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D I £ N B A N KHOA HOC cdT'^O^TRIET LY THIET K
! ^CONG TRINH TANG MOfi
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I 'GS TS NGUYEN HlfU DAU Tdm tdi: Phdn nav gidi thi^u ca sa ly ihuyei riia triet ly thidt kddiXa trin ly tJmxel do lin cay sd dung trong thidt kecdng trinh (dng Hal mdc thiet kdtheo mik dg id cdo den thdp gom : iheo xdc sudt phd hoai. theo chi sn dq tin cdy dd duac gidi thieu.Phdn tiep theo ciia hat hdi gidi thieu nav se trinh bdy ngi dung mtic
^thiei ke thd ba : theo h^ sd rieng phdn,
PHlJ(5NG PHAP THIHT KH DL/A dicn difdc xac dinh sao cho xdc sud't pW TRHN 1)() TIN CAY hoai bdng hay thap hdn mdt gid trj cho
L Phffdng phap thie't kd'dffa tren dp phep. Xdc sual pha hoai linh dffdc b^ng tin cav - Mffc 3: cdch tich phdn nhieu ldp ham mat dp xic
Trong mffc 3, gid trj xdc .sud't phd hoai .sud'i phd'i hdp cda cac bid'n ngdu nhien dffdc ddnh gid trffe lidp vd kich thifdc tid't lrong mien phd hoai (Xem bidu thffc 1.1.)
(Ll.) d day : xi,X2,...Xn la cdc bid'n ba't djnh, Hdm mat dp xdc sud'i phdi hdp cd th^, fx ( xi,X2,...Xn ) Id ham mat dp xdc sual vi du nhff, bidu didn b^ng bieu thffc 1.2 phd'i hdp cda cdc bie'n ngdu nhien vd g(X) khi mpi bid'n ngdu nhien phdn bd lieu Id hdm trang thdi gidi ban. chud'n.
/x(x,C,)= (2;r)-"^^|C,r2 cxp - l ( x - - / / , f C;Xx - / / J
d day Cx Id ma Iran covariance vd ^ Id gid uj trung binh.
A
(1.2.)
-yViOr,)
Hinh 1.1. Y tU&ng vi xdc s / V ' j . »
i-^ji Bieit^liA
BI£N BAN KHOA HOC-
C6NGNGHf:
Hinh 1.1. trinh bIy S tffdng xdc sua't cin thie't, do dd difdc gpi Id cdc sd' gia pha hoai cho Uifdng hdp ddn gian hai bie'n ngdu nhien. Cdc phifdng phap nhff phifdng ddc lap, d day fxl(xl) vd fx2(x2) Id cdc phdp tffdng ding bdi sd' vd phifdng phdp hdm mat dp xdc sud't sdt gidi ban vd hinh lifdng dang luyd'n linh dang dffdc sff dung chudng fxlx2(xl, x2) Id hdm mat dp xdc rdng rdi ldm ihual lodn dd lao ra cdc sd' sua't phd'i hdp. Trong cdc trifdng hdp hai ngdu nhien ddng nhd'l. Hien lai, cung bie'n, phdn bd'mat dp xdc sual phd'i hdp cd gid'ng nhif vay, cdc hdm gdn sfn lrong the Uinh bIy nhff phan bd' hinh chudng cung Ihffdng sit dung cdc phifdng phdp ndy trong khdng gian ba chieu vd lich phan cho cdc ffng dung khdc nhau. Tuy nhien nhieu ldp cua chdng .se cho thd lich. Tich can lifu y rdng vd'n dc chidu ddi chu ky, la phan nhidu ldp lrong loan bd mien cho mot lrong cdc ydu clu cda thuat lodn lao trong the lich bdng 1. Xdc sud't phd hoai sd' ngdu nhien, dd lap trung vdo tnfdng dffdc cho bdi mien phd hoai cda hdm mat hdp cda phifdng phdp tffdng ding tuye'n dp xdc sud't phd'i hdp, nghia Id the tich cda tinh. Vi 1^' do dd, Ihffdng sit dung thual mien Z<0 Uong Hinh 1.1.. lodn khdc nhff Mersenne Twister. Ma Tuy nhien, dp dung tich phan nhieu ldp ngudn cda Mersenne Twister cd san tren nhff vay cho cdc vd'n dd thffc Id' Uong internet.
