CISM COURSES AND LECTURES
Series Editors: The Rectors Giulio Maier - Milan Jean Salençon - Palaiseau Wilhelm Schneider...
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CISM COURSES AND LECTURES
Series Editors: The Rectors Giulio Maier - Milan Jean Salençon - Palaiseau Wilhelm Schneider - Wien
The Secretary General Bernhard Schrefler - Padua
Executive Editor Paolo Serafini - Udine
The series presents lecture notes, monographs, edited works and proceedings in the field of Mechanics, Engineering, Computer Science and Applied Mathematics. Purpose of the series is to make known in the international scientific and technical community results obtained in some of the activities organized by CISM, the International Centre for Mechanical Sciences.
INTERNATIONAL CENTRE FOR MECHANICAL SCIENCES COURSES AND LECTURES - No. 503
CLASSICAL AND ADVANCED THEORIES OF THIN STRUCTURES MECHANICAL AND MATHEMATICAL ASPECTS
EDITED BY ANTONINO MORASSI UNIVERSITY OF UDINE, ITALY ROBERTO PARONI UNIVERSITY OF SASSARI, ITALY
This volume contains 32 illustrations
This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned specifically those of translation, reprinting, re-use of illustrations, broadcasting, reproduction by photocopying machine or similar means, and storage in data banks. © 2008 by CISM, Udine Printed in Italy SPIN 12048489
All contributions have been typeset by the authors.
ISBN 978-3-211-85429-7 SpringerWienNewYork
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N% 3 N% 3 N% N% N%
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( > N : ! )* .**)5 !23 D 23 )*. K) 5 D 5 ! >D D ; * ! !(* .*) 3N= 0 *)) * : ! *K ( ))( )-4" : 2 * 2EBB933 2% 3 D 2% 3 % * % & 2HJ3 >7;
#A-)( -)
! * ( )*. K) * * * .*)) . = )5 * % )*: 23 *.) )*. . K) ! !23 ! 23 D /
* / B%
2HL3
* !* K . ( * !/ /= 5 / * * . *) **. * 2/ 3 * . / = # %*)! 2/ 3 .* * . ) ) !)= 0 *%
D 2/ !3 D / %
2H93
( D !5 *
D D ; 4 /2 4 3 4 2/ 3&
2H<3
#
/ & D ; 4 2 4 3 4 2/ 3 E * . )* . . D & ( *%
K
2JB3
/ D ; 4 2 3 4 2/ 3& E
2JC3
C .% 2 4 3D E
2JE3
Strain, Stress and Linearized Elasticity C &(& 2 3D/ E
23 2JF3
# ( 2/ 3 .5 ( *% & D ; 4 % (
D /%
D ; 4 / %
2JG3
/ D //%
2JH3
* *)) 8-)( ) * 8-)( ) 5 %)= # */ % !) ( * ( / !O) .*))5 -* )*
. D & )* / *
*) . .. * &( *> D 4 / = ( ) . ) ( :%*) / * * / * * 8-)( -) = K.*) .* 5 . * ) * K/5 * **5 * % )!. * * *) /( ( K/= $ *5 / ! * E=G5 ) *) ) ( * / %*)!* *
D
D 2; 4 E 4 2/ 33 D
D C 4 4 2/ 3% *
D %
2JJ3
( . 2/ 35 .* ( = 2EB3= ) ))5 / -* .!)* 2EC3 * ! *: !. D B5 D C5 D C% E5 ( *%
! D C 4 4 4 2/ 3%
2JL3
* 5 ( . 2/ 35
! D 4 &
2J93
.)*)5 / )** = 2EG35 ) )( ( *) K/ D 5 * D C% E5 % / 0 D E &
2J<3
24
A. Morassi
) # ( -5 ) / * %)
) ! * D - = )* . . ( *%
D 2 & 3 D & D & = *)) K
.* ( /*
&
2; 4 3 D 2; 4 3 2; 4 3 2; 4 3 C 4
D C 4 &
# 5 * % )!. . / * >
" D &
" >7<
2LB3
!$ !) A-)( -)
. )* 2HH3 K.*)
.* = # .) * 5 * ( . * * * ( ( * = *!. !)* !5 * % )) ( ( > 23 D 23
% * % % 2LC3 23/ D /23 % / &( * % & 2LE3 5 % * ! D 235 ( / 2 3 %*% = 2LC35 2LE3 ()) %*)!* * D 5 * 2 3 D
/ % * = 0 .*)) %) ! / #*) *.)
