• Journal of the Korean Electrochemical Society
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• v.20 no.2
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• pp.34-40
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• 2017

Electric double layer capacitors (EDLC: electric double layer capacitors) have drew attention as an energy storage device for the next generation because of their outstanding power capability and durability. But their usage is somewhat limited due to low energy density over secondary batteries. One of methods to improve the energy of EDLC is expanding the voltage window of cell operation by increasing the charge cut-off voltage. In this study, $SBP-BF_4$ (spirobipyrrolidinium tetrafluoroborate), $TEA-BF_4$ (tetraethylammonium tetraflouroborate) and $EMI-BF_4$ (1-ethyl-3-methylimidazolium tetrafluoroborate) in AN (acetonitrile) were selected to evaluate the possibility of application at high voltage environment. The LSV (linear sweep voltammetry) measurements showed that the 1.5M SBP-BF4/AN electrolyte was stable over a wide potential window and showed the best electrochemical performance compared to other combinations of electrolytes at high voltage environments (over 3.0 V). Furthermore, TMSP (tris(trimethylsilyl) phosphite) was applied to 1.5M SBP-BF4/AN in order to maintain stable performance at high voltage for the long period of time. The electrolyte with TMSP additive showed the capacity retention of 93% after 10,000 cycles at 3.3 V.

• Journal of the Korean Institute of Gas
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• v.15 no.5
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• pp.25-30
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• 2011

Biogas obtained from the biodegradable organic wastes in an anaerobic digester consists of $CH_4$ and inert gases such as $CO_2$ and $N_2$. Since the composition of biogas varies by anaerobic digester conditions and the origin of wastes, it is necessary to respond to these variations so as to make stable combustion and accomplish high efficiency when it is used as a fuel for power generating SI engines. In this study, efforts have been made to investigate the effect of changes in the calorific values of biogas on the engine performance and exhaust characteristics. The biogas was simulated by supplying of $CH_4$ with $N_2$ dilution of various ratios, and ECM was developed to achieve accurate control of ignition and combustion. The results show that as the $CH_4$ concentration of the biogas decreases, the optimal spark timing is advanced due to the elevated thermal capacity and lowered $O_2$ concentration of the in-cylinder charge. Furthermore, since combustion temperature was reduced by increased inert gas, $NO_x$ emissions decreased, whereas THC emissions increased.

• Journal of the Korean Institute of Rural Architecture
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• v.19 no.1
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• pp.11-22
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• 2017

The purpose of this study is to analyze the actual situation of residents' participation in rural development projects, to identify their performance and problems, and suggest ways to develop desirable villages in rural areas. From reviewing relevant pre-studies, this study was done by interview, questionnaire, and observation targeting 140 leaders and residents of exampled village of the project in Jeollanam-do, as well as by listening opinions of relative experts. This study is largely classified into 4 parts, review of character and appearing background of village development project, review of theoretical discussion about residents' participation, evaluation of accomplishments and analysis of participation, and establishing a model for habitants-participating village development project and how to improve it. As a result of questionnaire, it was found urgent for habitants to convert their thinking about village development and their participation in it, to realize a model of this project, as well as political stimulus to promote that. Therefore, measures must be required to improve current village development projects and to promote them. First of all, a preparation period is required to sufficiently provide the village where habitants are willing to participate in, from the state of place selection. Besides, it is required to run away from profit-making businesses aiming at foreign people, to improvement of residents' welfare in a long term, and enhanced resources management in a broad view. Waste of working expenses seems to be solved through direct operation by a corporation in charge of profit-making businesses, under superstition of residents' community. Finally conclusion, expansion and practicalization of education to residents are essential, to promote their participation in rural development projects. Especially it must be practical education for habitants such as 'community-ship' or 'technology education in each interesting part,' rather than tour of other villages and unilateral lectures from experts. Along with this, a long term plan and systematic participation is more essential. Since planning itself can be mutual learning to enhance residents' capacity, a chance must be established to discuss and plan each part including resources-research, by making them participate in.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.4 no.3
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• pp.235-243
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• 2006

