• Journal of the Microelectronics and Packaging Society
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• v.30 no.3
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• pp.111-118
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• 2023

MXene, a two-dimensional transition metal carbide or nitride, has recently attracted much attention as a lightweight and flexible electromagnetic shielding material due to its high electrical conductivity, good mechanical strength and thermal stability. In particular, the Ti-based MXene, Ti₃C₂T_x and Ti₂CT_x are reported to have the best electrical conductivity and electromagnetic shielding properties in the vast MXene family. Therefore, in this study, Ti₃C₂T_x and Ti₂CT_x films were prepared by vacuum filtration using Ti₃C₂T_x and Ti₂CT_x dispersions synthesized by interlayer metal etching and centrifugation of Ti₃AlC₂ and Ti₂AlC. The electrical conductivity and electromagnetic shielding efficiency of the films were measured after heat treatment at high temperature. Then, X-ray diffraction and photoelectron spectroscopy were performed to analyze the structural changes of Ti₃C₂T_x and Ti₂CT_x films after heat treatment and their effects on electromagnetic shielding. Based on the results of this study, we propose an optimal structure for an ultra-thin, lightweight, and high performance MXene-based electromagnetic shielding film for future applications in small and wearable electronics.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.23 no.2
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• pp.173-188
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• 2024

With the advancement of autonomous vehicle (AV) technology, autonomous driving on real roads has become feasible. However, there are challenges in achieving complete autonomy due to perceptual blind areas, which occur when the AV's sensory range or capabilities are limited or impaired by surrounding objects or environmental factors. This study aims to analyze AV accident patterns and safety issues of perceptual blind area that may occur in urban areas, with the goal of developing test scenarios for Level 4+ autonomous driving. It utilized AV accident data from the California Department of Motor Vehicles (DMV) to compare accident patterns and characteristics between AVs and conventional vehicles based on activation status of autonomous mode. It also categorized AV disengagement data to identify types and real-world cases of disengagements caused by perceptual blind areas. The analysis revealed that AVs exhibit different accident types due to their safe driving maneuvers, and three types of perceptual blind area scenarios were identified. The findings of this study serve as crucial foundational data for developing Level 4+ autonomous driving test scenarios, enabling the design of efficient strategies to mitigate perceptual blind areas in various scenarios. This, in turn, is expected to contribute to the effective evaluation and enhancement of AV driving safety on real roads.

• KIPS Transactions on Software and Data Engineering
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• v.13 no.1
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• pp.1-16
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• 2024

Over recent years, 6 Sigma has become a key methodology in manufacturing for quality improvement and cost reduction. However, challenges have arisen due to the difficulty in analyzing large-scale data generated by smart factories and its traditional, formal application. To address these limitations, a big data-based 6 Sigma approach has been developed, integrating the strengths of 6 Sigma and big data analysis, including statistical verification, mathematical optimization, interpretability, and machine learning. Despite its potential, the practical impact of this big data-based 6 Sigma on manufacturing processes and management performance has not been adequately verified, leading to its limited reliability and underutilization in practice. This study investigates the efficiency impact of DX SS, a big data-based 6 Sigma, on manufacturing processes, and identifies key success policies for its effective introduction and implementation in enterprises. The study highlights the importance of involving all executives and employees and researching key success policies, as demonstrated by cases where methodology implementation failed due to incorrect policies. This research aims to assist manufacturing companies in achieving successful outcomes by actively adopting and utilizing the methodologies presented.

• Journal of the Korean Geotechnical Society
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• v.40 no.1
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• pp.5-14
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• 2024

PHC piles demonstrate superior resistance to compression and bending moments, and their factory-based production enhances quality assurance and management processes. Despite these advantages that have resulted in widespread use in civil engineering and construction projects, the design process frequently relies on empirical formulas or N-values to estimate the soil-pile friction, which is crucial for bearing capacity, and this reliance underscores a significant lack of experimental validation. In addition, environmental factors, e.g., the pH levels in groundwater and the effects of seawater, are commonly not considered. Thus, this study investigates the influence of vibrating machine foundations on PHC pile models in consideration of the effects of varying pH conditions. Concrete model piles were subjected to a one-month conditioning period in different pH environments (acidic, neutral, and alkaline) and under the influence of seawater. Subsequent repeated direct shear tests were performed on the pile-soil interface, and the disturbed state concept was employed to derive parameters that effectively quantify the dynamic behavior of this interface. The results revealed a descending order of shear stress in neutral, acidic, and alkaline conditions, with the pH-influenced samples exhibiting a more pronounced reduction in shear stress than those affected by seawater.

