Corner detector

Structure tensors have been shown to work well in segmenting and locating structures of specific shape. Several books published in the recent years present extensive literature reviews on structure tensors and their applications [13, 15, 19, 48]. In this chapter, we present in Section 2 a brief review of their application in image processing, focusing on their application to the analysis of seismic data. Section 3, describes the 2D first and second order structure tensors and their properties in more detail. Also, two well known corner detectors, based on the structure tensors, namely the Harris and the... 

Hessian-based (otherwise known as DET) corner detector are reviewed. In Section 4, we present the 3D first and second order structure tensors and their properties. Section 5 demonstrates the use of these tensors in the analysis of 2D and 3D seismic data, and in Section 6 we draw our conclusions. 

Harris Corner Detector. In this subsection, we briefly describe the detection of corners as introduced by Harris and Stephens [16]. They used the image structure tensor M with the window w x, y) being a Gaussian. Instead of estimating the eigenvalues Ai and A2 of M separately, they introduced a cornerness measure or corner response R which is a function of the eigenvalues but it can be expressed directly in terms of the matrix elements. Thus, the corner response is defined as... 

Enhanced Hessian-Based Corner Detector. The determinant of the... 

Harris Corner Detector Applied to Seismic Sections... 

Fig. 5. [Reproduced in colour in Plate 6 on page 424.] Corner pixels detected by the Harris corner detector for fc = 0.2, cr = 2.

When equation 12 is vaUd, the detector is said to be a background-limited infrared photodetector (BLIP). When this is the case, attempts often are made to improve D by cold shielding which reduces ( ). The ideal D is shown in Figure 3 as a function of wavelength with background photon flux as a parameter. The line of termination in the lower left corner represents TN values for a 180° (27T) detector field of view, 300 K ambient background... 

This interferometric dilatometer consists of a rather simple and small Michelson interferometer, in which the two arms are parallel, and of a 4He cryostat, in which the sample to be measured is hold. The sample is cooled to 4 K, and data are taken during the warm up of the cryostat. The optical path difference between the two arms depends on the sample length hence a variation of the sample length determines an interference signal. The Michelson interferometer consists of a He-Ne stabilized laser (A = 0.6328 xm), two cube corner prisms, a beam splitter, three mirrors and a silicon photodiode detector placed in the focal plane of a 25 mm focal length biconvex lens (see Fig. 13.1). 

The T junctions and corners of the layout currently used in synchronized cyclic CE contribute more to zone broadening than do the channel connections at the corners used in single-pass chips. In addition, a significant percentage of analyte is lost on each cycle as it passes by T junctions and the detector. These issues are under investigation. 

Figure 2 Schematic view of the apparatus used in studies of the steric effects in gas-surface scattering. A detail of the crystal mount with die orientation rod at 1 cm in front of the surface is shown in die right hand corner. A detailed drawing of the hexapole state selector is given below the main figure. The voltage is applied to die six small rods indicated by an arrow. Key Q quadrupole mass spectrometer R Rempi detector M, crystal manipulator SI, beam source for state selected molecules H electric hexapole state selector C mechanical beam chopper V pulsed gas source S2, continuous molecular beam source. From Tenner et al. [34].

The beam enters the 1.75 m Teflon-lined White cell containing a corner cube reflector (3) and undergoes 102 passes before exiting to the detector. Absorptions at least as low as 10 s can be measured which, for a total path length of 150 m corresponds to detection limits in the range 25 to 100 parts per trillion by volume for most atmospheric gases. 

The UV detector is in the upper left corner of the cubicle, viewing only the area inside the cubicle. The 10-pound bottle of Halon is in the opposite corner. When the flames from the torch enter the 90 viewing cone of vision of the detector inside the cubicle, the detector instantly signals a relay in its controller which closes and causes a detonator cap to rupture the disc on the Halon bottle - releasing the Halon. The Halon suppresses the flames on the torch and the unlighted torch falls harmlessly into the pan of gasoline. 

Clearly, we need a multiple-sensor system that can simultaneously measure the magnetic field at various positions over the scalp—say, one hundred positions—so that measurements could be completed in a matter of minutes. This would enable us to see patterns of activity as they shift from one area of brain to the next. The problem, though, is that we have to keep the sensors, the detector coils, very cold in liquid helium. You also need a good Dewar, and the present ones are rigid structures. It doesn t take you long to realize, when you study human heads, that they come in different sizes and shapes—round ones, flat ones, heads with corners and edges. To maximize sensitivity, you have to get those coils closer to the head, and we don t have that flexibility with current designs. If we had a room-temperature superconductor, we could do that very easily, because they d all be on tracks that could slide in nicely and you could fit them to a child. 

Figure 2.16. The schematic explaining the difference between point (the set of discrete dots), line (solid rectangle) and area (the entire picture) detectors, which are used in modem powder diflfactometry. The light trace extended from the center of the image to the upper left corner is the shade from the primary beam trap. The Bragg angle is zero at the center of the image and it increases along any line that extends from the center of the image as shown by the two arrows (also see Figure 2.34).

Risner, C. H. and Corner, J. M., A quantification of 4- to 6- ring polynuclear hydrocarbons in indoor air samples by high-performance liquid chromatography, Environ. Toxicol. Chem., 10, 1417-1423, 1991. Yamamoto, N., Nishiura, H., Honjo, T., and Inoue, H., Determination of ammonia in the atmosphere by gas chromatography with a flame thermionic detector. Anal. Sci., 7, 1041-1044, 1991. 

Figure 8.10 The solid angle between a point isotropic source and a detector with a rectangular aperture. Source is located directly above one corner of the detector.

All the microanalysis work was done in a Jeol-100 CX electron microscope fitted with a STEM unit, a X-ray detector and a Tracor-Northern 5500 console.The compositional microanalysis was carried out by energy dispersive spectrometry on bulky Adams Pt particles modified by Au deposition. Table 5 gives the mean composition of Pt particles. It appears that Au is preferentially deposited on particle rims (edges and corners) than on flat planes. 

The pulse velocity approach is best done in a transmission mode with the pulse created on one side of a concrete member and detected on the other side. It can be used at corners or in a reflective mode if necessary, but it loses effectiveness and interpretation gets harder. The impact-echo technique can be used with pulse generator and detector side by side as the echo is reflected back from defects. 

The volume of the detector cell should have a negligible influence on peak broadening and should, therefore, amount to less than 10% of the elution volume of the narrowest (first) peak. A cell volume of 8 pi is standard. Too small a cell volume impairs the detection limit (as a certain amount of product is needed to produce any signal at all). The figure must be well below 8 pi for micro-HPLC. The cell must have no dead corners which may prevent the peak being fully removed by subsequent eluent. 

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