• Asian Journal of Atmospheric Environment
• /
• 제8권1호
• /
• pp.25-34
• /
• 2014

In winter 2013, extreme air pollution by fine particulate matter ($PM_{2.5}$) in China attracted much public attention. In order to simulate the $PM_{2.5}$ pollution, the Community Multiscale Air Quality model driven by the Weather Research and Forecasting model was applied to East Asia in a period from 1 January 2013 to 5 February 2013. The model generally reproduced $PM_{2.5}$ concentration in China with emission data in the year 2006. Therefore, the extreme $PM_{2.5}$ pollution seems to be mainly attributed to meteorological (weak wind and stable) conditions rather than emission increases in the past several years. The model well simulated temporal and spatial variations in $PM_{2.5}$ concentrations in Japan as well as China, indicating that the model well captured characteristics of the $PM_{2.5}$ pollutions in both areas on the windward and leeward sides in East Asia in the study period. In addition, contribution rates of four anthropogenic emission sectors (power generation, industrial, residential and transportation) in China to $PM_{2.5}$ concentration were estimated by conducting zero-out emission sensitivity runs. Among the four sectors, the residential sector had the highest contribution to $PM_{2.5}$ concentration. Therefore, the extreme $PM_{2.5}$ pollution may be also attributed to large emissions from combustion for heating in cold regions in China.

• 한국신뢰성학회지:신뢰성응용연구
• /
• 제18권3호
• /
• pp.201-207
• /
• 2018

Purpose: To develop the reliability growth planning for a subsystem of guided weapon system using PM2-Continuous model. Methods: The target MTBF of the subsystem is set by allocating the system target MTBF to the lower level, where ARINC method is applied. Other model parameters such as initial MTBF, management strategy ratio and average fix effectiveness factor are chosen from historical growth parameter estimates. Given the values of model parameters, the reliability growth planning curve using PM2-Continuous model is constructed and the sensitivity analyses are performed for the changes of model parameters. Results: We have developed the reliability growth plan for a subsystem of guided weapon system using PM2-Continuous model. It was found that the smaller the ratio of initial MTBF to target MTBF, the smaller the management strategy ratio, the smaller the average fix effectiveness factor, and the shorter the development test period, the higher reliability growth is required. Conclusion: The result of this study will be used as a basis for establishing the reliability growth plan, the test period setting and the budget appropriation for the similar system entering the system development stage in the future.

• Asian Journal of Atmospheric Environment
• /
• 제5권4호
• /
• pp.263-277
• /
• 2011

Global atmospheric $CO_2$ distributions were simulated with a chemical transport model (GEOS-Chem) and compared with space-borne observations of $CO_2$ column density by GOSAT from April 2009 to January 2010. The GEOS-Chem model simulated 3-D global atmospheric $CO_2$ at $2^{\circ}{\times}2.5^{\circ}$ horizontal resolution using global $CO_2$ surface sources/sinks as well as 3-D emissions from aviation and the atmospheric oxidation of other carbon species. The seasonal cycle and spatial distribution of GEOS-Chem $CO_2$ columns were generally comparable with GOSAT columns over each continent with a systematic positive bias of ~1.0%. Data from the World Data Center for Greenhouse Gases (WDCGG) from twelve ground stations spanning $90^{\circ}S-82^{\circ}N$ were also compared with the modeled data for the period of 2004-2009 inclusive. The ground-based data show high correlations with the GEOS-Chem simulation ($0.66{\leq}R^2{\leq}0.99$) but the model data have a negative bias of ~1.0%, which is primarily due to the model initial conditions. Together these two comparisons can be used to infer that GOSAT $CO_2$ retrievals underestimate $CO_2$ column concentration by ~2.0%, as demonstrated in recent validation work using other methods. We further estimated individual source/sink contributions to the global atmospheric $CO_2$ budget and trends through 7 tagged $CO_2$ tracers (fossil fuels, ocean exchanges, biomass burning, biofuel burning, net terrestrial exchange, shipping, aviation, and CO oxidation) over 2004-2009. The global $CO_2$ trend over this period (2.1 ppmv/year) has been mainly driven by fossil fuel combustion and cement production (3.2 ppmv/year), reinforcing the fact that rigorous $CO_2$ reductions from human activities are necessary in order to stabilize atmospheric $CO_2$ levels.

