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Mechanically resilient,alumina-reinforced carbon nanotube arrays for in-plane shock absorption in micromechanical devices

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Microsystems & Nanoengineering 2023年第3期9卷 73-81页

作者： Eunhwan Jo Hojoon lee Jae-ik lee Jongbaeg Kim School of Mechanical Engineering Yonsei University50 Yonsei-roSeodaemun-guSeoul 03722Republic of Korea Department of Neurosurgery Massachusetts General HospitalHarvard Medical School25 Shattuck StBostonMA 02115USA

Microelectromechanical systems(MEMS)are of considerable interest due to their compact size and low power consumption when used in modern *** devices intrinsically incorporate three-dimensional(3D)microstructures for their intended operations;however,these microstructures are easily broken by mechanical shocks accompanying high-magnitude transient acceleration,inducing device *** various structural designs and materials have been proposed to overcome this limit,developing a shock absorber for easy integration into existing MEMS structures that effectively dissipates impact energy remains ***,a vertically aligned 3D nanocomposite based on ceramic-reinforced carbon nanotube(CNT)arrays is presented for in-plane shock-absorbing and energy dissipation around MEMS *** geometrically aligned composite consists of regionally-selective integrated CNT arrays and a subsequent atomically thick alumina layer coating,which serve as structural and reinforcing materials,*** nanocomposite is integrated with the microstructure through a batch-fabrication process and remarkably improves the in-plane shock reliability of a designed movable structure over a wide acceleration range(0-12,000g).In addition,the enhanced shock reliability through the nanocomposite was experimentally verified through comparison with various control devices.

关键词： shock plane arrays

Experimental and Computational Studies on Coanda Nozzle Flow for the Air Knife Application

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Journal of Thermal Science 2007年第2期16卷 164-169页

作者： Soon-Bum KWON Dong-Won lee Young-doo KWON School of Mechanical Engineering Kyungpook National University1370Sankyuk-dongDaegu 702-701Korea

To control the film thickness of zinc in the process of continuous hot-dip galvanizing, it is known from the early days that the gas wiping through an air knife is the most effective one. The gas wiping using in galvanizing process brings about a problem of splashing from the strip edge for a certain high speed of coating. So, in the present study, the effects of the deflection angle of Coanda nozzle on jet structure and the distribution of impinging pres- sure at the plate surface are investigated numerically and experimentally. In numerical analysis, the governing equations consisted of three-dimensional time dependent full Navier-Stokes equations, standard k-ε turbulence model to solve turbulent stTess and so on are employed. In experiment, 16 channel pressure scanning valve and 3-axis auto traversing unit are used to measure the impinging pressure at the strip surface. As a result, it is found that the smaller the deflection angle for the same nozzle slit of air knife is, the larger the impinging pressure is. To reduce the size of separation bubble and to enhance the cutting ability, it is recommendable to use an air knife with the Coanda nozzle.

关键词： Air knife Coanda effect edge splashing gas wiping hot-dip galvanizing impinging jet

Dynamic genetic features of eukaryotic plankton diversity in the Nakdong River estuary of Korea

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Chinese Journal of Oceanology and Limnology 2017年第4期35卷 844-857页

作者： lee Jee Eun CHUNG ik Kyo lee Sang-Rae Division of Earth Environmental System Oceanography Major Pusan National University Marine Research Institute Pusan National University

Estuaries are environments where freshwater and seawater mix and they display various salinity *** construction of river barrages and dams has rapidly changed these environments and has had a wide range of impacts on plankton *** understand the dynamics of such communities,researchers need accurate and rapid techniques for detecting plankton *** evaluated the diversity of eukaryotic plankton over a salinity gradient by applying a metagenomics tool at the Nakdong River estuary in *** samples were collected on three dates during summer and autumn of 2011 at the Eulsukdo Bridge at the mouth of that *** the 18 S rDNA allowed us to analyze 456 clones and 122 *** sequences revealed various taxonomic groups and cryptic genetic variations at the intra-and inter-specific *** analyzing the same station at each sampling date,we observed that the phylotypes presented a salinity-related pattern of diversity in *** variety of species within freshwater samples reflected the rapid environmental changes caused by freshwater *** phylotypes accounted for the highest proportion of overall diversity in the seawater *** diatoms and dinoflagellates were observed in the freshwater,brackish and seawater *** biological data for species composition demonstrate the transitional state between freshwater and ***,this metagenomics information can serve as a biological indicator for tracking changes in aquatic environments.

