• Title/Summary/Keyword: concrete operation

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Simulation of Blasting Demolition of Reinforced Concrete Structures and Ground Vibration using Finite Element Method (유한요소법을 이용한 구조물의 발파해체 붕괴거동 및 지반진동 모사에 관한 연구)

  • Choi, Joo-Hee;Jung, Jae-Woong;Jeon, Seok-Won
    • Tunnel and Underground Space
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    • v.19 no.3
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    • pp.190-202
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    • 2009
  • With the increasing demand for blasting demolition in urban areas, the simulation of structural collapse prior to the real blasting operation is a key process for ensuring the success and safety of the blasting demolition. The simulation of collapsing behavior of a structure is not only vital for preventing unexpected economic loss and casualties, but also helpful in minimizing public claims by precisely estimating the environmental impact resulting from the operation. This study proposes a new technique for simulation of a blast demolition using FEM based LS-DYNA codes. The technique tries to simplify the complex arrangement of reinforcing bars, and use the actual properties of the concrete and steel reinforcing bars, thereby improving the overall capability of the simulation to match well with the collapsing behavior of real-scale structures.

The Comparative Analysis between the Demanded Cognitive Levels of Science Textbooks for the Sixth Graders and the Students' Psychological Difficulty with the Textbooks (초등 6학년 과학 교과서의 요구 인지 수준과 학생의 심리적 난이도 비교 분석)

  • Jeong, Eun Young;Jang, Myoung-Duk
    • Journal of Korean Elementary Science Education
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    • v.36 no.4
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    • pp.356-366
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    • 2017
  • The purpose of this study is to analyze whether the required cognitive levels of the current 6th graders' science textbooks conform to the children's cognitive levels and to examine the students' sensed psychological difficulty of the current science textbooks. The eighty five students (boy: 39, girl: 46) from one elementary school were participated in this study. The results of the study are as follows. First, the 2/3 out of the contents in the six graders' science textbooks require concrete level of operation and the 1/3 out of the contents in the textbooks requires the formal level of operation. So the 70% students at the concrete operational level are likely to undergo difficulties with the 1/3 contents in the textbooks. Second, the students' psychological difficulty on the science textbooks is relatively low (approximately two out of five points) and there is not any special pattern between the cognitive level of the textbooks and the students' psychological difficulty of the textbooks.

The Research for the Activation of Treatment Related Service According to the 'Special Education Law': Focusing on Physical.Occupational Therapy ('장애인 등에 대한 특수교육법' 시행에 따른 치료지원서비스 활성화 방안 : 물리.작업치료를 중심으로)

  • Lee, Byoung-Hee;Jung, Jin-Hwa
    • Journal of Korean Physical Therapy Science
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    • v.16 no.2
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    • pp.45-55
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    • 2009
  • Background: This thesis aims at suggesting the direction for the introduction of public free treatment support system according to the establishment of [Special Education Law] and the right settlement of therapeutic support service. Method: It introduced the characteristics and the contents of school based PT & OT, diagnosis and evaluation, and operation method. It set up question items and presented intervention plan, and substantial intervention, beginning from the request of whole process. The diagnostic evaluation was described from 4 aspects, which are consideration matters in the time of document drawing and diagnostic evaluation, chiefly centering around SOAP. The flow of overall treatment support service, the allocation of 16 handicapped children for 1 therapist, and the weekly treatment frequency according to the treatment support location and environment were suggested in the concrete operation method. Result: The concrete method should be explored in order to provide handicapped students with requisite services, which are offered by various experts in the amended 'Special Education Law'. In addition, work condition and social welfare, which are equal to school teachers, should be provided for all experts. Conclusion: Along with these things, special education support center should establish the road-map for the education rehabilitation of the handicapped children from the evaluation of early diagnosis of the handicapped children to treatment support and lifelong education.

