Stress intensity factor histories of a steadily propagating crack under 3-D combined mode traction

Elastodynamic stress intensity factor histories of an unbounded solid containing a semi-infinite plane crack that propagates at a constant velocity under 3-D time-independent combined mode loading are considered. The fundamental solution, which is the response of point loading, is obtained. Then, stress intensity factor histories of a general loading system are written out in terms of superposition integrals. The methods used here are the Laplace transform methods in conjunction with the Wiener-Hopf technique.

Diversidad de artrópodos asociada a dos sistemas de manejo de plantación de Marango (Moringa oleifera Lam.) en la Finca Santa Rosa, Managua

Debido a pocos estudios sobre los artrópodos asociados a Moringa oleifera Lam., se llevó a cabo una caracterización de la diversidad dinámica poblacional y el rol potencial a nivel de orden familia y especie en dos sistemas de manejo de plantación para producción de semillas. La evaluación se llevó a cabo por un periodo de 12 semanas. La colecta se realizó a través del uso de trampas Pitfall y trampas aéreas en lotes de plantación de Moringa oleifera manejadas como monocultivo convencional; y manejo con enfoque agroecológico. Los parámetros registrados en cada sistema de manejo fueron: abundancia riqueza y, diversidad a partir del índice de Shannon Wiener. Los resultados reportan 1775 especímenes colectados, registrándose menor abundancia en manejo convencional (800 individuos) en comparación con manejo agroecológico (975 individuos). La fluctuación poblacional fue diferente en cada sistema de manejo, dándose un mayor incremento entre Noviembre y Enero en manejo agroecológico. La composición de artrópodos estuvo compuesta por 10 ordenes 55 familias y 73 especies. Los órdenes más representativos fueron Hymenoptera, Diptera, Orthoptera y Coleópeta. Las familias más representativas fueron Formicidae, Muscidae, Acrididae, Chrisopidae, Pyralidae y Blattellidae; reportando mayor índice de diversidad (3.2) en manejo agroecológico. La riqueza de especies fue más alta en manejo agroecológico (69) en comparación con manejo convencional (52). En cuanto al rol potencial de las especies en manejo agroecológico fue identificado 49.2% de defoliadores, 42.02% son benéficos mientras en manejo convencional 51.9% don defoliadores y 40.3 son especies benéficas.

迟滞系统随机响应问题基于函数级数的解法

本文提出了一个三次多项式的迟滞模型,并用Wiener-Hermite函数级数展开的方法求解,得到了不同阻尼及不同的非线性强度时系统响应的均方值σ(t)。不仅从理论上而且通过实验证实了用这种方法求解迟滞系统的响应是行之有效的、简便的。

Elastodynamic stress-intensity factors for a semiinfinite crack under 3-d combined mode loading

The dynamic stress intensity factor histories for a half plane crack in an otherwise unbounded elastic body are analyzed. The crack is subjected to a traction distribution consisting of two pairs of suddenly-applied shear point loads, at a distance L away from the crack tip. The exact expression for the combined mode stress intensity factors as the function of time and position along the crack edge is obtained. The method of solution is based on the direct application of integral transforms together with the Wiener-Hopf technique and the Cagniard-de Hoop method, which were previously believed to be inappropriate. Some features of solutions are discussed and the results are displayed in several figures.

Elastodynamic stress intensity factor history for a semi-infinite crack under three-dimensional transient loading

The dynamic stress intensity factor history for a semi-infinite crack in an otherwise unbounded elastic body is analyzed. The crack is subjected to a pair of suddenly-applied point loadings on its faces at a distance L away from the crack tip. The exact expression for the mode I stress intensity factor as a function of time is obtained. The method of solution is based on the direct application of integral transforms, the Wiener-Hopf technique and the Cagniard-de Hoop method. Due to the existence of the characteristic length in loading this problem was long believed a knotty problem. Some features of the solutions are discussed and graphical result for numerical computation is presented.

Développement des méthodes de stabilisation pour la conception des circuits hyperfréquences : application à l'optimisation d'un amplificateur de puissance spatial

209 p. : graf.

Erromaurreko Iberiar Penintsulako antzinaroari buruzko materialak : Iberiako hegoaldeko herri eta kulturak

Traducido por Iñaki Villoslada Fernández

About the limits of metalanguage: An essay on the modelisation of Latin grammatical lexicography

[EN] Progress in methodology in specific fields is usually very closely linked to the technological progress in other areas of knowledge. This justifies the fact that lexicographical techniques have had to wait for the arrival of the IT era of the last decades of the 20th century in order to be able to create specialised electronic dictionaries which can house and systemise enormous amounts of information which can later be dealt with quickly and efficiently. This study proposes a practical-methodological model which aims to solve the grammatical treatment of adverbs in Ancient Latin. We have suggested a list of 5 types, in a decreasing order from a greater to lesser degree of specialisation; technical (T), semi-technical (S-T), instrumental-valued (I-V), instrumental- descriptive (I-D), instrumental-expository (I-E).

