• Journal of the Korean Society for Nondestructive Testing
• /
• v.36 no.4
• /
• pp.295-299
• /
• 2016

Residual foreign objects at the secondary side (top of the tubesheet and tube support plates) of a steam generator are likely to cause a leak by causing wear in the tube. The extent of wear is significantly affected by the material, shape, and size of the foreign object, and the corrosion properties of the tube. The presence of foreign objects at the top of the tubesheet and tube support plates has been identified using remote visual inspection methods such as the foreign object search and retrieval and eddy current test (ECT). The detection of the residual foreign object at the secondary side of a steam generator has limitations that depend on the material properties and the condition of contact with the tube. In this study, which is vertical and horizontal from the upper tubesheet, the corresponding bobbin ECT signals were collected and analyzed to measure its ability to detect foreign objects.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.22 no.4
• /
• pp.402-410
• /
• 2002

Recently the necessity of study on optical measuring method using laser to detect the pipeline's defect in nuclear facilities, chemical industries and power plants has been increased. Because laser light can be delivered to a remote area without any difficulties, the application of laser in many industries can solve several difficulties from the limitation of access in danger area and reduce the risks of workers. Therefore, we applied a new experimental technique to the measurement of internal defects in pressure vessels with the combination of shearography and image processing technique and detected the internal cracks of pressure vessels in the former paper. In this paper, we used the same optical system as in the former study and found the optimum shearing magnitude by comparing the real length of specimen with experimental results. A variety of conditions were applied to certify the validity of this method. Actually, several specimens which have different lengths and depths were used in this experiment under the three diverse pressure. Consequently, we have carried out this experiment to determine the limit of measurement ability with analyzing errors.

• Journal of the Institute of Electronics Engineers of Korea CI
• /
• v.39 no.3
• /
• pp.1-17
• /
• 2002

In this paper, we present our experiences in using symbolic model checker(SMV) to analyze a number of properties of RACE cache coherence protocol designed by ETRI(Electronics and Communications Research Institute) and to verify that RACE protocol satisfies important requirements. To investigate this, we specified the model of the RACE protocol as the input language of SMV and specified properties as a formula in temporal logic CTL. We successfully used the symbolic model checker to analyze a number of properties of RACE protocol. We verified that abnormal state/input combinations was not occurred and every possible request of processors was executed correctly We verified that RACE protocol satisfies liveness, safety and the property that any abnormal state/input combination was never occurred. Besides, We found some ambiguities of the specification and a case of starvation that the protocol designers could not expect before. By this verification experience, we show advantages of model checking method. And, we propose a new method to generate automatically test cases which are used in simulation and testing.

• The Bulletin of The Korean Astronomical Society
• /
• v.42 no.2
• /
• pp.85.1-85.1
• /
• 2017

We develop a coronagraph to measure the coronal electron density, temperature, and speed by observing the linearly polarized brightness of solar corona with 4 different wavelengths. Through the total solar eclipse on 21 August 2017, we test an operating software of a prototype coronagraph working with two sub-systems of two motorized filter wheels and a CCD camera that are controlled by a portable embedded computer. A Core Flight System (CFS) is a reusable software framework and set of reusable software applications which take advantage of a rich heritage of successful space mission of NASA. We use the CFS software framework to develop the operating software that can control the two sub-systems asynchronously in an observation scenario and communicate with a remote computer about commands, housekeeping data through Ethernet. The software works successfully and obtains about 160 images of 12 filter sets (4 bandpass filters and 3 polarization angles) during the total phase of the total solar eclipse. For the future, we can improve the software reliability by testing the software with a sufficient number of test cases using a testing framework COSMOS. The software will be integrated into the coronagraph for balloon-borne experiments in 2019.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.22 no.2
• /
• pp.187-192
• /
• 2002

The open-connect type eddy current transducer for the flaw detection in continuously connected pipelines was developed. This eddy current transducer is for the on-line inspection of the tubes in industries, to which commercial encircling probes are not applicable. The excitation coil that consists of a ribbon type cable and a flat connector can be opened and closed on purpose. The sensing coils of this transducer are circumferentially arrayed near the outside of the tube wall but axially displaced from the exciter by about one and half tube diameter. In application to steel tubes, and the performance of this transducer was evaluated as a little behind those of magnetic saturation type in signal to noise ratio and flaw size decision, but usable to detect or to locate large size flaws in steel tubes. Surface cracks deeper than 19% of the tube thickness could be detected with good signal to noise ratio.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.9
• /
• pp.229-237
• /
• 2020

This study attempted to share the results of real-time online tests in online classes conducted by 33 students in the 4th grade of the department of nursing, K University, and to suggest ways to secure fairness in real-time online tests. Real-time online testing in this study utilized zoom cloud meetings. Students were invited to participate in the meeting at the same time with a desktop or laptop, including a mobile phone, and the instructor displayed a single question in real time on the screen and collected answers using private talk. Through this method, students' monitor screen, keyboard, mouse, and posture were monitored and controlled. As a result of the survey on the real-time online test, 93.8% of students answered that they were fair and satisfied overall, and 90.6% said they were willing to recommend the online test to others. In the upcoming future, remote lectures and online tests will become more active, so efforts should be made to gradually expand to other tests by developing a fairer, more systematic and easy-to-use online testing method.

