• Journal of the korean academy of Pediatric Dentistry
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• v.33 no.1
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• pp.25-34
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• 2006

Fluoride released from dental restorative materials effectively declines the incidence and activity of dental caries and inhibits tooth demineralization. This study investigated the fluoride release and uptake characteristics of one composite resin $(Z-250^{TM})$ three glass ionomer-based restorative material ($Dyract^{(R)}$ AP, Fuji II $LC^{(R)}$, Fuji IX GP $Fast^{(R)}$) Forty discs(6mm diameter and 1mm height) were prepared for each material. Each disc was immersed in 5ml of distilled water within polyethylene vial and stored at $37^{\circ}C$. The distilled water was changed every 24 hours and the release of fluoride was measured for 31 days. At the end of this period, each specimen was subjected to one of four treatments : (A) no fluoride treatment (control), (B) application of a fluoride dentifrice (500ppm) for three minutes three times; (C) application of the 1.23% acidulated phosphate fluoride(APF) foam for one minute once, (D) the same regimen as (B), plus application of the APF foam for one minute once. Then, all samples were reassessed for an additional 7 days. For all samples, the greatest fluoride release was observed after the first day of the study but diminished with time. On the 7th day of the study, fluoride release level was stabilized. Fuji II $LC^{(R)}$ and Fuji IX GP $Fast^{(R)}$ released higher amount of fluoride than other materials ; however, no statistically significant difference was found from Fuji II $LC^{(R)}$ and Fuji IX GP $Fast^{(R)}$. The amount of fluoride of $Dyract^{(R)}$ AP, Fuji II $LC^{(R)}$ and Fuji IX GP $Fast^{(R)}$ was increased after fluoride treatment, and diminished with time.

• Journal of Korean Society of Forest Science
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• v.32 no.1
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• pp.73-86
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• 1976

Two individuals ($sp_1$, $sp_2$) of purple and one individual ($sd_1$) of red hearted flower were selected from 18 years old Hibiscus syriacus trees obtained from the seeds treated with colchicine, and their morphological and physiological characteristics were investigated and following results were obtained. 1. The somatic chromosome number of the selected individuals, $sp_1$, $sp_2$, and $sd_1$ were 2n=160, while that of the check tree was 2n=80, indicating that the selected individuals, $sp_1$, $sp_2$ and $sd_1$ were tetraploid. 2. Peroxidase isoenzyme bands of high activity in selected individuals, $sp_1$, $sd_1$ and check tree were mostly in cathode, fixed band was f and v bands, and frequency of each band and their activity were not different between selected individuals, $sp_1$ and $sd_1$ and check tree. 3. The flowers of $sp_1$ individual were large in size and more dark purple than check tree's. The flowers of $sp_2$ individual were not increased in size, but they were dark purple and red heart at the base of the petal was expanded to 2/3 of the petal length. The flower of $sd_1$ individual was also large and some of the red lines from the petal base were extended to 2/3 of the petal length, which was much longer than those of the check tree. 4. Thickess of leaves, length of guard cells, diameter of pollens, wood fiber lengths and woody fiber widths were all increased in $sp_1$, $sp_2$ and $sd_1$ as compared to those of the check tree. 5. Survival percentage of cuttings was 80% with $sp_1$ and 36% with $sd_1$, and their growth performance were inferior to control in their second growing season.

• Journal of Korean Society of Forest Science
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• v.88 no.1
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• pp.73-85
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• 1999

This study was conducted to reveal the characteristics of the early growth by locality for Korean white pine planted in Gapyung and Kwangju, Kyunggi-Do and Youngdong, Choongchungbuk-Do. The effects of local climatic conditions as one of environmental factors on the growth were also analyzed. For this, several stand variables such as number of trees survived, mean DBH, mean height, basal area per hectare, and volume per hectare by stand age were measured and summarized for each locality. Based on these statistics, periodic annual increments for 8 years from stand age 10 to 18 were calculated for each of stand variables. A topoclimatological technique, for the estimation of local climatic conditions, which makes use of empirical relationships between the topography and the weather in study areas was applied to produce reasonable estimates of monthly mean, maximum, minimum temperatures, relative humidity, precipitation, and hours of sunshine over remote land area where routine observations are rare. From these monthly estimates, 17 weather variables such as warmth index, coldness index, index of aridity etc. which affect the tree growth, were computed for each locality. The periodic annual increments were then correlated with and regressed on the weather variables to examine effects of local weather conditions on the growth. Gapyung area provided the best conditions for the growth of Korean white pine in the early stage and Kwangju area ranked second. On the other hand, the growth pattern in Youngdong ranked last overall as expected. It is also found that the local growth patterns of Korean white pine in juvenile stage were affected by typical weather conditions. The conditions such as low temperature, high relative humidity, and large amount of precipitation provide favorable environment for the growth of Korean white pine. Especially, the diameter growth, basal area growth, and volume growth are mainly influenced by the amount of precipitation. However, it is proved that the height growth is affected by both the precipitation and temperature.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.21 no.2
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• pp.89-109
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• 1999

