• Bulletin of the Korean Chemical Society
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• v.35 no.10
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• pp.3015-3020
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• 2014

The behavior of benzo[a]pyrene-7,8-dione (BPQ) in aqueous solution and its interaction with native DNA was investigated using conventional absorption and linear dichroism (LD) spectroscopy. The appearance of a broad absorption maximum at long wavelengths and its proportional relationship to solvent polarizability suggested that BPQ adopts a aggregated state for all solutions examined. Disappearance of this absorption band at higher temperatures in aqueous solution also supported BPQ aggregation. When associated with DNA absorption spectral properties were essentially the same as that in aqueous solution. However, two isosbestic wavelengths were found in the concentration-dependent absorption spectrum of the BPQ-DNA complex, suggesting the presence of at least two or more DNA-bound BPQ species. Both species produced $LD^r$ spectra whose magnitude in BPQ absorption region is larger or comparable to that in the DNA absorption region, suggesting that the molecular BPQ plane is near perpendicular relative to the local DNA helical axis. Therefore, BPQ molecules are aligned along the DNA stem in both DNA-aggregated BPQ species.

• Bulletin of the Korean Chemical Society
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• v.25 no.3
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• pp.373-376
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• 2004

A novel Er(III) complex with oxydiacetate and 1,10-phenanthroline was synthesized and its structure and luminescence properties were characterized. The complex of $[Er(ODA){\cdot}(phen){\cdot}4H_2O]^+$ crystallizes in the monoclinic space group $P2_1$/n with a = 12.216(4) ${\AA}$, b = 16.680(2) ${\AA}$, c = 12.627(3) ${\AA}$, ${\beta}=108.30(2)^{\circ}$, V = 2442.7(11) ${\AA}^3$, Z = 4 and ${\rho}=1.841 g/cm^3$. When the complex is excited at the He-Cd 325-nm line, it produces two broad bands spanning the regions 350-650 nm and 1200-1650 nm. The emission band of the complex is characterized by a series of spectral dips in the visible emission profile. The complex exhibits sensitized near- IR emission via two kinds of energy transfers from phen to Er(III): nonradiative and radiative energy transfers.

• Korean Journal of Optics and Photonics
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• v.18 no.1
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• pp.14-18
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• 2007

Photonic crystal fibers(PCFs) with silica cores within an away of air holes have unique properties. Broad band single-mode and the octave-spanning supercontinuum generation, impossible to achieve in classical fibers, can be realized. The design of PCFs is very flexible. There are two parameters to manipulate: air hole diameter, and lattice pitch. We introduced a fabrication process for control of the parameters to obtain endlessly single mode PCF, which is single mode in a large wavelength range, and highly nonlinear PCF. The numerical analysis and experiments are included.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.546-546
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• 2013

Zinc silicate ($Zn_2SiO_4$) has been identified as a suitable host material for a wide variety of luminescent activators, such as transition metal and rare earth elements. In particular, manganese-activated $Zn_2SiO_4$ exhibits highly efficient photoluminescenceand cathodoluminescence, which allows this material to be used in fluorescent lamps and display applications. In this study, we investigated the green and yellow luminescence from Mn-doped $Zn_2SiO_4$ thin films that were synthesized using radio frequency magnetron sputtering followed by annealing at $600{\sim}1,200^{\circ}C$ The refractive index of the $Zn_2SiO_4$: Mn films showed normal dispersion behavior. It was found that the $Zn_2SiO_4$: Mn films annealed at $800^{\circ}C$ ossessed a mixture of alpha and beta phases. The obtained photoluminescence spectrum consisted of two emission bands centered at 525 nm in the green range and 574 nm in the yellow range. The green luminescence originates from the divalent Mn ions in alpha phase of $Zn_2SiO_4$, while the yellow luminescence comes from the divalent Mn ions in beta phase. The films annealed at and above $900^{\circ}C$ xhibited only the alpha phase. The broad PL excitation band was observed ranging from 220 to 300 nm with a maximum at around 243 nm.

• Journal of Satellite, Information and Communications
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• v.2 no.1
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• pp.56-62
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• 2007

UWB(Ultra Wide Band) system can transmits information with low power but it can achieve high transmission rate using broad frequency bands. Using CR(Cognitive Radio) technology, we can use and share frequency efficiently without interfere to satellite communication system. However, passive characteristics of satellite receiver makes it hard to implement. This paper propose additional structure of satellite receiver which add amplifier and antenna to local oscillator. Proposing structure emits satellite receiver's local oscillator signal and UWB terminal detects it by energy detection. We can find out the possibility of co-existence of UWB system and satellite communication system through the simulation result.

