Voltage-mode full-wave rectifier based on DXCCII

The paper deals with the design and performance analyses of a current conveyor based voltage-mode full-wave rectifier. In the structure of the proposed non-linear circuit the second-generation current conveyor and dual-X current conveyor have been used as active elements. In the circuit the current sourcing scheme of the diodes is used to enable high-frequency signal processing. Except the active elements and only two rectifying diodes, other two resistors are required, generally operating as simple voltage-to-current and current-to-voltage converters. Using the CMOS implementation of the active elements, the performance of the rectifier was analyzed by evaluating the frequency dependent RMS error and DC transient value for different values of input voltage magnitudes. Furthermore, using readily available integrated circuits, the performance of the proposed structure has also been verified by experimental measurements that show the feasibility of the voltage-mode full-wave rectifier.     

The theoretical strength of fcc crystals under multiaxial loading

Atomistic modeling of a special triaxial loading of six perfect fcc crystals is performed by means of pseudopotential density functional method. The triaxial stress state is simulated as a superposition of axial pressure and transverse biaxial stresses. The transverse stresses are treated as adjustable parameters and their influence on the theoretical compressive strength is evaluated for the 〈1 0 0〉 and the 〈1 1 1〉 crystallographic orientations of the loading axis. The obtained results revealed that the compressive strengths are increasing linear functions of the transverse compressive stresses. On the other hand, the tensile transverse stresses lower the compressive strength. This implies that the compressive strengths of individual crystals approach a zero value when some critical (characteristic) levels of tensile biaxial stresses are reached. These stresses are then considered to be the theoretical tensile biaxial strengths.     

Effects of (R)- and (S)-α-Hydroxylation of Acyl Chains in Sphingosine,Dihydrosphingosine, and Phytosphingosine Ceramides on Phase Behavior and Permeability of Skin Lipid Models

Ceramides (Cers) with α-hydroxylated acyl chains comprise about a third of all extractable skin Cers and are required for permeability barrier homeostasis. We have probed here the effects of Cer hydroxylation on their behavior in lipid models comprising the major SC lipids, Cer/free fatty acids (C ₁₆-C ₂₄)/cholesterol, and a minor component, cholesteryl sulfate. Namely, Cers with (R)-α-hydroxy lignoceroyl chains attached to sphingosine (Cer AS), dihydrosphingosine (Cer AdS), and phytosphingosine (Cer AP) were compared to their unnatural (S)-diastereomers and to Cers with non-hydroxylated lignoceroyl chains attached to sphingosine (Cer NS), dihydrosphingosine (Cer NdS), and phytosphingosine (Cer NP). By comparing several biophysical parameters (lamellar organization by X-ray diffraction, chain order, lateral packing, phase transitions, and lipid mixing by infrared spectroscopy using deuterated lipids) and the permeabilities of these models (water loss and two permeability markers), we conclude that there is no general or common consequence of Cer α-hydroxylation. Instead, we found a rich mix of effects, highly dependent on the sphingoid base chain, configuration at the α-carbon, and permeability marker used. We found that the model membranes with unnatural Cer (S)-AS have fewer orthorhombically packed lipid chains than those based on the (R)-diastereomer. In addition, physiological (R)-configuration decreases the permeability of membranes, with Cer (R)-AdS to theophylline, and increases the lipid chain order in model systems with natural Cer (R)-AP. Thus, each Cer subclass makes a distinct contribution to the structural organization and function of the skin lipid barrier.     

