Absorption of carbon dioxide in alkanolamines in the presence of fine activated carbon particles

The rates of absorption of CO₂ into water and 0.1 kmol/m³ aqueous solutions of MEA, DEA and AMP were measured in a stirred cell with a flat gas-liquid interface in the presence of fine activated carbon particles. Experiments showed that the rates of absorption increased significantly with increases in the loading of activated carbon up to about 6 kg/m³ and thereafter remained constant.     

MODELING AND PREDICTIVE CONTROL OF MIMO NONLINEAR SYSTEMS USING WIENER-LAGUERRE MODELS

In this work, a Weiner-type nonlinear black box model was developed for capturing dynamics of open loop stable MIMO nonlinear systems with deterministic inputs. The linear dynamic component of the model was parameterized using orthogonal Laguerre filters while the nonlinear state output map was constructed either using quadratic polynomial functions or artificial neural networks. The properties of the resulting model, such as open loop stability and steady-state behavior, are discussed in detail. The identified Weiner-Laguerre model was further used to formulate a nonlinear model predictive control (NMPC) scheme. The efficacy of the proposed modeling and control scheme was demonstrated using two benchmark control problems: (a) a simulation study involving control of a continuously operated fermenter at its optimum (singular) operating point and (b) experimental verification involving control of pH at the critical point of a neutralization process. It was observed that the proposed Weiner-Laguerre model is able to capture both the dynamic and steady-state characteristics of the continuous fermenter as well as the neutralization process reasonably accurately over wide operating ranges. The proposed NMPC scheme achieved a smooth transition from a suboptimal operating point to the optimum (singular) operating point of the fermenter without causing large variation in manipulated inputs. The proposed NMPC scheme was also found to be robust in the face of moderate perturbation in the unmeasured disturbances. In the case of experimental verification using the neutralization process, the proposed control scheme was found to achieve much faster transition to a set point close to the critical point when compared to a conventional gain-scheduled PID controller.     

Influence of Distributed Particle Size on the Determination of the Parabolic Rate Constant for Oxidation by the Powder Method

The established analysis for the study of oxidation using powder specimens is based on the assumption of monosized particles. The experiments, however, are conducted on powders with a distributed particle size. Here we present a statistical approach for the calculation of the rate constant for oxidation. The results of the analysis are applied to new data on oxidation studies of dense powders of silicon carbonitride amorphous ceramics. The monosized model requires a wide range of values for the rate constant to fit the short term and the long-term data, leading to considerable ambiguity in the estimate of the parabolic rate constant, k _p, for oxidation. In contrast the statistical model fits over the entire range of data, yielding a much more reliable value for k _p. For example, the monosized approach gave a value in the range 19.7 × 10⁻¹⁸ < k _p < 2.7 × 10⁻¹⁸ m²/s. In contrast, the statistical model yields a specific value of 4.5 × 10⁻¹⁸ m²/s.     

Synthesis and magnetorheological characteristics of ribbon‐like,polypyrrole‐coated carbonyl iron suspensions under oscillatory shear

One of the crucial problems of classical magnetorheological (MR) fluids is their high rate of sedimentation. This disadvantage may be substantially eliminated using core‐shell particles. The aim of this study is to prepare spherical carbonyl iron (CI) particles coated with conducing polymer polypyrrole (PPy) with ribbon‐like morphology. Scanning electron microscopy proved the formation of the ribbon‐like layer onto CI particles while Fourier transform infrared spectroscopy confirmed the chemical structure of PPy. The magnetic properties observed via vibrating sample magnetometer showed decreased magnetization saturation of core‐shell‐structured particles due to the existence of non‐magnetic surface layer. MR measurements performed under oscillatory shear flow as a function of the applied magnetic flux density, temperature, and particle concentration showed that core‐shell particle‐based MR suspension exhibits sufficient MR performance for practical applications. Moreover, the suspension stability is promoted significantly when core‐shell particles are used as a dispersed phase. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Fabrication and Characterization of Jute Fiber-Reinforced PET Composite: Effect of LLDPE Incorporation

The aim of the research was to study the effect of LLDPE incorporation in the jute fiber-reinforced PET composites (50% fiber by wt). The effect of LLDPE incorporation into PET was investigated by measuring the mechanical properties of the LLDPE blended jute fiber-reinforced PET composites. LLDPE was blended (20-80% by wt) with PET and the thin films were made by compression molding. Water uptake of the composites was also investigated. Degradation of all the composites was carried out in soil medium.     

THERMOHYDRAULICS OF LAMINAR FLOW THROUGH A CIRCULAR TUBE HAVING INTEGRAL HELICAL CORRUGATIONS AND FITTED WITH HELICAL SCREW-TAPE INSERT

The experimental friction factor and Nusselt number data for laminar flow through a circular duct having integral helical corrugations and fitted with a helical screw-tape insert are presented. Predictive friction factor and Nusselt number correlations are also presented. The thermohydraulic performance was evaluated. The major findings of this experimental investigation are that the helical screw-tape insert in combination with integral helical corrugations performs significantly better than the individual enhancement technique acting alone for laminar flow through a circular duct up to a certain value of the fin parameter. This research finding is useful in designing tubes carrying solar thermal mass of viscous oil in a parabolic trough solar collector used in environmentally sound and increasingly cost-effective solar thermal electric power plants. The result is also useful in designing heat exchangers used in process industries.     

Electromagnetic properties of aluminosilicate‐filled polymer composites of poly(vinyl alcohol)–poly(vinyl pyrrolidone)

Nanocomposites of aluminocilicate are of growing interest not only because they offer exceptional reinforcement at very low filler concentrations, but also because of their electromagnetic properties and natural origin. Aluminosilicate‐filled biodegradable composites of poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP) were prepared by a conventional solvent casting technique using glass plates as the casting surfaces. The aluminosilicate used in this study is a multicomponent natural clay material. Its average particle size is 23–24 nm. The dielectric and magnetic properties of composite materials of PVA‐PVP and aluminosilicate were investigated in wide frequency ranges from 1 MHz to 1 GHz. The complex permittivity spectra (ε* = ε′ – jε″) had a relaxation type frequency dispersion with an ill‐defined broad resonance line width of the dielectric losses (ε″). The magnetic properties of composites are very low and are independent of the filler concentration. The new nanobiocomposites are brick red in color and weakly ferromagnetic in nature. POLYM. COMPOS., 26:739–744, 2005. © 2005 Society of Plastics Engineers     

Highly Sensitive Plus Shaped Cavity in Silicon Fiber for RI Detection of Water Samples

Silicon - Fiber grating based sensors demonstrate great potential especially for the refractive index (RI) based sensing. However, a meticulous effort is still required to improve the sensitivity...