Modeling and Free Vibration Behavior of Rotating Composite Thin-walled Closed-section Beams with SMA Fibers

Smart structure with active materials embedded in a rotating composite thin-walled beam is a class of typical structure which is using in study of vibration control of helicopter blades and wind turbine blades. The dynamic behavior investigation of these structures has significance in theory and practice. However, so far dynamic study on the above-mentioned structures is limited only the rotating composite beams with piezoelectric actuation. The free vibration of the rotating composite thin-walled beams with shape memory alloy（SMA） fiber actuation is studied. SMA fiber actuators are embedded into the walls of the composite beam. The equations of motion are derived based on Hamilton＇s principle and the asymptotically correct constitutive relation of single-cell cross-section accounting for SMA fiber actuation. The partial differential equations of motion are reduced to the ordinary differential equations of motion by using the Galerkin＇s method. The formulation for free vibration analysis includes anisotropy, pitch and precone angle, centrifugal force and SMA actuation effect. Numerical results of natural frequency are obtained for two configuration composite beams. It is shown that natural frequencies of the composite thin-walled beam decrease as SMA fiber volume and initial strain increase and the decrease in natural frequency becomes more significant as SMA fiber volume increases. The actuation performance of SMA fibers is found to be closely related to the rotational speeds and ply-angle. In addition, the effect of the pitch angle appears to be more significant for the lower-bending mode ones. Finally, in all cases, the precone angle appears to have marginal effect on free vibration frequencies. The developed model can be capable of describing natural vibration behaviors of rotating composite thin-walled beam with active SMA fiber actuation. The present work extends the previous analysis done for modeling passive rotating composite thin-walled beam.

A trajectory shaping guidance law with field-of-view angle constraint and terminal limits

In this paper, a trajectory shaping guidance law,which considers constraints of field-of-view(FOV) angle, impact angle, and terminal lateral acceleration, is proposed for a constant speed missile against a stationary target. First, to decouple constraints of the FOV angle and the terminal lateral acceleration, the third-order polynomial with respect to the line-ofsight(LOS) angle is introduced. Based on an analysis of the relationship between the looking angle and the guidance coefficient,the boundary of the coefficient that satisfies the FOV constraint is obtained. The terminal guidance law coefficient is used to guarantee the convergence of the terminal conditions. Furthermore, the proposed law can be implemented under bearingsonly information, as the guidance command does not involve the relative range and the LOS angle rate. Finally, numerical simulations are performed based on a kinematic vehicle model to verify the effectiveness of the guidance law. Overall, the work offers an easily implementable guidance law with closed-form guidance gains, which is suitable for engineering applications.

Research on Cavitation Characteristics and Influencing Factors of Herringbone Gear Pump

Cavitation is a common issue in pumps,causing a decrease in pump head,a fall in volumetric efficiency,and an intensification of outlet flow pulsation.It is one of the main hazards that affect the regular operation of the pump.Research on pump cavitation mainly focuses on mixed flow pumps,jet pumps,external spur gear pumps,etc.However,there are few cavitation studies on external herringbone gear pumps.In addition,pumps with different working principles significantly differ in the flow and complexity of the internal flow field.Therefore,it is urgent to study the cavitation characteristics of external herringbone gear pumps.Compared with experimentalmethods,visual research and cavitation area identification are achieved through computation fluid dynamic(CFD),and changing the boundary conditions and shape of the gear rotor is easier.The simulation yields a head error of only 0.003%under different grid numbers,and the deviation between experimental and simulation results is less than 5%.The study revealed that cavitation causes flow pulsation at the outlet,and the cavitation serious area is mainly distributed in the meshing gap and meshing area.Cavitation can be inhibited by reducing the speed,increasing the inlet pressure,and changing the helix angle can be achieved.For example,when the inlet pressure is 5 bar,the maximumgas volume fraction in themeshing area is less than 50%.These results provide a reference for optimizing the design and finding the optimal design parameters to reduce or eliminate cavitation.

