Effects of geometrical and physical factors on light particles dispersion by agitation characteristic curve

In this study,the effects of geometrical and physical factors on light particles dispersion in stirred tank were investigated by agitation characteristic curve.The experiments and CFD simulations with discrete phase model(DPM)and volume of fluid model(VOF)were conducted in this paper.Five factors,which include four geometrical factors(submergence,impeller-to-tank ratio,number of impeller blades and baffling mode)and a physical factor(liquid viscosity)were considered.For each factor,the power consumption curve and agitation characteristic curve were drawn to compare the power consumption and mixing results in the stirred tank.Characteristics of the agitation characteristic curves were compared with the previous published literatures and theories.It is found that the agitation characteristic curves reflect the tendency of power consumption and particles distribution well in stirred tank.The good agreement indicates the applicability of the agitation characteristic curves for the study of light particles distribution in stirred tank.

Influence of geometric parameters on stress concentration factors of undermatched butt joint with single V-groove under three-point bending load

In order to improve the bending load-carrying capacity （BLCC） of undermatched butt joint under three-point bending load, the influence of joint geometric parameters on stress concentration factors （SCF） at the weld bottom center and the weld toe of uudermatched butt joint with single V-groove are studied respectively based on the finite element method in this paper. Results show that the reinforcement height and the cover pass width play decisive role in the BLCC for undermatched butt joint. BLCC of undermatched butt joint can be improved by choosing the appropriate joint geometric parameters.

Investigation of Geometric Factors of Convex Platforms in the Flat Evaporator of Loop Heat Pipes

This paper investigated the influence of geometric factors of vapor groove structures on the performance of flat evaporator of a loop heat pipe system. COMSOL multiphysics software was employed to simulate the heat transfer in the evaporator with convex platforms of different shapes,sizes and area ratios(φ)between convex platforms and the heated surface. The maximum temperature and temperature distribution of each model were obtained. The results showed that the decrease of the size of platforms and the increase of φ can lower temperatures and improve temperature distribution homogeneity of the heated surface. Compared with circle and oval platforms,square platforms achieved lower temperature. The results also indicated that φ had the most significant impact on the performance of the evaporator.

The influence of joint geometric parameters on shape factor of butt joint with center through crack

In this research, the influence of such joint geometric parameters as weld width and reinforcement on shape ~actor of butt joint with center crack subjected to static loading was investigated by finite element analyses method. According to the analytical resuhs, a well fracture resistant joint shape of butt joint with center crack has been approved.

Fatigue Magnification Factors of Arc-Soft-Toe Bracket Joints

Arc-soft-toe bracket(ASTB), as a joint structure in the marine structure, is the hot spot with significant stress concentration, therefore, fatigue behavior of ASTBs is an important point of concern in their design. Since macroscopic geometric factors obviously influence the stress flaws in joints, the shapes and sizes of ASTBs should represent the stress distribution around cracks in the hot spots. In this paper, we introduce a geometric magnification factor for reflecting the macroscopic geometric effects of ASTB crack features and construct a 3D finite element model to simulate the distribution of stress intensity factor(SIF) at the crack endings. Sensitivity analyses with respect to the geometric ratio Ht/Lb, R/Lb, Lt/Lb are performed, and the relations between the geometric factor and these parameters are presented. A set of parametric equations with respect to the geometric magnification factor is obtained using a curve fitting technique. A nonlinear relationship exists between the SIF and the ratio of ASTB arm to toe length. When the ratio of ASTB arm to toe length reaches a marginal value, the SIF of crack at the ASTB toe is not influenced by ASTB geometric parameters. In addition, the arc shape of the ASTB slope edge can transform the stress flowing path, which significantly affects the SIF at the ASTB toe. A proper method to reduce stress concentration is setting a slope edge arc size equal to the ASTB arm length.

Spatial distribution rules and affecting factors of BIF in Anshan-Benxi area

A detailed investigation on 3D spatial distribution rules of Banded Iron-bearing Formation(BIF) with methods of gravity-magnetic inversion and 3D modeling of iron mine is presented based on the former analysis in the Anshan-Benxi area.Three dimension spatial distribution types of BIF are concluded as hook-like,tabularlike and "W"-like.BIF was mainly developed in three types of space including(1) the syncline cores,(2)cover coverage area,and(3) the deeper buried area where the range of tectonic uplift is small.The influences of tectonism,magmatic intrusion and uplift-erosion on the spatial distribution shapes of BIF are clarified.

