• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.12 s.255
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• pp.1581-1587
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• 2006

An optimization formulation is proposed to minimize sound pressures in a two-dimensional cavity by controlling the attachment area of viscoelastic unconstrained damping materials. For the analysis of structural- acoustic systems, a hybrid approach that uses finite elements for structures and boundary elements for cavity is adopted. Four-parameter fractional derivative model is used to accurately represent dynamic characteristics of the viscoelastic materials with respect to frequency and temperature. Optimal layouts of the unconstrained damping layer on structural wall of cavity are identified according to temperatures and the amount of damping material by using a numerical search algorithm.

• The Korean Journal of Cytopathology
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• v.8 no.1
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• pp.98-102
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• 1997

Sinonasal undifferentiated carcinoma(SNUC) is a distinct, relatively rare neoplasm arising in the nasal cavity and paranasal sinuses composed of undifferentiated epithelial cells and clinically characterized by a fulminant course. We report a case of SNUC in a 56-year old man who have had bilateral neck masses since one month ago before coming to our hospital. The paranasal computed tomography showed soft mass density in the left maxillary sinus and the nasal cavity with bone destruction in the anterior medial and the inferior maxillary sinus wall. This mass was extruded into the left orbital wall. Biopsy of the nasal mass and fine needle aspiration(FNA) of the neck mass were done. FNA revealed medium-sized neoplastic cells forming clusters or individually dispersed. Nuclei were round to oval, slightly to moderately pleomorphic, and hyperchromatic. Chromatin was finely granular, but occasionally was coarsely granular. Nucleoli varied from large to inconspicuous and the cytoplasm was scanty.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.3 no.5
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• pp.386-394
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• 1991

Freezing of saturated porous media contained in a rectangular cavity has been studied experimentally. Water and different diameter glass beads consitituted the liquid and porous media. Solidification front shape, the effects of bead diameter and initial liquid temperature was investigated. When the hot wall temperature was below $4^{\circ}C$, the freezing rate was higher at the top than at the bottom due to the density inversion, but with increasing the hot wall temperature the freezing rate at the top was effected by the liquid temperature and was lower than at the bottom. With increasing the bead diameter, the difference of freezing rate between top and bottom was increased and depends on thermal conductivity. When the liquid temperature was low in the beginning, the freezing rate was high, but with increasing the time almost the same with those of high temperature liquid.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.19 no.1
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• pp.25-29
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• 1989

The author has evaluated the panoramic image clarity of the midfacial anatomic structures in dry skull according to the skull position. The radiopaque markers were attached to the anatomic structures: infraorbial rim, upper and lower borders of zygomatic arch, pterygomaxillary fissure, lateral pterygoid plate, pyriform aperture of nasal cavity, lateral wall of maxilla, orbital floor, infraorbital foramen, and nasal floor. Position of the skull were divided into four groups. standard, 25mm forward, chin-down, chin-up position. The results were as follows: 1. The pyriform aperture of nasal cavity, lateral wall of the maxilla, orbital floor, infraorbital foramen and nasal floor did net cast any discernible image. 2. Nearly all images of midfacial structures were blurred in the chin-up position. 3. The forward position provided good visualization of the maxillary sinus. 4. The chin-down position provided good visualization of the zygomatic arch, pterygomaxillary fissue, and lateral pterygoid plate.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.811-814
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• 2001

Warpage analysis of bobbin, molded by injection molding process was performed. Concerned with a mold design, cooling system was designed based on Taguchi method, the distance between cavity wall and cooling channel was most influent factor amongst four design variables like an inlet temperature of coolant, a coolant flow rate, a diameter of cooling channel, and the distance between cavity wall and cooling channel. Optimal packing processes to reduce the warpage of molded part was analyzed based on the response surface method by considering holding pressure. Their optimal processing conditions were 9.4 seconds, 5.3 seconds, 15.2 seconds, and 85MPa, respectively.

• Korean Journal of Cleft Lip And Palate
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• v.8 no.1
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• pp.45-52
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• 2005

Velopharyngeal Insufficiency(VPI); the failure of velum, the lateral wall and the posterior pharyngeal wall to separate the nasal cavity from pharyngeal cavity during speech, can be caused by congenital conditions include cleft palate, submucous cleft palate and congenital palatal insufficiency. Speech problems of VPI are characterized by hypernasality, nasal air emission, increased nasal air flow and decreased intelligibility. These speech problems of VPI can be treated with the surgical procedure, the application of temporary prosthesis and speech therapy. Biofeedback technique with Nasometer is a speech treatment method of VPI that commonly used as one component of a comprehensive procedure for improvement of speech in patients with VPI. In this article describes a case of VPI treated by biofeedback technique with Nasometer; which showed satisfactory result in nasalance and formant analysis after the speech therapy during 9 months.

