57,812 research outputs found
Investigating the Integration of Acquired Firms in High-technology Industries: Implications for Industrial Policy
Acquisition activity persists despite evidence that acquisitions do not improve firm performance. Further, government policy toward the defense industry has advocated consolidation in the name of nominal cost savings. We explore the role acquisitions play toward technology transfer and begin to identify factors associated with acquisition success through a review of existing research on post-acquisition performance that primarily considers acquiring firm stock performance. Using this research as a foundation, we build a model to analyze post-acquisition performance using a sample of high-technology firms. Results suggest critical success factors associated with post-acquistion stock performance are poorly understood. We conclude that proactive government policy toward high-technology industry mergers and acquisitions may be misguided due to difficulty in predicting acquisition outcome
An Initial Look at Technology and Institutions on Defense Industry Consolidation
Conventional wisdom holds that defense industry consolidation resulted from decreased defense spending. However, we maintain that understanding dynamic changes in key defense institutions helps provide a more complete explanation for observed consolidation. Specifically, we examine the interaction of evolving technology and changing institutions. Institutions reviewed include procurement policies, weapons requirements process and the procurement organizations. We take an initial look at the industry and highlight how these changes influenced transaction costs in the defense industry more fully explain the forces driving consolidation and provide greater insight to policy makers seeking to improve the performance of the defense industry. Further research is needed to build a robust institutional framework of the defense industry and the related government agencies to allow better policy prescriptions
Hopf algebras and characters of classical groups
Schur functions provide an integral basis of the ring of symmetric functions.
It is shown that this ring has a natural Hopf algebra structure by identifying
the appropriate product, coproduct, unit, counit and antipode, and their
properties. Characters of covariant tensor irreducible representations of the
classical groups GL(n), O(n) and Sp(n) are then expressed in terms of Schur
functions, and the Hopf algebra is exploited in the determination of
group-subgroup branching rules and the decomposition of tensor products. The
analysis is carried out in terms of n-independent universal characters. The
corresponding rings, CharGL, CharO and CharSp, of universal characters each
have their own natural Hopf algebra structure. The appropriate product,
coproduct, unit, counit and antipode are identified in each case.Comment: 9 pages. Uses jpconf.cls and jpconf11.clo. Presented by RCK at
SSPCM'07, Myczkowce, Poland, Sept 200
Community-based participatory irrigation management at local government level in Ghana
Ghana has attempted to decentralise the management of irrigation schemes to communities at local government level. This study examines the existing local participatory management structures and the principles of the Participatory Irrigation Management (PIM) strategy designed to promote sustainable management of irrigation schemes in Ghana. Two community-based irrigation projects, Bontanga and Golinga in the Northern Region of Ghana were selected for the research. The study demonstrated that farmers’ participation was minimal and limited to the discussion of irrigation service charges at the expense of other issues related to the sustainability of the projects/schemes. The study also established that there was less participation of women, and more than half of all the crop farmers on the two irrigation projects were reluctant to assume additional responsibilities without remuneration. The study therefore concluded that the sustainability of the PIM strategy depends on the adoption of an integrated management approach involving all stakeholders including local government, with appropriate incentives
Cygnus X-2, super-Eddington mass transfer, and pulsar binaries
We consider the unusual evolutionary state of the secondary star in Cygnus
X-2. Spectroscopic data give a low mass (M_2 \simeq 0.5 - 0.7\msun) and yet a
large radius (R_2 \simeq 7\rsun) and high luminosity (L_2 \simeq 150\lsun).
We show that this star closely resembles a remnant of early massive Case B
evolution, during which the neutron star ejected most of the \sim 3\msun
transferred from the donor (initial mass M_{\rm 2i}\sim 3.6\msun) on its
thermal time-scale yr. As the system is far too wide to result from
common-envelope evolution, this strongly supports the idea that a neutron star
efficiently ejects the excess inflow during super--Eddington mass transfer.
Cygnus X-2 is unusual in having had an initial mass ratio in a narrow critical range near . Smaller lead to long-period systems with the former donor near the Hayashi line,
and larger to pulsar binaries with shorter periods and relatively
massive white dwarf companions. The latter naturally explain the surprisingly
large companion masses in several millisecond pulsar binaries. Systems like
Cygnus X-2 may thus be an important channel for forming pulsar binaries.Comment: 9 pages, 4 encapsulated figures, LaTeX, revised version with a few
typos corrected and an appendix added, accepted by MNRA
On the duration of long GRBs: effects of black hole spin
In the frame of the collapsar model for long gamma ray bursts (GRBs), we
investigate the formation of a torus around a spinning BH and we check what
rotational properties a progenitor star must have in order to sustain torus
accretion over relatively long activity periods. We also study the time
evolution of the BH spin parameter. We take into account the coupling between
BH mass, its spin parameter and the critical specific angular momentum of
accreting gas, needed for the torus to form. The large BH spin reduces the
critical angular momentum which in turn can increase the GRB duration with
respect to the Schwarzschild BH case. We quantify this effect and estimate the
GRB durations in three cases: when a hyper accreting torus operates or a BH
spins very fast or both. We show under what conditions a given progenitor star
produces a burst that can last as short as several seconds and as long as
several hundred of seconds. Our models indicate that it is possible for a
single collapse to produce three kinds of jets: (1) a very short, lasting
between a fraction of a second and a few seconds, 'precursor' jet, powered only
by a hyper accreting torus before the BH spins up, (2) an 'early' jet, lasting
several tens of seconds and powered by both hyper accretion and BH rotation,
and (3) a 'late' jet, powered only by the spinning BH.Comment: 13 pages; 9 figures; ApJ in pres
Ray methods for free boundary problems
We discuss the use of the WKB ansatz in a variety of parabolic problems involving a small parameter. We analyse the Stefan problem for small latent heat, the Black–Scholes problem for an American put option, and some nonlinear diffusion equations, in each case constructing an asymptotic solution by the use of ray methods
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