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Browne, Michael John. "Feasability of using a gyratory compactor to determine compaction characteristics of soil." Thesis, Montana State University, 2006. http://etd.lib.montana.edu/etd/2006/browne/BrowneM1206.pdf.
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Kona, Srinand. "Compactions in Apache Cassandra : Performance Analysis of Compaction Strategies in Apache Cassandra." Thesis, Blekinge Tekniska Högskola, Institutionen för kommunikationssystem, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-12885.
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Context: The global communication system is in a tremendous growth, leading to wide range of data generation. The Telecom operators in various Telecom Industries, that generate large amount of data has a need to manage these data efficiently. As the technology involved in the database management systems is increasing, there is a remarkable growth of NoSQL databases in the 20th century. Apache Cassandra is an advanced NoSQL database system, which is popular for handling semi-structured and unstructured format of Big Data. Cassandra has an effective way of compressing data by using different compaction strategies. This research is focused on analyzing the performances of different compaction strategies in different use cases for default Cassandra stress model. The analysis can suggest better usage of compaction strategies in Cassandra, for a write heavy workload. Objectives: In this study, we investigate the appropriate performance metrics to evaluate the performance of compaction strategies. We provide the detailed analysis of Size Tiered Compaction Strategy, Date Tiered Compaction Strategy, and Leveled Compaction Strategy for a write heavy (90/10) work load, using default cassandra stress tool. Methods: A detailed literature research has been conducted to study the NoSQL databases, and the working of different compaction strategies in Apache Cassandra. The performances metrics are considered by the understanding of the literature research conducted, and considering the opinions of supervisors and Ericsson’s Apache Cassandra team. Two different tools were developed for collecting the performances of the considered metrics. The first tool was developed using Jython scripting language to collect the cassandra metrics, and the second tool was developed using python scripting language to collect the Operating System metrics. The graphs have been generated in Microsoft Excel, using the values obtained from the scripts. Results: Date Tiered Compaction Strategy and Size Tiered Compaction strategy showed more or less similar behaviour during the stress tests conducted. Level Tiered Compaction strategy has showed some remarkable results that effected the system performance, as compared to date tiered compaction and size tiered compaction strategies. Date tiered compaction strategy does not perform well for default cassandra stress model. Size tiered compaction can be preferred for default cassandra stress model, but not considerable for big data. Conclusions: With a detailed analysis and logical comparison of metrics, we finally conclude that Level Tiered Compaction Strategy performs better for a write heavy (90/10) workload while using default cassandra stress model, as compared to size tiered compaction and date tiered compaction strategies.
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Fortin, Jerome. "Compaction homogène et compaction localisée des roches poreuses.Etude expérimentale et théorique." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2005. http://tel.archives-ouvertes.fr/tel-00180388.
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Pour de nombreux problèmes de sismo-tectonique et d'ingénierie de réservoir, la capacité à prévoir l'ampleur de la déformation inélastique et les ruptures repose sur une compréhension de la phénoménologie et de la micromécanique de la dilatance et de la compaction dans les roches. Pour les roches poreuses, la compaction inélastique peut être diffuse ou localisée dans la roche. La compaction d'une roche sous une pression isotrope est le résultat de la destruction du réseau poreux. Pour quantifier l'évolution de l'endommagement pendant la compaction, nous utilisons un modèle de milieu effectif. Nous montrons ainsi comment le broyage des grains transforme la roche en un milieu granulaire, où, même à sec, le rapport Vp/Vs croit, ce qui n'avait jamais été observé. Lorsque la roche est soumise à champ de contrainte déviatorique, la compaction inélastique estlocalisée. Sous certaines pressions moyennes effectives, la déformation inélastique se développe sous forme de bandes de compaction. Pour comprendre la formation des bandes de compaction, nous avons enregistré, puis re-localisé les émissions acoustiques au cours de plusieurs expériences.
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Le, Guennec Yann. "Compaction conventionnelle et compaction grande vitesse : application aux produits multimatériaux et multifonctions." Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00605809.
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Parmi les procédés de mise en forme de pièces industrielles, la métallurgie des poudres autorise une haute cadence de production avec une faible perte de matière première. L'élaboration de composants multi-matériaux par compression et frittage permet de minimiser le nombre d'étapes de conception afin de combiner des propriétés complémentaires. L'objet de cette thèse est l'étude d'un procédé de compression innovant qui peut augmenter la cadence de production et diminuer les contraintes sur l'outillage : la CGV (compression grande vitesse), et de l'appliquer à la mise en forme de pièces multimatériaux. Une presse à grande vitesse a été développée au laboratoire afin d'étudier l'influence de la CGV sur deux couples de matériaux : un couple base Fe / base WC, associant dureté et ténacité, un couple Acier 1.4313 / Stellite 6 associant résistance mécanique et résistance à la corrosion. Des modélisations numériques des procédés de compression conventionnelle et CGV ont été réalisées dans le but de mieux analyser les phénomènes observés et de prévoir le comportement en compression de plusieurs poudres simultanément. Ce travail aboutit à des recommandations pour la mise en oeuvre de la compression de composants multi-matériaux et met au jour quelques caractéristiques de la CGV.
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Fortin, Jérôme. "Compaction homogène et compaction localisée des roches poreuses : étude expérimentale et théorique." Paris 6, 2005. https://tel.archives-ouvertes.fr/tel-00180388.
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Gaboriault, Jr Edward M. "The Effects of Fill-Nonuniformities on the Densified States of Cylindrical Green P/M Compacts." Digital WPI, 2003. https://digitalcommons.wpi.edu/etd-theses/853.
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"We focus attention on single-punch compaction of metal powders in cylindrical dies. In one case, we consider solid cylindrical compacts, and take the die walls to be frictionless in order to isolate the effects of initial nonuniformities in powder fill on the final green density distribution of the compact. First, a model is introduced in which the die is filled with n distinct powders that occupy concentric annular regions within the die. The model requires that the balance of mass, the balance of momentum, and a realistic equation of state be satisfied in each region, and includes a plausible constitutive relation that relates the induced radial pressure in each powder region to the corresponding axial pressure and the relative movements of the interfaces that confine the region. For specified powder properties, the model predicts the movements of the interface between the powders, the final density in each region, the pressure maintained in each region, and the total compaction load required. In the special case of two powders (n=2), we predict how the radial movement of the single interface depends on the mismatch between the properties of the two powders. For large values of n, and for powder properties that change gradually from one powder to the next, the model approximates a single powder filled nonuniformly in the die. Finally, a model is developed for a single powder with continuously varying powder properties. Formally, the model may be obtained by taking the limit of the n-powder model as n becomes unbounded. Employing the continuous model, we determine how nonuniformities in initial fill density can be offset by nonuniformities in other powder properties to yield perfectly uniform green densities. In a second case, we consider axisymmetric, hollow, cylindrical compacts, and include the effects of friction at the die wall and the core rod. The ratio of the induced radial pressure to the applied axial pressure is assumed to be constant throughout the compaction, and Coulomb friction acts between the powder and the die wall as well as between the powder and the core rod. We derive a closed form solution for the axial and radial variation of the axial pressure, radial pressure, and shear stress throughout the compact. This solution is combined with a plausible equation of state to predict the final green density distribution and the variation of applied load throughout the compact."
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Yap, Siaw Fung. "Micromechanics and powder compaction." Thesis, University of Birmingham, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.489036.
