• 천문학회지
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• 제28권2호
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• pp.245-253
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• 1995

We have analyzed the time series of Ca II H,K and ${\lambda}8498$ line profiles taken for a sunspot (SPO 5007) with the Echelle spectrograph attached to Vacuum Tower Telescope at Sacramento Peak Solar Observatory. Each set of spectra was taken simultaneously for 20 minutes at a time interval of 30 seconds. A total of 40 photographic films for each line was scanned by a PDS at Korea Astronomy Observatory. The central peak intensity of Ca II H ($I_{max}$), the intensity measured at ${\Delta}{\lambda}=-0.1{\AA}$ from the line center of ${\lambda}8498(I_{{\lambda}8489})$, the radial velocity ($V_r$) and the Doppler width (${\Delta}{\lambda}_D$) estimated from Ca II H have been measured to study the dynamical behaviors of the sunspot chromosphere. Fourier analysis has been carried out for these measured quantities. Our main results are as follows: (1) We have confirmed the 3-minute oscillation being dominant throughout the umbra. The period of oscillations jumps from 180 sec in the umbra to 500 to 1000 sec in the penumbra. (2) The nonlinear character of the umbral oscillation is noted from the observed sawtooth shaped radial velocity fluctuations with amplitudes reaching up to $5{\sim}6\;km/sec$. (3) The spatial distribution of the maximum powers shows that the power of oscillations is stronger in the umbra than in the penumbra. (4) The spatial distributions of the time averaged < $I_{max}$ > and < $V_r$ > across the spot are found to be nearly axially symmetric, implying that the physical quantities derived from the line profiles of Ca II H and ${\lambda}8498$ are inherently associated with the geometry of the magnetic field distribution of the spot. (5) The central peaks of the CaII H emission core lead the upward motions of the umbral atmosphere by $90^{\circ}$, while no phase delay is found in intensities between $I_{max}$ and $I_{{\lambda}8498}$, suggesting that the umbral oscillation is of standing waves.

• 천문학회보
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• 제40권1호
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• pp.59.2-59.2
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• 2015

We present the results of simultaneous observations of the H2O and SiO masers emitted from the circumstellar envelopes of the late-type stars. These observations have been carried out at the K and Q bands using KVN since 2014 August and were scheduled to test the feasibility of multi-frequency phase referencing analysis on the maser lines. In order to increase the accuracy of group delay solution in the fringe search on the continuum source, the IF channels were randomly distributed within the available bandwidth of 500 MHz in each band. The positions of all maser spots are relatively described with respect to the position of the reference continuum source through the source frequency phase referencing technique, and this provides the astrometric position accuracy. Therefore, the relative locations of the H2O maser spots with respect to the SiO maser spots are determined from our observations, and the capability of the simultaneous multi-band observation of KVN is proved to be powerful to study the maser pumping mechanism around the late-type stars.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2010년도 춘계학술대회
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• pp.512-515
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• 2010

공간상에 존재하는 전자파를 측정, 분석하여 신호정보(SIGINT; SIGnal INTelligence)를 획득하기 위해서 가장 중요한 것이 전자파의 주파수 정보이다. 특히 레이다 및 미사일에서 방사되는 초고주파 대역의 주파수를 순시 측정하는 방법으로, 지연선로의 위상차를 측정하여 주파수정보를 디지털데이터를 출력하는 부품으로 디지털 주파수 판별기(Digital frequency Discriminator; DFD)가 있다. DFD는 100nSec 이하의 짧은 시간동안에 존재하는 고주파 신호에 대해서도 초고주파신호의 주파수 정보를 실시간으로 측정하여 제공해야 한다. 본 논문에서는 광대역 4 채널의 지연선로와 코릴레이터로 구성된 고주파 입력부와 I/Q신호를 처리하여 주파수 정보를 얻어내는 디지털 처리부 및 정확한 주파수 정보를 얻기 위한 주파수 보정부로 이루어진 DFD의 구현방안을 제안하고 아주 짧은 펄스 형태의 모의 레이다 신호를 입력하여 얻은 시험결과를 토대로 설계의 타당성을 확인한다.

