Subregion graph: A path planning acceleration structure for characters with various motion types in very large environments

Modern computer graphics applications commonly feature very large virtual environments and diverse characters which perform different kinds of motions. To accelerate path planning in such a scenario, we propose the subregion graph data structure. It consists of subregions, which are clusters of locally connected waypoints inside a region, as well as subregion connectivities. We also present a fast algorithm to automatically generate a subregion graph from an enhanced waypoint graph map representation,which also supports various motion types and can be created from large virtual environments. Nevertheless,a subregion graph can be generated from any graphbased map representation. Our experiments show that a subregion graph is very compact relative to the input waypoint graph. By firstly planning a subregion path, and then limiting waypoint-level planning to this subregion path, over 8 times average speedup can be achieved, while average length ratios remain as low as102.5%.

Lie symmetry and Hojman conserved quantity of a Nielsen equation in a dynamical system of relative motion with Chetaev-type nonholonomic constraint

The Lie symmetry and Hojman conserved quantity of Nielsen equations in a dynamical system of relative motion with nonholonomic constraint of the Chetaev type are studied. The differential equations of motion of the Nielsen equation for the system, the definition and the criterion of Lie symmetry, and the expression of the Hojman conserved quantity deduced directly from the Lie symmetry for the system are obtained. An example is given to illustrate the application of the results.

Simulation method of near-fault pulse-type ground motion

The two characteristics of near-fault ground motions, i.e., the forward directivity effect and permanent displacement effect, result in long period and large velocity pulse in the velocity time history and large step pulse in the displacement time history. Considering the two effects, a simple expression of continuous function for equivalent velocity pulse time history is presented in this paper. The equivalent pulse model, in which the pulse period, peak velocity and pulse shape are described by five parameters, is highly advantageous to fit and simulate the pulse-type velocity time history. The equivalent pulse model comprises only one low-frequency component while the high-frequency component of a pulse-type earthquake record cannot be considered. Based on 28 records of 11 earthquakes, the pulse frequency of pulse-type records is generally less than 1 Hz. Therefore the low-frequency component and high-frequency component are simulated respectively and combined them together to generate a pulse-type ground motion.

Study on inelastic displacement ratio spectra for near-fault pulse-type ground motions

In displacement-based seismic design, inelastic displacement ratio spectra （IDRS） are particularly useful for estimating the maximum lateral inelastic displacement demand of a nonlinear SDOF system from the maximum elastic displacement demand of its counterpart linear elastic SDOF system. In this study, the characteristics of IDRS for near-fault pulse-type ground motions are investigated based on a great number of earthquake ground motions. The influence of site conditions, ratio of peak ground velocity （PGV） to peak ground acceleration （PGA）, the PGV, and the maximum incremental velocity （MIV） on IDRS are also evaluated. The results indicate that the effect of near-fault ground motions on IDRS are significant only at periods between 0.2 s - 1.5 s, where the amplification can approach 20%. The PGV/PGA ratio has the most significant influence on IDRS among the parameters considered. It is also found that site conditions only slightly affect the IDRS.

A LIMINF RESULT FOR HANSON-RUSSO TYPE INCREMENTS OF FRACTIONAL BROWNIAN MOTION

Let {X(t), t greater than or equal to 0} be a fractional Brownian motion of order 2 alpha with 0 < alpha < 1,beta > 0 be a real number, alpha(T) be a function of T and 0 < alpha(T), [GRAPHICS] (log T/alpha(T))/log T = r, (0 less than or equal to r less than or equal to infinity). In this paper, we proved that [GRAPHICS] where c(1), c(2) are two positive constants depending only on alpha,beta.

Lie symmetry and its generation of conserved quantity of Appell equation in a dynamical system of the relative motion with Chetaev-type nonholonomic constraints

Lie symmetry and conserved quantity deduced from Lie symmetry of Appell equations in a dynamical system of relative motion with Chetaev-type nonholonomic constraints are studied.The differential equations of motion of the Appell equation for the system,the definition and criterion of Lie symmetry,the condition and the expression of generalized Hojman conserved quantity deduced from Lie symmetry for the system are obtained.The condition and the expression of Hojman conserved quantity deduced from special Lie symmetry for the system under invariable time are further obtained.An example is given to illustrate the application of the results.

