권호 표지

Bulletin of the Korean Mathematical Society (대한수학회보)

Korean Mathematical Society

  • Bimonthly
  • /
  • 1015-8634(pISSN)
  • /
  • 2234-3016(eISSN)

Aim & Scope

This journal endeavors to publish significant research of broad interests in pure and applied mathematics. One volume is published each year, and each volume consists of six issues (January, March, May, July, September, November).

http://bkms.kms.or.kr/submission KSCI KCI SCOPUS SCI SCIE

Volume 45 Issue 2

  1. Ramadan, A.A.;El-Latif, A.A. Abd 207
    https://doi.org/10.4134/BKMS.2008.45.2.207 PDF KSCI
    We introduce and study the notions of supra fuzzy convergence of fuzzy filters, $s{\gamma}$-fuzzy open (closed) sets, $s{\gamma}(/TEX>$s{\gamma}^*)$-fuzzy continuous and $s{\gamma}$-fuzzy open mapping. Also. we investigate some of fundamental properties of these notions.
  2. Wada, Koukichi 221
    https://doi.org/10.4134/BKMS.2008.45.2.221 PDF KSCI
    In the study of normal (complex analytic) surface singularities, it is interesting to investigate the invariants. The purpose of this paper is to give a characterization of the vanishing of ${\delta}_2$. In [11], we gave characterizations of minimally elliptic singularities and rational triple points in terms of th.. second plurigenera ${\delta}_2$ and ${\gamma}_2$. In this paper, we also give a characterization of rational triple points in terms of a certain computation sequence. To prove our main theorems, we give two formulae for ${\delta}_2$ and ${\gamma}_2$ of rational surface singularities.
  3. Cho, Chung-Je 231
    https://doi.org/10.4134/BKMS.2008.45.2.231 PDF KSCI
    We obtain a necessary and sufficient condition for the existence of Mendelsohn triple systems excluding contiguous units with ${\lambda}$ = 1. Also, we obtain the spectrum for cyclic such systems.
  4. Kim, Rak-Joong 241
    https://doi.org/10.4134/BKMS.2008.45.2.241 PDF KSCI
    By means of a Riccati transform and averaging technique some oscillation criteria are established for perturbed nonlinear differential equations of second order $(P_1)\;(p(t)x'(t))'+q(t)|x({\phi}(t)|^{{\alpha}+1}sgnx({\phi}(t))+g(t,\;x(t))=0$ $(P_2)$ and $(P_3)$ satisfying the condition (H). A comparison theorem and examples are given.
  5. Ashraf, Mohammad;Ali, Shakir 253
    https://doi.org/10.4134/BKMS.2008.45.2.253 PDF KSCI
    In this paper, we introduce the notion of generalized left derivation on a ring R and prow that every generalized Jordan left derivation on a 2-torsion free primp ring is a generalized left derivation on R. Some related results are also obtained.
  6. Cho, Yong-Uk 263
    https://doi.org/10.4134/BKMS.2008.45.2.263 PDF KSCI
    Kaplansky introduced the Baer rings as rings in which every left (or right) annihilator of each subset is generated by an idempotent. On the other hand, Hattori introduced the left (resp. right) P.P. rings as rings in which every principal left (resp. right) ideal is projective. The purpose of this paper is to introduce the near-rings with Baer like condition and near-rings with P.P. like condition which are somewhat different from ring case, and to extend the results of Arendariz and Jondrup.
  7. Rao, Vidhyanath K. 269
    https://doi.org/10.4134/BKMS.2008.45.2.269 PDF KSCI
    We prove that a full jack field does not exist on the sum of a trivial bundle and the canonical bundle on $G_{2,4}$, the Grassmanian of 2-planes in 4-space.
  8. Kohnen, Winfried 273
    https://doi.org/10.4134/BKMS.2008.45.2.273 PDF KSCI
    We will give a short and elementary proof of the existence of infinitely many primes p such that a given positive integer a congruent 3 modulo 4 is a quadratic non-residue modulo p.
  9. Boyadzhiev, Khristo N.;Gadiyar, H. Gopalkrishna;Padma, R. 277
    https://doi.org/10.4134/BKMS.2008.45.2.277 PDF KSCI
    The paper deals with the values at the negative integers of a certain Dirichlet series related to the Riemann zeta function and with the expression of these values in terms of Bernoulli numbers.
  10. Baser, Muhittin;Harmanci, Abdullah;Kwak, Tai-Keun 285
    https://doi.org/10.4134/BKMS.2008.45.2.285 PDF KSCI
    For an endomorphism ${\alpha}$ of a ring R, the endomorphism ${\alpha}$ is called semicommutative if ab=0 implies $aR{\alpha}(b)$=0 for a ${\in}$ R. A ring R is called ${\alpha}$-semicommutative if there exists a semicommutative endomorphism ${\alpha}$ of R. In this paper, various results of semicommutative rings are extended to ${\alpha}$-semicommutative rings. In addition, we introduce the notion of an ${\alpha}$-skew power series Armendariz ring which is an extension of Armendariz property in a ring R by considering the polynomials in the skew power series ring $R[[x;\;{\alpha}]]$. We show that a number of interesting properties of a ring R transfer to its the skew power series ring $R[[x;\;{\alpha}]]$ and vice-versa such as the Baer property and the p.p.-property, when R is ${\alpha}$-skew power series Armendariz. Several known results relating to ${\alpha}$-rigid rings can be obtained as corollaries of our results.
