流动粉浆输送装置的研究

为减轻环卫工和建筑工人劳动强度和提高工作效率,在已有螺旋输送机的工作原理基础上,进行创新。将螺旋片由刚性连接改为柔性连接,将硬管改为软管。经过试验,在选择了一定的工艺参数后,使刚性的螺旋片和柔性的胶管之间,有较好的配合效果,从而实现了螺旋输送机械,可以在输送管道有一定弯曲的条件下,运送砂浆的功能。该研究有一定的实用价值和社会意义。加工制造工艺不复杂,有利于普及。     

航天器调度中的资源约束推理方法

资源水平边界的估计是构建资源利用可行计划中的一个基础问题。通过分析航天器资源约束的共享与分离并存、累积与瞬时消耗并存、过度订阅与区间调度并存等特点,提出了资源时间网络、时间约束网络和约束网络相结合的资源约束描述方法;构建了增量式基于包络的资源约束算法和最早开始时间链展开资源约束算法,以快速获取资源一致的柔性解。实例证明,该方法较好地解决了航天器调度的资源约束推理问题。     

Phenomenological modelling of flow behaviour of 20MnMoNi55 reactor pressure vessel steel at cryogenic temperature with different strain rates

In the present study a phenomenological constitutive model is developed to describe the flow behaviour of 20MnMoNi55 low carbon reactor pressure vessel (RPV) steel at sub-zero temperature under different strain rates. A set of uniaxial tensile tests is done with the variation of strain rates and temperature ranging from 10⁻⁴ s⁻¹ to 10⁻¹ s⁻¹ and -80 °C to −140 °C respectively. From the experimental data, family of flow curves at different temperatures and strain rates are generated and fitted exponentially. The strain rate and temperature dependence of the coefficients of the exponential flow curves are extracted from these curves and characterised through a general phenomenological constitutive coupled equation. The coefficients of this coupled equation are optimised using genetic algorithm. Finite element simulation of tensile tests at different strain rates and temperatures are done using this coupled equation in material model of Abaqus FEA software and validated with experimental results. The novelties of proposed model are: (a) it can predict precisely the flow behaviour of tensile tests (b) it is a simple form of equation where fitting parameters are both function of strain rate ratio and temperature ratio, (c) it has ability to characterize flow behaviour with decreasing subzero temperatures and increasing strain rates.     

van der Pol 振子在负反馈作用下的动力性态分析

本文从非线性振动理论和反馈控制论的角度研究了ｖａｎｄｅｒＰｏｌ振子在负反馈作用下的动力性态,用中心流形法和形式级数法分析了ｖａｎｄｅｒＰｏｌ振子的局部稳定性和Ｈｏｐｆ分叉行为,用Ｒｕｎｇｅ─Ｋｕｔｔａ法给出了仿真结果。     

Low velocity impact studies of E-glass/epoxy composite laminates at different thicknesses and temperatures

Low velocity impact experiments were carried out on E-glass/epoxy composite laminates having varying thicknesses at sub zero and elevated temperatures using hemi spherical steel impactor of 16 mm diameter with impact energies in the rage of 50–150 J. The performance of the laminates was assessed in terms of energy absorption, maximum displacement, peak force and failure behaviour. Results indicated that the effect of temperature on energy absorption of the laminate is negligible although the laminates are embrittling at sub zero temperatures. However it has influence on failure behaviour and displacement. Peak force has increased linearly with increase in laminate thickness from 5 to 10 mm. However it got reduced by 25% when temperature was increased from −20 °C to 100 °C. Based on experimental results, laminate perforation energies were predicted using curve fitting equations. Statistical analysis was carried out using Taguchi method to identify the global effects of various parameters on laminate performance and confirmed that the laminate thickness has significant influence as compared to temperature, for the studied range.     

