• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.5B
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• pp.318-325
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• 2008

HomePlug AV(HPAV) is the standard for distribution of Audio/video content as well as data within the home by using the power line. It uses a hybrid access mechanism that combines TDMA with CSMA/CA for MAC technology. The CSMA/CA protocol in HPAV has two main control blobs that can be used for access control: contention window(CW) size and deferral counter(DC). In this paper, we extensively investigate the impacts of CW and DC on performance through simulations, and propose an adaptive mechanism that adjusts the CW size to enhance the throughput in HPAV MAC. We find that the CW size is more influential on performance than the DC. Therefore, to make controlling the network easier, our proposal uses a default value of DC and adjusts the CW size. Our scheme simply increases or decreases the CW size if the network is too busy or too idle, respectively, We compare the performance of our proposal with those of the standard and other competitive schemes in terms of throughput and fairness. Our simulation and analysis results show that our adaptive CW mechanism performs very well under various scenarios.

• Proceedings of the Korean Society of Disaster Information Conference
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• 2017.11a
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• pp.260-261
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• 2017

최근 사회구조의 복잡화, 산업구조의 다변화, 기후변화 등에 의해 자연재해 및 산업재해, 도시재난이 급증하고, 그 규모 또한 대형화하고 있다. 이로 인해 에너지, 통신, 교통, 금융 등 공공 인프라의 피해가 급증하면서 작은 재해도 큰 재난으로 변하는 예가 늘어나고 있다. 한편 현대사회에 대한 IT의 관여도가 급속도로 늘어나면서 IT 서비스의 궁극적인 형태이자, 모든 산업을 수용하는 개념의 플랫폼(Platform)이 IT를 넘어서 글로벌 사회의 절대적 지배자로 등장했다. 또한 전 세계 유저들의 관점에서 보면 개개인들이 손에 든 스마트폰이 생활의 모든 분야에 걸쳐 소통, 정보, 쇼핑, 제보, 오락 등 모든 활동의 수단으로 절대적 가치를 창출하고 있다. 이는 스마트폰이 가진 스마트 데이터 생산 및 공유 기능에서 비롯된다. 이처럼 스마트 데이터를 기반으로 한 IT플랫폼이 중요한 위치를 점하지만, 아직 재난관리 분야에서 이를 본격적으로 도입, 활용하지 못하고 있다는 점은 큰 문제이다. 국내의 사정을 보면 다행히 벤처기업들을 중심으로 이 같은 플랫폼 구축 움직임이 시작되었으며, 여기에 활용될 데이터 자원을 창출할 수 있는 솔루션 및 특허기술들 역시 속속 등장하고 있다. 시민들이 재난현장을 스마트폰으로 실시간 공유하면 이 스마트 데이터들이 이미지 및 음향정보, 위치기반(GPS)정보, 시각정보, 3D정보, 빅데이터 정보, 센서정보 등으로 분류되어 플랫폼 안에서 인공지능(AI) 딥러닝 방식에 의해 분석되고, 이를 즉시 재난당국 및 시민들에게 재난긴급문자 등 자동으로 경보로 전해주는 것이 이 플랫폼의 핵심 기능이다. 몇몇 벤처기업이 보유한 특허기술을 기반으로 공공자본이 투입되어 이러한 플랫폼이 구축될 경우 국내 재난관리 수준의 획기적 발전은 물론 전 세계를 시장으로 한 플랫폼 수출 또는 글로벌 재난정보 수집능력에서도 엄청난 힘을 발휘할 것으로 기대된다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.7
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• pp.585-596
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• 2013

This study introduces a hybrid approach combining numerical results with pre-developed analytical calculations for the sound radiation from the modal vibration of a thick, finite length cylinder with various boundary conditions. Structural vibrations of the cylinder are numerically investigated with the finite element method, and distributions of vibratory displacements on the cylinder surface are idealized as simple mathematical expressions based on the numerical results. Sound radiations from the normal vibration of the cylinder are calculated based on idealized modal displacements using a previously introduced theoretical solution. The results are confirmed with numerical analyses using the boundary element method. Based on these results, it can be concluded that the solutions suggested in this study have good accuracies in calculating the vibro-acoustic properties of a thick, finite cylinder with various boundary conditions. Also, the sound radiation characteristics of many practical components such as brake drums and motor housings are expected to be investigated using the procedure proposed in this study.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.11
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• pp.982-986
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• 2013

The noise emitted from construction machinery has long been a cause of environmental disputes, especially to the nearby residents. In 2008, the Ministry of Environment adopted the construction machinery noise labeling system to encourage the development of the low noise construction machinery. After the implementation of the noise labeling system of the construction machinery, the noise emitted from the construction machinery has been decreased over the six years. But, as the quality of life improves, a growing number of people desire more comfortable and quite living environment. Under the situation, new systems like the low noise labeling system are considered to encourage the development of the low noise construction machinery. In accordance with the low noise labeling system, the construction machinery satisfying the standard of low noise are qualified to attach the low noise label in front of the products. Thus, the product qualified the low noise certification will be incentivized by the choice of the consumer. In this paper, we have studied the necessity of the low noise labeling system for the construction machinery and the considerations to adopt the low noise labeling system of construction machinery. And we have studied appropriate criterion to judge the low noise construction machinery. The considerations studied in this paper will be helpful to adopt the low noise labeling system of construction machinery in the future.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.6
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• pp.481-489
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• 2000

