Wind-sand flow simulation and radius optimization of highway embankment under different vertical curve radius

It is of great practical value to explore the correlation between the vertical curve radius of desert highway and the increase of sand accumulation in local lines,and to select the appropriate vertical curve radius for reducing the risk of sand accumulation.In this study,three-dimensional models of desert highway embankments with different vertical curve radii were constructed,and Fluent software was used to simulate the wind-sand flow field and sand accumulation distribution of vertical curve embankments.The results show that:(1)Along the direction of the road,the concave and the convex vertical curve embankments have the effect of collecting and diverging the wind-sand flow,respectively.When the radius of the concave vertical curve is 3000 m,5000 m,8000 m,10000 m and 20000 m,the wind velocity in the middle of the vertical curve is 31.76%,22.58%,10.78%,10.53%and 10.44%,higher than that at both ends.When the radius of the convex vertical curve is 6500 m,8000 m,10000 m,20000 m and 30000 m,the wind velocity at both ends of the vertical curve is 14.06%,9.99%,6.14%,3.22%and 2.41%,higher than that in the middle.The diversion effect also decreases with the increase of the radius.(2)The conductivity of the concave and convex vertical curve embankments with different radii is greater than 1,which is the sediment transport roadbed.The conductivity increases with the increase of radius and gradually tends to be stable.When the radius of the concave and convex vertical curves reaches 8000 m and 20000 m respectively,the phenomenon of sand accumulation is no longer serious.Under the same radius condition,the concave vertical curve embankment is more prone to sand accumulation than the convex one.(3)Considering the strength of the collection and diversion of the vertical curve embankment with different radii,and the sand accumulation of the vertical curve embankment in the desert section of Wuma Expressway,the radius of the concave vertical curve is not less than 8000 m,and the radius of the convex vertical curve is not less than 20000 m,which can effectively reduce the sand accumulation of the vertical curve embankment.In the desert highway area,the research results of this paper can provide reference for the design of vertical curve to ensure the safe operation of desert highway.

Generalized Numerical Radius of Real Quaternion Matrices with Symmetric Function

In the paper the generalized numerical radiuses of real quaternion matrices with symmetric function are defined and theirs inequalities are given.

Coupling mechanism of THM fields and SLG phases during the gas extraction process and its application in numerical analysis of gas occurrence regularity and effective extraction radius

The analysis of the coupling mechanism of thermal-hydraulic-mechanical(THM)fields,and solid-liquidgas(SLG)phases during gas extraction process is of profound significance to explore its numerical application in the gas occurrence regularity and its effective extraction radius.In this study,the Hudi coal mine in Qinshui basin is taken as the research area,the influencing factors of gas occurrence were analyzed,the differences in overburden load for gas pressure distribution and the factors influencing the effective extraction radius were further discussed by using the COMSOL software.The results show that the derivation of mathematical model in gas extraction shows that the process is a process the THM fields restrict each other,and the SLG phases influence each other.The longer the extraction time,the larger the influencing range of borehole,and the better the extraction effect.The larger the diameter of borehole,the larger the effective extraction radius,and the influence on gas extraction effect is smaller in the early stage and larger in the late stage.The borehole arrangement should be flexibly arranged according to the actual extraction situation.The higher the porosity,the higher the permeability,the better the gas extraction effect.The larger the overburden load of reservoir,the stronger the effective stress,which will result in the more severe the strain,and the closure of pore and fracture,which in turn will lead to the decrease of permeability and slow down the gas extraction.The relationship among extraction time,borehole diameter,negative pressure of gas extraction,permeability with effective extraction radius is exponential.This study has important theoretical and practical significance for clarifying and summarizing the gas occurrence regularity and its engineering practice.

A Note on Numerical Radius Operator Spaces

In this paper, we first study some -completely bounded maps between various numerical radius operator spaces. We also study the dual space of a numerical radius operator space and show that it has a dual realization. At last, we define two special numerical radius operator spaces and which can be seen as a quantization of norm space E.

On y-numerical Radius and Its Stability

Let A be an n×n complex matrix,and let y =(α1,...,αn) be an n-dimensional complex vector.The y-numerical radius of A,denoted by ry(A),is defined follows:r_y(A) = max {|sum form i=1 to n α_ix_i~* Ax_i|:x_i~* x_i = 1,x_i ∈ C^n},where Cn is an n-dimensional vector space over complex field C.In this paper we studynorm properties and stability of y-numerical radius.

