as no significant correlation was identified between magnetic susceptibility (χ) and element concentration. Use of GIS provided this study with an alternative method for data presentation. Usually covering large scale analyses, an interactive geovisual map of geochemical dispersal and compaction across the VPS provided a novel method of visualising results from an investigation of this scale.
382

User-centered Service Design for Sustainable Mobility Innovations : Mapping Users’ Needs and Service Requirements for Electric Car Sharing Service Design

Sopjani, Liridona January 2015 (has links)
Electric car sharing is gradually expanding as an innovative and more sustainable mobility alternative to private cars. Though, the use of such mobility service has not yet reached the desired levels worldwide despite attracting large number of customers. For car sharing operators, thus, it is imperative to understand the users and their needs beyond the existing demographics and quantitative data in order to design more desirable and useful services that expand customer acceptance and usage rate of such alternative. This thesis is an exploratory study about users’ needs, behaviors, and experiences toward electric car sharing and the service requirements resulting from these dimensions. Using user- centered service design approach, the study focuses in obtaining qualitative insights about users through workshops with focus groups in regards to LEV-pool, a research project that intends to field test a new approach to car sharing by offering small size electric vehicles for local mobility at a large workplace. Based on three user-centered service design methods: customer journey map, personas, and stakeholder map, a visual mapping of users, their needs, behaviors, and experiences, and service requirements is developed. The findings point at different user types with distinct purposes of using car sharing, whose needs for mobility (at work) are affected by external factors such as work activities and job occupation. Their mobility behavior differs in terms of how they interact with car sharing service and is partly influenced by the service offering. In general, users show various experiences toward car sharing systems, and many relate it to technical aspects of the service. In terms of service requirements, the results highlight available vehicles at the needed time, simple and easy booking system with many features responsive to users’ needs, maintenance and cleanliness of vehicles, effective communication of service offering, and simple pricing schemes. The underlying user dimensions explored show as relevant in shaping the users’ evaluation of a service and their decision to use a certain mobility alternative. / Electric car sharing offers a more sustainable mobility alternative to private cars. Though, the use of this service has not yet reached the desired levels worldwide despite attracting large number of customers. For car sharing operators, thus, it is imperative to understand the users and their needs in order to design more desirable and useful electric car sharing services. This thesis is an exploratory study of the users and the service of electric car sharing systems. Using user-centered service design approach, the study focuses in obtaining qualitative insights about users in regards to LEV-pool –a research project that intends to field test a new approach to car sharing by offering small size electric vehicles for local mobility at a large workplace. The study applies three user centered service design methods to capture and present a holistic understanding of users, their needs, behaviors, and experiences toward electric car sharing and the service requirements resulting from these dimensions. The findings suggest that users are distinct and have different needs for mobility (at work), which are shaped by the external factors such as work activities and job occupation. Their mobility behavior differs in terms of how they interact with car sharing service and is partly influenced by the service offering. In general, users have various experiences toward car sharing systems, and many relate it to technical aspects of the service. By exploring the users, the results point directly to different requirements that the service shall meet for it to enhance usage such as available vehicles at the needed time, simple and easy booking system with many features responsive to users’ needs, maintenance and cleanliness of vehicles, effective communication of service offering, and simple pricing schemes.
383

Modélisation de l'interaction de l'ion uranyle à l'interface eau/gibbsite par la dynamique moléculaire quantique et classique

