• Proceedings of the KIPE Conference
• /
• 2013.11a
• /
• pp.25-26
• /
• 2013

본 논문에서는 직류출력과 교류출력을 갖는 단상 Z-소스 전자변압기를 제안하였다. 제안된 시스템은 입력은 병렬로, 츨력은 직렬로 연결된 2대의 Quasi Z-소스 AC-AC 컨버터로 구성되어 있다. 교류 입력 전압에 대하여 Quasi Z-소스 AC-AC 컨버터의 출력 전압은 동상의 강압과 승압 고정 주파수 가변 전압 VVCF(Variable Voltage Constant Frequency)의 특성을 가지고 있다. 또한 Quasi Z-소스 AC-AC 컨버터의 Active 스위치 단에 벅-컨버터를 연결하여 48V 직류 전압도 동시에 출력 할 수 있다. 끝으로 PI제어된 직류 벅 컨버터에 의하여 일정한 직류전압을 출력할 수 있음을 PSIM 시뮬레이션과 실험을 통하여 확인하였다.

• Korean Journal of Mathematics
• /
• v.6 no.1
• /
• pp.127-135
• /
• 1998

Let ${\rho}(A)$ and ${\rho}(B)$ denote the orders of entire functions $A(z)$ and $B(z)$ respectively. Suppose that ${\rho}(A)$ > 1 and 0 < ${\rho}(B){\leq}\frac{1}{2}$, and that ${\rho}$(A) is not an integer. Then it is shown that every nonconstant solution $f$ of $f^{{\prime}{\prime}}+A(z)f^{\prime}+B(z)f=0$ is of infinite order if all the zeros of $A(z)$ lie in a certain angular sector depending on its genus. In addition, we investigate some growth properties of $A(z)$.

• Bulletin of the Korean Mathematical Society
• /
• v.48 no.6
• /
• pp.1303-1314
• /
• 2011

We consider meromorphic solutions of q-difference equations of the form $$\sum_{j=o}^{n}a_j(z)f(q^jz)=a_{n+1}(z),$$ where $a_0(z)$, ${\ldots}$, $a_{n+1}(z)$ are meromorphic functions, $a_0(z)a_n(z)$ ≢ 0 and $q{\in}\mathbb{C}$ such that 0 < |q| ${\leq}$ 1. We give a new estimate on the upper bound for the length of the gap in the power series of entire solutions for the case 0 < |q| < 1 and n = 2. Some growth estimates for meromorphic solutions are also given in the cases 0 < |q| < 1. Moreover, we investigate zeros and poles of meromorphic solutions for the case |q| = 1.

• YAKHAK HOEJI
• /
• v.6 no.1
• /
• pp.21-24
• /
• 1962

A report is given of microscopic study of the root Angelica gigas Nakai comparing with Ligusticum acutilobum S. et Z.(=Angelica acutiloba Kitagawa). The following characteristics are outstanding. 1. Angelica gigas Nakai is more tender and softer than Ligusticum acutilobum S. et Z. 2. Both Angelica gigas Nakai and Ligusticum acutilobum S. et Z. are alike in the form and arrangement of fundamental parenchyma in cortex and xylem. 3. No mechanical tissues are present but the substitute fibers in the Angelica gigas Nakai and Ligusticum acutilobum S. et Z. 4. The intercellular space are more numerous and larger in Angelica gigas Nakai than in Ligusticum acutilobum S. et Z. 5. Secretory tissue in Angelica gigas Nakai consists of numerous canals while in Ligusticum acutilobum S. et Z. very few.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
• /
• v.9 no.2
• /
• pp.168-172
• /
• 1998

Several kinds of surgical methods have been used to treat the submucous cleft palate with hypernasality. The purpose of this study was to evaluate the double opposing Z-plasty which is one of the newly established surgical methods by Dr. Furlow in three cases of submucous cleft palate with hypernasality operated in this department. There were a number of advantage of double opposing Z-plasty. The surgery is adaptable for use in early patient. Midfacial growth retardation and complication were not seen in all cases. Hypernasality was improved subjectively. Using the nasometer, the nasalance score of the postoperative period was compared with that of before surgery, much improvement were noted in 'Ah', 'PaPa'. And fiberoptic endoscope was used to evaluate the velopharyngeal closure pattern. Velopharyngeal closure pattern with velum was improved dramatically, Double opposing Z-plasty seem to be a good procedure for the treatment of submucous cleft palate with hypernasality.

