• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.6
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• pp.276-286
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• 2013

SVD-based deconvolution algorithm has been known as the most effective technique for CT perfusion image analysis. In this algorithm, in order to reduce noise effects, SVD coefficients smaller than a certain threshold are removed. As the truncation threshold, either a fixed value or a variable threshold yielding a predetermined OI (oscillation index) is frequently employed. Each of these two thresholding methods has an advantage to the other either in accuracy or efficiency. In this paper, we propose a Monte Carlo simulation method to evaluate the accuracy of the two methods. An extension of the proposed method is presented as well to measure the effects of image smoothing on the accuracy of the thresholding methods. In this paper, after the simulation method is described, experimental results are presented using both simulated data and real CT images.

• Industrial Engineering and Management Systems
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• v.15 no.1
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• pp.63-76
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• 2016

Multiperiod portfolio selection problem attracts more and more attentions because it is in accordance with the practical investment decision-making problem. However, the existing literature on this field is almost undertaken by regarding security returns as random variables in the framework of probability theory. Different from these works, we assume that security returns are uncertain variables which may be given by the experts, and take absolute deviation as a risk measure in the framework of uncertainty theory. In this paper, a new multiperiod mean absolute deviation uncertain portfolio selection models is presented by taking transaction costs, borrowing constraints and threshold constraints into account, which an optimal investment policy can be generated to help investors not only achieve an optimal return, but also have a good risk control. Threshold constraints limit the amount of capital to be invested in each stock and prevent very small investments in any stock. Based on uncertain theories, the model is converted to a dynamic optimization problem. Because of the transaction costs, the model is a dynamic optimization problem with path dependence. To solve the new model in general cases, the forward dynamic programming method is presented. In addition, a numerical example is also presented to illustrate the modeling idea and the effectiveness of the designed algorithm.

• The KIPS Transactions:PartC
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• v.9C no.6
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• pp.953-960
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• 2002

Rel-time application programs have constraints which need to be met between media-data. It is client-leading synchronization that is absorbing variable transmission delay time and that is synchronizing by feedback control and palyout control. It is the important factor for playback rate and QoS if the buffer level is normal or not. This paper, The method of maintenance buffer normal state transmits in multimedia server by appling feedback of filtering function. And synchronization method is processing adaptive playout time for smooth presentation without cut-off while media frame is skip. When audio frame which is master media is in upper threshold buffer level we decrease play out time gradually, low threshold buffer level increase it slowly.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.727-729
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• 2002

In this paper, we proposed quad variable rates ADPCM coding method and its implementation on C6000 DSP, which is modified from the standard ADPCM of ITU G.726 for speech quality improvement considering the environmental noise Four coding rates, 16Kbps, 24Kbps, 32Kbps and 40Kbps are used for speech window samples and the rate decision threshold is decided by the environmental noise level. The object of the proposed method is to reduce the coding rate while retaining the speech quality and the speech quality is considerably close to 40Kbps single rate coder with the coding rate close to 16Kbps single rate coder under the environmental noise. The environmental noise level affects the coding rate and the noise level is calculated per every speech window samples. At high noise level, more samples are coded at higher rates to enhance the quality, but at low noise level, only the big speech signals are coded at higher rates and more speech samples are coded at lower coding rates to reduce the coding rates. The influence of the noise on tile speech signal is considerably high for small signals and the small signal has the higher ZCR (zero crossing rate). The method is simulated in PC and to be implemented on C6000 floating point DSP board in real time operations.

• The Journal of the Korea Contents Association
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• v.2 no.4
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• pp.85-92
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• 2002

This paper proposes the cell scheduling algorithm proper to high-speed ATM switch. The proposed algorithm is the VRR(Variable weight Round Robin) combined the FRR to variant QLT. The FRR performs the cell service of the fixed weight by each buffer. So, FRR don't support the QoS of ATM service classes although it is easy to implement a high speed switch. VRR uses the method expaned to variable weight according to buffer state as well as schedules the cell according the Fixed weight based FRR. The simulation to evaluate the proposed algorithm was done by AweSim arid Visual C++. The result graphs show that the proposed algorithm is excellent, especially in the aspect of cell loss. This area is engaged by English Abstract.

