높은 광출력을 갖는 Laser Diode Bar의 열응력 개선: 마이크로-홈 도입을 통한 응력 분포 변화 분석

정지훈,이동진,오범환,Jeong, Ji-Hun,Lee, Dong-Jin,O, Beom-Hoan 한국광학회 2021 한국광학회지 Vol.32 No.5

Relief of thermal stress has received great attention, to improve the beam quality and stability of high-power laser diodes. In this paper, we investigate a microtrench structure engraved around a laser-diode chip-on-submount (CoS) to relieve the thermal stress on a laser-diode bar (LD-bar), using the SolidWorks® software. First, we systematically analyze the thermal stress on the LD-bar CoS with a metal heat-sink holder, and then derive an optimal design for thermal stress relief according to the change in microtrench depth. The thermal stress of the front part of the LD-bar CoS, which is the main cause of the "smile effect", is reduced to about 1/5 of that without the microtrench structure, while maintaining the thermal resistance. 열응력 완화 기술은 고출력 레이저 다이오드의 빔의 품질과 안정성을 향상시키기 위한 주요 요소기술로 큰 주목을 받고 있다. 본 연구에서는 레이저 다이오드 바(LD-bar) chip-on-submount (CoS)에 발생하는 열응력 분포 양상을 SolidWorks 소프트웨어를 사용하여 해석하고, 마이크로-홈 구조 도입에 따라 열응력 완화에 미치는 영향을 체계적으로 분석한다. 마이크로-홈 구조는 누적응력을 차단하는 효과가 있는 반면, 열흐름을 방해하는 역기능도 있으므로, 시스템 구조와 방열금속판 두께에 따라 홈 깊이를 최적화할 필요가 있다. 간단히 도입된 예시구조에 대하여, LD-bar CoS의 칩 홀더 금속판에 도입하는 마이크로-홈 구조 최적화를 통해 칩 전면부 표면 응력을 마이크로-홈 구조가 없는 경우의 약 1/5 정도로 낮추었다. 향후 초고출력 시스템에서 방열을 위한 열저항과 광출력 빔크기를 최소한으로 유지하면서, 열응력을 효과적으로 완화시키는 구조로 활용이 기대된다.

국내외 건강관련 스마트폰 앱 최신 동향

정지훈,Jeong, Ji-Hoon 한국정보통신학회 2011 한국정보통신학회지 Vol.12 No.1

VR·AR의 의학적 이슈 및 건강의학 분야의 활용

정지훈,Jeong, Ji-Hun 한국광학기기산업협회 2016 光學世界 Vol.163 No.-

최근 VR(Virtual Reality)와 AR(Augmented Reality) 관련한 기술 개발과 사업화로 커다란 글로벌 기업들이 치열한 경쟁을 하고 있다. 이런 상황에서는 흔히 기술 그 자체와 산업적인 부분에 매몰되는 부작용을 간과할 수가 있는데, 특히 의학분야에서도 우려가 되는 부분들이 없지 않다. 그렇지만, 역설적이게도 VR과 AR이 활용될 수 있는 가능성이 가장 높은 산업분야도 건강의학 분야다.

드론의 발전현황과 향후 시장전망

정지훈,Jeong, Ji-Hun 한국광학기기산업협회 2015 光學世界 Vol.158 No.-

드론은 군사용으로 제일 먼저 개발되어 시장을 형성했지만, 오픈소스 드론의 제작이 많아지면서 소비자 시장도 급속도로 확대되고 있다. 최근 중국의 DJI는 기업가치 100억 달러 이상을 넘볼 정도로 급성장을 하였고, 드론용 소프트웨어나 플랫폼을 확보한 스타트업 기업들에 대한 투자도 활발하게 이루어지고 있다. 구글이나 페이스북, 아마존 등은 자사의 서비스 강화를 위한 목적으로 드론 기술을 적극적으로 활용하고 있으며, 드론의 시장 확대에 따른 드론 시장 생태계도 크게 확장되고 있다. 최근 드론에 대한 관심이 뜨겁다. 특히 중국의 DJI는 모형 헬리콥터의 비행조종 시스템을 만들다가 전격적으로 소비자 드론 시장에 뛰어들었는데, 2014년 약 5억 달러 정도의 매출을 올렸다고 한다. 이는 2013년과 비교할 때 4배가 증가한 것이며, 2015년에는 또 다시 2배 이상 성장을 할 것으로 보여 올해에는 소비자 드론을 만드는 기업중에서 세계 최초로 10억 달러 매출을 달성할 것으로 예측된다. 당연히 기업가치도 크게 상승해서, 실리콘밸리에서는 DJI의 기업 가치를 100억 달러 이상으로 보고 있다.

광전기화학적 물 분해를 위한 BiVO₄ 기반 광음극 연구 동향

정지훈,변세기,신병하,Jeong, Ji-Hun,Byeon, Se-Gi,Sin, Byeong-Ha 한국태양광발전학회 2018 한국태양광발전학회지 Vol.4 No.3

Performance of Copeptin for Early Diagnosis of Acute Myocardial Infarction in an Emergency Department Setting

정지훈,Yiel Hea Seo,Jeong Yeal Ahn,Kyung Hee Kim,Ja Young Seo,Ka Yeong Chun,Yong Su Lim,Pil Whan Park 대한진단검사의학회 2020 Annals of Laboratory Medicine Vol.40 No.1

