Numerical investigation on the aerodynamic drag reduction based on bottom deflectors and streamlined bogies of a high-speed train

The complex structure of the bottom of a high-speed train is an important source of train aerodynamic drag.Thus,improving the bottom structure is of great significance to reduce the aerodynamic drag of the train.In this study,computational fluid dynamics(CFD)based on three-dimensional steady incompressible Reynolds-average Naiver-Stokes(RANS)equations and Realizable k-ε turbulence model were utilized for numerical simulations.Inspired by the concept of streamlined design and the idea of bottom flow field control,this study iteratively designed the bogies in a streamlined shape and combined them with the bottom deflectors to investigate the joint drag reduction mechanism.Three models,i.e.,single-bogie model,simplified train model,and eight-car high-speed train model,were created and their aerodynamic characteristics were analyzed.The results show that the single-bogie model with streamlined design shows a noticeable drag reduction,whose power bogie and trailer bogie experience 13.92%and 7.63%drag reduction,respectively.The range of positive pressure area on the bogie is reduced.The aerodynamic drag can be further reduced to 15.01%by installing both the streamlined bogie and the deflector on the simplified train model.When the streamlined bogies and deflectors are used on the eight-car model together,the total drag reduction rate reaches 2.90%.Therefore,the proposed aerodynamic kit for the high-speed train bottom is capable to improve the flow structure around the bogie regions,reduce the bottom flow velocity,and narrow the scope of the train’s influence on the surrounding environment,achieving the appreciable reduction of aerodynamic drag.This paper can provide a new idea for the drag reduction of high-speed trains.

Surpass Streamline血流导向术对颅内动脉瘤的疗效

目的了解Surpass Streamline血流导向术对颅内动脉瘤的疗效。方法选取2020年1月至2022年1月安徽医科大学附属宿州医院68例接受Surpass Streamline血流导向装置治疗的颅内动脉瘤患者。收集临床资料,观察患者术前术后血流动力学参数变化,以及术前和术后3、6、12个月的改良Rankin量表(mRS)评分变化,分析患者的影像学资料,观察动脉瘤闭塞情况。结果与术前相比较,患者术后的WSS、瘤颈血流速度降低,LSA、RRT、载瘤动脉及患侧M1的血流速度增加(P<0.05),而患者术前、术后对侧M1血流速度比较差异无统计学意义(P>0.05)。术后,随着时间的延长,患者的mRS评分为低级别占比逐渐增高,差异有统计学意义(P<0.05)。术后6个月及12个月患者的支架内狭窄发生率分别为7.35%、8.82%,动脉瘤完全闭塞发生率分别为52.94%、63.24%,差异无统计学意义(P>0.05)。68例患者经Surpass Streamline血流导向术治疗后,4例出现缺血性并发症,其中2例表现为视物模糊、皮质盲,1例为肢体无力,1例支架内血栓,经干预治疗均得到有效缓解。结论采用Surpass Streamline血流导向术治疗颅内动脉瘤有较好的疗效,能改善血流动力学,术后动脉瘤完全闭塞率较高,且安全性较好,值得临床推广。

Reversible solid-liquid conversion enabled by self-capture effect for stable non-flow zinc-bromine batteries

Non-flow aqueous zinc-bromine batteries without auxiliary components(e.g.,pumps,pipes,storage tanks)and ion-selective membranes represent a cost-effective and promising technology for large-scale energy storage.Unfortunately,they generally suffer from serious diffusion and shuttle of polybromide(Br^(-),Br^(3-))due to the weak physical adsorption between soluble polybromide and host carbon materials,which results in low energy efficiency and poor cycling stability.Here,we develop a novel self-capture organic bromine material(1,10-bis[3-(trimethylammonio)propyl]-4,4'-bipyridinium bromine,NVBr4)to successfully realize reversible solid complexation of bromide components for stable non-flow zinc-bromine battery applications.The quaternary ammonium groups(NV^(4+)ions)can effectively capture the soluble polybromide species based on strong chemical interaction and realize reversible solid complexation confined within the porous electrodes,which transforms the conventional“liquid-liquid”conversion of soluble bromide components into“liquid-solid”model and effectively suppresses the shuttle effect.Thereby,the developed non-flow zinc-bromide battery provides an outstanding voltage platform at 1.7 V with a notable specific capacity of 325 mAh g^(-1)NVBr4(1 A g^(-1)),excellent rate capability(200 mAh g^(-1)NVBr4 at 20 A g^(-1)),outstanding energy density of 469.6 Wh kg^(-1)and super-stable cycle life(20,000 cycles with 100%Coulombic efficiency),which outperforms most of reported zinc-halogen batteries.Further mechanism analysis and DFT calculations demonstrate that the chemical interaction of quaternary ammonium groups and bromide species is the main reason for suppressing the shuttle effect.The developed strategy can be extended to other halogen batteries to obtain stable charge storage.

