• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.618-621
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• 2014

This research is to review the possibility of reducing the noise radiated from the tube exit by controling the sound reflection coefficient at the inclined exit. The sound reflection coefficient at the inclined exit of flanged tube was measured by both transfer function method and standing wave ratio method. Accuracy on the sound reflection coefficient measured by transfer function method was verified through comparison with sound reflection coefficient measured by standing ratio method. The flanged tube had lower sound reflection coefficient than the tube which have no flange. Also the sound reflection coefficient was decreased in accordance with increasing the inclined angle of unflanged tube.

• Journal of Biosystems Engineering
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• 제24권3호
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• pp.259-266
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• 1999

This research was carried out to investigate the possibility of real time rice milling ratio measurement using the spectral reflection characteristics. In this study, various methods were compared such as \circled1 using the whiteness meter, \circled2 using the colorimeter, \circled3 using the Visible and the NIR reflection spectrum. The samples were milled in the domain of 84~96% by 0.5% interval classified by milling ratio. The NMG treatment method required about 20 minutes to determine the milled ratio and r2 was 0.0028 to 0.7959 that was very low. In case of whiteness meter, r2 was high but speed of measurement was 5 minutes that was very low. Measurement with the colorimeter required about 5 minutes and r2 was 0.60 to 0.85 that was low. The reflection spectrum were measured in the range of 400~2,500nm with 2nm interval and the MLR model with six-wavelength obtained from first derivative of spectra gave the best results(r2 = 0.967, SEP = 0.729%)

• 한국안전학회지
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• 제18권4호
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• pp.51-56
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• 2003

The goal of this study is to show the way to decrease the noise from air nozzles. The variables of this test are the shapes of air nozzles, air flow rate and the distance between a reflection plate and a nozzle tip. This experiment is aimed to find the most appropriate condition to minimize the noise. These are the results. If diameter ratio is more than 12:8, noise level increases by over 10 dB(A) regradless of the distance between a reflection plate and a nozzle and the existence of a reflection plate. And when $L_2$ of a nozzle is 5mm long, noise level rise relatively highly. So, it is strongly recommended that $L_2$ should be manufactured more than 10mm. The reason for a high intensity noise is that when diameter ratio is more than 12:8, the diameter of a nozzle tip($D_2$) turns small drastically, which increases the air velocity. It is assumed that when the vortes is great around the spots where a nozzle hole is suddenly smaller, great turbulent flow increases much noise.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.42-50
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• 2008

To evaluate rock bolt integrity, destructive test such as pull-out test has been commonly carried out. This method is known as time consuming, expensive, and inaccurate procedure. To improve destructive method, non-destructive techniques using transmitted guided ultrasonic waves were suggested. Note for the transmission method, the source for the generation of ultrasonic waves should be installed during the rock bolt construction. The purpose of this study is to investigate the reflection method using reflected guided ultrasonic waves to evaluate the integrity of the rock bolt grouted, and to compare the results evaluated by the reflection and transmission methods. The guided waves are generated by PZT element and received by AE sensor. The measured signals are analyzed by the wavelet transform. The results show that the energy velocities of guided ultrasonic waves increase with the defect ratio in both transmission and reflection method. The reflection method produces the lower velocity in all defect ratio. This research demonstrates that the reflection method may be suitable and easer method for the field tests.

• 조명전기설비학회논문지
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• 제25권5호
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• pp.1-6
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• 2011

By incorporating a polarization-diversity loop configuration (PDLC), we have demonstrated inline conversion between transmission and reflection spectra of a fiber Bragg grating (FBG) without reconfiguration of the fiber filter structure. The proposed apparatus consists of a polarization beam splitter, an FBG, and two quarter-wave plates (QWP's). The inline conversion operation between transmission and reflection spectra of the FBG was performed by proper adjustment of QWP's within the proposed filter. The band rejection ratio and side-mode suppression ratio in transmission and reflection modes of the fabricated filter were measured as ~17.0[dB] and ~16.4[dB], respectively.

• 한국광학회:학술대회논문집
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• 한국광학회 2007년도 하계학술발표회 논문집
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• pp.21-22
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• 2007

The periodic multilayer is considered as the X-ray reflection mirror. High X-ray reflectivity from the incident angle greater than the grazing critical angle can be obtained by the periodic multilayer structure. The Optical constants are investigated in order to determine the material for X-ray reflection mirror. The X-ray reflection mirror is designed for W, Si using computer simulation. The reflectivity is calculated for various incident angles and ratio of thickness.

