SiO2纳米孔超级绝热材料

对SiO2纳米孔超级绝热材料的研究进展进行了概述,并对SiO2纳米孔超级绝热材料的孔、密度和导热系数等性能特征进行了描述;与热流在多孔材料中传播方式相似,纳米孔超级绝热材料的传热有对流、辐射和热传导三种基本方式：对SiO2纳米孔超级绝热材料的制备方法及应用前景也进行介绍和分析。     

SiO2气凝胶提高岩棉保温性能的试验研究

以无水乙醇为溶剂,SiO_2气凝胶为溶质,制取SiO_2气凝胶改性溶液。采用浸润及常压干燥制备岩棉/SiO_2气凝胶复合板,研究SiO_2气凝胶的质量分数和浸润时间对岩棉/SiO_2气凝胶复合板的短期吸水量,导热系数以及抗压强度的影响。并选取某办公楼建筑为研究对象,利用建筑能耗模拟软件DeST,研究岩棉/SiO_2气凝胶复合板在以西安为代表的寒冷地区的建筑能耗。结果表明:随着SiO_2气凝胶的质量分数的增加,岩棉/SiO_2气凝胶复合板的短期吸水量逐渐变小,导热系数逐渐减小,其抗压强度略有提高。与未进行保温措施相比,厚度为30 mm的岩棉/SiO_2气凝胶复合板能耗节能率大于25%。     

不同超临界干燥工艺制备SiO2气凝胶的研究

以正硅酸乙酯为硅源,采用酸碱二步溶胶–凝胶法及CO_2超临界干燥工艺制备SiO_2气凝胶复合材料,研究不同超临界干燥工艺对SiO_2气凝胶制备的影响,结果表明液态CO_2置换干燥工艺和超临界CO_2萃取干燥工艺的干燥时间、乙醇回收率、乙醇分离效率等相差不大,但超临界CO_2萃取干燥工艺制备的产品导热系数优于液态CO_2置换干燥工艺,且工艺过程简单易操作,更适合规模化生产。     

SiO2气凝胶调湿性能的实验研究

对一种纳米级材料———SiO2气凝胶的吸、放湿性能及规律进行了实验研究,并与普通变色硅胶的调湿性能进行了实验比较.初步实验结果表明,SiO2气凝胶具有较好的调湿性能.     

SiO2气凝胶性能研究及其在建筑保温中的应用

简要介绍超临界和常压干燥制备SiO2气凝胶的工艺技术,对两种工艺制备的气凝胶性能指标进行比较,结果表明:超临界干燥工艺制备的SiO2气凝胶产品性能稳定,但成本高;以水玻璃为原料,采用常压干燥工艺制备的SiO2气凝胶产品具有较好的性价比.并进一步分析SiO2气凝胶在建材领域应用存在的问题及解决途径.     

纳米SiO2气凝胶/水泥复合隔热板的制备与性能研究

以白色硅酸盐水泥作为主要胶凝材料,采用注浆成型、常温常压干燥工艺制备新型无机纳米SiO2气凝胶/水泥复合隔热板(ACP).并通过FT-IR、氮气吸附等方法系统研究了SiO2气凝胶掺量对ACP微观结构和热物性参数的影响.结果表明:气凝胶掺量与导热系数、密度呈线性负相关,而与平均孔径和比表面积总体呈正相关.此外,其吸附/脱...     

纳米孔超级绝热材料的原理及制备

超级绝热材料的概念起源于20世纪90年代初期。随着纳米材料的研究在国内外的不断升温，纳米孔绝热材料的研究也不断向实用化与工程化发展。纳米孔超级绝热材料的设计原理仍然是依据热流在多孔材料中传播的3种基本方式，同时需考虑孔隙尺寸应小于空气分子的平均自由程（≤70nm）。纳米孔超级绝热材料的制备目前普遍采用将SiO2气凝胶进行增强的方法。     

原材料品质对SiO2气凝胶毡性能影响的研究

以正硅酸乙酯为硅源,采用酸碱二步溶胶–凝胶法,分别选用不同品质的正硅酸乙酯、玻璃纤维毡、乙醇、纯水等原材料制备SiO_2气凝胶复合材料,研究不同品质的原材料对SiO_2气凝胶复合材料性能的影响,结果表明,玻璃纤维毡的最佳密度范围为130～140 kg/m~3,硅酸乙酯-40和95%的乙醇等品质稍差的原材料也能制备出合格的气凝胶产品,其中制备出的SiO_2气凝胶复合绝热毡样品中导热系数最低,为0.0167 W/(m·K)。     

矿渣碱激发胶凝材料早期性能的响应曲面研究

基于响应曲面通用旋转组合设计法,选择碱激发剂模数、碱激发剂浓度、激固比作为配比变量,制定了矿渣碱激发胶凝材料制备的试验方案.测试了矿渣碱激发胶凝材料的凝结时间、2h抗压强度,观察了试件的表面特性.通过数据处理得到了各配比变量与材料初凝时间、2h抗压强度的响应曲面,分析了各配比变量对材料初凝时间及2h抗压强度的影响规律.结果表明:当碱激发剂模数为1.0~1.4,碱激发剂浓度为25%~30%(质量分数),激固比为0.50(质量比)时,各组分能充分发挥协同作用,使材料具有良好的早期性能,满足抢修工程应用的基本要求.     

