• Journal of the Korean Society for Heat Treatment
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• v.10 no.1
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• pp.47-54
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• 1997

Flake graphite cast irons with the high damping capacity have been used for the control of vibration and noise occuring in the members of various mechanical structures under vibrating conditions. However, the damping capacity which is morphological characteristics of graphite is one of the important factors in reducing the vibration and noise, but hardly any work has deal with this problem. Therefore, the authors have examined the damping capacity of various cast irons with alloying elements and studied the influences of the matrix, mechanical properties and morphological characteristics of graphite. The main results obtained are as follows: Effects of Ni on the damping capacities and mechanical properties are investigated in 3.9%C-0.3% Cu gray cast iron. At 0.2% Ni content, specific damping capacity showed the maximum value, and decreased with further increase in Ni content, Graphite continuity also showed same behavior. This indicates that the specific damping capacity has a close relation with graphite continuity. On the other hand, the damping capacity in pearlite matrix showed superior to that in ferrite. In contrast, with increasing the Ni content, both tensile strength and hardness increased due to the decrease of graphite length and eutectic cell size.

• Journal of Mushroom
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• v.16 no.3
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• pp.225-230
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• 2018

This study was conducted to reuse spent mushroom substrates (SMS) of Pleurotus ostreatus and improve their nitrogen content by bacterial treatment. Two kinds of bacteria were used to investigate the increase in total nitrogen (T-N) content. Bacillus sp. (GM20-4) was isolated from SMS of oyster mushroom, and Rhodobacter sphaeroides (RS) was obtained from Gwangju Si Agricultural Technology Center. SMS samples were collected from three oyster mushroom cultivation farms located in Gyeonggi-do province, Korea. When dried SMS was inoculated with 30% culture broth of GM20-4 and RS and incubated at room temperature ($25{\pm}2^{\circ}C$) for 5 days, T-N content increased. To investigate the T-N content of other SMS, three dried SMS samples (A, B, and C) were treated by the same method using GM20-4 and RS. As a result, the T-N content of sample B was 20% higher than that of the control, whereas the T-N content of samples A and C increased to 17% and 12%, respectively. The change in T-N content by bacterial treatment of wet SMS was slightly higher than that of the control. The changes in amino acid content were also found to be higher than those in the control in all SMS samples by GM20-4 and RS treatment. Aspartic acid and glutamic acid contents were the highest among all amino acid compositions. Especially, the aspartic and glutamic acid contents of sample B increased by 2.9 folds higher than the control.

• Asian Journal of Turfgrass Science
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• v.3 no.1
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• pp.24-33
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• 1989

This study was conducted to investigate the effect of paclobutrazol [(2 RS , 3 RS )1-(4- chlor-ophenyl )-4, 4- dimethyl -2- (1, 2, 4- triazol -1- yl )- pentan -3-01] on the tolerance of hi-gh temperature and drought stress as related to growth retardation , iranspiration rate , soil water content , nitrogen level and photosynthetic rate in perennial ryegrass ( Loliurn perenne L . ' Omega H , ). Plants were given a 30 ml soil drench of paclohutrazol at the concentrations of 0, 0.01, 0.1, 1.0, 10.. 0, mg / 6 .5cm- diameter pot . The rcsults were as follows : 1. Increasing concentrations of paclohutrazul reduced plant height , leaf area , fresh weight and dry weight , hut increased chlorophyll content per unit area . The number of tillers and leaf width were not affected hy the paclobutrazol concentrations . 2. The proper concentration of paclohatrazol on growth retardation in perennial ryegrass was about I mq /pot , hut leaf deformity and severe growth retardation were shown at high concentration of 10 mq / pot . 3. Perennial ryegrasses grown at 30˚C were shown significantly short plant height and low leaf nitrogen level compared with those grown at 20˚C. Increasing concentrations of paclohutrazol at 20˚C increased nitrogen level hut it could not increase nitrogen level at 30˚C . 4. During the drought stress , increasing temperatures significantly promoted transpiration rate and wilting time . It took about 5 days at 20˚C and 3 days at 30˚C to reach wilting time of leaves from water stress treatment . Soil water contents at wilting time of non-treated controls were averaged 6. 871% at 20˚C and 6. 17% at 30˚C 5. Paclohutrazol reduced transpiration rate at high temperature and drought stress . Wilting appeared at the lower water content of soil according to increasing concentrations of paclobutrazol at 30˚C hut there were no differences among concentrations of at 20˚C. 6.Paclohutrazol treatment at 1 rag /pot reduced injury rate of leaves from 67.1 % and 100 % in control plants to 15.7% and 80% at 20˚C and 3010, respectively. 7. Photosynthetic rate per unit area was significantly reduced at high temperature . Paclohutrazol stimulated photosynthetic rate with increase of concentrations at 20˚C but there was no increasing effect at 30˚C.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.341-346
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• 2002

