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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.
401

Seasonal Variations of Pavement Layer Moduli Determined Using In Situ Measurements of Pavement Stress and Strain

Swett, Lauren J. January 2007 (has links) (PDF)
No description available.
402

Prediction of permanent deformation in asphalt mixtures

Al-Mosawe, Hasan January 2016 (has links)
An asphalt mixture is combined of different sizes of aggregate, filler, and bitumen for application on the most common road construction materials. In asphalt pavement material there are different types of distress such as permanent deformation (rutting), fatigue cracking, ravelling, potholes, stripping, etc. There are many reasons for these types of distress, some of them related to the pavement structure, e.g. whether the underlying layers are weak, others related to the mixture properties. Other causes could be related to external conditions such as high temperature, high axle load, long duration of load application, etc. This research has focused on the permanent deformation (rutting) as a function of aggregate gradation. The aggregate gradations of more than twenty asphalt mixtures, manufactured with different gradations, were analysed by using the Bailey method of gradation analysis. The analysis was performed in relation to Repeated Load Axial Test (RLAT) testing results to study the performance of each mixture. The results showed that the Bailey method is not capable on its own to define the differences between the gradations of each mixture. Therefore, three more packing ratios were introduced to adequately describe the aggregate gradation. The aggregate particle packing was extensively studied through these packing ratios and it was shown how the different particle sizes interact with each other. Images were taken for two mixtures to validate the theory behind the ratios. The five packing ratios (two of Bailey and three new ratios) were used in Artificial Neural Network (ANN) and Adaptive Neuro-Fuzzy Inference System (ANFIS) techniques for all the mixtures as input data to predict the mixture performance (RLAT permanent deformation and Indirect Tensile Stiffness Modulus ITSM stiffness modulus) and they showed good prediction capability. After establishing the impact of aggregate packing on the performance, six mixtures were re-manufactured and re-tested with different variables; the selection of the mixtures was made to cover a range of different gradations (ratios). The aim of this step was to understand the effect of these variables on the asphalt mixture in the light of the packing ratios. The variables that were used were binder content, testing temperature and compaction effort. The binder content results showed an interesting effect on the permanent deformation and stiffness of the asphalt mixture. The packing of aggregate was very helpful in understanding the different mixture behaviour with different binder content. The effect of aggregate packing was not shown at relatively low testing temperature, but as the temperature rises the aggregate packing effect starts to appear. The effect of compaction which was represented by the number of gyrations in gyratory compactor was inconsistent; results show over-compaction can lead to poor performance. Finally, a linear viscous method was introduced aiming to predict the rutting in an asphalt mixture. The method was based on using a multilayer linear programme (BISAR) and using viscous parameters of the mixture as input. The non-linear properties of the material were incorporated by using the RLAT test. For this purpose, six mixtures were used and tested in a wheel tracking machine. The predicted results were compared with the wheel tracking rut depth in the laboratory and showed good agreement at different temperatures. However, at high temperature (50 °C) the material properties in the RLAT test did not behave as linear viscous, which resulted in a much poorer prediction. Trials were made to predict field rut but it was found that special requirements were needed for the approach which were not available at the time of the research. However, for the available field data, the method was found to be a good predictor.
403

Hardware architectures for infrared pedestrian detection systems

Walczyk, Robert January 2013 (has links)
Infrared pedestrian detection systems struggle with real-time processing performance. Known solutions are limited to either low resolution systems with basic functionality running at full frame rate, or software based techniques featuring higher detection rates with full set of features, however running only in off-line mode for statistical analysis. Here, a comprehensive solution for real-time pedestrian detection is described. This research project includes investigation of possible solutions, design, development and implementation of a pedestrian detection system, processing data from infrared video source in real-time. Design requirements include processing at full frame rate as well as low memory and system resource consumption. The memory utilization is one of the major concerns since high demand for memory resources is a critical aspect in most image processing applications. For the purpose of this task, a number of general purpose image processing techniques were revised, taking into consideration the suitability for infrared pedestrian detection. These tasks include background separation, acquisition noise removal and object detection through connected component labelling. They are discussed and addressed in individual chapters. Various techniques for background segmentation are discussed. A chronological review of popular techniques is provided. The proposed architecture for background subtraction is based on selective running average for adaptive background model, supported by adaptive thresholding based on histogram calculation. In order to remove acquisition noise, a dual decomposed architecture was introduced, based on mathematical morphology and basic set theory de�nitions. It includes both erosion and dilation performed in a pipeline. For the purpose of object detection and feature extraction, a connected component labelling technique was employed, based on a single pass approach to ful�l real-time processing requirement. The system was implemented, veri�ed and tested on XUP FPGA Development Board with Virtex-II Pro XC2VP30 chip from Xilinx. Details and limitation of the speci�c implementation are discussed. An overview of experimental pedestrian detection results is provided. The thesis concludes with system analysis and suggestions for future work.
404

