• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 2004년도 춘계공동학술대회 논문집
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• pp.331-334
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• 2004

There are many researches investigating a causal relationship among service performance level, customer satisfaction, and customer loyalty. It is believed that a high service performance level increases customer satisfaction, which again has a significant effect on customer loyalty and profitability. The premise in this work is that the effect of customer satisfaction on customer loyalty may be time-lagged. This paper aims to model a causal relationship among service performance level, customer satisfaction, and customer loyalty with such a time-lag consideration. This study is conducted on the very high-speed digital subscriber lines service, which is a highly advanced high-speed internet service, and the results also be discussed.

• 정보기술응용연구
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• 제3권2호
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• pp.25-48
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• 2001

최근 기업차원뿐 만 아니라 국가적 차원에서도 정보기술에 대한 투자 및 활용에 많은 노력을 기울이고 있다. 본 연구는 이러한 노력이 과연 가시적인 경제적 효과를 가져오는가를, 정보화수준과 생산성의 관계를 통해 알아보고자 한다. 특히, 거시적 차원에서 국가의 정보화수준이 국가경제생산성에 미치는 영향을 분석하기 위해, 주요 국가들의 정보화와 생산성에 관한 제반 통계자료를 수집하여 정보화지수 성장률과 총요소생산성(TFP : Total Factor Productivity) 및 노동생산성 성장률 등을 측정하고, 이들 개념간의 관계를 실증적으로 분석하였다.

• 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.

• 한국환경과학회지
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• 제31권2호
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• pp.141-148
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• 2022

In this study, the inhibition of ammonia on anaerobic digestion of butyric acid was evaluated and the potential alleviating effects of such ammonia inhibition by the addition of magnetite particles were investigated. Independent anaerobic batch tests fed with butyric acid as a sole organic source were conducted in twenty 60-mL glass bottles with 10 different treatment conditions, comprising ammonia: 0.5, 2.0, 4.0, 6.0, and 7.0 g total ammonia nitrogen (TAN)/L and magnetite particles: 0 mM and 20 mM. The increase in ammonia concentration did not cause significant inhibition on methane yield; however, a significant inhibition on lag time and specific methane production rate was observed. The IC₅₀ in the control treatments (without magnetite addition) was estimated as 6.2654 g TAN/L. A similar inhibition trend was observed in magnetite-added treatments; however, the inhibition effect by ammonia was significantly alleviated in lag time and specific methane production rate when compared to those in the control treatments. The lag time was shortened by 1.6-46.3%, specific methane production rate was improved by 6.0-69.0%. In the magnetite-added treatments, IC₅₀ was estimated as 8.5361 g TAN/L. This study successfully demonstrated the potential of magnetite particles as an enhancer in anaerobic digestion of butyric acid under conditions of ammonia stress.

• 조명전기설비학회논문지
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• 제23권2호
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• pp.45-52
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• 2009

본 연구는 Full-HD급 PDP의 고속 구동 구현을 위한 새로운 구동 방식에 관한 연구이다. 새로운 SPA (self-priming address) 구동 파형은 어드레스 구간에서 지속적인 프라이밍 방전을 유지하여 하전 입자 효과를 이용하여 어드레스 방전 지연 시간을 개선하기 위하여 제안되었다. 본 연구에서는 프라이밍 방전의 기본 특성에 대해 조사하였으며, 안정적인 프라이밍 방전을 유지할 수 있는 초기화 펄스 및 프라이밍 램프 펄스를 도출하였다. 특히, 프라이밍 램프 펄스의 기울기가 0.1[$V/{\mu}s$]의 미약한 프라이밍 방전의 경우에 대해서도 기존 방식의 1.2[${\mu}s$]의 어드레스 방전 지연 시간을 0.8[${\mu}s$]로 획기적으로 개선할 수 있는 것을 확인하였다.

• Journal of Biosystems Engineering
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• 제43권2호
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• pp.110-118
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• 2018

Purpose: In this study, the potential for biogas production, degradation rates, and lag-phase of diauxic growth of carbohydrate-based material, which is one of the proximate compositions, were investigated. Methods: This study was conducted using starch as a carbohydrate-based material. In experimental condition 1, the biogas potential of carbohydrate-based material was measured. In experimental condition 2, the effect of feed to microorganism ratio (F/M ratio) on lag-phase of diauxic growth from carbohydrate-based material was tested. Biochemical methane potential tests were performed at five different feed to microorganism ratios (0.2, 0.4, 0.6, 0.8, and 1.0) under mesophilic conditions. The biogas production patterns, lag-phase, total volatile fatty acids to total alkalinity ratio (TVFA/TA ratio), and time required for 90 percent biogas production were used to evaluate biogas production based on the biochemical methane potential tests. Results: In experimental condition 1, unlike previous studies, biogas was produced in the TVFA/TA ratio ranging from 1.131 to 2.029 (approximately 13-19 days). The methane content in the biogas produced from the digesters was 7% on day 9 and increased rapidly until approximately day 27 (approximately 72%). In experimental condition 2, biogas yield was improved when the feed to microorganism ratio exceeded 0.6, with an initial lag-phase. Conclusions: Even if the TVFA/TA ratio was greater than 1.0, the biogas production was processed continuously, and the $CO_2$ content of the biogas production was as high as 60%. The biogas yield was improved when the F/M ratio was increased more than 0.6, but the lag-phase of carbohydrate-based material digestion became longer starting with high organic loading rate. To clarify the problem of the initial lag-phase, our future study will examine the microbial mechanisms during anaerobic digestion.

