• Journal of Chest Surgery
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• v.39 no.9 s.266
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• pp.681-691
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• 2006

Background: The aim of this study was to investigate the mid-term outcomes of our modifications to the maze procedure using cryoablation for treating atrial fibrillation associated with rheumatic mitral valve disease. Material and Method: Between March 2000 and February 2004, 177 consecutive patients underwent the modified maze procedure with the use of cryoablation concomitant with mitral valve surgery for atrial fibrillation associated with rheumatic mitral valve disease, and were divided into three groups: (1) modified Cox-maze III (CM group, n=88): (2) modified Kosakai-maze (KM group, n=63): and (3) left atrial maze procedure (LA group, n=26). The postoperative and follow-up results were analyzed and compared between the groups. Result: There were three hospital deaths (1.7%) and no significant differences in the incidence of postoperative complications between the three groups. The operative time, such as the cardiopulmonary bypass and aortic crossclamp time, were significantly longer in the CM group than in the KM and LA groups, respectively (p<0.0001). The mean follow-up was $22.4{\pm}15.1$ months ($1\sim52.6$ months) for all patients. One late death developed in the CM group (0.0%). At last follow-up, 139 patients exhibited sinus rhythm (79.9%), which was also regained in 67 patients (77.9%) in the CM group, 50 (80.7%) in the KM group and 22 (84.6%) in the LA group (p=0.743). The actuarial freedom from stroke at 4 years was $84.5{\pm}9.4%$ in the CM group, $95.0{\pm}4.9%$ in the KM group, and $92.9{\pm}6.9%$ in the LA group (p=0.916). Conclusion: The modified maze procedure using cryoablation is safe and effective in treating chronic atrial fibrillation associated with rheumatic mitral valve disease.

• International Journal of Highway Engineering
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• v.11 no.2
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• pp.205-216
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• 2009

As a subsequent study, this paper presents a comparative evaluation of structural responses in asphalt pavements with stabilized foundations. The approach based on a finite element analysis which incorporates non-linear behaviors of pavement geomaterials is used to estimate each performance indicator under standard single axle loading condition. In addition, results from laboratory tests are used to provide physical and mechanical properties of stabilized geomaterials for analyzing various pavement structures. Changes in pavement responses with varying layer thickness and stabilizer contents were investigated. It is found that the effect of layer thickness and stabilizer content is a critical factor in structural response of stabilized pavements. Moreover, a design criterion is proposed for selecting minimum contents of stabilizer of coarse-grained geomaterials based on a result of unconfined compressive strength and proper layer thickness of foundations.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.43 no.5 s.311
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• pp.30-36
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• 2006

In this paper, a new type of written image segmentation based on relative comparison of region areas is proposed. The original image is composed of two distinctive regions; information and background. Compared with this binary original image, the observed one is the gray scale which is represented with complex regions with speckles and noise due to degradation or contamination. For applying threshold or statistical approach, there occurs the region-deformation problem in the process of binarization. At first step, the efficient iterated conditional mode (ICM) which takes the lozenge type block is used for regions formation into the binary image. Secondly the information region is estimated through selecting action and restored its primary state. Not only decision of the attachment to a region but also the calculation of the magnitude of its area are carried on at each current pixel iteratively. All region areas are sorted into a set and selected through the decision parameter which is obtained statistically. Our experiments show that these approaches are effective on ink-rubbed copy image (拓本 'Takbon') and efficient at shape restoration. Experiments on gray scale image show promising shape extraction results, comparing with the threshold-segmentation and conventional ICM method.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.4
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• pp.39-49
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• 2002

In this paper, the characteristics of RB(rubber bearing) were studied by various prototype tests on RB with low hardness rubber. The characteristics of RB were tested on displacements, repeated cycles, frequencies, vertical pressures, temperature, vertical stiffness and the capability of shear deformation. The prototype test showed that the displacement and vertical pressures were the most governing factors influencing on characteristics of RB. The effective stiffness and equivalent damping of RB showed small increment in high frequency range. After the repeated cyclic test with 50's cycles, the effective stiffness and equivalent damping of RB were almost constant compared with those of the 1st cycles due to low hysteretic damping. The shear modulus of RB was reduced after large deformation, and this value of RB was partly recovered after 40 days. Finally, the shear failure test of RB was conducted, the prototype was failed over 490% of shear strain, and real size RB was failed over 430% of shear strain.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.4
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• pp.501-508
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• 2022

