592 research outputs found
A dynamic convergence control scheme for the solution of the radial equilibrium equation in through-flow analyses
One of the most frequently encountered numerical problems in scientific analyses
is the solution of non-linear equations. Often the analysis of complex phenomena
falls beyond the range of applicability of the numerical methods available in
the public domain, and demands the design of dedicated algorithms that will
approximate, to a specified precision, the mathematical solution of specific
problems. These algorithms can be developed from scratch or through the
amalgamation of existing techniques. The accurate solution of the full radial
equilibrium equation (REE) in streamline curvature (SLC) through-flow analyses
presents such a case. This article discusses the development, validation, and
application of an 'intelligent' dynamic convergence control (DCC) algorithm for
the fast, accurate, and robust numerical solution of the non-linear equations of
motion for two-dimensional flow fields. The algorithm was developed to eliminate
the large extent of user intervention, usually required by standard numerical
methods. The DCC algorithm was integrated into a turbomachinery design and
performance simulation software tool and was tested rigorously, particularly at
compressor operating regimes traditionally exhibiting convergence difficulties
(i.e. far off-design conditions). Typical error histories and comparisons of
simulated results against experimental are presented in this article for a
particular case study. For all case studies examined, it was found that the
algorithm could successfully 'guide' the solution down to the specified error
tolerance, at the expense of a slightly slower iteration process (compared to a
conventional Newton-Raphson scheme). This hybrid DCC algorithm can also find use
in many other engineering and scientific applications that require the robust
solution of mathematical problems by numerical instead of analytical means
Tidal stream generators, current state and potential opportunities for condition monitoring
Tidal power industry has made significant progress towards commercialization over the past decade. Significant investments from sector leaders, strong technical progress and positive media coverage have established the credibility of this specific renewable energy source. However, its progress is being retarded by operation and maintenance problems, which results in very low operational availability times, as low as 25 %. This paper presents a literature review of the current state of tidal device operators as well as some commercial tidal turbine condition monitoring solutions. Furthermore, an overview is given of the global tidal activity status (tidal energy market size and geography), the key industry activity and the regulations-standards related with tidal energy industry. Therefore, the main goal of this paper is to provide a bird’s view of the current status of the tidal power industry to serve as a roadmap for the academia regarding the real needs of the tidal power industry
Four schools of European accounting thought
A feature of the history of accounting thought is the existence of contending theories of accounts in continental Europe. Four schools of accounting thought developed and are here briefly examined
Polymerization in magnetic metamaterials
We numerically study a mesoscopic system consisting of magnetic nanorings in
the presence of thermal magnetization fluctuations. We find the formation of
dipolar-field-mediated ``bonds" promoting the formation of annuli clusters,
where the amount of bonds between two rings varies between zero and two. This
system resembles the formation of polymers from artificial atoms, which in our
case are the annuli and where the valency of the atom is set by the ring
multipolarity. We investigate the thermodynamic properties of the resulting
structures, and find a transition associated with the formation of the bonds.
In addition, we find that the system has a tendency to form topological
structures, with a distinct critical temperature in relation to the one for
bond formation
Yang-Baxter maps and symmetries of integrable equations on quad-graphs
A connection between the Yang-Baxter relation for maps and the
multi-dimensional consistency property of integrable equations on quad-graphs
is investigated. The approach is based on the symmetry analysis of the
corresponding equations. It is shown that the Yang-Baxter variables can be
chosen as invariants of the multi-parameter symmetry groups of the equations.
We use the classification results by Adler, Bobenko and Suris to demonstrate
this method. Some new examples of Yang-Baxter maps are derived in this way from
multi-field integrable equations.Comment: 20 pages, 5 figure
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A validation of web-based surveys for exploratory research in the areas of business and entrepreneurship
In this study, we demonstrate that web-based surveys are suitable for data collection in academic Business-related research. Using one of our datasets from an online study on entrepreneurial orientation, we investigated the construct validity and reliability of the instrument used to collect the data. Our analysis supports that for 28 Likert-scaled questionnaire items, a sample size of 332 people was adequate to conduct principle component analysis (PCA) and load the items into five components that are supported by literature. Cronbach’s alpha was consistently high (α = 0.92), with no evidence that the reliability would increase if any of the survey items were dropped. We therefore conclude that for short web-based surveys ( 300 is suitable for exploratory factor analysis
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