An ontology for satellite databases

This paper demonstrates the development of ontology for satellite databases. First, I create a computational ontology for the Union of Concerned Scientists (UCS) Satellite Database (UCSSD for short), called the UCS Satellite Ontology (or UCSSO). Second, in developing UCSSO I show that The Space Situational Awareness Ontology (SSAO) (Rovetto & Kelso 2016)-—an existing space domain reference ontology—-and related ontology work by the author (Rovetto 2015, 2016) can be used either (i) with a database-specific local ontology such as UCSSO, or (ii) in its stead. In case (i), local ontologies such as UCSSO can reuse SSAO terms, perform term mappings, or extend it. In case (ii), the author’s orbital space ontology work, such as the SSAO, is usable by the UCSSD and organizations with other space object catalogs, as a reference ontology suite providing a common semantically-rich domain model. The SSAO, UCSSO, and the broader Orbital Space Environment Domain Ontology project is online at https://purl.org/space-ontology and GitHub. This ontology effort aims, in part, to provide accurate formal representations of the domain for various applications. Ontology engineering has the potential to facilitate the sharing and integration of satellite data from federated databases and sensors for safer spaceflight.     

空间碎片与空间环境

空间碎片起源于人类的航天活动,目前空间碎片的空间密度已经对航天器的安全造成威胁,且其数量仍在高速增长,已成为一个引人瞩目的环境问题,航天器受空间碎片撞击的事件时有发生。大空间碎片的撞击会使航天器姿态和轨道发生改变,更严重的是会导致航天器破损甚至完全解体;小空间碎片的撞击会使航天器表面性能改变,部分器件损伤或失效,使航天器丧失功能。目前地基设备只能对厘米级及更大的碎片进行观测、跟踪和编目,航天器可以根据空间碎片的轨道参数进行规避和机动飞行,以避免撞毁;小空间碎片(<1cm)数量众多,但无法进行轨道测量,只能通过天基直接探测和样品回收获得数据,数值建模和超高速撞击模拟实验是进行小空间碎片风险评估和撞击效应研究的有效方法。对小空间碎片只能采取被动防护的方法,在航天器总体设计、防护结构和材料方面着手,降低空间碎片的威胁。改善空间环境,减少空间碎片的最根本方法是对航天器采取钝化措施,减少空间碎片的产生,理论上还可以采取措施,清扫、清除或回收空间碎片。     

Optical and photometric studies of Earth orbiting small space objects

Variations of light curves for space objects are investigated. Optical observations and photometric measurements for small space debris on highly elliptical orbits (HEO) and geostationary orbits (GEO) are used to determine their orbital parameters. Light curves of small space debris with various area-to-mass ratios and orbital characteristics are discussed. Tracking of some objects shows very rapid brightness variations related to perturbations of the orbital parameters. Changes in brightness and equatorial coordinates of the studied objects are found in observational data. Our results allow improving the accuracy of space debris orbital elements.     

Chemical Classification of Space Debris

Space debris, here referring to all non-operating orbital objects, has steadily increased in number so that it has become a potential barrier to the exploration of space. The ever-increasing number of space debris pieces in space has created an increasingly threatening hazard to all on-the-orbit spacecraft, and all future space exploration activities have to be designed and operated with respect to the increasing threat posed by space debris. Generally, space debris is classified as large, medium and small debris pieces based on their sizes. The large debris piece is easily catalogued, but medium to small debris pieces are very difficult to track and also quite different in damage mechanisms from the large ones. In this paper, a scheme of chemical classification of space debris is developed. In our scheme, the first-order classification is employed to divide space debris into two groups: natural     

A dilatant,two-layer debris flow model validated by flow density measurements at the Swiss illgraben test site

We propose a dilatant, two-layer debris flow model validated by full-scale density/saturation measurements obtained from the Swiss Illgraben test site. Like many existing models, we suppose the debris flow consists of a matrix of solid particles (rocks and boulders) that is surrounded by muddy fluid. However, we split the muddy fluid into two fractions. One part, the inter-granular fluid, is bonded to the solid matrix and fills the void space between the solid particles. The combination of solid material and inter-granular fluid forms the first layer of the debris flow. The second part of the muddy fluid is not bonded to the solid matrix and can move independently from the first layer. This free fluid forms the second layer of the debris flow. During flow the rocky particulate material is sheared which induces dilatant motions that change the location of the center-of-mass of the solid. The degree of solid shearing, as well as the amount of muddy fluid and of solid particles, leads to different flow compositions including debris flow fronts consisting of predominantly solid material, or watery debris flow tails. De-watering and the formation of muddy fluid washes can occur when the solid material deposits in the runout zone. After validating the model on two theoretical case studies, we show that the proposed model is able to capture the streamwise evolution of debris flow density in time and space for real debris flow events.

