• 천문학회보
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• 제39권2호
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• pp.68.2-68.2
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• 2014

High Frequency Peakers (HFPs) are radio-loud Active Galactic Nuclei (AGN), which are regarded as being in the earliest evolutionary phase (102-103 years) of radio galaxies. They are expected to be small in size (< ~1 kpc) compared to their host galaxies (~a few 10s kpc), and have convex spectra, which are peaking at high radio frequency (> 5 GHz). Their size and spectral shape are the most obvious supporting evidence of extremely young ages. HFPs are therefore ideal targets to probe the earliest stage of radio sources. To date however, the young radio source classification has been relying mainly on the spectral shape which usually does not cover high enough frequencies where the true peak flux is located. Hence HFPs are often confused with blazars which may show a similar spectral shape and apparent compactness but are a somewhat evolved form of AGNs. Therefore, we have been challenging to identify HFPs among the sample of 19 candidates using the Korean VLBI Network (KVN) which enables us to extend the radio spectrum baseline up to 22 and 43 GHz. These are higher than the frequencies used in most previous studies of HFPs, allowing us to select genuine HFPs. By long-term monitoring of 18 epochs, we have also inspected the variability of the sample to select out blazars which are highly variable yet with a similar radio spectrum. In this work, we present the light curves and spectral properties of the HFP candidates. We discuss the results of our re-identification of HFPs.

• 아태비즈니스연구
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• 제9권3호
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• pp.71-82
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• 2018

This study verifies whether the sustainable tax strategy provides unique information on earnings persistence and brings about the difference of value relevance of accounting information. Sustainability is measured by the 5-year coefficient of variation in cash ETR, such as in McGuire et al.(2013), which measures variability in long-term performance of tax avoidance. The value relevance of accounting information in this study is modified by the Ohlson model(1995), which explains the value of the firm by using accounting information such as net assets and net income and other non-accounting information. The samples of this study are the firms listed on the securities market from 2004 to 2015 and the final samples are 3,133 firm-year. The results of this empirical analysis show that the value relevance of accounting information increases as firms have long-term and sustainable tax strategies. Most of the prior studies on tax strategies have examined the tax minimization strategy that minimizes the tax cost. However, this study is different in that the sustainability of the tax strategy affects the value relevance of accounting information. The results of this study will be useful for the users to make decision using the value relevance of accounting information.

• Nuclear Engineering and Technology
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• 제54권10호
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• pp.3682-3694
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• 2022

The expansion of a country's ecological footprint generates resources for economic development. China's import bill and carbon footprint can be reduced by investing in green transportation and energy technologies. A sustainable environment depends on the cessation of climate change; the current study investigates nuclear energy efficiency, economic complexity, air transportation, and industrial improvement for reducing environmental footprint. Using data spanning the years 1983-2016, the dynamic autoregressive distributed lag simulation method has demonstrated the short- and long-term variability in the impact of regressors on the ecological footprint. The study findings revealed that economic complexity in China had been found to have a statistically significant impact on the country's ecological footprint. Moreover, the industrial improvement process is helpful for the ecological footprint in China. In the short term, air travel has a negative impact on the ecological footprint, but this effect diminishes over time. Additionally, energy innovation is negative and substantial both in the short and long run, thus demonstrating its positive role in reducing the ecological footprint. Policy implications can be extracted from a wide range of issues, including economic complexity, industrial improvement, air transportation, energy innovation, and ecological impact to achieve sustainable goals.

• 대한통합의학회지
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• 제9권3호
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• pp.19-35
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• 2021

Purpose : Recently, there has been a growing social interest in aging well. Consequently, wellness tourism has begun to attract attention. However, no studies on whether wellness tourism has any objective health benefits have been carried out yet. In this study, we assess the health benefits as well as the degree of improvement in health of a wellness tourism program. Methods : The study involved 30 adults over the age of 19 who live in the Gyeongsangnam-do region. Participants were evaluated on health indicator before and after participating in wellness tourism program. Participants took heart rate variability (HRV) test, and LFT, RFT, CBC, FBS HbA1C, and CRP test were conducted before and after the tour. Additionally, a survey was conducted before and after the program, and participant satisfaction was evaluated. Statistical differences in the tests conducted before and after the program were analyzed using a design t-test, a Wilcoxon signed-rank test, and McNemar's test. Results : The study showed that participants were very satisfied with and had significant health improvements after the wellness tourism program. The program was also found to be beneficial in improving participants' emotions as follows: BDI (p<.001), fatigue recovery (p=.006), stress relief (p=.003), improved quality of life (p<.05), and improved sleep quality (p<.001). Conclusion : Wellness tourism programs are specifically beneficial for improving participants' emotions (depression, anxiety), fatigue, stress levels, quality of life, and sleep. Therefore, they are beneficial to the overall health. Further research in the future by way of a follow-up study on the long-term effects on health after short-term interventions will provide more validation data.