关键词： 18S rDNA clone library metagenome estuary salinity gradient

Magnesium citrate with a single dose of sodium phosphate for colonoscopy bowel preparation

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World Journal of Gastroenterology 2011年第2期17卷 242-248页

作者： Yong Sung Choi Jung Pil Suh Jong Kyu Kim In Taek lee Eui Gon Youk doo Seok lee Do Sun Kim doo Han lee Department of Gastroenterology Daehang Hospital Department of Surgery Daehang Hospital

AIM:To evaluate the efficacy and acceptability of magnesium citrate and a single dose of oral sodium phosphate(45 mL) solution for morning colonoscopy bowel preparation. METHODS:A total of 159 patients were randomly assigned to receive two split doses of 90 mg of sodium phosphate(GroupⅠ,n=79) or magnesium citrate(250 mL,the day before the procedure) followed by 45 mL of sodium phosphate(the day of procedure,GroupⅡ,n= 80) .The quality of bowel cleansing and the acceptability of each regimen were compared,including the satisfaction,taste,willing to repeat and adverse effects of each regimen. RESULTS:The quality of bowel cleansing of GroupⅡ was as good as that of GroupⅠ(An Aronchick scale score of good or excellent:70.9%vs 81.0%,respectively,P=0.34;the Ottawa system score:4.4±2.6 vs 3.8 ±3.0,respectively,P=0.76) .There was no statisticallysignificant difference between both groups with regard to acceptability,including the satisfaction,taste and willingness to repeat the regimen.A significantly greater number of older patients(over 65 years old) in Group Ⅱgraded the overall satisfaction as satisfactory(48.1% vs 78.1%,respectively;GroupⅠvs GroupⅡ,P=0.01) . There were no significant adverse reactions. CONCLUSION:Magnesium citrate and a single dose of sodium phosphate was as effective and tolerable as the conventional sodium phosphate regimen and is a satisfactory option.

关键词： Colonoscopy Bowel preparation Efficacy Acceptability Magnesium citrate Sodium phosphate

Alteration of the p53 gene during tree shrews' hepatocarcinogenesis

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Hepatobiliary & Pancreatic Diseases International 2003年第4期2卷 612-616页

作者： Young ik lee Bioscience Research Division Korea Research Institute of Bioscience and Biotechnology P. O. Box 115 Yusong Taejon 305-600 South Korea

OBJECTIVE: To detect the expression and variation of the p53 gene in hepatocarcinogenesis of tree shrews induced by hepatitis B virus (HBV) and aflatoxin B_1(AFB_1). METHODS: Tree shrews were divided into four groups: group A, infected with HBV and fed with AFB_1; group B, only infected with HBV; group C, fed with AFB_1 alone; and group D normal control. The tree shrews underwent liver biopsy every. 15 weeks. Liver and tumor tissues were detected by immunohistochemistry and molecular biotechnologies. RESULTS: The incidence of hepatocellular carcinoma (HCC) was higher in group A (66.7%) than in groups B (0) and C (30%). HCC occurrence was earlier in group A than in group C (120.0±16.6 wk vs 153.3±5.8 wk, t=3.336, P<0.01). Mutated p53 protein was not found in all groups before 75 weeks of experiment. At the 105th week, the expression rates of mutated p53 protein were 78.6%, 60.0% and 71.4% in groups A, B and C respectively, which were significantly higher than that in group D (10%) (X^2≥5.03, P<0.05). An abnormal band of the p53 gene was detected in groups A and C. The mutational points of the p53 gene in liver cancer of tree shrews were at codon 275, 78 and 13. Nucleotide sequence and amino acids sequence of tree shrew's wild-type p53 were 91.7% and 93.4% in homology, compared with those of human p53, respectively. CONCLUSIONS: Remarkable synergistic effect on HCC exists between HBV and AFB_1. Mutated p53 protein expressed before occurrence of HCC promotes the development of HCC. HBV and AFB_1 may synergistically induce p53 gene mutation.

