Characterization of Perineum Elasticity and Pubic Bone-Perineal Critical Distance with a Novel Tactile Probe: Results of an Intraobserver Reproducibility Study

Background: Tactile imaging provides biomechanical mapping of soft tissues. Objective biomechanical and anatomical assessment of critical structures within the vagina and pelvis may allow development and validation of a clinical tool that could assist with clinical decisions regarding obstetrical procedures and mode of delivery. Objective: To assess intraobserver reproducibility of measurements of perineal elasticity and pubic bone-perineal critical distance with a novel tactile probe in pregnant women. Methods: An Antepartum Tactile Imager (ATI) was designed with a vaginal probe resembling a fetal skull. The probe comprises 128 tactile sensors on a double curved surface and measures 46 mm in width and 72 mm in length. The probe has a motion tracking sensor that allows acquisition of 3D tactile images. There were two arms of the study. In the first arm, biomechanical mapping of the perineum and pelvic bone location was performed in 10 non-pregnant women for purposes of demonstrating safety and feasibility. In the second arm, biomechanical mapping was performed in 10 pregnant women to explore intraobserver reproducibility. Each subject had two standardized examinations over 3 - 5 minutes by the same observer. Examination comfort and pain levels were assessed by post-procedure survey. Reproducibility was analyzed by intraclass correlation coefficients (ICC) with 95% confidence intervals and Bland-Altman plots. Bias and the 95% limits of agreement were also calculated. Results: The safety and feasibility arm of the study demonstrated high degree of safety and tolerability and reliable acquisition of tactile signals. In the reproducibility arm, 10 pregnant women were recruited at mean gestational age of 34.2 ± 6.5 weeks. The mean perineum elasticity (Young’s modulus, E) was 9.8 ± 5.9 kPa, and the mean pubic bone-perineal critical distance (D) at 20 kPa load was 34.6 ± 6.2 mm. The ICC was 0.97 [95% confidence interval (CI) 0.91, 0.99] and 0.82 [CI 0.44, 0.95] for E and D respectively, consistent with excellent intrarater agreement. The bias and the 95% limits of agreement of E were -6.3% and -29.4% to +16.7%, respectively. The bias and the 95% limits of agreement of D were -2.6% and -25.3% to +20.2%, respectively. Conclusions: The tactile imaging data obtained in the study reproducibly characterized perineal elasticity and pubic bone-perineal critical distance. Further evaluation of this tool in clinical settings is warranted.

An Earth multi-body system elasticity and plasticity dynamics model

Research on the elasticity and plasticity dynamics of the Earth multi-body system, including the Earth multi-body system stratum-block's equivalent inertia force system and generalized inertia force, the Earth multi-body system stratum-block's equivalent inertia force system expressed with partial velocity and partial palstance, and Earth multi-body system generalized inertia force expressed with partial velocity and partial palstance. This research provides a theoretical foundation for further investigation of Earth multi-body dynamics.

不同盾构施工参数对地表沉降影响的数值分析

为研究盾构隧道施工阶段不同施工参数对地表沉降的影响规律,文中依托杭州某盾构隧道工程,运用Midas GTS NX数值软件建立盾构隧道施工三维模型,分析施工阶段注浆体弹性模量、注浆压力、掌子面推力等施工参数对地表沉降的影响。结果表明,不同施工参数工况下地表横向沉降曲线皆呈现倒V形,且最大值均位于隧道拱顶正上方;适当增大注浆压力、掌子面推力可以减小地表沉降量;注浆体弹性模量大小与地表沉降量成反比;不同施工参数对地表沉降量的影响作用由大到小排列依次为注浆压力、注浆体弹性模量、掌子面推力,研究成果可为相关工程提供参考借鉴。

多模态超声评估产次对会阴体及肛提肌功能影响的研究

目的运用二维灰阶超声联合实时剪切波弹性成像(SWE)探究产次对自然分娩产后早期会阴体(PB)及肛提肌(LAM)功能的影响。方法选取南充市中心医院产后6~8周自然分娩产妇为研究组,根据产次分为二次经产妇组46例及初产妇组55例。选择同期到本院做检查有性生活史未育的健康女性50例作为对照组。分别测量三组静息和最大收缩状态下会阴体长度、高度、杨氏模量值,静息、最大收缩以及Valsalva状态下双侧肛提肌杨氏模量值,计算差值,比较各组不同状态下超声参数变化情况。结果静息及最大收缩状态下二次经产妇组会阴体长度、高度、收缩幅度和杨氏模量值低于初产妇组和对照组,差异有统计学意义(P<0.05)。三组组间相同状态下肛提肌杨氏模量值与差值比较,差异均有统计学意义(P<0.05),对照组以及初产妇组组内不同状态下肛提肌杨氏模量值差异有统计学意义(P<0.05),二次经产妇组组内最大收缩状态下肛提肌杨氏模量值较Valsalva及静息状态增大,而Valsalva与静息状态比较,差异无统计学意义(P>0.05)。结论二次自然分娩对产后早期会阴体及肛提肌功能的影响较初次自然分娩更明显,二维灰阶超声联合实时剪切波弹性成像技术可以评估自然分娩不同产次会阴体及肛提肌功能的差异性。

