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49th International Congress and Exposition on Noise Control Engineering, INTER-NOISE 2020

作者： Lee, Incheol Zhang, Yingzhe Lin, Dakai Beijing Aircraft Technology Research Institute of Commercial Aircraft Corporation of China Ltd Beijing Key Laboratory of Simulation Technology for Civil Aircraft Design Future Science Park Changping District Xiaotangshan Beijing102211 China School of Aeronautic Science and Engineering Beihang University No. 37 Xueyuan Road Haidian District Beijing100191 China

ISBN: (纸本)9788994021362

A comprehensive database of noise from subsonic single-stream jets was acquired at various nozzle-operating conditions. The measured spectra were normalized with the concept of one velocity exponent and two velocity exponents. When the spectra were normalized with one velocity exponent, at aft angles, a noticeable scatter of spectra is observed if the Strouhal number is less than 0.5. Based on this observation, the Strouhal number of 0.5 is set to a reference for the calculation of two velocity exponents. The scatter at the Strouhal number smaller than 0.5 disappeared in the results of two velocity exponents. A new empirical method for the prediction of noise from single-stream jets is proposed based on the spectra normalized with two velocity exponents. The velocity exponent of the low Strouhal number region is used to scale the normalized spectra of the large-scale component, and the velocity exponent of the high Strouhal number region is used to scale the spectra of the fine-scale component. The prediction is in good agreement with the experimental data. The new concept of two velocity exponents provides excellent prediction capability of noise from subsonic single-stream jets. It will be extended to the prediction of noise from subsonic coaxial-stream jets. © Proceedings of 2020 International Congress on Noise Control Engineering, INTER-NOISE 2020. All rights reserved.

关键词： Velocity

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Modeling and Control of Liquid Metal Droplet in a two-dimensional Free Space

Modeling and Control of Liquid Metal Droplet in a two-dimens...

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IEEE International Conference on Robotics and Biomimetics

作者： Erlong Wang Jie Xie Xiangpeng Li Shiwu Zhang CAS Key Laboratory of Mechanical Behavior and Design of Materials University of Science and Technology of China Hefei China Robotics and Microsystems Center Collage of Mechanical and Electrical Engineering Soochow University Suzhou China

ISBN: (纸本)9781665405362

As an emerging multifunctional material, gallium based liquid metal has presented new and exciting opportunities for a variety of applications, ranging from microfluidics, smart machines, to soft robot. However, study on the motion control of liquid metal is still absent, which hinders their further applications. In this paper we develop a manipulation platform that would control the motion of a liquid metal droplet in a two-dimensional plane. A dynamic model of a liquid metal droplet immersed in the electrolyte under external voltages input is discussed first, followed by a tracking controller designed to drive the liquid metal droplet to track the desired trajectory with vision feedback. Based on the controller, a liquid metal manipulation platform is established. The effectiveness of this proposed method is verified by controlling a liquid metal droplet to track different trajectories. This proposed approach may generate profound impact on developing future microfluidic systems or tiny soft robots that can be driven accurately by liquid metal droplets.

关键词： Liquids Gallium Tracking Metals Soft robotics Trajectory Vehicle dynamics

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A direct relaxation process for particle methods in gas kinetic theory

arXiv

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arXiv 2021年

作者： Yang, Sirui Liu, Sha Zhong, Chengwen Cao, Junzhe Zhuo, Congshan School of Aeronautics Northwestern Polytechnical University Xi'an Shaanxi710072 China National Key Laboratory of Science and Technology on Aerodynamic Design and Research Northwestern Polytechnical University Xi'an Shaanxi710072 China

The multi-scale flow mechanism is crucial for force and heat loaded on near-space and reentry vehicles, the control of spacecraft by thrusters, the propelling and cooling of MEMS, etc. Since the continuum flow and rarefied flow often exist simultaneously, the modeling and prediction for such a multi-scale flow field is very complicated. One important and efficient way of predicting the multi-scale flow is constructing numerical methods by adapting the multi-scale properties of the temporal integral solutions (or equivalent characteristic line solutions) for the model equations in the gas-kinetic theory. The model equations can be classified into FP-type and BGK-type, and the numerical methods can have deterministic form or stochastic particle form. Since these numerical methods are strictly based on model equations, they are also restricted by the model equations. The difficulty and complexity in constructing model equation that has complete asymptotic preserving property for gas mixture with non-equilibrium internal energy will prevent the further extension of these methods. Therefore, this paper addresses the question whether a multi-scale numerical method can be established not on the model equations, but directly adapts the relaxation rates of macroscopic variables such as stress and heat flux. Since the algorithm of multi-scale particle method based on BGK-type equation is clear and simple, its collision step is modified in this work, where the macroscopic variables firstly evolve according to their relaxation rates, and then the molecules that participate in inter-molecular collisions get their after-collision velocities from the after-evolution macroscopic variables. Therefore, this direct relaxation process does not depend on the model equations anymore. Finally, the validity and accuracy of the particle method with direct relaxation process are examined with five test cases. © 2021, CC0.

