• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.4
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• pp.41-49
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• 2014

In this study, experimental research was carried out to evaluate the structural performance of the reinforced concrete beam using hybrid retrofitting with two materials (groove and embedding FRP rod, CFRP sheet) in existing reinforced concrete buildings. Seven reinforced concrete beams, retrofitted groove and embedding FRP rod (NER series) and groove and embedding FRP rod with CFRP sheet (NERL series), and standard specimen (NBS) were constructed and tested under monotonic loading. Design parameters of test specimens are the amount of groove and embedding FRP rod and lapping CFRP sheet. Test results showed that the maximum load carrying capacity of specimens with groove and embedding FRP rod and groove and embedding FRP rod with CFRP sheet (NERL series) were increased the by 12~46% and 22~77% respectively in comparison with the standard specimen NBS. Test specimens NER series were failed with the adhesion slip and concrete cover separation. And test specimens NERL series were failed with the adhesion slip due to the confining effect of lapping CFRP sheet.

• Journal of Platform Technology
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• v.6 no.4
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• pp.59-68
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• 2018

The objective of this study is to develop an embedded antenna structure with NFC and WPC composite functions. By selecting stable materials, the optimal component ratio of the polymer sheet was determined. The low cost embedded winding method compared to the existing FPCB was devised. During the winding process, characterization and process technology were developed. We also fabricated a ferrite mold to process the WPC grooves and developed the process technology for optimizing the WPC antenna. The following conclusions were obtained. (1) Optimum composition ratio was derived as Fe 87.5%, Si 7%, Al 5.5% and selected as the final material. (2) Optimal sheet conditions were derived from the experimental evaluation method and the experimental design method through the combination test of the optimized sheet and the conventional mass production FPCB. (3) According to coil diameter and inner diameter, Q value fluctuation, resistance value and efficiency fluctuation are obtained. Therefore, the most suitable coil condition is selected and Rx matching is performed. (4) The EMV load modulation test and the cognitive distance test of the polymer sheet and the ferrite sheet showed that the recognition distance of the polymer sheet at 1k and 4K was 32-33 mm and the recognition distance of the ferrite sheet at the same condition was 30-31 mm.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.5
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• pp.502-509
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• 2019

Studies have been made on performance evaluation of expansion joint systems for an ordinary highway or road bridge. However little study has been made for runway connection bridges at airports. A study on performance evaluated from computer code analysis and shrinkage, extension, and compression repetition tests based on KS F 4425 is conducted to a newly developed expansion joint system which has been installed in a runway connection bridge at Incheon Airport Extension 2 Construction Site. The MIDAS computer code is used to analyze the performance before the manufacture of the mock-up of expansion joint system on the basis of design requirements. Tests based on the KS F 4425 of 2001 year-version are conducted for the mock-up. Domestic codes and standards to validate the performance of the expansion joint system in a connection bridge have been developed for a vehicle. However the expansion joint system tested in this study is installed in a runway connection bridge for an aircraft. Conservatively the heaviest one among airplanes departing and landing at Incheon Airport is assumed level-F $468.4kN/m^2$ and adopted for the tests and analyses in this study. KS F 4425 method is selected for the shrinkage, extension, and compression repetition tests. No remarkable problem was observed for the 2,500-cycle shrinkage and extension and two million-cycle repeatition load tests. The results of this study are expected to contribute to establishment of code and standard for the performance validation of an expansion joint system installed in a runway connection bridge for an aircraft by providing performance test results and computer analysis results based on finite element methods.

• Journal of Digital Convergence
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• v.20 no.2
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• pp.499-509
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• 2022

This study was conducted to understand the effect of health assessment practical education on class participation, problem-solving process, academic self-efficacy, and academic achievement of nursing students. This study used a nonequivalent control group pretest-posttest design. The participants were 69 nursing university students located in C city. Data were collected on two separate occasions before and after the application of the program from February 2021 to July 2021. Data were analyzed by chi-square test, independent t-test, and ANCOVA using SPSS WIN 23.0. There were significant differences in class participation(F=15.003, p<.001), academic self-efficacy(F=13.288, p=.001) and academic achievement(F=19.755, p<.001) between the experimental group and the control group. In the problem-solving process, the experimental group was significantly higher than the control group in decision-making(F=6.948, p=.010), applying the solution(F=6.232, p=.015) and evaluation-reflection(F=5.364, p=.024). It is necessary to expand case-based learning to increase the problem-solving process, class participation, academic self-efficacy, and academic achievement of nursing students.

• The Journal of Korean Academy of Sensory Integration
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• v.21 no.1
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• pp.23-33
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• 2023

Objective : The purpose of this study is was to find ouetermine whether training to applying vibration stimulation to the biceps brachii of children in the late stages of spasticity hemiplegic cerebral palsy can helps to improve the function of the upper extremity. Methods : This The study was conducted on with three children with cerebral palsy, all between the ages of 13 and 15 years. Among the experimental research methods of used with individual subjects, an AB research design using multiple basic baseline individual experimental studies was used, and vibration stimulation was provided to the paralyzed hand during the intervention period. The An evaluation was conducted before and after each session used to measure the function of the upper extremity using was conducted after each session of the Rapael Smart Board and The Jebsen-Tayler hand function test and the Motor Activity Log (MAL) were conducted before and after the experiment. Results : As a result of measuring the smooth The average score and total scores of for using the Rapael Smart Board to measure the upper extremity function in following each therapeutic session using the Rafale smart pegboard showed that, Subject 3 did not showevidenced a no significant change in the average value, and but Subjects 1 and 2 did showed a significant changes in their average values. All three subjects showed significant changes in the Jepson-Taylor hand function test and in the Motor Activity Log test, as evaluated before and after the intervention. Conclusion : Training The using use of vibration stimulation showed a positive effect on in improving upper limb function and exercise in hemiplegia hemiplegic children with who had little experience on using their hemiplegic side.

