169,848 research outputs found
An Architecture for Supporting “Pay-per-use” Downloadable Systems based on Java 2 and JavaSpaces
No full text"Context-based Message Selection Strategies in a Biologically Inspired Ambient Intelligence System"
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Design guidelines for the choice between single and dual pressure layouts in organic Rankine cycle (ORC) systems
No full textThe efficiency benefits deriving from the staging of the evaporation process into multiple pressure levels are well known in the field of gas-steam natural gas combined cycles where dual and triple pressure bottoming cycles represent the standard layouts. A similar development of the cycle architecture has not been observed in the field of organic Rankine cycle systems (ORCs). In this paper the dual pressure layout is compared against the single pressure one at subcritical conditions in the utilization of a geothermal heat source in the range 100-200°C, and considering a set of working fluids wide enough to take advantage of the features of both layouts. The paper proposes simple and unambiguous design guidelines to avoid the unnecessary complexity of the dual pressure layout when the single pressure one already ensures the highest power output, while taking advantage of its full potential in all the other conditions. Results show that the power output gains deriving from the dual pressure configuration are particularly high (up to 29%) at lower geothermal fluid temperatures (100-125°C) and gradually diminish at higher temperatures (150-200°C) where some of the selected fluids already obtain the best thermal matching with the heat source in the single pressure configuration
The Webmetrics Project - Exploiting 'Software Tools on Demand’
No full textThis paper presents a client/server stateless server architecture to implement collaborative data collection by
means of several software tools. Each of the tools can be downloaded as needed in an “on demand” fashion.
Security and accounting features are supported. An implemented example is shown based on a metric collection
problem
A system for real-time synthesis of subtle expressivity for life-like MPEG-4 based Virtual Characters
No full textNon-verbal behaviors have a key role in making a virtual character appear life-like. We describe an extensible system for the specification, control and real-time generation of facial expressions and gestures. The system approximates in a MPEG-4 based virtual character the wide expressive range, dynamism (an expression's meaning significantly depends on its temporal evolution) and variability (an emotion is never expressed exactly in the same way by different people, and even by the same person at different times), typical of human nonverbal behavior. The MPEG-4 standard only allows high-level control of 6 basic emotions and does not explicitly support the description of an expression temporal evolution. Our approach has been that of creating a hierarchical model of expressiveness; expressions are defined in term of parameterized functions controlling low-level animation parameters trajectories (by means of an XML-based expression definition markup language). The real-time generation of those expressions is performed by an expression synthesis engine. The system allows to effectively modulate expressivity both at design-time (the developer tweaks the parameters to give the character a given expressive style), and at run-time (the engine automatically changes the way in which an expression is performed each time), producing controllable, but non-deterministic, behavior patterns, a key factor for enhancing believability
Performance comparison between single and dual pressure Organic Rankine Cycle systems
No full textOrganic Rankine Cycle (ORC) systems are a well-known technology for power generation from low-to-medium temperature heat sources such as geothermal resources, solar thermal heat and waste heat. The majority of the existing plants worldwide are single pressure ORC systems taking advantage of their simple configuration. Recently, more complex cycle architectures have been proposed in the literature to improve the system performance. In particular, in the dual pressure layout the organic fluid is evaporated at two different pressure levels to improve the heat recovery from the heat source (similarly to steam in dual pressure natural gas combined cycles). However, only specific applications have been investigated in the literature in which the more efficient heat recovery was binding to get a good performance so that the potential of this layout has not been fully explored till now. The aim of this work is to compare the performance of single and dual pressure ORC systems in the utilization of heat sources between 100 and 200°C, and find possible guidelines for the choice between the two cycle architectures. In both layouts evaporation pressures and degrees of superheating were taken as decision variables to maximize power output without any constraint on the minimum outlet temperature of the heat source. Results show that dual pressure ORC systems generally improve power output (on average by 20%) when the critical temperature is similar or higher than the heat source inlet temperature. However, when the working fluid has a critical temperature approximately 35°C lower than the heat source inlet temperature, single pressure ORC systems do give their best performance which is not overcome by the dual pressure layout. Thus, dual pressure ORC systems are to be preferred only when the best fluid has to be selected within a limited set of working fluids which do not fulfill this optimum temperature difference due to specific constraints on costs, environment, availability, material compatibility, etc
A flexible architecture for ambient intelligence systems supporting adaptive multimodal interaction with users
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