A crescente demanda por informações gravimétricas consistentes em âmbito sul-americano, visando, sobretudo, a unificação de um sistema altimétrico para o continente, foi a motivação maior deste trabalho. Nesse contexto, procurou-se evidenciar informações detalhadas, de cunho técnico e operacional, voltadas à execução de levantamentos gravimétricos. Assim, conceitos básicos introdutórios seguidos de uma resenha histórica da gravimetria no Brasil e no mundo, são delineados. É efetuada a proposta de uma nova abordagem para um sistema gravimétrico. Apresentam-se aspectos práticos detalhados sobre o manuseio do gravímetro LaCoste & Romberg. Sugerem-se, adicionalmente, procedimentos metodológicos para as diversas etapas de uma operação gravimétrica. Ao final, à guisa de estudo de caso, disponibilizam-se resultados que são analisados e comparados. / The increasing demand for consistent South American gravimetric informations, aiming, most of all, the unification of a height system for the continent, was the motivation for this work. Within this context, an effort was made to evince detailed technical and operational informations related to the execution of gravimetric surveys. Basic concepts are exposed, followed by a historical summary of gravimetry in Brazil and throughout the world. A proposal of a new approach for a gravimetric system is made and detailed practical aspects on the use of LaCoste & Romberg gravity meter are given. In addition, methodological procedures are suggested for the several stages of a gravimetric operation. Finally, as a case study, results are made available after analysis and comparisons.

This paper considers alternative methods to estimate econometric models based on bilateral data when only aggregate information on the dependent variable is available. Such methods can be used to obtain an indication of the sign and magnitude of bilateral model parameters and, more importantly, to decompose aggregate into bilateral data, which can then be used as proxy variables in further empirical analysis. We perform a Monte Carlo study and carry out a simple real world application using intra-EU trade and capital flows, showing that the methods considered work reasonably well and are worthwhile being considered in the absence of bilateral data. (authors' abstract)

Internet of Things, has started to mark its existence from past few years. Right from its inception with a coke machine at Carnegie Mellon University, it has come a long way, connecting billions of devices to internet. This journey is well supported by the advancements in networking, hardware miniaturization and sensing capabilities. Diverse nature of applications of Internet of Things, has cut the communication barriers between the varieties of fields ranging from manufacturing industry to health-care industry. Smart Home is one such application of Internet of Things. Connectivity of home appliances, to achieve automation in living, defines Smart Home. Out of welter of applications that are derived from Internet of Things, this thesis concentrates on Smart Home. Smart Home, in practical is expected to conserve lot of energy, by achieving automation of home appliances, on par with best living experience. Existing technologies such as Z-wave, One-Net, ZigBee, Insteon, had already occupied the Smart Home communication. However, these technologies face the problem of identifying the smart devices uniquely and also exhibit security vulnerabilities. Proposed scheme exploits accelerometer fingerprinting to identify the smart devices uniquely. Security vulnerabilities of existing protocols are addressed by encrypting the data on move with CCM mode of AES encryption.

No description available.

We consider the stability of black holes within both classical general relativity and the semiclassical thermodynamic description. In particular, we study linearised perturbations and their contribution to the gravitational partition function, addressing technical issues for charged (Reissner-Nordstrom) and rotating (Kerr-AdS) black holes. Exploring the connection between classical and thermodynamic stability, we find classical instabilities of Myers-Perry black holes and bifurcations to new black hole families.

We investigate the propagation of internal gravity waves in a rotating fluid with horizontal and vertical stratification. The modification of these waves by the presence of a vertically sheared geostrophic current is determined, and the rate of energy exchange between waves and current is estimated and compared to exchange rates of other interaction mechanisms. The effect of boundary conditions on the range of frequencies allowed for wave propagation is also considered. The wave amplitude has horizontal exponential dependence due to the horizontal density variation as well as to exchange of energy with the mean shear flow. The solution also shows a phase difference from surface to bottom. For waves propagating normally to a vertically sheared geostrophic current, the energy exchange mechanism is found to be weak when compared to other exchange mechanisms and is likely to be of little importance in the ocean. The imposition of boundary conditions on the wave solution alters the frequency range over which solutions may exist. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

