Multiband frequency reconfigurable substrate integrated waveguide antenna using copper strip for cognitive radio applicable to internet of things application

In this paper, a Multiband Frequency Reconfigurable Substrate Integrated Waveguide (FR-SIW) cavity backed slot antenna for Cognitive Radio appropriate to Internet of Things (IoT) technology is presented. The proposed antenna is developed to address the specific design challenges posed by the IoT based Cognitive Radio (CR) networks. Reconfiguration of frequency bands is achieved using copper strips. The antenna resonates during the selected five switching states of the copper strips at 2.9 GHz, 2.6 GHz, 2.824 GHz, 2.792 GHz, 2.872 GHz, 4.488 GHz, 4.724 GHz, 4.712 GHz, 5.476 GHz, 5.336 GHz, 5.448 GHz, 5.392 GHz, and 5.42 GHz. The multiple frequency bands are controlled by altering the electrical length of designed slots. Overall, the simulated and measured results showed good agreement and the designed antenna is a potential candidate for cognitive radio applications, especially to IoT applications.

     

Impacts of gold nanoparticles on MHD mixed convection Poiseuille flow of nanofluid passing through a porous medium in the presence of thermal radiation,thermal diffusion and chemical reaction

Impacts of gold nanoparticles on MHD Poiseuille flow of nanofluid in a porous medium are studied. Mixed convection is induced due to external pressure gradient and buoyancy force. Additional effects of thermal radiation, chemical reaction and thermal diffusion are also considered. Gold nanoparticles of cylindrical shape are considered in kerosene oil taken as conventional base fluid. However, for comparison, four other types of nanoparticles (silver, copper, alumina and magnetite) are also considered. The problem is modeled in terms of partial differential equations with suitable boundary conditions and then computed by perturbation technique. Exact expressions for velocity and temperature are obtained. Graphical results are mapped in order to tackle the physics of the embedded parameters. This study mainly focuses on gold nanoparticles; however, for the sake of comparison, four other types of nanoparticles namely silver, copper, alumina and magnetite are analyzed for the heat transfer rate. The obtained results show that metals have higher rate of heat transfer than metal oxides. Gold nanoparticles have the highest rate of heat transfer followed by alumina and magnetite. Porosity and magnetic field have opposite effects on velocity.

     

An efficient modified Polak–Ribière–Polyak conjugate gradient method with global convergence properties

The conjugate gradient (CG) method is one of the most popular methods for solving large-scale unconstrained optimization problems. In this paper, a new modified version of the CG formula that was introduced by Polak, Ribière, and Polyak is proposed for problems that are bounded below and have a Lipschitz-continuous gradient. The new parameter provides global convergence properties when the strong Wolfe-Powell (SWP) line search or the weak Wolfe-Powell (WWP) line search is employed. A proof of a sufficient descent condition is provided for the SWP line search. Numerical comparisons between the proposed parameter and other recent CG modifications are made on a set of standard unconstrained optimization problems. The numerical results demonstrate the efficiency of the proposed CG parameter compared with the other CG parameters.     

Routing protocols for underwater wireless sensor networks based on data forwarding: a review

Nowadays, underwater wireless sensor network (UWSN) is an important field for researchers due to its well know applications like seismic monitoring, disaster prevention, offshore exploration, pollution monitoring, oceanography data collection, equipment monitoring, assisted navigation, and tactical surveillance. Many research challenges are available for UWSN; the design of routing protocol is one of them. The majority of the researchers have designed the routing algorithms but still, the data forwarding mechanism needs improvement. The reliable communication between the source and sink nodes is really a complicated task due to the limitation of the acoustic channel, water pressure, and limited bandwidth. This review paper focuses on the problems of those routing protocols which are based on data forwarding. In this review paper, we further present the route development, data forwarding, and route maintenance of the proposed routing protocols. The key aspects of this review article present the limitations and advantages of data forwarding routing protocols. We also present analysis of data forwarding routing protocols with analytical and numerical simulation methods with their critical analysis. This review article helps the researchers to create further research in the field of routing protocols based on data forwarding.     

