Self and static interference mitigation scheme for coexisting wireless networks

High density of coexisting networks in the Industrial, Scientific and Medical (ISM) band leads to static and self interferences among different communication entities. The inevitability of these interferences demands for interference avoidance schemes to ensure reliability of network operations. This paper proposes a novel Diversified Adaptive Frequency Rolling (DAFR) technique for frequency hopping in Bluetooth piconets. DAFR employs intelligent hopping procedures in order to mitigate self interferences, weeds out the static interferer efficiently and ensures sufficient frequency diversity. We compare the performance of our proposed technique with the widely used existing frequency hopping techniques, namely, Adaptive Frequency Hopping (AFH) and Adaptive Frequency Rolling (AFR). Simulation studies validate the significant improvement in goodput and hopping diversity of our scheme compared to other schemes and demonstrate its potential benefit in real world deployment.     

A data mining approach for machine fault diagnosis based on associated frequency patterns

Bearings play a crucial role in rotational machines and their failure is one of the foremost causes of breakdowns in rotary machinery. Their functionality is directly relevant to the operational performance, service life and efficiency of these machines. Therefore, bearing fault identification is very significant. The accuracy of fault or anomaly detection by the current techniques is not adequate. We propose a data mining-based framework for fault identification and anomaly detection from machine vibration data. In this framework, to capture the useful knowledge from the vibration data stream (VDS), we first pre-process the data using Fast Fourier Transform (FFT) to extract the frequency signature and then build a compact tree called SAFP-tree (sliding window associated frequency pattern tree), and propose a mining algorithm called SAFP. Our SAFP algorithm can mine associated frequency patterns (i.e., fault frequency signatures) in the current window of VDS and use them to identify faults in the bearing data. Finally, SAFP is further enhanced to SAFP-AD for anomaly detection by determining the normal behavior measure (NBM) from the extracted frequency patterns. The results show that our technique is very efficient in identifying faults and detecting anomalies over VDS and can be used for remote machine health diagnosis.     

Analysis of optimized signal processing algorithms for smart antenna system

By the exponential increase in cellular communication area, the user demands and with their side problems also tend to increase. Several techniques such as cell splitting, frequency reuse, diversity and so on have already been applied to overcome these problems. In all these procedures, smart antenna is one of the best techniques used to boost capacities, enlarge bandwidth, raise the SIR ratios, minimize the effects of fading and improve MIMO communications. An ordinary antenna array which can turn up into a smart antenna array is due to the signal processing algorithms, which consists of angle of arrival (AOA) estimations and Beamforming. In this paper, I will discuss and analyse about the MUSIC algorithm for AOA estimation and least mean squares algorithm for Beamforming.     

Photocatalytic conversion of CO2 into methanol using graphitic carbon nitride under solar,UV laser and broadband radiations

Photocatalytic conversion of carbon dioxide into methanol using highly efficient g‐C₃N₄, in conjunction with three different radiations (solar radiation, broad‐band ultraviolet (UV)–visible lamp, and laser beam) is presented. The optical, structural, and morphological properties of the synthesized g‐C₃N₄ were studied using advanced analytical techniques like Fourier transform infrared spectroscopy, UV–visible spectrometer, X‐ray diffraction, high‐resolution transmission electron microscopy, high‐angle annular dark field, and X‐ray photoelectron spectroscopy. The relative merits of the three sources of radiation in the presence of g‐C₃N₄ were studied in terms of key figures of merit of the photocatalytic process, namely, methanol production yield and quantum yield. As expected, after 40 min of irradiation, 355‐nm laser (40 mJ/pulse, 10 Hz) with g‐C₃N₄ rendered the best methanol production yield (510 μmol g ^{? 1} h ^{? 1}), followed by solar radiation (130 μmol g ^{? 1} h ^{? 1}), and UV broadband lamp. This indicates that the photon flux and the spectral properties of incident light are the key factors for the enhancement of methanol production yield. Although the methanol production yield with 355‐nm laser radiation is quite impressive because of the inherent high photon flux and the monochromatic nature of laser, the methanol yield of 130 μmol g ^{? 1} h ^{? 1} with natural sunlight is quite an important result, as it can be used for the development of large‐scale solar fuel generation facilities by harnessing the naturally abundant solar radiation. Copyright © 2017 John Wiley & Sons, Ltd.     