Research on passenger flow control at metro transfer stations based on real-time flow calculation of streamlines

Purpose – The volume of passenger traffic at metro transfer stations serves as a pivotal metric for theorchestration of crowd flow management. Given the intricacies of crowd dynamics within these stations andthe recurrent instances of substantial passenger influxes, a methodology predicated on stochastic processesand the principle of user equilibrium is introduced to facilitate real-time traffic flow estimation within transferstation streamlines.Design/methodology/approach – The synthesis of stochastic process theory with streamline analysisengenders a probabilistic model of intra-station pedestrian traffic dynamics. Leveraging real-time passengerflow data procured from monitoring systems within the transfer station, a gradient descent optimizationtechnique is employed to minimize the cost function, thereby deducing the dynamic distribution of categorizedpassenger flows. Subsequently, adhering to the tenets of user equilibrium, the Frank–Wolfe algorithm isimplemented to allocate the intra-station categorized passenger flows across various streamlines, ascertainingthe traffic volume for each.Findings – Utilizing the Xiaozhai Station of the Xi’an Metro as a case study, the Anylogic simulation softwareis engaged to emulate the intra-station crowd dynamics, thereby substantiating the efficacy of the proposedpassenger flow estimation model. The derived solutions are instrumental in formulating a crowd controlstrategy for Xiaozhai Station during the peak interval from 17:30 to 18:00 on a designated day, yielding crowdmanagement interventions that offer insights for the orchestration of passenger flow and operationalgovernance within metro stations.Originality/value – The construction of an estimation methodology for the real-time streamline traffic flowaugments the model’s dataset, supplanting estimated values derived from surveys or historical datasets withreal-time computed traffic data, thereby enhancing the precision and immediacy of crowd flow managementwithin metro stations.

Effect of Streamlined Nose Length on the Aerodynamic Performance of a 800 km/h Evacuated Tube Train

The aerodynamic resistance of a train running in the open air limits the maximum speed that can be attained by the train.For this reason,evacuated tube trains(ETT)are being considered as valid alternatives to be implemented in the future.The atmosphere in the tube,the so-called blocking ratio and the length of the streamlined nose are the key factors affecting the aerodynamic performances of these trains.In the present work,we investigate evacuated tube trains with different lengths of the streamline nose on the basis of computational fluid dynamics(CFD).The three-dimensional steady compressible Navier-Stokes equations are solved.The running speed of the ETT is 800 km/h and the blocking ratio is 0.2.Results show that with the increase of the streamlined nose length,the aerodynamic drag and lift forces of the head car decrease gradually,and the drag and lift forces of the middle car change slightly.For the tail car,the drag force decreases,whereas the absolute value of the lift force increases.At a speed of 800 km/h,a slight shock wave appears at the rear of the tail car,which affects the aerodynamic forces acting on the train.

