No / Given that most of the working life of a brake pad life is spent in the bedded condition, it is important to examine the conditions of a fully bedded contact interface. An experimental and a numerical method are combined. Contact pressure and its effects (heat generation/partition and temperature rise) for the drag braking process with and without bedding are compared. The real contact area is also measured and found to be increased for the bedded interface. This results to the contact pressure being ¿more¿ evenly distributed than before. Spreading the contact pressure also results in increasing the total heat transfer between the disc and pad since now more heat can be transferred from the pad (where it is generated) to the disc. It is concluded that in order to have a reliable simulation it is recommended that the bedding-in effects are introduced in the simulations. / IMechE, RAE Travel Grant

Orientador: Newton de Oliveira Pinto Junior / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-04T00:14:58Z (GMT). No. of bitstreams: 1 Maas_CelsoRicardo_M.pdf: 5291856 bytes, checksum: eb48c5e46eeba69d2c7fae64e7014aea (MD5) Previous issue date: 2004 / Resumo: Os dois objetivos principais deste trabalho são verificar e analisar a redução da carga de ruptura de paredes de alvenaria estrutural, quando os blocos são assentados com argamassa apenas nas suas paredinhas longitudinais (argamassa longitudinal). Estas verificações e análises se fazem necessárias porque a NBR 8798 (1985) ainda especifica a colocação de argamassa em todas as paredes dos blocos (argamassa plena), embora o que mais se tem observado nas nossas construções é a colocação de argamassa apenas nas paredinhas longitudinais. Além disso, essas verificações se tornam mais necessárias quando se sabe que esse tipo de assentamento é o mais usado nos países mais ricos e desenvolvidos do mundo. Para a determinação do valor dessa redução, bem como para melhor compreender a ruptura das paredes com esses dois tipos de assentamento, foram ensaiados corpos-de-prova de blocos, prismas e paredes de 1,00 m de altura, na idade de 14 dias, com argamassa plena e longitudinal. Todos os ensaios foram feitos com blocos de concreto e com blocos cerâmicos. Finalizando, após evidenciar as deficiências dos atuais modelos de prismas, principalmente dos prismas com argamassa longitudinal, este trabalho tem como um último objetivo propor novos modelos de prismas para ensaios, em conformidade com os tipos de assentamento / Abstract: The two main aims of this work are to verify and analyze the reduction of the compressive strength of structural masonry walls, when the blocks are laid with mortar only in the outside faces of the block (face shell bedding). These verifications and analysis are important because, although the Brazilian code NBR 8798 (1985) still specifies that the entire block surface must be bonded (full mortar bedding), in Brazil the most used type of bedding is the face shell bedding. Besides, these verifications are important because we notice that the face shell bedding is used in the richest countries. In order to find the magnitude of this reduction and to understand the collapse of the two types of bedding, 14 days old specimens of blocks, prisms and wallettes of one meter height were tested, with face shell and full mortar bedding. All the tests were carried out with concrete and ceramic structural blocks. After realize the handicaps of the Brazilian prisms, mainly that ones bonded whit face shell bedding, the last aim of this work is to propose a new model of prisms, to be used in laboratory tests / Mestrado / Edificações / Mestre em Engenharia Civil

