Slow magnetic relaxation in a 3D dysprosium(III)-fluoro-oxalate framework containing zig-zag [Dy–F]n chains

Dysprosium complexes based on [F–Dy] or near-linear [F–Dy–F] unit are of great concern in the field of single-molecule magnets due to their large magnetic anisotropy. Here, the crystal structure and the magnetic relaxation dynamics were reported for a three-dimensional (3D) metal–organic framework (MOF): [DyF(C₂O₄)(H₂O)₂]_n·2nH₂O (1), which is the unique MOF containing zig-zag [Dy–F]_n chains. Magnetic susceptibility characterization reveals that 1 is one of the few 3D MOFs which show slow magnetic relaxation under zero dc field. And the effective energy barrier of 72 K for 1 is also higher than most Dy-based 3D MOFs. The diamagnetic ion dilution study shows that the ferromagnetic exchange couplings mainly transmitted by F^? bridges in 1 contribute little to the energy barrier, but effectively suppress the quantum tunneling process and result in a smooth hysteresis loop with no waist-restricted step.     

基于多层协议字典的通用化通信技术

针对靶场各试验区装备与装备间、装备与中心间以及靶场与外部系统间采用的接口标准与通信协议不规范、接口协议不一致的问题,研究设计基于多层软件设计架构的、底层隔离、功能通用的、可扩展的靶场试验信息互联通用软件,研究与之配套的多层次的通用数据传输规范协议字典技术和订阅发布重配置管理机制,使信息传输系统具有更大灵活性和扩展性,适用于所有格式传输规范的信息交换。     

新型纺织空调喷淋室的设计与应用

探讨新型纺织空调喷淋室的设计及应用效果.通过分析目前常用喷淋室的结构及缺陷,设计了新型纺织空调喷淋室.新型纺织空调喷淋室由两排至五排喷淋排管构成,并按照一定方式组合使用.通过喷淋室高密度水雾横喷、逆喷等方法,可以提高空气与水热湿交换效率及空气质量.以五排喷淋排管喷淋室为例对比说明:五排喷淋排管喷淋室能够实现冷却、加湿等多种功能,同时高效环保,是一种理想的纺织空调喷淋室.     

99.7 Per Cent Pure

The HEPA air filter is only capable of processing 99.7 per cent of airborne particles, leaving 0.3 per cent unaccounted for. Mason White describes the work of Canadian installation artist An Te Liu who made air-filtration appliances his main subject. Copyright © 2009 John Wiley & Sons, Ltd.     

快速换模技术在单机多工位模具中的应用

在单机多工位模具中,通过快速换模技术的运用,最大程度地缩短换模、模具维修、安装时间,有效提高了模具工作效率。本文主要介绍了快速换模结构设计及其工作过程。     

Effect of chromium poisoning on the electrochemical properties of NdBaCo2O5+δ cathode for IT-SOFCs

The effect of the Cr poisoning on the electrochemical properties of NdBaCo₂O_5+δ cathode for IT-SOFCs was investigated by the electrochemical impedance spectroscopy (EIS) and the cathodic polarization analysis. With the Cr poisoning, the area-specific resistances (ASRs) increased at 500–600 °C and did not increase with the increasing temperature. The Cr poisoning made a negative effect on the oxygen reduction reaction (ORR) below 600 °C. Besides, the Cr poisoning decreased the exchange current density i₀. The activation energies of i₀ were higher than those of the ASRs, indicating that the charge transfer process was the rate-determining step for the ORR. With or without the Cr poisoning, the polarization curves were independent of the on the sweep rate, indicating that there were no mass transport limitations on the ORR rate. Hence, the Cr poisoning deteriorated the charge transfer process of the ORR for NdBaCo₂O_5+δ and decreased the ORR activity.     

