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최현영,조민영,김진수,임재영,이동율,김종수,김민수 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.51
GaAs/Al_(0.3)Ga_(0.7)As quantum dots (QDs) were fabricated by using the droplet epitaxy (DE) method. A one-step rapid thermal annealing (RTA) treatment on all of the QD samples was performed at 740 ℃. Temperature and excitation power density dependences of photoluminescence (PL) were determined to investigate optical properties. When the temperature is increased from 15 to 200 K, the PL peak energy is red-shifted from 1.648 to 1.590 eV while the full width at half maximum (FWHM) is increased. Non-radiative recombination is found to be due to the PL quenching mechanisms at high temperatures. The activation energy (Ea) is approximately 32 meV. When the integrated PL intensity (_(PL)) is plotted against the excitation power density on log-log scale at different temperatures, we find that the superlinearity becomes stronger as the temperature increases. To investigate the effect of annealing temperature on the optical properties of the QDs, we carried out the two-step RTA treatment at various temperatures from 800 to 1000 ℃. As the temperature increases, the PL peak position is blue-shifted due to the change in the composition and the size distribution, and the highest PL intensity is observed for the sample annealed at 900 ℃. The I_(PL) versus the excitation power density shows a slope that changes with changing temperature in the two-step RTA.
최현영,이동율,김진수,김종수,손정식,이주인,임재영,김건식,조민영,전수민,김도엽,김민수,임광국,김형근 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.3
ZnO active layers were grown on Si (100) substrates by using plasma-assisted molecular beam epitaxy (PA-MBE). The initial regions of the ZnO active layers were deposited by using an interruption growth method (IGM), with the following ZnO active layers being grown in succession for 80 min without interruption. X-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL) measurements were carried out to investigate the structural and the optical properties of the ZnO active layers. The full width at half maximum (FWHM) of the rocking curve observed for the ZnO (002) XRD peak decreased from 0.191 to 0.176 and the intensity of the XRD peak increased with increasing Zn beam ON time. The surface morphology shows a net-like structure that changes with the Zn beam ON time. The PL intensity of the near-band-edge emission (NBE) peak is enhanced in the ZnO active layers grown on interrupted layers, and the NBE peak position is blue-shifted with increasing Zn beam ON time, which was caused by an enhancement of the tensile stress. The above results imply that the IGM is effective in improving the crystalline quality and the luminescence efficiency.
기업 사회공헌의 참여동기 및 진정성에 관한 질적연구: 지역사회복지관과 의료복지현장 사회복지사 인식을 중심으로
최현영,최서경,배이진,정희선 사단법인 사회적기업학회 2023 사회적기업연구 Vol.16 No.2
본 연구는 사회서비스 현장에서 인식하는 기업의 사회공헌 활동의 참여동기와 진정성에 대해 심층적 이해를 돕고자 사회복지관과 의료복지 현장의 사회복지사 인식을 통해 탐색하였다. 이를 위해 의도적 표집방법으로 두 복지현장의 사회공헌 및 대응 업무 경험이 있는 사회복지사 총 10명을 대상으로 개별 심층면접을실시한 자료를 활용하였다. 연구결과로는 의미있는 진술이 총 133개, 이 중 핵심주제는 7개, 부주제는 총10개로 나타났고, 공통요소는 4개, 차이요소는 3개로 구분되었다. 구체적인 핵심주제는 안심과 소통, 참여시기와 지속, 책임자 역할, 실무자역량으로 나뉘었고, 차이요소에서는 소통방법, 실무자역량, 코로나19시기관심변화로 구분되었다. 이러한 연구의 결과를 바탕으로 본 연구에서는 기업 사회공헌 활동의 참여동기 및진정성에 대하여 현장에서의 이해를 확장시킬 수 있었으며, 이를 기반으로 실천적, 정책적 제언을 제시하였다.
