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Local resonance metamaterial-based integrated design for suppressing longitudinal and transverse waves in fluid-conveying pipes

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Applied Mathematics and Mechanics(English Edition) 2024年第10期45卷 1821-1840页

作者： Donghai HAN Qi JIA Yuanyu GAO Qiduo JIN Xin FANG Jihong WEN Dianlong YU Laboratory of Science and Technology on Integrated Logistics Support National University of Defense TechnologyChangsha 410073China College of Intelligence Science and Technology National University of Defense TechnologyChangsha 410073China

To solve the problem of low broadband multi-directional vibration control of fluid-conveying pipes,a novel metamaterial periodic structure with multi-directional wide bandgaps is ***,an integrated design method is proposed for the longitudinal and transverse wave control of fluid-conveying pipes,and a novel periodic structure unit model is constructed for vibration *** on the bandgap vibration reduction mechanism of the acoustic metamaterial periodic structure,the material parameters,structural parameters,and the arrangement interval of the periodic structure unit are *** finite element method(FEM)is used to predict the vibration transmission characteristics of the fluid-conveying pipe installed with the vibration reduction periodic ***,the wave/spectrum element method(WSEM)and experimental test are used to verify the calculated results ***,the vibration attenuation characteristics of the structure under different conditions,such as rubber material parameters,mass ring material,and fluid-structure coupling effect,are *** results show that the structure can produce a complete bandgap of 46 Hz-75 Hz in the low-frequency band below 100 Hz,which can effectively suppress the low broadband vibration of the fluidconveying *** addition,a high damping rubber material is used in the design of the periodic structure unit,which realizes the effective suppression of each formant peak of the pipe,and improves the vibration reduction effect of the fluid-conveying ***,the structure has the effect of suppressing both bending vibration and longitudinal vibration,and effectively inhibits the transmission of transverse waves and longitudinal waves in the *** research results provide a reference for the application of acoustic metamaterials in the multi-directional vibration control of fluid-conveying pipes.

关键词： fluid-conveying pipe acoustic metamaterial multi-directional vibration reduction local resonance

Influence of contact curvature on frictional energy dissipation under varying tangential loads

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Friction 2024年第2期12卷 363-374页

作者： Sumin BAEK Seunghun BAEK School of Mechanical Engineering Pusan National UniversityPusan 46241Republic of Korea

This study investigates the effect of contact surface curvatures on the friction response under varying tangential loadings using a finite element(FE)*** results showed that the geometry of the surface influences the contact force at the interface and reduces the friction effect through an unsteady distribution of the contact *** relationship between the friction effect,excitation,and contact surface shape was also examined,revealing a linear inverse relationship between the friction and *** findings provide a comprehensive understanding of the frictional interactions between elastic bodies and highlight the role of curvature as a design parameter for regulating the friction effect.

关键词： frictional contact curvelinear contact frictional energy dissipation contact curvature

Operational requirements analysis method based on question answering of WEKG

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Journal of Systems Engineering and Electronics 2024年第2期35卷 386-395页

作者： ZHANG Zhiwei DOU Yajie XU Xiangqian MA Yufeng JIANG Jiang TAN Yuejin College of Systems Engineering National University of Defense TechnologyChangsha 410073China

The weapon and equipment operational requirement analysis(WEORA) is a necessary condition to win a future war,among which the acquisition of knowledge about weapons and equipment is a great challenge. The main challenge is that the existing weapons and equipment data fails to carry out structured knowledge representation, and knowledge navigation based on natural language cannot efficiently support the WEORA. To solve above problem, this research proposes a method based on question answering(QA) of weapons and equipment knowledge graph(WEKG) to construct and navigate the knowledge related to weapons and equipment in the WEORA. This method firstly constructs the WEKG, and builds a neutral network-based QA system over the WEKG by means of semantic parsing for knowledge navigation. Finally, the method is evaluated and a chatbot on the QA system is developed for the WEORA. Our proposed method has good performance in the accuracy and efficiency of searching target knowledge, and can well assist the WEORA.

