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Thin-walled tubular deployable composite boom (DCB) has gained significant attention due to its lightweight, simple structure and high packaging efficiency. The experimental and numerical simulation methods were employed in this paper to investigate the folding behavior of the DCB. Using T700/epoxy unidirectional reinforced prepreg as raw material, DCB specimens were prepared by the vacuum bag method. To complete the folding experiments of DCB specimens, a folding mechanism was designed and manufactured. Folding experiments of DCB specimens were conducted and folding moment versus rotational displacement curves were measured. In addition, a Finite Element Model (FEM) was established to predict the folding behavior of the DCB. Different failure criteria were considered in the numerical analysis, including the Tsai‐Hill criterion and maximum stress criterion. Prediction results using the FEM were compared with experimental results, and both sets of results were in good agreement. It is shown that the DCB can achieve the folding function without failure. The research results in this paper are of great significance to the practical engineering application of the DCB. [Display omitted] • Six tubular deployable composite boom specimens and a precise folding mechanism were designed and prepared. • Folding experiments were conducted to measure the folding moment and rotational displacement curves. • A finite element model for predicting the folding behavior of the tubular deployable composite boom was established. [ABSTRACT FROM AUTHOR]

Hydrogen is an ideal energy source and plays an important role in increasingly global energy issues and environmental problems. Liquid hydrogen (LH2) has many advantages over other storage methods, especially in terms of energy density. However, it may cause enormous harm once it leaks accidently. LH2 leakage is a complex multiphase process involving evaporation, condensation, transfer of mass and heat, and dispersion. In order to study LH2 transportation and storage systems safety, a research project has been carried out to develop a 3D numerical model using an open-source CFD code, OpenFoam, for investigating LH2 accidental release scenarios. Since the release of LH2 is a very complex process, our strategy is to study it step by step. Therefore, in this paper we present our research work at the first stage, a dispersion process of room-temperature gaseous hydrogen without multiphase flow. A small-scale hydrogen release conducted by Sandia National Laboratories is simulated. In this experiment, room-temperature gaseous hydrogen is injected upwards into the air from a small hole with a 1.91 mm diameter. The situations of Froude (Fr) number = 99, 152, and 268 are studied, respectively. The behavior of hydrogen at different Fr numbers is discussed. When high-speed hydrogen enters the air, the speed and concentration of hydrogen decrease rapidly. In addition, the greater the speed, the faster it decays. The result shows a close range of hydrogen reach. Details about the numerical model are introduced. The simulation results are used to verify the validity of the developing numerical model for dispersion and mixing of multi-species. The simulated concentrations and velocity distribution are analyzed and compared with experimental data. The simulation shows a good agreement with the data of Sandia National Laboratories. The agreement between experiments and simulations is measured using the Pearson correlation coefficient (>0.98), which indicates excellent consistency. In the next step, we will integrate the multiphase flow and phase change into the current model. The phase change of liquid hydrogen and air will be simulated to study the release of liquid hydrogen. • Using the open-source CFD code OpenFOAM for simulation of hydrogen jet. • A good agreement between the simulations results and experimental data has been found in this paper. • When high-speed hydrogen is injected into the air, both velocity and concentration drop rapidly. • Final concentration is not sensitive to different injection velocity. [ABSTRACT FROM AUTHOR]

This paper employs a numerical approach to investigate the impact of liquidity shocks on European options in modeling markets. To accurately capture the behavior of European options under liquidity shocks, a coupled system of differential equations is employed, consisting of a degenerate parabolic equation and a diffusion-free equation. The primary focus is on developing and analyzing implicit-explicit methods for numerically simulating European option pricing, specifically considering the presence of liquidity shocks while ensuring the positivity of the solution. The paper also includes convergence analysis and establishes the discrete comparison principle for the developed methods. Numerical experiments are conducted using both uniform and nonuniform meshes to validate the theoretical findings, demonstrating the efficiency and accuracy of the proposed methods. [ABSTRACT FROM AUTHOR]

Some errors exist in the above paper. [ABSTRACT FROM AUTHOR]

The Lennard-Jones (LJ) fluid, named after mathematician-physicist-chemist Sir John Lennard-Jones (1894–1954), occupies a special place among fluids. It is an ideal entity, defined as the fluid whose particles interact according to the Lennard-Jones potential. This paper expounds the history of the LJ fluid to throw light on the tensions between theory and computational practice. The paper argues for the following claims. Firstly, the computational approach—even prior to the computer—pragmatically aims at prediction, not truth. Secondly, computer simulation methods, especially "molecular dynamics" (MD), triggered a change in epistemology. Now, simulated model fluids became targets of investigation in their own right. The urge for prediction turned the LJ fluid into the most investigated fluid in engineering thermodynamics. Thirdly, MD took a huge upswing in the 1990s, due to exploratory options in simulation. We discuss how, under these conditions, predictive success might be fraught with problems of reproducibility. [ABSTRACT FROM AUTHOR]

