单涂层微波吸收材料参量的匹配机制分析

通过分析单涂层吸波材料内电磁波传输损耗机制,提出了单涂层吸波匹配设计的基本原则和匹配配解析式,得出了电磁参量取值规律,此外,还分析了电磁参量扰动对吸波性能的影响。     

关于单层门式刚架结构的设计优化的思考

随着经济的迅速发展,市场对纸和纸板的需求不断增加,纸和纸板的生产量迅速增加,因此造纸厂需要快速建造仓库对浆板和成品纸进行储存,而单层门式刚架结构刚好符合这类仓库的要求.本文结合当前单层门式刚架结构(以下简称“门式刚架”)的发展现状,从实际工程的门式刚架设计工作经验出发,分析了门式刚架结构的主构件设计、围护构件的优化设计...     

纸基吸波材料的制备及其电磁性能探究

通过造纸法制备了一种可用于制备吸波蜂窝的纸基吸波材料,分别选用短切碳纤维(CF)、短切碳化硅纤维(SCF)和碳纳米管(CNT)作为吸波剂,对位芳纶浆粕(PPTA)作为基体,对比了不同吸波剂及其用量对纸基吸波材料电磁参数及吸波性能的影响。结果显示,吸波剂用量(对绝干基的质量分数)在0.1%~50%的范围内,SCF-PPTA纸基吸波材料的复介电常数实部小于CF-PPTA和CNT-PPTA纸基吸波材料的。当吸波剂用量大于3%时,CNT-PPTA纸基吸波材料的介电损耗大于另外2种材料的。当吸波剂用量分别为1%、20%和3%时,对应CF-PPTA、SCF-PPTA和CNT-PPTA纸基吸波材料的反射率最低分别可达-15.08、-28.49和-13.69d B,此时纸基吸波材料对应的厚度分别为2.45、4.35和2.98 mm。     

单层砖柱厂房的抗震设计研究

随着我国工业经济的快速发展,建筑行业对于工厂厂房的抗震设计越来越关注了,特别是南方地区的工厂厂房的抗震设计。在南方的中小型企业中大多采用单层砖柱厂房,这类的厂房具有构造简单、选料比较低廉、施工比较简单,工期也比较短等特点。南方地区相对于北方地区来说属于地震多发区,所以要特别注意厂房的抗震功能,而砖柱厂房主要是由砖柱墙作为承重的,所选择的材料比较脆,相比混凝土来说抗震能力比较弱;相比民用房来说,砖柱厂房的内部比较空旷,而且隔墙之间的间距也比较大,所以抗地震倒塌能力就很弱。所以我们必须在认识到砖柱厂房的震害特点的基础上针对其弱点提出可行的具体措施,提高厂房的抗震能力。     

以DMTNF为电子传输材料的单层结构有机光导体的研究

本论文系统地研究了在由DMTNF（TNF的一种衍生物）为电子传输材料,DEH为空穴传输材料和Y－TiOPc或H2Pc为电荷产生材料构成的单层结构有机光导体的静电照相性能。研究结果表明光导体的量子收率和感光度与CGM浓度和充电极性有很大依赖关系。Y－TiOPc光导体的最高峰在800nm处,半衰曝光量为0.588μJ/cm^2（正充电）,0.828μJ/cm^2（负充电）：H2Pc光导体正充电最高峰在780nm处,半衰曝光量为1．50μJ/cm^2（正充电）,半衰曝光量为1．97μJ/cm^2（负充电）。     

