方轮

本文从刚体运动学角度出发，得到了方轮在无滑动的滚动过程中，若保持它的质心高度不变，路床的形状应是一系列的倒置的悬链线的结论；又从机械能守恒定律出发，得到了方轮在上述路床上做纯滚动的一些其它特点．

面粉厂吸尘机器人方轮式全方位行走机构及定位纠偏设计

针对目前面粉厂吸尘机器人全方位行走机构成本高、能耗高、效率低等问题,提出方轮式行走机构的设计方案,结合四肢跨步能确定步长和圆轮滚动能定向行走的特点。以行走轮、纠偏轮和辅助行走轮的设计和配合,实现全方位行走。通过多套光电移动检测传感器,解决未知环境中移动过程中定位纠偏问题;通过海绵接触型传感器高效地感知前进过程中的障碍物,解决行走中的碰撞问题。该全方位行走机构用于面粉厂吸尘机器人的设计,可实现粉尘的全面清扫并可降低成本,高效节能。

物理实验的计算机仿真与方轮运动的CAI

在 Ｗｉｎｄｏｗｓ 环境下，借助计算机仿真技术，使用高级语言对大学物理实验进行数据、图形采集及处理，并以方轮运动为例进行 Ｃ Ａ Ｉ 设计，将设计结果移植到文档或图像文件中去的过程。设计方法适用于处理大学物理中的多数问题。

方轮之外

特定的车轮可以在周期性轨道上纯滚动并保持轴的高度不变.车轮和轨道的形状方程可以通过求解转动角的参数方程得到.通过研究从理论上得到了周期性双曲余弦函数轨道上的多重对称性车轮,并制作了实际模型.

方轮运动的CAI设计

详细讨论了在Ｗｉｎｄｏｗｓ环境下，利用高级语言进行方轮运动的ＣＡＩ设计，并将设计结果移植到文档或图象文件中去的过程，文中的设计方法适用于处理大学物理中的多数问题。

方轮自行车

我们身边有许许多多自行车,这些自行车的轮胎无一例外,都是圆形。然而,本期封面上的小朋友骑着的自行车就不太一样。不过,只要行驶的路面合适,骑方轮自行车也可以一样平稳。

Use of a submodel method to check the bolt strength of marine equipment

A submodel method was proposed that works from computational models of marine gear cases to verify that the proposed bolts will give it sufficient structural integrity. Calculations for marine equipment using this system accorded well with conventional results. As an example, an anti-shock computation was processed for a gear case, and the submodel was then employed to check the strength of individual components. The results showed that the gear case connecting structure can satisfy relative anti-shock requirements, and the dynamic response characteristics seen in the bolt structures had a close relationship with the method used for attaching the bolt. This provides a new means for checking the strength of connecting structures on large-scale equipment and thus has significant reference value.

Numerical Study of a Novel Procedure for Installing the Tower and Rotor Nacelle Assembly of Offshore Wind Turbines Based on the Inverted Pendulum Principle

Current installation costs of offshore wind turbines(OWTs) are high and profit margins in the offshore wind energy sector are low, it is thus necessary to develop installation methods that are more efficient and practical. This paper presents a numerical study(based on a global response analysis of marine operations) of a novel procedure for installing the tower and Rotor Nacelle Assemblies(RNAs) on bottom-fixed foundations of OWTs. The installation procedure is based on the inverted pendulum principle. A cargo barge is used to transport the OWT assembly in a horizontal position to the site, and a medium-size Heavy Lift Vessel(HLV) is then employed to lift and up-end the OWT assembly using a special upending frame. The main advantage of this novel procedure is that the need for a huge HLV(in terms of lifting height and capacity) is eliminated. This novel method requires that the cargo barge is in the leeward side of the HLV(which can be positioned with the best heading) during the entire installation. This is to benefit from shielding effects of the HLV on the motions of the cargo barge, so the foundations need to be installed with a specific heading based on wave direction statistics of the site and a typical installation season. Following a systematic approach based on numerical simulations of actual operations, potential critical installation activities, corresponding critical events, and limiting(response) parameters are identified. In addition, operational limits for some of the limiting parameters are established in terms of allowable limits of sea states. Following a preliminary assessment of these operational limits, the duration of the entire operation, the equipment used, and weather-and water depth-sensitivity, this novel procedure is demonstrated to be viable.

