广电中、短波发射天线保护区可视化

随着社会发展,城市规模不断扩大,广播发射台周边违规兴建的建筑日益增多,给发射台天线、馈线等广电设施的安全和信号传输发射造成严重影响。本文选取中、短波发射天线为研究对象,依据《广播电视设施保护条例》相关规定,研究中、短波发射天线保护区的计算方法,结合地理信息系统技术,以线划图、混合影像图、移动巡查终端等方式首次实现天线保护区可视化,为发射台有效开展天线保护区监管巡查提供有效工具。

监测台中、短波广播频谱收测系统的设计与实现

中、短波广播频谱收测工作是广播监测工作的一个关键环节,它为掌握收测地区频谱资源占用情况提供了数据支撑,为上级管理部门进行中、短波广播频率、频道规划提供了重要依据。为提高频谱收测效率和收测质量,二九二台开发了一款基于Web的频谱收测系统。本文对频谱收测工作进行了介绍,同时结合当前频谱收测工作模式,提出了频谱收测系统的功能需求分析,并对系统架构、实现过程中使用的开发环境和技术及通过本系统进行频谱收测的流程进行了阐述。

中、短波天馈线系统的维护及数据建立

随着我国广播电视节目水平的不断提高,人民对电视广播节目的关注度越来越高。中短波天馈线系统能有效改善电视信号的接收效果,是广播电视传播过程中不可或缺的一部分。本文从中、短波广播以及中、短波天馈线系统的特征,详细的介绍了相关的维护和数据建立。

中、短波天馈线系统的维护及数据建立

伴随着我国人民对于精神文化的追求逐渐提高,我国广播电视进行了不断的创新,使其能够更好的满足我国人民的精神文化追求。中、短波天馈线系统能够提高广播电视接收信号的效率,是广播电视在进行传播时必不可少的构成。本篇文章对中、短波广播进行了简要的介绍,并分析了中、短波系统天馈线系统的特点,对中、短波天馈线系统的维护及数据建立进行了探讨,希望能够为相关工作人员提供理论借鉴依据。

DF100A型PSM短波发射机镇噪板工作原理及调整方法

本文主要介绍了DF100A型短波PSM发射机镇噪板工作原理,及实际工作中的调整方法。

广播交会测向系统建设及其场地选择的研究

文章通过在建设一套中短波广播交会定位测向系统之前,对测向站场地的选择时所遇到的问题,结合实际和案例分析,对广播交会测向系统中测向站的建设场地的选择问题进行了分析与研究。

Seasonal Changes of Energy Fluxes in an Estuarine Wetland of Shanghai,China

The energy budget and regulating factors were investigated over an estuarine wetland during one year of continuous measurement in 2006.The results show that the seasonal changes of the energy fluxes and Bowen ratio(β) were greatly affected by incoming shortwave radiation and canopy growth.During the non-growing season and early-growing season, sensible heat(H) dominated the energy flux, and β could reach a maximum of 2.5, while during most of the growing season, latent heat dominated the energy flux and β fluctuated from 0.4 to 1.0.The energy budget ratio in growing season was about 0.76, and the value would be higher if heat exchange during tidal flooding was in-cluded.During tidal flooding days, β was slightly higher than that at exposure days in most cases.Vegetation cover seems exert little effect on energy partitioning except in March when the standing dead grass intercepted the incoming radiation that might reach the soil surface and reduce the turbulence between soil and atmosphere, thus suppressing the evaporation from the soil though the soil mositure was high at that time.

Observations and Modeling of Incoming Longwave Radiation to Snow Beneath Forest Canopies in the West Tianshan Mountains, China

Forest canopy reduces shortwave radiation and increases the incoming longwave radiation to snowpacks beneath forest canopies. Furthermore, the effect of forest canopy may be changed by complex topography. In this paper, we measured and simulated the incoming longwave radiation to snow beneath forest at different canopy openness in the west Tianshan Mountains, China(43°16'N, 84°24'E) during spring 2013. A sensitivity study was conducted to explore the way that terrain influenced the incoming longwave radiation to snow beneath forest canopies. In the simulation model, measurement datasets, including air temperature, incoming shortwave radiation above canopy, and longwave radiation enhanced by adjacent terrain, were applied to calculate the incoming longwave radiation to snow beneath forest canopy. The simulation results were consistent with the measurements on hourly scale and daily scale. The effect of longwave radiation enhanced by terrain was important than that of shortwave radiation above forest canopy with different openness except the 20% canopy openness. The longwave radiation enhanced due to adjacent terrain increases with the slope increase and temperature rise. When air temperature(or slope) is relatively low, thelongwave radiation enhanced by adjacent terrain is not sensitive to slope(or air temperature), but the sensitivity increases with the decrease of snow cover area on sunny slope. The effect of longwave radiation is especially sensitive when the snow cover on sunny slope melts completely. The effect of incoming shortwave radiation reflected by adjacent terrain on incoming longwave radiation to snow beneath forest canopies is more slight than that of the enhanced longwave radiation.

Assessment of Dust Aerosol Optical Depth and Shortwave Radiative Forcing over the Northwest Pacific Ocean in Spring Based on Satellite Observations

Dust aerosol optical depth (AOD) and its ac-companying shortwave radiative forcing (RF) are usually simulated by numerical models.Here,by using 9 months of Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol product data in combination with Clouds and the Earth's Radiant Energy System Single Scanner Footprint (CERES/SSF) data,dust AOD and its shortwave RF were estimated over the cloud-free north-west (NW) Pacific Ocean in the springs of 2004,2005,and 2006.The results showed that in this region,the mean dust AOD and its shortwave RF were 0.10 and 5.51 W m 2,respectively.In order to validate the dust AOD de-rived by MODIS,results from the Goddard Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) model were also used here.The correlation coefficient between the monthly averaged dust AOD derived by MODIS measurements and the model simulation results was approximately 0.53.Since the estimates of the dust AOD and its shortwave RF obtained in this study are based mainly on satellite data,they offer a good reference for numerical models.

A Parametric Autoregressive Model for the Extraction of Electric Network Frequency Fluctuations in Audio Forensic Authentication

This paper proposes a new method for extracting ENF （electric network frequency） fluctuations from digital audio recordings for the purpose of forensic authentication. It is shown that the extraction of ENF components from audio recordings is realizable by applying a parametric approach based on an AR （autoregressive） model. The proposed method is compared to the existing STFT （short-time Fourier transform） based ENF extraction method. Experimental results from recorded electrical grid signals and recorded audio signals show that the proposed approach can improve the time resolution in the extracted ENF fluctuations and improve the detection of tampering with short alterations in longer audio recordings.