Effect of bolt inclination angle on shear behavior ofbolted joints under CNL and CNS conditions

Rock bolts are widely used in rock engineering projects to improve the shear capacity of the jointed rock mass.The bolt inclination angle with respect to the shear plane has a remarkable influence on the bolting performance.In this study,a new artificial molding method based on 3D scanning and printing technology was first proposed to prepare bolted joints with an inclined bolt.Then,the effects of the bolt inclination angle and boundary conditions on the shear behavior and failure characteristic of bolted joints were addressed by conducting direct shear tests under both CNL and CNS conditions.Results indicated that rock bolt could significantly improve the shear behavior of rock joints,especially in the post-yield deformation region.With the increase of bolt inclination angle,both the maximum shear stress and the maximum friction coefficient increased first and then decreased,while the maximum normal displacement decreased monotonously.Compared with CNL conditions,the maximum shear stress was larger,whereas the maximum normal displacement and friction coefficient were smaller under the CNS conditions.Furthermore,more asperity damage was observed under the CNS conditions due to the increased normal stress on the shear plane.

Preserved amplitude migration based on the one way wave equation in the angle domain

Traditional pre-stack depth migration can only provide subsurface structural information. However, simple structure information is insufficient for petroleum exploration which also needs amplitude information proportional to reflection coefficients. In recent years, pre-stack depth migration algorithms which preserve amplitudes and based on the one- way wave equation have been developed. Using the method in the shot domain requires a deconvolution imaging condition which produces some instability in areas with complicated structure and dramatic lateral variation in velocity. Depth migration with preserved amplitude based on the angle domain can overcome the instability of the one-way wave migration imaging condition with preserved amplitude. It can also offer provide velocity analysis in the angle domain of common imaging point gathers. In this paper, based on the foundation of the one-way wave continuation operator with preserved amplitude, we realized the preserved amplitude prestack depth migration in the angle domain. Models and real data validate the accuracy of the method.

PROPER CONDITIONS OF MESHING FOR Hy-Vo SILENT CHAIN AND SPROCKET

Proper meshing of Hy-Vo silent chain and sprocket is important for realizing the transmission of the silent chain with more efficiency and less noise. Based on the study of the meshing theory of the Hy-Vo silent chain with the sprocket and the roll cutting machining principle of the sprocket with the hob, the proper conditions of the meshing for the Hy-Vo silent chain and the sprocket are put forward with the variable pitch characteristic of the Hy-Vo silent chain taken into consideration, and the proper meshing design method on the condition that the value of the link tooth pressure angle is unequal to the value of the sprocket tooth pressure angle is studied. Experiments show that this new design method is feasible. In addition, the design of the pitch, the sprocket tooth pressure angle and the fillet radius of the sprocket addendum circle are studied. It is crucial for guiding the design of the hob which cuts the Hy-Vo silent chain sprocket.

Establishment of Dynamic Model for Axle Box Bearing of High-Speed Trains Under Variable Speed Conditions

In this study,a dynamic model for the bearing rotor system of a high-speed train under variable speed conditions is established.In contrast to previous studies,the contact stress is simplifed in the proposed model and the compensation balance excitation caused by the rotor mass eccentricity considered.The angle iteration method is used to overcome the challenge posed by the inability to determine the roller space position during bearing rotation.The simulation results show that the model accurately describes the dynamics of bearings under varying speed profles that contain acceleration,deceleration,and speed oscillation stages.The order ratio spectrum of the bearing vibration signal indicates that both the single and multiple frequencies in the simulation results are consistent with the theoretical results.Experiments on bearings with outer and inner ring faults under various operating conditions are performed to verify the developed model.