Los determinantes de la rentabilidad primaria de los bonos de titulización hipotecaria: la influencia de las estructuras multitramo

[ES] Este artículo analiza los determinantes de la rentabilidad primaria de los bonos de titulización hipotecaria (conocidos en la literatura como mortgage backed securities, o MBS) emitidos en España durante el periodo 1993-2011, periodo en el que el mercado español llegó a convertirse en el más importante de Europa continental. Los resultados obtenidos sobre el análisis de la población completa de MBS emitidos (262 tramos configurados sobre 94 fondos de titulización) indican que la estructuración multitramo de los MBS ha ayudado a reducir el riesgo percibido global de las emisiones de MBS, mediante la generación de mercados más completos y la reducción de los problemas derivados de la existencia de asimetrías informativas implícitas en el proceso de selección de los activos transmitidos por parte de la entidad cedente. Esta reducción del riesgo percibido ha tenido un efecto directo sobre la rentabilidad ofrecida por los bonos de titulización emitidos. Además, no se encuentran evidencias de que la emisión de MBS persiga la transmisión efectiva de riesgos, más bien al contrario. Las Entidades de crédito, por lo general, han retenido los tramos de primeras pérdidas, lo que ha contribuido a mantener en niveles muy bajos (por debajo de la rentabilidad de la deuda soberana) la rentabilidad ofrecida por los MBS. Precisamente, el escaso diferencial ofrecido por los bonos de titulización se debe a que los tramos retenidos no han ofrecido primas de rentabilidad ajustadas al riesgo inherente.

高等断裂力学

der="0" alt="" hspace="8" width="105" height="150" align="left" />《高等断裂力学》系统论述断裂力学的基本概念、理论基础、力学原理、分析方法以及断裂力学的实验测定和工程应用。深入阐明了断裂力学各个重要发展阶段的新颖学术思想和原创性工作，同时融会贯通地介绍了国内学者在作者熟悉的若干领域内的创造性贡献。　　《高等断裂力学》共14章。第1章介绍断裂力学的历史背景和发展脉络；第2～5章介绍线弹性断裂力学；第6～8章论述弹塑性断裂力学；第9及第10章分别介绍疲劳裂纹扩展和界面裂纹；第11～14章阐述裂纹体弹性动力学和裂纹动态扩展。　　《高等断裂力学》适合从事断裂力学研究和应用的科技工作者及工程师使用和参考，也可供力学专业的高年级本科生和研究生阅读参考.

Fishery resource surveys: beyond length-weight relationship models

Fisheries resource surveys are regular management tools for rational exploitation of commercial fisheries. In a growing number of cases, the use of these resource surveys has been largely restricted to assessment of the relative well being of fish stocks and the potential yields of such fisheries. This paper seeks to demonstrate that the data from such surveys can also be easily used to evaluate species diversity of such fisheries, both in terms of species richness and equitability of distribution. Using published data on two freshwater and two marine fisheries as case studies, Shannon-Wiener Diversity Function and Simpson's Index were computed for each of these fisheries. These biodiversity indices gave a deeper insight into the environmental status of each of these fisheries, beyond what the length-weight relationship models can reveal. Generally, while the marine fisheries showed more species richness, the freshwater fisheries apparently had more stable and equilibrated fish communities

Euskal autore zaharren irakaskuntza Lehen Hezkuntzan: proiektu berritzaile baten proposamena

Euskara: Lan honek euskal autore zaharrak Lehen Hezkuntzako ikasleei hurbiltzea du helburu. Ezinbestekoa da neska-mutilek ikasgeletan klasikoen ondarea ezagutzeko aukera izatea, euskal autore zaharren irakaskuntza-ikaskuntza prozesua suspertzeko. Izan ere, idazle klasikoak oinarrizko hezkuntzan duten tokia ez da handia izan, hauek lantzeak zailtasunak dakartzalako. Beraz, zailtasun horiek aztertuta eta lekuko idazle ezberdinen lan hautatuen egokitze-lana aintzat hartuz, proiektu berritzaile baten proposamena eskaini nahi da, euskarazko literatura zaharra irakurtzeko eta lantzeko zaletasuna sustatzeko bidea erakusteko asmoz. Horrela izanik, ikasleek euren neurrira eta interesetara moldatutako egitasmoa eskura izango dute, egungo hezkuntza-sisteman beharrezkoak diren oinarrizko gaitasunak barneratuz, beti ere gaiarekiko motibazioa eta jakin-mina aintzat hartuta.

Nonlinear dynamic transfer functions for certain retinal neuronal systems

The applicability of the white-noise method to the identification of a nonlinear system is investigated. Subsequently, the method is applied to certain vertebrate retinal neuronal systems and nonlinear, dynamic transfer functions are derived which describe quantitatively the information transformations starting with the light-pattern stimulus and culminating in the ganglion response which constitutes the visually-derived input to the brain. The retina of the catfish, Ictalurus punctatus, is used for the experiments.

