• Carbon letters
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• 제14권1호
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• pp.14-21
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• 2013

Physically and chemically activated carbons (ACs) exhibited high adsorption capacities for organic and inorganic pollutants compared with other adsorbents due to their expanded surface areas and wide pore volume distribution. In this work, seven steam-ACs with different burn-off have been prepared from cotton stalks. The textural properties of these sorbents were determined using nitrogen adsorption at $-196^{\circ}C$. The chemistry of the surface of the present sorbents was characterized by determining the surface functional C-O groups using Fourier transform infrared spectroscopy, surface pH, $pH_{pzc}$, and Boehm's acid-base neutralization method. The textural properties and the morphology of the sorbent surface depend on the percentage of burn-off. The surface acidity and surface basicity are related to the burn-off percentage. A theoretical model was developed to find a mathematical expression that relates the % burn-off to ash content, surface area, and mean pore radius. Also, the chemistry of the carbon surface is related to the % burn-off. A mathematical expression was proposed where % burn-off was taken as an independent factor and the other variable as a dependent factor. This expression allows the choice of the value of % burn-off with required steam-AC properties.

• 한국환경성돌연변이발암원학회지
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• 제24권2호
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• pp.91-98
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• 2004

Although 2,3,7,8-tetrachlorodibenzo-p-dioxin(TCDD) is a powerful carcinogen in several species, limited model system exist to study carcinogenicity of this compound at cellular level. To enhance our under-standing of carcinogenicity of TCDD at cellular level, we investigated micronucleus (MN) frequency as a index of genetic toxicity and whether TCDD can transform the human cells in culture. Normal human cell lines, skin keratinocyte HaCaT, Chang liver and breast MCF10A cells were used. TCDD did not affect the cell viability of the Chang liver, HaCaT and MCF10A cells. The frequency of micronucleus was increased after treatment of TCDD for 24hr in Chang liver and HaCaT cells, but not changed in MCF10A cells. And we observed putative transformed cells in Chang liver cells exposed to 1 $\mu$M TCDD for 2 weeks. The putative transformed cells were also observed in HaCaT cells with subsequent exposure to TCDD (0.1, 1, 10, 100 nM) for 2 weeks after initial exposure to MNNG, but not observed in MCF10A cells. Collectively, these results indicate that the ability of TCDD to induce micronuclei may be involved in cellular transformation of Chang liver and HaCaT cells. Our putative TCDD-transformed cells of Chang liver and HaCaT are expected to provide a clue to the elucidation of TCDD-induced transformation pathway.

• ALGAE
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• 제32권2호
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• pp.161-170
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• 2017

Fourier Transform Infrared (FTIR) spectroscopy was used to study carbon allocation patterns in response to N-starvation in the nearly ubiquitous diatom Chaetoceros muellerii. The role of gene expression, protein synthesis and transamination on the organic composition of cells was tested by using specific inhibitors. The results show that inhibition of key processes in algal metabolism influence the macromolecular composition of cells and and prior cell nutritional state can influence a cell's response to changing nutrient availability. The allocation of C can thus lead to different organic composition depending on the nutritional context, with obvious repercussions for the trophic web. This also shows that C allocation in algal cells is highly flexible and that C (and the energy associated with its allocation) can be variably and rapidly partitioned in algal cells in response to relatively short term perturbations. Furthermore, the data confirm and extend the utility of infrared spectroscopy as a probe of the metabolic state of autotrophic cells.