关键词： Numerical methods

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Site Occupation Regulation of Eu2+ by the Introduction of (Bo3)3- Group Towards Full-Visible-Spectrum Emission in a Singly Doped KK2BaSr(PO4)2:Eu2+ Phosphor

SSRN

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SSRN 2023年

作者： Xie, Guodong Si, Jiayong Li, Guihua Cai, Gemei Wang, Zhipeng Wang, Xiaojun College of Mechanical and Electrical Engineering Central South University of Forestry and Technology Hunan Changsha410004 China School of Materials Science and Engineering Central South University Hunan Changsha410083 China State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body Hunan University Hunan Changsha410082 China Department of Physics Georgia Southern University StatesboroGA30460 United States

Efficient regulation of activator site occupation is crucial for developing white light phosphors with excellent luminous properties. Herein, we report the synthesis of new borophosphate K2BaSr(PO4)2-x(BO3)x:0.04Eu2+ phosphors via an anion groups substitution strategy. In the pristine sample, there are three different cationic sites (Ba2+, Sr2+, and K+) with differed coordination environment where Eu2+ can occupy the Ba2+ and/or Sr2+ sites. In the process of (BO3)3- partially substituting (PO4)3- units, owing to the effect of increased cation disorder generated from the difference in geometric configurations between the two anion groups, new emission band centering around 535 nm appears in the emission spectra. The intensity of this band increases as more (PO4)3- units are substituted by (BO3)3-, resulting in the phosphor emission tuned from blue to white by controlling the (BO3)3- concentration. This emission band can be attributed to the occupation of Eu2+ for K+ sites induced by cation disorder through the analysis of structural and photoluminescent properties and first-principles calculation. A phosphor-converted LED (pc-LED) has been successfully fabricated using the phosphor at the optimized compositions, K2BaSr(PO4)1.8(BO3)0.2:0.04Eu2+, and a 365 nm near-ultraviolet chip, exhibiting a color rendering index of 81.3 and a correlated color temperature of 7024 K. Our findings demonstrate the effectiveness of the anion group modulation for developing new high-performance LED phosphors. © 2023, The Authors. All rights reserved.

关键词： Phosphors

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Study on the Process of Mass Transfer and Deterioration of Limestone Under Dynamic Dissolution of Co2 Solution

SSRN

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SSRN 2023年

作者： Li, Ze Dong, Wushu Shen, Linfang Liu, Wenlian Guo, Yakun Xu, Hanhua Kunming University of Science and Technology School of Architectural Engineering Yunnan Kunming650500 China Kunming Prospecting Design Institute of China Nonferrous Metals Industry Co. Ltd Kunming650051 China Faculty of Engineering and Informatics University of Bradford BradfordBD7 1DP United Kingdom Yunnan Key Laboratory of Geotechnical Engineering and Geohazards Kunming650051 China

The long-term erosion of underground aqueous solution is easy to induce the dissolution of carbonate rocks, leading to a series of karst problems such asdissolution cavities, underground caves, and solution channels. These problems will seriously impact the long-term safe operation of underground structure. Therefore, this study focuses on limestone and conducts dynamic dissolution experiments under deionized water and CO2 solution conditions to investigate the variations of surface morphology, volume loss rate, uniaxial compressive strength, and elastic modulus with test duration. Based on the changes in mass loss rate and Ca2+ concentration, the deterioration mechanism of limestone under non-equilibrium conditions is studied. Results demonstrate that the surface roughness and the volume loss rate of limestone continuously increase under immersion in the solution, while the uniaxial compressive strength and elastic modulus decrease. However, there are significant differences in the deterioration effects and mechanisms between different solution environments. Compared with deionized water, the degradation induced by CO2 solution is more serious. In the deionized water tests and the early stages of CO2 solution tests, the deterioration of the mechanical properties of the specimens is primarily controlled by the physical softening effect of the water solution. With increasing immersion time, the major rock-forming minerals in limestone gradually react with the CO2 solution, leading to precipitation of a large amount of Ca2+ from the mineral structure and a rapid exacerbation of the deterioration of specimen mechanical properties under these chemical dissolutions. The findings of this study provide a scientific basis for assessment of the long-term stability of underground engineering in limestone karst development areas. © 2023, The Authors. All rights reserved.

