• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.10
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• pp.1042-1048
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• 2008

Disc brake noise is an important customer satisfaction and warranty issue for many manufacturers as indicated by technical literature regarding the subject coming from Motor Company. This research describes results of a study to assess disk brake squeal propensity using finite element methods and optimal technique (Kriging). In this study, finite element analysis has been performed to determine likely modes of brake squeal. This paper deals with friction-induced vibration of disc brake system under contact friction coefficient. A linear, finite element model to represent the floating caliper disc brake system is proposed. The complex eigen-values are used to investigate the dynamic stability and in order to verify simulations which are based on the FEM model. In this paper, Kriging from among the meta-modeling techniques is proposed for an optimal design scheme to reduce the brake squeal noise.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.1888-1893
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• 2011

Considering the dynamic performance and stability of railroad vehicles has begun to grab the attention because of developing the high speed train recently. A development based on an analysis of dynamics and verification has to be required to study the stability of vehicle performance. Several ways of analysis were using the look-up table to apply the wheel-rail contact characteristics quickly, whereas there is a constraint of the wheelset lateral displacement. In this study, an development of searching the wheel-rail contact position has been provided. The 2-point contact between wheel and rail during the driving condition can be calculated by numerical analysis. Moreover, a reliability is verified by comparing the result with a commercial program.

• Communications for Statistical Applications and Methods
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• v.19 no.4
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• pp.537-546
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• 2012

In this paper, for analyzing binary data, Poisson regression with offset and logistic regression are compared with respect to the power via simulations. Poisson distribution can be used as an approximation of binomial distribution when n is large and p is small; however, we investigate if the same conditions can be held for the power of significant tests between logistic regression and offset poisson regression. The result is that when offset size is large for rare events offset poisson regression has a similar power to logistic regression, but it has an acceptable power even with a moderate prevalence rate. However, with a small offset size (< 10), offset poisson regression should be used with caution for rare events or common events. These results would be good guidelines for users who want to use offset poisson regression models for binary data.

• Journal of Korea Multimedia Society
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• v.15 no.12
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• pp.1409-1416
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• 2012

An image segmentation result depends on pre-processing steps such as contrast enhancement, edge detection, and smooth filtering etc. Especially medical images are low contrast and contain some noises. Therefore, the contrast enhancement and noise removal techniques are required in the pre-processing. In this study, we present an extension by a novel histogram equalization in which both local and global contrast is enhanced using neighborhood metrics. When checking neighborhood information, filters can simultaneously improve image quality. Most important is that original image information can be used for both global brightness preserving and local contrast enhancement, and image quality improvement filtering. Our experiments confirmed that the proposed method is more effective than other similar techniques reported previously.

• Journal of Korea Multimedia Society
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• v.15 no.12
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• pp.1417-1429
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• 2012

In neuroscientific research, image segmentation is one of the most important processes. The morphology of axons plays an important role for researchers seeking to understand axonal functions and connectivity. In this study, we evaluated the level set segmentation method for neuronal axons in a Brainbow confocal microscopy image. We first obtained a reconstructed image on an x-z plane. Then, for preprocessing, we also applied two methods: anisotropic diffusion filtering and bilateral filtering. Finally, we performed image segmentation using the level set method with three different approaches. The accuracy of segmentation for each case was evaluated in diverse ways. In our experiment, the combination of bilateral filtering with the level set method provided the best result. Consequently, we confirmed reasonable results with our approach; we believe that our method has great potential if successfully combined with other research findings.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.4
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• pp.342-348
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• 2013

In this paper, an improved non-isolated 3-level high step-up boost converter is proposed. By using the well known duality principle, the proposed converter is derived from two-phase buck converter. Compared with the traditional boost converter and 3-level boost converter, the proposed converter can obtain very high voltage conversion ratio and the voltage stress of switching devices and diodes is only 1/4 of the output voltage. A 1 kW prototype converter is built and tested to verify performances of the proposed converter.

• Journal of the Chungcheong Mathematical Society
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• v.29 no.4
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• pp.543-552
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• 2016

In this paper we investigate the local spectral properties of quasidecomposable operators. We show that if $T{\in}L(X)$ is quasi-decomposable, then T has the weak-SDP and ${\sigma}_{loc}(T)={\sigma}(T)$. Also, we show that the quasi-decomposability is preserved under commuting quasi-nilpotent perturbations. Moreover, we show that if $f:U{\rightarrow}{\mathbb{C}}$ is an analytic and injective on an open neighborhood U of ${\sigma}(T)$, then $T{\in}L(X)$ is quasi-decomposable if and only if f(T) is quasi-decomposable. Finally, if $T{\in}L(X)$ and $S{\in}L(Y)$ are asymptotically similar, then T is quasi-decomposable if and only if S does.

• Proceedings of the IEEK Conference
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• 2004.06a
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• pp.3-6
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• 2004

This paper. we investigate the OFDM-based wireless LAN systems operating in the 60 GHz frequency band as part of the fourth-generation (4G) systems. The 60 GHz band is of much interest since this is the band in which a massive amount of spectral space (5 GHz) has been allocated worldwide for dense wireless local communications. This paper gives an overview of 60 GHz indoor wireless channel characteristics and an effect on phase noise. The performance of OFDM system is severely degraded by the local oscillator phase noise, which causes both common phase error and inter-carrier interference. We provide the exact analysis of the phase noise effect on the OFDM system.

• Journal of Information Science Theory and Practice
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• v.5 no.3
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• pp.31-47
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• 2017

The narrow-down approach, separately composed of search and classification stages, is an effective way of dealing with large-scale hierarchical text classification. Recent approaches introduce methods of incorporating global, local, and path information extracted from web taxonomies in the classification stage. Meanwhile, in the case of utilizing path information, there have been few efforts to address existing limitations and develop more sophisticated methods. In this paper, we propose an expansion method to effectively exploit category path information based on the observation that the existing method is exposed to a term mismatch problem and low discrimination power due to insufficient path information. The key idea of our method is to utilize relevant information not presented on category paths by adding more useful words. We evaluate the effectiveness of our method on state-of-the art narrow-down methods and report the results with in-depth analysis.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.42 no.5 s.305
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• pp.35-42
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• 2005

In this study, we designed and developed an ultrasonic transducer which can measure urine volume based on the estimation of distance between the interior-wall and posterior-wall of bladder. Measurement of urine volume is a way to help patients with urinary incontinence by detecting the amount of urine before the urine is released from the bladder. With the results of this experiment, we can measure the urine volume more accurately and also develop an incontinence preventive system. This study can help patients with urinary incontinence and enuresis to live longer, healthier lives.