• Korean Journal of Plant Resources
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• v.35 no.5
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• pp.686-695
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• 2022

The grain yield and flour quality of winter wheat (Triticum aestivum L. 'Jokyung') were investigated in the paddy fields in which the double-cropping of wheat linked to rice (Oryza sativa L.) and its alternative crops [black soybean (Glycine max (L.) Merr.), sesame (Sesamum indicum L.), and perilla (Perilla frutescens (L.) Britton)] was applied. In the soils in which black soybean, sesame, and perilla as pre-crops were cultivated, the soil pH was higher and the electrical conductivity was lower than in the rice pre-cropped soil. In addition, the available phosphate (Av. P₂O₅), and contents of Ca²⁺ and Mg²⁺ were higher than in the rice pre-cropped soil. Winter wheat growth characteristics such as culm length, spike length, number of spikes and grains were generally favorable in the black soybean pre-cropped soil. However, the grain yield of winter wheat increased in the black soybean, sesame, and perilla pre-cropped soils by 100 kg/10a or more than in the rice pre-cropped soil. Furthermore, protein content and SDS-sedimentation value of the flour were higher, while amylose content was slightly lower, in the black soybean, sesame, and perilla pre-cropped soils than in rice pre-cropped soil. These results suggest that cultivation of rice alternative crops such as sesame, black soybean, and perilla as pre-crops in paddy soil could improve the physical and chemical properties of the soil and contribute to producing high-quality wheat flour more advantageous for the baking process.

• Journal of Adhesion and Interface
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• v.2 no.4
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• pp.10-23
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• 2001

In order to increase the lower values of % grafting and monomer conversion in the emulsion graft polymerization of methylmethacrylate(MMA) onto sodium alginate (SA; a polymer electrolyte) with alginic acid-g-PMMA, the graft polymerization with water soluble (methanol and acetone) and insoluble solvents was carried out using a varity of solvent amounts and agitating rates. And some physical properties of the graft polymer were also investigated. In the polymerizations with water insoluble solvent, there were pronounced improvements in both % grafting and MMA conversion by the promotion of MMA diffusion from the core to the SA adsorpted on the outer layer of particle and that of MMA complex formation with SA. And the effect was larger for the solvents (cyclohexane, decalin) which do not dissolve PMMA. On the other hand, in the polymerization with water soluble solvent, there was an significant increase in MMA conversion and a considerable increase in the % grafting by the destruction of electrical double layer around the SA chains, abstracting the hydrated water in the layer and the effect was more potential in the case of methanol which is a precipitant of PMMA.

• Korean Journal of Environment and Ecology
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• v.33 no.6
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• pp.708-721
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• 2019

This study was conducted to understand the plant community structure characteristics of warm-temperate forest in Geoje Island. Survey sites were set up on ridges, valleys, and slopes where evergreen broad-leaved trees predominated or distributed in canopy, sub-canopy, or shrub layers at Chunjangsan(Mt.). Thirty-one sites were located in the areas, such as vegetation community, ridges, valleys, and slopes, to observe vegetation structure and location changes. The community classification with TWINSPAN identified six groups: Neolitsea sericea-Platycarya strobilacea, N. sericea-Styrax japonicus, N. sericea-Euonymus oxyphyllus, Pinus thunbergii-N. sericea, N. sericea-Quercus serrata, and Q. variabilis-P. strobilacea. Considering the results of previous studies that reported that the successional pattern of the warm temperate forests progressed from deciduous to evergreen forests, the regions predominated by deciduous communities such as P. thunbergii, Q. serrata, P. strobilacea, Zelkova serrata, and Q. variabilis, is likely to transform into the evergreen forest predominated by N. sericea. The relationship between the impact of the environmental factors and the vegetation distribution showed that slope, Na +, K +, electrical conductivity, and clay among physical properties had direct or indirect effects on vegetation distribution.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.297-297
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• 2010

