Modeling of a synchronous reluctance machine accounting for space harmonics in view of torque ripple minimization

The paper deals with modeling of synchronous reluctance motor (SynRM) accounting for all phenomena responsible for torque ripple. Based on winding function approach, the proposed model consists in computing self and mutual inductances considering no sinusoidal distribution of stator windings, slotting effect and no sinusoidal reluctance variation caused by the rotor saliency. Then, optimal current waveforms are determined for each rotor position by solving a second order equation to reduce torque ripple. These currents are used within a vector control scheme. Satisfactory agreement between simulation and experimental results is obtained.     

Electropolymerization of phenol on a vitreous carbon electrode in alkaline aqueous solution at different temperatures

Electrochemical oxidation of phenol in basic aqueous solution has been studied on a vitreous carbon electrode at different temperatures in the range of 25-85 °C by cyclic voltammetry and chronoamperometry techniques. The electrochemical oxidation of phenol led to a complete deactivation of the electrode, whatever the temperature used, as a result of the deposition of an adhesive and insulating polymeric film. The electrochemical activity of the electrode was progressively restored by repeated potential scans in the range of water stability only when conducted at high temperatures; electrode reactivation was explained by an increase in the polymeric film permeability for both electrons (electron tunneling) and phenol molecules (diffusion). Chronoamperometric measurements carried out in the potential region of water stability have shown that electrode passivation was reduced or prevented at high temperatures. For chronoamperometry performed at the onset of oxygen evolution, the electrode remained active even at low temperatures because the discharge of water involved the production of hydroxyl radicals that destructively oxidized the polymeric film. The effect of temperature on electrode reactivation was determined by the measurement of current at an electrolysis time of 300 s; an increase of the temperature from 25 to 85 °C amplified the current from 0.212 to 5.373 mA.     

Cheese-Matrix Characteristics During Heating and Cheese Melting Temperature Prediction by Synchronous Fluorescence and Mid-infrared Spectroscopies

The structure and rheology characteristics of Comté (hard cheese) and Raclette (semihard cheese) cheeses as a function of temperature were investigated using dynamic testing rheology and mid-infrared and synchronous front-face fluorescence spectroscopies. The storage modulus (G′), the loss modulus (G″), and the complex viscosity (η*) decreased while strain and phase angle (tan δ) increased as the temperature increased from 20 to 80 °C. SF (250–500 nm with Δλ = 80) and MIR (3,000–2,800 (fat region), 1,700–1,500 (protein region), and 1,500–900 cm⁻¹ (fingerprint region)) spectra were recorded on cheese samples at 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, and 80 °C. The results showed that each spectroscopic technique provided relevant information related to the cheese protein and fat structures during melting, allowing the investigation of structural changes. In addition, the melting temperatures of cheese matrices and fats of the two cheeses were determined from the dynamic rheology data, SF spectra, and MIR spectra. Similar temperatures were obtained whatever the technique, since values of about 60 and 31 °C were obtained for matrix and fat melting temperatures of Comté and Raclette cheeses, respectively. No significant difference was observed between the results obtained with the three methods (significance level of 5%).     

Evaluation effects of biobased plasticizer on the thermal,mechanical, dynamical mechanical properties,and permanence of plasticized PVC

Sunflower oil (SO) is a renewable resource that can be epoxidized, and the epoxidized SO has potential uses as an environmentally friendly in polymeric formulations, especially for poly (vinyl chloride) (PVC). Epoxidized sunflower oil (ESO) was prepared by treating the oil with peracetic acid generated in situ by reacting glacial acetic acid with hydrogen peroxide. Epoxidation was confirmed using spectroscopic and titration methods. ESO was used as a coplasticizer in PVC for the partial replacement of di‐(2‐ethyl hexyl) phthalate (DEHP). The effect of ESO on the thermal stability of plasticized PVC was evaluated by using synmero scale for the sheets. In presence of ESO plasticized PVC samples showed a reduction in discoloration and the number of conjugated double bonds. By using thermogravimetry, the incorporation of 15/45 of ESO/DEHP in PVC presents the lowest weight loss. The results of the shore hardness and mechanical properties showed that a proportion of DEHP could be substituted by ESO. By use of DMA, the formulation which contains 25 % wt of ESO in plasticizer system shifts the glass transition temperature (T_g) to ambient temperature. The migration phenomenon was studied on PVC based samples plasticized with DEHP and ESO in varying amounts. The migration was monitored by the weight loss percentage of the samples immersed into n‐hexane or heated in an oven. The amount of extracted or volatilized DEHP is proportional to the added ratio of ESO in plasticizer system. All of this favored the partial replacement of DEHP by ESO as biobased plasticizer for flexible PVC. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Formalization of Fixed-Point Arithmetic in HOL

