• 반도체디스플레이기술학회지
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• 제12권4호
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• pp.21-25
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• 2013

This paper is for enhancing the breakdown voltage of MHEMTs with an InP-etchstop layer. The fully removed recess structure in the drain side of MHEMT shows that the breakdown voltage enhances from 2 V to 4 V in the previous work. This is because the surface effect at the drain side decreases the channel current and the impact ionization in the channel at high drain voltage. In order to increase the breakdown voltage at the same asymmetric gate-recess structure, the InGaAs channel structure is replaced with the InGaAs/InP composite channel in the simulation. The simulation results with InGaAs/InP channel show that the breakdown voltage increases to 6V in the MHEMT as the current decreases. In this paper, the simulation results for the InGaAs/InP channel are shown and analyzed for the InGaAs/InP composite channel in the MHEMT.

• 대한치과교정학회지
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• 제54권2호
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• pp.108-116
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• 2024

Objective: A three-dimensional-printed individual titanium plate was applied for maxillary protraction to eliminate side effects and obtain the maximum skeletal effect. This study aimed to explore the stress distribution characteristics of sutures during maxillary protraction using individual titanium plates in various directions and locations. Methods: A protraction force of 500 g per side was applied at forward and downward angles between 0° and 60° with respect to the Frankfort horizontal plane, after which the titanium plate was moved 2 and 4 mm upward and downward, respectively. Changes in sutures with multiple protraction directions and various miniplate heights were quantified to analyze their impact on the maxillofacial bone. Results: Protraction angle of 0-30° with respect to the Frankfort horizontal plane exhibited a tendency for counterclockwise rotation in the maxilla. At a 40° protraction angle, translational motion was observed in the maxilla, whereas protraction angles of 50-60° tended to induce clockwise rotation in the maxilla. Enhanced protraction efficiency at the lower edge of the pyriform aperture was associated with increased height of individual titanium plates. Conclusions: Various protraction directions are suitable for patients with different types of vertical bone surfaces. Furthermore, when the titanium plate was positioned lower, the protraction force exhibited an increase.

• Steel and Composite Structures
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• 제17권6호
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• pp.891-906
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• 2014

This study aims to present a three dimensional finite element model to investigate the wave propagation in a concrete filled steel tubular column (CFSC) due to transient impact load. Both the concrete and steel are regarded as linear elastic material. The impact load is simulated by a semi sinusoidal impulse. Besides the CFSC models, a concrete column (CC) model is established for comparing under the same loading condition. The propagation characteristics of the transient waves in CFSC are analyzed in detail. The results show that at the intial stage of the wave propagation, the velocity waves in CFSC are almost the same as those in CC before they arrive at the steel tube. When the waves reach the column side, the velocity responses of CFSC are different from those of CC and the difference is more and more obvious as the waves travel down along the column shaft. The travel distance of the wave front in CFSC is farther than that in CC at the same time. For different wave speeds in steel and concrete material, the wave front in CFSC presents an arch shape, the apex of which locates at the center of the column. Differently, the wave front in CC presents a plane surface. Three dimensional effects on top of CFSC are obvious, therefore, the peak value and arrival time of incident wave crests have great difference at different locations in the radial direction. High-frequency waves on the waveforms are observed. The time difference between incident and reflected wave peaks decreases significantly with r/R when r/R < 0.6, however, it almost keeps constant when $r/R{\geq}0.6$. The time duration between incident and reflected waves calculated by 3D FEM is approximately equal to that calculated by 1D wave theory when r/R is about 2/3.

