• Journal of Navigation and Port Research
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• v.45 no.3
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• pp.87-94
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• 2021

The IMO has adopted emission standards that strictly restrict the use of bunker C oil for vessels. Accordingly, research and bunkering pilot projects for LNG fueled ships are being actively carried out, which is expected to substantially reduce environmental pollution. In this study, we have adopted the turret moored Floating LNG Bunkering Terminal (FLBT) designed to receive the LNG from LNGCs and to transfer LNG to LNG bunkering shuttles in ship to ship moored condition. Numerical simulations have been performed with a 1-year return period of wind, wave, and current. Damping values of numerical model were adjusted from the results of model tests to obtain accurate simulation results. The results confirm safe berthing operation during the 1-year return period of environmental condition. Safety depends on the direction of environment, with increasingly stable operation facilitated by the application of heading-control function of FLBT to avoid beam-sea conditions.

• Journal of the korean academy of Pediatric Dentistry
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• v.48 no.1
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• pp.1-11
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• 2021

The purpose of this study is to investigate factors influencing the upper airway dimensions in skeletal Class II children and adolescents. In total, 67 patients were selected. Airway volume and minimal cross-sectional area were three-dimensionally assessed. Craniofacial morphology and skeletal maturity were assessed on generated two-dimensional cephalograms. The measurements were analyzed using Mann-Whitney test, one-way ANOVA, Pearson's correlation, and multiple regression analysis. Upper airway dimensions were significantly smaller in pre-peak stage group, and positively associated with age. Anterior facial height and age were the most relevant factors for airway volume. Mandibular width and age were the most relevant factors for minimal cross-sectional area. Upper airway dimensions were significantly associated with age, skeletal maturity and craniofacial morphology in all three planes.

• Journal of Oral Medicine and Pain
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• v.44 no.2
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• pp.45-53
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• 2019

Purpose: To determine whether crepitus may be a clinical indication for early temporomandibular joint (TMJ) osteoarthritis (OA) and to investigate the correlation between crepitus and the occurrence of TMJ OA with respect to factors, such as patient sex, age, chewing habits, and diagnosis. Methods: This is retrospective analysis of clinical data for 162 TMJs. The criteria for a joint to be included in this study was a minimum of two cone-beam computed tomography (CBCT) scans performed with no OA observed during the initial scan. The Diagnostic Criteria for Temporomandibular Disorders was used for OA diagnosis. Crepitus was recorded when it was objectively palpated during the follow-up period. Correlations between various patient factors and progression to TMJ OA were calculated using the Pearson's chi-square test. A linear-by-linear association was used to analyze trends of OA progression with increasing age. Results: Among the 162 joints, 101 progressed to OA and 61 did not. In the joints where crepitus had been present before OA was confirmed at next or last CBCT, OA progressed at a high rate, and especially higher in female and older patients (p<0.01). Patients in the pain-related disorder group with crepitus were observed to have higher rates of OA progression compared to patients in the intra-articular disorder group (p<0.01). Conclusions: If a patient experiences pain in the TMJs and crepitus, close monitoring through regular CBCT scans is necessary even if there is no evidence of radiologically confirmed OA after the first CBCT.

• Imaging Science in Dentistry
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• v.49 no.1
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• pp.19-26
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• 2019

Purpose: It has been proposed that using new prediction methods, such as neural networks based on dental data, could improve age estimation. This study aimed to assess the possibility of exploiting neural networks for estimating age by means of the pulp-to-tooth ratio in canines as a non-destructive, non-expensive, and accurate method. In addition, the predictive performance of neural networks was compared with that of a linear regression model. Materials and Methods: Three hundred subjects whose age ranged from 14 to 60 years and were well distributed among various age groups were included in the study. Two statistical software programs, SPSS 21 (IBM Corp., Armonk, NY, USA) and R, were used for statistical analyses. Results: The results indicated that the neural network model generally performed better than the regression model for estimation of age with pulp-to-tooth ratio data. The prediction errors of the developed neural network model were acceptable, with a root mean square error (RMSE) of 4.40 years and a mean absolute error (MAE) of 4.12 years for the unseen dataset. The prediction errors of the regression model were higher than those of the neural network, with an RMSE of 10.26 years and a MAE of 8.17 years for the test dataset. Conclusion: The neural network method showed relatively acceptable performance, with an MAE of 4.12 years. The application of neural networks creates new opportunities to obtain more accurate estimations of age in forensic research.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.45 no.1
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• pp.34-42
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• 2019

