A real-time, low-power implementation for high-resolution eigenvalue-based spectrum sensing

In this paper, a novel multiple antenna, high-resolution eigenvalue-based spectrum sensing algorithm based on the FFT of the received signal is introduced. The proposed platform overcomes the SNR wall problem in the conventional energy detection (ED) algorithm, enabling the detection of the weak signals at ?10 dB SNR. Moreover, the utilization of FFT for the input signal channelization provides a simple, low-power design for a high-resolution spectrum sensing regime. A real-time, low-area, and low-power VLSI architecture is also developed for the algorithm, which is implemented in a 0.18 μm CMOS technology. The implemented design is the first eigenvalue-based detection (EBD) architecture proposed to-date capable of detecting weak signals at ?10 dB. Despite having more algorithmic complexity in comparison to the ED, the proposed EBD architecture shows no significant increase in the core area and the power consumption, due to the FFT utilization for the input signal channelization. The proposed design occupies a total area of 3.4 mm² and dissipates 78 mW for a 40 MHz sensing bandwidth consisting of 32 sub-channels.     

An EWMA t chart with variable sampling intervals for monitoring the process mean

This paper proposes a variable sampling interval (VSI) version of the fixed sampling interval (FSI) exponentially weighted moving average (EWMA) t chart developed by Zhang et al. for monitoring the changes in the process mean. An optimal design strategy based on the average time to signal (ATS) is presented. We determine the optimal parameters for the VSI EWMA t chart using a Markov chain approach so that the chart has the desired robustness property against errors in estimating the process standard deviation or changing standard deviation. Also, we explain how the various parameters of this VSI EWMA t chart can be computed and how the use of the VSI feature improves the statistical efficiency of the FSI EWMA t and FSI EWMA X-bar charts in terms of out-of-control ATS performances. Comparisons with the FSI EWMA t and FSI EWMA X-bar charts are performed.     

Optimization of a seven-stage centrifugal compressor by using a quasi-3D inverse design method

This paper focuses on performance improvement of a centrifugal compressor. An inverse design method for 3D design approaches is formulated to address this concern. The design procedure encompasses two major steps. First, with the use of ball spine algorithm, which is an inverse design algorithm, on the meridional plane of impeller, the hub and shroud of impeller are computed based on a modified pressure distribution along them. Second, an original and progressive algorithm is developed for design of blade camber line profile on the blade-to-blade planes of impeller based on blade loading improvement. Full 3D analysis of the current and designed compressor is accomplished by using a Reynolds-averaged Navier-Stokes equations solver. A comparison between the analysis results of the current and designed compressor shows that the total-to-total isentropic efficiency and pressure ratio of the designed compressor under the same operating conditions are enhanced by more than 4.5% and 5%, respectively.     

Static deflection and pull-in instability analysis of an electrostatically actuated mirocantilever gyroscope considering geometric nonlinearities

In this paper, a mathematical modeling of a microcantilever gyroscope is presented considering the nonlinearities of the system due to electrostatic forces, fringing field, geometry and the inertial terms. The microgyroscope is actuated and detected by electrostatic methods and subjected to coupled bending oscillations. First a system of two nonlinear integro-differential equations is derived which describes flexural-flexural motion of electrostatically actuated and detected microbeam gyroscopes. Afterward, static deflection and pull-in instability of the microgyroscopes acted upon by DC voltages in both (driving and sensing) directions are studied for different parameters. The model’s predictions are in good agreement with the experimental data found in the literature and finite element simulation. Results show that the nonlinearities become important when pull-in happens.     

Efficient algorithms to accurately compute derating factors of digital circuits

Fast, accurate, and detailed Soft Error Rate (SER) estimation of digital circuits is essential for cost-efficient reliable design. A major step to accurately estimate a circuit SER is the computation of failure probability, which requires the computation of three derating factors, namely logical, electrical, and timing derating. The unified treatment of these derating factors is crucial to obtain accurate failure probability. Existing SER estimation techniques are either unscalable to large circuits or inaccurate due to lack of unified treatment of all derating factors. In this paper, we present fast and efficient algorithms to estimate SERs of circuit components in the presence of single event transients by unified computation of all derating factors. The proposed algorithms, based on propagation of error probabilities and shape of erroneous waveforms, are scalable to very large circuits. The experimental results and comparisons with Statistical Fault Injections (SFIs) using Monte-Carlo simulations confirm the accuracy (only 2% difference) and speedup (5–6 orders of magnitudes) of the proposed technique.     