Large diameter concrete pipes have been used in many areas of central Florida to carry pressured sewage flow. These pipes have been typically located at six feet below finished roadway elevation, and ranges in diameter from thirty six to sixty inches. The water table is typically located at shallow depth below finished roadway elevation, and generally fluctuates between five to ten feet depending on the relative roadway elevation to mean sea level. These pipes are under pressure when carrying the sewage flow, but return to normal atmospheric pressures when the flow stops. Since the water table encases most of the pipe circumference, no leaks is developed from the water table to the pipe when the pipe is under pressure. Once the pressure in the pipes returns to zero, the water starts seeping into the pipe while washing the subgrade with it into the pipe's interior. The subgrade washes into the pipe at the joint inverts between adjacent pieces of the pipe, since the invert is where the most tension exists in the joint under the weight of the soil and traffic loading above the pipe, making it the most probable location where a gap in the joint would form. This would cause the origination of a small void under the pipe, which creates pressure redistribution in the subgrade reaction under the pipe. As the void develops in the middle third of the bedding under the invert, pressure redistribution occurs to the outer two thirds of the bedding. As the stress increases in the outer portions of the bedding, more subgrade material is washed into the pipe when it is not under pressure, making the void larger. As the void becomes large, the moment in the pipe is greatly increased, and therefore the gap in the joint is increased due to the tension increase at the bottom of the pipe. More material is allowed into the pipe, and the void becomes deeper as fewer restrictions are encountered between the water table and the empty pipe. As the pipe becomes pressurized, more subgrade material is disturbed by the leak from the inside of the pipe to the outside, and void is constantly generated. The void then leads to the continuous settlement of the roadway. It is intended by this study to model the stresses in the subgrade around the pipe using a finite element software to determine the effects of void in the pipe's bedding on the stress around the pipe's outer perimeter. The stresses calculated as a result of the void will then be used in determining the increase in internal moment created in the pipe as the void is generated and became larger and deeper. Average stresses on the top and bottom of the pipe were calculated due to the soil profile dead load and live load caused by loading the soil profile with one and two HS-20 trucks. The average stresses were recalculated after the addition of void in the pipe bedding. The void width and depth were varied to come up with the case that would generate the highest unbalanced load on the pipe. The average bottom stress was subtracted from the average top stress to determine the unbalanced load on the pipe that would cause an internal moment in the pipe. At the most critical case, a forty kilo pounds per foot moment was caused by the existence of the void under the sixty inch diameter pipe used in the model. Such a moment is large to be resisted by either the pipe alone or the pipe reinforced by an additional structural support, unless such support is accompanied by void decrease and a mean to stop the subgrade from eroding into the pipe.

No description available.

International Telemetering Conference Proceedings / October 30-November 02, 1989 / Town & Country Hotel & Convention Center, San Diego, California / The Consultative Committee for Space Data Systems (CCSDS) is developing a set of communications protocols for Advanced Orbiting Systems (AOS). The National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA) are cooperating in an effort to extensively validate these AOS protocols. This paper describes the techniques and facilities being used to perform this validation. Validation of the AOS protocols consists of (1) developing a formal specification of the protocols using a standard formal definition technique (FDT), (2) developing implementations of the protocols, and (3) remote testing of the implementations. From the FDT specifications, each agency is developing independent implementations which are consistent with the FDT specifications of the AOS protocols. Errors, omissions, or discrepancies detected during the development of the FDT specification and the implementation will be reported to the CCSDS and changes to the main specification will be suggested. The independent implementations will be extensively tested locally by the developing agency and then remotely tested through a cooperative test setup between the agencies. The implementations will interact to communicate between the agencies thus providing proof that the FDT specifications are sufficiently specific to be interpreted by everyone in the same way. Significant variations in the interpretations will result in feedback to the CCSDS and any needed changes to the main specification will be suggested. The AOS protocols are divided into four categories: Path, Space Link ARQ Protocol (SLAP), Space Link (SL), and Management. Each agency has agreed to be either the leader or support agency for each of the categories. NASA has agreed to be leader for the validation of the SLAP and SLS categories while ESA has agreed to lead in the validation of the Path and Management categories. Testbeds at the European Space Research and Technology Centre (ESTEC) in Noordwijk, Holland and at the MITRE Corporation in McLean, Virginia have been constructed for the development of FDT specifications and AOS protocol implementations. Communications facilities are being obtained which will connect these testbeds. This paper describes these testbeds, the AOS FDT specifications, the protocol implementations being developed, and the results expected from the tests performed.

