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Transactions of Nonferrous Metals Society of China 2015年第4期25卷 1176-1184页

作者： C.w.nahm Semiconductor Ceramics Laboratory Department of Electrical Engineering Dongeui UniversityBusan 614-714 Korea

The effect of small changes in sintering temperature on microstructure, electrical properties, dielectric characteristics, and degradation behavior of V-Mn-Nb-Gd co-doped zinc oxide ceramics was investigated. with the increase of sintering temperature, the densities of the sintered pellets decreased from 5.54 to 5.42 g/cm3 and the average grain size increased from 4.1 to 11.7 μm. The breakdown field(E1 m A) decreased noticeably from 7138 to 920 V/cm with the increase of sintering temperature. The varistor ceramics sintered at 900 ℃ exhibited excellent nonohmic properties, which were 66 for the nonohmic coefficient and 77 μA/cm2 for the leakage current density. Concerning stability, the varistors sintered at 900 ℃ exhibited the strongest accelerated degradation characteristics, with ΔE1 mA =-9.2% for DC accelerated degradation stress of 0.85 E1 m A at 85 °C for 24 h.

关键词： ZnO-V2O5-based ceramics sintering electrical properties degradation behavior varistor

Human induced pluripotent stem cell-derived therapies for regeneration after central nervous system injury

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Neural Regeneration Research 2025年第11期20卷 3063-3075页

作者： Stephen Vidman Yee Hang Ethan Ma Nolan Fullenkamp Giles w.Plant Department of Neuroscience Ohio State UniversityColumbusOHUSA

In recent years,the progression of stem cell therapies has shown great promise in advancing the nascent field of regenerative *** the non-regenerative nature of the mature central nervous system,the concept that“blank”cells could be reprogrammed and functionally integrated into host neural networks remained *** work has also demonstrated the ability of such cells to stimulate intrinsic growth programs in post-mitotic cells,such as *** embryonic stem cells demonstrated great potential in treating central nervous system pathologies,ethical and technical concerns *** barriers,along with the clear necessity for this type of treatment,ultimately prompted the advent of induced pluripotent stem *** advantage of pluripotent cells in central nervous system regeneration is multifaceted,permitting differentiation into neural stem cells,neural progenitor cells,glia,and various neuronal *** precise spatiotemporal application of extrinsic growth factors in vitro,in addition to microenvironmental signaling in vivo,influences the efficiency of this directed *** the pluri-or multipotency of these cells is appealing,it also poses the risk of unregulated differentiation and teratoma *** of the neuroectodermal lineage,such as neuronal subpopulations and glia,have been explored with varying degrees of *** the risk of cancer or teratoma formation is greatly reduced,each subpopulation varies in effectiveness and is influenced by a myriad of factors,such as the timing of the transplant,pathology type,and the ratio of accompanying progenitor ***,successful transplantation requires innovative approaches to develop delivery vectors that can mitigate cell death and support ***,host immune responses to allogeneic grafts must be thoroughly characterized and further developed to reduce the need for *** to a clinical setting wi

关键词： axon regeneration central nervous system regeneration induced pluripotent stem cells neurotrauma regenerative medicine spinal cord injury stem cell therapy

Optimal Operation of Turbo Blowers Serially Connected Using Inlet Vanes

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Journal of Thermal Science 2011年第1期20卷 26-31页

作者： choon-Man Jang Plant Research Division Korea Institute of Construction Technology1190 IIsanseo-GuGoyang-Si411-712Korea

Optimal operation of the turbo blowers having an inlet vane has been studied to understand the blowers' operating *** analyze three-dimensional flow field in the turbo blowers serially connected,general analysis code,CFX,is introduced in the present *** turbulence model is employed to estimate the eddy *** the numerical analysis,it is found that the flow rates of the turbo blowers can be controlled at the vane angle between 90 (full open condition) degrees and 60 degrees effectively,because pressure loss rapidly increases below 60 degree of a vane *** also has almost the same values from 90 degrees to 60 degrees of a vane *** is noted that the distorted inlet velocity generated in the small vane angle makes performance deterioration of the turbo blowers due to the local leading edge separation and the following non-uniform blade loading.

