• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.3A
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• pp.321-327
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• 2006

In this paper, when a H-polarized plane wave is incident on the grating consisting of uniform resistive strips, electromagnetic scattering is analyzed using the moment of methods (MoM). The current density of each resistive strip on a grounded dielectric plane is fixed by zero at both edges. To satisfy the condition at both ends of each resistive strip, the induced surface current density is expanded in a series of cosine and sine functions. The scattered electromagnetic fields are expanded in a series of floquet mode functions. The boundary conditions are applied to obtain the unknown current coefficients. According to the variation of the involving parameters such as strip width and spacing and angle of the incident field, numerical simulations are performed by applying the Fourier-Galerkin moment method. The numerical results of the normalized reflected power for resistive strips case for zero and several resistivities are obtained.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.3
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• pp.77-86
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• 2002

위성은 일단 한 번 발사하고 나면 운용궤도상에서 수리 및 회수가 거의 불가능하기 때문에 위성에 들어가는 모든 개발 부품들은 완벽한 설계, 충분한 해석, 고 작업도의 제작, 그리고 다양한 시험이 반드시 수반되어야 한다. 위성시스템에서 전자 소자의 신뢰성에 영향을 주는 인자는 다양하다. 과도한 열은 전자소자의 실패를 유발해서 결과적으로는 전체 위성의 실패를 유도할 수 있다. 이 논문에서는 다목적 실용위성 2호의 고전력 소산 전장품의 열부하 완화를 위한 방안을 경우별로 연구 비교하였다. 고전력 소산 전장품의 열부하를 완화하기 위해서는 하우징 두께의 증가가 필요하며, 전력조절기의 다이오드나 트랜지스터처럼 전력소산이 큰 소자에 대해서는 장착위치를 변경하거나 장착 부분의 열전도율을 증가시키는 방법이 필요하다. 또한 전력조절기처럼 장착면이 좁은 경우에는 복사의 영향이 크며, 이러한 전장품의 열부하를 완화하기 위해서는 주위 벽면의 온도를 낮추거나 하우징 표면 방사율을 증가시키는 방법이 효과적임이 알 수 있다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.10a
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• pp.701-704
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• 2011

The reliability of a computer system largely depends on that of its memory systems, which are vulnerable to soft errors. Soft errors can be coped with a combination of an Error Detection & Correction circuit and scrubbing operation. Smaller geometries and lower voltage of advanced memories makes them more prone to suffer multibit soft errors. A memory structure against multibit soft errors and a suitable scrubbing scheme for it were proposed. This paper introduces a key issue for the scrubbing of the memories with protection against multibit soft errors and the result of the performance analysis from a reliability point of view.

• Fire Science and Engineering
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• v.20 no.3 s.63
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• pp.65-70
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• 2006

From the beginning of the construction stage, the fire protection regulation for the nuclear power plants conforms to the design requirements for the acquisition of the license permit. This regulation is based on the plant status of the normal operation, but it is not enough to be used as an application standard for fire protection at the transient mode of the plant and the outage time for refueling as well as for the plant decommissioning. While the advanced fire protection requirement that has been developed in America recently suggests the performance-based requirement and management rule applicable to the overall life time of the plant, it simply represents the conceptual application. It means that it can not be treated as appropriate standards because it does not deal with the qualitative and quantitative approach in specific ways. By the way, with the use of the performance-based fire risk analysis, the dynamic behavior of the heat and smoke at the fire compartment of the nuclear power plants can be analyzed and the thermal effect to the safety-related equipment and cables can be evaluated as well. At this paper, it suggests the ways to change the applicable fire protection regulations and the required evaluation items for the fire risk resulted from the plant configuration change with an intent to introduce the state-of-the-art quantitative fire risk analysis technology at the domestic nuclear power plants.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.2
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• pp.177-183
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• 2005

