Convective heat transfer and pressure drop study on nanofluids in double-walled reactor by developing an optimal multilayer perceptron artificial neural network

The effect of nanofluid on the cooling performance and pressure drop of a jacked reactor has experimentally been investigated. Aqueous nanofluids of Al₂O₃ and CuO was used as the cool ant inside the cooling jacket of the reactor. The application of the artificial neural networks (ANNs) to predict the performance of a double-walled reactor has been studied. Different architectures of artificial neural networks were developed to predict the convective heat transfer and pressure drop of nanofluids. The experimental results are used for training and testing the ANNs based on two optimal models via feed-forward back-propagation multilayer perceptron (MLP). The comparison of statistical criteria of different network shows that the optimal structure for predicting the convective heat transfer coefficient is the MLP network with one hidden layer and 10 neurons, which has been trained with Levenberg–Marquardt (LM) algorithm. The predicted pressure drop values by the MLP network with two hidden layers and 6 neurons in the each layer has been used from LM training algorithm, which showed a reasonable agreement with the experimental results.     

Studies on the impact of capacitor bank switching on grid connected transformers

Switching events in power system generate transients. These transients have unfavorable impact on grid connected EHV transformers due to their complex oscillatory wave shapes embodying wide spectrum of frequencies. One or more of these frequency components can often excite the natural resonant frequencies of the transformer windings while travelling through transformers and may result severe internal voltage amplification and development of abnormal voltage stresses on the transformer insulation. While designing insulation for grid connected EHV transformers, adequate considerations must therefore be given to the voltage stresses which are likely to develop on the insulation during such occurrences of oscillatory transient overvoltages. In this paper, the authors have analyzed the stresses developed in the windings of a 400/220/33 kV grid connected transformer operating in the National Power Grid of India by model based studies when natural frequencies of the windings are triggered by oscillatory transient overvoltages originated from deliberate switching of static capacitor banks at substation.     

Effect of Cathode Designs on Radiation Emission of Compact Diode (CD) Device

A comparative study on the radiation emission such as X-ray yield and efficiency has been carried out in compact diode device. Two different designs of cathode having sharp-edged razor blade (of 0.5 mm thickness with width 2 mm) and a sewing machine needle (of 0.5 mm diameter at tip with length of 39 mm) have been tested for this study. The radiation emission (X-ray yield) was determined by employing two set of PIN diodes at fixed positions. The maximum X-ray yield depends on cathode designs and electrodes separation in few mm. The yield of X-ray is small in the case of sharp-edged razor blade cathode than the sewing machine needle cathode. The X-ray yield, measured by 4π-geometry, shows its dependence on the cathode designs. The maximum X-ray yield is found to be 939.2 ± 65.7 mJ with efficiency of 0.4142 ± 0.0289%. This study indicates that the compact diode device could be optimized to a great extent for optimal X-ray yield by using an appropriate cathode design.     

Sequential learning for fingerprint based indoor localization

In this paper, we introduce a novel approach for improving performance of fingerprinting based indoor localization. Our proposal is a two-step procedure in which severe variation in the received signal strength is minimized during the first step via convex optimization, and distance metric learning is then used to estimate a more accurate location. Numerical results show that our proposal outperforms existing techniques in terms of accuracy and reliability.     

Dynamic environmental economic dispatch using multiobjective differential evolution algorithm with expanded double selection and adaptive random restart

The dynamic environmental economic dispatch (DEED) model is presented in this paper, in which the fuel cost and emission effect over a certain period of time are optimized as conflicting objectives. It is a high dimensional, nonlinear constrained multiobjective optimization problem when generators’ valve point effect, ramp rate limits and power load variation are considered. This paper proposes a modified adaptive multiobjective differential evolution (MAMODE) algorithm to solve the problem. In MAMODE, expanded double selection and adaptive random restart operators are proposed to modify the evolutionary processes for avoiding premature and a dynamic heuristic constraint handling (DHCH) approach is introduced to deal with the complicated constraints. The DHCH can lessen infeasible solutions gradually. To illustrate the effectiveness of the method, four cases based on three test power systems are studied. The simulation result indicates that the DEED can be solved quickly. Comparison of numerical results demonstrates the proposed method has higher performance.     