Comparison of Traffic Growth Factors in Three Major Highways of Bangladesh： A Case Study

The unanticipated increase in vehicle population and heavy axle loads has brought the road network of Bangladesh to a crumbling stage. The network is grossly short of its structural capacity, highly distressed and has started showing signs of premature failure. The RHD （Roads and Highways Department） of Bangladesh uses 8%-10% growth rate of traffic for structural design of these highways that need to be upgraded due to present high traffic volume demand. An attempt has been made through this case study, by using traffic flow data from different computerized toll plaza established in recent times, to predict traffic growth pattern of different highways of Bangladesh. The toll collectors of different computerized toll plaza have been recording and preserving round-the-year continuous flow data in a systematic manner. The study has taken this prospect of utilizing several years of flow data along Dhaka-Chittagong Highway （N-1）, Dhaka-Sylhet Highway （N-2）, Dhaka-North Bengal Highway （N-5） and found the traffic growth factor of 21.03%, 23.79% and 11.31%, respectively, which is much higher than that transport authority of Bangladesh is currently using. By the use of accurate traffic engineering parameters such as traffic growth factors, it is possible to resist frequent distress of pavement and sustainable pavement management can be implemented by RHD.

Hierarchic Computations in Geometric Space—Showing Sharp Diffraction in Quasicrystals

A quasi-structure factor method is used to show how sharp diffraction patterns are produced by aperiodic quasicrystals. Icosahedral symmetry is described for the tensor rank 3 solids with edge-sharing unit cells that are pentagonally close packed in hierarchic structures having a geometric reciprocal lattice. The hierarchic symmetry replaces translational symmetry in crystal diffraction. Details in the calculation show how the symmetry is simulated in diffraction.

Prevalence and risk factors for left ventricular hypertrophy and left ventricular geometric abnormality in the patients with hypertension among Han Chinese

Background Left ventricular hypertrophy （LVH） and geometric abnormality are associated with morbidity and mortality of cardiovascular disease and stroke. Hypertension is the major cause of LVH. Yet the prevalence and other risk factors of LVH and geometric abnormality in Chinese hypertensive population are unknown. The objective of this study was to investigate the prevalence and risk factors of LVH and geometric abnormality in community-based Chinese hypertensive population. Methods The study was a community-based cross-sectional study, and comprised 4270 hypertension patients with integrated clinical and echocardiographic data. Left ventricular mass was measured by transthoracic echocardiography. LVH was diagnosed by using the criteria of over 49.2 g/m^2.7 for men and 46.7 g/m^2.7 for women. LV geometric patterns （normal, concentric remodeling, concentric or eccentric hypertrophy） were calculated according to LVH and relative wall thickness. Logistic regression model was used to determine the odds ratio （OR） and 95% confidence intervals （CI） of the risk factors of LVH. Results The prevalence of LVH was 42.7% in 4270 hypertensive patients, with 37.4% in males and 45.4% in females, respectively. The prevalence of concentric remodeling, concentric or eccentric hypertrophy was 24.7%, 20.2%, and 22.6%, respectively. In Logistic regression model, female （OR 1.3, 95%C/ 1.1-1.5, P 〈0.01）, age （OR 1.02, 95%C/ 1.01-1.03, P 〈0.01）, body mass index （OR 1.2, 95%C/1.15-1.20, P 〈0.01）, systolic blood pressure （OR 1.02, 95%C/ 1.01-1.03, P 〈0.01 ）, and serum triglyceride （OR 1.10, 95% CI 1.00-1.20, P 〈0.01 ） were risk factors of LVH. Female, age, body mass index, systolic blood pressure and serum triglyceride were also risk factors of left ventricular geometric abnormality. Conclusions The echocardiographic LVH is the major complication of patients with hypertension in rural area of China, especially for women. To effectively treat hypertension, weight loss and control of serum triglyceride may help to prevent LVH in hypertensive population.

