Motor car acoustic response modelling and order reduction viabalanced model truncation

A novel practical application of the balanced model truncation (BMT) technique for the accurate and reduced order/complexity magnitude and phase modelling of the acoustic response of a motor car is described and demonstrated. The effectiveness and viability are illustrated through a sample car response modelling example     

Oxygen potentials,Gibbs' energies and phase relations in the Cu-Cr-O system

Thermodynamic properties of ternary compounds, cuprous and cupric chromites (CuCro₂, CuCr₂O₄), and oxygen potentials corresponding to three three-phase regions in the Cu-Cr-O system have been measured in the temperature range 900 to 1350 K using a solid state galvanic cell incorporating calcia-stabilized zirconia. Cuprous chromite was found to be nearly stoichiometric. The compositions of non-stoichiometric cupric chromite saturated with CuO and Cr₂O₃ have been determined using electron microprobe and energy dispersive X-ray analysis. The results of this study resolve discrepancies in Gibbs' energies of cuprous and cupric chromites reported in the literature. A ternary phase diagram for the Cu-Cr-O system at 1150 K and phase relations in air for the Cu₂O-CuO-Cr₂O₃ system as a function of temperature have been derived based on the new thermodynamic data. The phase diagram given in the literature is found to be inaccurate.     

Characterization of linear low density polyethylene by temperature rising elution fractionation and by differential scanning calorimetry

In this article we consider characterization of the branching distribution of LLDPE by analytical TREF and by DSC techniques. Qualitatively, both methods yield parallel information, provided that the DSC samples are prepared at very slow cooling rates. Analytical TREF provides more quantitative information, however, in that the mass fraction of material with different branch levels can be estimated. Full characterization of a polyethylene requires the use of a preparative TREF technique, in which fractions dissolved at preselected temperatures are investigated for branching with high resolution ¹³C NMR and for molecular weight distribution, with high temperature SEC analyses.     

Hydrolysis of sugars catalyzed by water-tolerant sulfonated mesoporous silicas

Mesoporous silicas are modified with sulfonic acid groups either by one-pot or by grafting method. In the hydrolysis of sucrose and starch, the sulfonated mesoporous silicas work as water-tolerant recyclable solid acid catalysts, showing higher conversion and turnover frequency than conventional Amberlyst-15, Nafion-silica and HZSM-5 catalysts.     

Robust control design of power system stabilizers using multivariable frequency domain techniques

H_∞ and structured singular value optimization techniques are used to design robust power system stabilizers (PSS) for a single-machine and a two-machine system with varying operating conditions. Realistic uncertainty models to represent the possible operating conditions as perturbations from a nominal operating condition are developed. System experience is used to select weighting functions to provide adequate damping and shape the controller frequency response. Computer simulations show that the PSS designed using the proposed technique provides improved damping compared to a conventional PSS.     

Thermal decomposition of CuCrO4·2CuO·2H2O and phase relations in the Cu-Cr-O system

The compound, CuCrO₄·2CuO·2H₂O has been synthesized by precipitating it from the aqueous solution containing chromium (VI) oxide and basic copper (II) carbonate. Thermal decomposition of CuCrO₄·2CuO·2H₂O has been studied by thermogravimetry and differential scanning calorimetry in flowing air and pure oxygen between 298 and 1373 K. The formation of different phases after each stage of decomposition were identified by X-ray diffraction analysis. The compound CuCrO₄ was found to be non-stoichiometric. Based on the results obtained in this study and those reported earlier, the isothermal section of the phase diagram of the Cu-Cr-O ternary system has been composed at 600 and 1150 K. Scanning electron microscopy studies of CuCrO₄·2CuO·2H₂O precipitate showed rectangular plate-like morphology. The decomposition of CuCrO₄·2CuO·2H₂O at 798 K in air resulted in the formation of a mixture of fine powder of CuCr₂O₄+CuO (Adkin's catalyst) having a uniform spherical geometry and a particle size less than 0.1 m.     

Design and economic optimization of shell-and-tube heat exchanger using cohort intelligence algorithm

In this paper, the stability analysis problem is investigated for a new class of discrete-time singular neural networks with Markovian jump and mixed time-delays. The jumping parameters are generated from a discrete-time homogeneous Markov process, which are governed by a Markov process with discrete and finite state space. The mixed time-delays are composed of discrete and distributed delays. The activation functions are not required to be strictly monotonic and be differentiable. The purpose of this paper is to derive some delay-dependent sufficient conditions such that the singular neural networks to be regular, causal and stochastically stable in the mean square. Finally, numerical examples are also provided to illustrate the effectiveness of the proposed methods.