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Multiple air route crossing waypoints optimization via artificial potential field method

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Chinese Journal of Aeronautics 2021年第4期34卷 279-292页

作者： Bizhao PANG Wei DAI Xinting HU Fuqing DAI kin huat low School of Mechanical and Aerospace Engineering Nanyang Technological UniversitySingapore 639798Singapore Air Traffic Management Research Institute Nanyang Technological UniversitySingapore 637460Singapore School of Air Traffic Management Civil Aviation University of ChinaTianjin 300300China

Air route crossing waypoint optimization is one of the effective ways to improve airspace utilization,capacity and resilience in dealing with air traffic congestion and ***,research is lacking on the optimization of multiple Crossing Waypoints(CWPs)in the fragmented airspace separated by Prohibited,Restricted and Dangerous areas(PRDs).To tackle this issue,this paper proposes an Artificial Potential Field(APF)model considering attractive forces produced by the optimal routes and repulsive forces generated by *** optimization framework based on the APF model is proposed to optimize the different airspace topologies varying the number of CWPs,air route segments and *** on the framework,an adaptive method is developed to dynamically control the optimization process in minimizing the total air route *** proposed model is applied to a busy controlled *** the obtained results show that after optimization the safety-related indicators:conflict number and controller workload reduced by 7.75%and 6.51%*** for the cost-effectiveness indicators:total route length,total air route cost and non-linear coefficient,declined by 1.74%,3.13%and 1.70%*** the predictability indicator,total flight delay,saw a notable reduction by 7.96%.The proposed framework and methodology can also provide an insight in the understanding of the optimization to other network systems.

关键词： Adaptive method Air route network Air traffic control Potential field Structure optimization

A Three-Dimensional kinematics Analysis of a Koi Carp Pectoral Fin by Digital Image Processing

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Journal of Bionic Engineering 2013年第2期10卷 210-221页

作者： Lei Wang Min Xu Bo Liu kin huat low Jie Yang Shiwu Zhang Department of Precision Machinery and Precision Instrumentation University of Science and Technology of China Hefei Anhui 230026 P. R. China School of Mechanical and Aerospace Engineering Nanyang Technological University Singapore 639798 Singapore

Pectoral fins fascinate researchers for their important role in fish maneuvers. By possessing a complicated flexible structure with several fin rays made by a thin film, the fin exhibits a three-dimensional （3D） motion. The complex 3D fin kinematics makes it challenging to study the performance of pectoral fin. Nevertheless, a detailed study on the 3D motion pattern of pectoral fins is necessary to the design and control ofa bio-inspired fin rays. Therefore, a highspeed photography system is introduced in this paper to study the 3D motion ofa Koi Carp by analyzing the two views of its pectoral fin simultaneously. The key motions of the pectoral fins are first captured in both hovering and retreating. Next, the 3D configuration of the pectoral fins is recon- structed by digital image processing, in which the movement of fin rays during fish retreating and hovering is obtained. Fur- thermore, the method of Singular Value Decomposition （SVD） is adopted to extract the basic motion patterns of pectoral fins from extensive image sequences, i.e. expansion, bending, cupping, and undulation. It is believed that the movement of the fin rays and the basic patterns of the pectoral fins obtained in the present work can provide a good foundation for the development and control of bionic flexible pectoral fins for underwater propeller.

关键词： highspeed photography Singular Value Decomposition (SVD) three-dimensional kinematics digital image proc-essing

Bio-inspired Flow Sensing and Prediction for Fish-like Undulating Locomotion： A CFD-aided Approach

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Journal of Bionic Engineering 2015年第3期12卷 406-417页

作者： Han Zhou Tianjiang Hu kin huat low Lincheng Shen Zhaowei Ma Guangming Wang Haijun Xu College of Mechatronics and Automation National University of Defense Technology Changsha 410073 China State Key Laboratory of High Performance Computing National University of Defense Technology Changsha 410073 China School of Mechanical and Aerospace Engineering Nanyang Technological University Singapore 639798

Feedback flow information is of significance to enable underwater locomotion controllers with higher adaptability and efficiency within varying environments. Inspired from fish sensing their external flow via near-body pressure, a computational scheme is proposed and developed in this paper. In conjunction with the scheme, Computational Fluid Dynamics （CFD） is employed to study the bio-inspired fish swimming hydrodynamics. The spatial distribution and temporal variation of the near-body pressure of fish are studied over the whole computational domain. Furthermore, a filtering algorithm is designed and implemented to fuse near-body pressure of one or multiple points for the estimation on the external flow. The simulation results demonstrate that the proposed computational scheme and its corresponding algorithm are both effective to predict the inlet flow velocity by using near-body pressure at distributed spatial points.

