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1
Sterritt, Garry. "Probabilistic procedures for lifetime management of reinforced concrete highway bridges." Thesis, Imperial College London, 2000. http://hdl.handle.net/10044/1/63189.
Full textAbstract:
The UK’s bridge stock is deteriorating due to a number of mechanisms that affect concrete durability. These include carbonation, thaumasite sulphate reaction, alkali-silica reaction, chloride ingress, freeze-thaw action and fatigue. There are limited resources available to maintain the bridge stock in a safe and operable condition. It is therefore essential that available funds are used to optimum effect for inspections, maintenance, assessment, repair or replacement. If a short term view is taken to bridge management then it is highly likely that a future backlog of essential work will build up which will result in severe financial and operational difficulties. In this context, methodologies that can predict the time-dependent deterioration of RC bridges would be highly beneficial to bridge owners and maintaining agents when developing bridge management strategies. A methodology has been developed in this thesis to estimate the time-dependent deterioration and structural reliability of RC components. Only chloride induced deterioration was modelled because it was found to be the dominant mechanism in the UK. Probabilistic techniques and spatial analysis are used to model the uncertainty inherent to chloride induced deterioration. Code based limit state equations are used with the deterioration models to create time-dependent failure margins. Standard reliability methods (FORM/SORM) are then applied to estimate failure probability time profiles over the life of the bridge. Furthermore, classical and Bayesian statistical techniques are used to update deterioration/reliability predictions. The deterioration models produce plots of area initiated or delaminated as a function of time. These may be used to plan inspection times and types. The ensuing limit state reliability analysis produce probability of failure profiles which may be used as a comparative tool for assessing similar bridge/component types, and thus a bridge management strategy can be developed on the basis of perceived criticality. The updating techniques are used to illustrate how model predictions can be improved when site data becomes available. It is shown that the development of models using typically available site data can be beneficial to bridge owners, but the quantity of such data needs to be enhanced. This is particularly evident for the wide diversity of bridge structures in the UK.
2
Cam, Umut Egemen. "Scour Countermeasure Design For Sequential Viaducts On Ankara - Pozanti Highway." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614171/index.pdf.
Full textAbstract:
Foundations of river bridges need to be protected with respect to excessive scouring.
Degree of protection depends on the severity of scouring action around bridge piers
and abutments. A case study is carried out to design appropriate protective measures
for sequential viaducts located on Ankara-Pozant highway in Turkey. A number of
analyses are conducted to obtain water surface profiles throughout the study reach.
Local scour depths at piers and abutments of the viaducts are then obtained. The
design process for countermeasures is performed concerning hydraulic, hydrologic,
constructional, and economical requirements. To this end, riprap, partially grouted
riprap, and articulated concrete blocks are studied in these view points. A criterion
based on a selection index, which is defined by the National Cooperative Highway
Research Program in the USA, is applied in this study. Implementation of partially
grouted ripraps at infrastructural elements is found to be an appropriate solution.
3
Li, Jingjuan. "A methodology for obtaining traffic data input to the NCHRP 1-37A PDG." Online access for everyone, 2005. http://www.dissertations.wsu.edu/Thesis/Summer2005/j%5Fli%5F080205.pdf.
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Avsar, Ozgur. "Fragility Based Seismic Vulnerability Assessment Of Ordinary Highway Bridges In Turkey." Phd thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/3/12610693/index.pdf.
Full textAbstract:
Recent devastating earthquakes revealed that bridges are one of the most vulnerable components of the transportation systems. These seismic events have emphasized the need to mitigate the risk resulting from the failure of the bridges. Depending on the seismicity of the bridge local site, seismic vulnerability assessment of the bridges can be done based on the fragility curves. These curves are conditional probability functions which give the probability of a bridge attaining or exceeding a particular damage level for an earthquake of a given intensity level. In this dissertation, analytical fragility curves are developed for the ordinary highway bridges in Turkey constructed after the 1990s to be used in the assessment of their seismic vulnerability. Bridges are first grouped into certain major bridge classes based on their structural attributes and sample bridges are generated to account for the structural variability. Nonlinear response history analyses are conducted for each bridge sample with their detailed 3-D analytical models under different earthquake ground motions having varying seismic intensities. Several engineering demand parameters are employed in the determination of seismic response of the bridge components as well as defining damage limit states in terms of member capacities. Fragility curves are obtained from the probability of exceeding each specified damage limit state for each major bridge class. Skew and single-column bent bridges are found to be the most vulnerable ones in comparison with the other bridge classes. Developed fragility curves can be implemented in the seismic risk assessment packages for mitigation purposes.
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Terdich, Nicola. "Impact of electrically assisted turbocharging on the transient response of an off-highway diesel engine." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/25395.
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Engine boosting via turbocharging is a method to increase the engine power output with minimal or no increase in engine parasitic, frictional and pumping losses. Turbocharging in conjunction with engine down-sizing and down-speeding allows a reduction of engine fuel consumption, while maintaining a high engine power output. However, turbocharging introduces a lag in engine transient response, caused by the finite amount of time required by the turbocharger to accelerate, which has to be minimized. Electric turbocharger assistance consists of coupling an electric motor/generator to a standard turbocharger. The scope of the motor/generator is to increase the power available to accelerate the rotor assembly, so that the time to boost is reduced. The motor/generator could also be utilized to brake the turbocharger to control boost and avoid over-speeds, thus replacing the conventional waste-gate. Furthermore, electric assistance allows turbocompounding to be implemented. Turbocompounding improves the engine efficiency by utilizing the turbine and motor/generator to recuperate additional exhaust flow energy. In this thesis, the electric turbocharger assistance impact on the turbocharger and engine performance is studied. An electrically assisted turbocharger prototype has been developed by industrial partners and it has been tested by the author of this thesis. The performance of the turbocharger turbine and motor/generator has been characterized over the full speed range and the impact of the electric assistance on the turbine flow has been investigated experimentally. It has not been possible to characterize the turbine up to choking conditions, so the data has been extrapolated via a mean-line model. The performance data obtained has been utilized to generate a model of the assisted turbocharger, which has been coupled to a one-dimensional model of a non-highway 7-litre diesel engine. This model has been utilized to study the impact of electric turbocharger assistance on the engine transient performance. The electrical machine characterization revealed that the switched reluctance motor/generator operates efficiently up to a speed of 135,000 rev/min, making it one of the fastest running switched reluctance machines of this size. The peak machine efficiency is 93% (excluding the turbocharger bearing losses) and the maximum power output measured is 5.3 kW in generating mode and 4.3 kW in motoring mode. The motor/generator rotor aerodynamic drag loss has been calculated via computational fluid dynamics software and has been found to be 63 W at 140,000 rev/min. Via a novel experimental technique, it has been possible to characterize the turbocharger turbine down to an expansion ratio of 1.00. This experiment revealed that the mass flow rate drops to zero at an expansion ratio higher than unity and that below this critical pressure ratio the turbine flow is reversed. The characterization of the turbine during speed transients showed that the operating point on the performance map deviates from the quasi-steady line. This indicates that minor unsteady effects occur in the turbine and exhaust manifold flow. A further experiment revealed that the motor/generator torque oscillations have a negligible impact on the turbine performance. The engine simulations showed that the ideal electric assistance motoring power for this application is in the 5 to 10 kW range. A 5 kW machine reduces the engine speed drop, which occurs when the engine load is suddenly increased, by up to 83%, depending on the initial load and load step size, and reduces the time to recover the original speed by up to 86%. The simulations also revealed that electric assistance is more effective than the turbine variable geometry system in improving the engine transient response, but the variable geometry system is useful to optimize boost for engine specific fuel consumption over different engine loading conditions.
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Celik, Gozde. "Verification Of Empirically Determined Support Systems Of The Kiliclar Highway Tunnel By Numerical Modelling." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613655/index.pdf.
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The aim of this study is to determine the geological and geotechnical characteristics of Kiliçlar Tunnel on Ankara-Kirikkale Highway, to suggest the appropriate support and excavation systems and verify these suggested support systems via numerical modeling. The length of Kiliç
lar Tunnel is 1110 m. The width of tunnel is 16 m, the height is 10 m and the maximum overburden height is 90 m. Since Ankara-Kirikkale Highway consists of 2x3 lanes, the tunnel is designed as a twin tube tunnel. Kiliç
lar Tunnel is planned to be excavated in Gabbro-Diabase and Serpentinite named as Artova Ophiolite Complex. The rock mass is classified by using RMR, Q and NATM classification systems and support systems are determined by using these classification methods. In addition to empirical approaches, 2D finite element analyses are conducted to check the stabilities of seven sections through the tunnel. Results of those analyses pointed out that the support materials determined empirically (4-6 m long bolt with intervals of 1-2 m, 10-20 cm shotcrete, steel sets (wherever required)) are compatible with those recommended after numerical modelling (4-5 m long bolt with intervals of 1.5-2.0 m, 10-20 cm shotcrete, steel sets for entrance and exit sections). Furthermore, the stabilities of the tunnel portals are also studied by numerical analyses and limit equilibrium analyses. Based on the stability analyses performed for both portals, no slope failure is expected at cut slopes with 1H/3V for forehead and for 1H/2V for side slope.