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Corrosion behaviors of cement mortar specimens with different cover thickness in natural sea water

  • Jeong, Jin-A;Jin, Chung-Kuk;Jeong, Eun-Seok
    • Journal of Advanced Marine Engineering and Technology
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    • v.40 no.2
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    • pp.107-111
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    • 2016
  • This paper presents electrochemical corrosion behaviors of cement mortar specimens in the high salinity condition. Chloride ion is known as the most detrimental parameter to cause the corrosion in reinforced concrete. Increasing the concrete cover thickness is one of the corrosion protection methods against chloride ion; so, this study mainly focuses on the effects of mortar cover thickness on corrosion protection. In specimens, rebar, which was a height of 200 mm and a diameter of 10 mm, was installed at the center of the small size form. Later on, mortar was injected into the form, and 10, 20, 30, 40, and 50 mm of the different mortar cover thicknesses were selected. Potential measurements, linear polarization resistance tests, and cyclic potentiodynamic polarization tests were performed for specimens that were exposed to seawater. These results were compared with visual inspection results of rebar. The results show that an increase in the cover thickness contributes to corrosion protection. In addition, the result of electrochemical corrosion tests generally agreed with that of an autopsy visual inspection.

Operation and Configurgation of Superconducting Machines and Devices in Utility System (초전도전력설비의 구성 및 운전)

  • 홍원표;이원규;곽희로
    • Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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    • 1996.11a
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    • pp.116-121
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    • 1996
  • An image of future power system which has introduced superconducting generator, cable, transformer, fault current limiter, SMES and so on is presented. Conceptual designs of each SC machines and devices are carried out. The SC cable and SFCL utilize the high Tc superconductor(HTS) cooled by liquid $N_2$Other devices use low temperature superconducting cooled by He. The SC power system models are proposed detailedly. In viewpoint of the operation and control SC power system, The concrete design direction and effective role of each SC apparatus are investigated. In this paper, it is pointed that superconducting fault limiters(SFCLs) should play an important part of the quenching current level coordination to prevent the other SC devices from quenching. Finially, SFCL are also expected to he very effective to introduce flexibility of power system configuration and operation due to their possibility to enhance transient stability and reduce short circuit current.

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A Case Study on the Reduction Costs Prediction of a Reinforced Concrete Bridge using LCC method (Life Cycle Cost 기법에 의한 RC Slab 교량의 절감비용 예측에 관한 연구)

  • Kwon, Suk-Hyun;Kim, Sang-Beom;Park, Yong-Jin
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.11 no.5
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    • pp.160-170
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    • 2007
  • This study predicts Life Cycle Cost of RC Slab bridge case in maintenance and operation level and calculated economic efficiency by the avoidable costs of a bridge. This result of the study can be summarized as follow: (1) LCC analysis model on the bridge case is suggested. (2) Maintenance and operation level of a bridge have been divided, and LCC of the bridge case has been predicted at current maintenance and operation level and required maintenance and operation level. (3) Reduction costs is predicted by LCC of the bridge case, and its economic efficiency is calculated.

Comparative Evaluation of Radioactive Isotope in Concrete by Heavy Ion Particle using Monte Carlo Simulation (몬테카를로 시뮬레이션을 통한 중하전입자의 콘크리트 방사화 비교평가)

  • Bae, Sang-Il;Cho, Yong-In;Kim, Jung-Hoon
    • Journal of radiological science and technology
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    • v.44 no.4
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    • pp.359-365
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    • 2021
  • A heavy particle accelerator is a device that accelerates particles using high energy and is used in various fields such as medical and industrial fields as well as research. However, secondary neutrons and particle fragments are generated by the high-energy particle beam, and among them, the neutrons do not have an electric charge and directly interact with the nucleus to cause radiation of the material. Quantitative evaluation of the radioactive material produced in this way is necessary, but there are many difficulties in actual measurement during or after operation. Therefore, this study compared and evaluated the generated radioactive material in the concrete shield for protons and carbon ions of specific energy by using the simulation code FLUKA. For the evaluation of each energy of proton beam and carbon ion, the reliability of the source term was secured within 2% of the relative error with the data of the NASA Space Radiation Laboratory(NSRL), which is an internationally standardized data. In the evaluation, carbon ions exhibited higher neutron flux than protons. Afterwards, in the evaluation of radioactive materials under actual operating conditions for disposal, a large amount of short-lived beta-decay nuclides occurred immediately after the operation was terminated, and in the case of protons with a high beam speed, more radioactive products were generated than carbon ions. At this time, radionuclides of 44Sc, 3H and 22Na were observed at a high rate. In addition, as the cooling time elapsed, the ratio of long-lived nuclides increased. For nonparticulate radionuclides, 3H, 22Na, and for particulate radionuclides, 44Ti, 55Fe, 60Co, 152Eu, and 154Eu nuclides showed a high ratio. In this study, it is judged that it is possible to use the particle accelerator as basic data for facility maintenance, repair and dismantling through the prediction of radioactive materials in concrete according to the cooling time after operation and termination of operation.

