• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.1
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• pp.29-35
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• 2004

When an optical pulse is propagated through the atmosphere space, it is attenuated and broadened by the effect of atmospheric turbulence. This pulse broadening is occurred by the fluctuation in the arrival time of pulse at an optical receiver. In digital optical communication, the attenuation is important factor but the pulse broadening is more important. In this paper, thus, we will find the broadening of pulse propagated through the turbulent atmosphere, present it as the function of the structure constant for the refractive index fluctuation, and simulate it to the turbulent strength and the transmission length.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.35 no.2
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• pp.33-38
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• 2003

In order to design the high strength corrugated fiberboard containers for agricultural products that can be used for the cold chain system, a large number of individual boxes were placed in various humidity environments at two different temperature of 5 and $20^{\circ}C$. The results indicated that temperature changes do not effect on physical strength of corrugated fiberboard containers as much as humidity changes did. The main conclusion from this study was that compression strength of corrugated fiberboard containers dropped significantly at high humidity condition, but the rates varied depending on the number of walls, temperature, and perimeter of containers. The packaging designer must consider the corrugated fiberboard boxes are also greatly affected by dimensional variations such as the length versus width ratio. Based on this study, water-resistant board would not be necessary if the ambient relative humidity does not reach to a critical point, 85 percent in the cold chain system. However, the designer must count for the unexpected fluctuation of rotative humidity resulting in severe loss of the compression strength of corrugated fiberboard container.

• Geomechanics and Engineering
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• v.38 no.1
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• pp.93-106
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• 2024

The present paper investigates the spatial variability effect of soil property on the three-dimensional probabilistic characteristics of the bearing capacity factor (i.e., mean and coefficient of variation) of a circular footing resting on clayey soil where both mean and standard deviation of undrained shear strength increases with depth, keeping the coefficient of variation constant. The mean trend of undrained shear strength is defined by introducing the dimensionless strength gradient parameter. The finite difference method along with the random field and Monte Carlo simulation technique, is used to execute the numerical analyses. The lognormal distribution is chosen to generate random fields of the undrained shear strength. In the study, the potential failure of the structure is represented through the failure probability. The influences of different vertical scales of fluctuation, dimensionless strength gradient parameters, and coefficient of variation of undrained shear strength on the probabilistic characteristics of the bearing capacity factor and failure probability of the footing, along with the probability and cumulative density functions, are explored in this study. The variations of failure probability for different factors of safety corresponding to different parameters are also illustrated. The results are presented in non-dimensional form as they might be helpful to the practicing engineers dealing with this type of problem.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.8
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• pp.923-928
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• 2005

The estimation of fatigue life at the design stage of the compressed air tank on board is very important in order to arrive at feasible and reliable solutions considering the total lifetime of the tank. In this paper the compressed air tank on board was selected as a model and the change of inside pressure of the tank during normal navigation period was measured and the cycle of fluctuation stress was presumed statistically based on this. Also the effect of stress concentration with the FEM analysis on the longitudinal weld and the mean stress effect on the fatigue strength of compressed air tank were discussed.

• The Journal of the Acoustical Society of Korea
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• v.35 no.3
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• pp.202-207
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• 2016

Most of noises from cars or home appliances accompany successive impulsive noise due to repeated operation. A human auditory system is able to perceive the successive impulsive noise as either a set of independent noise or amplitude modulated noise according to its occurrence period. This study is to identify main influence factors on understanding of impulsive characteristics and find most appropriate sound quality metrics to express the successive impulsive noise. To do this, the successive impulsive noises were designed and utilized to perform a listening test for identifying conditions where successive impulsive noise can be recognized to have impulsive characteristics. These results were analyzed with sound quality metrics such as loudness, fluctuation strength, and roughness in order to compare the subjective results with the objective results. Consequently, the results revealed that the successive impulsive noise exhibits impulsive characteristics when its occurrence frequency is less than 50 Hz. It was also observed that roughness and fluctuation strength results are not applicable to express the successive impulsive noise because they heavily depend on the amplitude modulation characteristics. On the other hand, loudness results are considered to be useful as an evaluation factor of the successive impulsive noise through the use of loudness limen because it does not depend on the amplitude modulation characteristics.

