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排序方式: 共有204条查询结果,搜索用时 281 毫秒
31.
32.
Photoconductive optically driven deformable membrane for spatial light modulator applications utilizing GaAs substrates 总被引:1,自引:0,他引:1
Haji-Saeed B Kolluru R Pyburn D Leon R Sengupta SK Testorf M Goodhue W Khoury J Drehman A Woods CL Kierstead J 《Applied optics》2006,45(12):2615-2622
The fabrication and characterization of an optically addressable deformable mirror for a spatial light modulator is described. Device operation utilizes an electrostatically driven pixellated aluminized polymeric membrane mirror supported above an optically controlled photoconductive GaAs substrate. A 5 microm thick grid of patterned photoresist supports the 2 microm thick aluminized Mylar membrane. A conductive ZnO layer is placed on the back side of the GaAs wafer. A standard Michelson interferometer is used to measure mirror deformation data as a function of illumination, applied voltage, and frequency. A simplified analysis of device operation is also presented. 相似文献
33.
Haji-Saeed B Sengupta SK Testorf M Goodhue W Khoury J Woods CL Kierstead J 《Applied optics》2006,45(14):3298-3306
We propose and demonstrate a new photorefractive real-time holographic deconvolution technique for adaptive one-way image transmission through aberrating media by means of four-wave mixing. In contrast with earlier methods, which typically required various codings of the exact phase or two-way image transmission for correcting phase distortion, our technique relies on one-way image transmission through the use of exact phase information. Our technique can simultaneously correct both amplitude and phase distortions. We include several forms of image degradation, various test cases, and experimental results. We characterize the performance as a function of the input beam ratios for four metrics: signal-to-noise ratio, normalized root-mean-square error, edge restoration, and peak-to-total energy ratio. In our characterization we use false-color graphic images to display the best beam-intensity ratio two-dimensional region(s) for each of these metrics. Test cases are simulated at the optimal values of the beam-intensity ratios. We demonstrate our results through both experiment and computer simulation. 相似文献
34.
Mecca FA Andrade ME Jakubiak RR Khoury HJ Dias SK Miquelin CA Nader A 《Radiation protection dosimetry》2012,148(4):452-456
The aim of this study was to evaluate the image quality of 29 computed tomography (CT) scanners in Brazil and to perform estimations of patient dose and image quality of common CT examinations at these equipment. The volume CT air kerma indexes (C(VOL)) were estimated, using normalised weighted air kerma indexes, supplied by the ImPACT group. The image quality tests were performed using the phantom and accreditation protocol from the American College of Radiology (ACR). The C(VOL) values for head scans varied between 8.7 and 108 mGy. The Hi-res chest examinations presented C(VOL) values varying from 0.4 to 32 mGy. For abdominal scans, the estimated C(VOL) values varied between 4.1 and 94 mGy. This wide variation of air kerma between different centres is related to the scanner type and also to the scanning parameters. The results also showed that the image quality did not attend all ACR CT accreditation requirements. 相似文献
35.
Understanding the control of the optical and plasmonic properties of unique nanosystems--gold nanostars--both experimentally and theoretically permits superior design and fabrication for biomedical applications. Here, we present a new, surfactant-free synthesis method of biocompatible gold nanostars with adjustable geometry such that the plasmon band can be tuned into the near-infrared region 'tissue diagnostic window', which is most suitable for in vivo imaging. Theoretical modelling was performed for multiple-branched 3D nanostars and yielded absorption spectra in good agreement with experimental results. The plasmon band shift was attributed to variations in branch aspect ratio, and the plasmon band intensifies with increasing branch number, branch length, and overall star size. Nanostars showed an extremely strong two-photon photoluminescence (TPL) process. The TPL imaging of wheat-germ agglutinin (WGA) functionalized nanostars on BT549 breast cancer cells and of PEGylated nanostars circulating in the vasculature, examined through a dorsal window chamber in vivo in laboratory mouse studies, demonstrated that gold nanostars can serve as an efficient contrast agent for biological imaging applications. 相似文献
36.
