• The Journal of the Acoustical Society of Korea
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• v.34 no.6
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• pp.470-478
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• 2015

A heuristic method treating a layered ocean bottom in a ray modeling is to use the plane wave reflection coefficient for multiple-layered structure, named an one-layer assumption in this paper. We examine the validity of one-layer assumption in the case of two-layered ocean bottom, and obtain a simple inequality condition depending on the sound speed ratio, the ratio of layer thickness to source-receiver range, and the grazing angle of first reflected ray. From this inequality condition, it is shown that an one-layer assumption can be applicable to ray propagation problems at mid frequencies. Finally, numerical experiments are performed in the ocean environment similar to the East Sea in Korea. Incoherent transmission loss is calculated by the geometrical beam model with the plane wave reflection coefficient for multiple-layered ocean bottom and compared with the result of SNUPE 2.0, which is a parabolic equation package developed in Seoul National University.

• Journal of Biosystems Engineering
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• v.27 no.4
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• pp.341-348
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• 2002

Quality evaluation of red ginsengs is determined by outer shape and inner qualities. Especially, the inner qualities are main grading criteria. Currently, red ginsengs are classified into 3-grades; heaven, earth and good. The best heaven grade must not include inner holes and sponge tissues. This study was conducted to develop a red ginseng sorting system using x-ray image processing technique. Because of lens characteristic, gray values of the central region in the x-ray image are higher and gradually decreased towards the edge regions. This difference of gray values gives trouble in segmentation and detection of inner holes in red ginseng image, so preprocessing technique is necessary. The preprocessing was done by subtracting source image from an empty background image. But, simple subtraction was not quite appropriate because of too small contrast between inner holes and sound part. Scaled subtraction images were obtained by multiplying all gray values by some numbers. However this method could not help to set threshold value because the gray values of root part are generally lower than body part when red ginseng is exposed to the x-ray. To determine threshold value for detecting inner holes, an algorithm was developed by increasing overall gray values of less clear images.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.233-236
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• 2000

The acoustical response of fish depends on size and physical structure na, most important, on the presence or absence of a swimbladder. Acoustic scattering models for swimbladdered fish represent a fish by an ideal pressure-release surface having the size and shape as the swimbladder. Target strength experiments of red seabream (Chrysophrys major) have been conducted using 38 (split-beam), 120 (split-beam) and 200kHz (dual-beam) frequencies. At each start of each experiment, the live fish are placed in the cage at the surface, then the cage is lowed to about $4{\cal}m$ depth where it remains during the measurements. To test the acoustic models, predictions of target strength based on swimbladder morphometries of 10 red seabream offish total length from $103{\cal}mm{\;}to{\;}349{\cal}mm$ ($3 <$TL/\lambda$ < 45)are compared with conventional target strength measurements on the same, shock-frozen immediately after caged experiments. X-ray was projected along dorsal aspect to know the morphological construction of swimbladder. and fish body. At high frequencies, Helmholtz-kirchhoff(HK) approximation would greatly enhance swimbladdered fish modeling. Sound scattering model [HK-ray approximation model] for comparison to experimental target strength data was used to model backscatter measurements from individual fish. The scattering data can be used in the inverse method along with multiple frequency sonar systems to investigate the adequacy of classification and identification of fish

• Journal of Digital Convergence
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• v.16 no.9
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• pp.239-245
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• 2018

In the current mainstream pop music scene, Stevie ray vaughan's status is a singer-songwriter and electric blues guitarist, who occupies a very large position despite his short period of activity. His influence has remained to the present day as the voice of many guitarists ranging from his unique sound to his explosive stage performances. Let's take a look at the technical parts of his performance, rhythm and solo performances, among the various traces of his constant reproduction. Based on one of his most famous works, 'Pride and Joy' I analyzed the solo and rhythm, scale that Stevie Ray Vaughan played. Through the African American blues, a peripheral heritage he has been trying to influence and influence, how his traces congregate in the center of today's mainstream pop music scene. This will give us little clues to appreciate before the research that will have a variety of influences and values.

• Imaging Science in Dentistry
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• v.34 no.3
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• pp.145-150
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• 2004

Purpose: To compare three digital radiographic imaging sensors by evaluating the visibility of endodontic file tips with interobserver reproducibility and assessing subjectively the clarity of images in comparison with the x-ray film images. Materials and Methods: Forty-five extracted sound premolars were used for this study. Fifteen plaster blocks were made with three premolars each and #8, 10, 15 K-flexofiles were inserted into the root canal of premolars. They were radiographically exposed using periapical x-ray films (Kodak Insight Dental film, Eastmann Kodak company, Rochester, USA), Digora imaging plates (Soredex-Orion Co., Helsinki, Finland), CDX 2000HQ sensors (Biomedisys Co., Seoul, Korea), and CDR sensors (Schick Inc., Long Island, USA). The visibility of endodontic files was evaluated with interobserver reproducibility, which was calculated as the standard deviations of X, Y coordinates of endodontic file tips measured on digital images by three oral and maxillofacial radiologists. The clarity of images was assessed subjectively using 3 grades, i.e. plus, equal, and minus in comparison with the conventional x-ray film images. Results: Interobserver reproducibility of endodontic file tips was the highest in CDR sensor (p < 0.05) only except at Y coordinates of #15 file. In the subjective assessment of the image clarity, the plus grade was the most frequent in CDR sensor at all size of endodontic file (p < 0.05). Conclusion : CDR sensor was the most superior to the other sensors, CDX 2000HQ sensor and Digora imaging plate in the evaluation of interobserver reproducibility of endodontic file tip and subjective assessment of image clarity.

