Unbalanced AltBOC: a Compass B1 candidate with generalized MPOCET technique

With the proposed new GNSS signals, enhanced navigation performance is expected in both civil and military applications. However, these new signals introduce the difficulty of combining multiple signal components into a constant-envelope signal. For the Compass B1 band, the problem is to multiplex a QPSK(2) signal and a new multiplexed binary offset carrier (MBOC) signal with a center frequency difference of 14.322 MHz. One approach for multiplexing spreading codes is the phase-optimized constant-envelope transmission (POCET) method proposed for the GPS L1 band. However, only binary spreading codes are considered in POCET. We first generalize the POCET method as a multilevel POCET (MPOCET) algorithm for multilevel coded signals. A new implementation of the alternative binary offset carrier (AltBOC) generator is derived from MPOCET. Secondly, the multiplexing problem for Compass is modeled by MPOCET. Multilevel subcarriers of AltBOC are adopted in the model. As a result, an 8-PSK unbalanced AltBOC (UAltBOC) modulation, which has a QPSK(2) signal at the lower sideband and a TMBOC signal at the upper sideband, is obtained. Simulations for signal model validation and power spectrum analysis are conducted. Numerical results indicate that UAltBOC successfully combines the QPSK and TMBOC signals with only 0.16-dB additional combining loss compared to AltBOC. The proposed MPOCET technique is demonstrated as a unified multiplexing method for navigation signals.     

敏捷开发在软件项目中的实践——以江苏省国土资源厅门户网站建设为例

介绍了敏捷开发方法,并基于此方法设计和实现了江苏省国土资源厅门户网站。该网站功能齐全、结构清晰,具有良好的交互性、可扩展性和可维护性,表现出稳定的性能,并取得了良好绩效。     

Virtual geographic environment-based integrated rockfall risk simulation method for canyon bridges

Bridges located in mountainous areas are vulnerable to rockfall accidents, posing a threat to bridge engineering construction and operation safety in these regions. Under the coupling effect of complex environments and engineering disturbances, integrated rockfall risk simulation has become increasingly important for canyon bridge structural protection in long-term construction and operation phases. One of the main scientific challenges in rockfall risk simulation is studying the interaction between rockfalls and the topography and engineering environments during consecutive contacts. To systematically simulate the integrated bridge rockfall risk, an integrated construction of multivariable elements coupled with rockfall risk environments and scenarios is required. In this article, we proposed a VGE-based integrated rockfall scenario simulation method that uses the “associated representation—integrated modelling—interactional simulation” core strategy. Our method constructs a virtual rockfall risk environment by fusing multisource data to represent rockfall factors that induce rockfall disasters, hazard-forming environments, and elements at risk. We design rockfall scenarios under different bridge engineering construction conditions and extreme environmental conditions to analyze the interactional rockfall risks. The results demonstrate that our method enables a systematic analysis of the potential integrated rockfall risk, providing realistic reference value for the timely and effective disposal of emergencies, and reducing the harm and losses caused by such emergencies.     

新媒体时代基于政务微博新平台建设服务型政府浅议

作为社会化媒体的重要类型,微博已经成为继新闻网站、论坛、博客之后,网络舆论生成的主要载体,＂微博问政＂成为热点和趋势,政务微博也成为政府信息公开、发布权威信息、提供公共服务、加强政民互动、引导网络舆论的重要平台。随着政务微博的快速发展,一系列新问题、新挑战也逐步显现。本文结合国土资源部政务微博的现状,就如何使用政务微博为民服务,提高政务微博应用水平,促进政务微博的健康发展,提升政府公信力,提出了对策建议。     

Multi‐Scale Qualitative Location: A Topology‐Based Model

Qualitative locations describe spatial objects by relating the spatial objects to a frame of reference (e.g. a regional partition in this study) with qualitative relations. Existing models only formalize spatial objects, frames of reference, and their relations at one scale, thus limiting their applicability in representing location changes of spatial objects across scales. A topology‐based, multi‐scale qualitative location model is proposed to represent the associations of multiple representations of the same objects with respect to the frames of reference at different levels. Multi‐scale regional partitions are first presented to be the frames of reference at multiple levels of scale. Multi‐scale locations are then formalized to relate multiple representations of the same objects to the multiple frames of reference by topological relations. Since spatial objects, frames of reference, and topological relations in qualitative locations are scale dependent, scale transformation approaches are presented to derive possible coarse locations from detailed locations by incorporating polygon merging, polygon‐to‐line and polygon‐to‐point operators.     

基于主成分分析的ENVISAT ASAR数据在福建省漳州市香蕉园地提取中的应用(英文)

Banana is one of the main economic agrotypes in Zhangzhou, Fujian Province. The multi-temporal ENVISAT ASAR data with different polarization are used to classify the banana fields in this paper. Principal component analysis (PCA) was applied for six pairs of ASAR dual-polarization data. For its large leaves, banana has high backscatter. So the value of banana fields is high and shows very bright in the 1st component, which makes it much easier for banana fields extraction. Dual-polarization data provide more information, and the VV and VH backscatter of banana show different characters with other land covers. Based on the analysis of the radar signature of banana fields and other land covers and the 1st component, banana fields are classified using object-oriented classifier. Compared to the field survey data and ASTER data, the accuracy of banana fields in the study area is 83.5%. It shows that the principal component analysis provides the useful information in SAR images analysis and makes the extraction of banana fields easier. Supported by the Program for New Century Excellent Talents in University (NCET-05-0573), Fujian Science and Technology Project (No.2006I0018), the Science Project of the Education Department of Fujian Province(No. 2006F5022).     

利用NOAA-AVHRR数据分析1982-2001年间中国植被的动态变化

The authors derived the normalized difference vegetation index (NDVI) from the NOAA/AVHRR Land dataset, at a spatial resolution of 8km and 15-day intervals, to investigate the vegetation variations in China during the period from 1982 to 2001. Then, GIS is used to examine the relationship between precipitation and the Normalized Difference Vegetation Index (NDVI) in China, and the value of NDVI is taken as a tool for drought monitoring. The results showed that in the study period, China’s vegetation cover h...     

建筑群负荷引起的大地水准面起伏及对高程的影响

The paper studies the ground vertical deformation and the geoid undulation caused by loading of neighboring buildings, based on the loading tides theory. The influence on elevation is also considered. The results show that the ground vertical deformation and the geoid undulation both reach millimeter magnitude. Therefore, it is obvious that the building loading significantly affects the precise engineering surveying, and it must be seriously considered in application.