• 한국ITS학회 논문지
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• 제7권1호
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• pp.68-74
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• 2008

SIW (Substrate Integrated Waveguide) cavity 공진기의 구조는 유전체기판에 다수의 via-hole 을 이용함으로써 나타낼 수 있으며, rectangular waveguide 와 유사한 특성을 갖는다. 그리고 $50-{\Omega}$ 마이크로스트립라인과 SIW cavity 공진기 중앙간의 결합구조를 통하여 대역저지 특성이 나타나도록 하였다. 이러한 특성을 갖는 SIW cavity 공진기를 이용하여 X-band(9.45 GHz) 발진기를 제작하였고, 위상잡음은 100kHz offset에서 -98.1 dBc/Hz 로 측정되었다. SIW cavity 공진기는 높은 QL 값을 갖고, 2차원 구조이기 때문에 저비용에 우수한 위상잡음 특성을 갖는 발진기 설계에 응용할 수 있다.

• Journal of Preventive Medicine and Public Health
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• 제57권3호
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• pp.279-287
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• 2024

Objectives: This study validated the Vietnamese version of the Disaster Adaptation and Resilience Scale (DARS) for use in vulnerable communities in Vietnam. Methods: This was a cross-sectional study involving 595 adults from 2 identified communities. The original DARS assessment tool was translated, and the validity and reliability of the Vietnamese version of DARS (V-DARS) were assessed. The internal consistency of the overall scale and its subscales was evaluated using Cronbach's alpha and McDonald's omega reliability coefficients. Confirmatory factor analysis (CFA) was employed to evaluate its construct validity, building upon the factor structure identified in exploratory factor analysis (EFA). Construct validity was assessed based on convergent and discriminant validity. Results: Following the established criteria for EFA, 8 items were removed, resulting in a refined V-DARS structure comprising 35 items distributed across 5 distinct factors. Both alpha and omega reliability coefficients indicated strong internal consistency for the overall scale (α=0.963, ω=0.963) and for each of the 5 sub-scales (all>0.80). The CFA model also retained the 5-factor structure with 35 items. The model fit indices showed acceptable values (RMSEA: 0.072; CFI: 0.912; TLI: 0.904; chi-square test: <0.01). Additionally, the convergent and discriminant validity of the V-DARS were deemed appropriate and satisfactory for explaining the measurement structure. Conclusions: Our findings suggest that the V-DARS is a valid and reliable scale for use within vulnerable communities in Vietnam to assess adaptive responses to natural disasters. It may also be considered for use in other populations.

• 한국전산유체공학회지
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• 제7권4호
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• pp.19-27
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• 2002

An efficient implicit multigrid method is presented for the Navier-Stokes and k-ω turbulence equations. Freezing and limiting strategies are applied to improve the robustness and convergence of the multigrid method. The eddy viscosity and strongly nonlinear production terms of turbulence are frozen in the coarser grids by passing down the values without update of them. The turbulence equations together with the Navier-Stokes equations, however, are consecutively solved on the coarser grids in a loosely coupled fashion. A simple limit for k is also introduced to circumvent slow-down of convergence. Numerical results for the unseparated and separated transonic airfoil flows show that all computations converge well without any robustness problem and the computing time is reduced to a factor of about 3 by the present multigrid method.

• Bulletin of the Korean Chemical Society
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• 제25권9호
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• pp.1403-1407
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• 2004

Dielectric relaxation measurements on 3-nitrotoluene (3-NT) mixture of dimethylacetamide (DMA), dimethylformamide (DMF) and dimethysulphoxide (DMSO) have been carried out across the entire concentration range using Time domain reflectometry technique at 15, 25, 35 and $45^{\circ}C$ over the frequency range from 10 MHz to 20 GHz. For all the mixtures, only one dielectric loss peak was observed in this frequency range and the relaxation in these mixtures can be well described by a single relaxation time using Debye model. Bilinear calibration method is used to obtain complex permittivity ${\varepsilon}^{*}({\omega})$ from complex reflection coefficient ${\rho}^{*}({\omega})$ over frequency range 10 MHz to 20 GHz. The excess permittivity, excess inverse relaxation time, Kirkwood correlation factor, molar energy of activation are also calculated for these mixtures to study the solute-solvent interaction.

