• Clean Technology
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• v.28 no.3
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• pp.210-217
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• 2022

Boron(B) is a rare resource used for various purposes such as glass, semiconductor materials, gunpowder, rocket fuel, etc. However, Korea depends entirely on imports for boron. Considering the global boron reserves and its current production rate, boron will be depleted on earth in 50 years. Thus, a process including proper adsorbent materials recovering boron from seawater is demanded. This research proposed carbonized nanofibers prepared from electrospun PAN(polyacrylonitrile) mats as promising materials to adsorb boron in aqueous solution. First, the mechanism of boron adsorption on carbonized nanofibers was investigated by DFT(density functional method)-based molecular modeling and the calculated energetics demonstrated that the boron chemisorption on the nitrogen-doped graphene surface by a two-step dehydration is possible with viable activation energies. Then, the electrospun PAN mats were stabilized in air and then carbonized in an argon atmosphere before being immersed in the boric acid aqueous solution. Analytically, SEM(scanning electron microscopy) and Raman measurements were employed to confirm whether the electrospinning and carbonization of PAN mats proceeded successfully. Then, XPS(X-ray photoelectron spectroscopy) peak analysis showed whether the intended nitrogen-doped carbon nanofiber surface was formed and boron was properly adsorbed on nanofibers. Those results demonstrated that the carbonized nanofibers prepared from electrospun PAN mats could be feasible adsorbents for boron recovery in seawater.

• Science of Emotion and Sensibility
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• v.25 no.4
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• pp.45-52
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• 2022

Recently, interest in and demand for sensors that recognize physical activity and their products are increasing. In particular, the development of wearable materials that are flexible, stretchable, and able to detect the user's biological signals is drawing attention. In this study, an experiment was conducted to improve the dip-coating efficiency of a single-walled carbon nanotube dispersion solution after fine holes were made in a hydrophobic material with a micro needle. In this study, dip-coating was performed with a material that was not penetrated, and comparative analysis was performed. The electrical conductivity of the sensor was measured when the sensor was stretched using a strain universal testing machine (Dacell Co. Ltd., Seoul, Korea) and a multimeter (Keysight Technologies, Santa Rosa, CA, USA) was used to measure resistance. It was found that the electrical conductivity of a sensor that was subjected to needling was at least 16 times better than that of a sensor that was not. In addition, the gauge factor was excellent, relative to the initial resistance of the sensor, so good performance as a sensor could be confirmed. Here, the dip-coating efficiency of hydrophobic materials, which have superior physical properties to hydrophilic materials but are not suitable due to their high surface tension, can be adopted to more effectively detect body movements and manufacture sensors with excellent durability and usability.

• Clean Technology
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• v.30 no.3
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• pp.159-174
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• 2024

The rapid increase in energy consumption based on fossil fuels is accelerating global warming. In particular, the road transportation sector has high carbon dioxide emissions, so transitioning towards electric vehicles is recommended. Thus, the importance of secondary batteries is increasing. Secondary batteries are reversible batteries that use energy and can be reused through a charging and discharging process. Currently, lithium-ion batteries are widely used. Secondary batteries place importance on six major factors: energy, output, lifespan, environmental friendliness, cost, and stability. Research is actively being conducted to satisfy all six factors by understanding the material characteristics of each component of the battery. As it is difficult to move away from lithium as a cathode material, researchers are investigating higher performance materials that mix materials such as cobalt, nickel, manganese, and aluminum with lithium and use graphite, silicon, and lithium metal to increase capacity. In the case of electrolytes, liquid electrolytes are still mainly used. However, solid electrolytes are being studied due to their stability, but additional research must be conducted to satisfy the energy and output factors. This review paper aims to provide an understanding of secondary batteries through an overview of secondary batteries, the materials and characteristics of their components, their technological trends, and their associated companies.

• Journal of the Korean Electrochemical Society
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• v.3 no.2
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• pp.100-103
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• 2000

Polymeric gel electrolytes based on polyacrylronitile blended with poly(vinylidene fluoride-co-hexafluoro-propylene)(P(VdF-co-HFP), which were reinforced with glass fiber cloth(GFC) to increase the mechanical strength, were prepared for the practical use in secondary battery. Test cell consisting of $LiCoO_2$ as a cathode and mesophase pich-based ca.bon fiber (MCF) as an anode material showed a capacity of 110 mAh/g based on the cathode weight at 0.2C rate at room temperature. Over $80\%$ of initial capacity was retained after 400cycles, indicating that GFC is suitable for a reinforcing material to increase the mechanical strength of gel based electrolytes.

• KSBB Journal
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• v.23 no.4
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• pp.285-290
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• 2008

Various methods (OECD 301B, ISO 9439 and ASTM 5864) for biodegradability test of lubricants were reviewed, and a standard procedure was developed. Most lubrication products are released in rivers or sea then is degraded by microbial action in aerobic condition. Most international method are based on $CO_2$ evolution test. Inoculum obtained from a sewage disposal plant and test compound are cultivated in a mineral medium. Organic carbon of the test compound is degraded and oxidized through the enzymatic actions of inoculum, and ultimately mineralized to carbon dioxide. Biodegradability test conditions of lubricant oils were optimized. The highest biodegradability was achieved when the same medium as in ASTM 5864 and inoculum concentration of $10^4{\sim}10^5$ cell/L were used. The optimum standard materials were selected as aniline and sodium acetate. Additionally the effects of inoculum type on microbial growth and biodegradability were examined. Finally the standard operating procedure (SOP) for biodegradability test method was proposed.