Precise control of the position and density of doping elements at the nanoscale is becoming a central issue for realizing state-of-the-art silicon-based optoelectronic devices. As dimensions are scaled down to take benefits from the quantum confinement effect, however, the presence of interfaces and the nature of materials adjacent to silicon turn out to be important and govern the physical properties. Utilization of visible light is a promising method to overcome the efficiency limit of the crystalline Si solar cells. Si quantum dots (QDs) have been proposed as an emission source of visible light, which is based on the quantum confinement effect. Light emission in the visible wavelength has been reported by controlling the size and density of Si QDs embedded within various types of insulating matrix. For the realization of all-Si QD solar cells with homojunctions, it is prerequisite not only to optimize the impurity doping for both p- and n-type Si QDs, but also to construct p-n homojunctions between them. In this study, XPS and SIMS were used for the development of p-type and n-type Si quantum dot solar cells. The stoichiometry of SiOx layers were controlled by in-situ XPS analysis and the concentration of B and P by SIMS for the activated doping in Si nano structures. Especially, it has been experimentally evidenced that boron atoms in silicon nanostructures confined in SiO2 matrix can segregate into the Si/$SiO_2$ interfaces and the Si bulk forming a distinct bimodal spatial distribution. By performing quantitative analysis and theoretical modelling, it has been found that boron incorporated into the four-fold Si crystal lattice can have electrical activity. Based on these findings, p-type Si quantum dot solar cell with the energy-conversion efficiency of 10.2% was realized from a [B-doped $SiO_{1.2}$(2 nm)/$SiO_2(2\;nm)]^{25}$ superlattice film with a B doping level of $4.0{\times}10^{20}\;atoms/cm^2$.

• Membrane Journal
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• v.31 no.6
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• pp.371-383
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• 2021

Anion exchange membranes have been used for water electrolysis, which can produce hydrogen, and fuel cells, which can generate electrical energy using hydrogen fuel. Anion exchange membranes operate based on hydroxide ion (OH^-) conduction under alkaline conditions. However, since the anion exchange membrane shows relatively low ion conductivity and alkaline stability, there is still a limit to its commercialization in water electrolysis and fuel cells. To address these issues, it is important to develop novel anion exchange membrane materials by rationally designing a polymer structure. In particular, the polymer structure and synthetic method need to be controlled. By doing so, for polymers, the physical properties, ionic conductivity, and alkaline stability can be maintained. Among many anion exchange membranes, poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) is commercially available and easily accessible. In addition, the PPO has relatively high mechanical and chemical stability compared to other polymers. In this review, we introduce the recent development strategy and characteristics of PPO-based polymer materials used in anion exchange membranes.

• Korean Journal of Environment and Ecology
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• v.36 no.1
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• pp.72-86
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• 2022

This study was conducted to identify structural characteristics of the evergreen broad-leaved forests distributed in Hak-dong, Geojae island. For a survey, 52 sites were set up in areas with changes in the vegetation community or location environment where Cinnamomum yabunikkei, Neolitsea sericea, and Machilus thunbergii dominated or appeared in the canopy, sub-canopy, or shrub layer. The community classification with TWINSPAN identified the following communities: N. sericea-C. yabunikkei, C. yabunikkei-Camellia japonica, Ca. japonica, Quercus variabilis-Ca. japonica, Pinus thunbergii-Ca. japonica, Castanopsis sieboldii, P. thunbergii, and Platycarya strobilacea-Mallotus japonicus. Considering the result of the study that succession series of warm-temperate forest reflecting the latent natural vegetation is the transition of conifers and deciduous broad-leaved forest to evergreen broad-leaved forest, the communities predominated by the communities predominated by the communities predominated by P. thunbergii, Q. variabilis, and Pl. strobilacea are likely to transform into the evergreen forest predominated by N. sericea and C. yabunikkei. The sites where C. yabunikkei, N. sericea, and Castanopsis sieboldii are dominant in the canopy and sub-canopy layers are likely to maintain the status quo if there is no artificial disturbance. The relationship between the impact of the environmental factors and the vegetation distribution showed silt among the physical properties of the soil directly or indirectly affected it, which was judged to be due to the fact that it was located on a steep slope. The soil acidity (pH) was 5-5.84, electrical conductivity 0.047-0.139 dS/m, and organic matter content was 3.32-12.06%. Although there were differences by the colony, they were generally low.

• Applied Chemistry for Engineering
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• v.30 no.6
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• pp.698-706
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• 2019

Over the last few decades, there have been a lot of efforts to develop soft actuators, which can be external stimuli-responsive and applied to the human body. In order to fabricate medical soft actuators with a dynamic precision control, the 3D crosslinked poly(acrylic acid) (PAAc)/poly(vinyl alcohol) (PVA)/poly(ethylene glycol) (PEG) hydrogels were synthesized in this study by using a radiation technique without noxious chemical additives or initiators. After irradiation, all hydrogels showed high gel fraction over 75% and the ATR-FTIR spectra indicated that PAAc/PVA/PEG hydrogels were successfully synthesized. In addition, the gel fraction, equilibrium water content, and compressive strength were measured to determine the change in physical properties of PAAc/PVA/PEG hydrogels according to the irradiation dose and content ratio of constituents. As the irradiation dose and amount of poly(ethylene glycol) diacrylate (PEGDA) increased, the PAAc/PVA/PEG hydrogels showed a high crosslinking density and mechanical strength. It was also confirmed that PAAc/PVA/PEG hydrogels responded to electrical stimulation even at a low voltage of 3 V. The bending behavior of hydrogels under an electric field can be controlled by changing the crosslinking density, ionic group content, applied voltage, and ionic strength of swelling solution.

