• Nuclear Engineering and Technology
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• 제52권2호
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• pp.230-237
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• 2020

In this part, an implicit time dependent solution is presented for the Boltzmann transport equation discretized by the analytic coarse mesh finite difference method (ACMFD) over the spatial domain as well as the simplified P₃ (SP₃) for the angular variable. In the first part of this work we proposed a SP₃-ACMFD approach to solve the static eigenvalue equations which provide the initial conditions for temp dependent equations. Having solved the 3D multi-group SP₃-ACMFD static equations, an implicit approach is resorted to ensure stability of time steps. An exponential behavior is assumed in transverse integrated equations to establish a relationship between flux moments and currents. Also, analytic integration is benefited for the time-dependent solution of precursor concentration equations. Finally, a multi-channel one-phase thermal hydraulic model is coupled to the proposed methodology. Transient equations are then solved at each step using the GMRES technique. To show the sufficiency of proposed transient SP₃-ACMFD approximation for a full core analysis, a comparison is made using transport peers as the reference. To further demonstrate superiority, results are compared with a 3D multi-group transient diffusion solver developed as a byproduct of this work. Outcomes confirm that the idea can be considered as an economic interim approach which is superior to the diffusion approximation, and comparable with transport in results.

• 대한인간공학회지
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• 제36권2호
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• pp.157-168
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• 2017

Objective: This study aims to understand the motorcycle accident characteristics of food delivery workers and to present basic guidelines on accident prevention through accident. Background: It is known that food delivery workers have a high ratio of self-employed and youth workers, and occupations with frequent disasters. Therefore the occupation is known to really be in need of accident prevention policy. Method: This study analyzed the data of motorcycle crashes of 1,310 food delivery workers that have been approved as on-duty industrial crashes since 2015. The accident characteristics were examined by dividing them into driver related factors and accident related factors. Results: Among the motorcycle crashes of food delivery workers, 99.2% of the victims were males, 82.6% had less than six months of work experience. 76.2% of the victims were employed by the companies with less than five workers. In addition, there was a difference in accident characteristics according to age, type of cuisine, accident time of the day, injured organs and injured body part. Conclusion: The results of this study can be used as baseline data to devise systematic measures to prevent motorcycle crashes of food delivery workers. Application: Preventative measures for novice young part time workers including safety education/training need to be established.

• 환경영향평가
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• 제2권2호
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• pp.27-32
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• 1993

The German society for promotion of EIA was founded in 1987 with the aim to support the introduction of EIA in Germany. The society with its center in Hamm where there is a plenty collection of literature, studies and further scientific sources does an enormous work in EIA-consulting all over the country. This work practically is done without any governmental support, only by private activities. The EIA society is structured within 9 regional as well as 19 specialized working groups and consisits of about 1,000 members. The unification of Germany in 1989/90 also influenced the development in this field, of course. While in the former Western part of Germany the already existing environmental administrations were able to react on the EIA-law of 1990 with their long time experiences, in the Eastern part the corresponding structures must be built up newly from the beginning. Since 1990 a great number of interested people also from Eastern Germany became numbers of the EIA-Society. By them an additional pool of knowledge and activity was brought into the society. This also applies for methods and means of EIA which were developed in the East during the time ago independently.

• Structural Engineering and Mechanics
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• 제53권2호
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• pp.325-336
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• 2015

This paper presents a study based on the damage due to the fatigue life of thrust ball bearings using vibratory analysis. The main contribution of this work lies in establishing a relation between modal damping and the rolling contact fatigue damage of the thrust ball bearing. Time domain signals and frequency spectra are extracted from both static and dynamic experiments. The first part of this research consists in measuring the damping of damaged thrust ball bearings using impact hammer characterization tests. In a second part, indented components representing spalled bearings are studied to determine the evolution of damping values in real-time vibration spectra using the random decrement method. Dynamic results, in good agreement with static tests, show that damping varies depending on the component's damage state. Therefore, the method detailed in this work will offer a possible technique to estimate the thrust ball bearing fatigue damage variation in presence of spalling.

