Abstract

The impact force of debris flow is not only an important indicator of the risk assessment of debris flow and the strength impact resistance of buildings against debris flow, but also an important parameter in the design of various debris flow prevention projects (such as the check dam and the drainage channel, etc.). The pressure sensors are arranged at different positions (monitoring points) on the upstream face of the check dam. By changing the slope of the drainage channel, the bulk density of debris flow and the slope gradient of the upstream face of the check dam, the time history curves of the impact force at the monitoring points under different experiment conditions are obtained. The characteristic value of impact force of debris flow acting on the surface of sand retaining dam is analyzed, and the evolution law of mean value and maximum value of impact force of debris flow at the same detection location with the above conditions is obtained. The mean value and maximum value of debris flow impact force at dif-ferent detection locations under the same working condition are analyzed to obtain the evolu-tion law of debris flow impact force at different locations, and then the distribution trend of debris flow impact force on the upstream face of the check dam is obtained. The research results provide scientific and reasonable theoretical basis and technical support for the stability analysis of the check dam, so as to better serve the disaster prevention and reduction of debris flow, which will improve the technical level of the debris flow prevention project to a certain extent.

Abstract

O presente trabalho tem como objetivo realizar análises comparativas (dinâmicas e estáticas) em seções transversais genéricas com inércias variáveis em mísulas parabólicas. Para isso foi desenvolvido um programa computacional em linguagem FORTRAN 90/95 via Método dos Elementos Finitos, sendo seus resultados comparados com resultados encontrados na literatura. Logo, por meio dos resultados de deslocamento, aceleração e velocidade encontrados nas análises, foi possível verificar a influência do carregamento dinâmico no comportamento estrutural de vigas e pórticos. Levou-se em consideração o amortecimento da estrutura, denominado amortecimento proporcional ou de Rayleigh, envolvendo as propriedades do material, que nesta pesquisa foram utilizados o aço e a madeira. Os elementos analisados têm seções transversais genéricas com a inércia variando em mísula parabólica ao longo do seu comprimento, para que possam ser utilizados em projetos arquitetônicos cada vez mais inovadores. Por fim, foi implementada a formulação correspondente ao Elemento Finito Tridimensional, que permite analisar estaticamente a estrutura com o elemento finito hexaédrico com oito nós (H8), elemento finito hexaédrico de vinte nós (H20).

Abstract

The present work aims to carry out comparative analyzes (dynamic and static) in generic cross-sections with variable inertias in parabolic corbels. For this, a computational program was developed in the language FORTRAN 90/95 via the Finite Element Method, and its results were compared with those found in the literature. Therefore, through the displacement, acceleration and velocity data found in the analyses, it was possible to verify the influence of dynamic loading on the structural behavior of beams and frames. The damping of the structure, called proportional damping or Rayleigh damping, was taken into account, including the properties of the materials used, which in this research were steel and wood. The analyzed element has generic cross-sections with the inertia varying in parabolic corbel along its length, so that they can be used in increasingly innovative architectural projects. Finally, the formulation corresponding to the Three-Dimensional Finite Element was implemented, which allows the static analysis of the structure with the hexahedral finite element with eight nodes (H8), hexahedral finite element with twenty nodes (H20).

Abstract

'''Preparation of fine ammonium perchlorate (AP) particles and thermal behaviour of it are known as the most important challenges in the crystallization and propellant sciences. We introduced an effective method of fine AP preparation named high rate cooling crystallization (HRC). This work presents application of Taguchi approach for optimizing the HRC method. In this study a set of experiments was designed according to the Taguchi L9 array. Experimental design was originated from four effective parameters containing; temperature, pressure, solvent type (water and ethanol) and anticaking agentsodium dodecyl sulfate (SDS). After preparation of fine AP particles average particle size (APS) was measured using laser mass spectrometry (LMS-30). APS, contribution, and the analysis of variance (ANOVA) were used to investigate performance factors affecting the operation condition. According to the data obtained, anti-caking agent and solvent type were represented the main effect on the preparation of micronized AP by using HRC method. Furthermore, the optimum condition in preparation of fine AP particles by using HRC method was ethanol solvent, 10atm pressure, 0.4 % SDS, and 60˚C temperature. Thermal behaviour of the optimized particles was investigated using TG/DSC analysis. Finety of the particles positively shifted the low temperature decomposition (LTD) region of fine optimized sample in comparison with coarse pure AP. Crystallinity of sample was confirmed by SEM and XRD analysis.

Abstract

In this study, the photocatalytic properties of nanoporous silica-titania membrane was investigated. For this purpose, nano-porous silica-titania membrane was prepared by sol-gel process using tetraethyl orthotitanate and tetraethyl orthosilicate with the intermediate layer of colloidal titania on α-alumina support. The as-prepared membrane was characterized by FTIR, XRD, FESEM and BET techniques. The specific surface area of microporouse silica -30% titania powder was 507 m2/gr. In addition, the photocatalytic activity of the as-prepared membrane was studied for methyl orange photo-degradation under UV light (λ