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>

골다공증의 위험인자 : 아산시 지역 주민을 대상으로

김용배,장원기,황보영,김화성,안규동,이병국,이용진,이남수,이상건,이상범,이상우,이선정,이성수 순천향대학교 2006 Journal of Soonchunhyang Medical Science Vol.12 No.1

Objective : As the average lifespan of human increases, osteoporosis and osteoporosis-related fractures have become major health care problems. Despite recent advances in medical treatment, few studies have assessed the recognition of osteoporosis in general adults. This study examined the recognition of osteoporosis and analyzed the relating factors. Method : A population-based sample of 1086 adults in Asan-city, Korea was investigated with questionnaires and height, weight, Information regarding the general characteristics(gender, age, economic state), lifestylef exercise, smoking, alcohol),medical history(progestin, GH, steroid, calcitonin, PTH), demographic parameter, obesity, stress, and family history was collected through an interview using a structural questionnaire. The level of obesity was measured by the body mass index(BMI). BMD(Bone mineral density) at the lumbar spine and femoral neck was measured by dual energy X-ray absorptiometry. Osteoporosis was considered to be T-score below -2.5. Results : The prevalence of osteoporosis increased progressively with age, decreased with BMI and predominant in women by the result of x^(2) -test, T-test. Age, weight, BMI were significantly correlated with osteoporosis by the result of Pearson correlation ana1ysis(P<0.05). And age, gender, BMI, family history of osteoporosis were proved to be significant risk factors of osteoporosis by the result of multiple logistic regression(P<0.05). Conclusion : These results suggest that age, gender, BMI might be the most important risk factors of osteoporosis. And the history taking about family history of osteoporosis is helpful for diagnosing osteoporosis.

고요산혈증의 위험인자 : 아산시 지역 주민을 대상으로

김용배,장원기,황보영,김화성,안규동,이병국,이용진,이종은,이준숙,이찬구,이한정,이성수 순천향대학교 2006 Journal of Soonchunhyang Medical Science Vol.12 No.1

Objective : Serum uric acid has now been identified as a marker for a number of metabolic and hemodynamic abnormalities. The aim of this study is to evaluate risk factors which influence hyperuricemia in the citizens of Asan. Method : The study design was cross-sectional and research subjects were 1086 citizens of Asan. General characteristics, cigarette smoking, alcohol consumption, and past history were obtained by interview using a structural questionnaire. Also, we measured height, weight and blood pressure, and serum uric acid of the subjects. Results : The mean serum uric acid level was 5.27 ㎎/㎗ in men and 4.01 ㎎/㎗, in women, In the multiple logistic regression analysis, statically significant risk factors of hyperuhcemia were gender, body mass index, blood lead concentration, and serum creatinine. Conclusion : Our results suggest that gender, body mass index, blood lead concentration, and serum creatinine might be the most important risk factors of hyperurcemia. Education program as well as routine check-up for serum uric acid was highly recommended for the effective prevention of hyperuricemia.

연작업자들의 신기능 평가에서 요중 δ-aminolevulinic acid 측정의 의의

이병국,이숙,김용배,리갑수,김화성,황규윤,장봉기,이성수,안규동 순천향대학교 산업의학연구소 1999 순천향산업의학 Vol.5 No.1

To clarify the effect of occupational lead exposure on renal function 241 lead workers working and 56 non lead workers were studied in 5 lead acid battery industries. Study variables for renal effect were urinary N-acetyl-β-D-glucosaminidase(NAG), urinary total protein(U-TP), blood urea nitrogen(BUN), serum creatinine(S-Cr), and serum uric acid(S-Ua). On the other hand, blood lead(PbB), zinc protoporphyrin in whole blood(ZPP), and delta-aminolevulinic acid in urine(δ-ALA) were selected for the variables of lead exposure. Information on age, work duration, smoking and drinking history were also obtained. The results obtained were as follows. While the mean values of lead exposure indicators of lead workers were significantly different from non-exposed ones, the mean values of BUN, U-TP and S-Cr of renal function indicators of exposed were also different from non-exposed. BUN, U-TP and NAG showed statistically significant correlation with PbB and ZPP, and NAG revealed also statistically strongly significant correlation with δ-ALA. On multiple regression using renal fuction indicators as a dependent variable and δ-ALA, age, work duration,lead exposure,smoking and drinking as independent variables, only δ-ALA contributed to NAG.