The effluent quality is directly affected by the separation of biological solids in a final clarifier because the majority of discharged $BOD_5$ and SS are virtually dependent on the results of biological solids in the sedimentation tank effluent. If a final clarifier is effectively designed and operated, the desired goal of clarification for wastewater can be achieved together with the cost reduction in the treatment of wastewater. To this end flow characteristics and the removal efficiency of SS are numerically investigated especially by the change of the inlet position and the installation of baffle to improve the performance of a rectangular final clarifier. The 2-D computer program developed in a rectangular coordinates has been successfully validated against experimental residence time distribution(RTD) curves obtained by tracing radio-isotope. The lowering of the inlet position weakens the density current and induces the settling of SS in the front zone of a clarifier. Thus the decreased traveling distance of the sludge increases the removal efficiency of SS in the effluent. The inlet baffle installed in the front region of clarifier prevents the short circuiting flow and induces to flow into the dense underflow, which eventually improves the effluent quality. In the case of lower inlet position, however, installation of baffle results in degradation of effluent quality. Consequently it is strongly recommended that in-depth numerical study be performed in advance for optimizing a clarifier design and retrofitting to improve effluent quality in a final clarifier.

• Journal of the Korean Society of Propulsion Engineers
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• v.26 no.2
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• pp.12-19
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• 2022

Propellant grains with embedded metal wires have been used for enhancement of burning rate while maintaining high loading density. For the performance design of a solid rocket motor using propellant grain with embedded metal wires, burn-back analysis is required according to number, location, arrangement angle of metal wires, and augmentation ratio of the propellant burning rate near a wire region. In this study, a numerical method to quickly calculate a burning surface area was developed in response to the design change of the propellant grain with embedded metal wires. The burning surface area derived from the developed method was compared with the results of a CAD program. Error rate decreased as the radial size of the grid decreased. Analysis for characteristics of burning surface area was performed according to the number and location of metal wires, the initial and final phases were shortened and the steady-state phase was increased when the number of metal wires increased. When arranging the metal wires at different radii, the burning surface area rapidly increased in the initial phase and sharply decreased in the final phase compared to the case where the metal wires were disposed in the same radius.

• Journal of the Korean GEO-environmental Society
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• v.15 no.12
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• pp.53-59
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• 2014

In order to obtain basic data for reasonable design of rockfall prevention net unreasonably being designed according to experiences, this paper determined a standard cross section and analyzed the effects of parameters such as inclination and height of slope faces, rockfall weight, separation distance on rockfall behaviors such as bounce height, kinetic energy and passage rate. The weight of rockfall changed from 400 kg to 700 kg and then to 1,000 kg. With the height of 20 m as the standard, the test was conducted with the inclination at $63^{\circ}$ and $55^{\circ}$ which may affect rockfall behaviors. Analysis was made while changing the fall height of rockfall from 3 m to 15 m and then to 20 m, thereby analyzing and evaluating changes in maximal kinetic energy occurring in the base of slope. According to the analysis result, in designing a rockfall prevention wire net, a design considering various conditions including inclination of the slope, expected size or weight of rockfall, situation of the slope and the shape of rockfall, and rockfall trace is judged necessary beyond the current uniform application.

• Journal of the Korean Geotechnical Society
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• v.33 no.4
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• pp.5-15
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• 2017

Three-hinge failure occurs in a jointed rock slope with a joint set parallel with slope and a conjugate joint set. Limit Equilibrium Method (LEM) and Finite Element Method (FEM) which are commonly used for slope design, are not suitable for evaluating stability against three-hinge failure, and this study performed parametric study to analyze the failure mechanism and to find influence factors causing three-hinge failure using UDEC which is a commercial two-dimensional DEM based numerical program. Numerical analyses were performed for various joint structural conditions and joint properties as well as ground water conditions. It was found that pore water pressure is the main factor triggering the three-hinge failure and the mode of failure depends on friction angle of basal joint and bedding joint set. The results obtained from this study can be used for adequate and economic footwall slope reinforcement design and construction.

