• 천문학회보
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• 제39권1호
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• pp.39.2-39.2
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• 2014

We present a photometric study of star clusters in the nuclear starburst region of NGC 253 using gVI, YJ, and H band images in the Hubble Space Telescope archive. We find about one thousand star clusters in about 200"x200" field by visual inspection with I<21. We also find about ten thousand star clusters in the same field by automated classification method with magnitude range of 21< I $$\leq_-$$ 24. Ages and masses of star clusters are estimated using spectral energy distribution fitting method. Age distribution of star cluster shows two distinguished young populations with peak ages at 3.5 Myr and 18 Myr. Old populations (>100 Myr) are exist, but their number is small. About thirty young massive star clusters (<10 Myr, ) are found in nuclear region of NGC 253 which are regarded as a result of the recent starburst. Mass function of young star clusters in NGC 253 is somewhat different with those of star clusters in other galaxies. This result suggests that initial cluster mass functions (ICMFs) for star clusters are not universial. Especially ICMF in starburst galaxies may be distinguishable compared with those in normal spiral galaxies. We discuss the implications of these results.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2002년도 추계종합학술대회
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• pp.656-661
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• 2002

라이다 광원용 다중통과 Ti-sapphire 증폭기를 각도다중 방식으로 설계하여 출력에너지 및 스펙트럼 특성을 개선하였다. 2-단의 다중통과 증폭기에서 파장이 790nm 일 때, 42mJ의 출력에너지와 21dB의 증폭이득 및 26%의 출력효율을 얻었으며, 715~930nm이 파장가변 영역에서 스펙트럼 선폭은 0.05$cm^{-1}$ / 이하였다. 780nm의 파장에서 35%의 SHG 변환효율과 390nm의 파장에서 13%의 THG 변환효율을 각각 얻었다. 결과적으로 240~306nm의 자외영역과 360~460nm의 deep-blue 영역에서 연속적으로 파장을 가변시킬 수 있었다.

• Journal of Power Electronics
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• 제13권1호
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• pp.170-176
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• 2013

Power converters produce a vast range of harmonics, subharmonics and interharmonics. Harmonics analyzing tools based on the Fast Fourier Transform (FFT) assume that only harmonics are present and the periodicity intervals are fixed, while these periodicity intervals are variable and long in the presence of interharmonics. Using FFT may lead to invalid and undesired results due to the above mentioned issues. They can also lead to problems such as frequency blending, spectral leakage and the picket-fence effect. In this paper, the group-harmonic weighting (GHW) approach has been presented to identify the interharmonics in a power system. Afterwards, a modified GHW has been introduced to calculate the proper bandwidth for analyzing the various values of interharmonics. Modifying this method leads to more precise results in the FFT of a waveform containing inter harmonics especially in power systems with a fundamental frequency drift or frequency interference. Numerical simulations have been performed to prove the efficiency of the presented algorithm in interharmonics detection and to increase the accuracy of the FFT and the GWH methods.

• 한국통신학회논문지
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• 제25권7A호
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• pp.986-993
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• 2000

In this paper, we analyze transmission characteristics of ultrashort laser pulses using the properties of high-order pulses which are systematically obtained following their orders. The high-order pulses are easily derived from a modified PRS system model. But we make clear they are very useful to cover wider area and to show more accurate transmission characteristics of ultrashort pulses than Gaussian or Sech pulse approximations used conventionally. These are based on the fact that the spectra and bandwidths of the high-order pulses are geautifully related to their orders. First modifying the generalized PRS system model, we propose a new model for deriving any type of high-order pulse. And we offer a novel analysis method of ultrashort pulse transmission varying the order of the pulse from n=1 to n=100, we obtain spectra of ultrashort pulses with 1(ps)∼150(fs) FWHM's, which are widely used in optical pulse communications. One-step further, we derive PSD's of their pulse-tr ins when they are applied to Unipolar signaling scheme. These PSD's are decided in the range of possible pulse intervals. All of these results are not only coincided with some conventional experimental works but will be applied to any pioneering ultrashort pulse in the future.

• Bulletin of the Korean Chemical Society
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• 제32권10호
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• pp.3610-3613
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• 2011

CdS nanoparticles (NPs) were synthesized in an aqueous phase in order to investigate their spectral behaviors as efficient fluorescence resonance energy transfer (FRET) donors for various organic dye acceptors. Our prepared CdS NPs exhibiting strong and broad emission spectra between 480-520 nm were able to transfer energy in a wide wavelength region from green to red fluorescence dyes. Rhodamine 6G (Rh6G), rhodamine B (RhB), and sulforhodamine 101 acid (Texas red) were tested as acceptors of the energy transfer from the CdS NPs. The three dyes and synthesized CdS NPs exhibited good FRET behaviors as acceptors and donors, respectively. Energy transfers from the CdS NPs and organic Cy3 dye were compared to the same acceptor Texas red dye at different concentrations. Our prepared CdS NPs appeared to exhibit better FRET behaviors comparable to those of the Cy3 dye. These CdS NPs in an aqueous solution may be efficient FRET donors for various organic dyes in a wide wavelength range between green and red colors.

