直流微网孤岛运行状态电压稳定性分析

直流电压是直流电网运行中重要的状态变量。文章针对由多种微电源及就地负载组成的直流微电网系统,以之作为研究对象,利用阻抗比例判据判别直流微电网电压的稳定性。该方法通过将电源子系统的总输出阻抗对负载子系统的总输入阻抗的比值看作一个等效回路增益,再用 Nyquist稳定性判据分析系统的稳定性。仿真结果表明了直流微电网母线电压稳定性与各参数之间的关系。     

基于储能SOC状态的微电网能量优化调度策略研究

为了满足微电网能量调度要求,根据储能系统在不同运行模式下的功能定位,提出了一种基于储能SOC状态的微电网能量优化调度策略。在调度响应方面,利用该策略可实现微电网与配电网功率交换遵循调度计划,保证调度计划的有效性。在经济运行方面,利用该策略可实现公共连接点配电变压器的最佳运行,降低电力系统损耗。该策略充分考虑了电力公司通过改变用电电价鼓励用户参与需求侧管理的需求,结合实时电价调整储能SOC状态实现用电成本最低。利用该策略可实现微电网离网时稳定运行,提高可再生能源利用率,保证重要负荷的供电,防止蓄电池的过充及过放等。     

Ionothermal synthesis of a new cobalt metal-organic framework based on tetranuclear cobalt clusters

A new metal-organic network (EMIM)[Co₂(hip)₂(μ₃-OH)]·H₂O (1), (H₂hip = 5-hydroxyisophthalic acid and EMIM = 1-ethly-3-methylimidazolium), has been synthesized by the ionothermal reaction of cobalt nitrate, H₂hip and [EMIM]Br ionic liquid. Single-crystal X-ray diffraction analysis reveals that 1 exhibits a two-dimensional (2D) bilayer constructed from tetranuclear [Co₄(μ₃-OH)₂] building units and hip²⁻ linkers. There are square cavities with the dimension of 10.161 × 10.868 Å. The [EMIM]⁺ cations are located in the cavities, which have the hydrogen bonding interactions with the bilayer. Further more, the strong hydrogen bonds between the carboxylate and hydroxyl oxygen atoms of hip²⁻ ligands and lattice water molecules extend the 2D layer into a 3D supramolecular network. The magnetic properties of 1 have been investigated by variable-temperature magnetic susceptibility and magnetization measurements, and the results reveal that there exist antiferromagnetic interactions.     

飞秒强激光脉冲与氢团簇相互作用产生的最大质子能量与团簇尺寸的相关性

报道了飞秒强激光脉冲(60 fs,790 nm,2×1016W/cm2)与纳米尺寸的氢团簇(半径rc约为1~3 nm)相互作用,产生的最大质子能量Emax对于团簇半径rc相关性的实验研究结果。从激光-氢团簇相互作用产生的质子的飞行时间谱测量以及团簇尺寸的瑞利散射诊断结果,得到Emax与r2c成线性正比关系,比例系数为0.75,与报道的理论模拟结果一致,表明氢团簇发生纯库仑爆炸。实验结果同时提示,进一步的理论模拟应考虑气体喷流中团簇的尺寸分布。     

Overlay Design Mechanisms for Heterogeneous, Large-Scale, Dynamic P2P Systems

Large-scale, heterogeneous peer-to-peer (P2P) systems impose a set of diverse requirements. Current solutions do commonly only address a subset of these requirements since there are a number of trade-offs and constraints due to the different dimensions and aims they address. We present a novel approach for designing overlay networks for large-scale, highly dynamic, and heterogeneous P2P systems. A set of mechanisms is proposed to meet the complete set of requirements while keeping the trade-offs and constraints in balance. To handle effectively the large number of peers, they are clustered in manageable groups considering the requirements on their stability. The novelty in this approach is in the identification of the core services and operations of the aforementioned systems. On the basis of the requirements of those services and operations, peers are assigned the most suitable roles. Role relationships are further introduced to enable (and provide) incentives for the peers to adopt the most suitable roles while selecting an efficient overlay structure to preserve efficiency, robustness, and scalability. The proposed set of mechanisms is realized in Omicron, a novel hybrid P2P approach.     

Observation by TEM of spontaneous alloying in nanometre-sized atom clusters in the Au-Al system

Cluster-size dependence of alloying behaviour in nanometre-sized atom clusters has been studied by transmission electron microscopy, using clusters in the Au-Al system, which forms several intermetallic compounds in the phase diagram. In gold clusters of approximately 6–12 nm mean size, rapid dissolution of aluminium atoms took place and Au₂Al or AuAl₂ clusters were formed. When the size of gold clusters was increased to approximately 40 nm, no such rapid spontaneous alloying occurred. These observations suggest that there exists a critical size of initial gold clusters below which aluminide clusters are successfully formed by spontaneous alloying.     

Limits of chemical effects on cold fusion

Cold fusion enhanced by chemical confinement of deuterons has been suggested as an explanation of recent reports of the production of neutrons in electrochemically-generated palladium deuterides. To test this suggestion local-density-functional cluster calculations were used to study the coulomb barrier between two deuterons within the octahedral cage in crystalline palladium. The calculated repulsive forces were always greater than the corresponding forces between deuterons in molecular D₂. These results imply that the room temperature fusion rate at this site is negligible.