Estudos sobre de métodos de preparo de solo são essenciais pela necessidade em se reduzir os impactos nos solos, decorrentes da intensificação da mecanização agrícola na cultura da cana-de-açúcar e pela busca de modelos que visem proporcionar uma maior qualidade para o solo e, consequentemente, a obtenção de melhores desenvolvimentos vegetativos e maiores produtividades. O presente trabalho teve como principal objetivo, a avaliação por meio de análises micromorfométricas, das alterações na estrutura do solo decorrentes de métodos distintos de preparo de solo. Foram avaliados o preparo convencional, a partir da mobilização do solo em área total, e o preparo profundo canteirizado, com a utilização de um modelo de implemento que permite realizar uma série de operações de preparo de solo de forma simultânea, que não mobiliza a região de passagem do rodado dos maquinários e delimita um canteiro preparado para o desenvolvimento das plantas. O solo da área experimental é classificado como Nitossolo Vermelho Eutrófico latossólico, de textura muito argilosa e foram abertas trincheiras nos tratamentos em momentos distintos do ciclo comercial da cultura, a fim de serem observadas as modificações de forma temporal. Nestas, foram coletadas amostras para análises de densidade do solo e amostras indeformadas de solo para a realização de análises micromorfométricas, para a quantificação e caracterização da área ocupada por poros, tanto na região de desenvolvimento da cultura (canteiro) quanto na área de passagem do rodado. Foi possível observar uma maior área ocupada por poros no canteiro do tratamento do preparo profundo canteirizado na primeira coleta, proporcionado pelo implemento, em relação ao preparo convencional, assim como uma maior participação de poros grandes complexos frente a poros de menor tamanho e arredondados. Porém, notou-se nas áreas sem influência do sistema radicular da planta, como na região de passagem do rodado e centro do canteiro, uma redução da área ocupada por poros entre uma coleta e outra, tanto por conta do tráfego agrícola quanto pela acomodação do solo desestruturado no preparo profundo canteirizado, podendo vir a acarretar em menores desenvolvimentos radiculares horizontalmente e deixando a área mais propicia a menores taxas de infiltração de água no solo, reduzindo o fluxo hídrico internamente e, consequentemente, aumentando os riscos da ocorrência de processos erosivos. Já no preparo convencional, os resultados indicaram uma manutenção da estrutura proporcionada pelo tipo de preparo entre as coletas, com poros menores e arredondados. / Studies about soil tillage methods are essential due to the necessity of reducing impact in soils caused by the intensification of mechanic agricultural operations in sugarcane. These studies are also important by the pursuit of models that enables a better quality to the soil and, as a consequence, obtaining better vegetative development and productivity. This study had as its main objective the evaluation of soil structural changes caused by different methods of soil tillage by micromorphometric analysis. Two soil tillage systems were evaluated, the conventional soil tillage, which mobilizes the soil in the whole area, and the deep bedding tillage, which is done by an agricultural implement that allows a series of operations simultaneously and does not mobilizes the soil in the wheel\'s path, delimiting a bed for the plant development. The soil of the experimental area is classified as a Eutric Nitisol with a high clay texture. Pitches were opened in the treatments in different timings during the commercial cycle of the culture aiming the observation of temporal modifications in the soil. Samples were collected for density analysis and undisturbed samples were collected for micromorphometric analysis, for quantification and characterization of the pore area in either the root development area (bed) or the wheel\'s path. It was possible to observe a largest pore area in the deep bedding tillage system on the first collection due to the implement when compared to the conventional, as well as a largest occurrence of complex pores against smaller rounded pores. However, it was observed in the areas without the direct influence of the root system, as in the wheel\'s path and bed center, a reduction of the pore area between the two collections because of agricultural machinery traffic and accommodation of the unstructured soil in the deep bedding tillage system. This occurrence might incur in lowering root development horizontally and letting the area prone to lower water infiltration, which reduces the water flow internally and increases the risk of erosive processes. As regards the conventional tillage system, the results indicated a structural maintenance enabled by the tillage method between the collections, presenting smaller rounded pores.

