Crystalline Sodium Selenocarboxylates – synthesis and characterization

A series of sodium selenocarboxylates 2 were isolated from the reaction of diacyl selenides with sodium ethanolate and characterized. A convenient preparation of the sodium salts 2 by the direct reaction of acyl chlorides with sodium selenide was also established. The salts are colourless to slightly pale yellow crystals and labile towards moisture. They readily react with alkyl iodides at room temperature to give the corresponding Se-alkyl esters 3 .     

Dissociation of fast HeH ions at glancing angle scattering from a crystal surface

Scattered H⁺ fragments resulting from glancing angle incidence of MeV HeH⁺ ions on the clean (001) surface of a SnTe crystal are distributed on an ellipse in the E-φ plane, where the angle φ is measured in the plane parallel to the surface and E is the energy of the fragment. The kinetic energies released upon dissociation derived from the diameters of the ellipses are smaller than those calculated from the explosion of fully ionized fragments.

Based on a simplified model, we have simulated the dissociative scattering of HeH⁺ ions at the surface, where the dissociation takes place via excitation of HeH⁺ ions and the charges of fragments change along the trajectory. It is concluded from the simulation that the cross section for dissociation in HeH⁺-electron collisions is of the order of 10⁻¹⁶ cm².     

Assessment of offshore wind farm characteristics with the cloud resolving storm simulator: A case study in Japan

Wind conditions and output power characteristics of a wind farm in Japan are evaluated with highly resolved weather predictions from the so‐called cloud resolving storm simulator. One year of 30‐hour‐ahead predictions with 2‐km spatial resolution and 1‐hour time resolution are evaluated against 10‐minute averaged measurements (averaged to hourly data) from the wind farm. Also, extremely detailed shorter‐term predictions with 200‐m spatial resolution and 1‐second time resolution are evaluated against 1‐Hz measurements. For the hourly data, wind speeds are predicted with an RMSE of 3.0 to 3.5 m/s, and wind power with about 0.3 per unit. Wind direction is predicted with a standard deviation of errors of 16° to 28° for hourly data, and generally below 10° for the 1‐Hz data. We show that wind power variability—here in terms of increments—can be assessed on the timescale of several hours. The measured and predicted wind spectra are found similar on both short and long timescales.     

非线性滑移滞回模型建模

目的为了对结构进行弹塑性动力分析以及评估其未来的性能，对结构的滞回特性需要建立合理的数学模型．方法利用三折线形式的函数关系来模拟试验滞回曲线的斜率与恢复力关系，并结合Duhem微分算子，建立描述滑移捏拢效应和刚度、强度退化的微分滞回模型．然后使用粒子群优化方法，基于最小二乘法准则识别出模型中的待定参数．结果用参数辨识结果得到的仿真滞回曲线与试验滞回曲线的对比表明，笔者建立的非线性滑移滞回模型与试验结果吻合较好，包括了强度退化、刚度退化以及捏拢效应．结论根据滞回曲线斜率与恢复力的关系并结合Duhem微分算子来构造滞回模型，比扩展Bouc—Wen模型具有更广泛的建模适应能力．对于试验滞回曲线的建模问题，当模型结构可辨识时，粒子群算法能够稳健地识别出模型中的参数．     

High Electrical Conductivity and High Fracture Strength of Sc2O3-Doped Zirconia Ceramics with Submicrometer Grains

The microstructure, crystal phase, electrical conductivity, and mechanical strength of less than 7-mol%-Sc₂O₃-doped zirconia ceramics fabricated by comparatively low-temperature sintering at 1200–1300°C for 1 h were investigated. Zirconia ceramics having a uniform microstructure (grain size < 0.5 μm) stabilized with 6 mol% Sc₂O₃ showed high electrical conductivity (0.15 S/cm at 1000°C) and high fracture strength (660 MPa). With the increase of Sc₂O₃ content from 3.5 to 7 mol%, the grain size, fracture strength, and electrical conductivity at 1000°C changed from 0.2 to 0.5 μm, 970 to 440 MPa, and 0.07 to >0.2 S/cm, respectively. Sc₂O₃-doped zirconia polycrystals with high fracture strength and high electrical conductivity are promising candidates for the electrolyte material of solid oxide fuel cells.     

Discontinuous Dynamics of Electric Power System With DC Transmission: A Study on DAE System

Transient stability of power systems with dc transmission is an important problem for planing and operation of future power networks. A differential-algebraic equation (DAE) system is proposed for transient stability analysis of a practical ac/dc power system which includes one synchronous generator operating onto both ac and dc transmissions. When transient stability analysis is performed using the DAE system, its solutions that represent dynamics of the ac/dc power system become discontinuous. This is because a constraint set, which is a set of variables satisfying algebraic equations of the DAE system, discontinuously changes at the onset of fault occurrence and clearing. We numerically and analytically examine such discontinuous solutions of the DAE system and associated transient dynamics of the ac/dc power system. The discontinuous nature of solutions shows that enhancement of transient stability via dc transmission is characterized by a dynamical system on a constraint set or a manifold controlled by input as installation of dc transmission.     

Multi-Fuel Capability of Solid Oxide Fuel Cells

One of the most attractive features of solid oxide fuel cells is their flexibility for fuels so that internal reforming and/or simple external reforming may be possible. In this study, equilibria in various possible fuel gases are considered, and C–H–O diagrams are constructed. Power generation characteristics for these fuels are measured and compared with those for simulated reformed gas in equilibrium compositions. We have succeeded to demonstrate direct-alcohol SOFCs for e.g. methanol, ethanol, and propanol. Mixtures of CH₄ and CO₂ are used as simulated biogas, and iso-octane (C₈H₁₈) and n-dodecane (C₁₂H₂₆) are highlighted as simulated gasoline and kerosene, respectively. Influence of fuel impurities on power generation characteristics is also discussed.