The deterministic condition for the ground reaction force acting point on the combined knee valgus and tibial internal rotation moments in early phase of cutting maneuvers in female athletes

Background:Combined knee valgus and tibial internal rotation(VL+IR)moments have been shown to stress the anterior cruciate ligament(ACL)in several in vitro cadaveric studies.To utilize this knowledge for non-contact ACL injury prevention in sports,it is necessary to elucidate how the ground reaction force(GRF)acting point(center of pressure(CoP))in the stance foot produces combined knee VL+IR moments in risky maneuvers,such as cuttings.However,the effects of the GRF acting point on the development of the combined knee VL+IR moment in cutting are still unknown.Methods:We first established the deterministic mechanical condition that the CoP position relative to the tibial rotational axis differentiates the GRF vector’s directional probability for developing the combined knee VL+IR moment,and theoretically predicted that when the CoP is posterior to the tibial rotational axis,the GRF vector is more likely to produce the combined knee VL+IR moment than when the CoP is anterior to the tibial rotational axis.Then,we tested a stochastic aspect of our theory in a lab-controlled in vivo experiment.Fourteen females performed 60˚cutting under forefoot/rearfoot strike conditions(10 trials each).The positions of lower limb markers and GRF data were measured,and the knee moment due to GRF vector was calculated.The trials were divided into anterior-and posterior-CoP groups depending on the CoP position relative to the tibial rotational axis at each 10 ms interval from 0 to 100 ms after foot strike,and the occurrence rate of the combined knee VL+IR moment was compared between trial groups.Results:The posterior-CoP group showed significantly higher occurrence rates of the combined knee VL+IR moment(maximum of 82.8%)at every time point than those of the anterior-CoP trials,as theoretically predicted by the deterministic mechanical condition.Conclusion:The rearfoot strikes inducing the posterior CoP should be avoided to reduce the risk of non-contact ACL injury associated with the combined knee VL+IR stress.

Rolling Force and Rolling Moment in Spline Cold Rolling Using Slip-line Field Method

Rolling force and rolling moment are prime process parameter of external spline cold rolling. However, the precise theoretical formulae of rolling force and rolling moment are still very fewer, and the determination of them depends on experience. In the present study, the mathematical models of rolling force and rolling moment are established based on stress field theory of slip-line. And the isotropic hardening is used to improve the yield criterion. Based on MATLAB program language environment, calculation program is developed according to mathematical models established. The rolling force and rolling moment could be predicted quickly via the calculation program, and then the reliability of the models is validated by FEM. Within the range of module of spline m=0.5-1.5 mm, pressure angle of reference circle α=30.0°-45.0°, and number of spline teeth Z=19-54, the rolling force and rolling moment in rolling process （finishing rolling is excluded） are researched by means of virtualizing orthogonal experiment design. The results of the present study indicate that： the influences of module and number of spline teeth on the maximum rolling force and rolling moment in the process are remarkable; in the case of pressure angle of reference circle is little, module of spline is great, and number of spline teeth is little, the peak value of rolling force in rolling process may appear in the midst of the process; the peak value of rolling moment in rolling process appears in the midst of the process, and then oscillator weaken to a stable value. The results of the present study may provide guidelines for the determination of power of the motor and the design of hydraulic system of special machine, and provide basis for the farther researches on the precise forming process of external spline cold rolling.

A generalized model for estimation of aerodynamic forces and moments for irregularly shaped bodies

A novel method for estimation of an aerodynamic force and moment acting on an irregularly shaped body (such as HE projectile fragments) during its flight through the atmosphere is presented. The model assumes that fragments can be approximated with a tri-axial ellipsoid that has continuous surface given as a mathematical function. The model was validated with CFD data for a tri-axial ellipsoid and verified using CFD data on aerodynamic forces and moments acting on an irregularly shaped fragment. The contribution of this method is that it represents a significant step toward a modeling that does not require a cumbersome CFD simulation results for estimation of fragment dynamic and kinematic parameters. Due to this advantage, the model can predict the fragment motion consuming a negligible time when compared to the corresponding time consumed by CFD simulations. Parametric representation (generalization) of the fragment geometrical data and the conditions provides the way to analyze various correlations and how parameters influence the dynamics of the fragment flight.

