Detecting Flaws in the Presence of Strong Geometry Signals in F100 Gas Turbine Engine Components

The inspection of F-100 gas turbine engine components using the Retirement For Cause (RFC) Eddy Current Inspection Station includes the requirement to scan three common but critical geometries: Antirotation windows (ARW), antirotation tangs (ART) and the live rim (LR) area at the component rim, as shown in Figures 1 and 2. These geometries have a common feature — edges, as shown in Figure 3 — that presents a challenge to successful inspection. The edges are sources of strong geometry signals that often have a higher amplitude than flaw signals, thus making a conventional amplitude inspection technique difficult. Therefore, a “frequency select” technique was developed which uses the frequency difference as a flaw determination criteria [1,2]. Using this technique, the RFC System has successfully detected both EDM notches and fatigue cracks in these geometries located in engine components fabricated of IN-100, waspaloy and titanium

A novel fast and reduced redundancy structure for multiscale directional filter banks

2007-2008 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Co-occurrence features of multi-scale directional filter bank for texture characterization

Author name used in this publication: N. F.LawAuthor name used in this publication: K. O. ChengAuthor name used in this publication: W. C. SiuRefereed conference paper2005-2006 > Academic research: refereed > Refereed conference paperVersion of RecordPublishe

Identification of coherent patterns in gene expression data using an efficient biclustering algorithm and parallel coordinate visualization

2007-2008 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Common correlates of suicidal ideation and physical assault among male and female university students in Hong Kong

This study examined prevalence and correlates of suicidal ideation and dating partner violence in a cohort of 651 university students in social sciences classes at three universities in Hong Kong. A standard questionnaire was completed within one class period to examine the rates of occurrence of physical assault perpetration and suicidal ideation. Separate rates are presented for male and female perpetrators and for severe and overall levels of violence. The differences between subjects having suicidal ideation are compared using t tests. Logistic regression is used to predict the presence or absence of physical assault in the preceding year of reporting and suicidal ideation based on the variables such as Personal Relationship Profile, age, relationship length, and socioeconomic status. Results showed that 55% of suicidal persons had a history of violence, whereas 39% of violent people had a history of suicidal ideation. Logistic regression showed that physical assault shared a total of seven associated factors with suicidal ideation. Suicidal ideation seems to have no direct relation to physical and sexual assault, but they do share some common associated factors that are essential for the development of suicide prevention. © 2007 Springer Publishing Company.postprin

Automated Eddy Current Detection of Edge Defects in a Complex Geometry Using a Magnitude Approach

The inspection capability on turbine engine disks is important to the safety of an airplane. Eddy current inspection has been widely accepted as an effective tool in detecting small fatigue cracks on engine disks. The inspection of simple geometries such as boltholes, webs and bores in a engine disk is less complicated than those of complex geometries such as antirotation windows, scallops, dovetails and non-circular holes. One of the main difficulties in inspecting complex geometries is due to the presence of irregular edges. Raatz [1] reported the influence of edges in measuring conductivity. Williams, Tilson and Blitz [2] minimized the change of phase angle variation around an edge by the proper selection of inspection frequency and coil size. Elsberry and Bailey [3] enhanced edge defect detection by using a shielded probe to collimate the field. Hoppe and Stubbs [4], on the other hand, used the frequency content of the edge signals to discern the edge defect in antirotation windows. This frequency approach was extended to the inspection of other complex geometries such as antirotation tangs and live rims by Ko [5]. Furthermore, Ko [6] used the edge signals in scallops to position a rotational probe in a scallop prior to inspection. These techniques [4–6] are limited to partial inspection of the geometries; however, a new technique is needed if an entire inspection of a complex geometry is required. This paper discusses the use of a simple mechanical mechanism to adapt to a complex geometry, and a signal processing technique for the detection of edge defects.</p

An XMM and Chandra view of massive clusters of galaxies to z=1

The X-ray properties of a sample of high redshift (z>0.6), massive clusters observed with XMM-Newton and Chandra are described, including two exceptional systems. One, at z=0.89, has an X-ray temperature of T=11.5 (+1.1, -0.9) keV (the highest temperature of any cluster known at z>0.6), an estimated mass of (1.4+/-0.2)x10^15 solar masses and appears relaxed. The other, at z=0.83, has at least three sub-clumps, probably in the process of merging, and may also show signs of faint filamentary structure at large radii,observed in X-rays. In general there is a mix of X-ray morphologies, from those clusters which appear relaxed and containing little substructure to some highly non-virialized and probably merging systems. The X-ray gas metallicities and gas mass fractions of the relaxed systems are similar to those of low redshift clusters of the same temperature, suggesting that the gas was in place, and containing its metals, by z=0.8. The evolution of the mass-temperature relation may be consistent with no evolution or with the ``late formation'' assumption. The effect of point source contamination in the ROSAT survey from which these clusters were selected is estimated, and the implications for the ROSAT X-ray luminosity function discussed.Comment: 9 pages, in Carnegie Observatories Astrophysics Series, Vol. 3: Clusters of Galaxies: Probes of Cosmological Structure and Galaxy Evolution, ed. J. S. Mulchaey, A. Dressler, and A. Oemler. See http://www.ociw.edu/ociw/symposia/series/symposium3/proceedings.html for a full-resolution versio

The X-ray spectrum of the Seyfert I galaxy Markarian 766: Dusty warm absorber or relativistic emission lines?

Competing models for broad spectral features in the soft X-ray spectrum of the Seyfert I galaxy Mrk 766 are tested against data from a 130 ks XMM-Newton observation. A model including relativistically broadened Lyalpha emission lines of O VIII N VII and C VI is a better fit to 0.3-2 keV XMM RGS data than a dusty warm absorber. Moreover, the measured depth of neutral iron absorption lines in the spectrum is inconsistent with the magnitude of the iron edge required to produce the continuum break at 17-18 Angstrom in the dusty warm absorber model. The relativistic emission line model can reproduce the broadband (0.1-12 keV) XMM EPIC data with the addition of a fourth line to represent emission from ionized iron at 6.7 keV and an excess due to reflection at energies above the iron line. The pro le of the 6.7 keV iron line is consistent with that measured for the low-energy lines. There is evidence in the RGS data, at the 3sigma level, of spectral features that vary with source flux. The covering fraction of warm absorber gas is estimated to be 12%. Iron in the warm absorber is found to be overabundant with respect to CNO, compared to solar values

Wavelet packet based approach for image retrieval in compressed domains

Author name used in this manuscript: K. O. ChengAuthor name used in this manuscript: N. F. LawAuthor name used in this manuscript: W. C. SiuRefereed conference paper2011-2012 > Academic research: refereed > Refereed conference paperAccepted ManuscriptPublishe

A fast approach for identifying similar features in retrieval of JPEG and JPEG2000 images

Author name used in this publication: K.O. ChengAuthor name used in this publication: N.F. LawAuthor name used in this publication: W.C. SiuRefereed conference paper2009-2010 > Academic research: refereed > Refereed conference paperVersion of RecordPublishe