• Geomechanics and Engineering
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• v.20 no.6
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• pp.497-503
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• 2020

In the Kingdom of Saudi Arabia, the shallower depth of the earth's crust is composed of loose dune or beach sand with soluble salts. The expansive behavior of salt bearing soil, fluctuation of ground water table and extreme environmental conditions offer a variety of geotechnical problems affecting safety and serviceability of the infrastructure built on it. Despite spending money, time and other resources on repair and rehabilitation, no significant attention is paid to explore the root causes of excessive differential settlement and cracking to these facilities. The scientific solution required to ensure safety and serviceability of the constructed infrastructure is to improve the strength and durability properties of the supporting ground. In this study, shredded plastic is employed as a low cost and locally available additive to improve strength characteristics of the desert sand. The study shows a remarkable increase in the shear strength and normal settlement of the soil. A seven (07) degree increase in angle of internal friction is achieved by adding 0.4 percent of the shredded plastic additive. The effect of different proportions and sizes of the plastic strips is also investigated to obtain optimum values. Such a long-lived solution will seek to reduce maintenance and repair costs of the infrastructure facilities laid on problematic soil along with reduction of environmental pollutants.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06c
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• pp.283-286
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• 1998

monaural 신호는 귀의 특성과 인간의 청취 특성을 정확하게 반영하지 못하는 문제점이 있다. 귀 자체의 특성이 binaural인 것을 생각하면 monaural 신호를 이용한 방법은 정확한 결과가 나오기 어렵다. 따라서 이 논문에서는 monaural 신호를 이용한 음질 평가 시스템의 단점을 보완하고 귀의 binaural 특성을 살린 binaural 음질 평가 시스템을 구현하였다. 소리에 대한 심리음향학 인자로는 monaural 평가에서 사용했던 loudness, sharpness, roughness, fluctuation strength, annoyance, pleasantness를 binaural에 맞도록 수정하였으며, monaural 평가에서는 사용하지 않았던 tonality를 추가하여 pleasantness의 annoyance의 계산식을 수정하였다.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06e
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• pp.85-88
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• 1998

심리음향학적으로 소리의 감성 요소를 평가하려는 시도가 계속되고 있으나 뚜렷한 결과가 나온 것은 많지 않다. 또한 감성 인자 평가에 대한 국제적인 표준도 정확히 나와있지 않다. 일반적으로 심리음향학 인자로 loudness, sharpness, roughness, fluctuation strength, pleasantness, annoyance를 사용하며, 이러한 인자들을 이용하여 바이노럴 음질 평가 시스템을 구현하였다. 구현된 바이노럴 음질 평가 시스템의 객관성을 평가하기 위해 인성 실험을 실시하였고 인성 실험 결과와 음질 평가 시스템을 이용한 평가 결과를 비교 분석하였다.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.1
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• pp.98-105
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• 2008

In this paper, the system for monitoring process of aluminum laser welding was developed using the light signal emitted from the plasma which comes from interaction between material and laser. Photodiode for monitoring system was selected based on the spectrum analysis of light from plasma and keyhole. Behavior of plasma and keyhole was analyzed through the sensor signals. Value of sensor signal represented the light intensity and fluctuation of signal indicated the stability of plasma and keyhole. For the relation between welding condition and sensor signals, the input power and weld geometry greatly effected on the average of each sensor signals. Using the feature values of signals, estimation model for tensile strength of weld was formulated with neural network algorithm. Performance of this model was verified through coefficient of determination and average error rate.

• Solar Energy
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• v.18 no.1
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• pp.81-89
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• 1998

In this paper an experimental was done to design combustion chambers which is required radiation strength of high temperature generator of absorption rigerator. Partiqularly, in combustion chamber radiative mediums were set and basic experiments were done according to its size by radiation strength and effects of heat transfer promotion. The results are as follows : 1) When radiative mediums were set in small combustion furnace burning nonframely radiative heat transfer was effected. 2) In case that area ratio($A/A_o$) of radiative medium is 0.82 or over, temperature fluctuation effects of furnace inside were not nearly. 3) In experimental boundary heat transfer effects were 1.8 times by setting up radiative medium. Specially, $q/{\Delta}T$ values of furnace inside were uniformed nearly by setting up radiative mediums.