• Journal of the Korean Ceramic Society
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• v.37 no.6
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• pp.524-529
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• 2000

Silica slab wavegudie was fabricated on Si substrates by FHD for planar optical passive devices. The slab waveguide consists of lower clad and core layers, where core layer index is controlled by GeO2 addition. Doping of GeO2 in silica is difficult because of the low deposition density due to nonspherical particle generation in FHD process. Silica core particles deposited at various conditions such as flame temperature and substrate scanning were analyzed by SEM and TEM. As the flame temperature increased, the surface roughness of the core layer was decreased up to 3.6 nm after consolidation. Index difference and thickness of core of slab waveguide were 0.3%, 8$\mu\textrm{m}$ respectively. Measured optical loss at TE mode was <0.04 dB/cm at 1.3$\mu\textrm{m}$ and <0.06 dB/cm at 1.55$\mu\textrm{m}$.

• Journal of the Korea Convergence Society
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• v.12 no.2
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• pp.29-34
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• 2021

In this paper, a cylindrical photonic crystal waveguide with a low-index core is first proposed. The core can be filled with air, liquid, or arbitrary dielectric materials. Exact analyses for the electromagnetic field characteristics of guided modes, by using appropriate Bessel functions and applying the boundary conditions, are performed to find out the guiding characteristics of the proposed waveguide. For verification and usage in design and manufacturing process, the computer-calculation of the waveguide transmission characteristics is also performed by applying the rigorous full-vectorial finite difference method. Providing variations of the effective area for the fundamental mode of the designed waveguide with different numbers of cladding layers, ranging from 2.6056 ㎛2 to 5.9673 ㎛2 over the operation wavelength, generally as the core refractive index n1 is higher, the mode area becomes smaller and the result leads to more optimistic effect for nonlinear device applications.

• Current Optics and Photonics
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• v.2 no.3
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• pp.226-232
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• 2018

We propose a triangular-multicore hollow optical fiber (TMC-HOF) design for uncoupled mode-division and space-division multiplexing. The TMC-HOF has three triangular cores, and each core has three modes: $LP_{01}$ and two split $LP_{11}$ modes. The asymmetric structure of the triangular core can split the $LP_{11}$ modes. Using the proposed structures, nine independent modes can propagate in a fiber. We use a fully vectorial finite-element method to estimate effective index, chromatic dispersion, differential group delay (DGD), and confinement loss by controlling the parameters of the TMC-HOF structure. We confirm that the proposed TMC-HOF shows flattened chromatic dispersion, low DGD, low confinement loss, low core-to-core crosstalk, and low crosstalk between adjacent modes. The proposed TMC-HOF can provide a common platform for MDM and SDM applications.

• Proceedings of the Optical Society of Korea Conference
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• 2006.02a
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• pp.87-88
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• 2006

Bragg fibers, consisting of a low index core (including air) surrounded by a series of periodic layers of alternate high and low refractive index materials, each being higher than that of the core, form a 1D photonic bandgap (PBG). In view of the multitude of individual physical parameters that characterize a Bragg fiber, they offer a wide choice of parametric avenues to tailor their propagation characteristics. Owing to their unique PBG guidance mechanism, Bragg fibers indeed exhibit unusual dispersion characteristics that are otherwise nearly impossible to achieve in conventional silica fibers. Solid core Bragg fibers, amenable to fabrication by the highly mature MCVD technology, could be designed to realize broadband supercontinuum light. This talk would review our recent works on modeling of propagation characteristics, dispersion tailoring in them for applications as metro as well as dispersion compensating fibers and also as supercontinuum light generators.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.29 no.2
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• pp.236-250
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• 2019

Objectives: The purpose of this study was to investigate the effect of intensive rehabilitation programs on pain, range of motion (ROM), lumbar muscle strength, core muscle endurance, disability, and depression in patients with traumatic low back injuries and to compare the efficacy of this therapy with that of conventional rehabilitation therapy. Methods: The study was performed with a retrospective medical chart review of patients with traumatic low back injury referred to the rehabilitation center at the Daegu Hospital of the Korean Workers Compensation and Welfare Service. Forty-four patients were allocated to either the conventional rehabilitation group (CRG; n = 22) or the intensive rehabilitation group (IRG; n = 22). The CRG group patients, who received 30-min therapist-supervised physical therapy and modality therapy five times per week for four weeks, were compared with the IRG group patients, who received 60-min therapist-supervised physical therapy, 30-min therapist-patient 1:1 matching rehabilitation therapy, and modality therapy five times per week for four weeks. Outcome measures were a numerical rating scale, ROM, lumbar muscle strength, lumbar core muscle endurance, thickness of lumbar deep focal core muscle (transverse abdominis and lumbar multifidus), Oswestry disability index (ODI), and depression (Korean version patient health questionnaire-9). Results: There were statistically significant improvements after treatment in all outcome measures in both groups (p < 0.05). In the intergroup comparison, NRS scores on the activity and thickness of lumbar deep focal core muscles increased significantly more in the IRG than in the CRG (p < 0.05). There were no statistically significant intergroup differences in NRS scores on resting, ROM except left lateral bending, lumbar muscle strength, core muscle endurance, ODI, and depression. Conclusions: We could confirm the superior effectiveness of an intensive rehabilitation program compared to conventional rehabilitation therapy in patients with traumatic low back injuries.

