17,652 research outputs found
Development and application of a unified balancing approach with multiple constraints
The development of a general analytic approach to constrained balancing that is consistent with past influence coefficient methods is described. The approach uses Lagrange multipliers to impose orbit and/or weight constraints; these constraints are combined with the least squares minimization process to provide a set of coupled equations that result in a single solution form for determining correction weights. Proper selection of constraints results in the capability to: (1) balance higher speeds without disturbing previously balanced modes, thru the use of modal trial weight sets; (2) balance off-critical speeds; and (3) balance decoupled modes by use of a single balance plane. If no constraints are imposed, this solution form reduces to the general weighted least squares influence coefficient method. A test facility used to examine the use of the general constrained balancing procedure and application of modal trial weight ratios is also described
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Cardiac Memory-induced T-wave Inversions
Introduction: Cardiac memory refers to T-wave inversions that result when normal ventricular activation resumes following a period of abnormal ventricular activation.Case Report: We present a case of a 29-year-old man with a pacemaker who presented with new, deep symmetric T-wave inversions caused by cardiac memory.Discussion: Abnormal ventricular activation is most commonly induced by ventricular pacing but can also occur in the setting of transient left bundle branch blocks, ventricular tachycardia, and intermittent ventricular pre-excitation.Conclusion: Recognition of this phenomenon may help to reduce unnecessary admissions, cardiac testing, and cardiac catheterizations
Probing the Solar Wind Acceleration Region with the Sun--Grazing Comet C/2002 S2
Comet C/2002 S2, a member of the Kreutz family of Sungrazing comets, was
discovered in white light images of the SOHO/LASCO coronagraph on 2002
September 18 and observed in \hi\, \lya\, emission by the SOHO/UVCS instrument
at four different heights as it approached the Sun. The \hi\, \lya\, line
profiles detected by UVCS are analyzed to determine the spectral parameters:
line intensity, width and Doppler shift with respect to the coronal background.
Two dimensional comet images of these parameters are reconstructed at the
different heights. A novel aspect of the observations of this sungrazing comet
data is that, whereas the emission from the most of the tail is blue--shifted,
that along one edge of the tail is red--shifted. We attribute these shifts to a
combination of solar wind speed and interaction with the magnetic field. In
order to use the comet to probe the density, temperature and speed of the
corona and solar wind through which it passes, as well as to determine the
outgassing rate of the comet, we develop a Monte Carlo simulation of the \hi\,
\lya\, emission of a comet moving through a coronal plasma. From the outgassing
rate, we estimate a nucleus diameter of about 9 meters. This rate steadily
increases as the comet approaches the Sun while the optical brightness
decreases by more than a factor of ten and suddenly recovers. This indicates
that the optical brightness is determined by the lifetimes of the grains,
sodium atoms and molecules produced by the comet.Comment: 17 pages, 17 figures. Accepted by Ap
Some Cognitive Transformations About the Dynamics of Desistance
This article explores the role of cognitive transformations in the process of desistance from crime. Based on our own and others’ subsequent research, clearly, some aspects of our initial theorizing warrant revisiting and adjustment. The discussion describes changes to ideas about the sequencing of various types of cognitive shifts, suggests the importance of emotional processes in tandem with changes in perspective, and highlights the need to move out of the comfort zone of crime itself when thinking about redefinitions that support desistance. Yet, a consistent notion remains that social and broader structural factors are deeply implicated—directly and indirectly—in all aspects of the change process. This includes the important area of “derailments” from a pattern of forward progress, where additional processual research is needed. The discussion concludes with the argument that individualistic policies and programs centered on cognitive deficits requiring correction are likely to be limited in their effectiveness
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