电流型阻抗源升压整流器

自Z源网络提出以来,阻抗源变流器得到了广泛的研究和应用,但大多是针对电压型及逆变器的。选择电流型准Z源整流器作为研究对象,在传统控制策略中加入了阻抗源电感电流的前馈控制和有源阻尼控制,得到了更高的输出范围和更好的输出波形,并通过仿真验证了控制策略的正确性。设计了1台1 kW量级的样机并进行实验验证。     

Finite element modeling of thermo-active diaphragm walls

There are two major challenges faced by modern society: energy security, and lowering carbon dioxide gas emissions. Thermo-active diaphragm walls have a large potential to remedy one of these problems, since they are a renewable energy technology that uses underground infrastructure as a heat exchange medium. However, extensive research is required to determine the effects of cyclic heating and cooling on their geotechnical and structural performance. In this paper, a series of detailed finite element analyses are carried out to capture the fully coupled thermo-hydro-mechanical response of the ground and diaphragm wall. It is demonstrated that the thermal operation of the diaphragm wall causes changes in soil temperature, thermal expansion/shrinkage of pore water, and total stress applied on the diaphragm wall. These, in turn, cause displacements of the diaphragm wall and variations of the bending moments. However, these effects on the performance of diaphragm wall are not significant. The thermally induced bending strain is mainly governed by the temperature differential and uneven thermal expansion/shrinkage across the wall.     

Synthesis of scalable 1T/2H–MoSe2 nanosheets with a new source of Se in basic media and study of their HER activity

In this report MoSe₂ nanosheets were fabricated using new precursors of MoCl₅ and Na₂SeO₃ and a very simple chemical procedure without using inert atmosphere and complex methods for preparing Se ion source. The structural properties of fabricated nanosheets were examined by means of XRD, field emission scanning electron microscopy (FESEM), elemental mapping of energy dispersive x-ray spectroscopy (EDS), transmission electron microscopy (TEM), atomic force microscopy (AFM), Raman spectroscopy and isotherm gas adsorption-desorption technique. The results showed the nanosheets are mixed phase metallic-semiconductor 1T-2H with thicknesses about 3.6–6.1 nm and are stable for several months. The effective surface area is obtained 28 m² g⁻¹ and mean pore size of 6–8 nm for MoSe₂ nanosheets. Electro-impedance spectroscopy showed low resistivity of nanosheets due to presence of metallic phase of MoSe₂. HER activity of nanosheets obtains a Tafel slope of 60 mV.dec⁻¹ and high current density values up to 150 mA cm⁻² and the value of over potential at 10 mA cm⁻² is 155 mV.     

石油工程岩石强度与变形尺度效应研究现状综述与展望

岩石强度与变形存在显著的尺度效应,致使实验室尺度的岩样强度与变形测试结果不能直接应用于工程范围的大尺度岩体或微纳米级尺度的岩屑(矿物)。实现岩石强度与变形的跨尺度表征,即基于常规岩心测试手段,结合跨尺度表征方法来预测其他尺度的岩石力学参数和变形规律对于油气高效、经济、安全开采具有重要意义。本文在充分调研了国内外关于岩石强度与变形尺度效应研究的基础上,介绍了当前研究岩石强度与变形尺度效应的主要理论、主要认识和影响因素,并对石油工程领域岩石强度与变形尺度效应的研究方向进行了展望。     

方腔内耦合传热传质非对称流动数值模拟

对带有质热源的方腔内流体传热传质进行数值研究。针对不同Ra、Nc、Sr和Df，探究对称方腔内流体传热传质的分岔特性。结果表明：存在临界Ra_c使流体流动形态发生转变，当Ra<Ra_c时，流体流线、温度场和浓度场对称分布；当Ra>Ra_c时，流体发生偏斜。增大浮升力，流体更易发生分岔现象。增强Soret和Dufour效应可增强传热对称性并增大流体发生分岔的临界Rayleigh数。     

Modelling of electron energy absorption and backscattering during EBW

A three-dimensional heat flux model for deep-penetrating electron beam welding (EBW) is established to mathematically describe the physical heat generation process during interaction between electrons and the dynamic molten pool free surface. Monte Carlo method is used to determine the electron-target interaction, and random distribution of initial electrons, progressive trajectory tracing and electron backscattering models are used to describe the spatial distribution of electrons absorption. The model is verified in preset keyholes and applied in the simulation on electron beam welding process, and the calculated bead shape shows a good consistency with experimental results.     

