• Journal of the Korean Data and Information Science Society
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• 제21권3호
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• pp.493-502
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• 2010

환율의 신뢰구간을 예측하기 위해 가장 중요한 요인은 분포의 추정이다. 그러나 시계열 자료의 분포를 추정하는 것은 많은 어려움이 따른다. 본 연구에서는 변동률 합의 분포를 비모수기법 중의 하나인 블록화 붓스트랩 방법을 사용하여 추정한다. 따라서 좀 더 쉽고 정확한 환율의 장단기 신뢰구간 예측 모형을 제시한다.

• Asian Journal of Atmospheric Environment
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• 제9권4호
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• pp.259-271
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• 2015

This study conducted analyses on biogenic volatile organic compounds (BVOC) emission sources contributing to urban ozone ($O_3$) concentration in Osaka Prefecture, Japan in summer 2010 by using the Weather Research and Forecasting model (WRF) version 3.5.1 and the Community Multiscale Air Quality model (CMAQ) version 5.0.1. This prefecture is characterized by highly urbanized area with small forest area. The contributions of source regions surrounding Osaka were estimated by comparing the baseline case and zero-out cases for BVOC emissions from each source region. The zero-out emission runs showed that the BVOC emissions substantially contributed to urban $O_3$ concentration in Osaka (10.3 ppb: 15.9% of mean daily maximum 1-h $O_3$ concentration) with day-by-day variations of contributing source regions, which were qualitatively explained by backward trajectory analyses. Although $O_3$ concentrations were especially high on 23 July and 2 August 2010, the contribution of BVOC on 23 July (35.4 ppb: 25.6% of daily maximum $O_3$) was much larger than that on 2 August (20.9 ppb: 14.2% of daily maximum $O_3$). To investigate this difference, additional zero-out cases for anthropogenic VOC (AVOC) emissions from Osaka and for VOC emissions on the target days were performed. On 23 July, the urban $O_3$ concentration in Osaka was dominantly increased by the transport from the northwestern region outside Osaka with large contribution of $O_3$ that was produced through BVOC reactions by the day before and was retained over the nocturnal boundary layer. On 2 August, the concentration was dominantly increased by the local photochemical production inside Osaka under weak wind condition with the particularly large contribution of AVOC emitted from Osaka on the day.

• 한국환경보건학회지
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• 제17권2호
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• pp.1-8
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• 1991

The stochastic variance and structures of time series data on air quality were examined by employing the techniques of autocorrelation function, variance spectrum, fourier series, ARIMA model. Among the air quality properties of atmosphere, SO$_{2}$ is one of the most siginificant and widely measured parameters. In the study, the air quality data were included hourly observations on SO$_{2}$ TSP and O$_{3}$. The data were measured by automatic recording instrument installed in Kwanghwamoon during February and March in 1991. The results of study were as follows 1. Hourly air quality series varied with the domiant 24 hour periodicity and the 12 hour periodic variation was also observed. 2. The correlation coefficients between SO$_{2}$ and O$_{3}$ is -0.4735. 3. In simulating or forecasting variation in SO$_{2}$ ARIMA models are on a useful tools. The multiplicative seasonal ARIMA (1, 1, 0) (0, 2, 1)$_{24}$ model provided satisfactory results for hourly SO$_{2}$ time series.

• 응용통계연구
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• 제30권3호
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• pp.323-334
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• 2017

실현변동성(RVs)이 지속적인 장기기억성과 상당히 큰 이상치의 존재로 인해 정상계열과 비정상계열의 경계에 위치한다는 것에 주목하였다. 실현변동성을 예측하기 위해 실현변동성 이상치 관측 유무에 따라 heterogeneous autoregressive (HAR) 모형과 integrated HAR (IHAR) 모형을 번갈아 사용하는 새로운 방법을 제안하였고, 이 방법을 IHAR-O-HAR라 칭하였다. 예측력 비교는 주요 지수인 S&P 500, Nasdaq과 Nikkei 225의 실현변동성 데이터를 이용하였으며 표본 외 예측력 비교에서 새로운 IHAR-O-HAR 방법은 RW 방법, HAR 방법이나 IHAR 방법의 예측력보다 우수함을 확인하였다.

