1,721,053 research outputs found
Transient heat conduction in wires with heat sources; lumped and distributed solution techniques
No full textThe aim of this study is to test the approximate lumped analysis against the more rigorous distributed parameter approach in the solution of 1D and 2D nonlinear heat conduction problems associated with electrical cables under a current load. The system of partial differential equations governing the distributed parameter model is replaced by a system of ordinary differential equations with total derivatives with respect to time. The number of temperature unknowns is highly reduced and the numerical solution, even though approximate, can be very fast. Furthermore, with the use of the thermal-electrical analogy, the lumped system can be described as an equivalent electric circuit composed of thermal resistances and capacitances properly connected and solved with dedicated software. In this work, the lumped approach is applied to the overheating effect of insulated electric cables under a current load both in a steady and a transient regime. For this application, the lumped methodology can be very useful owing to the presence of several regions of solution domain having negligible internal conductive resistance. The approximate solutions are compared with the distributed parameter approach obtained with a commercial FEM code. An empirical methodology is described for modeling single cables and composite flat cables in such a way as to minimize the difference between the approximate and the more rigorous solution, both in a steady state and in a dynamic regime. The difference can be limited to less than few percent and can be considered fully adequate for industrial design
Techno-economic evaluation of a community-based wind park in the city of Genoa
No full textThis study investigates the feasibility of supplying electricity to 500 residential units in Genoa, Italy using wind energy. Energy demand was modeled using Monte Carlo simulation with Weibull distribution. Results show that three 5 MW wind turbines and a 75 MWh lithium-bromide battery can meet demand with a levelized cost of electricity between 0.12-0.29 US$/kWh. Grid connection and future integration with PV systems are recommended to improve performance
Local context-based recognition of sketched diagrams
No full textWe present a new methodology aimed at the design and implementation of a framework for sketch recognition enabling the recognition and interpretation of diagrams. The diagrams may contain different types of sketched graphic elements such as symbols, connectors, text. Once symbols are distinguished from connectors and identified, the recognition proceeds by identifying the local context of each symbol. This is seen as the symbol interface exposed to the rest of the diagram and includes predefined attachment areas on each symbol. We argue that, in many cases, simple constraints on the local context of each symbol are enough to describe diagram languages defined on those symbols. Further refinement and interpretation of the set of acceptable diagrams is then provided through a visual grammar. We also describe the architecture of the framework and provide sample applications for the domains of flowcharts and binary trees
KeyScretch on android tablets and smartphones
No full textKeyScretch is a text entry method for mobile devices equipped with touch-screens, based on a menu-augmented soft keyboard. It improves the previously studied menubased methods by enabling the interpretation of compound strokes, corresponding to the input of particularly frequent character sequences. Here we describe the design of an application we developed for the Android system, runnable on tablets and smartphones. section briefly describes the KeyScretch method; Section 3 presents the design of the KeyScretch Android application; finally, Section 4 offers our conclusions and outlines the future work
Novice and Expert Performance of KeyScretch: a Gesture-Based Text Entry Method for Touch-Screens
No full textExtending local context-based specifications of visual languages
No full textIn this paper we present a framework for the fast prototyping of visual languages exploiting their local context based specification.In previous research, the local context specification has been used as a weak form of syntactic specification to define when visual sentences are well formed. In this paper we add new features to the local context specification in order to fully specify complex constructs of visual languages such as entity-relationships, use case and class diagrams. One of the advantages of this technique is its simplicity of application and, to show this, we present a tool implementing our framework. Moreover, we describe a user study aimed at evaluating the effectiveness and the user satisfaction when prototyping a visual language
Improving Shape Context Matching for the Recognition of Sketched Symbols
No full textIn this paper we present an approach to recognize multi- stroke hand drawn symbols, which is invariant with respect to scaling and supports symbol recognition independently from the number and order of strokes. The approach is an adaptation of the algorithm proposed by Belongie et al. in 2002 to the case of sketched images. This is achieved by introducing a new step in which the original Shape Context point-to-point cost matrix is updated according to stroke re- lated information. The approach has been evaluated on a set of symbols from the Military Course of Action domain and the results show that the new recognizer outperforms the original one
On the auto-completion of hand drawn symbols
No full textIn this paper, preliminary studies for a new eager recognition algorithm for online hand drawn symbols and the usefulness of symbol auto-completion through experiments with users working on a real application are briefly described. The recognition of individual symbols is often not enough, as a matter of fact most of the times graphical symbols are parts of diagrams and the approach is sensitive to the preprocessing performed to extract the primitives
RankFrag: A machine learning-based technique for finding corners in hand-drawn digital curves
No full textWe describe RankFrag: a technique which uses machine learning to detect corner points in hand-drawn digital curves. RankFrag classifies the stroke points by iteratively extracting them from a list of corner candidates. The points extracted in the last iterations are said to have a higher rank and are more likely to be corners. The technique has been tested on three different datasets described in the literature. We observed that, considering both accuracy and efficiency, RankFrag performs better than other state-of-art techniques
Heating and cooling building energy demand evaluation; a simplified model and a modified degree days approach
No full textDegree days represent a versatile climatic indicator which is commonly used in building energy performance analysis.
In this context, the present paper proposes a simple dynamic model to simulate heating/cooling energy consumption in buildings. The model consists of several transient energy balance equations for external walls and internal air according to a lumped-capacitance approach and it has been implemented utilizing the Matlab/Simulink® platform. Results are validated by comparison to the outcomes of leading software packages, TRNSYS and Energy Plus.
By using the above mentioned model, energy consumption for heating/cooling is analyzed in different locations, showing that for low degree days the inertia effect assumes a paramount importance, affecting the common linear behavior of the building consumption against the standard degree days, especially for cooling energy demand.
Cooling energy demand at low cooling degree days (CDDs) is deeply analyzed, highlighting that in this situation other factors, such as solar irradiation, have an important role. To take into account these effects, a correction to CDD is proposed, demonstrating that by considering all the contributions the linear relationship between energy consumption and degree days is maintained
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