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,PHN2ZyB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIHdpZHRoPSIzMiIgaGVpZ2h0PSIzMiIgZmlsbD0ibm9uZSI+PHBhdGggZmlsbD0iI0IyMEYwMyIgZD0iTTE2IDNhMTMgMTMgMCAxIDAgMTMgMTNBMTMuMDE1IDEzLjAxNSAwIDAgMCAxNiAzbTAgMjRhMTEgMTEgMCAxIDEgMTEtMTEgMTEuMDEgMTEuMDEgMCAwIDEtMTEgMTEiLz48cGF0aCBmaWxsPSIjQjIwRjAzIiBkPSJNMTcuMDM4IDE4LjYxNUgxNC44N0wxNC41NjMgOS41aDIuNzgzem0tMS4wODQgMS40MjdxLjY2IDAgMS4wNTcuMzg4LjQwNy4zODkuNDA3Ljk5NCAwIC41OTYtLjQwNy45ODQtLjM5Ny4zOS0xLjA1Ny4zODktLjY1IDAtMS4wNTYtLjM4OS0uMzk4LS4zODktLjM5OC0uOTg0IDAtLjU5Ny4zOTgtLjk4NS40MDYtLjM5NyAxLjA1Ni0uMzk3Ii8+PC9zdmc+);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: '9136901ffe5b3f80',cH: 'mOcUnmgI.hs1AR3yvA31J7VuWUOCjZ4gr1jUIIwSYIs-1739803545-1.2.1.1-.q5Ht0rMuMnLIaEJiYtvlnDAFojp2tHRuf3ROkno9WFUx6dHgkRM1FjRITr8crEb',cUPMDTk: "\/13626\/harvard?__cf_chl_tk=DdfrEljUV9YjnWjlEvjU2lSw0w5Rk.xrWAq8zUPiSRM-1739803545-1.0.1.1-Xf6g8OaTfS5ktm9QCmx_xxN6lGUxvXKq4dtAwgcI4A4",cFPWv: 'g',cITimeS: '1739803545',cTTimeMs: '1000',cMTimeMs: '120000',cTplC: 0,cTplV: 5,cTplB: 'cf',cK: "",fa: "\/13626\/harvard?__cf_chl_f_tk=DdfrEljUV9YjnWjlEvjU2lSw0w5Rk.xrWAq8zUPiSRM-1739803545-1.0.1.1-Xf6g8OaTfS5ktm9QCmx_xxN6lGUxvXKq4dtAwgcI4A4",md: "r3BCIjY2zynFAG9EZhcJqDytbgQgn2YiC7cXvPUCJIw-1739803545-1.2.1.1-SehnpyAdrtsPSiFbaDk0kNF2odqjWET7ABHXD9_uzCWp1LzV.lbk.dhO6rV9hKYlSZDW6h5EgZM6F0.0FNmZg6XerR.gL8fHZzUOkctfgaEGAvUuotr1EQhs4dnvHiW4C4k0J92Y5.2YCI5jmwD9GYM5gx8UxLgSfr3NS69TkDfO0yiVZJehontjywTMJzh6HXlY3vtgHsYmMcwv2OCX.MotgMnQwoiUn6w90.lWFVVaQ0gDlcVVKkEb23NxOqlVmrqkR4G27qnPoI0ZXoC0N66RM2a7enwy3XXyss6Gxw5uUUym.SR2DE_zpYZJ2h.AdA9LgUPrz887ZsMkJj2VRHdx0Fy4m3fv_Y4HYTtr4HTErIM.lDfbFgDqptbGY1j1dA.pp0nwBlw7vUnx9We1OszW7vZrcKBsaIZSO.1fyblsWDOWAM6dTurqwln0roelZwZueP3JRbTUgyZJSTTENhEFVMTn3SEyI7Vjy8xT8P3MbdI98RZnT6Z9Yu3wvZksIpFSvAxI2ea6ix_NCFkmEy9m_s7RMESPf82_87WSaLOSyJva8AqN2g_vJfbkOmC5Mh8ei4h8J64JpAOQL6m750.bPailxRzGy76R8p40p6VbtCY4KJgqjblMyN2w6J5XBH8GYVCZHM8JfKQLGyVn1k_e8BR1I.C4hRny_i9xIcmzeVtLj3SrOQDX.vharqvL_u6Sj_lRwxHsBC.c1JSyxtofFZW164BVtrpYOdUHA1tQ4_UCwFiobwWQl8d9YLd6WplXu5ECAd1RoKQgJHN02NQAwqiM_7aEBPCYwWmV1Tyf5X9KvtqpNxeiktKNfaPX0gkSmSD0iToOdfgS8MwSYO.LMWn44bKywMOmNje6g3ECNZGU9.XacgxvWTgp0ToM7P3Vk7eZaKkDxKBvH8O4LzCDIIFtO3LzgJAV4WdwX4xD6AADzoC1RGDNq7YNO_hYVRoA1kFfe_jgJ.riUkbg1pE2SjD9yJwzQ1xmj_yIJ93nxdT1N55sbbe0BFyq7gYmVpQYSVyDzkKs3B0T_W2nPGxXEv7uHYoPC0ryrY21D2Zm9jgxaShND__OC4TgVzoEAJbELwW1KMyqcZ8Z.j16W._POxHEViG42loRE_YcGTSZgQdMucYzQEz9Mx3Rec2EINPAEau4IHco1L2FNJ_FdpXVlxMY9T.Ri5ZXpmiA4gOJGHBbxQiM_2obDWxX6quakw5pOKAQCqk06tOWMdUI1EYRMlZgJ217BL12QIS8_KCGM.bfa5oJ1lD.y59W2QcMveUMzGqFKmBTtHMTP.WS._wRXIE7ecUg.dw.tQpxXLTgCUmdqkCBgj7YMP1aY0IegC0oNPrwWDygfMAorj34GQu8zfVfK70stuewb1VfDKGDmf3TfF5OEUWJb9MuAysRkH3s44ck4h.k6zYKaL6XLTJMoRMfYW6D6D7NGzkKfgbelsjb.aqOLhICWoJyLkcA4qdEs.3QYHOqiXH63z6FY12MnEfgN6EZ7lhyd1080ID0LbyOxTVanRKPxcviDtt4QITNPsd4sL.gcgY9RasywOoVmAbdJwYovFanQ2UlcKUxTG9zgDMH7an_1mv0EpQBi8.X1mRtbKMrjAKOcEvGnGgjEFjt2Szjg_KENaUhYT2a3vAorwRU1MoFB2T8FXEyW41QWulNbtth5z4hMSjEsMZ6IHM0MOQ8PSW7xxkOFm8Tcvi12MAhh10naLEviKYHY0kT6YApCZnRyk3n.AW9D3B3diAjb.rctnjU6rWQpQegIpxfYHSw5d281wc2WvDYRG2pOAAd6igAkLcKmCN.QsRRzxU7N.EECM8M54IKMK7QXX0aY.Akp9sIUZ5Nj9BhiK4WuylnQKEdbbun9vCebizpkZbv34.20XC.FxeTt4Q",mdrd: "5Di8eQG4GFU8Ta0.xYXMNoHnWGb8QF9vo0hwFmbdstw-1739803545-1.2.1.1-hxQtr5I3UYj5LjQcHLAmDSwDZGL6oCBF718W1fbfT6PtPmLOJdjuhn7uMIN.ozzmFmyiBox6xnOqJYAIh_2rXGQxpsqmctZWftPUyxaw5.s7.ZaKikbwxJd6cKNRiiAI3vhd6TIFTWI1Fq_yV4tsfjlhqtqKUACoqPnNjaDIYfvxkssw3SYGIEgCREOr9fyCxLn9b2_yys7Qx7AcFd8W6EnAJDgNd0fQSJoPO66T3t6zXpU1f9VWKYgqpgIv.JnGdeoFZ3BiMylbRpVUKiIaPow1k9yQLBVCnjjxIp7uq_KlPIpRx28Q3AiGY6GAuOBIRK16Hra0OvlF5FEIbDP1.MqLzvIuUOrPA68zm1QYYzc1tNH88_pQx6OKh0Vh2xuiv3sUwG3nsm8T5id4DnN3V3wpQLmfjKvBT98ACIYG26XEEGfp9R.vSGL6CYg6.sflck1NqBj3tFuMcyzfZ9P3P.aRWRsTKQBCb0.5yE2xCcDBvVRaRUNkrxxWJzz3yt97TD6Oadk1MB.Cnz_LJXGeLRSYEaTFazhLTMGNzYF65je6dmyggvdm2BD5R..gRQZ6rxLA2ikATdgzfq