Nonlinear profile order for three-dimensional hybrid radial acquisition applied to self-gated free-breathing cardiac cine MRI

This paper presents a nonlinear profile order scheme for three-dimensional（3D） hybrid radial acquisition applied to self-gated, free-breathing cardiac cine magnetic resonance imaging（MRI）. In self-gated, free-breathing cardiac cine MRI,respiratory and cardiac motions are unpredictable during acquisition, especially for retrospective reconstruction. Therefore,the non-uniformity of the k-space distribution is an issue of great concern during retrospective self-gated reconstruction. A nonlinear profile order with varying azimuthal increments was provided and compared with the existing golden ratio-based profile order. Optimal parameter values for the nonlinear formula were chosen based on simulations. The two profile orders were compared in terms of the k-space distribution and phantom and human image results. An approximately uniform distribution was obtained based on the nonlinear profile order for persons with various heart rates and breathing patterns.The nonlinear profile order provides more stable profile distributions and fewer streaking artifacts in phantom images. In a comparison of human cardiac cine images, the nonlinear profile order provided results comparable to those provided by the golden ratio-based profile order, and the images were suitable for diagnosis. In conclusion, the nonlinear profile order scheme was demonstrated to be insensitive to various motion patterns and more useful for retrospective reconstruction.

Prediction of Deformation and Footprint of High-speed Rotating Radial Tires

In this research,the tire deformations due to rotation are divided into three parts:tread,belt and carcass.Tread deformation is obtained by using a rotating hollow cylinder model,belt expansion is calculated according to the laminated composite shell theory,and a formula of dynamic equilibrium profile is built to investigate carcass deformation.Moreover,a simple method is used to predict the footprint changes caused by tire deformation.Results show that a large deformation is occurring at tire shoulder,a smaller one at tread centre,and the shoulder deformations are mostly caused by carcass.Length of footprint side edges increase with tire rolling speed increasing.The predicted tread,belt,carcass deformations and footprint changes are in good agreement with finite element analysis results.The proposed method and the results will offer a helpful guidance to tire and vehicle engineers.

The Axial and Radial Solid Loadings up the CFB-Riser

1 INTRODUCTIONThe determination of the solids hold-up and local solidfluxes is of paramount importance in the study ofthe hydrodynamics of a two-phase flow.Several tech-niques have been used during the past decades(Table1).These methods can be classified in two groups,depending on their possible disturbance of the two-

Prediction of Restriction Width of Carcass by Belts for Radial Tires :Theory, Experiment and Simulation

The restriction width of carcass by the belts( RWCB) as an important parameter of radial tire design has been neglected for a long time. In order to improve the accuracy and efficiency of tire profile design,the calculating method of RWCB is proposed. The equilibrium profile is calculated by geometric model and variational approach,based on it,the predicted model of RWCB is developed for tire design. Finally,four different designs of 12R22.5 tires are investigated by experiment and finite element method,which is used to validate the accuracy of the theoretical method. Results indicate that experimental and finite element analysis results are found to be in good agreement with theoretical results; linear relationships are existed between the cord length and RWCB,and also existed between the position of belt and RWCB; tires designed by the methods have smaller and more uniform displacement,so the method can be used for tire optimized design.

Study on Radial Position of Impurity Ions in Core and Edge Plasma of LHD Using Space-Resolved EUV Spectrometer

