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Search Results: 1 - 10 of 9823 matches for " Stefan "
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Comparison of Different Control Algorithms for a Gantry Crane System  [PDF]
Stefan Bruins
Intelligent Control and Automation (ICA) , 2010, DOI: 10.4236/ica.2010.12008
Abstract: For a gantry crane system, this paper presents a comparison between four control algorithms. These algo-rithms are being compared on simplicity, stability and robustness. Goal for the controller is to move the load on a gantry crane to a new position with minimal overshoot of the load and maximal speed of the load. An-other goal is to provide an insight in the behaviour of the possible controllers. In this article a parallel P-controller, cascade P-controller, fuzzy controller and an internal model controller are used. To be able to validate and design the controllers a model is derived from the gantry crane. The controllers and the model are being implemented in Matlab Simulink. Finally the controllers are validated and tuned in Labview on a laboratory gantry scrane scale model. Main conclusion is that all presented controllers can be used as a con-troller for the gantry crane system but the fuzzy controller is showing the best performance.
Simulation and Injection Molding of Ring-Shaped Polymer Bonded Nickel Braze Metal Composite Preforms Based on Rheological and Thermal Analyses  [PDF]
Stefan Kirchberg
Open Journal of Composite Materials (OJCM) , 2013, DOI: 10.4236/ojcm.2013.32004

Rheological and thermal properties of LD-PE and LD-PE + 65 vol% Ni composite were examined by viscosity, pvt and thermal conductivity measurements at a wide range of shear rate, temperature and pressure. The typical shear-thinning viscosity of LD-PE polymer melt was enhanced up to four times by adding 65 vol% Ni braze metal particles. LD-PE show increasing specific volume versus temperature, decreasing with pressure and braze particle filler content. Variation of specific volume of LD-PE was reduced to 5% by admixing 65 vol% rigid Ni braze metal particles. Thermal conductivity of LD-PE was increased up to 15 times in the composite, reduced by decreasing pressure at temperature exceeding 80. Furthermore, thermal analysis was performed in modulated DSC to determine the specific heat capacity in wide temperature range. Viscosity and pvt-data were fitted using Cross-WLF equation and 2-domain Tait-pvt model, respectively. Simulation of LD-PE and LD-PE + 65 vol% Ni composite was performed based on rheological and thermal properties to define processing parameters. Simulation and injection molding of ring-shaped LD-PE + 65 vol% Ni composite braze metal preforms were performed successfully.

Creating a Strategic Partnership for Educating Nurse Practitioner Students about Sexual Health  [PDF]
Stefan Rowniak
Creative Education (CE) , 2014, DOI: 10.4236/ce.2014.515156

Sexual health is an essential and often neglected component of primary care. Nurse practitioners are ideal members of the healthcare team to be providing sexual health information, diagnoses, and treatments. Unfortunately, this is an area that has been lacking in the education of all healthcare providers. This paper describes a program that incorporates sexual health into the curriculum for nurse practitioner students through collaboration between the university school of nursing and the local health department. Given the increasing shortage of clinical sites and the need to train nurse practitioners to be competent in the delivery of sexual health, this is a model that could benefit other schools of nursing.

On the Stability of Stochastic Jump Kinetics  [PDF]
Stefan Engblom
Applied Mathematics (AM) , 2014, DOI: 10.4236/am.2014.519300
Abstract: Motivated by the lack of a suitable constructive framework for analyzing popular stochastic models of Systems Biology, we devise conditions for existence and uniqueness of solutions to certain jump stochastic differential equations (SDEs). Working from simple examples we find reasonable and explicit assumptions on the driving coefficients for the SDE representation to make sense. By “reasonable” we mean that stronger assumptions generally do not hold for systems of practical interest. In particular, we argue against the traditional use of global Lipschitz conditions and certain common growth restrictions. By “explicit”, finally, we like to highlight the fact that the various constants occurring among our assumptions all can be determined once the model is fixed. We show how basic long time estimates and some limit results for perturbations can be derived in this setting such that these can be contrasted with the corresponding estimates from deterministic dynamics. The main complication is that the natural path-wise representation is generated by a counting measure with an intensity that depends nonlinearly on the state.
Generality Challenges and Approaches in WSNs  [PDF]
Int'l J. of Communications, Network and System Sciences (IJCNS) , 2009, DOI: 10.4236/ijcns.2009.21007
Abstract: Ignoring the generality in the design of Wireless Sensor Networks (WSNs) applications limits their benefits. Furthermore, the possibilities of future extension and adaptation are also restricted. In this paper, several methods to enhance the generality in WSNs are explained. We have further evaluated the suitability of these methods in centralized and de-centralized management scenarios.
Clean Coal & High Carbon Efficiency Energy Engineering  [PDF]
Stefan Petters, Kalvin Tse
Journal of Power and Energy Engineering (JPEE) , 2015, DOI: 10.4236/jpee.2015.34047