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Erkayaoglu, Mustafa. "Life Cycle Assessment Of Off-highway Trucks And Belt Conveyors For Sustainable Mining." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613630/index.pdf.
Full textAbstract:
In recent years increasing growth rate of all industrial fields generated an emerging
energy demand and consequent environmental problems worldwide. Defining
environmental profiles of products and systems using environmental tools, such as
Life Cycle Assessment (LCA), is a critical issue for sustainable mining. In order to
tackle the increasing environmental challenges and air emissions induced by surface
coal mining, alternative material handling options are needed to be evaluated. This
research study aims to provide a robust LCA model in selection of the alternative
material haulage systems as a decision support system. The main objectives of this
thesis study are: i) contributing to the national archived data by gathering data about
haulage systems from an open pit coal mine, ii) constructing life cycle inventory
from the acquired environmental data, iii) performing life cycle assessment of both
material haulage systems in an open pit coal mine according to their environmental
burdens, iv) conducting uncertainty assessment, and v) suggesting improvement in
stages where emissions are critical. In order to accomplish these objectives,
comparative LCA from cradle-to-grave was carried out in SIMAPRO 7.3 to
determine life cycle environmental impacts of off-highway mining trucks and belt
conveyors in coal transportation.
Climate change and acidification were selected as major impact categories
considered to be major concerns in mining industry. The results of this study
revealed that off-highway trucks had 1.9 times greater impact on acidification
category than belt conveyors, on the other hand, belt conveyors had 1.6 times
greater impact on climate change. NOx emissions caused 96 percent of the
acidification impact. CO2 emissions from fossil fuel combustion led to 95 percent of
the climate change effect. The obtained results also indicated that the highest impact
on all selected impact categories were generated from the utilization stage of the
trucks operated by diesel oil and utilization of belt conveyor systems operated by
electricity.
The main novelty of this study is that it is one of the first LCA studies in the Turkish
mining industry where considerable amount of emissions occur due to material
handling. This study also advances the current knowledge about environmentally
critical processes in material handling systems and places recommendations for
both alternatives aiming better decision making. The results of the study are
expected to provide a decision support system for the mining industry.
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CARVALHO, NEWTON FAGUNDES DE. "GEOTECHNICAL CHARACTERISTICS OF THE SOFT CLAY FROM BR 101 HIGHWAY IN SANTA CATARINA." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2000. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=1791@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORO presente trabalho apresenta um estudo sobre a argila mole da rodovia BR 101 em Santa Catarina, no qual são pesquisadas suas características geotécnicas a partir de ensaios de campo e laboratório. Os ensaios de campo realizados foram os de palheta, dilatométricos e de piezocone. O programa experimental de laboratório envolveu ensaios de caracterização, de adensamento e triaxiais consolidados não drenados (CIU). O solo foi caracterizado como argila mole flúvio-marinha, altamente plástica e de coloração cinza clara a escura, com sensibilidade entre baixa e média. Trata-se de um material de alta compressibilidade e baixa resistência. Os ensaios de laboratório complementaram os de campo, havendo concordância de resultados em alguns casos estudados. O ensaio dilatométrico apresentou valores de módulo de deformabilidade unidimensional próximos aos obtidos nos ensaios oedométricos, revelando-se, assim, uma ferramenta adequada à estimativa de recalques. A estimativa do fator de cone (NKT) deve ser tratada de forma cuidadosa, pois tal fator tem grande influência na determinação da resistência não drenada (Su). Esta apresentou valores entre 10 e 25kPa, nos ensaios de campo e triaxiais de laboratório (CIU) realizados nos depósitos de argila mole investigados nesse estudo. Finalmente, ressalta-se a importância dos ensaios de campo para a determinação dos parâmetros geotécnicos das argilas moles, devido à rapidez e maior facilidade para a realização.
The objective of this study is to characterize the soft clay of the BR 101 Highway in Santa Catarina, based on field and laboratory tests. Field tests consisted of vane test (VST), flat dilatometer test (DMT) and piezocone (CPTU). The experimental laboratory program included characterization, consolidation and consolidated undrained triaxial tests (CIU). The soil has been characterized as fluviomarine soft clay, highly plastic, presenting light to dark grey color, and low to medium sensibility. The material has shown high compression rate and low resistance. The laboratory tests have complemented the field investigation. Similar constrained modulus (M) values were obtained both from the dilatometer test and from the conventional consolidation test. Therefore, DMT showed to be a suitable test for settlement estimation. Cone factor (NKT) shall be carefully estimated due to its influence in the determination of the undrained shear strength (Su). Field and CIU tests performed in the soft clay deposits presented values between 10 and 25kPa. Emphasis is given in the importance of the field tests to determine the geothecnical parameters of the soft clay, due to their quick and easy performance.
EL presente trabajo presenta un estudio sobre la arcilla blanda de la carretera BR 101 en Santa Catarina. En éste, se investigan las características geotécnicas a partir de ensayos de campo y laboratorio. Los ensayos de campo realizados fueron los de paleta, dilatométricos y de piezocone. El programa experimental de laboratorio considera ensayos de caracterización, de adensamiento y triaxiales consolidados no drenados (CIU). El suelo fue caracterizado como arcilla blanda fluvio-marina, altamente plástica y de coloración gris claro a oscuro, con sensibilidad entre baja y media. Se trata de un material de alta compresibilidad y baja resistencia. Los ensayos de laboratorio complementaron los de campo, y los resultados coinciden en algunos casos estudiados. El ensayo dilatométrico presentó valores de módulo de deformabilidad unidimensional próximos a los obtenidos en los ensayos oedométricos, revelando así la herramienta adecuada en la estimativa de recalcos. La estimativa del factor de cono (NKT) debe ser tratada de forma cuidadosa, porque este factor tiene una gran influencia en la determinación de la resistencia no drenada (Su). La resistencia no drenado tuvo valores entre 10 y 25kPa, en los ensayos de campo y triaxiales de laboratorio (CIU) realizados en los depósitos de arcilla blanda investigados en este estudio. Finalmente, se resalta la importancia de los ensayos de campo para la determinación de los parámetros geotécnicos de las arcillas blandas, debido a la rapidez y facilidad en su realización.
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Bonjaku, Gokdemir Ornela. "Architecture As An Urban And Social Sign: Understanding The Nature Of Urban Transformation In Eskisehir Highway, Ankara." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/3/12610801/index.pdf.
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The buildings of a city such as shopping malls, plazas, world trade centers, hotels or even residential complexes are not only alternative urban building typologies but they represent power in social, economical, political and even religious terms. In this sense buildings should not be seen as specific design and research areas limited with single building scale but rather should be seen as urban statements in city scale. However the eclectic existence of these buildings in urban fabric causes a series of unexpected transformations in a larger scale.
The impact of a building in urban scale takes a very important place in the modern city &ndashtheir architectural expression is not limited with their individual scale but rather it becomes an integrated part of the whole city which is open to transform function, infrastructure, architectural meaning, image ability and other social problems. This building behaves as a cultural and social symbol and it is inevitable to consider the design process as an urban experience. However many of the contemporary examples are designed as individual architectural buildings&hellip
The integration of Turkey, but especially the city of Ankara to the global economic network providing new cultural identities presents a transformation of the city which natures could be seen &ldquo
in terms of rent theory&rdquo
and makes this city &ldquo
a place of competition for profit.&rdquo
To better present these transformations one of the most important regions EskiSehir Highway will be analyzed for the power it reflects as the buildings are set on the two sides of the highway as a new type of urban architecture proceeding spontaneously and reconfiguring boundaries based on the limits of the capital. The limits economic power decides about social, economic and physical order of places shapes the city as an urban product to be sold.
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Chandler, Yuell "Chuck" E. IV. "OPERA AND THE MODERN CULTURE OF FILM: THE GENESIS OF CINEMOPERA, ITS INTERTEXTUALITY AND EXPANSION OF OPERATIC SOURCE MATERIAL." UKnowledge, 2012. http://uknowledge.uky.edu/music_etds/1.
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The boundaries of opera, as in all art forms, are constantly being re-evaluated. This analysis examines one of the most recent developments in opera-the use of film as source material, and connections to the film world- through analyzing three operas: Austrian composer, Olga Neuwirth’s opera, Lost Highway, Chinese-American composer, Tan Dun’s opera, The First Emperor, and acclaimed American film composer, Rachel Portman’s opera, The Little Prince. Each of these works exemplifies the modern relationship of opera and film in different ways. To classify these newly film-influenced works, the term cinemopera is used in describing operas connected to or influenced by film.
