Influence of High-Speed Milling Process on Mechanical and Microstructural Properties of Ultrafine Grained Profiles Produced by Linear Flow Splitting

The effects of milling parameters on the surface quality,microstructures and mechanical properties of machined parts with ultrafine grained(UFG)gradient microstructures are investigated.The effects of the cutting speed,feed per tooth,cutting tool geometry and cooling strategy are demonstrated.It has been found that the surface quality of machined grooves can be improved by increasing the cutting speed.However,cryogenic cooling with CO_2 exhibits no significant improvement of surface quality.Microstructure and hardness investigations revealed similar microstructure and hardness variations near the machined groove walls for both utilized tool geometries.Therefore,cryogenic cooling can decrease more far-ranging hardness reductions due to high process temperatures,especially in the UFG regions of the machined parts,whilst it cannot prevent the drop in hardness directly at the groove walls.

Elliptic Flow Splitting between Particles and their Antiparticles in Au＋Au Collisions from a Multiphase Transport Model

The elliptic flow v2, for π±, K±, p and p in Au＋Au collisions at center-of-mass energies √sNN=7.7, 11.5, 14.5 and 19.6 GeV, is analyzed using a multiphase transport model. A significant difference in the v2 values for p and p is observed, and the values of v2 splitting are larger compared with π＋ and π-, K＋ and K-. The difference increases with decreasing the center-of-mass energy. The effect of the quark coalescence mechanism in a multi-phase transport model to the value of elliptic difference △v2 between p and p- has been discussed. The simulation of Au＋Au collisions at 14.5 GeV shows that the effect of hadron cascade to △v2 is not obvious, and a larger patton-scattering cross section can lead to a larger △v2.

Analytical and Computational Analysis of Flow Splitting in Multiple, Parallel Channels Systems

Previous analytical results on flow splitting are generalized to consider multiple boiling channels systems. The analysis is consistent with the approximations usually adopted in the use of systems codes (like RELAP5 and TRACE5, among others) commonly applied to perform safety analyses of nuclear power plants. The problem is related to multiple, identical, parallel boiling channels, connected through common plena. A theoretical model limited in scope explains this flow splitting without reversal. The unified analysis performed and the confirmatory computational results found are summarized in this paper. New maps showing the zones where this behavior is predicted are also shown considering again twin pipes. Multiple pipe systems have been found not easily amenable for analytical analysis when dealing with more than four parallel pipes. However, the particular splitting found (flow along N pipes dividing in one standalone pipe flow plus N -1 identical pipe flows) has been verified up to fourteen pipes, involving calculations in systems with even and odd number of pipes using the RELAP5 systems thermal-hydraulics code.

On Minimizing Delay with Probabilistic Splitting of Traffic Flow in Heterogeneous Wireless Networks

In the paper,we propose a framework to investigate how to effectively perform traffic flow splitting in heterogeneous wireless networks from a queue point.The average packet delay in heterogeneous wireless networks is derived in a probabilistic manner.The basic idea can be understood via treating the integrated heterogeneous wireless networks as different coupled and parallel queuing systems.The integrated network performance can approach that of one queue with maximal the multiplexing gain.For the purpose of illustrating the effectively of our proposed model,the Cellular/WLAN interworking is exploited.To minimize the average delay,a heuristic search algorithm is used to get the optimal probability of splitting traffic flow.Further,a Markov process is applied to evaluate the performance of the proposed scheme and compare with that of selecting the best network to access in terms of packet mean delay and blocking probability.Numerical results illustrate our proposed framework is effective and the flow splitting transmission can obtain more performance gain in heterogeneous wireless networks.

Hepatic flow optimization in full right split liver transplantation

Split liver transplantation for two adults offers a valuable opportunity to expand the donor pool for adult recipients.However,its application is mainly hampered by the physiological limits of these partial grafts.Small for size syndrome is a major concern during transplantation with partial graft and different techniques have been developed in living donor liver transplantation to prevent the graft dysfunction.Herein,we report the first application of synergic approaches to optimise the hepatic hemodynamic in a split liver graft for two adults. A Caucasian woman underwent liver transplantation for alcoholic cirrhosis(MELD 21)with a full right liver graft (S5-S8)without middle hepatic vein.Minor and accessory inferior hepatic veins were preserved by splitting the vena cava;V5 and V8 were anastomosed with a donor venous iliac patch.After implantation,a 16G catheter was advanced in the main portal trunk.Inflow modulation was achieved by splenic artery ligation.Intraportal infusion of PGE1 was started intraoperatively and discontinued after 5 d.Graft function was immediate withnormalization of liver test after 7 d.Nineteen months after transplantation,liver function is normal and graft volume is 110%of the recipient standard liver volume. Optimisation of the venous outflow,inflow modulation and intraportal infusion of PGE1 may represent a valuable synergic strategy to prevent the graft dysfunction and it may increase the safety of split liver graft for two adults.

