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: '91513ff92f38ce55',cH: 'yTkfIjtsY9fZsc.PoZ3IEt4M2cX8z.eAv2acJdk_Ujc-1740083378-1.2.1.1-PbKh6H8_DHNEUlebql7ycSrU.oARfmMu7J2c1f_x5vFvmomhYn0xc9h3CSvRcIsc',cUPMDTk: "\/abstracts\/search?q=manhole%20cleaner&__cf_chl_tk=ps7XLjt68eTp4cdqs.xQDLJ1vPz3G0JrpEc9kIQy3Wc-1740083378-1.0.1.1-HcavgLIXrr9Cwxchoc5lAyV_jSPl6JAW1o1bzolsJEg",cFPWv: 'b',cITimeS: '1740083378',cTTimeMs: '1000',cMTimeMs: '120000',cTplC: 0,cTplV: 5,cTplB: 'cf',cK: "unsupported-browser",fa: "\/abstracts\/search?q=manhole%20cleaner&__cf_chl_f_tk=ps7XLjt68eTp4cdqs.xQDLJ1vPz3G0JrpEc9kIQy3Wc-1740083378-1.0.1.1-HcavgLIXrr9Cwxchoc5lAyV_jSPl6JAW1o1bzolsJEg",md: "qvgzYNihDJT9C_dDQoG5tZ5arYsI93Ilo_CRVzvxlFw-1740083378-1.2.1.1-q6bI1_2dtXqS0ctLXrT1VFfGCQz3o5BhxzIc.1zhj_Jqv_GQwCmgdez0SAhsU1P54pkPSTFGNLBMsPTmvIbCNjm2X6BXLcQiyQdniEqm1ljNJiJc8rpEsMrxdu0yUwXYkPIUdFH.v8ehkpZ8Zkr7jmybLrkQmw__GN3UIkwXRsaE_ZPMfx_T4xyksOXbDjBZwSEI7OM.DggCJ5xhZPjRKaoKw6SuqqoM9EXWvMcZFl9aVpYLgtg2vaoAfwIMTcgvdEX0ftZQdG89z_Nxt2dSKGZ.2Bw2bkX3ZiZ4qkig6sEZ88WOceG.5L1QacnBflebu_pAQnGq0whk9cYEn2DumIgZfCWmU3XamWv4O_fSO7TUkuMywYt9.IcEFNu2zybzG_I6VyFQKRH6h2QiwYbCm7lDw.3z4ncwFnJYAVZVu4L1OwV23tjgsGjpZadnMXIjx3SgUTHsOcd1VWRgrynGWvvGEMJEdiAgpWjnz2Tri6rLmL9KiijURRAsguTlUD1r.waJBxgejOqo2Zw4Wmawy5Sn2mL8a5rHoOGs6DLKQIVgC1yLtI.ZcJlzTkPfqdSUQ2WYVk9VjlSFIkxGwpXx1K55EdKG0Tvqr1NxGs4MNOU._2X1SSsX0b26iWqPNwkm_H56KxsugP024ZCSSVKIF.jRCh6BqC7M97Nz5k9Zz6eRMNYiJ3yXRxEI6HIXuIHrX99sR4K5M_ajGK.1xgUF02Lo3lHxjs0dW0RUW1sVGyN6MoesCMOfEBFRHpK.wgsRP4gXeSM_bG49Q5RE0pf7U0J9bHX2tJ3n37SnuTqC2alRXcin2FS_HVSUz.4CfcUyO7K3KrT85VLDoJ38lmDqDFIJGgnVFTVs2zbkNd92tnNiyEJdBaAJdCZ0sC4I99Kfih3v5Zd51drGEwqAR8acWMZmoHxE1b9ocoMLM.VSEQIqa3A788uNgDSWvu0qPW0cflWHm_kcvhvVTg4t2tz6CB4LiUZmWkejbie.QMUv7SkLS1c5SJtXr.412xZ8tYKtIw