• Proceedings of the Materials Research Society of Korea Conference
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• 1994.11a
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• pp.1-1
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• 1994

;The electronic state calculations for various types of ceramic materials have beell performed by the use of $DV-X\;{\alpha}$ cluster method. The molecular orbital levels and wave functions for model clusters have been computed to study the electronic properties ami chemical bonding of the ceramics. For ${\beta}-sialon(Si_{6-z}Al_zO_zN_{8-z})$ which is a high temperature structural material based on ${\beta}-Si_3N_4$, we have made model cluster calculations to estimate the strength of chemical bonding between atoms by the Mulliken population analysis. It is found that the covalent bonding between Si and N atoms is very strong in pure ${\beta}-Si_3N_4$, but the covalency around solute atom is considerably weakened when Si atom is substituted by AI. This tendency is enhanced by an additional substitution of oxygen atom for N. The result calculated can well explain the experimental data of changes in mechanical properties such as the reductions of Young's modulus and Vickers hardness with increment of z-value in ${\beta}-sialon$. Various model clusters for transition metal oxides which show many interesting physical and chemical properties have also been calculated. High-valent perovskite-type iron oxides EMFe0_3E(M=Ca and Sr) possess very interesting magnetic and chemical properties. In these oxides, iron exists as $Fe^{4+}$ state, but the experimental measurement of Mossba~er effect suggests that disproportionation $2Fe^{4+}=Fe^{3+}+Fe^{5+}$ takes place for $CaFe0_3$ at low temperatures. The model cluster calculations for these compounds indicated the existence of considerably strong covalent bonding of Fe-O. The calculations of hyperfine interaction at iron neucleus show very good agreement with the experimental Mossbauer measurements. The result calculated also implies that the disproportionation reaction is strongly possible by assuming the quenching of breathing phonon mode at low temperatures.tures.

• Korean Journal of Microbiology
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• v.6 no.1
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• pp.22-28
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• 1968

Chlorella ellipsoidea cells were cultured in an iron, copper, zinc, manganese, molybdenum or boron-free medium. Biosynthetic activities of nucleic acids, protein and phospholipid in chlorella cells, which were growing in a microelement deficient medium were compared with those of the normal cells by measuring the contents of phosphate, amino acids or UV-absorbing substances in the various cell fractions. When the algae were grown in a molybdenum-free medium, the amounts of phosphate in the acid-soluble fraction of the cells increased, whereas the amounts of alkali-stable protein and RNA decreased compared with the normal cells showing that the synthesis of protein and RNA from the early products of photosynthesis was inhibited. When the algae were grown in a boron-free medium, amounts of alkali-labile protein and phospholipid of the cells decreased, while the amount of phosphate in acid-soluble fraction increased compared with the normal cells showing that the biosynthesis of protein and phospholipid from the early products of photosynthesis was retarded. In general, amounts of protein and RNA in the microelement deficient cells significantly decreased compared with those of the normal cells. Phosphate content in the acid-soluble fraction of the algal cell grown in an zinc, copper, molybdenum, or boron-free medium increased considerably, whereas that of the algal cell grown in an iron or manganese-free medium decreased remarkably compared with that of the control. It is considered, therefore, that molybdenum, zinc, copper and boron etc. play an important role in the biosyntbesis of macromolecule from acid-soluble phosphate compounds, in contrast to the principal action of iron and manganese on the photosynthetic process itself.

• Asian-Australasian Journal of Animal Sciences
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• v.30 no.1
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• pp.85-93
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• 2017

Objective: This study evaluated the effect of acid whey and freeze-dried cranberries on the physicochemical characteristics, lipid oxidation and fatty acid composition of nitrite-free fermented sausage made from deer meat and pork fat. Antioxidant interactions between acid whey and cranberry compounds were also explored. Methods: Four formulations of fermented venison sausage were prepared: F1 (control), F2 (with 5% liquid acid whey), F3 (with 0.06% of freeze-dried cranberries), and F4 (with 5% liquid acid whey and 0.06% of freeze-dried cranberries). Each sample was analyzed for pH, water activity ($a_w$), heme iron content, 2-thiobarbituric acid reactive substances (TBARS) value and conjugated dienes at the end of the manufacturing process and at 30 and 90 days of refrigerated storage. Fatty acid composition was measured once at the end of the manufacturing process. Results: At the end of ripening, all samples presented statistically different values for a pH range of 4.47 to pH 4.59. The sum of the unsaturated fatty acids was higher, while the conjugated diene and the TBARS values were lower in sausages with freeze-dried cranberries as compared to the control sausage. The highest content of heme iron (21.52 mg/kg) at day 90 was found in the sausage formulation with the addition of freeze-dried cranberries, which suggests that the addition of cranberries stabilized the porphyrin ring of the heme molecule during storage and thereby reduced the release of iron. The use of liquid acid whey in combination with cranberries appears to not be justified in view of the oxidative stability of the obtained products. Conclusion: The results suggest that the application of freeze-dried cranberries can lower the intensity of oxidative changes during the storage of nitrite-free fermented sausage made

