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반응표면법을 이용한 이종재질의 접합 계면부 강도평가 및 접합특성에 관한 연구
이승현(Seung-Hyun Lee),최성대(Seong-Dae Choi),김기만(Gi-Man Kim),이종형(Jong-Hyung Lee) 한국기계가공학회 2009 한국기계가공학회지 Vol.8 No.2
In this papers, Study on the Bonding property and Strength Evaluation in Bonding interface Joints of Dissimilar material using DOE. We found optimal condition that uses experimental design method (Response Surface Analysis, DOE) used temperature, pressure, time on experiment factor. And we could get bonding condition and strength that break and crack do not happen in mechanical processing about united dissimilar material. And progress 3 point bending tests and verified result.
방열특성 제어를 위한 PWM 전류제어 기반 LED 모듈 개발
이승현(Seung-Hyun Lee),문한주(Han Joo Moon),허성범(Seong-bum Hue),최성대(Seong-Dae Choi) 한국기계가공학회 2015 한국기계가공학회지 Vol.14 No.6
This paper shows significant methods that improve the lifespan of LED modules as well as efficiently using an aluminum heat-sink for LED module in high power. It proposes a method that raises stability and lifespan to protect LED modules and the power unit when the LED module has been used for a long hours at high temperatures. During the research, we applied a method of pulse-width modulation (PWM) in order to prevent the phenomenon that the entire power of a system is turned off and the lifespan is reduced when the LED nodule reacts to the high temperatures. To protect the LED module and SMPS based on high efficiency, a temperature sensor is attached underneath the circuit board and the sensor measures the temperature of circuit board when the LED module is powered on. The electrical power connected to SMPS is controlled by PWM when the temperature of the LED module reaches a particular temperature.
이승현(Lee, Seung Hyun),조성표(Cho, Seong Pyo),이기세(Lee, Ki Se) 한국국제회계학회 2020 국제회계연구 Vol.0 No.89
기업이 장기적인 자본조달을 목적으로 회사채를 발행하기 위해서 발행기업은 신용평가기관으로부터 신용등급평가를 받아야 하며, 신용평가기관은 신용평점의 신뢰성 제고를 위해 기업의 재무적인 요소 뿐 아니라 비재무적 요소까지 고려하여 신용등급을 결정하게 된다. 이는 기업이 회사채를 발행하는 가장 주된 이유가 향후 대규모의 투자를 위한 필요자금을 확보하기 위해서 이며, 이 때 신용평가기관의 입장에서는 미래에 이루어질 기업의 투자 성공여부를 경영자의 투자효율성을 통해 판단하여 이를 신용등급에 반영할 가능성이 높기 때문이다. 그래서 다양한 신용등급의 결정요인 중 투자효율성은 매우 중요한 변수가 될 수 있다. 이에 본 연구는 2007년부터 2018년까지의 회사채 발행기업을 대상으로 각 기업의 투자효율성이 신용등급에 미치는 영향을 분석하였다. 연구결과 첫째, 집단 차이분석에서 신용등급이 높은 기업은 낮은 기업에 비해 투자효율성이 높은 것으로 나타났으며 신용등급 상승집단 또한 하락집단과 비교하여 투자효율성이 높은 것으로 나타났다. 둘째, 로짓분석 결과 기업의 투자효율성이 높을수록 신용등급이 더 높은 것을 확인 할 수 있었으며 투자효율성이 신용등급의 변경에 미치는 영향을 분석한 결과에서는 투자효율성이 높을수록 신용등급의 상승가능성이 높은 것으로 나타났다. 마지막으로 투자효율성 증감이 신용등급변동에 미치는 영향을 분석한 결과 투자효율성이 증가하거나 감소한다고 해서 신용등급이 증가하거나 하락하지는 않음을 확인할 수 있었다. 본 연구는 각 기업의 투자효율성이 신용평점에 미치는 영향을 분석함으로써 신용등급의 결정에 있어 투자효율성이 유용한 변수가 될 수 있는지 살펴보았으며, 연구결과 기업의 투자효율성은 신용평점을 결정하는데 있어 매우 유용한 변수임을 알 수 있었다. 따라서 경영자들은 높은 신용등급을 유지 또는 획득하기 위해서는 효율적인 투자활동을 해야 함을 시사해 주고 있다. In order for an entity to issue corporate bonds for long-term capital, the issuing entity is required to receive a credit rating assessment from the credit rating agency to improve the reliability of the credit rating. it will determine the credit rating based on the financial and non-financial factors of the entity. Thus, corporate investment efficiency among the various credit rating determinants can be a very important variable. The main reason why an entity issues corporate bonds is to secure the necessary funds for future large investments. From the perspective of the credit rating agency, it is likely that the success of the entity’s future investments will be determined through the investment efficiency of the current management, and it will be considered in the credit rating. In response, this study analyzes the impact of each company’s investment efficiency on its credit rating for companies that issue corporate bonds from 2007 to 2018. First, the study found that companies with higher credit ratings had higher investment efficiency compared to those with lower credit ratings, and those groups with higher credit ratings also had higher investment efficiency compared to those with lower credit ratings. Second, the higher the investment efficiency of a company, the higher the credit rating was found in the logit analysis. An analysis of the impact of investment efficiency on the change of credit rating showed that the higher the efficiency of investment, the more likely the credit rating is to rise. Finally, an analysis of the effect of increase or decrease of investment efficiency on the changes in credit rating showed that increased or decreased investment efficiency did not increase or decrease the credit rating. This study suggests that corporate investment efficiency can be a useful variable in determining credit rating by analyzing the effect of investment efficiency of each company on credit rating, and it was found that the efficiency of an corporate investment was a very useful variable in determining credit rating. Therefore, management suggests that efficient investment activities must be carried out in order to maintain or obtain high credit ratings.
원통형 이종 접합 소재의 SiO<SUB>2</SUB>/Ag스퍼터 증착과 온도변화에 따른 기계적 특성에 관한 연구
이승현(Seung-Hyun Lee),최성대(Seong-Dae Choi),이종형(Jung-Hyong Lee) 한국기계가공학회 2012 한국기계가공학회지 Vol.11 No.3
The material used in this study is dielectric and ferrite. Because of the unique characteristics of the material, it is easily exposed to external shocks and pressure, which cause damage to the product. However, after being processed under high-temperature environment repeatedly, the mechanical strength of the product is greatly increased due to the change of the electrical properties. In this paper, dielectric and bonded ferrite material was tested for the material properties. The equipment for this experiment was produced and tested to allow Cylindrical and Three-dimensional geometry of the product for the vacuum deposition. For Cylindrical shape of the product, in order to obtain the equivalent film thickness, the device is constructed in a vacuum chamber which gives arbitrary revolving and rotating capability. The electrical performance of the product is obtained through this process as well. However, as mentioned above, with repeating processes under high temperature and exposure to external environment, the product is easy to be broken. This experiment has enabled us to find out a stable condition to apply the communication of the RF high frequency to each of the core elements, such as Ferrite and Dielectric which is then used for the mechanical strength of the Raw material, hetero-junction material, Hetero-junction Ag Coating material and hetero-junction Ag Coating SiO2 Coating material respectively.