Determination of Chlorine in Human Urine by Detecting Backscattering Signals with a New Optical Assembly

Detection of backscattering signals （BSS） generally suffers from the interference of reflected light, and it is hard to apply these signals for analytical purpose. Herein we provided an optical assembly, which effectively eliminated the interference of reflected light so that the scattering signals of analyte could be measured distinctly. With this assembly, chlorine in human urine could be detected with the limit of detection （LOD） of 2.0 ng/mL by measuring the enhanced BSS signals produced between the interactions of chlorine with silver nitrate.

Effect of trabecular bone material properties on ultrasonic backscattering signals

In this study, ultrasonic backscattering signals in cancellous bones were obtained by finite difference time domain （FDTD） simulations, and the effect of trabecular material properties on these signals was analyzed. The backscatter coefficient （BSC） and integrated backscatter coefficient （IBC） were numerically investigated for varying trabecular bone material properties, including density, Lame coefficients, viscosities, and resistance coefficients. The results show that the BSC is a complex function of trabecular bone density, and the IBC increases as density increases. The BSC and IBC increase with the first and second Lame coefficients. While not very sensitive to the second viscosity of the trabeculae, the BSC and IBC decrease as the first viscosity and resistance coefficients increase. The results demonstrate that, in addition to bone mineral density （BMD） and microarchitecture, trabecular material properties significantly influence ultrasonic backseattering signals in cancellous bones. This research furthers the understanding of ultrasonic backscattering in cancellous bones and the characterization of cancellous bone status.

The spectrum entropy estimation method for ultrasonic backscattering signal in cancellous bones

In the application of cancellous bone ultrasound diagnosis based on backscattering method, it is of great importance to estimate fast and accurately whether the valid backscattering signal exists in the received signal. We propose a fast estimation method based on spectrum entropy method. With 984 records of adult calcaneus clinical data, we estimate the validity of the backscatter signal using this method. The results of the proposed method and the results of experience-base judgement were compared and analyzed. And two key parameters, the signal range length and the segment number of the spectrum entropy, were analyzed. The results show when the signal range length is 13 I^s and the segment number is 15 20, this method can get the best result （accuracy〉95%, sensitivity〉99%, specificity〉87%）, while taking little calculation time （1.5 ms）. Therefore, this spectrum entropy method can satisfy the accuracy and real-time requirements in the ultrasonic estimation for cancellous bone.

The effect of a layer of varying density on spatial correlation of sea-bottom backscattering signal

The research is about the effect of a layer of varying density of sea-bottom sediments on spatial correlation of sea-bottom backscattering. The relationship between scattering cross section and spatial correlation is that backscattering cross section decreases quickly and the spatial correlation becomes stronger as the incident angle increases. Therefore, the density- depth profile is introduced into sea-bottom high-frequency backscattering echo model, which is used to simulate sea-bottom backscattering and calculate the function of spatial correlation. The influence of the density gradient on spatial correlation of sea-bottom backscattering is investigated by analyzing the relations between vertical gradient of density and the scattering cross section. As can be seen from the simulation results, the impact of the density gradient on the spatial correlation is found more significant. While the density gradient increases, the scattering cross-section and the radius of the spatial correlation broaden, the spatial correlation becomes stronger. At the same time, the scattering cross-section decreases more quickly as the incident angle increases.

Wind Velocity Measurement of Multi-Laser Beams Measurement System Based on Peak Delay Technique

Contactless measurement of wind flow has been utilized in many fields, such as weather forecasting, hurricane tracking, and aeronautic alarm. In this paper, a novel multi-laser beams measuring system （MLBM） for high precision detection of wind field based on optical scintillations and small perturbation theory was proposed and verified. According to the fluctuation intensity of laser backscatter received by two detectors, peak delay technique was adopted to determine the velocity of wind flow. Detailed procedure to deal with backscatter signals was also presented. Then, practical experiments and measurement results showed high precision of the proposed system for wind measurement with a relative error as 3.21%. Consequently, the MLBM system possesses obvious potential application in engineering project.