• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.7 no.4
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• pp.257-266
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• 2002

To estimate the nitrogen budget and assess the purification function of a tidal flat ecosystem, a field survey was carried out at Hajeon tidal flat in Gomso Bay, the southern part of Byeonsan Peninsula, Chollabuk-do, Korea. A study area of 3.0$\times$4.5 ㎢ was established on the tidal flat and the concentrations of chlorophyll-a, DIN, DON, and TN were measured in the water column during the period of April 17-18, 1999: From the budget analysis, the loss rate of Chl-a was estimated to be -0.05 mg Chl/㎡/hr, which is approximately 7% of that at Issiki tidal flat in Aichi Prefecture, Japan. The lower loss rate of Chl-a in the study area was attributable to the lower standing crop of phytoplankton, the lower temperature that may reduce metabolic rates of biotic components and the lower biomass of macrobenthos in the study area. Over the 13.5 ㎢ of study area, Hajeon tidal flat removed 8.36$\times$10$\^$2/ kg N/day of TN, 5.36$\times$10$\^$3/ kg N/day of PON and 1.62$\times$10$\^$2/ kg N/day of phytoplankton-related PON, showing that the tidal flats may play an important role in removing nitrogen in coastal waters. The removal rate of PON, compared to the removal cost of the existing waste water treatment facilities, indicates that the economic value of the purification function of Hajeon tidal flat (13.5㎢) may be more than that of two large facilities.

• Proceedings of the Korea Society of Information Technology Applications Conference
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• 2006.06a
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• pp.495-505
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• 2006

IT기술기반 교육시스템은 인터넷 등장 이전에도 가능성을 인정받아 지속적으로 개발되어 온 분야이며, 교육공학과의 연계로 지식 전날의 이론체계로 각광을 받고 있다. 사이버교유도 인터넷이전부터 다양한 통신방법을 응용하여 개발되었고, 최근 인터넷을 통하여 사이버 교육시스템은 완벽한 기술기반을 갖추게 되였다. 그러나 IT기술의 급격한 변화로 사이버교육시스템은 계속하여 신기술 변화에 적용해야만 한다. 현재 정보통신기술의 변화는 방송 통신망의 융합, 브로드 밴드 네트워킹, 스마트 디바이스의 다양화, 멀티미디어 기술의 고도화로 요약된다. 이 기술의 종합한 작용으로 유비쿼터스 사회의 기반으로 진화되고 있다. 그래서 e-Learning 분야도 기존 인터넷기반 시스템과는 달리 차세대 온라인교육시스템으로 친화되고 있다. IT융합가술 기반의 온라인 교육시스템은 각종 국제표준단체에서 표준안이 제시되고 있다. e-Learning 시스템이란 선기술 기반을 반영한 표준기술을 사용하는 온라인교육시스템을 포괄하는 개념이다. 본 연구에서는 e-Learning 시스템과 유비쿼터스 기술을 반영한 e-Learning을 비교하였다. 그리고 u-Learning 시스템의 기술정립과 EOD(Education On Demand) 시스템에 대하여 연구하였다. 1. u-Learning 정의 정보산업분야를 비롯한 문화, 교육 등 모든 분야에서 유비퀴터스라는 수식어가 붙어 다니고 있다. e- Learning 교육 업계에 따르면 10년 후에는 유비쿼터스는 대중화가 될 것이며, 부가가치 규모는 100조 원에 이를 것으로 추정된다. 그래서 교육산업도 주변 환경이 아날로그 방식에서 IT 기반에 의한 디지털 환경으로 변화되고 있다. 또한 e러닝, T러닝, m러닝, u러닝 등의 용어가 생성되고 있다.키지에어컨에서 사용되고 있는 밀폐형 압축기에 대해서 그림 2에서 나타내고 있는 냉방능력 10tons(120,000Btu/h) 이하를 중심으로 상기의 최근 기술 동향을 간략하게 소개하고자 한다.질표준의 지표성분으로 간주되는 진세노사이드의 절대함량과 그 성분조성 차이에 따른 임상효과의 차별성이 있는지에 대한 검토와, 특히 최근 실험적으로 밝혀지고 있는 사포닌 성분의 장내 세균에 의한 생물전환체의 인체 실험을 통한 효과 검정이 필요하다. 나아가서는 적정 복용량의 설정과 이와 관련되는 생체내 동태 및 생체이용율(bioavilability)에 관한 정보가 거의 없으므로 이것도 금후 검토해야 할 과제로 사료된다. 인삼은 전통약물로서 오랜 역사성과 그동안의 연구결과에 의한 과학성을 가지고 있으므로 건강유지와 병의 예방 및 회복촉진을 위한 보조요법제 또는 기능성 식품으로써의 유용성이 있는 것으로 판단된다. 앞으로 인삼의 활용성 증대를 위해서는 보다 과학적인 임상평가에 의한 안전성 및 유효성 입증과 제품의 엄격한 품질관리의 필요성이 더욱 강조되어야 할 것이다.xyl radical 생성 억제 효과를 보여 주었다. 본 실험을 통하여 BHT 를 제외하고 전반적으로 세포 수준에서의 oxidative stress 에 대한 억제 효과를 확인해 볼 수 있었으며 특히 수용성 항산화제들에서 두드러진 효과를 보여 주었다. 제공하여 내수기반 확충에도 노력해야 할 것 이다.있었다., 인삼이 성장될 때 부분적인 영양상태의 불충분이나 기후 등에 따른 영향을 받을 수 있기 때문에 앞으로 이에 대한 많은 연구가 이루어져야할 것으로 판단된다.태에도 불구하고 [-wh]의미의 겹의문사는 병렬적 관계의 합성어가 아니라 내부구조를 지니지 않은 단순한 단어(minimal $X^{0}$<