• The Journal of Asian Finance, Economics and Business
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• 제9권2호
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• pp.283-294
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• 2022

This holistic research focused on the interactive relationship of different factors with a unique relationship with the dependent variable. The first research objective of the study was to identify the most significant factor that has an impact on Job performance while being mediated. The second objective was to see the moderating effect of gender on the relationship between transformation leadership and innovation on job performance. This research followed a purely quantitative research paradigm with a structured questionnaire to quantify the information collected from 96 respondents for the empirical analysis. For testing the research hypotheses, IBM SPSS version 24 and SmartPLS version 3.2.8 softwares were used to run the structural equation modeling to establish the causal relationship between the study variables. Most of the variables were found with a significant impact on job performance. Further, the hypotheses H³, H⁶, and H¹⁰ were rejected as these contributed insignificant towards the research model. This research was limited to specific educational institutions and businesses, and the timeframe was restrictive. The findings of this research can benefit policymakers and the operational side of various industries. Future research may consider the difference in gender in predicting employee engagement through leadership and innovation.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 춘계학술대회 논문집
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• pp.491-497
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• 2005

Brake system is indispensible functional part to the transportation machines such as railroad cars, and all of industrial machines. It is mechanical element to stop the movement or slow the speed, transforming kinetic energy of motion object into thermal energy through solid friction. According that recently the railroad cars have become high-speed, the technique in braking domain to secure the overall braking effort is making rapid progress. In particular, material development and manufacturing process are so important to secure friction performance, which is the core in braking performance of mechanical brake units. Wear of brake disk could mainly result in the diminishment of its life span due to thermal cracking, so the endurance against high temperature is required. On the other hand, in this case, the problem is that the side wear of pad, relative material is slightly increased because of enlargement of plastic deformation. It is necessary, therefore, to develop a disk material that will be used in the Tilting System mechanical brake units. The purpose of this paper is to make a study prior to developing brake disk of Tilting Train travelling at 200km/h and to propose the component of brake disk. Accordingly, I will conduct sufficient researches on technical documents of brake disk, that are basic documentations, analyze an impact on components, and further, considering braking degree of train, study for the basic proposal on brake disk's component of the train travelling at 200km/h, which has relatively minor influence of heat stress and maintains the friction. In this respect, I would like to investigate friction characteristics between disk and relative friction material via Test on some possible test segments, analyze and propose friction performance, temperature impact and so forth coming from the contact with pad, relative material to demonstrate the friction characteristics.

• Journal of Power Electronics
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• 제16권6호
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• pp.2243-2257
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• 2016

This paper presents a two stage three-phase proton exchange membrane fuel cell (PEMFC) generation system. When the system is connected to a three-phase load, it is very sensitive to the characteristics and type of the load. Especially unbalanced three-phase loads, which result in a pulsating power that is twice the output frequency at the inverter output, and cause the dc-link to generate low frequency ripples. This penetrates to the fuel cell side through the front-end dc-dc converter, which makes the fuel cell work in an unsafe condition and degrades its lifespan. In this paper, the generation and propagation mechanism of low frequency ripple is analyzed and its impact on fuel cells is presented based on the PEMFC output characteristics model. Then a novel method to evaluate low frequency current ripple control capability is investigated. Moreover, a control scheme with bandpass filter inserted into the current feed-forward path, and ripple duty ratio compensation based on current mode control with notch filter is also proposed to achieve low frequency ripple suppression and dynamic characteristics improvement during load transients. Finally, different control methods are verified and compared by simulation and experimental results.

• 해양환경안전학회지
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• 제20권2호
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• pp.157-164
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• 2014

본 연구에서는 2010년부터 2013년까지 4년간 연안개발사업에 따른 일반해역이용협의서 133건을 분석하여 사업유형별 해양환경영향평가 개선방안을 제시하였다. 침식방지사업은 정확한 침식원인 분석이 선행되어야 하고 주변 해안의 상태와 구조물 설치 시 추가적인 문제점 발생 가능성에 대해 정확히 예측해야 하며, 사업시행 후 사후모니터링을 통한 침식방지 효과를 입증하는 체계적인 시스템이 마련되어야 한다. 호안 및 해안도로 건설사업의 경우, 무분별한 해안도로의 건설은 지양하고 구조물 안정성을 충분히 검토하여야 하며 반사파 증가에 따른 해안침식의 문제점을 함께 검토해야 한다. 그리고 침수방지 사업은 평가항목에 파랑을 선정할 필요가 있고 이상 파랑의 영향을 함께 고려해야 한다. 친수공간 조성사업은 종합적이고 체계적인 공간계획이 수립되어야 하고, 자연환경을 최대한 보전하고 자연과 융화될 수 있는 개발이 될 수 있도록 검토를 강화해야 할 것이다. 아울러 연안개발사업과 관련하여 많은 문제점이 내재되어있어 법 제도적 측면에서의 지원과 함께 추후 해역별, 사업별 특성이 다양하게 반영된 추가적인 연구가 필요할 것으로 판단된다.

