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<br />4-01 <br />SlCTIOI'1I: - ~ PEAK~:t - -AKAIo1'lmALe~ <br /> <br />W1. <br /> <br />. us:B: .,.~GIS AD 1IBE.rAfiQ JJNI.ftNJIS . <br />, ,- '.. - - ~ ," '. . <br /> <br />~ ~1ea); Mthod of c<l1I!Prt1ng a freq:t18llq eune 111 <br />bTdrolo9-c~~uen,.as1s l1m1 te4al1108t exclU81~ ,to curtas <br />ofllolll1ua.l -"'"'~ or~'wrl.1-ltreaflon for al}l8c1f1e4 <br />durat1oii(~l~ peak nan) 11114' IIIlIlU8l -~...,.pree1p1ta- <br />t~~ iImoant. for a's}l8df1e4 cJ.ura1;1on. Ia "1'&1., 'theresuJ.tl <br />obtained, b7 aZlalytiaal methods are cODll1cJerablt IIOre reliable <br />than tboee obt&11ie4 b7 grapb1cal proce4ures. 'l'heyllMe tlle <br />sddit1011al ad~lth&t the degree of reJ.1ab1l11o)- of fre- <br />queJlC7 estillateli c. be naluated, .as' UICll81ed. 1a ~:ph <br />10-03 . . <br /> <br />4-02. . lI:Ql1AfiOlS. USED <br /> <br />,.-. <br /> <br />;- /. <br />~ . Frequency eurieilare computed &Dal7t1call:1 bY'. the use <br />of maaents of the logaritbms, expressed. in tems of the meaD, M, <br />(first:_1;),st....If.."'dd..~atiOll, S, (seofllld_t)aadskn <br />coeffio~nt, g,.. (th1ri!....../rt f\lllCt1011). !he t1lree corresJOllding <br />lqUations used are as ~oll~ t , . <br /> <br />;, <br /> <br />!It. r;,x/H <br />2" 'tJ12 'i:J.2.(r;,x)2/H <br /> <br />S ;:::I -. <br /> <br />(2) <br /> <br />(3) <br /> <br />. "". -~ . <br /> <br />. .I!f :- 1.. <br /> <br />II ,.1 <br /> <br />I!f I;x3 <br /> <br />. "1'-..- '_.'. '''.- . '~. <br />, ... (I -1){!t -2)S' <br /> <br />-rEX3 _ 3D" EX 'r.x?- + 2{EX)3 . <br />"(I!f' . J):(w: ': ~)s3. . <br /> <br />in 1I'h1ch: . . <br />X;.o.~~u4e .rJt. an event (logarithli) .. <br />:1:, =,'X.,''' .,.deviation of & 8ingleevent from the meaD <br />,11' ..lIumber .(jf Irt'I.1;S in the record <br /> <br />g,. ~ types of cUllllllati... trequscY'curves fitted in <br />~olog1c engLnlMr!Dg do not. raquire _ts of a higher order <br />than tlies..etbiee;&.l1d Ord.1i:aarTfitt1ng Y1l1 require ~ the first <br />two. '1'herib no Il.ee4 .to tabulate the 1D.d1Tid.ual deviation for <br />each logarithm, as the seco!ld1!lL'l"tsof eqU&i;lons3and 4 ca 'be <br />used to compute the st,azIi1A"'fl deTiation IIZld skew coefficient much <br />more rapi~ ,directlt from the orig:l.!l&l logarithms. In computing <br />these qll&1ltities 1il.this -er, hOvaTer, :l.t :l.s essential tbat <br /> <br />- 15 - <br />