• Journal of the Korea Concrete Institute
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• v.23 no.6
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• pp.799-808
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• 2011

In this study, a standardized test method to analyze tensile properties of multi-directional GFRP plate was proposed. Presently, tensile strength test of FRP composite reinforced with isotropic and orthotropic fiber is standardized according to ISO standard. Also, even though many studies were performed on test method to analyze the dynamic properties, the properties of tensile strength for multi-directional GFRP plate were not clearly identified. Currently, the domestic test method in accordance with ASTM, which is applicable to unidirectional FRP plate, gave tensile test results greater than actual properties. Thus, in this study, GFRP tensile test was conducted using the method found to be commonly applicable to all standards based on literature review of domestic and international references. Then, anchorage length experiments were performed using the proposed tension test method to evaluate validity of the method. Finally, optimal anchorage length was estimated from the numerical analysis to propose the standardized tensile strength method for GFRP multi-directional composite evaluation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.2
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• pp.177-185
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• 2008

Low-cycle environmental fatigue tests of cast austenitic stainless steel CF8M at the condition of fatigue strain rate 0.04%/sec were conducted at the pressure and temperature, 15MPa, $315^{\circ}C$ of a operating pressurized water reactor (PWR). The used test rig was limited to install an extensometer at the gauge length of the cylindrical fatigue specimen inside a small autoclave. So the magnet type LVDT#s were used to measure the fatigue displacement at the specimen shoulders inside the high temperature and high pressure water autoclave. However, the displacement and strain measured at the specimen shoulders is different from the one at the gauge length for the geometry and the cyclic strain hardening effect. Displacement of the fatigue specimen gauge length calculated by FEM (finite element method) used to modify the measured displacement and fatigue life at the shoulders. A series of low cycle fatigue life tests in air and PWR conditions simulating the cyclic strain hardening effect verified that the FEM modified fatigue life was well agreed with the simulating test results. The process and method developed in this study for the environmental fatigue test inside the small sized autoclave would be so useful to produce reliable environmental fatigue curves of CF8M stainless steel in pressurized water reactors.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.7
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• pp.1416-1425
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• 2002

In this study, the effects of combined environmental factors on mechanical and thermal analysis properties of graphite/epoxy composites were evaluated by the use of an accelerated aging test. Environmental factors such as temperature, moisture. and ultraviolet were considered. A xenon-arc lamp was utilized for ultraviolet light. and exposure times of up to 3000 hours were applied. Several types of specimens - tensile. bending, and shear specimens those are transverse to the fiber direction, and bending specimens those are parallel to the tiber direction - were used to investigate the effects of environmental factors on mechanical properties of the composites. Also, glass transition temperature, storage shear modulus, loss shear modulus, and tan ${\delta}$ were measured as a function of exposure times through a dynamic mechanical analyzer. In addition. a suitable testing method for determining the effect of environmental factors on mechanical properties is suggested by comparing the results from using two different types of strain measuring sensors. Finally, composite surfaces exposed to environmental factors were examined using a scanning electron microscope.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.6
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• pp.1049-1060
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• 2018

Soil conditioning is one of the key factors for successfull tunnel excavations utilizing the earth pressure-balanced (EPB) shield tunnel boring machine (TBM) by increasing the tunnel face stability and extraction efficiency of excavated soils. In this study, conditioning agents are mixed with the weathered granite soils which are abundant in the Korean peninsula and the workability of the resulting mixture is evaluated through the slump tests to derive and propose the most suitable conditioning agent as well as the most appropriate agent mix ratios. However, since it is cumbersome to perform the slump tests all the time either in the laboratory or in-situ, a simpler test may be needed instead of the slump test; the fall cone test was proposed as a substitute. In this paper, the correlation between the slump value obtained from the slump test and the cone penetration depth obtained from the proposed fall cone test was obtained. Test results showed that a very good correlation between two was observed; it means that the simpler fall cone test can be used to assess the suitability of the conditioned soils instead of the more cumbersome slump test.

• Geomechanics and Engineering
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• v.33 no.1
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• pp.41-51
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• 2023

Cementitious materials such as Ordinary Portland Cement (OPC), fly ash, lime, and bitumen have been employed for soil improvement over the years. However, due to the environmental concerns associated with the use of OPC, substituting OPC with calcium sulfoaluminate (CSA) cement offers good potential for ground improvement because it is more eco-friendly. Although earlier research has investigated the stabilizing effects of CSA cement-treated sand, no attempt has been made to examine soil behavior under high confining pressure. As a result, this study aimed to investigate the shear strength and mechanical behavior of CSA cement-treated sand using a consolidated drained (CD) triaxial test with high confining pressure. The microstructure of the examined sand samples was investigated using scanning electron microscopy. This study used sand with CSA cement contents of 3%, 5%, and 7% and confining pressures of 0.5, 1.0, and 1.5 MPa. It revealed that the confining pressures and CSA cement content significantly affected the stress-strain and volumetric change behavior of CSA cement-treated sand at high confining pressures.

