An accelerated scheme with high quality mesh based on Lloyd iteration

High quality mesh plays an important role for finite element methods in science computation and numerical simulation.Whether the mesh quality is good or not,to some extent,it determines the calculation results of the accuracy and efficiency.Different from classic Lloyd iteration algorithm which is convergent slowly,a novel accelerated scheme was presented,which consists of two core parts:mesh points replacement and local edges Delaunay swapping.By using it,almost all the equilateral triangular meshes can be generated based on centroidal Voronoi tessellation(CVT).Numerical tests show that it is significantly effective with time consuming decreasing by 40%.Compared with other two types of regular mesh generation methods,CVT mesh demonstrates that higher geometric average quality increases over 0.99.

High-order schemes for predicting computational aeroacoustic propagation with adaptive mesh refinement

High-order schemes based on block-structured adaptive mesh refinement method are prepared to solve computational aeroacoustic （CAA） problems with an aim at improving computational efficiency. A number of numerical issues associated with high-order schemes on an adaptively refined mesh, such as stability and accuracy are addressed. Several CAA benchmark problems are used to demonstrate the feasibility and efficiency of the approach.

Removal of Volatile Organic Compounds (VOCs) Mixture by Multi-Pin-Mesh Corona Discharge Combined with Pulsed High-Voltage

Removal of single component and binary mixtures of benzene and m-xylene using a multi-pin-mesh reactor was studied to find the decomposition characteristics, carbon balance and CO2 selectivity. The decomposition rate of benzene in mixture was approximately 16% lower than that of single component benzene. However, the decomposition rate of m-xylene in mixture was slightly higher than that of single component m-xylene. Carbon balance of the mixture decomposition process achieved a lower level than that of single component benzene/m-xylene. Increase in the specific input energy was helpful to improve CO2 selectivity in the single component decomposition process, while the specific input energy had a negligible effect on CO2 selectivity in the mixture decomposition process. By changing the oxygen content in background gas, we found that different types of radicals showed different reaction activities toward benzene and m-xylene. Benzene was more likely to react with nitrogen-containing radicals, while m-xylene was more likely to react with oxygen-containing radicals.

High Scalp Tension after Three-Dimensional Titanium Mesh Repair for Skull Defect: 2 Case Reports

Rationale: The three-dimensional (3D) computer-made titanium mesh is widely used in the skull repair for those patients receiving decompression of the bone flap. It can restore normal anatomy to a greater extent and make a better appearance. Case Presentation: We reported two cases of patients admitted to our hospital who have experienced high scalp tension after skull repair. At first, these two patients underwent decompression of the bone flap, and the physical examination results showed a defect of skull. No neurological symptoms and signs were found. The 3D computed tomography (CT) reconstruction of skull was performed, and then the skull repair with 3D titanium mesh was conducted. But because of high scalp tension, they underwent a second operation, during which we re-trimmed and reduce the arc of the titanium mesh. The scalp incision of both patients healed well and no titanium mesh was exposed. Both patients have a good prognosis. Lessons: We highlight that the high tension of scalp due to overstretching after 3D titanium mesh repair for skull defect should be paid much attention to. Trimming and reducing the arc of titanium mesh is an effective treatment for this situation.

High-Order Leap-Frog Based Discontinuous Galerkin Method for the Time-Domain Maxwell Equations on Non-Conforming Simplicial Meshes

A high-order leap-frog based non-dissipative discontinuous Galerkin time-domain method for solving Maxwell's equations is introduced and analyzed.The proposed method combines a centered approximation for the evaluation of fluxes at the interface between neighboring elements,with a Nth-order leap-frog time scheme.Moreover, the interpolation degree is defined at the element level and the mesh is refined locally in a non-conforming way resulting in arbitrary level hanging nodes.The method is proved to be stable under some CFL-like condition on the time step.The convergence of the semi-discrete approximation to Maxwell's equations is established rigorously and bounds on the global divergence error are provided.Numerical experiments with high-order elements show the potential of the method.

