Seismic liquefaction potential assessment by using relevance vector machine

Determining the liquefaction potential of soil is important in earthquake engineering. This study proposes the use of the Relevance Vector Machine （RVM） to determine the liquefaction potential of soil by using actual cone penetration test （CPT） data. RVM is based on a Bayesian formulation of a linear model with an appropriate prior that results in a sparse representation. The results are compared with a widely used artificial neural network （ANN） model. Overall, the RVM shows good performance and is proven to be more accurate than the ANN model. It also provides probabilistic output. The model provides a viable tool for earthquake engineers to assess seismic conditions for sites that are susceptible to liquefaction.

Design on Tool Profile for Machining Cone Screw with Opposed Conical High Pressure Seawater Hydraulic Pump

In order to meet the requirements of the machining process of cone screw of the Opposed Conical High Pressure Seawater Hydraulic Pump,this work describes the design process to determine the theoretical profile of the tool,starting from the surface equation of the cone screw. Along with the expression of the theoretical tool profile,the equation of the contact line between the cone screw and the tool is established based on the coordinate transformation theory and the space meshing theory,as well as the surface equation and the position relationship between the screw and the tool during processing. By solving the contact condition based on the method of numerical discretization analysis via MATLAB,the contact line trajectory and theoretical tool profile curve are derived.The feasibility of the proposed method is verified by an example of tool profile design for machining the screw.

Regressive approach for predicting bearing capacity of bored piles from cone penetration test data

In this study, th e least sq u are su p p o rt v ecto r m achine （LSSVM） alg o rith m w as applied to predicting th ebearing capacity o f b ored piles e m b ed d ed in sand an d m ixed soils. Pile g eo m etry an d cone p e n e tra tio nte s t （CPT） resu lts w ere used as in p u t variables for pred ictio n o f pile bearin g capacity. The d ata u se d w erecollected from th e existing litera tu re an d consisted o f 50 case records. The application o f LSSVM w ascarried o u t by dividing th e d ata into th re e se ts： a train in g se t for learning th e pro b lem an d obtain in g arelationship b e tw e e n in p u t variables an d pile bearin g capacity, and testin g an d validation sets forevaluation o f th e predictive an d g en eralization ability o f th e o b tain ed relationship. The predictions o f pilebearing capacity by LSSVM w ere evaluated by com paring w ith ex p erim en tal d ata an d w ith th o se bytrad itio n al CPT-based m eth o d s and th e gene ex pression pro g ram m in g （GEP） m odel. It w as found th a t th eLSSVM perform s w ell w ith coefficient o f d eterm in atio n , m ean, an d sta n d ard dev iatio n equivalent to 0.99,1.03, an d 0.08, respectively, for th e testin g set, an d 1, 1.04, an d 0.11, respectively, for th e v alidation set. Thelow values o f th e calculated m ean squared e rro r an d m ean ab so lu te e rro r indicated th a t th e LSSVM w asaccurate in p redicting th e pile bearing capacity. The results o f com parison also show ed th a t th e p roposedalg o rith m p red icted th e pile bearin g capacity m ore accurately th a n th e trad itio n al m eth o d s including th eGEP m odel.

Study of CNC Grinding Machining Method About Isometric Polygon Profile

The formed principle and CNC grinding machining method of isometric polygonal profile are studied deeply and systematically. Equation about section curve of isometric polygon profile is set up by means of geometric principle. With the use of differential geometry theory, the curve is proved to be with geometric feature of convex curve. It is referred to as Isometric Polygonal Curve (IPC), because that is a kind of convex curve on which the distance between any parallel tangent lines is equal. Isometric Polygonal Profile (IPP) or Isometric Polygonal Cone Profile (IPCP) or Isometric Polygonal Topless Cone (IPTC) is formed with the IPC and straight line as generating curve. But the machining and measuring of the IPCP are so inconvenient that it has little value. Keeping in mind the characteristic of the IPP and IPTC, this paper puts forward the program method of CNC grinding machining. Isometric polygonal profile connection is a kind of polygonal profile connection. It has the superiority over keys (prismatic key & spline etc), and can be suit for the situations such as high rotative velocity, large torque, high precision, and small fixed room and vibration. Nowadays, some countries such as America, Russia, German and Switzerland applied CNC machining to the machining of polygon surface coupling parts, which makes their applications in machine productions such as motor engine, heavy machine increase day by day. But reports about concrete machining technology of isometric polygonal profile and programming of CNC machining program are very few. CNC grinding of the IPP and IPTC is one kind of the precision machining technology. It is of great importance to the popularization of the IPP and IPTC connection. From the forming mechanism, we can see that the machining and measuring of the IPP and IPTC are convenient, and therefore they have the value of the popularization. But the machining and measuring of the IPCP are so inconvenient that it has little value. In the programming the CNC grinding of the IPP and IPTC, it is more reasonable to calculate the coordinate of node according to the approaching method of equal error arc. According to the method of CNC grinding mentioned above to design the grinding machine, the structure is simple and of economical and practical.

