Splitting Based Scheme for Three-dimensional MHD with Dual Time Stepping

A new hybrid numerical scheme of combining an E-CUSP(Energy-Convective Upwind and Split Pressure) method for the fluid part and the Constrained Transport(CT) for the magnetic induction part is proposed.In order to avoid the occurrence of negative pressure in the reconstructed profiles and its updated value,a positivity preserving method is provided.Furthermore,the MHD equations are solved at each physical time step by advancing in pseudo time.The use of dual time stepping is beneficial in the computation since the use of dual time stepping allows the physical time step not to be limited by the corresponding values in the smallest cell and to be selected based on the numerical accuracy criterion.This newly established hybrid scheme combined with positivity preserving method and dual time technique has demonstrated the accurateness and robustness through numerical experiments of benchmark problems such as the 2D Orszag-Tang vortex problem and the3 D shock-cloud interaction problem.

Synthetical Efficiency-based Optimization for the Power Distribution of Power-split Hybrid Electric Vehicles

Now the optimization strategies for power distribution are researched widely, and most of them are aiming to the optimal fuel economy and the driving cycle must be preknown. Thus if the actual driving condition deviates from the scheduled driving cycle, the effect of optimal results will be declined greatly. Therefore, the instantaneous optimization strategy carried out on-line is studied in this paper. The power split path and the transmission efficiency are analyzed based on a special power-split scheme and the efficiency models of the power transmitting components are established. The synthetical efficiency optimization model is established for enhancing the transmission efficiency and the fuel economy. The identification of the synthetical efficiency as the optimization objective and the constrain group are discussed emphatically. The optimization is calculated by the adaptive simulated annealing （ASA） algorithm and realized on-line by the radial basis function （RBF）-based similar models. The optimization for power distribution of the hybrid vehicle in an actual driving condition is carried out and the road test results are presented. The test results indicate that the synthetical efficiency optimization method can enhance the transmission efficiency and the fuel economy of the power-split hybrid electric vehicle （HEV） observably. Compared to the rules-based strategy the optimization strategy is optimal and achieves the approximate global optimization solution for the power distribution. The synthetical efficiency optimization solved by ASA algorithm can give attentions to both optimization quality and calculation efficiency, thus it has good application foreground for the power distribution of power-split HEV.

Combined adaptive meshing technique and characteristic-based split algorithm for viscous incompressible flow analysis

A combined characteristic-based split algorithm and all adaptive meshing technique for analyzing two-dimensional viscous incompressible flow are presented. Tile method uses the three-node triangular element with equal-order interpolation functions for all variables of tile velocity components and pressure. The main advantage of the combined nlethod is that it inlproves the sohltion accuracy by coupling an error estinla- tion procedure to an adaptive meshing technique that generates small elements in regions with a large change ill sohmtion gradients, mid at the same time, larger elements in the other regions. The performance of the combined procedure is evaluated by analyzing one test case of the flow past a cylinder, for their transient and steady-state flow behaviors.

A Novel Basis Splitting Eavesdropping Scheme in Quantum Cryptography Based on the BB84 Protocol

We propose a novel strategy numed basis-splitting scheme to split the intercepted quanta into several portions based on different bases, for eavesdropping in the process of quantum cryptography. Compared with intercept- resend strategy, our simulation results of the basis-splitting scheme under the non-ideal condition show a greater performance, especially with the increase of the length of shifted bits. Consequently our scheme can aid eaves- dropper to gather much more useful information.