Coupled DEM-FDM analyses of the effects of falling rock’s shape and impact angle on response of granular cushion and rock shed

Rock shed is an effective protection measure against rockfall.To investigate the influences of falling rock’s shape and impact angle on the impact effect of the cushioned rock shed,a modeling approach for a rock shed with a cushion layer using PFC-FLAC.The granular cushion is modeled as an aggregate of discrete non-cohesion particles,while the concrete plate and the beam are modeled as zones.The falling rock with different sphericities and impact angles is modeled as a rigid assembly.The numerical model is validated by comparing the simulation results with experimental and numerical results from previous literature.This model is applied to analyze the effects of rock shape and impact angle on the dynamic interaction effects between falling rock and cushioned rock shed,including the impact force,transmitted bottom force,penetration depth,and plate deflection.The numerical results show that the variation in the falling rock’s shape has different effects on the falling rock with different impact angles.These findings could support rock shed design by revealing the limitations of the assumptions in the past research,which may result in unsafe rock sheds for some rockfall cases.

Fundamental Interaction Bridging Elements, in Supplement to the Standard Model

An interdisciplinary-field research brings new elements in bridging the gravitational interaction with the Standard Model, by focusing on 3 factors. The involvement of inductive and capacitive-like phase shifts in the gravitational interaction, the exploration of swapping between parameters of time and space, and the provision of a way to handle imaginary terms. The existence of phase shifts in the gravitational interaction is documented via re-interpretation of older quantitative predictions, and is specifically linked to the Higgs field mechanism. Same as in electronics, a phase shift splits energy into real and imaginary coordinates. This allows to quantitatively treat inertia as an inductive-like potential, alongside the swapping of parameters of time and space. That also allows to treat the Bernoulli pressure in quantitative analogy to a magnetic potential, as well as barrier penetration in quantitative symmetry to the crossing of displacement-current through a capacitor. The findings shed light on how fields & forces, including reaction forces function, while the role of imaginary numbers is analyzed. Interaction of fields with quantum particles is discussed to involve a Fourier-series effect that results in energy quantization. The role of phase shifts becomes essential in bridging between wave nature and effects of relativity, and the Weinberg angle is explained to have the role of an inductive-like shift. The precise value of this angle is proposed to link to elementary particles’ properties like spin, or the value of quarks’ charge. Symmetries introduced allow to address the abundance of matter over antimatter in certain analogy to theory from electronics, to address galaxy rotation curves through an interaction involving negative energy, and more. The new concepts open up room for advancements in energy exploitation over interdisciplinary areas.

基于神经网络的风力机叶片三维失速模型研究

以PhaeⅥ风力机为研究对象,采用CFD方法对多种工况风力机的流场进行计算,通过反向动量叶素理论方法提取攻角和翼型的三维气动数据。在此基础上,建立以周速比、实度、攻角、扭角和二维气动参数为输入参数,三维气动参数为输出参数的BP神经网络修正模型。所建BP模型预测的升阻力系数同CFD计算所得结果误差在5%以内。将该模型同动量叶素理论相结合对PhaseⅥ风力机进行计算,结果表明可显著提高风力机气动性能的预测精度。

浅圆仓地震侧压力计算公式推导与分析

仓壁侧压力是浅圆仓抗震设计的重要参数,在规范中没有给出确切的浅圆仓仓壁地震侧压力的理论计算公式。对此,基于极限平衡法,将浅圆仓看作特殊的曲线挡墙,取单位弧长的滑动楔体为研究对象,采用拟静力法与旋转地震角法简化地震力以进行极限平衡分析,并推导出浅圆仓锥堆与平堆工况下的地震侧压力计算公式。通过算例分析,比较满仓状态下地震侧压力的实测数据值及理论计算值,初步验证公式的正确性。对地震侧压力进行数值模拟与参数分析,结果表明模型拟合效果良好,仓壁摩擦力影响较大,在计算中不可忽视;在平堆工况下半径取值对大直径浅圆仓地震侧压力的影响较小,可将其简化为直线挡墙计算。研究成果可为完善筒仓规范中地震侧压力的计算推导提供一定的参考依据。

