Big Data Application Simulation Platform Design for Onboard Distributed Processing of LEO Mega-Constellation Networks

Due to the restricted satellite payloads in LEO mega-constellation networks(LMCNs),remote sensing image analysis,online learning and other big data services desirably need onboard distributed processing(OBDP).In existing technologies,the efficiency of big data applications(BDAs)in distributed systems hinges on the stable-state and low-latency links between worker nodes.However,LMCNs with high-dynamic nodes and long-distance links can not provide the above conditions,which makes the performance of OBDP hard to be intuitively measured.To bridge this gap,a multidimensional simulation platform is indispensable that can simulate the network environment of LMCNs and put BDAs in it for performance testing.Using STK's APIs and parallel computing framework,we achieve real-time simulation for thousands of satellite nodes,which are mapped as application nodes through software defined network(SDN)and container technologies.We elaborate the architecture and mechanism of the simulation platform,and take the Starlink and Hadoop as realistic examples for simulations.The results indicate that LMCNs have dynamic end-to-end latency which fluctuates periodically with the constellation movement.Compared to ground data center networks(GDCNs),LMCNs deteriorate the computing and storage job throughput,which can be alleviated by the utilization of erasure codes and data flow scheduling of worker nodes.

Simulation of Fracture Process of Lightweight Aggregate Concrete Based on Digital Image Processing Technology

The mechanical properties and failure mechanism of lightweight aggregate concrete(LWAC)is a hot topic in the engineering field,and the relationship between its microstructure and macroscopic mechanical properties is also a frontier research topic in the academic field.In this study,the image processing technology is used to establish a micro-structure model of lightweight aggregate concrete.Through the information extraction and processing of the section image of actual light aggregate concrete specimens,the mesostructural model of light aggregate concrete with real aggregate characteristics is established.The numerical simulation of uniaxial tensile test,uniaxial compression test and three-point bending test of lightweight aggregate concrete are carried out using a new finite element method-the base force element method respectively.Firstly,the image processing technology is used to produce beam specimens,uniaxial compression specimens and uniaxial tensile specimens of light aggregate concrete,which can better simulate the aggregate shape and random distribution of real light aggregate concrete.Secondly,the three-point bending test is numerically simulated.Thirdly,the uniaxial compression specimen generated by image processing technology is numerically simulated.Fourth,the uniaxial tensile specimen generated by image processing technology is numerically simulated.The mechanical behavior and damage mode of the specimen during loading were analyzed.The results of numerical simulation are compared and analyzed with those of relevant experiments.The feasibility and correctness of the micromodel established in this study for analyzing the micromechanics of lightweight aggregate concrete materials are verified.Image processing technology has a broad application prospect in the field of concrete mesoscopic damage analysis.

Chemical simulation teaching system based on virtual reality and gesture interaction

Background Most existing chemical experiment teaching systems lack solid immersive experiences,making it difficult to engage students.To address these challenges,we propose a chemical simulation teaching system based on virtual reality and gesture interaction.Methods The parameters of the models were obtained through actual investigation,whereby Blender and 3DS MAX were used to model and import these parameters into a physics engine.By establishing an interface for the physics engine,gesture interaction hardware,and virtual reality(VR)helmet,a highly realistic chemical experiment environment was created.Using code script logic,particle systems,as well as other systems,chemical phenomena were simulated.Furthermore,we created an online teaching platform using streaming media and databases to address the problems of distance teaching.Results The proposed system was evaluated against two mainstream products in the market.In the experiments,the proposed system outperformed the other products in terms of fidelity and practicality.Conclusions The proposed system which offers realistic simulations and practicability,can help improve the high school chemistry experimental education.