薄壁四点接触球轴承-腕部关节系统接触动力学分析

在机器人实际工况中,针对含有薄壁四点接触球轴承的机器人腕部关节系统的运动稳定性问题,对腕部系统模型进行了简化设计和仿真研究。在考虑薄壁结构的弹性变形和动态接触作用耦合影响的基础上,建立了刚柔耦合工业机器人腕部关节系统模型,分析了不同受载工况和正反转驱动下的变形规律和动态特性。首先,基于多体动力学和Hertz接触理论,设计了包含薄壁四点接触球轴承和中空轴及基座的腕部关节系统刚柔耦合接触动力学仿真模型;然后,考虑薄壁中空轴、基座、轴承套圈和保持架的结构弹性变形、钢球和套圈滚道、保持架的动态接触作用,研究了机器人腕部关节系统两种实际工况对保持架和钢球角速度、保持架和薄壁基座振动位移、钢球与套圈的动态接触力的影响;最后,计算分析了两种工况下腕部关节系统的动态载荷规律和振动响应特性。研究结果表明:在相对较大的径向载荷作用下,保持架和钢球会出现打滑现象,速度呈现周期波动,保持架和基座具有更好的运动稳定性,其薄壁轴承内部载荷降低,主副接触对均承担联合载荷,轴承内部载荷稳定性也更好。该仿真模型及结果可以为薄壁腕部关节系统的动力学分析与设计提供参考。

STABILITY ANALYSES ON DYNAMIC CONTROL FOR A MOVING BODY LEVITATED MAGNETICALLY OVER ELASTIC GUIDEWAYS

Based on the Floquet theory on ordinary differential equationswith periodically variable coefficients and the bifurcation approachto nonlinear equations, a numerical approach to determining thestability region of control parameters is established for a dynamiccontrol system composed of a moving body levitated magnetically overflexible guideways. The system is nonlinearly coupled among theelastic deformation of guideways, disturbance the levitation positionof the body and electromagnet- ic control forces.

Clinical characteristics of perineal endometriosis:A case series

BACKGROUND The prevalence of perineal endometriosis(PEM)is low among women with endometriosis(EM)treated by surgery.It manifests as hard or cystic nodules with pain in the perineal wounds and surrounding areas.Implantation theory is regarded as the main pathogenesis of PEM.There are few clinical studies on the incidence and clinical characteristics of PEM.This study aims to summarize the clinical data of 14 PEM cases and analyze the factors that may be related to the incubation period and pain.AIM To analyze the medical history,clinical manifestations,diagnosis,treatment and treatment effect of PEM.METHODS The present study is a case series.We collected the clinical data and follow-up data of 14 patients with PEM who visited The International Peace Maternal and Child Health Hospital Affiliated to Shanghai Jiaotong University from January 2009 to December 2019.Paired t test and Pearson correlation analysis were used for statistical analysis.P<0.05 was considered statistically significant.RESULTS The 14 patients included had a history of vaginal delivery.All patients underwent PEM lesion resection.Three patients were treated by levator ani muscle repair at the same time and 1 patient underwent extensive PEM lesion resection and anal sphincter repair.Body mass index(BMI)at delivery and BMI within 1 mo after delivery were negatively correlated with the latent period,respectively(R2=0.53/0.86,P<0.05).The average visual analog scale score in lesions at the third month after surgery was 0.57±1.28 for all patients,which was significantly lower than that prior to surgery(P<0.05).One patient relapsed during the sixth month after surgery,and to date,no recurrence occurred after the second surgery.CONCLUSION The higher the BMI during delivery and within 1 mo after delivery,the shorter the incubation period of PEM.It is very important to evaluate the location of lesions before surgery.Surgical resection of the lesion is the best treatment for PEM and results in significant alleviation of symptoms.Therefore,following the diagnosis of PEM,immediate surgery is recommended.

