• 충청수학회지
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• 제22권3호
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• pp.409-416
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• 2009

In this paper, we study the geometry of lightlike hypersurfaces of a semi-Riemannian manifold. We prove a classification theorem for lightlike hypersurfaces M with totally umbilical screen distributions of a semi-Riemannian space form.

• East Asian mathematical journal
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• 제31권3호
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• pp.337-344
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• 2015

We study screen quasi-conformal irrotational half lightlike submanifolds M of a semi-Riemannian space form $\bar{M}$ (c) equipped with a semi-symmetric non-metric connection subject such that the structure vector field of $\bar{M}$ (c) belongs to the screen distribution S(TM). The main result is a non-existence theorem for such half lightlike submanifolds.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 1999년도 추계연구발표회 논문개요집
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• pp.84-85
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• 1999

• 생물환경조절학회지
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• 제29권1호
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• pp.52-61
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• 2020

겨울철 벤로형 유리온실(W59×L68×H5.9m) 보온스크린 높이의 차이에 따른 실내온도 변화를 파악하기 위하여 00시부터 04시까지 30분 간격으로 열유동해석을 하였다. 초기에는 상대적으로 난방 외부접촉면적이 큰 보온스크린 설치높이 5.9m에서 보온스크린 설치높이 4.1m에 비해 온도감소가 빨라 낮은 온도를 나타냈으나 해석 2시간 이후부터는 상대적으로 온도감소가 느렸고 04시에는 0.6℃ 높았다. 그러나 해석시작1시간 후 실내온도가 약13℃까지 내려가고, 그 이전에 난방기가 작동해야 된다고 볼 때, 해석 2시간 동안 온도감소가 상대적으로 느렸던 보온스크린 설치높이 4.1m에서 5.1m에 비해 난방에너지 절감에 유리할 것으로 판단되었다. 토마토가 자라는 지면 2m 높이에서의 유동은 보온스크린 설치높이 5.9m에서 4.1m에 비해 상대적으로 넓고 빨랐으며 유동해석 1시간 후인 01시의 평균차이는 0.034m·s^-1였다. 여름철 차광스크린 설치높이를 5.7m와 3.9m로 달리하되70%닫힘 조건에서 12시부터 13시까지는 온실하부덕트 외부공기유입량 0.67㎥·s^-1 상태 그 후부터는 외부 유입공기를 3배로 증가하여 냉방효과를 비교하였다. 초기 12시부터 13시까지는 차광스크린 70%닫힘 상태에서 무차광에 비해 오히려 평균 약0.9℃ 높았지만 외부공기유입량이 증가하는 13시 이후 부터는 차광스크린 70%닫힘 조건에서 온도가 감소하였고 14시 30분에는 무차광에 비해 0.5℃ 낮았다. 차광스크린 70% 닫힘 조건에서 바닥면의 온도분포는 스크린 설치높이와 개방 정도에 비례하여 낮았으며 무차광에 비해 8℃이상 낮았다. 온실 내 상대습도는 차광스크린을 30% 개방하는 조건에서는 차광스크린의 높이나 개방정도에 따른 차이가 미미하였다.

• 인터넷정보학회논문지
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• 제13권2호
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• pp.21-32
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• 2012

본 논문은 씬클라이언트 환경에서 클라우드 컴퓨팅을 이용하여 N-Screen-as-a-Service(NaaS) 기반하여 통합 된 어플리케이션을 스트리밍하기 위한 Virtual Aggregation Gateway(VAG)를 제안한다. 또한, 본 논문에서는 인터넷을 통하여 대용량 멀티 클라이언트에서의 융합된 어플리케이션 스트림의 화면 공유 시 서버 측 문제에 대해 기술한다. 특히, 콘텐츠를 전달하기 위해 가능한 모든 미디어 시그널링을 효율적으로 관리를 하는 N-Screen 세션 관리자 프레임워크를 제안한다. 더 나아가, 사용자들에게 재생 멀티미디어 콘텐츠 (TV 드라마, 광고, 대본 등)를 제공한다. 제안한 N-Screen 세션 관리자의 목표는 다음과 같다. (1) 모든 통신 세션의 세션 상태를 관리 (2) 수신된 요구사항이나 답변들의 제어를 관리 (3) 사용자들에게 언제 어디서든 이기종 단말에 화면을 공유하면서 멀티미디어 콘텐츠를 재생 그리고 (4) 사용자들이 진행 중인 통신 세션을 이기종 단말로 전환을 가능하게 해준다. 마지막으로, Session Initiation Protocol (SIP)에서의 보안 문제점 및 재생 혹은 전송 세션에서의 지연을 최소화 하는 것에 대해 기술한다.

• 한국생산제조학회지
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• 제21권3호
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• pp.408-414
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• 2012

Screen printing is a printing method that uses a woven mesh to support an ink-blocking stencil by transferring ink or other printable materials in order to form an image onto a substrate. Recently, the screen printing method has applied to micro-electronic packaging by using solder paste as a printable material. For the screen printing of solder paste, metal masks containing a number of micro-holes are used as a stencil material. The metal mask undergoes deformation when it is installed in the screen printing machine, which results in the deformation of micro-holes. In the present study, finite element (FE) analysis was performed to predict the amount of deformation of a metal mask. For an efficient calculation of the micro-holes of the metal mask, the sub-domain analysis method was applied to perform FE analyses connecting the global domain (the metal mask) and the local domain (micro-holes). The FE analyses were then performed to evaluate the effects of slot designs on the deformation characteristics, from which more uniform and adjustable deformation of the metal mask can be obtained.

