GML Server的设计与实现

利用GML解决空间数据共享问题是当前的研究热门,在GML核心模式的基础上定制了大量的GML应用模式,GML数据大量涌现。然而缺少专门存储管理和发布GML数据的平台。本文针对OGC的服务规范,在对当前GIS服务器技术研究基础上,提出了GML Server服务平台,设计了一整套基于GML数据的Web服务系统。利用当前开源软件进行扩展,系统实现了发布基于GML数据的WFS,WMS,WCS服务及其各种空间分析查询功能。     

时间间隔计数器的研制

介绍了一种新研制的时间间隔计数器,并给出了实验结果和误差的定性分析。通过斜坡发生器,高速采样保持,A／D转换和器件时延平衡等电路的使用,该计数器在5MHz频标下可达到较高的测量精度和分辨率,该计数器亦可用于频率的精确测量。     

BPM短波授时台新的时频监控系统

陕西天文台BPM短波授时台搬迁后 ,其时频控制与监测工作从原BPM发播钟房转为由监控室监控钟房承担。介绍了新的控制系统原理与方法 ,并对发播的BPM时号精度作了分析。     

An improved time series model for monthly stream flows

This study aims to develop an improved time series model to overcome difficulties in modeling monthly short term stream flows. The periodic, serial dependent and independent components of the classical time series models are improved separately by information transfer from a surrounding long term gauging station to the considered flow section having short term records. Eventually, an improved model preserving the mathematical model structure of the classical time series model, while improving general and monthly statistics of the monthly stream flows, is derived by using the improved components instead of the short term model components in the time series modeling. The correlative relationships between the current short term and surrounding long term stations are used to improve periodic and serial dependent behaviors of monthly flows. Independent components (residuals) are improved via the parameters defining their theoretical probability distribution. The improved model approach is tested by using 50 year records of Göksu-Himmetli (1801) and Göksu-Gökdere (1805) flow monitoring stations located on the Ceyhan river basin, in south of Turkey. After 50 year records of the station 1801 are separated into five 10 year sub series, their improved and classical time series models are computed and compared with the real long-term (50 year) time series model of this station to reveal efficiencies of the improved models for each subseries (sub terms with 10 year observation). The comparisons are realized based on the model components, model estimates and general/monthly statistics of model estimates. Finally, some evaluations are made on the results compared to the regression method classically applied in the literature.     

Time-series modeling of reservoir effects on river nitrate concentrations

Saylorville Reservoir is a 24.1 km² impoundment of the Des Moines River located approximately 10 km north of the City of Des Moines, Iowa, USA. Surface water from the Des Moines River used for drinking water supply is impaired for nitrate–nitrogen. Monthly mean nitrate concentration data collected upstream and downstream of the reservoir for a 30-year period (1977–2006) were selected for time-series analysis. Our objectives were to (1) develop a model describing nitrate concentrations downstream of the reservoir as a function of the concentrations entering the reservoir and (2) use the model to provide a 1-month ahead forecast for downstream water quality. Results indicated that downstream nitrate can be effectively modeled using a transfer function approach that utilized inflow concentrations during the current and previous month as input variables. Inflow concentrations were modeled using an AR(20) model, with the higher order model consistent with temporal correlation noted by others. The transfer function model suggested that the reservoir is reducing nitrate concentrations by 22 ± 6%, a reduction that greatly exceeds previous estimates. Monthly nitrate forecasted with the model were nearly all within a 95% prediction interval of their actual measured values and did not appear greatly affected by flow variations.     

Coherence between lake ice cover, local climate and teleconnections (Lake Mendota, Wisconsin)

Ice duration has shortened and the ice-off date has become earlier for Lake Mendota from 1905 to 2000 as air temperatures have warmed and snowfall has increased. In addition, the ice record has cyclic components at inter-annual and inter-decadal scales. We examined the frequency domain relations between ice, local climate and the teleconnections, Southern Ocean Oscillation (SOI), Pacific Decadal Oscillation (PDO), North Atlantic Oscillation (NAO), and Northern Pacific Index (NP), through a three-tiered analysis of coherence. The coherence results provide evidence of linear relations between the three levels at inter-annual and inter-decadal frequencies. Of the three local climate variables analyzed, namely temperature, snowfall and snow depth, temperature is the variable that most significantly affects ice duration and ice-off date, at both inter-annual and inter-decadal frequencies. The most significant effect of teleconnections on local climate are the effects of PDO on snowfall and snow depth, and SOI on temperature, at inter-annual frequencies, and the effect of NAO on snowfall at inter-decadal frequencies. The teleconnections that most significantly affect ice-cover duration and ice-off date, particularly at inter-decadal frequencies, are the PDO and the NAO. The influence of PDO on ice-cover appears to be transmitted through temperature, while the influence of the NAO appears to be transmitted through temperature and snowfall. A cascading set of links between teleconnections, local climate, and lake ice explain some, but not all, of the dynamics in these time series.     

Nonlinear response analyses of a soil–structure interaction system using transformed energy transmitting boundary in the time domain

The energy transmitting boundary used in programs such as FLUSH and ALUSH is a very accurate and useful technique for the earthquake response analysis of soil–structure interaction systems. However, it is applicable only to linear analyses or equivalent linear analyses, because it can be calculated only in the frequency domain. The author has proposed methods for transforming frequency-dependent impedance into the time domain. In this paper, an earthquake response analysis method for a soil–structure interaction system, using the energy transmitting boundary in the time domain, is proposed. First, the transform of the transmitting boundary matrices to the time domain using the methods proposed by the author is studied. Then, linear and nonlinear time history earthquake response analyses using the boundary are performed. Through these studies, the validity and efficiency of the proposed methods are confirmed.     

地球系统科学数据共享网络平台的设计和开发

“地球系统科学数据共享网”是国家科学数据共享工程的试点之一,同时也是国家科技基础条件平台的组成部分,其目的是为地球系统科学的基础和前沿研究提供数据支撑服务。该系统平台(GEODATA)是一个分布式的数据交换体系,总体设计思路是利用元数据整合分散的地学数据资源,通过业务逻辑的技术封装提供地学数据的网络共享。设计的GEODATA体系是一个五层结构,即门户层、共享业务层、核心服务层、资源管理层和网络平台层,具体的业务逻辑处理功能被分解为13个功能模块。GEODATA的研发技术路线包括总中心和分中心两大部分,其中总中心采用“地学数据超市”理念进行功能组织;分中心基于Web Services技术,采用分布式数据管理的模式进行设计。两者的业务逻辑基于元数据的生命周期被串联成一个有机的整体。GEODATA原型系统利用J2EE开发,实现跨平台部署。应用实践表明这种平台构架模式非常适用于地球系统科学的学科特点。     

国际前寒武纪划分最新研究动态——国际前寒武纪地层分会Fremantle工作会议简介

新一届国际前寒武纪地层分会在32届国际地质大会期间正式成立,其任务是确定宙(Eon)和代(Era)级年代界线、建立完整的和自然的国际前寒武纪地质年表.分会现有15名投票委员和若干通讯委员.