关键词： operational requirement analysis weapons and equipment knowledge graph(WEKG) question answering(QA) neutral network

Rts: learning robustly from time series data with noisy label

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Frontiers of Computer Science 2024年第06期18卷 186332-186332页

作者： ZHOU Zhi JIN Yi-Xuan Li Yu-Feng national Key Laboratory for Novel Software Technology Nanjing university

Significant progress has been made in machine learning with large amounts of clean labels and static data. However, in many real-world applications, the data often changes with time and it is difficult to obtain massive clean annotations, that is, noisy labels and time series are faced simultaneously. For example, in product-buyer evaluation, each sample records the daily time behavior of users, but the long transaction period brings difficulties to analysis, and salespeople often erroneously annotate the user’s purchase behavior. Such a novel setting, to our best knowledge, has not been thoroughly studied yet, and there is still a lack of effective machine learning methods. In this paper, we present a systematic approach RTS both theoretically and empirically, consisting of two components, Noise-Tolerant Time Series Representation and Purified Oversampling Learning. Specifically, we propose reducing label noise’s destructive impact to obtain robust feature representations and potential clean samples. Then, a novel learning method based on the purified data and time series oversampling is adopted to train an unbiased model. Theoretical analysis proves that our proposal can improve the quality of the noisy data set. Empirical experiments on diverse tasks, such as the house-buyer evaluation task from real-world applications and various benchmark tasks, clearly demonstrate that our new algorithm robustly outperforms many competitive methods.

关键词： weakly-supervised learning time-series classification class-imbalanced learning

Bio-inspired Design and Inverse Kinematics Solution of an Omnidirectional Humanoid Robotic Arm with Geometric and Load Capacity Constraints

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Journal of Bionic Engineering 2024年第2期21卷 778-802页

作者： Zhichao Zhu Zirong Luo Yiming Zhu Tao Jiang Minghai Xia Shanjun Chen Boyu Jin College of Intelligence Science and Technology National University of Defense TechnologyChangshaChina

Inspired by the driving muscles of the human arm,a 4-Degree of Freedom(DOF)concentrated driving humanoid robotic arm is proposed based on a spatial double parallel four-bar *** four-bar mechanism design reduces the inertia of the elbow-driving unit and the torque by 76.65%and 57.81%,*** the human pose regulation strategy that the human arm picks up a heavy object by adjusting its posture naturally without complicated control,the robotic arm features an integrated position-level closed-form inverse solution method considering both geometric and load capacity *** method consists of a geometric constraint model incorporating the arm angle(φ)and the Global Configuration(GC)to avoid joint limits and singularities,and a load capacity model to constrain the feasible domain of the arm ***,trajectory tracking simulations and experiments are conducted to validate the feasibility of the proposed inverse solution *** simulated maximum output torque,maximum output power and total energy consumption of the robotic arm are reduced by up to 2.0%,13.3%,and 33.3%,*** experimental results demonstrate that the robotic arm can bear heavy loads in a human-like posture,effectively reducing the maximum output torque and energy consumption of the robotic arm by 1.83%and 5.03%,respectively,while avoiding joints beyond geometric and load capacity *** proposed design provides a high payload–weight ratio and an efficient pose control solution for robotic arms,which can potentially broaden the application spectrum of humanoid robots.

关键词： Humanoid robotic arm Bio-inspired design Inverse kinematics solution Load capacity constraint Geometric constraint

Robust cooperative multi-agent reinforcement learning via multi-view message certification

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Science China(Information Sciences) 2024年第4期67卷 131-145页

作者： Lei YUAN Tao JIANG Lihe LI Feng CHEN Zongzhang ZHANG Yang YU national Key Laboratory for Novel Software Technology Nanjing University Polixir Technologies

