基于红外热象技术的金属材料疲劳性能研究方法

金属材料的疲劳极限或疲劳寿命等性能是长寿命机械和结构抗疲劳设计的基本数据,探讨效率高、成本低而又准确的试验新方法,成为相关研究者十分感兴趣的课题。材料在循环载荷作用下产生的塑性变形经不断累积会引起疲劳破坏,这个过程所耗的塑性功绝大部分以热量形式耗散,因此寻找热耗散温度变化过程与疲劳极限及寿命之间的关系很有意义。就此问题,文中引入利用先进的红外热成象技术确定金属材料疲劳性能的试验研究方法,主要从原理和试验方法两方面进行介绍,并对45钢的试验过程和现象作较为详细地阐述,得到较准确的疲劳极限值和基于红外热象技术确定疲劳寿命的重要参量M。

模拟弹塑性碰撞的修正SPH方法

从基本的无网格光滑粒子法SPH(Smoothed Particle Hydrodynamics)近似出发,修正了模拟固体力学中大变形弹塑性碰撞的SPH方法.在边界处采用修正的边界条件,弹塑性分析过程中采用增量理论计算应力,迭代过程中用守恒光滑法进行滤波修正消除拉力不稳定.对SPH方法进行了程序实现,给出了杆弹塑性碰撞的算例.计算分析表明,SPH方法节点的影响域较大、精度较相同节点间距有限元法的结果有一定差距,但是通过增加粒子数量可以提高SPH的精度,保持了其简单性和计算大变形的特性.

钠离子与电子复合电离动力学的激波管研究

利用反射激波加热使试验气体电离,继之以强稀波快速冷却,构成一种新的激波管方法,并测定了在氩气氛中钠离子与电子三体复合速率系数。由于稀疏波冷却速度达10~6K/s,电离过程处于非平衡状态。选用氨基钠作为向实验体系中引入钠离子的源物质。用压电传感器和Langmuir静电探针分别监测反射激波后5区压力和离子浓度变化。稀疏波的冷却过程被视为绝热的。分析了探针工作状态,引入了探针鞘层内的弹性散射修正。测定了在800~2 600K温度范围内以惰性气体氩为碰撞第三体的钠离子与电子离复合速率系数k_r=3.43×10~(-14)T~(-3.77)cm~6s~(-1)。

A documentação de Paul Otlet : uma proposta para a organização racional da produção intelectual do homem

A pesquisa procura identificar e analisar as circunstâncias e motivações teóricas que levaram ao surgimento, no final do século XIX, da área de estudo denominada Documentação. Apresenta informações biográficas sobre os principais artífices deste projeto, os advogados e bibliógrafos belgas, Paul Otlet e Henri La Fontaine, que visaram ampliar a compreensão sobre o meio social e cultural em que atuaram. Procura ampliar a discussão sobre os fatores que motivaram em 1895 a proposta de organização racional de toda a produção intelectual do homem. Apresenta em linhas gerais a visão abrangente e integradora da Documentação que eliminando barreiras físicas, acessava acervos arquivísticos, bibliográficos e museológicos para o registro integral dos assuntos pesquisados. Discute a utilização da Classificação Decimal de Dewey (CDD) na criação do Repertório Bibliográfico Universal e analisa o processo que levou ao surgimento da Classificação Decimal Universal (CDU). Conclui sugerindo a inclusão desta visão extensiva e integradora da documentação ao referencial teórico da Ciência da Informação. Sugere que o resgate deste aporte teórico poderá contribuir para um melhor enfrentamento dos problemas da gestão do conhecimento registrado, produzido e acumulado até os dias atuais, nos mais diversos formatos, suportes e repositórios.

Hydrazides and hydrazones as versatile Michael-Donors for iminium-catalyzed conjugate addition reactions

396 : il., graf.

Euskararen normalizazioa hezkuntzan (2000-2010) : Ulibarri programa, euskarri teorikoa, metodologia eta faktore azalgarriak

422 p.

Structural study of CUG-repeating small RNAs complexed with silencing suppressor P19

The study is focused on structural aspects of interaction between silencing suppressor p19 and CUG-repeating small RNAs. The work involves crystal structure determination of a protein-unbound RNA form and RNA fragments of various lengths (19, 20, 21 nucleotides) complexed with p19-suppressor. Results prove the ability of silencing suppressor p19 to bind CUG-repeating small RNAs, as well as reveal features of U•U mismatches flanked by Watson-Crick C•G base pairs in p19-bound and p19-unbound states. In addition, structural data reveal a p19 specific site for anchoring extra nucleotides in small RNAs. In general, the study extends our knowledge about the mechanism of small RNA recognition by silencing suppressor p19.

Preços dos combustíveis no Brasil

Analisa aspectos econômicos e tributários que incidem sobre os combustíveis. No Brasil, o mercado de derivados de petróleo é regulamentado pela Agência Nacional do Petróleo, Gás Natural e Biocombustíveis – ANP, nos termos da Lei nº 9.478, de 6 de agosto de 1997.