High-order discontinuous Galerkin solver on hybrid anisotropic meshes for laminar and turbulent simulations

Efficient and robust solution strategies are developed for discontinuous Galerkin （DG） discretization of the Navier-Stokes （NS） and Reynolds-averaged NS （RANS） equations on structured/unstructured hybrid meshes. A novel line-implicit scheme is devised and implemented to reduce the memory gain and improve the computational eificiency for highly anisotropic meshes. A simple and effective technique to use the mod- ified Baldwin-Lomax （BL） model on the unstructured meshes for the DC methods is proposed. The compact Hermite weighted essentially non-oscillatory （HWENO） limiters are also investigated for the hybrid meshes to treat solution discontinuities. A variety of compressible viscous flows are performed to examine the capability of the present high- order DG solver. Numerical results indicate that the designed line-implicit algorithms exhibit weak dependence on the cell aspect-ratio as well as the discretization order. The accuracy and robustness of the proposed approaches are demonstrated by capturing com- plex flow structures and giving reliable predictions of benchmark turbulent problems.

High-order Lagrangian cell-centered conservative scheme on unstructured meshes

A high-order Lagrangian cell-centered conservative gas dynamics scheme is presented on unstructured meshes. A high-order piecewise pressure of the cell is intro- duced. With the high-order piecewise pressure of the cell, the high-order spatial discretiza- tion fluxes are constructed. The time discretization of the spatial fluxes is performed by means of the Taylor expansions of the spatial discretization fluxes. The vertex velocities are evaluated in a consistent manner due to an original solver located at the nodes by means of momentum conservation. Many numerical tests are presented to demonstrate the robustness and the accuracy of the scheme.

混杂网格增强超高性能混凝土双向板的弯曲性能

网格增强超高性能混凝土(ultra-high performance concrete,UHPC)具有轻质、高强、耐久性好等特性,已应用于薄壁结构和工程加固领域,但单一网格很难实现高效的增强增韧效应.为研究混杂网格增强UHPC双向板的抗弯性能,对3个钢丝网格与玻璃纤维网格混杂增强UHPC板、3个钢丝网格与玄武岩纤维网格混杂增强UHPC板、6个单一网格增强UHPC板和1个无网格UHPC对照板进行弯曲试验,研究网格种类、总层数及铺层方式对其破坏形态、承载能力和弯曲韧性的影响.结果表明:与单一钢丝网格板和单一玻璃纤维网格板相比,钢-玻璃纤维网格混杂板开裂后表现更显著的硬化现象,在连续网格与混杂短纤维协同效应下,板呈现多裂缝破坏模式,延性较理想.铺设2层网格时,钢-玻璃纤维网格混杂板的承载能力较单一钢丝网格板提升23.7%,且其在20 mm挠度处的残余承载力较单一玻璃纤维网格板提升28.2%;钢-玄武岩纤维网格混杂板峰前阶段的能量吸收值和20 mm挠度处的残余承载力均优于单一玄武岩纤维网格板.网格总层数为3层时,与单一玄武岩纤维网格板相比,2层钢丝网格与1层玄武岩纤维网格混杂增强板在峰前挠度为2 mm时的能量吸收值提高了21.6%,20 mm挠度处的残余承载力提高了42.6%.钢-玻璃纤维网格混杂板的网格强度利用率最理想,其承载能力、能量吸收值及弯曲韧性指标均高于钢-玄武岩纤维网格混杂板.最后,考虑网格强度有效利用率建立了混杂网格增强UHPC双向板抗弯承载力理论公式,适用性良好.

嵌套高分辨率网格对我国东南沿海登陆台风模拟的影响

嵌套高分辨率网格对台风模拟有十分重要的影响。基于COAWST(coupled ocean atmosphere wave sediment transport)模式,针对登陆广东、海南的11个台风,设计了2组模拟方案。一组是在9 km分辨率下嵌套3 km分辨率网格,另一组是采用单层9 km分辨率网格。将模拟结果与中国气象局热带气旋资料中心发布的最佳路径数据进行对比,以探讨嵌套高分辨率网格是否可以提高台风模拟的准确性。从台风路径的模拟结果来看,在9 km分辨率下嵌套3 km分辨率网格对台风路径模拟的误差较小,而单层9 km分辨率网格模拟的台风路径误差较大。通过对比两组方案模拟的台风路径、强度和结构,在模拟区域中使用嵌套高分辨率网格方案的模拟准确性有所提高。两种方案模拟的风场以及副热带高压十分接近。相比于单层网格,嵌套了高分辨率网格方案模拟的台风路径、强度误差更小,台风眼更小,位涡更强。

