可弱极大化拟凹映象的存在性

本文中,我们考察了具有有效决策K-上半连续、K-拟凹映象的存在性条件问题,并且给出了有关此类映象的一个定理,其中映象从仿紧凸空间到有序的拓扑向量空间.定理的证明用到了Brouwer不动点定理.     

钢筋套筒灌浆对接与搭接接头力学性能对比

为研究套筒灌浆对接和搭接接头力学性能差异,进行了24个对接和12个搭接接头单向拉伸试验,对比研究了接头的破坏形态、承载力、延性、力-位移曲线、套筒应变等.对接接头在加载过程中套筒中部灌浆料出现全截面开裂现象,加载结束发生了灌浆料从套筒中拔出破坏,搭接接头无以上现象.试验结果表明在套筒长度相同时,搭接接头承载力、总伸长率、刚度分别是对接接头的5~7倍、3~5倍、2~3倍,位移延性系数大于对接接头;在锚固长度相同时,搭接接头承载力、位移延性略大于对接接头,两者初始刚度差别不大,而搭接接头中后期刚度高于对接接头.对接接头套筒中部截面纵向受拉,而搭接接头加载前期受拉,后期受压,反映搭接接头对套筒抗拉强度要求较低;对接接头套筒中部截面环向受压,而搭接接头加载前期受压,后期受拉,说明搭接接头套筒中部对灌浆料约束作用大于对接接头.搭接接头力学性能优于对接接头,可运用于预制装配式结构钢筋连接.     

氮含量对500E抗震钢筋20MnVN组织和性能的影响

研究的Φ5 mm 500E抗震钢筋20MnVN（/%:0.19~0.20C,0.23~0.26Si,1.26~1.31Mn,0.016~0.023P,0.006~0.012S,0.10~0.11V,0.0038~0.0163N）的生产流程为50t顶底复吹转炉-LF-160 mm×160 mm方坯连铸-控轧控冷工艺。结果表明,随着钢中氮含量增加,500E 20MnVN钢盘条拉伸断口的韧窝变深,口径增大,组织中铁素体含量由63.6%增加至74.8%;增加氮含量有助于20MnVN钢盘条屈服强度、抗拉强度和伸长率的提高,当氮含量由0.0038%增加到0.0163%时,该钢屈服强度、抗拉强度和伸长率分别由513 MPa、650 MPa和10.5%提高到571 MPa、703 MPa和13.0%。分析了V-N微合金化和V（C,N）析出的强韧化机理。     

水电站运行本质安全问题探讨及解决策略

通过研究近年水电站运行工作相关的不安全事件,发现其原因可归纳为“安全意识、安全管理体系、人员习惯、设备健康、人员技能”五个方面的问题和不足。因此努力提升人员的安全意识、规矩意识,建立运转安全、高效、规范、有序的管理体系,培养和固化人员的安全行为习惯,改善设备的安全状态,提升人员的安全和业务技能是夯实运行工作的安全基础,依此便可达安全生产的目标。     

新型光降解体系对光/生物降解薄膜光降解行为的影响

研究了由光敏剂硬脂酸铁和抗氧剂 10 76组成的光降解体系的光 /生物双降解聚乙烯薄膜在紫外灯辐照下的断裂伸长率保留率、分子量、脆化期、诱导期等的变化规律。结果表明 ,硬脂酸铁具有促进光降解和抑制交联的双重作用 ;抗氧剂 10 76对薄膜光降解作用的影响没有硬脂酸铁显著 ;由它们组成的光降解体系具有较好的时控光降解效应 ,能使薄膜诱导期在较大时间范围内调控     

Progress toward the production of long-chain polyunsaturated fatty acids in transgenic plants

Long-chain PUFA such as eicosapentaenoic and docosahexaenoic acids are prevalent in fish oils, and these compounds have been demonstrated to play important roles in human health and nutrition. In particular, these n−3/omega-3 long-chain PUFA provide protection from cardiovascular disease and a collection of symptoms (termed metabolic syndrome) associated with progression toward type 2 diabetes and obesity. Within Western populations, a large increase in the occurrence of these conditions represents a major public health concern. Unfortunately, both marine fish stocks and (consequentially) consumption of fish oils are in steep decline, limiting the protective role of long-chain PUFA in human health. One alternative approach to the provision of these health-beneficial FA is via their synthesis in transgenic plants. This review will describe recent advances in the production of transgenic plant oils nutritionally enhanced to produce long-chain PUFA.     

甘肃省有色金属系统专门人才预测

本文根据预测原理,应用数学模型方法、预测甘肃省有色金属系统专门人才的需求数.     

定向冷冻明胶支架的原位细菌纤维素培养及支架中的细胞行为

本文以明胶(G)为原料,采用定向冷冻干燥法制备出定向明胶支架,通过原位培养技术在支架引入细菌纤维素(BC)纳米纤维网络,构筑出兼具微米多孔和纳米纤维结构的BC基定向微/纳支架,并使用场发射扫描电镜(FE-SEM)、激光共聚焦显微镜(CLSM)等对支架的微观结构生物学性能进行了表征。结果表明:与非定向支架的多孔结构相比,定向支架具有径向多孔和轴向通道结构,呈现各向异性,这种通道结构有利于氧气和营养物质的输送,能有效促进细胞生长。     

Microwave‐irradiated ring‐opening polymerization of D,L‐lactide under atmosphere

Poly(D ,L ‐lactide) (PDLLA) was synthesized by microwave‐irradiated ring‐opening polymerization catalyzed by stannous octoate (Sn(Oct)₂) under atmosphere. The effects of heating medium, monomer purity, catalyst concentration, microwave irradiation time, and vacuum level were discussed. Under the appropriate conditions such as carborundum (SiC) as heating‐medium, 0.15% catalyst, lactide with purity above 99.9%, 450 W microwave power, 30 min irradiation time, and atmosphere, PDLLA with a viscosity–average molecular weight (M_η) over 2.0 × 10⁵ and a yield over 85% was obtained. The dismission of vacuum to ring‐opening polymerization of D ,L ‐lactide (DLLA) under microwave irradiation simplified the process greatly. The temperature under microwave irradiation and conventional heating was compared. The largely enhanced ring‐opening polymerization rate of DLLA under microwave irradiation was the coeffect of thermal effects and microwave effects. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2244–2247, 2006