Low Complexity Preprocessing Approach for Wireless Physical Layer Secret Key Extraction Based on PCA

Achieving communication security, along with high computational efficiency, is one of the challenging issues in the advancement of modern resource constraint wireless networks. Wireless physical layer secure key extraction in conjunction with suitable preprocessing techniques may be a possible way out. Principal component analysis (PCA) is one of the dimensionality reduction techniques employed commonly in various domains for different applications. However, the physical layer secure key extraction employing PCA as dimensionality reduction is untouched so far. This paper presents a comprehensive study on PCA based wireless secret key extraction with real-time experimentation. In this work, we propose to apply PCA as a preprocessing technique to reduce the total number of numerical computations required in the key generation process, by cutting down the dimension of the input data set. We propose to select the extracted principal components to be processed further for key generation, based on their information content and cross-correlation. We analyzed the performance of the proposed in terms of bit disagreement rate, key randomness and pass ratio. The computational complexity of the proposed approach is derived and the effect of dimensionality reduction factor (\({\mathbf{R}}_{\mathbf{f}}\)) on the required numerical computations is analyzed. It is found that substantial improvement in bit disagreement performance is achieved along with a significant reduction in the required numerical computations. Remarkably, these outcomes are achieved by slightly modifying one of the blocks of the traditional key generation system. Furthermore, the practicability of the proposed technique is verified through real-time experimentation in different physical scenarios.

     

Influence of soil density on gas permeability and water retention in soils amended with in-house produced biochar

Biochar has been used as an environment-friendly enhancer to improve the hydraulic properties(e.g.suction and water retention) of soil.However,variations in densities alter the properties of the soil-biochar mix.Such density variations are observed in agriculture(loosely compacted) and engineering(densely compacted) applications.The influence of biochar amendment on gas permeability of soil has been barely investigated,especially for soil with diffe rent densities.The maj or obj ective of this study is to investigate the water retention capacity,and gas permeability of biochar-amended soil(BAS) with different biochar contents under varying degree of compaction(DOC) conditions.In-house produced novel biochar was mixed with the soil at different amendment rates(i.e.biochar contents of 0%,5% and 10%).All BAS samples were compacted at three DOCs(65%,80% and 95%) in polyvinyl chloride(PVC)tubes.Each soil column was subjected to drying-wetting cycles,during which soil suction,water content,and gas permeability were measured.A simplified theoretical framework for estimating the void ratio of BAS was proposed.The experimental results reveal that the addition of biochar significantly decreased gas permeability k_g as compared with that of bare soil(BS).However,the addition of 5%biochar is found to be optimum in decreasing kg with an increase of DOC(i.e.k_(g,65%) k_(g,80%) k_(g,95%)) at a relatively low suction range(200 kPa) because both biochar and compaction treatment reduce the connected pores.     

Sol-gel auto-combustion synthesis of Ba–Sr hexaferrite ceramic powders

We report the mechanism involved in sol-gel auto-combustion synthesis of Ba–Sr-hexaferrite (Ba_1-xSr_xFe₁₂O₁₉; x = 0, 0.25, 0.5, 0.75 and 1, BSFO) ceramic powders through the analysis of the phases evolved during annealing of the as-synthesized powders, along with their structure and morphological studies. The XRD patterns of the as-synthesized samples indicate the formation of barium/strontium monoferrite ((Ba/Sr)Fe₂O₄) and maghemite (γ-Fe₂O₃) phases along with a minute amount of hematite (α-Fe₂O₃) phase. Annealing of these samples facilitates formation of BSFO phase through the solid state reaction between BaFe₂O₄ and γ-Fe₂O₃ phase. Interestingly, after annealing the samples with x = 0, 0.5 and 1, at 1000 °C for 2 h, we observed that phase pure Ba–Sr hexaferrite structure forms, but for samples with x = 0.25 and 0.75, high amount of hematite (α-Fe₂O₃) phase is observed, especially for x = 0.75. The reason associated with this could be the large difference between the ionic radii of Ba²⁺ and Sr²⁺ ions occupying the oxygen site. Furthermore, our study on annealing dependent phase evolution confirms that, this difference in ionic radii forbids the formation of a single phase Ba–Sr hexaferrite. The growth of clear hexagonal-shaped plate-like particles with varied particle sizes was observed for all the samples. The particle size variation may be due to the influence of the ionic radii difference on the sinterability of the samples. Our study provides a better understanding of synthesis mechanism of Ba–Sr hexaferrite samples.     

Development of LTCC micro-hotplate with PTC temperature sensor for gas-sensing applications

Low temperature co-fired ceramic (LTCC) micro-hotplates show wide applications in gas sensors and micro-fluidic devices. It is easily structured in three-dimensional structures. This paper presents the low power consumption micro-hotplates which were developed with PTC (positive temperature coefficient) temperature sensor and inter-digitated electrodes. The paper presents two different structures for micro-hotplate with platinum as a heating element. The PTC temperature sensor using two different materials viz. PdAg and platinum paste are developed with micro-hotplates. The simulation has been achieved through COMSOL for LTCC and alumina micro-hotplates. The temperature variation with power consumption has been measured for the developed LTCC micro-hotplates. The change in resistance of PTC temperature sensors was measured with micro-hotplate temperature. The aim of this study was to place a temperature sensor with the gas sensor module to measure and control the temperature of micro-hotplate. A SnO₂ sensing layer is coated on LTCC micro-hotplate using screen printing and characterized for the sensing of carbon monoxide gas (CO). This study will be beneficial for designing hotplates based on LTCC technology with low power consumption and better stability of temperature for gas-sensing applications.     

