• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.2
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• pp.137-143
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• 2022

Composite materials, being light-weight and of high mechanical strength, are increasingly used in various industries such as the aerospace, automobile, sporting-goods manufacturing, and ship-building industries. Recently, manufacturing of composite materials using 3D printers has increased. 3D-printed composite materials are made in free-form and adapted for end-use by adjusting the fiber content and orientation. However, research on the machining of 3D printed composite materials is limited. The aim of this study is to develop a machine learning method to select machining conditions for machining of 3D-printed composite materials. The composite material was composed of Onyx and carbon fibers and stacked sequentially. The experiments were performed using the following machining conditions: spindle speed, feed rate, depth of cut, and machining direction. Cutting forces of the different machining conditions were measured by milling the composite materials. PCA, a method of machine learning, was developed to select the machining conditions and will be used in subsequent experiments under various machining conditions.

• Advances in concrete construction
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• v.13 no.2
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• pp.153-162
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• 2022

Prefabricated exterior wall panel is the main non-load-bearing component of assembly building, which affects the comprehensive performance of thermal insulation and durability of the building. It is of great significance to develop new prefabricated exterior wall panel with durable and lightweight characteristics for the development of energy-saving and assembly building. In the prefabricated sandwich insulation hanging wall panel, the selection of material for the outer layer and the arrangement of the connector of the inner and outer wall layers affect the mechanical performance and durability of the wall panels. In this paper, high performance cement-based composites (HPFRC) are used in the outer layer of the new type wall panel. FRP bars are used as the interface connector. Through experiments and analysis, the influence of the arrangement of connectors on the mechanical behaviors of thin-walled composite wall panel and the panel with window openings under two working conditions are investigated. The failure modes and the role of connectors of thin-walled composite wallboard are analyzed. The influence of the thickness of the wall layer and their combination on the strain growth of the control section, the initial crack resistance, the ultimate bearing capacity and the deformation of the wall panels are analyzed. The research work provides a technical reference for the engineering design of the light-weight thin-walled and durable composite sandwich wall panel.

• Steel and Composite Structures
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• v.52 no.4
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• pp.451-460
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• 2024

Hollow reinforced concrete columns confined with GFRP tubes (GRCH) are composite members composed of the outer GFRP tube, the PVC or other plastic tube as the inner tube, and the reinforced concrete between two tubes. Because of their high ductility, light weight, corrosion resistance and convenient construction, many researchers pay attention to the composite members. However, there are few studies on GRCH members under eccentric compression compared with those under axial compression. Eight hollow columns were tested under eccentric compression, including one axial compression column and seven eccentric compression columns. The failure modes and force mechanisms of GRCH members were analyzed, considering the varying in hollow ratio, reinforcement ratio and eccentricity. The test results showed that configuring steel bars can greatly increase the bearing capacity and ductility of the members. Each component (GFRP tube, concrete, steel bar) had good deformation coordination and the strength of each material could be fully utilized. But for specimens with larger eccentricity ratio (e_r=0.4) and larger hollow ratio (χ=0.55), the restraining effect of GFRP tube on concrete was significantly decreased.

• Journal of Sensor Science and Technology
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• v.6 no.1
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• pp.35-42
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• 1997

The optical biosensor using the electrically controlled release of reactive reagent is developed for the detection of peroxide. Rapid degradation of polymer complex of PEOx and PMAA occurs as the applied current increases and thus released amount of HPA increases. The degradation velocity of polymer and the amount of HPA released are linearly proportional to the applied current. Peroxide is reacted with the released reagent by peroxidase and then the product, a fluorescent dimer DBDA, is formed. The monochromic light from light source (150W Xe arc ramp) excites the DBDA and the excited light is transmitted through an optical fiber to be detected by a photodiode array. The change of fluorescence intensity is related to the change of peroxide concentration. The peroxidase is entrapped in Ca-alginate get on the inner surface. The biosensor has the linear signal range of 0.025mM-10.mM peroxide. By applying the step function of peroxide, reproducibility of biosensor has been investigated. The mathematical model is constructed by the combination of enzyme kinetics with reactor flow model. Good agreement is obtained between the experimental result and model prediction in the sensor signal.

