激光熔覆修复15-5PH不锈钢的拉伸性能及组织研究

研究了激光熔覆修复15-5PH沉淀硬化不锈钢激光熔覆修复比例(25%、50%、75%、100%)对其力学性能的影响,以及熔覆修复后试样的断口形貌、金相组织、内部缺陷和显微硬度。研究结果表明,15-5PH不同比例熔覆修复试样的抗拉强度均高于基材,但塑性随着修复比例的增大而降低,在所研究的4种熔覆修复比例的试样中,25%熔覆比例时抗拉强度最高,力学性能最好。熔覆修复冶金组织致密,分为修复区、热影响区和基材区,其中热影响区的组织呈现明显的方向性,晶粒均匀性好,无粗大晶粒,表面和内部无裂纹缺陷,显微硬度从修复区向基材区整体呈上升趋势,在热影响区内出现硬度峰值。熔覆界面的结合力较基体内部的结合力弱,修复试样的断口均呈V字形。     

基于5G的通导融合位置认证系统性能分析

随着无人化智能移动装备在工业、交通等安全敏感领域的普及应用，民用导航定位系统中的定位安全问题日益突出。位置认证是对终端的物理位置声明进行认证的过程，是导航定位安全技术的重要组成部分。基于第五代(5G)移动通信网络的通导融合位置认证系统具有覆盖范围广、认证精度高、用户容量大、建设运维成本低等多重优势。本文首先介绍了多基站位置认证系统的检测判决原理，提出了漏检平均距离的定义作为位置认证系统精度的量化评价指标。在此基础上，通过数值仿真分析了信号带宽、基站同步误差、信噪比对位置认证系统精度的影响，并利用5G信道模型评估了典型场景下的位置认证系统的性能。结果表明，在具备3个以上的视距基站时，基于5G的通导融合位置认证系统可以实现米级的位置认证精度。     

Analysis of Chang’e-5 lunar core drilling process

Chang’e-5 explorer successfully acquired lunar regolith core samples from depths of greater than 1 m of lunar surface. This study analyzed the lunar core drilling process based on the telemetry data, image information, and returned samples to optimize the sampling device design and enhance the understanding of the lunar regolith. In particular, a prediction method for the projected drilling path and local terrain fitting of drilling dip angle was proposed based on the flight events recorded during the core drilling process and the image information acquired before, during, and after sampling. The results revealed that the drilling dip angle of Chang’e-5 was approximately 2.3°, and the deviation of the drilling length and depth was less than 2 mm. For continuous drilling, a fusion method based on telemetry data and image information was applied to determine the demarcation point of drilling with and without the lunar soil. The position of the demarcation point implied that the drilling point remained at approximately 6 mm loose soil, thereby lagging the action of the force response. Additionally, a characteristic parameter comparison method was proposed for the lunar and ground drilling to analyze the status of the lunar soil. Furthermore, the analysis results revealed that the majority of the Chang’e-5 drilling samples were derived from 0–73.8 cm below the lunar surface and few samples were extracted below 73.8 cm, as the drilling encountered several rocky regions. Moreover, the drilling point exhibited two prominent stratification variations at ～28.7 cm and ～70 cm below the lunar surface. Ultimately, the preliminary relationship between sample dissected position in soft tube and drilling displacement was analyzed. The segmented estimation results can support research on subsurface lunar soil.     

Effect of the continental shelf in seasonal oceanographic conditions at the Northern edge of the Eastern Tropical Pacific

The continental shelf in front of Nayarit is located in the northern limit of the tropical Eastern Pacific, characterized by constituting a convergence zone of different masses of water, forming an area of significant hydrographic variability. Based on satellite remote sensing data and reanalysis between 2003 and 2019 of sea surface temperature (SST), wind stress, Ekman velocity, and geostrophic velocity, the contribution of the seasonal cycle to the variability of the study area were analyzed through climatological means, Hovmöhler diagrams, and Empirical Orthogonal Functions. The results show that in the zone in front of Matanchén Bay (21.5 °N) and the adjacent continental shelf, there is a core of warm surface water. The distribution of the SST is explained by the seasonal pattern of meridional/zonal variability in the thermal gradient, where the EOFs show the influence of the annual scale in both modes, with the only difference being that the first describes the meridional gradient as the dominant signal (66.2%), and the second shows the zonal behavior of the thermal gradient (16.6%). The summer weakening of the wind stress and Ekman speed is the product of the irregular shape of the coastline, the extension of the continental shelf, and the divergence of the North American monsoon around 21°N, whereas during the rest of the year an intensification of these parameters prevailed in front of Cabo Corrientes. On the other hand, the intense geostrophic flow in summer does not contribute to the increase in SST on the continental shelf because it diverges around 22.5°N. Likewise, during the winter, the formation of a cyclonic geostrophic gyre located inside the continental shelf, between the coast and the Marías Islands, stands out.     

