Bidirectional Drive with Inhibited Hysteresis for Piezoelectric Actuators.

Piezoelectric actuators with a flexible displacement amplification structure are widely used in the fields of precision driving and positioning. The displacement curve of conventional piezoelectric actuators is asymmetrical and non-linear, which leads to large non-linear errors and reduced positioning accuracy of these piezoelectric actuators. In this paper, a bidirectional active drive piezoelectric actuator is proposed, which suppresses the hysteresis phenomenon to a certain extent and reduces the non-linear error. Based on the deformation theory of the beam, a theoretical model of the rhombus mechanism was established, and the key parameters affecting the drive performance were analyzed. Then, the static and dynamic characteristics of series piezoelectric actuators were analyzed by the finite element method. A prototype was manufactured and the output performance was tested. The results show that the actuator can achieve a bidirectional symmetric output of amplification displacement, with a maximum value of 91.45 µm and a resolution of 35 nm. In addition, compared with the hysteresis loop of the piezoelectric stack, the nonlinear error is reduced by 62.94%.

Suppression of Tafazzin promotes thyroid cancer apoptosis via activating the JNK signaling pathway and enhancing INF2-mediated mitochondrial fission.

Tafazzin has been found to be associated with tumor progression. Mitochondrial homeostasis regulates cancer cell viability and metastasis. However, the roles of Tafazzin and mitochondrial homeostasis in thyroid cancer have not been explored. The aim of our study is to investigate the influences of Tafazzin on thyroid cancer apoptosis with a focus on mitochondrial fission. Our results indicated that Tafazzin deletion induced death in thyroid cancer via apoptosis. Biological analysis demonstrated that mitochondrial stress, including mitochondrial bioenergetics disorder, mitochondrial oxidative stress, and mitochondrial apoptosis, was activated by Tafazzin deletion. Furthermore, we found that Tafazzin affected mitochondrial stress by triggering inverted formin 2 (INF2)-related mitochondrial fission. The loss of INF2 sustained mitochondrial function and promoted cancer cell survival. Molecular investigation illustrated that Tafazzin regulated INF2 expression via the JNK signaling pathway; moreover, the blockade of JNK prevented Tafazzin-mediated INF2 expression and improved cancer cell survival. Taken together, our results highlight the key role of Tafazzin as a master regulator of thyroid cancer viability via the modulation of INF2-related mitochondrial fission and the JNK signaling pathway. These findings defined Tafazzin deletion and INF2-related mitochondrial fission as tumor suppressors that act by promoting cancer apoptosis via the JNK signaling pathway, with potential implications for new approaches to thyroid cancer therapy.

[Design and implementation of pupil auto-tracking system in the perimeter].

The pupil auto-tracking system is a key component of the full-automatic perimeter. Taking the advantage of integral image in counting characteristic value rapidly, we studied the relationship between training stages and total error detection rate based on the training of Adaboost strong classifier. Besides, a testing strategy of amplification detection window was introduced, and a multi-stage cascaded eye classifier for eye detection was proposed finally. It kept the same detection rate as the commonly trained strong classifier with a much lower error detection rate. In the meantime, the present article explaines the main arithmetic implement functions, as well as designs the motion control program for the jaw bracket system.

Bidirectional Active Piezoelectric Actuator Based on Optimized Bridge-Type Amplifier.

Piezoelectric actuators based on bridge displacement amplifying mechanisms are widely used in precision driving and positioning fields. The classical bridge mechanism relies on structural flexibility to realize the return stroke, which leads to the low positioning accuracy of the actuator. In this paper, a series bridge mechanism is proposed to realize a bidirectional active drive; the return stroke is driven by a piezoelectric stack rather than by the flexibility of the structure. By analyzing the parameter sensitivity of the bridge mechanism, the series actuation of the bridge mechanism is optimized and the static and dynamic solutions are carried out by using the finite element method. Compared with the hysteresis loop of the piezoelectric stack, the displacement curve of the proposed actuator is symmetric, and the maximum nonlinear error is improved. The experimental results show that the maximum driving stroke of the actuator is 129.41 µm, and the maximum nonlinear error is 5.48%.

Inherent mechanism of frequency drift affected by constraint conditions for rotary piezoelectric motors.

The optimum drive frequency of rotary piezoelectric motors is in the vicinity of the resonance frequency of piezoelectric vibrators. Previous studies reveal that the resonance frequency is inconstant and is drifting with the variation of constraint conditions, of which the solutions generally focused on optimizing the drive circuits and control algorithms, while the working principle and equivalent modeling about frequency drift are still indistinct. By introducing the unknown parameters including stiffness coefficients and loss factors, the equivalent physical models and mathematical derivation are investigated. Based on the measured values of the impedance characteristics, the relationship between the piezoelectric parameters and the varying constrained boundaries is discussed. Then, the introduced parameters are identified and utilized as the input parameters for modifying the traditional finite element method. The numerical results agree well with the measured values and are compared with the traditional calculation, which reveals that the identified parameters and physical models are effective for illustrating the inherent mechanism of frequency drift. In addition, the mathematical equations and numerical simulation are both analyzed for the undamped and damped vibrating system, which demonstrates that the piezoelectric motor is a small damping vibration system and the effect of the loss factor on frequency calculation can be omitted.

Noninvasive estimation of assist pressure for direct mechanical ventricular actuation.

Direct mechanical ventricular actuation is effective to reestablish the ventricular function with non-blood contact. Due to the energy loss within the driveline of the direct cardiac compression device, it is necessary to acquire the accurate value of assist pressure acting on the heart surface. To avoid myocardial trauma induced by invasive sensors, the noninvasive estimation method is developed and the experimental device is designed to measure the sample data for fitting the estimation models. By examining the goodness of fit numerically and graphically, the polynomial model presents the best behavior among the four alternative models. Meanwhile, to verify the effect of the noninvasive estimation, the simplified lumped parameter model is utilized to calculate the pre-support and the post-support left ventricular pressure. Furthermore, by adjusting the driving pressure beyond the range of the sample data, the assist pressure is estimated with the similar waveform and the post-support left ventricular pressure approaches the value of the adult healthy heart, indicating the good generalization ability of the noninvasive estimation method.