布里奇曼法生长碲镉汞晶体的固液界面形态研究

文中综述了布里奇曼法及加速坩埚旋转技术的布里奇曼法生工碲镉汞晶体过程中固液界面形态的研究结果，简单讨论了固液界面形态对组分分布的影响，并将两种技术所得的组分分布结果进行了比较，在分析影响固液界面形态因素的基础上，认为加速坩埚旋转技术是目前改善固液界面形态的有效方法。     

室外LED显示及其在交通领域的应用

介绍了室外LED显示技术及其在道路交通信息显示领域中的应用,指出目前国内室外LED显示屏普遍存在的主要问题.结合应用于高速公路收费站的LED显示屏的设计,给出解决或者克服这些问题的方法.介绍了室外LED显示的现状,预测了其发展趋势.     

Powder Deposition in Three Parallel-Oriented Dies of Different Shapes

Uniformity of bulk density distribution during the die filling process is required to minimize quality problems, such as distortion and cracking, for powder compacts. Understanding the die filling process is necessary in ensuring a uniform powder deposition. The second-generation pressure deposition tester (PDT-II) was used to investigate the deposition process and final pressure distribution of powder filling in toroidal, cylindrical, and E-shaped dies. All tests were conducted using a spray-dried free-flowing granular powder. The results indicated that for toroidal dies: (1) the area around 0° orientation (the leeward end) had the highest pressure values (1186.7 to 2498.0 Pa), with the average pressure values of the remaining area 353.7-648.0 Pa; (2) the pressure distribution was symmetrical about the centerline parallel to the feed shoe movement direction; (3) the highest feed shoe speed (500 mm/s) led to the most nonuniform pressure distribution among the three speeds; (4) higher feed shoe speed did not always result in higher final pressure values; and (5) the right die tended to have higher final pressure values (215.0 to 2498.0 Pa) than the center die (95.4 to 2052.5 Pa). For E-shaped dies: (1) the final pressure values of the middle leg (308.9 to 760.7 Pa) were higher than those of the left and the right legs (148.9 to 530.3 Pa); (2) the area along the backside had the highest final pressure value (1054.6 to 1303.8 Pa); (3) the pressure distribution was symmetrical about the centerline parallel to the feed shoe movement direction; and (4) neither the center die nor the right die always had higher pressure values than the other one at all locations. Comparison between cylindrical and toroidal dies indicated that: (1) neither of the two die shapes (cylinder and toroid) led to consistently higher or lower final pressure values at all locations and (2) for all three feed shoe speeds, the toroidal die had higher average final pressure values in the 0° orientation.     

Monte Carlo simulations to determine coating uniformity in a Wurster fluidized bed coating process

This paper presents a coating model to predict the mass coating uniformity in a Wurster fluid bed coater using a Monte Carlo method. The velocity and voidage data obtained using imaging techniques on the same Wurster coater are used as inputs to the model. The semi-circular Wurster fluid bed used in this work was 22.9 cm in diameter. A batch of 3.6 kg tablets was used to conduct coating experiments and the coating weight gain distribution results were compared to predictions from the simulation. The model rigorously considers the sheltering effect of particles as they move in the spray zone. Good agreement was obtained when comparing the results with an analytical model.Spray shape and orientation of discretization were found to play an important role in predicting the coating uniformity. A simple spray experiment in a particle-free bed showed that the direction of spray material, in general, was vertically upward. Simulation results confirmed that an upward cylindrical spray model gives better agreement with experimental results compared to a solid cone spray model. Finally, the model was used to predict the changes in coating uniformity with bed operating conditions such as gas velocity and gap height. A wider coating distribution was found for the case with the lower gas velocity and gap height.     

Characterization of temporal response, spectral responsivity and its spatial uniformity in photoconductive diamond detectors

Three photoconductive diamond detectors with highly oriented diamond (HOD) films fabricated by the same process were characterized with respect to temporal response, spectral responsivity and its spatial uniformity over the wavelength range from 190 to 250 nm. Temporal measurements showed a drift in the baseline, suggesting the presence of deep level carrier traps. The responsivity of specimen No. 2 was more than twice those of the other two specimens, but it showed an unpredictable current fluctuation. It was found that the spatial uniformities of all the specimens were too low for radiometric purposes. A prominent peak, thought to be due to photoemission, was found in the responsivity spatial distribution of specimen No. 3 under a negative applied voltage.     