• 한국대기환경학회지
• /
• 제32권1호
• /
• pp.82-99
• /
• 2016

This study was carried out to understand the regional contribution of Particulate Matter (PM) emissions from East Asia ($82^{\circ}{\sim}149^{\circ}E$, $18^{\circ}{\sim}53^{\circ}N$) to Seoul during high concentration period in February 2014. The Community Multi-scale Air Quality (CMAQ) version 5.0.2 with Decoupled Direct Method (DDM) was used to analyze levels of contributions over Seoul. In order to validate model performance of the CMAQ, predicted PM and its chemical species concentrations were compared to observations in China and Seoul. Model predictions could depict the daily and hourly variations of observed PM. The calculated PM concentrations, however, had a tendency of underestimation. The discrepancies are due to uncertainties of meteorological data, emission inventories and CMAQ model itself. The high PM concentration in Seoul was induced by stationary anticyclone over the West Coast of Korea during 24 to 27 February. The DDM in CMAQ was used to analyze the contributions of emissions from East Asia on Seoul during this PM episode. $PM_{10}$ concentration in Seoul is contributed by 39.77%~53.19% from China industrial and urban region, 15.37%~37.10% from South Korea, and 9.03%~18.05% North Korea. These indicate that $PM_{10}$ concentrations in Seoul during the episode period are dominated by long-range transport from China region as well as domestic sources. It was also found that the largest contribution region in China were Shandong peninsula during the PM event period.

• 대한전기학회논문지:시스템및제어부문D
• /
• 제52권9호
• /
• pp.560-567
• /
• 2003

EMG recordings of the electrical activity of muscle have proved to be a valuable tool in studying muscle function and reflex activity. SP(silent period) is elicited by a electrical stimulation on the chin during isometric contraction of jaw muscle. This paper proposes a model of the inhibitory reflex mechanism of jaw muscle after electrical stimulation. The SPs of jaw muscle after a electrical stimulation to the chin were divided into SP1 and SP2. SP1 is produced by the activation of periodontal receptors. The activation of nociceptors contributes to the SP2. As a result, the EMG signal generated by a proposed a model of inhibitory reflex mechanism is similar to real both EMG signal including SP1 and SP2. The present study have shown differences of SP1 and SP2 induced by inhibitory reflex mechanism.

• Journal of Biosystems Engineering
• /
• 제11권1호
• /
• pp.52-63
• /
• 1986

This study was performed to find out drying characteristics and develop drying model for the design of an efficient dryer or drying system of red peper. The basic model which describes drying phenomenon of red pepper was firstly established, and drying tests were conducted at 14-different drying conditions. In this test, the effects of drying air temperature and relative humidity on the rate of drying were undertaken. Finally, a new drying model based on these experimental results was developed to describe the drying characteristics of red pepper. The results from this study may be summarized as follows. 1. Drying constant of the basic model established from Lewis' experimental model and diffusion equation was theoretically deduced as a function of moisture content and inner-temperature of red pepper. 2. From the results of drying tests, drying air temperature was found to have the greatest effect on the rate of drying. However, the effect of temperature was small for the condition of high relative humidity, and for low temperature, the effect of relative humidity was found to be large even though the range of relative humidity was low. 3. Modified Henderson equation was found to be better than Chung equation as the EMC model for the estimation of the equilibrium moisture content of red Pepper. 4. Constant-rate drying period did not exist in the red pepper drying test. And falling-rate drying period was divided into three distinct phases. Drying rate was dependent on the moisture content, the inner-temperature of red pepper and the change of physical property due to drying. 5. Drying constant increased with decrease of free moisture content, but it decreased at the end of the drying period. Also, drying constant was dependent on the drying air temperature and relative humidity. 6. The new drying model developed in this study was found to be most suitable in describing the drying characteristics of red pepper. Therefore, it may be concluded that drying time could be accurately estimated by the new drying model.

