The influence of the horizontal magnetic field has not been sufficiently studied in contrast to study activity on the influence of the vertical magnetic field by researchers. The reason was that the influence of horizontal magnetic field to change the wear mass loss of ferromagnetic materials is smaller compared to the vertical magnetic field. However, the influence of horizontal magnetic field on rolling contact changes the subsurface crack initiation point toward surface is postulated by a researcher. Therefore, it is significance finding out how the horizontal magnetic field influences the tribological characteristics. This thesis presents a study on the influence of the horizontal magnetic field on wear in sliding contacts contributes for ascertainment the effect and mechanism of horizontal magnetic field on tribological characteristics of sliding contacts, through the experimental approach.The static magnetic field with densities of 0 and 1.1 Tesla and different orientations was applied to different contact conditions, different surface modifications and two sliding frequencies, using a ball-on-plate contact configuration. In conclusion, the presence of magnetic field enhances the chemical adsorption between iron or oxide iron and oxygen, and causes the transition of adhesive wear to oxidative wear. Besides, the presence of magnetic field combined with low sliding frequency forms the bulging on the wear surface and weakens the prevailing wear mechanism due to the low frictional temperature. On the other hand, the presence of magnetic field combined with high sliding frequency induces the transition to the oxidative wear mechanism and reduces the wear. Also, distinctly different appearances of wear surface are created by different magnetic field orientations. In the lubricated sliding contact, the magnetic field causes the reduction of wear and induction of oxide. It is postulated that the presence of magnetic field enhances the oxygen adsorption on the wear track by iron wear particles and hence varies the tribological behaviour. The influence of magnetic field on carbon steel coating consists in changes of oxide iron layer and steel layer, alterations of mechanical properties of the coating, and decrease in the mass loss and the surface roughness on the dry sliding contact. All these could be suggested the influence of adhesive strength of the interface between the base material and coating.

The recent intellectual movement away from universalism towards particularism can be witnessed in most divisions of social philosophical thought. Such a paradigmatic shift has radically transformed a number of theories including feminist ethics. In contrast, however, philosophical analyses of fairness in sport have retained allegiance to universalist accounts in that conceptions of fair play remain enshrined in formalist accounts of the nature of rules and laws that govern sporting games. In this thesis, it is argued that universalist accounts of fair play in sport are incomplete in so far as they fail to consider that what constitutes fairness in sport is more than just the interpretation of formal rule structures. The richer analysis of fair play in sport offered here highlights the importance of individual experiences and the structures that shape those experiences. The ethical investigation is compatible with certain feminist ethical commitments. In order to evaluate whether a given sporting ethos is ethical, the thesis is committed methodologically to a mixed model approach. The aim is to find out the beliefs, values and ideologies of the people involved. Hence, a context-respectful methodology collecting and utilising thick descriptions is employed. It is argued that an ethical ethos has no room for intentional rule violation. For a given ethos to be ethical its game must be practised in a certain way with a certain attitude. The evaluation in this thesis concludes that the ethos of English elite women's cricket is unethical. It is hoped that a potential outcome of the thesis will be a different understanding of fair play that may shape new forms of ethical enquiry and challenge existing methodologies. Argument: (1) In sport philosophical literature fair play has been characteristically understood in one way: the formalist account of the nature of rules and laws. (2) While it is true that one can not talk about fair play without reference to the rules and laws of an activity, this account is incomplete since it fails to consider ethos. (3) Part of what an ethos means derives from the beliefs, values and ideologies of players themselves who have constructed agreements as to how the game ought to be enacted. (4) To understand fair play in elite women's cricket, therefore, one must understand the rules and laws but also, crucially, its ethos.

