金属构件的损伤断裂与抗力衰减分析

现有的结构力学分析都假设结构为完好无损，然而结构在初始状态或使用过程中总存在各种损伤，而且损伤在使用过程中会不断积累和加剧。损伤不但缩短结构的使用寿命，而且引起结构力学性能下降。本文着重研究了具有宏观裂纹构件的强度和刚度随损伤发展的衰减规律；分析了平面应力、平面应变及弹塑性情况下带裂纹构件的强度衰减，提出了构件剩余抗力的计算方法；基于能量原理，推导了带裂纹构件的刚度；应用本文的方法分析了一个三杆结构，分析结果显示了裂纹引起的构件强度和刚度的变化对结构承载力和可靠度的显著影响。     

六相双Y移30°感应电机稳定性分析

以六相双Y移30°感应电机为对象,从建立电机数学模型入手,导出状态空间方程,应用特征值稳定判据分析多相感应电机的稳定性。该方法适合线性化的系统在稳定工作点附近微小振动的稳定性分析。针对电机定、转子参数和转动惯量的变化,对系统稳定性进行实例计算和分析。     

Tribological behavior of sialon ceramics sliding against steel lubricated by fluorine-containing oils

The friction and wear behavior of sialon ceramics sliding against steel and lubricated by perfluoropolyethers (PFPE), tetrakis (3-trifluoromethylphenoxy)-bis(4-fluoro-phenoxy)-cyclotriphosphazene (X-1P) and ionic liquid (1-methyl-3-octylimidazolium tetrafluoroborate, coded as L108) were investigated. It was found that the three fluorine-containing lubricants reduced friction coefficient and wear volume effectively. The effectiveness of the three lubricants in reducing wear volume could be ranked as L108>X-1P>PFPE. The antiwear films mainly consisting of organic oxyfluoride or carbonfluoride species and silicon fluoride are all observed for the three lubricants, while the degradation of PFPE during friction might account for the higher wear volume therewith. The lowest friction coefficient 0.065 was recorded for L108 under load of 0.5–400 N. This is dependent on the physically adsorbed ionic liquid on the rubbing surface and the formation of BN under the harsh conditions.     

锈蚀钢筋与混凝土间黏结性能试验

为研究锈蚀对钢筋与混凝土间黏结性能的影响,制作20个中心拉拔试件.通过电化学加速锈蚀得到理论锈蚀率为0%、0.5%、1%、2%、5%的拉拔试件,完成了不同锈蚀率下钢筋与混凝土的拉拔试验.从钢筋几何外形特征与混凝土强度在锈蚀过程中变化的角度分析了锈蚀率对极限黏结强度的影响,以割线刚度的方法定量研究了锈蚀率对黏结刚度的影响.阐述了锈胀裂纹、黏结刚度及试件破坏模式随锈蚀率变化的规律.试验结果表明:随着锈蚀率增大,钢筋与混凝土间的黏结强度、黏结刚度呈现先增大后减小趋势.黏结刚度的退化与锈胀裂纹的出现具有一定相关性.通过整理国内外学者黏结强度退化数据,得到了两段式黏结强度退化试验模型及一定程度上可供工程参考的黏结强度退化保守模型.最后,基于两段式黏结-滑移模型得到了不同锈蚀率下钢筋与混凝土间黏结-滑移本构模型.     

能量有效的频谱感知与接入策略联合优化算法

针对认知无线电网络中次用户节点能量受限问题,提出了一种联合考虑频谱感知和接入策略的能量有效优化算法。根据主用户非时隙接入信道可能与次用户发生碰撞的特点,基于连续时间马尔科夫理论对次用户的频谱感知和接入策略进行建模,在满足碰撞概率约束的条件下,通过合理设置次用户的感知时间和接入概率实现了感知性能与传输能效的有效折衷。仿真结果表明,相对于仅考虑感知时间或接入概率的传统优化算法,所提算法可使次用户的能量有效性得到显著提高。     

