Mutual Collision Research Articles

TO MEET AND CONTINUE ON THE SAME LINE The Új Symposion writer’s attitude to Antun Šoljan’s literary concept

The Croatian author Antun Šoljan (1932–1993) came to the attention of the emerging generations of writers and artists in Vojvodina in the first half of the 1950s. His sensibility as a poet, storyteller, and literary translator, as well as his activity as a newspaper editor and his commitment as a critic, influenced the Symposion generation mostly by encouraging them to follow in his steps, but also by stimulating discussion. My article discusses the multi-directional reception of this attitude, which regards high-quality aesthetic performance and commitment as a function, not of social status, but of free artistic creation, detailing those mutual ideological reference points, connections, or collision surfaces, that are characterized by intellectual self-representation that avoids the false heroism of national myths and continuity of tradition freed from the manic import and/or epigonism of recent trends in world literature.

Online dual robot–human collaboration trajectory generation by convex optimization

For dynamic collision-free trajectory planning in dual-robot and human collaborative tasks, this paper develops an online dual-robot Mutual Collision Avoidance (MCA) scheme based on convex optimization. A novel convex optimization formulation model, named Disciplined Convex programming by Shifting reference paths (DCS), is proposed for solving the single-robot trajectory optimization problem. Furthermore, a new dual-robot trajectory convex optimization algorithm is presented for online adjustment of the dual-robot trajectories according to the collaborative task priority. The overall pipeline, named DCS-MCA, generates collision-free and time-optimal dual-robot trajectories, while prioritizing the task accessibility of the high-priority robot. Simulation experiments demonstrate that DCS exhibits comparable performance to the current state-of-the-art single-robot motion planner, while the DCS-MCA outperforms common algorithms by up to 30% in time optimality for dual-robot collaborative tasks. The feasibility and dynamic performance of the proposed approach are further validated in a real collaborative cell, illustrating its suitability for collaborative dual-robot tasks in moderately dynamic environments.

CFD simulation of flyash fluidized-bed pulverization with superheated steam

The supersonic pulverization technology uses superheated steam generated by the boiler to generate supersonic airflow through the Laval nozzle, and accelerates the flyash fed into the crushing chamber by the screw feeder, and then the flyash can be crushed in mutual collision and friction process. The present paper conducted CFD simulation of fluidized-bed pulverization with superheated steam, and both the velocity filed and the particle tracks are obtained. Convergence test was performed firstly to verify the numerical results, and three different meshes and several different numbers of particles are employed here to show the average velocity of the particles through a certain horizontal plane. The effect of some key parameters, such as distance between the two opposite nozzles and feeding locations of the flyash to the velocity filed and the particle velocity are also numerically investigated. Results show that, the best distance between the two opposite nozzles of the four-nozzle case is 142 mm and the average particle velocity distribution varies little with the flyash feeding position for the present jet mill model.

Effects of injection schemes on the performance of powdered magnesium-liquid CO2 rocket engine

The effects of self-impinging injection and unlike-impinging injection on the performance of powdered magnesium-liquid carbon dioxide rocket engine have been investigated via numerical simulation and experimentation. The results indicate that the unlike-impinging injection achieves a combustion efficiency of 88.7%, which is 23% higher than that of self-impinging injection. Moreover, significant deposition of unburned magnesium particles is observed at the head of the combustor when using self-impinging injection, whereas unlike-impinging injection exhibits much less deposition. Self-impinging injection leads to an uneven temperature field distribution at the head of the combustion chamber, while high temperature areas under the unlike-impinging injection scheme are relatively concentrated. The mutual collision between carbon dioxide droplets also reduces the degree of mixing between carbon dioxide droplets and magnesium particles under self-impinging injection which is less likely to occur in the unlike-impinging injection scheme.