• Journal of The Korean Society of Grassland and Forage Science
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• v.26 no.3
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• pp.133-138
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• 2006

This experiment was conducted to determine the effect of wrap color on the quality of round baled grass silage at experimental field of Grassland and Forages Division, National Livestock Research Institute, RDA, Suwon from 1997 to 1998. The experiment was consist of randomized block design with three replications. The treatments were three wrap color(white, black and light green). Wrap color did not affect chemical composition. Fiber components(ADF and NDF) of all silages after 2 months were higher than those of forages at ensiling. Among tested wrap colors, white color wrap resulted in lower pH than others (p<0.05) but, there was no significant difference between black and light green color. Dry matter content of light green color was the highest among warp colors, but there was no signifiant difference (p<0.05). Acetic and butyric acid contents of all plots. were not found significant difference among wrap color and wrap color did not influence lactic acid and organic acid concentration. The effect of wrap color on the quality grade and DM loss also were not found significant difference. Results of this study indicate that wrap color does not influence the quality of silage.

• Fire Science and Engineering
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• v.30 no.4
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• pp.27-38
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• 2016

The paper reports the development of a distributed temperature sensing (DTS) system, which is a fire detection system using optical sensor linear detectors that depends on foreign and domestic technologies. This study accordingly analyzed the electrical signal patterns of Raman scattering light mainly used for temperature sensing among back-scattered light generated in optical fiber by using an oscilloscope. Through the measurement results, it could be verified that the Stokes signal patterns had little change by the temperature increase, but the temperature-sensitive anti-Stokes patterns had relative increase of the changes. This study developed a K-DTS system, which is an optical sensor linear fire detection system composed of an optical repeater and a receiver that can detect fires using Raman scattering light. It could be verified that the developed K-DTS system satisfied the type approval standards through the sensitivity tests using the rate of rise type and fixed temperature type sensitivity testers. In addition, performance experiments have been performed for performance evaluation of the K-DTS system developed in comparison with S-DTS system which has been imported from abroad and widely used in Korea. It can be confirmed from the results of the performance experiments using model tunnels that comparable performances can be obtained in fire detection locations and the measurements of fire temperatures.

• Journal of the korean academy of Pediatric Dentistry
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• v.37 no.1
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• pp.13-23
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• 2010

This study was performed to compare the quality of image processing between the newly developed prototype using light emitting diode(LED) and the conventional $DIFOTI^{TM}$ system(EOS Inc., USA). To estimate the optimal light emitting power for the improved images, primary enamel surfaces treated under Carbopol 907 de-mineralizing solution were taken daily during 20 days of experimental periods by both DIFOTI systems. The results of comparative analyses on the images obtained from both systems with polarized image as gold standard can be summarized as follows: 1. Trans-illumination indices of images taken from primary enamel surfaces were decreased with time in both systems. 2. The differences of intensity of luminance between sound and de-mineralized enamel surface in prototype DIFOTI system was shown to be relatively smaller than conventional $DIFOTI^{TM}$ system. 3. From the comparative analysis of images from both DIFOTI system with polarized images as gold standard, the difference between sound and de-mineralized enamel surface of intensity of luminance of $DIFOTI^{TM}$ system was more correlated to polarized images than prototype of DIFOTI system. With the optimal LED emitting power, the control of aperture of digital camera is considered as the another key factor to improve the DIFOTI images. For the best image quality and analysis, the development of the improved image processing software is required.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.6
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• pp.774-780
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• 2014

