A soft soil treatment technology combining tidal energy and vacuum preloading is proposed in this paper to achieve green municipal construction, energy saving and emission reduction, also to support the national strategic goals of “Carbon Peak and Carbon Neutrality”. This technology making full use of the tidal energy as the preloading with low frequency cyclic load, together with the constant vacuum preloading, enables the soft soil to be drained and consolidated by cyclic compressive stress, accelerates the dissipation of pore water pressure between soil particles, enhances soil compaction, and induces horizontal creep in the soil between prefabricated vertical drain. Consequently, the bearing capacity and stability of the foundation are improved while reducing rebound settlement. Model tests demonstrate that this technology enhances foundation bearing capacity, eliminates most rebound settlement, shortens construction periods, and reduces costs. Based on tidal characteristics, a practical solution using the principle of communicating vessels is proposed to apply tidal energy for soft soil treatment in coastal areas. A research- to-application transformation scheme is also outlined.
Stator asymmetric-paths winding of variable speed pump storage (VSPS) generator-motor can solve the problem of mismatch of unit speed, capacity and outlet voltage. However, different winding connection schemes will lead to the change of magnetomotive force (MMF) asymmetry of each branch, and then affect the electromagnetic force of generator-motor. In order to explore the effect of this winding type on the electromagnetic force, stator asymmetric-paths winding's MMF and electromagnetic force of 336 MW VSPS generator-motor is derived. Waveforms and harmonic contents of the stator asymmetric-paths winding MMF of the equal-pitch and unequal-pitch schemes are analyzed. Under the consideration constraints of factors such as minimizing MMF asymmetry and electromagnetic vibration, a reasonable asymmetric-paths winding scheme with unequal pitch is determined It is concluded that asymmetric-paths winding scheme with pitch of 14-15-16 can effectively weaken the low-order MMF harmonics and reduce the electromagnetic force under the limitation of asymmetric-paths winding form. The finite element model of VSPS generator-motor is further developed, and the electromagnetic force amplitude and spatial and temporal distribution characteristics under 6 winding schemes are calculated to verify the accuracy of the calculation model. The results of the study can provide technical support for the development of localized VSPS generator-motor.
Aiming at the nonlinear characteristics of synchronous reluctance motor(SynRM)caused by electromag-netic saturation and cross coupling of stator inductance,a position sensorless control method combining recursive least square method and pulse vibration high frequency current signal injection was proposed.The principle is to inject high fre-quency sinusoidal current signals with fixed amplitude into the direct axis of synchronous reluctance motor observation co-ordinate system,and extract voltage signals containing rotor position information from the quadrature axis.The recursive least square method with forgetting factor is used to realize the online identification of the motor resistance and inductance parameters.The position sensorless control of motor is realized by proper signal processing method.The simulation and prototype experiments are carried out to verify the accuracy and practicability of the proposed method.
The objective of this study is to discuss the hydrodynamic performance of a wave energy converter using floating panels. A scale model was built in the laboratory at Hohai University, and then was employed to investigate the performance of developed wave energy device. In the physical model, the water surface fluctuation, motion of floating panels and the voltage output of the dynamos are simultaneously measured. Wave reflection coefficient and the energy output can be estimated directly using these measurements. Experimental results show that the present device is effective in controlling the wave energy and reducing the threat to the coastal area. When subjected to longer waves, the average output power and conversion efficiency of the WEC can be up to 0.65 W and 2.73%, respectively. Moreover, it is found that the load of the energy device should be carefully designed to match the local wave climate, in order to obtain the best energy conversion efficiency.
Aiming at the problem that the mechanical properties of mica quartz schist are easy to deteriorate under dry-wet cycles， taking the mica quartz schist which widely distributed in Shiyan， Hubei Province as the research object， uniaxial compression test and electron microscope scanning test were carried out on mica quartz schist samples under different dry-wet cycles to reveal the law and mechanism of mechanical property degradation. The results showed that under the action of dry-wet cycles， the degradation effect of compressive strength and elastic modulus of mica quartz schist were obvious， the degradation rate was fast and the degradation range was large in the early stage， and the degradation rate was slow and the degradation range was low in the later stage. The macroscopic failure modes were gradually controlled by the schistosity planes， which gradually evolved from styles of "X" and "Y" failure to along the schistosity planes failure. The microstructure was characterized by continuous spalling and granulation of flake mineral particles， and the micro cracks and pores were gradually developed， expanded and connected. The mica quartz schist produce secondary minerals， ions and rock cuttings and leave the rock continuously under the dry-wet cycles which promotes the preferential expansion and cracking of schistosity， microcracks and other structural planes， and then degrades the overall mechanical properties of the mica quartz schist.
