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发表于 2016-2-15 19:51:33
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AC-arctan(AC/80)*80=1是数学问题。
1 W7 @" G# h$ R子子大侠既然读过VB,那么读VBA代码就应该没什么困难,核心是数值计算。 f7 E3 \7 Y' C, K# n( b
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7 W/ U/ b) E! P8 S3 \, b' J. P定义待求解函数:
0 H* M5 @) ~0 H+ T. HPublic Function QesFun(ByVal Var_AC As Double) As Double
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2 E5 g3 t' z& \$ T3 N' \) a QesFun = Var_AC - Atn(Var_AC / 80) * 80 - 1. B4 u& `) a, D# c
9 R) _: y" f3 u! Y; REnd Function; ^% A& S6 G& H! x; }9 G
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1.1 由 Arctan(AC/80)=(AC-1)/80
8 Z1 h6 A5 e$ _; n6 A" p7 R 知 -PI()/2<(AC-1)/80< PI()/2
. ?- W: y3 i* u- F% u" @ 即 1 -80*PI()/2<AC<1+ 80*PI()/2 z s6 p/ e5 [6 y1 \
++++++++++++++++++++++++++++++++++++++1 p, d- g; n/ t3 V+ V9 C
1.2定义求解函数:
; {9 j* H$ x, r1 J5 }+ [7 bPublic Function SolFunDic(ByVal MaxLim As Double, ByVal MinLim As Double) As Double/ q8 |9 ]& M3 n+ H
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Dim Res#, VarAdj#6 e4 r! U% a+ M% B# N
7 R1 l3 j: X! N+ V- qVarAdj = 10 ^ -6
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! l9 n2 P! u, }( _; y1 i* Y: r* ZIf QesFun(MinLim + VarAdj) < QesFun(MaxLim - VarAdj) Then* o% Q6 r+ t, S+ Q1 R8 t( X, L
0 T' ^2 F) t1 f! a' L4 N Do While (1)
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Res = (MaxLim + MinLim) / 2
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, C4 ^: }$ Y6 |8 L" V If Abs(QesFun(Res)) <= 10 ^ -12 Then
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SolFunDic = Res: Exit Do
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ElseIf (QesFun(Res) < 0) Then
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MinLim = Res
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Else4 z7 _% S1 `" v4 H
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MaxLim = Res
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) O/ g; ~: Z5 |; ]$ |% C) o Loop
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& v+ f: l, B+ d$ F9 J Do While (1)$ a, h" P) X# z U2 Q5 K$ ^
' Z& h6 t! z7 f Res = (MaxLim + MinLim) / 2
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If Abs(QesFun(Res)) <= 10 ^ -12 Then
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SolFunDic = Res: Exit Do) |) B; E: q& `$ S) g+ f
- x" S/ q1 e- F3 C O0 E. o ElseIf (QesFun(Res) > 0) Then
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8 u# @1 U' \" W+ [ MinLim = Res
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5 S: R$ M. ~2 `( q Else
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0 J- Y U% R# A7 N6 l. S: x MaxLim = Res6 m: X0 k/ N/ i {
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End If. z: N# U2 K' }# @: W% N2 d+ m
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Loop
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8 u. |! o1 n# j1 G3 \! M5 KEnd If
`. Y* D- O7 UEnd Function& M, ~ F2 V8 M: `2 T
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2. 牛顿法" H" u) E8 e1 d: A: ]6 c8 {$ v9 W
2.1 由 f(AC)=arctan(AC/80)*80+1-AC1 y) e3 [; {. Y% n% s
求导 f(AC)’=1/(1+(AC/80)^2)-1
1 n3 a, S5 p% q' _' K- k! l 即 AC_1=AC_0- f(AC)/ f(AC)’: S6 ]8 b+ h z5 R6 C5 b
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2.2定义迭代函数:: ^5 R* i- @1 b& _6 T# K: U
Public Function QesFunNew(ByVal Var_AC As Double) As Double& h2 h! @, l8 _, ^8 F* `# q9 ~8 [6 e
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QesFunNew = Var_AC - (Atn(Var_AC / 80) * 80 + 1 - Var_AC) / (1 / (1 + (Var_AC / 80) ^ 2) - 1)
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End Function W$ r: K2 z6 j7 }3 ~
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, T: x* ]8 t- S/ ] K- p2.3定义求解函数% c( v+ G7 B; g0 e' A9 E
Public Function SolFunNew(ByVal IniAC As Double) As Double
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Dim Res#; D6 Z! ~: v1 @/ w s' C+ y
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Do While (1)" T) v$ B( }, Z5 u- C+ y
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Res = QesFunNew(IniAC)
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$ _7 q6 {1 z8 z3 v6 D8 z L( p If Abs(QesFun(Res)) <= 10 ^ -12 Then
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6 h+ B/ ]0 ]4 H7 N: r& \$ W; Z- p+ L SolFunNew = Res: Exit Do9 B3 a& k2 q! ]1 @5 m6 N
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Else% J. V$ g) L" ]& E# z
7 S( g7 B- }: O* v1 [5 h IniAC = Res$ y2 M! ^3 B2 ?8 _3 Z5 D' D
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End If
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这样做可能有点麻烦,但涉及到循环,迭代时,可自由调用自定义VBA函数和工作表函数(矩阵计算连杆机构),还可控制输出表格,便于插图。计算冷却塔时,积分得用辛普逊;解汽水比,得解非线性方程。对这些问题,EXCEL 工作表自身好像很吃力。
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