• Proceedings of the Korea Water Resources Association Conference
• /
• 2006.05a
• /
• pp.1671-1676
• /
• 2006

홍수범람은 무제부에서의 하천수위 상승으로 인해 제내로 서서히 침수해가는 것과 월류로 인한 제방의 파괴를 동반하는 급격한 범람의 두 가지 형태가 있다. 기존연구들은 대부분이 월류에 의한 제방붕괴를 고려할 경우, 제방붕괴가 점진적으로 발생함에도 불구하고 이를 수치모형에 적용할 경우 갑작스럽게 지형을 낮추거나 초기지형으로써 제방붕괴를 가정하여 이를 고려해왔다. 본 연구에서는 제방붕괴를 시간의존적인 함수로 가정하고 이를 고려할 수 있는 서브프로그램의 개발을 통해 기존의 방법과 비교하여 그 영향을 검토하였다. 본 연구에 사용된 수치모형은 비선형의 2차원 천수방정식을 비구조적 격자계가 적용된 유한체적법을 이용하였으며, Riemann 해를 계산하기 위하여 approximate HLLC Riemann solver를 이용하였다. 기연구된 제방붕괴 고려방법과 본 연구의 시간의존적인 제방붕괴 고려방법을 통해 월류량을 비교하였을 때, 기존연구들의 홍수범람 해석결과가 과다예측 되었음을 알 수 있었다. 추후의 이루어질 연구들에서는 시간의존적인 제방붕괴를 반드시 고려해야됨과 동시에 이를 자연현상과 좀더 가깝고 효과적으로 고려할 수 있도록 연구가 필요하다.

• Communications of the Korean Mathematical Society
• /
• v.17 no.1
• /
• pp.165-173
• /
• 2002

We first review Ramaswami's find Apostol's identities involving the Zeta function in a rather detailed manner. We then present corrected, or generalized formulas, or a different method of proof for some of them. We also give closed-form evaluation of some series involving the Riemann Zeta function by an integral representation of ζ(s) and Apostol's identities given here.

• Communications of the Korean Mathematical Society
• /
• v.35 no.1
• /
• pp.161-184
• /
• 2020

In this article, we establish some new weighted Hardy-type inequalities involving some variants of extended Riemann-Liouville fractional derivative operators, using convex and increasing functions. As special cases of the main results, we obtain the results of [18,19]. We also prove the boundedness of the k-fractional integral operator on L_p[a, b].

• Bulletin of the Korean Mathematical Society
• /
• v.51 no.1
• /
• pp.29-41
• /
• 2014

In this paper, we prove that infinite-dimensional vector spaces of -dense curves are generated by means of the functional equations f(x)+f(2x)+${\cdots}$+f(nx) = 0, with $n{\geq}2$, which are related to the partial sums of the Riemann zeta function. These curves ${\alpha}$-densify a large class of compact sets of the plane for arbitrary small ${\alpha}$, extending the known result that this holds for the cases n = 2, 3. Finally, we prove the existence of a family of solutions of such functional equation which has the property of quadrature in the compact that densifies, that is, the product of the length of the curve by the $n^{th}$ power of the density approaches the Jordan content of the compact set which the curve densifies.

• Journal of applied mathematics & informatics
• /
• v.24 no.1_2
• /
• pp.31-48
• /
• 2007

The paper deals with the solution of some fractional partial differential equations obtained by substituting modified Riemann-Liouville derivatives for the customary derivatives. This derivative is introduced to avoid using the so-called Caputo fractional derivative which, at the extreme, says that, if you want to get the first derivative of a function you must before have at hand its second derivative. Firstly, one gives a brief background on the fractional Taylor series of nondifferentiable functions and its consequence on the derivative chain rule. Then one considers linear fractional partial differential equations with constant coefficients, and one shows how, in some instances, one can obtain their solutions on bypassing the use of Fourier transform and/or Laplace transform. Later one develops a Lagrange method via characteristics for some linear fractional differential equations with nonconstant coefficients, and involving fractional derivatives of only one order. The key is the fractional Taylor series of non differentiable function $f(x+h)=E_{\alpha}(h^{\alpha}{D_x^{\alpha})f(x)$.