成都天府绿道跨成昆铁路斜拉桥设计

成都天府绿道跨成昆铁路桥为(29.98+37.6+41.3+173.88)m独塔双索面斜拉桥,采用塔墩梁固结体系。桥塔采用水滴形钢筋混凝土塔,高95 m,与锦城湖水交相呼应,形态挺拔修长,线条简约柔美。预应力混凝土主梁采用单箱双室截面,外轮廓为带切角矩形,兼顾美观、降低风阻、增强横向抗弯刚度和抗扭刚度等需求。斜拉索采用环氧涂层平行钢绞线拉索,便于塔内狭小空间的架设工作。转体结构主要由下转盘、球铰、上转盘、转体牵引系统等组成。施工时在支架上现浇转体梁段,主梁平面转体就位后与主跨梁端支架现浇段合龙,转体时边跨侧、主跨侧主梁悬臂长度分别为111.48 m和166.3 m,悬臂总长277.78 m。采用MIDAS Civil软件建立全桥有限元模型,进行施工阶段和持久状况的静力、稳定性计算,结果满足规范要求。

经跗骨窦入路小切口空心螺钉内固定治疗跟骨骨折相关角度变化

目的 探讨跟骨骨折患者经跗骨窦入路小切口空心螺钉内固定治疗对跟骨相关角度的影响。方法 选择2020年6月至2023年7月在我院手术治疗的跟骨骨折患者107例作为研究对象,根据治疗方式不同分为A组(n=56,采用外侧L形切口结合钢板内固定)和B组(n=51,采用跗骨窦入路小切口空心螺钉内固定)。比较2组患者手术前后Bohler角、Gissane角、跟骨宽度、跟骨高度、美国矫形外科足踝协会(AOFAS)Maryland足功能评分、视觉模拟量表(VAS)评分。Pearson法分析手术前后各影像学指标间及与Maryland足功能评分、VAS评分间的相关性,以及手术前后影像学指标差值与Maryland足功能评分、VAS评分改善率间的关系。结果 2组患者术后Bohler角、Gissane角、跟骨宽度、跟骨高度均较术前显著改善(P<0.05)。B组患者术后1个月Bohler角小于A组(P<0.05),术后3个月和6个月Bohler角、术后3个月Gissane角和跟骨宽度大于A组(P<0.05)。2组患者术后1、3、6个月的VAS评分均较术前显著降低(P<0.05),Maryland足功能评分均较术前显著增加(P<0.05)。B组患者术后1、3、6个月Maryland足功能评分和VAS评分均明显优于A组(P<0.05)。手术前后Bohler角、跟骨宽度、Gissane角、跟骨高度间均相关(P<0.05);术前跟骨宽度、跟骨高度与Maryland足功能评分、VAS评分无关(P>0.05),术前Bohler角、Gissane角与Maryland评分及VAS评分相关(P<0.05);术后Bohler角、跟骨宽度、Gissane角、跟骨高度均与Maryland足功能评分及VAS评分相关(P<0.05)。Bohler角、Gissane角、跟骨宽度、跟骨高度手术前后差值与Maryland足功能评分、VAS评分改善率间均具有相关性(P<0.05)。结论 经跗骨窦入路小切口空心螺钉内固定治疗跟骨骨折后,Bohler角、Gissane角与跟骨高度均增加,跟骨宽度减小,疗效优于外侧L形切口结合钢板内固定治疗。Bohler角、Gissane角、跟骨宽度和跟骨高度的变化与临床疗效具有相关性。

面向“花瓣型”配电网的旋转潮流控制器两阶段转速功率控制策略

随着有源配电网建设的迅猛发展,“花瓣型”配电网已成为主流供电结构,为保障配电系统的安全供电,应当进一步研究适用于有源配电网的功率控制方法。电磁式旋转潮流控制器(RPFC)是有源配电网功率控制的一种可行方案。该文首先构建了基于瞬时无功理论的RPFC稳态功率解耦控制模型,然而由于旋转移相变压器转子位置角的协调控制难点,难以实现功率稳定控制;然后,通过伺服电动机两阶段转速控制和转速协调方案实现两转子角的稳定、无差控制,满足高精度、高可靠性和快速响应的功率调节需求;最后,研制了380 V/40 kV·A的RPFC样机及实验平台,并进行了功率调控和功率均衡实验。结果表明,所提控制方案能够在s级实现调控,且控制精度保持在4%以内,具有良好的动、静态性能,能够满足未来“花瓣型”配电网的柔性合环运行。

