Shape transition and propulsive force of an elastic rod rotating in a viscous fluid

The deformation of an elastic rod rotating in a viscous fluid is considered, with applications related to flagellar motility. The rod is tilted relative to the rotation axis, and experiments and theory are used to study the shape transition when driven either at constant torque or at constant speed. At low applied torque, the rod bends gently and generates small propulsive force. At a critical torque, the rotation speed increases abruptly, and the rod forms a helical shape with increased propulsive force. We find good agreement between theory and experiment. A simple physical model is presented to capture and explain the essential behavior.     

Ag掺杂p型ZnO薄膜及其光电性能研究

采用超声喷雾热分解法在石英衬底上以醋酸锌水溶液为前驱体,以硝酸银水溶液为Ag掺杂源生长了Ag掺杂ZnO(ZnO：Ag)薄膜.研究了衬底温度对所得ZnO：Ag薄膜的晶体结构、电学和光学性质的影响规律.所得ZnO：Ag薄膜结构良好,在室温光致发光谱中检测到很强的近带边紫外发光峰,透射光谱中观测到非常陡峭的紫外吸收截止边和较高的可见光区透过率,表明薄膜具有较高的晶体质量与较好的光学特性.霍尔效应测试表明,在500℃下获得了p型导电的ZnO：Ag薄膜,载流子浓度为5.30×10¹⁵cm关键词： ZnO：Ag薄膜 p型掺杂 超声喷雾热分解 霍尔效应     

化学战剂的分析测试进展

综述了气相色谱、液相色谱、红外光谱、色质联用、生化传感器、核磁共振、军用侦毒设备、分光光度计、毛细管电泳等仪器对化学战剂分析测试的应用进展情况．     

心率变异性基本尺度熵的多尺度化研究

将基本尺度熵的方法在时间上做多尺度化的扩展,并将其应用到心跳间隔序列的分析研究中.研究发现,健康人的心率变异性是小时间尺度下的模式特定性与大时间尺度下的模式丰富性相结合的,而充盈性心衰患者则正好相反.这说明充盈性心衰患者在小时间尺度下心脏动力系统的控制不力,导致随机性增加,而在大时间尺度下对外界环境变化反应又不够丰富,从而导致生命更容易受威胁.据此提出了以小时间尺度下的基本尺度熵值相对于大时间尺度下平台区基本尺度熵值的变异参数δ作为区分健康人和充盈性心衰患者的诊断依据.通过对72例健康人和44例充盈性心衰患者的计算,发现两组样本差异显著,证明了参数δ的有效性. 关键词： 多尺度化的基本尺度熵 心跳间隔序列 心率变异性 充盈性心衰     

基于不完全溢价信息的并购时机期权博弈研究

本文采用实物期权、最优停时的方法研究了考虑不完全信息并购溢价的并购阈值的确定问题。通过数值举例得出溢价比例的变化与并购阈值上下界呈反向变动关系的基本结论。并以此为基础,进一步分析了基于竞争对手溢价水平不完全信息下主并方的并购策略问题,得出了强弱竞争力情形下,主并方溢价水平的选择分别为调高或调低、大于或等于竞争对手的溢价水平,且应同时满足调整后的并购阈值上界至少等于竞争对手的期望溢价水平下的并购阈值上界。该结论可直接用于指导实践。     

An ultra-narrow band eight-pole dual-mode HTS patch filter

An ultra-narrow band eight-pole dual-mode HTS patch filter was designed and fabricated. The filter is constructed by four corner-cut square patches, each of which has two resonating modes. The influence of the change of the corner-cut position on the filter response was investigated by simulations. Four small rectangle patches were added in the topology of the filter as tuning tools. By employing this unique tuning structure, the simulated filter responses and current density distributions on the patches have been greatly improved. The filter was fabricated using double sided YBCO films on a 3 in. LaAlO₃ substrate. The measured results showed satisfactory performance with center frequency 2.494 GHz, fractional bandwidth 0.2%, return loss in passband better than 16 dB, and out-of-band rejection of the filter better than 90 dB at 15 MHz away from its center frequency.     