업종에 따른 연 취급 사업장의 기중 연 농도 및 연 노출 수준 평가

이병국,김용배,리갑수,안현철,김화성,이용진,황규윤,장봉기,이성수,안규동 순천향대학교 산업의학연구소 1999 순천향산업의학 Vol.5 No.1

In order to obtain an useful information for health management and biological monitoring of lead exposed workers, Authors tried to investigate air lead level and the lead exposed level of workers in lead industry according to occupational category. The subjects in our study were 2074 workers in 7 lead-using industries, and study subjects were divided into 4 occupational categories such as storage battery industry (type 1), primary smelting industry (type 2), secondary smelting industry (type 3) and litharge making industry (type 4). Blood zincprotoporphyrin concentration (ZPP), blood lead concentration (PbB) and urinary δ -aminolevulinic acid (ALAU), hemoglobin (Hb), hematocrit (Hct) were selected as the indices of lead exposure. Personal variables such as age, work duration were also collected. The results were as follows. 1. The geometric mean air lead in 9 lead-using industry was 0.1133±4.3120 ㎎/㎥, and that in type 1, 2, 3 and 4 was 0.1038±3.4952 ㎎/㎥, 0.0429±3.4329 ㎎/㎥, 0.1877±2.5123 ㎎/㎥ and 0.9961±5.2910 ㎎/㎥, respectively. 2. The mean ZPP in 9 lead-using industry was 53.1±28.0 ㎍/㎗, and that in type 1, 2, 3 and 4 was 52.0±24.8 ㎍/㎗, 48.0±16.4 ㎍/㎗, 109.8±85.6 ㎍/㎗ and 74.3±37.8 ㎍/㎗, respectively. There was significant difference in ZPP according to occupational category (P<0.01). The percents of lead workers whose ZPP were above 100 ㎍/㎗ in type 1, 2, 3 and 4 were 4.0%, 1.7%, 34.3% and 21.6%, respectively. 3. The mean PbB in lead-using industry was 26.0±11.2 ㎍/㎗, and that in type 1, 2, 3 and 4 was 25.3±11.1 ㎍/㎗, 26.7±8.8 ㎍/㎗, 50.3±15.2 ㎍/㎗ and 36.4±11.0 ㎍/㎗, respectively. There was significant difference in PbB according to occupational category (P<0.01). The percents of lead workers whose PbB were above 40 ㎍/㎗ in type 1, 2, 3 and 4 were 10.4%, 7.7% 71.9% and 43.2%, respectively. 4. While the correlation of Hb corrected PbB with ZPP was higher than non corrected PbB, the correlation of log-transformed ZPP with PbB was higher than non corrected ZPP. 5. Simple linear regressions of PbB and corrected PbB as independent variable with ZPP, log-transformed ZPP and ALAU as dependent variable were statistically significant (P0.01). Coefficient of determination of corrected PbB with other variables was higher than non corrected PbB. As the result of this study, it was suggested that reconsideration of environmental and biological monitoring program was highly recommended for secondary smelting and litharge making industry.

65세 이상의 노령층에서 고지혈증의 위험요인

김용배,장원기,황보영,김화성,안규동,이병국,이용진,김세훈,김승수,김승훈,김영록,김웅빈,이성수 순천향의학연구소 2006 Journal of Soonchunhyang Medical Science Vol.12 No.1

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Plant regeneration from callus of Iris odaesanensis Y. N. Lee native to Korea via organogenesis

Bae, Kee-Hwa,Yoo, Kyoung-Hwa,Lee, Mi-Hyun,Jeong, Jae-Hun,Choi, Yong-Eui,Yoon, Eui-Soo The Korean Society of Plant Biotechnology 2013 식물생명공학회지 Vol.40 No.3