Adiabatic expansion, local equilibrium and extended Maxwell distribution for fire-ball to describe multiple particle production (II)

The model of multiple particle production in [A. Ohsawa, Int. J. Mod. Phys. A (2023) 2350166.] assumes a fire-ball of a gas, consisting of grains, with the adiabatic and one-dimensional expansion, local equilibrium at the final state and the extended Maxwell distribution for the energy distribution of the grains. There are small and large [Formula: see text] (transverse momentum) processes for grains. The grain produces several hadrons to be observed in the experiments at the final state. The model describes well the pseudo-rapidity density distributions and the [Formula: see text] distributions at various incident energies. In this paper it is shown that the model reproduces well the incident energy dependences of [Formula: see text] (the average [Formula: see text] of produced particles), [Formula: see text] (the charged multiplicity) and [Formula: see text] (the pseudo-rapidity density at [Formula: see text]). Furthermore it is shown that the inelasticity is almost energy-independent and [Formula: see text] in the energy region of [Formula: see text][Formula: see text]GeV, and that the Feynman scaling law is violated. The model indicates that the fire-ball satisfies the conditions for quark-gluon plasma, that the grains of the large [Formula: see text] process may be identified with jets, and that [Formula: see text]’s of the grains in the large [Formula: see text] process are due to mutual collision of the grains during the one-dimensional expansion.

Phase analysis of complex non-metallic inclusions in Al-deoxidized 42CrMo4 steel after contact with MgO–C refractories

This study extensively investigated characteristic non-metallic inclusions in oxidized and deoxidized 42CrMo4 steel after contact to MgO–C refractories, proposing possible formation and modification mechanisms of non-metallic inclusions. The structures and compositions of different inclusion species were analyzed, revealing various types: crystalline, amorphous, and complex inclusions containing both crystalline and amorphous phases. The latter always consisted of an amorphous Mn–Si–Al–O matrix containing various crystalline phases such as Al2O3, MnAl2O4 and/or MnTiO3. The formation of amorphous Mn–Si–Al–O inclusions was attributed to steel melt oxidation, while pure crystalline corundum inclusions resulted from both the steel melt oxidation and deoxidation. Alumina inclusions exhibited different shapes, likely because of variations in aluminum and oxygen supersaturation in the steel melt during their formation. Complex inclusions were suggested to form through precipitation on existing inclusions and mutual collision of pre-existing inclusions, facilitated by the non-wetting behavior of solid alumina inclusions in the steel melt.

Planetesimal formation at the gas pressure bump following a migrating planet

Context. Planetesimal formation is still mysterious. One of the ways to form planetesimals is to invoke a gas pressure bump in a protoplanetary disc. In our previous paper, we proposed a new scenario in which the piled-up dust at a gas pressure bump created by a migrating planet forms planetesimals by streaming instability in a wide region of the disc as the planet migrates inwards. Aims. In the present work, we consider the global time evolution of dust and investigate the detailed conditions and results of the planetesimal formation in our scenario. Methods. We used a 1D grid single-sized dust evolution model, which can follow the growth of the particles in terms of their mutual collision and their radial drift and diffusion. We calculated the time-evolution of the radial distribution of the peak mass and surface density of the dust in a gas disc perturbed by an embedded migrating planet and investigated whether or not the dust satisfies the condition for planetesimal formation. Results. We find that planetesimals form in a belt-like region between the snowline and the position where the planet reaches its pebble-isolation mass when the strength of turbulence is 10−4 ≤ α ≤ 10−3, which is broadly consistent with the observed value of α. Whether the mechanism of the formation is streaming instability or mutual collision depends on the timescale of the streaming instability. The total mass of planetesimals formed in this scenario also depends on α; it is about 30–100 ME if the planetary core already exists at the beginning of the simulation and grows by gas accretion, but decreases as the timing of the formation of the planetary core gets later. We also provide simple approximate expressions for the surface density and total mass of the planetesimals and find that the total planetesimal mass strongly depends on the dust mass. Conclusions. We show that planetesimals form in a belt-like region by a combination of dust pile-up at the gas pressure bump formed by a planet and its inward migration.