Channel resolution enhancement through scalability of nano/micro-scale thickness and width of SU-8 polymer based optical channels using UV lithography

Microsystem Technologies - This paper reports on an approach for fabrication of micro-channels with nanometer thickness achieved by optimization of UV lithography processes. Rectangular...     

The effect of Nafion membrane fouling on the power generation of a microbial fuel cell

Microbial fuel cells (MFCs) are the most useful technologies for energy production and wastewater treatment due to their low cost and support of the environment. In this study, the membrane fouling and their effects on power generation were investigated using scanning electron microscope (SEM). Results demonstrate that proton exchange membrane (PEM) was affected by biofouling in a two-chamber H-type MFC, which would significantly affect coulombic efficiencies (CEs), and maximum power densities leading to reduced power generation. The power densities of both rice straw and potato peels were 119.35 mW/m² and 152.55 mW/m², respectively. Scanning Electron Microscope (SEM) showed substantial accumulation of bacteria and their end-products forming a thick biofilm on the surface of PEM leading to a decrease, if not, preventing the passage of protons from the anode side toward the cathode side. The decline in power generation may result mainly from the biofouling, not of electrodes but, of PEM membrane from both sides (Anode and Cathode) because of improper regular PEM cleaning.     

Ambient RF energy harvesting system: a review on integrated circuit design

This paper presents a comprehensive review of ambient RF energy harvester circuitry working on integrated circuits. The review covers 3 main blocks in an RF energy harvesting system implemented on chip. The blocks are the rectifier, impedance matching circuit and power management unit. The review of each block includes its operational principle, reported state-of-the-art circuit enhancement techniques, and design trade-offs. We compare the circuits in each block with respect to the techniques adopted to improve the performances for RF energy harvesting. To identify the benefits and limitations associated with the architecture we discuss the advantages and disadvantages of the circuit topologies in each block of an ambient RF energy harvester.     

Business model analysis of public services operating in the smart city ecosystem: The case of SmartSantander

As the deployment of Internet of Things and other enabling technologies is still in an initial phase worldwide, few research studies have addressed the associated business models. This paper aims to fill this gap. The main objective of this research is to gain a deeper knowledge about practical business models matching into a real-life smart city ecosystem. Hence, a benchmarking of eight urban services provided in the city of Santander has been carried out: waste management; water supply; traffic management; street lighting; augmented reality and tourism; incidences management, parks and gardens and citizen participation. Among the main results of our study, we highlight that those public services properly managed embedding IoT technology convey cost reductions in the long term. There is also a reduction in energy consumption and environmental impact with the consequent social impact. It should also be highlighted that most data are managed with the same platform. Last but not least, an emerging ecosystem of incentivized citizens has been proved to be arising.     

Optoelectronic properties of cubic BxInyGa1−x−yN alloys matched to GaN for designing quantum well Lasers: First-principles study within mBJ exchange potential

A Full-Potential Linearized Augmented Plane Wave calculation within density functional theory is performed to investigate the electronic and optical properties of cubic B_xIn_yGa_1−x−yN alloys matched to GaN with low-Boron content (x≤0.187). The exchange-correlation potential is treated by the local density approximation (LDA) to calculate the structural properties. The band structure and density of states of these compounds are well predicted by modified Becke–Johnson (mBJ) exchange potential compared to LDA and generalized gradient approximation (GGA). Also, the optical properties are calculated by the mBJ exchange potential. The computed structural parameters are found to be in good agreement with experimental and theoretical data. The B_xIn_yGa_1−x−yN alloy is expected to be lattice matched to GaN substrate for (x=0.125, y=0.187). The incorporation of B and In into GaN substrate allows the reduction of the band gap energy. The real and imaginary parts of the dielectric function, refractive index, reflectivity and absorption coefficient are discussed on the basis on the energy band structure and the calculated density of states. The optical properties of B_xIn_yGa_1−x−yN depend on the incorporated Boron content (with y=0.187). This means that B_xIn_yGa_1−x−yN could constitute an active layer in single quantum well for the design of high-efficiency solar cells and optoelectronic devices as Laser Diodes operating in the UV spectral region.