• Journal of Power Electronics
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• v.15 no.2
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• pp.555-566
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• 2015

A TRIAC dimming LED driver that can control the brightness of LED arrays for a wide range of source voltage variations is proposed in this paper. Unlike conventional PWM LED drivers, the proposed LED driver adopts a TRIAC switch, which inherently guarantees zero current switching and has been proven to be quite reliable over its long lifetime. Unlike previous TRIAC type LED drivers, the proposed LED driver is composed of an LC input filter and a variable switched capacitance, which is modulated by the TRIAC turn-on timing. Thus, the LED power regulation and dimming control, which are done by a volume resistor in the same way as the conventional TRIAC dimmers, can be simultaneously performed by the TRIAC control circuit. Because the proposed LED driver has high efficiency and a long lifetime with a high power factor (PF) and low total harmonic distortion (THD) characteristics, it is quite adequate for industrial lighting applications such as streets, factories, parking garages, and emergency stairs. A simple step-down capacitive power supply circuit composed of passive components only is also proposed, which is quite useful for providing DC power from an AC source without a bulky and heavy transformer. A prototype 60 W LED driver was implemented by the proposed design procedure and verified by simulation and experimental results, where the efficiency, PF, and THD are 92%, 0.94, and 6.3%, respectively. The LED power variation is well mitigated to below ${\pm}2%$ for 190 V < $V_s$ < 250 V by using the proposed simple control circuit.

• Korean Journal of Head & Neck Oncology
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• v.19 no.1
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• pp.52-57
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• 2003

Background and Objectives: Fine needle aspiration (FNA) cytology is a simple, safe and relatively accurate procedure of diagnosing thyroid nodules. Although the frozen section biopsy is well known as more reliable method than FNA and has high specificity, whether it is necessary it leaves room for adverse criticism. Authors have compared preoperative FNA cytology and frozen section biopsy with permanent histologic findings and evaluated the significance of FNA cytology and frozen section biopsy. Materials and Methods: The medical records of 110 patiens who underwent FNA cytology and frozen section during thyroidectomy from September. 1997 to December. 2001 at the Department of Otolaryngology, School of Medicine, Keimyung University were analyzed retrospectively. Results: Sensitivity, specificity, accuracy of FNA was 75%, 91.4%, and 85.5% respcetively. Sensitivity, specificity and accuracy rate of frozen section biopsy were 92.5%, 100% and 97.3% respectively. Conclusion: FNA is simple, with rare complication and its diagnostic accuracy is comparatively so high that it is being used as primary test to diagnosis thyroid nodules. But frozen section is more accurate and may be helpful to suspicious FNA findings or if it beyond capacity of FNA. Therefore despite of the fact that the intra-operative frozen is more expensive and time consuming, it is very helpful to the treatment of thyroid nodules by using jointly with FNA.

• Journal of the Korean Geotechnical Society
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• v.36 no.6
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• pp.35-46
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• 2020

The input parameters for numerical simulation of the liquefaction phenomenon need to be properly evaluated from laboratory and field tests, which are difficult to be performed in practical situations. In this study, the numerical simulation of the cyclic direct simple shear test was performed to analyze the applicability of Finn and PM4Sand models among the constitutive models for liquefaction simulation. The analysis results showed that the Finn model properly predicted the time when the excess pore water pressure reached the maximum, but failed to simulate the pore pressure response and the stress-strain behavior of post-liquefaction. On the other hand, the PM4Sand model properly simulated those behaviors of the post liquefaction. Finally, the evaluation procedure and the equations of the input parameters in the PM4Sand model were developed to mach the liquefaction cyclic resistance ratio corresponding to design conditions.

• Journal of the Korea Society of Computer and Information
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• v.26 no.12
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• pp.309-321
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• 2021

In this study, we proposed a hierarchy process analysis model for Kiosk known as technology-based self-service, In addition, we deduced the selection factors based on the literature review and calculated the weight of the factors. To estimate the priorities of selection factors, we used the data collected from consumers who have used Kiosks at cafe or fast food restaurant. The results of the study showed that the convenience among the factors in the first stage, consisted of safety, design, convenience, informativity, and responsiveness, revealed the most important factor in both cafe and fast food restaurant. Synthetic calculation of the first stage factors and the second stage factors showed that simple procedure was the most important factor. The results of comparing the priorities between cafe and fast food restaurant showed that consumers assessed their priorities differently in simple procedures, nutritional information, and fast menu provision.

• Journal of the Korea Convergence Society
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• v.12 no.5
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• pp.9-16
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• 2021

Due to the prolonged infectious disease of COVID-19 worldwide, there are various security threats due to network attacks on Internet of Things devices that are vulnerable to telecommuting. Initially, users of Internet of Things devices were exploited for vulnerabilities in Remote Desktop Protocol, spear phishing and APT attacks. Since then, the technology of network attacks has gradually evolved, exploiting the simple service discovery protocol of Internet of Things devices, and DRDoS attacks have continued to increase. Existing SSDPs are accessible to unauthorized devices on the network, resulting in problems with information disclosure and amplification attacks on SSDP servers. To compensate for the problem with the authentication procedure of existing SSDPs, we propose a hash-based SSDP that encrypts server-specific information with hash and adds authentication fields to both Notify and M-Search message packets to determine whether an authorized IoT device is present.

• Tunnel and Underground Space
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• v.32 no.6
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• pp.598-610
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• 2022

Avoiding a fault zone would be a best practice for safety in underground construction, which is only sometimes possible because of many restrictions and other field conditions. For instance, there is an ongoing conception of Korea-Japan subsea tunnels that inevitably cross a massive fault system in the Korea Strait. Therefore it was deemed necessary to find an efficient way of predicting the likely behaviour of underground structures under fault slip. This paper presents the findings from simple numerical analysis for investigating the stress induced at a normal fault with a dip of 45 degrees. We used a boundary element software that assumed constant displacement discontinuity, which allowed the displacement to be estimated separately at both the fault's hangingwall and footwall sides. The results suggested that a principal stress rotation of 45 degrees occurred at the edges of the fault during the slip, which was in agreement with the phenomenon for fault plane suggested in the body of literature. A simple numerical procedure presented in this paper could be adopted to investigate other fault-related issues associated with underground structure construction.

• Steel and Composite Structures
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• v.41 no.5
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• pp.697-711
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• 2021

In this work, a simple quasi 3-D parabolic shear deformation theory is developed to examine the bending response of antisymmetric cross-ply laminated composite plates under different types of mechanical loading. The main feature of this theory is that, in addition to including the transverse shear deformation and thickness stretching effects, it has only five-unknown variables in the displacement field modeling like Mindlin's theory (FSDT), yet satisfies the zero shear stress conditions on the top and bottom surfaces of the plate without requiring a shear correction factor. The static version of principle of virtual work was employed to derive the governing equations, while the bending problem for simply supported antisymmetric cross-ply laminated plates was solved by a Navier-type closed-form solution procedure. The adequacy of the proposed model is handled by considering the impact of side-to-thickness ratio on bending response of plate through several illustrative examples. Comparison of the obtained numerical results with the other shear deformation theories leads to the conclusion that the present model is more accurate and efficient in predicting the displacements and stresses of laminated composite plates.

• Archives of Plastic Surgery
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• v.50 no.3
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• pp.254-263
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• 2023

Background The three-dimensional (3D) evaluation of skeletal stability after orthognathic surgery is a time-consuming and complex procedure. The complexity increases further when evaluating the surgery-first orthognathic approach (SFOA). Herein, we propose and validate a simple time-saving method of 3D analysis using a single software, demonstrating high accuracy and repeatability. Methods This retrospective cohort study included 12 patients with skeletal class 3 malocclusion who underwent bimaxillary surgery without any presurgical orthodontics. Computed tomography (CT)/cone-beam CT images of each patient were obtained at three different time points (preoperation [T0], immediately postoperation [T1], and 1 year after surgery [T2]) and reconstructed into 3D images. After automatic surface-based alignment of the three models based on the anterior cranial base, five easily located anatomical landmarks were defined to each model. A set of angular and linear measurements were automatically calculated and used to define the amount of movement (T1-T0) and the amount of relapse (T2-T1). To evaluate the reproducibility, two independent observers processed all the cases, One of them repeated the steps after 2 weeks to assess intraobserver variability. Intraclass correlation coefficients (ICCs) were calculated at a 95% confidence interval. Time required for evaluating each case was recorded. Results Both the intra- and interobserver variability showed high ICC values (more than 0.95) with low measurement variations (mean linear variations: 0.18 mm; mean angular variations: 0.25 degree). Time needed for the evaluation process ranged from 3 to 5 minutes. Conclusion This approach is time-saving, semiautomatic, and easy to learn and can be used to effectively evaluate stability after SFOA.

• Korean Journal of Culture and Social Issue
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• v.17 no.3
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• pp.287-304
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• 2011

The Purpose of this study is to understand phases and paradigms related to voluntary services offered by undergraduates and the processes in which voluntary services are implemented. For this, interviews for 23(men: 10, women: 13) undergraduates were conducted from Aug., 2008 to Apr., 2009 were conducted and the data collected from those interviews were analyzed on the basis of the Grounded Theory. Main analysis procedure is known as codings(open coding, axial coding, selective coding). This analyses produced 119 concepts, 41 subcategories, and 16 categories in open coding. Then, axial coding was conducted to organize the basic framework of generic relationships among psychological motivation, social context, personal perception, practical action, psychological response, and psychological consequence. Core essence is "Volunteer types are categorized simple practice type, self-serving type, and community type." Finally, undergraduate volunteers were explained in 3 types(simple practice, self-serving, and community) on the basis of paradigms. These results were discussed in terms of further research and limitation.

• Clinical and Experimental Pediatrics
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• v.52 no.8
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• pp.910-916
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• 2009

Purpose : The arterial switch operation (ASO) has become the preferred procedure for the surgical management of transposition of the great arteries (TGA). We conducted a retrospective evaluation of our experience in 30 patients seen from January 2003 to July 2008, in order to determine outcomes and related risk factors after the arterial switch operation. Methods : Patients charts, surgical reports, and echocardiograms were retrospectively reviewed. And they were analyzed in 2 different groups: complex (n=16) versus simple TGAs (n=14). Complex TGAs are TGAs with VSD or the Taussig-Bing anomaly with or without aortic arch anomalies. Simple TGAs are defined as TGAs with intact ventricular septum having no such anomalies. Median follow-up time was 44 months (3-63 months). Results : Hospital mortality was 0%. However, follow-up echocardiographies revealed potential complications, including stenosis of the branch pulmonary arteries, neo-aortic and/or neo-pulmonary valvar regurgitation, and right or left ventricular outflow tract obstructions. Great arterial relationship (side-by-side), association of aortic arch anomalies, and the existence of the Taussig- Bing anomaly were assessed as significant risk factors of neo-aortic and/or neo-pulmonary valvar regurgitation in this series. On the other hand, right or left ventricular outflow tract obstructions were more frequently found in patients demonstrating VSD, side-by-side positioned great arteries, or associated coronary anomalies. Conclusion : The ASO is the procedure of choice in the treatment of TGA. However, special attention and follow-ups are needed to detect residual problems like the stenosis of the branch pulmonary arteries, neo-aortic and/or neo-pulmonary valvar regurgitation, as well as ventricular outflow tract obstructions.