• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1185-1186
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• 2007

The UTM-01 developed in 1998 was the first maglev vehicle in Korea for the urban transit maglev (UTM) system. Through the improvement of UTM-01 and development of UTM02, the commercialization of the UTM system is being prepared now. In order to prepare for the commercialization of maglev, it is necessary that an optimal design of the levitation magnet should be provided for the safe operation of the vehicle. The levitation force is formed through the function of magnetic flux density on the top of magnet poles and gap between magnet pole and guide rail. To generate a magnetic field that is high enough to levitate the vehicle, ferromagnetic materials, such as pure iron for magnet pole and SS400 for guide rail, were used. The heat generated by $I^2R$ loss of magnet conductor makes the thermal convection on the surface of magnet including coil and poles. As these two characteristics are nonlinear phenomena, this paper deals with the nonlinear analysis on the magnetic and thermal properties of the U-type levitation magnet by using 3-D finite element method (FEM). Base on the analysis results, a small scale U-type magnet was designed, manufactured, and tested and it was verified that the magnet manufactured was satisfactory to all the design specifications.

• Nuclear Engineering and Technology
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• 제45권3호
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• pp.401-414
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• 2013

HTR50S is a small modular reactor system based on HTGR. It is designed for a triad of applications to be implemented in successive stages. In the first stage, a base plant for heat and power is constructed of the fuel proven in JAEA's $950^{\circ}C$, 30MWt test reactor HTTR and a conventional steam turbine to minimize development risk. While the outlet temperature is lowered to $750^{\circ}C$ for the steam turbine, thermal power is raised to 50MWt by enabling 40% greater power density in 20% taller core than the HTTR. However the fuel temperature limit and reactor pressure vessel diameter are kept. In second stage, a new fuel that is currently under development at JAEA will allow the core outlet temperature to be raised to $900^{\circ}C$ for the purpose of demonstrating more efficient gas turbine power generation and high temperature heat supply. The third stage adds a demonstration of nuclear-heated hydrogen production by a thermochemical process. A licensing approach to coupling high temperature industrial process to nuclear reactor will be developed. The low initial risk and the high longer-term potential for performance expansion attract development of the HTR50S as a multipurpose industrial or distributed energy source.

• Archives of Plastic Surgery
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• 제37권4호
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• pp.477-480
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• 2010

Purpose: Ganglioneuromas are well-differentiated tumors derived from neuroectodermal neural crest cells. Although these tumors can occur anywhere along the sympathetic chain from the base of the skull to the pelvic cavity, they usually develop in the posterior mediastinum and retroperitoneum these tumors are rarely found in the cervical region. Method: We report the case of a 16-year-old male patient with neurofibromatosis type 1 who was admitted because of a palpable mass centrally located on the left side of the neck. A preoperative contrast-enhanced neck computed tomography image showed a low-density homogeneous mass on the parapharyngeal space along with marked displacement of the trachea and carotid vessels. Round and soft masses were also detected on both axillae. Results: The patient subsequently underwent complete excision of the neck mass via the transcervical approach. The mass was smooth and well encapsulated between the sternocleidomastoid muscle and the trachea. Further, the mass appeared to arise from the cervical sympathetic chain, which was preserved during surgery. Both the axillary masses were also excised. The histopathological findings were ganglioneuroma for the neck mass and neurofibroma for both the axillary masses. Conclusion: Cervical ganglioneuromas are rare tumors that present as enlarging parapharyngeal cervical masses in the oropharynx or neck. To our knowledge, a case of cervical ganglioneuroma associated with neurofibromatosis type 1 has never been reported. In patients with neurofibromatosis, multiple tumors may develop, and therefore periodic clinical and radiological follow-up is recommended. Further, repeated imaging analysis should be performed if the presence of another tumor is suspected.

