• 한국재료학회지
• /
• 제20권5호
• /
• pp.257-261
• /
• 2010

A non-volatile resistive random access memory (RRAM) device with a Cr-doped $SrZrO_3/SrRuO_3$ bottom electrode heterostructure was fabricated on $SrTiO_3$ substrates using pulsed laser deposition. During the deposition process, the substrate temperature was $650^{\circ}C$ and the variable ambient oxygen pressure had a range of 50-250 mTorr. The sensitive dependences of the film structure on the processing oxygen pressure are important in controlling the bistable resistive switching of the Cr-doped $SrZrO_3$ film. Therefore, oxygen pressure plays a crucial role in determining electrical properties and film growth characteristics such as various microstructural defects and crystallization. Inside, the microstructure and crystallinity of the Cr-doped $SrZrO_3$ film by oxygen pressure were strong effects on the set, reset switching voltage of the Cr-doped $SrZrO_3$. The bistable switching is related to the defects and controls their number and structure. Therefore, the relation of defects generated and resistive switching behavior by oxygen pressure change will be discussed. We found that deposition conditions and ambient oxygen pressure highly affect the switching behavior. It is suggested that the interface between the top electrode and Cr-doped $SrZrO_3$ perovskite plays an important role in the resistive switching behavior. From I-V characteristics, a typical ON state resistance of $100-200\;{\Omega}$ and a typical OFF state resistance of $1-2\;k{\Omega}$, were observed. These transition metal-doped perovskite thin films can be used for memory device applications due to their high ON/OFF ratio, simple device structure, and non-volatility.

• 융합경영연구
• /
• 제9권4호
• /
• pp.1-8
• /
• 2021

Purpose: This study empirically investigates what factors contribute to corporate value in the Korea New Exchange (KONEX) market and determines whether financial constraints contribute any effect on it. Research design, data and methodology: A fixed-effect panel regression model was utilized to analyze financial constraints on firm value for KONEX listed firms through the fiscal period from 2013 to 2020. Results: we find that firms' research and development, volatility, size, and sales growth give significant impacts to firm value, but the significance and direction are different. In addition, no significant relationship exists between the largest shareholder's equity ratio and firm value in all models. The debt-to-equity ratio did not show a significant relationship with corporate value. A significant negative relationship was found between R&D and corporate value in the entire sample. Volitility exhibited a positive relationship with corporate value in the entire sample and financially unconstrained companies. Firm size presented a significant negative relationship with company value in all models. Sales growth showed a significant negative relationship with corporate value in financially constrained companies. Conclusions: No difference is found between financially constrained and unconstrained companies in the KONEX market. We can infer that KONEX companies have a large difference with KOSPI or KOSDAQ. Further analysis is needed on the differences among these markets.

• International Journal of Fuzzy Logic and Intelligent Systems
• /
• 제11권4호
• /
• pp.247-253
• /
• 2011

A sustainability of electricity supply has emerged as a critical issue for low carbon green growth in South Korea. Wind power is the fastest growing source of renewable energy. However, due to its own intermittency and volatility, the power supply generated from wind energy has variability in nature. Hence, accurate forecasting of wind speed and power plays a key role in the effective harvesting of wind energy and the integration of wind power into the current electric power grid. This paper presents a short-term wind speed prediction method based on support vector regression. Moreover, particle swarm optimization is adopted to find an optimum setting of hyper-parameters in support vector regression. An illustration is given by real-world data and the effect of model regularization by particle swarm optimization is discussed as well.

• 농촌계획
• /
• 제23권3호
• /
• pp.147-161
• /
• 2017

Climate changes from global warming and reduction in agricultural land result in volatility of prices of agricultural products, causing a imbalance of food market in Korea. It is necessary to develop a transnational food industry cooperation system among Korea, China and Russia that directly or indirectly affect food industry in terms of the whole industrial network. This study analyzes the value chain and linkage in the agriculture, forestry and fisheries industries in three nations. The unit structure and the industrial patterns of three nations were derived using the World Input-output Table (WIOT) from 2004 to 2014 every five years. This paper is expected to contribute to develop food security cooperation in the northern part of the Korean peninsula and to promote the mutual growth of food industry through industry linkage and cooperation.

• 한국컴퓨터정보학회논문지
• /
• 제5권2호
• /
• pp.43-49
• /
• 2000

웹 공간은 정보의 보고가 되었으나 그 크기의 방대함과 데이터의 다양성 역동성으로 인하여 효율적인 검색도구의 필요성이 더욱 높아지고 있다. 본 연구에서는 대화형 수동형의 기존 정보검색 모델에서 능동적인 대리자 모델로 이행하기 위한 기술적 기반을 검토한다. 대안으로 선행적이고. 자율적인 정보검색 에이전트들이 학습 결과 보유한 정보를 필요에 따라 공유함으로써 검색 효율을 높이는 협동형 검색에이전트 모델을 제시한다.

• International Journal of Fuzzy Logic and Intelligent Systems
• /
• 제12권2호
• /
• pp.108-112
• /
• 2012

A sustainable production of electricity is essential for low carbon green growth in South Korea. The generation of wind power as renewable energy has been rapidly growing around the world. Undoubtedly wind energy is unlimited in potential. However, due to its own intermittency and volatility, there are difficulties in the effective harvesting of wind energy and the integration of wind power into the current electric power grid. To cope with this, many works have been done for wind speed and power forecasting. It is reported that, compared with physical persistent models, statistical techniques and computational methods are more useful for short-term forecasting of wind power. Among them, support vector regression (SVR) has much attention in the literature. This paper proposes an SVR based wind speed forecasting. To improve the forecasting accuracy, a fuzzy clustering is adopted in the process of SVR modeling. An illustrative example is also given by using real-world wind farm dataset. According to the experimental results, it is shown that the proposed method provides better forecasts of wind power.

