CINXE.COM

<!DOCTYPE html><html lang="en-US"><head><title>Just a moment...</title><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=Edge"><meta name="robots" content="noindex,nofollow"><meta name="viewport" content="width=device-width,initial-scale=1"><style>*{box-sizing:border-box;margin:0;padding:0}html{line-height:1.15;-webkit-text-size-adjust:100%;color:#313131;font-family:system-ui,-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,Helvetica Neue,Arial,Noto Sans,sans-serif,Apple Color Emoji,Segoe UI Emoji,Segoe UI Symbol,Noto Color Emoji}body{display:flex;flex-direction:column;height:100vh;min-height:100vh}.main-content{margin:8rem auto;max-width:60rem;padding-left:1.5rem}@media (width <= 720px){.main-content{margin-top:4rem}}.h2{font-size:1.5rem;font-weight:500;line-height:2.25rem}@media (width <= 720px){.h2{font-size:1.25rem;line-height:1.5rem}}#challenge-error-text{background-image:url(data:image/svg+xml;base64,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);background-repeat:no-repeat;background-size:contain;padding-left:34px}@media (prefers-color-scheme:dark){body{background-color:#222;color:#d9d9d9}}</style><meta http-equiv="refresh" content="120"></head><body class="no-js"><div class="main-wrapper" role="main"><div class="main-content"><noscript><div class="h2"><span id="challenge-error-text">Enable JavaScript and cookies to continue</span></div></noscript></div></div><script>(function(){window._cf_chl_opt={cvId: '3',cZone: "publications.waset.org",cType: 'non-interactive',cRay: '9133b86eb9ef4422',cH: '1Ner0qnt5OFo_iLYCQq2Sjmo0E2KhcA_T96ozbR.E6A-1739773739-1.2.1.1-zqZNy27WNbcIOrAEqQRIffxKptIwFACIAgffhWOKSl3R43kzPHLDkz4CIG0FtST6',cUPMDTk: "\/search?q=Kyunghee%20Ko&__cf_chl_tk=qHN0gCRh_1xmTm_BTITwBw3arhA14_B07UuoXJ3ammQ-1739773739-1.0.1.1-wt0zu10dG6f4VMu6hRPOycCeTojdgar2iIoZAEfkykE",cFPWv: 'b',cITimeS: '1739773739',cTTimeMs: '1000',cMTimeMs: '120000',cTplC: 0,cTplV: 5,cTplB: 'cf',cK: "",fa: "\/search?q=Kyunghee%20Ko&__cf_chl_f_tk=qHN0gCRh_1xmTm_BTITwBw3arhA14_B07UuoXJ3ammQ-1739773739-1.0.1.1-wt0zu10dG6f4VMu6hRPOycCeTojdgar2iIoZAEfkykE",md: "58FYzEPj0XHWdWxBPPruXBM9D6N8riPjEJ71ultTeC0-1739773739-1.2.1.1-t6IuUYBmaRCek.fqFBuKgXlnFL2BpCwrutCFDx5DIVwesR2.Dw_Q.nzqm1HXVJzaRkV.4JeelMo6gK5NDk.IHhyGV_FxUPxs3_h0Bbx7oQJzyZp6y7tPAjGNNnpwz0pah.CSqsZtCAgKZnCeB.dn56oHLVyi915U2T_AJP5agParACyswzgQv1ITk2ffB2Ay_oAFs2gEsp.dYNiJX33sHwKzJs1fK3JNx7qZCTiPtMcfdQV2djMef21UfjP4E2jGpyFj0yw3ybUW.JmGkouHEa0Tll9cbDrpUCdykGQh8wNFRbQA7xocfmgGGIzYKZ8zl1hlgiOEJp1yCXSboe6QbXw9N0b_vqwFss4GhuQLBHIHDqLnGj3D1K1EU0N2DnOS6sKKu_mSUOgv2zSZgJ77gwqWmKCDRPoGefXQRuuVlWGywwQiPIuXYiVpglB2Rr5nbETVWbcvq_WR2zIA1CJYp1QcXLe9mnmDWlsyb_hw1ry71IYn9A7sSyOLhQRdCH9am5zvf3TV1fLCRWyvbNbGBH_LlidakOsQtN6.I1SWsbO7kK6m1KlXbpXWrp9G.p30xVavNxS1t73qJVzFW3lX4082PGt0rxgaB7acrcmj1vgQJ4JLw9GFCS2MGTYwwgpHzSrR2.xOFQ0x2VxtpRSY29MUQ2XSW7XqA89tCwhciD.kUWhvxOo8an44iZ4Pft93oTYhCo4sisg8HvKIGqfI9Wl6nlfmLEcp1fMAuu5Ux5WYYNNJI.sdR2MBxmkMP3.EWhASCvWiPpIoOqKqgV.m3GyGOX2k0gS1Y9LfIkvy5k.ngFNa7V9O25A9sdsM6bLAuQiFPeimISoC_f9Ga8a.ThvPv0qGZLpX1nYJDPVBZBsfGs9qAOVlioTCSmwqdSySZ7Syk5p_RwWu4O5PlCV1kdIJvK7GFaSoomkhfHYBquZ.vu8A8cQ0VetnogUSHHYAqAgwgdSNuua2Br779n5wSSb8utfK.P7yuKL3SKytqSdEonDsynHIhqm1qi3ma9D3clvdny0HV7Lqwb_T8fAgZWfL6qZrN5nnsaqMsv_Vp3s6r7U_rkHhIbD4Qr9iK0evboufKPPA.lnXz0RW8vUtKIfv3SgX_Diz.P5gsGM.1IgQw62mrPvO3dk8eLFLI8dJO8PxSNqxVy6c3IsLfmDNwJz8nbHrZTO03yyfsMziY6iQ6JAr5S3xGI4GciWU.VpkJ7XpAx9Ze0PcBSzltabi9YfjnW7sJ0Z__Aer9Ob5v.bBabQ97gFuYutQaKasX7dvGEluRTKOz8hXflJRG73.VO3FHtx1Eeha5.8MJ9Pew55VgZxC5A1V85jRH.N4BIA5Zls9Z9JdY49CEcE2ACiSvI6GjcYW6ZmdnTX9_YCN1byKxRV2HNh5DVhgrTCJ.IG34YoL8EDhHZcb1PlJX17.O2IeMfuys.wLpGgRS1I6kInFBgV3VfAiNeTwA8yNvzKzr0ZVZVXCPSBEz5P0fvnrjcMhbYDNvN23ahLONTMbZbm69JmHclai7unVlQuz2AvPCmrFjdD_JCdJTKtPPHNJl1Hfyfww6qbWU..rYrQHnHhIFqGj3RCD7RWe7nsm317pBPCpzfyx8vGT2F1P6OLrIbq1UldHtwGcRuwvDOp4KFsoeh26WsNqCekqfYWzXKP3CmAjiqmwOAdr1NKC5CQj1YRxeyuvnge9dgac4PVqHeyf..RR_rn39t.Ixw0PgJW7tiPoxDB8.fMmkBKkXCA8pwBBywQp2HPTpLFVwok0FQOvRFkXqexdQXIigYlBs9WofQZmqCEMWTHiMNb3DEm483RlXdR.OzppbdSn204UN4LocP602OCg2SW2pxMEs1DeCBNMFtDDk7TnKeUJWPwTVUHPeUwwHmC.RwF9woraqATnK.VN4dE5d2bMbRVBUCiw",mdrd: "vIWX2g1gFqPXcHGG9CuVAQAO.bmjThHwTO8ljCv93fE-1739773739-1.2.1.1-n6SRjVLd0lM2YoJHrDMceKVQFl2EG4jF6WDXjSw_FY8xMpMQYTIWvO_0DB.G.nfuuQbRPqVDsa3FIaEeTUC3zutO_GPHKGA0jZ2XeDL0XYrXqB4lLTWXRf2eShJZjlZ6LYCdUa0KH3DN7xaVlFoEg6diB9hvK_35_Cf6Mmg00bmSeZ1X_AE4cUn1m7EJsumi3C1ZPZaoETE8gWixX8uXkQLpLJe1cTVLOeKrM2xt_DDkGqIi92H0gO0YTOOS.JxOYh0s57L6Q.fBrIZkYFgyAMgr5wiYFnuyQ.JjyI0UzPl_sn57eJJxtuITu_F_tiXNlvyfnCj7iV2L6nYVK6T_eytybIrsa3e9Ki.cGK8Cx1yGoY3MlJrJGL9g2kl9UbGdZTrFxfoa0VfnXyni0.kW7Ff0.nT7ARNBqYqonW4Y3M8JRHhqqwLCZ8wyVHRKOC_80O1zJ4Dwpi_N0olyynO53AVfyym4jHz5SF4PNRmziBceGUrtehvM8SHiJQQm4jmTEEC516Tqlo3.U60l1k52Ph4rIWpe5HUDU4WBXjWW3lhIUm0gMpqFK_5JJkprnfmO54avPhu_47Uo.B4Ar3Ib_v6rUk89MWuYF1wweRGvGVkmTmhKJEmwtWVnCepaEFFK0SgwOOhEVMjO8vEBc2.t7.bP8UnhVHczX6h8g7BkRLc5w38jyma6JifOwyhgheBnnwFtwKGsfmDOXuGE05KX7VM0_gxLCHuenP1T_pnFjRGU.ZOJCZ.kgYQDQxeo0rOASrKFanoMeUGuKPgV7LR3NRFFwyIuqm_tloapY.ieYq3hfOXlJWT.e.z05zMGrmCxtkJe9gzfiqweUIOPiJ9ldCNVLq8ZY9J0S9QsP0kkvQGKy46yFacFJjGEq2la3prRYJWYRaQ5qDtPEg.Ls8VwtEAsSScHFQf23EPn0OX6jEX.KySlqcd2NlcVC2EevZjoAtMrt.AARS_LiY0fnGWVPKyKLWlW9ZOT3YWwN3JFpSgbqOKmXQySXb3.kGO48kGGrJtJ_4A9BSmYoUzWkW5ZvkhHi8DbCeUfGTLtJ1kciZnKoff.D6BwpRMAH.chhieSDdcnKhry6zZ1yWGYJbK0Kg6OAK4dpWxOmUzZHzuZgXlPPYJZeYNST8s20OF7Ue2R0HIJCLyWL43IAZ0u3uVq4PXuzdIABofsOHqwUwiDaVWbuJ77NiY6fDTV_8hp_LAdb9buVlkBlWVNXwzsdl9VoK066CpNN6m.T1Y66RfbrvtClB6fnt8pDG4N3AJHxXAoUS0xN7ZEoQ1XcdQsq6sWZW0YI7X1LZdJ.EB9ZktoVXVz7pc9D8Ckm5ezmR1so4mQnpy1mJiNOVtwDZDfZyzCh7o6IXAEAXQO8bRqSB41Vsy20BO4At99cIfgzMI14JT7F83RiiAaX3xwL.PRzqCuY0zUO55PJNWYq6ktIhPCTBSCfDy3LTHwVAzb5PJJdnoQlMwQJsclvRzanjCrNFNRkXoZuBl1jfazZC7HuUzqhT32MeMRbjNgQPkt..b9lnJtMFGOquiMsvZWV6.R0Dum2w8RM9y.jVsUZSYeZl0wDWSqj1BrDnvZpALumr6H1khlXSNgIvMOGMpWYY222B.iEjtQ_gzUJ5FR4Nla4SfNvaCoTUgIWrBuDMVEjT2gdLkYeekve9XVOtM2epjbW.WQVxPdL4hdPY34cw33pgYADg2UMmqDYaN29vq9ivI4rTwN7lk6ZmlKeHhGDAet0K.srKF8odq1kYT5RVU5ZCGUWaXHQdgNA3rPPAc0zK4Bu9MFhjKxFyF0Vazuy_eILpD4nPTf07nVWmKkg_EY9ePHF4Xn5yb39W8YliQpb42S1qg7LLQETxWD1XjX_0e.GXCdDsn9jgJVZEPsX0m7ib1Rvxptfpgwt29s7NfbxjdT30vheTPIzYUTztOc1z8tLIAY0gbXn3sFWE4Y2stdbbNH_X5gy96fSYM1olCQZP3qUUXwmdKihTNv3tcAxuCtNP7hgQ"};var cpo = document.createElement('script');cpo.src = '/cdn-cgi/challenge-platform/h/b/orchestrate/chl_page/v1?ray=9133b86eb9ef4422';window._cf_chl_opt.cOgUHash = location.hash === '' && location.href.indexOf('#') !== -1 ? '#' : location.hash;window._cf_chl_opt.cOgUQuery = location.search === '' && location.href.slice(0, location.href.length - window._cf_chl_opt.cOgUHash.length).indexOf('?') !== -1 ? '?' : location.search;if (window.history && window.history.replaceState) {var ogU = location.pathname + window._cf_chl_opt.cOgUQuery + window._cf_chl_opt.cOgUHash;history.replaceState(null, null, "\/search?q=Kyunghee%20Ko&__cf_chl_rt_tk=qHN0gCRh_1xmTm_BTITwBw3arhA14_B07UuoXJ3ammQ-1739773739-1.0.1.1-wt0zu10dG6f4VMu6hRPOycCeTojdgar2iIoZAEfkykE" + window._cf_chl_opt.cOgUHash);cpo.onload = function() {history.replaceState(null, null, ogU);}}document.getElementsByTagName('head')[0].appendChild(cpo);}());</script></body></html>