Laser sensor for detection of SF6 leaks in high powerinsulated switchgear systems

A novel photoacoustic spectrometer (PA) has been developed for in-situ detection of SF₆ leaks in low concentrations. The developed system is equipped with a sound alarm system and has been tested in the laboratory for very minute SF₆ leaks. This newly developed SF₆ detection device utilizes a high quality factor resonant photoacoustic cell and continuous wave (CW) line tunable CO₂ laser at 10.55 μm wavelength. Whenever SF₆ is detected an acoustic signal is generated and no signal appears from ambient air if there is no leakage of SF₆. An electret microphone is used for the detection of these acoustic signals. The system is capable of detecting leaks of the order of 3.5 ppbv (parts per billion by volume) concentration. This device has been proved to have significant applications to industrial organizations that have electric power gas insulated systems (GIS). It could be also applied for other applications such as monitoring of environmental pollutants with minimal adjustments     

Pulsed Laser Photoacoustic Detection of SO(2) Near 225.7 nm

A trace concentration of SO(2) near 225.7 nm has been detected with a master-oscillator power-oscillator laser system for the first time, to our knowledge. A photoacoustic absorption spectrum of SO(2) has been recorded on the (1)A(2)-(1)B(2) (pi-pi*) transition. Parametric dependence of the photoacoustic signal has been investigated. A detection limit (signal-to-noise ratio of 1) of 1.3 parts in 10(9) [1.3 ppbv (parts per billion by volume)] for SO(2) have been determined at 1 atmospheric pressure inside a photoacoustic cell.     

Synthesis of highly active nanocrystalline WO3 and its application in laser-induced photocatalytic removal of a dye from water

Tungsten oxide nanoparticles were synthesized using the sol–gel process and applied for heterogeneous photocatalytic removal of a dye using a 355 nm laser radiation generated from Nd:YAG for the first time. Effect of various parameters, such as calcination temperature, calcination time, catalyst concentration and laser energy on the photocatalytic removal of dye has been investigated. The study showed that almost complete degradation of dye can be achieved within very short time of reaction (within few minutes) in presence of nanocrystalline WO₃ under laser irradiation. The removal process obeys first-order kinetics with an appreciable rate constant 0.146 min⁻¹. The main reason of high efficiency is the nanostructure nature of WO₃ and the laser as an excitation source as compared with the conventional setups using lamps and conventional microstructure catalysts.     

A group theoretic approach to construct cryptographically strong substitution boxes

In this paper, we present a method to construct a substitution box used in encryption applications. The proposed algorithm for the construction of substitution box relies on the linear fractional transform method. The design methodology is simple, while the confusion-creating ability of the new substitution box is complex. The strength of the proposed substitution box is evaluated, and an insight is provided to quantify the confusion-creating ability. In addition, tests are performed to assess the vulnerability of the encrypted data to algebraic and statistical attacks. The substitution box is critically analyzed by strict avalanche criterion, bit independent criterion, differential approximation probability test, linear approximation probability test, non-linearity test, and majority logic criterion. The performance of the proposed substitution box is also compared with those of some of the well-known counterparts including AES, APA, Gray, S₈, Skipjack, Xyi, and prime of residue substitution boxes. It is apparent that the performance, in terms of confusion-creating ability, of the new substitution box is better than those of some of the existing non-linear components used in encryption systems. The majority logic criterion is applied to these substitution boxes to further evaluate the strength and usefulness.     

Synthesis of cadmium sulfide‐reduced graphene oxide nanocomposites by pulsed laser ablation in liquid for the enhanced photocatalytic reactions in the visible light

The large‐scale applications of cadmium sulfide (CdS) nanoparticles (NPs) as a photo‐catalyst are limited by their poor stability (high aggregation tendency) and consequent reduction in the surface area and increased rate of recombination of photoinduced electron‐hole pairs, despite its inherent positive feature of being visible light active. It has been reported that the photocatalytic performance of CdS can be considerably improved if CdS is made as a composite material with reduced graphene oxide (rGO) in an optimum ratio. In this work, for the first time, we adopted the technique of pulsed laser ablation in liquids (PLAL) to synthesize highly pure CdS NPs and the required CdS/rGO nanocomposites using high purity (99.9%) microstructured CdS and graphene oxide as chemical precursors. PLAL is a simple and rapid 1‐step synthesis process (where the reaction time is reduced from several hours to a few minutes), which does not require high temperature, toxic chemicals, and the final treatment to remove the unwanted by‐products. The optical and morphological characterizations revealed that the anchoring of CdS on rGO transformed the CdS/rGO composite into an efficient photo‐catalyst by enhancing the following positive attributes required for a good photo‐catalyst: (1) The inherent tendency of aggregation of CdS is considerably reduced; CdS NPs with an average grain size of 20 nm are well placed on the rGO sheets; and hence, the surface area of the catalyst was significantly increased to provide more active sites. (2) The reduced rate of photoinduced electron‐hole recombination manifested in the photoluminescence spectrum indicated the effective charge separation. (3) The enhanced light absorption in the visible/infrared region ensured the effectiveness of this material in naturally abundant solar radiation. In the CdS/rGO composite, the rGO sheets play the role of a supporting matrix, cocatalyst, and electron acceptor for CdS. To evaluate the photo‐catalytic performance of CdS/rGO, we applied it as a visible light‐driven photo‐catalyst for degrading methylene blue dye and found that CdS/rGO nanocomposite was more efficient than pure CdS in the visible spectral region. Therefore, PLAL provides a simple and 1‐step route to synthesize high‐purity visible light–driven photo‐catalysts and solar cell material.