• Numerically investigate folding pattern and rigid-flexible coupled dynamics of satellite-sphere system. • Achieve a larger volume folding rate by pattern of inflatable sphere with orderly deployment. • Inflating process has great influence on satellite based on rigid-flexible coupled dynamic model. • Reduce influence by heavier satellite, small inflation rate and appropriate control torque. Inflatable spheres can be applied to the aerodynamic drag deorbiting device for satellites. It may bring about a complicated dynamic problem under the disturbance from the lightweight large-volume inflatable sphere to the satellite. In order to explore this problem, rigid-flexible coupled dynamics behaviors of satellite-sphere system during inflating process are numerically studied in this paper. The folding pattern of inflatable sphere is designed to obtain the parametric model in the folded state. The dynamic analysis model of this system is established to analyze dynamic behaviors, including the dynamics of the satellite-sphere system, the gas state of the airbag and the disturbance to the satellite, during the inflating process. Parameter effects on the attitude disturbance are studied. The results show that the satellite mass, inflating mass rate and control torque have a great impact on the attitude disturbance. These works provide theoretical bases and technical supports for the engineering development of inflatable sphere deorbiting devices. [ABSTRACT FROM AUTHOR]

On-orbit capturing is a crucial step in the application of dual-arm space robots, aiming to accurately grasp a moving target and avoid damage to the arms terminal parts (i.e. the end effectors) due to contact force saturation. This paper presents a synthetic control method with target sticking for on-orbit capturing using a dual-arm space robot system from the approaching phase to pre-grasping phase. In the approaching phase, an online trajectory planning method based on visual servoing is proposed to obtain the desired trajectories for end effectors in work space. Then the joint torques are designed by the inverse kinematics and inverse dynamics to track the desired trajectories. Different from most of the current research, a new sticking phase is proposed after the approaching phase and before the pre-grasping phase. In the sticking phase, a force and motion control method is designed to maintain a close relative distance between end effectors and the target, which can avoid saturation of contact forces and avoid damage to the end effectors. In what follows, an impedance control method is proposed in the pre-grasping phase to absorb the impact energy and grasp the target accurately. The synthetic control strategy integrates the controllers of all the phases mentioned above. Automatic switching among the phases is realized by using logic judgment according to the system real states, which is more consistent with the real capturing environment. Finally, numerical simulation results demonstrate the effectiveness of the proposed synthetic control scheme. The results can be applied to the trajectory planning and control of on-orbit capturing, avoiding contact force saturation and ensuring the safety of the system. [ABSTRACT FROM AUTHOR]

Nonlocal problems involving fourth-order terms pose several difficulties such as numerical discretization and its related convergences analysis. In this paper, the well-posedness of the extended Fisher-Kolmogorov equation with nonlocal diffusion is first analyzed using the Faedo-Galerkin technique and the classical compactness arguments. Moreover, we adopt a BDF2 scheme for time discretization and a mixed Galerkin scheme for spatial discretization. Then, we derive the optimal order convergence rates of the fully discrete system. Finally, some numerical simulations and convergence results are provided to confirm the theoretical results and the accuracy of the proposed scheme. [ABSTRACT FROM AUTHOR]

Hydrogen is considered a truly clean energy source with great potential for replacing fossil fuels. However, the special physical and chemical properties of this source make large-scale, safe, and efficient storage challenging, thus limiting its widespread use. Consequently, an underground hydrogen storage system inspired by underground methane storage and CO 2 geological sequestration has been proposed, and it is increasingly becoming a focus of research. Depleted oil reservoirs are ideal sites for such systems. Nevertheless, research on these types of underground hydrogen storage systems is limited to a few feasibility assessments, and the hydrogen seepage laws in reservoirs with residual oil are not well understood. In this paper, a study was conducted involving mathematical modeling and numerical simulation of underground hydrogen storage, which was converted from the SSZ low-permeability depleted oil reservoir in Bohaiwan Basin, eastern China, to reveal the seepage patterns between hydrogen and complicated in situ fluids (oil, gas, and water). First, a comprehensive analysis was conducted using numerous rock samples and experimental data to identify the composition, genesis, and distribution patterns of the sandstone reservoir, detailing its internal pore structure and fluid distribution postdepletion characteristics. Then, the hydrogen seepage properties in the presence of oil films in the three main throat types of low-permeability sandstone were analyzed, and corresponding mathematical models of the different throats were established. Finally, a numerical simulation of underground hydrogen storage was conducted to assess the impacts of various parameters, such as injection speed, reservoir heterogeneity, and residual oil saturation, on hydrogen seepage. The planar and vertical diffusion patterns of hydrogen were clarified, and the key factors affecting the efficiency of underground hydrogen storage were analyzed, offering suggestions for the establishment of stable and efficient underground hydrogen storage systems. • Selection and description of typical low-permeability reservoirs for UHS. • Mathematical model establishment for hydrogen percolation in porous rock. • Numerical simulation of the storage process of hydrogen. • Percolation laws of hydrogen in rock porous. [ABSTRACT FROM AUTHOR]

