• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.2
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• pp.171-181
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• 2009

The objective of this study was to analyse stress distribution of maxillary complex by use of face mask. The construction of the three-dimensional FEM model was based on the computed tomography(CT) scans of 13.5 years-old male subject. The CT image were digitized and converted to the finite element model by using the mimics program, with PATRAN. An anteriorly directed force of 500g was applied at the first premolar 45 degrees downwards to the FH plane and at the first molar 20 degrees downwards to the FH plane. When 45 degrees force was applied at maxillary first premolar, there were observed expansion at molar part and constriction at premolar part. The largest displacement was 0.00011mm in the x-axis. In the y-axis, anterior displacement observed generally 0.00030mm at maximum. In the z-axis, maxillary complex was displaced 0.00036 mm forward and downward. When 20 degrees force was applied at maxilla first molar, there were observed expansion at lateral nasal wall and constriction at molar part. The largest displacement was 0.001mm in the X-axis. In the Y-axis, anterior displacement observed generally 0.004mm at maximum. In the Z-axis, ANS was displaced upward and pterygoid complex was displaced downward. The largest displacement was 0.002mm.

• Journal of Dental Rehabilitation and Applied Science
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• v.29 no.3
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• pp.209-223
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• 2013

This study was to evaluate the stress distributions of prefabricated, customized abutments and fixtures according to their material and shape by three-dimensional finite element analysis. And to investigate the fatigue life and fracture characteristics. Mandibular models were fabricated by reconstruction of the CT scan of patients with normal occlusion. A total of six finite element models were designed, a load of 100 N was applied on the buccal cusps vertically, and 30 degree obliquely. 10 specimens each were fabricated for the more clinically widely used 4 type abutments and were loaded according to ISO 14801. Differences in stress distribution patterns were not found according to the materials of the abutments and fixtures. But a slight difference in the stress level was detected. Customized abutment groups showed lower crown stress levels. One-piece zirconia implant showed the lowest bone stress levels. In the fatigue test, highest values were measured in group 7. Prefabricated abutments showed less variation of fatigue life (P<0.05). Use of customized abutments can improve the fracture resistance of restorations. Especially, use of customized zirconia abutments reinforced by titanium screw connecting parts is recommended.

• Restorative Dentistry and Endodontics
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• v.33 no.3
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• pp.184-197
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• 2008

This study was to investigate the influence of combining composite resins with different elastic modulus, and occlusal loading condition on the stress distribution of restored notch-shaped non-carious cervical lesion using 3D finite element (FE) analysis. The extracted maxillary second premolar was scanned serially with Micro-CT. The 3D images were processed by 3D-DOCTOR. ANSYS was used to mesh and analyze 3D FE model. A notch-shaped cavity was modeled and filled with hybrid, flowable resin or a combination of both. After restoration, a static load of 500N was applied in a point-load condition at buccal cusp and palatal cusp. The stress data were analyzed using analysis of principal stress. Results showed that combining method such that apex was restored by material with high elastic modulus and the occlusal and cervical cavosurface margin by small amount of material with low elastic modulus was the most profitable method in the view of tensile stress that was considered as the dominant factor jeopardizing the restoration durability and promoting the lesion progression.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.2
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• pp.719-727
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• 2013

Four-step travel-demand modeling based on a trip-level has been widely used over many decades. However, there has been a wide variance between forecasted- and real-travel demands, which leads less reliable on the model implications. A primary reason is that person's real travel behavior is not properly captured throughout the model developments. An activity-based modeling (ABM) approach was proposed and developed toward increasing the accuracy and reality of person's travel behavior in the U.S. since 1990', and stands as a good alternative to replace the existing trip-based approach. The paper contributes to the understanding of how the ABM approaches are dissimilar to the trip-based modeling approach in terms of estimation units, estimation process, their pros and cons and etc. We examined three activity-based travel demand model systems (DaySim, CT-Ramp, and CEMDAP) that are most commonly applied by many MPOs (Metropolitan Planning Organization). We found that the ABM approach can effectively explain multi-dimensional travel decision-makings and be expected to increase the predictive accuracy. Overall, the ABM approach can be a good substitute for the existing travel-demand methods having unreliable forecasts.

• Tunnel and Underground Space
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• v.26 no.3
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• pp.220-234
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• 2016

Sprayable waterproofing membrane has been considered as a substitute for a sheet waterproofing membrane in a variety of underground excavation works. However, fundamental properties of sprayble waterproofing membrane have not been fully given yet. In this study, a new two-component sprayable waterproofing membrane prototype was developed. In addition, its physico-mechanical properties were measured and compared with those of two kinds of thin spray-on liners where constitutive materials and construction methods are very close to each other. From direct tensile tests, the sprayable waterproofing membrane with elongations at break between 250% and 300% showed much higher ductility than TSLs. However, the sprayable waterproofing membrane had a limitation as a support member since its bond strength and loading capacity was lower than those of TSLs. From three-dimensional X-ray CT images, the porosity of the sprayable waterproofing membrane was estimated to be 26.13%. However, most of pores which might have been generated during membrane curing were not observed to be interconnected but isolated.