Design and Experiment of Streamlined Piezoelectric Pump with Low Vortex and Large Flow Rate

Valveless piezoelectric pump is widely used in the medical,however,there is a general and difficult problem to be solved:Low vortex and large flow rate are not compatible,resulting in the blood prone to thrombosis during blood delivery.In this paper,a new valveless piezoelectric(PZT)pump with streamlined flow tubes(streamlined pump)is proposed.The design method and the working principle of the pump are analyzed.The velocity streamlines are simulated,and the results demonstrate that there are no obvious vortexes in the flow tube of the streamlined pump.Five prototype pumps(two cone pumps and three streamlined pumps)are designed and fabricated to perform flow rate and flow resistance experiments.The experimental results illustrate that the maximum flow rate of the streamlined pump is 142 mL/min,which is 179%higher than that of the cone piezoelectric pump,demonstrating that the streamlined pump has a large flow rate performance.This research provides an inspiration for future research on simple structure,low vortex and large flow rate volume-type pumps,and also provides a useful solution for thrombosis preventing.

Novel ternary metals-based telluride electrocatalyst with synergistic effects of high valence non-3d metal and oxophilic Te for pH-universal hydrogen evolution reaction

Electrocatalyst designs based on oxophilic foreign atoms are considered a promising approach for developing efficient pH-universal hydrogen evolution reaction(HER)electrocatalysts by overcoming the sluggish alkaline HER kinetics.Here,we design ternary transition metals-based nickel telluride(Mo WNi Te)catalysts consisting of high valence non-3d Mo and W metals and oxophilic Te as a first demonstration of non-precious heterogeneous electrocatalysts following the bifunctional mechanism.The Mo WNi Te showed excellent HER catalytic performance with overpotentials of 72,125,and 182 mV to reach the current densities of 10,100,and 1000 mA cm^(-2),respectively,and the corresponding Tafel slope of 47,52,and 58 mV dec-1in alkaline media,which is much superior to commercial Pt/C.Additionally,the HER performance of Mo WNi Te is well maintained up to 3000 h at the current density of 100 mA cm^(-2).It is further demonstrated that the Mo WNi Te exhibits remarkable HER activities with an overpotential of 45 mV(31 mV)and Tafel slope of 60 mV dec-1(34 mV dec-1)at 10 mA cm^(-2)in neutral(acid)media.The superior HER performance of Mo WNi Te is attributed to the electronic structure modulation,inducing highly active low valence states by the incorporation of high valence non-3d transition metals.It is also attributed to the oxophilic effect of Te,accelerating water dissociation kinetics through a bifunctional catalytic mechanism in alkaline media.Density functional theory calculations further reveal that such synergistic effects lead to reduced free energy for an efficient water dissociation process,resulting in remarkable HER catalytic performances within universal pH environments.

Reduced energy consumption by using streamlined gating systems

In foundries a lot of effort is done to minimize energy consumption in the production to reduce costs and hence increase the competitiveness. At the same time the foundries must live up to the increased demands for high quality castings. Traditional gating systems are known for a straight tapered down runner, a well base and 90° bends in the runner system. Previous work has shown that the traditional way of designing gating systems creates high inconsistency in flow patterns during filling. In the streamlined gating systems there are no sharp changes in direction and a large effort is done to confine and control the flow of the molten metal during mould filling. The main objective in the work presented here is to use the principles of the streamlined gating systems to reduce the weight of the gating system relative to the traditional layouts. By reducing the weight of gating system and thereby improving yield, the amount of molten iron needed is also reduced, hence reducing the energy consumption for melting. Experiments in real production lines have proven that it is possible to achieve a reduction in the poured weight by using the streamlined gating systems. In a layout for casting of three valve housings in a vertically parted mould the weight of the gating system was reduced by 1.1 kg changing from the traditional layouts to the streamlined gating systems. This weight reduction corresponds in this case to a 20% weight reduction for the gating system. Using streamlined gating systems with fan gates to give a beneficial heat distribution in the castings may be an efficient tool to eliminate the need for heat treatment. In the experiments the change in gating system from the traditional layout to the streamlined layout removed the need for heat treatment. This obviously means a huge energy saving in the foundry. The energy consumption for heat treatment of iron has been found to be 0.489 kWh/ kg. The valve housing in the experiments weighs 3 kg so when the need for heat treatment is removed, around 1.5 kWh is saved per casting. Along with the reduction in energy used the foundry also save the cost of handling the castings for the heat treatment and the production times is reduced considerably When the moulds for the vertical layout is produced on a DISAMATIC that produces 350 moulds an hour the total energy saved per hour for both melting and heat treatment becomes 2,000 kWh and per eight hour work day 16,000 kWh. Seen in this perspective the potential for saving energy in the foundries is substantial. Furthermore the experiments where ductile iron valve housings was cast also proved that it is possible to lower the pouring temperature from 1,400℃ to 1,300℃ without the risk of cold runs. This is possible due to a high flow rate during mould filling in combination with low velocities due to the use of fan gates. All of this has also been investigated in experiments using glass plate fronted moulds.

