• Restorative Dentistry and Endodontics
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• v.30 no.2
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• pp.128-137
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• 2005

In this study we measured the amount of light energy that was projected through the tooth material and analyzed the degree of polymerization by measuring the surface hardness of composites. For polymerization, Optilux 501 (Demetron, USA) with two types of light guide was used: a 12 mm diameter light guide with 840 nW/$cm^2$ light intensity and a 7 mm diameter turbo light guide with 1100 nW/$cm^2$. Specimens were divided into three groups according to thickness of penetrating tooth (1 mm, 2 mm, 0 mm). Each group was further divided into four subgroups according to type of light guide and curing time (20 seconds, 40 seconds). Vickers' hardness was measured by using a microhardness tester. In 0 mm and 1 mm penetrating tooth group, which were polymerized by a turbo light guide for 40 seconds, showed the highest hardness values. The specimens from 2 mm penetrating tooth group, which were polymerized for 20 seconds, demonstrated the lowest hardness regardless of the types of light guides (p < 0.05). The results of this study suggest that, when projecting tooth material over a specified thickness, the increase of polymerization will be limited even if light intensity or curing time is increased.

• Journal of Aquaculture
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• v.18 no.1
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• pp.26-30
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• 2005

A 10-week feeding trial was conducted to determine the optimum feeding rate of two extruded pellets (EP1 and EP2) and raw fish-based moist pellet (MP) for juvenile flounder. Two replicate groups of the fish (average weight of 27 g) were fed EP and MP three times daily at different feeding rate (satiation and $85\%$ satiation). Weight gain of fish was not affected by diet, but affected by feeding rate. Weight gain with satiation feeding group showed :t tendency to higher compared to that of fish with $85\%$ satiation feeding at the same diet. Feed efficiency of fish was affected by diet, but not feeding rate. Feed efficiency of fish fed the EP1 and EP2 was higher than that of fish fed the MP at the same feeding rate. Daily feed intake was affected by diet and feeding rate. Daily feed intake of fish fed with satiation was higher than that of fish with $85\%$ satiation at same diet, and this variable of fish fed the MP was higher than that of fish fed the EP 1 and EP2. Protein efficiency ratio of fish fed the MP was significantly lower than that of fish fed the EP1 and EP2 regardless of feeding rate. Lipid content of whole body was affected by diet, and that of fish fed the EP2 and MP at satiation feeding was the highest. It can be concluded that satiation feeding will be good and EP is better than MP for growth of juvenile flounder grown from 27 g to 51 g.

• Korean journal of food and cookery science
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• v.19 no.6
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• pp.783-793
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• 2003

The effects of various kinds of starch (mungbean, potato, corn and a blend of potato and com starch) on the quality characteristics of muhwakwa-pyun were studied according to the storage duration. The sweetness, pH and total acidity of muhwakwa extract were analyzed, as were the Visco/Amylograph viscosity profile and DSC thermodynamic characteristics of starches. For quality characteristics, color difference, instrumental texture characteristics and sensory characteristics were compared. The sweetness of muhwakwa extract was satisfactory but the total acidity was low for Kwa-pyun manufacture. Therefore, its pH was adjusted to 3.4 by adding 10％ citric acid with an amount of 1％ of total liquid. From the Visco/Amylograph viscosity profile and DSC thermodynamic characteristics of starches, a blend of potato and com starch was found to be easy to cook and form a gel but a little more resistant than the other starches in terms of retrogradatin. Lightness (L) and yellowness (b) of Kwa-pyun increased while its redness (a) decreased by the storage. The color became whiter and the clarity decrease regardless of the kinds of starch, which became obvious after 3 days of storage. The hardness, springiness, adhesiveness and cohesiveness tended to decrease with storage, which was weak in a blend starch. The overall acceptability of Kwa-pyun made with a blend of potato and com starch was evaluated as being the best among the samples tested. Therefore, for traditional kwa-pyun manufacture manufacture mungbean starch might be replaced with a blend of potato and corn starch which is less expensive and easily available in the market nowadays.