     

Are you Wittfogel or against him? Geophilosophy,hydro-sociality,and the state

Recent explorations of the “hydrosocial” cycle draw inspiration from Wittfogel’s basic concern with politics, power, and centralized authority, but move well beyond the limitations of previous scholarship. Most importantly, they have (re)introduced a conception of the social into the hydrological, and grappled with water’s materiality in ecumenical and creative ways. Understanding hydro-sociality requires an ontological approach to matter, flux, and flow. Water is the “universal solvent,” which makes it infinitely capable of mutation and connection. Yet, such indeterminacy proves difficult to capture in research and writing. Here I pinpoint some of the politico-discursive strengths of the hydrosocial approach, and also where I think its already strong ontological inclinations could be further developed. I draw from work in the area of “geophilosophy” as a way to explore hydro-sociality as a nonlinear process, developing a historicized account of irrigation politics, the flows of matter, and nonlinear dynamics in northwest Mexico’s Río Mayo Valley.     

Spatialities of data: mapping social media ‘beyond the geotag’

As emerging sources of so-called ‘big data’ are increasingly utilized in order to understand social and spatial processes, so too have these new data sources become the subject of harsh criticism from more critically-oriented geographers and social scientists. This paper argues that one of the major issues preventing a more productive dialogue between critical human geographers and those already engaging in the mapping and analysis of these new data sources is around the ways that space and spatiality are conceptualized in social media mapping. As such, this paper draws on and extends earlier critiques of the ‘spatial ontology of the geotag’, in which the geographic analysis of geotagged social media data over-privileges the single latitude/longitude coordinate pair attached to each individual data point, often leading to the kind of simplistic mappings and interpretations prevalent today. The goals of this paper are two-fold: first, to demonstrate how the spatial ontology of the geotag is implicitly operationalized within mainstream social media mapping exercises, and how this understanding of space remains incongruent with existing conceptions of space drawn from human geography. Second, using the example of tweeting in the wake of the August 2014 killing of an unarmed African–American teenager by a police officer in Ferguson, Missouri, this paper demonstrates how a more geographically-situated analysis of this kind of data, inspired by relational or multidimensional conceptualizations of space, can yield alternative understandings of the social processes embedded in such data.     

Monumental space and the uncanny

This paper takes up the attempt to theorize the relation between the subjectivity of the political actor and the ideological aura of the monumental site. It does this with reference to the spatial history of Strijdom Square in Pretoria, South Africa, a cultural precinct and monumental space which was the site of a series of brutal racist killings committed by the Square’s unrelated namesake, militant right-winger Barend Strydom. This troubling intersection of subjectivity, space and ideology represents something of an explanatory limit for spatio-discursive approaches, certainly in as much as they are ill-equipped to conceptualize the powerfully affective, bodily and fantasmatic qualities of monumental spaces. In contrast to such approaches I offer a psychoanalytically informed account which grapples with the individualized and imaginative identities of space, with space as itself a form of subjectivity. I do this so as understand the ideological aura of monuments as importantly linked to the ‘intersubjectivity’ of subject and personified space. I then turn to Freud’s notion of the uncanny as a theory able to explain a series of disturbing affects of monuments, such as those of ‘embodied absence’ and ‘disembodied presence’. These and similar affects of ‘ontological dissonance’ (such as unexplained instances of doubling or repetition) may function in an ideological manner, both so as to impose a ‘supernaturalism of power’, and to effect an uncanny form of interpellation.     