nhidu trifdng hdp rd't khd khdn. Tich phan Chuye'n cdc so ngdu nhien ddng nhd't nhieu ldp bac ba hay hdn ndi chung rat thdnh cdc phdn bd' xdc sua't khdc dffdc khd khdn. Trong mdt sd' trffdng hdp cdc thifc hien bang thao tdc nghjch dao hdm hdm mat dp xdc sud't phd'i hdp khdng the phdn bd' xdc sud't. Vi du bie'u thffc 1.3. sau trinh bIy trong dang hdm hien. Do dd day cd the dffdc dung de chuye'n thdnh Uong hlu he't cdc trffdng hdp , gid trj xdc cdc bie'n ngdu nhien lieu chua'n :
sud't phd hoai khdng ddnh gid trffe tie'p , ^ dffdc theo bie'u tiiffe 1.1. md bang md X - ™ / / 11 4 - ^ (j*})P" } (1.3.) phdng Monte Carlo (MCS).
Trinh Iff td'ng qudl cda MCS nhff sau : ^ ^^y ^j j ^ ^Q' ^gi^ ^hien ddng nha't, <!?
(1) Tao cdc sd gid ngau nhien (cdc sd j ^ hdm phan bd tich luy lieu chua'n chud'n, ngdu nhien ddng nhat). // vd V tifdng ffng Id gid trj Uung binh vd
(2) Cdc sd' ngdu nhien ddng nhdt dffdc ^d sd' bid'n ddng
chuye'n thdnh cdc sd ngdu nhien cd phan ' ^godi ra phifdng phdp do Box vd bd xdc sud't cin thie't vd mpt tffdng quan. duller de xud't cung dffdc ffng dung rdng
(3) An todn eua ke't ed'u lien quan dffdc ^ai dd chuydn thdnh cdc bie'n ngdu nhien ddnh gia bdng cdch sff dung td hdp cdc sd ^^^^ chud'n. Phffdng phdp chuydn khdc bao ngau nhien nhan dffdc. g^m phffdng phdp sff dung djnh ly gidi han
(4) Danh gid nhff tren dffdc thffc hien j^ung tam, nd sff dung mpl thffc te la td'ng mdt Iffdng thdi gian ldn, va sd Iffdng phdp ^^^ ^Q' ^gdu nhien ed phan bd xdc sud't thff dtfdc quye't djnh theo phd hoai chia g | n gig^g p^an bd tieu chua'n. Tuy nhien cho tdng sd cac phep thff de xdc djnh xdc ^hj ^p ^ung phtfdng phdp ndy can can sua't phd hoai. than khi xdt de'n tinh dp dung dtfdc cda Cdc sd ngdu nhien dtfdc mdy tinh tao p^ln cudi cda phan bd, do xdc sua't phd ra theo mdt quy luat nhd't dinh tdy theo stf jjoai ra't nhd thtfdng ddi hdi dd'i vdi ke't
Sd Tet 1-2 - Nam 2012 3 7
1^9 Bieit:iifli
BI£N B A NKHOA Hpc
C 6 N G N G H $ cau, vd dd ddnh gid chinh xdc xdc sual Theo Shooman, sai .sd € quy cho MCS phd hoai nhd nhtf vay can ldi lap lai chinh cd thd tinh difdc theo bidu thffc (1.7.). Theo xdc phan cud'i cua phdn bd' xdc dd cd the hidu rdng xdc sua't phd hoai nhd sual.Tifdng Uf, do xem xel ve tinh dp dung difdng nhtf gay .sai so Idn ne'u sd' Iln thff difdc cda phln cudi cua phan bd'ld rat can khdng dd. Do vay ddnh gid xdc .sud't dtfa Ihicl ddc bicl lrong ddnh gid gid Uj xdc trdn ,sd il iln thff do gdnh ndng tinh todn sual pha hoai. trdn tffng iln thff, cdn tuyet dd'i trdnh.Trong cdc trifdng hdp khi cdc bie'n i "
ngdu nhien la cd itfdng quan, cdc bicn ^z „ l ~~ ^^f O A n V
ngdu nhien ddc lap cin dd'i thdnh cdc bien ^ / o - J XZKJKJA ^^ ^ ^ ngdu nhien cd tifdng quan khi ddng ma ¥ ^f
Iran chuyen covariance. MCS Id phtfdng Nhidu pbifcJng phdp da difdc dd xualdd phdp dc nhan dtfdc ldi giai gdn ddng theo cai thien hieu qud linh loan cua MCS bieu ihifc 1.5. nhff mpl lifa chpn dc sff ddng lhdi duy tri difdc dp chinh xdc linh dung lich phan nhidu Idp nhff ndu lrong todn can thie't. Chung dffdc gpi chung Id bicu Ihffc 1.4. cdc ky thuat gidm sff thay dd'i (VRT). cdn
f frf /' W nl / /" W ^ ^ ^ nguyen ihuy khdng cd cdc ky thual Pf "^ J"" f teW^ ^ J y x W « * (1.4.) lay mdu ddc biel dffdc gpi Id phffdng phdp Monte Carlo thd. Trong tifdng lai cd the i V^ f / \ 1 nghT rdng VRT se difde sff dung nhff mpt Pf^~ZjA^y^j)-^\ (^'^) ky thudt chud'n.