Estudos sobre de métodos de preparo de solo são essenciais pela necessidade em se reduzir os impactos nos solos, decorrentes da intensificação da mecanização agrícola na cultura da cana-de-açúcar e pela busca de modelos que visem proporcionar uma maior qualidade para o solo e, consequentemente, a obtenção de melhores desenvolvimentos vegetativos e maiores produtividades. O presente trabalho teve como principal objetivo, a avaliação por meio de análises micromorfométricas, das alterações na estrutura do solo decorrentes de métodos distintos de preparo de solo. Foram avaliados o preparo convencional, a partir da mobilização do solo em área total, e o preparo profundo canteirizado, com a utilização de um modelo de implemento que permite realizar uma série de operações de preparo de solo de forma simultânea, que não mobiliza a região de passagem do rodado dos maquinários e delimita um canteiro preparado para o desenvolvimento das plantas. O solo da área experimental é classificado como Nitossolo Vermelho Eutrófico latossólico, de textura muito argilosa e foram abertas trincheiras nos tratamentos em momentos distintos do ciclo comercial da cultura, a fim de serem observadas as modificações de forma temporal. Nestas, foram coletadas amostras para análises de densidade do solo e amostras indeformadas de solo para a realização de análises micromorfométricas, para a quantificação e caracterização da área ocupada por poros, tanto na região de desenvolvimento da cultura (canteiro) quanto na área de passagem do rodado. Foi possível observar uma maior área ocupada por poros no canteiro do tratamento do preparo profundo canteirizado na primeira coleta, proporcionado pelo implemento, em relação ao preparo convencional, assim como uma maior participação de poros grandes complexos frente a poros de menor tamanho e arredondados. Porém, notou-se nas áreas sem influência do sistema radicular da planta, como na região de passagem do rodado e centro do canteiro, uma redução da área ocupada por poros entre uma coleta e outra, tanto por conta do tráfego agrícola quanto pela acomodação do solo desestruturado no preparo profundo canteirizado, podendo vir a acarretar em menores desenvolvimentos radiculares horizontalmente e deixando a área mais propicia a menores taxas de infiltração de água no solo, reduzindo o fluxo hídrico internamente e, consequentemente, aumentando os riscos da ocorrência de processos erosivos. Já no preparo convencional, os resultados indicaram uma manutenção da estrutura proporcionada pelo tipo de preparo entre as coletas, com poros menores e arredondados. / Studies about soil tillage methods are essential due to the necessity of reducing impact in soils caused by the intensification of mechanic agricultural operations in sugarcane. These studies are also important by the pursuit of models that enables a better quality to the soil and, as a consequence, obtaining better vegetative development and productivity. This study had as its main objective the evaluation of soil structural changes caused by different methods of soil tillage by micromorphometric analysis. Two soil tillage systems were evaluated, the conventional soil tillage, which mobilizes the soil in the whole area, and the deep bedding tillage, which is done by an agricultural implement that allows a series of operations simultaneously and does not mobilizes the soil in the wheel\'s path, delimiting a bed for the plant development. The soil of the experimental area is classified as a Eutric Nitisol with a high clay texture. Pitches were opened in the treatments in different timings during the commercial cycle of the culture aiming the observation of temporal modifications in the soil. Samples were collected for density analysis and undisturbed samples were collected for micromorphometric analysis, for quantification and characterization of the pore area in either the root development area (bed) or the wheel\'s path. It was possible to observe a largest pore area in the deep bedding tillage system on the first collection due to the implement when compared to the conventional, as well as a largest occurrence of complex pores against smaller rounded pores. However, it was observed in the areas without the direct influence of the root system, as in the wheel\'s path and bed center, a reduction of the pore area between the two collections because of agricultural machinery traffic and accommodation of the unstructured soil in the deep bedding tillage system. This occurrence might incur in lowering root development horizontally and letting the area prone to lower water infiltration, which reduces the water flow internally and increases the risk of erosive processes. As regards the conventional tillage system, the results indicated a structural maintenance enabled by the tillage method between the collections, presenting smaller rounded pores.

This study utilizes a sample of private equity backed acquisitions to test whether certain factors, evaluated and quantified on the date of transaction completion, serve as indicators of future transaction bankruptcy. The results of this paper suggest that the effective federal funds rate is significantly and positively correlated with the bankruptcy of private equity backed transactions. Other measured factors specific to the private equity sponsor, the target firm in the acquisition and the characteristics of the transaction are found to be insignificant. Analysis on the influence of these factors is performed using two types of binary-response models, which predict the likelihood of the occurrence of bankruptcy, and a matched sample model that tests for the difference of means between a non-bankrupt transaction group and a bankrupt transaction group. Limitations in the availability of data derived from the private nature of the industry resulted in a limited sample size of 259 transactions completed from 1989 to 2008. General insignificance in the results of this study merits further analysis on the contributing factors to private equity transaction failure.

