Retardation of High-Temperature Fuel Ash Corrosion of Fireside Boiler Tubes via Nanoparticles

The high-temperature corrosion rate of boiler tubes was studied as a function of inhibitor concentration, time, and temperature in the absence and presence of fuel ash. Samples of steel tubes were taken from boilers that operate in Northern Baghdad Station for Electric Power Generation. Fuel ash was collected from the boiler combustion chamber, as well. Normal and nano-MgO were used as a corrosion inhibitor in different mixing ratios. A weight loss technique was used to evaluate the corrosion rates, while scanning electron microscopy was used to study the surface morphology. It was seen that corrosion rates increased with both time and temperature, and decreased with the addition of inhibitors. The maximum inhibitor efficiency was 81 %, obtained via using nano-MgO at mixing weight ratio 2:1, 600 °C, and 10 h. The Presence of fuel ash had harmful effects on the steel surface.     

Design considerations of high performance optical code division multiple access: a new spectral amplitude code based on laser and light emitting diode light source

A new code of optical code division multiple access (OCDMA) based on spectral amplitude coding (SAC) is described and analysed. The coding technique is called random diagonal (RD) code. One of the important properties of this code is that the cross-correlation at data segment is always zero, which means that phase intensity induced noise (PIIN) is reduced. From the construction of RD code sequence, the authors can see that the RD code is constructed using code segment and data segment. Using this code property, RD code is implemented using coherent source (multi-laser) and incoherent source (light emitting diode) for the code segment and data segment, respectively. RD code using two multi-sources (incoherent and coherent) can be considered as an effective way for maximising the capacity while minimising the cost of SAC-OCDMA. It is shown that the system using this new code matrices not only suppresses PIIN, but also allows a larger number of active users compared with other codes.     

Four-wave mixing reduction technique based on smart filter approach

This paper proposed a new technique to suppress the four-wave mixing (FWM) effect by using a smart filter technique. The behaviour of FWM and the performance of wavelength division multiplexing systems with 4 and 16 channels were simulated in the presence of the proposed technique. The simulation was also performed under different parameters such as input power, number of channels and channel spacing. The FWM power drastically decreases by 12 and 19 dB for the 4 and 16 channels, respectively, when the smart filter is used as compared with the conventional system. In terms of system performance, the suggested approach for 4 and 16 channels at the first channel offers low bit error rate (BER) values of 3.23 × 10^?23 and 1.7 × 10^?21, respectively. The smart filter with the channel spacing variation for the 4-channel system subsequently improved the BER value at the fourth channel. Results confirm that the smart filter approach is an active solution that can suppress the FWM effect in optical transmission systems.     

Optimum lipid production using agro-industrial wastewater treated microalgae as biofuel substrate

Abundant wastewater discharges from palm oil industries in tropical nations being a valuable resource of biodiesel need proper exploration. Research hinted that such wastewater as economical nutrient source or substrate can support the cultivation of microalgae. In this experiment, we have tested the growth and lipid production of five different microalgal strains in palm oil mill effluent (POME). POME as a biofuel substrate is demonstrated to be lucrative for microalgae-assisted lipids production. POME is rich in macro- and micronutrients can be used as a growth medium for algal growth in order to reduce the growth medium cost and environmental pollutions. Among the five microalgal strains tested, Chlorella sorokiniana revealed optimum biomass and lipid production. The productivity was evaluated in terms of chlorophyll content, growth rate, biomass, and lipid content, which discerned to be 0.099/day, 8.0 mg/L day and 2.68 mg/mg cell dry weight (CDW). Furthermore, in this study, an optimization study was carried out to enhance the microalgae to produce high lipid content using carbon-to-nitrogen ratio and different light/dark periods. The presence of nitrogen combined glucose (with a carbon-to-nitrogen ratio 100:7) as an alternative source to carbon displayed higher lipid production of 2.68 (mg/mg CDW) by C. sorokiniana. This study confirms that 8:16 h light/dark condition at C:TN ratio of 100:7 supported to produce high lipid content of 17 mg lipid/mg CDW. The above results revealed that POME could be a suitable growth media for the alga C. sorokiniana to improve the maximum lipid yield for biofuels production.     

Design and Analysis of a Wavelet Packet Modulation Based Differential Chaos Shift Keying Communication System

Wireless Personal Communications - In this paper, a new multicarrier based DCSK system that is combined a wavelet packet modulation (WPM) with differential chaos shift keying (DCSK) and named...     