)*. / ! * / B= 0 *%> / 2 3 D 2; 4 / 3 D 2;3 4 /2;3 4 2;3 4 2/ 3% 2LF3 E ( 2/ 3 * . ( / 5 == ). 2/ 3/ D B= 0 *)) / 6 D 2;3 D 2;3 " 2LG3 )( 5 * ( / ( ! K!* = 23 D "2 3 *
6 ( *% 2;3 D "5 6 .& " 2LH3
Strain, Stress and Linearized Elasticity
25
(5 . .. %*%
3 3 3 3 D D D % 3 3 3 3 ! ! * 2;3 * .. !: =
2/ 3:. #*) %) . 2LF35 / ! ( *% 2LE3 ( D ; * / D /5 4 3 D 2;3 D 2;32/ D " 6 4 / " 6 4 2;3 D/ D 6 " 6 4 / " 6 4 2;3 D "
2LJ3
% 6 " 6 4 2;3 D " ( )* ) D 5 *)) 5 5 5 * / ! = # 5 ( *% 2 3
6 4 / " 6 4 D 2;3 4 /" E / " 6 3 4 2/ 3& 4 2 2;3 E
2LL3
0 * ( .! )* !% !* )*: , P .*)) /= = 2LL3 ( *%
D 2 3 D 2 3 D 2; 4
3
D
" 6 3 4 2/3 D 6 4/" 6 4 / 2 2;3 D" E / " 6 4 2/3 D 6 4/" 6 4 / 2;3 D"
4 2/3% 6 4 // " 6 4 / 2;3 D"
2L93
* / B&
# " ( ' ! ) ! 1 " . ' ) !! . ) ! " ' ! " " . $ % !! $ % " ! . ' . - / 0)
26
A. Morassi
*)) = 2GJ35 *! !*) "
4 2/33 2" 6 4 // " 6 4 / 2;3 4 2/332; 4 D 2C 4 / 4 2/332; 4 4 2/332" 6 4 // " 6 4 / 2;3 D 2C / /23 "32; 6 6 4 // " 6 4 / 2;3 4 D 2"
3
3 3
D
D
4 2/3 D
6 4 /" 6 4 // " 6 4 / 2;3 /23 " 6 4 2/3 D D" 6 C / 4 E/ " " 6 4 / 2;3 4 2/3& 6 D"
/ 2L<3 .* = 2L93 * 2L<3 % * : 6 D :5 )*:, P K!* *!*)5 * " P . *! = %5 / = 2L<3 6 D : *! *) )) ( * " &(:.. * )*. * = 6 D :5 =2L93 * 2L<3 ! %) $ " D 4 2/3%
" D 4 2/3
* / B%
29B3
* D " ( .= 5 !: .. 29C3 D 2;3 () .**) K!* = # )* *K :*)) - -- D D %
% % % D C% E% F&
29E3
0 )! ( * 2LC3 * 2LE3= # K )) ( / P* *.: P 23 D 23 % ( ) % * % 5 ( = ! ! ! 23 D = ! %* !) ( /*
3 2 233 3 23 3 23 D D 23 & I 238 D 3 3 3 $ % 2LE3 ( ! )) ( ()):& ( !) 2 -= F E=J3> * / &( * * + IB% E,85 2+3 D ; 4 +/ 4 2C +3 / &
29F3
Strain, Stress and Linearized Elasticity
27
2LC35 ( *% 23 23 D 23 23 % &
D 2+3 * = 29F35 ( + .*))= 2+3 D ; 4 +/ 4 + 5 * / &(5 ( /*
; 4 +/ 4 + 23 23 D ; 4 +/ 4 + 23 %
* 2*!. D 2% 3 !)* !3 +/ 23 D + 23 / 4 + & % / + * *& ). * + B5 )) (= >7=
" . !) $)(! .(- () ()
0 *)) )* !)/!. /). K )* K: .*) .* * . * K!* ( * *!*) * * :)* .**)= = 29B3 ( *% % D % 2 3 4 2/3
N% * / B&
29G3
0 *!. * *!*) / : .*))> . 2,3
D /.2,3
2N3&
29H3
# 5 / 2HL3 ( *% . 23
D . 23 4 2/3
N * / B&
29J3
= 29H35 29J3 = 2HH3 5 !)/!. !* / . 4 2/3 D B 4 . %
N * / B
* 5 ) .5 % 2 3 4 . D :
N%
29L3
( ()):& ( . **) P*) !* )*
