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Structural stability estimation of whirling unit

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中国有色金属学会会刊：英文版 2009年第B09期19卷 202-208页

作者： Son-jae HWAN Han-Chang woo Lee-Sang RYONG Lee-Young MOON Daegu Machinery Institute of Component & Materials Foundation Department of Automobile Yeungnam College of Science & Technology Department of Mechanical Engineering Kyung pook National University

Whirling is a cutting process in which a series of cutting edges on whirling ring remove material by turning over a rotating workpiece. In this study static and dynamic stability of whirling unit was estimated by using ADAMS and NASTRAN softwares. Each maximum force acting on the bearing attached to the spindle assembly and the cutting tool attached to the whirling ring with the rotating speed of 6 000 r/min was 235 N and 902 N respectively. The maximum stress of 0.74 MPa on the base frame is far smaller than the yield strength of 282 MPa. The calculated natural frequency of 148 Hz of the system is far from the frequency of the driving speed of 6 000 r/min. The experimentally obtained maximum cutting force of 792 N is smaller than that of calculated value. And the experimentally obtained natural frequency of 118 Hz is beyond the driving speed of 6000 r/min. From above results it can be judged that the whirling system is statically and dynamically stable.

关键词：旋转工件稳定性评价 NASTRAN软件动态稳定性结构单元固有频率行车速度

A Review of David Gottlieb’s Work on the Resolution of the Gibbs Phenomenon

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Communications in Computational Physics 2011年第3期9卷 497-519页

作者： Sigal Gottlieb jae-Hun jung Saeja Kim Mathematics Department University of Massachusetts DartmouthNorth DartmouthMA 02747USA Mathematics Department Suny BuffaloBuffaloNew York 14260-2900USA

Given a piecewise smooth function,it is possible to construct a global expansion in some complete orthogonal basis,such as the Fourier ***,the local discontinuities of the function will destroy the convergence of global approximations,even in regions for which the underlying function is *** global expansions are contaminated by the presence of a local discontinuity,and the result is that the partial sums are oscillatory and feature non-uniform *** characteristic behavior is called the Gibbs ***,David Gottlieb and Chi-Wang Shu showed that these slowly and non-uniformly convergent global approximations retain within them high order information which can be recovered with suitable *** this paper we review the history of the Gibbs phenomenon and the story of its resolution.

关键词： Gibbs phenomenon post-processing Galerkin approximation collocation approximation spectral methods exponential accuracy

Flexible and transparent thin-film light-scattering photovoltaics about fabrication and optimization for bifacial operation

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npj Flexible Electronics 2023年第1期7卷 388-397页

作者： Soo-Won Choi jae-Ho Park Ji-woo Seo Chaewon Mun Yonghun Kim Pungkeun Song Myunghun Shin jung-Dae Kwon Surface&Nano Materials Division Korea Institute of Materials ScienceChangwonGyeongnam 51508Republic of Korea Department of Materials Science and Engineering Pusan National UniversityBusan 46241Republic of Korea Cell R&D Team Hanhwa QCells202 Sansusandan 2-roLwol-myeonJincheon-gunChungcheongbuk-do 27816Republic of Korea School of Electronics and Information Engineering Korea Aerospace UniversityGoyangGyeonggi 10540Republic of Korea Department of Advance Materials Engineering University of Science and Technology(UST)217 Gajeong-roYuseong-guDaejeon 34113Republic of Korea

Flexible and transparent thin-film silicon solar cells were fabricated and optimized for building-integrated photovoltaics and bifacial operation.A laser lift-off method was developed to avoid thermal damage during the transfer of light-scattering structures onto colorless polyimide substrates and thus enhance front-incidence photocurrent,while a dual n-type rear window layer was introduced to reduce optical losses,facilitate electron transport for rear incidence,and thus enhance performance during bifacial *** introduction of the window layer increased the rear-to-front power conversion efficiency ratio to~86%.The optimized bifacial power conversion efficiency for front and rear irradiances of 1 and 0.3 sun,respectively,equaled 6.15%,and the average transmittance within 500–800 nm equaled 36.9%.Additionally,the flexible and transparent solar cells fabricated using laser lift-off exhibited good mechanical reliability(i.e.,sustained 500 cycles at a bending radius of 6 mm)and were therefore suitable for building-integrated photovoltaics.

