• Journal of the Korean GEO-environmental Society
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• v.15 no.5
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• pp.47-56
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• 2014

In winter season, the pore water inside the ground freezes and thaws repetitively due to the cold air temperature. When the freezing-thawing processes are repeated on the ground, the change in soil particle structure occurs and thus the damage of the infrastructure may be following. This study was performed in order to investigate the stiffness change of soils due to the freeze-thaw by using elastic waves. Sand-silt mixtures are prepared with in the silt fraction of 40 %, 60 % and 80 % in weight and in the degree of saturation of 40 %. The specimens are placed into the square freezing-thawing cell by the temping method. For the measurement of the elastic waves, a pair of the bender elements and a pair of piezo disk elements are installed on the cell, and a thermocouple is inserted into soils for the measurement of the temperature. The temperature of the mixtures is decreased from $20^{\circ}C$ to $-10^{\circ}C$ during freezing, is maintained at $-20^{\circ}C$ for 18 hours, is gradually increased up to the room temperature of $20^{\circ}C$ to thaw the specimens. The shear waves, the compressional waves and the temperature are measured during the freeze-thaw process. The experimental result indicates that the shear and the compressional wave velocities after thawing are smaller than those of before freezing. The velocity ratio of after thawing to before freezing of shear wave is smaller than that of the compressional wave. As silt fraction increases from 40 % to 80 %, the shear and compressional wave velocities are gradually increased. This study suggests that the freezing-thawing process in unsaturated soil loosens the soil particle structure, and the shear wave velocity reflects the effect of freezing-thawing more sensitively than the compressional wave velocity.

• Journal of The Korean Association For Science Education
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• v.18 no.4
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• pp.463-472
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• 1998

Biotechnology is the process of using biological system for the production of materials. Genetic engineering, a subset of biotechnology, is the process of altering biological systems by the purposeful manipulation of DNA It is a new field in biology and no topic in biology is more likely to impact our personal lives and is therefore more worthy of our attention and understanding. The purpose of this study was to investigate students' understanding of the concepts of biotechnology, and a test tool which is made up of 20 basic questions was developed for the study. The subject of this study was high school students and the sample size was 486. In order to find out the source of students' misunderstanding, we also analysed high school textbooks and teachers were given the same tool applied to students. Two-way ANOVA was used for the analysis. Major findings of this study are as following; 1. Mean score of students was 41, and there was a significant difference between the scores of boys and girls(p<0.05). Female students scored higher than male students. The variables "region" and "major" had no significant influence. 2. Students' the most misunderstood concepts were "monoclonal antibody" and "gene cloning". Many students thought that a plamid DNA originally has a useful DNA in it, which is apparently wrong. 3. Mean score of teachers was 82, and the variabes of gender and career did not have statistically significant influence on the result(p>0.05). 4. Teachers got the lowest scores on the concepts of "gene therapy", "the accomplishment of biotechnology in agriculture and medicine", and "plasmid DNA". The results of item analysis implied that teachers' misunderstanding might be a part of the sources of students' misunderstaning. 5. Out of 18 basic concepts selected in the study, only 10 concepts were explained well enough in most textbooks. The results of item analysis indicated that textbooks also could be a part of the source of students' misunderstanding.

• Tuberculosis and Respiratory Diseases
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• v.49 no.2
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• pp.217-224
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• 2000

Background : It is well known that when macrophages are stimulated with endotoxin, they produce a wide variety of cytokine mediators, including TNF-$\alpha$ and IL-1$\beta$. However, there is an alteration in the macrophages' responsiveness when they are challenged with repeated bouts of endotoxin, termed "endotoxin tolerance" which is regarded as a self-protective phenomenon from continuous stimulation. In this study, endotoxin tolerance in the peripheral blood monocytes of sepsis patients was evaluated. Methods : Fourteen patients with organism-documented sepsis were included. The severity of illness was evaluated by APACHE II score. Peripheral blood monocytes were isolated from the patients and diluted to $1{\times}10^5$ well. After stimulation with endotoxin (LPS of E. coli O114 : B4, 100 ng/ml), they were incubated at $37^{\circ}C$ in 5% $CO_2$ incubator for 24 hours. Supernatant was collected for the measurement of TNF-$\alpha$ and IL-1$\beta$ with ELISA method. Peripheral blood monocytes of seven healthy volunteers were used as control. Results : The APACHE II score (mean$\pm$SD) of the patients at the time of blood sampling was 12.2$\pm$5.7. The primary infection foci were urinary tract infection, pneumonia, subacute bacterial endocarditis, and catheter related infection, etc. The causative organisms were gram negative rods (10 cases), gram positive cocci (6 cases) with two cases of mixed infection. Serum TNF-$\alpha$ could be measured in 4 cases with 29.9$\pm$27.7 pg/ml. Serum IL-1$\beta$was measurable in only one patient. The TNF-$\alpha$ level of supernatant of cultured peripheral blood monocytes was 2,703$\pm$2,066 pg/ml in patients and 2,102$\pm$1914 pg/ml in controls. The IL-1$\beta$level of supernatant was 884$\pm$1,050 pg/ml in patients and 575$\pm$558 pg/ml in controls. There was no difference of TNF-$\alpha$ and IL-1$\beta$ level between patients and controls. Conclusion : We cannot prove the phenomenon of endotoxin tolerance in this study. Future study needs to be focused on the more severe sepsis patients who were taken for sampling earlier. Addition of serum to the culture medium could be an another valuable option for the success of this study.

