渗透剂对小鼠皮肤光学特性影响的实时动态监测

自行研制了一套双积分球系统,应用该系统对离体小鼠皮肤在渗透剂无水甘油作用下,光学特性参量的变化进行了实时监测。实验结果表明：在无水甘油作用下,随着时间的延长,小鼠皮肤的约化散射系数明显减小,吸收系数略有增加,并最终导致了有效衰减系数的减小;但当作用时间超过25min后,样品的光学特性参量会趋于恒定。为生物组织光学特性控制作用提供了新的方法,这对组织光学成像研究是非常重要的。     

Improving the Sound Absorption Properties of Flexible Polyurethane (PU) Foam using Nanofibers and Nanoparticles

Polyurethane foam as the most well-known absorbent materials has a suitable absorption coefficient only within a limited frequency range. The aim of this study was to improve the sound absorption coefficient of flexible polyurethane (PU) foam within the range of various frequencies using clay nanoparticles, polyacrylonitrile nanofibers, and polyvinylidene fluoride nanofibers. The response surface method was used to determine the effect of addition of nanofi- bers of PAN and PVDF, addition of clay nanoparticles, absorbent thickness, and air gap on the sound absorption coefficient of flexible polyurethane foam (PU) across different frequency ranges. The absorption coefficient of the samples was measured using Impedance Tubes device. Nano clay at low thicknesses as well as polyacrylonitrile nanofibers and polyvinyl fluoride nanofibers at higher thicknesses had a greater positive effect on absorption coefficient. The mean sound absorption coefficient in the composite with the highest absorption coeffi- cient at middle and high frequencies was 0.798 and 0.75, respectively. In comparison with pure polyurethane foam with the same thickness and air gap, these values were 2.22 times at the middle frequencies and 1.47 times at high frequencies, respectively. Surface porosity rose with increasing nano clay, but decreased with increasing polyacrylonitrile nanofibers and polyvinyl fluoride nanofibers. The results indicated that the absorption coefficient was elevated with increasing the thickness and air gap. This study suggests that the use of a combination of nanoparticles and nanofibers can enhance the acoustic properties of flexible polyurethane foam.     

基于光学相干层析术的组织光学性质测量

通过在光学相干层析成像(Optical Coherence Tomography,OCT)模型中考虑多重散射的影响,提出了一种提取出不同深度处的组织光学性质,包括散射系数和各向异性因子的算法.当把吸收系数作为算法中的第三个拟合参量时,能减少算法拟合过程中由于吸收作用的影响而带来的误差.基于包含吸收因子的OCT扩展模型,改进的算法也能够提取出吸收系数.这些算法的有效性通过对聚苯乙烯微球溶液样品的测量实验得到验证.     

双光子吸收效应对孤子和孤子对传输的影响

用分步傅立叶变换法求解含双光子吸收效应的光孤子NLS方程,研究了双光子吸收效应对一阶孤子和孤子对传输的影响,发现双光子吸收效应除对孤子产生等效损耗外,还影响了孤子对在传输中的相互作用。在特定的双光子吸收系数条件下双光子吸收效应可以使孤子对平行地向前传输。     

雷达波段内磁性吸波颗粒光散射特性分析

针对目前在微波雷达隐身技术中广泛运用的吸波材料颗粒,根据米氏(Mie)散射理论对磁性吸波颗粒在雷达波段内的光散射特性进行了数值模拟和计算分析.在Mie系数中引入磁导率变量,分别计算了磁导率、折射率及颗粒粒径等参数对吸波颗粒光散射特性的影响;同时对比分析了磁性与非磁性吸波颗粒的散射光强、散射系数、吸收系数等散射特性规律.数值计算结果表明,颗粒磁特性的变化对其散射性能造成影响,磁导率的增大将使颗粒的吸收性能增强而后向散射强度减弱,有利于吸波颗粒雷达散射截面的减小,同时磁导率变化对颗粒散射特性的影响受到复折射率的制约.     