Conjugated polyaniline as a result of the benzidine rearrangement

The mechanism of the oxidative polymerization of aniline is reviewed on the basis of the experimental evidence and reaction schemes proposed in the literature. It is demonstrated that the balance between the non‐protonated and protonated forms of the monomer and the growing chain is responsible for the diversity of the molecular structure, morphology and properties of aniline oxidation products. Various forms are oxidized by two oxidation mechanisms: (1) chain reaction of electrophilic substitution and (2) coupling of cation‐radical centres. At pH > 2.5, the non‐protonated reagents are oxidized with a chain reaction controlled by electrophilic substitution of the aromatic ring. The reaction leads to the formation of non‐conducting aniline oligomers with heterogeneous molecular structures. At pH = 2.5–4, the electrophilic substitution is reduced because of the protonation of the aniline, and the cyclic dimer, phenazine, becomes the main product of the oxidation. The growth of the conjugated chain proceeds at pH < 2.5, when the reactants are protonated. The reaction proceeds through coupling between the terminal cation radical and the monomer cation radical with formation of a π‐complex. The transformation of the π‐complex into a para‐substituted monomer unit is thermodynamically controlled and is produced through an intramolecular benzidine (semidine) rearrangement. The regular structure of the growing chains is a result of the high regioselectivity of the sigmatropic rearrangements and significant energy gain attained by the formation of protonated polyconjugated chains in the agglomerated state. © 2015 Society of Chemical Industry     

Local learning‐based adaptive soft sensor for catalyst activation prediction

This work presents an algorithm for the development of adaptive soft sensors. The method is based on the local learning framework, where locally valid models are built and maintained. In this framework, it is possible to model nonlinear relationship between the input and output data by the means of a combination of linear models. The method provides the possibility to perform adaptation at two levels: (i) recursive adaptation of the local models and (ii) the adaptation of the combination weights. The dataset used for evaluation of the algorithm describes a polymerization reactor where the target value is a simulated catalyst activity in the reactor. This dataset is also used to evaluate the performance of the proposed algorithm. The results show that the traditional recursive partial least squares algorithm struggles to deliver accurate predictions. In contrast to this, by exploiting the two‐level adaptation scheme, the proposed algorithm delivers more accurate results. © 2010 American Institute of Chemical Engineers AIChE J, 57, 2011     

Suspension polymerization of aniline hydrochloride in non‐aqueous media

The oxidation of aniline hydrochloride by ammonium peroxydisulfate in non‐aqueous media was studied, when the monomer or oxidant or both were not completely soluble. Polyaniline was formed in acetone, methanol and toluene. Aniline oligomers only were produced in chloroform and n‐butylacetate. No interaction of the monomer and the oxidant was observed in dimethylsulfoxide and N‐methylpyrrolidone. UV‐visible and Fourier transform infrared spectra were recorded in order to study the molecular structure of the final products. Conductivity was measured for conducting protonated forms and corresponding bases. An explanation of aniline hydrochloride oxidation in various organic media is offered. Copyright © 2011 Society of Chemical Industry     

Stability of bisphenol A diglycidyl ether and bisphenol F diglycidyl ether in water-based food simulants

Varnishes used for the inner coatings of food cans are often based on epoxy resins or vinylic organosols. The epoxy resins can be produced from bisphenol A (BPA) and bisphenol F (BPF), and these also contain bisphenol A diglycidyl ether (BADGE) or bisphenol F diglycidyl ether (BFDGE) as stabilising components. These compounds may break down during storage and also by the influence of food simulants. The stability of BADGE and BFDGE were studied using reverse-phase gradient high-performance liquid chromatography (RP-HPLC) with ultraviolet detection (UV). Three experimental conditions for spiked simulants were compared: (1) the storage at 25 °C (C1), (2) the storage at 40 °C (C2) and (3) the storage at 25 °C after 15 min heating at 120 °C (C3). Distilled water, 3% acetic acid and 10% ethanol were used as food simulants. It was observed that BADGE is more stabile than BFDGE. The loss of BADGE and BFDGE were minimal in 10% ethanol (39 and 46% at 25 °C, 60 and 69% at 40 °C, respectively) and highest in 3% acetic acid (60 and 63% at 25 °C, 76 and 82% at 40 °C, respectively). At experiment (C3), the hardest conditions, significant degradation was not shown in comparison with conditions (C1) and (C2), contrariwise BADGE and BFDGE in 10% ethanol were minimal degradated at conditions (C3) from all these experiments (loss of 5 and 8%, respectively).     

Correlation between Elastic and Electric Properties for Metal Foams: Theory and Experiment

Correlation between Young's modulus and electric conductivity is given in the explicit form for metal foams. Theoretical predictions are compared with the experimental measurements for AlMg1Si0.6 aluminum foams with porosity in the range 70 to 90%. The agreement is better than 10% in all cases.