Roller Compacted Concrete (RCC) has rapidly evolved from a concept to a material and a process which is used throughout the world for faster and more economical construction of dams. Currently, there are more than 250 RCC dams, completed or under construction, in the world. On the other hand, currently, there are only two RCC dams completed (Su&ccedil / ati and Cindere Dams) and two under construction (Beydag and &Ccedil / ine Dam) in Turkey. RCC dams are constructed in a series of compacted layers usually 30 cm in thickness. Therefore, appropriate bonding of successive layers is important and as a result, in between successive layers a bedding mix is often used to fill the surface voids in both the compacted layer below and the covering layer above, as well as to bond the two successive layers together. This study presents an experimental investigation on the bonding efficiency of RCC with different bedding mixes. The Beydag Dam RCC mixture was taken as the model for the preparation of laboratory-made RCC specimens. In the experimental study, 15 cm cubic specimens were prepared in two layers. Each layer was compacted using an electro pneumatic demolition hammer for 30 seconds. Four different time intervals between placement and compaction of two successive layers and two different bedding mix types were the selected cases for investigation. While preparing the specimens, the second layer was placed and compacted 0, 4, 8, 12 and 16 hours after the first layer was compacted. In between the two layers, two types of bedding mixes are placed in between previously compacted and freshly placed layer for joint treatment. One of the bedding mixes, having 200 kg/m3 cement content is termed poor while other one is termed rich having 400 kg/m3 cement content. RCC specimens are then subjected to compressive strength, splitting tensile strength and permeability tests. As a result of the experimental program, it was found that / a rich bedding mix was a more effective bonding agent between compacted RCC layers than the poor bedding mix for all time intervals between layers. Furthermore, it was concluded that bonding efficiency of RCC is not too dependent on time interval between layer compactions up to 16 hours. Finally, splitting tensile strength and sorptivity tests are shown to be applicable test methods for determination of bonding efficiency of RCC specimens if there is a definite bedding layer in between freshly placed and formerly compacted RCC.

Roof falls and accumulation of dangerous gasses are the most common hazards in any underground coal mine. Different mechanisms can jeopardize the stability of the roof in underground excavations and successful roof control can only be obtained if the failure mechanism is identified and understood properly. The presence of discontinuities, the inherent variability of the rock mass and discontinuity properties, and the uncertainties associated with directions and magnitudes of the in-situ stress makes the rock engineering problems challenging. The numerical modeling can assist the ground control engineers in designing and evaluating the stability of the underground excavations. If extensive geological and geotechnical data are available, then detailed predictions of deformation, stress and stability can be accomplished by performing numerical modeling. If not, still the numerical modeling can be used to perform parametric studies to gain insight into the possible ranges of responses of a system due to likely ranges of various parameters. The parametric studies can help to identify the key parameters and their impact on stability of underground excavations. The priorities of the material testing and site investigation can be set based on the selected key parameters from parametric studies. An underground coal mine in western Pennsylvania is selected as a case study mine to investigate the underlying causes of roof falls at this mine. The immediate roof at the case study mine consists of laminated silty shale, shale, or sandstone that changes from area to area, and the floor is shale or soft fireclay. This study was mainly focused in the stability analysis of the roofs with the laminated silty shale rock type, where the majority of roof falls had taken place in the roof with this type of roof material. Extensive laboratory tests were performed on the core samples obtained from the case study mine to estimate the intact rock and discontinuity properties of the materials that occur in large extent at the selected interest area of the case study mine. In this research, the three-dimensional distinct element method was used to investigate the stability of the roof in an underground room-and-pillar coal mine. The implemented technique was able to accurately capture the failure of the major discontinuities and rock masses which consist of intact rock and minor discontinuities. In order to accurately replicate the post failure behavior of the rock layers in the immediate roof area, the strain-softening material constitutive law was applied to this region. Extensive numerical parametric studies were conducted to investigate the effect of different parameters such as the variation of immediate roof rock mass strength properties, variation of discontinuity mechanical properties, orientations and magnitudes of the horizontal in-situ stresses, and the size of pillars and excavations on stability of the excavations. The distribution of post failure cohesion along with other measures such as accumulated plastic shear strain, distribution of Z-displacements at the roofline, failure state (joint slip and tensile failure) and displacement (normal and shear displacements) of discontinuities were used to accurately assess the roof stability in this case study. The research conducted in this dissertation showed that the bedding planes play an important role on the behavior of roof in underground excavations. Therefore, an appropriate numerical modeling technique which incorporates the effect of discontinuities should be employed to simulate the realistic behavior of the discontinuous rock masses such as the layered materials in roof strata of the underground coal mines. The three-dimensional distinct element method used in this research showed the clear superiority of this technique over the continuum based methods.