• Journal of the Korean Vacuum Society
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• v.21 no.1
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• pp.36-40
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• 2012

We have developed the detection method of the resonance frequency of micro/nano mechanical resonator using optical method. The optical interferometery method enabled us to detect the displacement change of resonators within several nm scale. The micro mechanical resonator was produced by attaching a micro mechanical cantilever to a piezo ceramic. The mass of cantilever was increased by evaporating Au using electron beam evaporator and the mass variation was estimated by detecting the resonance frequency changes.

• Journal of Digital Convergence
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• v.13 no.12
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• pp.187-192
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• 2015

If the software is developed to analyze the speech disorder, the application of various converged areas will be very high. This paper implements the user-friendly program based on CART(Classification and regression trees) analysis to distinguish between normal and pathological voices utilizing combination of the acoustical and HOS(Higher-order statistics) parameters. It means convergence between medical information and signal processing. Then the acoustical parameters are Jitter(%) and Shimmer(%). The proposed HOS parameters are means and variances of skewness(MOS and VOS) and kurtosis(MOK and VOK). Database consist of 53 normal and 173 pathological voices distributed by Kay Elemetrics. When the acoustical and proposed parameters together are used to generate the decision tree, the average accuracy is 83.11%. Finally, we developed a program with more user-friendly interface and frameworks.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.1
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• pp.1-7
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• 2015

The environmental regulations for CO2 emissions from the ship have been established recently, and fuel oil price has been increased continuously. In order to overcome these circumstances, Energy Saving Devices (ESDs) have been developed continuously to reduce the fuel oil consumption and improve the propulsive efficiency. This paper describes the trial performance of PBCF (Propeller Boss Cap Fins), SCHNEEKLUTH duct, Asymmetric rudder bulb and Mewis duct applied to handy-size bulk carriers. As a result, SCHNEEKLUTH duct is more effective than other energy saving devices at the reducing the fuel oil consumption and the improvement of the propulsive efficiency. In addition, it is confirmed that SCHNEEKLUTH duct is really effective in the vibration of the deck house. And the fuel oil consumption can also be reduced through main engine de-rating.

• The Journal of the Acoustical Society of Korea
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• v.21 no.5
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• pp.446-454
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• 2002

This paper presents the Doppler Scanning technique which enables us to detect the relative positions of moving distributed sources using Doppler frequency shift estimate when the moving source consists of distributed sources with different signature frequencies. Doppler frequency shifts of characteristic frequencies of machinery noise sources such as ship's generator and propeller, with tine along CPA (Closest Point of Approach of moving source) are unique, and can be functioned with respect to each source position. Therefore, this technique can be applied to estimate the relative geometrical positions between machinery noise sources. The Extended Kalman Filter (EKF) which has a high frequency resolution with high time resolution, is adopted for improving accuracy of Doppler frequency shift estimate geometric resolution of machinery positions since machinery noise sources show in general low frequency band characteristics with limited spacial distance. The performance of the technique is examined by the numerical simulations and is verified by the experiment using loudspeaker sources on the roof of the car.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.3C
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• pp.85-94
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• 2012

This paper described a centrifuge study in order to investigate ground-underground hollow structure interaction-induced rocking behavior in liquefied ground. Uplift of the underground hollow structures is initiated due to liquefaction in sandy grounds when the ground is exposed to a strong shaking during earthquakes because the apparent unit weight of these structures is smaller than that of the liquefied soil. In order to evaluate the dynamic behavior of the underground hollow structure and the effects of original subsoil during the uplifting, model tests were performed by changing the relative density of the original subsoil and installing an acrylic box as a trench. The results of the present study show that rocking behavior of the underground hollow structure due to shear deformation of the surrounding subsoil or lateral movement from the original subsoil contributed to large magnitude of the uplift due to strong shaking.

• Journal of Sensor Science and Technology
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• v.5 no.3
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• pp.65-73
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• 1996

One of the important factor in drug stuffs to a patient is to inject exact amount with stable flow rates. Since improper injection amount and flow rates would cause bad effect to recovery of a patient, the detecting sensors with high sensitivity is required for an injection pump systems' performance improvement. In this study, the three sensors, piezo film sensor, photo transistor and photo array, were compared to find best one for an injection pump monitoring system. Using suggested data processing technique and photo array sensors, we could minimize the effect of interference, disturbance, illumination, and sensitivity change caused by sensor's position. According to the experiments, the photo array showed the higher reliance than any other the three types of sensors.

• Computational Structural Engineering
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• v.3 no.4
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• pp.133-141
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• 1990

The nature of fluctuating air pressure inside building was studied by testing a building model in a wind tunnel. The model has a single room and a window opening. Various opening conditions were tested in both laminar uniform wind and turbulent boundary-layer wind. The RMS and the spectra of the fluctuating internal pressure were measured. The test results support a recent theory which predicts the behavior of internal pressure under high wind based on aerodynamic analysis.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.181-182
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• 2016

본 논문은 최대전력점 추종 제어기법의 성능 개선을 위한 독립형 태양광 발전시스템의 하이브리드 기법을 제안한다. 하나의 기법만을 사용하는 경우, 일사량 및 온도 조건에 따라 비선형적 출력특성을 갖는 태양전지의 최대출력점을 효율적으로 추종하기 어렵다. 제안한 방법은 가변 스텝 사이즈를 적용한 Perturb and Observe (P&O) 기법으로 과도상태의 추종성능을 보장하고, Incremental Conductance (InC) 기법으로 정상상태의 자려진동을 감소시켜 출력 전력의 효율을 높일 수 있다. 1.4kW 태양광 발전시스템을 모의하여 수행된 PSIM 시뮬레이션 결과로 제안한 알고리즘의 타당성을 검증하였다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.364-367
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• 2005

A series of computational simulations have been carried out for non-reacting and reacting flows in channel-type and divergent scramjet combustor configurations with and without a cavity. Transverse injection of hydrogen is considered with the injection pressure varying from 0.5 to 1.5 MPa. The detailed resolution of the oscillatory flow and flame dynamics are captured at sufficient scale to identify the underlying physical mechanisms, and the role of combustor configuration, cavity and amount of heat addition could be understood.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.44-47
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• 2002

A liner static and dynamic analysis for a golf shaft, which is made of carbon fiber reinforced composite materials, is presented in this study. Major mechanical parameters of golf shafts such as deflection, torsional angel, frequency of vibration(CPM), and kick point are analyzed by finite element method. The effects of major parameters on the performance of golf shafts are also discussed. The results show that the major parameters of golf shafts are strongly dependent on the material properties of fibers and design pattern of golf shafts. The present results will be useful to design sheet-rolled golf shafts.