• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.867-871
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• 2007

Noise map is very efficient tool to evaluate the road traffic noise. However, calculation time and accuracy of noise map heavily depend on the grid size of noise map. In this study, effects of grid size on the prediction results of road traffic noise map have been investigated in detail for urban and rural areas, respectively, and efficient grid size for the noise map has been proposed.

• 한국소음진동공학회논문집
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• 제20권2호
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• pp.199-204
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• 2010

Noise map is very efficient tool to evaluate the road traffic noise. However, calculation time and accuracy of noise map heavily depend on the grid size of noise map. In this study, effects of grid size on the prediction results of road traffic noise map have been investigated in detail for urban and rural areas, respectively, and efficient grid size for the noise map has been proposed.

• Journal of Radiation Protection and Research
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• 제42권4호
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• pp.197-204
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• 2017

Background: X-ray imaging detectors for the nondestructive cargo container inspection using MeV-energy X-rays should accurately portray the internal structure of the irradiated container. Internal and external factors can cause noise, affecting image quality, and scattered radiation is the greatest source of noise. To obtain a high-performance transmission image, the influence of scattered radiation must be minimized, and this can be accomplished through several methods. The scatter rejection method using an anti-scatter grid is the preferred method to reduce the impact of scattered radiation. In this paper, we present an evaluation the characteristics of the signal and noise according to physical and material changes in the anti-scatter grid of the imaging detector used in cargo container scanners. Materials and Methods: We evaluated the characteristics of the signal and noise according to changes in the grid ratio and the material of the anti-scatter grid in an X-ray image detector using MCNP6. The grid was composed of iron, lead, or tungsten, and the grid ratio was set to 2.5, 12.5, 25, or 37.5. X-ray spectrum sources for simulation were generated by 6- and 9-MeV electron impacts on the tungsten target using MCNP6. The object in the simulation was designed using metallic material of various thicknesses inside the steel container. Using the results of the computational simulation, we calculated the change in the scatter-to-primary ratio and the signal-to-noise ratio improvement factor according to the grid ratio and the grid material, respectively. Results and Discussion: Changing the grid ratios of the anti-scatter grid and the grid material decreased the scatter linearly, affecting the signal-to-noise ratio. Conclusion: The grid ratio and material of the anti-scatter grid affected the response characteristics of a container scanner using high-energy X-rays, but to a minimal extent; thus, it may not be practically effective to incorporate anti-scatter grids into container scanners.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 추계학술대회 논문집
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• pp.229-230
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• 2009

A method is suggested for the noise source identification using the sound intensity method. The suggested method does not need to install the grid using wire or thread during the sound intensity measurement for the noise source identification. It utilizes a camera to show the grid on the screen not installing the real grid for the sound intensity method.

• International journal of advanced smart convergence
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• 제8권2호
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• pp.199-203
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• 2019

In this paper, we propose the efficient impulsive noise mitigation scheme for power line communication (PLC) systems in smart grid applications. The proposed scheme estimates the channel impulsive noise information of receiver by applying machine learning. Then, the estimated impulsive noise is updated in data base. In the modulator, the impulsive noise which reduces the PLC performance is effectively mitigated through proposed technique. As an impulsive noise model, Middleton Class A interference model was employed. The performance is evaluated in terms of bit error rate (BER). From the simulation results, it is confirmed that the proposed scheme has better BER performance compared to the conventional model. As a result, the proposed noise mitigation improves the signal quality of PLC systems by effectively removing the channel noise. The results of the paper can be applied to PLC systems for smart grid.

• 한국안전학회지
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• 제11권4호
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• pp.135-142
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• 1996

Prolonged in-plant personnel exposure to high noise levels results in permant hearing damage. There are no way to correct this hearing damage by treatment or use of hearing aids. Therefore, every employer is responsible for providing a workplace free of such hazards as excessive noise. This study was carried out to evalute and predict a given noise environment based on specific limit as the noise guarantee for a newly-founded petrochemical plant. The maximum total sound level should not exceed 85dBA in the work area, except where the area is defined as a restricted area and 70dBA at the plant boundary. Prediction of the noise levels within the plant area for a newly-founded petrochemical plant was achieved by dividing all plant area into 20m$\times$20m regular grid spaces and noise level inside the area or unit that in-plant personel exposure to high noise levels was estimated computed into 5m$\times$5m regular grid spaces. The noise level at the grid point that was propagated from each of the noise sources(equipments) computed using the methematical formula was defined as follows : $SPL_2$=$SPL_1-20log{\frac{r_2}{r_1}}$(dB) where $SPL_1$ =sound pressure level at distance $r_1$ from the source $SPL_2$=sound pressure level at distance $r_2$ from the source As a result, the equipments exceeded noise limit or irritaring noise levels were identified on the specific grid coordinates. As for equipments in the area that show high noise levels, appropriate counter-measures for noise control (by barriers, enclosure, silencers, or the change of equipments, for example) should be reviewed. Methods for identifying sources of noise applied in this study should be the model for prediction of the noise levels for any newly-founded plant.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2003년도 The Fifth Asian Computational Fluid Dynamics Conference
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• pp.172-174
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• 2003

