• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2001년도 하계학술대회 논문집 C
• /
• pp.1747-1749
• /
• 2001

This paper simulated discharge progress and partial discharge using needle-plan electrodes system in $SF_6$, studied the distribution of frequency spectrum of the radiated electromagnetic waves using biconical antenna and spectrum analyzer. From results of this study, a method was introduced for measurement and analysis of the radiated electromagnetic waves in accordance with discharge progress in $SF_6$. Besides, according to the consideration of the mutual relation between frequency spectrum of the radiated electromagnetic waves and discharge progress, it was confirmed that detecting partial discharge and estimating discharge progress in $SF_6$ can be possible.

• 한국전자파학회:학술대회논문집
• /
• 한국전자파학회 2003년도 종합학술발표회 논문집 Vol.13 No.1
• /
• pp.555-559
• /
• 2003

Recently, in accordance with the commercialization of novel radio frequency utilization technologies, the radiated power must be rigorously limited for the purpose of protection of wireless facilities against frequency jamming or interference and for maintaining the quality of communication service. At present, the output power is measured from the conducted power for the domestic measurement criterion but is not a real radiated power and inaccurate. So, it is peformed to survey the more precisely accurate measurement scheme and analyze its criterion and methodology in comparison with foreign one. As a result of surveying and analyzing, it is concluded that the U.S. and E.U. is actually using the measurement method in consideration of terms of the Equivalent Isotropic Radiated Power(EIRP) and Effective Radiated power(ERP). In case of the frequency below 1 GHz, the half wave-length dipole antenna is used to measure the ERP and above 1 GHz the horn antenna as a reference antenna is used to measure the EIRP. Therefore, for the domestic purpose it is also necessary to take EIRP and ERP into consideration as a measurement criterion in order to make an accurate measurement and regulation.

• 한국소음진동공학회논문집
• /
• 제23권7호
• /
• pp.605-616
• /
• 2013

An important source of noise from railways is rolling noise caused by wheel and rail vibrations induced by acoustic roughness at the wheel-rail contact. In the present paper, characteristics of rail vibration and radiated sound power from concrete slab tracks for domestic high speed train(KTX) is investigated by means of a numerical method. The waveguide finite element and boundary element are combined and applied for this analysis. The concrete slab track is modelled simply with a rail and rail pad regarding the concrete slab as a rigid ground. The wave types which contribute significantly to the rail vibration and radiated noise are identified in terms of the mobility and decay rates. In addition, the effect of the rail pad stiffness on the radiated power is examined for two different rail pad stiffnesses.

• 한국해양환경ㆍ에너지학회지
• /
• 제19권3호
• /
• pp.185-193
• /
• 2016

본 연구에서는 부유식 풍력-파력 복합발전 플랫폼 안에 설치된 다수 파력발전기의 현 배치안을 부체 간의 상호 간섭효과를 고려하여 평가하였다. 다수 부체가 수면 위에 떠 있는 경우, 순수한 입사파와 함께 인접한 부체에 의해 발생하는 산란파와 방사파의 영향으로 인해 다수 부체 간의 상호작용 과정은 매우 복잡하다. 다수 파력발전기 배열에 따른 회절 및 방사 문제의 상호작용 해석을 위하여 고유함수전개법을 적용하였다. 해석해의 타당성을 검증하기 위하여 상용 프로그램인 WAMIT으로부터 계산된 수치계산 결과와 비교하였다. 다수 부체 간의 상호 간섭효과를 나타내는 q-factor를 이용하여 복합발전 플랫폼내의 24기 파력발전기의 현 배치안에 대한 전체 성능을 평가하였다.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2000년도 하계종합학술대회 논문집(4)
• /
• pp.186-189
• /
• 2000

In this paper, the relation between the vibration and the sound radiated due to the piezoelectric ESWL (Extra-corporeal Shock Wave Lithotripter) is examined And the relation between the focus and the vibration of the objects is examined. The same experiments with the objects that can be breton are done and the relation between the vibration and the break efficiency of the phantom is experimentally investigated. These results show that the relativity between the power of the peak frequency and the break efficiency can be confirmed.