双氢氧化物修饰镍金属网提升电磁屏蔽性能

针对镍金属网在电磁屏蔽中的低吸收效能(SE_(A))和较高反射(SE_(R))问题,通过电沉积方法在镍金属网(NM)表面负载镍铁双氢氧化物(NiFe LDH)纳米片,旨在提升材料的以吸收为主的屏蔽性能。处理后材料的微观结构和电磁特性得到显著改善,尤其是在X波段内实现了优异的56 dB的SE_(A)和2 dB的SE_(R)。同时,NiFe LDH纳米片优化了介电常数、磁导率、衰减常数和阻抗匹配,证明其在电磁屏蔽领域的广泛应用前景,合成简单且成本效益高。

大功率干扰监测下无线Mesh网络扰动容错方案

在无线Mesh网络中,常受到大功率动态干扰,MAC层协议扰动容错方案设计是提高Mesh网络抗大功率干扰,提高网络监测性能的关键技术。传统方法采用无线Mesh路由修复算法实现扰动容错方案设计,MAC层协议容错性能不好。提出一种基于自适应神经模糊系统网络动态大功率干扰监测的无线Mesh网络扰动容错方案,进行无线Mesh网络设计,在无线Mesh网络中,任何无线设备节点都可以同时作为AP和路由器,网络中的每个节点都可以发送和接收信号,在Sink对进行数据融合,实现大功率干扰监测数学模型构建。采用自适应神经模糊系统进行Mesh扰动容错方案设计,改进大功率干扰监测下无线Mesh网络扰动容错方案,提高Mesh网络抗大功率干扰能力。仿真实验表明,该方法具有较好的鲁棒性,该容错方案得到的网络生命周期延长了1.24倍和1.39倍,节省了能量,延迟了网络生命周期,保证无线Mesh网络系统的稳定性和高效性。

逼近误差有界的相容性高阶网格生成

文中提出了一种构造逼近误差有界的高质量相容性高阶网格的方法。给定两个定向的、拓扑同构的三角形网格和一组稀疏的对应点,此方法包含两个步骤:(1)生成满足误差有界的相容性高阶网格;(2)在确保逼近误差总是有界的前提下,降低网格的几何复杂度,并在该过程中通过优化控制顶点来降低相容性网格之间的扭曲以及与原始网格之间的几何近似误差。第一步先生成满足误差有界的相容性线性网格,然后升阶为高阶网格。第二步通过迭代地执行基于边长的重新网格化和增加相容性目标边长场,有效地降低了网格几何复杂度。从切空间的角度,推导出了3DBézier三角形之间映射的雅可比矩阵,从而可以有效地优化扭曲能量。通过对扭曲能量和几何近似误差能量的优化,有效地降低了相容性网格之间的扭曲以及相容性网格与原始网格之间的几何近似误差。通过大量实验,证明了此方法对于构造误差有界的高质量相容性高阶网格的有效性和实用性。

高目数氢氧化镁在PVC能源线缆中的应用

基于无机阻燃剂的高效阻燃和抑烟特性,采用机械法和风选相集合的方法制备了高目数氢氧化镁(MH),并将其添加到聚氯乙烯(PVC)能源线缆中制备成复合材料。利用热失重仪、极限氧指数、烟密度测试箱等对该电线电缆的热性能、燃烧性能、烟密度等物理性能进行了测试,并且采用拉曼光谱仪、扫描电镜和能谱仪对最终的燃烧残炭进行了相关检测。研究结果表明,高目数MH的添加能有效地提高复合材料的热稳定性,T5%和T50%分别提升了3.1%和39.8%,且能够显著提高燃烧后的残炭率。同时,也能够在一定程度上提升PVC复合材料的阻燃抑烟特性,LOI值提升了4.8%,最大烟密度和烟密度等级分别降低了20.9%和29.7%;高目数MH的添加还能够有效地改善残炭的晶化结构及有序化程度,对于炭层的力学强度有提升效果,即能够更有效地抵抗热流和质流的传递;另外,其高目数MH的添加使炭层表面更为致密连续,提升了凝聚相阻隔效果。综上所述,物理法制备的高目数MH在能源线缆中存在较大的应用潜力。

