• Journal of the Mineralogical Society of Korea
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• v.25 no.4
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• pp.185-195
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• 2012

Due to the high reduction and sorption capacity as well as the large specific surface area, nanosized mackinawite (FeS) is useful in reductively transforming chlorinated organic pollutants and sequestering toxic metals and metalloids. Due to the dynamic nature in its colloid stability, however, nanosized FeS may be washed out with the groundwater flow or result in aquifer clogging via particle aggregation. Thus, these nanoparticles should be modified such as to be built into permeable reactive barriers. This study employed coating methods in efforts to facilitate the installation of permeable reactive barriers of nanosized mackinawite. In applying the methods, nanosized mackinawite was coated on non-treated silica sand (NTS) and chemically treated silica sand (CTS). For both silica sands, the maximum coating of mackinawite occurred around pH 5.4, the condition of which was governed by (1) the solubility of mackinawite and (2) the surface charge of both silica and mackinawite. Under this pH condition, the maximum coating by NTS and CTS were found to be 0.101 mmol FeS/g and 0.043 mmol FeS/g respectively, with such elevated coatings by NTS likely linked with impurities (e.g., iron oxides) on its surface. Arsenite sorption experiments were performed under anoxic conditions using uncoated silica sands and those coated with mackinawite at the optimal pH to compare their reactivity. At pH 7, the relative sorption efficiency between uncoated NTS and coated NTS changed with the initial concentration of arsenite. At the lower initial concentration, uncoated NTS showed the higher sorption efficiency, whereas at the higher concentration, coated NTS exhibited the higher sorption efficiency. This could be attributed to different sorption mechanisms as a function of arsenite concentration: the surface complexation of arsenite with the iron oxide impurity on silica sand at the low concentration and the precipitation as arsenic sulfides by reaction with mackinawite coating at the high concentration. Compared to coated NTS, coated CTS showed the lower arsenite removal at pH 7 due to its relatively lower mackinawite coating. Taken together, our results indicate that NTS is a more effective material than CTS for the coating of nanosized mackinawite.

• Korean Security Journal
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• no.53
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• pp.63-79
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• 2017

Defence Security Command is the only military intelligence and investigation agency which is in charge of safeguarding military information and investigating specific crimes such as subversion and disloyalty in military. While the presidential security provided by Defence Security Command, along with Presidential Security Service(PSS) and the police, forms one of three pillars sustaining presidential security, its works and activities have been rarely known to the public due to the military confidentiality. This study looks into some data specialized into the presidential security among works of Defense Security Command by using various resources such as biographies of key people, media reports, and public materials. It reviews the presidential security works in a historical sense that the works have developed and changed in accordance with the historical changes of Defense Security Command, which was rooted in Counter-Intelligence Corps (Teukmubudae in Korean) in 1948 and leads to the present. The study findings are as follows. First, when the Korean War broke out in 1950 and since then the South Korea was under the threat of the North Korean armed forces and left wing forces, Counter-Intelligence Corps(Bangcheopdudae in Korean) took the lead in presidential security more than the police who was in charge of it. Secondly, even after the Presidential Security Office has founded in 1963, the role of the military on presidential security has been extended by changing its titles from Counter-Intelligence Corps to Army Security corps to Armed Forces Security Command. It has developed their provision of presidential security based on the experience at the president Rhee regime when they could successfully guard the president Rhee and the important government members. Third, since the re-establishment into Defence Security Command in 1990, it has added more security services and strengthened its legal basis. With the excellent expertise, it played a pivotal role in the G20 and other state-level events. After the establishment of the Moon Jaeinin government, its function has been reduced or abolished by the National Defense Reform Act. However, the presidential security field has been strengthening by improving security capabilities through reinforcing the organization. This strengthening of the security capacity is not only effective in coping with the current confrontation situation with the hostile North Korean regime, but also is important and necessary in conducting constant monitoring of the military movement and security-threat factors within military during the national security events.

• Applied Chemistry for Engineering
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• v.17 no.2
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• pp.183-187
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• 2006

The choice of solvents for electrolytes solutions is very important to improve the characteristics of charge/discharge in the Li-ion battery system. Such solvent systems have been widely investigated as electrolytes for Li-ion batteries. In this paper, the electrochemical properties of the solid electrolyte interphase film formed on carbon anode surface and the solvent decomposition voltage in 1 M LiPF6/EC:MA(x:y) electrolyte solutions prepared from the various mixing volume ratios are investigated by chronopotentiometry, cyclic voltammetry, and impedance spectroscopy. As a result, the solvent decomposition voltages are varied with the ionic conductivity of the electrolyte. Electrochemical properties of the passivation film were different, which are dependent on the mixture ratio of the solvents. Therefore, the most appropriate mixing ratio of EC and MA as a solvent in 1 M $LiPF_6/(EC+MA)$ system for Li-ion battery is approximately 1:3 (EC:MA, volume ratio).

