Partial electrical potential distribution around nanospheres in metallic nanostructured films

In light of the nanostructured surface model, where half-spherical nanoparticles grow out symmetrically from a plane metallic film, the mathematical model for the partial electrical potential around nanospheres is developed when a uniform external electric field is applied. On the basis of these models, the three-dimensional spatial distribution of the partial electrical potential is obtained and given in the form of a curved surface using a numerical computation method. Our results show that the electrical potential distribution around the nanospheres exhibits an obvious geometrical symmetry. These results could serve as a reference for investigating many abnormal phenomena such as abnormal infrared effects, which are found when CO molecules are adsorbed on the surface of nanostructured transition metals.     

Advances in digital holographic micro-PTV for analyzing microscale flows

The accurate three-dimensional (3D) velocity field measurement technique has been receiving large attention in the study of microfluidics. DHM-PTV technique was developed by combining the digital holographic microscopy and particle tracking velocimetry technique. DHM-PTV is an ideal method for measuring three-component-three-dimensional (3C-3D) velocity field in a microscale flow with a fairly good spatial resolution. The advances in the DHM-PTV technique enable the measurement of various microscale flows, such as transport of red blood cells in a microtube and 3D flows in microfluidic devices. DHM-PTV is also applied in studying the motile behavior of swimming microorganisms. DHM-PTV would play an important role in ascertaining the undiscovered basic physics in various microscale and biofluid flow phenomena. In the current study, the basic principle of the DHM-PTV technique and its typical applications to microscale flows are introduced and discussed.     

基于蒙特卡罗方法的α粒子细胞S值计算

在放射性免疫治疗以及硼中子俘获治疗（BNCT）等放射性治疗过程中,粒子通过与人体组织材料相互作用产生次级电子将能量传递给人体组织,放射性核素在细胞尺度分布的不均匀性将严重影响靶区剂量分布。为深入了解放射性核素在细胞中不同位置分布对靶区剂量影响,采用基于历史凝聚算法的Monte Carlo 工具包Geant4编写了细胞S值计算程序。计算了2种细胞尺寸,12种粒子能量,3种源分布方式的细胞S值,与医学内照射剂量（MIRD）委员会解析算法的计算结果进行对比,发现两者差异在1%以内。证明了Geant4在m尺度下细胞剂量计算的可行性,并对BNCT治疗过程中产生的粒子(1.47 MeV与1.78 MeV)的细胞S值进行计算。     

转筒黏度计测量液体黏度方法研究

用黏性流体力学理论求得测量装置中旋转液体径向速度梯度的理论公式,进而得到转筒法测量黏度的较精确公式.指出了国内的一些教材和文献在推导中使用近似公式的错误,用参数估计的方法求得测量装置的摩擦阻力力矩,使测量结果得到进一步校正.实验研究表明:按照近似公式与精确公式计算求得的径向速度梯度之差可达到13.1%,求得的液体黏度之差可达到28.6%;在蓖麻油的温度为25.5℃时测得测量装置的摩擦阻力力矩为9.482×10-5 N·m,相当于0.540克重物产生的力矩.     

以最大原子密度定义合金相中的第一近邻团簇

本文提出利用不同壳层所包含的径向原子密度, 即单位体积内的原子个数随着径向的分布, 来方便而精确地定义团簇, 即具有最大径向原子密度的且表面呈现三角密堆结构的完整壳层为第一近邻团簇. 最后以Al-Ni-Zr合金相为例说明了该方法的合理性与适用性, 及此方法所定义的团簇与非晶形成的关系.     

金属网栅法布里珀罗干涉仪测量太赫兹波波长

设计并制作了用于测量波长大于150 μm(频率低于2 THz)的太赫兹波波长的金属网栅法布里珀罗干涉仪(FPI)。采用光电子微纳制造工艺制作了五组周期不大于40 μm,线宽不大于10 μm的有衬底方形金属网栅,利用太赫兹时域光谱技术测量了金属网栅的太赫兹波段光电特性,得到了各组金属网栅在感兴趣频段的反射率和金属网栅FPI的反射精细度,结果表明所制作的金属网栅FPI均可用于测量波长大于150 μm的太赫兹波。实验搭建金属网栅FPI扫描测量了212 μm的太赫兹波波长,与理论结果吻合。研究了金属网栅FPI对太赫兹波偏振方向的依赖性以及对FPI腔镜平行度的要求,结果表明,方形金属网栅FPI对正入射太赫兹波偏振方向不敏感,而对FPI腔镜平行度很敏感。     

天然气超声速除湿器旋流分离数值研究

壁面型线决定了超声速除湿器的内部流场特征,进而对组分凝结特性和分离效率等产生重要影响。本文借助数值方法研究了内扩张型超声速除湿器流场径向分布特性以及组分凝结特性。计算结果表明除湿器内气流的周向速度、压力、温度在不同截面呈现出不同的径向分布特征。加速流道内壁面侧的气流温度低于外壁面侧,使组分凝结首先发生于流道内侧,为达到气液分离效果必须增加分离段长度。因此需要对除湿器加速段流道进行优化设计,以改善除湿器工作性能。     

Boson peak in Sm-Al-Co ternary metallic glasses and its possible structural origin

The low temperature specific heat of Sm-Al-Co ternary metallic glasses is investigated and a clear anomaly associated with the Boson peak is identified. While this anomaly depends slightly on the chemical composition, it has no dependence on external magnetic field. To figure out the mechanism of the Boson peak, we interpret the data within various model frameworks. Unlike earlier work, our study shows that this Boson peak is mainly ascribed to an additional T² term of the specific heat, which may originate from the quasi-two-dimensional and short-range ordered structure units possibly existing in the metallic glasses.     

Aerosol Measurement in Low‐Pressure Systems with Standard Scanning Mobility Particle Sizers

The scanning mobility particle sizer (SMPS) is one of the best known instruments for measuring particle size distributions in the submicron range. The SMPS consists of two parts: an electrostatic aerosol classifier (differential mobility particle analyser, DMA), followed by a counting device, in general a condensation particle counter (CPC). Unfortunately, commercial measurement devices such as the TSI DMA Model 3071 and the TSI CPC Model 3022 (TSI Inc., St. Paul, MN, USA), can be used only at nearly atmospheric pressure in the sampling line or in slight overpressure mode, but not in low‐pressure systems. A modification in the sampling line is shown which enhances the operating range of a standard SMPS system to low pressure. Samples taken under standard and low‐pressure conditions show good agreement in the measured particle size distributions and concentration. The behaviour observed in experimental studies agrees well with theoretical predictions.     

Induced electric fields and plasmonic interactions between a metallic nanotube and a thin metallic film

We have numerically simulated the induced electric fields and the plasmonic interactions of a metallic nanotube near a thin metallic film. Our study shows that the energies and intensities of the plasmon resonances depend strongly on the aspect ratio (the ratio of the inner to outer radius) of the nanotube as well as the separation between the center of the nanotube and the upper surface of the metallic film and the thickness of the film. The enhancement of the induced electric field of this system reaches ...