861 research outputs found
On integrability and aggregation of superior demand functions
When each of the members of a collective displays a demand behavior that is consistent with a homogeneous of degree one in income demand, it is well known that some properties carry over to the aggregate representative consumer. We investigate those issues when the components of the society are allowed to behave in agreement with less restrictive demand patterns, namely superior demand functions.
Gamification in factory management education : A case study with Lego Mindstorms
Research oriented teaching in universities provides opportunities to support the student's desire to explore. A student's learning success can benefit from gamified project work, especially when students face self-guided learning processes in demanding educational activities. Gamification is defined as the use of game elements in a non-game context. Games offer the chance to improve the motivation of students, support group work, train communication skills and introduce the capacity for experimenting in safe environments. Therefore the learning effect of prospective engineers can be increased through the integration of Gamification into educational activities. This leads to higher student participation in university courses and encourages the development of the student's social, personal and technical competences. In this paper a game concept for teaching in universities is introduced focusing on the impartment of the state of the art on manufacturing for value creation, e.g. production planning and control. The concept covers a level based storyline with rules and goals using physical artefacts of Lego Mindstorms. Due to the modular characteristic of Lego, which supports creativity by having a high number of possible combinations, a “free playing space” for students is established. In groups, the students work in a highly problem oriented way, e.g. finding cost savings for their factory due to a changing market condition. Feedback in the sense of the success of student's strategies is given directly through the designed Lego model and its functionality
Procedure for Experiential Learning to Conduct Material Flow Simulation Projects, Enabled by Learning Factories
Material flow simulation is a powerful tool to identify improvements in factory operation. For conducting simulation projects, experts are required who know how to prepare, execute and evaluate simulation studies. To date, training mostly focusses on textual case studies, whereby learners perform simulation studies based on a problem and data given in a description. However, this hardly reflects the ways engineers learn. They are mostly used to physically experiment based on their experience. In this paper, a procedure for experiential learning to conduct material flow simulation projects is elaborated, enabled by learning factories. A learning situation at Vietnamese-German University is described. Results indicate, that the students gain particular awareness about the challenges associated with the abstraction of the reality and the interpretation of the simulation outcomes
Language independent transfer of assembly knowledge
Transferring assembly knowledge for workers with different cultural and linguistic background is challenging. The established solution of translating written instructions into multiple languages is mostly cost intensive, holds a potential for mistakes and the result might be hard to understand. To cope with this challenge, three different assembly instructions with language reduced or language independent content have been tested in a study with students in Vietnam and Germany. The types of instructions were interactive 3D-PDF, Utility-Film and illustrated manual. Assembly errors, assembly time, safety symbol awareness and assembly sequences understanding are compared and evaluated based on students’ technical pre-knowledge and experience. The 3D-PDF showed to be the best solution to be applied in this complex environment, because users were able to assemble the parts faster and experienced a higher degree of interactivity compared to the other instructions
Supramolecular synthon pattern in solid clioquinol and cloxiquine (APIs of antibacterial, antifungal, antiaging and antituberculosis drugs) studied by 35Cl NQR, 1H-17O and 1H-14N NQDR and DFT/QTAIM
The quinolinol derivatives clioquinol (5-chloro-7-iodo-8-quinolinol, Quinoform) and cloxiquine (5-chloro-8-quinolinol) were studied experimentally in the solid state via 35Cl NQR, 1H-17O and 1H-14N NQDR spectroscopies, and theoretically by density functional theory (DFT). The supramolecular synthon pattern of O–H···N hydrogen bonds linking dimers and π–π stacking interactions were described within the QTAIM (quantum theory of atoms in molecules) /DFT (density functional theory) formalism. Both proton donor and acceptor sites in O–H···N bonds were characterized using 1H-17O and 1H-14N NQDR spectroscopies and QTAIM. The possibility of the existence of O–H···H–O dihydrogen bonds was excluded. The weak intermolecular interactions in the crystals of clioquinol and cloxiquine were detected and examined. The results obtained in this work suggest that considerable differences in the NQR parameters for the planar and twisted supramolecular synthons permit differentiation between specific polymorphic forms, and indicate that the more planar supramolecular synthons are accompanied by a greater number of weaker hydrogen bonds linking them and stronger π···π stacking interactions
Perfect magnetohydrodynamics as a field theory
We propose the generally covariant action for the theory of a self-coupled
complex scalar field and electromagnetism which by virtue of constraints is
equivalent, in the regime of long wavelengths, to perfect magnetohydrodynamics
(MHD). We recover from it the Euler equation with Lorentz force, and the
thermodynamic relations for a prefect fluid. The equation of state of the
latter is related to the scalar field's self potential. We introduce 1+3
notation to elucidate the relation between MHD and field variables. In our
approach the requirement that the scalar field be single valued leads to the
quantization of a certain circulation in steps of ; this feature leads,
in the classical limit, to the conservation of that circulation. The
circulation is identical to that in Oron's generalization of Kelvin's
circulation theorem to perfect MHD; we here characterize the new conserved
helicity associated with it. We also demonstrate the existence for MHD of two
Bernoulli-like theorems for each spacetime symmetry of the flow and geometry;
one of these is pertinent to suitably defined potential flow. We exhibit the
conserved quantities explicitly in the case that two symmetries are
simultaneously present, and give examples. Also in this case we exhibit a new
conserved MHD circulation distinct from Oron's, and provide an example.Comment: RevTeX, 16 pages, no figures; clarifications added and typos
corrected; version to be published in Phys. Rev.
