• Journal of Magnetics
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• 제16권3호
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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.

• 청정기술
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• 제21권1호
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• pp.12-21
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• 2015

전도성 고분자를 이용한 새로운 기능성 재료의 개발은 에너지, 환경, 나노 기술 분야 발전에 크게 기여할 것으로 기대를 모으고 있다. 최근에는 전도성 고분자에 기능성 도펀트(functional dopant)를 삽입하여 고성능화에 초점을 맞춘 연구들이 많이 수행되고 있다. 본 총설은 새로운 전도성 고분자 합성의 관점으로 쓰여진 다른 문헌들과 달리, 삽입되는 기능성 도펀트의 역할과 응용 분야를 중심으로 서술하였다. 대표적인 기능성 도펀트의 종류로는 산화환원 활성(redox-active) 분자, 카본나노물질, 바이오물질, 킬레이팅(Chelating) 분자 등이 있으며, 각각의 도펀트의 고유한 특징에 따라 베터리, 수처리용 분리막, 센서 등 다양한 분야에 활용될 수 있다. 본 총설에서는 각각의 기능성 도펀트가 첨가 되었을 때 장점과 응용 방향에 대해 살펴 보고, 전도성 고분자의 안정성 향상을 위한 방법과 고려해야 할 점들에 대하여 제안하고자 한다.

• 인지과학
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• 제2권2호
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• pp.205-220
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• 1990

물질적으로 존재하는 모든 실체는 질료인과 형상인을 갖춘 개별 물체로 실재하면서 어떤 기능을 할 \ 수도 있고,동력인과 기능인을 갖춘 비물체적 양상으로 실재하면서 기능망(functional network)으로서 형상을 가질 수도 있다.기능망은 신경망,신경기능망,심리기능망 등 차원을 다르게 하면서 상하로 연관된 계층으 이루고 있으며 심리기능망 안에서도 비언어적 기능망,언어적 기능망이 구별되어 차원적 언어기능을 가능하게 하는 것으로 볼수 있다.이러한 기능망의 실재성은 신경과학과 인공지능학의 발전에 따라 확인, 수정,보완될 수 있을 것이다.

• 한국정밀공학회지
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• 제30권5호
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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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• 한국초전도학회 1999년도 High Temperature Superconductivity Vol.IX
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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.

• 한국세라믹학회:학술대회논문집
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• 한국세라믹학회 2004년도 추계총회 및 연구발표회 초록집
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• pp.87.1-87.1
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• 2004

• Current Applied Physics
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• 제18권12호
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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.

• 자원ㆍ환경경제연구
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• 제28권3호
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• pp.437-465
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• 2019

본 연구에서는 장기 전력 수요와 GDP 사이의 소득계수를 시간과 GDP의 값에 따라 변화하도록 모형화한 Chang et al.(2016)에 기반을 두어 장기 에너지 수요의 예측에 관련된 새로운 방법을 제안한다. 본 논문에서는 장기 에너지와 GDP 사이의 소득계수를 함수로 표현하고, 함수 주성분 분석(Functional Principal Component Analysis)을 통하여 함수계수(Functional Coefficient)를 예측하고 이를 장기 에너지 수요 예측에 적용한다. 또한 함수계수를 비모수적으로 추정할 때 너비띠 모수를 예측 실험 오차를 최소화하도록 설정하는 방식을 제안하였고 개별 국가의 함수계수 변화 패턴을 반영하여 개별 국가의 특수성을 반영하는 예측 방법도 제시한다. 실증분석에서는 전 세계 에너지 데이터를 이용하여 한국의 장기 에너지 수요 예측을 본 논문에서 제시한 방법으로 예측하고, 기존의 방법들 보다 안정적인 장기 에너지 수요 예측이 가능함을 보였다.

• 공업화학전망
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• 제15권3호
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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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• 제31권6호
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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.