Development of multi-MHz Class-D soft-switching inverters

Wireless Power Transmission (WPT) systems are becoming rapidly mature and accessible to customers, and it is expected that they are going to take a large share of the electrical equipment market around the world in the near future. Many tech companies and university research labs have recently focused on design, development, and optimization of different blocks of these systems. WPT systems can be designed to transfer power either through electric fields or magnetic fields. Operating at the multi-MHz frequency will bring about the smaller size of the wireless link for both types of WPT systems. The advent of Wide Bandgap (WBG) devices like Gallium Nitride (GaN) FETs and Silicon Carbide (SiC) MOSFETs has paved the road to design multi-MHz inverters and use them as the Radio Frequency (RF) power source in the transmitter of WPT systems. Designing an efficient inverter which can maintain its soft-switching performance while facing variable load or delivering variable output power is one of the major design challenges in this field. The second challenge in this area is related to the difficulties of Electromagnetic Compatibility (EMC) of the inverter, which is the direct result of operating at MHz switching frequency range. The Electromagnetic Interference (EMI) level can be reduced by designing a stronger filter or trying to remove the harmonics from the switching source. In this thesis, to tackle the first challenge mentioned above regarding soft switching, the Dynamic Dead-Time Control (DDTC) approach is proposed and utilized to sustain the soft-switching of a multi-MHz Full-Bridge (FB) Class-D inverter over the full range of active load and output power. Simulation results are presented to show that dynamically controlling the Dead-Time (DT) during input DC voltage control and load variations, reduces switch-node voltage overshoot, prevents large current spikes in the switching devices, and reduces associated high switching loss. Finally, experimental results obtained from the prototype of the system are provided to validate the effectiveness of the proposed approach. Then, a soft-switching multi-MHz multi-level Class-D inverter is developed to address the second challenge of EMI issues associated with MHz switching frequency operation.The inverter is designed to eliminate the 3rd and 5th harmonics from its output voltage waveform. This will, in turn, make it possible to meet EMC and achieve the same level of harmonic attenuation on the output of the inverter with a smaller size and more efficient output EMI filter as opposed to utilizing a bulky, high-order, High-Quality (HQ) filter. The impact of DT on the modulation parameters of the multi-level inverter is investigated through mathematical analysis, and the results are utilized during the system simulations and practical implementation. A prototype is built to validate the theoretical and simulation analysis on a practical testbed. The harmonic analysis comparison carried out between the experimental results obtained from the multi-level inverter and FB Class-D inverter prototypes shows how the multi-level inverter is capable of suppressing unwanted 3rd and 5th harmonic to a much lower level which in turn leads to smaller size and more efficient output filter

Ekspresija i pročišćavanje površinskog lipoproteinskog antigena Lipl41 iz patogenih bakterija roda Leptospira

Pathogenic species of Leptospira lead to a zoonotic disease called leptospirosis, which is spread worldwide. A major topic of investigation is to detect the antigens that induce an immune response and to utilize them in diagnostic kits or vaccine development. The outer membrane proteins (OMPs) of Leptospira are potential candidates for this purpose. Lipl41 is an OMP that is conserved among pathogenic Leptospira. The aim of this study was to express and purify the Lipl41 recombinant protein in Iranian isolates. All collected Lipl41 protein sequences were compared and analyzed using bioinformatics tools from NCBI databases. Complete codon sequences of the Iranian pattern of Lipl41 recombinant protein were codon optimized and sub-cloned into a pET32a+ expression vector, and transformed into Escherichia coli BL21 (DE3). Optimal expression of recombinant Lipl41 (47kDa) was achieved post-induction with IPTG within the inclusion body. It was then purified by denaturation using serial concentrations of urea, and the recombinant protein was confirmed by western blot. In this study, sufficient amounts of Lipl41 were expressed and purified to be used for the development of a diagnostic kit and subunit vaccine.Patogene vrste Leptospira uzrokuju zoonotsku bolest leptospirozu koja je raširena u cijelom svijetu. Cilj istraživanja bio je dokazati antigene koji potiču imunosni odgovor i mogu se primijeniti u dijagnostičkim kompletima ili za razvoj cjepiva. Vanjska proteinska membrana (OMPs) leptospira potencijalni je kandidat za tu svrhu, a gen Lipl41 je dobro očuvan među patogenim leptospirama. Ekspresija i pročišćavanje rekombinantnog proteina Lipl41 provedeno je u izolatima iz Irana. Uspoređene su sve prikupljene sekvencije proteina Lipl41 i analizirane bioinformatičkim alatom iz baze podataka NCBI. Kompletne sekvencije kodona rekombinantnog proteina Lipl41 u izolatima su optimizirane, zatim subklonirane u pET32a+ vektor i pretvorene u bakteriju Escherichia coli BL21 (DE3). Optimalna ekspresija rekombinantnog Lipl41 (47kDa) postignuta je post-indukcijski pomoću isopropyl β-d-1-thiogalactopyranoside (IPTG). Zatim je pročišćena denaturacijom što je uključilo primjenu serijskih koncentracija ureje. Rekombinantni protein je potvrđen metodom western blot. Istraživanje potvrđuje mogućnost ostvarenja dostatne količine i ekspresije pročišćenog Lip141 da se može upotrijebiti za razvoj dijagnostičkih kompleta i subjediničnih cjepiva

