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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Use of Biogenic Gas Production as a Pre-Treatment to Improve the Efficiency of Dynamic Compaction in Saturated Silty Sand.

January 2018 (has links)
abstract: One of the most economical and viable methods of soil improvement is dynamic compaction. It is a simple process that uses the potential energy of a weight (8 tonne to 36 tonne) dropped from a height of about 1 m to 30 m, depending on the project requirement, on to the soil to be compacted hence densifying it. However, dynamic compaction can only be applied on soil deposits where the degree of saturation is low and the permeability of the soil mass is high to allow for good drainage. Using dynamic compaction on saturated soil is unsuitable because upon application of the energy, a part of the energy is transferred to the pore water. The technique also does not work very well on soils having a large content of fines because of the absence of good drainage. The current research aims to develop a new technology using biogenic gas production to desaturate saturated soils and extend the use of dynamic compaction as a ground improvement technique to saturated soils with higher fines content. To evaluate the feasibility of this technology an experimental program has been performed. Soil columns with varying soil types have been saturated with substrate solution, resulting in the formation of nitrogen gas and the change in soils volume and saturation have been recorded. Cyclic triaxial tests have been performed to evaluate the change in volume and saturation under elevated pressure conditions and evaluate the response of the desaturated soil specimens to dynamic loading. The experimental results showed that soil specimens treated with MIDP under low confinement conditions undergo substantial volume expansion. The amount of expansion is seen to be a factor of their pore size, which is directly related to their grain size. The smaller the grain size, smaller is the pore size and hence greater the volume expansion. Under higher confining pressure conditions, the expansion during gas formation is suppressed. However, no conclusive result about the effect of the desaturation of the soil using biogenic gas on its compactibility could be obtained from the cyclic triaxial tests. / Dissertation/Thesis / Data sheets / Masters Thesis Civil, Environmental and Sustainable Engineering 2018
2

Compaction mechanism to reduce test pattern counts and segmented delay fault testing for path delay faults

Jha, Sharada 01 May 2013 (has links)
With rapid advancement in science and technology and decreasing feature size of transistors, the complexity of VLSI designs is constantly increasing. With increasing density and complexity of the designs, the probability of occurrence of defects also increases. Therefore testing of designs becomes essential in order to guarantee fault-free operation of devices. Testing of VLSI designs involves generation of test patterns, test pattern application and identification of defects in design. In case of scan based designs, the test set size directly impacts the test application time which is determined by the number of memory elements in the design and the test storage requirements. There are various methods in literature which are used to address the issue of large test set size classified as static or dynamic compaction methods depending on whether the test compaction algorithm is performed as a post-processing step after test generation or is integrated within the test generation. In general, there is a trade-off between the test compaction achievable and the run-time. Methods which are computationally intensive might provide better compaction, however, might have longer run times owing to the complexity of the algorithm. In the first part of the thesis we address the problem of large test set size in partially scanned designs by proposing an incremental dynamic compaction method. Typically, the fault coverage curve of designs ramp up very quickly in the beginning and later slows down and ultimately the curve flattens towards the tail of the curve. In the initial phase of test generation a greedy compaction method is used because initially there are easy-to-detect faults and the scope for compaction is better. However, in the later portion of the curve, there are hard-to-detect faults which affect compaction and we propose to use a dynamic compaction approach. We propose a novel mechanism to identify redundant faults during dynamic compaction to avoid targeting them later. The effectiveness of method is demonstrated on industrial designs and test size reduction of 30% is achieved. As the device complexity is increasing, delay defects are also increasing. Speed path debug is necessary in order to meet performance requirements. Speed paths are the frequency limiting paths in a design identified during debug. Speed paths can be tested using functional patterns, transition n-detect patterns or path delay patterns. However, usage of functional patterns for speed path debug is expensive because generation of functional patterns is expensive and the application cost is also high because the number of patterns is large and requires functional testers. In the second part of the dissertation we propose a simple path sensitization approach that can be used to generate pseudo-robust tests, which are near robust tests and can be used for designs that have multiple clock domains. The fault coverage for path delay fault APTG can be further improved by dividing the paths that are not testable under pseudo robust conditions, into shorter sub-paths. The effectiveness of the method is demonstrated on industrial designs.
3

