• Current Optics and Photonics
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• v.6 no.2
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• pp.143-150
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• 2022

Anti-resonant hollow-core photonic crystal fiber (AR-HCF) has unique advantages, such as low nonlinearity and high damage threshold, which make it a promising candidate for high-power laser delivery at distances of tens of meters. However, due to the special structure, optical properties such as mode-field profile and bending loss of hollow-core fibers are different from those of solid-core fibers. These differences have limited the widespread use of AR-HCF in practice. In this paper we conduct numerical analysis of AR-HCFs with different structural parameters, to analyze their influences on an AR-HCF's optical properties. The simulation results show that with a 23-㎛ air-core diameter, the fundamental mode profile of an AR-HCF can well match that of the widely used Nufern's 20/400 fiber, for nearly-single-mode power delivery applications. Moreover, with the ratio of cladding capillary diameter to air-core diameter ranging from 0.6 to 0.7, the AR-HCF shows excellent optical characteristics, including low bending sensitivity while maintaining single-mode transmission at the same time. We believe these results lay the foundation for the application of AR-HCFs in the power delivery of high power fiber laser systems.

• Journal of the Mineralogical Society of Korea
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• v.18 no.3 s.45
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• pp.215-225
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• 2005

Numerous clay veins along fractures such as fault, joints, cracks and small fissures are found in granitic rocks in the Korean Peninsula. Granitic rocks of three geological stages (Jurassic, Cretaceous and Paleogene) occur in the Korean Peninsula, and are known as the Daebo, Bulguksa and Hoam granites, respectively. Specimens from clay veins composed or mainly mica clay mineral (illite) were dated using the K-Ar method with the hosted granitoids. The respective ages were as follows. Jurassic: granites 143.7 Ma and 160 Ma, clay mineral veins 104 Ma and 107 Ma: Cretaceous: granite 133.2 Ma, clay mineral veins 93.6 Ma, 84.2 Ma and 84.3 Ma: Paleogene: granite 39.7 Ma and 35.4Ma, clay mineral veins 27.1 Ma and 23.9 Ma. The ages of the clay veins in the Korean Peninsula are clearly much younger than those of their hosted granitoids. This contrasts with data for similar clay veins in Cretaceous and Paleogene granitoids in southwest Japan, where the K-Ar ages of mica clay minerals are slightly younger than their host rocks, or are almost the same.

• Knowledge Management Research
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• v.23 no.2
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• pp.123-142
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• 2022

The non-face-to-face environment accelerated by COVID-19 has speeded up the dissemination of digital virtual ecosystems and metaverse. In order for the metaverse to be sustainable, digital twins that are compatible with the real world are key, and critical technology for that is AR (Augmented Reality). In this study, we examined research trends about AR, and will propose the directions for future AR research. We conducted LDA based topic modeling on 11,049 abstracts of published domestic and foreign AR related papers from 2009 to Mar 2022, and then looked into AR that was comprehensive research trends, comparison of domestic and foreign research trends, and research trends before and after the popularity of metaverse concepts. As a result, the topics of AR related research were deduced from 11 topics such as device, network communication, surgery, digital twin, education, serious game, camera/vision, color application, therapy, location accuracy, and interface design. After popularity of metaverse, 6 topics were deduced such as camera/vision, training, digital twin, surgical/surgical, interaction performance, and network communication. We will expect, through this study, to encourage active research on metaverse AR with convergent characteristics in multidisciplinary fields and contribute to giving useful implications to practitioners.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.1
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• pp.18-25
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• 2011

This study presents the damage monitoring method in foundation-structure interface of harbor caisson using vibration-based autoregressive (AR) model. In order to achieve the objective, the following approaches are implemented. Firstly, vibration-based AR model is selected to monitor the damage in foundation-structure interface of caisson structure. Secondly, finite element analysis on a caisson structure model is implemented to evaluate the vibration-based damage monitoring method. Finally, vibration test on a caisson structure model is performed to evaluate applicability of vibration-based AR model method for foundation-structure interface of caisson structure.

• Journal of Sensor Science and Technology
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• v.23 no.2
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• pp.94-98
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• 2014

Aluminum nitride (AlN) thin films with a TiN buffer layer have been fabricated on SUS430 substrate by RF reactive magnetron sputtering at room temperature under 25~75% $N_2$ /Ar. The characterization of film properties were performed using surface profiler, X-ray diffraction, X-ray photoelectron spectroscopy(XPS), and pressure-voltage measurement system. The deposition rates of AlN films were decreased with increasing the $N_2$ concentration owing to lower mass of nitrogen ions than Ar. The as-deposited AlN films showed crystalline phase, and with increasing the $N_2$ concentration, the peak of AlN(100) plane and the crystallinity became weak. Any change in the preferential orientation of the as-deposited AlN films was not observed within our $N_2$ concentration range. But in the case of 50% $N_2$ /Ar condition, the peak of (002) plane, which is determinant in pressure sensing properties, appeared. XPS depth profiling of AlN/TiN/SUS430 revealed Al/N ratio was close to stoichiometric value (45:47) when deposited under 50% $N_2/Ar$ atmosphere at room temperature. The output signal voltage of AlN sensor showed a linear behavior between 26~85 mV, and the pressure-sensing sensitivity was calculated as 7 mV/MPa.