• The Journal of the Acoustical Society of Korea
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• v.25 no.6
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• pp.298-304
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• 2006

This paper proposes a ray-based forward modeling scheme which is suitable for the shallow water acoustic wave propagation simulations. The proposed model comprises of ray tracings for the layered media of which sound speed profiles are interpolated linearly. considerations of plane and spherical wave reflection coefficients. and calculations of the phases and the amplitudes of eigen rays. The main characteristic of the scheme is fast simulation time due to direct calculation of the broad-band time signals in the time-domain, i.e. without transformation of the frequency-domain solutions to the time si 밍 131s. Finally, we applied the model to 4-types of test environments and compared the resulting signals with those of ORCA and Ram in order to validate the proposed model.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.2
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• pp.82-89
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• 1998

The experimental results using the X -ray technique, the position and structure of mica crystal are not observed the phase change of aging and sound specimen respectively. However, We could observe the intensity difference of crystal element in both atmospheres. The analysis of mica-epoxy materials by optical microscope are shown that the each surface of sound and aging specimens are different in both atmospheres Also, the experimental results have shown that the potassium ions of mica cristal are substituted by hydrogen ions at boundary area of mica-epoxy and/or mica-mica. On components made of mica, a potassium ion of big atomic radius, is replaced by hydrogen ion of small atomic radius. The voids are created by the difference of radius progressed by combined stresses. Through these phenomena, it has been proposed that the conductive layers made of potassium enable the voids to form and the cracks to create by high electric field.

• Journal of Korea Foundry Society
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• v.28 no.5
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• pp.231-236
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• 2008

H-NCM(Hong-Nanocast Method)has several benefits such as a lower porosity defect and high quality casting comparing to conventional die casting. Influence of casting parameters of hybrid-lower arm in rheocasting process on the slurry flow and the amount of porosity defect was investigated using experimental and simulation methods. In the present study, the Carreau model was adopted to simulate the pattern of rheological flow. Optimal casting paremeters such as injection speed and stroke variations were established. Sound products with integral microstructure and sound shape of joinning different materials of Al and steel pipe without deforming the steel pipe were obtained by the H-NCM slurry and X-ray analysis also showed integral condition throughout the entire parts.

• Journal of Chest Surgery
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• v.14 no.2
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• pp.140-143
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• 1981

Thymolipoma is extremely uncommon benign mediastinal tumor consisting of fatty and thymic tissue. Only 50 verified cases have been reported in the world literatures. This one case is the first reported example of surgically treated thymolipoma associated with spontaneous pneumothorax. A thirty-two year old male patient had been in good health until two days prior to admission, when he noted sudden dyspnea associated with an aching pain over the left precordium. The dyspnea and chest pain had become progressively worse. The physical examination revealed that left hemithorax was tympanic sound on percussion and absence of breathing sound on auscultation and point of maximal impulse was located on the 4th intercostal space at the left sternal border. Emergency closed thoracostomy was performed under the impression of tension type spontaneous pneumothorax of the left lung. After closed thoracostomy, point of maximal impulse was not changed inspire of full expansion of the left lung and chest X-ray was strongly suggested pericardial effusion or cardiomegaly which couldn`t account for by clinical course and hemodynamic evidence. EKG, echocardiogram, bronchofiberoscophy, bronchogram and diagnostic thoracentesis was performed. On Dec. 8, 1980, operation was performed under the impression of mediastinal tumor in the anterior mediastinum. At left posterolateral thoractomy, a large fatty mass, measuring 35 x 27 x 13 Cm in dimension and weighing 3350 gm, was resected and multiple bullae on the apicoposterior segment of the left upper lobe was resected and continuously sutured. The pathologic diagnosis of the fatty mass was thymolipoma. The postoperative course was uneventful and discharged in good general conditions.

• Journal of Chest Surgery
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• v.14 no.2
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• pp.135-139
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• 1981

Thymolipoma is extremely uncommon benign mediastinal tumor consisting of fatty and thymic tissue. Only 50 verified cases have been reported in the world literatures. This one case is the first reported example of surgically treated thymolipoma associated with spontaneous pneumothorax. A thirty-two year old male patient had been in good health until two days prior to admission, when he noted sudden dyspnea associated with an aching pain over the left precordium. The dyspnea and chest pain had become progressively worse. The physical examination revealed that left hemithorax was tympanic sound on percussion and absence of breathing sound on auscultation and point of maximal impulse was located on the 4th intercostal space at the left sternal border. Emergency closed thoracostomy was performed under the impression of tension type spontaneous pneumothorax of the left lung. After closed thoracostomy, point of maximal impulse was not changed inspire of full expansion of the left lung and chest X-ray was strongly suggested pericardial effusion or cardiomegaly which couldn`t account for by clinical course and hemodynamic evidence. EKG, echocardiogram, bronchofiberoscophy, bronchogram and diagnostic thoracentesis was performed. On Dec. 8, 1980, operation was performed under the impression of mediastinal tumor in the anterior mediastinum. At left posterolateral thoractomy, a large fatty mass, measuring 35 x 27 x 13 Cm in dimension and weighing 3350 gm, was resected and multiple bullae on the apicoposterior segment of the left upper lobe was resected and continuously sutured. The pathologic diagnosis of the fatty mass was thymolipoma. The postoperative course was uneventful and discharged in good general conditions.