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Incremental forming of free surface with magnesium alloy AZ31 sheet at warm temperatures

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中国有色金属学会会刊：英文版 2008年第A01期18卷 165-169页

作者： Y.H.jI j.j.park Department of Mechanical and System Design Engineering Hongik University

The formabilityof AZ31 sheet begins to increase drastically at 150℃.The incremental forming technique was thus applied to AZ31 sheet at 150℃to utilize the formability to its fullest capacity at the lowest possible temperature for forming applications.A surface scanning technique was used followed by the tool path generation to incrementally form an egg *** thorough examination of various tool paths,the surface was most successfully produced by forming an intermediate shape followed by a series of tool *** scale stickers were devised to improve the accuracy in the measurement of grid deformation.

关键词：金属材料数控成形加工 AZ31镁合金板材

Strip Casting of High Performance Structural Alloys

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journal of Rare Earths 2004年第z2期22卷 78-84页

作者： S S park j G Lee Nack j Kim Center for Advanced Aerospace Materials Pohang University of Science and TechnologyPohang 790-784Korea Center for Advanced Aerospace MaterialsPohang University of Science and TechnologyPohang 790-784Korea Center for Advanced Aerospace MaterialsPohang University of Science and TechnologyPohang 790-784Korea

There exists a great need for the development of high performance alloys due to increasing demands for energy conservation and environmental protection. Application of strip casting shows a strong potential for the improvement of properties of existing alloys and also for the development of novel alloy systems with superior properties. The present paper reviews our Center's activities in the development of high performance alloys by strip casting. Examples include (1) Al alloys, (2) wrought Mg alloys, and (3) bulk metallic glass (BMG) alloys.

关键词： strip casting 6061 Al alloy AZ Mg alloy bulk metallic glass (BMG) alloy dispersion hardening

Deposition of Nano-Scaled Coatings Using Inductively Coupled Plasma

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journal of Rare Earths 2004年第z2期22卷 153-156页

作者： D H jung B park j j Lee School of Materials Science and Engineering College of EngineeringSeoul National UniversitySeoul 151-744Korea School of Materials Science and EngineeringCollege of EngineeringSeoul National UniversitySeoul 151-744Korea School of Materials Science and EngineeringCollege of EngineeringSeoul National UniversitySeoul 151-744Korea

Nano-scaled Ti-B-N coatings could be produced by inductively coupled plasma (ICP) assisted magnetron spurtering. The properties and microstructure of the coating can be changed drastically by applying ICP to conventional magnetron sputtering. In this work, an internal type rf ICP process is used. The core of this technology is the efficient production and control of self-depositing ions and reactive gas ions by an induced electric field. Ti-B-N coatings were prepared by using a TiB2 target and a gas mixture of N2 and Ar at 200 ℃ and a pressure of 60 mTorr. In addition to ICP, the effect of the substrate bias voltage on the structure and properties of the coating was investigated. By applying ICP and a bias voltage to the substrate the hardness of the Ti-B-N coating is increased by more than 75 GPa, as a result of enhanced ionization in the plasma. The Ti-B-N coating, which has the highest hardness, shows the best surface uniformity and a very dense structure with a grain size of 3 nm. This sample also shows a high crystallinity compared to the coating prepared using other deposition parameters.

关键词： nano-scaled coatings industively conpled plasma

Sensorless control for hysteresis compensation of AFM scanner by modified Rayleigh model

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journal of Central South University 2010年第6期17卷 1243-1246页

作者： park j K MOON W K Department of Mechanical Engineering Changwon National UniversityChangwon 641-773Korea Department of Mechanical Engineering Pohang Unive rsity of Science and TechnologyPohang 790-784Korea

A novel modified Rayleigh model was developed for compensating hysteresis problem of an atomic force microscope(AFM) *** high driving fields,piezoelectric actuators that integrated a scanner have severe hysteresis,which can cause serious displacement *** hysteresis is from various origins including movement of defects,grain boundary effects,and displacement of ***,because its characteristic is stochastic,it is almost impossible to predict the piezoelectric hysteresis ***,it was predicted phenomenologically,which means that the relationship between inputs and outputs is *** typical phenomenological approach is the Rayleigh ***,the model has the discrepancy with experiment result as the fields *** overcome the demerit of the Rayleigh model,a modified Rayleigh model was *** the modified Rayleigh model,each coefficient should be defined differently according to the field direction due to the increase of the asymmetry in the high *** applying an inverse form of this modified Rayleigh model to an AFM scanner,it is proved that hysteresis can be compensated to a position error of less than 5%.This model has the merits of reducing complicated fitting procedures and saving computation time compared with the Preisach model.

关键词： piezoelectric stack actuator hysteresis compensation Rayleigh model atomic force microscopy

Synchronization criteria for coupled Hopfield neural networks with time-varying delays

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Chinese Physics B 2011年第11期20卷 140-150页

作者： M.j.park O.M.Kwon ju H.park S.M.Lee E.j.Cha School of Electrical Engineering Chungbuk National University Department of Electrical Engineering Yeungnam University School of Electronic Engineering Daegu University Department of Biomedical Engineering School of MedicineChungbuk National University

This paper proposes new delay-dependent synchronization criteria for coupled Hopfield neural networks with time-varying delays. By construction of a suitable Lyapunov Krasovskii＇s functional and use of Finsler＇s lemma, novel synchronization criteria for the networks are established in terms of linear matrix inequalities （LMIs） which can be easily solved by various effective optimization algorithms. Two numerical examples are given to illustrate the effectiveness of the proposed methods.