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.

THE SOLUTION FOR TRANSIENT TWO-PHASE FLOW BY SPLIT FLUX VECTOR METHOD

In this paper the transient two-phase flow equations and their eigenvalues are first introduced. The flux vector is then split into subvectors which just contain a specially signed eigenvalue. Using one-sided spatial difference operators finite difference equations and their solutions are obtained. Finally comparison with experiment shows the predicted results produce good agreement with experimental data.

Theoretical Basis of Gene Splitting Technique and Its Application in the Control of Transgene Flow

Transgenic safety issues cause more and more controversies with the planting area of transgenie crops increased year by year. Gene flow from transgenie crops to wild relatives through pollen dispersal is one of the focus problems. Gene splitting technique provides a new strategy for the control of transgene flow by bio-logical containment. The construction of gene splitting technique is based on protein trans-splicing mediated by intein. Currently, it has been proved in Arabidopsis, tabaoco, wheat, etc. that active and functional proteins can be reassembled by intein mediated protein trans-splicing after gene splitting, which provides theoretical basis and experimental supporting for the limit of transgene flow by gene splitting technique. The theoretical basis of gene splitting technique and research progresses of its application on the control of transgene flow were reviewed in this paper.

TRANSONIC FLOW CALCULATION OF EULER EQUATIONS BY IMPLICIT ITERATING SCHEME WITH FLUX SPLITTING

Three dimensional Euler equations are solved in the finite volume form with van Leer's flux vector splitting technique. Block matrix is inverted by Gauss-Seidel iteration in two dimensional plane while strongly implicit alternating sweeping is implemented in the direction of the third dimension. Very rapid convergence rate is obtained with CFL number reaching the order of 100. The memory resources can be greatly saved too. It is verified that the reflection boundary condition can not be used with flux vector splitting since it will produce too large numerical dissipation. The computed flow fields agree well with experimental results. Only one or two grid points are there within the shock transition zone.

Flux vector splitting solutions for coupling hydraulic transient of gas-liquid-solid three-phase flow in pipelines

The gas-liquid-solid three-phase mixed flow is the most general in multiphase mixed transportation. It is significant to exactly solve the coupling hydraulic transient problems of this type of multiphase mixed flow in pipelines. Presently, the method of characteristics is widely used to solve classical hydraulic transient problems. However, when it is used to solve coupling hydraulic transient problems, excessive interpolation errors may be introduced into the results due to unavoidable multiwave interpolated calculations. To deal with the problem, a finite difference scheme based on the Steger- Warming flux vector splitting is proposed. A flux vector splitting scheme is established for the coupling hydraulic transient model of gas-liquid-solid three-phase mixed flow in the pipelines. The flux subvectors are then discretized by the Lax-Wendroff central difference scheme and the Warming-Beam upwind difference scheme with second-order precision in both time and space. Under the Rankine-Hugoniot conditions and the corresponding boundary conditions, an effective solution to those points located at the boundaries is developed, which can avoid the problem beyond the calculation region directly induced by the second-order discrete technique. Numerical and experimental verifications indicate that the proposed scheme has several desirable advantages including high calculation precision, excellent shock wave capture capability without false numerical oscillation, low sensitivity to the Courant number, and good stability.

难变形金属复杂构件电流辅助流动-分形旋压成形机理研究

针对采用传统多道次切削及插齿工艺所制备难变形金属复杂件存在的工艺流程长、强韧性不足等问题,提出采用电流辅助流动-分形旋压工艺实现此复杂件少无切削的近净成形。以具有“差异壁厚”和“差异结构”的30CrMnSiA合金结构钢复杂构件为研究对象,分析了电流辅助流动-分形旋压成形原理;基于ABAQUS软件建立了电流辅助流动-分形旋压成形有限元分析模型,并对模型精度进行了验证;分析了电流辅助流动-分形旋压成形机理并进行试验研究。结果表明:所构建的有限元模型对电流辅助流动-分形旋压成形工艺的预测精度较高,两种工艺的最大相对误差分别为6.72%和5.63%。电流辅助流动旋压的材料呈现三向压应力状态,在成形末期坯料壁部存在较大的拉应力和拉应变;电流辅助分形成形时,变形材料的应力分布则呈现齿槽材料呈现三向压应力状态,齿顶则为径向拉、其余两向压的应力状态;脉冲电流可降低了材料变形抗力,不仅缩小了流动旋压变形区的危险区,同时也可提高分形旋压时材料向径向填充的能力,进而减弱了齿形填充不满的现象。试验结果表明,电流辅助流动-分形旋压工艺可实现难变形复杂构件的高精度高强韧性制备。

