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Diagnosis parameters of mold filling pattern for optimization of a casting system

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China Foundry 2012年第4期9卷 376-380页

作者： Jun-ho hong young-Sim Choi ho-young hwang e-Design Center Korea Institute of Industrial Technology e-Design Center Korea Institute of Industrial TechnologyIncheonKorea

For optimal design of a gating system,the setting of diagnosis parameters is very *** this study,the permanent mold casting process was selected because most of the other casting processes have more complicated factors that influence the mold filling pattern compared to the permanent mold casting process,such as the surface roughness of mold,gas generation from the mold wash and binder of sand mold,and the gas permeability through a sand mold,*** diagnosis parameters(flow rate difference and arrival time difference) of molten metal flow pattern in the numerical simulation are suggested for design of an optimum casting system with a permanent *** results show that the arrival time difference can be used as one important diagnosis parameter of the complexity of the runner system and its usefulness has been verified via making aluminum parts using permanent mold casting(Fig.9).

关键词： mold filling pattern optimum casting system diagnosis parameter permanent mold casting process

Prediction of mechanical properties of Al alloys with change of cooling rate

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China Foundry 2012年第4期9卷 381-386页

作者： Quan-Zhi Dong young-Sire Choi Jun-ho hong ho-young hwang Dept.of Virtual Engineering University of Science and TechnologyIncheon 406-840Korea e-Design Center Korea Institute of Industrial TechnologyIncheon 406-840Korea

The solidification process significantly affects the mechanical properties and there are lots of factors that affect the solidification *** progress has been made in the research on the effect of solidification on mechanical *** them,the PF(Phase Field) model and CA(Cellular Automata) model are widely used as simulation methods which can predict nucleation and its growth,and the size and morphology of the grains during *** they can give accurate calculation results,it needs too much computational memory and calculation *** it is difficult to apply the simulation to the real production *** this study,a more practical simulation approach which can predict the mechanical properties of real aluminum alloys is proposed,by identifying through experiment the relationship between cooling rate and SDAS(Secondary Dendrite Arm Spacing) and mechanical *** experimentally measured values and the values predicted by simulation have relatively small differences and the mechanical properties of a variety of Al alloys are expected to be predicted before casting through use of the simulation.

关键词： mechanical properties dendrite structure aluminum alloy cooling rate solidification castingsimulation

Measurement of heat treatment induced residual stresses by using ESPI combined with hole-drilling method

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China Foundry 2010年第3期7卷 287-291页

作者： Jie Cheng Si-young Kwak ho-young hwang Department of Virtual Engineering University of Science ＆ Technology （UST） Daejeon 305-333 Korea e-Design Center KoreaInstitute of lndustrial Technology （KITECH） lncheon 406-840 Korea

In this study, residual stresses in heat treated specimen were measured by using ESPI (Electronic Speckle-Pattern Interferometry) combined with the hole-drilling *** specimen, made of SUS 304 austenitic stainless steel, was quenched and water cooled to room *** simulation using a hybrid FDM/FEM package was also carried out to simulate the heat treatment *** a result, the thermal stress fields were obtained from both the experiment and the numerical *** comparision of stress fields, results from the experimental method and numerical simulation well agreed to each other, therefore, it is proved that the presented experimental method is applicable and reliable for heat treatment induced residual stress measurement.

关键词： thermal stress heat treatment residual stress electron speckle-pattern interferometry hole-drillingmethod hybrid FDM/FEM

Study on accuracy of casting flow simulation

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China Foundry 2017年第5期14卷 333-338页

作者： youngsim Choi Jun-ho hong ho-young hwang Kyuhong Kim Dept.of Mechanical&Aerospace Engineering Seoul Nat.Univ.Republic of Korea Korea Institute of Industrial Technology(KITECH) Republic of Korea Institute of Advanced Aerospace Technology Seoul Nat.Univ.Republic of Korea

In the field of casting flow simulation, the application of body-fitted coordinate(BFC) has not been widely used due to the difficulty and low efficiency of grid generation, despite the availability of good quality analysis results. Cartesian coordinates, on the other hand, have been used predominantly in casting process simulations because of their relatively easy and fast grid generation. however, Cartesian grid systems cannot obtain accurate results because they cannot express the geometries properly. In this study, Cut Cell method was applied to solve this problem. The three-dimensional incompressible viscous governing equation was analyzed using a function defined for the volume and area of the casting in the cutting cell. Using the Cut Cell method, accurate flow analysis results were also obtained in the Cartesian grid systems. The tests of simple shape and the applications of actual casting product have been tried with Cut Cell method.

