Identification of mixing parameters in agitated pulp chests: A continuous time domain approach

Parameter identification is quite challenging in mixing, which is extensively employed in chemical process industry. Agitated pulp chests are more difficult to characterize because they handle non-Newtonian pulp suspensions and non-ideal flows such as short circuiting, recirculation and channeling. In the present study, we characterize the agitated pulp chests in the continuous time domain, which obviates the restrictions imposed by the discrete time approach. For this purpose, a robust and efficient hybrid genetic algorithm is utilized along with a differential-algebraic model of mixing. Necessary derivatives including auxiliary differential equations are obtained for gradient search. Using realistic large sets of mixing data, both the algorithm and the model are successfully validated before characterizing laboratory-scale agitated pulp chests. Superior characterizations are obtained compared to those yielded by the discrete time domain approach. This outcome highlights the benefit of the continuous time domain approach developed in this work.     

Vacuum-Deposited Thin Film of Aniline–Formaldehyde Condensate/WO3·nH2O Nanocomposite for NO2 Gas Sensor

A hydrated tungsten oxide (WO₃·nH₂O)-embedded aniline–formaldehyde condensate (AFC/WO₃·nH₂O) nanocomposite thin film was prepared on an indium tin oxide (ITO)-coated glass surface via vacuum-deposition technique. The resulting AFC/WO₃·nH₂O/ITO thin film was characterized using ultraviolet–visible spectroscopy (UV–Vis), Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), and electron microscopy (SEM). The composite thin film exhibited a crystalline surface morphology containing nanocrystals of WO₃·nH₂O with a diameter ranging from 15 to 20 nm. The AFC/WO₃·nH₂O/ITO film allowed for the low potential detection of NO₂ gas at a concentration range from 0 to 9000 ppm. The NO₂ gas sensing characteristics were studied by measuring the change in the current with respect to concentration and time. The current of the AFC/WO₃·nH₂O/ITO film linearly increased with an increase in concentration of NO₂ gas with a response of ~20 s.     

Investigation of Enhancement Band Using Double Screen Frequency Selective Surfaces with Koch Fractal Geometry at Millimeter Wave Range

Numerical and theoretical investigations are presented for a double screen frequency selective surface (DSFSS) with perfectly conducting Koch fractal patch elements. The work was developed in two steps, in the first step two Koch fractal FSS screens were designed using the commercial software Ansoft Designer^TM. In the second these FSS were cascaded and separated by an air gap layer, forming the so-called DSFSS, to improve the bandwidth behavior. Thereafter, a numerical cascading technique is used to analyze the effect of the air gap on the DSFSS. The results were compared and a good agreement was observed.     

Dual material gate junctionless tunnel field effect transistor

This paper proposes a junctionless tunnel field effect transistor (JLTFET) with dual material gate (DMG) structure and the performance was studied on the basis of energy band profile modulation. The two-dimensional simulation was carried out to show the effect of conduction band minima on the abruptness of transition between the ON and OFF states, which results in low subthreshold slope (SS). Appropriate selection of work function for source and drain side gate metal of a double metal gate JLTFET can also significantly reduce the subthreshold slope (SS), OFF state leakage and hence gives improved I _ON/I _OFF.     

Heat transport in magnetohydrodynamic physiological blood flow through a constricted artery

