• Journal of Power Electronics
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• 제17권6호
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• pp.1433-1444
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• 2017

A family of non-isolated DC-DC three-port converters (TPCs) that allows for a more flexible power flow among a renewable energy source, an energy storage device and a current-reversible DC bus is introduced. Most of the reported non-isolated topologies in this area consider only a power consuming load. However, for applications such as hybrid-electric vehicle braking systems and DC microgrids, the load power generating capability should also be considered. The proposed three-port family consists of one unidirectional port and two bi-directional ports. Hence, they are well-suited for photovoltaic (PV)-battery-DC bus systems from the power flow viewpoint. Three-port converters are derived by combining different commonly known power converters in an integrated manner while considering the voltage polarity, voltage levels among the ports and the overall voltage conversion ratio. The derived converter topologies are able to allow for seven different modes of operation among the sources and load. A three-port converter which integrates a boost converter with a buck converter is used as a design example. Extensions of these topologies by combining the soft-switching technique with the proposed design example are also presented. Experiment results are given to verify the proposed three-port converter family and its analysis.

• Smart Structures and Systems
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• 제7권5호
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• pp.365-378
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• 2011

Piezo-based active structural health monitoring (SHM) requires amplifiers specifically designed for capacitive loads. Moreover, with the increase in number of applications of wireless SHM systems, energy efficiency and cost reduction for this type of amplifiers is becoming a requirement. General lab grade amplifiers are big and costly, and not built for outdoor environments. Although some piezoceramic power amplifiers are available in the market, none of them are specifically targeting the wireless constraints and low power requirements. In this paper, a piezoceramic transducer amplifier for wireless active SHM systems has been designed. Power requirements are met by two digital On/Off switches that set the amplifier in a standby state when not in use. It provides a stable ${\pm}180$ Volts output with a bandwidth of 7k Hz using a single 12 V battery. Additionally, both voltage and current outputs are provided for feedback control, impedance check, or actuator damage verification. Vibration control tests of an aluminum beam were conducted in the University of Houston lab, while wireless active SHM tests of a wind turbine blade were performed in the Harbin Institute of Technology wind tunnel. The results showed that the developed amplifier provided equivalent results to commercial solutions in suppressing structural vibrations, and that it allows researchers to perform active wireless SHM on moving objects with no power wires from the grid.

• 한국수소및신에너지학회논문집
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• 제32권5호
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• pp.401-409
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• 2021

The combination of different concentrations of ZnSO₄ in acidic solution as electrolyte in Zn-air batteries was investigated by Zn symmetrical cell test, half-cell and full cell tests. Using 1 M ZnSO₄ + 0.05 M H₂SO₄ as electrolyte and MnO₂ as air cathode catalyst with Zn foil anode, this combination had a satisfactory performance with balance of electrochemical activity and stability. Its electrochemical activity was matched to or even better than the PtRu catalyst in different current density. And its cycle life was improved (more than 100 cycles stable) by suppressing the growth of zinc dendrites on anode obviously. This electrolyte overcame the shortcomings of alkaline electrolyte that are easy to react with CO₂ in the air, severely growth of Zn dendrites caused by uneven plating/stripping of Zn.

• 한국항공운항학회지
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• 제29권3호
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• pp.52-65
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• 2021

A large amount of time and cost is consumed due to congestions caused by an increasing number of cars which results in a lot of emissions. To overcome these problems, a new electric vertical takeoff and landing (eVTOL) aircraft is being considered. Since vertical take off and landing without a separate runway is realized and electricity is used as a power source, it could solve the saturated ground traffic congestions without emissions. In this paper, the initial sizing was performed based on the Nexus 6HX of Belltextron which is a tilt-ducted fan type. In this study, the electric propulsion system that only uses battery was implemented instead of current Nexus 6HX hybrid electric propulsion. Aerodynamic analyses were performed using OpenVSP and XFLR5. Power-to-weight ratio, wing loading, estimated weight were calculated with these analyses.

• 전기화학회지
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• 제21권4호
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• pp.68-79
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• 2018

최근 늘어나는 배터리 수요를 대처하기 위하여 배터리를 대체하거나 배터리의 구동시간을 늘리기 위한 방법으로 제시되고 있는 에너지 발전소자와 에너지 저장소자의 융합연구는 에너지 관련 기술분야에서 가장 관심받고 있는 분야중 하나이다. 본 리뷰논문에서는 물리에너지 발전소자의 최근 연구동향과 함께 에너지 발전소자와 저장소자의 융합연구 동향을 소개하고자 한다. 먼저, 물리에너지를 전기에너지로 변환하는 압전 특성과 마찰대전 특성을 이용한 에너지 발전소자 관련 연구동향을 소개한다. 또한 압전/마찰대전 에너지 발전소자와 에너지 저장소자의 융합 연구동향을 소개한다. 특히 자가충전 에너지소자의 물리에너지를 전기화학적 에너지로 변환하는 새로운 접근방법을 소개하고자 한다.