• 한국재료학회지
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• 제26권12호
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• pp.696-703
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• 2016

In this study, we intensively investigated the effect of conductive additive amount on electrochemical performance of organic supercapacitors. For this purpose, we assembled coin-type organic supercapacitor cells with a variation of conductive additive(carbon black) amount; carbon aerogel and polyvinylidene fluoride were employed as active material and binder, respectively. Carbon aerogel, which is a highly mesoporous and ultralight material, was prepared via pyrolysis of resorcinol-formaldehyde gels synthesized from polycondensation of two starting materials using sodium carbonate as the base catalyst. Successful formation of carbon aerogel was well confirmed by Fourier-transform infrared spectroscopy and $N_2$ adsorption-desorption analysis. Electrochemical performances of the assembled organic supercapacitor cells were evaluated by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy measurements. Amount of conductive additive was found to strongly affect the charge transfer resistance of the supercapacitor electrodes, leading to a different optimal amount of conductive additive in organic supercapacitor electrodes depending on the applied charge-discharge rate. A high-rate charge-discharge process required a relatively high amount of conductive additive. Through this work, we came to conclude that determining the optimal amount of conductive additive in developing an efficient organic supercapacitor should include a significant consideration of supercapacitor end use, especially the rate employed for the charge-discharge process.

• Bulletin of the Korean Chemical Society
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• 제32권4호
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• pp.1310-1314
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• 2011

Sodium beta-alumina (SBA) nano-powders were synthesized by the citrate sol-gel process, and the effects of the cationic surfactant n-cetyltrimethylammonium bromide surfactant (CTAB) were investigated. The structure and morphology of the nano-powders were characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM) techniques, respectively. The effects of CTAB on the citrate sol-gel process and the SBA formation were investigated by thermo gravimetric/differential thermal analysis (TG/DTA) and Fourier transform infrared spectroscopy (FTIR). The conductivity of ceramic pellets of SBA was measured by electrochemical impedance spectroscopy (EIS). The results showed that the CTAB inhibited the agglomeration of SBA powders effectively and consequently decreased the crystallization temperature of SBA, about $150^{\circ}C$ lower than that of the sample without CTAB. The measured conductivity of SBA was $1.21{\times}10^{-2}S{\cdot}cm^{-1}$ at $300^{\circ}C$.

• 전기학회논문지
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• 제67권10호
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• pp.1317-1321
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• 2018

PVDF as a semicrystal polymer, having a structure with C-F dipole moments, has been widely investigated because of its excellent chemical stability, mechanical strength, and ferroelectricity. In this study, ferroelectic ${\beta}$ type - PVDF layer was prepared by using an electrostatic spray deposition method and the effects of the addition of Ni-nitrate in precursor solution on the properties of PVDF layer were evaluated. Crystallinity and chemical structure of the PVDF layer were analyzed by a X-ray diffraction and Fourier Transform Infrared Spectrophotometer. Surface structure and fractured cross section of the layer were examined by a field emission-scanning electron microscope. LCR meter was used to obtain the dielectric properties of the layer. As the addition of an inorganic metal salt in PVDF sol, ${\beta}$ type - PVDF crystals were appeared in the hydrated metal salts doped-layer since the strong hydrogen bondings $(O-H{\cdots}F-C)_n$ due to high polarity of OH- were formed.

• 한국농촌건축학회논문집
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• 제14권4호
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• pp.97-105
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• 2012

Winsborough Hall built by Martin L. Winehart who was the missionary of the Presbyterian Church of America in 1927 was built by Mrs. Winsborough's birthday contribution. Winsborough Hall was clearly divided into the original form built in 1927 and remodelled form by extension. Most of walls were constructed with several kinds of bricks for both sides and opening in the original form and remodelled form. Each room divided by inner wall was kept with original form because it is difficult to remodel it on the characteristics of building. But, it was confirmed through the related literatures that security of opening at some rooms and annexation of rooms through removal of the wall on the 2nd floor which was relatively easy to transform wall compared to the first floor were made. Variability of the wall affected the truss structure of roof and it created rare double truss structure. Architectural value of Winsborough Hall was in its first architectural trial using red brick in Gwangju region since 1920s. It suggested that it was differential architectural trial from Korean-Western mixed building constructed by the missionaries from 1940 to 1910 and buildings made of gray bricks prevailed from 1911 to 1920 and it showed the advancement in the architectural structure and materials.