• Journal of the Korean Society of Food Science and Nutrition
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• v.21 no.4
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• pp.353-366
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• 1992

This study was devised to purify the compound from tuna that have cytotoxic activities against various cancer cell lines and to observe its immunopotentiating activities. The cytotoxic compound was partially purified 277 fold, from petroleum ehter extract (crude extract) of tuna by silicic acid column chromatography (fraction D) and thin layer chromatography (Spot I). Cytotoxic activity was monitored using human colon cancer cell, HCT-48. The active compound (Spot I) was composed of seven materials which are fatty acids of four kinds ($C_{14:0},\;C_{16:0},\;C_{17:1},\;and\;C_{18:0}$) and unknown three fat materials. The active compound has cytotoxic activities against various cancer cell lines, that is, murine leukemic lymphocytes (L1210, P388) and human rectal (HRT-18) and colon cancer cells (HCT-48, HT-29). The patterns of size distribution of HCT-48 cells in the medium containing tuna extract were shifted to direction of the small size region. Also, the microscopic shape of HCT-48 cells were shrinked and distracted. The number of plaque forming cell and immunoglobin fraction of serum protein obtained from tuna-treated mice were increased, but natural killer cell activity was not affected.

• 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 Korean Home Economics Education Association
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• v.19 no.4
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• pp.201-218
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• 2007

This study is a quasi-experimental study to find out the effect of school library-assisted instruction on middle school students' self-directed learning ability in Home Economics Education. For this purpose, the following research questions were established. 14 hours of school library-assisted instruction and traditional lecture were carried out to 164 9th grade female students(82 of experimental group, 82 of comparison group) of a girls' middle school in Jinju, Gyeongnam. To verify the instructional effect, a pre-test and a post-test for self-directed learning ability were carried out. SPSS 12.0 was used for statistical analysis. For statistical analysis, reliability analysis, frequency analysis, x2-test, t-test, repeated measures-ANOVA, and bivariate analysis were used. The results of this research were as follows: First, there was a statistically significant difference between experimental group and comparison group in the self-directed learning ability in all the subordinate items. Second, the change of self-directed learning ability by grade within the experimental group showed no interactional effect in all the sub-items except problem solving ability. Problem solving ability showed a meaningful difference in the rate of grade rising in accordance with academic achievement level and a higher synergy effect was shown in the low academic achievement group. Third, the experimental group showed a higher rate of rising in the self-directed learning ability than the comparison group, and the low academic achievement group showed a higher rising rate of grade than the high academic achievement group. Based on the results of this research, we concluded that the school library-assisted instruction was effective in enhancing middle school students' self-directed learning ability especially for the low academic achievement group.

• Journal of Korean Home Economics Education Association
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• v.30 no.1
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• pp.99-114
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• 2018

Textbooks are one of the most crucial variables that determine the quality of education and one of the most influential sources for education. Textbooks should be designed with inquiring tendencies so as to help students to practice self-directed learning. inquiring textbooks can not only intrigue students but also enhance the quality of class. Here, this author is going to analyze the inquiring tendencies of a core construct, 'management', in 12 different types of high school Technology & Home Economics textbooks reflecting the 2015 revised national curriculum based on the Romey method. According to the analysis results, only one type of textbook shows inquiring tendencies in the text, which means that the text is more oriented to delivering knowledge rather than to pursuing students' inquiry learning. Because analysis indexes for figures and diagrams fall under the range of desirable inquiring tendencies in 10 types of textbooks, the figures and diagrams presented in Home Economics textbooks are intended to induce particular learning activity. Learning activity indexes reveal 9 types of textbooks' inquiring tendencies, which means that Home Economics textbooks present a reasonable amount of learning activity in general in order to intrigue students and stimulate their inquiring mind. In terms of evaluation indexes, only 2 types of textbooks show inquiring tendencies. According to the results of examining each individual textbook, some of the Home Economics textbooks reflecting the 2015 revised national curriculum include inquiring elements in the text, figures and diagrams, activities, and evaluation all; however, some still need improvements. Regarding how to better the Home Economics textbooks, this researcher will suggest the following implications and complements. Home Economics textbooks should include inquiring elements to induce interactions properly in the class, and when they write the textbooks, the text, figures and diagrams, activities, and evaluation should be designed balancedly, and the questions need to be expressed in a way to develop students' inquiring mind.

