• Journal of the Korean Society for Nondestructive Testing
• /
• v.31 no.1
• /
• pp.62-67
• /
• 2011

Nanoparticles-coated and impact-damaged carbon-fiber reinforced plastics(CFRP) laminates were tested under compression-after-impact(CAI) mode and the propagation of damage due to compressive loading has been monitored by acoustic emission(AE). The impact damage was induced not by mechanical loading but by a simulated lightning strike. CFRP laminates were made of carbon prepregs prepared by coating of conductive nano-particles directly on the fibers and the coupons were subjected to simulated lightning strikes with a high voltage/current impulse of 10~40 kA within a few microseconds. The effects of nano-particles coating and the degree of damage induced by the simulated lightning strikes on the AE activities were examined, and the relationship between the compressive residual strength and AE behavior has been evaluated in terms of AE event counts and the onset of AE activity with the compressive loading. The degree of impact damage was also measured in terms of damage area by using ultrasonic C-scan images. From the results assessed during the CAI tests of damaged CFRP showed that AE monitoring appeared to be very useful to differentiate the degree of damage hence the mechanical integrity of composite structures damaged by lightning strikes.

• Asia pacific journal of information systems
• /
• v.21 no.2
• /
• pp.59-87
• /
• 2011

These days, firms are focusing on the improvement of relationships with business partners. The supply chain integrations are taking critical role in improving the relationships with business partners. In accordance with the development of the IT technology, it became possible for firms not only to integrate inner parts of the organization, but also to integrate the company with other organizations in the supply chain. Therefore, in e-Biz environments, it is imperative for firms to strengthen the core capacity through the supply chain, and to precisely determine the components of the determinants of e-Business integration which impact the firm performance. This study analyzed determinants that have impacts on e-business integration in e-business capacity perspectives in competitive environments. This study based on the premise that the resources and capacities that Grant(1991) and Hart(1995) emphasized do not directly influence the corporate performance. This study focused on the fact that corporate must create core competencies based on these capacities to establish competitive edge. Therefore, this study model analyzed to find out which e-Biz competencies are needed to integrate e-Biz according to competitive environment elements. This study designed to empirically analyze the impact of the e-Biz competencies to the e-Biz integration and to the corporate performance. Independent variables of this study-IT management, partner management, e-Biz knowledge, e-Biz establishment and proliferation, process innovation-are selected based on precedent studies on e-Biz competencies. We selected intermediate variables to verify that e-Biz competencies do not have direct impact on the corporate performance, but have impact on the e-Biz integration, which is intermediate effect. That is to verify that if the components of supply chain improve the integration level using e-Biz competencies, the overall supply chain performances will improve. Dependent variables are selected to verify that e-Biz integration has impacts on corporate performances. This study used factor analysis, path analysis, moderating effect analysis as statistical tests. First, we used exploratory factor analysis and confirmatory factor analysis to analyze reliability and validity. Because e-Biz competencies are presented variously by preceding studies, we used SPSS16.0 to verify if survey questionnaire used by theoretical backgrounds is properly composed. Second, we tested the property of structure model by AMOS. We did path analysis using AMOS16.0 to test structure that is composed of e-Biz competencies and e-Biz integration. Last, we tested moderating effects of measure factors. We analyzed 163 domestic companies to find out many significant suggestive points. First, relationship improvement capacity, e-business knowledge sharing capacity with business partners, and process innovation capacity are adopted as determinants of differentiation and competitive edges against competing firms. Second, e-business knowledge sharing capacity, and process innovation capacity are analyzed as the determinants of e-business integration in the firm which demand fluctuation in the market is high. On the other hand, among the determinants that require capturing ideas on new products, and strengthening the technological power, process innovation capacity are adopted as the determinants. These results provide us the foundation that the determinants that we have analyzed can impact the supply chain integration strategies which take into account the competitive environments.

