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Effect of friction on the contact stress of a coated polymer gear

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Friction 2020年第6期8卷 1169-1177页

作者： Su-Min BAE kuk-Jin SEO Dae-Eun KIM Department of Mechanical Engineering Yonsei UniversitySeoul 03722Republic of Korea

Polymer gears are used extensively in various ***,durability issues have been emerging because of friction at gear tooth contact *** extend the lifetime of polymer gears,a low-frictional coating has been considered as a possible *** this study,a finite element simulation method was performed to investigate the contact stress between a pair of coated polymer *** simulation included various friction coefficients(COFs)for studying the effects of friction during the *** results revealed that the friction causes the contact stress to shift over the roll angle,which is attributed to the direction of the sliding friction based on a free-body *** also investigated the effects of coating and found that a thin coating has little effect on the bulk deformation behavior of the ***,the stress distribution in the coating at the pitch point was investigated as the COF *** zero friction,three notable stress regions were observed:1)the center of the surface,2)the end of the contact,and 3)the overall contact *** COF was increased in the micro-slip region of the contact interface,both tensile and compressive stresses in the coating *** study provides significant aid to engineers for understanding the stress response of the coating applied to polymer gears to achieve an optimal design.

关键词： coating contact stress finite element method(FEM) friction polymer gear

Feasibility of wear reduction for soft nanostructured thin film through enhanced elastic recoverability and contact stress relief

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Friction 2023年第7期11卷 1292-1306页

作者： kuk-Jin SEO Hyun-Joon KIM Dae-Eun KIM Department of Mechanical Engineering Yonsei UniversitySeoul 03722Republic of Korea Department of Precision Mechanical Engineering Kyungpook National UniversitySangju 37224Republic of Korea Department of Advanced Science and Technology Convergence Kyungpook National UniversitySangju 37224Republic of Korea

This work shows that a soft,thin film comprising randomly aligned carbon nanotubes(CNTs)can reduce surface wear more effectively than a homogeneous thin film because of enhanced elastic recoverability and contact stress relief originating from its mesh *** investigate the wear characteristics of the mesh structure compared to those of the homogeneous thin film,multi-walled CNTs(MWCNTs)and diamond-like carbon(DLC)thin films were prepared to conduct nanoscale tribological experiments using the atomic force microscopy(AFM).The MWCNT thin film showed unmeasurably low wear compared with the DLC thin film under a certain range of normal *** demonstrate the wear reduction mechanism of the MWCNT thin film,its indentation and frictional behaviors were *** indentation behavior of the MWCNT thin film revealed repetitive elastic deformation with a wide strain range and a significantly lower elastic modulus than that of the DLC thin *** permanent deformation of the MWCNT thin film was observed through frictional experiments under relatively high normal load *** results are expected to provide insights into the design of highly wear-resistant surfaces using nanostructures.

关键词： carbon nanotube(CNT) thin film wear friction elastic recovery

Ion shielding functional separator using halloysite containing a negative functional moiety for stability improvement of Li–S batteries

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Journal of Energy Chemistry 2021年第9期30卷 334-340页

作者： Yong Min Kwon Jihoon Kim kuk Young Cho Sukeun Yoon Division of Advanced Materials Engineering&Institute for Rare Metals Kongju National UniversityChungnam 31080Republic of Korea Department of Materials Science and Chemical Engineering Hanyang UniversityGyeonggi 15588Republic of Korea

