• Journal of the Korean Society for Nondestructive Testing
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• v.14 no.2
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• pp.83-89
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• 1994

It is important for an ultrasonic testing to know the sound pressure field and the directivity of ultrasonic waves propagating in a solid. The directivity of ultrasonic wave is closely related to the sensitivity, the scanning pitch, the arrangement of angle probe, and the defect kind in ultrasonic testing. This paper describes on the directivity measurement of ultrasonic wave using ultrasonic wave visualization method. The directivity of the shear wave emitted from the angle probes were constant during propagation. The difference of directivity was existed between 2MHz and 4MHz angle probes. The centers of directivity were located backward from the incident poing and inside of the angle probe and were not changed during the wave propagation.

• Journal of ILASS-Korea
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• v.18 no.3
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• pp.126-131
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• 2013

This paper describes the effect of ultrasonic frequency(f) on the atomization and deformation characteristics of single water droplet in an acoustic levitation field. To achieve this, the ultrasonic levitator that can control sound pressure and velocity amplitude by changing frequency was installed, and visualization of single water droplet was conducted with high resolution ICCD and CCD camera. At the same time, atomization and deformation characteristics of single water droplet was studied in terms of normalized droplet diameter($d/d_0$), droplet diameter(d) variation and droplet volume(V) variation under different ultrasonic frequency(f) conditions. It was revealed that increase of ultrasonic frequency reduces the droplet diameter. Therefore, it is able to levitate with low sound pressure level. It also induces the wide oscillation range, large diameter and volume variation of water droplet. In conclusion, the increase of ultrasonic frequency(f) can enhance the atomization performance of single water droplet.

• The Journal of the Acoustical Society of Korea
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• v.35 no.4
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• pp.288-294
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• 2016

The space between tire and wheel guard acts as a path for tire pattern noise transmission. In this study, acoustic phenomenon occurring in the tire-wheel guard space is investigated using acoustic mode analysis and visualization of the sound pressure distribution over the wheel guard surface. We introduced a cavity over the wheel guard surface to reduce the tire pattern noise, where the cavity acts as an acoustic damper. The interior noise was reduced by 2 dB(A), and the noise control measures treated in this study may provide an efficient method to improve interior sound quality without increasing cost and weight at the final stage of the vehicle development.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.622-627
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• 2008

Experiment of active noise control on supersonic jet noise was conducted by use of microjet injection. The microjets were injected to the shear layer of the main jet through 22 small holes at the lip of a rectangular nozzle. Based on the measurement of farfield sound pressure, it was found that the jet noise was effectively reduced by several dB(in some cases up to 10 dB). The power levels of all measurement points were also reduced by use of microjet injection. The microjet affected not only the broadband noise but also the screech tone noise. The sound pressure level, the frequency of the screech tone, and the structure of the jet could be changed by the microjet. Flow visualization with schlieren technique was also made to observe the effect of microjet on the flow field.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.8
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• pp.3398-3405
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• 2011

Vibration intensity (VI) method is used to reduce sound source generated from air-conditioning rotary compressor. Generally VI method is a good tool to find a sound source through vibration power flow. In this paper, the vibrations are measured by using the 3 uni-axial accelerometer from both the shells of the normal compressor and the fault compressor. The VI method successfully found out the sound source position on the surface of the compressor. In addition, the main noise (3kHz ~ 6.3kHz) was deminished by applying the newly designed compressor inner part which is related to the orginal noise source.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.8B
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• pp.830-838
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• 2009

Oriental medicine lacks diagnosis data in fixed quantity possible to express visually to patients by depending on clinician's intuition than Western medicine that continues to development by various diagnosis devices. For that, this paper intends to examine relation between heart and voice signal regarded as center organ and source of life and mind in order to implement objectification through the visualization of oriental diagnosis method above all. According to because the heart is related to the tongue among five organs, by thinking with sounds, we would design the way of identifying existence of heart diseases focused on the fact that lingual sound pronunciation of heart patient is inexact. For this, we achieved a comparison, analysis of statistical bandwidth and morphological modeling of the second formants frequency about a lingual sound for their voice constituted subject group of heart diseases and normal people. Finally, we analyzed interrelationship to the result of experiment by designed method.