Growth of skipjack, Katsuwonus pelamis, and yellowfin, Thunnus albacares, tunas in the Eastern Pacific Ocean, as estimated from tagging data

ENGLISH: The average linear growth rate of skipjack in the eastern Pacific is less than 1 mm per day except for fish 375 to 424 mm in length at release. The growth rate shows a decrease with increasing length and increasing time at liberty. The growth rate of fish in the length range of about 43 to 57 cm is apparently more rapid in the eastern Pacific than in the western Pacific. Dsing data for the northeastern and southeastern Pacific combined, K and ~ were estimated to be 0.658 (on an annual basis) and 885 mm, respectively, by the ungrouped method and 0.829 and 846 mm, respectively, by the grouped method. Sensitivity analyses have shown however, that the estimates of these parameters are poorly determined by the sum of squares method used to derive them. Estimates of K and ~ for the eastern Pacific tend to be lower and higher, respectively, than those for the western Pacific. The average linear growth rate of yellowfin in the eastern Pacific is a little less than 1 mm per day for fish between about 25 and 100 cm in length at release. The growth appears to be most rapid in Area 2 (Revillagigedo Islands) and slowest in Areas 1 (Baja California), 5 (Central America- Colombia), and 6 (Ecuador-Peru). There is considerable variation in the growth rates of individual fish. The growth does not show a decrease with increasing length or increasing time at liberty so realistic estimates of the parameters of the von Bertalanffy or other similar equations cannot be calculated from these data. If realistic estimates of these parameters are to be secured larger fish must be tagged and released or many more long-term returns from fish to about 100 cm in length at release must be obtained. The growth patterns for the eastern Pacific, central Pacific and eastern Atlantic found by most other investigators differ from one another and from those found in the present study. Some of these differences may be real and others may be due to deficiencies in the data or the methods of analysis. Estimates obtained from tagging data are believed to be realistic provided the tags do not inhibit the growth of the fish. It appears that the growth rates of single- and double-tagged fish are the same; this indicates, though not unequivocally, that the tags do not inhibit the growth. SPANISH: La tasa media de crecimiento lineal del barrilete en el Pacífico oriental es inferior a lmm/día, excepto en el caso de peces de entre 375y 424mm de longitud de liberación. La tasa de crecimiento disminuye a medida que aumenta la longitud y el tiempo en libertad. La tasa de crecimiento de peces de entre unos 43 y 57 cm de longitud parece ser mayor en el Pacífico oriental que en el occidental. A partir de datos del Pacífico nororiental y suroriental combinados, se estimaron K y loo en 0.658 (anual) y 885mm, respectivamente, usando el método no agrupado, y 0.829 y 846mm, respectivamente, usando el método agrupado. Sin embargo, los análisis de sensitividad han demostrado que el método de suma de cuadrados utilizado para derivar las estimaciones de estos parámetros las determina con poca precisión. Las estimaciones de K y loo para el Pacífico oriental suelen ser inferiores y superiores, respectivamente, a los del Pacífico occidental. La tasa media de crecimiento lineal del aleta amarilla en el Pacífico oriental es ligeramente inferior a lmm/día para los peces de entre unos 25y 100cmde longitud de liberación. El crecimiento parece ser más rápido en el Area 2(Islas Revillagigedo),y más lento en las Areas 1(Baja California), 5 (Centroamérica-Colombia), y 6 (Ecuador-Perú). Las tasas de crecimiento de peces individuales varían considerablemente. El crecimiento no muestra una disminuciónconun aumento en la longitud o en el tiempo en libertad, y por consecuencia no se se pueden calcular estimaciones realistas de los parámetros de la ecuación de von Bertalanffy u otras ecuaciones similares a partir de estos datos. Para obtener estimaciones realistas de estos parámetros sería necesario marcar peces mayores u obtener muchas más devoluciones a largo plazo de marcas de peces de unos 100cm de longitud de liberación. Los patrones de crecimiento correspondientes al Pacífico oriental, Pacífico central, y Atlántico oriental descubiertos por la mayoría de los investigadores son diferentes entre síy también de los del presente estudio. Es posibleque algunas de estas diferencias sean verdaderas, mientras que otras se deban a faltas en los datos on en los métodos analíticos utilizados. Se considera que las estimaciones obtenidas a partir de los datos de marcado son realistas, suponiendo siempre que las marcas no impidan el crecimiento de los peces. Parece ser que las tasas de crecimiento de peces con una marca y con dos son idénticas, lo cual indica, aunque sin certeza total, que las marcas no ejercen tal efecto. (PDF contains 76 pages.)

Phase-dependent properties for absorption and dispersion in a closed equispaced three-level ladder system

It is shown that in a closed equispaced three-level ladder system, by controlling the relative phase of two applied coherent fields, the conversion from absorption with inversion to lasing without inversion (LWI) can be realized; a large index of the refraction with zero absorption can be gotten; considerable increasing of the spectrum region and value of the LWI gain can be achieved. Our study also reveals that the incoherent pumping will produce a remarkable effect oil the phase-dependent properties of the system. Modifying value of the incoherent pumping can change the property of the system from absorption to amplification and enhance significantly LWI gain. If the incoherent pumping is absent, we cannot get any gain for any value of the relative phase. (c) 2007 Elsevier GmbH. All rights reserved.

Enhancement of fish production in Borno State with extension services

Borno State possesses great potentials for fish production both from inland fisheries and aquaculture. The socio-economic and environmental production factors are suitable for fish production. If the potential of the State were well harnessed, it would be playing significant roles in achieving self-sufficiency in fish production in Nigeria. But the situation at the moment is that its fisheries potentials are not being optimally utilized. While the inland waters of Lake Chad are currently being recklessly exploited, aquaculture development is given little or no attention. It is evident that there is a missing link between research results and the potential end users. Because information in fish production variables is a pre-requisite for fisheries development, the gap that exists between two poles must be bridged, fisheries Extension provides this important link between research result and the end users of research findings. The paper examines the importance of extension services as the key to unlock fish production information that are usually consigned to the pages of academic journals and research publications