• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.6_spc
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• pp.697-704
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• 2016

The second shutdown drive mechanism (SSDM) that is classified into seismic category I as an active mechanical equipment shall maintain the structural integrity and its designed inherent safety functions during and/or after normal operation, anticipated operational occurrences, accidents and seismic occurrences. Therefore, not only a structural integrity assessment through numerical analyses but also a qualification test by using the prototype SSDM shall be conducted to verify the adequacy of the SSDM design. This paper describes a sort of seismic qualification test of the prototype SSDM to demonstrate that the structural integrity and operability (functionality) of SSDM are maintained during and/or after seismic excitations. From the results, this paper shows that the SSDM satisfies all design requirements without any malfunctions during and after the seismic test.

• Journal of Welding and Joining
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• v.1 no.2
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• pp.45-52
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• 1983

Many pressure vessels for the hot H$\sub$2//H$\sub$2/S service are made of 2+1/4Cr-1Mo steel with austenitic stainless steel overlay to combat agressive corrosion due to hydrogen sulfide. Hydrogen dissolves in to materials during operation, and sometimes gives rise to unfore-seeable damages. Appropriate precautions must, therefore, be taken to avoid the hydrogen induced damages in the design, fabrication and operation stage of such reactor vessels. Recently, hydrogeninduced cracking (or Disbonding) was found at the interface between base metal and stainless weld overlay of a desulfurizing reactor. Since the stainless steel overlay weld metal is subjected to thermal and internal-pressure loads in reactor operation, it is desirable for the overlay weld metal to have high strength and ductility from the stand point of structural safety. In section III of ASME Boiler and Pressure Vessel Code, Post-Weld Heat Treatment(PWHT) of more than one hour per inch at over 1100.deg. F(593.deg. C) is required for the weld joints of low alloy pressure vessel steels. This heat treatment to relieve stresses in the welded joint during construction of the pressure vessel is considered to cause sensitization of the overlay weld metal. The present study was carried out to make clear the diffusion of carbon migration by PWHT in dissimilar metal welded joint. The main conclusion reached from this study are as follows: 1) The theoretical analysis for diffusion of carbon in stainless steel overlay weld metal does not agree with Fick's 2nd law but the general law of molecular diffusion phenomenon by thermodynamic chemical potential. 2) In the stainless steel overlay welded joint, the PWHT at 720.deg. C for 10 hours causes a diffusion of carbon atoms from ferritic steel into austenitic steel according to the theoretical analysis for carbon migration and its experiment. 3) In case of PWHT at 720.deg. C for 10 hours, the micro-hardness of stainless steel weld metal in bonded zone increase very highly in the carburized layer with remarkable hardening than that of weld metal.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.7
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• pp.782-787
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• 2014

Due to the complicated steel structure and safety concern, it is very difficult to deploy wireless networks in power plants. This paper presents a hybrid network, named as $P^2HYMN$ (Power Plant HYbrid Maintenance Network), encompassing PLC (Power Line Communication), TLC (Telephone Line Communication), and Wireless LAN. The design goal of $P^2HYMN$ is to integrate multimedia data such as design drawings of control equipment, process data, and video image data for maintenance operation in electric power plants. A Multiplex Line Communication (MLC) device was designed and implemented to integrate PLC, TLC, and Wireless LAN into $P^2HYMN$. Performance test of $P^2HYMN$ has been conducted on a testbed under various conditions. The throughput of TLC was shown as 39 Mbps. Because the bandwidth requirement per camera is 8.5 Mbps on average, TLC is expected to support more thant four video camera at the same time.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.8 s.239
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• pp.1085-1092
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• 2005

The OHT(Over Head Transportation) Vehicle transports heavy products quickly and repeatedly at the industrial workplace. The belt in the OHT vehicle is used to support the weight of the OHT Cage. The fatigue of the belt is caused by the dynamic load during the operation time. Since the fatigue fracture of the belt affects the safety at the workplace, the correct prediction of the dynamic load is necessary to calculate the fatigue life of the belt on the design step. In this paper a computer aided analysis method is proposed for the belt in the early design stage using dynamic analysis, stress analysis, belt tensile test, belt fatigue test and fatigue lift prediction method. From the dynamic load time histories and the stress of the belt FE model, a dynamic stress time history is produced. Using linear damage law and cycle counting method, fatigue life cycle is calculated. The method developed in this paper is used to reduce the time and cost for designing the OHT belt in different environment and condition.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.8
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• pp.156-163
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• 2019

