• Communications of the Korean Mathematical Society
• /
• v.33 no.3
• /
• pp.823-831
• /
• 2018

We define progressive tax rate functions, study their properties, and describe some smooth models. The key requirement, defining the progressive nature of the taxation model, is that the progressive tax rate functions should have infinite contact with the zero function at the origin, in order to care the poor. In constructing a wide array of such functions, assisting functions are introduced.

• Transactions on Electrical and Electronic Materials
• /
• v.5 no.3
• /
• pp.120-121
• /
• 2004

YBaCuO thick films were fabricated by plasma enhanced chemical vapor deposition, and the crystallinity and the superconducting properties were investigated. The growth temperature to obtain the thick films was decreased by around 150$^{\circ}C$ due to plasma enhancement. The zero resistivity temperatures for films grown at 590$^{\circ}C$ and 620$^{\circ}C$ were 55 and 80 K, respectively.

• Honam Mathematical Journal
• /
• v.30 no.4
• /
• pp.659-670
• /
• 2008

We denote by $\mathcal{Q}$(A) the set of all real matrices with the same sign pattern as a real matrix A. A matrix A is an SN-matrix provided there exists a set S of sign pattern such that the set of sign patterns of vectors in the -space of $\tilde{A}$ is S, for each ${\tilde{A}}{\in}\mathcal{Q}(A)$. Some properties of SN-matrices arc investigated.

• 제어로봇시스템학회:학술대회논문집
• /
• 1992.10a
• /
• pp.912-916
• /
• 1992

In this paper we investigate the connection between the continuous-time FIR(finite impulse response) filter and the corresponding discrtet-time FIR filter with fast sampling. The interconnection is established by formulating the discrete-time case using delta operators which has superior numerical properties in discretizing prcedure. The aim of this paper is to present a unified FIR filter using the .delta.-operator and to show that, as sampling interval .DELYA. aperator to zero, the results of this filter converge to the corresponding continuous-time reuslts, which implies that the unified FIR filter unifies continous-time FIR filter and discrtet-time FIR filter.

• 제어로봇시스템학회:학술대회논문집
• /
• 1992.10a
• /
• pp.578-583
• /
• 1992

In this paper, we show that various navigation constant values in PNG law can result in as optimal gains when we introduce proper time-varying weighting functions into the cost function of an optimal control problem. we then apply this idea to the guidance problem where we are required to achieve a given impact angle as well as the zero miss distance. As a result, we obtain a set of optimal guidance laws each of which could be related to a navigation constant in PNG. Some basic properties of these guidance laws are also presented.

• 제어로봇시스템학회:학술대회논문집
• /
• 1992.10a
• /
• pp.572-577
• /
• 1992

In this paper, the optimal homing guidance problem is investigated for the general missile/target models described in the state-space. The closed-form solution of the optimal guidance law derived, and its asymptotic properties are studied as the time-to-go goes to infinity or zero. Futhermore, several approximate solutions of the optimal guidance law are suggested for real-time applications.

• Korean Journal of Mathematics
• /
• v.23 no.1
• /
• pp.171-180
• /
• 2015

It is discovered in [7] that a dielectric material is coated by a plasmonic material of negative permittivity with dissipation, then cloaking by anomalous localized resonance may occur as the dissipation tends to zero. In this paper, we investigate numerically the pointwise behavior of the potential in the shell when cloaking by anomalous localized resonance (CALR) occurs. By changing locations a dipole source, we can observe some localizing properties of the potential in the shell.

• Communications of the Korean Mathematical Society
• /
• v.23 no.2
• /
• pp.161-167
• /
• 2008

A ring R is called an $I_0$-ring if each left ideal not contained in the Jacobson radical J(R) contains a non-zero idempotent. If, in addition, idempotents can be lifted modulo J(R), R is called an I-ring or a potent ring. We study whether these properties are inherited by some related rings. Also, we investigate the structure of potent rings.

• Journal of applied mathematics & informatics
• /
• v.16 no.1_2
• /
• pp.125-142
• /
• 2004

We analyze the convergence properties of Powell's UOBYQA method. A distinguished feature of the method is its use of two trust region radii. We first study the convergence of the method when the objective function is quadratic. We then prove that it is globally convergent for general objective functions when the second trust region radius p converges to zero. This gives a justification for the use of p as a stopping criterion. Finally, we show that a variant of this method is superlinearly convergent when the objective function is strictly convex at the solution.

• The Mathematical Education
• /
• v.21 no.1
• /
• pp.19-21
• /
• 1982

In this paper, we define the z-S-closed spaces using the notions of zero-sets and S-closed spaces introduced by T. Thompson, and investigate some properties of these spaces. We also obtain the following results. If a space X is z-S-closed, then every cover of z-regular semiopen sets has a finite proximate subcover. A z-extremally disconnected z-QHC space is z-S-closed, z-S-closed is contagious.