최현영,신명철,박찬우,문중범,천성빈,이희영,이태훈,서정열,안희철,조준휘 대한응급의학회 2010 大韓應急醫學會誌 Vol.21 No.6
Purpose: Dynamic changes in the dimensions of the left ventricle (LV) during cardiac arrest might influence the efficacy of CPR. However, the relationship between change in LV dimensions during cardiac arrest and CPR hemodynamics and outcomes have not yet been addressed. In the present study, we investigated changes in left ventricular volume and area during prolonged, untreated ventricular fibrillation (VF); we related those change to coronary perfusion pressure (CPP) during CPR and resuscitation outcomes. Methods: In 12 domestic male pigs weighing 40±3 kg, VF was electrically induced and left untreated for 15 min. CPR was performed for 5 min prior to defibrillation. CPR was continued until the return of spontaneous circulation (ROSC) or for a maximum of 15 minutes. Mean aortic pressure and right atrial pressures were measured and CPP was calculated. LV dimensions were continuously assessed by echocardiographic measurement during the 15 minutes of interval VF. Results: Six animals were successfully resuscitated. During the 15 minute interval of VF, LV area and volume were reduced in all animals. In animals that were not resuscitated,LV dimensions were significantly lower than those in resuscitated animals (p<0.01). These differences were observed after 10 minutes of VF. The animals with greater reduction in LV dimension during VF achieved significantly lower CPP during CPR in contrast to animals with larger LVs during VF. Conclusion: Greater decreases in LV volume and area during cardiac arrest are associated with low CPP during CPR and poor resuscitation outcomes. LV dimensions prior to starting CPR might therefore modulate the effectiveness of resuscitation interventions.
무선통신기반 열차제어시스템의 사이버 보안 취약점 분석 및대응 기술에 관한 연구
최현영,채성윤 한국철도학회 2020 한국철도학회논문집 Vol.23 No.1
For safe and efficient railway operation, the train control system delivers the train control messages via wireless communication. In this radio-based train control system, the vital messages are transmitted between the onboard and wayside train control devices. When the integrity of train control messages is impaired due to the security threats, it causes fatal safety problems and major incidents. In addition, as the train control system is linked to networks, there are potential problems with cyber security threats such as message forgery and hacking. In this paper, we present the security threats and their corresponding security requirements for the radio-based train control system. We also propose the security device with authentication, encryption, and firewall function and perform its functional verification.
최현영,김민수,김진수,김종수,손정식,이주인,조민영,김건식,전수민,Gug Yim,김도엽,류혁현,임재영,이동율 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.5
ZnO thin films on molecular beam epitaxy (MBE) seed layers/Si (111) substrates were prepared by using the sol-gel method. The seed layers were grown at various growth temperatures ranging from 300 to 900 ℃. Atomic force microscopy (AFM), X-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL) measurements were carried out to investigate the effects of the seed layers’ growth temperature on the properties of the ZnO thin films. The grains of the seed layers become larger and rougher as the growth temperature is increased. The surface morphologies of the ZnO thin films are changed from elliptical to spherical and the particle size of the ZnO thin films surface is decreased as the growth temperature is increased. The (002) diffraction peaks for ZnO thin films with seed layers are observe to be higher and narrower compared to those of the ZnO thin films without a seed layer. Especially, the ZnO thin films on seed layers grown at a low growth temperature (300 ℃) exhibit the largest enhancement among the ZnO thin films with seed layers. In contrast to the XRD results, the PL intensity ratio of the ZnO thin films gradually increases as the growth temperature is increased due to an increase in the quantum efficiency attributed to the change in the surface morphologies of the ZnO thin films.
최현영,황종규 한국철도학회 2020 한국철도학회논문집 Vol.23 No.11
열차의 안전한 운행을 위해 열차제어시스템은 선로를 일정 구간으로 구분한 폐색 안에 하나의 열차만 점유하게 함으로 열차의 충‧추돌을 방호한다. 과거에는 이 폐색의 길이가 고정된 고정폐색 방식을 사용하였으나, 근래에는 무선통신을 통한 차-지상 제어장치 간 데이터 전송이 가능해짐에 따라 선‧후행 열차 간 간격을 제어하는 방식의 이동폐색이 사용되고 있다. 이러한 이동폐색 방식의 열차제어시스템은 기존의 고정폐색 기반의 시스템에 비해 선‧후행 열차 간간격을 현저히 줄일 수 있으므로 열차의 운전시격을 단축시킬 수 있다. 본 논문에서는 이동폐색 기반의 열차제어시스템 에서 열차 간 안전 간격에 따른 운전시격을 분석하고, 이를 계산하는 방법을 제안한다.