Effect of Ground Stack for Additional Internal Force and Deformation of Underground Pipeline

Based on a three-dimensional finite element model of an underground pipeline,the influence of additional ground loads on the stress characteristics of the pipeline was studied.Furthermore,the effects of different soil properties,load locations,and varying burial depths on the pipeline’s stress characteristics were analyzed.The research results show that as the distance between the load center and the pipeline axis increases,the positions of the pipe’s maximum displacement,bending moment,and shear force along the axis decrease significantly.However,when this distance reaches a certain value,the pipeline’s maximum vertical displacement and internal forces approach zero.Different pipelines exhibit minimum values of maximum axial displacement and vertical displacement in soft soil,while maximum axial displacement occurs in clay,and the largest vertical displacement is observed in sandy soil.The maximum axial displacement of UPVC pipes in clay is twice that of soft soil.The vertical displacement of pipes made from different materials increases with burial depth,but for concrete and steel pipes,the maximum axial tension increases significantly with depth,whereas the change in UPVC pipes is more gradual.

Forced Response of Fluid-Spacecraft Coupling System and Force and Moment of Fluid Acting on Container

In this paper, forced response of fluid-spacecraft coupling system and force and moment of acting on rect-angular container are studied. Firsily, the interrelation between the generaized coordinates of fluid velocity potential function and surface wave-height function is derived for liearized eqqations describing motion of contained fluid.The drnamical equations of coupling system is obtained by Lagrangian formulation. These equations provides some in-sights of fluid-spacecraft coupling characteristics.It is not in the sense of the whole modal mass that the fluid sloshing of corresponding order is excited by the vibration of the spacecratt.Then, the force and moment of the fiuid on the container are derived and discussed in detal. Latly, numerical simulation and conclusions are given.

FORCES AND MOMENTS OF THE LIQUID FINITE AMPLITUDE SLOSHING IN A LIQUID-SOLID COUPLED SYSTEM

Nonlinear coupling dynamics between a spring-mass system and a finite amplitude sloshing system with liquid in a cylindrical tank is investigated. Based on a group of nonlinear coupling equations of six degrees of freedoms, analytical formulae of forces and moments of the liquid large amplitude sloshing were obtained. Nonlinearity of the forces and moments of the sloshing was induced by integrating on final configuration of liquid sloshing and the nonlinear terms in the liquid pressure formula. The symmetry between the formula of Ox and Oy direction proves that the derivation is correct. According to the coupled mechanism, the formulae are available in other liquid-solid coupled systems. Simulations and corresponding experimental results arecompared. It is shown that the forces and moments formulae by integrating on the final sloshing configuration are more reasonable. The omitted high-dimensional modal bases and high-order nonlinear terms and the complexity of sloshing damping are main sources of errors.

Control of flight forces and moments by flapping wings of model bumblebee

The control of flight forces and moments by flapping wings of a model bumblebee is studied using the method of computational fluid dynamics. Hovering flight is taken as the reference flight： Wing kinematic parameters are varied with respect to their values at hovering flight. Moments about （and forces along） x, y, z axes that pass the center of mass are computed. Changing stroke amplitude （or wingbeat frequency） mainly produces a vertical force. Changing mean stroke angle mainly produces a pitch moment. Changing wing angle of attack, when down- and upstrokes have equal change, mainly produces a vertical force, while when down- and upstrokes have opposite changes, mainly produces a horizontal force and a pitch moment. Changing wing rotation timing, when dorsal and ventral rotations have the same timing, mainly produces a vertical force, while when dorsal and ventral rotations have opposite timings, mainly produces a pitch moment and a horizontal force. Changing rotation duration has very small effect on forces and moments. Anti-symmetrically changing stroke amplitude （or wingbeat frequency） of the contralateral wings mainly produces a roll moment. Anti-symmetrically changing angles of attack of the contralateral wings, when down- and upstrokes have equal change, mainly produces a roll moment, while when down- and upstrokes have opposite changes, mainly produces a yaw moment. Anti-symmetrically changing wing rotation timing of the contralateral wings, when dorsal and ventral rotations have the same timing, mainly produces a roll moment and a side force, while when dorsal and ventral rotations have opposite timings, mainly produces a yaw moment. Vertical force and moments about the three axes can be separately controlled by separate kinematic variables. A very fast rotation can be achieved with moderate changes in wing kinematics.