• Management & Information Systems Review
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• v.25
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• pp.83-114
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• 2008

We examine whether spinoffs improve long-run stock returns and analyze the factors of long run stock returns. The measures of long run stock returns are CAR(Cumulative Abnormal Returns) and BHAR(Buy and Hold Abnormal Returns). The expected factors of abnormal returns are methods of spinoffs, size, BV/MV, administrative costs, cashflow and Herfindahl index. We find that long-run returns of the case such as carve-out methods, small size, high BV/MV, low administrative costs, low cashflow and low Herfindahl index are larger than those of other cases. We show positive relationship between spinoffs and long-run stock returns(CAR and BHAR). The results supports spinoffs, as the methods of focusing on core business, are very usefulness of corporate restructuring.

• Korean Journal of Optics and Photonics
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• v.16 no.1
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• pp.79-84
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• 2005

To increase the tolerance for passive fiber alignment, a single mode polymer waveguide with a large core structure is demonstrated. The large core waveguide is designed to have a mode profile comparable to that of a thermally expanded core (TEC) fiber, and it can be connected to a high-contrast waveguide through an adiabatic transition taper structure. From a waveguide with a rectangular core of 25 ${\times}$ 25 ${\mu}{\textrm}{m}$$^2$, a single mode propagation is observed when the index contrast is as low as 0.0005. A UV-cured injection molding method is used to fabricate the thick core structure. Due to the large mode size, the insertion loss of the device is below 0.5 dB until the lateral displacement of the TEC fiber is 4.5 ${\mu}{\textrm}{m}$. The low insertion loss is important for reproducible passive alignment.

• The Research Journal of the Costume Culture
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• v.15 no.6
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• pp.996-1007
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• 2007

This study was focused on recognitive reaction. The purposes of this study was to analyze the fashion brands through correlation analysis between top of mind, recall, recognition, impact index and consumer behavior, and to identify the graveyard brand, niche brand and core brand. 33 questions about 20 fashion brands were asked to 442 males and females from the middle school students to age of 40. Data were analyzed mean, standard deviation, frequency, and correlation by using SPSS 12.0. The results were as follows: 1. Top of mind, recall and recognition affected recognizing the brands and including evoked setting, but it didn't lead the customer to purchase the brand. 2. Although top of the mind and recall are high, the percentage of purchasing the brand is relatively low if a consumer doesn't own the brand. 3. Brands 'B', 'L', 'PF', 'D' and 'BM' were represented as niche Brands which had high recognition and memory. 4. Brands 'TB', 'I', 'EN', 'ML', 'E' could be Graveyard brands that need special management. 5. Brands with the high impact index were 'A', 'T', 'I', 'C' and 'B'. These brands were recognized as the core brands by consumers.

• Journal of the Korea Convergence Society
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• v.12 no.2
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• pp.185-191
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• 2021

The characteristics of the foundry sand were analyzed for water jacket core required to prevent structural deformation from the heat generated in the cylinder bore during the casting of the cylinder block of an automobile. The sand core tensile strength tester, AFS-GFN, and optical microscope were used to evaluate the its properties. If the SiO2 content is high in the foundry sand, the dimensional defects and veining defects occur due to high temperature expansion. Also, if it is too low, the core breakage, porosities, chemical burn-on defects occur. The particle size index and grain shape influenced the core strength and resin consumption, resulting in fluctuations in defect types. The higher the alkalinity of the dried sand, the lower the core strength. And the more basic, the lower the core strength. At the resin content of 1.6~1.8%, the increase in core strength after 1 hour curing was approximately at its maximum.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.29 no.1
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• pp.53-67
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• 2023

Background: This study comparatively evaluated the effects of equipment-based pilates exercises (EPE) and lumbar stability exercises (LSE) in patients with chronic low back pain in terms of their Visual Analogue Scale(VAS), Oswestry Disability Index(ODI), and abdominal muscle thickness. Methods: A total of 30 participants were recruited and randomly assigned to either the EPE or the LSE. The VAS, ODI, and abdominal muscle thicknesses of the participants were measured before and after the intervention. Results: The EPE were more effective in terms of the duration of a sustained reduction in VAS scores. post hoc test revealed that EPE were more efficacious in terms of a sustained improvement in ODI scores. With respect to changes in abdominal muscle thickness, there was a significant difference in the thickness of internal oblique muscles(IO) and the external oblique muscles(EO) between the two groups. Conclusion: In this study, both types of exercise interventions resulted in improvements in the VAS, ODI scores, and abdominal muscle thickness in patients with chronic low back pain. However, EPE were found to be more effective than LPE in terms of longer sustained improvements in VAS and ODI scores. Also, with respect to abdominal muscle thickness, the thickness of EO and IO improved only in the EPE group.