• Journal of the Institute of Electronics Engineers of Korea SP
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• v.46 no.4
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• pp.124-131
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• 2009

A reliable detection of regions in radiography is one of the most important task before the evaluation of defects on welded joints. The extracted features is to be classified into distinctive clusters for each segmented region. But conventional segmentation techniques give unsatisfactory results for this task due to the spatial superposition of intensity and low signal-to-ratio(SNR) in radiographic images. The usage of global or local processes not only provide the necessary noise resistance but also fail in classification of regions. In this paper, we presents an appropriate approach for segmentation of region-based indications in industrial Computed Radiography(CR) images. The geometric differences between welded and non-welded area which is generated on radiography as the representative regions(background, thickness, middle and welded region in steel tube image) have constructed the hierarchical structure. Although this structure is contaminated by noise, the scheme between regions can be selected by the help of local clustering based on distinctive geometric property of each region. Because of the geometric nature of the considered region and so that the region is selected layer by layer, and that the real class represents the boundary between regions, the vertical and horizontal clustering process in each layer must be judicious. In order to show the effectiveness of this approach, a comparative experiment of various segmentation method is performed on industrial steel tube CR images.

• Journal of Astronomy and Space Sciences
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• v.19 no.4
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• pp.305-318
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• 2002

We have constructed two flight models of airglow photometer system (AGP) to be onboard Korea Sounding Rocket-III (KSR-III) for detection of MUV dayglow above the Korean peninsular. The AGP system is designed to detect dayglow emissions of OI 2972${\AA}$, $N_2$ VK(0,6) 2780${\AA}$, $N_2$ 2PG 3150${\AA}$ and background 3070${\AA}$ toward the horizon at altitudes between 100 km and 300 km. The AGP system consists of a photometer body, a baffle an electronic control unit and a battery unit. The MUV dayglow emissions enter through a narrow band interference filter and focusing lens of the photometer, which contains an ultraviolet sensitive photomultiplier tube. The photometer is equipped with an in-flight calibration light source on a circular plane that will rotate at the rocket's apogee. A bane tube is installed at the entry of the photometer in order to block strong scattering lights from the lower atmosphere. We have carried out laboratory measurements of sensitivity and in-flight calibration light source for the AGP flight models. Although absolute sensitivities of the AGP flight models could not be determined in the country, relative sensitivities among channels are well measured so that observation data during rocket flight in the future can be analyzed with confidence.

• Composites Research
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• v.36 no.1
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• pp.53-58
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• 2023

The PIC design method is assigning different stacking sequences for each shell element through the preliminary FE analysis. In previous study, machine learning was applied to the PIC design method in order to assign the region efficiently, and the training data is labeled by dividing each region into tension, compression, and shear through the preliminary FE analysis results value. However, since buckling is not considered, when buckling occurs, it can't be divided into appropriate loading type. In the present study, it was proposed PIC-NTL (PIC design using novel technique for analyzing load type) which is method for applying a novel technique for analyzing load type considering buckling to the conventional PIC design. The stress triaxiality for each ply were analyzed for buckling analysis, and the representative loading type was designated through the determined loading type within decision area divided into two regions of the same size in the thickness direction of the elements. The input value of the training data and label consisted in coordination of element and representative loading type of each decision area, respectively. A machine learning model was trained through the training data, and the hyperparameters that affect the performance of the machine learning model were tuned to optimal values through Bayesian algorithm. Among the tuned machine learning models, the SVM model showed the highest performance. Most effective stacking sequence were mapped into PIC tube based on trained SVM model. FE analysis results show the design method proposed in this study has superior external loading resistance and energy absorption compared to previous study.

• Journal of Radiation Protection and Research
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• v.22 no.2
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• pp.85-95
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• 1997

TLD and film badges have been traditionally used as formal dosimeters in personal monitoring and are still most widely used. Recently, electronic personal dosimeters based upon Si diode or miniature G-M tube were developed and are getting attractions due to their merits of active nature ; indication of dose rates and the commutative dose, and facilitation of record keeping and radiological control. Response characteristics of the electronic dosimeters including reproducibility, accuracy, linearity, energy and angular dependencies, detection threshold, and response time were examined for three commercial types ; EPD2, STEPHEN6000, and PD-3i. The results were compared with the relevant requirements of IEC standards and Ontario Hydro standards to conclude that their general performances were good. Some specific deficiencies, e.g. incapability of shallow dose measurement of STEPHEN6000, and PD-3i, however, should be corrected to be used as a formal dosimeter.

• Journal of Korean Society of Steel Construction
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• v.26 no.3
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• pp.169-176
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• 2014

This paper presents the experimental results of behavior of square CFT columns with large the width-ro thickness ratio strengthened with carbon fiber reinforced polymers (CFRP) sheets subjected to concentrated axial loading. The main parameters were b/t ratio and the number of CFRP layers and 6 specimens were fabricated. The values of b/t were ranged from 60 to 100. From the tests, Maximum increase of 16% was also achieved in axial-load capacity with three transverse layered CFRP applied on four sides of steel tubes. The load capacity decreased up to 41% comparing with nominal load capacity of unstrengthened CFT column. However, for CFRP strengthened CFT, the load capacity decreased up to 32%. Finally, from the load-strain relationships, the local buckling occurred before yield point of steel tubes. Also, from the load-strain relationships, it was observed that local buckling were delayed on CFT columns by CFRP sheets retrofitting.

