• Journal of radiological science and technology
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• v.18 no.1
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• pp.63-70
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• 1995

In this pauper, the back, forward, side and $45^{\circ}$ oblique scatter dose were measured the X-ray exposure conditions 60, 80, 100, 120kV, FFD 100cm, FS $20\times20cm$, toward the $25\times25cm\times10\sim20cm$ of solid water, paraffin and MiX-DP phantom, and Pb, Cu, Al, and styrofoam meterials, by the electrometer and 5.3 cc ionization chamber. The obtained results are summarized as following. 1. The percentage depth dose(PDD) at the range of the diagnostic x-ray energy were appeared 50 % depth dose at the 2 cm depth with 60 kV, and 5 cm depth with 120 kV X-ray, 10 % depth dose at the 10 cm depth with 60 kV and 14 cm depth with 120 kV X-ray, 5 % below depth dose at the 20 cm depth. 2. The back scatter dose which were generated the surface of Pb, Cu and Al metal plates were 10 % below, and than the back scatter dose at the Pb plate were a most amount of these which were about 10 %, and were appeared the order of Cu and Al. 3. The percentage forward scatter were appeared from 50 % to 65 %, and the more phantom thicknees become, the more forward scatter were increased with the ratio of 5 % per 5 cm thickness. 4. The percentage back scatter which were generated the tissue equivalence meterials solid water, paraffin and MiX-DP were from 20 % to 40 %, and than the back scatter dose at the solid water were a mest amount of those, and paraffin and MiX-DP were appeared with the next values. 5. The percentage $90^{\circ}$ lateral and $45^{\circ}$ oblique side scatter dose were measured from 4 % to 12 %. a most amount of scatter dose which were generated from the patient in radiography were the forward scatter, the next values were the back scatter, the third values were the $90^{\circ}$ lateral scatter.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.1
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• pp.47-56
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• 2017

In this study, the higher temperature thermal property of the fly ash-blast furnace slag system Geopolymer including alumina aggregate was investigated whether that Geopolymer will be or not useful as thermal-resistant construction materials. Under every mixing conditions, the crack on the surface of hardened body was not observed up to $800^{\circ}C$ and it corresponded with fact that level of changes was not significant before and after heating process. Residual compressive strength is most high when mixing Blast-Furnace Slag ratio is 60 wt% until temperature reaches $800^{\circ}C$. The major hydrates of hardened body of Geopolymer; amorphous halo pattern between $20{\sim}35^{\circ}$ (2theta) and mullite ($3Al_2O_3{\cdot}2SiO_2$) and quartz ($SiO_2$) was found during the experiment. Amorphous halo pattern was a aluminosilicate gel generated by geopolymeric polycondensation and it was found that the halo pattern of aluminosilicate gel was preserved up to $800^{\circ}C$. The patterns of aluminosilicate gel disappeared from $1,000^{\circ}C$ and crystal phases like gehlenite, calcium silicate, calcium aluminum oxide, microcline was observed with the increase of exposure temperature.

• ALGAE
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• v.18 no.1
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• pp.13-20
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• 2003