• Journal of the Korean GEO-environmental Society
• /
• v.7 no.6
• /
• pp.121-131
• /
• 2006

This study is performed to examine the ground reinforcement effect and the environmental impact of LW injection, which is widely used during the excavation of high-rise apartment buildings. In addition, it proved that by conducting field exploration and laboratory test the engineering ground reinforcement effect of LW injection in the ground has low coefficient of permeability. The environmentally friendly aspect was evaluated through an assessment of environmental impact. The results of laboratory test shows that LW coagulating material with SC type soil structure has significant improvement of uniaxial compressive strength, increasing by three times and the shear strength increasing by twice, coefficient of permeability decreasing six to seven times. And the result of environmental impact tests show that from 6 hour after where the pH increases until 7.96 to initially it diminished, it started and to 80 hour after it recovered a pH 7.25 initially with 7.30. The chemical composition analysis test result that unpolluted water and polluted water hydrogen ion concentration (pH) show that the unpolluted water pH 7.36, polluted water pH 7.85, which is inside the Ministry of Environment standard of drinking water (the pH 5.8~8.5). The assessment of environmental impact and chemical analysis test also demonstrate that the LW coagulating material is environmentally friendly. In the $Cr^{6+}$ and the salinity detection test, it was proven that the salinity is slight and the $Cr^{6+}$ is not detected.

• Composites Research
• /
• v.18 no.3
• /
• pp.38-46
• /
• 2005

In order to characterize the outstanding performance of three-dimensional (3D) composites, the low velocity impact test has been carried out. 3D fiber structures have been achieved by using the automated tape placement (ATP) process and a stitching method. Materials for the ATP and the stitching process were carbon/epoxy prepreg tapes and Kevlar fibers, respectively. Two-dimensional composites with the same stacking sequence as 3D counterparts have also been fabricated for the comparison of damage tolerance. For the assessment of damage after the impact loading, specimens were subjected to C-Scan nondestructive inspection. Compression after impact (CAI) tests were conducted to evaluate residual compressive strength. The damage area of 3D composites was greatly reduced $(30-40\%)$ compared with that of 2D composites. Although the CAI strength did not show drastic improvement for 3D composites, the ratio of retained strength was $5-10\%$ higher than 2D samples. The effect of stitching on the impact performance was negligible above the energy level of 35 Joules.

• Journal of the Korean Geosynthetics Society
• /
• v.16 no.4
• /
• pp.75-82
• /
• 2017

In this study, a new cleaning method using carbon dioxide pellet in the part of underground pipe cleaning method was proposed and verified. First of all, the commentary of The Society for Protective Coatings was examined in detail to determine the quantitative cleaning effects. Also, field tests were carried out to confirm the application of the new method. In the test, the surface condition of inner pipe after the application of the new method was investigated and two types of nozzles were compared in the tests. Also, the tests to measure the final impact pressure of air and carbon dioxide pellet mixtures were performed to investigate the losses of air pressure were investigated. Through this verification on the new method, it was found that the new method is very efficient for the removal of the rust in the pipe cleaning works. Also, the nozzle with excellent cleaning effect was also selected. As a result, this method will be able to largely contribute to the recycling of $CO_2$ which is limited to the use as a cooling agent or the storage of waste.

• Journal of the Korean Geotechnical Society
• /
• v.18 no.4
• /
• pp.271-283
• /
• 2002

P-wave velocity of concrete is a crucial parameter in determining the thickness of concrete lining, the location of cracks or other defects in Impact-Echo(IE) method. This study introduces an IE-SASW method that may determine the P-wave velocity on a surface of each testing area using the Spectral Analysis of Surface Wave (SASW) method. In numerical studies(Part I), it was verified that P-wave velocities could be obtained from SASW. In this paper(Part II), experimental studies were made in slab type concrete model specimens in which voids and waterproof sheet were included at the known locations. Accordingly, the feasibility of the proposed method was evaluated. The IE-SASW method was also performed in the precast model tunnel on ground and open-cut tunnel in ground. SASW tests were performed to determine the P-wave velocity of the concrete and then IE tests were carried at regularly spaced points along the testing lines to determine the thickness of structures. The nondestructive testing method which combined SASW and IE tests showed the great potential in the field applications.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2005.10a
• /
• pp.405-416
• /
• 2005

The rubblization technique is breaking the aged concrete pavement slab into rubblized concrete aggregate, and use it as an base material at its original position, then builds overlay above the rubblized base. This method has been successively used in USA due to the advantage of good contructibility, cost-effectiveness as well as the capability of preventing of reflection cracks. However, constructibility and economic performance of rubblization on typical Korean concrete pavements needed to be investigate since to typical Korean concrete pavements have thick slab, as well include lean concrete subbase course. This stud explored optimum breaking depth and suggested minimum 10cm based on reflection crack simulation test. Also proper head shape and impact energy were investigated based on small breaking field tests. It was found that $127kg/cm^2$ of stress with 52.3% of head contact area are breaking requirement. Also, Multi-head type breaker suitable for Korean condition was designed and developed. This multi-head type breaker was designed to rubblize old concrete to the suggested optimum rubblized-depth and rubblized-concrete-aggregate size to prevent reflection crack and maintain high bearing capacity. This machine was used for the test of rubblization of old concrete pavement on a non-use old concrete and a in-serviced road. In these two tests, engineering properties of rubblized base and constructability and cost were investigated. In both tests, the old concrete rubblized to targeted size and depth, and high-level bearing capacity was achieved. Also, superior constructability and lower cost compared with traditional reconstruction was examined.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.31 no.4
• /
• pp.343-350
• /
• 2011