Recycling of asphalt pavements in new bituminous mixes

Byrne, David A. January 2005 (has links)
No description available.
405

Predicting ride comfort with reclined seats

Basri, B. January 2012 (has links)
Reclined seats in transport suggest luxury and comfort, but a review of the literature revealed little study of how backrest inclination influences the discomfort caused by vibration of a seat or a backrest. This thesis seeks to advance understanding of the influence of backrest inclination on vibration discomfort and provides a model for evaluating vibration discomfort and metrics for optimising seats with different backrest inclinations. Vibration discomfort depends on the direction and location of vibration input to the body. Subjects used magnitude estimation to judge vibration magnitudes from thresholds of perception up to 2 ms-2 r.m.s. at the 11 preferred 1/3-octave centre frequencies from 2.5 to 25 Hz. The first two experiments determined absolute thresholds and discomfort with x-axis backrest vibration (Experiment 1) and z-axis backrest vibration (Experiment 2) with four backrest inclinations (0°, 30°, 60°, and 90° from vertical). The third experiment investigated discomfort with vertical seat pan vibration and five backrest conditions (no backrest and backrest inclined to 0°, 30°, 60°, and 90°). With x-axis vibration of the back, inclining the backrest had similar effects on thresholds and equivalent comfort contours. Thresholds increased at frequencies from 4 to 8 Hz with increasing inclination of the backrest. With inclined backrests, 40% greater magnitudes of vibration were required from 4 to 8 Hz, to cause discomfort equivalent to that with the upright backrest. Frequency weighting Wc in current standards predicted discomfort and perception of x-axis vibration of the upright backrest (0°) but weighting Wb was more appropriate for inclined backrests. Frequency weighting Wd was appropriate for both discomfort and perception of z-axis vibration of the back at all backrest inclinations. With vertical seat acceleration, the frequency of greatest sensitivity decreased with increasing vibration magnitude. Compared to an upright backrest, around the main resonance of the body the vibration magnitudes required to cause similar discomfort were 100% greater with 60° and 90° backrest inclinations and 50% greater with a 30° backrest inclination. The fourth experiment investigated whole-body vertical vibration on a rigid seat with no backrest and with four backrest inclinations. With an inclined backrest, discomfort caused by high frequency vibration increased at the head or neck but discomfort at the head or neck caused by low frequencies (5 and 6.3 Hz) reduced. With inclined backrests, the procedures in current standards overestimate overall discomfort at frequencies around 5 and 6.3 Hz but underestimate discomfort caused by frequencies greater than about 8 Hz. The final experiment investigated a model for predicting vibration discomfort with three compliant reclined seats. At each frequency, the measured seat dynamic discomfort, MSDD (the ratio of the vibration acceleration required to cause similar discomfort with a compliant seat and a rigid reference seat), was compared with seat effective amplitude transmissibility, SEAT value (the ratio of overall ride values with a compliant seat and a rigid reference seat using the weightings in current standards). The compliant seats increased vibration discomfort at frequencies around the 4-Hz resonance but reduced vibration discomfort at frequencies greater than about 6.3 Hz. The SEAT values provided appropriate indications of how the foam increased vibration discomfort at some frequencies but decreased vibration discomfort at other frequencies. Differences between the SEAT values and the measured seat dynamic discomfort are consistent with the need for different frequency weightings when the body is supported by an inclined backrest. An empirical model was evolved from the experiments for predicting vibration discomfort with reclined seats. It is concluded that reclining a backrest will tend to be detrimental at frequencies greater than about 10 Hz with greater discomfort in the head or neck induced by vibration of the backrest. At frequencies around 5 and 6.3 Hz, reclining a backrest can reduce discomfort.
406

