• Carbon letters
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• 제15권3호
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• pp.198-202
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• 2014

Amorphous agglomerates of carbon nanospheres (CNS) with a diameter range of 10-50 nm were synthesized using the solution combustion method. High-resolution transmission electron microscopy (HRTEM) revealed a densely packed high surface area of $SP^2$-hybridized carbon; however, there were no crystalline structural components, as can be seen from the scanning electron microscopy, HRTEM, X-ray diffraction, Raman spectroscopy, and thermal gravimetric analyses. Electrochemical and thermo catalytic decomposition study results show that the material can be used as a potential electrode candidate for the fabrication of energy storage devices and also for the production of free hydrogen if such devices are used in a fluidized bed reactor loaded with the as-prepared CNS as the catalyst bed.

• 한국세라믹학회지
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• 제50권3호
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• pp.173-179
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• 2013

Wurtzite nanomaterials, such as ZnO, GaN, and InN, have become a subject of great scientific and technological interest as they simultaneously have piezoelectric and semiconductor properties. In particular, the piezoelectric potential (piezopotential) created by dynamic straining in the nanowires drives a transient flow of current in the external load, converting mechanical energy into electricity. Further, the piezopotential can be used to control the carrier generation, transport, separation, and/or recombination at the metal-semiconductor junction or p-n junction, which is called the piezophototronic effect. This paper reviews the recent advances on the piezophototronic effect to better use the piezophototronic effect to control the carrier generation, transport, separation and/or recombination for improving the performance of optoelectronic devices, such as photon detectors, solar cells and LEDs. This paper also discusses several research and design studies that have improved the output performance of optoelectronic devices.

• Journal of Electrical Engineering and Technology
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• 제10권3호
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• pp.1015-1024
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• 2015

This paper introduces a low cost, high efficiency, high performance three-phase unified power quality conditioner (UPQC) by using four-switch three-phase inverters (FSTPIs) and an extra capacitor in the shunt active power filter (APF) side of the UPQC. In the proposed UPQC, both shunt and series APFs are developed by using FSTPIs so that the number of switching devices is reduced from twelve to eight devices. In addition, by inserting an additional capacitor in series with the shunt APF, the DC-link voltage in the proposed UPQC can also be greatly reduced. As a result, the system cost and power loss of the proposed UPQC is significantly minimized thanks to the use of a smaller number of power switches with a lower rating voltage without degrading the compensation performance of the UPQC. Design of passive components for the proposed UPQC to achieve a good performance is presented in detail. In addition, comparisons on power loss, overall system efficiency, compensation performance between the proposed UPQC and the traditional one are also determined in this paper. Simulation and experimental studies are performed to verify the validity of the proposed topology.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.587-587
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• 2013

ZnS is well-known direct band gap II-VI semiconductor, and it attracts intense interest due to its excellent properties of luminescence which enable ZnS to have promising materials for optical, photonic and electronic devices. Especially, the emission wavelength of ZnS falls in the UV absorption band of most organic compoundsand biomolecules, thus it is envisaged that ZnS based devices may find applications in increasingly important fluorescence sensing. We have developed a facile and effective one-step process for the fabrication of single-crystalline and pure-wurtzite ZnS nanostructures possessing sharp band-edge emission at room-temperature having diverse length-to-width ratios. Each of nanostructures was composed of chemically pure, structurally uniform, single-crystalline, and defect-free ZnS. These features not only suppress trap or surface states emission centered at 420 nm, but also enhance UV band-edge emission centered at 327 nm, which give as-synthesized our ZnS nanostructures possible sharp UV emission at room temperature. The reaction medium consisting of mixed solvents such as hydrazine, ethylenediamine, and water as well as proper reaction time and temperature have played an important role in the crystallinity and optical properties of ZnS nanostructures. As-synthesized our ZnS nanostructures possessing sharp UV emission guarantee high potential for both fundamental research and technological applications.

• 한국재료학회지
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• 제15권9호
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• pp.613-619
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• 2005

The ever increasing popularity and acceptance in the market place of portable systems, such as cell phones, PDA, notebook PC, etc., are fueling effects in further miniaturizing and lowering power consumption in these systems. The dynamic power consumption due to the CPU activities and the static power consumption due to leakage currents are two major sources of power consumption. Smaller devices and a lower de voltage lead to reducing the power requirement, while better insulation and isolation of devices lead to reducing leakage currents. All these can be harnessed in the SOI (silicon-on-insulator) technology. In this study, the key aspects of the SOI technology, mainly device electrical properties and device processing steps, are briefly reviewed. The interesting materials issues, such as SOI structure formation and SOI wafer fabrication methods, are then surveyed. In particular, the recent technological innovations in two major SOI wafer fabrication methods, namely wafer bonding and SIMOX, are explored and compared in depth. The results of the study are nixed in that, although the quality of the SOI structures has shown great improvements, the processing steps are still found to be too complex. Between the two methods, no clear winner has yet emerged in terms of the product quality and cost considerations.