火灾后钢筋混凝土结构的抗震性能研究

本文在火灾后钢筋与混凝土应用－－应变关系试验结果的基础上，通过大量数值计算，给出了火灾后钢筋混凝土构件的截面弯矩－曲率恢复力骨架曲线特征参数的统计公式，为利用杆系模型进行火灾后钢筋混凝土结构的地震反应分析并进行抗震加固奠定了基础。     

篮球运动竞技参赛过程特征研究

采用文献资料法,专家调查法和数理统计法,解析篮球竞技参赛过程,分析篮球运动竞技参赛过程主要特征,以确定篮球项目竞技参赛过程的主要环节和重点要素。研究结果表明：篮球运动竞技参赛过程中,参赛方案制订、比赛技能应用、训练条件保障、参赛准备总结、比赛名次评价、掌控局势能力、比赛体能分配、阵容配备能力、特定战术演练和参赛控制总结等要素权重依次排序前十位,是篮球运动竞技参赛过程的重点要素。     

A novel tuned heave plate system for heave motion suppression and energy harvesting on semi-submersible platforms

Deepwater offshore structures such as semi-submersible platforms suffer powerful ocean waves due to their location and site condition. The long distance away from the shore also brings many difficulties to energy supply for the platform operation. How to reduce the response of the platform and convert the wave energy into electrical power is a meaningful topic. In this paper, a tuned heave plate system (THP) is presented and designed to be employed on a semi-submersible platform for heave motion suppression and energy harvesting. This THP system is composed of spring supports, a power take-off system (PTO), and a heave plate. The PTO system is a permanent magnet linear generator (PMLG), which could directly convert the kinetic energy of the heave plate into electronic power. The stiffness of the spring supports is designed based on the principle of the tuned mass damper (TMD). The numerical model of the platform and the THP system is established according to the hydrodynamic analysis results of the platform. The model is tested and modified by scale model tests on the platform in the wave tank. A parameter study, including the size, tuned period, and damping ratio of the THP system, is conducted systematically based on the numerical model. The optimal parameters of the THP are selected due to the maximum heave motion reduction under severe wave conditions in South China Sea. The performance of the semi-submersible with and without the THP system under different wave conditions is analyzed. It is demonstrated that this novel tuned heave plate system could reduce the heave motion of the semi-submersible platform significantly and generate considerable power, which makes the THP system have a broad prospect for development.     

Pressure distributions on prism-shaped buildings in experimentally simulated downburst

Wind loading is one of the most significant factors in civil engineering that influences the structural design considerably.In this paper,a group of manufacturing equipments for downburst simulation based on impinging jet model was developed for investigating the wind loads on structures:including the centrifugal air bellows to generate airflow,a movable platform to realize multiple locations of the building and a freely rotatable turntable to implement alterable building angles.Hundreds of transducers were used to measure the wind action on all surfaces of the building.The pressure coefficients calculated from the observed data were utilized to evaluate the downburst wind load.Pressure distributions on three prism-shaped building models with different placements and angles were investigated to obtain the maximum wind action and mean pressure coefficients.The results showed that the maximum pressure coefficient would reach 1.0 on the top surface if the downburst just broke out over the edifice.Considering that the building was in the developing field of the downburst,the top and the front surfaces would be under high wind pressure and only the back surface would endure wind suction.When the downdraft happens away from the prismatic building,all surfaces,except the front surface,would subject to suction with different degrees.It was also found that the pressure coefficient on the right surface would get its negative peak at first and then go straight up to 0.6 as the angle changed from 0°to 45°and the wind pressure on the front surface would decrease slightly through the whole process.The assertive results provide elemental data for structural wind-resistant design in civil engineering for the downburst-prone areas.     

中山电网10kV线路合环转供电操作原则研究

10 kV线路合环转供电可提高供电的延续性,但由于线路的负荷、合环开关两侧存在电压差、相角差等原因,合环时产生的环流容易导致操作失败。在仿真软件计算的基础上,结合实际的操作经验,总结出中山电网10 kV线路合环转供电的操作原则,对降低合环操作的电网风险和提高供电可靠性具有重要意义。