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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

Item Response Theory Based Ensemble in Machine Learning

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International Journal of Automation and computing 2020年第5期17卷 621-636页

作者： Ziheng Chen Hongshik ahn Department of Applied Mathematics and Statistics Stony Brook UniversityNew York 11794−3600USA

In this article,we propose a novel probabilistic framework to improve the accuracy of a weighted majority voting *** order to assign higher weights to the classifiers which can correctly classify hard-to-classify instances,we introduce the item response theory(IRT)framework to evaluate the samples′difficulty and classifiers′ability *** assigned the weights to classifiers based on their *** models are created with different assumptions suitable for different *** making an inference,we keep a balance between the accuracy and *** our experiment,all the base models are constructed by single trees via *** explain the models,we illustrate how the IRT ensemble model constructs the classifying *** also compare their performance with other widely used methods and show that our model performs well on 19 datasets.

关键词： Classification ensemble learning item response theory machine learning expectation maximization(EM)algorithm

Reconstruction of Rabbit Corneal Layer Composed of Corneal Fibroblasts and Corneal Epithelium on the Lyophilized Amniotic Membrane

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Chemical Research in Chinese Universities 2006年第2期22卷 150-156页

作者： ahn Jae-il JANG In-keun YOON Mun-young SEO Young-kwon YOON Hee-hun KIN Jae-chan SONG Kye-yong YANG Eun-kyung PARK Jung-keug Department of Chemical and Biochemical Engineering Dongguk University Seoul Korea Department of Ophthalmology Chung-Ang University Hospital Seoul Korea Department of Pathology College of Medicine Chung-Ang University Seoul Korea R & D Center Bioland Ltd. Chun-An Korea

Many researchers have employed the cryopreserved amniotic membrane（CAM） and corneal epithelial cells in the treatment of a severely damaged burned cornea, with corneal epithelial cells cultured on an amniotic membrane （AM）. The lyophilized amniotic membrane（LAM） has a higher graft take and a longer shelf life; it is easier to store and safer because of gamma irradiation. Two Teflon rings（ ahn＇s supporter） were made for culturing the cells on the LAM, and were then used to support the LAM. To reconstruct a corneal layer composed of corneal fibroblasts and epithelium, the corneal fibroblasts were first cultivated on the stromal side of LAM for five days, foUowed by epithelial cells culture on the epithelial side, by using the air-liquid interface culture. The reconstructed corneal layer composed of corneal fibroblasts and corneal epithelial cells has a much healthier basal layer of corneal epithelium than the reconstructed corneal epithelium, which was got by using only corneal epithelial cells, and resembles the epithelium of normal corneas, without the horny layer. Thus, the reconstruction of the corneal layer by using a LAM is considered to be a good in vitro model, not only for its application in toxicological test kits, but also for transplantation in patients with a severely damaged cornea.

关键词： Lyophilized amniotic membrane Corneal layer Corneal fibroblast Corneal epithelium

Optimal intensity and duration of cupping for minimizing possible mechanical skin deformation

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Journal of Traditional Chinese Medicine 2021年第5期41卷 817-825页

作者： Bummo ahn Soobyeong Kim Robotics R&BD Group Korea Institute of Industrial TechnologyAnsan 15588Republic of Korea Department of Robotics and Virtual Engineering University of Science and TechnologyAnsan 15588Republic of Korea Wellness Technology R&D Center Natural Arin Medi CorporationSejongsi 30127Republic of Korea

