• International Journal of Computer Science & Network Security
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• v.21 no.6
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• pp.23-28
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• 2021

The article discusses the features of adaptation of the parameters of the physical layer of data transmission in self-organizing networks based on unmanned aerial vehicles operating in the conditions of "smart cities". The concept of cities of this type is defined, the historical path of formation, the current state and prospects for further development in the aspect of transition to "smart cities" of the third generation are shown. Cities of this type are aimed at providing more comfortable and safe living conditions for citizens and autonomous automated work of all components of the urban economy. The perspective of the development of urban mobile automated technical means of infocommunications is shown, one of the leading directions of which is the creation and active use of wireless self-organizing networks based on unmanned aerial vehicles. The advantages of using small-sized unmanned aerial vehicles for organizing networks of this type are considered, as well as the range of tasks to be solved in the conditions of modern "smart cities". It is shown that for the transition to self-organizing networks in the conditions of "smart cities" of the third generation, it is necessary to ensure the adaptation of various levels of OSI network models to dynamically changing operating conditions, which is especially important for the physical layer. To maintain an acceptable level of the value of the bit error probability when transmitting command and telemetry data, it is proposed to adaptively change the coding rate depending on the signal-to-noise ratio at the receiver input (or on the number of channel decoder errors), and when transmitting payload data, it is also proposed to adaptively change the coding rate together with the choice of modulation methods that differ in energy and spectral efficiency. As options for the practical implementation of these solutions, it is proposed to use an approach based on the principles of neuro-fuzzy control, for which examples of determining the boundaries of theoretically achievable efficiency are given.

• Sleep Medicine and Psychophysiology
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• v.28 no.1
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• pp.34-42
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• 2021

Objectives: This study investigated sleep quality in female full-time homemakers and evaluated the relationship of sleep disturbance with psychological and socio-environmental factors. Methods: This cross-sectional study adopted a structured survey and sequential recruitment method for randomized participation of community-dwelling full-time female homemakers. Sleep quality and mental health were measured using the Korean version of the Pittsburgh Sleep Quality Index (K-PSQI), Korean version of the Beck Depression Inventory-II (K-BDI-II), Korean version of the Beck Anxiety Inventory (K-BAI), and Korean version of the Beck Hopelessness Scale (K-BHS). The willingness-to-pay (WTP) method was selected to measure the self-evaluated monetary value of household service work. The relationship among the main relevant factors was statistically analyzed through a mediation model. Results: A total of 166 participants were analyzed and classified having poor versus good sleep quality (poor : 24.1%, n = 40 ; good : 75.9%, n = 126 ; cut-off point = 9 on the K-PSQI). Significant between-group differences were observed in mental health status (K-BDI-II, p < 0.001 ; K-BAI, p < 0.001 ; K-BHS, p = 0.003). The moderated mediation model was verified, indicating that depression may mediate the association between nurturing burden and sleep disturbance. The path from nurturing burden to depression may be moderated by average monthly household income. Conclusion: A relatively high portion of full-time female homemakers may suffer from sleep disturbance and interactions between psychological and socio-environmental factors might determine sleep quality, suggesting the need for public health policies targeting improvement of sleep quality and mental health among full-time homemakers.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.3
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• pp.377-383
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• 2021

Recently, in accordance with the 4th industrial revolution, The use of autonomous mobile robots for flexible logistics transfer is increasing in factories, the warehouses and the service areas, etc. In large factories, many manual work is required to use Simultaneous Localization and Mapping(SLAM), so the need for the improved mobile robot autonomous driving is emerging. Accordingly, in this paper, an algorithm for mapless navigation that travels in an optimal path avoiding fixed or moving obstacles is proposed. For mapless navigation, the robot is trained to avoid fixed or moving obstacles through Deep Q Network (DQN) and accuracy 90% and 93% are obtained for two types of obstacle avoidance, respectively. In addition, DQN requires a lot of learning time to meet the required performance before use. To shorten this, the target size change algorithm is proposed and confirmed the reduced learning time and performance of obstacle avoidance through simulation.

• The Journal of the Korea Contents Association
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• v.21 no.5
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• pp.129-138
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• 2021

Today we are getting a lot of information and various activities on our website through the internet. These websites are maintained by individuals or by website specialists. The basic method is to change the files that make up the running website. Changing the entire file in this process takes a long time and changes the files that do not need to be changed, so the efficiency is greatly reduced. When only the files that need to be changed are changed, it takes a lot of effort as a person must manually search each path to check the files and change the files one by one. To solve this problem, automatic distribution systems were developed. Additional resources and learning are required, resulting in additional cost, time and labor. Therefore, in this paper, we propose an automatic update system to minimize resource consumption by using the resources and technologies of the existing website. The proposed system does not require learning new skills. This aims to improve reliability and reduce time compared to human work.

• Explosives and Blasting
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• v.39 no.4
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• pp.1-11
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• 2021

In this study, the vibration data were obtained to analyze the vibration generated during dismantling of slab using the mechanical dismantling method. The obtained vibration data were classified according to the attachment device and then the waveform and dominant frequency analysis were performed. And the correlation was analyzed by the different methods of measuring the distance between the work section and the measurement point. As a result of the waveform analysis for each attachment device, there was little change in the phase of the vibration waveform and only the change in amplitude, which is the magnitude of the vibration velocity. And as a result of frequency analysis, the frequency band was lower when using a crusher method than a braker method and frequency band were close of the natural frequency of the structure to be dismantled. As a result of the correlation analysis, the separation distance was estimated a higher correlation when evaluated as the path through which the vibration propagates along the structure frame than the straight distance between the measurement point and the working section.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.5
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• pp.18-26
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• 2021

In this work, we have developed a 1D network model aimed at predicting eigenvalues for resonance frequency analysis in a lab-scale industrial gas turbine single nozzle combustion system. Modern industrial gas turbines generally adopt combustors with very complex geometry and flow path to meet various design requirements simultaneously. The current study has developed a network model for combustion systems with backflow at the same axial location. The modeling results of resonance frequencies and mode distributions for a given system using the network model were validated from comparisons with prediction results using a 3D Helmholtz solver.

