Actuating mechanisms effect

Many kinds of sensors are needed to measure the process parameters important for effective operation of any type of chemical process. The principles of manual or automated process control require, first of all, an appropriate variable, which needs to be measured—temperature, pressure, pH, viscosity, water content, etc.—in order to study the progress of the reaction or separation process. For the measured variable to be significant in the control of the process it must represent a control parameter, such as steam flow, pump speed, or acid addition rate which, when altered, will cause a response in the measured variable. Finally, there must be some actuating mechanism between the... 

Fig. 1.2 Schematic representation of the actuation mechanism for a CNT actuator. When a bias is applied to CNTs that are submerged in an electrolyte, ions will migrate to the surface of the CNTs, which is offset by the rearrangement in their electronic structure. This phenomenon, coupled with Coulombic effects, results in actuation [7]. Materials Today 2007, reprinted with permission...

Milella, P. and Petrangeli, G. (1983) Thermo-mechanical effects of a postulated spurious actuation of a core rescue system , RT/DISP(83)5, DISP/ENEA. 

The model introduced in Section 5.3 is linear, which has proven capable of capturing the material and device dynamics reasonably well. In the remainder of this chapter we discuss several refinements of the model to incorporate nonlinear electrochemical and mechanical effects in conjugated polymer actuators. In this section we examine the modeling of a key electrochemical nonlinearity in these materials, namely, the effect of the redox level on the ion transport dynamics. The redox level refers to the extent to which the conjugated polymer is reduced or oxidized, and is determined by the amount of ions incorporated into the polymer matrix. The effect of redox level on conductivity and Young s modulus has been documented [Boxall and Osteryoung (2004) Christophersen et al. (2006) De Rossi et al. 

The role of inherent polarization and ionic transport effects in actuation mechanism of EAPap actuators are investigated. To physically investigate the actuation mechanism, several tests are performed. X-ray diffraction (XRD) spectra are compared before and after electrical activation and the possibility of crystalline structure change is observed. Dielectric property measurement indicates a dependence of the dielectric constant on fiber direction, as well as on frequency, humidity, and temperature. Thus, we conclude that piezoelectric effect and ionic migration effect are in the EAPap at the same time associated with dipole moment of cellulose paper ingredients. The amount of these effects may depend on environmental condition. 

Nakama, Y., Kyokane, J., Ueda, T., Yoshino, K. The actuator mechanism and piezoelectric effect of fullerenol doped polyurethane elastomer (PUE). Synthetic Metals 135-136, 749-750 (2003)... 

Emergency isolation valves (EIVs) should be located based on two principles (1) the amount of isolatable inventory that is desired and (2) protection of the EIVs from the effects of external events. EIVs are normally required to have a fire safe rating (i.e., minimal leakage and operability rating) to a particular standard, e.g., API 607. Valves and their actuating mechanisms should be afforded adequate protection where they are required to be located in areas that have the potential for explosion and fire incidents. 

The overall electroactivity of carbon-based actuators, including CNTs, CDCs, or activated carbons, predicates on two main actuation mechanisms. The first principle is based on the electronic (metallic) conductivity of carbon material. Actuators of such type need high electrical potential (field) for actuation. Actuation occurs due to carbon-carbon interaction change due to high electrical field and increased temperature (electrothermal effect) (Liu et al. 2014 Zhang et al. 2014). Another principle is diffusion of ions and ion pairs induced by applied low potential as shown in Fig. 1. These transducers usually combine carbon materials with polymer matrix and some ionic conducting media. They seem to have much more possible applications in the near future (Asaka et al. 2013). 

A couple of additional aspects must be considered in characterization of electromechanical response. The electrochemically driven actuators can also heatup during the working cycle. In contrast to the eleetrothermally driven actuators, this effect is usually not desired in case of the electrochemically driven actuators, as die actuator s constituents can significantly change their mechanical and electrical properties. In an extreme case, the temperature of the separator polymer can increase over its melting point, causing the actuator to short-circuit in turn. 

A spool valve in an aviation hydraulic actuator is chosen as a case study to demonstrate the proposed PoF-based component failure behavior modeling approach. As discussed in Example 1, the performance parameter of the spool is its clearance. According to the result of failure mode, mechanism, effect analysis (Liao, 2013), the spool is subjected to two failure mechanisms, i.e., adhesive wear and abrasive wear. 

As a main difference with main-chain LSCEs, in side-chain LSCEs, the photoactive azo chromophores, which are responsible for the observed photo-mechanical effect, are connected to the polymeric main chain via flexible spacers. Therefore, it should be expected that the length of such flexible spacer, in other words, the flexible alkyl chain that links the azobenzene core to the main polysiloxane backbone, is one of the main factors affecting the mechanical response produced by artificial musclelike actuators based on this type of elastomeric materials (Garcia-Amoros et al. 2011a). 

In some sense the actuators, which generate action on command (i.e. information) form the counterpart to sensors which collect information about the surroundings. Actuators which change the composition have been implicitly addressed by the text (cf. e.g. electrochemical piunps). Actuators in a narrower sense cause mechanical effects (e.g. transfer of electrical into mechanical energy) and rely especially on the phenomenon of electrostriction (cf. piezoelectricity). For details the reader is referred to Ref. [573]. Also in this context perovskites play a dominant role (in particular perovskites based on lead titanate zirconates), and defect chemistry, even though not decisive, is of considerable importance (cf. Section 2.2.7). 

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