2SbQq_3PaPZ5VLedbXWJ_Kt9yj9WZfA.lPbIlu7Z5yEXr7ScRXICLLIe01xQXQj_G6NKwz3b92RXyO3KjOg1yb2xKJT4OvEyehw3aAz99IB_Z8mXmfY.uYPcc..vZQq_Uia8CewMrN9cmwDO_h7S.gfbR_e_B0H9LnMb0sCEah06_s8HwY3ifc2efMto96O1OHkAnoxFpRaWWw4hHB3lELI8bZa5fYuRM0kvvy6PSwb0PS5yw.hZfKa2FLP5BZHuWVGfM_qw7xgamFy1eGgoUsGE1s1hg.cAwN8csVMnwWew95QBqAoc9h7jXUEBm4aZ3NZ5tv6N8SitLATe2kKgsvews9dZcMIYqNaoY4vSfc6Z_rR4b3HsyHXPzI5ZAvwqreFuGFYPHJRs3MHyowMoas2UdH1O6BTCaGW8rTtLnkw2_vrS5DZN_Im2cuHp7.BpK72KkVT0UkTQFnC51lbym.KYYRhPhlVOlFIG8wbXtcVYRfU2DPev.3Q_2a7cY7NQtkeWy4gVSrjd0MvhTfZKVddsO4KyQX6weWTAFqU55B2srkIGHHq_QUvZxSNju8OexhfdIEs0G6YJ3Lq67vRYvflnoXjSWrgeNE.4dA.HhfCXOd_qpbG7k3ZeYnamfym3uyKOpAAECfnagZdvo9_6vfdtrqBmwu..3SzW27ztyNBgmrAneC_0KntAg9DhVeuQabES0A.A5XIkWML52D6vdeQ0F6zDmz6bTxiM52OePiCUy3L8RVp8Mw3AFPbF73NwL4Pp.Wql2AbIygEqwxup5VhEl6pOt0ag910Tr.0myKpFpLnjQUtlHx0DdvXRQfmeHaZ35Mnan5pU3E8waLMt6JKW6GbWXuchF9B60dAwYDxFTbb9TnUyS33O4HGbNBMVo.yI8pUsB8c9WbONoQVdPfdG1drz4V1NqKJzIDEmY",mdrd: "YwFg0MTvBrVSzHm3LUAVpLcpJ5Seqn8ncyao8vOzDns-1740083378-1.2.1.1-2vGHFqxrMwDti_n_M8zdVK1QZvMaeCjUXlO.AVRZfZwiAQd8SKfA_SmjTEcUXeUC8lH1NXQRwsammAxSHTekxPAKh.NrXlOm31DNDy2dOIALQ_XGuBkXP3ws7e56qeT3mGPvoPh57ny0jUJIrI_jgH9YwSwtzMcfL.4QShIgLlnpF4XIAuX.lvbukI3zZwSueBNr7Pd2mFm83cMyFx2miU9F24aFasLRpfPHLYlzCQekh2hUllrkWiybnND9BHEuJXtrolC2ZeUm2SellXtMjX9bkmnkv68zFTX9UZ4tX2b24WXHa0tXBOTqxFnsvT8rogj_ymxJqZ4TDuoiHHr2CvsXk_hOfySimjGzyMFkQt2nJ_1bBWXad.QUKgGYNRWdYKDIf7Ubx4Xp4bbhT6PT2UrVorSPl3BwAJjqY95a.TfhJ84kbTyMN8GR0U8Qb_ZdttLUP6NsXvekTltavP2M4Q.5L6AroQEFKZ3rg9vxwcET0TZvYa_ykhgMkRNji08IewQe_78i0ElVmJk6DpZmtOo2uHfAnQh_qvCsu6kazm.R.hFvF3IWoMSPrsM0J3bf6aid8wW1.DV9xi9XpDDtvGj0Wi0S9BNtisJmmG3XMJNO3Xwt7iIbUIG0l00TgQnD2KQe3CFioNFHy0cfSQ1hQfZtch8uKY8vbBOpQ8WGeMy15SqL1wRdYL8vBm07fLcUnSLBcHj169s96FBNrCa6g8QFqrIMep4Y7uBBwNqLdFrbXFAOeKvq