Preparation of aqueous dispersible polyurethane: Effect of acetone on the particle size and storage stability of polyurethane emulsion

An aqueous dispersible polyurethane was prepared by the reaction of hydroxyl‐terminated poly(ethylene adipate), dimethylol propionic acid, 4,4′‐diphenylmethane diisocyanate, and ethylene glycol. Formation of the dispersion was achieved by phase inversion of an acetone solution of the polyurethane with water, utilizing carboxylate anion groups as the internal emulsifying sites. The amount of acetone added has a large effect on the particle diameter (0.08 to 8.61 μm) and particle size distribution of the polyurethane emulsion. The storage stability was evaluated in terms of particle size distribution breadth. The aqueous emulsion obtained with no use of acetone was sufficiently stable in storage for at least 6 months. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3455–3461, 2004     

Stochastic Behavior of a 2-Unit Parallel Fuel Charging System

In a contribution to this TRANSACTIONS, Buzacott (1973) discussed a fuel charge/discharge system for a nuclear reactor. We consider the same parallel fuel charging system and derive more detailed results by making use of Markov renewal processes and renewal-type equations.     

Some Considerations for Multiple-Unit Redundant Systems with Generalized Repair Time Distributions

The mean time to system failure (MTSF) for a 2-out-of-n system with repair is intuitively derived. The improvement factor, the ratio of the MTSF for a 2 out of n system with repair to that system without repair, is evaluated and its asymptotic behavior is studied.     

Muscle stiffness sensor to control an assistance device for the disabled

An innovative sensor has been developed as a man–machine interface to control an assistance device for people with disabilities. This sensor is applied to a mechanical glove that has a grasping function, and its usefulness is demonstrated through experiments. The sensor is attached to the operators skin and detects noninvasively how much the muscle under the sensor has stiffened.This work was presented in part at the 8th International Symposium on Artificial Life and Robotics, Oita, Japan, January 24–26, 2003     

Application of cross-linked salmon atelocollagen to the scaffold of human periodontal ligament cells

The purpose of this study was to investigate the application of salmon atelocollagen (SAC) to a scaffold. SAC has a low denaturation temperature and needs to be cross-linked before being used as a scaffold. In the present study, SAC was cross-linked by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) or dehydrothermal treatment (DHT). The material properties (degree of cross-linking and solubility in phosphate-buffered saline) of the SAC scaffolds cross-linked by EDC (EDC-SAC) and DHT (DHT-SAC) were evaluated. It was found that EDC-SAC had a high degree of cross-linking and high stability compared with DHT-SAC. Human periodontal ligament (HPDL) cells were cultured in the scaffolds for 2 weeks in vitro, and the activities (proliferation rate and alkaline phosphatase [ALP] activity) of HPDL cells cultured in EDC-SAC and DHT-SAC were compared with those cultured in bovine atelocollagen (BAC) scaffolds cross-linked by EDC (EDC-BAC) and DHT (DHT-BAC), respectively. The proliferation rate of HPDL cells cultured in EDC-SAC was equivalent to that in EDC-BAC, and the ALP activity in EDC-SAC was found to be significantly higher than that in EDC-BAC. In the cross-linking by DHT, the cell proliferation rate and the ALP activity in DHT-SAC were lower than those in DHT-BAC. DHT seemed to provide insufficient cross-linking, and DHT-SAC was found to be breakable and contractile, resulting in less cell activity. In contrast, there was no difference in the thermal stability, porous structure, and cell proliferation rate between EDC-SAC and EDC-BAC. In addition, the collagen helix of EDC-SAC was found to be partially denatured, and this structure resulted in the enhancement of ALP activity of HPDL cells compared with that using EDC-BAC. In conclusion, our results indicate that EDC-SAC could be used as a scaffold for in vitro culture.     

极化SAR图像的多纹理最大似然估计

提出了一种新的极化SAR图像相干斑抑制的方法。该方法在多纹理乘性相干斑噪声模型的假设下,采用最大似然估计法来同时估计多个极化通道的纹理参数。该方法保存了极化信息,消除了极化通道间的耦合,取得较好的相干斑抑制效果;并与极化白化滤波法(PWF)作了比较。     

Photocatalytic oxidation of nitrogen oxide over titania–zeolite composite catalyst to remove nitrogen oxides in the atmosphere

The photooxidation of NO with oxygen over Hycom TiO₂ and zeolite (A and Y form zeolite: TiO₂-AZ and TiO₂-YZ) composite catalysts was studied to remove NO_x in the atmosphere. The photocatalytic oxidation activity of the titania in the composite catalyst in a proportion of AZ:TiO₂=3:7 is about three times larger than that in the bare titania. The adsorption behaviors of NO and NO₂ for the bare titania sample obey Langmuir adsorption equations of NO and NO₂, respectively. In the titania–zeolite composite catalysts, the adsorption data indicate the increase in the amount of NO adsorption on the TiO₂ phase and the decrease in the amount of NO₂ adsorption, compared with the bare titania. The acceleration of NO photooxidation rate, resulting from the increase in the amount of NO adsorbed and the decrease in the amount of NO₂ adsorbed, thus occurs on the TiO₂ phase. IR spectra, when irradiating the catalysts with UV, showed the immediate formation of nitrate and NO₂ species on the catalyst. The results lead to the conclusion that the zeolites promote the photocatalytic oxidation of NO over the titania.     

一种新的复值递归神经网络训练方法及其应用

一种新的基于数字滤波器理论的全互连复值递归神经网络训练方法被提出.每个递归神经元均具有复数ⅡR滤波器结构.通过优化ⅡR滤波器的系数来更新神经网络的权值,而优化过程则采用逐层优化(LBLO)技术和递归最小平方(RLS)方法.该算法的性能通过将其应用于复信道均衡来加以说明.计算机仿真结果表明,该算法具有较快的收敛速度.这为快速训练复值递归神经网络提供了一条新的途径.     

全极化合成孔径雷达(SAR)高度信息检测技术

从全极化合成孔径雷达(SAR)二维图像数据中,经过极化综合计,利用快速搜索算法计算每一个图像像素的极化椭圆方向角ψ、△ψ,从而提取雷达方位向的地势倾斜度信息,形成极化SAR三维图像.本文在极化合成孔径雷达(SAR)三维成像快速搜索算法的基础上,提出由Stokes矢量推导的极化椭圆方向角解模糊算法,并利用美国NASA1994年SIR-C采集的真实全极化合成孔径(SAR)二维图像数据,经计算机处理得到了极化合成孔径(SAR)三维成像结果.