连续鼓气对舰船冷却海水真空膜蒸馏强化效果的研究

通过连续运行试验考察舰船冷却海水膜蒸馏系统不鼓气时膜通量变化及膜污染情况,应用气液两相流试验考察连续鼓气流量与膜通量之间的关系,探讨不同温度下连续鼓气的强化效果.结果 表明,舰船冷却海水真空膜蒸馏系统不鼓气时,海水温度升高膜通量衰减加快,会在膜面形成碳酸钙等盐类结晶;0～30 L/min连续鼓气时膜通量随鼓气流量上升而增加,30～40 L/min连续鼓气时膜通量随鼓气流量上升而减小;连续鼓气能提高真空膜蒸馏通量,鼓气流量宜控制在30 L/min.     

“绕射积分偏移”的成象原理及提高其偏移剖面质量的探讨

“绕射积分偏移”的过程一直都是用绕射波收敛理论来描述的.但是这个理论不能解释为什么经过“绕射积分偏移”的剖面会有信噪比降低和弧形干扰的现象.在这时,我们用一个简单的数学模型,并理想化了一些条件,弄清了“绕射积分偏移”成像的真正原理.我们发现在任一CDP点下面的反射界面点的位置应与某一双曲线的顶点时间相当,这个双曲线正好处在与相应的反射t_0剖面上各道波至所形成的直线相切的位置上.在此结果的基础上,本文提出了减少干扰和改善剖面质量的有效措施.我们希望它能尽早为实际工作所采用.另外,本文也对目前流行的几种类型的所谓“克希霍夫积分偏移”进行评述并指出它们的缺点.     

混联电网背景下一起交流母线故障分析

在特高压交直流混联电网背景下,特高压交流元件故障的影响范围扩大、故障性质升级,对特高压交直流混联电网运行与控制提出了更高的要求.文章根据一起典型的交流母线故障的保护动作情况,结合故障定位与诊断,分析了交直流混联电网下母线故障对线路输出功率和直流换相的影响.     

Preparation of hyperbranched polymers by atom transfer radical polymerization

A cheap acrylic AB* monomer, 2‐(2‐chloroacetyloxy)‐isopropyl acrylate (CAIPA), was prepared from 2‐hydroxyisopropyl acrylate with chloroacetyl chloride in the presence of triethylamine. The self‐condensing vinyl polymerization by atom transfer radical polymerization (ATRP), a “living”/controlled radical polymerization, has yielded hyperbranched polymers. All the polymerization products were characterized by proton nuclear magnetic resonance spectroscopy (¹H NMR). CAIPA exhibited distinctive polymerization behavior that is similar to a classical step‐growth polymerization in the relationship of molecular weight to polymerization time, especially during the initial stage of the polymerization. However, a significant amount of monomer remained present throughout the polymerization, which is consistent with typical chain polymerization. Also, if a much longer polymerization time was used, the polymer became gel. As a result of the unequal reactivity of group A* and B*, the polymerization is different from an ideal self‐condensing vinyl polymerization: the branch structures of polymers prepared depend dramatically on the ratio of 2,2'‐bipyridyl to CAIPA. Hyperbranched polymers exhibit improved solubility in organic solvent, however, they have lower thermal stability than their linear analogs. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2114–2123, 2002     

面源污染中磷流失多重影响因素主成分分析

为全面了解对美国中部Illinois州具有浅层排水系统的轮作农业地区的面源污染问题,利用主成分分析方法及多元线性回归,对Little Vermillion River流域磷流失影响因素主成分进行分析.结果表明,磷流失的影响因素基本分为3大主成分:一是生物主成分,包括温度、植被类型、覆盖因子、生物量、散蒸量;二是水力主成分,降雨及流量;三是人为干扰主成分,施肥量及耕作内容.其中水力主成分对流失的影响最大,尤其是对浅层排水中磷流失的影响.     