Analytical techniques and historical perspectives, as well as revealing how these three operas are associated with the film world through their composers, source materials, and styles are the tools utilized to establish the characteristics of cinemopera as an operatic subcategory. Also, a definition and discussion of intertextuality in these operas reveals not only their cinematic features, but their ties to common practices in music history. Lost Highway is one of the most intertextual works containing sound effects, electronic music, and drawing heavily upon the David Lynch film of the same name as its source material. The First Emperor is an interesting study in modern ethnomusicology and contains many links to film in its source material as well. The Little Prince has a different kind of intertextuality than the preceding two operas because its source material is a French children’s book. However, since its composer, Rachel Portman, is a very distinguished film composer, it represents many elements of style commonly found in cinemopera.
Finally, opera as a business is changing due to its convergence with film. The visual aspect of opera productions is of increasing importance, as is a singer’s credibility in the role they are portraying. Singers must look their parts much more so now than even two decades ago. As cinemopera is explored herein and its effects on the business are discussed, so are the elements of style which clearly serve to classify an opera as cinemopera.
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Cicek, Ceren. "Implementation Of A Hazard Rating System To The Cut Slopes Along Kizilcahamam-gerede Segment Of D750 Highway." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12610547/index.pdf.
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The purpose of this study is to implement a rock fall hazard rating system to the cut slopes along Kizilcahamam-Gerede segment of D750 (Ankara-istanbul) Highway. The rating system developed by the Tennessee Department of Transportation was assessed for thirty six cut slopes which were selected based on a reconnaissance survey along D750 highway, between Kurtbogazi Dam (50 km northwest of Ankara) and AktaS village (15 km to Gerede town of Bolu province).
The stages of the investigation consist of project conception, field investigations and application of this system, assessment and presentation of data. The cut slopes were classified by implementing this method which requires a scoring on an exponential scale assigned to various parameters related to the site and roadway geometry and geologic characteristics. The rating process was completed at two stages: Preliminary and Detailed Rating. Based on the Tennessee RHRS, nineteen cutslopes were assessed according to these two stages while the other seventeen cut slopes were able to be classified only with the preliminary rating stage. Different modes of slope failure (planar, wedge, toppling, rock fall with differential weathering, raveling) throughout the selected segments of the highway were investigated and the slope and highway related parameters such as slope height, ditch effectiveness, average vehicle risk, road width, percent desicion site distance and rockfall history were identified for these nineteen cut slopes. After the scoring process was completed all cut slopes were classified based on their hazard ratings from the point of the problems that they may cause in transportation.
According to the rules of Tennessee RHRS, a total of thirty five cut slopes were rated. Among these slopes, nineteen of them are rated as A slopes which are considered to be potentially hazardous, while a total of seven are rated as C slopes which pose no danger. In placing a slope into a B category, it is considered that they are not as prone as A slopes to create a danger and a total of nine B slopes are detected. The detailed rating is accomplished for these nineteen A slopes and as a result of the scorings, it has been seen that the final RHRS scores range from 164 to 591. The slopes with scores over 500 can be counted as more hazardous slopes since they get very high scores both from site and roadway geometry and geologic hazard part.
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Arikan, Asli Huriye. "Assessment Of Slope Stability For A Segment (km: 25+600-26+000) Of Antalya-korkuteli Highway." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612265/index.pdf.
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The cut slopes at a segment between Km 25+600 and 26+000 of the Antalya-Burdur Breakaway-Korkuteli State Road to be newly constructed have slope instability problems due to the existence of highly jointed limestone.
The purpose of this study is to investigate the engineering geological properties of the units exposed at three cut slopes, to assess stability of the cut slopes, and to recommend remedial measures for the problematic sections.
In this respect, both field and laboratory studies have been carried out. The limestone exposed at the cut slopes are beige to gray, fine grained, fossiliferous, and highly jointed. It has two joint sets and a bedding plane as main discontinuities. The kinematic analysis indicates that planar failure is expected at Km: 25+900. Limit equilibrium analysis show that the cut slopes with bench have no slope instability problems except rockfalls which endanger the traffic safety. In this thesis it is recommended to covering the cut slope with wire mesh and fibre reinforced shotcrete
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Oztekin, Burak. "Assessment Of Degradation Mechanism And Stability Of A Cut Slope In Jointed And Sheared Limestone Along Ankara-eskisehir E90 Highway." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605631/index.pdf.
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Due to rapidly growing population of Ankara city (Turkey) and traffic load, it is required to widen some of the existing highways. One of them is Ankara-EskiSehir (E-90) highway that connects highly populated areas to the city center. During widening, several cut slopes were formed along the
highway route. However, some instability problems such as small-sized rock falls and rock detachments have occurred along a cut slope in highly jointed, folded and sheared limestone. They caused local degradation of the cut slope. The cut slope has a slope angle varying from 71°to 84°
and contains several shear zones. In this study, the relationships between the existing detachment zones and various parameters (e.g. block size, point load strength index, weathering, shear zone, daylight zone) considered to be important for slope instability were investigated using GIS-based statistical landslide susceptibility analyses in order to predict the further aerial extension of the detachment zones with time. During the overlay analyses, statistical index and weighting factor methods were used by means of TNT-MIPS software. The outcomes of the analyses using both methods are compared and evaluated together with the field observations to check the reliability of the methods and to assess the detachment zones that may develop in the future. Additionally, limit equilibrium analyses were also carried out for the determination of the possible large scale mass failures. The overlay analyses indicate some risky zones where detachments are likely to occur in the future. On the other hand, the limit equilibrium analysis of the rock mass using Bishop simplified method shows that except one section no mass failure is expected in the cut slope. Suitable remediation measures which include the use of wire mesh, shotcrete, toe support, and concrete barrier blocks or catch/barrier fences are recommended for these zones.
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Domanic, Arman Kemal. "Effects Of Vertical Excitation On Seismic Performance Of Highway Bridges And Hold-down Device Requirements." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609297/index.pdf.
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ABSTRACT EFFECTS OF VERTICAL EXCITATION ON SEISMIC PERFORMANCE OF HIGHWAY BRIDGES AND HOLD-DOWN DEVICE REQUIREMENT
Domaniç, Kemal Arman M.S., Department of Civil Engineering Supervisor: Assist. Prof. Dr. Alp Caner February 2008, 152 pages Most bridge specifications ignore the contribution of vertical motion in earthquake analyses. However, vertical excitation can develop significant damage, especially at bearing locations as indeed was the case in the recent 1999 izmit Earthquake. These observations, combined with recent developments in the same direction, supplied the motivation to investigate the effects of vertical component of strong ground motion on standard highway bridges in this study. Reliability checks of hold-down device requirements per AASHTO Bridge Specifications have been conducted in this context. Six spectrum compatible accelerograms were generated and time history analyses were performed to observe the uplift at bearings. Selected case studies included precast pre-stressed I-girders with concrete slab, composite steel I-girders, post-tensioned concrete box section, and composite double steel box section. According to AASHTO specifications, hold-down devices were required in two cases, for which actual forces obtained from time history analyses have been compared with those suggested per AASHTO. The only non-linearity introduced to the analyses was at the bearing level. A discussion of effects on substructure response as well as compressive bearing forces resulting from vertical excitation is also included. The results of the study confirmed that the provisions of AASHTO governing hold-down devices are essential and reasonably accurate. On the other hand, they might be interpreted as well to be suggesting that vertical ground motion components could also be included in the load combinations supplied by AASHTO, especially to be able to estimate pier axial forces and cap beam moments accurately under combined vertical and horizontal excitations.
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Bartels, Rusty. "Transient Bodies and the Whiteness of Memory: The “Nature” of Permanence in Big Sur, CA, 1862 - 1937." Oberlin College Honors Theses / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=oberlin1274413802.
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BRANDAO, LUIZ EDUARDO TEIXEIRA. "A DISCRETE TIME APPLICATION OF REAL OPTIONS THEORY FOR THE VALUATION OF A HIGHWAY CONCESSION PROJECT IN BRAZIL." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2002. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=5120@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORUm dos problemas da avaliação por Opções Reais é a exigência de se ter mercados completos para que possam ser utilizados métodos baseados no princípio da não arbitragem para a sua solução. Outro problema é a inclusão de duas ou mais fontes de incerteza na modelagem matemática do projeto, que aumenta a complexidade do problema, especialmente quando essas incertezas envolvem risco privado, não correlacionado com o mercado. Este trabalho sintetiza conceitos aplicados a Teoria das Opções Reais desenvolvidos por diversos autores com ferramentas de Decision Analysis para propor uma metodologia de avaliação de projetos em tempo discreto utilizando algoritmo próprio aplicado a modelo de árvore de decisão com malha binomial que pode ser implementada utilizando-se programas de software padrão já existentes no mercado. O método é computacionalmente intenso, mas de modelagem mais simples e intuitiva que os métodos tradicionais de Opções Reais, permitindo assim uma maior flexibilidade na elaboração do modelo. Esta metodologia é aplicada ao problema de valoração de uma concessão rodoviária no Brasil com flexibilidade gerencial em mercados incompletos e risco político.
