• Imaging Science in Dentistry
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• v.31 no.2
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• pp.109-115
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• 2001

The ameloblastic carcinoma is an extremely rare, aggressive odontogenic neoplasm of the jaws. It is described as an ameloblastoma in which there is histologic evidence of malignancy in the primary or recurrent tumors, regardless of whether it has metastasized. We report an aggressive case of ameloblastic carcinoma of the mandible. A 68-year-old man with the complaint of the left facial swelling and intermittent pain was referred to our hospital. Serial images of panoramic radiograph, computed tomograph, and magnetic resonance imaging showed an ill-defined destructive radiolucent lesion of the left mandible. The lesion had typically aggressive behavior with extensive local destruction of bone and extended to the adjacent soft tissues. Bone scan revealed increased uptakes in the left mandibular body and ramus regions. Histological features were generally resembled with those of an ameloblastoma but with cytologic features of epithelial malignancy.

• Structural Engineering and Mechanics
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• v.54 no.5
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• pp.955-971
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• 2015

In this paper, the influence of the polled direction of piezoelectric materials on the stress distribution is studied under time-harmonic dynamical load (time-harmonic Lamb's problem). The system considered in this study consists of piezoelectric covering layer and piezoelectric half-plane, and the harmonic dynamical load acts on the free face of the covering layer. The investigations are carried out by utilizing the exact equations of motion and relations of the linear theory of electro-elasticity. The plane-strain state is considered. It is assumed that the perfect contact conditions between the covering layer and half-plane are satisfied. The boundary value problems under consideration are solved by employing Fourier exponential transformation techniques with respect to coordinates directed along the interface line. Numerical results on the influence of the polled direction of the piezoelectric materials such as PZT-5A, PZT-5H, PZT-4 and PZT-7A on the normal stresses, shear stresses and electric potential acting on the interface plane are presented and discussed. As a result of the analyses, it is established that the polled directions of the piezoelectric materials play an important role on the values of the studied stresses and electric potential.

• Proceedings of the KSR Conference
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• 2003.05a
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• pp.337-342
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• 2003

The dynamic load effects are conveyed to the railway bridges through tracks which are generated by moving trains The dynamic load effects may vary due to the dynamic characteristics of the applied vehicle loads and the railway bridges containing the track system. However, the track effects have been neglected or simplified by spring elements in the most studies since it is quite complex to consider the track systems in the dynamic analysis models of railway bridges. In this study, track system on railway bridges is modeled using a three-dimensional discrete-support model that can simulate the load carrying behavior of tracks. In addition, this program is developed with the precise 20-car model and a continuous PSC(prestressed concrete) box girder bridge, which is the main bridge type of Korea Train express(KTX). Three-dimensional elements are used for both. The dynamic response of railway bridges is found to be affected depending on whether the track model is considered or not. The influencing rate depends on the traveling speed and different wheel-axle distance. The dynamic bridge response is decreased remarkably by the track systems around the resonant frequency. Therefore, the resonance effect can be reduced by modifying the track properties in the railway bridge.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.8
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• pp.1-7
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• 2008

In this paper, we propose a lossy MTM transmission line unit cell and retrieve the parameter values related with radiation effects. Based on this unit cell model, we plot dispersion diagrams and analyze resonance conditions. We also discuss the input impedance or admittance behavior when we terminate the load as open or short. Then, we examine the quality factor and return loss bandwidth. We also design a very compact unit cell antenna using the provided lossy MTM-TL model. The results based on EM simulations and measurements are shown to be in good agreement with those based on circuit simulation.

• Proceedings of the KSR Conference
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• 2002.10a
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• pp.715-720
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• 2002

The dynamic load effects, generated by moving trains, are transferred to the railway bridges through tracks. The dynamic load effects may vary due to the dynamic characteristics of the applied vehicle loads and the railway bridges including the track system. However, the track models have been neglected or simplified by spring elements in the most studies since it is quite complicated to consider the track systems in the dynamic analysis models of railway bridges. In this study track system on railway bridges are modeled using a three-dimensional discrete-support model that can simulate the load carrying behavior of tracks. A 40m simply supported prestressed concrete box-girder system adopted for high-speed railway bridges are modeled for simulation works. The train models are composed of 20 cars for KTX. The dynamic response of railway bridges are found to be affected depending on whether the track model is considered for not. The influencing rate depends on the traveling speed and different wheel-axle distance. The dynamic bridge response decreases remarkably by the track systems around the resonant frequency. Therefore, the resonance effect can be reduced by modifying the track properties in the railway bridge, especially for KTX trains.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.5
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• pp.305-312
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• 2000