• Journal of Korea Water Resources Association
• /
• v.34 no.2
• /
• pp.187-195
• /
• 2001

In this study, a numerical model describing the shallow-water equations is newly developed by using a TVD scheme. The model has a second-order accuracy in time and space and is free from nonphysical oscillations, even in the vicinity of large gradients. Because a upwind based TVD scheme requires a Riemann solver, the HLLC scheme is employed in this model. To calibrate the applicability and accuracy, the developed model is used to simulate dam-break waves in an ideal channel and a sloshing flow n a paraboloidal basin. Agreements between numerical predictions and analytical solutions are very resonable.

• Journal of the Chungcheong Mathematical Society
• /
• v.24 no.2
• /
• pp.247-252
• /
• 2011

We study some properties of the Riemann-Stieltjes integrals with respect to the Riesz-$N\acute{a}gy$-$Tak\acute{a}cs$ distribution $H_{a,p}$ and its inverse $H_{p,a}$ on the unit interval satisfying the equation 1 - a = $a^2$ and p = 1 - a. Using the properties of the dual distributions $H_{a,p}$ and $H_{p,a}$, we compare the Riemann-Stieltjes integrals of $H_{a,p}$ over some essential intervals with that of its inverse $H_{p,a}$ over the related intervals.

• Journal of The Korean Astronomical Society
• /
• v.34 no.4
• /
• pp.191-201
• /
• 2001

My contribution to these proceedings summarizes a general overview on High Resolution Shock Capturing methods (HRSC) in the field of relativistic hydrodynamics with special emphasis on Riemann solvers. HRSC techniques achieve highly accurate numerical approximations (formally second order or better) in smooth regions of the flow, and capture the motion of unresolved steep gradients without creating spurious oscillations. In the first part I will show how these techniques have been extended to relativistic hydrodynamics, making it possible to explore some challenging astrophysical scenarios. I will review recent literature concerning the main properties of different special relativistic Riemann solvers, and discuss several 1D and 2D test problems which are commonly used to evaluate the performance of numerical methods in relativistic hydrodynamics. In the second part I will illustrate the use of HRSC methods in several astrophysical applications where special and general relativistic hydrodynamical processes play a crucial role.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.29 no.5B
• /
• pp.429-439
• /
• 2009

When Catastrophic extreme flood occurs due to dam break, the response time for flood warning is much shorter than for natural floods. Numerical models can be powerful tools to predict behaviors in flood wave propagation and to provide the information about the flooded area, wave front arrival time and water depth and so on. But flood wave propagation due to dam break can be a process of difficult mathematical characterization since the flood wave includes discontinuous flow and dry bed propagation. Nevertheless, a lot of numerical models using finite volume method have been recently developed to simulate flood inundation due to dam break. As Finite volume methods are based on the integral form of the conservation equations, finite volume model can easily capture discontinuous flows and shock wave. In this study the numerical model using Riemann approximate solvers and finite volume method applied to the conservative form for two-dimensional shallow water equation was developed. The MUSCL scheme with surface gradient method for reconstruction of conservation variables in continuity and momentum equations is used in the predictor-corrector procedure and the scheme is second order accurate both in space and time. The developed finite volume model is applied to 2D partial dam break flows and dam break flows with triangular bump and validated by comparing numerical solution with laboratory measurements data and other researcher's data.

• Honam Mathematical Journal
• /
• v.37 no.4
• /
• pp.569-575
• /
• 2015

In this paper, we research some properties of quaternionic regular functions in Clifford analysis. We investigate the corresponding Cauchy-Riemann system and find regularities of some hypercomplex valued functions.