• Journal of the Society of Naval Architects of Korea
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• v.43 no.1 s.145
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• pp.22-31
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• 2006

Recent studies have shown that the short time solution of the equation of motion for the rolling of ships is important in deciding the possibility of capsize of ships due to the excessive heel. Since most of known solutions for nonlinear equations of motion are long time or steady periodic solutions, here a simple way is described to get the short time solutions of the Duffing equation, which was chosen for deriving a criterion for the capsize of the ship. With the small external rolling moment, we first assume the state of the small damping and near resonance. Then, for cases when the frequency of the external moment is higher than the resonant one, an inequality was derived as a criterion for the capsize. This gives the range of the initial condition and the magnitude of the external moment which should be avoided for a ship to be safe from capsize. Furthermore, from the linearized equation, it is also shown that a simple and self-explanatory solution can be obtained consistent with that for the case of no damping, which yields the well-known linear growth with time.

• Earthquakes and Structures
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• v.23 no.1
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• pp.101-113
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• 2022

A new type of fabricated subway station construction technology can effectively solve these problems. For a new type of metro structure form, it is necessary to clarify its mechanical properties, especially the seismic performance. A soil-structure elastoplastic finite element model is established to perform three-dimensional nonlinear dynamic time-history analysis based on the first fabricated station structure-Yuanjiadian station of Changchun Metro Line 2, China. Firstly, the nonlinear seismic response characteristics of the fabricated and cast-in-place subway stations under different seismic wave excitations are compared and analyzed. Then, a comprehensive analysis of several important parameters that may affect the seismic response of fabricated subway stations is given. The results show that the maximum plastic strain, the interlayer deformation, and the internal force of fabricated station structures are smaller than that of cast-in-place structure, which indicates that the fabricated station structure has good deformation coordination capability and mechanical properties. The seismic responses of fabricated stations were mainly affected by the soil-structure stiffness ratio, the soil inertia effect, and earthquake load conditions rarely mentioned in cast-in-place stations. The critical parameters have little effect on the interlayer deformation but significantly affect the joints' opening distance and contact stress, which can be used as the evaluation index of the seismic performance of fabricated station structures. The presented results can better understand the seismic responses and guide the seismic design of the fabricated station.

• Journal of Korean Dental Science
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• v.15 no.2
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• pp.132-140
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• 2022

Purpose: Dental diagnostic records derived from study models are a popular method of obtaining reliable and vital information. Conventional plaster models are the most common method, however, they are being gradually replaced by digital impressions as technology advances. Moreover, three-dimensional dental models are becoming increasingly common in dental offices, and various methods are available for obtaining them. This study aimed to evaluate the accuracy of the measurement of dental digital models by comparing them with conventional plaster and to determine their clinical validity. Materials and Methods: The study was conducted on 16 patients' maxillary and mandibular dental models. Tooth size (TS), intercanine width (ICW), intermolar width (IMW), and Bolton analysis were taken by using a digital caliper on a plaster model obtained from each patient, while intraoral scans were manually measured using two digital analysis software. A one-way analysis of variance test was used to compare the dental measurements of the three methods. Result: No significant differences were reported between the TS, the ICW and IMW, and the Bolton analysis through the conventional and two digital groups. Conclusion: Measurements of TS, arch width, and Bolton analysis produced from digital models have shown acceptable clinical validity. No significant differences were observed between the three dental measurement techniques.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.11
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• pp.3723-3737
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• 2022

Google Play is one of the largest Android phone app markets and it contains both free and paid apps. It provides a variety of categories for every target user who has different needs and purposes. The customer's rate every product based on their experience of apps and based on the average rating the position of an app in these arch varies. Fraudulent behaviors emerge in those apps which incorporate search rank maltreatment and malware proliferation. To distinguish the fraudulent behavior, a novel framework is structured that finds and uses follows left behind by fraudsters, to identify both malware and applications exposed to the search rank fraud method. This strategy correlates survey exercises and remarkably joins identified review relations with semantic and behavioral signals produced from Google Play application information, to distinguish dubious applications. The proposed model accomplishes 90% precision in grouping gathered informational indexes of malware, fakes, and authentic apps. It finds many fraudulent applications that right now avoid Google Bouncers recognition technology. It also helped the discovery of fake reviews using the reviewer relationship amount of reviews which are forced as positive reviews for each reviewed Google play the android app.

• Journal of the Society of Naval Architects of Korea
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• v.28 no.2
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• pp.285-292
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• 1991

In this paper, typical tubular joints' fatigue strength is investigated focussing un the Stress Concentration Factors calculation using Finite Element Methods. For the calculation of the SCF of the members, the joints are modeled using thin shell elements and comprehensive analysis are carried out. Related techniques for the numerical analysis are studied. Experimental studies are performed for the verification and comparison with the numerical analysis results. Model tests of K joints are carried out not only for finding SCF values but also for the calculation of fatigue lives of the joints using specially designed test facilities.

