Large-scale Spatial Structures Research Articles

Large-scale spatial data visualization method based on augmented reality

BackgroundA task assigned to space exploration satellites involves detecting the physical environment within a certain space. However, space detection data are complex and abstract. These data are not conducive for researchers' visual perceptions of the evolution and interaction of events in the space environment. MethodsA time-series dynamic data sampling method for large-scale space was proposed for sample detection data in space and time, and the corresponding relationships between data location features and other attribute features were established. A tone-mapping method based on statistical histogram equalization was proposed and applied to the final attribute feature data. The visualization process is optimized for rendering by merging materials, reducing the number of patches, and performing other operations. ResultsThe results of sampling, feature extraction, and uniform visualization of the detection data of complex types, long duration spans, and uneven spatial distributions were obtained. The real-time visualization of large-scale spatial structures using augmented reality devices, particularly low-performance devices, was also investigated. ConclusionsThe proposed visualization system can reconstruct the three-dimensional structure of a large-scale space, express the structure and changes in the spatial environment using augmented reality, and assist in intuitively discovering spatial environmental events and evolutionary rules.

Self-enhanced mobility enables vortex pattern formation in living matter.

Ranging from subcellular organelle biogenesis to embryo development, the formation of self-organized structures is a hallmark of living systems. Whereas the emergence of ordered spatial patterns in biology is often driven by intricate chemical signalling that coordinates cellular behaviour and differentiation1-4, purely physical interactions can drive the formation of regular biological patterns such as crystalline vortex arrays in suspensions of spermatozoa5 and bacteria6. Here we discovered a new route to self-organized pattern formation driven by physical interactions, which creates large-scale regular spatial structures with multiscale ordering. Specifically we found that dense bacterial living matter spontaneously developed a lattice of mesoscale, fast-spinning vortices; these vortices each consisted of around 104-105 motile bacterial cells and were arranged in space at greater than centimetre scale and with apparent hexagonal order, whereas individual cells in the vortices moved in coordinated directions with strong polar and vortical order. Single-cell tracking and numerical simulations suggest that the phenomenon is enabled by self-enhanced mobility in the system-that is, the speed of individual cells increasing with cell-generated collective stresses at a given cell density. Stress-induced mobility enhancement and fluidization is prevalent in dense living matter at various scales of length7-9. Our findings demonstrate that self-enhanced mobility offers a simple physical mechanism for pattern formation in living systems and, more generally, in other active matter systems10 near the boundary of fluid- and solid-like behaviours11-17.

Time behavior of hubble parameter by torsion

Consequences of the consistent exact solution of Einstein–Cartan equation on the time dependence of Hubble parameter are discussed. The torsion leads to a space and time-dependent expansion parameter which results into nontrivial windows of Hubble parameter between diverging behavior. Only one window shows a period of decreasing followed by increasing time dependence. Provided a known cosmological constant and the present values of Hubble and deceleration parameter this changing time can be given in the past as well as the ending time of the windows or universe. The comparison with the present experimental data allows to determine all parameters of the model. Large-scale spatial periodic structures appear. From the metric with torsion outside matter, it is seen that torsion can feign dark matter.

Multi-scale feature learning via residual dynamic graph convolutional network for hyperspectral image classification

ABSTRACT Thanks to the relevant spectral-spatial information, hyperspectral images (HSIs) have been widely exploited in Earth observation. Recently, graph convolutional networks (GCNs) have attracted increasing attention in HSI classification due to their advantages in processing non-Euclidean structure data. Unlike convolutional neural networks (CNNs), which perform convolution operations on regular square regions, GCNs can directly work on graph structure data to extract the relationships among adjacent land covers. However, extracting meaningful and deep discriminative spectral-spatial features from HSIs is still a challenging task. In this article, a novel multi-scale feature learning via residual dynamic graph convolutional network is designed for HSI classification, which can extract large-scale contextual spatial structures at superpixel-level graph and local spectral-spatial information at pixel-level, significantly improving the performance of HSI classification. Unlike from the existing GCN-based methods that operate on a graph with a fixed neighbourhood size, multiple graphs with diverse neighbourhood scales are built to comprehensively leverage spectral-spatial information and relationship at multiple scales, and these graphs are dynamically updated to generate more discriminative features (via dynamic GCN) during the convolution process. Moreover, to fully use the multi-scale features extracted from HSIs, a multi-scale feature fusion module is developed to emphasize important features and suppress irrelevant ones. Extensive experiments carried on three benchmark data sets demonstrate the superiority of the proposed approach over other state-of-the-art methods.

