Numerical simulation of an adaptive optics system with laser propagation in the atmosphere

A comprehensive model of laser propagation in the atmosphere with a complete adaptive optics (AO) system for phase compensation is presented, and a corresponding computer program is compiled. A direct wave-front gradient control method is used to reconstruct the wave-front phase. With the long-exposure Strehl ratio as the evaluation parameter, a numerical simulation of an AO system in a stationary state with the atmospheric propagation of a laser beam was conducted. It was found that for certain conditions the phase screen that describes turbulence in the atmosphere might not be isotropic. Numerical experiments show that the computational results in imaging of lenses by means of the fast Fourier transform (FFT) method agree well with those computed by means of an integration method. However, the computer time required for the FFT method is 1 order of magnitude less than that of the integration method. Phase tailoring of the calculated phase is presented as a means to solve the problem that variance of the calculated residual phase does not correspond to the correction effectiveness of an AO system. It is found for the first time to our knowledge that for a constant delay time of an AO system, when the lateral wind speed exceeds a threshold, the compensation effectiveness of an AO system is better than that of complete phase conjugation. This finding indicates that the better compensation capability of an AO system does not mean better correction effectiveness. (C) 2000 Optical Society of America.

Effects of Noise and Detection Error in a Dynamic Adaptive Optics System

It is well known that noise and detection error can affect the performances of an adaptive optics (AO) system. Effects of noise and detection error on the phase compensation effectiveness in a dynamic AO system are investigated by means of a pure numerical simulation in this paper. A theoretical model for numerically simulating effects of noise and detection error in a static AO system and a corresponding computer program were presented in a previous article. A numerical simulation of effects of noise and detection error is combined with our previous numeral simulation of a dynamic AO system in this paper and a corresponding computer program has been compiled. Effects of detection error, readout noise and photon noise are included and investigated by a numerical simulation for finding the preferred working conditions and the best performances in a practical dynamic AO system. An approximate model is presented as well. Under many practical conditions such approximate model is a good alternative to the more accurate one. A simple algorithm which can be used for reducing the effect of noise is presented as well. When signal to noise ratio is very low, such method can be used to improve the performances of a dynamic AO system.

Prudentia Iuris, 1990, n° 23 (número completo)

Contenido: Doctor Santiago de Estrada / Alfredo Di Pietro – Jornadas sobre “La reforma del Estado”: Las alternativas de financiamiento del mercado de capitales / Joaquín R. Ledesma – Una reflexión sobre la ley de reforma del Estado / Carlos Raúl Sanz – Las privatizaciones / Juan Carlos Cassagne – La concesión de obra pública / Rodolfo Barra – Constitucionalidad de las privatizaciones / Néstor Pedro Sagüés – Aspectos laborales de la ley 23.696 / Hugo R. Carcavallo – Estado nacional y bien común / José Giménez Rébora – Atribuciones, conducta y control de los funcionarios públicos en la época hispánica / Julio R. Lascano – Notas acerca de las relaciones Iglesia-Estado / Néstor Daniel Villa – Interdictos y acciones populares en Roma/ Fernando M. Zamora – Ciencias políticas: Ortega y la “sociedad de naciones” / Enrique Aguilar -- Documentos

Letras, 1990-1991, nº 23-24 (número completo)

Contenido: Un pequeño gran gigante. Más notas acerca de la hipérbole de lo corporal en la obra de Rabelais / Susana G. Artal – Una lectura de los cuatro cuartetos de T. S. Eliot (segunda parte) / Inés de Cassagne – Los estudios lingüísticos con base computacional / María Amalia García Jurado – Bucolismo en una carta de Sidonio Apolinar / Raúl Lavalle – La seducción estética de la barbarie como poesía de lo original originario / María Rosa Lojo – La elegía a María Blanchard / Lía Noemí Uriarte Rebaudi – Nota – Reseñas bibliográficas

南海北部湾23/25太阳区块海底工程地质调查与评价

<正> 本项成果,是承包美国太阳东方勘探公司任务而完成的。在系统分析总结了南海西部石油公司“南海—503工程地质取芯船”在南海北部湾23/25太阳区块所进行的测深、侧扫声纳、地震声学剖面测量,及4口孔深40米的工程地质浅钻土柱等材料的基础上,详细阐述了

[Discurso do Deputado Antunes de Oliveira : Sessão Conjunta do Congresso Nacional de 23 de novembro de 1978]

Afirma ser favorável à Proposta de Emenda Constitucional n. 14/78 do Senador Cattete Pinheiro, que estabelece representação política para o Distrito Federal. Compara a situação de Brasília com a de Washington, capital dos Estados Unidos.

Edital nº 23, de 28 de outubro de 1992 : concurso público para Agente de Segurança Legislativa

Em conformidade com o Edital nº 1/1992, torna público o resultado da prova de Conhecimentos Específicos do concurso público para o cargo de Agente de Segurança Legislativa.

Edital nº 14, de 23 de setembro de 1992 : concurso público para Operador de Audiovisual

Em conformidade com os Editais nº 1/1992 e nº 10/1992, comunica aos candidatos a data de realização da Prova Prática para a categoria funcional de Operador de Audiovisual.