INEQUALITIES OF JENSEN-PEČARIĆ-SVRTAN-FAN TYPE Jensen-Pečarić-Svrtan-Fan Type Inequalities CHAOBANG GAO AND JIAJIN WEN College Of Mathematics And Information Science Chengdu University Chengdu, 610106, P.R. China EMail: kobren427@163.com wenjiajin623@163.com Chaobang Gao and Jiajin Wen vol. 9, iss. 3, art. 74, 2008 Title Page Contents Received: 22 January, 2007 Accepted: 06 July, 2008 Communicated by: S.S. Dragomir 2000 AMS Sub. Class.: 26D15, 26E60. Key words: Jensen’s inequality, Pečarić-Svrtan’s inequality, Fan’s inequality, Theory of majorization, Hermite matrix. JJ II J I Page 1 of 17 Go Back Full Screen Close Abstract: By using the theory of majorization, the following inequalities of JensenPečarić-Svrtan-Fan type are established: Let I be an interval, f : I → R and t ∈ I, x, a, b ∈ I n . If a1 ≤ · · · ≤ an ≤ bn ≤ · · · ≤ b1 , a1 + b1 ≤ · · · ≤ an + bn ; f (t) > 0, f 0 (t) > 0, f 00 (t) > 0, f 000 (t) < 0 for any t ∈ I, then f (A(a)) fn,n (a) fk+1,n (a) fk,n (a) = ≤ ··· ≤ ≤ f (A(b)) fn,n (b) fk+1,n (b) fk,n (b) f1,n (a) A(f (a)) ≤ ··· ≤ = , f1,n (b) A(f (b)) the inequalities are reversed for f 00 (t) < 0, f 000 (t) > 0, ∀t ∈ I, where A(·) is the arithmetic mean and X 1 xi1 + · · · + xik fk,n (x) := n f , k = 1, . . . , n. k k Jensen-Pečarić-Svrtan-Fan Type Inequalities Chaobang Gao and Jiajin Wen vol. 9, iss. 3, art. 74, 2008 Title Page Contents 1≤i1 <···<ik ≤n Acknowledgements: This work is supported by the Natural Science Foundation of China (10671136) and the Natural Science Foundation of Sichuan Province Education Department (07ZA207). The authors are deeply indebted to anonymous referees for many useful comments and keen observations which led to the present improved version of the paper as it stands, and also are grateful to their friend Professor Wan-lan Wang for numerous discussions and helpful suggestions in preparation of this paper. JJ II J I Page 2 of 17 Go Back Full Screen Close Contents 1 Introduction 4 2 Proof of Theorem 1.1 6 3 Corollary of Theorem 1.1 12 4 A Matrix Variant 14 Jensen-Pečarić-Svrtan-Fan Type Inequalities Chaobang Gao and Jiajin Wen vol. 9, iss. 3, art. 74, 2008 Title Page Contents JJ II J I Page 3 of 17 Go Back Full Screen Close 1. Introduction In what follows, we shall use the following symbols: x := (x1 , . . . , xn ); f (x) := (f (x1 ), . . . , f (xn )); G(x) := (x1 x2 · · · xn )1/n ; x1 + x2 + · · · + xn ; Rn+ := [0, +∞)n ; Rn++ := (0, +∞)n ; n I n := {x|xi ∈ I, i = 1, . . . , n, I is an interval}; X 1 xi1 + · · · + xik fk,n (x) := n f , k = 1, . . . , n. k k 1≤i <···<i ≤n A(x) := 1 Jensen-Pečarić-Svrtan-Fan Type Inequalities Chaobang Gao and Jiajin Wen vol. 9, iss. 3, art. 74, 2008 k Jensen’s inequality states that: Let f : I → R be a convex function and x ∈ I n . Then Title Page Contents f (A(x)) ≤ A(f (x)). (1.1) This well-known inequality has a great number of generalizations in the literature (see [1] – [6]). An interesting generalization of (1.1) due to Pečarić and Svrtan [5] is: f (A(x)) = fn,n (x) ≤ · · · ≤ fk+1,n (x) ≤ fk,n (x) ≤ · · · ≤ f1,n (x) = A(f (x)). (1.2) In 2003, Tang and Wen [6] obtained the following generalization of (1.2): (1.3) fr,s,n ≥ · · · ≥ fr,s,i ≥ · · · ≥ fr,s,s ≥ · · · ≥ fr,j,j ≥ · · · ≥ fr,r,r = 0, where fr,s,n n n := (fr,n − fs,n ), r s fk,n := fk,n (x), 1 ≤ r ≤ s ≤ n. JJ II J I Page 4 of 17 Go Back Full Screen Close Ky Fan’s arithmetic-geometric mean inequality is (see [7]): Let x ∈ (0, 1/2]n . Then A(x) G(x) ≥ . A(1 − x) G(1 − x) (1.4) In this paper, we shall establish further extensions of (1.2) and (1.4) as follows: Theorem 1.1. Let I be an interval. If f : I → R, a, b ∈ I n (n ≥ 2) and Jensen-Pečarić-Svrtan-Fan Type Inequalities Chaobang Gao and Jiajin Wen (i) a1 ≤ · · · ≤ an ≤ bn ≤ · · · ≤ b1 , a1 + b1 ≤ · · · ≤ an + bn ; (ii) f (t) > 0, f 0 (t) > 0, f 00 (t) > 0, f 000 (t) < 0 for any t ∈ I, then (1.5) fn,n (a) fk+1,n (a) fk,n (a) f (A(a)) = ≤ ··· ≤ ≤ f (A(b)) fn,n (b) fk+1,n (b) fk,n (b) f1,n (a) A(f (a)) ≤ ··· ≤ = . f1,n (b) A(f (b)) vol. 9, iss. 3, art. 74, 2008 Title Page Contents JJ II J I The inequalities are reversed for f 00 (t) < 0, f 000 (t) > 0, ∀t ∈ I. The equality signs hold if and only if a1 = · · · = an and b1 = · · · = bn . Page 5 of 17 In Section 3, several interesting results of Ky Fan shall be deduced. In Section 4, the matrix variant of (1.5) will be established. Full Screen Go Back Close 2. Proof of Theorem 1.1 Lemma 2.1. Let f : I → R be a function whose second derivative exists and x ∈ I n , α ∈ Ωn = {α ∈ Rn+ : α1 + · · · + αn = 1}. Writing S(α, x) := 1 X f (α1 xi1 + · · · + αn xin ), n! i ···i 1 where P i1 ···in n denotes summation over all permutations of {1, 2, . . . , n}, S(α, a) F (α) := log , a, b ∈ I n , S(α, b) ui (x) := α1 xi1 + α2 xi2 + vi (x) := α1 xi2 + α2 xi1 + n X j=3 n X Jensen-Pečarić-Svrtan-Fan Type Inequalities Chaobang Gao and Jiajin Wen vol. 9, iss. 3, art. 74, 2008 Title Page Contents αj xij , αj xij , i = (i1 , i2 , . . . , in ). j=3 Then there exist ξi (a) between ui (a) and vi (a), and ξi (b) between ui (b) and vi (b) such that ∂F ∂F (2.1) (α1 − α2 ) − ∂α1 ∂α2 X f 00 (ξi (a))(ui (a) − vi (a))2 f 00 (ξi (b))(ui (b) − vi (b))2 1 X − , = n! i ···i 1≤i <i ≤i S(α, a) S(α, b) n n 3 1 2 P where i3 ···in denotes the summation over all permutations of {1, 2, . . . , n}\{i1 , i2 }. JJ II J I Page 6 of 17 Go Back Full Screen Close Proof. Note the following identities: 1 X X f (α1 xi1 + · · · + αn xin ) n! i ···i 1≤i 6=i ≤n n 3 1 2 1 X X = [f (ui (x)) + f (vi (x))]; n! i ···i 1≤i <i ≤n S(α, x) = n 3 1 2 ∂ ∂ [f (ui ) + f (vi )] − [f (ui ) + f (vi )] = [f 0 (ui ) − f 0 (vi )](xi1 − xi2 ); ∂α1 ∂α2 Chaobang Gao and Jiajin Wen vol. 9, iss. 3, art. 74, 2008 (2.2) ∂S ∂S − (α1 − α2 ) ∂α1 ∂α2 1 X X = [f 0 (ui ) − f 0 (vi )](α1 − α2 )(xi1 − xi2 ) n! i ···i 1≤i <i ≤n n 3 1 2 1 X X = [f 0 (ui ) − f 0 (vi )](ui − vi ). n! i ···i 1≤i <i ≤n Jensen-Pečarić-Svrtan-Fan Type Inequalities 3 n 1 2 By F (α) = log S(α, a) − log S(α, b) and (2.2), we have ∂F ∂F (α1 − α2 ) − ∂α1 ∂α2 ∂S(α, a) −1 ∂S(α, a) = (α1 − α2 ) [S(α, a)] − ∂α1 ∂α2 ∂S(α, b) −1 ∂S(α, b) −[S(α, b)] − ∂α1 ∂α2 Title Page Contents JJ II J I Page 7 of 17 Go Back Full Screen Close [f 0 (ui (a)) − f 0 (vi (a))][ui (a) − vi (a)] S(α, a) n 1≤i1 <i2 ≤n 3 [f 0 (ui (b)) − f 0 (vi (b))][ui (b) − vi (b)] − S(α, b) 00 X X f (ξi (a))[ui (a) − vi (a)]2 f 00 (ξi (b))[ui (b) − vi (b)]2 1 = − . n! i ···i 1≤i <i ≤n S(α, a) S(α, b) 1 X = n! i ···i 3 n X 1 2 Here we used the Mean Value Theorem for f 0 (t). This completes the proof. Lemma 2.2. Under the hypotheses of Theorem 1.1, F is a Schur-convex function or a Schur-concave function on Ωn , where F is defined by Lemma 2.1. Proof. It is easy to see that Ωn is a symmetric convex set and F is a differentiable symmetric function on Ωn . To prove that F is a Schur-convex function on Ωn , it is enough from [8, p .57] to prove that ∂F ∂F (2.3) (α1 − α2 ) − ≥ 0, ∀α ∈ Ωn . ∂α1 ∂α2 To prove (2.3), it is enough from Lemma 2.1 to prove (2.4) f 00 (ξi (a))[ui (a) − vi (a)]2 f 00 (ξi (b))[ui (b) − vi (b)]2 ≥ . S(α, a) S(α, b) Using the given conditions a1 ≤ · · · ≤ an ≤ bn ≤ · · · ≤ b1 , f (t) > 0 and f 0 (t) > 0, we obtain that aj ≤ bj (j = 1, 2, . . . , n) and the inequalities: (2.5) 1 1 ≥ > 0. S(α, a) S(α, b) Jensen-Pečarić-Svrtan-Fan Type Inequalities Chaobang Gao and Jiajin Wen vol. 9, iss. 3, art. 74, 2008 Title Page Contents JJ II J I Page 8 of 17 Go Back Full Screen Close By the given condition (i) of Theorem 1.1 and 1 ≤ i1 < i2 ≤ n, we have ai2 − ai1 ≥ bi1 − bi2 ≥ 0 and (2.6) [ui (a) − vi (a)]2 ≥ [ui (b) − vi (b)]2 ≥ 0. Jensen-Pečarić-Svrtan-Fan Type Inequalities From (2.5) and (2.6), we get (2.7) [ui (b) − vi (b)]2 [ui (a) − vi (a)]2 ≥ ≥ 0. S(α, a) S(α, b) Note that a, b ∈ I n , ui (a), vi (a), ui (b), vi (b) ∈ I, and min{ui (a), vi (a)} ≤ ξi (a) ≤ max{ui (a), vi (a)} ≤ min{ui (b), vi (b)} ≤ ξi (b) ≤ max{ui (b), vi (b)}. ξi (a) ≤ ξi (b) (ξi (a), ξi (b) ∈ I). If f 00 (t) > 0, f 000 (t) < 0 for any t ∈ I, from these and (2.8) we get (2.9) vol. 9, iss. 3, art. 74, 2008 Title Page Contents JJ II J I Page 9 of 17 Go Back It follows that (2.8) Chaobang Gao and Jiajin Wen f 00 (ξi (a)) ≥ f 00 (ξi (b)) > 0. Combining with (2.7) and (2.9), we have proven that (2.4) holds, hence, F is a Schur-convex function on Ωn . Full Screen Close Similarly, if f 00 (t) < 0, f 000 (t) > 0 for any t ∈ I, we obtain (2.10) −f 00 (ξi (a)) ≥ −f 00 (ξi (b)) > 0. Combining with (2.7) and (2.10), we know that the inequalities are reversed in (2.4) and (2.3). Therefore, F is a Schur-concave function on Ωn . This ends the proof of Lemma 2.2. Remark 1. When α1 6= α2 , there is equality in (2.3) if a1 = · · · = an and b1 = · · · = bn . In fact, there is equality in (2.3) if and only if there is equality in (2.5), (2.8), (2.9) and the first inequality in (2.6) or all the equality signs hold in (2.6). For the first case, by a1 ≤ · · · ≤ an ≤ bn ≤ · · · ≤ b1 , we get a1 = · · · = an , b1 = · · · = bn . For the second case, we have ai1 − ai2 = 0 = bi1 − bi2 . Since 1 ≤ i1 < i2 ≤ n and i1 , i2 are arbitrary, we get a1 = · · · = an , b1 = · · · = bn . Clearly, if a1 = · · · = an , b1 = · · · = bn , then (2.3) reduces to an equality. Proof of Theorem 1.1. First we note that if α = αk := k −1 , k −1 , . . . , k −1 , 0, . . . , 0 , | {z } Jensen-Pečarić-Svrtan-Fan Type Inequalities Chaobang Gao and Jiajin Wen vol. 9, iss. 3, art. 74, 2008 Title Page Contents JJ II J I Page 10 of 17 k Go Back we obtain that S(αk , x) = fk,n (x) and (2.11) Full Screen Close F (αk ) = log fk,n (a) . fk,n (b) By Lemma 2.2, we observe that F (α) is a Schur-convex(concave) function on Ωn . Using αk+1 ≺ αk for αk , αk+1 ∈ Ωn and the definition of Schur-convex(concave) functions, we have [8] (2.12) F (αk+1 ) ≤ (≥)F (αk ), k = 1, . . . , n − 1. It follows from (2.11) and (2.12) that (1.5) holds. Since αk+1 6= αk , combining this fact with Remark 1, we observe that the equality signs hold in (1.5) if and only if a1 = · · · = an , b1 = · · · = bn . This completes the proof of Theorem 1.1. Jensen-Pečarić-Svrtan-Fan Type Inequalities Chaobang Gao and Jiajin Wen vol. 9, iss. 3, art. 74, 2008 Title Page Contents JJ II J I Page 11 of 17 Go Back Full Screen Close 3. Corollary of Theorem 1.1 Corollary 3.1. Let 0 < r < 1, s ≥ 1, 0 < ai ≤ 2−1/s , bi = (1 − asi )1/s , i = 1, . . . , n, f (t) = tr , t ∈ (0, 1). Then the inequalities in (1.5) are reversed. Proof. Without loss of generality, we can assume that 0 < a1 ≤ · · · ≤ an . By bi = (1 − asi )1/s and 0 < ai ≤ 2−1/s (i = 1, . . . , n), we have 0 < a1 ≤ · · · ≤ an ≤ 2−1/s ≤ bn ≤ · · · ≤ b1 < 1. Jensen-Pečarić-Svrtan-Fan Type Inequalities Now we take g(t) := t + (1 − ts )1/s (0 < t ≤ 2−1/s ), so g 0 (t) = 1 − (1 − ts )(1/s)−1 ts−1 ≥ 0, i.e., g is an increasing function. Thus Chaobang Gao and Jiajin Wen vol. 9, iss. 3, art. 74, 2008 a1 + b 1 ≤ · · · ≤ an + b n . It is easy to see that f (t) = tr > 0, f 0 (t) = rtr−1 > 0, f 00 (t) = r(r − 1)tr−2 < 0, f 000 (t) = r(r − 1)(r − 2)tr−3 > 0 for any t ∈ (0, 1). By Theorem 1.1, Corollary 3.1 can be deduced. This completes the proof. Corollary 3.2. Let a ∈ (0, 1/2]n . Writing [AG; x]k,n := Y 1≤i1 <···<ik xi1 + · · · + xik k ≤n ! 1 n k () , we have (3.1) [AG; a]n,n A(a) = A(1 − a) [AG; 1 − a]n,n [AG; a]k,n [AG; a]k+1,n ≥ ··· ≥ ≥ [AG; 1 − a]k+1,n [AG; 1 − a]k,n G(a) [AG; a]1,n = . ≥ ··· ≥ [AG; 1 − a]1,n G(1 − a) Title Page Contents JJ II J I Page 12 of 17 Go Back Full Screen Close Equalities hold throughout if and only if a1 = · · · = an . (Compare (3.1) with [7, 10, 11]) Proof. We choose s = 1 in Corollary 3.1. Raising each term to the power of 1/r and letting r → 0 in (1.5), (3.1) can be deduced. This ends the proof. Corollary 3.3. Let f : I → R be such that f (t) > 0, f 0 (t) > 0, f 00 (t) > 0, f 000 (t) < 0 for any t ∈ I. Let Φ : I0 → I be increasing and Ψ : I0 → I be decreasing, and suppose that Φ + Ψ is increasing and sup Φ ≤ inf Ψ. Then R R f |I0 |−1 I0 Φdt f (Φ)dt ≤ RI0 (3.2) , R f (Ψ)dt −1 f |I0 | Ψdt I0 I0 where |I0 | is the length of the interval I0 . The inequality is reversed for f 00 (t) < 0, f 000 (t) > 0, ∀t ∈ I. f (A(a)) f (A(b)) A(f (a)) , A(f (b)) In fact, since (3.2) is an integral version of the inequality ≤ therefore (3.2) holds by Theorem 1.1. According to Theorem 1.1, (1.5) implies inequalities (1.1), (1.2) and (3.1), and the implication (3.1) to (1.4) is obvious. Consequently, Theorem 1.1 is a generalization of Jensen’s inequality (1.1), Pečarić-Svrtan’s inequalities (1.2) and Fan’s inequality (1.4). Note that Theorem 1.1 contains a great number of inequalities as special cases. To save space we omit the details. Jensen-Pečarić-Svrtan-Fan Type Inequalities Chaobang Gao and Jiajin Wen vol. 9, iss. 3, art. 74, 2008 Title Page Contents JJ II J I Page 13 of 17 Go Back Full Screen Close 4. A Matrix Variant P Let A = (aij )n×n (n ≥ 2) be a Hermite matrix of order n. Then tr A = ni=1 aii is the trace of A. As is well-known, there exists a unitary matrix U such that A = U diag(λ1 , . . . , λn )U ∗ , where U ∗ is the transpose conjugate matrix of U and the components of λ = (λ1 , . . . , λn ) are the eigenvalues of A. Thus tr A = λ1 +· · ·+λn . Let λ ∈ I n . Then, for f : I → R, we define f (A) := U diag(f (λ1 ), . . . , f (λn ))U ∗ (see [9]). Note that diag(λ1 , . . . , λn ) = U ∗ AU . Based on the above, we may use the following symbols: If, for A, we keep the elements on the cross points of the i1 , . . . , ik th rows and the i1 , . . . , ik th columns; replacing the other elements by nulls, then we denote this new matrix by Ai1 ···ik . Clearly, we have tr[U ∗ AU ]i1 ···ik = λi1 + · · · + λik . Thus we also define that X 1 λi1 + · · · + λik fk,n (A) := n f k k 1≤i1 <···<ik ≤n X 1 1 ∗ f tr[U AU ]i1 ···ik . = n k k 1≤i <···<i ≤n 1 k In particular, we have n 1X 1 f1,n (A) = f (λi ) = tr(f (A)); n i=1 n λ1 + · · · + λn 1 fn,n (A) = f =f trA ; n n n 1X trA − λi 1 E · trA − A fn−1,n (A) = f = trf , n i=1 n−1 n n−1 Jensen-Pečarić-Svrtan-Fan Type Inequalities Chaobang Gao and Jiajin Wen vol. 9, iss. 3, art. 74, 2008 Title Page Contents JJ II J I Page 14 of 17 Go Back Full Screen Close where E is a unit matrix. In fact, from trA − λ1 E · trA − A trA − λn ∗ U U = diag ,..., , n−1 n−1 n−1 we get X n trA − λi E · trA − A trf = f . n−1 n − 1 i=1 Based on the above facts and Theorem 1.1, we observe the following. Chaobang Gao and Jiajin Wen n Theorem 4.1. Let I be an interval and let λ, µ ∈ I . Suppose the components of λ,µ are the eigenvalues of Hermitian matrices A and B. If (i) λ1 ≤ · · · ≤ λn ≤ µn ≤ · · · ≤ µ1 , λ1 + µ1 ≤ · · · ≤ λn + µn ; 0 00 Jensen-Pečarić-Svrtan-Fan Type Inequalities vol. 9, iss. 3, art. 74, 2008 Title Page 000 (ii) the function f : I → R satisfies f (t) > 0, f (t) > 0, f (t) > 0, f (t) < 0 for any t ∈ I, and we have trf E·trA−A f n1 trA f (A) fk,n (A) trf (A) n−1 ≤ · · · ≤ k+1,n ≤ ≤ ≤ ··· ≤ . E·trB−B 1 f (B) f (B) trf (B) trf f n trB k+1,n k,n n−1 The