A new complete model of switch-mode plasma cutting power supply

A complete model of switch-mode plasma cutting power supply and its simulation are developed. The full bridge isolated pulse width modulation (PWM) buck converter in continuous conduction mode (CCM) for high watt plasma power supply is approached. Reduced ripple current and improved power factor are achieved in the plasma power supply. With a PID control strategy, circuit responses become more stable and faster with low overshoot during load and current changing. The converter achieved high efficiency under 3 to 15kW load conditions.     

Probabilistic safety assessment of self-centering steel braced frame

The main drawback of conventional braced frames is implicitly accepting structural damage under the design earthquake load, which leads to considerable economic losses. Controlled rocking self-centering system as a modern low-damage system is capable of minimizing the drawbacks of conventional braced frames. This paper quantifies main limit states and investigates the seismic performance of self-centering braced frame using a Probabilistic Safety Assessment procedure. Margin of safety, confidence level, and mean annual frequency of the self-centering archetypes for their main limit states, including PT yield, fuse fracture, and global collapse, are established and are compared with their acceptance criteria. Considering incorporating aleatory and epistemic uncertainties, the efficiency of the system is examined. Results of the investigation indicate that the design of low- and mid-rise self-centering archetypes could provide the adequate margin of safety against exceeding the undesirable limit-states.     

Proposal of an equivalent linearization method to predict seismic hysteretic energy demand considering stiffness degradation effects

To overcome complexities and shortcomings of previous studies, a new method is proposed to derive an equivalent linear model for predicting seismic hysteretic energy demand of bilinear single degree of freedom (SDOF) models. A new displacement spectrum is defined, which represents hysteretic energy. It is found that by increasing initial period and damping of a nonlinear system in the correct proportion and defining a linear model with these characteristics, the new developed displacement can be achieved. Error minimization is applied through an algorithm to find the optimum equivalent period corresponding to an equivalent damping utilizing two sets of far‐field and near‐field earthquakes. To analyze the effects of stiffness degradation, the proposed algorithm has been implemented on modified Clough hysteretic model as well. Comparing the results, effects of stiffness degradation on the ratio of equivalent to initial period is evident in the short period range, while with increasing initial period, the effect can almost be neglected at higher values of ductility. Nonlinear regression analysis is carried out to provide the equations for predicting equivalent linear parameters as a function of ductility. Despite the previous predictive equations, the proposed model is independent of earthquake characteristics and response‐related parameters, which has increased efficiency as well as simplicity.     

Design of improved‐reliability nanocircuits with mixed NBTI‐ and HCI‐aware gate‐sizing formulation

Negative bias temperature instability (NBTI) and hot carrier injection (HCI) are two important processes of reliability concern in nano‐scale integrated circuits. A circuit‐level design technique to combat NBTI degradation is gate oversizing. This paper presents a new technique based on PMOS and NMOS resistance variation for the NBTI‐ and HCI‐aware gate‐sizing problem for the first time. In this technique, the area of the circuit is minimized with constraints on degraded delay due to NBTI and HCI and the transitor size. Expreimental results for several gates and ISCAS'85 benchmark circuits show that this technique imposes an area overhead of less than 1% with respect to baseline design in most cases. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Preparation and characterization of an epoxy nanocomposite toughened by a combination of thermoplastic,layered and particulate nano-fillers

This paper reports the development of an epoxy-based nanocomposite toughened by the combination of thermoplastic, layered and particulate nano-fillers. The main objective of this work is to incorporate poly(acrylonitrile-co-butadiene-co-styrene) (ABS), clay (layered nano-filler) and nano-TiO₂ (particulate nano-filler) into epoxy matrix with the aim of obtaining the quaternary nanocomposite with higher impact strength and lower cost without attenuating the other desired mechanical properties such as tensile strength. Taguchi methodology was applied for the optimization and statistical determination of the significant factors influencing the mechanical properties of the quaternary nanocomposite. Impact and tensile strengths of the quaternary nanocomposite with optimum composition increased by 168% and 64% compared to neat epoxy, respectively. Furthermore, synergistic effect was observed with the addition of three type modifiers. It was found that ABS content has the most significant effect on mechanical properties of the obtained quaternary nanocomposite. Also correlation between morphological and mechanical properties of the nanocomposite was investigated. A dispersion of nano-size ABS and TiO₂ particles along with exfoliated clay nano-platelets in epoxy matrix was achieved as main morphological property of the quaternary nanocomposite. A new morphology was obtained for ABS phase in epoxy rich matrix.     

