160 research outputs found
Superposition of DC voltage and submicrosecond impulses for energization of electrostatic precipitators
No full textThis paper discusses the development of an impulsive microelectrostatic precipitation technology, which uses superposition of submicrosecond high-field pulses and dc electric field. Short impulses allow the application of higher voltages to the ionization electrodes of a precipitation system without the initiation of breakdown. These higher levels of electric field generate higher ionic concentrations, resulting in more efficient charging of the airborne particles, and can potentially improve precipitation efficiency. This work is focused on the analysis of the behavior of impulsive positive corona discharges in a coaxial reactor designed for precipitation studies. The efficiency of precipitation of coarse and fine particles has been investigated using different dc and impulse voltage levels in order to establish optimal energization modes
Dataset in support of the Southampton doctoral thesis 'The boatbuilding tradition of the Aegean during the Late Neolithic – Early Bronze Age periods. Typological classification, digital reconstruction and seakeeping assessment'
No full textDataset in support of the Southampton doctoral thesis 'The boatbuilding tradition of the Aegean during the Late Neolithic – Early Bronze Age periods. Typological classification, digital reconstruction and seakeeping assessment' Appendix D - Resistance data and Appendix C - Stability data.
This dataset is focused on two appendices:
Appendix D - Resistance data. D.1 Resistance data produced by the author via MAXSURF Resistance for this thesis.
Appendix C - Stability data
C1. Stability data – STIX and ISO criteria, produced by the author via MAXSURF Stability software for his thesis
This research was funded by Southampton Marine and Maritime Institute (SMMI), Vice-Chancellor's Scholarship, Greek Archaeological Committee UK (GACUK)
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Investigation of high altitude/tropospheric correction factors for electric aircraft applications
No full textWith rising fuel costs and CO2 emissions, the aviation industry is moving rapidly toward increased electrification of aircraft, and power demand for propulsion and safety critical systems necessitates a move to on-board distribution voltages in excess of 1 kV. The increased stress experienced by cable insulation, connectors and other equipment, combined with extreme and dynamic environmental conditions experienced in flight, presents a number of technical challenges.
This research project proposes to quantify the effect of atmospheric conditions on partial discharge thresholds in uprated aircraft electrical systems, and to derive atmospheric correction factors appropriate to in-service operating conditions to assist the aircraft electrical design engineer in the insulation coordination of modern aviation systems.
The development of a controlled atmospheric test facility for the precise replication of in-flight conditions is outlined, and an initial visual assessment of partial discharge activity in an ex-service wire harness at a range of pressures is presented. We also present plans for the ongoing development of the facility and test capabilities
Experimental Investigation of Rubber Swelling in Bitumen
No full textRubber swelling in bitumen, which is a diffusion-induced volume expansion process, plays a dominant role in the design of crumb rubber modified bitumen binders and their properties development. This study aims to investigate the kinetics of bitumen diffusion into truck tire rubber, the equilibrium swelling characteristics of rubber, and the mechanical properties of rubber before and after swelling at different high temperatures. Fourier transform infrared spectroscopy results indicate that no rubber dissolution happens during the interaction in the temperature range from 160°C to 200°C. Aliphatic compounds from bitumen preferentially diffused into rubber during the swelling process. The diffusion coefficients of bitumen into rubber were determined by the sorption test using the gravimetric method. The diffusion coefficient increases with the increase of temperature in an Arrhenius form. The volume expansion of rubber during swelling was captured by the X-ray computed tomography scan images. Rubber swells faster at the earlier stages, then the expansion rate slows down. The swelling ratio of rubber increased from 1.97 at 160°C to 3.03 at 200°C after 36 h interaction. Mechanical tests by dynamic shear rheometer reveal that swollen rubber becomes softer compared with the dry rubber and exhibits obvious viscoelastic behaviors. With the increase of temperature, the softening and viscous effect are more significant. The obtained parameters can be implemented to swelling and micromechanical models to better predict the binder properties.Accepted Author ManuscriptPavement Engineerin
Study on the Asphalt Pavement Response in the Accelerated Pavement Testing Facility
No full textAccelerated pavement testing (APT) is an effective method in evaluating pavement performance by applying wheel loading and speed under controlled conditions. This study aims to investigate the effects of wheel loading, speed and ambient temperature on the pavement responses at different directions and depths of pavement structure. A two-layer asphalt pavement structure was constructed on a base layer constructed 10 years ago. Strain gauges were installed both in the transversal and longitudinal directions of motion on the bottom of both layers. The response of the asphalt layers was monitored and the developed strains were recorded. The results show that maximum compressive strain increases with wheel load. In contrast, the maximum tensile strain decreases as load increases; this is probably due to the high confining pressure that occurs within the pavement structure when higher wheel load is applied. The maximum compressive and tensile strains decrease with wheel speed, because the asphalt mixture becomes stiffer at high wheel speed (frequency). The maximum compressive and tensile strains in the transversal direction increase with ambient temperature, because of the low stiffness of asphalt materials at high temperature, which appears to be the cause of rutting.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Pavement Engineerin
Development of a preliminary sizing tool forstrategic decision making in composite fuselages using weight and cost optimization
