• Title, Summary, Keyword: spike model

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Improved Algorithm for Fully-automated Neural Spike Sorting based on Projection Pursuit and Gaussian Mixture Model

  • Kim, Kyung-Hwan
    • International Journal of Control, Automation, and Systems
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    • v.4 no.6
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    • pp.705-713
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    • 2006
  • For the analysis of multiunit extracellular neural signals as multiple spike trains, neural spike sorting is essential. Existing algorithms for the spike sorting have been unsatisfactory when the signal-to-noise ratio(SNR) is low, especially for implementation of fully-automated systems. We present a novel method that shows satisfactory performance even under low SNR, and compare its performance with a recent method based on principal component analysis(PCA) and fuzzy c-means(FCM) clustering algorithm. Our system consists of a spike detector that shows high performance under low SNR, a feature extractor that utilizes projection pursuit based on negentropy maximization, and an unsupervised classifier based on Gaussian mixture model. It is shown that the proposed feature extractor gives better performance compared to the PCA, and the proposed combination of spike detector, feature extraction, and unsupervised classification yields much better performance than the PCA-FCM, in that the realization of fully-automated unsupervised spike sorting becomes more feasible.

A HIGH-ORDER MODEL FOR SPIKE AND BUBBLE IN IMPULSIVELY ACCELERATED INTERFACE

  • Sohn, Sung-Ik
    • Korean Journal of Mathematics
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    • v.20 no.3
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    • pp.323-331
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    • 2012
  • We present a high-order potential ow model for the motion of the impulsively accelerated unstable interface of infinite density jump. The Layzer model for the evolution of the interface is extended to high-order. The time-evolution solutions of the bubble and the spike in the interface are obtained from the high-order model. We show that the high-order model gives improvement on the prediction of the evolution of the bubble and the spike.

Measuring benefits of providing water for environmental improvement in Daechi-stream and Ji-stream

  • Hong, Seungjee
    • Korean Journal of Agricultural Science
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    • v.43 no.2
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    • pp.275-287
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    • 2016
  • This study attempts to estimate the benefits of using water ensuing from the Chilgap multipurpose reservoir for environmental improvement. The contingent valuation method (CVM) was used to elicit the willingness to pay (WTP) for providing environmental improvement water from the Chilgap reservoir to Daechi-stream and Ji-stream. The DCDB (double-bound dichotomous choice) survey method was used to collect data for the analysis. Due to the usually high cost of increasing the sample size, the use of follow-up questions was implemented as an inexpensive method of improving the efficiency of the estimation. A spike model was used in this study because a number of respondents showed zero WTP. The spike model can be estimated as easily as the conventional model. Results show that the average annual household's WTP is 4,516 won using the conventional model and 8,644 won using the spike model. Applying the estimated average annual household's WTP to the Chungnam and Daejeon regional levels, the benefits of environmental improvement water from the Chilgap reservoir is estimated at 11.9 billion won per year. The temporal benefits of providing water for environmental improvement, for a 50-year period at a 6.0% discount rate, is estimated at about 190 billion won in the Chungnam and Daejeon areas. These results could be useful especially when the government tries to determine an appropriate level of investment and to make a policy related to providing environmental improvement water.

COMPUTATION AND ANALYSIS OF MATHEMATICAL MODEL FOR MOVING FREE BOUNDARY FLOWS

  • Sohn, Sung-Ik
    • Journal of the Korean Mathematical Society
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    • v.37 no.5
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    • pp.779-791
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    • 2000
  • The nonlinear stage of the evolution of free boundary between a light fluid and a heavy fluid driven by an external force is studied by a potential flow model with a source singlarity. The potential flow model is applied to a bubble and spije evolution for constantly accelerated interface (Rayleigh-Taylor instability) and impulsively accelerated interface (Richtmyer-Meshkow instability). The numerical results of the model show that, in constantly accelerated intergace, bubble grows with constant velocity and the spike falls with gravitational acceleration at later times, while the velocity of the bubble in impulsively accelerated interface decay to zero asymp flow model for the bubble and spike for constantly accelerated interface and impulsively accelerated interface.

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Artificial Brain for Robots (로봇을 위한 인공 두뇌 개발)

  • Lee, Kyoo-Bin;Kwon, Dong-Soo
    • The Journal of Korea Robotics Society
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    • v.1 no.2
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    • pp.163-171
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    • 2006
  • This paper introduces the research progress on the artificial brain in the Telerobotics and Control Laboratory at KAIST. This series of studies is based on the assumption that it will be possible to develop an artificial intelligence by copying the mechanisms of the animal brain. Two important brain mechanisms are considered: spike-timing dependent plasticity and dopaminergic plasticity. Each mechanism is implemented in two coding paradigms: spike-codes and rate-codes. Spike-timing dependent plasticity is essential for self-organization in the brain. Dopamine neurons deliver reward signals and modify the synaptic efficacies in order to maximize the predicted reward. This paper addresses how artificial intelligence can emerge by the synergy between self-organization and reinforcement learning. For implementation issues, the rate codes of the brain mechanisms are developed to calculate the neuron dynamics efficiently.

