• Journal of Energy Engineering
• /
• v.14 no.2 s.42
• /
• pp.153-158
• /
• 2005

In order to investigate the short-term performance of polyethylene electrofusion joints, the mechanical tests and stress analysis have been conducted to the artificially defected weld joints. The defects of lack of fusion with a square-type were fabricated with 10, 20, 30, 40, 50, 60$\%$ size of the width of heat-ing wire zone, respectively. In this defect sires range, both tensile and bending test results showed the dependence of defect size to the electrofusion joints performance, but both sustained pressure and crush test results didn't. The numerical stress analysis results including the soil and internal pressures, tensile and bend-ing stresses clearly showed the dependence of fusion defect size. Based on both mechanical test and stress analysis results, the maximum acceptable defect size in polyethylene electrofusion joints is discussed.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.21 no.2
• /
• pp.197-203
• /
• 2001

Micro-defects induced by design and production failure or working environments are known as the cause of SCC(Stress Corrosion Cracking) in aged structures. Therefore, the evaluation of structural integrity based on micro-cracks is required not only a manufacturing step but also in-service term. So we introduce a new nondestructive inspection method using the magneto-optical film to detect micro-cracks. The method has some advantage such as high testing speed, real time data acquistion and the possibility of remote sensing by using of a magneto-optical film that takes advantage of the change of magnetic domains and domain walls. This paper introduces the concept of the new nondestructive inspection method using the magneto-optical film, also proves the possibility of this method as a remote testing system under oscillating load considering application on real fields by applying the method to four types of specimens.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.5 no.2 s.17
• /
• pp.1-8
• /
• 2005

Microwave tomographic imaging technology using a bi-focusing operator has been developed in order to detect the internal voids/objects inside concrete structures. The imaging system consists of several cylindrical or planar array antennas for transmitting and receiving signals, and a numerical focusing operator is applied to the external signals both in transmitting and in receiving fields. In this study, the authors developed 3-dimensional (3D) electromagnetic (EM) imaging technology to detect such damage and to identify exact location of steel rebars or dowel. The authors have developed sub-surface two-dimensional (2D) imaging technique using tomographic antenna array in previous works. In this study, extending the earlier analytical and experimental works on 2D image reconstruction, a 3D microwave imaging system using tomographic antenna way was developed, and multi-frequency technique was applied to improve quality of the reconstructed image and to reduce background noises. Numerical simulation demonstrated that a sub-surface image can be successfully reconstructed by using the proposed tomographic imaging technology. For the experimental verification, a prototype antenna array was fabricated and tested on a concrete specimen.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.30 no.4
• /
• pp.367-372
• /
• 2010

A power plant's heat exchangers work under poor conditions, such as high temperature, high pressure, corrosion, mechanical stress and vibration. Especially, partial joint-weld of heat exchanger's header to stub-tube is the place where incomplete penetration flaws can easily occur. But, it is hard to evaluate the safety of the structure by conventional nondestructive testing techniques. So it is necessary to test integrity of the weld inside and to develop testing technique and equipment that can detect the flaws at the weld point in order to enhance reliability of the test result. In this study, we developed a suitable automated ultrasonic testing system that can inspect the partial joint-weld of header to stub-tube of power plant. Finally, we showed the efficiency of the automated ultrasonic-testing-system from the application.

• Journal of the Korea Society of Computer and Information
• /
• v.17 no.9
• /
• pp.127-138
• /
• 2012

In this paper, we present a tool (named VMBootFailMonitor) to detect and analyze a failure of a VM boot creation caused by faults on virtual disks of a Xen-based VM. Also, we presents an architecture and detail analysis process of the virtual disk faults in our tool. Especially, VMBootFailMonitor provides a causual analysis result for a case of VM creation failure based on three modules which performs virtual disk analysis, virtualized system analysis and system log analysis. We also support a comparison result between boot times of normal VMs and fault detection times of VM creation based on abnormal virtual disks. At result, our tool detects VM boot failures (3~6 seconds) within normal VM boot times (8~16 seconds).

• Journal of the Korean Society for Nondestructive Testing
• /
• v.20 no.6
• /
• pp.545-554
• /
• 2000

Compton X-ray backscatter technique has been used to quantitatively assess the impact damage in quasi-isotropic laminated composites and to obtain a cross-sectional profile of impact-damaged laminated composites from the density variation of the cross section. An adaptive filter is applied to the Compton backscattering data for the reconstruction and noise reduction from many sources including quantum noise, especially when the SNR(signal-to-noise ratio) of the image is relatively low. A nonlinear reconstruction model is also proposed to overcome distortion of the Compton backscatter image due to attenuation effects, beam hardening, and irregular distributions of the fibers and the matrix in composites. Delaminations masked or distorted by the first few delaminations near the front surface are detected and characterized both in width and location, by application of an error minimization algorithm.

• Proceedings of the KIEE Conference
• /
• 2011.07a
• /
• pp.513-514
• /
• 2011

본 논문에서는 154kV 지중송전선로의 관로내 XLPE 케이블에서 발생하는 절연파괴 고장원인을 분석하였다. 일반적으로 케이블은 제조공정 과정에서 결함을 철저히 걸러내도록 조치하고 공장 출하시 시험을 통해 점거하고 있어, 케이블 자체고장은 현장에서 시공하는 접속함에 비해 매우 작지만 드물게 발생하고 있다. 케이블 자체에서 고장 발생시 고장원인 파악을 위해 제조 품질, 시공과정 등을 체계적으로 분석하고 검토하여 케이블 생산, 시공현장 품질저하 및 관리소홀 등으로 인한 케이블 고장을 최소화하고자 한다.

• Journal of Korea Foundry Society
• /
• v.44 no.2
• /
• pp.49-55
• /
• 2024

• Proceedings of the Korean Nuclear Society Conference
• /
• 2004.10a
• /
• pp.1173-1174
• /
• 2004

• 보일러설비
• /
• no.9 s.152
• /
• pp.137-141
• /
• 2006

우리나라 보일러 산업은 짧은 역사에도 불구하고 가스 수요의 증가와 함께 장족으로 발전을 하여왔다. 그러나 업계의 과잉경쟁에 의한 양적인 성장 이면에는 기술개발의 한계로 인한 제품자체의 결함이나 설치ㆍ시고상의 하자, 가스배관 내 이물질 등의 문제로 인한 가스보일러 사고가 종종 발생하고 있다. 우리 온돌 시공인이 일선 현장에서 가스보일러를 직접 설치ㆍ시공하는데 조금이나마 도움이 되어 가스보일러 사고를 예방함으로써 가스안전문화를 정착시키는데 기여했으면 한다.