• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.525-528
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• 1999

Abstract - In this paper, a segmentation method for brain Magnetic Resonance(MR) image using region clustering technique with statistical distribution of gradient image and fuzzy rules is described. The brain MRI consists of gray matter and white matter, cerebrospinal fluid. But due to noise, overlap, vagueness, and various parameters, segmentation of MR image is a very difficult task. We use gradient information rather than intensity directly from the MR images and find appropriate thresholds for region classification using gradient approximation, rayleigh distribution function, region clustering, and merging techniques. And then, we propose the adaptive fuzzy rules in order to extract anatomical structures and diseases from brain MR image data. The experimental results shows that the proposed segmentation algorithm given better performance than traditional segmentation techniques.

• The Journal of Natural Sciences
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• v.15 no.1
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• pp.47-56
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• 2005

The substituent dependence of geometric distortion through the two independent electronic substituent effects is analyzed for mono-substituted benzene derivatives of $C_{2v}$. Based on resonance structures, quantitative relationships expressing the resonance and field/inductive contribution terms in bond distortions are derived. The calculated field-effect parts of $C_{ipso}$_$C_{ortho}$ ring bonds increase and decrease compared to benzene for electropositive and electronegative substituents respectively. The nonbonded axial distance, $C_{ipso}$....$C_{para'}$ decreases for electronegative substituents and increases for electropositive substituents. As the electronegativity increases, the distance $C_{ortho}$....$C_{ortho'}$ increases. With the $\pi$-donors, $C_{meta}$....$C_{meta'}$ nonbonded distances are shorter compared to the ones of benzene, and for $\pi$-acceptors, the are longer. Our model based on valence bond approach predicts that the average bond length determined the area of ring, and the sum of the angles <$C_{ortho}$_$C_{ispo}$_$C_{ortho}$ and <$C_{meta}$_$C_{para}$_$C_{meta}$ determines the axial distance.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.82-89
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• 2007

Sound transmission characteristics are investigated on the corrugated steel and aluminium extruded panels used for railway vehicles. Sewell-Sharp-Cremer(SSC) model, equivalent orthotropic plate model and equivalent mass law are applied to predict the sound transmission loss. The predicted values of the sound transmission loss are compared with the measured values. The reliability and the limitation of the prediction models are investigated. For the corrugated panels and honeycomb panels, the coincidence and local resonance severely deteriorate the sound insulation performance around the corresponding frequency bands. The result of the study shows that the equivalent orthotropic plate model and the SSC model can be used as good prediction models, if the coincidence frequency or local resonance frequency is correctly applied.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.9 s.180
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• pp.2220-2227
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• 2000

In this paper, dynamic photoelastic hybrid method is developed and its validity is certified. The dynamic photoelastic hybrid method can be used on the obtaining of dynamic stress intensity factors and dynamic stress components. The effect of crack length on the dynamic stress intensity factors is less than those on the static stress intensity factors. When structures are under the dynamic mixed mode load, dynamic stress intensity factor of mode I is almost produced. Dynamic loading device manufactured in this research can be used on the research of dynamic behavior when mechanical resonance is produced and when crack is propagated with the constant velocity.

• Journal of the Korean Magnetic Resonance Society
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• v.20 no.2
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• pp.41-45
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• 2016

Chemical investigation of a marine-derived fungus, Penicillium sp. 108YD020, resulted in the discovery of six bile acid derivatives, glycocholic acid (1), glycocholic acid methyl ester (2), cholic acid (3), glycochenodeoxycholic acid (4), glycodeoxycholic acid methyl ester (5), and cholic acid methyl ester (6). The structures of six bile acid derivatives 1-6 were determined by the detailed analysis of 1D, 2D NMR and LC-MS data, along with chemical methods and literature data analysis.

• Journal of Korean Neurosurgical Society
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• v.48 no.5
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• pp.441-444
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• 2010

Fibrous dysplasia (FD) of craniofacial structures is well documented, however, its involvement of the clivus is seldom described. We report a case of clival FD in a young man who presented with headache localized to the occipital area. The radiological studies revealed a monostotic disease confined to the clivus, with typical findings of hypo intensity on magnetic resonance images and ground-glass density on computed tomography. The diagnosis of FD was confirmed on pathological examination of specimens taken through transsphenoidal surgery. The patient showed reduction of symptoms and no change of residual lesion on follow-up imaging taken 2.5 years later after surgery. This study includes clinical aspect, radiographic appearance, differential diagnosis and treatment strategy of this rare skull base lesion.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.257-261
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• 2011

The failures of local structure of marine medium-speed diesel engine occurred in durability test. The vibration response of the whole engine was in an acceptance level, but the local structures were broken. ODS test and vibration measurement were carried out in order to investigate the root cause of durability problem. These tests revealed that the root cause of failures was excessive vibration by $4.5^{th}$ resonance between engine body and local structure. The best solution to reduce the vibration response is to change the type of mount. After a rigid mount was replaced by a flexible mount, maximum vibration level dropped to 72%.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.778-783
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• 2003

The problem considered in this paper is about the collocation of sensor and actuator for the active control of sound and vibration. It is well-known that a point collocated sensor-actuator pair offers an unconditional stability with very high performance when it is used with a direct velocity feedback (DVFB) control, because the pair has strictly positive real (SPR) property. In order to utilize this SPR characteristics, a matched piezoelectric sensor and actuator pair is considered, but this pair suffers from the in-plane motion coupling problem with the out-of$.$plane motion due to the piezo sensor and actuator interaction. This coupling phnomenon limits the stability and performance of the matched pair with DVFB control. As a new alternative, a point sensor and piezoelectric actuator pair is also considered, which provides SPR property in all frequency range except at the first resonance in very low frequency. This non-SPR resonance could be minimized by applying a phase lag compensator.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.8
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• pp.661-667
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• 2004

The characteristics of noise and vibration by a heavy impact source was studied. The triggering method was used for increasing the reliability and stability to measure the level of sound pressure. sound intensity and vibration acceleration. A simple finite element model and a rigid body analysis method were suggested to calculate the natural frequencies of the multi-layer floor system. The results show that the resilient materials decrease the natural frequency of the reinforced concrete slab, make a resonance with dominant driving frequency in the low frequency region, and increase the vibration and noise level. A simple finite element model and rigid body models was suggested to calculate the natural frequencies of the floor systems.

• Selected Papers of The Society of Naval Architects of Korea
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• v.1 no.1
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• pp.4-14
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• 1993

A natural and an artificial harbor can exhibit frequency (or period) dependent water surface oscillations when excited by incident waves. Such oscillations in harbors can cause significant damages to moored ships and adjacent structures. This can also induce undesirable current in harbor. Many previous investigators have studied various aspects of harbor resonance problem. In the present paper, both a localized finite element method(LFEM) which is based on the functional constructed by Chen & Mei(1974) and Bai & Yeung(1974) and an integral equation method which was used by Lee(1969) are applied to harbor resonance problem. The LFEM shows computationally more efficient than the integral equation method. Our test results show a good agreement compared with other results. In the present computations, specifically two harbor geometris are treated here. The present method by LFEM can be extended to a fully three dimensional harbor problem.