• Journal of the Korean Society of Safety
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• v.35 no.5
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• pp.1-8
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• 2020

Mobile elevating work platforms (MEWPs) consist of a work platform, extending structure, and chassis, and are used to move persons to working positions. MEWPs are useful but are composed of pieces of equipment, and accidents do occur owing to equipment defects. Among these defects, accidents caused by the fracture of bolts fixed to the extension structure and swing system are increasing. This paper presents a failure analysis of the fixing bolts of MEWP. Standard procedure for failure analysis was employed in this investigation. Visual inspection, chemical analysis, tensile strength measurement, microstructural characterization, fractography analysis by Optical Microscope(OM) and Scanning Electron Microscopy(SEM), and finite element analysis (FEA) were used to analyze the failure of the fixing bolts. Using this failure analysis approach, we found the root cause of failure and proposed a means for solving this type of failure in the future. First, the chemical composition of the fixing bolt is obtained by a spectroscopy chemical analysis method, which determined that the chemical composition matched the required standard. The tensile test showed that the tensile and yield strengths were within the required capacity. The stress analysis was carried out at five different boom angles, and it was determined that the fixing bolt of MEWP can withstand the loads at all the boom angles. The outcomes of the fatigue analysis revealed that the fixing bolt fails before reaching the design requirements. The results of the fatigue analysis showed primarily that the failure of the fixing bolt was due to fatigue. A visual inspection of the fractured section of the fixing bolt also confirmed the fatigue failure. We propose a method to prevent failure of the fixing bolt of the MEWP from four different standpoints: the manufacturer, safety certification authority, safety inspection agency, and owner.

• Journal of the Korea Institute of Military Science and Technology
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• v.19 no.1
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• pp.35-42
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• 2016

Modern aircraft is facing the increase of power demands and thermal challenges. In accordance with the application of more electric technology and advanced mission requirement, aircraft system requires increase of power generation and it cause increase of internal heat generation. Simultaneously, restrictions have significantly been imposed to the thermal management system. Modern aircraft must maintain low radar observability and infra-red signature. In addition, new composite aircraft skins have reduced the amount of heat that can be rejected to the environment. The combination of these characteristics has increased the challenges faced by thermal management. In order to mitigate the thermal challenges, the concept of system level thermal management should be applied and new modeling and simulation tools need to be developed. To develop and utilize system level thermal management technology, three key points are considered. Firstly, the performance changes of subsystems and components must be assessed at an integrated thermal system. It is because that each subsystem and component interacts with other subsystems or components and it can directly effects on overall system performance. Secondly, system level thermal management requirements and solutions must be evaluated early in conceptual design process as vehicle and propulsion system configuration decisions are being made. Finally, new component level thermal management technologies must focus on reducing heat generation and increasing the availability of heat sinks.

• Journal of the Korea Institute of Military Science and Technology
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• v.20 no.4
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• pp.558-565
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• 2017

The vehicle-mounted mine detection system with large detection sensor modules can search wide areas with a fast detection speed. To mount the heavy mine detectors on a manned or unmanned vehicle, it is necessary to design the detector driving mechanism and control system based on the considerations driven from the characteristic analysis and the operation requirements of the detection system. Furthermore, while operating the mine detector mounted on a mobile vehicle, it is significant to keep the height from the ground to sensors within a certain distance in order to get a qualified detection performance. As the mine detection sensor, we used ground penetrating radar widely used to geotechnical exploration, mine detection and etc. In this paper, we introduce a driving mechanism through analyzing the characteristics of the vehicle-mounted mine detection system. We also suggest a method to automatically control the distance between the ground and GPR by utilizing the GPR output values, used to detect mines at the same time.

• Journal of KIISE:Software and Applications
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• v.32 no.2
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• pp.119-127
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• 2005

Product line analysis is an activity for analyzing requirements, their relationships, and constraints in a product line before engineering product line assets (e.g., architectures and components). A feature-oriented commonality and variability analysis (called feature modeling) has been considered an essential part of product line analysis. Commonality and variability analysis, although critical, is not sufficient to develop reusable and adaptable product line assets. Dependencies among features and feature binding time also have significant influences on the design of product line assets. In this paper. we propose a feature-oriented product line analysis model that extends the existing feature model in terms of three aspects (i.e., feature commonality and variability, feature dependency, and feature binding time). To validate the consistency among the three aspects we formally define the feature-oriented product line analysis model and provide rules for checking consistency.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.2
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• pp.632-637
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• 2014

In this paper the concept of the performance-based logistics (PBL) support for weapon systems is discussed and an enhancement is studied such that prior to the Operational phase, the development of the PBL can begin from the Engineering & Manufacturing Development (EMD) phase together with multiple performance indices considered. The genetic algorithm should be considered for the complex system to solve the maintenance policy optimization. In particular, the requirement of repair level analysis model is developed based on reflecting the PBL concept. To decide the maintenance policy prior to Operational phase in accordance with customer requirements, the PIDO(Process Integration and Design Optimization) technique useful in choosing the performance indices and changing the constraints was used. The genetic algorithm of PIDO tool, like PIAnO and ModelCenter, was verified that it could be applied to optimize the maintenance policy.