Proposed light sources for illuminating in Xuan paper and silk artwork with organic and inorganic pigments by evaluating color shifts in museum

Artworks based on Xuan paper or silk and painted by organic or inorganic pigments are highly responsive to light due to their materials and manufacturing technologies. They belong to the highest level of light responsive exhibits stipulated by International Commission on Illumination (CIE) and are vulnerable to fading and discoloration caused by radiation from light sources. The choice of light sources is the key of protection for artworks. It is indispensible and urgent to choose the lowest damage light sources according to the material characteristics of artworks. In this article, long-term irradiation of typical light sources on various substrates and pigments was used as experimental method, and CIE DE2000 color difference formula was used as the evaluation index. The laws of the influence of different light sources on the color change of various materials were obtained, and the relative damage coefficients of light sources were calculated. Finally, eight kinds of light sources suitable for illuminating responsive artworks with typical material combinations were proposed. However, there are some limitations in the study, because the ancient Chinese Xuan paper and silk used as experimental objects in the experiment are yellowish. Thus, the models derived in this article are not suitable for choosing reasonable display light sources for other works of art. However, suitable light sources for different materials could be obtained by the calculation method used in this article.     

江淮丘陵区马槽河流域污染源调查分析及治理建议

随着区域城市人口增加和人民生活水平提高，江淮丘陵区中小河流水环境污染问题日益突出，成为区域社会经济发展的主要制约因素之一。本文以位于江淮丘陵区马槽河流域为研究对象，通过资料收集、问卷调查、实地勘察等手段，查明该地区入河污染物指标 COD、氨氮、TN、TP 主要贡献因素及占比，其中生活污染（51%，40%，54%，28%）、面源污染(6%，38%，9%，42%)、畜禽养殖（39%，15%，17%，25%）三类型贡献占比 90%以上，内源污染和水产养殖较少。针对污染源调查结果特征，提出镇区管网完善、农村分散处理、畜禽粪污处理、养殖废水农田消纳、污染缓冲带设置、径流拦截与再利用、河流生态化改造等治理建议，可为今后中小河流污染源调查与治理提供借鉴。     

Weighted Self-Adaptive Threshold Wavelets for Interpolation Point Selection Used in Interconnect MOR

超高膨胀比涡轮噪声控制技术研究

赵辛午，黄洪雁

（哈尔滨工业大学 能源科学与工程学院，哈尔滨 150001）

中文说明：

气动噪声控制是提高鱼雷隐身性能的关键技术之一。本文讨论了局部进气的超高膨胀比涡轮气动噪声产生机理。相邻喷嘴与流道之间形成的三角形非出气区域引起的尾迹、圆周局部进气设计引起的不稳定性、喷嘴和转子之间区域形成的复杂激波系是这类涡轮气动噪声产生的三种主要来源。因此，本文提出了两种气动噪声控制方法，增加转静子之间的轴向间距，喷嘴下俯、双侧修型和尾缘吹气。数值模拟结果表明：在对原涡轮气动性能影响不大的情况下，优化后涡轮的气动噪声下降10 dB以上。

关键词：超高膨胀比涡轮、气动噪声、流动特性、优化

     

System identification with measurement noise compensation based on polynomial modulating function for fractional-order systems with a known time-delay

This study presents a system identification method based on polynomial modulating function for fractional-order systems with a known time-delay involving input and output noises in the time domain. Based on the polynomial modulating function and fractional-order integration by parts, the identified fractional-order differential equation is transformed into an algebraic equation. By using the numerical integral formula, the least squares form for the system identification is obtained. In order to reduce the effect of noises existing in the input and output measurements, the compensation method for the input and output noises is also studied by introducing an auxiliary high-order fractional-order system in the revised identification algorithm. Finally, the effectiveness of the proposed algorithm is verified by the simulation result of an illustrative example and the experimental result of temperature identification for a thermal system.