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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

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

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

Increased expression of the nitric oxide synthase gene and protein in corpus cavernosum by repeated dosing of udenafil in a rat model of chemical diabetogenesis

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Asian Journal of Andrology 2009年第4期11卷 435-442页

作者： GJ ahn HK Chung CH Lee KK Kang BO ahn Research Laboratory Dong-A Pharmaceutical Company Kiheung Yongin Kyunggi 446-905 Korea

Erectile dysfunction （ED） is a major complication of diabetes mellitus （DM）. This study investigates the relationship between ED and the downregulation of constitutive nitric oxide synthase （cNOS） in the corpus cavernosum （CC） of diabetic rats. It also examines the effects of udenafil, a phosphodiesterase type 5 （PDE5） inhibitor, on ED and cNOS expression levels. After 16 weeks of daily oral treatment with udenafil in diabetic rats, the intracavernous pressure/mean arterial pressure （ICP/MAP） ratio was recorded to measure erectile function, and cNOS expression was measured using reverse transcriptase （RT）-PCR and immunoblots. Although the ICP/ MAP ratio and the expression levels of endothelial NOS （eNOS） and neuronal NOS （nNOS） in the CC were markedly decreased in diabetic rats, long-term udenafil treatment improved the erectile function and increased cNOS expression compared with diabetic controls. These findings suggest that ED in DM is closely related to decreased cNOS expression in the CC and that udenafil has the ability to compensate for this pathological change by modulating cNOS expression. Udenafil also has an inhibitory role in cyclic guanosine monophosphate （cGMP） degradation.

关键词： cNOS diabetes mellitus erectile dysfunction udenafil

Intelligent SLAM Algorithm Fusing Low-Cost Sensors at Risk of Building Collapses

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Computers, Materials & Continua 2023年第1期74卷 1657-1671页

作者： Dahyeon Kim Junho ahn Computer Information Technology Korea National University of TransportationChungju27469Korea

When firefighters search inside a building that is at risk of collapse due to abandonment or disasters such as fire,they use old architectural drawings or a simple monitoring method involving a video device attached to a ***,using these methods,the disaster situation inside a building at risk of collapse is difficult to detect and ***,we investigate the generation of digital maps for a disaster site to accurately analyze internal *** this study,a robot combined with a low-cost camera and twodimensional light detection and ranging(2D-lidar)traverses across a floor to estimate the location of obstacles while drawing an internal map of the *** propose an algorithm that detects the floor and then determines the possibility of entry,tracks collapses,and detects obstacles by analyzing patterns on the *** robot’s location is estimated,and a digital map is created based on Hector simultaneous localization and mapping(SLAM).Subsequently,the positions of obstacles are estimated based on the range values detected by 2D-lidar,and the position of the obstacles are identified on the map using the map update method in semantic *** equipment are implemented using low-specification devices,and the experiments are conducted using a low-cost robot that affords near-real-time *** experiments are conducted in various actual internal environments of *** terms of obstacle detection performance,almost all obstacles are detected,and their positions identified on the map with a high accuracy of 89%.

关键词： Intelligence SLAM vision 2D-lidar low-cost algorithm

Generalized passivity-based chaos synchronization

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Applied Mathematics and Mechanics(English Edition) 2010年第8期31卷 1009-1018页

作者： C.K.ahn Faculty of the Division of Electronics and Control Engineering Wonkwang University

In this paper, a new passivity-based synchronization method for a general class of chaotic systems is proposed. Based on the Lyapunov theory and the linear matrix inequality （LMI） approach, the passivity-based controller is presented to make the synchronization error system not only passive but also asymptotically stable. The proposed controller can be obtained by solving a convex optimization problem represented by the LMI. Simulation studies for the Genesio-Tesi chaotic system and the Qi chaotic system are presented to demonstrate the effectiveness of the proposed scheme.

关键词： passivity-based synchronization linear matrix inequality (LMI) chaotic systems Lyapunov theory

TOWARDS ESTABLISHING DIFFUSION BARRIERS FOR INNOVATIVE GREEN BUILDING PRODUCTS: A SURVEy OF SIPS BUILDERS

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Journal of Green Building 2012年第2期7卷 153-176页

作者： A.P.McCoy y.H.ahn A.R.Pearce Department of Building Construction Virginia TechBlacksburgVAUSA Department of Construction Management East Carolina UniversityGreenvilleNC USA

The aim of this paper is to propose and demonstrate an approach for exploring diffusion barriers specific to innovative green building *** green building products aim at reducing environmental impacts during a product’s entire life-cycle,helping mitigate the substantial environmental degradation caused by current construction *** studies establish attributes that differentiate such products within the construction market,a key facet to increasing *** key stakeholders,product attributes can affect the rate of adoption and the nature of *** that end,this work:1)Collects attributes common to all innovative building products through literature review in residential construction innovation,diffusion and adoption attributes,and green products;2)utilizes a survey of certified green home builders as a sample population and Structural Insulated Panels as a“control”product to identify which product attributes specifically influence the use of green building products;and 3)Evaluates the relative influence of attributes on product adoption during initial trial of the product and for continued use of the *** attributes of green building products that influence adoption could enhance product development through reducing barriers to diffusion and commercialization across the residential construction *** work focuses on one specific product,Structural Insulated Panel systems(SIPS),from the standpoint of a population of green *** such,it attempts to serve as a scalable basis for future research.

关键词： innovation green innovation housing product innovation SIPS