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Olsson, Erik. "Micromechanics of Powder Compaction." Doctoral thesis, KTH, Hållfasthetslära (Avd.), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-159142.
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Compaction of powders followed by sintering is a convenient manufacturing method for products of complex shape and components of materials that are difficult to produce using conventional metallurgy. During the compaction and the handling of the unsintered compact, defects can develop which could remain in the final sintered product. Modeling is an option to predict these issues and in this thesis micromechanical modeling of the compaction and the final components is discussed. Such models provide a more physical description than a macroscopic model, and specifically, the Discrete Element Method (DEM) is utilized. An initial study of the efect of particle size distribution, performed with DEM, was presented in Paper A. The study showed that this effect is small and is thus neglected in the other DEM studies in this thesis. The study also showed that good agreement with experimental data can be obtained if friction effects is correctly accounted for. The most critical issue for accurate results in the DEM simulations is the modeling of normal contact between the powder particles. A unified treatment of this problem for particles of a strain hardening elastic-plastic material is presented in Paper B. Results concerning both the elastic-plastic loading, elastic unloading as well as the adhesive bonding between the particles is included. All results are compared with finite element simulation with good agreement with the proposed model. The modeling of industry relevant powders, namely spray dried granules is presented in Paper C. The mechanical behavior of the granules is determined using two types of micromechanical experiments, granule compression tests and nanoindentation testing. The determined material model is used in an FEM simulation of two granules in contact. The resulting force-displacement relationships are exported to a DEM analysis of the compaction of the granules which shows very good agreement with corresponding experimental data. The modeling of the tangential forces between two contacting powder particles is studied in Paper D by an extensive parametric study using the finite element method. The outcome are correlated using normalized parameters and the resulting equations provide the tangential contact force as function of the tangential displacement for different materials and friction coefficients. Finally, in Paper E, the unloading and fracture of powder compacts, made of the same granules as in Paper C, are studied both experimentally and numerically. A microscopy study showed that fracture of the powder granules might be of importance for the fracture and thus a granule fracture model is presented and implemented in the numerical model. The simulations show that incorporating the fracture of the granules is essential to obtain agreement with the experimental data.QC 20150122
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Okapala, Chukwuemeka J. "Compaction simulator performance analysis." Thesis, Liverpool John Moores University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363111.
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Song, Jin Hua. "Compaction of ceramic powders." Thesis, University of Newcastle Upon Tyne, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315656.
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Couch, Matthew. "Aggregation, sedimentation and compaction." Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260616.
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Idapalapati, Sridhar. "Compaction of metallic powders." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624169.
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Pouzet, Marc. "Compaction des langages fonctionnels." Paris 7, 1994. http://www.theses.fr/1994PA077327.
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La compaction des programme est la fabrication par le compilateur de paquets d'instructions elementaires executes en parallele. Les architectures concernees sont les architectures paralleles vliw (very long instruction word) ou super-scalaires. Jusqu'a present, la compaction etait appliquee aux langages imperatifs. Dans cette these, la compaction est etendue aux langages fonctionnels. Elle est formellement decrite par des regles de transformation de programmes en semantique naturelle. Le langage fonctionnel utilise est d'abord decrit puis on definit une semantique operationnelle de son execution sur une machine parallele de type vliw. Une equivalence dite structurelle mettant en relation les programmes ayant les memes dependances est donnee ainsi qu'une procedure de decision partielle. Suit la description de la compaction globale (parallelisme exploite dans les sections sans recursions) puis celle du pipeline logiciel (compaction etendue aux programmes quelconques). Ainsi, le principe du pipeline logiciel habituellement applique aux boucles est etendu aux fonctions recursives. Il est obtenu par la compaction globale et le depliage controle des fonctions et fournit un nouveau programme dont la compaction ne peut plus etre amelioree par depliage. Diverses methodes permettant de l'obtenir sont proposees.
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Bortzmeyer, Denis. "Compaction des poudres ceramiques." Paris, ENMP, 1990. http://www.theses.fr/1990ENMP0237.
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Le but de cette these est de mieux maitriser le procede de compaction des poudres de zircone en utilisant, en plus des outils classiques du ceramiste, le formalisme de la mecanique des milieux continus. Elle comporte une approche experimentale utilisant les outils classiques (compaction en matrice fermee, compaction hydrostatique, cohesion des crus) ainsi qu'une cellule triaxiale. Parallelement, elle contient une approche micromecanique reposant essentiellement sur la simulation numerique d'un empilement de grains dont les lois d'interaction sont connues. La loi de comportement determinee a l'aide de la cellule triaxiale est de type cap model. La surface de plasticite est donc limitee par une droite critique, et par un cap rectiligne ou elliptique ecrouit en densite. La loi d'ecoulement est non associee, notamment sur la droite critique. Nous avons introduit un modele a seuil diffus prenant en compte la plasticite en decharge. Cette loi de comportement a ete implantee dans le code de calcul de l'ecole des mines de paris, afin de simuler par elements finis la compaction de pieces de forme complexe. L'influence des caracteristiques de la poudre (granulometrie, rugosite, presence de liants) sur la loi de comportement a ete etudiee. Les resultats du programme de simulation micromecanique sont egalement divises en une partie classique (compaction, traction) et une partie mecanique (surface de plasticite, loi d'ecoulement). Les resultats de compaction sont en bon accord qualitatif avec l'experience. Le modele a montre que la compaction est constituee d'une succession de flambements de l'empilement. L'etude de la cohesion a egalement revele un aspect important: la resistance en traction d'un empilement cristallin est notablement diminuee lorsqu'on y introduit un faible desordre. La surface de plasticite et la loi d'ecoulement micromecaniques presentent par contre plusieurs differences avec le mate
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Mohanty, Biswajeet. "Impact of Cassandra Compaction on Dockerized Cassandra’s performance : Using Size Tiered Compaction Strategy." Thesis, Blekinge Tekniska Högskola, Institutionen för datalogi och datorsystemteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-13273.
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Context. Cassandra is a NoSQL Database which handles large amount of data simultaneously and provides high availability for the data present. Compaction in Cassandra is a process of removing stale data and making data more available to the user. This thesis focusses on analyzing the impact of Cassandra compaction on Cassandra’s performance when running inside a Docker container. Objectives. In this thesis, we investigate the impact of Cassandra compaction on the database performance when it is used within a Docker based container platform. We further fine tune Cassandra’s compaction settings to arrive at a sub-optimal scenario which maximizes its performance while operating within a Docker. Methods. Literature review is performed to enlist different compaction related metrics and compaction related parameters which have an effect on Cassandra’s performance. Further, Experiments are conducted using different sets of mixed workload to estimate the impact of compaction over database performance when used within a Docker. Once these experiments are conducted, we modify compaction settings while operating under a write heavy workload and access database performance in each of these scenarios to identify a sub-optimal value of parameter for maximum database performance. Finally, we use these sub-optimal parameters to perform an experiment and access the database performance. Results. The Cassandra and Operating System related parameters and metrics which affect the Cassandra compaction are listed and their effect on Cassandra’s performance has been tested using some experiments. Based on these experiments, few sub-optimum values are proposed for the listed metrics. Conclusions. It can be concluded that, for better performance of Dockerized Cassandra, the proposed values for each of the parameters in the results (i.e. 5120 for Memtable_heap_size_in_mb, 24 for concurrent_compactors, 16 for compaction_throughput_mb_per_sec, 6 for Memtable_flush_writers and 0.14 for Memtable_cleaup _threshold) can be chosen separately but not the union of those proposed values (confirmed from the experiment performed). Also the metrics and parameters affecting Cassandra performance are listed in this thesis.