• 한국전자파학회지:전자파기술
• /
• 제2권4호
• /
• pp.3-9
• /
• 1991

This paper presents the characteristics of antenna factors of half-wave resonance dipole antennas above a ground plane. The current distributions on a horizontal and vertical dipole antennas were analyzed by the Galerkin's method of moments, and these solutions are used for calculating the horizontal and vertical antenna factors above the ground plane. It is shown that accurate antenna factors of the horizontal and vertical dipole above the ground plane are required of the radiated emission test.

• Journal of Electrical Engineering and Technology
• /
• 제9권5호
• /
• pp.1724-1728
• /
• 2014

Heat sink has been used to help an electrical device operate in normal temperature condition. But heat sink radiates unwanted electromagnetic wave, which may cause electromagnetic interference problem. A resistance loaded grounding technique is proposed to reduce electromagnetic wave radiation by a heat sink. Numerical simulations are accomplished to find optimal loading resistance. Also electromagnetic fields radiated by from a heat sink are measured and compared with the simulation results. The test results verify the usefulness of the proposed technique.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2007년도 춘계학술대회논문집
• /
• pp.1062-1073
• /
• 2007

Acoustic Target Strength (TS) is a major parameter of the active sonar equation, which indicates the ratio of the radiated intensity from the source to the re-radiated intensity by a target. In developing a TS equation, it is assumed that the radiated pressure is known and the re-radiated intensity is unknown. This research provides a TS equation for polygonal plates, which is applicable to near field acoustics. In this research, Helmholtz-Kirchhoff formula is used as the primary equation for solving the re-radiated pressure field; the primary equation contains a surface (double) integral representation. The double integral representation can be reduced to a closed form, which involves only a line (single) integral representation of the boundary of the surface area by applying Stoke's theorem. Use of such line integral representations can reduce the cost of numerical calculation. Also Kirchhoff approximation is used to solve the surface values such as pressure and particle velocity. Finally, a generalized definition of Sonar Cross Section (SCS) that is applicable to near field is suggested. The TS equation for polygonal plates in near field is developed using the three prescribed statements; the redection to line integral representation, Kirchhoff approximation and a generalized definition of SCS. The equation developed in this research is applicable to near field, and therefore, no approximations are allowed except the Kirchhoff approximation. However, examinations with various types of models for reliability show that the equation has good performance in its applications. To analyze a general shape of model, a submarine type model was selected and successfully analyzed.

• 대한기계학회논문집A
• /
• 제26권6호
• /
• pp.1143-1148
• /
• 2002

This paper analyses the transient response of a spherical elastic shell located near fee surface and impinged by spherical step-exponential acoustic shock waves. The problem is solved through extension of a method (Huang, 1969) previously formulated for the excitation in an infinite domain, which employs the classical separation of variables, series solutions, and Laplace transform technique The effect of the free surface reflection is taken into account using the image source method. The reflection of the incident wave has been treated by the same image formulation. If the reflection of the pressure field scattered and radiated by the shell is considered, the problem becomes that of multiple scattering by two spheres. However, this is in general negligible considering errors inherent from other sources and that the scattered and radiated pressure waves emanating from the shell are small. Thus, the problem is reduced to that of a structure immersed in an infinite fluid and impinged upon the origin and the image incident.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2001년도 춘계학술대회논문집
• /
• pp.911-916
• /
• 2001

Structural acoustic modification method based on the structural mobility analysis is applied to reduce the structure-borne noise radiated from hard disk drive system. Sound intensity techniques and ODS(Operational Deflection Shape) techniques are also used in order to provide the structural acoustic information for the mobility modification. The sound intensity is for the acoustic visualization of the noise source locations, and the ODS is for the visualization of the vibration pattern and its dynamic characteristics of the noise sources. Using visualization information of sound and vibration, local structural input mobility is reduced in the frequency band of interest by designing asymmetrical wave-stringer structure in the wave-number domain as well as frequency domain. The overall sound pressure level is reduced by 4dB and its controlled sound power radiated from the disk drive is proved to under 2.8Bel in idle-spinning mode and 3.1 Bel in random-seeking mode, which are the lowest noise levels in the hard disk drive industry.