Lectez, Sébastien 03 July 2012 (has links) (PDF)
Ce travail qui a été effectué au sein du groupe radiochimie de l'IPN Orsay, participe à l'enrichissement des connaissances destinées à la compréhension du comportement des radionucléides à travers l'environnement. Le comportement et l'évolution des radionucléides sont des phénomènes souvent complexes à caractériser expérimentalement qui dépendent des interactions aux interfaces eau / surface minérale, lesquelles peuvent être modélisées grâce à des méthodes théoriques. Lors de cette étude, nous avons choisi d'utiliser des méthodes de dynamique moléculaire (DM), lesquelles permettent de considérer explicitement les effets du solvant, de la température et d'étudier la dynamique de l'ion uranyle. Dans un premier temps, des méthodes de dynamique moléculaire Car-Parrinello basées sur la théorie de la fonctionnelle de la densité (DFT) ont permis de caractériser finement les structures d'équilibres de l'ion uranyle en solution et à l'interface eau/ face (001) de gibbsite. Dans le cas d'un pH faible, les complexes d'adsorption présents à l'interface eau/ face (001) de gibbsite ont été identifiés et comparées aux données expérimentales disponibles. Leurs énergies relatives et les énergies d'activations impliquées dans le processus de sorption ont également été déterminées. Dans un deuxième temps, des méthodes de dynamique moléculaire classique ont été employées afin de modéliser des systèmes de plus grande taille, donc plus réalistes, sur des échelles de temps plus longues. La comparaison des résultats DM Car-Parrinello / DM classique a montré qu'une dynamique classique utilisée avec les potentiels non polarisables de Guilbaud, CLAYFF et SPC/E, permet de modéliser le comportement de l'ion uranyle à l'interface eau/ face (001) de gibbsite. Les longs temps de simulation permettent de mettre en avant le caractère diffusif de l'ion uranyle à l'interface eau/ face (001) de la gibbsite. Enfin, L'effet d'une élévation de la température a été étudié. La rétention de l'ion uranyle diminue avec la température.
384

Estimation paramétrique d'une diffusion ergodique observée à temps discret

Souchet, Sandie 13 January 1999 (has links) (PDF)
Cette thèse comporte cinq chapitres.<br /><br />Chapitre 1 : Schémas de discrétisation anticipatifs et estimation du paramètre de dérive d'une diffusion. <br />Pour estimer le paramètre de dérive d'une diffusion unidimensionnelle ergodique observée à pas d>0 et fixé, on construit des contrastes basés sur des schémas d'approximation anticipatifs (schéma du trapèze et de Simpson) couplés à la méthode d'estimation des moments généralisés. Les estimateurs obtenus présentent des biais d'estimation en d**2 pour le schéma du trapèze et en d**4 pour le schéma de Simpson. L'efficacité asymptotique est par ailleurs préservée à un facteur (1+O(d)) près.<br /><br />Chapitre 2 : Schéma d'approximation adapté à l'ordre p et estimation de la dérive d'une diffusion.<br />Pour estimer le paramètre de dérive d'une diffusion ergodique observée à pas d, nous approximons la vraisemblance exacte de l'échantillon par celle d'un processus gaussien dont l'espérance conditionnelle est approchée à l'ordre d**p. L'estimateur obtenu est asymptotiquement biaisé. Ce biais est explicite et est de l'ordre de d**p. L'efficacité asymptotique est par ailleurs préservée à un facteur près. <br /><br />Chapitre 3 : Estimation du paramètre de dérive d'une diffusion sous des conditions d'irrégularité de la dérive.<br />Le problème étudié est l'analogue de celui étudié par Chan pour les AR à seuil (Threshold, Ann. Stat. 1993). Ici, le temps n'est plus discret mais continu. La dérive de la diffusion est continue, mais à dérivées discontinues en un seuil r. Le problème étudié est celui de l'estimation de ce seuil r. Si le pas d'observation d_n tend vers 0 et si T=n*d_n tend vers l'infini, l'estimateur des Moindres carrés (associé au schéma d'Euler ) de r est consistant. Si de plus n*(d_n)**3 tend vers 0, il y a normalité asymptotique à une vitesse standard. <br /><br />Chapitre 4 : Estimation d'un CAR(p) incomplètement observé à partir des équations de Yule-Walker.<br />Un travail de Hyndman (JTSA, 93) présente les équations de Yule-Walker pour un CAR(p), X, (qui est aussi une diffusion p-dimensionnelle, Y=(X, X(1),...,X(p-1))) et l'estimation des paramètres déduite sur la base de ces équations et de l'observation complète de Y (temps continu et observation des p-composantes de Y). Adoptant une méthodologie identique, nous étudions ce problème d'estimation lorsque l'on ne dispose que de l'observation de X, la première composante de Y, et ceci à des instants discrets (au pas d). Nous proposons <br />un estimateur convergent des paramètres à un biais près de l'ordre de d.<br /><br />Chapitre 5 : Precision of systematic sampling and transitive methods.<br />Nous proposons une méthode d'estimation dérivée des méthodes transitives utilisées notamment dans le domaine de la stéréologie. Cette méthode permet d'estimer l'écart quadratique moyen d'estimateurs empiriques construits à partir d'un échantillonnage systématique.
385