Name: Analysis of an individual playing perfomance for younger pupils Objective: The aim of this study is to determine the technical level of the younger pupils AC Sparta Praha and SK Slavia Praha against Bohemans 1905. It is specifically the percentage success collecting of the ball, pass and shot. Further, as I will be interested in the failing collecting, shooting and passing the ball skills. Methods: The method that I used for processing work is called indirect observation of previously recorded video. Data were processed mainly quantitative method. Results: Using the results, we found that a skill that is among hard according to the literature, and handling of the ball had the highest success rate of all monitored. Furthermore, what I found is that the players have many more attempts each game activities played under pressure than no pressure on the players. Keywords: Football, pass, shoot, ball collecting

Philosophiae Doctor - PhD / Magnesium hydride has long been regarded as a promising candidate for lightweight hydrogen storage applications, owing to reasonably high theoretical capacity (7.6 wt. %). It is burdened by slow absorption/desorption kinetics which has been the target for improvement of many research groups over the years. Nanostructured MgH2 prepared by high energy reactive ball milling (HRBM) of Mg under hydrogen atmosphere with the addition of V or Ti results in modified MgH2 that demonstrates superior hydrogenation/dehydrogenation kinetics without a crippling compromise in storage capacity. Mg – FeV nanocomposites prepared via ball milling of Mg and FeV raw materials demonstrated up to 96.4% of the theoretical storage capacity and comparable kinetics to Mg - V prepared via the same method using pure refined V (which is far costlier than FeV). In both cases, the hydrogenation/dehydrogenation kinetics was much improved than pure Mg alone, as evidenced by faster hydrogenation times. In terms of cyclic stability, Mg – 10FeV demonstrated improvement over pure Mg with final absorption and desorption capacities of 4.93 ± 0.02 wt. % and 4.82 ± 0.02 wt. % respectively over 30 cycles. When compared against Mg – V, Mg – FeV showed slightly inferior improvements, attributed to incomplete hydrogenation of V in the presence of Fe. However, they share similar crystalline BCC, BCT – V2H and FCC - VH phases with the size of less than 10 nm and demonstrated the same behaviour at high temperatures; at temperatures approaching 400 °C, particle sintering became an issue for both nanocomposites resulting in a drop in absorption capacity even in the first cycle. The further inclusion of carbonaceous species showed several effects, one of which was an improvement in hydrogen uptake speed as well as kinetics for the addition of 5 wt. % activated carbon. For the sample with 5 wt. % graphite, the appearance of an initial incubation period of up to 60 minutes was noted, presumably corresponding to the duration of time when the carbon was sheared and crushed before hydrogenation commences.

The transformations occurring in the sub-stoichiometric Ti(C,N) – W - Al system processed by high energy ball mill were investigated. The milling parameters included the milling time and the temperature comprising milling at subzero temperature and above 25°C. Two sub-stoichiometric Ti(C,N) stocks were selected, the Ti(C0.5N0.05) containing more interstitial elements than the Ti(C0.5N0.5)0.6.The transformation stages and mechanisms of alloying are discussed with respect to the changes in crystal structures of the powder constituents. The milling atmosphere had an effect on the lattice strain of milled products, and hence on the kinetics of solid state dissolution between the powder constituents, but it did not affect the fracturing process. The release of the stored crystallite lattice strain energy was the major determinant in mechanical alloying, with particle size reduction playing a necessary, but less significant role. The strain energy and the fine particle size contributed to the increased chemical reactivity with oxygen of the powders milled for shorter times. The affinity of the powders with oxygen decreased after W dissolution in Ti(C,N), and the subsequent decrease in lattice strains. The annealing behaviour of Ti(C0.5N0.05) - 40wt% W and Ti(C0.5N0.5)0.6 - 40wt% W mechanically alloyed powders were investigated using XRD, TEM, SEM and DTA techniques. It was observed that the reaction start and finish temperatures between constituents were lower in the system that had higher residual lattice strains after milling. The compositions of the intermetallic compounds and the solid solutions formed were dependent on the milling conditions and the annealing temperature. Thermal alloying was observed during annealing of Ti(C0.5N0.05) - 40wt% W mechanically alloyed products, whereas de-mixing of W-rich phases from the metastable solid solution occurred during annealing of the Ti(C0.5N0.5)0.6 - 40wt% W milled powders. The effects of Al addition and milling at subzero temperatures on the transformation of Ti(C0.5N0.05)-W powder mixtures were investigated. Addition of Al powder improved the kinetics of solid solution between powder constituents. The effect of Al was ascribed to the increase of lattice strain during short milling time followed of relaxation at longer time, and to the fast diffusion of atoms. Also, it was noticed that the high viscosity of the process control agent could inhibit the alloying process. Multiple three-component compounds could be formed. Aluminium preferably reacted with tungsten. The W(Al,C) and W(Al,Ti) formed were stable, thus solubility of W in Ti(C0.5N0.05) in the presence of Al was limited. The evolution of the morphologies of Ti(C,N)-W mixtures show that fracturing of hard particles dominated in the early stage of milling in the absence of Al, whereas with Al, plastic deformation of particles and cold welding of Ti(C,N) and W particles by the softer Al prevailed at the same time. Longer milling time improved the homogeneity and the formation of nanostructured binder pools in the sintered products. Lower oxygen contents in sintered PcBN were achieved by mechanically alloying Ti(C,N), W and Al in the high energy ball milling stage. Low level of Co in the infiltration layer was also achieved when sintering PcBN with this type of binder. A link was established between the addition of Al at the attrition milling stage and high oxygen content in the sintered PcBN, thus should be avoided. The pressure and temperature applied during sintering or annealing had a strong effect on the compositions and the crystal structures of the phases formed in the mechanically alloyed binder. The lattice strains of the binder and the PcBN were higher in the sintered materials prepared with the Ti(C0.5N0.5)0.6-W binder than in those made using the Ti(C0.5N0.05)-W alloys.

