复合岩体的TBM破岩机理数值模拟

为了指导TBM刀盘刀具的研制和不同地质条件下刀盘刀具的选型,TBM破岩机理的研究成为核心。在TBM滚刀的作用下,岩体中裂纹的生成、扩展和连接规律是深刻理解TBM破岩机理的前提,因此,TBM滚刀破岩机理的研究具有重要的工程应用价值。目前,TBM滚刀破岩机理的研究主要集中在单一岩体中,但在TBM施工过程中会遇到各种复杂的地质条件。笔者采用离散元方法,研究了复合岩体的破岩机理,复合岩体中岩片的形成不同于单一岩体,其裂纹的最终连接是由起裂于复合岩体交界面上的微裂纹的扩展,将两滚刀之间的赫兹裂纹连接,最终形成岩片。因此,在一定情况下复合岩体更有利于TBM隧道施工。     

Influence of a high‐head dam as a dispersal barrier to fish community structure of the Upper Mississippi River

In river systems, high‐head dams may increase the distance‐decay of fish community similarity by creating nearly impermeable dispersal barriers to certain species from upstream reaches. Substantial evidence suggests that migratory species are impacted by dams, and most previous studies in stream/river networks have focused on small streams and headwaters. Here, we assess whether a high‐head dam (Lock and Dam 19; LD 19) on a large river, the Upper Mississippi River (UMR), substantially alters fish community structure relative to variability expected to occur independent of the dam's effect as a fish dispersal barrier. Using fish catch per unit effort data, we modelled the distance‐decay function for the UMR fish community and then estimated the similarity that would be expected to occur across LD19 and compared it with measured similarity. Measured similarity in the fish community above and below LD19 was close to the expected value based on the distance‐decay function, suggesting LD19 does not create an abrupt transition in the fish community. Although some migratory fish species no longer occur above LD19 (e.g., skipjack herring, Alosa chrysochloris), these species do not occur in high abundance below the dam and so do not drive variation in fish community structure. Instead, much of the variation in species structure is driven by the loss/gain of species across the latitudinal gradient. Lock and Dam 19 does not appear to be a clear transition point in the river's fish community, although it may function as a meaningful barrier for particular species (e.g., invasive species) and warrant future attention from a management perspective.     

一种基于深度信息的人头检测方法

针对目前人头检测方法对光线变化敏感和易受阴影干扰的问题,提出了一种基于深度图像的人头检测方法.首先通过运动目标检测,得到运动人员所在区域;然后对该区域使用改进的立体匹配算法,该匹配算法对传统的WTA匹配算法进行改进,只对强纹理点进行匹配,对弱纹理点只进行视差验证,并根据三角投影原理计算出深度图.由于深度图中人员与周围场景的深度分布不同,根据深度分布将人头区域提取出来,得到候选区域,最后将候选区域经过形态学运算并根据区域轮廓的特征来判断是否为人头.实验结果表明:该方法在不同光线环境条件下的检测正确率为94%以上,误检测率仅为5.77%,检测精度高,对光线和阴影的抗干扰性良好,能够很好地适应复杂环境.     

施工宽缝对整体式闸首底板的受力影响研究

鉴于整体式闸首底板在顺水流方向易出现裂缝,严重危害船闸的使用安全。本文提出的设置施工宽缝的施工方案可以有效改善整体式闸首底板开裂问题。首先运用ANSYS软件建立模型,对闸首结构进行有限元分析,进一步探索出施工宽缝对整体式闸首底板的应力与变形的影响,将应力计算结果转换成内力,最终研究出满足工程要求的最优合缝时间和设缝位置,从而为整体式船闸的施工提供参考。     

基于分簇的传感网虚拟MIMO协议

提出一种应用于无线传感网的新型分簇式虚拟MIMO协议。协议基于簇头轮换,避免大量重新分簇带来的拓扑维护开销,从而提高网络能量效率。在簇间路由中,提出一种新型的“跨跳”操作,以平衡网络中不同节点与簇的能耗和生命周期。仿真实验结果表明,该协议较现有的的虚拟MIMO在能耗总量和均衡上均具有更好的效果。     