• Journal of the military operations research society of Korea
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• v.34 no.3
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• pp.31-40
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• 2008

The aircraft manufacturing industry is a profitable business and has the potential to be an important export business. Our trade deficit needs to be improved in aircraft manufacturing part. Our national aircraft industry, which has been recognized for its quality in many domestic and international Air Shows, has developed the T/A-50 aircraft from the origins of the KT-1. With the ongoing development of the next generation fighter planes and helicopters, business for the next generation domestic air cargo has bright prospects. Judging by the history of the overseas air force dispatch during the Vietnam, Gulf, and Iraqi wars whose main mission was air transportation, there will be many opportunities to show the excellence of Korean air cargo in the future. The purpose of this study is to discover the optimal scale of air cargo development using the AHP method. The authors evaluated the scale of air cargo in size and capacity based on the following 5 standards used Korean developing airliner: usability, economics, technology, safety, and environmental friendliness. Then, the authors modified specific standards suitable for air cargo based on literature review Decision-making groups were chosen for suitability of expert staff in charge because they could represent for leading opinions in this specialized area especially as in practical aspects. The participants of the evaluation were pilots, transportation officers and management staff in the KAI who have experienced over 5years.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.3
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• pp.205-212
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• 2013

The objective of this study was to investigate the feasibility of replacing a conventional plate fin-tube evaporator with a spiral fin-tube evaporator by comparing the performance of domestic refrigerator-freezers adopting either the plate fin-tube evaporator or spiral fin-tube evaporator. Experiments were conducted for the domestic refrigerator-freezers using either a 2-column and 15-row plate fin-tube evaporator or three spiral fin-tube evaporators with 11, 13, and 15 tube rows (N). The optimum refrigerant charge decreased with a decrease in the number of tube rows. The power consumptions of the domestic refrigerator-freezers using the spiral fin-tube evaporators with N = 11 and 13 were 2.8% and 1.5% lower than those using the plate fin-tube evaporator, respectively. In addition, the cooling capacity of the spiral fin-tube evaporator with N = 13 was 3%-7% higher than that of the plate fin-tube evaporator under the frosting condition. In a cooling speed test, all of the evaporators showed similar performances.

• Journal of the Korean Electrochemical Society
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• v.17 no.1
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• pp.49-56
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• 2014

As an electrolyte additive, the effects of lithium bis(oxalate)borate (LiBOB) on the electrochemical properties of a carbon-coated silicon monoxide (C-coated SiO) negative electrode are investigated. The used electrolyte is 1.3M $LiPF_6$ that is dissolved in ethylene carbonate (EC), fluoroethylene carbonate (FEC), and diethyl carbonate (DEC) (5:25:70 v/v/v) with or without 0.5 wt. % LiBOB. In the LiBOB-free electrolyte, the film resistance is not so high in the initial period of cycling that lithiation is facilitated to generate the crystalline $Li_{15}Si_4$ phase. Due to repeated volume change that is caused by such a deep charge/discharge, cracks form in the active material to cause a resistance increase, which eventually leads to capacity fading. When LiBOB is added into the electrolyte, however, more resistive surface film is generated by decomposition of LiBOB in the initial period. The crystalline $Li_{15}Si_4$ phase does not form, such that the volume change and crack formation are greatly mitigated. Consequently, the C-coated SiO electrode exhibits a better cycle performance in the later cycles. At an elevated temperature ($45^{\circ}C$), wherein the effect of film resistance is less critical, the alloy ($Li_{15}Si_4$ phase) formation is comparable for the LiBOB-free and added cell to give a similar cycle performance.

• Applied Chemistry for Engineering
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• v.31 no.1
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• pp.97-102
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• 2020

Recently, various degradation mechanisms of lithium secondary battery cathode materials have been revealed. As a result, many studies on overcoming the limitation of cathode materials and realizing new electrochemical properties by controlling the degradation mechanism have been reported. Li-rich layered oxide is one of the most promising cathode materials due to its high reversible capacity. However, the utilization of Li-rich layered oxide has been restricted, because it undergoes a unique atomic structure change during the cycle, in turn resulting in unwanted electrochemical degradations. To understand an atomic structure deterioration mechanism and suggest a research direction of Li-rich layered oxide, we deeply evaluated the atomic structure of 0.4Li₂MnO₃_0.6LiNi_1/3Co_1/3Mn_1/3O₂ Li-rich layered oxide during electrochemical cycles, by using an atomic-resolution analysis tool. During a charge process, Li-rich materials undergo a cation migration of transition metal ions from transition metal slab to lithium slab due to the structural instability from lithium vacancies. As a result, the partial structural degradation leads to discharge voltage drop, which is the biggest drawback of Li-rich materials.

