• Proceedings of the KSME Conference
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• 2002.08a
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• pp.783-786
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• 2002

The unsteady turbulent flow characteristics of NACA4406 airfoil at close proximity to the pound are numerically investigated, especially focused on the noise generation mechanism near the blunt trailing edge. The unsteady two-dimensional compressible Wavier-Stokes equations with a Spalart-Allmaras turbulence closure model are solved by the 6th-order compact scheme and the 4th-order Runge-Kutta scheme. The computation shows a noise generation by a feedback mechanism at the blunt tailing edge, where the acoustic-fluidic coupling occurs between the wall-reflected sound waves and the periodically disturbed turbulent shear layer.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.8 s.239
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• pp.921-926
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• 2005

In the idealized model problem of the interaction between a planar travelling shock and a symmetric vortex, the physics of shock distortion and quadrupole sound generation are well known to many researchers. However, the authors have distinguished the weak waves reflected and transmitted by the complicated photograph images obtained from a shock tube experiment. In this paper, we introduces a parametric study based on Navier-Stokes simulation and Rankin vortex model to see the difference of shock deformation shapes. Four combination of the strength of shock and vortex are respectively selected from a parameter plane of shock and vortex strength extended to the strong vortex region. The result shows clearly discernable wave morphology for the main parameters, which is not yet explicitly mentioned by other researchers.

• Journal of KSNVE
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• v.4 no.2
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• pp.187-198
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• 1994

This study is to describe the effects of the duct termination conditions conditions upon the active noise attenuation system. The adaptive filtering algorithm using FIR filter is implemented for duct noise attenuation. To avoid the instability caused by the acoustic feedback, two methods are considered. One is to use a compensating FIR filter. The other is to utilize uni-directional detecting microphone and uni-directional control speaker. Experimental results show that the reflections of sound from duct terminations greatly reduce the performance of ANC system. The directionality of detecting microphone and control speaker is a major factor to decide ANC performance. When there are some reflections from both duct terminations, the noise attenuation using finite FIR filter is not enough to model the duct plant. Especially, the reflection from the upstream termination reduces the noise attenuation in the frequencies related to the distance between control speaker and upstream termination. The performance of the noise attenuation is found to be largely enhanced by using uni-directional coupler, both on detecting microphone and control speaker, even if the duct system has an arbitrary termination conditions.

• Journal of the Korean Society of Safety
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• v.5 no.3
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• pp.8-26
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• 1990

It is important to have exact information about the contact pressure distribution in the design of connected parts of machines and structures. In previous works, stress analyses on a two body contact problem have been carried out in large numbers. Besides, the measurement of contact stress is important to confirm the adequateness of the theoretical analysis, to verify appropriateness of Hertzian contact theory and to know the practical pressure distribution, but an excellent measuring method con't be found at present. Therefore, a quantitative measurement of contact pressure by means of ultrasonic waves using a normal probe and an angle has been proposed to measure the contact pressure distribution between two rough flat surfaces. At first, in a new proposed calibration method, the relation between mean contact pressure and sound pressure of reflected waves is obtained by using calibration blocks with various surface roughnesses made of the same material as the rectangular section beams And then, this experimental results are compared with the analytical ones, and the utility of this method is discussed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.59-65
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• 2005

The research is an objective which prevents a construction noise by developing prediction program on utility, helps comprehension of construction noise by case study. The program developed with Visual Basic of the Excel Logic. The standard noise is a data with report of the construction machine (National Institute of Environmental Research), construction noise of sound pressure level applied the distance decrease of the point source. The decrease effect of the barrier noise wall used the data of 5, 10, 15, 20dB where the diffraction is reflected. used a program, case study is suggested Prevention method to prevent noise of construction site.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.6 no.1
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• pp.9-15
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• 1995

Bowing of the vocal cords may be due to aging. atrophy. bilateral superior laryngeal nerve paralysis. injudicious vocal cord surgery, of an idiopathic cause. The bowing usually produces a dysphonia characterized by breathiness due to air escape : however, it can produce aphonia. This report reviews vocal function after surgical correction of bowing of the vocal cords for diagnosis and management. The vocal function of 13 patients with sulcus vocalis and 12 patients with vocal cord atrophy was evaluated with the use of a test battery of multidimensional evaluation items. The voice was improved postoperatively in most patients. The voice improvement was reflected objectively in maximum phonation time, mean air flow rate during phonation, stroboscopic findings. sound pressure level range and fundamental frequency range of phonation, and results of acoustic analyses of tape-recorded voice. The vocal function after surgical correction of the sulcus vocalis and vocal cord atrophy was improved postoperatively in most patient, but the results were not satisfactory.