• The Journal of the Acoustical Society of Korea
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• v.11 no.4
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• pp.5-13
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• 1992

The vibration of a vehicle, which is caused by and transmitted from the engine, has significant effect on the ride comfort and the dynamic characteristics of the engine mount system has direct influence on the vibration and noise of the vehicle. This paper examines the body shake caused by the engine excitation force on engine key-off of a jeep by experiment and computer simulation using a general purpose mechanical system program, DADS. The computer simulation model consists of the engine, body including frame, and front and rear axles and each axle has right and left tires. The force element between body and suspension is modeled as a combination of suspension spring and damper, and the unsprung mass has roll and pitch motion. The body shake obtained from experiment was compared with the result of computer simulation. Parametric study of the body shake on engine key-off is performed with changing the stiffness of engine mount rubber, the engine mount installation angle and position of engine mounts by using the verified computer simulation model.

• Magazine of the Korean Society of Agricultural Engineers
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• v.16 no.4
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• pp.3572-3584
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• 1974

본 논문은 Thrower의 양곡성능에 관한 예측 방정식을 차원해석법을 적용하여 유도하는데 있다. Thrower의 능률에 큰 영향을 미친다고 생각되는 인자들간의 관계식들을 Buckingham의 $\pi$이론에 의하여 구하여 졌으며 본연구에 사용한 Thrower는 현재 농촌에서 사용되고 있는 자동탈곡기의 Thrower와 유사한 형으로 제작된 것이며 실험에 사용된 시료는 벼의 경우는 통일벼와 미네히까리 품종이고 보리 품종으로서는 나맥이며, Thrower의 Impeller 직경, 속도 및 투입량을 변화시켜 가면서 각 시료에 대하여 양곡높이를 측정하여 그 예측방정식을 유도하였다. 본 논문에서 얻은 결과는 다음과 같다. 1. Thrower의 양곡성능에 지대한 영향을 미친다고 생각되는 주요 인자들을 Thrower의 양정, impeller의 직경과 속도, 투입량, 곡립의 밀도, 중력가속도등이라 간주하여 Buckingham의 $\pi$이론을 적용하여 이들에 관한 $\pi$항들을 결정하였으며 그 결과는 다음과 같다. {{{{ pi 1= { D} over {H } , pi 2= { { DN}^{ { 1} over {2 } } } over { { g}^{ { 1} over { 2} } }, pi 3= { Q} over { { g}^{ { 1} over {2 } } { rho D}^{ { 2} over {6 } } }}}}} 2. 실험에 의하여 구해진 $\pi$항문의 관계식을 합성하여 Thrower의 양곡성능에 관한 시료별 예측방정식을 구하였으며 이 식들은 아래와 같다. 통일 : $\pi$1=0.1223($\pi$2)-1.1813$\times$($\pi$3)-0.1864 미네히까리 : $\pi$1=0.1185($\pi$2)-0.9663$\times$($\pi$3)-0.1575 나맥 : $\pi$1=0.1599($\pi$2)-1.2350$\times$($\pi$3)-0.1382 3. 현재 농촌에서 사용되고 있는 자동탈곡기체 부착된 Thrower의 회전수, Impeller의 직경 및 투입량은 각각 1,100rpm, 30cm 및 150gr/sec 정도로서 이와같은 수준의 변량들을 기초로 하여 본 논문에서 유도한 예측방정식을 적용하여 Thrower의 양정을 산출한 결과, 통일벼의 경우는 2.6m정도였고 미네히까리 품종과 나맥의 양정은 각각 2.4m, 2.9m 정도였다. 이와같은 사실로부터 1m내외의 양정만으로 되어있는 자동탈곡기 Thrower의 경우 제작비절감, 소요동력 감소를 기하고 아울러 과립의 손상을 줄이기 위해서는 설계 또는 작동조건의 변경을 통해 Thrower의 회전수를 현재 수준이하로 줄일 필요가 있다고 판단되었다.