ACTUATION OF SLOSHING MODULATED FORCE AND MOMENT ON LIQUID CONTAINER DRIVEN BY JITTER ACCELERATIONS ASSOCIATED WITH SIEW MOTION IN MICROGRAVITY

The mathematical formulation of sloshing dynamics for a partially liquid filleddewar container driven by the gravity jitter acceleration associated with slew motion isstudied.Explicit mathematical expressions to manage jitter accelerption associated withslew motion which is acting on the fluid systems in microgravity are derived. Thenumerical computation of sloshing dymamics is based on the non-inertia framecontainer bound coordinate and the solution of time-dependent three-dimensionalformulations of partial differential equations subject to initial and boundary conditions.The numerical computation of fluid viscous stress forces and moment fluctuationsexerted on the dewar container driven by jitter acceleration associated with slew motion is investigated.

Operation and Force Analysis of the Guide Wire in a Minimally Invasive Vascular Interventional Surgery Robot System

To develop a robot system for minimally invasive surgery is significant,however the existing minimally invasive surgery robots are not applicable in practical operations,due to their limited functioning and weaker perception.A novel wire feeder is proposed for minimally invasive vascular interventional surgery.It is used for assisting surgeons in delivering a guide wire,balloon and stenting into a specific lesion location.By contrasting those existing wire feeders,the motion methods for delivering and rotating the guide wire in blood vessel are described,and their mechanical realization is presented.A new resistant force detecting method is given in details.The change of the resistance force can help the operator feel the block or embolism existing in front of the guide wire.The driving torque for rotating the guide wire is developed at different positions.Using the CT reconstruction image and extracted vessel paths,the path equation of the blood vessel is obtained.Combining the shapes of the guide wire outside the blood vessel,the whole bending equation of the guide wire is obtained.That is a risk criterion in the delivering process.This process can make operations safer and man-machine interaction more reliable.A novel surgery robot for feeding guide wire is designed,and a risk criterion for the system is given.

Analysis of Electrical Dipoles Interaction Forces as a Function of the Distance and of the Form of Electrical Force Law

Here, we initially introduced and demonstrated two principles: orientation OR principle and attraction AT principle of electrical dipoles. The OR principle stipulates that any two electrical dipoles P1A, P1B, from two bodies A and B, at any distance in the free state each, will be reciprocally oriented parallel and in the same sense if the electrical interaction forces F between them are of decreasing type with distance r. If the electrical interaction forces F are of increasing type with distance, the two dipoles will be reciprocally oriented parallel but on the opposite sense. The AT principle stipulate that any two electrical dipoles P1A, P1B, at any distance in the free state each, will present always a reciprocal force of attraction FD in both cases of orientation accordingly to OR principle in case of any type of electrical force F decreasing or increasing with distance. These findings may complete our previous work where we found that FD force, between two electrical dipoles P1A, P1B considered at atomic and nuclear level, is in fact the actual gravitation Newton force FN. The paper must be considered together with this work for more consistency.

THE METHOD OF THE RECIPROCAL THEOREM OF FORCED VIBRATION FOR THE ELASTIC THIN RECTANGULAR PLATES(Ⅱ)——RECTANGULAR PLATES WITH TWO ADJACENT CLAMPED EDGES

In this paper, applying the method of reciprocal theorem, we give the distributions of the amplitude of bending moments along clamped edges and the amplitude of deflections along free edges of rectangular plates with two adjacent clamped edges under harmonic distributed and concentrated loads.