The Wiener formulation of the white-noise theory is shown to be impractical and difficult to apply to a physical system. A different formulation based on crosscorrelation techniques is shown to be applicable to a wide range of physical systems provided certain considerations are taken into account. These considerations include the time-invariancy of the system, an optimum choice of the white-noise input bandwidth, nonlinearities that allow a representation in terms of a small number of characterizing kernels, the memory of the system and the temporal length of the characterizing experiment. Error analysis of the kernel estimates is made taking into account various sources of error such as noise at the input and output, bandwidth of white-noise input and the truncation of the gaussian by the apparatus.

Nonlinear transfer functions are obtained, as sets of kernels, for several neuronal systems: Light → Receptors, Light → Horizontal, Horizontal → Ganglion, Light → Ganglion and Light → ERG. The derived models can predict, with reasonable accuracy, the system response to any input. Comparison of model and physical system performance showed close agreement for a great number of tests, the most stringent of which is comparison of their responses to a white-noise input. Other tests include step and sine responses and power spectra.

Many functional traits are revealed by these models. Some are: (a) the receptor and horizontal cell systems are nearly linear (small signal) with certain "small" nonlinearities, and become faster (latency-wise and frequency-response-wise) at higher intensity levels, (b) all ganglion systems are nonlinear (half-wave rectification), (c) the receptive field center to ganglion system is slower (latency-wise and frequency-response-wise) than the periphery to ganglion system, (d) the lateral (eccentric) ganglion systems are just as fast (latency and frequency response) as the concentric ones, (e) (bipolar response) = (input from receptors) - (input from horizontal cell), (f) receptive field center and periphery exert an antagonistic influence on the ganglion response, (g) implications about the origin of ERG, and many others.

An analytical solution is obtained for the spatial distribution of potential in the S-space, which fits very well experimental data. Different synaptic mechanisms of excitation for the external and internal horizontal cells are implied.

Os novos movimentos de classe: reflexões sobre a organização política da classe trabalhadora brasileira

O trabalho de pesquisa apresentado tem como objetivo analisar e discutir centralmente o processo de reconfiguração da classe trabalhadora brasileira, suas transformações e impactos ocasionados no contexto da reestruturação produtiva e das políticas neoliberais. Serão abordados aspectos referentes às características de sua organização política e sindical debatendo as potencialidades dos novos movimentos de classe, que se articulam enquanto ferramentas de transformação societária. Este novo processo de organização dos trabalhadores é tratado como fruto da realidade objetiva que os integra: precarizados e desempregados da cidade, sem-terras e sem-emprego do campo, indicando uma realidade onde a classe trabalhadora define-se de forma diferente daqueles trabalhadores que, em fins de 1970, iniciavam as greves em São Bernardo do Campo. Os novos movimentos de classe, aqui considerados, articulam a luta por uma contra-hegemonia no campo das ações políticas, de organização da classe e no campo da gestão econômica. São novos, por expressarem o resgate e a inovação de experiências políticas da classe trabalhadora em um momento onde esta sofre grandes transformações.

Os contextos de autonomia e vulnerabilidade: histórias e particularidades de mulheres vivendo com HIV/Aids

O estudo teve o objetivo de identificar os contextos de vulnerabilidade e autonomia de mulheres vivendo com HIV/Aids antes e depois do diagnóstico. Essas mulheres são participantes do Grupo Parceiras da Vida, atendidas pelo Núcleo de Epidemiologia e pelo Serviço Social do Hospital Universitário Pedro Ernesto/UERJ. O referido grupo tem como proposta oferecer suporte e informação além de estimular o exercício da autonomia feminina. Nossa análise teve como referência os Direitos Humanos, entendendo que as desigualdades de gênero, propiciam uma série de violações de direitos das mulheres, que nos permitem refletir acerca dos processos de vulnerabilidade e autonomia vivenciados pelas mesmas. Foi utilizada a metodologia qualitativa, através do uso da história de vida de mulheres vivendo com HIV/Aids, bem como a observação participante das atividades do grupo de mulheres. Sendo assim, foram abordados os eixos temáticos da seguinte forma: Percepção social da doença na ótica de Gênero; Acesso e Política de Assistência as Pessoas vivendo com HIV/Aids e a Dinâmica de rede sócio familiar: o grupo Parceiras da Vida. Identificamos que as inserções de classe, etnia, escolaridade, associados as particularidades do processo histórico vivido pelas mulheres, podem definir maiores ou menores magnitudes de situações de vulnerabilidade e autonomia. Constatamos, ainda, que o grupo Parceiras da Vida é referenciado enquanto grupo de apoio, bem como contribui para o fortalecimento e para a construção de sujeitos mais autônomos no processo de adoecimento pelo vírus HIV/Aids.