关键词： transparent scattering film

Tailoring uniform γ-MnO2 nanosheets on highly conductive three-dimensional current collectors for high-performance supercapacitor electrodes

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Nano Research 2015年第3期8卷 990-1004页

作者： Sangbaek Park Hyun-woo Shim Chan woo Lee Hee Jo Song Ik jae Park jae-Chan Kim Kug Sun Hong Dong-Wan Kim Department of Materials Science and Engineering Seoul National University Seou1151-744 R. O. Korea School of Civil Environmental and Architectural Engineering Korea University Seou1136-713 R. O. Korea

Recent efforts have focused on the fabrication and application of three- dimensional （3-D） nanoarchitecture electrodes, which can exhibit excellent electrochemical performance. Herein, a novel strategy towards the design and synthesis of size- and thickness-tunable two-dimensional （2-D） MnO2 nanosheets on highly conductive one-dimensional （l-D） backbone arrays has been developed via a facile, one-step enhanced chemical bath deposition （ECBD） method at a low temperature （-50 ℃）. Inclusion of an oxidizing agent, BrO3-, in the solution was crucial in controlling the heterogeneous nucleation and growth of the nanosheets, and in inducing the formation of the tailored and uniformly arranged nanosheet arrays. We fabricated supercapacitor devices based on 3-D MnO2 nanosheets with conductive Sb-doped SnO2 nanobelts as the backbone. They achieved a specific capacitance of 162 F·g-1 at an extremely high current density of 20 A·g% and good cycling stability that shows a capacitance retention of -92% of its initial value, along with a coulombic efficiency of almost 100% after 5,000 cycles in an aqueous solution of I M Na2SO4. The results were attributed to the unique hierarchical structures, which provided a short diffusion path of electrolyte ions by means of the 2-D sheets and direct electrical connections to the current collector by 1-D arrays as well as the prevention of aggregation by virtue of the well-aligned 3-D structure.

关键词： nanosheets manganese oxide chemical bath deposition SnO2 nanobelts supercapacitor

Ectopic peritoneal paragonimiasis mimicking tuberculous peritonitis:A care report

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World Journal of Clinical Cases 2022年第16期10卷 5359-5364页

作者： jung woo Choi Chang Min Lee Seong Je Kim Se In Hah Ji Yoon Kwak Hyun Chin Cho Chang Yoon Ha woon Tae jung Ok jae Lee Department of Internal Medicine Gyeongsang National University College of Medicine and Gyeongsang National University HospitalJinju 52727South Korea Institute of Health Sciences Gyeongsang National UniversityJinju 52828South Korea

BACKGROUND The most common site of paragonimiasis is in the *** migratory route passes through the duodenal wall,peritoneum,and diaphragm to the lungs;thus,the thoracic cavity and central nervous system,as well as the liver,intestine,and abdominal cavity may be ***,we present a case of intraperitoneal paragonimiasis without other organ involvement,mimicking tuberculous *** SUMMARY A 57-year-old man presented with recurrent abdominal pain for 4 *** examination revealed tenderness in the right lower *** findings showed complete blood counts within the normal range without *** reactive lymph nodes and diffuse peritoneal infiltration were noted on abdominal computed tomography(CT).There were no abnormalities on chest CT or *** findings of diagnostic laparoscopy for the differential diagnosis of tuberculous peritonitis and peritoneal carcinomatosis included multiple small whitish nodules and an abscess in the *** reports confirmed the presence of numerous eggs of Paragonimus westermani(***).A postoperative serum enzyme-linked immunosorbent assay revealed *** *** and repetitive history-taking led him to retrospectively recall the consumption of freshwater *** 3 d of treatment with praziquantel(1800 mg;25 mg/kg),he recovered from all *** In patients who require diagnostic laparoscopy for the differential diagnosis of tuberculous peritonitis and peritoneal carcinomatosis,repetitive history-taking and preoperative serologic antibody tests against Paragonimus may be helpful in diagnosing intraperitoneal paragonimiasis without other organ involvement.

