• Nuclear Engineering and Technology
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• v.51 no.5
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• pp.1279-1288
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• 2019

The vortex-type fluidic diode (FD) is a key safety component for inherent safety in various advanced reactors such as the sodium fast reactor (SFR) and the molten salt reactor (MSR). In this study, topology optimization is conducted to optimize the design of the vortex-type fluidic diode. The optimization domain is simplified to 2-dimensional geometry for a tangential port and chamber. As a result, a design with a circular chamber and a restrictor at the tangential port is obtained. To verify the new design, experimental study and computational fluid dynamics (CFD) analysis were conducted for inlet Reynolds numbers between 2000 and 6000. However, the results show that the performance of the new design is no better than the original reference design. To analyze the cause of this result, detailed analysis is performed on the velocity and pressure field using flow visualization experiments and 3-D CFD analysis. The results show that the discrepancy between the optimization results in 2-D and the experimental results in 3-D originated from exclusion of an important pressure loss contributor in the optimization process. This study also concludes that the junction design of the axial port and chamber offers potential for improvement of fluidic diode performance.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.3
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• pp.306-312
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• 2019

This paper investigates to design a controller for maritime autonomous surface ship (MASS) by means of adaptive super-twisting algorithm (ASTA). A input-out feedback linearization method is considered for multi-input multi-output (MIMO) system. Sliding Mode Controller (SMC) is suitable for MASS subject to ocean environments due to its robustness against parameter uncertainties and disturbances. However, conventional SMC has inherent disadvantages so-called, chattering phenomenon, which resulted from the high frequency of switching terms. Chattering may cause harmful failure of actuators such as propeller and rudder of ships. The main contribution of this work is to address an appropriate controller for MASS, simultaneously controls surge and yaw motion in severe step inputs. Proposed control mechanism well provides convergence bewildered by external disturbances in the middle of steady-state responses as well as chattering attenuation. Also, the adaptive algorithm is contributed to reducing non-overestimated value of control gains. Control inputs of surge and yaw motion are displayed by smoother curves without excessive control activities of actuators. Finally, no overshoot can be seen in transient responses.

• Journal of the Korea Safety Management & Science
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• v.25 no.3
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• pp.31-36
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• 2023

The use of hanging scaffolding for exterior wall painting and cleaning in building construction and maintenance carries the inherent risk of fall accidents. While periodic rope replacement is crucial for preventing accidents resulting from rope breakage, current regulations lack specificity in determining appropriate disposal period for fiber ropes. This study analyzed the tensile strength of the most commonly used PP fiber ropes with different diameters (16 mm, 20 mm) in the domestic construction industry. Additionally, the effect of outdoor exposure was examined by measuring the tensile strength of new ropes and ropes exposing to outdoor conditions for 30 days and 90 days. The results showed that the new ropes and those exposed to outdoor for 30 days met the KS (Korean Standards) criteria for tensile strength. However, a significant decrease in tensile strength was observed in ropes exposed to outdoor for 90 days compared to both the new ropes and those exposed for 30 days. Furthermore, the ropes exposed for 90 days did not meet the KS criteria. These findings indicate the degradation of PP fiber ropes due to UV (Ultra Violet) radiation, highlighting the importance of considering this factor when determining the replacement period for fiber ropes used in scaffolding work.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.33 no.4
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• pp.412-418
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• 2023

As advances in artificial intelligence (AI) increasingly approach areas once relegated to the realm of science fiction, there is growing public interest in using these technologies for practical everyday tasks in both the home and the workplace. This paper explores the applications of and implications for of using ChatGPT, a conversational AI model based on GPT-3.5 and GPT-4.0, in the field of occupational health and safety. After gaining over one million users within five days of its launch, ChatGPT has shown promise in addressing issues ranging from emergency response to chemical exposure to recommending personal protective equipment. However, despite its potential usefulness, the integration of AI into scientific work and professional settings raises several concerns. These concerns include the ethical dimensions of recognizing AI as a co-author in academic publications, the limitations and biases inherent in the data used to train these models, legal responsibilities in professional contexts, and potential shifts in employment following technological advances. This paper aims to provide a comprehensive overview of these issues and to contribute to the ongoing dialogue on the responsible use of AI in occupational health and safety.

• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.2
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• pp.33-44
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• 2008

Most of the civil structure - bridges, offshore structures, plant, etc. - have been designed by the classical approaches which deal with all the design parameters as deterministic variables. However, some more advanced techniques are required to evaluate the inherent randomness and uncertainty of each design variable. In this research, a seismic safety assessment algorithm based on the structural reliability analysis has been formulated and computerized for more reasonable seismic design of turbine-generator foundations. The formulation takes the design parameters of the system and loading properties as random variables. Using the proposed method, various kinds of parametric studies have been performed and probabilistic characteristics of the resulted structural responses have been evaluated. Afterwards, the probabilistic safety of the system has been quantitatively evaluated and finally presented as the reliability indexes and failure probabilities. The proposed procedure is expected to be used as a fundamental tool to improve the existing design techniques of turbine-generator foundations.

