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An Experimental Study On The Behavior Of Box-shaped Culverts Buried In Sand Under Dynamic ExcitationsUlgen, Deniz 01 September 2011 (has links) (PDF)
Seismic safety of underground structures (culvert, subway, natural gas and water sewage systems) plays a major role in sustainable public safety and urban development. Very few experimental data are currently available and there is not generally accepted procedure to estimate the dynamic pressures acting on underground structures. This study aims to enhance the state of prevalent information necessary in understanding the dynamic behavior of box culverts and the stresses acting under dynamic excitations through experimental analyses. For this purpose, a series of shaking table tests were conducted on box-type culverts buried in dry sand. To simulate the free-field boundary conditions, a laminar box was designed and manufactured for use in a 1-g shake table. Four culvert models having different rigidities were tested under various harmonic motions in order to examine the effect of flexibility ratio on dynamic lateral soil pressures. Based on the tests results, a simplified dynamic pressure distribution acting on sidewalls of the culvert model was suggested. Then, a dynamic lateral coefficient was defined for the proposed peak pressure value in the distribution. The values of this coefficient were obtained as a function of shear strain and relative stiffness between the soil and underground structure. Finally, a simplified frame analysis approach was suggested for the assessment of the forces on the structure, to help to carry out a preliminary design of box-type culverts. In this approach, it was assumed that the culvert was fixed at bottom and subjected to lateral stresses on sidewalls and shear stresses on the upper face. For the confirmation of the method, centrifuge tests were conducted on a box-type culvert model under the Seventh Framework Programme of European Union with Grant Agreement No.227887. Results show that the proposed simplified procedure can be used in reasonable accuracy as a practical approach for the preliminary assessment of box-type culverts buried in dry sand under seismic action.
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Influence Of Deformable Geofoam Bufers On The Static And Dynamic Behaviors Of Cantilever Retaining WallsErtugrul, Ozgur Lutfi 01 September 2011 (has links) (PDF)
Static and dynamic interaction mechanism of the retained soil-compressible geofoam buffer and yielding retaining structures requires further investigation. The present study, initiated on this motive, discusses the results of 1-g physical model tests and numerical analyses of cantilever retaining walls with and without deformable geofoam buffers between the wall and cohesionless granular backfill. 0.7m high walls with various wall thicknesses were utilized in the physical modeling. Dynamic tests were carried out by using a laminar container placed on a uni-axial shaking table.
Influence of buffer thickness, geofoam type and wall flexibility as well as base excitation characteristics on the lateral earth pressures and flexural wall deflections were under concern. Outcomes of the analyses performed with FLAC-2D (v6.0) finite difference code were validated against the results of the physical model tests. It was observed that the arching effect induced in the retained soil by the lateral compression of the lower half of the geofoam buffer has a positive effect, as this zone is able to absorb a portion of the total unbalanced lateral force exerted by the backfill thus causing a reduction in the static and seismic lateral wall pressures.
Relative thickness and stiffness of the geofoam buffer appear to be the most dominant factors affecting the reduction in earth thrust. Lateral earth pressure coefficients determined from physical model tests were compared with those calculated using methods available in the literature. Good agreement was observed between the predictions. Graphs were provided to estimate the static and dynamic lateral earth pressure coefficients for various combinations of wall stiffness and buffer characteristics.
Analysis of a 6m high prototype cantilever wall subjected to an excitation recorded in August 17, 1999 Kocaeli earthquake by finite difference method exhibited the contribution of geofoam buffers on seismic performance of cantilever earth retaining walls. It was observed that the presence of an EPS geofoam inclusion provides a reduction of the permanent flexural wall deflections as well as total seismic thrust likely to be experienced by the wall during an earthquake.
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Knowledge for Understanding Table-Form DocumentsSUGIE, Noboru, LUO, Qin, WATANABE, Toyohide 20 July 1994 (has links)
No description available.
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Efficient digital baseband predistortion for modern wireless handsetsBa, Seydou Nourou 10 November 2009 (has links)
This dissertation studies the design of an efficient adaptive digital baseband predistorter for modern cellular handsets that combines low power consumption, low implementation complexity, and high performance. The proposed enhancements are optimized for hardware implementation. We first present a thorough study of the optimal spacing of linearly-interpolated lookup table predistorters supported by theoretical calculations and extensive simulations. A constant-SNR compander that increases the predistorter's supported input dynamic range is derived. A corresponding low-complexity approximation that lends itself to efficient hardware design is also implemented in VHDL and synthesized with the Synopsys Design Compiler. This dissertation also proposes an LMS-based predistorter adaptation that is optimized for hardware implementation and compares the effectiveness of the direct and indirect learning architectures. A novel predistorter design with quadrature imbalance correction capability is developed and a corresponding adaptation scheme is proposed. This robust predistorter configuration is designed by combining linearization and I/Q imbalance correction into a single function with the same computational complexity as the widespread complex-gain predistorter.
