Classification of DoS Attacks in Smart Underwater Wireless Sensor Network

As per the most recent literature, Orthogonal Frequency Division Multiplexing (OFDM), a multi access technique, is considered most suitable for the 3G, 4G and 5G techniques in high speed wireless communication. What made OFDM most popular is its ability to deliver high bandwidth efficiency and superior data rate. Besides it, high value of peak to average power ratio (PAPR) and Inter Carrier Interference (ICI) are the challenges to tackle down via appropriate mitigation scheme. As a research contribution in the present work, an improved self-cancellation (SC) technique is designed and simulated through Simulink to mitigate the effect of ICI. This novel proposed technique (Improved SC) is designed over discrete wavelet transform (DWT) based OFDM and compared with conventional SC scheme over different channel conditions i.e. AWGN and Rayleigh fading environments. It is found that proposed DWT-OFDM with Improved SC scheme outperforms conventional SC technique significantly, under both AWGN and Rayleigh channel conditions. Further, in order to justify the novelty in the research contribution, a Split-DWT based Simulink model for Improved SC scheme is investigated to analyse the BER performance. This Split-DWT based Simulink model presented here foretells the future research potential in wavelet hybridization of OFDM to side-line ICI effects more efficiently.

     

Impact of ac/dc spark anodizing on the corrosion resistance of Al–Cu alloys

An ac/dc spark anodization method was used to deposit an oxide film (6 ± 3 μm in thickness) on the Al–Cu alloy AA2219. The oxide films were formed at 10 mA/cm² for 30 min in an alkaline silicate solution, showing three main stages of growth. Scanning electron microscopy and electron microprobe analysis revealed that the oxide films are not uniform and consist of three main layers, an inner Al-rich barrier layer (∼1 μm), an intermediate Al–Si mixed oxide layer (∼2 ± 1 μm), and an outer porous Si-rich layer (∼3 ± 3 μm). In addition, microscopic analysis showed that the Al₂Cu intermetallics present in the alloy have not been excessively oxidized during the anodization process and thus are retained beneath the oxide film, as desired. The coating passivity and corrosion resistance, evaluated using linear sweep voltammetry (LSV) in pH 7 borate buffer solution and electrochemical impedance spectroscopy (EIS) in 0.86 M NaCl solution, respectively, were both significantly improved after spark-anodization.     

NMOS IC's for clock and data regeneration in gigabit-per-secondoptical-fiber receivers

The design and performance of two essential analog circuits in optical-fiber receivers is described. A time-interleaved decision circuit is capable of regenerating 35-mV nonreturn-to-zero (NRZ) data inputs to full logic levels at 1.1 Gb/s with 10^-11 bit error rate (BER), and a phase-locked loop (PLL) extracts the clock from a 2 ²³ long pseudorandom sequence at 1.5 Gb/s with 13-ps r.m.s. jitter. The two circuits have been implemented as 1-μm NMOS ICs, and in their core area dissipate 200 and 350 mW, respectively     

Behavior of Structural Composite Lumber T-Beam Bridge Girders after Fatigue Loading

Recent innovation in the engineered wood industry has produced structural composite lumber (SCL) that achieves excellent strength, stiffness, and efficient use of wood. Product variations of SCL, such as laminated veneer lumber (LVL) and parallel strand lumber (PSL), are currently being used in transportation to produce bridge girders and decks for rural and other low traffic volume roads. Although the elastic and shear properties of SCL are available, no attempt has been made to estimate the fatigue performance of bridge girders. This study tested 12 new and 2 old, weathered SCL T-beam bridge girders with material and preservative variations for AASHTO-specified flexural fatigue under a stress-controlled test setup simulating 60?years of service. Transverse posttension was applied to the girders simulating a real-life situation. Results from the study indicate that the girders are capable of withstanding the repetitive loads without much physical damage. A few of the LVL girders had severe delamination at the SCL-epoxy interface. The fatigued girders were loaded statically up to failure and compared with the ultimate flexural strength of fresh girders. The girders did not show any appreciable strength loss because of one million cycles of fatigue loading. There was no effect of SCL type and preservative treatment on fatigue strength.     