基于三维地质建模技术的煤矿隐蔽致灾因素透明化研究

隐蔽致灾因素是制约煤矿智能开采建设的关键问题,而三维地质建模是实现隐蔽致灾因素透明化的主要技术手段。目前煤矿三维地质建模技术以几何建模为主、属性建模为辅,缺少针对隐蔽致灾因素的灾害属性建模。针对上述问题,以陕北某煤矿作为研究对象,对煤层厚度、顶底板构造起伏、积水区、浅埋煤层地形地貌等隐蔽致灾因素进行三维地质建模。首先,完成对地质资料、物探、钻探等成果的数字化工作,建立煤矿地质数据库。其次,利用DepthInsight建模软件从全矿井和工作面2个尺度开展建模工作,即以钻孔分层数据作为地层控制点,通过煤层及地表等高线、虚拟钻孔等数据联合控制地层层序,并处理初始层面模型中的穿层异常,构建地层面模型和地质体模型,再运用数字高程模型对工作面进行地表模型构建。然后,采用岩体建模构建采空区、积水区模型并标注温度、气体等信息,利用工作面回采测量数据构建回采实测模型。最后,创建截断网格模型,通过序贯高斯模拟生成含水层渗透率、富水系数模型,实现区内水文隐蔽致灾因素透明化显示。基于三维地质模型,从地层、煤层及工作面、采空区及其积水区、水文属性多角度分析隐蔽致灾因素的分布及影响。研究成果可为煤矿隐蔽致灾因素的精准治理提供靶区,助力煤矿智能开采建设。

甘肃鼢鼠头骨几何形态地理分异及其影响因素分析

【目的】从形态学角度揭示地下啮齿动物甘肃鼢鼠(Eospalax cansus)的适应性进化过程。【方法】选取高低海拔分布的4个甘肃鼢鼠种群,使用几何形态学分析其头骨形态的种内变异,并选取海拔、年均温、年降水量及植被归一化指数作为生态因子,利用偏最小二乘(Two-block partial least squares,Two-block PLS)研究头骨形变与环境之间的联系。【结果】不同海拔分布下的甘肃鼢鼠种群间头骨大小无显著差异,但头骨形状间差异显著,基于头骨形状数据可以将4个地理种群准确判别;鼻骨、顶嵴、枕骨、听泡、臼齿及颌颌缝等具有重要生态功能的结构形状随海拔、年降水量及植被归一化指数变化的趋势明显,反映了环境在甘肃鼢鼠种群间头骨形状差异形成中的作用。此外,甘肃鼢鼠的头骨形状进化符合“距离隔离”模型。【结论】甘肃鼢鼠种群间头骨形状差异显著;在海拔、降水及植被等生态因子的影响下,头骨背面结构鼻骨、顶嵴及枕骨等和头骨腹面结构听泡、臼齿及颌颌缝等具有明显的形变趋势,反映了不同环境下甘肃鼢鼠头骨的适应性进化。

超高速公路设计标准研究综述与展望

从超高速公路概念与分级、驾驶适应性与人因、几何线形设计标准、沿线设施设计标准、交通组织与管理等方面的研究现状进行归纳和综述。结果表明:超高速公路最高设计速度取140~160 km/h时,通过提速改造或新建的方式满足当前普通小客车的思路,更适合当前的交通发展现状;超高速驾驶适应性、人因与驾驶行为方面的研究还未系统开展;几何线形设计标准方面相关研究普遍基于车辆动力学理论推荐,但结果存在一定的差异;缺少基于驾驶人和车辆超高速行驶适应性和稳定性的验证研究,缺少交通流基础规律和适应交通量标准研究;缺少互通式立交、隧道、服务设施、安全设施、路面条件等设施方面的研究,应进一步结合人因与驾驶行为、车辆动力学特性系统开展相关研究;缺少交通流组织与管理方式方面的研究,当前条件下,如何从空间上分离不同特性的车辆、降低干扰、保证超高速功能的发挥,需要从驾驶行为规则、限速管理、车道管理、车型管理等方面开展研究;应加强不良天气管理、应急救援管理、日常养护管理等方面的研究,确保超高速公路功能正常发挥;研究手段方面,考虑到驾驶人和车辆超高速行驶适应性、规律性和稳定性方面的问题,应该大量补充基于实车试验、驾驶模拟试验等手段的研究。