Assessment of nonlinear trends and seasonal variations in global sea level using singular spectrum analysis and wavelet multiresolution analysis

The main purpose of this paper is to apply the singular spectrum analysis (SSA), based on the phase space, and the wavelet multiresolution analysis (WMA), based on the frequency space, to the weekly time series of global sea level anomaly (GSLA) derived from satellite altimetry data over 1993–2013, in order to assess its nonlinear trends and its seasonal signals. The SSA results show that the GSLA time series is mainly dominated by a nonlinear trend explaining 89.89 % of the total GSLA variability, followed by annual and semi-annual signals with an explained variance of 9.15 and 0.32 %, respectively. For the annual signal, both methods give similar results. Its amplitude is less than 14 mm with an average of about 11 mm, and its minimum and maximum occur in April and October, respectively. The calculation of sea level trend, by both methods, is direct without removing the seasonal signals from the original GSLA time series as the most commonly used in the literature. The global sea level trend obtained from the WMA is about 2.52 ± 0.01 mm/year which is in good agreement with 2.94 ± 0.05 mm/year estimated from the SSA. Furthermore, the SSA method is most suitable for seasonal adjustment, and the WMA method is more useful for providing the different rates of sea level rise. Indeed, the WMA reveals that the global sea level has risen with the rate of 3.43 ± 0.01 mm/year from January/1993 to January/1998, 0.66 ± 0.01 mm/year from February/1998 to May/2000, 5.71 ± 0.03 mm/year from June/2000 to October/2003, and 1.57 ± 0.01 mm/year since January/2004.     

Situating the geographies of injustice in democratic theory

Post-Marxist and poststructuralist ontologies of the political have been important reference points for recent discussions of democracy in critical human geography and related fields. This paper considers the conceptual placement of contestation in a strand of democratic theory often denigrated by these approaches, namely theories of deliberative democracy informed by post-Habermasian Critical Theory. It is argued that this concern with contestation derives from a focus on the relationships between different rationalities of action. It is proposed that this tradition of thought informs a distinctively phenomenological approach to understanding the situations out of which democratic energies emerge. In elaborating on this phenomenological understanding of the emergence of political space, the paper proceeds in three stages. First, it is argued that the strong affinities between ontological conceptualisations of ‘the political’ and the ontological register of canonical spatial theory squeezes out any serious consideration of the plural rationalities of ordinary political action. Second, debates between deliberative and agonistic theorists of democracy are relocated away from questions of ontology. These are centred instead on disputed understandings of ‘normativity’. This move opens up conceptual space for the analysis of phenomenologies of injustice. Third, using the example of debates about transnational democracy in which critical theorists of deliberative democracy explicitly address the reconfigurations of the space of ‘the political’, it is argued that this Critical Theory tradition can contribute to a distinctively ‘topological’ sense of political space which follows from thinking of political action as emerging from worldly situations of injustice. In bringing into focus this phenomenological approach to political action, the paper has lessons for both geographers and political theorists. Rather than continuing to resort to a priori models of what is properly political or authentically democratic, geographers would do well to acknowledge the ordinary dynamics and disappointments which shape political action. On the other hand, political theorists might do well to acknowledge the limits of the ‘methodological globalism’ that characterises so much recent work on the re-scaling of democracy.     

Comparison of debris-flow volumes from burned and unburned areas

The goals of this work are to show the range of debris-flow volumes and watershed characteristics for several locations, and the differences in flow volumes for events triggered soon after wildfire. A dataset of 929 events was divided into groups based on location and burn status. The three unburned locations show significant differences: debris flows from the Italian Alps are larger and generate more debris per unit basin area or unit channel length than flows in the Western USA or in the Pacific Northwest. However, some of the observed differences may be attributed to the skew of the Italian Alps dataset towards larger events, and the small size and limited range of the Pacific Northwest data. For burned watersheds in the Western U.S. events, there is a clear progression in decreasing volume in debris flows as basins recover from the wildfire: it takes approximately 1 year, or at a few locations, as much as 3 years, for debris production to return to pre-fire rates. The difference is most apparent when the data are normalized for basin area (the area yield, which is 2× larger for burned basins) or for channel length (the length yield, which is 1.6× larger for burned basins). When normalized simultaneously for basin area, channel length, and channel gradient, burned areas produce significantly more debris (2.7–5.4 times as much). Burned areas in the Western USA are more sensitive to wildfire and produce larger debris flows than burned areas in more humid climates such as the Pacific Northwest.     