Lithium–sulfur batteries are one of the attractive next-generation energy storage systems owing to theienvironmental friendliness,low cost,and high specific energy ***,the low electrical conductivity of sulfur,shuttling of soluble intermediate polysulfides between electrodes,and low capacitretention have hampered their commercial *** address these issues,we use a halloysitemodulated(H-M)separator in a lithium–sulfur battery to mitigate the shuttling *** H-M separator acts as a mutual Coulombic repulsion in lithium-sulfur batteries,thereby selectively permitting Lions and efficiently suppressing the transfer of undesired lithium polysulfides to the Li anode sideMoreover,the use of halloysite switches the surface of the separator from hydrophobic to hydrophilicconsequently improving the electrolyte wettability and adhesion between the separator and cathodeWhen sulfur-multi-walled carbon nanotube(S-MWCNT)composites are used as cathode active materialsa lithium–sulfur battery with an H-M separator exhibits first discharge and charge capacities of 1587 an1527 m Ah g-1,***,there is a consistent capacity retention up to 100 cyclesAccordingly,our approach demonstrates an economical and easily accessible strategy for commercialization of lithium–sulfur batteries.

关键词： Li–S batteries Halloysite Ion shielding Negative functional moiety Lithium polysulfides

Prussian blue and its analogues as advanced supercapacitor electrodes

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Journal of Energy Chemistry 2020年第11期29卷 206-229页

作者： Emad S.Goda Seungho Lee Muhammad Sohail kuk Ro Yoon Organic Nanomarerials Lab Department of ChemistryHannam UniversityDaejeon 34054Republic of Korea Department of Chemistry Hannam UniversityDaejeon 34054Republic of Korea Fire Protection Laboratory National Institute of Standards136.Giza 12211Egypt Advanced Energy and System Engineering University of Science and TechnologyDaejeon 34113Republic of Korea

Remarkable attention has been directed to Prussian blue(PB) and its analogues(PBA) as one of the most widely used metal-organic frameworks(MOFs) especially in the field of energy storage devices due to their fabulous features such as 3D open framework, high surface area, controllable distribution of pores and the low cost. Nevertheless, their depressed conductivity causes some insulation when being used as an electrode for supercapacitors leading to be restricted in further applications particularly the electronics. To the best of our knowledge, our review aimed primarily to give a total picture of the research that was done on utilizing PB and PBA for fabricating the electrodes of supercapacitor, studying their synthesis approaches in addition to the hybridization with other materials such as graphene, CNTs and conducting polymer. It also addresses the transformation of PB or PBA into other interesting nanostructures such as oxides, sulfides, and bicomponent of graphitic carbon nitride/metal oxides, as well. Furthermore,It exhibits various avenues for overcoming their disadvantages of bad cycle life, retention rate and not achieving the desired values of energy/power densities opening the door for enlarging the number of researches on their application as supercapacitors.

关键词： Metal hexacyanoferrates Supercapacitors Electrolyte Energy density Cyclic stability

Efficacy of stool multiplex polymerase chain reaction assay in adult patients with acute infectious diarrhea

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World Journal of Clinical Cases 2020年第17期8卷 3708-3717页

作者： Jae Sung Ahn Seung In Seo Jinseob Kim Taewan Kim Jin Gu Kang Hyoung Su Kim Woon Geon Shin Myoung kuk jang Hak Yang Kim Department of Internal Medicine Kangdong Sacred Heart HospitalSeoul KS013South Korea Department of Internal Medicine Kangdong Sacred Heart HospitalHallym University College of MedicineSeoul KS013South Korea Institute for Liver and Digestive Diseases Hallym UniversityChuncheon KS013South Korea Department of Epidemiology School of Public HealthSeoul National UniversitySeoul KS013South Korea