Advancements in bulk metallic glass thermoplastic forming unleash the potential to fabricate microscale metallic features with unparalleled precision and durability, i.e. microspine gripping structures for mobility platforms on planetary or in-space robots. Four designs of grippers were fabricated and rigorously tested. Coefficient of friction on four test surfaces were measured and compared to SiC paper and Velcro. The hardness and elasticity of the bulk metallic glasses make them a game-changer in the field, offering a superior alternative to conventional nonmetallic grippers. • Microspine grippers were manufactured via thermoplastic forming of bulk metallic glasses using silicon-on-insulator molds. • The microspines excelled on textured surfaces, where sharp points anchor on to pores or softer regions. • Mechanical behavior of microspines were studied using nanoindentor-based micro-compression and computer simulations. [ABSTRACT FROM AUTHOR]

The paper presents a case study of the data analysis in the CDHS scattering experiment of particle physics performed in 1983. The case study compares the function of computer simulation in the data analysis with recent philosophical work on the role of simulations in high energy physics (HEP) and the theory-ladenness of the data. In the data analysis of CDHS, computer simulations entered an iterative process of probabilistic data correction. The computer simulation was a crucial ingredient of the data analysis that served to increase the accuracy of the measurement. The way in which simulation was used corresponds in a certain sense to the function of "models as mediators" (Morgan and Morrison), by mediating knowledge about measurement errors and the way of correcting them. I argue that this use of simulation did not give rise to a vicious circle of adjusting data to theory and vice versa but only to a weak, or benign, theory-ladenness of the data compatible with scientific realism. In the publication of the CDHS results, the measurement outcomes are called "observed data", indicating a realist attitude of the physicists towards the measured quantities which does not exactly fit in with entity realism or theory realism. [ABSTRACT FROM AUTHOR]

Paper (Maniar and Bhattacharyay, 2021) introduces a discrete random-walk (RW) model with a site dependent waiting time and an external force i.e. a site dependent drift. The RW is compared with a Smoluchowski equation in continuous space and time with space dependent diffusivity and space dependent damping. Using numerical simulations in Maniar and Bhattacharyay (2021) it is shown that the equilibrium distribution satisfies locally the Stokes–Einstein relation i.e. there is a constant temperature in the whole system. Here we show that the result can be recovered analytically with a continuous limit in the RW master equation. Moreover, we evidence that the RW model should be carefully defined in order to satisfy locally Stokes–Einstein relation, indeed a different definition of the discrete RW process describes a system that satisfies the Smoluchowski equation with constant damping, where the temperature is not uniform. [ABSTRACT FROM AUTHOR]

In order to understand and master the diffusion mechanism and spatial concentration distribution of hydrogen leakage in the engine room, this paper studies the diffusion behavior and concentration distribution of hydrogen under the coupling effect of multiple factors, and further explores the optimal installation location of the sensors. The results indicate that when the ventilation rate increases by 1, 2, and 3 times, the diffusion volume of hydrogen decreases by about 0.4, 0.5, and 0.6 times. The harm of the increase in leakage diameter is greater than the leakage pressure. And the temperature has a greater impact on the hydrogen volume fraction in areas below 4 % and a smaller impact on areas above 4 %. In this environment, the sensors should be installed at or above 5.5 m in the rear of the engine room and above the axis of the hydrogen transport pipeline interface, valves and other places prone to leakage. • Taking a ship engine room as the research object. • The influence of various factors on hydrogen distribution is compared. • The spatial concentration distribution of hydrogen leakage is analyzed. • Explored the installation position of the sensors. [ABSTRACT FROM AUTHOR]

This paper proposes a method to describe the bi-modular behavior of quasi-brittle materials. The approach is based on using multiple loading functions that are associated with the stress state of the material point. The model also includes degradation laws that control the evolution of the internal variables under tension and compression, which allows the representation of the material response with fidelity. The following approach outlines an objective methodology for improving classical models and provides a theoretical framework for developing new constitutive models. This work also presents an updated version of the Mazars damage model, with improved material parametrization through multiple damage laws. Similarly, the modified von Mises model has been extended to include different functions for damage evolution, combining exponential and continuum polynomial laws for tension and compression. A third model was developed to showcase the full potential of the proposed formulation. This model formulates the Lemaitre and Chaboche criterion, typically used for ductile materials, to describe quasi-brittle materials. The model provides a comprehensive characterization of the tension and compression behavior by utilizing various loading functions and multiple damage laws. Numerical simulations of experimental benchmarks are presented to show the performance of the proposal, including a nonlocal approach to avoid strain localization and mesh dependency problems. • A formulation to represent simply the bi-modularity of quasi-brittle materials by isotropic damage models is presented. • The proposal provides versatility to prescribe any damage law, especially with fill constitutive parameters. • The strategy is applied to classical models present in literature providing an enhancement of the model behavior. • The approach can be extended and applied to other models presented in the literature. [ABSTRACT FROM AUTHOR]

