• Korean journal of applied entomology
• /
• v.26 no.3 s.72
• /
• pp.171-178
• /
• 1987

Pathogenic isolates of Alternaria mali produced host-specific toxin(AM-toxin) in liquid culture. The toxin was also released by germinating spores of the fungus. The physiological event of apple leaves induced by germinating spores was an increased loss of electrolytes from susceptible leaves. This reaction was evident soon after spore inoculation, indicating that the leakage was caused by AM-toxin from germinating spores. Typical symptoms were developed only in susceptible leaves of apple within 48hr after inoculation with pathogenic spores. Similar symptoms occurred on susceptible leaves when non-pathogenic isolates plus AM-toxin were used.

• Journal of the Korean Electrochemical Society
• /
• v.14 no.4
• /
• pp.196-200
• /
• 2011

The formation of niobium oxide microcones on niobium substrates was investigated in NaF to the HF electrolytes. This condition builds on the uniqueness of the microstructures niobium oxide. The dimensions and integrity of the bulk microstructures were found to be strongly dependent on potential, temperature, electrolyte composition, and anodization time. The anodic oxide was initially amorphous at all temperatures, but crystalline oxide nucleated during anodization. From XRD patterns of the anodized specimens, the microcones consisted of crystalline $Nb_2O_5$. We demonstrated niobium oxide microcone structures with nanorods. The anodized niobium oxide microcone texture revealed nanorod bundles. The surface of $Nb_2O_5$ microcones is very regular and has a nano-scale. The surface morphologies of the nanorods were examined using FE-SEM. EDS analyses show that the anodically prepared niobium oxide consists of $Nb_2O_5$. The aim of this study is to find the condition of forming the favorable nanorods by anodization method.

• Korean Chemical Engineering Research
• /
• v.56 no.4
• /
• pp.447-452
• /
• 2018

Titanium nanotubes (TNT) of various lengths ranging from $0.34^{\circ}C$ to a maximum of $8.9^{\circ}C$ were prepared by anodizing a titanium metal sheet in an electrolyte containing fluorine ion ($F^-$) of HF, NaF and $NH_4F$. When TNT prepared by anodizing was calcined at $450^{\circ}C$, anatase crystals with photo activity were formed. The TNT-based dye-sensitized solar cell (DSSC) showed a maximum conversion efficiency of 4.71% when the TNT length was $2.5{\mu}m$. This value was about 18% higher than photo conversion efficiency of the FTO-based DSSC coated with titania paste. And the short circuit current density ($J_{sc}$) of the TNT-DSSC was $9.74mA/cm^2$, which was about 35% higher than the $7.19mA/cm^2$ of FTO-DSSC. The reason for the higher conversion efficiency of TNT-DSSC solar cells is that photoelectrons generated from dyes are rapidly transferred to the electrode surface through TNT, and the recombination of photoelectrons and dyes is suppressed.

• Korean Journal of Materials Research
• /
• v.11 no.4
• /
• pp.329-334
• /
• 2001

Microstructures of barrier-type oxide layers on aluminum was studied by XRD, TEM and RBS. Fer formation of oxide layer. aluminum was anodized in a boric acid solution. The thickness of the oxide film subjected to applied voltage increased linearly at ratio of 1.54nm/V. For oxide layer anodized at 300V, amorphous structure of oxide layer was not transformed after heat treatment at 50$0^{\circ}C$ , while for oxide layers anodized at higher voltages the amorphous structure crystallized into a ${\gamma}$-alumina without any heat treatment. It was also found that the amorphous structure of oxide layer formed at 100V transformed into crystalline structure by electron irradiation. The structure was identified as ${\gamma}$-alumina.

• Journal of the Korean Chemical Society
• /
• v.33 no.6
• /
• pp.614-622
• /
• 1989

The electrochemical reduction of ${\alpha},{\beta}$-dibenzyl N-benzylidene L-aspartate in 0.1M LiCl ethanol solution was investigated by direct current (DC), differential pulse (DP) polarography, cyclic voltammetry and controlled potential coulometry(CPC). The irreversible reductive amination of imino group proceeded to form ${\alpha},{\beta}$-dibenyl N-benzyl L-aspartate by CEC or CE electrochemical reaction mechanism at the first reduction step (-0.92 volts vs. Ag-AgCl). The polarographic reduction wave was slightly suppressed due to inhibitory effect of micelle, while the irreversibility was increased according to the increase of Triton X-100 concentration. Upon the basis of product analysis and polarogram interpretation with pH change, possible CE electrode reaction mechanism was suggested.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.1 no.1
• /
• pp.25-39
• /
• 2003

This study proposed a new electrolytic reduction technology that is based on the integration of simultaneous uranium oxide metallization and Li$_2$O electrowinning. In this electrolytic reduction reaction, electrolytically reduced Li deposits on cathode and simultaneously reacts with uranium oxides to produce uranium metal showing more than 99% conversion. For the verification of process feasibility, the experiments to obtain basic data on the metallization of uranium oxide, investigation of reaction mechanism, the characteristics of closed recycle of Li$_2$O and mass transfer were carried out. This evolutionary electrolytic reduction technology would give benefits over the conventional Li-reduction process improving economic viability such as: avoidance of handling of chemically active Li-LiCl molten salt increase of metallization yield, and simplification of process.

