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Weldability evaluation and tensile strength estimation model for aluminum alloy lap joint welding using hybrid system with laser and scanner head

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中国有色金属学会会刊：英文版 2012年第S3期22卷 596-604页

作者： dong-Yoon kim Young-Whan PARK Department of Mechanical Engineering Pukyong National University

Aluminum welding using a hybrid system with a laser and scanner welding head was performed under various welding conditions to verify the feasibility of applying an aluminum alloy to a car *** experimental material was 5J32 aluminum alloy,and the laser power,welding speed,and laser incidence angle were used as the control *** weld bead shape and the tensile shear strength were evaluated in order to understand the aluminum lap joint weld *** of variance (ANOVA) was conducted to identify the effect of the process variables on the tensile shear *** strength estimation models using three different regression models were also *** input variables were the laser power,welding speed,and laser incidence angle,and the output was the tensile shear *** the models,the second-order polynomial estimation model had the best estimation performance,and the average error rate of this model was 0.058.

关键词： laser welding scanner remote welding 5J32 aluminum alloy regression model

EXPLICIT BOUNDS OF EIGENVALUES FOR STIFFNESS MATRICES BY QUADRATIC HIERARCHICAL BASIS METHOD)

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Journal of Computational Mathematics 2003年第2期21卷 113-124页

作者： Sang dong kim Byeong Chun SHIN Department of Mathematics Kyungpook National UniversityTaegu 702-701KoreaDepartment of MathematicsChonnam National UniversityGwangju 500-757Korea

The bounds for the eigenvalues of the stiffness matrices in the finite element discretization corresponding to Lu := - u' with zero boundary conditions by quadratic hierarchical basis are shown explicitly. The condition number of the resulting system behaves like O(1/h) where h is the mesh size. We also analyze a main diagonal preconditioner of the stiffness matrix which reduces the condition number of the preconditioned system to O(1).

关键词： hierarchical basis multilevel

New magnifying endoscopic classification for superficial esophageal squamous cell carcinoma

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World Journal of Gastroenterology 2017年第24期23卷 4416-4421页

作者： Su Jin kim Gwang ha kim Moon Won Lee Hye Kyung Jeon dong Hoon Baek Bong Eun Lee Geun Am Song Department of Internal Medicine Pusan National University School of Medicine and Research Institute for Convergence of Biomedical Science and TechnologyPusan National University Yangsan Hospital Department of Internal Medicine Pusan National University School of Medicine and Biomedical Research InstitutePusan National University Hospital

To assess the accuracy of a new magnifying endoscopy (ME) classification for predicting depth of invasion of superficial esophageal squamous cell carcinoma (SESCC). METHODSThis study included a total of 70 lesions in 69 patients with SESCC who underwent ME with narrow-band imaging (ME-NBI) before resection from August 2010 to July 2016. Accuracy of ME-NBI for predicting depth of invasion of SESCC was analyzed by using a new ME classification proposed by the Japan Esophageal Society (JES), and interobserver agreement was assessed. RESULTSOverall accuracy of ME-NBI for estimating depth of invasion of SESCC was 78.6%. Sensitivity and specificity of type B1 for tumors limited to the epithelial layer (m1) or invading into the lamina propria (m2) were 71.4% and 100%, respectively. Sensitivity and specificity of type B2 for tumors invading into the muscularis mucosa (m3) or superficial submucosa (≤ 200 μm, sm1) were 94.4% and 73.1%, respectively, while those of type B3 for tumors invading into the deep submucosa (> 200 μm, sm2) were 75.0% and 97.8%, respectively. Interobserver agreement was excellent (κ = 0.86, 95%CI: 0.76-0.95). CONCLUSIONThe recently developed JES ME classification is useful for predicting depth of invasion of SESCC, with reliable interobserver agreement.

关键词： Narrow-band imaging Esophageal cancer Squamous cell carcinoma Magnifying endoscopy

On the global existence of weak solutions for the Cucker-Smale-Navier-Stokes system with shear thickening

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Science China Mathematics 2018年第11期61卷 2033-2052页

作者： Seung-Yeal ha Hwa Kil kim Jae-Myoung kim Jinyeong Park Department of Mathematical Sciences and Research Institute of Mathematics Seoul National University Seoul 08826 Republic of Korea Korea Institute for Advanced Study Seoul 02455 Republic of Korea Department of Mathematics Education Hannam University Daejeon 34430 Republic of Korea Department of Mathematical Sciences Seoul National University Seoul 08826 Republic of Korea Department of Mathematics and Research Institute of Natural Sciences Hanyang University Seoul 04763 Republic of Korea

We study the large-time dynamics of Cucker-Smale(C-S)flocking particles interacting with nonNewtonian incompressible *** of particles and fluids were modeled using the kinetic Cucker-Smale equation for particles and non-Newtonian Navier-Stokes system for fluids,respectively and these two systems are coupled via the drag force,which is the main flocking(alignment)mechanism between particles and *** present a global existence theory for weak solutions to the coupled Cucker-Smale-Navier-Stokes system with shear *** also use a Lyapunov functional approach to show that sufficiently regular solutions approach flocking states exponentially fast in time.