In the present comment, the results of recently published by Li Shu and Yonglin Ju "Numerical Study on the Condensation Characteristics of Various Refrigerants Outside a Horizontal Plain Tube at Low Temperatures" in International Journal of Thermal Sciences 2022 are discussed. It is shown that one of the conclusions of the work that "at low saturation temperatures, the periodic-averaged heat transfer coefficient in the numerical simulation is lower than that calculated with Nusselt's equation, especially at large wall subcooling", is not supported by the results of simulation performed by the author of this comment. [ABSTRACT FROM AUTHOR]

The parameter L 0 with a unit length (=1.0 m) was omitted in our paper, and the unit of loading speed s 1 and the expression of parameter c 7 were not shown, which result in that the dimensions of shear strain and shear strain rate shown in Eq.(16) were misinterpreted. In this response paper, we added the L 0 in the expressions of parameters c 6 and q , and explained the unit of s 1 , as well as gave the expression for the c 7. The addition of L 0 do not change the simulation results and conclusions of our paper. [ABSTRACT FROM AUTHOR]

Volatile Organic Compounds (VOCs) are widely concerned owing to their serious harm to the ecological environment and human health. In this paper, the adsorption effect of VOCs on a new type of swirling fluidized bed was studied from two aspects of numerical simulation and experimental research, which expanded the application of the device in the field of VOC removal. It was found that the adsorption efficiency of activated carbon in the cyclone fluidized bed was inversely proportional to the inlet concentration and the height of the spinning core column, and was proportional to the mass of the adsorbent and the diameter of the spinning core column. When SAC-3 activated carbon and cyclone fluidized bed S 16–22 were selected, the highest adsorption efficiency was up to 100%, and the damage rate of activated carbon was not more than 3%. The simulation results showed that the maximum axial velocity and the maximum tangential velocity existed in the annular space. The axial velocity and tangential velocity on the cross-section first increased and then decreased with the increase of the radius. The axial velocity was proportional to the flow rate, the diameter, and height of the spinning core. The tangential velocity first increased and then decreased with the increase of the flow rate, diameter, and height of the spinning core. The overall pressure increased with the increase of the flow rate, the pressure increased with the increase of the radius in the cross-section, and the pressure decreased rapidly with the increase of the height in the axial direction. In this paper, a new type of cyclone fluidized bed is used to replace the existing fixed bed and carry bed system, and the optimal activated carbon, the best working conditions, and the best rotary fluidized bed structure are screened by the cyclone fluidized bed experiment. [Display omitted] • A new cyclone fluidized bed was developed for the adsorption treatment of VOC. • CFD method was used to study the internal flow field characteristics. • The best experimental conditions are explored. • The cyclone fluidized bed can effectively treat VOC with sustainable operation. [ABSTRACT FROM AUTHOR]

The Shuiyindong gold mine in Guizhou is used as a case study in this paper to study patterns of dust pollution occurring with traditional electric-rake operation. In particular, the study uses the northern quarry of the twenty-third line in the first middle section of the second mining area and establishes a three-dimensional simulation model of equal size. It uses Computational Fluid Dynamics (CFD) to simulate and analyse the airflow traces and distribution of dust concentration in the relevant roadway during each stage of the electric-rake operation. The simulation results show that the airflow in the working roadway has a spiral movement and produces reverse dirty-wind circulation towards the end. Dust flows out of the working roadway from the 8th second of operation, and dust concentration reaches a peak in the working roadway at the 12th second of operation at an average dust concentration of 37.5 mg/m³. The dust concentration drops rapidly from the 120th second and reaches the maximum dust concentration permitted for operation at the 180th second of operation. The validity of the simulation is tested by comparing the actual measured data at the site with the simulation results. Finally, the simulation results are analysed using violent Python, and the solution is used to divide the roadway into areas according to the human breathing range. The paper analyses the distribution of dust concentration at an average human breathing height, providing an established theoretical basis for dust-control work in mines. [Display omitted] [ABSTRACT FROM AUTHOR]

• An optimal nutation reduction method based on a flexible contactor is proposed. • A highly efficient data-driven model is established to describe the contact process. • The nutation of a tumbling satellite can be reduced efficiently in the early stage of the de-tumbling tasks. Stabilizing tumbling satellites is a crucial step in ensuring safe on-orbit capture. A new de-tumbling method has been proposed that uses a flexible device, such as a brush or rod, to make contact with the target object and avoid potential collisions. However, this method faces two challenges: (i) The complex rotary motion makes it very difficult to determine the contact position on the target satellite, which is crucial to reduce nutation during de-tumbling. (ii) The conventional finite-element-based dynamic model of the flexible contactor is high-dimensional, leading to unacceptable computing time for on-orbit simulation. To address these problems, this paper proposes an optimal method to efficiently reduce the nutation by predicting the initial contact position for each contact process. Additionally, a fast computation model of the de-tumbling system is established based on a data-driven approach to support real-time prediction. Finally, numerical simulations are conducted to demonstrate the effectiveness and high efficiency of the proposed method. [ABSTRACT FROM AUTHOR]