• 한국농림기상학회지
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• 제4권2호
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• pp.103-113
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• 2002

Calibration experiments were executed to document pertinent calibration methods for open-path infrared gas analyzer (OP-2) in field operations and to quantify their performance characteristics in continuous long-term flux measurements. Based on our results, we concluded: (1) flow rate of 2.0 L min$^{-1}$ can be used for calibration instead of the recommended 0.5 L min$^{-1}$ . Such faster flow rate brings the sampled air in the calibration hood at equilibrium within 5 min for $CO_2$ and 10 min for $H_2O$; (2) after reaching equilibrium, two-minute average sampling for related variables per each concentration may be sufficient; (3) use of four concentration is needed to derive the nonlinear calibration equation for water vapor with 1% uncertainty of flux measurement; and (4) the resultant calibration interval for OP-2 for both $CO_2$ and $H_2O$ is approximately one month.

• The Korean Journal of Pain
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• 제22권3호
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• pp.229-233
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• 2009

Background: Sacroiliac (SI) joint pain is a challenging condition that causes lower back or buttock pain; however, there is no universally accepted long-term treatment. There have been several reports of ligament prolotherapy for SI joint pain, but these have had inconsistent results, probably due to the lack of a specific diagnosis for patient selection and variability in the volume, number and sites of injection. Therefore, this study was conducted to assess the efficacy of intraarticular prolotherapy for relieving SI joint pain diagnosed by local anesthetic intraarticular injection. Methods: Twenty-two patients with SI joint pain confirmed by 50% or more improvement in response to local anesthetic block underwent intraarticular prolotherapy with 25% dextrose water every other week three times. The numeric rating scale (NRS) for pain and Oswestry disability index (ODI) were assessed at the initial visit and after completion of a series of prolotherapy and the NRS was checked during monthly follow-up sessions to evaluate the long-term effectiveness of this technique. Results: Twenty patients completed prolotherapy and followed up as scheduled. The NRS and ODI were significantly improved from 6 (4-8) and $34.1{\pm}15.5$ to 1 (0-3) and $12.6{\pm}9.8$ (P < 0.01), respectively, at 1 month after prolotherapy. The mean duration of pain relief of 50% or more was 12.2 months (95% CI, 10.0-14.3) as determined by Kaplan-Meier survival analysis. Conclusions: Intraarticular prolotherapy provided long-term relief of sacroiliac joint pain and may have more benefits than ligament prolotherapy or neurolysis.

• 생태와환경
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• 제44권2호
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• pp.214-225
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• 2011

The objectives of the study were to evaluate seasonal patterns of epilimnetic water quality, and determine interannual eutrophication patterns at the dam site of Yong-dam Reservoir using long-term data during 2002~2009. Ionic dilutions, based on specific conductivity, occurred in the summer period in response to the intense monsoon rain and inflow, and suspended solid analysis indicated that the reservoir was clear except for the monsoon. Seasonality of nitrogen contents varied depending on the types of nitrogen and responded to ionic dilution; Ammonia-nitrogen ($NH_4$-N) peaked at dry season but nitrate-nitrogen ($NO_3$-N) peaked in the monsoon when the ionic dilution occurred. The maxima of $NO_3$-N seemed to be related with external summer N-loading from the watershed and active nitrogen fixation of bluregreens in the summer. $NO_3$-N was major determinant (>50%) of the total nitrogen pool and relative proportion of $NH_4$-N was minor. Long-term annual $NO_3$-N and TDN showed continuous increasing trends from 2004 to 2009, whereas TP and TDP showed decreasing trends along with chlorophyll-a (CHL) values. Empirical model analysis of log-transformed nutrients and N : P ratios on the CHL showed that the reservoir CHL had a stronger linear function with TP ($R^2$=0.89, p<0.001) than TN ($R^2$=0.35, p=0.120). Overall results suggest that eutrophication progress, based on TP and CHL, is slow down over the study period and this was mainly due to reduced phosphorns, which is considered as primary nutrient by the empirical model.