Hardware qualification for scientific ballooning missions

The European Stratospheric Balloon Observatory (ESBO) initiative aims at simplifying the access to stratospheric balloon missions. We plan to provide platforms and support with instrument design in order to support scientists. During the design process, the inevitable question of qualification for the harsh flight conditions arises. Unfortunately, there is no existing standard for qualification of stratospheric ballooning hardware. Thus, we developed a qualification procedure for use within ESBO and similar projects.In this paper, we present our analysis of the environmental conditions in the stratosphere. While conditions at typical balloon float altitudes are similar to the space environment, there are also some relevant differences. For example, the thermal environment is dominated by radiation and thermal conduction, but the remaining atmosphere still supports a certain amount of convection. The remaining atmospheric pressure in the stratosphere also leads to reduced arcing distances. Vibrational loads are far less than for space missions, but quasi-static or shock loads may occur. The criticality of radiation increases with mission duration.Based on the environmental conditions, we present the qualification procedures for ESBO, which are based on the European Cooperation for Space Standardization (ECSS) standards for space systems. Overtesting against too high requirements leads to overengineering, driving mission cost and mitigating the advantages of balloons over space missions. Therefore, we modified the ECSS standards to fit typical scientific ballooning missions over several days at altitudes up to 40 km. Furthermore, we analyzed design rules for space systems with regard to their relevance for scientific ballooning, including material and component selection. We present the experience from the hardware qualification process for the ESBO prototype STUDIO (Stratospheric UV Demonstrator of an Imaging Observatory). Even though boundary conditions are different for each individual mission, we aimed for a broader approach: We investigated more general requirements for scientific ballooning missions to support future flights.     

Comprehensive evaluation of Satellite-Based and reanalysis precipitation products over the Mediterranean region in Turkey

Precipitation is an important component of the hydrological and energy cycles, as well as a key input parameter for many applications in the fields of hydrology, climatology, meteorology, and weather forecasting research. As a result, estimating precipitation accurately is critical. The purpose of this research is to conduct a comprehensive and comparative evaluation of grid-based precipitation products over Turkey's Mediterranean region from 2017 to 2021 at monthly and grid scales, using data from 193 ground-based meteorological stations as a reference. PERCIANN CCS, PDIR-Now, GSMaP MVK, PERSIANN CDR, CHIRPS, IMERG v6, GSMaP Gauge, and ERA5 are the eight grid-based precipitation products. Several prospective were used to evaluate the products, including magnitude agreement with gauge stations for the entire region and the six hydrological sub-basins included in the region, performance in capturing various intensity categories, and elevation dependency. According to the evaluation results, PERCIANN CDR, CHIRPS, IMERG v6, GSMaP Gauge, and ERA5 performed well in all evaluation aspects, whereas PERCIANN CCS, PDIR-Now, and GSMaP MVK performed poorly in all metrics. The majority of the products underestimated heavy rainfall events, while all products performed better at low and moderate precipitation events. As a result, the products performed better in the summer and spring months (March to October) than in the winter months (December to February). Furthermore, the results showed that the performance of the majority of the products degraded for elevations greater than 1000 m. The evaluation suggests that PERSIANN CDR, CHIRPS, IMERG v6, GSMaP Gauge, and ERA5 can be used as good precipitation data sources and as a complement to ground-based meteorological stations in Turkey's Mediterranean region.     

激光熔化沉积15-5PH沉淀硬化不锈钢组织及拉伸性能

利用激光熔化沉积技术制备15-5PH沉淀硬化不锈钢板,利用金相显微镜(OM)、扫描电镜(SEM)、透射电镜(TEM)、电子探针(EPMA)技术,对沉积态组织进行分析,测试沉积态组织的室温拉伸性能。结果表明:激光熔化沉积15-5PH不锈钢沉积态组织由沿沉积增高方向贯穿多层外延生长的柱状晶组成,柱状晶内包含多个细长整齐排列的胞状树枝晶,枝晶内为马氏体组织,枝晶间为铁素体;沉积态组织中弥散分布大量细小的NbC析出相,尺寸12～20 nm;15-5PH不锈钢沉积态组织具有良好的力学性能,纵向抗拉强度和延伸率分别为1 128.5 MPa和14.0%,横向抗拉强度和延伸率分别为1 101 MPa和12.25%。     

5G微基站环境下GNSS接收机性能及观测质量分析

我国已全面进入5G时代，为研究5G微基站电磁环境对全球卫星导航系统（GNSS）接收机工作性能及观测数据质量的影响，基于自主建设差分基准站的零基线观测数据，采用静态相对定位方法，通过观测数据质量分析、载波与伪距的双差残差序列、对比相对静态定位结果，综合评估5G微基站对GNSS接收机工作性能及观测数据质量的影响。实验表明：当前环境下，GNSS差分基准站及接收机处于近距离建设的5G微基站时，载波相位观测噪声变化范围为5cm，伪距观测噪声变化范围为15cm，零基线测试结果变化范围为1mm。在实验距离内，5G微基站对于GNSS接收机工作性能及数据观测质量影响较小，可以忽略。     

通信导航融合定位技术发展综述

详细分析了蓝牙、Wi-Fi、超宽带、移动通信网络等多种无线网络通信导航融合定位技术的发展现状，并阐述了其面临的挑战，提出了多网融合方法可以提升室内无缝高精度位置服务的可靠性。利用5G移动通信网络，与北斗/GNSS卫星导航系统结合，可以实现相互增强。最后，从天地一体定位导航与授时体系和仿生通信定位导航两方面介绍了通信导航融合定位技术的未来发展趋势。