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Chan, Charlotte. "Compaction Simulation for Prepreg-AutoclaveManufacturing : Improvements and Simplifications of Two Compaction Simulation Methodologies." Thesis, KTH, Lättkonstruktioner, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-262035.
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In a competitive market such as the aerospace industry, the use of manufacturing process simulation is vital to decrease time and cost of tooling and process development. In the autoclave process, to obtain an uniform part with no void, it is crucial to understand the compaction phenomenon. Through the last decades, compaction simulation methodologies have been developed but only rather simple geometry and/or small parts have been studied. At Airbus Helicopters Deutschland, compaction simulation methodology needs to be able to predict outcomes of rather large and complex helicopter parts such as the final thickness, porosity, wrinkles, thickness deviation, etc. In the two existing Airbus Helicopters Deutschland simulation methodologies, the main problems are the complexity of the simulation process, high computational costs and substantial set-up for rather simple parts. The research presented in this Master thesis aims at providing improvements and optimisations of the two simulations. A comparison of the two methods is also performed in terms of applicability, accuracy, set-up time and computational cost to assess which method should be favoured depending on the problem. Samples previously built at Airbus or during this thesis are used for the simulations’ calibration and validation. For the first method based on the soil approach, parameters such as the autoclave cycle length, the shear stiffness of the fibres, pore pressure boundary condition, number of contacts, mesh size and radius discretisation are investigated. This method is capable of predicting’ accurately the final thickness and the thickness distribution behaviour for flat and curved parts. However, at lower consolidation pressures, the accuracy decreases. Furthermore, this simulation methodology requires high computational and set-up times. During the calibration of the method, CPU and setup times are reduced by using smaller model and coarser mesh while still achieving a correct result. For the second methodology based on membrane elements while neglecting flow effects, the contact modelling is calibrated: the contact stiffness is correctly altered to fit the thickness variation during the manufacturing process. Calibration is done for flat parts. However, wrinkles start to form in the curved part model where no such defect was observed in the samples. This issue needs to be investigated first to continue the simulation calibration. The method shows accurate results for each pressure cycle with lower computational cost and faster set-up than the first method. In addition, wrinkles can be visualized directly in the simulation and core material such as honeycomb and foam sandwich cores can be taken into account. This method looks quite promising but needs further investigation.Aerospace industrin måste ständigt möta upp mot höga kvalitetskrav samtidigtsom den är utsätts för hård konkurrens från andra aktörer. Användningenav processimulering är viktig för ett företags konkurrenskraft genom att detger minskad uppstartstid tid, skapar robusta tillverkningsmetoder och minskarverktygskostnaderna. I autoklavprocessen, vilken används för tillverkning avavancerade strukturella kompositkomponenter, är det exempelvis av yttersta viktatt med hjälp av modeller förstå och prediktera materialkonsolideringen. Olikametoder har presenterats under de senaste decennierna för att kunna bestämma gradav konsolidering, men de har samtliga varit begränsade till ganska enkla geometrieroch/eller studier på små detaljer. Vid Airbus Helicopters Tyskland behöver sådanasimuleringar tex kunna förutsäga slutlig materialtjockled, porhalt, veckbildningoch tjockleksvariationer vid tillverkning av stora och komplexa geometrier. De tvåexisterande simuleringsmetodiker som används av företaget idag är för komplicerade,kostsamma (kräver mycket datorkraft) och omständliga att sätta igång även försimulering av ganska enkla delar. Forskningen som presenteras i denna avhandlingsyftar till att förbättra och optimera den existerande simuleringsmetodiken påföretaget. En jämförelse mellan de två metoderna är genomförd för att undersökavilken metod är att föredra för olika typer av problem. Vid jämförelsen studerasmetodernas applicerbarhet, noggrannhet, uppstartningstid och beräkningskostnad.Verkliga komponenter som fanns tillgängliga sedan tidigare eller som har tillverkatsvid Airbus Helicopters under tiden för uppsatsen har använts för kalibrering ochvalidering.Den första metoden är baserad på en soil approach och parametrar såsom autoklavens processcykel, fibermaterialets skjuvstyvhet, portryck, antalkontaktpunkter, storlek på beräkningsnätet och beräkningsradiernas diskretisation ärundersökta. Metoden gör det möjlig att prediktera slutlig komponenttjocklek samttjockleksvariationer för plana och krökta delar. Emellertid minskar noggrannheten vidsimuleringar av låga processtryck. Dessutom kräver metodiken långa uppstartstidersamt simuleringstider. Genom att kalibrera metoden för halverad modell eller grövreberäkningsnät kan dock både CPU-tid och uppstartstid reduceras.För den andra metoden, som är baserad på skalelement och bortser frånmatrisflödeseffekter, har arbetet i uppsatsen handlat om att kalibrera kontaktvillkoren.Kontaktstyvheten har anpassats för att passa de tjockleksvariationerna som uppstårunder tillverkning. Dessvärre uppstår veck i den härdade, dubbelkrökta komponentenvilket inte korrelerar med beräkningarna. Detta måste utvärderas vidare genomförbättrad beräkningskalibrering. Metoden visar upp resultat med god noggrannhetför samtliga simulerade tillverkningscykler, samtidigt som detta sker med kortareuppstartstid än den första metoden samt till lägre beräkningskostnad. Dessutommöjliggör metoden att veck kan visualiseras direkt i simuleringarna och att bådehoneycomb- och skumkärnor kan inkluderas och tas hänsyn till i beräkningarna.Metoden verkar mycket lovande men kräver vidare utredning.
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Vikas, Narayan. "Computational complexity of graph compaction." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq24360.pdf.
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Wang, Kai-Ting Amy. "Code compaction for VLIW instructions." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ63035.pdf.
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Skrinjar, Olle. "Cold compaction of composite powders." Doctoral thesis, Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-417.
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Cameron, I. M. "Powder characterisation for compaction modelling." Thesis, Swansea University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636198.
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In this thesis, experimental investigations into powder-die friction and powder yielding measurement techniques, and numerical modelling work on powder-die friction mechanisms are presented. The experimental friction work explores the use of a shear-plate technique to measure the frictional characteristics between a compacted powder and a target surface. The study confirms that the shear-plate technique is valid to measure these frictional characteristics. Surface roughness and hardness was explored fully for both Iron and an Alumina power. This confirmed the major impacts of surface hardness, roughness and roughness orientation on the friction coefficient. With regard to static friction, benefit may be obtained by using a very smooth surface finish, however, the minimum level of dynamic friction coefficient is not always associated with the smoothest surface. Comparisons between different experimental techniques for characterising the yielding of powders are presented. Three techniques were compared using an iron powder: triaxial testing, instrumented die testing and shear-box testing. The techniques were compared with a particular view to measuring the applicability of the less well recognised experiments with the more established triaxial experiment. Predicted yield surfaces from a single instrument die test compared very well with the yield surfaces obtained triaxial tests. Results from shear-box experiments show that it defines the region in which it is appropriate to use the yield surfaces obtained from the instrumented die, for modelling purposes. Beyond this limit yielding of the powder is achieved by a shearing mechanism.
