Algorithm for simulating fracture processes in concrete by lattice modeling

To simulate fracture behaviors in concrete more realistically, a theoretical analysis on the potential question in the quasi-static method is presented, then a novel algorithm is proposed which takes into account the inertia effect due to unstable crack propagation and meanwhile requests much lower computational efforts than purely dynamic method. The inertia effect due to load increasing becomes less important and can be ignored with the loading rate decreasing, but the inertia effect due to unstable crack propagation remains considerable no matter how low the loading rate is. Therefore, results may become questionable if a fracture process including unstable cracking is simulated by the quasi-static procedure excluding completely inertia effects. However, it requires much higher computational effort to simulate experiments with not very high loading rates by the dynamic method. In this investigation which can be taken as a natural continuation, the potential question of quasi-static method is analyzed based on the dynamic equations of motion. One solution to this question is the new algorithm mentioned above. Numerical examples are provided by the generalized beam (GB) lattice model to show both fracture processes under different loading rates and capability of the new algorithm.

A simple method to simulate shrinkage-induced cracking in cement-based composites by lattice-type modeling

A new numerical procedure is proposed to investigate cracking behaviors induced by mismatch between the matrix phase and aggregates due to matrix shrinkage in cement-based composites. This kind of failure processes is simplified in this investigation as a purely spontaneous mechanical problem, therefore, one main difficulty during simulating the phenomenon lies that no explicit external load serves as the drive to propel development of this physical process. As a result, it is different from classical mechanical problems and seems hard to be solved by using directly the classical finite element method (FEM), a typical kind of "load -> medium -> response" procedures. As a solution, the actual mismatch deformation field is decomposed into two virtual fields, both of which can be obtained by the classical FEM. Then the actual response is obtained by adding together the two virtual displacement fields based on the principle of superposition. Then, critical elements are detected successively by the event-by-event technique. The micro-structure of composites is implemented by employing the generalized beam (GB) lattice model. Numerical examples are given to show the effectiveness of the method, and detailed discussions are conducted on influences of material properties.

Numerical investigation of crack growth in concrete subjected to compression by the generalized beam lattice model

The beam lattice-type models, such as the Euler-Bernoulli (or Timoshenko) beam lattice and the generalized beam (GB) lattice, have been proved very effective in simulating failure processes in concrete and rock due to its simplicity and easy implementation. However, these existing lattice models only take into account tensile failures, so it may be not applicable to simulation of failure behaviors under compressive states. The main aim in this paper is to incorporate Mohr-Coulomb failure criterion, which is widely used in many kinds of materials, into the GB lattice procedure. The improved GB lattice procedure has the capability of modeling both element failures and contact/separation of cracked elements. The numerical examples show its effectiveness in simulating compressive failures. Furthermore, the influences of lateral confinement, friction angle, stiffness of loading platen, inclusion of aggregates on failure processes are respectively analyzed in detail.

Electrical and optical interconnects for high-performance computing

Technology scaling has enabled drastic growth in the computational and storage capacity of integrated circuits (ICs). This constant growth drives an increasing demand for high-bandwidth communication between and within ICs. In this dissertation we focus on low-power solutions that address this demand. We divide communication links into three subcategories depending on the communication distance. Each category has a different set of challenges and requirements and is affected by CMOS technology scaling in a different manner. We start with short-range chip-to-chip links for board-level communication. Next we will discuss board-to-board links, which demand a longer communication range. Finally on-chip links with communication ranges of a few millimeters are discussed.

Electrical signaling is a natural choice for chip-to-chip communication due to efficient integration and low cost. IO data rates have increased to the point where electrical signaling is now limited by the channel bandwidth. In order to achieve multi-Gb/s data rates, complex designs that equalize the channel are necessary. In addition, a high level of parallelism is central to sustaining bandwidth growth. Decision feedback equalization (DFE) is one of the most commonly employed techniques to overcome the limited bandwidth problem of the electrical channels. A linear and low-power summer is the central block of a DFE. Conventional approaches employ current-mode techniques to implement the summer, which require high power consumption. In order to achieve low-power operation we propose performing the summation in the charge domain. This approach enables a low-power and compact realization of the DFE as well as crosstalk cancellation. A prototype receiver was fabricated in 45nm SOI CMOS to validate the functionality of the proposed technique and was tested over channels with different levels of loss and coupling. Measurement results show that the receiver can equalize channels with maximum 21dB loss while consuming about 7.5mW from a 1.2V supply. We also introduce a compact, low-power transmitter employing passive equalization. The efficacy of the proposed technique is demonstrated through implementation of a prototype in 65nm CMOS. The design achieves up to 20Gb/s data rate while consuming less than 10mW.

An alternative to electrical signaling is to employ optical signaling for chip-to-chip interconnections, which offers low channel loss and cross-talk while providing high communication bandwidth. In this work we demonstrate the possibility of building compact and low-power optical receivers. A novel RC front-end is proposed that combines dynamic offset modulation and double-sampling techniques to eliminate the need for a short time constant at the input of the receiver. Unlike conventional designs, this receiver does not require a high-gain stage that runs at the data rate, making it suitable for low-power implementations. In addition, it allows time-division multiplexing to support very high data rates. A prototype was implemented in 65nm CMOS and achieved up to 24Gb/s with less than 0.4pJ/b power efficiency per channel. As the proposed design mainly employs digital blocks, it benefits greatly from technology scaling in terms of power and area saving.

