A gradient boosting machine learning approach in modeling the impact of temperature and humidity on the transmission rate of COVID-19 in India

Applied Intelligence - Meteorological parameters were crucial and effective factors in past infectious diseases, like influenza and severe acute respiratory syndrome (SARS), etc. The present study...     

PolyDADMAC and dimethylamine as precursors of N-nitrosodimethylamine during ozonation: reaction kinetics and mechanisms

Interactions of ozone with organic precursors during water treatment may generate carcinogenic N-nitrosodimethylamine (NDMA) byproduct. This study investigates the reaction mechanisms responsible for NDMA formation from ozonation of the commonly used poly(diallyldimethylammonium chloride) (polyDADMAC) coagulant. Upon ozonation, polyDADMAC yields the highest amount of NDMA among several water treatment polymers, including polyamines and cationic polyacrylamides. Ozonation transforms polyDADMAC to dimethylamine (DMA) and NDMA formation is correlated to polyDADMAC degradation and DMA release. Hydroxyl radicals generated from ozone play an important role in the degradation of polyDADMAC's quaternary ammonium ring groups and subsequent release of secondary amine. Although nitrite and formaldehyde are detected as ozonation products of DMA and polyDADMAC, contribution of formaldehyde-enhanced nitrosation pathway is determined to be insignificant in NDMA formation. In contrast, reaction of hydroxylamine, another ozonation product of DMA, with DMA in the presence of ozone is deemed critical in the formation of NDMA during ozonation. The study results show that that contact of polyDADMAC with ozone will lead to release of the more potent NDMA precursor DMA but may not generate a significant amount of NDMA under typical drinking water treatment conditions due to low yield. The mechanistic understanding from this study can help develop source control strategies for minimization of NDMA formation risk at water and wastewater utilities.     

Bituminous polyurethane network: Preparation,properties, and end use

Industrial‐grade bitumen (85:25) was treated with 4,4′‐diphenyl methane diisocyanate as a blocking agent to make it compatible with polyurethane resin. Optimization of treatment conditions for the bitumen such as isocyanate dose (～3 wt % of bitumen), reaction temperature (180°C), and treatment time (120 min) was done on the basis of estimating its residual acid value and unreacted ? NCO groups. Formation of the urethanized bituminous species after treatment resulted in a reduction in the glass‐transition temperature of the base bitumen from ?9.63°C to ?17.09°C and in moisture vapor transmission from 16.95 to 12.21 g 24 h^?1 m^?2. The bituminous networks were prepared from these treated/SBS‐modified treated bitumen and polyurethane prepolymers by in situ and conventional liquid blending methods. Lack of low‐temperature flexibility in the bituminous network made from the blending method restricted its use for waterproofing/sealing purposes. Modulated differential scanning calorimetry showed the presence of two overlapping glass‐transition temperatures and an endothermic peak in the in situ prepared networks similar to the base bitumen, evidence of a close intermixing of the bitumen constituents with the polyurethane phases. Rheological studies revealed that the SBS‐modified bituminous polyurethane network exhibited superior behavior than that of other systems in terms of stiffness and elasticity over a wide range of frequencies. The compounded bituminous networks satisfied the requirements of standard specifications and can be suitably used for waterproofing purpose and sealing of concrete joints. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 217–226, 2006     

An integrated model of dynamic cellular manufacturing and supply chain system design

In a global dynamic environment, there is a need to develop organizations and facilities significantly more flexible and responsive. This work proposes an integrated model of dynamic cellular manufacturing and supply chain design with consideration of various issues such as multi-plant locations, multiple markets, multi-time periods, reconfiguration, etc. The model objective was to minimize the sum of various costs such as facility/plant to market transportation cost, part holding cost at a facility/plant, part outsourcing cost, machine procurement cost, machine maintenance overhead cost, machine repair cost, production loss cost due to machine breakdown, machine operation cost, setup cost, tool consumption cost, inter-cell travel cost, intra-cell travel cost, and system reconfiguration cost for the entire planning time horizon. To study the model, three procedures—LINGO, artificial immune system, and hybrid artificial immune system—are used to perform computational experiment on some problems from existing literature. The best result generally is found by the hybrid artificial immune system algorithm.