Diffusion Based Channel Gains Estimation in WSN Using Fractional Order Strategies

In this study, it is proposed that the diffusion least mean square (LMS) algorithm can be improved by applying the fractional order signal processing methodologies. Application of Caputo’s fractional derivatives are considered in the optimization of cost function. It is suggested to derive a fractional order variant of the diffusion LMS algorithm. The applicability is tested for the estimation of channel parameters in a distributed environment consisting of randomly distributed sensors communicating through wireless medium. The topology of the network is selected such that a smaller number of nodes are informed. In the network, a random sleep strategy is followed to conserve the transmission power at the nodes. The proposed fractional order modified diffusion LMS algorithms are applied in the two configurations of combine-then-adapt and adapt-then-combine. The average squared error performance of the proposed algorithms along with its traditional counterparts are evaluated for the estimation of the Rayleigh channel parameters. A mathematical proof of convergence is provided showing that the addition of the nonlinear term resulting from fractional derivatives helps adjusts the autocorrelation matrix in such a way that the spread of its eigenvalues decreases. This increases the convergence as well as the steady state response even for the larger step sizes. Experimental results are shown for different number of nodes and fractional orders. The simulation results establish that the accuracy of the proposed scheme is far better than its classical counterparts, therefore, helps better solves the channel gains estimation problem in a distributed wireless environment. The algorithm has the potential to be applied in other applications related to learning and adaptation.     

Detection Avoidance and Priority-Aware Target Tracking for UAV Group Reconnaissance Operations

In this paper, we present a novel approach for stationary target tracking in reconnaissance operations with a small UAV group. A reconnaissance mission has multiple competing requirements, such as short scan time and repetitive scanning of the entire area, target recognition, and target tracking. Especially in real-world military reconnaissance scenarios, different types of targets with hostile characteristics exist. The UAVs must scan and track the targets while avoiding detection by enemies. Although small UAVs are unlikely to be detected, they become prone to detection if their path is predictable. To meet these competitive requirements, we propose an attractive pheromone-based cooperative path planning method that makes path prediction almost impossible by ensuring a random path selection mechanism. To avoid detection during target tracking, we implement a new discrete-time tracking scheme with random time intervals and random path planning for multiple UAVs. The proposed model enables a UAV group to sporadically scan the entire area, quickly locate the targets, and simultaneously track the targets based on their priority. In addition, it offers a mechanism that permits the command and control center to balance between reconnaissance and target tracking operations to meet every mission requirement.     

Heavily doped silicon:A potential replacement of conventional plasmonic metals

The plasmonic property of heavily doped p-type silicon is studied here.Although most of the plasmonic devices use metal-insulator-metal(MIM)waveguide in order to support the propagation of surface plasmon polaritons(SPPs),metals that possess a number of challenges in loss management,polarization response,nanofabrication etc.On the other hand,heavily doped p-type silicon shows similar plasmonic properties like metals and also enables us to overcome the challenges pos-sessed by metals.For numerical simulation,heavily doped p-silicon is mathematically modeled and the theoretically obtained re-lative permittivity is compared with the experimental value.A waveguide is formed with the p-silicon-air interface instead of the metal-air interface.Formation and propagation of SPPs similar to MIM waveguides are observed.     

Real-time scheduling algorithm for safety-critical systems on faulty multicore environments

An algorithm (called FTM) for scheduling of real-time sporadic tasks on a multicore platform is proposed. Each task has a deadline by which it must complete its non-erroneous execution. The FTM algorithm executes backups in order to recover from errors caused by non-permanent and permanent hardware faults. The worst-case schedulability analysis of FTM algorithm is presented considering an application-level error model, which is independent of the stochastic behavior of the underlying hardware-level fault model. Then, the stochastic behavior of hardware-level fault model is plugged in to the analysis to derive the probability of meeting all the deadlines. Such probabilistic guarantee is the level of assurance (i.e., reliability) regarding the correct functional and timing behaviors of the system. One of the salient features of FTM algorithm is that it executes some backups in active redundancy to exploit the parallel multicore architecture while other backups passively to avoid unnecessary execution of too many active backups. This paper also proposes a scheme to determine for each task the number of backups that should run in active redundancy in order to increase the probability of meeting all the deadlines. The effectiveness of the proposed approach is demonstrated using an example application.     

