用于超宽带信号数据采集的高精度可编程定时器研究

超宽带信号的数字化在很大程度上取决于采样时刻的准确性，因此是否具有高精度的可编程定时器是实现超宽带信号数据采集的关键。本文基于斜波发生器原理实现了高精度可编程定时电路，可编程计数范围为16bit，实际最小定时单位达8ps，折合采样频率高达50GHz，迄今为止尚未有关于同样指标产品的报道。该定时器已应用于作者研制的地质雷达信号数据采集系统中，取得了很好的实际应用效果。     

The boundary layer characteristics in the heavy fog formation process over Beijing and its adjacent areas

By utilizing the Atmospheric Boundary Layer (ABL) observational data made available from the project "973" under the auspices of the Ministry of Science and Technology of the People's Republic of China - entitled the Beijing City Air Pollution Observation Field Experiment (BECAPEX), including the measurements by a wind profiler, captive airships, tower-based boundary layer wind and temperature gradient observational instruments (ultrasonic anemometers and electronic thermometers), air composition samplers, conventional upper-air, surface and Automatic Weather Stations (AWS) observations, this paper herewith analyzes, in a comprehensive manner, the occurrence of a heavy fog event over Beijing in February 2001, including its formation, development, persistence, dynamic and thermodynamic features as well as evolving stratification structures within the boundary layer at different stages. The results suggested: (i) as a typical case of urban heavy fog, before the fog onset over Beijing, a temperature inversion existed in the lower atmosphere, the smokes and the pollutants like SO2 and NO2 had been accumulated at a lower level. Proceeding the fog event, with the increase of SO2 and NO2 concentrations, condensability increased sharply. On the contrary, during the fog process, with increasing condensability, SO2 and NO2 concentrations decreased. This indicated that, acting as condensation nucleus, these accumulated pollutants were playing a key role in catalyzing the fog condensation. (ii) By analyzing mean gradient-, pulsation- and turbulence-distribution patterns derived from the wind measurements taken by the aforementioned tower-based instruments, they all indicated that about 10 hours before the fog onset, a signal foretelling potential strong disturbances in the lower boundary layer was detected, and a significant rise of both mean and disturbance kinetic energies was observed, revealing that the low-level wind shear was strengthened before the fog onset, consequently creating a favorable condition for the outbreak of turbulences. This strong signal seemed to be very meaningful in monitoring and predicting fog occurrence and its development. (iii) Once the fog was in shape, its condensation feedback effects tended to lift the height of temperature inversion layer within the mid and upper levels of the lower atmosphere, which in return determined the fog persistence and restructuring process.     

基于GIS的磁测信号奇异值分解应用研究

本介绍了奇号异值分解的原理．采用混合编程的方式．实现了奇异值分解程序与GIS平台的无缝集成；结合鄂尔多斯盆地某地区铀资源勘查项目．基于GIS平台把磁测数据作为二维实矩阵进行奇异值分解。通过对不同奇异值对应的正交空间基进行组合．在区域场与局部场的分离、砂岩型铀矿弱信息提取及断裂构造识别等应用领域取得了较好的试验效果。     

ADVANCES IN SECOND-ORDER CALIBRATION

Several multivariate methods are now available for the calibration of second-order or hyphenatedinstruments(e.g.GC/MS).When applied to bilinear data,it has been shown that calibration can beperformed in the presence of unknown interferences-a significant advantage over first-order calibration.In this paper,non-bilinear rank annihilation(NBRA),a method which has the potential of handling,second-order non-bi-linear data,is studied through theoretical analysis and computer simulation.It isfound that the second-order advantage can be carried over to non-bilinear data if a property defined asnet analyte rank(NAR)holds for the analyte of interest.The net analyte signal(NAS)is definedaccordingly for second-order calibration and the analogy to and difference from lower-order calibrationare discussed.With NAS,some analytical figures of merit such as signal-to noise ratio,selectivity,sensitivity and limit of determination can be calculated for second order calibration.An application toMS/MS data is also given.     