^ j ^ \ Phffdng phdp lay mdu quan irpng la A . . T ,. , . . . . . , "^dl VRT dien hinh. Phifdng phap nay dffa Cf day I la ham xac dinh pha hoai. Bidu hdm mat dp ldy mdu h(x) Uong bidu thffc thffc uen trd thanh I < 0 vd bdng khdng (i.s.) vdo bidu tiiffe (1.4.). Dd xdc dinh doi vdi cac irtfdng hdp khdc. hdm mat dp Id'y mdu, thdng lin vd didm Khi dung MCS .so lan tiitf cdn chpn th.di kd nhdn difde theo FORM, nhtf Uinh can than VI Unh gid In cua gan ddng Uong hSv riifri; ,*3., A.^.^ ^ i- . -- u-^
Ki^'n fv„i'^ 1 < i ^ - i , " ' -. ^' .. xZ ," ^^y dffdi day, difdc dung trong rat nhieu bieu thffc 1.5. doi hoi mol so cdc phdp thff. ini-r^na h^r, r . i „ i.,s. ^ \ - u-- >- Tr^„„A/fr-c -'1-^ ,uv x- u , ir»dng hdp. Can Iffu ^ rdng vice thidI lap Trong MCS so lun thff ndi ehung chon sao rhfnh viSr h-^m rv,3./IA i-' s ' ^ u>?ji Adu&of<w' A- X A ^' , ; , . ^">"" ^^c ham mat dd lay mdu cd Uie dan de he so bien dpng cda xdc .sudt phd hoai ddn hdi lu tha'p
(bieu thffc (1.6.)) ,se trd nen dd nhd.
fxi^)
Pf ^
(1.8.)Cdc phifdng phdp cai thien hidu qua
N^To^r.^r""*"'^'''•'""'^^^^^ T-'fj r ^-'^-^ *-'^'--"^ ^^^^
chuoi Markov Monte Carlo, Phtfdng phdp
38
Sd TS't 1-2-Nam 2012
Bieit^d
BifiN B A N KHOA H O C • C 6 N G N G H £lay mdu Hybercube Latin...Cdc phifdng phdp khdc sit dung Day khdc biel tha'p dtfdc gpi Id cdc sd' ngdu nhien quasi nhifng khdng sit dung cdc sd' gid ngdu nhien sc dtfdc Innh bIy dtfdi day.
IL Phtfdng phap thid't kd'dffa trdn dd tin cay - Mffc 2;
Mffc dp 2 ddnh gid chi sd' tin cdy P thay cho xdc .sud't phd hoai, nhdm xdc djnh kich thffdc tiet dien ngang sao cho cd dffdc gid trj p ldn hdn mdt gid trj cho phep. Xdc sud't pha hoai cua ke't ca'u giam khi chi so lin cay ldng. Trong mot sd' tnfdng hdp chi sd' tin cay trifdc day thifdng dffdc gpi Id chi sd an loan. Tuy nhien d day se sit dung thual ngff "chi sd' tin cay" (Thual ngff chi sd lin cay cung da dffdc sit dung lrong ISO 2394
vd cdc ldi lieu tidu chud'n qud'c id'khdc).
Chi .sd tin cay P vd xdc sud't phd hoai pf cd quan he nhff trinh bIy lrong bidu thffc (2.1.). Hinh 2.1 Id trinh bdy dd thi cda quan he ndy.
p ^ - < ^ ( - / ? ) - l ™ 0 ( / ? ) (2.1.)
d day ^l' la hdm phdn bd lich luy tieu chud'n chua'n.
