• Kyungpook Mathematical Journal
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• 제58권4호
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• pp.697-709
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• 2018

In the present paper, we introduce and investigate two new subclasses, namely; the class of strongly ${\alpha}$-bi-spirallike functions of order ${\beta}$ and ${\alpha}$-bi-spirallike functions of order ${\rho}$, of the function class ${\Sigma};$ of normalized analytic and bi-univalent functions in the open unit disk $$U=\{z:z{\in}C\;and\;{\mid}z{\mid}<1\}$$. We find estimates on the coefficients ${\mid}a_2{\mid}$, ${\mid}a_3{\mid}$ and ${\mid}a_4{\mid}$ for functions in these two subclasses.

• Kyungpook Mathematical Journal
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• 제64권1호
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• pp.47-55
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• 2024

This paper introduces two new subclasses of analytical functions with negative coefficients and derives coefficient estimates for these novel subclasses. Further, inclusion relations and necessary and sufficient conditions for the Poisson distribution series to belong to these subclasses are established.

• 대한수학회보
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• 제42권3호
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• pp.563-569
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• 2005

In [2], Jahangiri studied the harmonic starlike functions of order $\alpha$, and he defined the class T$_{H}$($\alpha$) consisting of functions J = h + $\bar{g}$ where hand g are the analytic and the co-analytic part of the function f, respectively. In this paper, we introduce the class T$_{H}$($\alpha$, $\beta$) of analytic functions and prove various coefficient inequalities, growth and distortion theorems, radius of convexity for the function h, if the function J belongs to the classes T$_{H}$($\alpha$) and T$_{H}$($\alpha$, $\beta$).

• 대한수학회논문집
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• 제37권1호
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• pp.113-123
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• 2022

In the present paper, we introduce the subclasses 𝔅_1Σ(𝜇), B_1Σ(𝜇, 𝛾) and U_Σ(𝜇, 𝛾) of bi-univalent Bazilevič functions which are defined in the open unit disk 𝔻. Further, we obtain sharp estimates on initial coefficients a₂, a₃, a₄ and also sharp estimate on the Fekete-Szegö functional a₃ - ka²₂ for the functions belong to these subclasses.

• 대한수학회지
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• 제51권3호
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• pp.567-592
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• 2014

Complex-valued harmonic functions that are univalent and sense-preserving in the open unit disk are widely studied. A new methodology is employed to construct subclasses of univalent harmonic mappings from a given subfamily of univalent analytic functions. The notions of harmonic Alexander operator and harmonic Libera operator are introduced and their properties are investigated.

• Kyungpook Mathematical Journal
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• 제49권4호
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• pp.751-761
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• 2009

In this paper, we introduce and study a comprehensive family of harmonic univalent functions which contains various well-known classes of harmonic univalent functions as well as many new ones. Also, we improve some results obtained by Frasin [3] and obtain coefficient bounds, distortion bounds and extreme points, convolution conditions and convex combination are also determined for functions in this family. It is worth mentioning that many of our results are either extensions or new approaches to those corresponding previously known results.

• Korean Journal of Mathematics
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• 제32권1호
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• pp.173-182
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• 2024

In this paper, we derive the necessary and sufficient conditions for the Gaussian hypergeometric function to be in some subclasses of analytic functions.

• 대한수학회논문집
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• 제33권2호
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• pp.437-444
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• 2018

Let S denote the class of analytic and univalent functions in the open unit disk $D=\{z:{\mid}z{\mid}<1\}$ with the normalization conditions f(0) = 0 and f'(0) = 1. In the present article, an upper bound for third order Hankel determinant $H_3(1)$ is obtained for a certain subclass of univalent functions generated by Ruscheweyh derivative operator.

• 대한수학회보
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• 제50권1호
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• pp.1-10
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• 2013

In the present paper we derive various useful properties and characteristics for certain class of analytic functions by using the techniques of differential subordination. Some interesting corollaries and applications of the results presented here are also discussed.

• Kyungpook Mathematical Journal
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• 제62권2호
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• pp.257-269
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• 2022

In the present paper, a subclass of analytic and bi-univalent functions is defined using a symmetric q-derivative operator by means of Gegenbauer polynomials. Coefficients bounds for functions belonging to this subclass are obtained. Furthermore, the Fekete-Szegö problem for this subclass is solved. A number of known or new results are shown to follow upon specializing the parameters involved in our main results.