一种高效的OpenFlow流表拆分压缩算法

在软件定义网络中,OpenFlow通过丰富的匹配字段提供了网络流的细粒度管理,同时也带来了流表规模庞大的问题,给OpenFlow交换机的TCAM存储资源提出了严峻的挑战.为此,本文基于匹配域间关系,提出一种高效的OpenFlow流表拆分压缩算法.该算法首先分析了流表匹配字段之间的共存和互斥关系,并据此将流表划分出多个规模较小的子流表,进而针对每个字段建立判定条件,对子流表做进一步压缩,以实现OpenFlow流表的高效存储.最后,借助实际网络流量样本,对本文所提算法的流表压缩性能进行了实验评估.实验结果表明:本文所提算法的流表压缩率明显高于现有压缩算法,可有效节省流表存储资源.

中低转速下静子可调对变循环分离风扇流通能力的影响研究

可调静子是变循环分离风扇在中低转速下实现更大流通能力的关键手段。本文针对“2+1”和“1+2”两种构型变循环分离风扇的极限流通能力随进口导叶(IGV)和静子调节的变化规律展开了数值模拟研究。研究结果表明,涵道比和可调静子组合调节情况下,“1+2”变循环分离风扇的极限流通能力更强;而涵道比固定为0.3时,“2+1”变循环分离风扇的极限流通能力更强。进一步的分析表明,IGV的调节角度决定了第一级风扇流量-压比特性线位置,从而决定了风扇的理论极限流通能力;而所有可调静子叶片的调节角度决定了第一级风扇与后面级风扇的匹配状态,从而决定了第一级风扇在自身特性线上匹配的最大流量状态,进而决定了风扇的实际极限流通能力。涵道比和可调静子组合调节情况下,“1+2”变循环分离风扇可用的IGV调节角度更大,因此其极限流通能力更强;涵道比固定情况下变循环分离风扇的极限流通能力与初始状态下各级的匹配有关,对于本文研究的两种构型变循环分离风扇,涵道比为0.3时“2+1”变循环分离风扇各级匹配状态有利于获得更大的可用IGV调节角度,因此其极限流通能力更强。

An efficient unstructured WENO method for supersonic reactive flows

An efficient high-order numerical method for supersonic reactive flows is proposed in this article.The reactive source term and convection term are solved separately by splitting scheme.In the reaction step,an adaptive time-step method is presented,which can improve the efficiency greatly.In the convection step,a third-order accurate weighted essentially non-oscillatory（WENO）method is adopted to reconstruct the solution in the unstructured grids.Numerical results show that our new method can capture the correct propagation speed of the detonation wave exactly even in coarse grids,while high order accuracy can be achieved in the smooth region.In addition,the proposed adaptive splitting method can reduce the computational cost greatly compared with the traditional splitting method.

Seismic evidence for the existence of an entrained mantle flow coupling the northward advancing Indian plate under Tibet

The Tibetan Plateau, known as "the roof of the world" and "the third pole of the earth", is a product of the collision between India and Asia during the last ～50 Ma.The regional tectonics–in particular, growth and expansion of the plateau–has been attributed primarily to deformation within the lithosphere.The role and pattern of the underlying asthenospheric flow, however, remain mostly unaddressed.In light of recent seismic tomographic images and published seismic anisotropic descriptions of the upper mantle, here we propose that an entrained mantle flow is likely to exist under Tibet, induced by the northward advancing Indian plate.The direction of mantle flow is characterized by a gradual rotation from northward in the south to eastward in the north as a result of deflection by the deep root of the Tarim block.The presence of an underlying mantle flow is not only able to account for the west-east oriented fast-axis of seismic anisotropy in northern Tibet, but can also adequately explain the sporadic null splitting in southern Tibet.Specifically, the null splitting results, at least in part, from upwellings of asthenospheric flow through tears of the underthrusting Indian plate that have been revealed by various seismic observations.The mantle flow may in turn promote the block extrusion under Tibet that has been observed in GPS measurements; hot asthenospheric upwellings may also lead to widespread post-collisional magmatism in southern Tibet.

