• 천문학회보
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• 제41권2호
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• pp.41.1-41.1
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• 2016

The Galactic center, Sagittarius A* (Sgr A*), is the closest supermassive black hole and emits synchrotron radiation. It provides great opportunity to study the origin of mm/sub-mm emission. Currently, two competing models have been suggested as a jet base and a radiatively inecient accretion flow (RIAF). To unveil the properties, the extremely high resolution(${\sim}10{\mu}as$) corresponding to the projected Schwarzschild radius of ~0.1AU is necessary. With KVN, a jet model can be tested by multi- frequency simultaneous observations because the optically thick surface in a jet (i.e. radio core) moves toward the center at a higher frequency. We conducted 8 observations with KVN at 43/86GHz in 2015, and found that the measured positional shift to the reference calibrator, J1744-3116, was ~0.3 mas to the south of Sgr A* using the source frequency phase referencing (SFPR) at Q/W bands for the first time. With the result, in the future, we will attempt to measure the variation of source position shifts that can constrain the direction of approaching jets and the variability of black hole activity of Sgr A*.

• Asian Pacific Journal of Cancer Prevention
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• 제13권4호
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• pp.1683-1686
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• 2012

In the present case control study mRNA expression of the GSTP1 gene, encoding a phase II enzyme that detoxifies via glutathione conjugation, was investigated using semiquantitative PCR followed by SSCP for 49 confirmed head and neck (HN) cancer and 49 control samples. It was found that GSTP1 was upregulated in significantly higher number of cancers (OR 4.2, 95% CI 1.2-15.3). Grade wise correlation was also observed with more up regulation in patients with more advanced grades of HN carcinomas. We also found that 5 patients showed variation in mRNA with a larger product size than expected. Sequencing revealed insertion of an intronic segment between the $6^{th}$ and $7^{th}$ exon of the GSTP1 gene. Germline screening was performed showing mobility shifts which suggested mutation at the DNA level resulting in intronic portion retention. This study is of prime importance for drug design and treatment selection to overcome increased resistance of HN cancers to drugs due to alteration in the GSTP1 gene.

• 한국주거학회논문집
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• 제25권3호
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• pp.115-121
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• 2014

This paper draws the home into the stream of information and communications technology (ICT) development. Considering that homes and our home life are constantly affected by persistent change influenced by ICT, it is remarkable that ICT has been relatively neglected as an object of research in the field of housing studies. This study provides an overview of conceptual movements in ICT/home relationships and their design and social impact through a critical discourse analysis. The conceptual movements must be considered by professionals in the field of housing and built environment to stay attuned to changes in the 21st Century. Diverse debates took place in the discourse about ICT in relation to home. The stream of thought was started by futurists who saw the electronic cottage as a solution to the social problems caused by the separation of work and home life in industrial cities. ICT has now entered a new phase, with WiFi P2P networks and location-based social media that encourage sharable homes. Based on the analysis of the discourse on ICT and home, we drew from three issues related to the paradigm shifts in homes in the context of ICT development to provide future directions for housing studies: from space programming to time scheduling, from individual ownership to shared access, and from live+work dwelling to live+work+community.

• 수면정신생리
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• 제13권1호
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• pp.5-10
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• 2006

Alcohol has extensive effects on sleep and daytime sleepiness. Alcohol has a sleep inducing effect and the effect of increased non-REM sleep and suppressed REM sleep during the first half portion of night sleep, but alcohol induces the effect of decreased non-REM sleep and increased light sleep and frequent awakenings and REM rebound during the second half portion of night sleep. Alcohol provokes chronobiological change such as the changes of amplitude or the phase shifts of hormones or core body temperature. The sleep disruption resulting from alcohol drinking may lead to daytime fatigue and sleepiness. The elderly are at particular in the increased risk of alcohol-related sleep disorders because they achieve higher levels of alcohol in the blood and brain than do younger adults after consuming an equivalent dose. Bedtime alcohol consumption among older adults may lead to unsteadiness if walking is attempted during the night, with increased risk of falls and injuries. Continued alcohol use for sleep induction often induces aggravation of insomnia, alcoholism or sleep related breathing disorders such as obstructive sleep apnea. Alcohol should not be used as substitution of sleep pill because of the dependence and tolerance for sleep inducing effect, and the sleep disruption produced by alcohol withdrawal.

• Nuclear Engineering and Technology
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• 제49권4호
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• pp.668-674
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• 2017

Experimental verification of boron species in fuel CRUD (Chalk River Unidentified Deposit) would provide essential and important information about the root cause of CRUD-induced power shifts (CIPS). To date, only bonaccordite and elemental boron were reported to exist in fuel CRUD in CIPS-troubled pressurized water reactor (PWR) cores and lithium tetraborate to exist in simulated PWR fuel CRUD from some autoclave tests. We have reevaluated previous analysis of similar threadlike crystals along with examining some similar threadlike crystals from CRUD samples collected from a PWR cycle that had no indications of CIPS. These threadlike crystals have a typical [Ni]/[Fe] atomic ratio of ~2 and similar crystal morphology as the one (bonaccordite) reported previously. In addition to electron diffraction study, we have applied electron energy loss spectroscopy to determine boron content in such a crystal and found a good agreement with that of bonaccordite. Surprisingly, such crystals seem to appear also on corroded surfaces of Alloy 600 that was exposed to simulated PWR primary water with a dissolved hydrogen level of $5mL\;H_2/kg\;H_2O$, but absent when exposed under $75mL\;H_2/kg\;H_2O$ condition. It remains to be verified as to what extent and in which chemical environment this phase would be formed in PWR primary systems.