Numerical simulation of influence of shear dilatancy on deformation characteristics of shear band-elastic body system

The paper was numerically focused on investigation of deformation, failure and instability of shear band-surrounding elastic rock system in plane strain direct shear test considering shear dilatancy according to fast lagrangian analysis of continua (FLAC). The adopted failure criterion was a composite Mohr-Coulomb criterion with tension cut-off and post-peak constitutive relation of rock, i.e. linear strain-softening. Numerical results show that dilation angle affects the responses of elements, the number and the position of yielded elements. Increasing dilation angle results in higher load-carrying capability of elements, higher deformation or strain corresponding to peak stress, less brittle post-peak stress-deformation curve. Strain-hardening behavior can occur if dilation angle is high. Therefore, shear band-elastic rock body system tends to be stable and rock burst does not occur as dilation angle is increased. Moreover, the number of yielded elements is in- creased with dilation angle increase and two parallel plastic zones initially generated in the middle of two loading ends of specimen no longer remain collinear, reflecting increase in deformation resistant of the system. Evolution of volumetric strain rate was investigated based on three-dimensional curved surface diagrams. Approximately, volumetric strain rate concentration regions coincide with plastic zones. Volumetric strain rate in yielded elements is very evident. However, in elastic zones volumetric strain has not been nearly changed throughout the numerical tests.

Measurement of elastic modulus and evaluation of viscoelasticity of foundry green sand

Elastic modulus is an important physical parameter of molding sand; it is closely connected with molding sand’s properties. Based on theories of rheology and molding sand microdeformation, elastic modulus of molding sand was measured and investigated using the intelligent molding sand multi-property tester developed by ourselves. The measuring principle was introduced. Effects of bentonite percentage and compactibility of the molding sand were experimentally studied. Furthermore, the essential viscoelastic nature of green sand was analyzed. It is considered that viscoelastic deformation of molding sand consists mainly of that of Kelvin Body of clay membrane, and elastic modulus of molding sand depends mainly on that of Kelvin Body which is the elastic component of clay membrane between sands. Elastic modulus can be adopted as one of the property parameters, and can be employed to evaluate the viscoelastic properties of molding sand.

Analysis of Skin Parameters of Korean Men According to the Parts of the Body for Integumentary Physiotherapy Research

Studies have demonstrated that some cutaneous biophysical properties vary with the part of the body. The results to date of skin conditions in human skin of multiple parts of the body have not yet been well established. In this study, we assessed the differences in the skin’s sebum, moisture, pores, wrinkles, pigmentation, and elasticity of each body part in Korean men in their 20s. A total of 34 healthy men were enrolled. A Skin Diagnosis Meter was used to measure the skin’s surface sebum, moisture, pores, wrinkles, pigmentation, and elasticity of each body part. The sebum content was significantly higher on the face than at other sites. Moisture was significantly high on the feet. Pores were significantly high on the face. Wrinkles were significantly high on the face. Pigmentation was high on the face and neck, but not significantly. Elasticity was significantly high on the hands. In the correlation analysis results, sebum and pore were positively correlated, but sebum and moisture and wrinkle and elasticity were negatively correlated. For nearly the first time, this study resulted in systematic reference values for standardized biophysical measuring methods and body parts reflecting the skin physiology of healthy South Korean men. The results show that skin’s surface sebum, moisture, pores, wrinkles, pigmentation, and elasticity vary with the part of the body.

Shear stress distribution and characteristics of deformation for shear band-elastic body system at pre-peak and post-peak

The distributed shear stress and the displacement across shear band, the evolution of plastic zones, and the load-carrying capacity of rock specimen were investigated in plane strain direct shear test according to Fast Lagrangian Analysis of Continua (FLAC). And then the shear displacement distribution in normal direction of system composed of localized shear band and elastic rock was analyzed based on gradient-dependent plasticity. The adopted failure criterion was a composite of Mohr-Coulomb criterion, that is, the relation between tension cut-off and post-peak constitutive of rock was linear strain-softening. Numerical results show that shear stress field approximately undergoes three different stages. At first, shear stress is only concentrated in the middle of top and base of specimen. Next, shear stress in the middle of specimen tends to increase, owing to superposition of shear stresses. Interestingly, two peaks of shear stress appear far from the loading ends of specimen, and the peaks approach with the increase in timestep until elements at the center of specimen yield. Finally, relatively lower shear stress level is reached in large part of specimen except in the regions near the two ends. As flow stress decreases, the analytical shear displacement distribution in shear band based on gradient-dependent plasticity becomes steep; outside the band, it is linear and its slope tends to decrease. These theoretical results qualitatively agree with that of the present numerical predicted results. Main advantage of the analytical solution over the numerical results according to FLAC is that it is continuous, smooth and non-linear (except at elastic stage).