Nnumerical investigations of the tip vortical characteristics were conducted with lateral tip blowing to reduce Blade-Vortex Interaction (BVI) noise. The predictions of BVI noise were performed using a combined method of an unsteady Euler code with an aeroacoustic code based on Ffowcs- Williams and Hawkings formulation. A moving overlapped grid system with three types of grids (blade grid, inner and outer background grid) was used to simulate BVI of helicopter with two OLS-airfoil blades in forward/ descending flight condition. The calculated waveform of BVI noise, which is characterized by the distinct peaks caused during blade vortex interaction, clearly shows the effect of lateral blowing at tip to reduce BVI noise

• 한국방사선학회논문지
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• 제17권4호
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• pp.573-579
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• 2023

본 연구는 자동노출조절장치를 사용하는 흉부 후·전 방향 방사선검사(Chest PA) 시 격자 사용 유·무 및 가상격자 사용에 따른 선량과 영상 품질의 차이 비교를 통해, Chest PA 시 임상적으로 새로운 격자 조합을 제안하고자 한다. 본 연구는 인체모형팬텀을 대상으로 Chest PA 자세에서 진행했다. 선량계는 흉추 6번 높이에 위치하였고, 조사 조건은 110 kVp, 320 mA, 1.6 mAs, SID는 180 cm, 조사야 크기는 17" × 17"로 동일하게 적용하였다. 물리적 격자를 적용한 상태와 미적용 상태에서 각각 30개의 영상을 얻었고, 물리적 격자 미적용 영상에 가상격자를 적용한 영상 30개를 추가로 획득하였다. 선량은 입사표면선량(ESD)을 측정하였고, 화질은 신호대잡음비(SNR)와 대조도대잡음비(CNR)를 측정하여 비교 분석하였다. 본 연구 결과 ESD는 물리적 격자를 사용하지 않을 경우 약 48%의 감소 효과가 있었다. SNR은 물리적 격자 미사용 시가 사용 시보다 약 32% 증가하였고, 가상격자를 사용한 경우에는 격자 사용 시 보다 약 18% 증가하였다. CNR은 물리적 격자 미사용 시가 사용 시보다 약 30% 증가하였고, 가상격자를 사용한 경우에는 격자 사용 시보다 약 16% 증가하였다. 본 연구의 결과, 물리적인 격자 대신 가상격자 사용 시 영상의 품질은 유지하되, 환자 선량은 감소시킬 수 있을 것으로 생각된다.

• 전기학회논문지
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• 제64권1호
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• pp.196-200
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• 2015

The switching noise in the power electronics of the power conversion equipment (Power Conditioning System) for large energy storage devices are generated. Since the burst-level transient noise from being generated in the power system at a higher power change process influences the control circuit of the low voltage driver circuit. Noise may cause the malfunction of the control device even if no dielectric breakdown leads to a control circuit. To overcome this, this paper proposes the installation of an additional nano-surge protection device on the power supply DC output circuit of the battery management unit.

• 한국소음진동공학회논문집
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• 제17권5호
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• pp.448-455
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• 2007

As Decentralized Generation(DG) becomes more reliable and economically feasible, it is expected that a higher application of DG units would be interconnected to the existing grids. This new market penetration of DG technologies is linked to a large number of factors like technologies costs and performances, interconnection issues, safety, market regulations, environmental issues or grid connection constrains. This paper describes the procedures and results for the mechanical, electrical, and environmental tests of MGT on actual grid-connection under Korean regulations. As one of the achievements, the simulation model of MGT was developed, so that it will be able to analyze or propose new distributed generation system using MGT. The field test was conducted in order to respond to a wide variety of needs for noise reduction and utilization and its performance was evaluated in consideration of its operational problems. The MGT is successfully supplying electricity to Korean grids with satisfying various regulations. The suggested strategy and experience for the evaluation of the distributed generation will be used for the introduction of other distributed generation technologies into the grid in the future.