京津冀平原浅层地下水漏斗演变规律与影响因素

为研究华北地区河湖生态补水对地下水漏斗演变的影响,以京津冀平原浅层地下水漏斗2003年至2022年的相对变化作为识别目标,从气象因素、地形因素、人为因素和含水层水力学特性4个方面进行考虑,选取8个具体指标构建特征变量数据集,使用逻辑回归(logistic regression, LR)、支持向量机(support vector machine, SVM)和随机森林(random forest, RF)方法建立漏斗演变识别模型,并利用敏感度、特异度和决定系数R^(2)对拟合效果进行对比评价,结果显示随机森林为最优模型。进而利用模型分析研究区地下水漏斗演变规律,阐明具体因素对漏斗演变的影响作用。研究表明:京津冀平原区浅层地下水漏斗在2010年之前整体呈扩张趋势,之后在部分地区呈现缩减和消失的态势。河湖补水前,地下水漏斗发展主要受开采影响,其重要度约50%;2018年后河湖补水对抑制漏斗扩张发挥了较为明显的作用,重要度达16%。从发展过程来看,地下水开采依然是控制京津冀平原浅层地下水漏斗变化最重要的因素。对比宁柏隆和高蠡清两个典型浅层地下水漏斗的发展变化可知,河道生态补水对宁柏隆漏斗变化的贡献率接近10%,而对高蠡清漏斗变化影响的重要度仅为1%,因此持续的河流生态补水对宁柏隆漏斗水位恢复会产生积极影响,而对于高蠡清漏斗则需要以水源置换压减农业灌溉地下水量为关键手段实现水位恢复。

榛子高效破壳机的研制

目的:解决榛子机械脱壳效率低和碎仁率高等问题。方法:设计通过压簧实现自动调节间隙的立锥式破壳机,破壳机关键结构由立锥式内辊筒、板条筛式外辊筒、压簧装置3个核心部件组成,分析榛子在破壳机脱壳腔内的受力状况。结果:立锥式榛子破壳机的主要参数为匀料锥锥度30°,内辊筒母线倾角75°,半锥角15°,表面凹槽为螺旋纹,凹槽深度3 mm;外辊筒母线倾斜角73°,半锥角17°;压簧设计自由行程230 mm,中径160 mm,线径24 mm,有效圈数6,总圈数8,内辊筒有效转速范围为229.2~881.5 r/min。结论:该设计通过喂入量自动调节立锥式破壳机压缩量,调整破壳间隙,可适应不同榛子的果形尺寸,使榛子脱壳效率和整仁率得以提高。

基于CBCT中牙髓和牙体体积的机器学习用于青少年儿童年龄推断

目的利用锥形束计算机体层成像(cone beam computed tomography,CBCT)影像中左上颌中切牙与左上颌尖牙的牙髓体积和牙体体积,采用逐步回归法和机器学习方法分别推断青少年儿童年龄,并对推断效果进行比较分析。方法收集498例上海市汉族青少年儿童口腔颌面CBCT影像,测量左上颌中切牙与尖牙的牙髓体积和牙体体积并加以运算,运用K-最近邻、岭回归和决策树3种机器学习算法以及逐步回归法建立4个年龄推断模型,计算并比较决定系数、平均误差、均方根误差、均方误差和平均绝对误差等指标。绘制相关性热图,对参数间的单调关系进行可视化分析。结果K-最近邻模型(R^(2)=0.779)和岭回归模型(R^(2)=0.729)相对于逐步回归法(R^(2)=0.617)表现更为优越,而决策树模型(R^(2)=0.494)的拟合效果较差。相关性热图显示,年龄和牙髓体积、牙髓与牙体硬组织的体积比以及牙髓与牙体的体积比之间呈单调负相关。结论牙髓体积及牙髓体积占比与年龄之间存在密切关系,采用基于CBCT的机器学习方法能够提供更为准确的年龄推断结果,为进一步开展基于CBCT的深度学习牙龄推断研究奠定基础。

