• Journal of the Ergonomics Society of Korea
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• v.30 no.2
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• pp.339-347
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• 2011

Objective: The purpose of this study was to evaluate of various material of pillows by using biomechanical variables such as the cervical stability, head pressure distribution, and muscle activity. Method: Eight subjects participated in the experiment. Three different materials such as polyester sponge, memory foam and the buckwheat shell used for Korean traditional pillow were tested. Electro-goniometer, six channels of electromyography(EMG), ten channels of the head pressure sensors were used to measure the biomechanical responses. Surface electrodes were attached to the right/left semispinals capitis(RSC, LSC), the right/left sternocleidomastoid(RSM, LSM), the right/left upper trapezius(RUT, LUT). The cervical stability was evaluated by the angle deviated from the standing neck position. The head pressure distribution was evaluated by the pressure per unit area recorded on the sensors and the intensity of peak pressure. Electromyography(EMG) data were analyzed by using root mean square(RMS) and mean power frequency(MPF). Results: The buckwheat shell material showed a higher stability in the cervical spine then the other pillows during spine position. In terms of head pressure distribution, the memory form indicated the lowest pressure at supine position, buckwheat shell material indicated the lowest pressure during lying down to side, and polyester cushion recorded the highest pressure at all postures. Conclusion: The buckwheat shell material has a biomechanical advantage to maintain a healthy neck angle and reduce the pressure on the head, which means the buckwheat shell is a potential material for ergonomic pillow design. The pillow with memory form showed second best biomechanical performance in this study. Application: The shape of the buckwheat shell pillow and the characteristics of materials can be used to design the pillow preventing neck pain and cervical disk problems.

• Korean Journal of Head & Neck Oncology
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• v.33 no.2
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• pp.71-73
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• 2017

Dysplastic epiglottis is extremely rare congenital malformation, which usually occurs in association with other laryngeal anomalies. Hypoplasia is the most common type in epiglottic malfomations. Other abnormalities include rudimentary, aplasia and bifid etc. Mostly, they are found in infancy and early childhood, and diagnosis at adulthood is extremely rare. A 69-year-old man with chronic cough and globus sense visited our clinic. Laryngoscopic findings revealed a unique form of epiglottis. He had no history of laryngeal trauma, tumors, head and neck surgery, and radiation. There was no another anomaly in the laryngo-pharynx. Because of a mass-like lesion at the apex of epiglottis, we performed the laryngeal microsurgery. The pathology revealed as granulation tissue. We report a rare and unique case of dysplastic epiglottis in elderly patient with a brief literature review.

• Korean Journal of Audiology
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• v.24 no.4
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• pp.210-213
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• 2020

Fungal balls consist of rounded conglomerates of fungal mycelia, which can form within a preexisting cavity. They are mostly found in the paranasal sinuses in the head and neck regions. Cholesterol granuloma is a fibrotic lesion that develops as a tissue response to a foreign body such as cholesterol crystals or hemosiderin and is often associated with chronic otitis media. We present the unusual case of a 62-year-old male who was treated for chronic otitis media, which was histologically confirmed as a fungal ball and cholesterol granuloma in the middle ear cavity following tympanomastoidectomy. This is the first reported case of synchronous fungal ball and cholesterol granuloma in the middle ear cavity.

• Journal of Audiology & Otology
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• v.24 no.4
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• pp.210-213
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• 2020

Fungal balls consist of rounded conglomerates of fungal mycelia, which can form within a preexisting cavity. They are mostly found in the paranasal sinuses in the head and neck regions. Cholesterol granuloma is a fibrotic lesion that develops as a tissue response to a foreign body such as cholesterol crystals or hemosiderin and is often associated with chronic otitis media. We present the unusual case of a 62-year-old male who was treated for chronic otitis media, which was histologically confirmed as a fungal ball and cholesterol granuloma in the middle ear cavity following tympanomastoidectomy. This is the first reported case of synchronous fungal ball and cholesterol granuloma in the middle ear cavity.

