• 공업화학
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• 제10권8호
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• pp.1200-1209
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• 1999

무수프탈산 생산 공정의 조업 조건에서 실측한 이중 고정층 촉매 반응기의 온도분포, 수율 및 냉매의 입출구 온도에 대한 최적 적합으로부터 최적 매개변수 값을 추정함으로써 예측 모델을 구성하였다. 최대 전화율과 수율을 얻을 수 있는 고정층 촉매 반응기를 설계하기 위하여 반응기 길이 및 반경을 변화시켜 그 영향을 고찰하였다. 활성이 균일한 단일 고정층 촉매 반응기의 경우, 반응기 반경 r =0.01241 m에서 전 촉매층 길이 z =2.8 m, 그리고 이중층 반응기의 경우, 반응기 반경 r = 0.01254 m에서 전 촉매층 길이 2,80 m(상부촉매층: 1.88 m, 하부촉매층: 0.92 m)에서 우수한 성능을 보였다. 반응기 반경 변화의 경우, 반경 증가는 냉매로의 열전달 시간의 지연에 의해 열점 온도가 상승하였으며, 반경의 감소는 그 반대의 결과를 보였다.

• The Journal of Asian Finance, Economics and Business
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• 제8권2호
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• pp.453-463
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• 2021

Economic globalization provides a good channel for the development of foreign trade around the world. Due to this background, this paper sets the Organization for Economic Co-operation and Development (OECD) countries as a sample to explore the importance of international logistics in foreign trade. An annual panel data from 2000 to 2017 will be used to conduct an empirical estimation under the panel unit root test and the fixed effect model. Foreign trade is treated as an explained variable and international logistics is treated as explanatory variables. The findings show that international logistics have a positive spillover effect on export trade and the speed of international logistics development has a regulatory effect on the relationship between both of them, which presents a U-shaped curve. When the speed of international logistics development is slow, an increase of it restrains the positive spillover effect of international logistics on export trade. However, when it rises to a certain extent, this increase releases the positive spillover effect of international logistics on export trade. As can be seen by the evidence that this paper provides, the impact of international logistics on foreign trade is dynamic. Moreover, this paper also puts forward some corresponding measures about the relationship between both of them.

• Journal of Astronomy and Space Sciences
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• 제36권4호
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• pp.293-306
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• 2019

In this study, the observational arc-length effect on orbit determination (OD) for the Korea Pathfinder Lunar Orbiter (KPLO) in the Earth-Moon Transfer phase was investigated. For the OD, we employed a sequential estimation using the extended Kalman filter and a fixed-point smoother. The mission periods, comprised between the perigee maneuvers (PM) and the lunar orbit insertion (LOI) maneuver in a 3.5 phasing loop of the KPLO, was the primary target. The total period was divided into three phases: launch-PM1, PM1-PM3, and PM3-LOI. The Doppler and range data obtained from three tracking stations [included in the deep space network (DSN) and Korea Deep Space Antenna (KDSA)] were utilized for the OD. Six arc-length cases (24 hrs, 48 hrs, 60 hrs, 3 days, 4 days, and 5 days) were considered for the arc-length effect investigation. In order to evaluate the OD accuracy, we analyzed the position uncertainties, the precision of orbit overlaps, and the position differences between true and estimated trajectories. The maximum performance of 3-day OD approach was observed in the case of stable flight dynamics operations and robust navigation capability. This study provides a guideline for the flight dynamics operations of the KPLO in the trans-lunar phase.

• 국제지역연구
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• 제22권2호
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• pp.3-18
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• 2018

본고는 2003~2013년 기간 동안 62개 국가의 양자 무역자료를 이용하여 양자 간의 수출과 수입에 FTA와 FTA의 파급효과가 미치는 영향을 분석하였다. 이를 분석하기 위해 본고에서는 1) FTA더미변수와 2) FTA더미변수를 이용한 가중평균수출입 규모를 FTA의 파급효과 변수로 구축하였으며, GMM, 패널 고정효과 및 확률효과, 그리고 PPML 추정방법을 이용하였다. 분석결과, FTA변수는 양자 간의 수출과 수입에 양(+)의 관계를 보여, 양자 간의 FTA가 무역창출 및 무역전환 효과에 의해 수출입을 증가시키는 것으로 나타났다. FTA의 파급효과를 나타내는 FTA 가중평균수출입 규모 변수도 모든 분석모형에서 양(+)의 값을 갖는 것으로 분석되어, 주변국 또는 제3국들의 다양한 FTA 체결은 양자 간의 무역규모를 증가시키는 것으로 나타났다. 따라서 본고는 무역을 증가시키기 위해서는 다양한 FTA를 체결한 국가와의 무역을 하는 것이 바람직하며, 향후 FTA의 분석은 기존의 2개국 모형에서 3개국 모형 분석으로 확대될 필요성이 있다는 시사점을 제시하였다.