SY5X型石英信号钟的技术改造

采用全集成化分频全电子讯号输出的方法，对５型钟进行了改造，达到了预期的效果。改造后的５型钟可提供时分秒同步电脉冲信号，时分号串行输出方式，使笔绘记录与光记录兼容。守时精度可达Ⅱ类台站用钟标准。     

主分量变换在油气异常信息提取中的作用

本文介绍了机载细分红外图像增强油气信息的计算机图像处理方法和主分量变换对提取油气信息的作用以及处理后的结果。     

高分辨率勘探与地震仪器

本文较系统地讨论了地震勘探中振幅动态范围与仪器动态范围的基本概念,指出仪器动态范围是开展高分辨率勘探的极为重要的一个基本条件,它要根据浅层强信号与深层高频弱信号的振幅动态范围来设计.如果仪器动态范围小,就录制不上高频信号,必然降低分辨率.文中也简介了在高分辨率地震勘探中如何选取最佳仪器因素的一些做法.     

浅层地震勘探在某工业区工程地质勘察中的应用

本文简要地介绍了浅层地震勘探为解决工程地质问题所采用的野外工作、资料处理与解释的方法技术,以及“五小二高”的工作方法,讨论了结合反射波法开展折射波法的必要性。结果表明,浅层地震对查明基岩埋深及断裂有独到的作用,可为开发区整体工业布局提供比较准确可靠的地质依据。     

GPS现代化信号体制与系统裕量分析

为了加强全球定位系统（GPS）对美军现代化战争的支撑作用、保持其在全球民用导航领域中的领先地位，美国提出了GPS现代化计划。本文总结了GPS现代化信号体制下，新增民码L2C、L5、L1C以及军码M码的特点以及新导航电文的变化。通过理论分析GPS现代化体制下系统裕量的改善状况，说明GPS现代化以后，广播新导航电文，干扰容限将提高8～9dB，系统抗干扰性能将得到较大提升，特别是应用点波束增强技术，M码信号的抗干扰性能将得到很大提升。     

Interannual Thermocline Signals and E1 Nino-La Nina Turnabout in the Tropical Pacific Ocean

One of the fundamental questions concerning the nature and prediction of the oceanic states in the equatorial eastern Pacific is how the turnabout from a cold water state (La Ni?na) to a warm water state (El Ni?no) takes place, and vice versa. Recent studies show that this turnabout is directly linked to the interannual thermocline variations in the tropical Pacific Ocean basin. An index, as an indicator and precursor to describe interannual thermocline variations and the turnabout of oceanic states in our previous paper (Qian and Hu, 2005), is also used in this study. The index, which shows the maximum subsurface temperature anomaly (MSTA), is derived from the monthly 21-year (1980–2000) expendable XBT dataset in the present study. Results show that the MSTA can be used as a precursor for the occurrences of El Ni?no (or La Ni?na) events. The subsequent analyses of the MSTA propagations in the tropical Pacific suggest a one-year potential predictability for El Ni?no and La Ni?na events by identifying ocean temperature anomalies in the thermocline of the western Pacific Ocean. It also suggests that a closed route cycle with the strongest signal propagation is identified only in the tropical North Pacific Ocean. A positive (or negative) MSTA signal may travel from the western equatorial Pacific to the eastern equatorial Pacific with the strongest signal along the equator. This signal turns northward along the tropical eastern boundary of the basin and then moves westward along the north side of off-equator around 16N. Finally, the signal returns toward the equator along the western boundary of the basin. The turnabout time from an El Ni?no event to a La Ni?na event in the eastern equatorial Pacific depends critically on the speed of the signal traveling along the closed route, and it usually needs about 4 years. This finding may help to predict the occurrence of the El Ni?no or La Ni?na event at least one year in advance.