A multiobjective optimization framework for design of integrated biorefineries under uncertainty

A systematic approach for development of a reliable optimization framework to address the optimal design of integrated biorefineries in the face of uncertainty is presented. In the current formulation, a distributed strategy which is composed of different layers including strategic optimization, risk management, detailed mechanistic modeling, and operational level optimization is applied. In the strategic model, a multiobjective stochastic optimization approach is utilized to incorporate the tradeoffs between the cost and the financial risk. Then, Aspen Plus models are built to provide detailed simulation of biorefineries. In the final layer, an evolutionary algorithm is employed to optimize the operating condition. To demonstrate the effectiveness of the framework, a hypothetical case study referring to a multiproduct lignocellulosic biorefinery is utilized. The numerical results reveal the efficacy of the proposed approach; it provides decision makers with a quantitative analysis to determine the optimum capacity plan and operating conditions of the biorefinery. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3208–3222, 2015     

A Novel Fault-Locator System; Algorithm, Principle and Practical Implementation

This paper presents a novel fault-locator system for radial distribution feeders based on the feeder architecture and voltage and current measurements at a subtransmission substation (63/20 kV). The proposed algorithm determines the fault location precisely by considering the variable characteristic of the load, unbalanced condition, and unsymmetrical nature of distribution feeders. Load variations affect the accuracy of fault-locator systems significantly. Real-time load estimation is implemented to reduce the differences between the calculated fault location and the actual fault location. In addition, self-supervisory characteristics are added to the system to increase the accuracy of the collected data. Actual test results demonstrate the effectiveness of the system in practical applications.     

Ammonia sensing properties of (SnO2–ZnO)/polypyrrole coaxial nanocables

In this work, (SnO₂–ZnO)/polypyrrole (PPy) coaxial nanocables have been synthesized through simple chemical routes. The SnO₂–ZnO composite nanofibers with narrow distribution of diameter size and an average of 75 nm were synthesized via the electrospinning method. In this experiment, we were able to polymerize a shell of PPy, as a typical conducting polymer, on surface of SnO₂–ZnO nanofibers using the vapor-phase polymerization of Pyrrole monomer. The prepared nanomaterial exhibits a linear response to Ammonia (NH₃) concentrations at room temperature. The obtained results make NH₃ detection and determination of its concentration feasible. The superior features of this nanomaterial include simple synthesis method, high sensitivity, and quick response and recovery times. The aforementioned characteristics of this nanomaterial indicate the potential of industrial applications.     

Optimal design of nonuniform multirate filter banks

The design of general nonuniform filter banks is studied. Contrary to uniform filter banks, in nonuniform filter banks, it may not be possible to achieve perfect reconstruction, but in some cases by using optimization techniques, we can design acceptable filter banks. Here, the initial finite impulse response (FIR) analysis filters are designed according to the characteristics of the input. By the design procedure, the FIR synthesis filters are found so that theH-norm of an error system is minimized over all synthesis filters that have a prespecified order. Then, the synthesis filters obtained in the previous step are fixed, and the analysis filters are found similarly. By iteration, theH-norm of the error system decreases until it converges to its final value. At each iteration, the coefficients of the analysis or synthesis filters are obtained by finding the least squares solution of a system of linear equations. If necessary, the frequency characteristics of the filters can be altered by adding penalty terms to the objective function.This research was supported by the Natural Sciences and Engineering Research Council of Canada.     

Modeling of the bulk versus SOI CMOS performances for the optimal design of APS circuits in low-power low-voltage applications

In this paper, we present the top-down design of an active pixel sensor (APS) circuit using an analytical model of its architecture. The model is applied to compare the performances of bulk versus silicon-on-insulator (SOI) CMOS processes and devices on the designs and performance of several 50-frames/s imagers in 2-/spl mu/m and 0.25-/spl mu/m CMOS with different pixels array sizes. For 2-/spl mu/m SOI, results show a reduction by two of the power consumption and a dynamic range increase of 0.85 V under a 3-V supply. This results in an SNR of 79 dB instead of 76. Fixed pattern noise (FPN) is also reduced from 2.7 to 1.8 mV which represents 0.26% and 0.08% of the dynamic range, respectively. For 0.25-/spl mu/m CMOS SOI, results show a reduction by 6.5 of the power consumption, FPN more than five time better, and a dynamic range increase of 0.29 V under a 1.5-V supply. However, because of the increase of the thermal noise due to the particular design choice, an SNR of 60.3 dB is achieved compared to 63 in bulk. A better SNR in SOI than in bulk can be achieved but at the expense of power consumption and FPN. However, this could be combined with an increase in pixels number in SOI compared to bulk. Potential results achievable in SOI have to our knowledge never been reached by bulk APS imagers up to now.     

Physically based wall boundary condition for dissipative particle dynamics

In this paper, we present a novel wall boundary condition model, which stands just on the physical facts, for the dissipative particle dynamics (DPD) method. After the validation of this model by means of the common benchmarks such as the Couette and the Poiseuille flows, we study the effects of this model on the diffusion coefficient in a wide variety of different coarse-graining levels. The obtained results show that the proposed model preserves the thermodynamics of the system, also eliminates the spurious effects of the wall, and consequently is able to preserve the accurate structural characteristics of the working DPD fluid in the wall’s vicinity. We also study the fluid flow through a channel with the polymer-coated walls. A comprehensive investigation into the wall–solvent–polymer interactions is presented for the solvents with different qualities. Since the working DPD fluid’s structure is heterogeneous, the working fluid’s structure, its density variations and the force field that is experienced by the working DPD fluid particles near the wall cannot be predicted before the simulation. Hence, all of these data have to be determined systematically during the simulation. We show that the force field experienced by the particles near the wall depends substantially upon the solvent quality. We also show that the force fields experienced by the particles from different types (solvent/polymer) in the wall’s vicinity are significantly different from each other except in the athermal solvent.