• Clean Technology
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• v.22 no.4
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• pp.258-268
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• 2016

In this work, carboxymethylcellulose-based composite superabsorbent hydrogels were prepared by electron beam radiation. The composition of carboxymethylcellulose (CMC) varied from 4 wt%, 5 wt%, and 6 wt% to 7 wt% based on the amount of distilled water in the syntheses of hydrogels. Graphite oxide, reduced graphene oxide, activated carbon, and bentonite were used as additives for the synthesis of composite superabsorbent. The effect of CMC composition and the type of additives on the gel properties of the prepared hydrogels was investigated. In order to verify the functional groups in the prepared materials, Fourier transform infrared spectroscopy was used. In addition, mechanical strength, gel fraction, swelling kinetics, and equilibrium swelling ratios were measured for the prepared hydrogels. Swelling experiments were carried out in distilled water, urea solution, and physiological saline water. Prepared hydrogels were reused for 5 times, and gel fraction and swelling ratio were measured at every 24 hours. Among the prepared hydrogels, $C_{5%}GO$ and $C_{5%}rGO$ exhibited excellent mechanical property and relatively high swelling ratios for urea solution and physiological saline water with promising applicability as slow-release fertilizers.

• Applied Chemistry for Engineering
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• v.9 no.5
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• pp.654-660
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• 1998

In preparing PSZT powder by hydrothermal synthesis, effects of reaction temperature, concentration of raw materials and mineralizer on crystallinity, particle size distribution, and dielectric constant were investigated. By varying the concentration of mineralizer and the ratio of Pb to Sr or Zr to Ti, crystalline PSZT powder, having the mean particle size of $0.3{\sim}15{\mu}m$, was prepared by hydrothermal synthesis in the temperature range of $120{\sim}200^{\circ}C$ for a 2h reaction. PSZT ceramics, having dielectric constant of 1000~3000, were prepared at $1150^{\circ}C$ for a 2h sintering reaction of the PSZT powders. Experimental results showed that the weight mean particle size of $0.5{\mu}m$ was obtained when the concentration of KOH in the solution was 10 wt % and the ratio of Pb to Sr was 0.95/0.05, that of Zr to Ti was 0.52/0.48. It also showed that the ceramics of dielectric constant of 2900 were prepared through sintering of this PSZT powder. Size of PSZT particles became smaller with its narrow distribution as the concentration of KOH increased up to 10 wt %. However, it came to be larger at this concentration and above. By adding small amount of Sr that would not affect that crystallinity of particles we can improve dielectric property of sintered materials. Addition of Zr may shift the major crystal phase of synthetic PSZT powder from tetragonal to rhombohedral phase.

• Resources Recycling
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• v.31 no.6
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• pp.52-59
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• 2022

Calcium silicate based cement (CSC) is a low-carbon cement that emits less CO₂ by up to 70% compared to ordinary Portland cement during its manufacture. Most developed countries have commercialized CSC, whereas Korea is still investigating the manufacturing characteristics and basic properties of CSC. This paper provides a review of methods for manufacturing CSC using domestic raw materials and discusses the possibility of CSC localization based on an evaluation of the basic physical properties of manufactured CSC. The experimental results of this study indicate that the primary mineral components of CSC were CS, C₃S₂ C₂S, and unreacted SiO₂. This suggests the possibility of manufacturing CSC using domestic raw materials that exhibit mineral compositions similar to that of theoretical CSC. The compressive strength of CSC mortar is less than 1MPa at the age of 7 d under wet curing. This implies that hydration does not affect the property development of CSC mortar. Meanwhile, during carbonation curing, the compressive strength is 56 MPa or higher after 7 d, which indicates excellent early strength development. Furthermore, results of Thermogravimetric Analysis Differential scanning calorimetry (TG/DSC) show that a significant amount of CaCO₃ is formed, which is consistent with the results of previous studies. This implies that carbonation is associated significantly with the properties of CSC.

