• Journal of the Korean Institute of Intelligent Systems
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• v.18 no.1
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• pp.122-126
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• 2008

Integrating a 3D solid modeler with a general purpose FEM code, an automatic stress intensity factor analysis system of the 3D crack problems has been developed. A geometry model, i.e. a solid containing one or several 3D cracks is defined. Several distributions of local node density are chosen, and then automatically superposed on one another over the geometry model by using the fuzzy knowledge processing. Nodes are generated and quadratic tetrahedral solid elements are generated by the Delaunay triangulation techniques. Finally, the complete finite element(FE) model generated, and a stress analysis is performed. This paper describes the methodologies to realize such functions, and demonstrates the validity of the present system.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.19 no.6
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• pp.77-86
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• 2016

Due to aging of the rural and mountain populations the labor force is reduced. However work intensity continues to increase, thus, there is a need to improve the current effectiveness of forest operations. This study compared and analyzed the Operation productivity and efficiency of planting containerized seedlings using a battery-powered planting auger and a mattock. Growth was also investigated by looking into the initial growth increments in the planted seedlings. Tasks were investigated by analyzing the process and operation time needed to plant 1 containerized seedling using a planting auger and a mattock. The time spent on the various elements of the planting process was measured with a stopwatch but observations were done continuously. Result of the study shows that with the use of a lightweight planting auger the average time spent to plant a containerized seedling is 18.61 seconds while with the use of a mattock it took an average of 26.96 seconds which clearly demonstrates that the planting auger is more efficient in terms of working hours. Working intensity was also analyzed with the use of a portable heart rate monitor (Polar V800). The average increase in heart rate and work intensity index were analyzed for one planting cycle. It was observed that when using the lightweight planting auger, there was a 46.51% increase in the average heart rate while a 74.67% increase in heart rate when the mattock was used which shows that there is a significant increase in heart rate when mattock is used. In addition, work intensity index was observed to be 29.95% and 47.83% when the planting auger and mattock were used respectively. With the continuous use, work intensity index is significantly higher with the use of the mattock as compared to that of the lightweight planting auger. There were no significant differences on the growth increment of seedlings planted using the different tools until a year after planting, however differences in growth increment were observed after a year. A difference of 15.1 cm in height and 3.41 mm in diameter was observed which shows that the use of lightweight planting auger is excellent for planting containerized seedlings.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.5
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• pp.2156-2170
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• 2020

This paper presents a fire detection algorithm with a minimal false detection rate, intended for a thermal imaging surveillance environment, whose properties vary depending on temporal conditions of day or night and environmental changes. This algorithm was designed to minimize the false detection alarm rate while ensuring a high detection rate, as required in fire detection applications. It was necessary to reduce false fire detections due to non-flame elements occurring when existing fixed threshold-based fire detection methods were applied. To this end, adaptive flame thresholds that varied depending on the characteristics of input images, as well as the center of gravity of the heat-source and hot-source regions, were analyzed in an attempt to minimize such non-flame elements in the phase of selecting flame candidate blocks. Also, to remove any false detection elements caused by camera shaking, one of the most frequently raised issues at outdoor sites, preliminary decision thresholds were adaptively set to the motion pixel ratio of input images to maximize the accuracy of the preliminary decision. Finally, in addition to the preliminary decision results, the texture correlation and intensity of the flame candidate blocks were averaged for a specific period of time and tested for their conformity with the fire decision conditions before making the final decision. To verify the fire detection performance of the proposed algorithm, a total of ten test videos were subjected to computer simulation. As a result, the fire detection accuracy of the proposed algorithm was determined to be 94.24%, with minimum false detection, demonstrating its improved performance and practicality compared to previous fixed threshold-based algorithms.

• Geomechanics and Engineering
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• v.7 no.3
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• pp.233-246
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• 2014

Estimation of fracture initiation pressure is one of the most difficult technical challenges in hydraulic fracturing treatment of vertical or horizontal oil wells. In this study, the influence of in-situ stresses and pore pressure values on fracture initiation pressure and its profile in vertical and horizontal oil wells in a normal stress regime have been investigated. Cohesive elements with traction-separation law (XFEM-based cohesive law) are used for simulating the fracturing process in a fluid-solid coupling finite element model. The maximum nominal stress criterion is selected for initiation of damage in the cohesive elements. The stress intensity factors are verified for both XFEM-based cohesive law and analytical solution to show the validation of the cohesive law in fracture modeling where the compared results are in a very good agreement with less than 1% error. The results showed that, generally by increasing the difference between the maximum and minimum horizontal stress, the fracture pressure and its profile has been strongly changed in the vertical wells. Also, it's been clearly observed that in a horizontal well drilled in the direction of minimum horizontal stress, the values of fracture pressure have been significantly affected by the difference between overburden pressure and maximum horizontal stress. Additionally, increasing pore pressure from under-pressure regime to over-pressure state has made a considerable fall on fracture pressure in both vertical and horizontal oil wells.

