国内外纳米科技研究应用现状及发展趋势分析

介绍了国内外纳米材料及其技术在电子工业、环保工业、建材工业、金属工业、文物保护、医学等领域的开发应用现状 ,并对纳米科技未来的发展趋势和市场前景进行了预测和展望     

太阳电池用多晶硅及其吸杂研究现状

综述了几类主要的太阳电池用多晶硅及其吸杂研究现状.评述了当前太阳电池领域涉及到的几类多晶硅如铸造多晶硅、冶金法多晶硅、西门子法多晶硅等的优缺点.详细描述了多晶硅的吸杂类型、吸杂过程、吸杂影响因素等.给出了本课题组关于冶金法多晶硅吸杂实验的一些初步研究结果.展望了多晶硅及其吸杂技术的发展.     

新型功能梯度材料研究现状及发展方向

介绍了功能梯度材料的研究现状及发展方向,针对功能梯度材料研究的核心问题——材料合成技术,综述了低温制备工艺研究现状,最后对功能梯度材料进行了展望。     

Multivariate crash modeling for motor vehicle and non-motorized modes at the macroscopic level

Macroscopic traffic crash analyses have been conducted to incorporate traffic safety into long-term transportation planning. This study aims at developing a multivariate Poisson lognormal conditional autoregressive model at the macroscopic level for crashes by different transportation modes such as motor vehicle, bicycle, and pedestrian crashes. Many previous studies have shown the presence of common unobserved factors across different crash types. Thus, it was expected that adopting multivariate model structure would show a better modeling performance since it can capture shared unobserved features across various types. The multivariate model and univariate model were estimated based on traffic analysis zones (TAZs) and compared. It was found that the multivariate model significantly outperforms the univariate model. It is expected that the findings from this study can contribute to more reliable traffic crash modeling, especially when focusing on different modes. Also, variables that are found significant for each mode can be used to guide traffic safety policy decision makers to allocate resources more efficiently for the zones with higher risk of a particular transportation mode.     

Industrial application of RAM modeling: Development and implementation of a RAM simulation model for the Lexan plant at GE Industrial, Plastics

A RAM (reliability, availability and maintenance) model has been built for the GE Industrial, Plastics Lexan^® plant in Bergen op Zoom, The Netherlands. It was based on a Reliability Block Diagram with a Monte Carlo simulation engine. The model has been validated against actual plant data from two different sources, and against local expert opinions, resulting in a satisfactory simulation model. The model was used to assess two key decisions that were (to be) made by GE Industrial, Plastics concerning operation and shutdown policies of the plant. The model results showed that the operation and maintenance could be further improved, and that in doing so the annual production loss could be reduced further.     

粉状纳米材料的表面研究进展与展望

粉状纳米材料表面是决定其性能的关键性因素之一。用热物理法,化学法和机械制造法都可制得纳米粉,但其表面却有所不同。热物理法能得到表面比较纯净的纳米粉。纳米粉表面与其成分、结构和形态有关,它对纳米粉的化学和物理性能有着决定性的影响。因此,粉状纳粉材料应用前景也决取于其表面研究的进展。     

Research on Cs Beam Frequency Standards at the PTB: Beam Optics, Majorana Transitions

Results on theoretical and experimental studies on Cs beam optics using quadrupole and hexapole magnets and a combination of both, are reported. The efficiency of the deflection system and the velocity distribution in the beam have been computed for extended beam sources and compared with experimental results. An appropriate combination of magnets yielded a strong beam with a narrow relative half-width velocity range of about 7 percent. Design problems of Cs standards are discussed. A new wedge-shaped analyzer flop-in magnet is under study. Frequency shifting effects due to Majorana transitions are reported and the frequency shifting mechanism is discussed.     

The Status and Trend of Research on Standards for Ecological Textile in China

The products of ecological textile have represented nowadays the new trend of global consumption and production of textile while become an important means for some countries to utilize "green barrier" as a limitation of import of textile products. Following the entrance of China into the WTO, the position of "green barrier "becomes significantly important in the trade of textile products. As China is a big country of textile production,speeding up the research on standards for products of ecological textile, countering the latest situation appearing in international trade of textile, to take as quickly as possible responsive measures is a very urgent problem in port, to enhancing the ability of international market competition and to promoting the stable development of foreign oriented economy.     

Efficiencies of master, replica, and multilayer gratings for the soft-x-ray-extreme-ultraviolet range: modeling based on the modified integral method and comparisons with measurements

The near-normal-incidence efficiencies of a 2400-groove/mm holographic master grating, a replica grating, and a multilayer grating are modeled in the soft-x-ray-extreme-ultraviolet (EUV) regions and are compared with efficiencies that are measured with synchrotron radiation. The efficiencies are calculated by the computer program PCGrate, which is based on a rigorous modified integral method. The theory of our integral method is described both for monolayer and multilayer gratings designated for the soft-x-ray-EUV-wavelength range. The calculations account for the groove profile as determined from atomic force microscopy with a depth scaling in the case of the multilayer grating and an average random microroughness (0.7 nm) for the short wavelengths. The refractive indices of the grating substrate and coatings have been taken from different sources because of the wide range of the wavelengths (4.5-50 nm). The measured peak absolute efficiency of 10.4% in the second diffraction order at a wavelength of 11.4 nm is achieved for the multilayer grating and is in good agreement with a computed value of approximately 11.5%. Rigorous modeling of the efficiencies of three similar gratings is in good overall agreement with the measured efficiency over a wide wavelength region. Additional calculations have indicated that relatively high normal incidence efficiency (of at least several percent) and large angular dispersion in the higher orders can be achieved in the 4.5-10.5-nm range by application of various multilayer coatings.     

