• 대한전자공학회논문지
• /
• 제27권12호
• /
• pp.1916-1924
• /
• 1990

In this paper attenuation effect on the measurement and the tomography of nonlinear parameter is discussed. We perform computer simulation with the method using harmonic components and the method using secondary wave components, and then estimate attenuation effect through the results and compare two measurement techniques. According to simulation result the attenuation effect is more intensive as large n and \ulcorner, and the degree of the attenuation effect is represented as error functions. In the aspect of measuremnet techniques, the method using secondary wave components is more insensitive to attenuation effect than the method using harmonic compnents. We obtain the same result in the nonlinear tomography, and show that the attenuation compensive filter is required because the whole tomogram is affected by frequency dependent attenuation(or nonlinear attenuation)

• 한국지진공학회논문집
• /
• 제24권1호
• /
• pp.9-17
• /
• 2020

The stochastic point-source model has been widely used in generating artificial ground motions, which can be used to develop a ground motion prediction equation and to evaluate the seismic risk of structures. This model mainly consists of three different functions representing source, path, and site effects. The path effect is used to emulate decay in ground motion in accordance with distance from the source. In the stochastic point-source model, the path attenuation effect is taken into account by using the geometrical attenuation effect and the inelastic attenuation effect. The aim of this study is to develop accurate equations of ground motion attenuation in the Korean peninsula. In this study, attenuation was estimated and validated by using a stochastic point source model and observed ground motion recordings for the Korean peninsula.

• 대한전자공학회논문지
• /
• 제27권12호
• /
• pp.1925-1932
• /
• 1990

In this paper, we consider the effect of diffraction due to the finite-sized aperture and propose the new correction method of errors in measurements of attenuation coefficient owing to the diffraction effect. In the existing correction method, we obtained the attenuation coefficient after correct the spectrum at each depth. However, this paper obtain the attenuation coefficient using lg-spectral difference approach and then correct errors. As a proposed method is not correction for the spectrum at each depth but the difference spectrum, we reduce the calculation. Also the correction is performed through the total frequency range, the accurate attenuation coefficient in whole bandwidth is produced.

• 한국화재소방학회논문지
• /
• 제34권4호
• /
• pp.7-12
• /
• 2020

본 연구에서는 미세물분무의 특성이 열복사 감쇠에 미치는 영향을 살펴보기 위한 수치해석 연구를 수행하였다. 고온의 복사 패널로부터 전파되는 열복사가 미세물분무를 통과하여 약화되는 과정을 FDS를 이용하여 해석하였고, 미세물분무의 분사유량, 액적평균입경과 분무각에 따른 영향을 분석하였다. 해석 결과로부터 분사유량의 증가와 액적크기의 감소가 열복사 감쇠 효과를 증가시키는 것을 알 수 있었다. 복사열이 통과하는 분무 공간 분포의 영향을 살펴보기 위해 분사각을 변화시켜 열복사 특성을 분석하였으며 분사각이 클수록 복사 감쇠 효과가 커지는 것을 확인하였다. 이것은 유사한 액적크기분포와 유량조건에서도 액적들이 공간적으로 더 넓게 퍼져 있는 경우 복사의 감쇠 효과가 더 커질 수 있음을 보여준다.

• Nuclear Engineering and Technology
• /
• 제46권2호
• /
• pp.217-224
• /
• 2014

The present work used the efficiency transfer method used to calculate the full energy peak efficiency (FEPE) curves of the (2"*2" & 3"*3") NaI (Tl) detectors based on the effective solid angle subtended between the source and the detector. The study covered the effect of the self attenuation coefficient of the source matrix (with a radius greater than the detector's radius) on the detector efficiency. $^{152}$ An Eu aqueous radioactive source covering the energy range from 121.78 keV up to 1408.01 keV was used. In this study an empirical formula was deduced to calculate the difference between the measured and the calculated efficiencies [without self attenuation] at low and high energy regions. A proper balance between the measured and calculated efficiencies [with self attenuation] was achieved with discrepancies less than 3%, while reaching 39% for calculating values [without self attenuation] due to working with large sources, or for low photon energies.

• 한국컴퓨터정보학회논문지
• /
• 제19권5호
• /
• pp.37-42
• /
• 2014

본 연구의 목적은 170 dB 수준의 충격 소음원에서 주파수별 귀마개의 차음성능을 확인하고, 주파수 특성과 패턴 형상을 분석하는데 있다. 충격 소음에서의 Combat Arm Earplug와 3M Form types 1100 Earplug의 주파수별 귀마개 차음성능을 산출하였다. 차음성능을 확인하기 위해서 B&K Head and Torso Simulator와 Ear Simulator를 제작하여 충격 소음원의 주파수별로 차음성능을 비교하였다. 기존의 연구들은 충격 소음원이라 할지라도 대부분 140 dB 수준의 고충격 소음원이였으나, 본 연구는 그보다 더 높은 수준의 충격 소음원이라는 특징을 가지고 있다. 연구결과, 주파수별 충격소음의 차음효과는 평균 28.58 dB 인 것으로 나타났다.