Probabilistic model and analysis of coupled train-ballasted track-subgrade system with uncertain structural parameters

Random dynamic responses caused by the uncertainty of structural parameters of the coupled train-ballasted track-subgrade system under train loading can pose safety concerns to the train operation.This paper introduced a computational model for analyzing probabilistic dynamic responses of three-dimensional(3D)coupled train-ballasted track-subgrade system(TBTSS),where the coupling effects of uncertain rail irregularities,stiffness and damping properties of ballast and subgrade layers were simultaneously considered.The number theoretical method(NTM)was employed to design discrete points for the multi-dimensional stochastic parameters.The time-histories of stochastic dynamic vibrations of the TBSS with systematically uncertain structural parameters were calculated accurately and efficiently by employing the probability density evolution method(PDEM).The model-predicted results were consistent with those by the Monte Carlo simulation method.A sensitivity study was performed to assess the relative importance of those uncertain structural parameters,based on which a case study was presented to explore the stochastic probability evolution mechanism of such train-ballasted track-subgrade system.

Energy increment criteria for evaluation of train derailment

The criteria for evaluation of train derailment were studied. The worldwide commonly used evaluation criteria for wheel derailment were summarized and their main problems were pointed out. The mechanism of train derailment was expounded on the basis of system dynamics stability concept. And the energy increment criteria were proposed to evaluate train derailment. By applying the criteria, the calculated results concerning 6 cases of freight train derailment on tangent railway line and 6 cases of freight train derailment on bridge were obtained, which are all in agreement with the practical situation. The safety, comfort and stability results concerning 3 cases of freight train running on bridge were analyzed. In addition, the running speed limits of freight train on the Yanconggou and Donggou bridge in the Beijing-Tonghua railway line of 50km/h and 60km/h, respectively, were proposed. And the running speed of freight train on the Nanjing Yangtze River Bridge can reach 70km/h.

释“方马埋轮”与“拐子马”

《孙子·九地篇》“方马埋轮”四字本不误,意思是“缚住战马、埋起车轮”。但“方马埋轮”并非中国古代车战阵法之一,这里只是一个假设,用以突出置士卒于必死之地以激发战斗力的重要性。拐子马记载中的“韦索”是个关键词语,不是用来把三匹战马联在一起,而是把骑兵和自己的战马联在一起,这样在冲锋陷阵时不易坠落。且三人为一组,可以互相照应,从而大大地提高了骑兵的战斗力。“方马埋轮”与“拐子马”的共同之处在于,以往的解释都有作战时把战马绑在一起的说法,都是出于不合实际的牵强附会。

Multi-objective evolutionary approach for UAV cruise route planning to collect traffic information

Unmanned aerial vehicle(UAV)was introduced as a novel traffic device to collect road traffic information and its cruise route planning problem was considered.Firstly,a multi-objective optimization model was proposed aiming at minimizing the total cruise distance and the number of UAVs used,which used UAV maximum cruise distance,the number of UAVs available and time window of each monitored target as constraints.Then,a novel multi-objective evolutionary algorithm was proposed.Next,a case study with three time window scenarios was implemented.The results show that both the total cruise distance and the number of UAVs used continue to increase with the time window constraint becoming narrower.Compared with the initial optimal solutions,the optimal total cruise distance and the number of UAVs used fall by an average of 30.93% and 31.74%,respectively.Finally,some concerns using UAV to collect road traffic information were discussed.

New method for calculating face gear tooth surface involving worm wheel installation errors

The machining principle and realization method for the continuous generative grinding face gear by a worm wheel are introduced. Based on a five-axis linked CNC grinding machine, a new method is presented to deprive the equation of face gear error tooth surface by assuming the tool surface as the error surface, where actual tool installation position error is introduced into the equation of virtual shaper cutter. Surface equations and 3-D models for the face gear and the worm wheel involving four kinds of tool installation errors are established. When compared, the face gear tooth surface machined in VERICUT software for simulation based on this new method and the one obtained based on real process(grinding face gear by using a theoretical worm wheel with actual position errors) are found to be coincident, which proves the validity and feasibility of this new method. By using mesh planning for the rotating projection plane of the face gear work tooth surface, the deviation values of the tooth surface and the difference surface are acquired, and the influence of four kinds of errors on the face gear tooth surface is analyzed. Accordingly, this work provides a theoretical reference for assembly craft of worm wheel, improvement of face gear machining accuracy and modification of error tooth surface.

Meshing Theoretical Study and Simulation on Cylindrical Tri-sine Oscillating Tooth Gear Drive

The structure of cylindrical tri-sine oscillating tooth gear drive is presented. Based on the space meshing theory, equations of meshing and tooth profile are established and its meshing theory is studied. Using Pro/E, this system is modeled and simulated,which is compared with the above-established equations.