Radiation modulation via violation of total internal reflection with excitation of a waveguide mode

The transverse transmission coefficient of a multilayer structure with a planar waveguide is numerically simulated under the conditions of modulation of the refractive index or absorption coefficient of the waveguide. The optical properties of this structure are shown to be highly sensitive to variation in the refractive index or absorption (amplification) coefficient of its waveguide layer. The influence of optical and geometric characteristics of the structure on its optical properties is analyzed. Modulation of the transmission and reflection coefficients of the structure containing a waveguide with an amplifying medium is considered.     

Sound absorption properties of a sunflower composite made from crushed stem particles and from chitosan bio-binder

A recent study investigated the mechanical, thermal and acoustical properties of a bio-based composite made from crushed particles of sunflower stalks binded together by chitosan, a bio-based binder. The acoustical performance in absorption was found to be poor as the material was highly compacted and with low porosity. The present study focuses on the acoustical properties of a higher porosity composite, with lower density while the mechanical rigidity remains fairly high. A higher absorption coefficient is obtained. The experimental results on the absorption coefficient are compared to the prediction of a model involving 5 physical parameters (porosity, tortuosity, airflow resistivity, thermal and viscous characteristic lengths). The characterization methods to determine these parameters are described. The comparison between experimental and theoretical results shows that this material exhibits peculiar microstructural features. It is found that the sound absorption properties can involve dead-end pores or clusters and multiple porosity scales in the material.     

Defect-induced enhancement of absorption coefficient and electroabsorption properties in GaN/AlGaN centered defect quantum box (CDQB) nanocrystal

In this paper, effect of an introduced cubic defect on electrical and optical properties of cubic quantum dot is studied. Self-consistent solution of the Schrödinger-Poisson equations for evaluation of the proposed complex quantum dot is used. Optical properties (absorption and electroabsorption properties associated with intersublevel transition) of the proposed structure are also investigated using density matrix method. Effects of defect size on energy levels, carrier density, matrix element and optical linear absorption coefficient of centered defect quantum box (CDQB) are examined. It is shown that with increasing the defect size a considerable enhancement in magnitude of the absorption coefficient and also red-shift in resonance frequency are achievable. We show that the CDQB has higher absorption peak (at least 80 times) and tunable absorption spectra, due to increase of the matrix element and modified energy sublevels, compared quantum box structure without defect. Also, it is shown that the defect enhances electroabsorption properties (modulation bandwidth and the maximum variation of absorption peak with external field) of the quantum box structure.     

立方型Ti-B-N的光学性质的计算

立方型TiBN材料的光学性质对于深刻理解TiBN薄膜材料的光学性质,以及监测和控制TiBN薄膜材料的生长过程起着重要作用。使用基于密度泛函理论的平面波超软赝势方法计算了立方型TiBN的电子结构和光学性质,给出了电子态密度、介电常数、吸收系数、反射力、折射系数、消光系数等计算结果,并对计算结果作了分析。态密度图显示,存在源于B的2p态的态密度峰,分析认为这对立方型TiBN的光学吸收造成了明显影响。同时还计算了立方型TiBN的色度坐标,并根据计算结果对工艺参量与TiBN薄膜材料色度坐标之间的联系作出了分析。     

Absorption of finite amplitude focused ultrasound

Predictions of the absorption of focused finite amplitude waves based on weak shock theory have been tested experimentally. The characteristics of this absorption are qualitatively different from those associated with small signal losses. Under appropriate conditions, the absorption of finite amplitude ultrasound is determined largely by source amplitude, field geometry, and the nonlinear properties of the medium and is only weakly dependent upon the small signal absorption coefficient of the material. These effects are seen most dramatically in sharply focused sound fields. To emphasize nonlinear absorption in an experimental test of these predictions, measurements of heating were made in agar which has a very small linear absorption coefficient. Under appropriate conditions, nonlinear losses can make the effective absorption coefficient of this poorly absorbing material somewhat greater than the soft tissues of the body.     

