2,874 research outputs found
Dichotomous Hamiltonians with Unbounded Entries and Solutions of Riccati Equations
An operator Riccati equation from systems theory is considered in the case
that all entries of the associated Hamiltonian are unbounded. Using a certain
dichotomy property of the Hamiltonian and its symmetry with respect to two
different indefinite inner products, we prove the existence of nonnegative and
nonpositive solutions of the Riccati equation. Moreover, conditions for the
boundedness and uniqueness of these solutions are established.Comment: 31 pages, 3 figures; proof of uniqueness of solutions added; to
appear in Journal of Evolution Equation
Generation of Porous Particle Structures using the Void Expansion Method
The newly developed "void expansion method" allows for an efficient
generation of porous packings of spherical particles over a wide range of
volume fractions using the discrete element method. Particles are randomly
placed under addition of much smaller "void-particles". Then, the void-particle
radius is increased repeatedly, thereby rearranging the structural particles
until formation of a dense particle packing.
The structural particles' mean coordination number was used to characterize
the evolving microstructures. At some void radius, a transition from an
initially low to a higher mean coordination number is found, which was used to
characterize the influence of the various simulation parameters. For structural
and void-particle stiffnesses of the same order of magnitude, the transition is
found at constant total volume fraction slightly below the random close packing
limit. For decreasing void-particle stiffness the transition is shifted towards
a smaller void-particle radius and becomes smoother.Comment: 9 pages, 8 figure
Calculation of the spectrum of 12Li by using the multistep shell model method in the complex energy plane
The unbound nucleus Li is evaluated by using the multistep shell model
in the complex energy plane assuming that the spectrum is determined by the
motion of three neutrons outside the Li core. It is found that the ground
state of this system consists of an antibound state and that only this
and a and a excited states are physically meaningful
resonances.Comment: 9 pages, 5 tables, 7 figures, printer-friendly versio
The good character at work: an initial study on the contribution of character strengths in identifying healthy and unhealthy work-related behavior and experience patterns
Purpose: Positive psychological functioning has been related to various positive work-related outcome variables, such as job satisfaction or work engagement. The aim of the present study was to examine the relations between morally positively valued traits (i.e., strengths of character) and work-related behaviors. Method: A sample of 887 adult women completed the Values in Action Inventory of Strengths (VIA-IS) and the Work-related Behavior and Experience Patterns Questionnaire (AVEM) in an online survey. Results: Those assigned to healthy work-related behavior and experience patterns differed in their strengths profiles from those that demonstrated unhealthy patterns (i.e., burnout type) in a predictable way. Especially the strengths of zest, persistence, hope, and curiosity seemed to play a key role in healthy and ambitious work behavior. Conclusions: The study underlines the relevance of character strengths in work settings and suggests that interventions based on character strengths could substantiate interventions already existing at the workplace in order to enhance positive work outcomes further (e.g., work satisfaction, engagement
Observation of vortex-nucleated magnetization reversal in individual ferromagnetic nanotubes
The reversal of a uniform axial magnetization in a ferromagnetic nanotube
(FNT) has been predicted to nucleate and propagate through vortex domains
forming at the ends. In dynamic cantilever magnetometry measurements of
individual FNTs, we identify the entry of these vortices as a function of
applied magnetic field and show that they mark the nucleation of magnetization
reversal. We find that the entry field depends sensitively on the angle between
the end surface of the FNT and the applied field. Micromagnetic simulations
substantiate the experimental results and highlight the importance of the ends
in determining the reversal process. The control over end vortex formation
enabled by our findings is promising for the production of FNTs with tailored
reversal properties.Comment: 20 pages, 13 figure
Can Action Research Strengthen District Health Management and Improve Health Workforce Performance? A Research Protocol.
The single biggest barrier for countries in sub-Saharan Africa (SSA) to scale up the necessary health services for addressing the three health-related Millennium Development Goals and achieving Universal Health Coverage is the lack of an adequate and well-performing health workforce. This deficit needs to be addressed both by training more new health personnel and by improving the performance of the existing and future health workforce. However, efforts have mostly been focused on training new staff and less on improving the performance of the existing health workforce. The purpose of this paper is to disseminate the protocol for the PERFORM project and reflect on the key challenges encountered during the development of this methodology and how they are being overcome. The overall aim of the PERFORM project is to identify ways of strengthening district management in order to address health workforce inadequacies by improving health workforce performance in SSA. The study will take place in three districts each in Ghana, Tanzania and Uganda using an action research approach. With the support of the country research teams, the district health management teams (DHMTs) will lead on planning, implementation, observation, reflection and redefinition of the activities in the study. Taking into account the national and local human resource (HR) and health systems (HS) policies and practices already in place, 'bundles' of HR/HS strategies that are feasible within the context and affordable within the districts' budget will be developed by the DHMTs to strengthen priority areas of health workforce performance. A comparative analysis of the findings from the three districts in each country will add new knowledge on the effects of these HR/HS bundles on DHMT management and workforce performance and the impact of an action research approach on improving the effectiveness of the DHMTs in implementing these interventions. Different challenges were faced during the development of the methodology. These include the changing context in the study districts, competing with other projects and duties for the time of district managers, complexity of the study design, maintaining the anonymity and confidentiality of study participants as well as how to record the processes during the study. We also discuss how these challenges are being addressed. The dissemination of this research protocol is intended to generate interest in the PERFORM project and also stimulate discussion on the use of action research in complex studies such as this on strengthening district health management to improve health workforce performance
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