化学气相反应法在C/C复合材料抗氧化处理中的应用

通过把硅蒸气渗入预制体孔隙与碳直接反应生成SiC的化学气相反应(CVR)方法,提高初始密度和预制体结构均不同的C／C复合材料的抗氧化能力,研究了C／C复合材料的密度变化与微观结构,并对其进行了氧化试验。结果表明,因CVR温度、C／C复合材料初始密度不同,抗氧化处理后的密度增加量有显著不同。针刺炭布C／C／SiC复合材料在马福炉中于1160℃经65min氧化后,其失重率仅2．6％,而密度为1．95g／cm^3的同结构C／C复合材料相在同条件下失重率高达32％。     

Simulation and analysis of chemical release in the ionosphere

Ionospheric inhomogeneous plasma produced by single point chemical release has simple space-time structure, and cannot impact radio wave frequencies higher than Very High Frequency (VHF) band. In order to produce more complicated ionospheric plasma perturbation structure and trigger instabilities phenomena, multiple-point chemical release scheme is presented in this paper. The effects of chemical release on low latitude ionospheric plasma are estimated by linear instability growth rate theory that high growth rate represents high irregularities, ionospheric scintillation occurrence probability and high scintillation intension in scintillation duration. The amplitude scintillations and the phase scintillations of 150?MHz, 400?MHz, and 1000?MHz are calculated based on the theory of multiple phase screen (MPS), when they propagate through the disturbed area.     

Establishment of atmospheric weighted mean temperature model in the polar regions

Due to the special geographical location and extreme climate environment, the polar regions (Antarctic and Arctic) have an important impact on global climate change. Atmospheric weighted mean temperature (Tm) is a crucial parameter in the retrieval of precipitable water vapor (PWV) from the zenith wet delay (ZWD) of ground-based Global Navigation Satellite System (GNSS) signal propagation. In this paper, the correlation between weighted mean temperature and surface temperature (Ts) is studied firstly. It is shown that the correlation coefficients between Tm and Ts are 0.93 in the Antarctic and 0.94 in the Arctic. The linear regression Tm model and quadratic function Tm model of the Antarctic and the Arctic are established respectively using the radiosonde profiles of 12 stations in the Antarctic and 58 stations in the Arctic from 2008 to 2015. The accuracies of the linear regression Tm model, the quadratic function Tm model and GPT2w Tm model which is a state-of-the-art global Tm model are verified using the radiosonde profiles from 2016 to 2018 in the Antarctic and Arctic. Root Mean Square (RMS) errors of the linear regression Tm model, the quadratic function Tm model and GPT2w Tm model in the Antarctic are 3.07 K, 2.87 K and 4.32 K respectively, and those in the Arctic are 3.53 K, 3.38 K and 4.82 K, which indicates that the quadratic function Tm model has a higher accuracy compared to linear regression Tm model, and the accuracies of the two regional Tm models are better than that of GPT2w Tm model in the polar regions. In order to better evaluate the accuracy of Tm in the PWV retrieval, the PWV values of radiosondes are used for comparisons as the reference value. The RMS errors of PWV derived from the two Tm models are similar for 1.28 mm in the Antarctic and 1 mm in the Arctic respectively. In addition, the spatial and temporal variation characteristics of Tm are analyzed in the polar regions by spectral analysis of Tm data using fast Fourier transform. The results show that the Tm has obvious seasonality and annual periodicity in the polar regions, and the maximum difference between warm season and cold season is about 63 K. After comparing and analyzing the influences of latitude, longitude and elevation on the Tm in the polar regions, it is found that latitude and elevation have a greater influence on the Tm than the longitude. As the latitude and elevation increase, the Tm decreases, and vice versa in the polar regions.     

A theoretical method for solving shock relations coupled with chemical equilibrium and its applications

In this study, a theoretical method is proposed to solve shock relations coupled with chemical equilibrium. Not only shock waves in dissociated flows but also detonation waves in combustive mixtures can be solved. The global iterative solving process is specially designed to mimic the physical and chemical process in reactive shock waves to ensure good stability and fast convergence in the proposed method. Within each global step, the single-variable equations of normal and oblique shock relatio...     