• Journal of the Korean Society of Combustion
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• v.7 no.4
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• pp.36-44
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• 2002

Carbon molecules with closed-cage structures are called fullerenes $(C_{60},\;C_{70})$, whose applications include super-conductors, sensors, catalysts, optical and electronic device, polymer composites, and biological and medical materials. The synthesis of fullerenes has been recently studied with low-pressure benzene/argon/oxygen flames. The formation of fullerene is known as molecular weight growth processes of PAHs (polycyclic aromatic hydrocarbon). This study presents results of PAHs and fullerene measurements performed in a low-pressure benzene/argon/oxygen normal co-flow laminar diffusion flame. Through the central tube of the burner, benzene vapors carried by argon are injected. The benzene vapors are made in a temperature-controlled bubbler. The burner is located in a chamber, equipped with a sampling system for direct collection of condensable species from the flame, and exhausted to a vacuum pump. Samples of the condensable are analyzed by HPLC (High Performance Liquid Chromatography) to determine the yields of PAHs and fullerene. Also, we computed mole fraction of fullerene and PAHs in a nearly sooting low pressure premixed, one-dimensional benzene/argon/oxygen flame (equivalence ratio ${\Phi}=2.4$, pressure=5.33kPa). The object of computation was to investigate the formation mechanism of fullerenes and PAHs. The computations were performed with CHEMKIN/PREMIX. As a result of this study, fullerenes were synthesized in a low pressure (20torr) $C_6H_6/Ar/O_2$ flames and the highest concentration of fullerene was detected just above the visible surface of a flame.

• Radiation Oncology Journal
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• v.6 no.2
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• pp.263-268
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• 1988

This paper presents dose distributions in water around Fletcher-Suit colpostat containing $^{137}Cs$ tube, and shielding effect of Internal lead shield. Using ready packed film, author measured dose distribution in water around the colpostat containing cesium source. Nine sheets of films on one side of the colpostat are packed with acryl frames cut out so as to fill water, and irradiated in water by cesium source in the colpostat. Dose distributions on transverse plane and upper plane 0.5cm from upper surface of the colpostat were measured. Shielding effect was greater in upper medial direction than in lower medial direction. And that was the greatest around $30^{\circ}$ from the axis of the colpostat on upper side and around $50^{\circ}$on lower side. In the region 7cm from the center of the colpostat, shielding efficiency was 0.23 to 0.35 on the lower $50^{\circ}$ and 0.26 to 0.42 on the upper $30^{\circ}$, and decreased with increase of distance.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.5
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• pp.541-548
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• 2017

A theoretical study on gas-liquid two-phase flow flushing systemnitrogen gas to the oil used for existing flushing equipment was conducted on the basis of ISO code so as to improve performance of existing high-temperature oil flushing equipment used in ocean plant facility drying field. For study, we analyzed process simulation results mixed fluid mixing ratio, temperature, Reynolds number and liquid hold up affectcleaning performance after designing oil-nitrogen gas mixture flushing system process. As a result, as the volume flow rate of mixed fluid increases with the tube diameter the volume fraction of the gas phase constant, the liquid fraction difference value at the inlet and outlet of horizontal hydraulic piping increases. It was found that the phase distribution between oil and nitrogen gas bubbles varies depending on the position the pipe lengthdirection. This change in phase distribution is expected to have a significant impact on the clean performance of an oil-nitrogen gas mixture flushing system.

• Journal of Korea Water Resources Association
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• v.49 no.4
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• pp.347-359
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• 2016

Flow input from the basin will not remain the same as before due to climate changes. Since the predictions on river discharge due to climate change is given by scenarios, various discharge scenarios were prepared in this study. For a long term and reach prediction, semi-two dimensional sediment transport model, GSTARS, was used. The flood water surface elevations predicted by GSTARS model were analysed statistically and it was concluded that the model is applicable for the South Han River. Three stream tubes is the most suitable to simulate two dimensional river geometric change River geometric changes. For sediment load computation, Ackers and White equation and Yang equation were resonable. River will become narrower regardless of discharge variation, more discharge results in deeper channel.

• Journal of the Korea Society of Computer and Information
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• v.25 no.7
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• pp.65-73
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• 2020

Viral video advertising is being used in the advertising and film industry for pre-promotion of certain products or pre-release films which has a lot of effect on investment. An analysis of viral video recognition is needed to predict future development directions. In response, the study conducted a survey on viral videos, focusing on college students in their 20s, who are the most exposed to advertisements and movies. Through this, the survey was conducted on recognition of viral videos, memorable viral videos, satisfaction level, message propagation method, positiveness of viral videos, expected future development, and desired viral video type. The survey showed that viral video recognition was 16.7% and the most memorable viral video; the "Let it Go" viral video from the movie "Frozen" was 69.1 %, according to the survey. The satisfaction level was not high at 31.2 %, and 73.5% of people sent messages to others after watching viral videos, which was very high. Negative opinions on viral videos were low at 13.7 %. 64.5% of the surveyors said the future of the viral videos would "develop" and 6.7% said would "not develop."