关键词： Limestone

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Sharp convergence to steady states of Allen-Cahn

arXiv

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arXiv 2021年

作者： Li, Dong Quan, Chaoyu Tang, Tao Yang, Wen Department of Mathematics The Hong Kong University of Science & Technology Clear Water Bay Kowloon Hong Kong SUSTech International Center for Mathematics Southern University of Science and Technology Shenzhen China Guangdong Provincial Key Laboratory of Computational Science and Material Design Southern University of Science and Technology Shenzhen China Division of Science and Technology BNU-HKBU United International College Zhuhai China Wuhan Institute of Physics and Mathematics Chinese Academy of Sciences P.O. Box 71010 Wuhan430071 China Innovation Academy for Precision Measurement Science and Technology Chinese Academy of Sciences Wuhan430071 China

In our recent work we found a surprising breakdown of symmetry conservation: using standard numerical discretization with very high precision the computed numerical solutions corresponding to very nice initial data may converge to completely incorrect steady states due to the gradual accumulation of machine round-off error. We solved this issue by introducing a new Fourier filter technique for solutions with certain band gap properties. To further investigate the attracting basin of steady states we classify in this work all possible bounded nontrivial steady states for the Allen-Cahn equation. We characterize sharp dependence of nontrivial steady states on the diffusion coefficient and prove strict monotonicity of the associated energy. In particular, we establish a certain self-replicating property amongst the hierarchy of steady states and give a full classification of their energies and profiles. We develop a new modulation theory and prove sharp convergence to the steady state with explicit rates and profiles. Copyright © 2021, The Authors. All rights reserved.

关键词： Energy gap

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Time-varying Characteristics of mmWave Channel based on the Clustered Sparsity Model

Time-varying Characteristics of mmWave Channel based on the ...

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IEEE Conference on Vehicular technology (VTC)

作者： Lijun Yang Haitao Lu Xinchao Ge Zhixin Sun Pan Cao School of Internet of Things Nanjing University of Posts and Telecommunications Nanjing China RAN System Design Dept. ZTE Corporation Shenzhen China Shenzhen Key Laboratory of 5G RAN Security Technology Research and Application Shenzhen China School of Modern Posts Nanjing University of Posts and Telecommunications Nanjing China School of Physics Engineering and Computer Science University of Hertfordshire Hatfield UK

A better understanding of the mmWave channel coherence time will play a significant role in both communication and sensing. Traditional literatures consider that the channel coherence time in mmWave communication will be very short due to high frequency, which makes the channel estimation more difficult. However, we believe that the propagation characteristics of the mmWave channel will affect its coherence time, i.e., channel sparsity may limit its time variability. In this paper, we investigate the time-varying nature of mmWave channel by analyzing its Doppler spread based on the clustered sparsity model. After the derivation of Doppler spectrum DPS and the simulation analysis based on the two-cluster channel, we found that the maximum angle between clusters and the power distribution between clusters are two main factors limiting the Doppler spread. Finally, the realistic mmWave NYUSIM model is used for Doppler spread comparative analysis with Clarke’s model and find that Doppler spread of NYUSIM channel is far less than that estimated based on Clarke’s model. Thus, it is demonstrated that even if the mmWave frequency is high, the clustered sparsity characteristics makes its channel coherence time not as short as thought intuitively, which is meaningful for mmWave vehicular sensing and communication.

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The Age of Generative AI and AI-Generated Everything