On low power test and DFT techniques for test set compaction

Remersaro, Santiago 01 January 2008 (has links)
The objective of manufacturing test is to separate the faulty circuits from the good circuits after they have been manufactured. Three problems encompassed by this task will be mentioned here. First, the reduction of the power consumed during test. The behavior of the circuit during test is modified due to scan insertion and other testing techniques. Due to this, the power consumed during test can be abnormally large, up to several times the power consumed during functional mode. This can result in a good circuit to fail the test or to be damaged due to heating. Second, how to modify the design so that it is easily testable. Since not every possible digital circuit can be tested properly it is necessary to modify the design to alter its behavior during test. This modification should not alter the functional behavior of the circuit. An example of this is test point insertion, a technique aimed at reducing test time and decreasing the number of faulty circuits that pass the test. Third, the creation of a test set for a given design that will both properly accomplish the task and require the least amount of time possible to be applied. The precision in separation of faulty circuits from good circuits depends on the application for which the circuit is intended and, if possible, must be maximized. The test application time is should be as low as possible to reduce test cost. This dissertation contributes to the discipline of manufacturing test and will encompass advances in the afore mentioned areas. First, a method to reduce the power consumed during test is proposed. Second, in the design modification area, a new algorithm to compute test points is proposed. Third, in the test set creation area, a new algorithm to reduce test set application time is introduced. The three algorithms are scalable to current industrial design sizes. Experimental results for the three methods show their effectiveness.
4

Design and Analysis of "High Vacuum Densification Method" for Saturated and Partially Saturated Soft Soil Improvement

Tabatabaei, SeyedAli 15 May 2014 (has links)
No description available.
5

Pseudofunctional Delay Tests For High Quality Small Delay Defect Testing

Lahiri, Shayak 2011 December 1900 (has links)
Testing integrated circuits to verify their operating frequency, known as delay testing, is essential to achieve acceptable product quality. The high cost of functional testing has driven the industry to automatically-generated structural tests, applied by low-cost testers taking advantage of design-for-test (DFT) circuitry on the chip. Traditional at-speed functional testing of digital circuits is increasingly challenged by new defect types and the high cost of functional test development. This research addressed the problems of accurate delay testing in DSM circuits by targeting resistive open and short circuits, while taking into account manufacturing process variation, power dissipation and power supply noise. In this work, we developed a class of structural delay tests in which we extended traditional launch-on-capture delay testing to additional launch and capture cycles. We call these Pseudofunctional Tests (PFT). A test pattern is scanned into the circuit, and then multiple functional clock cycles are applied to it with at-speed launch and capture for the last two cycles. The circuit switching activity over an extended period allows the off-chip power supply noise transient to die down prior to the at-speed launch and capture, achieving better timing correlation with the functional mode of operation. In addition, we also proposed advanced compaction methodologies to compact the generated test patterns into a smaller test set in order to reduce the test application time. We modified our CodGen K longest paths per gate automatic test pattern generator to implement PFT pattern generation. Experimental results show that PFT test generation is practical in terms of test generation time.
6

