Gao Xiaorong

Gain Improvement of Fiber Parametric Amplifier via the Introduction of Standard Single-Mode Fiber for Phase Matching

We investigate and experimentally demonstrate the gain improvement of single-pump fiber parametric amplifiers by using a suitable length of standard single-mode fiber (SSMF) inserted between two high-nonlinear fibers (HNLFs). The SSMF with different dispersion properties from the HNLF is employed for phase matching of the parametric processes, and the signal gain is improved as compared with the absence of the SSMF with experiment results. Furthermore, the effect of the input pump power and the fiber length of the SSMF on the output signal gain are discussed with experimental investigation.

Phased array ultrasonic probe simulation and designing for railway axle inspection

When the solid axle is detected by the conventional ultrasonic probes, the inspecting coverage of axle is very limited, especially for the press-fit part of axle where the signal-to-noise ratio of detection is very low, and the echoes are difficult to distinguish, which easily leads to false judgment or missing judgment. In view of this phenomenon, a kind of dedicated phased array ultrasonic probe is introduced in this paper. Based on the advantages of phased array ultrasonic technology, relative theoretical analysis and simulation comparison are conducted. Finally, this probe is proved to have superior detection ability of railway axle inspection by comparison test.

A pre-calculation beamformer design based on FPGA for ultrasound SA imaging

The previous studies of real-time imaging process using directly delay calculation design on FPGA, because the limited number of memory on chip. In this paper, to achieve higher frequency, a look-up table which carries the distance information has been introduced in. As the operation frequency of memory on Field-programmable gate array (FPGA) can reach to as high as 400MHz, which is much higher than directly calculation. After the design of hardware language and compile, the performance of this beamformer was assessed on an Altera Stratix IV FPGA. The final performance shows the highest frequency is 300MHz. Experiment on total focus method SA imaging processing with 64 channels, our FPGA-based SA beamformer can achieve 32 frames per second (fps) processing (100MHz sample frequency, 16 bits resolution, frame size 256×256 pixels). According the experimental result, the beamformer can be used as real-time ultrasound processor modules.

Wheel profile and tread surface defect detection based on phase measuring profilometry

With the rapid development of high-speed and heavy-load in modern rail transit, the abrasion and surface defect of wheel tread are getting serious, and the demand of measuring the wheel profile and tread surface defect has been increasing. Phase Measuring Profilometry (PMP), due to its good characters of non-contact, high precision, easy to control automatically etc., is often used for precise 3D shape reconstruction. In this paper, PMP technology and Stoilov phase shift algorithm are adopted, three deformed fringe patterns of wheel are collected with fixed phase shift between them, and branch cut phase unwrapping algorithm is used, based on which the three-dimensional surface shape of the wheel is reconstructed and the artificial surface flaws on the tread are restored and measured. This method provides a good reference for the precise online detection of the wheel abrasion and surface defect.

Way-side wheel crack detecting using arrayed ultrasonic probes

Wheelset is one of the vital components of the train. Normally, the wheels are regularly detected by using ultrasonic technology to check cracks, especially in wheel rim. In order to eliminate the failure risks of wheels, daily dynamic wheelset inspecting system is needed during the light maintenance period. A way-side arrayed ultrasonic technology is described in this paper to detect wheel cracks. By using a specially designed track structure, the arrayed ultrasonic probes are arranged between the double-track for wheel rim inspection. From the testing results, Φ3mm side drill hole in the wheel rim can be well detected at the running speed of 30∼40km/h. The noise is effectively suppressed by filtering algorithm, thus to improve the signal to noise ratio and the positive alarming rates. At present, the technology has been successfully used in Chinese high-speed train maintenance centers, rolling stocks and locomotive maintenance depots.

Solid axle defect detection technique based on phased array ultrasonics

The quality of train axles is especially important for the safety of railway transportation. A technique and system based on the newest Olympus phased array ultrasonic instrument, the FOCUS PX, for the detection of defects in on-train solid axles is presented in this paper. Advanced phased array ultrasonic technology, the ultrasonic transmitting and receiving principle, and the ultrasonic testing method for solid axle defect detection are explained in detail. With this technique, transverse defects in axles can be detected by coupling from the end face of solid axles. There is no need to dismount wheel-sets from the train or remove coating for ultrasonic inspection. A real inspection system based on this technique, named the LZM In-Service Automatic Ultrasonic Inspection System for Solid Axles (hereinafter referred to as “LZM system”), which has a high level of efficiency and reliability, is described in detail. Half of the axle can be covered by ultrasonic beams from each side, and ultrasonic data can be acquired in 20 seconds. The inspection results are displayed in A-scans and B-scans for correlative data analysis, and all inspection data are recorded.

Composite railway health monitoring system based on fiber optic bragg grating sensing array

During the long-time working circle, railroad transport system will be damaged to a certain degree caused by the wearing, the impact, the loads, the climate and so on. In order to monitor the health of the railways and reduce the potential losses, many effective methods are used in railway health monitoring, but few of the techniques can reach the demand of the comprehensive inspection such as operating the rail-inspection and wheel-inspection at the same time. A monitoring scheme for the railway health based on composite sensing technique has been investigated in this paper. The system discussed in the article is based on the fiber Bragg grating (FBG) sensor array. By collecting and analyzing the data from the sensors which are distributed on rails and bodies, we can evaluate the speed, loads and traffic status of trains.

The impacts of temperature on the absorption spectral lines of carbon monoxide

In order to study the change of temperature on the effects of carbon monoxide absorption spectral lines, first of all proceed from the principle of absorption spectra, using theoretical analysis method, and the transmission and absorption database of the high-resolution molecular educed the carbon monoxide absorption spectrum intensity of spectral lines, integrated widening line type function and absorption coefficient concerned with temperature, then we got the change curve between carbon monoxide absorption spectrum intensity of spectral lines, integrated widening line type function and absorption coefficient with temperature by the numerical simulation of MATLAB, and analyzed and discussed the relationship between the temperature and them .The results showed that the temperature on the effects of carbon monoxide absorption spectral lines, especially on an Integrated widening line type function is complex, and different laser frequencies will also affect the relationship of the line type function and the absorption coefficient change with temperature, which has important reference value for the absorption and measurement of carbon in practical application.