关键词： hepatocellular carcinom gene p53 hepatitis B virus aflatoxin B_1 tree shrew

Generation of Discrete Bicubic G^1 B-Spline Ship Hullform Surfaces from a Given Curve Notwork Using Virtual Iso-Parametric Curves

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Journal of Computer Science & Technology 2006年第2期21卷 265-271页

作者： Joong-Hyun Rhim doo-Yeoun Cho Kyu-Yeul lee Tao-Wan Kim EzGragh Co.Ltd.Seoul 135-080 Koren Department of Naval Architecture & Ocean Engincering Seoul National UniversitySeoul 151-744Korea Department of Naval Architecture & Ocean Engincering and Research Institute of Macine Systems Engineering Seoul National University Seoul 151-744Korea

We propose a method that automatically generates discrete bicubic G^1 continuous B-spline surfaces that interpolate the curve network of a ship ***,the curves in the network are classified into two types;boundary curves and ＂reference curves＂,The boundary curves correspond to a set of rectangular（or triangular）topological type that can be representes with tensot-product （or degenerate）B-spline surface ***,in the interior of the patches,surface fitting points and cross boundary derivatives are estimated from the reference curves by constructing ＂virtual＂isoparametric ***,a discrete G^1 continuous B-spline surface is gencrated by a surface fitting *** smooth ship hullform surfaces generated from curve networks corresponding to actual ship hullforms demonstrate the quality of the method.

关键词： curve netowork interpotation discrete G^1 continuous B-spline surface,iso-parametric curve,ship hullform

Systematic study of(MoTa)_(x)NbTiZr medium-and high-entropy alloys for biomedical implants-In vivo biocompatibility examination

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Journal of Materials Science & Technology 2021年第19期78卷 183-191页

作者： Muhammad Akmal Ahtesham Hussain Muhammad Afzal Young ik lee Ho Jin Ryu Department of Materials Science and Engineering KAISTYuseongDaejeon 34141South Korea lee's Biotech Co. Ltd.#415C-Dong13 Techno-4-roYuseong-guDaejeon34013South Korea Department of Mechanical Engineering KAISTYuseongDaejeon34141South Korea Department of Nuclear and Quantum Engineering KAISTYuseongDaejeon 34141South Korea

In this study,the application of medium-and high-entropy(Mo Ta)_(x)Nb Ti Zr alloys in biomedical implants was systematically *** alloy with the best combination of mechanical properties was selected and characterized for in vitro and in vivo response for the first time to examine its biomedical properties.A logarithmic increase in the hardness and the yield strength was observed as a function of the Mo and Ta *** with up to 0.4 mol fraction of Mo and Ta showed a plastic strain of more than 30%under *** nanoindentation results showed that the addition of Mo and Ta increased the elastic modulus of the system *** was surmised that the addition of Ta and Mo above a critical concentration(mole fraction=0.4)was unfavorable from a biomedical perspective as it increased the brittleness and elastic modulus and decreased the ductility of the ***,the(Mo Ta)_(0.2)Nb Ti Zr alloy is a potential structural material for biomedical implants because of its excellent strength and *** developed alloy was investigated for its corrosion properties and compared with commercial biomedical ***,the biocompatibility of the alloy was examined using an in vivo *** alloy was implanted in the skeletal muscles of mice for four weeks and the histology of the surrounding tissue was *** alloy exhibited strong passive behavior in a phosphate buffer solution and non-toxic soft tissue response.