Demand Analysis of English Language Service Value Based on Data Mining Ecosystem

INTRODUCTION: Language is a bridge between people, an indispensable component of information exchange and communication, and an essential part of social culture. As the most widely used language in the world, English occupies an essential position in the social language, generating value demands related to it, ranging from the needs of individuals for their development to the needs of social industries or fields for their development to the national language strategy.
 OBJECTIVES: The purpose of this paper is that due to the implementation of the "One Belt, One Road" policy, more and more cultures of the countries along the route are coming into China's vision, and at the same time, Chinese culture should also be promoted, and only through the correct use of language can we promote the Chinese civilization and other civilizations to seek common ground and put aside their differences, appreciate each other, and eliminate the clash of cultures in the process of mutual collision and fusion of different civilizations.
 METHODS: Based on the data mining ecosystem, this study examines the demand analysis of the value of English language services in today's environment, explores the explicit and implicit benefits regarding the value of English language services, and analyzes and explores the explicit and implicit economic benefits of language services and the economic, social, and cultural benefits they encompass at different levels.
 RESULTS: The research suggests that we need to focus on the value of multiform English language services, strengthen English language industry research and studies, and conduct a scientific English language economic program.
 CONCLUSION: Language services and language economy are two closely related concepts. Analyzing language services from multiple perspectives can reveal their explicit and implicit economic, social and cultural benefits.

Co-treatment of spent automotive catalyst and copper-bearing electroplating sludge to alloy platinum group metals with base metal matrices

Spent automotive catalyst (SAC) is an important secondary metal resource of platinum group metals (PGMs). However, the traditional smelting process for recovering valuable metals from SAC generally has the problems such as high reagents consumption and increased solid waste. Thus, a novel co-treatment process of SAC and copper-bearing electroplating sludge (CBES) was proposed in this study, where CBES was first used as the capture agent and fluxing material in the pyro-capture process of PGMs. The effects of separation behaviors of PGMs and copper under different smelting conditions were studied systematically. The optimum conditions for this process are as follows: m(CBES)/m(SAC) of 2.0, m(SiO2)/m(Al2O3) of 3.00, basicity of 0.80, 5.0 wt% Na2B4O7, oxidative temperature of 1460 ℃, oxidative time of 30 min, NC/Cu of 1.250, reductive temperature of 1300 ℃, and reductive time of 90 min. Under these conditions, the sulfur removal rate exceeds 99% while the recoveries of Pt, Pd, Rh and Cu are 99.26%, 98.53%, 99.96% and 97.60%, respectively. The addition of pure reagents is only about 47% of the total waste mass. Furthermore, the capture process of Cu-Fe alloy for PGMs was discussed, which can consist of three steps: reduction of copper and iron, mutual migration and collision of the reduced metal atoms, and alloying. Finally, the produced slag was synthesized into non-hazardous glass-ceramics material successfully. To sum up, this study achieved the efficient recycling of two hazardous wastes simultaneously.

Membership‐based aircraft parking stand allocation system with time window constraints: An event‐based time–space separated algorithm

AbstractOutsourcing maintenance service providers are vital to guarantee safe operation in airline industry. To reduce the workload and avoid incompatible arrangement schemes in traditional manual arrangement, this article constructs an intelligent system with a novelly designed model and algorithm for membership‐based aircraft parking stand allocation problem. This problem arises from outsourcing maintenance service providers. They need to first serve membership orders, while guaranteeing punctual delivery of other orders. In particular, mutual collision should be strictly avoided between aircrafts. To solve this problem, first, a mathematical model is constructed to optimize timetable and aircraft parking stand allocation scheme. Second, to quickly obtain feasible scheduling scheme, three kinds of mechanisms, including information guidance mechanism, boundary arrangement mechanisms and local optimal adjustment mechanism, are novelly proposed. Moreover, event‐based time–space separated heuristic algorithm is subtly designed based on time–space separation characteristics. In addition, coding schemes are proposed through problem analysis. Finally, three cases with different scales are utilized and six comparison algorithms are selected to illustrate the superiority of our proposed algorithm.