阻抗阶跃渐变层结构纤维素/Ti3C2Tx气凝胶材料的制备及其吸波性能

为拓宽吸波频段,获得高效吸波材料,以纤维素纳米纤维（CNF）为骨架、二维过渡金属碳化物（Ti₃C₂T_x）为导电填料,制备了三维多孔气凝胶吸波材料。通过扫描电镜及透射电镜、红外光谱仪、X射线光电子能谱及衍射仪、矢量网络分析仪表征了其结构与各项性能。结果表明：基于气凝胶的多孔结构及Ti₃C₂T_x的导电损耗,使得CNF/Ti₃C₂T_x复合气凝胶具有吸波效能,改变Ti₃C₂T_x含量及气凝胶厚度可调节吸波带宽和峰值。根据三维电磁仿真软件CST STUDIO SUITE仿真模拟结果,制备Ti₃C₂T_x质量分数依次为1%、25%、50%的CNF/Ti₃C₂T_x复合气凝胶,在电磁波入射方向按照特征阻抗从大到小叠层构建阻抗阶跃渐变的多层复合结构吸波材料,该材料具有更好的阻抗匹配和衰减损耗性能,反射损耗最小可达-15.9 dB,有效吸收带宽覆盖整个X波段。     

新型紫外线吸收剂的合成及应用

通过重氮化、偶合和氧化成环反应合成了苯并三唑类紫外线吸收剂A,再经酰胺化反应合成了3只不同结构的紫外线吸收剂B、C、D,利用核磁共振谱和熔点测定等手段确证了其结构.采用DMF为溶剂,测量了4只紫外线吸收剂的最大吸收波长;分析了紫外线吸收剂质量浓度与吸光度的关系.将4只紫外线吸收剂经分散后用高温高压浸染法对涤纶织物进行抗紫外线整理,通过测量涤纶织物的UPF值及紫外线透过率,研究了其抗紫外线效果.结果表明:4只紫外线吸收剂均具有优异的抗紫外线性能.     

一种新的均三嗪类紫外线吸收剂ZLG-1的合成及表征

以三聚氯氰、间二甲苯为原料,经过Friedel-Craft反应,合成了2-氯-4,6-二（2＇,4＇二甲基苯基）-1,3,5-均三嗪（Ⅰ）,化合物Ⅰ在三氯化铝作用下再与间苯二酚反应,得到了2-（2’,4＇-二羟苯基）-4,6-二（2”,4”-二甲基苯基）-1,3,5-均三嗪（Ⅱ）．化合物Ⅱ在碱性条件下与环氧氯丙烷缩合并水解得到了该均三嗪类的紫外线吸收剂2-[2’-羟基-4’-（2＇＇＇,3＇＇＇）-二羟基丙烷氧基苯基]-4,6-二（2”,4”）-二甲基苯基-1,3,5-均三嗪（ZLG-1）,总收率为61．8％．讨论了反应温度、时间及反应物配比对各步反应收率的影响;并对化合物Ⅱ和ZLG-1的结构用IR、^1HNMR、MS进行了表征．由ZLG-1的UV光谱数据表明其紫外线吸收性能和三嗪-425相当．     

垂直管吸收器内泡式吸收热质传递过程分析

通过建立垂直管吸收器内泡式吸收过程中传热传质的数学物理模型,研究了泡式吸收方式;利用模型对吸收过程中出现的搅拌流、活塞流、泡状流等分别进行分析,获得了泡式吸收方式吸收过程中的一些传热传质特性.     

Shelf life extension of ground meat stored at 4 °C using chitosan and an oxygen absorber

The combined effect of chitosan (1%) and an oxygen absorber on shelf life extension of fresh ground meat stored at 4 °C was investigated. Parameters monitored over a 10‐day storage period were Total Viable Count (TVC), Pseudomonas spp., Brochothrix thermosphacta, lactic acid bacteria, Enterobacteriaceae, pH, thiobarbituric acid (TBA), colour, odour and taste. Microbial populations were reduced by 0.4–2.0 log CFU g^?1 for a given sampling day using either chitosan or the oxygen absorber, with the more pronounced effect being achieved by the combination of two. Thiobarbituric acid values for all samples increased during storage with the exception of samples treated with both chitosan and the oxygen absorber in which Thiobarbituric acid values decreased. Changes in pH values with time/different treatments were statistically insignificant. Colour parameters were affected by most treatments. On the basis of microbiological and sensory evaluation, a shelf life extension of 5–6 days was obtained for samples treated with the chitosan and the oxygen absorber combination.     