• The Journal of the Korea Contents Association
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• v.13 no.12
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• pp.869-879
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• 2013

Modern medicine has not yet conquered behavior therapy for cancer radiation treatment, which is one of the professional groups involved in the justification of the act and reasonable human resources was analyzed. Radiation Oncology(Therapeutic Radiology) installed the role of the medical physicist in the current law, the act must have been within the limits given licenses, but the legitimacy of the act which can be given the current laws and regulations are not clear. Thus, certification and testing outside the medical physicist's research institutions, including the measures to be reflected in national legislation sought. Medical physicists, with the inherent illegality act because one of the areas to precluding the illegality of the content-based "medical law" and "Nuclear Safety Law", "medical technology in the field of radiation safety standards on management" was based on the interpretation. In conclusion, "medical law" and "in the field of medical technology on the management of radiation safety standards" that are consistent with the recognition of qualifications, increased activity in the radiation therapy and radiation safety management must deal with this will be feasible.

• Journal of the Korean Society of Systems Engineering
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• v.11 no.2
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• pp.13-29
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• 2015

With the era of big data, the big data has been expected to have a large impact in the NPP safety areas. Although high interests of the big data for the NPP safety, only a limited researches concerning this issue are revealed. Especially, researches on the logical/physical structure and systematic design methods for the big data platform for the NPP safety were not dealt with. In this research, we design a new big data pilot platform for the NPP safety especially focusing on health monitoring and early warning services. For this, we propose a tailored design process based on SE approaches to manage inherent high complexities of the platform design. The proposed design process is consist of several steps from elicitate stakeholders to integration test via define operational concept and scenarios, and system requirements, design a conceptual functional architecture, select alternative physical modules for the derived functions and assess the applicability of the alternative modules, design a conceptual physical architecture, implement and integrate the physical modules. From the design process, this paper covers until the conceptual physical architecture design. In the following paper, the rest of the design process and results of the field test will be shown.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.8 no.2
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• pp.45-52
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• 2009

The off-state impedance of LED signal head is greater than that of a traditional bulb signal head, and the traffic controller has inherent off-state output leakage current. These two characteristics make the field trouble and reduce signal safety when the LED signal head is installed with traffic controller. In this Paper, a complement method of the LED signal head and traffic controller local standard (220vac line voltage) for improving signal safety is suggested. The point of designed complement method is to reduce the output leakage current of the traffic controller under 3mA, to increase the voltage feedback threshold to $70{\pm}5V$, and to make LED signal head maintain off-state in 0-95vac with 10Kohm maximum impedance.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.47 no.3
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• pp.248-256
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• 2011

The inherent efficiency of a ship would be prior to any other quality factors in ship's safety, because lack of it may give rise to a serious sea casuality even if it were a light mistake in operation. And the representative casualty comes from a deficiency of stability and an operating error combined would be capsizing. The Korean offshore large purseiner looks to have a structural weak point with small range of stability in spite of her big initial metacentric height, and have various type of roll reduction devices in order to cover up the defect. The aim of this study is to grasp for the roll reduction characteristics of the purseiner with bilge keel only and a stern keel additionally attached. The results are summarized as follows; The rolling angle of the model ship was increased in accordance with increase of the wave period and height, especially at close to the natural wave period of her, and the trends were more distinguished in the situation of bilge keel only installation than in the stern keel additionally installed. And stern keel has not noticeable effect on the reduction of the roll in the light ship condition, but has a little effect in full load condition.

• Computers and Concrete
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• v.26 no.2
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• pp.127-136
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• 2020

There is an inherent randomness for concrete microstructure even with the same manufacturing process. Meanwhile, the concrete material under the aqueous environment is usually not fully saturated by water. This study aimed to develop a stochastic micromechanical framework to investigate the probabilistic behavior of the unsaturated concrete from microscale level. The material is represented as a multiphase composite composed of the water, the pores and the intrinsic concrete (made up by the mortar, the coarse aggregates and their interfaces). The differential scheme based two-level micromechanical homogenization scheme is presented to quantitatively predict the concrete's effective properties. By modeling the volume fractions and properties of the constituents as stochastic, we extend the deterministic framework to stochastic to incorporate the material's inherent randomness. Monte Carlo simulations are adopted to reach the different order moments of the effective properties. A distribution-free method is employed to get the unbiased probability density function based on the maximum entropy principle. Numerical examples including limited experimental validations, comparisons with existing micromechanical models, commonly used probability density functions and the direct Monte Carlo simulations indicate that the proposed models provide an accurate and computationally efficient framework in characterizing the material's effective properties. Finally, the effects of the saturation degrees and the pore shapes on the concrete macroscopic probabilistic behaviors are investigated based on our proposed stochastic micromechanical framework.