Discrete‐time sector based hands‐off control for nonlinear system

This article presents a hands‐off control design for discrete‐time nonlinear system with a special type of nonlinear sector termed as “discrete‐time sector.” The design method to define the boundary of a discrete‐time sector is done with control‐Lyapunov function. The generalization of nonlinear system is viewed in the perspective of a comparison function. By means of a proposed sector, a switching control is designed such that no control action is experienced inside the sector thus, saving unnecessary control efforts. However, to study the robustness for discrete‐time system, a hands‐off control is modified to ensure the monotonic decrease in the energy of the system. Finally, the proposed approach is verified with the simulation results.     

Sol- gel synthesis of Ga2O3 nanorods and effect of precursor chemistry on their structural and morphological properties

Synthesis of mono-crystalline Ga₂O₃ Nanorods was done by sol-gel transformation of gallium(III) isopropoxide (Ga(OPrⁱ)₃). XRD studies were done to determine the planes and crystal structure of synthesized nanorods that showed the synthesis of β-Ga₂O₃(a). TEM studies of synthesized Ga₂O₃ confirmed the synthesis of monocrystalline β-Ga₂O₃ nanorods. To study the effect of precursor chemistry and to determine role of precursor structures on the crystal structure, phase and morphology of the Ga₂O₃, a new modified precursor complex was synthesized. The reaction of Ga(OPrⁱ)₃ with N-phenylsalicylaldimine, [C₆H₄(OH)CH=N(C₆H₅)] in 1:1?M ratio yielded [{(H₅C₆)N?=?CH-C₆H₄O}Ga(OPrⁱ)₂]. The newly synthesized complex was characterized by elemental analyses, molecular weight measurement, FT-IR and NMR (¹H and ¹³C) spectral studies. Spectral studies of the modified complex suggest the presence of bi-dentate mode of attachment of Schiff's base in the solution state. Sol-gel transformations of [{(H₅C₆)N?=?CH-C₆H₄O}Ga(OPrⁱ)₂] in organic medium, yielded γ-Ga₂O₃(b), as found by XRD studies. TEM image of the sample (a) revealed the formation of nano-rods of oxide with average diameter of ~100?nm whereas the TEM image of sample (b) showed presence of nano-sized particles of oxide with average particle size of 10?nm. Morphological and compositional studies of synthesized samples (a) and (b) were carried out using SEM and EDX. The method provides a possibility of large scale synthesis of dissimilar shaped and pure Ga₂O₃ nanoparticles.     

APuML: An Efficient Approach to Detect Mobile Phishing Webpages using Machine Learning

Wireless Personal Communications - The recent trend in wireless technology has been tremadously increased the demand of higher frequency bands from every corners of the mobile technology. As next...     

Impact of crystal structure and microstructure on electrical properties of Ho doped lead-free BCST piezoceramics

Conventional solid state sintering method was used to synthesize lead-free (Ba_0.91Ca_0.09Sn_0.07Ti_0.93)O₃-xHo₂O₃ (x?=?0, 1.2,1.4,1.6,1.8 and 2.0?mol%) ceramics. The influence on electrical properties of the system as a result of the structural and microstructural changes introduced by the incorporation of rare earth Ho³⁺ ions has been investigated. The X-ray diffraction analysis reveals that Ho³⁺ ions completely diffuse into the (Ba_0.91Ca_0.09Sn_0.07Ti_0.93)O₃ lattice to form a homogeneous solid solution with a pure perovskite structure having tetragonal symmetry. Evidence of Ho³⁺ substituting Ti⁴⁺ via the oxygen vacancy compensation mechanism exists in the range of 0–1.6?mol % Ho content, while the self-compensation mode is the preferred mechanism beyond 1.6?mol %. The average grain size exhibits a drastic reduction from 16?μm to 0.7?μm as the Ho content increases from 0 to 1.6?mol%, followed by a slight increase at higher Ho concentration. It suggests that addition of Ho³⁺ inhibits grain growth in the ceramics. In the composition range studied, increasing Ho³⁺ content produces a gradual decrease in the relative density from 93% to 81%, room temperature dielectric constant (ε_rt) from 3997 to 807, electromechanical coupling factor (k_p) from 0.23 to 0.06, and piezoelectric charge constant (d₃₃) from 102 to 38?pC/N. This degradation in the properties is attributed to the crystalline and microstructural changes driven by the increasing presence of Ho content in the ceramics.     

A combined experimental‐numerical framework for residual energy determination in spent lithium‐ion battery packs

The present research proposes a combined framework that evaluates remaining capacity, material behavior, ions concentration of remaining metals, and current rate of chemical reactions of spent Li‐ion batteries accurately. Voltage, temperature, internal resistance, and capacity were studied during charging and discharging cycles. Genetic programming was applied on the obtained data to develop a model to predict remaining capacity. The results of experimental work and those estimated from model were found to be correlated, confirming the validation of model. Materials structure and electrochemical behavior of electrodes during cycles were studied by cyclic voltammetry, scanning electron microscopy, and energy dispersion spectrum.