• 한국세라믹학회지
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• 제50권1호
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• pp.1-17
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• 2013

Since their first discovery, carbon nanotubes (CNTs) have become a material central to the field of nanotechnology. Owing to their splendid physical, structural and chemical properties, they have the potential to impact a wide range of applications, including advanced ceramics, nanoelectronic devices, nanoscale sensors, solar cells, battery electrodes, and field emitters. This review summarizes the synthetic methods of preparing CNTs and focuses on the chemical vapor deposition (CVD) method, especially catalytic CVD. In order to stabilize and disperse the catalyst nanoparticles (NPs) during synthesis, zeolite was implemented as the template to support metal-containing NPs, so that both CNTs in the bulk and on a 2D substrate were successfully synthesized. Despite more challenges ahead, there is always hope for widespread ever-new applications for CNTs with the development of technology.

• 전자공학회논문지
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• 제54권4호
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• pp.44-49
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• 2017

헬스케어 및 의료분야를 위한 배터리 기반 웨어러블 디바이스가 많이 제품화되고 있으나, 효과적인 전력 관리 미흡으로 자주 충전해야 하는 사용자의 불편함이 존재한다. 본 연구에서는 HW에서 제공하는 전력 관리 회로도를 효과적으로 활용할 수 있는 Tickless 기반 운영체제 및 전력 관리 알고리즘을 제시하고, 보드 레벨에서 최소 전력을 소모하는 Cold Restart 기법을 제안한다. 제안된 기법의 운영체제는 기존 운영체제에 비해 웨어러블 디바이스의 응용을 모델링한 4가지 시나리오에서 2배에서 최대 33배의 전력 소모 절감을 가져왔다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1998년도 추계학술대회 논문집
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• pp.25-28
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• 1998

Lithiated cobalt and nickel oxides are becoming very attractive as active cathode materials for secondary lithium ion secondary battery. $LiCoO_2$ is easily synthesized from lithium cobalt salts, but has a relatively high oxidizing potential on charge. LiNiOz is synthesized by a more complex procedure and its nonstoichiometry significantly degraded the charge-discharge characteristics. But $LiNiO_2$ has a lower charge potential which increases the system stability. Lithiated cobalt and nickel oxides are iso-structure which make the preparation of solid solutions of $LiNi_{1-x}Co_xO_2$ for O$LiCoO_2 and LiNiO_2$ electrode. The aim of the presentb paper is to study the electrochemical behaviour, as weU as the possibilities for practical application of layered Iithiated nickel oxide stabilized by $Co^{3+}$ substitution as active cathode materials in lithium ion secondary battery.

• 아동학회지
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• 제13권2호
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• pp.203-216
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• 1992

The purpose of this study was to investigate the utility of the Luria-Nebraska Battery-Children's Revision (LNNB-CR) in the clinical situation in Korea: LNNB-CR was applied clinically in order to examine how well it differentiates brain damaged children from normals. Subjects were 30 children with the average age of 10 years. Among them 15 were diagnosed as the 'brain damaged' group, and the remaining 15 were normal. All subjects of the two groups were tested on all items in accordance with LNNB-CR manual. Data were analyzed by percentage, correlation coefficient, and t-test. The results were (1) the degree of consistency between testers averaged 97.2％ which confirmed the stability of the scoring system. (2) Split-half reliability was ranged from .75 on the Tactile Scale (C3) to .95 on the Memory Scale (C10). Thus, consistency of items within the scales appeared high. (3) Internal consistency reliability ranged from .74 on the Visual Scale (C4) to .98 on the Reading Scale (C9). Thus, the homogenity of items within the scales appeared high. (4) In the diagnostic discriminative power test between the two groups, both individual scales and total scores showed significant differences at the level of p<.001. (5) The discriminative power test between two groups on all items showed significant differences at the level of p<.05 or better in 126(85％) out of 149 items. These results are supportive of the diagnostic utility of the application of LNNB-CR to the clinical situation in Korea. However, extensive additional research is needed in order to prove its worth.

• 전력전자학회논문지
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• 제23권3호
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• pp.161-167
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• 2018

In battery-operated systems, an isolated converter is used to interface the utility grid with the system to increase stability when charging and discharging batteries. Systems such as vehicle-to-grids (V2Gs), on-board chargers, and energy storage systems (ESSs) have recently become popular, and the roles of isolated converters have become important considerations in fabricating such devices. A fixed-frequency LLC converter, which is a type of isolated converter, presents the advantages of high efficiency and high power density by performing zero-voltage switching (ZVS) over wide frequency ranges. However, the magnetizing inductance of the LLC converter should be designed to enable ZVS in all switching devices. Therefore, in this study, the operating characteristics of the LLC circuit are analyzed, and an optimal design method for ZVS operation is established. Moreover, an 8 kW LLC high-efficiency and high-power-density resonant converter is designed and tested for ESS application. The LLC converter achieves 98% efficiency at rated power.

