• Journal of computational fluids engineering
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• v.14 no.3
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• pp.105-114
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• 2009

A numerical study of the flow characteristics inside a U-type circular tube is carried out in this paper. The numerical simulations carried out by using a Navier-Stokes code which is commercially available. Before detailed numerical simulations, validation of present numerical approach is made by comparing numerical solutions with experimental data. Numerical simulations are performed to study the effect of curvature on the flow characteristics inside a U-type tube. Numerical solutions show that a significant effect on the secondary flow structure in the cross section of the tube, especially in the curved section is shown when the curvature ratio, ratio of curvature to tube diameter, is smaller than about 3.5. As the curvature ratio decreases below 3.5, a counter rotating vortex is found below the primary vortex in the cross section of the tube. Another dramatic change of the flow structure is the formation of streamwise separation zone when the curvature ratio is decreased below 1.25.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.6
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• pp.1281-1286
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• 2012

In the information age, internet was developed from the wired access to the wireless Internet access. When a surge in demand for wireless Internet access, efficiency and performance of 2.4GHz band which leads to saturation of the communication was significantly fall. in this paper, the U-slot microstrip array antenna in the 5 GHz band have been studied to improve the drawback of a narrow bandwidth of the T-slot micro strip antenna. The characteristics of single antenna and array antenna was investigated to obtain the optimum frequency properties. The optimal U-slot microstrip array antenna possibility was confirmed.

• Journal of electromagnetic engineering and science
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• v.17 no.1
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• pp.44-49
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• 2017

A compact planar microstrip-fed ultra-wideband (UWB) antenna with a dual band-notched for UWB application is presented and analyzed. By inserting a U-shaped slot and inverted U-shaped slot into the pot-shaped radiator, two notched bands are achieved. By optimizing the width and length of the U-shaped slots and inverted U-shaped slot, a desired bandwidth of voltage standing wave ratio (VSWR) less than 2.0 can be achieved, ranging from UWB bands with notched dual bands. The proposed antenna is fabricated on an inexpensive FR-4 substrate with overall dimensions of $28.0mm{\times}39.5mm$. The measured results confirm that the proposed antenna covers from 1.775 to over 13.075 GHz with two rejection bands of around 3.325-3.925 GHz and 5.3125-6.025 GHz. In addition, the proposed antenna showed good radiation characteristics and gains in the UWB bands.

• Biotechnology and Bioprocess Engineering:BBE
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• v.3 no.1
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• pp.44-47
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• 1998

Maximum cellulase production was sought by comparing the activities of the cellulases produced by different Trichoderma reesei strains and Aspergillus niger. Trichoderma reesei Rut-C30 showed higher cellulase activity than other Trichoderma reesei stains and Aspergillus niger that was isolated from soil. By optimizing the cultivation conditions during shake flask culture, higher cellulase production could be achieved. The FP(filter paper) activity of 3.7U/ml and CMCase (Carboxymethylcellulase) activity of 60U/ml were obtained from shake flask culture. When it was grown in 2.5L fermentor, where pH and DO levels are controlled, the enzyme activities were 133.35U/ml (CMCase) and 11.67U/ml(FP), respectively. Ammonium sulfate precipitation method was used to recover enzymes from fermentation broth. The dried cellulase powder showed 3074.9U/g of CMCase activity and 166.7U/g of FP activity with 83.5% CMCase recovery.

• Journal of Chest Surgery
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• v.49 no.5
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• pp.383-386
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• 2016

Anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA) is an extremely rare, potentially fatal, congenital anomaly with a high mortality rate in the first year of life. It occurs rarely in adulthood and may appear with malignant ventricular arrhythmia or sudden death. We report a case of a 49-year-old woman with ALCAPA who presented with dyspnea on exertion. Management was coronary artery bypass grafting to the left anterior descending artery and obtuse marginal arteries, closure of the left main coronary artery ostium, and reestablishment of the dual coronary artery system.

• Digital Contents
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• no.5 s.120
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• pp.28-31
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• 2003

우리나라를 IT 선도국가로 우뚝 세울 '유비쿼터스 IT코리아 포럼(Ubiquitous IT Korea Forum,약칭 u-Korea 포럼)'이 지난달 15일 공식 출범했다. 이날 창립총회에서는 오길록 한국전자통신연구원(ETRI)원장이 u-Korea 포럼 초대의장으로 한국네트워크연구조합 최승태 전무가 감사로 각각 선임됐다. 또 실질적인 포럼 운영을 위해 이성국 u-Korea 포럼 준비위원장(ETRI 정보화기술연구소장)과 유한용 삼성종합기술원 전무, 장성환 KT 경영연구소장, 오해석 숭실대학교 교수, 한수용 SK 경영경제연구소 상무 등이 참여하는 운영위원회도 구성 됐다.u-Korea 포럼의 초대 의장으로 선임된 오길록 ETRI 원장을 만나 유비쿼터스 사회의 특징과 이를 위한 각계의 역할에 대해 들어보는 시간을 가졌다.

• East Asian mathematical journal
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• v.32 no.5
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• pp.651-658
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• 2016

In a bounded domain, we consider $$u_{tt}-{\Delta}u+{\normalsize\displaystyle\smashmargin{2}{\int\nolimits_0}^t}\;g(t-{\tau}){\Delta}ud{\tau}+u_t={\mid}u{\mid}^pu$$, where p > 0 and g is a nonnegative and decaying function. We establish a general decay result which is not necessarily of exponential or polynomial type.

• Korean Journal of Mathematics
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• v.5 no.1
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• pp.29-33
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• 1997

In this paper we investigate the existence of positive solutions of a nonlinear biharmonic equation under Dirichlet boundary condition in a bounded open set ${\Omega}$ in $\mathbf{R}^n$, i.e., $${\Delta}^2u+c{\Delta}u=bu^{+}+s\;in\;{\Omega},\\u=0,\;{\Delta}u=0\;on\;{\partial}{\Omega}$$.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.10a
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• pp.355-360
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• 2000

This paper presents properties of piecewise cubic B-spline function and Rayleigh-Ritz method to compute the smallest eigenvales. In order to compute the smallest eigenvalues, Rayleigh quotient approach is used and four different types of finite element approximating functions corresponding to the statical deflection curve, spanned by the linearly independent set of piecewise cubic B-spline functions with equally spaced 5 knots from a partion of [0, 1], each satisfying homogeneous boundary conditions with constraining effects are used to compute the smallest eigenvalues for a Sturm-Lionville boundary equations of u"＋ λ²u＝0, u(0.0)＝u(0.0)＝0, 0≤x≤1.0.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.17 no.2
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• pp.75-81
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• 2007

Densification and grain growth have been investigated in 5 wt% $U_3O_8$ seeded $UO_2$ and compared with those of the common $UO_2$ pellet. $UO_2$ compacts and $U_3O_8$ seeded $UO_2$ compacts were sintered at $1300{\sim}1700^{\circ}C$ for 0 h to 4 h. Density and grain size of the sintered pellets were measured by the water immersion method and the image analyzer, respectively. The seeded pellet has a slightly lower density during the intermediate sintering stage. However, the difference of density between two pellets decreases to about 0.5%TD with increasing the sintering temperature. The grain size of the two pellets is similar until $1600^{\circ}C$ but that of the seeded pellet rapidly increases with increasing the sintering temperature.