金属微粒-半导体薄膜中小胶粒的光吸收和散射

金属微粒-半导体薄膜具有特殊的电学、光学及光电特性。本文讨论了埋藏于半导体基体中金属小胶粒光吸收和光散射公式。这些胶粉可以是球形,也可以是长球或扁球形。本文以银胶粒-氧化铯半导体为例,讨论了胶粒大小、椭球的偏心率对相对光吸收系数和光散射系数的影响,并给出这些系数随波长改变的曲线。 关键词：     

基于双积分球的宽光谱组织光学参数测量系统与方法研究

组织光学参数测量是生物医学光子学的主要研究内容之一,人体组织光学性质与其生理病理状态密切相关。近年来,利用组织光学特性,特别是吸收与散射特性进行组织成像诊断及无创成分检测成为生物医学光子学领域研究热点,为肿瘤早期诊断、代谢动态监护及光动力治疗等临床应用提供了基础。双积分球方法能够同时测量离体组织吸收系数、散射系数等,具有测量准确、快速,适用范围大等优点,作为光学参数测量的标准方法得到广泛研究与应用。利用双积分球及超连续激光器搭建了宽光谱的组织光学参数测量系统,分析了积分球测量传递函数与误差来源及系统最佳测量条件,建立了基于BP-MCML的系统校正正向模型与L-M算法的光学参数反构算法。在此基础上,测量了1 100～1 400 nm连续宽谱范围内Intralipid溶液光学参数,实验结果表明改进后反构算法测量结果比较准确,多次测量标准偏差在3%以内,不同波长下约化散射系数及吸收系数测量结果与其他研究小组得到的测量结果对比,偏差小于3.4%。     

小麦品质的太赫兹波段光学与光谱特性研究

采用太赫兹时域光谱技术(THz-TDS),以储藏小麦为研究对象,研究了霉变、虫蛀、发芽等小麦与正常小麦样品在0.2～1.6 THz波段的光学与光谱特性,采用傅里叶变换得到被测样品的频域光谱,并计算获得THz吸收系数和折射率等光学参数。结果表明,不同品质小麦具有不同的折射率和吸收系数,其中正常小麦比霉变、虫蚀和发芽小麦的吸收系数和折射率都高,且吸收系数在有效波段随频率的增加而增加,进而可以根据其在THz波段的特征谱进行判别。THz-TDS在小麦品质检测中的应用,为该技术在储粮品质检测和分析中提供新的实验方法,具有重要的应用前景。     

Sound absorption characteristics of a high-temperature sintering porous ceramic material

This article is dedicated to sound absorption properties of porous zeolite with macropores, a ceramic material fabricated by high-temperature sintering. Acoustical properties of this ceramic material are studied by two analytical models, Delany–Bazley model and Johnson–Allard model, where the latter one shows a better fit to the experimental results. Moreover increasing the thickness of samples would improve the sound absorption in the low frequency ranges. Raising the porosity could increase the highest sound absorption coefficient. The resonance frequencies of the materials with 3–5 mm particles are more obvious. Comparing with glass wool, porous zeolite has a better sound absorption.     

基于表观光谱反演黄东海水体固有光学量研究

水色遥感反演算法中半分析模型的建立需要已知水体同有光学量,文章基于现场实测数据建立了由遥感反射率反演同有光学量模型.对2003年春季黄东海航次所测数据进行了介绍,详细阐述了遥感反射率、颗粒物后向散射和吸收系数的测量方法.基于生物光学模型,利用单纯形优化算法由遥感反射率来反演水体同有光学量,并将反演结果与实测数据进行了比...     