Cornell Id ngifdi ddu tien xay dffng cdng thffc chi so tin cay P Do phtfdng phdp ndy chi sff dung cdc md men bdc nhal vd bdc hai (Itfdng ffng dffdc gpi la trj sd' trung binh vd dp bid'n ddng) cda ham trang thai gidi ban, nen dffdc gpi la Phifdng phdp md men bdc nha't vd bdc hai
Pf
1
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10-3
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Ar\'Q
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Hinh 2.1. Quan he giiia Chi sd tin cay vd Xdc sudt phd hoai.
Gia sff rang hdm trang thdi gidi ban Z tin eay ed the nhan dffdc tff bie'u thffc chi ddn gidn bao gdm hai bid'n sffe khdng (2.2.). Hinh 2.2. trinh bIy each the hien dd R vd hieu qua tdc ddng S (Z=R-S), chi sd thj.
So Tet 1-2 - Nam 2012
39
^ieaihd
D I £ N S A N KHOA HQC CdNG NGH^fi
MR- f^s
4^1
+ <T,5« (2.2.)^ la Ui sd uung binh vd -^ Id dp Idch tieu chuan.
Tren day Id bidu thffc cho trifdng hdp hai bie'n, Trong bidu ihitc long qudl hdn cua FOSM hdm Irang lhdi gidi ban g da difdc phdl tridn chung quanh gid Iri trung binh cda nd theo phifdng phdp md idng
/z(^)
bdng chudi Taylor.Trung binh vd dp lech lieu chud'n cda hdm trang lhdi gidi ban difdc ddnh gid bdng cdch ddng cdc thuat ngff ddng cho bdc nhd'l nhtf da trinh bIy trdn Hinh 1.1.
Khi hdm trang thdi gidi ban bao gdm cdc bid'n ngdu nhidn ddc lap lifdng hd x,(i= 1 ,...n), gid trj tiling binh vd dp lech lieu chuan difdc ddnh gid lifdng ffng bdi cdc bidu thffc (2.3.) va (2.4.). Can kai f rang cdch bidu dien khdc di khi cdc bien cd itfdng quan.
Failure
Hinh 2.2. Chi sd tin cdy P.
Bidu tiiffe (2.6.) cho chi sd tin cay (2.3.)
/ ? = . ' Mg)
cr(g)
(2.6.)M u=gH
(2.4.)CT
W=JZ
/ = !
/^i:> ^ ^
ydXfjj
cr xi (2.5)d day f^ Id trj sd trung binh vd ^ la dp lech tieu chua'n. Ky hieu - di cdng vdi cdc bie'n nhtf X vd xi ehi gid tri tmng binh cda ky hieu dd.
Chi so tin cay difdc xdc djnh theo FOSM cd cdc nhifde diem nhtf sau : nd khdng phan dnh phdn bd' xdc sud't cda cdc bie'n ngdu nhidn. Nd sff dung gin ddng luyd'n tinh cda gid trj uung binh cda hdm trang thdi gidi ban, khdng xdt de'n phdn bd xdc sud't dtfa tren cdc bie'n ngdu nhien, nd ed die cho sai sd khdng Uie bd qua khi hdm trang thdi gidi han Id phi Uiyen , nd cho cdc chi sd tin cay khde nhau tuy theo stf khde nhau Uong cdc dang bieu didn hdm Uang thdi gidi ban da sff dung (vi du
40
So Tet 1-2 - Nam 2012a Bieu^iid DI£N BAN KHOA HOC C6NG NGH£:
Z=R-S vd Z=R/S 1). Do vay, tai thdi bie'n ngdu nhien lieu chud'n ddng lhdi cho die'm hien lai, ndi chung da sit dung cdc cdng cdc gid trj cda mat dp xdc sua't vd each tie'p can chinh xdc hdn so vdi FOSM, phan bd' xdc sud't lai vj tri quan lam dtfdc trinh bIy dtfdi day. Tuy vay trong (chuyen phln cudi tieu chuan). Do muc cdc tnfdng hdp khi muc tieu thim djnh Id lieu d ddy Id tim xdc .sud't phd hoai, dang long bie'n dang vd mffc dp phd hoai cda cda phdn bd phln cudi khdng anh hffdng ke't cdu nhan dffdc theo phan lich phan