• Bulletin of the Korean Chemical Society
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• v.34 no.11
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• pp.3367-3371
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• 2013

MgO nanorods were fabricated by the thermal evaporation of $Mg_3N_2$. The influence of ZnO sheathing and hydrogen plasma exposure on the photoluminescence (PL) of the MgO nanorods was studied. PL measurements of the ZnO-sheathed MgO nanorods showed two main emission bands: the near band edge emission band centered at ~380 nm and the deep level emission band centered at ~590 nm both of which are characteristic of ZnO. The near band edge emission from the ZnO-sheathed MgO nanorods was enhanced with increasing the ZnO shell layer thickness. The near band edge emission from the ZnO-sheathed MgO nanorods appeared to be enhanced further by hydrogen plasma irradiation. The underlying mechanisms for the enhancement of the NBE emission from the MgO nanorods by ZnO sheathing and hydrogen plasma exposure are discussed.

• Journal of The Korean Astronomical Society
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• v.37 no.5
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• pp.583-587
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• 2004

With the aim to investigate the statistical properties and the connection between thermal and non-thermal properties of the ICM in galaxy clusters, we have developed a statistical magneto-turbulent model which describes, at the same time, the evolution of the thermal and non-thermal emission from galaxy clusters. In particular, starting from the cosmological evolution of clusters, we follow cluster. mergers, calculate the spectrum of the magnetosonic waves generated in the ICM during these mergers, the evolution of relativistic electrons and the resulting synchrotron and Inverse Compton spectra. We show that the broad band (radio and hard x-ray) non-thermal spectral properties of galaxy clusters can be well accounted for by our model for viable values of the parameters (here we adopt a EdS cosmology).

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.4
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• pp.564-570
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• 1996

We have observed the red and blue luminescence from porous silicon (PS) without any rapid thermal oxidation. Aged porous silicon specimens prepared in dilute HF concentration, especially for the short duration of etching, display the increase of the blue band. The measured luminescence decay time at room temperature exhibits a decay time of about 100 ps and shows appreciably faster decay time than that of 20 K. No photoluminescence (PL) peak maximum shift is observed for the blue PL band at 77 K. However, the red PL band shows the blue shift and displays yellow luminescence at 77 K. The origin of red luminescence has some properties related to Si crystallites, whereas blue luminescence seems to be associated other than Si crystallites.

• ETRI Journal
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• v.38 no.2
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• pp.265-271
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• 2016

We analyzed the interface characteristics of Zn-based thin-film buffer layers formed by a sulfur thermal cracker on a $Cu(In,Ga)Se_2$ (CIGS) light-absorber layer. The analyzed Zn-based thin-film buffer layers are processed by a proposed method comprising two processes - Zn-sputtering and cracker-sulfurization. The processed buffer layers are then suitable to be used in the fabrication of highly efficient CIGS solar cells. Among the various Zn-based film thicknesses, an 8 nm-thick Zn-based film shows the highest power conversion efficiency for a solar cell. The band alignment of the buffer/CIGS was investigated by measuring the band-gap energies and valence band levels across the depth direction. The conduction band difference between the near surface and interface in the buffer layer enables an efficient electron transport across the junction. We found the origin of the energy band structure by observing the chemical states. The fabricated buffer/CIGS layers have a structurally and chemically distinct interface with little elemental inter-diffusion.

• Bulletin of the Korean Chemical Society
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• v.32 no.11
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• pp.4005-4010
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• 2011

We investigated thermal behavior of spin-coated films of P(HB-co-HHx)/PEG blends by using infraredreflection absorption (IRRAS) spectroscopy and 2D correlation spectroscopy. Based on 2D IRRAS correlation spectra, we could determine the sequence of spectral intensity changes with increasing temperature that PEG band changes first and then a band for crystalline component of P(HB-co-HHx) changes before a band for amorphous component. The intensities of bands for PEG and amorphous P(HB-co-HHx) were changed greatly as PEG weigh % of P(HB-co-HHx)/PEG blends increased. Transition temperatures of P(HB-co-HHx)/PEG blends were successfully determined by 2D gradient mapping method. The transition temperature of spincoated films of 98/2 and 90/10 P(HB-co-HHx)/PEG blends and 80/20 P(HB-co-HHx)/PEG blend determined by 2D gradient map are, respectively, about 137.5 and $132.5^{\circ}C$. Furthermore, P(HB-co-HHx)/PEG blends show an additional transition temperature that have been interpreted in terms of different lamellar thicknesses in spin coated films.

