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An Analysis of the Geometrical and Optical Characteristics of Prisms Used in Elementary Schools
Jhun Youngseok 한국물리학회 2023 새물리 Vol.73 No.1
In this report, I describe investigations of the dispersive prisms used in elementary-school science classes to determine the extent to which they are uniform and accurate. As samples, I selected eight prisms that are widely used in schools, and I measured their refractive indices as functions of the wavelength of the light as well as their physical properties, such as shape and density. I measured the refractive index at each wavelength using a red He–Ne laser and yellow, green, and blue laser pointers. To ensure the precision of the measurements, I employed a threaded needle fixed to a stand as an indicator to determine the exact path of the light. In addition, rather than measuring the vertex, incident, and deviation angles directly, I obtained them by measuring the side lengths of a triangle drawn along the light path and then calculating the angles using the cosine law. As a result of this investigation, I found that prisms typically used in schools are neither right nor regular and that a variety of widely used materials—especially plastics—have varying densities and refractive index distributions. I also confirmed that some prisms had narrow dispersion, making it difficult to produce a clear spectrum.
Vitamin D Status in South Korean Military Personnel with Acute Eosinophilic Pneumonia: A Pilot Study
Jhun, Byung Woo,Kim, Se Jin,Kim, Kang,Lee, Ji Eun,Hong, Duck Jin The Korean Academy of Tuberculosis and Respiratory 2015 Tuberculosis and Respiratory Diseases Vol.78 No.3
Background: A relationship between low vitamin D levels and the development or outcomes of respiratory diseases has been identified. However, there is no data on the vitamin D status in patients with acute eosinophilic pneumonia (AEP). We evaluated the vitamin D status in patients with AEP among South Korean military personnel. Methods: We prospectively compared the serum levels of total 25-hydroxyvitamin D [25(OH)D], 25(OH)D3, and 25(OH)D2 among patients with AEP, pulmonary tuberculosis (PTB), and community-acquired pneumonia (CAP). Results: In total, 65 patients with respiratory diseases, including AEP (n=24), PTB (n=19), and CAP (n=22), were identified. Of the 24 patients with AEP, 2 (8%) had deficient total 25(OH)D levels (<10 ng/mL), 17 (71%) had insufficient total 25(OH)D levels (${\geq}10$ to <30 ng/mL), and only 5 (21%) had sufficient total 25(OH)D levels (${\geq}30$ to <100 ng/mL). The difference in the total 25(OH)D levels among patients with AEP, PTB, and CAP was not statistically significant (p=0.230). The median levels of total 25(OH)D, 25(OH)D3, and 25(OH)D2 were 22.84, 22.84, and 0.00 ng/mL, respectively, and no differences in the 25(OH)D level were present among patients with AEP, PTB, and CAP with the exception of the total 25(OH)D level between patients with AEP and PTB (p=0.042). Conclusion: We have shown that low vitamin D levels are frequently found in patients with AEP and are comparable with those in patients with PTB and CAP.
