氢分子吸附碳纳米管场发射性质的密度泛函理论研究

使用第一原理密度泛函理论方法,对吸附氢分子的开口(5,5)单壁碳纳米管在有电场和无电场情况下的性质进行研究。研究结果表明在有电场发射条件下,吸附氢分子后的结构更加稳定。氢分子吸附后,费米能级处的局域态密度增加。     

从日昇昌看旅行社管理

日昇昌票号自创立以来,凭借其非同寻常的经营管理办法,推动了当时社会经济的迅猛发展,并且对我们今天的企业发展,尤其是对旅行社的发展有着重大的启迪作用.其先进的股份制和严格的用人制度是值得我们借鉴的.     

Synthesis of mesoporous polymeric carbon nitride exhibiting enhanced and durable visible light photocatalytic performance

A thiourea precursor was employed to synthesize mesoporous carbon nitride(C3 N4) by a thermal polycondensation process with high surface area SiO2 and nanosphere SiO2 as two types of hard templates. The resultant mesoporous C3 N4 samples have high surface areas(105–112 m2/g) and mesopores with narrow sizes distribution(9.3 nm). Photocatalytic performance was evaluated by removal of NO in air under visible light irradiation. The results showed that mesoporous C3 N4 samples exhibited significantly improved photocatalytic activity in comparison with bulk C3 N4, which also exceeded that of N-doped TiO2 and C-doped TiO2. The activity enhancement can be ascribed to the synergistic effects of large surface area and pore volume, enhanced light-harvesting ability, increased redox potential, and reduced recombination of charge carriers. In addition to the high activity, the mesoporous C3 N4 samples also showed high photochemical stability. The mesoporous C3 N4 photocatalysts with enhanced and durable activity could provide a new efficient material for environmental pollution control.     

Modeling decarburization kinetics of grain-oriented silicon steel

A mathematic model has been presented to predict the decarburization kinetics of grain-oriented silicon steel sheet in the gas mixture of N2–H2–H2O during annealing.This model is based on the carbon flux balance between the oxidation reaction at the surface and the carbon diffusion inside the steel sheet.It can be numerically solved to quantify the influences of annealing temperature and atmosphere on decarburization kinetics when the boundary conditions are properly determined.In case that a humid gas mixture is employed during annealing,the most influential process parameter is temperature rather than compositions of the gas mixture,because the diffusion of carbon in ferrite is the rate-limiting step.Therefore,a higher temperature is required for the efficient decarburization of the thicker silicon steel sheet using the industrial continuous annealing production line.     

深部含水层二氧化碳运移的热流固耦合模型研究

应用混合物连续介质理论,考虑二氧化碳溶解建立了深部含水层二氧化碳运移的热流固耦合数学模型,利用该模型计算了深部含水层二氧化碳运移过程中二氧化碳饱和度、溶解质量分数和孔隙压力随时间的演化和扩散规律,对比了热流固耦合模型与传统渗流模型的计算精度。计算结果表明：二氧化碳在深部含水层运移过程中耦合效应十分明显且考虑二氧化碳溶解的热流固耦合数学模型具有较高的计算精度,可以满足实际工程需求。     

重力式碳钢-萘热管的热稳定性及相容性

本文着重对萘的热稳定性以及碳钢萘间的相容性进行实验研究.在研究中,对萘进行了430℃左右的长期加热实验以及在相同的实验条件下对碳钢萘相容性实验结果进行了分析.为取得更为可靠的结果,特将碳钢-萘热管在400℃左右工作温度下进行3000h寿命实验.结果令人满意.可以认为碳钢-萘热管在400℃左右工作温度下运行是可靠的,并具有良好的传热性能,加热段热流密度可达10~5W/m~2,与文献[1]结果一致.     

碳纤维用PAN原丝的结构与性能

采用以二甲基亚砜（DMSO）为溶剂的连续溶液聚合和一步湿法纺丝技术，在10t／a中试实验装置上成功地制备了碳纤维用聚丙烯腈（PAN）原丝批量产品。通过不断地优化聚合和纺丝工艺条件，实现了PAN原丝的中试稳定化。实验结果表明，采用连续溶液聚合技术在实现单体高度转化的同时获得了高分子量的PAN共聚物，通过调整凝固成型工艺条件和牵伸配比制备了具有圆形截面且结构致密的高取向度PAN原丝。将批量PAN原丝产品进行预氧化、低温碳化和高温碳化后．获得PAN基碳纤维，其束丝强度、模量和断裂伸长率的平均值分别达到3．74GPa，223GPa和1．7％。     

石家庄市开放源颗粒物化学组成特征分析

分析了石家庄市城市扬尘、道路尘、土壤尘、建筑尘四种开放源的粒径组成和无机元素含量,结果表明,四种开放源颗粒物样品中细颗粒物的累积效应更为明显。各种水溶性离子中,阴离子浓度最高的是SO42-,阳离子浓度较高的是Ca2+;存在二次有机碳污染,SOC是颗粒物的重要组成部分;各种元素的含量存在一定差异,Ca、Mg、Al、Si、Fe、K等元素含量较高,受人为污染严重。     

Enhanced low-humidity performance of proton-exchange membrane fuel cell by introducing hydrophilic CNTs in membrane electrode assembly

Hydrophilic carbon nanotubes (HCNTs) were introduced into the membrane electrode assembly (MEA) to improve its low-humidity performance. The effects of types, placement, loading, and relative humidity on the MEA performance were investigated. It has been found that the MEA with 20 ?wt% HCNTs loading both in anode and cathode achieved the best self-humidifying performance. Its current density reached 1550 ?mA ?cm^?2 at 0.6 ?V, with a maximum power density of 953 ?mW/cm² at 70 ?°C, 30 psi and 30% relative humidity conditions. Besides, the stability test shows that its current density at 0.6 ?V only decreased by 6.4% after 44 ?h performance test, while the performance of blank MEA without HCNTs decreased by 45% within 6 ?h testing period. This extraordinary performance under low humidity condition is ascribed to that the HCNTs contained in the MEA improve the water management and mass transportation by functioning as a dispersant and hydrophilic agent.     

碳纤维增强复合材料加固混凝土粘结性能试验

碳纤维增强复合材料(carbon fiber reinforced polymer, CFRP)加固混凝土技术在桥梁工程与建筑工程中有大量应用,而直接影响工程结构加固维修的关键因素是其界面粘结性能,因此开展相关试验研究对保障工程安全具有重大意义。以一种基于专门设计的试验装置进行弯曲剪切试验来研究CFRP-混凝土界面的粘结性能。利用数字图像相关(digital image correlation, DIC)法得到的应变场确定碳纤维布的脱粘长度,同时对碳纤维增强材料的性能进行了理论分析,探讨了试验中的力学响应。结果表明：弯剪破坏的原因是弯矩的增大导致界面粘结强度和极限荷载的降低。通过对比弯剪试验和理论应变分布曲线,证明试验的有效性。粘结区在弯曲作用下产生的正应力有一个固定的有效区域,在该区域以外不会产生正应力。因此,在工程应用中,确定碳纤维布板的剥离长度可以减少维护工作,碳纤维布-钢筋混凝土在受弯曲和拉伸的共同作用下,可以在加载端有效应力区域内进行再加固,增加使用寿命。