• Korean Journal of Materials Research
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• v.19 no.4
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• pp.192-197
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• 2009

Carbon nanotubes (CNT) were used as a catalyst support where catalytically active Pd and Pt metal particles decorated the outside of the external CNT walls. In this study, Pd and Pt nanoparticles supported on $HNO_3$-treated CNT were prepared by microwave-assisted heating of the polyol process using $PdCl_2$ and $H_2PtCl_6{\codt}6H_2O$ precursors, respectively, and were then characterized by SEM, TEM, and Raman. Raman spectroscopy showed that the acid treated CNT had a higher intensity ratio of $I_D/I_G$ compared to that of non-treated CNT, indicating the formation of defects or functional groups on CNT after chemical oxidation. Microwave irradiation for total two minutes resulted in the formation of Pd and Pt nanoparticles on the acid treated CNT. The sizes of Pd and Pt nanoparticles were found to be less than 10 nm and 3 nm, respectively. Furthermore, the $SnO_2$ films doped with CNT decorated by Pd and Pt nanoparticles were prepared, and then the $NO_2$ gas response of these sensor films was evaluated under $1{\sim}5\;ppm$ $NO_2$ concentration at $200^{\circ}C$. It was found that the sensing property of the $SnO_2$ film sensor on $NO_2$ gas was greatly improved by the addition of CNT-supported Pd and Pt nanoparticles.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.3
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• pp.181-185
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• 2020

Hazardous and noxious substance (HNS) detection sensors were fabricated using multi-walled carbon nanotubes (MWCNTs) and various binder materials for ion batteries. To obtain uniformly printed films, the printing precision according to the substrate cleaning method was monitored, and the printing paste mixing ratio was investigated. Binders were prepared using styrene butadiene rubber + carboxymethyl cellulose (SBR+CMC), polyvinylidene fluoride + n-methyl-2-pyrrolidene (PVDF+NMP), and mixed with MWCNTs. The surface morphology of the printed films was examined using an optical microscope and a scanning electron microscope, and their electrical properties are investigated using an I-V sourcemeter. Finally, sensing properties of MWCNT printed films were measured according to changes in the concentration of the chemical under the various applied voltages. In conclusion, the MWCNT printed films made of (SBR+CMC) were found to be feasible for application to the detection of hazardous and noxious chemicals spilled in seawater.

• Journal of Mechanical Science and Technology
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• v.20 no.6
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• pp.738-747
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• 2006

The friction behaviour of Si-wafer, diamond-like carbon (DLC) and two self-assembled monolayers (SAMs) namely dimethyldichlorosilane (DMDC) and diphenyl-dichlorosilane (DPDC) coated on Si-wafer was studied under loading conditions in milli-newton (mN) range. Experiments were performed using a ball-on-flat type reciprocating micro-tribo tester. Glass balls with various radii 0.25 mm, 0.5 mm and 1 mm were used. The applied normal load was in the range of 1.5 mN to 4.8 mN. Results showed that the friction increased with the applied normal load in the case of all the test materials. It was also observed that friction was affected by the ball size. Friction increased with the increase in the ball size in the case of Si-wafer. The SAMs also showed a similar trend, but had lower values of friction than those of Si-wafer In-terestingly, for DLC it was observed that friction decreased with the increase in the ball size. This distinct difference in the behavior of friction in DLC was attributed to the difference in the operating mechanism. It was observed that Si-wafer and DLC exhibited wear, whereas wear was absent in the SAMs. Observations showed that solid-solid adhesion was dominant in Si-wafer, while plowing in DLC. The wear in these two materials significantly Influenced their friction. In the case of SAMs their friction behaviour was largely influenced by the nature of their molecular chains.

• Korean Journal of Agricultural and Forest Meteorology
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• v.22 no.4
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• pp.233-238
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• 2020

Process-based model (PBM), based on the interactions between endogenous physiological processes and many environmental factors, can be a powerful tool for estimating crop growth and productivity. Carbon acquisition and biomass accumulation are the main components in PBM, so it has become important to understand and integrate gas exchange process in crop model. This study aimed to assess the applicability of FvCB model (a leaf model of C3 photosynthesis proposed by Farquhar, von C aemmerer, and Berry (1980)) in onion (Allium cepa L.). For parameterization, two early-maturing onion cultivars, 'Singsingball' and 'Thunderball', grown in a temperature gradient plastic film house, were used in measuring leaf net CO2 assimilation rate (A), and then, parameter estimation was carried out for four parameters including Vcmax (maximum rate of carboxylation), Jmax (maximum rate of electron transport), TPU (rate of triose phosphate utilization), and Rd (Dark respiration rate). The gas-exchange model calibrated in this research is expected to be able to explain the photosynthetic responses of onion under various environmental conditions (R2=0.95***).

