• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.42-47
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• 2014

In this paper, fatigue life analysis of each structure was performed through theoretical analysis method at design stage in order to verify the success or failure of the store's acoustic noise durability according to the Method 515.5 standard of MIL-STD-810F. In addition, experimental analysis was carried out through the ground and flight test by manufacturing the measuring store, and verification of the sound durability was completed through the flight test after manufacture of the actual store. Furthermore, the commercial FEM code through the PSD calculation method applying measured SPL enables verify the durability of new store components development for the future.

• 설비공학논문집
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• 제26권5호
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• pp.206-211
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• 2014

The objective of the present study was to identify ventilation problems, and also to suggest new axial fan systems for the improvement of IAQ in the underground parking lots. Numerical results for air mean-velocity, local mean age, and sound power level are presented along with some of fan angles. The results showed the influence of airflow patterns on the fan performances installed in the underground parking lots. Discharge air volume is increased with the angle of the blade. And also, the main factors affecting the noise of the ventilation fan was found to be a rotational speed.

• 대한기계학회논문집A
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• 제25권9호
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• pp.1475-1482
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• 2001

Nowadays reduction of gear noise in power transmission is very important, because the noise regulation is severe and demand of customer on noise is increased. To reduce gear noise, it is necessary to understand the noise characteristics of helical gear. In this work, we designed test rig for the study of gear noise and installed in semi-anechoic chamber. By using this rig, sound pressure level is measured under varying rotational speed and torque. The frequency characteristics of helical gear noise on the effect of lead errors and torque are discussed.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.240-243
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• 2005

A design procedure using spatial Fourier transform is presented for a structural-acoustic coupled radiator that can emit sound in the desired direction with high power and low side lobe level. The design procedure consists of three steps. Firstly, the structural-acoustic coupled radiator is chosen to obtain strong coupling between structural vibration and acoustic pressure. The radiator is composed by two spaces which are separated by a wall. Spaces can be categorized as reverberant finite space and unbounded semi-infinite space, and the wall are composed of two plates and an opening. The velocities on the wall are predicted. Secondly, directivity and energy distribution of radiator are predicted in wave number domain using spatial Fourier transform. Finally, optimal design variables are calculated using a dual optimal algorithm. Its computational example is presented including the directivity and resulting pressure distribution using proposed procedure.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.782-785
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• 2004

In the Well-being age, many people use a city park for rest deeply think and constitutional walk. The city park is located at near side by traffic road in urban. Citizens are not satisfied with it's fuction as a haven of peace due to road traffic noise. Thus, this study is for a research on the actual noise condition of a city park in Nowon go. This study uses a prediction method called ASJ-model in order to calculate PWLs of road traffic noise. Using calculated PWLs, noise levels in a park are predicted and compared with measured values.

• 한국음향학회지
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• 제40권3호
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• pp.241-246
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• 2021

현재 라우드스피커 시스템은 다양한 입력 채널 및 앰프를 포함하는 액티브 스피커로 변화하고 있다. 이러한 액티브 스피커의 경우 기존 패시브 스피커 혹은 유닛 단품 측정 표준인 IEC 60268-5 만으로 측정이 불가능한 경우가 많다. 본 논문은 IEC한국 대표로 IEC60268-21 표준을 제정하면서 새롭게 정의한 아날로그, 디지털 입력 및 유선, 무선 입력 채널을 가지고 다양한 제어 기능을 가진 파워 앰프를 내장한 액티브 스피커 측정 표준에 대해 상세하게 알아보고자 한다.

• Advances in aircraft and spacecraft science
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• 제9권4호
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• pp.319-333
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• 2022

This work presents a numerical investigation of the aerodynamics and aero acoustics of the HVAB rotor in hover conditions. Two fully turbulent models are employed, the one-equation Spalart-Allmaras model and the two-equation k-ω SST model. Transition effects are investigated as well using the Langtry-Menter γ-Re θt transition transport model. The noise generation and propagation are being investigated using the Ffows-Williams Hawking model for far-field noise and the broadband model for near-field noise. Comparisons with other numerical solvers and with the PSP rotor test data are presented. The results are presented in terms of thrust and power coefficients, the figure of merit, surface pressure distribution, and Sound pressure level. Velocity, pressure, and vortex structures generated by the rotor are also shown in this work. In addition, this work investigates the contribution of different blade regions to the overall noise levels and emphasizes the importance of considering specific areas for future improvements.

• 한국학교수학회논문집
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• 제10권2호
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• pp.173-185
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• 2007

매우 빠른 속도로 진행되고 있는 현재의 고령화 사회에 맞추어, 평생 교육의 중요성은 나날이 증대되고 있다. 온전한 삶을 살아가는 가치가 확산됨으로써 치매예방이나 건강한 두뇌를 위해서 뇌 활동이 강조되고 있다. 본고는 이를 위한 새로운 방안으로 노인교육의 일환으로 수학이라는 학문을 도입하여 노인의 정서적 인지적 수준에 적합한 수업내용을 고안하여 적용하는 수학교육 실천을 제안하고 있다. 노인의 기억력 증진과 사고력과 논리력을 신장시킬 수 있고, 게임 활동을 통하여 흥미를 유발시킬 수 있으며 궁극적으로는 자아개념과 자긍심을 높일 수 있는 '실버수학'을 제안하고, 이러한 '실버수학'의 구체적인 연구가 진행될 수 있도록 그 기본 요구 사항들을 제안하였다.

• 전자공학회논문지
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• 제54권1호
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• pp.157-163
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• 2017

본 논문은 주파수대역검출센서(FBDS)를 이용하여 전력 케이블에서 부분방전(PD)가 발생했을 때 이것을 검출하고 진단하는 시스템 개발에 관한 논문이다. 주파수대역검출센서는 각 주파수대역에서 발생하는 부분방전을 음향학적으로 변환하여 검출한다. 부분방전은 그 음향학적 신호 형태로 잡음과 유사하다. 따라서 본 논문에서 상대적 레벨교차율(RLCR)과 주파수에너지 스펙트럼을 이용하여 정상과 비정상을 구별하여 부분방전을 검출하였다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.1042-1049
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• 2007

Recently, a theoretically-sound design approach, using an elastic multilayer model, is attempted in trackbed designs for the construction of high speed railways and new lines of conventional railways. In the elastic multilayer model, the stress-dependent resilient modulus($E_R$) is an important input parameter, that is, reflects substructure performance under repeated traffic loading. However, the evaluation method for resilient modulus using repeated loading triaxial test is not fully developed for practical purpose, because of costly equipment and the significantly fluctuated values depending on the testing equipment and laboratory personnel. In this study, the paper will present an indirect method to estimate the resilient modulus using dynamic properties. The resilient modulus of crushed stone, which is the typical material of sub-ballast, was calculated with the measured dynamic properties and the range of stress level of the sub-ballast, and approximated with the power model combined with bulk and deviatoric stresses. The resilient modulus of coarse grained material decreases with increasing deviatoric stress at a confining pressure, and increases with increasing bulk stress. Sandy soil(SM classified from Unified Soil Classification System) of subgrade was also evaluated and best fitted with the power model of deviatoric stress only.