加气混凝土砌块专用砂浆施工性能研究

加气混凝土砌块是迄今为止唯一能够同时满足墙材革新和节能50%要求的单一墙体材料,对于夏热冬暖地区来说,具有不可比拟的优势．相应的配套砌筑、抹面砂浆的研制工作也取得了不小的成绩。本文主要研究专用砂浆薄层施工对墙体性能有无影响以及影响程度如阿。阐述了专用砂浆薄层施工的可行性,以及在施工时的注意事项。     

鱼雷型混铁车摇枕及车侧架等的创新修复

针对邯钢运输部鱼雷型混铁车各个部位磨耗严重、侧架与轴箱磨耗间隙偏大、摇枕与侧架接触处间隙过大的问题,对鱼雷型混铁车铸钢件等专用的校验工具作了改进.通过优化焊修方法,减少了机加工等工序,用改进的校验模具完成了鱼雷型混铁车铸钢件的磨耗修复.提高了车辆检修效率,增加了车辆安全运行系数,每年可创效益31.2万元.     

一族非隔离双向直流变换器

提出一族基于反向耦合电感的非隔离双向直流变换器(bi-directional DC converter,BDC),通过引入反向耦合电感,利用电感感应电势阻断不工作MOSFET的体二极管,消除了传统双向变换器中开关管寄生体二极管的反向恢复问题;通过反向耦合电感与滤波电感等效电路的分析,将反向耦合电感与滤波电感用一个同向耦合电感代替,提出一族基于PCI的非隔离双向直流变换器。所提出的变换器控制与传统单向变换器相同,不需要专门的软启动电路,兼顾了较高变换效率、控制简单和高可靠性。给出拓扑推演过程,详细分析拓扑工作原理,并通过实验验证理论分析的正确性。     

基于RTDS的光伏发电系统低电压穿越建模与控制策略

基于实时数字仿真器(RTDS)提出了一种光伏发电系统低电压穿越(LVRT)实时数字仿真方案。首先,通过RTDS的大步长模型和小步长模型构建了整套LVRT仿真平台,具体包括电压跌落发生器、光伏阵列、隔离变压器和光伏并网逆变器等。然后,设计了光伏并网逆变器在三相电网电压正常和对称跌落2种运行工况下的LVRT控制策略。最后,以一台250kW光伏并网逆变器为例,进行了LVRT仿真测试和现场检测实验。仿真和实验表明:该RTDS仿真平台能较好地模拟现场检测平台,且所述控制策略在LVRT过程中具有良好的动、静态特性。     

太阳能热气流发电系统辅助加热与塔囟高度研究

对太阳能塔囱热气流发电系统中辅助加热与塔囱高度的关系进行了分析研究,提出了在塔囱内对上升热气流进行二次辅助加热的设想,以增加气流速度,提高塔囱抽力,降低塔囱高度.以乌海沙漠太阳能热风气流发电系统为例,在塔囱压差和底部入口气流速度不变的情况下,最佳辅助加热气流温度为90℃;塔囱高度为80 m时,辅助加热位置设在塔囱内距地面50 m处较为合适.     

成型工艺条件对铈锆铝复合载体性能的影响

采用压缩成型法对铈锆铝复合载体进行了放大制备,考察放大制备过程中造粒粉含水量、成型压力、焙烧温度等成型工艺条件对载体机械强度、吸水量、密度、织构性质及晶相的影响。结果表明,造粒粉含水量是影响颗粒成型的主要因素,含水量过高,颗粒不能成型或容易层裂;成型压力是影响载体强度、吸水量、密度等机械性能的主要影响因素,适宜的成型压力有助于获得各项机械性能均衡的载体;焙烧温度是影响载体比表面积及晶相结构的关键因素。结合生产要求确定最佳工艺条件为造粒粉含水量为15%,半成品强度(7~9)N·mm-1,焙烧温度(800~900)℃。     

