不同生长条件对铜绿微囊藻生长的影响

目前,愈演愈烈的水体富营养化现象给水处理工艺带来了十分严峻的考验。为了深刻理解水处理工艺中主要运行条件对铜绿微囊藻生长代谢的影响,试验以藻细胞个数和胞外分泌物浓度为指标,在长达30 d的试验周期内研究了藻细胞繁殖阶段中水温、光照和振动等参数与铜绿微囊藻生长代谢变化之间的相互联系。结果发现改变水温和水力学条件对藻细胞的生长代谢有着十分重要的影响。环境条件的改变（如提高水温和增加振动频率）虽然有利于藻细胞的灭活,但也可能导致胞外分泌物含量的激增,这对水处理效果有着严重负面影响。     

600（300）MW机组加热器系统事故分析和处理措施

分析了一例哈尔滨汽轮机厂汽轮机3#高加加热器疏水液位高、正常疏水管路振动的原因,针对类似情况,从高加疏水系统设备结构、系统运行方式等方面提出了相应的解决措施,解决了疏水管路的振动,保证了机组安全经济运行.并对另一例哈尔滨汽轮机厂600 MW机组轴封加热器水侧管束破裂,凝结水大量进入轴封加热器汽侧,满水后,进入轴封系统,进入汽轮机事故进行分析,提出轴封系统及其他系统如何进行排查,系统设置中存在类似的问题,采取相应措施进行整改的具体方法进行了介绍.     

二维超声振动辅助磨削氧化铝陶瓷的磨削力对比研究

冲击力、材料硬度的变化以及超声振动的施加方式是磨削力降低的主要原因。在普通磨削的基础上加入二维超声振动,分析磨削力的影响机制,在相同的磨削参数条件下,对氧化铝陶瓷进行普通磨削和二维超声振动磨削对比实验研究,分析工件进给速度、砂轮线速度、磨削深度对磨削力的影响。结果表明：二维超声磨削的法向、切向磨削力均小于普通磨削,磨削力降幅随着工件进给速度和砂轮线速度的增大而减小,随着磨削深度的增大而增大;普通磨削和二维超声磨削的法向、切向磨削力均随着工件进给速度和磨削深度的增大而增大,随着砂轮线速度的增大而减小。     

超声振动对含LPSO结构的Mg98Y1.0Ni0.5Al0.5合金显微组织与力学性能的影响(英文)

低Y、Ni含量的LPSO结构增强镁合金具有低成本、优异力学性能的特点。为进一步提升其综合力学性能,掺杂Al元素及熔体超声振动处理是可行的途径。通过扫描电子显微镜、能谱分析、透射电子显微镜、X射线衍射和纳米压痕测试研究掺杂Al元素后低Y、Ni含量的Mg98Y1.0Ni0.5Al0.5合金的显微组织,对比超声振动对显微组织与力学性能的影响。掺杂Al后LPSO结构的含量降低,且在块状LPSO结构相邻处析出圆整的Al₂NiY相。Al₂NiY相与LPSO结构和Mg基体在界面处均不共格。通过对熔体施加超声振动处理后,Al₂NiY相被有效细化为短片状,并均匀分布在基体中,阻碍微裂纹的产生和扩展,从而提高Mg₉₈Ni_0.5Y_1.0Al_0.5合金的力学性能。与未经超声处理Mg₉₈Ni_0.5Y_1.0Al_0.5合金相比,其极限抗拉强度和伸长率提升至187 MPa和7.9...     

滑块式球形转子泵的振动抑制研究

滑块式球形转子泵结构简单,无工作死点且一周双排量,适用于超微型液压泵,但旋转盘的往复式运动和流量脉动会造成振动加剧。对球形泵进行动力学建模,得到活塞的惯性力偶矩,以及旋转盘运动时产生的陀螺力矩。由力矩曲线可知整体力矩大小取决于陀螺力矩。建立球形泵的容积方程,对其用插值法取得流量变化曲线。采用多泵合成的减振措施,抵消陀螺力矩和流量脉动,降低振动。通过ADAMS-Vibration对整机在力矩作用下的振动响应进行仿真,MATLAB模拟多泵的流量变化曲线,多泵的振动幅值和流量脉动均大幅减小,证明减振措施的有效性。     

Tragverhalten von geschichteten Deckenelementen aus Normal‐ und Porenleichtbeton

Load bearing behaviour of layered ceiling elements made of regular and porous lightweight concrete Lightweight and efficiently bearing steel reinforced elements may be achieved through the application of regular and porous concrete in a three‐layer cross‐section. While exterior layers of higher strength carry bending moments, a lightweight core layer material holds up to shear stresses. In order to quantify the potential of this construction method, the bearing behaviour of 18 layered ceiling elements with six different geometries was investigated. The goals were both to identify different failure modes, as well as evaluate the suitability of commonly used calculation procedures. The following paper shows that an optimal usage of cross‐sections of ceiling elements can already achieved by using concrete with strengths between 5 MN/m² and 20 MN/m². The efficiently bearing elements are characterized by the fact, that both the concrete, the reinforcing steel and the layer's interface are highly stressed both under pressure and tension. The tested specimens showed both a tensile bending and interface failure with a partly very high utilization of the flexural compressive zone.     

