Experimental and numerical investigations of the compressive behavior of carbon fiber-reinforced polymer-strengthened tubular steel T-joints

A method for strengthening damaged tubular steel T-joints under axial compression by wrapping them with carbon fiber-reinforced polymer (CFRP) sheets was proposed and evaluated. The influence of the CFRP strengthening on the failure mode and load capacity of T-joints with different degrees of damage was investigated using experiments and finite element analyses. Five T-joints were physically tested: one bare joint to obtain the peak load and corresponding displacement (D_1m), two reinforced joints to provide a reference, and two pre-damaged then retrofitted joints to serve as the primary research objects. The ratio of the pre-loaded specimen chord displacement to the value of D_1m was considered to be the degree of damage of the two retrofitted joints, and was set to 0.80 and 1.20. The results demonstrate that the maximum capacity of the retrofitted specimen was increased by 0.83%–15.06% over the corresponding unreinforced specimens. However, the capacity of the retrofitted specimen was 2.51%–22.77% lesser compared with that of the directly reinforced specimens. Next, 111 numerical analysis models (0.63≤b≤0.76, 9.70≤g≤16.92) were established to parametrically evaluate the effects of different geometric and strengthening parameters on the load capacity of strengthened tubular T-joints under different degrees of damage. The numerical analysis results revealed that the development of equivalent plastic strain at the selected measuring points was moderated by strengthening with CFRP wrapping, and indicated the optimal CFRP strengthening thickness and wrapping orientation according to tubular T-joint parameters. Finally, reasonable equations for calculating the load capacity of CFRP-strengthened joints were proposed and demonstrated to provide accurate results. The findings of this study can be used to inform improved CFRP strengthening of damaged tubular steel structures.     

混凝土框架结构负弯矩区围板型粘钢加固节点抗震空间效应研究

本文以某办公楼改造工程为实例,对框架结构负弯矩区围板型粘钢加固方法的空间效应进行研究。通过ANSYS有限元软件,采用模态分析、谱分析、时程分析对3组模型进行仿真计算,对3组模型的抗震空间效应结果进行对比分析,结果均显示围板型粘钢加固方法具有较好的抗震性能。本文结果对多层或高层结构某区域梁负弯矩加固后的局部效应具有指导意义。     

含铅固废协同冶炼过程PbO-CaO-SiO2-Fe2O3-ZnO五元渣系相平衡研究

在1 000~1 250 ℃范围内,采用高温平衡-淬冷-EDS方法研究了含铅固废协同冶炼过程PbO-CaO-SiO₂-Fe₂O₃-ZnO五元渣系在空气气氛下的相平衡规律。研究结果表明,渣中存在的主要物相有尖晶石(Zn_xFe_3-yO_4+z)、红锌矿(ZnO)、黄长石(Pb_vCa_2-vZn_wSi₂O₇)、赤铁矿(Fe₂O₃)、磁铁铅矿(PbFe₁₀O₁₆)和硅钙石(Ca_2-tPb_tSiO₄)。在1 250 ℃、1 200 ℃、1 170 ℃、1 130 ℃和1 100 ℃下,PbO-CaO-SiO₂-Fe₂O₃-ZnO体系的液相点分布测试结果与MTDATA6.0软件模拟液相线基本吻合。在1 000~1 250 ℃范围内,随着结晶过程的进行,PbO-CaO-SiO₂-Fe₂O₃-ZnO体系液相成分中Fe₂O₃含量从16.83%减少到7.67%,ZnO含量从7.62%减少到2.98%,(PbO+CaO+SiO₂)含量从75.55%增加到89.36%。     

Does interior color contrast enhance spatial memory?

This study investigated the effect of contrast in neutral-, warm-, and cool-colored spaces on spatial memory. Spatial memory was measured in terms of architectural scale and recollection of architectural elements and furniture. Participants (N = 114) viewed a short virtual simulation video of a residential studio and were asked to sketch a map of the architectural elements on distributed grid paper. Spatial memory was measured in terms of scale, and item recall rate. Contrast and hue had no significant effect on the memorization of proportional scale. However, high-contrast schemes allowed for a significantly higher recollection of architectural elements than low-contrast schemes. In comparing the effect of hues, a significant difference was seen in recalling detailed furniture and lighting items. Participants reported significantly better spatial memory of neutral and warm color schemes than of cool color schemes. There was no interaction effect between contrast and hue in the color combinations. These results can be applied in the design of color schemes for architectural spaces requiring enhanced spatial cognition and memory.     

煤炭生产、消费与工业SO2排放关系计量研究——以西部8省为例

研究目的：探究工业SO₂排放与煤炭生产、消费存在必然的联系。研究方法：相关分析方法和改进的物理学重心模型。研究结果表明：(1)时序特征显示:西部煤炭生产、煤炭消费量和工业SO₂排放量整体都呈现上升趋势,三者增长率均呈现多波峰“M”状波动。2)重心轨迹显示:工业SO₂排放轨迹呈现为“倒L”型,煤炭生产和消费轨迹呈现为“J”型。(3)综合对比发现:煤炭生产从源头上影响工业SO₂排放,煤炭消费从空间上影响工业SO₂排放,为消减工业SO₂排放改善生态环境,必须在优先减少煤炭消费增加清洁能源比重的同时,更应该关注对煤炭生产过程的管控。     