Two isolated Antarctic marine diatoms, Chaetoceros neogracile VanLandingham and Stellarima microtrias (Ehrenberg) Hasle and Sims were examined to show changes of growth and uptake rate of nitrate due to UV-B irradiance. Chlorophyll (chl) a concentration was regarded as the growth index of diatom. The diatoms were treated with UV-B radiation and cultured for 4 days under cool-white fluorescent light without UV-B radiation. Two levels of UV-B exposures were applies: 1 and 6 W $m^{-2}$. Durations of UV-B treatment were 20, 40 and 60 minutes under 6 W $m^{-2}$ and 1, 2, 3, 4 and 5 hrs under 1 W $m^{-2}$. The control groups were cultured at the same time without UV-B radiation. The growth rates of two diatoms decreased under 1 and 6 W $m^{-2}$ UV-B irradiances than that of control group. After 4 days, chl a concentrations of C. neogracile were increased more than 4 times from 133 μgo$l^{-1}$ to 632 μgo$l^{-1}$ in control group. However, the concentration of experimental groups under 1 W $m^{-2}$ UV-B were only increased from 139 μgo$l^{-1}$ to 421 μgo$l^{-1}$ during one hour and the chl a concentrations were decreased from 144 μgo$l^{-1}$ to 108 μgo$l^{-1}$ during five hour. Growth of diatom dramatically more decreased under 6 W $m^{-2}$ UV-B than 1 W $m^{-2}$ UV-B. The chl a concentration of experimental groups under 6 W $m^{-2}$ UV-B for one hour was only increased from 111 μgo$l^{-1}$ to 122 μgo$l^{-1}$. In the case of S. microtrias showed also similar pattern to C. neogracile by UV-B radiation. The uptake rates of nitrate by the two strains were decreased abruptly under 6 W $m^{-2}$ UV-B irradiances. When two strains were treated under 1 and 6 W $m^{-2}$ UV-B during one hour, the strains were only continued growth and uptake of nitrate under 1 W $m^{-2}$ UV-B. This experimental evidence shows that exposure to UV-B radiation especially to high irradiance of UV-B decreases diatom survival and causes lower decrease of nutrient concentrations by microalgae in Antarctic water. Furthermore, evidence suggests that microalgal communities confined to near-surface waters in Antarctica will be harmed by increased UV-B radiation, thereby altering the dynamics of Antarctic marine ecosystems.

• Ocean and Polar Research
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• v.25 no.4
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• pp.427-435
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• 2003

Growth and pigment responses to different levels of solar radiation with or without ultraviolet (UV)-B component $({\lambda}=280-315nm)$ were investigated in Antarctic rhodophytes, Kallymenia antarctica and Palmaria decipiens, collected around King George Island during the summer of 2000. In K. antarctica specific growth rate, based on thallus area or fresh weight, decreased with increasing solar irradiances while P. decipiens were relatively insensitive to the effects of light. It is noticeable that the presence or absence of UV-B had no significant effect on growth for either species. However, K. antarctica showed a more pronounced reduction in chlorophyll (Chl a) concentrations at higher irradiances in the presence of UV-B. In P. decipiens, Chl a concentrations did not differ despite radiation level fluctuations being lower albeit than initial measurements. Thallus thickness was greater in K. antarctica than in P. decipiens. There were higher relative amounts of UV-absorbing pigments (UVAPs) in P. decipiens than in K, antarctica. The single absorbance peak obtained from the methanol extracts was resolved into three (316,332 and 346nm) in K. antarctica and four peaks (315,326,333 and 349 nm) in Palmaria as a result of the fourth-derivative. After 7 days exposure to solar radiation, the amount of UVAPs in K. antarctica was significantly reduced to a similar degree at all light levels, whereas that of P. decipiens remained unchanged except at 5% of surface irradiance. High performance liquid chromatography (HPLC) analysis of purified extracts indicated that P. decipiens possesses porphyra-334 in addition to three other mycosporine-like anlino acids (MAAs; asterina-330, palythine, shinorine), which are commonly present in K. antarctica. Significantly lower tolerance of K. antarctica to high levels of solar radiation may be connected with its usual absence in the eulittoral, while the active growth and elastic pigment responses of P. decipiens over a wide range of solar irradiance levels up to full sunlight seems to correspond well with its wide vertical distribution from rock pools down to 25-30m.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.34 no.1
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• pp.12-16
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• 2012