An effective denoising strategy for wave equation migration based on propagation angles

We present an effective denoising strategy for two-way wave equation migration. Three dominant artifact types are analyzed and eliminated by an optimized imaging condition. We discuss a previously unsolved beam-like artifact, which is probably caused by the cross-correlation of downward transmitting and upward scattering waves from both the source and receiver side of a single seismic shot. This artifact has relatively strong cross- correlation but carries no useful information from reflectors. The beam-like artifact widely exists in pre-stack imaging and has approximately the same amplitude as useful seismic signals. In most cases, coherent artifacts in the image are caused by directionally propagating energy. Based on propagation angles obtained by wavefield gradients, we identify the artifact energy and subtract its contribution in the imaging condition. By this process most artifacts can be accurately eliminated, including direct wave artifacts, scattering artifacts, and beam- like artifacts. This method is independent of the wavefield propagator and is easy to adapt to almost all current wave equation migration methods if needed. As this method deals with the physical artifact origins, little damage is caused to the seismic signal. Extra k-domain filtering can additionally enhance the stacking result image quality. This method succeeds in the super-wide-angle one-way migration and we can expect its success in other two-way wave equation migrations and especially in reverse time migration.

Instrument for insulation conditions detection of roof insulator on high-speed-train

With the rapid development of high-speed-railway,environment around high voltage device on train roof becomes very complicated. Most train accidents happened due to occurrence of flashover on roof insulator,but the insulation condition estimation of insulator in such environment is much difficult. To ensure the insulation property of electric equipment,and guarantee the operation safety of high-speed-train,here established an instrument with high reliability which can on-line monitor insulation condition of roof insulator and give out advanced alarm before the incipient insulator flashover. The instrument consists of three parts,Data Acquisition & Sensor,Data Processing and Back Processing. Anti-interference and protection methods are processed to Rogowski coil sensor for better leakage current signal. To avoid the fluctuation from railway power supply,four modules are set to filter the power supply waveform. Through laboratory measurement,it is shown that the leakage current and the impedance angle can be detected by the instrument accurately. From the comparison of leakage current and impedance angle results under different moisture condition and the alarm operation when leakage current value reached threshold,this instrument can give out enough information for staff to understand the insulation condition of insulator.

Two-Mode Steady-State Entanglement in a Four-Level Atomic System

We investigate the continuous variable entanglement in a four-level atom according to the criterion proposed by Duan et al.[Phys.Rev.Lett.84(2000)2722].The atomic coherence is introduced using two external classical driving fields.We study the steady-state entanglement of the system in the presence of losses,concluding that the creation of entangled states can be achievable under certain conditions.

Computational Fracture Analysis of an AFM-Specimen under Mixed Mode Loading Conditions

Fracture processes in ship-building structures are in many cases of a 3-D character. A finite element （FE） model of an all fracture mode （AFM） specimen was built for the study of 3-D mixed mode crack fracture behavior including modes Ⅰ,Ⅱ, and Ⅲ. The stress intensity factors （SIFs） were calculated by the modified virtual crack closure integral （MVCCI） method, and the crack initiation angle assessment was based on a recently developed 3-D fracture criterion--the Richard criterion. It was shown that the FE model of the AFM-specimen is applicable for investigations under general mixed mode loading conditions, and the computational results of crack initiation angles are in agreement with some available experimental findings. Thus, the applicability of the FE model of the AFM-specimen for mixed mode loading conditions and the validity of the Richard criterion can be demonstrated.

Reflectivity Model of Low Grazing Angle Radar Sea Clutter

The commonly used reflectivity models of radar sea clutter are summarized. Among these models, the adjusted Barton model and the adjusted Morchin model are compared. From the analysis result, the γ-p reflectivity model is presented for low grazing angle radar sea clutter by the adjustment of the original Barton reflectivity model. The model takes into account radar frequency, grazing angle, sea condition, and polarization property. The influences of these factors on the proposed model are analyzed. The model absorbs the merits from commonly used reflectivity models for sea clutter. It introduces several researchers' opinions, and extends them. And it accounts for the reflectivity at arbitrary radar frequency from VHF to X-band, arbitrary low grazing angle, arbitrary sea condition and different polarization property. One of the main results is the proposed γ-p reflectivity model can reflect the influence of polarization on sea clutter reflectivity to some extent. The proposed γ-p reflectivity model of low-angle radar-sea clutter is validated by comparing the simulated and statistically experimental data.