• A method of uncertainty analysis based on the MP-II model was proposed to examine a case of adhesive assembly. • Uncertainty transfer was constructed by a combination of finite-element simulation and a B-spline surrogate model. • The effect of the uncertainties of three types of bonding defects on the center-of-mass drift was understood. • The reliability index was improved and the parameter intervals of the bonding defects were optimized. Multi-source and strong uncertainties of the adhesive assembly process for high-precision inertial devices are critical issues that result in the current low assembly accuracy and poor assembly consistency. This paper addresses the resulting uncertainty in the center-of-mass drift of the float components of a high-precision inertial device. An interval-based non-probabilistic convex model is used to characterize the uncertainty of the bonding defect parameters of the adhesive assembly process, and the uncertainty transferring from those parameters to the center-of-mass drift is constructed by using a surrogate model and numerical simulations. A reliability analysis is carried out to understand the effect of the uncertainties of three types of bonding defects on the center-of-mass drift, and the sensitivities of the center-of-mass drift to the bonding defects are also found. The results show that the reliability index of the center-of-mass drift obtained under the initial parameter intervals is 0.689, indicating the center-of-mass drift at the risk of being out of the accuracy requirement. By adjusting the parameter intervals of the bonding defects to stabilize the center-of-mass of the assembled components, the reliability index is then improved to greater than 1. [ABSTRACT FROM AUTHOR]

This paper presents a numerical study of counterflow methane/n-heptane dual fuel flames, investigating the influence of pressure on flame structure and NO generation characteristics. The results demonstrate that, as pressure increases, the peak temperature and heat release rate of the flame increase, while the NO emission index decreases. The prompt NO emission index experiences a monotonic reduction as pressure increases, while the thermal NO emission index initially increases and then decreases. NO emission index via reburn route displays non-monotonicity with increasing pressure. Elevated pressure induces a decline in the mole fraction of radicals (CH, CH 2 and HCCO) crucial for prompt NO formation, consequently suppressing the formation of prompt NO. The principal reaction responsible for the consumption of reburn NO at lower pressures is HCCO+NO CO+HCNO, whereas the primary reaction for generating reburn NO is H+HNO H 2 +NO. However, at higher pressures, the reaction H+HNO H 2 +NO takes precedence as the dominant reaction consuming NO. • NO emission index decreases with increasing pressure. • Sensitivity analysis of NO generation under different pressures is conducted. • The formation routes of NO under different pressures are identified and analyzed. • The primary NO formation route changes from prompt to thermal as pressure rises. [ABSTRACT FROM AUTHOR]

This paper mainly studies the high-order stable numerical solutions of the time-space fractional diffusion equation. The Fourier spectral method is used for discretization in space and the Spectral Deferred Correction (SDC) method is used for numerical solutions in time. Therefore, a high-precision numerical discretization scheme for solving the fractional diffusion equation is obtained, and the convergence and stability of the scheme are proved. Finally, several numerical examples are given to illustrate the effectiveness and feasibility of the numerical scheme. [ABSTRACT FROM AUTHOR]

Plasma gasification technology is a harmless and resourceful solid waste treatment method. As a hazardous waste, studying the plasma gasification treatment of oil-based drilling cuttings has practical significance. Therefore, this paper uses Aspen Plus to establish a plasma gasification model. Based on model validation, the effects of input power, oxygen equivalence ratio, and carrier gas type on the plasma gasification process of oil-based drilling cuttings were discussed. In addition, by designing a quadratic regression orthogonal experiment, a nonlinear quadratic regression equation was established between the three factors of gasification pressure, input power, and equivalence ratio, as well as different gasification indicators, namely gas yield, lower heating value, and gasification efficiency. By solving the equation, it was found that when the gasification power is 70 kW, the gasification pressure is 10 atm, and the equivalence ratio is 0.1, the gas yield reaches its maximum of 0.74 kg/m3; When the gasification power is 15 kW, the gasification pressure is 10 atm, and the equivalence ratio is 0.1, the lower heating value of gas production reaches its maximum of 9.68 MJ/m3; When the gasification power is 15 kW, the gasification pressure is 1 atm, and the equivalence ratio is 0.1, the gasification efficiency reaches its maximum of 37.6%. At the same time, it was found that the influence of gasification pressure, input power, and equivalence ratio on gasification indicators was ranked in descending order as equivalence ratio, input power, and gasification pressure. The above research provides certain reference values for the practical operation of plasma gasification of oil-based drilling cuttings. • Analyzed the effects of different factors on plasma gasification of OBDC. • Optimum parameters of plasma gasification of OBDC are studied. • Ranked the degree of influence of different factors on plasma gasification of OBDC. • Analyzed the efficiency of plasma gasification of OBDC. [ABSTRACT FROM AUTHOR]