In this study, an experimental study on the sorption properties of uranium(VI) onto a bentonite colloid generated from Gyeongju bentonite which is a potential buffer material in a high-level radioactive waste repository was performed as a function of the pH and the ionic strength. The bentonite colloid prepared by separating a colloidal fraction was mainly composed of montmorillonite. The concentration and the size fraction of the prepared bentonite colloid measured using a gravitational filtration method was about 5100 ppm and 200-450 nm in diameter, respectively. The amount of uranium removed by the sorption reaction bottle walls, by precipitation, and by ultrafiltration was analyzed by carrying out some blank tests. The removed amount of uranium was found not to be significant except the case of ultrafiltration at 0.001 M $NaClO_4$. The ultrafiltration was significant in the lower ionic strength of 0.001 M $NaClO_4$ due to the cationic sorption onto the ultrafilter by a surface charge reversion. The distribution coefficient $K_d$ (or pseudo-colloid formation constant) of uranium(VI) for the bentonite colloid was about $10^4{\sim}10^7mL/g$ depending upon pH and ionic strength of $NaClO_4$ and the $K_d$ was highest in the neutral pH around 6.5. It is noted that the sorption of uranium(VI) onto the bentonite colloid is closely related with aqueous species of uranium depending upon geochemical parameters such as pH, ionic strength, and carbonate concentration. As a consequence, the bentonite colloids generated from a bentonite buffer can mobilize the uranium(VI) as a colloidal form through geological media due to their high sorption capacity.

• Journal of the Korea Concrete Institute
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• v.29 no.3
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• pp.237-248
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• 2017

Frequent terror or military attack by explosion, impact, fire accidents have occurred recently. These attacks and incidents raised public concerns and anxiety of potential terrorist attacks on important infrastructures. However, structural behavioral researches on prestressed concrete (PSC) infrastructures such as Prestressed Concrete Containment Vessel (PCCV) and Liquefied Natural Gas (LNG) storage tanks under extreme loading are significantly lacking at this time. Also, researches on possible secondary fire scenarios after terror and bomb explosion has not been performed yet. Therefore, a study on PSC structural behavior from an blast-induced fire scenario was undertaken. To evaluate the blast-fire combined resistance capacity and its protective performance of bi-directional unbonded PSC member, blast-fire tests were carried out on $1,400mm{\times}1,000mm{\times}300mm$ PSC specimens. Blast loading tests were performed by the detonation of 25 kg ANFO explosive charge at 1.0 m standoff distance. Also, fire and blast-fire combined loading were tested using RABT fire loading curve. The test results are discussed in detail in the paper. The results can be used as basic research references for related research areas, which include protective design simulation under blast-fire combined loading.

• Korean Chemical Engineering Research
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• v.54 no.6
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• pp.746-752
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• 2016

In this study, soft carbon was prepared by carbonization of carbon precursor (pitch) obtained from PFO (pyrolysis fuel oil) heat treatment. Three carbon precursors prepared by the thermal reaction were 3903 (at $390^{\circ}C$ for 3 h), 4001 (at $400^{\circ}C$ for 1 h) and 4002 (at $400^{\circ}C$ for 2 h). After the prepared soft carbon was ground to a particle size of $25{\sim}35^{\circ}C$, the soft carbon was synthesised by the chemical treatment with boric acid ($H_3BO_3$). The prepared soft carbon were analysed by XRD, FE-SEM and XPS. Also, the electrochemical performances of soft carbon were investigated by constant current charge/discharge test, cyclic voltammetry and impedance tests in the electrolyte of $LiPF_6$ dissolved inorganic solvents (EC:DMC=1:1 vol%+VC 3 wt%). The coin cell using soft carbon of $25{\sim}35^{\circ}C$ with 3903 soft carbon ($H_3BO_3$/Pitch=3:100 in weight) has better initial capacity and efficiency (330 mAh/g, 82%) than those of other coin cells. Also, it was found that the retention rate capability of 2C/0.1C was 90% after 30 cycles.