• 대한의용생체공학회:의공학회지
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• 제5권1호
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• pp.77-84
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• 1984

A prototype of a linear real-time ultrasound B-scanner has been developed which has an axial resolution of 1-2mm and lateral resolution of 2-3mm. In the actual hardware and software implementations of the B-scanner, the following features were emphasized; (1) a dynamic focusing to improve resolution; (2) signal processing to obtain low noise image; (3) various functions for the user's convenience' (4) simplification of the system by an extensive use of recently developed LSI's; (5) development of a prototype at the level of a commercial product. This paper reports the experimental results of the overall system and the design approach of the analog part. The work on the digital part of the B-scanner is reported in part (II) seperately.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2022년도 봄 학술논문 발표대회
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• pp.87-88
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• 2022

For an earthquake-safe urban environment, the Republic of Korea conducts seismic performance evaluation in accordance with laws and guidelines to assign safety ratings and implement necessary management measures such as repairs and reinforcements. In the seismic performance evaluation result, structures lacking in preparation for earthquakes are prioritized and classified into measures such as repair, reinforcement, or careful observation to respond to physical risks such as earthquakes. Such repair and reinforcement work is not a one-time thing, but it is necessary to further enhance the effect through continuous follow-up observation. In this study, the location of the vertical and horizontal displacement measuring part of the construction part is displayed so that the post-construction status of the reinforcement construction part can be visually checked by identifying the problems in the process of post-monitoring in 2022 for the maintenance and reinforcement work of local governments' public facilities carried out in 2021. We propose a plan to institutionalize the installation of, inspection tools, and crack gauges at certain locations in the construction department, and to have facility managers periodically inspect and manage them with a smartphone program or the 'Facility Autonomous Safety Inspection' app.

• 대한기계학회논문집B
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• 제20권10호
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• pp.3361-3370
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• 1996

Micro-Macro approach is conducted for the mixture solidification to handle the closely linked phenomena of microscopic solute redistribution and macroscopic solidification behavior. For this purpose, present work combines the efficiency of mixture theory for macro part and the capability of microscopic analysis of two-phase model for micro part. The micro part of present study is verified by comparison with experiment of Al-4.9 mass% Cu alloy. The effect of back diffusion on the macroscopic variables such as temperature and liquid concentration, is appreciable. The effect, however, is considerable on the mixture concentration and eutectic fraction which are indices of macro and micro segregation, respectively. According to the diffusion time, the behavior near the cooling wall where relatively rapid solidification permits short solutal diffusion time, approaches Scheil equation limit and inner part approaches lever rule limit.

• Journal of Power Electronics
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• 제15권4호
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• pp.1139-1147
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• 2015

In this paper, an algorithm based on a model analysis of the online calculation of the root-mean-square (RMS) value of welding current for single-phase AC resistance spot welding (RSW) was developed. The current is highly nonlinear and typically non-sinusoidal, which makes the measuring and controlling actions difficult. Though some previous methods focused on this issue, they were so complex that they could not be effectively used in general cases. The electrical model of a single-phase AC RSW was analyzed, and then an algorithm for online calculation of the RMS value of the welding current was presented. The description includes two parts, a model-dependent part and a model-independent part. Using a previous work about online measurement of the power factor angle, the first part can be solved. For the second part, although the solution of the governing equation can be directly obtained, a lot of CPU time must be consumed due to the fact that it involves a lot of complex calculations. Therefore, a neural network was employed to simplify the calculations. Finally, experimental results and a corresponding analysis showed that the proposed algorithm can obtain the RMS values with a high precision while consuming less time when compared to directly solving the equations.

• Nuclear Engineering and Technology
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• 제53권4호
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• pp.1088-1099
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• 2021

Time-frequency analysis technique is an effective analysis tool for non-stationary processes. In the field of reactor neutron noise, the time-frequency analysis method has not been thoroughly researched and widely used. This work has studied the time-frequency analysis of the reactor neutron noise experimental signals under bubble disturbance and control rod vibration. First, an experimental platform was established, and it could be employed to reactor neutron noise experiment and data acquisition. Secondly, two types of reactor neutron noise experiments were performed, and valid experimental data was obtained. Finally, time-frequency analysis was conducted on the experimental data, and effective analysis results were obtained in the low-frequency part. Through this work, it can be concluded that the time-frequency analysis technique can effectively investigate the core dynamics behavior and deepen the identification of the unstable core process.

• 산경연구논집
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• 제13권7호
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• pp.37-45
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• 2022

Purpose: Leisure time is an intrinsic part of the work-life balance that enables people to rejuvenate their energy and provides a platform to maintain their health while sustaining their productivity levels. The purpose of this study is to investigate the effects of changes in leisure consumption culture on the modern economy through various research materials. Research design, data and methodology: To have completeness in published systematic reviews and meta-analyses, the use of the standard Preferred Reporting Items for Systematic Reviews and Meta-Analyses checklist is essential and the present research selected this research design. Results: This research figured out that individuals who spend most of their leisure time watching TV have been shown to experience lesser satisfaction in their job designation and less happiness overall and also found that Leukocyte Telomere Length is influenced by the type of leisure an individual engages in. Conclusions: Overall, this research points out that the income effect may provide an inverse relationship between work time and labor in that high income from labor makes an individual less inclined to work to make the same money they made before the increased benefits. It is a narrative that may need further research in finding the principles that govern leisure in the labor force.