THE METHOD OF THE RECIPROCAL THEOREM OF FORCED VIBRATION FOR THE ELASTIC THIN RECTANGULAR PLATES(Ⅲ)--CANTILEVER RECTANGULAR PLATES

In this paper,applying the method of the reciprocal theorem,we give the stationary solutions of the forced vibration of cantilever rectangular plates under uniformly distributed harmonic load and concentrated harmonic load acting at any point of the plates,the figures and tables of number value of bending moment and the deflection amplitudes as well.

Theoretical and Practical Studies of Determining the Force of the Lifting-Lowering of the Roll Box

The lifting and lowering mechanism of the roll box of the saw gin, being an integral part of the ginning process, is used when starting the electric motor of the saw cylinder until its rated speed is reached to prevent an increase in the load current on it, as well as to start the ginning process. The article defines the kinematics of the movement, and also studies the regularity of the movement of the roll box of the saw gin when lifting it with the help of a pneumatic drive. The kinematics of the roll box movement was determined through experimental studies. Knowing the equation of motion, using the second-order Lagrange equation, the regularity of the change in the lifting force of the roll box was determined. Here the system is closed, its degree of freedom is equal to one. The angle of rotation of the roll box is taken as a generalized coordinate. Numerical results were obtained using the Matlab software environment. The theoretical analysis and graphs for determining the lifting force of the roll box are presented. To study the kinematics of lifting the roll box, a method and a test bench have been developed. According to him, when the roll box was raised, its movement was recorded on video, the image was processed using the After Effect and CorelDraw programs, and the movement of the rod attachment point to the roll box was determined. And also the equation for changing the angle of rotation of the roll box is determined using the Matlab Curve Fiting program.

Rolling centrifuge repulsion Force Spacecraft

A Rolling Centrifugal Repulsion force UFO Introduction: Any object that rolls along a straight line will generate a centrifugal repulsive force that is away from the body being rolled, it is rolling centrifugal repulsive force. Utilizing this phenomenon, rolling the round ring along the edge of the UFO's disk will produce a constant lift, and then use the electric wheel technology to set the ballast rock at the bottom of the UFO to change the position of the ballast stone at the bottom of the chamber. In order to change the position of the center of gravity of the UFO, the purpose of driving the UFO can be achieved.

LASG Global AGCM with a Two-moment Cloud Microphysics Scheme:Energy Balance and Cloud Radiative Forcing Characteristics

Cloud dominates influence factors of atmospheric radiation, while aerosol–cloud interactions are of vital importance in its spatiotemporal distribution. In this study, a two-moment(mass and number) cloud microphysics scheme, which significantly improved the treatment of the coupled processes of aerosols and clouds, was incorporated into version 1.1 of the IAP/LASG global Finite-volume Atmospheric Model(FAMIL1.1). For illustrative purposes, the characteristics of the energy balance and cloud radiative forcing(CRF) in an AMIP-type simulation with prescribed aerosols were compared with those in observational/reanalysis data. Even within the constraints of the prescribed aerosol mass, the model simulated global mean energy balance at the top of the atmosphere(TOA) and at the Earth’s surface, as well as their seasonal variation, are in good agreement with the observational data. The maximum deviation terms lie in the surface downwelling longwave radiation and surface latent heat flux, which are 3.5 W m-2(1%) and 3 W m-2(3.5%), individually. The spatial correlations of the annual TOA net radiation flux and the net CRF between simulation and observation were around 0.97 and 0.90, respectively. A major weakness is that FAMIL1.1 predicts more liquid water content and less ice water content over most oceans. Detailed comparisons are presented for a number of regions, with a focus on the Asian monsoon region(AMR). The results indicate that FAMIL1.1 well reproduces the summer–winter contrast for both the geographical distribution of the longwave CRF and shortwave CRF over the AMR. Finally, the model bias and possible solutions, as well as further works to develop FAMIL1.1 are discussed.