Background: Rapid and accurate diagnosis of acute myocardial infarction (AMI) is critical for initiating effective treatment and achieving better prognosis. We investigated the performance of copeptin for early diagnosis of AMI, in comparison with creatine kinase myocardial band (CK-MB) and troponin I (TnI). Methods: We prospectively enrolled 271 patients presenting with chest pain (within six hours of onset), suggestive of acute coronary syndrome, at an emergency department (ED). Serum CK-MB, TnI, and copeptin levels were measured. The diagnostic performance of CK-MB, TnI, and copeptin, alone and in combination, for AMI was assessed by ROC curve analysis by comparing the area under the curve (AUC). Sensitivity, specificity, negative predictive value, and positive predictive value of each marker were obtained, and the characteristics of each marker were analyzed. Results: The patients were diagnosed as having ST elevation myocardial infarction (STEMI; N=43), non-ST elevation myocardial infarction (NSTEMI; N=25), unstable angina (N=78), or other diseases (N=125). AUC comparisons showed copeptin had significantly better diagnostic performance than TnI in patients with chest pain within two hours of onset (AMI: P =0.022, ≤1 hour; STEMI: P =0.017, ≤1 hour and P =0.010, ≤2 hours). In addition, TnI and copeptin in combination exhibited significantly better diagnostic performance than CK-MB plus TnI in AMI and STEMI patients. Conclusions: The combination of TnI and copeptin improves AMI diagnostic performance in patients with early-onset chest pain in an ED setting.

Compensation of Sensor Gain Difference in Measuring Straightness Errors Using a Mixed Sequential Two-probe Method

정지훈,Jeong Seok Oh,정성종 한국정밀공학회 2019 International Journal of Precision Engineering and Vol.20 No.3

We present a compensation method for the sensor gain difference when a mixed sequential two-probe method (MTPM) is applied for precision measurements of straightness error. According to theoretical analysis of the effect of sensor gain error, much of the measurement error comes from the sensor gain difference. Also, measurement error caused by misalignment of the straight-edge is dramatically amplified by the sensor gain difference. Therefore, the measurement error in MTPM can be significantly reduced by compensating for the sensor gain difference. To compensate for sensor gain difference, we propose a very simple approach that uses sensor outputs for two different alignment conditions of the straight-edge. To verify the proposed compensation method, experiments were performed with a hydrostatic linear motion table. Experimental results show that the gain difference of the two sensors used in the experiments was about 3.4%. Before compensation, the deviation in the calculated straightness error depending on the alignment conditions was 1.30 μm, which was reduced to 0.08 μm after compensation. The compensated measurement results were compared with results obtained by a reversal method. The maximum deviation between the two methods was 0.22 μm. These results demonstrate that the proposed compensation method is very effective for the measurement of straightness error with sub-micron accuracy and in addition it is practical because compensation can be performed on the actual measurement setup.

의과대학생이 만날 미래, 어떻게 준비할 것인가?

정지훈,Jeong, Jihoon 연세대학교 의과대학 2014 의학교육논단 Vol.16 No.3

This study focused on investigating the future medicine and health care industry paradigm shift and suggesting the right direction for the medical education system in order for students to be better prepared in the near future. Here, I will discuss four issues related to the future of medicine: Health 2.0, digital health, personalized medicine, and innovations of the public healthcare system. Every issue has lessons for medical education and teaching for students who major in health professions. However, it is obvious that the present is an important period of time as, currently, we are at an early stage in the future health care environment. Recently, there have been rapid transformations in various fields of medicine. Therefore, if we fail to lead medical education in the right direction, medical students will suffer from major problems in coping with these changes.

문학축제의 미학

정지훈(Jeehoon Jeong) 한국동서비교문학학회 2014 동서 비교문학저널 Vol.0 No.30

This article discusses the aesthetic characteristics of Literature Festivals through a comparative analysis between ‘Bloomsday’ in Ireland and the memorial festival of ‘Kim Yoo-Jeong’ in Korea. Literature Festivals interact with visitors and texts, as well as the main characters in the texts. Bloomsday has been one of the best literature festivals in the world. Bloomsday is a commemoration and celebration of the life of Irish writer James Joyce during which the events of his novel Ulysses (which is set on 16 June 1904) are relived. It is observed annually on 16 June in Dublin and elsewhere. In this context, Bloomsday in Dublin makes visitors feel like Leopold Bloom so that it is easy to bring about an aesthetic affection. However, the memorial festival of Kim Yoo-Jeong’s Literature Festival makes visitors experience the materials in the novels of Kim Yoo-Jeong. Bloomsday is much more attractive than other Literature Festivals because the visitors at the festival are absorbed into the main character emotionally by acting like Bloom in the novel. However, Bloomsday’s aesthetic experience has a limitation in that visitors is depart from each other individually. Therefore, it seems to fail to interact with visitors together or make visitors feel like communicating with each other. On the other hand, the memorial festival of Kim Yoo-Jeong in Sile makes visitors experience unique material from his novels. However, it seems to fail to make visitors feel an aesthetic empathy about his literature because they do not completely immerse themselves in his texts. From this perspective, going forward, I suggest Kim Yoo-Jeong’s memorial festival create a better main character experience that encourages visitors to act like the main character. In addition, it is possible for visitors to experience a story, for example in the third person, that reflects a point of Kim Yoo-Jeong’s novels.

수소 및 암모니아 혼소에 따른 가스터빈 작동점 및 성능 분석

정지훈(Ji Hun Jeong),박호성(Ho Sung Park),김동섭(Tong Seop Kim) 대한기계학회 2022 대한기계학회 춘추학술대회 Vol.2022 No.11