A New ZVS-PWM Full-Bridge Boost Converter

Pulse-width modulated (PWM) full-bridge boost converters are used in applications where the output voltage is considerably higher than the input voltage. Zero-voltage-switching (ZVS) is typically implemented in these converters. The objective of this thesis is to propose, analyze, design, implement, and experimentally confirm the operation of a new Zero-Voltage-Switching PWM DC-DC full-bridge boost converter that does not have any of the drawbacks that other converters of this type have, such as a complicated auxiliary circuit, increased current stresses in the main power switches and load dependent ZVS operation. In this thesis, the general operating principles of the converter are reviewed, and the converter’s operation is discussed in detail and analyzed mathematically. As a result of the mathematical analysis, key voltage and current equations that describe the operation of the auxiliary circuit and other converter devices have been derived. The steady state equations of each mode of operation are used as the basis of a MATLAB program that is used to generate steady-state characteristic curves that shows the effect that individual circuit parameters have on the operation of the auxiliary circuit and the boost converter. Observations as to their steady-state characteristics are made and the curves are used as part of a design procedure to select the components of the converter, especially those of the auxiliary circuit. An experimental full-bridge DC-DC boost converter prototype is built based on the converter design and typically waveforms are presented to confirm the feasibility of the converter, as well as computer simulation results. The efficiency of the proposed converter operating with the auxiliary circuit is compared to that of a hard-switched PWM DC-DC full-bridge boost converter and the increased efficiency of the proposed converter is confirmed. Keywords: Power conversion, DC-DC converter, Full-bridge converter, Boost Converter, Zero-voltage-switching, Soft-switching

Adsorption properties of hydrazine on pristine and Si-doped Al₁₂N₁₂ nano-cage

The interaction of hydrazine (N₂H₄) molecule with pristine and Si-doped aluminum nitride (Al₁₂N₁₂) nano-cage was investigated using the density functional theory calculations. The adsorption energy of N₂H₄ on pristine Al₁₂N₁₂ in different configurations was about -1.67 and -1.64 eV with slight changes in its electronic structure. The results showed that the pristine nano-cage can be used as a chemical adsorbent for toxic hydrazine in nature. Compared with very low sensitivity between N₂H₄ and Al₁₂N₁₂ nano-cage, N₂H₄ molecule exhibits high sensitivity toward Si-doped Al₁₂N₁₂ nano-cage so that the energy gap of the Si-doped Al₁₂N₁₂ nano-cage is changed by about 31.86 and 37.61 for different configurations in the SiAlmodel and by about 26.10 in the SiNmodel after the adsorption process. On the other hand, in comparison with the SiAlmodel, the adsorption energy of N₂H₄ on the SiNmodel is less than that on the SiALmodel to hinder the recovery of the nano-cage. As a result, the SiNAl₁₂N₁₁ is anticipated to be a potential novel sensor for detecting the presence of N₂H₄ molecule. © 2016 Taylor & Francis Group, LLC

Electric Field Effect in CO Adsorption on the (6,0) Zigzag Single-walled Aluminum Nitride Nanotube: an Ideal Method for CO Adsorption

The behavior of the monoxide carbon (CO) adsorbed on the external surface of H-capped (6,0) zigzag single-walled aluminum nitride nanotube was studied under the parallel and transverse electric fields with strengths 0-140 × 10-4 a.u. by using density functional calculations. Geometry optimizations were carried out at the B3LYP/6-31G* level of theory using the Gaussian 03 suite of programs. The binding energies obtained from these calculations at different applied parallel and transverse electric field strengths indicate that with increasing parallel electric field intensity, the binding energy values are increased, especially in the higher parallel field strength, whereas the BE values for the applied transverse electric field show a significant reverse trend. Results of this study indicate that with increasing parallel electric field intensity the pristine AlNNT can be used as CO storage and the parallel electric field effect is an ideal method for adsorption, storage, and fabrication of CO sensors. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3518

Adsorption Study of Cyanate Ion on the Single-wall BC2N Nanotubes: a Computational Study

Cyanate adsorption on the external surface of H-capped (6,0) zigzag single-walled BC2N nanotube was studied by using density functional theory calculations. We present the nature of the cyanate interaction in different sites of the nanotube. This nanotube can absorb the cyanate ion in its pristine form without manipulating its structure through doping, chemical functionalization, making defect, etc, and the nanotube can be used as cyanate storage. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3518

Phenol interaction with different nano-cages with and without an electric field: A DFT study