In this paper, we present the process of developing an automatic carrying and arming system for testing ammunition. When carrying out shooting tests at a domestic rifle range, most of the ammunition operations are carried out by human manpower The series of test processes, such as transporting, arming and firing of heavy munitions, is repeated by employing human. If the ammunition is loaded via manpower, then problems can occur such as loss of reliability of test results, musculoskeletal disorders of humans and also safety accidents can occur. To address these problems, an automated system was developed for the transport and operation of ammunition. This paper covers the design, manufacture and operation of the developed system. In addition, this study validated the effectiveness of the system as compared to the human operation. Our results show that the developed system can be easily adapted to testing ammunition at a domestic rifle range.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.2
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• pp.92-101
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• 2000

The objective of this paper is to design the controller for longitudinal vehicle following which makes the vehicle follow the lead vehicle and keeps a safety distance without human driver operation. This paper presents a sliding mode control algorithm for the ACC system. The controller is based on three sliding surfaces. Each surface plays an individual control-deviation control, throttle control and brake control. In addition to sliding mode control, we propose some additional schemes to enhance controller performance. The first one is a gear shift-down controller which makes tractive force increase with a change of gear ratio. The other is a predictive correction method which reduces slinky effect.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.33 no.2
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• pp.337-344
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• 2023

Modern OSs, including Linux, show high scalability by adopting a monolithic kernel design, but have weak security because they share all memory space. This study presents a kernel module that are isolated inside the kernel using WebAssembly. WebAssembly provides a high-performance virtual machine by defining a low-level instruction set while guaranteeing memory safety. In this paper, the WebAssembly execution environment is implemented inside the kernel, allowing developers to control the operation of kernel modules and achieving higher security.

• Aerospace Engineering and Technology
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• v.4 no.2
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• pp.163-170
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• 2005

According to the KSLV program of KARI, it is planed to develop various launch vehicle and satellite 10 years hereafter. Large-scale test facilities, such as ReTF and PTA-II, are needed to fulfill this launch vehicle/satellite development project. The authors intend to arrange and describe various indexes that are needed in test facility design, construction and operation process. This technical paper is describing model analysis of damage prediction of accident in KSLV Integrated Propulsion System Test Facility based on propellant storage quantity and layout. In addition, the result can be used to produce safer design of test facility.

• Korean Chemical Engineering Research
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• v.60 no.2
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• pp.223-228
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• 2022

In chemical processes, unintended faults can make serious accidents. To tackle them, proper fault diagnosis models should be designed to identify the root cause of faults. To design a fault diagnosis model, a process and its data should be analyzed. However, most previous researches in the field of fault diagnosis just handle the data set of benchmark processes simulated on commercial programs. It indicates that it is really hard to get fresh data sets on real processes. In this study, real faulty conditions of an industrial polystyrene process are tested. In this process, a runaway reaction occurred and this caused a large loss since operators were late aware of the occurrence of this accident. To design a proper fault diagnosis model, we analyzed this process and a real accident data set. At first, a mode classification model based on support vector machine (SVM) was trained and principal component analysis (PCA) model for each mode was constructed under normal operation conditions. The results show that a proposed model can quickly diagnose the occurrence of a fault and they indicate that this model is able to reduce the potential loss.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.9
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• pp.3882-3888
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• 2012

In order to operate trains both mainline railroad platform and metropolitan subway line platform, it is necessary to develop the doorstep equipment of the rolling stock regardless of low(500mm, mainline) and high level platforms(1,135mm, metropolitan subway line) because of the requisite door safety system. In this study, two different types of platforms were examined. On closer examination, it seems that the conceptual design is suitable for telescopic sliding type doorstep equipment to minimize damage to the carbody underframe of railway vehicles and can also minimize the variation of the distance between the railway platform. Furthermore, the operation process and control flowchart of doorstep equipments by stages are proposed by various performance requirements.