A vertex‐fed hexa‐band frequency reconfigurable antenna for wireless applications

Present article embodies the design and analysis of an octagonal shaped split ring resonator based multiband antenna fed at vertex for wireless applications with frequency‐band reconfigurable characteristics. The proposed antenna is printed on FR4 substrate with electrical dimension of 0.4884 λ × 0.4329 λ × 0.0178 λ (44 × 39 × 1.6 mm³), at lower frequency of 3.33 GHz. The antenna consists of SRR based vertex fed octagonal ring as the radiation element and switchable reclined L‐shaped slotted ground plane. Antenna achieves six bands for wireless standards viz: upper WLAN (5.0/5.8 GHz), lower WiMAX (3.3 GHz), super extended C‐band (6.6 GHz), middle X band (9.9 GHz—for space communication), and lower K_U band (15.9 GHz—for satellite communication systems operating band). Stable radiation patterns are observed for the operating bands with low cross polarization. The proposed design achieves hexa band characteristics during switching ON state of PIN diode located at reclined L‐shaped slot in the ground plane. Experimental characteristic of antenna shows close agreement with those obtained by simulation of the proposed antenna.     

Chatter and dynamic cutting force prediction in high-speed ball end milling

Machine tool chatter is a serious problem which deteriorates surface quality of machined parts and increases tool wear, noise, and even causes tool failure. In the present paper, machine tool chatter has been studied and a stability lobe diagram (SLD) has been developed for a two degrees of freedom system to identify stable and unstable zones using zeroth order approximation method. A dynamic cutting force model has been modeled in tangential and radial directions using regenerative uncut chip thickness. Uncut chip thickness has been modeled using trochoidal path traced by the cutting edge of the tool. Dynamic cutting force coefficients have been determined based on the average force method. Several experiments have been performed at different feed rates and axial depths of cut to determine the dynamic cutting force coefficients and have been used for predicting SLD. Several other experiments have been performed to validate the feasibility and effectiveness of the developed SLD. It is found that the proposed method is quite efficient in predicting the SLD. The cutting forces in stable and unstable cutting zone are in well agreement with the experimental cutting forces.     

Alginic acid‐g‐poly(N‐vinylformamide) graft copolymer: Synthesis,characerization, swelling,and flocculation property

The graft copolymer of N‐vinylformamide with alginic acid was synthesized by free radical polymerization using potassium peroxymonosulphate and thiourea as redox pair in inert atmosphere. The optimum conditions for maximum grafting have been determined by varying the concentrations of N‐vinylformamide, potassium peroxymonosulphate, thiourea, sulfuric acid, alginic acid as well as time duration and temperature. The grafting parameters increase up to the certain concentrations of N‐vinylformamide, potassium peroxymonosulhate, thiourea, and hydrogen ion while thereafter grafting parameters decrease. The effect of alginic acid concentration on grafting parameters has been observed to decrease continuously. It has also been found that grafting parameters increase up to certain time and temperature, respectively, and thereafter decrease. The swelling properties of graft copolymer in terms of swelling ratio and percent swelling are investigated. Flocculation property of pure and grafted sample for both coking and noncoking coals is also investigated for the treatment of coal mine waste water. The graft copolymer has been characterized by Fourier transform infrared spectroscopy as well as thermogravimetic analysis. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Pharmacophore Synergism in Diverse Scaffold Clinches in Aurora Kinase B

Aurora kinase B (AKB) is a crucial signaling kinase with an important role in cell division. Therefore, inhibition of AKB is an attractive approach to the treatment of cancer. In the present work, extensive quantitative structure–activity relationships (QSAR) analysis has been performed using a set of 561 structurally diverse aurora kinase B inhibitors. The Organization for Economic Cooperation and Development (OECD) guidelines were used to develop a QSAR model that has high statistical performance (R²_tr = 0.815, Q²_LMO = 0.808, R²_ex = 0.814, CCC_ex = 0.899). The seven-variable-based newly developed QSAR model has an excellent balance of external predictive ability (Predictive QSAR) and mechanistic interpretation (Mechanistic QSAR). The QSAR analysis successfully identifies not only the visible pharmacophoric features but also the hidden features. The analysis indicates that the lipophilic and polar groups—especially the H-bond capable groups—must be present at a specific distance from each other. Moreover, the ring nitrogen and ring carbon atoms play important roles in determining the inhibitory activity for AKB. The analysis effectively captures reported as well as unreported pharmacophoric features. The results of the present analysis are also supported by the reported crystal structures of inhibitors bound to AKB.     