• 한국산학기술학회논문지
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• 제13권5호
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• pp.1996-2001
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• 2012

본 시각 검사시스템은 전자 부품과 같이 잘 형성된 표면 재료에 널리 사용되고 있다. 반사 능력이 나쁜 재료의 경우, 시각 검사시스템이 도입될 때 많은 문제점이 발생한다. 혼합 생산 라인에서 진위의 모델을 알 수 없을 때 저 반사비와 많은 노이즈에도 잘 작동할, 강인한 시각 검사시스템을 개발하였다. 유형을 인식하기 위하여 k-means를 이용한 작업물 인식 기법이 제안되었다. 인식 유형에 기반하여 active contour라는 노이즈에 강인한 분할 기법이 영상에서 특징을 분할하는데 응용되었다. 오차 변화를 조정하는데 Kalman 필터가 사용되었다. 자동시각 검사시스템의 실험은 프로젝터를 이용한 수작업 측정의 정확도 수준을 보여준다.

• 한국지반공학회논문집
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• 제31권6호
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• pp.27-44
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• 2015

일정수심상에서 임의반사율을 갖는 부분중복파와 흐름이 공존하는 경우 얕은 두께를 포함한 유한두께 및 무한두께의 해저지반내에서 동적응답을 나타내는 해석해를 유도한다. 해석해에서 반사율이 0인 경우는 진행파와 흐름과의 공존장으로, 반사율이 1인 경우는 완전중복파와 흐름과의 공존장으로 간단히 변환된다. Biot의 압밀이론에 기초하여 해저지반은 투과탄성매체로, 간극유체는 압축성으로, 그리고 지반내 간극수의 흐름은 Darcy법칙으로 각각 가정된다. 도출된 해석해는 기존의 해석결과와의 비교 검토로부터 검증되며, 실제 계산에서는 반사율, 흐름속도, 입사파의 주기 및 지반두께 등의 변화에 따른 지반변위, 간극수압, 유효응력 및 전단응력의 변동특성을 면밀히 검토한다. 이로부터 흐름이 존재하는 경우 흐름으로 인한 입사파와 반사파의 주기 및 파장의 변화로 인하여 흐름이 없는 경우의 지반내 동적응답과는 큰 차이를 나타내며, 또한 반사율의 크기에 따라 동적응답에서 큰 차이가 나타난다는 것을 확인할 수 있다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.392-399
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• 2005

Shear modulus (or rigidity) of dam material is an important parameter which can be directly associated with the deformation of dam. Seepage or leakage of water can cause the defects or cracks of dam body. The existence of cracks and rigidity of dam body are decisive information for the estimation of dam safety. Rigidity of material is mainly determined from S-wave velocity and the defects of dam body can be detected by seismic reflection survey. Therefore, seismic reflection survey will be a desirable method which can give a solution about dam safety problem. Among various physical properties of dam body, S-wave velocity is the most important information but it is not easy to get the information. In this study, diverse measuring techniques of S-wave reflection survey were attempted to get the information about S-wave velocity of dam body. Ultimately, S-wave velocity could be estimated by the analysis of SH reflection events which can be easily observed in shot gather data obtained from SH measuring technique. Meanwhile, P-wave reflection survey was also performed at the same profile. P-beam radiation technique which can reduce the surface waves and reinforce the P-wave reflection events was applied for giving a help to analyse P-wave velocity. In the end, P-and S-wave velocity, Vs/Vp, Poisson's ratio distribution of the vertical section under the profile could be acquired.

• 한국태양에너지학회 논문집
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• 제36권5호
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• pp.1-8
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• 2016

In this paper, we evaluated the effect of a silica-based Anti-Reflection(AR) coating for PV modules. The coating technique can be easily applied to large-scale PV modules at room temperature with improvements of the optical properties that is qualified by the optical transmission measurements on the coated cover glass of the modules. The power improvement of the large-scale PV modules shows the increasing about 2.4% at standard condition of the coating technique on average. To improve the AR coating effect of the PV modules, we have characterized the individual PV modules by the measurements of DC power output, modified performance ratio(PRm) and the regression. The results show that the significant improvements of the AR coating effect are 6.4%, 5.5% and 4.5% of increasing of the performances by using the measurements of DC power output, modified performance ratio(PRm) and the regression, respectively.