短波地空通信链路电磁计算与仿真

基于短波地空通信链路复杂特性是研究短波地空通信的关键和难点等问题.介绍了短波地空通信链路特性,探讨了进行短波地空通信链路电磁计算的主要参数,并利用ITS软件系列进行短波地空链路的电磁仿真并得出计算结果.计算结果可显示到地理图上,协助拟定频率规划方案,并可得出相应的电磁性能.     

Bonding performance of melamine-urea-formaldehyde and phenol-resorcinol-formaldehyde adhesives in interior grade glulam

Wood moisture content (MC) affects the glued laminated beam (glulam) bonding strength. Selected adhesives were Phenol-Resorcinol-Formaldehyde (PRF) and Melamine-Urea-Formaldehyde (MUF) adhesives with 1, 1.5 and 2% (w/w) carboxymethyl cellulose (CMC) formic acid solutions. Douglas fir (pseudotsuga menziesii) from North America was used in the test. The bonding behavior of these adhesives with wood at 12 and 18% MC were investigated. The study focused on the effect of 18% MC on shear strength performance of MUF and PRF adhesives and optimizing the formula of CMC formic acid solution. Compressive shear strength of wood with MUF adhesive with 2% (w/w) formic acid solution at 12 and 18% MC stabilized at 10.6 and 10.0 MPa, respectively, which were 17 and 16% higher than that with PRF adhesive at the same condition. At 12–18% MC, MC had a little effect on bonding strength. However, 18% MC wood with PRF adhesive had 52.2% less initial strength increasing rate than that of 12% MC wood. 18% MC wood with MUF adhesives with 1, 1.5 and 2% (w/w) CMC formic acid solutions had 16.0, 15.5 and 27.0% less initial strength increasing rates than that of 12% MC wood, respectively. MUF adhesive using 2% CMC formic solution required the shortest press time at 12 and 18% MC about 1.6 and 2.7 h, respectively. The strength of PRF adhesive was significantly affected by wood MC and enough press time is essential for the proper bonding strength.     

平衡纸二次浸胶工艺及其可行性分析探讨

二次浸胶工艺是一项技术革新,其在平衡纸浸渍过程中的应用在一定程度上提高了平衡纸的性能,并且降低了地板制造成本.     

乏燃料后处理厂核材料衡算仿真

为优化乏燃料后处理设施的核材料衡算,寻找核材料衡算不平衡差（MUF）的主要因素,采用基于数值模拟的系统仿真方法,以核材料衡算视角构建乏燃料后处理设施核材料衡算仿真模型。改变模型工艺参数仿真不同规模的后处理设施中各环节核材料的流通量,然后以正态分布随机变量模拟各铀钚衡算测量点的随机误差,将这些带有随机特征的测量值叠加相应测量的系统误差作为核材料的仿真测量值。仿真计算结果表明,1AF中Pu、U含量测量的系统误差的方差分别占整体MUF方差的50%、40%以上,是主要误差来源。1AF的体积测量误差较小,占比MUF方差小于15%。废液中U和Pu含量很低,U和Pu含量测量的误差分别为10%和30%,对MUF方差影响不大,占比MUF方差分别小于3%和1%,废液的体积测量误差较小,占比MUF方差小于1%。U和Pu产品测量误差的方差占比MUF方差界于1AF和废液的测量之间,不是MUF误差的主要来源。     

ITU-R P.434计算F2层基本最高可用频率与实测值的比较

利用我国2011年1月和7月10条斜测电路的F₂层基本最高可用频率(MUF)月中值数据,与ITU-R P.434方法计算的F₂层基本MUF进行了比较,分析了该方法在中国地区的适用性。结果表明:ITU-R P.434方法在中国地区具有较好的适用性,但在某些电路的个别时段偏差较大。其中,1月份在中纬地区日出时段,该方法给出的基本MUF与月中值相比偏低20%~30%,在日落时段则偏高20%~30%;低纬地区夜间时段两者的相对偏差较大,最大值达到40%.7月份,该方法的结果与各条电路的实测结果基本一致,相对偏差在-10%~20%之间。上述结果对短波通信的选频等具有一定的指导意义。     

