Actuation normal mode

Plate 4 Normal mode analysis results for an IPMC diaphragm (radius of electrode =8.5 mm) (a) first mode (b) second mode (Reproduced with permission from Lee, S., Kim, K.J. and Park, H.C. (2006) Modeling of an IPMC Actuator-driven Zero-Net-Mass-Flux Pump for Flow Control, J. Intelligent Mat. Systems and Structures, 17, 6, 533-41. Sage Publications). (See Figure 9.14)... 

Electrostatic held components in parallel with the polarization direction induce normal mode actuation, see Eq. (4.19). Not visible in the constitutive equation, but explainable by a behavior corresponding to Poisson s effect included in the piezoelectric constants, the signs of strains or stresses parallel and transverse to the applied electrostatic fields are opposed. The deformation of a piezoelectric cube subjected to electrostatic fields in the direction of polarization is shown in Figure 4.3. 

When shear appears in the planes with corresponding piezoelectric coupling, as shown in Figure 4.6, in addition to the intended normal mode actuation or sensing, then it needs to be examined with regard to the electric boundary conditions. At first, the complications induced by electrodes on surfaces other than those associated with the individual shear case will be ignored. Therefore, the theoretically possible electric boundary conditions have the following implications, which correlate with the above assumptions ... 

For the intended normal mode actuation or sensing with electrodes responsible for the polarization direction, the latter case is practically not possible, while the prior needs to be further examined. The complications considered in... 

As a specific example to study the characteristics of the controller, the problem involving four modes of longitudinal oscillations is considered herein. The natural radian frequency of the fundamental mode, normalized with respect to 7ra/L, is taken to be unity. The nominal linear parameters Dni and Eni in Eq. (22.12) are taken from [1], representing a typical situation encountered in several practical combustion chambers. An integrated research project comprising laser-based experimental diagnostics and comprehensive numerical simulation is currently conducted to provide direct insight into the combustion dynamics in a laboratory dump combustor [27]. Included as part of the results are the system and actuator parameters under feedback actions, which can... 

Retractable Pins. The retractable pin tool (RPT) consisted of an actuated pin within a rotating shoulder (Ref 94, 95) to allow pin length adjustment during FSW (Fig. 2.18). The normal operational mode for these tools was to retract the pin at a prescribed rate as the tool traversed forward. This allowed the closure of the exit hole in circumferential friction stir welds. 

CEDM incorporates a rotary step motor used for motion of control rods under all normal and emergency modes of NSSS operation. The step motor is backed up with a spring-type actuator that inserts the rods in the core in case of loss of power to the step motor or control system under any position of the reactor, including its capsizing. Implementation of this engineering solution is especially important having in view that the reactor is to be mounted on a ship. 

A solenoid is normally energized in normal process operation. It is de-energized when a dangerous condition is detected and vents air from a pneumatic actuator. If the solenoid coil fails short circuit and burns out, the solenoid will de-energize. How should this failure mode be classified ... 

Consistent vrith current practice, active systems are used as first defense level against more probable events. These systems "termed as non-safety systems" establish and m ntain safe shutdown conditions. This requires at least one non-safety AC power source to be available. These systems include the Chemical and Volume Control System (CVCS), the Startup Feed Water System (SFWS), the Normal Heat Removal System (RNS), Spent Fuel pit cooling System (SFS), and the Diverse Actuation System (DAS). The later provides the defense in depth function of system actuation to back up the Safety Monitoring System (PMS) and to protect against common mode failure. 

The reactor has natural coolant circulation in the primary circuit under all modes of operation. Before returning to the reactor, the secondary coolant passes through a system of parallel finned tubes which form the heat exchanger to atmosphere of the PDHRS. To ensure adequate heat transfer from these tubes, they are contained in a vertical duct designed to enhance the air flow. However such heat transfer is undesirable in normal operation so the entry to and exit from the tube region of the duct are closed by a system of louvres. When the temperature in the chamber between the louvres rises to 80 - 90C, direct actioning devices (thermostatic or based on a shape-memory material ) will actuate to open the louvres and initiate the PDHRS action to cool the reactor. 

Actuation mode (manual/automatic) A Flow rate (kg/s) 1034 kg/s normal total 41 kg/s auxiliaiy... 

Both EdF reference sets of EOPs cover aU plant modes from normal power operation down to hot and cold shutdown, cold shutdown with RCS open, and refueUing. The diagnosis procedure is valid for all shutdown plant modes where automatic protection signals no longer exist or are actuated with long delay. 

Under normal operating conditions, the internal space of the air-cooled heat exchanger is filled with gas (nitrogen) and the heat exchanger does not operate. If the load decreases in the consumer system, the pressure in circuit HI increases, the gas-steam separation boundary is shifted upwards and the air-cooled heat exchanger is actuated to remove heat to the atmosphere in this way, heat removal from circuit III is maintained at a level close to the nominal mode of operation. 

Operability requirements for reactivity control devices, including requirements for redundancy or diversity as stated in the safety analysis report, and their position indicators should be stated for the various modes of normal operation. These operability requirements should specifically define the proper sequence and the actuation and insertion times for reactivity control devices. Operating times for reactivity control devices should be consistent with, or more conservative than, the design assumptions. 

Figure 13.14 Stress normalized to the shear modulus as a function of the extension for a dielectric elastomer. E = 0 indicates the rubber elasticity theoiy when no external electric field is applied. EMI, EB and indicate, respectively, the pull-in, the electric breakdown and the overstretching failure modes that can occur in a dielectric elastomer actuator. The dashed lines represent the maximum isotonic (constant stress) aetu-ation strokes at three different starting prestrains longer lines indicate higher strokes.

The manual actuation mode operates in parallel to independently actuate the final devices, and is made possible by hard-wiring the controls located in the main control room directly to the final loads in a way that completely bypasses the normal path through the PMS cabinets and the DAS automatic logic. 

In Section 2.5.1, the various beam actuation concepts are presented using the classification illustrated in Figure 2.10. Analogously applying to sensing, we distinguish between normal (lengthwise) and shear mode actuation in the plane of the wall as well as between its consistent and sectorial application across the plane of the cross-section. 

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