• KIEE International Transactions on Electrophysics and Applications
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• 제5C권3호
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• pp.131-137
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• 2005

This paper describes a new approach to the algorithm and fundamental characteristics of the device for monitoring the leakage currents flowing through zinc oxide (ZnO) surge arresters. In order to obtain a technique for a new on-line monitoring device that can be used in the deterioration diagnosis of ZnO surge arresters, the new algorithm and on-line leakage current detection device for extracting the resistive and capacitive currents using the phase shift addition method were proposed. The computer-based on-line monitoring device can sense accurately the power frequency leakage currents flowing through ZnO surge arresters. The on-line leakage current monitoring device of ZnO surge arresters proposed in this work has the high sensitivity compared to the third harmonic leakage current detection devices. As a consequence, it was found that the proposed leakage current monitoring device would be useful for forecasting the defects and degradation of ZnO surge arresters.

• 한국멀티미디어학회논문지
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• 제25권2호
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• pp.440-449
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• 2022

In recent years, the air pollution and Air Quality Index (AQI) has been a pivotal point for researchers due to its effect on human health. Various research has been done in predicting the AQI but most of these studies, either lack dense temporal data or cover one or two air pollutant elements. In this paper, a hybrid Convolutional Neural approach integrated with recurrent neural network architecture (CNN-LSTM), is presented to find air pollution inference using a multivariate air pollutant elements dataset. The aim of this research is to design a robust and real-time air pollutant forecasting system by exploiting a neural network. The proposed approach is implemented on a 24-month dataset from Seoul, Republic of Korea. The predicted results are cross-validated with the real dataset and compared with the state-of-the-art techniques to evaluate its robustness and performance. The proposed model outperforms SVM, SVM-Polynomial, ANN, and RF models with 60.17%, 68.99%, 14.6%, and 6.29%, respectively. The model performs SVM and SVM-Polynomial in predicting O3 by 78.04% and 83.79%, respectively. Overall performance of the model is measured in terms of Mean Absolute Error (MAE), Mean Absolute Percentage Error (MAPE) and the Root Mean Square Error (RMSE).

• 한국항만경제학회지
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• 제24권3호
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• pp.57-77
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• 2008

본 연구에서는 기존의 물동량 전망에 적용한 방법론이 아닌 개별 항만별 예측방법을 적용하여 인천항에서 경유하는 수출 화물 물동량을 전망하였다. 물동량 전망에 있어 기존의 통계적, 계량경제학적인 분석 대신 시스템 분석을 적용하였다. 대부분의 기존연구에서 적용하였던 총량적 접근방법은 전국의 총 화물물동량을 각 품목별 특성에 따른 계량모형을 통해 추정한다. 이는 전국권역을 기반으로 항만 O/D에 따라 향후 권역별 항만 개발계획 및 개별입지변화를 반영하여 체계적인 방법으로 배분함으로써 전국 항만의 물동량을 도출했다. 본 연구에서는 이러한 기존방법론이 아닌 개별항만의 주변상창이나 직접적인 영향을 미치는 산업단지의 현황을 토대로 물동량을 도출해 내는 방법이다. 본 연구에 있어 기초자료는 인천항을 배후권역으로 하는 수출 화물의 기종점인 배후산업단지의 소요면적에 대한 자료를 토대로 조사하였다. 이는 수출의 대부분을 창출하는 산업단지의 소요면적을 파악하여 이에 원단위를 적용함으로써 산단별 입출되는 물량을 도출할 수 있다. 여기에 산단별 분양률, 업종비중, 가동률, 그리고 산단별 수출 비중을 적용하여 인천항의 수출 화물 물동량을 전망하였다. 본 연구는 기존의 전망치와 비교를 함으로써 연구방법론의 다양화와 비교연구를 수행하는 연구성과를 거두었다.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
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• pp.620-621
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• 2008

