Size-fractionated measurements of ambient ultrafine particle chemical composition in Los Angeles using the NanoMOUDI

Ambient ultrafine particles have gained attention with recent evidence showing them to be more toxic than larger ambient particles. Few studies have investigated the distribution of chemical constituents within the ultrafine range. The current study explores the size-fractionated ultrafine (10-180 nm) chemical composition at urban source sites (USC and Long Beach) and inland receptor sites (Riverside and Upland) in the Los Angeles basin over three different seasons. Size-fractionated ultrafine particles were collected by a NanoMOUDI over a period of 2 weeks at each site. Measurements of ultrafine mass concentrations varied from 0.86 to 3.5 microg/m3 with the highest concentrations observed in the fall. The chemical composition of ultrafine particles ranged from 32 to 69% for organic carbon (OC), 1-34% for elemental carbon (EC), 0-24% for sulfate, and 0-4% for nitrate. A distinct OC mode was observed between 18 and 56 nm in the summer, possibly indicating photochemical secondary organic aerosol formation. The EC levels are higher in winter at the source sites due to lower inversion heights and are higher in summer at the receptor sites due to increased long-range transport from upwind source areas. Nitrate and sulfate were measurable only in the larger particle size ranges of ultrafine PM. Collocated continuous measurements of particle size distributions and gaseous pollutants helped to differentiate ultrafine particle sources at each site.     

Buoyancy forces and activation energy on the MHD radiative flow over an exponentially stretching sheet with second‐order slip

The current study explores the effects of second‐order slip and activation energy (AE) on the magnetohydrodynamic and radiative fluid flow caused by a surface with exponential stretching. The binary chemical reaction with mixed convection is considered in this physical model to discover the heat transfer phenomenon. The governing system of equations leads to a set of nonlinear ordinary differential equations by using scaling analysis. The transformed system is calculated computationally by using the most powerful Shooting procedure with the support of MATLAB software. The characteristics of various flow parameters on the governing flow field are exhibited pictorially and deliberated. The results revealed that the coefficient of heat and mass transfer upsurge with growing values of the second‐order slip parameter and skin friction coefficient has a reverse effect on the first‐order slip parameter. The thermal measure of the fluid in the presence of suction and slip conditions is seen to be lesser than that with the nonslip and nonsuction conditions. The heat measure of the fluid augments with the rising buoyancy parameter. The influence of slips coupled with AE is significant in the fluid flow and heat transfer characteristics. The outputs of the current investigation are validated by comparing the Nusselt number with the available results and are found to closely agree as a limiting case.     

A unified model for multi-turn closed-loop pulsating heat pipe

Numerical modeling of  the multi-turn closed-loop pulsating heat pipe (CLPHP) in the bottom, horizontal, and top heat mode is presented in this paper, with water as working fluid. Modeling is carried out for 2-mm ID CLPHP having 5, 16, and 32 turns at different orientations for 10 different cases. Momentum and heat transfer variations with time are investigated by numerically solving the one-dimensional governing equations for vapor bubble and liquid plugs. Instead of considering all the vapor bubble at saturation temperature, vapor bubbles are allowed to remain in super-heated condition. Film thickness is found using a correlation. Two-phase heat transfer coefficient is calculated by considering conduction through the thin film at liquid–vapor interface. Liquid plug merging and splitting result in continuous variation in the number of liquid plugs and vapor bubble with time, which is also considered in the code. During the merging of liquid plugs, a time step-adaptive scheme is implemented and this minimum time step was found to be 10⁻⁷ s. Model results are compared with the experimental results from literature for heat transfer and the maximum variation in heat transfer for all these cases is below ±39%.     

Enhancement of condensate water quantity and coefficient of performance of an air conditioning system: An experimental study

The objective of the present work is to increase the quantity of condensate water from atmospheric air during the air conditioning (A/C) process by using two techniques: increasing moisture content in atmospheric air by adding steam and passing compressed air instead of atmospheric air, respectively. The experiment was performed with both capillary valve and thermostatic expansion valve operations for assessing the volume flow rates (VFRs) of condensate and coefficient of performance (COP) concerning the air A/C arrangement. The control valve operated for the steam supply case was at half valve opening and one-fourth opening, respectively. The R-22 refrigerant was used in this study. From this study, it was perceived that the condensate water quantity was increased by adding the moisture to the inlet air for the A/C system simultaneously with the usage of compressed air. Furthermore, the COP of the system was also compared to normal atmospheric air admission conditions. The compressed air and steam admission to the A/C system has shown a tremendous increase in COP together with the VFR of the system rather than atmospheric air admission conditions.     