One of the problems of the evaluation for Real Options is the need to have complete markets so that non arbitrage methods can be used for its solution. When that is not the case, or when the determination of a dynamic portfolio of market securities that replicate the stochastic characteristics of the project is not feasible for any reason, the alternative is to use an exogenous and arbitrary discount rate. Another problem is the inclusion of two or more uncertainty sources in the mathematical modeling of the project, which brings a certain degree of complexity to the problem, especially when those uncertainties involve private risk, not correlated with the market. This work synthesizes some Real Options Theory concepts developed by several authors with Decision Analysis tools to propose a method for evaluation of projects in incomplete markets by dynamic programming using an innovative algorithm to model the project`s stochastic process with a binomial lattice and decision tree. The method is computationally intense, but simpler and more intuitive than that the traditional methods of Real Options, allowing for a greater flexibility in the modeling of the problem. This methodology is applied to the problem of the valuation a highway concession in Brazil with managerial flexibility in incomplete markets and political risk.
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OLIVEIRA, ANDRE TEIXEIRA DE MIRANDA. "GOVERNMENT GUARANTEES IN PPP PROJECTS: AN APPLICATION OF THE LPVR MODEL TO THE BR-116/324 HIGHWAY PROJECT." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2008. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=13037@1.
Full textAbstract:
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOA partir da década de 90 houve um aumento da participação do setor privado em projetos de infra-estrutura no Brasil. Esta participação deu-se principalmente por meio de concessões tradicionais regidas pela Lei das Concessões. Contudo, para tornar economicamente viáveis projetos de baixa atratividade para o setor privado devido ao seu alto risco, o governo brasileiro passou a analisar formas de redução destes riscos, como as Parcerias Público- Privadas (PPPs), incluindo a flexibilização do prazo de concessão, garantias de tráfego, de risco cambial ou até mesmo garantias de financiamento. Neste trabalho é utilizado o modelo LPVR (Menor Valor Presente das Receitas) de prazo de concessão variável aliado a uma garantia de tráfego mínimo para a avaliação do caso do projeto da rodovia BR-116/324 através da metodologia das Opções Reais. Os resultados indicam que o uso deste modelo permite uma redução dos riscos tanto para o Governo, pela limitação de ganhos excessivos da concessionária, quanto para o investidor privado, pela flexibilidade do prazo e garantia de tráfego concedida. Concluímos que o modelo LPVR associado a uma garantia de tráfego mínimo de 80% aumenta em média o VPL do projeto em mais de 60%. Embora esta garantia represente um custo adicional para o Governo, ela é compensada pelo aumento da atratividade do investimento para o setor privado.
Since the 90`s, there has been an increasing participation of the private sector in infrastructure projects in Brazil. This participation, however, took place mainly through traditional concessions, governed by the Concessions Law. However, to become economically viable projects that would not have attractiveness to the private sector due to its high risks, Brazilian government started to analyze some ways to reduce these risks such as the Public Private Partnerships (PPPs), including the term flexibility, traffic guarantee, guarantee of foreign currency risk or even assurance of funding. In this project it`s used the LPVR model (Least Present Value of Revenue) with variable period concession, ally to a minimum traffic guarantee and applying the case to the BR-116/324 highway project through the Real Options Methodology. The results show that the use of this model allows a reduction on the risks both for the government, avoiding excessive gains by the concessionaire, and for the private investor, either for the term flexibility or the guarantee of the traffic granted. So, we can conclude that the LPVR model associated with a minimum traffic guarantee of 80%, increases the VPL in an average of 60%, although this guarantee represents a further cost to the government which is compensated by the increasing attractiveness of the investment to the private sector.
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Unal, Leyla. "Modeling Of Freight Transportation On Turkish Highways." Phd thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12610783/index.pdf.
Full textAbstract:
Transportation planners are often faced with the problem of estimating passenger and freight flows between regions. In the literature there are many models for passenger flows. However, models about freight flows are more limited. Modeling freight flow is also more complex than modeling passenger flow and there are many agents related with freight flows. In addition, data availability is a critical factor. In this research, freight flows between provinces in Türkiye are forecasted by demand analysis. Transportation is one of the important activities of human beings and plays an important role for spatial interactions in economic growth. In other words, there is a very strong linkage between economic growth and the freight flow, thus transportation demand. Regional trade as spatial flow appears on transportation systems as freight flows. In this study, using the existing limited data and surveys in Tü
rkiye, nationwide origin-destination (O-D) matrix of freight flows between provinces is obtained. Using this empirical matrix, the generation of freight flows of provinces is formulated depending on the socioeconomic and demographic variables by means of multiple linear regression analysis. In addition, interactions of freight flows between provinces and economic growth of regions are investigated. The generations and attractions of provinces as freight flow are distributed between provinces with traditional gravity model. By comparing observed O-D matrix and simulated O-D matrix, gravity model is calibrated. Calibration is also performed by freight trip length distribution. In this research, two steps of traditional &ldquo
four-step analysis&rdquo
, &ldquo
trip generation&rdquo
and &ldquo
trip distribution&rdquo
, are applied to develop nationwide freight demand model between the provinces in Tü
rkiye. The developed model is single-mode, single commodity and nationwide.
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Freitas, Andrea Karla Breunig de. "ESTRESSE, COPING E SÍNDROME DE BURNOUT EM POLICIAIS RODOVIÁRIOS FEDERAIS." Universidade Federal de Santa Maria, 2013. http://repositorio.ufsm.br/handle/1/8309.
Full textAbstract:
The profession of the Federal Highway Police is considered one of the most stressful professions. It is a profession of risk by the nature of their functions, which are faced with in their daily practice, in extreme situations, where the emotional resources are put on test. These situations raise the level of stress and when not addressed adequately may lead to burnout. The present study aims to contribute to a deeper knowledge of these professionals, in order to evaluate the perception of job stress, which coping strategies that people adopt to minimize this stress in order not to reach burnout. This is a field study, descriptive, exploratory quantitative approach. The research involved the identification and characterization of the subjects from a questionnaire as well as the application of socio-demographic form. The study population was composed of the Federal Highway Police Central region of Rio Grande do Sul. The results obtained from statistical analysis were 73.08 % in high stress and low stress at 26.92 % , the most used strategies were problem solving and indicative of burnout syndrome in this population was 3.84% . Thus , it is understood that the importance of this work lies in the fact that with your participation will be helping to spread awareness about this job category , which could result in better working conditions and respect for health.A profissão de Policial Rodoviário Federal é considerada uma das profissões de maior estresse. Trata-se de uma profissão de risco pela natureza de suas funções, onde são confrontadas na sua prática diária, com situações limite, onde os recursos emocionais são postos a prova. Estas situações elevam o nível de estresse e quando não enfrentadas de forma adequada podem levar ao Burnout. O presente estudo tem como propósito contribuir para um conhecimento mais aprofundado destes profissionais, com o intuito de avaliar a percepção de estresse no trabalho, quais as estratégias de enfrentamento que esta população adota para minimizar este estresse a fim de não atingirem o burnout. Trata-se de um estudo de campo, descritivo, exploratório com abordagem quantitativa. A pesquisa consistiu na identificação e caracterização dos sujeitos a partir de um questionário, bem como da aplicação do Formulário sócio demográfico. A população do estudo foi composta por Policiais Rodoviários Federais da região Central do Estado do Rio Grande do Sul. Os resultados obtidos através da análise estatística foram de 73,08% em alto estresse e 26,92% em baixo estresse, as estratégias mais utilizadas foram à resolução de problemas e os indicativos da Síndrome de Burnout nesta população foram de 3,84%. Deste modo, entende-se que a importância deste trabalho está no fato de que com a sua participação estarão contribuindo para difundir o conhecimento acerca desta categoria profissional, o que poderá acarretar em melhores condições de trabalho e respeito à saúde.
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Rehn, Matilda. "Do the citizens matter? : A study of citizen participation during the planning process of the extension of state highway 1 - Puhoi to Wellsford, Auckland, New Zealand." Thesis, Uppsala universitet, Kulturgeografiska institutionen, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-192985.
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Tapkin, Serkan. "A Recommended Neural Trip Distributon Model." Phd thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/3/663807/index.pdf.
