Showing 5 results for Electrical Properties
E. Sharifi, A.h. Bouchali , M. Saviz,
Volume 9, Issue 2 (9-2018)
Abstract
Aims: Computation of the field distribution and the penetration of electromagnetic fields induced in the body and biological tissues are one of the major issues discussed in the bioelectromagnetic field; with access to the geometry of the cell and its organelles, the contribution of each component to the field's reception and the field distribution as well as the computation of impedance can accurately be estimated. The aim of this study was to create 3D geometric models of cells and organelles for bioelectromagnetic simulations.
Materials and Methods: The present study is a computational research study. In this study a complete electrical model for several cell types of the epidermis layer of human skin with its organelles was created by SAVI 1 software and innovative new algorithms. In this geometric model, organelles such as mitochondria, Golgi body, melanin pigments, ribosome, lysosome, and intracellular nucleus were considered. The microscopic 2D image was used to create organelles.
Findings: The geometric model was created for the organelles and the cellular sample was created for all layers of the epidermis in accordance with reality. The cells of basal cortex were nucleated in cubic form, the cells of spinosum cortex were polygonal and nucleated, the cells of granular cortex were flat and nucleated, and the stratum corneum had complete flat cells without nucleus.
Conclusion: Creating 3D geometric model of cells and organelles within it is possible for bioelectromagnetic simulations. This 3D model can be saved in mat, stl, and vox formats and retrieved in SAVI, CST studio, and MATLAB software.
Volume 14, Issue 15 (3-2015)
Abstract
In this study, commercially pure copper samples were severely deformed by equal channel angular pressing (ECAP) up to 8 passes in room temperature. The effect of sever plastic deformation on the microstructure, mechanical properties, electrical conductivity and electrical wear resistance of the cupper were investigated. In addition, the effect of induced strain on mechanical properties of the extruded cupper in each pass was studied. Field emission scanning electron microscope micrographs show the extreme evaluation of the microstructure after 4 to 8 ECAP passes, in which a large amount of nano and ultra-fine grains are observable. The mechanical properties of the pure cupper in each pass were estimated by compression testing and Brinell hardness method at room temperature. Yield strength and hardness increased by ∼390 MPa and 75HB respectively after 5-pass ECAP due to finer boundary spacing. Increasing the strength of pure copper led to only a minor decrease of the electrical conductivity. Hence, by applying ECAP, one can obtain the ultra-fine pure copper that can improve the mechanical properties without impairing the electrical conductivity. By reducing the applied strain in each pass (25%) of the ECAP process can be obtain the pure copper with higher strength. The electrical wear behavior of the samples was investigated by electrical discharge machining (EDM). The results indicate that, electrical wear of the extruded samples reduces compare to the original samples.
Volume 17, Issue 2 (7-2017)
Abstract
Annually, various concrete infrastructures are damaged and may collapse due to the presence of destructive factors. In this regard, the Structural Health Monitoring (SHM) provides a way to evaluate the safety and durability of a structure during its service life in order to ensure the serviceability and sustainability of it. Therefore, the sensor technology is a critical part to operate SHM system for recording of relevant data through its lifespan. Sensor is a device which is capable of identifying the probability or the value of parametric changes and showing them as a relevant output (typically electrical or optical signal. Making materials electrically conductive may be useful in many different ways such as creating piezoresistive sensors with the ability to acquire stress-strain or load-displacement data or creating sensors with the ability to acquire data on the extent of damage to the concrete. The piezoresistive sensor is capable of detecting the applied forces to the structure based on the changes in the electrical resistance. But the damage detection sensor operates based on the contacting conduction of CNTs. This means that by increasing the amount of CNTs in concrete, the three-dimensional contacting network of CNTs is built. When the amount of CNTs exceeds the percolation threshold, the contacting conduction will affect the electrical conduction of nanocomposites. One of the most significant and economical types of the sensor is the damage detection sensor which is provided by mixing conductive fibers (such as carbon nanotubes (CNT)) with concrete. For preparing damage detection sensor, CNTs and surfactants were mixed in the water for 10 minutes using a magnetism stirrer at 5000 rpm. Then, the mix was prepared at one ultrasonic dispersion energy. Then the cement and CNTs were added to high-speed mixer to be uniformly mixed. After adding the aggregate to the mixer, the concrete was placed in pre-oiled molds and by applying appropriate vibration, any air that may have been trapped was released. The specimens were curing for 28 dayes and they were tested under the static loading by Instron-Tech. test equipment. In order to remove the effect of polarization which is due to the movement of free ions in the concrete sensor during the measurement, an alternating current generator with the magnitude was used to nullify this phenomenon. After preparing the sensors, two main factors affecting the performance of concrete sensors are the amount of CNTs and their dispersion quality in the mixture. The goal of this study is to determine the optimum amount of CNTs with regard to the combined effects of the surfactant and the CNTs dispersion quality on the performance of the sensor using various criteria such as sensitivity of the sensor (Se), the standard deviation of the prediction error as electrical criteria and comparison and flexural strength as mechanical critera. The results have demonstrated that the sensor provided by 0.15 wt% CNTs, superplasticizer and SDS as a surfactant has the best performance. Also, The static criteria indicated that the quality of the dispersion (using proper surfactant material) and the amount of CNTs are effective on the sensitivity and the standard deviation of the prediction error, respectively.
Volume 19, Issue 5 (9-2017)
Abstract
Nondestructive physical tests can be considered as recent trends for quality evaluation of agricultural products. Required information on postharvest quality of fruits and vegetables makes it possible to use their electrical properties as a novel method for nondestructive quality evaluation purposes. In this study, the electrical resistance of harvested apple fruits (Golden Delicious variety) was nondestructively measured by developing and employing special plate electrodes using a load cell to adjust the force holding the samples between two electrodes. Electrical resistance measurements were performed at two frequencies; 120 Hz and 1 kHz. Precise fruit weight was also measured along with electrical resistance measurements. The relationship between the electrical resistance and the weight loss was investigated during the storage period. The experiment ran for a total of 24 days. Results showed that in the 15 initial days of experiment, the electrical resistance decreased by increasing the storage period. But with further increase in the storage period, the electrical resistance also increased. The loss of the fruit moisture content, during the early stage of storage, may be attributed to the decrease of the fruit electrical resistance. However, as the stored apples lost more moisture, the concentration of ions, in soft tissues of samples, highly increased and this could be responsible for the increase of apple electrical resistance during the final days of the experiment.
Volume 19, Issue 8 (8-2019)
Abstract
In this research, Cu-30Zn alloy was subjected to severe plastic deformation (SPD) by Multi-Directional Forging (MDF) process up to 6 passes at room temperature. After the samples fabrication, microstructure, mechanical, and electrical properties were investigated. Mechanical properties of the samples were measured by shear punch, tensile, and hardness tests at room temperature after each pass of MDF process. In addition, electrical properties of the samples were evaluated by Eddy Current method. The results of microstructure characterization by scanning electron microscopy equipped with EBSD attachment showed that the grain size of the initial annealed specimen reduced from about 230 µm to less than 1 µm, after 6 passes of MDF process. Furthermore, grain size reduction was accompanied by slip process, formation of twinning, and shear bonds in a specific direction. According to the results, mechanical properties were significantly improved after 6 passes of MDF. MDF process led to a 212% increase in hardness, enhancement of 105% and 73% in shear yield and ultimate shear strengths, and also improvement of 298% and 190% in tensile yield and ultimate tensile strengths, respectively. The results of the electrical conductivity showed that the electrical conductivity of the Cu-30Z alloy reduced slightly during the MDF process. Comparison of mechanical and electrical properties results demonstrated that high-strength alloys can be obtained in the MDF process without significantly reduction in the electrical conductivity.