Image processing based three-dimensional model reconstruction for cross-platform numerical simulation

Numerical simulation is the most powerful computational and analysis tool for a large variety of engineering and physical problems.For a complex problem relating to multi-field,multi-process and multi-scale,different computing tools have to be developed so as to solve particular fields at different scales and for different processes.Therefore,the integration of different types of software is inevitable.However,it is difficult to perform the transfer of the meshes and simulated results among software packages because of the lack of shared data formats or encrypted data formats.An image processing based method for three-dimensional model reconstruction for numerical simulation was proposed,which presents a solution to the integration problem by a series of slice or projection images obtained by the post-processing modules of the numerical simulation software.By means of mapping image pixels to meshes of either finite difference or finite element models,the geometry contour can be extracted to export the stereolithography model.The values of results,represented by color,can be deduced and assigned to the meshes.All the models with data can be directly or indirectly integrated into other software as a continued or new numerical simulation.The three-dimensional reconstruction method has been validated in numerical simulation of castings and case studies were provided in this study.

Numerical simulation of tritium behavior under a postulated accident condition for CFETR TEP system

China Fusion Engineering Test Reactor(CFETR)is China's self-designed and ongoing next-generation fusion reactor project.Tritium confinement systems in CFETR guarantee that the radiation level remains below the safety limit during tritium handling and operation in the fuel cycle system.Our tritium technology team is responsible for studying tritium transport behavior in the CFETR tritium safety confinement systems of the National Key R&D Program of China launched in 2017,and we are conducting CFETR tritium plant safety analysis by using CFD software.In this paper,the tritium migration and removal behavior were studied under a postulated accident condition for the Tokamak Exhaust Processing system of CFETR.The quantitative results of the transport behavior of tritium in the process room and glove box during the whole accident sequence(e.g.,tritium release,alarm,isolation,and tritium removal)have been presented.The results support the detailed design and engineering demonstration-related research of CFETR tritium plant.

Towards Production and Energy Coupling System Modeling and Simulation for Energy Optimization in the Process Industry

The production and energy coupling system is used to mainly present energy flow, material flow, information flow, and their coupling interaction. Through the modeling and simulation of this system, the performance of energy flow can be analyzed and optimized in the process industry. In order to study this system, the component based hybrid Petri net methodology (CpnHPN) is proposed, synthesizing a number of extended Petri net methods and using the concept of energy place, material place, and information place. Through the interface place in CpnHPN, the component based encapsulation is established, which enables the production and energy coupling system to be built, analyzed, and optimized on the multi-level framework. Considering the block and brief simulation for hybrid system, the CpnHPN model is simulated with Simulink/Stateflow. To illustrate the use of the proposed methodology, the application of CpnHPN in the energy optimization of chlorine balance system is provided.

Computer Modeling and Simulation of Ultrasonic System for Material Characterization

In this paper the system for simulation, measurement and processing in graphical user interface implementa- tion is presented. The received signal from the simulation is compared to that of an actual measurement in the time domain. The comparison of simulated, experimental data clearly shows that acoustic wave propaga- tion can be modeled. The feasibility has been demonstrated in an ultrasound transducer setup for material property investigations. The results of simulation are compared to experimental measurements. Results ob- tained fit some much with those found in experiment and show the validity of the used model. The simula- tion tool therefore provides a way to predict the received signal before anything is built. Furthermore, the use of an ultrasonic simulation package allows for the development of the associated electronics to amplify and process the received ultrasonic signals. Such a virtual design and testing procedure not only can save us time and money, but also provide better understanding on design failures and allow us to modify designs more efficiently and economically.

Local Torrential Rainfall Event within a Mei-Yu Season Mesoscale Convective System:Importance of Back-Building Processes

An extreme rainfall event occurred over Hangzhou,China,during the afternoon hours on 24 June 2013.This event occurred under suitable synoptic conditions and the maximum 4-h cumulative rainfall amount was over 150 mm.This rainfall event had two major rainbands.One was caused by a quasi-stationary convective line,and the other by a backbuilding convective line related to the interaction of the outflow boundary from the first rainband and an existing low-level mesoscale convergence line associated with a mei-yu frontal system.The rainfall event lasted 4 h,while the back-building process occurred in 2 h when the extreme rainfall center formed.So far,few studies have examined the back-building processes in the mei-yu season that are caused by the interaction of a mesoscale convergence line and a convective cold pool.The two rainbands are successfully reproduced by the Weather Research and Forecasting(WRF)model with fourlevel,two-way interactive nesting.In the model,new cells repeatedly occur at the west side of older cells,and the backbuilding process occurs in an environment with large CAPE,a low LFC,and plenty of water vapor.Outflows from older cells enhance the low-level convergence that forces new cells.High precipitation efficiency of the back-building training cells leads to accumulated precipitation of over 150 mm.Sensitivity experiments without evaporation of rainwater show that the convective cold pool plays an important role in the organization of the back-building process in the current extreme precipitation case.

