• 융복합기술연구소 논문집
• /
• 제11권1호
• /
• pp.33-37
• /
• 2021

The application of multicopters using a battery is limited by the short endurance due to the low energy density. A propeller is one of crucial components that determine the performance of the multicopter. In the present study, a systematic method for predicting the endurance of multicopters is described. Propeller performance database are constructed using the data from UIUC Propeller Data Site. Using the 'trendline' function of MS Excel software, the performance of the commercial propellers are represented as a function of polynomials. The multicopter's endurance is computed iteratively using Peukert's Law and considering the voltage drop effect. We evaluated the endurance of multicopters that use commercial propellers. The endurance of the multicopter was within the range of 28 min. to 36 min. It is expected that the present method can be utilized for optimal propeller selection for the given multicopters.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제15권12호
• /
• pp.4385-4399
• /
• 2021

The Internet of Things (IoT) eHealth systems composed by Wireless Body Area Network (WBAN) has emerged recently. Sensor nodes are placed around or in the human body to collect physiological data. WBAN has many different applications, for instance health monitoring. Since the limitation of the size of the battery, besides speed, reliability, and accuracy; design of WBAN protocols should consider the energy efficiency and time delay. To solve these problems, this paper adopt the end-edge-cloud orchestrated network architecture and propose a transmission based on reinforcement algorithm. The priority of sensing data is classified according to certain application. System utility function is modeled according to the channel factors, the energy utility, and successful transmission conditions. The optimization problem is mapped to Q-learning model. Following this online power control protocol, the energy level of both the senor to coordinator, and coordinator to edge server can be modified according to the current channel condition. The network performance is evaluated by simulation. The results show that the proposed power control protocol has higher system energy efficiency, delivery ratio, and throughput.

• 한국정보통신학회:학술대회논문집
• /
• 한국정보통신학회 2021년도 춘계학술대회
• /
• pp.312-314
• /
• 2021

정부는 드론을 미래 핵심 성장 동력으로 보고 국가 주도 드론 산업 육성 방안을 마련하고 물품 수송, 산림 보호 및 감시, 시설물 안전 진단 등 다양한 분야에서 시범사업을 하고 드론활용에 적극적이다. 특히, 경찰에서는 실종자 수색을 위해 드론 활용을 시도하고 있으나 기존드론은 배터리 시간의 제약으로 운용시간이 짧고 야산이나 수풀이 우거진 현장에서는 산위에서 항공촬영으로 수색할 수밖에 없어서 효과성이 미흡하다. 본 연구에서는 실종자 수색의 한계점을 극복할 수 있는 드론으로서 가상현실을 활용한 FPV(First Person View)드론을 제안하다.

• 공학기술논문지
• /
• 제5권4호
• /
• pp.349-353
• /
• 2012

Recently, Mobile multimedia equipments as smart phone and tablet pc requirement is increasing and this market is also being expanded. These mobile equipments require large multi-media function, so more power consumption is required. For these reasons, the needs of power management IC as switching type dc-dc converter and linear regulator have increased. DC-DC buck converter become more important in power management IC because the operating voltage of VLSI system is very low comparing to lithium-ion battery voltage. There are many people to be concerned about digital DC-DC converter without using external passive device recently. Digital controlled DC-DC converter is essential in mobile application to various external circumstance. This paper proposes the DC-DC Buck Converter using the AVR RISC 8-bit micro-processor control. The designed converter receives the input DC 18-30 [V] and the output voltage of DC-DC Converter changes by the feedback circuit using the A/D conversion function. Duty ratio is adjusted to maintain a constant output voltage 12 [V]. Proposed converter using the micro-processor control was compared to a typical boost converter. As a result, the current loss in the proposed converter was reduced about 10.7%. Input voltage and output voltage can be displayed on the LCD display to see the status of the operation.

• Journal of Electrochemical Science and Technology
• /
• 제15권1호
• /
• pp.51-66
• /
• 2024

Modern society is making numerous efforts to reduce reliance on carbon-based energy systems. A notable solution in this transition is the adoption of lithium-ion batteries (LIBs) as potent energy sources, owing to their high energy and power densities. Driven by growing environmental challenges, the application scope of LIBs has expanded from their initial prevalence in portable electronic devices to include electric vehicles (EVs) and energy storage systems (ESSs). Accordingly, LIBs must exhibit long-lasting cyclability and high energy storage capacities to facilitate prolonged device usage, thereby offering a potential alternative to conventional sources like fossil fuels. Enhancing the durability of LIBs hinges on a comprehensive understanding of the reasons behind their performance decline. Therefore, comprehending the degradation mechanism, which includes detrimental chemical and mechanical phenomena in the components of LIBs, is an essential step in resolving cycle life issues. The LIB systems presently being commercialized and developed predominantly employ graphite anode and layered oxide cathode materials. A significant portion of the degradation process in LIB systems takes place during the electrochemical reactions involving these electrodes. In this review, we explore and organize the aging mechanisms of LIBs, especially those with graphite anodes and layered oxide cathodes.

