电子俘获材料的研究现状及在红外检测方面的应用

电子俘获材料在辐射剂量测定、光信息处理、光存储、红外光检测等许多技术领域具有广泛的应用。本文详细介绍了电子俘获材料的发光原理、材料种类、制备方法以及研究现状,并针对该材料在红外光检测方面的应用,提出了在室温下该材料存在红外光检测上限的观点。针对电子俘获材料存在性质不稳定及在制备过程中需用到硫化类材料易造成污染等问题,建议进一步改进材料制备方法。最后,文中指出玻璃陶瓷类电子俘获材料会有很好的发展前景,并对该种材料未来的发展前景进行了展望。     

Analysis of coir fiber acoustical characteristics

Coir fiber from coconut husk is an important agricultural waste in Malaysia. Acoustic absorption coefficient of the fiber as a porous material is studied in this paper. Two types of fiber are investigated, fresh from wet market and industrial prepared mixed with binder. Moreover two analytical models, namely; Delany–Bazley and Biot–Allard are used for analysis. Experimental measurements in impedance tube are conducted to validate the analytical outcomes. Results show that fresh coir fiber has an average absorption coefficient of 0.8 at f > 1360 Hz and 20 mm thickness. Increasing the thickness is improved the sound absorption in lower frequencies, having the same average at f > 578 Hz and 45 mm thickness. Delany–Bazley technique can be used for both types of fiber while Biot–Allard method is compensated for the industrial prepared fiber considering the binder additive. This form generally shows poor acoustical absorption in low frequencies. Inevitably, fiber has to be mixed with additives in commercial use to enhance its characteristics such as stiffness, unti-fungus and flammability. Hence other approaches such as adding air gap or perforated plate should be used to improve the acoustical properties of industrial treated coir fiber.     

一种测量微量有机材料磁化率各向异性的光学方法

提出了一种测量有机材料的磁化率各向异性的方法。原理是利用掺杂对丝状液晶磁场扭曲费雷德里克兹转变影响的现象,将待测有机材料作为掺杂物,采用光学相位延迟法测量掺杂丝状液晶磁场扭曲费雷德里克兹转变阈值和过程,从而获得待测有机材料的磁化率各向异性。通过实验测量,从原理和方法上验证了测量方法的可行性。测得有机材料磁化率各向异性的同时也为有机材料的表征提供了一种方法。测量方法适用于无固有磁矩的有机材料。     

纳米技术及其在纺织上的应用

对纳米技术的基本情况进行了论述，同时详细介绍了纳米材料和技术在纺织纤维材料加工方面的应用领域和产品特点，指出在纺织上利用纳米技术对于研究，开发、生产新一代的功能性化学纤维织物，绿色环保织物，扩大纺织品的应用范围，应对国际市场具有积极意义。     

Characterization of the variation of the material properties in a freestanding inhomogeneous thin film

This Letter presents a new technique for measuring the variation of the material properties along the thickness in a freestanding inhomogeneous thin film. The analytical results reveal a simple relation between the material properties and the set of cut-off frequencies of Lamb waves. The influence of the graded properties on the variation of cut-off frequencies in three different kinds of models, including artificial FGM model, sub-surface damage model, and nano-porous thin film model, is discussed. These results provide theoretical guidance for characterizing the material property variations of MEMS/NEMS.     

Three-dimensional analytical solution for a transversely isotropic functionally graded piezoelectric circular plate subject to a uniform electric potential difference

This paper studies the problem of a functionally graded piezoelectric circular plate subjected to a uniform electric potential difference between the upper and lower surfaces. By assuming the generalized displacements in appropriate forms, five differential equations governing the generalized displacement functions are derived from the equilibrium equations. These displacement functions are then obtained in an explicit form, which still involve four undetermined integral constants, through a step-by-step integration which properly incorporates the boundary conditions at the upper and lower surfaces. The boundary conditions at the cylindrical surface are then used to determine the integral constants. Hence, three-dimensional analytical solutions for electrically loaded functionally graded piezoelectric circular plates with free or simply-supported edge are completely determined. These solutions can account for an arbitrary material variation along the thickness, and thus can be readily degenerated into those for a homogenous plate. A numerical example is finally given to show the validity of the analysis, and the effect of material inhomogeneity on the elastic and electric fields is discussed. Supported by the National Natural Science Foundation of China (Grant Nos. 10472102 and 10432030) and the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20060335107)     

火焰原子吸收光谱法测定医药原料黄体酮中的铬

本文研究了黄体酮中微量元素铬的火焰原子吸收分光光度法的测定,方法简便、快速,省时,具有良好的精密度和准确度。平均相对标准偏差为３．０２％,平均回收率为９８．８％。     

Underwater Directional Acoustic Source Based on Pentamode Material

An underwater directional acoustic emitter is conceived with a highly anisotropic lattice material,whose acoustic charac-teristics manifest strong dependence on the orientation of the lattice material's principal axis.Exploiting these features,a cylindrical structure made of such anisotropic lattice material is engineered to possess distinct impedance values in different directions,thereby facilitating wave emission along the principal axis while inducing reflection in other directions.Notably,through numerical simulations,it is demonstrated that the emission direction can be effectively manipulated by adjusting the principal axis orientation,concurrently enhancing the emitted power.In contrast to previous directional acoustic struc-tures,the compact emitter presented in this study can get rid of the size-wavelength constraint,enabling effective control of low-frequency waves.