The Neuroprotective Effects of Curcumin Nanoparticles on The Cerebral Ischemia-Reperfusion Injury in The Rats-The Roles of The Protein Kinase RNA-Like ER Kinase/Extracellular Signal-Regulated Kinase and Transcription Factor EB proteins

Objective: Reduction of cerebral ischemia-reperfusion injury (IRI)/re-oxygenation injury, is defined as the paradoxicalexacerbation of the cellular dysfunction and death, following restoration of the blood flow to previously ischemic tissues.The re-establishment of blood flow is essential to salvage the ischemic tissues. As a result, the treatment of IRI withnovel therapies, which have fewer side effects, are of great importance. Therefore, this study aimed to investigate theeffects of curcumin nanoparticle (CN) pre-treatment on the cerebral I/R rat model.Materials and Methods: In this experimental study, CN was administered to rats orally five days before the bilateralcommon carotid artery occlusion (BCCAO) and continued for three days. The intensity of oxidative stress, the activities ofantioxidant enzymes, glutathione (GSH) content, the activity of mitochondrial enzymes, including succinate dehydrogenase(SDH), malate dehydrogenase (MDH) and lactate dehydrogenase (LDH), curcumin bioavailability, pERK/ERK expressionratio and TFEB protein were studied. Data analysis was performed using Graphpad Prism V.8 software, one-way analysisof variance (ANOVA) with the statistical package for the social sciences (SPSS V.26 software).Results: Cerebral IRI-damage significantly increased the oxidative stress (P=0.0008) and decreased the activityof the antioxidant enzymes including catalase (CAT) (P<0.001), super oxide dismutase (SOD) (P<0.001), reducedGSH (P<0.001), mitochondrial enzymes, pERK/ERK expression ratio (P=0.002) and TEFB protein (P=0.005) in rats’brains. In addition, the pre-treatment of the rats with CN resulted in a decrease in the reactive oxygen species (ROS),and an increase in the activities of antioxidants and mitochondrial enzymes. This in turn up-regulated the pERK/ERKexpression ratio and TEFB expression.Conclusion: CN has neuroprotective effects on the cerebral IRI condition due to its antioxidant properties and is ableto overexpress the pERK and TFEB proteins; thus, it can be considered as a suitable treatment option during and afterthe incidence of stroke

Solid flux in travelling fluidized bed operating in square-nosed slugging regime

The performance of gas-fluidized bed reactors depends significantly on their hydrodynamics. Among the important properties that dictate the characteristics of a gas-fluidized bed, local solid flux plays a significant role, influencing vital parameters such as bed-to-surface heat exchange and solid circulation rate. Developing techniques that can provide accurate measurements of solid flux is extremely important for: 1) assessing the accuracy of other measurement techniques applicable to industrial units, and 2) validation of CFD models. Comparison of different measurement techniques that provide similar hydrodynamic information is helpful in assessing the errors associated with each methodology. Most measurement techniques for obtaining solid flux in gas-fluidized beds are based on intrusive probes that can simultaneously measure solid velocity and voidage. Previously (1), the novel travelling fluidized bed (TFB) was operated to determine particle velocity from radioactive particle tracking (RPT), positron emission particle tracking (PEPT) and borescopy with silica sand particles of mean diameter 292 μm at superficial gas velocities from 0.4 to 0.6 m/s. In this study, the TFB, operated under identical conditions, was deployed to compare RPT and PEPT for the investigation of solid flux in square-nosed slugging. Both techniques provided solid flux data of the same order, but there were significant quantitative differences. Differing physical properties of tracer particles and the bed material, and differences in the tracer localization techniques are among the factors that contributed to the observed discrepancies. The results provide useful insights on the merits and challenges associated with advanced techniques for measuring solids flux in gas-fluidized beds. REFERENCES S. Tebianian, K. Dubrawski, N. Ellis, R. A. Cocco, R. Hays, S.B.R. Karri, T. W. Leadbeater, D.J. Parker, J. Chaouki, R. Jafari, P. Garcia-Trinanes, J.P.K. Seville, J.R. Grace. Comparison of Particle Velocity Measurement Techniques in a Fluidized Bed Operating in the Square-Nosed Slugging Flow Regime. Powder Technol., 2015. doi:http://dx.doi.org/10.1016/j.powtec.2015.08.040