Automobilių gendamumo garantiniu laikotarpiu tyrimas / Investigation of Automobiles Faults During Warranty Period

Tilvikas, Kęstutis 18 June 2010 (has links)
Lengvųjų automobilių negendamumo užtikrinimas garantiniu laikotarpiu viena iš priemonių didinančių konkurencingumą. Nepaisant sukuriamų naujų gamybos technologijų, garantiniu laikotarpiu atsiranda lengvųjų automobilių gedimų. Siekiant įgyvendinti visavertį vartotojų aptarnavimą būtina užtikrinti, kad garantiniu laikotarpiu gedimai būtų šalinami kaip įmanoma greičiau. Tam pasiekti būtina, kad pardavėjai savo sandėliuose turėtų optimalų kiekį atsarginių detalių bei žinodami gedimų tikimybės priklausomybę nuo ridos galėtų atlikti prevencinius darbus gedimams išvengti. Tikimąsi, kad nustačius lengvųjų automobilių gendamumą garantiniu laikotarpiu būtų lengviau optimizuoti garantinio aptarnavimo procesą. Eksperimentinių tyrimų tikslas yra nustatyti lengvųjų automobilių gendamumą garantiniu laikotarpiu. UAB „Sostena“ atliktų tyrimų duomenimis „Renault“ markės lengvųjų automobilių gedimų įvyksta per visą garantinį laikotarpį. Nepatikimiausia garantiniu laikotarpiu yra automobilių važiuoklė. Didžiausia tikimybė, kad automobilio važiuoklės sistemoje bus pastebėta gedimų, yra automobiliui nuvažiavus 40–50 tūkst. kilometrų. Automobilį eksploatuojant iki 10 tūkst. kilometrų tikimybė, kad atsiras gedimų, yra mažiausia. Tyrimais nustatyta, kad beveik penkis kartus rečiau nei važiuoklė yra pažeidžiami automobilių varikliai, elektros bei aušinimo sistemos. / Assurance of reliability in passenger cars during the warranty period is one of the means increasing competitiveness. Although novel manufacturing technologies have been designed recently, there are some possible flaws in passenger cars that can be encountered during the warranty period. Seeking to implement a complete customer attendance it has to be made sure that during the warranty period all the faults should be mended as soon as possible. To attain this objective, first of all, it is necessary that all dealers have an optimum stock of spare parts in their warehouses and secondly, actions designed to prevent faults and failures have to be implemented based on the statistical likelihood for the most common failures to occur. It is hoped that it would be easier to optimize a process of after-sales service if a failure of passenger cars during the warranty period is established. The purpose of the experimental study is to determine a fault/flaw of passenger cars during the warranty period. The findings of research done by Ltd. “Sostena” suggest that failures of “Renault“ passenger cars occur during the whole period of warranty. Chassis was found to be the most unreliable part during the warranty period. The research evidence also indicates that the highest likelihood for the flaws to be noticed in a chassis is after a car has done from 40 to 50 thousand kilometres. The least probability for the flaws to manifest themselves was determined before a passenger car had done 10... [to full text]
386

FSC forest management certification analysis in Lithuaniua and Russia / FSC miškų vadybos sertifikavimo analizė Lietuvoje ir Rusijoje

