Induction-motor sensorless vector control with online parameter estimation and overcurrent protection

Sensorless drive control has been widely studied in recent years due to the numerous advantages regarding potential failures of position sensors, especially in applications such as automotive or aerospace. Among vector-control drives, indirect rotor-flux-oriented control (IRFOC) type is one of the most popular and tested options. However, it is still a challenging field since several aspects can be improved, such as the low-speed behavior, parameter detuning, and current control. The present scheme includes temperature estimation to correct the deviation in steady state, a new control scheme with skin-effect estimation to improve the transient accuracy, and overcurrent protection to be able to control the stator currents while allowing a good performance. The parameter estimation is carried out using lumped-parameter models, the control scheme is modified and is able to account for static friction, and the overcurrent protection improves the performance allowing transient currents over the rated value. The validity and usefulness of the proposed scheme is experimentally tested on a TMS320C31 digital signal processor (DSP) from the Simulink/Matlab environment.     

VOLUME-BASED THERMODYNAMICS GLOBAL PHASE STABILITY ANALYSIS

In this study we propose a method for phase stability analysis at pressure and temperature specifications, in the frame of a “volume-based” thermodynamics. The formulation of the tangent plane distance (TPD) criterion in terms of the Helmholtz free energy is used in this work for testing phase thermodynamic stability at p-T conditions, using component molar densities as primary variables. The phase stability problem is non-convex; the TPD function may exhibit multiple local minima and saddle points, the use of global optimization methods for its minimization being appropriate. For the unconstrained minimization of the TPD function we use the tunneling global optimization method, which has shown its ability in efficiently solving difficult non-convex, highly nonlinear problems. The method is tested for a variety of mixtures ranging from binaries to mixtures with many components, with emphasis on difficult conditions. The proposed method proved to be an efficient and reliable tool for phase stability analysis.     

Pipe inspection using a laser-based transducer and automated analysis techniques

This paper presents a new sensing methodology for the automated inspection of pipes. Standard inspection systems, as they are for example used in waste pipes and drains, are based on closed-circuit television cameras which are mounted on remotely controlled platforms and connected to remote video recording facilities. Two of the main disadvantages of such camera-based inspection systems are: 1) the poor quality of the acquired images due to difficult lighting conditions and 2) the susceptibility to error during the offline video assessment conducted by human operators. The objective of this research is to overcome these disadvantages and to create an intelligent sensing approach for improved and automated pipe-condition assessment. This approach makes use of a low-cost lighting profiler and a camera which acquires images of the light projections on the pipe wall. A novel method for extracting and analyzing intensity variations in the acquired images is introduced. The image data analysis is based on differential processing leading to highly-noise tolerant algorithms, particularly well suited for the detection of small faults in harsh environments. With the subsequent application of artificial neural networks, the system is capable of recognizing defective areas with a high success rate. Experiments in a range of waste pipes with different diameters and material properties have been conducted and test results are presented.     

Kinetics of solid vanadium-nitrogen reactions at high temperatures

Thermogravimetric studies were made to determine the kinetics of the reaction between 99.83 pct vanadium sheet and purified nitrogen gas in the temperature range of 1173 to 1723 K, at pressures of 9.3 × 10⁴ to 9.3 Pa (700 to 7 × 10^-2 torr) and times up to 160 h. Metallographic and X-ray diffraction techniques were used to examine the reaction products. The data followed either parabolic, cubic, or linear kinetics. In general it was observed that the initial kinetics were parabolic. At high temperatures and near atmospheric pressures, the reaction kinetics changed from parabolic to cubic at longer times. At the lowest pressure the preparabolic kinetics were linear. Weight gains in the parabolic region were mainly due to solution and diffusion of nitrogen in vanadium with the weight gain shown by the equation (ΔW/A)² = 3.2 × 10^-4 Te162-000/RT _t. The cubic region was related to the formation of an outer layer of VN over an intermediate layer of V₃N and a core of the saturated solution of nitrogen in vanadium with the approximate weight gain shown by the equation (ΔW/A)³ = 1.24 × 10^-3 Te- ^208,000/RT _t Linear weight gains at low pressure were presumed to be controlled by the rate of nitrogen adsorption.     