Dynamic-mode-decomposition of the wake of the NREL-5MW wind turbine impinged by a laminar inflow

Dynamic mode decomposition (DMD) has been applied to the wake of the NREL-5MW wind turbine invested by a uniform inflow, to identify the most dynamically relevant coherent structures characterizing this flow. The decomposition has been applied on a snapshot dataset obtained by Large-Eddy Simulation of the flow impinging on the wind turbine, whose tower and nacelle are modeled by the immersed boundary method, whereas rotor blades are modeled using the actuator line method. The Sparsity-Promoting DMD algorithm allows one to select a limited number of dynamic modes optimally reconstructing the snapshot sequence. Among the largest-amplitude selected modes, we found the tip vortices, oscillating at an angular frequency equal to three times the rotational frequency of the turbine. Interestingly, the remaining selected modes are characterized by low frequencies and large-scale spatial structures, reaching the frequency range of the wake meandering. This small set of dynamic modes is highly relevant for the formulation of accurate reduced-order models, which would eventually lead to the design of optimized wind farms layout and control to increase the energy density produced.

A Survey of Space Robotic Technologies for On-Orbit Assembly

The construction of large structures is one of the main development trends of the space exploration in the future, such as large space stations, large space solar power stations, and large space telescopes. It is one of important development tendency, which aims to make full use of space robots to assemble space structures autonomously in the aerospace industry. Considering that on-orbit assembly is an effective method to solve the problem of construction of large-scale spatial structures, it is necessary to motivate and facilitate the research of space robotics technologies for on-orbit assembly. Therefore, in this paper, the development status of space robot technology and the relevant space robot on-orbit assembly technology in recent decades are summarized. First, based on the space robot motion planning and assembly sequence planning, the development of space robot planning algorithms is introduced. For space robot assembly task, the space robot assembly method is summarized. From the control point of view, how to solve the vibration suppression and compliant assembly of on-orbit assembly is reviewed, which provides a reference for the autonomous intelligent assembly of space robots for large-scale structures in space. In order to simulate the space assembly scene on the ground, this paper introduces the development of ground verification experiments and provides ideas for the effective verification of space on-orbit assembly technology. In summary, though some of these problems have been satisfactorily solved in the past research, further research is still necessary in the future. Finally, it looks forward to the future research direction of space machine on-orbit assembly.

Progress and Development Trend of Space Intelligent Robot Technology

Since space intelligent robots are not restricted by physiological conditions, it is an attractive choice for the development of automation technology to use them for space exploration and utilization. It is currently the key development direction of the major space powers over the world. This paper first investigates the robotic manipulators and humanoid robot systems for space station applications and reviews theories and methods for robots to achieve large-range stable motion and intelligent dexterous manipulation. Then, the intelligent robot systems for on-orbit satellite maintenance are reviewed, and the related technologies of multirobot collaboration are analyzed. Finally, we investigate the intelligent robot systems for on-orbit assembly of large-scale spatial structures and summarize the technologies of modular assembly and on-orbit manufacture. Overall, this paper reviews the technological progress and development trends of space robots, which provides a good reference for further technical research in this field.

Improved multi-objective Hybrid Genetic Algorithm for Shape and Size Optimization of Free-form latticed structures

Industrial and public buildings generally adopt spatial latticed structures as roofs, where the number of members is too large for the traditional genetic algorithm (GA) to conduct size optimization. In this paper, an improved multi-objective hybrid genetic algorithm incorporating the fully stressed design (FSD), called NSGA-II-FSD, is proposed for the shape and size optimization of large-scale free-form spatial latticed structures. The proposed method uses the B-spline theory, which makes it easier to generate free-form surfaces that meet the aesthetic requirements. The total mass and strain energy of the structure are selected as the objective functions, and the strength, as well as the stability of the member, are taken as the constraints. By incorporating the FSD, one can also set the stress ratio limit and get an optimal set of cross-sections of the members under the desired margin of safety. Besides, a significant mutation strategy is proposed in order to expand the searching boundary, which can avoid premature convergence. Through numerical examples of a cylindrical latticed shell and a free-form space truss , it is proved that the proposed method is effective, and engineers can choose the solution according to their preferences in practical design. • Method for shape and size optimization of latticed structures is proposed. • Proposed method can handle multi-objective optimization problems. • A significant mutation strategy is proposed to expand the searching boundary. • The improved FSD is effective to solve the problems with multiple load cases. • All individuals in Pareto front can be directly adopted by designers.

