RESUMO
The review deals with new trends in modeling the vestibular function of the hemispheric channels (HC) involved in the head angular movements. The trends were spurred by the growing significance of computers in both mathematical modeling and direct simulation of the HC structure and processes, and conditions of experiments. Literature analysis reveals the following trends in the CH modeling: 1) reconstruction, 2) micromodeling, 3) integral modeling, 4) simulation (imitation), and 5) alternative modeling. The article gives several examples of the modern trends in HC modeling.
Assuntos
Simulação por Computador/tendências , Modelos Teóricos , Equilíbrio Postural/fisiologia , Vestíbulo do Labirinto/fisiologia , Animais , HumanosRESUMO
Popular hypothesis based on the idea of simple feedback mechanism that correlates gravity level and weight of test mass cannot explain the variety of the effects of altered gravity on development and function of gravireceptors. The reaction of organisms to the change of gravity depends on the gravisensitivity of the physical and chemical processes corresponding to specific phases of development and may have no relation to any feedback mechanisms of compensation of altered weight of the test mass. The present work analyzes the hypothesis of feedback and shows the ambiguity of possible effects of the altered gravity on formation and function of gravireceptors basing on the data from mollusks and fish.
Assuntos
Orelha Interna/crescimento & desenvolvimento , Peixes/fisiologia , Sensação Gravitacional/fisiologia , Gravidade Alterada , Moluscos/fisiologia , Neurônios Aferentes/fisiologia , Animais , Orelha Interna/citologia , Retroalimentação/fisiologia , Peixes/anatomia & histologia , Células Ciliadas Auditivas/fisiologia , Mecanotransdução Celular/fisiologia , Moluscos/anatomia & histologia , Membrana dos Otólitos/citologia , Membrana dos Otólitos/crescimento & desenvolvimentoRESUMO
This paper concerns the robustness of discrete wavelet transform (DWT) compression in terahertz pulsed imaging (TPI). TPI datasets consist of terahertz time-domain series which are sampled at each 'pixel' of the image, leading to file sizes which are typically of the order of several megabytes (MB) per image. This makes efficient compression highly desirable for both transmission and storage. However, since the data may be required for diagnostic purposes it is essential that no relevant information is lost or artefacts introduced. We show that for a nylon step wedge the estimates of refractive index and absorption coefficients are not significantly altered when the terahertz data are reconstructed from only 20% of DWT coefficients.
Assuntos
Aumento da Imagem/métodos , Armazenamento e Recuperação da Informação/métodos , Micro-Ondas , Refratometria/métodos , Processamento de Sinais Assistido por Computador , Análise Espectral/métodos , Algoritmos , Artefatos , Diagnóstico por Imagem/instrumentação , Diagnóstico por Imagem/métodos , Fenômenos Eletromagnéticos/instrumentação , Fenômenos Eletromagnéticos/métodos , Nylons , Imagens de Fantasmas , Controle de Qualidade , Refratometria/instrumentação , Reprodutibilidade dos Testes , Tamanho da Amostra , Sensibilidade e Especificidade , Análise Espectral/instrumentaçãoRESUMO
A full-field, time-resolved interferometric method for the characterization of sparse, polydisperse spray systems is reported. The method makes use of the angular intensity oscillations in the wide-angle forward-scatter region. A pulsed laser is used to illuminate a planar sheet through the spray, which is imaged, out of focus, from the 45°direction. The image consists of a set of out-of-focus spots, each of which represents an individual droplet, and superimposed on which is a set of fringes corresponding to the angular intensity oscillations of that droplet. Macrophotographic recording with high-resolution digitization for image analysis provides a full-field capability. The spatial frequency of fringes on each spot in the image plane is dependent on the diameter of the corresponding droplet in the object plane, and a simple geometric analysis is shown to be appropriate for the calculation of the spatial frequency of fringes as a function of droplet size. Images are analyzed automatically by a software suite that uses Gaussian blur, Canny edge detection, and Hough transforms to locate individual droplets in the image field. Fringe spatial frequency is then determined by least-squares fitting to a Chirp function. The method is applicable to droplets with diameters in the range of several millimeters to several hundred millimeters and number densities of up to 10(3) to 10(4). The accuracy of the method for droplet-size determination has been evaluated by measurements of monodisperse aerosols of known droplet size, and measurements of droplet-size distribution in a polydisperse aerosol produced by a gasoline fuel injector are also presented. An extension of the method, using high-speed photography to measure two components of velocity in addition to size and position, is discussed. A two-wavelength approach may also offer the capability to measure the concentration of model fuel additives in droplets, and the results of a feasibility study are described.