• Applied Chemistry for Engineering
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• v.31 no.2
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• pp.172-178
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• 2020

In this study, the optimization of the biodiesel production process from waste oil using microwave with response surface methodology (RSM) was conducted. The microwave irradiation time and power in addition to the alcohol/oil mole ratio were chosen as process parameters. Also the fatty acid methyl ester (FAME) content (over 96.5%) and kinematic viscosity (1.9~5.5 cSt) were selected as response values. From basic experiments, the range of quantitative factors were set as following; 4~6 min, 400~600 W, and 7~9 for the microwave irradiation time and power, and alcohol/oil molar ratio, respectively. The optimum conditions for the methanolysis were 5.0~5.1 min, 481.3~525.5 W, 7.9~8.4, and 2.0 or 3.0 mg KOH/g for the microwave irradiation time and power, methanol/oil molar ratio, and each acid value, respectively. The FAME content and kinematic viscosity were predicted as 97.49~96.34% and 4.01~4.12 cSt, respectively, under the condition above. Under the optimum experimental conditions, the results showed that the FAME content and kinematic viscosity of 97.82~96.42% and 4.07~4.16 cSt, respectively were measured and the mean error rates were 0.22% and 0.98%, respectively.

• Current Research on Agriculture and Life Sciences
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• v.31 no.3
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• pp.193-199
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• 2013

This study dyed rayon fabric using loess as a natural colorant. To obtain the optimal dyeing conditions, various dyeing conditions were examined (temperature, pH, time, and concentration). The color fastness was evaluated using standard washing and rubbing fastness tests. The results were as follows: The loess powder particle size ranged from 0.4 to $1.7{\mu}m$ with a distribution range of 1.1 to $1.4{\mu}m$, representing a fine and uniform manufactured loess powder. The loess component analysis showed a large amount of silicon dioxide and aluminum oxide. TheFT-IR spectra showed that the ammonium group in the rayon fabric produced N-H banding at $1,540cm^{-1}$. The highest K/S value for the rayon fabric was obtained when the pH was 8.0, and this value increased rapidly with a longer dyeing time and when increasing the loess concentration to 30% (w/v). Pre-treatment with a soybean solution produced the highest K/S value for the rayon fabric with a loess concentration of 30% (w/v). The SEM analysis showed a higher amount of loess adhered to the rayon fabric surface when increasing the loess concentration. However, pre-treatment with a cationic agent and soybean solution resulted in a much higher attachment of loess to the fabric surface. Thus, the experimental results showed that using a cationized fabric and pre-treatment with a soybean solution are more effective when dyeing rayon fabric with loess than when using only loess.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.11
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• pp.5284-5289
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• 2011

This study focused to evaluate thermal transmittance(U-value) performance of sliding type of aluminum alloy window frame(AAWF) with double glazing(DG) and glazing spacer and that without thermal breaker in winter and summer season by two dimensional steady state heat transfer analysis. The AAWE was installed to an existing educational facilities in Seosan area which is the southern region of the Korean Peninsula. Analysis of 2D steady-state heat transfer was performed through the use of BISCO as calculation and simulation program. U-value and temperature factors were calculated. The results are as followed. First, the isotherm simulation shows that AAWF with double glazing have serious differences from recently proposed window thermal performance standards such as Insulation Performance of Windows and Doors of Building Energy Saving Design Standards and the results of calculation of thermal transmittance performance of AAWF and DG are U=9.631 W/$m^2K$, U=2.382 W/$m^2K$ respectively during winter and summer season. Second, the results of analysis of heat transfer analysis, calculated by simulation, shows that 225% of heat is lost comparing with thermal performance standards U=4.0 W/$m^2K$ of general double glazing among those standards on AAWF without thermal breaker.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.10
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• pp.618-627
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• 2016

This study numerically analyzes the characteristics of the velocity distribution for each location of a square-sectional $180^{\circ}$ bent duct using a Reynolds Stress Turbulent model. The flow parameters were varied, including the working fluids, inlet velocity, surface roughness, radius of curvature, and hydraulic diameter. The boundary conditions for computational fluid dynamics analysis were inlet temperatures of air and water of 288 K and 293 K, inlet air velocity of 3-15 m/s, inner surface roughness of 0-0.001 mm, radius of curvature of 2.5-4.5 D, and hydraulic diameter of 70-100 mm. The working fluid characteristics were highly affected by changes in the viscous force. The maximum velocity profiles in the bent duct were indicated when the $90^{\circ}$ section was in the region of X/D=0.8 and the $180^{\circ}$ section was in the region of Y/D=0.8. Lower surface roughness and higher radius of curvature resulted in a higher rate of velocity change. Also, an efficient measuring location downstream of the bent duct is suggested since the flow deviations were the most stable when the straight duct length was in the region of L/D=30. The minimum deviations at the same velocity conditions according to the hydraulic diameter were mostly indicated in the range of L/D=15-30 based on the standard deviation characteristics.