• Journal of Mushroom
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• v.13 no.1
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• pp.74-78
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• 2015

The 'Heuktari', a new mid-high temperature adaptable variety of oyster mushroom for the bottle culture, was bred by mating with monokaryons isolated from 'P11056' and 'MT07156'. The optimum temperature for the mycelial growth was $23{\sim}26^{\circ}C$ on PDA medium and that for the primordia formation and the growth of fruiting body of 'Heuktari' was $18{\sim}19^{\circ}C$ on sawdust substrate. In case of bottle cultivation, the period of mycelial growth was required about 30 days. In addition, the period of primordia formation and growth of fruiting body was 4 days and 5 days, respectively. In the characteristics of fruiting body, shape and color of pilei were round type and dark grayish brown, stipe color was white color and stipe shape was short and thick. The yield of fruiting bodies was 180 g/900 ml bottle which was 15% higher than that of Suhan-1ho. The gumminess and brittleness of stipe tissue were 110% and 140% stronger than those of Suhan-1ho, respectively.

• Journal of the Korean Society of Radiology
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• v.3 no.4
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• pp.35-38
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• 2009

Flat-panel x-ray detectors using a phosphor and photoconductor material have been used for application in various medical modalities. In this study, the monte carlo simulation, optical and x-ray response characteristics were investigated in the conversion structure obtained by a columnar CsI:Na scintillation layer with a photosensitive amorphous selenium layer. Firstly, from the measurement of luminescent spectrum of CsI:Na and absorption spectrum of a-Se layer, the signal conversion characteristics are analysed. And also, the x-ray sensitivity is measured and compared with conventional a-Se($500{\mu}m$) as a function of electrical field. From the experimental result, the x-ray sensitivities of the CsI:Na($180{\mu}m$)/a-Se($30{\mu}m$) detector and the a-Se($500{\mu}m$) detector were $7.31nC/mR-cm^{2}$ and $3.95nC/mR-cm^{2}$at an electric field of $10V/{\mu}m$, respectively.

• Reproductive and Developmental Biology
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• v.33 no.1
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• pp.25-28
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• 2009

This study was carried out to investigate the general characteristics, such as volume, pH, sperm motility and sperm concentration of the semen collected from Beagle dogs (age $24{\sim}48$ months, weight $10{\sim}15\;kg$) by using the method of digital manipulation of the penis, and the effect of preservation temperature and time on motility of fresh semen. Multiple ejaculates were collected from 4 male Beagles. The average volume, pH, motility and sperm concentration of the second fraction (contained with small volume of the third fraction) per ejaculation were $2.94{\pm}0.24(SD)\;ml$, $6.43{\pm}0.42(SD)$, $97.04{\pm}3.50(SD)%$ and $1.67{\pm}0.23(SD){\times}10^8\;cells/ml$, respectively. Average semen volume per ejaculate, semen pH, sperm motility and sperm concentration of the first fraction from the ejaculate were $1.24{\pm}0.20(SD)\;ml$, $6.03{\pm}0.26(SD)$, $1l.30{\pm}4.02(SD)%$ and $7.25{\pm}1.02(SD){\times}10^5\;cells/ml$. Those of second fraction were $2.52{\pm}0.32(SD)\;ml$, $6.32{\pm}0.31(SD)$, $96.25{\pm}3.52(SD)%$ and $2.35{\pm}0.35(SD){\times}10^8\;cells/ml$. Those of third fraction were $2.71{\pm}0.27\;(SD)\;ml$, $6.52{\pm}0.20(SD)$, $95.65{\pm}2.78(SD)%$ and $5.72{\pm}0.29(SD){\times}10^7\;cells/ml$. Motility of semen was higher at $17^{\circ}C$ preservation temperature than $5^{\circ}C$ or $36^{\circ}C$ during preservation period. When preservation temperature was $17^{\circ}C$, motility was $96.54{\pm}2.05(SD)%$ at 1 h, $90.20{\pm}3.90(SD)%$ at 6 h, $89.05{\pm}2.01(SD)%$ at 12 h, $78.21{\pm}3.50(SD)%$ at 18 h, $45.24{\pm}6.25\;(SD)%$ at 24 h and $30.75{\pm}17.24(SD)%$ at 30 h, respectively.

