Standing wave brass-PZT square tubular ultrasonic motor

This paper reports a standing wave brass-PZT tubular ultrasonic motor. The motor is composed of a brass square tube with two teeth on each tube end. Four PZT plates are attached to the outside walls of the brass tube. The motor requires only one driving signal to excite vibration in a single bending mode to generate reciprocating diagonal trajectories of teeth on the brass tube ends, which drive the motor to rotate. Bi-directional rotation is achieved by exciting different pairs of PZT plates to switch the bending vibration direction. Through using the brass-PZT tube structure, the motor can take high magnitude vibration to achieve a high output power in comparison to PZT tube based ultrasonic motors. Prototypes are fabricated and tested. The dimension of the brass-PZT tube is 3.975 mm × 3.975 mm × 16 mm. Measured performance is a no-load speed of >1000 RPM, a stall torque of 370 μNm and a maximum output power of 16 mW when a sinusoidal driving voltage of 50 V is applied. The working frequencies of the motor are 46,050 Hz (clockwise) and 46,200 Hz (counter-clockwise).     

Feasibility of using Nakagami distribution in evaluating the formation of ultrasound-induced thermal lesions

The acoustic posterior shadowing effects of bubbles influence the accuracy for defining the location and range of ablated thermal lesions during focused ultrasound surgery when using ultrasonic monitoring imaging. This paper explored the feasibility of using Nakagami distribution to evaluate the ablated region induced by focused ultrasound exposures at different acoustic power levels in transparent tissue-mimicking phantoms. The mean value of the Nakagami parameter m was about 0.5 in the cavitation region and increased to around 1 in the ablated region. Nakagami images were not subject to significant shadowing effects of bubbles. Ultrasound-induced thermal lesions observed in the photos and Nakagami images were overshadowed by bubbles in the B-mode images. The lesion size predicted in the Nakagami images was smaller than that predicted in the photos due to the sub resolvable effect of Nakagami imaging at the interface. This preliminary study on tissue-mimicking phantom suggested that the Nakagami parameter m may have the potential use in evaluating the formation of ultrasound-induced thermal lesion when the shadowing effect of bubbles is strong while the thermal lesion was small. Further studies in vivo and in vitro will be needed to evaluate the potential application.     

Ternary Monolithic ZnS/CdS/rGO Photomembrane with Desirable Charge Separation/Transfer Routes for Effective Photocatalytic and Photoelectrochemical Hydrogen Generation

Highly efficient and easy recyclable monolithic photocatalysts with ideal separation/transport route for photogenerated charge carriers are much desired. In this work, a ZnO seed‐induced growth approach is developed to fabricate a ternary monolithic photomembrane, that is, ZnS/CdS heterojunction nanorods in situ grow into the interspaces of multilayer reduced graphene oxide (rGO) sheets (denoted as ZnS/CdS/rGO). The monolithic ZnS/CdS/rGO photomembrane can serve as an efficient visible‐light photoactive membrane for photocatalytic (PC) or photoelectrochemical (PEC) hydrogen generation. The fast electron transport of 1D CdS nanorods, the excellent electronic conductivity of multilayer stacked rGO sheets, the intense visible‐light absorption of CdS, the unique hierarchical structure, and double heterojunctions (ZnS/CdS and CdS/rGO) efficiently boost the photogenerated electron‐hole pairs separation and transfer across the interfacial domain of the photomembrane under visible‐light irradiation. Furthermore, the superior stability and reusability of the photomembrane is achieved by the ideal process of photogenerated electron‐hole pair separation/transfer, i.e., holes transfer to ZnS and electrons transfer to rGO to inhibit CdS from photocorrosion.     

Algebraic conditions for <Emphasis Type="Italic">t</Emphasis>-tough graphs

We give some algebraic conditions for t-tough graphs in terms of the Laplacian eigenvalues and adjacency eigenvalues of graphs.     

Packet error rate analysis of OOK, DPIM and PPM modulation schemes for ground-to-satellite optical communications

Packet error rate of OOK, DPIM and PPM modulation schemes are researched for ground-to-satellite optical communication systems. Analysis process is based on threshold detection for OOK and DPIM, and optimal detection for PPM. Packet error rate of these three modulation schemes are compared for both uplink and downlink, with consideration of the turbulence introduced intensity fluctuation in the ground-to-satellite laser link. Numerical results are given, and based on it, the advantages of PPM and DPIM are discussed, with the comparison to OOK. This work can be helpful for modulation scheme selection in the ground-to-satellite laser communication system design.     