Fast, all-optical Rayleigh wave microscope: imaging on isotropic and anisotropic materials

A fast, non-contact Rayleigh wave scanning microscope is demonstrated, which is capable of scan rates of up to a maximum of 1000 measurements/s with typical speeds of up to 250 measurements/s on real samples. The system uses a mode-locked, Q-switched Nd:YAG laser operating at a mode-locked frequency of 82 MHz and a Q-switch frequency of 1 kHz. The Q-switch frequency determines the upper limit of the scanning rate. The generating laser illumination is delivered and controlled by a computer-generated hologram (CGH). The generating laser produces around 30 pulses at 82 MHz and additional harmonics at 164 and 246 MHz and above. The microscope can operate at these harmonics provided the spatial bandwidth of the optics and the temporal bandwidth of the electronics are suitable. The ultrasound is detected with a specialized knife-edge detector. The microscope has been developed for imaging on isotropic materials. Despite this, the system can be used on anisotropic materials, but imaging and interpreting images can be difficult. The anisotropy and grain structure of the material can distort the Rayleigh wavefront, leading to signal loss. A model has been developed to simulate polycrystalline-anisotropic materials; this is discussed along with possible solutions that would overcome the problems associated with anisotropy. Rayleigh wave amplitude images are demonstrated on silicon nitride at 82 and 164 MHz and on polycrystalline aluminium at 82 MHz.     

叶轮机械弯扭叶片的研究现状及发展趋势简评

叶片的联合弯扭气动成型概念是王仲奇教授和前苏联的费里鲍夫 (Г .А .Филиппов)于 6 0年代初提出的。叶片沿高度的周向弯曲 ,增加了叶轮机械气动设计的自由度。理论分析和试验研究表明 ,应用了这一概念而设计出的“正弯”涡轮导叶 ,可以形成两端高、中部低的沿叶高静压分布 ,从而将两端端壁低能的边界层流体吸入叶片中部而降低能量损失。这种“正弯”涡轮导叶还可以使叶片两端压力面和吸力面之间的压差减小 ,从而降低与此有关的二次流损失。利用这个设计自由度 ,可以有效控制叶根反动度 ,从而消除动叶根部分离 ,改善整个涡轮的流…     

我国高比表面积活性炭研究现状与发展对策

简述了外高比表面积活性炭发展概况,叙述了我国高比表面积活性炭研究现状,并就我国该材料的发展提出了对策。     

中国科技馆磁浮展车刚-弹性动力学建模和转向架固有频率分析

以中国科技馆载人磁浮车演示车为原型,将其转向架视为刚、柔体组合,基于多体动力学整车分析,建立了11个自由度的刚-弹性车辆动力分析模型,解算了转向架的固有频率,探讨了影响转向架固有频率特性的主要参数.结果表明:转向架的扭转频率与悬挂弹簧刚度为叠加关系,扭转刚度几乎不受弹簧刚度影响;转向架相对于其它广义坐标的固有频率受悬挂弹簧刚度的影响较大;除扭转外,转向架的其它运动均有动力学耦合.     

Polysilicon high frequency devices for large area electronics: Characterization, simulation and modeling

Laser Crystallised Polysilicon Thin Film Transistors have now sufficient good conduction properties to be used in high-frequency applications. In this work, we report the results for 5 μm long polysilicon TFTs obtained at frequencies up to several hundred MHz for applications such as RFID tags or System-On-Panel. In order to investigate the device operation, DC and AC two-dimensional simulations of these devices in the Effective Medium framework have been performed. In the light of simulation results, the effects of carrier trapping and carrier transit on the device capacitances as a function of dimensions are analysed and compared. An equivalent small-signal circuit which accounts for the behaviour of these transistors in all regions of operation is proposed and a model for the most relevant elements of this circuit is presented. To validate our simulation results, scattering-parameters (S-parameters) measurements are performed for several structures such as multi-finger, serpentine and linear architectures and the most meaningful parameters will be given. Cut-off frequencies as high as 300 MHz and maximum oscillation frequencies of about 600 MHz have been extracted.     

火炸药双螺杆挤出工艺的研究现状与发展*

综合叙述了国内外双螺杆挤出工艺在火炸药中的应用研究现状,指出国内在双螺杆挤出机结构设计、安全、工艺等方面的研究水平较国外存在较大的差距,制约了双螺杆挤出工艺在火炸药自动化制备中的应用。为使双螺杆挤出工艺在火炸药行业得到长足发展,建议进行双螺杆挤出机结构设计、安全设计、制备工艺等方面的研究,培养相关的专业人才。