• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.4
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• pp.315-322
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• 2008

Valves in power plants are leaking internally by various damages including insertion of foreign objects on seat, seat crack, defects and fatigue crack of stem packing or welds etc. due to severe operating conditions such as high temperature and high pressure for extended period time. Acoustic emission(AE) technology should be applied in order to diagnose precisely and evaluate these valve internal leak. In this paper, results of studies which have accomplished in actual power plant are presented. We have analyzed background noise, AE signal level and frequency spectrum through laboratory tests on the basis of various actual conditions in power plant, and also have considered evaluation methods on the background noise, AE properties and the detectable minimum leak rate according to valve leak conditions through comparing with results of field tests in power plant. As a result of these studies, we conformed that evaluation of internal leak conditions including discrimination of leak or not, and the detectable minimum leak rate is possible, and also it is expected to contribute to safe operation and prevention of energy loss in power plants.

• Korean Journal of Organic Agriculture
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• v.19 no.spc
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• pp.17-20
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• 2011

Plant biomass is a huge carbon-complex that has potential as a nutrient. Therefore we extracted and separated useful materials for plant growth from tea leaf and stem. The pre-treatment process including high temperature ($200^{\circ}C$) and pressure (20-40 kgf/$cm^2$) was treated for several minutes and extracted at $120^{\circ}C$ for 30-60 minutes. After that the chemical compositions and ingredients were analyzed from that plant-nutrient. As a result of mineral contents, calcium and magnesium concentrations are higher than other minerals. Also the result of carbohydrates analyses has shown that the sugar oligomer consists of xylose(95.3%) and glucose(4.7%), and the sugar monomer consists in the order of xylose (52.7%) > manose (22.8%) > arabinose (10.8%) > galactose (10.2%) > glucose (3.5%). Before applied to field, in vitro plant growth system and formulation were examined. To evaluate the effect of the nutrients, both strawberry green-house and persimmon fields were used in this test. The treated persimmons were heavier than controls scored at 13-22%. In addition, the storage-period was extended in the treated strawberries. Interestingly in the treated strawberry, the contents of polyphenols were increased (38-57%). These results suggest that the plant-nutrient can afford to help for plant growth and storage, and it can be substituted for other commercial nutrients. In conclusion, this plant-nutrient may help to extend eco-friendly or organic farming in Hadong-gun area.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.25 no.1
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• pp.12-17
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• 1989

A field experiment was carried out of confirm the effect of underwater sound on the luring of fish school of chub mackerel in the coast of Idousyo Island. Underwater sound that was made use of luring of fish school was pure sound and interval pure sound which the frequencies of the sound were 150Hz and 200Hz, respectively. The results of the observation of hooking and recording paper of fish finder indicate that the effect of emitting sound at 20m in the depth of water was remarkable for the luring of fish school of chub mackerel. The vertical pure sound pressure level at 150Hz and 200Hz of the water layer that was lured the fish school of chub mackerel were 140.1dB and 146.dB at 30m, 121.0dB and 126.6dB at 70m and 141.9dB and 120.5dB at 120m in the depth of water, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.9
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• pp.2354-2360
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• 2009

Healthcare is a field where ubiquitous computing is most widely used. We propose a mining-based healthcare multi-agent system for ubiquitous computing environments. This proposed scheme select diagnosis patterns using mining in the real-time biosignal data obtained from a patient's body. In addition, we classify them into normal, emergency and be ready for an emergency. This proposed scheme can deal with the enormous quantity of real-time sensing data and performs analysis and comparison between the data of patient's history and the real-time sensory data. We separate Association rule exploration into two data groups: one is the existing enormous quantity of medical history data. The other group is real-time sensory data which is collected from sensors measuring body temperature, blood pressure, pulse. Proposed system has advantage that can handle urgent situation in the far away area from hospital through PDA and mobile device. In addition, by monitoring condition of patient in a real time base, it shortens time and expense and supports medical service efficiently.

• Journal of the Korean institute of surface engineering
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• v.47 no.5
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• pp.239-243
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• 2014

The electrical and optical properties of amorphous In-Tin-Zinc-Oxide(ITZO) deposited at room temperature using rf-magnetron sputtering were investigated. The amorphous ITZO thin films were obtained at the composition of In:Sn:Zn = 6:2:2, 4:3:3, and 2:4:4, but the ITZO (8:1:1) showed a crystalline phase of bixbyite structure of In2O3. The resistivity of ITZO could be controlled by oxygen pressure in the sputtering ambient. The resistivity of post-annealed ITZO thin films exhibited the dependence on the amount of Indium. Optical energy band gap and transmittance increased as the amount of indium in ITZO increased. For the device application with ITZO, the bottom-gated thin-film transistor using ITZO as a active channel layer was fabricated. It showed a threshold voltage of 1.42V and an on/off ratio of $5.63{\times}10^7$ operated with saturation field-effect mobility of $14.2cm^2/V{\cdot}s$.

