新型等离子弧焊炬

介绍了等离子体弧焊的工作原理,给出了新型等离子弧焊炬的结构。     

Gas Sensors Based on Nano/Microstructured Organic Field‐Effect Transistors

Benefiting from the advantages of organic field‐effect transistors (OFETs), including synthetic versatility of organic molecular design and environmental sensitivity, gas sensors based on OFETs have drawn much attention in recent years. Potential applications focus on the detection of specific gas species such as explosive, toxic gases, or volatile organic compounds (VOCs) that play vital roles in environmental monitoring, industrial manufacturing, smart health care, food security, and national defense. To achieve high sensitivity, selectivity, and ambient stability with rapid response and recovery speed, the regulation and adjustment of the nano/microstructure of the organic semiconductor (OSC) layer has proven to be an effective strategy. Here, the progress of OFET gas sensors with nano/microstructure is selectively presented. Devices based on OSC films one dimensional (1D) single crystal nanowires, nanorods, and nanofibers are introduced. Then, devices based on two dimensional (2D) and ultrathin OSC films, fabricated by methods such as thermal evaporation, dip‐coating, spin‐coating, and solution‐shearing methods are presented, followed by an introduction of porous OFET sensors. Additionally, the applications of nanostructured receptors in OFET sensors are given. Finally, an outlook in view of the current research state is presented and eight further challenges for gas sensors based on OFETs are suggested.     

Chemical composition of Cold Lake bitumen

A detailed analysis has been carried out on the deasphaltened Cold Lake bitumen using two different series of chromatographic separations followed by i.r., u.v., n.m.r. and computerized GC/MS studies of the separated fractions: saturates (21.3), monoaromatics (8.3), diaromatics (3.6), polyaromatics and non-specific polar compounds (24.35), acids (15.2), bases (6.38), and neutral nitrogen compounds (1.15% of bitumen). The acyclic paraffin content of the maltene is low but decidedly higher than in the related Athabasca bitumen, indicating that the Cold Lake bitumen suffered a less complete biodegradation. Straight-chain paraffins and the isoprenoids phytane and pristane are present. The mono- and diaromatic fractions were analysed by high-voltage, low-resolution mass spectrometry. The monoaromatic fraction contains alkylbenzenes, naphthenebenzenes and dinaphthenebenzenes in a ratio of approximately 1:1:1. The ratio for naphthalenes, acenaphthenes + dibenzofurans and fluorenes in the diaromatic fraction is approximately 1:0.9:0.6. The composition of Cold Lake bitumen closely resembles that of the Athabasca bitumen except that its asphaltene content is somewhat lower and its acidic and saturate content is slightly higher.     

Studies on the Stability of a La0.8Pr0.2NiAl11O19 Catalyst for Syngas Production by CO2 Reforming of Methane

CO₂ reforming of CH₄ was studied over a magnetoplumbite-type hexaaluminate La_0.8Pr_0.2NiAl₁₁O₁₉ catalyst, which showed very high activity for over 300 h without deactivation at 1023 K. This catalyst showed good resistance to carbon deposition, which in this reaction and in CH₄ decomposition was investigated by means of XPS and TEM. It is suggested that nano-tube-like carbon is an intermediate in this reaction and a spillover of carbon from crystalline Ni onto the hexaaluminate oxide occurred during the reaction.     

颞下颌关节内软组织的模拟方式

对比分析关节盘周围软组织的不同模拟方式对颞下颌关节（TMJ）内各结构的位移和应力分布的影响。选择一位无TMJ症状的志愿者,基于其头部CT扫描建立下颌骨和TMJ的3维有限元模型,关节盘周围软组织分4种方式进行模拟,关节盘及其周围软组织和关节软骨层间考虑接触,施加正中咬合的载荷。结果表明,将关节盘周围软组织建立为实体模型,使得关节盘偏离正常位置,且TMJ的功能区（髁突前斜面-关节盘中带-关节结节后斜面）都是低应力区。将双板区建立为实体模型,关节盘接近正常的位置,但仍没体现出TMJ的功能区应力较高的现象。用非线性缆索元来模拟关节盘前、后附着,关节盘处于正常位置,且髁突和颞骨的最大应力都出现在前部区域,关节盘的最大应力出现在中带。当研究重点是TMJ时,应该采用缆索元来模拟双板区和关节盘前附着,同时考虑关节盘与关节软骨层之间的接触。     

