Three-dimensional steady-state closed form solution for multilayered fluid-saturated anisotropic finite media due to surface/internal point source

A three-dimensional(3 D)steady-state solution of fluid saturated anisotropic finite media is presented.The eigenequation method and the pseudo-Stroh formalism are used to obtain the exact solution for homogeneous saturated finite media.The propagator matrix method is introduced to deal with the corresponding multilayered poroelastic media.The poroelastic solutions due to surface or internal point fluid source are obtained.The comparison of the results of the saturated isotropic media in a half space and those obtained by the finite element method is given to illustrate the accuracy of the solution in a finite domain.Numerical solutions of a sandwich poroelastic medium are presented to analyze its hydromechanical behaviors.Two ratios of the horizontal permeability to vertical permeability and different source positions are investigated.The results show that the fluid parameters and source positions have great influence on the hydromechanical behaviors of the layered media.

Fractal detector design and application in maritime target detection

The fractal properties of sea clutter are proposed and applied to the maritime target detection. Calculation of the measured data shows that, the Hurst exponent of the sea clutter with targets and the sea clutter without targets are different, which enables us to detect low-observable targets within the sea clutter. This paper explains the reason why the Hurst exponent can distinguish the presence or absence of targets in theory and proposes a fractal detector based on the Hurst exponent. Comparing the fractal detector proposed in this paper to the energy detector by the detection results of 140 frames data of the real sea clutter, it is demonstrated that the fractal detection method has a better detection performance. In order to get systemic conclusions, the new sea clutter data with different signal-to-clutter ratios (SCRs) are constructed in the way that add the sea clutter data with targets to the pure sea clutter data. The results show that the fractal detection method has a better performance than the statistical method on detection of maritime targets, especially maritime weak targets with low SCR. ? 1990-2011 Beijing Institute of Aerospace Information.

Reference satellite selection method for GNSS high-precision relative positioning

Selecting the optimal reference satellite is an important component of high-precision relat/ve positioning because the reference satellite directly influences the strength of the normal equation. The reference satellite selection methods based on elevation and positional dilution of precision （PDOP） value were compared. Results show that all the above methods cannot select the optimal reference satellite. We introduce condition number of the design matrix in the reference satellite selection method to improve structure of the normal equation, because condition number can indicate the ill condition of the normal equation. The experimental results show that the new method can improve positioning accuracy and reliability in precise relative positioning.

基于ARIMA和GM(1,1)模型的煤炭市场需求预测研究

"富煤贫油少气"的能源禀赋决定了煤炭在中国能源生产和消费中的绝对主导地位,但长期大量使用煤炭导致了严重的环境问题,东部沿海经济发达地区的生态压力尤为突出,"控煤"已经成为各界共识和现实政策。分析煤炭消费现状,预测未来煤炭需求,是统筹煤炭消费减量替代与经济发展、环境保护的基础和起点。本文从行业、区域等角度分析了中国煤炭消费的主要特点,进而采用ARIMA模型、GM(1,1)模型与组合预测模型,对全国及京津冀、长三角、珠三角地区2017~2025年煤炭消费需求总量进行了预测,发现全国2020年煤炭消费总量能够达到预定目标,但仍面临煤炭消费需求不断扩大的压力;京津冀、长三角、珠三角地区的煤炭消费需求总体上都呈现缓慢持续下降趋势,其中珠三角地区煤炭消费总量和减少速度最为理想,京津冀地区次之,长三角地区煤炭消费总量和减少速度都不理想。最后,本文提出了加大节煤减排力度,进一步淘汰落后产能,严控煤炭增量消费,促进煤炭的清洁利用,鼓励煤炭消费终端"煤改气""煤改电"与清洁能源消费,禁煤和能源替代等政策逐步由京津冀、长三角、珠三角地区向其他重点城市和省区推广。

A simulation study of a high-resolution fast neutron imaging detector based on liquid scintillator loaded capillaries

Background At present,the highest spatial resolution of a fast neutron imaging detector,mainly determined by the range of secondary particles generated by fast neutrons,is about hundreds of microns.In view of the above inherent spatial resolution limitation,a capillary-based scintillation detector that can improve the spatial resolution of fast neutron imaging by recording and reconstructing the recoil proton track was developed.Purpose The purpose of this paper is to develop a detector for recognizing recoil proton events,reconstructing particle track and improving the position resolution with track reconstruction method to reconstruct the position of interaction.Methods The proposed detector consists of a 1000×1000 array of glass capillaries loaded with a high refractive index liquid scintillator.Each glass capillary was 10μm in diameter and 5 cm in length.The recoil protons generated by the incident neutrons move within the detector and produce scintillation light within each capillary that they traverse.The light emitted from the capillary array can be recorded by employing an intensified CCD camera.We used Geant4 to simulate the detector performance and CERN ROOT analysis framework to record physical information of recoil proton,including position,energy deposition in each capillary and track length.Based on Hough transform,a rapid,computerized and efficient proton track reconstruction procedure was developed.Conclusion The recoil proton events display a continuous extended structure.The track reconstruction algorithms can reconstruct individual track precisely,and when the counting rate was relatively low,the track reconstruction results were in good agreement with simulation data.Moreover,for intensive overlap conditions,this algorithm also reconstructs periphery tracks with high rate of accuracy.