• Ocean Science Journal
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• v.41 no.2
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• pp.97-104
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• 2006

A useful radiance-converting method was developed to convert the Landsat-7 ETM+thermal-infrared (TIR) band's radiance ($L_{{\lambda},L7/ETM+}$) to that of Landsat-5 TM TIR ($L_{{\lambda},L5/TM+})$ as: $L_{{\lambda},L5/TM}=0.9699{\times}L_{{\lambda},L7/ETM+}+0.1074\;(R^2=1)$. In addition, based on the radiance-converting equation and the linear relation between digital number (DN) and at-satellite radiance, a DN-converting equation can be established to convert DN value of the TIR band between Landsat-5 and Landsat-7. Via this method, it is easy to integrate Landsat-5 and Landsat-7 TIR data to retrieve the sea surface temperature (SST) in coastal waters on the basis of local empirical algorithms in which the radiance or DN of Lansat-5 and 7 TIR band is usually the only input independent variable. The method was employed in a local empirical algorithm in Daya Bay, China, to detect the thermal pollution of cooling water discharge from the Daya Bay nuclear power station (DNPS). This work demonstrates that radiance conversion is an effective approach to integration of Landsat-5 and Landsat-7 data in the process of a SST retrieval which is based on local empirical algorithms.

• Transactions of Materials Processing
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• v.12 no.4
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• pp.358-363
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• 2003

Adiabatic shear bands have been observed in the serrated chip during high strain rate metal cutting process of medium carbon steel and titanium alloy The recent microscopic observations have shown that dynamic recrystallization occurs in the narrow adiabatic shear bands. However the conventional flow stress models such as the Zerilli-Armstrong model and the Johnson-Cook model, in general, do not predict the occurrence of dynamic recrystallization (DRX) in the shear bands and the thermal softening effects accompanied by DRX. In the present study, a strain hardening and thermal softening model is proposed to predict the adiabatic shear localized chip formation. The finite element analysis (FEA) with this proposed flow stress model shows that the temperature of the shear band during cutting process rises above 0.5Τ$_{m}$. The simulation shows that temperature rises to initiate dynamic recrystallization, dynamic recrystallization lowers the flow stress, and that adiabatic shear localized band and the serrated chip are formed. FEA is also used to predict and compare chip formations of two flow stress models in orthogonal metal cutting with AISI 1045. The predictions of the FEA agreed well with the experimental measurements.s.

• Bulletin of the Korean Chemical Society
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• v.33 no.7
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• pp.2333-2337
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• 2012

We report the synthesis and thermal annealing of Si-core/ZnO-shell nanorods using a two-step process comprising the metal-assisted electroless etching of Si and the sputter deposition of ZnO. Transmission electron microscopy and X-ray diffraction analysis showed that the cores of the annealed core-shell nanorods were single crystal diamond cubic-type Si, whereas the shells of the annealed core-shell nanorods were single crystal wurtzite-type ZnO. The PL spectra of Si nanorods consisted of a broad red emission band and a weaker blue emission band. The major emission band of Si nanorods was shifted from 700 nm (in the red region) to 440 nm (in the violet region) by ZnO coating. The violet emission of the core-shell nanorods was enhanced in intensity considerably by annealing in an oxidizing atmosphere. The origin of the PL enhancement by annealing is also discussed.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.323-329
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• 2002

The thermal effluent discharged from nuclear power plants can affect the offshore ecosystem change. The ability of measuring sea surface temperature in high resolution with Airborne MSS thermal spectral band(8.5 $\mu$m ~ 12.5 $\mu$m) and Landsat ETM+(10.4$\mu$m ~ 12.5 $\mu$m) gives us an information of spread range of thermal effluent. This information can be used as one of major factors fur analyzing the impact of the fish farm damage around the nuclear power plants. Every season from November 1999, this research has been conducted to investigate the extent of diffusion of thermal effluent discharged from KoRi, UlJin and WolSung Nuclear Power Plant located at the coastline of the East Sea of Korea.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.281-286
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• 1999

Nonlinear temperature distribution induced by the hydration heat generates thermal stress in mass concrete. At early ages, such thermal stress may induce thermal cracks in the structure which can affect on the durability and safety of the structure. Up to now, a lot of works have focused on the prediction of temperature distribution and thermal stress in the structure. In most of such works, however, the inside of structure was considered as adiabatic state to predict temperature distribution and the thermal stress. And due to the lacks of appropriate analysis models after crack, there was little research on the crack occurrence. This paper deals with the prediction of the temperature distribution in the structure using the rate of hydration heat generation and also estimates the behavior of structure before and after cracking due to hydration heat using crack band model.