Full textAbstract:
In this dissertation, it is aimed to develop an approach for the trip distribution
element which is one of the important phases of four-step travel demand modelling.
The trip distribution problem using back-propagation artificial neural networks has
been researched in a limited number of studies and, in a critically evaluated study it
has been concluded that the artificial neural networks underperform when compared
to the traditional models. The underperformance of back-propagation artificial
neural networks appears to be due to the thresholding the linearly combined inputs
from the input layer in the hidden layer as well as thresholding the linearly combined
outputs from the hidden layer in the output layer. In the proposed neural trip
distribution model, it is attempted not to threshold the linearly combined outputs
from the hidden layer in the output layer. Thus, in this approach, linearly combined
iv
inputs are activated in the hidden layer as in most neural networks and the neuron in
the output layer is used as a summation unit in contrast to other neural networks.
When this developed neural trip distribution model is compared with various
approaches as modular, gravity and back-propagation neural models, it has been
found that reliable trip distribution predictions are obtained.
22
Rickardsson, Johan. "A Study of Traffic Capacity with Regards to Heavy vehicle Share and Level of Service through Microsimulation." Thesis, KTH, Transportplanering, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-302528.
Full textAbstract:
The 2+1-road is a specific three lane road which aims to increase the safety of the predecessor 13 meter wide four lane roads. As a lane is removed and a weaving section is introduced the capacity is severely lowered, sometimes halved. A very demanding part of the traffic system with regards to capacity are heavy vehicles, especially in conjunction with the 2+1-roads. However, exactly how the share of heavy vehicles impacts the traffic system with regards to 2+1 roads and freeways is not previously studied, which grants the opportunity of this work. The work has been carried out in connection with an assignment from The Swedish Transport Administration of analyzing the E4 going north from Gävle. This study analyzes how the share of heavy vehicles and level of service affect the speed on the two types of roads. The Swedish Transport Administration currently bases their current relationships on speed, capacity, and level of service on a share of heavy vehicles of 12%, which may give slightly wrong results depending on which system is being analyzed. The study has been carried out through micro simulation, which is a method that is very dependent on what data it is given, such as behavioral parameters and other input. The results of the study show how the relationship between share of heavy vehicles and level of service affect the speed, and that the 2+1-roads are highly dependent on the share of heavy vehicles, whereas the freeways have much larger tolerances.Den mötesfria vägen (s.k. 2+1-väg) tillkom på 90-talet och gav upphov till mycket mer trafiksäkra vägar än sina föregångare 13-metersvägarna från mitten av 1900-talet. Till följd av säkerhetsökningen kom uppoffringar i kapacitet i och med vävningssträckor, som mer än halverar kapaciteten i jämförelse med en tvåfilig väg. En mycket kapacitetskrävande del av trafiksystemet är lastbilar, framförallt i dessa vävningssträckor. Men exakt hur lastbilsandelar påverkar systemet är inte riktigt bearbetat än, vilket ger upphov till detta examensarbete. Studien har utförts i samband med ett uppdrag från Trafikverket angående simulering av E4:an norr om Gävle. Detta examensarbete granskar alltså hur lastbilsandelen och belastningsgraden påverkar punkthastigheten på de två vägtyperna mötesfri väg och motorväg. Trafikverket baserar sina effektsamband på en lastbilsandel på 12 %, vilket kan ge både för låga och för höga värden beroende på vilken plats som man granskar. Arbetet har genomförts med hjälp av mikrosimuleringsmodeller, vilka är mycket beroende av vilka parametrar och indata de får. Resultatet av studien visar hur punkthastigheten beror på lastbilsandel och belastningsgrad, och visar på att de mötesfria vägarna är mycket beroende av lastbilsandelen, medan motorvägar har betydligt större tolerans.
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Zhang, Qinghe. "Development of skew correction factors for live load shear and reaction distribution in highway bridge design a dissertation presented to the faculty of the Graduate School, Tennessee Technological University /." Click to access online, 2009. http://proquest.umi.com/pqdweb?index=0&did=1707210441&SrchMode=1&sid=2&Fmt=6&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1268938179&clientId=28564.
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Wei, Xin 1971. "HIV-1 reverse transcription initiation : impact of A-rich loop deletion and M184V substitution and development of novel antiretroviral strategies." Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=84447.
Full textAbstract:
Reverse transcription of human immunodeficiency virus type-1 (HIV-1) is primed by cellular tRNALys3, which is selectively packaged into viral particles where it is bound at its 3' terminus to a complementary sequence of viral RNA termed the primer binding site (PBS). In addition to the PBS, other regions within the viral genome also interact with tRNALys3. Initiation of HIV-1 reverse transcription requires specific recognition of the viral genome, tRNA primer, and reverse transcriptase (RT). In this work, we study the important role played by the initiation complex in the initiation of HIV-1 reverse transcription. An "A-rich loop" located upstream of the PBS has been shown to interact with the anticodon loop of tRNALys3 and deletion of this A-rich loop caused diminished viral replication fitness. We have now studied the mechanisms involved in the altered replication capacities of the deletion-containing viruses in the context of both wild type HIV-1 and viruses also containing the M184V substitution in RT. We found that the M184V mutation in RT compromises the ability of deletion-containing viruses to restore wild-type replication. Further biochemical study indicates that both the M184V mutation in RT and deletion of sequences upstream of PBS caused diminished viral replication fitness by compromising the efficiency of reverse transcription initiation.Since the initiation of DNA synthesis was shown to be a highly specific process, it represents a potential target for the development of novel antiviral agents. We developed strategies for inhibition of the HIV-1 replication via interference with the tRNALys3/viral RNA complex. To target primer tRNALys3, we employed oligodeoxyribonucleotides (ODNs) that are complementary to different parts of the tRNA primer. To target viral RNA, we devised a tRNALys3-like molecule, termed tRNA Lys*, that contained sequence alterations that direct initiation from a region distant from the natural PBS, designated PBS*. PBS* is involved in the formation of the natural tRNA/PBS complex and binding of tRNALys* was shown to interfere specifically with the initiation of reverse transcription. Inhibition of the synthesis of (-) strand strong-stop DNA was achieved successfully with both strategies by interfering with the formation of the initiation complex.
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Speelmon, Emily. "Innate mechanisms of HIV-1 protection in highly exposed, seronegative individuals /." Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/4998.
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Rahman, Syeda Sharmin. "Measurement and characterization of HIV inhibitory Clade A Serpins in the cervical mucosa of highly HIV-1 exposed seronegative individuals." American Chemical Society (ACS) Publications, 2011. http://hdl.handle.net/1993/5065.
Full textAbstract:
Objective: Serpins are serine protease inhibitors that are involved in a wide variety of biological functions in nature. They are known to regulate inflammation processes as well as provide host defense against microorganisms. Recent evidence has associated many types of mucosal serpins with a protective phenotype against HIV infection in women. Our hypothesis is that serpins with known antiviral activity against HIV-1 are correlated with protection in a group of HIV exposed seronegative individuals (HIV-resistant) from the Pumwani sex worker cohort. Study design: Cervico-vaginal lavage (CVL) fluid was collected from 66 HIV-positive, 82 HIV-negative and 84 HIV-resistant sex workers from the cohort. Clinical and epidemiological information was recorded at the time of sample collection. CVL protein levels were determined by BCA assay and serpin (A1 and A3) concentrations by a commercially available ELISA kit. Mucosal serpin concentrations were compared against clinical and epidemiological factors as well as sexual practices. Results: Serpin A1 was significantly higher in the HIV-resistant group compared to the HIV-negative controls (Anova: p=0.0470*). Total concentration of serpin A3 did not reach statistical significance between groups. Serpins did not correlate with age, sexual practices, contraceptive use or number of pregnancies. Serpins were differentially abundant during different stages of the menstrual cycle whereas serpin A1 was elevated during the proliferation phase but not in secretory phase (p=0.0275*).
Conclusion: Serpin A1 was correlated with HIV-protection in this group of HESN women. This work will contribute to a more complete understanding of mechanisms of resistance and susceptibility to HIV infection.
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Egerton, Jack Samuel. "Ultrasonic inspection of highly attenuating media." Thesis, Imperial College London, 2018. http://hdl.handle.net/10044/1/62627.