一种大倾角单独像对相对定向混合算法

立体像对相对定向是摄影测量三维重建中的重要步骤。为解决初始值不理想导致的相对定向迭代解算不收敛、鲁棒性差的问题,提出了一种大倾角单独像对相对定向的混合算法。首先基于高精度同名像点坐标观测值构建非线性的共面条件方程组,再通过信赖域折线算法进行解算并将方程组解作为后续迭代初始值;最后采用非线性共轭梯度法进行迭代以提高相对定向参数解算精度。无人机航空影像数据集的对比实验结果表明,该算法的相对定向精度可达1μm,具有解算精度高、稳定性好的优点。

Novel Method for Spatial Angle Measurement Based on Rotating Planar Laser Beams

Spatial angle measurement, especially the measurement of horizontal and vertical angle, is a basic method used for industrial large-scale coordinate measurement. As main equipments in use, both theodolites and laser trackers can provide very high accuracy for spatial angle measurement. However, their industrial applications are limited by low level of automation and poor parallelism. For the purpose of improving measurement efficiency, a lot of studies have been conducted and several alternative methods have been proposed. Unfortunately, all these means are either low precision or too expensive. In this paper, a novel method of spatial angle measurement based on two rotating planar laser beams is proposed and demonstrated. Photoelectric receivers placed on measured points are used to receive the rotating planner laser signals transmitted by laser transmitters. The scanning time intervals of laser planes were measured, and then measured point＇s horizontal/vertical angles can be calculated. Laser plane＇s angle parameters are utilized to establish the abstract geometric model of transmitter. Calculating formulas of receiver＇s horizontal/vertical angles have been derived. Measurement equations＇ solvability conditions and judgment method of imaginary solutions are also presented after analyzing. Proposed method for spatial angle measurement is experimentally verified through a platform consisting of one laser transmitter and one optical receiver. The transmitters used in new method are only responsible for providing rotating light plane signals carrying angle information. Receivers automatically measure scanning time of laser planes and upload data to the workstation to calculate horizontal angle and vertical angle. Simultaneous measurement of multiple receivers can be realized since there is no human intervention in measurement process .Spatial angle measurement result indicates that the repeatable accuracy of new method is better than 10＂. Proposed method can improve measurement＇s automation degree and speed while ensuring measurement accuracy.

COMMON DEFINITION FOR END-SURFACE CONTACT RATIO OF GEARS AND ITS APPLICATIONS

Common definition and calculating expressions of end-surface contact ratiofor all type of gears are put forward, and with calculation expressions for involute gears,micro-segments profile gears, and sine-curved profile gears being discussed. The end-surface contactratio of gears is defined as the ratio of the action angle (the rotation angle of gear from gear-into gear-out for one pair of teeth) to the rotation angle per pitch (or central angle per tooth).According to the theory of gearing, equation of the meshing line can be deduced from the toothprofiles of basic rack. Having obtained the equation of the meshing line, and being given theaddendum outline of the gears, the contact ratio can be calculated with the calculation expressions.For the involute gears, this definition has same effect as the well-known definition: ratio of thecontact line to the base pitch. This definition of contact ratio is also suitable to othernon-involute gears, such as micro-segments profile gears, sine-curved profile gears, and can givemore reliable results.

Grain refinement and improved properties through electromagnetic stirring in Al alloy MIG welds

This paper described the effects of external excitatory parameters of current and frequency on the microstructure and mechanical properties of weld metal in MIG welding with longitudinal electromagnetic field. With a high speed video camera capturing the images of arc shape, the mechanism of arc rotation and how the periodic contraction and expansion of arc affected the movement of molten pool were investigated. The technique resulted in fine equiaxed grains in weld metal and optimum parameters of electromagnetic stirring were suggested based on the extent of refinement. Fine-grained weld metal exhibited better yield strength and significant improvement in elongation.

