• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.6
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• pp.1-8
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• 2019

To resolve the conservative requirements for clear headed-bar spacing in KBC 2016 and ACI 318-08, two 2/3-scale exterior beam-column connections were tested under cyclic seismic loading. The seismic tests primarily explored the effect on their seismic performance of using (a) small clear spacings and (b) multiple layers of headed reinforcements in the beam. Also, the previous test data were thoroughly analyzed. It was concluded that the clear bar spacing of 2d_b or the use of two bar layers might be permitted for headed reinforcements embedded in exterior beam-column connections.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.256-256
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• 2009

에폭시수지에 층상실리케이트 나노입자를 충진함량별로 충진시킨 나노콤포지트를 제조하여 충진함량의 변화와 분산제 첨가를 통하여 분산제효과를 조사하였다, 충진함량의 변화는 1, 3, 5, 7, 9wt%과 분산제 변화를 05, 1.5, 2.5wt%로 구조적, 열적, 전기적 특성을 조사하였다. 분산처리는 초음파 기법을 적용하여 분산하였다. 구조적 특성으로 X-RD조사한 결과 0.5wt%분산제처리를 한 경우 완전한 박리를 가져오지 못하였고, 부분적인 박리를 가져왔다. 이는 분산제 처리량이 나노입자 표면정체를 제어할수 없기 때문으로 사료된다. 분산제 1.5wt%를 첨가한경우로 충진함량별 X-RD특성은 1wt%는 완전한 박리를 나타내었고 함량의 증가에 따라 박리정도가 약간 낮아지는 경우를 알 수 있다. 이런 경우 전기적특성중 단시간 절연파괴특성에서 나타내고 있다. 충진함량이 낮을수록 스케일파라미터의 값이 높고, 함량이 증가할수록 낮아지는 경우이다. 이는 분산정도에따라 절연파괴강도에 영향을 주고 있음을 알 수 있다. 열적특성에서 유리천이온도는 1,3,5wt%에서는 증가하는 결과를 더욱 충진함량이 증가하면 오히려 감소되는 특성을 나타내고 있다. 결국은 분산정도에따라 전기적 특성 및 열적특성이 크게 변화되는 특성을 나타내었다.

• Journal of the Korean Society for Nondestructive Testing
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• v.31 no.5
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• pp.516-521
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• 2011

The basilar membrane, an important functional part of the cochlea, is responsible for spectral separation of vibration signals transmitted from the stapes. In current study, scaled-up polymer membranes designed by mimicking the human basilar membrane were used for investigation of the frequency-separation characteristic. Displacement field formed on each polymer membrane was acquired by Laser Doppler scanning vibrometer and post-processed frequency-wise. The locations of the maximum displacement along the centerline were identified and collected for individual frequency range to produce the frequency-position map of individual polymer membrane. The influences of the membrane thickness and material properties on the variation of the frequency separability were discussed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.1
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• pp.596-602
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• 2018

Nanoimprint lithography (NIL) is an emerging technology that enables cost-effective and high-throughput nanofabrication. In ultraviolet (UV) NIL, low-cost and high-speed production can be achieved using a non-vacuum environment at room temperature and low pressure. However, there are problems with the formation of bubble defects in such an environment. This paper investigates the shape of the mold cavity and the bubble defect formation in UV NIL in a non-vacuum environment. The bubble defect formation was simulated using two-dimensional flow analysis and the VOF method for commonly used cavity mold shapes (rectangular, elliptical, and triangular). The characteristics of the resist flow front and various contact angles were also analyzed. The shape of the mold cavity had a very significant effect on the bubble defect formation. For all cavity shapes, a smaller contact angle with the mold and larger contact angle with the substrate decreased the possibility of bubble defect formation. The elliptical shape was the most effective for preventing bubble defect formation.

• Journal of Korea Multimedia Society
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• v.4 no.4
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• pp.306-315
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• 2001

In noise reduction method from noisy speech for speech recognition in noisy environments, conventional spectral subtraction method has a disadvantage which distinction of noise and speech is difficult, and characteristic of noise can't be estimated accurately. Also, noise reduction method in the wavelet transform domain has a disadvantage which loss of signal is generated in the high frequency domain. In order to compensate theme disadvantage, this paper propose spectral subtraction method in continuous wavelet transform domain which speech and non- speech intervals is distinguished by standard deviation of wavelet coefficient, and signal is divided three scales at different scale. The proposed method extract accurately characteristic of noise in order to apply spectral subtraction method by end detection and band division. The proposed method shows better performance than noise reduction method using conventional spectral subtraction and wavelet transform from viewpoint signal to noise ratio and Itakura-Saito distance by experimental.

