• Journal of the Korean Ceramic Society
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• v.40 no.10
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• pp.991-997
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• 2003

The effect of A1$_4$C$_3$ additive on the thermoelectric properties of SiC ceramics were studied. Porous SiC ceramics with 47∼59% relative density were fabricated by sintering the pressed $\alpha$-SiC powder compacts with A1$_4$C$_3$at 2100∼220$0^{\circ}C$ for 3 h in Ar atmosphere. Crystalline phases of the sintered bodies were identified by powder X-Ray Diffraction (XRD) and their microstructures were observed with a Scanning Electron Microscope (SEM). In the case of A1$_4$C$_3$ addition, the phase transformation of 6H-SiC to 4H-SiC could be observed during sintering. The Seebeck coefficient and electrical conductivity were measured at 550∼95$0^{\circ}C$ in Ar atmosphere. In the case of undoped specimens, the Seebeck coefficients were positive (p-type semiconducting) possibly due to a dominant effect of the acceptor impurities (Al, Fe) contained in the starting powder and electrical conductivity increased as increasing sintering temperature. Electrical conductivity of A1$_4$C$_3$doped specimen is larger than that of undoped specimen under the same condition, which might be due to the reverse phase transformation and increasing of carrier density. And the Seebeck coefficient of A1$_4$C$_3$ doped specimen is also larger than that of undoped specimen. The density of specimen, the amount of addition and sintering atmosphere had significant effects on the thermoelectric property.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.62 no.1
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• pp.66-72
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• 2017

Potato greening determines the shelf life and affects the marketability of this tuber. Various stresses during handling and storage interact to affect the tuber's physiological status and can affect the rate of greening. This study investigated the effects of storage temperature on tuber greening and shelf life in unwashed and washed potatoes of the cultivar Superior. Physiological and biochemical changes were examined during 15 days at room temperature ($23{\pm}2^{\circ}C$) under cool-white fluorescent light after storage for 1 month at different temperatures ($4^{\circ}C$, $20^{\circ}C$). Hunter a values were negative (-) for washed potatoes after 3 days (-0.8) and 15 days (-2.5) at room temperature following 1 month of storage at $4^{\circ}C$ while positive (+) values were observed for unwashed potatoes after 15 days at room temperature. The Hunter ${\Delta}E$ values of washed potatoes previously stored at $4^{\circ}C$ for 1 month increased after 3 days at room temperature compared with those of unwashed potatoes. The total chlorophyll content of washed potatoes was higher than that of unwashed potatoes. The highest correlation was observed between the Hunter ${\Delta}E$ value and Hunter a value (-0.93506), while a positive correlation coefficient (0.89806) was observed between greening criteria and Hunter ${\Delta}E$ value by using colorimetry. We conclude, therefore, that there is a biosynthetic link between temperature-induced chlorophyll accumulation and tuber greening in storage.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.18
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• pp.54-87
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• 1975