Beitrag zur Fallgewichtsverdichtung in sandigem Boden

Pankrath, Holger 12 August 2019 (has links)
In der vorliegenden Arbeit wurden Experimente zur Fallgewichtsverdichtung in Modellversuchen im Erdschwerefeld (1g) durchgeführt. Ziel der Versuche war es, das Verformungsverhalten eines Versuchssandes in hoher räumlicher und zeitlicher Auflösung zu erfassen und Nachrechnungen im Sinne von Benchmark-Tests zu ermöglichen. Die messtechnische Erfassung des Bodenverhaltens erfolgte vor allem durch die optische Messmethode der digitalen Bildkorrelation (DIC, englisch: Digital Image Correlation). Ein wichtiger Teil der Arbeiten war in diesem Zusammen-hang die Eignungsprüfung der Messmethode an den eigenen Versuchsständen. Im Rahmen einer Variantenstudie mit 22 Modellkonfigurationen wurde zudem die Bedeutung von Steuergrößen der Fallgewichtsverdichtung hinter-fragt. Numerische Berechnungen wurden mit der Finite-Elemente-Methode (FEM) durchgeführt. Mit den Versuchen konnte Verschiebungen des Versuchssandes an der Sicht-ebene in hoher räumlicher Auflösung gemessen werden. Für die Erfassung bodendynamischer Vorgänge konnte die DIC-Auswertung von Hochge-schwindigkeitsaufnahmen sowie von Beschleunigungssensoren im Boden erfolgreich eingesetzt werden. Die DIC-Messung eines Granulats hinter einer transparenten Sichtebene führt zu einer Streuung der Verschiebungsergebnisse, was wiederum negative Auswirkung auf die Ermittlung von kleinräumigen Dehnungen hat. Eine besondere Herausforderung stellte in diesem Zu-sammenhang die Erfassung einer Änderung der Dichte bzw. Porenzahl über die naturgemäß kleinen Betragsänderungen der volumetrischen Dehnung dar. Das Verformungsverhalten des Versuchssandes zeigte bei der Fallgewichts-verdichtung große Ähnlichkeiten zu Versuchen mit statischer Auflast. Ergebnisse der Variantenstudie zeigen Zusammenhänge zwischen Steuergrößen der Fallgewichtsverdichtung und der Einflusstiefe auf. Es wird deutlich, dass die in der Baupraxis verbreitete Größe der potentiellen Fallenergie nur begrenzt für eine Klassifizierung von Fallgewichtskonfigurationen geeignet ist.:1 Einleitung 1 2 Zur praktischen Bedeutung der Fallgewichtsverdichtung 6 2.1 Geschichte der Verdichtung mit Fallgewichten 6 2.2 Anwendungsbereiche 6 2.3 Bodenmechanische Vorgänge während der Verdichtung 8 2.4 Wellenausbreitung bei impulsförmigem Energieeintrag 8 2.5 Bewertung des Verdichtungserfolges 9 3 Überblick zu experimentellen und rechnerischen Untersuchungen zur Fallgewichtsverdichtung 11 3.1 Feldversuche 11 3.2 Modellversuche 12 3.3 Berechnungsverfahren 29 4 Versuchstechnische Grundlagen 34 4.1 Geotechnische Experimente und deren Anforderung 34 4.2 Konzeption von Modellversuchen 35 4.3 Wahl und Realisierung von Randbedingungen 38 4.4 Erfassung und Auswertung von Messgrößen 38 4.5 Digital Image Correlation (DIC) 40 5 Versuchssand, Versuchsstände und Einbaumethoden 52 5.1 Versuchssand 52 5.2 Versuchsstand-C 54 5.3 Versuchsstand-S 57 5.4 Versuchsstand-M 61 5.5 Einbaumethoden 68 5.6 Kontrolle der Probenhomogenität 73 6 Versuche mit statischer Auflast 79 6.1 Versuchsprogramm und Ziele 79 6.2 Kompressionsversuche 81 6.3 Streifen- und Kreisfundamentversuche 93 6.4 Ergänzende Messungen 103 6.5 Zusammenfassung 106 7 Versuche mit skalierten Fallgewichten 108 7.1 Versuchsprogramm und Ziele 108 7.2 Fallgewichtsversuche im ebenen Verformungszustand 109 7.3 Fallgewichtsversuche als Halbmodell 115 7.4 Ergebnisse zusätzlicher Sondierungen 122 7.5 Ergänzende Messungen 125 7.6 Kinematik 130 7.7 Versuchsstudie zur Fallgewichtsverdichtung 133 7.8 Zusammenfassung 150 8 Vergleich zwischen statischen und dynamischen Versuchen 153 9 Numerische Berechnungen mit der Finite-Elemente-Methode 157 9.1 Grundlagen der verwendeten Finite-Elemente-Methode 157 9.2 Bestimmung der Stoffmodellparameter 160 9.3 Simulation der Kompressionsversuche 161 9.4 Simulation der Streifenfundamentversuche 170 9.5 Simulation der Fallgewichtsversuche 176 9.6 Kinematik 182 9.7 Zusammenfassung 186 10 Zusammenfassung 188 11 Ausblick Literaturverzeichnis 196 Anhang A Versuchsstudie zur Fallgewichtsverdichtung 204 A.1 Einzelversuche am Versuchsstand-S 204 A.2 Einzelversuche am Versuchsstand-M 208 Anhang B DIC-Studien an idealisiertem Versuchsaufbau 213 Anhang C Studie zu Zwischenbezugsschritten in ISTRA4D 220 Anhang D Studie zur Ermittlung von Dehnungen in ISTRA4D 223 Anhang E Kalibrierung der Stoffmodellparameter in Abaqus 227 Anhang F Hypoplastisches Stoffmodell ohne intergranulare Dehnung 229 Anhang G Hypoplastisches Stoffmodell mit intergranularer Dehnung 232 / A quantitative validation of numerical simulations of soil dynamic problems and the derivation of physical relationships needs appropriate experimental data. Within the scope of the present work, experiments on the heavy tamping in small-scaled models in earth's gravity (1g) were developed. The aim of the experiments was to record the deformation behavior of a test sand in high spatial and temporal resolution and to allow re-calculations in the sense of benchmark tests. The optical measuring method of digital image correlation (DIC) were mainly carried out for the metrological recording of the soil behavior. By comparing discrete image areas of a few grains of sand (patches), it is possible to full-field capture soil displacements behind a vertical viewing plane. In this context, an important part of the work was the suitability test of the measuring method at the own experiments. A variant study with 22 model