Objectives: Various bone graft substitute materials are used to enhance bone regeneration in the maxillofacial skeleton. In the recent past, synthetic graft materials have been produced using various synthetic and natural calcium precursors. Very recently, eggshell-derived hydroxyapatite (EHA) has been evaluated as a synthetic bone graft substitute. To assess bone regeneration using EHA in cystic and/or apicectomy defects of the jaws through clinical and radiographic evaluations. Materials and Methods: A total of 20 patients were enrolled in the study protocol (CTRI/2014/12/005340) and were followed up at 4, 8, 12, and 24 weeks to assess the amount of osseous fill through digital radiographs/cone-beam computed tomography along with clinical parameters and complications. Wilcoxon matched pairs test, means, percentages and standard deviations were used for the statistical analysis. Results: The sizes of the lesions in the study ranged from 1 to 4 cm and involved one to four teeth. The study showed significant changes in the formation of bone, the merging of material and the surgical site margins from the first week to the first month in all patients (age range, 15-50 years) irrespective of the size of the lesions and the number of teeth involved. Bone formation was statistically significant from the fourth to the eighth week, and the trabecular pattern was observed by the end of 12 weeks with uneventful wound healing. Conclusion: EHA showed enhancement of bone regeneration, and healing was complete by the end of 12 weeks with a trabecular pattern in all patients irrespective of the size of the lesion involved. The study showed enhancement of bone regeneration in the early bone formative stage within 12 weeks after grafting. EHA is cost effective and production is environment friendly with no disease transfer risks. Thus, natural bioceramics will play an important role in the reduction of costs involved in grafting and reconstruction.

• Journal of Ocean Engineering and Technology
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• v.33 no.1
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• pp.33-41
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• 2019

Estimating fatigue damage is a very important issue in the design of ships. The springing and whipping response, which is the hydro-elastic response of the ship, can increase the fatigue damage of the ship. So, these phenomena should be considered in the design stage. However, the current studies on the the application of springing and whipping responses at the design stage are not sufficient. So, in this study, a prediction method was developed using fluid-structural interaction analysis to assess of the fatigue damage induced by springing and whipping. The stress transfer function (Stress RAO) was obtained by using the 3D FE model in the frequency domain, and the fatigue damage, including linear springing, was estimated by using the wide band damage model. We also used the 1D beam model to develop a method to estimate the fatigue damage, including nonlinear springing and whipping by the vertical bending moment in the short-term sea state. This method can be applied to structural members where fatigue strength is weak to vertical bending moments, such as longitudinal stiffeners. The methodology we developed was applied to 325K VLOC, and we analyzed the effect of the springing and whipping phenomena on the existing design.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.31 no.6
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• pp.381-388
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• 2018

This paper presents a generalized finite element formulation for plastic hinge modeling based on lumped plasticity in the classical Euler-Bernoulli beam elements. In this approach, the plastic hinges are effectively modeled using proper enrichment functions describing weak discontinuities of the solution. The proposed methodology enables the insertion of plastic hinges at an arbitrary location without modifying the connectivity of elements. The formations of plastic hinges are instead achieved by hierarchically adding degrees of freedom to existing elements. Convergence analyses such as h- and p-extensions are performed to investigate the effectiveness of the proposed method. The analysis results indicate that the proposed generalized finite element method can achieve theoretical convergence rates for both cases where plastic hinges are located at nodes and within an element, thus demonstrating its accuracy.