Today we live in a world of Hydrocarbon Energy Carriers, where Carbon is always used as a Carrier for Hydrogen 1) Biomass (CH1.44O0.66 or C6H12O6); 2) Natural Gas [NG] (CH4); 3) Water Gas [C+H2O]; 4) Gasoline (C6H12, C7H18, C8H18, etc.); 5) Kerosene (C17H36, C18H38, C19H40, C20H42, C21H44, C22H46, etc.) and; 6) Crude Oil. The Carbon aggregates are all storable and have worthwhile, logistically manageable energy densities. But whenever recovering Energy from the Carbon molarities, CO2 gets emitted into the atmosphere, while separate use of Hydrogen Energy contents carried by the Carbon moieties would just generate water vapor. Hydrogen is also the most important intermediary in Refineries, hydrogenating lower grade Hydrocarbons into higher potencies, or for removing Sulfur by the formation of Hydrogen Sulfur, that can be dissociated after its segregation from the Hydrocarbon products. But most of the internal Hydrogen yields in Refineries today is used for onsite production of Ammonia as a basis for Energy fertilizers in high performance agriculture. Because Hydrogen is awkward to store and transport, most of it is currently used captive within large size centralized plants as a reactant for producing Hydrocarbon energy carriers, using the Carbon as a carrier for the Hydrogen moieties, to then be distributed over big enough areas for consumption of the such large scale plants’ volumes. With recently proven achievements of Hydrogen production from excess Wind & Solar Power by electrolysis, Hydrogen could become available in abundant quantities, to be distributed locally within the coverage area of the transmission grid such Wind & Solar installations are feeding into. In combination with Carbon as a reactant such abundant Hydrogen could also be synthesized into Hydrocarbon Energy Carriers and substitute fossil commodities.

Gravitational Forces Explained as the Result of Anisotropic Energy Exchange between Baryonic Matter and Quantum Vacuum  [PDF]
Stefan L. Hahn
Journal of Modern Physics (JMP) , 2015, DOI: 10.4236/jmp.2015.68117
Abstract: Gravitational forces are explained as a result of energy exchange between baryonic matter having the property of mass and the Quantum Vacuum. The derivations are starting with a hypothesis that baryonic matter, particles, atoms and molecules exchange energy with the Quantum Vacuum with zero balance. It is assumed that in absence of an external gravitation field the emission pattern is isotropic. There is no recoil force of radiation. The application of an external gravitation field induces an anisotropy which results in a recoil force of radiation. An ellipsoidal radiation pattern is applied. The eccentricity of the ellipsoid is defined using the maximum possible value of any gravitation field estimated to have the value about 5 × 1012 [m/s2]. A formula is derived for calculating the power of the isotropic radiation. It was shown that two masses attract due to the fact that gravitation field lowers the energy density of the Quantum Vacuum. Using the results of measurements of a binary neutron star by Taylor and Hulse (Nobel Prize in Physics 1993) it was shown that possibly gravitational waves carry negative energy.
Gravity in View of the Theory of Orbiting Binary Stars  [PDF]
Stefan L. Hahn
Journal of Modern Physics (JMP) , 2018, DOI: 10.4236/jmp.2018.910124
Abstract: In this paper, we investigate orbiting of two stars having equal masses. We consider two models: with a circular orbit and with two elliptical orbits having a common center of a mass located in a common focal point. In the case of the circular orbit, we applied the notion of the instantaneous complex frequency. The paper is illustrated with numerous formulas, derivations and discussion of results.
Web based Interactive 3D Learning Objects for Learning Management Systems
Stefan Hesse,Stefan Gumhold
Journal of Systemics, Cybernetics and Informatics , 2012,
Abstract: In this paper, we present an approach to create and integrate interactive 3D learning objects of high quality for higher education into a learning management system. The use of these resources allows to visualize topics, such as electro-technical and physical processes in the interior of complex devices. This paper addresses the challenge of combining rich interactivity and adequate realism with 3D exercise material for distance elearning.
Finite-Size Corrections for Ground States of Edwards-Anderson Spin Glasses
Stefan Boettcher,Stefan Falkner
Physics , 2011, DOI: 10.1209/0295-5075/98/47005
Abstract: Extensive computations of ground state energies of the Edwards-Anderson spin glass on bond-diluted, hypercubic lattices are conducted in dimensions d=3,..,7. Results are presented for bond-densities exactly at the percolation threshold, p=p_c, and deep within the glassy regime, p>p_c, where finding ground-states becomes a hard combinatorial problem. Finite-size corrections of the form 1/N^w are shown to be consistent throughout with the prediction w=1-y/d, where y refers to the "stiffness" exponent that controls the formation of domain wall excitations at low temperatures. At p=p_c, an extrapolation for $d\to\infty$ appears to match our mean-field results for these corrections. In the glassy phase, w does not approach the value of 2/3 for large d predicted from simulations of the Sherrington-Kirkpatrick spin glass. However, the value of w reached at the upper critical dimension does match certain mean-field spin glass models on sparse random networks of regular degree called Bethe lattices.
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