关键词： emergence flocking Cucker-Smale model Navier-Stokes equation non-Newtonian fluid

Complete characterization of ultrafast optical fields by phase-preserving nonlinear autocorrelation

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Light(Science & Applications) 2022年第10期11卷 2451-2462页

作者： Alexander Gliserin Soo Hoon Chew Seungchul kim dong Eon kim Department of Optics and Mechatronics Engineering College of Nanoscience and NanotechnologyPusan National University2 Busandaehak-ro 63beon-gilBusan 46241South Korea Department of Cogno Mechatronics Engineering College of Nanoscience and NanotechnologyPusan National University2 Busandaehak-ro 63beon-gilBusan 46241South Korea Max Planck Center for Attosecond Science Max Planck POSTECH/Korea Research Initiative77 Cheongam-roPohang 37673South Korea Department of Physics Center for Attosecond Science and TechnologyPohang University of Science and Technology77 Cheongam-roPohang 37673South Korea

Nonlinear autocorrelation was one of the earliest and simplest tools for obtaining partial temporal information about an ultrashort optical pulse by gating it with ***,since the spectral phase is lost in a conventional autocorrelation measurement,it is insufficient for a full characterization of an ultrafast electric field,requiring additional spectral information for phase ***,we show that introducing an intensity asymmetry into a conventional nonlinear interferometric autocorrelation preserves some spectral phase information within the autocorrelation signal,which enables the full reconstruction of the original electric field,including the direction of time,using only a spectrally integrating *** call this technique Phase-Enabled Nonlinear Gating with Unbalanced Intensity(PENGUIN).It can be applied to almost any existing nonlinear interferometric autocorrelator,making it capable of complete optical field characterization and thus providing an inexpensive and less complex alternative to methods relying on spectral measurements,such as frequency-resolved optical gating(FROG)or spectral phase interferometry for direct electric-field reconstruction(SPIDER).More importantly,PENGUIN allows the precise characterization of ultrafast fields in non-radiative(e.g.,plasmonic)nonlinear optical interactions where spectral information is *** demonstrate this novel technique through simulations and experimentally by measuring the electric field of~6-fs laser pulses from a Ti:sapphire *** results are validated by comparison with the well-established FROG method.

关键词： autocorrelation nonlinear characterization

Atomic layer deposition for nanoscale oxide semiconductor thin film transistors:review and outlook

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International Journal of Extreme Manufacturing 2023年第1期5卷 153-180页

作者： Hye-Mi kim dong-Gyu kim Yoon-Seo kim Minseok kim Jin-Seong Park Division of Materials Science and Engineering Hanyang University222 Wangsimni-roSeongdong-guSeoul 04763Republic of Korea

Since the first report of amorphous In–Ga–Zn–O based thin film transistors,interest in oxide semiconductors has *** offer high mobility,low off-current,low process temperature,and wide flexibility for compositions and ***,depositing oxide semiconductors using conventional processes like physical vapor deposition leads to problematic issues,especially for high-resolution displays and highly integrated memory *** approaches have limited process flexibility and poor conformality on structured *** layer deposition(ALD)is an advanced technique which can provide conformal,thickness-controlled,and high-quality thin film ***,studies on ALD based oxide semiconductors have dramatically increased *** so,the relationships between the film properties of ALD-oxide semiconductors and the main variables associated with deposition are still poorly understood,as are many issues related to *** this review,to introduce ALD-oxide semiconductors,we provide:(a)a brief summary of the history and importance of ALD-based oxide semiconductors in industry,(b)a discussion of the benefits of ALD for oxide semiconductor deposition(in-situ composition control in vertical distribution/vertical structure engineering/chemical reaction and film properties/insulator and interface engineering),and(c)an explanation of the challenging issues of scaling oxide semiconductors and ALD for industrial *** review provides valuable perspectives for researchers who have interest in semiconductor materials and electronic device applications,and the reasons ALD is important to applications of oxide semiconductors.

