• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1275_1276
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• 2009

Micropump is very useful component in micro/nano fluidics and bioMEMS applications. Using the flexural vibration mode of PZT bar, a piezopump is successfully made. The PZT bar is polarized with thickness direction. The proposed structure for the piezo-pump consists of an input and an output port, piezoelectric ceramic actuator, actuator support, diaphragm. The traveling flexural wave along the bar is obtained by dividing two standing waves which are temporally and spatially phase shifted by 90 degrees from each other. Fluid is drawn into a forming chamber, eventually the forming chamber closes trapping the fluid therein.

• 전기학회논문지
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• 제62권9호
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• pp.1217-1222
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• 2013

It is very important to diminish noise source of electric motor systems that are used for home appliance area. We have studied on the noise reduction of BLDC motor, mainly focusing on reducing noise source from cogging torque. This noise source causes resonance of fan & motor systems. This study showed that the higher harmonic component of the cogging torque was the main factor for noise generation. Therefor, to reduce noise of bldc motor for refrigerator, this study suggested peanut shaped magnet which surface flux has similar sinusoidal wave form.

• 한국공작기계학회논문집
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• 제10권3호
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• pp.61-67
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• 2001

The remaining life estimation for the aged component is very important because mechanical properties of the compo-nents are degraded with time of service exposure in high temperature etc. The destructive method is widely used for the estimation of material degradation, but it has a difficulty in preparing specimens from in-service industrial facilities. In order to evaluate the feasibility of ultrasonic evaluation method for properties of high temperature materials, 2.25Cr-1Mo steel specimens which were prepared by the isothermal aging heat treatment at 63$0^{\circ}C$ were evaluated by ultra-sonic measurements investigating the change of velocities and attenuation coefficient. In this results, attenuation coefficient was found to be sensitive to material degradation mainly attributed to the change of grain size and the precipitation of impurities in grain boundaries, but velocity was not for all specimens.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2001년도 추계학술대회(한국공작기계학회)
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• pp.304-310
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• 2001

Flow pulsation often causes vibration and noise in piping systems and therefore has been a troublesome concern for fluid system engineers. According to frequency increase in this paper under the influence wave form of velocity in springly flow and viscosity are drop coefficient of viscosity become increase so that impedance and resistance. The transient variations of flow rate are measured by a modified impedance tube method which is realized by virtue of the present analytical technique. At pipe line in order to eliminate vibration, confirm happened intermittently impedance characteristics. We make a test and frequency analysis and have to minimize obstructive component at hydraulic circuit.

• 비파괴검사학회지
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• 제30권6호
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• pp.548-557
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• 2010

An ultrasonic resonance scattering spectroscopy technique is developed and applied for reconstructing elastic constants of a transversely isotropic cylindrical component. Immersion ultrasonic measurements are performed on tube samples made from a boron/aluminum composite material to obtain resonance frequencies and dispersion curves of different guided wave modes propagating in the tube. Theoretical analysis on the acoustic resonance scattering from a transversely isotropic cylindrical tube is also performed, from which complete backscattering and resonance scattering spectra and theoretical dispersion curves are calculated. A sensitive change of the dispersion curves to the elastic properties of the composite tube is observed for both normal and oblique incidences; this is exploited for a systematic evaluation of damage and elastic constants of the composite tube samples. The elastic constants of two boron/aluminum composite tube samples manufactured under different conditions are reconstructed through an optimization procedure in which the residual between the experimental and theoretical phase velocities (dispersion curves) is minimized.

• Journal of information and communication convergence engineering
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• 제9권2호
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• pp.207-211
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• 2011

This paper presents a method for facial feature representation and recognition from the Covariance Matrices of the Gabor-filtered images. Gabor filters are a very powerful tool for processing images that respond to different local orientations and wave numbers around points of interest, especially on the local features on the face. This is a very unique attribute needed to extract special features around the facial components like eyebrows, eyes, mouth and nose. The Covariance matrices computed on Gabor filtered faces are adopted as the feature representation for face recognition. Geodesic distance measure is used as a matching measure and is preferred for its global consistency over other methods. Geodesic measure takes into consideration the position of the data points in addition to the geometric structure of given face images. The proposed method is invariant and robust under rotation, pose, or boundary distortion. Tests run on random images and also on publicly available JAFFE and FRAV3D face recognition databases provide impressively high percentage of recognition.

• Journal of information and communication convergence engineering
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• 제6권3호
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• pp.249-254
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• 2008

Moored ocean buoys are technically feasible approach for making sustained time series observation in the oceans and will be an important component of any long-term ocean observing system. The 3M disc buoy carried Zeno 3200, MCCB, Orbcomm, Global Star and Bluetooth module. The deployments have relied on Orbcomm and Global Star as the primary satellite communications system. In addition to detailing our practical experience in the use of Orbcomm and Global Star as high latitudes, we will present some of scientific sensor results regarding real-time oceanographic and meteorological parameters such as wind speed, wave height and etc. In this paper we present the design and implementation of a small-scale buoy sensor network. One of the major challenges is that the network is hard to access after its deployment and hence both hardware and software must be robust and reliable.

• 한국통신학회논문지
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• 제17권5호
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• pp.521-528
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• 1992

본 논문에서는 IGBT를 사용한 새로운 PAM-PWM 인버터를 제안한다. 제안된 PAM-PWM 인버터의 출력파형을 이론과 실험적으로 연구하였다. 선간전압파형은 기본파 성분과 캐리어주파수의 사이드밴드로집중되며 저차고조파는 출력파형에 포함되지 않았으며, 각 인\ulcorner립各\ulcorner아암은 2/3주 기간동안 휴지기간을 설정하므로서 소자의 발열도 줄어든다. 그러므로 방열판의 감소에 의하여 인버터의 시스템의 크기도 작아진다.

• Transactions on Electrical and Electronic Materials
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• 제10권5호
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• pp.156-160
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• 2009

In an ultrasonic motor, a piezoelectric ceramic material forms the active element which vibrates the stator, thus initiating the rotational motion. In the operation of ultrasonic motors, many factors exist that can affect the resonance characteristics of the piezoelectric ceramic component. For examples, these factors are the bonding conditions with the piezoelectric element, the magnitude of the input voltage, the normal force in the frictional drive and the emission of heat due to vibration and friction etc. Therefore, it is important to research properly the inclination for variation of piezoelectric ceramics in the circumstance where complex elements are involved. In this paper, we focus on the analysis of the resonance characteristics of an ultrasonic motor as a function of the magnitude of the input voltage and the normal force.

• Tribology and Lubricants
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• 제26권6호
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• pp.341-345
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• 2010

The NAUT(Non contact Air coupled Ultrasonic Testing) is one of the ultrasonic wave inspection methods. It compensates High power ultrasound Pulser Receiver, pre-amp, air probe of high sensitivity in air to generate loss energy by NAUT methods. Generally, in case of ultrasound inspection, it applies contact methods by using couplant. However it can inspect of UT without couplant by this NAUT. The ultrasound transmission reception is composed in stable condition in NAUT. It can inspect high low material or the specimen of rough part, the narrow spot, too. The spot welding is applying the inosculation of automobile component, car body, all boards. The CFRP is necessity of NDE because of the solidity changes material according to lamella tearing. Therefore it checked on realization whether and commercialization in the spot welding and CFRP inspection that the NAUT would be applied them.