Stability of spatial dependence structure of extreme precipitation and the concurrent risk over a nested basin

Extreme low and high precipitation can cause natural disasters (e.g., drought and flood events) which have devastatingeffects on natural environment and the human society. In this study, we present a framework for assessing the stability of spatial dependence of extreme precipitation and their concurrence probability in a nested catchment. The Pearl River basin was used as a case study to test the applicability of the framework. This framework is threefold. This first part involves modeling spatial dependence of both summer maxima and winter minima precipitation between pairs of scattered gauges over the basin by employing the pair-copula constructions as a baseline model. The second part of this framework aims to identify the variability of spatial dependence as a result of the effects of external drivers. Specifically, variations in the spatial dependence of extreme precipitation in the Pearl River basin over different periods associated with the influence of large-scale climate signals were examined. The final part quantifies the probability of occurring extreme precipitation-related events simultaneously over broader areas related to a specific event at a given gauge and the possible spatial extents being affected. The results indicate that the presented framework is able to capture the large-scale spatial dependence structures of both summer maxima and winter minima precipitation. It also allows for explicitly estimating the pairwise concurrence probability of extreme high and low precipitation events and event-impacted areas across the basin.

Contemporary Odeon Buildings as a Sustainable Environment for Culture

The subject of this study is contemporary odeons in Poland, where 11 covered amphitheaters (odeons) have been built since 2005. The odeons were selected from a wider collection of 57 functioning amphitheaters. The study collected data on location, form, function, and construction. The data sources included the literature, archival research, design documentation, and competition entries. Descriptive and graphical comparative analyses of the phenomena, based on the statistics for completed structures and on design experiments in the case of unbuilt structures, were the two main research methods used in this study. The emergence and development directions of the typology of open cultural spaces from amphitheaters to odeons are presented in a global and regional context. Their interrelationships, affecting form and function, were also analyzed. The influence of high-end materials that were used to create these complex, large-scale spatial structures, and their impact on the environment, has been presented. The contemporary roofs covering the entertainment and stage complex were analyzed in relation to environmental factors, determining the location of the odeons. The functional aspects of these buildings and their cultural significance on a local, regional and global scale were discussed. The odeon in Biała Podlaska, built in 2019, was chosen as a case study to show, in detail, the complexity of the formation of contemporary odeons. In the discussion on the direction of the further evolution of open spaces for culture, an example of an unrealized competition design proposal of mobile roofing forms for the eighteenth-century amphitheater in the Royal Baths Park in Warsaw, Poland, was presented. The conclusions emphasize the environmental, spatial, functional, social and economic values of the establishment and functioning of contemporary odeons as open spaces of culture that are compliant with the principles of sustainable development.

Field measurement of wind pressure on a large-scale spatial structure and comparison with wind tunnel test results

Due to the features of light weight, high flexibility, and slight damping, large-scale spatial structures are very sensitive to wind load. Thus, special attention must be paid to wind effect on large-scale spatial structures. A wind pressure field measurement was carried out to characterize the actual wind pressure of a large-span spatial structure. Meanwhile, it is also intended to provide reliable full-scale measurements for verification of wind tunnel test results widely used in the design and construction of structure. In this study, both wind tunnel test and field measurement are utilized to investigate the properties of the wind pressure acting on a typical large-scale spatial structure. Specifically, wind pressure coefficients, spatial distribution, probability density distribution (PDF), non-Gaussian characteristics, and power spectral density (PSD) are fully compared and discussed based on the results of the wind tunnel test and long-term field measurement. The comparison results show that generally the results of the wind tunnel test have good agreement with those of the field measurement. In the meanwhile, the discrepancies between them are also observed. This study aims to fully investigate the wind effects on large-scale spatial structure and enhance the understanding of wind loads.