The Perineal Membrane: Its Composite Fibers and Nerve Content, and Relationship to the Levator Ani and Deep Transverse Perineal Muscles

The perineal membrane (PM) is a thick, elastic fiber-rich, smooth muscle-poor membrane extending along the vestibule and lower vaginal wall and embedding the urethrovaginal sphincter and compressor urethrae muscles. To provide a better understanding of the topographical relationship between the PM and the levator ani muscle, we examined histological sections from 15 female cadavers. The composite fibers of the PM were usually continuous with that of a fascia covering the inferior or lateral surface of the levator ani (fascia diaphragmatis pelvis inferior) rather than the endopelvic fascia covering the superior or medial surface of the latter muscle. However, this fascial connection was sometimes interrupted by a venous plexus. The deep transverse perineal muscle was consistently adjacent to the posterolateral aspect of the PM, but whether it extended superficially or deeply to the PM depended on size of the muscle. In contrast to the endopelvic fascia embedding abundant middle-sized nerves (cavernous and sphincter nerves;0.05 - 0.1 mm in thickness), the PM contained very thin nerves: many in 10 cadavers but few in 5 cadavers. Most of the nerves seemed to be sensory on the basis of immunohistochemistry. The levator ani muscle was considered likely to provide traction force to the PM, but active elevation appeared to be difficult because of the highly elastic nature of the PM and the interrupting venous plexus. Loss of nerves in the PM might be one of a number of factors that can accelerate pelvic organ prolapse.

Nonstationary plane contact problem in theory of elasticity for conformal cylindrical surfaces

A numerical–analytical approach is described to investigate the process of impact interaction between a long smooth rigid body and the surface of a circular cylindrical cavity in elastic space. A non-stationary mixed initial boundary value problem is formulated with a priori unknown boundaries moving with variable velocity. The problem is solved using the methods of the theory of integral transforms, expansion of desired variables into a Fourier series, and the quadrature method to reduce the problem to solving a system of linear algebraic equations at each time step. Some concrete numerical computations are presented.The cylindrical body mass and radius impact on the proile of the transient process of contact interaction has been analysed.

Creep Property of Solidifying Backfill Body of High-Water Material

On the basis of the creep test of bigh-water materisl solidifying backfill body(abb. HW body), This paper discusses its creep properties- The visco-elasto-plastic model, which shows the creep properties of HW body, is developed, and the creep contitutive equations are deduced. The visco-elastoplastic model is proved by the experiments and practice.

Surrounding rock deformation analysis of underground caverns with multi-body finite element method

Discontinuous deformation problems are common in rock engineering. Numerical analysis methods based on system models of the discrete body can better solve these problems. One of the most effective solutions is discontinuous deformation analysis （DDA） method, but the DDA method brings about rock embedding problems when it uses the strain assumption in elastic deformation and adopts virtual springs to simulate the contact problems. The multi-body finite element method （FEM） proposed in this paper can solve the problems of contact and deformation of blocks very well because it integrates the FEM and multi-body system dynamics theory. It is therefore a complete method for solving discontinuous deformation problems through balance equations of the contact surface and for simulating the displacement of whole blocks. In this study, this method was successfully used for deformation analysis of underground caverns in stratified rock. The simulation results indicate that the multi-body FEM can show contact forces and the stress states on contact surfaces better than DDA, and that the results calculated with the multi-body FEM are more consistent with engineering practice than those calculated with DDA method.

基于CFD/CSD耦合的高速射弹尾拍载荷特性研究

为提高射弹尾拍载荷的预测精度,建立了一套基于计算流体动力学(CFD)/计算结构动力学(CSD)双向耦合分析的计算方法和程序。射弹流体计算主控方程采用耦合SSTk-ω湍流模型和Schnerr-Sauer空化模型的Navier-Stokes方程,射弹结构计算采用基于模态叠加法简化的结构动力学方程,流固耦合界面插值采用径向基函数法,网格变形采用弹簧网格法。分别对泡型计算方法和流固耦合方法进行验证,在此基础上,计算对比1 000 m/s速度下射弹刚体和弹性体的尾拍泡型、结构变形和尾拍流体载荷特性差异。计算表明:弹性体尾拍过程,射弹泡型会产生弹身“二次拍击”、“局部沾湿”和沾湿面积增大等特殊现象,结构变形由弹性一弯模态主导,较大的变形引起流体载荷增大27%~105%,尾拍姿态角增大13%,尾拍频率增加20%,流固耦合效应对尾拍泡型、尾拍载荷和尾拍弹道均产生了较强的影响。