This study deals with the dynamic response of a rotor in Switched Reluctance Motor(SRM) caused by the unbalance force such as the unbalanced mass and electromagnetic force. The method to analyze the mechanical response of the rotor supported on the bearing is based on an extension of the 3-dimensional Transfer Matrix Method(TMM) coupled with the electromagnetic force calculated by Maxwell stress tensor. The displacement of the rotor as a function of frequency according to the position of the unbalanced mass is evaluated from the frequency response function (FRF). The rotor behaviour with the electromagnetic force is compared with that without the electromagnetic force. In addition, the resonance speeds and the vibration modes are analyzed and demonstrated in this paper. These results are useful in designing the mechanical rotor and in balancing properly the rotor to reduce vibration and noise.

• Smart Structures and Systems
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• v.20 no.6
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• pp.657-668
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• 2017

In this research, an active vibration suppression of a smart beam having piezoelectric sensor and actuators is investigated by designing separate controllers comprising a linear quadratic regulator and a neural network. Firstly, design of a smart beam which consists of a cantilever aluminum beam with surface bonded piezoelectric patches and a designed mechanism having a micro servomotor with a mass attached arm for obtaining variations in the frequency response function are presented. Secondly, the frequency response functions of the smart beam are investigated experimentally by using different piezoelectric patch combinations and the analytical models of the smart beam around its first resonance frequency region for various servomotor arm angle configurations are obtained. Then, a linear quadratic regulator controller is designed and used to simulate the suppression of free and forced vibrations which are performed both in time and frequency domain. In parallel to simulations, experiments are conducted to observe the closed loop behavior of the smart beam and the results are compared as well. Finally, active vibration suppression of the smart beam is investigated by using a linear controller with a neural network based adaptive element which is designed for the purpose of overcoming the undesired consequences due to variations in the real system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.799-804
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• 2001

Nonlinear normal mode (NNM) vibration, in a nonlinear dual mass Hamiltonian system, which has 6th order homogeneous polynomial as a nonlinear term, is studied in this paper. The existence, bifurcation, and the orbital stability of periodic motions are to be studied in the phase space. In order to find the analytic expression of the invariant curves in the Poincare Map, which is a mapping of a phase trajectory onto 2 dimensional surface in 4 dimensional phase space, Whittaker's Adelphic Integral, instead of the direct integration of the equations of motion or the Birkhotf-Gustavson (B-G) canonical transformation, is derived for small value of energy. It is revealed that the integral of motion by Adelphic Integral is essentially consistent with the one obtained from the B-G transformation method. The resulting expression of the invariant curves can be used for analyzing the behavior of NNM vibration in the Poincare Map.

• Archives of Craniofacial Surgery
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• v.20 no.2
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• pp.139-143
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• 2019

Here we report a case of a focal atypical proliferative nodule (PN) arising from a congenital melanocytic nevus (CMN). Diagnosis was challenging because it had both benign and malignant clinical features. Unusual histopathology, immunohistochemistry, and intraoperative findings of this atypical PN are discussed. A 5-year-old girl was admitted for a congenital $5{\times}5cm$ sized scalp mass. This hemangioma-like soft mass showed biphasic characteristics such as a slow, gradual, and benign increase in size but worrisome dural invasion with cranial bone defect. We removed the scalp mass with clear resection margins. Interoperatively, we found that the cranial bone defect had already filled. Histopathologic examination showed CMN with focal atypical PN. The nodule showed sharp demarcation and cellular pleomorphism. However, in immunohistochemical study, Ki-67 proliferation index and expression levels of protein S-100 and Melan-A were very low. These were unusual findings of atypical PNs. Despite her worrisome preoperative radiologic features, she showed an indolent clinical course compatible with previously reported biologic behavior. The patient underwent follow-up inspection with magnetic resonance imaging every 6 months for up to 3 years. The nodule appeared to be stationary at the last visit.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.4
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• pp.36-42
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• 2021

In this study, the impregnation of Lyocell fabrics was performed using phosphoric acid, ammonium phosphate, diammonium hydrogen, triammonium phosphate as phosphorus flame retardant, to fabricate continuous graphite fabrics using lyocell fiber. The physical and chemical structure changes were investigated by thermogravimetric, Fourier-transform infrared spectroscopy, C-nuclear magnetic resonance, X-ray diffraction, and weight analyses, By analyzing the thermal behavior of phosphorus flame retardant, conditions for the temperature, gas, and residual time of the pyrolysis process were set. Graphite fabrics with a tensile strength of 1,007.19±11.47 N/5 cm and yield of 25.3% were fabricated using continuous pyrolysis, carbonization and graphitization process.