Field-oriented vector control of synchronous motors with additional field winding

This paper presents a new method to control a synchronous motor in such a way to resemble the characteristics of a DC motor. The method suggests including a second field winding to the rotor of a voltage-source-inverter-fed synchronous motor. The angular frequency of the inverter is made equal to the angular rotor speed, (of a self-controlled synchronous motor drive). The added field winding is in space quadrature to the main field winding and is properly excited in such a way as to diminish the direct axis component of the stator current at every load conditions. The motor is controlled to operate with zero power angle from the inverter side and zero direct axis current from the rotor excitation side. Therefore, it operates with minimum stator current and with unity power factor. The addition of the second field winding will not complicate the design because it is just a control winding. This winding may be made with smaller wire cross-section and a larger number of turns. The control on this winding is not complicated and it can be easily created. The synchronous motor along with the added field and the required control loops are simulated and tested extensively. The test results show excellent motor performance in motoring and regenerating modes of operation.     

Control and Navigation Framework for Quadrotor Helicopters

This paper presents the development of a nonlinear quadrotor simulation framework together with a nonlinear controller. The quadrotor stabilization and navigation problems are tackled using a nested loops control architecture. A nonlinear Backstepping controller is implemented for the inner stabilization loop. It asymptotically tracks reference attitude, altitude and heading trajectories. The outer loop controller generates the reference trajectories for the inner loop controller to reach the desired waypoint. To ensure boundedness of the reference trajectories, a PD controller with a saturation function is used for the outer loop. Due to the complexity involved in controller development and testing, a simulation framework has been developed. It is based on the Gazebo 3D robotics simulator and the Open Dynamics Engine (ODE) library. The framework can effectively facilitate the development and validation of controllers. It has been released and is available at Gazebo quadrotor simulator (2012).     

High-throughput approach to the catalytic combustion of diesel soot

A methodology for the evaluation of diesel soot oxidation catalysts by high-throughput (HT) screening was developed. The optimal experimental conditions (soot amount, catalyst/soot ratio, type of contact, composition and flow rate of gas reactants) ensuring a reliable and reproducible detection of light-off temperatures in a 16 parallel channels reactor were set up. The temperature profile measured in the catalyst/soot bed under TPO conditions when the exothermic combustion of soot takes place was shown to provide an accurate measurement of the ignition. Its reproducibility and relevance were checked. The results obtained with a reference noble metal free catalyst (La_0.8Cr_0.8Li_0.2O₃ perovskite) agree very well with literature data. Qualitative mechanistic features could be derived from these experiments, stressing the likely limiting step of oxygen transfer from catalyst surface to soot particulates to ignite the soot combustion. Ceria material was shown to be more appropriate than perovskite one. From an HT screening of a large diverse library (over 100 mixed oxides catalysts) under optimized conditions, about 10 new formulations were found to perform better than selected noble metal free reference materials.     

Optimization of a natural gas SI engine employing EGR strategy using a two-zone combustion model

Natural gas has been recently used as an alternative to conventional fuels in order to satisfy some environmental and economical concerns. In this study, a natural gas spark-ignition engine employing cooled exhaust gas recirculation (EGR) strategy in a high pressure inlet condition was optimized. Both engine compression ratio and start of combustion timing were optimized in order to obtain the lowest fuel consumption accompanied with high power and low emissions. That was achieved numerically by developing a computer simulation of the four-stroke spark-ignition natural gas engine. A two-zone combustion model was developed to simulate the in-cylinder conditions during combustion. A kinetic model based on the extended Zeldovich mechanism was also developed in order to predict NO emission. In addition, a knocking model was incorporated with the two-zone combustion model in order to predict any auto-ignition that might occur. It was found that the value of the compression ratio at which the minimum fuel consumption occurs varies with the engine speed. A minimum fuel consumption of about 200 g/kW h was achieved at an engine speed of 1500 rpm, inlet conditions of 200 kPa and 333 K, and a compression ratio of about 12. Also, it was found that cooled EGR can significantly reduce NO emission at high compression ratio conditions. NO emission decreased by about 28% when EGR was increased from 20% at compression ratio of 10 to 27% at compression of 12 at the same engine speed of 3000 rpm.     

An Eco-Friendly Approach to the Control of Pathogenic Microbes and Anopheles stephensi Malarial Vector Using Magnesium Oxide Nanoparticles (Mg-NPs) Fabricated by Penicillium chrysogenum