Numerical simulation of enhancing coalbed methane recovery by injecting CO_2 with heat injection

The technology used to enhance coalbed methane(CBM) recovery by injecting CO_2(CO_2-ECBM) with heat, combining heat injection with CO_2 injection, is still in its infancy; therefore, theoretical studies of this CO_2-ECBM technology should be perused. First, the coupling equations of the di usion–adsorption–seepage–heat transfer fields of gas are established. The displacement processes under di erent pressures and temperatures are simulated by COMSOL. Finally, the displacement effects, a comparison of the CO_2 storage capacity with the CH_4 output and the e ective influencing radius of CO_2 injection are analyzed and discussed. The results show that(1) the displacement pressure and temperature are two key factors influencing the CH_4 output and the CO_2 storage capacity, and the increase in the CO_2 storage capacity is more sensitive to temperature and pressure than the CH_4 output.(2) The gas flow direction is from the injection hole to the discharge hole during the displacement process, and the regions with high velocity are concentrated at the injection hole and the discharge hole.(3) A reduction in the CH_4 concentration and an increase in the CO_2 concentration are obvious during the displacement process.(4) The e ective influencing radius of injecting CO_2 with heat increases with the increase in time and pressure. The relationship between the e ective influencing radius and the injection time of CO_2 has a power exponential function, and there is a linear relationship between the functional coe cient and the injection pressure of CO_2. This numerical simulation study on enhancing CBM recovery by injecting CO_2 with heat can further promote the implementation of CO_2-ECBM project in deep coal seams.

Numerical simulation of the temperature fields of stainless steel with different roller parameters during twin-roll strip casting

The temperature field of stainless steel during twin-roll strip casting was simulated by experiment and a finite element （FE） model. By comparing the measured result with the simulated values, it is found that they fit close to each other, which indicates this FE model is effective. Based on this model, the effects of roll gap （t） and roll radius （R） on solidification were simulated. The simulated results give the relationship between t or R and the position of the freezing point. The larger the t is and the smaller the R is, the closer the position of the freezing point is to the exit.

Significance-based optimization of processing parameters for thin-walled aluminum alloy tube NC bending with small bending radius

Thin-walled aluminum alloy tube numerical control （NC） bending with small bending radius is a complex process with multi-factor coupling effects and multi-die constraints. A significance-based optimization method of the parameters was proposed based on the finite element （FE） simulation, and the significance analysis of the processing parameters on the forming quality in terms of the maximum wall thinning ratio and the maximum cross section distortion degree was implemented using the fractional factorial design. The optimum value of the significant parameter, the clearance between the tube and the wiper die, was obtained, and the values of the other parameters, including the friction coefficients and the clearances between the tube and the dies, the mandrel extension length and the boost velocity were estimated. The results are applied to aluminum alloy tube NC bending d50 mm×1 mm×75 mm and d70 mm×1.5 mm×105 mm （initial tube outside diameter D0 × initial tube wall thickness t0 × bending radius R）, and qualified tubes are produced.

Numerical simulation on the shape of liquid surface of TIG full-penetrated weld pool

Based on the analysis of the three-dimensional liquid surface behavior of TIG penetrated weld pool,the three-dimensional shape models of weld pool with different values of the back fusion zone radius RB were obtained.The effects of arc on the penetrated weld pool were studied by numerical simulation with finite elements analysis software Surface Evolver.The results show that the size and shape of the back weld pool are not affected obviously by the arc,and the top surface of the weld pool is lowered by arc.From pulse background to pulse peak,the increase of the arc voltage(or the arc light intensity) is due to two factors.One is the increase of the current,and the other is the lowering of the top weld pool surface.

Norm Properties of Y-numerical Radii

Given an n×n complex matrix A and an n-dimensional complex vector y=(ν1 , ··· , νn ), the y-numerical radius of A is the nonnegative quantity ry(A)=max{n∑j=1ν*jAx︱:Axj︱: x*jxj=1,xj ∈Cn}.Here Cn is an n-dimensional linear space overthe complex field C. For y = (1, 0, ··· , 0) it reduces to the classical radius r(A) =max {|x*Ax|: x*x=1}.We show that ry is a generalized matrix norm if and only ifn∑j=1νj≠ 0.Next, we study some properties of the y-numerical radius of matrices andvectors with non-negative entries.

