Rotating fluidized bed with a static geometry: Guidelines for design and operating conditions

Computational fluid dynamics (CFD) simulations of the hydrodynamic behavior of rotating fluidized beds in static geometry (RFB-SG) are carried out for gas–solid flows. The rotating motion of the reactor bed is induced by the tangential injection of the gas along the circumference of the fluidization chamber. Steep gradients in the gas velocity fields both in radial and tangential direction generate turbulence. The radial and tangential drag forces fluidize the particle bed in both radial and tangential direction.An Eulerian two-fluid model is used. Gas phase turbulence is accounted for by a k–ε model adapted for rotational flows. The RFB-SG simulations provide guidelines for a design and operation with a high efficiency in gas–solid momentum transfer, excellent gas–solid separation and limited solids losses. Hydrodynamic variables like the centrifugal force, the injection pressure, the radial and tangential slip velocities, solids hold-up are calculated for both polymer particles (300 μm, 950 kg/m³, Geldart Group B) and glass beads (70 μm, 2500 kg/m³, Geldart Group A) to allow for a comparison among different fluidization chamber designs. Unstable bed behavior, like slugging and channeling, is also numerically predicted.     

Interface Trap Charges Analysis on DC and High Frequency Characteristics of UTBB-FDSOI FET

Silicon - In this paper, we have studied effect of localised charges on performance of UTBB FDSOI FET. Purpose behind this work is to understand the performance of UTBB FDSOI FET under the...     

Experimental investigation of an indirect-type solar cooker for indoor cooking based on a parabolic dish collector

In the present research article, an indirect type solar cooking system has been developed for indoor cooking. In the proposed cooking system, a cooking pot has been placed at a distance of 5 m from the parabolic dish collector, and the heat has been transmitted from the collector to the cooking pot by means of heat transfer fluid. A gear pump of 40 W and insulated pipes have been used to circulate the fluid. A number of experiments have been performed to analyze the performance of the cooking system. During the investigation, the system achieved the temperature of the heat transfer fluid up to 175°C. The time taken for cooking the rice and the black grams has been observed 21 and 68min, respectively. The average thermal efficiency of the proposed system for the entire day has been achieved at 13.11%.     

Application of response surface methodology to optimize diesel engine parameters fuelled with pongamia biodiesel/diesel blends

ABSTRACT

In the present scenario, the rate of fossil fuel consumption is very high and increasing rapidly which lead to a further increase in air pollution levels. Due to an increase in pollution level, researchers are striving to discover some cleaner and environment-friendly fuels for the diesel engines. This study was focused on the optimization of the input parameters of the diesel engine running on pongamia biodiesel for improvement in the engine performance. The input parameters selected for optimization were fuel injection pressure, fuel injection timing, pongamia biodiesel blends, and engine load with respect to BTE, BSFC, exhaust gas temperature, and P_max. An experimental analysis was performed according to the response surface methodology technique. The best engine input parameters setting for getting optimum performance was found at fuel injection timing 25 bTDC, fuel injection pressure 226 bar, 40% of pongamia biodiesel blending, at 74% of maximum rated engine load. Experimental and optimized results of the output responses at optimum input parameters were compared and found in the suggested error range.     

Clustering assisted artificial neural network for handling noisy big data: An application for estimation of parameter in combined mode conduction and radiation heat transfer

A pattern net assisted mapping artificial neural network (PAMANN) model for estimation of parameters in problem with large data (1300 × 121 matrix size) is reported. A pattern net-based multilayer perceptron neural network (MLPNN) model for clustering the data, followed by mapping MLPNN model for mapping the target with the input, is developed as PAMANN model. A heat transfer problem with combined mode conduction and radiation in porous medium is solved numerically, and is called direct model. In the inverse model, a PAMANN model is developed by using data generated through the direct model. The PAMANN model is able to estimate two parameters (extinction coefficient β and convective coupling P₂) after taking temperature profile as input. The model is tested for different number of neurons in hidden layer, and different levels of noise in input data. Twelve different algorithms are explored in training of mapping MLPNN, and compared for performance. Levenberg–Marquardt algorithm is found to estimate the parameters with high accuracy, but took high CPU time. Bayesian regularization is found to consume very high CPU time with moderate accuracy in estimation of parameters. Variations in hidden layer neuron number and noise in input data, were done to analyze the performance of mapping MLPNN with different training algorithms. Algorithms O-Step Secant, conjugate gradient with Polak-Ribiére updates, and conjugate gradient with Fletcher-Reeves updates are able to handle all variations of noise and number of neurons in hidden layer, with good accuracy of estimation and low CPU time consumption. Under high computational resource LM algorithm can be used for all cases. Up to 0.99132 value of regression coefficient is obtained in mapping MLPNN model with 15 hidden neurons, indicating the high accuracy of the model. With the help of PAMANN model, highly accurate (absolute error 1.78%) estimation of parameters is obtained. The model can handle upto 1% noise in input data, while giving accurate results.     