基于图案解析与视觉在线检测的电喷印控制方法

随着柔性传感器的发展,传统加工工艺难以满足其高精度生产要求。电喷印作为一种新兴的微纳加工工艺,在复杂图案加工和高精度加工方面具备明显优势。研发了一种具备反馈功能的电喷印软件控制系统,实现了图案解析和机器视觉的在线监测。首先研究了不同形式打印目标的复杂图案解析方法,进行了响应曲面法设计实验,设计了对应的实时在线视觉监测算法和复杂图案的打印路径的优化算法,建立了电喷印关键工作参数的预测数学模型,并进行了测试分析。结果表明:该控制系统实现了打印过程的自动反馈,显著缩短了工作时间,使得电喷印过程的泰勒锥可准确地按需控制,打印线段相对偏差的统计值由±11%左右,减小至±6%左右,并打印出了最小半径为103μm的液滴和最小线宽为151μm的线段。研究成果为柔性微纳制造工艺提供了更高效、精确的生产方法。

Liquefaction prediction using support vector machine model based on cone penetration data

A support vector machine(SVM)model has been developed for the prediction of liquefaction susceptibility as a classification problem,which is an imperative task in earthquake engineering.This paper examines the potential of SVM model in prediction of liquefaction using actual field cone penetration test(CPT)data from the 1999 Chi-Chi,Taiwan earthquake.The SVM,a novel learning machine based on statistical theory,uses structural risk minimization(SRM)induction principle to minimize the error.Using cone resistance(q_(c))and cyclic stress ratio(CSR),model has been developed for prediction of liquefaction using SVM.Further an attempt has been made to simplify the model,requiring only two parameters(q_(c)and maximum horizontal acceleration a_(max)),for prediction of liquefaction.Further,developed SVM model has been applied to different case histories available globally and the results obtained confirm the capability of SVM model.For Chi-Chi earthquake,the model predicts with accuracy of 100%,and in the case of global data,SVM model predicts with accuracy of 89%.The effect of capacity factor(C)on number of support vector and model accuracy has also been investigated.The study shows that SVM can be used as a practical tool for prediction of liquefaction potential,based on field CPT data.

基于遗传算法的圆锥量规中轴线提取方法

通过研究圆锥量规中轴线的拟合方法,提出了一种基于遗传算法拟合圆锥量规中轴线的方法。根据圆锥量规表面点云数据,利用圆锥量规表面与中轴线的特征关系建立数学模型,将遗传算法与点云数据结合,模拟实验并进行实际验证显示,基于遗传算法的圆锥量规点云中轴线提取方法可以有效减小误差,相比坐标测量机传统方法更加准确和稳定。

B_(4)C陶瓷电火花工艺温度场仿真及试验研究

B_(4)C陶瓷具有硬度高、密度低等特性,在军工装甲等领域应用前景广阔,但由于硬度高、脆性大,传统加工方法难以胜任孔、槽等加工。考虑半导电特性,拟采用电火花方法对其进行孔加工技术研究。利用ANSYS软件对电火花放电过程中的单脉冲温度场进行仿真建模,输出凹坑半径、深度及温度场数值,并引入锥角物理量进行仿真和试验比对。结果表明:凹坑半径、深度随峰值电流、脉冲宽度增加而增加,温度场特点满足高斯热源正态分布;随着峰值电流、脉冲宽度的增加,仿真锥角和试验锥角数值更贴合。

基于UG和VERICUT的牙轮钻头牙轮数控加工仿真研究

牙轮钻头作为石油钻井作业中重要的破岩工具,其加工质量成为了钻头使用寿命长短的重要因素。为了解决牙轮零件加工精度要求高、工序繁多,且需多次装夹等问题,对牙轮零件整体加工工艺进行优化改进。通过UG软件对牙轮整体加工进行工艺规划和数控编程,模拟加工仿真刀路运动轨迹。基于VERICUT软件建立XYZBC五轴车铣复合数控机床运动学模型、开发控制系统、创建刀具库并搭建虚拟仿真平台,模拟仿真零件的实际加工过程,验证和优化加工程序和加工工艺。将加工结果与实际牙轮零件进行分析比较。结果表明:与传统工艺相比,优化后的工艺一次装夹即可完成牙轮零件的一体式加工,大幅提高了牙轮的加工效率,使牙轮产品加工质量保持稳定,牙轮的寿命也得到了相应改善。

纳秒脉冲下圆台形可加工陶瓷真空沿面耐电特性测试与仿真分析

真空中绝缘子表面的沿面闪络现象极大地限制了电真空设备的发展进程。为此,将一种具有优良可加工性能和良好耐电性能的可加工陶瓷引入真空绝缘领域,结合工程实际中经常采用圆台形绝缘结构,将其加工成不同角度的圆台形绝缘子,在ns脉冲电压下对试品进行了真空沿面耐电性能的测试,并分析了锥角对阴极三结合点处电场、表面电荷分布和初始电子运动轨迹的影响。结果发现:正锥角的闪络电压明显高于负锥角,而45°绝缘子的闪络电压最高。分析认为,锥角对绝缘子阴极三结合点处的电场和表面电荷分布影响很大,正锥角时阴极三结合点处的电场和表面电荷密度较小,而负锥角时两者较大,同时负锥角时电子的自由程变短,减小了电子与绝缘子碰撞时的能量。

