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Friction and wear of textured surfaces produced by 3D printing

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Science China(Technological Sciences) 2017年第9期60卷 1400-1406页

作者： HONG Yi ZHANG Peng LEE kwang-hee LEE Chul-hee Department of mechanical Engineering Inha University Incheon 402-751 Korea

Surface texture patterns have great potential for improving tribological performance in terms of reducing friction and wear. The most com.on methods for surface texatring are laser and injection molding. The 3D printing method is also used to build parts, patterns, and molds that feature fine details for a wide range of applications because texture manufacturing by 3D printing is faster, more flexible, and less expensive than traditional techniques. To date, there has been no research on textured surfaces produced by 3D printing. Therefore, a new fabrication method using 3D printing to improve friction and wear properties is a topic worth exploring. In this study, a reciprocating friction tester was used to evaluate the friction and wear properties of different surface textures produced by 3D printing. The surface of specimens was examined by electron microscope and scanning electron microscope before and after the test. The results show that surface texturing can be applied to 3D printed parts to improve their friction and wear performance.

关键词： three-dimensional (3D) printing texture friction wear

Research on Cavitation Characteristics and Influencing Factors of Herringbone Gear Pump

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Computer modeling in Engineering & Sciences 2024年第6期139卷 2917-2946页

作者： Jinlong Yang kwang-hee Lee Chul-hee Lee Department of mechanical Engineering of Inha University Incheon22212South Korea

Cavitation is a com.on issue in pumps,causing a decrease in pump head,a fall in volumetric efficiency,and an intensification of outlet flow *** is one of the main hazards that affect the regular operation of the *** on pump cavitation mainly focuses on mixed flow pumps,jet pumps,external spur gear pumps,***,there are few cavitation studies on external herringbone gear *** addition,pumps with different working principles significantly differ in the flow and complexity of the internal flow ***,it is urgent to study the cavitation characteristics of external herringbone gear *** with experimentalmethods,visual research and cavitation area identification are achieved through computation fluid dynamic(CFD),and changing the boundary conditions and shape of the gear rotor is *** simulation yields a head error of only 0.003%under different grid numbers,and the deviation between experimental and simulation results is less than 5%.The study revealed that cavitation causes flow pulsation at the outlet,and the cavitation serious area is mainly distributed in the meshing gap and meshing *** can be inhibited by reducing the speed,increasing the inlet pressure,and changing the helix angle can be *** example,when the inlet pressure is 5 bar,the maximumgas volume fraction in themeshing area is less than 50%.These results provide a reference for optimizing the design and finding the optimal design parameters to reduce or eliminate cavitation.

关键词： Herringbone gear pump cavitation rotating speed inlet pressure helix angle Twinmesh

Effect of stick-slip on magneto-rheological elastomer with a magnetic field

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Friction 2017年第4期5卷 383-391页

作者： Chenglong LIAN kwang-hee LEE Jun-wook AN Chul-hee LEE Department of mechanical Engineering Inha University100 InharoNam-guIncheon 22212Republic of Korea Department of Construction machinery Engineering Inha University100 InharoNam-guIncheon 22212Republic of Korea

This study investigated the stick-slip characteristics of a magneto-rheological elastomer (mRE) against an aluminum ***,the mRE was manufactured,and a stick-slip tester was employed to evaluate the stick-slip performance of the mRE under different velocities and load conditions with and without a magnetic *** fast Fourier transform (FFT) of the friction force of the stick-slip and the roughness of the aluminum plate surface were calculated to confirm the stick-slip *** the tests,the wear surfaces were observed to evaluate the wear properties of the mRE regarding the *** showed that the stick-slip was smaller at lower *** higher velocity,the reduction of the stick-slip under a magnetic field was more clearly ***,the wear reduced with reduced stick-slip under a magnetic field.

关键词： stick-slip friction wear magneto-rheological elastomer

Xanthogranulomatous cholecystitis managed by laparotomy may go through troublesome clinical course: Reflection of severe inflammation

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Hepatobiliary & Pancreatic Diseases International 2023年第2期22卷 210-212页

作者： hee Ju Kim kwang Yeol Paik Department of Surgery Yeoiudo St.Mary’s HospitalCollege of MedicineThe Catholic University of Korea College of MedicineSeoul 07345Korea

To the Editor: Xanthogranulomatous cholecystitis(XGC) is an uncom.on inflammatory disease of the gallbladder, and its incidence is reported to be 1.3%-5.2% [1]. XGC is diagnosed by histopathological examination, characterized by severe inflammatory destruction followed by a granulomatous reaction, marked proliferative fibrosis, and infiltration of inflammatory cells [2].

