Curve-fit analysis of chlorophyll fluorescence spectra: Application to nutrient stress detection in sunflower

The in vivo laser-induced chlorophyll fluorescence (LICF) spectra of healthy and nutrient-deficient sunflower plants were measured on a Jobin Yvon monochromator with He---Ne laser excitation. To correctly determine the peak center and to evaluate the relative contributions of the bands in the total fluorescence spectrum, the steady state LICF spectra were analyzed with a nonlinear iterative procedure using Gaussian, Lorentzian, Pearson, Voigt, and exponential Gaussian spectral functions. It was observed that curve fitting performed by using two Gaussian peaks centered at 690 and 730 nm usually fits well to the chlorophyll fluorescence spectra. After curve fitting, the mean peak centers of the red and far-red chlorophyll bands of control plants were observed at 688.2 and 725.4 nm, respectively. A blue shift of as much as 9 nm in the peak position of the far-red band was observed with nutrient stress, whereas the shift in position of the red band was only of the order of a few nanometers. Further, the width at half maximum of the far-red band was found to increase by as much as 20 nm with nutrient stress. Curve fitting could thus separate out the red and far-red fluorescence spectra from a pair of normally distributed curves centered at 690 and 730 nm wavelengths, thereby differentiating the effects due to reabsorption from those due directly to changes in photosynthetic electron transport. The F690/F730 fluorescence intensity ratio obtained from curve-fitted parameters was found to be more sensitive to plant stress than were fluorescence values alone. Results indicate that a curve-fitting analysis of LICF spectra using Gaussian spectral functions is a very useful and sensitive method of evaluating spectral features from a statistical point of view and for accurate determination of contributions from constituent bands in the whole leaf fluorescence spectrum.     

Compact slotline fed enhanced gain dipole antenna for 5.2 GHz/5.8‐GHz applications

A high‐efficiency and high‐gain slotline fed directive dipole antenna is developed for microwave applications. The antenna offers an average gain of 7.9 dBi with a front to back ratio better than 20 dB and a cross polar level better than ?20 dB. Design equations of the antenna are developed and validated on different substrates. The simulation and experimental results show that the proposed antenna exhibits high gain and robust radiation patterns in the entire frequency band. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013.     

Reconfigurable Antennas for Advanced Wireless Communications: A Review

Wireless Personal Communications - Modern era of wireless communication relies on the evolution of adaptive antennas. This influences the new age antenna designs to adapt themselves to the changing...     

Modelling and Detection of Worm Propagation for Web Vehicular Ad Hoc Network (WVANET)

Wireless Personal Communications - Web Vehicular Ad Hoc Network becomes the major research platform these days. This web vehicular ad hoc network is fundamentally different from the earlier...     

Microwave Dielectric Properties of Rutile Filled PEEK Composites

Ceramic-filled PEEK composites were prepared by sigma mixing followed by thermolamination. Rutile-grade titanium dioxide, particle size less than 5 μm, was used as the particulate filler in the PEEK matrix to tailor the dielectric properties of the composite matrix. The dispersion of the particular filler in the PEEK matrix was studied using scanning electron microscopy. The dielectric properties of the PEEK/TiO₂ composite materials were measured in the low frequency region up to 13 MHz using an impedance analyzer. Dielectric properties in the microwave region were measured using cavity perturbation technique to evaluate the use of the composites as packaging material. Experimental results were compared with theoretically predicted values using the Lichtenecker equation. The present study shows that temperature-stable packaging materials can be realized in the PEEK/TiO₂ systems by judiciously controlling the ceramic filler concentration.     