Vascular spasm which has been reported to occur in 25% of clinical cases continues to be a problem in microvascular surgery; When prolonged and not corrected, it can lead to low flow, thrombosis, and replant or free flap failure. Ischemia, intimal damage, acidosis and hypovolemia have been implicated as contributors to the vascular spasm. Although much work has been done on the etiology and prevention of vasospasm, a spasmolytic agent capable of firmly protecting against or reversing vasospasm has not been found. Therefore vascular freezing was introduced as a new safe method that immediately and permanently relieves the vasospasm and can be applied to microsurgical transfers. Cryosurgery can be defined as the deliberate destruction of diseased tissue or relief the vascular spasm in microvascular surgery by freezing in a controlled manner. 96 Sprague Dawley rats each weighing within 250g were used and divided into 2 group, experimental 1 and 2 group. In the experimental 1 group, right epigastric vessels (artery and vein) were freezed with a cryoprobe using $N_2O$ gas for 1 min. In the experimental 2 group, after freezing for 1 min, thawing for 30 secs and repeat freezing for 30 secs. Left side was chosen as control group in both group. We sacrified the experimental animals by 1 day, 3 days, 1 week, 2 weeks, 4 weeks & 5 months and observed the sequential change that occur during regeneration of epigastric vessels using a histologic, histomorphometric, immunohistochemical and SEM study after the vascular freezing. The results were as follows1. In epigastric arteries, internal diameters had statistically significant enlargement in 1 day, 3 days of Exp-1 group and 1 day, 3 days, 1 week & 2 weeks of Exp-2 group. Wall thickness had statistically significant thinning in 2 weeks of Exp-2 group. 2. In epigastric veins, internal diameters had enlargement of statistical significance in 1 day of Exp-1 and Exp-2 group. 3. The positive PCNA reactions in smooth muscle appeared in 1 week and increased until 2 weeks, decreased in 4 weeks. There was no statistical significance between Exp-1 and Exp-2 group. 4. The positive ${\alpha}$-SMA reaction in smooth muscles showed weak responses until 1 week and slowly increased in 2 weeks and showed almost control level in 4 weeks. 5. The positive S-100 reactions in the perivascular nerve bundles showed markedly decrease in 1 day, 3 days and increased after 1 week and showed almost control level in 4 weeks. Exp-1 group had stronger response than Exp-2 group. 6. In SEM, we observed defoliation of endothelial cell and flattening of vessel wall. Exp-2 group is more destroyed and healing was slower than Exp-1 group. To sum up, relief of vasospasm (vasodilatation) by freezing with cryoprobe was originated from the damage of smooth muscle layer and perivascular nerve bundle and the enlargement of internal diameter in vessels was similar to expeimental groups, but Exp-2 group had slower healing course and therefore vessel freezing in microsurgery can be clinically used, but repeat freezing time needs to be studied further.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.21 no.4
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• pp.360-365
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• 1999

This study was aimed to suggest to better treatment method of jaw cyst that the maximum diameter was wider than 3cm, using different treatment and clinical and radiographic result. We divided the 60 patients into three groups, group A(20 patients) were treated with cyst enucleation and Decalcified Freeze-Dried Allogeneic Bone(DFDB) graft, group B(20 patients) were treated with cyst enucleation and autogenous bone graft, group C(20 patients) were treated with only cyst enucleation. Each group was evaluated with panoramic radiograph and clinical sign & symptom at pre-op and post-op(immediate, 6, 12, 24, 36 month). Bone density was evaluated with disital densitometer. The result was as follows : 1. Post-Op infection was higher in group C(4 pts.) than in group A(1 pt.) and B(1 pt.) 2. Post-Op gingival recession was higher in group C(3 Pts.) than in group A(1 pt.) and B(1 pt.) 3. Anatomic distortion was higher in group C(3 Pt.) than in group A(1 Pt.), and B(1 pt.) 4. Reoperation was done in two patients who were in group C 5. There were donor site morbidity in two patients 6. There was no significant difference between group A and B in their bony density in their follow up period(p>0.05). 7. There were significant differences between group A, B and group C in their bony density until post-op 24 months but a little differences at post-op 36 months(P<0.01)

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.5
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• pp.208-215
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• 2005

The 10mm diameter aggregates made of clay, carbon and $Fe_2O_3$ were prepared to investigate the mechanism of black core formation. The specific gravity, absorption rate, percent of black core area, fracture strength, total Fe analysis, and XRF were measured at various compositions, sintering temperatures, sintering times, sintering atmospheres, and sintering methods. Small addition of $Fe_2O_3$ did not affect physical properties of the aggregates; however, the percent of black core area increased with increasing carbon contents and increasing sintering temperature. Specific gravity of the aggregates decreased and the water absorption ratio increased with increasing percent of black core area. The aggregates sintered at oxidation atmosphere showed clear border between shell and black core area. Hence, the aggregates sintered at reduction atmosphere showed only black core area in the cross-section of the aggregates. The specific gravity of the aggregates sintered at reduction atmosphere increased with increasing carbon contents and that was the lowest of all comparing other aggregates sintered at different atmospheres. Adsorption rate increased with increasing carbon contents at all atmospheres. The fast sintered aggregates showed lower specific gravity, higher absorption rate, and more black core area than the normally sintered aggregates. It was turned out that the aggregates having more black core area showed higher fracture strength than that of aggregates with no black core area. From the total Fe analysis, the concentration of Fe and FeO was higher at black core area than at shell. Because the concentration of $Fe_2O_3$ in the shell was higher than other area, the color of the shell appeared red. It was also turned out from the XRF analysis that carbon was exist only at black core area.

• Journal of the Korean Institute of Gas
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• v.24 no.2
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• pp.1-8
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• 2020

Centrifugal pump is a facility that transfers energy to fluid through centrifugal force, which is usually generated by rotating the impeller at high speed, and is a major process facility used in many LNG production bases such as vaporization seawater pump, industrial water and fire extinguishing pump using seawater. to be. Currently, pumps in LNG plant sites are subject to operating conditions that vary depending on the amount of supply desired by the customer for a long period of time. Pumps in particular occupy a large part of the consumption strategy at the plant site, and if the optimum operation condition is not available, it can incur enormous energy loss in long term plant operation. In order to solve this problem, it is necessary to identify the performance deterioration factor through the flow analysis and the result analysis according to the fluctuations of the pump's operating conditions and to determine the optimal operation efficiency. In order to evaluate operation efficiency through experimental techniques, considerable time and cost are incurred, such as on-site operating conditions and manufacturing of experimental equipment. If the performance of the pump is not suitable for the site, and the performance of the pump needs to be reduced, a method of changing the rotation speed or using a special liquid containing high viscosity or solids is used. Especially, in order to prevent disruptions in the operation of LNG production bases, a technology is required to satisfy the required performance conditions by processing the existing impeller of the pump within a short time. Therefore, in this study, the rotation difference of the pump was applied to the ANSYS CFX program by applying the modified 3D modeling shape. In addition, the results obtained from the flow analysis and the curve fitting toolbox of the MATLAB program were analyzed numerically to verify the outer diameter correction theory.

• Clean Technology
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• v.20 no.4
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• pp.390-397
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• 2014

This study was performed to investigate the effects of fluidizing media on $N_2O$ production in fluidized bed incineration of sewage sludge. The fluidized media were prepared in a form of 2 mm bead by mixing zeolite powders in our lab. Sand having 0.4 mm of the mean size showed 0.44 m/s of minimum fluidization velocity ($U_{mf}$), while the prepared zeolite media 0.5 m/s. When the ratio of fluidizing media height to the inside diameter of the incinerator (bed aspect ratio) increased from 1.4 to 3.1, it was found that $U_{mf}$ of the zeolite media was varied from 0.5 m/s to 0.7 m/s. Under the operation conditions in 1.79 of excess air ratio, $909^{\circ}C$ of bed temperature and ca. 1.65 m/s of superficial velocity, as the weight of fluidizing meadia was increased, $O_2$ concentration in the flue gas was slightly decreased, and $CO_2$ increased. Above 6 kg of fluidizing media weight (1.98 of bed aspect ratio), it was observed that $N_2O$ concentration was significantly reduced, which might result from the decomposition of $N_2O$ on the zeolite media rather than transformation of $N_2O$ to NOx. On the other hand, in a variation of the zeolite media mixing ratio to sand and bed temperature at a constant total bed height, significant difference was exhibited in $N_2O$ emission concentration according to the temperature. Considering the operation temperature in the incineration, the effective calcination temperature of the zeolite media was suggested to be around $900^{\circ}C$.