Use of artificial neural network to evaluate the vibration mitigation performance of geofoam-filled trenches

Development activities in a city often generate ground vibration that can cause discomfort to the occupants in nearby buildings, disturbances to the activities undertaken in the buildings and possible damage to nearby structures. This ground vibration is caused by construction activities such as pile driving, ground compaction etc., and road and rail traffic. The use of trenches has been an effective way to mitigate the adverse effects of such ground vibration. The effectiveness of the trench depends on many parameters including the properties of the vibration source, soil medium and trench in-fill material, trench dimensions and the requirements of the receiver. The process of selecting an effective trench for vibration mitigation can therefore become complex due to the influence of a number of parameters and their wide range of values. This paper investigates the use of artificial neural network (ANN) as a smart and efficient tool to predict the effectiveness of geofoam-filled trenches to mitigate ground vibration. Towards this end, a database is developed from an extensive study on the effects of the controlling parameters through numerical simulations with a validated finite element (FE) model. At a certain distance from the vibration source, a geofoam-filled trench is introduced to evaluate the efficiency of vibration mitigation with changes in key parameters such as excitation frequency, amplitude of load, trench configuration (i.e. depth and width), soil shear wave velocity, soil density and damping ratio. These were selected as the input parameters for the ANN while amplitude reduction ratio and peak particle velocity (PPV) were considered as outputs. A multilayer feed forward network was used and trained with the Levenberg-Marquardt algorithm. Neural networks with different configurations were evaluated by comparing coefficient of determination (R²) and mean square error (MSE). The optimum architecture was then used to predict previous results, which revealed the accuracy and the effectiveness of the ANN approach. The findings of this study will provide useful information for vibration mitigation using geofoam-filed trenches.     

天津滨海Z2号线盾构隧道接头螺栓比选及抗弯刚度研究

针对不同形式螺栓接头,充分考虑复杂接缝间的不连续性及接头预紧力,以天津滨海Z2号线盾构隧道管片纵缝为研究对象,分析比较了直螺栓、斜螺栓和弯螺栓三种接头在不同弯矩和轴力条件下对管片接缝力学性能的影响。根据分析结果给出了三种螺栓接头的适用性,以及三种螺栓接头在不同埋深、弯矩作用下的抗弯刚度建议值。研究结果表明:螺栓形式对螺栓最大受力位置影响很小;螺栓拉应力和接缝张开量随轴力的增大而减小,但接头抗弯刚度均随之增大;螺栓拉应力、接缝错台量和张开量随弯矩的提升而增大,但接头抗弯刚度随之减小。     

小半径平面曲线隧道地震响应分析

基于某实际工程,建立了小半径平面曲线隧道三维分析模型,探讨其在单向水平激振下的地震响应规律。其中考虑了隧道弯曲角度、地震动幅值和类型等因素的影响。通过分析得出了小半径平面曲线隧道的地震响应规律:①响应幅值方面,横向抗震段的响应最大,曲线段其次,纵向抗震段最小;②响应差异方面,曲线部分对隧道加速度影响较小,主要影响隧道的变形;③震动能量方面,随着隧道从横向抗震逐渐过渡到纵向抗震,其震动能量逐渐降低。     

充气式张弦穹顶结构静力性能与稳定性研究

基于Tensairity结构概念设计了跨度80m的充气式张弦穹顶结构,建立了精细化的有限元模型,实现了零状态、初始态和荷载态的全过程数值模拟,分析了结构在不同工况下的静力性能和稳定性。研究表明：该结构体系具有良好的静力性能和稳定性,内压在1~4kPa范围内即可保证充气气囊对刚性构件的支撑作用;整体结构没有出现明显的弹性失稳问题,导致结构失效的主要原因是构件的材料破坏和膜材的应力松弛;当内压较低时,结构因上层膜面松弛而失效;当内压较高时,结构因刚性上弦大范围进入塑性状态而破坏。自振特性分析表明,该结构的整体刚性较大,但绕中心轴的抗扭刚度较为薄弱。