This study is intended to check the possibility to estimate water content by heat-drying method with variation of W/C and slump. According to the results, in case of electric range method, when water content is less than 165kg/m$^3$ in mixture, it is estimated more and in more than 165kg/m$^3$, it is estimated less. It shows that water content in gas burner method is estimated less by about 2kg/m$^3$. Also, estimated water content shows difference by less than 12kg/m$^3$ in electric range method and by less than 12kg/m$^3$ in gas burner method. Therefore, it is thinked that if tested without error from preparing a sample to calculating amount of water, water content will be estimated exactly in the construction field.

• Microbiology and Biotechnology Letters
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• v.32 no.1
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• pp.84-90
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• 2004

Diglyceride (DG) was prepared by reaction of soybean oil and glycerol in the presence of lipase. The initial rate of DG production was greatly affected by the amount of lipase. However the DG content at equilibrium was hardly affected by the amount of lipase added to the reaction mixture. The initial rate of FFA formation was highly affected by the moisture content between 0.5 and 2.3%, but at higher water content (3.3-5.2%), there was a small increase in the rate. And DG content at equilibrium slowly increased with the increase of the water content in glycerol up to 4.4%. However, there was a sharp decrease in DG content at higher water content (5.2-6.4%) due to higher free fatty acid production. The highest yield of DC was obtained at the temperature ranges of 30-5$0^{\circ}C$. The final yield of DG was not dependent on the glycerol (GL) to triglyceride (TG) molar ratio. However, at the molar ratio of 0.75:1 (GL/TG), the enzyme-catalyzed reaction was highly efficient and utilized all the glycerol. In optimized conditions for glycerolysis a yield of approximately 45% DG was obtained. 66% of total DG was 1,3-DG.

• Journal of the Korean Magnetics Society
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• v.5 no.3
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• pp.191-196
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• 1995

NiCuZn ferrites were prepared by a solid-state reaction and sintered at $900^{\circ}C$ for 5 hours. Its properties were investigated by controlling the ferrite composition and processing. NiCuZn ferrite with a composition of ${(Ni_{0.2}Cu_{0.2}Zn_{0.6}O)}_{1.02}{(Fe_{2}O_{3})}_{0.98}$ was found to have the maximum initial permeability as a result of the variation of Cu content and the (Ni+Cu)/Zn ratio. Curie temperature($T_{c}$) of NiCuZn ferrite was decreased with the larger Cu content and increased with the larger Ni content. NiCuZn ferrites of ${(Ni_{0.2}Cu_{0.2}Zn_{0.6}O)}_{1-w}{(Fe_{2}O_{3})}_{1+w}$ composition milled for 20~80 hours had the maximum initial permeability at w=-0.015 and Curie temperature ($T_{c}$) was decreased with the increasing of $Fe_{2}O_{3}$ deficiency(w).

• Journal of the Korean Ceramic Society
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• v.29 no.6
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• pp.463-470
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• 1992

Corundum single crystals were grown in cryolite flux with the composition of Na3AlF6:Al2O3=80:20 wt%. This mixture was melted at 115$0^{\circ}C$, followed by slow cooling at a rate of 2$^{\circ}C$/hr to 96$0^{\circ}C$. And by adding of La2O3 to the flux, the change of crystal forms were observed. Crystal forms of corundum grown in cryolite flux had the habits of hexagonal plate which consist of well developed {0001} face and small {101} face. As La2O3 was added and its content was increased, {223} and {110} faces were developed, and crystal habits of equidimensional forms changed into hexagonal prism form. In a charge of 8 mole% B2O3, Al2O3:La2O3=15:1, transparent corundum single crystals of equent form were grown. As the content of B2O3 was increased, twineed crystals which have twin law of 2-fold parallel to [0001], and composition plane of (110) were grown.