Enhanced electrocoagulation–electroflotation for turbidity removal by Opuntia ficus indica cladode mucilage

The optimisation of the electrocoagulation‐electroflotation (EC‐EF) process assisted by the mucilage of the Opuntia ficus indica (OFI), on the turbidity removal was performed through the response surface methodology (RSM). For a solution of 300 mg/L of silica gel, high turbidity removal (93.14% ± 1.31) was obtained under the optimal conditions of 2.5 mg/L, 21.2 V, 9.65 and 2.61 mS/cm for the mucilage concentration, voltage, pH and conductivity, respectively, this experimental value was close to the predicted value of 92.96% ± 0.3. OFI mucilage increases turbidity removal efficiency and reduces specific energy consumption at a fixed current density. The turbidity removal of the EC‐EF process was improved by 30.94% compared with the conventional EC–EF (EC–EF without OFI mucilage) which shows 62.02% ± 1.45 of turbidity removal.     

Optimization of anaerobic acidogenesis of an aquatic plant, Canna indica L., by rumen cultures

Anaerobic acidogenesis of Canna indica L. (canna) by rumen cultures was investigated in this study. Fractional factorial design (FFD) was used to explore the roles of the growth factors such as substrate concentration and pH in such a bioconversion, whereas response surface methodology (RSM) was employed for optimizing this acidogenic process. The optimum substrate concentration and pH for the acidogenesis of canna were found to be 8.2 g VSl(-1) and 6.6, respectively, and the corresponding degradation efficiency of canna was 52.3%. Volatile fatty acid yield peaked at 0.362 g g(-1)VS degraded at a substrate concentration of 6.9 g VSl(-1)and pH 6.7. These results were confirmed by the experimental results.     

A new method to investigate the energy absorption characteristics of thin-walled metal circular tube using finite element analysis

A numerical study is made to investigate the energy absorbing rule of thin-walled metal circular tube made of three different materials (steel, copper, aluminum) by using response surface methodology (RSM). At the same time, the application prospect of RSM in terms of the research on the energy absorption rule of energy absorption structure can be explored. The test result shows that, the compression process of thin-walled metal circular tube can be divided into three stages: elastic stage, yielding plateau stage, compact stage; To get the greatest value of average plateau force (APF) , a tube with a shorter height and thicker wall should be adopted; To get the greatest length energy absorption (LEA), a tube with thicker wall should be adopted and the ratio of its height and diameter should be as big as possible; To get the greatest specific energy absorption (SEA), a tube with a thicker wall should be adopted and the ratio between its height and diameter should be as big as possible. Thus, it can be seen that, RSM is an advanced experiment design method, and it can be widely used in the research on the energy absorption characteristics of thin-walled metal circular tube and has a promising application prospect in the development of new energy absorbing material and structure.     

Prediction of flyrock induced by mine blasting using a novel kernel-based extreme learning machine

Blasting is a common method of breaking rock in surface mines. Although the fragmentation with proper size is the main purpose, other undesirable effects such as flyrock are inevitable. This study is carried out to evaluate the capability of a novel kernel-based extreme learning machine algorithm, called kernel extreme learning machine (KELM), by which the flyrock distance (FRD) is predicted. Furthermore, the other three data-driven models including local weighted linear regression (LWLR), response surface methodology (RSM) and boosted regression tree (BRT) are also developed to validate the main model. A database gathered from three quarry sites in Malaysia is employed to construct the proposed models using 73 sets of spacing, burden, stemming length and powder factor data as inputs and FRD as target. Afterwards, the validity of the models is evaluated by comparing the corresponding values of some statistical metrics and validation tools. Finally, the results verify that the proposed KELM model on account of highest correlation coefficient (R) and lowest root mean square error (RMSE) is more computationally efficient, leading to better predictive capability compared to LWLR, RSM and BRT models for all data sets.     