Polystyrene/Sr2Ce2Ti5O15 composites with low dielectric loss for microwave substrate applications

Sr₂Ce₂Ti₅O₁₅ (Strontium Cerium Titanate or SCT) ceramic was prepared by solid‐state route. A composite of polystyrene/Sr₂Ce₂Ti₅O₁₅ was made using melt mixing technique in a Kneading machine. The microstructure of the composite was investigated using a Scanning Electron Microscope. The dielectric properties of the composites were studied at radio frequency and microwave frequencies. It is observed that relative permittivity and loss tangent increase with volume fraction of the ceramics. The mechanical properties of the composites were investigated using microhardness tester. For 50 volume percentage loading of the ceramic, the composite has relative permittivity of 13.6and dielectric loss of 4.28 × 10^?4. The experimentally observed permittivity was compared with the theoretical models. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Smart Fraud Detection in E-Transactions Using Synthetic Minority Oversampling and Binary Harris Hawks Optimization

Fraud Transactions are haunting the economy of many individuals with several factors across the globe. This research focuses on developing a mechanism by integrating various optimized machine-learning algorithms to ensure the security and integrity of digital transactions. This research proposes a novel methodology through three stages. Firstly, Synthetic Minority Oversampling Technique (SMOTE) is applied to get balanced data. Secondly, SMOTE is fed to the nature-inspired Meta Heuristic (MH) algorithm, namely Binary Harris Hawks Optimization (BinHHO), Binary Aquila Optimization (BAO), and Binary Grey Wolf Optimization (BGWO), for feature selection. BinHHO has performed well when compared with the other two. Thirdly, features from BinHHO are fed to the supervised learning algorithms to classify the transactions such as fraud and non-fraud. The efficiency of BinHHO is analyzed with other popular MH algorithms. The BinHHO has achieved the highest accuracy of 99.95% and demonstrates a more significant positive effect on the performance of the proposed model.     

Detection of mosaic virus disease in cassava plants by sunlight-induced fluorescence imaging: a pilot study for proximal sensing

Cassava mosaic disease (CMD) is a prominent virus infection that causes considerable crop damage and yield reduction. Early detection of crop damage by remote sensing could be a useful tool for initiating remedial measures to reduce further crop damage. This article presents a non-destructive method for detection and classification of CMD infection, based on the red:far-red chlorophyll (chl) fluorescence image ratio. This pilot study was carried out in 14 varieties of potted cassava plants (Manihot esculenta Crantz) with a multispectral imaging system (MSIS) consisting of an electron multiplying charge coupled device (EMCCD) camera. Sunlight-induced chl fluorescence (SICF) images of plant leaves were recorded using the MSIS at the Fraunhofer lines of O₂-B at 687 nm and O₂-A at 759.5 nm and their off-lines at 684 and 757.5 nm. The recorded images were analysed using the Fraunhofer line discrimination (FLD) technique to extract the SICF from the solar reflectance in the recorded images. The chl fluorescence image ratio (red:far-red, F₆₈₇:F₇₆₀) was computed and correlated with the laser-induced chl fluorescence (LICF) ratio (F₆₈₅:F₇₃₅) determined by point monitoring, chl content variation, and the net photosynthetic rate (P_n). The scatter plot of the F₆₈₇:F₇₆₀ image ratio showed good discrimination between different levels of CMD infection as evidenced by the high sensitivity and specificity values. It is observed that the fluorescence image ratio (F₆₈₇:F₇₆₀) has a good correlation with P_n (coefficient of determination (R²) = 0.85), chl content (R² = 0.82), and the LICF ratio (F₆₈₅:F₇₃₅) (R² = 0.80), thereby highlighting the potential of the SICF image ratio in the discrimination of CMD infection. The results clearly indicate that changes in the red:far-red fluorescence image ratio due to CMD stress can easily be detected at an early stage and the technique has great potential for monitoring the health of crops and vegetation from proximal sensing platforms.     

Compact CPW‐Fed slot antenna with harmonic suppression

A compact coplanar waveguide (CPW)‐fed uniplanar antenna with harmonic suppression characteristics is presented. The above characteristics are achieved by properly modifying the ground plane and adjusting the signal strip of an open‐ended CPW‐fed transmission line. The simulated and experimental characteristics of the antenna are presented, compared, and discussed. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.