Prediction of tread block forces for a free-rolling tyre in contact with a rough road

This paper describes a new approach to model the forces on a tread block for a free-rolling tyre in contact with a rough road. A theoretical analysis based on realistic tread mechanical properties and road roughness is presented, indicating partial contact between a tread block and a rough road. Hence an asperity-scale indentation model is developed using a semi-empirical formulation, taking into account both the rubber viscoelasticity and the tread block geometry. The model aims to capture the essential details of the contact at the simplest level, to make it suitable as part of a time-domain dynamic analysis of the coupled tyre-road system. The indentation model is found to have a good correlation with the finite element (FE) predictions and is validated against experimental results using a rolling contact rig. When coupled to a deformed tyre belt profile, the indentation model predicts normal and tangential force histories inside the tyre contact patch that show good agreement with FE predictions. © 2012 Elsevier B.V..

A Physical Interpretation of Stagnation Pressure and Enthalpy Changes in Unsteady Flow

This paper provides a physical interpretation of the mechanism of stagnation enthalpy and stagnation pressure changes in turbomachines due to unsteady flow, the agency for all work transfer between a turbomachine and an inviscid fluid. Examples are first given to illustrate the direct link between the time variation of static pressure seen by a given fluid particle and the rate of change of stagnation enthalpy for that particle. These include absolute stagnation temperature rises in turbine rotor tip leakage flow, wake transport through downstream blade rows, and effects of wake phasing on compressor work input. Fluid dynamic situations are then constructed to explain the effect of unsteadiness, including a physical interpretation of how stagnation pressure variations are created by temporal variations in static pressure; in this it is shown that the unsteady static pressure plays the role of a time-dependent body force potential. It is further shown that when the unsteadiness is due to a spatial nonuniformity translating at constant speed, as in a turbomachine, the unsteady pressure variation can be viewed as a local power input per unit mass from this body force to the fluid particle instantaneously at that point. © 2012 American Society of Mechanical Engineers.

并行计算模型参数动态分析软件包设计

并行计算模型的发展引入越来越多的模型参数。对并行计算模型参数动态采集分析软件包DEMPAT的整体框架进行研究,实现基于硬件性能计数器的存储层次参数采集模块。实验表明,该模块能够准确快速地获取存储层次参数且具有较好的可移植性。

黄土高原典型草原区草地土壤种子库的动态分析

采用野外调查取样和室内试验相结合的方法,研究了黄土高原典型草原区草地土壤种子库的物种组成、密度、时空格局和物种多样性等特征。结果表明,(1)土壤种子库中共统计到37个物种,隶属于16科,其中禾本科、菊科、唇形科、豆科和毛茛科的植物占优势。(2)从返青期到枯黄期,种子库中豆科、禾本科、堇菜科所占比例呈下降趋势,唇形科和菊科所占比例明显提高,种子库的密度也显著提高。(3)种子库中种子数量在垂直分布上呈现出由表层土壤向深层逐层减少的变化规律;在水平分布上的变化规律为:封禁>放牧;阴坡>阳坡;下坡>中坡>上坡。(4)封禁地土壤种子库中的Margalef丰富度和Shannon—Wienner指数都高于放牧地,Pielou均匀性指数低于放牧地。从返青期到枯黄期,封禁地和放牧地土壤种子库的Margalef丰富度、Shannon—Wienner指数、Pielou均匀性指数都呈下降趋势。

Speed of the internal pellet target in CSRm

Pellet target is one of the main candidate targets in CSRm (cooler storage ring’s main ring) for hadron physics studies. Pellet speed is an important physical parameter for the target. Larger pellet speed could shorten the interacting time interval between the pellet and the cyclotron beam, and thus results in a small temperature variation for the pellet. This could make the pellet facility work in a stable condition. A fluid dynamic simulation was carried out for the pellet speed, and it was found that the maximum speed for the target pellet may be restricted to about 100 m/s even if all working parameters were set to their optimal values.

Speed of the internal pellet target in CSRm

Pellet target is one of the main candidate targets in CSRm (cooler storage ring’s main ring) for hadron physics studies. Pellet speed is an important physical parameter for the target. Larger pellet speed could shorten the interacting time interval between the pellet and the cyclotron beam, and thus results in a small temperature variation for the pellet. This could make the pellet facility work in a stable con-dition. A fluid dynamic simulation was carried out for the pellet speed, and it was found that the maxi-mum speed for the target pellet may be restricted to about 100 m/s even if all working parameters were set to their optimal values.