• Tribology and Lubricants
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• v.18 no.1
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• pp.24-33
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• 2002

The basic equations are derived for the analysis of a staggered labyrinth gas seal which are generally used in high performance compressors and steam turbines. The Bulk-flow is assumed for a single cavity control volume and the flow is assumed to be completely turbulent in circumferential direction. Moody's wall-friction-factor formula is used for the calculation of wall shear stresses in the single cavity control volume. For the reaction force developed by the seal, linearized zeroth-order and first-order perturbation equations are developed for small motion about a centered position. Integration of the resultant first-order pressure distribution along and around the seal defines the rotordynamic coefficients of the staggered labyrinth gas seal. Theoretical results of leakage and rotordynamic characteristics for the staggered labyrinth gas seal are compared with those of the plain seal and see-through labyrinth seal.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.1081-1086
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• 2006

Curtainwall systems has been applied to buildings widely for constructability. However, as cutainwall system include many building materials, they become to damaged vapor barrier and incur condensation. Natural ventilation of an air cavity in a curtainwall is expected to be an prevention of condensation in inner wall and reduce cooling energy in summer. The objective of this experimental study is to evaluating the insulation and condensation Performance of ventilated curtainwall with ventilated cavity depth and ratio of opening area.

• Restorative Dentistry and Endodontics
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• v.29 no.6
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• pp.532-540
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• 2004

The aim of this study was to measure the cusp deflection during composite restoration for MOD cavity in premolar and to examine the influence of cavity dimension, C-factor and restoration method on the cusp deflection. Thirty extracted maxillary premolar were prepared to four different sizes of MOD cavity and divided into six groups. The width and depth of the cavity were as follows. Group 1; $1.5{\;}{\times}{\;}1{\;}mm$, Group 2; $1.5{\;}{\times}{\;}2{\;}mm$, Group 3; $3{\;}{\times}{\;}1{\;}mm$, and Group 4-6; $3{\;}{\times}{\;}2{\;}mm$ respectively. Group 1-4 were restored using bulk filling method with Z-250 composite. However, Group 5 was restored incrementally, and Group 6 was restored with an indirect resin inlay. The cusp deflection was recorded at the buccal and lingual cusp tips using LVDT probe for 10,000 seconds. The measured cusp deflections were compared between groups, and the relationship between the cube of the length of cavity wall/the cube of the thickness of cavity wall ($L^3/T^3$). C-factor and cusp deflection or % flexure ($100{\;}{\times}$ cuspal deflection / cavity width) was analyzed. The cusp deflection of Group 1-4 were $12.1{\;}\mu\textrm{m},{\;}17.2{\;}\mu\textrm{m},{\;}16.2{\;}\mu\textrm{m}{\;}and{\;}26.4{\;}\mu\textrm{m}$ respectively. The C-factor was related to the % flexure rather than the cusp deflection. There was a strong positive correlationship between the $L^3/T^3$ and the cusp deflection. The cusp deflection of Group 5 and 6 were $17.4{\;}\mu\textrm{m}{\;}and{\;}17.9{\;}\mu\textrm{m}$ respectively, which are much lower value than that of Group 4.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.9
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• pp.645-651
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• 2008

For a high speed train driving at 300 km/h, aero-acoustic noise is a dominant component among various noise sources. The aeroacoustic noise is mainly due to inter-coach spacings because discontinuities in the train surface significantly disturb turbulent flows. This often leads to the uncomfortableness of passengers. Interestingly, the aero-acoustic noise reduces with decreasing the mud-flap spacing of the inter-couch spacing. We perform numerical simulations to investigate flow characteristics around the inter-coach spacing. We model the inter-coach spacing as a simple 2-D cavity with flaps, and calculate the velocity and pressure field using two equation turbulence models, varying the flap spacing. The results show that a wider flap spacing develops a higher inflection point in mean velocity profiles over the cavity. It is likely that large eddies generated near the inflection point persist longer in the downstream since they are less affected by the wall. This probably induces the more aero-acoustic noises. The wider spacing also results in the larger pressure difference between the inside and outside of the cavity. This is also responsible for the increased noise since the large difference would cause a strong flow oscillations in and out of the cavity.