Human response to combined noise and vibration

Huang, Yuan January 2012 (has links)
The discomfort caused by the noise and vibration in cars is investigated in this thesis to improve understanding of how subjective judgements of noise and vibration affect each other, how the relative discomfort of noise and vibration depend on their magnitudes and their durations, and how the total discomfort caused by simultaneous noise and vibration can be predicted. Two experiments were designed to determine the magnitude-dependence of the relative discomfort caused by noise and vertical whole-body vibration. Subjects were presented with various combinations of different levels of noise and different magnitudes of vibration, and rated the discomfort caused by noise relative to the discomfort caused by vibration, and also vibration discomfort relative to noise discomfort. The subjective equivalence between noise and vibration was highly dependent on whether noise was judged relative to the vibration or vibration was judged relative to the noise. When judging noise, higher magnitude vibrations appeared to mask the discomfort caused by low levels of noise. When judging vibration, higher level noises appeared to mask the discomfort caused by low magnitudes of vibration. The duration-dependence of the relative discomfort of noise and vibration was then investigated. Subjects were presented with 49 combinations of seven levels of noise and seven magnitudes of vertical whole-body vibration, and with five durations (2, 4, 8, 16, and 32 s). Either the discomfort caused by noise relative to the discomfort caused by vibration, or vibration discomfort relative to noise discomfort were rated in two sessions. The findings indicate that noise discomfort and vibration discomfort have a similar dependence on duration. The slopes expressing the levels of noise (sound pressure level or sound exposure level) judged equivalent to the levels of vibration (logarithms of the r.m.s. acceleration or vibration dose value) increased with increasing duration when judging noise relative to vibration, but were independent of duration when judging vibration relative to noise. As the durations increased from 2 to 32 s, the masking effect of vibration on noise discomfort decreased, whereas the masking effect of noise on vibration discomfort did not change. Finally the noise discomfort in the presence of vibration, vibration discomfort in the presence noise, and the combined discomfort of simultaneous noise and vibration were investigated by employing the method of absolute magnitude estimation. Subjects judged noise discomfort, vibration discomfort, and their total discomfort in different sessions. The results suggest that, within the range of stimuli magnitudes investigated, the discomfort caused by vibration was reduced by noise whereas the judgement of noise discomfort was not significantly influenced by vibration. The total discomfort caused by simultaneous noise and vibration was well predicted by ψc = [(ψv)2+ (ψs)2]0.5, where ψv, ψs, and ψc, represent vibration discomfort, noise discomfort, and their total discomfort, respectively. In conclusion, the relative discomfort caused by noise and vibration varies according to whether subjects are asked to judge noise discomfort relative to vibration discomfort or vibration discomfort relative to noise discomfort. There are masking effects of noise on the judgement of vibration discomfort, and of vibration on the judgement of noise discomfort, depending on the relative magnitudes of the two stimuli. The influence of vibration on the judgement of noise discomfort decreases with increasing duration of the stimuli, whereas the influence of noise on the judgement of vibration discomfort is independent of the duration. The discomfort caused by a combination of noise and vibration can be predicted by root-sums-of-squares of the discomfort caused by noise and the discomfort caused by vibration when these stimuli are presented alone.
407