This paper addresses the formalization in higher-order logic of fixed-point arithmetic. We encoded the fixed-point number system and specified the different quantization modes in fixed-point arithmetic such as the directed and even quantization modes. We also considered the formalization of exceptions detection and their handling like overflow and invalid operation. An error analysis is then performed to check the correctness of the quantized result after carrying out basic arithmetic operations, such as addition, subtraction, multiplication and division against their mathematical counterparts. Finally, we showed by an example how this formalization can be used to enable the verification of the transition from floating-point to fixed-point algorithmic level in the signal processing design flow.     

Incremental development of UML specifications using operation refinements

In an incremental specification development process, operations are used to model dynamic aspects and can be refined gradually. We propose four kinds of operation refinement in order to control modifications when developing and refactoring UML specifications. Each refinement is described with its properties and illustrated by an example, showing which verifications can be done, using the B formal method.     

Hierarchical formal verification using a hybrid tool

We describe a hybrid formal hardware verification tool that links the HOL interactive proof system and the MDG automated hardware verification tool. It supports a hierarchical verification approach that mirrors the hierarchical structure of designs. We obtain the advantages of both verification paradigms. We illustrate its use by considering a component of a communications chip. Verification with the hybrid tool is significantly faster and more tractable than using either tool alone. Published online: 19 November 2002     

Application of Noise Reduction Technique in the Inverse Analysis Using Kalman Filter

Abstract

The inverse techniques usually employ the sensor measurement to estimate the unknown quantities. Regardless of sensor accuracy, the measurements contain some degrees of uncertainty and error, inadvertently. Inasmuch as, the inverse problems are ill-conditioned in general term, the measurement errors cause instabilities, perturbations, and excursions in the solution procedure. To handle the noise difficulties, a novel approach is proposed in the current study. In this method, the measurement errors are filtered to alleviate the noise priori to utilization of inverse method. The Kalman filter is implemented to remove the noise from the original sensor readings. Thereafter, the Levenberg–Marquardt method is implemented to predict the unknown. To evaluate the accuracy and robustness of the developed approach, a high nonlinear test case containing moving boundary heat conduction problem is investigated. Comparing the obtained results illustrates the improvement of inverse solution procedure by employing the noise filtering technique.     

Performances prediction study for proton exchange membrane fuel cells

In this work, we propose to study the influence of the membrane physical properties on the performance of a single PEM cell through the polarization curve. A thermal approach describing the main heat transfer aspects was also discussed. For this study, we have developed and used a simulation tool called Performances Prediction Fuel Cell tool (2PFC tool) based on simplified charge, mass and even heat transfer equations. This tool aims to visualize the main evolutions in the heart of a single cell, and the results should help users to understand the variation of some operating conditions and component properties on the output cell voltage by offering a variety of sensitivity parameter studies. For this sensitivity analysis, three separated simulations are launched. The first simulation regards the effect of the resistive losses and charge transfer coefficient on the cell voltage. The second simulation concerns the influence of the water content of the membrane and the cell operating temperature on it proton conductivity. The last simulation takes in consideration the effect of water activity variation on the proton membrane conductivity, and the results proved the direct and strong relation of the charge transfer coefficient and of the water content of the membrane on the output cell voltage. In the thermal approach part, we have proposed to study the temperature distribution between two cathodes with the presence of an implemented cooling channel.