No full textThis study is an attempt to develop a preliminary composite fuselage sizing tool for the decision making process utilizing analytical structural analysis equations and a bottom-up cost approach to estimate weight and cost. Previous research by several authors and companies is reviewed in order to define the knowledge gaps that the project is going to fill. The objectives of this project are divided into two directions. The first one is the weight and cost fuselage design, and the second, is the weight and cost optimization process. After examining the existing literature both from academia and industry a different approach is proposed for each sector. In the structural design an analytical based model is proposed to assess the components integrity while cost equations for fully learned manufacturing processes are used based on the Advanced Composites Cost Estimation Manual (ACCEM). An experience-driven optimization algorithm is proposed afterwards, taking into account manufacturing considerations and design rules of thumb. By combining these tools, a general tool for fuselage design that is completely suited for the preliminary design phase is proposed. Τhe trade-off studies can provide important knowledge on the effect of different decisions and establish new design guidelines. The study concludes that an increase of the number of stiffeners and frames, in a fuselage structure, leads to a general decrease in weight and an increase in manufacturing cost. The addition of more stringers or frames after a certain level leads to an increase in weight, while the cost follows the same trend. The manufacturing constraints and the design rules-of-thumb applied lead to an increase in structural weight. Finally, the comparison between skin-stiffened and sandwich designs, shows that the weight saving potential is comparable for both configurations, and the cost saving potential is higher for the sandwich design.Aerospace Engineerin
Ageing Behavior of Porous and Dense Asphalt Mixtures in the Field
No full textBitumen ageing is one of the principal factors causing the deterioration of asphalt pavements. As bitumen ages, the pavement loses its ability to relax stresses during loading/unloading and thermal cooling process, thus the risk of cracking increases. Oxidation and ultraviolet (UV) radiation are believed to be the main factors that can cause bitumen ageing during pavement service life. The aim of this study is to evaluate the mechanical behavior of porous and dense asphalt pavements during field ageing. Pavement test sections were constructed in 2014 and are being exposed to actual environmental conditions since then. To investigate the effect of UV radiation on ageing, UV reflective glass-plates were utilized to cover part of the pavement surface. To study the evolution of the pavements’ mechanical properties, asphalt cores were collected from the test sections periodically (at one-year intervals). The changes in the stiffness modulus of the mixtures were determined via cyclic indirect tensile tests. The results show that the effect of mineral aggregate packing, and hence of air-void distribution and connectivity, on the ageing sensitivity (both thermal and UV ageing sensitivity) of the pavements with time was found to be significant, as the changes of the stiffness of the porous mixtures were greater than that of dense mixtures.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Pavement Engineerin
Study of Influence of Operating Parameters on Braking Distance
No full textStopping distance includes driver thinking distance and braking distance. Braking distance is one of the basic standards for road design and maintenance practices. Adequate tire–pavement skid resistance plays a significant role in reducing braking distance and consequently enhancing road safety. With technology such as the antilock braking system, the friction force is maximized by applying the brakes repeatedly, in an on-and-off pattern, such that the braking distance is shortened. Several studies have shown the effect that some parameters, such as water film thickness, tire inflation pressure, and wheel load, have on braking distance. Less discussed is the effect of slip ratio, temperature, and pavement surface characteristics. Measuring the braking distance in the field is energy-consuming and time-consuming, and there are uncertainties in the environmental conditions as well. General approaches to calculating braking distance are based on basic mechanics principles. To the authors’ knowledge, a model that can simulate the whole braking process is not available. The presented study proposes a way to predict braking distance by means of finite element modeling only. A model that can include the effect of parameters such as temperature, slip ratio, and pavement surface characteristics on the braking distance is introduced.Accepted Author ManuscriptPavement Engineerin
A parameter back-calculation technique for pavements under moving loads
No full textMaintenance and rehabilitation strategies of pavements are usually made based on the results of performance evaluation. An efficient tool for pavement structural evaluation at network level is the traffic speed deflectometer (TSD) test. In order to deal with TSD measurements, this paper proposes a parameter back-calculation technique. Firstly, the sensitivity of the surface response for an elastic pavement structure with hysteretic damping to different structural parameters is investigated. Then, the ability of the parameter backcalculation technique is verified by conducting a case study. The results show that the proposed technique is able to back-calculate the structural parameters of pavements by analysing TSD measurements. The presented work contributes to the development of parameter back-calculation techniques for the TSD test.Accepted author manuscriptPavement EngineeringDynamics of Structure
Mechanisms in Healing of Bitumen and the Impact of Normal Force
No full textDamage in pavements is known to reduce over time when the material is left to rest, this phenomenon is known as healing. It has been shown that healing is an important influence factor in pavement performance. However, an accepted method to assess the healing capability of a pavement is currently not available. Healing of cracks is assumed to be the sum of two processes, cracked surfaces coming into contact (wetting) and strength gain of surfaces in contact (intrinsic healing). The paper describes influencing parameters of these two processes. The healing potential of bitumen is assessed using a novel test method. In this method two pieces of bitumen are brought together and left to heal under controlled condi-tions. After healing the amount of healing is assessed by testing the specimens us-ing a direct tensile test. From the results it can be seen that normal force has a sig-nificant impact on the observed healing, indicating that the process of two surfaces coming into contact (wetting) has a significant impact on healing behavior of the bitumen.Pavement Engineerin
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