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Lee, Keon Hwa,Park, Hyun Jung,Kim, Seung Hwan,Asadirad, Mojtaba,Moon, Yong-Tae,Kwak, Joon Seop,Ryou, Jae-Hyun Optical Society of America 2015 Optics express Vol.23 No.16
<P>We study light-extraction efficiency (LEE) of AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs) using flip-chip (FC) devices with varied thickness in remaining sapphire substrate by experimental output power measurement and computational methods using 3-dimensional finite-difference time-domain (3D-FDTD) and Monte Carlo ray-tracing simulations. Light-output power of DUV-FCLEDs compared at a current of 20 mA increases with thicker sapphire, showing higher LEE for an LED with 250-관m-thick sapphire by ~39% than that with 100-관m-thick sapphire. In contrast, LEEs of visible FCLEDs show only marginal improvement with increasing sapphire thickness, that is, ~6% improvement for an LED with 250-관m-thick sapphire. 3D-FDTD simulation reveals a mechanism of enhanced light extraction with various sidewall roughness and thickness in sapphire substrates. Ray tracing simulation examines the light propagation behavior of DUV-FCLED structures. The enhanced output power and higher LEE strongly depends on the sidewall roughness of the sapphire substrate rather than thickness itself. The thickness starts playing a role only when the sapphire sidewalls become rough. The roughened surface of sapphire sidewall during chip-separation process is critical for TM-polarized photons from AlGaN quantum wells to escape in lateral directions before they are absorbed by p-GaN and Au-metal. Furthermore, the ray tracing results show a reasonably good agreement with the experimental result of the LEE.</P>
Who Becomes Exposed to Celebrity Activism on Twitter?
Seulgi Jang,Yujin Kim,Byung Joon Lee,Kyu S. Hahn 한국언론학회 2015 Asian Communication Research Vol.12 No.1
Twitter has significantly amplified celebrity presence on civic affairs. Although celebrities hold little expertise on policy affairs, they can be quite influential since their popularity allows them to reach large audiences. There is an ongoing debate concerning the democratic implications of increasing celebrity influence in policy affairs. In the current study, taking Oisoo Lee as a test case, we investigate the political implications of celebrity following on Twitter. We first compare Lee’s followers with those of ten news outlets, based on the co-following pattern among 1,442,317 Twitter users. We also had access to supplementary survey data on 11,725 members of an online survey panel who had provided their Twitter screen names. For these survey participants, we are able to match their following behavior with individual level attributes. Our results reveal that Lee’s followers are not ideologically skewed in either direction. Indeed, our survey findings confirmed that a vast majority of Lee’s followers identified themselves as independent. On the other hand, survey results show that Oisoo Lee is more likely to attract those lacking the ability to process one-sided information in a balanced manner. This raises a concern that they could be easily misinformed or misled.
Ti-6Al-4V 합금의 동적변형특성과 탄도충격성능 : 1. 초고속 폭발충격 특성 1. Ultra-high-speed Exploding Properties
이유환,이동근,이성학,이종수,최준홍,허선무 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.10
The effects of microstructural morphology on ultra-high-speed exploding properties of Ti-6Al-4V alloy were investigated in this study. Exploding bridge wire (EBW) test was conducted on equiaxed and bimodal microstructures, which were processed by different heat treatments. From the test, moving velocity of free surface vs time profiles were obtained to measure strength at Hugoniot elastic limit (HEL) and spall strength and to subsequently predict ballistic mass efficiency. The EBW results indicated that impact resistance of the bimodal microstructure was better than that of the equiaxed microstructure when the measured strength at HEL and spall strength were considered. It was also learned from the observation of fractured EBW specimens that fracture occurred by the initiation and propagation of long cracks in the equiaxed microstructure, whereas a number of microcracks were formed and connected each other in a zig-zag pattern to reduce the driving force for crack propagation in the bimodal microstructure. Since the EBW test helped experimentally estimate ultra-high-speed deformation and fracture behavior, it could be effectively used for the prediction of ballistic impact performance.