• 한국전자통신학회논문지
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• 제14권3호
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• pp.519-528
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• 2019

현재의 브레이크 시스템은 운동에너지를 열에너지로 변경하여 거의 마찰형 브레이크로 공기 중에 발산하여 제동한다. 시스템 내에는 제동력을 발생시키는 리타더라는 장치가 있다. 전기에너지의 소모를 절약하기 위해 리타더의 제동에너지 일부를 활용하는 리타더의 고속 응답 특성에 관한 고도기술 연구는 이미 선진국에서 진행 중이다. 본 논문에서는 배터리 충전을 위해 리타더에서 발생한 3상 전압을 24V 직류 전압으로 변환하고 실험을 통해 타당성을 검증하는 DC-DC 컨버터를 제안한다.

• Korean Chemical Engineering Research
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• 제57권5호
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• pp.735-742
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• 2019

이온 선택성 표면이 가지는 파상구조와 전기와류 불안정성 간의 전기동역학적 상호작용을 수치해석을 통하여 연구하였다. 유한요소법을 이용하여 전기장-이온 이동현상-유동장을 완전결합 해석을 하였다. 이를 통해 파상구조가 제공하는 전기와류 생성 기작인 Dukhin's mode의 유효성 및 역할을 제시하였다. Runinstein's mode와 경쟁관계에 놓이는 Dukhin's mode는 (i) 과한계 영역으로의 전이 전압을 낮춰주고 (ii) 혼돈계인 과한계 영역에서 전류를 비선형적으로 증가시켜준다. 또한, (iii) 전기와류 불안정성에서 발생하는 비효율적 혼합의 원인인 고주파수 Fourier 성분을 배제하여 전기와류의 혼합 효율을 상승시켜 준다. 결론적으로, 본 연구에서 제시한 기작은 전기투석, 화학전지 등의 이온 선택성 이동현상 시스템에 대한 에너지 효율적인 기작으로 활용 가능할 것이다.

• International Journal of Computer Science & Network Security
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• 제22권4호
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• pp.17-26
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• 2022

Sensor Nodes play a major role to monitor and sense the variations in physical space in various real-time application scenarios. These nodes are powered by limited battery resources and replacing those resource is highly tedious task along with this it increases implementation cost. Thus, maintaining a good network lifespan is amongst the utmost important challenge in this field of WSN. Currently, energy efficient routing techniques are considered as promising solution to prolong the network lifespan where multi-hop communications are performed by identifying the most energy efficient path. However, the existing scheme suffer from performance related issues. To solve the issues of existing techniques, a novel hybrid technique by merging particle swarm optimization and game theory model is presented. The PSO helps to obtain the efficient number of cluster and Cluster Head selection whereas game theory aids in finding the best optimized path from source to destination by utilizing a path selection probability approach. This probability is obtained by using conditional probability to compute payoff for agents. When compared to current strategies, the experimental study demonstrates that the proposed GTPSO strategy outperforms them.

• 융합경영연구
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• 제10권4호
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• pp.13-24
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• 2022

Purpose: Although numerous research has covered content on trends in the adoption and use of wearable devices, their uses across several sectors such as healthcare, gaming, and fashion, there seems to be a considerable paucity with regard to empirical research focusing on the solutions for factors that undermine the effectiveness of wearable devices in healthcare. The present research aims to highlight what has been covered on wearable devices in healthcare while highlighting the limitations for future research. Research design, data, and methodology -The present authors conducted one of the most famous qualitative literature approach which has been called as PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analysis) statement. The selecting criteria for eligible prior studies was estimated by whether studies are suitable for the current research, identifying they are peer-reviewed and issued by notable publishers between 2017 and 2022. Result - Our results indicated that (1) Increasing the Affordability and User Education on Wearable Devices in Healthcare (2) Tackling the Technological Issues in Wearable Devices to Promote Healthcare Delivery (3) Solving Security and Privacy Issues Associated with Wearable Devices (4) Promoting Standards and Appropriate Regulations for Wearable Devices. Conclusion - To add, resolving the technological issues associated with wearable devices in healthcare will ensure that the new devices in the market will have longer battery life, multiple functions, and enhanced accuracy, thus ensuring that patients receive better care. Necessary interventions are taken on time to avoid any deleterious consequences such as proliferating mortality rates among the different patient groups.

• Corrosion Science and Technology
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• 제21권6호
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• pp.487-494
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• 2022

Anodizing is a typical electrochemical surface treatment method that can improve the corrosion and insulating properties of aluminum alloys. The anodization process can obtain a dense structure. It can be used to artificially grow the thickness of an anodization film. Aluminum 3003 alloy used in this study is the most commonly used alloy for batteries due to its high strength and excellent formability as well as its weldability and corrosion resistance. Aluminum 3003 alloy was anodized at 0 ℃ with 0.3 M oxalic acid at 20 V, 40 V, or 60 V for 1 hour, 6 hours, or 12 hours. As a result of analyzing the composition of each specimen with an Energy Dispersive Spectrometer (EDS), aluminum was converted into an oxide film. The thickness of the formed anodization film increased when the applied voltage and anodization time increased. High corrosion potential values and low corrosion current density values were observed for the thickest oxide layer. The anodization film formed by anodization acted as a protective layer. The electrical resistance increased as the applied voltage and anodization time increased.