Light-extraction efficiency control in AlGaN-based deep-ultraviolet flip-chip light-emitting diodes: a comparison to InGaN-based visible flip-chip light-emitting diodes.

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.

휴대폰 카메라용 자동초점 구동기의 충격해석

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.

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.

염산용액에서 비누화 PC88A에 의한 용매추출로 Gd와 Sm의 분리

이만승,이광섭,이진영,김성돈,김준수 대한금속재료학회 2005 대한금속·재료학회지 Vol.43 No.5

Solvent extraction experiments have been performed to separate Gd and Sm from chloride solution with PC88A and saponified PC88A. The effects of extraction conditions on the distribution coefficients of Gd and Sm were investigated. The distribution coefficients of Gd were higher than those of Sm in the experimental ranges of experimental conditions of this study. A solvent extraction model was developed to predict the distribution coefficients of metals and separation factor between Gd and Sm from the initial extraction conditions. The measured distribution coefficients of Gd and Sm with PC88A and saponified PC88A showed good agreements with the predicted values. (Received March 3, 2005)

Ultra-energy-efficient analog-to-digital converters based on single-electron transistor/CMOS hybrid technology for biomedical applications

Lee, Jieun,Choi, Changmin,Park, Sungwook,Chung, In-Young,Kim, Chang-Joon,Park, Byung-Gook,Kim, Dong Myong,Kim, Dae Hwan Institute of Physics 2009 Semiconductor science and technology Vol.24 No.11

<P>Ultra-energy-efficient analog-to-digital converters (ADCs) based on single-electron transistor (SET)/complementary metal-oxide-semiconductor (CMOS) hybrid technology are proposed as a solution to sense and process biomedical signals. Our results show the energy efficiency of 0.82 pJ/state, which is lower than that in previously reported energy-efficient ADCs. The performance and dissipated power of proposed ADCs are estimated and compared with those of CMOS ADCs by using Lee's SPICE model including non-ideal effects of the experimental data. While the proposed ADC shows an operating power lower by two orders of magnitude than that of the CMOS flash-type ADC, the number of required transistors is about 10% of that in the CMOS flash-type ADC. The peak-to-valley current ratio in Coulomb oscillation of SETs used in the circuit implementation has the range of 1.15–1.5, which is consistent with the experimental result of top-down approached Si-based SETs at <I>T</I> = 77–100 K. From the perspective of the immunity to the gate capacitance <I>C<SUB>cg</SUB></I> mismatch and the background charge <I>Q</I><SUB>0</SUB> noise, it is shown that the criteria of SET/CMOS hybrid ADCs are Δ<I>C<SUB>cg</SUB></I> ⩽ 0.02 × <I>C<SUB>cg</SUB></I> (with <I>C<SUB>cg</SUB></I> = 0.24 aF) and Δ<I>Q</I><SUB>0</SUB> ⩽ 0.23<I>q</I>, respectively.</P>

Development of a Monitoring System for Water-borne Bacteria by a Molecular Technique, PCR-RELP-sequence Analysis

이혜영,--,--,--,--,--,-- THE KOREAN SOCIETY FOR BIOMEDICAL LABORATORY SCIEN 2003 Journal of biomedical laboratory sciences Vol.9 No.3

Since water borne infection causes acute diseases and results in spread of diseases by secondary infection, the prevention is very important. Therefore, it is necessary to have a method that is rapid and effective to monitor pathogenic bacteria in drinking water. In this study, we employed a systematic method, Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) analysis, to develop an effective monitoring system for possible bacterial contaminants in drinking water. For this purpose, PCR primers were derived from 992 bp region of the 16s rRNA gene that is highly conserved through the different species of prokaryotes. To test whether the PCR primers designed are indeed useful for detecting all the possible microbial contaminants in the water, the primers were used to amplify 16s rRNA regions of different microbial water-borne pathogens such as E. coli, Salmonella, Yersinia, Listeria, and Staphylococcus. As expected, all of tested microorganisms amplified expected size of PCR products indicating designed PCR primers for 16s rRNA indeed can be useful to amplify all different microbial water-borne pathogens in the water. Furthermore, to test whether these 16s rRNA based PCR primers can detect bacterial populations present in the water, water samples taken from diverse sources, such as river, tap, and sewage, were used for amplification. PCR products were for then subjected for cloning into a T-vector to generate a library containing 16s rRNA sequences from various bacteria. With cloned PCR products, RFLP analysis was done using PCR products digested with restriction enzyme such as Hae Ⅲ to obtain species-specific RFLP profiles. After PCR-RFLP, the bacterial clones which showed the same RFLP profiles were regarded as the same ones, and the clones which showed distinctive RFLP profiles were subsequently subjected for sequence analysis for species identification. By this PCR-RFLP analysis, we were able to reveal diverse populations of bacteria living in water. In brief, in unsterilized natural river water, over 60 different species of bacteria were found. On the other hand, no PCR products were detected in drinking tap-water. The results from this study clearly indicate that the PCR-RFLP-sequence analysis can be a useful method for monitoring diverse, perhaps pathogenic bacteria contaminated in water in a rapid fashion.

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.