Modification of CaO by Organic Alumina Precursor for Enhancing Cyclic Capture of CO2 Greenhouse Gas

The modification of CaO sorbent with organic alumina precursor to enhance the sorption capacity during cyclic capture is demonstrated in this study. The results indicate that during the 10?min sorption time for each cycle, the CO2 sorption capacity of original CaO sorbent is significantly decreased from 0.27 to 0.19 and 0.12?g CO2/g sorbent after 5 and 60?cycles, respectively. On the other hand, the organic alumina modified CaO has a fresh capacity of 0.22?g CO2/g sorbent, it increases to 0.24?g CO2/g sorbent after 5?cycles, and then decreases to around 0.15?g CO2/g sorbent after 60?cycles. When increasing the sorption time to 60?min at the 66th cycle, the sorption capacity of original CaO is 0.2, whereas it is 0.26?g CO2/g sorbent for organic alumina modified CaO. The results demonstrate that by adding only 5% by weight of Ca12Al14O33 species into the CaO sorbent, the CO2 sorption capacity can be enhanced up to ～ 27% by weight.     

Experimental and theoretical studies of a two-stage pulse tube cryocooler operating down to 3 K

The development of a two-stage Pulse Tube Cryocooler (PTC) which produces a no-load temperature of ～3 K and delivers a refrigeration power of ～250 mW at 5 K is reported in this work. The system uses stainless steel meshes along with lead (Pb) granules and combinations of Pb, Er₃Ni and HoCu₂ in layered structures as the first and second stage regenerator materials respectively. With Helium as a working fluid, the pressure oscillations are generated using a 6 kW water-cooled Helium compressor along with an indigenous rotary valve. Different configurations of pulse tube systems have been experimentally studied, by both varying the dimensions of pulse tubes and regenerators as well as the second stage regenerator material composition. The pulse tube Cryocooler has been numerically analyzed by using both the isothermal model and the model based on solving the energy equations. The predicted refrigeration powers as well as the temperature profiles have been compared with the experimental results for specific pulse tube configurations.     

Sarcastic user behavior classification and prediction from social media data using firebug swarm optimization-based long short-term memory

Sarcasm is a type of speech where people use positive words to convey a negative message. Recently, only a few research have been presented that focus on the entire spectrum of sarcasm in order to identify sarcastic sentiments present in both the image and the text. This work presents a novel firebug swarm optimization-based long short-term memory (FSO-LSTM) architecture to identify the sarcastic sentiments present in tweets. To identify the facial expressions of the users, the proposed FSO-based LSTM architecture is trained using the CK?+?dataset. The FSO algorithm is used to optimize the weighting factors of the LSTM architecture and also minimize the root-mean-square error (RMSE) and mean absolute error. The proposed method primarily attempts to address two challenging issues in sarcasm detection: the high number of false negatives and the fact that polite tweets often go undetected. The user's mood changes (sarcastic) such as rude, polite, furious, and impassive can be identified using the proposed model. Hence, the proposed classifier is capable of analyzing the behavior change of the user by collecting the past twitter account history. The efficiency of the proposed methodology is evaluated using different performance metrics such as accuracy, RMSE, confusion matrix, and loss. The proposed methodology offers an average classification accuracy of 97.25% classification accuracy when compared to the state-of-the-art approaches.

     

A Survey of Computation Offloading for Mobile Systems

Mobile systems have limited resources, such as battery life, network bandwidth, storage capacity, and processor performance. These restrictions may be alleviated by computation offloading: sending heavy computation to resourceful servers and receiving the results from these servers. Many issues related to offloading have been investigated in the past decade. This survey paper provides an overview of the background, techniques, systems, and research areas for offloading computation. We also describe directions for future research.     

Sonochemically Prepared GdWNFs/CNFs Nanocomposite as an Electrode Material for the Electrochemical Detection of Antibiotic Drug in Water Bodies

The work demonstrates the development of an electrochemical sensor for quantification of Chloramphenicol (CA) using pencil graphite electrode (PGE) modified with Gadolinium tungstate nano flakes and carbon nano fibers composite (PGE/GWNfs/CNFs). The composite was further characterized and confirmed by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy, transmission electron microscopy analysis. The prepared GWNfs/CNFs nano composite was fabricated by drop casting method to get PGE/GWNfs/CNFs working electrode. The modified electrode is then analyzed by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV) methods for its electrochemical and electrocatalytic property. The electrochemical investigation of developed sensor shows enhanced activity towards electro-oxidation of CA. The DPV studies revealed high efficacy characteristics such as sensitivity in the range 0.03984 µA µM^?1 cm^?2, selectivity, good linear range (5–50 μM), and low detection limit (0.4 μM). The study benchmarks the use of GWNfs/CNFs as an excellent transducer material in electrochemical sensing of CA in standard samples thus, it finds an efficient potential application in the analysis of CA in environment sample analysis.

