Arbuscular mycorrhizal fungi improve the growth of olive trees and their resistance to transplantation stress

Two native Algerian mycorrhizal fungi (Glomus mosseae and Glomus intraradices) were tested for their effect on the growth of micropropagated olive tree (Olea europaea L.). The effect of inoculation of plantlets with G. mosseae was also compared with chemical fertilization using osmocote. Specific molecular techniques were then used to detect the presence of the two fungi. Highly significant increases in growth were evident for inoculated plants compared with uninoculated ones. For a slightly lower shoot growth, G. mosseae doubled the root growth of the inoculated plantlets, compared to that of the fertilized plants. This change in the root: shoot ratio permitted greater utilization of soil resources and strengthened the plant’s capacity to resist transplantation shock and water stress. The abundance of the two fungi in the roots of wild olives just as in the inoculated olives is indicative of thepredominance of G. intraradices when the natural microflora is present

Mechanical characterization of an electrostrictive polymer for actuation and energy harvesting

Electroactive polymers have been widely used as smart material for actuators in recent years. Electromechanical applications are currently focused on energy harvesting and actuation, including the development of wireless portable electronic equipment autonomous and specific actuators such as artificial muscles. The problem to be solved is to make its devices the most efficient, as possible in terms of harvested energy and action. These two criteria are controlled by the permittivity of the electrostrictive polymer used, the Young\u27s modulus, and their dependence on frequency and level of stress. In the present paper, we presented a model describing the mechanical behaviour of electrostrictive polymers with taking into account the mechanical losses. Young\u27s modulus follows a linear function of strain and stress. However, when the elongation becomes higher, the data obtained from this strain linear trend and significant hysteresis loops appear the reflections on the existence of mechanical losses. In this work, to provide the analysis of the experimental observations, we utilized a theoretical model in order to define a constitutive law implying a representative relationship between stress and strain. After detailing this theoretical model, the simulation results are compared with experimental ones. The results show that hysteresis loss increases with the increase of frequency and strain amplitude. The model used here is in good agreement with the experimental results

Enhancement of electrostrictive polymer efficiency for energy harvesting with cellular polypropylene electrets

The purpose of this paper is to propose new means for harvesting energy using electrostrictive polymers. The recent development of electrostrictive polymers has generated new opportunities for high-strain actuators. At the current time, the investigation of using electrostrictive polymer for energy harvesting, or mechanical-to-electrical energy conversion, is beginning to show its potential for this application. The objective of this work was to study the effect of cellular polypropylene electrets after high-voltage corona poling on an electrostrictive polyurethane composite filled with 1 vol.% carbon black at a low applied voltage in order to increase the efficiency of the electromechanical conversion with electrostrictive polymers. Theoretical analysis supported by experimental investigations showed that an energy harvesting with this structure rendered it possible to obtain harvested power up to 13.93 nW using a low electric field of 0.4 V/mu m and a transverse strain of 3% at a mechanical frequency of 15 Hz. This represents an efficiency of 78.14% at low frequency. This percentage is very significant compared to other structures. Finally, it was found that the use of polypropylene electrets with electrostrictive polymers was the best way to decrease the power of polarization in order to obtain a good efficiency of the electromechanical conversion for energy harvesting

Modelling and diagnostic of an ultrasonic piezoelectric actuator

Modeling of piezoelectric motors is a difficult task because their characteristics are affected by various factors such as materials properties, electrical and mechanical boundary conditions. This work presents the modeling of piezoelectric motor via bond graph method and used for the diagnostic. This method is an innovative way to analyse the effects of different design variables on the objective function but can be also considered as an optimization stage of the study. The validation and the development of bond graph models are based on physical insight to aid in structural damage detection and use the technique of optimal sensors placement

Multimodal Vibration Damping of a Smart Beam Structure using Modal SSDI-Max Technique

Advanced materials such as carbon fiber, composite materials et al. are more and more used in modern industry. They make the structures lighter and Stiffer. However, they bring vibration problems. Researchers studied numerous methods to eliminate the undesirable vibrations. These treatments are expected to be a compact, light, intellectual and modular system. Recently, nonlinear techniques which are known as Synchronized Switch Damping (SSD) technique was proposed. These techniques synchronously switched when structure got to its displacement extremes that leading to a nonlinear voltage on the piezoelectric elements. This paper presents a performance analysis of an improved modal SSDI approach called "SSDI Max". The particularity of this new approach is to maximize the self generated voltage amplitude by a proper definition of the switch instants according to the chosen targeted mode. This paper presents simulations performed on a model representative of a smart beam. Damping results are given in the case of multimodal excitations. The paper analyses the control time window influence on the damping performance of the system. Results show that substantial damping increase can be obtained with very slight modification of the control architecture and the same control energy

Particulate Fillers in Thermoplastics

The characteristics of particulate filled thermoplastics are determined by four factors: component properties, composition, structure and interfacial interactions. The most important filler characteristics are particle size, size distribution, specific surface area and particle shape, while the main matrix property is stiffness. Segregation, aggregation and the orientation of anisotropic particles determine structure. Interfacial interactions lead to the formation of a stiff interphase considerably influencing properties. Interactions are changed by surface modification, which must be always system specific and selected according to its goal. Under the effect of external load inhomogeneous stress distribution develops around heterogeneities, which initiate local micromechanical deformation processes determining the macroscopic properties of the composites