Effect of gear teeth finishing method on properties of teeth surface layer and its resistance to pitting wear creation

This work presented the characteristics of two gear teeth finishing methods, due to the properties of gear teeth surface layer obtained at the tooth working depth. These methods are: 1) the teeth carburization, hardening to a hardness of HRC 60-62 and then grinding, 2) the soft gear shaving as the final mechanical treatment and then carburizing and hardening to the hardness of HRC60-62. This work included the test results of the contact fatigue strength carried out on the circulating power system. The Wohler curves were plotted due to the obtained results, as the basis for the practical evaluation of the considered gear finishing methods. The parameters like volume distribution of the voids, content of the retained austenite, compressive residual stress value, but also the results of contact fatigue strength tests, are more favorable for the teeth shaving method than for the teeth grinding method.

Flow Properties of Turbulent Fiber Suspensions in a Stock Pump Impeller

A numerical method for predicting fiber orientation is presented to explore the flow properties of turbulent fiber suspension flowing through a stock pump impeller. The Fokker-Planck equation is used to describe the distribution of fiber orientation. The effect of flow-fiber coupling is considered by modifying the constitutive mode.The three-dimensional orientation distribution function is formulated and the corresponding equations are solved in terms of second-order and fourth-order orientation tensors. The evolution of fiber orientation, flow velocity and pressure, additional shear stress and normal stress difference are presented. The results show that the evolutions of fiber orientation are different along different streamlines. The velocity and its gradient are large in the concave wall region, while they are very small in the convex wall region. The additional shear stress and normal stress difference are large in the inlet and concave wall regions, and moderate in the mid-region, while they are almost zero in most downstream regions. The non-equilibrium fiber orientation distribution is dominant at the inlet and the concave wall regions. The flow will consume more energy to overcome the additional shearing losses due to fibers at the inlet and the concave wall regions. The change of flow rates has effect on the distribution of additional shear stress and normal stress difference. The flow structure in the inlet and concave wall regions is essential in the resultant rheological properties of the fiber suspension through the stock pump impeller, which will directly affect the flow efficiency of the fiber suspension through the impeller.

Parental involvement and gender differences in the psychological profile of freshmen collegiate athletes

Background： The parent-to-child influences can be adaptive and contribute to the optimal psychological well-being and positive perception of the athlete. Contrary to the healthy parental involvement, a family can also have negative effects on an athlete development. The purpose of this study was to determine gender, father involvement, and mother involvement differences in the psychological profiles of collegiate freshmen athletes as measured by perfectionism, physical self-concept, and psychological well-being. Methods： Eighty-two male and 73 female collegiate freshmen responded to self-reported measures of family involvement, perfectionism, physical self-concept, and psychological well-being. Three separate 2 x 2 x 2 （gender x mother involvement x father involvement） factorial multivariate analysis of variance （MANOVAs） were carried out on the respective subscales from the reported measures. Results： There were significant differences for gender as well as father involvement in perfectionism （p 〈 0.01）. Freshmen females had lower concern over mistakes, and greater levels of organization as well as planfulness than males. Furthermore, freshmen athletes with high involved fathers showed greater levels of high standards for others as well as organization. Conclusion： Father involvement and mother involvement impact perfectionism, physical self-concept, and psychological well-being. perspective. extends through the freshmen year in college as shown in the athletes＇ Future research should develop better measures and utilize a family systems Copyright @ 2012, Shanghai University of Sport. Production and hosting by Elsevier B.V. All rights reserved

Method for Selecting the Optimal Solution for the Design of the Gear Train

Some researchers in mechanical engineering have developed systems for the design of gear transmission boxes, but almost no calculation methods exist for widespread synthesis. In this article, we outline methods for automatic determination of toothed helical gear trains and the selection criteria for the optimal choice of gear trains. In this work two methods were applied. As first design to use an expert system for the design and then optimize the design that is why we used Kappa PC and Catia for CAD.

Design of Model Following Variable Structure Controller for Three-axle Vehicle

An optimal control procedure is developed for the front and rear wheels of a three-axle vehicle moving on a complex typical road based on model following variable structure control strategy. The actual vehicle may be considered as an uncertain system. Cornering stiffness of front and rear wheels and external disturbances are varied in a limited range. The model-following variable structure control method is used to control both front and rear wheels steering operations of the vehicle, so that steering responses of the vehicle follow from those of the reference model. By numerical results obtained from computer simulation, it is demonstrated that the control system model can cope with the effects of parameter perturbations and outside disturbances.