• The Transactions of the Korean Institute of Electrical Engineers
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• v.45 no.2
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• pp.216-223
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• 1996

The active power factor control AC/DC converter needs a current loop compensator to obtain better dynamic characteristics and power factor performance, but the optimal design of a current loop compensator is difficult because the AC/DC converter is a nonlinear system having periodically varying poles and zeros. The predictive current control scheme generates a control input using the dynamic equations of the AC/DC converter so that the dynamic of the AC/DC converter is included in the controller and the necessary bandwidth and the gain characteristics of the current control loop are satisfied. And as a result, a compensator becomes unnecessary and the current loop shows the improved current loop characteristics. In this paper, a power factor controller without current loop compensator by adopting a predictive current control scheme is designed and the designed power factor controller is modelled by using a small signal perturbation modelling technique, and simulated to investigate its small signal characteristics. A 200 W power factor control AC/DC converter is built to verify the effectiveness of the proposed power factor controller.

• Journal of Astronomy and Space Sciences
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• v.32 no.1
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• pp.21-32
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• 2015

We have carried out photometric follow-up observations of bright transiting extrasolar planets using the CbNUOJ 0.6 m telescope. We have tested the possibility of obtaining high photometric precision by applying the telescope defocus technique, allowing the use of several hundred seconds in exposure time for a single measurement. We demonstrate that this technique is capable of obtaining a root-mean-square scatter of sub-millimagnitude order over several hours for a V~10 host star, typical for transiting planets detected from ground-based survey facilities. We compared our results with transit observations from a telescope operated in in-focus mode. High photometric precision was obtained due to the collection of a larger amount of photons, resulting in a higher signal compared to other random and systematic noise sources. Accurate telescope tracking is likely to further contribute to lowering systematic noise by exposing the same pixels on the CCD. Furthermore, a longer exposure time helps reduce the effect of scintillation noise which otherwise has a significant effect for small-aperture telescopes operated in in-focus mode. Finally we present the results of modelling four light-curves in which a root-mean-square scatter of 0.70 to 2.3 milli-magnitudes was achieved.

• Biomolecules & Therapeutics
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• v.29 no.5
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• pp.506-518
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• 2021

The imprinted tumour suppressor NOEY2 is downregulated in various cancer types, including ovarian cancers. Recent data suggest that NOEY2 plays an essential role in regulating the cell cycle, angiogenesis and autophagy in tumorigenesis. However, its detailed molecular function and mechanisms in ovarian tumours remain unclear. In this report, we initially demonstrated the inhibitory effect of NOEY2 on tumour growth by utilising a xenograft tumour model. NOEY2 attenuated the cell growth approximately fourfold and significantly reduced tumour vascularity. NOEY2 inhibited the phosphorylation of the signalling components downstream of phosphatidylinositol-3'-kinase (PI3K), including phosphoinositide-dependent protein kinase 1 (PDK-1), tuberous sclerosis complex 2 (TSC-2) and p70 ribosomal protein S6 kinase (p70S6K), during ovarian tumour progression via direct binding to vascular endothelial growth factor receptor-2 (VEGFR-2). Particularly, the N-terminal domain of NOEY2 (NOEY2-N) had a potent anti-angiogenic activity and dramatically downregulated VEGF and hypoxia-inducible factor-1α (HIF-1α), key regulators of angiogenesis. Since no X-ray or nuclear magnetic resonance structures is available for NOEY2, we constructed the three-dimensional structure of this protein via molecular modelling methods, such as homology modelling and molecular dynamic simulations. Thereby, Lys15 and Arg16 appeared as key residues in the N-terminal domain. We also found that NOEY2-N acts as a potent inhibitor of tumorigenesis and angiogenesis. These findings provide convincing evidence that NOEY2-N regulates endothelial cell function and angiogenesis by interrupting the VEGFR-2/PDK-1/GSK-3β signal transduction and thus strongly suggest that NOEY2-N might serve as a novel anti-tumour and anti-angiogenic agent against many diseases, including ovarian cancer.

• Journal of the Korean Geophysical Society
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• v.10 no.1
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• pp.13-25
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• 2007

We investigated the undulation of Moho depth and the crustal structure of the continental margin in the East Sea along the Korea Peninsula from inversion and modelling using potential data and previous seismic results. Free-air gravity anomalies generally reflect topography effect. Bouguer gravity anomalies increase toward the Ulleung Basin, indicating that Moho depth is shallower under the Ulleung Basin. Positive magnetic anomalies exist along the continental margin and decrease toward the Ulleung Basin. In analytic signal, the small anomaly in the Hupo Bank infers that the Hupo Bank is uplifted by igneous intrusion and the strong anomaly on the continental slope denotes existence of SDR(seaward dipping reflectors), which are in accordance with the location of SDR detected in previous seismic studies. The inversion result of Bouguer gravity anomaly and the 2-dimensional gravity modelling indicate that the undulation of Moho depth shallows from the continental shelf toward the Ulleung Basin. This is in good agreement with the Moho depth calculated by the previous seismic velocity model using ocean bottom seismometer(OBS). The 2-dimensional gravity modelling infers magmatic underplating zone under the lower continental crust on the continental margin of the East Sea, indicating the possible rifiting of the continental margin.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2005.11a
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• pp.190-200
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• 2005

