共查询到20条相似文献,搜索用时 31 毫秒
1.
便携式激光生化探测仪采用LIBS(Laser Induced Breakdown Spectroscopy),即激光诱导击穿光谱分析技术。用一束短脉冲激光聚焦到被测样品上,产生局部等离子体,样品物质的电子跃迁至高能态,返回初始能态时会发出特定光谱辐射,每一种物质都对应各自的特征光谱。用高分辨率光谱仪对该光谱进行适时在线快速分析,在几秒钟内就可以得到被测物质的成分和浓度,可在现场对各种不明固体(炭疽杆菌等有害生化物质)、液体(如有毒饮料)、气体(如各种挥发物,即神经毒气弹等)等生化物进行在线快速探测和辨别。 相似文献
2.
Quantitative determination of material viscoelasticity using a piezoelectric cantilever bimorph beam
The objective of this paper is to formulate the governing equation of a cantilever bimorph beam associated with a tip mass in contact with a viscoelastic material, which is modeled by a stiffness and a damper in parallel. From the eigenvalue problem, we can obtain the resonant frequencies as functions of the tip mass and material stiffness. The relation between the spectrum and material damping is established by the half-power bandwidth. It is found that the resonant frequencies increase as the material stiffness increases or the tip mass decreases, and the spectrum decreases by increasing the damping. From the analytic results, a cantilever could provide a technique to assess material viscoelasticity by simple measurements of the resonant frequency and the spectrum. Since the cantilever's behavior scales with its geometry, the device can be designed specifically for mechanical measurement of a microscopic system such as living cells and biomaterials. 相似文献
3.
惯性约束聚变靶材料面密度及其均匀性分布可以通过β射线束透射法进行测量,要完成这一测量,需首先用一系列面密度已知、组成成分与待测材料相同的标准材料对测量装置进行刻度。针对惯性约束聚变靶材料一类还处于研制阶段的新材料的密度测量,提出了用成分相近的材料作为替代标准进行刻度的方法,并用蒙特卡罗方法模拟计算了不同能量电子穿过不同材料的透射率,得到了这种刻度方法对测量结果带来的误差大小,用纸作标准测量CH泡沫靶材料的误差只有百分之几,这一误差在实际测量中可以由蒙特卡罗模拟方法得到修正。该刻度方法解决了惯性约束聚变靶材料一类新材料面密度用β透射法测量中的定标问题。 相似文献
4.
Xia Ma Paul T. GiguereBalaji Jayaraman Duan Z. Zhang 《Journal of computational physics》2010,229(20):7819-7833
When using the time explicit material point method to simulate interaction of materials accompanied by large deformations and fragmentation, one often encounters a numerical instability caused by small node mass, because acceleration on a mesh node is obtained by dividing the total force on the node by the mass of the node. When the material points are in the far sides of the cells containing the node, typically happening near material interfaces, the node mass can be very small leading to artificially large acceleration and then numerical instability. For the case of small material deformations, this instability is typically avoided by placing the material points away from cell boundaries. For cases with large deformations, with the exception of initial conditions, there is no control on locations of the material points. The instability caused by small mass nodes is often encountered. To avoid this instability tiny time steps are usually required in a numerical calculation. 相似文献
5.
Method for reducing debris and thermal destruction in femtosecond laser processing by applying transparent coating 总被引:1,自引:0,他引:1
D. Kawamura A. Takita Y. Hayasaki N. Nishida 《Applied Physics A: Materials Science & Processing》2006,82(3):523-527
A cavity processed by a tightly focused femtosecond laser pulse is surrounded by a ring-shaped protrusion, debris, and small
droplets. In order to reduce these undesired damages, we propose processing with a coating of transparent material on a target
material. PMMA (poly-methyl methacrylate) with the thickness that its surface is not ablated by a single pulse irradiation
reduces dissolution and vaporization caused by the interaction between a high-density hot vapor plume and the target material.
Furthermore, the material at the target surface does not escape freely due to the coating layer. As a result, a submicrometer-sized
cavity is produced with a reduction of debris and a smaller thermal-destruction area.
PACS 44.10.+i; 61.80.Ba; 79.20.Ds 相似文献
6.
