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Two-dimensional Form (two-dimensional + form)

Distribution by Scientific Domains
Earth and Environmental Science28%

Selected Abstracts

CONCEPTUAL CLUSTERING AND CASE GENERALIZATION OF TWO-DIMENSIONAL FORMS

COMPUTATIONAL INTELLIGENCE, Issue 3-4 2006
Silke Jänichen
Case-based object recognition requires a general case of the object that should be detected. Real-world applications such as the recognition of biological objects in images cannot be solved by one general case. A case base is necessary to handle the great natural variations in the appearance of these objects. In this paper, we will present how to learn a hierarchical case base of general cases. We present our conceptual clustering algorithm to learn groups of similar cases from a set of acquired structural cases of fungal spores. Due to its concept description, it explicitly supplies for each cluster a generalized case and a measure for the degree of its generalization. The resulting hierarchical case base is used for applications in the field of case-based object recognition. We present results based on our application for health monitoring of biologically hazardous material. [source]

Seismic base-isolation by use of a telescoping stepping mechanism

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 3 2005
Maria D. Martinez-Rodrigo
Abstract A new base-isolation mechanism corresponding to a variance of the stepping A-shaped frame is proposed and its seismic performance is investigated numerically for strong ground accelerations with peak values in the range from 0.5 to 1g. In its simplest two-dimensional form, the system consists of a frame with two telescoping legs pinned at the apex at a sharp angle. The legs are attached to the foundation through a spring and a damper acting in parallel. Both the springs and viscous dampers have bilinear characteristics that make them very stiff in compression but very soft in tension. As the structure rocks sideways, the length of the loaded leg remains essentially constant while the length of the unloaded leg increases. When the ground acceleration changes direction, the process is reversed. The resulting system has three main characteristics: (i) as the structure steps on a rigid leg, the maximum acceleration that can be transmitted to the superstructure is limited to a value which is approximately independent of the amplitude of the ground motion; (ii) there is a systematic lifting of the superstructure with kinetic energy being systematically transformed into potential energy during the strong phase of the ground motion; and (iii) the system is slowly self-centering at the end of the earthquake. The seismic performance of the system is evaluated for a tall bridge pier and for a smaller frame that could be used in a multi-story building. The results obtained for the 1940 El Centro ground motion scaled to 1g and for the near-field Rinaldi ground motion recorded during the Northridge earthquake show that substantial reductions of the absolute acceleration can be obtained with reasonable relative displacements of the superstructure and small strokes in the isolation devices. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Spatial frequency content of the Cardiff and related acuity tests

OPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 1 2006
W. N. Charman
Abstract In the Cardiff acuity test, simple pictures on an otherwise neutral grey card are defined by borders consisting of a relatively broad white band flanked by black bands each half the width of the white band. Higher levels of acuity correspond to the ability to detect figures defined by narrower borders, the figure size remaining constant. It is sometimes implied that the acuity limit corresponding to each card can be equated with different levels of grating resolution, the total width of the border corresponding to the overall grating period. It is shown that although the spatial frequency spectra of the Cardiff figures, like those of other vanishing optotypes, lack very low-frequency components, they have a complex two-dimensional form. The figures have wide spatial bandwidth and no well-defined discrete frequency components. As a result, the relationship between measured Cardiff and grating acuity will vary somewhat, depending upon the particular optical, neural or other deficits of the individual being tested. [source]

Background error covariance functions for vector wind analyses using Doppler-radar radial-velocity observations

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 621C 2006
Qin Xu
Abstract A two-dimensional form of cross-covariance function between the radar radial- and tangential-components (with respect to the direction of radar beam) of background wind errors is derived. Like the previously derived auto-covariance function for the radial component, this cross-covariance function is homogeneous but non-isotropic in the horizontal. The auto- and cross-covariance functions are used with the statistical interpolation technique to perform a vector wind analysis from Doppler radial-velocity observations on a conical surface of low-elevation radar-scans. The structures of the two covariance functions are compared and interpreted in terms of the influence of a single-point radial-velocity observation on the analysed vector wind field. The utility and value of these covariance functions are demonstrated through analysis experiments that use either simulated radial-velocity data from idealized flows or real radar observations. The results of the statistical interpolation scheme utilizing the proposed covariance functions are shown to be superior to the results of traditional VAD technique. The proposed technique can actually be considered a generalization of the traditional VAD technique. Copyright © 2006 Royal Meteorological Society [source]