• 대한금속재료학회지
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• 제48권12호
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• pp.1064-1069
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• 2010

Thin films have been used in a large variety of technological applications such as solar cells, optical memories, photolithographic masks, protective coatings, and electronic contacts. If thin films experience frequent temperature changes, thermal stresses are generated due to the difference in the coefficient of thermal expansion between the film and substrate. Thermal stresses may lead to damage or deformation in thin film used in electronic devices and micro-machined structures. Thus, knowledge of the thermomechanical properties of thin films, such as the coefficient of thermal expansion, is an important issue in determining the stability and reliability of the thin film devices. In this study, thermal cycling of Cu and Ag thin films with various microstructures was employed to assess the coefficient of thermal expansion of the films. The result revealed that the coefficient of thermal expansion (CTE) of the Cu and Ag thin films increased with an increasing grain size. However, the effect of film thickness on the CTE did not show a remarkable difference.

• 센서학회지
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• 제27권6호
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• pp.414-420
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• 2018

To augment emotion and immersion in virtual reality (VR), technological research based on scent displays have increased in recent years. The results of extensive studies have enabled the development of methods to interface head mounted displays (HMDs) with scent devices, and the possibility of VR applications of this development was identified via several demonstrations in actual VR environments. Despite all these efforts, more practical methods and conditions for scent display in VR environments are yet to be developed. To efficiently interface VR and scent, this study proposes three ways to set the position for scent display and scent conditions. The first is scent display using local positioning in the VR engine, the second is scent display using the relative distance and orientation between user and object in VR environments, and the third is scent display using time setting. In this study, we developed scent devices using a piezo actuator to validate the proposed method and successfully conducted demonstrations and experiments.

• The Journal of Asian Finance, Economics and Business
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• 제8권8호
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• pp.637-645
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• 2021

Mobile devices have become attractive learning devices for education. The digitalization of the higher education system in Sri Lanka by 2020 is part of the government's effort to modernize and enhance the country's overall education system particularly in view of the COVID-19 pandemic. Theoretically, this study contributes to the M-Learning model in higher education institutions via the integration of literature on technology adoption (TAM and UTAUT) with the variables of Perceived Usefulness, Perceived Ease of Use, Attitude, Effort Expectancy, Social Influence, and Facilitating Condition. The attitude towards M-Learning amongst higher education students was gauged via an online questionnaire survey. The convenience sample comprised 344 students from the Advanced Technological Institutes (ATI) in Batticaloa District, Sri Lanka. Descriptive statistics, a measurement, and structural model, and hypotheses testing were used to analyze the derived data. The findings indicate that mobile learning is significantly affected by perceived ease of use, social influence, effort expectancy, and facilitating condition, but negatively affected by attitude and perceived usefulness. The exhaustive literature review revealed that there are very few M-Learning studies related to digital learning in the context of higher education in the Batticaloa district.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권10호
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• pp.2658-2681
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• 2023

In edge computing scenarios, IoT end devices play a crucial role in relaying and forwarding data to significantly improve IoT network performance. However, traditional routing mechanisms are not applicable to this scenario due to differences in network size and environment. Therefore, it becomes crucial to establish an effective and reliable data transmission path to ensure secure communication between devices. In this paper, we propose a trusted path selection strategy that comprehensively considers multiple attributes, such as link stability and edge cooperation, and selects a stable and secure data transmission path based on the link life cycle, energy level, trust level, and authentication status. In addition, we propose the Stability-based On-demand Multipath Distance Vector (STAOMDV) protocol based on the Ad hoc AOMDV protocol. The STAOMDV protocol implements the collection and updating of link stability attributes during the route discovery and maintenance process. By integrating the STAOMDV protocol with the proposed path selection strategy, a dependable and efficient routing mechanism is established for IoT networks in edge computing scenarios. Simulation results validate that the proposed STAOMDV model achieves a balance in network energy consumption and extends the overall network lifespan.

• 한국과학교육학회지
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• 제37권5호
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• pp.813-824
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• 2017

과학적 모형의 사회적 구성과 관련한 기존 연구에서는 학생들이 모형을 형성하는 과정에서 다양한 난점들이 나타났는데, 이 연구에서는 이를 보완할 수 있는 대체 방안으로서 스마트 기기를 도입하여 그 역할을 살펴보고자 하였다. 이를 위해 서울시 소재의 초등학교 5학년 2개 학급 60명을 대상으로 하여 스마트기기를 도입, 태양계 모형을 구성하는 수업 실시하여 그 역할을 살펴보았다. 연구 결과, 모형 형성 과정 전반에서 학생들은 스마트기기의 다양한 기능을 통해 모형 형성을 할 수 있었다. 특히 스마트기기는 학생들의 요구에 맞는 설명력이 높고 권위 있는 정보를 제공했으며, 상호작용이 가능한 3D이미지를 활용하여 학생들이 원하는 다양한 시각에서 행성을 관찰할 수 있는 기회를 제공했다. 또한 자신이 표현하고자 하는 바를 수월하게 표현하고 공유할 수 있는 방법을 제공하였으며, 스마트기기의 온라인 게시판 기능을 통해 다양한 교육 주체들이 모형 구성 과정에 참여하여 더 나은 모형을 형성할 수 있도록 도울 수 있다는 것을 알 수 있었다. 그러나 이러한 스마트기기의 역할이 제대로 이뤄지기 위해서는 관련 환경 개선이 필요하고, 학생들의 관련 기술적 소양 향상이 필요하다.