Model-Based Split-Range Algorithm for the Temperature Control of a Batch Reactor

In the manufacturing processes of high value-added products in the pharmaceutical, fine chemical polymer and food industry, insufficient control might produce off-grade products. This can cause significant financial losses, or in the pharmaceutical industry, it can result in an unusable batch. In these industries, batch reactors are commonly used, the control of which is essentially a problem of temperature control. In the industry, an increasing number of heating-cooling systems utilising three different temperature levels can be found, which are advantageous from an economic point of view. However, it makes the control more complicated. This paper presents a split-range designing technique using the model of the controlled system with the aim to design a split-range algorithm more specific to the actual sys- tem. The algorithm described provides high control performance when using it with classical PID-based cascade temperature control of jacketed batch reactors;however, it can be used with or as part of other types of controllers, for ex- ample, model-based temperature controllers. The algorithm can be used in the case of systems where only two as well as where three temperature levels are used for temperature control. Besides the switching between the modes of opera- tion and calculating the value of the manipulated variable, one of the most important functions of the split-range algo- rithm is to keep the sign of the gain of the controlled system unchanged. However, with a more system-specific split-range solution, not only can the sign of the gain be kept unchanged, but the gain can also be constant or less de- pendent on the state of the system. Using this solution, the design of the PID controller becomes simpler and can be implemented in existing systems without serious changes.

Modulus-Based Matrix Splitting Iteration Methods for a Class of Stochastic Linear Complementarity Problem

For the expected value formulation of stochastic linear complementarity problem, we establish modulus-based matrix splitting iteration methods. The convergence of the new methods is discussed when the coefficient matrix is a positive definite matrix or a positive semi-definite matrix, respectively. The advantages of the new methods are that they can solve the large scale stochastic linear complementarity problem, and spend less computational time. Numerical results show that the new methods are efficient and suitable for solving the large scale problems.

改进的YOLOv5图书梯标检测算法

对于印刷行业而言,确保每本书的页码、页面正确排序是提高印刷厂生产率的重点。为了解决目前印刷厂对于图书梯标的检测存在漏检、误检的问题,提出了一种改进YOLOv5的梯标检测算法。该算法增加一个检测尺度以解决漏检问题和提高梯标的识别精度,将主干网络中的C3数量减少,使用深度可分离卷积替代颈部网络中的部分卷积,在能够保证精度稳定的同时降低模型的参数量和计算量;使用SPConv替换Resunit结构里的Conv,形成SPConv-C3结构,SPConv-C3结构不仅能够降低模型的参数量,还能提升网络对图书梯标的检测精度;根据深度可分离卷积和SPConv-C3结构设计特征融合网络结构,能够大幅度提升网络模型的特征融合能力。将所改进的检测算法在自建数据集上进行验证,结果表明,改进后的算法Pm,A@0.5∶0.95达到了64.7%,比原YOLOv5s提高7.5百分点,参数量下降了3.16%,能够满足实际需求。

Modeling and Solving Lot-Splitting Scheduling Problem Based on Process

In flexible job-shop batch scheduling problem, the optimal lot-size of different process is not always the same because of different processing time and set-up time. Even for the same process of the same workpiece, the choice of machine also affects the optimal lot-size. In addition, different choices of lot-size between the constrained processes will impact the manufacture efficiency. Considering that each process has its own appropriate lot-size, we put forward the concept of scheduling with lot-splitting based on process and set up the scheduling model of lot-splitting to critical path process as the core. The model could update the set of batch process and machine selection strategy dynamically to determine processing route and arrange proper lot-size for different processes, to achieve the purpose of optimizing the makespan and reducing the processing batches effectively. The experiment results show that, comparing with lot-splitting scheduling scheme based on workpiece, this model optimizes the makespan and improves the utilization efficiency of the machine. It also greatly decreases the machined batches （42%） and reduces the complexity of shop scheduling production management.

面向大电流密度电解水的碳基催化剂研究进展

电解水体系可以在温和条件下制备氢气。得益于高比表面积、高电子传输性和原料丰富等优点,碳基电催化剂备受关注。商业用电解水装置需要在较低过电位下实现较大交换电流,进而实现氢气的持续快速生产。然而当前实验室研究的重心大多放在小电流服役工况,对于大电流工况下的系列问题关注较少。研究表明,电解水体系在不同电流密度下表现出的问题差异较大,其影响因素包括气泡、电催化剂局域微环境和电极稳定性等。本综述,首先对碳基电解水催化剂的发展现状进行了总结,大电流模式下暴露出的问题与挑战进行了讨论,并提出可能有效的解决方法,以实现能满足大电流密度要求的高活性高稳定性碳基电催化剂的研发。