• Convergence Security Journal
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• v.22 no.2
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• pp.105-114
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• 2022

This paper is presents an intelligent control system that visualizes the direction of arrival for hearing impaired using personal mobility, and aims to recognize and prevent dangerous situations caused by sound such as alarm sounds and crack sounds on roads. The position estimation method of sound source uses a machine learning classification model characterized by generalized correlated phase transformation based on time difference of arrival. In the experimental environment reproducing the road situations, four classification models learned after extracting learning data according to wind speeds 0km/h, 5.8km/h, 14.2km/h, and 26.4km/h were compared with grid search cross validation, and the Muti-Layer Perceptron(MLP) model with the best performance was applied as the optimal algorithm. When wind occurred, the proposed algorithm showed an average performance improvement of 7.6-11.5% compared to the previous studies.

• Cartoon and Animation Studies
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• s.35
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• pp.329-346
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• 2014

Art is the product from the combination of politics, economy, and social and cultural aspects. Recent development of digital media has affected on the expansion of visual expression in art. Digital media allow artists to use sound and physical interaction as well as image as an plastic element for making a work of art. Also, digital media help artists create an interactive, synaesthetic and visual perceptive environment by combining viewers' physical interaction with the reconstruction of image, sound, light, and among other plastic elements. This research was focused on the analysis of the relationship between images in art work and the viewer and data visualization using sound from the perspective of visual perception. This research also aimed to develop an interactive art by visualizing physical data with sound generating from outer stimulus or the viewer. Physical data generating from outer sound can be analyzed in various aspects. For example, Sound data can be analyzed and sampled within pitch, volume, frequency, and etc. This researcher implemented a new form of media art through the visual experiment of LED light triggered by sound frequency generating from viewers' voice or outer physical stimulus. Also, this researcher explored the possibility of various visual image expression generating from the viewer's reaction to illusionary characteristics of light(LED), which can be transformed within external physical data in real time. As the result, this researcher used a motif from Piet Mondrian's Broadway Boogie Woogie in order to implement a visual perceptive interactive work reacting with sound. Mondrian tried to approach at the essence of visual object by eliminating unnecessary representation elements and simplifying them in painting and making them into abstraction consisting of color, vertical and horizontal lines. This researcher utilized Modrian's simplified visual composition as a representation metaphor in oder to transform external sound stimulus into the element of light(LED), and implemented an environment inducing viewers' participation, which is a dynamic composition maximizing a synaesthetic expression, differing from Modrian's static composition.

• 한국HCI학회:학술대회논문집
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• 2006.02a
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• pp.46-51
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• 2006

청각 장애인은 집에서 발생하는 여러 가지 소리나 가전 제품의 신호를 감지하지 못하므로 생활의 불편을 상당히 느끼고 있다. 이러한 사람들을 위해 소리 정보를 시각 정보로 변경하여, 사용자들의 시야에 보여주는 것을 목적으로 연구를 시작하였다. 본 연구에서는 집이라는 환경에서 사용자의 위치와 오리엔테이션 정보를 습득하여, 사용자에게 필요한 정보를 시야에 들어오는 범위에 방해되거나 불편하지 않게 표시하는 시스템을 제안한다. 프로젝터에 부착된 카메라를 이용하여 사용자를 인식하고, 사용자를 따라다니며 화면을 디스플레이 하는 기존 방법의 단점들을 해결하기 위해 위치 센서로 사람의 위치와 방향을 파악하여 사용자에게 필요한 정보를 사용자가 현재 바라보는 곳에 디스플레이 하는 방법을 제안한다. 3D 모델로 제작된 집의 구조를 이용하여, 프로젝터의 방향과 초점 제어를 사전에 계산하여 보다 정확한 위치에 정보가 디스플레이 되도록 하였다. 본 논문에서 제안하는 방법이 기존의 PDA 나 PC 모니터를 이용해 정보를 제공하는 방법보다 사용자들이 정보를 인지하는 데 걸리는 시간이 좀더 빠르고 이 방법을 선호하기 때문에, 청각 장애인에게 정보를 제공하는 시스템으로 적합하다는 결론을 도출하였다.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.23-26
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• 2002

Two modes of shock waves propagating in He II (superfluid helium), this is a compression and a thermal shock waves, were studied experimentally by using superconductive temperature sensors, piezo pressure transducers and Schlieren visualization method with an ultra-high-speed video camera (40,500 pictures/sec). The shock waves are induced by a gas dynamic shock wave impingement upon a He II free surface. It is found that the shock Mach number of a transmitted compression shock wave is up to 1.16, and the shock Mach number of a thermal shock wave coincides well with the second sound velocity under each compressed He II state condition. The temperature rise ratio of an induced thermal shock wave to that of an incident gas dynamic shock wave was found to be very small, as small as 0.003 at 1.80K.