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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.

Copper shaft-hole axes and early metallurgy in south-eastern Europe : an integrated approach

Heeb, Julia Maria January 2011 (has links)
Although the copper axes with central shaft-hole from south-eastern Europe have a long history of research, they have not been studied on a transnational basis since the 1960s. What has also been missing is an integrated or holistic approach, trying to use as many methods as possible and better understand the production, use and context of these enigmatic objects. This present research therefore approaches the axes from different angles. A database was compiled in order to find answers on questions such as the patterns of distribution, context, fragmentation and deformation of axes. For the distribution of axes in general as well as different attributes like fragmentation and typology, the content of the database was imported into GIS software and analysed. Aspects of production were considered through experimental archaeology, metallographic analysis and a re-discovered axe blank with missing shafthole. Especially the missing moulds make it difficult to fully understand the production sequence. The typology was re-evaluated and modified to ensure comparability across modern national boundaries. The context and background was developed through a thorough review of the literature and combined with theoretical considerations. The integration of all these approaches yielded some interesting results. The great variability in shape combined with the results of metallographic analyses clearly shows that a variety of production techniques were used, but it is as yet difficult to relate these to specific geographic areas or even cultural groups. In fact the typology as well as the practice of marking the axes indicate that traditional archaeological ‘cultures’ rarely correspond to the distribution of a type or to the practice of marking the axes. They show instead that there were different spheres of influence, some even more localised and others much larger (like the Carpathian Basin) than specific ceramic traditions. These different levels of belonging, as well as the increasing visibility of the individual in the archaeological record, show that it was a period of complex cultural patterns and interactions. The axes were a part of these networks of the daily life on many different levels from the strict utilitarian to the ritualised placement in burial contexts.

Modelagem e simulação do circuito de britagem de córrego do Sí­tio I com desenvolvimento de modelo para moinho de martelos. / Modeling and simulation of the crushing circuit of Córrego do Sítio I with development of model for hammer mill.

Felipe, Rafael Alves de Souza 26 March 2019 (has links)
Etapas de cominuição representam uma grande parcela do capital e custo operacional em uma usina de processamento mineral. Em 1983, Cohen estimou que os processos de cominuição podem ser responsáveis por 30% a 50% do consumo energético da usina representando tipicamente 50% dos custos operacionais de uma mineração. Sendo assim, sua otimização está diretamente relacionada com a redução destes custos de operação. Entre os equipamentos de britagem, o moinho de martelos é aquele dedicado às operações que visam a alta taxa de redução com geração controlada de finos. Este britador é recomendado para minérios friáveis e pouco abrasivos, apresentando alta capacidade produtiva. O presente trabalho tem por objetivo propor e validar um modelo matemático para modelagem e simulação de moinho de martelos, visando a simulação do circuito da britagem industrial de beneficiamento de minério de ouro do Córrego do Sítio I, localizada em Santa Bárbara - MG. As simulações visaram identificar gargalos operacionais e estabelecer cenários que permitam otimizar o circuito estudado. A amostragem foi executada conforme o plano traçado. As amostras obtidas foram utilizadas tanto para a caracterização do minério quanto para a calibração do modelo do Caso Base da operação da usina. As simulações indicaram acréscimos significativos de vazão de alimentação na usina, a partir do aumento da velocidade de rotação do moinho de martelos, com uma tendência de geração maior de finos no processo. Para simulação do aumento de velocidade de rotação dos martelos foi criado um modelo com base na energia de quebra das partículas, associada aos incrementos correspondentes na energia cinética dos martelos. A fim de validar o modelo proposto, foram planejados ensaios específicos em moinho de martelos de laboratório, e executados com o mesmo minério alimentado na usina industrial selecionada. Os ensaios consistiram em variações de velocidade de rotação dos martelos, de forma a corresponder às simulações anteriormente realizadas do equipamento industrial. O modelo criado foi validado com base em campanha experimental específica. / Comminution represents a large portion of the capital and operating cost of a mineral processing plant. In 1983, Cohen estimated that comminution processes could account for 30% to 50% of the power consumption of the mill, and typically represents 50% of the operating costs of a mine. Therefore, its optimization is directly related to reduction of these operating costs. Among the crushing equipment, the hammer mill is one which is dedicated to operations that aim for high reduction ratio with controlled generation of fines. This crusher is recommended for friable and low abrasive ores presenting a high productive capacity. This study aims to develop a stepwise approach that allows the use of the classical crusher model (Whiten-Andersen) in modeling and simulation of circuits containing a hammer mill, simulating the resulting product according to variation of rotation speed within the equipment. The existing model for crushers developed by Whiten-Andersen considers the Perfect Mixing Model, which represents crushing through equations related to selection and breakage functions, that provide an equilibrium condition. The present work aims at the validation of a mathematical model of hammer mill, aiming at a simulation of the circuit of the industrial crushing of gold ore of Córrego do Sítio I, located in Santa Bárbara - MG. The simulations aimed at identifying operational bottlenecks and establishing scenarios that allow optimizing the studied circuit. Sampling was performed according to the drawn plan. The samples obtained were used both for the characterization of the ore and for the calibration of the Base Case model of the plant operation. The simulations indicated significant increases in feed flow at the plant, due to the increase in the speed of rotation of the hammer mill, with a trend of higher generation of fines in the process. To simulate the increase of rotational velocity of the hammers, a model was created based on the energy of breaking of the particles, associated to the corresponding increments in the kinetic energy of the hammers. In order to validate the proposed model, specific tests were planned in laboratory hammer mill, and executed with the same ore fed in the selected industrial plant. The tests consisted of variations in the speed of rotation of the hammers, in order to correspond to the previous simulations of the industrial equipment. The model created was validated based on specific experimental campaign.


