H型截面单层单跨钢框架火灾行为试验

对2榀H型截面单层单跨钢框架进行了火灾行为的足尺试验研究.全部试验采用自行研制的火灾试验炉,试验结果表明炉子性能稳定,使用方便.试验中考虑了不同受火工况对钢框架火灾行为的影响.通过试验得出了钢框架温度场分布和变形的变化规律.试验结果表明:火灾下,梁柱全部受火的单层单跨钢框架(节点受到保护)破坏方式为钢柱压屈破坏,破坏位置在受到保护的钢节点下部的钢柱上.试验研究为今后钢结构火灾行为的研究提供依据.     

大口径光学透镜瞬态温度场模拟

为考察热辐射效应对光学元件稳、瞬态温度场的影响,给出了考虑辐射和导热耦合换热情况下复杂几何结构光学透镜稳、瞬态热特性的适体坐标下离散坐标法.对喷管形和圆柱形介质进行计算并与其他方法比较表明,建立的适体坐标系下辐射与导热耦合换热计算方法精度较好.对两端为球缺中间为圆柱的大口径透镜内的辐射与导热耦合换热过程进行了数值模拟.计算结果表明,为了精确地预测半透明介质如透镜内的温度分布,应该考虑辐射与导热耦合作用,且应当考虑介质的光谱特性.     

小型加热炉炉温微机控制系统

针对小型试验反应器的特点,介绍了PID自整定、串级控制、采样调节、程序适应控制、程序升降温等多种控制策略在该种反应器温度控制上的应用。结果表明,反应器内温稳态温度控制精度高,升降温曲线能很好地跟踪开停工工艺条件,开停工简单方便,参数整定方便,适应性强,控制方式灵活,减轻了操作人员的劳动强度,提高了试验装置的自动化水平。     

Oxidation behavior of in-situ Al2O3/TiAl composites at 900℃ in static air

In-situ Al2O3/TiAl composites were successfully synthesized from the starting powders of Ti, Al, TiO2 and Nb2O5. The oxidation behavior of the composites at 900℃ in static air was investigated. The results indicate that the composite samples present a much lower oxidation mass gain. Under long-time intensive oxidation exposure, the formed oxide scale is multi-layer. The formation of the outer TiO2 layer is fine and dense, the internal Al2O3 scale has good adhesiveness with the outer TiO2 scale, and the TiO2+Al2O3 mixed layer forming the protective oxide scale is favorable for the improvement of oxidation resistance. It is believed that the incorporation of Al2O3 particulates into the metal matrix decreases the coefficient of thermal expansion of the substrate, and forms a local three-dimensional network structure that can hold the oxide scale. The formation of the oxide scale with fmer particle size, stronger adherence, less micro-defects and slower growth rate can contribute to the improvement of oxidation resistance. Nb element plays an important role in reducing the internal oxidation action of the materials, restraining the growth of TiO2 crystals andpromoting thc stable formation of the Al 2O3-riched layer,which is benfeicial to improve the oxidation properties.     

Effects of annealing temperature on the microstructure and properties of the 25Mn-3Si-3Al TWIP steel

Microstructures and mechanical properties of the 25Mn twinning induced plasticity (TWIP) steel at different annealing temperatures were investigated. The results indicated that when the annealing temperature was 1000°C,the 25Mn steel showed ex-cellent comprehensive mechanical properties,the tensile strength was about 640 MPa,the yield strength was higher than 255 MPa,and the elongation was above 82%. The microstructure was analyzed by optical microscopy (OM),X-ray diffraction (XRD),and transmission electron...     

F68大单体/HEMA共聚水凝胶的制备及性能研究(Ⅰ):温度敏感性

本文以温度敏感性Pluronic F68与甲基丙烯酸缩水甘油酯(GMA)反应制备可光聚合的F68/GMA大分子单体,再在水溶液中与丙烯酸(AA)单体和甲基丙烯酸β-羟乙酯(HEMA)经紫外光原位聚合制备温度敏感水凝胶。详细地研究了水凝胶在不同温度下的溶胀性能。溶胀动力学测量的结果表明,该水凝胶具有温度响应性且具有可逆性。     

Temperature distribution and dynamic control of secondary cooling in slab continuous casting

To predict and optimize the temperature distribution of slab continuous casting in steady operational state, a three-dimensional model (named offline model) based on the heat transfer and solidification theories was developed. Both heat transfer and flux distribution characteristics of the nozzle sprays on the slab were considered, and the complicated boundary condi-tions, such as spray cooling, natural convection, thermal radiation as well as contact cooling of individual rolls were involved in the model. ...     

Effects of main factors on remedying northern landscaping water by hybrid ecological filter

Natural zeolite and coal cinder were layered as main packing medium of the ecological filter instead of traditional filling to remedy the static lake water in Northern China.The ecological filter was running in a combined upward and downward flow mode.Dynamic experiments were carried out to study the effects of retention time and ambient temperature on pollutants’ removal efficiency of the hybrid ecological filter.The function of plant was also studied by contrast test.It is showed that the removal efficiencies of NH4+-N and TP are increased when the retention time is changed from 1 h to 2 h and 4 h,but the removal efficiency of TN is decreased,the removal efficiency of NH4+-N is increased from 91.5% to 98% and that of TP is increased from 31.8% to 52.5%.When the temperature declines,the temporal removal efficiency of NH4+-N is reduced,but the removal efficiency of 24 h and 48 h is remained.The removal efficiency of TP after 24 h and 48 h is decreased when the temperature declines evidently.The retention time plays an important role in NH4+-N and TP removal,and the ambient temperature is significant for TP removal.The plant favors for TP and organic matter removal but has little effect on TN removal.     

Shut-cut nitrification characteristics of aerobic granule in a sequencing batch airlift reactor at low temperature

To investigate the shut-cut nitrification characteristics of aerobic granule,an aerobic granular sequencing batch airlift reactor(AG-SBAR) was carried out with mixed carbon sources of sodium acetate and glucose at 10±1 ℃.Results indicated that ammonia oxidizing bacteria was accumulated inside the aerobic granules and the reactor performed stably with shut-cut nitrification for a long term at low temperature.During the stable operation period,the effluent ammonia nitrogen concentration was maintained at 13.6 mg/L without nitrate and nitrite when the COD/N ratio was 20:1.However,the effluent concentration of ammonia nitrogen was below 0.5 mg/L with effluent nitrosation ratio of 96.7% on average when the COD/N ratio was reduced to 15:1 and 10:1.And the effluent phosphorus concentration was less than 0.4 mg/L during the stable period with the sludge retention time of 30 d.The phosphorus removal efficiency was not strongly influenced by the adjustment of COD/N ratio in this experiment.The removal efficiencies for COD,NH4+-N and PO43--P were 91.3%-94.6%,97.9%-99.7% and 97.1%-99.5%,respectively.     

火电机组过热汽温神经网络控制的研究

研究了单神经元PID控制器和BP神经网络PID控制器在火电机组过热汽温的应用．实验结果表明,神经网络PID控制结构简单,有较强的鲁棒性,取得了较好的控制效果．