Electronic structure of charged bilayer and trilayer phosphorene
Jhun, Bukyoung,Park, Cheol-Hwan American Physical Society 2017 Physical Review B Vol.96 No.8
<P>We have investigated the electronic structure of charged bilayer and trilayer phoshporene using first-principles density functional theory calculations. We find that the effective dielectric constant for an external electric field applied perpendicular to phosphorene layers increases with the charge density and is twice as large as in an undoped system if the electron density is around 5 x 10(13) cm(-2). It is known that if few-layer phosphorene is placed under such an electric field, the electron band gap decreases, and if the strength of the electric field is further increased, the band gap closes. We show that the electronic screening due to added charge carriers reduces the amount of this reduction in the band gap and increases the critical strength of the electric field for gap closure. If the electron density is around 4 x 10(13) cm(-2), for example, this critical field for trilayer phosphorene is 40% higher than that for a charge-neutral system. The results are directly relevant to experiments on few-layer phosphorene with top and bottom electrical gates and/or with chemical dopants.</P>
Jhun, Hyung-Joon,Kim, Ho,Cho, Sung-Il The Korean Academy of Medical Sciences 2011 JOURNAL OF KOREAN MEDICAL SCIENCE Vol.26 No.5
<P>We examined time trend and age-period-cohort effects on acute myocardial infarction (AMI) mortality in Korean adults from 1988 to 2007. Annual AMI mortality data and population statistics from 1988 to 2007 were obtained from the STATISTICS KOREA website. Age adjusted mortality for four 5-yr calendar periods (1988-1992 to 2003-2007) was calculated by direct standardization using the Year 2000 WHO world standard population. A log-linear Poisson regression model was used to estimate age, period, and cohort effects on AMI mortality. In both genders, age-adjusted AMI mortality increased from period one (1988-1992) to period three (1998-2002) but decreased in period four (2003-2007). An exponential age effect was noted in both genders. The rate ratio of the cohort effect increased up to the 1943 birth cohort and decreased gradually thereafter, and the rate ratio of the period effect increased up to period three (1998-2002) and decreased thereafter. Our results suggest that AMI mortality in Korean adults has decreased since the period 1998-2002 and age, period, and cohort effects have influenced on AMI mortality.</P>
Jhun, Hyung-Joon,Seo, Hong-Gwan,Lee, Do-Hoon,Sung, Moon-Woo,Kang, Yoon-Dan,Syn, Hee Chul,Jun, Jong Kwan The Korean Academy of Medical Sciences 2010 JOURNAL OF KOREAN MEDICAL SCIENCE Vol.25 No.5
<P>This study examined urinary cotinine levels and self-reported smoking among pregnant women in Korea and the factors associated with smoking during pregnancy. The subjects were selected from pregnant women who visited 30 randomly sampled obstetric clinics and prenatal care hospitals in Korea in 2006. Smoking status was determined by self-reporting and urinary cotinine measurement. A total of 1,090 self-administered questionnaires and 1,057 urine samples were analyzed. The percentage of smoking revealed by self-reporting was 0.55% (95% confidence interval [CI], 0.11-0.99) and that revealed by urinary cotinine measurement (>100 ng/mL) was 3.03% (95% CI, 1.99-4.06). The kappa coefficient of agreement between self-reported smoking status and urinary cotinine measurement was 0.20 (95% CI, 0.03-0.37). Multiple logistic regression analysis revealed that early gestational period, low educational level, and being married to a smoker were significant risk factors for smoking during pregnancy. Smoking among pregnant women in Korea is not negligible, and those who are concerned to maternal and child health should be aware of this possibility among pregnant women in countries with similar cultural background.</P>
Evidence for the Ras-Independent Signaling Pathway Regulating Insulin-Induced DNA Synthesis
Jhun, Byung H . 생화학분자생물학회 2000 BMB Reports Vol.32 No.2
The existence of the Ras-independent signal transduction pathway of insulin leading to DNA synthesis was investigated in Rat-1 fibroblasts overexpressing human insulin receptor (HIRc-B) using the single-cell microinjection technique. Microinjection of a dominant-negative mutant Ras^(N17) protein into quiescent HIRc-B cells inhibited the DNA synthesis stimulated by insulin. Microinjection of oncogenic HRas^(V12) protein (H-Ras^(V12)) (0.1 ㎎/㎖) induced DNA synthesis by 35%, whereas that of control-injected IgG was induced by 20%. When the marginal amount of oncogenic H-Ras^(V12) protein was coinjected with a dominant-negative mutant of the H-Ras^(V12) protein (H-Ras^(N17)), DNA synthesis was 35% and 74% in the absence and presence of insulin, respectively. This full recovery of DNA synthesis by insulin suggests the existence of the Ras-independent pathway. The same recovery was observed in the cells coinjected with either H-Ras^(V12) plus H-Ras^(V12) plus SH2 domain of the p85 subunit of PI3-kinase (p85^(SH2-N)) or H-Ras^(V12) plus H-Ras^(N17) plus interfering anti-Shc antibody. When coinjected with a dominant-negative Rac1^(N17), the DNA synthesis induced by the Ras-independent pathway was blocked. These results indicate that the Rasindependent pathway of insulin leading to DNA synthesis exists, bypassing the p85 of PI3-kinase and Shc protein, and requires Rac1 protein.