Development of a new cold binder course emulsion asphalt

Dulaimi, A. F. D. January 2017 (has links)
Hot Mix Asphalt (HMA) is the most commonly used material in the construction of asphalt pavements. Approximately 650 million tonnes of asphalts for road pavements were produced, worldwide, in 2014. However, the HMA industry is responsible for a substantial consumption of energy, the creation of health and safety issues and has a negative impact on the environment. These shortcomings initiated substantial discussion within the industry with the aim to develop more environmental friendly, sustainable and economic pavement materials. These have resulted in the development of cold bitumen emulsion mixtures (CBEMs). However, to date, low early life stiffness, a slower rate of curing, the length of time necessary to achieve full strength, high air void contents and the presence of moisture in these mixtures have prevented them from being fully embraced by pavement authorities. This led to them being considered inferior to HMA because of a lack of essential mechanical properties. Currently, the use of CBEMs in pavement construction is limited to low traffic road surface course, reinstatement works and footways. Because of this, the development of CBEMs with high early strength and minimal time delay requirements before structural loading, would be considered as a breakthrough in CBEM research. This research aims to develop a novel, fast-curing and environmentally friendly, cold binder course emulsion asphalt (CBCEA) for heavily trafficked roads. The new CBCEA mixture comprises the same gradation as conventional dense bitumen macadam (DBM) mixtures which are normally used as a binder course and base in road pavements in the UK. The new CBCEA incorporates a new cementitious material, alkali activated binary blended cement filler (ABBCF), made from Paper Making Sludge Ash (PMSA) and a Fluid Catalytic Cracking Catalysts Residue (FC3R) activated by a waste NaOH solution (W-NaOH). Incorporation of the PMSA and FC3R was achieved through the replacement of conventional limestone filler (LF), while W-NaOH replaced the pre-water necessary to wet the aggregate in the CBCEA. It was found that the glass phases of the new filler particles were broken and reacted with Ca(OH)2 creating C-S-H gel through the hydration process. This results in a very high early strength and improved mechanical properties. Balanced oxide compositions, within the new filler, were identified as responsible for an enhanced hydration reaction. A laboratory programme of testing measured the stiffness modulus, conducted at 1, 3, 7, 14, 28, 90 and 180 days. Susceptibility to temperature, wheel track testing to establish rutting resistance, fatigue resistance measured by a four-point beam bending test, fracture resistance testing via semi-circular bending tests, moisture damage resistance and ageing tests were successfully performed. Advanced techniques for microstructure assessment, i.e. Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD), were used to provide scientific data to provide a deeper understanding of the microstructure and internal composition. An environmental investigation was performed using a Toxicity Characteristic Leaching Procedure (TCLP) test. The new ABBCF mixture offers a significant improvement in stiffness modulus compared to HMA and the reference cold binder course mixture containing conventional limestone filler (LF). Target stiffness, according to British and European standards, can be surpassed after less than one day of curing. The new ABBCF mixture offers a stiffness modulus which is 27 times better than the LF mixture after 3 days. This will overcome restrictions caused by the length of time required to achieve acceptable stiffness by traditional CBEMs. More remarkably, the new ABBCF mixture is 78% better than mixtures treated with Ordinary Portland Cement (OPC) in terms of ITSM after 3 days. Furthermore, the impact of a rise in temperature on stiffness modulus from 5 to 45°C, was much larger in LF and both HMA mixtures in comparison to ABBCF, revealing the potential to use these mixes in severe conditions, both hot and cold weathers. ABBCF mixtures displayed considerably reduced susceptibility to permanent deformation, demonstrating the potential advantage of using this material on heavily trafficked roads. Fatigue resistance was noticeably improved by the use of ABBCF in comparison to the reference LF and HMAs. Improved water sensitivity for progressive hydration with the new ABBCF was also established resulting in an enhanced long ageing performance meaning that these mixtures can be considered durable. SEM observation and XRD analysis confirmed the formation of hydration products at various curing times. The concentration of heavy metals in the samples incorporating ABBCF was observed to be less than the regulatory levels determined for hazardous materials. Microwave treatment has proven to be an effective technique to reduce the air void contents of the ABBCF mixture and achieve acceptable levels of porosity. Finally, achieving the aim of the current research will theoretically increase the application of such mixtures and allow them to be used as structural pavement materials. On a further positive note, the inclusion of waste and by-product materials in CBEMs results in more sustainable practice and eliminates disposal problems.
408

The viability of British urban transport planning in the post Buchanan period : a systematic study

Puvanachandran, Vallipuram Malavarayamudali January 1982 (has links)
Long term transport plans produced by county borough councils between 1960 and 1974 had low implementation. This thesis examines the degree and likely causes of low-implementation in a detailed and systematic manner. The findings are then used to recommend improvements to structure and local planning including transport planning. The thesis is in five parts. Part 1 begins with justifications for the research. In Chapter II, the land use-transport planning process in its historical context is comprehensively presented. Research by others has been used in Chapter III to identify key factors affecting implementation. These may be grouped as: (l) Institutional - e.g. local government re-organisation (2) Shortage of funds. (3) Socio-political. (4) Inaccurate transport provision and forecasting. The first three groups are further distinguished between national and local factors. In Chapters 4 and 5 the following two measures are developed to assess implementation. FMR is a ratio of plans recommended and implemented TO recommended infrastructure in plan for a given period. FMQ measures recommended and implemented works AS A proportion of total capital works undertaken, FMQ is satisfactory but FMR is low. Parts II and III examine the causes for low FMR. Part II, (Chapters 7 to 9) examines national factors - shortage of funds, political and pressure group resistances and technical deficiencies as reasons. Part III examines local factors - shortage of funds, changes in political control in councils, public resistance and chief officers' influences. In each case variations in local factors and variations in FMR are correlated. The last three factors together explains nearly 90 percent of the variation in FMR. In Part IV chapter 15 deals with changes in influence of factors, in the post-1974 period and chapter 16 concludes implementation analysis. In Part V (the last 4 chapters) present day land use-transport planning is critically reviewed and improvements are outlined.
409

