高强度螺栓连接抗力不定性影响因素的模糊聚类分析

本文应用模糊聚类分析理论,对钢结构中高强度螺栓连接的抗力不定性影响因素进行了计算和归类,在此基础上提出了抗力不定性概率统计分析的数学模型及简化的实用性模型。本文结论为高强度螺栓连接的可靠度分析奠定了基础。     

偏铁酸钠催化合成共轭亚油酸

以红花菜籽油中亚油酸为原料,偏铁酸钠为催化剂,在单因素试验的基础上,选取反应温度、反应时间、催化剂用量为考察因素,以异构化产物共轭亚油酸(CLA)转化率为响应值,通过响应面分析法对异构化反应进行优化,并建立相应的回归模型,试验结果表明,红花菜籽油中亚油酸异构化为CLA的最佳工艺为：反应温度195℃、反应时间4.7 h、催化剂用量0.6 g,在此条件下得到CLA转化率为92.90%,与预测值93.92%相比,误差为1.02%。然后再通过脲素包合纯化、经2%的H₂SO₄-CH₃OH溶液甲酯化后,用气相色谱-质谱联用仪检测CLA含量为64.27%。     

基于CiteSpace的核素扩散迁移问题的研究发展趋势分析

为探索放射性核素在环境中迁移扩散的研究热点与发展趋势,以CNKI上2001～2020年的相关文献为基础,应用CiteSpace软件进行文献计量处理,从作者合作、机构发文情况、关键词共现与聚类分析和关键词突现等方面对国内核素扩散迁移问题的科研力量、研究热点、发展趋势和研究前沿进行分析.结果表明:核素扩散迁移领域的研究成果...     

薄壁带筋轮座注射成型表面气纹形成机理与缺陷消除

以某薄壁带筋轮座件为研究对象,针对零件表面气纹缺陷,基于Moldflow仿真对熔体流动规律和气纹的形成机理进行分析,利用金相显微镜对熔体结合位置冷却后的微观形貌进行观测,对结合位置的气泡与表面气纹的联系进行了分析,结果表明在熔体结合位置缺少相应排气时,熔体前端的空气难以排出,易产生气纹;基于表面气纹缺陷分析,结合模具和...     

Hydrogen peroxide and applications in green hydrocarbon nitridation and oxidation

Basic organic chemicals and high value-added products are mainly produced by hydrocarbon nitridation and oxidation.However,several drawbacks limit the application of the traditional oxidation and nitrida-tion technologies in the future,such as complex processes,poor intrinsic safety,low atom utilization,and serious environmental pollution.The green nitridation and oxidation technologies are urgently needed.Hydrogen peroxide,a well-known green oxidant,is widely used in green hydrocarbon oxidation and nitridation.But its industrial production in China adopts fixed-bed technology,which is fall behind slurry-bed technology adopted by advanced foreign chemical companies,limiting the development of hydrogen peroxide industry and green hydrocarbon nitridation or oxidation industry.This article reviews the industrial production technologies of hydrogen peroxide and basic organic chemicals such as capro-lactam,aniline,propene oxide,epichlorohydrin,phenol,and benzenediol,especially introduces the green production technologies of basic organic chemicals related with H2O2.The article also emphasis on the efforts of Chinese researchers in developing its own slurry-bed technology of hydrogen peroxide produc-tion,and corresponding green hydrocarbon nitridation or oxidation technologies with hydrogen perox-ide.Compared with traditional nitridation or oxidation technologies,green production technologies of caprolactam,propene oxide,epichlorohydrin,and benzenediol with hydrogen peroxide promote the nitrogen atom utilization from 60％ to near 100％ and the carbon atom utilization from 80％ to near 100％.The waste emissions and environmental investments are reduced dramatically.Technological blockade against the green chemical industry of China are partially broken down,and technological upgrade in the chemical industry of China is guaranteed.     

Minimising non-selective defects in ultrathin reduced graphene oxide membranes with graphene quantum dots for enhanced water and NaCl separation

Reduced graphene oxide (rGO) membranes have been intensively evaluated for desalination and ionic sieving applications,benefiting from their stable and well-confined interlayer channels.However,rGO membranes generally suffer from low permeability due to the high transport resistance resulting from the narrowed two-dimensional (2D) channels.Although high permeability can be realized by reducing membrane thickness,membrane selectivity normally declines because of the formation of non-selective defects,in particular pinholes.In this study,we demonstrate that the non-selective defects in ultrathin rGO membranes can be effectively minimised by a facile posttreatment via surface-deposition of graphene quantum dots (GQDs).The resultant GQDs/rGO membranes obtained a good trade-off between water permeance (14 L·m-2·h-1·MPa-1) and NaCl rejection (91％).This work provides new insights into the design of high quality ultrathin 2D laminar membranes for desalination,molecular/ionic sieving and other separation applications.     

氯化铁改性椰壳活性炭去除2,4-二氯苯酚的吸附性能研究

以椰壳活性炭为原料,进行氯化铁改性,探究其对2,4-二氯苯酚吸附性能影响的研究。通过静态吸附实验得到了最佳改性条件,使得对2,4-二氯苯酚吸附性能进一步得到提升,并结合实际水体酸碱性探究,对模拟废水实验进行了pH探究,进一步优化了材料对实际水体的适用性。研究表明,氯化铁浓度为0.8 mol/L、改性时间为24 h条件下改性得到的炭材料(BC-F)吸附性能最佳,吸附剂的最佳使用量应为0.04 g,吸附过程应在弱酸或碱性环境中进行,在实际水体中实用性较好;且该吸附过程符合准一级动力学和Freundlich等温吸附方程,以化学吸附为主。     

不同季铵盐作用下的CO2水合物相平衡

CO₂气体水合物形成热力学性质是实施海水淡化、沼气纯化、碳捕集和封存、能源利用、天然气储存等技术的关键。采用恒容温度搜索法,在温度272.75~294.35 K,压力0.35~4.50 MPa的范围内,探究了四种季铵盐促进剂对CO₂气体水合物相平衡的影响。结果表明,相同条件下,季铵盐作用下CO₂水合物的相平衡温度由高到低分别为：四丁基氟化铵（TBAF）>四丁基溴化铵（TBAB）>四丁基氯化铵（TBAC）>苄基三乙基氯化铵（TEBAC）。基于Clausius-Clapeyron方程,计算了不同体系的相变潜热,探讨了其对水合物稳定性的影响。可以看出,水合物的相平衡压力对数与温度倒数呈线性关系,其中,TBAF、TBAB作用下的CO₂水合物相变潜热相接近且明显高于其他季铵盐,说明其促进效果最好,所对应的水合物生成条件也最为温和。利用Chen-Guo模型,结合PR状态方程和改进Joshi经验活度模型,分别计算了TBAF、TBAB、TBAC和TEBAC作用下CO₂水合物热力学相平衡数据,计算结果与实验数据吻合良好,最大平均相对误差为7.50%。