Selective vapor sorption by polymers and cavitands on acoustic wave sensors: is this molecular recognition?

Selectivity patterns for the sorption of organic vapors from the gas phase into cavitand monolayers on acoustic wave sensors are very similar to those seen for sorption of the same vapors by amorphous polymers, demonstrating that the vapor/cavitand selectivity patterns are determined primarily by solubility interactions. The amorphous polymers serve as controls demonstrating that the three-dimensional structure of a cavitand layer is not primarily responsible for the selectivity observed. Binding and selectivity in the examples cited are governed primarily by general dispersion interactions and not by specific oriented interactions that could lead to molecular recognition.     

全固态裸露式Ag／AgCl参比电极的研制及应用

该文报道了一种树脂接界全固态裸露式Ag／Agcl参比电极,勿需电镀氯化,制备工艺简单,性能稳定,是对电解型Ag／AgCl参比电极的一大改进。可代替饱和甘汞电极作为通用型参比电极,同时可减少汞对环境所造成的二次污染,在温度大于75℃时仍能保持良好性能,突破了甘汞电极的局限。     

Semi‐global output feedback tracking control for fully actuated ships

An output feedback trajectory tracking controller for a kind of 3 degrees of freedom (DOF) ship motion nonlinear model is designed. The closed‐loop control system is proven to be uniformly semi‐globally exponential stable with a separate stability result for the observer by applying nonlinear cascaded system theory. Simulation results on a model ship, Cybership II, are presented to validate the proposed control scheme. Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

火灾烟雾环境下人员逃生行为仿真研究

针对火灾时避难人员流动的基本特性及建筑物的设计布局对人群拥挤状况的影响,引入烟雾时逃生人员产生作用力的公式,并加入到社会力中,在保留计算疏散时间的基础上,提出了方向指示灯和避难方向指示灯对避难人员自驱力的影响方法.仿真实验结果表明,指示灯的设置以及设置的个数,对避难行为有重大的影响;对建筑设计人员具有一定的参考价值,同时给消防人员提供了救援过程中的最短时间要求.     

EDA9033A在分布式风机性能测试系统中的应用

针对以单片机为核心的风机性能测试系统存在稳定性差、抗干扰能力差、精度低等问题,开发了以PLC为核心、采用互感式采集模块EDA9033A采集风机电参数的分布式风机性能测试系统,给出了该风机性能测试系统的结构,详细介绍了EDA9033A的硬件及软件设计。实际应用表明,EDA9033A采集的风机电参数结果稳定、快速、准确。     

初探民间竹制品之设计意匠——以浙江省缙云地区竹制品的研究为例

英国学者李约瑟在深入研究中国科技史后认为,东亚文明乃是"竹子文明,中国人民的血液里流着竹子的文化"。我国不仅竹资源丰富,更是在竹资源的开发与利用上历史最为悠久的国家。我国南方有着大面积的竹产地,竹子及竹制品对当地的社会经济、民俗文化都有很大的影响。如何对"竹"这一传统材料进行创新性的开发和利用,最大限度的实现竹自身的价值,使制竹产业焕发出新的活力,成为当前研究的主要问题。     

Ordered mesoporous Pd/SnO2 synthesized by a nanocasting route for high hydrogen sensing performance

Ordered mesoporous SnO₂ and mesoporous Pd/SnO₂ have been successfully synthesized via nanocasting method using the hexagonal mesoporous SBA-15 as template. Two different procedures, impregnation technique and direct synthesis, were utilized for the doping of Pd in the mesoporous SnO₂. The results of small angle X-ray diffraction (SAXD), nitrogen adsorption–desorption and transmission electron microscopy (TEM) demonstrate that the SnO₂ and Pd/SnO₂ display ordered mesoporous structures and high surface areas. Wide angle X-ray diffraction (WAXD) and X-ray photoelectron spectroscopy (XPS) reveal tetragonal structure of SnO₂ and the existence of Pd element. The sensing properties of mesoporous SnO₂ and mesoporous Pd/SnO₂ for H₂ were detected. The sensor utilizing mesoporous Pd/SnO₂ via direct synthesis method exhibits excellent response and recovery behavior and much higher sensitivity to H₂, compared to those using mesoporous SnO₂ and mesoporous Pd/SnO₂ via impregnation technique. It is believed that its high gas sensing performance is derived from the large surface area, high activity and well dispersion of Pd additive, as well as high porosity, which lead to highly effective surface interaction between the target gas molecules and the surface active sites.     

Utility function of TCP

Understanding the TCP congestion control mechanism from a global optimization point of view is not only important in its own right, but also crucial to the design of other transport layer traffic control protocols with provable properties. In this paper, we derive a global utility function and the corresponding optimal control law, known as TCP control law, which maximizes the global utility. The TCP control law captures the essential behaviors of TCP, including slow start, congestion avoidance, and the binary nature of congestion feedback in TCP. We find that the utility function of TCP is linear in the slow start phase and is proportional to the additive increase rate and approaches the well-known logarithm function as the data rate becomes large in the congestion avoidance phase. We also find that understanding the slow start phase with a fixed threshold is critical to the design of new transport layer control protocols to enable quality of service features. Finally, as an application, we design a Minimum Rate Guaranteed (MRG) traffic control law that shares the same utility function as the TCP control law. Our simulation study of the MRG control law indicates that it is indeed TCP friendly and can provide minimum rate guarantee as long as the percentage of network resource consumed by the MRG flows is moderately small.