configurations also questioned the importance of control factors of heavy tamping. The numerical calculations were performed with the finite element method (FEM) in Abaqus. Therefore, the simulation of individual special tests with static load were done using classical Lagrangian FEM. Experiments as well as with large soil deformations as well as heavy tamping were modeled using the Coupled Eulerian Lagrangian (CEL) method. As material model, a formulation of the hypoplasticity with extension to the concept of intergranular strains was used. The experiments showed that the optical measuring method of the DIC is capable of reliably detecting shifts of the test sand at the viewing plane in high spatial resolution. For the acquisition of soil dynamic processes, the DIC evaluation of high-speed recordings as well as of acceleration sensors in the soil could be successfully carried out. Experimental and metrological challenges resulted from the effects of optical refraction through the viewing plane as well as the detection and tracking of patterns of individual patches. In comparison to direct measurement on rigid bodies, the detection of a granulate behind a transparent viewing plane leads to a greater scattering of the displacement results, which in turn has a negative effect on the determination of small-scale strains in the measuring plane. A particular challenge in this context was the detection of a change in the density or pore number over the inherently small changes in the magnitude of the volumetric strain. Remarkably, the deformation behavior of the sand in medium-dense storage showed under the influence of falling-weight compacting great similarities to the deformation behavior under static loading. With both load models, the measurement results point to successful compaction work below and to the side of the load transfer, which are due to vertical or horizontal strain components. The results of the study on heavy tamping show correlations between the control factors of heavy tamping to an influence depth. The study shows that the size of the potential fall energy, which is common in construction practice, is only limitedly suitable for the classification of heavy tamping configurations. The evaluation of a series of drops proves the possibilities of correlation between state variables of a soil such as void ratio or degree of compaction and the velocity of the propagation waves in the soil. In numerical calculations, the deformation behavior of static load tests could be reproduced well. It showed the importance of a sufficient consideration of boundary conditions like friction between sand and container wall, container deformations and silo effects in narrow containers. Recalculations of the heavy tamping tests led to plausible results with a significant compaction effect below the drop weight, which is amplified in further drops and extended to greater depths. This also corresponds to the experimental results as well as the contexts known in practical engineering.:1 Einleitung 1 2 Zur praktischen Bedeutung der Fallgewichtsverdichtung 6 2.1 Geschichte der Verdichtung mit Fallgewichten 6 2.2 Anwendungsbereiche 6 2.3 Bodenmechanische Vorgänge während der Verdichtung 8 2.4 Wellenausbreitung bei impulsförmigem Energieeintrag 8 2.5 Bewertung des Verdichtungserfolges 9 3 Überblick zu experimentellen und rechnerischen Untersuchungen zur Fallgewichtsverdichtung 11 3.1 Feldversuche 11 3.2 Modellversuche 12 3.3 Berechnungsverfahren 29 4 Versuchstechnische Grundlagen 34 4.1 Geotechnische Experimente und deren Anforderung 34 4.2 Konzeption von Modellversuchen 35 4.3 Wahl und Realisierung von Randbedingungen 38 4.4 Erfassung und Auswertung von Messgrößen 38 4.5 Digital Image Correlation (DIC) 40 5 Versuchssand, Versuchsstände und Einbaumethoden 52 5.1 Versuchssand 52 5.2 Versuchsstand-C 54 5.3 Versuchsstand-S 57 5.4 Versuchsstand-M 61 5.5 Einbaumethoden 68 5.6 Kontrolle der Probenhomogenität 73 6 Versuche mit statischer Auflast 79 6.1 Versuchsprogramm und Ziele 79 6.2 Kompressionsversuche 81 6.3 Streifen- und Kreisfundamentversuche 93 6.4 Ergänzende Messungen 103 6.5 Zusammenfassung 106 7 Versuche mit skalierten Fallgewichten 108 7.1 Versuchsprogramm und Ziele 108 7.2 Fallgewichtsversuche im ebenen Verformungszustand 109 7.3 Fallgewichtsversuche als Halbmodell 115 7.4 Ergebnisse zusätzlicher Sondierungen 122 7.5 Ergänzende Messungen 125 7.6 Kinematik 130 7.7 Versuchsstudie zur Fallgewichtsverdichtung 133 7.8 Zusammenfassung 150 8 Vergleich zwischen statischen und dynamischen Versuchen 153 9 Numerische Berechnungen mit der Finite-Elemente-Methode 157 9.1 Grundlagen der verwendeten Finite-Elemente-Methode 157 9.2 Bestimmung der Stoffmodellparameter 160 9.3 Simulation der Kompressionsversuche 161 9.4 Simulation der Streifenfundamentversuche 170 9.5 Simulation der Fallgewichtsversuche 176 9.6 Kinematik 182 9.7 Zusammenfassung 186 10 Zusammenfassung 188 11 Ausblick Literaturverzeichnis 196 Anhang A Versuchsstudie zur Fallgewichtsverdichtung 204 A.1 Einzelversuche am Versuchsstand-S 204 A.2 Einzelversuche am Versuchsstand-M 208 Anhang B DIC-Studien an idealisiertem Versuchsaufbau 213 Anhang C Studie zu Zwischenbezugsschritten in ISTRA4D 220 Anhang D Studie zur Ermittlung von Dehnungen in ISTRA4D 223 Anhang E Kalibrierung der Stoffmodellparameter in Abaqus 227 Anhang F Hypoplastisches Stoffmodell ohne intergranulare Dehnung 229 Anhang G Hypoplastisches Stoffmodell mit intergranularer Dehnung 232
7