Effects of process parameters on numerical control bending process for large diameter thin-walled aluminum alloy tubes

Numerical control(NC) bending experiments with different process parameters were carried out for 5052O aluminum alloy tubes with outer diameter of 70 mm, wall thickness of 1.5 mm, and centerline bending radius of 105 mm. And the effects of process parameters on tube wall thinning and cross section distortion were investigated. Meanwhile, acceptable bending of the 5052O aluminum tubes was accomplished based on the above experiments. The results show that the effects of process parameters on bending process for large diameter thin-walled aluminum alloy tubes are similar to those for small diameter thin-walled tubes, but the forming quality of the large diameter thin-walled aluminum alloy tubes is much more sensitive to the process parameters and thus it is more difficult to form.

Analysis of Cutter Radius Compensation

Cutter radius compensation （CRC） is a very important function of numerical control（NC） system. We refer to a large number of NC information and sum up the CRC function. We illustrate how to realize rough machining ＆ finish machining by the same program, machining matching surface by the same program, simplify pro- gramming methods, realize direct programming by parts contour, remove machining allowance by the increase of CRC value, control the parts size precision by adjusting the CRC value, state the essence of the CRC, and elucidate the physical meaning of the CRC value.

Solving Large Scale Unconstrained Minimization Problems by a New ODE Numerical Integration Method

In reference [1], for large scale nonlinear equations , a new ODE solving method was given. This paper is a continuous work. Here has gradient structure i.e. , is a scalar function. The eigenvalues of the Jacobian of;or the Hessian of , are all real number. So the new method is very suitable for this structure. For quadratic function the convergence was proved and the spectral radius of iteration matrix was given and compared with traditional method. Examples show for large scale problems (dimension ) the new method is very efficient.

Gas-solid coupling analysis and numerical simulation of the dynamic process of gas drainage

Based on the basic theory of gas seepage and coal seam deformation, using the numerical simulation method, this paper established the gas-solid coupling model of gas drainage from borehole. Using multi-physical coupling analysis software, the authors studied the stress change conditions around the drainage borehole, the influence of the gas drainage effect caused by the drilling gap, and the gas drainage effect under the conditions of different borehole radius and different permeabilities. The results show that the effective drainage radius is 1.03 m during 30 days of drainage. The effect of the diameter change of the drainage borehole is limited, but the influence of coal seam permeability is much bigger. After the same drainage period, the greater the permeability of coal seam is, the bigger the drainage radius is. For a low permeability coal seam, coal miners should take pressure-relief measures and increase the permeability to improve the drainage effects before draining gas through drilling.

LD端面抽运Z型腔的Nd∶GdVO_(4)激光器稳定性研究

为了提升半导体激光二极管端面抽运Z型腔固体激光器的稳定性,以Nd∶GdVO_(4)固体激光器为例,采用数值模拟的方法,在考虑晶体热透镜效应的情况下,研究了Z型谐振腔的臂长、镜片曲率半径等参数对高斯光束的影响,得到了晶体热透镜焦距随抽运光功率变化的关系曲线、谐振腔稳定性随热透镜焦距变化的关系曲线、以及高斯光束束腰半径随谐振腔分臂长和镜片曲率半径变化的关系曲线,并绘制了高斯光束的轮廓曲线。结果表明,适当选取Z型腔的分臂参数可在晶体主平面和后端镜处获得较小的束腰尺寸。本研究结果可对Z型固体激光器谐振腔的搭建提供理论参考及依据。

小半径隧道盾构施工对铁路桥梁的影响

随着城市轨道交通线网的完善,单一的直线型隧道已不能满足需求,而新建隧道也不可避免地近接建构筑物,势必危及建构筑物,甚至引发严重的安全问题。基于郑州地区某工程,运用有限元软件Midas GTS NX进行数值模拟,研究小半径隧道盾构施工期间隔离桩防护措施的作用效果,并结合监测数据验证数值计算的准确性。研究结果表明:1)在无隔离桩防护措施下,小半径盾构隧道施工会引起地表横向沉降变形,危及铁路线路运营安全;2)在隔离桩防护措施下,小半径盾构隧道施工对铁路桥梁的影响在可控范围内,能有效降低盾构隧道施工引起的铁路桥梁变形及其附加内力,有利于铁路线路的运营安全;3)监测数据与数值计算的对比表明,隔离桩防护措施对于保障铁路线路的运营安全是有效的。本文研究结果可为盾构隧道安全穿越铁路桥梁施工提供重要的工程实用价值。