• 대한두경부종양학회:학술대회논문집
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• 1992.11a
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• pp.133-134
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• 1992

• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.5
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• pp.499-508
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• 2017

This paper uses optimization techniques to obtain bow hull form of a 66,000 DWT bulk carrier in calm water and in waves. Parametric modification functions of SAC and section shape of DLWL are used for hull form variation. Multi-objective functions are applied to minimize the wave-making resistance in calm water and added resistance in regular head wave of ${\lambda}/L=0.5$. WAVIS version 1.3 is used to obtain wave-making resistance. The modified Fujii and Takahashi's formula is applied to obtain the added resistance in short wave. The PSO algorithm is employed for the optimization technique. The resistance and motion characteristics in calm water and regular and irregular head waves of the three hull forms are compared. It has been shown that the optimal brings 13.2% reduction in the wave-making resistance and 13.8% reduction in the added resistance at ${\lambda}/L=0.5$; and the mean added resistance reduces by 9.5% at sea state 5.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.1
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• pp.146-154
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• 2009

In recent tissue engineering field, it is being reported that the fabrication of 3D scaffolds having high porous and controlled internal/external architectures can give potential contributions in cell adhesion, proliferation and differentiation. To fabricate these scaffolds, various solid free-form fabrication technologies are being applied. The solid free-form fabrication technology has made it possible to fabricate solid free-form 3D microstructures in layer-by-layer manner. In this research, we developed a multi-head deposition system (MHDS) and used design of experiment (DOE) to fabricate 3D scaffold having an optimized internal/external shape, Through the organization of experimental approach using DOE, the fabrication process of scaffold, which is composed of blended poly-caprolactone (PCL), poly-lactic-co-glycolic acid (PLGA) and tricalcium phosphate (TCP), is established to get uniform line width, line height and porosity efficiently Moreover, the feasibility of application to the tissue engineering of MHDS is demonstrated by human bone marrow stromal cells (hBMSCs) proliferation test.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.1
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• pp.290-296
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• 2019

Head-up displays for vehicles play an important role in displaying various information about the safety and convenience of driving on the windshield of the vehicle. In this study, ultra-precision machining was performed and evaluated as a method for machining a large-area aspheric free-form mirror that is applicable to augmented reality technology. Precision diamond cutting is highly accurate and suitable for the production of advanced parts with excellent surface integrity, low surface roughness, and low residual stress. By using an aspheric free-form mold, it is possible to improve the optical transfer function, reduce the distortion path, and realize a special image field curvature. To make such a mold, the diamond cutting method was used, and the result was evaluated using an aspherical shape-measuring machine. As a result, it was possible to the mold with shape accuracy (PV) below $1{\mu}m$ and surface roughness (Ra) below $0.02{\mu}m$.

• Korean Journal of Head & Neck Oncology
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• v.26 no.2
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• pp.240-242
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• 2010

Primary squamous cell carcinoma of the thyroid gland is a very rare event, representing much less than 1% of all malignant tumors of the thyroid gland. The cancer is characterized by rapidly progressive clinical course in spite of its differentiated morphologic features. In most cases, a squamous epithelium is believed to be a result of metaplasia of a follicular epithelium, although in rare exceptions, it can originate from a remnant of the thyroglossal duct or ultimobranchial body. Squamous cell carcinoma of the thyroid gland can occur in a pure form or mixed with adenocarcinoma. Because their clinical behavior is more aggressive than that of other malignant neoplasm of thyroid gland, the tumor should be treated more vigorously at its initial stage. Recently, authors experienced one case of primary squamous cell carcinoma of the thyroid gland. We report our case with a brief review of literature.

• Transactions of Materials Processing
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• v.18 no.8
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• pp.607-616
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• 2009

There are three sub-processes associated with the assembly of the valve seat and cylinder head; heat fitting, cold fitting, and shrink fitting. In the heat fitting stage, the cylinder head is heated to a specified temperature and then squeezed toward the outer diameter of the valve seat. The cold fitting process cools the valve seat and safely squeezes it toward the inner diameter of cylinder head. However, these methods increased the installations & running cost and curtailed productivity. To address these problems, we analyzed the shrink fitting process using the contact pressure caused by fitting interference between the outer diameter of the valve seat and the inner diameter of the cylinder head. In this study, a closed form equation for predicting the contact pressure and fitting load is proposed. For quality control of the assembly line, principal factors of the shrink fitting process influenced in contact pressure were simulated by the FEM. Actual loads measured in the field showed good agreement with the results obtained by theoretical and finite element analysis.