Os moinhos de bolas são equipamentos presentes em plantas de mineração, sendo uma máquina importante no circuito de cominuição de minérios. Em função de inúmeros fatores como, por exemplo, projeto, fabricação, sobrecarga no equipamento, falta de manutenção e procedimentos de operação inadequados, são desenvolvidas descontinuidades nos componentes estruturais desse equipamento. Os componentes estruturais dos moinhos, basicamente, corpo, tampas e munhões, além do custo elevado, possuem prazos de fabricação que podem variar de dois a três anos dependendo da demanda do mercado. Portanto é cada vez mais necessário que as descontinuidades detectadas nesses componentes sejam corretamente avaliadas. Neste trabalho analisaram-se pela mecânica da fratura a criticalidade de descontinuidades, tais como trincas constatadas em um munhão de um moinho de bolas e compararam-se os valores teóricos de taxa de propagação (crescimento) dessas descontinuidades com valores reais obtidos por meio de inspeções periódicas realizadas neste componente. A nucleação das trincas foi causada por falta de lubrificação nos mancais do moinho, gerando esforços térmicos circunferenciais no munhão, em que a temperatura estimada do contato munhão e bucha atingiu a faixa de 100 °C a 150 °C. No período analisado, os resultados obtidos por meio da norma BS7910 mostraram-se mais próximos dos valores reais do que a norma ASME Seção XI, Apêndice A. O tamanho da trinca mais crítica foi aceito pelos critérios da norma BS7910 e aprovado apenas na condição de emergência da norma ASME Seção XI, Apêndice A. / The grinding ball mills are equipments present in mining plants, being important in the ore comminution circuits. Depending on numerous factors, such as, for example, design, manufacturing, overloads, poor maintenance and inadequate operating procedures, flaws are developed in the structural components of this equipment. The structural components of a mill, basically, shell, heads and trunnions, besides high costs, have lead times that might vary from two to three years, according to market demand. Therefore, it becomes increasingly necessary that any flaws in those components to be properly evaluated. This paper analyzed the fracture mechanics of the criticality of flaws, such as cracks observed in a ball mill trunnion and compared the theoretical values of growth rate of these defects with actual values obtained through periodic inspections performed in this component. The cracks nucleation was caused by lack of lubrication in the trunnion bearings, generating circumferential thermal stresses, thus the estimated temperature of the trunnion and bushing contact achieved the range 100 °C to 150 °C. During the analyzed period, the results obtained by the standard BS7910 proved to be closest to the actual values than the standard ASME, Section XI, Appendix A. The most critical crack size was accepted by the criteria of the BS7910 and approved only on emergency condition of ASME Section XI, Appendix A.