Chitti, Abhishek 01 May 2019 (has links)
The aim of this research is to assess the material properties of concrete like modulus of elasticity, compressive strength, and Poisson’s ratio using various nondestructive Testing (NDT) methods like Ultrasonic Pulse Velocity (UPV) and Rebound Hammer (RH). Assessment of material properties of concrete is very important as they are used for structural design process. Various NDT methods are applied to ensure the quality of concrete specimens but they can also be used to find material properties. UPV is a NDT method which is used to test the internal condition of the concrete specimen. RH is a surface hardness testing method and can be used to test the homogeneity of the specimen. For this study, several batches of concrete samples with three different design strengths of 6000 psi, 8000 psi, and 12000 psi were casted. Modulus of elasticity and Poisson’s ratio were calculated from UPV P-wave and S-wave velocities. A Nomogram was developed by combining the longitudinal ultrasonic pulse velocities, rebound numbers, and compressive strengths measured from UPV, RH, and compressive strength tests respectively. This combined NDT correlation curve (Nomogram) can be used to estimate compressive strength of concrete if UPV and rebound values are known. The accuracy of these NDT methods were determined by comparing estimated strength to the actual strength. Furthermore, the effect of moisture content on UPV and rebound values was reviewed and also studied dynamic modulus of elasticity and its relation with static modulus of elasticity of the concrete was investigated for better understanding.

Peak pressures due to steam bubble collapse-induced water hammer

Perkins, Garry Wayne. January 1979 (has links)
Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1979. / Bibliography: leaf 31. / by Garry Wayne Perkins. / Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1979.

Introdução a analise dinâmica de fundações de máquinas. / Introduction to the dynamic analysis of machine foundations.

Almeida Neto, Edgard Sant'Anna de 23 November 1989 (has links)
Este trabalho apresenta conceitos e procedimentos que devem ser considerados na análise dinâmica de fundações de máquinas. São discutidas as abordagens e os métodos de cálculo à disposição dos engenheiros, assim como os fatores que influenciam a escolha e o desenvolvimento de modelos matemáticos adequados. Três tipos diferentes de fundação (fundações em bloco rígido, fundações de martelos e fundações aporticadas) são examinados, e são utilizados exemplos para demonstrar a eficácia de técnicas simples de modelagem. / This paper presents concepts and procedures necessary to the dynamic analysis of machine foundations. Analytical approaches available to the designer, and factors which influence the choice and development of a suitable analytical model are discussed. Three different foundations (block foundations, hammer foundations and framed foundations) are examined and examples are given to demonstrate the effectiveness of simple modeling techniques.