• Applied Chemistry for Engineering
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• v.18 no.1
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• pp.77-83
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• 2007

It is essential that second order nonlinear optical materials have low optical propagation losses in the wavelengths of second harmonic generation for practical applications in waveguides. Three dipolar chromophores substituted with nitro, cyano, and alkyl sulfone as an electron withdrawing group were prepared. The UV-Vis absorption spectra of the cyano and alkylsulfone chromophores showed a blue-shift compared to the nitro chromophore. The introduction of oxadiazole segment in the chromophore structure led to similar spectral shift. The blue-shift can produce low optical loses at second harmonics. The chromophores were successfully attached to a polyimide, yielding side chain polymers. The nonlinear optical property of the prepared optical polymers was determined by measuring electro-optic coefficient at 1.55 mm. The polymers exhibited high glass transition temperature of over $185^{\circ}C$ and thermal stability to $300^{\circ}C$ through differential scanning calorimeter analysis and thermal gravimetric analysis.

• The korean journal of orthodontics
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• v.30 no.4 s.81
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• pp.475-481
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• 2000

The purpose of this study was to evaluate the effect of oral environment on the strength of resin bracket wings by comparing fracture mode according to water immersion and thermocycling. Seventy-five resin brackets(Spirit MB, Ormco, California) were divided into three groups and treated for six months as follows; (1) untreated, (2) water immersion in distilled water at $37^{\circ}C$, (3) water immersion in distilled water at $37^{\circ}C$ with total 2,100 times of thermocycling taken 350 times each month. Fracture mode of the wing was tested on universal testing machine. In addition to resin brackets, 25 metal brackets were used as controls. Through the statistical analyses, following results were obtained. 1. Resin bracket wings showed significantly lower fracture strength than metal brackets(p<0.001). 2. Water immersion and water immersion with thermocycling groups showed significantly lower fracture strength than open air condition group(p<0.001). 3. Water immersion with thermocycling group showed significantly lower fracture strength than water immersion group(p<0.001). The above results suggest that the mechanical property of resin bracket wing nay be influenced by oral environment and further research is needed to improve the strength of the wing in the resin bracket.

• Journal of the Korean Vacuum Society
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• v.17 no.6
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• pp.560-565
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• 2008

$(Pb_{0.98}La_{0.08})(Zr_{0.65}Ti_{0.35})O_3$ (PLZT) thin films with $TiO_2$ buffer layers were deposited on Pt/Ti/$SiO_2$/Si substrates by an R.F. magnetron sputtering method in order to improve the ferroelectric characteristics of the films. And the ferroelectric properties and crystallinities of the PLZT thin films were investigated in terms of the effects of the post annealing temperatures of $TiO_2$ buffer layers between a platinum bottom electrode and PLZT thin film. The ferroelectric properties of the PLZT thin films improved as increasing of the post annealing temperatures of $TiO_2$ layers, thereby reaching their maximum at $600^{\circ}C$.

• Korean Journal of Microbiology
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• v.51 no.3
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• pp.241-248
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• 2015

Although studies on probiotics have been performed mostly with viable microbes, the beneficial functions of dead or heat-killed form of probiotic strains have also been examined. In this study, live and heat-killed forms of Lactobacillus acidophilus CBT LA1 were investigated in vitro and in vivo to evaluate the properties necessary for gut barrier protection. Cell surface hydrophobicity (CSH), autoaggregation (AA), cell adhesion, and lipopolysaccharide (LPS)-binding properties were evaluated. In addition, the suppressive effect on LPS-induced interleukin (IL)-8 expression was investigated in HT-29 cells. To identify optimal conditions for CBT LA1 to adhere to HT-29 cells, CBT LA1 cells were heat-treated at 80, 85, 90, 95, 100, or $121^{\circ}C$ for 10 min; cells treated at $80^{\circ}C$ for 10 min showed the highest adhesion. Heat-killed bacteria at $80^{\circ}C$ showed higher levels of LPS-binding, CSH, AA, adhesion to HT-29, and suppression of IL-8 expression than did live CBT LA1. In vivo imaging was performed to evaluate the ability of live or heat-killed CBT LA1 to remove LPS from the intestine in a rat model of infection. At 16 h after infection, fluorescence from FITC-conjugated LPS had mostly disappeared from the intestine of the rats administered with live or heat-killed CBT LA1; the effect was greater with heat-killed CBT LA1 at $80^{\circ}C$. These results suggest that heat-killed CBT LA1 as well as its live form can be applied as a pharmabiotic for protection of the gut barrier.