Phase formation and texture development in mullite/zirconia composites fabricated by templated grain growth

Mullite is a promising candidate for advanced ceramic applications but its low fracture toughness and difficulties in sintering are the main limitations for more widespread industrial applications. Therefore, mullite/zirconia composites were prepared from a reactive mixture of alumina and zircon powders. Additives, TiO₂ and MgO, were used to modify aluminosilicate glass to increase densification and <001> aluminum borate templates were incorporated to texture mullite in [001] by templated grain growth. Mullite/zirconia phase formation was complete at 1450°C in the presence of both templates and additives, as compared to 1500°C for the samples with only additives and to 1600°C for the samples with only templates. Dense mullite/zirconia composites with highly <001>-textured mullite grains (Lotgering factor ∼1) and a retention of ∼13% tetragonal ZrO₂ were fabricated after sintering at 1450°C for 2 h. A high quality of mullite texture with a degree of orientation parameter of 0.22 and a narrow distribution of elongated mullite grains within 8.8° around [001] were successfully obtained in the composites.     

Preparation and antibacterial properties of hybrid-zirconia films with silver nanoparticles

The antimicrobial effect of incorporating silver nanoparticles (AgNps) into zirconia matrix–polyether glycol was studied. AgNps of 4–6 nm in size were synthesized using the inverse micelles method, and different doses of metallic nanoparticles were incorporated into zirconia–polyether glycol mixtures during the ageing procedure. Atomic force microscopy (AFM) of the modified hybrid film showed a homogenous distribution of 20–80 nm diameter AgNps, indicating agglomeration of these structures during film modification; such agglomerations were greater when increasing the dosage of the colloidal system. The AgNps-hybrid films showed higher antimicrobial activity against Gram-positive bacteria than for Gram-negative bacteria. Hybrid films prepared with dioctyl sodium sulfosuccinate (AOT) stabilized AgNps presented enhanced antibacterial activity compared to that obtained through the addition of a high AgNO₃ concentration (0.3 wt%).     

Evolution of endoglucanase activity in olives during ripening and storage and its relationship with cellulolytic microorganisms

Summary Cellulolytic enzymes are responsible for many of the changes associated with the ripening process in olive fruits (Olea europaea). Evolution of endoglucanase activity (EC 3.2.1.4.) was studied in olives during their ripening and softening, both on the tree and after being picked and stored, and was related to the presence of microorganisms. The time course of cellulolytic activity was measured for four stages of ripeness (green, turning colour, black and ripe black) and was related to the total number of cellulolytic bacteria. The increases in activity during ripening and storage gave an indication of how normal flora influences during the olive ripening process.

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Aktivität der Endoglucanase-Entwicklung der Olive während der Reifung und des Weichwerdens und die Beziehung mit cellulolytischen Mikroorganismen

Zusammenfassung Die cellulolytischenEnzyme sind für viele Veränderungen während des Reifens der Olive verantwortlich. Es wurde daher die Aktivität der Enzyme während der Entwicklung der Olive bei der Reifung und dem Weichwerden studiert, und zwar am Baum, nach der Ernte und nach dem Lagern, was auch in Beziehung zu der Gegenwart von Mikroorganismen steht. Es wurde die cellulolytische Aktivitätsentwicklung während der vier Reife-Zustände (grün, farbenwechselnd, schwarz und zartes schwarz) studiert und auf die Gesamtzahl der cellulolytischen Bakterien bezogen. Der Aktivitäts-Zuwachs während des Reifens und Lagerns gibt einen Hinweis, wie die normale Flora auf das Reifen der Oliven einwirkt.

     

Microencapsulated di-ammonium hydrogen phosphate (DAHP) with a polyurethane shell: characterization and its properties in wood

European Journal of Wood and Wood Products - This work deals with the microencapsulation of di-ammonium hydrogen phosphate (DAHP) in polyurethane using an interfacial polymerization method. The...