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实验研究了钛合金和高反射型陶瓷涂层材料抗连续型激光烧蚀的损伤及温度分布特性,并从热效应影响角度对比分析了二者在抗激光损伤效果方面的差异性。研究结果表明:相比于钛合金,高反射型陶瓷涂层材料能有效增强钛合金基底抗激光损伤的能力;在同等激光功率密度辐照下,陶瓷涂层材料能有效提升钛合金基底耐受激光辐照的时间长度。实验结果表明该陶瓷涂层材料的激光损伤阈值比钛合金高约5.8倍。实验发现陶瓷涂层温升速率高于钛合金,但由于陶瓷材料具有较高的反射特性,以及良好的热吸收和热传导特性,因此能使由激光辐照产生的热量在其表面较快地扩散,而降低向基底方向传导的程度,最终提升陶瓷涂层的抗激光损伤阈值。 相似文献
3.
《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2020,65(7):1789-1802
Urban heat island (UHI) is emerged as a ubiquitous phenomenon that affects the outdoor thermal comfort. Hence urban microclimatic studies using numeric simulation software to find out adaption strategies are attracting the great attention of researchers and policymaker. Number of scientists carried out their research on this topic using different tools and technique whereas ENVI-met model is the most widely used simulation tools. The present study intended to examine the implication of green infrastructure of the town on enhanced microclimatic condition and to evaluate the best suitable mitigation strategy modelling cool city with ENVI-met software (V4). Five greening condition such as existing UHI condition (C1), 100% greening of roof (C2), 100% greening of roof and walls (C3), 50% greening of roof and walls (C4) and: Plantation at suitable area with 50% greening of roof and walls (C5) have been taken into consideration for the microclimate simulation for all three selected sites. Among these five conditions, C3 for the open mid-rise and compact low-rise, C5 for the open low-rise are identified as one of the most suitable strategies which can reduce the air temperature of peak hours by 2.6 °C, 1.33 °C and 1.87 °C respectively. These models are validated by simple linear regression between simulated and existing air temperature in case of existing UHI condition (C1) and in all the cases coefficient of determination value is high such as for open mid-rise, compact low-rise and open low-rise, it is 0.92, 0.92 and 0.75 respectively. Therefore it can be concluded that the application of those strategies can improve the urban thermal environment as well as the outdoor thermal comfort of English bazaar Town and its surroundings. 相似文献
4.
Mohammad Hossein Mokhtari Amir Ahmadikhub Hamid Saeedi-Sourck 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(10):3106-3124
Land surface temperature (LST) as an important environmental variable provides valuable information for earth environmental system modelling. Currently, LST is obtained through satellite thermal sensors at various spatial and temporal resolutions. Although spatially continuous satellite-based LST measurements are intended to overcome the shortcomings of sparse ground-based LST measurements, LST images often contain anomalous values due to the existence of clouds or sensor malfunctioning. The problem becomes more serious where the users deal with high spatial resolution characterized by low temporal resolution. This study examines the capability of a newly developed graph signal processing (GSP) method using two-dimensional single-date thermal data. For this purpose, four Landsat/TIRS datasets are analyzed. The data of five elliptical regions on thermal images are eliminated and then reconstructed through the GSP method and using the LST values of the enclosing rectangles containing the ellipsoids. The results indicate that the temperature variation determined by the GSP method generally conforms to the original image LST values. According to a correlation test conducted on the original image LST and those obtained through the GSP method, the values vary from 58% to 95%, which is an above-the-average rate (RMSE from 0.69 to 2.27). The statistical analysis of the original image LST in both the elliptical regions and the enclosing rectangles containing the ellipsoids indicates that an increase in the variance of LST data causes an increased error in the calculation of temperature by the GSP method, and vice versa. The results of the analysis of variance (ANOVA) and Duncan test indicated that an increase in the number of the non-zero spectral bins would result in increased RMSE values for all the dates and the regions. Moreover, the model errors were significant at the 0.05 level across all the image date and five elliptical study regions. Based on the results, the use of this method is recommended for the reconstruction of LST missing values, where dissimilarity of atmospheric conditions limits the use of other methods that depend on the time series data of various dates and a great deal of data calculation. 相似文献
5.
《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2020,65(7):1701-1713
Equatorial plasma bubbles (EPBs) are common features of the equatorial and low-latitude ionosphere and are known to cause radio wave scintillation which leads to the degradation of communication and navigation systems. Although these structures have been studied for decades, a full understanding of their evolution and dynamics remains important for space weather mitigation purposes. In this study, we present cases of EPBs occurrences around April and July 2012 geomagnetic storm periods over the African equatorial sector. The EPBs were observed from the Communications/Navigation Outage Forecasting System (C/NOFS) and generally correlated well to the ionospheric irregularities observed from the Global Positioning System total electron content (GPS-TEC) measurements (rate of TEC change, ROT). This study revealed that the evolution of the EPBs during moderate storms is controlled by the strength of the daytime equatorial electrojet (EEJ) currents regardless of the strength of the equatorial ionization anomaly (EIA), the latter is observed during the July storm case in particular. These effects were more evident during the main and part of the early recovery phases of the geomagnetic storm days considered. However, the evening hours TEC gradients between regions of the magnetic equator and ionization crests also played roles in the existence of ionospheric irregularities. 相似文献
6.
《中国航空学报》2020,33(2):391-406
A thermal-solid-liquid complex operational environment induces structural interface developing a typical coupling sliding/impact wear behavior. It results in contact damage until systems fail, which may cause significant economic losses and catastrophic consequences. The key point of solving this problem is to reveal the coupling damage mechanism of the sliding/impact behavior in typical systems and life characterization under a complicate evolving environment. This has been a hot topic in the area of mechanical reliability. The main work in this paper can be concluded as follows. Firstly, the main industries in which the “sliding/impact behavior” takes place have been introduced. Then, existing studies on the wear mechanism and degree analysis are presented, which includes surface morphology analysis, wear debris analysis, and wear degree measurement. Meanwhile, existing problems in theoretical modeling and experiments in current research are summarized, so as to point out a bright direction for future research on wear prediction. They include interface contact modeling, mathematic coupling mechanism modeling, wear equation establishment, and wear life characterization, which can provide some new ideas for improving the existing studies on the sliding/impact wear behavior. 相似文献
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分析了 K8、 JL8机翼接头孔精加加后与检验量规位置协调的条件,介绍了为提高它们之间协调准确度所采取的措施及其效果。 相似文献
9.
赵承龙 《南京航空航天大学学报》1990,(2)
本文在阐述基准的热力学概念基础上,提出了燃气基准的计算方法,应用CHAPPELL推荐的有关燃气热力性质表达式,导出计算燃气基准的公式,通过微机计算,将结果整理成燃气基准的有关表、图。 相似文献
10.
涡旋真空泵在工作过程中动、静涡盘之间间隙存在泄漏损失,它是影响涡旋真空泵工作性能的重要因素;总结了涡旋真空泵的工作原理;介绍了涡旋真空泵的密封设计与选择、间隙的确定。从材料和结构两方面阐述了密封的几种结构形式,说明了各自的工作原理,及需要注意的问题,阐明这些问题是影响泵性能指标的重要因素。 相似文献