Compressive sensing of wind speed data of large-scale spatial structures with dedicated dictionary using time-shift strategy

The real-time wind monitoring is widely used to evaluate the wind effect on the large-scale spatial structures. Wireless sensor network (WSN) is usually the first choice for the large-scale spatial structures to collect wind monitoring data because of its super-large size. Compressive sensing (CS) has great potential in solving the energy problem of WSN and reduces the difficulty in transmission of massive data based on sparsity. However, wind signals are often not naturally sparse on the traditional bases (e.g., Fourier basis). This paper proposes a new method of constructing a dedicated dictionary for wind speed signals using the time-shift strategy. With this proposed dictionary, the signals can be compressed by random sampling and recovered by ℓ1-norm sparse regularization. The performance of the improved CS methodology is evaluated using two large-scale spatial structures. The results show that the proposed CS methodology has better performance than the traditional CS algorithm with the Fourier basis and the linear interpolation method. Furthermore, the influences of the relevant critical parameters (regularization parameter, lag, sliding window size, and compression ratio) of the improved CS methodology are comprehensively explored.

Development of laser-based displacement monitoring system and its application to large-scale spatial structures

Proper deformation process is essential for forming the shape of cable net structures during construction. This highlights the importance of identifying uneven and excessive deformation when building large-scale cable net structures. As such, the deformation of large-scale cable net structures should be accurately monitored in a real-time manner during the construction process. This study is to develop a laser-based displacement monitoring system for tracing the real-time deformation of large-scale spatial structures. The developed displacement monitoring system combines wireless sensor networks (WSN) and laser ranging technology. The laser-based displacement monitoring system is implemented on the National Speed Skating Oval (NSSO), which is a large-scale cable net structure, to obtain the relative displacement change between the cable net structure and the supporting system. On the other hand, the finite element (FE) model of the NSSO is established to simulate the deformation process. Then, the measured displacement results are compared with the FE model-derived counterparts. It is shown that the simulated and measured results have a good agreement, which indicates the effectiveness of the laser-based displacement monitoring system.

The Usage of Iterative Methods of Implementation of Complex Civil Engineering Projects Based on Stadium Canopy Large-Scale Spatial Structures

The term iteration (from the Latin „iteratio” - repetition) deals with actions based on repeating a specific process as a method of achieving the desired objective. The iterative approach is used in computer science in creating programming algorithms. The iterative method is based on the assumption that a complicated program is created as the sum of individual iterations – separate steps that are increasingly detailed. The implementation of civil engineering projects is often indicated by computer science theorists as an example of not using the iterative methodology to solve complex problems. This is justified by the necessity to create a plan of realization for subsequent, different actions based on a previously prepared interdisciplinary design. However, there is an entire group of large-scale spatial structures whose characteristics point to the possibility of using iterative methodology both during the design phase, as well as in its implementation. Such facilities are oval stadium canopies based on using a repetitive spatial element in the construction structure, which in determining a clearly dominant architectural form constitutes a separate iteration also in the temporal sense. Testing the accuracy of the above-mentioned thesis is based on analyses of selected examples of stadium canopies as far as layout forms, as well as the principles of the functioning of constructional structures, exceptional due to extensive span and force. It is necessary to conduct an analysis of the characteristic features of these facilities, their structures, as well as the relationship between the spatial shape with the algorithms used and types of repetitive components. The implementation methods based on prefabrication of the elements of the constructional structure, as well as repetitive production and assembly schemes, should also be tested. In the tested multi-scale spatial facilities with clearly defined, often rhythmical structures such as stadium canopies, there are algorithms made up of clear iterations. Both singular, as well as sequential iterations, are used, the latter being a consequence of adapting the layout shape to the functional system of the stadium in case of facilities on the plan of an ellipse. In the facilities based on the plan of a circle, there is an algorithm with one type of an iteration with a scale resulting from the assumed constant constructional rhythm. The iterative approach is an immanent feature of designing and implementing large-scale oval stadium canopy spatial structures. The iterative method also concerns the process of constructional optimization of each individual element of the structure. Facilities created with the use of the iterative methodology are characterized by purity, honesty, and clarity of the synthetic architecture which corresponds in full to the thoroughly optimized construction. In addition, the postulate of the unity of function, form, and construction in architecture is also fulfilled.