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Modeling Constitutive Behavior And Hot Rolling Of SteelsPhaniraj, M P 12 1900 (has links)
Constitutive behavior models for steels are typically semi-empirical, however recently neural network is also being used. Existing neural network models are highly complex with a large network structure i.e. the number of neurons and layers. Furthermore, the network structure is different for different grades of steel. In the present study a simple neural network structure, 3:4:1, is developed which models flow behavior better than other models available in literature. Using this neural network structure constitutive behavior of 8 steels: 4 carbon steels, V and V-Ti microalloyed steels, an austenitic stainless steel and a high speed steel could be modeled with reasonable accuracy.
The stress-strain behavior for the vanadium microalloyed steel was obtained from hot compression tests carried out at 850-1150 ï°C and 0.1-60 s-1. It is found that a better estimate of the constants in the semi-empirical model developed for this steel could be obtained by simultaneous nonlinear regression.
A model that can predict the effect of chemical composition on the constitutive behavior would be industrially useful for e.g., in optimizing rolling schedules for new grades of steel. In the present study, a neural network model, 5:6:1, is developed which predicts the flow behavior for a range of carbon steels. It is found that the effect of manganese is best accounted for by taking Ceq=C+Mn/6 as one of the inputs of the network. Predictions from this model show that the effect of carbon on flow stress is nonlinear.
The hot strip mill at Jindal Vijaynagar Steel Ltd., Toranagallu, Karnataka, India, was simulated for calculating the rolling loads, finish rolling temperature (FRT) and microstructure evolution. DEFORM-2d a commercial finite element package was used to simulate deformation and heat transfer in the rolling mill. The simulation was carried out for 18 strips of 2-4 mm thickness with compositions in the range and 0.025-0.139 %C. The rolling loads and FRT could be calculated within ï±15 % and ï±15 ï°C respectively. Analysis based on the variation in the roll diameter, roll gap and the effect of roll flattening and temperature of the roll showed that an error of ï±6 % is inherent in the prediction of loads. Simulation results indicated that strain induced transformation to ferrite occurred in the finishing mill. The microstructure after rolling was validated against experimental data for ferrite microstructure and mechanical properties.
The mechanical properties of steels with predominantly ferrite microstructures depend on the prior austenite grain size, strain retained before transformation and cooling rate on the run-out table. A parametric study based on experimental data available in literature showed that a variation in cooling rate by a factor of two on the run-out table gives rise to only a ï±20 MPa variation in the mechanical properties.
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Efficient Online Path ProfilingVaswani, Kapil 10 1900 (has links)
Most dynamic program analysis techniques such as profile-driven compiler optimizations, software testing and runtime property checking infer program properties by profiling one or more executions of a program. Unfortunately, program profiling does not come for free. For example, even the most efficient techniques for profiling acyclic, intra-procedural paths can slow down program execution by a factor of 2. In this thesis, we propose techniques that significantly lower the overheads of profiling paths, enabling the use of path-based dynamic analyzes in cost-sensitive environments.
Preferential path profiling (PPP) is a novel software-only path profiling scheme that efficiently profiles given subsets of paths, which we refer to as interesting paths. The algorithm is based on the observation that most consumers of path profiles are only interested in profiling a small set of paths known a priori. Our algorithm can be viewed as a generalization of the Ball-Larus path profiling algorithm. Whereas the Ball-Larus algorithm assigns weights to the edges of a given CFG such that the sum of the weights of the edges along each path through the CFG is unique, our algorithm assigns weights to the edges such that the sum of the weights along the edges of interesting paths is unique. Furthermore, our algorithm attempts to achieve a minimal and compact encoding of the interesting paths; such an encoding significantly reduces the overheads of path profiling by eliminating expensive hash operations during profiling. Interestingly, we find that both the Ball-Larus algorithm and PPP are essentially a form of arithmetic coding. We use this connection to prove that the numbering produced by PPP is optimal.
We also propose a programmable, non-intrusive hardware path profiler (HPP). The hardware profiler consists of a path detector that detects paths by monitoring the stream of retiring branch instructions emanating from the processor pipeline. The path detector can be programmed to detect various types of paths and track architectural events that occur along paths. The second component of the hardware profiling infrastructure is a Hot Path Table (HPT), that collects accurate hot path profiles.