• Korean Journal of Soil Science and Fertilizer
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• v.24 no.2
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• pp.130-136
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• 1991

This study was carried out under the appropriate conditions of moisture content(60~70%), C/N ratio(25~30), and C/P ratio(30~35) on the mixed materials of cow dung and rice hulls. The good mixing ratio of cow dung and rice hulls was woth to one on volume basis which was able to adjust to the moisture content and C/N ratio of the mixing material. During fermentation pile period, the mixing ratio of control, non-aerated pile with turning was two to one and that of aerated pile with blower was two ti one. In fermentation pile period, average temperature of aerated pile was $55{\sim}65^{\circ}C$ and it was more higher than control of $40{\sim}50^{\circ}C$ non-aerated pile. While total nitrogen content of aerated pile was lower than that of the control, total carbon content and C/N ratio were higher. In cure pile period, the temperature and C/N ratio of aerated pile were increased at the early stage and then they were decreased, but total nitrogen and total carbon contents of aerated pile were increased in process of days. Final product in aerated pile had more fine particles and was good for the growth of cucumber seedlings than control.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.4
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• pp.791-799
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• 2015

This study focuses on the algae growth restraining. Many researches on a critical damage from algae growth are published, but it is hard to find how th restrain. Abnormal algae increasing is a problem, because it makes red tides, biodeterioration, etc. Therefore this study aims to decrease the damage from algae growth. Some metal ions have been used microorganism killing materials from old times. Especially, Cu ions are highly effective. Based on these uses of the metal ions, a functional mortar which restrains algae growth is developed. The mortar contains soluble glass which dissolve in water. The soluble glass was made of Cu ions and phosphates. When the soluble glass is dissolved, Cu ions are soaked out stably from the soluble glass. Culture mediums which incubate algae were made to evaluate the developed mortar specimens. Culture mediums were filled with fresh water and sea water. Algae were incubated for fourteen days in culture mediums. The evaluating methods are measuring volume of the dissolved organic carbon and the chlorophyll. Using these two measurements, the mortar specimens are judged that can restrain algae or not. According to the result, the functional mortars of culture medium filled with fresh and sea water shows similar trend. The functional mortar for restraining algae growth performs that's role well.

• The Journal of the Acoustical Society of Korea
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• v.30 no.1
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• pp.33-41
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• 2011

To substitute TLS in the hybrid system which is combined with Sagnac interferometer and fiber bragg grating (FBG) it is necessary to investigate how the laser source (TLS and CW) and sensor material variate the response of fiber optic sensor. Two different hollow cylinder type mandrel materials are proposed which are PTFE and PTFE+carbon and 18 m optical fiber is wounded at the mandrel surface. CW laser source experiments had been done in the oil tank which is filled with transformer oil in the 1 kHz~20 kHz frequency range. Also Sagnac interferometer fiber optic sensor is combined with FBG called hybrid system and TLS used as a light source. Based on the experimental results PTFE sensor showed more higher magnitude of detection signal rather than carbon sensor and this result is agreement with the McMahon's theoretical results. Phase variation is inversely proportional to the elastic modulus of the mandrel material. In PTFE fiber sensor, tunable laser source showed more higher performance rather than CW case. Therefore, TLS fiber optic sensor can be applied to the hybrid system which is combined with Sagnac and FBG.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.12
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• pp.4963-4968
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• 2014

Background: We evaluated whether providing health risk appraisal for Koreans (KHRA) in terms of 'health age' during smoking cessation program would effectively help smokers quit smoking or not. Materials and Methods: A total of 332 male smokers aged between 30-65 years old, registered for a smoking cessation program in a public health center in a city, were recruited and underwent a baseline survey from January 2010 to February 2011. They were then prospectively randomized to a conventional counseling group (n=165) or a KHRA group (n=167), and received conventional counseling or KHRA-based counseling for six months. Abstinence rates were identified through carbon monoxide measurement (at the $4^{th}$ and $24^{th}$ weeks) or urinary cotinine level (at the $12^th$ week). Results: The abstinence rate confirmed by exhaled carbon monoxide was significantly higher in the KHRA group (61.1%) than the control group (49.1%) at the $4^{th}$ week (absolute difference 12.0%, 95% CI: 1.4%-22.6%). However, there was no difference in abstinence rates between the two groups at the 12th and 24th weeks. The predicting factors of 24 week's smoking cessation success were age, older than 50 years old (OR 2.02, 95% CI: 1.16-3.52), lower Fagerstr$\ddot{o}$m Test for Nicotine Dependence score less than 4 (OR 1.84, 95% CI: 1.03-3.29), and higher Self Efficacy/Temptation score (OR 1.79, 95% CI: 1.05-3.06). Conclusions: Smoking cessation counseling with KHRA could be effective compared to conventional counseling in the short period of smoking cessation. Further study is needed to evaluate the long-term efficacy of KHRA in tobacco dependence treatment and to establish the indication and target population of this tool.

• Composites Research
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• v.23 no.3
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• pp.31-36
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• 2010

A new material, carbon-nanofiber/polypyrrole (CNF/PPy) composite films, with different CNF weight ratios were fabricated electrochemically. Compared to the fabrication process based on simple physical mixing, the flexibility of the new film has been improved much better than the previous similar material. Pure PPy films were also fabricated by the new electrochemical process for the comparison of difference. Several SEM images were taken at two locations (electrode-side and solution-side) and at the cross section of the samples. Electrical conductivity of the composite films was measured by the four-probe method. The conductivity of the pure PPy film 0.013cm thick was 79.33S/cm. The CNF/PPy composite film with 5% CNF showed a conductivity of 93S/cm. One with 10% CNF showed a conductivity of 126 S/cm. The conductivity of PPy improves, as the CNF weight ratio increases. The good conductivity of CNF/PPy composites makes them a candidate for a small bending actuator. A bending sensor consists of PPy and PVDF, which can be operated in the air, was designed and the bending deflection was calculated using FEM.