关键词： High-entropy alloys Medium-entropy alloys Biomedical applications In vivo Biocompatibility

Analysis of expanded criteria to select candidates for active surveillance of low-risk prostate cancer

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Asian Journal of Andrology 2015年第2期17卷 248-252,I0008,I0009页

作者： Jung Ki Jo Hart Sol lee Young ik lee Sang Eun lee Sung Kyu Hong Department of Urology Seoul National University Bundang Hospital Seongnam Korea.

We aimed to analyze the value of each criterion for clinically insignificant prostate cancer （PCa） in the selection of men for active surveillance （AS） of low-risk PCa. We identified 532 men who were treated with radical prostatectomy from 2006 to 2013 who met 4 or all 5 of the criteria for clinically insignificant PCa （clinical stage 〈 T1, prostate specific antigen [PSA] density 0.15, biopsy Gleason score 〈 6, number of positive biopsy cores 〈 2, and no core with 〉 50% involvement） and analyzed their pathologic and biochemical outcomes. Patients who met all 5 criteria for clinically insignificant PCa were designated as group A （n -- 172）, and those who met 4 of 5 criteria were designated as group B （n = 360）. The association of each criterion with adverse pathologic features was assessed via logistic regression analyses. Comparison of group A and B and also logistic regression analyses showed that PSA density 0.15 ng ml-1 and high （〉7） biopsy Gleason score were associated with adverse pathologic features. Higher （〉 Tlc） clinical stage was not associated with any adverse pathologic features. Although 〈 3 positive cores were not associated with any adverse pathology, 〉4 positive cores were associated with higher risk of extracapsular extension. Among potential candidates for AS, PSA density ~ 0.15 ng ml-~ and biopsy Gleason score ~ 6 pose significantly higher risks of harboring more aggressive disease. The eligibility criteria for AS may be expanded to include men with clinical stage T2 tumor and 3 positive cores.

关键词： prediction prostate prostatectomy prostatic neoplasms risk

Fabrication of 3D Printed PCL/PEG Polyblend Scaffold Using Rapid Prototyping System for Bone Tissue Engineering Application

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Journal of Bionic Engineering 2018年第3期15卷 435-442页

作者： Su A Park Sang Jin lee Ji Min Seok Jun Hee lee Wan doo Kim Il Keun Kwon Department of Nature-Inspired Nanoconvergence Systems Korea Institute of Machinery and Materials 156 Gajeongbuk-ro Yuseong-gu Daejeon 34103 Republic of Korea Department of Dental Materials School of Dentistry Kyung Hee University 26 Kyungheedae-ro Dongdaemun-gu Seou102447 Republic of Korea

Three-dimensional （3D） printing is a novel process used to manufacture bone tissue engineered scaffolds. This process allows for easy control of the architecture at the micro structure. However, the scaffold properties are typically limited in terms of cellular activity at the scaffold surface due to the printed materials properties. In this study, we developed a polycaprolactone （PCL） blended with polyethylene glycol （PEG） 3D printed scaffold using a rapid prototyping system. The manufactured scaffolds were then washed out to form small pores on the surface in order to improve the scaffolds hydrophilicity. We analyzed the resultant material by using Scanning Electron Microscopy （SEM）, water absorption, water contact angle, in vitro WST-1, and the Bradford assay. Additionally, cells incubated on the fabricated scaffolds were visualized by Confocal Laser Scanning Microscopy （CLSM）. The developed scaffolds exhibited small pores on the strand surface which served to increase hydrophilicity as well as improve cellular proliferation and increase total protein content. Our findings suggest that the presence of small pores on the scaffolds can be used as an effective tool for improving implant cellular interaction. This research indicates that these modified scaffolds can be considered useful for bone tissue engineering applications to improve human health.

关键词： polycaprolactone polyethylene glycol polyblend 3D printing porosity bone tissue engineering