Effectiveness of PANI/Cu/TiO2 ternary nanocomposite on antibacterial and antistatic behaviors in polyurethane coatings

Surfaces with antibacterial and antistatic functionalities are one of the new demands of todays' industry. Therefore, a facile method for the preparation of multifunctional polyaniline/copper/TiO₂ (PANI/Cu/TiO₂) ternary nanocomposite based on in situ polymerization is presented. This nanocomposite was characterized through the different techniques and was utilized for induction of antibacterial and antistatic properties in polyurethane coatings. Measurement of the conductivity of PANI/Cu/TiO₂ ternary nanocomposite indicated higher electrical conductivity of this nanocomposite compared to pure PANI. The antibacterial activity of the modified polyurethane coatings was tested against Gram-positive and Gram-negative bacteria which led to remarkable reduction in bacterial growth. Besides, it was observed that polyurethane coating with 2 wt % content of ternary nanocomposite has a surface electrical resistance equal 4 × 10⁸ Ω/sq which acquires surface electrical resistance of standard antistatic coatings. The final coatings were also characterized in terms of thermal and mechanical properties to investigate the effect of the ternary nanocomposite on improvement of these properties. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48825.     

Unconfined compressive strength prediction of soils stabilized using artificial neural networks and support vector machines

This study aims to improve the unconfined compressive strength of soils using additives as well as by predicting the strength behavior of stabilized soils using two artificial-intelligence-based models. The soils used in this study are stabilized using various combinations of cement, lime, and rice husk ash. To predict the results of unconfined compressive strength tests conducted on soils, a comprehensive laboratory dataset comprising 137 soil specimens treated with different combinations of cement, lime, and rice husk ash is used. Two artificial-intelligence-based models including artificial neural networks and support vector machines are used comparatively to predict the strength characteristics of soils treated with cement, lime, and rice husk ash under different conditions. The suggested models predicted the unconfined compressive strength of soils accurately and can be introduced as reliable predictive models in geotechnical engineering. This study demonstrates the better performance of support vector machines in predicting the strength of the investigated soils compared with artificial neural networks. The type of kernel function used in support vector machine models contributed positively to the performance of the proposed models. Moreover, based on sensitivity analysis results, it is discovered that cement and lime contents impose more prominent effects on the unconfined compressive strength values of the investigated soils compared with the other parameters.     

Synthesis,characterization, and swelling kinetic study of porous superabsorbent hydrogel nanocomposite based on sulfonated carboxymethylcellulose and silica nanoparticles

New superabsorbent nanocomposite was synthesized by free-radical graft polymerization of sulfonated-carboxymethyl cellulose (SCMC) with acrylic acid (AA) in the presence of polyvinylpyrrolidone (PVP) and silica nanoparticles. Carboxymethyl cellulose (CMC) was first sulfonated using chlorosulfonic acid, and then AA monomers were grafted onto SCMC. FTIR results confirmed that sulfonation of CMC as well as grafting of AA monomers onto SCMC has been performed successfully. Moreover, the presence of silica nanoparticles into superabsorbent nanocomposite was evaluated with EDX analysis. The element mappings show a homogenous distribution of silica nanoparticles throughout the hydrogel nanocomposite. SEM images exhibited porous morphology for hydrogel nanocomposite, which was due to the incorporation of PVP in its network. The experimental findings from TGA analysis indicated that incorporation of PVP and silica nanoparticles into the hydrogel network improved thermal stability of superabsorbent nanocomposite. Swelling kinetic studies revealed that superabsorbent nanocomposite hydrogel had higher equilibrium swelling capacity and swelling rate compared with the neat hydrogel sample. Besides that, superabsorbent nanocomposite depicted excellent salt and pH-sensitive behavior in different saline and pH solutions. As a consequence, this hydrogel nanocomposite acts as useful water reservoir, which might be most profitable in agricultural applications.     

An EM based probabilistic two-dimensional CCA with application to face recognition

Recently, two-dimensional canonical correlation analysis (2DCCA) has been successfully applied for image feature extraction. The method instead of concatenating the columns of the images to the one-dimensional vectors, directly works with two-dimensional image matrices. Although 2DCCA works well in different recognition tasks, it lacks a probabilistic interpretation. In this paper, we present a probabilistic framework for 2DCCA called probabilistic 2DCCA (P2DCCA) and an iterative EM based algorithm for optimizing the parameters. Experimental results on synthetic and real data demonstrate superior performance in loading factor estimation for P2DCCA compared to 2DCCA. For real data, three subsets of AR face database and also the UMIST face database confirm the robustness of the proposed algorithm in face recognition tasks with different illumination conditions, facial expressions, poses and occlusions.     

Evaluation of initial deposition rate of electroless Ni–P layers by QCM method

Electroless nickel–phosphorus (ENP) initial deposition rates from a glycine bath were studied by means of the quartz crystal microbalance (QCM) method. SEM and EDX methods were also used to study the morphology and elemental analysis of deposits. The effect of pH, temperature and the type of activation process on the initial deposition rate, surface morphology and surface elemental analysis of deposits were evaluated. Increasing the pH and the temperature cause an increase in deposition rate and a decrease in P content of deposits. The phosphorus content of obtained deposits in pre-plate method was greater than in sensitizer–activator process under the same conditions of the alloy deposition. The surface morphology depends on P content of deposits. By decreasing the P content of deposits, the grain size increases.