Nonlinear optical properties of organic materials: A theoretical study

Replacement of electronic switching circuits in computing and telecommunication systems with purely optical devices offers the potential for extremely high throughput and compact information processing systems. The potential application of organic materials containing molecules with large nonresonant nonlinear effects in this area have triggered intensive research during the last decade. Interest on this area was due to two facts: (1) that many organic materials show nonlinearities that are orders of magnitude larger than those of conventional inorganic materials such as lithium niobate and potassium dihydrogen phosphate; and (2) that organic materials show much flexibility in terms of molecular designs. Some of the desirable characteristics that these materials should have are that they be transparent to the frequency of the incident laser and its second or third harmonic, that they have a high damage threshold, and, in the case of second-order effects, that their crystal structure or molecular orientation be accentric. Since polymeric assemblages can enhance the nonlinear response of organic molecules severalfold, efforts have been directed toward the synthesis of thin films with interpenetrating lattices of electroactive molecules. The goal of this theoretical investigation is to predict the magnitude of the molecular polarizabilities of organic molecules that could be incorporated into films. These calculations are intended to become a powerful tool to assist material scientists in screening for the best candidates for optical applications. The procedure that was developed for the present calculations is based on the static-field approach, and is a modification to the method developed by Dewar and Stewart, 1984 for calculating molecular linear polarizabilities

Advanced Computational Modeling of Vapor Deposition in a High-Pressure Reactor

In search of novel approaches to produce new materials for electro-optic technologies, advances have been achieved in the development of computer models for vapor deposition reactors in space. Numerical simulations are invaluable tools for costly and difficult processes, such as those experiments designed for high pressures and microgravity conditions. Indium nitride is a candidate compound for high-speed laser and photo diodes for optical communication system, as well as for semiconductor lasers operating into the blue and ultraviolet regions. But InN and other nitride compounds exhibit large thermal decomposition at its optimum growth temperature. In addition, epitaxy at lower temperatures and subatmospheric pressures incorporates indium droplets into the InN films. However, surface stabilization data indicate that InN could be grown at 900 K in high nitrogen pressures, and microgravity could provide laminar flow conditions. Numerical models for chemical vapor deposition have been developed, coupling complex chemical kinetics with fluid dynamic properties

Source characteristics of volatile organic compounds during high ozone episodes in Hong Kong, Southern China

International audienceMeasurements of Volatile Organic Compounds (VOC) are analyzed to characterize the sources impacting the Hong Kong area. The ratios of different VOC species, m,p-xylenes-to-ethylbenzene, C6H14-to-toluene and p-xylene-to-total xylenes are used for diagnostic analyses. Photochemical age analysis shows that the sources of reactive aromatics, the most important contributor to the photochemical reactivity, do not appear to be preferentially located in downtown Hong Kong. In addition, they do not appear to be dominated by mobile emissions based on the analyses of speciated VOC data from an earlier study, but related to industrial, waterfront, and fuel-storage activities. The ratios, p-xylene-to-total xylenes and dSO2/dNOy, suggest that the anomalously high pollutant concentrations in western Hong Kong in the early morning hours of two episode days appear to have come from transport of urban-type emissions. Comparison of observed ambient ratios of selected VOC and their ratios in the speciated VOC emission inventories for Hong Kong and adjacent Pearl River Delta (PRD) Region give mixed results. The observed ratio C6H14-to-toluene is consistent with the speciated version of the VOC emission inventory. The ratios of selected alkanes are not. This may be caused by the inaccuracies in the inventory and/or the speciation method

Wow!! : Objetos bizarros de la vida moderna

En la actualidad, ¿realmente todos los productos que se nos presentan como “útiles” para llevar una vida más plena lo son? ¿O sirven para satisfacer deseos raros y peculiares? Este trabajo está enfocado en construir y reverenciar de manera extraña objetos ridículos e inútiles abordándolo desde lo multidisciplinar y usando como motor principal la creatividad, la imaginación y el humor. Acompañado de estrategia de marketing como video publicitario, stickers, volantes y afiche, mi propósito es hacer una parodia sobre el consumismo moderno. ¿Cómo? utilizando materiales incongruentes, generando en todo su conjunto, una estética “Kitsch”, es decir cursi, pretenciosa y vulgar.Facultad de Arte

A study on the vertical propagation of planetary waves and the effects of the upper boundary condition

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Meteorology, 1979.Microfiche copy available in Archives and Science.Bibliography : leaves 119-120.by Carlos Antonio Cardelino.M.S

A contrario selection of optimal partitions for image segmentation

We present a novel segmentation algorithm based on a hierarchical representation of images. The main contribution of this work is to explore the capa- bilities of the a contrario reasoning when applied to the segmentation problem, and to overcome the limitations of current algorithms within that framework. This ex- ploratory approach has three main goals. Our first goal is to extend the search space of greedy merging algorithms to the set of all partitions spanned by a certain hierarchy, and to cast the segmentation as a selection problem within this space. In this way we increase the number of tested partitions and thus we potentially improve the segmentation results. In addition, this space is considerably smaller than the space of all possible partitions, thus we still keep the complexity controlled. Our second goal aims to improve the locality of region merging algorithms, which usually merge pairs of neighboring regions. In this work, we overcome this limitation by introducing a validation procedure for complete partitions, rather than for pairs of regions. The third goal is to perform an exhaustive exper- imental evaluation methodology in order to provide reproducible results. Finally, we embed the selection process on a statistical a contrario framework which allows us to have only one free parameter related to the desired scale