A new method for identifying dynamical transitions in rubble-pile asteroid scenarios

Context. Evidence supports the idea that asteroids are rubble piles, that is, gravitational aggregates of loosely consolidated material. This makes their dynamics subject not only to the complex N-body gravitational interactions between its constituents, but also to the laws of granular mechanics, which is one of the main unsolved problems in physics. Aims. We aim to develop a new method to identify dynamical transitions and predict qualitative behavior in the granular N-body problem, in which the dynamics of individual bodies are driven both by mutual gravity, contact and collision interactions. Methods. The method has its foundation in the combination of two elements: a granular N-body simulation code that can resolve the dynamics of granular fragments to particle-scale precision, and a theoretical framework that can decode the nature of particle-scale dynamics and their transitions by means of ad hoc indicators. Results. We present here a proof-of-concept of the method, with application to the spinning rubble-pile asteroid problem. We investigate the density-spin parameter space and demonstrate that the approach can identify the breakup limit and reshape region for spinning rubble-pile aggregates. Conclusions. We provide the performance of several ad hoc indicators and discuss whether they are suitable for identifying and predicting the features of the dynamical problem.

Coordinated flight path planning for a fleet of missiles in high-risk areas

AbstractThis paper addresses the flight path planning problem for multiple missiles engaging stationary targets in high-risk areas. Targets protected by air defence are preferably engaged by a fleet or swarm of missiles, not individual missiles. The concept of a swarm attack is that a large number of approaching missiles overwhelm air defence. The deployment of missiles is often part of a broader mission including further participants. Flight path planning is then an integral element of mission planning, requiring strict timing coordination of all members involved. The flight times of the missiles are dictated by the master planning. We present algorithms for offline planning and online re-planning of flight paths for a fleet of missiles with flight time constraints. The algorithms are based on an advanced bidirectional RRT* algorithm that generates risk-minimizing flight paths with predefined flight times. Online planning generates the flight paths of the fleet sequentially, maintaining a safety distance between the missiles to prevent mutual collision. Offline planning uses a global optimization approach to determine an optimal selection of flight paths from a large set of potential paths. The selection is performed by a branch and bound algorithm that determines optimal cliques in the path compatibility graph. The optimization is embedded in an iterative algorithm that allows to successively improve the mission success.

Legal Systems and Boundaries for the Punishment of International Commercial Crimes

This paper focuses on the definition of international commercial crime, how to punish international commercial crime, what legal systems have been introduced to punish international commercial crime, and how to distinguish international commercial crime from ordinary commercial behavior. With the continuous development of the globalization of the world, the mutual integration and collision of economy, commerce, culture, and politics have become more and more obvious and frequent. The mutual integration of different countries and regions in commerce and economy has led to various manifestations of commercial behavior, which inevitably lead to some commercial activities that go beyond normal commercial behavior under the guise of commercial behavior. These behaviors have a negative impact on the international business environment to make huge profits. Some of these acts have even harmed the interests of other countries to the extent of being illegal and criminal.

Consensus Control of Large-Scale UAV Swarm Based on Multi-Layer Graph

An efficient control of large-scale unmanned aerial vehicle (UAV) swarm to establish a complex formation is one of the most challenging tasks. This paper investigates a novel multi-layer topology network and consensus control approach for a large-scale UAV swarm moving under a stable configuration. The proposed topology can make the swarm remain robust in spite of the large number of UAVs. Then a potential function-based controller is developed to control the UAVs in realizing autonomous configuration swarming under the consideration of mutual collision, and the stability of the controller from the individual UAV to the entire swarm system is analyzed by a Lyapunov approach. Afterwards, a yaw angle adjustment approach for the UAVs to reach consensus is developed for the multi-layer swarm, then the direction state of each UAV converges with a fast rate. Finally, simulations are performed on the large-scale UAV swarm system to demonstrate the effectiveness of the proposed scheme.