A time-frequency analysis method was developed to analyze the dispersive waves caused by impact loads in structural members such as beams and plates. Stress waves generated by ball drop and pencil lead break were recorded by ultrasonic transducers and acoustic emission (AE) sensors. Wavelet transform (WT) using Gabor function was employed to analyze the dispersive waves in the time-frequency domain, and then to find the arrival time of the waves as a function of frequency. The measured group velocities in the beam and the plate were compared with the predictions based on the Timoshenko beam theory and Rayleigh-Lamb frequency equations, respectively. The agreements were found to be very good.

• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.3
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• pp.188-194
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• 2016

We propose an acousto-optic technique for the nondestructive evaluation of adhesion properties of a Pt/Ti thin-film interface. Since there are some problems encountered when using prevailing techniques to nondestructively evaluate the interfacial properties of micro/nano-scale thin-films, we applied an interferometer that combined the acoustic and optical methods. This technique is based on the Michelson interferometer but the resultant surface of the thin film specimen makes interference instead of the mirror when the interface is excited from the acoustic transducer at the driving frequency. The thin film shows resonance-like behavior at a certain frequency range, resulting in a low-contrast fringe pattern. Therefore, we represented quantitatively the change in fringe pattern as a frequency spectrum and discovered the possibility that the interfacial adhesion properties of a thin film can be evaluated using the newly proposed technique.

• Journal of Korea Multimedia Society
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• v.5 no.4
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• pp.405-414
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• 2002

In this paper, we propose a new objective speech quality measure using noise masking threshold for speech quality assessment of mobile telephone network environments, and verify the effectiveness of the proposed method through the experiments. For such a purpose, well known objective speech quality measures such as BSD and PSQM are first evaluated for digital mobile telephone network environments. However, these conventional methods does not have good performance under mobile networks environments compared to literary results. To be mote effective objective speech quality measure under mobile telephone environments, the proposed method employs human psychoacoustic masking effect. The DMOS, instead of MOS, is used as a subjective speech quality measure for performance evaluation. The performance comparison are carried out with speech data collected from digital mobile telephone environments. As results, the proposed measure have and average 4% higher performance, in terms of correlation, than existing objective speech quality measures such as BSD and PSQM.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.10a
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• pp.629-632
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• 2009

The interactive art and design can be interpreted as an intelligent system in the aspect of engineering. Because this information is treated and analyzed in real time and then such results is expressed in various media such as image, graphic, sound and etc. after these information are input through the sensor, camera and etc., for the efficient communication between human and production, namely, to communicate the interactive reaction, The image utilizing such interactive is being gradually developed as it widens its region in various art design fields. This research is purposed to make the system, which lets the citizens contact the information naturally by mixing the information for the environment with the interactive art of the arty type, and which lets the citizens feel the surrounding environment directly. This research will construct the live mood in the space itself and is utilized for the public art that can be directly experienced. It can provide the experience in the participation type that acquires the information being harmonized with the human naturally in the more developed type than the concept of the existing static installation. Therefore, it is sincerely required to research the interactive art in utilizing the public design.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.10a
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• pp.267-273
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• 2004

This paper targets to define controlling factors of pressure-coupled combustion response and estimate their effects on droplet evaporation process. Dynamic characteristics of hydrocarbon propellant vaporization perturbed by acoustic pressure are numerically simulated and analyzed. 1-D droplet model including phase equilibrium between two phases is applied and acoustic wave is expressed by harmonic function. Effects of various design factors and acoustic pressure on combustion response are investigated with parametric studies. Results show that driving frequency of acoustic perturbation and ambient pressure have important roles in determining magnitude and phase of combustion response. On the other hand, other parameters such as gas temperature, initial droplet size and temperature, and amplitude of acoustic wave cause only minor changes to magnitude of combustion response. Resultant changes in phase of heat of vaporization and thermal wave in droplet highly influence magnitude and phase of combustion response.

• Journal of the Korea Society of Computer and Information
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• v.26 no.10
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• pp.37-43
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• 2021

Using the acoustic features of speech, important social and linguistic information about the speaker can be obtained, and one of the key features is the dialect. A speaker's use of a dialect is a major barrier to interaction with a computer. Dialects can be distinguished at various levels such as phonemes, syllables, words, phrases, and sentences, but it is difficult to distinguish dialects by identifying them one by one. Therefore, in this paper, we propose a lightweight Korean dialect classification model using only MFCC among the features of speech data. We study the optimal method to utilize MFCC features through Korean conversational voice data, and compare the classification performance of five Korean dialects in Gyeonggi/Seoul, Gangwon, Chungcheong, Jeolla, and Gyeongsang in eight machine learning and deep learning classification models. The performance of most classification models was improved by normalizing the MFCC, and the accuracy was improved by 1.07% and F1-score by 2.04% compared to the best performance of the classification model before normalizing the MFCC.