关键词： Turbo Blower Inlet Vane Refuse Collection System Efficiency Numerical Simulation

Characteristics analysis and library development for piezoelectric transformer to drive a ballast for a 35 w class fluorescent lamp using PSPICE modeling

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Journal of Central South University 2016年第1期23卷 169-180页

作者： KIM Young-choon Division of Mechanical and Automotive Engineering College of Engineering Kongju National University

PSPICE model driven by an electric equivalent circuit of a piezoelectric circuit is presented. In order to confirm this model to be effective, an independent model of cold cathode fluorescent lamp(CCFL) driving circuit is used to conduct simulations, leading to a precise modeling. A library is configured through modeling and its accuracy is verified through simulations for widely used and representative lamps such as CCFL, fluorescent lamps, HID lamps, and electrodeless fluorescent lamps. On the basis of experiments, a lamp simulation is also performed using PSPICE, which allows us to take advantage of the lamp library easily. Also, PSPICE model driven by an electric equivalent circuit of a piezoelectric transformer is presented. In order to confirm this model to be effective, an independent model of CCFL driving circuit is used to conduct simulations, leading to a precise modeling. In addition, a new type of electronic ballast is proposed, which allows 35 w-class(T5-class) fluorescent lamp to work. This system is built by a rectifier which has improved power factor and half-bridge series resonant inverter. Also, with size of 27.5 mm high, 27.5 mm wide and 2.5 mm thick, the produced piezoelectric transformer has a high step-up ratio, through which it is possible for the electric ballast circuit to be lighter, smaller and more efficient. After the produced ballast is used to drive the fluorescent lamp for 25 min, it yields 0.95 in power factor correction, 86% in efficiency, 35.07 w in output voltage and 20.5 °C in temperature increase while meeting the characteristics of the 35 w-class fluorescent lamp.

关键词： PSPICE 35 w-class cold cathode fluorescent lamp (CCFL) fluorescent lamp library

The IOSS Chaos Synchronization Method

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Chinese Physics Letters 2011年第1期28卷 32-35页

作者： choon Ki Ahn Faculty of the Department of Automotive Engineering Seoul National University of Science&Technology172 Gongneung 2-dongNowon-guSeoul 139-743Korea

A new synchronization method, called the input/output-to-state stable synchronization (IOSSS) method, is proposed for a general class of chaotic systems with external disturbance. By introducing Lyapunov stability theory and linear matrix inequality (LMI) for the first time, the IOSSS controller is shown to not only guarantee the synchronization of the chaotic systems, but also reduce the effect of external disturbance. The proposed IOSSS controller can be obtained by solving the LMI, which can easily be done using standard numerical packages. A numerical example is given to demonstrate the availability of the proposed method.

关键词： method chaotic inequality

Low-temperature crystalline lead-free piezoelectric thin films grown on 2D perovskite nanosheet for flexible electronic device applications

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Nano Research 2019年第10期12卷 2559-2567页

作者： Jong-Hyun Kim Sang Hyo Kweon Sahn nahm KU-KIST Graduate School of Converging Science and Technology Korea University145 Anam-roSeongbuk-guSeoul 02841Republic of Korea Department of Material Science and Engineering Korea University145 Anam-roSeongbuk-guSeoul 02841Republic of Korea Department of Mechanical Engineering Kobe University1-1 Rokkodai-choNadaKobe 657-8501Japan

A monolayer of Sr2Nb3Oio(SNO)is deposited on the Pt/Ti/SiCwSi(Pt?Si)or Pt/Ti/polyimide(Pt-Pl)substrate by using the Langmuir-Blodgett method and employed as a seed-layer for the growth of a crystalline(Nai_xKx)NbO3(NKN)film at 350℃.The crystalline NKN film is grown along the[001]direction on the SNO/Pt-Si(or SNO/Pt-PI)*** to the presence of oxygen vacancies in the SNO seed-layer,the NKN film exhibits low ferroelectric properties and large leakage *** ameliorate these properties,the SNO/Pt-Si substrate is annealed in a 50 Torr oxygen atmosphere at 300℃,which removes the oxygen ***,the NKN film deposited on this substrate exhibits promising electrical properties,namely a dielectric constant of 278,dissipation factor of 1.7%,a piezoelectric 8nstant of 175 pm`V^-1,and a leakage current density of 6.47 x 10^-7 A cm^-2 at-0.2 MV *** electrical properties are obtained from the NKN film grown on the flexible SNO/Pt-PI substrate at 350°***,the NKN films grown on the SNO seed-layer at 350°C can be applied to electronic devices with flexible polymer substrates.

