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Spike-triggered Clustering for Retinal Ganglion Cell Classification
안정렬,유용석,구용숙 한국뇌신경과학회 2020 Experimental Neurobiology Vol.29 No.6
Retinal ganglion cells (RGCs), the retina’s output neurons, encode visual information through spiking. The RGC receptive field (RF) represents the basic unit of visual information processing in the retina. RFs are commonly estimated using the spike-triggered average (STA), which is the average of the stimulus patterns to which a given RGC is sensitive. Whereas STA, based on the concept of the average, is simple and intuitive, it leaves more complex structures in the RFs undetected. Alternatively, spike-triggered covariance (STC) analysis provides information on second-order RF statistics. However, STC is computationally cumbersome and difficult to interpret. Thus, the objective of this study was to propose and validate a new computational method, called spike-triggered clustering (STCL), specific for multimodal RFs. Specifically, RFs were fit with a Gaussian mixture model, which provides the means and covariances of multiple RF clusters. The proposed method recovered bipolar stimulus patterns in the RFs of ON-OFF cells, while the STA identified only ON and OFF RGCs, and the remaining RGCs were labeled as unknown types. In contrast, our new STCL analysis distinguished ON-OFF RGCs from the ON, OFF, and unknown RGC types classified by STA. Thus, the proposed method enables us to include ON-OFF RGCs prior to retinal information analysis.
안정렬(J.R. Ahn),전태원(T.W. Chun),이홍희(H.H. Lee),김흥근(H.G. Kim),노의철(E.C. Nho) 전력전자학회 2005 전력전자학술대회 논문집 Vol.- No.-
The stroke of piston in the linear compressor driven by LPMSM can be obtained from integrating the input voltage and current of LPMSM, and may be diverged due to dc components in the voltage and current. The strategy to prevent the divergence of stroke using both the high-pass filter and dc offset compensation was suggested. The equations for the magnitude and phase of the stroke and also dc offset including the stroke are derived as a function of the cut-off frequency of HPF. The performance of stroke calculation scheme has been verified by experimentally on a linear compressor drive system, where the control was implemented by a 16-bit DSP.
안정렬(J.R. Ahn),T.Q. Vinh,전태원(T.W. Chun),김흥근(H.G. Kim),노의철(E.C. Nho) 전력전자학회 2008 전력전자학술대회 논문집 Vol.- No.-
In this paper, the techniques for implementing the dashboard functions of a SHEV bus are development by using a touch panel. The algorithms for controlling linearly the angle of each gauge according to the measured sensors values. The hardware technique presentation and the development for implementing the On/Off information of each telltale lamp in the touch panel. The system is implemented by the 32-bit DSP, and it is installed and tested on the real SHEV bus. Also on/off switching status of all telltale lamps cab be investigated through the touch panel.
안정렬(J.R. Ahn),전태원(T.W. Chun),이홍희(H.H. Lee),김흥근(H.G. Kim),노의철(E.C. Nho) 전력전자학회 2005 전력전자학술대회 논문집 Vol.- No.-
In this paper, the PWM inverter-motor drive system including sensor is controlled through the network. The algorithm to compensate for the time delay of ac current and ac voltage sensors due to the network is proposed. The delay time of sensors is kept nearly constant, using the synchronous signal and timers. The error between the real and estimated ac signals can be reduced by using two slopes for estimating the value of ac signals. The proposed algorithms are verified with the simulation studies and experiments.
안정렬(J.R.Ahn),전태원(T.W.Chun),이홍희(H.H.Lee),김흥근(H.G.Kim),노의철(E.C.Nho) 전력전자학회 2003 전력전자학술대회 논문집 Vol.2003 No.7(1)
A reciprocating compressor with a rotary motor used in a refrigerator has low efficiency, because it has the large mechanical losses due to the crank mechanism The linear compressor which has the free piston driven by a linear motor, was developed to Increase the efficiency of compressor by reducing mechanical losses. The TRIAC has been widely used for controlling the piston, because It has simple structure<br/> However, as it is able to control only stator voltage, It is very difficult to obtain good efficiency. Recently, PWM Inverter which is able to control the voltage as well as the frequency, is applied to linear compressor drive system to overcome above problem<br/> In This paper, the variations for efficiency and power factor of linear compressor are investigated by changing both the mechanical resonant frequency and electrical resonant frequency of linear compressor, and also the inverter frequency. The optimum relationships between both resonant frequencies and the inverter frequency is derived in order to obtain the maximum efficiency and also good power factor
DTC를 사용한 3레벨 인버터-유도전동기 구동시스템의 토크리플 저감방법
안정렬(J.R. Ahn),전태원(T.W. Chun),이홍희(H.H. Lee),김흥근(H.G. Kim),노의철(E.C. Nho) 전력전자학회 2006 전력전자학술대회 논문집 Vol.- No.-
This paper proposes a simple technique to reduce the torque ripple in the direct torque control(DTC) of induction motor driven by 3-level inverter. In the traditional DTC method, both the sampling time and the measurement time delay of sensor value have much influence on the stator flux ripple as well as torque ripple. The dithering technique where the high frequency triangular wave is added to the torque error component, is applied to the DTC using the 3-level inverter in order to reduce the torque ripples. The performances of the proposed method are verified with simulation results.
안신영,김수관,최영옥,김완배,강태호,박정렬,김상호,하정완 대한치과이식임플란트학회 2002 The Korean Academy of Implant Dentistry Vol.21 No.1
Sinus lifting is performed to increase the bone thickness before placement of osseointergrated implants in areas of posterior maxilla where is insufficient bone between the inferior border of the maxillary sinus mucosa and alveolar bone. Full sectional information should be available to the surgeon before the sinus lift operation so that the outcome can be predicted and to allow for assessment of the volume of bone graft required. It is also useful to assess the success of procedure before placement of implant, and to choose the implant length and orientation required for initial stability. The purpose of this study was to evaluate the efficiency of sinus lift, cause of failure, and preventive method.