关键词： atomic layer deposition(ALD) oxide semiconductor thin film transistor(TFT)

Heterostructures in two-dimensional colloidal metal chalcogenides:Synthetic fundamentals and applications

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Nano Research 2019年第8期12卷 1750-1769页

作者： Yuho Min Eunmi Im Geon-Tae Hwang Jong-Woo kim Cheol-Woo Ahn Jong-Jin Choi Byung-dong hahn Joon-Hwan Choi Woon-ha Yoon dong-Soo Park dong Choon Hyun Geon Dae Moon Functional Ceramics Department Powder & Ceramics DivisionKorea Institute of Materials Science (KIMS)ChangwonGyeongnam51508Republic of Korea Department of Polymer Science and Engineering Kyungpook National UniversityDaegu41566Republic of Korea dongrtam Regional Division Korea Institute of Industrial TechnologyBusan46938Republic of Korea

As a new class of two-dimensional materials, two-dimensional (2D) heterostructures constructed from metal chalcogenides (MCs) have been gaining tremendous attention due to their unprecedented physical and chemical phenomena, mainly originated from their distinct structural features such as composition, architecture type, spatial arrangement of each component, crystal structure, exposed facet and interface, dimensionality in their heterostructures. Towards the realization of practical applications, synthetic approaches need a rational design with a variety of architecture types including laterally-combined, vertically-aligned, and conformally-coated 2D MC heterostructures. Among various synthetic routes, solution-based synthesis is thought of as an alternative to fabrication through high-cost setups since it can control those structural features in a cheap fashion. This review presents recent progress on solution-based synthesis to produce various 2D MC heterostructures with a focus on the synthetic fundamentals in terms of thermodynamic and kinetic aspects related to the growth mechanism. Four different synthetic approaches are reviewed: seeded growth, cation exchange reaction, colloidal atomic layer deposition, direct synthesis including one-step process and modified electrochemical method. We also provide some representative applications of 2D MC heterostructures and their hybrid composites in various fields including optoelectronics, thermoelectrics, catalysis, and battery. Finally, we offer an insight into challenges and future directions in a synthetic improvement of 2D MC heterostructures.

关键词： metal chalcogenide heterostructure anisotropic nanomaterials two-dimensional (2D) nanomaterials solution-based synthesis

Variation in dynamic deformation behavior and resultant yield asymmetry of AZ80 alloy with extrusion temperature

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Journal of Materials Science & Technology 2020年第11期42卷 225-236页

作者： Sang-Hoon kim Sang Won Lee Byoung Gi Moon ha Sik kim Sung Hyuk Park School of Materials Science and Engineering Kyungpook National UniversityDaegu702701South Korea Implementation Research Division Korea Institute of Materials ScienceChangwon51508South Korea

In this work,variation in the dynamic recrystallization(DRX)and dynamic precipitation behavior of AZ80 alloy during extrusion due to changes in extrusion temperature was investigated,and the resultant microstructure and yield asymmetry were *** the extrusion temperature increases from 250℃to 350℃,the primary DRX mechanism changes from twin-induced DRX to discontinuous DRX,resulting in an increase in the DRX area fraction and un DRXed grain *** addition,as the extrusion temperature rises,Mg17Al12 precipitation during extrusion decreases sharply throughout the extruded *** reduction in the compressive yield strength(CYS)with increasing extrusion temperature is more pronounced than it is for the tensile yield strength(TYS),which ultimately increases the yield asymmetry of the extruded *** higher extrusion temperature has less of an influence on the TYS due to the promotion of certain hardening *** the other hand,the greater reduction in the CYS is attributed to the increased fraction and size of regions in which{1012}twins predominantly form and the lower amount of precipitates,which effectively facilitates{1012}twinning.

关键词： Magnesium alloys Extrusion Recrystallization Precipitation Yield asymmetry

Preparation of patterned SiC and SiCN microstructures

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Science China(Technological Sciences) 2006年第2期49卷 164-171页

作者： SUNG In-kyung kim dong-pyo Department of Fine Chemical Engineering and Chemistry of Chungnam National University TaejonSouth Korea 305-764

Patterned SiC and SiCN microstructures were successfully fabricated on the silicon substrates by using polydimethylsiloxane (PDMS) elastometric stamp as template, polycarbosilane (PCS) and polysilazane (PSZ) as preceramic polymers. The preparing process was followed by precursor infiltration, the curing of the precursor, demolding of the template and pyrolysis of the cured preceramic polymer pattern. It shows that the dimen- sions of the ceramic patterns can be tailored by using the PDMS molds with different di- mensions. The produced ceramic microstructures can be potentially applied in high tem- perature and high pressure environments due to the advanced properties of the SiC and SiCN ceramics.

关键词： micro-fabrication technique, soft lithography, elastomeric stamp, non-oxide ceramics, patterning.