纳米SiO2超高强高流态混凝土及改性机理

通过正交试验提出纳米超高强高流态混凝土的胶凝材料配合比设计参数,并研究了纳米SiO₂的掺入对传统掺硅灰、粉煤灰超高强水泥基胶凝材料强度及工作性能的影响。在保证水胶比不变的条件下,开展了混凝土配合比试验,并研究了纳米SiO₂对混凝土抗压强度的影响及其微观机理。结果表明：超高强高流态混凝土中胶凝材料最优比例为：纳米SiO₂：硅灰：粉煤灰：水泥=1：8：20：71;在胶凝材料用量为600~1 000 kg/m³范围内,随着其掺量的增加,混凝土流动度不断增加,抗压强度先增大后减小,当其掺量为800 kg/m³时,抗压强度最大。分析认为,纳米SiO₂、硅灰与粉煤灰形成的三元多尺度堆积体系能优化粉体材料在混凝土中的微集料密实填充效应,纳米SiO₂的二次水化反应也有效改善了硬化水泥石的微观结构,并优化其形态分布,进一步增大其强度。     

工业区及周边农业区土壤中二噁英污染水平及暴露风险

选取复合产业工业区及周边农业区土壤进行研究,重点研究了土壤中二噁英的污染水平及土壤摄食暴露风险。通过对14个采样点(包括1个背景点)的研究发现,工业区ΣPCDD/Fs的质量浓度为:1.00×10~3~1.87×10~4 ng/kg,毒性当量为:I-TEQ 3.32~22.9 ng/kg;农业区果园地ΣPCDD/Fs的质量浓度为:117~795 ng/kg,毒性当量为:I-TEQ 0.479~1.11 ng/kg;农业区菜地ΣPCDD/Fs的质量浓度为:717~1.48×10~3 ng/kg,毒性当量为:I-TEQ 1.35~1.76 ng/kg。背景点土壤中二噁英浓度相对较低,质量浓度值为:132 ng/kg,毒性当量为:0.331 ng/kg。对工业区及周边农业区土壤二噁英土壤摄食暴露风险研究结果表明,儿童土壤摄食暴露风险要高于成年人;同时无论是儿童还是成年人,其二噁英的土壤摄食暴露量都比较低。     

盾构隧道功能梯度混凝土管片的研发及性能研究

武汉长江隧道工程所面临的高压富水环境要求衬砌结构管片具有高抗渗、长寿命的性能。引入功能梯度材料设计原理,对钢筋混凝土管片进行功能梯度设计与优化,实现管片外层高防水抗渗、结构层提供强度及内衬层耐火的多重功能。同时采用适当的界面处理技术,保证管片各功能层的性能均匀过渡,实现功能和结构一体化设计。对结构层混凝土、保护层材料性能分别进行测试,测试结果表明,保护层材料具有优良的抗渗性能,相比普通混凝土氯离子扩散系数降低一个数量级,寿命提高10倍以上,优于目前国际上已报道的最好水平(6×10-13m2/s);结构层、保护层混凝土力学性能优良,强度满足设计要求,保护层材料强度达C70以上,主体结构层达到C50;保护层材料与结构层材料体积稳定性良好;耐酸性气体腐蚀性能大大增强,90d中性化深度不足1mm;同时,管片内衬层通过刷涂防火抗爆材料有效提升了管片的内层耐火性能,耐火极限是未经处理试件的4.72倍;最后通过实际的生产及检测,进一步证明了功能梯度混凝土管片具有较好的服役性能。     

SiO2-TiO2复合气凝胶的制备工艺研究

以钛酸四丁酯(TBT)、正硅酸乙酯(TEOS)为原料,制备出TiO2和SiO2溶胶,研究了不同水解抑制剂以及水解抑制剂的用量对TiO2溶胶的影响.最终确定以HC1为水解抑制剂制备出稳定的TiO2溶胶;两种溶胶混合后,研究了pH值对复合凝胶透明度的影响.结果表明,当pH值为5.5时,凝胶时间适当且复合湿凝胶透明度较好;随着TiO2含量的增加,比表面积减小、锐钛矿衍射峰强度增强;从TEM图可以看出,锐钛矿型TiO2晶体均匀分散在SiO2气凝胶网络结构中.