• 한국컴퓨터정보학회논문지
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• 제20권4호
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• pp.87-93
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• 2015

최근에 사용자 스스로가 네트워크를 구축하여 자신이 소유한 AP의 일부 대역폭을 다른 사람과 공유하는 방법이 대두되었는데 이러한 네트워크를 공유 네트워크라 한다. 응용 애플리케이션으로 공유 네트워크에서 SVC 기술을 사용하는 비디오 스트리밍 전송 시스템을 구축하는 방안이 제안되었는데, 서버로부터 클라이언트에게 비디오 스트림을 보내기 위해서는 루트는 서버이고 내부노드는 공유 AP이며 리프는 클라이언트인 트리 구조를 만들게 된다. 기존의 연구들은 공유 AP의 공유대역폭의 합을 최소로 사용해서 모든 클라이언트를 서비스하는 최소 공유대역폭 트리를 구축하는데 주안점을 두고 있다. 본 논문에서는 공유 AP들의 집합이 주어졌을 때 클라이언트의 비디오 스트림 요구를 최대로 만족시키는 최대 요구대역폭 트리를 구축하는 문제가 NP-하드임을 증명하였다. 또 이 문제를 해결하기 위한 효율적인 휴리스틱 알고리즘을 개발하고, 실험을 통해 성능을 평가하였다.

• 한국식품저장유통학회지
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• 제8권3호
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• pp.274-278
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• 2001

항균력의 우수성이 확인된 천연항균소재인 대황추출물, 황련추출물 및 자몽종자추출물을 시설채소산물인 호박의 선도유지용 표면처리제 및 포장소재로 개발하여 저장실험을 실시한 견과는 다음과 같다. 호박을 항균소재에 침지처리한 후, 항균필름에 포장하고 1$0^{\circ}C$에서 저장하면서 저장호박의 경도, ascortbic acid함량, 중량손실을, 미생물 성장도 및 부패율을 측정한 결과, 대조구에 비교해서 긍정적인 결과를 얻을 수 있었다. 이는 대조구(LDPE) 필름에 비교해서 항균소재에 침지 처리후, LDPE 필름으로 포장한 경우에 대체적으로 조직의 연화 지연되었고, ascorbic acid함량의 감소폭도 완만한 것으로 나타났으며 또한 중량손실 데 있어서도 긍정적인 결과를 확인하였다. 부패미생물의 성장도 억제에 따른 부패율도 감소하는 것으로 나타났다. 아울러, 항균필름과 항균소재를 병용처리하는 것이 항균필름만으로 포장하는 경우와 침지처리만 하는 경우보다 부패율 변화 및 호박의 품질변화에 있어서 더욱 긍정적 효과를 나타내는 것을 확인할 수 있었다.

• 한국환경복원기술학회지
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• 제4권1호
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• pp.57-66
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• 2001

The floating islands have been constructed for the water quality improvement and the biodiversity conservation in an disturbed aquatic ecosystem. We made floating islands consisted of a special float and substrates of coconut fibers implanted with four emergent macrophytes such as Phragmites australis, Zizania latifolia, Iris pseudoacorus, Typha angustifolia. Vegetation structure and plant growth were compared between on the floating islands and on ground in order to select suitable plants for the construction of floating islands. Emergent-macrophytic vegetation on the floating islands showed lower coverages and higher plant biodiversity due to natural introduction of various hydrophytes and hygrophytes. Shoot density was increased on floating islands except for Zizania latifolia. From the point of coverage and density of plants, Phragmites australis and Iris pseudoacorus were suitable for floating islands. Total biomass of emergent macrophytes was decreased on the floating islands. The belowground/aboveground biomass ratio of floating islands was higher than that of the ground. Out of planted macrophytes, Iris pseudoacorus with a high belowground/aboveground biomass ratio could be evaluated a suitable plant for the floating islands because a plenty of its root is profitable to adapt with the nutrient-limited environment of floating islands.