Rotational moulding is a versatile polymer shaping process used to create enclosed parts from powdered precursors using heat and multi-axis rotation. Controlling the heating process and mould motion is critical to producing high-quality parts, and failures due to incorrect mould coverage or variable wall thickness are common. To date, limited simulation tools exist to predict the motion of the powder within the mould, and operators rely on unreliable prior experience to avoid defects. This paper presents an SPH simulation framework to predict particle flow patterns and powder contact time within a rotating mould. The powder-to-wall contact time was derived from the transient rigid body force (RBF) of different sensors on the mould. The method was compared with the results of DEM simulation and validated by the particle flow pattern of two experimental results. Results showed that the SPH method was capable of simulating particle flow macroscopic properties. The great computing efficiency of SPH compared to DEM simulation was also demonstrated. • Couple the SPH framework with a soil material model to simulate the polymer flow motion during rotational moulding process. • Modelling framework validated by two experimental benchmarks. • Present a significant benefit compared to the DEM method when simulating particle flow with millions of particles. [ABSTRACT FROM AUTHOR]

• The mechanical formula of SSBC shape is derived, revealing the evolution characteristics of SSBC progressive forming. • DIC monitors the evolution characteristics of SSBC, which shows a semi-ellipse deflecting towards the high side. • The roadway stability is controlled by improving stress concentration, and an asymmetric support scheme is proposed. The asymmetric deformation of surrounding rock in inclined coal seam roadway is serious, and its stability is difficult to control. Based on the PU's arch theory and considering the development process of the progressive formation of the self stable balance circle (SSBC), this paper establishes a mechanical model of the SSBC for the right-angle trapezoidal roadway in the inclined coal seam. The mechanical analysis and morphological characterization of the forming process were carried out, and the numerical simulation and physical similarity simulation test were carried out to verify. On this basis, the stability control method of roadway in inclined coal seam is improved, and the asymmetric support scheme of roadway is optimized, which is verified by numerical simulation and field monitoring. The results show that the roadway surrounding rock forms a quasi elliptical SSBC after self stabilization, and the mechanical formula of the shape of the SSBC is derived and characterized. Through numerical simulation and physical similarity simulation experiments, the dynamic evolution process of SSBC is depicted, and the gradual forming evolution characteristics of SSBC are revealed. With the increase of the deformation of the surrounding rock, the effective height and width of the roadway gradually increase, and finally a quasi elliptical SSBC deflecting to the left side of the roadway is formed. Based on this, the asymmetric support principle that can control the stability of surrounding rock by improving the asymmetric stress concentration is proposed, and the asymmetric support scheme is designed, that is, "the anchor bolts (cables) are arranged to the right sidewall, and the sidewall angle weakening area is intensively supported". Through numerical simulation and field monitoring, the support effect is remarkable. [ABSTRACT FROM AUTHOR]

This paper investigates the dynamics and digital control issues of deploying a tethered satellite using constrained tether tension. To cater to the requirements of the digital techniques applied in engineering applications, unlike existing results, this study develops a digital feedback control strategy to achieve the rapid and stable tether deployment. The proposed digital control law consists of discretized and quantized tether states and is derived based on continuous-time dynamical model instead of the discrete-time one. To keep tether tension at a positive value when implementing control action, the constraint on tether tension is explicitly accounted for during controller design. Furthermore, the discretization and quantization errors are treated as the uncertain terms in the closed-loop system which can be handled by robust analysis and synthesis techniques. A Lyapunov functional, together with an integral performance index, is made to prove the stability of the system, and the desired controller is obtained by solving an optimization problem. Finally, the effectiveness of the proposed controller is demonstrated by numerical simulation. [ABSTRACT FROM AUTHOR]

The paper investigates the integrated guidance and control (IGC) issue for flight vehicle equipped with strapdown seeker. Distinguished from the routine flight vehicle in literatures, the equipped strapdown seeker is fixedly connected with the vehicle body and thus asymmetric body line of sight (BLOS) constraint is imposed, which makes the IGC design more challenging. Focusing on the point, an intelligent integrated guidance and control approach is proposed by virtue of two specific mechanisms. The improved explicit reference governor technique is adopted to generate auxiliary reference command to ensure asymmetric BLOS limitation not to be violated. On the other hand, the reinforcement learning-based adaptive dynamic programming algorithm is further integrated to guarantee the fine tracking of the auxiliary reference command. Consequently, the satisfactory miss distance is achieved despite of the asymmetric BLOS constraint and unmatched uncertainties, and the stability of the closed-loop system is analyzed. The numerical simulation results demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, the cooling effect of seawater spraying on the offshore launching platform used by the CZ-8X rocket at different takeoff heights is studied. The rocket plume model using the realizable k- ε turbulence model is established, which is based on the three-dimensional Navier-Stokes equations. The injected seawater for cooling the deck surface is described by the Eulerian dispersed phase (EDP) model. The numerical results are compared with the experimental data in the literature to verify the validity and accuracy of the numerical model. The coupled flow field of the CZ-8X rocket plume and seawater at different takeoff heights and different spray velocities are simulated. The results show that the thermal environment on the deck surface of the platform is the worst when the takeoff height reaches 30 m. The seawater spraying velocity shall be moderate before the takeoff height reaches 30 m. A low spraying velocity will lead to poor cooling effect on deck surface, and a high spraying velocity could lead to increased diffusion of plume flow in non-spraying direction. After the takeoff height rises to 40 m, a low water spraying velocity makes the injection position of seawater far away from the jet core area, and the seawater evaporation rate is low, which is conducive to the accumulation of seawater layer on the deck surface. The cooling effect of thermal barrier layer is very obvious. The research shows that when the rocket is launched at sea, the launch platform can be cooled by pumping and spraying seawater, and the water spraying rate can be adjusted appropriately according to the takeoff height to achieve the best cooling effect. [ABSTRACT FROM AUTHOR]