In the classical design method for gravity dams, the designs are conducted in the linear elastic isotropic material domain. For many decades the so-called ‘classical method’ (or conventional method) was used to design gravity dams. This method is based on the Bernoulli shallow beam theory. Despite much criticism expressed by academics regarding the basis of the theory, dam design engineers are still using the classical method to design gravity dams. Currently, in most dam building countries the various codes of practice are standardised and based on this method, and engineers have confidence in these codes. This state of affairs will probably continue until structural engineers come up with a viable alternative for designing gravity dams more precisely. The perception of increased risk is always a critical aspect to overcome when introducing an alternative design method, especially when the established, well-known methodology has proved to be safe. However, when so-called ‘back analyses’ are performed on existing dams, it is not so straightforward to assess the safety margin of these structures. Material properties and their yielding or failure characteristics are now becoming important in evaluating these structures accurately in the non-linear domain. With the growing popularity of roller compacted concrete as a dam building material, the attractiveness of gravity dams has also increased and the author is of the opinion that the finite element method could be utilised more efficiently to optimise gravity dams. But, as with any new or alternative design method, the parameters and means of evaluation should be developed to establish a workable and reliable technique. The objective of this dissertation is to develop a practical methodology for the non-linear analysis of gravity dams by means of the non-linear finite element method. A further aspect of this dissertation is the inclusion of a broad guideline on the application of the latest dam design standards used in South Africa for both the classical and finite element methods. In order to gain a better understanding of the basic design criteria, a literature survey was conducted on the evolution of dams and the various theories developed in the past to design and optimise gravity dams. The literature survey included the examination of gravity dam safety criteria and some available statistics on dam failures. The International Committee on Large Dams (ICOLD) has interesting statistics on dam failures and their causes. A few typical dam failures are presented to illustrate what can go wrong. During this literature research, a thorough study was done on the non-linear material theory, with special reference to the Mohr-Coulomb and Drucker Prager material models. The findings of the study are used to illustrate how the non-linear material models are incorporated into the finite element method and in what manner the different material parameters have an influence on the accuracy of the results. As already mentioned, currently the classical method is still a recognised design standard and for this reason a summary is presented of the South African Department of Water Affairs and Forestry’s practice for designing gravity dams. This includes the latest concepts on load combinations and factors of safety for these load conditions. This summary of current practice is used as a stepping stone for the proposed load combinations that could be used for the finite element method as these are not always compatible. However, this dissertation does not deal with the full spectrum of load combinations and the scope is limited to hydrostatic loads. Although the finite element method is a very powerful structural engineering tool, it has some serious potential deficiencies when used for dam design. The most serious problem concerns the singularities and mesh density, which develop high stress peaks at the heel of the dam wall. This problem is illustrated and some practical finite element examples are given. Some solutions for addressing this problem are also presented. It is concluded that an effective method for overcoming the singularity problem is to use the non-linear material yielding model. In order to calibrate the non-linear Drucker Prager model, several finite element benchmarks were conducted, based on work done by other researchers in the fracture mechanics field. Although the theory of the Drucker Prager model is not based on fracture mechanics principles, this model simulates the failure of the concrete material very well. To demonstrate this, various benchmarks were conducted, such as a pure tension specimen, a beam in pure bending, a beam combined with bending and shear, the flow models of Chen (1982), a model of a gravity dam and, finally, a full-size gravity dam. The next step in the study was to calibrate the Drucker Prager model with the concrete material properties used in existing dams of different construction methods and ages. The material strength of the concrete was statistically analysed and the average strength was calculated. The important ratio of tensile strength to compression strength (ƒt/ƒc) was also examined and the findings are presented. This ratio is important to get accurate results from the Drucker Prager model. The normal input parameters for the Drucker Prager model are the internal friction angle of the material (φ) and the cohesion (c). Scrutiny of the work done by Chen (1982) helped to find a useful solution to obtaining the parameters for the non-linear finite element method without determining the ö and c values, but by using the material tensile and compression strengths instead. The formulation is demonstrated in the chapter on theory. To illustrate the usefulness of the non-linear yielding model a few case studies were conducted. A hypothetical triangular gravity dam structure was analysed because it was widely used in other literature studies and a useful comparison could be made. Then, a case study of an 80-year-old concrete gravity dam was performed. The uniqueness of this dam lies in the fact that it was designed before the theory of underdrainage was used in South Africa and the dam has a characteristic shape due to its relatively steep downstream slopes compared with today’s standards. A study of material strength sensitivity was also done on this dam to evaluate its stability under severe load conditions. The last case study presented is on a recently designed 75-m-high roller compacted concrete gravity dam, optimised primarily by the classical method. The non-linear Drucker Prager yield model was used to evaluate this structure, with the actual material strengths taken from the laboratory design mix results. Although the finite element method was used during the design stage of this dam, it was used mainly to check the results of the classical method. The finite element method was also used to do studies on this dam where the classical method could not be used, such as studies of temperature and earthquake load conditions (not included in this research). The factor of safety against sliding was also determined using the results obtained from the finite element method and compared with the results obtained from the classical method. This case study gives an approximate comparison between the classical method and the finite element method. Finally, a methodology is proposed for analysing a gravity dam. Procedural steps are given to describe the methodology. With regard to the future, the advantage of the non-linear finite element method is that it can easily be extended to contemporary 3-D analysis, still using the same concept. Many dams can only be accurately evaluated by a full 3-D analysis. There is a modern tendency to design gravity dams in 3-D as well so as to evaluate their stability against sliding in the longitudinal direction. The non-linear 3-D finite element method is also used for arch dams, for which very few alternative numerical analysis methods are available. Moreover, the non-linear finite element method can be extended to earth and rock-fill embankments. / Dissertation (MEng)--University of Pretoria, 2009. / Civil Engineering / unrestricted

