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为了提高高马赫飞行下光学窗口的光学性能,对比分析了基于气动光学效应三种飞行器模型不同攻角的马赫数场、密度场、温度场和压力场的流场结构及对光学性能的影响.首先, 根据飞行器与来流的迎风面,建立了三种飞行器典型模型;继而, 给出了0、5和10攻角飞行工况;然后,建立了基于Navier-Stokes方程和湍流模型的三种攻角流场分布;最后, 对比分析了宽平头体飞行器中三种攻角温度场作用下的光学系统传递函数.结果表明,马赫数场与密度场、温度场与压力场分别具有相似分布形式;相同飞行速度和攻角下,大迎风面的飞行器光学窗口周围温度与压力较小迎风面大;相同飞行器,较大攻角对应较大流场强度,攻角为0、5和10时传递函数分别为0.188,0.097和0.028.此分析结果可为高马赫飞行下光学窗口优化提供一定的理论依据. 相似文献
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Shadab Md. Alka Ahuja Roop K. Khar Sanjula Baboota Krishna Chuttani 《Journal of Dispersion Science and Technology》2013,34(9):1318-1324
Mucoadhesive chitosan microspheres of acyclovir were prepared to prolong the gastric residence time using simple emulsification phase separation technique. The particle morphology of drug-loaded formulations was measured by SEM and the particle size distribution was determined using an optical microscope. The release profile of acyclovir from microspheres was examined in simulated gastric fluid (SGF pH 1.2). The particles were found to be discreet and spherical with the maximum particles of an average size (31.62 ± 4.64). The entrapment efficiency was found to be in the range of 40.24 to 67.29%. The concentration of the glutaraldehyde (25%v/v) as a cross-linker 2 ml and drug polymer ratio of 1:2 caused an increase in the entrapment efficiency and the extent of drug release. The optimized chitosan microspheres were found to possess good bioadhesion (79.89 ± 1.01%). The gamma-scintigraphy study showed the gastric residence time of more than 6 hours which revealed that optimized formulation could be a good choice for gastroretentive systems. 相似文献
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In recent years,in comparison to the light in the visible range(400~700 nm)and first near-infrared window(NIR-Ⅰ,700~1000 nm),the light in the second near-infrared window(NIR-Ⅱ,1000~ 1700 nm)possess the merits of the lowest optical scattering and absorption in the bio-tissue. So NIR-Ⅱ fluorescence imaging with deeper tissue penetration depths,high spatiotemporal resolution and signal to noise ratio(SNR)plays an important role in the fields of angiography,lymphangiography and so on. Herein, Nd3+ sensitized fluorescent nanoprobe (U/DNPs,NaGdF4 ∶Yb(18% mole fraction),Ho(2%),Ce(30%) @NaGdF4 ,Nd(60%)@NaGdF4 ,Nd(10%)) with core-shell-shell is synthesized through high-temperature coprecipitation and epitaxial growth method. Under the irradiation of 808 nm,the NIR-Ⅱ fluorescence at 1056 nm and 1332 nm are obtained via down-conversion process for further vascular imaging. Furthermore,it can emit red upconversion fluorescence with high red to green(R/G)ratio(I647 /I540 = 22. 6),possessing greatly potential application for photodynamic therapy. After successful modification of polyvinyl pyrrolidone(PVP) via ligand-exchange strategy,the U/DNPs-PVP nanomaterials possess excellent solubility in water and good biocompatibility,and can achieve the NIR-Ⅱ fluorescence vessels imaging with spatial resolution of 336. 3 µμm in vivo. © 2022, Science Press (China). All rights reserved. 相似文献
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Anna-Lena Leistner Susanne Kirchner Johannes Karcher Tobias Bantle Mariam L. Schulte Peter Gödtel Christian Fengler Dr. Zbigniew L. Pianowski 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(31):8094-8099
Molecular photoswitches triggered with red or NIR light are optimal for photomodulation of complex biological systems, including efficient penetration of the human body for therapeutic purposes (“therapeutic window”). Yet, they are rarely reported, and even more rarely functional under aqueous conditions. In this work, fluorinated azobenzenes are shown to exhibit efficient E→Z photoisomerization with red light (PSS660nm >75 % Z) upon conjugation with unsaturated substituents. Initially demonstrated for aldehyde groups, this effect was also observed in a more complex structure by incorporating the chromophore into a cyclic dipeptide with propensity for self-assembly. Under physiological conditions, the latter molecule formed a supramolecular material that reversibly changed its viscosity upon irradiation with red light. Our observation can lead to design of new photopharmacology agents or phototriggered materials for in vivo use. 相似文献
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研究表明,立方氧化锆可作为冲击波实验中的窗口材料.为了使得该材料在常态下保持结构稳定,需添加稳定剂——氧化钙.然而,掺杂会导致其在29 GPa的冲击压力下从立方转变为斜方Ⅱ结构相.因此,该材料在冲击压缩下的电子结构和光学吸收性质以及作为光学窗口的适用压力范围是值得研究的重要问题.本文运用第一性原理的方法,分别计算了在100 GPa范围内两种结构氧化锆的电子结构和光学吸收性质.结果表明:(1)在立方结构相区,冲击压力将导致其吸收边蓝移,而在斜方Ⅱ结构相区,却使得其吸收边红移;(2)在立方结构相区,掺杂将引起能隙变窄(吸收边红移),但对于斜方II相区,却导致能隙变宽(吸收边蓝移);(3)冲击结构相变使得能隙变窄,吸收边红移.本文数据建议,掺氧化钙的立方氧化锆在95GPa的冲击压力范围内可作为光学窗口材料. 相似文献
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次级电子倍增效应引起的输出窗失效问题往往给微波器件造成灾难性的影响, 是限制微波器件功率进一步提升的瓶颈. 以S波段高功率盒形窗为研究对象, 针对盒形窗内无氧铜金属边界与陶瓷介质窗片相对的区域, 建立了研究法向电场作用下次级电子倍增效应的Monte-Carlo模型. 通过拟合这两种材料间双面次级电子倍增以及单面次级电子倍增效应的敏感曲线, 对次级电子倍增发展特点进行详细分析, 获得了金属与介质之间的次级电子由双面倍增向单面倍增演变的规律. 相似文献
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In this paper, we will focus on an IR transmittance enhancement technique from the window material point of view by using metal oxides, especially nickel oxide (NiO). At first, anti-reflection (AR) coatings were modeled by using the optical properties of NiO films. The transmittance of the model was predicted using Swanepoel’s model and verified with NiO film prepared by rf magnetron sputtering. Also, post-deposition annealing was performed and was found to change the optical properties of the NiO film. Therefore, we analyzed the annealing effect on the IR optical properties of the NiO film. Furthermore, we confirmed the durability of the NiO film and verified the possibility of this material being used in infrared optics. 相似文献