• 경제분석
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• 제27권3호
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• pp.33-60
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• 2021

본 연구에서는 2010년부터 2018년까지 산업연관표 패널 자료를 이용하여 정부지출 승수를 추정한다. 정부지출의 내생성을 고려하여, 최초기 부문별 정부지출의 비중을 도구변수로 사용하였다. 패널 고정효과 도구변수 추정 방법을 사용한 경우, 정부지출 당기 승수에 대한 추정치는 시간 추세를 통제하는 방법에 따라 1.15~1.22이고, 정부지출이 산출에 영향을 미치는 시차를 고려한 누적 승수에 대한 추정치는 1.23~1.32이다. 부문별 자료를 이용한 추정식에서 경제 전체의 일반균형 효과가 시간 고정효과에 의해 흡수되기 때문에 미시 자료로 추정된 승수값이 경제 전체의 승수값과 다를 수 있다. 본 연구에서는 중앙은 행의 반응, 조세정책의 변화, 산업간 유발 효과 등 일반균형 효과의 요소들이 미치는 영향을 검토하면서 부문별 자료로 측정한 정부지출 승수와 경제 전체 승수와의 관계에 대해 논의한다.

• 한국물환경학회지
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• 제18권4호
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• pp.379-386
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• 2002

In this study, estimation model for iron compound originated from upflow, anaerobic fixed bed reactor, which treats sewage domestic wastewater, was developed. The estimation model was formulated by a mathematical expression which was based on the mass balance. Below the HRT of 60 minute, sulfide concentration combining with iron $FeS_2$ is the highest because the maximum sulfate consumption rate $V_{maxS}$ and half-saturation constant of sulfate $K_{mS}$ exert an important effect on the estimation model as temperature was increased. But increment of $FeS_2$ concentration is weakened above the HRT of 60 minutes and represent the lowest value at the HRT of 108 minutes. It implies that liquid phase distribution ratio of sulfide ${\alpha}r$ becomes lower as temperature was increased. While phosphorus concentration combining with iron $Fe_3(PO_4)_3$ is increased as HRT and temperature are increased, which is affected by phosphorus removal rate constant $k_p$. As the result of estimating the iron concentrations of corrosion by the model, the concentration of iron corrosion is higher than any other at the HRT of 108 minute and $20^{\circ}C$. The predicted values were compared with measured ones at different HRT(13.5, 27, 54, 108 min) and temperature(20, 25, $30^{\circ}C$). The experimental data could be fitted with the simulated curves. Therefore, the mathematical expression could be applicable to design full-scale wastewater treatment plants.

• Journal of Korea Trade
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• 제25권4호
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• pp.146-163
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• 2021

Purpose - This paper examines China's impact on Korea's ICT exports considering the direct competition channel, the production shift channel, and the indirect demand channel at once. This paper also takes China's economic rebalancing into account and discusses whether it makes any differences in the effect of the three channels. Design/methodology - To quantify the effect of the three channels, I constructed a linear panel regression model and estimated it with various estimation methods including the system GMM. China's exports toward the same destination as Korea's exports, Korea's exports toward China, and the third countries' exports toward China respectively reflect the three channels. China's GVC indicators are included as well to evaluate the effect of further China's economic rebalancing. Since the present paper has a greater interest in the effect of China rather than the determinant of bilateral trade, a (fixed effect) panel model becomes more appropriate than the gravity model because timeinvariant variables in the gravity model, such as the distance and the language, are eliminated during the estimation process. Findings - The estimation results indicate that Chinese ICT exports are complementary to Korea's ICT exports in general. However, when markets are considered in subgroups, China's ICT exports could have a negative effect in the long run, especially for SITC75 and SITC76 markets, implying a possible competitive threat of China. The production shift effect turns significant during China's economic rebalancing in the markets for the advanced economies and the SITC76 product. China's indirect demand channel is also in effect significantly for the advanced economy and SITC75 commodities during China's economic rebalancing periods. In addition, this paper shows that China's transition toward upstream in the global value chain could have a positive impact on Korea's ICT exports, especially at the Asian market. Originality/value - The contribution of this paper is threefold. First, it focuses on the ICT industry for which Korea increasingly depends on China and China becomes a global hub of the GVC. Second, this paper quantitatively studies three channels in a model in contrast to the literature which mostly examines those channels separately and pays less attention to the GVC aspect. Third, by utilizing relatively recent data from the period of 2001-2017, this paper discusses whether China's economic rebalancing affects the three channels.

