Synthesis of silver nanoparticles by gelcasting using a low toxic monomer and optimization of gelation time using the Taguchi method

Silver nanoparticles were synthesized using a gelcasting process, which includes using in situ polymerization for forming the samples followed by calcination. Methacrylamide (MAM) was used as a monomer and N,N′-methylene-bis-acrylamide (MBAM) was used as a cross-linker to form a cross-linked polymer network. The effects of monomer content, cross-linker to monomer ratio, and silver salt to monomer ratio on gelation time were investigated using the Taguchi experimental design method. A set of 16 experiments was conducted at a constant temperature and agitation speed. The results from the Minitab design of experiments (DOE) analysis indicate that the cross-linker to monomer ratio had the greatest effect on gelation time. Finally, silver nanoparticles were synthesized by burning out a gel sample in a furnace. Scanning electron microscopy (SEM) analysis showed that the average size of the silver nanoparticles was approximately 42 nm.     

An integrated virtual environment for feasibility studies and implementation of aerial MonoSLAM

This work presents a complete framework of an integrated aerial virtual environment (IAVE), which could effectively help implementing MonoSLAM (single-camera simultaneous localization and mapping) on an aerial vehicle. The developed system allows investigating different flight conditions without using any preloaded maps or predefined features. A 3D graphical engine integrated with a full 6 DOF aircraft dynamic simulator together with its trajectory generator completes the package. The 3D engine generates and accumulates real-time images of a general camera installed on the aerial vehicle. We effectively exploit C++ to develop the 3D graphics engine (3DGE) and all its associated visual effects, including different types of lighting, climate conditions, and moving objects. The existing 3DGE exploits the so-called Frenet Adapted Frames (FAF) with constrained angular velocities that is very effective in motion modeling of both ground and aerial moving objects. An in-house-developed MATLAB GUI puts into service the offline MonoSLAM system, which is very user friendly. The current version of IAVE effectively employs the so-called Inverse Depth Parameterization notions for features?? depth estimation in monocular SLAM, where different case studies show its dependable results for low-cost aerial navigation of a general aviation low-speed aircraft.     

Influence of the Disk Diameter and Baffle Position on the Performance of Generated Colloidal Gas Aphrons

Aphrons are surfactant‐stabilized microbubbles with thick soapy shells. Colloidal gas aphrons (CGA) with an average diameter of 50 μm have some unique properties: a high interfacial area due to their small size, a thick soapy shell and, above all, high stability compared to conventional foams. Various factors that can influence the performance of CGA dispersion, such as the type and concentration of surfactant, mixing time and processing parameters, have already been extensively studied. However, although CGA applications in various fields continue to advance, the influence of the disk diameter and baffle position of the aphron generator on the performance of CGAs has not been well studied. In this experimental work, the influences of the spinning disk diameter and baffle position inside the aphron generator have been investigated. Analyzing the drainage curve of various experimental runs revealed that the disk diameter and baffle position might have a positive impact on the stability of CGA dispersion particularly when the generation time or surfactant concentration is low. The experimental findings have been supported by other techniques such as half‐life time and a new stability index, T_0.1, the time elapsed when the drained liquid from CGA dispersion reaches ten percent of its final height.     

A thermodynamically consistent framework for non-isothermal modelling of local heat generation and electromotive force in SOFC single electrodes

Mathematical models for single electrode reversible heat and non-isothermal electromotive force (EMF) of a solid oxide fuel cell (SOFC) are developed. These models estimate the volumetric reversible heat generation and EMF of electrochemical reactions, within each electrode at local conditions of temperature and pressure, based on entropy change of half reactions. The resulting equations are thermodynamically consistent. They inherently obey the conservation of energy law as the electrochemical energy released added to the heat of reactions at each electrode equate the enthalpy change of the reacted species. The equations are implemented to model electrodes in a tubular micro- solid oxide fuel cell (TμSOFC). The thermodynamic consistency of the model is numerically confirmed as the enthalpy of the reactants equates the electric energy released by the cell plus the sum of electrode heats plus electrolyte Ohmic heat. The effect of thermal gradients on the cell's overall EMF is found to be negligible. The reversible and irreversible heat generation of each electrode are distinguished. Overall, the anode is found to be endothermic, and the cathode exothermic.     

Hydrodynamic and heat transfer properties of magnetic fluid in porous medium considering nanoparticle shapes and magnetic field-dependent viscosity

The purpose of this paper is to study the characteristics of the combined convection heat transfer and a micropolar nanofluid flow passing through an impermeable stretching sheet in a porous medium. The nanofluid flow field is affected by a magnetic field perpendicular to the sheet. The dynamic viscosity of the micropolar nanofluid changes under the influence of the magnetic field. The continuity, linear momentum, angular momentum, and energy equations are first simplified using the order of magnitude technique that, along with the applied boundary conditions and the definition of the appropriate parameters, are transferred to the similarity space using the similarity analysis. Then the resulting equations are solved using the Runge–Kutta method.The distinction of the macroscale and microscale flow fields and temperature fields resulting from different nanoparticle shapes was clarified. Increasing the Hartmann number, the vortex viscosity parameter, the magnetic parameter, the nanoparticle volume fraction, and the permeability parameter of the porous media increased the surface friction on the sheet. Increasing the vortex viscosity parameter, the magnetic parameter, and the volume fraction of the nanoparticles increases the Nusselt number.     