Purpose: The purpose of this study is to evaluate the effect of exposure of hydroxyapatite coating on the amount of bone formation and stability in the dogs. Methods: In this study, hydroxyapatite coated implants (HAPTITE) was placed over the femur bone surface of four dogs about 1 mm. The experimental group was divided into 4 weeks group of 8 implants and 8 weeks group of 8 implants, and then they were sacrificed. The stability of implants was evaluated twice with Osstell$^{TM}$ mentor (Osstell AB, Goteborg, Sweden) at right after placement and sacrifice. The amount of bone formation was evaluated through histomorphometric examination. Results: The stability of implants was in normal range, and tended to increase as time goes by. Mean percentages of new bone formation rates were $90.5{\pm}6.6$ at uppermost 1 mm bone level adjacent to soft tissues (level 1) and $92.9{\pm}4.1$ at next 1 mm bone level (level 2) in 4 weeks group, $90.1{\pm}11.5$ at level 1 and $95.9{\pm}2.3$ at level 2 in 8 weeks group. Mean percentages of bone-implant contact rates were $85.1{\pm}10.8$ at level 1 and $88.1{\pm}13.8$ at level 2 in 4 weeks group, $88.5{\pm}14.4$ at level 1 and $95.3{\pm}3.1$ at level 2 in 8 weeks group. There was no statistically significant difference of new bone formation rate and bone-implant contact rate between uppermost 1 mm bone level adjacent to soft tissues and next 1 mm bone level. However, there was no significant difference in bone formation between 4 and 8 weeks groups. Conclusion: These results suggested that exposed hydroxyapatite coated implants to soft tissue showed favorable bone formation and implant stability.

• Journal of Bio-Environment Control
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• v.7 no.1
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• pp.71-77
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• 1998

The root-zone environment is an important factor to the plant growth and it is closely related to the thermal characteristics of the root media. In this study thermal characteristics of root media with ambient environmental conditions were analyzed. The temperatures of nutrient solution as well as inside air of culture bed were measured in Nutrient Film Technique(NFT) and Deep Flow Technique(DFT) systems, and also the temperatures of root media measured in aggregate culture systems , The temperature of nutrient solution of NFT system with as low as 3$\ell$/min of flow rate was 3$^{\circ}C$ higher than that with 5 $\ell$/min of flow rate in the daytime, and the temperature of inside air was 2$^{\circ}C$ higher at night. And the temperature of nutrient solution of DFT system with as low as 0.8 cm of water level was 1-2$^{\circ}C$ higher than that with 1 8 cm in the daytime, and the temperature of inside air was almost same at night. The root-zone temperatures in the perlite and rockwool granulate systems with film mulching were 3$^{\circ}C$ higher than those without film mulching in the daytime. However, the rockwool slab system with film mulching showed the same trend as rockwool granulate system, but relatively higher temperature than any other medium because of the exposure of media surface to the ambient air. Additionally the temperature below the plant was measured 3$^{\circ}C$ lower than that between plants.

• Journal of Wetlands Research
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• v.22 no.2
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• pp.161-170
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• 2020

Constructed wetlands (CWs) are widely used to solve water quality problems caused by diffuse pollution from agricultural areas; however, phytoplankton blooms in CW systems can occur due to long hydraulic retention time (HRT), high nutrient loading, and exposure to sunlight. This study was conducted to evaluate the efficiency of a CW designed to treat agricultural diffuse pollution and develop a design concept to improve the nature-based capabilities of the system. Monitoring was conducted to assess contribution of individual wetland components (i.e. water, sediments, and plants) in the treatment performance of the system. During dry days, the turbidity and particulates concentration in the CW increased by 80 to 197% and 10 to 87%, respectively, due to the excessive growth of phytoplankton. On storm events, the concentration of particulates, organics, and nutrients were reduced by 43% to 70%, 22% to 49%, and 15% to 69% due to adequate water circulation and constant flushing of pollutants in the system. Based on the results, adequate water circulation is necessary to improve the performance of the CW. Free water surface CWs are usually designed to have a constant water level; however, the climate in South Korea is characterized by distinct dry and rainy seasons, which may not be suitable for this conventional design. This study presented a concept of multifunctional design in order to solve current CW design problems and improve the flood control, water quality management, and environmental functions of the facility.

