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Terahertz Propagation in Tissues and Its Thickness Limitation
Published in Lingyan Shi, Robert R. Alfano, Deep Imaging in Tissue and Biomedical Materials, 2017
Preparation of samples can also affect the transmission of THz pulses. Freezing tissues rapidly as in snap freezing which employ liquid nitrogen can result in reduced of ice crystals as compared to regular slow freezing processes. This can reduce scattering losses, which can enhance differences between healthy and diseased brain tissue [43].
Recent initiatives in effective modeling of spray drying
Published in Drying Technology, 2021
Ramin Razmi, Hasan Jubaer, Michał Krempski-Smejda, Maciej Jaskulski, Jie Xiao, Xiao Dong Chen, Meng Wai Woo
While Zbiciński[37] integrated this detailed complexity into the one-dimensional model, the validation data provided was only derived from the comparison with outlet air measurements. More detailed validation was, however, subsequently reported by Pearce[9] using the same theoretical framework. In the study,[9] a sampling device and a snap freezing method involving liquid nitrogen were used to measure the diameter of the spray at different axial position of the conical spray. The droplet size was taken to delineate the rate of evaporation in the spray cone region. Results from that pilot scale experiment (measurements only undertaken in the spray zone) were in good agreement with the proposed model by Zbiciński.[37] Comparing these earlier works cited above, it is interesting to note that more recent one-dimensional simulation works[7,8,10,36] also reported reasonable agreement for comparison with experimental data, despite not capturing the spray dispersion phenomenon (uniform distribution as shown in Figure 1a). It is noteworthy that all of these validation works, apart from that reported by Pearce,[9] rely mainly on comparison at the outlet. More detailed measurements within the dryer need to be undertaken to fully ascertain the importance of capturing dispersion effect. Perhaps, a more simplified approach (avoiding the need for dispersion modeling) combining both frameworks reported so far can be to assume an ‘equivalent chamber’ diameter with uniformly distributed droplets based on the developed spray cone diameter (if can be estimated a priori) or the size of the annular drying air inlet. While these amount to some pragmatic suggestions, the use of the latter approach based on the annular drying air inlet has been recently adopted by Jubaer et al.[40] for estimating the particle residence time in a contract manufacturing scale spray dryer.