• 전자공학회논문지 IE
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• v.48 no.3
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• pp.10-15
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• 2011

In the case of designing an acoustic transducer for high power application, we usually aim to transfer the source electric energy to the output acoustic energy as large as possible. For this purpose, we should match the impedance of the power amplifier to the impedance combined with the acoustic transducer impedance and the radiation impedance. Especially if we have electrical source with almost zero impedance, we need improve the power factor of the acoustic transducer in the load. In this paper, we propose a broad band impedance matching method by the improvement of power factor, which applies ABCD matrix.

• Journal of Ubiquitous Convergence Technology
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• v.2 no.1
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• pp.51-55
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• 2008

A digital home is a ubiquitous environment that is expected to be realized in the near future. All information appliances in a house are connected to each other through wired and/or wireless home networks. Authenticated user can access the various services provided by the digital home, and the access is not restricted by equipment, time, or location. The technologies that form the digital home can be grouped into two categories: wired networking technologies and wireless networking technologies. For the purpose of ubiquitous environments, wireless-networks offer suitable and seamless high-quality services. A wireless LAN can be created simply by equipping a single access point. For that reason, the cost of establishing such a network is low and using it is easy. Of course, there is an exciting new wireless technology. It is the Ultra Wide Band (UWB). However, it is not enough to bring wireless convenience, although offering a broad range of high-speed data transfer capabilities, Because of unstable. Thus, of the wireless-networking systems, we focus on the wireless LAN. We quantitatively analyze its capabilities. The dynamic and adaptive wireless LAN provides a foundation for the evolution toward the next generation of wireless and adaptive networks. The difference between wired LAN and wireless LAN in upload and download rates is small. Although the wireless LAN experiences a greater loss rate than the wired LAN, the difference is minimal. We conclude that a wireless LAN is suitable for use in an apartment environment.

• Journal of electromagnetic engineering and science
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• v.13 no.4
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• pp.224-232
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• 2013

This paper describes composite cavity-backed crossed scythe-shaped dipoles with wide-beam circularly polarized (CP) radiation for use in Global Navigation Satellite Systems. Each branch of the dipole arm contains a meander line, with the end shaped like a scythe to achieve a significant reduction in the size of the radiator. For dual-band operation, each dipole arm is divided into two branches of different lengths. The dipoles are crossed through a $90^{\circ}$ phase delay line of a vacant-quarter printed ring to achieve CP radiation. The crossed dipoles are incorporated with a cavity-backed reflector to make the CP radiation unidirectional and to improve the CP radiation beamwidth. The proposed antennas have broad impedance matching and 3-dB axial ratio bandwidths, as well as right-hand CP radiation with a wide-beamwidth and high front-to-back ratio.

• Journal of the Korean Ceramic Society
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• v.54 no.5
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• pp.422-428
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• 2017

Single-phase yellow phosphor, $CaGd_{2-x}ZrSc(AlO_4)_3:xCe^{3+}$ ($CGZSA:Ce^{3+}$), possessing cubic symmetry with varied $Ce^{3+}$ concentrations, was synthesized using the solid-state reaction method. The samples were characterized using X-ray diffraction (XRD), excitation spectra, emission spectra, thermal quenching, and decay curves. The cubic phase of $CGZSA:Ce^{3+}$ phosphor was confirmed via XRD analysis. The photoluminescence spectra of $CGZSA:Ce^{3+}$ phosphor demonstrated that the phosphor could be excited at the wavelength of 440 nm; a broad yellow emission band was centered at 541 nm. These results indicate that the phosphors are adequately excited by blue light and have the potential to function as yellow-emitting phosphors for applications in white light-emitting diodes.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.5
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• pp.450-456
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• 2006

In this paper, we report the changes of morphology, transmittance and photoluminescence (PL) in hydrogenated amorphous $As_{40}Ge_{10}Se_{15}S_{35}$ thin films, thermally deposited at the vapor incidence angles (${\theta}$) of $0^{\circ},\;45^{\circ}\;and\;80^{\circ}$. The hydrogenation was carried out under the condition of a $H_2$ pressure ($P_H$) of 20 atm and an annealing temperature range, $T_{Anneal}$ of $150^{\circ}C{\sim}210^{\circ}C$. A columnar structures with an inclination angle of approximately $65{\sim}70^{\circ}$ was formed in $80^{\circ}$-deposited films and then the columnar was broken after hydrogenation. Transmittance increases with an increase of deposition angle and by the hydrogenation. In particular, a broad PL band on the extended region is observed in obliquely deposited films and it increases during the hydrogenation.