• Nuclear Engineering and Technology
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• 제53권4호
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• pp.1157-1166
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• 2021

In this study, a numerical sensitivity analysis was performed to determine the fire suppression time for a large number of water mist nozzles in a large fire compartment. Fire simulations were performed using FDS (Fire dynamics simulator) 6.5.2 under the same condition as the test scenario 5 of the International Maritime Organization (IMO) 1165 test protocol. The sensitivities of input parameters including cell size, extinguishing coefficient (EC), droplets per second (DPS), and peak heat release rate (HRR) of fuel were investigated in terms of the normalized HRR and temperature distribution in the compartment. A new method of determining the fire suppression time using FDS simulation was developed, based on the concept of the cut-off time by cut-off value (COV) of the heat release rate per unit volume (HRRPUV) and the cooling time by the HRR cooling time criteria value (CTCV). In addition, a method was developed to determine the average EC value for the simulation input, using the cooling time and cut-off time.

• 한국환경과학회지
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• 제18권4호
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• pp.369-374
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• 2009

To examine the trend on the flowering time in some weather flora including Prunus serrulata var. spontanea, Cosmos bipinnatus, and Robinia pseudo-acacia in Busan, the changes in time series and rate of flowering time of plants were analyzed using the method of time series analysis. According to the correlation between the flowering time and the temperature, changing pattern of flowering time was very similar to the pattern of the temperature, and change rate was gradually risen up as time goes on. Especially, the change rate of flowering time in C. bipinnatus was 0.487 day/year and showed the highest value. In flowering date in 2007, the difference was one day between measurement value and prediction value in C. bipinnatus and R. pseudo-acacia, whereas the difference was 8 days in P. mume showing great difference compared to other plants. Flowering time was highly related with temperature of February and March in the weather flora except for P. mume, R. pseudo-acacia and C. bipinnatus. In most plants, flowering time was highly related with a daily average temperature. However, the correlation between flowering time and a daily minimum temperature was the highest in Rhododendron mucronulatum and P. persica, otherwise the correlation between flowering time and a daily maximum temperature was the highest in Pyrus sp.

• 대한교통학회지
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• 제17권5호
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• pp.43-55
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• 1999

화물의 시간가치 연구는 운송과정에서 화물이 갖는 중요도를 평가하며 운송중의 재고비용까지 나타내어 효율적인 물류관리를 위한 방향을 제시해 준다. 화물의 시간가치는 화물의 업종에 따라 차이를 보이며, 동일한 업종내에서도 화주의 특성에 따라 차이를 보인다. 이것은 운송시간의 절감에 보이는 화주의 행태가 다르며, 그로 인해 운송시간의 절감에 대한 화주의 지불용이가 각각 다르게 나타나기 때문이다. 본 연구에서는 우리나라 제조업체의 화주를 대상으로 지역간 화문운송의 시간가치를 추정하였다. 연구방법은 화주가 공로운송수단을 선정할 때 중요한 기준이 되는 인식요소를 추출하고, 그에 따라 화주돈을 동질의 업종으로 분할한 후 다항로짓모형을 추정하여 화주집단별 시간가치를 도출하였다. 연구의 결과 지역간 화물운송의 시간가치는 화물업종마다 차이를 보였으며, 평균적으로 한시간의 운송시간을 줄이기 위해서는 출하차량 1대당 1.680원(톤당 389원)을 지불해야 하는 것으로 나타났다. 이를 화물 업종별로 분류하면 의류·직물, 사무기계 ·가전제품, 통신·정밀과학 등은 2,906원으로 추정되었고, 음식료품, 비금속광물, 제1차금속산업, 조립금속산업 및 자동차부품 등은 1,248원으로 나타났다. 그리고 가구, 출판·인쇄물, 화학제품 등은 1,041원의 크기를 보였다. 다음으로 운송중의 재고비용은 평균적으로 화물가격의 9.54%로 추정되었으며, 사무기계·가전제품 등 고가의 화물은 화물가격의 약 50%에 달하는 반면에 비금속광물 등 저가의 화물은 낮은 재고비용을 갖는 것으로 평가되었다.

• 대한교통학회지
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• 제20권7호
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• pp.167-175
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• 2002

본 연구의 목적은 화주가 공로화물운송에서 나타내는 효용을 화물의 품목에 따라 나타내고 자 하였다. 화물교통에서 화주의 효용은 시간가치의 크기를 이용하여 얻을 수 있다. 화물의 특성은 매우 다양하기 때문에 화주의 효용 또한 매우 폭넓게 변화한다. 최근에 화물운송의 시간가치를 산정하는 소수의 연구가 있었으나 대부분 철도나 해운을 포함하여 공로화물운송에 대한 독자적인 시간가치는 얻지 못하였다. 연구에서는 화물의 품목분류에 따라 공로화물운송의 시간가치를 산정하였다. 시간가치의 산정을 위해 현시선호 방법과 이항로짓모형이 이용되었고 연구자료는 1998년도에 수도권을 대상으로 시행된 물동량 조사자료를 이용하였다. 조사자료는 화물품목분류에 따라 분할하였고 분할된 그룹에 따라 19개의 이항로짓모형이 추정되었다. 연구결과 화물운송의 시간가치는 화물의 품목에 따라 16,441원/시간·대부터 66.769원/시간·대까지 분포하는 것으로 나타났다.