Kamenosochařská a řezbářská díla Jana Karla Hammera ve středních a jižních Čechách / Jan Karel Hammer's Stone Sculptural and Woodcarving Work in Central and South Bohemia

Šiková, Terezie January 2012 (has links)
The aim of this thesis is to record and evaluate from art-historical point of view the stone sculptural and woodcarving work of Jan Karel Hammer, whose activity was documented between the years 1737 and 1757 on the border of central and southern Bohemia. The topic of thesis was chosen due to the fact, that this interesting artist has not yet been introduced to the professional public. Automatic attribution of all sculptural and woodcarving work in the area around Čimelice, where Jan Karel Hammer spent the last two decade of his life, to his hand together with a sharp increase of works, that are assumed to belong to him, led to the need for critical review. With the exceptions of Hammer's works the information was drawn from topografical, historical and regional literature and from archival sources. Because of the literary character and limited number of sources the main emphasis was placed on formal analysis. The examined material was divided into several cathegories, as can be seen in the structure of final catalogue. Thanks to detailed knowledge of works it was possible to identify author's distinctive style, which can be detected also in the workshop production, and all specifics of his work. Attention focused on the sources of inspiration and style orientation took us to the Prague art center...

Alterations in Strength Characteristics for Isometric and Dynamic Mid-Thigh Pulls in Collegiate Throwers Across 11 Weeks of Training

Hornsby, W. Guy, Haff, G. Gregory, Sands, William A., Ramsey, Michael W., Beckham, George K., Stone, Michael H. 01 December 2013 (has links)
Aim: The purpose of this study was: 1) to investigate the alterations and relationships among training variables, performance variables, and physiological variables and 2) investigate the effects of strength training on potentiation complexes. Methods: The study enrolled nine D-1 collegiate throwers and four control subjects. The throwers participated in an 11-week resistance training and throws program. Resistance training volume load and throwing volume were recorded for 11 weeks. Measurements of maximal strength (isometric mid-thigh pulls) and dynamic mid-thigh pulls (DMTP) across a spectrum of loads: Males- 60kg, 140kg, 180kg, 220kg, 140kg, 30% isometric peak force (IPF), Females- 60kg, 80kg, 100kg, 120kg, 80kg, 30% IPF), were measured at weeks 1, 7, and 11. The control group was tested for isometric maximum strength at T1 (week 1) and T3 (week 11) Results: The throwers increased at each time point in isometric peak force (IPF), allometrically scaled IPF (IPFa), and isometric impulse. The throwers strength (IPF and IPFa) was significantly greater than the controls and the throwers experienced statistically significant changes in maximum strength from T1 to T3 when compared to the controls. The throwers demonstrated statistically significant changes in total load variables (variable for load 1+ load 2 + load 3 etc.) for DMTPs. Conclusion: As a whole these data suggest a potential for increased performance capabilities specific to throwing. Some data trends indicate that potentiation can occur as a result of performing a heavy pull before a lighter one. However, increasing maximum strength as a result of focusing on strength training did not enhance this potentiation effect.

Relative age dating of the Wahianoa moraines, Mount Ruapehu, New Zealand : thesis submitted in partial fulfilment of the degree of Master of Science in Quaternary Science at Massey University, Palmerston North, New Zealand