太赫兹谱定量测试中朗伯比尔定律表征形式分析

探讨了朗伯比尔定律在太赫兹谱段的应用,研究了单一氨基酸压片样品(谷氨酰胺)和两种氨基酸混合压片(苏氨酸和胱氨酸)在不同浓度情况下对朗伯比尔定律的适用程度。分析了吸光度和吸收系数在描述物质的太赫兹光学特性的区别。通过对比单一组分在1.72 THz附近的吸收系数值和吸光度值,验证物质对太赫兹波在两种吸收表征量下吸收随浓度变化的情况,利用拟合优度的R2指标研究了各表征量下物质太赫兹吸收与浓度的线性关系的好坏;分析两组分混合物在0.3～2.6 THz有效谱段的两种吸收表征量的太赫兹吸收情况,利用相似性系数和估计浓度误差作为评价指标,明确了在太赫兹谱定量测试中应采用吸光度的加和性而非吸收系数的加和性,进一步明确朗伯比尔定律在太赫兹波段的应用。     

芳纶纤维复合材料对激光的吸收特性研究

 利用双积分球光电管系统实验研究了不同厚度的芳纶纤维复合材料在不同强度的1.06μm激光辐照下（低于烧蚀阈值的激光强度）的反射和透射特性，在材料厚度一定时，反射率随着激光功率密度的增加而增加，透射率则呈现指数衰减；激光功率一定时，反射率随着材料厚度的增加而增加，透射率则呈现衰减。通过反射率和透过率可以确定出表面吸收和体吸收的激光能量份额。     

On optimal design of half-wave resonators for acoustic damping in an enclosure

Acoustic design parameters of a half-wave resonator are studied experimentally for purely acoustic tuning of the resonator. According to the standard acoustic-test procedures, acoustic-pressure signals in the model enclosure with the resonators are measured. Based on the signals, quantitative acoustic properties of damping factor and sound absorption coefficient are evaluated and thereby, the acoustic-damping capacity of the resonator is characterized. Sound absorption coefficient has the advantages of the damping factor in various aspects. The coefficient indicates clearly the tuning frequency of the resonator, absorption effectiveness as a function of frequency, and overall damping capacity. The diameter and the number of a half-wave resonator, its distribution, and the blockage ratio at its inlet are selected as design parameters for optimal tuning of the resonator in the model enclosure. The resonators with larger diameter have the advantage of those with smaller one with respect to purely acoustic damping at the tuning frequency. The optimum number of resonators or the optimum open-area ratio decreases as boundary absorption decreases. When the open-area ratio exceeds the optimum value, over-damping appears, leading to a decrease in peak absorption coefficient and a broadening of absorption bandwidth. Blockage at the resonator inlet controls both peak absorption coefficient and its absorption bandwidth and it can be considered one of design factors for acoustic tuning.     

Photoacoustic spectroscopy analysis of thin semiconductor samples

This paper is an analysis of determination possibility of the optical absorption coefficient spectra of thin semiconductor layers from their normalized photoacoustic amplitude spectra. Influence of multiple reflections of light in thin layers on their photoacoustic and optical absorption coefficient spectra is presented and discussed in detail. Practical formulae for the optical absorption coefficient spectrum as a function of the normalized photoacoustic amplitude spectrum are derived and presented. Next, they were applied for computations of the optical absorption coefficient spectra of thin In₂S₃ thin layers deposited on a glass substrate. This method was experimentally verified with the optical transmission method.     

基于双光路原理的海水IOPs高光谱测量仪方案

设计了基于双光路原理的海水固有光学参数测量仪。该仪器可同步测量水体光谱吸收系数a、光束衰减系数c和体散射系数b。其中吸收系数a采用反射式吸收管测量,光束衰减系数c采用全吸收式样品池测量,体散射系数b根据c=a+b计算。光信号由光纤收集、光谱仪分光后用CCD探测器测量。光谱分辨率为4nm,灵敏度为0 001m-1。该仪器直接在水下工作,由水泵抽取被测海水,水下最大工作深度为200m。测量数据可以自动记录,同时也可以通过水下电缆实时传输到调查船实验室。