• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.40 no.6
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• pp.272-277
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• 2014

Objectives: Non-vascularized iliac crest bone graft (NVIBG) is a known treatment option in mandibular reconstruction following jaw resection, but no documented review of patients treated with NVIBG exists for northern Nigeria. The experience and technique from a Nigerian tertiary hospital may serve as baseline data for comparison and improvement of practice for other institutions. Materials and Methods: A retrospective review of medical records and patient case files from January 2012 to December 2013 was undertaken. All case files and other medical records of patients who had reconstruction with NVIBG for benign or malignant lesions with immediate or delayed reconstruction were selected for review. Results: Twenty patients had mandibular reconstruction with NVIBG during the study period. Two patients were excluded because of incomplete medical records. Eighteen patients' (male=14, female=4) records were reviewed. Their ages ranged from 13 to 62 years (mean $26.0{\pm}10.6years$). Indications for NVIBG included jaw tumors (n=16; 88.3%), jaw cyst (n=1; 5.6%) and gunshot injury (n=1; 5.6%). Jaw tumors seen were ameloblastoma (n=15; 83.3%) and osteosarcoma (n=1; 5.6%). Treatments done were mandibular resection with condylar resection (n=7; 38.9%), mandibular segmental resection (n=10; 55.6%) and subtotal mandibulectomy (n=1; 5.6%). Patients' postoperative reviews and radiographs revealed good facial profile and continued bone stability up to 1 year following NVIBG. Conclusion: NVIBGs provide an acceptable alternative to vascularized bone grafts, genetically engineered bone, and distraction osteogenesis for mandibular reconstruction in resource-limited centers.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.6 s.360
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• pp.31-39
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• 2007

In this paper, a system for real-time or periodic measurement and analysis of RF parameters such as forward transmit power and pilot power in CDMA base station systems is proposed. Such RF characteristic parameter measurement can be prevented from system fault and used to achieve optimal service quality and maximum investment return through cell coverage expansion, subscriber capacity increase and so on. For forward power measurement, the local oscillator frequency for the detector is varied so that the transmit power for all channels can be measured. The channel power measurement can be used to analyze the variation in transmit power for changes in voice traffic. By comparing to forward $E_c/I_o$, the pilot channel power can be deducted, which can be used to determine uy degradation in transmit section modules such as the high dover amplifier. Since an accurate analysis of carefully measured data using the CDMA level detector must be made, the system is designed so that measurement errors due to changes in crest factor with modulation method can be overcome.

• The Journal of Korean Academy of Prosthodontics
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• v.37 no.2
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• pp.185-199
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• 1999

This study was peformed to investigate the distribution and magnitude of stress at supporting tissue of abutment teeth and residual ridge tissue with remaining unilateral posterior teeth. Four types of removable partial dentures that included clasp retained removable partial denture, attachment retained removable partial denture, telescopic removable partial denture, and swing-lock partial denture were designed, and strain gauge was used for stress analysis. Each prosthesis was subjected to simulated vertical and oblique load. The following conclusions were drawn from this study. 1. The clasp retained removable partial denture generally distributed simulated vertical force more evenly to the supporting structure. 2. The stress at buccal side of 1st premolar was the lowest in swing-lock partial denture and that was highest in attchment retained removable partial denture. The stress at lingual side of 1st premolar was the lowest in telescopic partial denture. 3. In clasp retained removable partial denture, stress was lower at load site and ridge crest at mid-line, but it was higher at 1st premolar area on vertical load. 4. In attachment removable partial denture, stresses at buccal side of 1st premolar. lingual side of 1st premolar on vertical load, and ridge crest at midline on oblique load were higher. 5. In telescopic removable partial denture, stress at lingual side of 1st premolar was the least in all removable partial dentures, but the stress at load site was higher. 6. In swing-lock removable partial denture, stress at buccal side of 1st premolar was the lowest, and stresses at load site and distal end of residual ridge crest were higher.

• Journal of Periodontal and Implant Science
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• v.50 no.1
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• pp.28-37
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• 2020

Purpose: The aim of our study was to determine the prevalence and degree of lingual concavities in the first molar region of the mandible to reduce the risk of perforating the lingual cortical bone during dental implant insertion. Methods: A total of 163 suitable cross-sectional cone-beam computed tomography images of edentulous mandibular first molar regions were evaluated. The mandibular morphology was classified as a U-configuration (undercut), a P-configuration (parallel), or a C-configuration (convex), depending on the shape of the alveolar ridge. The characteristics of lingual concavities, including their depth, angle, vertical location, and additional parameters, were measured. Results: Lingual undercuts had a prevalence of 32.5% in the first molar region. The mean concavity angle was 63.34°±8.26°, and the mean linear concavity depth (LCD) was 3.03±0.99 mm. The mean vertical distances of point P from the alveolar crest (Vc) and from the inferior mandibular border were 9.39±3.39 and 16.25±2.44, respectively. Men displayed a larger vertical height from the alveolar crest to 2 mm coronal to the inferior alveolar nerve (Vcb) and a wider LCD than women (P<0.05). Negative correlations were found between age and buccolingual width at 2 mm apical to the alveolar crest, between age and Vcb, between age and Vc, and between age and LCD (P<0.05). Conclusions: The prevalence of lingual concavities was 32.5% in this study. Age and gender had statistically significant effects on the lingual morphology. The risk of lingual perforation was higher in young men than in the other groups analyzed.

• Imaging Science in Dentistry
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• v.51 no.2
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• pp.155-165
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• 2021

Purpose: This study aimed to evaluate changes of the alveolar bone and interdental bone septum of the mandibular incisors through cone-beam computed tomography (CBCT) after orthodontic treatment of mandibular dental crowding without dental extraction. Materials and Methods: The sample consisted of 64 CBCT images(32 pre-treatment and 32 post-treatment) from 32 adult patients with class I malocclusion and an average age of 23.0±3.9 years. The width and height of the alveolar bone and interdental septum, the distance between the cementoenamel junction (CEJ) and the facial and lingual bone crests, and the inclination of the mandibular incisors were measured. Results: The distance between the CEJ and the marginal bone crest on the facial side increased significantly (P<0.05). An increased distance between the CEJ and the bone crest on the facial and lingual sides showed a correlation with the irregularity index (P<0.05); however, no significant association was observed with increasing mandibular incisor inclination (P>0.05). The change in the distance between the CEJ and the marginal bone crest on the facial side was correlated significantly with bone septum height(P<0.05). Conclusion: Bone dehiscence developed during the treatment of crowding without extraction only on the incisors' facial side. Increasing proclination of the mandibular incisor was not correlated with bone dehiscence. The degree of dental crowding assessed through the irregularity index was associated with the risk of developing bone dehiscence. The interdental septum reflected facial marginal bone loss in the mandibular incisors.

• Ocean Systems Engineering
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• v.11 no.1
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• pp.83-97
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• 2021

The submerged U-shape breakwater interaction with the solitary wave is simulated by the Boussinesq equations using the finite-difference scheme. The wave reflection, transmission, and dissipation (RTD) coefficients are used to investigate the U-shape breakwater's performance for different crest width, Lc1, and indent breakwater height, du. The results show that the submerged breakwater performance for a set of U-shape breakwater with the same cross-section area is related to the length of submerged breakwater crest, Lc1, and the distance between the crests, Lc2 (or the height of du). The breakwater has the maximum performance when the crest length is larger, and at the same time, the distance between them increases. Changing the Lc1 and du of the U-shape breakwaters result in a significant change in the RTD coefficients. Comparison of the U-shape breakwater, having the best performance, with the averaged RTD values shows that the transmission coefficients, Kt, has a better performance of up to 4% in comparison to other breakwaters. Also, the reflection coefficients KR and the diffusion coefficients, Kd shows a better performance of about 30% and 55% on average, respectively. However, the model governing equations are non-dissipative. The non-energy conserving of the transmission and reflection coefficients due to wave and breakwater interaction results in dissipation type contribution. The U-shape breakwater with the best performance is compared with the rectangular breakwater with the same cross-section area to investigate the economic advantages of the U-shape breakwater. The transmission coefficients, Kt, of the U-shape breakwater shows a better performance of 5% higher than the rectangular one. The reflection coefficient, KR, is 60% lower for U-shape in comparison to rectangular one; however, the diffusion coefficients, Kd, of U-shape breakwater is 35% higher than the rectangular breakwater. Therefore, we could say that the U-shape breakwater has a better performance than the rectangular one.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.48 no.2
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• pp.85-93
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• 2022

