54 research outputs found
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Signal-to-Noise Behavior for Matches to Gradient Direction Models of Corners in Images
Gradient direction models for corners of prescribed acuteness, leg length, and leg thickness are constructed by generating fields of unit vectors emanating from leg pixels that point normal to the edges. A novel FFT-based algorithm that quickly matches models of corners at all possible positions and orientations in the image to fields of gradient directions for image pixels is described. The signal strength of a corner is discussed in terms of the number of pixels along the edges of a corner in an image, while noise is characterized by the coherence of gradient directions along those edges. The detection-false alarm rate behavior of our corner detector is evaluated empirically by manually constructing maps of corner locations in typical overhead images, and then generating different ROC curves for matches to models of corners with different leg lengths and thicknesses. We then demonstrate how corners found with our detector can be used to quickly and automatically find families of polygons of arbitrary position, size and orientation in overhead images
Shape description and matching using integral invariants on eccentricity transformed images
Matching occluded and noisy shapes is a problem frequently encountered in medical image analysis and more generally in computer vision. To keep track of changes inside the breast, for example, it is important for a computer aided detection system to establish correspondences between regions of interest. Shape transformations, computed both with integral invariants (II) and with geodesic distance, yield signatures that are invariant to isometric deformations, such as bending and articulations. Integral invariants describe the boundaries of planar shapes. However, they provide no information about where a particular feature lies on the boundary with regard to the overall shape structure. Conversely, eccentricity transforms (Ecc) can match shapes by signatures of geodesic distance histograms based on information from inside the shape; but they ignore the boundary information. We describe a method that combines the boundary signature of a shape obtained from II and structural information from the Ecc to yield results that improve on them separately
On the beneficial effect of noise in vertex localization
A theoretical and experimental analysis related to the effect of noise in the task of vertex identication in unknown shapes is presented. Shapes are seen as real functions of their closed boundary. An alternative global perspective of curvature is examined providing insight into the process of noise- enabled vertex localization. The analysis reveals that noise facilitates in the localization of certain vertices. The concept of noising is thus considered and a relevant global method for localizing Global Vertices is investigated in relation to local methods under the presence of increasing noise. Theoretical analysis reveals that induced noise can indeed help localizing certain vertices if combined with global descriptors. Experiments with noise and a comparison to localized methods validate the theoretical results
Married women’s decision making power on family planning use and associated factors in Mizan-Aman, South Ethiopia: a cross sectional study
BACKGROUND: Women’s use of family planning service is influenced by many factors, especially by their decision making power. A woman’s decision-making power, be it individual or decision made in collaboration with a partner, is the most important factor in the use of family planning in a household. The purpose of this study was to assess the impact of women’s decision making power on family planning use and its associated factors. METHODS: A community-based cross-sectional study was conducted on married women in the child bearing age. The women who were living in Mizan city were selected using the simple random sampling method. Trained nurses collected the data by interview, using a structured and pre-tested questioner. Bivariable and multivariable binary logistic regression analysis was used to identify the associated factors, and the odds ratio with a 95 % CI was computed to assess the strength of the association. Collinearity was also assessed by looking at standard errors in the final fitted model. RESULT: Overall, more than two-thirds [67.2 %: 95 % CI (63–71 %)] of the married women were found to be more autonomous to decide family planning use. Secondary education [AOR: 9.04, 95 % CI: (4.50, 18.16)], government employment [AOR: 4.84, 95 % CI: (2.03, 11.52)], being wives of government employed spouses [AOR 2.71, 95 % CI: (1.24, 7.97)], having husbands with college or university education [AOR: 11.29, 95 % CI: (4.66, 27.35)], and being in the younger age [AOR: 0.27, 95 % CI :(0.09, 0.75)] were significantly associated with women’s decision-making power on family planning. CONCLUSIONS: In this study, women had a high decision making power in family planning use. Age category (34–44-years), formal education, and occupational status had effects on women’s decision making power. Promoting parental adult education and engaging women in out of house employment is essential to improve their decision making power in using family planning
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Fiscal Year 2006
This image analysis project is constructing a tool for performing computer assisted detection of defects in large CT data sets. We address two primary challenges: proving an algorithm that can reliably highlight the objects of interest, and coupling this algorithm to efficient and effective data management and interface routines. The goal of this project is to create an end to end tool that will efficiently extract from large CT data sets a manageable set of candidate defects that highlights 100% of the unambiguous (to a trained analyst) true defects and as many as possible of the ambiguous objects. Objective metrics for defect ambiguity are elusive given the ill defined nature of both the defects and their CT images (e.g., variations in size and contrast, defect/object density gradients). Therefore the true metric of success will be gaining the confidence of the Weapons Program NDE analysts in this tool, which will be a qualitative function of efficiency and accuracy. In consultation with Weapons Program NDE analysts voids it was decided to focus this initial effort on searching for small voids (order of tenths to tens of millimeters in extent). The program has produced a Tungsten ring with surrogate defects drilled into it (Figure 1) that they use for studying the ability of their systems and analysts to detect this class of defects
A Taguchi approach for optimization of design parameters in a tube with coiled wire inserts
This study presents the determination of the optimum values of the design parameters in a tube with equilateral triangular cross-sectioned coiled wire inserts. The effects of the design parameters such as the ratio of the distance between the coiled wire and test tube wall to tube diameter (s/D), pitch ratio (P/D), ratio of the side length of equilateral triangle to tube diameter (a/D) and Reynolds number (Re) on heat transfer and pressure drop were investigated by using Taguchi method. The Nusselt number and friction factor were considered as performance parameters. An L9(34) orthogonal array was chosen as experimental plan. The goal of this study is to reach maximum heat transfer (i.e. Nusselt number) and minimum pressure drop (i.e. friction factor). First of all, each goal was optimized, separately. Then, all the goals were optimized together, considering the priority of the goals. Contribution ratios for each parameter on the heat transfer and pressure drop were determined. Consequently, the optimum results were found to be s/D = 0.0357, P/D = 1, a/D = 0.0714 and Re = 19800. © 2011 Elsevier Ltd. All rights reserved
Forced convective two phase flow analysis in a circular tube equipped with twisted tapes
In forced convection boiling systems, it is important to know the dynamic behavior for understanding and predicting the local and global stability of the system. Besides this, the instability phenomenon in the industrial processes in which two phase flow takes part becomes more of an issue. So, the mechanisms of instabilities and the ways of decreasing the stabilities are of interest of the researchers for a long time. In this study, the effects of pitch ratio, inlet temperature and the mass flow rate on two phase flow instabilities in a horizontal circular tube are investigated. The experiments are conducted under constant system pressure, and a constant heat input of 24 kW is applied to the outer surface of the circular test pipe having constant exit restriction. The results of two different pitch ratios are also compared with the smooth tube. For all investigated cases, the results are evaluated in terms of pressure drop type and density wave type oscillations. The time dependent measurements of top wall temperature, bottom wall temperature, inlet pressure and mass flow rate variations are also presented. The boundaries of the oscillations are found for both twisted tape and smooth channel. It is found that the unstable region of the flow extends while the distance between boundaries increases. It is observed that the system is more stable in the case of the lowest pitch ratio, and the increase of the pitch ratio causes system to be less stable. By the decrease of the inlet temperature, the single phase liquid region extends in the test tube and thus the system becomes more stable. © Sila Science
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