• 전자공학회논문지
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• 제50권6호
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• pp.246-253
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• 2013

위상 펼침 (phase unwrapping)과 최소자승(least-squares) 기법들을 이용한 기존 디지털 주파수 변별기 (Digital Frequency Discriminator: DFD) 설계를 바탕으로, 본 논문에서는 주파수 판별 대역이 4배 확장한 새로운 DFD 설계를 제안한다. 구체적으로, 주파수 판별 대역을 기존 2-6GHz에서 2-18GHz로 4배 확장함에 따라 주파수 판별 정확도를 높이기 위해 DFD 내의 지연선 수가 증가되고, 이에 따른 주파수 추정 연산량이 증가되는데, 본 논문에서는 이러한 2-18GHz 대역 주파수 판별을 위해 보다 효율적인 주파수 추정 알고리즘을 제안한다. 특히, 제안하는 주파수 추정 방법에서는 기존 방법인 위상 펼침 기법을 기반으로 펼친 위상의 후보군을 만들되, 각 지연선에서 발생할 수 있는 위상 잡음을 미리 추정하여, 적절한 펼친 위상 후보군을 선택하는 새로운 주파수 후보군 선택 방법을 제안한다. 이렇게 선택된 위상 후보군만을 최소자승 기법에 적용하여 주파수를 추정함으로써, 결과적으로 기존 DFD의 주파수 추정에 비해 연산량을 줄일 수 있다. 끝으로, 제안한 DFD에 대한 주파수 변별 방법을 비교 분석하고, 시뮬레이션을 통해 제안된 방법의 주파수 판별 성능을 검증한다.

• 한국전자파학회논문지
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• 제25권5호
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• pp.515-525
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• 2014

본 논문에서는 저 위상잡음을 갖는 전압 제어 평판형 복합공진기 발진기(Vt-PCRO: Voltage-tuned Planar Composite Resonator Oscillator)를 설계, 제작하였다. 설계된 발진기는 공진기, 2개의 위상천이기, 증폭기로 구성된다. 공진기는 dual mode SIW(Substrate Integrated Waveguide) 공진기를 이용하여 구성하였으며, 약 40 nsec의 높은 군지연을 갖도록 하였다. 2개의 위상천이기 중(PS1, PS2: Phase Shifter 1 및 Phase Shifter 2) PS1은 $360^{\circ}$의 위상천이량을 가지며, 제작된 발진기의 전송선로 길이에 관계없이 개루프 이득(open loop gain) 발진조건을 만족하도록 한다. PS2는 약 $70^{\circ}$의 위상천이량을 가지며 발진 주파수 조정용으로 사용된다. 증폭기는 제작 시 발생한 큰 삽입손실의 문제를 보완하기 위해 2단으로 구성하였다. 개루프 이득 측정을 통해 발진 조건을 만족하는 PS1의 전압을 측정한 뒤, 폐루프로 구성하여 발진기를 구현하였다. 발진기 측정 결과, 5.345 GHz의 발진 주파수에서, 위상 잡음은 100 kHz offset 주파수에서 -130.5 dBc/Hz를 얻었다. 이때 출력 전력은 약 3.5 dBm, 전기적 주파수 조정 범위는 0~10 V의 조정 전압에서 약 4.2 MHz를 보였다.