arXiv

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arXiv 2023年

作者： Du, Hongyang Niyato, Dusit Kang, Jiawen Xiong, Zehui Zhang, Ping Cui, Shuguang Shen, Xuemin Mao, Shiwen Han, Zhu Jamalipour, Abbas Vincent Poor, H. Kim, Dong In School of Computer Science and Engineering Nanyang Technological University Singapore639798 Singapore School of Automation Guangdong University of Technology Key Laboratory of Intelligent Information Processing and System Integration of IoT Ministry of Education Guangzhou510006 China Guangdong-HongKong-Macao Joint Laboratory for Smart Discrete Manufacturing Guangzhou510006 China Pillar of Information Systems Technology and Design Singapore University of Technology and Design Singapore487372 Singapore State Key Laboratory of Networking and Switching Technology Beijing University of Posts and Telecommunications China Chinese University of Hong Kong Shenzhen China Department of Electrical and Computer Engineering University of Waterloo WaterlooONN2L 3G1 Canada Department of Electrical and Computer Engineering Auburn University AuburnAL36849-5201 United States Department of Electrical and Computer Engineering University of Houston HoustonTX77004 United States Department of Computer Science and Engineering Kyung Hee University Seoul446-701 Korea Republic of School of Electrical and Information Engineering University of Sydney SydneyNSW2006 Australia Department of Electrical and Computer Engineering Princeton University PrincetonNJ08544 United States Department of Electrical and Computer Engineering Sungkyunkwan University Suwon16419 Korea Republic of

Generative AI (GAI) has emerged as a significant advancement in artificial intelligence, renowned for its language and image generation capabilities. This paper presents "AIGenerated Everything" (AIGX), a concept that extends GAI beyond mere content creation to real-time adaptation and control across diverse technological domains. In networking, AIGX collaborates closely with physical, data link, network, and application layers to enhance real-time network management that responds to various system and service settings as well as application and user requirements. Networks, in return, serve as crucial components in further AIGX capability optimization through the AIGX lifecycle, i.e., data collection, distributed pre-training, and rapid decision-making, thereby establishing a mutually enhancing interplay. Moreover, we offer an in-depth case study focused on power allocation to illustrate the interdependence between AIGX and networking systems. Through this exploration, the article analyzes the significant role of GAI for networking, clarifies the ways networks augment AIGX functionalities, and underscores the virtuous interactive cycle they form. This article paves the way for subsequent future research aimed at fully unlocking the potential of GAI and networks. © 2023, CC BY.

关键词： Decision making

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Sensitivity-Analysis-Based Reliability Enhancement for Networked Control Systems

Sensitivity-Analysis-Based Reliability Enhancement for Netwo...

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System Reliability and Safety Engineering (SRSE), International Conference on

作者： Ying Gao Qiang Dong Mo Tao Wei Zheng Zhiwu Ke Yi Feng School of Reliability and Systems Engineering Beihang University Beijing China Science and Technology on Thermal Energy and Power Laboratory Wuhan China Wuhan Second Ship Design and Research Institute Wuhan China

ISBN: (纸本)9781665401616

Aiming at improving the reliability of networked control systems, this paper first investigates the three types of redundancy methods, including dynamic, static and hybrid redundancy. A sensitivity-analysis-based reliability enhancement method is proposed for networked control systems. Using this method, the key components affecting the system reliability can be found through the reliability sensitivity analysis. The reliability sensitivity analysis result illustrates which components need to be improved first, and either static redundancy, dynamic redundancy or hybrid redundancy can be used to improve the reliability of the networked control system. Finally, a double loop networked control system is used as a case to verify the effect of our method. The static redundancy method is applied on those components which are more sensitive to the system reliability, and the system reliability is effectively improved.

关键词： Networked control systems Sensitivity analysis Redundancy Reliability engineering Safety Reliability

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Empirical prediction of noise from subsonic dual-stream jets using the concept of two components of single-stream jet noise 49

Empirical prediction of noise from subsonic dual-stream jets...

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49th International Congress and Exposition on Noise Control Engineering, INTER-NOISE 2020

ISBN: (纸本)9788994021362

A new empirical method for the prediction of noise from a subsonic coaxial-stream jet is proposed. The new prediction defines that the spectra of a coaxial-stream jet consist of three sources, the primary, secondary, and mixed jet sources. The single-jet prediction, based on the concept of two components, the fine-scale and large-scale components, was applied to each source. Thus, coaxial-stream jet noise could have six potential components, two components from each source. Among them, three components were selected for the prediction of subsonic coaxial-stream jet noise: the large-scale primary, the large-scale secondary, and the fine-scale mixed components. An adjusted diameter is adopted on the primary component for the proper consideration of the peak shift at aft angles. There is an excellent spectral agreement between the prediction and static model-scale data at all angles and frequencies over a wide range of BPR up to 20 and the velocity ratio from 0.57 to 1.14. It can be concluded that the new method can be applied for the prediction of jet noise from high-bypass-ratio turbofan engines of the current and next generation without arbitrary filter function for the adjustment of the contribution of three components. © Proceedings of 2020 International Congress on Noise Control Engineering, INTER-NOISE 2020. All rights reserved.

关键词： Forecasting

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