A Study of the Development of a Concrete Floating Breakwater for an Open Sea Fish Farm (외해 양식장 콘크리트 부유식 방파제 개발에 관한 연구)

  • Choi, Gun-Hwan;Kim, Mi-Jeong;Jang, Ki-Ho;Jun, Je-Cheon;Park, Jung-Jun
    • Journal of Ocean Engineering and Technology
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    • v.33 no.6
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    • pp.648-656
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    • 2019
  • The ecological changes in the ocean due to the drastic global warming require that action be taken to sustain the productivity of fisheries. Proper ocean facilities could help prevent the loss of the expenditures made on marine aquaculture and reduce the related compensation for various ocean conditions. The aim of this study was to develop a floating ocean wave-breaker using an eco-friendly concrete and conducting a site survey, a structural analysis, and a test of towing the tank. As a result, the wave at the fish farm would be reduced. The results of the holding power of anchors and the capability of moving the floating structures were considered in the design of the wave-breaker. The analyses of the material properties of concrete and the steel structures, as well as the CAPEX and OPEX analyses of the manufacturing and operation processes confirmed the superiority of the floating concrete wave-breaker. In particular, this study demonstrated that the concrete floating breakwater can protect the fish farm against typhoons and reverse-waves, thereby reducing losses of the fish.

Reconstruction of internal structures and numerical simulation for concrete composites at mesoscale

  • Du, Chengbin;Jiang, Shouyan;Qin, Wu;Xu, Hairong;Lei, Dong
    • Computers and Concrete
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    • v.10 no.2
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    • pp.135-147
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    • 2012
  • At mesoscale, concrete is considered as a three-phase composite material consisting of the aggregate particles, the cement matrix and the interfacial transition zone (ITZ). The reconstruction of the internal structures for concrete composites requires the identification of the boundary of the aggregate particles and the cement matrix using digital imaging technology followed by post-processing through MATLAB. A parameter study covers the subsection transformation, median filter, and open and close operation of the digital image sample to obtain the optimal parameter for performing the image processing technology. The subsection transformation is performed using a grey histogram of the digital image samples with a threshold value of [120, 210] followed by median filtering with a $16{\times}16$ square module based on the dimensions of the aggregate particles and their internal impurity. We then select a "disk" tectonic structure with a specific radius, which performs open and close operations on the images. The edges of the aggregate particles (similar to the original digital images) are obtained using the canny edge detection method. The finite element model at mesoscale can be established using the proposed image processing technology. The location of the crack determined through the numerical method is identical to the experimental result, and the load-displacement curve determined through the numerical method is in close agreement with the experimental results. Comparisons of the numerical and experimental results show that the proposed image processing technology is highly effective in reconstructing the internal structures of concrete composites.

Recognition of Concrete Surface Cracks Using Enhanced Max-Min Neural Networks (개선된 Max-Min 신경망을 이용한 콘크리트 균열 인식)

  • Kim, Kwang-Baek;Park, Hyun-Jung
    • Journal of the Korea Society of Computer and Information
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    • v.12 no.2 s.46
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    • pp.77-82
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    • 2007
  • In this paper, we proposed the image processing techniques for extracting the cracks in a concrete surface crack image and the enhanced Max-Min neural network for recognizing the directions of the extracted cracks. The image processing techniques used are the closing operation or morphological techniques, the Sobel masking for extracting for edges of the cracks, and the iterated binarization for acquiring the binarized image from the crack image. The cracks are extracted from the concrete surface image after applying two times of noise reduction to the binarized image. We proposed the method for automatically recognizing the directions of the cracks with the enhanced Max-Min neural network. Also, we propose an enhanced Max-Min neural network by auto-tuning of learning rate using delta-bar-delta algorithm. The experiments using real concrete crack images showed that the cracks in the concrete crack images were effectively extracted and the enhanced Max-Min neural network was effective in the recognition of direction of the extracted cracks.

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