Resistance of stainless steel CHS columns based on cross-section deformation capacity

A conceptually new structural design approach has recently been proposed by the authors to predict the resistance of stainless steel members subjected to various types of loading with cross-sections formed from thin flat plates including angles, channels, lipped channels, I-sections and rectangular hollow sections (RHS). The proposed method does not follow the traditional cross-section classification approach, which primarily relies on the assumption of a bilinear, elastic-perfectly-plastic material model. Instead, deformation capacity of a cross-section is determined directly from the local buckling characteristics of the constituent plate elements. This is then used to obtain the corresponding local buckling stress utilising an appropriate material model. This basic concept is extended herein to predict compression resistance of stainless steel columns with circular hollow sections (CHS). Available test and finite element (FE) results have been used to develop the basic design equation to predict the compression resistance of cross-sections and to propose column curves to determine flexural buckling resistances. The predicted resistances have been compared to those obtained using the current Eurocode; the predictions are significantly more accurate and more consistent than those given by the existing Eurocode.     

Customer choice of reliability in spinning reserve procurement and cost allocation using well-being analysis

A novel pool-based market-clearing algorithm for spinning reserve (SR) procurement and the cost allocation associated with provision of spinning reserve among customers (DisCos) is developed in this paper. Rational buyer market model is used to clear energy and spinning reserve markets in the proposed algorithm. This market model gives DisCos the opportunity to declare their own energy requirement together with their desired reliability levels to the ISO and also they can participate in the SR market as a interruptible load. The DisCos’ desired reliability levels are selected from a hybrid deterministic/probabilistic framework designated as the system well-being model. Using the demand of each DisCo and its associated desired reliability level, the overall desired system reliability level is determined. The market operator then purchases spinning reserve commodity from the associated market such that the overall desired system reliability level is satisfied. A methodology is developed in this paper to fairly allocate the cost associated with providing spinning reserve among DisCos based on their demands and desired reliability levels. An algorithm is also presented in this paper for implementing the proposed approach. The effectiveness of the proposed technique is examined using the IEEE-RTS.     

A unique mechanism for methyl ester formation via an amide intermediate found in myxobacteria

Secondary metabolism involves a broad diversity of biochemical reactions that result in a wide variety of biologically active compounds. Terminal amide formation during the biosynthesis of the myxobacterial electron-transport inhibitor, myxothiazol, was analyzed by heterologous expression of the unique nonribosomal-peptide synthetase, MtaG, and incubation with a synthesized substrate mimic. These experiments provide evidence that the terminal amide is formed from a carrier protein-bound myxothiazol acid that is thioesterified to MtaF. This intermediate is transformed to an amide by extension with glycine and subsequent oxidative cleavage by MtaG. The final steps of melithiazol assembly involve a highly similar protein-bound intermediate (attached to MelF, a homologue of MtaF), which is transformed to an amide by MelG (homologue of MtaG). In this study, we also show that the amide moiety of myxothiazol A can be hydrolyzed in vivo to the formerly unknown free myxothiazol acid by heterologous expression of melJ in the myxothiazol producer Stigmatella aurantiaca DW4/3-1. The methyltransferase MelK can finally methylate the acid to give rise to the methyl ester, which is produced as the final product in the melithiazol A biosynthetic pathway. These experiments clarify the role of MelJ and MelK during melithiazol assembly.     

Second law analysis of forced convection in a circular duct for non-Newtonian fluids