• 동력기계공학회지
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• 제13권5호
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• pp.52-58
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• 2009

A gas turbine consists of an upstream compressor and a downstream turbine with a combustion chamber, and also the compressor and the turbine are generally coupled using a single shaft. Many casing bolts are used to assemble two horizontally separated casings, the gas turbine casing and the compressor casing, in both of axial and vertical directions. Because drilled holes for casing bolts in vertical direction are often too close to drilled holes for casing bolts in axial direction, one can observe cracks in the area frequently during operations of a gas turbine. In this study of the root cause analysis for the cracking initiating from the drilled holes of the casings of a gas turbine, the finite element analysis(FEA) was applied to evaluate the thermal and mechanical characteristics of the casings. By applying the field operation data recorded from combined cycle power plants for FEA, thermal and thermo-mechanical characteristics of a gas turbine are analyzed. The crack is initiated at the geometrical weak point, but it is found that the maximum stress is relieved when the same type of cracks is introduced on purpose during FEA. So, it is verified that the local fracture could be delayed by machining the same type of defects near the hole for casing flange bolts of the gas turbine, where the crack is initiated.

• 품질경영학회지
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• 제48권3호
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• pp.511-520
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• 2020

Purpose: The purpose of this study was to devise an accurate machine learning model for predicting silica concentrations following the addition of impurities, through time series analysis of mining data. Methods: The mining data were preprocessed and subjected to time series analysis using the machine learning model. Through correlation analysis, valid variables were selected and meaningless variables were excluded. To reflect changes over time, dependent variables at baseline were treated as independent variables at later time points. The relationship between independent variables and the dependent variable after n point was subjected to Pearson correlation analysis. Results: The correlation (R2) was strongest after 3 hours, which was adopted as a dependent variable. According to root mean square error (RMSE) data, the proposed method was superior to the other machine learning methods. The XGboost algorithm showed the best predictive performance. Conclusion: This study is important given the current lack of machine learning studies pertaining to the domestic mining industry. In addition, using time series analysis in mining data will show further improvement. Before establishing a predictive model for the proposed method, predictions should be made using data with time series characteristics. After doing this work, it should also improve prediction accuracy in other domains.

• 대한한방내과학회지
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• 제29권3호
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• pp.778-786
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• 2008

Objectives : This study was to investigate the short time effect of caffeine on heart rate variability(HRV) and the effect of Neiguan(PC6) acupuncture stimulation on HRV. Methods : 27 healthy adult volunteers were randomly allocated to two groups: Neiguan group (N=13) or placebo group (N=14). The study was carried out under a randomized double-blinded placebo-controlled trial method. Each group orally received the same tablets with 200 mg caffeine. After 1 hour, acupuncture was applied to the Neiguan(PC6) points for the Neiguan group, and for the placebo group was applied to a non-acupuncture point. Both groups were estimated with HRV 3 times, before and after caffeine ingestion, 20 minutes after acupuncture stimulation. Results : After taking caffeine, pulse rate, mean-HRV, and pNN50(the proportion derived by dividing NN50 by the total number of NN intervals) decreased, SDNN(standard deviation of all normal-to-normal (NN) intervals), RMSSD (the root square of successive differences), TP log, HF(high frequency), and HRV index was increased. There were significant changes to the autonomic nervous system after taking caffeine. There were no significant differences between the two groups after acupuncture at Neiguan. Conclusion : Caffeine could induce general activation of the autonomic nervous system. Neiguan acupuncture stimulation may not have significant influence on the autonomic nervous system.

• 동의생리병리학회지
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• 제26권6호
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• pp.947-952
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• 2012

This Study was conducted to investigate Muscle Test of Point Selection through CRA(Contact Reflex Analysis) Muscel Diagnosis. So this study used to compare and analyze the effects of Muscel(Deltoid Muscel of Posterior) RMS(Root Mean Squared) and MEF(Median Edge Frequency) Among Groups that do not respond to questionnaire, Tonguibogam Naegyeongpyeon Small Intestine Group, Small Intestine MeridianPathway Primary Symptom and Secondary Symptom Group and Kwanwon(CV4) meridian Principal action Group. The questionnaire is composed of 23 items. The questionnaire was intended to elicit information on assorting into 4 groups. After Survey, Subject had to Muscle test subjects. Muscle experimental methods are as follows: Holding the shoulder without contacting Kwanwon. Holding the shoulder contacting Kwanwon. The first iteration. Group 1,2,3 were increased sEMG RMS compared with First experiment and Second experiment. Group 4(Including Uterus and Intestinal Flora Problem) were decreased sEMG RMS compared with First experiment and Second experiment. This test means that it is similar to diagnosis CRA and Small intestine channel of hand taiyang muscle, not Small Intestine MeridianPathway. It is suggested that subjects with a Small Intestine problem(Uterus and Intestinal Flora Problem) shows the results of decreasing posterior Deltoid Muscular strength. It means that CRA muscle diagnosis is associated with Alarm points diagnosis. But it doesn't consider influence of fat on the surface EMG.