Our experimental evaluation shows that PPP reduces the overheads of profiling paths to 15% on average (with a maximum of 26%). The algorithm can be easily extended to profile inter-procedural paths at minimal additional overheads (average of 26%). We modeled HPP using a cycle-accurate superscalar processor simulator and find that HPP generates accurate path profiles at extremely low overheads (0.6% on average) with a moderate hardware budget. We also evaluated the use of PPP and HPP in a realistic profiling scenarios. We find that the profiles generated by HPP can effectively replace expensive profiles used in profile-driven optimizations. We also find that even well-tested programs tend to exercise a large number of untested paths in the field, emphasizing the need for efficient profiling schemes that can be deployed in production environments.
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How graduating students perceive the staffing and recruitment industry : A study on corporate reputationBroman, Christopher, Cabander, Robin, Karlsson, Emilia January 2008 (has links)
<p>Purpose: The purpose of this study is to measure and compare the corporate reputation of four staffing and recruitment companies, from the perspective of graduating students.</p><p>Background: Corporate reputation is a concept that has interested researchers for the last four decades, and still the concept incorporates a number of varied definitions, contexts and measurement methods (Gotsi & Wilson, 2001). Along with definition ambiguity comes also measurement concerns such as whether to aggregate or disaggregate several perspectives into one general index of a company’s reputation. Most researchers agree that corporate reputation is a suitable concept when describing the perceptions that stakeholders have of a company, and that it can only be ascribed to one company. This study takes the perspective to investigate one external stakeholder group of staffing and recruitment companies - graduating students. The group is of interest because it can possibly become an internal stakeholder group - employees.</p><p>Method: For this study a quantitative method has been applied and an investigation has been made through a survey. Methodology about measuring corporate reputation is discussed, and lay ground for the empirical data collection. An altered version of the Harris-Fombrun Reputation Quotient (RQ) is used, in order to achieve better fit of the instrument and to attain higher reliability and validity.</p><p>Conclusion: The purpose of this study has been fulfilled by measuring corporate reputation from the perspective of graduating students. empirical data from 125 students has been collected, and four corporate reputations of staffing and recruitment companies have been measured. The findings are not valid for generalisability but enough to give a good estimation of the population of interest. In addition, a disaggregated analysis of the RQ components has confirmed the findings. Using the methodology of the theoretically based Harris- Fombrun Reputation Quotient further validates the findings. Graduating students perceive Academic Work in the most positive way, in respect to the other companies.</p> / <p>Syfte: Syftet med denna studie är att mäta och jämföra anseendet av fyra bemannings- och rekryteringsföretag, utifrån avgångsstudenters perspektiv.</p><p>Bakgrund: Företagets anseende är ett teoretiskt koncept som har intresserat forskare de senaste årtiondena och fortfarande råder delade meningar om definitioner, sammanhang och mätmetoder rörande konceptet (Gotsi & Wilson, 2001). Med tvetydiga definitioner kommer även oklarhet gällande mätningsmetod, som till exempel om man ska summera flera intressenters åsikter till ett övergripande index eller inte. Forskare är eniga om att företagets anseende är ett passande koncept när man ska beskriva de åsikter intressenter har om ett företag. Denna studie undersöker en specifik grupp av bemannings- och rekryteringsföretags externa intressenter, nämligen avgångsstudenter. Denna grupp är intressant då de kan komma att bli interna intressenter, via anställning av ett företag.</p><p>Metod: Denna studie har en kvantitativ inriktning och undersökningen har utförts med hjälp av en enkät. Metodiken i att mäta företags anseende genom att använda sig av league tabeller och pilotstudier diskuteras och ligger till grund för empiriinsamling. Användandet av en anpassad version av Harris-Fombrun Reputation Quotient (RQ) ger studien ökad validitet och reliabilitet.</p><p>Slutsats: Syftet med denna studie har blivit uppnått genom att mäta företagens anseende ur avgångsstudenters perspektiv. Empirisk data från 125 studenter har samlats ihop och fyra bemannings- och rekryteringsföretags företagsanseenden har blivit uppmätta. Resultatet kan inte generaliseras för en större population, men den kan användas för att ge en bra indikation hur åsikterna för den specifika populationen är. Vidare har en uppdelad analys av komponenterna i RQ gjorts vilket har kunnat säkerställa resultaten i den totala RQ. Användandet av den teoretiskt grundade RQ ger ytterligare validitet åt resultaten. Avgångsstudenter har mest positiva åsikter om Academic Work i jämförelse med de andra undersökta företagen.</p>
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Shaping Church Culture: Table Fellowship and Teaching in Luke-ActsHebert, Andrew Clayton 18 June 2015 (has links)
This thesis examines Luke-Acts to explore if, how, and in what ways Jesus and early church leaders intentionally shaped the culture of their followers. In Luke, table fellowship was the primary means Jesus used to shape the culture of his followers, as demonstrated through the prominence of eleven meal scenes. In Acts, teaching was the primary means early church leaders used to shape the organizational culture of the early church, as demonstrated through five paraenetic sermons addressed to the church. Table fellowship and teaching affected the behavior, values, and underlying beliefs of the early church related to Jew/Gentile relations (Acts 11; Acts 15), who should be considered as insiders/outsiders (Luke 5:29-39; Luke 7:36-50, Luke 19:1-10), hypocrisy (Luke 11:37-54), Sabbath regulations (Luke 6:1-5), status and humility (Luke 14:1-24; Luke 22:14-34), Jesus' identity (Luke 9:10-17; Luke 24:13-43); the disciples' obedience (Luke 9:10-17; Luke 10:38-42), and leadership (Acts 1:15-26; Acts 20:17-38).