Iris odaesanensis Y. N. Lee. is an important endangered and native plant belonging to the family Iridaceae in Korea. This study describes a method for rapid micropropagation of this species via from leaf, rhizome and root explants derived calli. Leaf, rhizome and root explants were cultured on Murashige and Skoog (MS) medium supplemented with 2,4-dichlorophenoxy acetic acid (2,4-D) for callus induction. Rhizome explants yielded calli at a frequency of 72% when cultured at 1.0 mg/l 2,4-D. Calli were maintained at 1.0 mg/l 2,4-D. These calli were transferred to MS medium supplemented with 0, 0.5, 1.0, and 2.0 mg/l 2,4-D in combination with 0, 0.5, 1.0, and 3.0 mg/l BA for adventitious shoot induction. The highest number of adventitious shoot (228.9 per petri-dish) were formed at 1.0 mg/l 2,4-D and 1.0 mg/l BA. WPM medium was the best to convert calli into plantlets, where up to 98.2% of calli were regenerated into plantlets. This in vitro propagation protocol should be useful for conservation of this endangered plant.

모 축전지 회사 근로자들의 연폭로 지표에 대한 경시적 관찰

강명식,김용배,이용진,리갑수,김화성,황규윤,장봉기,이성수,안규동,이병국 순천향대학교 산업의학연구소 1998 순천향산업의학 Vol.4 No.1

Lead poisoning is still prevalent and one of important occupational disease in Korea. To prevent undue high lead burden and maintain good health condition of lead workers in lead using industries, periodic health examination and regular biological monitoring of lead workers are often required in addition to the fundamental improvement of their working condition. To evaluate the effect of comprehensive occupational health program with regular biological monitoring on the level of lead exposure of lead workers in lead using industries, 11 year database from 1983 to 1994 of one storage battery factory was reviewed. From 1983 to end of 1986 only periodic health examination was provided to the lead workers, but from 1987 comprehensive occupational health program with regular biological monitoring was provided to maintain better health condition of lead workers. Selected study variables for lead exposure were blood lead(PbB), zinc protoporphyrin in blood(ZPP), δ-aminolevulinic acid in urine(ALAU), hemoglobin(Hb), hematocrit(HCT). Information on sex, age and work duration was also reviewed. 5 years data from 1983 to 1987 and 3 years data from 1990, 1993 and 1994 were available for all lead exposure indices except ALAU which has only 5 years data from 1983 to 1997. The results of 11 years longitudinal observation of lead indices are all follows: 1. The mean value of ZPP of lead workers in 1983 was 148.7±73.1 ㎍/㎗(Male: 145.5±72.3, Female: 168.1±79.1), whereas that of ZPP of lead workers in 1994 was decreased to 64.3±32.7 ㎍/㎗(Male: 60.2±28.8, Female: 95.2±43.4). 2. The mean value of PbB of lead workers in 1983 was 56.4±18.8 ㎍/㎗(Male: 55.59±19.1, Female: 59.6±19.1), whereas that of PbB of lead workers in 1994 was dcreased to 35.4±11.9 ㎍/㎗(Male: 35.7±12.0, Female: 32.8±10.8). 3. The mean value of Hb of lead workers in 1983 was 14.1±1.4 g/㎗(Male: 14.4±1.1, Female: 11.7±0.8), whereas that of Hb of lead workers in 1994 was increased to 15.6±1.5 g/㎗(Male: 15.9±1.2, Female: 12.9±1.1). 4. Blood lead is most highly correlated with ZPP(r=0.522, male:0.54 and female:0.50) and also correlated with ALAU and work duration also. 5. The simple regression analysis of PbB and ZPP showed different coefficient of regression by the measurement year, but there was no difference of coefficient of regression between sex. The slope of equation of pooled data for 1983-1986 without comprehensive occupational health program was 2.16 and differed from that of pooled data for 1987-1994(1.25). This difference suggests that the unit effect of blood lead on ZPP was relatively smaller in later period of comprehensive occupational health program than carly period without comprehensive program. The slope change in the analysis of linear regression of PbB on ZPP in lead workers can be used to evaluate the possible effect of health intervention to prevent undue high lead absorption in lead using industries. 6. 11 years occupational health service in this storage battery factory brought out considerable improvement of health status of lead workers in terms of decrease of PbB and ZPP and increase of Hb and the improvement was more remarkable after the introduction of comprehensive occupational health program.