• Journal of the Korean Electrochemical Society
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• v.4 no.2
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• pp.53-57
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• 2001

When an EV is parked for a long period time, the battery capacity naturally decreases due to selfdischarge. Therefore, this effect must be considered for the accurate measurement of the state of charge of EV battery. Battery selfdischarge simulations using the design of experiments among computer simulation methods are compared with experimental data for Ni/MH batteries for electric vehicles. The motivation is to predict the selfdischarge rate of the battery for electric vehicle at all temperature conditions and standing time when electric vehicle could be operated. We developed a general equation representing the seudischarge rate of the electric vehicle battery using design of experiments, and the equation is determined by temperature and standing time of the battery. We selected Ni/MH battery, 12 V-95 Ah, for pure electric vehicle for this study. ID develop the equation using design of experiments we selected temperature range of $-20^{\circ}~30^{\circ}C$ and standing time of 1 day$\~15$ days. We conducted several selfdischarge tests of Ni/MH battery to verify the integrity of the equation. The results showed that the computation values were in good agreement with experimental data.

• Journal of the Korean Electrochemical Society
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• v.15 no.1
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• pp.27-34
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• 2012

$Li_3V_2(PO_4)_3$/carbon composite materials are synthesized from a sucrose-containing precursor. Amorphous $Li_3V_2(PO_4)_3/C$ (a-LVP/C) and crystalline $Li_3V_2(PO_4)_3/C$ (c-LVP/C) are obtained by calcining at $600^{\circ}C$ and $800^{\circ}C$, respectrively, and electrochemical performance as the negative electrode for lithium secondary batteries is compared for two samples. The a-LVP electrode shows much larger reversible capacity than c-LVP, which is ascribed to the spatial $Li^+$ channels and flexible structure of amorphous material. In addition, this electrode shows an excellent rate capability, which can be accounted for by the facilitated $Li^+$ diffusion through the defect sites. The sloping voltage profile is another advantageous feature for easy SOC (state of charge) estimation.

• KSBB Journal
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• v.17 no.2
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• pp.153-157
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• 2002

A fusion protein, consisting of a human epidermal growth factor as the recognition domain and human angiogenin as the toxin domain, can be used as a targeted therapeutic against breast cancer cells among others. The fusion protein was expressed as an inclusion body in recombinant E. coli, yet when the conventional solution-phase refolding process was used the refolding yield was very low due to severe aggregation, probably because of the opposite surface charge resulting from the vastly different pl values of each domain. Accordingly the solid-phase refolding process, which exploits the ionic interactions between a solid matrix and the protein, was tried, however the ionic binding yield was also very low regardless of the resins and pH conditions used. Therefore, to provide a higher affinity toward the solid matrix, six Iysine residues were tagged to the N-terminus of the hEGF domain. When cation exchange resins, such as heparin- or CM-Sepharose, were used as the matrix, the adsorption capacity increased 2.5~3-fold and the subsequent refolding yield increased nearly 15-fold compared to the conventional process. A similat result was also obtained when an Ni-NTA metal affinity resin was used.

• Journal of the Korean Electrochemical Society
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• v.4 no.3
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• pp.104-108
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• 2001

Naphthalene derived mesophase pitch WP) was spun into short fibers by using melt-blown technology. The pitch fibers oxidative stabilization were carried out heating rates of $2^{\circ}C/min,\;5^{\circ}C/min\;and\; 10^{\circ}/min$. The heating rate was a key factor to maximate the capacity of the Li-ion secondary battery through controlling the morphology of the graphitized fiber. The diameters of the melt-blown fibers prepared were in the range of $4{\mu}m\~16{\mu}m$ with functions of air jet speed, air temperature and the temperature of the nozzle. The graphitized fibers of $10{\mu}m$ diameters showed various morphological structure with heating rate of the stabilization. Radial, radial-random and skin-core cross-sectional structure of the fibers were observed at the respective heating rate of $2^{\circ}C/min\;5^{\circ}C/min\;and\;10^{\circ}C/min$. Most crystalline structure of graphite was obtained from the fiber stabilized at heating rate of $10^{\circ}C/min$ exhibiting the best anode performance with 400 mAh/g of capacitance and $96.8\%$ of charge/discharge efficiency.