It is proved that the bearing history display is an effective method to detect weak signal. There is an interface between multibeam data and brightness modulation display system in digital sonar. The system gain obtai...It is proved that the bearing history display is an effective method to detect weak signal. There is an interface between multibeam data and brightness modulation display system in digital sonar. The system gain obtained from signal processing system may be lost in this interface. A right choice of conversion algorithm will reduce this lose to minimum. The Grey Scale Conversion ( GSC) algorithm proposed in this paper is a real time digital operation technique. This technique can be used to improve the detection ability for weak signals, in the meantime there is no serious effect on strong signal detection. The method described in this papr is easy to implement in hardware. The simulation results with a computer show a good agreement with the theoretical analysis. A brief outline of hardware design is also illustrated.展开更多
Studies on soil wind erosion began with single factors affecting soil wind erosion; with increasing quantities of data being accumulated,the wind erosion equation(WEQ),the revised wind erosion equation(RWEQ),the wind ...Studies on soil wind erosion began with single factors affecting soil wind erosion; with increasing quantities of data being accumulated,the wind erosion equation(WEQ),the revised wind erosion equation(RWEQ),the wind erosion prediction system(WEPS),and other soil wind erosion models have been successively established,and great advances have been achieved.Here we briefly review the soil wind erosion research course and analyze the advantages and disadvantages of the current soil wind erosion models.From the perspective of the dynamics of wind erosion,we classified the factors affecting soil wind erosion into three categories,namely,wind erosivity factors(WEF),soil antierodibility factors(SAF),and roughness interference factors(RIF).We proposed the concept of a standard plot of soil wind erosion to solve the problem of uncertainty of the soil wind erosion modulus on a spatial scale,and provided methods to set similarity conditions in wind tunnel simulation experiments and to convert the spatial scale of the wind erosion modulus from the standard plot to a large scale field.We also proposed a conceptual model on the basis of the dynamics of soil wind erosion with the theoretical basis that wind produces a shear force on the soil surface.This shear force is partitioned by barely erodible soil surfaces and roughness elements on the ground,and the amount of soil loss by wind should be calculated by comparing the shear force of the wind on barely erodible soil surfaces with the anti-erosion force of the surface soil.One advantage of this conceptual model is that the calculated soil wind erosion modulus is not subject to changes of spatial scale.Finally,we recommended continual improvement of the existing models while also establishing new models.展开更多
文摘It is proved that the bearing history display is an effective method to detect weak signal. There is an interface between multibeam data and brightness modulation display system in digital sonar. The system gain obtained from signal processing system may be lost in this interface. A right choice of conversion algorithm will reduce this lose to minimum. The Grey Scale Conversion ( GSC) algorithm proposed in this paper is a real time digital operation technique. This technique can be used to improve the detection ability for weak signals, in the meantime there is no serious effect on strong signal detection. The method described in this papr is easy to implement in hardware. The simulation results with a computer show a good agreement with the theoretical analysis. A brief outline of hardware design is also illustrated.
基金supported by the National Natural Science Foundation of China(Grant No.41330746)
文摘Studies on soil wind erosion began with single factors affecting soil wind erosion; with increasing quantities of data being accumulated,the wind erosion equation(WEQ),the revised wind erosion equation(RWEQ),the wind erosion prediction system(WEPS),and other soil wind erosion models have been successively established,and great advances have been achieved.Here we briefly review the soil wind erosion research course and analyze the advantages and disadvantages of the current soil wind erosion models.From the perspective of the dynamics of wind erosion,we classified the factors affecting soil wind erosion into three categories,namely,wind erosivity factors(WEF),soil antierodibility factors(SAF),and roughness interference factors(RIF).We proposed the concept of a standard plot of soil wind erosion to solve the problem of uncertainty of the soil wind erosion modulus on a spatial scale,and provided methods to set similarity conditions in wind tunnel simulation experiments and to convert the spatial scale of the wind erosion modulus from the standard plot to a large scale field.We also proposed a conceptual model on the basis of the dynamics of soil wind erosion with the theoretical basis that wind produces a shear force on the soil surface.This shear force is partitioned by barely erodible soil surfaces and roughness elements on the ground,and the amount of soil loss by wind should be calculated by comparing the shear force of the wind on barely erodible soil surfaces with the anti-erosion force of the surface soil.One advantage of this conceptual model is that the calculated soil wind erosion modulus is not subject to changes of spatial scale.Finally,we recommended continual improvement of the existing models while also establishing new models.