• The Journal of Asian Finance, Economics and Business
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• 제8권12호
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• pp.75-83
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• 2021

Variation in demand, natural resource availability, and technological advancement within a country are the main reasons for necessitating export and import activities between nations. Accordingly, this paper aims to analyze the effect of economic openness on Multifactor Productivity (MFP) in selected Asian countries (Vietnam, Thailand, The Philippines, Indonesia, Cambodia, China, Japan, Malaysia, South Korea, and Singapore) based on data for the period 1990-2018. The analysis conducted in the study employed the panel ARDL approach based on the estimation by Pooled Mean Group (PMG), Mean Group (MG), and Dynamic Fixed Effect (DFE). The Hausman test conducted indicates that the PMG estimation is better than that of MG and DFE since it has a higher variability value than the significance value. The results revealed that economic openness is able to elicit significant and positive effects on short-term and long-term MFP growth. In addition, the study established that other variable, such as the number of schooling years, are also able to produce a positive and significant effect on MFP growth in the long term. Since economic openness can impact MFP growth, every country should thus increase its export activities through more capital and worker inputs that will stimulate greater production.

• 노동경제논집
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• 제43권1호
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• pp.93-114
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• 2020

롤모델 효과에 따라 여성 교수의 존재는 여학생에게 유의한 영향을 미칠 수 있다. 특히 남학생이 많은 '남초학과'로 전공을 선택하거나, 대학원으로의 진학을 결정하는 데 여성 교수의 존재가 연관이 있을 수 있다. 다만 학부 입학, 박사과정 학생의 성취도 등과 관련하여 교수의 성별이 여학생에게 미치는 영향을 분석한 연구는 있으나 교수의 성비에 따른 여학생 취업에 관한 실증적인 연구가 부족하여 실제로 여성 교원의 비율이 여학생의 취업에 얼마나 영향을 주는지 판단하기 어렵다. 이에 본 연구는 여성 교수의 존재가 여성 대졸자의 취업에 미치는 영향을 분석하였다. 대학알리미 자료를 이용하여 분석한 결과, 합동회귀모형 추정에서는 전임교원 중 여성의 비율이 1%포인트 증가하면 여학생의 취업률이 0.102%포인트 유의하게 상승하는 것으로 나타났으나 학교-학과의 고정효과를 고려한 분석에서는 유의한 결과가 나타나지 않았다. 여성 교원의 비율이 여학생의 취업률에 미치는 영향을 전공계열별로 구분하여 살펴보아도 이와 유사한 결과가 도출되었다. 학생의 취업률은 본 연구에서 사용한 변수 외에 관측되지 않는 개인의 성향, 능력, 가정환경 등 여러 기타 요인에 영향을 받을 수 있다. 즉, 본 연구의 추정에서는 우리나라 대학의 여학생 취업에 있어서 여성 교수의 롤모델 효과에 대한 실증적 증거를 발견하지 못하였다.

• The Journal of Asian Finance, Economics and Business
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• 제6권3호
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• pp.41-53
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• 2019

Building a target capital structure is one of the most important decisions in corporate financial management. The purpose of this article is to identify the determinants of capital structure and adjustment mechanism toward the target leverage. The partial adjustment model was applied on a sample of 306 non-financial companies listed on Vietnam stock exchange market during the period of 2008-2017. By the fixed effect model estimation method, the research results have discovered the factors of growth opportunities, firm size, tangible fixed assets and firm's unique characteristics have a positive effect on the target capital structure of enterprises. Besides, profitability and dividend payment have a negative effect on the target capital structure of enterprises. Accordingly, the research results show that the average adjustment speed toward target leverage of the firms is 90.03%. Research results also demonstrate firms have higher or lower debt ratio than the target debt ratio, capital surplus or capital deficit also have an impact on the adjustment rate toward the target capital structure. The research results are consistent with the Dynamic Trade-off Theory. From this result, this article has provided policy implications for non-financial companies listed on Vietnam's stock market in building a reasonable target capital structure according to operating timeline to maximize enterprise value.