• Journal of Mechanical Science and Technology
• /
• v.17 no.8
• /
• pp.1203-1210
• /
• 2003

Emission of ultrasonic vibration to turbulent flow promotes the turbulence generation due to the resonantly oscillating pressure field and thereby induced cavitation. In addition, ultrasonic vibration is well transmitted through water and not dissipated easily so that the micro-bubbles involved in the fluid induce the gaseous cavitation if the bubbles are resonated with the ultrasonic field. In the present study, we found through LDV measurement that the gaseous cavitation induced by ultrasonic vibration to CO$_2$saturated water flow in the rectangular cross-sectioned straight duct enhances turbulence much more than the case of non-ultrasonic or normal ultrasonic conditions without gaseous cavitation. We also found that the fluctuating velocity component induced by emitting the ultrasonic vibration in normal direction of a rectangular channel flow can be redistributed to stream-wise component by the agitation of gaseous cavitation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1997.10a
• /
• pp.263-270
• /
• 1997

For a cylinder in a uniform flow stream, sound is generated by the fluctuating pressure on the cylinder surface due to the vortex shedding behind the cylinder. It is known that the major parameters to predict the sound pressure are the characteristic length of the flow along the cylinder axis and the fluctuating lift coefficient. These parameters strongly depend on the Reynolds number and the yaw angle of the cylinder to the free stream. In this experimental study the effects of yaw on the flow parameters, and consequently on the generated sound are investigated. The surface pressure and the radiated sound are measured simultaneously for different yaw angles and showed that the reduced normal velocity component to the cylinder axis reduces the unsteady lift fluctuation which results in lowered sound press-are level, However, experimental result shows that "the cosine law" which uses the normal velocity component as a characteristic velocity for noise Generation from a yawed cylinder needs to be carefully reviewed. reviewed.

• Journal of Biosystems Engineering
• /
• v.28 no.3
• /
• pp.261-268
• /
• 2003

Ten MHz pulsed NMR spectrometer was used to measure the magnetic resonance characteristics of Korean red ginseng. The difference in the internal structures of good and bad red ginsengs was examined by their NMR characteristics. Average values of $T_1$ and free induction decay(FID) ratios of under grade Korean red ginseng were the highest among the three groups categorized as normal, medium and under grades Korean red ginseng and average values of $T_2$ and $T_2$$^{＊}$ of them were the lowest among the three groups. Principal component analysis(PCA) was used to observe the contribution of measured NMR values to the grade of Korean red ginseng. The measured $T_1$, $T_2$, $T_2$$^{＊}$ and FID ratio of 79 Korean red ginsengs classified as normal grade, medium grade and under grade were examined using PCA analysis. Cumulative variance of PC1 through PC3 occupied more than 90% of total variance at first and second NMR measurement. Plots of PC scores for the most important PCs showed that normal red ginseng samples were distributed around the left region of PC1 axis and most of the undergrade red ginseng samples were scattered around the right region of PC1 axis.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.10 no.12
• /
• pp.5464-5484
• /
• 2016

Few samples face recognition has become a highly challenging task due to the limitation of available labeled samples. As two popular paradigms in face image representation, sparse component analysis is highly robust while parts-based paradigm is particularly flexible. In this paper, we propose a probabilistic generative model to incorporate the strengths of the two paradigms for face representation. This model finds a common spatial partition for given images and simultaneously learns a sparse component analysis model for each part of the partition. The two procedures are built into a probabilistic generative model. Then we derive the score function (i.e. feature mapping) from the generative score space. A similarity measure is defined over the derived score function for few samples face recognition. This model is driven by data and specifically good at representing face images. The derived generative score function and similarity measure encode information hidden in the data distribution. To validate the effectiveness of the proposed method, we perform few samples face recognition on two face datasets. The results show its advantages.

