• Journal of the Society of Disaster Information
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• v.17 no.4
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• pp.755-768
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• 2021

Purpose: Due to the nature of heatwave research, where research is conducted for a variety of subjects and purposes, it is important to anticipate research trends and development directions in order to improve the quality of the research. Therefore, in order to provide basic data that can suggest the current status of heatwave research and the direction of future research, we tried to examine the trends of heatwave-related research. Method: Heatwave studies published in academic journals registered with the National Research Foundation of Korea from 2011 to 2020 were analyzed by classifying them according to the research period, the purpose of the study, the research subjects and the research method. Result: The main research results are as follows. First, as interest in heatwaves increases, the number of heatwave studies also increases. Second, the purpose of heatwave research is biased and needs to be studied from various perspectives. Third, although various research subjects were used, an even study was not conducted. Fourth, under the influence of the research purpose, the bias of the research method appeared together. Conclusion: The damage caused by the heat wave is persistent and has a widespread impact. In order to manage, prevent, and respond to such heat waves as disasters, equal research should be conducted in various fields.

• Electronics and Telecommunications Trends
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• v.36 no.3
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• pp.53-64
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• 2021

As the 5G service market is expected to grow rapidly, the development of high-power, high-efficiency power amplifiers for the 5G communication infrastructure is indispensable. Gallium nitride (GaN) is attracting great interest as a key device in power devices and integrated circuits due to its wide bandgap, high carrier concentration, high electron mobility, and high-power saturation characteristics. In this study, we investigate the technology trends of Ka-band GaN radio frequency (RF) power devices and integrated circuits for operation in the millimeter-wave band of recent 5G mobile communication services. We review the characteristics of GaN RF high electron mobility transistor (HEMT) devices to implement power amplifiers operating at frequencies around 28 GHz and compare the technology of foreign companies with the device characteristics currently developed by the Electronics and Telecommunication Research Institute (ETRI). In addition, the characteristics of Ka-band GaN monolithic microwave integrated circuit (MMIC) power amplifiers manufactured using various GaN HEMT device technologies are reviewed by comparing characteristics such as frequency band, output power, and output power density of integrated circuits. In addition, by comparing the performance of the power amplifier developed by ETRI, the current status and future direction of domestic GaN power devices and integrated circuit technology will be discussed.

• Applied Chemistry for Engineering
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• v.34 no.1
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• pp.94-97
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• 2023

2,7-bis(3',6'-diphenyl-[1,1':2',1"-terphenyl]-4'-yl)-9,9'-spirobi[fluorene] (BTPSF) and 2,7-bis(1,4-diphenyltriphenylen-2-yl)-9,9'-spirobi[fluorene] (BDTSF) were successfully synthesized as novel blue-emission materials for organic light-emitting diodes (OLEDs) based on the spirobifluorene (SBF) moiety. BTPSF and BDTSF were obtained in high purity via a Diels-Alder reaction, without the use of a catalyst. Photoluminescence spectra of the synthesized materials showed maximum emitting wave-lengths of approximately 381 and 407 nm in solution and 395 and 434 nm in the film state, for BTPSF and BDTSF, respectively, indicating ultra-violet and deep blue emission colors. BDTSF was applied as an emissive layer (EML) in non-doped devices and achieved a current efficiency of 0.61 cd/A and an external quantum efficiency (EQE) of 0.46%.

• The Journal of the Acoustical Society of Korea
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• v.42 no.5
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• pp.422-428
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• 2023

Ultrafast ultrasound imaging has been applied to various imaging approaches, including shear wave elastography, ultrafast Doppler, and super-resolution imaging. However, these methods are still challenging in real-time implementation for three Dimension (3D) or portable applications because of their massive data rate required. In this paper, we proposed an adaptive quantization method that effectively reduces the data rate of large Radio Frequency (RF) data. In soft tissue, ultrasound backscatter signals require a high dynamic range, and thus typical quantization used in the current systems uses the quantization level of 10 bits to 14 bits. To alleviate the quantization level to expand the application of ultrafast ultrasound imaging, this study proposed a depth-sectional quantization approach that reduces the quantization errors. For quantitative evaluation, Field II simulations, phantom experiments, and in vivo imaging were conducted and CNR, spatial resolution, and SSIM values were compared with the proposed method and fixed quantization method. We demonstrated that our proposed method is capable of effectively reducing the quantization level down to 3-bit while minimizing the image quality degradation.

• The Journal of Internal Korean Medicine
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• v.44 no.2
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• pp.117-128
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• 2023

Objective: This study reported the improved symptoms of integrative Korean medicine-based treatment in a patient diagnosed with Systemic Lupus Erythematosus (SLE) who persistently complained of fatigue and chest tightness. Methods: A 51-year-old female SLE patient persistently complaining of fatigue and chest tightness underwent an 18-day treatment with Kracie Shihogayonggolmoryo-tang, Cheongpajeon-H, Gwanjeol-go, acupuncture, pharmacopuncture, cupping therapy, deep tissue meridian hot pack therapy, manual therapy, Interferential Current Therapy, and Extracorporeal Shock Wave Therapy. The Brief Fatigue Inventory (BFI) and Numeric Rating Scale (NRS) for each symptom were measured on admission, at one week, two weeks of hospitalization, and upon discharge. Clinical outcomes were assessed using these two figures. Results: After treatment, there was a reduction in the BFI score (7 to 3). The NRS score of chest tightness with hot flashes decreased from 8 to 5, neck pain lessened from 7 to 5, pain in both ankles diminished from 6 to 4, the cold hypersensitivity of both feet fell from 6 to 4, and heartburn decreased from 5 to 2. In order, the biggest clinical improvement was to heartburn, fatigue, and chest tightness with hot flashes. Conclusion: This case study shows that integrative Korean medicine-based treatment can improve symptoms of a Systemic Lupus Erythematosus patient persistently complaining of fatigue and chest tightness with hot flashes and suggests that Shihogayonggolmoryo-tang may be an effective option for managing and treating SLE patients.

