Ultrasonic tomographic velocimeter for visualization of axial flow fields in pipes

An ultrasonic tomographic velocimeter to provide quantitative images of axial flow fields in pipes is developed and presented in this work. To detect the flow in various directions and positions, a novel transducer configuration strategy is proposed. All-in-one transducers are mounted in two sectional planes of the pipe. In each plane, N transducers are equally spaced along the circumference. Overlapped propagation paths are introduced by the configuration strategy, and the influence of the vortex flow can be eliminated theoretically by averaging the line velocities of the overlapped paths. To achieve a fast detection speed, the projection data is collected via an electrical scan in a fan-beam mode. After rearrangement and interpolation of the projection data, the parallel beam filtered back projection (FBP) algorithm is implemented to reconstruct the axial flow field. Numerical simulations with the theoretical velocity profiles were performed. The compensation method for the vortex flow is proved to be effective and necessary, and the number of transducers required for reconstruction of common flow profiles was estimated. Accordingly, an ultrasonic tomographic velocimeter consisting of 2×12 transducers was fabricated. Experiments were conducted in the straight pipe and downstream of a single bend pipe and compared with the computational fluid dynamics (CFD) simulation results. As demonstrated, the ultrasonic tomographic velocimeter was capable of visualizing both symmetric and asymmetric axial flow fields with high reliability.     

Groundwater exploration using resistivity and magnetic data at the northwestern part of the Gulf of Suez,Egypt

The present study aims to investigate the ground water accumulations present in the area located west of the Gulf of Suez, to face the new urbanization settlements of industrial national projects in the study area using geoelectrical and magnetic measurements. Magnetic data interpretation was carried out using the RTP magnetic data (or, through analyzing the RTP aeromagnetic map) to determine the depth to the surface of basement rocks and delineate the trends of structural elements. The results of magnetic interpretation indicated that the depth to the basement surface is ranging from 1200 to 3500 m and the trends of encountered structural elements are mainly NE–SW, NW–SE, NNW–SSE and E–W directions. Seventeen vertical electrical soundings of Schlumberger configuration were measured with AB/2 ranging from 1.5 m to 1500 m at the southern part of the study area. The results of quantitative interpretation of geoelectrical data indicated that the subsurface section consists of six different geoelectrical units; the first unit represents the Quaternary gravel and sand of high resistivity values and thickness of about a few meters. The second geoelectrical unit exhibits moderate resistivity values ranging from 23 to 100 ohm m and thickness ranging from 4.5 to 67 m which represents the fresh water aquifer in the study area, while the lithology of this layer consists of sandstone and limestone which belongs to the Upper Miocene. The third geoelectrical unit is composed of sandy clay and limestone which belongs to the Middle Miocene deposits and shows low resistivity values ranging from 6 to 7 ohm m and thickness ranging from 44.5 m to 66 m. This third layer represents the second aquifer (brackish water). The fourth geoelectrical unit consists of limestone and clayey limestone which belongs to the Lower Miocene deposits and exhibits moderate resistivity values ranging from 16 to 33 ohm m, while the thickness of this unit ranges from 47–102 m. This layer represents the third aquifer (brackish water). The fifth geoelectrical unit reveals very low resistivity values of about 2–5 ohm m and consists of clay and sandstone of the Oligocene and Upper Eocene deposits. The sixth geoelectrical unit is the bottommost unit in the studied subsurface section and exhibits moderate resistivity values in a range of about 22–35 ohm m and consists of limestone of the Middle Eocene deposits.     

有孔内基础平台的竖直孔空心砖结构设计探讨

孔内基础平台设置在现有模数空心砖孔洞的上部,在孔洞内形成小平台,其能阻止砂浆掉落孔洞内,使空心砖的保温功能得以实现。孔内基础平台的设置将砖缝层平面摩擦改变为曲面摩擦,每一个孔洞的孔内基础砂浆与砖缝层面砂浆合为一体,砖缝层面摩擦力提升,墙体抗震能力提升。     

Passive fuel cell/lithium-ion capacitor hybridization for vehicular applications

Electric recreational vehicles represent a new challenge in terms of power supply systems compared to the current light-duty electric vehicles, which achieve high performance and long-range. The recreational vehicles need to heed the limited dimension requirements while assuring the high requested power. This paper proposes an integration of Lithium-Ion Capacitor (LIC) with Fuel Cell (FC) without any power electronic device for a three-wheel electric motorcycle. Unlike other hybrid power supply systems, the proposed FC-LIC passive configuration is lighter, compact, more efficient, and simpler to implement. Due to the different impedance of the components the system is self-management, in which FC supplies the average power component and LIC operates as a low-pass filter. In this respect, a simulator is built based on experimental tests to study the system performance in terms of hydrogen consumption and FC degradation. Subsequently, the system is tested under three standard motorcycle driving cycles at three different FC system lifespan stages. The obtained results demonstrate that a passive topology can supply the requested power along different FC stages of life and reported just an increment of 12% of hydrogen consumption at the oldest condition compared to the new condition.     