In this paper we aim to construct infinite dimensional versions of well established Piecewise Deterministic Monte Carlo methods, such as the Bouncy Particle Sampler, the Zig-Zag Sampler and the Boomerang Sampler. In order to do so we provide an abstract infinite dimensional framework for Piecewise Deterministic Markov Processes (PDMPs) with unbounded event intensities. We further develop exponential convergence to equilibrium of the infinite dimensional Boomerang Sampler, using hypocoercivity techniques. Furthermore we establish how the infinite dimensional Boomerang Sampler admits a finite dimensional approximation, rendering it suitable for computer simulation. [ABSTRACT FROM AUTHOR]

This paper presents an innovative prescribed-time moving path following control strategy for a stratospheric airship subject to time-varying error constraints and external disturbances. With the help of a new time-varying constraining function, the strict constraint requirements on initial conditions of the system are relaxed. A novel error transformation mechanism is incorporated into the guidance method to tackle the error constraint. The constructed prescribed-time disturbance observer can provide estimates of unknown disturbances and model dynamic couplings within the predefined time. The proposed scheme guarantees that the predetermined precision requirement can be implemented within the prespecified settling time regardless of initial conditions. Numerical simulations demonstrate the effectiveness of the presented control strategy. • A prescribed-time MPF control method is proposed for a stratospheric airship with time-varying error constraints and disturbances. • The initial constraint requirements are removed by a new prespecified error constraint function. • A novel error transformation mechanism is integrated into the control algorithm to address the error constraint. • Estimates of model dynamic couplings and disturbances are obtained from the PTDO. [ABSTRACT FROM AUTHOR]

Metal heat pipe evacuated collector tube (ECT) suffer from cracks in the joint between the glass outer layer and the metal heat pipe due to the large difference in thermal expansion coefficients of glass and metal, resulting in non-industrialization. In this paper, the metal heat pipe is replaced with a glass heat pipe to form an all-glass heat pipe ECT to address the air-tight sealing problem. The results show that the thermal stress at the seal joint is approximately zero, below 0.279 MPa, far below than the bearing range of 40-120 MPa. At the same time, it was also shows that by adding a reflective film to the lower half of the outer layer glass, the optical efficiency was increased by 0.17 %. The energy output in the quasi-equilibrium state is 87 W, which is 8 W higher in the simulation. Water-vapor directly reaches the condensation section to reduce the formation of vortices under conditions where it absorbs sufficient energy to overcome its own gravity and ambient pressure, thus reducing heat loss and increasing thermal efficiency. Fig. 1. All-glass heat pipe vacuumed collector. [Display omitted] • A metal heat pipe is replaced with glass to form an all-glass heat pipe evacuated collector tube. • Maximum thermal stress of 0.279 MPa is well below than the bearing range of 40–120 MPa. • All-glass structure fully copes with the transient local heating changes. • Optical efficiency is increased by 0.17% by the addition of the reflective film. • Yielding an energy output of 87 W in the quasi-thermal equilibrium state. Metal heat pipe evacuated collector tube (ECT) suffer from cracks in the joint between the glass outer layer and the metal heat pipe due to the large difference in thermal expansion coefficients of glass and metal, resulting in non-industrialization. In this paper, the metal heat pipe is replaced with a glass heat pipe to form an all-glass heat pipe ECT to address the air-tight sealing problem, and a reflective film was added to the lower part of the outer tube to improve energy. According to these results, the thermal stress of 0.279 MPa is well below the bearing range of 40–120 MPa, and the maximum thermal strain of 0.175 mm/mm is also far less than the affordable value of 120 mm/mm, inducting the all-glass structure fully copes with the transient local heating changes. The optical efficiency is increased by 0.17 % by the addition of the reflective film, and yielding an energy output of 87 W and a maximum volume fraction of 4.8 % for liquid–water in the quasi-thermal equilibrium state. At the same time, the evaporation operating speed of the vapor can be increased by improving the solar radiation flux density and reducing thermal losses, and optimizing the multi-level and cross-scale vapor vortices can also improve the convective heat transfer rate, so they are future directions for development. However, there are the limitations of decreasing the thermal conductivity and increases the resistance due to the heat pipe conversion from metal to glass. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel fractional-order hyperchaotic system is investigated. • Existence of chaotic attractors just in the fractional-order case, in this system, are reported. • Bifurcation diagrams and corresponding Lyapunov spectrum are computed. • The work reports the first example that shows existence of chaotic attractors that exist only in fractional-order case. Studying chaotic dynamics in fractional- and integer-order dynamical systems has let researchers understand and predict the mechanisms of related non-linear phenomena. Phase transitions between the fractional- and integer-order cases is one of the main problems that have been extensively examined by scientists, economists, and engineers. This paper reports the existence of chaotic attractors that exist only in the fractional-order case when using the specific selection of parameter values in a new hyperchaotic (Matouk's) system. This paper discusses stability analysis of the steady-state solutions, existence of hidden chaotic attractors and self-excited chaotic attractors. The results are supported by computing basin sets of attractions, bifurcation diagrams and the Lyapunov exponent spectrum. These tools verify the existence of chaotic dynamics in the fractional-order case; however, the corresponding integer-order counterpart exhibits quasi-periodic dynamics when using the same choice of initial conditions and parameter set. Projective synchronization via non-linear controllers is also achieved between drive and response states of the hidden chaotic attractors of the fractional Matouk's system. Dynamical analysis and computer simulation results verify that the chaotic attractors exist only in the fractional-order case when using the specific selection of parameter values in the Matouk's hyperchaotic system. An example of the existence of hidden and self-excited chaotic attractors that appears only in the fractional-order case is discussed. So, the obtained results give the first example that shows chaotic states are not necessarily transmitted between fractional- and integer-order dynamical systems when using a specific selection of parameter values. Chaos synchronization using the hidden attractors' manifolds provides new challenges in chaos-based applications to technology and industrial fields. [ABSTRACT FROM AUTHOR]