)*= # / ! * 2HH3 * / ! * )* .)*)=
28
A. Morassi
$ )! 5 !/ / * 5 / ! * %*)! /: ). )* )* * / .!)* * )) (> K : )*. K) !5 ! > N 5 ! () 5 )! % 2!3 4 . D : N% 2!3 D 3 N% 23 2993 !D 3 N% ( * * !.* * ) 2!)*3 **5 %)5 * 3 N 3 N D 3N= $ - ( *)) . !! * - !) /). 23 K = 29935 *) 2EBBG35 * 2C7>
- , ) !! !( () ()5 .(-
$ ( *)) .*) ( 23 /). 2993 . ! ) * !.* / ! * > % 2!3 4 . D : N% 2!3 D : 3 N% 29<3 23 !D: 3 N% 6 ( 3 N D 5 3 N D 5 36 N 3 N D 5 3 N 3 N D 3N= 0 *)) ! )) ( *: *!. > 3 2 -) N3 N * 5 / ! * !/ 5 D F5 * * / ! * 3N )* ( * 5
A . %5 N 5 ( B= 3 2 -))( 3 # )* > N .. 2 D 5 . 5 D 5 % % % D C% E% F35 * . .. D D 5 % % % D C% &&&% A . %5 ) %- N> - ) ( B ! * 23 ) 5
! 2' 2 ,' , ' 2' ! . , $% 2 $,% . 3 $ %' . $ %' ' ' 3 $,% ' 3 $% . , 3 $ % ) 3 $ % . 3 $
%
& 3 $
% )
Strain, Stress and Linearized Elasticity
29
% . *== NA K*))5 2N35 * 2N35 % % % D C% &&&% = 3 2 ))3 # / .5 . > N 5 !* # " ' = */) N> . D
%5 ( *)) *!. * / ! * 3 N ( )*. % 2* !*) 3 () = )> - 3 N ! * 3N 2 3 3 N% ( 2 3 D ' = 0 *% )) ( ()):& ( !)= " - >7;7 1, ) -, 12 .(- ' - ( ) -) ))2 % ). # ) - 3 .(- 29<3 ) ) ( 2N35 # 27<7 2N3 = D 4
)/ * $ 2N35 ( .
5 0 *)) ! )) ( * .5 2C<9J3= " - >7=7 . ) (. ) ) ( !2% 3 > ) .()3 3 # - 5 4233 4 > 3 . ) () ) )( 5 !3 , ) ) ! 2% 3 D 4 23 # & 2
= $ ! ! * * 0 K D $ 2N3 % $ D : 3 N )/ * ( . = .!)) !)/!. !*
"' $2%) # 1' 2' $% . $% ! ) $2% 2) ! . 2' "
$2% 1 )) ) 1 )
30
A. Morassi
/ $ 5 * / * * *& / ! * 29<3 5 29<3 * !5 ( /* = 2 *
4 23 > K / ! $% 2<E3 ! 2!% $3 D
4 2$3 D
. $&
2
* = 2
* 4 23 ! != # . ! 2% 3 /% !) /)* * ! ! 5 / *!: (* !*)5 ( *% ! 2$ % $ 3
$ $ %
2
( D ! 23 = # % % ! 2% 3 ( ( * - * * * ( B ! * ! 2$% $3 *$
% $ &
%- ( *% 2$3 & ! 2$% $3 )
2<J3
$ .* . /) ( : . K.*) * ( *)) ( . * !*)5 5 -*.)5 2$3 , *1% * )& 2C<9<3= )9 !)( N / * / ! .* )* ( * 5 * ! * N 5 E= % $ 2N% 3 ! * $D:
3N 23%
( . 3N5 ( *% $ $ %
2
Strain, Stress and Linearized Elasticity
31
( ( B * * ) * =
+ 0 !)( N / * / ! .* )* ( * 5 5 * ! * N 5 E= % $ 2N% 3 ! * 3N 23%
$D:
( . 3N5 ( *% $ 2$3 %
2<93
( ( B * * ) * = (5 / *@1 * , 1 !*) ( *% $ 2C 4 3 2$3 %
2<<3
* ! 2$% $3 % > ! 2$% $3
) $ 2C 4 3
% $ &
2CBB3
* . ( * )! * - * !! )! 29<3= *))5 / $ D ! 2 !