• The Korean Journal of Applied Statistics
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• v.23 no.1
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• pp.13-28
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• 2010

Assuming a mixture distribution for credit evaluation studies, we discuss estimating threshold methods to minimize errors that default borrowers are predicted as non defaults or non defaults are regarded as defaults. A method by using statistical hypotheses tests, the most powerful test and generalized likelihood ratio test, for the probability density functions which are defined with the score random variable and the parameter space consisted of only two elements such as the default and non default states is proposed to estimate a threshold. And anther optimal thresholds to maximize classification accuracy measures of the accuracy and the true rate for ROC and CAP curves are estimated as equations related with these probability density functions. Three kinds of optimal thresholds in terms of the hypotheses testing, the accuracy and the true rate are obtained from normal random samples with various means and variances. The sums of the type I and type II errors corresponding to each optimal threshold are obtained and compared. Finally we discuss about their efficiency and derive conclusions.

• The Korean Journal of Pain
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• v.12 no.2
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• pp.195-199
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• 1999

Background: At present, there is no reliable objective test for the diagnosis of myofascial trigger points (MFTP). We evaluated the usefulness of skin resistance point finder for the diagnosis of MFTP. Methods: 40 subjects with clinical MFTPs at the upper trapezius muscle were included in this study. Using skin resistance point finder (UNIQUE S-2010$^{(R)}$, Seik medical, Korea), we tried to find out the point of low skin resistance. At three different current level, sensitivity and specificity of this method for the diagnosis of clinically identified MFTP was evaluated. Pressure threshold for pain of low skin resistance point was measured using Pressure Threshold Meter$^{(R)}$ (Pain Diagnostics and Thermography, U.S.A.). 3 groups of point detected at different current were compared in mean pressure threshold. Results: Fixed single current of skin resistance point finder showed variable sensitivity and specificity. But, by adjusting current level, skin resistance point finder detected all of 40 clinically identified MFTPs. Although it is partially statistically significant, the mean pressure threshold of points detected at high current was high. Conclusion: Skin resistance finder can be used as objective diagnostic tool of MFTPs. There is possibility that it can be useful in evaluating treatment effect. However, more investigation is necessary.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2004.04a
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• pp.201-205
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• 2004

The digital color image can be distorted by noise for a transmission or other elements of system. It happens to vague of a boundary side in the division of a color image object, especially, boundary side of an input color image is very important because it can be determined to the division and detection element in pattern recognition. Therefore it is boundary part In this paper, it detects the optimal edge with applying this color image to WCNN algorithm, after it does level up a boundary side of a color image by using the adaptive morphology as the threshold of an input color image. Also, it is used not a conventional fixed mask edge detection method but variable mask method which is cal led a variable BBM. It is confirmed by simulation that the proposed algorithm can be got the batter result edge at the place of closing to each edges and having smoothly curved line.

• Journal of Digital Contents Society
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• v.2 no.2
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• pp.129-138
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• 2001

With the explosive growth and pervasive of the Internet, dynamic bandwidth allocation is nessary for ATM streams that carry various traffic. In order to provide quality of service(QoS) guarantees and to give the minimum cell rate, new bandwidth allocation scheme requires to be implemented. DFBA(Differential Fair Buffer Allocation) scheme is one of the methods for ATM GFR(Guaranteed Frame Rate) services. DFBA scheme treats cells selectively in a region between low buffer occupancy threshold and high buffer occupancy threshold. A big unbalance is introduced when the value being selected by DFBA scheme is greater than minimum rate. In a try to reduce the unbalance modified DFBA scheme is proposed. Selecting parameter according to the situation of network, this scheme is very effective to control the bandwidth in the various network situation.

• The Korean Journal of Applied Statistics
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• v.23 no.5
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• pp.943-953
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• 2010

From a mixture distribution of the score random variable for credit evaluation, there are many methods of estimating optimal thresholds. Most the research news is based on the assumption of normal distributions. In this paper, we extend non-normal distributions such as Weibull, Logistic and Gamma distributions to estimate an optimal threshold by using a hypotheses test method and other methods maximizing the total accuracy and the true rate. The type I and II errors are obtained and compared with their sums. Finally we discuss their e ciency and derive conclusions for non-normal distributions.