Electrical capacitance techniques

Electrical capacitance techniques were also used to monitor the anisotropic liquid absorption in multidirections in a nonwoven fabric plane. The principle of the method is based on the fact that the dielectric constant of water is about 15—40 times higher than that of normal fibres and fabrics, and therefore, the capacitance of the transducers in a measuring system wdl be very sensitive to the amount of liquid absorbed by a fabric. The computer-integrated capacitance system is able to provide both dynamic (real-time) and multidirectional measurements of the wicking rate in terms of the volume of liquid absorbed. 

Ito, H. and Muraoka, Y. Water Transport Along Textile Fibers as Measured by an Electrical Capacitance Technique, Textile Res. J. 1993,63(7), 414-420. 

Ito, H. and Y. Muraoka, Water transport along textile fibers as measured by an electrical capacitance technique. Textile Research Journal, 1993, 63(7), 414 20. 

Many of the variations developed to make pressure sensors and accelerometers for a wide variety of appHcations have been reviewed (5). These sensors can be made in very large batches using photoHthographic techniques that keep unit manufacturing costs low and ensure part-to-part uniformity. A pressure differential across these thin diaphragms causes mechanical deformation that can be monitored in several ways piezoresistors implanted on the diaphragm are one way changes in electrical capacitance are another. 

J. P. K. Seville, A. Ingram, X. Fan, and D. J. Parker, Positron Emission Imaging in Chemical Engineering Fei Wang, Qussai Marashdeh, Liang-Shih Fan, and Richard A. Williams, Electrical Capacitance, Electrical Resistance, and Positron Emission Tomography Techniques and Their Applications in Multi-Phase Flow Systems... 

Electrical Capacitance, Electrical Resistance, and Positron Emission Tomography Techniques and Their Applications in Multi-Phase Flow Systems... 

In bulk heterojunction solar cells, the metal/semiconductor interface is even more complex. Now the metal comes into contact with two semiconductors, one p-type (typically the polymer) and one n-type (typically the fullerene) semiconductor. A classical electrical characterization technique for studying the occurrence of charged states in the bulk or at the interface of a solar cell is admittance spectroscopy. If a solar cell is considered as a capacitor with capacitance C, the complex admittance Y is given by... 

The fluidized bed systems have been utilized extensively in many physical, chemical, petrochemical, electrochemical, and biochemical processes. Successful applications of the fluidization systems lie in a comprehensive understanding of hydrodynamics, heat and mass transfer properties, and mixing. Various non-intrusive measurement techniques, such as electric capacitance tomography and radioactive particle tracking technique, are available to advance the fundamental understanding of the microscopic and macroscopic phenomena of fluidization. Till date, the... 

Various techniques are used for these measurements. The most popular are capacitance-voltage (C-V) profiling, spreading resistance and secondary ion mass spectroscopy (SIMS). SIMS is not a strictly electrical characterization technique, but is included here because it is routinely used to measure the dopant atom distribution. The basis for these three techniques are very different and I will briefly describe them. 

Experimental confirmation of the elastohydrodynamic lubrication theory has been obtained in certain selected systems using electrical capacitance, x-ray transmission, and optical interference techniques to determine film thickness and shape under dynamic conditions. Research is continuing in this area, including studies on micro-EHL or asperity lubrication mechanisms, since surfaces are never perfectly smooth. These studies may lead to a better understanding of not only lubricant film formation in high-contact-stress systems but lubricant film failure as well. 

Several examples of experimental approaches to thin-film lubrication have been reported [3]. It is important in examining these techniques to make the distinction between methods that are used to determine lubricant film thickness under hydrodynamic or elastohydrodynamic conditions (e.g., optical interference, electrical capacitance, or x-ray transmission), and methods that are used to determine the occurrence or frequency of contact. As we will see later, most experimental studies of synovial joint lubrication have focused on friction measurements, using the information to determine the lubrication regime involved this approach can be misleading. 

Makkawi, Y.T., and Wright, P.C. (2004), Electrical capacitance tomography for conventional fluidized bed measurements-Remarks on the measuring technique, Powder Technology, 148(2-3) 142-157. 

Advanced measuring techniques With the advent of sophisticated imaging and velocimetry techniques, better understanding of the flow behavior and consequently a better prediction of regime transition is possible. The techniques used in the literature are listed below with the corresponding references. Readers interested in a specific technique may refer to these references Electrical capacitance tomography (ECT) (Bennett et al. 1999 Tapp et al. 2003) Electrical impedance tomography (EIT) (Tapp et al. 2003)... 

Tomographic techniques allow to reconstruct the instantaneous particle holdup (porosity) of a 3D fluidized bed, thus allows to extract information especially on the bubble phase. Well-known techniques include electrical capacitance tomography. X-ray tomography, and magnetic resonance imaging (MRI). 

The electrical techniques described in the paper are Electrical Capacitance Tomography (ECT) and Electrical Resistance Tomography (ERT). Both techniques used non-invasive passive metal electrodes, with low amplitude electrical excitation. The techniques are rugged, low-cost, low-impact and fast. Absolute accuracy, on the other hand, is currently not better than 5%. 

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