dd'n xdc sud't phd hoai ndu mat dp xdc sual ffng ddng phi luyd'n, vd khi linh loan xdc vd phan bd' xdc sud't la nhif nhau. Ddng sud't phd hoai vd chi sd' tin cay sit dung lhdi chuye'n thdnh cdc bidn ngdu nhien MCS nhif da ndi d trdn hay FORM vd lieu chud'n trdn se khdng gay ra sai sd' SORM se md la dtfdi day, md gap phai trong xdc sud't phd hoai. Tid'p theo, trong khd'i Itfdng tinh todn rat ndng, Uii vice sit trifdng hdp khi cdc bie'n ngdu nhien Id tieu dung FOSM dtfdc xem nhtf phifdng dn dd chua'n vd cdng ttfdng quan ldn nhau, chdng ddng vd ddn gian de linh dp tin cay. cin phai chuye'n thdnh id hdp tuydn linh
Hasofer vd Lind dd de xud't chi sd' lin cda cdc bid'n ngdu nhidn lieu chud'n ddc cay khac phuc dtfdc cdc tiiid'u sdt cda lap theo phdp phdn ly Cholesky. Hdn nffa FOSM. Chi sd ndy cho ke't qud chinh xdc lrong tnfdng hdp cdc bie'n ngdu nhien ndi trong pham vi gin ddng bac nhd't khi cdc chung Iffdng quan ldn nhau (cdc bie'n ngdu bie'n ngdu nhien Id tidu chua'n. Rackwilz nhien khdc vdi lieu chuan), cung cin sff vd Fiesler gin day dd de xud't mot phifdng dung phdp chuye'n Resenblatl, phdp phdp md rdng phffdng phdp ndy cho chuye'n Nataf,...
trifdng hdp cda cdc bie'n ngdu nhien khdc Khi sit dung FORM de ddnh gid chi sd' vdi cdc bie'n lieu chud'n. Phifdng phdp cda tin cay, cin tim khoang cdch ngan nhd't hp dffdc gpi Id FORM (Phifdng phdp dp tin giffa diem gd'c cda khdng gian lieu chud'n cay bac nhd't). hda vd be mat cong Uang thdi gidi han.
Trong FORM cdc bie'n ngdu nhien Do vay phffdng phdp ndy cd the xem nhff dffdc chuyen thdnh cdc bie'n ngdu nhien loai van de td'i ifu hda. Cdc Uinh tff khdc lieu chuan chuan ddc lap tffdng hd vd hdm nhau de linh ehi sd' tin cay da dffdc dd trang thdi gidi han thdnh khdng gian lieu xua't, bao gdm phifdng phdp tinh hdi quy chua'n hda bao gdm cdc vdc td bie'n ngdu Uen hd tpa dp ban diu. Bdt cff phifdng nhien lieu chuan chua'n de ddnh gid. Sau phdp ndo dffdc sff dung, cin lifu y rang cdc dd tie'n hdnh mdt nghien cffu dd xdc djnh trifdng hdp md hdi tu rd't chdm hay khdng khoang ngan nhd't tff gd'c cda khdng gian xd'y ra cd the nhan thdy sff phu thudc vdo lieu chud'n hda de'n bd mdt cong trang thdi cdc dieu kien. Nhff Uinh bIy dffdi day, gidi han (be mat cong khi hdm trang thdi trinh iff tim khoang ngan nhd't ddi hdi tinh gidi ban tie'n de'n khdng). Khoang cdch lodn eosin chi phifdng, dd Id vi phan rieng nay dtfdc djnh nghia Id chi sd' tin cay. phln cua hdm trang thdi gidi ban. Tuy
Cin phai lifu f mdt sd' diem lien quan nhien ne'u khdng the vi phan rieng phln de'n chuyen thanh eac bie'n ngdu nhien theo giai tich thi cd the sff dung vi phan tieu chua'n chua'n. Diu tien Id, trong sd'.
Irtfdng hdp cdc bie'n ngdu nhien khdc vdi tieu chua'n, chdng dtfdc chuyen thdnh cdc
Sd Tet 1-2 - Nam 2012 41
I^^Q -KB
9
DI£N B A N
KHOA HQC
C 6 N GNGH$
x?;
g(xi', X2*)=0
•order approximation X7;)>0
->-xr
//i«/i 2.3. Chi sdtin cdy trong FORM.