Binary Galois field based asynchronous scheduling protocol for delay tolerant networks

Wireless Networks - Neighbour discovery plays a crucial role for communication in sparsely dense mobile networks, especially in delay tolerant networks, where neighbour discovery latency is...     

Life cycle cost analysis of natural indigo dye production from Indigofera tinctoria L. plant biomass: a case study of India

Clean Technologies and Environmental Policy - The emerging demand of natural indigo dye due to the environmental and sociological concerns imparted by the synthetic dye helps in leveraging the...     

A comparative study to evaluate the corrosion performance of Zr incorporated Cr3C2-(NiCr) coating at 900 °C

In this study zirconium incorporated Cr₃C₂-(NiCr) coating has been sprayed on three superalloys viz. Superni 718, Superni 600 and Superco 605 using D-gun technique. A comparative study has been carried out to check the cyclic oxidation in air and hot corrosion in simulated incinerator environment (40%Na₂SO₄-40%K₂SO₄-10%NaCl-10%KCl) for the coated specimens at 900 °C for 100 cycles. Oxidation kinetics has been established for all the specimens using weight change measurements. Corrosion products have been characterized using X-ray diffractometer (XRD) and scanning electron microscopy/energy-dispersive analysis (SEM/EDAX). Cr₃C₂-(NiCr) + 0.2%wtZr coating provides very good corrosion resistance in air oxidation for all the three coated superalloys. As all the three coated superalloys shows parabolic behaviour with parabolic rate constant as 0.07 × 10^?10 (g² cm^?4 s^?1) for Superni 718, 0.43 × 10^?10 (g² cm^?4 s^?1) for Superni 600 and 0.3 × 10^?10 (g² cm^?4 s^?1) for Superco 605 This coating is also effective in the molten salt environment but coating on Co-based superalloy Superco 605 did not perform satisfactorily. The parabolic rate constants for coated Superni 718 is 0.61 × 10^?10 (g² cm^?4 s^?1), for coated Superni 600 is 6.72 × 10^?10 (g² cm^?4 s^?1) and for coated Superco 605 is 17.5 × 10^?10 (g² cm^?4 s^?1).     

Phthalonitrile-carbon fiber composites

Phthalonitrile polymers offer promise as matrix materials for advanced composite applications. The phthalonitrile monomer is readily converted to a highly crosslinked thermosetting polymer in the presence of thermally stable organic amine catalysts. Rheometric studies were conducted to elucidate the optimum amine concentration for composite formulations. High quality composite panels were processed in an autoclave using unsized IM7 carbon fibers. Mechanical properties of the phthalonitrile/carbon composite are either better than or comparable to the state-of-the-art PMR-15 composites. Dynamic mechanical analysis reveal that samples postcured at elevated temperatures (375°C) do not exhibit a glass transition temperature up to 450°C and also retain °90% of their initial modulus at 450°C. Flame resistance of phthalonitrile/carbon composites, evaluated by cone calorimetric studies, excels over that of other polymeric composites for marine applications. The composites also show low water uptake, <1% after exposure to water for 16 months.     

Fabrication of nonextruded recycled rubber–polyethylene composites

This study was conducted to investigate the possibility of one-stage molding process skipping compounding extrusion for the fabrication of cross-linked polyethylene (PE)-ground tire rubber (GTR) composites. The process resulted in a wide range of composites with various properties. Response surface methodology technique based on central composite design was employed with variables: polyethylene content (PE: % per polymer fraction), dicumyl peroxide (DC: % per polymer fraction), molding residence time (RT: min), and filler content (F: % per total mass). A quadratic model was able to significantly describe tensile strength, elongation at break (EB), and impact resistance/energy of the composites as a function of PE, DC, RT, and F. Tensile strength (TS) was positively affected by PE, DC, and RT; however, it was negatively affected by the filler content. Tensile EB and impact resistance of the composites were improved by DC and RT, while reduced by PE and filler increment. Composites with TS, ultimate elongation, and impact resistance of 11.5 MPa, 140%, 244 MJ/m², respectively, were obtained under optimized conditions. The nonextrusion molding process is recommended for the fabrication of PE-GTR composites due to the higher stiffness/tensile modulus and a slightly lower strength of nonextruded composites compared to the extruded composites.