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.     

Sulphonated Tetramethyl Poly(ether ether ketone)/Epoxy/Sulphonated Phenol Novolac Semi‐IPN Membranes for Direct Methanol Fuel Cells

The sulphonated phenol novolac (PNBS) which was used as a curing agent of epoxy was synthesised from phenol novolac (PN) and 1, 4‐butane sultone and confirmed by FTIR and ¹H NMR. The degree of sulphonation (DS) in PNBS was calculated by ¹H NMR. The semi‐IPN membranes composed of sulphonated tetramethyl poly(ether ether ketone) (STMPEEK) (the value of ion exchange capacity is 2.01 meq g^–1), epoxy (TMBP) and PNBS were successfully prepared. The semi‐IPN membranes showed high thermal properties which were measured by differential scanning calorimeter (DSC) and thermogravimetric analyses (TGA). With the introduction of the cross‐linked TMBP/PNBS, the mechanical properties, dimensional stability, methanol resistance and oxidative stability of the membranes were improved in comparison to the pristine STMPEEK membrane. Although the proton conductivities of the semi‐IPN membranes were lower than those of the pristine STMPEEK membrane, the higher selectivity defined as the ratio of the proton conductivity to methanol permeability was obtained from the STMPEEK/TMBP/PNBS‐14 semi‐IPN membrane. The results indicated that the semi‐IPN membranes could be promising candidates for usage as proton exchange membranes in direct methanol fuel cells (DMFCs).     

3.5-Year tritium aging effect on isotopic exchange at constant flow rate between gaseous hydrogen and palladium deuteride

Isotopic exchange experiments were performed between gaseous hydrogen flows with constant rate through packed-powder beds of 0-year and 3.5-year tritium aged palladium deuteride. X-ray diffraction (XRD) indicated that the crystal lattice of palladium swelled due to the decayed ³He which existed in the interstitial void of 3.5-year tritium aged palladium. The effluent curves of isotopic exchange reaction were simulated by plate theory of chromatography separation, and the reasons which influenced isotopic exchange performance were analyzed by rate theory of chromatography separation. After 3.5-year tritium aged, the isotopic exchange effluent curve went smooth, and the isotopic exchange efficiency declined. The results of isotopic exchange experiments accorded well with the theory simulated results. After exchange temperature raised, isotopic exchange performance of 3.5-year aged palladium increased, moreover, isotopic exchange performance of 3.5-year aged palladium was sensitive to temperature change.     

以实为屏，以园为心——河南省老干部活动中心建筑方案设计

如今我们的社会在迅速向老龄化发展。老吾老以及人之老,遵循老年人的行为特点,结合基地具体情况、设计服务于老年人的建筑空间是一项重要课题。文章结合河南省老干部活动中心的设计分析,围绕建构中原之园、意趣之园、和谐之园的理念,讨论了适宜老年人交流需求的空间组织方式。     

Magnetic characterization of MnPt/CoFe bilayers using the MOKE technique

The performance of magnetoresistive devices (spin valves, tunnel junctions), made of two ferromagnetic (FM) layers and separated by a non-magnetic spacer, rely on the existence of two well separated resistance states. For this to occur, one of the FM layer is deposited just adjacent to an antiferromagnetic (AFM) layer. Due to the exchange interaction at the AFM/FM interface, the reversal of the magnetization (M) of such FM-pinned layer occurs at a high applied magnetic field. The magnetization of the other FM layer reverses almost freely when a small magnetic field is applied. Here we study the exchange bias effect in the MnPt (t)/CoFe (50 Å) system, using the Magneto-Optical Kerr Effect (MOKE) and domain imaging techniques. The exchange (H_E) and coercive (H_c) fields increase with increasing AFM thickness, saturating for t > 200 Å (H_E ≈ 670 Oe and H_c ≈ 315 Oe). Furthermore, we observe that the value of the exchange field is almost independent of the applied magnetic field sweeping rate (up to ≈ 300 kOe/s). Domain imaging allowed us to conclude that magnetization reversal in the studied system proceeds essentially by coherent magnetic moment rotation.     

Performance Analysis of a Stationary Fuel Cell Thermoelectric Cogeneration System

The main purpose of our study was to use an experimental method and system dynamic simulation technology to examine a proton exchange membrane fuel cell thermoelectric cogeneration system that provides both high‐quality electric power and heated water. In the second part of our study, we experimentally verified the development of key components of the fuel cell and conducted a comprehensive analysis of the subsystems, including the fuel cell module, hydrogen supply subsystem, air supply subsystem, humidifier subsystem, and heat recovery subsystem. Finally, we integrated all of the subsystems into a PEM fuel cell thermoelectric cogeneration system and performed efficiency tests and analysis of power generation, heat recovery, and thermoelectric cogeneration. After comparing this system's efficiency results using simulation and experimentation, we determined that the accuracy of the simulation values when compared to the experimental values was >95%, showing that this system's simulation nearly approached the efficiency of the actual experiment, including more than 53% for power generation efficiency, more than 39% for heat recovery efficiency, and more than 93% for thermoelectric cogeneration combined efficiency.