• Journal of applied mathematics & informatics
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• 제28권3_4호
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• pp.945-952
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• 2010

In this paper, existence criteria of one solution to a nonlinear first-order periodic boundary value problem of impulsive dynamic equation on time scales are obtained by using the well-known Schaefer fixed-point theorem.

• 한국조리학회지
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• 제24권3호
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• pp.35-46
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• 2018

This study investigated the quality characteristics of makpyeon made of dry milled rice powder according to soaking time. Makpyeon samples made of dry milled rice powder were analyzied with various soacking time, the moisture content, pH, Hunter's color value texture characteristics, attribute difference test and acceptance test. The moisture content of makpyeon did not indicate difference among samples. pH resulted in MS90 showed the lowest moisture content. The L-value (lightness) and a-value (greenness) result in that MS0 showed the highest and decreased according to soaking time. The b-value (yellowness) increased according to soaking time, MS90 showed the highest. TPA resulted in that MS90 indicated the highest hardness, chewiness, gumminess and the lowest adhesiveness. Hardness of makpyeon samples was higher than sulgitteok samples, adhesiveness was lower than those of sulgitteok in each soaking time. Based on attribute difference test, the score of brightness, moistness, glossy, particle size were decreased and firmness were increased according to soaking times. Flavor, taste and mouth feel attribute was stronger in makpyeon samples with the longer soaking time. Acceptance results showed that MS0 and MS30 (soaking for 30 min) were preferred the most. Also limitations and future research directions of this study were discussed.

• 가정과삶의질연구
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• 제21권1호
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• pp.61-72
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• 2003

This study examines the problematic fact that most housewives are excluded from receiving the benefits of the National Pension Plan in South Korea. The National Pension Plan assigns no value to housework or household production, which in turn discourages full-time housewives from participating voluntarily in the Plan. In this article, I propose to utilize Credit Splitting and Pension Sharing in order to take into account full-time housewives' economic contribution in the National Pension Plan. In this article, I also discuss the ranges and application methods of the Credit Splitting and Pension Sharing. For this study, I have analyzed the data of 11,967 unemployed married women living with spouses published in“Research Data on Everyday Life Time Usage”by the Korea National Statistical Office in 1999. The value of the full-time housewives' labor varies depending on the methods of estimation. However, all estimated values exceed the average value assigned to the housewives by the National Pension Corporation. It is clear that full-time housewives' unpaid labor contributes a great deal to the formation of household property and wealth, which is a valid reason for Pension Sharing and Credit Splitting. This article also provides logical factors to consider in the process of Pension Sharing and Credit Splitting, which can be used for developing computerized software to determine a full-time housewives' labor value at the time of divorce or for any other purpose.

• 무역학회지
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• 제46권6호
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• pp.191-209
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• 2021

In this paper, various time series analysis models and machine learning models are presented for long-term prediction of export growth rate, and the prediction performance is compared and reviewed by RMSE and MAE. Export growth rate is one of the major economic indicators to evaluate the economic status. And It is also used to predict economic forecast. The export growth rate may have a negative (-) value as well as a positive (+) value. Therefore, Instead of using the ReLU function, which is often used for time series prediction of deep learning models, the PReLU function, which can have a negative (-) value as an output value, was used as the activation function of deep learning models. The time series prediction performance of each model for three types of data was compared and reviewed. The forecast data of long-term prediction of export growth rate was deduced by three forecast methods such as a fixed forecast method, a recursive forecast method and a rolling forecast method. As a result of the forecast, the traditional time series analysis model, ARDL, showed excellent performance, but as the time period of learning data increases, the performance of machine learning models including LSTM was relatively improved.

• The Journal of Asian Finance, Economics and Business
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• 제7권8호
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• pp.69-76
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• 2020

The study examines lagged economic effects of research and development (R&D) investment on the market value of manufacturing firms listed on the Shanghai Stock Exchange or the Shenzhen Stock Exchange in China. This study applies panel data analysis methods to address the following issues: 1) There might be an adjustment lag in the impact of R&D investment on corporate market value, and 2) Unobserved firm effects must be taken into account. The balanced panel data includes a total of 1,462 observations with 34 cross-sections of manufacturing firms listed on Chinese stock markets and with 27 time-specific quarterly periods from 2007 to 2017. The results indicate that the R&D investment of Chinese manufacturing firms tends to yield favorable market value of the firm with some adjustments to time. The results show that R&D investment exhibits a strong positive impact on their market value of manufacturing firms in Chinese stock markets. Moreover, R&D investment has a positive time-lag effect on the market value of the firm. Interestingly, the R&D investment of Chinese manufacturing firms generate a relatively constant positive effect on their market value, supporting the notion that the corresponding returns of R&D investment for such firms yield lagged but added market values.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2000년도 전력전자학술대회 논문집
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• pp.748-751
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• 2000

in this paper the design procedure of three phase voltage source inverter output filter is described. The 'd' axis transfer function of the filter output voltage to the load current is described with the capacitor value and the system time constant including the controller. This means that the relation between the filter capacitor value and the system time constant is given as the closed form. By using the above closed form the capacitor value can be calculated with the system time constant is given as the closed,. form the capacitor value can be calculated with the system time constant which can be implemented practically not using the try and error method. And as the effect of the load is connected.