Investigation on a Linear Piezoelectric Actuator Based on Stick-Slip/Scan Excitation

To perform a high resolution and long stroke application in optical precision instruments, a linear piezoelectric actuator operated in stick-slip/scan modes for driving a linear motion table is presented. The proposed piezoelectric actuator is a piezoelectric composite structure, which includes a metal elastomer, a piezoelectric stack, and a frictional ball. The purpose of this paper is to describe the operation principle, design, and the running test and resolution test of the linear motion table driven by the proposed piezoelectric actuator. The notable feature is the flexible hinges of the actuator, including composite hinge, pre-pressure adjustment flexible hinge, and transmission flexible hinge, which are designed for decoupling the motion in the action direction of the piezoelectric stack and the direction in which the pre-pressure is applied. A prototype has been fabricated and two operation modes of the piezoelectric actuator, stick-slip and scan mode, were utilized to test the driving characteristics of the linear motion table. Experimental results show that the finest step resolutions in stick-slip mode and scan mode achieved 12 nm and 4 nm, respectively

Design and evaluation of a needle tip measurement system based on binocular vision

The precise location of the needle tip is critical in robot-assisted needle-based percutaneous interventions. An automatic needle tip measuring system based on binocular vision technology with the advantages of non-contact, excellent accuracy and high stability is designed and evaluated. First the measurement requirements of the prostate intervention robot are introduced. A laser interferometer is used as the reference for measuring the position of the needle tip whose relative position variation is described as the needle tip distance in the time domain. The parameters of the binocular cameras are obtained by Zhang’s calibration method. Then a robust needle tip extraction algorithm is specially designed to detect the pixel coordinates of the needle tip without installing the marked points. Once the binocular cameras have completed the stereo matching, the 3D coordinates of the needle tip are estimated. The measurement capability analysis (MCA) is used to evaluate the performance of the proposed system. The accuracy of the system can be controlled within 0.3621 mm. The agreement analysis is conducted by the Bland-Altman analysis, and the Pearson correlation coefficient is 0.999847. The P/T ratio value is 16.42% in the repeatability analysis. The results indicate that the accuracy and stability of the binocular vision needle tip measuring system are adequate to meet the requirement for the needle tip measurement in percutaneous interventions

High Step-Up Ratio DC-AC Converter Using Fourth-Order LCLC Resonant Circuit for Ultrasonic Fingerprint-Sensor Drivers

Ultrasonic fingerprint sensors are becoming more widely used in thick or flexible displays. In order to better identify fingerprint information, ultrasonic sensors need to generate more ultrasonic energy, which can be transmitted to the display surface through media with higher acoustic impedance. In this paper, a DC-AC converter with a high lift ratio was proposed to enhance the transmission energy of the ultrasonic fingerprint sensor, thus helping to improve the identification. The converter comprises a full-bridge inverter and two LC resonant circuits. The introduction of an additional LC resonant circuit into the traditional Class-D LC resonant converter effectively increases the boost ratio of the proposed converter from 5 to 22. When used as a part of the ultrasonic fingerprint sensing system, the proposed converter can amplify the 20-V low-voltage DC required to drive the piezoelectric organic film to 376 V high-voltage AC. The voltage of the wave received from this new driver is equal to 970 mV, which greatly exceeds the 376 mV achieved by using the Class-D converter alone. In this paper, the topology proposed by the ultrasonic fingerprint sensor converter driver was experimentally verified, which greatly improved the boost ratio and can be considered suitable for wider applications

Modeling and Design Optimization of a New Piezoelectric Inchworm Actuator with Screw Clamping Mechanisms