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Anderson, Stephen. "Differential compaction in alluvial sediments." Thesis, Cardiff University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.536314.
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Differential compaction within alluvial sediments results from the inherent juxtaposition of sand, si It, clay and peat on the floodplain. Differential compaction is primarily dependent on (a) the nature of overbank mudstone compaction, and (b) the relative timing of channel and adjacent overbank sediment deposition. Results from the analysis of modern overbank sediments indicate that the near-surface porosity of alluvial overbank sediment Is controlled by the complex interaction of grain shape, grain size, clay content, groundwater fluctuations, evaporation and transpiration, suggesting that the subsequent compaction of these sediments would be an extremely heterogeneous process, with n'o single controlling parameter. Porosity-depth curves derived from modern sediment analysis indicate that a significant amount of compaction occurs during the first few metres of burial. Examination of samples suggest that ·porosity loss may be due to the expulsion of water from the sediment pores, and the rearrangement of grains from an unstable packing arrangement to a more stable one. Early differential compaction will affect floodplain topography, and therefore directly influence the subsequent pattern of facies distribution. However, as significant amounts of compaction have occurred during very early burial, later stages of compaction will have a less marked effect on alluvial stratigraphy than has been previously suggested. In particular, simulation models such as Bridge & Leeder (1979) which suggest that channel "packing" increases with depth may not be entirely correct. If, within an alluvial sequence, there is no compactional deformation of features such as alluvial channel wings, it is unlikely that channel packing will have increased with depth. Studies of the Middle Jurassic alluvial sediments of North Yorkshire and the Cretaceous of the Isle of Wight, illustrate that the effects of differential compaction can be observed on several scale~: (a) channel belt, (b) individual channel or bedform, and (c) microscopic
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Yu, Shen. "Roll compaction of pharmaceutical excipients." Thesis, University of Birmingham, 2013. http://etheses.bham.ac.uk//id/eprint/4137/.
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Roll compaction is commonly used as a dry granulation technique in the pharmaceutical industry to produce tablets for formulations sensitive to heat and moisture. This thesis reports systematic studies on the behavior of pharmaceutical excipients in associated unit operations (i.e. roll compaction, milling, tabletting), as well as their correlations. Roll compaction experiments were carried out using an instrumented roll compactor with a gravity feeding system. The influence of the process parameters, material properties and powder conditioning were investigated Ribbons produced in roll compaction were granulated using an oscillating mill to investigate the milling process. A first order kinetics equation was introduced to describe the mass throughput of the granules. Using positron emission particle tracking technique, which provided a measurement of instantaneous velocity and the location of the ribbons, two milling regions (i.e. impact and abrasion) involving distinct fracture mechanisms were identified. Tabletting of the granules was performed using a universal test machine. A reduction in the compressibility and compactibility of the granules compared to the feed powders, due to work hardening, was also observed. A method was introduced to determine the optimized process conditions for roll compaction and milling through a close examination of the correlation between the unit operations.
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Troost, Jan J. "Factors influencing laboratory vibratory compaction." Master's thesis, University of Cape Town, 1987. http://hdl.handle.net/11427/17651.
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Includes bibliography.The thesis consists of a literature review and a limited experimental investigation in a soils laboratory. The objective of the literature review is to determine what standard laboratory test methods based on vibration exist for the control of compaction, to what soil types these tests are applicable and what the factors are which affect laboratory vibratory compaction. The study revealed that extensive research has been carried out in the USA and Europe, where standard laboratory compaction tests exist for the determination of the maximum dry density of cohesionless, free-draining soil. The US methods are based on the use of a vibratory table, while the European practice is based on the use of a vibratory tamper. No standard tests appear to exist for soil exhibiting cohesion, though limited research has been carried out in the USA into the behaviour of such soils under laboratory vibratory compaction. The factors; frequency, amplitude, mould size and shape surcharge intensity and manner of application, soil type, time of vibration, number of layers and moisture content are all reported to have an effect on the maximum dry density achievable. It has been recognised that significant interaction occurs between the factors affecting vibratory compaction, but the extent of the interaction appears to be only partly understood. The objective of the limited experimental program was to determine whether a specific graded crushed stone could be compacted to Modified AASHTO maximum dry density with a laboratory vibratory compaction technique using a vibratory table, and how this could best be achieved. The effects on dry density of changing the frequency, the time of vibration, mould size, surcharge pressure, grading and moisture content were investigated. It is concluded that the graded crushed stone in question can be compacted to Mod. AASHTO maximum dry density but that before reliable reproducible results can be achieved with this type of test further work is necessary. Such research should be aimed at investigating the interaction effect between the amplitude of vibration, the soil type and the type and intensity of the applied surcharge pressure.
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Kelfkens, Rex Willem Constantyn. "Vibratory hammer compaction of Bitumin stabilized materials /." Thesis, Link to the online version, 2008. http://hdl.handle.net/10019/1998.
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Fredenburg, David Anthony. "Shock compaction and impact response of thermite powder mixtures." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37130.
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This dissertation focuses on developing a predictive method for determining the dynamic
densification behavior of thermite powder mixtures consisting of equivolumetric
mixtures of Ta + Fe₂O₃ and Ta + Bi₂O₃. Of primary importance to these highly reactive
powder mixtures is the ability to characterize the stress at which full compaction occurs,
the crush strength, which can significantly influence the stress required to initiate reaction
during dynamic or impact loading. Examined specifically are the quasi-static and dynamic
compaction responses of these mixtures. Experimentally obtained compaction responses
in the quasi-static regime are analyzed using available compaction models, and an analysis
technique is developed that allows for a correct measurement of the apparent yield strength
of the powder mixtures. The correctly determined apparent yield strength is combined with
an equation of state to yield a prediction of the shock densification response, including the
dynamic crush strength of the thermite powder mixtures. The validated approach is also extended
to the Al + Fe₂O₃ thermite system. It is found that accurate predictions of the crush
strength can be obtained through determination of the apparent yield strength of the powder
mixture when incorporated into the equation of state. It is observed that the predictive
ability in the incomplete compaction region is configurationally dependent for highly heterogeneous
thermite powder systems, which is in turn influenced by particle morphology
and differences in intrinsic properties of constituents (density, strength, etc.).
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Tuma, Fischer Sebastian, and Jojje Sundblad. "Autonomous Compaction Roller : Temporarily convert a non autonomous compaction machine to become autonomous during endurance testing." Thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-16728.
