• Journal of Magnetics
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• v.16 no.3
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• pp.201-205
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• 2011

We performed total energy and electronic structure calculations for the basic ground state properties of Fe using the conventional generalized gradient approximation (GGA) and screened hybrid functionals as the form of the exchange-correlation functional. To that end, we calculated structural (equilibrium lattice constants, bulk moduli, and cohesive energies) and electronic (magnetic moments and densities of states) properties. Both functional calculations gave the correct ground state, the ferromagnetic bcc phase, in which the structural parameters agreed well with experimental results. However, the description of the cohesive energies and magnetic moments at the ground state exhibited different behavior from each other: the unusually small cohesive energy and large magnetic moment were observed in the screened hybrid functional calculations compared to the GGA calculations. The reason for the difference was examined by analyzing the calculated electronic structures.

• Clean Technology
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• v.21 no.1
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• pp.12-21
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• 2015

Development of novel conducting polymers (CPs) is expected to facilitate the advancement of functional materials used for energy, environmental, and nanotechnology. Recent research efforts are focused on doping CPs with functional dopants to enhance their performance or add additional functions that are not inherent in CPs. This review surveys literatures about the doped CPs focusing on the roles of functional dopants, unlike other reviews focusing on the development of new conducting polymer backbones. The functional dopants presented in this review include redox active molecules, carbon nanomaterials, biopolymers, and chelating molecules. Depending on the dopants and their physicochemical properties, the doped CPs can be used for a variety of applications such as polymer batteries, membranes for waste water treatment, and chemical sensors. A major challenge of the CPs is presented and the ways to overcome the challenge is also suggested for the future development of stable, high performance CPs.

• Korean Journal of Cognitive Science
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• v.2 no.2
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• pp.205-220
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• 1990

Material substance may exist in two different modes of reality:real as physcal objects that comprise material cause and formal cause, and real as function networks that comprise efficient cause and functional cause.Functional networks are real as a mode of material substance because their efficient cause is energy consuming.Neural functional network, in this sense, are different from neural networks.In the same way, mental functional networks are real, for they are energy consuming and they function as a network.Mental functional networks, in turn, may divide into non-lingustic functional networks and linguistic functional networks.And further distinctions among the different levels of mental functional networks will be specified, and hence their reality confirmed more specifically as the research in cognitive science advances.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.5
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• pp.467-473
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• 2013

Diverse approaches for reducing the total energy consumption of machine tools have been introduced and developed, to cope with rapid increase of total energy costs in world-wide manufacturing industries. To realize the improvement of the energy efficiency, systematic and integrated strategies must be considered, including energy-saving design, optimized control operation and concrete evaluation of the energy efficiency. This paper proposes key enabling technologies required to improve the energy efficiency of 5-axis multi-functional machining tools, considering both of system design and operation in the real production environments. Related standardized procedures of the energy efficiency evaluation is also represented.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.310-314
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• 1999

A prototype of Flywheel Energy Storage System with high Tc superconducting bearings was fabricated and tested to verify its applicability for the energy industry. The moment of inertia of assembled wheel with rotor magnets is about 1.072${\times}$10$^{-1}$ Kg-m$^2$. The wheel was designed to withstand its integrity up to the rotation speed of 20,000 rpm. YBCO bulk superconductors prepared by seed growth method were used as bearing to levitate and stabilize the rotating wheel. High speed rotation of the flywheel without mechanical contact was achieved by using specially designed Halbach type motor. The flywheel system showed very high stability during test operation performed up to the speed of about 10,000rpm. The energy loss measured by free decay test performed between 9,300 rpm and 7,000 rpm was calculated as about 45 W.

• Proceedings of the Korean Ceranic Society Conference
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• 2004.10a
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• pp.87.1-87.1
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• 2004

• Current Applied Physics
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• v.18 no.12
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• pp.1507-1512
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• 2018

The development of an organic-based aqueous redox flow battery (RFB) using quinone as an electroactive material has attracted great attention recently. This is because this battery is inexpensive, produces high energy density, and is environment friendly in stationary electrical energy storage applications. Herein, we investigate the redox potentials and solubilities of indole-5,6-quinone and indole-4,7-quinone derivatives in terms of the substituent effects of functional groups using theoretical calculations. Our results indicate that full-site substituted derivatives of indolequinone are more useful as active materials compared to single-site substituted derivatives. In particular, our calculations reveal that the substitution of $-PO_3H_2$ and $-SO_3H$ functional groups with multiple polar bonds is very effective in increasing the activity of the aqueous RFB. As a strategy to overcome the limitation that the aqueous solubility is intrinsically low because they are organic molecules, we suggest the substitution of functional groups with multiple polar bonds to the backbones of active organic materials. Among 180 indolequinone derivatives, 17 candidates that meet the redox potential standards ($${\leq_-}0.2V$$ or $${\geq_-}0.9V$$) and eight candidates with solubility exceeding 2 mol/L are identified. Three indolequinone derivatives that satisfy both conditions are finally presented as promising electroactive candidates for an aqueous RFB.

• Environmental and Resource Economics Review
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• v.28 no.3
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• pp.437-465
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• 2019

In this study, we propose a new method to forecast long-term energy demand in Korea. Based on Chang et al. (2016), which models the time varying long-run relationship between electricity demand and GDP with a function coefficient panel model, we design several schemes to retain objectivity of the forecasting model. First, we select the bandwidth parameters for the income coefficient based on the out-of-sample forecasting performance. Second, we extend the income coefficient using the functional principal component analysis method. Third, we proposed a method to reflect the elasticity change patterns inherent in Korea. In the empirical analysis part, we forecasts the long-term energy demand in Korea using the proposed method to show that the proposed method generates more stable long term forecasts than the existing methods.

• Prospectives of Industrial Chemistry
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• v.15 no.3
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• pp.39-48
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• 2012

현대 컴퓨터산업의 진보는 제일원리 전산법이 여러 연구개발 분야에 널리 사용되는 길을 열었다. 이 논문에서는 제일원리 전산법을 이용한 신 재생에너지의 고성능 나노 소재개발 및 디자인 연구사례를 통해 그 기초 원리와 다양한 응용분야 및 실험과의 효율적인 연계성 등을 소개하고자 한다.

• Composites Research
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• v.31 no.6
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• pp.355-364
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• 2018

Flexible energy-storage devices (FESDs) have been studied and developed extensively over the last few years because of demands in various fields. Since electrochemical performance and mechanical flexibility must be taken into account together, different framework from composition of conventional energy-storage devices (ESDs) is required. Numerous types of electrodes have been proposed to implement the FESDs. Herein, we review the works related to the FESDs so far and focus on free-standing electrodes and, especially substrate-based ones. The way to utilize carbon woven fabric (CF) or carbon cloth (CC) as flexible substrates is quite simple and intuitive. However, it is meaningful in the point of that the framework exploiting CF or CC can be extended to other applications resulting in multifunctional composites. Therefore, summary, which is on utilization of carbon-based material and conductive substrate containing CF and CC for ESDs, turns out to be helpful for other researchers to have crude concepts to get into energy-storage multi-functional composite. Moreover, polymer electrolytes are briefly explored as well because safety is one of the most important issues in FESDs and the electrolyte part mainly includes difficult obstacles to overcome. Lastly, we suggest some points that need to be further improved and studied for FESDs.