Avaliação de empresas juniores de engenharia florestal no Brasil e sua contribuição na formação de futuros profissionais

Trabalho de Conclusão de Curso (graduação)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Florestal, 2019.Este trabalho buscou conhecer as empresas juniores florestais do Brasil através de uma avaliação da estrutura organizacional e a caracterização do perfil dos participantes. Uma vez que ao final da graduação os recém-formados engenheiros florestais são requisitados ter experiência profissional, um ambiente como o de uma EJ é ideal para o desenvolvimento profissional, trabalhar habilidades de liderança, trabalho em equipe e gestão empresarial. Apesar de uma EJ simular uma empresa, ela pode apresentar problemas de organização, relativamente baixo número de projetos e por consequência pouco desenvolvimento dos participantes se estes não tiverem iniciativa. Através de questionários e de suas respostas foi possível entender o histórico da EJ entre os anos de 2016 e 2018. O questionário foi direcionado aos presidentes, onde estes responderam a perguntas gerais da empresa, como quantos funcionários, principais áreas de atuação, lista de projetos por ano e faturamento anual dos serviços florestais prestados. O questionário 2 foi destinado a todos os membros da empresa com objetivo de entender quais dinâmicas e como a empresa os capacita, através de treinamentos tradicionais, banco de dados, rodas de conversa, troca de experiência, aprender na prática e ao final, foi preenchido um questionário resumido com 5 perguntas chaves, sobre as principais problemáticas deste trabalho. Com estes dois formulários preenchidos foi evidenciado uma organização estrutural de hierarquia tradicional e também uma desorganização com o histórico de atividades e serviços prestados em anos anteriores. Há um bom número de participantes por EJ, porém não reflete em mais serviços sendo executados. Os membros das empresas responderam o questionário 2 com boas notas em quase todos os aspectos, confirmando as suposições que EJ buscam desenvolver e compartilhar conhecimentos através de pequenos projetos, troca de experiências entre experientes e novatos, sendo um ambiente motivador e de constante aprendizado individual e social. Nestes quesitos o trabalho conclui que os respondentes acreditam estarem mais preparados, estão satisfeitos com seu desempenho e com o de sua EJ e assim, terão uma inserção no mercado de trabalho mais rápida. Por fim, este trabalho, exploratório com empresas juniores florestais, deve ser replicado para outros cursos como forma de auto avaliação e de avaliação empresarial, para que uma EJ possa melhorar sua estrutura organizacional, impactando no crescimento e amadurecimento da mesma e seus membros.This study aimed to describe the context of Junior Enterprises from forestry engineering degrees in Brazil through an analysis of the organizational structure and the characterization of its participants' profile. Since graduating forestry engineers will be required to have professional experience prior to their bachelor's, an environment such as a JE is ideal for professional development, development of leadership skills, teamwork and how to work and manage a business. Although a JE simulates a company, it can present organizational problems, a relatively low number of projects and consequently poor development of their participants if they are not proactive. Through a pair of surveys and their answers, it was possible to understand the background of each JE in 2016, 2017 and 2018. Questionnaire 1 was addressed to presidents, where they would answer general questions about the company, such as how many employees worked there, their main services areas, list of projects provided and annual revenues based on all services provided. The second questionnaire was intended for all company members to understand which are the dynamics and how the company instructs them, via traditional training, reading of past JE archives, through conversation meetings, exchange of experiences, on-job-training and others. In the end, 5 key questions about the main problems of this study were presented. These two completed surveys showed a structural organization of traditional hierarchy and also disorganization with the history of activities and services provided in previous years. There are a good number of employees per JE, but it does not mean more services being done. The employees answered Questionnaire 2 with good grades in almost every aspect, confirming the assumptions that a JE seeks to develop and share knowledge through small projects, a knowledge exchange via social interactions between veterans and sophomores, thus being a driving learning environment for mass and individuals. As a result, the study concludes that respondents believe they are better prepared, are satisfied with their performance as well as of their JE and so, they will find a job offer sooner. Finally, this exploratory work with junior enterprises should be replicated to other courses as a form of selfassessment and as business evaluation, so that a JE can improve its organizational structure, influencing the growth and maturity of the company and its members

Sensitivity Modeling Study for an Ozone Occurrence during the 1996 Paso Del Norte Ozone Campaign

Surface ozone pollution has been a persistent environmental problem in the US and Europe as well as the developing countries. A key prerequisite to find effective alternatives to meeting an ozone air quality standard is to understand the importance of local anthropogenic emissions, the significance of biogenic emissions, and the contribution of long-range transport. In this study, an air quality modeling system that includes chemistry and transport, CMAQ, an emission processing model, SMOKE, and a mesoscale numerical meteorological model, WRF, has been applied to investigate an ozone event occurring during the period of the 1996 Paso del Norte Ozone Campaign. The results show that the modeling system exhibits the capability to simulate this high ozone occurrence by providing a comparable temporal variation of surface ozone concentration at one station and to capture the spatial evolution of the event. Several sensitivity tests were also conducted to identify the contributions to high surface ozone concentration from eight VOC subspecies, biogenic VOCs, anthropogenic VOCs and long-range transportation of ozone and its precursors. It is found that the reductions of ETH, ISOP, PAR, OLE and FORM help to mitigate the surface ozone concentration, and like anthropogenic VOCs, biogenic VOC plays a nonnegligible role in ozone formation. But for this case, long-range transport of ozone and its precursors appears to produce an insignificant contribution

Source characteristics of volatile organic compounds during high ozone episodes in Hong Kong, Southern China

Author name used in this publication: Wang, T.2007-2008 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe