关于电磁场边界条件的讨论

对由相同和不同介质所组成的电磁场场域的边界条件进行了整理和讨论.并用积分形式的麦克斯韦方程组对两种介质分界面上的电磁场边值关系进行了简洁推导,以这种普遍的边值关系为基础导出了理想导体表面上的边界条件,并对该边界条件作了详细的说明.

Effect of PMD-induced Pulse Broadening on Sensitivity and Frequency Spectrum

The PMD-induced pulse broadening may cause the degradation ofreceiver sensitivity and has negative effects on the power spectrumof received signals. The expression s of PMO-induced pulse broadeningeffects on receiver sensitivity are derived based on the concept ofman square pulse width. The effects of PMD on the spectrum ofreceived power are analyzed in detail. Finally, the scheme isdiscussed with which the poser of a certain frequency component isextracted as a feedback control signal in a PMD compensation system.

Study on Control Strategy of Sulfur Dioxide Concentration in the Urban Area of Shijiazhuang

Two Gaussian air quality dispersion models, the industrial source complex short-term model (ISCST3) with and without modification have been used to simulate the pollutant concentration distribution in urban areas based on the meteorological data and the emissions distribution of sulfur dioxide. The verified data show that the modified model is more accurate in the urban area of Shijiazhuang. Using the modified model predictions, the control strategies of sulfur dioxide in the urban area have been studied, and the result show that the second long-term (to 2010) strategy can mitigate air pollution significantly and maintain pollution levels within permissible limits.

Detection of the Lehmann discontinuity beneath Tonga with short-period waveform data from Hi-net

The undulation and characteristics of the Lehmann discontinuity at the base of the Low Velocity Zone in the upper mantle are significant for understanding the coupling between the lithosphere and asthenosphere, and corresponding geodynamic processes. Vertical waveform data from six earthquakes with focal depths between 75 and 150 km and magnitudes Mb 5.0–6.0 since 2004 were collected from the short-period Hi-net array. Selected waveform data were processed for each event network pair using the Nth-root slant stack method to retrieve the SdP conversion phases from the possible 220 km(Lehmann) discontinuity. The conversion points related to the SdP phases show that there is a clear and flat velocity interface around 230 km, suggesting that there is a sinking of the Lehmann discontinuity beneath Tonga with no obvious undulation. The 230 km depth of the Lehmann discontinuity in this location could be explained by an hypothesis of transition in the deformation mechanism from dislocation creep to diffusion creep.

Noise decomposition and parameter optimization method for high sensitivity fiber optic gyroscope

A novel random walk coefficient(RWC) model of the interferometric fiber optic gyroscope(IFOG) to decompose fundamental noise sources, namely the shot noise, the excess noise, the thermal noise, and the detection circuit noise, from the overall noise was developed. The coefficients of the model were extracted from the measured RWC instead of by calculating the accurate IFOG parameters, which is simpler and more accurate. The correctness and the accuracy of the model were verified by experiments. Using this model, the RWC of the experimental IFOG was predicted and the quantitative contributions of the noise sources were determined. According to the predicted results, the parameters of the IFOG were optimized. Finally, based on the model, a noise decomposition and parameter optimization method was proposed for high sensitivity IFOG design.

Estimation of tropical cyclone parameters and wind fields from SAR images

The traditional method of Synthetic Aperture Radar(SAR)wind field retrieval is based on an empirical relation between the near surface winds and the normalized radar backscatter cross section to estimate wind speeds,where this relation is called the geophysical model function(GMF).However,the accuracy rapidly decreases due to the impact of rainfall on the measurement of SAR and the saturation of backscattered intensity under the condition of tropical cyclone.Because of no available instrument synchronously monitoring rain rate on the satellite platform of SAR,we have to derive the precipitation of the SAR observation time from non-simultaneous passive microwave observations of rain in combination with geostationary IR images,and then use the model of rain correction to remove the impact of rain on SAR wind field measurements.For the saturation of radar backscatter cross section in high wind speed conditions,we develop an approach to estimate tropical cyclone parameters and wind fields based on the improved Holland model and the SAR image features of tropical cyclone.To retrieve the low-to-moderate wind speed,the wind direction of tropical cyclone is estimated from the SAR image using wavelet analysis.And then the maximum wind speed and the central pressure of tropical cyclone are calculated by a least square minimization of the difference between the improved Holland model and the low-to-moderate wind speed retrieved from SAR.In addition,wind fields are estimated from the improved Holland model using the above-mentioned parameters of tropical cyclone as input.To evaluate the accuracy of our approach,the SAR images of typhoon Aere,typhoon Khanun,and hurricane Ophelia are used to estimate tropical cyclone parameters and wind fields,which are compared with the best track data and reanalyzed wind fields of the Joint Typhoon Warning Center(JTWC)and the Hurricane Research Division(HRD).The results indicate that the tropical cyclone center,maximum wind speed,and central pressure are generally consistent with the best track data,and wind fields agree well with reanalyzed data from HRD.

Thermal Management Controller for Heat Source Temperature Control and Thermal Management

In many heat recovery processes,temperature control of heat source is often required to ensure safety and high efficiency of the heat source equipment.In addition,the management of recovered heat is important for the proper use of waste heat.To this aim,the concept of thermal management controller(TMC),which can vary heat transfer rate via the volume variation of non-condensable gas,was presented.Theoretical model and experimental prototype were established.Investigation shows that the prototype is effective in temperature control With water as the working fluid,the vapor temperature variation is only 1.3℃when the heating power varies from 2.5 to 10.0 kW.In variable working conditions,this TMC can automatically adjust thermal allocation to the heat consumer.