慢性病共病、相位角与老年人肌少症相关的肌肉质量减少的关系研究

目的·探讨慢性非传染性疾病(慢性病)共病、相位角与老年人肌少症相关的肌肉质量减少的相关性,以及慢性病共病、相位角对老年人肌肉质量减少的预测价值。方法·对2018年8月1日—2019年7月31日入住上海交通大学医学院附属仁济医院老年科,年龄≥60岁的患者进行回顾性筛查。收集患者基本情况(性别、年龄、用药数、共病数、有无骨质疏松症、有无吸烟史等),以及实验室检查指标(血红蛋白、白蛋白、血肌酐、血尿酸、铁蛋白、维生素D、三酰甘油、总胆固醇、高密度脂蛋白、低密度脂蛋白等)结果。计算年龄调整后查尔森合并症指数(age-adjusted Charlson comorbidity index,aCCI)。采用InBody S10生物电阻抗身体成分检测仪进行人体成分测试,记录身体质量指数(body mass index,BMI)、骨骼肌质量指数(skeletal muscle mass index,SMI)、相位角(phase angle,PhA)。部分患者接受握力测量。肌肉质量减少采用2019年亚洲肌肉减少症工作组(Asian Working Group for Sarcopenia,AWGS)推荐的SMI值(男性≤7.0 kg/m^(2)、女性≤5.7 kg/m^(2))进行诊断。根据测定的SMI值将患者分为肌肉质量正常组与肌肉质量减少组。采用单因素和多因素Logistic分析老年患者发生肌少症相关的肌肉质量减少的危险因素。并进一步运用受试者操作特征曲线(receiver operator characteristic curve,ROC曲线)及曲线下面积评估相关因素预测肌肉质量减少的价值。结果·共入组慢性病共病患者359例,其中男性226例,女性133例;肌肉质量正常组241例,肌肉质量减少组118例,老年人肌少症相关的肌肉质量减少发生率为32.9%。单因素Logistic回归分析提示年龄(OR=1.036,95%CI 1.013~1.060)、共病数(OR=1.117,95%CI1.025~1.217)、aCCI(OR=1.123,95%CI 1.031~1.222)、高密度脂蛋白(OR=3.688,95%CI 2.065~6.622)与老年人肌肉质量减少的风险呈正相关,BMI(OR=0.514,95%CI 0.443~0.597)、PhA(OR=0.195,95%CI 0.126~0.303)、血红蛋白(OR=0.984,95%CI 0.972~0.996)、三酰甘油(OR=0.606,95%CI 0.424~0.866)与老年人肌肉质量减少的风险呈负相关。多因素Logistic回归模型提示PhA(OR=0.338,95%CI 0.119~0.959)、BMI(OR=0.634,95%CI 0.476~0.844)与老年人肌肉质量减少的风险呈负相关。BMI、PhA预测老年人肌少症相关的肌肉质量减少的ROC曲线下面积分别为0.893(95%CI 0.855~0.931)和0.786(95%CI 0.736~0.837),敏感度分别为0.724和0.676,特异度分别为0.916和0.762;BMI联合PhA预测老年人肌肉质量减少的ROC曲线下面积为0.917(95%CI 0.883~0.951),敏感度为0.867,特异度为0.860。结论·aCCI与老年人肌少症相关的肌肉质量减少具有相关性。随着BMI、PhA的下降,老年人肌肉质量减少的风险升高。BMI联合PhA具有较高的老年人肌少症相关的肌肉质量减少的预测价值。未发现慢性病共病对其的预测价值。

The Significance of Solutions Obtained from Ill-Posed Systems of Linear Equations Constituted by Synchrotron Radiation Based Anomalous Small-Angle X-Ray Scattering

Synchrotron radiation based experimental techniques known as Anomalous Small-Angle X-ray Scattering (ASAXS) provide deep insight into the nanostructure of uncountable material systems in condensed matter research i.e. solid state physics, chemistry, engineering and life sciences thereby rendering the origin of the macroscopic functionalization of the various materials via correlation to its structural architecture on a nanometer length scale. The techniques constitute a system of linear equations, which can be treated by matrix theory. The study aims to analyze the significance of the solutions of the stated matrix equations by use of the so-called condition numbers first introduced by A. Turing, J. von Neumann and H. Goldstine. Special attention was given for the comparison with direct methods i.e. the Gaussian elimination method. The mathematical roots of ill-posed ASAXS equations preventing matrix inversion have been identified. In the framework of the theory of von Neumann and Goldstine the inversion of certain matrices constituted by ASAXS gradually becomes impossible caused by non-definiteness. In Turing’s theory which starts from more general prerequisites, the principal minors of the same matrices approach singularity thereby imposing large errors on inversion. In conclusion both theories recommend for extremely ill-posed ASAXS problems avoiding inversion and the use of direct methods for instance Gaussian elimination.