이형숙,김현주,조재현,이승원,김현아,최준혁,송영준,김대중,이관우,정윤석 대한내분비학회 2003 Endocrinology and metabolism Vol.18 No.5
연구배경 및 방법: 골형성부전증은 비교적 희귀한 유전병으로 교원질 대사 장애로 인한 골의 취약성과 다발성 골절 및 척추측만증 등을 특징으로 한다. 유전방식과 표현형의 발현 정도에 따라 다양한 임상 양상을 보이며, 임상적 중증도에 따라 4가지 형태로 분류된다. 지금까지 국내 보고는 분만과정이나 태아 진찰시 골격이상으로 발견된 증례보고가 주였다. 저자들은 비교적 경미한 임상 양상을 보이는 예를 포함한 다수의 골형성부전증 환자들의 전반적인 임상적 특징에 대해 보고하는 바이다. 결과: 2001년 6월부터 2003년 2월까지 골형성부전증으로 진단받은 6 가계, 10예를 대상으로 하였다. 평균 나이는 27.3(5∼56)세였고 소아가 2예였다. 모두 상염색체 우성으로 유전되었으며, 제 I형이 4예, 제 III형이 4예, 그리고 제 IV형이 2예였다. 전 예에서 다수의 골절 경험이 있었고, 골밀도 저하와 골피질 두께 감소 소견이 관찰되었다. 전신의 평균 골밀도는 0.690(0.421∼1.039) g/cm²였다. 골형성지표로 측정된 sAlk는 소아의 경우만 증가되어 있었고, 골흡수지표로 측정된 uDPD의 평균치는 12.9(4.4∼36.3) nM/mM Cr으로 증가된 소견을 보였다. mobility score는 대부분 3,4단계에 속해 있었다. 중증형일수록 진단 시의 mobility score가 낮은 경향을 보였다. 결론: 한국인 골형성부전증 환자의 임상적 특징을 살펴본 결과 기존의 보고된 II형 외에도 I, III, IV형이 다양하게 존재함을 알 수 있었으며, 모든 예에서 상염색체 우성으로 유전됨을 확인할 수 있었다. 또한 모든 예에서 증가된 골흡수로 인한 골밀도 저하와 골절을 확인할 수 있었다. Osteogenesis Imperfecta (OI) is a relatively rare hereditary disease, which is characterized by multiple bone fractures and spine scoliosis, due to the fragility of bone, and is often associated with blue sclerae, deafness and dentinogenesis imperfecta. Four types of OI can be distinguished, according to the clinical findings. Although mutations affecting type I collagen are responsible for the disease in most patients, the mechanism by which the genetic defects cause abnormal bone development remains to be fully understood. Here, the clinical characteristics of 10 OI patient cases are reported, with a review of the literature. All the cases, including 4 type I, 4 type III and 2 type IV, inherited OI as an autosomal dominant trait. All the subjects had multiple old fractures and decreased bone densities. In this study, the biochemical marker of bone formation, serum alkaline phosphatase, was found to be increased only in the pediatric OI patients, while the biochemical marker of bone resorption, urinary deoxypyridinoline, was increased in all cases. The mobility score was found to correlate with the severity of the type on diagnosis (J Kor Soc Endocrinol 18:496∼503, 2003).
복압성요실금(Stress urinary incontinence)과 절박성요실금(Urge incontinence)환자에서 TVT 수술 결과의 비교
이경구,이준호,권용욱,정태융,심희영,이상익 관동대학교 의과대학 의과학연구소 2005 關東醫大學術誌 Vol.9 No.1
Tension-free vaginal tape(TVT) has been widely used in the management of stress urinary incontinence(SUI), and has been applied to urge incontinence (UI). We evaluated and compared the outcomes between SUI and UI for patients who had undergone TVT. Patients were categorized into SUI(33 patients) and UI(26 patients). Before treatment, we asked about LUTSs using female bladder questionnaire. And we asked about sexual function. After treatment, the same questionnaires were repeated. During the postperative period, the objective and subjective success rate were evaluated. For operation outcome results, in SUI group there were 29 cases of cure (87.9%)and 2 of improvement(6.1%), and in UI group there were 20 cases of cure(76.9%)and 3 of improvement(11.5%) (p>0.05). The operation satisfaction rate of patients was 90.9% in SUI group and 84.6% in UI group(p>0.05). Improvement of sexual satisfaction occurred in 6(20.0%) of SUI group, and 3 (18.8%) of UI group, respectively(p>0.05). The objective success rate, satisfaction rate and sexual satisfaction of SUI patients did not significantly differ from the women with UI. Also, these results shows that TVT procedure improves some LUTSs in both groups. We consider the TVT procedure to be an effective treatment not for stress urinary incontinence but also urge incontinenece.
이만승,이광섭,이진영,김성돈,김준수 대한금속재료학회 2004 대한금속·재료학회지 Vol.42 No.10
Solvent extraction experiments of Sm were performed from chloride solution with PC88A and saponified PC88A. Solvent extraction reaction of Sm with PC88A and the corresponding equilibrium constant were evaluated from the experimental and ionic equilibria data as follows Sm^(3+)_(aq)+ 1.5H₂A_(2,org)= SmA_(3,org)+ 3H^(+)_(aq) , K = 0.33. The predicted distribution coefficients of Sm agreed well with the experimental results. The distribution coefficients of Sm with saponified PC88A and the values of equilibrium pH depended on the initial extraction conditions. When the concentration of PC88A was in excess of that of Sm, saponification of PC88A greatly enhanced the extraction of Sm. (Received June 21, 2004)