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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.
이성민,김봉석,송준호,이수훈,이혜진,이문구,송준엽,이창우 한국공작기계학회 2008 한국공작기계학회 춘계학술대회논문집 Vol.2008 No.-
Recently, the robustness against daily impact is important according to portablization and downsizing of mobile electronics. Especially, almost parts of cellular phone should undergo drop test when they fall 1.5 m above ground. This test simulates the case when cellular phone slips through user's fingers while he is talking on the phone. This paper studies a drop test of auto focusing (AF) actuator for camera module in cellular phone. This component is composed of voice coil motor (VCM) as an actuator and leaf spring as a guide and suspension. The leaf spring's deformation is essential for the test because its permanent distortion disables the focusing, and then, a high quality photograph cannot be obtained. Up to now the drop test has been carried out after fabricating real AF actuator. We propose a dropt test model which simulates the drop test based on finite element analysis. This model makes us enable investigate the stress acting on the clamping and curved parts of leaf spring. Stress over Von Mises criterion lets the spring deformed permanently, and then AF actuator malfunctioned, It helps us to design and modify AF actuator without manufacturing the real product. And also, it saves the time and cost for the development of new products.
Miscanthus sinensis 와 타 식물과의 친근성에 관한 연구
정일구(Il Koo Lee),이호준(Ho Joon Lee),이경순(Kyung Soon Lee) 한국식물학회 1970 Journal of Plant Biology Vol.13 No.4
Althought allelopathy has been cleary established for Pinus densiflora by Lee-Monsi, the auther suspected that Miscanthus sinensis which grows vigrously in such Korean pine forests might also exhibit the phenomenon. A total of 33 species having an affinity in the Miscanthus group were recorded in the field. Out of these, five species; Patrinia scabiosaefolia, Lespedeza crytobotrya. Oenothera odorata, Raphanus sativus var. acanthiformis, and Zoysia japonica were considered the A group. Five other species which have no affinity to Miscanthus sinensis, Amaranthus patulus, Solanum nigrum, Capsella bursa-pastorris var. triangularis, Chemopodium album var. centrorubrum and Alopeculus amurensis were considered the B group. Extracts of Miscanthus sinensis were applied to determine relative germination and growth. It was found the growth in the B group was promoted by a cold water extract of Miscanthus stems and leaves, but inhibited remarkably by an extract obtained by passing cold water through Miscanthus root. As expected, growth in the A group was promoted by both experimental treatments.
서울의 Penicillinase Producing Neisseria gonorrhoeae 발생빈도(1998)
김재홍,김준호,반재용,이정우,황성주,정준규,정성태,강진문,조흔정,홍창의,정혜신,이한승,김이선,이봉길,이종호,선영우,한기덕,윤성필,이성훈,안종성,박석범,문승현,조항래,김형섭,류지호,황재영,박준홍,손상욱 한양대학교 의과대학 2001 한양의대 학술지 Vol.21 No.1
In recent years, gonorrhea has been pandemic and remains one of the most common STDs in the world, especially in developing countries. For the detection of a more effective therapeutic regimen and assessing the prevalence of Penicillinase Producing Neisseria gonorrhoeae(PPNG), we have been trying to study the patients who have visited the Venereal Disease Clinic of Choong-Ku Public Health Center in Seoul since 1980 by menas of the chromogenic cephalosporin method. In 1998, 93 strians of N. genorrhoeae were isolated, among which 60(64.5%) were PPNG. The prevalence of PPNG in Seoul, which had been decreased to 39% in 1996 after a peak of 74.3% in 1993, is increased to 64.5% in 1998.
이진경,박영철,이규창,최일국,이준현 한국비파괴검사학회 2001 한국비파괴검사학회지 Vol.21 No.6
형상기억복합재료는 복합재료내에 압축잔류응력을 발생시킴으로써 재료의 인장강도를 증가시키는데 사용되어지고 있다. 본 연구에서는 형상기억복합재료를 제조하기 위하여 TiNi 강화재와 A16061 기지재를 사요하였으며 핫프레스 방법에 의해 TiNi/A16061 형상기억복합재료를 제조하였다. 그러나 핫 프레스 방법에 의해 제조된 형상기억복합재료는 하중을 받을시 강화재와 기지재 사이에 계면손상현상이 발생하였으며 이를 위하여 냉간압연을 실시하였다. 냉간압연을 받은 시험편은 냉간압연을 받지 않은 시험편에 비하여 인장강도가 현저히 증가하였다. 또한 본 연구에서는 고온에서 형상기억복합재료의 미시적 손상을 평가하기 위하여 음향방출기법을 이용하였다. Shape memory alloy has been used to improve the tensile strength of composite by the occurrence of compressive residual stress in matrix using its shape memory effect. In order to fabricate shape memory alloy composite, TiNi alloy and Al6061 were used as reinforcing material and matrix, respectively. In this study, TiNi/Al6061 shape memory alloy composite was made by using hot press method. However, the specimen fabricated by this method had the bonding problem at the boundary between TiNi fiber and Al matrix when the load was applied to it. A cold rolling was imposed to the specimen to improve the bonding effect. It was found that tensile strength of specimen subjected to cold rolling was more increased than that of specimen which did not underwent cold rolling. In addition, acoustic emission technique was used to quantify the microscopic damage behavior of cold rolled TiNi/Al6061 shape memory alloy composite at high temperature.
충남대학교 학술림 산책로 훼손실태 및 관리방안에 관한 연구
이준우,김명준,최윤호,전용준,오도교,김민호,이소연,이경형 충남대학교 농업과학연구소 2004 농업과학연구 Vol.31 No.2
This study concentrates an the trail of the CNU(Chungnam National University) forest. The amount of use and the pattern of damage are considered, as well as the extent of environmental damage. Finally, some managerial strategies are proposed in connection with sustainable maintenance. The trail of the university forest is composed of three sections; one is the neighborhood park and the Institute of Information Technology/Communications, the second is the Institute of Information Technology/Communications and the Dormitory, and the third section is the Dormitory and the Foreign prof's Apt. The total length of the trail is 2.6km. The daily amount of use is 1,269 visitors per day. The amount of using increased three times the amount of that in 1998. This study shows the pattern of damage of the trail in the order of root-exposure, widening, rock-exposure, deepening and the divergence in the frequency of occurrence of all these factors. Environmental damage is also graded thus: grade 3 is 27.4m, grade 4 is 0.8m, grade 5 is 1.5m, and grade 6 is 0.2m. Accordingly, some managerial strategies were proposed in connection with the sustainable trail maintenance.
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).