2C 4 3 . & )
2CBC3
# -5 !! * */) )* )* /). * / % .)*)= $ !)5 ( *)) *: ( * ( 3 N D 3 N D =
32
A. Morassi
" - >7>7 1, ) ( .(- ' - ))2 % ). # ) - 3 .( # 23 4 D : N% 2CBE3 12 D: 3N%
) ) ( 2N3 D > N 2N3 % D : 3N )
2CBF3 % ' ( B ) ) ( % % % ) 5 5 # )) ( *. ) 23 = 5 ( *)) )) ( ()):& ( % *@ !*) 2N3= N / * / ! .* 5 E5 ( / ! * 3N ( * 5 * ! * N = # - ( B5 ) * 5 ! * $ $ % $ 2N3& 2CBG3
# , 1 !*) 2N3 * * )) (> ! */ % *!.: N5 ( *% $ E 2$3 % $ 2N3& 2CBH3
$ *5 * )* !)* ! 5 */ % !*) )) ( . C C 2$3 D $ 4 2 % $3 % $ 2N3& E E
" - >7?7 1, ) -) .(- ' - ))2 ) ( .)( (. - 6 D :3 D :5 !3 ). # ) - 3 .( # 23 4 D : N% 2CBJ3 12 23 D : 3N%
Strain, Stress and Linearized Elasticity
33
) ) ( 2N3 ) D :% 23 D :&
2CBL3
# %
2CB93
' ( B ( 3 3 3 ) 5 5 $ * % ( & !/* 2N3
K / $ D :% $ 2$3 D : & D $ 2N3
# % /)* . ! 2% 3 )) ( . ( !*) /) (= )9 0 !)( ' */ % *!. N5 ( *% $ C $ $ % $ 2N3 % N
2CB<3
( ) * = + 0 !)( ' */ % *!. N5 ( *% $ C $ 2$3 $ N
% $ 2N3 %
2CCB3 ( ) * = ! ( !*)5 # . )) ( *. ) * 23 * 23 =
-)% >7@7 $ *)) % ! /).5 /)* . ! 2% 3 .: .5 * ! 2!% $3 D ! 2$% !35 % $% ! = $ * )! ! * )* /). * / ! / )%: %** *) /). 2!3 D . 2$3 %
( 2$3 D
! 2$% $3
4 2$3 *) /).=
34
A. Morassi
% '(- $ ( *& = !* ))* * ** .*!=
= 5 )( )(5 ! 5 * )5 C<9J= == *)5 )-))( ()5 * ( - 76 ! - )( ()4 5 )%5 . *.5 EBBG= = ) 5 - )5 ' ) 1 C<9J5 *5 #!5 C<9J= = *5 , - ()= $ ) . $ 5 *?E5 5 ); )/; ( &5 C>5 C9L;C
= #! ))5 ! (- - )5 5 ); )/; ( &5 C<JJ= #= +*)5 ) *)( .(- ()5 5 ); )/; ( &5 C<99=
! %&&'&( #'&! % $&! %&&) 0I
"" """# & $ !" "# !! && # " && # "% " " #" " " " % ! ""% ! $ " !"" !" " " "! #! " # ! "
&$!'&!
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
36
R. Paroni
-1 1(-, 2B? HIN;NCIH OM?> NBLIOABION CM KOCN? MN;H>;L> 4CNB *CH 1SG ;H> 1- Q? >?HIN? NB? M?N I@ JIMCNCP? FCH?;L NL;HM@ILG;NCIHM NB? M?N I@ JIMCNCP? >?HCN? MSGG?NLC= NL;HM@ILG;NCIHM ;H> NB? M?N I@ LIN;NCIHM L?MJ?=NCP?FS 2B? #O=FC>?;H $LIO=N CM >?HIN?> <S ;H> NB? =ILL?MJIH>CHA HILG <S ! ! 2B? AL;>C?HN CM >?HIN?> <S # ;H> ; <;L IP?L >?HIN?M NB? =FIMOL? I@ $CH;FFS ; M?N >?HIN?M NB? =FIMOL? @IL CHMN;H=? NB? =IHMN;HNM ;L? >?HIN?> <S NB? F?NN?L NB? P;FO? I@ G;S =B;HA? @LIG FCH? NI FCH?