• Journal of Korean Society of Forest Science
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• v.82 no.4
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• pp.337-346
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• 1993

Experiments were performed to find out the effects of simulated acid rain(SAR) of pH 4.0 or pH 2.5 for 12 weeks on stomatal resistance, wettability and anatomical changes in Quercus acutissima and Ginkgo biloba seedlings. As a control, distilled water with a pH 6.5 was also sprayed. Stomatal resistance of Q. acutissima and of G. biloba remarkably increased after exposure to SAR. SAR increased the wettability of Q. acutissima leaves measured with water blue solution and of G. biloba leaves measured by leaf contact angle method. Anatomical changes in the leaves of Q. acutissima affected by SAR were the partial damage of epidermis and parenchymatous cells. Scanning electron microscopical observation showed that the number of trichomes in the leaves of Q. acutissima treated with SAR markedly decreased and the erosion of epicuticular wax was significant. No distinct damage was found in the G. biloba leaves at pH 4.0, while epidermis and vascular tissue were collapsed at pH 2.5. No significant alteration of surface structures in this tree species was observed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.1
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• pp.120-127
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• 2015

The purpose of this study is to improve the fire prevention performance using the fire venetian blind louver subjected to burning by fire flame. The investigation is based on testing 2 full scale specimens, which is $3m{\times}3m$ module, $850mm{\times}1,500mm$ open, and $900mm{\times}900mm{\times}175mm$ venetian blind louver. Two louver thickness (1.5 and 2.0mm) were adopted. The specimens were exposed to fire flame temperature levels of ISO834 at the lower surface of the fire venetian blind louver specimens with exposure duration of one hour in Korea Institute of Construction Technology (KICT). It was found from the test results that the values of distributed temperature, decreased for all specimens for protecting to fire flame by venetian blind louver. The results of tests were a good fire prevention performance between in initial to 6 mins. At 60 minutes around ISO 834 fire loading, the percentages of distributed temperature in 500mm and 800mm height ranged between 11 and 10% respectively, regardless of louver thickness. This study, therefore, will improve the fire venetian blind louver for fire protection and prevention performance.

• Journal of Periodontal and Implant Science
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• v.29 no.4
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• pp.821-838
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• 1999

On the basis of the evidences that electrical stimulation could enhance proliferation and differentiation of bone cells and promote healing and regeneration of bone, this study was performed to investigate the effects of electrical stimulation on human periodontal ligament cells and gingival fibroblasts in vitro, which also have important roles in regeneration of periodontium, and to evaluate the potential of clinical application of electrical stimulation. Human periodontal ligament cells and gingival fibroblasts were primarily cultured from the root surface of extracted premolar and the adjacent gingiva without periodontal diseases. In control group, the cells ($5{\times}10^4$ cells/ml)were incubated only in Dulbecco's Modified Eagle's Medium contained with 10% fetal bovine serum. In test groups, electrical stimulation was given at the current intensity of $0.25{\mu]A$(test group 1), $1.0{\mu}A$(test group 2), and $2.5{\mu}A$(test group 3) for 12 hours to the same culture media with the control group. After 12 hour exposure of electrical stimulation, the cells were incubated for 2 and a half days(60 hours), and then each group of cells was analyzed for cell proliferation, protein level, and activity of alkaline phosphatase. The results were as follows ; 1. The Rate of cell proliferation of every test group increased significantly in both periodontal ligament cells and gingival fibroblasts, and in periodontal ligament cells, test group 3 showed significantly increased proliferation compared to the other test groups(p<0.05). 2. In the protein levels, neither periodontal ligament cell nor gingival fibroblast showed statistically significant differences between control and test groups. 3. The activity of alkaline phosphatase in periodontal ligament cells increased significantly in all test groups(p<0.05), but there were no significant differences between 3 test groups. In gingival fibroblasts, the activity of alkaline phosphatase increased significantly only in test group 3(p<0.05). From the above results, it is concluded that electrical stimulation may have beneficial effects on the regeneration of destructed periodontal tissue in regard of the stimulation of periodontal ligament cells and gingival fibroblasts as well as electrically stimulated bone formation that has been known, and that electrical stimulation may have the potential of clinical application.