分级加载电压下考虑有效电势变化的软黏土电渗固结理论

分级加载电压技术能够有效延长电渗处理的时间,改善地基的处理效果并能有效降低能耗。在利用分级加载电压技术开展电渗试验时,随着土体的排水固结,土体各点的电势会发生明显的变化,这与现有的电渗固结理论假设土体各点电势保持不变有所差异。利用自主设计的电渗试验仪器开展了分级加载电压下的电渗室内试验,分析了电渗过程中土体有效电势变化的规律。基于该规律并结合Esrig固结理论建立了在阳极处不排水、阴极处排水条件下考虑土体有效电势变化的电渗固结理论,得到了分级加载电压条件下考虑土体有效电势变化的超静孔隙水压力和平均固结度的解析表达式。研究表明,在电压分级加载过程中,土体有效电势变化规律表现为随时间先基本保持不变,后呈抛物线状先增后减。通过试验案例验证了考虑土体有效电势变化所求得解析解的合理性,且该数值计算结果相较于Esrig数值计算结果,前者更加接近实测值,该固结方程的建立为后续分级加载电压技术的推广应用提供了理论依据,也为实际工程提供了参考。     

Feasibility and sustainability analyses of carbon dioxide – hydrogen separation via de-sublimation process in comparison with other processes

Hydrogen (H₂) plays a vital role both as a reactant in petrochemical processes and as an energy carrier and storage medium. When produced from carbon-containing feed stocks, such as fossil fuels and biomass, hydrogen is typically produced as a mixture with carbon dioxide (CO₂), and must be subsequently separated by the associated energy, with an invertible energy penalty. In this study, the process for the removal of carbon dioxide from CO₂ - H₂ mixtures by de-sublimation was analysed. This process is particularly relevant to the production of liquid hydrogen (LH₂) at cryogenic temperatures, for which cooling of the H₂ stream is already necessary. The solid – gas equilibrium of CO₂ - H₂ was studied using the Peng-Robinson equation of state which provided a wide range of operating conditions for process simulation. The de-sublimation process was compared with selected conventional separation processes, including amine-based absorption, pressure swing adsorption and membrane separation. In the scenario in which the resulting products, carbon dioxide and hydrogen, were subsequently liquefied for transportation and storage at 10 bar and −46 °C, and 1 bar and −251.8 °C, respectively. The overall energy consumption per kg of CO₂ separated (MJ/kgCO₂₎, was found to follow the order: 8.19–11.21 for monoethanolamine (MEA) absorption; 1.81–8.93 for membrane separation; 1.53–5.69 for pressure swing adsorption; and 0.81–3.35 de-sublimation process. Each process was evaluated and compared on the bases of electricity demand, cooling water usage, high-pressure steam usage, and refrigeration energy requirements. Finally, the advantages and disadvantages were discussed and the feasibility and sustainability of the processes for application in the production of liquid hydrogen were assessed.     

西藏燕麦主要种植区灌溉定额空间分布及影响因素

燕麦为西藏自治区典型牧草之一,由于种植区地域辽阔,灌溉试验结果受限,西藏燕麦主要种植区的灌溉定额尚不明确。本文在西藏燕麦主要种植区内选取28个典型站点进行资料收集,遵循农业气候相似原则进行区域划分,基于水量平衡法揭示了西藏燕麦主要种植区灌溉定额的空间分布特征,并根据统计学原理分析了其影响因素。研究表明:燕麦主要种植区的灌溉定额呈由西藏中部至东部呈现先递增后递减的趋势,50%水文年下的燕麦灌溉定额在56~265 mm之间变化。降雨量是影响研究区内燕麦灌溉定额的主要因素(R²为0.515),ET₀次之(R²为0.152);其它气象因素中,日照时数对研究区燕麦灌溉定额影响较大(R²为0.462),且呈正相关关系;相对湿度对燕麦灌溉定额影响较小。西藏燕麦主要种植区的灌溉定额及其空间分布可为西藏自治区灌溉用水管理提供支撑。     

Modeling and thermodynamic analysis of thermal performance in self-pressurized liquid hydrogen tanks

Liquid hydrogen (LH₂) is one of the most economic methods for large-scaled utilization of hydrogen energy. However, safe operation and storage of LH₂ relies on accurate prediction of the pressure rise and adequate investigation on thermal behaviors inside LH₂ tank. In light of this, a modified thermal multi-zone model (TMZM) considering heat and mass transfer between vapor and liquid is developed in this paper. The model has a maximum relative error of 4.67% in predicting pressure rise against the experimental results from NASA. A thermodynamic analysis method is proposed to clarify the influences of key parameters including the temperature, compressibility factor and density of vapor, and working conditions including heat leakage and initial superheated degree on the pressurization rate. The results indicate that temperature of vapor in the ullage and vapor-liquid interfacial mass transfer rate are two main parameters determining the pressurization rate, and the effects of the two parameters are different between different stages. The distinction of stages depends on heat leakage and initial superheated degree. For the working condition with an initial filling rate of 50% and a heat leakage of 10 W, temperature of vapor is the parameter dominates pressurization rate during 96.8% of the whole self-pressurization process. Heat leakage also has a vital impact on the distinction of stages, when heat leakage increases to 80 W, the temperature of vapor dominating stage will reduce to 46.4%. Furthermore, pressurization rate is sensitive to initial superheated degree in the ullage. An increase of 4 K of the initial superheated degree leads to a 53.3% decrease of the pressurization rate. This study provides a useful method for the reliable design and quick optimization of high performance LH₂ tanks.