• Honam Mathematical Journal
• /
• v.15 no.1
• /
• pp.75-85
• /
• 1993

For A and B, $-1{\leq}B<A{\leq}1$, let P[A, B] be the class of functions p analytic in the unit disk E with P(0) = 1 and subordinate to $\frac{1+Az}{1+Bz}$. We introduce the class $T_{\alpha}[A,B]$ of functions $f:f(z)=z+\sum\limits_{n=2}^{{\infty}}a_nz^n$ which are analytic in E and for $z{\in}E$, ${\alpha}{\geq}0$, $[(1-{\alpha}){\frac{f(z)}{z}}+{\alpha}f^{\prime}(z)]{\in}P[A,B]$. It is shown that, for ${\alpha}{\geq}1$, $T_{\alpha}[A,B]$ consists entirely of univalent functions and the radius of univalence for $f{\in}T_{\alpha}[A,B]$, $0<{\alpha}<1$ is obtained. Coefficient bounds and some other properties of this class are studied. Some radii problems are also solved.

• Communications of the Korean Mathematical Society
• /
• v.26 no.3
• /
• pp.427-443
• /
• 2011

In [6, 8], we showed that any ideal of $\mathbb{Z}_4[X]/(X^l\;-\;1)$ is generated by at most two polynomials of the `standard' forms when l is even. The purpose of this paper is to find the `standard' generators of the cyclic codes over $\mathbb{Z}_{p^a}$ of length a multiple of p, namely the ideals of $\mathbb{Z}_{p^a}[X]/(X^l\;-\;1)$ with an integer l which is a multiple of p. We also find an explicit description of their duals in terms of the generators when a = 2.

• The Bulletin of The Korean Astronomical Society
• /
• v.43 no.2
• /
• pp.55.1-55.1
• /
• 2018

Theoretical models of reionization require that approximately 10% of the Lyman Continumm (LyC) photons escape from their host dark matter haloes and re-ionize neutral hydrogen in the Universe. However, observations of Lyman break galaxies (LBGs) at z~3 report much lower escape fractions of $f_{esc}{\sim}1%$. In an attempt to understand the discrepancy, we perform radiation-hydrodynamics simulations of isolated disk galaxies using RAMSES-RT with high resolution (maximum ~ 9 pc). We find that $f_{esc}$ is ~6% on average for the reference run ($Z=0.1Z{\odot}$), whereas the fraction decreases to ~1% in the case of metal-rich disk ($Z=1Z{\odot}$). This happens because dense metal-poor gas clumps are disrupted early due to strong Lya pressure and supernova explosions, while star particles are trapped for a longer period of time in the metal-rich environments. We also find that $f_{esc}$ is still significant (~4%) even when the amount of metal-poor gas is increased by a factor of 5. Our preliminary results suggest that the low escape fractions in LBGs may be better explained by (locally) metal-enriched gas near young stars than high gas fractions in galaxies.

• Korean Journal of Mathematics
• /
• v.29 no.4
• /
• pp.775-784
• /
• 2021

For the polynomial P(z) of degree n and having all its zeros in |z| ≤ k, k ≥ 1, Jain [6] proved that $${{\max\limits_{{\mid}z{\mid}=1}}\;{\mid}P^{\prime}(z){\mid}{\geq}n\;{\frac{{\mid}c_0{\mid}+{\mid}c_n{\mid}k^{n+1}}{{\mid}c_0{\mid}(1+k^{n+1})+{\mid}c_n{\mid}(k^{n+1}+k^{2n})}\;{\max\limits_{{\mid}z{\mid}=1}}\;{\mid}P(z){\mid}$$. In this paper, we extend above inequality to its integral analogous and there by obtain more results which extended the already proved results to integral analogous.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2010.06a
• /
• pp.299-299
• /
• 2010

In this study, microwave properties with compositions and frequency of the $Ba_3Co_2Fe_{24}O_{41}$ ceramics with Zn substitution for Co were investigated. From the XRD patterns, hexagonal structure of Z-type phase was existed as main phase. Diffraction peaks of Z-type phase were shifted to lower angle by Zn substituted for Co site. The permittivity was increased with Zn additions. In all composition, loss tangent of permittivities were increased with frequency. Permeability and magnetic resonance frequency were increased with Zn additions. Permeability was increased and loss tangent of permeability was decreased rapidly over 600 MHz~800 MHz. The loss tangent of permeability did not changed with composition ratio. In the case of $Ba_3Co_{1.6}Zn_{0.4}Fe_{24}O_{41}$ ceramics sintered at $1250^{\circ}C$ for 3 hours, the permittivity, loss tangent of permittivity, permeability and loss tangent of permeability were 28.277, 0.193, 22.992 and 0.065 at 310 MHz, respectively.