• Journal of the Korean Geotechnical Society
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• v.20 no.3
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• pp.107-117
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• 2004

This paper is to investigate the reinforcing effects of newly devised Tire-cell mat made of waste tires in sand. Parametric study on number of connection bolts between Tirecells, relative density of sand, embedded depth, number of reinforced layers and width of Tirecell mat was made by using plate loading tests. It is found that the number of connection bolt was enough to maintain the given pressure. The bearing capacity ratio(BCR), which is defined as the rate of ultimate bearing capacity of reinforced soil to that of unreinforced soil, is the highest at the lowest density. And the reinforcing effect can be obtained in case of embedded depth within 1.0B, where B is loading width. Also settlement reduction is the highest at the lowest density of sand. The effect of number of Tirecell reinforced layers with 0.4B to 0.5B interval is limited to 2 layers and further reinforcing effects can not be obtained beyond 3 layers. Especially, the bearing capacity increased remarkably at 1 layer of reinforcement and the degree of increase was small from 1 layer to 2 layers of reinforcement. The effect of mat width of Tirecell was not significant because of high stiffness of Tirecell although the maximum bearing capacity was shown at the 2.0B mat width and the reinforcing effects of Tirecell, in general, was prominent compared with those of commercial Geoweb.

• Journal of the Korean Geotechnical Society
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• v.20 no.3
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• pp.129-139
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• 2004

During the construction of circular underground pipe, the non-proper compaction along the pipe and the decrease of compaction efficiency have been the main problems to induce the failure of underground pipe or facility. The use of CLSM (controlled low strength materials) should be one of the possible applications to overcome those problems. In this research, the small-scaled model test and the numeric analysis using PENTAGON-3D FEM program were carried out for three different cases on the change of backfill materials, including the common sand, the soil from construction site, and the CLSM.. From the model test in the lab, it was found out that the use of CLSM as backfill materials reduced the vertical and lateral deformation of the pipe, as well as the deformation of the gound surface. The main reason for reducing the deformation would be the characteristics of the CLSM, especially self-leveling and self-hardening properties. The measured earth pressure at the surround of the corrugated pipe using the CLSM backfills was smaller than those in the other cases, and the absolute value was almost zero. Judging from the small-scaled model test and FEM analysis, the use of CLSM as backfill materials should be one of the best choices reducing failure of the underground pipes.

• Journal of the Korean Chemical Society
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• v.64 no.3
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• pp.159-174
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• 2020

The purpose of this study is to examine 'Design Thinking' based Chemistry Class program as an education strategy for core competence of creative convergence talent. The program stages were modified and supplemented into eight stages, including 'Knowledge Understand', 'Empathy', 'Sharing perspective', 'Ideate', '1st Prototype', '1st Test', '2nd Prototype', and '2nd Test', so that the 'Design Thinking Process in Science Education' can be applied to the chemistry class. Considering the linkage between the 2015 and 2009 revised national curriculum, the achievement criteria were selected, and the lesson plans and student activity sheet were developed according to the themes to be met. Four thematic educational programs were developed and applied to Chemistry I for the second grade of high school students from March to August. The results were verified through qualitative data analysis of the class scene and pre- and post-test based on inventories of 'Empathy' 'STEAM educational competence', 'Problem solving process'. As a result of applying the developed program, 'empathy' showed a significant improvement in empathy with others and empathy with the problem situation. In 'STEAM educational competence', there was a significant enhancement in science and design competence. In the 'problem finding process', the problem definition, problem solution design, and problem-solving review were significantly improved in the 'problem-solving process'. The results of this study provided implications for the applicability of design thinking - based chemistry classes and its educational effect.

• Journal of Life Science
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• v.20 no.3
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• pp.356-364
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• 2010

This study was carried out to investigate the exposure pathway of PBDEs in human breast milk collected from new mothers residing in Chuncheon, a comparatively clean area in Korea. The congeners of PBDE in 22 human breast milk samples were analyzed using a high resolution gas chromatography with a high resolution mass detector. The residue level of ${\sum}PBDEs$ was higher in primipara subjects than in multipara subjects (p<0.05). The levels in this study were similar to those of people in some Asian and European countries, but were lower than those of people in north America. In the congener profiles, BDE-47 (mean contribution=36.1%) was predominant, followed by BDE-153 (27%), BDE-99 (11.7%), BDE-100 (11.1%), BDE-28 (7.9%) and BDE-183 (3.5%). The sum of BDE-47 and BDE-153 accounted for more than 50% of ${\sum}PBDEs$ in most samples. BDE-47 was highly correlated with ${\sum}PBDEs$ (r=0.94, p<0.001). No strong trend was observed between PBDE levels and a number of key biological factors (women's age, weight, height and body mass index) examined in this study, however, weak correlations were observed in PBDE levels measured against dietary habits, particularly in fish consumption frequency. It seems that Korean people might be exposed to multiple sources including products of PBDEs, and particularly food resources.