关键词： granuloma cholecystitis inflammation

Selecting suitable sites for mountain ginseng(Panax ginseng)cultivation by using geographically weighted logistic regression

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Journal of mountain Science 2017年第3期14卷 492-500页

作者： HAN hee JANG kwang-min CHUNG Joo-sang Department of Forest Engineering Resources and ManagementCollege of ForestryOregon State UniversityCorvallisOR 97331USA Department of Forest Sciences College of Agriculture and Life SciencesSeoul National UniversitySeoul 08826Republic of Korea Research Institute for Agriculture and Life Sciences Seoul National UniversitySeoul 08826Republic of Korea

With the well-being trends to pursue a healthy life, mountain ginseng(Panax ginseng) is rising as one of the most profitable forest products in South Korea. This study was aimed at evaluating a new methodology for identifying suitable sites for mountain ginseng cultivation in the country. Forest vegetation data were collected from 46 sites and the spatial distribution of all sites was analyzed using GIS data for topographic position, landform, solar radiation, and topographic wetness. The physical and chemical properties of the soil samples, including moisture content, p H, organic matter, total nitrogen, exchangeable cations, available phosphorous, and soil texture, were analyzed. The cultivation suitability at each site was assessed based on the environmental conditions using logistic regression(LR) and geographically weighted logistic regression(GWLR) and the results of both methods were compared. The results show that the areas with northern aspect and higher levels of solar radiation, moisture content, total nitrogen, and sand ratio are more likely to be identified as suitable sites for ginseng cultivation. In contrast to the LR, the spatial modeling with the GWLR results in an increase in the model fitness and indicates that a significant portion of spatialautocorrelation in the data decreases. A higher value of the area under the receiver operating characteristic(ROC) curve presents a better prediction accuracy of site suitability by the GWLR. The geographically weighted coefficient estimates of the model are nonstationary, and reveal that different site suitability is associated with the geographical location of the forest stands. The GWLR increases the accuracy of selecting suitable sites by considering the geographical variations in the characteristics of the cultivation sites.

关键词： Panax ginseng Site suitability Logistic regression Geographically weighted logistic regression Geographic Information System South Korea

Two-stage dynamic recrystallization and texture evolution in Al-7mg alloy during hot torsion

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International Journal of minerals,metallurgy and materials 2024年第8期31卷 1900-1911页

作者： kwang Tae Son Chang hee Cho myoung Gyun Kim Ji Woon Lee School of mechanical Industrialand Manufacturing EngineeringOregon State UniversityCorvallis OR 97331USA Department of materials Science Engineering Northwestern UniversityEvanston IL 60208USA Research Institute of Industrial Science and Technology(RIST) Pohang 37673Rep.of Korea Division of Advanced materials Engineering Kongju National UniversityCheonan 31080Rep.of Korea Center for Advanced materials and Parts of Powders Kongju National UniversityCheonan 31080Rep.of Korea

Hot torsion tests were performed on the Al-7mg alloy at the temperature ranging from 300 to 500℃ and strain rates between 0.05 and 5 s^(-1) to explore the progressive dynamic recrystallization(DRX)and texture *** DRX behavior of the alloy manifested two distinct stages:Stage 1 at strain of≤2 and Stage 2 at strains of≥*** Stage 1,there was a slight increase in the DRXed grain fraction(X_(DRX))with predominance of discontinuous DRX(DDRX),followed by a modest change in X_(DRX) until the transition to Stage *** 2 was marked by an accelerated rate of DRX,culminating in a substantial final X_(DRX) of~*** backscattered diffraction(EBSD)analysis on a sample in Stage 2 revealed that continuous DRX(CDRX)predominantly occurred within the(121)[001]grains,whereas the(111)[110]grains underwent a geometric DRX(GDRX)evolution without a noticeable sub-grain ***,a modified Avrami’s DRX kinetics model was utilized to predict the microstructural refinement in the Al-7mg alloy during the DRX *** this kinetics model did not accurately capture the DDRX behavior in Stage 1,it effectively simulated the DRX rate in Stage *** texture index was employed to assess the evolution of the texture isotropy during hot-torsion test,demonstrating significant improvement(>75%)in texture randomness before the commencement of Stage *** initial texture evolution is attributed to the rotation of parent grains and the substructure evolution,rather than to an increase in X_(DRX).

