低纹波低功耗自动控制APD偏压电路

全站仪红外测距系统接收电路采用APD雪崩光电二极管作为接收器件,它的精度对后级的信号处理及测量精度起着决定性的影响,针对其高精度要求,提出两种APD偏压电路。前者采用交流反馈网络消除冲击电压,提高了开关管寿命,采用三级滤波网络极大的降低了电路纹波从而提高了测量精度;后者采用专用芯片控制电路电源,使储能电感处于非连续工作状态,大大降低了电路的功耗,同时采用4个变容二极管既升高了电压,又减小了纹波。两种电路均具有可自动控制,且能对APD的内部增益进行全范围补偿的优点。实践证明,电路工作性能理想,提高了测距精度。     

VLBI技术测月的数学模型探讨

近年各国已纷纷制定测月计划,采用何种技术对月球进行定位,变得尤为重要。本文通过对VLBI技术特点进行分析,VLBI是目前大地测量中精度最高的技术手段,但只适用于深空探测,因为深空射电信号到达地面时,可看作平行信号。本文针对VLBI技术特点及数学模型,对存在不可忽略视差的VLBI测月模型,通过级数展开,解决月面射电信号到达地球时的视差问题,并顾及地球自转得出最终数学模型,通过站间一次差分消除钟差等影响,得出VLBI对近轨天体(月球)表面射电源定位的数学模型。     

Introducing a Novel Approach for Oil-Oil Correlation based on Asphaltene Structure:X-ray Diffraction

Asphaltenes have always been an attractive subject for researchers. However, the application of this fraction of the geochemical field has only been studied in a limited way. In other words, despite many studies on asphaltene structure, the application of asphaltene structures in organic geochemistry has not so far been assessed. Oil-oil correlation is a well-known concept in geochemical studies and plays a vital role in basin modeling and the reconstruction of the burial history of basin sediments, as well as accurate characterization of the relevant petroleum system. This study aims to propose the X-ray diffraction (XRD) technique as a novel method for oil-oil correlation and investigate its reliability and accuracy for different crude oils. To this end, 13 crude oil samples from the Iranian sector of the Persian Gulf region, which had previously been correlated by traditional geochemical tools such as biomarker ratios and isotope values, in four distinct genetic groups, were selected and their asphaltene fractions analyzed by two prevalent methods of XRD and Fourier-transform infrared spectroscopy (FTIR). For oil-oil correlation assessment, various cross-plots, as well as principal component analysis (PCA), were conducted, based on the structural parameters of the studied asphaltenes. The results indicate that asphaltene structural parameters can also be used for oil-oil correlation purposes, their results being completely in accord with the previous classifications. The average values of distance between saturated portions (dr) and the distance between two aromatic layers (dm) of asphaltene molecules belonging to the studied oil samples are 4.69? and 3.54?, respectively. Furthermore, the average diameter of the aromatic sheets (La), the height of the clusters (Lc), the number of carbons per aromatic unit (Cau), the number of aromatic rings per layer (Ra), the number of sheets in the cluster (Me) and aromaticity (fa) values of these asphaltene samples are 10.09?, 34.04?, 17.42?, 3.78?, 10.61? and 0.26?, respectively. The results of XRD parameters indicate that plots of dr vs. dm, dr vs. Me, dr vs. fa, dm vs. Lc, Lc vs. La, and fa vs. La perform appropriately for distinguishing genetic groups. A comparison between XRD and FTIR results indicated that the XRD method is more accurate for this purpose. In addition, decision tree classification, one of the most efficacious approaches of machine learning, was employed for the geochemical groups of this study for the first time. This tree, which was constructed using XRD data, can distinguish genetic groups accurately and can also determine the characteristics of each geochemical group. In conclusion, the obtaining of structural parameters for asphaltene by the XRD technique is a novel, precise and inexpensive method, which can be deployed as a new approach for oil-oil correlation goals. The findings of this study can help in the prompt determination of genetic groups as a screening method and can also be useful for assessing oil samples affected by secondary processes.     