Moments and limiting distribution of a portfolio of whole life annuity policies

A dual random model of a portfolio of variable amount whole life annuity is set with the mth moment of the present value of benefits, and the respective expressions of the moments under the assumption that the force of interest accumulation function is Wiener process or Ornstein-Uhlenbeck process. Furthermore, the limiting distribution of average cost of this portfolio is discussed with the expression of the limiting distribution under the assumption that the force of interest accumulation is an independent increment process.

On Solution of the Problem of Bending of Orthotropic Plates on the Basis of Bimoment Theory

This paper is devoted to the development of new theory of orthotropic thick plates with account of internal forces, moments and bimoments. An equation of motion of plates is described by two systems with nine equations each. Boundary conditions depended on displacements, forces, moments and bimoments are given. An exact solution of the bending of thick plate under the effect of sine load is built. Numerical results for maximal values of displacements and stresses of the plate are obtained.

基于影响矩阵和精英遗传算法的斜拉桥索力优化

由于传统索力优化方法不能自动优化和兼顾全桥结构性能,以及与智能优化算法相结合后存在计算量大、耗时长、效率低和收敛速度慢等缺点,以Ansys和Matlab分别作为结构计算器和主控程序,以最小弯矩能为控制目标,将影响矩阵和精英保留策略引入到遗传算法中,实现成桥阶段的索力优化.该方法能够同时兼顾主梁与主塔的受力特性,而且影响矩阵的应用可以解决每一代都需要有限元评估的问题,大大减少了计算量.与传统的影响矩阵法相比,所提方法在吸取影响矩阵法优点的基础上,还考虑参数迭代过程,可在结构的关键截面添加特殊的约束要求,使得优化过程更加符合实际,而精英保留策略的引入可以提高进化迭代收敛的速度与进化过程的稳定性.最后,通过一个实际工程应用验证了所提方法的可行性.

自复位转动摩擦阻尼器弯矩-转角恢复力性能研究

为了满足减震结构对可恢复功能的要求,针对传统摩擦阻尼器不具备自复位能力震后存在较大残余变形的问题,提出了一种基于形状记忆合金的自复位转动摩擦阻尼器,由摩擦耗能装置和形状记忆合金自复位装置组合而成。介绍了该SCRF(self-centering rotating friction)阻尼器的构造形式、工作原理,通过理论推导建立了SCRF阻尼器的弯矩-转角恢复力模型,通过ABAQUS软件有限元数值分析结果对弯矩-转角恢复力模型进行了验证,分析了低周往复荷载作用下SCRF阻尼器的滞回性能,并进行了参数分析。结果表明:有限元计算结果与阻尼器恢复力模型结果吻合良好;提高接触面间的摩擦因数与斜面高度可以提高阻尼器的最大承载力、耗能能力、有效刚度,但是超过一定限值的斜面高度会降低阻尼器的自复位能力;施加SMA螺栓预紧力可以提高阻尼器的摩擦启动弯矩,对于阻尼器的耗能能力与最大承载力影响不大。

受限空间下打纬机构力矩平衡分析及其调控策略

针对打纬机构惯性打纬力与打纬阻力不平衡造成的不利影响,建立打纬机构的力学模型,以四连杆打纬机构为例,确定打纬机构结构方向的调节方法,考虑空间受限情况进行定量仿真分析,对比分析不同调节方案对驱动力矩和输出力矩的影响,并分析不同杆长设计参数带来的运动特性。仿真结果表明:通过增设平衡构件和改变杆长比例可以有效地调控惯性打纬力;当打纬力不足时,转动惯量与角加速度后打纬力矩分别提升了约14.5%与3%,共同调节提升约17.8%;当打纬力过大时,通过尺度调节后力矩降低了约7.6%;转动惯量和角加速度是惯性打纬力的主要控制变量,通过调节这两个变量可满足不同条件下的织造工艺需求,并为打纬机构尺度及结构设计提供理论参考。