Hot Dynamic Consolidation Of Alfevsi Alloy Powders

Kotan, Sevkiye Ezgi 01 May 2005 (has links) (PDF)
The experimental alloy powders of 1% Mg treated Al-8Fe-1.8V-8Si were obtained by air atomization. The screen analysis of powders was made by sieves with meshes ranging from +90&micro / m, +63&micro / m, +53&micro / m, +45&micro / m, +38&micro / m to -38&micro / m. Unreinforced and TiC particulate reinforced specimens were produced by hot dynamic consolidation which is known as hot swaging. Powders were canned into pure aluminium tubes of about 10cm length and 2.2cm diameter. Single action and double action cold pressing were applied to some of the specimens before hot dynamic compaction and some specimens of canned loose powder were also processed. The diameters of the hot compacts were decreased in a two step process by swaging machine (rotary dynamic compaction). During the first step, after canning, compacts had been held at 480&deg / C for 1 hour and swaged, thus the diameter decreased from 2.2 cm to 1.97cm. Secondly, the compacts were reheated to 480&ordm / C and held for 1 hour and further swaged to obtain a diameter decrease from 1.97cm to 1.54cm. Generally, the microstructures of the hot dynamic compacted specimens were homogeneous except the specimens produced by using -63 &micro / m +53 &micro / m powder size fraction. By SEM study, a vanadium free cross like AlFeSi phase was observed near the outer regions of the specimen. No considerable coarsening of the dispersoids was observed after hot dynamic compaction of +63 &micro / m size powder. For -90&micro / m +63&micro / m size powders, maximum flexural strength values obtained by three point bending test increased by addition of 10% TiC to from 152 MPa to 285 MPa at double pressed condition and from 76MPa to 190MPa at loose powder canning condition. By hardness tests, it was observed that hardness values were inversely proportional to powder size and increased from 107 BHN to 147 BHN for corresponding powder size range of +90&micro / m to -38&micro / m. Porosity values obtained by Archimedes principle for single pressing varied between 0.03 % and 1.10% for corresponding size range of +38&micro / m to +90&micro / m. No considerable porosity was detected for double pressing. Porosity values of canned loose powder were between 3% and 10% for the range of +38 &micro / m- +45 &micro / m. By X-Ray analysis, it was revealed that Mg2Si reaction did not form after artificial aging of specimens up to 8 hours at 190&deg / C. Also, x-ray analysis of individual powders and specimens obtained by hot dynamic compaction of the same powder showed that / after hot dynamic compaction, the alloy powders were stable and no new phase formation was detected for +63&micro / m size. DSC examination of the specimens produced from +90&micro / m, +63&micro / m, +53&micro / m, -38&micro / m powder confirmed the microstructure stability up to the melting temperature. Melting temperature was detected to be in the range of 560&deg / C-575&deg / C by DSC.
8

Decision Tree for Ground Improvement in Transportation Applications

Yenco, Aileen C. January 2013 (has links)
No description available.

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