Effect of projectile parameters on opening behavior of PELE penetrating RC target

When a penetrator with enhanced lateral effect (PELE) impacts on a reinforced concrete (RC) target, the target is damaged with a large opening. An understanding of how PELE projectile parameters affect the opening dimension, is essential for effective design of the PELE projectile. In this study, under the condition that the impact velocity and target parameters (strength and thickness) were fixed values, the important influence factors of the PELE (jacket wall thickness B, jacket material strength Y1, filling material strength Y2 and angle of monolithic jacketθ) were determined by a dimensional analysis. Tests and simulations of the PELE penetrating the RC target were conducted to analyze the influence of these factors on opening diameter ((D), an equivalent diameter under relative kinetic energy). Based on the test and simulation results, it is found that the influence of these factors B, Y1 andθon the deformation mode of the jacket shows a similar trend:as values of the three factors decrease, the jacket deforms from small bending deformation to large one, and then to curling deformation. This causes the opening diameter to first increase with the decrease of these three factors, and then decreases. It is well known that the bending resistance of the jacket is related to these factors B, Y1 andθ. Therefore, a plastic limit bending moment (M0) of the jacket was quoted to characterize the influence of these factors on the bending deformation of the jacket and the opening diameter of the target. The influence factor Y2 causes (D) to first increase with the increase of Y2, and then decreases. A formula was developed to predict the opening diameter, whose influence parameters were considered in a dimensionless way. It has been shown that the dimensionless opening diameter (D)/d1 is dependent on two dimensionless parameters Q = (d31fc/M0) and G = (fc/Y2), where d1 and fc are the outer diameter of the projectile and the compressive strength of the target, respectively.     

Firm embedding behavior of annular grooved projectiles impacting ductile metal targets

Annular grooved projectiles (AGPs) have drawn ongoing concerns as an advanced penetrator for their excellent anti-rebound capability in impacting metal plates. They could become embedded solidly in the target surface during low-velocity impact. In this investigation, the firm embedding behavior of AGP was observed by impact experiments. Corresponding numerical simulations provided a better understanding of this process. Experimental and numerical results indicated that the firm embedding behavior of AGP was mainly due to the filling-material in the groove rather than the friction between the projectile and target, unlike traditional shape such as conical projectile. According to observation, firm embedding process can generally be subdivided into four stages: initial-cratering stage, groove-filling stage, filling-material failure stage and rebound vibration stage. Moreover, the damage mechanics of target material around crater was obtained through microscopic tests. A comparison of the cross-sectional figures between the experiment and simulation proved that the analysis and the proposed method were reasonable and feasible, which further demonstrated that the firm embedding behavior has application potential in new concept warheads.     

氯酸钾对不锈钢在硫酸和盐酸混合溶液中的缓蚀行为

研究了缓蚀剂ＫＣｌＯ３在７０％Ｈ２ＳＯ４和０．２％ＨＣｌ溶液中对１８—８不锈钢的缓蚀行为。运用线性极化技术测定了缓蚀剂的缓蚀效率为９６％。动电位极化曲线、循环极化曲线及交流阻抗的测量表明,缓蚀剂ＫＣｌＯ３是一种阳极钝化型缓蚀剂,添加缓蚀剂ＫＣｌＯ３后,不锈钢表面氧化膜进一步加强,从而有效地抑制不锈钢的均匀腐蚀和孔蚀。     

An Exploratory Study of the Decision to Refrain from Killing in the Accounts of Military and Police Personnel

Although previous studies have examined killing as an outcome-oriented measure, few have explored non-killing as a socially organized process. Using letters written by soldiers, police officers, and security professionals found in the magazine Soldier of Fortune, this study examines cases in which they refrain from killing their opponents. Our results indicate that refrained killings by these actors are socially organized in ways that are shaped by situational, environmental, technological, administrative, and moral factors. In addition, it was found that when police officers and soldiers realized the humanity of their opponents, they employed alternative methods to subdue or control without using lethal force, despite situational and legal justifications for doing so. Implications for the sociology, psychology, and ethics of killing – or not killing – are discussed.     

基于MPI+CUDA的异构并行可压缩流求解器

在CPU/GPU异构体系结构计算集群上,建立了基于MPI+CUDA的异构并行可压缩流求解器。讨论了异构结构上的可压缩流并行算法的并行模式,在CPU上执行计算密集度低、指令复杂的计算任务,在GPU上执行计算密集度高、指令单一的计算任务。通过数个算例,对比了异构并行计算和传统CPU并行计算计算结果和计算效率。将该算法运用于高超声速流动的数值模拟中,数值结果显示,基于MPI+CUDA的异构并行可压缩流求解器鲁棒性好,计算效率较CPU同构并行计算提高10倍以上。