使用简易测试平台检测马哈克扭力仪的性能

本文描述简易测试平台的原理与制作，对马哈克MAIHAK MDS－820型扭力仪检测模拟负载的准确性进行探讨。     

A LATE PLEISTOCENE INTERTIDAL BOULDER PAVEMENT FROM AN ISOSTATICALLY EMERGENT COAST,DUNDALK BAY,EASTERN IRELAND

Late Pleistocene sequences around Dundalk Bay, eastern Ireland, record glaciomarine sedimentation near the margin of a grounded ice lobe around 15 ka BP. A coastal exposure at Cooley Point consists of four major facies deposited outside this ice limit. (1) A basal mud facies deposited from sediment plumes accumulated following the initial ice marginal retreat inland. It contains a well-preserved Arctic microfauna dominated by the foram Elphidium clavatum and the ostracod Roundstonia globulifera. (2) A flat to undulating boulder facies (pavement), mostly one clast thick, is found pressed into the mud and is characterized by bevelled and striated upper clast surfaces. Pavement attributes are a result of intertidal activity in a cold climate. The boulder source is due to rafting by ice floes from glacigenic debris deposited during an ice advance. (3) Laminated sand facies drape the pavement and are a result of variable current activity. (4) The overlying gravel facies is separated from the sand facies by a marine erosion surface. The gravel facies is subaqueous, channelized and is overlain by late glacial raised beach ridges. Locally the gravels have been deformed by ice pressure from partially floating ice floes. Facies changes record terrestrial submergence and provide evidence for changes in relative sea level during part of the last deglacial cycle. The boulder pavement and deformed gravel facies suggest that ice floes and sea ice effects may be more common within stratigraphies along emergent coasts than previously thought, though they have a low preservation potential. Extreme conditions during the deglacial favoured opportunistic microfaunas during mud deposition. This event may be related to a major meltwater event within the Irish Sea Basin.     

A Statistical Model for Stock Assessment of Southern Bluefin Tuna with Temporal Changes in Selectivity

Assessment of the status of southern bluefin tuna (SBT) by Australia and Japan has used a method (ADAPT) that imposes a number of structural restrictions, and is similar to methods used for a number of stocks world-wide. A flexible method for assessment of the SBT population is presented that is much less restrictive and has potentially wide applicability. The three key features are: (1) all fitting to data is within the context of maximum likelihood, (2) catch-at-age data are not assumed to be without error (as in existing methods), but rather to be random variables, while age-specific selectivity is allowed to change over time within the bounds of specific structure, and (3) autocorrelation in recruitment processes is considered within the likelihood framework of the model. While the results suggest the stock has been depleted considerably from its virgin biomass, and are generally consistent with previous assessments, they also indicate that it is not as much below the biomass that will produce maximum suitable yield as previously estimated and that the extent of stock rebuilding necessary may not be as large as has been argued. The available data are shown to provide little information on the steepness parameter of the stock-recruitment function, and hence on sustainable catch levels for the stock.     

A transition in weather over the Agulhas Current

Aircraft observations were used to investigate contrasting weather conditions over the northern edge of the warm Agulhas Current south of George, South Africa, during June 1989. A sea surface temperature front of 7°C over 10 km was observed near 35°S, 23°E. Surface-sensible and latent heat fluxes increased by a factor of five on the warm side. A deepening of the moist unstable layer was indicated by increased equivalent potential temperatures over the warm side. Most significantly, convectively generated turbulence, as inferred from variances in air pressure, increased exponentially with sea surface temperature and surface layer winds doubled south of 35°S. The sea state, initially smooth over the continental shelf, became rough seawards of the northern edge of the Agulhas Current. Numerical model simulations were performed to assess air-sea interactions. Model-simulated thermodynamic variables responded in close agreement with observations, but the increase in cross-frontal winds was not fully resolved. The aircraft observations provide evidence that the Agulhas Current affects the large-scale pressure field and may enhance the rain-bearing capacity of transient weather systems.     

The 26 December 2004 Sumatra tsunami recorded on the coast of West Africa

Analysis of sea-level data obtained from the Atlantic Global Sea Level Observing System (GLOSS) sea-level station at Takoradi, Ghana, West Africa, clearly reveals a tsunami signal associated with the M_w = 9.3 Sumatra earthquake of 26 December 2004 in the Indian Ocean. The tsunami arrived at this location on 27 December 2004 at approximately 01:38 UTC (which is close to the expected tsunami arrival time at that site), after travelling for more than 24 hours. The first wave was negative (trough), in contrast with the South African stations where the first wave was mainly positive (crest). The dominant observed period at Takoradi was about 42 minutes. The maximum trough-to-crest wave height (41cm) was observed on 28 December at 00:15 UTC. There were two distinct tsunami 'bursts', separated in time by about 14 hours, the larger being the second burst. A small residual lowering of the sea level (～15cm) during the tsunami and for several days afterwards, and a delayed (～4.5 days) lowering of seawater temperature (up to ～4.5°C), was observed, possibly indicating the presence of internal waves through the Gulf of Guinea associated with propagating tsunami waves. The prominent tsunami signal found in the Takoradi record suggests that tsunami waves could also be found at other sites off the West African coast.     