Spatial winding: cooperative heterogeneous multi-robot system for fibrous structures

This research presents a cooperative heterogeneous multi-robot fabrication system for the spatial winding of filament materials. The system is based on the cooperation of a six-axis robotic arm and a customized 2 + 2 axis CNC gantry system. Heterogeneous multi-robot cooperation allows to deploy the strategy of Spatial Winding: a new method of sequential spatial fiber arrangement, based on directly interlocking filament-filament connections, achieved through wrapping one filament around another. This strategy allows to create lightweight non-regular fibrous space frame structures. The new material system was explored through physical models and digital simulations prior to deployment with the proposed robotic fabrication process. An adaptable frame setup was developed which allows the fabrication of a variety of geometries within the same frame. By introducing a multi-step curing process that integrates with the adaptable frame, the iterative production of continuous large-scale spatial frame structures is possible. This makes the structure’s scale agnostic of robotic reach and reduces the necessary formwork to the bare minimum. Through leveraging the capacities of two cooperating machines, the system allows to counteract some of their limitations. A flexible, dynamic and collaborative fabrication system is presented as a strategy to tailor the fiber in space and expand the design possibilities of lightweight fiber structures. The artifact of the proposed fabrication process is a direct expression of the material tectonics and the robotic fabrication system.

Nonlinear dynamic analysis method for large-scale single-layer lattice domes with uncertain-but-bounded parameters

Currently, nonlinear dynamic analysis for large-scale single-layer domes is commonly performed using deterministic numerical methods. However, in practical engineering cases, complex large-scale single-layer domes have many uncertain parameters that cannot be considered using deterministic methods. Therefore, there is a growing awareness that classical deterministic methods need to be extended towards the introduction of the uncertain aspects in dynamic analysis, and a non-deterministic analysis method for large-scale spatial structures is required. In this paper, a new method is presented by introducing uncertainties into the nonlinear dynamic analysis for large-scale single-layer lattice domes. The method accounts for uncertainties in material properties, structural imperfections, loads, and damping with bounds. The focus is on the treatment of uncertainty in damping and the adopted geometric shape, which is different from that of conventional approaches. Finite element dynamic analyses for sample structures with multiple sources of uncertainty subjected to dynamic loads are performed. Results show that the variability of the variables with an associated uncertainty imposes significant negative effects on the dynamic properties, dynamic demands, and safety of a dome. Uncertain damping in a structure plays the most important role in determining structural performance. The numerical results reveal the differences between conventional analysis methods with deterministic parameters used in previous practical applications and the uncertain analysis method. Finally, a parametric study is performed, and the impacts of sample size on statistical dynamic demands, single uncertain source on structural failure, and single uncertain source on damping coefficients are discussed.

YY1-MEDIATED PROMOTER-SUPER ENHANCER INTERACTIONS REGULATE MSC MULTIPOTENCY DURING REPLICATIVE AGING

Mesenchymal stem cells (MSC) are versatile in stem cell therapy and regenerative medicine, due to its capacity of in-vitro expansion and multilineage differentiation. However, how the MSC’s functions and the underlying epigenomic features are affected by aging and cellular senescence remains poorly understood. Here we used culture expanded human MSC isolated from umbilical cord tissue as an ex vivo model to characterize the chromatin 3D conformational changes associated with aging and senescence and correlate these changes to the changes in MSC stem cell functions during aging. By comparing late passage (P15) vs early passage (P5) MSC, no fundamental changes were found on the large-scale chromatin spatial structures including compartment switching and TAD boundaries. However, when focused on super enhancers, which act as major cis-regulatory hubs associated with lineage-specific functions, a large number of significant promoter-super enhancer interaction changes were discovered. Further examination revealed that YY1, a key regulator of promoter-enhancer looping, was highly enriched in these promoters and their corresponding super-enhancers. The expression of the genes involved in such changes is positively correlated with the variation of promoter-super enhancer interaction, indicating that the spatial communications between promoter and super-enhancer positively regulate gene expression. GO-term and TFBS enrichment analysis showed that these genes involved in cell cycle, adipocyte and osteoblast differentiation. Collectively, these results suggest that YY1-mediated promoter-super enhancer looping is an important regulatory mechanism for MSC multipotency during replicative aging.