Full textAbstract:
The aim of the project was to improve the ultrasonic array inspection of high-density polyethylene (HDPE) heat-fused pipe joints of cooling water pipework that is installed in EDF Energy's nuclear power stations. Whereas ultrasound array inspection is now established for safety-critical metal components, HDPE poses a hugely challenging problem, that the ultrasound waves are heavily attenuated by the material. This impacts multiple aspects of the inspection and of the modelling that is needed to design and qualify inspection. The thesis reports a range of research that was needed to overcome this challenge. The work of the thesis has: - obtained accurate acoustic properties of HDPE that are necessary for improved simulated or real ultrasonic array imaging of HDPE pipe joints - developed a simulation technique for representing ultrasound in such inspections that has both high accuracy and efficiency - extended analytical analysis of ultrasound scattering from cylindrical voids from elastic media to general, attenuative media - used the Huygens-Fresnel principle to represent ultrasound scattering from volumetric and planar voids, to image sub-wavelength features of these defects in an ideal circular array setup, and to image angled ultrasonic array nondestructive evaluation (NDE) of potential defects occurring in HDPE pipe joints - devised an automated and antidispersive system for reducing coherent and incoherent noise in waveforms with an isolated wave reflection signal - produced an imaging and analysis method for ultrasonic array NDE that can represent defects in a refractive, reflective, and scattering environment in attenuating media, which is applied to data from the above developed simulation technique - applied much of the above imaging and analysis method to defects machined into HDPE pipe material, with an experimental ultrasonic array controller, yet with an array of limited suitability - specified parameters for ultrasonic arrays and a water-filled wedge, which are optimum for HDPE pipe joint inspection, and have been designed and built by Imasonic SAS, France, for research use at Imperial College London.
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Van, Pamel Anton. "Ultrasonic inspection of highly scattering materials." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/29423.
Full textAbstract:
Ultrasonic Non-Destructive Evaluation (NDE) relies on the scattering of waves from discontinuities, such as fractures or voids, to probe media otherwise invisible to the naked eye. Whilst this has been industrially exploited for several decades within acoustically transparent materials, many materials maintain a microstructure that causes scattering of the propagating waves. This undermines the aforementioned premise as it becomes exceedingly difficult to discern the features of interest from the scattering inherent to microstructural features, thereby limiting the range of materials which can be reliably inspected, non-destructively. Experimental investigations confirm the challenges and significant shortcomings for the inspection of future industrial components where such microstructures are desirable for their mechanical properties. It is demonstrated that the rapid increases in scattering with the insonifying frequency severely limit the achievable sensitivity of conventional ultrasound techniques. A review of the latest advances in ultrasound technology, including signal processing and imaging algorithms, explore the opportunities to exceed current limitations and advance the capability of ultrasonic NDE. Establishing these advances, and those of future approaches, requires a rigorous definition of performance. In contrast to commonly adopted strategies, a novel strategy which considers the probabilities of detection and false alarms is proposed as a valuable benchmark that can be used to make objective comparisons in terms of performance between competing algorithms. Future progress will also rely on a better scientific understanding of scattering, which can be provided by powerful modelling tools. Here, Finite Element modelling is established to be very useful; it captures the complex scattering physics and allows an investigative flexibility which can provide extremely useful insights. Whereas previous studies have often been restricted to weak scattering assumptions, the present FE modelling capability now enables the study of more complex, highly scattering environments. This is demonstrated by investigating ultrasonic arrays, where through optimising their engineering, especially in terms of their configuration, significant performance enhancements are shown to be possible. These important scientific tools have enabled the assessment of the latest imaging algorithms, the optimisation of inspection configurations, and increased our understanding of scattering phenomena. Their use in the future enables wide possibilities towards further pursuing the ultrasonic inspection of highly scattering materials.
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Yilmaz, Aylin. "Antiretroviral treatment of HIV-1 in the central nervous system /." Göteborg : Department of Infectious Diseases, The Sahlgrenska Academy at Göteborg University, 2007. http://hdl.handle.net/2077/4438.
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Paina, Federica. "De novo synthesis of highly substituted pyridines." Thesis, Imperial College London, 2008. http://hdl.handle.net/10044/1/1243.
Full textAbstract:
This thesis is divided into three chapters. Chapter 1 provides a brief survey of the methodologies currently available for the de novo synthesis of cyclopentadienes. Particular relevance is given to the more general methods and to the preparation of structurally interesting compounds. Mechanistic details will also be given for interesting or unusual reaction pathways. Chapter 2 presents research findings in the field of the application of the decarboxylative Claisen rearrangement (dCr) reaction to the synthesis of aromatics. The development of a novel methodology for the preparation of substituted pyridines will be described. Firstly, the feasibility of the method will be shown by detailing the preparation of simple pyridines, carrying alkyl and aryl substituents. Subsequently, efforts to expand the scope of the methodology will be discussed and attempts to prepare diversely substituted, chiral and cyclofused compounds detailed. Finally, some preliminary results concerning the use of the dCr reaction for the synthesis of cyclopentadienes and cyclopentadienyl anions will be presented. Chapter 3 provides the experimental details and the characterisation data for all the compounds synthesised.
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Hejdeman, Bo. "Studies on medical and immunological interventions in HIV-1 infection /." Stockholm, 2004. http://diss.kib.ki.se/2004/91-7140-019-2/.
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Schreiner, Hilson Deneys. "Volume change of compacted highly plastic African clays." Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/47643.
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Behbahani, Homira. "Immune dysregulation in HIV-1 infected lymphoid tissue /." Stockholm, 2002. http://diss.kib.ki.se/2002/91-7349-193-4.
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Guled, Fatuma Hassan. "Characterisation of functional properties of Envelopes of highly neutralisation resistant HIV-1 isolates." Master's thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/29293.
Full textAbstract:
An effective antibody-based HIV-1 vaccine would ideally elicit potent antibodies capable of neutralising a wide range of HIV-1 isolates to better cover the human population. A primary concern is the virus’ ability to rapidly escape an antibody response. A strong neutralising response elicited by a vaccine may, in principle, select for viruses that are highly antibody resistant thereby significantly reducing the benefit of a vaccine. It is therefore important to study and better understand highly neutralisation resistant viruses. To this effect, we characterized sets of subtype C and CRF02_AG viruses whose neutralisation phenotype were well defined using within subtype neutralisation (neutralisation by subtype matched sera). Our main aim was to determine if there exists a relationship between neutralisation resistance and entry efficiency. Very highly neutralisation resistant viruses appear under-represented in the population. We hypothesised that this may be at least partially explained by decreased entry efficiency as changes to Envelope (Env) during escape could affect the entry process and provide opposing selective pressure that discourages the appearance of very highly neutralisation-resistant viruses. By comparing entry efficiencies of tier 3 viruses (highly resistant) to tier 2 (moderately resistant) and 1B (sensitive), we observed that the tier 3 viruses generally exhibited higher entry efficiency. This was the opposed of what we hypothesised at the outset of these experiments. We also measured characteristics of resistant HIV-1 Envs that can be inferred from the primary sequence such as the variable loop lengths, number of glycans and net charge. We found that the V2 net charge and the V5 loop length were associated with neutralisation resistance in subtype C viruses and the V2 loop length was associated with resistance in the CRF02_AG viruses. By analysing glycosylation patterns between the groups, we found that the presence of an N-linked glycan at position 413 and the lack of a glycan at N332 were predictors of neutralisation resistance in subtype C viruses. Tier 3 viruses were also more resistant than tier 2 and 1B viruses to the PGT121 (V3/glycan), 4E10 (MPER) and the CD4 binding site broadly neutralising antibodies VRC01 and 3BNC117; suggesting that the epitopes of these antibodies are important for driving resistance. Furthermore, we found no significant relationship between susceptibility to the entry inhibitors Maraviroc and PSC RANTES (CCR5 antagonists) and the fusion inhibitor T20 and resistance, indicating that neutralisation resistance did not alter inhibitor target sites. Based on our findings, it is clear that reduced entry efficiency does not explain why highly resistant viruses are not more common. We may speculate that the evolutionary steps needed to reach very high neutralisation resistance may be difficult to go through and/or that other countervailing selective pressures may be involved. In the context of an antibody based intervention, highly resistant viruses with increased entry efficiency circulating in the population could be a set back in the control of the HIV-1 epidemic. Therefore, for any long-term antibody-based intervention to be globally relevant it must elicit responses that limit occurrence of resistance and also increase chances that escape would lead to severely impaired viral fitness.
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Luo, Jian Yang. "Calculation of turbulent shear layers over highly curved surfaces." Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/11500.
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Wilkinson, Christian Marco Raymond. "The durability of highly loaded, case hardened steel gears." Thesis, Imperial College London, 1998. http://hdl.handle.net/10044/1/8725.
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Gao, Kun. "Highly Mismatched GaAs(1-x)N(x) and Ge(1-x)Sn(x) Alloys Prepared by Ion Implantation and Ultrashort Annealing." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-158921.
