Study on maximum power point tracking of photovoltaic array in irregular shadow

Traditional maximum power point tracking (MPPT) methods can hardly find global maximum power point (MPP) because output characteristics curve of photovoltaic (PV) array may have multi local maximum power points in irregular shadow, and thus easily fall into the local maximum power point. To address this drawback, Considering that sliding mode variable structure (SMVS) control strategy have such advantages as simple structure, fast response and strong robustness, and P&O method have the advantages of simple principle and convenient implementation, so a new algorithm combining SMVS control method and P&O method is proposed, besides, PI controller is applied to reduce system chattering caused by switching sliding surface. It is applied to MPPT control of PV array in irregular shadow to solve the problem of multi-peak optimization in partial shadow. In order to verity the rationality of the proposed algorithm, the experimental circuit is built, which achieves MPPT control by means of the proposed algorithm and P&O method. The experimental results show that compared with the traditional P&O algorithm, the proposed algorithm can fast track the global MPP, tracking speed increases by 60% and the relative error decreased by 20%. Moreover, the system becomes more stable near the MPP, the fluctuations of output power is greatly reduced, and thus make full use of solar energy.     

Relationship between adjustment of low water level and utilization of water depth in Shashi Reach in middle Yangtze River

Hydrological, sediment, and bathymetric data of the Shashi Reach in the middle Yangtze River for the period of 1975–2018 were collected, and the characteristics of low water level changes and their impacts on utilization of water depth for navigation were investigated. The results showed that, during the study period, the Shashi Reach riverbed was significantly scoured and incised, with cross-sectional profiles showing overall narrowing and deepening. This indicated a strong potential to improve the water depth of the channel. The analysis of the temporal variation of in-channel topographical features showed that the Taipingkou diara underwent siltation and erosion, with its head gradually scoured and relocated downstream after 2008, and the Sanbatan diara continued to shrink and migrate leftwards. Low water levels with the same flow rate over the study period decreased. For instance, from 2003 to 2020, the water level at the Shashi hydrological station decreased to 1.37 m with a flow rate of 6 000 m³/s. Furthermore, the designed minimum navigable water level of the Shashi Reach was approximately 2.11 m lower than the recommended level. In terms of utilization of the channel water depth, continuous scouring of the river channel is expected to result in a reduction in discharge at the Taipingkou mouth, which will improve the water depth conditions of the channel during the dry season in the Shashi Reach. With several channel regulation projects, the 3.5-m depth of the Shashi Reach would basically be unobstructed. This promotes utilization of the shipping route from the Taipingkou south branch to the Sanbatan north branch as the main navigation channel during the dry season. Considering the factors of current water depth and the clear width limitation of the navigation hole at the Jingzhou Yangtze River Bridge, this route can still be favored as the main navigation channel with a 4.5-m depth during the dry season.     

南方某市供水管网水质在线监测管理系统的建立

以南方某市为例，介绍了其供水管网水质在线监测管理系统的建立过程。首先，对系统进行总体设计，确定在线监测点的位置、数量和在线监测指标，选定在线监测仪器和在线数据传输方式。其次，基于管网水质在线监测信息建立了水质在线监测管理系统，可实现数据库连接、列表、查询、统计报表打印、实时监测数据显示等功能。最后，依据统计分析与人工智能的方法建立了三种水质预测模型，并将其与水质在线管理系统集成，实现了对供水管网主要水质指标的在线监测、管理与预测。对该系统采用管网实测数据进行考核、验证，结果令人满意。     

天津港综合业务楼暖通监理控制方法

主要介绍了监理的概念及设计监理的重要性，并重点介绍了暖通施工监理在工程实施的各阶段质量控制的具体操作方法。     

膨润土钻井液深钻技术在渤海某油田的应用

通过分析渤海某油田的沉积环境、地质油藏概况和优化井身结构及井眼轨迹,优选钠基膨润土,添加增黏剂、烧碱和纯碱等添加剂提高动、静切力和确保p H值大于10,并在淡水配制后让充分水化形成的膨润土钻井液深钻至馆陶组(垂深2 000 m左右),实现了快速钻进,钻速由50~70 m/h提高至90~100 m/h,扩大了上部井段的井径(由?342.9 mm扩至?374.65mm)、减少了起下钻和下套管作业的阻卡风险,而且节约了钻井液成本,形成了渤海油田降本增效和钻井提效典型技术。     

Numerical evaluation on shell buckling of empty thin-walled steel tanks under wind load according to current American and European design codes

Liquid storage steel tanks are vertical above-ground cylindrical shells and as typical thin-walled structures, they are very sensitive to buckling under wind loads, especially when they are empty or at low liquid level. Previous studies revealed discrepancies in buckling resistance of empty tanks between the design method proposed by the American Standard API 650 and the analytical formulas recommended by the European Standard EN1993-1-6 and EN1993-4-2. This study presents a comparison between the provisions of current design codes by performing all types of numerical buckling analyses recommended by Eurocodes (i.e. LBA-linear elastic bifurcation analysis, GNA-geometrically nonlinear elastic analysis of the perfect tank and GNIA-geometrically nonlinear elastic analysis of the imperfect tank). Such analyses are performed in order to evaluate the buckling resistance of two existing thin-walled steel tanks, with large diameters and variable wall thickness. In addition, a discussion is unfolded about the differences between computational and analytical methods and the conservatism that the latter method imposes. An influence study on the geometric imperfections and the boundary conditions is also conducted. Investigation on the boundary conditions at the foot of the tank highlights the sensitivity to the fixation of the vertical translational degree of freedom. Further, it is indicated that the imperfection magnitude recommended by the EN1993-1-6 is extremely unfavorable when applied to large diameter tanks. Comments and conclusions achieved could be helpful in order to evaluate the safety of the current design codes and shed more light towards the most accurate one.     

Gd2Fe14Cr3化合物的本征磁致伸缩

通过X射线衍射及磁测量手段研究了Gd2Fe14Cr3化合物的热膨胀性质及本征磁致伸缩性质.研究结果表明,Gd2Fe14Cr3化合物在294～692K范围内,具有单相的Th2Zn17型菱方相结构;磁测量的研究结果表明,Gd2Fe014Cr3化合物的居里温度约为540K,比其母合金Gd2Fe17高约30K;在452～512...     

冷轧硅钢片磁性能测量因素的分析

采用硅钢片磁性能测试系统,分析了测试环境温度(10～30℃)、试样质量(642～667 g)和剪切应力(剪切1～5次)对国内外不同牌号0.27～0.50 mm取向和无取向冷轧硅钢片磁性能的影响.结果表明,随环境温度升高,冷轧硅钢片的铁损和磁感降低;随试样质量增加,铁损增加,磁感降低;随剪切次数增加铁损递增,磁感递减.文中归纳出磁性能测量的适合条件和注意事项.     

胶凝材料与外加剂相容性关系的探讨

本文根据流变学原理,研究了水泥、粉煤灰、矿粉等几个方面的因素对相容性的影响。采用减水剂饱和点掺量、水泥净浆流动度、流动度经时损失,作为宏观评价指标,对影响减水剂与水泥及掺合料相容性的原因进行了探讨,提出了一些解决相容性问题的方法,研究了相容性的差异对混凝土性能的影响,最后综合以上评价指标,提出了相容性的定量评价方法。     

抗渗混凝土膨胀无缝加强带在施工中的应用实例

本文介绍超长结构膨胀无缝加强带施工的基本原理,通过日照市岚山区无害化垃圾处理场工程渗沥液调节池工程实例说明了在超长无缝抗渗混凝土膨胀无缝加强带替代后浇带的技术要点。