Effect of oxygen absorber on accumulation of free fatty acids in brown rice and whole grain wheat during storage

Because rapid rancidities of lipids in unpolished grains, such as brown rice and whole grain wheat, are often problematic, Suppressions of their lipid degradations during postharvest therefore important for their further utilization. In this study, effect of oxygen absorber on lipid deterioration in unpolished grain during storage was investigated. Kernels and flours of brown rice, rice with germ and whole grain wheat were stored for eight weeks at 4 °C and 26 °C, with and without oxygen absorber. Free fatty acids (FFAs) accumulation in the unpolished grains during storage was accelerated by polishing, milling and storage at high temperature (26 °C), because these storage conditions stimulated activities of their lipid hydrolyses. When oxygen absorber was added and the storage system was sealed, additional FFAs accumulations in these unpolished grains. Decreases both in absolute amounts of linoleic acids of the lipids and in total tocochromanols contained in these unpolished grains were depressed by addition of oxygen absorber to the storage system, which was confirmed by an anti-oxidative effect of oxygen absorber. These results suggested that introduction of oxygen absorber into the storage system of unpolished grains would be effective under the condition where their hydrolytic activities of lipids are suppressed.     

非局部反应扩散方程组解的整体存在与爆破

研究了一类具有非局部源的反应扩散方程组的初边值问题,首先利用上下解方法,构造出不同结构的上解,结合比较原理,得到解的整体存在的充分条件,其次利用特征函数和常微分方程的解,构造问题在有限时刻爆破的下解,得出了解在有限时间内爆破的充分条件．     

中固辊设计方法及其应用

本文从轧辊受均布载荷下挠度的微分方程出发,求得找曲线方程的一般解,以及如何根据边界条件确定常数。提出了固辊使用的两种最佳配对形式及其计算方法。     

一类Kirchhoff方程最小能量变号解的存在性

研究一类Kirchhoff方程最小能量变号解的存在性,其中非线性项满足指数增长.首先用Brouwer不动点定理证明M是非空的,其次寻找能量泛函在M中的极小值点,最后应用形变引理证明极小值点就是方程的最小能量变号解.方程中由于非局部项的出现导致通常的变分方法不再适用,因此将方程对应的能量泛函限制在M上,最终得到了方程变号解的存在性结果.     

Effect of oxygen absorber, nitrogen flushing, packaging material oxygen transmission rate and storage conditions on quality retention of raw whole unpeeled almond kernels (Prunus dulcis)

The present study investigated the effect of active packaging, nitrogen flushing, container oxygen barrier and storage conditions on quality retention of raw whole unpeeled almonds. Almond kernels were packaged in: a) polyethylene terephthalate//low-density polyethylene (PET//LDPE), and b) low-density polyethylene/ethylene vinyl alcohol/low-density polyethylene (LDPE/EVOH/LDPE) pouches under N_2, with or without an oxygen absorber, heat-sealed and stored for a period of 12 months. Quality parameters monitored were: peroxide value (PV), hexanal content, color, fatty acid composition and volatile compounds. PV ranged between 0.17 for fresh almonds and 9.22 meq O₂/kg oil for almonds packaged in PET//LDPE pouches under N₂ exposed to light at 20 °C after 12 months of storage. Respective values for hexanal were <28.5 μg/kg and 4.88 mg/kg. Polyunsaturated fatty acids (PUFA) and saturated fatty acids (SFA) increased with a parallel decrease of monounsaturated fatty acids (MFA) after 12 months of storage in all treatments. Likewise, volatile compounds such as aldehydes, ketones, alcohols, alkanes and aromatic hydrocarbons increased indicating enhanced lipid oxidation. Color was the parameter least affected. Use of the oxygen absorber provided a shelf life of at least 12 months for all samples irrespective of container oxygen barrier, lighting conditions and storage temperature.     

纺织用导电纤维及其应用

介绍导电纤维的分类,金属纤维、碳纤维和有机导电纤维的性能与主要特点以及导电纤维在几类纺织品中的应用,分析了各类导电纤维适宜的应用条件,并展望了纺织用导电纤维的发展前景。