Required essential technique is to determine the maximum recharge pressure in the well with condition of non-ground failure for the recovery of the groundwater. Based on the classical soil mechanics, the maximum recharge pressure was estimated with the numerical anlaysis and laboratory triaxial test. In the numerical analysis, the maximum recharge pressure is defined as the ground failure stress. The ground failure of the sand was defined as the piping and the one of the caly was to the undrained failure by the confined pressure increment. In the triaxial test, the recharge pressure in the ground was modified by the back pressure in the specimen. In case of sand, the volume strain was dramatically increased at the 93 % of the maximum back pressure, same meaning of the 0 effective stress state. In case of clay, the only radial volume strain was to reached 1.5 % without failure. Therefore, The maximum recharge pressure could be determined with the numerical analysis and triaxial test.

• Economic and Environmental Geology
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• v.54 no.2
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• pp.233-245
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• 2021

Many studies on the microstructures in rocks have been conducted using experimental methods with various equipment as well as natural rock studies to see the development of microstructures and understand their mechanisms. Grain boundary migration of mineral aggregates in rocks could cause grain growth or grain size changes during metamorphism or deformation as one of the main recrystallization mechanisms. This study suggests improved ways regarding the analog material experiments with reformed equipment to see sequential observations of these grain boundary migration. It can be more efficient than the existing techniques and carry out an appropriate microstructure analysis. This reformed equipment was implemented to enable optical manipulation by mounting polarizing plates capable of rotating operation on a stereoscopic microscope and a deformation rig capable of experimenting with analog materials. The equipment can automatically control the temperature and strain rate of the deformation rig by microcontrollers and programming and can take digital photomicrographs with constant time intervals during the experiment to observe any microstructure changes. The composite images synthesized using images by rotated polarizing plates enable us to see more accurate grain boundaries. As a rock analog material, norcamphor(C7H10O) was used, which has similar birefringence to quartz. Static grain growth and simple shear deformation experiments were performed using the norcamphor to verify the effectiveness of the equipment. The static grain growth experiments showed the characteristics of typical grain growth behavior. The number of grains decreases and the average grain size increases over time. These case experiments also showed a clear difference between the growth curves with three temperature conditions. The result of the simple shear deformation experiment under the medium temperature-low strain rate showed no significant change in the average grain size but presented the increased elongation of grain shapes in the direction of about 53° regarding the direction perpendicular to the shearing direction as the shear strain increases over time. These microstructures are interpreted as both the plastic deformation and the internal recovery process in grains are balanced by the deformation under the given experimental conditions. These experiments using the reformed equipment represent the ability to sequentially observe changing the microstructure during experiments as desired in the tests with the analog material during the entire process.

• Journal of the Korean Society for Railway
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• v.20 no.1
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• pp.64-75
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• 2017

The role of a track subgrade is to provide bearing capacity and distribute load transferred to lower foundation soils. Track subgrade soils are usually compacted by heavy mechanical machines in the field, such that sometimes they are attributed to progressive residual settlement during the service after construction completion of the railway track. The progressive residual settlement generated in the upper part of a track subgrade is mostly non-recoverable plastic deformation, which causes unstable conditions such as track irregularity. Nonetheless, up to now no design code for allowable residual settlement of subgrade in a railway trackbed has been proposed based on mechanical testing, such as repetitive triaxial testing. At this time, to check the DOC or stiffness of the soil, field test criteria for compacted track subgrade are composed of data from RPBT and field compaction testing. However, the field test criteria do not provide critical design values obtained from mechanical test results that can offer correct information about allowable permanent deformation. In this study, a test procedure is proposed for permanent deformation of compacted subgrade soil that is used usually in railway trackbed in the laboratory using repetitive triaxial testing. To develop the test procedure, an FEA was performed to obtain the shear stress ratio (${\tau}/{\tau}_f$) and the confining stress (${\sigma}_3$) on the top of the subgrade. Comprehensive repetitive triaxial tests were performed using the proposed test procedure on several field subgrade soils obtained in construction sites of railway trackbeds. A permanent deformation model was proposed using the test results for the railway track.

