Mars Rover Localization Based on A2G Obstacle Distribution Pattern Matching

Rover localization is one of the perquisites for large scale rover exploration. In NASA's Mars 2020 mission, the Ingenuity helicopter is carried together with the rover, which is capable of obtaining high-resolution imagery of Mars terrain, and it is possible to perform localization based on aerial-to-ground (A2G) imagery correspondence. However, considering the low-texture nature of the Mars terrain, and large perspective changes between UAV and rover imagery, traditional image matching methods will struggle to obtain valid image correspondence. In this paper we propose a novel pipeline for Mars rover localization. An algorithm combing image-based rock detection and rock distribution pattern matching is used to acquire A2G imagery correspondence, thus establishing the rover position in a UAV-generated ground map. Feasibility of this method is evaluated on sample data from a Mars analogue environment. The proposed method can serve as a reliable assist in future Mars missions.Comment: 8 pages, in Chinese language, 9 figure

Microstructure morphology and solute segregation in non-equilibrium solidification of metastable immiscible Cu50Co50 alloy

AbstractNon-equilibrium solidification of undercooled metastable immiscible Cu50Co50 alloy was performed by using glass-fluxing coupled with cyclic superheating method. The evolutions of microstructure morphology and solute segregation were elucidated as a function of initial undercooling. As for the samples undercooled by 62K and 105K, α-Co dendrites form primarily from the homogeneous liquid phase and then break into granular grains during the recalescence process. Moreover, the growth of dendrite changes from the solute-controlled mode to thermal-controlled mode with increasing undercooling, which generates the reduction of trunk size and the increase of solute content. In contrast, dual-layer structure prevails for larger undercoolings, i.e., 188K and 220K, where the strengthened immiscible effect leads to the decrease of solute content in separated phases and the occurrence of second separation. As for the sample with separated melt structure, nucleation triggering was adopted and serious shrinkage cavities can be observed due to the inadequate feeding of residual liquid

High-precision optical fiber sensing beyond 1000{\deg}C

Sapphire fiber can withstand around 2000{\deg}C, but it is multimoded, giving poor precision sensors. We demonstrate a single-mode sapphire fiber Bragg grating temperature sensor operating up to 1200{\deg}C. The repeatability above 1000{\deg}C is within {\pm}0.08%.Comment: 4 Pages, 5 Figure

Landscape ecological risk assessment and its driving factors of multi-mountainous city

Urban land has been expanding under the background of rapid urbanization, which leads to the increasingly prominent problem of regional ecological security in multi-mountainous cities. In order to scientifically formulate land use policies and maintain regional ecological security pattern, it is necessary to assess regional landscape ecological risk (LER), explore its influencing factors, and simulate the LERs under different scenarios in the future. This study takes Guiyang, a typical mountainous city in the karst area of southwest China, as the study area. Based on the three-phase remote sensing images, the landscape pattern index and the Geodetector method (GDM) were used to assess LER and the corresponding driving factors from 2000 to 2020, and the PLUS model was used to simulate LER under different urban development scenarios in 2030. The results showed: (1) The average landscape ecological risk index (LERI) in 2000, 2010, and 2020 were 0.0341, 0.0320, and 0.0304, respectively. This shows that the overall LER of Guiyang is low and gradually decreases over time. (2) The LER pattern has significant positive spatial autocorrelation, but the autocorrelation decreases with the development of the city. (3) From 2000 to 2020, ecological driving factors were the main influencing factors of LER, but the impact of social driving factors on LER was growing with time. (4) The LER change of Guiyang in 2030 varies significantly under different scenarios, among which the area of the risk up zone in the natural development scenario is the largest, followed by the farmland protection scenario, and the ecological priority scenario is the smallest. This study will provide a scientific basis and reference for the overall development planning of multi-mountainous cities, regional ecological protection planning, and the formulation of relevant land use policies

Inhibition of Grain Growth by a Ce-rich Precipitate During the Annealing of Spray-Casted Magnesium Alloy

The grain refinement and thermal stability behavior of a spray-casted AZ91D magnesium alloy were investigated with the addition of 0.75 wt% Ce. The results showed that the adoption of non-equilibrium solidification leads to remarkable grain refinement and the formation of a supersaturated solid solution, which suppresses the needle-like Al11Ce3 phase with a low cooling rate. After annealing at 420 °C, the grain morphology of rapidly solidified AZ91D+0.75Ce alloy changed from a granular to polygonal shape. Moreover, Mg12Ce particles precipitated and distributed homogeneously, which played an important role in grain boundary pinning at an elevated temperature. Consequently, the grain growth occurring during the isothermal annealing stage could be suppressed and the resultant grain size varied slightly, as did for the time, which increased from 2 h to 8 h

Potential recreation service efficiency of urban remnant mountain wilderness: A case study of Yunyan District of Guiyang city, China

As the precious resource of Karst mountainous city, urban remnant mountain wilderness (URMWs) can provide various of ecosystem services to the city. Taking the built-up area of the central urban area of Guiyang city center as the study area and the URMWs as the research object, an evaluation system of potential recreation service efficiency (PRSE) of URMWs was constructed through fuzzy Delphi method (F-Delphi), analytic hierarchy process (AHP) and entropy weight method (EWM), and PRSE of 69 URMWs in study area was evaluated and mapped. The recreation service characteristics of URMWs were analyzed from the perspective of supply and demand. Finally, the correlation of PRSE and the landscape features of URMWs was analyzed. Results showed that: (1) URMWs were mostly distributed in low and medium kernel density zones, and they had significant spatial agglomeration characteristics. (2) PRSE of URMWs was jointly affected by recreation potential, recreation opportunity and recreation demand. Among the 18 evaluation factors of PRSE evaluation system, the perfection of recreation service facilities, viewshed and green vision perception were the most important factors. In addition, PRSE of URMWs was significantly improved after park utilization. (3) PRSE of URMWs in the study area had significant spatial differences in suburban areas, which was higher in suburban areas than in urban centers and boundaries. The spatial mismatch between the supply and demand of recreation services was important reason for the low PRSE of URMWs. (4) PRSE of URMWs was significantly correlated with its three-dimensional features. The evaluation system constructed in this study could quantify PRSE of each URMW, reflect its spatial pattern, and provide a reference for the protection, development and utilization of URMWs in mountainous cities of Karst area