关键词： Differential diagnoses Intraperitoneal abscess Paragonimiasis Paragonimus westermani Peritonitis Tuberculosis Case report

Radial growth response of Pinus densiflora and Quercus *** topographic and climatic factors in South Korea

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Journal of Plant Ecology 2013年第5期6卷 380-392页

作者： jae Gyun Byun woo Kyun Lee Moonil Kim Doo Ahn Kwak Hanbin Kwak Taejin Park woo Hyuk Byun Yowhan Son jung Kee Choi Young Jin Lee Joachim Saborowski Dong Jun Chung Jin Hyun jung Institute for Environmental Research(Biology V) RWTH Aachen UniversityWorringerweg 152074 AachenGermany Division of Environmental Science and Ecological Engineering Korea UniversitySeoul136-701Korea GIS/RS Center for Environmental Resources Korea UniversitySeoul 136-173Korea Department of Forest Management Kangwon National UniversityChunchon 200-701Korea Department of Forest Resources Kongju National UniversityKongju 341-701Korea Institute of Forest Biometry and Informatics Georg-August-University Gottingen37077 GottingenGermany National Forestry Cooperative Federation Daejeon 306-808Korea

Aims This study aimed to develop radial growth models and to predict the potential spatial distribution of Pinus densiflora(Japanese red pine)and Quercus spp.(Oaks)in South Korea,considering topographic and climatic *** We used a dataset of diameter at breast height and radial growth estimates of individual trees,topographic and climatic factors in systematic sample plots distributed over the whole of South *** the basis that radial growth is attributed primarily to tree age,we developed a radial growth model employing tree age as an explanatory *** estimated standard growth(SG),defined as radial growth of the tree at age 30,to eliminate the influence of tree age on radial *** addition,SG estimates including the Topographic Wetness Index,temperature and precipitation were calculated by the Generalized Additive *** Findings As a result of variogram analysis of SG,we found spatial autocorrelation between SG,topographic and climatic *** temperature had negative impacts on radial growth of *** and positive impacts on that of Quercus *** was associated with positive effects on both tree *** on the model,we found that radial growth of *** would be more vulnerable than that of Quercus *** climatic *** simulation with the radial growth model,it was predicted that *** stands would be gradually replaced with Quercus *** in eastern coastal and southern regions of South Korea in the *** models developed in this study will be helpful for understanding the impact of climatic factors on tree growth and for predicting changes in distribution of *** and Quercus *** to climate change in South Korea.

关键词： standard radial growth general additive model climatic factors climate change forest-cover change

Development of enterohepatic fistula after embolization in ileal gastrointestinal stromal tumor: A case report

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World Journal of Gastroenterology 2013年第43期19卷 7816-7819页

作者： Yun Ho Lee Ja Seol Koo Chang Ho jung Sang Yoon Chung jae Joong Lee Seung Young Kim Jong Jin Hyun Sung woo jung Rok Seon Choung Sang woo Lee Jai Hyun Choi Division of Gastroenterology Department of Internal MedicineKorea University Ansan Hospital516 Gojan-dongDanwon-guAnsan-siGyeonggi-do 425-707South Korea

Gastrointestinal stromal tumor(GIST)is a rare mesenchymal tumor of the gastrointestinal tract that has been associated with the formation of fistulas to adjacent organs in few case ***,GIST with enterohepatic fistula has not been *** we report the case of an enterohepatic fistula that occurred after embolization of a liver mass originating in the distal *** 87-year-old woman was hospitalized for *** initial conventional endoscopy,a bleeding focus in the gastrointestinal tract was not *** of massive hematochezia,enteroscopy was performed through the anus.A protruding,ulcerative mass was found in the distal ileum that was suspected to be the source of the bleeding;a biopsy sample was *** was not successful in controlling the bleeding;therefore,embolization was *** embolization,the patient developed a high fever and severe abdominal tenderness with rebound ***-up abdominopelvic computed tomography revealed an enterohepatic fistula between the liver and distal *** fistula was treated surgically by segmental resection of the distal ileum and unlooping of the liver mass.