     

Use of highly-ordered TiO(2) nanotube arrays in dye-sensitized solar cells

We describe the use of highly ordered transparent TiO(2) nanotube arrays in dye-sensitized solar cells (DSCs). Highly ordered nanotube arrays of 46-nm pore diameter, 17-nm wall thickness, and 360-nm length were grown perpendicular to a fluorine-doped tin oxide-coated glass substrate by anodic oxidation of a titanium thin film. After crystallization by an oxygen anneal, the nanotube arrays are treated with TiCl(4) to enhance the photogenerated current and then integrated into the DSC structure using a commercially available ruthenium-based dye. Although the negative electrode is only 360-nm-thick, under AM 1.5 illumination the generated photocurrent is 7.87 mA/cm(2), with a photocurrent efficiency of 2.9%. Voltage-decay measurements indicate that the highly ordered TiO(2) nanotube arrays, in comparison to nanoparticulate systems, have superior electron lifetimes and provide excellent pathways for electron percolation. Our results indicate that remarkable photoconversion efficiencies may be obtained, possibly to the ideal limit of approximately 31% for a single photosystem scheme, with an increase of the nanotube-array length to several micrometers.     

Bifunctional mesoporous Cu–Al–MCM-41 materials for the simultaneous catalytic abatement of NOx and VOCs

This study explored the possibility of using waste organic solvent as the source of volatile organic compound (VOC) and it served as a reducing agent of selective catalytic reduction (SCR) deNO_x process, in which the VOC itself can be catalytically oxidized on the mesoporous Cu and/or Al substituted MCM-41 catalysts. The synthesized Cu–Al–MCM-41 catalysts were extensively characterized by powder low-angle X-ray diffraction (XRD), N₂ adsorption–desorption measurements, transmission electron microscopy (TEM), UV–Visible diffuse reflectance spectroscopy (UV–Vis DRS), ²⁷Al magic angle spinning-nuclear magnetic resonance spectroscopy (MAS-NMR), electron paramagnetic resonance spectroscopy (EPR) and inductively coupled plasma–mass spectrometer (ICP–MS) analysis. The XRD, TEM and N₂ adsorption–desorption studies clearly demonstrated the presence of a well ordered long range hexagonal array with uniform mesostructures. The Cu–Al–MCM-41 materials showed a better long-term-stability than that of copper ion-exchanged H–ZSM-5 (Cu–ZSM-5) zeolite. The Cu–Al–MCM-41 material was found to be an efficient catalyst than that of Cu–MCM-41 without aluminum for the simultaneous catalytic abatement of NO_x and VOCs, which was attributed to the presence of well dispersed and isolated Cu²⁺ ions on the Cu–Al–MCM-41 catalyst as observed by UV–Vis DRS and EPR spectroscopic studies. And the presence of aluminum (Al³⁺ ions) within the framework of Cu–Al–MCM-41 stabilized the isolated Cu²⁺ ions thus it led to higher and stabilized activity in terms of NO_x reduction.     

Application of finite-difference time domain to dye-sensitized solar cells: The effect of nanotube-array negative electrode dimensions on light absorption

We examine the light absorbing behavior of dye-sensitized solar cells (DSCs) having cathodes (negative electrodes) comprised of highly ordered TiO₂ nanotube arrays using the electromagnetic computational technique, finite-difference time domain (FDTD). The highly ordered nanotube arrays, grown using anodic oxidation of titanium foils or thin films, feature an open end with the other end fixed on a dense oxide layer (barrier layer). The numerical simulation model is comprised of nanotube arrays on a transparent conducting glass substrate under front-side illumination. In the FDTD analysis, a transverse electromagnetic (TEM) wave is incident onto a N719 dye-coated nanotube array initially passing through the barrier layer; light that emerges from the nanotubes is reflected by a perfectly conducting layer (perfect electric conductor—PEC) boundary that simulates the effect of the DSC platinum counter electrode. An observation plane placed between the electromagnetic source and DSC detects the intensity of both the incident wave and the wave returning back from the DSC structure. The absorbance and transmittance spectra are determined in the wavelength range 300–700 nm as a function of nanotube-array dimensions including length, pore size, barrier layer thickness, and surface roughness while keeping the wall thickness constant at 12 nm. The validity of the computational simulations is experimentally verified. A significant increase in the light absorption by the dye-coated nanotubes was observed for increasing nanotube length; smaller pore sizes, and increased surface roughness. Changes in the barrier layer thickness had a negligible effect on the absorbance spectrum. Our efforts demonstrate FDTD to be a broadly applicable technique capable of guiding design of an optimal DSC architecture.     

A novel CRT-based watermarking technique for authentication of multimedia contents

Digital watermarking techniques have been proposed as a solution to the problem of copyright protection of multimedia data. In this paper, we propose a novel Chinese remainder theorem (CRT)-based technique for digital watermarking. The use of CRT for this purpose provides additional security along with resistance to some familiar attacks. We have shown that this technique is quite resilient to addition of the noise. We have compared performance of the proposed technique with recently reported two singular value decomposition (SVD)-based watermarking techniques and shown its superior performance in terms of tampering assessment function (TAF), computational efficiency and peak signal to noise ratio (PSNR). For example, the embedding time of the proposed CRT-based scheme is 6 and 3 times faster than the SVD-based Schemes 1 and 2, respectively. This technique can also be applied to document, audio and video contents.