Streamlined System

WANG Xianlong didn＇t expect it would take only five working days to register his business, an outdoor products company based in Yiwu, a city in east China＇s Zhejiang Province. ＂Previously, getting administrative approval used to take at least three weeks.＂ Wang said. ＂1 would have to go back and forth between several government departments. But now, the Yiwu Administration Service Center offers a onestop service for enterprises. It＇s much faster.＂

基于贝叶斯优化支持向量回归的流线型箱梁颤振气动外形优化方法

为解决风洞试验耗时费力和计算流体动力学(CFD)计算量大的问题,提出了一套新型流线型箱梁断面颤振性能气动外形优化方法.以风嘴参数为设计变量,利用CFD获取断面三分力系数,以准定常理论估算的颤振临界风速为优化目标.根据贝叶斯优化支持向量回归构建代理模型,利用混合加点法更新模型,通过寻优算法确定最优断面.以虎门大桥为例,得到桥梁在可行域内颤振性能最佳的断面方案.结果表明,风嘴升高,颤振临界风速先增后减,相对高度为0.6时整体性能较优,相对高度为0.7时可获得最优断面.底板宽增加,颤振性能显著降低,下斜腹板倾角为14°~16°时颤振性能最优.断面优化后桥梁颤振临界风速相比原始断面提升约31%.

基于NSGA-Ⅱ遗传算法的Myring流线型量水槽体型优化设计

Myring流线型在水下航行器领域应用较为广泛,而量水槽在渠道中的受阻状态与潜水器潜行时受到的阻力情况具有一定的相似之处,因此本文借鉴潜水器的结构特点进行量水槽体型设计,探究量水槽受阻最小的较优线型。基于FLOW-3D软件,采用最优拉丁超立方设计方法,以流线型的收缩段长度和锐度因子、扩散段长度和离去角为变量设计了40组数值模拟方案,得到对应的水头损失百分比和上游佛汝德数。以数值模拟变量为输入、结果为输出,训练RBF神经网络,结合NSGA-Ⅱ遗传算法获得Patero前沿解,通过TOPSIS评价法筛选出最优解并得出其线形参数:优化模型收缩段长度为45.9 cm、收缩段锐度因子为0.74、扩散段长度为49.2 cm、扩散段离去角为14.63°,并通过等比例缩放得到6组收缩比,在9组流量下进行模型试验分析水力性能。结果表明,优化后线型过流较顺畅,水力性能较优,预测结果和模拟结果误差不超过5%;不同工况下上游佛汝德数均小于0.5,满足测流规范要求,收缩比为0.58~0.66时各项水力性能均较优;基于临界流测流和量纲分析原理得到的测流公式精度较高,平均相对误差为2.09%。本研究证明了将流线型运用于量水槽领域研究以及通过神经网络和遗传算法寻优的可行性,优化后Myring流线型量水槽具有良好的性能和测流精度,在灌区渠道中具有较好的运用前景。

微电子专业人才培养改革思路探索

如今欧美国家对于我国微电子行业发展的限制与针对力度日益加重,要想在此领域继续把握一定的国际话语权与地位,国内微电子行业人才培养是十分重要且关键的一环。因此,作为我国微电子技术行业人才的重要来源,高校微电子专业本科生的培养教育显得尤为重要。为从根本上保证高质量高素质的微电子人才培养与输送,该文针对这一形势以及国内当前教育发展的实际需要,结合当前高校微电子专业人才培养的实际情况,分析传统人才培养模式的不足和局限,讨论国内高校微电子专业课程设置、实验实习计划、教学课程的改革创新等问题,提出新时期、新局势下我国高校微电子专业课程体系的改革思路探索。