• The korean journal of orthodontics
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• v.23 no.4 s.43
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• pp.503-527
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• 1993

This paper describes a new method to create an animal model for TMJ internal derangement in the New Zealand white rabbits and the light and electron microscopical changes of posterior attachment of them. Twenty six rabbits(2.5-3.0kg), four normal and twenty two experimental, were used. The right disc of experimental animal was displaced anteriorly without sectioning the posterior attachment and tied to the zygomatic arch with nylon not to be reduced to the original position. The left TMJ was sham-operated to be compared with its right experimental one. Normal animals were sacrificed one day and eight weeks after experiment. Experimental animals were sacrificed one day, ten days, three weeks, five weeks and eight weeks after surgery respectively. They were fixed intravenously with $2\%$ glutaldehyde under general anesthesia and the samples of them were processed for light and electron microscopic examination. The purpose of this experiment is to make a suitable animal model of disc displacement without reduction for studying and understanding the cellular and morphologic events in posterior attachment of TMJ including early changes which were difficult to be observed in human TMJs. The results of this investigation suggest the following conclusions : 1. Authors induced anterior disc displacement surgically in rabbits with new method to examine histologic changes of posterior attachment. Tissue reactions of this model seem to be similar to those observed in human disc displacement. We think this animal model for anterior disc displacement may be used to explore and evaluate objectively the effects of many treatment modalities in disc displacements. 2. The animal disease model showed inflammation at early stage(one and ten days). At this stage there were mild-to-severe mononuclear inflammatory cell infiltration, numerous newly formed vessels, vessel dilatation and engormement and many fibroblasts. 3. At middle stage(three weeks), fibrosis occurred, where fibroblasts decreased in number, but their cytoplasm was profuse indicating high activity. Collagen fibers increased in number and the tissue looked more dense. 4. At late stage(five weeks and eight weeks) showed degenerative changes including perforation of posterior attachment, disintegration of collagen fiber bundles, degeneration of fibroblasts, metastatic ossification, and dystrophic calcification.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.1
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• pp.302-309
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• 2017

The influence of the pile diameter, center to center pile spacing, internal friction angle of embankment soil, and height of embankment on the arching efficacy of the embankment pile was investigated. The arching efficacy, which was derived by the arch model developed in the embankment soil was calculated using two methods, one that considers crown failure of the arch and the other that considers load on the pile cap and critical relative spacing ratio for which the arching efficacy calculated by the two methods are the same. According to the computed results in this study, the arching efficacy calculated from a consideration of the load on pile cap governs when the relative spacing ratio becomes smaller and that calculated from the theory of crown failure governs when the relative spacing ratio becomes larger. The critical relative spacing ratio below which the arching efficacy calculated from a consideration of the load on pile cap governs the design decreases with increasing value, which is defined by the ratio of the pile diameter to the pile center to center spacing. Critical relative spacing ratios, which correspond to the values of 0.5 and 0.2 were 0.35 and 0.85, respectively. Considering the computed results, the critical relative spacing ratio decreases with increasing Rankine passive earth pressure coefficient and critical relative spacing ratios, which correspond to values of 5 and 2, were 0.23 and 0.85, respectively. The arching efficacy, which corresponds to the area ratio of 9%, was 54% and the one that corresponds to the value of 3 was 61%; the critical relative spacing ratios, which correspond to those arching efficacies, were greater than 0.5.

• Journal of the korean academy of Pediatric Dentistry
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• v.35 no.2
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• pp.297-304
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• 2008

The purpose of this study was to evaluate a 3-Dimensional laser scanner for the space analysis after loss of a primary first molar. Six children with premature loss of a primary first molar were examined using study models taken before and after the extraction. The results were as follows: 1. There was no change in primary molar space after the extraction of a maxillary primary first molar However, 2 out of 3 children experienced primary molar space loss in extraction side of a mandibular primary first molar. 2. Arch width and arch perimeter showed no difference between initial and final model. 3. All primary canines did not show any changes in inclination. Maxillary primary second molars had similar changes in both extraction and control side. However, 2 out of 3 mandibular primary second molars in extraction side showed more lingual tipping compared to control side. Mandibular permanent first molars tipped more lingually in extraction side. 4. In angulation, primary canines showed nothing of significance. Mandibular primary second molars tipped more mesially in extraction side than in control side. Maxillary permanent first molars have increased distal angulation after extraction of primary first molars in both side.

• The Journal of Korean Academy of Prosthodontics
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• v.57 no.3
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• pp.304-311
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• 2019

After the teeth were extracted, maxillary and mandibular alveolar ridges show the opposite resorption pattern and as a result, the mandibular arch is enlarged than maxillary arch relatively. In this situation, we should evaluate both alveolar ridge relationship and arrange the artificial teeth properly for stability of removable prosthesis. This case is a 77 years old male patient who wishes to make removable prosthesis and has atrophic alveolar ridge. By use of model scanner and CAD software, the angle between interalveolar crest line and occlusal plane was easily measured. Depending on the measurement, the artificial teeth are arranged in unilateral cross bite and after completion, patient was satisfied with the denture which showed proper stability, retention, support.

• The korean journal of orthodontics
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• v.17 no.2
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• pp.185-200
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• 1987

This paper was undertaken to observe the displacement of craniofacial complex with cervical headgear and to compare narrowing or widening effect of palate by use of contraction or expansion face-bow, respectively. The 3-dimensional finite element method(FEM) was used for a mathematical model composed of 597 nodes and 790 elements and an electrical resistance strain gauge investigation was performed to validate the finite element model. The outer bow of cervical headgear was adjusted to be placed below the occlusal plane by $25^{\circ}$ and met the midsagittal plane by $40^{\circ}$, and was loaded 1kg on each right and left hook toward posterior direction. The results were as follows 1. Generally, the maxillary teeth and facial bone were displaced in posterior, medial and downward direction. 2. It was the maxillary 2nd bicuspid that moved bodily. 3. The craniofacial complex rotated in a clockwise direction around the rotating axis which lay from the most posterior and lowest point connecting nasal crest of maxillary bone and vomer, progressively toward a more posterior, lateral and upward direction, anterior and upper area of pterygomaxillary fissure, base of medial pterygoid plate and laterally to the contact area of zygomatic arch with squamous part of temporal bone. 4. No contraction effect was observed by contraction face-bow when compared to the standard face-bow. 5. In case of expansion face-bow, the areas of maxillary 2nd bicuspid, molars and palate were expanded remarkably.