• Nuclear Engineering and Technology
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• v.43 no.2
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• pp.187-194
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• 2011

Korea Nuclear Fuel is developing the X-GEN fuel which shows high performance and robust reliability for the worldwide supply. However, the simplified code systems such as CESEC-III which were developed in 1970s are still used in the current Non-LOCA safety analysis of OPR1000 and APR1400 plants. Therefore, it is essential to secure an advanced safety analysis methodology to make the best use of the merits of X-GEN fuel. To accomplish this purpose, the $\b{i}$ntegrated $\b{s}$afety $\b{a}$nalysis $\b{m}$ethodology (iSAM), is developed by selecting the best-estimate thermal-hydraulic code RETRAN. iSAM possesses remarkable advantages, such as generality, integrity, and designer-friendly features. That is, iSAM can be applied to both OPR1000 and APR1400 plants and uses only one computer code, RETRAN, in the whole scope of the non-LOCA safety analyses. Also the iSAM adopts the unique and automatic initialization and run tool, $\b{a}$utomatic $\b{s}$teady-$\b{s}$tate $\b{i}$nitialization and $\b{s}$afety analysis too l (ASSIST), to enable unhandy designers to use the new design code RETRAN without difficulty. In this paper, a brief overview of the iSAM is given, and the results of applying the iSAM to typical non-LOCA transients being checked during the reload design are reported. The typical non-LOCA transients selected are the single control element assembly withdrawal (SCEAW) accident, the asymmetric steam generator transients (ASGT), the locked rotor (LR) accident, and bank CEA withdrawal (BCEAW) event. Comparison to current licensing results shows a close resemblance; thus, it reveals that the iSAM can be applied to the non-LOCA safety analysis of OPR1000 and APR1400 plants.

• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.4
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• pp.403-413
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• 2007

As rock bolts become one of the main support systems in tunnels and underground structures, the integrity of the rock bolts affects the safety of these types of structures. The purpose of this study is the evaluation of rock bolt integrity using Fourier and wavelet transforms of the guided ultrasonic waves. After five rock bolt specimens with various defect ratios are embedded into a large scale concrete block, guided waves are generated by a PZT (lead zirconate titanate) element and measured by an acoustic emission (AE) sensor. The captured signals are analyzed in the frequency domain using the Fourier transform, and in the time-frequency domain using the wavelet transform based on a Gabor wavelet. The spectrum obtained from the Fourier transform shows that a portion of high frequency contents increases with increase in the defect ratio. Peak values in the time-frequency domain represent the interval of travel time of each echo. The energy velocities of the guided waves increase with the defect ratio. This study shows that the spectrum ratio and the energy velocity may be indicators fur the evaluation of rock bolt integrity.

• Journal of Korean Tunnelling and Underground Space Association
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• v.10 no.3
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• pp.221-232
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• 2008

Rock bolts have been installed into rockmass as a main support system. In order to evaluate the rock bolt integrity using non-destructive technique, the transmission method of the guided ultrasonic wave has been successfully performed. For the transmission method, however, the source for the generation o# guided ultrasonic waves should be installed at the end of the steel bar during construction of the rock bolt in the field. The purpose of this study is to suggest a reflection method that the source and the receiver are installed on the head of the steel bar. The reflection method is compared with the transmission method using non-embedded rock bolts and rock bolts embedded in concrete block. In this experiment, the piezo disc element is used as the source and the AE sensor is used as the receiver. The wavelet transform is applied to determine the energy velocity. The experimental studies show that the reflection method produces almost identical value of the transmission method, and the energy velocity increases with the defect ratio. This study suggests that the reflection method of the guided ultrasonic wave may be a suitable method fur the rock bolt integrity evaluation in the field.

• Aerospace Engineering and Technology
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• v.6 no.1
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• pp.230-236
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• 2007

The quality control of composite structure includes inspection, testing and monitoring in all processes from receiving inspection to part fabrication. The purpose of these activities is to ensure that the design objectives are consistently achieved. The quality factors include material, receiving inspection, storage and shelf-life control, environmental control, testing, inspection and record control. This paper presents the process verification method using destructive test and quality control method in composite structure of aircraft. And it is believed that the destructive test will be basis to obtain a reliability of non-destructive test in complex composite structure and to ensure the design requirements in composite part.

• Structural Engineering and Mechanics
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• v.47 no.2
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• pp.227-245
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• 2013

The term "constructability" in regard to cast-in-place concrete construction refers mainly to the ease of reinforcing steel placement. Bar congestion complicates steel placement, hinders concrete placement and as a result leads to improper consolidation of concrete around bars affecting the integrity of the structure. In this paper, a multi-objective approach, based on the non-dominated sorting genetic algorithm (NSGA-II) is developed for optimal design of reinforced concrete cantilever retaining walls, considering minimization of the economic cost and reinforcing bar congestion as the objective functions. The structural model to be optimized involves 35 design variables, which define the geometry, the type of concrete grades, and the reinforcement used. The seismic response of the retaining walls is investigated using the well-known Mononobe-Okabe analysis method to define the dynamic lateral earth pressure. The results obtained from numerical application of the proposed framework demonstrate its capabilities in solving the present multi-objective optimization problem.

