• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2008.04a
• /
• pp.345-349
• /
• 2008

In this paper, environmental noise analysis was performed for large power plant and desalination plant. Ray tracing method was used to predict inside noise of turbine building. It is important to design the plant with the allowable noise level. To improve the accuracy, main noise sources were estimated based on the field data. As the results of analysis, it was concluded that noise levels slightly exceed the specified noise limit in turbine building inside. In order to reduce the noise level, adding sound-absorbing materials to inside wall of turbine building was suggested and verified with the confirmed analysis model.

• The KSFM Journal of Fluid Machinery
• /
• v.6 no.3 s.20
• /
• pp.7-14
• /
• 2003

It is addressed that the turbulent broadband sound power from a sirocco fan can be modeled by the trailing edge noise. The trailing edge noise is usually influenced by inflow turbulence, separation, and boundary layer thickness on the blade. The design parameters such as solidity (c/s) and stagger angle are specified to predict performance and noise level because the separation and slip velocity are strongly affected by them along with the flow coefficient. This paper reports the effects of the stagger angle upon the trailing edge noise for various trailing edge shapes. It is believed that the serrated trailing edge provides break-up mechanism for organized convecting vortices, thereby reduce the overall noise level for every case of stagger angle.

• International Journal of Fuzzy Logic and Intelligent Systems
• /
• v.12 no.1
• /
• pp.77-85
• /
• 2012

This paper describes a novel approach to adaptive courseware generation. This approach adopts its structure from existing intelligent tutoring systems and introduces a new component called pedagogical scenario model to support pedagogical flexibility in the adaptation process of courseware generation system. The adaptation is carried out using Dynamic Constraint Satisfaction Problem framework, which is a variant of classical Constraint Satisfaction Problem, to deliver courseware tailored to individual learner. Such a framework provides a high level of expressiveness to deal with the particular characteristics of courseware generation problem. Further, it automatically designs a sound courseware satisfying the design constraints imposed by the domain, the pedagogical scenario and learner models.

• Proceedings of the KIEE Conference
• /
• 2001.11c
• /
• pp.420-423
• /
• 2001

In this paper, the Multi-FNNs(Fuzzy-Neural Networks) architecture is identified and optimized using HCM(Hard C-Means) clustering method and genetic algorithms. The proposed Multi-FNNs architecture uses simplified inference and linear inference as fuzzy inference method and error back propagation algorithm as learning rules. Here, HCM clustering method, which is carried out for the process data preprocessing of system modeling, is utilized to determine the structure of Multi-FNNs according to the divisions of input-output space using I/O process data. Also, the parameters of Multi-FNNs model such as apexes of membership function, learning rates and momentum coefficients are adjusted using genetic algorithms. An aggregate performance index with a weighting factor is used to achieve a sound balance between approximation and generalization abilities of the model. To evaluate the performance of the proposed model we use the time series data for gas furnace and the NOx emission process data of gas turbine power plant.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2000.05b
• /
• pp.283-286
• /
• 2000

In this study, the acoustic transducer of a thin circular disc-type with PZT/Metal was manufactured. The piezoelectric transducer with 200kHz resonance frequency was designed by considering the sharp directivity and the sound pressure. The dielectric and piezoelectric properties of 0.5 weight percent $MnO_2$ and NiO doped $0.1Pb(Mg_{1/3}Nb_{2/3})O_3-0.45PbTiO_3-0.42PbZrO_3$ ceramics were investigated aiming at acoustic transducer applications. Also, the acoustic characteristics of a thin circular disc-type with metal-piezoceramics have been Investigated.

• Proceedings of the KIEE Conference
• /
• 2005.10b
• /
• pp.382-384
• /
• 2005

When a hearing aid' s user is listening through telephone or cellular phone, he/she usually suffers from severe electrical magnetic interference noise. It is because hearing aids amplify voice signal as well as background noise. A telecoil, an induction coil, is a possible solution for the problem. Because a telecoil has the characteristic of high pass filter, it has some problem of resulting increased high frequency noise. For solving this problem, we can use a capacitor connected with the telecoil in parallel. According to capacitance, receiving signal quality may change. In this paper, proper capacitor values for the best sound quality are investigated by experimental work.

• Proceedings of the KIEE Conference
• /
• 2005.10b
• /
• pp.551-553
• /
• 2005

When a hearing aid' s user is listening through telephone or cellular phone, he/she usually suffers from severe electrical magnetic interference noise. It is because hearing aids amplify voice signal as well as background noise. A telecoil, an induction coil, is a possible solution for the problem. Because a telecoil has the characteristic of high pass filter, it has some problem of resulting increased high frequency noise. For solving this problem, we can use a capacitor connected with the telecoil in parallel. According to capacitance, receiving signal quality may change. In this paper, proper capacitor values for the best sound quality are investigated by experimental work.

• Journal of the Korean Home Economics Association
• /
• v.44 no.4 s.218
• /
• pp.175-190
• /
• 2006

The purpose of this research is to investigate consumers' experience of using Internet used-item markets in order to determine their motives in such activity. In terms of the Internet used-item market, (1) it contributes to a sound culture of consumption by recycling, (2) as a C2C market, it retains characteristics fundamentally different from the existing one-way type of market, (3) and it offers different characteristics from existing offline-based flea markets. Two significant themes emerged from the study results. First, users of Internet used-item markets passed through various stages such as novice, addict, and expert and learned the techniques for utilizing the used-item market. Second, for fast transactions with generalized Internet banking and the increasing trend for price bargaining emotional exchange among members is being transformed into the pursuit of transactional efficiency.

• Fashion & Textile Research Journal
• /
• v.3 no.1
• /
• pp.61-69
• /
• 2001

The purpose of this study was to analyze the purchasing behavior related factors of Small Store User in Yhasi street of Dong-Sung Ro, Daegu. Frequency, $X^2$-test MANOVA, ANOVA and Duncan multiple range test were used to analyze the sample. The results of this study were as follows: 1) The largest sample were as follows: un married female, college students of twenties, 101-200 thousand won for salaries. 2) The factors of purchasing behavior were classified into 8 factors, enjoy shopping, store image, unique goods, culture space, salesperson, low price, information seeking, value via price orientation. 3) There were significant differences found between attitude on information source, number of seeking store, music in shop, music sound, size, display, price, street, in their factors of purchasing behavior (unique goods, value via price, low price, store image, enjoy shopping) 4) There were significant differences found between demographic characteristics (personal sales, location, transportation) in their factors of purchasing behavior (salesperson, cultural space, store image).

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.21 no.8
• /
• pp.726-732
• /
• 2011

Straight absorptive silencers have been designed to reduce the noise level of a centrifugal blower. Three-dimensional boundary element method is used for the design of absorptive silencers which consist of a perforated main pipe and a outer chamber filled with fibrous material. The experimental results show that the absorptive silencer reduces up to 8 dB(A) in the overall sound pressure level of the blower and up to 15 dB at the blade passing frequency. It is also found that the gap between the silencer and the impeller may substantially alter the acoustic performance of the silencers. The transmission loss predicted by the boundary element method follows overall trends of the measured insertion loss. The experiments also show that the impact of the silencers on the aerodynamic performance of the blower is minimum.