Vaccination with recombinant 4×M2e.HSP70c fusion protein as a universal vaccine candidate enhances both humoral and cell-mediated immune responses and decreases viral shedding against experimental challenge of H9N2 influenza in chickens

As cellular immunity is essential for virus clearance, it is commonly accepted that no adequate cellular immunity is achieved by all available inactivated HA-based influenza vaccines. Thus, an improved influenza vaccine to induce both humoral and cell-mediated immune responses is urgently required to control LPAI H9N2 outbreaks in poultry farms. M2e-based vaccines have been suggested and developed as a new generation of universal vaccine candidate against influenza A infection. Our previous study have shown that a prime-boost administration of recombinant 4 × M2e. HSP70c (r4M2e/H70c) fusion protein compared to conventional HA-based influenza vaccines provided full protection against lethal dose of influenza A viruses in mice. In the present study, the immunogenicity and protective efficacy of (r4M2e/H70c) was examined in chickens. The data reported herein show that protection against H9N2 viral challenge was significantly increased in chickens by injection of r4M2e/H70c compared with injection of conventional HA-based influenza vaccine adjuvanted with MF59 or recombinant 4 × M2e (r4M2e) without HSP70c. Oropharyngeal and cloacal shedding of the virus was detected in all of the r4M2e/H70c vaccinated birds at 2 days after challenge, but the titer was low and decreased rapidly to reach undetectable levels at 7 days after challenge. Moreover, comparison of protective efficacy against LPAI H9N2 in birds intramuscularly immunized with r4M2e/H70c likely represented the ability of the M2e-based vaccine in providing cross-protection against heterosubtypic H9N2 challenge and also allowed the host immune system to induce HA-homosubtype neutralizing antibody against H9N2 challenge. This protective immunity might be attributed to enhanced cell-mediated immunity, which is interpreted as increased lymphocytes proliferation, increased levels of Th1-type (IFN-γ) and Th2-type (IL-4) cytokines production and increased CD4+ to CD8+ ratios, resulting from the injection of four tandem repeats of the ectodomain of the conserved influenza matrix protein M2 (4×M2e) genetically fused to C-terminus of Mycobacterium tuberculosis HSP70 (mHSP70c). © 2014 Elsevier B.V

Monitoring of particle motions in gas-solid fluidized beds by electrostatic sensors

Gas-solid fluidized beds are widely applied in numerous industrial processes. Particle motions significantly affect the performance of fluidized bed reactors and the characterization of particle movements is therefore important for fluidization quality monitoring and scale-up of reactors. Electrostatic charge signals in the fluidized bed contain much dynamic information on particle motions, which are poorly understood and explored. In this work, correlation velocities of Geldart B and D particles were measured, analyzed and compared by induced electrostatic sensors combined with cross-correlation method in the fluidized bed. The results indicated that the average correlation velocity of particle clouds increased and the normalized probability density distributions of correlation velocities broadened when the superficial gas velocity increased in the dense-phase region. Both upward and downward correlation velocities could be acquired in the dynamic bed level region. Under the same excess gas velocity, the average correlation velocity of Geldart D particles was significantly smaller than that of Geldart B particles, which was caused by the smaller bubble sizes caused by the dominant bubble split over coalescence and less volume of gas forming bubbles for Geldart D particles. The experimental results verified the reliability and repeatability of particle correlation velocity measurement by induced electrostatic sensors in the gas-solid fluidized bed, which provides definite potential in monitoring of particle motions

Dynamic State Estimation in Power Systems

Research in the area of power system transient stability has recently focused on dynamic state estimation using high rate Phasor Measurement Unit (PMU) data. Several mathematical models for synchronous machine are developed and various estimation approaches are proposed for this purpose. In this thesis, the mathematical formulation of nonlinear state space modeling and the principles of Kalman Filter are explained. Extended and Unscented Kalman Filters (EKF and UKF), as two nonlinear estimation methods, are applied for state and parameter estimation in an induction motor. In the next stage, after presenting a thorough explanation about modeling of the synchronous machine, dynamic state estimation is applied on different power system case studies and the results of estimation methods are compared. The simulation results provided in this thesis show the great potential of the proposed estimation approaches for accurately estimating the states of the machine as well as reducing the effect of noise on input signals