基于Wave Mesh的煤仓煤位监测系统

设计了一种基于Wave Mesh的无线测量系统。系统采用26 GHz高频雷达式物位传感器采集煤位数据,雷达传感器将微波信号通过自身的电子线路部分自动转换成煤位信号,并将输出的煤位信号送入STM32F104单片机微处理器进行转换、存储,通过Wave Mesh无线自组网技术实现测量装置与上位机的远距离无线传输。系统的应用情况表明:设计的煤仓煤位测量系统能够方便工作人员实时监测煤位的变化,及时调节输煤机的开关,控制煤位在一个正常的范围内,确保矿井工作的安全正常运行。

无线Mesh网络的小型化研究

介绍无线Mesh网络的概念。根据Mesh网络的结构、特点及应用,研究其技术方式及所需条件,找出其在宽带降低、低时延、无线干扰方面存在的主要问题,并提出相应的解决方案。

宽带无线Mesh在输电线路在线监测的应用研究

从智能输电线路在线监测业务及通信需求分析出发,结合无线Mesh通信技术特性,提出高可靠性无线Mesh系统建设方案及输电线路在线监测系统塔上供电方案,为宽带无线Mesh在输电线路在线监测中的应用提供参考。在输电线路在线监测应用中,通过具有多跳组网的高可靠性宽带无线Mesh技术,采用双链路备份方案实现高压输电线路的宽带无线网络覆盖,可有效提高输电线路无线网络健壮性,实时监控电力输电线路及杆塔运行状态。

面向高深宽比微细嵌入式金属网格结构的选择性镀铜工艺

高深宽比微细嵌入式金属网格结构具有出色的光电性能和机械稳定性,可广泛应用于柔性触摸/显示器、太阳能电池、智能窗户等领域,但是传统的制备方法存在难以形成高深宽比结构、分辨率不足或材料利用率低等问题。借助电流体喷墨打印高分辨率按需喷印的优势结合选择性镀铜的特点实现高深宽比微细嵌入式金属网格的制备。通过实验研究,揭示了镀液温度、铜离子质量浓度、电流密度、电镀时间等参数对铜生长的速率和截面质量的影响规律,并对比了电镀和化学镀的优劣。结果表明,在电流密度约为1.5 A/dm^(2)时,电镀铜15 min能够实现线宽为10μm、深宽比为1的微细凹槽结构内金属铜的完全填充。最后,通过优化后的镀铜工艺参数结合电流体喷印,制备了线宽为10μm、深宽比为1、周期为800μm的28 mm×60 mm的嵌入式金属网格,其透过率(可见光波段550 nm处)为87.3%,方阻约为0.26Ω/□,品质因数(FOM)达到10 318,达到行业较高水准,可为高性能柔性光电子器件的制备提供新途径。

十叠层模块化高频筛分机的技术研究及工业应用

介绍了十叠层高频筛分机的基本原理、结构特点及主要性能参数,分析了十叠层高频筛分机的技术优势;应用结果表明,十叠层高频筛分机具有物料处理量大、筛分效率高、运行稳定,而且噪声低、维护量小的优势,其应用可带来显著的经济与社会效益。

高应力软岩巷道差异化协同支护技术研究

为解决高应力软岩巷道的支护与底鼓治理技术难题,保证巷道安全使用,对杨河煤业31151回风巷底抽巷复杂采动影响下巷道支护失稳及破坏机理进行分析,采用数值模拟技术进行围岩稳定性分析,研究高应力软岩巷道底鼓机理围岩控制技术,并提出针对性的锚网索强化支护方案及底板锚网索+注浆支护技术方案。经现场实践,两段巷道受采动影响后,巷道最大离层深度1.8 m,最大位移量为210 mm,最大底鼓量为230 mm,所有最大变形量均在设计允许变形范围内,支护强度满足巷道支护要求。

基于室外无线Mesh网络的应急通信技术应用

针对在电力应急通信中对于数据传输的可靠性、传输带宽等方面的要求,而无线Mesh网络作为一种无线自组织网络,以其组网灵活方便、可靠、自愈性强等特点,成为了能够在突发状况下支持应急通信的有效技术。文中在对无线Mesh网络应急通信系统建设模式及终端部署方案进行分析与研究的基础上,给出了无线自组织网络应急通信系统整体网络的各组成部分、系统结构及功能设计方案,并针对电力应急场景需求和特点,对具体无线Mesh网络结构进行了分析和设计。仿真实验的结果验证了该无线Mesh网络能够满足应急通信中对网络稳定性和高带宽的需求。