1ClKgZoK64dHK4NrGgsYX7zVABEP8H.Th.jMsZwKTJoK2F_2qsCbfkVIly4qDnxF5.EXW8dTXK.wUuBj4JZaZTydug.rJJ2vBepnseFzhHkfOaDT.3JKaseKwBL5X6_qQp7Yhsk3FPkllIKI69AEue76h5x2MYODkUGWRIMn1xXG.EwjytHwR8yAArIsb_xUB4IBqxvFDxrTVeeXBgjL2u_pEB7VyR34ud5.3Z.vW3V4ddQmu5ZTJnYCc5dRQAfet4CMiCgrYDjzdBewHexOatingN66F9ozRM6mFWkuSuSOa.Fgt6HoPMtkaU_zg2P75eQWevgqBVVhbrMLfm21MvoaK1IIynYjTpzfr8Lex7NECmpRgiDHMU1jzQ9ZDkP.fdspUBDcehZy0cNS6ofMvTFSwBOPqFtaoW_Omp6PhtlSLx6.BIrJggPnrkfZXQa7FyoBBw.tD5KDul3paxHR05G17nFvtFnXt3wghZksgsNgtz1U_0ptDN8naD6a91N3XxzF4gSMvKdYLjvQCDfG8nN7I6ldK5ya8jg0yp9wNQMvEsvp3n12hOmgzhM7lHoIb5DXWS0pGDXHzAiC4hx3reax4MoPDdOb3fhWroWyX7ydT..YpvDXL4UYGkHrr0EBrGw4Du2vpZxdHdTxILRAVfdw2S2UAcvzJ.s1FLYmfyUHTBcpRmSxvfryANK.rQyCz9WV7PVgBgiXLr2O5e1UBi61NsZo3O.0aL11UMU58HzGoPb9h3u0OL8IolZdJDMlTdUZLj9qeM9uxfFRD2hmky8jzHUA0gHt0jQ6pMB1kxRlOtlIljJve2Mpd22.x.m23PBtDN84eskkRwdt9effX0x9HWyw8Wk5SfrP43AknPgGU0tlGCUpbNAdZ2o7pZLzBGbcfrOajcKwR7ri7y.fhxjNDoN0ACx27rll26mAzy_8nJxag6RhglkDOmC6B2VFEjgPiIEF.WwHkr1gOaLDHzfeIp8JYFAd2unJ__ayfGVgoeiQcKWt6q8B0AA4yq2TpFTdVpNg9juMWqKMCAGP5mQ8gUSsp_cXG83Mpbyv.zFVerNKb_xgu2maJ.9nmho.gIcxTzJEC6ihmS5Hfnv1bXXely2WDEMKI1nCnTIRXDWi70D8zywKxMN0P.oxNXT9LX8RDjLMaMelepxGkBjc6Bauj9qq2AsxIt5UW9qH_q2oxuFlQG3aKHClwCBABY3.iDTiz_4JmW.M"};var cpo = document.createElement('script');cpo.src = '/cdn-cgi/challenge-platform/h/b/orchestrate/chl_page/v1?ray=91513ff92f38ce55';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, "\/abstracts\/search?q=manhole%20cleaner&__cf_chl_rt_tk=ps7XLjt68eTp4cdqs.xQDLJ1vPz3G0JrpEc9kIQy3Wc-1740083378-1.0.1.1-HcavgLIXrr9Cwxchoc5lAyV_jSPl6JAW1o1bzolsJEg" + window._cf_chl_opt.cOgUHash);cpo.onload = function() {history.replaceState(null, null, ogU);}}document.getElementsByTagName('head')[0].appendChild(cpo);}());</script></body></html>