• 한국전자파학회논문지
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• 제15권10호
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• pp.938-943
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• 2004

본 논문에서는 CPW에 식각된 T자형 DGS를 제안하고 전송이론을 이용하여 전파 방사를 포함한 손실률, BW(3-dB fractional bandwidth) 등을 closed-form 형태의 수식으로 유도하고 이의 영향에 대해 분석한다. 제안된 T자형 DGS 구조는 기존의 아령형 DGS 구조보다 약 5.5배정도 큰 커패시턴스(C) 조절 특성을 가진다. 또 DGS 등가회로의 R, L, C값과 손실률, BW, 저지대역 공진 각주파수($\omega_0$)의 상관관계를 정량적으로 이끌어낸다.

• 한국토양비료학회지
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• 제49권2호
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• pp.125-131
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• 2016

The biodegradable film application can escape from plastic environmental pollution. This experiments studied the effect of biodegradable mulch film on the soil microbial community using fatty acid methyl ester method in soybean production field. The soil $NO_3$-N content in polyethylene mulch film (PE) soil was significantly higher than biodegradable mulch film soil (p < 0.05). The soil microbial community of Gram negative bacteria showed significantly higher in biodegradable mulch film soil than PE mulch film soil (p < 0.05). In addition, biodegradable mulch film soil had significantly low ratio of cy17:0 to $16:1{\omega}7c$ and cy19:0 to $18:1{\omega}7c$ compared with those of PE mulch film soil (p < 0.05), indicating that microbial stress decreased. The ratio of cy17:0 to $16:1{\omega}7c$ and cy19:0 to $18:1{\omega}7c$ should be considered as a potential responsible factor for the obvious differentiation that was observed between the biodegradable mulch film soil and PE mulch film soil in a upland field. The results of this experimentation show the potential of using biodegradable mulch film in place of PE.

• 한국지진공학회논문집
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• 제3권2호
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• pp.9-18
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• 1999

현행 내진설계 기준과는 달리 내진설계기준연구(II) 에서는 6층 미만의 건물도 내진설계를 적용하도록 제안하고 있다 이 제안서가 향후 내진설계 기준의 근간이 된다면 저층 건물에 대하여서도 내진설계가 수행되어야 할 것으로 예상된다 지진의 세기로 구분할 때 국내의 약지진동 지역으로 구분되며 이와 같은 지역에서의 저층 건물의 초과강도 계수 $\Omega$는 매우 크다고 기조의 연구자들이 보고하고 있다 따라서 본 연구에서는 국내 4층 RC 모멘트 연성 골조의 경우에$\Omega$를 고찰하고자 스팬과 경간(bay)를 변화시키면서 모델을 설계하고 이를 2차원 push-over 해석하였다 수치해석 결과 경간의 수 또는 스팬 길이가 증가함에 따라$\Omega$의 값이 증가하는 추세를 보였다 이는 내진설계시 우발 비틀림 모멘트를 고려함으로 스팬 길이 또는 경간 수의 증가에 비하여 외부기중의 설계강도증가율이 크기 때문이다 또한 외부 기둥의 강도증가는 강기동-약보 모델에 근접한 붕괴기구를 형성하므로 $\Omega$의 증가에 영향을 미치는 것으로 고찰되었다

• Journal of Nutrition and Health
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• 제52권4호
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• pp.323-331
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• 2019

Purpose: Glucocorticoids (GCs) are implicated in secondary osteoporosis, and the resulting fractures cause significant morbidity. Polyunsaturated fatty acids (PUFAs) play a vital role in bone metabolism. However, few trials have studied the impact of omega-3 PUFA-containing oils against GC-induced osteoporosis. Therefore, the present study was undertaken to determine whether supplementation with omega-3 PUFA-containing dietary oils such as fish oil, flaxseed oil or soybean oil can impede the development of GC-induced osteoporosis. Methods: The fatty acids (FAs) content of oils was determined using gas chromatography. Male rats were subdivided into 5 groups (8 rats each): normal control (balanced diet), prednisolone control (10 mg/kg prednisolone daily), soybean oil (prednisolone 10 mg/kg + soybean oil 7% w/w), flaxseed oil (prednisolone 10 mg/kg + flaxseed oil 7% w/w), and fish oil (from cod liver; prednisolone 10 mg/kg + fish oil 7% w/w). Results: The study data exhibited a significant depletion in bone mineral density (BMD) and femur mass in the prednisolone control compared to the normal control, accompanied with a marked decrease in the levels of plasma calcium and 1,25-$(OH)_2$-vitamin $D_3$, and elevated levels of C-terminal telopeptide (CTX), tumor necrosis factor-alpha (TNF-${\alpha}$) and malondialdehyde (MDA). Supplementation with fish oil, soybean oil or flaxseed oil helped to improve plasma calcium levels, and suppress oxidative stress and inflammatory markers. Additionally, bone resorption was suppressed as reflected by the decreased CTX levels. However, fish oil was more effective than the other two oils with a significant improvement in BMD and normal histological results compared to the normal control. Conclusion: This study demonstrated that supplementation with dietary oils containing omega-3 PUFAs such as fish oil, soybean oil or flaxseed oil can play a role in the prevention of bone loss and in the regulation of bone metabolism, especially fish oil which demonstrated a greater level of protection against GC-induced osteoporosis.