Effective dust growth in laminar circumplanetary discs with magnetic wind-driven accretion

ABSTRACT It has been considered that large satellites around gas planets form in situ circumplanetary discs (CPDs). However, dust particles supplied into CPDs drift toward the central planets before they grow into satellitesimals, building blocks of the satellites. We investigate the dust growth in laminar CPDs with magnetic wind-driven accretion. In such laminar discs, dust particles can settle on to the mid-plane and grow large by mutual collision more efficient than in classical turbulent CPDs. First, we carry out 3D local MHD simulations of a CPD including all the non-ideal MHD effects (Ohmic resistivity, Hall effect, and ambipolar diffusion). We investigate if the disc accretion can be governed by magnetic wind-driven accretion and how laminar the disc can be, in a situation where the magnetic disc wind can be launched from the disc. Secondly, we model 1D steady CPDs consistent with the results of the MHD simulations and calculate the steady radial distributions of the dust profiles in the modelled discs, taking account of the collisional growth, radial drift, fragmentation, and vertical stirring by the Kelvin–Helmholtz instability. We show that satellitesimals can form in such CPDs if the dust-to-gas mass ratio of the inflow to the discs is larger than 0.02, which is 50 times smaller than the critical value in turbulent CPDs. This condition can be satisfied when enough amount of dust piles up at the gas pressure bump created by the planets. This result shows that satellitesimals would form in laminar CPDs with magnetic wind-driven accretion.

Ionizing protoplanetary discs in pebble collisions

ABSTRACT We introduce collisions of solids as a new and efficient ionization mechanism for gas in protoplanetary discs, which especially operates in the dense midplane of protoplanetary discs. This idea is sparked by laboratory experiments where we found that charge, which is exchanged by grains in mutual collision (tribocharging), is not tied to their surfaces alone. As kind of collateral effect, charges also become entrained into the gas phase, i.e. collisions ionize the protoplanetary disc. Therefore, solids are not only sinks of charges in discs but also sources. A first estimate shows that ionization rates in the midplane at 1 AU in the range of $10^{-19}\!-\!10^{-15}\,{\rm s}^{-1}$ seem feasible depending on the assumption of rather calm or highly turbulent conditions with radial particle pile up.

Option-Based Multi-Agent Reinforcement Learning for Painting With Multiple Large-Sized Robots

To ensure an efficient and conflict-free task allocation, this paper presents an option-based multi-agent reinforcement learning (OMARL) method for a cooperative multi-station multi-robot system in aircraft painting application. The problem can be described as a fully-connected graph, whose nodes and edges represent stations and trajectories between stations, respectively. The aim is to minimize the maximum execution time of conflict-free aircraft painting with multiple robots. Traditional methods cannot handle mutual collision avoidance well when robots are in large size. Therefore, this work solved the planning problem with multi-agent reinforcement learning algorithm based on option framework. The moving trajectories were pre-planned by a simplified 2D A* algorithm, which is fast and reduces rotations. The agents would finish the whole task with less time, and potential collisions were punished at every time step. Hierarchical option-based model with shared network parameters greatly reduced the complexity of training for painting planning scenarios. A fuzzy clustering method was introduced, and the clustering scores of stations would contribute to greedy agents. Comparisons were made on static and dynamic situations among several planning methods. OMARL can give optimal schedules as well as, or better than the most efficient traditional method does. Furthermore, OMARL can provide satisfactory adjustments in real time when practical process is different from plan or there is one broken robot. In contrast, traditional methods take lots of time to recalculate the plan. The results indicate that OMARL can achieve better performance in multi-station multi-robot task allocation when the collision between robots cannot be ignored.

