电磁波垂直入射到平面多层旋波煤质的反射

本文首先给出旋波煤质基本公式，然后从传输线理论出发，用阻抗法解决了线极化平面被垂直和入射到多层平面旋波媒质的反射向题，处理方法简单方便，且易理解。文中最后给出了一些数值模拟计算结果，并将其与另外的方法进行了比较．结果吻合得很好。

INFLUENCE AND CORRECTION OF SIGNAL SOURCE DISTORTION TO EVALUATION OF EFFECTIVE BITS OF WAVEFORM RECORDERS

In most effective bits evaluation of waveform recorders, the prerequisite is that there is no signal source distortion, or the distortion can be neglected. But when the distortion can be neglected or how it affects the evaluation when it can't be neglected it is not determined yet. In this paper, the influence of signal source distortion to the evaluation of the effective bits of waveform recorders is discussed, then, the correction method of the effective bits error caused by the distortion influence is given. Finally , the error limit of the effective bits is given and how to selecte the calibrator is introduced. In the end , some simulation results of the new method in test are described.

Study on the wave extreme parameters of the Bohai Sea with the numerical simulation using SWAN

Wave fields in Bohai Sea from 1985 to 2004 were simulated using SWAN wave model by inputting high-resolution hindcast wind fields dataset. Comparisons of wave heights between simulation and observation show good agreement in general. According to the annual extreme values of simulation, this paper gives wave extreme parameters with different return-period for all computation grids in Bohai sea.

A new model to estimate significant wave heights with ERS-1/2 scatterometer data

A new model is proposed to estimate the significant wave heights with ERS-1/2 scatterometer data. The results show that the relationship between wave parameters and radar backscattering cross section is similar to that between wind and the radar backscattering cross section. Therefore, the relationship between significant wave height and the radar backscattering cross section is established with a neural network algorithm, which is, if the average wave period is ≤7s, the root mean square of significant wave height retrieved from ERS-1/2 data is 0.51 m, or 0.72 m if it is >7s otherwise.

Cranny density parameters and porosity measured by elastic wave method in quasi-isotropic cranny rock masses

According to the characteristic of elastic waves propagation in medium and the application of elastic waves method in rock mass engineering, the cranny mass with random crannies was regarded as quasi-isotropic cranny mass. In accordance with the rock rupture mechanics, principle of energy balance and Castiglano＇s theorem, the relationship of effective dynamic parameters of elasticity （E, v, G） and cranny density parameters or porosity was put forward. On this basis, through the theory of elastic waves propagation in isotropic medium, the relationship between the elastic wave velocity and cranny density parameters and porosity was set up. The theoretical research results show that, in this kind of cranny rock masses, there is nonlinear relationships between the effective dynamic parameters of elasticity and wave velocities and the cranny density parameter or porosity; and with the increase of cranny density parameter or porosity of cranny rock masses, the effective dynamic modulus and the elastic wave velocities of cranny rock masses will decrease; and at the same time, when the cranny density parameter or porosity is very small, the effective dynamic modulus of elasticity and the elastic wave velocities change with the cranny density parameter, which can explain the sensitivity of effective elastic parameters and elastic wave velocities to cranny rock masses.

Assimilating Amounts of Precipitation Using a New Four-Dimensional Variational Method

Observations of accumulated precipitation are extremely valuable for effectively improving rainfall analysis and forecast. It is, however, difficult to use such observations directly through sequential assimilation methods, such as three-dimensional variational data assimilation or an Ensemble Kalman Filter. In this study, the authors illustrate a new approach that makes effective use of precipitation data to improve rainfall forecast. The new method directly obtains an optimal solution in a reduced space by fitting observations with historical time series generated by the model; it also avoids the implementation of tangent linear model and its adjoint. A lot of historical samples are produced as the ensemble of precipitation observations with the fully nonlinear forecast model. The results show that the new approach is capable of extracting information from precipitation observations to improve the analysis and forecast. This method provides comparable performance with the standard fourdimensional variational data assimilation at a much lower computational cost.

Brightness Temperature Model of Sea Foam Layer at L-band

Permittivity of a sea foam layer is very important in investigating ocean brightness temperature model. At microwave frequency, the Rayleigh method is developed to estimate the effective permittivity of the sea foam layer. To simplify the tedious calculation of sea foam effective permittivity at L band （1.4GHz）, Pade＇ approximation is adopted to fit the sea foam effective permittivity computed by the Rayleigh method. With this fitting formula, a new brightness temperature model of sea foam layer defined by certain geophysical parameters, such as air volume fraction （AVF）, sea surface temperature （SST）, sea surface salinity （SSS） and thickness of foam layer d, is given. Furthermore, the sensitivities of the brightness temperature model to SST, SSS, d and AVF of a sea foam layer at L band are discussed. The sensitivities are ranked from most to least in the order： （1） d; （2） AVF; （3） SSS; （4） SST. This result indicates that the measurement errors old and AVF have significant impacts on the retrievals of SSS and SST. With the experimental brightness temperature data, the SSS and AFV are retrieved by cost function.

Design of a compact athermalized infrared seeker

In order to meet the application requirement of a certain long wavelength infrared （LWIR） seeker, a small volume, light weight and passively athermalized infrared OR） objective is designed in this paper. The two-lens telephoto struc- ture is adopted by merely using aluminum alloy as the housing material. By balancing the thermo-optical coefficient and thermal expansion coefficient of materials, an athermalized IR seeker with effective focal length of 90 mm and F number of 1.2 is achieved. The whole optical length is 75 ram, and the weight is only 234 g. The objective can remain fine imaging quality under temperature range from -40 ℃ to 60 ℃, which is beneficial to the lightweight design oflR seekers.

Positron Energy Levels in Cd-Based Semiconductors

Using the full potential linearized augmented plane wave FP-LAPW method within local density ap-proximation LDA, we have studied positron diffusion and surface emission in Cd-based semiconductors. This requires the calculation of electron and positron band structures. In the absence of experimental and theoretical data for CdX (X=S,Se,Te) we have treated the Si, which has been studied by several authors, as a test case. Predictive results on positron effective masses, deformation potentials, positron work functions, diffusion constants and positron mobilities are presented for CdX (X=S, Se, Te). Our calculated data for Si are compared with experimental and recent theoretical results.