基于平台巴西劈裂试验下WC-Co硬质合金的动态响应与失效特性

为获取WC-Co硬质合金在动态拉伸加载下的力学性能和失效机制,设计了动态平台巴西劈裂试验。结果发现,WC-Co硬质合金具有典型的弹脆性特征,且断裂应变随着加载应变率的增加而略有增加。在一维应力波加载下,WC-Co硬质合金的动态抗拉强度随应变率的增加而增加,表明其应变率效应具有明显的正相关性,该效应的产生机制与典型陶瓷类材料是一致的,即由I型裂纹的亚临界扩展决定。对回收破碎试样进行微观形貌观察,发现平台圆盘中间位置处微观断裂模式主要为沿晶断裂,且在拉应力作用下形成韧窝断裂形貌;在靠近加载点位置区域,受多向应力作用,材料不仅存在韧窝断裂,在单个晶粒的局部劈裂表面还存在河流花样的解理断裂。宏观角度上,WC-Co硬质合金表现出明显的脆性特征,但微观角度却发现有局部塑性变形特征。

炭材料在电解水制氢耦合有机氧化方面的研究进展

利用可再生能源(太阳能、风能)发电进行电解水制氢是获取“绿氢”的必经之路。然而,目前电解水制氢仍面临电解效率低和能耗高的巨大挑战。通过将电解水体系与热力学上更有利的有机氧化反应耦合是解决上述问题的重要途径,在有效提升阴极产氢效率的同时还可以在阳极获得高附加值化学品(用于进一步分摊并降低制氢成本)。这一新兴领域的发展关键在于制备具有高选择性和高稳定性的催化材料。碳基材料具有来源丰富、比表面积高、孔隙率高等优点,在高性能有机电氧化和电解水析氢催化剂方面引起了科研人员的广泛关注。本研究总结了碳基材料在电解水制氢耦合有机氧化方面的最新研究进展,并讨论了该材料在这一新兴电催化领域的发展前景和面临挑战,以推进新型炭材料的发展。

双碳目标下绿色制氢技术的进展

发展高能效、低成本、零碳排放的可再生能源电解水制氢技术是实现“碳中和”“碳达峰”的重要途径。随着可再生能源的价格持续下降,利用可再生能源来实现高效的电解水制氢正逐渐成为未来氢能的主流技术路线。围绕当前绿色制氢技术的研究进展,重点阐述电解水制氢、太阳能分解水制氢以及生物质制氢等“绿氢”技术的产氢机理、技术难题和发展现状,并对未来绿色制氢技术的应用前景和发展方向进行分析和讨论。