• 융합정보논문지
• /
• 제10권3호
• /
• pp.67-75
• /
• 2020

본 연구에서는 주식시장과 채권시장간의 정보 이전효과(information flow effect)를 살펴보기 위해 우리나라 KOSPI의 일일지수와 초단기 채권형 펀드(money market fund : MMF) 수익률 자료를 이용하여 분석하였다. 전체 분석대상 기간은 1997년 5월 2일부터 2019년 8월 30일까지 이다. 1997년 5월 2일부터 2008년 12월 30일 글로벌금융위기전 기간, 2008년 12월 30일부터 2019년 8월 30일까지 글로벌금융위기 후 기간과 전체기간으로 세분하여 실증분석을 하였다. 분석결과 비대칭적 변동성을 고려한 EGARCH 모형이 적합한 것으로 나타났다. 주식시장과 채권시장 간에는 가격이전효과와 변동성 이전효과가 양방향으로 존재하는 것으로 나타났으며, 가격이전효과는 두 시장 간에 글로벌금융위기전 기간이 후보다 더 크게 나타났다. 주식시장과 채권시장간의 정보에 대한 비대칭적 변동성이 두 시장에 존재하는 것으로 나타났다.

• 한국물환경학회지
• /
• 제29권2호
• /
• pp.212-222
• /
• 2013

A watershed model was constructed using Hydrological Simulation Program Fortran to quantitatively predict the stream flows at major tributaries of Nakdong River basin, Korea. The entire basin was divided into 32 segments to effectively account for spatial variations in meteorological data and land segment parameter values of each tributary. The model was calibrated at ten tributaries including main stream of the river for a three-year period (2008 to 2010). The deviation values (Dv) of runoff volumes for operational stream flow forecasting for a six month period (2012.1.2 to 2012.6.29) at the ten tributaries ranged from -38.1 to 23.6%, which is on average 7.8% higher than those of runoff volumes for model calibration (-12.5 to 8.2%). The increased prediction errors were mainly from the uncertainties of numerical weather prediction modeling; nevertheless the stream flow forecasting results presented in this study were in a good agreement with the measured data.

• Journal of the Korean Data and Information Science Society
• /
• 제22권2호
• /
• pp.335-351
• /
• 2011

오경주와 김태윤 (2007) 등은 위기 관련 데이터의 희귀성 에서 발생하는 문제를 해결하기 위해 과거 금융시장이 안정적이었던 구간을 기준 구간으로 설정하고 기준 구간의 금융시장 움직임을 점 근 자기회귀 모형으로 적합한 후 현재의 금융시장 상황과 비교하여 불안정 지수를 도출할 것을 제안하였다. 그러나 비모수 기법인 신경망을 사용하여 도출된 불안정 지수가 기준 구간의 데이터에 지나치게 의존하는 관계로 불안정 지수가 종종 실제 경제상황을 제대로 반영하지 못하는 것으로 관찰되고 있다. 본 연구에서는 비모수 기법인 신경망과 모수 기법인 선형모형을 이용하여 기준구간에 대한 적합을 독립적으로 수행하여 두 종류의 불안정성 지수들을 도출한 후 이 둘을 결합한 통합 불안정성 지수를 사용할 것을 제안한다. 두 지수의 적절한 통합을 위해 신경망과 선형모형을 통해 도출된 두 지수의 최적 결합비율을 부여하는 방법을 제안하며 제안기법의 타당성을 국내 주식시장 대상으로 검증하였다.

• 응용통계연구
• /
• 제26권6호
• /
• pp.1019-1032
• /
• 2013

최근 급격한 기대수명의 증가에 따라 미래 복지정책 등에 커다란 영향을 주는 장래 사망력의 정확한 예측은 중요한 이슈가 되고 있다. 사망력의 정확한 예측을 위하여 최적의 추정모형의 선택도 중요하지만 사망력에 대한 시계열 적용기간도 매우 중요한 이슈다. 이는 우리나라의 사망률 시계열이 짧고, 특히 1982년 이전 자료가 다소 불완전해서 이에 대한 고려가 필수적이기 때문이다. 본 논문에서는 우리나라 사망력 시계열을 기간에 따라 2개의 그룹(1976~2005년, 1983~2005년)으로 나누어서, 남녀별로 LC모형과 LC 코호트효과 확장모형에 대한 모수 추정값, 사망력지수와 코호트지수의 모형화 및 예측, 장래 기대수명의 예측 적합력을 각각 분석한 후 향후에 장래 기대수명 추계시 고려할 시사점을 제시하고자 한다.