Theoretical studies of displacement deposition of nickel into porous silicon with ultrahigh aspect ratio

A model is developed to address the uniformity of displacement deposition of nickel inside porous silicon with an ultrahigh aspect ratio as high as 200. The nickel distribution is treated as a current distribution issue as in electrodeposition. It is shown that the deposition distribution along the pore depth exhibits a strong dependence on a polarization parameter ξ. High values of ξ correspond to mass transport limitations and lead to non-uniform distributions, whereas small ξ values, representing interfacial reaction control, produce uniform distributions. Non-uniform deposition primarily occurs at an initial stage in which the reaction is dominated by mass transfer. As the deposition process continues, the deposition rate drops to a low value, and the deposition uniformity shifts from Ni²⁺ mass transport limitations to its interfacial reaction control, leading to uniform Ni²⁺ concentration and deposition rate distributions. It is predicted that the non-uniformity at the initial stage could be remedied by increasing the bulk concentration of the nickel ions and decreasing the plating bath pH. In addition, the uniformity of the deposition distribution can be significantly improved by introducing inhibiting additive coumarin to the plating solution.     

Experimental Study on the Expansion Uniformity of Armature

A measurement system has been developed based on high-precision printed probes in printed circuit board (PCB) and steep rising-time probe adapters,which can be applied to study the expansion uniformity of armature in a helical magnetic flux compression generator (HFCG).The influences of wall thickness and initiation position on the expansion uniformity of armature in HFCG were experimentally investigated.The results show that the armature with thinner wall thickness will easily rupture due to the high pressure of detonation products inside,the armature with larger wall thickness will easily crack due to the tensile stress on the outer surface of the wall,the influence of the end effect on the expansion uniformity can be ignored if the distance between the first group of probe and the initiation point is more than 3 times the armature diameter.     

Optimal Design of Two-Chamber Gas Distributor with CFD Approach

Computational fluid dynamics( CFD) is used to investigate a new type of two-chamber natural gas distributor,which has a natural gas inlet and nine nozzle outlets. The uniformity at the outlet of distributor is practice proven to have significant degree influence on its comprehensive performance. To improve the uniformity at the nozzles of the gas distributor,CFD modeling with the RNG k-ε turbulence model is undertaken to understand the mass flow rate of nozzles with reference to different length of chambers and the most optimal length is obtained. The internal flow pattern of the natural gas distributor is analyzed. It is found that the local maximum deviation of the nozzle outflow rate increases with the increase of chambers length when the length is more than 64 mm. The results provide useful suggestions for the optimal design of two-chamber natural gas distributor.     

基于TEM图像的CNT溶液分散均匀性分形方法

针对传统评价方法的不足,提出了一种以分形理论为数学模型基础的碳纳米管长度分布及分布均匀性的定量评价方法.将碳纳米管溶液TEM图像进行处理,得到简化矩阵,以简化矩阵的第1个元素为原点,提取不同步长及该步长内所有元素的和,在双对数坐标中以拟合直线的斜率作为碳纳米管长度分布参数p1.以TEM图像的中心为圆心做圆,提取不同半径圆内的碳纳米管数量,在双对数坐标中以拟合直线斜率的倒数作为分散均匀性参数p2.将该方法应用于不同方法分散的碳纳米管分散均匀性的描述,结果验证了该方法能正确地评价碳纳米管的长度分布及其分布均匀性.     

激光熔覆用高硬度铁基合金的研究与应用

研究了激光熔覆Fe-Ni-Cr—B—Si合金粉末时粉末中的碳含量对于熔覆层组织、开裂敏感性、硬度和硬度均匀性的影响。结果表明，粉末含碳量的微小变化能显著改变熔覆层的组织和性能；在相同工艺条件下，粉末含碳量在一定范围内可显著提高熔覆层的硬度、降低熔覆层开裂敏感性，从而获得高硬度无裂纹的熔覆层；碳含量的增加可提高熔覆层的硬度均匀性。本文还报道了用自制Fe基合金粉末成功修复大型轧辊的实例。