Chi sd' tin cay dung lrong FORM cd thd bidu didn nhtf tren Hinh 2.3 dd'i vdi Utfdng hdp ddn gian hai bid'n dpe lap nhtf cdc bie'n ngdu nhien. Ddc diem cda FORM Id sff dung gin ddng tuye'n tinh cda hdm Uang thdi gidi ban vdi mdt didm nhd't djnh (diem thie't kd) lam tam die'm de ddn gidn hda khd khdn trong khdng gian hai chieu, nhff trinh bIy tren Hinh 2.2. vd bidu didn ehi sd' tin cay nhff Id khoang cdch giffa diem gd'c vd die'm phd hoai, khdng tinh de'n the tich ndy (trong Uffdng hdp hai bidn) nhff the hien tren Hinh 1.1. Sff that Id sai so ddt d die'm nhd nhd't Uong gin ddng ndy cd tim quan Upng sd'ng cdn. Vi dd la diem md d dd mat dp xdc sua't phd'i
hdp cho thdy gid Uj ldn nhd'l cda nd uen mdt cong Uang thdi gidi han (be mdt md d dd hdm Uang lhdi gidi ban bdng khdng).
Hinh 2.3. khde vdi Hinh I.l. d ehd cdc bie'n da dffdc chuydn thdnh khdng gian tidu chud'n hda, ke't qua Id mat dp xdc suat phd'i hdp cd gid Ui Idn nhd't tai didm gd'c vd dtfdc bieu didn b^ng cdc dtfdng ddng tdm. Nhtf vdy diem tiiie't ke' la diem cho khodng cdch ngdn nha't tff diem gd'c de'n be mdt cong trang tiidi gidi han.
Trong Utfdng hdp cdc bie'n ngdu nhidn Id tieu chua'n vd khdng cd ttfdng quan Idn nhau tiii theo Hasofer vd Lind, chi sd' tin cay dtfdc bidu didn bing bieu thffc (2.7.):
42
S6 Tet 1-2 - Nam 20129
BI£N BAN KHOA HOC - C6NG NGH£:
P- Mz
G'
n f
\
dx,
X*)k-^;)
z
i
"hz
r
a^^^ dZ
^dX,
V
dXi rj
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^x,
r)^^
a
X,(2.7.)
XI
O day : Z : hdm trang thdi gidi ban;
X: gid tri bie'n ba't djnh tai diem phd hoai;
^ Id trj sd' tiling binh vd
^ Id dp lech tidu chuan.
Trinh Iff tinh lodn chi sd' tin cay ddi hdi tinh he .sd dp nhay Ot bidu didn bdng bidu thffc (2.8.). He sd'dd nhay Ct Id mdt he sd' gin tuye'n tinh vdi hdm trang lhdi gidi han.
( / - 1 , 2 , •%«)
(2.8.) d d d y :
x; Xf -Mx.
a
X, (2.9.)Bie'u ihffc (2.8.) bie'u thj cosin chi phifdng cda chi sd' tin cay dd'i vdi mdi true bie'n ngdu nhien lrong khdng gian lieu chuan hda (xem Hinh 2.4.). He sd dp nhdy cd gid tii dffdng dd'i vdi cdc thdng sd tren phia sffc khang vd cd gid trj dm dd'i vdi cdc thdng sd' Uen phia anh hffdng tdc ddng, tdng binh phffdng cda chdng bdng 1
khi cdc bid'n ngdu nhien khdng cd md'i tffdng quan ldn nhau. Nhff tha'y rd tren hinh ve, gid trj tuyet dd'i cua he sd' dp nhay cda mdt bie'n tie'n de'n 1, gid Uj lieu chua'n hda cda didm phd hoai tie'n de'n trdng nhau gin hdn vdi chi sd' tin cay.
Dieu dd cd nghia Id bie'n ndy cd anh hifdng ldn de'n chi sd tin eay.
Trong trffdng hdp cdc bie'n ngau nhien cd Ufdng quan ldn nhau, he so tifdng quan p giffa cdc bie'n ngdu nhien dffdc xem xel Uong dp lech lieu chuan vd he so dp nhay cua ham Uang thdi gidi han, nd dffdc bieu didn tifdng ffng bdng cdc bie'u thffc (2.10.) vd (2.11.).
n n
r
^.'=JSS
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dZ
V
dXf
^' dz x*\ dXj
\
x'J
Py y ^Y ^y (2.10)
^/
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n
ex
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rJ PXnXj^Xj hz
(2.11)Sd Tet 1-2 - Nam 2012
43
Bieit^bd
DI£N B A NKHOA HOC
C 6 N GNGH$
Sff dung FORM du dd tinh lodn chinh xdc chi sd' tin cay lrong pham vi gan ddng bac nhd'l. Tuy nhidn can lifu y riing FORM da sit dung gdn ddng bdc nhal cda hdm Uang thai gidi ban dd tinh chi sd lin cay.