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How can a non-autonomous compaction roller be converted to become temporarily autonomous while it performs a 500hours endurance test? Particularlysince the compaction rollers in question is not built to be autonomous and shall not be autonomous after the endurance test is completed. The autonomous system shall also be adaptable to all compaction rollers which Dynapac is developing and shall be moved to another machine when the endurance test is completed. In this thesis a concept is engineered of how the whole autonomous system will work and a prototype is fabricated of how to convert the current manual mechanical steering to be performed by a computer. The steering prototype has been tested on a Dynapac CC4200 double drumasphalt compaction roller and worked as intended. To develop this, anextensive risk analysis is also established andwith it a requirements list of what's needed to be fulfilled when performing autonomous testing of a compaction roller. The work has been done using the method “design thinking” which is a collection of multiple methods to create new concepts and ideas. The final concept resulted in a navigation system which uses GNSS for path planning and limitation of the operation area. It also uses radar to detect foreign objects in its path to prevent a collision. Multiple systems arealso proposed to be used for malfunction detection of the roller, which is a major part of a human operator’sjob when testing out new machines. The test track for the machine was undefined and also hadto be engineeredas part of the concept. It resultedin closing the area of operation with a mesh fence to prevent access to the area from unauthorised personnel and geo-fence to prevent the machine from escaping. Access to the area is only granted to authorized personnel and only when the autonomous rolleris shut off. Due to the machines in question isn’t fully developed, theycan’t be trusted enough to have people inside the area of operation asthe autonomous machineis operating.Hur kanen icke-autonom vägvältomvandlas tillatt bli tillfälligt autonom medan den utför ett 500timmar långttidsprov?Särskilt sedanvägvältenifrågainte ärbyggd för att vara autonom och ska intevara autonom efter attlångtidsprovetär slutfört. Det autonoma systemet skaävenkunna anpassas tillalla vältar som Dynapac utvecklar och ska flyttas till en annan maskin närlångtidsprovetär klart. Idenna avhandling konstrueras ett koncept för hur hela det autonoma systemet kommer att fungera ochenprototyp tillverkaspå hur man konverterar den nuvarande manuella mekaniska styrningen till attstyras av en dator. Styrprototypen testades på en Dynapac CC4200 asfaltsvält med dubbla valsar ochfungerade bra. En omfattande riskanalys utvecklades ochlika såen kravlista över vad som behöveruppnås vid autonom testning av en vägvält. Arbetet har gjorts med hjälp av metoden “designthinking”, vilket är en samling av flera metoder för att skapa nya koncept och idéer. Det slutgiltigakonceptet resulterade i ett navigationssystem som använder GNSS för navigering och begränsning avkörområdet. Den använder också radar för att upptäcka främmande föremål i sin vägvilketförhindrarkollision. Flera system föreslås användasförfunktionsfelsdetektering på välten, vilket är en viktig delav en mänskligoperatörs arbetevid provning av nya maskiner. Maskinen kommer att vara i ett slutetområde som är avskilt med ett nätstängsel.Tillträde till området ges endast till behörig personal ochendast när den autonoma välten är avstängd. På grund avmaskinerna ifråga inte är fullt utvecklade,kan de inte litas på tillräckligt för att ha personer inom körområdet medan det autonoma systemet är idrift.
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KATIKI, REDDY RAHUL REDDY. "Improving Efficiency of Data Compaction by Creating & Evaluating a Random Compaction Strategy in Apache Cassandra." Thesis, Blekinge Tekniska Högskola, Institutionen för programvaruteknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-20182.
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Background: Cassandra is a NoSQL database, where the data in the background is stored in the immutable tables which are called SSTables. These SSTables are subjected to a method called Compaction to reclaim the disk space and to improve READ performance. Size Tiered Compaction Strategy and Leveled Compaction Strategy are the most used generic compaction strategies for different use cases. Space Amplification and Write Amplification are the main limitations of the above compaction strategies, respectively. This research aims to address the limitations of existing generic compaction strategies. Objectives: A new random compaction strategy will be created to improve the efficiency and effectiveness of compaction. This newly created random compaction strategy will be evaluated by comparing the read, write and space amplification with the existing generic compaction strategies, for different use cases. Methods: In this study, Design Science has been used as a research method to answer both the research questions. Focus groups meetings have been conducted to gain knowledge on the limitations of existing compaction strategies, newly created random compaction strategy, and it’s appropriate solutions. During the evaluation, The metrics have been collected from Prometheus server and visualization is carried out in Grafana server. The compaction strategies are compared significantly by performing statistical tests. Results: The results in this study showed that the random compaction strategy is performing almost similar to Leveled Compaction Strategy. The Random Compaction Strategy solves the space amplification problem and write amplification problem in the Size Tiered Compaction Strategy and Leveled Compaction Strategy, respectively. In this section, eight important metrics have been analyzed for all three compaction strategies. Conclusions: The main artefact of this research is a new Random Compaction Strategy. After performing two iterations, a new stable random compaction strategy is designed. The results were analyzed by comparing the Size Tiered Compaction Strategy, Leveled Compaction Strategy and Random Compaction Strategy on two different use cases. The new random compaction strategy has performed great for Ericsson buffer management use case.
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Berg, Sven. "Ultra high-pressure compaction of powder." Doctoral thesis, Luleå tekniska universitet, Material- och solidmekanik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-16908.
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Sintering at high-pressure improves the properties of the material, either through new sintering aids becoming available or through improving intergranular bonding. This gives the manufactured products potential advantages like faster cut rates, and more precise and cleaner production methods that add up to cost efficiency and competitive edge. The production of synthetic diamond products demands tooling that can achieve high pressures and deliver it with a high degree of certainty. The common denominator for almost all high-pressure systems is to use capsules where a powder material encloses the core material. Numerical analysis of manufacturing processes with working conditions that reach ultra high pressure (above 10 GPa) requires a constitutive model that can handle the specific behaviours of the powder from a low density to solid state. The work in this thesis deals with characterization and simulation of the material behaviour during high-pressure compaction in powder pressing. Some of the work was focused on investigating the material when used as compressible gasket in high-pressure systems. The aim was to increase the knowledge of the high-pressure pressing process. This includes a better understanding of how mean stress develops in the compact during pressing and an insight into the development material models concerning highpressure materials. Both experimental and numerical investigations were made to gain knowledge in these fields. The mechanical behaviour of a CaCO3 powder mix was investigated using the Brazilian disc test, uniaxial compression testing and closed die experiments. The aim of the experimental work was to provide a foundation for numerical simulation of CaCO3 powder compaction at higher pressures. Friction measurements of the powder were also conducted. From the experimental investigations, density dependent material parameters were found. An elasto-plastic Cap model was developed for ultra high-pressure powder pressing. To improve the material model, density dependent constitutive parameters were included. The model was implemented as a user-defined material subroutine in a nonlinear finite element program. The model was validated against pressure measurements using phase transitions of Bismuth. The measurements were conducted in a Bridgman anvil apparatus. The simulations showed that thin discs with small radial extrusion generate a plateau at a low-pressure level, while thick discs with large radial extrusion generate a pressure peak at a high-pressure level. The results showed that FE-results can be used to engineer pressure peaks needed to seal HPHT-systems. For compressible gaskets, it was found that diametral support increases the phase transformation load. Higher initial density of the powder compact and diametral support generate higher pressure per unit thickness. The results from the validation using pressure measurements showed that the simulation model was indeed capable of reproducing load–thickness curves and pressure profiles, up to 9 GPa, close to the experimental curves.Godkänd; 2011; 20111020 (bersve); DISPUTATION Ämnesområde: Hållfasthetslära/Solid Mechanics Opponent: Professor Javier Oliver, Dept of Strength of Materials and Structural Analysis, Technical University of Catalonia, Barcelona, Spain, Ordförande: Bitr professor Pär Jonsén, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Tid: Torsdag den 15 december 2011, kl 09.00 Plats: E246, Luleå tekniska universitet
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Fernando, M. S. D. "Traction induced compaction of maize powder." Thesis, Imperial College London, 1987. http://hdl.handle.net/10044/1/38311.
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Ozkan, Necati. "Compaction and sintering of ceramic powders." Thesis, Imperial College London, 1994. http://hdl.handle.net/10044/1/42997.