兰州CSRm小丸内靶热力学和流体力学的研究

兰州CSRm内靶终端是进行强子物理实验的平台，可开展奇异介子产生和衰变的研究、重子谱的研究、多夸克态的研究及介子介质效应和手征对称破缺与恢复等多方面的研究。这些物理目标都需要内靶实验终端提供足够多的事件率，并能进行准确的径迹构建。在众多候选的内靶装置中，小丸靶具有其它内靶所欠缺的优点，如可以获得与外靶实验相比拟的实验亮度，可以配置4π立体角的探测器单元等。因此，小丸靶被确定为CSRm内靶实验终端中的主要内靶之一。小丸内靶（Pellet Internal Target）就是将氦以外的某种气体通过低温冷却而形成的固体微球。小丸内靶靶束与储存环离子束在反应室正交并发生相互作用，其反应事例被反应室周围环绕的探测器单元探测到并被记录下来。这篇论文对小丸内靶装置的结构进行了简要的介绍，并对小丸在反应室内的热力学行为进行了模拟。计算表明，靶丸速度是影响靶丸在反应区正常运行的重要因素之一。靶丸速度越大，靶丸在反应室内爆炸的可能性越小。通过对小丸的速度进行的流体动力学分析，发现即使对所有实验条件进行优化，小丸内靶的速度至多能达到100 m/s左右

GAS-PHASE SYNTHESIS OF DERIVATIVE OF C-60-C60S+

Gas phase ion-molecular reactions of C-60 with the ion system of CS2 have been studied in the ion source of mass spectrometer. It was found for the first time that the sulfuric derivative of C-60-C60S+ was the main ions in the ion source, they did not react with C-60 to form adduct ions due to their highly saturated structures. According to the dynamic analysis, the product ion came from the reaction of C-60 with the fragment ion S+. The adduct ion may have the structure of epsulfide that is advantageous in energy.

A simple and low-cost airlift photobioreactor for microalgal mass culture

A simple, low-cost, and efficient airlift photobioreactor for microalgal mass culture was designed and developed. The reactor was made of Plexiglas, and composed of three major parts: outer tube, draft tube and air duct. The fluid-dynamic characteristics of the airlift reactor were studied. The system proved to be well suited to the mass cultivation of a marine microalga, Chlorella sp. In batch culture, the biomass volumetric output rate of 0.21 g l(-1) d(-1) was obtained at the superficial gas velocity of 4 mm s(-1) in the draft tube.

Comparison of photobioreactors for cultivation of Undaria pinnatifida gametophytes

Undaria pinnatifida gametophytes were grown in 2.5 l bubble column and airlift reactor at 25 degreesC and light intensity of 40 mumol m(-2) s(-1) for 6 days. With aeration at 1 l min(-1), the airlift reactor yielded higher growth rate (0.12 mg DW ml(-1) d(-1)) than a bubble column (0.08 mg DW ml(-1) d(-1)). The advantages were related to the more homogeneous fluid dynamic characteristics of the airlift reactor.

Winter counter-wind currents off the southeastern China coast: A review

This review covers the discovery and studies of the year-round northeastward currents off the southeastern China coast, paying special attention to its upwind characteristic in winter, mainly focusing on work by Chinese oceanographers. This current system is a prominent and unique phenomenon in the shelf circulation of the world ocean. The general features of the current system are summarized. The evidence for the existence and the variation of the three parts of the currents-the South China Sea Warm Current, the Taiwan Strait Warm Current and the Taiwan Warm Current-are separately elucidated. The formation mechanisms of the current as a whole are explained using dynamic analysis and numerical simulation results. Some suggestions for further studies are also made.

有限元结构动力分析的广义特征值的神经计算

广义特征值问题是结构动力分析计算的关键之一.应用Reyle igh极小值原理,将神经网络的能量函数的极小点对应于广义特征值问题的最小特征值所对应的特征向量,在神经网络朝着能量函数极小点运动的同时得到了最小特征值所对应的特征向量的精确解答.从特征值的变分特性出发,给出了基于罚函数法的其他特征值的神经网络求解方案,从而在理论上给出了广义特征值问题的所有特征值的神经网络求解方法.仿真计算表明,该方法正确、有效可行.

可重构单体机器人动力学分析与控制

给出了可重构机器人在移动过程中的动力学模型,并提出了相应两种控制方法,即构形调整法和状态调整法。通过仿真试验得到,构形调整法能够在不影响状态的情况下,同时满足机器人运动稳定性和越障性的要求,增强了机器人运动的鲁棒性。

一种6自由度柔索并联机器人的动力学研究

采用串联约束 /并联驱动的原理 ,通过加入约束机构 ,设计一种新型柔索驱动并联机器人。然而由于约束机构的引入 ,机器人的动力学分析变得更为复杂。在对机器人进行运动学分析的基础上 ,利用牛顿 欧拉法建立机器人动力学方程。仿真结果证明了该方法的有效性

带式输送机停机动态过程的计算机仿真

研究了带式输送机停机过程的动态设计 ,通过分析提出了输送机停机过程的力学模型为两种 :第 1模型与启动过程的力学模型相同 ,第 2模型为具有固定端的振动模型·分析了制动力的传动机理 ;在综合各种停机方式的基础上给出了停机过程的分类 ,提出了控制速度停机、自由停机和制动停机的计算方式及其计算方法 ;开发了带式输送机动态分析软件BCD .2 0的停机计算部分 ;应用软件对停机过程进行仿真研究 ,对停机过程进行了分析 ;给出了停机过程的动态设计方法和拉紧装置行程的计算式 ;得出了不同的停机方式结束后输送带的张力分布是不同的结果·所提出的方法可用于大型带式输送机停机过程的合理设计 ,避免事故的发生