A kind of new idea based on electromagnetic theory is presented, and it is used in research of the shaping law of electrochemical perforation with fixed cathode. The changing laws of the electric field vectors at cert...A kind of new idea based on electromagnetic theory is presented, and it is used in research of the shaping law of electrochemical perforation with fixed cathode. The changing laws of the electric field vectors at certain point on the surface of the anode workpiece with machining time, such as the electric field intensity E , the current density j and so on, are introduced. The mathematical model of the perforating velocity is presented, moreover, the experimental result to verify it is given at the end of the paper.展开更多
A new type of explosive ink formulation that can be quickly cured was prepared with unsaturated polyester as binder,styrene as active monomer,2,4,6-trimethylbenzoyl-diphenylphosphine oxide as photoinitiator,and hexani...A new type of explosive ink formulation that can be quickly cured was prepared with unsaturated polyester as binder,styrene as active monomer,2,4,6-trimethylbenzoyl-diphenylphosphine oxide as photoinitiator,and hexanitrohexaazaisowurtzitane(CL-20)as the main explosive.Then the explosive inkdirect writing technology was used to charge the micro-sized energetic devices,the curing mechanism of the explosive ink was discussed,and the microstructure,safety performance and explosive transfer performance of the explosive ink molded samples were tested and analyzed.Results indicate that the composite material has a fast curing molding speed,its hardness can reach 2H within 8 min.The crystal form of CL-20 in the molded sample is still type.The CL-20 based UV-curing explosive ink formulation has good compatibility,its apparent activation energy is increased by about 3.5 kj/mol.The composite presents a significant reduction in impact sensitivity and its characteristic drop height can reach 39.8 cm,whichis about 3 times higher than the raw material.When the line width of charge is 1.0 mm,the critical thickness of the explosion can reach 0.015 mm,and the explosion velocity is 7129 m/s when the charge density is 1.612 g/cm^(3).展开更多
Recently, virtualization has become more and more important in the cloud computing to support efficient flexible resource provisioning. However, performance interference among virtual machines(VMs) has become a challe...Recently, virtualization has become more and more important in the cloud computing to support efficient flexible resource provisioning. However, performance interference among virtual machines(VMs) has become a challenge which may affect the effectiveness of resource provisioning. In a virtual cluster which runs the Map Reduce applications, the performance interference can also affect the performance of the Map and Reduce tasks and thus cause a performance degradation of the Map Reduce job. Accordingly, this paper presents a Map Reduce scheduling framework to mitigate this performance degradation caused by the performance interference. The framework includes a performance interference prediction module and an interference aware scheduling algorithm. To verify its effectiveness, we have done a set of experiments on a 24-node virtual Map Reduce cluster. The experiments illustrate that the proposed framework can achieve a performance improvement in the virtualized environment compared with other Map Reduce schedulers.展开更多
ZA27 alloy has the best performance and the widest applications in high aluminum zinc based die casting alloy series. One of its main applica-tions is used as abrasion resistant alloy,instead of nonferrous alloys such...ZA27 alloy has the best performance and the widest applications in high aluminum zinc based die casting alloy series. One of its main applica-tions is used as abrasion resistant alloy,instead of nonferrous alloys such as copper alloy.The frictional wear p展开更多
虚拟同步发电机(virtual synchronous generator,VSG)在引入同步机二阶转子运动方程,增大电力系统等效惯量的同时,也引入了同步发电机的振荡特性,有功低频振荡等动态稳定性问题也随之而来。引入调速侧电力系统稳定器(governor power sys...虚拟同步发电机(virtual synchronous generator,VSG)在引入同步机二阶转子运动方程,增大电力系统等效惯量的同时,也引入了同步发电机的振荡特性,有功低频振荡等动态稳定性问题也随之而来。引入调速侧电力系统稳定器(governor power system stabilizer,GPSS)能有效抑制VSG的功率低频振荡,但其在超调量及调节时间方面的控制效果仍有待提高。通过建立VSG的小信号模型从极点配置角度分析其稳定性,揭示基于GPSS的VSG控制策略在功率动态响应上存在较高超调和较长调节时间的原因。基于此,参考GPSS控制思想,提出了一种基于超前滞后环节附加前馈阻尼补偿的虚拟同步发电机控制策略。并从理论上分析验证了所提控制策略在不影响系统稳态特性的前提下,能够提供调整自由度更高的正阻尼,在有效地抑制功率超调的同时提高了系统的调节速度,从而更好地抑制了有功功率的低频振荡。最后通过MATLAB/Simulink进行对比仿真,仿真结果与理论分析结果一致,证明了所提控制策略的正确性和有效性。展开更多
为推动钢渣在道路工程中的应用,缓解钢渣堆放造成的土地占用与环境污染问题,对钢渣陈化过程中的理化特征及钢渣沥青混合料性能进行了研究。采用粒度粒形、X射线荧光光谱试验探究钢渣陈化前后的形貌特征和矿物组成。随后,利用未处理钢渣...为推动钢渣在道路工程中的应用,缓解钢渣堆放造成的土地占用与环境污染问题,对钢渣陈化过程中的理化特征及钢渣沥青混合料性能进行了研究。采用粒度粒形、X射线荧光光谱试验探究钢渣陈化前后的形貌特征和矿物组成。随后,利用未处理钢渣、陈化钢渣和玄武岩制备了沥青混合料,对比评价了3种沥青混合料的体积膨胀性、水稳定性、高温稳定性和低温抗裂性能。此外,通过灰色关联法分析了集料特性与混合料性能的关联性。结果表明,钢渣的高粗糙度、高棱角性使其成为玄武岩等天然集料的理想替代品。然而,未陈化钢渣体积稳定性差,遇水易膨胀,导致无法满足路面使用要求。值得注意的是,CaO和Fe 2 O 3含量是影响钢渣体积稳定性的重要因素,而陈化处理可以在一定程度上降低这些负面影响,从而改善钢渣沥青混合料的路用性能。综合各项分析,陈化钢渣沥青混合料具有较好综合路用性能,钢渣的二次利用对于实现道路基础设施的可持续发展具有重要意义。展开更多
文摘A kind of new idea based on electromagnetic theory is presented, and it is used in research of the shaping law of electrochemical perforation with fixed cathode. The changing laws of the electric field vectors at certain point on the surface of the anode workpiece with machining time, such as the electric field intensity E , the current density j and so on, are introduced. The mathematical model of the perforating velocity is presented, moreover, the experimental result to verify it is given at the end of the paper.