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Numerical Simulation and Experiment on Supersonic Air-Breathing Laser-Spike Propulsion Vehicle (초음속 공기 흡입식 레이저 스파이크 추진 비행체에 관한 수치 해석 및 실험적 연구)

  • Kim Sukyum;Kim Young-Taek;Jeong In-Seock
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.57-61
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    • 2004
  • As a kind of application of laser propulsion, air-breathing laser-spike engine can be designed for aircraft in atmospheric flight. Laser-spike engine generates thrust using the blast wave induced by laser energy instead of combustion process. And this engine use air as propellant, therefore, it need no on board propellant. For experimental study, supersonic wind tunnel and spark generator were used. Flow visualization was performed using 2-dimensional laser-spike engine model And numerical simulation of the corresponding case for the experiment was done and compared with experimental case. Detailed results will be discussed at the presentation.

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Analysis on Aerodynamic Heating on Spike and Dome Configuration (스파이크와 돔 형상의 공력 가열 해석)

  • Jung Suk Young;Yoon Sung Joon;Byon Woosik
    • 한국전산유체공학회:학술대회논문집
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    • pp.109-113
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    • 2002
  • Numerical analysis of aerodynamic heating for KPSAM is performed using aerodynamic heating model suitable to KPSAM, which has complex flow field resulting from the spike attached to the dome, such as large separation area and the strong shock/boundary layer interaction region around reattachment point on the dome. The aerodynamic heating model is validated and modified through the comparison between the flight test measurement and the thermal analysis results. TFD temperature sensors are installed on the dome to measure surface temperature during the flight. Computation results, obtained from the heat transfer analysis on the sensors, agree well with flight test data. The aerodynamic heating model provides heat transfer rate into surface as a boundary condition of unsteady 1D/axisymmetric thermal analysis on the missile structure. The axisymmetric thermal analysis using FLUENT is more versatile than the 1D analysis and can be applied to the heating problem related with complex structures and multi-dimensional heat transfer problems such as prediction of temperature rise at contact surface of different materials.

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Spike Response Model and Coding of Neurons (뉴런의 스파이크 응답 모델과 코딩)

  • Lee, Ho-Suk
    • Proceedings of the Korean Information Science Society Conference
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    • pp.5-8
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    • 2007
  • This paper discusses the spike response model of neurons. First, this paper discusses the coding of spikes, the function of spikes, and the construction of the spikes of neurons by the superposition of simple kernel functions. This paper discusses the method of kernel superposition is general than the response of the IF (Integrate-and-Fire) neuron model, too. Next, this paper discusses the coincidence detection and the input weight computation of spiking neurons and the activity of neuron populations in some detail.

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Estimation of Willingness to Pay for Reduction of Environmental Mortality Risk (환경오염으로 인한 위해도 감소에 대한 지불의사금액 추정에 관한 연구)

  • 김예신;이용진;박화성;남정모;김진흠;신동천
    • Environmental Analysis Health and Toxicology
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    • v.18 no.1
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    • pp.1-13
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    • 2003
  • To estimate the annual WTP for risk reduction of environmental problems such as outdoor and indoor air pollution, and drinking water contamination, a questionnaire survey was conducted by dichotomous contingent valuation method in Seoul. Several covariate models based on Turnbull, Weibull and Spike models were developed and applied to WTP estimation with uncertainty analysis. WTP estimates for risk reduction of air pollution were 13,000 won, 12,000 won, and 10,000 won per month in low-bounded Turnbull, Weibull and Spike models, respectively. The estimates for indoor air pollution were 17,000 won,20,000 won and 21,000 won and these for drinking water contamination were 10,000 won, 13,000 won and 14,000 won in each model, respectively. Goodness of fit for Weibull model was better than those for other models. WTP estimates for indoor air pollution were higher than those for other pollution problems.

Estimating Spot Prices of Restructured Electricity Markets in the United States (미국 전기도매시장의 전기가격 추정)

  • Yoo, Shiyong
    • Environmental and Resource Economics Review
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    • v.13 no.3
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    • pp.417-440
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    • 2004
  • For the behavior of the wholesale spot price, a regime switching model with time-varying transition probabilities was estimated using the data from the PJM (Pennsylvania-New Jersey-Maryland) market. By including the temperature as an explanatory variable in the transition probability equations, the threshold effect of changing regime is clearly enhanced. And hence the predictability of the price spikes was improved. This means that the model showed a very clear threshold effect, with a low probability of switching for low loads and low temperatures and a high probability for high loads and high temperatures. And temperature showed a clearer threshold effect than load does. This implies that weather-related contracts may help to hedge against the risk in the cost of buying electricity during a summer.

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