An improved method of detecting and processing for the beacon in satellite-to-ground laser communication links

In satellite-to-ground laser communication links, the motion and vibration of the satellite are important factors that affect the real-time requirements of pointing, acquiring, and tracking. In order to acquire again the beacon quickly and accurately after losing it for a short time, we propose an improved method of detecting and processing for the beacon. In contrast to the conventional design of processing systems for the beacon, the advantage of the system we designed is provided by the spatial environment, where the optical communication terminal is located, and the motion trace of the beacon can be predicted effectively. We perform numerical simulations and simulation experiments, with a sampling frequency of the CCD in a system of 60 Hz and frequency and amplitude of the simulation vibration signal of 1 Hz and 0.1 mrad, respectively. We assume the motion of the satellite to be of translation type. The prediction precision is not more than 6 pixels of the CCD after the algorithm converges and the experimental results correspond fairly to the numerical simulation.     

Droplet-based interfacial capacitive sensing

This paper presented a novel droplet-based pressure sensor using elastic and capacitive electrode-electrolyte interfaces to achieve ultrahigh mechanical-to-electrical sensitivity (1.58 μF kPa(-1)) and resolution (1.8 Pa) with a simple device architecture. The miniature transparent droplet sensors, fabricated by one-step laser micromachining, consisted of two flexible polymer membranes with conductive coating and a separation layer hosting a sensing chamber for an electrolyte droplet. The sensing principle primarily relied on high elasticity of the sensing droplet and large capacitance presented at the electrode-electrolyte interface. A simple surface modification scheme was introduced to the conductive coating, which reduced hysteresis of the droplet deformation without substantially compromising the interfacial capacitance. Moreover, the major concern of liquid evaporation was addressed by a mixture of glycerol and electrolyte with long-term stability in a laboratory environment. Theoretical analyses and experimental investigations on several design parameters (i.e., the dimensions of the sensing chamber and the droplet size) were thoroughly conducted to characterize and optimize the overall sensitivity of the device. Moreover, the environmental influences (e.g., temperature and humidity) on the capacitive measurement were further investigated. Finally, the simply constructed and mechanically flexible droplet sensor was successfully applied to detect minute blood pressure variations on the skin surface (with the maximum value less than 100 Pa) throughout cardiovascular cycles.     

Influence of reflector temperature gradients on bit-error rate in periscope laser communication systems in the presence of detector noise and platform vibrations

We consider the influence of thermal deformations of elliptic reflectors in periscope laser communication terminals on the bit-error rate (BER) taking into account the satellite-platform vibrations and the detector noise. We study the relationship between the average BER and temperature gradients of elliptic reflectors in inter-satellite laser communication systems at different values of the light beam wavelength and truncation rate, and different vibration amplitudes. The average BER increases with increase in the vibration amplitude, and it is noteworthy that the average BER increases with increase in the beam truncation rate, which contradicts the result obtained in [1] without taking noise into account. We find that for some temperature gradients there is an optimum communication wavelength that provides the minimum average BER. We use the back-fixing method for fixing the elliptic reflectors, which has proved to be much less sensitive to temperature gradients compared to the traditional around-fixing method by a press board.     

An Infrared Sensitive Negative-Differential-Resistance Device for High-Temperature Application

In this paper, a novel infrared sensitive negative-differential-resistance (NDR) device has been achieved. This device can be operated at 100°C, indicating its excellent characteristic. Under daylight, the device exhibits a negative-differential-resistance property and the peak-to-valley current ratio (PVCR) is still prominent at 100°C. When the device's forward bias is fixed, device's current changes with infrared light power. So, it is sensitive to infrared light. Its operational mechanism is interpreted in detail, too.     

稀土三氟醋酸盐晶体的光谱特性

本文合成了系列稀土三氟醋酸盐晶体[Re(CF3COO)3·3H2O](Re=Eu,Gd,Tb,Dy)和[TbxY1-x(CF3COO)3·3H2O]2(x=0.05,0.10,0.15,0.20,0.25mol),测定其晶体结构属单斜晶系,空间群为P21/c;较详细地讨论了Eu3+,Gd3+,Tb3+,Dy3+在这些化学计量化合物中的光谱特性,以及在[TbxY1-x(CF5COO)3·3H2O]中Tb3+的发光强度随其浓度的变化规律。