面向半分布式P2P系统的可靠节点交换机制

P2P系统中广泛使用的来源交换(PEX)技术为系统用户提供了丰富的节点资源,加快了节点交换速度,同时也带来了不可避免的安全隐患,恶意节点可以通过来源交换对正常节点的邻居列表进行污染。首先分析了现有来源交换技术存在的安全隐患,讨论了导致这些安全隐患的核心因素;其次,以来源交换的安全性分析为基础,提出了一种面向半分布式P2P系统的安全节点交换机制。该机制借鉴基于信任评估的激励技术,通过给出超级节点的信任评估方案,引入节点来源信任的概念,以节点的来源交换信任值为支撑,控制节点间的来源交换。最后,对提出机制进行了实验性能分析。实验结果表明,由于网络异构性所存在的信任值错误计算问题,所提出的交换机制虽然会导致约2.5%比例正常的节点交换失效,但可大幅度降低正常节点参与恶意节点传播和污染的情况,从而在总体上提升了P2P系统的可靠性。     

基于DXF的数控切割优化排序算法的研究与实现

采用Visual C++ 6.0开发平台实现了DXF文件读取的接口技术。针对图元排序问题,提出了一种优化排序算法,包括封闭图形的有序化处理、矢量化判断轮廓顺逆方向和包络矩形法结合基于射线法判断轮廓岛屿关系。针对全局路径优化问题,提出一种易于实现的相邻最短路径优化算法,通过实例证实了算法的有效性和实用性。该算法有效缩短了数控切割加工的辅助时间,提高了加工效率,并且能广泛应用于自动编程数控系统中。     

Surface characteristics and electrolysis efficiency of a Palladium-Nickel electrode

In view to finding a better electrode for water electrolysis-the hydrogen and oxygen evolution efficiencies of a Pd-80 at% Ni electrode along with its surface oxidation-reduction characteristics were investigated in alkaline medium using cyclic voltammetry. On cycling the electrode in between the potential range of ?1.0 to +0.65 V, two oxidation and two reduction transformations were observed. The origins of the transformations were found out. Most of the transformation peak potentials were found to be different than that of Pd and Ni electrodes. The generation of (PdNi)(III) species over the electrode surface identified to be the crucial for the oxygen evolution and continuous cycling up to 100 min succeeded to obtain its saturated layer. Tafel plots for both the hydrogen and oxygen evolution reactions (HER and OER) showed two regions. The kinetic parameters for the HER and OER, i.e., exchange current density at zero overpotential (i_o) and slope (b) values for both the low and high overpotential (η) regions were found out. For the HER, the i_o and b values are found to be 6.17 × 10^?2 and 4.36 mA/cm² and 137.0 and 343.9 mV/dec, respectively. For the OER, the values are 2.83 × 10^?3 and 2.35 mA/cm² and 72.8 and 215.1 mV/dec, respectively. On comparing these kinetic values with that available for Pd, Ni and Pd-50 at% Ni, it is realized that the investigated Pd-80 at% Ni electrode showed better electrolysis efficiencies than that of its component materials and Pd-50 at% Ni electrode.     

Electrochemical performance of La0.9Sr0.1Co0.8Ni0.2O3−δ-Ce0.8Sm0.2O1.9 composite cathode for solid oxide fuel cells

The mixed ionic and electronic conductors (MIEC) of La_0.9Sr_0.1Co_0.8Ni_0.2O_3−δ (LSCN)-Ce_0.8Sm_0.2O_1.9 (SDC) were investigated for potential application as a cathode material for solid oxide fuel cells (SOFCs) based on a SDC electrolyte. Electrochemical impedance spectroscopy (EIS) technique was performed over the temperature range of 600-850 °C to determine the cathode polarization resistance, which is represented by area specific resistance (ASR). This study systematically investigated the exchange current densities (i₀) for oxygen reduction reaction (ORR), determined from the EIS data and high-field cyclic voltammetry. The 70LSCN-30SDC composite cathode revealed a high exchange current density (i₀) value of 297.6 mA/cm² at 800 °C determined by high-field technique. This suggested that the triple phase boundary (TPB) may spread over more surface of this composite cathode and revealing a high catalytically active surface area. The activation energies (E_a) of ORR determined from the slope of Arrhenius plots for EIS and high-field techniques are 96.9 kJ mol⁻¹ and 90.4 kJ mol⁻¹, respectively.