• 전기학회논문지
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• 제64권7호
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• pp.992-998
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• 2015

The ESS is composed of Battery Package, PCS(Power Conditioning System) Package, BCU(BESS Control Unit). In Jeju smart grid test-bed, we have developed a business model by ESS power system, renewable energy, transportation, such as customers, and have demonstrated above things. We have analyzed the EMS(Energy Management System) model of KPX where manages supply and demand of domestic electrical power system. We modified and launched EMS for microgrid but the cost was expensive and the system was large size. For releasing this system from industry as a whole, it is imperative to develop PMS(Power Management System) for microgrid. However, the cost of EMS for microgrid is expensive, some systems because it is a large development of the all of the first fruits in urgent PMS(Power Management System) for microgrid to be used in industry in general. Therefore, in this paper, we propose the ESS model considering the power systems characteristics and extensibility in korea. and also we propose the PMS to manage the ESS systems.

• 한국군사과학기술학회지
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• 제17권5호
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• pp.611-619
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• 2014

Combining similar data provides larger data sets through conducting test for homogeneity of several samples under various production processes or samples from different LOTs. The test for homogeneity has been applied to either variable or attribute data, and for variable data set physical homogeneity has been tested without consideration of the specification to the set. This paper proposes a method for test of homogeneity based on quality level through using both variable data and the specification. Quality-based test for homogeneity as a way of combining data is implemented by test for coefficient of variation in the proposed method. The method was verified through the application to the data set in open literature. And possibility to combine performance data for various types of thermal battery was discussed in order to estimate operation reliability.

• 한국분말재료학회지
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• 제19권4호
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• pp.271-277
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• 2012

$SnO_2$ nanotubes were successfully synthesized using an electrospinning technique followed by calcination in air. The nanotubes were the single phase nature of $SnO_2$ and consisted of approximately 14 nm nanocrystals. SEM and TEM characterizations demonstrated that uniform hollow fibers with an average outer diameter of around 124 nm and wall thickness of around 25 nm were successfully obtained. As anode materials for lithium ion batteries, the $SnO_2$ nanotubes exhibited excellent cyclability and reversible capacity of $580mAhg^{-1}$ up to 25 cycles at $100mAg^{-1}$ as compared to $SnO_2$ nanoparticles with a capacity of ${\sim}200mAhg^{-1}$. Such excellent performance of the $SnO_2$ nanotube was related to the one-dimensional hollow structure which acted as a buffer zone during the volume contraction and expansion of Sn.

• Journal of Biosystems Engineering
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• 제32권2호
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• pp.91-96
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• 2007

In this study, a prototype remote controlled weeder using solar module was developed and the evaluations of weeding, side walking and weeding performance were conducted to see if actual application was feasible in the paddy field. When traveling, the loss electric current was 8 to 15 A depending on operating and soil conditions. The average traveling speed was 0.25 m/s and the average slippage was 18%. When it side walked row by row, electric current consumption was 7 A on the average. When wheel rotors line went initially up and last down, electric current consumption was 12 to 15 A due to soil resistance. Electric current consumption when shifting wheel rotors line was less than 5 A due to no resistance. Field efficiency was 105 min/10a based on the test field. Operation was able to be done for 4.16 hours continually by 52 AH battery based on 300 W average maximum power consumption and 4.6 hours under sunny day considering solar module.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제50권3호
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• pp.107-114
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• 2001

Electro-mechanical battery (EMB) consists of a high-speed fly wheel with an integral motor/ generator suspended on magnetic bearings and in an evacuated housing. Permanent magnet (PM) machines as the EMB motor/ generator are a popular choice, since there are no excitation losses which means substantial increase in the efficiency. In this paper we present the comparison of conventional slotted and slotless ring-wound types, aimed at EMB and other high-speed drives. We firstly discuss the topology of each machine for this particular application. these machines are primarily designed as 1kW two-pole PM generator with the rated speed of 40000 rpm. the motoring torque of 0.51 Nm has to be enough to accelerate the flywheel to the rated speed. We then present the comparison of the open-circuit field, the armature reaction field and winding inductance. next we analyze the induced voltage and the developed torque per unit stack length and unit weight of different machines. Finally, we estimate and compare the losses and the efficiency at motoring and generating modes.