• Restorative Dentistry and Endodontics
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• v.27 no.5
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• pp.535-542
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• 2002

The purpose of this study was to evaluate the effect of EDTA irrigant according to application time and temperature. 31 human mature extracted teeth with a single canal were sectioned with microtome in 3mm thickness and gained 62 samples of root canals. They were distributed randomly into 6 groups of 10 specimens each and control group of 2 specimens. Each specimen was prepared with GT rotary file (Dentsply, Maillefer Co., Swiss) and irrigated with 3 ml sodium hypochlorite every minute. Then smear layer was removed with EDTA solution (PULPDENT$^{\circledR}$, PULPDENT Co., USA.) except two control specimens. Specimens of each group were irrigated with 17% EDTA. The time and temperature of application were as follows : (Table omitted) All specimens were split longitudinally and prepared for examination by scanning electron microscopy. A set of reference micrographs was used to award a debris score as follows: 0 = no smear layer, all tubules clean and open; 1 = no superficial smear layer, tubule openings visible, but some contain debris plug or soft tissue remnants: 2 = moderate smear layer, some tubules open and others closed; 3 = heavy smear layer, most/all tubule openings obscured. Results were evaluated with Kruskal-Wallis test to determine whether there was statistically significant difference among six groups. Pairs of groups were analyzed using the Student-Newman-Keuls Method and Mann-Whitney test. The results were as follows : 1. Control specimens showed heavy smear layer at the canal walls 2. Among the groups applied with EDTA for 2 minutes, group 1 showed the heaviest smear layer, and there was statistically significant difference between group 1 and the other groups(p<0.05). 3. Among the groups applied with EDTA for 5 minutes, group 4 and group 6 showed smear layer but there was no significant difference between them. 4. Among the groups applied with EDTA for the same temperature, group 1 showed heavier smear layer than group 4, and there was statistically significant difference(p<0.05). 5. Among the groups applied with EDTA for the same temperature, group 2 showed heavier smear layer than group 5 and group 3 showed heavier smear layer than group 6. But there was no statistically significant difference among them. From the results above, it could be concluded, EDTA solution is effective in removing of smear layer when it is applied for 5 minutes. If EDTA is applied for 2 minutes, it should be applied above room temperature.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.10
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• pp.1013-1020
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• 2008

To evaluate the pollutant removal efficiency and clarify the cause of low removal efficiency of the wetland, temporal and spacial distributions of water quality were investigated at 16 sites in the Sihwa constructed wetland. The removal efficiency showed a tendency to decrease since the construction of the wetland, except for TN. In addition, the efficiency was largely varied with season, especially BOD and TP. No removal efficiency of BOD was observed in April and July when algal bloom was occurred in lower part open water of the wetland. On the other hand, TP showed no removal efficiency from April to August showing -291% of removal efficiency in August. From the horizontal distribution in closed water regions, SS concentration for the central area was significantly higher than for left and right areas(p = 0.013, center > left > right areas). From the results of this study, we infer that anaerobic condition due to the excessive accumulation of organic matters and lack of uniformity of water flow distribution are major factors of the low removal efficiency of the wetland.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.29 no.4
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• pp.464-476
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• 2019

Objectives: This study aimed to assess the exposure levels of tollbooth workers to diesel particulate matter using black carbon (BC) and to find the correlations among variables associated with BC using the motor vehicle management act regulated by the Ministry of Land, Infrastructure and Transport. Methods: This study was performed over 14 days at a university in Seoul. BC levels were monitored using an aethalometer and were conducted around the breathing zones of the workers. There were three sampling locations: inside the tollbooth (front gate and rear gate) and an office as a control group. T-test, correlation, and multiple linear regression analysis were performed using SPSS. Results: The geometric mean (GM) of BC_30min concentrations in the exposure group was 2.44 ㎍/㎥, approximately 1.4 times higher than the control group (1.75 ㎍/㎥). The GM of BC_30min concentrations was 2.75 ㎍/㎥ during the heavy traffic time (9-10 am) and 2.30 ㎍/㎥ during non-heavy traffic times (p<0.001). The multiple linear regression analysis shows that the number of all types of vehicles and PM_2.5 concentrations in the atmosphere were factors increasing the GM of BC(ln(BC_30min)) concentrations (adjusted R²=0.42, p<0.001). The workers were constantly exposed to low concentrations (GM of BC_30min=2.44 ㎍/㎥), but they were exposed to peak concentrations instantly (BC_10sec=3545.04 ㎍/㎥). When the GM of BC_30min concentrations was momentarily represented as high, it was identified that a vehicle mainly using diesel fuel or an aging vehicle had passed. Conclusions: A ventilation system should be installed in the closed tollbooth or aging vehicles should be controlled so as not to pass tollbooths.

