• 한국해양공학회지
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• 제35권4호
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• pp.273-286
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• 2021

In recent years, as human casualties and property damage caused by hazardous waves have increased in the East Sea, precise wave prediction skills have become necessary. In this study, the Simulating WAves Nearshore (SWAN) third-generation numerical wave model was calibrated and optimized to enhance the accuracy of winter storm wave prediction in the East Sea. We used Source Term 6 (ST6) and physical observations from a large-scale experiment conducted in Australia and compared its results to Komen's formula, a default in SWAN. As input wind data, we used Korean Meteorological Agency's (KMA's) operational meteorological model called Regional Data Assimilation and Prediction System (RDAPS), the European Centre for Medium Range Weather Forecasts' newest 5th generation re-analysis data (ERA5), and Japanese Meteorological Agency's (JMA's) meso-scale forecasting data. We analyzed the accuracy of each model's results by comparing them to observation data. For quantitative analysis and assessment, the observed wave data for 6 locations from KMA and Korea Hydrographic and Oceanographic Agency (KHOA) were used, and statistical analysis was conducted to assess model accuracy. As a result, ST6 models had a smaller root mean square error and higher correlation coefficient than the default model in significant wave height prediction. However, for peak wave period simulation, the results were incoherent among each model and location. In simulations with different wind data, the simulation using ERA5 for input wind datashowed the most accurate results overall but underestimated the wave height in predicting high wave events compared to the simulation using RDAPS and JMA meso-scale model. In addition, it showed that the spatial resolution of wind plays a more significant role in predicting high wave events. Nevertheless, the numerical model optimized in this study highlighted some limitations in predicting high waves that rise rapidly in time caused by meteorological events. This suggests that further research is necessary to enhance the accuracy of wave prediction in various climate conditions, such as extreme weather.

• Bulletin of the Korean Chemical Society
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• 제31권3호
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• pp.630-634
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• 2010

The synthesis and ion binding properties of calix[4]pyrrole bearing pyrene moieties appended to one side of the calix[4]pyrrole are reported. The key feature is the presence of flexible fluorescence arms attached to the calix[4]pyrrole ring in a cis-fashion. The preliminary solution phase anion and cation binding studies revealed that the systems can be in fact as viable sensors for anionic guest.

• Macromolecular Research
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• 제14권5호
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• pp.510-516
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• 2006

Lactide was produced from oligomeric PLA by back-biting reaction of the OH end groups. For optimization of the reaction conditions, the effects of temperature, pressure, PLA molecular weight, and catalyst type on the lactide synthesis were examined. The fraction of D,L-lactide decreased with increasing temperature. Among the various Sn-based catalysts, the D,L-lactide fraction was maximized when SnO was used. A higher yield with lower racemization was observed at lower pressure. The conversion of PLA was maximized at an oligomeric PLA molecular weight of ca. 1380. The yield of lactide increased but the fraction of D,L-lactide decreased with increasing molecular weight. The highest conversion with the lowest racemization degree was obtained at a catalyst concentration of 0.1 wt%. The lactide was more sensitive to racemization because of the entropic effect.

• 유기물자원화
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• 제10권1호
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• pp.109-119
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• 2002

본 연구에서는 음식물쓰레기의 자원화방안으로 메탄발효를 고려하여 메탄발효과정에서 음식물쓰레기와 생분해성 음식물쓰레기 전용봉투가 투입되었을 때 실제적으로 생분해성 플라스틱이 분해가 잘 이루어지며 생분해성 플라스틱이 미생물의 활성이나 분해반응에 영향이 있는지를 연구하였다. 30%생분해성 플라스틱의 경우, 미생물에 의한 무게감량에서 중온은 최대6%, 고온은 최대 10%밖에 분해가 되지 않았다. 신장율은 중옹이 약 150%, 고온이 약 120%까지 감소하였으며, 인장강도에서는 중온이 약 $180kgf/cm^2$, 고온이 $200kgf/cm^2$ 정도 감소하였다. 대체로 온도가 높고 미생물의 활성이 좋은 고온 혐기성 소화에서 중온보다 많은 무게감소를 보였으며 HDPE계열보다는 LLDPE계열의 플라스틱이 무게감량과는 상관없이 신장율과 인장강도에서 많은 감소를 보였다. 100%생분해성 플라스틱의 경우 미생물에 의한 무게감량에서 중온은 최대 8%, 고온은 최대 33%정도 감소가 있었다. 신장율은 중온이 약 230%, 고온이 약440%까지 감소하였으며, 인장강도에서는 중온이 약 $380kgf/cm^2$, 고온이 $400kgf/cm^2$ 정도 감소하였다. 이러한 결과 30%생분해성 플라스틱은 음식물쓰레기전용봉투로의 사용이 부적합하며 100% 생분해성 플라스틱의 경우 음식물쓰레기 전용봉투로 사용이 가능하나 제품이 고가이기 때문에 경제적 부담을 줄일 수 있는 방법이 요구된다.