硅溶胶/聚丙烯酸酯复合乳液的制备及其性能研究

以正硅酸乙酯(TEOS)水解缩合后形成的硅溶胶代替商用硅溶胶,采用乳液聚合法合成了硅溶胶/聚丙烯酸酯复合乳液.研究了TEOS水解pH值、乳液聚合温度、TEOS用量(质量分数)等因素对复合乳液性能的影响,并用傅里叶红外光谱(FTIR)仪和透射电子显微镜(TEM)对复合乳液微观结构进行分析.结果表明:最佳TEOS水解pH值为5.7～6.5,最佳乳液聚合温度为75℃;随着TEOS用量的增大,复合乳液的稳定性增强,乳液涂膜硬度也增大,但当TEOS用量过大时,复合乳液发生沉降,涂膜也发生开裂,故TEOS的最佳用量为9%～13%;TEOS在水中发生了水解缩合反应,复合乳液是SiO2和聚丙烯酸酯的复合物;TEOS水解缩合产生的SiO2可起到稳定剂的作用,因此乳液聚合过程中不添加其他稳定剂.     

Probabilistic analysis of ultimate seismic bearing capacity of strip foundations

This paper presents a reliability analysis of the pseudo-static seismic bearing capacity of a strip foundation using the limit equilibrium theory. The first-order reliability method (FORM) is employed to calculate the reliability index. The response surface methodology (RSM) is used to assess the Hasofer–Lind reliability index and then it is optimized using a genetic algorithm (GA). The random variables used are the soil shear strength parameters and the seismic coefficients (k_h and k_v). Two assumptions (normal and non-normal distribution) are used for the random variables. The assumption of uncorrelated variables was found to be conservative in comparison to that of negatively correlated soil shear strength parameters. The assumption of non-normal distribution for the random variables can induce a negative effect on the reliability index of the practical range of the seismic bearing capacity.     

微硅粉改性磷酸镁水泥砂浆试验研究

以过烧镁砂和磷酸二氢铵为主要原料,掺入少量微硅粉和石英砂来制备磷酸镁水泥(MPC)砂浆,研究了微硅粉掺量对磷酸镁水泥砂浆性能的影响,并采用X射线衍射(XRD)和扫描电镜(SEM)等对其水化产物进行分析.结果表明:随着微硅粉掺量的增加,磷酸镁水泥砂浆的凝结时间和流动性呈下降趋势,而早期强度先增后减;微硅粉的掺入可大幅提高磷酸镁水泥砂浆的耐水性;微硅粉的掺入大幅提高了磷酸镁水泥砂浆水化产物结构的密实性,同时生成了麻花状硅酸镁晶体,该晶体将鸟粪石和未反应的MgO连接在一起,提升了磷酸镁水泥砂浆的力学性能和耐水性.     

Process modeling and analysis of palm oil mill effluent treatment in an up-flow anaerobic sludge fixed film bioreactor using response surface methodology (RSM)

In this study, the interactive effects of feed flow rate (QF) and up-flow velocity (V up) on the performance of an up-flow anaerobic sludge fixed film (UASFF) reactor treating palm oil mill effluent (POME) were investigated. Long-term performance of the UASFF reactor was first examined with raw POME at a hydraulic loading rate (HRT) of 3 d and an influent COD concentration of 44300 mg/l. Extreme reactor instability was observed after 25 d. Raw POME was then chemically pretreated and used as feed. Anaerobic digestion of pretreated POME was modeled and analyzed with two operating variables, i.e. feed flow rate and up-flow velocity. Experiments were conducted based on a central composite face-centered design (CCFD) and analyzed using response surface methodology (RSM). The region of exploration for digestion of the pretreated POME was taken as the area enclosed by the feed flow rate (1.01, 7.63 l/d) and up-flow velocity (0.2, 3 m/h) boundaries. Twelve dependent parameters were either directly measured or calculated as response. These parameters were total COD (TCOD) removal, soluble COD (SCOD) removal, effluent pH, effluent total volatile fatty acid (TVFA), effluent bicarbonate alkalinity (BA), effluent total suspended solids (TSS), CH4 percentage in biogas, methane yield (Y M), specific methanogenic activity (SMA), food-to-sludge ratio (F/M), sludge height in the UASB portion and solid retention time (SRT). The optimum conditions for POME treatment were found to be 2.45 l/d and 0.75 m/h for QF and V up, respectively (corresponding to HRT of 1.5 d and recycle ratio of 23.4:1). The present study provides valuable information about interrelations of quality and process parameters at different values of the operating variables.     

高活性偏高岭土及粉煤灰对碱骨料反应的抑制作用

为研究偏高岭土及粉煤灰对活性骨料膨胀的抑制作用及机理,采用快速砂浆棒法,研究了用石英玻璃为骨料,以5%,10%,15%,20%,25%高活性偏高岭土等质量取代水泥或以10%,20%,30%,35%,40%,45%粉煤灰等质量取代水泥的砂浆棒膨胀率,并采用扫描电镜对其机理进行了分析.结果表明:高活性偏高岭土抑制碱骨料反应(ASR)具有少量高效的特点,而粉煤灰要在等质量取代水泥35%及以上时才能有效抑制ASR;高活性偏高岭土颗粒明显小于粉煤灰颗粒,且具有更高的活性,掺入水泥砂浆后所生成的胶凝材料更加致密.