Effect of sensor quantity on measurement accuracy of log inner defects by using stress wave

Wood nondestructive testing （NDT） is one of the high efficient methods in utilizing wood. This paper explained the principle of log defect testing by using stress wave, and analyzed the effects of sensor quantity on defect testing results by using stress wave in terms of image fitting degree and error rate. The results showed that for logs with diameter ranging from 20 to 40 cm, at least 12 sensors were needed to meet the requirement which ensure a high testing accuracy of roughly 90% of fitness with 0.1 of error rate. And 10 sensors were recommended to judge the possible locations of defects and 6 sensors were sufficient to decide whether there were defects or not.

Parameters analysis and application of the differential excitation detection technology

A differential excitation probe based on eddy current testing technology was designed. Sheet specimens of Q 235 steel with prefabricated micro-cracks of different widths and of aluminum with prefabricated micro-cracks of different depths were detected through the designed detection system. The characteristics of micro-cracks can be clearly showed after signals processing through the short-time Fourier transform（ STFT）. By changing the parameter and its value in detecting process,the factors including the excitation frequency and amplitude,the lift-off effect and the scanning direction were discussed,respectively. The results showed that the differential excitation probe was insensitive to dimension and surface state of the tested specimen,while it had a high degree of recognition for micro-crack detection. Therefore,when the differential excitation detection technology was used for inspecting micro-crack of turbine blade in aero-engine,and smoothed pseudo Wigner-Ville distribution was used for signal processing,micro-cracks of 0. 3 mm depth and 0. 1 mm width could be identified. The experimental results might be useful for further research on engineering test of turbine blades of aero-engine.

A diagnostic kit to screen individuals with glucose-6-phosphate dehydrogenase defect and its application on anti-malaria spot in the countryside

Objective To prepare a kit for screening individuals with glucose 6 phosphate dehydrogenase (G6PD) defect. The kit is easy to use and to get the fast as well as reliable results. Especially it is suitable for the anti malaria spots usually located in the remote countryside where no electricity is available. Methods The double filter paper method and other 2 techniques, the quantitative method and the single filter paper method, were used to determine G6PD activity in 70 samples of human erythrocytes. It was found that the results of the double filter paper method and those of the single filter paper method in the first 8 hours after the drying of the blood soaked filter paper were consistent with those of the quantitative method. When a piece of blood soaked paper is left under room temperature more than 24 hours, G6PD in the erythrocytes deteriorated spontaneously and consequently the number of positive cases increased along with the elapse of time.Results Satisfactory results were achieved when the kit was used to screen cases of G6PD defect from 151 farmers who were receiving anti mararia therapy. The kit was made according to a technique named “double filter paper” method.Conclusions These findings suggest that the double filter paper method can reveal the level of G6PD activity and the results are rapidly obtained when the method is used on the anti malaria spot.