Radial profiles of impurity ions of carbon, neon and iron were measured for high- temperature plasmas in large helical device （LHD） using a space-resolved extreme ultraviolet （EUV） spectrometer in the wavelength range of 60A to 400 A. The radial positions of the impurity ions obtained are compared with the local ionization energies, El of these impurity ions and the electron temperatures T,z there. The impurity ions with 0.3 keV 〈_ Ei ≤ 1.0 keV are always located in outer region of plasma, i.e., 0.7 ≤ p ≤ 1.0, and those with Ei ≤ 0.3 keV are located in the ergodic layer, i.e., 1.0 ≤ p≤ 1.1, with a sharp peak edge, where p is the normalized radial position. It is newly found that Tez is approximately equal to Ei for the impurity ions with Ei ≤ 0.3 keV, whereas roughly half the value of El for the impurity ions with 0.3 keV≤ Ei ≤ 1.0 keV. It is known that Tez is considerably lower than Ei in the plasma edge and approaches to Ei in the plasma core. Therefore, this result seems to originate from the difference in the transverse transport between the plasma edge at p 〈1.0 and the ergodic layer at p ≥ 1.0. The transverse transport is studied with an impurity transport simulation code. The result revealed that the difference appearing in the impurity radial positions can be qualitatively explained by the different values of diffusion coefficient, e.g., D=0.2 m2/s and 1.0 m2/s, which can be taken as a typical index of the transverse transport.

液环真空泵叶轮与壳体型线的协同优化

为研究液环泵叶轮与壳体型线对其性能的耦合影响关系,采用高阶Bezier曲线和直接自由曲面变形(DFFD)方法对叶轮及壳体型线进行参数化控制,根据拉丁超立方(LHS)抽样方法,建立液环泵叶轮和壳体型线参数与真空度和效率间的径向基函数(RBF)代理模型,基于NSGA-Ⅱ算法实现液环泵叶轮和壳体型线耦合多目标优化。结果表明:叶轮与壳体耦合多目标优化得到的模型K(真空度最优模型)的真空度提高了11.2%,模型J(效率最优模型)的效率提高了4.1%;叶片包角的增大和扩张的吸气段壳体型线有助于提高泵的进口真空度,出口安放角的增大、收缩的吸气段型线以及扩张的排气段型线可降低泵内水力损失,提升效率;叶轮与壳体型线的耦合优化效果明显优于独立优化;在相同代理模型条件下,叶轮与壳体的分步优化与耦合优化结果基本一致。

基于多目标粒子群算法的隔膜压缩机膜腔曲线优化

膜腔曲线直接影响着隔膜压缩机排气量与膜片可靠性,原始膜腔曲线不能较好满足今后加氢站隔膜压缩机高压力、大流量工况需求。针对此问题,依据隔膜压缩机工作原理,采用多目标粒子群算法对膜腔曲线进行面积与弧长的双目标优化计算,得到了一种新曲线。同时,结合压缩机工程实际对膜腔曲线进行了改进,并对改进后的膜腔曲线与原始曲线进行容积计算与有限元应力对比。研究结果表明:在给定新曲线内参数m=0.95、n=2.5且膜腔半径与膜片厚度不变的情况下,新曲线膜腔下膜片气侧最大径向应力较原始曲线降低了13.89%,膜腔容积较原始曲线增加13.72%。

Statistics for Size and Radial Wind Profile of Tropical Cyclones in the Western North Pacific

The 6-yr best-track data of tropical cyclones （TCs） in the western North Pacific are used to study the statistical features of TC size and radial wind profile. A TC size is defined as the azimuthal mean radius of 34-kt surface wind. On average, the TCs in the western North Pacific have a size of 203 km, and the size is larger for stronger TCs. Further analyses show that larger TCs tend to move faster than smaller ones, with a 23–24 km difference in size corresponding to a difference of about 10 km h -1 in moving speed. The TCs that recurve from westward to eastward moving have a mean size of 218 km, significantly larger than that of those without a turning point （179 km）. Regional TC distributions demonstrate that the TCs affecting the Korean Peninsula and southwestern Japan have the largest mean size （250–280 km）. There are also some large TCs affecting southern Philippines, while TCs over the South China Sea are generally small in size. Comparison of intensity and size of all TCs during their lifespan demonstrates that a TC tends to reach its maximum size 6 h after it reaches its maximum intensity, and the decrease rate of size during the weakening stage of a TC is much smaller than the increase rate of size during its developing stage. Thus, linear regression relations between TC size and intensity are established for its developing and weakening stages respectively, which can be used as a forecast tool for TC size. Features of TC radial wind profile are studied by analyzing a parametric wind model based on the radius data of 34-, 50-, and 64-kt surface winds. The results show that the shape parameter d most frequently takes the values of 0.3, 0.4, and 0.5. It generally increases （decreases） as the TC develops （weakens）, implying a sharper （flatter） radial wind profile. Changes in d leads the tendency of intensity. The two parameters for the asymmetric model, namely p and q, are mostly 0.85–1.05 and 0–0.2, respectively, embodying the fact that the asymmetric component is generally much smaller than the symmetric component. The asymmetry in 34-kt surface wind is much stronger than that in 50and 64-kt surface winds, with the maximum radius often in the northeast quadrant.

