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: '9134db458acd4090',cH: 'UlkubDyb_Tz2S4eeElLU1Q4RpAKPhcYX4slWXawEuII-1739785652-1.2.1.1-JutBUbQMqGCSTcItsWvv65PZmXZWYnvmMtU5CkP2ZJR5Np3dHz4EehCuQYlxVf0c',cUPMDTk: "\/10001456\/harvard?__cf_chl_tk=.amgjPf3JcOJtbqhCyVS4iN7WToQGsUchxufRYH1Pik-1739785652-1.0.1.1-ADvBGraaAGoVKSOmdzgE73ewZQqVgY65SvN9aKD.udU",cFPWv: 'b',cITimeS: '1739785652',cTTimeMs: '1000',cMTimeMs: '120000',cTplC: 0,cTplV: 5,cTplB: 'cf',cK: "",fa: "\/10001456\/harvard?__cf_chl_f_tk=.amgjPf3JcOJtbqhCyVS4iN7WToQGsUchxufRYH1Pik-1739785652-1.0.1.1-ADvBGraaAGoVKSOmdzgE73ewZQqVgY65SvN9aKD.udU",md: "o0pc6svDfNNQgiRnjP5BqSc05aOlDnBMNozR6jOTztE-1739785652-1.2.1.1-U_SlnpJxIJRr0UD6U1Ad55YX5tZbdaxvJXYls5.1E8z4d_izPnZMl6RJgQOCqIKicWNp6oI1CoKg8YNlnAC7JPjPd5_NzW5L4kMX_g9zGr_VxT2YaU7hlkHioCz.F.CLET8IMcc8dXN0iw5L4u1XZyQcKiMv0jo1KYsAihFi8pePaRm_BPpIyRYWvgN48UKVfsOy9XXY1HJCVswmjtrasNif7_u0yLyu7WVbBec1MtI1Net3qlnfhkmqh2T3DiGsu5r_1McoDd_m0U2l524GHWm9z2IoNqSZpf_RF_T5WS5YqdxzYJWIQ6VpWg63zoc8XGbK4dKoEbQvmdzWlRy78KUaReopujLXMhIQMkd8a5xPKFCL7OsPp9QuS9vMs7s6ywIgOSWaWwacYvJE_es7VdHU5eZC1Xbh5FXvNTr8BdUOycxQsF.qReZUfGhkc9ow8UtJfzxMIP8i7As1Ni6EPThAue0PmtirLKdxuA.X98GodHoQA8caUWI1lREgFDkR2165JXAgOFcwICUjCeZ9cTz011fR8YhlOeO5TMOPLfs0NM9l8oyfehzffIFNLDyWEPKDCQKeMQooBGC8iM.qSZXQk9vORBBqiBstVN.qnV26Lh_B6HP9L2t3wjmkJ_VLvkKjXMVtK0BiJiuv__7Sgq3r_ZNdI0H4HU0cPRVYJLIsjP6nChk.yluAK41fdeJdnCHRWl3FJ29j_mM3ZTsTmN_sTQDquqE48c7r3xcmZDejsVCKrIMJ8yfFfpM2X6I.FMfZL5bLR6bCDnBZavsFCN1mYF64trgheH_TOHXfFVYz_uWX4g1oL3o8r5ou8BK2due29FZec4naR8Sjxz7hcaXHe3ntyBUsCI.bS1NhrN96aDB7uMRxSdQqUXvyrC4pXknzBacqkbS0J253j13Dd6od6JPylw5ihzci_2O.rRAN8XWiISLraYG.err5gQ_4bi7TiCLTb.JNIvdMViaShX6rKh9iGbJ2JMXxuxrOoLATEUNNVcAkZw2ccKdXqgF4fBG.9wkmE37YpO.c3QRA0QTN2WySbLlcFor4MbSW50T.o5iLiB4vlOxUnRw7GfjoSXpViFkB.NyZtYjAE1PNXrjKKjsikMoVkktR4fpbGQg7DMDILn5A3TFsXzqt7WqxRK6pCo3oWeOVxZBglST5d178SBlLDE9tUxJm6pu3JMuM4BLme7uKmdwxmIKYAh78pxhKQ.FLURP3atMXK0fCbiZzqGRlPoJ_13dqvlTQn81OeScOTsknzqL3nSximarsMxocXI2p9Kgi.lsSO9Jui9tP5SGx95J6gvi2.VPjBTGSzBIx8o.SMGcuD3BxFtcU40e0gEslDj7pROD42IcfBBFb2AHvcB5gw.AplM6WBp.Zp38KZOkMNbMXE7na_aRQXqjfy1ByWCAUR8oyaJMadeddyopTVpu.pzEPIKwoBN4zYzuKy8rt5.DT2QKdIUuJ41v7pIoHkZiHJuxtwJcRsSjf2ph2IjjuSA3zxV3HIA7zntrOdob53nmcvYtUj4_zSq88rY8.fh1UaYOW61GQ..sRUz5_hz_n41oP6drOPq7.5.q5gI_ykKgaEvWD2uSfsY3fkLL4Jn.9fo9CHpppmF8M9_Lg7e7FyH84WStPKVjooVo8mQotWM3sBznAUxD6CEtb1mAXwE_ZIM5FoxqHy9mhFwBBeJAE4l9VCh7mdo.IZ7_K_aXypHhUbXTeeVGYRf8ZfZr7ovkc2SZcj2CjjJFj3oyhMCd6Gtb4zjfEDOBeWALcvmDHYhNZu2NlRvM34gZ.T1WEv_i3iqHr4cqoep_VmiMcC6yuY2PUOSf_8BIQvpYkXcgyXtESn1rWaa6fS.HHX2hWjI_Ns610kiLCaneJxNPsLo1s00X_bG.SQ2s",mdrd: "0PK4tfz_gdpy0HE8U6aEZNJhe8XjP5xpjldqRDswAiA-1739785652-1.2.1.1-a.SKkm5OXMtkE7gj7ZqqNzKak83R6MT7THBA6eXEHP9YEki3FB8GDjrIz4ksv.xL9gL1Fdj7L66MScR9681IaN7_WVI2_D.cIFtXpvfRU_UjI7tG6YeSn6qp7TDhs.zW5SUYCZ2gt08PlbqiibFz9Mn_SO5kXvIGjOayMwP1pyhA9xbuJBhcu7yBH1pn0tQu8ZD4BKnk9bVXpAk4WgkmrRMhxZlw_Z8PG.aGWImD_tbodwavd2zo9WBUU0JrwHkk6k0Vbdf03C4YheugPlkdAqv6X93cNptbuuvAcIFaNVf7nT0_O7AplyQ9I1uNe2ho7NFbxbtM30VOoSS6XBnyUHSJ6lGcwQTDmiapW18DvWfSiUIKv3b1SbyFHgLPmSw116exsND9zzfKo_JCnD532LR3zQAcEt1ZTh0VItaW3hRmGGgpqc.va7QRZvdQtZNYkOWZ7l0HDBv27EovMbXhVfXieITclReRyGpeCNMdpw0wglDJF2IMpcoT8YRh7pvj1Rkm2TQlEpUd1vBOv0OezXPhOeJF.tBFm1SPKVmrwV1T_8ymBe7cqe5wsZtWuzBlrlhaAftV..n.fD7dLnVg8JXQ5RVFlTNG2hw6xXyWqZi5i3PkjmyrZrTU3V_7gHDfkAilAgINqLrIggsyeSi.UoxckoMhahFj8A6G_f_9VrLWKRakOmPhBEfRWjZLlYzORAy3MxA7FrVE.5JF9dD8VWXXA78VJ5wz9nLrTHwv1eEepmBHsOLP4tNXbG7S4sWE4Rf4KUuChrIz1E66szVnXY0hXV3LGwAgkwlpkTOmNvCjpvcMJXHe2f48_DdYyvZbZR7x5y8f6TnjKGRR8kdBw_TKonZFdecp1cuGTPxfd2Me3HKJp2D3NaoV4HpP1qEW2gwdKZP8rifbR6xelDas5Wgck.CeZu4fGLFxl1TyFsoG6FV1YYC4iqpOiVWAXCffDsVPlJP8o4Il_MDT7.hBTuICpjtSU3d4lM2s.5X0070kAK74we2wMtdYe6Q30NW.magfe5Jz1OV_S8UYFIqFn0PdyO_N71cMIRRFVGe8iVwPBSDhKzxBTHi2ELE8wYgPl_8JiGEY0I96W4SeCofZ9cAb2HNPJ1Gnvg0SWMtRXxgsMlirU2etRwdsm3vKS4ao0UJCb.NyXRC6I14YUCj1tf7osEGXdUGtrCmkRD85J.VQkeEqaPbYwyaI3m9KBKsAseQJm0d840Blv5TL45oQXqQZQjzgGQftqBKZZmooHKmuej0yBh02wBL7p2yQh4pPk6OBzVkZ47iAfvr2Qcv5FPnS1hFq6__7.KIdwdH6yJ66kZczjxS4gqROYbifSmb9l0WT9c5bLIe6JwyQUzSKvZVzL9TG6WrntOPKMdQC9Cs6daS7Fy6pkguM0FToFr3CBuoduiYodC8jpVofTHdyqrykZZXv7ZJ4PhM0MIT_5h2D8g5dpZciRAyWqOEPlB4F0nY5omcpE_0Uah9jSCXbKehYolwujvHfVq14SIeXUHZwz22FXwFH9JAxWL4upyxiaQi13zpiATSrLtnzcBhUNhf5FLxitw_LFFiKiDzx4MaRxjYXbj9B0Oj7D8GUVw3SRx_BMUAtGkMUXNs28wDHtkriMWlNlI8a7pOeidlKAgwyY0f.tQkK_35p7shR8OPD9VGD3w_8zt93i0oT5lFyh60WAI7PzHeHRQay8.d.VOTLlUPBOinRKVgaJ1fS2AdBwrDm4eRTYnWL6GNkDVU1qZlF_VoFAlDVlVBmKjlZaliNJ7cGK4Dgm2oSoO0KsJk6aVfqjOv5.Qs6j1YZP9_zBZ6lbiGMkfnIvsAXWQWnrs2t7ilpAlIHg7V4POW68jvtgfobd25WujoiFmlFsfBrdAL_IpPel_x1WC6h8rw1l_ram.W3AdhBt5n1ejvxiWGlol0O9E3VXkcDwK0FtBjS0ab9kGzgtgQjW6iQ9_S4ojQFmbcab.nOE0eZNVCESUIg"};var cpo = document.createElement('script');cpo.src = '/cdn-cgi/challenge-platform/h/b/orchestrate/chl_page/v1?ray=9134db458acd4090';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, "\/10001456\/harvard?__cf_chl_rt_tk=.amgjPf3JcOJtbqhCyVS4iN7WToQGsUchxufRYH1Pik-1739785652-1.0.1.1-ADvBGraaAGoVKSOmdzgE73ewZQqVgY65SvN9aKD.udU" + window._cf_chl_opt.cOgUHash);cpo.onload = function() {history.replaceState(null, null, ogU);}}document.getElementsByTagName('head')[0].appendChild(cpo);}());</script></body></html>