BACKGROUND Recently,stool multiplex polymerase chain reaction(PCR)tests have been developed for identifying diarrhea-causing bacterial ***,fecal calprotectin is a well-known effective marker for intestinal mucosal *** To evaluate the efficacy of stool multiplex PCR and fecal calprotectin in acute infectious *** Overall,400 patients with acute infectious diarrhea were enrolled from Kangdong Sacred Heart Hospital(January 2016 to December 2018).Multiplex PCR detected 7 enteropathogenic bacteria including Salmonella,Campylobacter,Shigella,Escherichia coli O157:H7,Aeromonas,Vibrio,and Clostridium *** reviewed clinical and laboratory findings using stool multiplex *** Stool multiplex PCR test detected considerably more bacterial pathogens than stool culture(49.2%vs 5.2%),with Campylobacter as the most common pathogen(54%).Patients with positive stool PCR showed elevated fecal calprotectin expression compared to patients with negative stool PCR(1124.5±816.9 mg/kg vs 609±713.2 mg/kg,P=0.001).C-reactive protein(OR=1.01,95%CI:1.001-1.027,P=0.034)and sigmoidoscopy-detected colitis(OR=4.76,95%CI:1.101-20.551,P=0.037)were independent factors in stool PCR-based detection of bacterial *** and specificity of calprotectin were evaluated to be 70.5%and 60.9%,respectively(adjusted cut-off value=388 mg/kg).CONCLUSION Stool multiplex PCR test has increased sensitivity in detecting pathogens than conventional culture,and it is correlated with calprotectin *** multiplex PCR and calprotectin may be effective in predicting clinical severity of infectious diarrhea.

关键词： Acute infectious diarrhea Stool multiplex polymerase chain reaction Calprotectin

Differentiation of acute and chronic hepatitis B in IgM antiHBc positive patients

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World Journal of Gastroenterology 2015年第13期21卷 3953-3959页

作者： Ji Won Park Kyeong Min Kwak Sung Eun Kim Myoung kuk jang Dong Joon Kim Myung Seok Lee Hyoung Su Kim Choong Kee Park Department of Internal Medicine Hallym University Medical CenterAnyang 431-070South Korea Department of Occupational and Environmental Medicine Hallym University Medical CenterAnyang 431-070South Korea Department of Internal Medicine Hallym University Sacred Heart Hospital of Hallym University Medical Center Seoul 134-701South Korea Department of Internal Medicine Hallym University Medical CenterChuncheon 200-704South Korea

AIM: To identify the factors that differentiate acute hepatitis B(AHB) from chronic hepatitis B with acute exacerbation(CHB-AE).METHODS: From 2004 to 2013, a total of 82 patients(male n = 52, 63.4%; female n = 30, 36.6%) with clinical features of acute hepatitis with immunoglobulin M antibodies to the hepatitis B core antigen(Ig M antiHBc) were retrospectively enrolled and divided into two groups; AHB(n = 53) and CHB-AE(n = 29). The AHB group was defined as patients without a history of hepatitis B virus(HBV) infection before the episode and with loss of hepatitis B surface antigen within 6 mo after onset of acute hepatitis. Biochemical and virological profiles and the sample/cutoff(S/CO) ratio of Ig M anti-HBc were compared to determine the differential diagnostic ***: The multivariate analysis demonstrated that, the S/CO ratio of Ig M anti-HBc and HBV DNA levels were meaningful factors. The S/CO ratio of Ig M anti-HBc was significantly higher in the AHB group, while the HBV DNA level was significantly higher in the CHB-AE group. The optimal cutoff values of Ig M anti-HBc and HBV DNA levels for differentiating the two conditions were 8 S/CO ratio and 5.5 log10 IU/m L, respectively. The sensitivity and specificity were 96.2% and 89.7% for the S/CO ratio of Ig M anti-HBc and 81.1% and 72.4% for HBV DNA levels, respectively. The area under receiver operating characteristic curves of both the S/CO ratio of Ig M anti-HBc and HBV DNA levels were not significantly different(0.933 vs 0.844, P = 0.105). When combining Ig M anti-HBc and HBV DNA, the diagnostic power significantly improved compared to HBV DNA alone(P = 0.0056). The combination of these factors yielded a sensitivity and specificity of 98.1% and 86.2%, ***: The combination of the S/CO ratio of Ig M anti-HBc and HBV DNA levels was a useful tool for differentiating AHB from CHB-AE in patients with positive Ig M anti-HBc.