• Tribology and Lubricants
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• v.38 no.1
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• pp.8-14
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• 2022

Amorphous carbon (a-C) has excellent wear resistance and, therefore is used as a coating to protect numerous mechanical components to prolong their lifetimes. Among the a-C coatings, diamond-like carbon (DLC) and DLC-containing silicon (Si-DLC) receive extensive attention owing to their enhanced wear resistance and low frictional characteristics. In this study, the friction and wear characteristics of DLC and Si-DLC coatings are analyzed. For comparative analysis, DLC-coated and Si-DLC-coated vanes are utilized with the counterpart of a roller for the friction tests. Since the lubricated mechanical components are generally vulnerable to wear when a lubricant film does not form properly, friction tests are conducted under boundary lubrication conditions to promote wear. A cylinder-on-cylinder type tribometer is used to perform the friction tests with various normal load conditions. After the friction test, a 3D laser confocal microscope is used for quantifying the wear volume to calculate the wear rate of each specimen. Consequently, the DLC-coated specimen shows a lower coefficient of friction (COF) and wear rate than the specimen without the coating, while the Si-DLC coating shows a higher COF than the bare specimen. The results of this study are expected to contribute to improving the efficiency and reliability of compressors.

• Journal of Bio-Environment Control
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• v.19 no.2
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• pp.109-116
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• 2010

Chicons are kinds of sprout vegetables which forced from the roots of chicory (Cichorium intybus L.). Experiments were performed to investigate the proper cultivation period and region of chicories which are 3 different cultivars for improving storability of chicon. The fresh weight of chicon packed with 20 ${\mu}m$ LDPE film decreased less than 0.5% during the storage at $10^{\circ}C$ in all treatments, and Chuncheon region treatment and 'Focus' cultivar treatment showed higher fresh weight loss than the others. And it decreased higher, as the cultivation periods was longer. The oxygen content in film was from 8% to 17% during storage at $10^{\circ}C$. There was not any significantly different oxygen content among cultivar treatments and cultivation region treatments, but 100 days' cultivation period treatment showed the highest content than the others. The carbon dioxide content in film showed around 3% during storage at $10^{\circ}C$. It also did not influenced by cultivars and cultivation regions, but 100 days' cultivation period treatment showed the lowest content than the others. The ethylene content in film was changed dramatically from 2 to 14 ${\mu}l{\cdot}l^{-1}$, and it showed around 8 ${\mu}l{\cdot}l^{-1}$ as approaching to 21 days after storage at $10^{\circ}C$. The visual quality of chicon deteriorated below marketability level from 12 days after storage at $10^{\circ}C$, and that of 'Metafora' cultivars decreased the highest. That of Pyeongchang region treatment was kept higher, and 'Vintor' cultivar treatment showed highest visual quality than the others which were grown in Pyeongchang region. The firmness of chicon increased, as the cultivation period was longer regardless of cutlivars and cultivation regions. The russet spotting that is ethylene injury symptom of chicon appeared at the latter term of storage and was higher in Chuncheon region treatment. Conculsionally, chicory that is for producing chicon should be grown more than 120 days in Kangwon region and grown in high-land region like Pyeongchang to improve the storability of chicon.

• Korean Journal of Soil Science and Fertilizer
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• v.40 no.4
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• pp.311-325
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• 2007

The concept of metal bioavailability, rather than total metal in soils, is increasingly becoming important for a thorough understanding of risk assessment and remediation. This is because bioavailable metals generally represented by the labile or soluble metal components existing as either free ions or soluble complexed ions are likely to be accessible to receptor organismsrather than heavy metals tightly bound on soil surface. Consequently, many researchers have investigated the bioavailability of metals in both soil and solution phases together with the key soil properties influencing bioavailability. In order to study bioavailability changes various techniques have been developed including chemical based extraction (weak salt solution extraction, chelate extraction, etc.) and speciation of metals using devices such as ion selective electrode (ISE) and diffusive gradient in the thin film (DGT). Changes in soil metal bioavailability typically occur through adsorption/desorption reactions of metal ions exchanged between soil solution and soil binding sites in response to changes in environment factors such as soil pH, organic matter (OM), dissolved organic carbon (DOC), low-molecular weight organic acids (LMWOAs), and index cations. Increasesin soil pH result in decreases in metal bioavailability through adsorption of metal ions on deprotonated binding sites. Organic matter may also decrease metal bioavailability by providing more negatively charged binding sites, and metal bioavailability can also be decreases as concentrations of DOC and LMWOAs increase as these both form strong chelate complexeswith metal ions in soil solution. The interaction of metal ions with these soil properties also varies depending on the soil and metal type.