Recently, as the catastrophic disasters due to earthquake happen frequently all over the world, it draws lots of attention to seismic capacity evaluation and/or structural integrity assessment of deteriorated civil infra-structures. However, there have been few studies on the existing dam flood gates, expecially in Korea. In this study, a proper vibration testing method applicable to a dam flood gate has been suggested, since the dynamic characteristics of a darn flood gate can be fundamental data for seismic capacity evaluation or structural integrity assessment. The frequency domain decomposition technique has been incorporated for modal parameter identification. Two kinds of vibration tests using an impact hammer and ambient vibration sources were carried out on two types of dam floodgates with different shapes. Through the field tests, the effectiveness of the ambient vibration tests were verified.

• Journal of Pharmaceutical Investigation
• /
• v.34 no.1
• /
• pp.57-71
• /
• 2004

The objective of this study was to provide a better understanding of SUPAC-IR and its application in handling postapproval changes to immediate release solid oral dosage forms. Originally, SUPAC-IR was aimed at reducing the regulator burdern of the industry when they were making postapproval changes, but still at maintaining the formulation quality and performance of a drug product. The postapproval changes that were covered under SUPAC-IR included variations in the components ad composition of formulation, the site of manufacturing, batch size, manufacturing equipment, and manufacturing process. The guidance defined levels of changes, based on the likelihood of risk ocurrence and potential impact of postapproval changes upon the safety and efficacy of a drug product I suggested what a type of fing report should be submitted to the FDA for each level of change. Chemist, manufacturing, and control tests to be executed were also recommended for each change level The important tests specified in the guidance included batch release, stability, in vitro dissolution, and in vivo bioequivalence tests. However, there have been strong demands on revising the current SUPAC-IR in order to resolve some issues and to improve its usefulness in evaluating postapproval changes to immediate release solid oral dosage forms. In particular, the rigorous requirement of case C dissolution test and the definition of batch size were challenged by both academia and the industry. A revision work was in progress to reflect these inputs and to expand the utility of SUPAC-IR. As a result of these concerted efforts, an updated 2nd version of SPAC-IR would be likely to be issued ver soon to the public.

• Transactions of the Korean Society of Pressure Vessels and Piping
• /
• v.10 no.1
• /
• pp.100-106
• /
• 2014

There is a growing need to introduce advanced pressure vessel steels with higher strength and toughness for the optimizatiooCn of the design and construction of longer life and larger capacity nuclear power plants. SA508 Gr.4N Ni-Cr-Mo low alloy steels have superior strength and fracture toughness, compared to SA508 Gr.3 Mn-Mo-Ni low alloy steel. Therefore, the application of SA508 Gr.4N low alloy steel could be considered to satisfy the strength and toughness required in advanced nuclear power plants. The purpose of this study is to characterize the microstructure and mechanical properties of SA508 Gr.4N low alloy steels. 1 ton ingot of SA508 Gr.4N model alloy was fabricated by vacuum induction melting followed by forging, quenching, and tempering. The predominant microstructure of the SA508 Gr.4N model alloy is tempered martensite having small packet and fine Cr-rich carbides. The yield strength at room temperature was 540MPa, and it was decreased with an increase of test temperature while DSA phenomenon occurred at around $288^{\circ}C$. Overall transition property of SA508 Gr.4N model alloy was much better than SA508 Gr.3 low alloy steel. The index temperature, $T_{41J}$, of SA508 Gr.4N model alloy was $-132^{\circ}C$ in Charpy impact tests, and reference nil-ductility transition temperature, $RT_{NDT}$ of $-105^{\circ}C$ was obtained from drop weight tests. From the fracture toughness tests performed in accordance with the ASTM standard E1921 Master curve method, the reference temperature, $T_0$ was $-147^{\circ}C$, which was improved more than $60^{\circ}C$ compared to SA508 Gr.3 low alloy steels.