基金Equipment Development Department of China(61406190401).
文摘A new type of explosive ink formulation that can be quickly cured was prepared with unsaturated polyester as binder,styrene as active monomer,2,4,6-trimethylbenzoyl-diphenylphosphine oxide as photoinitiator,and hexanitrohexaazaisowurtzitane(CL-20)as the main explosive.Then the explosive inkdirect writing technology was used to charge the micro-sized energetic devices,the curing mechanism of the explosive ink was discussed,and the microstructure,safety performance and explosive transfer performance of the explosive ink molded samples were tested and analyzed.Results indicate that the composite material has a fast curing molding speed,its hardness can reach 2H within 8 min.The crystal form of CL-20 in the molded sample is still type.The CL-20 based UV-curing explosive ink formulation has good compatibility,its apparent activation energy is increased by about 3.5 kj/mol.The composite presents a significant reduction in impact sensitivity and its characteristic drop height can reach 39.8 cm,whichis about 3 times higher than the raw material.When the line width of charge is 1.0 mm,the critical thickness of the explosion can reach 0.015 mm,and the explosion velocity is 7129 m/s when the charge density is 1.612 g/cm^(3).
基金supported in part by the National Key Technology R&D Program of the Ministry of Science and Technology (2015BAH09F02, 2015BAH47F03)National Natural Science Foundation of China(60903008,61073062)the Fundamental Research Funds for the Central Universities(N130417002, N130404011)
文摘Recently, virtualization has become more and more important in the cloud computing to support efficient flexible resource provisioning. However, performance interference among virtual machines(VMs) has become a challenge which may affect the effectiveness of resource provisioning. In a virtual cluster which runs the Map Reduce applications, the performance interference can also affect the performance of the Map and Reduce tasks and thus cause a performance degradation of the Map Reduce job. Accordingly, this paper presents a Map Reduce scheduling framework to mitigate this performance degradation caused by the performance interference. The framework includes a performance interference prediction module and an interference aware scheduling algorithm. To verify its effectiveness, we have done a set of experiments on a 24-node virtual Map Reduce cluster. The experiments illustrate that the proposed framework can achieve a performance improvement in the virtualized environment compared with other Map Reduce schedulers.
文摘ZA27 alloy has the best performance and the widest applications in high aluminum zinc based die casting alloy series. One of its main applica-tions is used as abrasion resistant alloy,instead of nonferrous alloys such as copper alloy.The frictional wear p
文摘虚拟同步发电机(virtual synchronous generator,VSG)在引入同步机二阶转子运动方程,增大电力系统等效惯量的同时,也引入了同步发电机的振荡特性,有功低频振荡等动态稳定性问题也随之而来。引入调速侧电力系统稳定器(governor power system stabilizer,GPSS)能有效抑制VSG的功率低频振荡,但其在超调量及调节时间方面的控制效果仍有待提高。通过建立VSG的小信号模型从极点配置角度分析其稳定性,揭示基于GPSS的VSG控制策略在功率动态响应上存在较高超调和较长调节时间的原因。基于此,参考GPSS控制思想,提出了一种基于超前滞后环节附加前馈阻尼补偿的虚拟同步发电机控制策略。并从理论上分析验证了所提控制策略在不影响系统稳态特性的前提下,能够提供调整自由度更高的正阻尼,在有效地抑制功率超调的同时提高了系统的调节速度,从而更好地抑制了有功功率的低频振荡。最后通过MATLAB/Simulink进行对比仿真,仿真结果与理论分析结果一致,证明了所提控制策略的正确性和有效性。
文摘为推动钢渣在道路工程中的应用,缓解钢渣堆放造成的土地占用与环境污染问题,对钢渣陈化过程中的理化特征及钢渣沥青混合料性能进行了研究。采用粒度粒形、X射线荧光光谱试验探究钢渣陈化前后的形貌特征和矿物组成。随后,利用未处理钢渣、陈化钢渣和玄武岩制备了沥青混合料,对比评价了3种沥青混合料的体积膨胀性、水稳定性、高温稳定性和低温抗裂性能。此外,通过灰色关联法分析了集料特性与混合料性能的关联性。结果表明,钢渣的高粗糙度、高棱角性使其成为玄武岩等天然集料的理想替代品。然而,未陈化钢渣体积稳定性差,遇水易膨胀,导致无法满足路面使用要求。值得注意的是,CaO和Fe 2 O 3含量是影响钢渣体积稳定性的重要因素,而陈化处理可以在一定程度上降低这些负面影响,从而改善钢渣沥青混合料的路用性能。综合各项分析,陈化钢渣沥青混合料具有较好综合路用性能,钢渣的二次利用对于实现道路基础设施的可持续发展具有重要意义。