• 한국수소및신에너지학회논문집
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• 제32권6호
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• pp.565-572
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• 2021

Hydrogen is currently produced from natural gas reforming or industrial process of by-product over than 90%. Additionally, there are green hydrogens based on renewable energy generation, but the import of green hydrogen from other countries is being considered due to the output variability depending on the weather and climate. Due to low density of hydrogen, it is difficult to storage and import hydrogen of large capacity. For improving low density issue of hydrogen, the gaseous hydrogen is liquefied and stored in cryogenic tank. Density of hydrogen increase from 0.081 kg/m³ to 71 kg/m3 when gaseous hydrogen transfer to liquid hydrogen. Density of liquid hydrogen is higher about 800 times than gaseous. However, since density and boiling point of liquid hydrogen is too lower than liquefied natural gas approximately 1/6 and 90 K, to store liquid hydrogen for long-term is very difficult too. To overcome this weakness, this paper introduces storage method of hydrogen based on liquid/solid (slush) and facilities for producing slush hydrogen to improve low density issue of hydrogen. Slush hydrogen is higher density and heat capacity than liquid hydrogen, can be expected to improve these issues.

• 대기
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• 제15권2호
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• pp.101-118
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• 2005

Atmospheric ozone changes temporally and spatially according to both anthropogenic and natural causes. It is essential to quantify the natural contributions to total ozone variations for the estimation of trend caused by anthropogenic processes. The aims of this study are to understand the intrinsic natural variability of long-term total ozone changes and to estimate more reliable ozone trend caused by anthropogenic ozone-depleting materials. For doing that, long-term time series for Seoul of monthly total ozone which were measured from both ground-based Dobson Spectrophotometer (Beck #124)(1985-2004) and satellite TOMS (1979-1984) are analyzed for selected period, after dividing the whole period (1979~2004) into two periods; the former period (1979~1991) and the latter period (1992~2004). In this study, ozone trends for the time series are calculated using multiple regression models with explanatory natural oscillations for the Arctic Oscillation(AO), North Atlantic Oscillation(NAO), North Pacific Oscillation(NPO), Pacific Decadal Oscillation(PDO), Quasi Biennial Oscillation(QBO), Southern Oscillation(SO), and Solar Cycle(SC) including tropopause pressure(TROPP). Using the developed models, more reliable anthropogenic ozone trend is estimated than previous studies that considered only QBO and SC as natural oscillations (eg; WMO, 1999). The quasi-anthropogenic ozone trend in Seoul is estimated to -0.12 %/decade during the whole period, -2.39 %/decade during the former period, and +0.10 %/decade during the latter period, respectively. Consequently, the net forcing mechanism of the natural oscillations on the ozone variability might be noticeably different in two time intervals with positive forcing for the former period (1979-1991) and negative forcing for the latter period (1992-2004). These results are also found to be consistent with those analyzed from the data observed at ground stations (Sapporo, Tateno) of Japan. In addition, the recent trend analyses for Seoul show positive change-in-trend estimates of +0.75 %/decade since 1997 relative to negative trend of -1.49 %/decade existing prior to 1997, showing -0.74 %/decade for the recent 8-year period since 1997. Also, additional supporting evidence for a slowdown in ozone depletion in the upper stratosphere has been obtained by Newchurch et al.(2003).

• 해양환경안전학회지
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• 제20권6호
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• pp.601-608
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• 2014

본 연구에서는 동해 연안정지관측 8개 지점(감포, 울기, 장기갑, 포항, 죽변, 동해(묵호), 주문진, 속초)에서 43년(1971-2013)간 조사한 표층수온을 이용하여 지역별 수온의 유사도에 따른 군집분석과 수온의 장기 변화를 살펴보았다. 수온의 유사도에 의한 군집분석결과, 본 연구지역은 크게 그룹 A(동해, 주문진, 속초)와 그룹 B(감포, 울기, 장기갑, 포항, 죽변)로 구분되었다. 여기서 A 그룹의 속초와 B 그룹의 죽변, 포항, 감포를 중심으로 한 수온과 수온편차의 장기 변화에서 수온은 10년 규모의 변동을 보였다. 각 지역별 수온은 43년간 증가 경향을 보였고, 1988년을 기준으로 고수온기와 저수온기로 구분되었다. 각 지역에서 43년간 수온은 속초가 $2.26^{\circ}C$, 죽변이 $1.99^{\circ}C$, 포항이 $1.11^{\circ}C$, 감포는 $0.89^{\circ}C$ 각각 증가하였고, 지역적으로는 동해 남부에서 북부로 갈수록 수온의 증가 속도가 크게 나타났다. 계절별 수온의 증가는 추계와 동계의 경우 속초>죽변>포항>감포의 순이었고, 춘계와 하계는 죽변>속초>포항>감포의 순으로 나타났다.