损伤变量对复合材料损伤演化过程的影响分析

复合材料层合板损伤模型中的刚度退化需要通过损伤变量来实现。针对通常采用的2种损伤变量定义,给出了统一表达式。此外,损伤刚度矩阵是损伤变量的函数,基于应变等效假设推导了三维损伤刚度矩阵,从而避免了对损伤刚度矩阵的人为假定。最后,通过复合材料层合板在冲击载荷作用下的数值模拟,讨论了损伤变量的2种定义对数值结果的影响,表明损伤变量的不同定义对分层和基体损伤分布存在一定的影响,对冲击载荷的影响不大。建议在复合材料损伤模拟中,应予关注损伤变量。     

计及源-荷多灵活备用资源的随机优化调度

大规模新能源并网给电力系统的调度运行带来了新的挑战。为缓解系统的备用压力,提出一种计及源-荷多灵活备用资源的随机优化调度方法。首先,基于场景生成方法建立可变场景模型,考虑了风电并网容量和光伏并网面积对新能源出力不确定性的影响。其次,建立电力系统中多种灵活资源的备用模型:在源侧,分别建立常规机组和风电/光伏的备用模型,并考虑了风电/光伏备用的不确定性;在负荷侧,引入激励型需求响应,对需求侧备用进行建模。然后,基于两阶段随机优化方法建立备用调度模型。该模型考虑了日前的运行和备用决策以及日内不确定场景下的弃风、弃光以及切负荷风险。最后,基于改进的IEEE RTS-24测试系统验证了所提模型的有效性。     

BPEL流程监视的可视化实现

When a BPEL process is executed, it is necessary to dynamically monitor the process. BPEL is a executable language, which is not suitable for visual monitoring. On the other hand, BPMN is designed to visually describe business process and is more intuitive for monitoring. To visually monitor a BPEL process, transformation from BPEL to BPMN is necessary. However, current study of transformation from BPEL to BPMN does not support the transformation of "link" activity. Besides, no work has been done to add supplementary information into BPMN during transformation. In this paper, we transform nested BPEL process into a flat BPMN process graph without hierarchy through applying a flattening strategy. Especially, we analyze various scenarios of the transformation of link activity, and provide a method to deal with it. Besides, we analyze the mapping between BPEL activities and BPMN graph, through which we found out that some supplementary information cannot automatically obtained from BPEL process. These supplementary information need to be added during transformation. At the end of this paper, we present the structure of our monitoring tool which is based on our transformation algorithm.     

用于矢量水听器的压电单晶面剪切模式加速度计设计

面剪切振动模式产生于[011]极化方向zxt-45°切型的压电单晶,因具有高压电系数、高机械品质因数、高柔顺系数和低串扰效应等优点,故面剪切模式成为小尺寸、高灵敏度压电传感器的理想选择,在矢量水听器中有着良好的应用前景。该文通过分析面剪切模式振动原理,推导了面剪切模式压电加速度计的电压灵敏度表达式。利用有限元分析软件构建面剪切加速度计模型,研究结构参数对面剪切压电加速度计电压灵敏度和谐振频率的影响规律,优化结构尺寸,最终仿真得到面剪切加速度计开路电压灵敏度为389.72 mV/g,工作频带为20 Hz~3 kHz,横向灵敏度小于3.45%。研究结果表明,与传统的剪切式加速度计相比,所设计的面剪切式加速度计在质量块质量降低50%的同时,电压灵敏度提高了11.6%,这为降低水听器的平均密度、提升水声探测性能提供了新思路。     

基于损伤容限设计的冶金桥式起重机疲劳寿命研究

以180t×24．85m冶金桥式起重机为研究对象,通过无损探伤发现桥架北主梁的下盖板上有裂纹,应用有限元分析和损伤容限设计方：去对起重机裂纹的疲劳寿命进行计算。结果表明,起重机裂纹扩展到临界尺寸需要大约5年的时间。