净水厂生产废水回用中丙烯酰胺的风险控制

以西安市某地表水厂为例,针对生产废水回用后出厂水中丙烯酰胺含量超标问题,进行了相关的风险控制研究.研究结果表明:对不同浓度的污泥,投加阴离子型和阳离子型PAM均能有效降低污泥比阻值,改善污泥的脱水性能,但使用阴离子型PAM,出厂水丙烯酰胺含量更低.综合考虑污泥脱水效果及脱水分离液中丙烯酰胺的残留量,采用阴离子型PAM,投药量在0.09～0.16g/L之间时,可有效控制出厂水中丙烯酰胺含量超标的风险.     

公路桥梁施工中预应力的应用

经济的发展离不开交通的完善。特别是当今时代,经济的高速发展对桥梁和道路建设的要求在不断提高。为了更好地、更安全地促进我国经济的进步,公路桥梁工程的质量至关重要。论文主要对公路桥梁预应力施工技术进行探讨,以期进一步促进我国桥梁建设和经济发展的进步。     

某大长宽比及大高宽比的筒体偏置高层结构设计

由于大高宽比、大长宽比、筒体偏置高层建筑结构和传统高宽比、长宽比的筒体结构受力特点不同,主要表现在两轴刚度差异较大、偏置墙体受拉等。首先对筒体与框架连接区域的楼板结构形式的方案进行比选,对比结果显示：梁板结构比厚板结构对提高刚度的效果更明显。结构设计时,通过加强底部加强区及以上部分重要墙体配筋,加强楼板薄弱相关部分配筋,结构主要指标、墙体偏拉、楼板应力、损伤等均能满足相关的规范要求,并满足既定的性能目标。     

An application of the shortest path algorithm for the identification of weak MHD mode

The identification of magnetohydrodynamic(MHD) modes is a crucial issue in the control of magnetically confined plasmas. This paper proposes a novel method for identifying the evolution of MHD modes from a signal with a low signal-to-noise ratio. The proposed method generates a weighted directed graph from the time-frequency spectrum and calculates the evolution of the mode frequency by solving the shortest path. This method addresses the limitations posed by the lack of data channels and the di...     

Power supply for generating frequency-variable resonant magnetic perturbations on the J-TEXT tokamak

To further research the response of the tearing mode(TM) to dynamic resonant magnetic perturbation(DRMP) on the J-TEXT tokamak, a modified series resonant inverter power supply(MSRIPS) with a function of discrete variable frequency is designed for DRMP coils in this study. The MSRIPS is an AC–DC–AC converter, including a phase-controlled rectifier, an LC filter, an insulated gate bipolar transistor(IGBT) full bridge, a matching transformer, three resonant capacitors with different capacitance values, and three corresponding silicon controlled rectifier(SCR) switches. The function of discrete variable frequency is realized by switching over different resonant capacitors with corresponding SCR switches while matching the corresponding driving frequency of the IGBT full bridge. A detailed switching strategy of the SCR switch is put forward to obtain sinusoidal current waveform and realize current waveform smooth transition during frequency conversion. In addition, a resistor and thyristor bleeder is designed to protect the SCR switch from overvoltage. Manufacturing of the MSRIPS is completed, and the MSRIPS equipment can output current with an amplitude of 1.5 kA when its working frequency jumps among different frequencies. Moreover, the current waveform is sinusoidal and can smoothly transition during frequency conversion. Furthermore, the transition time when the current amplitude rises from zero to a steady state is less than 2 ms during frequency conversion. By using the MSRIPS, the expected discrete variable frequency DRMP is generated, and the phenomenon of the TM being locked to the discrete variable frequency DRMP is observed on the J-TEXT tokamak.     

上海浦东张家浜生态清洁小流域建设探索与实践

生态清洁小流域建设是系统提升水环境、水生态和改善人居环境的重要手段。该研究以超大城市水系统治理现代化需求为发展导向,聚焦张家浜生态清洁小流域的防治体系、防治措施、防治新技术和方法、经典案例和治理成效等方面,探索特大型城市水土保持系统治理、复苏河湖生态的新路径,成为引领都市宜居与绿色发展典范。     

比拟法在矿区矿坑涌水量预测应用实例

通过工程实例，介绍比拟法计算坑涌水量的具体方法。     

知识库机制

<正> 未来十年,第五代计算机系统工程的主要目标之一是为建立具有智能管理的知识信息系统提供方法。第五代计算机系统主要内容是问题求解的知识。本文,我们叙述知识库基本机制的研究发展(R、D)计划。为了支撑知识信息处理系统获取知识,已计划设计一种知识表达系统。该系统包括知识表达语言、知识库编辑程序和调试程序。还期望有一种执行元推理的系统。为了看     

无铅焊接工艺及失效分析

综述了目前无铅焊接工艺回流焊和波峰焊的工艺特点,指出了焊接中存在的几大主要失效问题,包括开裂、焊点空洞、晶须和板材胀裂,并介绍了避免或减弱这些失效问题的方法。     

中浓度气力输送弯管压力降数值模拟研究

对于中等浓度气力输送90°弯管内的气固流动状态进行数值模拟研究,并对水平转垂直、垂直转水平,不同弯径比(R/D=1.5~6.0)的90°弯管,均匀和非均匀粉体颗粒流过弯管的压力降Δp进行了模拟计算。结果表明,在同一气体流速下,不同R/D的弯管的Δp变化显著;存在一个使Δp最小的R/D值。在模拟的条件范围内,弯管内粉体颗粒的速度分布随R/D变化。并讨论了不同R/D的粉体颗粒流动对弯管压力降及管壁磨损的影响。在同样操作条件下,对煤粉输送进行了弯管压力降数据模拟,其模拟计算结果与周建刚等人的试验结果吻合良好。