基于“放管服”改革珠江流域水行政“审、批分离”的探索研究

为深入贯彻“放管服”改革,珠江流域各级水行政主管部门积极探索尝试“审、批分离”。结合珠江流域“审、批分离”试行情况,对比分析了现行审批模式和“审、批分离”模式,对比发现“审、批分离”能提高审批质量和审批效率并降低廉政风险。总结了目前“审、批分离”存在的问题,并结合“放管服”改革的要求提出了改进措施建议,为探索推进“审、批分离”提供有益的工作探讨与借鉴。

射流与气固两相流混合过程的测试与分析方法

湍流射流是气固快速反应过程中气相原料与固体颗粒的理想混合形式,采取有效的测试技术与分析方法获得射流与气固两相流的混合行为对研究反应过程具有重要意义。本文采用光纤探针技术获得了颗粒浓度动态数据,以提升管内颗粒聚团的传统分析方法为基础,结合小波分析,提出了射流与气固两相流混合过程中颗粒聚团的确定方法,并将射流影响区内气固间的瞬时接触状态分为颗粒聚团相、散式颗粒相以及未与颗粒充分混合的射流相。结合附壁射流理论,利用气体示踪技术获得的射流特征浓度分布结果,对理想条件下的射流中心线方程进行了修正,所得结果可预测气固两相流中射流的发展趋势。利用臭氧分解示踪技术,获得了原料射流与气固两相流混合过程中的局部反应结果,将其与气固动态混合特征及射流轨迹模型相结合,可分析流动参数对反应的影响。

以“一件事一次办”为突破口持续优化营商环境

“一件事一次办”是提升政务服务标准化、规范化、便利化水平的重要内容,是加快政府职能转变、优化营商环境的核心要义,其实质是以公众诉求为导向,重塑政府流程,提升政府整体效能与公共福祉。借助制度经济学和新公共管理范式的整体治理理论,以“一件事一次办”政务服务改革为突破口,充分发挥区域比较优势,以大数据赋能打造透明高效的“数智”环境、持续优化公平正义的法治环境、竞争有序的市场环境和互利共赢的国际化的营商环境,充分释放行政改革集成效应。

阴阳转子型双螺杆结构的实验研究

为了设计出更加高效的双螺杆,提升挤出膨化机的工作效率;提出了一种引进阴阳转子的非对称双螺杆模型,基于螺旋式的螺杆模型,设计了阴阳转子型双螺杆,与传统双螺杆进行了仿真对比分析,并对新型双螺杆的准确性进行了实验验证;采用SolidWorks软件建模,利用ANSYS模拟流道数值,求得物料在机筒内的工作状态,分析阴阳转子型双螺杆的宏观压力、速度矢量和速度流线,并研究了不同转速对阴阳转子型双螺杆输送速度和挤出量的影响。研究结果表明:阴阳转子型双螺杆的宏观压力呈递增状态,速度矢量分布不均匀,速度流线混乱,能增加机筒内物料的传输速度,改变物料输送状态,提高物料挤出量。研究结果丰富了双螺杆的研究思路,为高效率挤出膨化机的设计与应用提供了理论依据。

镁合金尾翼类构件径向同步加载工艺研究

目的针对常规挤压工艺成形尾翼类构件飞行时翼片径向产生挠曲变形的问题,提出了一种可调控金属流动的径向同步加载成形方法。方法结合ANSYS、Deform-3D有限元模拟和物理实验,分析径向同步加载的金属流动行为、等效应变和金属流线分布,通过拉伸实验测试成形翼片挤压方向(Extrusion Direction,ED)和横截面方向(Transverse Direction,TD)的力学性能,并通过观察显微组织揭示径向强化机理。结果径向同步加载通过对坯料施加周向压应力促进了金属径向流动,形成了沿径向分布良好的金属流线,有利于提升径向力学性能;采用该工艺试制构件表面质量良好,无宏观缺陷,且形成沿径向分布的宏观流线;翼片径向力学性能显著提升,屈服强度提升了57.8 MPa,抗拉强度提升了80.1 MPa,延伸率提升了1.4%,其强塑性的提升与纤维组织和块状LPSO相的纤维强化密切相关。结论实现了尾翼类构件的径向同步加载整体成形,通过调控金属流动形成径向分布良好的金属流线,提升了成形翼片径向强度,为高性能镁合金尾翼类构件的整体成形提供了理论基础和技术支撑。

