Active fin control for yacht using virtual instrumentation

Virtual instrumentation represents a PC based control system which incorporates manipulation of data acquired from physical transducers in specific ways using a very high level graphical environment. The deployment of this non-traditional approach is demonstrated in this paper by application to design of a fin control system for a yacht. One of the disadvantages of the traditional stabilizer system is the enormous hardware involved in the controllers and instrumentation panels, which make maintenance and troubleshooting difficult. With the help of virtual instrumentation, design of the stabilization controller and instrumentation panels can be carried out much more effectively, in comparison with the traditional hardware approach. A multi-disciplinary approach is adopted here and it consists of the assessment of the hydrodynamic coefficients of the yacht using a numerical package, representation of the hydrodynamic coefficients by suitable polynomial functions, identification of the time dependent fundamental frequency in the roll disturbance signal sample, generation of control signal for an appropriate fin angle based on the fin lift characteristics of the chosen fin and employment of feedback control to maintain the fin at the appropriate angle for maximum control. Once the ship based hydrodynamic coefficients are generated, the entire control algorithm is developed in the virtual instrumentation mode using LabVIEW environment. The effectiveness of the system is verified through laboratory tests on a yacht hull form. The control algorithm permits choice of frequency dependent hydrodynamic coefficients by use of a harmonic distortion analyzer in the virtual instrumentation environment.     

GPS RTK中虚拟基准站技术的运用方法探讨

本文试图寻找一种常规GPS RTK在使用上的新方法,用以解决常规GPS RTK的缺陷。GPS RTK虚拟基准站就是一种在实践中摸索出来的新方法,文中讲述了该方法的理论基础以及野外采集的要求,内业转换的办法,最后对该方法在使用范围及条件上提出了建议。     

虚拟现实技术在城市规划方面的应用研究

介绍了计算机虚拟现实技术概念,探讨了虚拟现实技术应用于城市规划的优势和特点,给出了虚拟现实技术在城市规划设计和规划审批辅助决策中的两个应用研究实例。     

儒家文化对宋代测绘科技的驱动

世界著名的中国科技史专家李约瑟博士在其闻名于世的《中国科学技术史》一书中指出"每当人们研究中国文献中考察任何一种具体的科技史料,往往会发现它的焦点就在宋代。"宋代创造了领先世界的包括测绘科技在内的辉煌科技成就,其中中国四大发明的三大发明:印刷术、指南针和火药等都出现宋代。笔者认为,推动宋代测绘科技发展的一个重要原因就是宋代理学(新儒学)的繁荣和发展。     

Virtual Earth API在Web地图服务中的应用

自2005年地图搜索服务兴起以及Google公司在线地图Google Map的发布,web地图服务成为新一轮竞争热点,微软、雅虎及亚马逊等公司纷纷参与竞争。本文介绍了微软Virtual Earth API最为重要的几个功能及其实现方法,演示了使用Virtual Earth技术建立Web地图服务的方法,为学习微软Virtual Earth制图技术和使用Virtual Earth地图控件提供借鉴。     

Virtual observatories for space and solar physics research

As soon as the first data became available online over the Internet, it was obvious that different sites holding related datasets should appear to the end user as a single data system, even if the data itself is stored at multiple locations. To achieve this objective in the context of continuing parallel development of multiple data centres, in 2003 several actors in the realm of space plasmas created the international consortium Space Physics Archive Search and Extract (SPASE). Since 2005 US participation in SPASE has been supported by NASA, and early in 2006 NASA funded five new Virtual Observatories to cater for different aspects of solar system plasma science. This paper outlines the current status of the SPASE effort, the opportunities it offers, its specificities with respect to other parts of the astronomical virtual observatory, and the possibilities it offers for space weather.

A tile-based method for geodesic buffer generation in a virtual globe

Geometric buffers are important for spatial analysis in many applications of geographic information systems (GISs), such as environmental measurement and management, human health, urban planning, etc. Geometric buffer generation algorithms are well studied in the Euclidean space where the buffer distance is measured by Euclidean metrics; however, very few algorithms are available for generating geometric buffers on the terrain surface in a virtual globe where the buffer distance is measured by geodesic metrics. This paper proposes a tile-based method for geodesic buffer generation according to the characteristics of a virtual globe. It extends the vector tile model (VTM) to organize terrain and vector data, and the XYH algorithm is improved to build geodesic distance fields for terrain meshes. Based on the data organization and the improved XYH algorithm, a geodesic buffer is generated via three main steps: selecting and assembling tiles, updating geodesic distance fields and tracing the boundaries of buffer zones. This method is implemented with multi-scale terrain and vector data, and the experimental results show that it is valid and exact and can be applied in practical applications.     