inequalities are reversed for f 00 (t) < 0, f 000 (t) > 0, ∀t ∈ I. Equalities hold throughout if and only if λ1 = · · · = λn and µ1 = · · · = µn . Remark 2. If I = (0, 1/2], 0 < λ1 ≤ · · · ≤ λn ≤ 1/2, B = E − A, then the precondition (i) of Theorem 4.1 can be satisfied. Remark 3. Lemma 2.2 possesses a general and meaningful result that should be an important theorem. Theorem 1.1 is only an application of Lemma 2.2. Remark 4. If f (t) < 0, f 0 (t) < 0 for any t ∈ I, then we can apply Theorem 1.1 to −f . Remark 5. In [12, 13], several applications on Jensen’s inequalities are displayed. Contents JJ II J I Page 15 of 17 Go Back Full Screen Close References [1] D.S. MITRINOVIĆ, J.E. PEČARIĆ AND A.M. FINK, Classical and new inequalities in analysis, Kluwer Academic Publishers, Dordrecht/Boston/London, 1993. [2] J.E. PEČARIĆ, Inverse of Jensen-Steffensen’s inequality, Glasnik, Math., 16(3) (1981), 229–233. Jensen-Pečarić-Svrtan-Fan Type Inequalities [3] J.E. PEČARIĆ AND V. VOLENEC, Interpolation of the Jensen inequality with some applications, Ostereich Akad, Wissensch. Math. naturwiss klasse, Sitzungsberichte, 197 (1988), 229–233. Chaobang Gao and Jiajin Wen [4] J.E. PEČARIĆ, Remark on an inequality of S.Gabler, J. Math. Anal. Appl., 184 (1994), 19–21. Title Page vol. 9, iss. 3, art. 74, 2008 Contents [5] J.E. PEČARIĆ AND D. SVRTAN, Refinements of the Jensen inequalities based on samples with repetitions, J. Math. Anal. Appl., 222 (1998), 365–373. JJ II [6] X.L. TANG AND J.J. WEN, Some developments of refined Jensen’s inequality, J. Southwest Univ. of Nationalities (Natur. Sci.), 29(1) (2003), 20–26. J I Page 16 of 17 [7] W.L. WANG AND P.F. WANG, A class of inequalities for symmetric functions, Acta Math. Sinica, 27(4) (1984), 485–497. [8] A.W. MARSHALL AND I. OLKIN, Inequalities: Theory of Majorization and its Applications, New-York/London/Toronto /Sydney/San Francisco, 1979. [9] B. MOND AND J.E. PEČARIĆ, Generalization of a matrix inequality of Ky Fan, J. Math. Anal. Appl., 190 (1995), 244–247. Go Back Full Screen Close [10] J.E. PEČARIĆ, J.J. WEN, W.L. WANG AND T. LU, A generalization of Maclaurin’s inequalities and its applications, Mathematical Inequalities and Applications, 8(4) (2005), 583–598. [11] J.J. WEN AND W.L. WANG, The optimization for the inequalities of power means, Journal Inequalities and Applications, 2006, Article ID 46782, Pages 1-25, DOI 10.1155/JIA/2006/46782. [12] J.J. WEN AND W.L. WANG, The inequalities involving generalized interpolation polynomial, Computer and Mathematics with Applications, 56(4) (2008), 1045–1058. [ONLINE: http://dx.doi.org/10.1016/ j.camwa.2008.01.032]. [13] J.J. WEN AND C.B. GAO, Geometric inequalities involving the central distance of the centered 2-surround system, Acta. Math.Sinica, 51(4) (2008), 815–832. Jensen-Pečarić-Svrtan-Fan Type Inequalities Chaobang Gao and Jiajin Wen vol. 9, iss. 3, art. 74, 2008 Title Page Contents JJ II J I Page 17 of 17 Go Back Full Screen Close