This research aims to investigate the superstructure characteristics of the CFRP-yachts whose hulls are made of the light-weight material CFRP. CFRP-yachts, which belong to light-weight yachts, have a tendency of having very small superstructures compared to other vessels of the same length, and such a tendency is closely related to stability. In this research, a comparison of shape characteristics was made between common composite-plastic yachts and CFRP-yachts to find out the shape characteristics of CFRP-yacht. In the meantime, a case study was conducted concerning shape changes in superstructure to understand the effect of such changes on stability. For this purpose the shapes of a total of 10 GFRP-yachts and CFRP-yachts were comparatively analyzed, and the result showed the tendency of their hulls and superstructures. Whereas the case study on stability assessment involved various superstructure shapes of CFRP yachts, for assessment by superstructure size. Stability assessment was according to ISO 12217 (Small craft Stability and buoyancy assessment and categorization). A program was also developed based on stability assessment process due to rolling in beam waves and wind, and it was applied to the case study. The result of the case study showed that the windage area distribution tendency of the yachts whose hulls were made of the light-weight material CFRP was similar to that of the GFRP-yachts, but that the superstructure shapes of the CFRP-yachts were about 50% smaller than those of the GFRP-yachts. In addition, the stability assessment involving various superstructure areas of the CFRP-yachts showed that problems with stability occurred when their superstructure sizes were similar to, or larger by about 10% than, those of the GFRP-yachts.

• Food Engineering Progress
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• v.13 no.4
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• pp.297-301
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• 2009

This study was performed to develop a prediction model of sugar content for strawberry. Near-infrared (NIR) spectroscopy has been prevailed for on-line and portable applications for non-invasive quality assessment of intact fruit. This work presents effects of illumination method and coating of reflection surface of light source on prediction result of sugar content. Effect of preprocessing methods was also examined. A low-cost commercially available VIS/NIR spectrometer was used for estimation of total soluble solids content (Brix). To predict sugar contents of strawberry, the best results were obtained with the spectrum data measured under intensive illuminations at three locations induced from the light source with fiber optic bundles. Gold coating of reflection surface of light source lamp gave favorable effect to prediction result. The best results in validation of PLSR model were $r_{SEP}$ = 0.891 and SEP = 0.443 Brix under OSC preprocessing and those of PCR were $r_{SEP}$ = 0.845, SEP $r_{SEP}$= 0.520 Brix, under no preprocessing.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.8
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• pp.253-263
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• 2013

Frequency Scanning Interferometry(FSI) system, one of the most promising optical surface measurement techniques, generally results in superior optical performance comparing with other 3-dimensional measuring methods as its hardware structure is fixed in operation and only the light frequency is scanned in a specific spectral band without vertical scanning of the target surface or the objective lens. FSI system collects a set of images of interference fringe by changing the frequency of light source. After that, it transforms intensity data of acquired image into frequency information, and calculates the height profile of target objects with the help of frequency analysis based on Fast Fourier Transform(FFT). However, it still suffers from optical noise on target surfaces and relatively long processing time due to the number of images acquired in frequency scanning phase. 1) a Polarization-based Frequency Scanning Interferometry(PFSI) is proposed for optical noise robustness. It consists of tunable laser for light source, ${\lambda}/4$ plate in front of reference mirror, ${\lambda}/4$ plate in front of target object, polarizing beam splitter, polarizer in front of image sensor, polarizer in front of the fiber coupled light source, ${\lambda}/2$ plate between PBS and polarizer of the light source. Using the proposed system, we can solve the problem of fringe image with low contrast by using polarization technique. Also, we can control light distribution of object beam and reference beam. 2) the signal processing acceleration method is proposed for PFSI, based on parallel processing architecture, which consists of parallel processing hardware and software such as Graphic Processing Unit(GPU) and Compute Unified Device Architecture(CUDA). As a result, the processing time reaches into tact time level of real-time processing. Finally, the proposed system is evaluated in terms of accuracy and processing speed through a series of experiment and the obtained results show the effectiveness of the proposed system and method.