• Korea Information Processing Society Review
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• v.29 no.2
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• pp.23-31
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• 2022

• Journal of the Korean Society of Food Science and Nutrition
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• v.33 no.1
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• pp.83-90
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• 2004

This study was conducted to examine the effects of $\beta$3-adrenergic receptor polymorphism on the blood glucose level and obesity in 530 volunteers, who attended a weight loss program in a local obesity clinic. The age differences in total subjects and the distribution of male and female were 26.55$\pm$0.31 yr, 9.1% (n=48), 90.9% (n=492). The genotype distribution of $\beta$3-AR gene polymorphism were WW type 75%, WR type 22% and RR type 3%. Among many parameters, fasting blood glucose was significantly higher in WR＋RR type (p=0.001) compared with WW type. When the subjects were divided into two groups by 6.105 mmol/L of the fasting blood glucose level, the frequency of hyperglycemia was 23.3% in WW type subjects, while there was a increase to 35.6% in WR＋RR type subjects (p=0.011, $\chi$$^2$-analysis). When hyperglycemia group was compared with normoglycemia group, obesity index (p=0.044), %body fat (p=0.046) and TG (p=0.000) were significantly higher, and HDL (p=0.006) was significantly lower in the hyperglycemia. When all of the above factors were included in stepwise logistic regression analysis to find risk factors of hyperglycemia, the results were that the odds ratio for hyperglycemia were 2.015 (p=0.011) for WR+RR type of $\beta$3-AR gene, 2.165 (p=0.000) for TG and 0.419 (p=0.059) for HDL cholesterol. There was a significantly positive correlation between the blood glucose vs BMI, WHR, body fat in the WW type (r=0.099, 0.119, 0.082) However, in the WR and RR type there were no significance between the blood glucose vs BMI, WHR, body fat. These data suggest that the WR＋RR genotype of $\beta$3-AR has a very strong association with increased blood glucose level and might be a significant risk factor for hyperglycemia among Korean subjects.

• Proceedings of the KIEE Conference
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• 2005.11a
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• pp.21-23
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• 2005

The electron transport coefficients, the electron drift velocity W, the longitudinal diffusion coefficient $ND_L$ in $C_{3}F_{8}-Ar$ mixture gases were measured by Double shutter drift tube and calculated by multi-term approximation of the Boltzmann equation over the wide E/N range from 0.03 to 100 Td. And an inelastic collision cross sections for $C_{3}F_{8}$ molecular gas were redetermined for quantitative characteristic analysis.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.23-26
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• 2006

Modernized GPS will have three frequencies modulated with three signals, which will be accessible to all users in the near future. This new frequency provides an opportunity to resolve the double differenced (DD) integer ambiguity very fast and with almost no baseline constraints. In order to study the performance of triple frequency system for Ambiguity Resolution (AR) over the medium baseline under different ionospheric levels, the Klobuchar Model was implemented and used in our triple simulation to generate the ionospheric delay. Furthermore, the White-Gaussian noise applying to distance-dependent parameters was added to the DD ionospheric delay. For medium baseline (defined as here 20 to 40kms), success rates of AR has been pretty improved. In this paper, the medium baseline AR strategies that take advantage of carrier phase measurement on the third frequency will be discussed.

• Journal of Chest Surgery
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• v.37 no.8
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• pp.652-659
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• 2004

Background: In this study, we retrospectively analyzed the outcomes of aortic valvuloplasty in pediatric age. Material and Method: Between January 1993 and March 2004, 35 patients underwent aortic valvuloplasty for aortic stenosis (AS) or aortic regurgitation (AR). The mean age was 81.1$\pm$61.5 (1∼223) months. The mean follow up was 50.8$\pm$30.2 (3∼121) months. Nine patients had AS, 21 had AR, and 6 had AS and AR. Valve morphology was tricuspid in 24 patients, bicuspid in 9, quadricuspid in 1, and unicuspid in 1. The mean peak pressure gradients of AS were 72.0$\pm$33.0 mmHg, and the mean grades of AR were 3.1$\pm$0.9. Result: There was one late mortality without early mortality. After operation, AS improved with mean peak pressure gradients of 23.5$\pm$21.0 mmHg (p < 0.05), and AR improved with mean grades of 1.9$\pm$0.8 (p < 0.05). At mean follow up of 35.0$\pm$23.0 months, AS maintained with mean peak pressure gradients of 31.5$\pm$24.0 mmHg, but AR progressed with mean grades of 2.8$\pm$1.3 (p < 0.05). Reoperation was required in 6 patients 38.3$\pm$21.8 months after the original operation. The actuarial figures for freedom from reoperation at 2, 5 and 8 years were 96.9$\pm$3.1%, 79.5$\pm$5.5%, and 56.8$\pm$11.4%, respectively. Age at operation, presence of AS, preoperative severity of AS or AR, and morphology of aortic valve were not significant risk factors for reoperation, and improvement of AS or AR. Conclusion: Aortic valvuloplasty showed good immediate postoperative valve function. Aortic valvuloplasty offers children many years with tolerable valve function and allows to postpone aortic valve replacement or Ross procedure in pediatric patients.