• Journal of Power Electronics
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• 제15권3호
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• pp.621-633
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• 2015

This paper proposes the analysis and design of a DC-side symmetrical zero-current-switching (ZCS) Class-D current-source driven resonant rectifier to improve the low power-factor and high line current harmonic distortion of lighting applications. An analysis of the junction capacitance effect of Class-D ZCS rectifier diodes, which has a significant impact on line current harmonic distortion, is discussed in this paper. The design procedure is based on the principle of the symmetrical Class-D ZCS rectifier, which ensures more accurate results and provides a more systematic and feasible analysis methodology. Improvement in the power quality is achieved by using the output characteristics of the DC-side Class-D ZCS rectifier, which is inserted between the front-end bridge-rectifier and the bulk-filter capacitor. By using this symmetrical topology, the conduction angle of the bridge-rectifier diode current is increased and the low line harmonic distortion and power-factor near unity were naturally achieved. The peak and ripple values of the line current are also reduced, which allows for a reduced filter-inductor volume of the electromagnetic interference (EMI) filter. In addition, low-cost standard-recovery diodes can be employed as a bridge-rectifier. The validity of the theoretical analysis is confirmed by simulation and experimental results.

• 한방재활의학과학회지
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• 제29권1호
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• pp.21-29
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• 2019

Objectives This study is designed to verify the effectiveness of electroacupuncture (EA) on both side acupuncture point GB12, GB20 for chronic tension type headache (CTTH). Methods Subjects aged 18-65 years who had suffered from CTTH for more than 3months were recruited from September 2016 to May 2017. Thirty subjects were voluntarily recruited and they were randomly divided into 2 groups; 15 to EA group, another 15 to sham-EA group. The treatment sessions were performed every 2-4 days for a total of three sessions over 1 week. The symptoms of headache were assessed before the treatment and after a week from the last treatment by visual analogue scale (VAS), headache frequency (HF), Korean Headache Impact Test-6 (KHIT-6). Demographic characteristics of all participants were compared between the groups upon using chi-square test. Wilcoxon signed rank test was used to evaluate the values between baseline and follow-up. Wilcoxon rank sum test was performed to evaluate the differences between groups. p-values less than 0.05 were considered as significant. Results Before and after the intervention, no difference in VAS and KHIT-6 was observed between groups. HF of EA group decreased significantly compared with that of sham-EA group. Within the EA group VAS, HF and KHIT-6 decreased significantly after the treatment. Meanwhile, only KHIT-6 decreased significantly after the treatment in sham-EA group. Conclusions This study suggests that EA on both side acupuncture point GB12 and GB20 is applicable to improve symptoms in patients with CTTH.

• 보존과학회지
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• 제38권4호
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• pp.277-288
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• 2022

'Eve 58-1', the subject of this study is a statue made of plaster and its structural stability was evaluated by utilizing the CAE program in order to prevent the risk of damage arising from impact and vibration that are generated during the packaging and transportation process given its material characteristics. CAE is an abbreviation for Computer Applied Engineering for realization by predicting changes at the time of application of virtual physical energy. It is applied by reflecting the physical property conditions and each boundary condition of plaster, and the digital images of the internal and external structure of the work were acquired through 3D scanning and CT analysis for interpretation by executing finite element modeling. When acceleration is applied to the work in the direction of its own weight, the left-right side and the front-rear side, it was possible to confirm a maximum displacement value of 15.24 mm in the head section of the front-rear side direction that has been tilted by approximately 27° from the Y-axis and the largest stress value of 12.46 MPa was at the left ankle section. The corresponding results confirmed that the left ankle section is the most vulnerable area and the section for which precautions need to be exercised and supplemented at the time of transporting the work by means of objective values.