基于风况预测误差自适应的海上风电场尾流偏转控制方法

风电场尾流偏转控制是降低尾流效应、提升整场发电量的重要手段。风况预测值是风电场尾流偏转控制的重要输入,其误差给实际控制效果带来巨大影响,甚至导致全场发电量“不增反降”,极大限制了风电场尾流偏转控制技术的工程应用。以某海上风电场实际运行数据为例,探索了分钟级风速和风向预测误差对风电场尾流偏转控制效果的影响,提出了风况预测误差自适应的海上风电场尾流偏转控制方法及基于深度神经网络的控制模型。研究结果表明:与不考虑风况预测误差自适应的传统风电场尾流偏转控制方法相比,所提方法的全场发电量提高了1.77%。

基于GADF融合RDSAN的跨工况轴承故障诊断

针对在不同工况下获取到的滚动轴承振动数据特征分布存在差异,以及由于存在噪声而导致故障特征不明显的问题,提出了一种融合格拉姆角差场(GADF)与残差深度子领域自适应(RDSAN)模型的跨工况轴承故障诊断方法。首先,为充分利用GADF在故障特征差异化显示上的优势,利用GADF来生成滚动轴承一维振动时域信号对应的图像数据集;其次,将数据集输入RDSAN模型,其中使用由改进图像集预训练的ResNet-18网络结构进行源域与目标域通用特征的进一步提取,并引入局部最大均值差异(LMMD)计算匹配条件分布距离进行子领域自适应;最后,在添加0.5 dB高斯白噪声的CWRU滚动轴承数据集上进行跨工况试验验证,结果表明所提方法的平均诊断精度达到96.8%;将所提出的方法与不同的诊断方法进行比较分析,结果验证了该方法的有效性和优越性。

背压扰动平衡盘对涡旋压缩机黏性内流压力影响研究

在变转速工况下,电动涡旋压缩机背压腔中润滑油产生的背压力无法准确平衡轴向气体力。针对这一问题,提出了一种带有扰动片的背压扰动平衡盘,研究了背压扰动平衡盘对涡旋压缩机黏性内流压力的影响。首先,对背压扰动平衡盘作用原理进行了分析,使用贝塞尔曲线构建了扰动片型线,对润滑油被扰动后的静压增量进行了公式推导,计算了扰动片出口安装角和扰动片数对润滑油静压的影响;然后,建立了含背压扰动平衡盘的背压腔模型,将流体域分为旋转域和静止域,采用旋转坐标系的方法进行了数值模拟,研究了背压腔内润滑油的压力场;最后,根据理论计算,模拟了润滑油在不同出口安装角和扰动片数下的润滑油静压,对润滑油静压与压缩机所需最佳背压进行了对比分析。研究结果表明:采用背压扰动平衡盘可以使润滑油静压增加21%,且静压增量随主轴转速的增加而增大,适当增大扰动片出口安装角可使润滑油静压增加0.032 MPa;对比最佳背压可知,扰动前润滑油静压与最佳背压相差26%,而合理设计扰动片后的润滑油静压与最佳背压相差仅为9%,极大改善了电动涡旋压缩机在变转速下的轴向平衡。

基于合体袖山结构模型的袖山缩缝量计算方法

为解决衣袖袖山与衣身袖窿精准匹配的问题,提出了一种基于衣袖袖山结构模型的袖山缩缝量计算方法。通过构建合体型袖山缩缝量结构模型,利用椭圆形周长计算公式推导出袖山缩缝量计算系数,经过设计试验和袖山缩缝量回归系数模型计算,得出袖山缩缝量计算公式为y=0.6x,并运用SPSS软件对试验数据进行了回归分析。试验结果表明:基于衣袖袖山结构模型的袖山缩缝量计算方法可以获得不同款式风格和面料所需的袖山缩缝量,能够为实现衣袖袖山与衣身袖窿的合理匹配提供必要的精准数据。