• 한국포장학회지
• /
• 제29권3호
• /
• pp.211-221
• /
• 2023

This study was conducted as a basic study for the selection of tags suitable for logistics management in the palletized unit-load unit and the development of various technologies to activate the palletized unit-load shipment of agricultural products through local APCs. Three types of passive RFID tags of UHF 900 MHz and one type of active RFID tag of 2.4 GHz band designed and manufactured through this study were used to analyze the receiving strength according to the tag's attachment location and distance of the palletized unit-load of agricultural products. In the passive RFID tag, there was a large difference in receiving strength by the tag's attachment location and a large amount of data loss depending on the distance within 30 m, whereas, in the active RFID tag, it was superior to the passive tags in terms of both receiving strength and data loss. Therefore, active tags are desirable from the perspective of multiple identification of warehouses with large spaces in relation to the application of RFID tags for palletized unit-loads of agricultural products, but the development of low-power technologies such as software wakeup power management as well as hardware to minimize battery power consumption is necessary.

• 한국분말재료학회지
• /
• 제31권4호
• /
• pp.293-301
• /
• 2024

All-solid-state lithium batteries (ASSLBs) are receiving attention as a prospective next-generation secondary battery technology that can reduce the risk of commercial lithium-ion batteries by replacing flammable organic liquid electrolytes with non-flammable solid electrolytes. The practical application of ASSLBs requires developing robust solid electrolytes that possess ionic conductivity at room temperature on a par with that of organic liquids. These solid electrolytes must also be thermally and chemically stable, as well as compatible with electrode materials. Inorganic solid electrolytes, including oxide and sulfide-based compounds, are being studied as promising future candidates for ASSLBs due to their higher ionic conductivity and thermal stability than polymer electrolytes. Here, we present the challenges currently facing the development of oxide and sulfide-based solid electrolytes, as well as the research efforts underway aiming to resolve these challenges.

• Applied Microscopy
• /
• 제50권
• /
• pp.24.1-24.11
• /
• 2020

The development of the femtosecond laser (fs laser) with its ability to provide extremely rapid athermal ablation of materials has initiated a renaissance in materials science. Sample milling rates for the fs laser are orders of magnitude greater than that of traditional focused ion beam (FIB) sources currently used. In combination with minimal surface post-processing requirements, this technology is proving to be a game changer for materials research. The development of a femtosecond laser attached to a focused ion beam scanning electron microscope (LaserFIB) enables numerous new capabilities, including access to deeply buried structures as well as the production of extremely large trenches, cross sections, pillars and TEM H-bars, all while preserving microstructure and avoiding or reducing FIB polishing. Several high impact applications are now possible due to this technology in the fields of crystallography, electronics, mechanical engineering, battery research and materials sample preparation. This review article summarizes the current opportunities for this new technology focusing on the materials science megatrends of engineering materials, energy materials and electronics.

• 전기화학회지
• /
• 제18권1호
• /
• pp.17-23
• /
• 2015

$Li_4Ti_5O_{12}$는 우수한 안정성으로 자동차용 리튬 이온 이차전지의 음극 활물질로서 각광 받고 있다. 그러나 넓은 밴드갭에 기인한 절연체 특성으로 고율 충/방전을 가능하게 하기 위해서는 전자 전도도의 개선이 필수적이다. 본 연구에서는 Cr 도핑을 통해 $Li_4Ti_5O_{12}$의 전자 전도도 개선을 목표로 하였으며, wet-mixing법을 통한 물질 합성시 도판트인 Cr 프리커서의 용해도 차이에 의한 Cr-doped $Li_4Ti_5O_{12}$의 전기화학적 특성 변화를 고찰하고자 하였다. 시료의 물리적 특성은 ICP, XRD, SEM, EXAFS을 통하여 확인하였고 1.0V~3.0V (vs. $Li/Li^+$) 하에서 충/방전 특성을 조사하였다. 프리커서의 용해도는 합성된 물질의 상(phase) 및 모폴로지에 큰 영향을 미쳤으며, 가장 용해도가 높은 $Cr(NO_3)_2$ 프리커서로부터 합성된 경우 Bare $Li_4Ti_5O_{12}$와 비교하여 약 2배 개선된 고율 충/방전 특성(130 mAh/g @ 10 C)을 확인하였다.

• 한국재난정보학회 논문집
• /
• 제16권2호
• /
• pp.392-401
• /
• 2020

연구목적: 본 연구는 비상시의 예비전원장치로 사용 가능한 리튬이온커패시터의 동작 특성을 분석하고, 충·방전시의 선형비례특성을 이용하여 전압을 측정하는 것으로도 예비전원장치의 동작 이상 유무를 판단 할 수 있는 실험근거의 제공을 목적으로 한다. 연구방법: 본 연구를 위한 방법으로 먼저 기존 예비전원장치와 리튬이온커패시터에 대한 동작원리 및 특성을 분석하고, 다음으로 실험에 사용한 유도등의 구성도와 시스템 블록도에 따라 리튬이온커패시터의 전압 측정을 통해 배터리의 보유 전력량을 확인하는 전압대역별 방전전력량 측정 값 테스트와 유도등을 이용한 동작 테스트 실험으로 진행한다. 연구결과: 리튬이온커패시터의 선형비례특성을 이용한 충전전압을 확인하는 것만으로도 정확하게 유도등 램프의 유효동작 시간을 추론 할 수 있는 근거를 제시하고 있다. 결론: 재난 상황 시 리튬이온커패시터를 비상유도등의 예비전원장치로 사용함으로써 비상유도등의 완전 방전을 미연에 방지하고, 예비전원장치의 정상 작동 수행의 문제가 발생하지 않게 하며, 간단한 전압측정만으로도 예비전원장치의 이상 유무를 확인 할 수 있게 하여 향후 피난설비 적용에 많은 활용도를 제시하고자 하였다.