Label‐QoS switching protocol for quality of service assurance in dynamic swarm robot local network

This paper presents the modeling and analysis of a proposed label–quality of service (QoS) switching protocol for heterogeneous robot in a swarm. Establishing the data communication and network in multirobot task allocation is an important aspect in robot collaboration. Instead of passing the data through the cloud network, each robot can be configured as a node in its swarm for intercommunication. This research was conducted to model and propose aggregation and classification methods in a swarm robot network inspired from multiprotocol label switching, namely, label‐QoS switching protocol. Each packet of data is forwarded with a proposed 2‐side label values that are concerned with addressing and QoS. This proposed protocol was applied in each of the node's routing, and it was set up with forwarding information table. The simulation and analysis were conducted in 2 situations: (1) with a constant n–label switch mobile robot and a number of packet data increasing with time and (2) with a constant number of packet and varying n–label switch mobile robot by time. With reference to the network parameter performances, it shows that the anomaly treatment by the proposed protocol is able to prioritize the data forwarding between the robots at the edge of the swarm with class of service although the robot community at the center is increasing or getting crowded.     

Improved BER based on intensity noise alleviation using developed detection technique for incoherent SAC-OCDMA systems

The major drawback of incoherent spectral-amplitude coding optical code-division multiple-access (SAC-OCDMA) systems is their inherent intensity noise originating due to the incoherency of the broadband light sources. In this paper, we propose a developed detection technique named the modified-AND subtraction detection for incoherent SAC-OCDMA systems. This detection technique is based upon decreasing the received signal strength during the decoding process by dividing the spectrum of the utilized code sequence. The proposed technique is capable of mitigating the intensity noise effect, as well as suppressing the multiple-access interference impact. Based on modified quadratic congruence (MQC) code, the analytical results reveal that the modified-AND detection offer best bit-error rate (BER) performance and enables MQC code to support higher transmission rate up to 1.25?Gb/s compared to conventional AND detection. Furthermore, we ascertained that the proposed technique enhances the system performance using a simulation experiment.     

Absorption of Aramid Prestressing Rods in Aggressive Solutions

Fiber-reinforced plastic (FRP) reinforcing bars are not prone to classical electrochemical corrosion. However, this material may suffer from other degradation mechanisms when exposed to moisture, alkaline, or acid solutions for a long period of time. In the present study, the absorption characteristic of aramid fiber-reinforced plastic (AFRP) prestressing rods with epoxy matrix was investigated in terms of weight gain or loss by immersing the rods in water, alkaline, and acid solutions for more than a year. The results showed that the weight of the 8 mm diameter AFRP rods immersed in water increased in weight marginally. The weight of the rods immersed in an alkaline or acid solution increased significantly. A scanning electron microscope photograph showed the penetration zone at the cross section of the rods when immersed in three different solutions. An electron probe microscope analyzer examination is useful to detect the presence of the ion Na+ from the NaOH solution where the rods were immersed. A Simplified Diffusion Model can predict the depth of penetration and was verified by a scanning electron microscope measurement.     

Risk assessment of combined photogenotoxic effects of sunlight and food additives

The presence of flavored colorants (peach and raspberry), flavors (caramel, citric acid and vanilla) and food preservatives (sodium nitrite, sodium nitrate, sodium benzoate, benzoic acid, potassium sorbate and sodium chloride) in Escherichia coli suspension during exposure to sunlight did not change the extent of cell survival. No effect on viability and mutation induction (kanamycin resistant) was also seen when cells were kept in contact with any of the additives for 80 min in the dark. However, when the relevant additive was present in cell suspension during sunlight exposure the number of induced mutations was increased to varying extents over that seen with sunlight alone. Raspberry and peach increased the number of mutations in a dose dependent manner, while vanilla produced mutations in an additive fashion. Nitrite, nitrate, benzoate, sorbate and benzoic acid increased mutation somewhat additively over that of sunlight. Sodium chloride and citric acid were not effective. The impact of this investigation reflects the significance of combination of sunlight and chemical food additives as potential risk, which requires special attention and necessitates further investigations to evaluate the risk.     

Fast and Highly Sensitive Ionic‐Polymer‐Gated WS2–Graphene Photodetectors

The combination of graphene with semiconductor materials in heterostructure photodetectors enables amplified detection of femtowatt light signals using micrometer‐scale electronic devices. Presently, long‐lived charge traps limit the speed of such detectors, and impractical strategies, e.g., the use of large gate‐voltage pulses, have been employed to achieve bandwidths suitable for applications such as video‐frame‐rate imaging. Here, atomically thin graphene–WS₂ heterostructure photodetectors encapsulated in an ionic polymer are reported, which are uniquely able to operate at bandwidths up to 1.5 kHz whilst maintaining internal gain as large as 10⁶. Highly mobile ions and the nanometer‐scale Debye length of the ionic polymer are used to screen charge traps and tune the Fermi level of the graphene over an unprecedented range at the interface with WS₂. Responsivity R = 10⁶ A W^?1 and detectivity D* = 3.8 × 10¹¹ Jones are observed, approaching that of single‐photon counters. The combination of both high responsivity and fast response times makes these photodetectors suitable for video‐frame‐rate imaging applications.