声波测井多尺度成像方法在压裂效果评价中的综合应用

多极子阵列声波测井记录了丰富的井筒声场信息,各类声波的探测视角和深度各有不同,是实现地层精细评价的重要信息来源。基于储层压裂评价的需要,主要阐述常见阵列声波测井数据中可利用的成像方法系列,即基于斯通利波的井壁裂缝成像、基于纵波的径向声速层析成像和基于反射声波的远探测成像,分别对应浅(探测深度小于0.3 m)、中(探测深度约1.0 m)、深(探测深度大于5.0 m)这3种探测尺度。为适配压裂评价场景,重点讨论斯通利波成像过程、径向声速层析的正反演机制以及远探测的优化成像策略。实际中,首次将此测井声波多尺度成像技术应用到中国西部某储层压裂,分别对压裂前裸眼井和两次压裂后采集的3次阵列声波测井数据执行成像处理和统一对比分析,分析结果与现场应用结果相吻合,取得良好的应用效果,为明确压裂裂缝在近场-远场的变化关系提供可视化依据。

台风结构与强度以及环境场对西北太平洋台风尺度估计的影响研究

台风风场径向廓线模型对台风灾害的评估以及台风尺度的研究具有重要的价值.利用西北太平洋2001-2020年的台风最佳路径观测数据,评估了目前国际上应用比较广泛的六个分别基于经验参数和物理过程的台风风场径向廓线模型对台风尺度(台风大风半径,R17)的估计精度,并探讨了台风结构、强度等内部因素以及垂直风切变和移动速度等环境因子对模型精度的影响.评估发现,所有模型均高估了R17较小的台风而低估了R17较大的台风,且R17越小,高估越明显,R17越大,低估越严重.总体而言,Willoughby et al发展的基于参数的模型具有最小的估计偏差且与观测记录之间最高的相关性.研究还发现,台风内核尺度(最大风速半径,RMW)和强度(最大地面风速,V_(max))对不同模型的影响具有显著的差异性.此外,在高环境风切变和高移速条件下,模型的估计偏差的量级会显著增加.以上研究为进一步完善适用于不同环境条件下,不同结构与强度台风的风场模型提供参考.

Characteristics of elution profile in radial chromatography under linear conditions

Based on the mass balance equations of solute transfer in the radial chroma-tographic column,the theoretical expression to describe the column efficiency and shape of elu-tion profile is obtained under linear isotherm case.Moreover,the tendency for the variation of column efficiency and symmetry of peak profile is systematically discussed.The results showed that in radial chromatography the relationship between the column efficiency and volumetric flow rate is similar with that relationship in axial chromatography;relatively high column efficiency still can be obtained under high flow rate in radial chromatography.Accompanying the increase of retention factor of solutes and injection time,the column efficiency decreases monotonously.The effect of column diameter and column length on the column efficiency interfere with each other.It is more advantageous to increase the column efficiency by applying columns with larger column diameter and shorter column length.According to the discussion of the effect of diffusion on the column efficiency,radial chromatography is proved to be suitable for the separation of samples with relatively high diffusion coefficient,which predicts its obvious advantage in the preparative separation of samples such as proteins and DNA.