超弹性NiTi合金夹芯体的冲击性能分析

基于机械形状记忆合金(SMAs)模型的有限元分析方法,分析了一定位移载荷下的NiTi合金夹芯体单元,得到夹芯体结构的应力和腹板数关系曲线、应力和应变曲线、马氏体的体积分数分布图、功和能时程关系、冲击力时程曲线等。结果表明:腹板不同的结构应力相差1178 MPa,当结构的腹板长宽比10≤l/b≤60时,结构的安全性和经济性分别提高5倍和降低40%,此外,材料的马氏体转变和主应力有直接关系,结构的应力-应变曲线耗能迟滞环面积为5.9(位移70 mm载荷),且随变形增加耗能迟滞环增大到10.3(位移100 mm载荷),产生的较大非线性变形可以完全自动恢复。结构具有至少8%可恢复应变的超弹性、抗冲击性和耗能能力。

考虑弹性振动的城市轨道车辆频变吸振器减振方法

车体轻量化设计是城市轨道车辆技术发展趋势,然而轻量化后的车体可能会引起车辆的弹性振动加剧,导致运行过程中车辆平稳性和乘坐舒适性下降问题。为了有效抑制城市轨道车辆弹性车体的垂向振动、提高车辆乘坐舒适性,利用变刚度机构的系统频率呈非线性变化的特点,建立包含频变吸振器的城市轨道车辆弹性车体垂向动力学模型,提出利用频变吸振器抑制弹性车体垂向振动的减振方法,分析不同速度、不同位置安装频变吸振器的减振效果,指明频变吸振器的优点。通过对比频变吸振器与传统被动式吸振器的减振效果,对频变吸振器抑制车体振动进行评价。结果表明:频变吸振器在不同速度、不同位置均能有效抑制车辆刚性与弹性振动;频变吸振器的优点在于一定程度上能够拓宽被动式吸振器的减振频带,提升吸振器在复杂工况下的减振能力。该工作为利用频变吸振器在城市轨道车辆上的应用提供了参考依据。

山棕-乳胶床垫力学性能及翻身过程中的体压分布

为探究山棕-乳胶床垫在静态及翻身过程中的人-床界面体压分布,对山棕、乳胶进行了抗压缩测试,比较分析各试件的应力-应变曲线,探讨山棕、乳胶的力学性能。同时,利用Tactilus实时压力分布测量系统,测量12名参试者在山棕-乳胶床垫3种睡姿下、4个部位静态及翻身过程中的体压分布。利用峰值压力、平均压力、人-床接触面积评估乳胶的减压性能。结果表明:山棕作为横观各向同性材料,其割线弹性模量约为44.06 kPa。乳胶作为一种可压缩的超弹性材料,Ogden本构模型在整个压缩应变历程下能很好地描述其力学行为,其决定系数R 2约为0.969。人体静息状态下,3种睡姿下的肩部和臀部的峰值压力最大为21.86和25.81 kPa。在0°仰卧向30°卷曲侧卧翻身过程中,人体平衡主要靠肩部、臀部、大腿维持,接触面积减小,易发生倾覆,为保持身体稳定需不断调整姿态,导致人-床界面压力波动变化。乳胶弹性模量小、质地柔软等特点使人体表面紧密贴合床垫,有效增加人-床接触面积,对肩部、臀部峰值压力有21.72%~32.50%、18.95%~28.10%的减压效果。通过对山棕、乳胶的力学性能和组合床垫动静态体压分布研究,得到乳胶的本构模型和减压性能,为后续床垫设计提供了理论参考。

浅埋海底隧道围岩应力复势函数显式解

利用弹性复变函数理论将浅埋海底隧道简化为半无限平面问题,考虑围岩自重和海水压力的影响,对隧道开挖后的围岩应力分布进行研究.采用分式映射函数将围岩域映射为像平面圆环域,在圆环域内将复势单值解析函数展开为Laurent级数.利用无穷远点应力有界性对Laurent级数幂次项进行确定,根据地表边界和孔口不均匀应力边界条件得到Laurent级数系数迭代表达式,将已确定的Laurent级数条件代入迭代表达式中得出复势函数显式解,从而实现复势函数系数从低次幂迭代至高次幂.根据应力分量的复变函数表达式即可得到隧道周围各点应力分量.研究了两个单值解析函数取不同幂次时对结果的影响,分析了浅埋隧道埋深对环向压应力的影响.研究结果表明:幂级数解具有较高的可靠性,在隧道上半部分幂级数解与有限元数值解吻合效果良好,在隧道下半部分幂级数解最终计算结果比有限元结果相对保守;为了保证计算结果的准确性复势函数需取足够多项;随着隧道埋深增大,隧道底部及两侧孔腰处环向压应力不断增大;腰部与底部环向应力的差值也随之增大.