The adsorption properties of the phenol molecule (C6H5OH) upon the outer surfaces of C24, B12P12, B12N12, Al12N12, and Al12P12 were investigated using density functional theory calculations. Our calculations reveal that the phenol molecule can be chemisorbed on the sidewalls of Al12N12 and Al12P12 with adsorption energies of -1.03 and -0.76 eV, respectively. While the adsorption energy of C6H5OH on Al12N12 is typically more than that of Al12P12 cluster. We also considered the adsorption of the C6H5OH molecule under a strong electric field over Al12N12. The results indicate that Al12N12 has high sensitivity to the phenol molecule in the presence of an electric field. © Springer Science+Business Media 2014

BN Nanotube Serving as a Gas Chemical Sensor for N₂O by Parallel Electric Field

Density functional theory calculations were performed to understand the electronic properties of C₂₄, B₁₂N₁₂, B₁₂P₁₂, and (6, 0) BNNT interacted with N₂O molecule in the presence and absence of an external electric field using the B3LYP method and 6-31G** basis set. The adsorption of N₂O from O-side on the surface of (6, 0) BNNT has high sensitivity in comparison with B₁₂N₁₂ nano-cage. The adsorption energy of N₂O (O-side) on the sidewalls of B₁₂N₁₂ and BNNT in the presence of an electric field are −21.01 and −15.48 kJ mol⁻¹, respectively. Our results suggest that in the presence of an electric field, the B₁₂N₁₂ nano-cage is the more energetically notable upon the N₂O adsorption than (6, 0) BNNT, C₂₄, and B₁₂P₁₂. Whereas, our results indicate that the electronic property of BNNT is more sensitive to N₂O molecule at the presence of an electric field than B₁₂N₁₂ nano-cage. It is anticipated that BNNT could be a favorable gas sensor for the detection of N₂O molecule. © 2016, Springer Science+Business Media New York

A DFT study of 5-fluorouracil adsorption on the pure and doped BN nanotubes

Abstract The electronic and adsorption properties of the pristine, Al-, Ga-, and Ge-doped BN nanotubes interacted with 5-fluorouracil molecule (5-FU) were theoretically investigated in the gas phase using the B3LYP density functional theory (DFT) calculations. It was found that the adsorption behavior of 5FU molecule on the pristine (8, 0) and (5, 5) BNNTs are electrostatic in nature. In contrast, the 5FU molecule (O-side) implies strong adsorption on the metal-doped BNNTs. Our results indicate that the Ga-doped presents high sensitivity and strong adsorption with the 5-FU molecule than the Al- and Ge-doped BNNTs. Therefore, it can be introduced as a carrier for drug delivery applications. © 2015 Elsevier Ltd

Kinetic model for polyhydroxybutyrate (PHB) production by Hydrogenophaga pseudoflava and verification of growth conditions

A kinetic model that describes microbial growth, biopolymer production and substrate consumption is used to predict the performance of batch fermentation of Hydrogenophaga pseudoflava. H. pseudoflava DSMZ 1034 is useful in synthesizing polyhydroxyalkanoates (PHAs).The experimental data was also fitted with the logistic equation that can provide adequate description for PHA synthesized by H. pseudoflava. The Lineweaver-Burk plot defined biokinetic coefficients which were described by a simplified Monod’s rate model. The specific growth rates, max and the Monod constants, Ks, for various substrates such as glucose, fructose were 0.36, 0.24, h-1 and 106, 80 g/l, respectively. A good agreement was found between the experimental and the predicted values, which indicated that the model with differential equations would describe fermentation process for the PHA formation

HSE Management System Criteria Ranking to Evaluate Contractors Prequalification Using the Analytical Hierarchy Process in the Fifth Refinery of South Pars Gas Complex

According to the International Association of Oil and Gas Producers (OGP) statistics, the number of oil and gas industries contractors has had a rising trend; on the other hand, there has been a considerable increase in both the frequency of the time wasted due to the injuries and the risk exposure ratio, based on the contractors statistics. South Pars Gas Complex (SPGC), like other large companies, uses the capabilities of numerous organizations as contractors to execute its programs. Based on the studies and internal audits, these contractors only few of which hold the regulated and modern system of the health, safety and environment (HSE) are responsible for approximately 85% of the incidents occurred in SPGC. The lack of adequacy and efficiency of the criteria presented in contractors HSE prequalification checklist prior to signing the contract as well as improperly prioritizing these criteria regarding the compan