注浆-冻结联合工法加固地铁隧道地表融沉特性研究

在地铁隧道修建过程中若遇到复杂不良地质,单一工法有时无法将冻胀融沉位移控制在预期范围内,而采用注浆-冻结联合工法施工,能够有效控制土体融沉位移的施工参数。本文以广州地铁三号线某折返线隧道冻结工程为背景,隧道所处地层为砂质黏土地层,采用有限元数值分析软件,建立水热力耦合模型分析地铁隧道冻胀融沉位移场的发展规律,并与实测数据进行对比验证了模型可靠性,建立不同注浆半径的地铁隧道模型。通过对比其注浆控制效果,得出该法能够控制地表融沉位移的最佳注浆半径,并在此基础上研究了不同水泥掺量对土体融沉位移的影响,进一步得出能够有效控制土体融沉位移的施工参数。结果表明,采用水泥预加固-人工冻结联合工法施工,注浆半径选取4~5 m对融沉的控制效果最佳,注浆半径在4 m以上时土体融沉位移的效率开始有了明显的减弱。水泥掺量大于9%时,改善土体融沉位移的效率开始提高;而水泥掺量达到12%以后,改善土体融沉竖向位移的效率变缓。注浆半径设定在4 m,水泥掺量设定为12%,此时与原施工方案对比,自然解冻末期地表融沉量减小了73%。本研究的设计参数可为其他类似工程施工提供理论依据。

基于换热管束优化布置的固态储氢反应器储氢性能模拟研究

为探究固态储氢反应器内的热质传递过程,建立了反应器的二维数值计算模型,分析了反应器内固态储氢材料的径向反应分率分布特性,以及储氢材料床层厚度与换热管径对饱和半径的影响规律,进而开展了换热管束优化布置研究。结果表明:换热管存在对应的最大饱和半径,且随管径增加而增大;当管半径为1.00~6.00 mm的单管布置时,最大饱和半径分别为2.60、3.30、3.50、3.70、3.80、3.90 mm,其中半径为1.00、2.00、3.00 mm的换热管体积分数较小,分别为7.72%、14.24%、21.30%,当这3种换热管以管束布置时,较优的管间床层厚度分别为4.86、6.09、6.38 mm;此外,增设换热管束可有效改善反应器内反应死区的储氢性能。在半径2.00 mm换热管束的反应器内,与未增设换热管束相比,在反应死区增设12根半径1.00 mm换热管后储氢时间减少了40.00%,为267 s,而换热管束体积分数仅增加了1.92%,储氢量仅减少2.17%。该研究成果可为固态储氢反应器的优化设计奠定基础,并为后续的工程应用提供指导。

多孔质气体静压径向轴承的可压流动建模及数值求解

为研究可压流动下多孔质静压径向轴承的静特性,基于雷诺润滑方程、多孔质达西方程、气体压力-密度方程,建立了多孔质径向轴承的流动模型.提出了一种处理多孔质轴向端面压力边界条件的Laplace-Neumann虚拟节点法,结合有限差分法、松弛迭代法、压力-密度耦合迭代法对流动模型进行数值求解.分析了可压流动下轴承半径间隙和供给压力对静压特性的影响,并与不可压流动计算结果进行对比.结果表明:在同一最小膜厚下,随着半径间隙和供给压力的增大,可压流动与不可压流动的承载能力、质量流量和功耗均增大.可压流动下的承载能力在半径间隙0.01 mm和0.03 mm下小于不可压流动,在半径间隙0.05 mm下大于不可压.可压流动下的质量流量和功耗均大于不可压流动.本研究可为多孔质静压径向轴承的设计及快速计算提供参考.

一种数值阻尼耗散可控的结构动力方程积分方法

数值耗散是数值积分方法的重要特性,直接影响数值仿真结果的准确性.对于含有虚假高频振动的动力系统,数值耗散能够改善数值仿真结果,但是对于具有真实高频振动的动力系统,数值耗散则会导致计算结果失真.该研究针对结构动力系统的求解,提出了一种数值耗散可控的两子步隐式数值积分方法.基于理论推导,详细介绍了新积分方法的谱半径、稳定性、振幅衰减和周期延长等数值特性.新隐式积分方法通过算法参数α能够对高频虚假振动数值耗散完全可控,相应的耗散比例为1-α,其中-1≤α≤1.通过单自由度动力系统、高频虚假振动系统和多自由度非线性弹簧质量系统三个典型算例,分别证明了新隐式积分方法在计算精确性、高频数值耗散和非线性求解能力方面的优越性.