• 한국정보과학회논문지:소프트웨어및응용
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• 제26권12호
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• pp.1542-1552
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• 1999

자료 병렬성이란 자료 집합의 원소들에 대하여 동일한 작업을 동시에 수행하므로써 얻어지는 병렬성을 말한다. 함수형 언어에서 자료 집합에 대한 반복 수행은 재귀적 자료형에 대한 재귀 함수에 의하여 표현된다. 본 논문에서는 이러한 재귀 함수를 자료 병렬 프로그램으로 변환하기 위한 병렬화 방법을 제시한다. 생성되는 병렬 프로그램의 병렬 수행 구조로는 일반적인 형태의 재귀적 자료형에 대하여 정의되는 다형적인 자료 병렬 연산을 사용하여 트리, 리스트 등과 같은 일반적인 재귀적 자료 집합에 대한 자료 병렬 수행이 가능하도록 하였다. 재귀 함수의 병렬화를 위해서는, 함수를 이루는 각각의 계산들의 병렬성을 재귀 호출에 의해 존재하는 의존성에 기반하여 분류하고, 이에 기반하여 각각의 계산들에 대한 적절한 자료 병렬 연산을 사용하는 병렬 프로그램을 생성하였다.Abstract Data parallelism is obtained by applying the same operations to each element of a data collection. In functional languages, iterative computations on data collections are expressed by recursions on recursive data structures. We propose a parallelization method for data-parallel implementation of such recursive functions. We employ polytypic data-parallel primitives to represent the parallel execution structure of the object programs, which enables data parallel execution with general recursive data structures, such as trees and lists. To transform sequential programs to their parallelized versions, we propose a method to classify the types of parallelism in subexpressions, based on the dependencies of the recursive calls, and generate the data-parallel programs using data-parallel primitives appropriately.

• Journal of Electrical Engineering and Technology
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• 제10권6호
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• pp.2277-2287
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• 2015

In recent times, multilevel inverters are given high priority in many large industrial drive applications. However, the reliability of multilevel inverters are mainly affected by the failure of power electronic switches. In this paper, open-switch and short-switch failure of multilevel inverters and its identification using a high performance diagnostic system is discussed. Experimental and simulation studies were carried out on five level cascaded H-Bridge multilevel inverter and its output voltage waveforms were analyzed at different switch fault cases and at different modulation index values. Salient frequency domain features of the output voltage signal were extracted using the discrete wavelet transform multi resolution signal decomposition technique. Real time application of the proposed fault diagnostic system was implemented through the LabVIEW software. Artificial neural network was trained offline using the Matlab software and the resultant network parameters were transferred to LabVIEW real time system. In the proposed system, it is possible to precisely identify the individual faulty switch (may be due to open-switch (or) short-switch failure) of multilevel inverters.

• Mass Spectrometry Letters
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• 제9권3호
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• pp.81-85
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• 2018

In this study, the chemical composition of bacterial melanin isolated from the Streptomyces glaucescens strain was elucidated by ultra-high-resolution Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. Ultra-high-resolution mass profiles of the microbial melanin product were acquired using a 15 Tesla FT-ICR mass spectrometer in positive and negative ion modes via electrospray ionization to obtain more complete descriptions of the molecular compositions of melanin-derived organic constituents. A mass resolving power of 500,000 (at m/z 400) was achieved for all spectra while collecting 400 scans per sample with a 4 M transient. The results of this analysis revealed that the melanin pigment isolated from S. glaucescens predominantly exhibits CHON and CHO species, which belong to the proteins class of compounds, with the mean C/O and C/N ratios of 4.3 and 13.1, thus suggesting that the melanin could be eumelanin. This analytical approach could be utilized to investigate the molecular compositions of a variety of natural or synthetic melanins. The compositional features of melanins are important for understanding their formation mechanisms and physico-chemical properties.