园林工程反季节栽植技术

作为市政建设的基础配套工程,园林绿化在城市建设中的地位越来越高。随着城市化进程的加快和社会的发展,反季节绿化出现并发展,打破了传统绿化的季节限制。结合反季节绿化的实际情况,分析了其施工过程中存在的难点和问题,并探讨了如何更好地利用反季节栽植技术及其注意事项。     

Integrated Game Based Guidance with Nonlinear Autopilot Design for Maneuvering Target Interception

The integrated game theory based guidance law with nonlinear autopilot (GGNA) system is presented in this paper. The guidance law is designed based on linear differential game theory while considering the motion of the target in 3‐D space such that the distance between the missile and the target is minimized faster than before. The autopilot system based on quaternion representation is developed using sliding mode control method to generate the attitude command. The stability of the integrated guidance and nonlinear autopilot system is analyzed with Lyapunov stability theory. In addition, this research assumes wingless missiles in our context in order to reduce the nonlinear effect from the aerodynamics. Furthermore, in order to extend the operation range of missiles from endo‐atmosphere to exo‐atmosphere, the missiles are equipped with Thrust Vector Control (TVC) mechanisms and Divert Control System (DCS). Finally, extensive simulations incorporating aerodynamic models are demonstrated to verify the validity of the proposed integrated guidance/autopilot systems. Moreover, the simulation results reveal that the mission of intercepting a maneuvering target is successfully accomplished.     

视线交互中两类扫视运动的人机工效评估研究

Fitts法则是人机交互领域预测人机工效的一个有效模型,在许多交互方式中都得到了验证,是传统人机工效研究的理论基础。然而在视线交互中,由于眼动肌肉神经控制机制与肢体运动不同,Fitts法则并不适用。近两年的相关研究提出了一个新的专门针对视线点击任务的难度指数IDeye,它比经典的Fitts指数更能准确预测视线交互的工效。然而,在新模型的有效性验证实验中并没有考虑两种典型的扫视运动(向心和离心运动)的差异。为此,在前期研究的基础上设计组织实验,验证了视线交互中离心和向心这两种眼球运动所带来的人机工效和稳定性的差异,并证实新的IDeye模型仍然能有效预测单纯的离心或向心扫视条件下的人机工效,是对视线交互工效研究的重要补充。     

幂律流体三维脉动流场数值模拟

利用ANSYS软件，模拟了振动诱导单螺杆挤出机熔体输送段中非牛顿幂律流体的三维脉动流场，得到了三维脉动流场的瞬时速度分布及螺槽中物料的流动轨迹。结果表明，在脉动流场作用下，非牛顿流体的瞬时速度响应与在驱动壁面上所施加的正弦形式的脉动驱动形式不同，横螺槽方向的环流中心位置受幂律指数影响，且发生周期性改变。振动的引入使得在相同的时间内，物料的流动路程增加，且可增大物料的平均停留时间，有利于改善混合效果。     

A note on pressure drop for the cross-flow of power-law liquids and air/power law liquid mixtures past a bundle of circular rods

The steady flow of non-Newtonian polymer solutions on their own and together with air transverse to a bundle of circular rods, has been studied experimentally. In particular, the frictional pressure drop has been measured as a function of non-Newtonian power-law constants, flow rates, voidage of bundles and the input fraction of air over wide ranges of conditions as: power-law flow behaviour index, 0.5 to 1; voidage values of 0.78 and 0.87-0.88; air velocity (superficial), 0.09 to 0.28 m/s and liquid velocity (superficial) 0.018 to 0.5 m/s. While the single phase flow results for power-law liquids are in excellent agreement with an existing equation, the two-phase pressure drop results are also in accordance with the form of the well-known Lockhart-Martinelli correlation. Based on these results, it is suggested that a value of 5-10 for the Reynolds number based on rod diameter marks the limit of the laminar flow in such systems.     

丁羟聚氨酯弹性体的老化规律研究

针对丁羟聚氨酯弹性体的老化及其对材料性能的影响,制备了丁羟弹性体胶片试样,对试样进行了加速老化试验,测试了不同老化阶段弹性体的密度、力学性能、交联密度及红外光谱.通过对测试结果的分析,指出了丁羟弹性体体系内部发生的化学反应及其对力学性能的影响,总结了丁羟弹性体的老化规律.研究发现在老化过程的前期,MAPO与TDI也发生了交联反应,使弹性体的交联密度有所增加,弹性体内的化学反应主要以降解断链为主,通过弹性体熵弹性的降低来影响其力学性能,该阶段弹性体的力学性能并不随交联密度而变化.在老化过程的后期,弹性体内部以氧化交联反应为主.     

美国对“国有企业私有化抵消补贴”的认定及我国的策略

美国商务部判断国有企业私有化抵消补贴方法经历了几次修改。1989年美国商务部认为国有企业独立交易实现的私有化将会消除过去得到的补贴;1991年美国商务部又得出相反的结论。1993年美国商务部推出了“三步法”,要求被申请人自行证明私有化过程中补贴利益的完全偿还,以证明补贴利益没有被传递。目前美国商务部运用的是“同一主体法”,即如果交易前后的实体为同一个实体,则补贴将会传递给新所有者,私有化之后的企业会获得补贴利益;反之,则不会获得补贴利益。我国的策略是坚持WTO主张的独立交易法进行认定。     

应变空间中一般加载规律的弹塑性本构关系

为了建立多维应力、应变空间的弹塑性本构关系,将一般加载规律一维全量理论的简单弹塑性模型推广到一般加载规律的多维增量理论,并且给出应力空间的加载函数和应变空间的加载函数以及它们之间的正确的变换关系.在此基础上,在应变空间中建立了推导一般加载规律的多维增量理论的本构关系的一种途径.应用这种途径,从应变空间的加载函数出发,推导了等向强化材料的一般加载规律的弹塑性本构关系.理论和实例表明,这种途径对等向强化材料、随动强化材料、理想弹塑性材料和热弹塑性问题都适用.     

A new model for evaluating the electrical conductivity of nonferrous slag

Electrical conductivity of molten slag is an important physicochemical property for designing the refining process in electric smelting furnaces.Though conductivities of many slag systems have been measured,the quantitative relationships of conductivity with slag composition and temperature are still very limited.In this article,the Arrhenius law was used to describe the experimental data of conductivities for CaO-MgO-Al2O3-SiO2,CaO-Al2O3-SiO2,CaO-MnO-Al2O3-SiO2,as well as CaO-MgO-MnO-Al2O3-SiO2 systems,and...     

Average cluster sizes and cluster size distributions of superfine nickel particles in light media

Effects of shear rates on average cluster sizes (ACSs) and cluster size distributions (CSDs) in uni- and bi-systems of partly charged superfine nickel particles were investigated by Brownian dynamics, and clustering properties in these systems were compared with those in non-polar systems. The results show that the ACSs in bi-polar systems are larger than those in the non-polar systems. In uni-polar systems the behavior of clustering property differs: at the lower ionic concentration (10%), repulsive force is not strong enough to break clusters, but may greatly weaken them. The clusters are eventually cracked into smaller ones only when concentration of uni-polar charged particles is large enough. In this work, the ionic concentration is 20%. The relationship between ACS and shear rates follows power law in a exponent range of 0.176–0.276. This range is in a good agreement with the range of experimental data, but it is biased towards the lower limit slightly. Foundation item: Projects(50474037, 50874087) supported by the National Natural Science Foundation of China; Project (BK2006078) supported by the Natural Scientific Funds of Jiangsu Province, China