• 수산해양기술연구
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• 제39권1호
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• pp.8-18
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• 2003

한국 남서해 연안 해역인 나로도 주변 어장에서 2000년 동계, 춘계, 하계 및 추계에 조사한 해양 관측 자료를 이용하여 이 어장의 해황 특성을 분석한 결과를 요약하면 다음과 같다. 1) 나로도 주변해역에 출현하는 동계의 수온, 염분 및 클로로필의 분포 범위는 각각 4.3∼10.$\circ_C$, 33.1-34.9psu 0.1-26.2$ug$/$\Omega$ 이었고, 춘계에는 8.1∼13.$7\circ_C$, 33.1∼34.3psu, 0.1-24.4$ug$/$\Omega$이었다. 또한, 하계에는 14.5∼24.$2\circ_C$, 30.5∼34.1psu, 0.1∼30.0$ug$/$\Omega$이었으며, 추계에는 14.8∼18.$6\circ_C$, 30.1∼34.0psu, 0.1∼19.1$ug$/$\Omega$이었다. 2) 수온은 외해보다는 연안에서 더 높았으나, 염분은 연안역에서 낮고 외해에서 높은 정향을 나타내고 있다. 또한, 수온과 염분은 동계와 추계에 연직 혼합을 일으키고, 춘계에는 수평적인 분포를 하며, 하계에는 표층과 중층 사이에 수온 약층과 조밀한 염분 분포를 형성하였다. 3) 클로로필의 분포는 연안수에 의해 공급되는 영양염류의 농도에 크게 지배되고 있는 연안역이 외해역보다 높고, 주로 표층보다는 저층에서 클로로필의 분포가 높게 나타나고 있다. 또한, 동계와 추계에 연직분포를 하고, 춘계와 하계에는 수평적인 분포를 하였다. 4) 연안수의 유엽은 어장의 북쪽으로부터 유입되고 외해수의 연안 유입은 소리도의 남쪽 외해측으로부터 이루어지고 있는 것으로 관측되었다.

• 전기학회논문지
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• 제61권2호
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• pp.199-208
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• 2012

This paper proposes a quasi Z-source DVR(Dynamic Voltage Restorer) system with a series connection of the output terminals, to compensate the voltage variations in the 6.6[kV]/60[Hz] power distribution system. The conventional DVR using one quasi Z-source AC-AC converter has the advantage which it can compensate the voltage variations without the need for the additional energy storage device such as a battery, but it is impossible to compensate for the 50[%] under voltage sags. To solve this problem, a DVR system using two quasi Z-source AC-AC converters with the series connection of the output terminals is proposed. By controlling the duty ratio D in the buck-boost mode, the proposed system can control the compensation voltage. For case verification of the proposed system, PSIM simulation is achieved. As a result, in case that the voltage sags-swells occur 10[%], 20[%], 60[%] in power distribution system, and, in case that the 50[%] under voltage sags-swells continuously occur, all case could compensate by the proposed system. Especially, the compensated voltage THD was examined under the condition of the 10[%]~50[%] voltage sags and the 20[${\Omega}$]~100[${\Omega}$] load changes. The compensated voltage THD was worse for the higher load resistances and more severe voltage sags. Finally, In case of the voltage swells compensation, the compensation factor has approached nearly 1 regardless of the load resistance changes, while the compensation factor of voltage sags was related to the load variations.