Slippery interfaces: control and evaluation of the anchoring effect for the reduction of driving voltage (Conference Presentation)

Constant light power operation of an ultraviolet (UV) LED based on portable low-cost instrumentation and a monolithically integrated monitoring photodiode (MPD) has been reported for the first time. UV light irradiation has become one of the essential measures for disinfection and sterilization. Monitoring and maintaining a specified light power level is important to meet the criteria of sterilization. We built a module composed of a monolithically integrated UV LED and MPD, a transimpedance amplifier, an Arduino Uno card, a digital-to-analog converter and a Bluetooth transceiver. An Android App that we wrote remotely controlled the UV LED module via Bluetooth. The Arduino Uno card was programmed to receive demands from the smartphone, sent a driving voltage to the LED and returned the present MPD voltage to the smartphone. A feedback loop was used to adjust the LED voltage for maintaining a constant light output. We successfully demonstrated the functioning of remote control of the App, and the resultant UV LED measured power remained the same as the setting power. This setup can also be applied to visible or white LEDs for controlling/maintaining mixed light’s chromaticity coordinates or color temperature. With such controlling and internet capability, custom profiling and maintenance of precision lighting remotely would be possible.

Download Full-text

Research on a Piezoelectric Pump with Flexible Valves

Applied Sciences ◽

10.3390/app11072909 ◽

2021 ◽

Vol 11 (7) ◽

pp. 2909

Author(s):

Weiqing Huang ◽

Liyi Lai ◽

Zhenlin Chen ◽

Xiaosheng Chen ◽

Zhi Huang ◽

...

Keyword(s):

Flow Rate ◽

Fluid Transport ◽

Smooth Transition ◽

Driving Voltage ◽

Piezoelectric Pump ◽

Venous Valve ◽

Output Pressure ◽

Small Flow ◽

Working Principle ◽

Opening And Closing

Imitating the structure of the venous valve and its characteristics of passive opening and closing with changes in heart pressure, a piezoelectric pump with flexible valves (PPFV) was designed. Firstly, the structure and the working principle of the PPFV were introduced. Then, the flexible valve, the main functional component of the pump, was analyzed theoretically. Finally, an experimental prototype was manufactured and its performance was tested. The research proves that the PPFV can achieve a smooth transition between valved and valveless by only changing the driving signal of the piezoelectric (PZT) vibrator. The results demonstrate that when the driving voltage is 100 V and the frequency is 25 Hz, the experimental flow rate of the PPFV is about 119.61 mL/min, and the output pressure is about 6.16 kPa. This kind of pump can realize the reciprocal conversion of a large flow rate, high output pressure, and a small flow rate, low output pressure under the electronic control signal. Therefore, it can be utilized for fluid transport and pressure transmission at both the macro-level and the micro-level, which belongs to the macro–micro combined component.

Download Full-text

Evaluation of VTH and RON Drifts during Switch-Mode Operation in Packaged SiC MOSFETs

Electronics ◽

10.3390/electronics10040441 ◽

2021 ◽

Vol 10 (4) ◽

pp. 441

Author(s):

Marcello Cioni ◽

Alessandro Bertacchini ◽

Alessandro Mucci ◽

Nicolò Zagni ◽

Giovanni Verzellesi ◽

...

Keyword(s):

Field Effect Transistors ◽

Oxide Semiconductor ◽

Driving Voltage ◽

Drain Voltage ◽

Current Increase ◽

Mode Operation ◽

Switch Mode ◽

Gate Signal ◽

A Current ◽

Parameter Monitoring

In this paper, we investigate the evolution of threshold voltage (VTH) and on-resistance (RON) drifts in the silicon carbide (SiC) power metal-oxide-semiconductor field-effect transistors (MOSFETs) during the switch-mode operation. A novel measurement setup for performing the required on-the-fly characterization is presented and the experimental results, obtained on commercially available TO-247 packaged SiC devices, are reported. Measurements were performed for 1000 s, during which negative VTH shifts (i.e., VTH decrease) and negative RON drifts (i.e., RON decrease) were observed. To better understand the origin of these parameter drifts and their possible correlation, measurements were performed for different (i) gate-driving voltage (VGH) and (ii) off-state drain voltage (VPH). We found that VTH reduction leads to a current increase, thus yielding RON to decrease. This correlation was explained by the RON dependence on the overdrive voltage (VGS–VTH). We also found that gate-related effects dominate the parameter drifts at low VPH with no observable recovery, due to the repeated switching of the gate signal required for the parameter monitoring. Conversely, the drain-induced instabilities caused by high VPH are completely recoverable within 1000 s from the VPH removal. These results show that the measurement setup is able to discern the gate/drain contributions, clarifying the origin of the observed VTH and RON drifts.

Download Full-text

Optical Response Associated with the Orientation and Structure of Liquid Crystals with Respect to Phosphatidylcholine Concentration

Crystals ◽

10.3390/cryst11060678 ◽

2021 ◽

Vol 11 (6) ◽

pp. 678

Author(s):

Yuqi Han ◽

Yan Jiang ◽

Wei Guo ◽

Bing Li ◽

Lu Zhang ◽

...