7scUB1F1Ib9nT7zJC63k8YeGQAUZWCeX3RvKTjADDcHip2MZza.vhgcZNhmXRrQniPKPeb26KXaj0MMxuopVaL7GkpaP3mcpguOE87rzUMYlsjHlFP0uKMLR7AC0h4EdU3M7daOC4fBez86T4IdhMO0AxhV3_F2xOh7T679GThw89Bl6FXceS94ds1Jo_BttTrzwarZ2aQw8DW1XHHfeSWvmnANycNBoW991c4sAAM9mVv4NoSQeCh1s6qqm2okmn9VsiNjQaiyC0WDnIyH5TzR7_8cR5xFiZ7IdWGZ0moYuNI2pOli5FMODQLl8DmBQFLWUAkb72hADIM_RUFHlXGfnbDgC9Sdn7GnJZsuypq2.DzGhHx3MJqUJPRqqQqHxwWLxl5x06oQMfyPynLy0YA4h05vW7ideifXtBwcr3M19A2l61ROWVamzYP5VVsccIrZ8b82H71J.MUrFPxzhqE0gc3uNcMyr0ZT7TJITewhiuaqmTg9pBe2I5jcKwFIqwLRgIxuDU0eFpcICL.RMAf5n9Xf3owiaVJZkGiyRMGU2E8z5JThvGkFw.QFe1_WUySe2CPRN7pz1R9eC97KGZlg4O3Wi3nWXiWZJihp5DXk8M.zb_adyW1qQJ3.ukAqZn2Mh66Qak3jB5yaffGoWEhyOBU8OXhRlkWde0gDe9EwlGm.xh9dxwUM64Q_Cbr.sSDOw71C7VVDh70kuMBeyPD4yDEpsJ_Dus33GmF6AxXxk3pGsyemQ5Mlk2aJcMMNOYljpzETAyhFzOpBE9j8i4LzI.429O1Njik5J_6qyucpqei851_s0pKMuAmDY.WvzGZ4iyVbUz1MOCOhbTr4I8TT7Yvi_50k4Tz5_Dq8ebASLYoKuMCcdKLomhFENJRxYukjEAOCp6kBcZLlPyky5CyiG0.THI7IAXYGTmh6EAx0V27HMrw0j1puO1qtyIeVygk8vN1BRRXsTfnmAs0HyMME5PZsgJQbDvikDBwmtCmQzDo4XGf5m5lYyZ0T75e7Ctf_cEzmN514UMZ9dHug73gm1jTWHs_TMKTuoNnavx9bjKPqOkMSON1iY0jq9F4SQf_kWjys1ai8XHJeM_76UlA0rWTz9xnUqR6w5vlvDzXS89_XUG90e.M9zO7HoOWqs5PVRKLr7qalGJ0yHm6.0GXstJIB0nnklBOfgubmloKD_k1HdYMUtl3ecDADHz_zRL6laZQ14oKUBpYnsCFxDl.zHKTbAzgnfpZWGx10GilNU26vBcCaRUgJsn9IqXV7HYoh05uJVTa9IMp1.G3nGY0Vhz9N06xftzaSM3Wf.C20WDUhefhB75nEZplm52mc_zDcFZl2_G3D4ftZD9cgTB4eWuhFujRcSamD7b0T5douyc7JrBklvfRSEEvPLrz0QxnvIenmw"};var cpo = document.createElement('script');cpo.src = '/cdn-cgi/challenge-platform/h/g/orchestrate/chl_page/v1?ray=9136901ffe5b3f80';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, "\/13626\/harvard?__cf_chl_rt_tk=DdfrEljUV9YjnWjlEvjU2lSw0w5Rk.xrWAq8zUPiSRM-1739803545-1.0.1.1-Xf6g8OaTfS5ktm9QCmx_xxN6lGUxvXKq4dtAwgcI4A4" + window._cf_chl_opt.cOgUHash);cpo.onload = function() {history.replaceState(null, null, ogU);}}document.getElementsByTagName('head')[0].appendChild(cpo);}());</script></body></html>