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Purpose The purpose of this study is to reveal the usability of waste paper sludge on the production of composite materials and the printability of their surfaces were investigated. Design/methodology/approach First, composite plates were produced by using dried and milled waste sludge together with polyester resin and epoxy. Screen printing using water, solvent and UV-based inks were carried out. Findings It was determined that UV and solvent-based inks in both resin groups were permanently attached to the surface of composite plates produced using paper mill waste sludge, while it was found that the adhesion was not achieved sufficiently in cardboard factory waste sludge. Originality/value The unique aspect of this study is obtained the composite plates from paper mill and cardboard mill waste sludge and improved the printability of them.

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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.

During this period, the total number of confirmed cases reached 148,067, according to figures reported by the Ministry of Health-Turkey. In our previous study, where we employed the SIR model to predict the progress of the COVID-19 pandemic, it was emphasized how imperative it is to forecast the pandemic's progression in the coming future to devise an appropriate policy response. 1 Besides predicting the future progress of the pandemic, an equally maybe more critical policy question concerns the timing for easing and eventually lifting limitations such as curfews and closure of schools and businesses. As of now, since there is no preventive vaccine or prophylactic drug for COVID-19, it is widely accepted that the transmission can only be reduced by isolation 127 127 127