• 한국물환경학회지
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• 제33권4호
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• pp.387-393
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• 2017

A chemical batch tests were conducted to evaluate if microwave heating enhances phosphorous release from waste activated sludge (WAS) at pH 2.5, 5, 7, 9 and 11. Polyphosphate-accumulating organisms have a unique physiological feature, which releases intracellular polyphosphate granules when they are exposed under high temperature environments. Microwave irradiation was found to encourage large amount of phosphorus release from WAS, depending on pH and temperature conditions. Most of phosphorus was released below $59^{\circ}C$ within 30 min. A marked increase in phosphorus release was observed under alkaline or acidic conditions. However, based on control tests for phosphorus release under different pH conditions without microwave heating, the largest amount of phosphorus released by microwave irradiation was found at pH 7, followed by 5, 9, 11. On the other hand, crystallization was conducted to obtain magnesium ammonium phosphate (MAP) from phosphate released by microwave heating at pH 7. X-ray diffraction analysis confirmed that the recovered crystalline materials were MAP. MAP is an environmentally friendly fertilizer, which slowly releases ammonia and phosphorus in response to the demand of plant root. Thus, the recovered MAP as a phosphate fertilizer is fully expected to play a important role in the reduction of agricultural non-point pollution.

• Wind and Structures
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• 제31권4호
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• pp.373-380
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• 2020

For large-scale 5MW offshore wind turbines, the discrete equation of fluid domain and the motion equation of structural domain with geometric nonlinearity were built, the three-dimensional modeling of the blade considering fluid-structure interaction (FSI) was achieved by using Unigraphics (UG) and Geometry modules, and the numerical simulation and the analysis of the vibration characteristics for wind turbine structure under rotating effect were carried out based on ANSYS software. The results indicate that the rotating effect has an apparent effect on displacement and Von Mises stress, and the response and the distribution of displacement and Von Mises stress for the blade in direction of wingspan increase nonlinearly with the equal increase of rotational speeds. Compared with the single blade model, the blade vibration period of the whole machine model is much longer. The structural coupling effect reduces the response peak value of the blade displacement and Von Mises stress, and the increase of rotational speed enhances this coupling effect. The maximum displacement difference between two models decreases first and then increases along wingspan direction, the trend is more visible with the equal increase of rotational speed, and the boundary point with zero displacement difference moves towards the blade root. Furthermore, the Von Mises stress difference increases gradually with the increase of rotational speed and decreases nonlinearly from the blade middle to both sides. The results can provide technical reference for the safe operation and optimal design of offshore wind turbines.

• 대한공간정보학회지
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• 제12권3호
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• pp.23-31
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• 2004

지적측량은 토지를 지적공부에 등록하거나 등록된 경계를 지표에 복원할 목적으로 각 필지의 경계 또는 좌표와 면적을 정하는 측량으로 크게 기초측량과 세부측량으로 구분되며, 세부측량은 다시 도해지적측량과 수치지적측량으로 나누어진다. 본 연구에서는 전산화사업으로 구축된 필지중심토지정보시스템(PBLIS) 자료에 의한 도해적인 평판측량과 경계점좌표에 의한 수치지적측량을 비교하여 그 정확도를 평가하였다. 그 결과 평판에 의한 도해지적측량 위치오차가 0.766m, 토털스테이션을 이용한 수치지적측량 위치오차는 0.638m로 관측되어 도해지적측량에 의한 성과보다 수치지적측량에 의한 성과가 더 정확한 것으로 분석되었으며, 향후 지적경계측량을 할 경우 PBLIS 사용 가능성을 제시하였다.