• Journal of the Korea Institute of Construction Safety
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• v.6 no.1
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• pp.7-11
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• 2024

Pump car is an equipment that transports concrete products as needed to the place where they are poured. In order to pour a large amount of concrete in a short period of time, using a pump car is the most efficient in terms of economic efficiency and quality control. However, recently, many casualties have occurred due to boom damage during concrete pouring, so this study suggests that improvements are needed in the equipment manufacturing stage, inspection standards for old equipment, and equipment rental system. The reason is that, as a result of the finite element analysis of the pump car, the significant stress acting at the second stage of the boom and the maximum stress at the top of the boom were found to be 895.39 MPa, and M.S. Since it was evaluated the lowest at 0.04, the need for reinforcement was recognized. And it was confirmed that the 2nd stage boom was the most stressful and vulnerable part of the 1st to 5th stage booms. Therefore, it is necessary to increase the thickness and rigidity of members at the design and manufacturing stage, and to reinforce the steel plates of currently used equipment. In addition, it is urgent to establish a system that makes non-destructive testing mandatory for all general construction machinery and holds inspection agencies responsible for missing boom defects during non-destructive testing and regular inspections.

• Information Systems Review
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• v.22 no.4
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• pp.185-203
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• 2020

With the advent of 4th industrial revolution, the manufacturing industry is converging with ICT and changing into the era of smart manufacturing. In the smart factory, all machines and facilities are connected based on ICT, and thus security should be further strengthened as it is exposed to complex security threats that were not previously recognized. To reduce the risk of security incidents and successfully implement smart factories, it is necessary to identify key security factors to be applied, taking into account the characteristics of the industrial environment of smart factories utilizing ICT. In this study, we propose a 'hierarchical classification model of security factors in smart factory' that includes terminal, network, platform/service categories and analyze the importance of security factors to be applied when developing smart factories. We conducted an assessment of importance of security factors to the groups of smart factories and security experts. In this study, the relative importance of security factors of smart factory was derived by using AHP technique, and the priority among the security factors is presented. Based on the results of this research, it contributes to building the smart factory more securely and establishing information security required in the era of smart manufacturing.

• Composites Research
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• v.37 no.3
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• pp.238-245
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• 2024

In this study, as part of the development of a monitoring system for the efficient maintenance of steel pipes, an experimental study was conducted to evaluate the performance of steel pipes treated with modified polyethylene coating. In the case of the conventional mechanical pre-coating method, there was a deterioration in polyethylene adhesion during expansion testing, which led to the application of a chemical pre-treatment process using a calcium-mixed phosphate zinc film to resolve this issue. SEM and EDX analyses showed that the densest structure was observed at a Zn/Ca ratio of 1.0, and improved heat resistance compared to the conventional method was confirmed. Additionally, to prevent coating detachment during expansion, an evaluation of adhesion and elongation was conducted on steel pipes with modified polyethylene coating, incorporating materials such as elastomers based on maleic anhydride grafting, metal oxides, blocking agents, and slip agents. Experimental results showed that the specimen (S4) containing all modified materials exhibited more than a 25% performance improvement compared to the specimen (S2) containing only metal oxides. Lastly, the development and performance evaluation of wedge-shaped socketing and pressing wheels, which are part of the pipe fixing accessories, were conducted to prevent surface coating damage on the completed pipes.