Thesis advisor: Zhifeng Ren / Solid state cooling and power generation based on thermoelectric principles are regarded as one of the technologies with the potential of solving the current energy crisis. Thermoelectric devices could be widely used in waste heat recovery, small scale power generation and refrigeration. It has no moving parts and is environmental friendly. The limitation to its application is due to its low efficiency. Most of the current commercialized thermoelectric materials have figure of merit (ZT) around 1. To be comparable with kitchen refrigerator, ZT is required at room temperature. Skutterudites have emerged as member of the novel materials, which potentially have a higher ZT. In the dissertation, my investigation will be focused on the optimization of CoSb₃ &ndash based skutterudites. Starting with Co and Sb elements, CoSb₃ will form through a high energy ball mill. Unfortunately, even after 20 hours, only a small percentage of the powders have transformed in into CoSb₃. Then the powders will be compacted into bulk samples by DC-controlled hot press. CoSb₃ single phase will form after press. Characterization of the structure and thermoelectric properties will be presented with details. The effects of synthesis conditions on thermoelectric properties of skutterudites were studied and discussed. Several possible methods of improving the ZT of N type skutterudites were applied. The highest obtained ZT thus far is about 1.2 from Yb doped CoSb₃. For a group of samples with nominal composition Yb_xCo₄Sb₁₂, the increased Yb concentration in our samples not only enhanced the power factor due to electron doping effect but also decreased the thermal conductivity due to a stronger rattling effect. In addition, the increased grain boundary density per unit volume due to the small grains in our bulk skutterudite materials may have also helped to enhance the phonon scattering and thus to reduce the thermal conductivity. Single and double doping methods with different combinations were also tried. So far, none of them have surpassed ZT of 1.2. Mixing different materials with Yb_0.35Co₄Sb₁₂ so far to increase the phonon scattering was also performed. No dramatic thermal conductivity reduction was observed. Small amounts of Fe/Mn substitution on Co sites will decrease the power factor to undesired degrees. Some results with Nd filled P type sample will be briefly introduced. P type samples are also obtained through substitution on Sb site. Preliminary work on preparing the electrode for CoSb₃ will be presented in the dissertation. CoSi₂ has low resistivity, and a similar coefficient of thermal expansion (CTE) as of doped CoSb₃. It is good electrode candidate. DC controlled hot press is used to make the contact. Thermal stability of the contact was tested. Small cracks will form in the contact area, further improvement is necessary. Finally, my previous work on ZnO nanowire growth is briefly introduced. Large throughput of ZnO nanowire could be obtained with NaCl as the support to promote the conversion of Zn powder to ZnO. / Thesis (PhD) — Boston College, 2010. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Physics.