Discussion on the geometric factor in the detection of high energy electrons in geospace

High energy electron is a kind of sources to be detected in the geospace environ- ment. Generally, the particle telescope with much thick semiconductor detector is used as the sensor for energetic electrons because they can penetrate deeply into the detector. The more energy of the electrons is, the deeper they can penetrate into, so that the geometric factor varies with energy of the incident electrons. We discuss the geometric factor of particle radiation detector (PRD), which is a payload on ZY-1 (CBERS-1 and CBERS-2) satellites to monitor the high energy particle ra- diation inside the satellites. According to the NASA’s AE8 model, the geometric factors of electrons for the low energy bin (0.5―1.0 MeV) and the high energy bin (> 2.0 MeV) are 2.468 and 1.736 cm2·sr, respectively. These results are much differ- ent from the traditional calculation of the geometric factor that is 1.18 cm2·sr. The angle-response function of the telescope is also derived, which can be useful for design of the telescope and analysis of the directional distribution.

The geometric factor of high energy protons detector on FY-3 satellite

Geometric factor is the key parameter for inversion of particle spectrum in space particle detection. Traditional geometric factor is obtained through the method of numerical calculation with the actual structure of the detector as the input condition. The degree of accuracy for data inversion is reduced since traditional geometric factor fails to take into account the physical process of interaction between the particle and substance as well as the influence of factors such as the particle interference between different energy channels on the measurement result. Here we propose an improved geometrical factor calculation method, the concept of which is to conduct actual structural modelling of the detector in the GEANT4 program, consider the process of interaction between the particle and substance, obtain the response function of the detector to particles of different energy channels through the method of Monte Carlo simulation, calculate the influence of contaminated particle on the geometrical factor, and finally get the geometrical factors for different energy channels of the detector. The imrpoved geometrical factor obtained through the method has carried out inversion for the data of high energy protons detector on China's FY-3 satellite, the energy spectrum after which is more in line with the power law distribution recognized by space physics. The comparison with the measured result of POES satellite indicates that the FY-3 satellite data are in good accordance with the satellite data, which shows the method may effectively improve the quality of data inversion.

面向地震动估计需求的区域传播介质参数

地震动估计是抗震设计和风险评估的重要输入来源。地震动估计中,地震波在地壳介质中的传播可用几何扩散项和非弹性衰减项表达。文中针对这2项区域传播介质特性,从几何扩散项和非弹性衰减项2个角度分别开展研究。首先,以地震记录丰富的日本东北部地区为研究区,使用遗传算法反演几何扩散项参数并讨论震级、震源深度及莫霍面深度的影响。结果表明:莫霍面埋深对几何扩散项参数的影响最大。将此结果用于中国西部的四川、新疆和云南地区,按照莫霍面深度分区并分段拟合几何扩散项参数。在此基础上,从地质学的角度重新划分区域,借助遗传算法反演得到不同分区的非弹性衰减项参数Q0和η等。结果表明:在大地热流数值较高、莫霍面较浅、上地壳剪切波速较低、地震活动较强烈的地区,地震波衰减较快,通常Q值较低;在地质年代由古及今、高程增加的情况下,Q值逐渐减小。面向地震动估计所需的区域地壳介质参数Q值,给出了反演区域范围的划分方案,即四川的东部地区和新疆天山地区为高Q值区域,云南、四川中西部地区和新疆喀什地区为低Q值区域。其中,云南西北部和四川中西部为Q值相对更低的地区。

几何形状对气垫升力的影响研究

One of the crucial and challenging issues for researchers is presenting an appropriate approach to evaluate the aerodynamic characteristics of air cushion vehicles(ACVs)in terms of system design parameters.One of these issues includes introducing a suitable approach to analyze the effect of geometric shapes on the aerodynamic characteristics of ACVs.The main novelty of this paper lies in presenting an innovative method to study the geometric shape effect on air cushion lift force,which has not been investigated thus far.Moreover,this paper introduces a new approximate mathematical formula for calculating the air cushion lift force in terms of parameters,including the air gap,lateral gaps,air inlet velocity,and scaling factor for the first time.Thus,we calculate the aerodynamic lift force applied to nine different shapes of the air cushions used in the ACVs in the present paper through the ANSYS Fluent software.The geometrical shapes studied in this paper are rectangular,square,equilateral triangle,circular,elliptic shapes,and four other combined shapes,including circle-rectangle,circle-square,hexagonal,and fillet square.Results showed that the cushion with a circular pattern produces the highest lift force among other geometric shapes with the same conditions.The increase in the cushion lift force can be attributed to the fillet with a square shape and its increasing radius compared with the square shape.