• Journal of the Korean Institute of Gas
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• v.2 no.3
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• pp.49-53
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• 1998

It takes quite a long time for an analyzer, such as gas chromatography, to measure a bulk property of a system, which prevents on-line measurements. Also, the cost of installation and maintenance is very high. Consequently, some other means is needed for on-line measurements of properties and the development of soft sensors based on process variables like temperature and pressure is of great interest. In the field of gas industry, the development of a soft sensor which makes indirect on-line measurements of gas compositions and flow rate, is in progress. In this paper, we proposed a hybrid inner model PLS which improved the prediction performance by taking into account the data structure, as an empirical modeling algorithm. When applied to a design of a soft sensor of a distillation tower, the hybrid inner model PLS showed better prediction performance than other methods.

• Journal of Drive and Control
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• v.13 no.2
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• pp.19-25
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• 2016

Recently, drivers have begun to regard comfort in the cabin as one of the most important factors in construction equipment like forklifts. Accordingly, it has become more important to design a forklift cabin with a better sound quality as well as lower sound level, which can make a driver more comfortable. In this paper, the correlation between subjective evaluation and Zwicker's sound quality index was analyzed through a blind test by a few workers in forklifts and other construction equipment in several countries. Correlation analysis showed that Loudness and Sharpness were ranked in sequence, and tendencies were different from country to country. Also, contribution analysis for Loudness and Sharpness using operational transfer path analysis (OTPA), which is widely used in the field of noise, vibration, and harshness (NVH), was performed. However, Loudness and Sharpness cannot be used with OTPA directly because there are no linear relationships between the sources and receivers. In this paper, both are calculated by applying the DIN 45631 method with a contribution rate (%) of 1/3 Octave Sound Pressure Level by OTPA method in addition to considering spectral masking.

• Geomechanics and Engineering
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• v.22 no.5
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• pp.449-460
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• 2020

The double-lane arrangement model is frequently used in underground coal mines because it is beneficial to improve the mining efficiency of the working face. When the double-lane arrangement is used, the service time of the reserved roadway increases by twice, which causes several difficulties for the maintenance of the roadway. Given the severe non-uniform deformation of the reserved roadway in the Buertai Coal Mine, the stress distribution law in the mining area, the failure characteristics of roadway and the control effect of support resistance (SR) were systematically studied through on-site monitoring, FLAC 3D numerical simulation, mechanical model analysis. The research shows that the deformation and failure of the reserved roadway mainly manifested as asymmetrical roof sag and floor heave in the region behind the working face, and the roof dripping phenomenon occurred in the severe roof sag area. After the coal is mined out, the stress adjustment around goaf will happen to some extent. For example, the magnitude, direction, and confining pressure ratio of the principal stress at different positions will change. Under the influence of high-stress rotation, the plastic zone of the weak surrounding rock is expanded asymmetrically, which finally leads to the asymmetric failure of roadway. The existing roadway support has a limited effect on the control of the stress field and plastic zone, i.e., the anchor cable reinforcement cannot fully control the roadway deformation under given conditions. Based on obtained results, using roadway grouting and advanced hydraulic support during the secondary mining of the panel 22205 is proposed to ensure roadway safety. This study provides a reference for the stability control of roadway with similar geological conditions.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.160-160
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• 2019

Water is a limited source that needs to be properly managed and distributed to the ever-growing population of the world. Rapid urbanization and development have increased the overall water demand of the world drastically. However, there is loss of billions of liters of water every year due to leakages in water distribution systems. Such water loss means significant financial loss for the utilities as well. World bank estimates a loss of $14 billion annually from wasted water. To address these issues and for the development of efficient and reliable leakage management techniques, high efforts have been made by the researchers and engineers. Over the past decade, various techniques and technologies have been developed for leakage management and leak detection. These include ideas such as pressure management in water distribution networks, use of Advanced Metering Infrastructure, use of machine learning algorithms, etc. For leakage detection, techniques such as acoustic technique, and in recent yeats transient test-based techniques have become popular. Smart Water Grid uses two-way real time network monitoring by utilizing sensors and devices in the water distribution system. Hence, valuable real time data of the water distribution network can be collected. Best results and outcomes may be produced by proper utilization of the collected data in unison with advanced detection and management techniques. Long term reduction in Non Revenue Water can be achieved by detecting, localizing and repairing leakages as quickly and as efficiently as possible. However, there are still numerous challenges to be met and future research works to be conducted in this field.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.10
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• pp.83-92
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• 2019

A pump is considered to be submersible when a motor and a pump are integrated and operate while submerged in water. Submersible pumps mainly function as rejection pumps to prevent foods in densely populated areas, as cold water circulation pumps in large power plants, as pumps to supply irrigation water, as drainage pumps to prevent flooding of agricultural lands, as water supply intake pumps, and as inflow pumps for sewage treatment. The flow in such turbomachines (submersible pumps) inevitably involves various eddy currents. Since it is almost impossible to accurately grasp the complex three-dimensional flow structure and characteristics of a rotating turbomachine through actual testing, three-dimensional numerical analysis using computational fluid dynamics techniques measuring the flow field, velocity, and the pressure can be accurately predicted. In this study, the shape of the impeller was developed to reduce vibration and noise. This was done by increasing the efficiency of the existing submersible pump and reducing turbulence. In order to evaluate the pump's efficiency and turbulence reduction, we tried to analyze the flow using ANSYS Fluent V15.0, a commercial finite element analysis program. The results show that the efficiency of the pump was improved by 4.24% and the Reynolds number was reduced by 15.6%. The performance of a developed pump with reduced turbulence, vibration, and noise was confirmed.