Keyword(s):

Liquid Crystal ◽

Liquid Crystals ◽

Reflectance Spectrum ◽

Optical Response ◽

The Self ◽

Cholesteric Liquid Crystals ◽

Anchoring Effect ◽

Self Assembling ◽

Sensitization Effect ◽

Structure Of Liquid

Based on the anchoring effect due to the self-assembling behavior of the phospholipid molecules at the interface between the liquid crystal and water phases on the orientation of liquid crystals, the optical response associated with the orientation and structure of liquid crystals with respect to the concentration of 1,2-didodecanoyl-sn-glycero-3-phosphocholine solution has been investigated. The optical response owing to changes in the orientation and structure of the mixed cholesteric liquid crystals with respect to the change in the concentration of phosphatidylcholine has been obtained. Moreover, the feasibility of using as-prepared mixed cholesteric liquid crystals to measure the phosphatidylcholine concentration has been verified. A methodology to measure the reflectance spectrum by using mixed cholesteric liquid crystals to sensitize the phosphatidylcholine concentration has been further realized. The sensitization effect of the mixed cholesteric liquid crystals on the measurement of phosphatidylcholine concentration was also verified.

Download Full-text

Exploring the anchoring effect and catalytic mechanism of 3d transition metal phthalocyanine for S8/LiPSs: A density functional theory study

Applied Surface Science ◽

10.1016/j.apsusc.2021.149928 ◽

2021 ◽

Vol 558 ◽

pp. 149928

Author(s):

Bin Yu ◽

Qiu He ◽

Yan Zhao

Keyword(s):

Density Functional Theory ◽

Transition Metal ◽

Density Functional ◽

Catalytic Mechanism ◽

Density Functional Theory Study ◽

Metal Phthalocyanine ◽

Functional Theory ◽

Anchoring Effect

Download Full-text

Analysis of surrounding rock anchoring effect under the condition of squeezed mountain

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1315/669/1/012028 ◽

2021 ◽

Vol 669 (1) ◽

pp. 012028

Author(s):

Yujun Ma ◽

Chao Su ◽

Heng Zhang

Keyword(s):

Surrounding Rock ◽

Anchoring Effect

Download Full-text

Improving Output Performance of a Resonant Piezoelectric Pump by Adding Proof Masses to a U-Shaped Piezoelectric Resonator

Micromachines ◽

10.3390/mi12050500 ◽

2021 ◽

Vol 12 (5) ◽

pp. 500

Author(s):

Jian Chen ◽

Wenzhi Gao ◽

Changhai Liu ◽

Liangguo He ◽

Yishan Zeng

Keyword(s):

Flow Rate ◽

Maximum Flow ◽

Working Fluid ◽

Driving Voltage ◽

Piezoelectric Resonator ◽

Piezoelectric Pump ◽

Compact Structure ◽

Output Performance ◽

Volume Efficiency ◽

Working Efficiency

This study proposes the improvement of the output performance of a resonant piezoelectric pump by adding proof masses to the free ends of the prongs of a U-shaped piezoelectric resonator. Simulation analyses show that the out-of-phase resonant frequency of the developed resonator can be tuned more efficiently within a more compact structure to the optimal operating frequency of the check valves by adjusting the thickness of the proof masses, which ensures that both the resonator and the check valves can operate at the best condition in a piezoelectric pump. A separable prototype piezoelectric pump composed of the proposed resonator and two diaphragm pumps was designed and fabricated with outline dimensions of 30 mm × 37 mm × 54 mm. Experimental results demonstrate remarkable improvements in the output performance and working efficiency of the piezoelectric pump. With the working fluid of liquid water and under a sinusoidal driving voltage of 298.5 Vpp, the miniature pump can achieve the maximum flow rate of 2258.9 mL/min with the highest volume efficiency of 77.1% and power consumption of 2.12 W under zero backpressure at 311/312 Hz, and the highest backpressure of 157.3 kPa under zero flow rate at 383 Hz.

Download Full-text

Numerical calculation and experimental study on response characteristics of pneumatic solenoid valves

Measurement and Control ◽

10.1177/0020294019866853 ◽

2019 ◽

Vol 52 (9-10) ◽

pp. 1382-1393 ◽

Cited By ~ 1

Author(s):

Xiang Zhang ◽

Yonghua Lu ◽

Yang Li ◽

Chi Zhang ◽

Rui Wang

Keyword(s):

Switching Time ◽

Response Characteristic ◽

Test System ◽

Solenoid Valve ◽

Circuit Model ◽

Inlet Pressure ◽

Driving Voltage ◽

Response Characteristics ◽

Aerodynamic Model ◽

Set Up

In order to analyze the response characteristics of the solenoid valve in depth, the flow field of the solenoid valve is analyzed by means of the computational fluid dynamics, and the aerodynamic parameters that are difficult to be obtained by the traditional methods are obtained with software FLUENT. We also set up the mathematical model of the solenoid valve, including the aerodynamic model, the circuit model, the magnetic circuit model and the mechanical motion model. The calculation is completed in the Simulink, and the results of the calculation are analyzed. A set of the solenoid valve response characteristic test system is built, and the response characteristic parameters such as response time and maximum action frequency of the solenoid valve are tested. The experimental results are verified by comparing them with the simulation results. The final result shows that the response characteristics are basically irrelevant to the action frequency at a suitable working frequency. The open switching time of the solenoid valve decreases with the increase in the inlet pressure and the driving voltage and increases with the increase in the number of coil turns. The close switching time increases with the increase in the inlet pressure, the driving voltage and the number of coil turns.

Download Full-text