Design and Analysis of UWB Filter with Single Notch Band

Wireless Personal Communications - In this article, design and electrical analysis of UWB filter with a notch band is presented. Initially basic UWB filter is designed by using parallel coupled...     

Development of a Reconfigurable and Miniaturized CPW Antenna for Selective and Wideband Communication

The Planar microwave antennas with simultaneously selectively narrowband and wideband resonance characteristics are essential for the diversity applications. The paper presents modeling, fabrication and experimental verification of a coplanar waveguide excited antenna with a complementary patch which exhibits a narrow-band resonance at 2.47 GHz, and a wideband resonance between 5.52 and 11 GHz. A reconfigurability in the antenna design was achieved by placing a PIN diode across the slot position, and the wideband resonance was switched to the narrowband resonance with a center frequency of 9.56 GHz. The device was fabricated on a foam-based substrate of relative permittivity ε _r  = 2.2 and loss factor tanδ = 0.007. The tested antenna shows a comparable matching with the simulated results and a superior performance over the other reported reconfigurable CPW antennas was achieved.

     

Homotopy perturbation method for fractional Fornberg–Whitham equation

This article presents the approximate analytical solutions to solve the nonlinear Fornberg–Whitham equation with fractional time derivative. By using initial values, the explicit solutions of the equations are solved by using a reliable algorithm like homotopy perturbation method. The fractional derivatives are taken in the Caputo sense. Numerical results show that the HPM is easy to implement and accurate when applied to time-fractional PDEs.     

Influence of carbonization conditions on the gasification of acacia and eucalyptus wood chars by carbon dioxide

Gasification rates of cubic shaped acacia and eucalyptus wood chars were measured thermogravimetrically in a carbon dioxide atmosphere at temperatures in the range 810–960 °C. The effects of wood species and carbonization conditions, such as temperature, heating rate and soaking time, were determined. Both reactivity and the activation energy for the gasification of wood chars were found to be strongly influenced by the carbonization conditions employed during their preparation and wood type. The reactivities of both the acacia and eucalyptus wood chars decreased with increasing preparation temperature; while the activation energy for their gasification increased. Slow carbonization (heating rate: 4 °C min⁻¹) led to the production of wood chars having lower reactivities and higher activation energies than those of the wood chars prepared under rapid carbonization (heating rate: 30 °C min⁻¹) at the same temperature. With increasing soaking time, at carbonization temperatures of 800 and 1000 °C, the reactivity of resulting wood chars was reduced. The results also show that the reactivities of acacia wood chars are higher than those of similarly prepared eucalyptus wood chars.     

Restricted affine motion compensation and estimation in video coding with particle filtering and importance sampling: a multi-resolution approach

In this paper, we propose a multi-resolution affine block-based tracker for motion estimation and compensation, compatible with existing video coding standards such as H.264 and HEVC. We propose three modifications to traditional motion compensation techniques in video coding standards such as H.264 and HEVC. First, we replace traditional search methods with an efficient particle filtering-based method, which incorporates information from both spatial and temporal continuity. Second, we use a higher order linear model in place of the traditional translation motion model in these standards to efficiently represent complex motions such as rotation and zoom. Third, we propose a multi-resolution framework that enables efficient parameter estimation. Results of extensive experimentation show reduced residual energy and better Peak Signal-to-Noise Ratio (PSNR, hereafter) as compared to H.264/HEVC for instance, especially in regions of complex motion such as zooming and rotation.     

Design of high gain/directional ultra‐wideband antenna for radar imaging systems

A compact size of 40 × 40 mm² ( λ₀ × λ₀ ) semi‐elliptical slotted ground structure (SESGS) directional ultra‐wideband (UWB) antenna is proposed for radar imaging applications. A vertical semi‐elliptical slot is inserted into ground and subsequently, an axis of semi‐ellipse is rotated diagonally (with 45°) in direction of the substrate. Axes of semi‐ellipse are optimized symmetrically around the circular patch to work antenna as a reflector. Furthermore, semi‐elliptical slot is rotated horizontally (with 90°) again to improve the impedance bandwidth. Proposed antenna achieves fractional bandwidth around 83% covering the UWB frequency range from 4.40 to 10.60 GHz (S₁₁ < ?10 dB) having 4.5/6/7/8/9.3/10.2 GHz resonant frequencies. Also, antenna is capable to send low‐distortion Gaussian pulses with fidelity factor more than 95% in time‐domain. Measured gain and half power beam width (HPBW) are 6.1‐9.1 dBi and 44°‐29° in 4.40‐10.60 GHz band, respectively, which show an improvement of 1‐3 dBi in gain and half power beam‐width is reduced by 5°‐10° when compared with previously designed antennas. Experimental results show good agreement with CST simulation.