Volume phase transition of polyelectrolyte gels in dimethyl sulfoxide/ tetrahydrofuran mixtures

Copolymer gels were prepared from 2-(acrylamido)-2-methylpropanesulfonic acid (AMPS), N,N-dimethylacrylamide (DMAA, comonomer) and N,N′-methylenebis(acrylamide) (BIS). The mole fraction of AMPS were 0.2674 and 0.4318, respectively, with the same BIS mole fraction of 0.013. These gels with counterions H⁺, Na⁺, and K⁺ were swollen at 25°C in mixtures of dimethyl sulfoxide (DMSO) and tetrahydrofuran (THF). A volume phase transition was observed at the THF volume fraction of about 0.58, indicating that the volume phase transition in a polyelectrolyte gel occurs when the medium polarity decreases sufficiently for ion-pair formation. On changing the counterion, the fraction of DMSO in the solvent mixture which is required to initiate swelling decreases in the order Na⁺, H⁺, and K⁺, the same as for counterion condensation in identical gels.     

Investigation of free volume,interfacial, and toughening behavior for cyanate ester/bentonite nanocomposites by positron annihilation

Effects of filler on microstructure and toughening behavior of cyanate ester (CE)/bentonite (BT) nanocomposites with different content of BT have been studied by positron annihilation lifetime spectroscopy, X‐ray diffraction, transmission electron microscopy, dynamic mechanical analysis, etc. The interesting results found by PALS indicate that the size and concentration of the free volume holes and the apparent free volume fraction increased with increasing the content of BT, which indicates that adding nano‐layers to thermosetting materials can lead to the high crosslinking density structure “looser.” The experimental results reveal that the increases in size of free volume holes and apparent free volume fraction are related to the increasing conversion of cure reaction. On the other hand, the mechanism of toughening (by adding the nano‐clay to the thermosetting material) has been discussed by combining free volume and interfacial property. It is shown that, for the high crosslinking thermosetting material‐based nanocomposites, both the property of free volume and dispersion state of nano‐layers are the two key factors in determining toughening property. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1509–1515, 2006     

A fuzzy neural network approach for online fault detection in waste water treatment process

In this paper, an effective strategy for fault detection of sludge volume index (SVI) sensor is proposed and tested on an experimental hardware setup in waste water treatment process (WWTP). The main objective of this fault detection strategy is to design a system which consists of the online sensors, the SVI predicting plant and fault diagnosis method. The SVI predicting plant is designed utilizing a fuzzy neural network (FNN), which is trained by a historical set of data collected during fault-free operation of WWTP. The fault diagnosis method, based on the difference between the measured concentration values and FNN predictions, allows a quick revealing of the faults. Then this proposed fault detection method is applied to a real WWTP and compared with other approaches. Experimental results show that the proposed fault detection strategy can obtain the fault signals of the SVI sensor online.     

Molar volume and ultrasonic studies of europium soaps in mixed organic solvents

The ultrasonic velocity and density measurements of europium soaps in a mixture of benzene and methanol (3:2, vol/vol) were used to evaluate various acoustic parameters and molar volume and to determine the critical micelle concentration. The results showed that the ultrasonic velocity, specific acoustic impedance, molar sound velocity, and molar compressibility increase, and intermolecular free length, adiabatic Compressibility, and relative association decrease with increasing concentration and chainlength of the soap. The results were interpreted in terms of soap-solvent interaction.     

海上溢油漂移扩散的数值模拟

该文基于三维自由水面垂向分层动网格的Euler-Lagrangian模式,采用VC方式(Vertex-Centered)的非结构化有限体积方法离散三维浅水方程,模拟渤海的潮汐水流运动过程。以此为水动力背景场,采用油、水分离的Lagrangian粒子追踪模型,对渤海海域发生的溢油漂移扩散问题进行模拟。其油品的蒸发、乳化和溶解等风化作用以引入综合衰减系数的方式考虑。模型对油膜的漂移路径、厚度和面积进行了实时模拟和预测,用多个测站的同步连续实测值对水动力模式进行了参数率定与模型验证,油膜输运扩散的计算结果也与相关报告数据进行了对比,均吻合良好,说明模型具有较高的可靠性与重现性。     

城市径流总量控制指标分解及实现路径探索与实践

针对海绵城市径流总量控制目标,提出一种在城市规划体系中控制性详细规划和修建性详细规划阶段分解落实年径流总量控制率的方法。在控制性详细规划阶段分解径流总量控制指标时,分步骤先后确定各项低影响开发措施的面积率和下沉深度;在修建性详细规划阶段,配合径流总量控制指标分解结果,给出适宜的各项低影响开发措施的技术实施导则,以保证各单项指标的正确实施,并以某项目为例介绍了技术实施导则的构建方法。     

高流态大掺量粉煤灰混凝土的研制及应用

通过混凝土配合比的正交试验及有关因素影响效果的分析,确定了高流态大掺量粉煤灰混凝土配合比的最优方案,进而成功用于最深的混凝土防渗墙工程中,为高流态大掺量粉煤灰混凝土的广泛应用提供了参考。     

一种用于目标跟踪的波形自适应选择算法

提出了一种用于雷达目标跟踪的自适应广义调频波形设计算法。该算法根据跟踪器的动态需求,以广义调频信号为样板波形自适应设计下一时刻的发射波形,其目的是最小化预测的目标跟踪均方误差,并假定高信噪比条件,且目标跟踪运动模型和观测模型均为线性,利用与某一波形相对应的克拉美--罗下限（CRLB）以及卡尔曼滤波器,通过最小化预测的跟踪均方误差来实现广义调频波形的自适应设计。仿真结果表明：在信噪比相同的情况下,与使用固定参数、自适应参数的线性调频波形设计算法相比,所提出的算法能够获得更低的目标跟踪均方误差。     

基于背景和帧间差分法的运动目标提取

在自动人脸识别系统中,人体目标的检测是该系统识别人脸的前期关键步骤之一。为了能快速准确地检测出运动的人体目标,提出了背景差分法和帧间差分法相结合的运动目标提取检测方法。针对视频中的背景因镜头摆动或物体的移入/移出而有所变动,给出了几种提取背景的方法,比较各种方法后决定采用中值法快速地进行背景建模,随后采用自适应背景更新,结合两种差分法检测运动目标。通过实验验证了本文算法的有效性。     

Free volume in two differently plasticized poly(vinyl chloride)s: a positron lifetime and PVT study

The temperature dependence of the specific volume, V, and of the mean size of local free volumes (holes), v_h, of poly(vinyl chloride) containing 10 wt% (PVC-h) and 30 wt% (PVC-s) of the plasticizer di-n-butyl phthalate (DBP) were studied by pressure-volume-temperature (PVT) and positron annihilation lifetime spectroscopy (PALS) experiments. Using the Simha-Somcynsky equation-of-state, the hole fraction h was calculated from the PVT data. It was found that the thermal expansivity of the specific volume V, the specific free volume V_f=hV, and v_h increase with the content of plasticizer. From the comparison of V and V_f with v_h the hole number per gram N′_h is estimated. Other than v_h, N′_h does not depend on the temperature nor on the content of plasticizer.