모 연취급장 근로자들의 연폭로지표들과 혈압과의 관련성

임상복,김용배,이용진,리갑수,김화성,황규윤,장봉기,이성수,안규동,이병국 순천향대학교 산업의학연구소 1998 순천향산업의학 Vol.4 No.1

In order to investigate the relationship between blood lead with other lead exposure indices and blood pressure in occupationally lead exposed male workers, 629 workers(515 lead exposed workers and 114 non lead exposed workers) in a storage battery factory were studied. Blood lead(PbB), zinc protoporphyrin(ZPP) and urinary δ-aminolevulinic acid(ALAU) were selected as an index of lead exposure. Height and weight were also meaured with calibrated automatic height-weight machine to produce fatness index directly. Personal information on smoking and drinking history were also collected. Blood pressure was mearured by trained nurses with automatic sphingomanometer. All workers took at least 30 minute rest before their measurement of blood pressure. The results obtained were as follows: 1. The prevalence rate of hypertension of lead exposed and non-exposed workers were 3.5% in both group without any difference. 2. There were no differences of systolic and diastolic pressure between groups divided by lead exposure, smoking habit, drinking habit. but the increase of age group made the difference of diastolic pressure, and only differenct of systolic pressure observed in age group of less than 20 and that of more than 40. 3. In pearson's correlation analysis, PbB was correlated with systolic pressure significantly, but not with diastolic pressure. PbB was also correlated with pressure difference(systolic pressure-diastolic pressure). 4. There were no significant increase of systolic, diastolic pressure and pressure difference by the increase of PbB and ZPP grouping. 5. Stepwise multiple regression analysis using systolic pressure as dependent variable and PbB, ZPP, ALAU, age, work duration, smoking habit, drinking habit and fatness (weight*0.9/height-100) as independent variables, revealed that PbB, age, drinking habit and fatness in order were significantly contributed to the dependent variable. 6. Stepwise multiple regression analysis using diastolic pressure as dependent variable and PbB, ZPP, ALAU, age, work duration, smoking habit, drinking habit and fatness (weight*0.9/height-100) as independent variables, revealed that ALAU, age and fatness in order were significantly contributed to the dependent variable. 7. Stepwise multiple regression analysis using pressure difference as dependent variable and PbB, ZPP, ALAU, age, work duration, smoking habit, drinking habit and fatness(weight*0.9/height-100) as independent variables, revealed that PbB, age and fatness in order were significantly contributed to the dependent variable. 8. Logistic analysis of hypertensive conditions with categorized blood lead and other selected categorized independent variables indicated that only age(40> and 40≤) and fatness(1.0> and 1.0≤) were significantly contributed to dependent variable with 95% significant odd ratio confidence interval. With above results, lead exposure in terms of blood lead seemed to be minimally contributed to the raise of blood pressure, and the effect of blood lead was found to be more prominent on the pressure difference than the systolic and diastolic pressure themselves.

내구재 시장에서 제품의 품질에 대한 신호에 관한 연구

李和姸,金容寬 한국국제경제학회 2004 국제경제연구 Vol.10 No.3

내구재 시장에서 소비자들이 제품의 품질을 잘 모르는 경우 독점기업이 가격과 광고를 신호로 이용하여 제품의 품질을 효과적으로 알릴 수 있음을 보인다. 이를 위하여 독점기업과 소비자 간의 신호게임모형을 만들고 분리균형을 중심으로 분석한다. 먼저 반복적 열등전략삭제 조건을 충족시키는 분리균형이 유일함을 보인다. 아울러 균형에서 가격과 광고가 동시에 신호로 사용되는 경우의 조건을 찾는데, 이는 제품의 품질을 알고 있는 소비자의 비율이 지나치게 높거나 낮지 않고 높은 품질의 제품과 낮은 품질의 제품간의 생산비 차이가 크지 않을 경우임을 밝혀낸다. Extending Bagwell and Riordan's (1991) durable good market model, we study whether both dissipative advertisements and price could be used as signals for the product quality. It is shown that both of them can play the role of signals simultaneously when the proportion of informed consumers is not too high or too low and the cost difference between two qualities of the commodity is sufficiently small. This is in contrast to Bagwell and Riordan in which only price is considered as a signal for quality, since a high quality firm can differentiate itself from a low quality firm with both a lower price and advertising in our model. It is a crucial assumption of this paper that a higher-quality product is more costly to produce. So even if price and advertising are considered as equivalent signals, they affect profits in different ways. Advertising affects the profit of either type equally, whereas the signaling cost of price is higher for a low quality firm than a high quality firm.