High-strength functionalized pectin/fibroin hydrogel with tunable properties: A structure–property relationship study

Hydrogels possessing high mechanical strength and well-controlled properties are of utmost interest in bone tissue engineering. In the current study, a strong self-crosslinked hydrogel with variable properties has been developed from a combinatory composition of functionalized pectin and silk fibroin. Pectin chains underwent partial oxidation to be decorated with aldehyde functionalities. Later on, functionalized polysaccharide and protein were blended with different ratios, and corresponding variations in crystalline structure as well as in morphological, mechanical, and rheological properties have been monitored. Some theories have been used to better perceive the relation between blending ratio and hydrogel properties. Avrami equation based on time sweep rheological analysis elucidated that in sample with equivalent ratio of oxidized pectin and fibroin, the crystallization was highly delayed due to dominance of Schiff's base reaction. The Herschel–Bulkley model based on flow curve rheology test corroborated that aforesaid composition revealed the most noticeable shear thinning behavior and accordingly the strongest crosslinked network. Finally, rubber elastic theory based on dynamic mechanical analysis implied that said formulation possessed the highest crosslinking density due to higher availability of aldehyde to amine functionalities. Moreover, cell culture studies proved that P50 F50 sample prevailed over other compositions with respect to cell viability and function. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48859.     

Fast procedure for constructing an accurate dynamic average-value model of synchronous machine-rectifier systems

The analytical derivation of the average-value models (AVMs) for synchronous-machine-fed rectifier systems depends on many factors and is challenging in general. Various models presented in the literature rely on a single operating mode and a dc filter configuration. A recently proposed parametric approach utilizes a detailed simulation as a basis to establish an AVM that uses a proper full-order qd generator model. This paper presents a procedure to extract the appropriate nonlinear algebraic functions to represent the rectifier averaged behavior. In contrast to existing methods, the proposed procedure does not require significant analytical derivations and/or computational resources and results in a highly accurate dynamic AVM. The proposed methodology is validated with the results of detailed simulation and hardware experiment, and is shown to be very accurate in predicting the large-signal time-domain transients as well as the small-signal frequency-domain characteristics.     

An iterative simulation algorithm for large oscillation of the applicable 2D-electrical system on a complex nonlinear substrate

Engineering with Computers - An iterative algorithm is a mathematical procedure that uses an initial value to generate a sequence of improving approximate solutions for a class of problems, in...     

Parasitics Realization in State-Space Average-Value Modeling of PWM DC–DC Converters Using an Equal Area Method

Average-value modeling of pulsewidth-modulation dc-dc converters is often based on the assumption of piecewise-linear waveforms of the circuit variables, whereas considering parasitics introduces waveform nonlinearity and complicates the model derivation. This paper presents a new approach that considers averaging with nonlinear waveforms using the equivalent area method, and proposes a state-space averaged model that is fairly accurate and seamlessly functional in both continuous and discontinuous conduction modes. The resulting average-value model is applicable for large-signal transient studies as well as for linearization and subsequent small-signal analysis. The proposed model is validated with a hardware prototype and a detailed simulation, and is shown to be an improvement over previously established models in the time and frequency domains.