• Journal of The Korean Astronomical Society
• /
• v.29 no.spc1
• /
• pp.143-144
• /
• 1996

Two-component models (normal star and degenerate star components) are the simplest realization of clusters with a mass spectrum because the high mass stars quickly evolve off leaving degenerate stars behind, while low mass stars survive for a long time as main-sequence stars. In the present study we examine the post-collapse evolution of globular clusters using two-component Fokker-Planck models that include three-body binary heating. We confirm that a simple parameter ${\epsilon}{\equiv} (E_{tot}/t_{rh})/(E_c/t_{rc})$ well describes the occurrence of gravothermal oscillations of two-component clusters. Also, we find that the degree of instability depends on the steepness of the mass function such that clusters with a steeper mass function are less exposed to instability.

• Proceedings of the KOR-BRONCHOESO Conference
• /
• 1987.05a
• /
• pp.7.2-7
• /
• 1987

Waver 와 Bray (1930) 가 cochlear microphonic을 처음 발견한 이래 Derbyshire 와 Davis (1935)는 summating potential을 각각 처음 기술하여 이 세가지 전위를 electrocochleogram 이라 칭하였고 이는 감음신경성 난청의 감별진단 및 청각생리연구에 이용되어 왔다. 저자들은 정상 guinea pig 10 마리를 대상으로 DANAC 7E ERA청각계기를 사용하여 정원창에서 action potential과 summating potential을 측정하였으며 주파수에 따른 역치 자극간 간격 및 두 potential의 상호관계를 분석하여 다음과 같은 결과를 얻었다. 1) 주파수가 증가함에 따라 그 역치는 점차 감소하였다. 2) 자극음의 강도와 action potential의 $N_1$ component 진폭은 상호 비례관계를 보여 주었으며 주파수 증가에 따라 $N_1$ component 진폭은 점차 증가하였다. 3) Action potential 의 $N_1$ component latency는 주파수가 증가할수록 역비례 관계를 보여 주었다. 4) N$_1$ component의 진폭과 자극간 간격(interstimulus interval, ISI)과의 관계는 ISI가 80~160m sec사이에서 plateau를 형성하였다. 5) summating potential은 자극음의 강도가 증가함에 따라 그 진폭이 증가하였으며 action potential도 증가하였으나, SP/AP는 감소하는 경향을 보였다.

• Journal of the Korean Solar Energy Society
• /
• v.21 no.1
• /
• pp.43-49
• /
• 2001

Informations of the solar radiation component are essential for modeling various solar energy systems. These Informations are particularly used for middle and high temperature applications, those need concentrating direct normal insolation. In order to estimate the performance of concentrating systems, it is necessary to know the intensity of the beam radiation, as only this component can be concentrated. The Korea Institute of Energy Research(KIER) has began collecting solar radiation component data since August, 1996. KIER's component data will be extensively used by concentrating system users or designers as well as by research institutes.

• Journal of KSNVE
• /
• v.9 no.2
• /
• pp.401-408
• /
• 1999

A method is presented for the vibration analysis of steam turbine-generator rotor system based on the component mode synthesis method. The motion of each component of the system is described by superposing constraint mode associated with boundary coordinates and constrained normal modes associated with internal coordinates. This method using real fixed-interface modes allows for significant reduction in system model size while retaining the essential dynamic characteristics of the lower modes. The capability of this method is demonstrated in the natural frequency and unbalance response analysis of the steam turbine-generator rotor system in which the dynamics of the pedestal is considered. The results by the present method are compared with finite element method and trnasfer matrix method in terms of the accuracy and computing time.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.35 no.7
• /
• pp.261-271
• /
• 1986

This paper describes a method for the state estimation considering current measurement component and detection of the bad data. The state values are estimated by weighted least square method in which measurement vector included bus injection current and line current. The bad data are detected using standardized variable of normal distribution and identified using sensitivity coefficients. When the bad data were occured by the bad measurement values. The results of the application to the model power system reveal the effectiveness of the presented algorithms.

• Proceedings of the Korean Fiber Society Conference
• /
• 2003.10a
• /
• pp.5-6
• /
• 2003

Kinetic study on the colloidal crystallization of single component and mixture of different sizes or densities of spheres was made in the exhaustively deionized suspensions and in microgravity, and compared with the results in normal gravity. Colloidal crystallization rates were retarded in microgravity for single component of spheres, whereas rates of alloy crystallization were enhanced substantially in microgravity. The rotational diffusion coefficients of colloids and the formation reaction rates of colloidal silica spheres were also studied in microgravity.