The second law characteristics of fluid flow and heat transfer inside a circular duct under fully developed forced convection for non-Newtonian fluids are presented. Heat flux is kept constant at the duct wall. Analytical expressions for dimensionless entropy generation number (_NS$N_{\mathrm{S}}$), irreversibility distribution ratio (Φ  ), and Bejan number (Be$\mathit{Be}$) are obtained as functions of dimensionless radius (R$R$), Peclet number (Pe$\mathit{Pe}$), modified Eckert number (Ec$\mathit{Ec}$), Prandtl number (Pr), dimensionless temperature difference (Ω  ), and fluid index (m$m$ or n$n$). Spatial distributions of local and average entropy generation number, irreversibility ratio, and Bejan number are presented graphically. For a particular value of fluid index, n=1$n=1$ (or m=2$m=2$), the general entropy generation number expression for a non-Newtonian power-law fluid reduces to the expression for Newtonian fluid as expected. Furthermore, entropy generation minimization is applied to calculate an optimum fluid index (_nEGM$n_{\mathrm{EGM}}$). A correlation is proposed that calculates _nEGM$n_{\mathrm{EGM}}$as a function of group parameter (Ec×Pr/Ω$\mathit{Ec}\times \mathit{Pr}/\Omega$) and Peclet number (Pe$\mathit{Pe}$) within ±5% accuracy. Finally, for some selected fluid indices, the governing equations are solved numerically in order to obtain Nusselt number. It is observed that the numerically obtained asymptotic Nusselt number shows excellent agreement with the analytically obtained Nusselt number.     

Indirect evaporative cooling: Past,present and future potentials

This paper reported a review based study into the Indirect Evaporative Cooling (IEC) technology, which was undertaken from a variety of aspects including background, history, current status, concept, standardisation, system configuration, operational mode, research and industrialisation, market prospect and barriers, as well as the future focuses on R&D and commercialisation. This review work indicated that the IEC technology has potential to be an alternative to conventional mechanical vapour compression refrigeration systems to take up the air conditioning duty for buildings. Owing to the continuous progress in technology innovation, particularly the M-cycle development and associated heat and mass transfer and material optimisation, the IEC systems have obtained significantly enhanced cooling performance over those the decade ago, with the wet-bulb effectiveness of greater than 90% and energy efficiency ratio (EER) up to 80. Structure of the IEC heat and mass exchanger varied from flat-plate-stack, tube, heat pipe and potentially wave-form. Materials used for making the exchanger elements (plate/tube) included fibre sheet with the single side water proofing, aluminium plate/tube with single side wicked setting (grooved, meshed, toughed etc), and ceramic plate/tube with single side water proofing. Counter-current water flow relevant to the primary air is considered the favourite choice; good distribution of the water stream across the wet surface of the exchanger plate (tube) and adequate (matching up the evaporation) control of the water flow rate are critical to achieving the expected system performance. It was noticed that the IEC devices were always in combined operation with other cooling measures and the commonly available IEC related operational modes are (1) IEC/DEC system; (2) IEC/DEC/mechanical vapour compression system; (3) IEC/desiccant system; (4) IEC/chilled water system; and (5) IEC/heat pipe system. The future potential operational modes may also cover the IEC-inclusive fan coil units, air handle units, cooling towers, solar driven desiccant cycle, and Rankine cycle based power generation system etc. Future works on the IEC technology may focus on (1) heat exchanger structure and material; (2) water flowing, distribution and treatment; (3) incorporation of the IEC components into conventional air conditioning products to enable combined operation between the IEC and other cooling devices; (4) economic, environment and social impacts; (5) standardisation and legislation; (6) public awareness and other dissemination measures; and (7) manufacturing and commercialisation. All above addressed efforts may help increase the market ratio of the IEC to around 20% in the next 20 years, which will lead to significant saving of fossil fuel consumption and cut of carbon emission related to buildings.     

Brinkman–Forchheimer modeling for porous media thermoacoustic system

In this paper, analytical studies have been conducted on the flow and thermal fields of unsteady compressible viscous oscillating flow through channels filled with porous media representing stacks in thermoacoustic systems. The flow in the porous material is described by the Brinkman–Forchheimer–extended Darcy model. Analytical expressions for oscillating velocity, temperature, and energy flux density are obtained after linearizing and solving the governing differential equations with long wave, short stack, and small amplitude oscillation approximations. Experimental work is also conducted to verify the temperature difference obtained across the porous stack ends. To produce the experimental results, a thermoacoustic heat pump is designed and constructed where reticulated vitreous carbon (RVC) is used as the stack material. A very good agreement is obtained between the modeling and the experimental results. The expression of temperature difference across the stack ends obtained in the present study is also compared with the existing thermoacoustic literature. The proposed expression surpasses the existing expression available in the literature. The system of equations developed in the present study is a helpful tool for thermal engineers and physicist to design porous stacks for thermoacoustic devices.