Universality and variability in basin outlet spacing: implications for the two-dimensional form of drainage basins

BASIN RESEARCH, Issue 2 2009
Rachel C. Walcott
ABSTRACT It has been observed that the distance between the outlets of transverse basins in orogens is typically half of the distance between the main divide and the range front irrespective of mountain range size or erosional controls. Although it has been suggested that this relationship is the inherent expression of Hack's law, and/or possibly a function of range widening, there are cases of notable deviations from the typical half-width average spacing. Moreover, it has not been demonstrated that this general relationship is also true for basins in morphologically similar nonorogenic settings, or for those that do not extend to the main drainage divide. These issues are explored by investigating the relationship between basin outlet spacing and the 2-dimensional geometric properties of drainage basins (basin length, main valley length and basin area) in order to assess whether the basin outlet spacing-range width ratio is a universal characteristic of fluvial systems. We examined basins spanning two orders of magnitude in area along the southern flank of the Himalayas and the coastal zone of southeast Africa. We found that the spacing between basin outlets (Los) for major transverse basins that drain the main divide (range-scale basins) is approximately half of the basin length (Lb) for all basins, irrespective of size, in southeast Africa. In the Himalayas, while this ratio was observed for eastern Himalayan basins (a region where the maximum elevations coincided with the main drainage divide), it was only observed in basins shorter than ,30 km in the western and central Himalayas. Our analysis indicates that basin outlet spacing is consistent with Hack's law, apparently because the increase in basin width (represented by outlet spacing) with basin area occurs at a rate similar to the increase in main stream length (Lv) with basin area. It is suggested that most river systems tend towards an approximately diamond-shaped packing arrangement, and this applies both to the nonorogenic setting of southeast Africa as well as most orogenic settings. However, in the western Himalayas shortening associated with localised rock uplift appears to have occurred at length scales smaller than most the basins examined. As a result rivers in basins longer than ,30 km have been unable to erode in a direction normal to the range front at a sufficiently high rate to sustain this form and have been forced into an alternative, and possibly unstable, packing arrangement. [source]

Construction of Resolvable Spatial Row,Column Designs

BIOMETRICS, Issue 1 2006
E. R. Williams
Summary Resolvable row,column designs are widely used in field trials to control variation and improve the precision of treatment comparisons. Further gains can often be made by using a spatial model or a combination of spatial and incomplete blocking components. Martin, Eccleston, and Gleeson (1993, Journal of Statistical Planning and Inference34, 433,450) presented some general principles for the construction of robust spatial block designs which were addressed by spatial designs based on the linear variance (LV) model. In this article we define the two-dimensional form of the LV model and investigate extensions of the Martin et al. principles for the construction of resolvable spatial row,column designs. The computer construction of efficient spatial designs is discussed and some comparisons made with designs constructed assuming an autoregressive variance structure. [source]

The architecture of the GroEL,GroES,(ADP)7 chaperonin complex.

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 5 2003

Molecular forms are considered with vertices that have integral coordinates (the indices) with respect to a symmetry-adapted basis and which are left invariant by a point group of crystallographic scale-rotations (represented in this basis by invertible integral matrices). The composite form enclosing the chaperonin complex GroEL,GroES,(ADP)7 is derived and decomposed into heptagrammal forms. These are generalizations of the two-dimensional forms based on sevenfold star polygons. In the chaperonin complex, nine such heptagrammal molecular forms are found: three for each ring (trans and cis) of GroEL and three for GroES. These forms correspond to a splitting of the monomer into adjacent segments. The change in the folding of the chains in the cis ring of GroEL arising from binding to GroES leaves the chain segmentation invariant. [source]