The effects of various weather factors on yield components of rice, year variation of yield components within regions, and regional differences of yield components within year were investigated at three Crop Experiment Stations O.R.D., Suweon, Iri, Milyang, and at nine provincial Offices of Rural Development for eight years from 1966 to 1973 for the purpose of providing information required in improving cultural practices and predicting the yield level of rice. The experimental results analyzed by standard partial regression analysis are summarized as follows: 1. When rice was grown in ordinary seasonal culture the number of panicles greatly affected rice yield compared to other yield components. However, when rice was seeded in ordinary season and transplanted late, and transplanted in ordinary season in the northern area the ratio of ripening was closely related to the rice yield. 2. The number of panicles showed the greatest year variation when the Jinheung variety was grown in the northern area. The ripening ratio or 1, 000 grain weight also greatly varied due to years. However, the number of spikelets per unit area showed the greatest effects on yield of the Tongil variety. 2. Regional variation of yield components was classified into five groups; 1) Vegetation dependable type (V), 2) Partial vegetation dependable type (P), 3) Medium type (M), 4) Partial ripening dependable type (P.R), and 5) Ripening dependable type (R). In general, the number of kernel of rice in the southern area showed the greatest partial regression coefficient among yield components. However, in the mid-northern part of country the ripening ratio was one of the component!; affecting rice yield most. 4. A multivariate equation was obtained for both normal planting and late planting by log-transforming from the multiplication of each component of four yield components to additive fashion. It revealed that a more accurate yield could be estimated from the above equation in both cases of ordinary seasonal culture and late transplanting. 5. A highly positive correlation coefficient was obtained between the number of tillers from 20 days after transplanting and the number of panicles at each(tillering) stage 20 days after transplanting in normal planting and late planting methods. 6. A close relationship was found between the number of panicles and weather factors 21 to 30 days, after transplanting. 7. The average temperature 31 to 40 days after transplanting was greatly responsible for the maximum number of tillers while the number of duration of sunshine hours per day 11 to 30 days after transplantation was responsible for that character. The effect of water temperature was negligible. 8. No reasonable prediction for number of panicles was calculated from using either number of tillers or climatic factors. The number of panicles could early be estimated formulating a multiple equation using number of tillers 20 days after transplantation and maximum temperature, temperature range and duration of sunshine for the period of 20 days from 20 to 40 days after transplantation. 9. The effects of maximum temperature and day length 25 to 34 days before heading, on kernel number per panicle, were great in the mid-northern area. However, the minimum temperature and day length greatly affected the kernel number per panicle in the southern area. The maximum temperature had a negative relationship with the kernel number per panicle in the southern area. 10. The maximum temperature was highly responsible for an increased ripening ratio. On the other hand, the minimum temperature at pre-heading and early ripening stages showed an adverse effect on ripening ratio. 11. The 1, 000 grain weight was greatly affected by the maximum temperature during pre- or mid-ripening stage and was negatively associated with the minimum temperature over the entire ripening period.

• Korean Journal of Soil Science and Fertilizer
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• v.37 no.3
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• pp.131-135
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• 2004

This study was carried out for the analysis of temperature characteristics on soil surface using soil heat flux which is one of the important parameters forming soil temperature. Soil surface temperature was estimated by using the soil temperature measured at 10 cm soil depth and the soil heat flux measured by flux plate at 5 cm soil depth. There was time lag of two hours between soil temperature and soil heat flux. Temperature changes over time showed a positive correlation with soil heat flux. Soil surface temperature was estimated by the equation using variable separation method for soil surface temperature. Arithmetic mean using temperatures measured at soil surface and 10 cm depth, and soil temperature measured at 5 cm depth were compared for accuracy of the value. To validate the regression model through this comparison, F-validation was used. Usefulness of deductive regression model was admitted because intended F-value was smaller than 0.001 and the determination coefficient was 0.968. It can be concluded that the estimated surface soil temperatures obtained by variable separation method were almost equal to the measured surface soil temperature.

• Korean Journal of Materials Research
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• v.18 no.9
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• pp.475-481
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• 2008

Positive temperature coefficient of resistivity (PTCR) characteristics of (1-x)$BaTiO_3-x(Bi_{0.5}K_{0.5})TiO_3$ ceramics doped with $Nb_2O_5$ were investigated in order to develop the Pb-free PTC thermistor available at high temperatures of > $120^{\circ}C$. The PTCR characteristics appearing in the ($B_{i0.5}K_{i0.5})TiO_3$ (< 5 mol%) incorporated $BaTiO_3$ ceramics, which might be mainly due to $Bi^{+3}$ ions substituting for $Ba^{+2}$ sites. The 0.99$BaTiO_3-0.01(Bi_{0.5}K_{0.5})TiO_3$ ceramics showed good PTCR characteristics of a low resistivity at room temperature (${\rho}_r$) of $31{\Omega}{\cdot}cm$ a high ${\rho}_{max}/{\rho}_{min}$ ratio of $5.38{\times}10^3$, and a high resistivity temperature factor (${\alpha}$) of $17.8%/^{\circ}C$. The addition of $Nb_2O_5$ to 0.99$BaTiO_3-0.01(Bi_{0.5}K_{0.5})TiO_3$ ceramics further improved the PTCR characteristics. Especially, 0.025 mol% $Nb_2O_5$ doped 0.99$BaTiO_3-0.01(Bi_{0.5}K_{0.5})TiO_3$ ceramics exhibited a significantly increased ${\rho}_{max}/{\rho}_{min}$ ratio of $8.7{\times}10^3$ and a high ${\alpha}$ of $18.6%/^{\circ}C$, along with a high $T_c$ of $148^{\circ}C$ despite a slightly increased ${\rho}_r$ of $31{\Omega}{\cdot}cm$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.12
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• pp.929-935
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• 2010