关键词： Acute hepatitis Differential diagnosis Chronic hep

Two faces of Schwann cell dedifferentiation in peripheral neurodegenerative diseases:pro-demyelinating and axon-preservative functions

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Neural Regeneration Research 2014年第22期9卷 1952-1954页

作者： Jong kuk Kim Hye Jeong Lee Hwan Tae Park Department of Neurology Mitochondria Hub Regulation Center(MHRC)College of MedicineDong-A UniversityBusanSouth Korea Department of Pharmacology Mitochondria Hub Regulation Center (MHRC)College of MedicineDong-A UniversityBusanSouth Korea Department of Physiology Mitochondria Hub Regulation Center (MHRC)College of MedicineDong-A UniversityBusanSouth Korea

Schwann cells are glial cells that are responsible for the synthesis and maintenance of the myelin sheath in the peripheral nerve system. Under pathological conditions, such as physical nerve injury and inflammatory neuropathies, Schwann cells undergo a substantial phenotype transformation that is not related to their intended function. For example, Schwann cells dedifferentiate into immature states and thereby cease to express myelin genes after nerve injury.

关键词： cell Two faces of Schwann cell dedifferentiation in peripheral neurodegenerative diseases

Experimental study on the characteristics of DBD plasma coal liquefaction by using coal nanopowder

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Plasma Science and Technology 2019年第11期21卷 86-92页

作者： Song Chol PAK kuk Song HAN Yong Jun KIM Hak Chol CHOE Faculty of Physical Science Kimchaek University of Technology

A new method for liquefying coal using dielectric barrier discharge plasma has been *** utilizing waste oil as the solvent and processing coal nano powder in the plasma for 10 min,we have attained a liquid yield of more than 80%.The experiment shows that not only the coal nanopowder promoted the liquefaction process,but hydrogen radicals improved the liquid yield *** the plasma processing,the phenomenon of the changing color of the nanopowder solution and not producing a solid residue has been obviously *** rational parameters that affected the liquefaction of coal nanopowder have been achieved through the experiment,and the liquefied products have been analyzed.

关键词： liquefaction DBD plasma coal nanopowder

An englacial image and water pathways of the Fourcade glacier on King George Island, Antarctic Peninsula, inferred from ground-penetrating radar

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Science China Earth Sciences 2010年第6期53卷 892-900页

作者： LEE Joohan KIM Ki Young HONG Jong kuk JIN Young Keun Korea Polar Research Institute Songdo Techno Park7-50 Songdo-dong Yeonsu-gu Incheon 406-840 Korea Department of Geophysics Kangwon National UniversityChunchon 200-701 Korea

The distribution of small fractures and water content of the Fourcade glacier on King George Island, Antarctica, was investigated in November 2006 and December 2007 by two ground-based (470-and 490-m-long profiles) and one helicopter-borne (470-m-long profile) ground-penetrating radar (GPR) surveys using 50-, 100-, and 500-MHz antennas. Radar images in the pre-migrated GPR sections are characterized by a smooth ice surface and irregular bed topography, numerous diffraction hyperbolas in the ice and at the glacier bed, strong scattering noise, and near-surface folded layers. Scattering noise above a mound in the center of the profiles is associated with an area of dense fractures extending down from the ice surface that has relatively low reflection strength. Near the northeast ends of the profiles where few englacial fractures occur, scattering noise may result from the presence of warmer ice. A water-filled conduit and an air-filled cavity are interpreted as the source of two distinct hyperbolas in sub-glacial valleys based on the polarity of the reflections. Through migration velocity analysis on 106 hyperbolas, radar velocities were obtained for the 100-MHz ground-based profile. Using the velocities and Paren’s mixture formula, we calculated the water content of the ice to have been in the range of 0.00–0.09. High water content occurs near the glacier margin, in sub-glacial valleys, and in zones of scattering noise.

关键词： GPR water content Fourcade glacier scattering noise migration velocity analysis fractures