Digital Simulation Platform for Satellite Launch Mission Verification

To simulate the satellite launch mission under a general platform which could be used in a full-digital mode as well as in a semi-physical way, is an important way to certify the mission design performance as well as technical feasibilities, and it relates to complex system simulation methods such as multi-disciplinary coupling, multi-language modeling as well as interactive simulation and virtual simulation technologies. This paper introduces the design of a digital simulation platform for satellite launch mission verification.The platform has the advantages of high generality and extensibility, being easy to build up. The Functional Mockup Interface(FMI) Standard is adopted to achieve integration of multi-source models. A WebGL based 3D visual simulation tool is also adopted to implement the virtual display system which could display the rocket launch process and rocket-satellite separation with high fidelity 3D virtual scenes. A configuration tool was developed to map the 3D objects in the visual scene with simulation physical variables for complex rocket flight control mechanisms, which greatly improves the platform's generality and extensibility. Finally the real-time performance had been tested and the YL-1 launch mission was adopted to demonstrate the functions of the platform.The platform will be used to construct a digital twin system for satellite launch missions in the future.

Three-dimensional finite element simulation and reconstruction of jointed rock models using CT scanning and photogrammetry

The geometry of joints has a significant influence on the mechanical properties of rocks.To simplify the curved joint shapes in rocks,the joint shape is usually treated as straight lines or planes in most laboratory experiments and numerical simulations.In this study,the computerized tomography (CT) scanning and photogrammetry were employed to obtain the internal and surface joint structures of a limestone sample,respectively.To describe the joint geometry,the edge detection algorithms and a three-dimensional (3D) matrix mapping method were applied to reconstruct CT-based and photogrammetry-based jointed rock models.For comparison tests,the numerical uniaxial compression tests were conducted on an intact rock sample and a sample with a joint simplified to a plane using the parallel computing method.The results indicate that the mechanical characteristics and failure process of jointed rocks are significantly affected by the geometry of joints.The presence of joints reduces the uniaxial compressive strength (UCS),elastic modulus,and released acoustic emission (AE) energy of rocks by 37%–67%,21%–24%,and 52%–90%,respectively.Compared to the simplified joint sample,the proposed photogrammetry-based numerical model makes the most of the limited geometry information of joints.The UCS,accumulative released AE energy,and elastic modulus of the photogrammetry-based sample were found to be very close to those of the CT-based sample.The UCS value of the simplified joint sample (i.e.38.5 MPa) is much lower than that of the CT-based sample (i.e.72.3 MPa).Additionally,the accumulative released AE energy observed in the simplified joint sample is 3.899 times lower than that observed in the CT-based sample.CT scanning provides a reliable means to visualize the joints in rocks,which can be used to verify the reliability of photogrammetry techniques.The application of the photogrammetry-based sample enables detailed analysis for estimating the mechanical properties of jointed rocks.

Development of a Microcomputer System for 3D Kinematic Simulation

Software system is developed for real-time processing of 3D graphics by Visual C + + calling functions in PpenGL under the environment of Windows NT(Windows 95). By 3D modeling after mathematics modeling automatic generation of 3D soid and real-time processing of 3D animaation are realized, and a microcomputer system is developed for real-time kinematic simulation.

Pre-processing and post-processing method for geostress simulation using seismic interpretation results

In order to carry out numerical simulation using geologic structural data obtained from Landmark(seismic interpretation system), underground geological structures are abstracted into mechanical models which can reflect actual situations and facilitate their computation and analyses.Given the importance of model building, further processing methods about traditional seismic interpretation results from Landmark should be studied and the processed result can then be directly used in numerical simulation computations.Through this data conversion procedure, Landmark and FLAC(the international general stress software) are seamlessly connected.Thus, the format conversion between the two systems and the pre-and post-processing in simulation computation is realized.A practical application indicates that this method has many advantages such as simple operation, high accuracy of the element subdivision and high speed, which may definitely satisfy the actual needs of floor grid cutting.