Nanostructured ZnO thin films by chemical bath deposition in basic aqueous ammonia solutions for photovoltaic applications

This paper presents further insights and observations of the chemical bath deposition (CBD) of ZnS thin films using an aqueous medium involving Zn-salt, ammonium sulfate, aqueous ammonia, and thioure. Results on physical and chemical properties of the grown layers as a function of ammonia concentration are reported. Physical and chemical properties were analyzed using scanning electron microscopy (SEM), X-ray energy dispersive (EDX), and X-ray diffraction (XRD). Rapid growth of nanostructured ZnO films on fluorine-doped SnO₂ (FTO) glass substrates was developed. ZnO films crystallized in a wurtzite hexagonal structure and with a very small quantity of Zn(OH)₂ and ZnS phases were obtained for the ammonia concentration ranging from 0.75 to 2.0 M. Flower-like and columnar nanostrucured ZnO films were deposited in two ammonia concentration ranges, respectively: one between 0.75 and 1.0 M and the other between 1.4 and 2.0 M. ZnS films were formed with a high ammonia concentration of 3.0 M. The formation mechanisms of ZnO, Zn(OH)₂, and ZnS phases were discussed in the CBD process. The developed technique can be used to directly and rapidly grow nanostructured ZnO film photoanodes. Annealed ZnO nanoflower and columnar nanoparticle films on FTO substrates were used as electrodes to fabricate the dye sensitized solar cells (DSSCs). The DSSC based on ZnO-nanoflower film showed an energy conversion efficiency of 0.84%, which is higher compared to that (0.45%) of the cell being constructed using a photoanode of columnar nanoparticle ZnO film. The results have demonstrated the potential applications of CBD nanostructured ZnO films for photovoltaic cells.     

采用阶梯形弹性基底的磁致伸缩/压电复合结构磁电响应研究

利用阶梯形变幅杆的应变放大作用,构造了磁致伸缩/阶梯形弹性基底/压电复合结构. 采用等效电路法分析了沿长度方向振动复合结构的一阶磁电响应. 计算了Terfenol-D/阶梯形铍青铜基底/PZT-5H复合结构的磁电响应,并与实际结构的磁电响应进行了比较,由于理论分析中忽略了胶层产生的损耗,理论值和实验结果的变化规律相似,但是谐振频率点和磁电电压转换系数有一定的差异. 同时比较了阶梯形基底和等截面杆基底复合结构,分析表明前者具有更高的磁电电压转换系数. 研究了阶梯形弹性基底长度比及层厚比对复合结构纵振动一阶模 关键词： 磁电效应 磁致伸缩/压电复合结构 磁电响应     

Photoluminescence investigation of ZnO:P nanoneedle arrays on InP substrate by pulsed laser deposition

Phosphorus-doped ZnO nanoneedle arrays were prepared by phosphorus diffusion from InP substrate using a pulsed laser deposition (PLD) technique. The optical properties of ZnO nanoneedle were investigated by photoluminescence (PL) spectroscopy. Low-temperature photoluminescence spectrum measurements exhibited five acceptor-related emission peaks. The excitation intensity and temperature dependent photoluminescence spectra confirmed that the emission peaks corresponded to neutral-acceptor bound exciton, free electron to acceptor, donor-acceptor pairs, and their first and second photon replicas transitions. Acceptor-binding energy was determined to be 135-167 meV, which agrees well with the best-fitting result of the temperature dependent photoluminescence measurements and is reasonable in terms of theoretic prediction in ZnO.     

First-principles calculations of hydrogen molecule adsorption on Ti (0 0 0 1)-(2 × 1) surface

Adsorption of H₂ molecule on the Ti (0 0 0 1)-(2 × 1) surface was studied by density functional theory with generalized gradient approximation (GGA). The parallel and vertical absorption cases were investigated in detail by adsorption energy and electronic structure analysis, we obtained three stable configurations of FCC-FCC (the two H atoms adsorption on the two adjacent fcc sites of Ti (0 0 0 1) surface, respectively), HCP-HCP (the two H atoms adsorption on the two adjacent hcp sites of Ti (0 0 0 1) surface, respectively) and FCC-HCP (the one H atom adsorption on the fcc site and the other adsorption on the near hcp site) based on the six different parallel adsorption sites after the H₂ molecule dissociates. However, all the end configurations of four vertical adsorption sites were unstable, H₂ molecule was very easy to desorb from Ti surface. The H-H bond breaking and Ti-H bond forming result from the H₂ molecule dissociation. H-H bond breaking length ranges from 1.9 Å to 2.3 Å for different adsorption configurations due to the strong Ti-H bond forming. The H₂ dissociative approach and the end stable configurations formation in parallel adsorption processes are attributed to the quantum mechanics steering effects.