Correlation kinetic energy of many-electron systems: a modified Colle-Salvetti approach

The Colle and Salvetti approach [Theoret. Chim. Acta, 37, 329 (1975)] to the calculation of the correlation energy of a system is modified in order to explicitly include into the theory the kinetic contribution to the correlation energy. This is achieved by deducing from a many electrons wave function, including the correlation effects via a Jastrow factor, an approximate expression of the one-electron reduced density matrix. Applying the latter to the homogeneous electron gas, an analytic expression of the correlation kinetic energy is derived. The total correlation energy of such a system is then deduced from its kinetic contribution inverting a standard procedure. At variance of the original Colle-Salvetti theory, the parameters entering in both the kinetic correlation and the total correlation energies are determined analytically, leading to a satisfactory agreement with the results of Perdew and Wang [Phys. Rev. B 45, 13244 (1992)]. The resulting (parameter-free) expressions give rise to a modified-local-density approximation that can be used in self-consistent density-functional calculations. We have performed such calculations for a large set of atoms and ions and we have found results for the correlation energies and for the ionization potentials which improve those of the standard local-density approximation.Comment: 26 page

Enhanced exploration for primordial black holes using pulsar timing arrays

We investigate the capability of pulsar timing arrays (PTAs) as a probe of primordial black holes (PBHs), which might constitute the Galactic dark matter. A PBH passing nearby the Earth or a pulsar gives an impulse acceleration and induces residuals on otherwise orderly pulsar timing data. We show that the timing residuals induced at pulsars are optimal for searching heavier PBHs than those at the Earth, and the two probes are highly complemental. Future facilities like SKA could detect PBHs with masses around 10^(22-28) g even if only a small fraction (< 1%) of the Galactic dark matter consists of these PBHs.Comment: 6 pages, 3 figures, accepted for publication in MNRA

Ensuring Compliance: The Case of the Private Rented Sector

regulation, law and economics, governance, compliance, renting

The Relationship Between Intra-Organizational And Inter-Organizational Coordination And Its Influence On Product Quality Improvement

A sample of 225 firms is analyzed, using structural equation modeling, to test five hypotheses.&nbsp; This study seeks to gain a better understanding of the practice of coordination among functional areas within the buying firm as well as between buyer firms and their key suppliers.&nbsp; The implications of this research suggest that it is important for firms to focus on their long-term success as they work with key suppliers.&nbsp; The research shows when the stakeholders of the firm support its efforts to coordination and cooperation with its key suppliers, the firm benefits.&nbsp; Evidence shows cross-functional coordination enhances the firm&rsquo;s capability to cooperate with its key suppliers.&nbsp; The findings are significant to supply chain manager and to the various functional managers in charge of quality, production, R&amp;D, and customer service and their respective counter parts in supplier firms.&nbsp; Finally, this study expands prior research and fills a gap in the literature by showing the importance of inter-organizational coordination between the buyer&rsquo;s supply management/purchasing function and the supplier&rsquo;s operations function. This study reveals that conformance to specifications, product reliability and overall product quality performance can be significantly improved when these inter-organizational functional areas coordinate their requirements.&nbsp; The study also shows that product quality can be significantly improved when intra-organizational and inter-organizational coordination occurs simultaneously

An Analysis of Driver Reactions to Tire Failures Simulated with the National Advanced Driving Simulator (NADS)

Analyses of real-world tire tread belt detachment and/or sudden air loss events as well as vehicle testing of those events have been presented in scientific literature since the 1990’s. These confirm that such tire failures are complex and semi-random events that produce numerous sensory feedback cues to real-world drivers. These analyses further demonstrate that vehicles representing a full spectrum of steering characteristics are typically controllable and are controlled by drivers both during and after the tire disablement event. In 2003, the National Highway Traffic Administration (NHTSA) sponsored a study using the National Advanced Driving Simulator (NADS) to evaluate the technical hypothesis that there is a correlation between vehicle linear range understeer gradient and the likelihood of control loss when subject drivers experience a simulated tread belt detachment. The NADS subjects “drove” three simulated “vehicles” with different understeer gradients in a simulated tread separation even. The study’s authors reached conclusions regarding the drivers’ ability to control the “vehicles” which were inconsistent with real-world research. This paper presents an analysis of the NADS study performed to identify possible causes of the conflicting results and provides commentary upon several deficiencies noted in the NADS vehicle/tire modeling and validation. A more comprehensive understanding of the reported driver reactions when viewed in light of real vehicle experiments, real-world data, and an understanding of the limitations of the simulations is provided

Guiding e-learning: introducing online informal learning to a global voluntary organisation

The World Association of Girl Guides and Girl Scouts (WAGGGS) is the umbrella organisation for Member Organisations from 145 countries around the world, with a total membership of ten million. While Member Organisations offer training and development within their own countries, WAGGGS offers international opportunities. This project seeks to explore how technology can be used to offer similar opportunities to those provided by the face-to-face courses to a much wider audience, while retaining the community and interactive learning aspects of the existing programmes