• Korean Chemical Engineering Research
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• v.44 no.2
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• pp.179-186
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• 2006

Two types of $TiO_2$, nanotube and nanoparticle, were used for the mesoporous coatings by doctor blade technique followed by calcining at $450^{\circ}C$. The coatings were used as working materials for dye-sensitized solar cells (DSCs) later on and their photovoltaic characterization was carried out. The nanoparticle was synthesized from hydrogen titanate nanotube by hydrothermal treatment at $180^{\circ}C$ for 24 hr. The solar energy conversion efficiency (${\eta}$) of DSCs prepared by this nanoparticle reached 8.07％ with $V_{OC}$ (open-circuit potential) of 0.81 V, $I_{SC}$ (short-circuit current) of $18.29mV/cm^2$, and FF (fill factor) of 66.95％, respectively. For the preparation of nanotube, the concentration of NaOH solution varied from 3 M to 5 M. In the case of DSCs fabricated with nanotubes from 3 M NaOH solution, the ${\eta}$ reached 6.19％ with $V_{OC}$ of 0.77 V, $I_{SC}$ of $12.41mV/cm^2$, and FF of 64.49％, respectively. On the other hand, in the case of 5 M solution, the photovoltaic ${\eta}$ was decreased with 4.09％ due to a loss of photocarriers. In conclusion, it is demonstrated that the solar energy conversion efficiency of DSCs made from $TiO_2$ nanoparticle showed best results among those under investigation.

• Computational Structural Engineering
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• v.7 no.3
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• pp.95-103
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• 1994

The safety related components in the nuclear power plant should be designed to withstand the seismic load. Among these components the integrity of reactor internals under earthquake load is important in stand points of safety and economics, because these are classified to Seismic Class I components. So far the modelling methods of reactor internals have been investigated by many authors. In this paper, the dynamic behaviour of reactor internals of Yong Gwang 1&2 nuclear power plants under SSE(Safe Shutdown Earthquake) load is analyzed by using of the simpled Global Beam Model. For this, as a first step, the characteristic analysis of reactor internal components are performed by using of the finite element code ANSYS. And the Global Beam Model for reactor internals which includes beam elements, nonlinear impact springs which have gaps in upper and lower positions, and hydrodynamical couplings which simulate the fluid-filled cylinders of reactor vessel and core barrel structures is established. And for the exciting external force the response spectrum which is applied to reactor support is converted to the time history input. With this excitation and the model the dynamic behaviour of reactor internals is obtained. As the results, the structural integrity of reactor internal components under seismic excitation is verified and the input for the detailed duel assembly series model could be obtained. And the simplicity and effectiveness of Global Beam Model and the economics of the explicit Runge-Kutta-Gills algorithm in impact problem of high frequency interface components are confirmed.

• Journal of dental hygiene science
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• v.10 no.6
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• pp.465-472
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• 2010

This study surveyed salivary flow rate, salivary viscosity, and salivary buffering capacity in order to intensively analyze salivary factors among factors of occurrence in dental caries for finding mutually different factors that function in occurrence of dental caries depending on each individual. Even the acid body within dental plaque has great influence upon dental caries. Thus, the comparative analysis was carried out by surveying the hydrogen ion concentration in dental plaque. The following results were obtained in this study. 1. The average decayed teeth in the survey subjects stood at 1.67 piece. The extracted teeth caused by dental caries stood at 0.47 piece. The filled teeth were indicated to be 6.31 pieces. Accordingly, the average permanent dental caries experience teeth were surveyed to be 8.44 pieces. 2. The results according to dental caries activity test method were indicated to be $12.56{\pm}4.15ml$ for the average stimulated salivary flow rate, $3.89{\pm}1.83ml$ for non-stimulated salivary flow rate, $1.49{\pm}0.69$ for salivary viscosity, and $8.51{\pm}2.44$ for salivary buffering capacity. The hydrogen ion concentration test in dental plaque was indicated to be $5.62{\pm}0.50$ for before brushing teeth, $5.23{\pm}0.58$ for 5 minutes after brushing teeth, $5.25{\pm}0.56$ for 10 minutes after brushing teeth, $5.29{\pm}0.62$ for 15 minutes after brushing teeth, $5.34{\pm}0.58$ for 20 minutes after brushing teeth, $5.40{\pm}0.53$ for 25 minutes after brushing teeth, and $5.61{\pm}0.59$ for 30 minutes after brushing teeth. 3. Stimulated salivary and non-stimulated salivary flow rate, salivary viscosity, and salivary buffering capacity were indicated to be higher in group with non-caries than group with caries. However, it was statistically insignificant. The hydrogen ion concentration in dental plaque showed wholly statistical significant in the relationship with people with dental caries under progression. However, people without dental caries were indicated to be higher than people with dental caries. 4. As for correlation between caries activity test methods, the stimulated salivary flow rate had significantly positive correlation with non-stimulated salivary flow rate(p<0.001). Non-stimulated salivary flow rate showed negative correlation with salivary buffering capacity(p<0.01). The hydrogen ion concentration test in dental plaque showed positive correlation according to the passage of time after brushing teeth. However, there was no significant correlation with salivary viscosity and salivary buffering capacity(p>0.05).