The discovery of eco-friendly, rapid, and cost-effective compounds to control diseases caused by microbes and insects are the main challenges. Herein, the magnesium oxide nanoparticles (MgO-NPs) are successfully fabricated by harnessing the metabolites secreted by Penicillium chrysogenum. The fabricated MgO-NPs were characterized using UV-Vis, XRD, TEM, DLS, EDX, FT-IR, and XPS analyses. Data showed the successful formation of crystallographic, spherical, well-dispersed MgO-NPs with sizes of 7–40 nm at a maximum wavelength of 250 nm. The EDX analysis confirms the presence of Mg and O ions as the main components with weight percentages of 13.62% and 7.76%, respectively. The activity of MgO-NPs as an antimicrobial agent was investigated against pathogens Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, Escherichia coli, and Candida albicans, and exhibited zone of inhibitions of 12.0 ± 0.0, 12.7 ± 0.9, 23.3 ± 0.8, 17.7 ± 1.6, and 14.7 ± 0.6 mm respectively, at 200 µg mL⁻¹. The activity is decreased by decreasing the MgO-NPs concentration. The biogenic MgO-NPs exhibit high efficacy against different larvae instar and pupa of Anopheles stephensi, with LC50 values of 12.5–15.5 ppm for I–IV larvae instar and 16.5 ppm for the pupa. Additionally, 5 mg/cm² of MgO-NPs showed the highest protection percentages against adults of Anopheles stephensi, with values of 100% for 150 min and 67.6% ± 1.4% for 210 min.     

Energy Metabolites as Biomarkers in Ischemic and Dilated Cardiomyopathy

With more than 25 million people affected, heart failure (HF) is a global threat. As energy production pathways are known to play a pivotal role in HF, we sought here to identify key metabolic changes in ischemic- and non-ischemic HF by using a multi-OMICS approach. Serum metabolites and mRNAseq and epigenetic DNA methylation profiles were analyzed from blood and left ventricular heart biopsy specimens of the same individuals. In total we collected serum from n = 82 patients with Dilated Cardiomyopathy (DCM) and n = 51 controls in the screening stage. We identified several metabolites involved in glycolysis and citric acid cycle to be elevated up to 5.7-fold in DCM (p = 1.7 × 10⁻⁶). Interestingly, cardiac mRNA and epigenetic changes of genes encoding rate-limiting enzymes of these pathways could also be found and validated in our second stage of metabolite assessment in n = 52 DCM, n = 39 ischemic HF and n = 57 controls. In conclusion, we identified a new set of metabolomic biomarkers for HF. We were able to identify underlying biological cascades that potentially represent suitable intervention targets.     

SOLUBILITY OF CARBON DIOXIDE IN AQUEOUS AND ANHYDROUS MIXTURES OF METHYLDIETHANOLAMINE AND TRIETHYLENE GLYCOL MONOMETHYL ETHER

Mixed solvents are a combination of chemical and physical solvents and are used for the removal of acid gases from gas streams. The solubility of CO₂ in a mixed nonaqueous solution of methyldiethanolamine (MDEA) (50 wt.%) and triethylene glycol monomethj'l ether (TEGMME) (50 wt.%) has been measured at 40°C. The data are compared with solubility data of CO₂ in pure TEGMME. The solubility of CO₂ has been measured at 40°C and 100°C in an aqueous mixed solvent consisting of MDEA (40 wt.%) and TEGMME (40 wt. %) and water (20 wt.%) at partial pressures of CO₂ up to 12 MPa. The solubility results were compared with the solubility in the nonaqueous mixed solvent and previously reported data of aqueous MDEA. The solubility model of Deshmukh and Mather was used to correlate the data.     

Face relighting using discriminative 2D spherical spaces for face recognition

As part of the face recognition task in a robust security system, we propose a novel approach for the illumination recovery of faces with cast shadows and specularities. Given a single 2D face image, we relight the face object by extracting the nine spherical harmonic bases and the face spherical illumination coefficients by using the face spherical spaces properties. First, an illumination training database is generated by computing the properties of the spherical spaces out of face albedo and normal values estimated from 2D training images. The training database is then discriminately divided into two directions in terms of the illumination quality and light direction of each image. Based on the generated multi-level illumination discriminative training space, we analyze the target face pixels and compare them with the appropriate training subspace using pre-generated tiles. When designing the framework, practical real-time processing speed and small image size were considered. In contrast to other approaches, our technique requires neither 3D face models nor restricted illumination conditions for the training process. Furthermore, the proposed approach uses one single face image to estimate the face albedo and face spherical spaces. In this work, we also provide the results of a series of experiments performed on publicly available databases to show the significant improvements in the face recognition rates.     

The solubility of CO2 in triethylene glycol monomethyl ether

The solubility of CO₂ in triethylene glycol monomethyl ether (TEGMME) has been measured at 40, 70 and 100°C at pressures up to 8.8 MPa. The results were correlated with the Peng-Robinson (1976) equation of state. The interaction parameters and Henry's constants were derived.     

Synthesis and characterization of saturated and unsaturated copolyesters based on bis-1,4-(dicarboxymethoxy) benzene

Saturated copolyester were prepared by copolyesterification of bis-1,4-(dicarboxymethoxy) benzene and phthalic anhydride with diethylene glycol, triethylene glycol, tetraethylene glycol, 1,4-butane diol, 1,2-propane diol, and 1,6-hexamethylene glycol. Also, unsaturated copolyesters were prepared by copolyesterification of bis-1,4-(dicarboxymethoxy) benzene and maleic anhydride with the same glycols. All the copolyester resins obtained have been characterized and unsaturated copolyesters in the form of films were determined. IR and ¹H-NMR spectroscopy were used for both qualitative and quantitative analysis of the copolyesters resins and their hydrolyzate products, after curing with styrene. © 1992 John Wiley & Sons, Inc.