• Journal of the Korea Convergence Society
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• v.13 no.4
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• pp.421-432
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• 2022

The purpose of this study was to analyze whether there are country differences in the intention to use Welfare Technology among older adults. Based on Technology Acceptance Model and Structural Equation Model, we surveyed total 334 older adults aged 65 and over living in Korea and the U.S. and analyzed the path differences between the perceived ease of use, perceived usefulness, attitude toward use, and intention to use of Welfare Technology between two countries. Results showed that the effect of 'perceived usefulness' on 'attitude toward use' was the highest in Korea at 0.74 (p<0.001), and 'Perceived ease of use' in 'Perceived Usefulness' in the United States at 0.75(p<0.001), with the differences being statistically significant. Findings indicate that 'Long-term Orientation' may explain the differences between the two countries. Practical and policy implications are presented in conclusion.

• Safety and Health at Work
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• v.13 no.1
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• pp.40-50
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• 2022

Background: Underground mines have several hazards that could lead to serious consequences if they come into effect. Acquiring, evaluating, and using the real-time data from the atmospheric monitoring system and miner's positional information is crucial in deciding the best course of action. Methods: A graphical user interface-based software is developed that uses an AutoCAD-based mine map, real-time atmospheric monitoring system, and miners' positional information to guide on the shortest route to mine exit and other locations within the mine, including the refuge chamber. Several algorithms are implemented to enhance the visualization of the program and guide the miners through the shortest routes. The information relayed by the sensors and communicated by other personnel are collected, evaluated, and used by the program in proposing the best course of action. Results: The program was evaluated using two case studies involving rescue relating to elevated carbon monoxide levels and increased temperature simulating fire scenarios. The program proposed the shortest path from the miner's current location to the exit of the mine, nearest refuge chamber, and the phone location. The real-time sensor information relayed by all the sensors was collected in a comma-separated value file. Conclusion: This program presents an important tool that aggregates information relayed by sensors to propose the best rescue strategy. The visualization capability of the program allows the operator to observe all the information on a screen and monitor the rescue in real time. This program permits the incorporation of additional sensors and algorithms to further customize the tool.

• Nuclear Engineering and Technology
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• v.54 no.4
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• pp.1421-1430
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• 2022

The computation of the solid angle and the detector efficiency is considering to be one of the most important factors during the measuring process for the radioactivity, especially the cylindrical γ-ray NaI(Tl) detectors nowadays have applications in several fields such as industry, hazardous for health, the gamma-ray radiation detectors grow to be the main essential instruments in radiation protection sector. In the present work, a generic numerical simulation method (NSM) for calculating the efficiency of the γ-ray spectrometry setup is established. The formulas are suitable for any type of source-to-detector shape and can be valuable to determine the full-energy peak and the total efficiencies and P/T ratio of cylindrical γ-ray NaI(Tl) detector setup concerning the truncated conical radioactive source. This methodology is based on estimate the path length of γ-ray radiation inside the detector active medium, inside the source itself, and the self-attenuation correction factors, which typically use to correct the sample attenuation of the original geometry source. The calculations can be completed in general by using extra reasonable and complicate analytical and numerical techniques than the standard models; especially the effective solid angle, and the detector efficiency have to be calculated in case of the truncated conical radioactive source studied condition. Moreover, the (NSM) can be used for the straight calculations of the γ-ray detector efficiency after the computation of improvement that need in the case of γ-γ coincidence summing (CS). The (NSM) confirmation of the development created by the efficiency transfer method has been achieved by comparing the results of the measuring truncated conical radioactive source with certified nuclide activities with the γ-ray NaI(Tl) detector, and a good agreement was obtained after corrections of (CS). The methodology can be unlimited to find the theoretical efficiencies and modifications equivalent to any geometry by essential sufficiently the physical selective considered situation.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.4_2
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• pp.699-706
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• 2022

In this study, Directed energy deposition (DED) among additive manufacturing is applied to repair damaged spindle key parts of planner miller. The material of the spindle key is SCM415, and the P21 Powder is used. In order to find the optimal deposition conditions for DED equipment, a single-line deposition experiment is conducted to analysis five parameters. The laser power affects the width, and the height is a parameter affected by coaxial gas and powder gas. In addition, laser power, powder feed rate, coaxial gas, and powder gas are parameters that affect dilution. Otimal deposition is that 400 W of laser power, 4.0 g/min of powder feed rate, 6.5 L/min of coaxial gas, 3.0 L/min of powder gas and 4.5 L/min of shield gas. By setting the optimum conditions, a uniform deposition cross section in the form of an ellipse can be obtained. Damage recovery process of spindle key consists of 3D shape design of the base and deposition parts, deposition path creation and deposition process, and post-processing. The hardness of deposited area with P21 powder on the SCM415 spindle key is 336 HV for the surface of the deposition, 260 HV for the boundary area, and 165 HV for the base material.