• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.9 s.90
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• pp.785-791
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• 2004

The objective of this research is to suggest anoise prediction method for a centrifugal compressor. It is focused on the Blade Passing Frequency component which is regarded as the main part of the rotating impeller noise. Navier-Stokes solver is used to simulate the flow-field of the centrifugal compressor, and the time-dependent pressure data are calculated to perform the near-field noise prediction by using Ffowcs Williams - Hawkings formulation. Indirect Boundary Element Method is applied to consider the noise propagation effect. Pressure fluctuations of the inlet and the outlet in the centrifugal compressor impeller are presented and the sound pressure level prediction results are compared with the experimental data.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.1206-1212
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• 2003

Shell vibrations of the rotary compressor, which account for considerable portion of the noise from compressor, are caused by various sources. Among them is the vibration of the in nor part or cylinder assembly, which undergoes severe compression process and rotational motion. But little researches have been carried out about the behavior and effect of the inner part because of its structural complexity. Furthermore, the shell of the rotary compressor is hermetic type that experimental approach is very difficult. This research studied the structure-born noise of the Rotary compressor using FE an analysis. The comparison between sound pressure spectrum and natural frequencies of the shell vibration implies that shell vibrations contribute significantly to the noise. It is found that inner part vibrations are responsible for those through the FE analysis. Design modification of the inner part, which shifts the target frequencies, reduced overall noise level of the compressor.

• Proceedings of the KSR Conference
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• 1998.05a
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• pp.265-272
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• 1998

In this paper, the intoner noise reduction for subway railroad vehicles was studied by improving transmission loss of carbody panels and side doors, and on-line tests were conducted to examine the exterior noise levels at various running conditions. Also the transmission loss for design candidates of the carbody specimen was measured in two reverberation rooms. From the results of the tests, side door gap is the most dominant factor affecting the Interior noise level of subway railroad cars with a sliding typed side door. The next one is revealed to transmission loss of a floor panel. To improve the transmission loss of the carbody, many activities were conducted such as, treatment of resilient and sound-absorbing materials and reducing the gap of the side door by adopting a brush and rubber, etc. The estimated interior noise level for modified car which is designed with improved carbody panels is lower than original car by about 5㏈.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.1077-1082
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• 2004

With increasing the number of tunnel constructions, more reliable analysis methods for tunnel excavation is needed to accomplish technically sound design, and stable and economical constructions. For this purpose, a series of construction procedures, which include excavation and support stages of tunneling, need to be considered. In this study, therefore, rock-support response behavior due to railway tunnel construction has been examined by using analytic methods and numerical calculations. For examining rock-support response behavior, the effects of shotcrete, thickness and time of installation have been considered. Through analytic and numerical calculations, it is shown that support pressure becomes higher with increasing the shotcrete thickness and stiffness, and hence the tunnel deformation tends to be stable. It is also important to notice that there is a significant effect of shotcrete installation time on the tunnel deformation, although no significant change in support pressure is observed.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.5
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• pp.112-121
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• 1999

본 연구에서는 사운드 합성에 응용할 목적으로 설계된 오디오 복호화기에 대한 내용을 담고 있다. 악기음을 ROM에 저장한 후 그 데이터를 이용하여 사운드 합성을 하는 PCM 방식에서 많은 악기음 데이터를 저장하면 할수록 더욱 좋은 음질의 사운드를 합성할 수 있다. 따라서 한정된 용량에 더욱 많은 악기음을 저장하기 위해서는 압축이 꼭 필요하다. 이를 위해서는 미리 압축한 악기음을 ROM에 저장한 후 그것을 필요시 복호화해 줄 복호화기만 있으면 된다. 그와 동시에 많은 악기음을 내기 위해서는 빠른 복호화기 필수적이다. 그래서 MPEG-1 오디오의 layer-1을 기본으로 하여 44.1 KHz의 샘플링 주파수로 32가지 악기음에 대한 실시간 복호화를 수행한다. 여기서는 음원 압축이라는 특수한 목적에 맞추어 압축의 효율성을 높이고 스스로 루프를 만들어서 합성의 편의를 제공하고 기존의 MPEG-1 오디오 layer-1에서 변형이 된 새로운 포맷과 추가된 기능에 관한 내용을 담고 있으며 이러한 복호화기를 설계하고 FPGA를 이용하여 검증하였다.

• Journal of Industrial Technology
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• v.32 no.A
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• pp.15-20
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• 2012

For emergency patients as heart disease, fast treatment is very important. This paper describes a smart phone software to detect emergency circumstance and request rescue. Detection of emergency condition of heart disease patients is based on physical motion and biological heart signals as electrocardiogram. Most smart phones have three axis acceleration sensor. On emergency condition, patients remain stationary. Thus the software detect stationary condition by using acceleration sensor data. For more precise detection, it combines electrocardiogram of patients. To request rescue, it sends help messages to designated persons. In addition, it generates emergency sound to surrounding people and plays a video of emergency measure that any person on the place can help the patient temporarily.

• Phonetics and Speech Sciences
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• v.1 no.1
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• pp.77-86
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• 2009

This study observes how the combined intervention program effects on the acquisition reading pronunciation of Korean phonological process words and the acquisition aspects of each phonological process rules to four Korean learners whose first language is Chinese. The training program is the combination of multisensory Auditory, Visual and Kinethetic (AVK) approach, wholistic approach, and metalinguistic approach. The training purpose is to evaluate how accurately they read the words of the phonological process which have fortisization, nasalization, lateralization, intermediate sound /ㅅ/ (/${\int}iot"$/). We access how they read the untrained words which include the four factors above. The intervention effects are analyzed by the multiple probe across subjects design. The results indicate that the combined phonological process rule explanation and the words activity intervention affects the four Chinese subjects in every type of word. The implications of the study are these: First, it suggests the effect of Korean pronunciation intervention in a concrete way. Second, it offers how to evaluate the phonological process and how to train people who are learning Korean language.

• 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 KIPE Conference
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• 2005.07a
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• pp.36-38
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• 2005

In home appliances, electric energy is optimally controlled by using power electronics technology, creating a comfortable environment in terms of energy saving, low sound generation, and reduced time consumption. Usually simplicity and robustness make the three phase induction motor attractive for use in domestic appliance, including washing machines. Two main types of domestic washing machine have evolved. We focus on the front loading machine favored in Europe, which has a horizontal drum axis. The efficiency improvement in home appliances is very important for customers. Induction motor efficiency can be improved by means of loss reduction, which can be realized by motor selection and design, improvement of the waveforms supplied by power Inverter, utilizing a suitable control method. So this paper describes the architecture and feature of washing machine fed induction motor drive under minimizing losses vector control.

• Journal of the Korean Institute of Educational Facilities
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• v.6 no.1
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• pp.5-20
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• 1999

With the advent of internet, the modern society is enjoying the benefits of the information age. As one of undesirable side effects of utilization of internet, however, it is often mentioned that young students are helplessly exposed to inappropriate and unqualified information. Therefore, in this paper, we will clarify the nature of inappropriate information to the younger generation and will argue for the needs of protecting the youth from inappropriate information. Especially the merits and limits of often motioned five different protective and regulatory measures are presented and analyzed, those are, establishment of acceptable use policy, active utilization of supervisory organization, promotion of Internet rating system, installation of filtering software, and legal and regulatory protection. As a fundamental means of resolving the problems, however, enforcement of systematic information literacy education, promotion of active utilization of sound information, development of search engines for the youth, design of diverse filtering softwares which can be selected by users, and increased attention by parents and teachers are suggested.