Analysis of arrhenius activation energy and chemical reaction in nanofluid flow and heat transfer Over a thin moving needle

Objective: A numerical and theoretical study is developed to analyze the combined effect of activation energy and chemical reaction in the flow of nanofluids due to the thin moving needle using the mathematical nanofluid model offered by Buongiorno. A passively controlled nanoparticle volume fraction boundary is assumed rather than actively controlled. Methods: A similarity transformation is utilized to convert the governing partial differential equations to a set of ordinary differential equations which are then solved numerically by Runge-Kutta Shooting Method (RKSM). The physical characteristics of flow, heat and mass transfer are illustrated via graphs and tables for some set of values of governing parameters. Results: In addition, the basic non-linear governing equations are solved analytically using semi-analytical technique called Differential transform method (DTM) and the comparison has been made with the numerical and the published results. Conclusion: The present study reveals that the ratio between the needle velocity and the composite velocity brings out to increase the velocity distribution with λ<0. Moreover, the activation energy influences the chemical species to react from the thickness of the concentration layer η=0.6 and the fraction of nanoparticles to the fluid is significantly more away from the needle surface.

Systematic oxygen impurity reduction in smooth N-Polar GaN by chemical potential control

Process chemical potential control (CPC) and dislocation reduction were implemented to control oxygen concentration in N-polar GaN layers grown on sapphire substrates via metal organic chemical vapor deposition (MOCVD). Process CPC offers a systematic and predictive framework for MOCVD experimental design relating the universal thermodynamic parameter, supersaturation directly to oxygen incorporation in N-polar GaN. As process supersaturation was changed from ~30 to 3,400, the formation energy of the oxygen point defect increased, which resulted in a 25-fold decrease in oxygen incorporation. Reducing dislocations by approximately a factor of 4 (to ~10^9 cm^-3) allowed for further reduction of oxygen incorporation to the low-10^17 cm^-3 range. Smooth N-polar GaN layers with low oxygen content were achieved by a two-step process, whereas first a 1 µm thick smooth N-polar layer with high oxygen concentration was grown, followed by low oxygen concentration layer grown at high supersaturation.

Within-day and between-day chlorophyll a dynamics during summer in Guanting Reservoir, Beijing, China

&lt;p&gt;Recognizing intra- and inter-daily dynamics of Chlorophyll a (Chl-a) and its related environmental variables in consecutive days play an important role in assessing and managing water quality and eutrophication. In this study, the water temperature, nutrients, Chl-a concentration&amp;#160; and meteorological factors were collected at six sampling times in Guanting reservoir during summer. Chl-a concentration generally decreased from last May to primary September. At both test times, thermal stratification and mixing in the water column controlled the variation of maximum Chl-a concentration layer at both temporal and vertical scale. The position of the maximum Chl-a concentration layer between days generally followed the same dynamics as thermocline. Daily stratifications were temporary and maximum Chl-a concentration layer varies downwelling by wind driven; hence, the vertical distribution of Chl-a concentration was homogenized at night. Surface Chl-a concentration decreased during the day and increased at night, except on rainy days. The results of Person correlations and principal component analysis indicated that raw surface and daily average Chl-a concentration generally changed as a negative function of solar radiation, wind speed, water temperature and air temperature. However, when a five hour time lag is considered, the relationship between surface Chl-a concentration, water temperature and all meteorological factors became significantly positive.&lt;/p&gt;