• 대한화학회지
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• 제55권6호
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• pp.960-968
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• 2011

A series of isonicotinyl hydrazones and their 4-thiazolidinones have been synthesized by condensation of isonicotinic acid hydrazide with various aromatic aldehydes to yield Schiff's bases, followed by the cyclocondensation of Schiff's bases with 2-mercaptoacetic acid to yield their 4-thiazolidinones. The synthesized compounds have been characterized by their elemental, analytical and spectral studies. All these compounds were evaluated for their invitro antimicrobial activity against a spectrum of non-resistant and resistant microbial organisms. These studies proved that compounds 5e,i against B. subtilis; 5e,f,h against B. anthracis; 5g,i against S. aureus showed good activity at lower concentrations. Compounds 5d-5i displayed significant activity against resistant strain of K. pneumonia with minimum inhibitory potency in the concentration range of 2-16 ug/ml.

• Bulletin of the Korean Chemical Society
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• 제28권5호
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• pp.791-794
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• 2007

A new azocalix[4]arene, 5,14,17,23-tetra[(2-benzoic acid)(azo)phenyl] calix[4]arene (2), has been prepared by hydrolysis of its ester derivative and characterized by 1H NMR, IR, UV-Vis spectroscopy and elemental analysis. Based on UV spectral changes, we found that 2 exhibits Pb2+ ion selectivity. In basic media, Pb2+ forms a 1:1 complex with the ligand. Beer's law is obeyed in the range of 2.0 × 10?6 ? 2.4 × 10?5 mol L?1 of Pb2+. The molar absorptivity (ε ) of 2-Pb2+ complex is 1.89 × 104 L mol?1 cm?1 at 440 nm, and the detection limit is 1.6 × 10?6 mol L?1.

• 대한전자공학회논문지TC
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• 제45권12호
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• pp.133-138
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• 2008

본 연구는 미래의 무선 및 유비쿼터스 통신을 위한 광/밀리미터파 신호의 직접 변환(생성) 실험을 50-60 GHz 범위에서 광 기술을 응용하여 성공적으로 수행하였다. 이 실험에서 22.5mW의 광신호가 광 도파로 내에 입사되었고, 밀리미터파 도파관 내부로 방사된 밀리미터파 신호는 밀리미터파 검출기에 의해 검출되었다. 밀리미터파 신호의 스펙트럼 선폭은 1 KHz이하를 나타냈다. 또, 50-60GHz 범위에서, 밀리미터파 신호의 Power 피크치 변위가 1.2dBm 이하인 이득특성을 나타냈다.

• 천문학논총
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• 제30권2호
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• pp.251-254
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• 2015

Low resolution spectra of Nova Delphini 2013 (V339 Del) in the optical range have been obtained at Bosscha Observatory, Indonesia during its maximum light (V = 4.3). Spectra were observed from August 16 to 27, 2013. The GAO-ITB RTS 20.3 cm telescope, and SBIG DSS-7 spectrograph and SBIG ST-7 XE as the detector have been employed throughout the observations. The spectra show P-Cygni profiles in Balmer, NaI'D' and Fe II lines, from which we determined shell expansion velocities of $1421.66{\pm}39.18km/s$, $1227.54{\pm}21.57km/s$ and 1402.86 km/s, respectively. Our spectroscopic observations followed the spectral evolution of V339 Del from the pre-maximum phase to early Orion phase. The characteristics of the nova Delphini 2013 resembles those of Fe II-type novae.

• Structural Engineering and Mechanics
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• 제55권5호
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• pp.1055-1086
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• 2015

The dynamic response of two-dimensional unbounded domain on the rigid bedrock in the time domain is numerically obtained. It is realized by the modified scaled boundary finite element method (SBFEM) in which the original scaling center is replaced by a scaling line. The formulation bases on expanding dynamic stiffness by using the continued fraction approach. The solution converges rapidly over the whole time range along with the order of the continued fraction increases. In addition, the method is suitable for large scale systems. The numerical method is employed which is a combination of the time domain SBFEM for far field and the finite element method used for near field. By using the continued fraction solution and introducing auxiliary variables, the equation of motion of unbounded domain is built. Applying the spectral shifting technique, the virtual modes of motion equation are eliminated. Standard procedure in structural dynamic is directly applicable for time domain problem. Since the coefficient matrixes of equation are banded and symmetric, the equation can be solved efficiently by using the direct time domain integration method. Numerical examples demonstrate the increased robustness, accuracy and superiority of the proposed method. The suitability of proposed method for time domain simulations of complex systems is also demonstrated.