• Korean Chemical Engineering Research
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• v.47 no.2
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• pp.208-212
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• 2009

The nano-clay is widely used in polymer-nanocomposites due to the high aspect ratio, heat resistance and nano-scale dimension. In recent researches, the thermal and mechanical properties of polyurethane foam were improved with introducing the nano-clay. In this study, we describe the influence of ultrasonic treatment and content of nano-clay on properties of polyurethane foam. The nano-clay/polyurethane foam were characterized using their recovery time, compressive deflection, cell morphology and tensile test. The ultrasonic treatment was very effective for dispersion of nano-clay. Moreover, we found that introducing over 3 wt% of nano-clay bring the decrease of properties due to the poor dispersion. Expecially, ultrasonically treated 20A/polyurethane foam(1 wt%) showed greatly improved properties, such as homogeneous cell size and good dimension stability. We expect that our results could be applied to insulating materials for construction.

• Journal of The Korean Association of Information Education
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• v.12 no.2
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• pp.235-244
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• 2008

According to develop the computer and communication technology, recently educational environment is growing to ubiquitous learning with direction which select the studying content, studying time and a studying order oneself. In order to raise effect of studying in the ubiquitous learning(u-Learning), the help or advice of the specialist is necessary earnestly. Accordingly, if it will combine the scaffolding and the mentoring in the u-Learning, a studying effect will be maximize. This paper design the u-SM(Scaffolding and Mentoring) teaching and learning model which applies the scaffolding and e-mentoring. In addition, it embodies and applies the designed u-SM model. Then it examines it affects in studying achievements and attitudes of students and verifies the application possibility of the u-SM teaching and learning.

• The Journal of the Acoustical Society of Korea
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• v.22 no.4
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• pp.299-307
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• 2003

There have been many studies on speaker normalization which aims to minimize the effects of speaker's vocal tract length on the recognition performance of the speaker independent speech recognition system. In this paper, we propose a simple vector quantizer based linear warping speaker normalization method based on the observation that the vector quantizer can be successfully used for speaker verification. For this purpose, we firstly generate an optimal codebook which will be used as the basis of the speaker normalization, and then the warping factor of the unknown speaker will be extracted by comparing the feature vectors and the codebook. Finally, the extracted warping factor is used to linearly warp the Mel scale filter bank adopted in the course of MFCC calculation. To test the performance of the proposed method, a series of recognition experiments are conducted on discrete HMM with thirteen mono-syllabic Korean number utterances. The results showed that about 29% of word error rate can be reduced, and that the proposed warping factor extraction method is useful due to its simplicity compared to other line search warping methods.

• Composites Research
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• v.28 no.5
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• pp.285-290
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• 2015

Multiscale multiphysics in structural batteries make mechanical property testing difficult. In this research, the effect of electrolyte-coating on the mechanical performance of carbon fabric was studied using a suitable mechanical test method for structural batteries. For this experiment, two types of specimens were determined their dimension according to ASTM. One type of specimen was smaller than the standard dimension. The specimens were coated by spreading the electrolyte material on carbon fabric, hardened using epoxy, and tested for tensile properties using universal testing machine. As a result, it was found that the mechanical properties of carbon fabric were not influenced by electrolyte coating. In addition, the small-scale specimen used in this experiment was determined to be sufficiently reliable.

• Journal of the Korea Concrete Institute
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• v.21 no.5
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• pp.599-609
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• 2009

This paper discusses generalized modeling schemes for both reinforced concrete (RC) and post-tensioned (PT) flat plate buildings. In this modeling approach, nonlinear behavior due to slab flexure, moment and shear transfer at slab-column connections, and punching shear was included along with linear secant stiffness of each member or connection that accounts for concrete cracking. This generalized model was capable of simulating all different scenarios of slab-column connection failures such as brittle punching, flexure-shear interactive failure, and flexural failure followed by drift-induced punching. Furthermore, automatic detection of drift-induced punching shear and subsequent backbone curve modifications were realistically modelled by incorporating the limit state model, in which gravity shear versus drift capacity relations were adopted. The validation of the model was conducted using one-third scale two-story by two-bay RC and PT flat plate frames. The comparisons revealed that the model was robust and effective.