• Journal of Fisheries and Marine Sciences Education
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• v.13 no.1
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• pp.1-18
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• 2001

The purpose of this research was to develop curricula for the department of marine products marketing in fisheries high schools. The specific objectives were as follows; 1) To investigate the demand of students, teachers in fisheries high schools, and workers in marine products marketing for the educational program. 2) To analyze the jobs of the marine products marketing fields. 3) To develop curricula for the department of marine products marketing on the basis of the theoretical background and the result of the objective 1) and 2). In order to achieve these objectives, domestic and foreign literatures, research reports, and theses were referred to in order to know the academic classification of fisheries economics and curricula of junior colleges and universities were collected and analyzed. To achieve the first objective, the degree of the students' knowledge of marine products marketing through fisheries management textbook was investigated. And the questionnaire survey of the demand was conducted on the subject of professors at the departments of fisheries management, teachers in the charge of the related courses and those who work for marine products marketing-related firms. The questionnaire was composed of 22 items about the knowledge of marine products marketing and 27 items about the job capacity. To achieve the second objective, the occupations were surveyed on the subjects of the works who work for marine products marketing. They were sampled randomly among the marine products buyers, wholesalers, auctioneers and salespersons. The results of this research were as follows; Taking grades and credits at each subject were made out on the consultation of the experts in marine products marketing. The curriculum of the professional subjects related to marine products marketing in fisheries high schools is suggested as follows; General Fisheries(10th grade, 6 credits, curricular discretionary class), General Oceanography(10th grade, 4 credits, curricular discretionary class), Fisheries Marine Transportation Information(11th grade, 8-12 credits), Marine Products Marketing(11th grade, 8-12 credits), Fishery Sale and Management(11th grade, 8-12 credits), General Fisheries Management(11th grade, 6-8 credits), Accounting Principle(11th grade, 4-6 credits), Marine Products Processing(12th grade, 4-8 credits), Commercial Law(12th grade, 4-6 credits), Management Practice(12th grade, 4-6 credits), Computer Practical Business(12th grade, 4-6 credits), Marketing(12th grade, 4-8 credits), General Marketing Management(12th grade, 6-8 credits), Marketing Information Practical Business(12th grade, 4-6 credits) Marketing Management I(12th grade, 4-6 credits), Marketing Management II(12th grade, 4-6 credits). If this curriculum is adopted, it will meet the demands of the educational aims and the industrial society.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.22 no.4
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• pp.194-199
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• 2012

The $LiMn_{1.5}Ni_{0.5}O_4$, substituting a part of Mn with Ni in the $LiMn_2O_4$, the spinel structure has good charge-discharge cycle stability and high discharge capacity at 4.7 V. In this study $LiMn_{1.5}Ni_{0.5}O_4$ powders were synthesized by polymerization complex method. The effect on the characteristics of synthesized $LiMn_{1.5}Ni_{0.5}O_4$ powders was studied with citric acid (CA) : metal ion (ME) molar ratio (5 : 1, 10 : 1, 15 : 1, 30 : 1) and calcination temperature ($500{\sim}900^{\circ}C$). Single phase of $LiMn_{1.5}Ni_{0.5}O_4$ was observed from XRD analysis on the powders calcined at low ($500^{\circ}C$) and high temperatures ($900^{\circ}C$). The crystalline size and crystallinity increased with calcination temperature. At low calcination temperature the particle size decreased and specific surface area increased as the CA molar ratio increased. On the other hand, high particle growth rate at high calcination temperature interfered the particle size reduction and specific surface area increase induced by the increase of CA molar ratio.

• Journal of the Korean Electrochemical Society
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• v.18 no.2
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• pp.58-67
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• 2015

The effects of electrolyte additives, lithium bis(oxalate)borate (LiBOB), fluoroethylene carbonate (FEC), vinylene carbonate (VC), 2-(triphenylphosphoranylidene) succinic anhydride (TPSA), on high-temperature storage properties of $Li(Ni_{1/3}Co_{1/3}Mn_{1/3})O_2$/graphite are investigated with coin-type full cells. The 1 wt.% LiBOB-containing electrolyte showed the highest capacity retention after high temperature ($60^{\circ}C$) storage for 20 days, 86.7%, which is about 5% higher than the reference electrolyte, 1.15M lithium hexafluorophosphate ($LiPF_6$) in ethylene carbonate/ethyl methyl carbonate (EC/EMC, 3/7 by volume). This enhancement is closely related to the formation of semi-carbonate compounds originated from $BOB^-$ anions, thereby resulting in lower SEI thickness and interfacial resistance after storage. In addition, the 1 wt.% LiBOB-containing electrolyte also exhibited better cycle performance at 25 and $60^{\circ}C$ than the reference electrolyte, which indicates that LiBOB is an effective additive for high-temperature performance of $Li(Ni_{1/3}Co_{1/3}Mn_{1/3})O_2$/graphite chemistry.