Correction to: Double Vision Model Using Space-Time Function Control within Silicon Microring System

Silicon - The original version of this article unfortunately contained a mistake in the “Acknowledgments” section.     

Facile synthesis of novel optically active poly(amide‐imide)s containing N,N′‐(pyromellitoyl)‐bis‐l‐phenylalanine diacid chloride and 5,5‐disubstituted hydantoin derivatives under microwave irradiation

Pyromellitic dianhydride (1,2,4,5‐benzenetetracarboxylic acid 1,2,4,5‐dianhydide) (1) was reacted with L‐phenylalanine (2) in a mixture of acetic acid and pyridine (3 : 2) at room temperature, then was refluxed at 90–100°C and N,N′‐(Pyromellitoyl)‐bis‐L ‐phenylalanine diacid (3) was obtained in quantitative yield. The imide‐acid (3) was converted to N,N′‐(Pyromellitoyl)‐bis‐L ‐phenylalanine diacid chloride (4) by reaction with thionyl chloride. Rapid and highly efficient synthesis of poly(amide‐imide)s (6a–f) was achieved under microwave irradiation by using a domestic microwave oven from the polycondensation reactions of N,N′‐(Pyromellitoyl)‐bis‐L ‐phenylalanine diacid chloride (4) with six different derivatives of 5,5‐disubstituted hydantoin compounds (5a–f) in the presence of a small amount of a polar organic medium that acts as a primary microwave absorber. Suitable organic media was o‐cresol. The polycondensation proceeded rapidly, compared with the conventional melt polycondensation and solution polycondensation, and was almost completed within 10 min, giving a series of poly(amide‐imide)s with inherent viscosities about 0.28–0.44 dL/g. The resulting poly(amide‐imide)s were obtained in high yield and are optically active and thermally stable. All of the above compounds were fully characterized by means of FTIR spectroscopy, elemental analyses, inherent viscosity (η_inh), solubility test and specific rotation. Thermal properties of the poly(amide‐imide)s were investigated using thermal gravimetric analysis (TGA). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 516–524, 2004     

Generalized linear mixed model for monitoring autocorrelated logistic regression profiles

Profile monitoring is used to monitor the regression relationship between a response variable and one or more explanatory variables over time. Many researches have been done in this area, but in most of them, the distribution of the response variable is assumed to be normal. However, this assumption is violated in many real case problems. In these instances, classic methods cannot be used for monitoring the profiles. For example, when the response variable is binary, logistic regression methods should be used rather than ordinary least square or other classic regression methods. There are some methods for monitoring logistic profiles in the literature, but the basic assumption of these methods is the independency of the consecutive observations, while this assumption is violated in some instances for example when the successive samples are taken in short intervals. This paper considers the effect of autocorrelation presence between the observations in different levels of the independent variable in a logistic regression profile on the monitoring procedure (T ² control chart) and proposes two remedies to account for the autocorrelation within logistic profiles. In one of the remedies, upper control limit of the traditional T ² control chart is modified. In the second one, we use a generalized linear mixed model (GLMM) to estimate the regression parameters and then use the T ² control chart for monitoring autocorrelated logistic regression profiles. Simulation studies show the better performance of T ² control chart when the regression parameters are estimated by the GLMM method under both step shifts and drifts.     

Combining continuous catalytic regenerative naphtha reformer with thermally coupled concept for improving the process yield

Advancements in the catalytic naphtha reforming process, as one of the main processes in petrochemical industry, contributed to development of continuous catalytic regenerative naphtha reformer units. Increasing the yield of aromatic and hydrogen as well as saving the energy in this process through the application of thermal coupling technique is a potentially interesting idea. This novel idea has been assessed in this paper. In the proposed configuration, continuous catalyst regeneration naphtha reforming process is coupled with hydrogenation of nitrobenzene in a two co-axial reactor separated by a solid wall, where the generated heat in nitrobenzene hydrogenation reaction transfers to naphtha reforming reaction medium through the surface of the tube. A steady-state, homogeneous, two-dimensional model is used to describe the performance of this configuration and a kinetic model including 32 pseudo-components with 84 reactions is considered for naphtha reforming reaction. After validating the model with the commercial data of a domestic plant, the obtained results of coupled reactor are compared by the conventional one. The obtained results show the superiority of CCR coupled reactor against the conventional one.     

自复原电网的前景

最近全世界不断发生的停电事故,将电力系统的可靠性变成了引人瞩目的焦点.这些停电事故造成的社会和经济损失累计起来每年达到数十亿美元.随着数字时代的到来,以计算机和电力电子为基础的效率更高的制造工艺在行业里占据了优势地位,随着电力在总能源消耗中所占比重继续增加,电力系统可靠性的价值也在增加.在如何提高监测和控制水平,改善电力系统方面,存在各种解决方案,本文试图探讨一些最新解决方案的前景.