• Horticultural Science & Technology
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• v.32 no.3
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• pp.330-339
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• 2014

Growth and anthocyanins of lettuce (Lactuca sativa L., 'Mid-season') grown under LED lamps with blue light in the range of 430-470 nm or with red light in the range of 630-670 nm were analyzed in this study. Cool-white fluorescent light was used a s the control. P hotosynthetic photon flux, p hotoperiod, air temperature, relative humidity, and $CO_2$ concentration in a closed plant production system were $201{\pm}2\;{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$, 16/8 hours (day/night), $22/18^{\circ}C$, 70%, and $400{\mu}mol{\cdot}mol^{-1}$, respectively. At 21 days after light quality treatment, growth characteristics and anthocyanins content of lettuce as affected by the peak wavelength of blue or red LED were significantly different. Among peak wavelengths treated in this stusy, R1 treatment (peak wavelength 634 nm) and R6 treatment (peak wavelength 659 nm) were effective for increasing leaf width, leaf area, shoot fresh weight, and photosynthetic rate of lettuce. B5 treatment (peak wavelength 450 nm) and B4 treatment (peak wavelength 446 nm) increased the anthocyanins concentration and chlorophyll content in lettuce leaves, respectively. Anthocyanins in lettuce leaves increased linearly with decreasing hue value of leaf color and with increasing SPAD value of lettuce leaves. From these results, it was concluded that the red LED with peak wavelengths of 634 nm and 659 nm and the blue LED with peak wavelengths of 450 nm can be used as potential light spectra for increasing the yield and anthocyanins accumulation of leafy vegetable.

• Physical Therapy Rehabilitation Science
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• v.4 no.1
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• pp.28-31
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• 2015

Objective: Psychomotor imagery has been widely used to improve motor performance and motor learning. Recent research suggests that during visualization, changes occur in neurophysiological networks that make physical practice more effective in configuring functional networks for skillful behaviors. The aim of our pilot study was to determine if there was change and to what extent there was differentiation in modulation in electroencephalography (EEG) frequencies between visualizing a state of rest and a state of exercise performance and to identify the preponderant frequency. Design: Quasi-experimental design uncontrolled before and after study. Methods: EEG brain wave activity was recorded from 0-40 Hz from nine cerebral cortical scalp regions F3, Fz, F4, C3, Cz, C4, P3, POz, and P4 with a wireless telemetric EEG system. The subjects, while sitting on a chair with eyes closed, were asked to visualize themselves in a state of routine rest/relaxation and after a period of time in a state of their routine exercise performance. Results: The gamma frequency, 31-40 Hz, (${\gamma}$) was the predominant wave band in differentiation between visualizing a state of rest versus visualizing a state of exercise performance. Conclusions: We suggest these preliminarily findings show the EEG electrocortical activity for athletes is differentially modulated during visualization of exercise performance in comparison to rest with a predominant ${\gamma}$ wave band frequency observed during the state of exercise. Further controlled experimental studies will be performed to elaborate these observations and delineate the significance to optimization of psychomotor exercise performance.

• Journal of The Korean Association For Science Education
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• v.31 no.6
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• pp.942-957
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• 2011

The purpose of this research was to examine the concept of elementary school teachers of combustion. The participants were selected from the elementary school teachers who had various career experiences, 6th grade science teaching experiences, and academic backgrounds on science. For the purpose of this study, 12 elementary school teachers took the concept-test formed five questions on combustion and were interviewed. The concept-test was composed with 'The definition of combustion', 'The reason that the candle was blown out when glass was closed.', 'The existence of oxygen and carbon dioxide of before and after combustion in glass', 'Combustion of iron', 'Combustion products'. And the collected data by semi-structured interviews based on responses to the concept-test. During the analysis of the data, additional interviews by phone, e-mail and Internet messenger were conducted if necessary. The answers to each question were classified into three levels: (Scientific-concept(S), Partial-concept(P), Misconcept(M)). The research results showed that all teachers had misconceptions or partial-concept of more than 50 percent of each question. Teachers who had the 6th grade science teaching experience acquired scientific concepts of the combustion more than teachers who did not have the 6th grade science teaching experience. We should develop visualization materials about the change of gases during combustion and use these materials for implementation of the scientific concept.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.3
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• pp.69-76
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• 2008