Synthetic seismic illumination of small-scale growth faults,paralic deposits and low-angle clinoforms: A case study of the Triassic successions on Edgeøya,NW Barents Shelf

Fault activity and sandstone-body geometries and spread, all bear significant weight to understanding the potential hydrocarbon systems on the NW Barents Shelf. Synthetic seismic modelling of onshore sedimentary successions provides insight into the seismic resolution and expression of various sedimentological features on Edgeøya: (i) sandy growth basins in pro-delta mudstones (ii) paralic sedimentary deposits and (iii) low-angle tidally influenced progradational successions.Synthetic modelling suggests that the lithological contrast associated with sand-infilled growth basins in pro-deltaic shales, even with offsets as small as 50–75 m, will create distinct geometries in seismic data. Modelling suggests that while optimal 90° illumination, low frequency bands and more typical sedimentary velocities around 2000 m/s will generate very clear discernible growth faults, the angular lithological contrast should generate discernible features even with the high velocities and typical 20–30 Hz frequency band of seismic sections on the NW Barents Shelf. Comparing to actual seismic data in which multiples, noise and in places overburden are influential, it is possible to identify growth-fault geometries more confidently, and to link them to larger planar fault activity.Modelling other features identified in the paralic sedimentary system it is apparent that many of the massive channel or lenticular shaped sandstone bodies should be identifiable in the actual seismic, although their expression is less distinct and more easily misinterpreted than that of growth faults. It is apparent that features such as igneous intrusions, unless imaged in a “perfect” survey, can be difficult to properly identify, particularly near-vertical connections. The velocity contrast creates strong impedance along horizontal sections, but heavily fractured igneous intrusions with lower velocities could easily be assumed to be isolated sandstone bodies. While the modelling appreciates the overall wedging nature of the successions, the simplified lithological observations onshore cannot predict the probable erosion/condensation contrast associated with low-angle clinoforms which are visible in the seismic data, and hence not reproduce them easily in the models.     

National Virtual Core Library HyLogging data and Ni–Co laterites: a mineralogical model for resource exploration,extraction and remediation

The National Virtual Core Library (NVCL) HyLogging core-scanning system generates mineralogical information from visible, short-wave infrared and thermal infrared spectroscopic data. Currently, HyLogging data are freely available for more than 1500 drill holes via the AuScope Discovery Portal and various Geological Survey websites. With any new technology, there is commonly a lag between provision and take-up by users that can be aided by the publication of case studies in the scientific literature. This paper uses the Mt Davies nickel–cobalt (Ni–Co) laterite deposits, located in northwest South Australia, as a case study to assess the accessibility and representation of HyLogger data and provides an example of its application to all aspects of resource mining: exploration, extraction and processing, and remediation. In this study, we combine HyLogger-derived scalars indicating Fe-oxide and clay mineralogy with historical geological logs and assay data. In general, background Ni grades (<0.1 wt%) are linked to the presence of montmorillonite + hematite ± goethite, moderate grades (0.1–1.0 wt%) are associated with goethite ± nontronite ± saponite ± kaolinite ± montmorillonite, and higher grades (1.0–2.0 wt%) are coincident with goethite and minimal clay alteration, suggesting that goethite hosts Ni mineralisation. Gibbsite, where it occurs, is found immediately above zones of moderate to high Ni grades and may be an important proximal indicator mineral of nickeliferous laterite. Such a case study serves to suggest opportunities for further data modelling and search and query functionality that could facilitate increased use of this important digital geoscience data resource by the Australian minerals industry for all aspects of resource exploitation: exploration, extraction, processing, and environmental remediation.     

The international outer planets watch atmospheres node database of giant-planet images

The Atmospheres Node of the International Outer Planets Watch (IOPW, formerly known as International Jupiter Watch; Russell et al., 1990) intends to encourage and coordinate the imaging observations and study of the atmospheres of the Giant Planets. The main activity of the atmospheres node is to provide an interaction between the professional and amateur astronomical communities maintaining a large database of images of the giant planets (primarily Jupiter and Saturn but with increasing contributions of Uranus and Neptune too). The observational datasets of Jupiter and Saturn correspond to images obtained in the visible range (300 nm-1 μm), during the last decade, most of them performed by amateur observers. We here describe the organization and structure of the database as posted on the Internet and in particular the PVOL software (Planetary Virtual Observatory Laboratory) designed to manage the site in the spirit of the Virtual Observatory projects. We also describe with examples the important role of the amateur-professional collaboration in the study of the atmospheres of Jupiter and Saturn in an epoch of large telescopes and spacecraft observations of both planets.