A new piezoelectric inchworm actuator with screw clamping mechanisms has been developed recently for the wing folding mechanism of a small unmanned aircraft where the actuator power density is a great concern. Considering that the prototype actuator was designed just with engineering intuition and the performance optimization through experimental developments would take a vast amount of cost and time, a mathematical model was developed to investigate the actuator’s critical design parameters and optimize its presently undesirable performance. Based on the lumped parameter method reported previously, and taking full account of the detailed modeling of the complex actuator housing and the actual nonlinear behaviors from the high-force contact and friction occurring at the screw-nut interface, as well as the output performance of the main drive elements including the piezoelectric stack and hollow ultrasonic motors (HUSMs), this model was built and then was experimentally verified for its accuracy and availability. Finally, nine design parameters were studied for their individual effect on the actuator’s output using the proposed model. The simulation results indicate that the performance can be considerably improved by performing a slight modification to the prototype, and the dynamic modeling and parameter optimization methods used in this study can also serve as a useful reference for the design of similar piezoelectric inchworm actuators with intermittent clamping behaviors

Characteristics of sodium and water retention in rats with nephrotic syndrome induced by puromycin aminonucleoside

Abstract Introduction Nephrotic syndrome (NS) is characterized by renal sodium and water retention. The mechanisms are not fully elucidated. Methods The NS rat model was established by single intraperitoneal injection of 100 mg/kg puromycin aminonucleoside (PAN). The plasma electrolyte level and urinary sodium excretion were monitored dynamically. The changes of some sodium transporters, including epithelial Na+ channel (ENaC), Na+/H+ exchanger 3 (NHE3), Na+-K+-2Cl− cotransporter 2 (NKCC2) and Na+-Cl− cotransporter (NCC) in renal cortex at different time points and the level of peripheral circulation factors were detected. Results The urinary sodium excretion of the model group increased significantly on the first day, then decreased compared with the control group, and there was no significant difference between the model group and the control group on the 12th day. The changes of peripheral circulation factors were not obvious. Some sodium transporters in renal cortex increased in varying degrees, while NKCC2 decreased significantly compared with the control group. Conclusions The occurrence of NS edema may not be related to the angiotensin system. The decrease of urinary sodium excretion is independent of the development of albuminuria. During the 18 days of observation, it can be divided into three stages: sodium retention, sodium compensation, and simple water retention. The mechanism is related to the increased expression of α-ENaC, γ-ENaC, NHE3 and NCC in a certain period of time, the compensatory decrease of NKCC2 expression and the continuous increase of aquaporin 2 (AQP2) expression

Sulfonated hierarchical H-USY zeolite for efficient hydrolysis of hemicellulosecellulose

Sulfonated hierarchical H-USY zeolite for efficient hydrolysis of hemicellulosecellulos

Licorice protects against ulcerative colitis via the Nrf2/PINK1‐mediated mitochondrial autophagy

Abstract Purpose Study of the effects and mechanisms of licorice in the treatment of ulcerative colitis (UC) from the perspective of mitochondrial autophagy. Methods BALB/C mice were induced with 3% dextran sodium sulfate to build an animal model of UC. After 7 days of modeling, different doses of licorice were administered for 7 days. Hematoxylin and eosin staining is used to detect pathological changes in the colon. Mitochondrial membrane potentials and reactive oxygen species (ROS) contents were detected by flow cytometry, and autophagy of mitochondria was observed by transmission electron microscopy. Determination of inflammatory cytokines by enzyme‐linked immunosorbent assay. The oxidizing factors are detected by the kits. Western blot analysis was used to detect expressions for nuclear factor called erythropoietin (Nrf2), pten‐induced protein kinase 1 (PINK1), Parkin, HO‐1, P62, and LC3. Results Licorice improved the pathological condition of UC mice, increasing the mitochondrial membrane potential and decreasing the ROS content. Promotes the emergence of autophagosomes and autophagosomes. The contents of interleukin (IL)‐1β, IL‐6, IL‐17, and tumor necrosis factor‐alpha were downregulated, the contents of superoxide dismutase and glutathione peroxidase were upregulated and the contents of malondialdehyde were downregulated. In addition, licorice promotes the expression of Nrf2, PINK1, Parkin, HO‐1, P62, and LC3. Conclusion Licorice was shown to reduce levels of inflammatory factors and oxidative stress in mice with UC, possibly by promoting mitochondrial autophagy through the activation of the Nrf2/PINK1 pathway