• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.7
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• pp.58-65
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• 2021

Research on general particle image velocimetry (PIV) has been conducted extensively, but studies on granular PIV are relatively insufficient. In addition, the parameters used for analyzing granular PIV need to be optimized. In this study, we analyzed the error of velocity measurements based on the interrogation area (64-192 pixel), frame per second (30-120 FPS), and video resolution [ultrahigh definition (UHD) and high definition (HD)] within the velocity range typically measured in hoppers. The estimated errors of the granular PIV were below 5%, which is generally acceptable. However, considering the data reliability, the flow velocity in the hopper could be measured with less than 5% error at 120 FPS or higher in the HD resolution and 30 FPS or higher in the UHD resolution.

• Journal of the Korean Geotechnical Society
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• v.25 no.12
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• pp.119-130
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• 2009

To measure the soil deformation, two common techniques of the digital image analysis-Particle Image Velocimetry (PIV) and Digital Image Correlation (DIC)-have been used. To generally apply these techniques to the soils, the accuracy of these techniques should be evaluated under various conditions. In this study, the influence factors including the image resolution, the degree of displacement and deformation, the size of pixel subsets, and analysis techniques were analyzed. The deformation of an idealized particle assembly using the discrete element method was measured by the digital image analyses, and then the results were compared with the actual deformations. To conduct the optimal digital image analysis, various factors are systematically analyzed in terms of the degree of the displacement and the deformation.

• Pediatric Infection and Vaccine
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• v.27 no.3
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• pp.198-204
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• 2020

Cytomegalovirus (CMV) disease is rare in children who receive anticancer chemotherapy and have no history of stem cell transplantation (SCT). We report a case of CMV retinitis that developed during maintenance chemotherapy for acute leukemia. A 7-year-old boy developed decreased visual acuity and persistent pancytopenia during maintenance chemotherapy. Laboratory investigations initially showed significant CMV antigenemia (51 positive cells/200,000 leukocytes); however, antiviral therapy was not deemed necessary in this patient who had no history of SCT. CMV antigenemia worsened to 170 positive cells/200,000 leukocytes over 3 weeks. Ophthalmological examination revealed multiple bilateral retinal infiltrates and granular lesions. He was diagnosed with CMV retinitis and was treated with a 4-week course of intravenous ganciclovir and intravitreal injection of ganciclovir 6 times, followed by a 1-month course of orally administered valganciclovir. A CMV antigenemia assay showed negative results, and follow-up fundoscopy revealed lesser retinal infiltration after the sixth intravitreal ganciclovir injection. Future studies should focus on the development of standardized screening methods and preemptive therapeutic strategies for CMV disease in high-risk children.