OBJECTIVE:To identify the optimal intensity and duration of cupping that would minimize mechanical skin ***:We developed an optical measurement probe and system for measuring skin color values in real *** applied cupping at the following five Bladder Meridian *** investigate optimal intensity,negative pressure intensity was increased every 2 min up to 80 k *** investigate optimal time,10 measurement sites were selected and negative pressure intensities of 30,60,and 80 k Pa were applied for 5 min *** color information was analyzed by the following skin color values:red color saturation,erythema index,and melanin ***:The red color saturation and erythema index increased steadily up to 60 kpa negative pressure intensity,then decreased between 60 and 80 k ***,maximal values were observed at 60 k *** melanin index consistently increased with increasing negative pressure *** red color saturation and erythema index did not change after 20 s at 60 k Pa negative pressure *** negative pressure intensities below 80 k Pa,significant changes in melanin index were not observed after 20 *** 80 k Pa negative pressure intensity,the melanin index exhibited an increasing pattern for200 s,then showed no ***:To minimize skin deformation,60 k Pa and 20 s were the appropriate intensity and duration when using red color saturation and erythema index as diagnostic *** of the increasing pattern up to 80 k Pa negative pressure intensity,the optimal intensity of melanin index could not be *** applying 80 k Pa negative pressure intensity and using melanin index as the diagnostic index,we recommend a duration of 200 s.

关键词： ecchymosis petechiae pigmentation erythema melanins

Nanotribological properties and scratch resistance of MoS_(2)bilayerona SiO_(2)/Si substrate

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Friction 2023年第1期11卷 154-164页

作者： Si-hwan KIM Hyo-sok ahn Department of Transdisciplinary Studies Seoul National UniversitySeoul 08826Republic of Korea Department of Manufacturing Systems and Design Engineering Seoul National University of Science and TechnologySeoul 08826 Republic of Korea

The tribological properties and scratch resistance of MoS_(2)bilayer deposited on SiO_(2)/Si substrates prepared via chemical vapor deposition are *** force microscopy(FFM)is employed to investigate the friction and wear properties of the MoS_(2)bilayer at the nanoscale by applying a normal load ranging from 200 to 1,000 *** resistance is measured using the scratch mode in FFM based on a linearly increasing load from 100 to 1,000 *** probe force microscopy(KPFM)is performed to locally measure the surface potential in the tested surface to qualitatively measure the wear/removal of Mos,layers and identify critical loads associated with the individual failures of the top and bottom *** analysis of the contact potential difference values as well as that of KPFM,friction,and height images show that the wear/removal of the top and bottom layers in the MoS_(2)bilayer system occurred *** FFM and KPFM results show that the top MoS_(2)layer begins to degrade at the end of the low friction stage,followed by the bottom layer,thereby resulting in a transitional friction stage owing to the direct contact between the diamond tip and SiO_(2)*** the stable third stage,the transfer of lubricious MoS_(2)debris to the tip apex results in contact between the MoS_(2)-transferred tip and SiO_(2).Nanoscratch test results show two ranges of critical loads,which correspond to the sequential removal of the top and bottom layers.

关键词： chemical vapor deposition(CVD)-grown MoS,bilayer friction force microscopy(FFM) nanoscratch test Kelvin probe force microscopy(KPFM) scratch resistance

Effect of carrier gas species on the microstructure and compressive deformation behaviors of ultra-strong pure copper manufactured by cold spray additive manufacturing

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Journal of Materials Science & Technology 2022年第2期97卷 264-271页

作者： Young-Kyun Kim Kee-ahn Lee Department of Materials Science and Engineering Inha UniversityIncheon 22212Republic of Korea

Cold spray(CS)which has recently become a promising additive manufacturing(AM)technology,was used to fabricate ultra-strong pure *** addition,the effects of carrier gas species on the microstructural characteristics,mechanical properties and deformation mechanisms were systemically *** CSAM copper manufactured with N_(2) carrier gas reveals a heterogeneous bimodal microstructure consisting of ultra-fine grains at the particle interface and relatively coarse grains in inner *** He carrier gas,a homogeneous grain structure consisting of ultra-fine grains in most areas was *** tests showed that N_(2) and He carrier gasses enabled ultra-high yield strengths of 340 and415 MPa,*** values are comparable to severely plastic deformed copper,which has extremely low ductility and shape *** the other hand,both samples showed a strain-softening phenomenon that does not commonly occur at room *** deformation microstructures revealed that dynamic recovery(DRV)and dynamic recrystallization(DRX)phenomena were generated despite being deformed at room *** on the above findings,the overall deformation mechanisms according to the carrier gas species in the CSAM copper manufacturing process were ***,the work hardening and softening behaviors of CSAM Cu are predicted by using a constitutive equation.