• Journal of the Korea Concrete Institute
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• v.23 no.1
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• pp.77-86
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• 2011

The concrete creep deformation of a hybrid composite section can cause additional deformation of the composite section and the stress relaxation of pre-compressive stress on the concrete section due to partial restraint of the deformation. In this study, the stress relaxation coefficient method (SRCM) is derived for simple analysis of complicate hybrid or composite sections for engineering purpose. Also, an equation of the stress relaxation coefficient (SRC) required for the SRCM is proposed. The SRCM is derived with the parameters of a creep coefficient, section and loading properties using the same method as the constant-creep step-by-step method (CC-SSM). The errors of the SRCM is improved by using the proposed SRC equation than the average SRC's which were estimated from the CC-SSM. The root mean square error (RMSE) of the SRCM with the proposed SRC equation for concrete with creep coefficient less than 3 was less than 1.2% to the creep deformation at the free condition and was 3.3% for the 99% reliability. The proposed SRC equation reflects the internal restraint of composite sections, and the effective modulus of elasticity computed with the proposed SRC can be used effectively to estimate the rigidity of a composite section in a numerical analysis which can be applied in analysis of the external restrain effect of boundary conditions.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.6
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• pp.1045-1058
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• 2017

This paper is a study on railway tunnel behavior characteristic of shallow overburden under the existing road. In order to understand the behavior characteristics of the ground deformation during tunnel excavation, a horizontal rod extensometers were installed in the passage area of the shallow overburden tunnel under the road, and the measurement and analysis were carried out. To compare the in situ measurement, three dimensional numerical analysis with ground condition and construction step was carried out using MIDAS NX. As a result of the field measurement, large preceding settlement occurred where the poor ground condition with shallow overburden excavation has been conducted. As a result of the numerical analysis, the largest settlement occurred at the shallow overburden point where the ground condition was poor. Therefore, in the shallow overburden section where the soil condition is poor and a sufficient depth can't be secured and the arching effect of the ground around the tunnel can't be expected, careful attention should be paid to the application of stiffness reinforcement measures and to minimize ground loosening.

• Journal of Digital Convergence
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• v.13 no.1
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• pp.383-396
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• 2015

This study aims to identify factors related to rescreening the private health screening center. Data from private health screening center with seven district centers were analyzed. The number of subjects was 70,250 from 2008 through 2015. Socio-demographic characteristics, morbidity, history, physical measurement, laboratory test, and health behavior factors were analyzed the association with health rescreening using chi-square test and negative binominal regression. 19.2% of subjects were recheck their health status on each year from 2008 to 2012. The socio-demographic characteristics related to reuse private health screening center were male, 30-40 aged, Daegu, Gwangju, Jeonnam and Gyeongnam region residents. And overweight and pre-hypertension were also factors association with number of using the private health screening program. People who control their health risk factors such as alcohol intake, smoking and mental health and execute physical exercise tend to use health screening program regularly. Our finding suggest that customer relationship management can execute and private health screening center enable their strategic plan based on data-evidence.

• Journal of the Korean Chemical Society
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• v.32 no.4
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• pp.342-350
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• 1988

An experimental investigation is made to determine the mechanism of the aquation of $[Co(en)_2Cl_2]^+$ in $Hg^{2+}$ aqueous solution. The progress of reaction is followed UV/vis-spectrophotometrically by a measurment of the absorbance at a specific wavelength of Co(III) complex as a function of time. The aquation of cis-$[Co(en)_2Cl_2]^+$ and trans-$[Co(en)_2Cl_2]^+$ has been found to be first order and second order with respect to the concentration of $Hg^{2+}$ catalyst, respectively. It has been found that the reaction rate for aquation of the trans-form is faster than that of cis-form, and that the product of either cis-form or trans-form is always in the mixture ratio of 97 % to 3 %. Plausible reaction mechanism is proposed for the reaction system on the basis of kinetic data and activation parameters. Theoretical rate equation derived from the proposed mechanism is consistent with the observed one.

• Korean Journal of Food Science and Technology
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• v.38 no.2
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• pp.176-182
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• 2006

Sensitive and specific monoclonal antibody (MAb) was produced from hybridoma (1H11-5) obtained by fusion of myeloma cell (V653) and spleen cell isolated from mouse immunized sulfamthazine (SMZ)-HG-KLH. Direct competitive ELISA was developed for rapid detection of SMZ in milk samples using MAb against SMZ with optimized conditions between MAb and SMZ-HG-HRP conjugate, and applicable conditions for analysis of milk samples were established. Detection range of immunoassay was 0.1 to 100 ppb. Recoveries from spiked raw milk and processed milk samples averaged 82.1-120.7 and 82.1-97.1%, respectively.

• Korean Journal of Materials Research
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• v.8 no.10
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• pp.969-974
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• 1998

The effect of vanadium, which is known to decrease the stacking fault energy of Fe-base alloys, on the microstructure and elevated temperature sliding wear resistance of Fe-20Cr- 1.7C- 1Si alloy was investigated. The maximum amount of vanadium maintaining the austenitic matrix seems to be about 3wt.% in Fe-20Cr- 1.7C-1Si-xV (x = 0, 1, 3, 6. lOwt.%) alloys and the austenitic alloys showed better wear resistance than ferritic alloys. It was considered to be due to the low stacking fault energy and $\gamma->\alpha$ strain-induced phase transformation at rmm temperature. It was shown from elevated temperature sliding tests up to .$225^{\circ}C$ that the addition of vanadium increases the temperature, at which the transition from oxidative wear to adhesive wear occur, and the amount of d formed at $225^{\circ}C$. Thus, it was considered that the addition of vanadium improves the elevated temperature sliding wear resistance of Fe-20Cr- 1.7C - 1Si by reducing the increasing rate of stacking fault energy with temperature and by increasing Ma temperature.