Radial profile of bottom quarks in jets in high-energy nuclear collisions

Angular correlations between a heavy quark(HQ)and its tagged jet are potentially new tools to gain insight into the in-medium partonic interactions in relativistic heavy-ion collisions.In this work,we present the first theoretical study on the radial profiles of B mesons in jets in Pb+Pb collisions at the Large Hadron Collider(LHC).The initial production of a bottom quark tagged jet in p+p is computed by SHERPA,which matches the next-to-leading order matrix elements with contributions of parton showers,whereas the massive quark traversing the quark-gluon plasma is described by a Monte Carlo model,SHELL,which can simultaneously simulate light and heavy flavor in-medium energy loss within the framework of Langevin evolution.In p+p collisions,we find that at lower PQ/T the radial profiles of heavy flavors in jets are sensitive to the heavy quark mass.In 0-10%Pb+Pb collisions at√SNN=5.02 TeV,we observe an inverse modification pattern of the B meson radial profiles in jets at4PQ/T<20 GeV compared to those of D mesons:the jet quenching effects narrow the jet radial profiles of B mesons in jets while broadening those of D mesons in jets.We find that in A+A collisions,the contribution dissipated from the higher PQ/T>20 GeV region naturally has a narrower initial distribution and consequently leads to a narrower modification pattern of the radial profile;however the diffusion nature of the heavy flavor in-medium interactions will give rise to a broader modification pattern of the radial profile.These two effects consequently compete and offset with each other,and the b quarks in jets benefit more from the former and suffer less diffusion effect compared to that of c quarks in jets.These findings can be tested in the future experimental measurements at the LHC to gain better understanding of the mass effect of jet quenching.

11R22.5全钢载重子午线轮胎胎圈轮廓设计

分析全钢载重子午线轮胎胎圈损坏问题,以轻量化11R22.5全钢载重子午线轮胎胎圈为例,设计轮胎胎圈仿生轮廓。该轮廓可以使胎圈与轮辋装配更加贴合,为轮胎负载提供支撑,还可以将胎体反包端点锚定,使胎圈损坏几率减小,有效提高轮胎耐久性能和高速性能,延长轮胎使用寿命。

295/60R22.5低断面全钢载重子午线轮胎的设计

介绍295/60R22.5低断面全钢载重子午线轮胎的设计。结构设计:外直径922 mm,断面宽294 mm,行驶面宽度246 mm,行驶面弧度高9.5 mm,胎圈着合宽度248 mm,胎圈着合直径569.5 mm,断面水平轴位置(H_(1)/H_(2))0.9155,采用4条纵向花纹沟设计。施工设计:采用双复合挤出胎面,1^(#)带束层采用4+3×0.33ST钢丝帘线,2^(#)和3^(#)带束层采用3+8×0.33HT钢丝帘线,4^(#)带束层采用5×0.30HI钢丝帘线,胎体采用3×0.24+9×0.225CCST钢丝帘线,采用一次法成型机成型、热板硫化机硫化。成品性能试验结果表明,轮胎的充气外缘尺寸、强度性能、耐久性能和高速性能均符合国家标准和设计要求。

利用阵列声波测井技术监测压裂裂缝参数的方法与应用

水力压裂是高效开发低渗储层的关键技术手段,监测地下压裂裂缝参数对于评价压裂改造效果、优化后续设计具有重要意义。然而由于海上作业环境的特殊性及成本限制,常规裂缝监测技术在海上应用效果不佳。通过前期开展的大量阵列声波测井测试资料,基于阵列声波测井技术建立了一套评价压裂裂缝参数的方法,利用横波波幅、声波各向异性以及径向速度剖面监测裂缝高度,利用声波远探测技术监测裂缝延伸距离,并进行了现场综合应用。结果表明:应用该方法能较为精准地监测缝高,同时能定性评价裂缝延伸距离,为渤海油田低渗储层压裂效果评价提供了一套有效的思路和方法。

