• Proceedings of the Korean Institute of Industrial Safety Conference
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• 1998.05a
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• pp.77-82
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• 1998

The residual strength of a specimen with MSD was investigated experimentally and numerically. The used materials for specimens are 2024-T3 and S50C. In each specimen, one main crack and 4 small cracks are machined by using electrical discharge wire cutting and saw cutting. The residual strengths are measured for 3 cases of crack configurations, and the measured values are compared with the values obtained numerically by using elasto-plastic average uncracked ligament stress link-up criteria.

• Journal of the Korean Society of Safety
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• v.14 no.4
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• pp.43-52
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• 1999

In this study, theoretical stress field analysis near the crack tip under tension-compression loading was performed. The results of the theoretical stress analysis were compared to the results of Finite Element Method(FEM). From this study, generation of tensile residual stress at crack tip was proved after 1-cycle of tension-compression loading, and the fracture toughness and the fracture load of a structure can be decreased by the residual stress.

• Journal of the Korean Society of Safety
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• v.12 no.2
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• pp.27-36
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• 1997

This paper evaluates the static and fatigue bending strengths of CFRP (carbon fiber reinforced plastic) laminates subjected to hygrothermals. The specimens which had different stacking composition, orthotropic and quasi-isotropic laminated plates, were prepared for this experiment. A steel ball launched by the air gun collides against CFRP laminates to generate impact damages, and the 3-point fatigue bending test is carried out by using the impacted laminates to investigate the influence of hygrothermals on the effect on the residual bending fatigue strength of CFRP laminates.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.872-877
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• 2004

Welding residual stresses are the main topics of welding research fields. The residual stresses and distortion of structures by welding exert negative effect on the safety of mechanical structures. That is, expansion of material by high temperature and distortion by cooling during welding process are caused by tensile and compressive residual stresses in welding material, and this residual stresses can induce fracture and fatigue problems of welding structures. The accurate prediction of residual stress and relaxation due to mechanical loading of weld zone is very important to improve the quality of weldment. In this study, a finite element modeling technique is developed to simulate the relaxation of residual stresses due to mechanical loading. The effects of load ratio for static and cyclic loading are evaluated based on analytical results.

• Journal of Applied Biological Chemistry
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• v.57 no.3
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• pp.235-242
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• 2014

The purpose of this study is the establishment of scientific processes for making food safety policies. Thus, we investigated pesticide residue level of the agricultural commodities from market, and performed risk assessment. Fifteen agricultural items are chosen based on the frequency of Korean consumption. The samples were collected from 9 cities where populations are more than one million. Total 283 active ingredients were monitoring ( total sample number =232). Single-analysis of target pesticides was for three kinds of possible growth regulators and the multicomponent analysis was for 280 kinds of pesticides, a total of 283 species were selected to perform the pesticide residues. Before monitoring the analytes, the improvements of the analytical methods were done by method validations under the CODEX analytical method development guidelines and can produce metrics that represent the international standards applied in accordance with the guidelines. In addition to residual pesticides detected during monitoring we compare the ADI to EDI values using detected result and dietary consumption data which is extracted from annual market basket survey. The 163 samples were non-detected in the total 232 samples so it means that every agricultural commodity will residual pesticides-free in 70.3%. The detected residual pesticides showed for a total of 69 cases (29.7%). Two of samples violate Korean MRL (0.9%). The ratio of EDI compared to ADI resulted in only from 0.00087 to 0.902%. In result, we can assume that all detected residual pesticides are very safe level and current policies of Korean pesticides control may be working.

• Journal of Welding and Joining
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• v.33 no.1
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• pp.24-29
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• 2015

Residual stresses arising from the materials processing such as welding and joining affect significantly the structural integrity depending on the external loading condition. The quantitative measurement of the residual stresses is of great importance in order to characterize the effects of the residual stresses on the structural safety. In this paper, we introduce a newly devised destructive technique, the contour method (CM), which is applied for the measurements of the residual stress distributions through the thickness of a 80 mm thick steel weld. Residual stresses are evaluated from the contour, which is the normal displacement on a cut surface produced by the relaxation of residual stresses, using a finite element model. The CM provides a two-dimensional map of the residual stresses normal to the cut surface. The CM developed in the present study was validated in comparison with the residual stress distribution determined by a well-established neutron-diffraction residual stress instrument (RSI) instrumented in HANARO neutron research reactor.

• Journal of Applied Biological Chemistry
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• v.62 no.1
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• pp.11-17
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• 2019

Strawberries are one of the main commodities in Korea and have been exported over 40 million dollar. Because the strawberry cultivation using hydroponics has increased, treatment of pesticide by drenching draw interest recently. However, detailed researches for drenching treatment of pesticide are limited, which results in difficulties in proper pesticide applications in agricultural fields. To activate use of drenching and improve safety in agricultural products, In this study, time-dependent residual characteristic of pesticides were compared with between different applications of pesticides in strawberries. The characteristics of azoxystrobin, prochloraz and thiamethoxam were investigated with drenching treatment at different applications: the time of treatment, concentration etc. at hydroponic cultivation for 40 days. Azoxystrobin and prochloraz were not detected at 14 day after application. Thiamethoxam was detected from 0.02 to 0.85 mg/kg. Crop uptake of pesticides was strongly affected with octanol-water partition coefficient and solubility in water. Residual amount in crops are highly dependent on the concentration of active ingredient of pesticides.

• Nuclear Engineering and Technology
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• v.46 no.1
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• pp.27-38
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• 2014

The Fukushima Dai-Ichi accident in 2011 has affected various aspects of the nuclear society worldwide. The accident revealed some problems in the conventional approaches used to ensure the safety of nuclear installations. To prevent such disastrous accidents in the future, we have to learn from them and improve the conventional approaches in a more systematic manner. In this paper, we will cover three issues. The first is to identify the key issues that affected the progress of the Fukushima Dai-Ichi accident greatly. We examine the accident from a defense-in-depth point of view to identify such issues. The second is to develop a more systematic approach to enhance the safety of nuclear installations. We reexamine nuclear safety from a risk point of view. We use the concepts of residual and unknown risks in classifying the risk space. All possible accident scenarios types are reviewed to clarify the characteristics of the identified issues. An approach is proposed to improve our conventional approaches used to ensure nuclear safety including the design of safety features and the safety assessments from a risk point of view. Finally, we address some issues to be improved in the conventional risk assessment and management framework and/or practices to enhance nuclear safety.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2002.05a
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• pp.62-66
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• 2002

• Nuclear Engineering and Technology
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• v.56 no.4
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• pp.1347-1356
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• 2024

Measuring the residual stress in the components in nuclear power plants is crucial to their safety evaluation. The instrumented indentation technique is a minimally invasive approach that can be conveniently used to determine the residual stress in structural materials in service. Because the indentation behavior of a structure with residual stresses is closely related to the elastic-plastic behavior of the indented material, an accurate understanding of the elastic-plastic behavior of the material is essential for evaluation of the residual stresses in the structures. However, due to the analytical problems associated with solving the elastic-plastic behavior, empirical equations with limited applicability have been used. In the present study, the impact of the non-equibiaxial residual stress state on indentation behavior was investigated using finite element analysis. In addition, a new nonequibiaxial residual-stress prediction methodology is proposed using a convolutional neural network, and the performance was validated. A more accurate residual-stress measurement will be possible by applying the proposed residual-stress prediction methodology in the future.