• The Korean Journal of Ecology
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• v.24 no.3
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• pp.157-168
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• 2001

Herbicides have been used to control weeds for decades. If detoxification upon exposure to herbicides requires considerable amounts of energy, it could affect the pattern of resource allocation to growth and reproduction of crops. We examined the effects of three levels of a herbicide (Control, Low, and High) on germination, growth and reproductive characters of Glycine max treated twice, i.e., before and after seed germination. Since flowering time of G. max was separated into two groups, flowering time was also considered as a variable in this study. The rate of seed germination tended to be higher at the low level of herbicide compared to other levels. Chlorosis and shape variation of leaves were apparent after the second herbicide treatment, but completely disappeared after six weeks of treatment. The herbicide effects on growth characters were somewhat different between early and late flowering plants, but plants treated with both low and high levels of herbicide reduced their growth compared to those in the control group regardless of flowering time. Plants at the high level of herbicide exhibited the highest growth rate later in the season, suggesting that plants compensated to some extent for reduced growth. However, growth reduction among plants at the high level of herbicide was persistent until the end of growing season. Among plants flowered late in the season, plants in the control level bore a higher number of nodules per plant than those in other levels; such a pattern did not exist among plants flowered early in the season. Plants treated with low and high levels of herbicide produced a lower number of flowers than those in the control. Thus, the herbicide examined affected not only the growth and reproductive characters of non-target crops but also the development and growth of root nodules.

• Applied Chemistry for Engineering
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• v.19 no.5
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• pp.477-483
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• 2008

$La_{0.7}Sr_{0.3}Co_{0.2}Fe_{0.8}O_{3-{\delta}$ oxide was synthesized by a citrate method and a typical dense membrane of perovskite oxide has been prepared using as-prepared powder by pressing and sintering at $1300^{\circ}C$. Precursor of $La_{0.7}Sr_{0.3}Co_{0.2}Fe_{0.8}O_{3-{\delta}$ prepared by citrate method was investigated by TGA and XRD. Metal-citrate complex in precursor was decomposed into perovskite oxide in the temperature range of $260{\sim}410^{\circ}C$ but XRD results showed $SrCO_3$ existed as impurity at less than $900^{\circ}C$. Electrical conductivity of membrane increased with increasing temperature but then decreased over $700^{\circ}C$ in air atmosphere ($Po_2=0.2atm$) and $600^{\circ}C$ in He atmosphere ($Po_2=0.01atm$) respectively due to oxygen loss from the crystal lattice. The oxygen permeation flux increased with increasing temperature and maximum oxygen permeation flux of $La_{0.7}Sr_{0.3}Co_{0.2}Fe_{0.8}O_{3-{\delta}$ membrane with 1.6 mm thickness was about $0.31cm^3/cm^2{\cdot}min$ at $950^{\circ}C$. The activation energy for oxygen permeation was 88.4 kJ/mol in the temperature range of $750{\sim}950^{\circ}C$. Perovskite structure of membrane was not changed after permeation test of 40 h and the membrane was stable without secondary phase change with 0.3 mol Sr addition.

• Clean Technology
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• v.27 no.4
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• pp.359-366
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• 2021

Halloysite nanotubes (HNTs), the multiwalled clay mineral with the composition of Al₂Si₂O₅(OH)₄·nH₂O, have been highlighted as a low-cost adsorbent for the removal of dyes from wastewater. Although a powder of halloysite presents a high specific surface area, forming media are significantly considered due to sludge-clogging induced by the water-bound agglomeration. However, higher firing temperature to achieve the structural durability of the media and lower utilization rate due to longer penetration depth into the media act as hurdles to increase the dye-adsorption capacity. In this work, the retention of the adsorption capacity of halloysite was evaluated with methylene blue solution after the heat treatment at 750 ℃. In order to improve the utilization rate, tubular media were fabricated by extrusion. The images taken by transmission electron microscopy show that HNTs present excellent structural stability under heat treatment. The HNTs also provide superb capacity retention for MB adsorption (93%, 18.5 mg g^-1), while the diatomite and Magnesol^® XL show 22% (7.65 mg g^-1) and 6% (11.7 mg g^-1), respectively. Additionally, compositing with lignin enhances adsorption capacity, and the heat treatment under the hydrogen atmosphere accelerates the adsorption in the early stage. Compared to the rod-type, the tubular halloysite media rapidly increases methylene blue adsorption capacity.