• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.844-847
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• 2008

As customer's demands are varying, the type of floor plan of apartment is changed into expanded type with balcony unified to living room from general type with balcony separated from living room and so is changing the layout of L(living room), D(dining room) and K(kitchen). This study aims to examine how the type of floor plan of living room affects the floor impact sound insulation performance and to propose fundamental idea to floor plan layout of apartment in terms of floor impact sound reduction.

• The Journal of the Acoustical Society of Korea
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• v.15 no.5
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• pp.30-37
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• 1996

In the communication system, adaptive equalizer using LMS algorithm has slow convergence rate in spite of effectiveness and simplicity. In this paper, we designed the wavelet transform based adaptive equalizer to overcome this problem. The performance of this new approach is compared with that of the time domain LMS algorithm by convergence rate with respect to change of channel distortion and filter order. As a result, the wavelet transform based adaptive equalizer shows the improvements in the speed of convergence compared with LMS algorithm based adaptive equalizer.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.3
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• pp.53-60
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• 1988

The behavior of plane buoyant jet issuing vertically upwards into cross flow is analysed by experiments and integral scheme. The integral scheme is based on the self similarity and characteristic length scales to governing equations of continuity, momentum and constituent transport equation, in the horizontal and vertical flow region, respectively. Jet trajectories and the temperature distributions of jet centerlines obtained from experiments are analysed for various velocity ratios and densimetric Froude numbers. It was found that the analytical results about the trajectories and temperatures of jet center lines agree with the experiments and can be expressed as power laws.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.6
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• pp.792-801
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• 2000

The problem of phase change from liquid to solid in the inviscid plane-stagnation flow is theoretically investigated. The solution at the initial stage of freezing is obtained by expanding it in powers of time, and the final equilibrium state is determined from the steady-state governing equations. The transient solution is dependent on the three dimensionless parameters, but the equilibrium state is determined by one parameter of (temperature ratio/conductivity ratio). The effect of the fluid flow on the growth rate of the solid in the pure conduction problem can be clearly seen from the solution of the initial stage and the final equilibrium state. The characteristics of the transient heat transfer at the surface of the solid and the liquid side of the solid-liquid interface for all the dimensionless parameters are elucidated.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1990.04a
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• pp.151-162
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• 1990

Occupational disease among typists such as Carpal Tunnel Syndrome(CTS) and tendonitis has increased along with rapid expansion of office automation. During typing, the posture can be defined as forearm pronation, ulnar abduction, wrist extension and finger flexion. The CTS results from awkward posture between forearm-wrist-hand and the keyboard arrangement. Therefore, ergonomic principles should be emphasized in keyboard design. The objective of the study is to improve keyboard design by analyzing anatomical posture of forearm and hand during typing. An experimental study was performed to investigate relationships between a keyboard and typing performance. Results showed that typing performance is dependent to angles and slopes of a keyboard. Statistical analysis indicated that the suggested ergonomic keyboard improved typing speed significantly(17%).

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.5
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• pp.588-594
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• 1998

Heat transfer characteristics of distance between impinging surface and a plane jet were experi-mentally investigated. The local heat transfer coefficients were measured by a thermochromic liq-uid crystal(TLC) The jet Reynolds number studied was varied over the range from 10,000310 to 30,000310 the nozzle-to-plate distance (H/B) from 4 to 10. It was observed that the Nusselt number increases with Reynolds number the occurrence of the secondary peak in the Nusselt number is within the potential core region the potential core of the jet flow can reach the impinging surface so that the wall jet can a transition from laminar to turbulent flow resulting in a sudden increase in the heat transfer rate.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2006.05a
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• pp.216-220
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• 2006

평면 광 신호 분리기와 광 케이블의 정밀결합을 위하여 V-groove를 제작하였다. V-groove 는 실리콘웨이퍼 (100) 면을 KOH 용액으로 선택적 습식 식각하여 제작되었다. V-groove 를 효과적으로 제작하기 위하여 KOH 의 조성 (10, 20, 30, 33, 40 wt%)과 온도 (50, 60, 70, $80^{\circ}C$)를 변화시켜 식각률과 표면조도를 측정하였다. 식각률은 $80^{\circ}C$에서 20 wt.% KOH 로 식각했을 경우 $1.84{\mu}m/min$ 로 가장 빨랐으며, 표면조도는 $80^{\circ}C$에서 33 wt.% KOH로 식각했을 경우 1.6nm로 가장 양호하였다.

• The Journal of the Acoustical Society of Korea
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• v.15 no.1
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• pp.40-45
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• 1996

In this paper, a nonlinear optimal design technique is presented to find an optimal beam pattern. With this technique, the beam width is minimized with respect to a given maximum allowable side-lobe level considering the self- and mutual radiation impedances of vibrators. The proposed method is applied to design a planar array consisting 37 vibrators which are symmetric in X, Y and $45^{circ}$ axes. The results show that significantly low side-lobe level maintaining a main beam width can be obtained using this method.

• Computational Structural Engineering
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• v.11 no.4
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• pp.287-294
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• 1998

입면의 형태가 임의의 층에서 큰 차이를 보이는 3차원 비정형 setback 구조물의 동적 거동 특성과 이들 구조물의 동적 거동에 미치는 바닥 슬래브의 면내 변형 효과를 분석하였다. 비정형 setback 구조물의 전반적인 동적 거동특성을 분석하기 위하여 베이스 부분의 평면적과 타워 부분의 평면적 비(R?), setback 발생위치(L?)등을 매개 변수로 사용하였다. 48개의 비정형 setback 구조물들에 대한 해석 수행 결과 setback 구조물은 정형 구조물에 비해 횡방향 1차 모드의 유효 모드 중량(effective modal weight)이 작게 나타나는 경향을 보이기 때문에 setback 구조물의 동적 거동을 파악하기 위해서는 등가 정적 해석법 대신에 동적 해석을 수행할 필요가 있음을 알 수 있었다. 바닥슬래브의 면내 변형은 보다 긴 구조물의 고유 진동 주기값을 가져오며 모드 순서 및 모드 형상에도 변화를 준다. 이러한 사실은 바닥슬래브의 면내 변형으로 인하여 횡방향 저항 요소들간의 전단력 분포와 층 변위가 영향을 받을 수 있다는 것을 의미한다. 이러한 현상은 횡방향 저항 요소들간의 강성 차가 심한 프레임-전단벽 시스템에서 두드러지게 나타난다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.3
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• pp.260-270
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• 1998

The viscous plane stagnation-flow solidification problem is theoretically investigated. An analytic solution at the beginning of solidification is obtained by expanding the temperature and thickness of solidified layer in powers of time. An exact expression for the steady-state thickness of solidified layer is also obtained. The .fluid flow toward the cold substrate inhibits the solidification process. As Stefan number becomes larger, or Prandtl number becomes smaller, the solidification is more strongly inhibited by the fluid flow. The transient heat flux at the liquid side of solid-liquid interface is increased, as Stefan number or Prandtl number is increased.