• Journal of Biosystems Engineering
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• v.8 no.2
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• pp.62-68
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• 1983

This study was to examine the drying characteristics of barley and the effect of moisture content of barley on milling performance. A barley variety, Jogang, having 35.0% of initial moisture content was used for this experiment. Thermo-hydrostatic dryer which consists of blower, condensor, heater, humidifier, drying chamber and control box, etc., was used for the drying experiment. The change in the weight of a barley sample was continuously measured by means of the ring type load cell installed inside the drying chamber. Milling test runs the samples having the predetermined moisture content were taken from each drying test run. A laboratory type barley miller was used for the milling test. The results of the study are summarized as follows: 1. The drying constants (k) applied for the thin layer drying model, (M-Me)/(Mo-Me) = $Ae^{-kt}$ were 0.155, 0.259 and 0.548, respectively, at the three levels of drying temperatures, $40^{\circ}C$, $50^{\circ}C$ and $60^{\circ}C$. The drying constants complied with the Arrhenius Equation, K = Ko exp (-C/T), were determined as $Ko=1.901455{\times}10^8$ and C = 6563. 2. The laboratory milling test indicated that the highest milled and head barley recovery was resulted from the sample which was dryed at $40^{\circ}C$. In general, the increase in the drying temperature from $40^{\circ}C$ to $60^{\circ}C$ indicated a negative effect on milling yields. 3. Also, the sample having 15% M.C. presented the highest milled and head barley recovery among the five moisture content levels (12, 15, 18,21 and 24%).

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.5
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• pp.402-410
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• 2000

The electrical properties and stability of Pr$_{6}$/O$_{11}$-based ZnO wvaristors consisting of ZnO-Pr$_{6}$/O$_{11}$-CoO-Dy$_{2}$/O$_{3}$ based ceramics were investigated in the Dy$_{2}$/O$_{3}$ additive content range o 0.0 to 2.0 mol%. The density was nearly constant 5.62 g/cm$^3$corresponding to 97% of theoretical density as Dy$_{2}$/O$_{3}$ additive content increases up to 0.5 mol%. However the density decreased as Dy$_{2}$/O sub 3/ additive content is further additive content. Pr$_{6}$/O$_{11}$-based ZnO varistors doped with 0.5mol% Dy$_{2}$/O$_{3}$ exhibited a good nonlinearity, which is 37.76 in the nonlinear exponent and 5.36 $mutextrm{A}$ in the leakage current. And they exhibited very stress (0.80 V$_{1mA}$/9$0^{\circ}C$/12h)+(0.85 V$_{1mA}$/115$^{\circ}C$/12h)+(0.95 V$_{1mA}$/1$25^{\circ}C$/12h). Consequently it was estimated that ZnO-0.5 mol% Pr$_{6}$/O$_{11}$-1.0 mol% CoO-0.5 mol% Dy$_{2}$/O$_{3}$ based ceramics will be sufficiently used as a basic composition to develop the advanced Pr$_{6}$/O$_{11}$-based ZnO varistors in the future.he future.uture.he future.

• Macromolecular Research
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• v.11 no.4
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• pp.256-259
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• 2003

Measurements of Young's modulus, dielectric loss and a.c. conductivity have been carried out on EPDM rubber samples loaded with different concentrations of $CrCl_3$ (0,2,4 and 6 phr). The values of Young's modulus was found to be linearly dependent on the $CrCl_3$ content. Variation of the dielectric loss with temperature showed that $CrCl_3$ may act as plasticizer. However, at higher frequencies the dielectric loss was found to be independent of frequency and the rubber samples may behave as non-polar dielectric. Investigations of the a.c conductivity suggested that the conduction in these rubber samples can be described by small polaron tunneling. In addition, conductivity was found to increase with $CrCl_3$ content.