关键词： lead-free piezoelectric thin films low-temperature-deposition process two-dimensional(2D)nanosheet seed-layers polymer substrates

Contrast evaluation methods for natural color images in display systems: within- and cross-content evaluations

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Journal of Zhejiang University-Science C(Computers and Electronics) 2011年第11期12卷 897-909页

作者： choon-woo KIM School of Information and Communication Engineering Inha University

Contrast evaluation can be used as a criterion to evaluate performance of contrast enhancement algorithms and to compare contrast capability of display systems. This paper deals with contrast evaluation models for natural color images. Two separate models are defined for within- and cross-content evaluations. The former is to differentiate the perceived contrast of the images with the same content. The latter is to discriminate the differences in contrast among the images with different contents. Perception mechanisms are quite different for within- and cross-content evaluations. Local contrast plays an important role in within-content evaluation. In contrast, global contrast dominates the contrast perception for cross-content evaluation. Results of human visual experiments show that the proposed evaluation models outperform previous methods for both within- and cross-content evaluations.

关键词： Contrast evaluation Global contrast Local contrast within content Cross content Statistical significance

L_2-L_∞ learning of dynamic neural networks

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Chinese Physics B 2010年第10期19卷 1-6页

作者： choon Ki Ahn Department of Automotive Engineering Seoul National University of Technology 172 Gongneung 2-dong Nowon-gu Seoul 139-743 Korea

This paper proposes an y2-y∞ learning law as a new learning method for dynamic neural networks with external disturbance. Based on linear matrix inequality （LMI） formulation, the y2-y∞ learning law is presented to not only guarantee asymptotical stability of dynamic neural networks but also reduce the effect of external disturbance to an y2-y∞ induced norm constraint. It is shown that the design of the y2-y∞ learning law for such neural networks can be achieved by solving LMIs, which can be easily facilitated by using some standard numerical packages. A numerical example is presented to demonstrate the validity of the proposed learning law.

关键词： y2-y∞ learning law dynamic neural networks linear matrix inequality Lyapunovstability theory

Improvement in the Adhesion Between Electrode of a SOFC and Ag Paste as a Current Collector by Au Deposition

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Journal of Materials Science & Technology 2015年第3期31卷 257-263页

作者： Sang Koo Jeon Seung Hoon nahm Oh Heon Kwon Department of Safety Engineering Pukyong National University Center for Energy Materials Metrology Korea Research Institute or Standards and Science

This paper reports the use of Au films to improve the performance of the stacked solid oxide fuel cell(SOFC) based on the characterization of the interface and the adhesion between the electrodes of the SOFCs and the Ag paste. The specimens were manufactured to perform the experiment as follows. A Si O2 wafer with a 300 mm notch was attached to the electrodes of a SOFC by a Ag paste and Au film, which were deposited on the electrodes by sputtering for 1 min or 5 min deposition time and annealed at300 C for 1 h. The four-point bending test was performed, which resulted in the formation of an extended crack at the tip on the wafer notch, and the crack propagation was observed using a stereo microscope equipped with a charge-coupled device(CCD). Consequently, the interfacial adhesion energy and the effect of the Au film between the each electrode and the Ag paste can be evaluated. On the cathode, the interfacial adhesion energy without Au film was 2.59 J/m2(upper value) and the adhesion energy increased to 11.59 J/m2(upper value) and 15.89 J/m2(lower value) with the Au film. On the anode,the interfacial adhesion energy without Au film was 1.74 J/m2(upper value), which increased to 11.07 J/m2(upper value) and 14.74 J/m2(lower value) with the Au film. In addition, the interface areas were analyzed by scanning electron microscopy(SEM) and energy dispersive spectroscopy(EDS) to estimate the interface delamination.

关键词： Solid oxide fuel cell Au film Interfacial adhesion

Chaos Synchronization of Nonlinear Bloch Equations Based on Input-to-State Stable Control

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Communications in Theoretical Physics 2010年第2期53卷 308-312页

作者： choon Ki Ahn Faculty of the Division of Electronics and Control Engineering Wonkwang University

In this paper, we propose a new input-to-state stable （ISS） synchronization method for chaotic behavior in nonlinear Bloch equations with external disturbance. Based on Lyapunov theory and linear matrix inequality （LMI） approach, for the first time, the ISS synchronization controller is presented to not only guarantee the asymptotic synchronization but also achieve the bounded synchronization error for any bounded disturbance. The proposed controller can be obtained by solving a convex optimization problem represented by the LMI. Simulation study is presented to demonstrate the effectiveness of the proposed synchronization scheme.

关键词： chaos synchronization input-to-state stable (ISS) control nonlinear Bloch equations linear matrix inequality (LMI) Lyapunov theory