• Journal of Navigation and Port Research
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• v.48 no.4
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• pp.274-283
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• 2024

Climate change is currently one of the most pressing environmental issues, primarily caused by carbon emissions from fossil fuel usage. As a result, alternative fuels that effectively reduce carbon emissions are garnering more attention. Among these alternatives, hydrogen has numerous advantages, such as its ability for large-scale storage and transport. However, it is crucial to prioritize safety measures, particularly in facilities that handle hydrogen, due to its highly flammable and fast-spreading nature. This study aims to compare and analyze the placement of supply and exhaust vents to efficiently release hydrogen in the event of a leak in an enclosed space. The experiments involved six different scenarios, each with various combinations of supply and exhaust vents. To ensure the experimental process's safety, helium, which shares similar physical properties with hydrogen, was used to analyze the internal oxygen concentration during ventilation system operations. The results revealed that among the six scenarios, Case 2, which employed a lower side supply vent and an upper side exhaust vent, exhibited the shortest ventilation time of 4 minutes and 30 seconds. Additionally, the decrease rate in oxygen concentration was examined in the upper, middle, and lower areas. Ventilation utilizing an upper surface supply vent and two exhaust vents on the upper surface and upper side (Case 6), showed lower oxygen concentration values in the upper area, while Case 2 yielded lower values in the middle and lower areas. Therefore, it is crucial to select an appropriate supply and exhaust vent configuration considering the space's characteristics and usage environment.

• Journal of Food Hygiene and Safety
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• v.23 no.2
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• pp.98-107
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• 2008

The ozone has the oxidizing power which is powerful the fluorine and the antimicrobial spectrum of wide scope. Researches were carried out to use the merits that ozone has in various fields including the food industry, and many studies are also conducted nowadays for more efficient use of ozone. The ozone was permitted legally as a food additive and was practically used in the United States, Australia, Japanese etc. In November 2007, ozone water was permitted as a food additive in Korea and the interest in the use of ozone water has been on the rise in the Korea's food industry. As a olisinfectant method, ozone has many advantages. The maintenance and management expenses of ozone are lower than the installation cost at early stages and no by-products are generated after use it compared to others. Recently the demand of ozone as a olisinfectant method is increasing drastically. Although ozone water is popularly used to sterilize raw foods like fruits, vegetables and meats, the cases are still limited and were verified by the survey results. However, the use of ozone water is gradually being increased and is focused on food services. Ozone water refers to a state where ozone is dissolved into water to more conveniently use ozone. Accordingly, ozone water should be managed in regards with the amount and time of water-dissolved ozone, and the control of discharged ozone concentration is required for safe use of ozone water. The items to control mentioned above are directly related to the performance of the devices, and therefore, it is required to newly establish the performance criteria of ozone water manufacturing devices.

• Journal of Biosystems Engineering
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• v.7 no.2
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• pp.18-29
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• 1983

A low cost and versatile data acquisition system for the field and laboratory use was developed by using a single board microcomputer. Data acquisition system based on a Z80 microprocessor was built, tested and modified to obtain the present functional system. The microcomputer developed consists of 6 kB ROM, 5 kB RAM, 6-seven segment LED display, 16-Hex. key and 8 command key board. And it interfaces with an 8 channel, 12 bits A/D converter, a microprinter, EPROM programmer for 2716, and RS232C interface to transfer data between the system and HP3000 mini-computer manufactured by Hewlett Packard Co., A software package was also developed, tested, and modified for the system. This package included drivers for the AID converter, LED display, key board, microprinter, EPROM programmer, and RS232c interface. All of these programs were written in 280 assembler language and converted to machine codes using a cross assembler by HP3000 computer to the system during modifying stage by data transferring unit of this system, then the machine language wrote to the EPROM by this EPROM programmer. The results are summarized as follows: 1. Measuring program developed was able to control the measuring intervals, No. of channels used, and No. of data, where the maximum measuring speed was 58.8 microsec. 2. Calibration of the system was performed with triangle wave generated by a function generator. The results of calibration agreed well to the test results. 3. The measured data was able to be written into EPROM, then the EPROM data was compared with original data. It took only 75 sec. for the developed program to write the data of 2 kB the EPROM. 4. For the slow speed measurements, microprinter instead of EPROM programmer proved to be useful. It took about 15 min. for microprinter to write the data of 2 kB. 5. Modified data transferring unit was very effective in communicating between the system and HP3000 computer. The required time for data transferring was only 1~2 min. 6. By using DC/DC converting devices such as 78-series, 79-series. and TL497 IC, this system was modified to convert the only one input power sources to the various powers. The available power sources of the system was DC 7~25 V and 1.8 A.