Thesis advisor: Zhifeng Ren / Thermoelectric (TE) technology is an environment-friendly one due to reduction of carbon emission, which can be widely used either for power generation or for refrigeration. Basically applications of TEs are based on TE effects, which involve the transition between heat and electricity. Despite the superior advantages of being solid state and providing a clean form of energy, TE technology so far only finds its niche area of application due to the relatively less efficiency compared to traditional methods. The efficiency of a thermoelectric device is solely determined by the dimensionless figure-of-merit (ZT) of thermoelectric materials. According to the definition, ZT is equal to square of Seebeck coefficient times electrical conductivity times absolute temperature divided by thermal conductivity. Therefore, a good thermoelectric material should possess high Seebeck coefficient and electrical conductivity while low thermal conductivity, so called phonon glass electron crystal (PGEC). In bulk materials, it is challenging to further improve ZT or independently vary individual parameters without affecting others, mainly due to the interrelated relationships among these three parameters. Fortunately, nano approach gives us some independent control in parameters adjustment. One important aspect of nano idea lies in the fact that enhanced boundary scattering due to the increased intensities of interfaces arising from nano-sized grains could reduce the thermal conductivity more than the electrical conductivity, which is practically realized in our material system. Since the introduction of nano idea, large ZT as high as above two has been achieved in the superlattice system. Due to the high fabrication cost of superlattices, they are not scalable for mass production. Theoretical calculations indicate that thermal boundary resistance is the main mechanism for the low thermal conductivity in superlattices, rather than the periodicity. Basically, we hope to achieve the supplattice-like ZT in the less costly bulk nanograined materials, based on the idea that reduction of thermal conductivity which is responsible for ZT enhancement in superlattices can be realized in bulk materials with embedded nanostructures as well. Inspired by the nanocomposite idea, in my thesis work I applied the technique of ball milling and then hot press to various thermoelectric materials, from low temperature to high temperature, demonstrating the feasibility of the approach. By ball milling alloyed ingot into nanopowders and DC hot pressing them, we have achieved a 62-89% ZT improvement for p-type half-Heusler samples, mainly due to the significantly enhanced Seebeck coefficient and partially due to the moderately reduced thermal conductivity. Microstructure studies indicated that increased boundaries due to smaller nano-sized grains is the cause for change of parameters. For our ball milled samples, the trend of decreasing thermal conductivities with increasing ball milling time is observed, further substantiating our nano-approach idea because longer ball milling time gives rise to smaller grain sizes and thus stronger boundary scattering. By applying the same technique to n-type half-Heuslers, we also successfully obtained pronounced enhancement in ZT especially at medium and low temperature ranges, which might be useful in medium temperature power generation. By ball milling a mixture of individual constituent elements into alloyed nanopowders and then DC hot pressing them, we did not gain improvement in ZT initially for n-type BiTeSe system mainly due to the simultaneous reduced power factor with the thermal conductivity. Considering anisotropic properties of the n-type BiTeSe single crystal and randomization effect of ball milling process, we repressed the as-pressed bulk samples in a bigger diameter die, during which lateral flow took place, resulting in preferred grain orientation. As a result, a 22% improvement in the peak ZT from 0.85 to 1.04 at 125 oC in n-type Bi₂Te_2.7Se_0.3 has been successfully achieved, arising from the more enhanced power factor than the thermal conductivity. Compared with single crystal, we benefit from the small nano-sized grains in bulk materials. Taking into account the in-plane power factor of single crystal, we still have much room for further ZT improvement if more ab orientation is promoted into the disk plane and/or the crystal plate size and thickness are reduced. By applying our technique of ball milling and then hot press to p-type skutterudites system, we have achieved a peak ZT of 0.95 at 450 <super>o</super>C in NdFe_3.5Co_0.5Sb₁₂, which is comparable to that of the state-of-the-art ingot. Our approach has the advantage of being less costly and more time-efficient compared to traditional fabrication methods. Besides, even lower thermal conductivity and hence higher ZT can be expected, provided that the nanosize of the precursor powder is preserved during hot press. The nanocomposite idea has been substantiated and the feasibility and generality of our ball milling and then hot press approach has been demonstrated, based on the thermoelectric properties data we obtained and the microstructure studies we carried out from various thermoelectric material systems, from low temperature to high temperature. We believe that continued effort in the area of thermoelectrics by our approach should be paid with superlattice-like ZT if ingenious methods are devised to control the grain growth during consolidation. / Thesis (PhD) — Boston College, 2010. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Physics.

Práce vystihuje teoretické poznatky z oblasti teorie hromadné obsluhy a simulace a následně jsou aplikovány poznatky do praxe. Pro případovou studii je využíván simulační software Simul8 a podpůrný program Crystal Ball, pomocí nichž je vytvořen model. Cílem je navrhnout nejlepší řešení daného problému a zhodnotit systém z hlediska struktury a funkčnosti. S modelem je provedeno několik experimentů a následně je posouzena vhodnost či nevhodnost použití jednotlivých variant.

Project management is a field in which risk management can be applied. There must be a business case for any project to recognize its benefits for the company. A business case generally uses point estimation of input parameters and evaluates financial criteria for individual variants such as the net present value, pay-back period or internal rate of return. A simulation enables to design a model for the business case analysis while making use of the probability distribution. The model then turns from a deterministic into a stochastic one. The Monte Carlo simulation method, calculating a large number of variants, is employed in projects. The simulation can identify major risk factors, assess their probability and the significance of the impact on the evaluated financial criterion. The analysis outputs suggested by the simulation are the fundamentals of proper risk management. The Crystal Ball simulation software was employed for the calculation in this thesis.