• 상하수도학회지
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• 제35권6호
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• pp.417-424
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• 2021

Algal bloom is an ongoing issue in the management of freshwater systems for drinking water supply, and the chlorophyll-a concentration is commonly used to represent the status of algal bloom. Thus, the prediction of chlorophyll-a concentration is essential for the proper management of water quality. However, the chlorophyll-a concentration is affected by various water quality and environmental factors, so the prediction of its concentration is not an easy task. In recent years, many advanced machine learning algorithms have increasingly been used for the development of surrogate models to prediction the chlorophyll-a concentration in freshwater systems such as rivers or reservoirs. This study used a light gradient boosting machine(LightGBM), a gradient boosting decision tree algorithm, to develop an ensemble machine learning model to predict chlorophyll-a concentration. The field water quality data observed at Daecheong Lake, obtained from the real-time water information system in Korea, were used for the development of the model. The data include temperature, pH, electric conductivity, dissolved oxygen, total organic carbon, total nitrogen, total phosphorus, and chlorophyll-a. First, a LightGBM model was developed to predict the chlorophyll-a concentration by using the other seven items as independent input variables. Second, the time-lagged values of all the input variables were added as input variables to understand the effect of time lag of input variables on model performance. The time lag (i) ranges from 1 to 50 days. The model performance was evaluated using three indices, root mean squared error-observation standard deviation ration (RSR), Nash-Sutcliffe coefficient of efficiency (NSE) and mean absolute error (MAE). The model showed the best performance by adding a dataset with a one-day time lag (i=1) where RSR, NSE, and MAE were 0.359, 0.871 and 1.510, respectively. The improvement of model performance was observed when a dataset with a time lag up of about 15 days (i=15) was added.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.728-731
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• 2009

A negative waveform having inverted polarity of conventional waveform during reset and sustain periods was proposed to improve the driving characteristics. In order to control the negative wall-charge distribution, a positive bias on the scan electrode was applied during reset period. Compared to 0 V scan-bias condition, at 8 V scan-bias the formative time lag was improved about 23.95 % and the average time lag was improved about 14.91 %. All experiments were performed with the 42-inch PDP module in XGA resolution.

• 수면정신생리
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• 제4권1호
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• pp.57-65
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• 1997

누구나 시차가 큰 여행을 할 때 몇일 간 비행시차증이라고 불리우는 증상을 경험하게 된다. 비행시차증은 수면박탈, 비행요인, 지연요인의 복합적인 원인으로 인해 생기는 하나의 증상군이라고 말할 수 있다. 특히 빠른 시차변화로 인한 생리적 지연효과(Jet lag)는 외적 비동조화, 내적 비동조화, 그리고 수면상실의 결과를 낳는다. 인간의 수면을 조절하는 기전에 있어 일중체계가 중요하다. 즉, 평균적인 수면-각성주기는 중심체온의 주기와 내적 비동조화가 일어나더라도 수면경향, 졸리움, 자발적 수면 기간, 그리고 렘수면 경향은 중심체온의 내인성 일중주기에 따라 통제된다. 수면의 구성요소중에서 서파수면은 중심체온의 주기보다는 수면시작시간에 따라 나타나며 이전에 깨어있었던 기간이 길수록 강력하게 나타난다. 따라서 수면은 일중체계와 항상성 기전의 상호작용으로 조절된다. 비행시차 후에 변화되는 수면양상을 이해하는데 있어 일중 체계 이외에 도항상성 기전을 고려하여야한다. 수면에 대한 일중리듬체계의 영향과 수면의 항상성 과정이 비행시차후 도착지에서의 수면양상을 설 명할 수 있을 것이다. 도착지에서의 적응은 통과한 시간대 수, 여행 방향, 일주기 리듬의 부조화에 적응 할 수 있는 개인별 능력에 따라 다르다. 도착지의 시간적 단서에 빨리 노출되어 일중체계의 위상반응곡선에 의한 재동조화를 촉진시키고 수면의 항상성 과정을 고려하여 도착지의 밤 이전까지 충분히 깨어 있는 것이 Jet Lag를 극복하고 적응하는 지름길일 것이다.

• 한국주거학회논문집
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• 제23권2호
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• pp.99-106
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• 2012

Compared to Packaged Terminal Air Conditioning Systems, Radiant Cooling Systems have the advantage of energy saving and thermal comfort. Thermally Activated Building System (TABS) is one of the radiant heating and cooling systems. The main difference between TABS and other radiant systems lies in the usage of the time-lag effect of storing heat energy in the concrete. Current energy usage in summer time is concentrated within a specific time by using Packaged Terminal Air-Conditioner (PTAC). Due to the time-lag effect of TABS, energy usage can be distributed to other time zones. To maximize this effect, it is important to determine the appropriate operating mode, which for TABS is dependent upon the cooling load generated by the occupancy schedule. In this study, occupancy schedules are determined for various residential types. The operating modes of TABS for these residential types are estimated by using a dynamic computational simulation method. The results indicate that the operating modes of TABS can be determined by residential type and occupancy schedule. The load handled ratio by TABS is set up differently according to the cooling load profile obtained from residential type and occupancy schedule. By using TABS, energy consumption could be reduced by 20% compared to PTAC.