Crack propagation in high modulus asphalt mixtures

Sewell, Anthony J. January 2017 (has links)
This Thesis was undertaken at the University of Nottingham which has a world class history of research into the fatigue of asphalt materials. The work described in this thesis was part of a research project funded by EPSRC, which attempts to gain a greater understanding of fatigue crack propagation in High Modulus Base (HMB) materials. Following on from Pell, Brown and Read this research has introduced the Compact Tension (CT) Test and Fracture Mechanics principles to examine the behaviour of HMB materials which had relatively little fatigue behavioural understanding on commencement of this research. This research investigated the fatigue cracking behaviour of twelve High Modulus Base (HMB) binders and mixtures. The research was instigated in response to the introduction of these HMB binders from France, as it was thought that these materials were not particularly well understood. In hindsight, this view was proven to be correct, as numerous problems have been experienced after using such materials. The Compact Tension test has been proved to be an effective means of testing bituminous mixtures for their crack propagation resistance, allowing the study of temperature effects. Crack propagation is dramatically affected by both binder hardness and temperature. In a pavement, the current approach to design, assuming a single fatigue characteristic, underestimates the life of 35 and 25 pen mixtures. However, it probably overestimates the life of 15 pen mixtures by not accounting for the effects of low temperatures.
410

Robust cooperative positioning using DGPS and UWB for V2X applications

Gao, Yang January 2017 (has links)
Road transportation injuries, environmental pollution, and traffic congestion have resulted in a considerable cost to society annually. They have led to an increasing demand for a new generation of Intelligent Transportation Systems (ITS) road applications, which promise to tackle these widespread issues. A common element of such applications is the positioning system, and its performance has been highlighted as one of the key enablers. With the rapid expansion of Global Navigation Satellite Systems (GNSS), satellite-based positioning and navigation will continue to be the predominant positioning solution for most of ITS road applications. GNSS positioning systems offer global coverage, they are primarily free of charge, operate in all weather conditions, and are available all day, every day. However, there are challenges for GNSS-based positioning for ITS applications; in particular, the limited availability and degraded performance of GNSS signals in urban canyons. These challenges could impede the adoption of ITS applications, such as collision avoidance systems, lane departure warning systems, connected and autonomous vehicles. There is a gap between the positioning performance of GNSS-based systems and the positioning performance demanded by ITS applications. To bridge this gap, this research considers multi-sensor integration and cooperative positioning based on vehicle-to-vehicle, vehicle-to-infrastructure, and vehicle-to-pedestrian communications (collectively known as V2X communication). In comparison to other radio frequency augmentation techniques, Ultra-Wideband (UWB) is of particular interest for multi-sensor integration due to its fine time resolution and robust performance in high signal multipath environments. In addition to this benefit, Dedicated Short Range Communication (DSRC), as a key enabling communication component in V2X communication, not only allows vehicles to exchange their position information but also to share traffic safety-related information such as real-time congestion, accident and incident details, and variable speed limits. By taking advantage of DSRC, a vehicle in a GNSS hostile environment can calculate its position based on data shared from surrounding road users. This thesis utilises Global Positioning System (GPS) as a representative of GNSS and proposes to augment Differential GPS (DGPS) with UWB ranging observations attained from surrounding vehicles and infrastructure. It is accomplished by tightly integrating double-difference (DD) code pseudo-range GPS observations and UWB ranging observations using a Robust Kalman Filter. The performance of the proposed Robust Cooperative Positioning (RCP) method is evaluated using real and simulated GPS code pseudo-range and UWB ranging observations supported by assumed DSRC transmission. This thesis carries out a thorough assessment of the ranging performance, error sources and positioning performance of the Thales UWB Lock-on Model LD2. The assessment is completed by conducting a series of tests in different static and dynamic situations. In addition to this in-field assessment of the UWB device, the positioning performance of the proposed RCP method is demonstrated in both favourable and hostile GPS environments. The proposed RCP method effectively eliminates the impact of observed outliers, and the integrated RCP solution outperforms the DGPS-only solution, especially when the GPS signal is partially or fully obstructed. The results based on simulated UWB ranging observations and real GPS code pseudo-range observations on the roof of the Nottingham Geospatial Building achieve sub-metre three-dimensional accuracies when three DD code pseudo-ranges and four UWB ranging observations are available.

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