Full textAbstract:
Doping allows us to modify semiconductor materials for desired properties such as conductivity, bandgap, and / or lattice parameter. A small portion replacement of the highly mismatched isoelectronic dopants with the host atoms of a semiconductor can result in drastic variation of its structural, optical, and / or electronic properties. Here, the term "mismatch" describes the properties of atom size, ionicity, and / or electronegativity. This thesis presents the fabrication of two kinds of highly mismatched semiconductor alloys, i.e., Ge(1-x)Sn(x) and GaAs(1-x)N(x). The structural and optical properties of the prepared Ge(1-x)Sn(x) and GaAs(1-x)N(x) have been investigated. The results suggest an efficient above-solubility doping induced by non-equilibrium methods of ion implantation and ultrashort annealing. Pulsed laser melting promotes the regrowth of monocrystalline Ge(1-x)Sn(x), whereas flash lamp annealing brings about the formation of high quality GaAs(1-x)N(x) with room temperature photoluminescence. The bandgap modification of Ge(1-x)Sn(x) and GaAs(1-x)N(x) has been verified by optical measurements of spectroscopic ellipsometry and photoluminescence, respectively. In addition, effective defect engineering in GaAs has been achieved by flash lamp annealing, by which a quasi-temperature-stable photoluminescence at 1.3 µm has been obtainedDotierung ermöglicht es, die Eigenschaften von Halbleitermaterialien, wie Leitfähigkeit, aber auch Bandabstand und / oder Gitterkonstanten gezielt zu verändern. Wenn ein Halbleiter mit einer kleinen Menge unterschiedliche Fremdatome dotiert wird, kann dies in einer drastischen Modifikation der strukturellen, optischen und / oder elektronischen Eigenschaften resultieren. Der Begriff "unterschiedlich" bedeutet hier die Eigenschaften von Atomgröße, Ioniztät und / oder Elektronegativität. Diese Doktorarbeit beschreibt die Herstellung von zwei Arten von stark fehlangepassten Halbleiterlegierungen: Ge(1-x)Sn(x) und GaAs(1-x)N(x). Die strukturellen und optischen Eigenschaften von Ge(1-x)Sn(x) und GaAs(1-x)N(x) wurden untersucht. Die Ergebnisse deuten auf eine effiziente Dotierung oberhalb der Löslichkeit, induziert durch die Nicht-Gleichgewichtsverfahren Ionenimplantation und Ultrakurzzeit-Ausheilung. Gepulstes Laserschmelzen ermöglicht das Nachwachsen von monokristallinem Ge(1-x)Sn(x), während die Blitzlampenausheilung in der Bildung von GaAs(1-x)N(x) hoher Qualität mit Photolumineszenz bei Raumtemperatur resultiert. Die Änderung der Bandlücke von Ge(1-x)Sn(x) und GaAs(1-x)N(x) wurde durch die optischen Methoden der spektroskopischen Ellipsometrie und Photolumineszenz verifiziert. Darüber hinaus konnte in ausgeheiltem GaAs eine quasi-temperaturstabile Photolumineszenz bei 1,3 µm beobachtet werden
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Testa, Maria Rita. "Will highly educated women have more children in the future?" Verlag der Österreichischen Akademie der Wissenschaften, 2017. http://epub.wu.ac.at/6314/1/040_Testa.pdf.
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"Will highly educated women have more children in the future?" In this contribution,
I address this question by looking at both fertility and fertility intentions; i.e., the
number of children people plan to have over their reproductive lives. Intended births are highly correlated with actual births, and in low-fertility settings, childbearing has become associated with the couple's agency.
On the other hand, education, which is a marker of income and social status, has remained an important driver of fertility choices. Hence, understanding the reproductive decision-making of women and men with low, medium, and high levels of education is crucial when seeking to determine whether - and if so, to what extent - there is scope for additional policy interventions aimed at raising fertility levels.
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Abidat, Miloud. "Design and testing of a highly loaded mixed flow turbine." Thesis, Imperial College London, 1991. http://hdl.handle.net/10044/1/40057.
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A method of designing a new generation of highly loaded mixed flow turbines for turbocharger application is described. A review of the published work concerning radial turbines and closely related to mixed flow turbines is presented. A 1-D design method was developed. It is used to define the over all turbine dimensions and to analyse its performance at the off design conditions. The method is applicable to both radial and mixed flow turbines. A series of designs had been produced and then analysed by the off design performance prediction method. The effects of several geometrical parameters on the performance of the designs were investigated. This had led to the selection of an optimum rotor design for further analysis. An analytical method based on the Bezier polynomials is used to define the three dimensional blade geometry . The rotor geometry is optimised by means of a quasi three-dimensional method for the flow analysis. The effect on the flow inside the rotor of three factors influencing the blade geo metry has been investigated. These consist of the rotor blade angle variation along the leading edge, the rotor length and the blade curvature. Two mixed flow turbine prototype s have been manufactured and experimentally tested. These differ mainly in the rotor inlet, which is a constant blade angle in one case, and a notionally constant incide nce ang le at design conditions in the other case. The former turbine showed significantly higher efficiencies across the operating range, and possible reasons for this are discussed. The experimental analysis concerns the measurement of the turbine overall performance, the pressure distribution along the rotor shroud and the flow field downstream of the rotor exit.
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Kim, Youngkyoo. "Organic solar cells based on highly self-organizing semiconducting polymers." Thesis, Imperial College London, 2006. http://hdl.handle.net/10044/1/49917.
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In this thesis I have studied organic solar cells (photovoltaic devices) based on a highly self-organizing polymer, regioregular poly(3-hexyIthiophene) (P3HT), because of its particular crystallization tendency leading to high charge carrier mobilities, good light-harvesting in red parts, and suitable energy band structure for an electron-donor. Prior to organic solar cell study, the pristine P3HT films have been investigated to understand their optical/electrical property and nanocrystal structure changes upon thermal annealing. As an electron-acceptor for organic solar cells, two candidates were employed: One is polymer [poly(poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT)), another is big small molecule [[6,6]-phenyl Cgi-butyric acid methyl ester (PCBM)]. The kinds of blends used for organic solar cell fabrication were P3HT:F8BT, P3HT:PCBM, and P3HT:PCBM:F8BT. Organic solar cells were fabricated by spin-coating these blend films onto transparent conductive oxide coated substrates followed by depositing metal electrodes (sometimes inserting LiF). For better understanding of device performance changes, blend films have been examined with optical absorption, photoluminescence including time-resloved system, normal reflection mode x-ray diffraction, grazing incidence x-ray diffraction (Synchrotron), atomic force microscopy, scanning electron microscopy, high resolution transmission electron microscopy with field emission gun, transient absorption spectroscopy, and time-of-flight mobility measurement. As a result, P3HT:F8BT solar cells (maximum external quantum efficiency=~3%) showed poorer efficiency than P3HT:PCBM solar cells (maximum external quantum efficiency=~73%), though both blends have P3HT components, which is attributed to the low electron mobility of F8BT compared to PCBM. The power conversion efficiency of P3HT:PCBM solar cells has reached 4.4-5.5% at 85~8.5mW/cm^ (air mass 1.5 simulated solar illumination), which is ascribed mainly to the formation of vertical phase segregation upon thermal annealing leading to pseudo layered p-n junction. This layered structure might reduce the charge recombination between P3HT positive polaron (radical cation) and PCBM negative polaron (radical anion), a parameter that has been quantitatively analysed using a new model proposed in this work.
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Paraskevopoulou, Sivylla. "Resource-efficient algorithms and circuits for highly-scalable BMI channel architectures." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/18676.
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The study of the human brain has for long fascinated mankind. This organ that controls all cognitive processes and physical actions remains, to this day, among the least understood biological systems. Several billions of neurons form intricate interconnected networks communicating information through through complex electrochemical activities. Electrode arrays, such as for EEG, ECoG, and MEAs (microelectrode arrays), have enabled the observation of neural activity through recording of these electrical signals for both investigative and clinical applications. Although MEAs are widely considered the most invasive such method for recording, they do however provide highest resolution (both spatially and temporally). Due to close proximity, each microelectrode can pick up spiking activity from multiple neurons. This thesis focuses on the design and implementation of novel circuits and systems suitable for high channel count implantable neural interfaces. Implantability poses stringent requirements on the design, such as ultra-low power, small silicon footprint, reduced communication bandwidth and high efficiency to avoid information loss. The information extraction chain typically involves signal amplification and conditioning, spike detection, and spike sorting to determine the spatial and time firing pattern of each neuron. This thesis first provides a background to the origin and basic electrophysiology of these biopotential signals followed by a thorough review of the relevant state-of-the circuits and systems for facilitating the neural interface. Within this context, novel front-end circuits are presented for achieving resource-constrained biopotential amplification whilst additionally considering the signal dynamics and realistic requirements for effective classification. Specifically, it is shown how a band-limited biopotential amplifier can reduce power requirements without compromising detectability. Furthermore through the development of a novel automatic gain control for neural spike recording, the dynamic range of the signal in subsequent processing blocks can be maintained in multichannel systems. This is particularly effective if now considering systems that no longer requiring independent tuning of amplification gains for each individual channel. This also alleviates the common requirement to over-spec the resolution in data conversion therefore saving power, area and data capacity. Dealing with basic spike detection and feature extraction, a novel circuit for maxima detection is presented for identifying and signalling the onset of spike peaks and troughs. This is then combined with a novel non-linear energy operator (NEO) preprocessor and applied to spike detection. This again contributes to the general theme of achieving a calibration-free multi-channel system that is signal-driven and adaptive. Another original contribution herein includes a spike rate encoder circuit suitable for applications that are not are not affected by providing multi-unit responses. Finally, spike sorting (feature extraction and clustering) is examined. A new method for feature extraction is proposed based on utilising the extrema of the first and second derivatives of the signal. It is shown that this provides an extremely resource-efficient metric than can achieve noise immunity than other methods of comparable complexity. Furthermore, a novel unsupervised clustering method is proposed which adaptively determines the number of clusters and assigns incoming spikes to appropriate cluster on-the-fly. In addition to high accuracy achieved by the combination of these methods for spike sorting, a major advantage is their low-computational complexity that renders them readily implementable in low-power hardware.