飞秒激光倒锥微孔加工的反射式扫描装置设计

基于道威棱镜扫描原理，设计了由高速旋转电机驱动三片K字形排布反射镜组成的反射式扫描装置，并分析了扫描钻孔准确度．结果表明：该扫描装置可用于飞秒激光高准确度环切钻孔系统，钻孔准确度不受光束质量影响，钻孔扫描速度二倍于电机转速且钻孔效率高、兼容多光谱波段；与道威棱镜系统相比，该系统装调准确度要求低，能避免透射系统中色散引起的飞秒激光脉宽展宽现象．测试结果显示该装置可以实现直径0．05～O．2mm、加工准确度小于±2μm倒锥孔的高效率加工．

基于机器视觉的筒子纱缺陷在线检测系统

为提高筒子纱检测过程的自动化程度,设计了一种基于机器视觉的筒子纱缺陷在线检测系统。该系统由2个工业相机、条形LED光源、对照式光电开关和计算机组成。首先,相机与同步光源分时采集筒子纱顶面和侧面过曝模式及正常模式图像。然后通过对顶面过曝图像自适应分割来定位筒子纱中心。其次,通过极坐标变换展开顶面正常图像。最后,在顶面展开图中,分别利用垂直方向边缘分布的投影特征、纹理及强度一致性、局部方向直方图纹理识别菊花芯、多源纱和网纱缺陷;在筒子纱侧面图中,通过投影法快速确定边界位置,并通过轮廓拟合程度识别多层台缺陷。结果表明,该系统可实时识别多层台、网纱、菊花芯、多源纱等筒子纱缺陷,具有较好的检测效果。

槽筒材质和表面状态对纱线毛羽的影响

纱线毛羽形成于细纱工序,增长于络筒工序,为控制纱线毛羽的增长,研究了1332M型络筒机的槽筒材质和表面状态对纱线毛羽的影响。测试了CJ 27.8 tex纱的1 mm^9 mm管纱毛羽与筒纱毛羽,并对四种不同材质和表面状态的槽筒产生的毛羽数量进行了统计对比。通过对3 mm筒纱毛羽数量与3 mm管纱毛羽数量的比值(倍增系数)进行比较,认为:经过络筒工序后,纱线的毛羽数量增加3倍~5倍,钢质槽筒增加的毛羽数量最少,胶木槽筒增加的毛羽数量最多。

基于斜置锥台的五轴数控机床加工精度预测技术

为缩短基于斜置锥台评价五轴联动加工精度的时间和降低评价的费用，用多轴机床误差理论研究了基于锥台的五轴机床联动加工精度预测，提出了一种新的五轴机床加工精度评价方法。该方法利用齐次坐标变换理论建立斜置锥台的五轴加工运动误差模型，在计算机辅助制造（CAM）软件上进行斜置锥台的仿真加工得到斜置锥台刀侧铣削的数控（NC）代码，并利用运动误差模型和NC代码通过刀具与工件之间的空间位置关系计算出锥台侧面的圆度误差，据此对五轴联动数控机床的加工精度进行预测。对所提出的五轴加工精度预测方法进行了仿真分析，结果表明该方法简单实用，可以用于五轴联动加工精度的评价。

锥形电极在改善微小孔电解加工定域性中的作用

分析了影响微细电解加工定域性的因素,在自制的加工装置上,制备了微细锥形电极,并利用制备出的电极进行了相关的微小孔电解加工试验,通过试验研究了锥形电极对加工定域性的影响。结果表明:采用锥形电极、较小的锥形电极杆身直径、较大的锥形电极锥度有利于提高微小孔电解加工定域性。

控制络纱毛羽措施的研究

探索减少络纱毛羽的有效措施。通过采取优选络纱速度和退绕张力,合理控制筒纱卷绕硬度,加装气圈控制环,增大细纱卷绕动程,加强设备基础维修,减少筒纱回倒次数等措施进行控制,可以有效降低络筒毛羽的增长,达到提高纱线质量的目的。

深锥浓密机底流浓度预测与外部结构参数优化

针对困扰支持向量机(SVM)模型参数选择问题,结合遗传算法(GA),建立了深锥浓密机底流放砂浓度的GA-SVM预测模型,研究了不同结构参数状态下底流浓度的变化规律,进行了深锥浓密机的外部结构参数优化选择。以司家营铁矿为例,在最优底流放砂浓度为72%的条件下,经外部结构参数优化后的深锥浓密机锥高10m、锥角为30°,系统稳定可靠、底流连续均匀,动力荷载较同类矿山降低约15%,压耙停机故障降低80%。