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This Thesis describes a study of the compaction and the sintering of ceramic powders within the context of their "near net shape forming" into dense bodies. The operation of near net shape forming is the manufacture of ceramic parts with a required external dimensional tolerance combined with a defect free internal microstructure. The current study considers these requirements by focusing upon the fundamental facets of near net shape forming operations. The effects of the processing and material parameters on the compaction behaviour of agglomerated alumina powders have been investigated experimentally. It has been shown that the green compacts, formed from the agglomerated alumina powders by the uniaxial die pressing technique, possess certain density distribution patterns due to the frictional forces during the compaction process, and these density distributions depend primarily upon the properties of the agglomerates and the lubrication state of the die wall. The density distributions in the green compacts have been determined experimentally using the coloured layer technique and predicted using a first order model. Due to the inhomogeneous density distributions in the green compacts, the shrinkage of the compacts was not homogeneous. As a result, the shapes of the sintered compacts were not geometrically linear scaled replicas of the green compacts and the shape distortions in the sintered compacts have been characterised. It has been shown that there is a relationship between the extent of the shape distortions and the density distributions in the green compacts; that is, the more inhomogeneous green compacts the more is the shape distortions in the resulting sintered compacts. Sintering and grain growth equations, modified from established relationships, have been used for the sintering simulations in order to predict both the progression of the density and grain size of the sintered compacts. In order to predict the overall shape of the sintered compacts, a first order model has been developed by combining the predicted density distributions in the green compacts and the predicted density of the sintered compacts. The extent of the shape distortions have been reduced by optimising the properties of the agglomerates and the state of the die wall lubrication condition.
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Mapfumo, Emmanuel. "Soil and plant response to compaction." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq23028.pdf.
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Mohammed, Hussein. "Contact mechanical aspects of pharmaceutical compaction." Thesis, Imperial College London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.411047.
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Baird, K. S. "The explosive compaction of metallic powders." Thesis, Queen's University Belfast, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381900.
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Larhrib, El Hassane. "Characterisation & compaction of polyethylene glycols." Thesis, Liverpool John Moores University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242150.
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Ho, A. Y. K. "Time dependent characteristics in tablet compaction." Thesis, Open University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375495.
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A single punch tablet machine has been instrumented to measure top and bottom punch force and punch displacement. A system has been developed for instrumenting rotary tablet machines using radio telemetery techniques and compared with conventional instrumentation systems. It is shown that the positioning of the measuring devices is critical for accurate measurements of forces and punch displacement. Samples of Micro crystalline cellulose (Avicel PH-102) and various grades of Lactose have been characterised and their compaction properties measured by a variety of techniques including breaking strength, changes in bed density under compaction and stress relaxation. The properties were determined using a specially constructed laboratory compaction simulator capable of reproducing compaction events typical of full scale production. It is shown that none of the conventional indices of compaction behaviour adequately predict the compaction properties of materials as described by their breaking strength: force profile. A phenomenon is described whereby the measurement of maximum force is not coincidental with the measurement of maximum punch penetration. Using model materials it is suggested that these differences are due to the visco elastic and plastic components of materials during compression. A new index - rise time - (the time between the initiation of compression and the point of maximum force application) is proposed as a useful means of predicting the behaviour of pharmaceutical solids during compression.
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Ogbonna, Nkemdirim. "Indentation and compaction of inelastic solids." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320043.
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Zody, Michael Charles. "Tin plating using liquid dynamic compaction." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/37514.
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Chilukwa, Nathan Ntanda. "Vibratory hammer compaction of granular materials." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/80132.
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Thesis (MScEng)--Stellenbosch University, 2013.ENGLISH ABSTRACT: Compaction is one of the key processes in the construction of road pavement layers. Not only is it significant in ensuring the structural integrity of the material in the road layers, but it also has an influence on the engineering properties and performance of the soil material. A poorly compacted material is characterised by low density, high porosity and below standard shear strength. This, as a result causes rutting, moisture susceptibility, potholing, corrugations and passability problems on the road. Therefore, it is vitally important that field compaction is done correctly. For this reason, laboratory compaction methods have been developed to simulate the field compaction process in the laboratory. The Mod AASHTO test has long been used as the laboratory compaction method of choice by virtue of its simplicity and the lack of bulky equipment required. However, previous studies have established that the Modified AASHTO method does not adequately simulate field compaction criteria especially for cohesionless materials. Two reasons have been advanced; The Mod AASHTO compaction method does not adequately simulate the compaction done in the field when the granular mix is laid; The compaction method may cause disintegration of the material. Alternative tests have been considered and much research has focused upon the use of a modified demolition hammer (vibratory hammer) for laboratory compaction of granular materials. This study undertook to evaluate the influence of test factors pertinent to the vibratory hammer compaction method. The influence of these test factors on compaction time and obtainable material density was assessed with the objective of developing a compaction method for granular materials. Vibratory hammer compaction tests were conducted on G3 hornfels, G4 hornfels and G7 sandstone material types and to a lesser extent, reclaimed asphalt (RA). Densities obtained were referenced to Mod AASHTO compaction density. Findings of the study showed that, the mass of the tamping foot has a significant influence on the obtainable compaction density. Other factors such as, moisture content, frequency and frame rigidity were also found to affect compaction with the vibratory hammer. In addition, it is shown that the surcharge load does not significantly influence the obtainable compaction density but does contribute to the confinement of the material and restricts the upward bounce of the hammer. On the basis of the results and findings, a compaction method was proposed, incorporating test parameters and factors that would provide ideal results for a set compaction time. Repeatability tests showed that, the developed vibratory hammer compaction method was effective in compacting graded crushed stone material types (i.e. G3 and G4) and probably RA. The test was not as effective on the G7 material. Further studies on this material (G7) are required. In addition to the previous testing regime, a comparative assessment of the developed vibratory hammer compaction method in relation to the vibratory table method was done. The results show that the vibratory hammer is capable of producing specimens of densities comparable to those of the vibratory table. A sieve analysis undertaken before and after compaction showed that compaction with the developed vibratory hammer compaction method does not result in any significant material disintegration. Based on the results of this study, a specification for the determination of maximum dry density and optimum moisture content of granular material using the vibratory hammer is recommended.