• Journal of the Korean Chemical Society
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• v.38 no.8
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• pp.547-551
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• 1994

A series of samples in the $Nd_{1-x}Ba_xFeO_{3-y}$ system has been prepared by heating the reactants to$1200^{\circ}C$ under an ambient atmosphere, and the solid solutions were identified by X-ray power diffraction analysis. The crystal systems of samples with x = 0.00 and 0.25 were found to be orthorhombic whose local symmetry is similiar to the distorted octahedral with orthoferrite type one, whereas those with x = 0.50 and 0.75 to be the cubic system. Since Fe ions in the solid solutions are a mixed valence state between $Fe^{3+}\;and\;Fe^{4+}$ ions, the nonstoichiometric chemical formulas could be determined from the mole ratio of $Fe^{4+}$ ion and oxygen vacacies. According to the Mossbauer spectroscopic analysis, the presence of 5-coordinated $FeO_5$ was evidenced only in the barium compounds along with $FeO_6,\;and\;FeO_4$, but not in the strontium and calcium compounds. The samples with x = 0.25 and 0.50 show a spectrum of superparamagnetism, which might be due to the formation of a domain of the ferromagnetic interaction between the $Fe^{3+}\;and\;Fe^{4+}$ ions. The electrical conductivities of all samples are within semiconducting range. Since the $Fe^{4+}$ ion acts as an electron acceptor level during the electron transfer between the Fe through intermediate $O^{2-}$ ions, the activation energy of the compounds decreases with the increment of $Fe^{4+}$ content.

• Journal of the Korean Vacuum Society
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• v.20 no.2
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• pp.155-163
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• 2011

Carbon nanotubes (CNT) have been attracted much attention since they have been expected to be used in various areas by virtue of their outstanding physical, electrical, and chemical properties. In order to make full use of their prominent electric conductivity in some areas such as electron emission sources, device interconnects, and electrodes in energy storage devices, direct growth of CNT with vertical alignment is definitely beneficial issue because they can maintain mechanical stability and high conductivity at the interface between substrates. Here, we report direct growth of vertically aligned CNT (VCNT) on Cu foils using thermal chemical vapor deposition and characterize the field emission property of the VCNT. The VCNT's height was controlled by changing the growth temperature, growth time, and catalytic layer thickness. Optimum growth condition was found to be $800^{\circ}C$ for 20 min with acetylene and hydrogen mixtures on Fe catalytic layer of 1 nm thick. The diameter of VCNT grown was smaller than that of usual multi walled CNT. Based on the result of field emission characterization, we concluded that the VCNT on Cu foils can be useful in various potential applications where high conductivity through the interface between CNT and substrate is required.

• Analytical Science and Technology
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• v.6 no.5
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• pp.479-487
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• 1993

Potassium-Graphite Fiber Intercalation Compounds(K-GFIC) have been prepared from well oriented pitch-based Graphite fiber by the transformed two-bulbs method with variation of reaction temperatures of graphite($T_g$ : $450^{\circ}C$, $400^{\circ}C$, $350^{\circ}C$, $300^{\circ}C$, $250^{\circ}C$). The stage transition process of K-GFICs was studied by X-ray diffraction methods, and we have observed peaks with d-values of (001) diffraction of $5.40{\AA}$ and $8.78({\pm}0.01){\AA}$, which are charecteristic for the stage 1 and stage 2, respectively. The stage stability and energy states of K-GFICs were studied by UV/VIS spectrophotometer. As a results, We found that the minimum values of reflactance of K-GFICs with pure stage was moved to higher energy pristine Graphite fiber's. But because of mixtured stage, we could not observe minimum reflectance in the visible region at high reaction temperatures($400^{\circ}C$, $450^{\circ}C$). From X-ray diffraction and UV/VIS sepctrophotometry data, we can suggest that K-GFICs with lower stage has many charge carriers existed between C atoms of graphite Layers. And then, these results also provides information on the electrical and other physical properties of K-GFICs.