Numerical simulation and optimization of the cylinder head water jacket based on the two-phase flow boiling heat transfer

Boiling heat transfer and the controllability of the thermal load of the cylinder head were studied. The thermodynamic phase change characteristics of the cylinder head coolant were considered and the mass, momentum and energy transfers between two phases were calculated with the interface transfer sub-models by using the computational fluid dynamics software CFX. Results showed that compared with the single-phase flow without considering the boiling heat transfer, the sub-cooled boiling heat transfer of the cylinder head was greatly increased. According to the results of the numerical simulation, an optimized structure of the water jacket was proposed. Finally, temperature and velocity of coolant, diameter of flow passage and mean bubble diameter that influences sub-cooled boiling were studied using the orthogonal experiment method.     

Head Orientation Stability of Underwater Snake-Like Robot Swimming

In prior research,the orientation of head of the snake-like robot is changed according to the sinusoidal wave. To solve this problem,we propose Central Pattern Generator( CPG)-based control scheme with head-controller to stabilize the head of the underwater snake-like robot. The advantage of the CPG-based control scheme with head-controller is that the head of the underwater snake-like robot is direct to the target orientation during swimming. The relation between CPG parameters and orientation stability of head is discussed.The adaptation of the proposed method to environment changes is tested. The influences of CPG parameters and hydrodynamic forces on the orientation offset of head are investigated. The target orientation( the input of headcontroller) with an experimental optimization is calculated through a convenient method. To prove the feasibility of the proposed methodology,the different swimming modes have been implemented in our simulation platform.The results show that the oscillation of head’s orientation is inhibited effectively,and the proposed method has strong adaptation to environment and CPG parameters changes.     

切削参数对锯片铣刀切削振动特性的影响研究

锯片铣刀切削加工过程中,普遍存在严重的振动问题.为研究锯片铣刀的切削振动特性,设计了多种切削条件下的锯片铣刀切削实验.在理论计算锯片铣刀固有频率的基础上,对实验结果进行了分析和讨论.结果表明:锯片铣刀切削系统的频率仅仅取决于系统的固有频率,基本不受切削参数的影响.因此,通过增加刀具系统的刚度或改变切削速度,使激振频率远离刀具系统的固有频率可有效降低和控制切削系统的振动.     

可调角度弯钻杆的研制

在处理井下事故特别是藏鱼头事故时,由于鱼头不居中,甚至贴在井径变化较大处,因此很难实施普通打捞。现场普遍采用可弯肘节和折弯钻杆的方式进行寻找落鱼,实施打捞,有可能多次折弯钻杆,造成浪费,甚至造成井下更复杂情况的发生。根据这一情况,设计了可调角度弯钻杆。可调角度弯钻杆由上接头、花键体、调整套、下接头等组成,通过调节调整套和花键体等机构,可实现弯钻杆0°-4°调节。已完成可调角度弯钻杆的样机制造,并在多口井中进行应用。结果表明,采用可调角度弯钻杆可有效实施藏鱼头打捞,井口调节方便,应用取得了成功;单井可节约近30万元。     

地下水源热泵含水层水头分布及温度场的模拟分析

为使地下含水层能量更好为实际工程所用,进一步保护地下水空间,通过对地下水源热泵系统地下含水层中渗流场的分析,建立一抽一灌(对井抽灌)系统和一抽两灌系统地下水渗流数值模型,应用数值模拟方法对地下含水层渗流场水头分布及温度场进行模拟分析。结果表明:在相同的运行周期内,一抽两灌系统温度场的影响半径相对较小,并且抽灌井周围的等水头线分布较疏,水头变化缓慢,更利于地下水的回灌。尽量使回水井远离取水井,可以有效避免热贯通现象的发生。