Surface characterization of zincated aluminium and selected alloys at the early stage of the autocatalytic electroless nickel immersion process

In this work the changing structure of nickel–phosphorus deposits on aluminium and its alloys at the early stage of electroless nickel phosphorus deposition using hypophosphite ion as reducing agent has been studied. Prior to electroless nickel deposition, zincating is used for pre-treatment of aluminium substrates. The surface morphology and structure of the electroless Ni–P layers were characterized by scanning electron microscopy and X-ray diffraction analysis. Results show that Ni–P deposition is closely related to the dissolution of the zincating layer, followed by progressive nickel nucleation. The nuclei serve as a catalytic surface for further Ni–P deposition which increases with deposition time. The growth and coalescence of the nuclei on the aluminium substrate results in crystalline layers of Ni–P.     

Dental erosion potential of beverages and bottled drinking water in Bangladesh

Dental erosion is a growing health problem linked to the exceptional increase in the consumption of soft drinks, fruit juices, and sport drinks in many countries including Bangladesh. Dental erosion is the chemical dissolution of the dental hard tissues by acids without the involvement of microorganisms. Hydrogen ions (H⁺) from acidic solutions can replace the calcium ions (Ca²⁺) of the enamel, consequently breaking the crystal structure of the enamel and initiating dental erosion. Erosive tooth wear can lead to severe impairment of esthetics along with loss of hardness and functionality. Sources of the erosive acidic challenges can be intrinsic (i.e., gastroesophaegal reflux disease) and/or extrinsic (i.e., exposure from acidic foods and beverages). Continuous intake of drinks or food with pH lower than the critical erosive pH of enamel (5.2–5.5) and root dentin (~6.7) are considered to be responsible for dental erosion. Drinks with low pH and high titratable acidity (TA) have more potential to dissolved enamel and root dentin; on the other hand, drinks with low degree of saturation can stimulate leaching of minerals. In Bangladesh, there is limited scientific information available to assess the potential of dental erosion of the commercially available beverages and drinking water. This research aims to characterize the dental erosion potential of soft drinks, energy drinks, fruit juices, and bottled drinking water available in Bangladesh by determining their pH, TA, calcium (Ca²⁺), and phosphate (PO₄^3?). The degrees of saturation of the selected samples were calculated from the experimental results of pH, calcium, and phosphate levels. Soft drinks were found to have high erosion potential followed by energy drinks, fruit juices, and bottled drinking water. Most of the beverages locally available were found highly acidic. Phosphate levels were high in black cola drinks. Total TA was highest for the energy drinks, and moderate for soft drinks and fruit juices. Fruit juices contained high level of calcium compared with other beverages. The degree of saturation was moderate for fruit juices, and very low for few of the soft drinks and most of the bottled drinking waters. This study will be useful as a reference line for the health professionals and regulatory authorities for quality control of the beverages and bottled drinking water available in the local market.     

Cluster Estimation in Terrestrial and Underwater Sensor Networks

Wireless Personal Communications - In Wireless Sensor Network (WSN), clustering is considered as an efficient network topology which maximizes the received data at the sink by minimizing a direct...     

Decision and clock recovery circuits for gigahertz optical fiber receivers in silicon NMOS

New design techniques for implementing a data and clock recovery circuit on a silicon NMOS monolithic IC employing 1-μm feature sizes, and operating at speeds greater than 2 Gbit/s are described. A clocked comparator can resolve a 60-mV peak-to-peak signal into logic levels at 2 Gbit/s. The circuit can tolerate a 100° phase margin between the incoming signal and the clock. An NRZ data rate of 4 Gbit/s may be resolved by two such multiplexed circuits following a preamplifier in the same technology. A VCO capable of operation at 2 GHz in a PLL, that does not require off-chip components, is also described. An observer loop concept is employed in the PLL to align the recovered clock signal with the incoming data.     

Energy Conservation Using RR Algorithm in Dynamic Cluster Based WSN

Wireless Personal Communications - The energy consumption during the cluster head selection phase in a hierarchal and dynamic cluster based wireless sensor network had been considered insignificant...