关键词： casting flow Cut Cell Cartesian coordinates body-fitted coordinates filling pattern conservationof momentum

A study on effects of ceramic foam filter on flow aspect through water modeling experiment

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China Foundry 2017年第3期14卷 216-225页

作者： ho-young hwang Cheol-Hee Nam young-Sim Choi Jun-ho hong Xun Sun Cyber Manufacturing Process Group Korea Institute of Industrial Technology Incheon 21999 South Korea Department of Robotics and Virtual Engineering Korea University of Science and Technology Daejeon 34113 South Korea Materials Science and Engineering Kyoto University Kyoto 606-8501 Japan Shenyang Research Institute of Foundry Shenyang 110022 China

Casting defects that are closely related to entrapped air bubbles and metallic oxides occur very frequently in the sand mold casting process. Many researchers have shown that these defects can be reduced by adopting an appropriate gating system design. however, it is difficult for field engineers to identify a specific gating system that is more appropriate for their products. In this study, we tried to draw a comparison between two gating system designs with and without a ceramic foam filter. The ceramic foam filter was added to the horizontal runner just after the down sprue to prevent air bubble generation and reduce turbulence without a change of gating system design. The water modeling experiment was conducted with four different amounts of the initial volumes of water in the reservoir to verify the effects of initial pouring velocity. The results of the experiment applying the filter showed remarkably changed flow characteristics. The use of the filter was found to convert the flow pattern of water in the desired direction. The ceramic foam filter performed well to reduce flow velocity and stabilize the water *** flow pattern without a filter can be improved significantly even with the the use of just a 10 PPI irregular filter. Although the study confirmed that use of the filter may change the flow characteristics, it needs to be noted that the use of the ceramic filter alone cannot solve all the problems caused by a poorly designed gating system.

关键词： ceramic foam filter sprue gating system design sand mold casting casting defect

Recent progress and future research directions for electrochromic zinc-ion batteries

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Journal of Energy Chemistry 2024年第3期90卷 220-232,I0007页

作者： Tae Gwang Yun Byungil hwang Jun young Cheong Department of Molecular Science and Technology Ajou UniversitySuwon 16499Republic of Korea School of Integrative Engineering Chung-Ang UniversitySeoul 06974Republic of Korea Bavarian Center for Battery Technology(Bay Batt)and Department of Chemistry University of Bayreuth95447 BayreuthGermany

In recent times,future energy storage systems demand a multitude of functionalities beyond their traditional energy storage *** line with this technological shift,there is active research and development of electrochromic-energy storage systems designed to visualize electrochemical charging and discharging *** conventional electrochromic-energy storage devices primarily integrated supercapacitors,known for their high power density,to enable rapid color ***,the low energy density of supercapacitors restricts overall energy storage capacity,acting as a significant barrier to expanding the application range of such *** this review,we introduce electrochromic zinc(Zn)-ion battery systems,which effectively overcome the limitation of low energy density,and provide illustrative examples of their applicability across diverse *** many recent research works are present for electrochromic Zn-ion batteries,little review has so far taken *** objective is to discuss on the current progress and future directions for electrochromic Zn-ion batteries,which are applicable for wearable electronics applications and energy storage *** review provides an initial milestone for future researchers in electrochromic energy storage and zinc-ion batteries,which will lead to a stream of future works related to them.

关键词： Electrochromic Zn-ion battery Flexible Transition metal oxide Conductive polymer

Direct 4D printing of functionally graded hydrogel networks for biodegradable,untethered,and multimorphic soft robots

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International Journal of Extreme Manufacturing 2024年第2期6卷 407-416页

作者： Soo young Cho Dong Hae ho Sae Byeok Jo Jeong ho Cho Department of Chemical and Biomolecular Engineering Yonsei UniversitySeoul 03722Republic of Korea Department of Mechanical Engineering Virginia TechBlacksburgVA 24061United States of America School of Chemical Engineering Sungkyunkwan UniversitySuwon 16419Republic of Korea SKKU Institute of Energy Science and Technology(SIEST) Sungkyunkwan UniversitySuwon 16419Republic of Korea

Recent advances in functionally graded additive manufacturing(FGAM)technology have enabled the seamless hybridization of multiple functionalities in a single *** robotics can become one of the largest beneficiaries of these advances,through the design of a facile four-dimensional(4D)FGAM process that can grant an intelligent stimuli-responsive mechanical functionality to the printed ***,we present a simple binder jetting approach for the 4D printing of functionally graded porous multi-materials(FGMM)by introducing rationally designed graded multiphase feeder *** graded cross-linking agents gradually form stable porous network structures within aqueous polymer particles,enabling programmable hygroscopic deformation without complex mechanical ***,a systematic bed design incorporating additional functional agents enables a multi-stimuli-responsive and untethered soft robot with stark stimulus *** biodegradability of the proposed 4D-printed soft robot further ensures the sustainability of our approach,with immediate degradation rates of 96.6%within 72 *** proposed 4D printing concept for FGMMs can create new opportunities for intelligent and sustainable additive manufacturing in soft robotics.