Enzymic synthesis of fatty esters by hydrophobic lipase derivatives immobilized on organic polymer beads

Lipase fromCandida rugosa was modified with several hydrophobic modifiers before being adsorbed onto organic polymer beads. The effects of different enzyme modifiers, supports, solvents, reaction temperatures, fatty acids, and alcohols on the activity of the immobilized enzyme were investigated. The immobilized lipases were good biocatalysts for esterification reactions in organic solvents. They exhibited high activities in all solvents tested, including polar solvents. The activity seemed to depend on the type of support rather than on the modifier of the enzyme. The medium polar support, XAD7, appeared to be the best for the modified lipases. The immobilized lipase favored the medium-chain fatty acids rather than the long-chain fatty acids as acyl donors. The alcohol selectivity of the enzyme was unchanged upon immobilization. The native and immobilized lipases favored the short-chain and terpene alcohols as nucleophiles.     

Amidination of lipase with hydrophobic imidoesters

Lipase fromCandida rugosa was chemically modified by amidination with imidoester hydrochlorides of different hydrophobicity. The modified enzyme showed a higher ester synthesis activity but a lower ester hydrolysis activity compared with the native enzyme. The maximum specific activity of the modified enzyme depended on its degree of derivatization. Benzene was found to be the best solvent for the synthesis reaction. The optimal temperature for the reaction was not affected by modification of the lipase. The modified lipase was more thermostable and solvent-stable than the native enzyme. When fatty acids of different carbon chainlength were tested as substrates in the synthesis of esters with the modified lipase, the highest activity was observed with myristic acid and propanol.     

Botnet detection techniques: review,future trends,and issues

In recent years, the Interact has enabled access to widespread remote services in the distributed computing environment; however, integrity of data transmission in the distributed computing platform is hindered by a number of security issues. For instance, the botnet phenomenon is a prominent threat to Intemet security, including the threat of malicious codes. The botnet phenomenon supports a wide range of criminal activities, including distributed denial of service （DDoS） attacks, click fraud, phishing, malware distribution, spam emails, and building machines for illegitimate exchange of information/materials. Therefore, it is imperative to design and develop a robust mechanism for improving the botnet detection, analysis, and removal process. Currently, botnet detection techniques have been reviewed in different ways; however, such studies are limited in scope and lack discussions on the latest botnet detection techniques. This paper presents a comprehensive review of the latest state-of-the-art techniques for botnet detection and figures out the trends of previous and current research. It provides a thematic taxonomy for the classification of botnet detection techniques and highlights the implications and critical aspects by qualitatively analyzing such techniques. Related to our comprehensive review, we highlight future directions for improving the schemes that broadly span the entire botnet detection research field and identify the persistent and prominent research challenges that remain open.     

Review:Botnet detection techniques: review,future trends,and issue

In recent years, the Internet has enabled access to widespread remote services in the distributed computing environment; however, integrity of data transmission in the distributed computing platform is hindered by a number of security issues. For instance, the botnet phenomenon is a prominent threat to Internet security, including the threat of malicious codes. The botnet phenomenon supports a wide range of criminal activities, including distributed denial of service(DDoS) attacks, click fraud, phishing, malware distribution, spam emails, and building machines for illegitimate exchange of information/materials. Therefore, it is imperative to design and develop a robust mechanism for improving the botnet detection, analysis, and removal process. Currently, botnet detection techniques have been reviewed in different ways; however, such studies are limited in scope and lack discussions on the latest botnet detection techniques. This paper presents a comprehensive review of the latest state-of-the-art techniques for botnet detection and figures out the trends of previous and current research. It provides a thematic taxonomy for the classification of botnet detection techniques and highlights the implications and critical aspects by qualitatively analyzing such techniques. Related to our comprehensive review, we highlight future directions for improving the schemes that broadly span the entire botnet detection research field and identify the persistent and prominent research challenges that remain open.     

Quantifying the color palettes of Naghsh-e Jahan Square in Isfahan

In the 1960s, Jean-Philippe Lenclos introduced a structured methodology for determining the color palettes of urban environments. After half a century, this method is widely used all over the world. Since this process contains subjective and time-consuming steps, we propose a quantitative improvement of Lenclos' methodology by introducing a fully digital procedure. This removes observer subjectivity and dependence on local illumination conditions. We applied the digital process to the four monumental buildings of Naghsh-e Jahan Square in Isfahan, a masterpiece of world architecture. The resulting color palettes are more accurate than those obtained in earlier studies. We obtained more accurate color coordinates, characterized by a wider color gamut, and quantified color variations within buildings and between monuments as well.