DFTopoSim: Modeling Topographically-Controlled Deposition of Subseismic Scale Sandstone Packages Within a Mass Transport Dominated Deep-Water Channel Belt

Facies bodies in geostatistical models of deep-water depositional environments generally represent channel-levee-overbank-lobe morphologies. Such models adequately capture one set of the erosional and depositional processes resulting from turbidity currents traveling downslope to the ocean basin floor. However, depositional morphologies diverge from the straight forward channel-levee-overbank-lobe paradigm when the topography of the slope or the shape of the basin impacts the timing and magnitude of turbidity current deposition. Subaqueous mass-transport-deposits (MTDs) present the need for an exception to the channel-levee-overbank-lobe archetype. Irregular surface topography of subaqueous MTDs can play a primary role in controlling sand deposition from turbidity currents. MTD topography creates mini-basins in which sand accumulates in irregularly-shaped deposits. These accumulations are difficult to laterally correlate using well-log data due to their variable and unpredictable shape and size. Prediction is further complicated because sandstone bodies typical of this setting are difficult to resolve in seismic-reflection data. An event-based model is presented, called DFTopoSim, which simulates debris flows and turbidity currents. The accommodation space on top of and between debris flow lobes is filled in by sand from turbidity currents. When applied to a subsurface case in the Molasse Basin of Upper Austria, DFTopoSim predicts sand packages consistent with observations from core, well, and seismic data and the interpretation of the sedimentologic processes. DFTopoSim expands the set of available geostatistical deep-water depositional models beyond the standard channel-levee-overbank-lobe model.     

Design and Implementation of Space Dust Database

Space debris is very dangerous to the security of on-the-orbit spacecrafts, and it is increasing in number at high speed with the expansion of human space exploration. Space debris has become a serious space pollutant noticed by many astronomers. The increase of space dust sources and the development of research on space dust urgently need space dust data sharing and exchanging. It is necessary for us to establish the Space Dust Database to realize the sharing and canonical management of the data. The Space Dust Database (SDD) management system,based on the 3-layer B/S computer mode, was designed and implemented in this paper. The system‘s features include significantly improved runtime efficiency, good scalability and maintainability. The Space Dust Database can pTovide some scientific bases for the study of the chemical constituents, mineral composition, origin and sources of space dust, but also provide excellent data services and decision-making support for the protection of space and model construction of space dust.     

A geo-ontology-based approach to decision-making in emergency management of meteorological disasters

Ontology as a kind of method for knowledge representation is able to provide semantic integration for decision support in emergency management activities of meteorological disasters. We examine a meteorological disaster system as composed of four components: disastrous meteorological events, hazard-inducing environments, hazard-bearing bodies, and emergency management. The geospatial characteristics of these components can be represented with geographical ontology (geo-ontology). In this paper, we propose an ontology representation of domain knowledge of a meteorological disaster system descending from an adapted geospatial foundation ontology, designed to formally conceptualize the domain terms and establish relationships between those concepts. The class hierarchy and relationships of the proposed ontology are implemented finally at top level, domain level/task level, and application level. The potential application of the ontology is illustrated with a case study of prediction of secondary disasters and evacuation decision of a typhoon event. The multi-level ontology model can provide semantic support for before-, during-, after-event emergency management activities such as risk assessment, resource preparedness, and emergency response where the formed concepts and their relationships can be incorporated into reasoning sentences of these decision processes. Furthermore, the ontology model is realized with a universally used intermediate language OWL, which enables it to be used in popular environments. This work will underlie the semantic integration among human beings, between heterogeneous systems and between human beings and systems, enable spatial semantic reasoning, and will be useful in guiding advanced decision support in emergency management of meteorological disasters.     