• 한국재료학회지
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• 제17권10호
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• pp.509-515
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• 2007

In order to fabricate adhesiveless 2-layer flexible copper clad laminate (FCCL) used for COF (chip on film) with high peel strength, polyimide (PI; Kapton-EN, $38\;{\mu}m$) surface was modified by reactive $O_2^+$ and $N_2O^+$ ion beam irradiation. 300 mm-long linear electron-Hall drift ion source was used for ion irradiation with ion current density (J) higher than $0.5\;mA/cm^2$ and energy lower than 200 eV. By vacuum web coating process, PI surface was modified by linear ion source and then 10-20 nm thick Ni-Cr and 200 nm thick Cu film were in-situ sputtered as a tie layer and seed layer, respectively. Above this sputtered layer, another $8-9{\mu}m$ thick Cu layer was grown by electroplating and subsequently acid and base resistance and thermal stability were tested for examining the change of peel strength. Peel strength for the FCCLs treated by both $O_2^+$ and $N_2O^+$ ion irradiation showed similar magnitudes and increased as the thickness of tie layer increased. FCCL with Cu (200 nm)/Ni-Cr (20 nm)/PI structure irradiated with $N_2O^+$ at $1{\times}10^{16}/cm^2$ ion fluence was proved to have a strong peel strength of 0.73 kgf/cm for as-received and 0.34 kgf/cm after thermal test.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2000년도 제13회 춘계학술대회 및 임시총회 학술발표 논문집
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• pp.28-35
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• 2000

데이터 웨어하우스에서 실체화 할 뷰들을 알맞게 선택하는 것은 분석적인 질의에 대한 정확하고 신속한 응답을 얻기 위해서 대단히 중요한 문제이다. 기존의 알고리즘들에서는 릴레이션 전체가 실체화 뷰들로서 고려되었다. 그러나, 릴레이션의 부분 대신 전체를 실체화한다는 것은 시간과 공간 비용측면에서 좋지 못한 성능을 초래한다. 따라서, 우리는 이러한 문제를 해결함과 동시에 데이터 웨어하우스의 성능을 향상시키기 위해서 새로운 실체화 뷰 선택 알고리즘을 제안한다. 제안된 알고리즘 ASVMR(Algorithm for Selection of Views to Materialize using Reduced table)에서는 먼저 속성-값들의 농도에 기반을 둔 자동 클러스터링을 사용하여 축약 테이블들을 데이터 웨어하우스에서 생성하고, 그리고 원래의 베이스 릴레이션들의 조합 대신에 축약 테이블들의 조합을 실체화 뷰들로 고려한다. 실험결과에서 시간 및 공간 모두에서 기존 알고리즘들보다 약 1.8배의 성능향상이 있음을 알 수 있다.

• 한국지리정보학회지
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• 제12권3호
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• pp.143-151
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• 2009

임상도는 산림자원이 어디에 어떻게 얼마나 분포하고 있는가를 보여주는 대표적인 산림지도로 전국 산림에 대해 임상, 영급, 경급, 소밀도 등 다양한 산림정보를 제공하여 산림정책 수립의 주요한 자료로 활용될 뿐만 아니라 토지적성평가, 생태자연도 제작 등 다양한 분야의 기초 자료로 활용되고 있다. 최초의 수치임상도는 1차 NGIS 사업을 통해 제작되었는데 당시 수치임상도제작 표준의 부재로 도엽 간 경계 및 속성 불일치 등 여러 가지 유형의 오류가 발생하였다. 또한 임상도의 제작시기, 항공사진 촬영시기, 속성 설명 등 임상도에 관한 보다 자세한 정보를 알기 어려웠다. 이러한 문제점을 해결하기 위해 본 연구에서는 수치임상도 DB 설계부터 수치화, 메타데이터 입력, 품질관리 등의 수치임상도 전 제작과정을 3단계 33개 단위 공정으로 구조화하고 이를 최적화하여 표준화한 수치임상도 표준제작체계를 개발하였다. 본 수치임상도 표준제작체계를 토대로 전국 수치임상도를 일관된 품질로 제작하고 수치임상도에 대한 보다 상세한 정보를 표준메타데이터를 통해 제공할 수 있게 되었다.

• 한국추진공학회지
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• 제16권4호
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• pp.33-41
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• 2012

KM6 단기추진제의 저장수명을 감마과정 이론을 이용한 확률론적 방법으로 추산하였다. 장기 저장에 따른 안정제 함량의 저하량이 0.8%일 때를 상태고장으로 보았으며 정상감마과정으로 가정하였을 때 형상함수의 상수와 척도모수를 모멘트법으로 추정하였다. 저장기간별 확률밀도함수로부터 각 저장기간에서의 상태분포를 확인할 수 있으며 누적고장분포함수 곡선에서 누적고장확률이 10%인 $B_{10}$수명은 25년이며 $B_{50}$수명은 36년으로 추산되었다. 실용적 관점에서 볼 때 $B_{50}$수명을 평균저장수명으로 볼 수 있으며 확률과정론을 이용하면 저장수명을 분포곡선으로 표현할 수 있다.