• Journal of Wind Energy
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• v.13 no.4
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• pp.26-41
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• 2022

Three similarities (i.e., geometrical similarity, kinematic similarity and dynamic similarity) between a prototype and model must be satisfied to perform an experiment for a floating offshore wind turbine (FOWT). For dynamic similarity, most of the model tests in ocean engineering basins are performed based on the Froude number, so the scale effect for the wind turbine of an FOWT occurs by different Reynolds numbers between the prototype and model. In this study, various model test techniques for overcoming the scale effect of the wind turbine part of the FOWT are investigated. Firstly, model test techniques using simple approaches are reviewed, and the advantages and disadvantages of the simple approaches are summarized. Secondly, the model test techniques in recent projects that apply improved approaches are introduced including advantages and disadvantages. Finally, new approaches applying digitalization are reviewed, and the characteristics of the new approaches are introduced.

• Tunnel and Underground Space
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• v.34 no.5
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• pp.571-598
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• 2024

Nuclear power generation, which belongs to the eco-friendly energy category, has a comparative advantage over other power generation methods in terms of cost and efficiency, and its share of electricity energy has recently shifted to an increasing trend worldwide. In Korea, various empirical studies have been conducted centering on KURT (KEARI Underground Research Tunnel) to secure elemental technology necessary for safe and efficient disposal of high-level radioactive waste inevitably generated during the operation of nuclear power plants. Considering the domestic rock type and geological conditions, the multi-barrier system is evaluated as the most effective among various high-level radioactive waste disposal methods. The objectives of this study were, first, to evaluate the hydraulic characteristics of deep and low-permeable rock masses and second, to secure quantitative information on the hydraulic connectivity between boreholes for establishing a large-scale in-situ test system necessary for the proper design and stability evaluation of the multi-barrier system. In this regard, diverse borehole tests using DHTS (Deep borehole Hydraulic Testing System) were performed in the two research modules in KURT, and in particular, the injection type cross-hole hydraulic connectivity tests were successfully completed for the first time in Korea. In this paper, we briefly introduced MDST (Mini Downhole Shut-in Tool) developed to update the performance of DHTS and mainly discussed the key results obtained from the stepwise in-situ borehole tests.

• Journal of the Korean Recycled Construction Resources Institute
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• v.1 no.1
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• pp.8-16
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• 2013

Currently, global warming has advanced by the usage of fossil fuels such as coal and petroleum. and the atmosphere temperature in the world of 100 years(1906~2005) has been risen $0.74^{\circ}C{\pm}0.18^{\circ}C$, IPCC announced that the global warming effect of last decade was nearly doubled compared to the changes($0.07^{\circ}C{\pm}0.02^{\circ}C$/10year) in the past 100 years. Moreover, due to the global warming, heat wave, heavy snow, heavy rain, super typhoon, were caused and are increasing to happen in the world continuously causing damages and destruction of social infrastructures, where concrete structures are suffering deterioration by long-term extreme climate changes. to solve these problems, the new construction technology and codes are necessary. In this study, to solve these problems, experiments on a variety of cases considering the temperature and humidity, the main factors of climate factors, were performed, and the cases are decided by temperature and humidity. The specimens were tested in compressive strength test and split tensile test by the curing age(3,7,28 days) morever, performance based design(PBD) method was applied by using the satisfaction curve developed from the experiment date. PBD is the design method that gathers the current experimental analysis and past experimental analysis and develops the material properties required for the structure, and carries out the design of concrete mix, and it is recently studied actively worldwide. Also, it is the ultimate goal of PBD to design and perform on structures have sufficient performance during usage and to provide the problem solving for various situations, Also, it can achieve maximum effect in terms of functionality and economy.

• Journal of the Korea Concrete Institute
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• v.27 no.5
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• pp.521-530
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• 2015

Design of fiber reinforced ultra-high strength concrete members should be verified with analytical or experimental methods for safety. Members with compressive strength larger than limitation of current design code usually be designed with analytical verification using stress-strain relation of concrete and reinforcements. For this purpose, mechanical characteristics of steel fiber reinforced ultra-high strength concrete were defined under uniaxial compression. Mix proportions of test specimens were based on reactive powder concrete and straight steel fibers were mixed with different volume fraction. Compressive strength of matrix were distributed from 80 MPa to 200 MPa. Effect of fiber inclusion were investigated : increase of compressive strength of concrete, elastic modulus and strain corresponding to peak stress. For the wide range application of investigation, previously tested test specimens were collected and used for investigation and estimation equation. Based on the investigation and evaluation of previous research results and estimation equation of mechanical characteristics of concrete, regression equations were suggested.

• Journal of the Korea Concrete Institute
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• v.23 no.5
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• pp.637-645
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• 2011

It is well known that high strength concrete with compressive strength higher than 50 MPa shows severe material and structural damages under fire due to spalling. To understand degradation of structural capacity of fire damaged high strength concrete structures, not only thermo-mechanical behavior needs to be defined, but also structural behavior of high strength concrete member under high temperature needs to be investigated. In this study, structural tests are performed by applying axial loads on high strength concrete columns exposed at elevated temperatures for assigned amount of time. The tested columns are prepared to have different concrete strength and polypropylene fiber percentage. The test results show that structural capacity of the columns decreased with increased compressive strength of concrete under same heating condition. Especially, it is interesting to note that high strength concrete columns with polypropylene fiber for spalling proof did not improve structural capacity compared to the columns without polypropylene fiber. The findings from the test are able to improve fire proof design of high strength concrete structural members and predicting structural performance of fire damaged structural members.