Ideal Stars and General Relativity
We study a system of differential equations that governs the distribution of
matter in the theory of General Relativity. The new element in this paper is
the use of a dynamical action principle that includes all the degrees of
freedom, matter as well as metric. The matter lagrangian defines a relativistic
version of non-viscous, isentropic hydrodynamics. The matter fields are a
scalar density and a velocity potential; the conventional, four-vector velocity
field is replaced by the gradient of the potential and its scale is fixed by
one of the eulerian equations of motion, an innovation that significantly
affects the imposition of boundary conditions. If the density is integrable at
infinity, then the metric approaches the Schwarzschild metric at large
distances. There are stars without boundary and with finite total mass; the
metric shows rapid variation in the neighbourhood of the Schwarzschild radius
and there is a very small core where a singularity indicates that the gas laws
break down. For stars with boundary there emerges a new, critical relation
between the radius and the gravitational mass, a consequence of the stronger
boundary conditions. Tentative applications are suggested, to certain Red
Giants, and to neutron stars, but the investigation reported here was limited
to polytropic equations of state. Comparison with the results of Oppenheimer
and Volkoff on neutron cores shows a close agreement of numerical results.
However, in the model the boundary of the star is fixed uniquely by the
required matching of the interior metric to the external Schwarzschild metric,
which is not the case in the traditional approach.Comment: 26 pages, 7 figure
Investigation of nucleon - unbound states in 29 Si and 29 P by the reaction 28 Si (d, pn)
The deuteron break-up reaction is a good tool to study nucleon unbound states o f
atomic nuclei [1, 2]. In the present paper we are studying the proton unbound states o f
29P and the neutron unbound states o f 29Si via the 28Si(d, p n )28Si reaction. The experimental
results and an analysis limited to the most prominent peaks in the spectra o f this
reaction were published in an earlier work [3], Now an extended analysis is presented,
based on the “ summed spectra” method [4] which enables us to identify even weak states
in complicated spectra
Plasticity and learning in a network of coupled phase oscillators
A generalized Kuramoto model of coupled phase oscillators with slowly varying
coupling matrix is studied. The dynamics of the coupling coefficients is driven
by the phase difference of pairs of oscillators in such a way that the coupling
strengthens for synchronized oscillators and weakens for non-synchronized
pairs. The system possesses a family of stable solutions corresponding to
synchronized clusters of different sizes. A particular cluster can be formed by
applying external driving at a given frequency to a group of oscillators. Once
established, the synchronized state is robust against noise and small
variations in natural frequencies. The phase differences between oscillators
within the synchronized cluster can be used for information storage and
retrieval.Comment: 10 page
Continuous and discrete Clebsch variational principles
The Clebsch method provides a unifying approach for deriving variational
principles for continuous and discrete dynamical systems where elements of a
vector space are used to control dynamics on the cotangent bundle of a Lie
group \emph{via} a velocity map. This paper proves a reduction theorem which
states that the canonical variables on the Lie group can be eliminated, if and
only if the velocity map is a Lie algebra action, thereby producing the
Euler-Poincar\'e (EP) equation for the vector space variables. In this case,
the map from the canonical variables on the Lie group to the vector space is
the standard momentum map defined using the diamond operator. We apply the
Clebsch method in examples of the rotating rigid body and the incompressible
Euler equations. Along the way, we explain how singular solutions of the EP
equation for the diffeomorphism group (EPDiff) arise as momentum maps in the
Clebsch approach. In the case of finite dimensional Lie groups, the Clebsch
variational principle is discretised to produce a variational integrator for
the dynamical system. We obtain a discrete map from which the variables on the
cotangent bundle of a Lie group may be eliminated to produce a discrete EP
equation for elements of the vector space. We give an integrator for the
rotating rigid body as an example. We also briefly discuss how to discretise
infinite-dimensional Clebsch systems, so as to produce conservative numerical
methods for fluid dynamics
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