%& )"$%& &$%
'H A?H?L;F C?M G;>? I@ >C?L?HN G;N?LC;FM C?L?HN G;HH?LM 2BCM >C?L?HN CH =IHNCHOOG G?=B;HC=M QCNB ; =IHMNC NONCP? ?KO;NCIH NB;N CM ; L?F;NCIH MNL;CH 'H QB;N @IFFIQM Q? MOGG;LCT? NB? JLCH=CJ;F =IH=?JNM I@ NB? NB?ILS ;H> Q? L?@?L NI NB? ?FF @IL @OLNB?L >?N;CFM *?N ; S ;H> ; JF;=?G?HN I@ NB? S CH NB? #O=FC>?;H MJ;=?
(&2/$ *?N OM =IHMC>?L ; M?=IH> JF;=?G?HN I@ NB? S ;H> F?N NB? G;JJCHA @LIG NB? L?@?L?H=? =IHAOL;NCIH M?? $CAOL? NI NB? M?=IH> JF;=?G?HN =IHMC>?L?> 4? MB;FF >?HIN? <S # NB? >?@ILG;NCIH AL;>C?HN $ ,(1(-, G;N?LC;F CM M;C> NI $* 01(" C@ NB? !;O=BS MNL?MM CM >?N?LGCH?> <S NB? >?@ILG;NCIH AL;>C?HN 2B;N CM NB?L? ?RCMNM ; G;JJCHA V MO=B NB;N 5 V
QB?L? 5 2B? G;JJCHA V CM =;FF?> NB? L?MJIHM? QCNB L?MJ?=N NI
Constitutive Equations and Variational Elasticity
37
1CH=? NB? L?F;NCIH NB? !;O=BS MNL?MM N?HMIL M?? +IL;MMC CM ACP?H <S >?N
Q? B;P? @IL ;H ?F;MNC= G;N?LC;F >?N V
$ ,(1(-, H ?F;MNC= G;N?LC;F CM '6.$/$* 01(" C@ NB? .CIF;)CL=BBI MNL?MM B;M ; JIN?HNC;F NB;N CM C@ NB?L? ?RCMNM ; M=;F;L @OH=NCIH *CH MO=B NB;N
2B? M=;F;L @OH=NCIH CM =;FF?> NB? MNIL?>?H?LAS @OH=NCIH 2B? H?RN NB?IL?G QBIM? JLII@ =;H @IOH> CH NB? GINCP;N?M NB? >?HCNCIH I@ BSJ?L?F;MNC=CNS '$-/$+ ( &-.$ )3 $- #3* , &-.$ $! ( )(&3 $! "$0 ( (3 *,. ( (3 .$' $(. ,0& 6+ + 8 .# 1),% 9 +
$- ()(( ".$0 $( &)- *,) -- -
! $ ! '$&!
*?N OM =IHMC>?L NQI L?@?L?H=? =IHAOL;NCIHM ;H> I@ NB? S ;H> F?N
*?N M?? $CAOL? ;H> NQI G;JJCHAM @LIG ;H> L?MJ?=NCP?FS NI NB? M;G? JF;=?G?HN ;H> F?N #
#
1CH=? Q? F?N @OLNB?LGIL?
38
R. Paroni
(&2/$
*?N ;H> NB? LMN .CIF;)CL=BBI MNL?MM N?HMILM QCNB L?MJ?=N NI NB? L?@?L?H=? =IHAOL;NCIHM ;H> L?MJ?=NCP?FS '@ >?HIN?M NB? !;O=BS MNL?MM N?HMIL Q? B;P? >?N
2BOM
>?N
>?N
;H> B?H=?
>?N >?N
>?N >?N
*?N NB? MNIL?> ?H?LAS >?HMCNS QCNB L?MJ?=N NI NB? L?@?L?H=? =IHAO L;NCIH *?N OM M?N >?N QCNB
3MCHA NB? =B;CH LOF? ;H> ?KO;NCIH Q? =;H ?;MCFS MIFP? NB? @IFFIQCHA 5$/"(0$ #)1 .#.