关键词： Cold spray additive manufacturing Carrier gas Pure Cu Mechanical properties Deformation behavior

DC Motor Speed Regulator via Active Damping Injection and Angular Acceleration Estimation Techniques

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IEEE/CAA Journal of Automatica Sinica 2021年第3期8卷 641-647页

作者： Seok-Kyoon Kim Choon Ki ahn Department of Creative Convergence Engineering Hanbat National UniversityDaejeon 341-58Republic of Korea School of Electrical Engineering Korea UniversitySeoul 136-701Republic of Korea

This paper suggests a novel model-based nonlinear DC motor speed regulator without the use of a current *** current dynamics,machine parameters and mismatched load variations are *** proposed controller is designed to include an active damping term that regulates the motor speed in accordance with the first-order low-pass filter dynamics through the pole-zero ***,the angular acceleration and its reference are obtained from simple first-order estimators using only the speed *** effectiveness is experimentally verified using hardware comprising the QUBEServo2,myRIO-1900,and LabVIEW.

关键词： Active damping injection angular acceleration estimator DC motor(DCM) speed regulation

Stabilized sub-grain and nano carbides-driven 1.2 GPa grade ultra-strong CrMnFeCoNi high-entropy alloy additively manufactured by laser powder bed fusion

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Journal of Materials Science & Technology 2022年第22期117卷 8-22页

作者： Young-Kyun Kim Kee-ahn Lee Department of Materials Science and Engineering Inha UniversityIncheon 22212Republic of Korea Korea Institute of Materials Science(KIMS) Changwon 51508Republic of Korea

High-entropy alloys(HEAs)with interstitial atoms that are produced by additive manufacturing have gained intensive interest in the materials science community because of their suitability for constructing high-strength net-shape ***,a strategy to additionally enhance the strength of selective laser melted carbon-containing HEAs was *** as-built carbon-containing HEAs(C_(x)(Cr_(20)Mn_(20)Fe_(20)Co_(20)Ni_(20))_(100-x)(x=0.5 at.%,1.0 at.%,and 1.5 at.%))contain supersaturated carbon,and the extent of supersaturation increases as the carbon content *** subjected to aging treatment at 650°C for 1 h,the microstructure of the three alloys did not change at the grain ***,the microstructure at the sub-grain scale changed markedly,and these changes influenced the tensile properties and deformation *** particular,the tensile strength of aged 1.5C-HEA at 650°C was∼1.2 GPa at room temperature,which is higher than those reported for CrMnFeCoNi ***,the main deformation mechanism changed from deformation twinning to dislocation-mediated slip,resulting in much higher strain hardening capacity after the aging *** work led to the development of an alternative promising method that involves tailoring the microstructure,to enhance the mechanical properties of additively manufactured metallic materials that contain interstitial atoms.

关键词： Selective laser melting High-entropy alloy Carbon contents Aging Microstructure evolution Tensile property Deformation mechanism

Effects of upper lid blepharoplasty on visual quality in patients with lash ptosis and dermatochalasis

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International Journal of Ophthalmology(English edition) 2016年第9期9卷 1320-1324页

作者： Scoung Hyun An Sang Wook Jin Yoon Hyung kwon Won Yeol Ryu Woo Jin Jeong Hee Bae ahn Department of Ophthalmology Dong-A University College of Medicine Busan 602-715 Korea

AIM：To assess the effects of upper lid blepharoplasty on visual ***：Seventy-three eyelids of 39 patients were subjected to upper lid ***- and postoperative contrast sensitivity,visual acuity,vertical palpebral aperture and the degree of lash ptosis were ***：The mean log contrast sensitivities under photopic（P =0.017） and scotopic conditions（P =0.009）were improved after surgery,and these differences were *** degree of lash ptosis was also decreased after blepharoplasty（P〈0.001）.CONCLUSION：In our study,a significant increase in contrast sensitivity was found after *** results suggest that upper lid blepharoplasty can be helpful for improving visual quality.

关键词： blepharoplasty visual quality contrast sensitivity