Transparent electronics has been one of the key terminologies forecasting the ubiquitous technology era. Several researchers have thus extensively developed transparent oxide-based thin-film transistors (TFTs) on glass and plastic substrates although in general high voltage operating devices have been mainly studied considering transparent display drivers. However, low voltage operating oxide TFTs with transparent electrodes are very necessary if we are aiming at logic circuit applications, for which transparent complementary or one-type channel inverters are required. The most effective and low power consuming inverter should be a form of complementary p-channel and n-channel transistors but real application of those complementary TFT inverters also requires electrical- and even photo-stabilities. Since p-type oxide TFTs have not been developed yet, we previously adopted organic pentacene TFTs for the p-channel while ZnO TFTs were chosen for n-channel on sputter-deposited $AlO_x$ film. As a result, decent inverting behavior was achieved but some electrical gate instability was unavoidable at the ZnO/$AlO_x$ channel interface. Here, considering such gate instability issues we have designed a unique transparent complementary TFT (CTFTs) inverter structure with top n-ZnO channel and bottom p-pentacene channel based on 12 nm-thin nano-oxide/self assembled monolayer laminated dielectric, which has a large dielectric strength comparable to that of thin film amorphous $Al_2O_3$. Our transparent CTFT inverter well operate under 3 V, demonstrating a maximum voltage gain of ~20, good electrical and even photoelectric stabilities. The device transmittance was over 60 % and this type of transparent inverter has never been reported, to the best of our limited knowledge.

• 조명전기설비학회논문지
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• 제15권3호
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• pp.67-73
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• 2001

본 논문에서는 ZnO 피뢰기 소자에 대한 내구성 평가와 열화실험을 위한 저항분 누설전류 검출장치의 개발과 열화진단기법에 대하여 기술하였다. 저항분 누설전류는 ZnO 피뢰기 소자가 정상상태인지 불안정상태인지에 대한 판단의 지표로서 사용할 수 있다. 본 논문에서는 보상회로로 구성된 저항분 누설전류 측정시스템을 설계하여 구성하고, 실증실험으로서 ZnO 소자에 대한 저항분 누설전류의 측정과 고속프리에 변환기법(Fast Fourier transform)을 통해 저항분 누설전류의 주파수특성을 조사·분석하였다. 분석결과 제안한 저항분 누설전류의 측정 시스템은 실험실에서 산화아연 바리스터의 전기적·물성적 특성을 연구하고, 전력계통에 있어서 ZnO 피뢰기의 열화의 진단과 예측기술을 개발하는데 유용하게 활용할 수 있다.

• 국제학술발표논문집
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• The 9th International Conference on Construction Engineering and Project Management
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• pp.823-830
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• 2022

The risk of project execution increases due to the enlargement and complexity of Engineering, Procurement, and Construction (EPC) plant projects. In the fourth industrial revolution era, there is an increasing need to utilize a large amount of data generated during project execution. The design is a key element for the success of the EPC plant project. Although the design cost is about 5% of the total EPC project cost, it is a critical process that affects the entire subsequent process, such as construction, installation, and operation & maintenance (O&M). This study aims to develop a system using machine-learning (ML) techniques to predict risks and support decision-making based on big data generated in an EPC project's design and construction stages. As a result, three main modules were developed: (M1) the design cost estimation module, (M2) the design error check module, and (M3) the change order forecasting module. M1 estimated design cost based on project data such as contract amount, construction period, total design cost, and man-hour (M/H). M2 and M3 are applications for predicting the severity of schedule delay and cost over-run due to design errors and change orders through unstructured text data extracted from engineering documents. A validation test was performed through a case study to verify the model applied to each module. It is expected to improve the risk response capability of EPC contractors in the design and construction stage through this study.