• Journal of Dental Rehabilitation and Applied Science
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• v.31 no.4
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• pp.316-328
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• 2015

Purpose: The objects of this study was to evaluate the accuracy of the dental stone casts made from alginate impressions according to storage condition and stone pouring time. Materials and Methods: Each of upper and lower impressions of dental model was taken. The dental stone models were made immediately, 10, 30, 60, 180, 360 minutes after the impressions were taken at each storage condition. 3D models were constructed by scanning the stone model using 3D laser scanner. With Reference points, positioned on digital models, linear measurements of the dimensional change were compared by 3D metrology software, 3D average models were made and superimposition to identify the specific site of dimensional change and to measure surface deviation (mm). Results: Dental stone models which were made immediately after taking the impression showed the smallest linear dimensional change. As the stone pouring time was prolonged, the linear dimensional change was increased. More than 180 minutes after impression taking, linear dimensional change and surface distortion increased in the posterior molar region, regardless of the storage condition. Conclusion: For the optimum accuracy of the dental stone casts, alginate impression should be poured as soon as possible. If there were a need for storing, a humidor with 100% relative humidity must be used and be stored less than 180 minutes to fabricate the accurate dental model.

• Korean Journal of Food Science and Technology
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• v.29 no.2
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• pp.266-272
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• 1997

In order to investigate the compression and decompression properties of cucumber, radish, garlic, ginger and potato, edible parts of samples were prepared to size of ${\Phi}\;5\;mm{\times}H\;5\;mm$, and force deformation relationship during application and removal of force were observed. Compositions of sample and cell characteristics were measured, and correlations between them were investigated. Deformation rate was large in initial stage of compression and decreased afterward, but the reverse trends were observed in the decompression. The time and deformation to 9 N were large of 5.30 sec and 1.344 mm in potato, and small of 4.62 sec and 0.896 mm in garlic, respectively. Force(y)-deformation(x) curve between compression and decompression were clearly showed hysteresis loop and relationship of x and y were as follows: y=esp (a+b log(x)). The maximum work was $3.888{\sim}5.099{\times}10^{-3}\;J$ for potato in compression and $2.09{\times}10^{-3}\;J$ for garlic in decompression. Irrecoverable work were large as $77{\sim}96%$ in cucumber, radish and potato, and small as $36{\sim}42%$ in garlic. Compression deformation were large as $1.016{\sim}1.344\;mm$ in potato, and small as $0.656{\sim}0.896\;mm$ in garlic. Degree of elasticity were large as $0.756{\sim}0.777$ in garlic, and small as $0.301{\sim}0.465$ in radish and potato. Compression and decompression characteristic values were showed high correlation with moisture, viscosity of juice, ceil size, density and regularity.

• Journal of the Korean Arthroscopy Society
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• v.4 no.1
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• pp.25-31
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• 2000

Introduction : This study compared the clinical results with biceps rerouting fer the isolated posterolateral instability (PLI) and for the PLI combined with PCL injuries. Methods : 21 cases of isolated PLI (group I) and 25 cases of PLI combined with PCL rupture were included in the study. The PLI was reconstructed by modified biceps femoris rerouting technique with PCL reconstructions performed prior to the PLI correction in cases of combined injury The clinical results were reviewed and analyzed. Results : Pre-operatively positive reverse pivot shift test turned negative in 43 cases post-operatively. Increased preoperative external rotation thigh foot angle (ERTFA) showed significant differences between the two groups and all fell within normal limits post-operatively At a mean follow-up of 40.3 months, the average Lysholm knee score and. The Hospital for Special Surgery Knee Ligament Score for group I and group II revealed above 90 points without statistically significant difference between the groups. 3 cases of tenodesis failure developed and re-operation was performed. Discussion and Conclusion : The advantages of modified Clancy technique include reduced surgical damages to the iliotibial band and fixation of the biceps tendon at the isometric position. The modified biceps rerouting technique is recommended for the reconstruction of both isolated and combined PLI except in patients with severe damages at the attachment of biceps tendon.