考虑货主满意度的“一对多”车货匹配模型

随着网络货运平台市场的发展,车货信息不对称的问题得到有效缓解,车主与货主满意度、车辆满载率、货主担负的成本还有改善空间。在运力供应大于货运需求的背景下,货主的满意度成为影响车货匹配效率与平台竞争力的关键。为使平台车货匹配的结果能更好地贴合匹配方需求,吸引更多客户,针对货主方构建了一种新型的匹配满意度模型。首先引入物流流线网络定义,将车货匹配的双方视为参与物流服务的客户方和提供服务方,综合考虑货主在货物完好性、运输时间和运输费用的需求与车主提供实际运输服务的情况之间的贴近程度,定义匹配满意度的含义;随后构建匹配满意度模型,以最大化匹配满意度为目标,设计改进的遗传算法并利用Python进行求解;最后针对网络货运平台的车源货源数据,在不同车货匹配模式的模型下进行求解并比较优劣。结果表明:考虑货主匹配满意度的“一对多”车货匹配模型比“一对一”模型平均车辆满载率提高了31.2%,货主担负成本降低了4.3%;考虑货主匹配满意度的“一对多”车货匹配模型比以运输成本为目标的“一对多”模型货主平均满意度提高了16.2%,货主担负成本降低了2.9%。考虑货主满意度的“一对多”车货匹配模型更符合现实需求情景,降低了货主担负的总成本,保持了较高的货主满意度和车辆满载率。

聚合物驱流线数值模拟技术研究

利用传统有限差分数值模拟技术处理大型复杂油藏模型时,存在计算耗时长、精度低等缺点,而流线法具有计算精度高、计算速度快等特点,因此对聚合物驱模拟开展流线求解技术研究。首先根据油水两相渗流方程和毛管力方程,建立压力方程并采用隐式方法求解;然后基于达西定律,由压力场生成网格界面上的流速场;再由流速场,利用Pollock流线追踪方法确定流体质点在空间的运动轨迹,就可以生成流线;最后通过求解饱和度和聚合物浓度方程获得流线上不同位置处的参数场分布。利用上述方法 研制了聚合物驱流线数值模拟软件。为验证计算的准确性,建立多井组聚合物驱模型进行流线数值模拟计算。结果表明,流线数值模拟计算结果 与有限差分数值模拟计算结果基本一致,验证了流线数值模拟方法的可靠性和准确性。与有限差分法相比,流线法的计算速度可提高1倍以上。

大国智造的“器”质:机器人驱动工业高质量发展的机理与效能

工业机器人是大国制造的新引擎,驱动着制造业智能化、高端化、绿色化发展。本文以工业机器人应用为出发点,以人员精简化、技能高级化、分工精细化、产业多样化为衔接点,以工业高质量发展战略目标为落脚点,阐释机器人驱动工业高质量发展的机理并评估效能。基准回归结果表明,机器人应用显著地促进了工业高质量发展。经内生性矫正和稳健性检验后发现,机器人应用产生的工业提质效应依然显著。机制检验结果显示,机器人应用正是通过促进人员精简化、技能高级化、分工精细化、产业多样化4重渠道,驱动了工业高质量发展。异质性分析结果进一步发现,机器人应用产生的工业提质效应在大城市、西部地区以及超老龄社会阶段更为强劲。研究结论为理解工业机器人何以赋能工业高质量发展提供了理论逻辑和经验证据,为加速迈向“中国智造”提出了新思路和新抓手。