Atomistic modeling of the effect of codoping on the atomistic structure of interfaces in α-alumina

Sintering aids or dopants have often been used successfully to limit the grain growth of alumina during sintering. Recently codoping of alumina with transition elements has been reported to produce additional effects in comparison to single doping in enhancement of creep and real in-line transmittance of light. The current study attempts to address the issue of the atomistic mechanism behind these experimentally observed codoping effects. The effect of codoping on the atomistic structure of a series of La–Y, Mg–Y, La–Mg codoped α-alumina interfaces was studied using energy minimization calculations. The segregation energy for single doping as well as codoping is negative for all the surfaces and grain boundaries. While, there is no significant energetic gain for La–Y cosegregation in comparison to single doping whereas segregation energies for Mg–Y and Mg–La codoping is more negative than single doping. A specific arrangement of dopants (associative effect) is also observed in La–Y codoped interfaces. Both mechanisms can thus contribute to the improved microstructures and properties.     

Characterization of a Cyclic Nucleotide‐Activated K+ Channel and its Lipid Environment by Using Solid‐State NMR Spectroscopy

Voltage‐gated ion channels are large tetrameric multidomain membrane proteins that play crucial roles in various cellular transduction pathways. Because of their large size and domain‐related mobility, structural characterization has proved challenging. We analyzed high‐resolution solid‐state NMR data on different isotope‐labeled protein constructs of a bacterial cyclic nucleotide‐activated K⁺ channel (MlCNG) in lipid bilayers. We could identify the different subdomains of the 4×355 residue protein, such as the voltage‐sensing domain and the cyclic nucleotide binding domain. Comparison to ssNMR data obtained on isotope‐labeled cell membranes suggests a tight association of negatively charged lipids to the channel. We detected spectroscopic polymorphism that extends beyond the ligand binding site, and the corresponding protein segments have been associated with mutant channel types in eukaryotic systems. These findings illustrate the potential of ssNMR for structural investigations on large membrane‐embedded proteins, even in the presence of local disorder.     

Transmittance from visible to mid infra-red in AZO films grown by atomic layer deposition system

We report transmittance and conductivity measurements of aluminum-doped zinc oxide films grown by atomic layer deposition. The results show that the films have 80–90% transmittance in the visible region and good transmittance in the infrared. To our knowledge, this is the first time that the transmittance of aluminum-doped zinc oxide is reported to extend beyond 2500–5000 nm. Following annealing, an optimal sheet resistance of 25 Ω/□ was obtained for a 575 nm thick film with a carrier density of 2.4 × 10²⁰ cm^?3 without compromising the transmittance in the visible regime.     

Dependence of bacterial growth rate on dynamic temperature changes

Temperature is an important determinant of bacterial growth. While the dependence of bacterial growth on different temperatures has been well studied for many bacterial species, prediction of bacterial growth rate for dynamic temperature changes is relatively unclear. Here, the authors address this issue using a combination of experimental measurements of the growth, at the resolution of 5 min, of Escherichia coli and mathematical models. They measure growth curves at different temperatures and estimate model parameters to predict bacterial growth profiles subject to dynamic temperature changes. They compared these predicted growth profiles for various step‐like temperature changes with experimental measurements using the coefficient of determination and mean square error and based on this comparison, ranked the different growth models, finding that the generalised logistic growth model gave the smallest error. They note that as the maximum specific growth increases the duration of this growth predominantly decreases. These results provide a basis to compute the dependence of the growth rate parameter in biomolecular circuits on dynamic temperatures and may be useful for designing biomolecular circuits that are robust to temperature.Inspec keywords: microorganisms, temperature, environmental factors, mean square error methods, parameter estimationOther keywords: bacterial growth rate, dynamic temperature changes, bacterial species, bacterial growth profiles, generalised logistic growth model, escherichia coli, model parameter estimation, coefficient of determination, mean square error, environmental conditions     

Effect of Zn, Sr, and Y Addition on Electrical Properties of PZT Thin Films

We have investigated methods to increase the efficiency of piezoelectric micromachined ultrasonic transducers (pMUTs). pMUTs are driven by a thin piezoelectric layer on a Si membrane. The efficiency of pMUTs can be increased using a film with better ferroelectric properties. We have used Zn, Sr, and Y doping on PZT-based thin films along the morphotropic phase boundary (MPB) composition to increase their piezoelectric properties. The results obtained were then extended to compositions on both sides of the MPB. The sol–gel method was used to prepare precursor solutions, which were then spin coated on a Pt(100)/Ti/SiO₂/Si substrate to prepare the PZT thin films. It was found that Zn and Sr together had the most significant effect on the ferroelectric properties in which a saturation polarization of 108 μC/cm² and remanent polarization of 54 μC/cm² were achieved.