Parallel algorithm of solidification process simulation for large-sized system of liquid metal atoms

A parallel arithmetic program for the molecular dynamics (MD) simulation study of a large sized system consisting of 50 000100 000 atoms of liquid metals is reformed, based on the cascade arithmetic program used for the molecular dynamics simulation study of a small sized system consisting of 5001 000 atoms. The program is used to simulate the rapid solidification processes of liquid metal Al system. Some new results, such as larger clusters composed of more than 36 smaller clusters (icosahedra or defect icosahedra) obtained in the system of 50 000 atoms, however, the larger clusters can not be seen in the small sized system of 5001 000 atoms. On the other hand, the results from this simulation study would be more closed to the real situation of the system under consideration because the influence of boundary conditions is decreased remarkably. It can be expected that from the parallel algorithm combined with the higher performance super computer, the total number of atoms in simulation system can be enlarged again up to tens, even hundreds times in the near future.

基于AutoForm的天地盖成型起皱仿真研究

为了解天地盖工件的成形起皱机理,以995铝合金为研究对象,通过有限元分析方法,利用Auto Form软件定量模拟坯料在不同形状、压边力、冲压速度、摩擦因数、圆角半径和凸模工艺面宽度下的成形起皱。结果表明:与长方形和圆角形坯料相比,采用切角的八边形坯料可以减轻工件的成形起皱;冲压速度对工件的成形起皱影响较小,几乎可以忽略不计,而压边力、摩擦因数和圆角半径的影响则相对较大,选用较大压边力、摩擦因数和圆角半径可以减轻工件的成形起皱;凸模工艺面宽度越小,工件成形起皱越小。该研究结果为实际生产提供了理论依据。

Vapor-Liquid Equilibrium of Ethylene ＋ Mesitylene System and Process Simulation for Ethylene Recovery

The amount of ethylene in refinery off-gas is high with a mass fraction of 20%,but the refinery off-gas is usually used as fuel gas in most refineries.The separation and recovery of ethylene is of remarkable significance for saving energy and reducing carbon dioxide emission.The aim of this paper is to use a novel absorbent mesitylene for the ethylene absorption process and assess its application feasibility through the ethylene + mesitylene vapor-liquid equilibrium data measurement and its binary interaction parameter correlation,as well as the simulation for ethylene separation process.

Software Architecture for Modeling and Simulation of Underwater Acoustic Information Systems

The simulation of underwater acoustic information flow is an important way to research sonar performance and its engagement effectiveness in the ocean environment.This paper analyzes the significance of modeling an open and sophisticated simulation software architecture by object-oriented method,and introduces the modeling processes and expression method of simulation architecture.According to the requirements of simulation system and the underwater acoustic information flow,the logical architecture of simulation software system is modeled by the object-oriented method.A use-case view captured the system requirements.The logical view shows the logical architecture of software system.The simulation software is decomposed into the loose coupling constituent parts by layering and partitioning the packages for maintainability.The design patterns enabled the simulation software to have good expansibility and reusability.The simulation system involving multi-targets and multi-sonar is developed based on the architecture model.Practices show that the model meets the needs for simulating an open and sophisticated system.

NUMERICAL SIMULATION OF THE THERMO-MECHANICAL PROCESS FOR BEAM BLANK CONTINUOUS CASTING

The aim of this study was to simulate the solidification process of beam blank continuous casting, and then find the reasons for the typical defects of the beam blank. A two-dimensional transient coupled finite element model has been developed to compute the temperature and stress profile in beam blank continuous casting. The enthalpy method was used in the heat conduction equation. The thermo-mechanical property in the mushy zone was taken into consideration in this calculation. It is shown that at the mold exit the thickness of the shell had its maximum value at the flange tip and its minimum value at the fillet. The temperature had a great fluctuation on the surface of the beam blank in the secondary cooling zone. At the unbending point, the surface temperature of the web was in the brittleness temperature range under the present condition. To ensure the quality, it is necessary to weaken the intensity of secondary cooling. At the mold exit the equivalent stress and strain have higher values at the flange tip and at the web. From the spray 1 to the unbending point, the maximum values of stress and strain gradually moved to the internal section of the flange tip and the web. However, whenever, there were bigger stress and strain values near the flange tip and the web than in the other parts, it must be very easy to generate cracks at those positions. Now, online verification of this simulation has been developed, which has proved to be very useful and efficient to instruct the practical production of beam blank continuous casting.