$(1-x)BaTiO_3-x(Bi_{0.5}Na_{0.5})TiO_3$ ($0.01{\leq}x{\leq}0.10$) ceramics were fabricated with muffled sintering by a modified synthesis process. Their positive temperature coefficient of resistivity (PTCR) characteristics were investigated systematically. All specimen showed a perovskite structure with a tetragonal symmetry. Both the lattice parameter of a and c axes were slightly decreased with increasing $(Bi_{0.5}Na_{0.5})TiO_3$ (BNT) content. Grain growth was achieved when the incorporated BNT was increased to 6 mol% and the inhibition of grain growth is considered to be due to the appearance of Ba vacancy ($V^{"}_{Ba}$) in the $(1-x)BaTiO_3-x(Bi_{0.5}Na_{0.5})TiO_3$ ($0.08{\leq}x$). With 4 mol% BNT addition, room temperature resistivity decreased to $48 \Omega{\cdot}cm$ and a resistivity jump ($\rho_{max}/\rho_{min}$) was as high as $1.1{\times}10^4$, respectively. Curie temperature was also increased to $171^{\circ}C$ with increasing BNT content.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1254_1255
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• 2009

The composites were fabricated by adding 30, 35, 40, 45[vol.%] Zirconium Diboride(hereafter, $ZrB_2$) powders as a second phase to Silicon Carbide(hereafter, SiC) matrix. The physical, mechanical and electrical properties of electroconductive SiC ceramic composites by Spark Plasma Sintering(hereafter, SPS) were examined. Reactions between $\beta$-SiC and $ZrB_2$ were not observed in the XRD analysis. The relative density of SiC+30[vol.%]$ZrB_2$, SiC+35[vol.%]$ZrB_2$, SiC+40[vol.%]$ZrB_2$ and SiC+45[vol.%]$ZrB_2$ composites are 88.64[%], 76.80[%], 79.09[%] and 88.12[%], respectively. The XRD phase analysis of the electroconductive SiC ceramic composites reveals high of SiC and $ZrB_2$ and low of $ZrO_2$ phase. The electrical resistivity of SiC+30[vol.%]$ZrB_2$, SiC+35[vol.%]$ZrB_2$, SiC+40[vol.%]$ZrB_2$ and SiC+45[vol.%]$ZrB_2$ composites are $6.74{\times}10^{-4}$, $4.56{\times}10^{-3}$, $1.92{\times}10^{-3}$ and $4.95{\times}10^{-3}[{\Omega}{\cdot}cm]$ at room temperature, respectively. The electrical resistivity of SiC+30[vol.%]$ZrB_2$, SiC+35[vol.%]$ZrB_2$, SiC+40[vol.%]$ZrB_2$ and SiC+45[vol.%]$ZrB_2$ are Positive Temperature Coefficient Resistance(hereafter, PTCR) in temperature ranges from 25[$^{\circ}C$] to 500[$^{\circ}C$]. It is convinced that SiC+40[vol.%]$ZrB_2$ composite by SPS can be applied for heater or electrode.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.7
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• pp.667-674
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• 2020