Constitutive Equations and Variational Elasticity
39
#KO;NCIH ;FFIQM NI =;F=OF;N? NB? MNIL?>?H?LAS >?HMCNS QCNB L?MJ?=N NI ; L?@?L?H=? =IHAOL;NCIH IH=? CM EHIQH NB? MNIL?>?H?LAS >?HMCNS QCNB L?MJ?=N NI ;HINB?L L?@?L?H=? =IHAOL;NCIH FMI ?KO;NCIH MBIQM NB;N NB? >?HC NCIH I@ ; BSJ?L?F;MNC= S >I?M HIN >?J?H> IH NB? L?@?L?H=? =IHAOL;NCIH
&$ )&$)
*?N ; L?@?L?H=? =IHAOL;NCIH ;H> M?? $CAOL? *?N OM =IHMC>?L ; J;LNC=OF;L =;M? I@ NB? G;JJCHA =IHMC>?L?> CH NB? JL?PCIOM M?=NCIH QCNB 1- QB?L? 1- >?HIN?M NB? M?N I@ LIN;NCIHM 2B? G;JJCHA MCGJFS LIN;N?M NB? S ;LIOH> NB? JICHN *?N OM >?HIN? <S NB? JF;=?G?HN *?N ;H> NB? MNIL?>?H?LAS >?HMCNC?M QCNB L?MJ?=N NI NB? L?@?L?H=?M ;H> L?MJ?=NCP?FS
(&2/$ '@ Q? =;H H> ; 1- MO=B NB;N
BIF>M @IL ?P?LS *CH Q? MB;FF B;P? MBIQH NB;N NB? L?MJIHM? I@ NB? JICHN CM DOMN NB? M;G? QCNB L?MJ?=N NI NB? NQI L?@?L?H=? =IHAOL;NCIHM =IHMC>?L?> ;H> 2B;N CM NB? MNIL?> ?H?LAS >?HMCNS =;H HIN >CMNCHAOCMB NB? NQI L?@?L?H=? =IHAOL;NCIHM 2B? LIN;NCIHM 1- @IL QBC=B BIF>M >?HIN? MSGG?NLC?M I@ NB? G;N?LC;F I==OJSCHA NB? JF;=?G?HN 4? >?HIN? <S 1- ?KO;NCIH BIF>M
40
R. Paroni
2B? M?N CM =;FF?> NB? 06++$1/6 &/-2. I@ NB? JICHN CH NB? JF;=?G?HN
5$/"(0$ #)1 .#. $- ",)/* $LIG QCNB ;H> Q? H> QBC=B CM
*CH
2BOM @LIG ;H> Q? =;H ?;MCFS H> NB;N 1-
*CH
$ ,(1(-, H ?F;MNC= G;N?LC;F CM M;C> NI (0-1/-.(" ;N C@
&$ $ $
$IL I@ NB? JLCH=CJF? I@ . ,$& ,' ($ , ( 2B?M? NQI JLCH=CJF?M ;L? ?KOCP;F?HN M?? JA I@ 2LO?M>?FF 'H NB? JL?PCIOM M?=NCIH Q? LIN;N?> NB? L?@?L?H=? =IHAOL;NCIH HIQ Q? E??J NB? L?@?L?H=? =IHAOL;NCIH R?> ;H> Q? MOJ?LCGJIM? ; LCAC> GINCIH NI NB? ;=NO;F JF;=?G?HN
(&2/$ *?N ;H> ; >?@ILG;NCIH M?? $CAOL? *?N OM =IHMC>?L ; LIN;NCIH 1- ;LIOH> NB? JICHN NB;N CM
Constitutive Equations and Variational Elasticity
41
QCNB 4? NB?H B;P? # #
# 6 8
2B? ,$($*& )! . ,$& ,' ($ , ( GIL? JL?=CM?FS NB? JLCH=CJF? I@ /* ,$'*)- $"$ ).$)(- MN;N?M NB;N NB? MNIL?> ?H?LAS >?HMCNS CM CHP;LC;HN OH>?L MOJ?LCGJIM?> LCAC> GINCIHM NB;N CM
@IL ;HS 1- *CH ;H> *?N OM 1SG 2BOM <S +;N?LC;F $L;G? 'H>C?L?H=? Q? B;P? QBC=B G?;HM NB;N NB? MNIL?> ?H?LAS >?HMCNS >I?M HIN >?J?H> IH NB? @OFF >?@ILG;NCIH AL;>C?HN