• 한국항행학회논문지
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• 제20권4호
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• pp.361-366
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• 2016

본 논문은 S-파라미터를 어드미턴스 파라미터로 변환하는 것을 바탕으로 비대칭 분배되면서 동시에 임의의 임피던스로 변환시킬 수 있는 임피던스 변환기를 나타내었다. 회로 해석 방법을 우수/ 기수 모드 방법과 비교하면 본 논문의 파라미터 변환을 통한 방법은 위상 지연 정보와 임의의 포트 임피던스 값을 포함시키고 그리고 비대칭 구조등을 해석하는데 간단함을 알 수 있다. 이 설계 방법의 타당성을 확인하기 위해서 중심주파수 1 GHz에서 3:1의 비대칭 분배비율을 갖고 있고 $50{\Omega}$을 $12.5{\Omega}$ 비율로 변환되는 임피던스 변환기를 설계하였다. 임피던스 변환기를 구현하는 방법은 유도된 수식으로부터 계산된 작은 임피던스 선로를 병렬 오픈스터브가 연결된 전송선로를 사용하여 구현하였고, 이것의 실험 결과는 시뮬레이션 결과와 동일하게 나옴을 확인하였다.

• 대한기계학회논문집B
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• 제26권1호
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• pp.1-11
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• 2002

Flow of fluid has been studied in various fields of fluid engineering. To hydraulic engineers, the unsteady flow such as pulsation and liquid hammering in pipes has been considered as a serious trouble. So we are supposed to approach the formalized mathematical model by using more exact momentum equation for fluid transmission lines. Most of recent studies fur pipe line have been studied without considerations of variation of viscosity and temperature, which are the main factors of pressure loss causing the friction of fluid inside pipe line. Frequency response experiments are carried out with use of a rotary sinusoidal flow generator to investigate wave equation take into account viscosity and temperature. But we observed that measured value of gains are reduced as temperature increased. And it was respectively observed that the measured value of gains are reduced and line width of gain is broadened out, when temperature was high in the same condition. As we confessed, pressure loss and phase delay are closely related with the length, diameter and temperature of pipe line. In addition, they are the most important factors, when we decide the momentum energy of working fluid.

• 한국전자파학회논문지
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• 제20권5호
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• pp.413-420
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• 2009

본 논문에서는 $2{\times}2$ 배열 안테나에 적용하여 분할된 원추형 빔 형성이 가능한 새로운 급전 구조를 제안한다. 제안된 급전 구조에는 네 개의 $90^{\circ}$ 하이브리드, 한 개의 크로스오버, 네 개의 $90^{\circ}$ 지연선을 사용하며, 이들은 서로 대칭적인 구조를 갖는다. 급전 구조의 성능을 검증하기 위하여 중심 주파수 2.57 GHz에서 동작하는 마이크로스트립 형태의 $2{\times}2$ 배열 안테나와 급전 구조를 제작하였고, 방사 패턴을 측정하였다. 측정된 안테나의 주 빔방향은 입력 포트의 선택에 따라 고도 방향으로는 $45^{\circ}$에서, 방위각 방향으로는 $45^{\circ}$, $135^{\circ}$, $225^{\circ}$, $315^{\circ}$에서 최대지향성을 갖는 것을 확인하였다.

• The Korean Journal of Physiology and Pharmacology
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• 제24권6호
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• pp.493-502
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• 2020

Apigenin, a naturally occurring flavonoid, is known to exhibit significant anticancer activity. This study was designed to determine the effects of apigenin on two malignant mesothelioma cell lines, MSTO-211H and H2452, and to explore the underlying mechanism(s). Apigenin significantly inhibited cell viability with a concomitant increase in intracellular reactive oxygen species (ROS) and caused the loss of mitochondrial membrane potential (ΔΨm), and ATP depletion, resulting in apoptosis and necroptosis in monolayer cell culture. Apigenin upregulated DNA damage response proteins, including the DNA double strand break marker phospho (p)-histone H2A.X. and caused a transition delay at the G₂/M phase of cell cycle. Western blot analysis showed that apigenin treatment upregulated protein levels of cleaved caspase-3, cleaved PARP, p-MLKL, and p-RIP3 along with an increased Bax/Bcl-2 ratio. ATP supplementation restored cell viability and levels of DNA damage-, apoptosisand necroptosis-related proteins that apigenin caused. In addition, N-acetylcysteine reduced ROS production and improved ΔΨm loss and cell death that were caused by apigenin. In a 3D spheroid culture model, ROS-dependent necroptosis was found to be a mechanism involved in the anti-cancer activity of apigenin against malignant mesothelioma cells. Taken together, our findings suggest that apigenin can induce ROS-dependent necroptotic cell death due to ATP depletion through mitochondrial dysfunction. This study provides us a possible mechanism underlying why apigenin could be used as a therapeutic candidate for treating malignant mesothelioma.

