The Role of Three-Dimensional Shock Wave Interaction in the Complex Hypersonic Heating

A shock-expansion tube/tunnel is a ground-based test facility to generate hypervelocity test flows for the study of atmospheric reentry physics. Such a high enthalpy test flow features thermochemically non-equilibrium which may lead to critical difficulties in flow diagnostics and measurements. In addition, the test time of such an impulse facility is extremely short which implies a requirement of transducers with high-frequency response capability for model tests or flow diagnostics. In the present work, computations for non-equilibrium reacting flow are conducted to diagnose the key flow parameters and evaluate the test flow for facility upgrading. A conic nozzle is appended to the original facility and to obtain a larger test section and larger Mach numbers. Further experiments are conducted to visualize the overall flow structures over the test models by self-illumination of radicals at high-energy states post strong shock waves. The heat flux at the stagnation point is measured with specially designed thermal couples

Effect of Applied Potentials on the Formation of Self-Assembled Monolayers of Alkanethiol

应用电位阶跃法,在不同组装电位下制备金/正十二硫醇自组装单分子膜.交流阻抗谱表征该硫醇膜的电化学性质,发现金基底的电位对硫醇自组装膜的形成有重要影响.在-0.8~-0.4 V的电位区间内,随着组装电位的增加,该自组装膜的致密性、有序性增加,缺陷减少,并于0.4 V时达到最佳.组装电位高于0.4 V,膜的致密性、有序性降低,缺陷增多.本文为硫醇及其衍生物的电位调控组装提供了重要依据.The self-assembled monolayers(SAMs)of n-dodecanethiol were prepared on gold substrates under electrochemical conditions using potential step technique.Electrochemical impedance spectroscopy was employed to characterize the SAMs prepared under different substrate potentials.It is found that the potential applied to gold substrate has great influence on the formation of SAMs.Within potential regime-0.8 V to 1.2 V,the increase of applied potential firstly leads to the formation of SAMs with higher packing density,better ordering and less defects.However,after reaching the maximum at 0.4 V,the packing density and the ordering of SAMs begin to deteriorate when the substrate potential is further increased.This work provides solid experimental basis for potential-controlled formation of SAMs from alkanethiols and their derivatives.作者联系地址：北京航空航天大学材料科学与工程学院应用化学系,北京航空航天大学材料科学与工程学院应用化学系,北京航空航天大学材料科学与工程学院应用化学系,北京科技大学冶金与生态工程学院物理化学系,北京航空航天大学材料科学与工程学院应用化学系,北京航空航天大学材料科学与工程学院应用化学系 北京100083,北京100083,北京100083,北京100083,北京100083,北京100083Author's Address: *1,WANG Xiao-ning~1,HOU Qun-Chao~1,GUO Min~2,XIANG Min~1,ZHANG Qi~11.Department of Applied Chemistry,School of Materials Science & Engineering,Beijing University of Aeronautics & Astronautics,Beijing 100083,China,2.Department of Physical Chemistry,School of Metallurgical & Ecological Engineering,University of Science&Technology Beijing,Being 100083,Chin

刈割时间与留茬高度对沙生灌草营养价值的影响

试验研究刈割时间、留茬高度对沙生灌草营养价值和饲用价值的影响。试验以库布其沙漠地区7种灌草(柠条锦鸡儿、沙柳、花棒、梭梭、羊柴、甘草、华北驼绒藜)为研究对象,测定其酸性洗涤纤维(ADF)、中性洗涤纤维(NDF)、粗蛋白(CP)、粗脂肪(EE)等饲用指标。结果显示,7种沙生灌草的酸性洗涤纤维含量为32.33%～61.57%、中性洗涤纤维含量为55.12%～76.17%、粗蛋白含量为5.17%～15.63%、粗脂肪含量为5.47%～12.70%。不同植物在生长季不同阶段的相对饲用价值不同,随着时间增加,除柠条和花棒外,所有植物ADF和NDF含量均逐渐增加,并在9月达到最大值;粗脂肪含量也逐渐增加,而粗蛋白含量逐渐降低。不同留茬高度对植物营养成分的影响不大。研究表明,为保证灌草的最大饲用价值,柠条锦鸡儿、花棒、梭梭、羊柴应在7月平茬,沙柳应在7月或9月平茬,甘草和华北驼绒藜应在5月平茬