• Journal of the Optical Society of Korea
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• 제17권6호
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• pp.548-558
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• 2013

In this work, laser induced breakdown spectroscopy (LIBS) is used to investigate soil samples collected from different desert areas of Riyadh city in Saudi Arabia. Both qualitative analysis and plasma parameters are studied via the observed LIBS spectra. These experiments have been done using a Spectrolaser-7000 system with 50 mJ fundamental wavelength of Nd:YAG laser and detection delay time of 1 microsecond. Many spectral lines are highly resolved for many elements like Al, Fe, Mg, Si, Mn, Na, Ca and K. The electron temperatures Te and electron densities Ne, for the constituent of generated LIBS plasma, are determined for all the collected samples. It is found that both Te and Ne vary from one desert area to other. This variation is due to the change of the elemental concentration in different desert areas that affects the sample's matrices. Time dependent measurements have also been performed on the soil samples. While the signal-to-base ratio (SBR) reached its optimal value at 1 microsecond, the plasma parameters Ne and Te reach values of $4{\times}10^{17}cm^{-3}$ and 9235 K, respectively, at 2.5 microsecond. The later indicate that the plasma cooling processes are slow in comparison to the previously observed results for metallic samples. The observed results show also that in the future it is possible to enhance the exploitation of LIBS in the remote on-line environmental monitoring application, by following up only the values of Ne and Te for one element of the soil desert sample using an optical fiber probe.

• 한국기후변화학회지
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• 제7권2호
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• pp.143-155
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• 2016

Present work aims to establish the countermeasure for the better maintenance and preservation of insular floristic diversity at the South Sea of Jeollanamdo Province, ROK, where unique ecosystems are under threat due to climate change, anthropogenic disturbance and habitat destruction. Numerous flora reports from 15 inhabited islands and 60 uninhabited islands as well as field survey data are collated for the compilation of floristic data base and island biogeographical analysis. Out of the 1,940 vascular plant species from 180 families occurring in studies areas, 30.1 percentage or 584 plant species are physiognomically belonging to arboreal plants. Average number of species at individual island is numbered about 222 species, but it varies from about 591 species at the inhabited islands to 129 species at the uninhabited islands. Only 0.15 percentage of species with high proportion above 0.9 in its relative occurrence rate occurs at 68 islands and it includes three species, such as Pinus thunbergii, Eurya japonica and Pteridium aquilinum var. latiusculum. However, about 68 percentage of plant species occurring in study area is confined their distribution to less than seven islands. Presence of high proportion of notable plants in small islands, i.e., 10 critically endangered species compared with 5.5 species in average, 9 endangered species (average 4.2 spp.) at Sonjookdo, and 7 critically endangered species, 8 endangered species at Sokomundo may due to existence of diverse geological and topographical environmental diversity as well as lower human population density and remoteness from the mainland. Since island is small in size and geographically isolated, minor environmental and ecological burdens can cause the critical damages to the diversity of flora and vegetation, urgent island biogeographical research is needed for the scientific conservation and management of island biodiversity.

• 한국수소및신에너지학회논문집
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• 제30권4호
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• pp.303-311
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• 2019

Reversible solid oxide fuel cell (RSOFC) has become a prospective device for energy storage and hydrogen production. Many studies have been conducted around the world focusing on system efficiency improvement and realization. The system should have not only high efficiency but also a certain level of simplicity for stable operation. External waste steam utilization was proved to remarkably increase the efficiency at solid oxide electrolysis system. In this study, RSOFC system coupled with waste steam was proposed and optimized in term of simplicity and efficiency. Ejector for fuel recirculation is selected due to its simple design and high stability. Three system configurations using ejector for fuel recirculation were investigated for performance of design condition. In parametric study, the system efficiencies at different current density were analyzed. The system configurations were simulated using validated lumped model in EBSILON(R) program. The system components, balance of plants, were designed to work in both electrolysis and fuel cell modes, and their off-design characteristics were taken into account. The base case calculation shows that, the system with suction pump results in slightly lower efficiency but stack can be operated more stable with same inlet pressure of fuel and air electrode.