Many multi-agent scenarios require message sharing among agents to promote coordination,hastening the robustness of multi-agent communication when policies are deployed in a message perturbation environment. Major relevant studies tackle this issue under specific assumptions, like a limited number of message channels would sustain perturbations, limiting the efficiency in complex scenarios. In this paper,we take a further step in addressing this issue by learning a robust cooperative multi-agent reinforcement learning via multi-view message certification, dubbed CroMAC. Agents trained under CroMAC can obtain guaranteed lower bounds on state-action values to identify and choose the optimal action under a worst-case deviation when the received messages are perturbed. Concretely, we first model multi-agent communication as a multi-view problem, where every message stands for a view of the state. Then we extract a certificated joint message representation by a multi-view variational autoencoder(MVAE) that uses a product-of-experts inference network. For the optimization phase, we do perturbations in the latent space of the state for a certificate guarantee. Then the learned joint message representation is used to approximate the certificated state representation during training. Extensive experiments in several cooperative multi-agent benchmarks validate the effectiveness of the proposed CroMAC.

关键词： multi-agent reinforcement learning robust communication adversarial training multi-view learning message certification

Overview of radar detection methods for low altitude targets in marine environments

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Journal of Systems Engineering and Electronics 2024年第1期35卷 1-13页

作者： YANG Yong YANG Boyu School of Electronic Science National University of Defense TechnologyChangsha 410073China

In this paper,a comprehensive overview of radar detection methods for low-altitude targets in maritime environments is presented,focusing on the challenges posed by sea clutter and multipath *** performance of the radar detection methods under sea clutter,multipath,and combined conditions is categorized and summarized,and future research directions are outlined to enhance radar detection performance for low-altitude targets in maritime environments.

关键词： radar sea clutter multipath scattering detection low altitude target

CFD-based hull optimization in calm water using adaptive grid deformation method

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Journal of Hydrodynamics 2024年第2期36卷 241-262页

作者： Shuguang Wang Yonghwan Kim Department of Naval Architecture and Ocean Engineering Seoul National UniversitySeoulKorea

This paper presents an adaptive grid deformation technique for optimizing ship hull forms using computational fluid dynamics(CFD).The proposed method enables accurate and smooth updates of the hull surface and 3-D CFD grids in response to design *** technique incorporates a two-level point-transformation approach to move the grid points by a few design ***,generic B-splines are utilized to transform grid points according to the displacements of the control points within a defined control *** ensures surface modification accuracy and smoothness,similar to those provided by non-uniform rational ***,radial basis functions are used to interpolate the movements of the control points with a limited set of design *** developed method effectively maintains the mesh quality and simulation *** applying this method to surface and grid adaptation,a regression model is proposed in the form of a second-order polynomial to represent the relationship between the geometric parameters and design *** polynomial is then used to introduce geometric ***,a radial basis function surrogate model for the calm-water resistance is constructed to approximate the objective *** enhanced optimization framework is proposed for CFD–based hull optimization and applied to KVLCC2 to validate its feasibility and efficiency.

关键词： Hull-form optimization adaptive grid deformation ship resistance OpenFOAM radial basis function(RBF)surrogate model

Requirements ranking based on crowd-sourcing high-end product USs

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Journal of Systems Engineering and Electronics 2024年第1期35卷 94-104页

作者： MA Yufeng DOU Yajie XU Xiangqian JIA Qingyang TAN Yuejin College of Systems Engineering National University of Defense TechnologyChangsha 410003China

Based on the characteristics of high-end products,crowd-sourcing user stories can be seen as an effective means of gathering requirements,involving a large user base and generating a substantial amount of unstructured *** key challenge lies in transforming abstract user needs into specific ones,requiring integration and ***,we propose a topic mining-based approach to categorize,summarize,and rank product requirements from user ***,after determining the number of story categories based on py LDAvis,we initially classify“I want to”phrases within user ***,classic topic models are applied to each category to generate their names,defining each post-classification user story category as a ***,a weighted ranking function is devised to calculate the importance of each ***,we validate the effectiveness and feasibility of the proposed method using 2966 crowd-sourced user stories related to smart home systems.

关键词： high-end product complex system crowd-sourcing user stories topic mining requirements ranking