Mesospheric bores at southern midlatitudes observed by ISS-IMAP/VISI: a first report of an undulating wave front

Abstract. Large-scale spatial structures of mesospheric bores were observed by the Visible and near-Infrared Spectral Imager (VISI) of the ISS-IMAP mission (Ionosphere, Mesosphere, upper Atmosphere and Plasmasphere mapping mission from the International Space Station) in the mesospheric O2 airglow at 762 nm wavelength. Two mesospheric bore events in southern midlatitudes are reported in this paper: one event at 48–54∘ S, 10–20∘ E on 9 July 2015 and the other event at 35–43∘ S, 24∘ W–1∘ E on 7 May 2013. For the first event, the temporal evolution of the mesospheric bore was investigated from the difference of two observations in consecutive passes. The estimated eastward speed of the bore is 100 m s−1. The number of trailing waves increased with a rate of 3.5 waves h−1. Anticlockwise rotation with a speed of 20∘ h−1 was also recognized. These parameters are similar to those reported by previous studies based on ground-based measurements, and the similarity supports the validity of VISI observation for mesospheric bores. For the second event, VISI captured a mesospheric bore with a large-scale and undulating wave front. The horizontal extent of the wave front was 2200 km. The long wave front undulated with a wavelength of 1000 km. The undulating wave front is a new feature of mesospheric bores revealed by the wide field of view of VISI. We suggest that nonuniform bore propagating speed due to inhomogeneous background ducting structure might be a cause of the undulation of the wave front. Temperature measurements from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) onboard the Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics (TIMED) satellite indicated that bores of both events were ducted in a temperature inversion layer.

On-orbit assembly mission planning considering topological constraint and attitude disturbance

This paper investigates the on-orbit assembly mission planning problem of a large space antenna structure. The study is significantly important for the construction of large-scale spatial structures. The flexible connection between the antenna pieces and the topological constraint are taken into consideration. Several innovative approaches are presented to realize the mission planning process. First, the mesh model from the fly net dynamics is adopted and modified to create a mapping between the vibrations of the antenna plate during the assembly process and the assembly path. Second, the geometrical model is developed to implement the topological constraint into the system. Finally, a hybrid method combining the branch-and-bound method and the modified ant colony algorithm is proposed to solve the optimization problem. The simulation results show that the proposed algorithm can efficiently obtain a solution which respects the topological constraint and suppresses the vibration disturbance as much as possible.

Internal atmospheric noise characteristics in twentieth century coupled atmosphere\u2013ocean model simulations

The statistical characteristics of the atmospheric internal variability (hereafter internal atmospheric noise) for surface pressure (PS) in twentieth century simulations of a coupled general circulation model are documented. The atmospheric noise is determined from daily post-industrial (1871–1998) Community Climate System Model 3 simulations by removing the SST and externally forced responses from the total fields. The forced responses are found from atmosphere-only simulations forced by the SST and external forcing of the coupled runs. However, we do not address the influence of the SST variability on the synoptic scale high frequency weather noise.The spatial patterns of the main seasonal modes of atmospheric noise variability are found for boreal winter and summer from empirical orthogonal function analyses performed globally and for various regions, including the North Atlantic, the North Pacific, and the equatorial Pacific. The temporal characteristics of the modes are illustrated by power spectra and probability density functions (PDF) of the principal components (PC). Our findings show that, for two different realizations of noise, the variability is dominated by large scale spatial structures of the atmospheric noise that resemble observed patterns, and that their relative amplitudes in the CGCM and AGCM simulations are very similar. The regional expression of the dominant global mode, a seasonally dependent AO-like or AAO-like pattern is also found in the regional analyses, with similar time dependence. The PCs in the CGCM and the corresponding SST forced AGCM simulations are uncorrelated, but the spectra and PDFs of the CGCM and AGCM PCs are similar.The temporal structures of the noise PCs are white at timescales larger than few months, so that these modes can be thought of as stochastic forcings (in time) for the climate system. The PDFs of the noise PCs are not statistically distinguishable from Gaussian distributions with the same standard deviation. The PDFs do not change substantially between the first and second half of the twentieth century.