• Korean Journal of Environment and Ecology
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• v.17 no.4
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• pp.324-336
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• 2004

This study was achieved to present ecological administration plan by analyzing vegetation structure and condition rating class(environmental damage degree) of Sangnim Woods Natural Monument in Hamyang-gun, Korea. In vegetation structure part, actual vegetation was classified by 22 patterns and Quercus serrata Carpinus tschonoskii community(31.8％), Quercus serrata community(14.6％) ranged extensively. Main plant community was 8 types, and is fractionated by 13 plant communities according to stratigraphy development degree it is Quercus serrata community, Quercus serrata Carpinus tschonoskii community, Quercus aliena community, Quercus acutissima community, Carpinus tschonoskii community, Carpinus tschonoskii Quercus serrata community, Zelkova serrata-Quercus serrata community, and Planted area with korean landscape woody plants. Age of old growth trees that diameter of breast height over 38cm was 61∼77years. In condition rating class, area of class 3 was 51,960$m^2$(32.8％), area of class 4 was 6,583$m^2$(3.5％), and area of class 5 was 4,086$m^2$(2.6％) and gross area of class 3∼6 need artificial restoration was 61,619$m^2$(38.9％). Considering actual vegetation, plant community structure, and condition rating class biotope was classified by total 14 types. While distribution area of Queens spp. old growth forest of shrub damaged(51,246$m^2$, 32.4％) and deciduous broad leaved old growth forest of simple-layer structure(19,906$m^2$, 12.6％) is large and that of deciduous broad-leaved old growth forest of multi-layer structure(2,085$m^2$, 1.3％) and Queens spp. old growth forest of multi-layer structure may have to manage with user control by administration plan for stabilization of Sangnim Woods ecosystem for long-term. Also, both vegetation of shrub damaged and simple-layer structure as negative restoration area should be restored for ecological succession and both grassland and planted area with korean woody plants as positive restoration area should be revegetated by using ecological planting model of native vegetation structure in Sangnim Woods.

• Korean Journal of Environment and Ecology
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• v.28 no.6
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• pp.657-663
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• 2014

This study was conducted to investigate the difference in feeding habits of Red-Tongued Viper Snakes, according to available foods sources and areas. The effects of differences in food sources were found on Red-Tongued Viper Snake inhabited in the Jeju Island and its islet Gapado, from May 2006 to Nov. 2010. The food sources for the Red-Tongued viper snake population in the Jeju Island were found to be as follows: Chinese red-headed centipedes (Scolopendra subspinipes mutilans), Jeju Salamanders (Hynobius quelpaertensis), Japanese tree Frogs (Hyla japonica), Narrow-mouthed Toad (Kaloula borealis), Dybowski's Brown Frogs (Rana dybowskii), Black-spotted Pond Frogs (Rana nigromaculata), Smooth Skinks (Scincella vandenburghi), Asian Keelback Snakes (Amphiesma vibakari), Lesser White-toothed Shrews (Crosidura shantungensis), Hallasan Shrews (Sorex caecutiens hallamontanus), and Jeju Striped Field Mice (Apodemus chejuensis). This implies that Red-Tongued Viper Snakes mainly feed on amphibians, reptiles, and small mammals. Among these, amphibians occupied the highest portion at 55.2% followed by mammals at 20.7%, centipedes at 13.8%, and reptiles at 10.3%. On the contrary, Red-tongued viper snake population in Gapado only feed on Chinese red-headed centipedes and Smooth Skinks (S. vandenburghi). Since only a small amount of nutrient can be obtained from Chinese red-headed centipeds or Smooth Skinks, this feeding habit for Red-tongued viper snake would adversely effect on the growth or regeneration. The reason why Red-Tongued viper snake population in the Gapado mainly feed on Lizard and Centipedes in spite of relatively various available food sources, might be due to the low density of other food sources in the Gapado. Red-Tongued viper snake could be feeding on foods that are low in quality but are easily accessible, to minimize energy consumption on searching for other more nutritious foods. A snake tends to select the size of its food depending on the size of its own head. The positive correlation was found between the size of the heads of Red-Tongued viper snakes from the Jeju island and the diameter of their foods. The head size was larger in the males than females in viper snake population from the Jeju Island, which might effect on their selection of foods. However, no significant difference was found between the sizes of the head and the food in the Red-Tongued viper snake population from the Gapado. The findings of this study would provide meaningful data, which directly shows that even within the same viper species they choose different available food sources according to their inhabitance. This leads to their growth and adaptation to their environment which is beneficial for sustaining of its population.