Makrickas, Evaldas 01 June 2011 (has links)
First time name of certification were mentioned 1990s concerning a problems with bad forest practices, hard improvement of governmental regulations especial in tropics. Later this concern were growing to 1992 Rio de Janeiro conference. And so, need of strict forest system in 1993 established Forest Stewardship Council (FSC). Main activities started later 1996 in Canada with small group of people which started developing countries regional standards (Claros, 2009). Now FSC program is one of the biggest forest certification and accreditation providing company providing wood and their products and certification service. This program supports LEED Lumber, IKEA, biggest companies buying wood in the world, non governamental organisations World wild Fund (WWF), Green peace (www.fsc.org). The curiosity of how FSC forest certification impact forest management in Lithuania and Russia and lack of FSC standard studies with national law encouraged to create such study. We want to analyze FSC certification annual public reports raised CAR’s (Corrective action request) from Forest Management Units (FMU) - enterprises, leaseholders in Lithuania and Russia. The first aim was to find, what main CAR’s in Lithuania, Russia and distribute CAR’s to environmental, economical, social type aspects. In later stages analyze Lithuanian and Russian FSC standards Smart Wood, SGS Qualifor and Russian national. In the last step to compare FSC standards with state law for each country. Analysis of... [to full text] / Pagal FSC standartus miškai pradėti sertifikuoti nuo 1993 metų. Patogi sertifikavimo sistema leido minėtam standartui išplisti visame pasaulyje. Bolivijoje, Brazilijoje, Indonezijoje FSC sertifikavimas vis dar plečiamas (Claros, 2009). Sertifikacijos dėka gerinama miškų valdymo kokybė, biologinės įvairovės apsauga, sprendžiamos darbuotojų saugos problemos. Šio standarto visapusišku naudingumu neabejoja daugelis FSC rėmėjų: LEED Lumber, IKEA, bei didžiausios miško produktus superkančios ar nevyriausybinės organizacijos, Pasaulio gamtos fondas (World wild Fund WWF), Green peace (www.fsc.org). Mokslinių darbų, nagrinėjančių miškų sertifikaciją objektyviai, yra nedaug ir miškų sertifikavimo tema nėra plačiai nagrinėjama palyginus su socialiniais, miško gyvosios ir negyvosios gamtos sąveikos tyrimais. Miškų sertifikavimo standartų palyginamųjų darbų taip pat yra negausu. Šio darbo sukūrimo pagrindas – galimybė išanalizuoti skirtumus tarp FSC sertifikuotų kaimyninių šalių (Lietuvos ir Rusijos) miškų tvarkymo vienetų ir naudojimo standartų (MTV – Lietuvoje valstybinių miškų įmonių urėdijų ir Rusijoje miškų ūkių ir miškų nuomotojų). Taip pat norima sužinoti, ar Lietuvoje ir Rusijoje susiduriama su skirtingais sertifikavimo pažeidimais. Šių pažeidimų koregavimo veiksmų reikalavimų (KVR) aspektų pagalba palyginti Lietuvos ir Rusijos FSC miškų valdymo sertifikacijos standartus bei su standartais susijusi šalių miškų teisė. Kita šio darbo dalis, skirta ištirti kokią įtaką ekonominės... [toliau žr. visą tekstą]
387

Car Users' Switching to Public Transport for the Work Commute

Eriksson, Lars January 2011 (has links)
The general aim of the present thesis was to investigate the determinants of car users’ switching to public transport when driving to work. Since the quality of services is particularly low in medium-sized cities, making the car a much more attractive option, the studies focus on car-use in such cities. Four studies were conducted. In the first (Paper I), an Internet survey addressing what people using their cars to commute to work in a medium-size city believe would make them reduce their car-use as well as what improvements to public transport services they believe would make them use those services was conducted. The results showed that, the further to work and/or bus stops - the more the participants desired increased frequencies and shorter travel times, but less often lower fares. In the second study (Paper II), using a web-based experimental simulation, participants were given the task of planning their travel to and from work, including the performing of additional activities in accordance with predetermined agendas. The main results of this were that shorter travel times and good access to bus stops led to greater bus use while constraints imposed by a busy daily agenda led to greater car-use, in particular if car costs were low. In the third study (Paper III) a scale for measuring satisfaction with travel was developed. A new measure of travel-related subjective well-being (SWB), a 9-item self-report Satisfaction with Travel Scale (STS), was developed. The results showed that STS is reliable and differentiates between changes in travel conditions. In the fourth study (Paper IV) which attributes other than time and cost contribute to the preference of car over bus in the choice of travel mode was investigated. Using STS, developed in Paper III the effect of different travel modes on satisfaction with travel was studied. The conclusions of this thesis are that a public transport system must appear attractive, not only to its present users, but also to prospective users who currently use their cars. To appear attractive, it must not be too expensive and must have timetables and routes that allow users to travel in an efficient manner. One measure that can be used to force commuters out of their cars is higher car-use costs; however, car-use costs may need to be substantially higher than the cost of using public transport in order to be effective. As the present research has indicated, the perceived difficulty of using public transport is also an important factor. Raising car-use costs will thus be insufficient unless changes are made to public transport services. A factor complicating this is activity patterns, which are often complex. As has been indicated in the present research, the more complex the activity pattern - the more the car is used as a means of transport.
388