  11. Agwo, Hassan A. 299
    https://doi.org/10.4134/BKMS.2008.45.2.299 PDF KSCI
    In this paper, we establish some oscillation criteria for nonautonomous second order neutral delay dynamic equations $(x(t){\pm}r(t)x({\tau}(t)))^{{\Delta}{\Delta}}+H(t,\;x(h_1(t)),\;x^{\Delta}(h_2(t)))=0$ on a time scale ${\mathbb{T}}$. Oscillatory behavior of such equations is not studied before. This is a first paper concerning these equations. The results are not only can be applied on neutral differential equations when ${\mathbb{T}}={\mathbb{R}}$, neutral delay difference equations when ${\mathbb{T}}={\mathbb{N}}$ and for neutral delay q-difference equations when ${\mathbb{T}}=q^{\mathbb{N}}$ for q>1, but also improved most previous results. Finally, we give some examples to illustrate our main results. These examples arc [lot discussed before and there is no previous theorems determine the oscillatory behavior of such equations.
  12. De, Uday Chand;Jun, Jae-Bok;Gazi, Abul Kalam 313
    https://doi.org/10.4134/BKMS.2008.45.2.313 PDF KSCI
    The object of the paper is to study a Sasakian manifold with quasi-conformal curvature tensor.
  13. Cho, Sang-Hyun;Choi, Jae-Seo 321
    https://doi.org/10.4134/BKMS.2008.45.2.321 PDF KSCI
    Let $\bar{M}$ be a smoothly bounded pseudoconvex complex manifold with a family of almost complex structures $\{L^{\tau}\}_{{\tau}{\in}I}$, $0{\in}I$, which extend smoothly up to bM, the boundary of M, and assume that there is ${\lambda}{\in}C^{\infty}$(bM) which is strictly subharmonic with respect to the structure $L^0|_{bM}$ in any direction where the Levi-form vanishes on bM. We obtain explicit estimates for the $\bar{\partial}$-Neumann problem in Sobolev spaces both in space and parameter variables. Also we get a similar result when $\bar{M}$ is strongly pseudoconvex.
  14. Nadarajah, Saralees 339
    https://doi.org/10.4134/BKMS.2008.45.2.339 PDF KSCI
    The distributions of products and ratios of random variables are of interest in many areas of the sciences. In this paper, the exact distributions of the product |XY| and the ratio |X/Y| are derived when X and Y are independent Pearson type VII random variables.
  15. Song, Seok-Zun;Kang, Kyung-Tae;Shin, Hang-Kyun 355
    https://doi.org/10.4134/BKMS.2008.45.2.355 PDF KSCI
    For a Boolean rank 1 matrix $A=ab^t$, we define the perimeter of A as the number of nonzero entries in both a and b. The perimeter of an $m{\times}n$ Boolean matrix A is the minimum of the perimeters of the rank-1 decompositions of A. In this article we characterize the linear operators that preserve the perimeters of Boolean matrices.
  16. Friedrich, Thomas;Kim, Eui-Chul 365
    https://doi.org/10.4134/BKMS.2008.45.2.365 PDF KSCI
    We prove a lower bound for the first eigenvalue of the Dirac operator on a compact Riemannian spin manifold depending on the scalar curvature as well as a chosen Codazzi tensor. The inequality generalizes the classical estimate from [2].
  17. Jung, Hwan-Yup 375
    https://doi.org/10.4134/BKMS.2008.45.2.375 PDF KSCI
    Let $k={\mathbb{F}}_q(T)$ and ${\mathbb{A}}={\mathbb{F}}_q[T]$. Fix a prime divisor ${\ell}$ q-1. In this paper, we consider a ${\ell}$-cyclic real function field $k(\sqrt[{\ell}]P)$ as a subfield of the imaginary bicyclic function field K = $k(\sqrt[{\ell}]P,\;(\sqrt[{\ell}]{-Q})$, which is a composite field of $k(\sqrt[{\ell}]P)$ wit a ${\ell}$-cyclic totally imaginary function field $k(\sqrt[{\ell}]{-Q})$ of class number one. und give various conditions for the class number of $k(\sqrt[{\ell}]{P})$ to be one by using invariants of the relatively cyclic unramified extensions $K/F_i$ over ${\ell}$-cyclic totally imaginary function field $F_i=k(\sqrt[{\ell}]{-P^iQ})$ for $1{\leq}i{\leq}{\ell}-1$.
  18. Kim, Hwa-Kyung 385
    https://doi.org/10.4134/BKMS.2008.45.2.385 PDF KSCI
    For a positive integer m and a digraph D, the m-step competition graph $C^m$ (D) of D has he same set of vertices as D and an edge between vertices u and v if and only if there is a vertex x in D such that there are directed walks of length m from u to x and from v to x. Cho and Kim [6] introduced notions of competition index and competition period of D for a strongly connected digraph D. In this paper, we extend these notions to a general digraph D. In addition, we study competition indices of tournaments.
  19. Lee, Yang-Hi 397
    https://doi.org/10.4134/BKMS.2008.45.2.397 PDF KSCI
    In this paper, we modify L. $C\breve{a}dariu$ and V. Radu's result for the stability of the monomial functional equation $\sum\limits_{n=0}^{n}n\;C_i(-1)^{n-i}f(ix+y)-n!f(x)=0$ in the sense of Th. M. Rassias. Also, we investigate the superstability of the monomial functional equation.