一种双层智能膜的制备及在指示三文鱼新鲜度中的应用

为了提高天然花青素作为新鲜度指示剂在食品包装中的稳定性,本研究将结冷胶和桑葚花青素作为内层膜用于指示三文鱼新鲜度,壳聚糖-聚乙烯醇形成致密隔氧的外层保护膜,通过逐层组装制备食品新鲜度指示膜,并用于三文鱼的新鲜度可视化检测。结果表明：当外层膜中壳聚糖和聚乙烯醇的体积比为1∶1时,双层膜的机械性能最好,其中拉伸强度为40.65 MPa,断裂伸长率为54.36%,膜的水蒸气透过系数最低;扫描电子显微镜结果表明,外层膜壳聚糖和聚乙烯醇的体积比为1∶1时,膜的结构相容性最好,该体系下桑葚花青素稳定性最好。将双层膜用于三文鱼新鲜度指示,在4 ℃贮藏环境下,随着贮藏时间的延长,三文鱼的总挥发性盐基氮含量不断上升,6 d后,总挥发性盐基氮含量大于30 mg/100 g,硫代巴比妥酸反应产物值为0.921 mg/kg,pH值为6.75,且通过肉眼可以直观看到膜的颜色由暗红变为淡紫色,最后变成蓝褐色,鱼肉已经腐败。结论：基于壳聚糖-聚乙烯醇/结冷胶花青素组成的双层膜既可降低花青素氧化作用提高其稳定性,又可用于三文鱼新鲜度指示。     

Nitrile rubber/sliding graft copolymer damping material with significantly improved strength and damping performance

Nitrile rubber (NBR)/sliding graft copolymer (SGC) composites with significantly improved strength and damping property are successfully prepared. SGC is a novel kind of supramolecular material with sliding crosslink junctions. The micromorphology analyses of NBR/SGC composites indicate that the SGC phase with particle size less than 500 nm is fairly uniformly dispersed in the NBR matrix. As SGC content increases, the loss factors (tan δ) of NBR/SGC composites increase gradually. Specifically, the tan δ of NBR/SGC (100/40) is about 1.2 times higher than that of pristine NBR rubber. The tensile strength and elongation at break of NBR/SGC composites are unexpectedly improved after the addition of SGC. The significantly improved damping performance and tensile strength can be ascribed to the pulley effect of SGC and the strong interfacial hydrogen bonds between SGC and NBR. The high damping performance and good mechanical strength make the NBR/SGC composite a promising high-performance damping material. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47188.     

Effect of sintering temperature on electrical properties of SiC/ZrB2 ceramics

SiC/20?wt% ZrB₂ composite ceramics were fabricated via pressureless solid phase sintering in argon atmosphere at different temperature. The effect of sintering temperature on microstructure, electrical properties and mechanical properties of SiC/ZrB₂ ceramics was investigated. Electrical resistivity exhibits twice significant decreases with increasing sintering temperature. The first decrease from 1900?°C to 2000?°C is attributed to the obvious decrease of continuous pore channels in as-sintered materials. The second decrease from 2100?°C to 2200?°C results from the improvement of carbon crystallization and the disappearance of amorphous layers enveloping ZrB₂ grains. Additionally, the increase of sintered density with increasing temperature caused greatly advance of flexural strength, elastic modulus and Vickers hardness. But excessive temperature is detrimental to flexural strength because of SiC grain growth.     

Tea components influencing bioavailability of fluoride and potential transport mechanism in the Caco-2 cell line model

Previous work showed that the bioavailability of fluoride in dark tea was lower than NaF solution. However, limited information is available indicating the effects of tea components on the fluoride bioavailability. In this study, the effects of the components in tea on the bioavailability of fluoride were evaluated in the Caco-2 cell line model. Additionally, the mechanism of effect of aluminium on fluoride transport was investigated. The result showed that 10–100 μm of epigallocatechin gallate (EGCG) could not influence fluoride transport. Al³⁺ significantly decreased fluoride transport in both apical-basolateral and basolateral-apical directions. Moreover, aluminium could form different forms of aluminium fluoride complexes, which were transported through Caco-2 cells by different pathways. F⁻ transport was mainly dependent on the paracellular pathway and active transport involving Cl⁻ channels. The paracellular pathway played a predominant role in transport of AlF₃. The paracellular pathway and active transport both participated in AlF₂⁺ transport.