• Earthquakes and Structures
• /
• v.20 no.2
• /
• pp.149-160
• /
• 2021

Buildings made using the locally available clay materials are amongst the least expensive forms of construction in many developing countries, and therefore, widely popular in remote areas. It is despite the fact that these low-strength masonry structures are vulnerable to seismic forces. Since transporting imported materials like cement and steel in areas inaccessible by motorable roads is challenging and financially unviable. This paper presents, and experimentally investigates, adobe masonry structures that utilize the abundantly available local clay materials with moderate use of imported materials like cement, aggregates, and steel. Shake-table tests were performed on two 1:3 reduce-scaled adobe masonry models for experimental seismic testing and verification. The model AM1 was confined with vertical lightly reinforced concrete columns provided at all corners and reinforced concrete horizontal bands (i.e., tie beams) provided at sill, lintel, and eave levels. The model AM2 was confined only with the horizontal bands provided at sill, lintel, and eave levels. The models were subjected to sinusoidal base motions for studying the damage evolution and response of the model under dynamic lateral loading. The lateral forcedeformation capacity curves for both models were developed and bi-linearized to compute the seismic response parameters: stiffness, strength, ductility, and response modification factor R. Seismic performance levels, story-drift, base shear coefficient, and the expected structural damages, were defined for both the models. Seismic performance assessment of the selected models was carried out using the lateral seismic force procedure to evaluate their safety in different seismic zones. The use of vertical columns in AM1 has shown a considerable increase in the lateral strength of the model in comparison to AM2. Although an R factor equal to 2.0 is recommended for both the models, AM1 has exhibited better seismic performance in all seismic zones due to its relatively high lateral strength in comparison to AM2.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.23 no.3
• /
• pp.236-251
• /
• 2020

As remote sensing technologies are evolving, and more satellites are orbited, the demand for using satellite data for disaster monitoring is rapidly increasing. Although natural and social disasters have been monitored using satellite data, constraints on establishing an integrated satellite-based near real-time disaster monitoring system have not been identified yet, and thus a novel framework for establishing such system remains to be presented. This research identifies constraints on establishing satellite data-based near real-time disaster monitoring systems by devising and testing a new conceptual framework of disaster monitoring, and then presents a feasible disaster monitoring system that relies mainly on acquirable satellite data. Implementing near real-time disaster monitoring by satellite remote sensing is constrained by technological and economic factors, and more significantly, it is also limited by interactions between organisations and policy that hamper timely acquiring appropriate satellite data for the purpose, and institutional factors that are related to satellite data analyses. Such constraints could be eased by employing an integrated computing platform, such as Amazon Web Services(AWS), which enables obtaining, storing and analysing satellite data, and by developing a toolkit by which appropriate satellites'sensors that are required for monitoring specific types of disaster, and their orbits, can be analysed. It is anticipated that the findings of this research could be used as meaningful reference when trying to establishing a satellite-based near real-time disaster monitoring system in any country.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2006.05a
• /
• pp.462-466
• /
• 2006

Close-to-nature stream evaluation is one of the processing to make the streams over in order to keep them natural. It is integral to evaluate and make an accurate analysis of them on the purpose of maintaining streams healthy. For many instances, there are, stream organization evaluation for restoration by German government, evaluation for ecosystem protection in natural preserves by New Zealand government, and stream-view evaluation for restoration by Britain government so on. In case of the country there are analysis and evaluation of stream physical organization by Cho, Yong-hyun, Close-to-nature stream evaluation for restoration by Kim, Dong-chan, evaluation of stream properties in korea by Park, Bong-jin. Close-to-nature evaluation by Lim, Chan-uk, that is advanced version of Park, Bong-jin's, shows form of stream including waterway curve, sand bar, diversity of flow, river bed material, diversity of minor bed, minor bed bank protection works, bank protection material. It also does environment of stream including side of minor bed vegetation, width of surface of the water/width of the river etc.. By the way, this evaluation does not have free access to apply those details above in the field, it often happens that you get various outcome from the one spot. so you must need more realistic testing method to obtain more accurate data. Remote sensing method is highly recommended because this is very useful for collecting realistic data of vegetation index. what is more, it can not only scan even the minimum area within its resolving power but also do obtain data anytime. Vegetation index indicates Ratio vegetation index, Normalized difference vegetation index, Soil adjusted vegetation index, Atmospherically resistant vegetation index etc.. The research is focusing on Cheokgwa stream which is the branch of Taehwa river and shows 19 sectioned Close-to-nature stream performed according to the method by Lim, chan-uk. Besides let you know vegetation index came from image data of satellite landsat 7 with the variation of buffering area, of the day 9. may. 2003. Of all, the outcome 0.758 at 200m buffer-zone of NDVI was the best we have got so far.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.46 no.4
• /
• pp.28-38
• /
• 2009

In this study, a remote air quality monitoring system for underground spaces was developed by using NDIR-based CO$_2$ sensor. And the remote monitoring system based on wireless sensor networks was installed practically on the subway station platform. More than 6.5 million citizens commutate everyday by the Seoul subway transportation that is the most typical public transportation. They concern about air quality with increasing interest on public health or many workers in subway stations or underground shopping centers. Recently, the Korean Ministry of Environment has operated the air quality monitoring system in some subway stations for testing phase. However, it showed many defects which are large-scale, high-cost and maintenance of precision sensors imported from abroad. Therefore this research includes the reliability test and a theoretical study about the inexpensive commercialized CO$_2$ sensor for reliable measurement of air quality which changes rapidly by the surrounding environments. And then we develop the wireless sensor nodes and the gateway applied for remote air quality monitoring. In addition, web server program was realized to manage air quality in the subway platform. This result will be valuable for a basic research for air quality management in underground spaces for future study.