• Current Optics and Photonics
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• v.7 no.1
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• pp.1-14
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• 2023

Wavefront-coding imaging can achieve high-quality imaging along with a wide range of defocus. In this paper, the anti-laser detection and damage performance of wavefront-coding imaging systems using different asymmetric phase masks are studied, through modeling and simulation. Based on FresnelKirchhoff diffraction theory, the laser-propagation model of the wavefront-coding imaging system is established. The model uses defocus distance rather than wave aberration to characterize the degree of defocus of an imaging system. Then, based on a given defocus range, an optimization method based on Fisher information is used to determine the optimal phase-mask parameters. Finally, the anti-laser detection and damage performance of asymmetric phase masks at different defocus distances and propagation distances are simulated and analyzed. When studying the influence of defocus distance, compared to conventional imaging, the maximum single-pixel receiving power and echo-detection receiving power of asymmetric phase masks are reduced by about one and two orders of magnitude respectively. When exploring the influence of propagation distance, the maximum single-pixel receiving power of asymmetric phase masks decreases by about one order of magnitude and remains stable, and the echodetection receiving power gradually decreases with increasing propagation distance, until it approaches zero.

• Korea Trade Review
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• v.41 no.2
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• pp.123-157
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• 2016

As the WTO·DDA continues to stagnate, mega FTAs such as the TPP will likely play the leading role in rule-making of trade for some time to come, creating a 'spaghetti bowl' of trade rules. FTAs, notably high-standard and broad-based regional or mega-FTAs, are the appropriate means to achieve this objective, because they cover many of the policy measures that are needed for the development of global value chains(GVC). The highest quality FTAs are increasingly adding new features like regulatory harmonization that may also foster GVC growth in partner countries. Complementary relationships among markets along value chains, involving both goods and services, also complicate analysis. This is particularly relevant when thinking about policy, since the traditional tendency to think about policies and regulate markets in unconnected silos can lead to unintended and undesirable results. This paper examines the current states of FTAs to determine which are more likely to push this latest wave of globalization further and faster, and explores the plans that are most helpful for GVC growth.

• Restorative Dentistry and Endodontics
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• v.46 no.1
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• pp.5.1-5.13
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• 2021

Objectives: The aim of the current study was to assess whether the amount of extruded debris differs for straight and severely curved root canals during retreatment using H-files, R-Endo, Reciproc and ProTaper Universal Retreatment (PTU-R) files. Additionally, the area of residual filling material was evaluated. Materials and Methods: Severely curved (n = 104) and straight (n = 104) root canals of maxillary molar teeth were prepared with WaveOne Primary file and obturated with gutta-percha and AH Plus sealer. Root canal filling materials were removed with one of the preparation techniques: group 1: H-file; group 2: R-Endo; group 3: Reciproc; group 4: PTU-R (n = 26). The amount of extruded material and the area of the residual filling material was measured. The data were analyzed with 2-way analysis of variance (ANOVA) and 1-way ANOVA at the 0.05 significance level. Results: Except for Reciproc group (p > 0.05), PTU-R, R-Endo, and H-file systems extruded significantly more debris in severely curved canals (p < 0.05). Each file system caused more residual filling material in severely curved canals than in straight ones (p < 0.05). Conclusions: All instruments used in this study caused apical debris extrusion. Root canal curvature had an effect on extruded debris, except for Reciproc system. Clinicians should be aware that the difficult morphology of the severely curved root canals is a factor increasing the amount of extruded debris during the retreatment procedure.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.3C
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• pp.159-166
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• 2008

The stress-strain behavior of soils can usually be regarded as non-linear, while it is also known that the soil exhibits the linear-elastic behavior at pre-failure state (very small strain range, $<10^{-3}%$). This study aims to analyze the variation of anisotropic elastic shear moduli of granular soils in various stress conditions. The stress probe experiments with the triaxial testing device equipped with local strain gages and multi-directional bender elements were conducted. When the stress ratio exceeds the range between -0.5 and 1.5, the elastic shear stiffness in the axial direction deviates from the empirical correlation with current stresses, which indicates that the yielding of soils alters the internal pathway through which the elastic shear wave propagates. The experimental results show that the variation of elastic shear moduli in the horizontal direction closely relates to the volume change of soils.

• 한국노년학
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• v.30 no.4
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• pp.1225-1237
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• 2010

This study aims to analyze the factors affecting consumption inequality in the 10 years following the financial crisis, applying the cohort method on the data for the first to the eleventh wave of the Korean Labor and Income Study produced by the Korean Labor Institute. The study found that consumption inequality increased rapidly immediately following the financial crisis, and then decreased gradually until increasing again from 2005 onward. Analyzed in terms of age-time-cohort effects, there was a significant change in consumption inequality around the age of mid-forties, and the decrease in consumption inequality was smaller in the younger generations than in the older ones. This suggests that as the current younger generations age over time, consumption inequality may become greater. Also, when the factors in population-cohort-age effects from 1998 onward are analyzed, the age effect in consumption inequality becomes smaller, whereas the role of the rising average age due to demographic shifts seems to be increasing. This means that consumption inequality may become a serious problem in the rapidly aging society. Therefore, there is a need to consider ways to bolster social security and to provide further public assistance in the low-income retiree.