• Steel and Composite Structures
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• 제43권5호
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• pp.533-552
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• 2022

The current article deals with the dynamic stability, and structural improvement of vibrating electrically curved screen on the viscoelastic substrate. By considering optimum value for radius curvature of the electrically curved screen, the structure improvement of the system occurs. For modeling the electrically system, the Maxwell's' equation is developed. Hertz contact model in employed to obtain contact forces between impactor and structure. Moreover, variational methods and nonlinear von Kármán model are used to derive boundary conditions (BCs) and nonlinear governing equations of the vibrating electrically curved screen. Galerkin and Multiple scales solution approach are coupled to solve the nonlinear set of governing equations of the vibrating electrically curved screen. Along with the analytical solution, 3D finite element simulation via ABAQUS package is provided with the aid of a FE package for simulating the current system's response. The results are categorized in 3 different sections. First, effects of geometrical and material parameters on the vibrational performance and stability of the curves panel. Second, physical properties of the impactor are taken in to account and their effect on the absorbed energy and velocity profile of the impactor are presented. Finally, effect of the radius and initial velocity on the mode shapes of the current structure is demonstrated.

• 농업과학연구
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• 제43권3호
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• pp.496-505
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• 2016

The purpose of this study was to investigate the economic effects of a flame retardant aluminum screen developed by a company Economic effects were analyzed in terms of micro and macro-economic aspects. In the macro-economic aspect, economic effects were analyzed under the assumptions that the total import volume of flame retardant aluminum screen was approximately $50m^2$ in 2015 and that possible import substitution rates were 100%, 80%, and 60%. Results showed economic values of 2.25 billion won (100% import substitution rates), 1.8 billion won (80% import substitution rates), and 1.35 billion won (60% import substitution rates). If existing farms which had been using imported flame retardant aluminum screen replaced it newly developed with the flame-retardant aluminum screen developed in this study at rates of 100%, 80%, and 60%, the farms could save 750 million won, 60 million won, and 45 million won, respectively. Furthermore, the social cost savings from fire prevention could be 1.184 billion won. In the micro-economic aspect, if a farm with a typical-size ($1,000m^2$) greenhouse growing red pepper wanted to install flame retardant aluminum screen instead of generic aluminum screen, the farm may only pay an additional cost of 720,000 won. In comparison, if the farm chose fire insurance instead of flame-retardant aluminum screen, then the farm would pay 21,000,000 won for fire insurance. The above results show that the economic effect of flame retardant aluminum screen developed by the company would be be very efficient compared to the imported one.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.873-876
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• 2000

Characteristics of piezoelectric thick films prepared by screen printing method were investigated. The piezoelectric thick films were printed using Pb(Mg,Nb)O$_3$-Pb(Zr,Ti)O$_3$system. The lower electrodes were coated with various thickness of Ag-Pd by screen printing to investigate the effect as a diffusion barrier and deposited with Pt by sputtering on Ag-Pd. The ceramic paste was prepared by mixing powder and binder with various ratios using three roll miller. The fabricated thick films were burned out at 650$^{\circ}C$ and sintered at 950$^{\circ}C$ in the O$_2$condition for each 20, 60min after printing with 350mesh screen. The thickness of piezoelectric thick film was 15∼20 $\mu\textrm{m}$ and the Ag-Pd electrode acted as a diffusion barrier above 3 $\mu\textrm{m}$ thickness. When the lower electrode Ag-Pd was 6 $\mu\textrm{m}$ and the piezoelectric thick films were sintered by 2nd step (650$^{\circ}C$/20min and 950$^{\circ}C$/1h) using paste mixed Pb(Mg,Nb)O$_3$-Pb(Zr,Ti)O$_3$$.$ MnO$_2$+ Bi$_2$O$_3$. V$_2$O$\_$5/ and binder in the ratio of 70:30, the remnant polarization of thick film was 9.1 ${\mu}$C /cm$^2$.

• 환경영향평가
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• 제9권3호
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• pp.249-255
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• 2000

The comparison of three different kind of simulation by screen3 model, Tem-8 model and EPA formula were undertaken to get a potential concentration and hourly maximum concentration of fugitive dust produced from each construction site in the downtown area of puchon city. The amount of dust estimate U.S EPA formula and fugitive dust formula 22.6078g/sec, 27.9572g/sec respectively. Hourly maximum concenstration at the distance from each construction site by screen3 model are average of $78.89{\sim}728.40{\mu}g/m^3$ and Tem-8 model are $97{\mu}g/m^3$ in site-1, $241{\mu}g/m^3$ in site-2, $268{\mu}g/m^3$ in site-3, $232{\mu}g/m^3$ in site-4, $69{\mu}g/m^3$ in site-5, $36{\mu}g/m^3$ in site-6. Through our experiment, Screen3 model is more encouragingly used than any other model.