• Nuclear Engineering and Technology
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• 제37권1호
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• pp.91-100
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• 2005

Kyung-hee Thorium Fuel (KTF), a heterogeneous thorium-based seed and blanket design concept for pressurized light water reactors, is being studied as an alternative to enhance proliferation resistance and fuel cycle economics of PWRs. The proliferation resistance characteristics of the KTF assembly design were evaluated through parametric studies using neutronic performance indices such as Bare Critical Mass (BCM), Spontaneous Neutron Source rate (SNS), Thermal Generation rate (TG), and Radio-Toxicity. Also, Fissile Economic Index (FEI), a new index for gauging fuel cycle economy, was suggested and applied to optimize the KTF design. A core loaded with optimized KTF assemblies with a seed-to-blanket ratio of 1: 1 was tested at the Korea Next Generation Reactor (KNGR), ARP-1400. Core design characteristics for cycle length, power distribution, and power peaking were evaluated by HELIOS and MASTER code systems for nine reload cycles. The core calculation results show that the KTF assembly design has nearly the same neutronic performance as those of a conventional $UO_2$ fuel assembly. However, the power peaking factor is relatively higher than that of conventional PWRs as the maximum Fq is 2.69 at the M$9^{th}$ equilibrium cycle while the design limit is 2.58. In order to assess the economic potential of a heterogeneous thorium fuel core, the front-end fuel cycle costs as well as the spent fuel disposal costs were compared with those of a reference PWR fueled with $UO_2$. In the case of comprising back-end fuel cycle cost, the fuel cycle cost of APR-1400 with a KTF assembly is 4.99 mills/KWe-yr, which is lower than that (5.23 mills/KWe-yr) of a conventional PWR. Proliferation resistance potential, BCM, SNS, and TG of a heterogeneous thorium-fueled core are much higher than those of the $UO_2$ core. The once-through fuel cycle application of heterogeneous thorium fuel assemblies demonstrated good competitiveness relative to $UO_2$ in terms of economics.

• Journal of the Optical Society of Korea
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• 제8권2호
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• pp.83-89
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• 2004

A variable optical attenuator with a bending-sensitive fiber (BSF) that can be used in optical networks is developed. The refractive index profile of the BSF is divided into four regions which are inner core, center dip of inner core, outer core and clad. The 3-dimensional finite difference beam propagation method (3D FD-BPM) is utilized to find the characteristics of the BSF, so the mode profile of the BSF and optical power attenuation according to the bending are investigated, and the equivalent model of the BSF is made. By using this equivalent model of the BSF, the BSF is fabricated, and the refractive index profile of the BSF is measured, which is similar to refractive index profile of the proposed BSF. The fabricated variable optical fiber attenuator (VOFA) consists of the BSF in a rectangular rubber ring with a fixed bend radius (BR) in a steady state. The VOFA using the proposed BSF was able to attenuate the optical power by more than about －38 ㏈ at certain wavelengths (1540∼1560 nm) based on adjusting the mechanical pressure applied to the upper surface of the rectangular rubber ring with the bent BSF. In addition, the proposed VOFA produced an insertion loss of 0.68 ㏈, polarization dependent loss (PDL) of about 0.5 ㏈, and return loss of less than －60 ㏈.

• 천문학회지
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• 제55권2호
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• pp.59-66
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• 2022

Stellar magnetic activity is important for formulating the evolution of the star. To represent the stellar magnetic activity, the S index is defined using the Ca II H+K flux measure from the Mount Wilson Observatory. Mg II lines are generated in a manner similar to the formation of Ca II lines, which are more sensitive to weak chromospheric activity. Mg II flux data are available from the International Ultraviolet Explorer (IUE). Thus, the main purpose of this study was to analyze the magnetic activity of stars. We used 343 high-resolution IUE spectra of 14 main-sequence G stars to obtain the Mg II continuum surface flux and Mg II line-core flux around 2,800 Å. We calculated S index using the IUE spectra and compared it with the conventional Mount Wilson S index. We found a color (B - V ) dependent association between the S index and the Mg II emission line-core flux. Furthermore, we attempted to obtain the magnetic activity cycles of these stars based on the new S index. Unfortunately, this was not successful because the IUE observation interval of approximately 17 years is too short to estimate the magnetic activity cycles of G-type stars, whose cycles may be longer than the 11 year mean activity cycle of the sun.

• PNF and Movement
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• 제15권2호
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• pp.195-200
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• 2017

Purpose: This study attempts to identify the effects of stretching and core exercise using proprioceptive neuromuscular facilitation (PNF) on the pain and functional disability index of patients with chronic lower back pain. Methods: A total of 20 patients with chronic lower back pain were randomly divided into either the experimental group (n=10), who received PNF stretching and core exercise, or the control group (n=10), who received conventional physiotherapy. Both interventions were applied three times a week for six weeks. The visible analogue scale (VAS) was measured in order to determine the level of pain, while the Oswestry Disability Index (ODI) was used to measure the change in the functional disability index. We conducted a paired t-test to compare the within-group change before and after the intervention. To compare the between-group difference, we used an independent t-test. The statistical significance level was set at ${\alpha}=0.05$ for all the variables. Results: The experimental group showed a significant within-group change in both the VAS and the ODI (p<0.01). The control group also showed a significant change (p<0.01). A significant difference was observed between the experimental group and the control group with regard to the change in both the VAS and the ODI after the interventions (p<0.01). Conclusion: In this study, the application of stretching and core exercise using PNF for subjects who complain of chronic lower back pain proved effective in reducing both pain and functional disability. We therefore expect that this intervention can be applied in the future as a useful program for patients with chronic lower back pain.

• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.282-282
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• 2006

Nanoporous organosilicate thin films were realized by the microphase separation of pore generating components mixed with an organosilicate matrix. The refractive index of such nanoporous organosilicate films can be tuned in the range of $1.40{\sim}1.22$. With a nanoporous single layer with n ${\sim}1.225,\;99.85\;%$ transmittance in the visible range was achieved. In order to overcome the limitation on the narrow wavelength for high transmittance imposed by single nanoporous thin films, bilayer thin films with different reflectance for each layer were prepared by inserting high refractive index layer with a refractive index of 1.447. It is demonstrated that the novel broadband antireflection coating with improved transmittance can be easily achieved by the nanoporous bilayer thin films described in present study.

• 한국과학교육학회지
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• 제30권8호
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• pp.1031-1043
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• 2010

이 연구의 목적은 과학 교수-학습프로그램의 두뇌 기반 분석을 위한 정성적 정량적 분석방법을 제시하는 것이다. 연구목적 달성을 위해, 첫 번째로 두뇌기반 분석을 위한 분석방법의 고안에는 중학교 과학 교수-학습프로그램 중 한 단원을 연구대상으로 선정하여 분석하였다. 제시된 분석방법의 유용성 검증에는 7차 및 2007 개정 교육과정의 초등학교 과학 교수-학습프로그램 중 네 단원을 연구대상으로 선정하여 검증하였다. 그 결과, 교수-학습 프로그램을 CORE Brain Map을 통해 정성적으로 컨설팅 할 수 있었다. 또한 네트워크 이론으로부터 정량적 분석을 위한 두뇌맞춤지수 산출식(BCI=$\frac{L_o}{11(N_o-1)}{\cdot}{\sum}\limits_{i=1}^4l_iw_i$)을 유도하였다. 이를 통해 단원 및 교육과정에 따른 연구대상 교수-학습프로그램들 간의 정량적 차이를 확인할 수 있었다. 이 연구를 통해 개발된 두뇌기반 과학 교수-학습 프로그램의 정성적 정량적 분석방법은 두뇌기반 다양한 과학 교수-학습 프로그램의 분석 및 진단에 활용 가능할 것으로 전망된다.

• 한국추진공학회지
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• 제19권6호
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• pp.91-97
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• 2015

HTPB/AP/Al 계열의 혼합형 열경화 추진제를 적용한 로켓 연구개발에 있어서의 추진제 기계물성 규격을 정하는 일련의 과정을 고찰하고, 공정지수를 통하여 추진제 제조에서의 공정관리를 분석하였다. 이를 근간으로 기계물성간의 종속성을 분석하고 최적화 물성을 제시함으로서 불량률을 제거하는 공정 안전도 향상뿐만 아니라 추진제 그레인의 구조적 안전도 상승에도 기여할 것이다.

• Steel and Composite Structures
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• 제20권3호
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• pp.513-543
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• 2016

Third order shear deformation theory is used to evaluate electro-elastic solution of a sandwich plate with considering functionally graded (FG) core and composite face sheets made of piezoelectric layers. The plate is resting on the Pasternak foundation and subjected to normal pressure. Short circuited condition is applied on the top and bottom of piezoelectric layers. The governing differential equations of the system can be derived using Hamilton's principle and Maxwell's equation. The Navier's type solution for a sandwich rectangular thick plate with all edges simply supported is used. The numerical results are presented in terms of varying the parameters of the problem such as two elastic foundation parameters, thickness ratio ($h_p/2h$), and power law index on the dimensionless deflection, critical buckling load, electric potential function, and the natural frequency of sandwich rectangular thick plate. The results show that the dimensionless natural frequency and critical buckling load diminish with an increase in the power law index, and vice versa for dimensionless deflection and electrical potential function, because of the sandwich thick plate with considering FG core becomes more flexible; while these results are reverse for thickness ratio.

• 한국운동역학회지
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• 제26권4호
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• pp.383-390
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• 2016

Objective: Gymnastics on rings needs a high level of muscle strength with balance ability for controlling the body. A study on a new balance training program is necessary for elite gymnasts. Therefore, the purpose of this study was to investigate the effects of an 8-week pilates core-muscle training on balance ability and asymmetry index of the L-sit on the rings in male elite gymnasts. Method: Ten elite gymnasts (age: $20.6{\pm}0.7years$, height: $169.9{\pm}4.9cm$, weight: $65.4{\pm}5.6kg$, career duration: $20.6{\pm}0.7years$), who are students at K-university, participated in this study. Results: First, the range of the COM tended to decrease in the anterior-posterior direction. Second, the left hip joint angle and knee extension and ankle dorsiflexion angles significantly increased after the pilates training. Third, the ROM also increased. Fourth, the symmetry value increased in the hip angle, while the symmetry index in all joints of the ROM decreased. As a result, the pilates core-muscle training influenced the static balance ability during the L-sit on the rings. Conclusion: Accordingly, the pilates core-muscle training is suitable in enhancing the basic balance ability in gymnastics on rings.

• 한국도서관정보학회지
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• 제43권1호
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• pp.371-397
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• 2012

이 연구는 공공도서관의 지적자본과 평가지표를 통한 도서관의 지적자본 평가모형을 설계하고자 하였다. 공공도서관은 지식정보서비스 기반 지적자본과 사회자본의 창출자이다. 연구에서는 정보생태환경에 기반을 둔 도서관의 핵심역량과 지표, 지적자본 평가지표를 제시하고 이에 대한 평가모형을 도서관에 적용 가능하도록 하였다. 이 연구의 결과는 도서관의 내외적 환경에 대한 가치와 역량을 정량과 정성적으로 평가할 수 있는 지표가 될 것이다.