• Journal of Digital Contents Society
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• v.19 no.1
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• pp.165-171
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• 2018

Shadow is a physical phenomenon observed in natural scenes and has a negative effect on various image processing systems such as intelligent video surveillance, traffic surveillance and aerial imagery analysis. Therefore, shadow detection should be considered as a preprocessing process in all areas of computer vision. In this paper, we define and analyze various feature elements for shadow detection in a single natural image that does not require a reference image. The shadow elements describe the intensity, chromaticity, illuminant-invariant, color invariance, and entropy image, which indicate the uncertainty of the information. The results show that the chromaticity and illuminant-invariant images are effective for shadow detection. In the future, we will define a fusion map of various shadow feature elements, and continue to study shadow detection that can adapt to various lighting levels, and shadow removal using chromaticity and illuminance invariant images.

• The Journal of Korean Physical Therapy
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• v.13 no.1
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• pp.139-149
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• 2001

We found out that there exists threshold dose for the decreased platelet count when we apply change of the platelet count to the defense of the ultrasound experiment. Those diminution is definite effects from the defense of the ultrasound. The number of the platelet count is decreased when we are exposed to ultrasound simultaneously. This should not be occurred. It is easy to use the number of the platelet count in the measurement of the biological dosage and intensity in high dosage relatively due to definite quantative relationship. The biological index to understand synergic effects. which are present when two harmful environmental factors are operating at the same time is functionally assending and antagonistic. There are scattered many factors as physical, Chemical, or physiochemically elements which are harmful to human body in the environment in consideration of ultrasound and the other factors. This experiment is demonstrating that we can use the change of the platelet as an index representing synergic effects of ultrasound.

• Journal of Environmental Science International
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• v.3 no.4
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• pp.305-315
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• 1994

The field observation was carried out to investigate the characteristics of surface inversion layer at Kimhae using the feild observed date and upper layer meteorological data during 4-5 February 1993. The results of the study can be summarized as follows : The maximum height of surface inversion layer observed at Kimhae is 193m and the height of upper level inversion layer ranges from 2nm to 300m. The surface weather elements was influenced the formation of surface inversion layer. According to the pasquill stability and time variation of temperature with height, both the surface heating from insolation and the disturbance of upper level of inversion layer was influenced the disappearance of inversion layer. And the stability of surface temperature inversion layer generally belongs to the class of F, that of upper level temperature inversion layer commonly to the class of E.

• Journal of Industrial Technology
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• v.27 no.B
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• pp.221-227
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• 2007

This research investigates the turbidity and flow of river for an year, 2005, in order to examine the relation of the generation of turbidity according to the outflow of min water. For this research, the region of Jawoon river where is the area of high land vegetable growing in the upper Soyang Reservoir is selected to observe actual floating materials that generate negative nutrition and turbidity of the Reservoir water and the changes of water quality by raining of each month. In addition, the researcher has conducted statistical inspection methods, such as correlation analysis and regression analysis on strength of raining force, and rain continuance time among the elements affecting the outflow of floating materials.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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• pp.187-194
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• 2002

Bridge dynamic behaviors and the failure of the foundation are examined in this study under seismic excitations including the local scour effect. The simplified mechanical model, which can consider the effect of various influence elements, is proposed to simulate the bridge motions. The scour depths around the foundations are estimated by the CSU equation recommended by the HEC-18 and the local scour effect upon global bridge motions is then considered by applying various foundation stiffness based upon the reduced embedded depths. From the simulation results, it is found that seismic responses of a bridge with the same scour depth for both foundations increase due to the local scour effect. The bridge scour is found to be significant under weak and moderate seismic intensity. The recovery durations of the foundation stiffness after local scour are found to be critical in the estimation of the probability of foundation failure under earthquakes. Therefore, the safety of the whole bridge system should be conducted with the consideration of the scour effect upon the foundations and the recovery duration of stiffness should be determined rationally.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.450-453
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• 2004

A tactile stimulator array using stacked PZT is fabricated and evaluated in this paper. The purpose of this research is the development of a tactile stimulator to represent the obstacle information for the visually disabled. As a first step of this research, we investigate the physiological characteristics of tactile stimuli and design a tactile stimulator based on the investigated results. Also we evaluated a fabricated tactile stimulator. The prototype of tactile stimulator which has 2$\times$2 tactor elements with 3mm spacing is fabricated using stacked PZT actuator. In order to evaluate the characteristics of this tactile stimulator, physiological experiments are carried out. In the experiment, the threshold of tactile stimulus intensity within a frequency range of 5-500Hz at various stimulus amplitudes are investigated. According to the obtained experimental result, the input signal of tactile stimulator for the effective transfer of obstacle information is determined. Also physiological experiments of multi-stimuli recognition such as shift and rotation are carried out