• Korean Chemical Engineering Research
• /
• v.53 no.2
• /
• pp.131-136
• /
• 2015

The nanostructural graphene/vanadium oxide (graphene/$V_2O_5$) composite with enhanced capacitance was synthesized by the electro-deposition in 0.5 M $VOSO_4$ solution. The morphology of composites was characterized using scanning electron microscopy (SEM), x-ray diffraction pattern (XRD), and x-ray photoelectron spectroscopy (XPS). The oxidation states of the electro-deposited vanadium oxide was found to be $V^{5+}$ and $V^{4+}$. The morphology of the prepared graphene/$V_2O_5$ composite exhibits a netlike nano-structure with $V_2O_5$ nanorods in about 100 nm diameter, which could lead a better contact between electrolyte an electrode. The composite with a deposition time of 4,000 s exhibits the specific capacitance of $854mF/cm^2$ at a scan rate of 20 mV/s and the capacitance retention of 53% after 1000 CV cycles.

• Journal of the Korean Chemical Society
• /
• v.50 no.4
• /
• pp.307-314
• /
• 2006

The redox characteristics of 2-ketohydrazono-3-phenyl-5-substituted-2,3-dihydro-1,3,4-thiadiazoles and its derivatives (1a-h) has been investigated in nonaqueous solvents such as 1,2-dichloroethane (DCE), dichloromethane (DCM), acetonitrile (AN), tetrahydrofuran (THF), and dimethylsulfoxide (DMSO) containing 0.1 mol.dm-3 tetra n-butylammonium perchlorate (TBAP) as supporting electrolyte at platinum ectrode. Through controlled potential electrolysis, the oxidation and reduction products of the investigated compounds can be separated and indentified. The redox mechanism is suggested and proved. It was found that all the investigated compounds are oxidized in two irreversible one-electron processes following the well known pattern of EC-mechanism. On the other hand, these compounds are reduced in a single two electron or in a successive two one electron processes following the well known pattern of EEC-mechanism according to the nature of the substituent

• Journal of the Korean Chemical Society
• /
• v.37 no.1
• /
• pp.83-91
• /
• 1993

The eletrochemical behavior of light lanthanide complexes has been investigated by several electrochemical techniques in alkaline solutions. The composition of the complexes was determined by spectrophotometric method to be 1 : 1 and reduction mechanism was two steps 1 electron transfer reaction. The half wave potential of first peak depended on pH and cathodic current showed remarkably adsorptive properties. The results of DC and CV investigation demonstrated the quise-reversible nature of the electron transfer. The anion radical formed after first one electron reduction process, dimerizes to form dimer. The apparent irreversible behavior of the second wave is a result of the existence of a fast protonation following the second electron transfer. An exhaustive electrolysis was carried out at controlled potential of -1.80 V, deep blue color of the solution became progressively weaker, and then the solution became colorless solution. The final product of an exhaustive electrolysis is electro-inactive. The appearance of four steps may be explained by the fact the reduction of Ln-OCP elucidated ECEC mechanism.

• Clean Technology
• /
• v.21 no.1
• /
• pp.45-52
• /
• 2015

We have introduced switching poles in the conventional electrolysis for the removal of ammonia in aquaculture wastewater to prevent the fouling on the electrode surface by the deposition of insoluble metallic compounds. We have also tried to locate the optimal period of switching poles considering the effect of the current loss during switching poles on the free chlorine generation. First, we have observed the decrease of free chlorine generation with the decrease of the period of switching poles due to the expected current loss, and this would lead to the decrease of ammonia removal efficiency. Meanwhile, the measurement of calcium and magnesium concentration in wastewater vs. the period of switching poles have demonstrated that a properly low level of fouling on the electrode surface could be retained with a period of switching poles of less than 60 sec by the decomposition of metallic compounds during switching poles. In a summary, we have optimized the period of switching poles to gain a high level of free chlorine generation and a high level of fouling prevention on the electrode at the same time.