• Environmental Engineering Research
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• v.19 no.1
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• pp.9-14
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• 2014

Fenton reaction with zerovalent iron (ZVI) and $Fe^{2+}$ ions was studied to treat pharmaceutical wastewaters (PhWW) including antibiotics and non-biodegradable organics. Incremental biodegradability was assessed by monitoring biochemical oxygen demand (BOD) changes during Fenton reaction. Original undiluted wastewater samples were used as collected from the pharmaceutical factory. Experiments were carried out to obtain optimal conditions for Fenton reaction under different $H_2O_2$ and ion salts (ZVI and $Fe^{2+}$) concentrations. The optimal ratio and dosage of $H_2O_2$/ZVI were 5 and 25/5 g/L (mass basis), respectively. Also, the optimal ratio and dosage of $H_2O_2/Fe^{2+}$ ions were 5 and 35/7 g/L (mass basis), respectively. Under optimized conditions, the chemical oxygen demand (COD) removal efficiency by ZVI was 23% better than the treatment with $Fe^{2+}$ ion. The reaction time was 45 min for ZVI and shorter than 60 min for $Fe^{2+}$ ion. The COD and total organic carbon (TOC) were decreased, but BOD was increased under the optimal conditions of $H_2O_2$/ZVI = 25/5 g/L, because organic compounds were converted into biodegradable intermediates in the early steps of the reaction. The BOD/TOC ratio was increased, but reverse-wise, the COD/TOC was decreased because of generated intermediates. The biodegradability was increased about 9.8 times (BOD/TOC basis), after treatment with ZVI. The combination of chemical and biological processes seems an interesting combination for treating PhWW.

• Journal of the Korea Organic Resources Recycling Association
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• v.24 no.3
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• pp.53-61
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• 2016

The reaction of zero-valent iron (ZVI) with oxygen can produce reactive oxidants capable of oxidizing organic compounds. Thus, the aim of this study was to investigate the effect of pre-treatment on sludge solubilization by ZVI and aeration. The results demonstrated that the aeration pre-treatment with ZVI method was more effective than the only aeration for improving sludge solubilization, indicating that ZVI increased the extent of sludge solubilization. In addition, removal rate of $NH_3-N$ by ZVI and aeration was found to be 34%, while only aeration was 24%. Thus, ZVI and aeration can be employed as an efficient pre-treatment option to achieve higher sludge solubilization and decrease the toxic effect of $NH_3-N$ for sludge digestion.

• Journal of Microbiology and Biotechnology
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• v.29 no.6
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• pp.973-983
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• 2019

It is well known that iron is critical for bacterial growth and pathogenic virulence. Due to chemical similarity, $Ga^{3+}$ competes with $Fe^{3+}$ for binding to compounds that usually bind $Fe^{3+}$, thereby interfering with various essential biological reactions. In our present study, gallium(III) nitrate [$Ga(NO_3)_3$] could repress the growth of V. splendidus Vs without complete inhibition. In the presence of $Ga(NO_3)_3$, the secretion of homogentisic acid-melanin (HGA-melanin) in V. splendidus Vs cells could be increased by 4.8-fold, compared to that in the absence of $Ga(NO_3)_3$. HGA-melanin possessed the ability to reduce $Fe^{3+}$ to $Fe^{2+}$. In addition, HGA-melanin increased the mRNA levels of feoA and feoB, genes coding Fe2+ transport system proteins to 1.86- and 6.1-fold, respectively, and promoted bacterial growth to 139.2%. Similarly, the mRNA expression of feoA and feoB was upregulated 4.11-fold and 2.71-fold in the presence of $640{\mu}M$ $Ga(NO_3)_3$, respectively. In conclusion, our study suggested that although $Ga(NO_3)_3$ could interfere with the growth of V. splendidus Vs, it could also stimulate both the production of $Fe^{3+}$-reducing HGA-melanin and the expression of feoA and feoB, which facilitate $Fe^{2+}$ transport in V. splendidus Vs.

• Journal of the Korean Society for Heat Treatment
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• v.37 no.2
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• pp.49-57
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• 2024

We investigated the changes in microstructure and surface roughness of the compound layer of GC250D gray cast iron, commonly used in brake discs, during gas nitriding. The gas atmosphere of the nitriding process was controlled with a hydrogen partial pressure of 49.5%, and the process was conducted at a nitriding temperature of 520℃ with various process times. As the nitriding process time of the GC250D material increased, both the depth of hardening and the thickness of the compound layer increased, with a maximum surface hardness of approximately 1265 HV_0.1 was measured. Additionally, the surface roughness increased with the process time. Phase analysis of the compound layer revealed an increase in the proportion of the γ' phase as the nitriding process time increased. Changes in the formation of the compound layer were observed depending on the orientation of graphite within the material, leading to the formation of wedges. Therefore, the increase in surface roughness appears to be attributed to the uneven compounds, the expansion of the compound layer and wedges formed on the surface during the nitriding process.