关键词： Al-7mg alloys hot deformation hot torsion tests dynamic recrystazlliation microstructure texture

Detection of stacking orientation error of CFRP composite laminates using ultrasound waves

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中国有色金属学会会刊：英文版 2009年第B09期19卷 124-127页

作者： Sun-Kyu KIm David HSU Young-Hwan SEO kwang-hee Im Division of mechanical System Engineering Chonbuk National University Center for Nondestructive Evaluation Iowa State University Department of Physical Education Chosun University Department of Automotive Engineering Woosuk University

A jig was developed for generating a shear wave. A pyramid with an isosceles triangle with two 45o was made of aluminum to generate shear waves using two longitudinal transducers based on ultrasonic-polarized mechanism. Also, the signal splitter was connected to the pulser jack on the pulser/receiver and to the longitudinal transducers. Therefore, an experimental way was performed in order to make shear wave on the bottom of aluminum alloyed pyramid. Also, a jig was manufactured and developed for generating a shear wave based on the computer numerical simulation. It is found that the experimentally shear wave variation of newly-designed jig is consistent with computer numerical simulation results and shear wave ultrasonic application can be very useful to detect the defects in CFRP composites.

关键词：碳纤维复合材料误差检测超声波复合材料层板计算机数值模拟堆垛脉冲发生器信号分配器

Observational Study of Surface Wind along a Sloping Surface over mountainous Terrain during Winter

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Advances in Atmospheric Sciences 2018年第3期35卷 276-284页

作者： Young-hee LEE Gyuwon LEE Sangwon JOO kwang-Deuk AHN Department of Astronomy and Atmospheric Sciences Kyungpook National University Numerical Data Application Division Numerical Modeling Center

The 2018 Winter Olympic and Paralympic Games will be held in Pyeongchang, Korea, during February and march. We examined the near surface winds and wind gusts along the sloping surface at two outdoor venues in Pyeongchang during February and march using surface wind data. The outdoor venues are located in a complex, mountainous terrain, and hence the near-surface winds form intricate patterns due to the interplay between large-scale and locally forced winds. During February and march, the dominant wind at the ridge level is westerly; however, a significant wind direction change is ob- served along the sloping surface at the venues. The winds on the sloping surface are also influenced by thermal forcing, showing increased upslope flow during daytime. When neutral air flows over the hill, the windward and leeward flows show a significantly different behavior. A higher correlation of the wind speed between upper- and lower-level stations is shown in the windward region compared with the leeward region. The strong synoptic wind, small width of the ridge, and steep leeward ridge slope angle provide favorable conditions for flow separation at the leeward toot of the ridge. The gust factor increases with decreasing surface elevation and is larger during daytime than nighttime. A significantly large gust factor is also observed in the leeward region.

关键词： flow separation gust factor leeward region sloping surface

Immunostimulating activities and anti-cancer efficacy of rhamnogalacturonan-I rich polysaccharide purified from Panax ginseng leaf

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FOOD BIOSCIENCE 2023年第3期53卷 1218-1227页

作者： Son, Seung-U Lee, hee Won Shin, kwang-Soon Kyonggi Univ Dept Food Sci & Biotechnol Suwon 16227 South Korea Korea Univ Dept Integrated Biomed & Life Sci Transdisciplinary Major Learning Hlth Syst Seoul 02841 South Korea

This study aimed to evaluate the anti-cancer effects as well as stimulation of various immune related factors such as complementary system, macrophages, and NK cells of polysaccharides isolated from Panax ginseng (P. ginseng) leaf. The polysaccharide fractions (PGEP, PGEP-I, -II, and -III) isolated from P. ginseng were contained rhamnose (Rha), arabinose (Ara), galactose (Gal), galacturonic acid (GalA), and glucuronic acid (GlcA), all of which are typical sugar com.onents of rhamnogalacturonan (RG)-I. Only PGEP-I reacted with the beta-glucosyl Yariv reagent (37.29%), indicating the presence of type-II arabinogalactan. Additionally, methylation analysis indicated the PGEP-I mainly comprised 19 different sugar linkages including 4-linked GalpA, 2,4-linked Rhap, 3,6-linked Galp, 5-linked Araf, terminal GlcpA, and terminal Arap which are characteristics of RG-I. meanwhile, PGEP-I enhanced the production of cytokines such as interleukin (IL)-6, IL-12, and tumor necrosis factor-alpha and augmented the complement system. The intravenous administration of PGEP-I activated the natural killer (NK) cells in a dosedependent manner against YAC-1. Prophylactic intravenous administration of PGEP-I significantly suppressed Colon26-m3.1 carcinoma inoculation-induced lung cancer (48.7%). moreover, the anti-cancer effects of PGEP-I were significant even though NK cell functions were blocked by anti-asialo Gm1. The findings suggest that PGEPI, an RG-I polysaccharide, not only activates the complement system, macrophages and NK cells, but also has strong anticancer effects that inhibit lung cancer.

关键词： Immune system Panax ginseng Rhamnogalacturonan-I