A precise sensor fault detection technique using statistical techniques for wireless body area networks

One of the major challenges in wireless body area networks (WBANs) is sensor fault detection. This paper reports a method for the precise identification of faulty sensors, which should help users identify true medical conditions and reduce the rate of false alarms, thereby improving the quality of services offered by WBANs. The proposed sensor fault detection (SFD) algorithm is based on Pearson correlation coefficients and simple statistical methods. The proposed method identifies strongly correlated parameters using Pearson correlation coefficients, and the proposed SFD algorithm detects faulty sensors. We validated the proposed SFD algorithm using two datasets from the Multiparameter Intelligent Monitoring in Intensive Care database and compared the results to those of existing methods. The time complexity of the proposed algorithm was also compared to that of existing methods. The proposed algorithm achieved high detection rates and low false alarm rates with accuracies of 97.23% and 93.99% for Dataset 1 and Dataset 2, respectively.     

Control of the structure,morphology and dielectric properties of bismuth titanate ceramics by praseodymium substitution using an intermediate fuel agent-assisted self-combustion synthesis

The volatilization of bismuth (Bi) species and bismuth oxide (Bi₂O₃) leads to the presence of the oxygen vacancies (V _O⁰⁰) and consequently restrains the properties of bismuth titanate (BIT; Bi₄Ti₃O₁₂). This report presents the incorporation of different atomic ratios of praseodymium ion (Pr³⁺: x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0) into the BIT (Bi_4−x Pr _x Ti₃O₁₂) ceramics through an intermediate fuel agent-assisted self-combustion synthesis (IFSC). X-ray diffraction and Raman spectroscopy results revealed that some of bismuth ion (Bi³⁺) in the pseudo-perovskite layer containing Ti–O octahedra was substituted by Pr³⁺ ion. The substitution by ion with a smaller ionic radius caused the structure distortion and consequently resulted in the phase transformation from an orthorhombic symmetry to a tetragonal symmetry. Besides, it suppressed the volatilization of Bi and Bi₂O₃ and increased the stability of metal–oxygen octahedra in the BIT. These play a crucial role to control the crystal growth, as well as limit the V _O⁰⁰. Dense ceramic with a relative density up to 96.2% was obtained by incorporating Pr³⁺ with atomic ratio of 1.0. It exhibited high dielectric constant as 908.19 and low dissipation factor as 0.0011. The results address the possibility to control the structure, morphology and dielectric properties of BIT ceramic by incorporating Pr³⁺ ion through IFSC.     

A Novel and Simple Process for Nanosized Mg‐Mn Ferrite Preparation from Solution Combustion Method and Study of its Characteristics

A novel solution combustion method has been used to prepare Mg‐Mn ferrites of various compositions, Mg_0.9Mn_0.1Fe_1‐xO₄ where x = 0.2, 0.4, 0.6, 0.8, and the properties were investigated in the present work. Nano‐size Mg‐Mn ferrite particles with diameter in the range of 8~ 15 nm were successfully formed via this method. The combustion temperature of the oxidation‐reduction was apparently occurred at 200°C. The result of X‐ray diffraction (XRD) analysis indicated that the as‐burnt powder affords a pure single spinel ferrite phase at low temperature. The thermal analysis of nitrate–citrate gels was characterized by DTA‐TG. The TEM and SEM observations give the morphology and microstructure of the products. The dielectric properties of the sintered Mg‐Mn ferrites were investigated by using HP/Agilent 4291B RF impedence/material analyzer. It was found that there was no maximum dielectric loss within the measured frequency range until 1 GHz due to excellent compositional control in this method.     

GRAPES-3—A high-density air shower array for studies on the structure in the cosmic-ray energy spectrum near the knee

The change in the spectral index from about -2.7 to -3.1 at 3×10¹⁵ eV in the all-particle energy spectrum of primary cosmic rays is very significant for learning about the nature of cosmic sources of ultra-high energy particles and their acceleration and propagation in the galactic disk. Any observation of a fine structure in the spectrum would be important for improving our understanding of these physical processes. The GRAPES-3 air shower array has been designed to achieve higher precision in determination of various shower parameters to enable observation of any fine structure in the energy spectrum, if it exists. The details of the shower detectors, shower trigger and the data acquisition system are presented here along with estimates of trigger efficiencies from Monte Carlo simulations for primary photons (γ-rays) and several nuclei.     

Phase formation and dielectric properties of Ba<Subscript>0.5</Subscript>Sr<Subscript>0.5</Subscript>TiO<Subscript>3</Subscript> by slow injection sol–gel technique

A simple sol–gel process incorporating slow precursor injection technique was employed to synthesize homogeneous Ba_0.5Sr_0.5TiO₃ nano powders. The Ba_0.5Sr_0.5TiO₃ samples were subjected to calcination temperatures from 600 to 1,100 °C and sintering temperatures from 1,250 to 1,350 °C for the study of phase formation, crystallite size, particle distribution, and dielectric properties. Single phase Ba_0.5Sr_0.5TiO₃ with a cubic perovskite structure was successfully synthesized after calcination at 800 °C. The average size of the nano particles is 42 nm with a narrow size distribution, and a standard deviation of 10%. The highest values recorded within the investigated range for dielectric constant, and dielectric loss measured at 1 kHz are 1,164 and 0.063, respectively, for Ba_0.5Sr_0.5TiO₃ pellets calcined at 800 °C and sintered at 1,350 °C. Leakage current density measured at 5 V for the Ba_0.5Sr_0.5TiO₃ pellet was found to be 49.4 pA/cm².     