Lattice Boltzmann simulation of particles inertial migration with slippery surface and moderate concentration in circular tube flow

Hydrodynamic migration of spherical slippery particles suspended in a cylindrical channel flow is numerically studied in this paper. The effects of the particle concentration of particle ([Formula: see text], tube-to-particle diameter ratio ([Formula: see text] and Knudsen number (Kn), respectively, with ranges of [Formula: see text] and [Formula: see text] with the channel Reynolds number of [Formula: see text], are concerned in the simulations. The objective of this work is to explore the pipeline transportation of relatively large and moderately dense particles with slippery surface, for which the characteristics have not been comprehensively exhibited in the literature. Such particle-resolved suspension flow is solved by a three-dimensional lattice Boltzmann method, where a curved kinetic boundary condition is adopted to resolve the velocity slip phenomenon at the fluid-particle interface, and the particle-particle collision is performed by a repulsive force model. The results elucidate that the effect of particle focusing is less marked at intermediate concentrations. At larger [Formula: see text], some particles may migrate to the center of channel due to the aggravation of the mutual collision. The increase of Re contributes to the particle focusing at low [Formula: see text], but not for the case of higher [Formula: see text]. On the other hand, the [Formula: see text] generally has a negative effect on the inertial focusing. Furthermore, the migration velocity of particles reduces and the behavior of inertial focusing is enhanced simultaneously, with the increase of Kn.

70 Years of Logic in China, 1949-2019

This article outlines the history of logic in China from 1949 to 2019. Firstly, it presents a rough picture of Chinese logic before 1949 using broad brushstrokes. Secondly, it divides the whole process of development into two stages. In the first 30 years from 1949 to 1979, Chinese logic made some achievements, but also went along some detours, and its overall situation was unsatisfactory. In the latter 40 years from 1979 to 2019, due to Deng Xiaoping’s reform and opening up, many Chinese logicians went abroad for academic visits or to study degrees in foreign universities or research institutes, gradually became familiar with and even integrated into the international mainstream of logic teaching and research, and ushered in the great flourishing of logic in China we see today. Finally, it draws four lessons from this process of development, as follows. 1) Let politics and academia live in peace, by respecting and adhering to the idea of academic freedom. 2) Academic advances cannot be achieved in isolation from the world, so we should fully embrace the international academic community, while insisting on our own independent thinking. 3) We should always adhere to the policy of “letting a hundred flowers blossom and a hundred schools of thought contend”, so that different academic viewpoints and tendencies can be improved and developed in their mutual collision. 4) We should cultivate academic self-confidence, gradually make the change from pure follow-up learning to original work in some fields of logic.

Efficient Industrial Solution for Robotic Task Sequencing Problem With Mutual Collision Avoidance & Cycle Time Optimization

In the automotive industry, several robots are required to simultaneously carry out welding sequences on the same vehicle. Coordinating and assigning welding points between robots is a manual and difficult phase that needs to be optimized using automatic tools. The cycle time of the cell strongly depends on different robotic factors such as the task allocation among the robots, the configuration solutions and obstacle avoidance. Moreover, a key aspect, often neglected in the state of the art, is to define a strategy to solve the robotic task sequencing with an effective robot-robot collision avoidance integration. In this paper, we present an efficient iterative algorithm that generates a high-quality solution for Multi-Robotic Task Sequencing Problem. This latter manages not only the mentioned robotic factors but also aspects related to accessibility constraints and mutual collision avoidance. In addition, a home-developed planner ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RoboTSPlanner</i> ) handling 6 axis has been validated in a real case scenario. In order to ensure the completeness of the proposed methodology, we perform an optimization in the task, configuration and coordination space in a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">synergistic</i> way. Comparing to the existing approaches, both simulation and real experiments reveal positive results in terms of cycle time and show the ability of this method to be interfaced with both industrial simulation software and ROS-I tools.