The adsorption of reactive orange 16 (RO 16) dye by activated carbon was investigated using the amount of adsorbent, pH, initial concentration, contact time and temperature as adsorption variables. The investigated process parameters were separation coefficient, rate constant, rate controlling step, activation energy, enthalpy, entropy, and free energy. The adsorption of RO 16 was the highest at pH 3 due to the electrostatic attraction between the cations (H⁺) on the surface of the activated carbon and the sulfonate ions and hydroxy ions possessed by RO 16. Isotherm data were fitted into Langmuir, Freundlich and Temkin isotherm models by applying the evaluated separation factor of Langmuir (RL=0.459~0.491) and Freundlich (1/n=0.398~0.441). Therefore, the adsorption operation of RO 16 by activated carbon was confirmed as an appropriate removal method. Temkin's adsorption energy indicated that this adsorption process was physical adsorption. The adsorption kinetics studies showed that the adsorption of RO 16 follows the pseudo-second-order kinetic model and that the rate controlling step in the adsorption process was the intraparticle diffusion step. The positive enthalpy change indicated an endothermic process. The negative Gibbs free energy change decreased in the order of -3.16 <-11.60 <-14.01 kJ/mol as the temperature increased. Therefore, it was shown that the spontaneity of the adsorption process of RO 16 increases with increasing temperature.

• Journal of Bio-Environment Control
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• v.13 no.2
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• pp.73-80
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• 2004

Two red pepper(Capsicum annuum L.) cultivars, 'Geumtap' and 'Bugang', were cultivated at main producing areas in Korea and harvested four times in 1998 and 1999. Length, weight, dry matter ratio and color of red peppers were measured at each harvest. The relations between external characteristics with regional climatic elements such as total accumulated air temperature, total amount of precipitation and duration of sunshine during the fruit growing periods were compared. Length and fruit weight decreased by delayed harvest. These characteristics were shown significant difference according to cultivars, but not to growing year. Dry matter ratio had a tendency to increase at the 3rd and 4th harvest. The red color as measured a${\times}$L values of pepper powder, increased with being later in harvesting, but the trend was uncertain. In fruit growth, fruit length showed a positive correlation with total accumulated air temperature in later growth period of fruits(from 1st to 20th day before harvesting), and fruit weight had relationships with accumulated air temperature and total amount of precipitation in later growth period of fruit. There was no relation between dry matter ratio and climate elements. The red color was shown high correlations with total amount of precipitation and duration of sunshine. There was highest coefficient of determination($r^2$) in all external characteristics.

• The Journal of Korean Medicine
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• v.27 no.1 s.65
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• pp.165-183
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• 2006

Objectives : We implemented the Artemisia Extract Moxibustion Method and had the clinical tests for the diabetes with it. Methods : We implemented Artemisia extract made by extracting the vasodilator and antioxidant compounds from Artemisia-CH2C12 fraction and the moxibustion method constructed with DC Power supply, controller, Artemisia pad. single and multiple heating terminal with PTC(Positive Temperature Coefficient) thermistor. And we performed to estimate the efficiency on the questionnaire and the clinical tests with 23 cases of the diabetics. Results : We have estimated the improvement over 60% the symptoms that were the upper and lower limbs pain, frequent urination, spontaneous perspiration, thirst, decrease of body weight, and malaise after the moxibustion treatment on 5 cases among 23 cases. And the 19 cases took the biochemical check-up after the moxibustion treatment. From the results of biochemical check-up, the average HbAlc of before treatment was 8.400%, and after treatment 7.632%. The average HbAlc was decreased significantly after treatment (P<0.001). And the average urinary blood of before treatment was 0.73 and after treatment 0.27. The average urinary blood was decreased significantly after treatment (P<0.001). In addition the average FBS before treatment was 182.64 mg/dl, after treatment 161.77 mg/dl. Conclusions : We could estimate that our proposed moxibustion method was a significant treatment method for the diabetes.