超临界碳氢燃料蒸汽重整一维模型研究

为了获得关键参数对超临界碳氢燃料蒸汽重整化学热沉分布特性的影响,建立了超临界碳氢燃料蒸汽重整非稳态一维计算模型,通过与实验数据的对比验证了模型的准确性,并基于该模型采用RP-3的四组分替代模型对RP-3蒸汽重整过程中入口流速、压力和含水量等关键参数对热沉沿流向分布特性的影响进行了研究。结果表明：随着入口流速的增加,蒸汽重整反应化学热沉的峰值减小,且出现峰值的位置逐渐向出口移动。随着压力的升高,相同位置处的化学热沉都减少,但是出现峰值的位置不变。在入口含水量由5%增大到12%的过程中,微通道同一位置处的化学热沉增大,且化学热沉的最大值也是增大的,峰值出现的位置向微通道出口移动。     

过滤式阴极电弧沉积类金刚石薄膜的特性分析

利用自行研制的过滤式阴极电弧沉积装置,在硅片和高速钢基体材料上获得了类金刚石薄膜,分别采用扫描电镜、原子力显微镜、喇曼光谱以及磨损实验等手段对薄膜进行了分析研究。结果表明,所获得的类金刚石薄膜为非晶态,sp3含量最高达70%;基体材料对成膜质量影响较大,在硅片上薄膜的摩擦系数可达0.08;同时偏压的变化会引起喇曼谱线中D峰和G峰位置向低频移动,半高宽σG增大、σD减小。     

Ti（Y）N镀覆刀具及膜-基界面状态的研究

研究了离子镀ＴｉＮ和Ｔｉ（Ｙ）Ｎ镀层对刀具寿命及膜－基界面状态的影响。结果表明：刀具镀覆Ｔｉ（Ｙ）Ｎ后寿命显著提高,试验数据分散度减小,可信度大大提高,这主要是膜－基界面状态改善,结合力大大提高之故。并对微观机制进行了较为系统的讨论     

真空汽相焊冷却速率对多层板焊点质量的影响

为解决多层印制板真空汽相焊由于焊后冷却不足导致的焊点纹路问题,本文确定多层板焊点纹路出现的根本原因,对焊后冷却区进行改造,进而研究不同焊接工艺对焊点表面形貌、内部组织形貌及焊点力学性能的影响。实验结果表明,快冷下焊点形成的界面金属化合物（IMC）更薄,焊点组织也更加均匀,即Pb在Sn中的分布更弥散。快冷下形成的IMC层晶粒直径在1μm左右,剪切强度为17.26 MPa,较慢冷提高了43%,达到细晶强化的目的。此外,由于冷却速度过慢导致的焊点表面纹路缺陷也得到明显改善。     

Validation on MERSI/FY-3A precipitable water vapor product

The precipitable water vapor is one of the most active gases in the atmosphere which strongly affects the climate. China's second-generation polar orbit meteorological satellite FY-3A equipped with a Medium Resolution Spectral Imager (MERSI) is able to detect atmospheric water vapor. In this paper, water vapor data from AERONET, radiosonde and MODIS were used to validate the accuracy of the MERSI water vapor product in the different seasons and climatic regions of East Asia. The results show that the values of MERSI water vapor product are relatively lower than that of the other instruments and its accuracy is generally lower. The mean bias (MB) was ?0.8 to ?12.7?mm, the root mean square error (RMSE) was 2.2–17.0?mm, and the mean absolute percentage error (MAPE) varied from 31.8% to 44.1%. On the spatial variation, the accuracy of MERSI water vapor product in a descending order was from North China, West China, Japan -Korea, East China, to South China, while the seasonal variation of accuracy was the best for winter, followed by spring, then in autumn and the lowest in summer. It was found that the errors of MERSI water vapor product was mainly due to the low accuracy of radiation calibration of the MERSI absorption channel, along with the inaccurate look-up table of apparent reflectance and water vapor within the water vapor retrieved algorithm. In addition, the surface reflectance, the mixed pixels of image cloud, the humidity and temperature of atmospheric vertical profile and the haze were also found to have affected the accuracy of MERSI water vapor product.     

煤油液滴高压蒸发特性

采用真实流体模型描述高压下流体热物理性质的非理想性,并采用状态方程（EoS）法计算多组分高压气-液相平衡及环境气体溶解性,在此基础上建立包含亚临界和超临界两种不同机制的瞬态液滴高压蒸发模型。针对中国新一代高压补燃液氧/煤油发动机,详细研究了煤油液滴在超临界环境下的高压蒸发特性及各因素影响机理。结果表明：高压环境会显著加快液滴温升速率,但弱超临界环境下仍然为相平衡控制的亚临界蒸发状态;只有强超临界环境下才较容易发生扩散控制的超临界蒸发状态。在高压、高温环境下,忽略气相溶解性将导致液滴蒸发速率明显偏小。针对弱超临界环境,温度升高会使液滴蒸发速率单调增加;压力升高则在低温下降低蒸发速率,而在高温下加快蒸发速率。针对强超临界环境,温度升高只提升初始亚临界蒸发阶段的蒸发速率,而超临界蒸发阶段的蒸发速率与环境温度无关;压力升高则同样会提升初始亚临界蒸发阶段的蒸发速率,但会降低超临界蒸发阶段的蒸发速率,此时的总蒸发寿命随压力升高小幅下降。