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OPTIMAL INTERPOLATION AND ISARITHMIC MAPPING OF SOIL PROPERTIES III CHANGING DRIFT AND UNIVERSAL KRIGING 总被引:2,自引:0,他引:2
Universal kriging is a form of interpolation that takes account of local trends in data when minimizing the error associated with estimation. The presence of such trends, or drifts as they are known, is identified qualitatively, and their form found quantitatively by structural analysis, which simultaneously estimates semi-variances of the differences between the drift and actual data. The resulting semi-variograms are then used for the interpolation. The method was applied to measurements of electrical resistivity made in the soil at 1 m intervals at Bekesbourne, Kent. Analysis showed that the data could be adequately represented as a series of linear drifts over distances of 4 m to 8 m and with negligible nugget variance. Semi-variances of residuals from the drift were computed, and used to krige missing values and so complete an isarithmic map of the site. The method is by no means universally applicable in soil survey, mainly because of the large nugget variances usually encountered. These effectively prevent any distinction between constant and changing drift. They arise in part because measurements are made on small widely separated volumes of soil. Universal kriging is likely to be profitable only where measurements are made on contiguous volumes of soil or after substantial bulking. 相似文献
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Recurrent facilitation in the cat's spinal cord has been studied in deep peroneal and quadriceps motoneurons with the use of intracellular recording. The presence of facilitation was indicated by several criteria, among them increased firing index of the cells or decreased latency of firing. In many, but not all, facilitated cells the conditioning volley caused a small visible depolarization. Subthreshold synaptic potentials were frequently increased in magnitude by the conditioning volley, which also increased the effectiveness of a stimulus applied through the microelectrode. Facilitation was found in a large percentage of the motoneurons investigated and was clearly able to bring about pronounced changes in the excitability and firing behavior of these cells. 相似文献
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RICHARD BURGESS BVM&S STEVE ELDER BS MS PhD RON McLAUGHLIN DVM DVSc Diplomate ACVS PETER CONSTABLE BVSc MS PhD Diplomate ACVIM 《Veterinary surgery : VS》2010,39(2):208-215
Objective— To compare biomechanical properties of 3 new generation polyethylene sutures (FiberTape [FT], FiberWire [FW], and OrthoFiber [OF]) with nylon leader line (NL) for use during extraarticular fixation of cranial cruciate deficient stifles. Study Design— In vitro biomechanical testing of suture loops under monotonic tensile and cyclical loading until failure. Sample Population— Constructs of FT, FW, OF, and NL. Methods— Twenty loops of each of 12 combinations of fixation and suture had monotonic tensile and cyclical loading. Two knotting techniques (square knot [SQ], slip knot [SL]) and a crimp clamp (CR) system were evaluated. Elongation, stiffness, and strength of constructs was tested. The main effects of group, loop material, and their interaction were evaluated. Results— Knotted FT, FW, and OF had less elongation than knotted NL under monotonic tensile and cyclical loading. Under monotonic tensile loading, knotted FT and OF were stiffer than knotted NL. CR FT, CR FW, and CR OF were stiffer than CR NL and CR FT, CR FW, and CR OF were stiffer than knotted FT, FW, and OF. FW and OF knotted loops were weaker than knotted NL. CR FT was stronger than CR NL. CR FT and CR OF were weaker than knotted FT and OF. Conclusions— Polyethylene sutures are stronger, stiffer and elongate less than nylon leader. Crimping suture alters the biomechanical properties of the loop. Clinical Relevance— FW, FT, and OF may perform better in reconstructive procedures, where increased strength and stiffness are considered to be beneficial. 相似文献
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WILGENS RENÉ BenoÎT CÔTÉ CLAUDE CAMIRÉ MAGDALENA BURGESS JAMES W. FYLES 《Journal of plant nutrition》2013,36(1):118-142
Plantations of hybrid poplars adapted to relatively poor soils and cold conditions are being established in abandoned fields and forest sites in southern Quebec. Hybrids of Populus maximowiczii are well adapted to these sites but little is known about their nutritional requirements. The objectives of this study were to develop nutritional norms (CVA, DRIS, CND) for three of these hybrids: 915508, Populus euramericana or canadensis X Populus maximowiczii; 3729, Populus nigra X Populus maximowiczii; and 915303, Populus maximowiczii X Populus balsamifera, and to apply the norms on some sites recently planted in southern Quebec. Six plantations (two per clone) were used for the determination of nutritional norms. In each plantation, individual trees were fertilized with nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) according to a factorial design with three levels of application for each nutrient (35 = 243 treatments). Tree diameter and height, unit foliar mass and foliar chemistry (N, P, K, Ca, and Mg) of each tree were determined two years after fertilization. CVA, DRIS and CND norms were determined using a boundary-line approach with each plantation. Nutritional norms could be established for most combinations of clones and nutrients. CVA, DRIS and CND indices produced with published optimum nutrient concentrations for hybrid poplars closely related to P. maximowiczii were generally in agreement with the ones developed in our study. Differences in nutritional norms among P. maximowiczii hybrids/clones were small but hybrid/clone specific norms could provide more precise estimates of tree nutrition. The application of the norms on some representative sites of southern Quebec revealed more frequent nutrient imbalances than true nutrient deficiencies with generally excessive Ca and Mg, and limiting N, P, and K. 相似文献