• 한국동물번식학회:학술대회논문집
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• 한국동물번식학회 2000년도 국제심포지움
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• pp.10-12
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• 2000

Members of the glycoprotein family, which includes CG, LH, FSH and TSH, comprise two noncovalently linked $\alpha$- and $\beta$-subunits. Equine chorionic gonadotropin (eCG), known as PMSG, has a number of interesting and unique characteristics since it appears to be a single molecule that possesses both LH- and FSH-like activities in other species than the horse. This dual activity of eCG in heterologous species is of fundamental interest to the study of the structure-function relationships of gonadotropins and their receptors. CG and LH $\beta$ genes are different in primates. In horse, however, a single gene encodes both eCG and eLH $\beta$-subunits. The subunit mRNA levels seem to be independently regulated and their imbalance may account for differences in the quantities of $\alpha$ - and $\beta$ -subunits in the placenta and pituitary. The dual activities of eCG could be separated by removal of the N-linked oligosaccharide on the $\alpha$-subunit Asn 56 or CTP-associated O-linked oligosaccharides. The tethered-eCG was. efficiently secreted and showed similar LH-like activity to the dimeric eCG. Interestingly, the FSH-like activity of the tethered-eCG was increased markedly in comparison with the native and wild type eCG. These results also suggest that this molecular can implay particular models of FSH-like activity not LH-like activity in the eCG/indicate that the constructs of tethered molecule will be useful in the study of mutants that affect subunit association and/or secretion. A single-chain analog can also be constructed to include additional hormone-specific bioactive generating potentially efficacious compounds that have only FSH-like activity. The LH/CG receptor (LH/CGR), a membrane glycoprotein that is present on testicular Leydig cells and ovarian theca, granulosa, luteal, and interstitial cells, plays a pivotal role in the regulation of gonadal development and function in males as well as in nonpregnant and pregnant females. The LH/CGR is a member of the family of G protein-coupled receptors and its structure is predicted to consist of a large extracellular domain connected to a bundle of seven membrane-spanning a-helices. The LH/CGR phosphorylation can be induced with a phorbol ester, but not with a calcium ionophore. The truncated form of LHR also was down-regulated normally in response to hCG stimulation. In contrast, the cell lines expressing LHR-t63I or LHR-628, the two phosphorylation-negative receptor mutant, showed a delay in the early phase of hCG-induced desensitization, a complete loss of PMA-induced desensitization, and an increase in the rate of hCG-induced receptor down-regulation. These results clearly show that residues 632-653 in the C-terminal tail of the LHR are involved in PMA-induced desensitization, hCG-induced desensitization, and hCG-induced down-regulation. Recently, constitutively activating mutations of the receptor have been identified that are associated with familial male-precocious puberty. Cells expressing LHR-D556Y bind hCG with normal affinity, exhibit a 25-fold increase in basal cAMP and respond to hCG with a normal increase in cAMP accumulation. This mutation enhances the internalization of the free and agonist-occupied receptors ~2- and ~17-fold, respectively. We conclude that the state of activation of the LHR can modulate its basal and/or agonist-stimulated internalization. Since the internalization of hCG is involved in the termination of hCG actions, we suggest that the lack of responsiveness detected in cells expressing LHR-L435R is due to the fast rate of internalization of the bound hCG. This statement is supported by the finding that hCG responsiveness is restored when the cells are lysed and signal transduction is measured in a subcellular fraction (membranes) that cannot internalize the bound hormone.