• Journal of Environmental Science International
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• v.32 no.1
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• pp.1-9
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• 2023

In this study, a horticultural therapy program was performed by employing the anger experienced by people during daily life activities in the emotion regulation strategy-based program to identify the influence of the horticultural program on anger control in the caregivers for patients with dementia. To measure this influence, two tools were used: a self-administered questionnaire survey, which is a subjective test, and an instrumental test, which can measure the physical index that detects the physical changes through anger. For the preliminary test, depression, stress, self-esteem, anxiety, and anger state-characteristic were tested using the self-administered questionnaire. For the follow-up test, the self-administered survey and the test using the physical index were performed in a manner similar to that of the preliminary test. The self-administered questionnaire comprised questions suitable to this study and considered the age, education level, and economic aspect of the subjects. The test results indicated that the experimental group subjected to the emotion regulation strategy-based horticultural therapy showed very significant reduction in depression and anger and significant reduction in stress, self-esteem, and anxiety. In the physical index test, the systolic and diastolic blood pressures were reduced, and the pulse rate and respiration rate reduced before and after the therapy, thus, proving the effectiveness of the therapy in anger control.

• Journal of the Korean Geotechnical Society
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• v.36 no.10
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• pp.57-71
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• 2020

Liquefaction-induced sand boils were observed during the Pohang earthquake (Moment magnitude, 5.4) on November 15, 2017, specifically in the region of agricultural fields and park areas near the epicenter. This was recorded as the first observed liquefaction phenomenon in Korea. This paper analyzes liquefaction potentials at the key sites at Pohang area. The simplified methods and current design standard were used to evaluate the occurrence of liquefaction. The seismic demand was estimated based on the NGA-WEST2 ground motion prediction equations (GMPEs). The liquefaction resistance of the ground was determined using the in-situ tests: standard penetration test (SPT) and cone penetration test (CPT). The liquefaction potentials were quantified by liquefaction potential index (LPI), which were compared with those from the previous studies.

• Journal of the Korean Wood Science and Technology
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• v.36 no.2
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• pp.39-45
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• 2008

Formaldehyde and volatile organic compounds (VOCs) are emitted from wood-based panels that have been made using wood particles, wood fiber, wood chips, formaldehyde-based resins and so on. In this study, we examined formaldehyde and total VOCs (TVOC) emission behaviors for plywood overlaid with water-soluble phenolic resin impregnated linerboard (PL), and two kinds of surface materials (decorative veneer and pre-impregnated finishing foil) that were adhered onto the PL that named DPL and PPL. EVA (ethyl vinyl acetate) was used to overlay the decorative veneer and pre-impregnated finishing foil on the plywood with water-soluble phenolic resin impregnated linerboard by a hot press instrument. The debonding test and accelerated aging test were conducted to assess their mechanical properties. Formaldehyde and TVOC emission concentrations were measured using the FLEC method and a VOC Analyzer, respectively. The debonding test results of PL, DPL and PPL were 1.2, 1.5, and $0.5N/mm^2$, respectively. The surface appearance of the samples were not changed after the accelerated aging test. The PL and DPL exhibited reduced formaldehyde and TVOC emission levels, respectively. In the case of PPL, the VOC value was relatively higher than those of PL and DPL.

• Journal of Environmental Science International
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• v.13 no.10
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• pp.955-963
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• 2004

This study was conducted to find and explain characteristics of diverse social groups' attitudes toward nuclear power plant. 7 hypotheses were constructed and statistically tested. In order to test 7 hypotheses, both Nuclear Energy Attitude Scale and Environmental Attitude Scale were distributed and field surveyed on 839 respondents representing a diverse range of subject groups. The results showed that 6 hypotheses were statistically accepted while 1 hypothesis statistically rejected. Contrary to the first hypothesis, this test found that people in close proximity to the nuclear power plant had more positive attitudes toward nuclear power than those living in distance from the nuclear power plant. Males had more positive nuclear energy attitudes than females. Academic backgrounds were not related to nuclear energy attitudes. Environmental attitudes showed negative relationship with nuclear energy attitudes. While anti-nuclear citizen action groups had the most negative attitudes, nuclear power plant workers had the most positive attitudes among responding groups. Finally, university students majoring in nuclear engineering had more positive attitudes than those of religious studies.

• Journal of Environmental Health Sciences
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• v.38 no.2
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• pp.128-135
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• 2012

Objectives: This study was aimed at determining the optimum coagulation dosage in a high turbid kaolin water sample using streaming current detection (SCD) as an alternative to the jar test. Methods: SCD is able to optimize coagulant dosing by titration of negatively charged particles. Kaolin particles were used to mimic highly turbid water ranging from 50 to 600 NTU, and polyaluminum chloride (PAC, 17%) was applied as a titrant and coagulant. The coagulation consisted of rapid stirring (5 min at 140 rpm), reduced stirring (20 min at 70 rpm), and settling (60 min). To confirm the coagulation effect, a jar test was also compared with the SCD titration results. Results: SCD titration of kaolin water samples showed that the dose of PAC increased as the pH rose. However, supernatant turbidity less than 1 NTU after coagulation was not achieved for high turbid water by SCD titration. Instead, a conversion factor was used to calculate the optimum PAC dosage for high turbid water by correlating a jar test result with that from an SCD titration. Using this approach, we were able to successfully achieve less than 1 NTU in treated water. Conclusions: For high turbid water influent in a water treatment plant, particularly during summer, the application of SCD control by applying a conversion factor can be more useful than a jar test due to the rapid calculation of coagulation dosage. Also, the interpolation of converted PAC dose could successfully achieve turbidity in the treated water of less than 1 NTU. This result indicates that an SCD system can be effectively used in a water treatment plant even for high turbid water during the rainy season.