联合热红外与微波的作物辐射方向性模型研究

热红外遥感提供地表表层辐射信息为主,被动微波遥感可更好地提供植被和土壤背景垂直结构的辐射信息。结合热红外与被动微波遥感的优势协同反演植被和土壤组分温度是提高组分温度反演精度的一种思路。本文在对热红外辐射传输模型和微波辐射模型进行比较的基础上,构建均匀作物的统一场景,将统一场景的参数分为直接参数和间接参数。基于统一场景,修改微波辐射模型的场景结构及叶倾角分布,并增加组分温度参数以计算辐射亮温,最终构建热红外与微波辐射联合模拟模型(UEasmmes模型)。针对均匀玉米作物,利用UEasmmes模型进行联合模拟,分析了组分温度、组分发射率、叶面积指数LAI及叶倾角分布LAD对热红外与微波的方向性亮温DBT的敏感性响应差异。分析结果表明:协同热红外与被动微波遥感反演植被和土壤组分温度是可行的,但对于如何克服组分发射率、LAI及LAD对植被有效发射率的影响而导致的微波辐射亮温变化以及实现热红外表皮温度与微波等效温度之间的转化仍是需要深入研究和探讨的问题。     

TROPICAL CYCLONE GENESIS EFFICIENCY：MID-LEVEL VERSUS BOTTOM VORTEX

Cloud resolving Weather Research and Forecasting(WRF)model simulations are used to investigate tropical cyclone(TC)genesis efficiency in an environment with a near bottom vortex(EBV)and an environment with a mid-level vortex(EMV).Sensitivity experiments show that the genesis timing depends greatly on initial vorticity vertical profiles.The larger the initial column integrated absolute vorticity,the greater the genesis efficiency is.Given the same column integrated absolute vorticity,a bottom vortex has higher genesis efficiency than a mid-level vortex.A common feature among these experiments is the formation of a mid-level vorticity maximum prior to TC genesis irrespective where the initial vorticity maximum locates.Both the EMV and EBV scenarios share the following development characteristics:1)a transition from non-organized cumulus-scale(~5 km)convective cells into an organized meso-vortex-scale(~50 to 100 km)system through upscale cascade processes,2)the establishment of a nearly saturated air column prior to a rapid drop of the central minimum pressure,and 3)a multiple convective-stratiform phase transition.A genesis efficiency index(GEI)is formulated that includes the following factors:initial column integrated absolute vorticity,vorticity at top of the boundary layer and vertically integrated relative humidity.The calculated GEI reflects well the simulated genesis efficiency and thus may be used to estimate how fast a tropical disturbance develops into a TC.     

碱改性凹凸棒石对土壤中镉化学形态及环境风险的影响

凹凸棒石进行碱改性后性能的提高,为其钝化修复重金属污染土壤提供重要基础.本文采用不同比例的氢氧化钠对凹凸棒石进行改性,利用扫描电镜(SEM)、X射线衍射(XRD)和傅里叶变换红外光谱法(FTIR)分析改性前后凹凸棒石理化特性的变化,并在人工配制的重金属Cd污染土壤上进行钝化实验,研究氢氧化钠改性凹凸棒石对污染土壤中Cd...     

大口径望远镜反射面日照温度场效应实验研究

针对大口径射电望远镜主反射面在日照作用下产生温度梯度及形变问题,建立了完整的温度测量及精度评估的系统。在特定的测量条件下,利用红外热像仪测量了望远镜主反射面的温度,获得了不同时刻的温度分布情况,并得到最大温差为7.8℃。采用全息法分析主反射面的精度变化情况,得到由于温度变化导致的最大误差为0.33 mm。结果表明:温度对望远镜主反射面的精度影响较大,需采取合适的测试系统实时监测温度,并调整主反射面板以提高精度。