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Manning, Susan Diane. "Ion channels in highly purified human platelet surface and intracellular membranes." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/46431.
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Yoon, Hong. "Highly localised surface plasmon polaritons in active metallo-organic multilayer structures." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/9768.
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Amplification of surface plasmon polaritons in plasmonic systems have been of great interest for realizing active nanophotonic devices. In this thesis, we present a study about optical gain of SPPs supported in planar metallo-organic multilayer structures based on the Kretchmann geometry. First, we present the effect of varying the geometry on behaviours of surface plasmon propagation, which appear as the change of angular reflectivity. A theoretical approach explains the characteristics well. A kind of conjugated polymer material is introduced to the structures for obtaining gain. A film of this material with nanometer thickness is attached close to a metallic layer, being optically excited to supply energy. For understanding the interaction between surface plasmon polaritons and the active films, we experimentally investigate energy transfer channels from the active material to surface plasmons with an aid of a theoretical analysis. This result provides a strong evidence of being capable of exciting surface plasmon polaritons via dipole excitation. We also report an experimental demonstration of optical gain properties in conventional waveguide structures where the active material acts as propagating channel by measuring amplified spontaneous emission phenomena, providing information of achievable optical gain. Based on the strong evidences of both the active and passive properties, we demonstrate plasmonic gain in the structure incorporating the polymer film for the first time. For this, a double lock-in amplifier system is introduced. Plasmonic modal gain is explained with a support of theoretical estimates. The achieved modal gain is 9 cm-1. This work suggests the design principle for active nano plasmonic devices.
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Cwik, Tomasz. "Highly instrumented static, dynamic, and impact testing of high performance materials." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/29364.
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This thesis presents an investigation into potential improvements in the ballistic performance of high performance composite materials by hybridizing them with other polymer materials. The main focus is on extraction of quantitative information from ballistic trials with armour grade composite materials. The primary goal of the research in this thesis is to understand the behaviour of high performance composites and polymer materials during ballistic impact events. To design a novel hybrid composite material system, an in-depth knowledge of the hybrid material constituents must be gained. The research performed to meet this objective is presented in this thesis and is divided into four main parts, preceded by a literature review of these topics (Chapter 2). It is believed that the ballistic performance of armour grade composite materials is dependent to a certain extent on the tensile properties of the reinforcement phase (i.e. fibres). Therefore, the first part of the thesis (Chapter 3) presents an evaluation of the static tensile yarn performance of 16 different high tenacity fibres. The goal of part two of the research was to evaluate dynamic properties of the same fibres in dynamic conditions by means of a tensile split Hopkinson bar. Chapter 4 presents conclusions from the experiments employing standard Hopkinson pressure bar for fibre testing. The third part of the thesis (Chapter 5) focuses on the evaluation of the ballistic performance of various materials which could be utilized in a hybrid armour system. A highly instrumented ballistic setup was established to measure armour deformation characteristics during the impact event. The measured ballistic data allowed the derivation of the ballistic limit of each material system and for a relative comparison of the ballistic performance between the different material systems and their applicability as an armour. The damage within the ballistic panels were further investigated using Computed Tomography and Computed Laminography scans. The final part of this thesis (Chapter 6) presents studies dedicated to the design of novel material systems of improved ballistic performance. A wide range of hybrids were investigated and conclusions drawn on the optimum route to improve the ballistic limit of a polymer amour system.
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Lindström, Anna. "Resistance to antiviral drugs in HIV and HBV /." Stockholm, 2005. http://diss.kib.ki.se/2005/91-7140-239-X/.
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Chiarandini, Marco. "Stochastic Local Search Methods for Highly Constrained Combinatorial Optimisation Problems." Phd thesis, [S.l. : s.n.], 2005. https://tuprints.ulb.tu-darmstadt.de/595/1/ChiarandiniPhD.pdf.
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Graph colouring is a combinatorial optimisation problem consisting in colouring the vertices of a graph such that no vertices connected by an edge receive the same colour. The minimal number of colours for which such a colouring exists is an intrinsic property of the graph and is called chromatic number. Many real life situations, such as the frequency assignment in mobile networks or the scheduling of courses at a university, can be modelled in this way. Colouring planar graphs, such as maps can be easy, and four colours suffice, but real life systems are much more complex. When modelled by graph colouring, they entail general graphs of large size and include more sophisticated constraints than those representable by simple unweighted edges. Stochastic Local Search (SLS) methods are approximate techniques for efficiently solving these complex combinatorial optimisation problems. They typically consist of construction algorithms, iterative improvement algorithms, and meta-components, better known as metaheuristics. The first two are strongly problem dependent and require the exploitation of problem-specific knowledge, while the last are more general concepts to guide the first two components. The instantiation of SLS algorithms arises from the combination of concrete algorithmic components. This task is complex due to the many possible combinations and the need of determining a certain number of parameters. Empirical tests become then necessary to take the correct decisions. The starting point of this work is the definition of the statistical methods that are appropriate for the analysis of SLS algorithms. We argue that the assumptions for the application of parametric tests are often violated and opt for two alternative methods: permutation and rank-based tests. Our work contributes to the development of permutation tests and to their introduction in the analysis of SLS algorithms. In addition, we transfer a graphical representation of results through simultaneous confidence intervals from the parametric to the non-parametric cases. This representation has the advantage of conveying in one single graph both descriptive and inferential statistics. The developed statistical methods serve for the analysis of SLS algorithms on the graph colouring problem and one of its many possible generalisations, the set T-colouring problem. Several SLS algorithms have been proposed in the literature for the graph colouring problem but no ``unbiased'' comparison has been attempted. A similar situation holds for the set T-colouring problem. In both cases, we design new algorithms, re-implement the most prominent methods, and finally compare them in a rigorous experimental analysis. As the final step, we study SLS algorithms for solving a university course timetabling problem. The design of algorithm components stems from the knowledge gained on the graph colouring problems but the assemblage and configuration of these components is carried out with a systematic methodology. The focus in this context was on the selection of one single algorithm to submit to an algorithm competition. The methodology is presented as an engineering process characterised by the interaction of SLS components design and empirical tests. We deem that this methodological approach is appropriate for the application of SLS methods to complex real life problems. The main results are the following: on the graph colouring problem, the simple Tabu Search with one-exchange neighbourhood remains a very competitive approach and the use of a very large scale neighbourhood is not profitable; on the set T-colouring problem, the best overall algorithm is an Adaptive Iterated Greedy also based on Tabu Search with one-exchange neighbourhood which, under certain circumstances, can be further improved by a restricted exact reassignment of colours; the use of an engineering methodology based on sequential testing is particularly suitable for the application of SLS methods, as it led us to devise the algorithm whose solutions for course timetabling ranked the best out of 24 feasible submissions at the International Timetabling Competition held in 2003.
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Nieuwkerk, Pythia Tjitske. "Highly active antiretroviral therapy for HIV-1 infection: patients' quality of life and treatment adherence." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2006. http://dare.uva.nl/document/89610.
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Dean, Nolan Edward. "Metal ion complexing properties of the highly preorganized ligand 1, 10-phenanthroline-2,9-dicarboxylic acid /." Electronic version (PDF), 2007. http://dl.uncw.edu/etd/2007-3/deann/nolandean.pdf.
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Ingleson, Michael James. "Transition metal complexes partnered with the highly alkylated carborane anion, [1-H-CLOSO-CB₁₁Me₁₁]⁻." Thesis, University of Bath, 2004. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.403685.
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Harada, Tomika. "Membrane-type matrix metalloproteinase-1(MT1-MMP) gene is overexpressed in highly invasive hepatocellular carcinomas." Kyoto University, 1999. http://hdl.handle.net/2433/181703.
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