支流入汇对干流航道通航条件影响模拟研究

自然河流由于支流的汇入,在交汇区与干流相互混掺顶托,改变了原有的水流形态,形成复杂的水流结构,对内河船舶航运的操纵性和安全性均造成一定影响。采用数值模拟试验方法,基于分离式(MMG)水动力模型,系统地研究了不同交汇角、汇流比以及干支流河道宽度比情况下交汇区船舶通航条件,即船舶航行时的漂角和偏航距离因素,并以此为基础,基于Design-Export响应面分析软件,得出了无量纲化后的最大偏航距离与交汇角、汇流比以及干支流宽度比之间的响应函数。

S弯收扩喷管过膨胀状态下流动分离特性研究

为了研究S弯收扩喷管过膨胀状态下的流动分离特性,数值模拟了不同落压比(NPR)下S弯收扩喷管内的流动特征。结果表明:在落压比为2.0时,喷管内发生非对称分离,出现非对称的双“λ”激波结构,喷流整体向上偏转,上侧出现限制性流动分离RSS,下侧出现自由性流动分离FSS,并产生三维分离涡,喷流出现明显的三维效应。随着落压比从高度过膨胀状态下开始增加,喷管下侧保持FSS不变,喷管上侧RSS逐渐向后移动,直至与外界大气相连,转变为FSS,之后随着落压比增加,上下侧分离结构逐渐对称。推力矢量角随着落压比的增加先增加,后在极小的落压比变化范围内快速降低,直至变为0°,之后保持0°不变。

不同入流条件及偏航角下的单风机尾流特性

随着大型风电基地建设,上游风机在运行时会使下游风场风速下降,湍流度增大,造成下游风机发电功率降低,加剧风机的疲劳破坏并缩短其服役周期。因此,亟需开展风机尾流研究,明确其特性及演化规律。为了揭示不同入流及偏航角下的单风机尾流特性,基于单风机尾流风洞试验,验证基于大涡模拟(Large Eddy Simulation,LES)结合致动线模型(Actuator Line Model,ALM)数值模拟方法的准确性;基于LES-ALM模拟方法研究入流风场(包括风速及湍流度)及偏航角对风机尾流特性的影响,阐明正负偏航角下单风机尾流的对称性。结果表明:随着背景湍流度的增大,风机尾流恢复速度加快;当入流条件相同时,风机设置正负对称偏航角,其尾流风速也表现出一定的对称性;风机偏航角越大,风机尾流膨胀宽度会逐渐减小,并降低尾流风速的亏损程度。

基于弹性反射波正演表达的转换波逆时偏移与反偏移

针对线性化弹性反射波方程无法直接用于弹性转换波反偏移模拟的问题,本文提出基于高频近似的一次反射波模拟新方法.该方法基于地震波传播的散射理论,先对地下速度扰动的空间变化进行高频近似,再基于散射波传播方程推导得到线性化一次反射波传播方程.基于弹性反射地震数据表达,本文采用线性算子的伴随估计反射系数,实现反射波逆时偏移.根据该线性表达,联合背景速度和成像值来模拟一次反射横波传播,实现了弹性波角度域反偏移,并进一步导出成像值关于波速的梯度.数值实验表明,基于弹性反射地震数据表达的偏移成像方法,既克服了极性反转效应,又使成像结果包含了更为丰富的反射角信息;一次反射波模拟方法获得的弹性地震数据具有较高的精度和稳定性,得到的弹性波场的振幅和相位信息与理论解析解吻合较好,有效保证了成像域层析速度反演梯度的稳定求解.

翅片管式换热器翅片结构对空气侧性能的影响

建立5mm管径翅片管式换热器百叶窗翅片的物理模型和数学模型,模拟分析百叶窗翅片开窗角度和换热器管间距对空气侧性能的影响,结果表明:在相同迎面风速下,空气侧的换热量及表面传热系数均随百叶窗开窗角度的增大而增大,风机功率随之大幅增加;空气侧的换热量及表面传热系数均随管间距的减小而增大;综合考虑换热量、风机功率及空气侧表面传热系数,开窗角度20°、管间距17.1 mm时换热器空气侧性能更优。