• 한국정보통신학회논문지
• /
• 제3권4호
• /
• pp.779-785
• /
• 1999

위성전송신호는 위성 전송로 상에 강우가 있을 경우 신호감쇠를 겪게된다. 강우에 의한 신호 열화량은 10 GHz 이상의 주파수를 사용한 경우 강수에 의한 감쇠 영향을 받게 되며, 높은 주파수 신호일수록 감쇠 정도가 심각하다. 강우에 의한 신호 열화량은 강우의 세기인 강우강도에 좌우되며, 강우 강도 분포 특성을 추정하기 위해서는 적어도 10년 이상의 장기간 데이터로부터 유도된 분포에 의해 가능하다. 본 논문에서는 창원-마산지역의 강우데이터(88년-97년)로부터, Moupfouma New Model을 이용하여 강우강도의 년 시간율 특성을 도출한 후, ITU-R모델, Global모델, SAM모델을 이용하여 강우감쇠를 예측하고 강우의 영향을 분석하였다.

• 한국운동역학회지
• /
• 제30권3호
• /
• pp.197-204
• /
• 2020

Objective: The purpose of this study was to investigate the effect of increased running speed on the magnitude of impact shock attenuation in high frequency (9~20 Hz) at support phase on the treadmill running. Method: Twenty-four healthy male heel-toe runners participated in this study. Average age, height, mass, and preference running speed were 23.43±3.78 years, 176.44±3.38 cm, 71.05±9.04 kg, and 3.0±0.5 m/s, respectively. Three triaxial accelerometer (Noraxon, USA) were mounted to the tuberosity of tibia, PSIS (postero-superior iliac spine), and forehead to collect acceleration signals, respectively. Accelerations were collected for 20 strides at 1,000 Hz during treadmill (Bertec, USA) running at speed of 2.5, 3.0, 3.5, and 4.0 m/s. Power Spectrum Density (PSD) of three acceleration signals was calculated to use in transfer function describing the gain and attenuation of impact shock between the tibia and PSIS, and forehead. One-way ANOVA were performed to compare magnitude of shock attenuation between and within running speeds. The alpha level for all statistical tests was .05. Results: No significant differences resulted for magnitude of the vertical and resultant impact shock attenuation between the tibia and PSIS, and forehead between running speeds. However, significant differences within running speed were found in magnitude of the vertical shock attenuation between tibia and PSIS, tibia and forehead at speed of 2.5, 3.0 m/s, respectively. Conclusion: In conclusion, it might be conjectured that muscles covering the knee and ankle joints and shoe's heel pad need to strengthen to keep the lower extremities from injuries by impact shock at relatively fast running speed that faster than preferred running speed.

• 한국안전학회지
• /
• 제25권4호
• /
• pp.42-47
• /
• 2010

Recently, many techniques have been developed for the inspection of pipelines using guided waves. However, few researches have been made on the application of those techniques for buried underground pipes. Guided wave motions in the buried pipes are somewhat different from those of on-ground pipes which have traction-free (air) boundary condition on outer pipe walls and thus are strongly affected by the mechanical property of the surrounding soils. Therefore, it should be investigated the effect of soil properties on the guided wave behavior in buried pipe. On the other hand, the mechanical property of soil is largely depending on its moisture conditions nevertheless of other influential factors such as void ratio. In this study, the effect of moisture conditions in soils on mode attenuation of guided waves in the buried pipe is investigated. To this end, numerical study is performed to characterize mode attenuation behavior in buried pipes and the effective mode which is suitable for long range inspection is identified.

• 한국해양공학회지
• /
• 제26권2호
• /
• pp.14-19
• /
• 2012

There are insufficient data to consider the effect zone for the marine life of coastal fisheries, because no standard has been defined for the sound level of marine life. In this study, equations for distance attenuation were used to determine the effect zone for oceanic noises. A reference noise level was divided into 4 parts to consider the characteristics of the fishes, and the effect zone of each reference noise level was determined. To increase the reliability of the effect scope, approximately 100 repetitions of blasting work split into several parts by the boring depth, the sound level of the source caused by an increase in weight, and the effect zone were calculated using the prediction equation. According to the prediction, the maximum distance of the effect zone was 4.92 km.