• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.389-392
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• 2000

In this paper, we propose a novel post processing method of deconvolution for SAR images based on phase extension inverse filtering, which improves spatial resolution as well as effectively eliminates sidelobes with low computational complexity. It extends the bandwidth only to control the magnitude of the processed SAR data without distortions of the phase in frequency domain unlike the other techniques such as spatially variant apodization (SVA), and other deconvolution techniques. We compare the image processed by the proposed method with images processed by uniform weighting function, Hamming weighting function whose coefficient is 0.75, and SVA.

• Proceedings of the KIEE Conference
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• 1997.07f
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• pp.2240-2242
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• 1997

A new group of magnetic coupled high power factor converter with a single-switch /single-stage is proposed. The proposed converter gives the good power factor correction, low current harmonic distortions, and tight output voltage regulation. The prototype shows the IEC555-2 requirements are met satisfactorily with nearly unity power factor.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.582-584
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• 1996

A new single stage AC/DC converter with a high power factor is proposed. The proposed converter gives good power factor correction, low current harmonic distortions, and tight output regulations. This converter also has an high efficiency by employing Active-clamp method and synchronous rectifiers. To verify performances of the proposed converter, 90W-converter is designed. This prototype meets the IEC555-2 requirements satisfactorily with nearly unity power factor.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.348-350
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• 1996

A new reset winding clamped forward converter with transformer voltage feedback technique for power factor correction with a single-switch/single-stage is proposed. The proposed converter gives the good power factor correction, low current harmonic distortions, and tight output voltage regulation. The prototype shows the IEC555-2 requirements are met satisfactorily with nearly unity power factor.

• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.2
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• pp.148-155
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• 1998

A novel single-switch, single-stage, AC/DC forward converter with transformer magnetic energy feedback technique for power factor correction is proposed. The operational principle and analysis of the proposed converter is presented. The proposed converter gives the good power factor correction, low line current harmonic distortions, and tight output voltage regulation. The prototype shows the IEC 555-2 requirements are met satisfactorily with nearly unity power factor.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2003.09a
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• pp.563-566
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• 2003

Quality measures play an important role in the field of image processing. Such measures are commonly used to assess the performance of different algorithms that are designed to perform a specific image processing task. In this paper we propose two novel measures for image quality assessment based on the notion of correlation between fuzzy sets. Two different definitions fur the correlation between fuzzy sets have been used. In order to calculate the proposed quality measures two approaches were evaluated, one with direct application of the measures to the image′s pixels and the other using the fuzzy set corresponding to the normalized histogram of the image. A comparative study of the proposed measures is performed by investigating their behavior using images with different types of distortions, such as impulsive "salt at pepper" noise, additive white Gaussian noise, multiplicative speckle noise, blurring, gamma distortion, and JPEG compression.

• Journal of the Korean Data and Information Science Society
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• v.20 no.2
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• pp.453-458
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• 2009

In this paper, we consider Jarque-Bera (JB) normality test for the innovations of ARMA-GARCH models. In financial applications, JB test based on the residuals are routinely used for the normality of ARMA-GARCH innovations without a justification. However, the validity of JB test should be justified in advance of the actual practice (Lee et al., 2009). Through the simulation study, it is found that the validity of JB test depends on the shape of test statistic. Specifically, when the constant term is involved in ARMA model, a certain type of residual based JB test produces severe size distortions.

• KDI Journal of Economic Policy
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• v.38 no.3
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• pp.37-52
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• 2016

This paper analyzes the effects of allocative efficiency on productivity in the manufacturing sector of Korea following Hsieh and Klenow (2009). The results of this research indicate that the overall allocative efficiency declined from 1990 to 2012. Using the method of Oberfield (2013), which allows inter-industry resource movement as well as intra-industry reallocation, we confirm that intensified misallocation generally results from intra-industry allocative inefficiency. The potential loss from instances of worsening misallocation is estimated to be approximately 0.6% points for each year, which is considerable in terms of the overall TFP. In terms of the firm size distribution, initially large establishments are more likely to expand if distortions are removed in most countries. One notable feature in Korea is that this pattern is pronounced. This implies that subsidies to unproductive small-sized establishments are heavily implemented.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.14 no.4
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• pp.249-273
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• 2010

Often in practice, the implied volatility of an option is calculated to find the option price tomorrow or the prices of, nearby' options. To show that one does not need to adhere to the Black- Scholes formula in this scheme, Figlewski has provided a new pricing formula and has shown that his, alternating passive model' performs as well as the Black-Scholes formula [8]. The Figlewski model was modified by Henderson et al. so that the formula would have no static arbitrage [10]. In this paper, we show how to construct a huge class of such static no arbitrage pricing functions, making use of distortions, coherent risk measures and the pricing theory in incomplete markets by Carr et al. [4]. Through this construction, we provide a more elaborate static no arbitrage pricing formula than Black-Sholes in the above scheme. Moreover, using our pricing formula, we find a volatility curve which fits with striking accuracy the synthetic data used by Henderson et al. [10].

• Journal of KSNVE
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• v.4 no.3
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• pp.307-318
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• 1994

Existence of any nonlinearity in responses of a nonlinear system is tested using a kurtosis or a fourth moment which has been widely used to characterize signal patterns. By inputting a harmonic signal to a system and investigating the distortions of an output signal from a harmonic pattern, which are due to violations of proportionality between the input and the output, it is judged whether the output is generated from a nonlinear system or not. Through applying the method presented in this work to simulation studies on detections of nonlinearities of a single degree of freedom system, in which three kinds of nonlinearities are treated as restoring force terms, feasibilities of the method are shown and the range of both frequency and input amplitude, in which the system generates nonlinear responses, is determined.