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AKGÜL, AHMET

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AKGÜL

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    Günümüz Dijital Ofset Kalıp Teknolojisi
    (2003-09-30) AKGÜL, AHMET; ACAR BÜYÜKPEHLİVAN, GÜLHAN; ÜNAL H., AKGÜL A., ACAR BÜYÜKPEHLİVAN G., KAYGUSUZ A.
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    PublicationOpen Access
    Analysis of the parameters determining the effect of coated and uncoated papers on print quality
    (2023-10-01) SESLİ, YASEMİN; AKGÜL, AHMET; OKTAV, MEHMET; SESLİ Y., HAYTA P., AKGÜL A., OKTAV M.
    Both paper and ink are the two main raw materials in the manufacture of printed materials. The visual quality of the printed product is very important. Printing an image on paper with ink in high resolution is dependent on the quality of the interfacial relationship between paper and ink. Newsprint, book paper, and pure cellulose-based high-grade paper pulp where the mechanical wood pulp is intensively utilized have porous structures. Coldset offset printing is used for printing on these papers. The coldset offset printing is a printing process where drying occurs late by evaporation of the liquid portion of the ink and absorption into the paper. The ink can sometimes take several days to dry completely (solidify). During this drying process, the ink penetrates the cellulose capillaries in the paper in the vertical direction and behaves the same in the horizontal direction. The dot diameter, which mechanically grows due to the printing pressure (dot gain), grows even larger by spontaneous micro-steps during the drying process. It tends to cross to the back surface of the paper in a vertical direction. For this reason, the paper-ink interfacial behavior is a critical parameter that should be maintained under control as much as possible. The rough surface, porous structure and humidity of the paper, the viscosity and amount of ink printed on the paper surface, the printing pressure at the NIP point, and the physical conditions of the printing room are influential in this interfacial relationship. In this study, the factors that affect the image quality in printing on uncoated and coated papers were investigated by test printing. The CMYK test scale, which was specially prepared for the examination of print quality, was printed with Coldset Offset Printing on smooth papers coated with woodfree coated paper and woodfree uncoated paper, which are the best examples of uncoated papers and are widely used especially in book production. After printing, the surface of the papers was measured with a spectrophotometer and the dot growth and trapping values were determined. Surface and interfacial images of the prints were taken with a stereoscopic microscope and visual examinations were undertaken.
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    PublicationOpen Access
    A simple mathematical tool to forecast COVID-19 cumulative case numbers
    (ELSEVIER - DIVISION REED ELSEVIER INDIA PVT LTD, 2021-10) AKGÜL, AHMET; Balak, Naci; Inan, Deniz; Ganau, Mario; Zoia, Cesare; Sonmez, Sinan; Kurt, Batuhan; Akgul, Ahmet; Tez, Mujgan
    Objective: Mathematical models are known to help determine potential intervention strategies by providing an approximate idea of the transmission dynamics of infectious diseases. To develop proper responses, not only are more accurate disease spread models needed, but also those that are easy to use. Materials and methods: As of July 1, 2020, we selected the 20 countries with the highest numbers of COVID-19 cases in the world. Using the Verhulst-Pearl logistic function formula, we calculated estimates for the total number of cases for each country. We compared these estimates to the actual figures given by the WHO on the same dates. Finally, the formula was tested for longer-term reliability at t = 18 and t = 40 weeks. Results: The Verhulst-Pearl logistic function formula estimated the actual numbers precisely, with only a 0.5% discrepancy on average for the first month. For all countries in the study and the world at large, the estimates for the 40th week were usually overestimated, although the estimates for some countries were still relatively close to the actual numbers in the forecasting long term. The estimated number for the world in general was about 8 times that actually observed for the long term. Conclusions: The Verhulst-Pearl equation has the advantage of being very straightforward and applicable in clinical use for predicting the demand on hospitals in the short term of 4-6 weeks, which is usually enough time to reschedule elective procedures and free beds for new waves of the pandemic patients.