• Journal of Bio-Environment Control
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• v.19 no.1
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• pp.49-54
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• 2010

The study was conducted to compare the postharvest physiology and storability of fresh cut paprika fruits classified by normal, blossom end rot(BER), and misshapen (or knots) fruit. Some disordered paprika fruits that were produced frequently during high temperature season in highland, were sorted out to non-marketable products. These fruits are mostly wasted, but some of them may be used for fresh cut. The respiration rate of fresh cut paprika fruits was lower and ethylene production rate was higher in normal fruits than in disordered fruits, but there was no significant difference. The fresh-cut paprika fruits were stored in MAP conditions at $4^{\circ}C$, $9^{\circ}C$ and room temperature in 25 ${\mu}m$ and 50 ${\mu}m$ thickness ceramic film packaging. The fresh weight of fresh cut paprika fruits decreased below to 1.1% regardless of fruit types, but the fresh weight loss increased in thinner packaging materials and lower storage temperatures. There were not significant different carbon dioxide and oxygen contents in MAP of all fruit types, while $4^{\circ}C$ storage temperature treatment and 25 ${\mu}m$ thickness ceramic film treatment had lower carbon dioxide and higher oxygen contents. Moreover, the carbon dioxide and oxygen contents were changed rapidly at 9 days in $4^{\circ}C$ storage and at 6 days in $9^{\circ}C$ storage when the visual quality of fresh cut decreased dramatically. The ethylene concentration of packages was below 7 ${\mu}l{\cdot}l^{-1}$ in all treatments during storage, while the treatments of thinner packaging material and lower storage temperature showed lower ethylene concentration. The fresh cut of disordered fruits showed less visual quality than normal fruit treatment in both $4^{\circ}C$ and $9^{\circ}C$ storage temperatures, but there was no significant difference. The value of $4^{\circ}C$ treatment that measured 12 days in storage was higher than $9^{\circ}C$ treatment that measured 9 days in storage. The results suggest that the disordered fruits may be used to fresh cut product without any concerns that they will decreased the value of commodities more quickly than the fresh cut made of marketable paprika fruits. As the fresh cut paprika fruits stored in MAP condition, the more effective storage temperature is $4^{\circ}C$ that may have induced chilling injury a whole fruit of the paprika.

• Journal of the Korean Ceramic Society
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• v.53 no.4
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• pp.393-399
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• 2016

We have successfully fabricated 3D (3-dimensional) nanostructures of $TiO_2$ coated with a $g-C_3N_4$ layer via hydrothermal and sintering methods to enhance photoelectrochemical (PEC) performance. Due to the coupling of $TiO_2$ and $g-C_3N_4$, the nanostructures exhibited good performance as the higher conduction band of $g-C_3N_4$, which can be combined with $TiO_2$. To fabricate 3D nanostructures of $g-C_3N_4/TiO_2$, $TiO_2$ was first grown as a double layer structure on FTO (Fluorine-doped tin oxide) substrate at $150^{\circ}C$ for 3 h. After this, the $g-C_3N_4$ layer was coated on the $TiO_2$ film at $520^{\circ}C$ for 4 h. As-prepared samples were varied according to loading of melamine powder, with values of loading of 0.25 g, 0.5 g, 0.75 g, and 1 g. From SEM and TEM analysis, it was possible to clearly observe the 3D sample morphologies. From the PEC measurement, 0.5 g of $g-C_3N_4/TiO_2$ film was found to exhibit the highest current density of $0.12mA/cm^2$, along with a long-term stability of 5 h. Compared to the pristine $TiO_2$, and to the 0.25 g, 0.75 g, and 1 g $g-C_3N_4/TiO_2$ films, the 0.5 g of $g-C_3N_4/TiO_2$ sample was coated with a thin $g-C_3N_4$ layer that caused separation of the electrons and the holes; this led to a decreasing recombination. This unique structure can be used in photoelectrochemical applications.

• Korean Journal of Food Science and Technology
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• v.30 no.2
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• pp.272-277
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• 1998

In order to study storage stability of fresh jujube fruits (Zizyphus jujuba Miller) controlled atmosphere storage, polyethylene film packaging and non-packaging were compared. Jujube fruits were stored on the following gas compositions: 1.5% carbon dioxide and 5, 8, 10, 12% oxygen at $7^{\circ}C$, respectively. And 0.05 mm PE packaging and non-packaging were stored at $1^{\circ}C,\;4^{\circ}C\;and\;7^{\circ}C$. Safe storage period of Bokjo jujube fruits was four weeks when stored in CA condition of $O_2\;10%\;and\;CO_2\;1.5%$ in terms of their overall quality. The rate of weight loss was not much changed either by storage method of CA or by PE film packaging. In surface color the a value of jujube fruits increased but L and b values decreased during the storage period. Hardness showed the trend of increase in all the treatment for 2 weeks of storage while in CA it decreased more than the others after 4 weeks of storage. Soluble solids and titratable acidity were changed slightly. Vitamin C contents were gradually decreased in all treatments, but non-packed jujubes at $1^{\circ}C$ were slightly increased.