Structural characteristics and dielectric properties of neodymium doped barium titanate

Neodymium (Nd) doped barium titanate powder (Ba_(1−x)Nd _x TiO₃) with x value varying from 0, 0.01, 0.03, 0.05, 0.07, 0.10 and 0.13 was prepared using the sol gel method. The powder samples were calcined at 700 °C and tetragonal phase appeared in the powders before they were sintered at 1250 °C for 3 h. The undoped samples have a polycrystalline tetragonal structure, but Nd doping into the BaTiO₃ caused phase transformation from tetragonal to cubic. The smaller grains (0.35 μm) produced with the addition of Nd is associated to the inhibition of grain growth of samples. The powders for each composition were pressed into pellets and tested as dielectric resonator antenna (DRA). It was found that on the actual antenna circuit, each sample showed a resonance frequency at X-band application and a dielectric constant value in the range of 51.25–56.89 and tangent loss was 0.039–0.045, depending on the concentration of the Nd at room temperature.     

Effect of heat treatment on WO3-loaded TiO2 nanotubes for hydrogen generation via enhanced water splitting

We determined the optimum phase structure of WO₃-loaded TiO₂ nanotubes (WTNs) for hydrogen generation via photoelectrochemical (PEC) water splitting by controlling the annealing temperature. The surface morphology of WTNs was closely related to crystal growth and phase transformation. The nanotubular structure completely collapsed at 700 °C due to the anatase–rutile phase transformation. In PEC studies, high-crystallinity anatase-phase WTNs exhibited a higher photocurrent density (2.4 mA/cm²) than WTNs of amorphous or polycrystalline (anatase+rutile) phases. This can mainly be attributed to better charge carrier separation and transportation in PEC water splitting by providing an effective way to address recombination losses.     

Photoactivity of anatase–rutile TiO2 nanotubes formed by anodization method

Titania (TiO₂) nanotubes were prepared by anodizing titanium (Ti) foils in an electrochemical bath consisting of 1 M glycerol with 0.5 wt.% NH₄F.The pH of the bath was kept constant at 6 and the anodization voltage was varied from 5 V, 20 V to 30 V. It is found that the morphology of the anodized titanium is a function of anodization voltage with pits-like oxide formed for the sample made at 5 V and samples made at 20 V and 30 V consisted of well-aligned nanotubes growing perpendicularly on the titanium foil. However, the nanotubes formed on the samples made at 30 V were not uniform in terms of the nanotubes' diameter and wall thickness. Regardless of the anodization voltage, as anodised samples were amorphous. The crystal structure evolution was studied as a function of annealing temperatures and was characterised by X-ray diffraction and Raman spectroscopy analyses. Crystallization of the nanotubes to anatase phase occurred at 400 °C while rutile formation occurred at 700 °C. Disintegration of the nanotube arrays was observed at 600 °C and the structure completely vanished at 700 °C. TiO₂ nanotube annealed at 400 °C and containing 100% anatase revealed the highest photocatalytic activity for the degradation of methyl orange. Consequently, these results indicate that diameter, wall thickness, crystal structure and degree of crystallinity of the TiO₂ nanotube arrays are the important factors influencing the efficiency of the photocatalytic activity.     

Carbon-incorporated TiO2 photoelectrodes prepared via rapid-anodic oxidation for efficient visible-light hydrogen generation

Carbon-incorporated titanium dioxide (TiO₂) photoelectrodes with different structural features were prepared via rapid-anodic oxidation under different electrical potentials and exposure times. The interstitial carbon arising from the pyrogenation of ethylene glycol electrolytes induced a new C2p occupied state at the bottom of the conduction band, which lowered the band gap energy to ∼2.3 eV and consequently enabled the visible-light responsiveness. Photoelectrodes with nanotubular structures provided higher photoconversion efficiency (η) and hydrogen (H₂) evolution capability than those with irregular structures. The increased aspect ratio, wall thickness, and pore size of the nanotube arrays contributed to η through greater photon excitation and penetration. However, this contribution is limited by the high recombination of the charge carriers at ultra-high aspect ratios. Photoelectrodes with a nanotube length of ∼19.5 μm, pore size of ∼103 nm, wall thickness of ∼17 nm, and aspect ratio of ∼142.5 exhibited remarkable capability to generate H₂ at an evolution rate of up to ∼508.3 μL min⁻¹ cm⁻² and η of ∼2.3%.