The processes occurring in near and far space have a significant impact on the safety of space flights. Processes such as explosions of supernovae and relativistic jets have a particularly great impact. They arise in quasars, black holes, protostars. Often such structures are observed during the formation of new stars. Such jets have a great impact on the safety of space flights. For example, there is currently no radiation shelter on the International Space Station, so astronauts are at serious risk of getting radiation sickness. In addition, the skin of the orbital station modules consists of aluminum, which accumulates secondary radiation. The formation process of new star systems is the result of complex processes that occur in interstellar gas. These processes include nonlinear interactions of turbulence, gravity, collisions of molecular clouds with each other, as well as rotation and several other factors. The evolution of the formation of superdense substance begins from the moment when it gathers in turbulent flows or is formed by supersonic collisions of molecular clouds with each other, or are formed during the intereaction of molecular clouds with supersonic waves, which are formed during the explosions of supernovae, until the moment when these superdense areas reach the prestellar density. Further, depending on several factors, these superdense formations either collapse or disintegrate and return to the interstellar medium. The analysis of observations allows to conclude that a significant part of the molecular clouds is not gravitationally bound. These conclusions are made based on the virial theorem, which expresses the connection between gravitational and kinetic energy. In this paper, a simulation of large molecular clouds collision in a three-dimensional formulation on ultra-high-resolution grids is carried out. Execution of such calculations requires a lot of computer capacity. The paper presents the results of computer modeling of large-scale processes of filament formation and superdense, gravitationally coupled structurally parallel computation clusters with hybrid architecture. Parallel simulation on supercomputers was conducted with author's software, which uses a modified second-order Godunov method of accuracy of the Total Variation Diminishion type. Calculations were conducted on grids that contain more than one billion cells (1024 × 1024 × 1024). The gravitational potential is calculated on graphic processors. To refine the calculations, the method of adaptive refinement of the AMR grid is used. Simulation results are presented for cases of frontal collision of two molecular clouds, which density is distributed along the radius according to certain laws. • The processes of formation of new stellar systems are studied in this work in 3D simulation. • Appearance of clumps and filaments is discussed. • Morphing of high compression clumps set in possible stars formation zone is discussed. • The calculation program is based on a modified scheme of a high order of accuracy. [ABSTRACT FROM AUTHOR]

In this paper, we consider output tracking and disturbance rejection for a 1-D wave equation with in-domain feedback/recirculation of an intermediate point velocity. The performance output is an intermediate point displacement and the control matches the general disturbance. We first use the active disturbance rejection control method to design a disturbance estimator to estimate the disturbance. Then, we propose an observer and show that the obtained observer converges exponentially to the original system. Finally, an output feedback controller is constructed in terms of the designed observer. It is verified that the resulting closed-loop system is well-posed and all internal signals are bounded. Moreover, the output exponentially tracks the reference signal. Some numerical simulations are given to validate the theoretical results. [ABSTRACT FROM AUTHOR]