Water Supply Maps for the Western Front (Belgium and Northern France) Developed by British,German and American Military Geologists during World War I: Pioneering Studies in Hydrogeology from Trench Warfare

Abstract

Innovations for the British Army during World War I included use of a military geologist to compile 'water supply' maps and to guide well drilling. Between June 1915 and November 1918, W. B. R. King served as a staff lieutenant at General Headquarters of the British Expeditionary Force deployed on the Western Front. He pioneered British development of water supply maps for parts of Belgium and northern France, in several different styles and at scales of 1 : 100 000, 1 : 250 000 and 1 : 40 000. These assisted planning for advances into enemy-occupied territory or the development of water supply infrastructure within the region held ultimately by five British armies: in total about 1,500,000 men with some 500,000 horses and mules, each man/animal requiring on average 10 gallons (45 L) per day of potable water. The maps guided emplacement of over 470 military boreholes to supply drinking water to British forces, especially in provinces underlain by Cretaceous Chalk: Picardy and Artois. German forces also made use of military geologists at the Front, but in much greater number: up to about 300 in total. Water supply tasks were given high priority, and German water supply maps were finally standardized like other medium scale German geotechnical maps at 1 : 25 000. Six geologists were deployed with the American Expeditionary Force late in the war, and for their sector of the Front compiled at least two water supply maps at 1 : 80 000, and 11 at 1 : 50 000 that were supported by explanatory reports. Wartime imperatives thus generated expertise in hydrogeology that became available for civilian use post-war, and laid the foundation for further military development during World War II.     

Artificial Neural Networks as a Method of Spatial Interpolation for Digital Elevation Models

This paper examines the performance of artificial neural networks (ANNs) as a method of spatial interpolation, when presented with irregular and regular samples of elevation data. The results of the ANN interpolation are compared with results obtained by kriging. Tests of spatial bias in the systematic errors contained in each of the neural network-derived DEMs were conducted using four attributes: slope, aspect, average direction and average distance from the nearest sampled value. Based on RMS and other evaluation measures, the accuracy of estimated DEMs from regular and irregular sample distributions using neural networks is lower than the accuracy level derived from kriging. The accuracy level of the ANN interpolators also decreases as the range of elevation values in DEMs increases. As reported in the literature, ANNs are approximate interpolators, and the pattern of under-prediction and over-prediction of elevation values in this study revealed that all estimated values fell within the range of sample elevations. Neural networks cannot predict values outside the range of elevation values contained in the sample, a property shared by other interpolators such as inverse weighted distance.     

Spatial Resolution and Algorithm Choice as Modifiers of Downslope Flow Computed from Digital Elevation Models

This research investigated the dependence of computing downslope flow from digital elevation models (DEMs) on two basic elements of the flow calculation: the spatial resolution of the DEM and the algorithm used to compute the downslope flow, specifically how it defines topographic slope and aspect. Six algorithms for downslope flow and downslope accumulation were implemented in MATLAB using different assumptions about components of the computation from the terrain analysis literature. We analyzed the results of downslope flow statistically, thresholded the values to yield streams, and compared the different results with the actual surface streams in the National Hydrographic Database. We repeated the computations using DEMs of 3-m, 30-m, and 90-m resolutions, covering a test area near Santa Barbara, California. We conclude that downslope flow computations are overestimates, and that they are fraught with critical algorithmic assumptions and scale effects. They should be approached with great caution in GIS-based analyses.     

Assessment of Shuttle Radar Topography Mission Elevation Data Based on Topographic Maps in Turkey

Depending on scale, topographic maps depicting the shape of the land surfaces of the Earth are produced from different data sources. National topographic maps at a scale of 1:25 000 (25K maps) produced by General Command of Mapping are used as the base map set in Turkey. This map set, which consists of approximately 5500 sheets, covers the whole country and is produced using photogrammetric methods. Digital Elevation Models (DEMs) created from these maps are also available. Recently, another data source, Synthetic Aperture Radar (SAR) interferometric data, has become more important than those produced by conventional methods. The Shuttle Radar Topography Mission (SRTM) contains elevation data with 3 arc-second resolution and 16 m absolute height error (90 percent confidence level). These data are freely available via the Internet for approximately 80 percent of the Earth's land mass. In this study, SRTM DEM was compared with DEM derived from 25K topographic maps for different parts of Turkey. The study areas, each covering four neighboring 25K maps, and having an area of approximately 600 km², were chosen to represent various terrain characteristics. For the comparison, DEMs created from the 25K maps were obtained and organized as files for each map sheet in vector format, containing the digitized contour lines. From these data, DEMs in the resolution of 3 arc-second were created (25K-DEM), in the same structure as the SRTM DEM, allowing the 25K-DEMs and the SRTM DEM to be compared directly. The results show that the agreement of SRTM DEM to the 25K-DEM is within about 13 m, which is less than the SRTM's targeted error of 16 m. The spatial distribution of the height differences between SRTM-DEM and the 25K-DEM and correlation analysis show that the differences were mainly related to the topography of the test areas. In some areas, local height shifts were determined.     

Exploring the Hidden Potential of Common Spatial Data Models to Visualize Uncertainty

Common Spatial Data Models (SDMs) such the vector, raster, and quadtree have well understood and widely practiced conventions of storage and visualization. This paper explores what happens when the conventions of visualization are not strictly adhered to, and the SDMs are used in an atypical fashion. A framework based on a quasi similarity measure is presented, which quantifies (in terms of "distance") the relationship between the storage format and the visualization output, following an accepted protocol. This research used a transformation process (Tp) to define this distance. Then, the atypical use of the quadtree SDM to represent choropleth spatial boundary uncertainty and attribute uncertainty was quantified using the same framework. This research shows that if a SDM is used outside of its original context, then the distance between the storage format and its visual output can alter; in our case, the distance decreased. This result was interpreted as evidence for the creation of a new spatial data structure. The formalization of the relationship between an SDM and its visual output will be valuable for future exploration of the non-conventional visualization of common SDMs.