Isospin splitting of nucleon effective mass and isospin effect in heavy-ion collisions

Two different isospin splittings of nucleon effective mass in nuclear medium as the form of mn*>mp* and mn*<mp* have been implemented in an isospin and momentum dependent transport model.Their impacts on the isospin emission in heavy-ion collisions is investigated thoroughly.It is found that the yield ratios of energetic neutrons to protons squeezed out during the compression stage of two colliding nuclides are sensitive to the isospin splitting.The elliptic flows of free nucleons are also to be promising observables for extracting the nucleon effective mass splitting.Further experimental measurements are being expected,in particular at the CSR-CEE platform in Lanzhou.Several observables are proposed for constraining the density dependence of symmetry energy,such as the transverse flow difference of neutrons and protons,double ratios of n/p and π-/π+,excitation functions of π-/π+ and K0/K+.

Branch Quality Control of Gas-Liquid Two-Phase Flow Using a Novel T-Junction Type Distributor

In order to eliminate mal-distribution and ensure the side arm to produce desirable gas quality a special distributor is proposed. The experimental distributor mainly consists of a straight through section,a gas extraction line,a liquid extraction line and a side arm branch. A gas orifice and a liquid orifice are mounted at the gas and liquid extraction line respectively to control the outlet gas quality. The diameter of the liquid orifice was set to 2. 50 mm and three gas orifices with different size( dG= 2. 65,5. 00,10. 00 mm) were tested. The experiments were carried out at an air-water two-phase flow loop. The gas superficial velocity ranged from 6. 0 to 20. 0 m /s and the liquid superficial velocity was in the range of 0. 02- 0. 18 m /s. Flow patterns such as wave flow,slug flow and annular flow were observed. The gas quality of the side arm branch was found mainly determined by the flow area ratio of the gas orifice to the liquid orifice and independent of gas and liquid superficial velocity,flow patterns and extraction flux.

AN INVESTIGATION ON INTERNAL THERMAL FLOW OF NON-NEWTONIAN FLUID

In the present paper an unsteady thermal flow of non-Newtonian fluid is investigated which is of the flow into axisymmetric mould cavity. In the second part an unsteady thermal flow of upper-convected Maxwell fluid is studied. For the flow into mould cavity the constitutive equation of power-law fluid is used as a Theological model of polymer fluid. The apparent viscosity is considered as a function of shear rate and temperature. A characteristic viscosity is introduced in order to avoid the nonlinearity due to the temperature dependence of the apparent viscosity. As the viscosity of the fluid is relatively high the flow of the thermal fluid can be considered as a flow of fully developed velocity field. However, the temperature field of the fluid flow is considered as an unsteady one. The governing equations are constitutive equation, momentum equation of steady flow and energy conservation equation of non-steady form. The present system of equations has been solved numerically by the splitting difference method. The numerical results show that the splitting difference method is suitable for the 2D problem of non-Newtonian fluid. The present application of the splitting diffference method is at first developed by us for non-Newtonian case. For the unsteady flow in the tube the finite difference scheme is given which leads to a tridiagonal system of equations.

PEM燃料电池阴极侧分流式流道研究

流道是PEM燃料电池里面负责反应物运输和产物排除的场所,因此流道结构对PEM膜燃料电池性能有重要影响。因为阳极通的是纯氢气,氢气扩散系数较大。阳极不会出现氢气量满足不了反应需要的情况,所以本文不研究阳极的反应情况。阴极侧是主要的反应场所,阴极侧流道需要让尽可能多的氧气参与反应同时要有更好的排水能力。基于传统流道的研究现状,设计了1种分流式的阴极侧流道。利用多物理场耦合软件COMSOL对新型流道做了数值模拟和分析比较。结果表明:与传统直流道相比,阴极侧采用分流式流道设计的燃料电池比阴极侧采用传统直流道设计的燃料电池能提供更大质量分数更均匀的氧气分布、减少水的质量分数、更均匀的电流密度分布。

关于5G双域快网的实现方案

中国电信5G双域快网,是指在5G定制网的“比邻”模式下,基于中国电信边缘UPF设备,为特定用户(指行业客户的特定群体,如师生、政务员工、医护人员等)和非特定用户(指到访客户指定的特定区域的所有电信5G用户,如普通游客)提供数据流量本地卸载和就近处理,使中国电信5G移动业务用户、物联网5G用户不换卡、不换号,可同时访问客户内网和互联网。文章主要说明5G双域快网基于增强型ULCL分流方式和DNN分流方式,实现4G和5G网络均可以访问客户内网和互联网的功能,同时增加域名分流和DNS重定向的方案以实现附加的功能。