Global ETD Search

1	Isotropic-Helicoidal Transition of Semiflexible Polymers Confined to a Spherical Surface Zhang, Wuyang January 2008 (has links) A semiflexible polymer confined to a spherical surface is used as a basic model for understanding DNA conformation in restricted space. By means of Monte Carlo simulation for a bead-rod chain generated on a spherical surface, we find an ordered helicoidal phase at sufficiently high surface density and determine the critical density of the isotropic-helicoidal phase transition for various persistence lengths. We verify that the excluded volume effect is the key factor to cause the helicoidal state. In addition to Monte Carlo simulations, we utilize the model of wormlike chain with Onsager's excluded volume interaction and examine the Landau expansion of the free energy involving both the orientational and spatial order parameters. We also analytically figure out the critical density and transition gap for various ratios of persistence lengths of the polymer chain and the radius of spherical surface. The results from both simulation and analysis are consistent with each other. Isotropic Conformation Helicoidal Conformation Semiflexible Polymers Spherical Surface Physics
2	Isotropic-Helicoidal Transition of Semiflexible Polymers Confined to a Spherical Surface Zhang, Wuyang January 2008 (has links) A semiflexible polymer confined to a spherical surface is used as a basic model for understanding DNA conformation in restricted space. By means of Monte Carlo simulation for a bead-rod chain generated on a spherical surface, we find an ordered helicoidal phase at sufficiently high surface density and determine the critical density of the isotropic-helicoidal phase transition for various persistence lengths. We verify that the excluded volume effect is the key factor to cause the helicoidal state. In addition to Monte Carlo simulations, we utilize the model of wormlike chain with Onsager's excluded volume interaction and examine the Landau expansion of the free energy involving both the orientational and spatial order parameters. We also analytically figure out the critical density and transition gap for various ratios of persistence lengths of the polymer chain and the radius of spherical surface. The results from both simulation and analysis are consistent with each other. Isotropic Conformation Helicoidal Conformation Semiflexible Polymers Spherical Surface Physics
3	Desvendando a matemática do GPS Lima, Davi Dantas 12 April 2013 (has links) The purpose of this monograph is to study the mathematical principles behind the Global Positioning System, the so-called GPS. We start with a historical approach of the evolution of this technology. Then we show some theorems in geometry: plane, spatial and analytic, which together with some physical principles (average speed, speed of light, the Doppler effect,...) guided the creators of this powerful tool that determines with remarkable accuracy the position (latitude, longitude and altitude) of a transmitter. Finally, we suggest activities to be performed at the level of basic education, to stimulate students curiosity by scientific knowledge contained therein. / A presente monografia tem como objetivo evidenciar os princípios matemáticos por trás do funcionamento do Sistema de Posicionamento Global conhecido por GPS. Após uma abordagem geral da evolução ocorrida até chegarmos a essa tecnologia, demonstraremos alguns teoremas das geometrias: plana, espacial e analítica que, aplicados juntamente com alguns princípios da Física (velocidade média, velocidade da luz, efeito Doppler,...), nortearam os criadores desta poderosa ferramenta que determina com notáveis precisão e exatidão, em qualquer parte do globo terrestre incluindo a atmosfera, a hora e a posição (latitude, longitude e altitude) de um transmissor. E, a partir daí, sugerir atividades interdisciplinares, a serem desenvolvidas em nível de educação básica, que estimulem a curiosidade dos alunos pelos conhecimentos científicos nelas contidos. Geometria Sistema de Posicionamento Global Matemática aplicada Coordenadas geográficas Superfícies (Matemática) GPS Latitude Longitude Altitude Trilateração Superfície esférica Applied mathematics Geographical positions Geometry Global Positioning System Surfaces Satellites Latitude Longitude Altitude Trilateration Spherical surface Interdisciplinary
4	Pravděpodobnosti porušení keramické součásti s využitím Weibullovy teorie nejslabšího článku / Failure probability of the ceramics part using Weibull weakest link theory Kovář, Jaroslav January 2018 (has links) This thesis compares Weibull weakest link theory with inclusion of one and all three principal stresses. Principal stresses needed for this theory were calculated with finite element method. The informational research is in the introduction of this thesis. It includes ceramic materials, Weibull weakest link theory, Gaussian quadrature over spherical surface and ceramic head of hip joint endoprothesis. Theoretical part is used for next calculations of probability of failure. The probability of failure of ceramic rod loaded by four-point bending is calculated in first calculations. This task is solved as contact in the next step. Next part of this thesis is about selection of suitable method of numerical integration. This method will be used in the calculation with all three principal stresses. The results of calculation with all three principal stresses are compared with the results of the calculation which includes only first principal stress. Firstly, this is done for cylindrical body and then used on head of hip joint endoprothesis. In the last part of this thesis, probability of fracture of head hip joint endoprothesis with shape deviation of nominal conicity is calculated.

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