5MW全钢和钢-混凝土风力发电塔在不同地震作用下数值分析

为了探究多种风力发电结构在不同地震动类型作用下的抗震性能,利用ABAQUS软件建立了传统的5 MW风力发电结构和新型的钢-混凝土组合风力发电结构的三维有限元模型,采用非线性时程分析,研究并比较了它们在具有前方向性效应的近场脉冲地震动、具有滑冲效应的近场脉冲地震动、近场无脉冲地震动和远场地震动4条同源地震动作用下动力响应的差异。结果表明,风力发电结构受地震动类型的影响很大。此外,在相同地震作用下,不同的风力发电结构的地震响应差异很大。

MOTION VELOCITY SMOOTH LINK IN HIGH SPEED MACHINING

To deal with over-shooting and gouging in high speed machining, a novel approach for velocity smooth link is proposed. Considering discrete tool path, cubic spline curve fitting is used to find dangerous points, and according to spatial geometric properties of tool path and the kinematics theory, maximum optimal velocities at dangerous points are obtained. Based on method of velocity control characteristics stored in control system, a fast algorithm for velocity smooth link is analyzed and formulated. On-line implementation results show that the proposed approach makes velocity changing more smoothly compared with traditional velocity control methods and improves productivity greatly.

Emission spectrum of a harmonically trapped Λ-type three-level atom

We theoretically investigate the emission spectrum for a A-type three-level atom trapped in the node of a standing wave. We show that the atomic center-of-mass motion not only directly affects the peak number, peak position, and peak height in the atomic emission spectrum, but also influences the effects of the cavity field and the atomic initial state on atomic emission spectrum.

Vibrating-Sliding Motion of Caisson Breakwaters Under Various Breaking Wave Impact Forces

Sliding is one of the principal failure types of caisson breakwaters and is an essential content of stability examination in caisson breakwater design. Herein, the mass-spring-dashpot model of caisson-base system is used to simulate the vibrating-sliding motion of the caisson under various types of breaking wave impact forces, i.e., single peak impact force, double peak impact force, and shock-damping oscillation impact force. The effects of various breaking wave impacts and the sliding motion on the dynamic response behaviors of caisson breakwaters are investigated and the calculation of relevant system parameters is discussed. It is shown that the dynamic responses of the caisson are significantly different under different types of breaking wave impact forces even when the amplitudes of impact forces are equal. The amplitude of dynamic response of the caisson is lower under single peak impact excitation than that under double peak impact or shock-damping oscillation impact excitation. Though the displacement of the caisson is large due to sliding, the rotation, the sliding force and the overturning moment of the caisson are significantly reduced.

VIBRATING-UPLIFT ROCKING MOTION OF CAISSONBREAKWATERS UNDER VARIOUS BREAKINGWAVE IMPACT FORCES

Overturning is one of principal failure types of caisson breakwaters and is an essential content of stability examination in caisson breakwater design. The mass-spring-dashpot model of caisson-foundation system is used to simulate the vibrating-uplift rocking motion of caisson under various types of breaking wave impact forces, i.e., single peak impact force, double peak impact force, and shock-damping oscillation impact force. The effects of various breaking wave types and the uplift rocking motion on dynamic response behaviors of caisson breakwaters are investigated. It is shown that the dynamic responses of a caisson are significantly different under different types of breaking wave impact forces even when the amplitudes of impact forces are equal. Though the rotation of a caisson is larger due to the uplift rocking motion, the displacement, the sliding force and the overturning moment of the caisson are significantly reduced. It provides the theoretical base for the design idea that the uplift rocking motion of caisson is allowed in design.

面向MPEG Type-1视频编码器的UMHexagonS算法

针对Type-1视频编码平台中的帧间预测仅有全搜索算法,从而计算复杂度很高的问题,提出了改进的UMHexa-gonS快速搜索算法.该算法采用了UMHexagonS算法的框架,针对该算法在参考帧数目和编码模式受限的条件下,建立了一种起始位置运动矢量预测模型;同时,为了解决UMHexagonS算法中第2类提前截止阈值计算不准确而导致编码性能下降的问题,提出了利用空间相关性的阈值修正方式.在Type-1平台中的实验结果表明,该算法的搜索精度较高,并且能够较好地适应不同序列的纹理特性.相比于全搜索算法,平均节省97%以上的时间,同时编码效率下降控制在平均0.032 dB以内.得出结论:改进的算法能够提升编码效率,同时节省平均运动搜索时间.