基于残差注意力机制的泥石流沟谷识别

针对泥石流灾害沟谷图像分类问题,文章对Resnet18网络进行改进,提出了一种改进的卷积神经网络模型。通过在网络结构中加入残差注意力模块,解决了原模型提取图像特征较差、边缘模糊的问题,改进后的网络能精确捕捉到泥石流灾害沟谷图像中的轮廓和内部山脊信息。此外,文章还对多种注意力机制结构进行了实验对比,分析其差异性,得出最适合泥石流灾害沟谷数据分类的注意力机制网络。实验表明改进后的网络模型在泥石流灾害沟谷图像的分类准确率达到75.42%,其分类性能在Resnet18网络模型的基础上提升了5.1%。     

Simulation of interactions among multiple debris flows

Adjacent debris flows may interact in many ways: two or more concurrent debris flows may merge; one debris flow can run out over an existing debris flow fan. Such interactions may cause debris flow properties to change in the mixing process as well as more severe adverse effects than those caused by a single debris flow. This paper aims to investigate the interactions among channelized debris flows originated from adjacent catchments. Both concurrent and successive debris flows are considered. If several debris flows originate from different locations concurrently and merge, the volumetric sediment concentration (i.e., the ratio of the volume of solid material to the total volume of debris flow), C _v, is a good index to capture the mixing process of these debris flows. The change in C _v reflects where mixing occurs and the mixing degree. The debris flow properties (e.g., yield stress and dynamic viscosity) evolve in the mixing process and can be captured by the change in C _v. The debris flow with a larger volume dominates the mixing process, and the properties of the mixed debris flow are more similar to those of the larger debris flow. The inundated areas and runout distances of successive debris flows are smaller than those of concurrent debris flows of the same total volume due to the smaller scales of the individual events and blockage by the earlier debris flows. However, the deposit depth in the interacting part of the debris flow fans of successive debris flows can be much larger than that of concurrent debris flows, leading to more destructive cascading hazards (e.g., the formation of debris barrier lakes). The sequence of successive debris flows not only significantly influences the runout characteristics of the debris flows but also substantially affects the cascading hazards.     

Mount ontake landslide simulation by the Cellular Automata model SCIDDICA-3

Cellular Automata (CA), a paradigm of parallel computing, represent an alternative to differential equations and are used for modelling and simulating very complex phenomena; CA models have been developed by our research group for the simulation of landslides. We present SCIDDICA-3, our most efficient model, a two-dimensional CA model together with the simulation results of the Mount Ontake (Japan) debris avalanche which occurred in 1984. Landslides are viewed as a dynamic system based exclusively on local interactions with discrete time and space, where space is represented by square cells, whose specifications (states) describe physical and chemical characteristics (friction, viscosity, altitude, debris thickness, etc.) of the corresponding portion of space. At the time t=0, cells are in states which describe initial conditions; the CA evolves then changing the state of all cells simultaneously at discrete times. Input for each cell is given by the states in the adjacent cells; the outflow computation from the cells gives the evolution of the phenomenon. The comparison between the real and simulated event is satisfying within limits to forecast the surface covered by debris.     

改进麻雀搜索算法的自然电位数据反演

自然电位法是一种成本低廉,野外观测操作简便的天然源地球物理勘探方法。自然电位数据反演具有病态和非线性的特征。常规反演算法分为局部优化类和全局搜索类,但基于梯度运算的局部优化算法难以求得全局最优解且反演效果依赖于初始模型的构建,而传统全局搜索算法又存在收敛速度慢,易陷入局部极值和不稳定的缺点。基于此,对一种新的全局优化策略(麻雀搜索算法)进行改进,通过混沌映射叠加反向学习策略初始化麻雀种群,再依随机概率使用Levy飞行策略更新麻雀个体位置来进一步提升算法对于解空间的探索能力和增强算法跳出局部极值的可能性。将改进前后的麻雀搜索算法分别应用于合成自然电位数据(不含与含10%、30%的随机噪声)与来自印度和法国的实测数据的反演解释中以对比检验改进算法的反演效果。理论测试结果表明：麻雀搜索算法(SSA)在无噪声干扰下的垂直圆柱和倾斜板模型数据反演误差为0.42%和0.25%,相同情况下改进麻雀搜索算法(ISSA)的反演误差为0.06%和0.07%,改进后算法拟合精度提高到3～7倍,对比目标函数收敛曲线图中ISSA的收敛速度与收敛精度都要明显优于SSA;SSA反演参数的稳定性、精度和异常响应曲线拟...