AFRIKAANSE OPSOMMING: Kompaksie is een van die belangrikste prosesse in die konstruksie van die padplaveisel. Dit is nie net waardevol vir die versekering van strukturele integriteit van die materiaal, maar dit het ook 'n invloed op die ingenieurseienskappe en vermoë van die grond materiaal. 'n Swak gekompakteerde materiaal word gekenmerk deur 'n laë digtheid, hoë porositeit, on onvoldoende skuifweerstand. Die kenmerke maak die material vatbaar vir vogen. Lei tot spoorvorming, slaggate, golwe en deurgangs probleme op die pad. Dit is dus uiters noodsaaklik dat veld kompaksie korrek gedoen word. Om hierdie rede, is kompaksie metodes in die laboratorium ontwikkel om sodaend veldkompaksie te simuleer. Die “Mod AASHTO” laboratorium kompaksie toets is die gekose laboratorium kompaksie metode op grond van sy eenvoudigheid en gebruik van minimale toerusting. Vorige studies het egter bevestig dat die “Mod AASHTO”-metode nie veldkompaksie akkuraat kan simuleer nie, veral vir kohesielose materiaal. As gevolg van twee hoofredes; Die Mod AASHTO kompaksiemetode is nie ‘n realistiese en vergelykende simmulering van kompaksie soos dit in die veld gedoen word nie; Die kompaksie metode mag verbrokkeling van die materiaal veroorsaak. Alternatiewe toetse was oorweeg en baie navorsing het gefokus op die gebruik van 'n aangepaste vibrerende hamer. Hierdie studie het onderneem om verskeie relevante toetsfaktore van die vibrerende hamer en hul invloed op die kompaksie en verkrygbare digtheid te bestudeer. Die invloed van hierdie toetsfaktore op kompaksietyd en verkrygbare materiaal digtheid was geassesseer met die doel om 'n kompaksiemetode vir granulêre materiaal te ontwikkel. Vibrerende hammer kompaksietoetse was uitgevoer op G3 hornfels, G4 hornfels en G7 sandsteen materiaal en tot 'n mindere mate herwinde asfalt. Digthede verkry was verwys na die Mod AASHTO kompaksie digtheid. Resultate van die studie het getoon dat die gewig van die stamp voet ‘n merkwaardige invloed het op die verkrygbare kompaksie digtheid. Ander faktore soos voginhoud, frekwensie en raam styfheid het ook getoon om kompaksiedigtheid te beïnvloed met die vibrerende hammer. Benewens was ook getoon dat die toeslaglading geen beduidende invloed het op die verkrygbare kompaksie digtheid nie, maar wel bydrae tot die inperking van die materiaal en verhoed die vertikale terugslag van die hammer. Gebaseer op die resultate en bevindinge was ‘n kompaksiemetode voorgestel wat toets parameters integreer met toetsfaktore en tot volg ideale resultate vir ‘n gegewe kompaksietyd voorsien. Herhaalde kalibrasie toetse het getoon dat die ontwikkelde kompaksiemetode effektief is in die kompaktering van gegradeerde gebreekte klip materiaaltipes (G3 en G4) en moontlik herwanne asfalt. Die toets was nie so doeltreffend op die G7 materiaal nie. Verdere studies op hierdie materiaal (G7) is dus nodig. Addisioneel tot die vorige toets, is bevind dat ‘n vergelykende assesering van die ontwikkelde vibrerende hammer kompaksiemetode in verhouding tot die vibrerende tafel. Die resultate wys dat die vibrerende hammer die vermoë het om toetsmonsters met digthede vergelykbaar met die vibrerende tafel te produseer. Sifanalise voor en na kompaksie het getoon dat verdigting met die ontwikkelde vibrerende hamer kompaksie metode nie lei tot die disintegrasie van die materiaal nie. Gebasseer op die resultate van dié studie was ‘n spesifikasie vir die bepaling van maksimum droé digtheid en optimale voginhoud van granulêre material aangeraai.
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Chang, Cheng-Fu. "Compaction of chromatin in Saccharomyces cerevisiae." Master's thesis, University of Cape Town, 2006. http://hdl.handle.net/11427/4247.
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Word processed copy.Includes bibliographical references.
This study investigated the link between the association of the yeast linker histone homologue, Hholp, and the compaction of the yeast genome during stationary phase. The relative gene content of condensed chromatin, fractionated and isolated by sucrose gradient ultracentrifugation from stationary and exponential phase cultures was compared using genome-wide technologies. This study showed that condensed chromatin of stationary phase culture contained an enriched density of genes on all the chromosomes, indicating global compaction of the yeast genome during stationary phase.
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Venz, Gary Jon. "Hot shock compaction of nanocrystalline alumina." Thesis, Queensland University of Technology, 2002.
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Souriou, David. "Compaction conventionnelle et compaction grande vitesse (CGV) de céramiques : influence du procédé de compactage sur le frittage." Phd thesis, Ecole Nationale Supérieure des Mines de Saint-Etienne, 2007. http://tel.archives-ouvertes.fr/tel-00489885.
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L'amélioration des propriétés des pièces céramiques passe par une meilleure compréhension des phénomènes intervenant au cours de la mise en forme et du frittage. Les comprimés céramiques sont classiquement mis en forme par pressage uniaxial quasi-statique (pressage conventionnel) dans des matrices acier ou carbure. Mais une technique de mise en forme par impact, la Compaction Grande Vitesse (CGV), utilisée pour la mise en forme d'objets céramiques, apporte des résultats différents en terme de propriétés microstructurales. L'objectif de notre étude est d'identifier l'origine des différences microstructurale constatée entre ces deux méthodes de mise en forme. Des poudres d'alumine formulées sont testées pour identifier les paramètres les plus influant en terme de propriétés macrostructurale et microstructurale des comprimés céramiques à vert mis en forme conventionnellement ou par CGV. La finesse de la poudre, la nature et la quantité des ajouts organiques sont identifiés comme des paramètres influant sur les propriétés des comprimés ; mais une plus grande vitesse de compression apporte des améliorations significatives aux comprimés en terme de densité et de taille de pore réduite. De plus, une modélisation phénoménologique de la compaction permet d'identifier l'intensité des paramètres de fragmentation, de déformation plastique, et de vitesse d'élimination de la porosité. Il ressort que les phénomènes de déformation plastique des granules et de réarrangement granulaire sont favorisés en CGV. Par ailleurs, l'élaboration directe de pièces de forme complexe en CGV permet une étude plus approfondie des mouvements granulaires. Malgré le temps très court de l'impact (3 ms), il n'y a pas seulement des mouvements verticaux des grains, mais aussi des déplacements latéraux ; de plus, des effets de bord sur les comprimés sont dus à des phénomènes de frottement des grains contre la matrice en périphérie des pièces. Les pièces élaborées par chacune des voies de mise en forme sont ensuite frittées. L'objectif est de voir comment la microstructure initiale d'un comprimé céramique peut influer sur son comportement au frittage et sur la qualité des pièces en terme d'homogénéité de densité et de tailles de grains, ceci avec des géométries de pièces variables (dimensions, forme). Il est montré que la plus grande présence de pores de petite taille est à l'origine d'une meilleure densification et d'une microstructure plus fine. Les résultats du frittage sont donc reliés à ceux de la mise en forme et mettent en évidence l'aspect positif de la CGV sur la qualité des pièces frittées.
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Eseme, Emmanuel. "Oil shales: compaction, petroleum generation and expulsion." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=981527256.
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Li, Yanfeng. "Use of a BCD for compaction control." Diss., Texas A&M University, 2004. http://hdl.handle.net/1969.1/2696.
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Compaction of soil is essential in the construction of highways, airports, buildings, and bridges. Typically compaction is controlled by measuring the dry density and the water content of the compacted soil and checking that target values have been achieved. There is a current trend towards measuring the soil modulus instead or in addition to density. The reasons are that the density measurements are made using nuclear density meter, an undesirable tool in today??s political environment and that pavement design uses moduli as an input parameter. Although there are many apparatus available to measure soil modulus in the field such as Falling Weight Deflectometer, Dynamic Cone Penetrometer and Seismic Pavement Analyzer, a light weight and easy to use device which can measure the soil modulus fast and accurately is in great need. Briaud Compaction Device (BCD) is a portable device which can measure a soil modulus in several seconds. The principle of the BCD is to use the bending of a plate resting on the ground surface as an indicator of the modulus of the soil below. Numerical simulations show that within a certain range, the soil modulus is simply related to the plate bending. Strain gauges are glued on the top of the plate of BCD and a double half Wheatstone bridge is used to measure the strain. BCD tests were done in parallel with plate tests of the same size. A good correlation was found between the ratio of the plate pressure over the bending strain measured with a BCD and the reload soil modulus obtained from the plate test. This correlation can be incorporated into the BCD processor to display the soil modulus directly. To transit from dry density based compaction control to modulus based compaction control, BCD tests were also performed in the laboratory on top of a soil sample compacted inside the Proctor mold followed by plate tests. That way, a soil modulus versus water content curve is developed which parallels the approach for the dry density versus water content. The soil modulus versus water content curve can be used to provide the target values for compaction control in the field.