基于加工误差仿真的半球谐振子优化设计

针对半球谐振陀螺谐振子制造过程中存在的加工误差,采用有限元仿真,分析了半球谐振子结构参数、尺寸公差和形位公差变化对其工作模态频率和临近模态频率的影响,研究了半球谐振子形位公差变化对频率裂解和品质因数的影响。通过仿真分析可知,半球谐振子结构参数壁厚、半球中心半径及内倒角半径都会影响模态频率;半球谐振子形位公差中的内外球心距离误差对其工作模态影响较大,中心轴平行误差对频率裂解和品质因数影响较大;半球谐振子壁厚、内倒角半径、小柱半径及内外球心距离误差变化会使工作模态频率与相邻模态间存在干扰。在此基础上,提出了半球谐振子结构参数及形位公差优化设计建议,并通过半球谐振子品质因数Q值和频率裂解测量对该建议进行了验证。

基于液滴长短轴变化对彩虹色散效应的研究

本文将彩虹的几何理论与菲涅尔波动理论相结合,总结了影响彩虹现象的因素,并对空气中液滴的长短轴变化产生的影响进行了讨论,通过理论分析、计算机模拟和实验验证,发现当液滴长短轴相等时,半径的变化与产生虹的光强成正比,入射光强越强,正比的系数即变化的程度越大;当长短轴不相等即为椭球体时,需要将光束汇聚和光束能量综合,以判断不同长短轴椭球形成彩虹的观测角度。该研究有利于理解彩虹现象,了解光学的几何理论与菲涅尔公式的综合应用。

成熟因子映射的双系统选星方法

传统的选星方法通常以遍历为手段,在可见星较多的情形下往往计算量很大。常规的遗传算法通常固定交叉和变异概率,产生不必要的时间消耗。针对这些问题,提出了引入成熟因子映射交叉概率和变异概率的双系统遗传选星算法,目的在于快速地找到最优解或可接受的次优解。该方法以几何精度因子(Geometric Dilution of Precision,GDOP)为适应度,构造单染色体种群,定义成熟度来指导交叉变异操作,再经过每代精英保留策略和隔代种群数量控制,最终搜索得到符合门限的可接受解。实验结果表明,在进化200代的条件下,成熟因子映射遗传算法比常规遗传算法的搜索时间平均节省约24.75%,引入种群数量控制机制后搜索时间进一步节省了约55.32%。该方法可以快速获得稳定数学期望的可用选星集合。

半分离式斜腹板双箱梁大跨单肋拱桥颤振临界风速分析

为研究低扭弯频率比大跨度桥梁的颤振性能,以某主跨180 m的半分离式斜腹板双箱梁大跨单肋拱桥为背景(主梁扭弯频率比接近1.0),进行颤振临界风速分析。采用有限元法分析该桥动力特性,计算桥梁颤振稳定性;对比《公路桥梁抗风设计规范》(JTG/T 3360-01—2018)推荐的3组理想平板颤振临界风速估算公式,基于Scanlan半逆解法的理想平板颤振临界风速,考虑主梁形状与攻角修正系数确定颤振临界风速范围;采用强迫振动数值模拟识别颤振导数,获得精确颤振临界风速,进一步计算半分离式斜腹板双箱梁的形状和攻角系数。结果表明:该桥主梁扭弯频率比较低,颤振稳定性低于500 m级大跨度双肋拱桥;规范推荐的理想平板颤振临界风速估算公式在小扭弯频率比时差异较大;半分离式斜腹板双箱梁形状修正系数小于分离式双箱梁而大于P-K梁、带斜腹板箱梁,攻角修正系数略大于这3种形式主梁。