As the technology scales, the number of transistors on the chip grows. This necessitates a corresponding increase in the bandwidth of the on-chip wires. In this dissertation, we take a close look at wire scaling and investigate its effect on wire performance metrics. We explore a novel on-chip communication link based on a double-sampling architecture and dynamic offset modulation technique that enables low power consumption and high data rates while achieving high bandwidth density in 28nm CMOS technology. The functionality of the link is demonstrated using different length minimum-pitch on-chip wires. Measurement results show that the link achieves up to 20Gb/s of data rate (12.5Gb/s/$\mu$m) with better than 136fJ/b of power efficiency.

Cartas enviadas por José Manuel Barrenechea a Justo Garate entre 1981 y 1982

4 cartas (manuscritas) ; entre 210x260mm y 150x200mm

Monica Alis Brick Lane: A tale of two cities or How Nazneen left her fate

O objetivo desta dissertação é analisar o romance Brick Lane (2003), da escritora Monica Ali, focalizando o processo de empoderamento da protagonista Nazneen. Usando os conceitos de lugar e não-lugar propostos por Marc Augé, pretendo examinar passagens do romance que caracterizem a sensação de não-pertencimento vivida pela personagem. Nazneen recorre às memórias de sua infância com a irmã Hasina em Bangladesh para tentar se distanciar do espaço físico de Brick Lane (a comunidade onde reside em Londres), que se constitui em um não-lugar, pois ali não é possível reconstruir sua identidade fragmentada pelo deslocamento de uma cultura para outra. Considerando aspectos históricos e culturais de Bangladesh, terra natal de Nazneen, este trabalho pretende discutir as experiências da protagonista e de outros sujeitos diaspóricos do romance, além de analisar o papel crucial que Hasina (e suas cartas) desempenham na narrativa. O atual contexto multicultural e cosmopolita da cidade de Londres também será investigado, com a discussão de situações que afetam os imigrantes e suas representações no romance. Esta dissertação também considera o caráter gendrado dos movimentos migratórios contemporâneos que possibilitam novas perspectivas acerca das consequências da diáspora. A análise de passagens selecionadas do romance ratifica o processo gradual de autonomia de Nazneen que, por fim, consegue se sentir em casa novamente

超分辨近场功能薄膜的膜层结构及其机理研究进展

超分辨近场结构光盘是最有希望达到100 GB以上的存储容量方式之一,而其记录和读出机理是研究中的重点,在近年文献研究的基础上,阐述了超分辨近场功能薄膜的膜层结构及其机理的研究进展。

网络的发展对光盘应用的影响

一、引言21世纪是数字化和多媒体化的信息时代,随着社会和经济的发展,特别是IT产业的快速发展,全球信息每年以指数方式上升。最近IDC的研究报告指出,2006年,全球的信息量为1610亿GB;到2010年,全球数字信息量预计为9880亿GB。中国的数字信息总量,也将从2006年的127.1亿GB增加到900.5亿GB,占全球信息总量的9.1%。同时,根据国家信息产业部的年度

Meio Ambiente sob a ótica da sustentabilidade dos Jogos Olímpicos de 2016 no Rio de Janeiro: aspectos da gestão de resíduos.

A cidade do Rio de Janeiro foi eleita sede dos Jogos Olímpicos e Paraolímpicos de 2016 e são previstos impactos significativos em investimento e na geração de emprego, atrelados a isto existe a preocupação com as questões ambientais e a sustentabilidade do evento. No dossiê de candidatura do Rio de Janeiro a sede dos Jogos Olímpicos de 2016, existia o compromisso com a gestão dos resíduos sólidos. As grandes linhas de ações foram definidas quando do lançamento da candidatura do Rio de Janeiro a sede do evento, fato este que se concretizou em 02 de outubro de 2009. A gestão dos resíduos para 2016 é ainda carente de informações quantitativas de sua geração, das necessidades de adaptações das instalações para o período de realização do evento, bem como da definição de metas para que a gestão dos resíduos devidamente alinhadas com os preceitos do desenvolvimento sustentável. O objetivo deste estudo é avaliar sub o conceito de desenvolvimento sustentável a gestão de resíduos sólidos durante a realização dos Jogos Olímpicos de 2016 na cidade do Rio de Janeiro. A metodologia consiste no levantamento histórico dos Jogos Olímpicos com especial detalhamento nas questões ligadas ao conceito de desenvolvimento sustentável e gestão de resíduos, análise dos Jogos Pan-americanos do Rio de Janeiro, levantamento em campo da preparação dos Jogos Olímpicos de Londres, observações em campo na cidade do Rio de Janeiro e a análise de dados para o cálculo da estimativa de geração de resíduos durante a realização dos Jogos de 2016. As comparações com outros eventos demonstraram semelhanças e diferenças com os Jogos Olímpicos de 2016 e possibilitou a apresentação de proposições para a gestão de resíduos sólidos. A projeção de geração de resíduos durante o evento é significativa e aponta a necessita de atenção para potencializar as ações como coleta seletiva, reciclagem e compostagem. São indicados estudos futuros sobre a gestão dos resíduos, em especial da construção civil durante as obras das futuras instalações, algumas delas já em curso.