Bilen, ett tekniskt system : 3-åringars uppfattning kring bilen som ett tekniskt system och dess komponenter / The car, a technical system : 3-year-olds view around the car as a technical system and their components

Allard, Marie-Louise January 2014 (has links)
The purpose of the survey is to find out what perception children in preschool have about the car as a technical system, how its components interact, and also their perception on various components of the traffic system. Qualitative interviews were conducted with eleven children in the age of three about their experiences on this.   The result shows that most of the children in the study have experience on the components that are most prominent on a car such as steering wheel, wheels and engine. The results are mixed in terms of knowledge of the components' importance and how they interact with each other. The survey also shows that the children who have the greatest knowledge of the components' importance are those who have been with an adult when changing tires, refueling, minor repairs, etc. According to the results, most of the kids know that there must be roads to drive on and they recognize for example traffic lights and Mr. Gårman plate available at pedestrian crossings. However, there is general uncertainty about the significance of them. / Syftet med undersökningen är att ta reda på vad barn i förskolan har för uppfattning om bilen som ett tekniskt system, hur dess komponenter samverkar, samt vad de har för uppfattning kring olika komponenter i trafiksystemet. För att ta reda på det har kvalitativa intervjuer genomförts med elva barn i treårsåldern om deras erfarenheter kring detta.   Resultatet visar att de flesta barnen i undersökningen har erfarenhet av de komponenter som är mest framträdande på en bil som t.ex. ratt, hjul och motor. Resultatet är blandat vad gäller kunskapen kring komponenternas betydelse och samverkan med varandra. Undersökningen visar också att de barn som har störst kunskap kring komponenternas betydelse också är de som fått vara med någon vuxen vid däckbyte, tankning, enklare reparationer etc. Enligt resultatet har de flesta av barnen kunskap om att det måste finnas vägar att köra på och de känner igen t.ex. trafikljus och Herr Gårmanskylten som finns vid övergångsställen. Däremot finns överlag en osäkerhet kring betydelsen av dem.
389