Analysis of optimal spinning reserve procurement with demand response resources under social cost minimization

This paper evaluates the effect of demand response (DR) resources that are utilized in the reserve market using an optimal probabilistic mixed integer programming (MIP)‐based spinning reserve scheduling method. In order to analyze the DR utilization effect from a theoric point of view, the objective of the adopted framwork is social cost minimization. To be consistent with the increasing reliability requirements of loads and considering increasing uncertainity in the generation side because of penetration of intermitent renewable resources, both single and double outage contingencies are considered. Furthremore, for reduction of the computational burden, a two‐level optimization method is developed. Roy‐Bilinton test system (RBTS) is used in numerical simulations and the results are presented. The numerical results show that increase in the uncertainty at supply side resources, increases the need for the DR resources. The numerical results also show the effectiveness of the developed optimization method in reducing the computational time. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Determination of cyclamate in artificial sweeteners and beverages using headspace single-drop microextraction and gas chromatography flame-ionisation detection

A new method for determination of cyclamate was developed using headspace single-drop microextraction (HS-SDME) and gas chromatography (GC). The method is based on the reaction of cyclamate and nitrite in the acidic media and microextraction of cyclohexene formed for subsequent determination with GC. Conditions for both derivatisation and HS-SDME have been optimised. The calibration curve for cyclamate determination showed good linearity in the range of 30–1000 μmol L⁻¹ (R² = 0.9992) and the limit of detection (S/N = 3) was estimated to be 5 μmol L⁻¹. The repeatability and reproducibility for a 200 μmol L⁻¹ of cyclamate were 4% and 4.8% (N = 5), respectively. The purposed method was successfully applied for determination of cyclamate in beverages and sweetener tablets. The average recovery of spiked samples was 97%. The results demonstrated that the developed method is simple, rapid, inexpensive, accurate and remarkably free from interference effects.     

In Situ Solvothermal Crystallization of TiO2 Nanostructure on Alumina Granules for Photocatalytic Wastewater Treatment

Synthesis of nanostructure titania powders and in situ crystallization of anatase coating layer on sintered alumina granules by solvothermal method were investigated. In coating process, addition of polyvinyl alcohol (PVA) as binder to solvothermal solution was also studied. Microstructure analyses of powders showed that crystallization and growth of nanostructure anatase phase in a thin gel layer were enhanced with temperature increase. The titania nanopowders synthesized at 120 °C and 8 h represented photodegradation of methyl orange solution as model wastewater up to maximum 94% yield in slurry photoreactor. However, in coating process, with increasing temperature to 220 °C and coating time to 24 h, adhesion and photocatalytic properties of the coated layer were improved. Furthermore, PVA binder addition led to formation of more uniform layer with less attrition loss in the reactor.     

Non-thermal plasma assisted synthesis and physicochemical characterizations of Co and Cu doped Ni/Al2O3 nanocatalysts used for dry reforming of methane

Ni/Al₂O₃ nanocatalysts doped with Co and Cu were prepared by co-impregnation and modified by non-thermal plasma. The nanocatalysts were characterized by XRD, FESEM, TEM, EDX dot-mapping, BET, FTIR, TGA-DTG, and XPS analysis. According to XRD and XPS results, good interaction between active phase and support can be observed in both Ni–Co/Al₂O₃ and Ni–Cu/Al₂O₃ nanocatalysts. A uniform morphology, high surface area, and well dispersed particles of active sites in Ni–Co/Al₂O₃ nanocatalyst were observed that shows the effect of cobalt in controlling Ni ensemble size. In contrast Ni–Cu/Al₂O₃ nanocatalyst had no homogenous dispersion of active phase due to sintering of copper particles. The activity measurements illustrated better Ni–Co/Al₂O₃ nanocatalyst activity in comparison to Ni/Al₂O₃ and Ni–Cu/Al₂O₃ in terms of CH₄ and CO₂ conversion. H₂ and CO yield were higher for Ni–Co/Al₂O₃ and higher H₂/Co ratio was obtained as well. Whereas Ni/Al₂O₃ and Ni–Co/Al₂O₃ did not experience deactivation, Ni–Cu/Al₂O₃ suffered from activity loss by ca. 22% and 16% for CH₄ and CO₂ conversion, respectively. Sintering most likely happened in Ni–Cu/Al₂O₃ nanocatalyst due to high temperature of calcination while cobalt by controlling the size of Ni particles, alternated the size of active sites to a size range in which carbon formation was suppressed. Ni/Al ratio from XPS analysis which signifies Ni dispersion on alumina support was 5.15, 9.16, and 6.35 for Ni/Al₂O₃, Ni–Co/Al₂O₃, and Ni–Cu/Al₂O₃ nanocatalysts respectively. The highest ratio of Ni/Al was for Ni–Co/Al₂O₃ nanocatalyst that shows the best coverage of support by Ni active phase in this nanocatalyst.     

Electrochemical hydrogen evolution of multi-walled carbon nanotube/micro-hybrid composite decorated with Ni nanoparticles as catalyst through electroless deposition process

Hydrogen evolution of multi-walled nanotube (MWCNT)/micro-hybrid polymer composite, decorated with Ni nanoparticles through electroless deposition process is studied by the electrochemical method. Cyclic voltammetry (CV) is utilized to clearly study the electrochemical hydrogen storage/evolution behavior of the composite through a potential window ranging from ? 1.60 to + 0.60 V (vs. Ag/AgCl). Hydrogen adsorption/desorption peaks are positioned at ? 1.52 and ? 0.05 V, respectively. Chronoamperometry is also applied to estimate active surface area (0.145 m² g^? 1) of the composite as well as the diffusion coefficient (3.4 × 10^? 11 m² s^? 1) of adsorbed hydrogen process. According to the chrono-charge/discharge technique, the capacity of fabricated Ni-MWCNT/micro-hybrid composite is estimated to be 2.98 wt.% during charging for a certain time (40 min).