Effects of surface modification of self‐healing poly(melamine‐urea‐formaldehyde) microcapsules on the properties of unsaturated polyester composites

Poly(melamine‐urea‐formaldehyde) (MUF) microcapsules used as self‐healing component of composites were prepared by in situ polymerization. The surface of MUF microcapsules was modified by 3‐aminopropyltriethoxy silane‐coupling agent (KH550). The interfacial interactions between MUF microcapsules and KH550 were studied by Fourier transform infrared spectra (FTIR). FTIR results show that the silane‐coupling agent molecule binds strongly to the MUF microcapsules surface. A chemical bond (Si? O? C) is formed by the reaction between the Si? OH and the hydroxyl group of MUF microcapsule. This modification improves the thermal properties of microcapsules. Optical microscope (OM) and scanning electron microscope (SEM) show that a thin layer is formed on the surface of MUF microcapsules. The interfacial adhesion effect between MUF microcapsules and unsaturated polyester matrix was investigated. MUF microcapsules disperse evenly in the composites. When crack propagated, the microcapsules were broken and the repair agent flowed from the microcapsules to react with the curing agent. Then the crosslinking structure was formed and the composite was repaired. The tensile properties, impact properties, and dynamic mechanical properties of composites have been evaluated. The results indicate that the silane‐coupling agent plays an important role in improving the interfacial performance between the microcapsules and the matrix, as well as the mechanical properties of the composites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

平衡纸二次浸胶工艺及其可行性分析探讨

二次浸胶工艺是一项技术革新,其在平衡纸浸渍过程中的应用在一定程度上提高了平衡纸的性能,并且降低了地板制造成本。     

高温气冷堆核材料衡算方法研究

高温气冷堆（HTR）采用球形包覆颗粒燃料元件,采用不停堆换料运行方式。因此,其运行方式、燃料元件的形式、换料方式等与压水堆核电站差别较大。HTR的特点决定了其核材料的监管方式既不同于传统压水堆,也不同于散料核设施,不易采用传统压水堆的件料管理模式和散料核设施的散料管理模式进行核材料衡算管理。为此,本文针对HTR核材料管理,提出一种适于HTR核材料衡算及其不明损失量（MUF）评价的方法。该方法根据HTR的燃料元件、运行方式和换料方式的特点,综合考虑件料和散料衡算两种模式,通过对HTR核材料衡算平衡区合理划分、关键测量点设置和实物盘存方式选取等的研究,最终选取件料+散料的衡算模式进行核材料衡算管理和评估,为HTR核材料监管提供技术基础。目前,该方法已应用于我国HTR的核材料管理,取得了预期的效果。     

三聚氰胺添加方式对MUF胶粘剂性能的影响

以三聚氰胺作为脲醛树脂(UF)的共聚改性剂制备MUF(三聚氰胺甲醛树脂)胶粘剂。探讨了三聚氰胺的添加方式对MUF胶粘剂性能的影响,同时对其固化特性、分子结构和耐热性等进行了分析。结果表明:三聚氰胺2次投料法可有效降低MUF胶粘剂的甲醛释放量,但其胶接强度也随之下降;同时,该MUF固化体系的外推固化温度、表观活化能和反应级数均有所增加,耐热性降低;另外,2次投料体系使MUF的相对分子质量降低、相对分子质量分布变宽。     

三聚氰胺改性脲醛树脂胶黏剂在E0级强化木地板基材中的使用特性分析

生产E0级强化木地板基材的三聚氰胺改性脲醛树脂胶黏剂对热压温度和热压时间非常敏感。当热压温度和热压时间在较小范围内波动时,使用此类胶黏剂制造的中/高密度纤维板内结合强度和24h吸水厚度膨胀率均变化较大。少量固化剂的添加也会影响强化木地板基材的两项指标。相同工艺制造的不同批次的胶黏剂其凝胶时间变化较大,不同的凝胶时间应对应不同的热压温度和热压时间。