设计稳定的钌基析氢和析氧反应催化剂的基本原理

清洁和可再生能源具有地域性和间歇性,需要能量转换和存储技术来解决这些问题.氢气(H_(2))具有无毒、易得、经济、储量丰富和零碳排放的优势,作为能源媒介展现出巨大的潜力.而电分解水技术,因其高效性和便利性,成为了一种极具吸引力、应用前景广阔且可靠的能源技术.研究表明,在较宽的pH范围内,贵金属催化剂仍然是最优的析氢反应(HER)和析氧反应(OER)催化剂.其中,钌(Ru)作为一种相对便宜的铂族金属,显示出在HER中替代商业铂碳(Pt/C)催化剂以及在OER中替代铱(Ir)的潜力.然而,尽管在提高钌基催化剂的催化活性方面取得了很大进展,但其稳定性问题仍然是阻碍其实际应用的主要障碍.因此,迫切需要全面梳理和综述关于设计稳定钌基HER和OER催化剂的基本原理和最新进展,更好地理解钌基催化剂的催化机理,深入认识影响其稳定性的关键因素,以期为解决这一挑战提供有力的理论支持和实践指导.本文系统总结了钌基催化剂在电分解水反应中关于稳定性研究的最新进展.首先,简要介绍了钌基催化剂在HER/OER中的反应机理以及与之相关的理论计算、原位表征技术、稳定性测试手段和评价标准等方面的研究进展.接下来,详细探讨了钌基催化剂在HER/OER过程中的失活机制,包括载体腐蚀、奥斯特瓦尔德成熟、团聚、颗粒脱离、活性位点中毒、金属溶解、过度氧化和晶体结构坍塌等.基于以上对失活机制的认识,进一步归纳了提高钌基催化剂稳定性的设计策略和机制.在HER方面,从引入导电基底、构筑核壳结构、形成镶嵌结构、增强金属-载体相互作用、相转变工程以及调节中间体吸附和脱附行为等方面阐述了提高钌基催化剂稳定性的策略.对于OER过程,也总结了一系列提高钌基催化剂OER稳定性的策略,包括与铱杂化、构筑核壳结构、引入稳定的载体、化学掺杂、形成固溶体以及转变反应路径.在分析了各种策略的优缺点并提出改进方向后,还概述了钌基催化剂在全电解水以及器件中的研究现状.最后,指出了钌基催化剂稳定性研究所面临的挑战和未来的研究方向:(1)需要更贴近工业实际的稳定性测试策略和评价标准;(2)对失活机制的进一步研究;(3)原位技术的进一步发展和应用;(4)探索更多先进的改性策略,如非晶态载体、范德华异质结、自旋态调节以及微环境调节等;(5)关注实际应用中可能遇到的问题,如催化剂大规模制备、双功能催化剂的设计以及杂质的影响.综上,本文系统地总结了钌基催化剂的反应机制、稳定性测试方法与评价标准、失活机制、设计策略、研究进展、具体应用以及目前存在的挑战,希望能够进一步促进该领域深入水平研究.同时,本文对光催化、热催化、酶催化等催化领域的研究也提供一定的参考和借鉴.

在Split-Merge框架下进行基于图的图像分割

Split-Merge算法是图像分割领域的经典算法,思路简洁、运算效率高,但因分裂位置和形状固定,导致出现方块效应和边界定位不准确等问题。现有的各种改进算法不能从根本上解决这些问题,为此本文将基于图的分割算法纳入到Split-Merge框架中来,提出了在Split-Merge框架下进行基于图的分割。新算法把传统的基于图割值的算法作为分裂阶段的处理手段,在合并阶段采用本文提出的一种与访问次序无关的合并算法。新算法既解决了Split-Merge算法中因分裂位置和形状固定而带来的各种问题,也有效地消除了在基于图的分割中常见的"过分割"现象,取得了满意的分割效果。

碳基跨尺度纤维增强混凝土劈拉性能及微观界面研究

为改善碳纤维增强混凝土(CFRC)内部的纤维/基体(F/M)界面性能,提出利用碳纳米管-碳纤维跨尺度增强体(CNTs-CF)对F/M微观界面进行改性的技术方法。设计制作了CNTs-CF体积分数分别为0%、0.1%、0.2%、0.3%和0.4%的跨尺度纤维增强混凝土(CCFRC)试件,进而对其开展了劈裂抗拉实验,并与CFRC进行对比分析。结果表明,在相同的纤维掺量情况下,CCFRC能够在劈拉破坏失效时维持更好的整体性,而且CCFRC的劈裂抗拉强度明显高于CFRC。CCFRC的劈裂抗拉强度随纤维掺量的增加呈先逐渐升高后略有下降的变化趋势,当CNTs-CF的体积分数为0.3%时达到最大值,较之普通混凝土(PC)和CFRC,增长幅度分别达37.67%和13.21%。CNTs-CF兼具碳纤维和碳纳米管的优良特性,能够充分发挥跨尺度协同改性效应,强化F/M界面。CCFRC在工程结构抗力提升,以及基础设施电磁防护领域具有广阔的应用发展前景。

乳化沥青冷再生基层施工技术研究

为提高公路维修过程中产生的铣刨废旧沥青混合料利用率,结合实际工程对乳化沥青冷再生技术展开研究。采用5种乳化沥青用量(3.2%、3.7%、4.2%、4.7%和5.2%)和3种水泥剂量(1.0%、1.5%和2.0%)的混合料进行力学性能试验。试验结果得到,采用水泥剂量为1.5%,乳化沥青用量为4.2%,拌和用水量为5.1%时,混合料性能最佳,此时混合料残留稳定度大于75%,动稳定度在5000~6000次/mm,7 d、28 d无侧限抗压强度达到3~5 MPa,路用性能指标均满足技术要求。