Vi du nhtf khi dicn lich gach cheo Irdn Hinh 2.4. the hien viing phd hoai ihifc Id', FORM lay gan ddng nd bdng difdng cham chdm ircn hinh vc. gay nen sai ,sd' lif(}ng ffng vdi dicn lich nam giffa difdng lien vd dtfdng cham chdm. Do vay lrong cac
trifdng hdp khi bd mdi cong trang lhdi gidi ban cho Ihd'y linh phi tuye'n rat manh thi FORM cd thd cd sai .so khdng the bd qua.
Mpl cdch liep can de giai quyd'l khd khan vd'n cd cua FORM , PhifcJng phdp dp lin cay bdc hai (SORM) da dtfdc dd xud'l.
SORM hieu chinh chi so' lin cay nhan dtfdc Iff I'ORM phd hdp vdi dp cong cda bd mdi cong trang lhdi gidi ban, nhif irinh bay lrong bidu thffc (1.20.).
z=o
.First-order approximation
R'
Hinh 2.4. Chi sdtin cdy P vd He sddg nhdy Ct .
-1-1/2
Ki^-
dyf
(2.12)
d day P Id chi sd tin cay theo FORM, Ki Id dp cong chinh cua be mdt cong trang thdi gidi ban tiiff i.
Diem quan Upng trong phdn tich dd tin cdy la Iff a chpn dung d^n mdt phtfdng phdp chinh xdc phd hdp vdi cdc ddc tinh cda van dd lien quan,
Mdt diem khdc cin ItfU ^ trong phan
44
So Tet 1-2 - Nam 2012t'^^^ ^9
9
BI£N BAN
KHOA HOC -
C6NG NGH£:tich dp tin cay Id va'n dd ttf tifdng quan vd xdc sud't phd hoai cin dtfdc ddnh gid rieng phln cda cdc ddc tnfng cda da'l. Dd't khi xem xdt ddng ddn ttfdng quan ddc biel u l m tich ttf nhien cd khoang ttfdng quan theo chidu dffng. Vd'n dd ndy Id cite ky nhidu chuc mdt theo chieu ngang vd nhieu quan trpng de gidi quye't cdc khd khan nhff met theo chieu dffng. Do dd chi sd' lin cdy phan lich phd hoai Irifdl cung trdn.
Hd s6' bid'n ddng V ciia ctfdmg dd dd't ndn 1) Cung trtfdt nhd : Sd n cac ldp dd't ddc ldp bdt dinh bi cdt qua bdri cung
trtfot nhd la nhd.
2) Cung trtfpft Idn : Sd n cac Idrp dd't ddc ldp bdt dinh bi clt qua bdi cung trtfot ldn la ldm.
Hinh 2.5. Anh hucmg cua tu tucmg quan rieng phdn.
Hinh 2.5. md ta theo sd dd vd'n de ndy khi sff dung cdc vd'n de phd hoai Uifdt cung trdn ldm vi du. Ne'u ttfdng quan theo chidu dffng da dffdc xem xdt, sd' Idp dd't ddc lap bat dinh md cda eung trffdt nhd cdt qua vd cua cung trffdt ldn se khde nhau, nhff the hien tren hinh ve. Trong trffdng hdp nhff vay , he sd' bie'n ddng cda sffc khdng trffdt se khdc phu thudc vdo kich thffdc cda cung. Vi du nhff khi gid tiiie't dd ddn gian hda Id cdc Idp da't ldn hdn nhieu met mdt phln ddc ldp, hd sd bie'n ddng sffc khdng khi mdt eung cat qua n ldp ddc
. *»
lap cd thd bieu dien nhff ndng lifdng thff nl/2 cda V Khi ddnh gid gid trj xac sud't phd hoai sff dung MCS, cdc dac Uifng vat 15^ cda nen dd't cd the ldy mdu phu hdp vdi hdm tff tifdng quan.
(Cdn tiep)
Tham khao : Technical Standards and Commentaries for Port and Harbour Facilities in Japan. The Overseas Coastal Area Development Institute of Japan.
Tokyo. 2009.
Sd Tet 1-2 - Nam 2012
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