In this paper, the image modelling of road's lane markings is established using view frustum(VF) modeling. This algorithm also involve the real time processing of the 3D position coordinate and the distance data from the camera to the points on the 3D world coordinate by the camera calibration. In order to reduce their measurement error, an useful algorithm for which analyze the geometric variations clue to traveling vehicle's fluctuation using VF model is proposed. In experiments, without correction, for instance, the $0.4^{\circ}$ of pitching rotation gives the error of $0.4^{\sim}0.6m$ at the distance of 10m, but the more far distance cause exponentially the more error. We confirmed that this algorithm can be reduced less than 0.1m of error at the same condition.

• Journal of Korea Multimedia Society
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• v.6 no.7
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• pp.1131-1138
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• 2003

Active noise control(ANC) is an approach to noise reduction in which a secondary noise source destructively interferes with the unwanted noise is introduced. Generally, the performance of ANC is determined how well a secondary noise tracks noises. A secondary noise is generated from the cancelling speaker and a error sensor pick up error signal. The transfer function between the cancelling speaker and the error sensor is not flat and distorts secondary noises. Consequently, the performance of ANC is degraded by the transfer function. In this paper, a single sensor ANC which considers the characteristics of the speaker and the error sensor is proposed. To reduce distortion of secondary noises, the transfer function is estimated by adaptive inverse modelling and the primary noises are estimated by Kalman filter. Experimental results show that the proposed single sensor ANC effectively attenuates noises.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.1 no.1
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• pp.95-104
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• 1997

This paper deals with an analysis of multipath which affect a transmission performance in underwater acoustic channel. For the test of autonomous underwater vehicle(AUV), underwater acoustic channel with multipath structure is introduced to mathmatical modelling for a basin environment. In this paper, SMR(Signal to Multipath Ratio) which is defined as a parameter of mulipath's effect is presented as a mathmatical equation, and the equation or SMR is simulated by MATLAB program.

• Journal of the Institute of Convergence Signal Processing
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• v.8 no.2
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• pp.119-123
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• 2007

This paper investigates a speed sensorless control of induction motor. The control strategy is based on MRAS(Model Reference Adaptive System) using load-torque observer as a reference model for flux estimation. The speed response of conventional MRAS controller characteristics is affected by variations of load torque disturbance. In the proposed system, the speed control characteristics using a load-torque observer control isn't affected by a load torque disturbance. Control algorithm that propose whole system through MATLAB SIMULINK because do modelling simulation result are presented to prove the effectiveness of the adaptive sliding mode controller for the drive variable load of induction motor. Therefore we hope to be extended in industrial application.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.29B no.2
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• pp.18-26
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• 1992

MR(Model Reduction) is presented in order to estimate the frequency of multiple sinusoids from the finite noisy data with the white or colored noises. MR, using the reduced rank models, is designed, appling the approximation of linear system to LP(Linear Prediction). The MR method is analyzed. Monte-carlo simulations are conducted for MR and Lp. The results are compared with in terms of mean, root-mean square and relative bias. MR eliminates effectevely the extremeous and exceptional poles appearing in LP and improves the accuracy of LP. Especially, MR gives promising results in short noisy measurements, low SNR's and colored noises. Power spectral density and angular frequency position are showed by figures, for examples. Finally, the new method is utilized to the communication and biomedical systems estimating the characteristics of the signal and the system identification modelling the dynamic systems from experimental data.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.51 no.12
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• pp.562-570
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• 2002

The Purpose of this paper is to design and manufacture an educational system in order to demonstrate the causes and effects of electromagnetic induction.'rho educational system described in this study is a "jumping ring apparatus". This system demonstrates the principle of electromagnetic induction, a force from AC sources, Lenz's law of repulsion and transformer. The educational system is composed of a jumping ring apparatus, a sensor array, encoder, A/D converter, D/A converter and nonlinear controller. The educational system is controlled by 586 PC using Turbo C program. The sensor array is composed of 20 optical sensors. The nonlinear controller consists of nonlinear control algorithm and control board included SCR, FET and phase controller. The A/D converter is used to show the height of ring position to analog for an education purpose. The control signal calculated from the nonlinear control of algorithm send control board through 8 bit D/A convertor. Experiment results are given to verify that Proposed nonlinear controller is useful in on line control of the educational system.al system.