• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 추계학술대회 논문집
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• pp.143-146
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• 2007

Birnessite-type manganese dioxide($MnO_2$) was coated uniformly onto carbon nanotubes (CNTs) through a spontaneous direct redox reaction between CNTs and permanganate ions($MnO_4\;^-$). The initial specific capacitance of the $MnO_2/CNT$ nanocomposite in an organic electrolyte at a large current density of 1 A/g was 250 F/g, which is equivalent to 139 mAh/g based on the total weight of the electrode material including the electroactive material, conducting agent and binder. The specific capacitance of the $MnO_2$ in the $MnO_2/CNT$ nanocomposite was as high as 580 F/g (320 mAh/g), indicating excellent electrochemical utilization of the $MnO_2$. The addition of CNTs as a conducting agent can improve the high rate capability of $MnO_2/CNT$ nanocomposite considerably. An analysis of the in-situ X-ray absorption near-edge structure (XANES) showed an improvement in the structural and electrochemical reversibility of the $MnO_2/CNT$ nanocomposite by heat-treatment.

• Journal of Electrochemical Science and Technology
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• 제11권1호
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• pp.14-25
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• 2020

Li ion battery (LIB) is one of the most remarkable energy storage devices currently available in various applications. With a growing demand for high-performance batteries, the role of electrochemical analysis for batteries, especially, electrode reactions are becoming very important and crucial. Among various analytical methods, cyclic voltammetry (CV) is very versatile and widely used in many fields of electrochemistry. Through CV, it is possible to know electrochemical factors affecting the reaction voltage and reversibility, and furthermore, quantitative analysis on Li⁺ diffusivity as well as intercalation and capacitive reactions, and also anionic redox reaction. However, the explanation or interpretation of the results of CV is often deficient or controversial. In this mini-review, we briefly introduce the principle of cyclic voltammetry and its applications in LIB to bring a better understanding of the electrochemical reaction mechanisms involved in LIB.

• 한국안광학회지
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• 제8권1호
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• pp.59-64
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• 2003

Photochoromic lens에 광을 조사하면 darkening 상태와 fading상태에서photo-transmittance는 감소한다. 광의 조사를 제거하면 fading 상태가 되어 photo-transmittance는 원래 상태로 회복하는 가역과정을 갖는다. 자체 제작한 Photochoromic lens에서 darkening과 fading 과정에서 Photochromism의 분광측색계를 이용하여 CIE $L^*a^*b^*$의 색 좌표을 얻는다. darkening과 fading상태에서 색 좌표($a^*-b^*$)는 일차 곡선이고 (-) 기울기를 이며, 선형적으로 변한다. 색 좌표 이동량은 Blue ${\rightarrow}$ Yellow, Red ${\rightarrow}$ Green형태이다. fading상태에서 색 좌표는 darkening 상태보다 $b^*$ 값이 낮고, Photochromism 좌표의 이동은 darkening 상태와 반대로 이동한다. Photochoromic lens에 대한 Photochoromism 평가 방법은 darkening과 fading에 대한 색 좌표 이동으로 이용 할 수 있다.

• 자원리싸이클링
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• 제8권3호
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• pp.18-25
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• 1999

화학제염이나 전지화학제염을 통해 발생된 방사성 폐액을 정화처리할 수 있는 새로운 방법으로, 다공성 활성탄소섬유(ACF)상에서 폐액중 코발트이온의 전기적 흡·탈착에 대한 연구를 수행하였다. 회전원판 전극을 사용하여 순환전압전류법으로 전기이중층 충전만이 발생하는 전위 영역을 조사하였다. ACF 전극을 사용한 회분식 전기흡착 실험결과, 음의 전위 가용은 저위 미가용 시의 흡착에 비해 코발트이온의 흡착을 증가시켰다. 또한 흡착된 코발트 이온은 역전된 가용전위에 의해 용액으로 용출되었으며 이와 동시에 탄소체 전극이 재생되어, 전기흡착 공정의 가역성을 확인 할 수 있었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 C
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• pp.965-967
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• 1999

In order to solve to instability in air and to format dentrite, we used carbonized phenol resin electrode which is amorphous carbon. The structure and properties of deeply Li-doped carbonized phenol resin have been investigated in association with their utilization as electrodes in rechargeable batteries. Resol type phenol resin used as starting material. The doped lithium was found neither in metallic nor in ionic states even in the most deeply doped state($C_{2.2}$Li stage). It has also been confirmed that the carbonized phenol resin electrode has a large capacity with good stability and reversibility. These results strongly suggest that the carbonized phenol resin can make an excellent anode material for secondary batteries. Finally, we discuss that the carbonized phenol resin doped up to the $C_2Li$ stage can exhibit an energy density per volume as high as lithium metal. We know that carbonized phenol resin can used as cathode as well as anode by cyclic voltammogram.