• 대한산업공학회지
• /
• 제40권2호
• /
• pp.195-204
• /
• 2014

The transition from fossil to renewable energy is inevitable due to fossil depletion. So, Renewable energy is very important for energy security and economic growth although it's R&D is long-term and high risky project. We propose new valuation method which combined system dynamics and compound real option method for long-term and high risk projects such as renewable energy. This method can show dynamic valuation results for the complex causal interaction and be easy for Monte-Carlo simulation to estimate volatility. And it can reflect the value of flexible decision for uncertainty. We applied the empirical analysis for Korea's photovoltaic industry by using this method. As results by empirical analysis, photovoltaic's R&D has high valuation using this method compared by traditional valuation methods such as DCF.

• 응용통계연구
• /
• 제37권2호
• /
• pp.255-263
• /
• 2024

GDP는 한 나라의 가계, 기업, 정부 등 모든 경제 주체가 일정 기간 동안 창출한 재화와 서비스의 시장 가치의 합을 나타낸다. GDP를 통하여 국가의 경제 규모를 파악할 수 있으며, 정부의 정책 방향에 영향을 미치는 대표적인 경제 지표이므로 이에 대한 연구가 다양하게 이루어지고 있다. 본 논문에서는 G20 국가들의 주요 거시경제 지표를 활용하여 dynamic factor model 기반의 GDP 성장률 예측 모델을 제시하였다. 추출된 factor를 다양한 회귀분석 방법론과 결합하여 그 결과들을 비교하였으며, 기존의 전통적인 시계열 예측방법인 ARIMA 모델, common component를 이용한 예측 등도 함께 비교하였다. COVID 이후 지표의 변동성이 큰 점을 고려하여 예측 시기를 COVID 전후로 나누었으며, 그 결과 factor에 대해 ridge regression과 lasso regression을 적용하여 예측한 경우 가장 좋은 성능을 나타내었다.

• 국제지역연구
• /
• 제21권4호
• /
• pp.41-63
• /
• 2017

외국인 직접투자는 국내투자와 함께 생산과정에 흡수되어 생산유발효과를 창출할 수도 있고, 아니면 외부요인으로 존재하면서 GDP의 변동성을 키우는 경우도 있다. 이러한 외국인 투자의 상이한 역할에 대하여 연구하는 것이 본 논문의 목적이다. 경제이론으로는 내생적 성장론을 사용하였고, 통계분석방법으로는 GARCH와 VAR모형을 이용하였다. 실증연구 대상으로는 미얀마를 선택하였는데, 미얀마는 장기간 군사정부 상태로 있었고 2011년 4월 민선정부가 출범하였다. 군사독재정부시절에는 외국인 직접투자는 주로 석유 가스와 전력산업에 투입되었고, 2011년 문민정부로 전환됨과 동시에 서방의 경제제재가 완화되면서 외국인 직접투자가 동남아에서 가장 활발한 국가이다. 한국도 이에 동참하고 있어 미얀마 국가의 경제발전과 한국과 미얀마의 경제적 상호관계의 발전을 위하여 본 연구가 필요하다. 산업별 패널분석의 결과에 의하면, 미얀마에서 외국인 투자가 주로 이루어진 산업은 석유 가스 부분인데, 산업유발효과보다는 수입을 위한 달러조달의 의미가 크다. 생산유발효과가 높은 제조업에는 외국인 직접투자는 낮은 수준이고 생산량 변화와의 관계를 찾을 수가 없었다. 시계열 분석은 결과는 민선정부 출범이전 기간(2006.01~2011.12)에서는 GARCH의 존재가 확인되지만 외국인 직접투자가 미얀마 국내총생산에 영향을 주지 않는 것으로 판단되었다. 민선정부 출범이후 기간(2011.04~2015.12)에서는 외국인 직접투자가 미얀마 국내총생산에 영향을 주는 것으로 판단되었고, GARCH의 존재가 확인되었다. 그러나 외국인 직접투자가 국내총생산에 기여하는 정도는 상당히 낮은 것으로 판단되었다. 그랜저 인과관계 검증을 통하여 GARCH에 외국인 직접투자가 영향을 주는 것으로 추정되었는데, 이는 외국인 직접투자가 국내총생산의 변동성을 키운 것을 의미한다. VAR에 의하여도 외국인 직접투자가 국내 총생산에 영향을 주지만 그 영향은 적고 기간도 길지 않았다. 본 연구에 의하여 외국인 직접투자는 국내총생산에 내부화되는 부분과 잔차항의 변화를 증대시키는 부분으로 구분될 수 있다는 사고가 검증되었고, 미얀마의 경우는 후자가 더 큰 것으로 나타났다.

• 신재생에너지
• /
• 제7권2호
• /
• pp.18-27
• /
• 2011

Management flexibility to adapt its future actions in response to altered future market conditions can expand the value of an investment opportunity by improving its upside potential without the change in the downside losses. Module manufacturers in solar industry continuously have to decide how much and when its production capacity should be expanded with regards to the demand in the global markets. Either over- or under-investment can cause sunk and/or opportunity costs to the module manufacturers. Option of exercising the additional investments only on favorable opportunities can increase total value of the investment. This paper analyzes the case which shows that the expansion of production capacity with more expandibility can have more value than the rigid plan of capacity expansion. The expansion option value is equivalent to KRW 38.286 billion, thus switching the negative NPV of the initial investment opportunity into the positive value. High volatility and the high growth in the cashflows as the major business features of the renewable energy provide condition where real options can play the crucial role in increasing the investment value as well as in determining the size and timing of capacity expansion in the course of capital budgeting process.