• Restorative Dentistry and Endodontics
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• v.43 no.4
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• pp.42.1-42.7
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• 2018

Objectives: The purpose of this study was to investigate the C-shaped root canal anatomy of mandibular second molars in a Korean population. Materials and Methods: A total of 542 teeth were evaluated using cone-beam computed tomography (CBCT). The canal shapes were classified according to a modified version of Melton's method at the level where the pulp chamber floor became discernible. Results: Of the 542 mandibular second molars, 215 (39.8%) had C-shaped canals, 330 (53%) had 3 canals, 17 (3.3%) had 2 canals, 12 (2.2%) had 4 canals, and 8 (1.7%) had 1 canal. The prevalence of C-shaped canals was 47.8% in females and 28.4% in males. Seventy-seven percent of the C-shaped canals showed a bilateral appearance. The prevalence of C-shaped canals showed no difference according to age or tooth position. Most teeth with a C-shaped canal system presented Melton's type II (45.6%) and type III (32.1%) configurations. Conclusions: There was a high prevalence of C-shaped canals in the mandibular second molars of the Korean population studied. CBCT is expected to be useful for endodontic diagnosis and treatment planning of mandibular second molars.

• Smart Structures and Systems
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• v.24 no.3
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• pp.333-343
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• 2019

The possibility of adopting vibration-powered wireless nodes has been largely investigated in the last years. Among the available technologies based on the piezoelectric effect, the most common ones consist of a vibrating beam covered by electroactive layers. Another energy harvesting strategy is based on the use of piezoelectric strips attached to a hosting structure subjected to dynamic loads. The hosting structure, for example, can be the system to be equipped with wireless nodes. Such strategy has received few attentions so far and no analytical studies have been presented yet. Hence, the original contribution of the present paper is concerned with the development of analytical solutions for the electrodynamic analysis and design of piezoelectric polymeric strips attached to relatively large linear elastic structural systems subjected to random vibrations at the base. Specifically, it is assumed that the dynamics of the hosting structure is dominated by the fundamental vibration mode only, and thus it is reduced to a linear elastic single-degree-of-freedom system. On the other hand, the random excitation at the base of the hosting structure is simulated by filtering a white Gaussian noise through a linear second-order filter. The electromechanical force exerted by the polymeric strip is negligible compared with other forces generated by the large hosting structure to which it is attached. By assuming a simplified electrical interface, useful new exact analytical expressions are derived to assess the generated electric power and the integrity of the harvester as well as to facilitate its optimum design.

• The korean journal of orthodontics
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• v.49 no.5
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• pp.326-337
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• 2019

Objective: The objective of this study was to develop new parameters based on the foramina of the trigeminal nerve and to compare them with the conventional cephalometric parameters in different facial skeletal types. Methods: Cone-beam computed tomography (CBCT) scans and cephalograms from 147 adult patients (57 males and 90 females; mean age, 26.1 years) were categorized as Class I ($1^{\circ}$ < ANB < $3^{\circ}$), Class II (ANB > $5^{\circ}$), and Class III (ANB < $-1^{\circ}$). Seven foramina in the craniofacial area-foramen rotundum (Rot), foramen ovale (Ov), infraorbital foramen, greater palatine foramen, incisive foramen (IF), mandibular foramen (MDF), and mental foramen (MTF)-were identified in the CBCT images. Various linear, angular, and ratio parameters were compared between the groups by using the foramina, and the relationship between the new parameters and the conventional cephalometric parameters was assessed. Results: The distances between the foramina in the cranial base did not differ among the three groups. However, the Rot-IF length was shorter in female Class III patients, while the Ov-MTF length, MDF-MTF length, and Ov-MDF length were shorter in Class II patients than in Class III patients of both sexes. The MDF-MTF/FH plane angle was larger in Class II patients than in Class III patients of both sexes. Most parameters showed moderate to high correlations, but the Ov-MDF-MTF angle showed a relatively low correlation with the gonial angle. Conclusions: The foramina of the trigeminal nerve can be used to supplement assessments based on the conventional skeletal landmarks on CBCT images.