Optimization of loss and gain multilayers for reducing the scattering of a perfect conducting cylinder
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Reduction of electromagnetic scattering from a conducting cylinder could be achieved by covering it with optimized multilayers of normal dielectric and plasmonic material. The plasmonic material with intrinsic losses could degrade the cloaking effect. Using a genetic algorithm, we present the optimized design of loss and gain multilayers for reduction of the scattering from a perfect conducting cylinder. This multilayered structure is theoretically and numerically analyzed when the plasmonic material with low loss and high loss respectively is considered. We demonstrate by full-wave simulation that the optimized nonmagnetic gain-loss design can greatly compensate the decreased cloaking effect caused by loss material,which facilitates the realization of practical electromagnetic cloaking, especially in the optical range. 相似文献
7.
An account is given of a study of free vibrations of a simply-supported beam with non-linear material properties. The material is of the Ramberg-Osgood type. Non-linear programming technique was used to find the response of the system. The variation of frequency with amplitude has been obtained for different values of material properties. The results indicate that the beam behaves like a soft spring for the type of non-linearity introduced by the material. This method can be used for all modes directly without reference to the lower modes. 相似文献
8.
Wave propagation in a wooden bar 总被引:2,自引:0,他引:2
In this paper we will present a method to determine the material properties of a wooden bar with rectangular cross-section using guided waves in the measurement. We modelled the wood as an orthotropic material with nine independent constants. We determined the dispersion curves theoretically in the three-dimensional case using a semi-analytical finite element method. In our laboratory we excited transversal and longitudinal waves in wooden bars of 2.5-4 m length by piezoceramic transducers. We measured the displacement or the velocity of the surface of the bar by a laser-interferometer. The dispersion curves of the bar are determined from the measurement by the linear prediction method. We related the dispersion curves and the material properties. We found the material properties by parametric model fitting. 相似文献
9.
通过微结构设计提升脆性功能材料的冲击塑性, 将有助于避免或延缓失效的发生. 提出在脆性材料中植入特定的微小孔洞以改善其冲击塑性的设计方法. 采用一种能够定量表现脆性材料力学性质的格点-弹簧模型, 研究了孔洞排布方式对脆性材料冲击响应的影响. 孔洞随机排布的多孔脆性材料具有明显高于致密脆性材料的冲击塑性, 而设计规则的孔洞排布方式将有助于进一步提升脆性材料的冲击塑性. 对150 m/s活塞冲击下气孔率5%的多孔样品的介观变形特征分析表明, 孔洞规则排布的样品中孔洞贯通和体积收缩变形占主导, 而孔洞随机排布的样品中剪切裂纹长距离扩展和滑移与转动变形占主导. 尽管在宏观的Hugoniot应力-应变曲线上, 两种孔洞排布方式的样品都表现出三段式响应特征(线弹性阶段、塌缩变形阶段和滑移与转动变形阶段), 但孔洞规则排布时孔洞塌缩变形阶段对整体冲击塑性的贡献更大. 研究揭示的规则排布孔洞增强脆性材料冲击塑性的原理, 将有助于脆性材料冲击诱导功能失效的预防. 相似文献
10.
nmSiO2对聚合物光纤光栅封装材料的改性研究 总被引:3,自引:1,他引:2
分析了刚性纳米粒子改性聚合物的原理,重点分析了nmSiO2/硅氧烷(硅橡胶)复合材料的改性机理,采用120号溶剂性汽油为分散剂,通过共混法制得nmSiO2—乙烯基硅氧烷、含氢硅氧烷硫化而成的复合材料,用AJ-Ⅲa型原子力显微镜分析研究了该材料的组团结构并测试了其力学性能,结果表明,硅氧烷橡胶改性后,材料的弹性模量增加了15.4%;拉伸强度增加了19.4%;扯断伸长率增加了30%,用改性后的硅氧烷聚合物材料封装光纤Bragg光栅(FBG)压力传感器,可有效改善封装材料与光纤光栅的耦联性能;通过粒子含量控制可以增韧增强硅氧烷,从而可制作变量程压力传感器,同时可以延长传感器的使用寿命, 相似文献
11.
Ernst-Georg Neumann 《Fiber and Integrated Optics》1982,4(2):203-211
The pure bend loss of a curved dielectric optical waveguide can be reduced effectively with only a slight change in the transverse field distribution by replacing the cladding material outside the caustic by another material with a smaller refractive index. This is demonstrated by microwave model experiments. 相似文献
12.