This work proposes a 12b 1kS/s 65uA 0.35um CMOS algorithmic ADC for sensor interface applications such as accelerometers and gyro sensors requiring high resolution, ultra-low power, and small size simultaneously. The proposed ADC is based on an algorithmic architecture with recycling techniques to optimize sampling rate, resolution, chip area, and power consumption. Two versions of ADCs are fabricated with a conventional open-loop sampling scheme and a closed-loop sampling scheme to investigate the effects of offset and 1/f noise during dynamic operation. Switched bias power-reduction techniques and bias circuit sharing reduce the power consumption of amplifiers in the SHA and MDAC. The current and voltage references are implemented on chip with optional of-chip voltage references for low-power SoC applications. The prototype ADC in a 0.35um 2P4M CMOS technology demonstrates a measured DNL and INL within 0.78LSB and 2.24LSB, and shows a maximum SNDR and SFDR of 60dB and 70dB in versionl, and 63dB and 75dB in version2 at 1kS/s. The versionl and version2 ADCs with an active die area of $0.78mm^2$ and $0.81mm^2$ consume 0.163mW and 0.176mW at 1kS/s and 2.5V, respectively.

• Journal of Adhesion and Interface
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• v.2 no.3
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• pp.9-15
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• 2001

To estimate the effect of the surface state of the EVA foam on an adhesion, the surface was treated with solvents having different values of a solubility parameter and a surface tension. The morphology and the contact angle were measured by SEM and contact angle tester, respectively. The value of the critical surface tension(${\gamma}_{c,0}$) of the EVA foam calculated by Zismann plot was 27.08 dyne/cm. The surface state and the ${\gamma}_c$ of the EVA foam were changed by solvent treatment. The swelling ratio of EVA foam was influenced by solubility parameter of a solvent, on the other hand the degree of change in the surface state was dependent on a surface tension of a solvent. When a surface tension of solvent. When a surface tension of solvent is lower than ${\gamma}_{c,0}$ of the EVA foam, the wettability of a solvent was good and the surface state was greatly changed. The adhesion strength of EVA foam was greatly improved to above 600% as compared to that of the untreated one. As the ${\gamma}_c$ of EVA was closed to the surface tension of the primer, the good adhesion strength was obtained.

• Journal of Gifted/Talented Education
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• v.15 no.1
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• pp.67-84
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• 2005

In this study we investigated the adequacy of tools for distinction gifted students through the comparison these mutual relation on the basis of data, like paper test, the depths interview score, and the rest data((TTCT: Torrance Tests of Creative Thinking, IQ test, FASP: Find A Shape Puzzle, V.T: Visualization Tests and Exp: experimental ability test), and analysis data of EEG test for examining the adequacy of tools for identification gifted students. So, we developed Brain Wave gifted Index(G-Index) for finding another distinction ability as using brain waves data. The standard of index development use gifted brain characteristic in closed-eyes rest state which is judged like that characteristic of distinction between gifted and normal students is the most clear and consistence. That is, the degree of unified pattern between each object and gifted PCA pattern was defined by Pearson method which added spatial mutual index to weight concept. This refer to mean number of spatial PCA pattern. Searching for the possibility of distinction gifted gave distinction effect in 76%. The result of regression analysis on the basis of mutual relation between the rest data is . The probability formula for distinct gifted group is as follow. $$P=\frac 1{1+e^{-[-0.018(TTCT)+0.057(IQ)+1.916(FASP)+0.682(V.T)+0.088(Exp.)+0.034(G-Index)-57.510]}}$$ The result of this calculation showed that probability for distinct in gifted group was very good(95.0%). On the basis of upper result, tools for identification gifted students should be estimated as using many-sided estimation data whatever possible. And following study about development, and operation of tools for distinction suitable to gifted student in science should be progressed.

• Tunnel and Underground Space
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• v.15 no.3 s.56
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• pp.223-227
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• 2005

The physical and mechanical properties of volcanic glass, which is distributed in the Samho area, South Korea were studied. Laboratory rock tests were carried out in order to obtain the various properties of rocks. Specific gravity, water content, absorption, porosity and wave velocity were measured for the physical properties. Uniaxial and triaxial compressive tests, Brazilian test and point load test were also performed for the mechanical properties. The tests of volcanic glass revealed that the apparent specific gravity, water content and absorption were 2.28, $1.67\%$ and $1.72\%$, respectively. Porosity $(3.87\%)$ was lower, whereas P-wave velocity (5330m/s) and S-wave velocity (2980 m/s) were relatively higher. Brazilian tensile strength ot 7.2MPa, and point load strength of 2.6MPa were among the mechanical properties of the rock. Uniaxial compressive strength (62.4MPa) estimated ken point load strength was very closed to the value (66.0MPa) from the uniaxial compressive test. Young's modulus and Poisson's ratio were E=43.2 GPa and v=0.28, respectively. Drawing the tangent line to Mohr-Coulomb failure criterion showed the cohesion of 20.1MPa and internal fraction angle of $28.6^{\circ}$.