关键词： Gastrointestinal stromal tumor Enterohepatic fistula Therapeutic embolization Bleeding Ileal gastrointestinal stromal tumor

Segmented tomographic evaluation of structural degradation of carbon support in proton exchange membrane fuel cells

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Journal of Energy Chemistry 2022年第11期31卷 359-367,I0010页

作者： jung A.Hong Min-Hyoung jung Sung Yong Cho Eun-Byeol Park Daehee Yang Young-Hoon Kim Sang-Hyeok Yang woo-Sung Jang jae Hyuck Jang Hyo June Lee Sungchul Lee Hu Young Jeong Young-Min Kim Department of Energy Science Sungkyunkwan University(SKKU)Suwon 16419Republic of Korea Fuel Cell Core Parts Development Cell Hyundai Mobis Co.Ltd.Uiwang 16082Republic of Korea Electron Microscopy&Spectroscopy Team Korea Basic Science Institute(KBSI)Daejeon 34133Republic of Korea Graduate School of Semiconductor Materials and Devices Engineering Ulsan National Institute of Science and Technology(UNIST)Ulsan 44919Republic of Korea

The variation of the three-dimensional(3D)structure of the membrane electrode of a fuel cell during proton exchange cycling involves the corrosion/compaction of the carbon *** increasing degradation of the carbon structure continuously reduces the electrocatalytic performance of proton exchange membrane fuel cells(PEM-FCs).This phenomenon can be explained by performing 3D tomographic analysis at the ***,conventional tomographic approaches which present limited experimental feasibility,cannot perform such evaluation and have not provided sufficient structural information with statistical significance thus ***,a reliable methodology is required for the 3D geometrical evaluation of the carbon ***,we propose a segmented tomographic approach which employs pore network analysis that enables the visualization of the geometrical parameters corresponding to the porous carbon structure at a high *** approach can be utilized to evaluate the 3D structural degradation of the porous carbon structure after cycling in terms of local surface area,pore size distribution,and their 3D *** geometrical parameters of the carbon body were demonstrated to be substantially reduced owing to the cycling-induced *** information enables a deeper understanding of the degradation phenomenon of carbon supports and can contribute to the development of stable PEM-FC electrodes.

关键词： Electron tomography Fuel cell Proton exchange membrane Membrane electrode assembly Carbon corrosion

Influence of undissolved second-phase particles on dynamic recrystallization behavior of Mg–7Sn–1Al–1Zn alloy during low-and high-temperature extrusions

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Journal of Materials Science & Technology 2021年第12期71卷 87-97页

作者： Hyun Ji Kim Sang-Cheol Jin jae-Gil jung Sung Hyuk Park School of Materials Science and Engineering Kyungpook National UniversityDaegu41566Republic of Korea Implementation Research Division Korea Institute of Materials ScienceChangwon51508Republic of Korea

This study investigates the effects of fine and coarse undissolved particles in a billet of the Mg–7 Sn–1 Al–1 Zn(TAZ711)alloy on the dynamic recrystallization(DRX)behavior during hot extrusion at low and high temperatures and the resultant microstructure and mechanical properties of the *** this end,partially homogenized(PH)and fully homogenized(FH)billets are extruded at temperatures of250 and 450°*** PH billet contains fine and coarse undissolved Mg_(2) Sn particles in the interdendritic region and along the grain boundaries,*** fine particles(<1μm in size)retard DRX during extrusion at 250°C via the Zener pinning effect,and this retardation causes a decrease in the area fraction of dynamically recrystallized(DRXed)grains of the extruded *** addition,the inhomogeneous distribution of fine particles in the PH billet leads to the formation of a bimodal DRXed grain structure with excessively grown grains in particle-scarce *** contrast,in the FH billet,numerous nanosized Mg_(2) Sn precipitates are formed throughout the material during extrusion at 250°C,which,in turn,leads to the formation of small,uniform DRXed grains by the grain-boundary pinning effect of the *** the PH billet is extruded at the high temperature of 450°C,the retardation effect of the fine particles on DRX is weakened by their dissolution in theα-Mg matrix and the increased extent of thermally activated grain-boundary *** contrast,the coarse Mg_(2) Sn particles in the billet promote DRX during extrusion through the particle-stimulated nucleation phenomenon,which results in an increase in the area fraction of DRXed *** both low and high extrusion temperatures,the extruded material fabricated using the PH billet,which contains both fine and coarse undissolved particles,has a lower tensile strength than that fabricated using the FH billet,which is virtually devoid of second-phase *** lower strength of the former is attributed mai

关键词： Mg–Sn alloy Second-phase particle Extrusion Homogenization Dynamic recrystallization