• Proceedings of the Korea Information Processing Society Conference
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• 2023.11a
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• pp.506-508
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• 2023

비접촉 음파 센서와 기계학습을 결합하여 도로 표면의 투명한 블랙아이스 감지 및 노면 분류 97%의 정확도를 달성한 새로운 접근 방법을 제안한다. 개발된 시스템은 블랙아이스를 포함한 다양한 물질의 반사 특성을 분석하여 미끄러운 도로 상황을 실시간 감지 및 예측이 가능하여 도로 안정성을 향상한다. 본 연구에서는 테스트 벤치와 투명하고 미끄러운 물질을 이용하여 블랙아이스를 감지할 수 있는 기술의 정확도를 비교하며, 실험 결과를 통해 제안된 블랙아이스 감지 방법의 타당성을 입증하고자 한다.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.2
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• pp.120-125
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• 2015

With rapid urbanization, the volume of traffic in urban area has been significantly increased. This in turn led to problem which can be described as Road Traffic Noise. Currently, to alleviate the road traffic noise damage, a demand for installation of soundproofing walls is rising. Among different shapes of soundproof walls being installed, the reflection-type acoustical insulation panel is highly drawing attentions of residents due to the fact that it does not obstruct their field of vision in contrast with the opaque acoustical insulation panel. On the other hand, improving the soundproofing wall of the reflection-type acoustical insulation barrier panel needs to be focused on since it has a possibility to cause a secondary damage by reflected sounds. Therefore, in this research, study has been carried out to improve the forms in order to minimize travelling of reflected sounds through changing the frontal surface shape and geometrical shape of the reflection-type soundproofing panel. A result from comparison between the normal reflection-type soundproofing panel and the improved soundproofing panel, with reduction effects in the noise reflection, showed that the curved type of soundproofing panel has an impact on reducing the noise up to 1.5 dB. Furthermore, from the research conducted, it appears that the increase and decrease in the reflected sounds can be changeable depending on various design factors. Thus, it turns out that the study shows a potential possibility to develop a reduction technology of the reflected sounds pertaining to overall condition on the soundproofing walls.

• Journal of the Korea Society of Computer and Information
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• v.19 no.6
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• pp.93-100
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• 2014

The objective of this study is to propose the measurement system implementation method for the evaluation and measurement of the indoor-impulsive over 170 dB noise source. For the purpose of measuring impulse noise, design and implementation constructed followed subsystems of the testing center, microphone, ear simulator, head and torso simulator and so on. Measurement systems for the accuracy and reliability of impulse noise are implemented when measuring 3 ways of measurements method by the simultaneous measurement system design. For the accuracy and reliability of three mutually indoor-impulse noise measurements were compared, three kinds of measuring methods in accordance with the peak sound pressure level and octave band. Comparing the results of data, the indoor-impulse noise by analyzing a frequency characteristic was validated in difference for the statistical significance. Result are determined by the influence of the reflected wave. Therefore, the flexible size of the interior test site while interior impulse noise measurement system was constructed. Throughout this system can be affected by parameters that are the impulse noise source and the corresponding frequency-characteristic analysis to determine the spectrum of the reflected wave. And, in the near future, indoor impulse noise measurement systems for acquisition and analysis are utilized in useful data.

• Journal of Agricultural Extension & Community Development
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• v.3 no.1
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• pp.17-41
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• 1996

In the situation of rapid industrialization based on the lopsided development of economy since 1960, Korean rural society has faced a crisis of disruption. As a result, the civilian government has tried a few actions to change the circumstance. However, it is said that the coral polices were not satisfactory. Those who were concerned with the rural problems of these days argue that it is necessary to adopt new policies and further to change the policymakers` philosophies concerning the matter. The arguments are certainly based on the beliefs that the sound policies come from the sound philosophies. This study aims to analyze the existing rural polices and their policymakers` philosophies and to design of a new paradigm. For the purpose, this study was set there specific objectives: First, to overview the moor points of Quantitative Utilitarianism of Jeremy Bentham and the Social Justice Theory of John Rawls, the contrasting frameworks of the moral philosophies; Second, to trace the major or trade of the rural policies since 1960s in Korea; Third, to analyze the policymakers` philosophies reflected on the rural policies; Fourth, to design a new paradigm of the rural policies. This study mainly adopted descriptive method based on the various source of government and non-government statistics, white papers and other researches. The major findings of this study may be summarized as follows: 1. The historical epochs of the rural policies in Korea was divided into the periods: (1) An organizational and institutional establishment for self-reliance of main crops and the New Village Movement $(1969{\sim}70)$; (2) An initiation of `open-door` policies to the foreign farm products $(1970{\sim}80)$; (3) Completion of the UR meetings and the recommendations of the Rural and Fishery Development Commission (1980-present). 2. It was found that the philosophical foundations of coral policies were directly reflected from the utilitarianism of the national development. Under the philosophy it was the modem sector of economy that was to spearhead the national development, and the rural sector was situated to the peripheral position and hardly in the spot-light. Therefore, it may be said that the present situation of the rural society was largely rooted in the model of economic development. 3. As a new direction of the coral policies, many studies were focussing on the NTC (non-trade concerns) functions of agriculture for the present and future society. The researchers argue that the cost of protecting and supporting agriculture and rural society may be higher than that of the burden which the nation should be bear in the case of failure of agriculture. Although it tray be true, however, it should be noted that the argument is another type of utilitarianism which prevailed in the past. As a philosophy of rural policies, utilitarianism is straight forward and persuasive, however, it has also limitations in terms of relativism in broad sense or social justice in specific manna. 4. This study suggests to set the philosophical foundations of rural policies on the basis of Rawl`s Theory of Justice mentioned earlier. It emphasizes the inviolability of social justice which was neglected for the national benefits timing the period of development dictatorship in 1960s and 1970s. The principles of social justice for coral people were identified as twofold; (1) The principle of the t equal liberty; (2) (a) Difference principle, (b) The principle of fair equality of opportunity.