消能锥形阀过流状态研究与优化

消能锥形阀是一种用于中、高水头下的消能控流阀门,其内部结构设计的好坏直接影响着控流效果。为探究消能锥形阀在不同开度下,过流流量及内部流场的变化情况。进行了模型试验与CFD数值模拟计算,试验中发现开度从100%关至85%时出现了流量反而上升、进口压力下降的情况。利用CFD数值模拟的方法对内部流场进行了可视化研究。研究结果表明,在全开状态下锥形阀内部存在以下问题:过强的局部高速高压区域、低速流动死区范围过大、涡流区过度影响高速过流部分。并对锥形阀进行了一定的结构改进,优化了其内部流场情况。     

The Importance of Shallow‐Low Velocity Habitats to Juvenile Fish in the Middle Mississippi River

Habitat management is a crucial aspect of fisheries management. Without knowledge of habitat associations, fisheries scientists are unable to effectively make habitat conservation or restoration recommendations. This becomes especially prominent when trying to manage commercially harvested populations and protect threatened or endangered species. To determine juvenile fishes habitat associations in the Middle Mississippi River, we analysed mini‐trawl catch data of six common juvenile fish species: blue catfish (Ictalurus furcatus), channel catfish (Ictalurus punctatus), channel shiner (Notropis wickliffi), freshwater drum (Aplodinotus grunniens), paddlefish (Polyodon spathula), and shovelnose sturgeon (Scaphirhynchus platorynchus). Overall, we conducted 2251 mini‐trawl sampling efforts between 2002 and 2013, resulting in the capture of 23,742 target specimens. Catch per unit effort was evaluated by structural habitat (i.e. velocity, depth, and substrate). Overall, these data suggest that juvenile fish species are more prevalent in shallow water and slower velocities. Ultimately the information garnered during this evaluation should be incorporated when considering habitat modifications, especially those modifications that impact the availability of shallow‐low velocity habitats. Copyright © 2016 John Wiley & Sons, Ltd.     

疏水缔合类聚丙烯酰胺溶液性质研究

综述了疏水缔合类聚丙烯酰胺溶液性质的影响因素以及测定溶液微观形态的研究方法。     

横流环境中两孔热水浮射流数值模拟研究

为了达到热废水排放过程中热水快速稀释的目的,采用Fluent中Realizable k-ε模型基于SIMPLEC算法,研究了热射流过程中,射流孔间距、初始流速对射流流场、温度场的影响规律。研究表明:随着射流孔间距的增大,第1孔射流对第2孔射流影响程度逐渐减弱且第2孔射流的弯曲程度随之增加;射流与横流作用促使反向涡对的产生,加快了热水与环境水体的掺混度,横断面温度场出现"肾形"分布;当相对孔间距相同时,随着射流初始流速的增加,第1、2孔射流温度衰减速率随之增大;射流初始流速相同时,射流孔间距的增加对第1孔射流轴线温度稀释度影响较小,对第2孔射流的轴线温度稀释度影响相对复杂;S/D=2时,增大热射流的初始流速,为本研究中热水快速稀释的最优方案。     

Characterization of ramie yarn treated with sodium hydroxide and crosslinked by 1,2,3,4‐butanetetracarboxylic acid

Ramie yarns were treated with various concentrations of NaOH at room temperature and subsequently crosslinked with 1,2,3,4‐butanetetracarboxylic acid (BTCA). The microstructure and tensile properties of the treated yarns were characterized. X‐ray diffraction (XRD) and FTIR were used to study the crystalline structure of the resultant ramie yarns. The results showed that the maximum change in the structure of the alkali‐modified ramie took place at 16% NaOH, which would completely transform cellulose I to cellulose II. At the same time, the crystallinity index and fiber orientation decreased to the minimum value while the absorption properties were enhanced. The average degree of polymerization (DP ) of the treated ramie yarns slightly decreased after NaOH treatment. Tensile properties including tenacity, breaking elongation, and modulus of the treated yarns were also investigated. Scanning electron microscopy (SEM) was used to investigate the breakage of the treated yarns. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1857–1864, 2004     

玉米芯木聚糖硫酸酯化条件的研究

用碱提法从玉米芯中提取木聚糖,采用氯磺酸吡啶法进行硫酸酯化,通过正交试验确定最佳工艺条件为:吡啶与氯磺酸摩尔比1∶1,温度65℃,时间6h;木聚糖硫酸酯wisX-S通过DEAESepharoseFF层析柱分离得到一个相对分子量为1.3×104的组分,硫酸基取代度为2.24。对此木聚糖硫酸酯进行红外光谱分析,结果显示在波数1259、1228和813cm-1处分别有S=O和C-O-S键的特征吸收峰。     

基于Monte Carlo随机模拟的综合交通网络布局评价与决策方法

针对综合交通网络评价指标权重及属性值具有主观性和随机性的特点,提出了基于模拟运算的布局规划方案排序选优的群体随机决策方法.仿真生成满足集结的多个专家对指标重要性偏好排序统计分布的权重,同时考虑交通需求的不确定性对指标值的影响,结合客观熵权计算方案的综合评价值,由多次模拟得到的排序优势度确定方案的优劣差异.根据设计的仿真流程通过算例说明了方法应用的有效性,评价中考虑了主客观因素及随机性特征,可以为网络布局提供科学决策依据.     

复杂体制雷达辐射源信号特征的集对分析

为解决复杂体制雷达辐射源信号特征的评价问题,提出了基于集对分析理论的复杂体制雷达辐射源信号特征分析模型.首先对复杂体制雷达辐射源信号特征评价指标体系的指标权重作层次分析,再通过集对分析理论对复杂体制雷达辐射源信号特征评估的决策矩阵进行同一度分析,最后联合指标权重矩阵和决策同一度矩阵对复杂体制雷达辐射源信号特征进行综合评判.仿真结果表明,该模型是有效、可行的,能够更好地实现对复杂体制雷达辐射源信号特征的分析和评估.     

基于有限状态自动机的人眼开度PERCLOS实现算法

针对驾驶员驾驶过程中因疲劳引起的眼睛开度变化问题, 在原有PERCLOS(percentage of eyelid closure over the pupil over time)标准的基础上, 提出了一种基于有限状态自动机的人眼开度PERCLOS计算方法, 并将其应用到疲劳驾驶预警系统中。该系统首先采用红外摄像头实时获取驾驶员的脸部视频图像, 使用ASM(active shape models)算法进行人脸检测, 在定位到的人脸范围内搜索人眼区域并计算人眼开度, 为了避免人与摄像头距离变化影响计算结果, 对人眼开度进行归一化处理; 然后依据建立的有限状态自动机模型计算PERCLOS值; 最后根据制定的预警机制实现基于人眼开度的疲劳预警。实验结果表明本方法能够实时监测驾驶员疲劳状况, 具有对光照变化、脸部配饰不敏感的特点。     

PVC-U异型材塑化度的评价

比较了4种评价PVC-U塑化度的方法:目测法简单;溶剂法迅速,容易操作;拉伸法可定量判断,但需要大量样品;DSC法准确、方便。