A wind tunnel simulation of the dynamic processes involved in sand dune formation on the western coast of Hainan Island

The western coast of Hainan Island exhibits a savanna landscape. Many types of sand dunes, including transverse dune ridges, longitudinal dune ridges, elliptical dunes, coppice dunes, and climbing dunes, are widely distributed in the coastal zone. In winter, high-frequency and high-energy NE winds （dominant winds） are prevalent, with a resultant drift direction （RDD） of S35.6°W. In spring, low-frequency and low-energy SW secondary winds prevail, with a RDD of N25.1°E. Wind tunnel simulations revealed that the airflow over the dune surface is the main factor controlling the erosion and deposition patterns of dune surfaces and the morphological development of dunes. In the region＇s bidirectional wind environment, with two seasonally distinct energy levels, the airflow over the surface of elliptical dunes, barchan dunes, and transverse dune ridges will exhibit a transverse pattern, whereas the airflow over longitudinal dunes ridges exhibits a lateral pattern and that over climbing dunes exhibits a climbing-circumfluent pattern. These patterns represent different dynamic processes. The coastal dunes on the western coast of Hainan Island are influenced by factors such as onshore winds, sand sources, coastal slopes, rivers, and forest shelter belts. The source of the sand that supplements these dunes particularly influences the development pattern： when there is more sand, the pattern shows positive equilibrium deposition between dune ridges and dunes; otherwise, it shows negative equilibrium deposition. The presence or absence of forest shelter belts also influences deposition and dune development patterns and transformation of dune forms. Coastal dunes and inland desert dunes experience similar dynamic processes, but the former have more diversified shapes and more complex formation mechanisms.

Safety analysis of wheel brake system based on STAMP/STPA and Monte Carlo simulation

The wheel brake system safety is a complex problem which refers to its technical state, operating environment, human factors, etc., in aircraft landing taxiing process. Usually, professors consider system safety with traditional probability techniques based on the linear chain of events. However, it could not comprehensively analyze system safety problems, especially in operating environment, interaction of subsystems, and human factors. Thus,we consider system safety as a control problem based on the system-theoretic accident model, the processes(STAMP) model and the system theoretic process analysis(STPA) technique to compensate the deficiency of traditional techniques. Meanwhile,system safety simulation is considered as system control simulation, and Monte Carlo methods are used which consider the range of uncertain parameters and operation deviation to quantitatively study system safety influence factors in control simulation. Firstly,we construct the STAMP model and STPA feedback control loop of the wheel brake system based on the system functional requirement. Then four unsafe control actions are identified, and causes of them are analyzed. Finally, we construct the Monte Carlo simulation model to analyze different scenarios under disturbance. The results provide a basis for choosing corresponding process model variables in constructing the context table and show that appropriate brake strategies could prevent hazards in aircraft landing taxiing.

EFFECT OF UNEQUAL DEFORMATION IN DEVELOPMENT OF ADVANCED PLASTIC PROCESSING TECHNOLOGIES

An effect of unequal deformation in development of advanced plasticprocessing technologies is researched by studying an in-plane bending process of strip metal underunequal compressing. The research results show the following: If appropriately controlled, unequalplastic deformation can play an important role not only in the improvement of quality of partsobtained by plastic processing technologies, but also in the development of new processes foradvanced plastic working technologies. A coordinated growth of unequal plastic deformation candevelop the deformation potentiality of material to the fall. The degree of unequal plasticdeformation can be used as bases for optimization design of processes and dies of plastic forming.