• 보존과학회지
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• 제35권3호
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• pp.197-208
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• 2019

목조문화재의 생물피해는 보존환경과 밀접한 관계가 있고, 급속한 기후변화로 인해 피해가 가속화될 수 있으므로 문화재 보존을 위해서는 환경 특성을 파악하는 것이 중요하다. 따라서 본 연구에서는 순천 선암사의 조사당을 대상으로 흰개미 피해 현황과 미기상, 중기상, 국지기상의 주요 환경인자 특성을 관찰하였다. 그 결과, 조사당 북서쪽 기둥에서 뚜렷한 육안피해와 흰개미 탐지견 반응이 있었고, 북동쪽 기둥에서 흰개미 탐지반응이 추가되었다. 이 기둥들은 전면에 위치한 기둥보다 표면온도가 낮고 표면 수분량과 함수율이 높은 특징이 있었다. 각 기상의 전체 시간 평균온도는 비슷하였으나 상대습도는 차이가 있었고, 미기상은 70% 이상의 높은 상대습도가 빈번히 나타났다. 특히 조사당 내부에서 흰개미 활동 일수가 가장 많았던 것으로 산출되었다. 통계 분석 결과에서는 F 비를 통해 세 기상 간 차이가 있음을 확인하였다. 또한 온도와 상대습도의 t 통계량을 통해 환경인자 간의 차이는 온도보다 습도가 더 크고, 중기상과 국지기상에서는 상대습도 차이가 더 큰 것이 확인되었다.

• 한국멀티미디어학회논문지
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• 제18권4호
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• pp.473-482
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• 2015

Doppler weather radar is an important tool for meteorological research. Through several decades of development, Doppler weather radar has enormous progress in understanding, detection and warning of meso and micro scale weather system. It makes a significant contribution to weather forecast and weather disaster warning. But the large amount of data process limits the application of Doppler weather radar. This paper proposed for fast weather radar data processing based on CUDA. CDUA is a powerful platform for highly parallel programming developed by NVIDIA. Through running plenty of threads, radar data can be calculated at same time. In experiment, CUDA parallel program can significantly improve weather data processing time.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 춘계학술대회 논문집
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• pp.99-104
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• 2004

Micro/meso cutting is getting more important in the fields of precision machining technology. A micro-turning lathe is one of parts to consist the Micro Factory. It accepts stepwise motion actuators that are used for feeding system instead of the conventional mechanism. It is consisted of two Piezoelectric ceramics; one is for feeding the slider, and the other is for clamping the slider in the guide way of the body. The linearity and positional accuracy of the actuators are good enough for high precision motion. The spindle unit is operated with DC motor on the top of the slider. The motion is communicated with miniaturized linear encoder attached on each side of axis. A mono crystal diamond tool is used for cutting tool. This micro-lathe has been made a machining experiment to see the characteristics of micro-machining.

• Advances in aircraft and spacecraft science
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• 제2권1호
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• pp.1-16
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• 2015

In this paper, geometrical and mechanical approaches are proposed for the simulation of the draping of woven fabric onto complex parts. The geometrical discrete approach allows to define the ply shapes and fibres orientation in order to optimize the composite structural properties and the continuum meso-structural mechanical approach allows to take into account the mechanical properties of fibres and resin and the various dominating mode of deformation of woven fabrics during the forming process. Some numerical simulations of forming process are proposed and compared with the experimental results in order to demonstrate the efficiency of our approaches.

• Ocean Systems Engineering
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• 제2권1호
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• pp.1-16
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• 2012

Offshore wind turbines are complex structural and mechanical systems located in a highly demanding environment. This paper proposes a multi-level system approach for studying the structural behavior of the support structure of an offshore wind turbine. In accordance with this approach, a proper numerical modeling requires the adoption of a suitable technique in order to organize the qualitative and quantitative assessment in various sub-problems, which can be solved by means of sub-models at different levels of detail, both for the structural behavior and for the simulation of loads. Consequently, in a first place, the effects on the structural response induced by the uncertainty of the parameters used to describe the environmental actions and the finite element model of the structure are inquired. After that, a meso-level FEM model of the blade is adopted in order to obtain the detailed load stress on the blade/hub connection.

• Bulletin of the Korean Chemical Society
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• 제29권2호
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• pp.339-341
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• 2008

Catalytic trimerization of isobutene to produce triisobutenes has been performed over cation-exchange resin and zeolite catalysts. Resin catalysts have the advantage of long lifetime and high trimers selectivity even though the regeneration of an aged catalyst is not satisfactory. On the contrary, zeolite catalysts can be regenerated facilely by simple calcination in air even though the lifetime is short and trimers selectivity is low probably due to small pore size and strong acidity, respectively. It is, therefore highly desirable to develop an inorganic acid catalyst with macro- or meso-pores to show catalytic performances similar or superior to those of macroporous resin catalysts.