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Hure, Jérémy. "Adhésion, délamination et compaction de plaques minces." Phd thesis, Université Paris-Diderot - Paris VII, 2012. http://pastel.archives-ouvertes.fr/pastel-00713495.
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Nous avons étudié dans cette thèse des exemples de grandes déflexions de plaques minces soumises à diverses sollicitations (gravité, capillarité, géométrique), allant en termes d'échelle de cloques de délamination de graphène à l'emboutissage, en utilisant des expériences modèles macroscopiques et une analyse par des modèles analytiques ou en lois d'échelle. Le fil conducteur qui relie ces différents exemples est l'effet du changement de courbure de Gauss et ses conséquences mécaniques sur les déformations des plaques minces. Dans une première partie, nous avons rappelé la modélisation et les caractéristiques des plaques minces que nous avons illustrées au moyen de deux problèmes modèles. Nous nous sommes intéressés aux cloques de délamination qui apparaissent lorsqu'une plaque mince adhère partiellement sur un substrat plan. Nous avons montré quelles informations peuvent être déduites de ces cloques pour faire de la métrologie. Nous avons décrit ensuite les principales caractéristiques du contact entre une plaque mince et une sphère adhésive, à savoir la taille de la zone de contact et l'aspect général du motif. Enfin, nous avons étudié la compaction d'une plaque entre deux calottes sphériques, qui conduit à l'apparition de plis radiaux dont nous avons expliqué les caractéristiques et modélisé la réponse mécanique.
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Ghafoori, Roozbahany Ehsan. "Flow behavior of asphalt mixtures under compaction." Doctoral thesis, KTH, Byggnadsmaterial, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-219857.
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Asphalt compaction is one of the most important phases of road construction, being the decisive phase when the structure of the asphalt pavement layer is formed. In spite of its importance, the knowledge about this construction phase is still based on empirical and technological background and therefore surprisingly limited. This lack of knowledge is also due to the fact that the existing laboratory scale compaction devices for mix design are not fully capable of simulating the field compaction. The simulation of asphalt compaction in the laboratory is normally focused on the vertical rearrangements of asphalt particles whereas the flow behavior of these particles in other directions is mostly neglected. However, existing literature suggests that the neglected flow is one of the most important factors for the quality of the road construction, particularly in special cases such as asphalt joints. Therefore, building up a better understanding of the flow behavior of asphalt mixtures subjected to compaction loads is needed for improving the quality of the pavements. In this study, a new test setup, the so called Compaction Flow Test (CFT), was developed to simulate the flow behavior of asphalt mixtures at early stages of compaction. In the first step, feasibility tests were performed, substituting asphalt mixtures by model materials with simple geometries and less complex properties. X-ray Computed Tomography (CT) was utilized for capturing 2D radiography images of the flow patterns in the model material during the test. Results of the CFT showed the capability of the new test setup to clearly distinguish between model mixtures with different characteristics. Hence, in the next step, the CFT was applied to real asphalt mixtures and the obtained results were found to support the findings of the feasibility tests with the model materials. The results from the feasibility tests encouraged examining the possible use of an ultrasonic sensor as alternative to the complex and costly X-ray imaging for flow measurements during the CFT. Hence, the CFT was used along with a distance measuring ultrasonic sensor for testing asphalt mixtures with different characteristics. The test results confirmed that an ultrasonic sensor could be effective for capturing the differences of the flow behavior of asphalt mixtures tested by the CFT. In addition, a parametric study with the X-ray setup was carried out to examine the capability of the CFT in reflecting the possible changes of the flow behavior in asphalt mixtures due to the change of construction parameters such as lift thickness, bottom roughness and compaction modes. The results obtained also confirmed the capability of the CFT in showing the possible differences in the flow behavior of the mixtures under the chosen conditions. The encouraging results suggested that the CFT may have potential to become a simple but effective tool for assessing compactability of the mixtures on-site, right after production in an asphalt plant or before placing the mixture on the road. Hence, discrete element method (DEM) was utilized to understand both the influence of selected boundaries of the CFT and the effect of its design on the results. As one specific example of application, an investigation was carried out using the CFT to find the most suitable tracking method for flow measurements in the field. Based on the literature review and feasibility tests, a tracking method with the highest potential for conducting flow measurements during field compaction was introduced. X-ray radiography confirmed the validity of the results obtained with the suggested method. The overall results obtained from this study suggest that the recommended CFT along with the suggested field tracking method may be helpful in building up a comprehensive basis of knowledge on the flow and compaction behavior of asphalt mixtures thus helping to close the gap between the field and laboratory.QC 20171214
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Thompson, Mark Jason. "Experimental verification of roller-integrated compaction technologies." [Ames, Iowa : Iowa State University], 2007.
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Colley, Zahra J. Lee Yoon Y. "Compaction of switchgrass for value added utilization." Auburn, Ala., 2006. http://repo.lib.auburn.edu/2006%20Spring/master's/COLLEY_ZAHRA_56.pdf.
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Shang, Chenglong. "Modelling powder compaction and breakage of compacts." Thesis, University of Leicester, 2012. http://hdl.handle.net/2381/10824.
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Experimental and numerical simulation studies were carried out to enhance the understanding of the compaction behaviour of powder materials and to study the breakage behaviour of tablets after compaction. In order to simulate powder compaction and post compaction behaviour an appropriate constitutive model is required. To calibrate the constitutive model (e.g. a Drucker-Prager Cap model) a series of experiments were carried out including closed die compaction, uniaxial and diametrical compression tests. A newly developed apparatus consisting of a die instrumented with radial stress sensors was used to determine constitutive parameters as well as friction properties between the powder and die wall. The calibration of constitutive models requires accurate stress-strain curves. During die compaction the deformation of the powder material is determined by considering the elastic deformation (or compliance) of the system. The effect of different compliance correction methods was evaluated with regards to the accuracy of models predicting the pressing forces. A method for accounting for non-homogeneous stress states in instrumented die compaction was also developed. A complete data extraction procedure was presented. The breakage behaviour of flat and curved faced tablets was investigated and the breakage patterns of tablets were examined by X-Ray computed tomography. An empirical equation that relates the material strength to the break force was proposed. The constitutive model was implemented into the finite element package Abaqus/Standard to simulate powder compaction and breakage. A range of failure criteria have been evaluated for predicting break force of flat and curved faced tablets under diametrical compression.
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Htewash, El-Mabruk S. "The compaction of fine dense asphaltic mixtures." Thesis, Heriot-Watt University, 2002. http://hdl.handle.net/10399/372.
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O'Reilly, Myles Patrick. "Predictions of the performance of compaction plant." Thesis, Heriot-Watt University, 1985. http://hdl.handle.net/10399/1622.
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