Objectives: The aim of this study was to compare morbidities and duration of surgery, as well as bone formation in alveolar defects reconstructed with symphysis bone combined with allograft and iliac crest bone graft in patients with cleft palate. Patients and Methods: This randomized clinical trial was performed with 22 patients with unilateral alveolar cleft with a follow-up period of 12 months. In 12 patients, alveolar defects were reconstructed with chin bone graft plus allograft (Group A), while for the other 10 patients, iliac bone crest was used as donor site (Group B). Duration of surgery as well as occurrence of morbidities and complications were recorded. In addition, cone-beam computed tomographic (CBCT) scans were performed before surgery and 12 months after surgical procedures in order to compare bone formation between the two groups. Results: Postoperative CBCT demonstrated a mean bone fill percentage of 76.9% of the alveolar defect in Group A, compared with 77.0% in Group B. Paresthesia in the lower lip or chin did not occur in any patients of Group A. The mean duration of the surgical process was significantly shorter for Group A (40 minutes vs 76 minutes, P<0.001). In addition, patients in Group A regained normal gait faster than patients in Group B (1 day vs 9.5 days). Conclusion: Mandibular symphysis bone graft in combination with allograft results in favorable outcomes in patients with unilateral alveolar clefts.

• Journal of Ocean Engineering and Technology
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• v.36 no.5
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• pp.326-339
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• 2022

Recently, not only Korea but also the world has been suffering from problems related to coastal erosion. The hard defense method has been primarily used as a countermeasure against erosion. However, this method is expensive and has environmental implications. Hence, interest in other alternative methods, such as the eco-friendly vegetation method, is increasing. In this study, we aim to analyze the hydraulic characteristic of submerged rigid vegetation according to the cross-sectional change through a hydraulic experiment and numerical simulation. From the hydraulic experiment, the reflection coefficient, transmission coefficient, and energy dissipation coefficient were analyzed according to the density, width, and multi-row arrangement of the vegetation zone. From numerical simulations, the flow field, vorticity distribution, turbulence distribution, and wave distribution around the vegetation zone were analyzed according to the crest depth, width, density, and multi-row arrangement distance of the vegetation zone. The hydraulic experiment results suggest that the transmission coefficient decreased as the density and width of the vegetation zone increased, and the multi-row arrangement condition did not affect the hydraulic characteristics significantly. Moreover, the numerical simulations showed that as the crest depth decreased, the width and density of vegetation increased along with vorticity and turbulence intensity, resulting in increased wave height attenuation performance. Additionally, there was no significant difference in vorticity, turbulence intensity, and wave height attenuation performance based on the multi-row arrangement distance. Overall, in the case of submerged rigid vegetation, the wave energy attenuation performance increased as the density and width of the vegetation zone increased and crest depth decreased. However, the multi-row arrangement condition did not affect the wave energy attenuation performance significantly.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.35 no.5
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• pp.102-108
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• 2023

In this study, hydraulic model tests were performed to investigate the stability of armor units at harbor side slope for rubble mound structures. The armor units on the rear slope were rocks. The Korean design standard for harbor and fishery port suggested the design figures that showed the ratio of the armor weight for each location of rubble mound structures and it could be known that the same weight ratio was needed to the sea side and rear side slope of rubble mound structures. The crest elements were commonly applied to the design process of rubble mound structures in Korea and the investigation of the effects of super structures would be needed. The damage rate (S =2) was applied and the stable wave height was measured for each test condition. The results were suggested as the armor weight ratio of the rear side slope(armor rock) to the sea side slope (tetrapod) in relation to the relative crest height.

• International Journal of Stem Cells
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• v.16 no.2
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• pp.135-144
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• 2023

Background and Objectives: Melanocyte (MC), derived from neural crest stem cell (NCSC), are involved in the production of melanin. The mechanism by which NCSC differentiates to MC remains unclear. N6-methyladenosine (m6A) modification was applied to discuss the potential mechanism. Methods and Results: NCSCs were isolated from hair follicles of rats, and were obtained for differentiation. Cell viability, tyrosinase secretion and activity, and transcription factors were combined to evaluated the MC differentiation. RT-qPCR was applied to determine mRNA levels, and western blot were used for protein expression detection. Total m6A level was measured using methylated RNA immunoprecipitation (MeRIP) assay, and RNA immunoprecipitation was used to access the protein binding relationship. In current work, NCSCs were successfully differentiated into MCs. Fat mass and obesity associated gene (FTO) was aberrant downregulated in MCs, and elevated FTO suppressed the differentiation progress of NCSCs into MCs. Furthermore, microphthalmia-associated transcription factor (Mitf), a key gene involved in MC synthesis, was enriched by FTO in a m6A modification manner and degraded by FTO. Meanwhile, the suppression functions of FTO in the differentiation of NCSCs into MCs were reversed by elevated Mitf. Conclusions: In short, FTO suppressed the differentiating ability of hair follicle-derived NCSCs into MCs by m6A modifying Mitf.