• International Area Studies Review
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• v.20 no.2
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• pp.113-140
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• 2016

This paper first extracts the main basis for the Middle-Income Trap(MIT) to apply these grounds to reality of the Chinese economy. And then confirmed crisis factors of China economy. Also discussed then the economic reforms of China in order to not fall into the MIT. After reviewing previous research extracted six factors the results will correspond to comply with the Chinese economy. Those are 'Over-investment', 'excess capacity' 'reduction of TFP continued,' 'disappearance and the aging of the population bonus', 'excessive debt and structural adjustment and financial instability of the company', 'income unequal expansion', 'low financial and information infrastructure accessibility', and 'low transparency index'. China's policy direction to avoid the MIT generally set properly, but proof that implementation process not easy, was appearing everywhere. After all, China economy should be modified now to a reforms of 'government failure' and promotion of function for ongoing restructuring system in the market. Because of the SDR incorporation from 2015, it is inevitable to face major constraints in the external aspects.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.31 no.1 s.49
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• pp.59-64
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• 2005

In case of lipsticks, observer's subjective sensitivity has been the main index to estimate gloss and gloss-lasting capability. The glossmeter has been applied to measure the gloss of make-up cosmetics like nail enamel, however is not effective for lipstick because of uneven sampling. Also gloss-lasting capability couldn't have been measured. In this study, we optimized measurement methods of gloss and gloss-lasting capability of lipsticks, which are highly correlated to subjective sensory tests. We set up the standard methods of gloss measurement by changing application conditions, for example, materials, sizes and application number of times and so on. And we introduced optimizing measurement system, in which shaking speed and temperature were controlled to measure gloss-lasting capability. Applying our methods, the gloss values were very close to the results of sensory tests, and we could express the gloss and gloss-lasting capability of lipsticks numerically Repeatability and reproducibility of our methods were certified by six-sigma statistical tool.

• Nuclear Engineering and Technology
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• v.18 no.2
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• pp.97-106
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• 1986

System thermal-hydraulic parameters and simulated, using the best-estimate system code(RELAPS/MODl/NSC), based upon the sequence of events for the KNU1 (Korea Nuclear Unit 1) loss of offsite power transient at 77.5% power which occurred on June 9,1981. The results are compared with the actual plant transient data and show good agreements. After the flow coastdown following the trips of both reactor coolant pumps, the establishment of natural circulation by the temperature difference between the hot and the cold legs is confirmed. The calculated reactor coolant flowrate closely approximates the plant data indicating the validity of relevant thermal-hydraulic models in the RELAP5/MOD1/NSC. Results also show that the sufficient heat removal capability is secured by the appropriate supply of the auxiliary feedwater without the operation of S/G PORVs. In addition, a scenario accident at full power, based upon the same sequence of events described above, is also analysed and the results confirmed that the safety of KNU1 is secured by the appropriate operation of the S/G PORVs coupled with the supply of auxiliary feedwater which ensures sufficient heat removal capability. The characteristics of the non-safety related components such as the turbine stop valve closing time, S/G PORV settings etc. are recognized to be important in the transient analyses on a bestestimate basis.

• Journal of Korea Foundry Society
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• v.41 no.5
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• pp.419-433
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• 2021

Al-Si-Cu alloys benefit from the addition of copper for better hardness and strength through precipitation hardening, which results in remarkably strong alloys. However, the addition of copper expands the solidification range of Al-Si-Cu alloys, and due to this, these alloys become more prone to hot tearing, which is one of the most common and serious fracture phenomena encountered during solidification. The conventional evaluation method of the hot tearing properties of an alloy is a relative and qualitative analysis approach that does not provide quantitative data about this phenomenon. In the present study, the mold itself part of a device developed in Instone et al. was partially modified to obtain more reliable quantitative data pertaining to the hot tearing properties of an Al-Si-Cu casting alloy. To assess the influence of Cu element, four levels of Cu contents were tested (0.5, 1.0, 3.0, and 5.0 wt.%) in the Al-Si-Cu system alloy and the hot tearing properties were evaluated in each case. As the Cu content was increased, the hot tearing strength decreased to 2.26, 1.53, 1.18, and 1.04 MPa, respectively. At the moment hot tearing occurred, the corresponding solid fraction and solidification rate decreased at the same temperature due to the increase in the solid-liquid coexistence range as the Cu content increased. The morphology of the fracture surfaces was changed from dendrites to dendrites covered with residual liquid, and CuAl₂ phases were observed in the vicinity of hot tearing.