基于转子齿两侧开槽的开关磁阻电机振动抑制方法研究

振动的抑制是近年来开关磁阻电机研究的热门领域。该文提出一种在转子齿两侧开槽的方法,通过改变转子齿形来改变转子表面气隙磁密的方向,可以减小气隙中的径向磁密,同时增大切向磁密,达到抑制电磁振动的目的。利用二维瞬态有限元法,验证了转子齿两侧开槽对径向力波的削弱和转矩脉动的抑制效果,研究了开槽尺寸变化对仿真结果的影响规律,并对5.5k W、1000r/min、12/8极开关磁阻电机的开槽参数进行了优化,进行了样机的试制和试验。试验结果表明:该方法对开关磁阻电机的电磁振动有较好的抑制效果,但对电机的运行效率有一定影响。

下行床入口段流体力学及混合行为

针对工业快速反应对气固进料混合过程的特殊需求，在内径140mm，高4.7m的并流下行循环流化床中，采用双光路光纤密度测量技术及磷光颗粒示踪技术，对两种不同的气固并流下行床分布器结构的流动及颗粒混合行为进行了研究．分别考察了人口段颗粒浓度径向分布沿轴向的变化规律及颗粒轴径向混合行为．实验结果表明，下行床入口段颗粒浓度随轴向位置的变化可划分为分布器影响区及湍流控制区．分布器结构对入口段颗粒密度分布有较大影响，利用侧向喷嘴并降低入口处颗粒的射流可以获得较好的径向均布效果．侧向喷嘴的分布器结构更有利于颗粒的径向混合．还考察了入口结构对颗粒混合的影响因素，给出了对Pe_a及Pe_r的关联式．

含Li^+的径向梯度折射率棒透镜的研究

研究发现在硼硅酸盐系统玻璃中 ,利用 Li+/Na+离子交换来制取径向梯度折射率( GRIN)棒透镜时 ,基质玻璃中重要的成分 L i2 O含量对径向 GRIN棒透镜的象差和数值孔径值有着明显的影响 ,并着重分析和讨论了实验中 Li2 O含量对径向 GRIN棒透镜中折射率分布、数值孔径及象差影响机制 .进一步指出实验中 Li2 O含量存在一个最佳值 ,既能够满足径向

纵波走时层析成像技术在非常规储层压裂评价中的应用

应用声波各向异性评价储层压裂效果的传统方法存在很多局限性,为了满足储层压裂效果评价的需求,引入了纵波走时层析成像技术。受钻井、工程压裂等影响,井壁附近的地层弹性波速度与远离井壁处的原状地层的速度相比有较大的变化,应用纵波走时可以对井壁附近的径向速度变化进行层析成像,获取井壁附近地层的径向速度剖面,用来确定钻井及工程压裂在地层中造成的破损范围的大小进而预测岩石脆性以及评价压裂效果。速度剖面在评价压裂效果方面与传统的各向异性方法对比体现了独有优势,当传统的各向异性方法评价压裂效果失效时,应用速度剖面可以很好地评价储层的压裂效果;压裂效果的好坏与压前的脆性指示有较好的一致性。

基于环量分布的离心叶轮S2流面设计与优化

采用准三维气动设计方法,用Bezier曲线表示环量沿轮毂和轮盘的流向分布,子午面环量分布由拉普拉斯方程确定,设计了3种不同负荷分布的离心式叶轮。采用CFD模拟,对比叶轮内流动和气动性能的优劣,结果表明:均匀加载型式的叶轮性能优于前加载或后加载的叶轮,最优设计的叶轮负荷分布是"两端小,中间大"。通过Laplace方程和Bezier多项式控制环量可以达到灵活控制叶片载荷的目的。