• 새물리
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• 제68권12호
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• pp.1324-1330
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• 2018

The elastic scatterings for the ${\alpha}+^{40}Ca$ and the ${\alpha}+^{58}Ni$ systems at $E_{lab}=240MeV$ have been analyzed within the framework of the Coulomb-modified Glauber model using two kinds of Gaussian density parameters for the target nuclei. The first one is to use Gaussian density parameters obtained from the root-mean-square radius. The second one is to use parameters calculated by matching the Gaussian density to the two-parameter Fermi density. The results with surface-matched Gaussian densities provide reasonable agreement with the experimental data, but the results without matching do not. The oscillatory structures observed in the angular distributions of both system can be interpreted as being due to the strong interference between the near-side and the far-side scattering amplitudes. The differences between the phase shifts obtained from the two methods are examined. We also investigate the effect of these differences on the differential and reaction cross sections, the transmission functions and the strong absorption radii.

• Journal of Magnetics
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• 제20권1호
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• pp.11-20
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• 2015

In this work, Monte Carlo simulation was employed to model the stretchable Ising monolayer film to investigate the effect of the spatial distance variation among magnetic atoms on magnetic behavior of the film. The exchange interaction was considered as functions of initial interatomic distance and the stretched distance (or the strain). Following Bethe-Slater picture, the magnetic exchange interaction took the Lennard-Jones potential-like function. Monte Carlo simulations via the Wolff and Metropolis algorithms were used to update the spin systems, where equilibrium and dynamic magnetic profiles were collected. From the results, the strain was found to have strong influences on magnetic behavior, especially the critical behavior. Specifically, the phase transition point was found to either increase or decrease depending on how the exchange interaction shifts (i.e. towards or away from the maximum value). In addition, empirical functions which predict how the critical temperatures scale with initial interatomic distance and the strain were proposed, which provides qualitatively view how to fine tune the magnetic critical point in monolayer film using the substrate modification induced strain.

• Journal of Power Electronics
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• 제19권5호
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• pp.1203-1215
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• 2019

Sensorless brushless DC (BLDC) motor drive systems are often subjected to inaccurate commutation signals and can produce high current peaks and conduction consumption. To achieve accurate commutation, a fast commutation shift regulation method for sensorless BLDC motor drive systems considering the influence of the inductance freewheeling process is presented to compensate inaccurate commutation signals. The regulation method is effective in both steady speed and variable speed operations. In the proposed method, the commutation error is gained from the line-voltage difference integral in a 60 electrical-degree conduction period and the outgoing phase current before commutation. In addition, the detection precision of the commutation error is improved due to the consideration of the freewheeling period. The commutation error is directly obtained, which avoids successive optimization and accelerates the convergence rate of the proposed method. Moreover, the commutation error features a positive or negative sign, which can be utilized as an indicator of advanced or delayed commutation. Finally, experiments are conducted to validate the effectiveness and feasibility of the proposed method. The results obtained show that the proposed method can accurately regulate commutation signals.

• Structural Engineering and Mechanics
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• 제70권5호
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• pp.623-637
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• 2019

This paper analyzes the non-stationary vibration and super-harmonic resonances in nonlinear dynamic motion of viscoelastic nano-resonators. For this purpose, a new coupled size-dependent model is developed for a plate-shape nano-resonator made of nonlinear viscoelastic material based on modified coupled stress theory. The virtual work induced by viscous forces obtained in the framework of the Leaderman integral for the size-independent and size-dependent stress tensors. With incorporating the size-dependent potential energy, kinetic energy, and an external excitation force work based on Hamilton's principle, the viscous work equation is balanced. The resulting size-dependent viscoelastically coupled equations are solved using the expansion theory, Galerkin method and the fourth-order Runge-Kutta technique. The Hilbert-Huang transform is performed to examine the effects of the viscoelastic parameter and initial excitation values on the nanosystem free vibration. Furthermore, the secondary resonance due to the super-harmonic motions are examined in the form of frequency response, force response, Poincare map, phase portrait and fast Fourier transforms. The results show that the vibration of viscoelastic nanosystem is non-stationary at higher excitation values unlike the elastic ones. In addition, ignoring the small-size effects shifts the secondary resonance, significantly.

• Journal of Electrochemical Science and Technology
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• 제14권2호
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• pp.194-204
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• 2023

Models based on diffusion-limited aggregation (DLA) have been extensively used to explore the mechanisms of dendritic particle aggregation phenomena. The physical and chemical properties of systems in which DLA aggregates emerge are given in their fractal. In this paper, we present a comprehensive study of the growth of electrodeposited copper dendrites in flat plate electrochemical cells from a fractal perspective. The effects of growth time, applied voltage, copper ion concentration, and electrolyte acidity on the morphology and fractal dimension of deposited copper were examined. 'Phase diagram' set out the variety of electrodeposited copper fractal morphology analysed by metallographic microscopy. The box counting method confirms that the electrodeposited dendritic structures manifestly exhibit fractal character. It was found that with the increase of the voltage and copper ion concentration. The fractal copper size becomes larger and its morphology shifts towards a dendritic structure, with the fractal dimension fluctuating around 1.60-1.70. In addition, the morphology of the deposited copper is significantly affected by the acidity of the electrolyte. The increase in acidity from 0.01 to 1.00 mol/L intensifies the hydrogen precipitation side reactions and the overflow path of hydrogen bubbles affects the fractal growth of copper dendrites.