9 research outputs found
Employee shirking and overworking:modelling the unintended consequences of work organisation
Underworking (i.e. shirking) and overworking of employees can have detrimental effects for the individual and the organisation. We develop a computational model to investigate how work structure, specifically the way in which managers distribute work tasks amongst employees, impacts work intensity and working time. The model draws on theories from economics, psychology and management, and on empirical observations. The simulations show that when managers correctly estimate task difficulty, but undervalue the employee’s competence, opportunities for shirking are provided due to longer deadlines. Similarly, if managers overvalue the employee’s competence, they set tighter deadlines leading to overwork. If task difficulty is misjudged, initially only influence on employee working time is observed. However, it gradually generates competence misjudgements, indirectly impacting the employee’s effort level. An interaction between competence misjudgement and task uncertainty slows the manager’s ability to correctly estimate employee competence and prolongs initial competence misjudgements. The study highlights the importance of applying dynamic modelling methods, which allows for testing theory assumptions in silico, generating new hypotheses and offers a foundation for future research. Practitioner summary: A computational model was developed to investigate how the structure of work allocation influences opportunities for shirking and overworking by employees. The paper demonstrates how dynamic modelling can be used to explain workplace phenomena and develop new hypotheses for further research. Abbreviations: KSA: knowledge, skills, attitudes; MIT: motivation intensity theory
Magnetorotational Instability in Core-Collapse Supernovae
We discuss the relevance of the magnetorotational instability (MRI) in
core-collapse supernovae (CCSNe). Our recent numerical studies show that in
CCSNe, the MRI is terminated by parasitic instabilities of the Kelvin-Helmholtz
type. To determine whether the MRI can amplify initially weak magnetic fields
to dynamically relevant strengths in CCSNe, we performed three-dimensional
simulations of a region close to the surface of a differentially rotating
proto-neutron star in non-ideal magnetohydrodynamics with two different
numerical codes. We find that under the conditions prevailing in proto-neutron
stars, the MRI can amplify the magnetic field by (only) one order of magnitude.
This severely limits the role of MRI channel modes as an agent amplifying the
magnetic field in proto-neutron stars starting from small seed fields.Comment: Proceedings in Acta Physica Polonica B, Proceedings Supplement, Vol.
10, No. 2, p.361, 4 pages, 1 figur
General Relativistic versus Newtonian: a universality in radiation hydrodynamics
We compare Newtonian and general relativistic descriptions of the stationary
accretion of self-gravitating fluids onto compact bodies. Spherical symmetry
and thin gas approximation are assumed. Luminosity depends, amongst other
factors, on the temperature and the contribution of gas to the total mass, in
both -- general relativistic () and Newtonian () -- models. We
discover a remarkable universal behaviour for transonic flows: the ratio of
respective luminosities is independent of the fractional mass of
the gas and depends on asymptotic temperature. It is close to 1 in the regime
of low asymptotic temperatures and can grow by one order of magnitude for high
temperatures. These conclusions are valid for a wide range of polytropic
equations of state.Comment: 8 pages, 4 figure
"Analysis of readmissions to the emergency department among patients presenting with abdominal pain"
Gastric Crohn's disease as a cause of gastrointestinal bleeding after gastroscopy : diagnostic difficulties
How to form a millisecond magnetar? Magnetic field amplification in protoneutron stars
International audienceExtremely strong magnetic fields of the order of 1015G are required to explain the properties of magnetars, the most magnetic neutron stars. Such a strong magnetic field is expected to play an important role for the dynamics of core-collapse supernovae, and in the presence of rapid rotation may power superluminous supernovae and hypernovae associated to long gamma-ray bursts. The origin of these strong magnetic fields remains, however, obscure and most likely requires an amplification over many orders of magnitude in the protoneutron star. One of the most promising agents is the magnetorotational instability (MRI), which can in principle amplify exponentially fast a weak initial magnetic field to a dynamically relevant strength. We describe our current understanding of the MRI in protoneutron stars and show recent results on its dependence on physical conditions specific to protoneutron stars such as neutrino radiation, strong buoyancy effects and large magnetic Prandtl number