Nolan, Erin Unknown Date (has links)
This study attempts to determine a relative age of the Wahianoa moraines, Mt Ruapehu using three relative age dating techniques: Lichenometry, Schmidt hammer and Boulder roundness. There were three study areas used, termed the Wahianoa ‘A’, ‘B’ and ‘C’ moraines. Upon determining a relative age for these moraines, their timing of their formation was placed within New Zealand’s glacial timescale. This is the first study of its kind conducted on Mt Ruapehu and has left the door open for more research in this field. The species of lichens measured on the Wahianoa moraines were Rhizocarpon subgenus, which the largest diameters were measured using callipers. A total of 606 lichens were measured in the Wahianoa Valley and were processed using the growth curve and size frequency methods. A lichenometric growth curve was constructed from lichens growing in the Ohakune cemetery. The dates derived from both methods placed the formation of the Wahianoa moraines during the Little Ice Age. An L-type Schmidt hammer was used on the boulders in the Wahianoa Valley. A total of 280 measurements were taken off the boulders on the Wahianoa moraines. The results of this method, when compared to Winkler’s (2005) study in the South Island placed the formation of the Wahianoa moraines pre-Little Ice Age. Although no definitive ages could be derived from this comparison due to differences in lithology between the two studies, it provided an idea as to where the formation of these moraines could belong. This is the first time that the Boulder roundness method has been used in New Zealand, having only been developed by Kirkbride (2005). This method was used to determine which of the ridges in the Wahianoa Valley were older. It was found that the Wahianoa ‘A’ moraines were the oldest in the valley followed by Wahianoa ‘B’ and ‘C’ respectively. A climate reconstruction was also conducted for the Wahianoa Valley to see what conditions may have been in existence during the formation of the Wahianoa moraines. The paleo-ELA for the Wahianoa Glacier was estimated using the Accumulation-Area Ratio (AAR), Terminus to Headwall Ratio (THAR), Maximum Elevation of the Lateral Moraines (MELM) and Extrapolation methods. The current ELA was estimated using the AAR, THAR and Extrapolation methods. The difference between these estimates was used to determine what temperature decrease would have caused the formation of the Wahianoa moraines. The average paleo-ELA was found to be c. 1715m, while the current ELA was found to be 2475m which lead to a 4.5°C decrease. This temperature decrease correlates well with that of the Last Glacial Maximum. This study found significant differences in relative age of the Wahianoa moraines. There are a number of factors that can affect the growth of lichens such as micro-environmentalconditions and the fact that a growth curve was constructed off site. Factors such aspetrography can affect the Schmidt hammer results and the Boulder roundness measurements. In addition, precipitation can affect the ELA values which can then cause the wrong placement within a glacial event. Further research lies in the use of the Schmidt hammer on a known age surface such as the Mangatepopo moraines which will aide in a better correlation of relative age. Also, further research using climate reconstructions on Mt Ruapehu and the effect of precipitation will also aide in a better correlation with a glacial event.

Mix Design and Impact Response of Fibre Reinforced and Plain Reactive Powder Concrete

Gao, Xiang, S3090502@student.rmit.edu.au January 2008 (has links)
Concrete is the most broadly used material in construction worldwide and Reactive Powder Concrete (RPC, a type of ultra high performance concrete) is a relatively new member of the concrete family. In this work the critical parameters of RPC mix design are investigated and the mix design is explored through a program of concrete casting and testing. Owing to the enhanced microstructure of RPC, porosity and permeability can be significantly decreased in the concrete matrix. This benefits the durability characteristics of RPC elements resulting in a longer service life with less maintenance costs than conventional concrete. It has been used for high integrity radiation waste material containers because of its low permeability and durability. Fibre reinforced RPC is also ideal for use in long span and thin shell structural elements without traditional reinforcement because of its advantageous flexural strength. Moreover, due to improved impact resistance, RPC can be widely employed in piers of bridges, military construction and blast protection. There is no standard approach to assessing the impact resistance of concrete. This investigation utilises relatively well accepted impact equipment to evaluate the mechanical properties of RPC under dynamic loading. The compressive and flexural tensile strengths of plain and fibre reinforced RPC are investigated using a variety of specimens and apparatus. The dynamic increase factor (DIF) is evaluated to indicate the strain rate sensitivity of the compressive and flexural strength.

Bandesign för Multiplayerspel

Åkesson, Peter January 2009 (has links)
<p>Denna rapport är en undersökning om hur man gör en bana i ett FPS-spel så att banan blirintressant och rolig så att så många spelare som möjligt vill spela den. För att komma framtill det har jag skapat en bana i Hammer till spelet Team Fortress 2 för att göra vissa testerpå den för att därigenom komma fram till mitt resultat.</p><p>Slutligen kom jag fram till att det viktigaste när man skapar en bana är variation och att hamed något som passar alla. Dessutom kan det ha en viss vikt hur banan ser ut annarskommer folk inte ens testa banan.</p>

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