• Journal of Electrochemical Science and Technology
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• 제6권2호
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• pp.50-58
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• 2015

There is a great deal of current interest in the development of rechargeable batteries with high energy storage capability due to an increasing demand for electric vehicles (EVs) with driving ranges comparable to those of gasoline-powered vehicles. Among various types of batteries under development, a Li-O₂ battery delivers the highest theoretical energy density; thus, it is considered a promising energy storage technology for EV applications. Despite the fact that extensive research efforts have been made in the field of Li-O₂ batteries in recent years, there are still many technical challenges to be addressed, such as low round-trip efficiency, poor reversibility, and poor power capability. In this article, we provide a short review on the fundamental electrochemistry of Li-O₂ batteries with non-aqueous electrolytes and on electrode materials that have been employed in cathodes (oxygen electrodes). The major aim of this mini-review is to highlight the physical and electrochemical origins of scientific challenges facing Li-O₂ battery technology and to overview the strategies proposed to overcome them.

• Journal of Pharmaceutical Investigation
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• 제31권4호
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• pp.273-279
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• 2001

The purpose of this study is to characterize the iontophoretic transport of growth hormone releasing peptides (GHRP-6) through hairless mouse skin from aqueous solution. The effect of various factors, such as pH, poloarity, current profile, current density, current duration, ionic strength, drug concentration, and enhancer application was studied to obtain basic knowledge on the transport. We have also studied the stability of GHRP-6 in solution with/without current. The donor chamber was filled with phosphate buffer solution containing GHRP-6 and the receptor chamber was filled with phosphate buffer solution (pH 7.4). Ag/AgCl electrode was used for their stability and reversibility. At a predetermined time interval, sampling was made and the concentration of drug was analysed using HPLC system. The results showed that, compared to passive flux, the total amount of drug transported increased markedly by the application of anodal current. Cathodal flux was similar to passive flux. Flux increased with the current density, the duration of current application and drug concentration. The effect of enhancers on the flux was studied using hydrophilic (5% N-methyl pyrrolidone) and hydrophobic (5% propylene glycol monolaurate, 5% oleic acid) enhancers. Application of enhancer also increased the flux.

• 분석과학
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• 제6권1호
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• pp.83-92
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• 1993

0.05M TEAP를 지지전해질로 한 아세톤용액에서, 란탄늄 및 네오디늄과 몇 가지 리간드의 착물에 대한 전기화학적 거동인 환원전류의 유형, 가역성, 안정도상수, 전류함수 등을 폴라로그래피와 순환전압전류법으로 조사하였다. 환원파는 2단계로 나타났으며, 반응은 확산지배적이고 비가역적이었다. 또한 란탄족 금속이온의 착물에 대하여 안정도상수를 측정하였다.

• 한국감성과학회:학술대회논문집
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• 한국감성과학회 2008년도 추계학술대회
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• pp.90-93
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• 2008

In natural language, it is common that repetitive constituents in an expression are to be left out and it is necessary to figure out the constituents omitted at analyzing the meaning of the sentence. This paper is on recognition of boundaries of parallel noun phrases by figuring out constituents omitted. Recognition of parallel noun phrases can greatly reduce complexity at the phase of sentence parsing. Moreover, in natural language information retrieval, recognition of noun with modifiers can play an important role in making indexes. We propose an unsupervised probabilistic model that identifies parallel cores as well as boundaries of parallel noun phrases conjoined by a conjunctive particle. It is based on the idea of swapping constituents, utilizing symmetry (two or more identical constituents are repeated) and reversibility (the order of constituents is changeable) in parallel structure. Semantic features of the modifiers around parallel noun phrase, are also used the probabilistic swapping model. The model is language-independent and in this paper presented on parallel noun phrases in Korean language. Experiment shows that our probabilistic model outperforms symmetry-based model and supervised machine learning based approaches.

• Macromolecular Research
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• 제13권6호
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• pp.483-490
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• 2005

A novel, polysaccharide-based, superabsorbent hydrogel was synthesized through crosslinking graft copolymerization of methacrylic acid (MAA) onto kappa-carrageenan ($_{k}C$), using ammonium persulfate (APS) as a free radical initiator in the presence of methylenebisacrylamide (MBA) as a crosslinker. A proposed mechanism for $_{k}C$­g-polymethacrylic acid ($_{k}C$-g-PMAA) formation was suggested and the hydrogel structure was confirmed using FTIR spectroscopy. The effect of grafting variables, including MBA, MAA, and APS concentration, was systematically optimized to achieve a hydrogel with the maximum possible swelling capacity. The swelling kinetics in distilled water and various salt solutions were preliminarily investigated. Absorbency in aqueous salt solutions of lithium chloride, sodium chloride, potassium chloride, calcium chloride, and aluminum chloride indicated that the swelling capacity decreased with increased ionic strength of the swelling medium. This behavior can be attributed to the charge screening effect for monovalent cations, as well as ionic crosslinking for multivalent cations. The swelling of super absorbing hydrogels was measured in solutions with pH ranging from 1 to 13. In addition, the pH reversibility and on-off switching behavior, at pH levels of 3.0 and 8.0, give the synthesized hydrogels great potential as an excellent candidate for the controlled delivery of bioactive agents.