• Journal of Biomedical Engineering Research
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• v.24 no.6 s.81
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• pp.515-522
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• 2003

Pharynx is a system transporting foods by peristaltic motion(contraction and expansion movement! into the esophagus and functioning as airway passages. In this study, structural changes of pharyngeal dysfunction are analyzed by biomechanical model using CT and FEM(finite clement method). Loading condition was assumed that equal pressure was loaded sequentially to inside of pharyngeal tissue. In order to analyze the pharyngeal muscular dysfunction by biomechanical model. the pharyngeal dysfunctions was classified into 3 cases. Taking into account the clinical complication by neuromuscular symptoms such as pharyngeal dysfunction after stroke. we assumed that a change of material property is caused by muscular tissue stiffness. A deformation of cross sectional area of the pharynx is analyzed increasing the stiffness $25\%,\;50\%,\;75\%$ in each case on the basis of stress-strain relationship. Based on three-dimensional reconstruction of pharyngeal structure using limited factor - techniques and the optimization procedure by means of inverse dynamic approach. the biomechanical model of the human pharynx is implemented. The results may be used as clinical index illustrating the degree of pharyngeal muscular dysfunction. This study may be used as useful diagnostic model in discovering early deglutitory impediment caused by physiological or pathological pharyngeal dysfunction.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.5
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• pp.293-300
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• 2021

In this study, the microstructure and thermal conductivity correlation was investigated for concrete materials used in concrete thermal energy storage (CTES) among real-time energy storage devices. Graphite was used as admixture to increase the thermal conductivity performance of the CTES. Concrete specimens of 10% and 15% substitution of cement by mass with graphite, as well as ordinary portland cement (OPC) specimens were prepared, and the microstructural changes and effects on thermal conductivity were analyzed. Porosities of OPC and concrete with graphite were compared using micro-CT, and the microstructural characteristics were quantified using probability functions. Three-dimensional virtual specimens were constructed for thermal analysis, to confirm the effect of microstructural characteristics on thermal conductivity, and the results were compared with the measured conductivity obtained using the hot-disc method. To identify thermal conductivity of graphite for thermal analysis, solid phase conductivity was inversely determined based on simulation and experimental results, and the effect of graphite on thermal conductivity was analyzed.

• Journal of Dental Rehabilitation and Applied Science
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• v.38 no.1
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• pp.42-51
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• 2022

Esthetic restoration of maxillary anterior implant heavily depends on the direction of installation of implant fixture. In patients with malpositioned implant, it is crucial to communicate the limitations of prosthetic outcome with the patient before starting on a restoration. To facilitate the communication, three-dimensional virtual representation by superimposing facial and intraoral digital scans with Computed Tomography (CT, dicom file) was used for visualization of the limitations of prosthesis. Through digital diagnostic wax-up, the profile of right maxillary anterior incisor implant was expected to be protrusive, which the patient was not satisfied with. Since the patient already had done root canal treatment on left maxillary anterior incisor due to previous trauma, a new prosthetic design including both right and left maxillary anterior incisors was presented to the patient. The second design was chosen and his comments were delivered to dental lab. The patient was satisfied with the new prosthesis, aesthetically and functionally.

• Korean Journal of Radiology
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• v.22 no.3
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• pp.464-475
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• 2021

Objective: This study aimed to evaluate the tumor doubling time of invasive lung adenocarcinoma according to the International Association of the Study for Lung Cancer (IASLC)/American Thoracic Society (ATS)/European Respiratory Society (ERS) histologic classification. Materials and Methods: Among the 2905 patients with surgically resected lung adenocarcinoma, we retrospectively included 172 patients (mean age, 65.6 ± 9.0 years) who had paired thin-section non-contrast chest computed tomography (CT) scans at least 84 days apart with the same CT parameters, along with 10 patients with squamous cell carcinoma (mean age, 70.9 ± 7.4 years) for comparison. Three-dimensional semiautomatic segmentation of nodules was performed to calculate the volume doubling time (VDT), mass doubling time (MDT), and specific growth rate (SGR) of volume and mass. Multivariate linear regression, one-way analysis of variance, and receiver operating characteristic curve analyses were performed. Results: The median VDT and MDT of lung cancers were as follows: acinar, 603.2 and 639.5 days; lepidic, 1140.6 and 970.1 days; solid/micropapillary, 232.7 and 221.8 days; papillary, 599.0 and 624.3 days; invasive mucinous, 440.7 and 438.2 days; and squamous cell carcinoma, 149.1 and 146.1 days, respectively. The adjusted SGR of volume and mass of the solid-/micropapillary-predominant subtypes were significantly shorter than those of the acinar-, lepidic-, and papillary-predominant subtypes. The histologic subtype was independently associated with tumor doubling time. A VDT of 465.2 days and an MDT of 437.5 days yielded areas under the curve of 0.791 and 0.795, respectively, for distinguishing solid-/micropapillary-predominant subtypes from other subtypes of lung adenocarcinoma. Conclusion: The tumor doubling time of invasive lung adenocarcinoma differed according to the IASCL/ATS/ERS histologic classification.

• Journal of the Korean Society of Radiology
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• v.82 no.4
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• pp.876-888
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• 2021

Purpose The aim of this study was to compare the diameter and volume of liver metastases on CT images in relation to overall survival and tumor response in patients with gastric cancer liver metastases (GCLM) treated with chemotherapy. Materials and Methods We recruited 43 patients with GCLM who underwent chemotherapy as a first-line treatment. We performed a three-dimensional quantification of the metastases for each patient. An independent survival analysis using the Response Evaluation Criteria in Solid Tumors (RECIST) was performed and compared to volumetric measurements. Overall survival was evaluated using Kaplan-Meier analysis and compared using Cox proportional hazard ratios following univariate analyses. Results When patients were classified as responders or non-responders based on volumetric criteria, the median overall survival was 23.6 months [95% confidence interval (CI), 8.63-38.57] and 7.6 months (95% CI, 3.78-11.42), respectively (p = 0.039). The volumetric analysis and RECIST of the non-progressing and progressing groups showed similar results based on the Kaplan-Meier method (p = 0.006) and the Cox proportional hazard model (p = 0.008). Conclusion Volumetric assessment of liver metastases could be an alternative predictor of overall survival for patients with GCLM treated with chemotherapy.