近断层脉冲型地震动下调谐黏滞质量阻尼器减震结构易损性分析

选择典型脉冲型近断层地震动记录分别对一安装有调谐黏滞质量阻尼器(tuned viscous mass damper,TVMD)、黏滞阻尼器(viscous damper, VD)和无阻尼器的6层3跨钢框架结构进行增量动力分析,进而基于增量动力分析结果得到3种结构不同损伤状态的易损性曲线。易损性分析结果对比表明:随着惯容单元的引入,减震结构可靠性显著提升;相较于相同阻尼的VD,TVMD可以更有效地提升结构的抗震性能,减小结构在不同损伤状态下的失效概率。随着质量比的增加,TVMD减震结构在不同损伤状态下的失效概率减小,TVMD对结构性能状态的提升不会随非线性的增加而减小,且在结构经历弹性、弹塑性直至倒塌的整个过程中减震控制性能发挥稳定。进一步选取3组不同脉冲周期的近断层地震动记录对三种结构进行时程分析,讨论TVMD在不同脉冲周期近断层地震动下的减震控制效果。结果表明,在近断层脉冲型地震动作用下,TVMD并不都会实现阻尼单元“阻尼增效”,阻尼器的性能发挥与地震动的特性有关。相较于VD,当T_1/T_p≥2时,TVMD可以更好地减少结构能量输入但其能量耗散效率低于VD,不能实现“阻尼增效”;当T_1/T_p <2时,TVMD可以减小结构残余位移,具有更优的减少能量输入和增大能量耗散效率的双重效应,体现了惯容的“阻尼增效”。

机载水稻抛秧装置输送顶出机构优化设计及仿真

水稻抛秧具有效率高、秧苗损伤小等优势。基于此,设计一种连续型秧苗自动输送及顶出机构,对输送机构进行设计及受力分析,得到中间仿形架受力最大约为23.47 N,静力学分析得出仿形架最大应力为36 MPa,最大位移变形量为0.6 mm,最大应变为0.012。对钵体顶出及斜抛过程进行受力分析,计算出钵体质心到底面距离为9.71 mm,得出钵体脱盘时的最小翻滚角度与翻滚角速度、下落垂直距离的关系。对顶针进行参数优化,当顶针总长为50 mm,凸台长度为5 mm时,钵体顶出完整性较好。以顶针安装角、顶出力为试验因素,以钵体顶出后的二维空间位移为指标,进行ADAMS运动学仿真试验及正交试验,当仿真试验水平和竖直位移达到最小值时,顶针安装角为25°、顶出力为1.5 N;进行正交试验验证仿真结果,当试验因素水平一致时,水平和竖直位移达到最小值。通过分析得出安装角对指标影响极显著,顶出力对指标影响较显著。研究结果可为水稻抛秧装置设计和作业参数优化提供重要参考。

RENEWAL OF BASIC LAWS AND PRINCIPLES FOR POLAR CONTINUUM THEORIES(Ⅶ)—INCREMENTAL RATE TYPE

The purpose is to establish the rather complete equations of motion, boundary conditions and equation of energy rate of incremental rate type for micropolar continua. To this end the rather complete definitions for rates of deformation gradient and its inverse are made. The new relations between various stress and couple stress rate tensors are derived. Finally, the coupled equations of motion, boundary conditions and equation of energy rate of incremental rate type for continuum mechanics are obtained as a special case.

Interval Type-2 Fuzzy Logic Control of Mobile Robots

Navigation of autonomous mobile robots in dynamic and unknown environments needs to take into account different kinds of uncertainties. Type-1 fuzzy logic research has been largely used in the control of mobile robots. However, type-1 fuzzy control presents limitations in handling those uncertainties as it uses precise fuzzy sets. Indeed type-1 fuzzy sets cannot deal with linguistic and numerical uncertainties associated with either the mechanical aspect of robots, or with dynamic changing environment or with knowledge used in the phase of conception of a fuzzy system. Recently many researchers have applied type-2 fuzzy logic to improve performance. As control using type-2 fuzzy sets represents a new generation of fuzzy controllers in mobile robotic issue, it is interesting to present the performances that can offer type-2 fuzzy sets by regards to type-1 fuzzy sets. The paper presented deep and new comparisons between the two sides of fuzzy logic and demonstrated the great interest in controlling mobile robot using type-2 fuzzy logic. We deal with the design of new controllers for mobile robots using type-2 fuzzy logic in the navigation process in unknown and dynamic environments. The dynamicity of the environment is depicted by the presence of other dynamic robots. The performances of the proposed controllers are represented by both simulations and experimental results, and discussed over graphical paths and numerical analysis.