高校网络安全建设的探索与思考

The construction of cybersecurity is an important part of the information construction in university. It is an indispensable condition to help the information construction and a strong guarantee to serve the information support of teachers and students in uni- versity. The cybersecurity environment, atmosphere and guarantee ability of university need to be improved. Based on the related work and achievements of cybersecurity construction, some general schemes are put forward to provide reference for cybersecurity construction in university.     

Team O2AS' approach for the task-board task of the World Robot Challenge 2018

ABSTRACT

In this paper, we describe the approach of Team O2AS to complete the task-board task of the World Robot Challenge 2018, held in Tokyo. We use a custom gripper and graspable tools with in-built compliance to work with various kinds of parts, increase robustness against uncertainties, and to avoid complicated control strategies. The robots are able to finish all the sub-tasks without the need to exchange grippers. The main idea is to use mechanical compliance and self-centering mechanisms to deal with uncertainty. This is achieved by aligning the objects using either the gripper and tools, or by the design of the robot motions.     

几种多态含能材料构型转变的DFT研究

为了从分子层面上对含能材料不同分子构型间的转变情况有一个直观认识,借助Gaussian 09软件,运用密度泛函理论(DFT),采用TS算法搜寻β-RDX→α-RDX、γ-HMX→β-HMX、ε-CL-20→β-CL-20及β-FOX-7→α-FOX-7在分子构型转变过程中的过渡态结构,确定了它们的构型转变过程;并通过计算吉布斯自由能随构型转变路径的变化,比较多态含能材料分子构型转变的难易程度。结果表明,由亚稳晶型到稳定晶型的转变首先会越过过渡态,克服自由能能垒转变为亚稳态结构,实现β-RDX→α-RDX、γ-HMX→β-HMX、ε-CL-20→β-CL-20及β-FOX-7→α-FOX-7分子构型转变分别需要克服的自由能能垒分别为5.25、22.21、9.69和10.24kJ/mol。因此,常温常压下β-RDX→α-RDX、γ-HMX→β-HMX、ε-CL-20→β-CL-20及β-FOX-7→α-FOX-7构型转变的难度大小排序为:HMX>>FOX-7>CL-20>RDX。     

真空热处理炉布料矩阵优化仿真分析

为了获得更高的加热效率和更好的温度均匀性,采用有限元软件建立了真空热处理炉加热过程仿真模型,并耦合PID算法用于温度控制。通过与实测温度对比,验证了仿真模型的准确性。借助该模型,模拟研究了布料矩阵对两种典型形状零件在真空热处理炉内加热特性的影响。模拟装炉时基于零件几何形状特征,对圆棒形工件采用顺排、叉排和环形排列3种形式,对圆盘形工件采用横排式和竖排式。研究结果表明:尽管零件形状和数量相同,但是随着布料矩阵的变化,加热效率和温度均匀性都会改变。对于圆棒形工件,采用环形排列不仅可以提高内部工件的加热速率,而且相较于叉排式可以将最大温差减小36 ℃;对于圆盘形工件,由水平式改为竖直式布料可以将最大温差由248 ℃减小至171 ℃。     

A finite line source simulation model for geothermal systems with series- and parallel-connected boreholes and independent fluid loops

A model for the simulation of geothermal systems with parallel- and series-connected boreholes is presented. Mass and heat balance problems are formulated for each component in the system and are assembled into system-level problems. A third problem is formulated to account for heat transfer in the bore field, using the finite line source solution. This third problem is coupled to the system-level heat balance problem by an analytical solution of the heat transfer inside boreholes with multiple U-tubes. The simulation model allows for any number of independent fluid loops within the bore field or within individual boreholes and allows for combinations of specified inlet fluid temperatures and heat extraction rates in independent fluid loops. The model accounts for the axial variation of the fluid and borehole wall temperatures and heat extraction rates. The capabilities of the model are demonstrated through three example simulations.     

基于过程免疫力的动态电压恢复器优化配置

优质电力园区以最低成本满足用户对电能质量的特殊需求,成为解决电压暂降问题的新途径,已在国内外开展了广泛的试点应用。针对中国优质电力园区规划缺少经济高效的优化配置方法的实际情况,提出了一种基于过程免疫力的动态电压恢复器优化配置方法。基于工业过程电压暂降免疫力,以满足用户用电需求为目标,以治理设备购置费用最低为约束,采用遗传算法对园区供电质量分级制定动态电压恢复器的优化配置方案,实现工业园区电压暂降治理的经济性。对大型精密温控系统的电压暂降治理装置的优化配置方法进行仿真计算,验证了所提方法的有效性与经济性。