RADIOACTIVE OR NATURAL TRACER。TECHNIQUES FOR LEAK DETERMINING OF DAM ABUTMENT

Infiltration and localization of preferential infiltration zones at the dam abutment are measured using radioactive tracer tests of flow in boreholes,meanwhile interconnection between boreholes and the energing water points is analysed.The theory and practice of radioactive tracer synthetic detective method are described to give methods and calculation formulae used under the condition of stable flow in single well to measure permeability coefficient and hydrostatic heads.Major single hole techniques including measurement for seepage line,velocity,rate of seepage flow and relationship of recharge of groundwater in aquifers are introduced briefly.The possibilities offered by natureal tracers are analysed,uincluding electric-conduct,pH-value and temperature of water as well as stable isotopes(D,^18O) and tritium.Furthermore,the sensibilities of this theory and methods were confirmed by detecting seepage flow field of Xinanjiang Dam.     

全数字高清晰度电视中8—VSB传输系统

分析了全数字高清晰度电视（ＨＤＴＶ）中地面广播信道的干扰及抑制措施，给出了抑制同频干扰的梳状滤波器的设计方法和ＨＤＴＶ中８－ＶＳＢ基本原理及传输方案，并基于传信率１／Ｔ＝２３．５４８Ｍｂｐｓ的８－ＶＳＢ作了计算机模拟。     

松材线虫病害高光谱时序与敏感特征研究

采用高光谱仪ASD FieldSpec Pro FR,连续观测了健康和发病马尾松针叶的时序高光谱,分析了松材线虫病害光谱的时序特征、敏感时期和敏感特征。结果表明:与健康马尾松相比,病害马尾松时序光谱差异较大;病害首先造成红边区域内光谱反射率减低,然后再出现红边蓝移的2阶段光谱变化规律;感染松材线虫的马尾松9月初已经出现了病态植被典型的光谱特征;近红外平台内最大的一阶微分值、红边内一阶微分的总和(SDr)与蓝边内一阶微分的总和(SDb)的比值等是指示病害发生的显著性高光谱特征。     

A Cellular Automata Based Rainfall-Runoff Model for Urban Inundation Analysis Under Different Land Uses

Recently many runoff models based on cellular automaton (CA) have been developed to simulate floods; however, the existing models cannot be readily applied to complex urban environments. This study proposes a novel rainfall-runoff model based on CA (RRCA) to simulate inundation. Its main contributions include a fine runoff generation process that considers 12 urban scenarios rather than a single land use type and the confluence process determined by the new transition rules considering water supply and demand (WS-WD transition rules). RRCA was compared with another CA based flood model (E2DCA). With the benchmark model, the results showed that there was good agreement, with an R-squared greater than 0.9, and that RRCA was more sensitive to waterlogging levels than E2DCA. Furthermore, the simulated vegetation interception, infiltration and drainage processes had varying degrees of impact on waterlogging. Corresponding measures can be taken in urban flood management according to the identification of areas experiencing drainage difficulties.

     

电位滴定法研究~(99)Tc-HMDP和~(99)Tc-HEDP中Tc的氧化态

~(99)Tc-HMDP和~(99)Tc-HEDP溶液是在相应的螫合剂存在下,用过量SnCl_2还原~(99)TcO_4-制得。用标准I_2液对SnCl_2进行了剩余量电位滴定,确定了在pH～3的介质中,~(99)Tc-HMDP和~(99)Tc-HE-DP中~(99)Tc的氧化态均为+4。全部实验在N_2气流中进行。~(99)Tc-HMDP和~(99)Tc-HEDP的紫外光谱表明:在用I_2滴定的过程中,~(99)Tc只处于一种氧化态+4;将它们放置在空气中,一小时后仍较稳定。     

Toward practical adoption of i* framework: an automatic two-level layout approach

Requirements Engineering - Bridging the gap between academia and industry is an important issue to promote the practicality of i* framework. Researchers have been dealing with this issue from...     

基于双闭环系统的起重机位置控制技术研究

传统的起重机位置控制技术大多是以位移或速度为反馈量构成的单闭环控制,只能对系统的一个状态量进行控制,易造成系统的超调、振荡,难以实现真正意义上的位置控制;研究采用位移和速度的双闭环位置控制技术[1],以位移环为外环、速度环为内环,位移环根据位移的当前值与给定值的差,通过位移调节器给速度环提供给定速度,速度环通过速度调节器控制系统的运动速度,最终实现对系统的位置控制;通过对单闭环控制和双闭环控制的仿真结果对比分析,双闭环系统的位置和速度的控制精度均比单闭环精度高,最后通过实验,证明了双闭环系统在实践上的可行性。     

MMA7361L的高精度角度检测平台设计

倾角是许多控制系统中需要测量的一个重要参数。针对倾角测量,设计了一种基于ARM微控制器和加速度传感器的角度测量平台。该平台采用基于ARMCortex—M3内核的STM32F103VE为数据处理的核心,利用高精度加速度传感器MMA7361L为测角传感器,同时配置液晶屏和小型键盘实现了人机交互。该平台具有测量精度高、灵敏度高、价格低的特点,应用前景广阔。     

基于uIP与AJAX的动态Web服务器设计

针对远程信息监测系统中数据的实时采集更新问题,将AJAX和CGI应用到嵌入式Web服务器的设计中,实现了服务器与浏览器之间的动态信息交互。本文首先分析了uIP协议栈,并在协议栈之上设计了Web服务器,然后利用CGI服务程序处理来自客户端的XMLHttpRequest对象请求,实现动态Web功能。现场实验结果表明,嵌入式Web服务器降低了服务器端的资源开销,提高了响应速度。     

单片机教学改革初探

本文针对目前单片机课程的教学现状,提出了一些关于单片机教学改革的措施和方法。