3D打印水泥基材料高温后劈裂拉伸尺寸效应试验研究

为探究3D打印水泥基材料高温后劈裂拉伸尺寸效应,共设置5种温度和3种尺寸,应用液压伺服机对3D打印水泥基材料展开劈裂拉伸力学性能试验研究,分析高温和尺寸效应对3D打印水泥基材料劈裂拉伸力学性能的影响规律。主要得到以下结论:随着温度升高,试件抗拉强度逐步降低,不同尺寸试件的抗拉强度受高温影响降低幅度基本相同,最大降低幅度为87.97%。随着尺寸增加,试件抗拉强度逐步降低,温度的提高导致试件抗拉强度受尺寸效应影响变化幅度逐步增大。受尺寸效应影响,不同试件高温后的抗拉强度变化区间为18.488%~26.165%。同时,基于尺寸效应律提出3D打印水泥基材料高温下抗拉强度计算模型,并应用微观测试技术揭示其力学性能演化机理。

动态分流采样技术在评价压缩气体系统中的应用

目的:通过检测数据评价医用压缩气体系统中的气体质量是否满足使用标准,在开展评价工作时应识别到医用气体的压力特性,避免因检测技术的缺陷而导致临床使用风险。方法:根据医用气体的压力特性,利用分流采样技术开展验证试验,模拟设计压缩气体系统的多种运行工况,以0.5μm的颗粒物为评测对象开展循证实践,凭借测试数据研判不同工况时压缩气体系统的运行状态。结果:共收集5组测试数据,其中D组数据的变异系数为0.49,在试验组中最大;E组的数据均值为833158,在试验组中最高。结论:E组数据间的变异系数虽然仅为0.06,但数据的均值最大,说明压缩气体系统在500L/min的输出状态下过滤组件的净化效果已失效;结合D组数据的均值与变异系数,认为300 L/min为被测压缩气体系统的临界流量状态。

钌基氢析出反应电催化剂的研究进展

钌具有与铂相近的氢析出反应(HER)催化活性,价格约为铂的一半,是一种替代铂的理想金属。研究高效、稳定并且价格低廉的钌基HER电催化剂是实现氢能源社会的有效途径。介绍了HER机理,总结了最近钌基氢析出反应电催化剂的4种设计策略,展望了钌基氢HER电催化剂的机遇和挑战。

固化剂与水泥稳定工业副产石膏路用性能试验分析

针对工业副产石膏用于路面底基层的力学性能分析,通过6%水泥与0.3 L/m^(3)固化组合稳定工业副产石膏,开展无侧限抗压强度、劈裂强度、抗压回弹模量及单轴压缩弹性模量的力学性能评价,并与常规底基层类型12%灰土进行对比分析。结果表明:随着养生时间的增加,12%灰土和水泥与固化剂稳定工业副产石膏的抗压强度随着养生时间的增加而逐渐增大,增长速率先快后慢,7 d内强度增长速度最快,不浸水的条件下,两种材料均达到了28 d强度的75%左右,表明两种材料的强度形成主要在前期;随着浸水时间的增加,两种材料的无侧限抗压强度和劈裂强度逐渐减小,浸水48 h条件下的无侧限抗压强度、劈裂强度损失率大,水泥与固化剂稳定工业副产石膏的抗压强度和劈裂强度受浸水的影响小于12%灰土,其水稳定性更好。12%灰土和水泥与固化剂稳定工业副产石膏的抗压回弹模量分别为391 MPa和1207 MPa,弹性模量分别378 MPa和2247 MPa。水泥与固化剂稳定工业副产石膏的模量优于12%灰土,主要是由于固化剂与水泥的加入,增加了颗粒之间的黏结力,赋予了石膏较强的抵抗竖向变形的能力。