近断层脉冲型地震作用下大跨拱桥动力响应分析

为了研究近断层脉冲型地震动的速度脉冲特性和参数对大跨拱桥动力响应的影响规律,首先引入分解叠加(record-decomposition incorporation,RDI)法合成人工近断层脉冲型地震动,对比研究了不同等效脉冲模型的准确性,进而优化和验证了合成方法;然后以某大跨拱桥为工程背景,采用优化后的RDI方法合成了具有不同参数特征的人工近断层地震动,探讨了脉冲成分与残余分量对拱桥动力响应的影响机制;最后研究了不同脉冲参数对拱桥动力响应的影响规律。研究表明:优化后的RDI合成方法能有效模拟原始近断层脉冲型地震动,并得到具有不同脉冲参数的人工地震动;近断层地震记录的高频成分对拱桥结构动力响应具有显著的不利影响;随着脉冲幅值的增大,向前方向性效应和滑冲效应对拱桥动力响应的影响均明显增大;随着脉冲周期的增大,两种脉冲效应对拱桥动力响应均有显著的不利影响;对于脉冲个数的影响,双向脉冲的近断层地震动相比多向脉冲会引起拱桥更大的面内响应。

近断层地震动作用下土石坝加速度分布研究

近断层地震动较远场地震动具有频率高、速度快、能量更加集中的特点,在短时间内会释放大量能量,对工程结构具有严重危害。规范提供的加速度分布系数不适用于高度超过150 m的大坝,随着技术不断进步,我国超过150 m的土石坝越来越多,规范已不能满足现有需求。基于中国台湾集集近断层地震动记录,建立随机脉冲型地震动模型,分别对高度为40 m、70 m、150 m和200 m的土石坝进行随机动力分析,研究坝体的动态分布系数。结果表明,近断层地震动的低频速度脉冲使坝体的加速度反应谱有较宽的敏感段,易覆盖坝体自振周期,显著增加坝体的加速度。该研究通过总结近断层区域土石坝的加速度分布规律,建议了近断层脉冲型地震动区域的土石坝坝体动态分布系数,为近断层高地震风险情况下土石坝的抗震理论和方法提供参考。

高烈度区铁路简支梁桥双曲面球型减隔震支座的适应性

双曲面球型减隔震支座性能优异且在我国铁路桥梁中应用广泛,但其在不同结构参数、不同场地等应用场景下的适应条件及范围有待明确。为深入理解双曲面球型减隔震支座工作机理并揭示地震动特性、结构特性对减震效果的影响,本文以采用双曲面球型减隔震支座的原型桥梁为研究对象,构建了12个等墩高模型与9个不等墩高模型,系统研究各场地条件下不同结构参数(墩高、墩高差)及长周期地震动对减隔震简支梁桥地震响应的影响,明确不同特性下双曲面球型减隔震支座的适应条件及范围。结果表明:位于Ⅰ~Ⅲ类场地等墩高简支梁桥,桥墩纵向刚度应不小于339 kN/cm;存在墩高差时,相邻桥墩纵向刚度比应大于0.48。在远场长周期地震动作用下,桥墩纵向刚度应大于1641 kN/cm。

具有变/定转轴的一类分岔2Rv广义并联机构构型综合

现有大部分2R并联机构靠近定平台的第1个转轴方向矢量不变,靠近动平台的第2个转轴方向矢量只随着第1个转轴而变化,第2转轴相对于动平台不变。本文利用有限旋量理论,在具有变/定转轴分岔1Rv(Rv表示变转轴转动)并联机构基础上,提出一类具有变/定轴线的2Rv并联机构。分析了机构装配条件和驱动配置。此种分岔2Rv并联机构包含4种运动模式,即定-定转轴运动模式、定-变转轴运动模式、变-定转轴运动模式和变-变转轴运动模式。将传统的2条定转轴2R并联机构拓展为具有变/定转轴(变转轴和定转轴)的分岔2Rv广义并联机构。