关键词： bio-inspired fish undulating locomotion flow sensing near-body pressure flow velocity estimation Computational Fluid Dynamics (CFD)

Tactical conflict resolution in urban airspace for unmanned aerial vehicles operations using attention-based deep reinforcement learning

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Green Energy and Intelligent Transportation 2023年第4期2卷 43-57页

作者： Mingcheng Zhang Chao Yan Wei Dai Xiaojia Xiang kin huat low School of Mechanical and Aerospace Engineering Nanyang Technological UniversitySingapore 639798Singapore College of Intelligence Science and Technology National University of Defense TechnologyChangsha 410073China Air Traffic Management Research Institute Nanyang Technological UniversitySingapore 637460Singapore

Unmanned aerial vehicles(UAVs)have gained much attention from academic and industrial areas due to the significant number of potential applications in urban airspace.A traffic management system for these UAVs is needed to manage this future *** conflict resolution for unmanned aerial systems(UASs)is an essential piece of the puzzle for the future UAS Traffic Management(UTM),especially in very low-level(VLL)urban *** conflict resolution in higher altitude airspace,the dense high-rise buildings are an essential source of potential conflict to be considered in VLL urban *** this paper,we propose an attention-based deep reinforcement learning approach to solve the tactical conflict resolution ***,we formulate this task as a sequential decision-making problem using Markov Decision Process(MDP).The double deep Q network(DDQN)framework is used as a learning framework for the host drone to learn to output conflict-free maneuvers at each time *** use the attention mechanism to model the individual neighbor's effect on the host drone,endowing the learned conflict resolution policy to be adapted to an arbitrary number of neighboring ***,we build a simulation environment with various scenarios covering different types of encounters to evaluate the proposed *** simulation results demonstrate that our proposed algorithm provides a reliable solution to minimize secondary conflict counts compared to learning and non-learning-based approaches under different traffic density scenarios.

关键词： Unmanned aircraft system traffic management Tactical conflict resolution Double deep Q network Attention mechanism Secondary conflict

Gait Study and Pattern Generation of a Starfish-Like Soft Robot with Flexible Rays Actuated by SMAs

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Journal of Bionic Engineering 2014年第3期11卷 400-411页

作者： Shixin Mao Erbao Dong Hu Jin Min Xu Shiwu Zhang Jie Yang kin huat low Department of Precision Machinery and Precision Instrumentation University of Science and Technology of China Hefei 230026 P. R. China School of Mechanical and Aerospace Engineering Nanyang Technological University Singapore 639798 Singapore

This paper presents the design and development of a starfish-like soft robot with flexible rays and the implementation of multi-gait locomotion using Shape Memory Alloy （SMA） actuators. The design principle was inspired by the starfish, which possesses a remarkable symmetrical structure and soft internal skeleton. A soft robot body was constructed by using 3D printing technology. A kinematic model of the SMA spring was built and developed for motion control according to displacement and force requirements. The locomotion inspired from starfish was applied to the implementation of the multi-ray robot through the flexible actuation induced multi-gait movements in various environments. By virtue of the proposed ray control patterns in gait transition, the soft robot was able to cross over an obstacle approximately twice of its body height. Results also showed that the speed of the soft robot was 6.5 times faster on sand than on a clammy rough terrain. These experiments demonstrated that the bionic soft robot with flexible rays actuated by SMAs and multi-gait locomotion in proposed patterns can perform successfully and smoothly in various terrains.

关键词： soft robot bio-inspiration multi-gait locomotion rough terrains SMA actuators

Locomotion and Depth Control of Robotic Fish with Modular Undulating Fins

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International Journal of Automation and computing 2006年第4期3卷 348-357页

作者： kin huat low School of Mechanical and Aerospace Engineering Nanyang Technological University 50 Nanyang AvenueSingapore 639798Republic of Singapore

This paper presents an environmental-friendly robotic system mimicking the undulating fins of a *** mimic the actual flexible fin of real fish,a fin-like mechanism with a series of connecting linkages is modeled and attached to the robotic fish,by virtue of a specially designed *** link is able to turn and slide with respect to the adjacent *** driving linkages are then used to form a mechanical fin consisting of several fin segments,which are able to produce undulations,similar to those produced by the actual fish *** to the modular and re-configurable design of the mechanical fin,we are able to construct biomimetic robotic fish with various swimming modes by fin *** qualitative and workspace observations by experiments of the robotic fish are shown and discussed.