采用超声法将定量的荧光性含铕类水滑石(Eu-HTLc)掺混到导电性聚苯胺(PAN-CSA)中,获得一类新型的含铕类水滑石/聚苯胺导电性荧光复合材料(Eu-HTLc/PAN-CSA)。采用电导率测试、荧光光谱、红外光谱、X射线衍射和热分析等手段对其进行表征。研究结果表明:该复合材料的电导率σ=7.97×10-3(S/cm);在紫外光下该复合材料可发出红色荧光(613nm),其荧光寿命为441.32μs;热分析结果显示,该复合材料比PAN-CSA具有更高热稳定性,有望作为一类新型荧光材料而获得应用。 相似文献
13.
针对核武器/核材料识别系统中核材料浓度识别的关键技术问题,采用Monte Carlo方法,通过建立252Cf源驱动核材料裂变中子信号样本库,模拟分析了随探测器距离和角度及核材料浓度变化的裂变脉冲中子信号特点,基于深度学习之卷积神经网络,构建了一种252Cf源驱动核材料浓度识别方法,实现了对测试样本浓度的识别,且还与BP神经网络和K最近邻方法进行了对比试验研究。结果表明,卷积神经网络算法进行核材料浓度识别,得到了高达92.05%识别准确率,不仅解决了因探测器距离和角度变化时对核材料浓度识别准确率影响的难题,而且还获得了优于BP神经网络和K最近邻算法对核材料浓度识别的认识,这为252Cf源驱动核材料浓度识别提供了一种新的途径。 相似文献
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The elastic band structure of a two-dimensional phononic crystal (PC) with electrorheological (ER) material is investigated and the plane-wave-expansion (PWE) method is adopted to solve the problem in this paper. The ER material is used to act as a tunable elastic composite inserts and its material parameter can be changed by the applied electric fields. Variations of the band gaps for the phononic composite system are also calculated with various electric fields and it is found to have a significant effect on the band gaps of the phononic system with ER material inserts. The band gaps of the smart system can be controlled and the acoustic characteristics of the system are also changed by applied different electric fields. 相似文献
17.
H. Risken 《Zeitschrift für Physik A Hadrons and Nuclei》1964,180(2):150-169
The mode structure and the diffraction losses of a Perot-Fabry-Interferometer filled with an active material are calculated analytically with aGreen's function method. The active material is described by a complex susceptibility. The mode pattern and the diffraction losses derived here are in good agreement with the results of Fox andLi, who obtained the mode pattern and the diffraction losses of the decaying modes of a Perot-Fabry-Interferometer by a machine calculation. Furthermore the case of different dielectric constants between the active material and the outer space and the example of a Perot-Fabry-Interferometer with infinite mirrors are discussed. Throughout the paper only a single mode is treated and it is assumed that the inversion in the active material is constant. 相似文献
18.
Ultrasonic impregnation is thought to be an effective way of permeation of liquid into material through the material-surface reforming with the attack by an ultrasonic cavitation jet or by the shock wave emitted from a collapsing bubble, or through dynamic transformation of material like a sponge. The action of a cavitation bubble can also provide penetration of liquid into the interior of the material. This paper investigates whether there is a correlation between the intensity of sonoluminescence (SL) measured at different positions and the increment in the mass of the wood material (cedar) after sonication with immersion into water in order to clarify the role of cavitation bubbles for ultrasonic impregnation. It was found that a high mass change was obtained for the material located at the position for high (the maximum) SL intensity. The number density of ultrasonic cavitation bubbles that are able to collapse leading to the emission of SL is correlated with the degree of ultrasonic impregnation. 相似文献
19.
C. V. Durgadas C. P. Sharma W. Paul M. R. Rekha K. Sreenivasan 《Journal of nanoparticle research》2012,14(9):1-12
A certified reference material, ERM-FD100, for quality assurance and validation of various nanoparticle sizing methods, was developed by the Institute for Reference Materials and Measurements. The material was prepared from an industrially sourced colloidal silica containing nanoparticles with a nominal equivalent spherical diameter of 20?nm. The homogeneity and stability of the candidate reference material was assessed by means of dynamic light scattering and centrifugal liquid sedimentation. Certification of the candidate reference material was based on a global interlaboratory comparison in which 34 laboratories participated with various analytical methods (DLS, CLS, EM, SAXS, ELS). After scrutinising the interlaboratory comparison data, 4 different certified particle size values, specific for the corresponding analytical method, could be assigned. The good comparability of results allowed the certification of the colloidal silica material for nanoparticle size analysis. 相似文献