关键词： Hopfield neural networks coupling delay synchronization Lyapunov method

Leader-following consensus criteria for multi-agent systems with time-varying delays and switching interconnection topologies

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Chinese Physics B 2012年第11期21卷 144-153页

We consider multi-agent systems with time-varying delays and switching interconnection topologies. By con- structing a suitable Lyapunov-Krasovskii functional and using the reciprocally convex approach, new delay-dependent consensus criteria for the systems are established in terms of linear matrix inequalities （LMIs）, which can be easily solved by using various effective optimization algorithms. Two numerical examples are given to illustrate the effectiveness of the proposed methods.

关键词： consensus multi-agent systems time delay Lyapunov method

Event-triggered bipartite consensus over cooperation-competition networks under DoS attacks

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Science China(Technological Sciences) 2021年第1期64卷 157-168页

作者： HU AiHua park j H CAO jinDe HU ManFeng LUO YiPing School of Science Jiangnan UniversityWuxi 214122China Department of Electrical Engineering Yeungnam UniversityKyongsan 38541Korea School of Mathematics Southeast UniversityNanjing 210096China College of Electrical and Information Engineering Hunan Institute of EngineeringXiangtan 411104China

This paper addresses the bipartite consensus over cooperation-competition networks affected by denial-of-service(DoS) *** that a network consists of multiple interactive agents, and the relationship between neighboring agents is cooperative or competitive. Meanwhile, information transmission among the agents is unavailable during the intervals of attacks. In order to save communication resources and exclude the Zeno behavior, an event-triggered scheme depending on the sampled-data information from neighboring agents is proposed, and efficient defense strategies in response to the attacks are put *** that the frequency and duration of DoS attacks meet certain requirements, then according to the signed graph theory,the La Salle’s invariance principle, and the convergence of monotone sequences, the results of bipartite consensus via the eventtriggered protocol are provided, which are mainly related to the communication topology of the network, the sampling period,and the threshold parameters in the event-triggered scheme. It is shown that the bipartite consensus is realized even though the DoS attacks take place frequently. Furthermore, this paper discusses the bipartite consensus in the presence of DoS attacks with a random unsuccessful rate. Finally, numerical simulations illustrate the theoretical results.

关键词： bipartite consensus denial-of-service(DoS)attack event-triggered scheme structural balance multiagent system

H∞ synchronization of chaotic neural networks with time-varying delays

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Chinese Physics B 2013年第11期22卷 244-252页

作者： O. M. Kwon M. j. park ju H. park S. M. Lee E. j. Cha School of Electrical Engineering Chungbuk National University Department of Electrical Engineering Yeungnam University School of Electronic Engineering Daegu University Department of Biomedical Engineering School of Medicine Chungbuk National University

In this paper, we investigate the problem of H∞ synchronization for chaotic neural networks with time-varying delays. A new model of the networks with disturbances in both master and slave systems is presented. By constructing a suitable Lyapunov–Krasovskii functional and using a reciprocally convex approach, a novel H∞ synchronization criterion for the networks concerned is established in terms of linear matrix inequalities （LMIs） which can be easily solved by various effective optimization algorithms. Two numerical examples are given to illustrate the effectiveness of the proposed method.

关键词： chaotic neural networks time-varying delays H∞ synchronization Lyapunov method

Heavy Metals in Brown Rice(Oryza sativa L.) and Soil After Long-Term Irrigation of Wastewater Discharged from Domestic Sewage Treatment Plants

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Pedosphere 2011年第5期21卷 621-627页

作者： B.Y.CHUNG C.H.SONG B.j.park j.Y.CHO Advanced Radiation Technology Institute Korea Atomic Energy Research Institute(KAERI) Korea Testing & Research Institute(KTR) Department of Horticultural Science Chungbuk National University Department of Bio-environmental Chemistry Chonbuk National University

A pot experiment was conducted in a plastic film house to evaluate the translocation and uptake of heavy metals(Pb,Cd,Cu,and Zn) into brown rice(Oryza sativa L.) and the heavy metals residues in soils which had previously been irrigated with domestic wastewater for a long time(3 years).The range of Pb,Cd,Cu,and Zn was 5.10 ± 0.01,0.105 ± 0.017,5.76 ± 0.42,and 23.56 ± 1.40 mg kg-1,respectively in the domestic wastewater-irrigated soil,and 0.370 ± 0.006,0.011 ± 0.001,0.340 ± 0.04,and 2.05 ± 0.18 mg kg-1,respectively,in the domestic wastewater-irrigated brown *** results indicated that application of domestic wastewater to arable land slightly increased the levels of Pb,Cd,Cu,and Zn in soil and brown rice(P joint FAO/WHO Expert Committee on Food ***,the continuous monitoring and pollution control of hazardous materials from domestic wastewater are needed in order to prevent excessive build-up of heavy metals in the food chain.

关键词： accumulation domestic wastewater ground water irrigation P2O5 total N