关键词： Fin mechanisms locomotion depth control workspace undulating fins modular and re-configurable

A Computational Fluid Dynamics (CFD) Analysis of an Undulatory Mechanical Fin Driven by Shape Memory Alloy

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International Journal of Automation and computing 2006年第4期3卷 374-381页

作者： Yong-Hua Zhang Jian-Hui He Jie Yang Shi-Wu Zhang kin huat low Department of Precision Machinery and Precision Instrumentation University of Science and Technology of China Hefei PRC School of Mechanical and Aerospace Engineering Nanyang Technological University Singapore Republic of Singapore

Many fishes use undulatory fin to propel themselves in the underwater environment. These locomotor mechanisms have a popular interest to many researchers. In the present study, we perform a three-dimensional unsteady computation of an undulatory mechanical fin that is driven by Shape Memory Alloy （SMA）. The objective of the computation is to investigate the fluid dynamics of force production associated with the undulatory mechanical fin. An unstructured, grid-based, unsteady Navier-Stokes solver with automatic adaptive remeshing is used to compute the unsteady flow around the fin through five complete cycles. The pressure distribution on fin surface is computed and integrated to provide fin forces which are decomposed into lift and thrust. The velocity field is also computed throughout the swimming cycle. Finally, a comparison is conducted to reveal the dynamics of force generation according to the kinematic parameters of the undulatory fin （amplitude, frequency and wavelength）.

关键词： Computational Fluid Dynamics (CFD) undulatory mechanical fin unsteady flow unstructured mesh Shape Memory Alloy (SMA)

Multiplex real-time PCR revealed very high prevalence of soil-transmitted helminth infections among aborigines in Peninsular Malaysia

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Asian Pacific Journal of Tropical Medicine 2020年第12期13卷 550-556页

作者： Nurulhasanah Othman Noorizan Miswan Weng-kin Wong Boon-huat Lim Rahmah Noordin Institute for Research in Molecular Medicine Universiti Sains Malaysia11800 PenangMalaysia School of Health Sciences Universiti Sains Malaysia16150 KelantanMalaysia

Objective:To determine the true prevalence of soil-transmitted helminth infections in the Malaysian aborigines using real-time ***:A total of 122 aborigines from seven tribes were recruited from settlements and nearby hospitals which served the communities,located in four states in Peninsular *** stool samples were examined for the presence of soil-transmitted helminth using real-time PCR and *** latter included the direct wet mount and formalin-ether concentration technique(FECT).The infection load in FECT-positive samples was determined by the Kato-Katz *** real-time analyzer detected five helminth species using two sets of ***:The real-time PCR detected soil-transmitted helminth in 98.4% samples(n=122),which were 1.56 times higher than by *** lumbricoides and Trichuris trichiura were detected in more than 90% of the samples,while hookworm was detected in 46.7%(Necator americanus) and 13.9%(Ancylostoma sp.)of the *** with previous reports on the Malaysian aborigines showed that the real-time PCR markedly improved the detection of Ascaris lumbricoides,hookworm and Strongyloides *** real-time PCR detected poly-helminths in 92.6%of the samples compared to 28.7% by *** addition,27 samples(22.1%) showed amplification of Strongyloides stercoralis ***:The real-time PCR showed very high prevalence rates of soil-transmitted helminth infections in the aborigines and is the recommended method for epidemiological investigation of soiltransmitted helminth infections in this population.

关键词： prevalence infections markedly

Detection of Entamoeba histolytica in experimentally induced amoebic liver abscess:comparison of three staining methods

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Asian Pacific Journal of Tropical Biomedicine 2012年第1期2卷 61-65页

作者： Tan Zi Ning Wong Weng kin Shaymoli Mustafa Arefuddin Ahmed Rahmah Noordin Tan Gim Cheong Olivos-Garcia Alfonso Lim Boon huat School of Health Sciences Universiti Sains Malaysia Institute for Research in Molecular Medicine Universiti Sains Malaysia Department of Medical Microbiology ParasitologySchool of Medical SciencesUniversiti Sains Malaysia Departamento de Medicina Experimental Facultad de Medicina.Universidad National Autonoma de Mexico

Objective:To compare the efficacy of three different tissue stains,namely haematoxylin and eosin(H&E),periodic-acid Schiff(PAS)and immunohistochemical(1HC)stains for detection of Entamoeba histolytica(***)trophozoites in abscessed liver tissues of ***:Amoebic liver abscess was experimentally induced in a hamster by injecting 1×10~6of axenically cultured virulent *** trophozoites(HM1-IMSS strain)into the portal *** a week post-inoculation,the hamster was sacrificed and the liver tissue sections were stained with H&E,PAS and IHC stains to delect the amoebic ***:The three stains revealed tissue necrosis and amoebic trophozoites,but with varying clarity.H&E and PAS stained the trophozoites pink and magenta,respectively,however it was difficult to differentiate the stained trophozoites from the macrophages because of their similarity in size and *** the other hand,IHC stain revealed distinct brown appearance of the trophozoites in the infected liver ***:It can be concluded that out of the three *** is the best for identification of *** trophozoites in tissue sections.

关键词： Entamoeba histolytica Amoebic liver abscess H&E PAS IHC Trophozoite