Trajectory shaping guidance law based on virtual angle with terminal constraints

A trajectory shaping guidance law based on virtua angle （TSGLBVA） is proposed for a re-entry vehicle with the constraints of terminal impact angles and their time derivatives. In the view of differential properties of the maneuvering trajectory, a virtual angle and a virtual radius are defined. Also, the shaping trajectory of the vehicle is established by the polynomials of the virtual angle. Then, four optimized parameters are selected according to the theorem of parameters transformation presented in this paper. Finally, a convergent variant of the Nelder-Mead algorithm is adopted to obtain the reference trajectory, and a trajectory feedback tracking guidance law is designed. The simulation results demonstrate that the TSGLBVA ensures the re-entry vehicle to impact a target precisely from a specified direction with smal terminal load factor command, as well as to obtain a maximum or constrained terminal velocity according to various requirements.

Trajectory shaping guidance law with terminal impact angle constraint

In order to strike hard targets underground or warships and tanks with expected impact angle by missiles or guided bombs, trajectory shaping guidance law with terminal position and impact angle constraints is derived based on linear quadratic optimal control theory. The required accelera- tion expressed by impact angle and heading error is obtained in lag-free guidance system in order to find the optimal relationship of those angles in terminal phase. The adjoint systems of miss distance and impact angle error of first-order guidance system are established based on statistical linearization adjoint method （SLAM） in order to study the impact performances of the guidance law. Simulation results show that the miss distance and impact angle error of trajectory shaping guidance law are both according with the impact position and angle constraint and the required acceleration at impact can be decreased by an optimal relationship of impact angle and heading error.

The differential interference angle of ~2Π [Case(a)] diatom on rotational energy transfer in NO (X^2Π ) collision with He,Ne and Ar system

To study theoretically the relationship between the differential interference angle and the scattering angle in collisional quantum interference （CQI）, we have investigated the differential interference angle of the atom-diatomic [case（a）] molecule system in detail. For the 2∏ electronic state in Hund＇s case （a）, the degree of the differential interference is also discussed. The differential interference angles of NO（X^2∏） are calculated quantitatively for the rotational energy transfer in Hund＇s case （a） induced by collision with He, Ne and Ar atoms. The method to calculate the differential interference angle is presented. Several factors that affect the differential interference angle are investigated. Finally the variation of the differential interference angle with the impact parameter and relative velocity is discussed.

Stability Loss of Rotating Elastoplastic Discs of the Specific Form

A method of calculating a possible stability loss by a rotating circular annular disc of variable thickness is suggested within the theory of perfect plasticity with the help of small parameter method. A characteristic equation for a critical radius of a plastic zone is obtained as a first approximation. The formula for the critical angular velocity, determining the stability loss of the disc according to the self-balanced form, is derived. The method using which we can take into account the disc’s geometry and loading parameters is also specified. The efficiency of the proposed method is shown in Section 5 while considering an illustrative example. The values of critical angular velocity of rotating are found numerically for different parameters of the disc.

Analysis of Dynamics of Boundary Shape Perturbation of a Rotating Elastoplastic Radially Inhomogeneous Plane Circular Disk: Analytical Approach

For a rotating inhomogeneous circular disk a way of calculating dynamics of boundary shape perturbation and failure of bearing capacity is proposed in terms of small parameter method. Characteristic equation of plastic zone critical radius is obtained as a first approximation. A formula of critical angular velocity is derived which determines the stability loss of the disc according to the self-balanced form. Efficiency of the proposed method is shown by an illustrative example considered in Section 7. Values of critical angular velocity of rotation are found numerically for different parameters of the disc.

Relationship Between Differential Interference Angle and Parameter of Experiment in Molecular Beam

Collisional quantum interference （CQI） was observed in the intramolecular rotational energy transfer in the experiment of the static cell, and the integral interference angles were measured. To observe more precise information, the experiment in the molecular beam should be taken,from which the relationship between the differential interference angle and the scattering angle can be obtained. In this paper, the theoretical model of CQI is described in an atom-diatom system in the condition of the molecular beam, based on the first-Born approximation of time-dependent perturbation theory, taking into accounts the long-range interaction potential. The method of observing and measuring correctly the differential interference angle is presented. The changing tendency of the differential interference angle with the impact parameter and relative velocity is discussed. The changing tendencies of the differential interference angle with the parameter of experiment in the molecular beam, including the impact parameter and the velocity are discussed. This theoretical model is important to understand or perform the experiment in the molecular beam.