To produce cast steel crankshafts, risering and gating systems are developed. Filling and solidification simulations of the steel crankshaft rigging are carried out to confirm that the rigging developed will produce a low porosity casting. A sand mold is created with Computer-aided design software, based on the developed crankshaft and rigging. Two prototype crankshafts are cast from the sand molds, and analyzed for porosity. The porosity analysis results are compared directly to the simulated porosity, and found to be in good agreement. From the analysis of the prototype crankshaft, rigging systems for a two-on and single-throw crankshaft are developed. A new casting method for steel is developed. The counter-gravity with pressurization during solidification casting method utilizes vacuum pressure of 7.3 psia to draw liquid steel into a mold, where it is held until the inlet has solidified. Once the inlet has solidified, the vacuum pressure is released, and the pressure of the entire system is raised to 45 psia. Exothermic hot topping keeps the top of the riser liquid while the rest of the casting forms a solid shell. Therefore, the pressure only acts on the liquid metal at the top of the riser, forcing the liquid metal to feed farther into the casting. The new method is tested with simple bar castings. Analysis of cast bars shows that centerline porosity is fed by the riser when pressurized, while the gravity-filled control casting is not.

In the middle and upper atmosphere, dynamics of scales from tens of meters to thousands of kilometers primary arise due to the influence of gravity waves propagating from lower altitudes. In order to understand the structure and variability of these regions of our planet's atmosphere, we must understand the propagation, influences, and dissipation of gravity waves. However, gravity waves and their influences are difficult to measure. Their largest and most observable effects occur in the remote mesosphere and lower thermosphere and the relevant spatial scales extend across many orders of magnitude. The EBEX group discovered a novel method to observe polar mesospheric clouds, which are a sensitive tracer of gravity waves and their associated dynamics. This discovery motivated the Polar Mesospheric Cloud Turbulence (PMC Turbo) experiment. Polar mesospheric clouds form an extremely thin but bright layer at roughly 80 kilometer altitude in which we can observe brightness fluctuations created by gravity wave dynamics and the resulting instabilities. PMC Turbo included seven pressure vessels, each of which contained an optical camera, hard drives, and computers that controlled the image capture, flight control, and communication with ground stations. The cameras captured spatial scales from gravity waves with wavelengths of roughly 10-100 kilometers, instability dynamics at scales from about 1-10 kilometers, and the fine structure at the inner scale of turbulence down to 20 meters. PMC Turbo flew at 38 kilometer altitude and remained afloat for nearly six days. During this time, it travelled from Esrange Space Center in Sweden to the Northwest Passage in Canada. Complementary data from other instruments provides additional atmospheric context to the PMC Turbo measurements. During flight, the PMC Turbo cameras captured images of polar mesospheric clouds tracing Kelvin-Helmholtz instabilities with a high signal-to-noise ratio. Kelvin-Helmholtz instabilities play major roles in energy dissipation and structure of geophysical fluids, and they have a close relationship with gravity waves. The PMC Turbo images include complicated interactions and secondary instabilities leading to turbulence. These dynamics provide insight into the atmospheric conditions and rate of energy dissipation in the mesosphere and lower thermosphere.

My diploma thesis deals with measuring the center of gravity (CG) the motorcycle. The first part is outlined with legislation and the types of motorcycle division. I mention the theoretical types of measuring the CG the motocycle there too. These methods are applied to the issue of motor vehicles. The chosen one way of measuring the center of gravity which is used for practical measurements of gravity the motocycle. The practical part included the weighing of the different types of motorcycles with a different occupancy. These values are then processed and the resulting CG are calculated for each motorcycle. The values of CG were compared by experiment with the program for the analysis of road accidents and reconnoitred the measured results with this program results. In the last chapter is the evaluation of individual CG motorcycle and the influence of changes in occupancy due to a motorcycle.