• Journal of information and communication convergence engineering
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• v.6 no.2
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• pp.122-128
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• 2008

Multiprocessor architectures and platforms, such as, a multiprocessor system on chip (MPSoC) recently introduced to extend the applicability of the Moore's law, depend upon concurrency and synchronization in both software and hardware to enhance design productivity and system performance. With the rapidly approaching billion transistors era, some of the main problem in deep sub-micron technologies characterized by gate lengths in the range of 60-90 nm will arise from non scalable wire delays, errors in signal integrity and non-synchronized communication. These problems may be addressed by the use of Network on Chip (NOC) architecture for future System-on-Chip (SoC). We have modeled a concurrent architecture for a customizable and scalable NOC in a system level modeling environment using MLDesigner (from MLD Inc.). Varying network loads under various traffic scenarios were applied to obtain realistic performance metrics. We provide the simulation results for latency as a function of the buffer size. We have abstracted the area results for NOC components from its FPGA implementation. Modeled NOC architecture supports three different levels of quality-of-service (QoS).

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.668-674
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• 2002

Structural integrity assessment is indispensable for preventing catastrophic failure of industrial structures/components/facilities. This diagnosis of operating components should be done periodically for safe maintenance and economical repair. However, conventional standard methods for mechanical properties have the problems of bulky specimen, destructive and complex procedure of specimen sampling. Especially, the mechanical properties at welded zone including weldment and heat affected zone could not be evaluated individually due to their size requirement problem. So, an advanced indentation technique has been developed as a potential method for non-destructive testing of in-field structures. This technique measures indentation load-depth curve during indentation and analyzes the mechanical properties related to deformation such as yield strength, tensile strength and work-hardening index. Also indentation technique can evaluate a residual stress based on the concept that indentation load-depth curves were shifted with the direction and the magnitude of residual stress applied to materials. In this study, we characterized the tensile properties and welding residual stress of various industrial facilities through the new techniques, and the results are introduced and discussed.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.12
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• pp.6092-6115
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• 2017

This paper demonstrates a case for an end-to-end pure Application Security Layer for reliable and confidential communications within an Internet of Things (IoT) constrained environment. To provide a secure key exchange and to setup a secure data connection, Transport Layer Security (TLS) is used, which provides native protection against replay attacks. TLS along with digital signature can be used to achieve non-repudiation within app-to-app communications. This paper studies the use of TLS over the JavaScript Object Notation (JSON) via a The Constrained Application Protocol (CoAP) RESTful service to verify the hypothesis that in this way one can provide end-to-end communication flexibility and potentially retain identity information for repudiation. As a proof of concept, a prototype has been developed to simulate an IoT software client with the capability of hosting a CoAP RESTful service. The prototype studies data requests via a network client establishing a TLS over JSON session using a hosted CoAP RESTful service. To prove reputability and integrity of TLS JSON messages, JSON messages was intercepted and verified against simulated MITM attacks. The experimental results confirm that TLS over JSON works as hypothesised.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2001.04a
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• pp.91-94
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• 2001

A structural test of the wind turbine rotor blade must be required to evaluate the uncertainty in design assessment due to use of material, design concepts, production processes and so on, and the possible impact on the structural integrity. In the full-scale static strength test, the measuring parameters are strain, displacements, loads, weight and the center of gravity. There are test equipments, measuring sensors, a test rig and fixtures to obtain measuring parameters. In order to simulate the aerodynamics load, the three-point loading method instead of the one-point loading method is applied. There is slightly some difference between the measured results and the predicted results with the reference fiber volume fraction of 60%. However, the agreement between the measured results and the predicted results with the actual fiber volume fraction of 52.5% is good. Even though a slightly non-linearity from 80% loading to 100% loading, a linear static solution is sufficient for the design purpose as the amount of the non-linearity is relatively small. Comparison between measured and predicted strain results at the maximum thickness positions of the blade profile for 0.236R(5.56m), 0.493R(11.59m) and 0.574R(13.43m), under 20%, 40%, 60%, 80% and 100% loadings for the upper part of the blade. The predicted values are in good agreement with the measured values.

• Smart Structures and Systems
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• v.13 no.6
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• pp.1041-1063
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• 2014

This work introduces a two-module robotic pipe inspection system with ultrasonic NDE device to evaluate the integrity of pipe structures. The proposed robotic platform has high mobility. The two module mobile robot platform overcomes pipe obstacle structures such as elbow, or T-branch joints by cooperative maneuvers. Also, it can climb up the straight pipeline at a fast speed due to the wheel driven mechanism. For inspection of pipe structure, SH-waves generated by EMAT are applied with additional signal processing methods. A wavelet transform is implemented to extract a meaningful and specific signal from the superposed SH-wave signals. Intensity ratio which is normalized the defect signals intensity by the maximum intensity of directly transmitted signals in the wavelet transforms spectrum is applied to evaluate defects quantitatively. It is experimentally verified that the robotic ultrasonic inspection system with EMAT is capable of non-destructive inspection and evaluation of defects in pipe structure successfully by applying signal processing method based on wavelet transform.