• The KIPS Transactions:PartA
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• v.8A no.4
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• pp.345-352
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• 2001

In this paper, a VoIP (Voice on Internet Protocol) terminal system, which can process voice in real time based on Linux, is designed and implemented. The hardware of it is designed using a i486 processor and a DSP codec chip which encodes and decodes voice data in real time. As an operating system, RTLinux, which is a real-time operating system based on Linux, is ported to manage real-time voice processing. The voice processing module of the system uses G.723.1 voice codec of ITU-T standard. It transfers voice data within 30ms to assure good voice quality. In order to satisfy the real time requirements and QoS (Quality-of-Service) for the voice data, the real-time voice processing device driver is designed and implemented. To verify the system, the chatting application program is developed and tested for QoS of the system.

• The KIPS Transactions:PartD
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• v.9D no.3
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• pp.511-522
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• 2002

WBI (Web-Based Instruction), a web-based tool for teaching the students at a long distance, makes possible to Interact between learners and instructors, provides a wide variety of learning materials, has an advantage of overcoming spatial constraints. In this paper, as a model of using the web for education, a web-based education-evaluation system has been designed and implemented. Web-based education-evaluation system has to be equipped with both of the online setting question mode and the upload setting question mode, the former makes questions on web and the latter uploads the setted questions on offline with settling a defeat of the existing systems on setting questions. And the system has to be equipped with the function of analyzing the questions that gives teacher several kinds of analysis information and makes possible to feedback to questions by adjusting the difficulty and revising the questions. In this paper, a system that reflects the above requirements has been designed and implemented with PHP script language and MySQL database system.

• Journal of Korean Society of Steel Construction
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• v.23 no.4
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• pp.515-522
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• 2011

The purpose of this study was to evaluate the material characteristics of SHN400 steel, which is suitable as a steel material for building structures, using the experimental approach. For this purpose, the chemical composition test, tensile test, macro test, micro test, and charpy notch impact test were conducted with specimens taken from the highest, thickest, and commonly used H-beams for girder or beam members. Each test was conducted under the Korean Standard(KS) test conditions. All the test results satisfied the requirements of KS (KS D 3866) and the steel material for seismic design. The carbon equivalent value (Ceq), which is related to weldability, and the yield ratio, which is related to inelastic behavior, showed especially good results. Thus, SHN400 is definitely suitable as the steel material for building structures.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.37-37
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• 2010

Silicate-silsesquioxane or siloxane-silsesquioxane hybrid thin films are strong candidates as matrix materials for ultra low dielectric constant (low-k) thin films. We synthesized the silicate-silsesquioxane hybrid resins from tetraethoxyorthosilicate (TEOS) and methyltrimethoxysilane (MTMS) through hydrolysis and condensation polymerization by changing their molar ratios ([TEOS]:[MTMS] = 7:3, 5:5, and 3:7), spin-coating on Si(100) wafers. In the case of [TEOS]:[MTMS] 7:3, the dielectric permittivity value of the resultant thin film was measured at 4.30, exceeding that of the thermal oxide (3.9). This high value was thought to be due to Si-OH groups inside the film and more extensive studies were performed in terms of electronic, ionic, and orientational polarizations using Debye equation. The relationship between the mechanical properties and the synthetic conditions of the silicate-silsesquioxane precursors was also investigated. The synthetic conditions of the low-k films have to be chosen to meet both the low orientational polarization and high mechanical properties requirements. In addition, we have investigated a new solution-based approach to the synthesis of semiconducting chalcogenide films for use in thin-film transistor (TFT) devices, in an attempt to develop a simple and robust solution process for the synthesis of inorganic semiconductors. Our material design strategy is to use a sol-gel reaction to carry out the deposition of a spin-coated CdS film, which can then be converted to a xerogel material. These devices were found to exhibit n-channel TFT characteristics with an excellent field-effect mobility (a saturation mobility of ${\sim}\;48\;cm^2V^{-1}s^{-1}$) and low voltage operation (< 5 V). These results show that these semiconducting thin film materials can be used in low-cost and high-performance printable electronics.

• Journal of Internet Computing and Services
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• v.11 no.1
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• pp.143-151
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• 2010

According to increasing requirements in embedded systems. embedded software has been more complicated then before. a optimum software is difficult in embedded system. software developer make a difficult optimum software. this paper suggests a software profiling tool with which a software developer can easily profiling the embedded system software in cross-development environments. the suggested tool is designed based on host/target architecture. this tool insert program source for make profiling log to target program. a target program executed in target system. a target system communicate profiling log to host system. this tool in host system analyze profiling log data. and make a XML of profiling log and a profiling report. a profiling report is graphic viewer based GUI. a target system in this tool needs a few computing power. and XSLT can conversion of profile log XML to other format data. and suggested tool based on eclipse plug-in, therefore developer can use operates in eclipse.