In this paper, we study how the magnetohydrodynamic (MHD) pulsatile flow of blood and heat transfer works through a constricted artery with a flexible wall. The human circulatory network consists of veins and arteries that sometimes contain constrictions, allowing the impact of the applied magnetic field on flow fields to be observed. The walls of the flowing medium are considered to be a function of time. The flowing blood is hypothesized as shear-thinning fluid, emulating Yeleswarapu's viscosity replica. Additionally, we consider the energy equation to understand the impact of a magnetic field on heat transfer rates for such flows. The vorticity transport equation along with the stream function equation is obtained using the vorticity–stream function technique. Numerical solutions of the governing nonlinear MHD equations and energy equation in addition to physically pertinent flow conditions were achieved by adapting a finite difference scheme. Considerable attention has been paid to ensure an accurate comparison between the current and previous results. The two sets of numbers appear to match closely. For an even deeper understanding of the flow and heat transport process, the effects of height of stenosis and diverse physiological parameters on time-averaged wall shear stress (TAWSS), rate of heat transport, and so on are explored in depth through their graphical depiction. In the vicinity of the constriction, it is observed that the separation becomes longer with increasing constriction height. Higher magnetic force strength leads to a reduction in separation length. Newtonian fluids transfer heat more rapidly in their narrowing regions and downstream than fluids with non-Newtonian behavior.     

CO2 Capture by Liquid Solvents and their Regeneration by Thermal Decomposition of the Solid Carbonated Derivatives

The chemical capture of CO₂ by either aqueous Na₂CO₃ and K₂CO₃ or nonaqueous solutions of the amines 2‐amino‐2‐methyl‐1‐propanol (AMP) or piperazine (PZ) is described. The captured CO₂ is stored as solid NaHCO₃, KHCO₃, and AMP or PZ carbamates. Solid NaHCO₃ and KHCO₃ are decomposed at 200 °C and 250 °C, respectively, to regenerate the carbonates for their reuse. In the experiments with AMP or PZ, the solid carbamates are decomposed at 80 °C–110 °C to regenerate the free amines. The absence of water in the desorption‐regeneration step is intriguing and could have the potential of reducing one of the major disadvantages of aqueous absorbents, namely the energy cost of the regeneration step and amine degradation, yet preserving the efficiency of the absorption in the liquid phase.     

Verification of distributed systems with local�Cglobal predicates

This paper describes a methodology for developing and verifying a class of distributed systems in which the state space may be discrete or continuous. Our focus is on systems where changes are local in that a small number of components change state while the remainder of the system is unchanged. A proof methodology is developed that ensures global properties, such as invariants and convergence, by guaranteeing local properties within subsystems. This methodology is used to prove the correctness of concrete examples. We present a PVS library of theorems and proofs that can be used to reduce the work required to develop and verify programs in this class. A transformation of these libraries to Java is also outlined.     

Novel defects in Al–Pd–Fe complex metallic alloys: A micromechanical modelling approach

Transmission electron microscopy investigations have revealed that in the face centred complex metallic alloy of C₂–Al–Pd–Fe, the dislocations mediating plastic flow are decorated by localized regions of body centred structure in the compressive part of their strain field thus forming composite defects. We calculated the properties of these defects using a micromechanical model. The Eshelby method was employed to estimate the energies involved in the formation of such defects in the face-centred C₂ phase. We could reproduce the experimentally observed features of the defects in terms of their size and spatial configuration. The model describes a unique mechanism of a non-equilibrium defect, i.e., a dislocation, being stabilized by the formation and interaction with another non-equilibrium defect, i.e., a nanometre sized inclusion of different structure.     

Left ventricular morphology in chronic renal failure by echocardiography

M-mode, two-dimensional, and Doppler echocardiography were performed in 38 chronic renal failure (CRD) patients on conservative management, 35 patients on hemodialysis, and 36 matched controls. The controls were matched for age, sex, and comorbidities. The incidence of hypertension, left ventricular (LV) end diastolic volume, LV end systolic volume, and LV mass index were significantly higher in patients on hemodialysis compared to the controls. The LV parameters in the predialysis patients were not significantly different from the controls, except the LV end systolic internal dimensions were significantly higher in the CRF patients. Multiple regression analysis underscored the strong association between increase in LV mass index (LVMI) and hypertension. The diabetic patients with renal failure had large LV internal diameter and end diastolic volume compared to non-diabetics. Systolic function was well preserved even in hypertensive and diabetic patients with uremia. The incidence of diastolic dysfunction and asymmetrical septal hypertrophy were not significantly different in the three groups of patients.