F. P. van der Meer R. Al‐Khoury L. J. Sluys 《International journal for numerical methods in engineering》2009,77(2):240-260
This paper presents new time‐dependent finite element shape functions suitable for modeling high‐gradient transient conductive heat flow in geothermal systems. The shape functions are made adaptive by enhancing the approximation functions with time‐dependent variables, which may vary according to the transient process without adding extra degrees of freedom or applying mesh adaptation. Two different approaches are presented. First, an iterative method is proposed, in which an exponential approximation function, which is optimized continually during the transient process, is incorporated in the shape function. Second, an analytical method is suggested, in which an analytical solution of a simplified process is incorporated in the shape function, enabling an explicit update of the shape functions in each time step. A methodology for modeling the variation of temperature in one and two dimensions is introduced. The ability of the method to capture high‐gradient temperature profiles using relatively large elements is illustrated with numerical examples of cases in which equally large standard finite elements fail. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
37.
The pressures of human population and patterns of development frequently jeopardize the integrity of river systems worldwide.
An integrated approach to water resources management is essential, particularly in developing countries. This study presents
the results of the water resources optimization conducted for the Lower Litani River Basin in Lebanon. The overall aim of
the project is to develop, test, and critically evaluate an innovative approach to water resources management in the Mediterranean
region. The method explores the ways in which multiple environmental, economic, and social benefits can be achieved through
integrated management of water resources. The Water Resources Model was utilized to assess the efficiency of the baseline
model scenario and for the optimization process of the different scenarios of the Litani Lower Basin. Strengths, weaknesses,
opportunities and threats analysis was applied in order to derive the objectives and constraints. Results revealed that the
potential retained scenarios aim at decreasing water consumption and demand, losses, and return flow. These scenarios mainly
include the shift to drip irrigation, awareness campaigns, and losses control in domestic supply pipes. Other retained scenarios
having a higher shortfall rely on the use of the Channel concrete lining to decrease losses and return flow, in addition to
the awareness campaigns in both domestic and irrigation sectors, and less consumptive/more efficient irrigation methods such
as sprinkler and drip irrigation at variable application percentages. Hence, most of the interventions or measures proposed
are generally not costly and can be implemented. 相似文献
38.
Khoury Naji 《International Journal of Pavement Engineering》2018,19(7):651-660
In recent years, there has been an increased interest in determining the influence of moisture changes on the resilient modulus (MR) of subgrade soils beneath pavement structures. Efforts have also been made to develop mathematical models that predict the change in MR values with moisture. These models are expected to account for seasonal variations in subgrade moisture content. This study evaluates the variation of resilient modulus with post-compaction moisture content of soils in the State of Oklahoma and the State of Pennsylvania. A series of specimens was compacted at optimum moisture content and then tested for resilient modulus; other series of specimens were prepared at optimum moisture content and then either wetted or dried prior to MR testing. Employed wetting and drying procedures are time-efficient in developing the MR–moisture relationships. Results showed that MR–moisture content relationships varied with soil types and MR values varied inversely with changes of moisture content. In addition, an MR–moisture model predicting the variation of resilient modulus with moisture contents is proposed. This model can be used to predict changes in the bearing capacity of pavements due to seasonal variations of moisture content. 相似文献
39.
SK Agarwal GA McLorie D Grewal BD Joyner DJ B?gli AE Khoury 《Canadian Metallurgical Quarterly》1997,158(2):580-582
PURPOSE: Resolution of reflux in meningomyelocele patients is a reflection of improved bladder storage. We correlated resolution of reflux with changes observed in sequential urodynamic studies. MATERIALS AND METHODS: The study included 27 children with meningomyelocele born between 1975 and 1985 who presented with or developed vesicoureteral reflux. Resolution of reflux was observed during the 10-year followup period as they were treated with a regimen of clean intermittent catheterization and pharmaco-therapy. Urodynamic studies were performed when vesicoureteral reflux was present and subsequent to its resolution. The urodynamic parameters compared in the 2 studies included bladder capacity, pressure specific bladder volume, bladder compliance and leak point pressure. RESULTS: Significant increases in bladder capacity, pressure specific bladder volume and bladder compliance were noted. Leak point pressure appeared to be decreased subsequent to resolution of reflux. CONCLUSIONS: Resolution of reflux in meningomyelocele patients correlates with changes in parameters of bladder storage observed on sequential urodynamic studies. 相似文献
40.