Novel Materials Used in Hydrogen Energy Economy

The purpose of this study was to do some efforts in developing some novel polymer materials which could have the potential use in hydrogen pipelines and PEM fuel cell. In the project of developing hydrogen pipelines, sulfonated PET, sulfonated PET/Clay and PET/Clay were produced by the method of solvent-mixing. Characterizations with TEM, SAXS were made to determine the exfoliation degree of nanocomposites. TGA was carried out to measure the thermal stability, and hydrogen permeability was also taken in order to measure the H2 gas barrier performance. It was found that the addition of clay into S-PET or PET could decrease the hydrogen permeability in polymer nanocomposites. In the other project of polymer electrolye membrane in fuel cell, our research objective is to synthesize novel polymer electrolyte membrane (PEM) based on poly(1,3-cyclohexadiene) (PCHD) with outstanding potential for use in methanol fuel cells at temperatures well above 100 °C. After the consecutive crosslinking, aromatization and sulfonation reactions, or the consecutive crosslinking and sulfonation reactions, some novel PEM materials based on PCHD were synthesized. And a series of characterizations including FT-IR, elemental analysis, water-uptake, scanning electron microscopy (SEM), thermo gravimetric analysis (TGA), and proton conductivity were carried out

A Non-Intrusive Pressure Sensor by Detecting Multiple Longitudinal Waves

Pressure vessels are widely used in industrial fields, and some of them are safety-critical components in the system - for example, those which contain flammable or explosive material. Therefore, the pressure of these vessels becomes one of the critical measurements for operational management. In the paper, we introduce a new approach to the design of non-intrusive pressure sensors, based on ultrasonic waves. The model of this sensor is built based upon the travel-time change of the critically refracted longitudinal wave (LCR wave) and the reflected longitudinal waves with the pressure. To evaluate the model, experiments are carried out to compare the proposed model with other existing models. The results show that the proposed model can improve the accuracy compared to models based on a single wave

Mars Rover Localization Based on A2G Obstacle Distribution Pattern Matching

Rover localization is one of the perquisites for large scale rover exploration. In NASA's Mars 2020 mission, the Ingenuity helicopter is carried together with the rover, which is capable of obtaining high-resolution imagery of Mars terrain, and it is possible to perform localization based on aerial-to-ground (A2G) imagery correspondence. However, considering the low-texture nature of the Mars terrain, and large perspective changes between UAV and rover imagery, traditional image matching methods will struggle to obtain valid image correspondence. In this paper we propose a novel pipeline for Mars rover localization. An algorithm combing image-based rock detection and rock distribution pattern matching is used to acquire A2G imagery correspondence, thus establishing the rover position in a UAV-generated ground map. Feasibility of this method is evaluated on sample data from a Mars analogue environment. The proposed method can serve as a reliable assist in future Mars missions.Comment: 8 pages, in Chinese language, 9 figure

Offset quantum-well method for tunable distributed Bragg reflector lasers and electro-absorption modulated distributed feedback lasers

A two-section offset quantum-well structure tunable laser with a tuning range of 7 nm was fabricated using offset quantum-well method. The distributed Bragg reflector (DBR) was realized just by selectively wet etching the multiquantum-well (MQW) layer above the quaternary lower waveguide. A threshold current of 32 mA and an output power of 9 mW at 100 mA were achieved. Furthermore, with this offset structure method, a distributed feedback (DFB) laser was integrated with an electro-absorption modulator (EAM), which was capable of producing 20 dB of optical extinction

Pressure measurement based on multi-waves fusion algorithm

Measuring the pressure of a pressure vessel accurately is one of fundamental requirements of the operation of many complex engineering systems. Ultrasonic technique has been proposed to be a good alteration of non-intrusive measurement. Based on the study of acoustoelastic effect and thin-shell theory, it has been identified that the travel-time changes of the critically refracted longitudinal wave (LCR wave) and other reflected longitudinal waves are all proportional to the inner pressure. Considering the information redundancy in these waves, we proposed an approach for pressure measurement by using the information fusion algorithm on multiple reflected longitudinal waves. In the paper, we discussed the fusion algorithm in details and proposed a pressure measurement model, which represents an accurate relationship between the pressure and the travel-time changes of multiple waves. Through the experiment, the analysis of data collected from experiment system showed that the pressure measurement based on the multi-wave model is notably more accurate than the one based on the single-wave model (the average relative error (ARE) can be less than 7.24% and the root-mean-square error (RMSE) can be lower than 0.3MPa)

The vibration frequency analysis of the screw feeding system with spring supports

Ball screw feeding system has wide application in machine tools, and its dynamic research is very important. The drive screw can be seen as a rotating Timoshenko beam under the pre-tension force. Considering the bearing stiffness, the boundary condition of the screw is spring supported. Also, considering the contact deformation between the screw and the worktable and the worktable moving, the screw is added an intermediate moving spring-mass system. Using boundary conditions and continuity conditions, the lateral and longitudinal frequency equations of the screw feeding system are derived considering the effect of gyroscope, the pre-tension force, the bearing stiffness, the contact between the worktable and the screw and the moving of the worktable. The effect of the system parameters on the natural frequency is studied. The diameter, the pre-tension force, the bearing stiffness, the contact stiffness and the rotational speed of the screw have effect on the vibration frequency and the frequency varies when the worktable moves along the screw from the left to the right end. This work supplies a base for designing the drive system to avoid resonance and to improve the stability of the system