Estimating Freeway Travel Time Reliability for Traffic Operations and Planning

Yang, Shu, Yang, Shu January 2016 (has links)
Travel time reliability (TTR) has attracted increasing attention in recent years, and is often listed as one of the major roadway performance and service quality measures for both traffic engineers and travelers. Measuring travel time reliability is the first step towards improving travel time reliability, ensuring on-time arrivals, and reducing travel costs. Four components may be primarily considered, including travel time estimation/collection, quantity of travel time selection, probability distribution selection, and TTR measure selection. Travel time is a key transportation performance measure because of its diverse applications and it also serves the foundation of estimating travel time reliability. Various modelling approaches to estimating freeway travel time have been well developed due to widespread installation of intelligent transportation system sensors. However, estimating accurate travel time using existing freeway travel time models is still challenging under congested conditions. Therefore, this study aimed to develop an innovative freeway travel time estimation model based on the General Motors (GM) car-following model. Since the GM model is usually used in a micro-simulation environment, the concepts of virtual leading and virtual following vehicles are proposed to allow the GM model to be used in macro-scale environments using aggregated traffic sensor data. Travel time data collected from three study corridors on I-270 in St. Louis, Missouri was used to verify the estimated travel times produced by the proposed General Motors Travel Time Estimation (GMTTE) model and two existing models, the instantaneous model and the time-slice model. The results showed that the GMTTE model outperformed the two existing models due to lower mean average percentage errors of 1.62% in free-flow conditions and 6.66% in two congested conditions. Overall, the GMTTE model demonstrated its robustness and accuracy for estimating freeway travel times. Most travel time reliability measures are derived directly from continuous probability distributions and applied to the traffic data directly. However, little previous research shows a consensus of probability distribution family selection for travel time reliability. Different probability distribution families could yield different values for the same travel time reliability measure (e.g. standard deviation). It is believe that the specific selection of probability distribution families has few effects on measuring travel time reliability. Therefore, two hypotheses are proposed in hope of accurately measuring travel time reliability. An experiment is designed to prove the two hypotheses. The first hypothesis is proven by conducting the Kolmogorov–Smirnov test and checking log-likelihoods, and Akaike information criterion with a correction for finite sample sizes (AICc) and Bayesian information criterion (BIC) convergences; and the second hypothesis is proven by examining both moment-based and percentile-based travel time reliability measures. The results from the two hypotheses testing suggest that 1) underfitting may cause disagreement in distribution selection, 2) travel time can be precisely fitted using mixture models with higher value of the number of mixture distributions (K), regardless of the distribution family, and 3) the travel time reliability measures are insensitive to the selection of distribution family. Findings of this research allows researchers and practitioners to avoid the work of testing various distributions, and travel time reliability can be more accurately measured using mixture models due to higher value of log-likelihoods. As with travel time collection, the accuracy of the observed travel time and the optimal travel time data quantity should be determined before using the TTR data. The statistical accuracy of TTR measures should be evaluated so that the statistical behavior and belief can be fully understood. More specifically, this issue can be formulated as a question: using a certain amount of travel time data, how accurate is the travel time reliability for a specific freeway corridor, time of day (TOD), and day of week (DOW)? A framework for answering this question has not been proposed in the past. Our study proposes a framework based on bootstrapping to evaluate the accuracy of TTR measures and answer the question. Bootstrapping is a computer-based method for assigning measures of accuracy to multiple types of statistical estimators without requiring a specific probability distribution. Three scenarios representing three traffic flow conditions (free-flow, congestion, and transition) were used to fully understand the accuracy of TTR measures under different traffic conditions. The results of the accuracy measurements primarily showed that: 1) the proposed framework can facilitate assessment of the accuracy of TTR, and 2) stabilization of the TTR measures did not necessarily correspond to statistical accuracy. The findings in our study also suggested that moment-based TTR measures may not be statistically sufficient for measuring freeway TTR. Additionally, our study suggested that 4 or 5 weeks of travel time data is enough for measuring freeway TTR under free-flow conditions, 40 weeks for congested conditions, and 35 weeks for transition conditions. A considerable number of studies have contributed to measuring travel time reliability. Travel time distribution estimation is considered as an important starting input of measuring travel time reliability. Kernel density estimation (KDE) is used to estimate travel time distribution, instead of parametric probability distributions, e.g. Lognormal distribution, the two state models. The Hasofer Lind - Rackwitz Fiessler (HL-RF) algorithm, widely used in the field of reliability engineering, is applied to this work. It is used to compute the reliability index of a system based on its previous performance. The computing procedure for travel time reliability of corridors on a freeway is first introduced. Network travel time reliability is developed afterwards. Given probability distributions estimated by the KDE technique, and an anticipated travel time from travelers, the two equations of the corridor and network travel time reliability can be used to address the question, "How reliable is my perceived travel time?" The definition of travel time reliability is in the sense of "on time performance", and it is conducted inherently from the perspective of travelers. Further, the major advantages of the proposed method are: 1) The proposed method demonstrates an alternative way to estimate travel time distributions when the choice of probability distribution family is still uncertain; 2) the proposed method shows its flexibility for being applied onto different levels of roadways (e.g. individual roadway segment or network). A user-defined anticipated travel time can be input, and travelers can utilize the computed travel time reliability information to plan their trips in advance, in order to better manage trip time, reduce cost, and avoid frustration.
390

The Effect of Residency Requirements on Police as Capable Guardians

Pritchard, David 16 April 2010 (has links)
The debate over police residency requirements dates to the advent of the modern police force in the early 19th Century. Many reasons have been put forth regarding these requirements, from effectiveness to availability to economic impact. On the other hand, opponents have argued that quality of life, employee retention, and applicant pool should be considered in the decision to have residency mandates. This study seeks to determine the effectiveness of resident police officers within the context of the Routine Activities Theory. In particular, it considered whether police officers are more capable guardians when they live in the jurisdictions where they work, specifically when using a marked take home police vehicle as a place keeper. Data was collected regarding police residency, Group A crime, Group B crime, and social disorganization in 25 apartment complexes in Chesterfield County, VA, during a six month period. It was found that police residency had a statistically significant and moderately strong negative effect on the rate of Group A crime and signs of social disorganization, as measured by police calls for service. Police residency showed a weak negative effect on Group B crime, but it was not statistically significant.

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