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: '9134bb9ac9fc406a',cH: 'TmchAmadOgObzZzUxnR23e3SWz8urH0c6pb08O5zGrQ-1739784355-1.2.1.1-WHjXtkp7SUb5rg3SudXV3ezgPmUPUpDAuy8Kt3G61foqDNNnM_hYvMCj0C1n88Y6',cUPMDTk: "\/183\/harvard?__cf_chl_tk=WQEtjr0OKG9VG4Nz1skSBMrygXL8iC3sGOVuu55K2GY-1739784355-1.0.1.1-HSto3XIlxw2Mlx4Fq4JdB3m4eBIU2OKLkH1UHum5VJg",cFPWv: 'b',cITimeS: '1739784355',cTTimeMs: '1000',cMTimeMs: '120000',cTplC: 0,cTplV: 5,cTplB: 'cf',cK: "",fa: "\/183\/harvard?__cf_chl_f_tk=WQEtjr0OKG9VG4Nz1skSBMrygXL8iC3sGOVuu55K2GY-1739784355-1.0.1.1-HSto3XIlxw2Mlx4Fq4JdB3m4eBIU2OKLkH1UHum5VJg",md: "xaV3DYn.4Tk5Pz.eTVguVRexpADfs2BuRCWbocubrCo-1739784355-1.2.1.1-cpIib4Hb.EijJhcOQwsF6bD1UeBr6pPBvkmVolUzmSDf8zMrry0wz1dj7bYjxilU7nabi5VFd2ROCzrwO9tBmf1IVeQp0z4FUbRzIv9.zaXVN0f1Oe0VaONCXXrZde5q9Pt58yZh_fuym8SwBuS3EZtBKgBWJEDPLZDUVFxoOQGqct7oRUvVbYHGsVPS6YPnxYXmt0phJut8MxltUkP_ZGY5prGsVaVXsGioiroWRY.Neu0USFtDcmGCLdWb9OtfXM3z7p5mMfclePYFOtv.xaa528j.otJspnbmdwTupNCr7s1okN.xe6.EABFSN1meANaX4MXFkbFRhivtB62b1OcS13Hn4u.8vTfGN2K.8hIMBSF3Wc5zzk7d.Oc4ouoRXI1ui3Du21_.CvSkbHqmFSOkUr9u8G3xu5cNZSUMDd_c1oZJKAi7UFtJYAMK3GvZusLEUN8OVEcVgR4lZmtbnSPCmWs02HB3k6bLmjhVonDvBg_0e7FyBV1u56GYfjwXLJSgA0.POXmeuAjHD5b0pezgJlvPetkRBFCHBZrZZM2guZSpWp1kCvTEL2v7MAekU9e0JGT4c_8oVmGijsGkfTJ_._Neftlg_E_wwyFjprmYgP6zXp4KA6__FMJyLhsLICO.RAv0qBDxwPCcnF1Q3JrfZunIDasxCPwxyE3kTr9OPV4lFakCv9Qg3fEW_pjLBgM74ecIRzl44WEbBP2AaXlcFgFk56DVKP2DbJfrx2rcdaXO5BMrblmA4P1y3AIAN2eudsD9NDcnqGzeNeQGjUopgzlL2qb9uod8l9HTc5v7RsUwgGK2ES0nql1z9k.D1sn7lOtw5l17q4tFKIZ4_sN84zkzStDPmVv5q87cabwxKHs6IESpK.kf_WgG2IxT86Eh8t58pbQvb8ojOpScbhzzYBpjSUHMp3BfKL8WxzILOafVkpwcoK8w0Qxg_wOQXdYLZnOazgPH.Se4A_Pdfy5nW6PgXmmILmkKLRdXjJhv_Sm4Pr0TSMvTSmwjeIz7EG5pIQyF_dKDAt_lZY7onVU6TG38zo5N0exSFCJNnK0jTHRfHCPkgPYpGE1b1pTFToT724wODx_akLPKoQg2VgA6GlsW.RL7KAdtKpnUyKysMtcJ3eWhgiYHF396ycSUOtpzgibSb62qAHPrh.1Mj9s6Aw5xs8PXTr1gW4O4.qZxwH8.x_K6PZyRwt7S6uNKngz_ro7Ug6kM6kTV__vdlk3K4vru0wb5J_B2vQpy_1kWShwSXHmy_kEOz4wQmVqOgLpiGOW9auJgj3Hla7gcT36pBYQK5s3aEJZVf.9wjQ6rKzf5A8LVVDMUI.JmJLhb5DEN7l.cXkActQQDkU6LKe7JQnY4c1DkWnkWV2Q_N3iu2KQ1JYs1iYxQVcszYpzVOVSsMWxwyrYiGENWBoAVTKXXF2Ko_tyW8HEH4oYWrSd3FJH21w8hzsrVDQk1ca11QJ3r_ES_9PwcfgGGxnkFEeOhsRY9rhxPbRtMOeOMqKISlwOHOnfBvWW4eIRcoUc59RJf6IKslcdNCa_IafVFzxHPBEGqgZVlhyln.sJALUJEbzx9voRr_MgQRgWXnfklLMXkKFSaZl6J0pMsXEL67ibAP.diyf6Igd3ctA6rc1svOsbv67hCUZgMycdERkX65ostwy2KJwaTWarZG_ye3ki_CAKYc1YtAgHxWt28hVHlLYe8CPUIw9E5fxMLBSwHICURvXjk28OgBDiaBP4xOyJ3eY3Yjm6zxdnA19.opmcnGFXauxGZ04fO_zVPlGPj10OQSNJ1v_Y7ckqUxh3_ChytQELfM1QOnXIdZyoOk8J_vKxaET1DimFzKUe1fjH8y8cIL46k8H3yY_HcXes_hshSAZ7lL2GpdBT6nXi6J0Y",mdrd: "t02xTttMYuaIL247c36zK5oxhGF7ZgH0NT2yhdr_w0g-1739784355-1.2.1.1-XIlBcdK6K0qqafgy6Ag4YX3hOPZzcIanq6sxYFNGp59hMQ_K.zkGQenwI8IoqLBjYACJ0jDhPgRGCROwENTFyUZZEENI1_JztPiFizy0TN6qLVPNzPuNnUgU1LLGQt7Zp_FOZqDBHztlOxUPXHK2Uo7wlE7LvNc9ZITxUVc_1renZiJ_RqAi14h1.SHUl_OVsOudN4Em70Hv4XR4A9pUv.7wPFx.59zuy9Ota6eXcf34JH2YBEDyIcb7Q3PE_gGvcRaStXqk_4_sMgRCaMPYYIs8fJyuvhpOngesCmDifyomShEdeCROhDKSsCoa06LhzFuXywU9wzdEKmqlZfRL9Dl5j6IKfM0Uu1LFJe7OtmuOb0AG4A95eJeolkEfxh4r6bvQmX2tzWTzrSYFiKfY8LugVCyT6WfwTAiL9SezOfGTkJJQUoQtfmPsYgUOyGCl3tH9KyMxQz.sOJMjNmEGf61lh4iHHFNdoRun8A0gUl88Inl.EH9h8X_9djWt2wKlRcU6kxxWdq9EAU8GVhDdRX08TKq22jtjkU7CkWbYg2lC07Almq3wM7ypGrNpl7U0ECcfegqNjLhPWhJWY4rLmd1eagDlqP.y9UQ8cjwuyJq66hyvbue.WLNhtHT5T12VcK4z1yrtu3qifK0flfhW68cm3hRNnOEptjY7OO.7L.X8gxrwVuSKVjebSAeybFLlXRlY7bKydYAU29o.BQe2CbDix2w6IOko249vvoJPUJAjGfFcLqchUsGFCp.IEEjidqU_cpvVdNSMtnN2s9qegme9WFVwSBy27_jWOffZDWdPX4.1PIKNR5iQMBFUaUsK1.vMmDpK34c_KfTIxDdvZCHvs20XWnAVDV7gXB3ZDBm3zuHapwuAKr03s80cYRkxY1SOCKUPAm5q4mx.k1THE_R9s9VJ5jvrdzDJtZVWlIG86nMvnEtx8JviQjzJqz034rfcC_a971XpNWrML68hGkAfwrH47stbLtO83_t2fbReasiW7Uv7mp26L7Eky1mbzhfaBCPWzdsZ5CwURNGk6rbzWOgsFcqCjQ0qnIu.TuGC4NWJiKWyA6BHgM69sLg7EYmK7171KYlK0lkyW74VQ.bikvQWk03LOOc5NIq1kNhq_BT0wYW9Bfs3y8k6x2Ffds4Xq75BKMnAuySfTnvTMUDVgIF97sDJj4bT52Sht2A0KEJHAmziCuX3J9Pu_2v5Mha6clCyjNIKti.cyKdJQ7YRDGBgYuTHdnpAFrQZ9FIxd2VAk0a04G6GwrB04TMoVa1FKCmCW5bj5vh40Q_ILTNOiwbXdruGzbjuqs0rY7IgX.94YbaAFmWCQZue2Tybncl97YBXidH93_aZ1P.4Y0uFy0XSjqduK855Sm_VA6XU5CRIkYVcsYK6MMQLG9PwXnt16bPmraZ8YdxSdBrCAb1AISw3wQb7ihOuY_VI7cnKwoNNMKva1z9iGLZcAyO2OVwdivfgeI6G7q3xnmWvimcd2rhUg22R3jmb6FiCzkdj13Tt58UCKzjpAyvTp7UHgwON7xWcjk_JtDf.Zk5cdQnzVK0tQ9aWPPqaN5KCaPhdLPfADYjvDGY_BRq3zDWw5CXMHpPBv7ZApi3m46sdpbXKZHEmhO_7TPdrE4MG5szq.SppzpSeydNEkmP06PK6VY0K4AJ6cBcVi2Q3sMtZWkR2WiquWsdBblAAQabRbO1kUwZ0FXu67IamaH0es9IdfQlpB61vVVEYAKdC7QlXw32SMBIpaN0C6gQyWY_B1d8iEa3E7zY3rje5SdD.x_RpK5V1_HT2JfVUrUYgbKlLnqRriNxuC7osDHqdSmBQEFtsjMy2Tpp6BLdtcq2cQTX.bJDU2SAJoTZmAs06.XYV1HtqMudDVRqo499qckC_uvfvppEdaKsRZ20mY7feK_KiUX4kMq54FjM0k79fKOoT6K1LzSFXDVVA_ybJCDMNlw8"};var cpo = document.createElement('script');cpo.src = '/cdn-cgi/challenge-platform/h/b/orchestrate/chl_page/v1?ray=9134bb9ac9fc406a';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, "\/183\/harvard?__cf_chl_rt_tk=WQEtjr0OKG9VG4Nz1skSBMrygXL8iC3sGOVuu55K2GY-1739784355-1.0.1.1-HSto3XIlxw2Mlx4Fq4JdB3m4eBIU2OKLkH1UHum5VJg" + window._cf_chl_opt.cOgUHash);cpo.onload = function() {history.replaceState(null, null, ogU);}}document.getElementsByTagName('head')[0].appendChild(cpo);}());</script></body></html>