• Korean Journal of Environmental Agriculture
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• v.11 no.3
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• pp.225-234
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• 1992

Thermal decomposition was conducted to investigate the influence of the various factors on stability of a new insecticide, [O, O-Diethyl O-(1-phenyl-3-trifluoromethyl-5-pyrazoyl) thiophosphoric acid ester : KH-502], in view of those informations applicable for industrial exploitation. In the thermal decomposition experiment, KH-502 was, after mixing with Fe, Cu and adjustment of moisture and pH conditions, subjected to three temperatures, 25, 50, and $100^{\circ}C$. Results for stability, and degradation pattern of KH-502 from the above experiment can be summarized as follows: 1. Main products of the thermal decomposition when this was conducted in the closed system were identified as following five compounds:O, O, O-Triethylthiophosphoric acid(TEPA), 1-Phenyl-3-trifluoromethyl-5-ethoxypyrazole(PTMEP), 1-Phenyl-2-ethyl-3-trifluoromethyl-5-hydroxypyrazole(PETMHP), O, O-Diethyl O-(1-phenyl-3-trifluoromethyl-5-pyrazoyl)phosphoric acid ester(KH-502 oxo form), O, S-Diethyl O-(1-phenyl-3-trifluoromethyl-5-pyrazoyl)phospho rothiolate(S-ethyl KH-502). However, compounds such as oxo form and S-ethyl KH-502 were not identified when the thermal decomposition was proceeded in the open system. 2. KH-502 was stable at 25 and 50$^{\circ}C$, but it was decomposed at 100$^{\circ}C$ following the first-order kinetics at the early stages of decomposition. 3. Rate constants for the thermal decomposition of KH-502 at 100$^{\circ}C$ were in the orders of Cu powder addition 0.344>Cu plate addition 0.21>moisture addition 0.05>closed system=open system=iron addition=pH 5.5 adjustment 0.04>pH 8.5 adjustment 0.027 day$^{-1}$, representing KH-502 was decomposed fast at Cu powder treatment and slow at pH 8.5 adjustment. 4. Half-life for the thermal decomposition of KH-502 at 100$^{\circ}C$ was in the orders of Cu powder addition 2.02

• Korean Chemical Engineering Research
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• v.44 no.2
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• pp.136-148
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• 2006

A foundry makes various machinery parts made by iron. For manufacturing machinery parts, they usually uses wooden mold with molding sand and pour the molten iron into wooden mold through inlet. A foundry have many processes including Furan process, In Furan process workers prepares a wooden mold in the molding sand. So they fixes wooden mold in sand housing and then they fill the molding sand in the sand housing. Molding sand should be sticky enough to sustain the shape of wooden mold, so several materials are needed to prepare the suitable molding sand. The first step of Furan process is making the molding sand with molding sand and Voltaic Organic Compounds (VOC) and the second step of Furan process is pour the molding sand into the wooden molding housing. This two step of process generated noxious VOC and various size of dust. So the process is very dirty and dangerous one. Because of these, Workers frequently shrink out of the plant. The company related with foundry usually faced on the difficult situation for engagement and always have shortage of hiring problem. Through this study, we developed a system which removes toxic VOC and dust simultaneously. We design and construct real system and install it at real plant. Before setting up this system, the working surroundings VOC (for formaldehyde) 15 ppm and Dust(for $PM_{10}$) $8,000{\mu}g/m^3$. After setting up this system, working surroundings is improved by VOC (for formaldehyde) 0 ppm, Dust(for $PM_{10}$) $4{\mu}g/m^3$, and the work evasion factor is removed. So we contribute to solve hiring problem of this company and increasing the productivity also.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.1
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• pp.33-40
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• 2003

Fusobacterium nucleatum, one of the bacteria causing halitosis, produces the volatile sulfur compounds (VSC) such as $H_2S$ in the media containing sulfur components, and forms FeS by binding with iron component. The various factors of oral cavity affect the concentration of sulfur compounds produced by Fusobacterium nucleatum. In this study, the effect of nutrients and pH on the production of sulfur compounds by Fusobacterium nucleatum was studied with the following results. 1. The optical density of broth was increased to $0.817{\pm}0.032$ and $1.297{\pm}0.024$ by adding 1.0% sodium thiosulfate and 0.05% L-cysteine hydrochloride in the media, respectively. 2. Though the optical density of broth was $0.799{\pm}0.032$ by adding volatile sulfur compounds (VSC) only in the media, it was increased to $1.775{\pm}0.003$ and $1.648{\pm}0.022$ by adding xylitol combined with glucose and fructose, respectively. 3. The concentration of VSC was above 20,000 ppb in the media above pH 5.5. The optical density of broth was still high in the media with L-cysteine hydrochloride of higher concentration, being low in the media of lower pH. 4. The concentration of VSC was high when there was distilled water or saline solution on the media, and their amount was small. These results suggest that the production of sulfur compounds by Fusobacterium nucleatum was inhibited by xylitol and acid.