Multi-temporal evaluation and optimization of ecological network in multi-mountainous city

In karst multi-mountainous areas, there are a large number of urban remnant mountains (URMs) in urban built-up areas, which are an important part of urban green space system and have important and unique ecosystem service functions. However, the densifying development inside the city has been leading to the reduction of the number and area of the URMs and the decrease of the connectivity of the urban green space system, resulting in the fragile urban ecological environment. The construction and optimization of ecological network (EN) is an effective way to protect important urban ecological patches and improve the stability of urban green space ecosystem. Taking the central area of Anshun, a typical multi-mountainous city, as the study area, based on the land use data of 2007, 2012 and 2017, the ecological sources were identified by morphological spatial pattern analysis (MSPA) and the potential ecological corridors were extracted by the minimum cumulative resistance model (MCR), and the ENs of the three periods were identified. 18 ecological sources were selected for each of the three periods, with a total area of 833.67 hm2, 713.25 hm2 and 806.85 hm2, respectively and the intersection area of ecological sources reached 650.58 hm2. The ecological corridors and ecological sources dwindled with time. The Gravity model was used to extract the important EN corridor, the InVEST model was used to quantify the comprehensive habitat quality. The EN was optimized by adding extra ecological sources, mending ecological breakpoints and extracting habitat quality map patches. It is suggested to add 6 ecological sources and 34 ecological corridors, protect ecological nodes and build stepping stone patches. The results of this study could not only provide a scientific and reasonable basis for the ecological protection and the development of ecological protection strategies in the urban central area of Anshun, but also enrich the theoretical research of urban biodiversity conservation planning and ecological restoration practice in multi-mountainous cities

Vulnerability assessment of urban remnant mountain ecosystems based on ecological sensitivity and ecosystem services

Urban remnant mountains (URMs) are precious natural green habitat patches that can provide a series of ecosystem services for multi-mountainous cities. The increase in ecological sensitivity and degradation of ecosystem services affected by urban expansion and climate change have led to an increasing vulnerability of urban remnant mountain ecosystems (URMEs). To explore the vulnerability of URMEs, taking the central urban built-up area of the Guiyang city as the study area and URMs as the research object, the vulnerability of URMEs under natural factors and human disturbance was analyzed based on the Pressure-State-Response (PSR) model. The results showed that: (1) Karst rocky desertification, human disturbance, and road density within the buffer zones around URMs were the most important factors affecting the vulnerability of URMEs. Karst rocky desertification was the most likely eco-environmental problem of URMs, and carbon storage was the most important ecosystem service of URMEs. (2) Characteristics of fragile karst habitats in URMs and unreasonable human activities led to high ecological vulnerability, mainly with moderate and severe vulnerability predominating, and the low vulnerability of URMEs when they had moderate park utilization. (3) The ecological vulnerability of small URMs and those distributed in the urban center is higher, and the invulnerable URMEs and the slightly vulnerable URMEs are mainly distributed in the urban edge. The results of this study could provide references for ecological restoration and protection of URMs, and offer a basis for improving the resilience of multi-mountainous cities

Response of habitat quality to urban spatial morphological structure in multi-mountainous city

Revealing the relationship between urban spatial morphological structure (USMS) and habitat quality (HQ) is of great significance for high-quality urban development. In this study, the central urban area of a typical multi-mountainous city (Guiyang, China) was taken as research area. Two-dimensional (2D) and three-dimensional (3D) characteristic indicators system of USMS was constructed. The InVEST model was used to evaluate the HQ in the study area, and the spatial pattern characteristics of USMS and HQ in the multi-mountainous city were analyzed. Finally, the response relationship of HQ to USMS was revealed through Pearson correlation analysis and curve fitting. The results showed that: (1) The average level of HQ in the study area is low and the spatial aggregation effect is obvious; the spatial distribution difference between the high value area and the low value area is significant; the high value area is mainly distributed in the area where the large area of urban green space (UGS) and the urban remnant mountains (URMs) are located, while the low value area is mainly distributed in the high-intensity urban construction area. (2)The URMs have a significant impact on the USMS within the city, the intelligibility(I), spatial permeability, spatial aggregation degree, and spatial traffic attraction potential were poor; the buffer zone within 4 km of the urban center is the core area of urban development, and the buffer zone within 15 km is the rapid urban development area. (3)Among the USMS indicators, Choice(C) was significantly positively correlated with the HQ, while the Connectivity(Con), I, Average height(AVH), and Otherness(O) were significantly negatively correlated with the HQ. (4)Stepwise regression results showed that USMS could explain the difference of HQ in the study area well, and the values of fitting coefficient R2 were 0.975, 0.837 and 0.945 in 2008, 2013 and 2018, respectively. (5)There was a quadratic function relationship between HQ and USMS principal component factor f, and there was a threshold effect, and the thresholds were 0.798 in 2008, 0.905 in 2013 and 0.474 in 2018, respectively. This study confirmed the response relationship of HQ to USMS and demonstrates the existence of a threshold, which has important reference significance for urban biodiversity conservation and high-quality urban development