Search for serendipitous TNO occultation in X-rays

To study the population properties of small, remote objects beyond Neptune's orbit in the outer solar system, of kilometer size or smaller, serendipitous occultation search is so far the only way. For hectometer-sized Trans-Neptunian Objects (TNOs), optical shadows actually disappear because of diffraction. Observations at shorter wave lengths are needed. Here we report the effort of TNO occultation search in X-rays using RXTE/PCA data of Sco X-1 taken from June 2007 to October 2011. No definite TNO occultation events were found in the 334 ks data. We investigate the detection efficiency dependence on the TNO size to better define the sensible size range of our approach and suggest upper limits to the TNO size distribution in the size range from 30 m to 300 m. A list of X-ray sources suitable for future larger facilities to observe is proposed.Comment: Accepted to publish in MNRA

A unified gas-kinetic particle method for frequency-dependent radiative transfer equations with isotropic scattering process on unstructured mesh

In this paper, we extend the unified kinetic particle (UGKP) method to the frequency-dependent radiative transfer equation with both absorption-emission and scattering processes. The extended UGKP method could not only capture the diffusion and free transport limit, but also provide a smooth transition in the physical and frequency space in the regime between the above two limits. The proposed scheme has the properties of asymptotic-preserving, regime-adaptive, and entropy-preserving, which make it an accurate and efficient scheme in the simulation of multiscale photon transport problems. The methodology of scheme construction is a coupled evolution of macroscopic energy equation and the microscopic radiant intensity equation, where the numerical flux in macroscopic energy equation and the closure in microscopic radiant intensity equation are constructed based on the integral solution. Both numerical dissipation and computational complexity are well controlled especially in the optical thick regime. A 2D multi-thread code on a general unstructured mesh has been developed. Several numerical tests have been simulated to verify the numerical scheme and code, covering a wide range of flow regimes. The numerical scheme and code that we developed are highly demanded and widely applicable in the high energy density engineering applications

Feasibility and Reliability of Grain Noise Suppression in Monitoring Highly Scattering Materials Using Baseline Subtraction

This paper studies the feasibility and reliability of using the baseline subtraction method [1] to suppress grain noise in monitoring highly scattering materials. Monitoring is usually done with permanently installed sensors but this is not always possible and here we investigate the feasibility of subtracting A-scans extracted from repeat C-scans. It is important that the transducer standoff and angle relative to the testpiece are set consistently in the repeat scans and the influence of errors in these settings has been investigated. The successive C-scans can be registered by cross correlation and the effect of errors in the registration is illustrated. The experimental results demonstrate that the residual grain noise after baseline subtraction is around 15dB lower than the original grain noise; this will give a significant improvement in defect sensitivity. Successive tests may be carried out at different temperatures and with different transducers of similar specification. Compensation methods for temperature variations [2] and transducer frequency response changes are then proposed, and their effectiveness is tested experimentally. The addition of these two effects reduces the typical improvement in the signal to noise ratio obtained via baseline subtraction to about 10 dB which is still potentially valuable in some applications

Application of Detecting Part's Size Online Based on Machine Vision

AbstractIn order to use a method untouched to measure part's size, detection system is built. The research is on characteristic point detection, CCD camera calibration and distance detection between two special points. Firstly, the theory of edge detection based on Gauss point spread function is introduced. Secondly, it is calibrated using the characteristic points on the edge. Then a simple CCD calibration method of resolving the solution is deduced to solve the related parameters of model. Finally, 3D special coordinates of characteristic points detected can be obtained by the model. It is realized to detecting part size process online by calculating the distance between two special points. The experimental result shows that when physical length is 0.6 times than focal length, the given precise of measuring result can reach nearly 0.006mm. The precise of image is stable