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Patterns of water table dynamics and runoff generation in a watershed with preferential flow networksAnderson, Axel Edward 05 1900 (has links)
Our understanding of subsurface flow depends on assumptions of how event characteristics and spatial scale affect the relationships between subsurface water velocity, discharge, water table dynamics, and runoff response. In this thesis, three chapters explore some of these patterns for a hillslope and small watershed in coastal British Columbia. In the first chapter, tracers were applied under natural and steady state conditions to determine the relationship between lateral tracer velocities and various hillslope and event characteristics; such as hillslope subsurface flow, rainfall intensity, water table level, hillslope length, and antecedent condition. The results showed that preferential flow made up a large percentage of the subsurface flow from the gauged hillslope. Flow velocities as measured by tracers were affected by slope length and boundary conditions. The flow velocity was most closely related to the rainfall intensity, and changes in flow velocity were large compared to the changes in the water table. In the second chapter, the preferential flow features that transmitted water during steady state were investigated by staining the soil with a food dye solution and excavating the soil. These data were used to explore the link between the topographical factors (slope and contributing area), the network of preferential features and soil properties. The contributing area appeared to be an indicator of the size of the preferential features and their connectivity. In the final manuscript chapter, water table level and stream discharge measurements were used to determine if areas within a watershed with runoff dominated by preferential flow could be grouped based on the observable physical information such as slope, contributing area, distance to stream, and vegetation. Preferential flow made the water table responses dynamic and thus, distinct zones could not be identified. Models of the water table – runoff were not able to predict the water table response for other sites with similar physical characteristics. Even though there was high variability in the results, the patterns and relationships revealed in this thesis conform to existing conceptual models of hillslope subsurface preferential flow. These patterns and relationships may be useful in developing or validating numerical models.
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2x2列聯表模型下MLE與MPLE之比較 / The comparison between MLE and MPLE under two-by two contingency table models郭名斬 Unknown Date (has links)
Arnold and Strauss (1991) 探討2x2列聯表中的3個方格 (cell) 有相同機率θ的問題,他們比較了參數θ的最大概似估計值與最大擬概似估計值,發現參數θ的最大概似估計值與最大擬概似估計值是不相同的。在本論文中,我們將2x2列聯表中的3個方格的參數值 (機率值),從限制為相同θ,放寬為成某種比例,並證明了在一般情況下參數θ的最大概似估計值與最大擬概似估計值也不相同。我們也提出一些使參數θ的最大概似估計值及最大擬概似估計值相同的特殊條件,諸如三個方格內的觀察值跟機率值成比例或格子內的觀察值有某些特定值。本論文也透過電腦模擬的結果,發現最大概似估計式較最大擬概似估計式來得精確,而且當參數θ在參數空間之中點附近時,最大概似估計值與最大擬概似估計值的差異為最大。 / Arnold and Strauss (1991) study the cases that three of the four cells in the 2x2 contingency table have the same cell probability θ. In particular, Arnold and Strauss (1991) compare the maximum likelihood estimate (MLE) and maximum pseudolikelihood estimate (MPLE) of the parameter θ. They find that MLE and MPLE of the parameter are not the same. In this thesis, we relax the assumptions so that those three cell probabilities may not be the same and each is proportional to a parameter θ. We find that, in general, MLE’s of θ are still not the same as MPLE’s of θ. Some special cases that make MLE the same as MPLE are also given. We also find, through computer simulations, that MLE’s are accurate than MPLE’s and that the difference between MLE and MPLE is getting larger when the parameter θ is closer to the midpoint of its space.
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