关键词： intelligent and sustainable additive manufacturing multi-material four-dimensional printing untethered soft robot multi-stimuli-responsive soft robot biodegradable soft robotics

Multiphase cooperation for multilevel strain accommodation in a single-crystalline BiFeO3 thin film

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Chinese Physics B 2024年第9期33卷 57-66页

作者： Wooseon Choi Bumsu Park Jaejin hwang Gyeongtak Han Sang-Hyeok Yang Hyeon Jun Lee Sung Su Lee Ji young Jo Albina Y.Borisevich Hu young Jeong Sang ho Oh Jaekwang Lee young-Min Kim Department of Energy Science Sungkyunkwan University(SKKU)Suwon 16419Republic of Korea Samsung Electronics Hwaseong 18448Republic of Korea Department of Physics Pusan National UniversityBusan 46241Republic of Korea LG Energy Solution Daejeon 34122Republic of Korea Department of Materials Science and Engineering Kangwon National UniversityRepublic of Korea School of Materials Science and Engineering Gwangju Institute of Science and Technology(GIST)Gwangju 61005Republic of Korea Center for Nanophase Materials Sciences Oak Ridge National LaboratoryTN 37831USA Graduate School of Semiconductor Materials and Devices Engineering Ulsan National Institute of Science and Technology(UNIST)Ulsan 44919Republic of Korea Department of Energy Engineering KENTECH Institute for Energy Materials and DevicesKorea Institute of Energy Technology(KENTECH)Naju 58330Republic of Korea

The functionalities and diverse metastable phases of multiferroic BiFeO3(BFO)thin films depend on the misfit *** mixed phase-induced strain relaxation in multiphase BFO thin films is well known,it is unclear whether a singlecrystalline BFO thin film can accommodate misfit strain without the involvement of its ***,understanding the strain relaxation behavior is key to elucidating the lattice strain–property *** this study,a correlative strain analysis based on dark-field inline electron holography(DIH)and quantitative scanning transmission electron microscopy(STEM)was performed to reveal the structural mechanism for strain accommodation of a single-crystalline BFO thin *** nanoscale DIH strain analysis results indicated a random combination of multiple strain states that acted as a primary strain relief,forming irregularly strained *** STEM-based bond length measurement of the corresponding strained nanodomains revealed a unique strain accommodation behavior achieved by a statistical combination of multiple modes of distorted structures on the unit-cell *** globally integrated strain for each nanodomain was estimated to be close to􀀀1.5%,irrespective of the nanoscale strain states,which was consistent with the fully strained BFO film on the SrTiO3 *** functional theory calculations suggested that strain accommodation by the combination of metastable phases was energetically favored compared to single-phase-mediated *** discovery allows a comprehensive understanding of strain accommodation behavior in ferroelectric oxide films,such as BFO,with various low-symmetry polymorphs.

关键词： BiFeO_(3) scanning transmission electron microscopy electron holography multiferroic material strain mapping

Hydrangea serrata extract exerts tumor inhibitory activity against hepatocellular carcinoma HepG2 cells via inducing p27/CDK2-mediated cell cycle arrest and apoptosis

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Asian Pacific Journal of Tropical Biomedicine 2024年第2期14卷 65-72,I0002-I0005页

作者： Ye-eun Kim Jeonghye hwang Ki-young Kim Graduate School of Biotechnology Kyung Hee UniversitySeocheonGiheungYonginGyeonggi-do 446-701Republic of Korea Department of Genetics and Biotechnology College of Life SciencesKyung Hee UniversitySeocheonGiheungYonginGyeonggi-do 446-701Republic of Korea

Objective:To examine the inhibitory effect of Hydrangea serrata extract against hepatocellular carcinoma HepG2 cells and its underlying ***:The effects of Hydrangea serrata extract on growth inhibition of tumor cells and spheroids were assessed using MTT and 3D culture *** real-time PCR and Western blot analyses were employed to investigate the changes in mRNA and protein expression levels of molecules related to cell cycle and ***:Hydrangea serrata extract effectively inhibited the growth of both tumor cells and *** extract also significantly upregulated p27 mRNA expression and downregulated CDK2 mRNA expression,leading to cell cycle ***,increased BAX/Bcl-2 ratio as well as caspase-9 and-3 were observed after treatment with Hydrangea serrata extract,indicating the induction of tumor cell ***:Hydrangea serrata extract has the potential to alleviate tumors by effectively modulating cell-cycle-related gene expressions and inducing apoptosis,thereby inhibiting tumor growth.

关键词： Hydrangea serrata Hepatocellular carcinoma Liver cancer Anticancer Cell cycle arrest Apoptosis