Analysis of Sluice Foundation Seepage Using Monitoring Data and Numerical Simulation

For sluices built on soil foundations, seepage safety of the foundation is one of the most concerns during operation of sluices. Monitoring data could reflect the real seepage behavior in the foundation, but of which the shortcoming is that generally only the local seepage states can be measured. The seepage field in the whole foundation can be analyzed by numerical simulation. The permeability coefficients of the foundation materials significantly affect the numerical simulation results; however, it is difficult to accurately determine the values of permeability coefficients. In this paper, an approach based on response surface method (RSM) for calibration of permeability coefficients was proposed, and the efficiency of parameter calibration is improved by constructing the response surface equation instead of time-consuming finite element calculation of foundation seepage. The seepage in a sluice foundation was analyzed using monitoring data and numerical simulation. The monitoring data showed that the seepage pressure in the foundation periodically varies with high value in flood season and low value in dry season. After calibration of the permeability coefficients of the foundation materials using the measured seepage pressure, the seepage fields in the foundation for different water levels were numerically simulated to investigate the cause for the periodical variation of the seepage pressure and the seepage safety of the foundation was assessed with the calculated seepage gradients. The methods adopted in this study could be applied to seepage analysis for sluice foundations with similar geologic conditions and antiseepage measures.

X-ray pulsar-based navigation method using one sensor and modified time-differenced measurement

X-ray pulsar-based navigation method using one sensor (XNAVO) could fix the position of satellites by sequentially observing X-ray pulsars at the cost of loading one X-ray sensor, which drops the demand on the loading capability of satellite and is feasible for practice. However, subjected to the current research status of astronomical measure and the radiation mechanism of pulsar, there are unexpected systematic biases in XNAVO, which would greatly worsen the positioning performance of XNAVO. In addition, the systematic biases compensation methods previously proposed for X-ray pulsar-based navigation using three sensors would fail when being applied to XNAVO, due to the sequential observation strategy. In order to solve the problem, this paper introduces a positioning algorithm for XNAVO based on the modified time-differenced measurement. The propagation of systematic biases is analysed, revealing the systematic biases behave a quasi-periodical variation. Thus, a modified time-differenced measurement is proposed in accordance of the quasi-periodicity. A navigation filter that propagates sigma points to generate the improved time-differenced measurement model without linearisation has been given. The results of simulation have shown that the proposed method could reduce the major impact of investigated systematic biases.

Aerodynamic Design and Numerical Analysis of Supersonic Turbine for Turbo Pump

Supersonic turbine is widely used in the turbo pump of modern rocket. A preliminary design method for supersonic turbine has been developed considering the coupling effects of turbine and nozzle. Numerical simulation has been proceeded to validate the feasibility of the design method. As the strong shockwave reflected on the mixing plane, additional numerical simulated error would be produced by the mixing plane model in the steady CFD. So unsteady CFD is employed to investigate the aerodynamic performance of the turbine and flow field in passage. Results showed that the preliminary design method developed in this paper is suitable for designing supersonic turbine. This periodical variation of complex shockwave system influences the development of secondary flow, wake and shock-boundary layer interaction, which obviously affect the secondary loss in vane passage. The periodical variation also influences the strength of reflecting shockwave, which affects the profile loss in vane passage. Besides, high circumferential velocity at vane outlet and short blade lead to high radial pressure gradient, which makes the low kinetic energy fluid moves towards hub region and produces additional loss.

The Nonlinear Dynamics Characteristics of Stock Market and its Variation

The stock market is a kind of complex system with all kinds of interactions. It also shows a nonlinear characteristic. In this paper, we analysed the time series from Dow Jones indexes itself and the time series from its fluctuation difference and extracted its correlation dimension and Lyapunov exponent, which shows a chaotic dynamic characteristic in it. Moreover,we also analysed the variation of chaotic characteristic indexes in long term, and found that the correlation dimension has a quasi-periodical variation and some rapid drops in some specific years.The variation of the correlation dimension can be used to reflect some internal changes in stock market.

Suspended Sediment Transport in Lianyungang Nearshore Area

Hydrological observations at 13-19 stations were conducted synchronically in Lianyungang nearshore area during the spring and half tide in winter and summer respectively. Data of suspended sediment concentrations (SSC), currents and water levels at observation stations were used to study the suspended sediment transport by the method of mechanism decomposition. The advection transport plays an important role during the whole observations, with the direction generally same to the flood current. The tidal pumping transport plays a significant role in the nearshore area, which is the main factor for the periodical variation of SSC. The direction of the tidal pumping transport is mainly toward the land, which indicates that the periodic component of SSC is transport to the land with the form of peaks in the bottom layer. The results may help to improve understanding of the coastal engineering and environmental applications related to sediment transport.