2,295 research outputs found
The polynomial approach to the LQ non-Gaussian regulator problem
No full textA new approach for the solution of the regulator problem for linear discrete-time dynamical systems with non-Gaussian disturbances is proposed. This approach generalizes a previous result concerning the definition of the quadratic optimal regulator. It consists in the definition of the polynomial optimal algorithm of order v for the solution of the linear quadratic non-Gaussian stochastic regulator problem for systems with partial state information. The validity of the separation principle has also been proved in this case. Numerical simulations show the high performance of the proposed method with respect to the classical linear regulation techniques
An approach to assessing virtual environments for synchronous and remote collaborative design
No full textReceived 4 March 2011 Accepted 14 June 2012 Available online 31 July 2012
Keywords:
Collaborative design Virtual environments Metrics
Design review Benchmarking method
1. Introduction
Market globalisation, short delivery times and the rapid evolu- tion of customer requirements highly influence how the product design process must be performed. It is becoming increasingly important to consider different competencies in the early process phases, which implies organising the cooperative work of a geo- graphically distributed team. Generally, team configuration dynamically changes based on specific objectives. To manage this flexible cooperation, a new approach called Collaborative Product Design (CPD) has been developed. In this case, people belong to a virtual design team. However, traditional design tools have not generally been conceived to support the collaborative teamwork in a distributed design space. New technologies have recently emerged that allow creating Virtual Design Environments (VDEs) to facilitate CPD through easy interaction and data sharing among all participants. Though several collaborative software applications
⇑ Corresponding author. Tel.: +39 71 2204969/2204790; fax: +39 71 2204801. E-mail address: [email protected] (M. Germani).
URL: http://www.univpm.it (M. Germani).
1474-0346/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.aei.2012.06.003
abstract
This paper considers applying novel Virtual Environments (VEs) in collaborative product design, focusing on reviewing activities. Companies are usually anchored to commercial ICT tools, which are mature and reliable. However, two main problems emerge: the difficulty in selecting the most suitable tools for specific purposes and the complexity in evaluating the impact that using technology has on design col- laboration. The present work aims to face both aspects by proposing a structured benchmarking method based on expert judgements and defining a set of benchmarking weights based on experimental tests. The method considers both human–human interaction and teamwork-related aspects. A subsequent evaluation protocol considering both process efficiency and human–human interaction allows a closed-loop verification process. Pilot projects evaluate different technologies, and the benchmarking weights are verified and adjusted for more reliable system assessment. This paper focuses on synchro- nous and remote design review activities: three different tools have been compared according to expert judgements. The two best performing tools have been implemented as pilot projects within real indus- trial chains. Design collaboration has been assessed by considering both process performance and human–human interaction quality, as well as benchmarking results validated by indicating some correc- tive actions. The final benchmarking weights can thus be further adopted for an agile system benchmark in synchronous and remote design. The main findings suggest defining both an innovative process to ver- ify the expert benchmark reliability and a trusty benchmarking method to evaluate tools for synchronous and remote design without experimental testing. Furthermore, the proposed method has a general valid- ity and can be properly set for different collaborative dimensions
Optimal quadratic solution for the non-Gaussian finite-horizon regulator problem
No full textIn this paper, the problem of the optimal quadratic regulator for non-Gaussian discrete-time stochastic systems with a quadratic cost function is considered. The main result here obtained is that such optimal control can be derived from the classical LQG solution by substituting the linear filtering part with a quadratic optimal filter. Numerical results show high performance of this method. (C) 1999 Elsevier Science B.V. All rights reserved
Method for the production of binary clathrate hydrates of hydrogen
No full textA method for the effective production of binary clathrate hydrates of hydrogen and a co-former is provided, said method comprising the formation of water-in-oil nanoemulsions, such as, e.g., surfactant reverse micelles in an organic solvent, and the formation of clathrate hydrate nanocrystals from the water droplets thus obtained
Effect of conditioners upon the thermodynamics and kinetics of methane hydrate formation. A preliminary structure-properties relationship study
No full textThe synthesis and stability of gas hydrates was found to be heavily affected by the presence of small quantities of additives, or conditioners, particularly surfactants. In a recent work, we showed that the enhancement of hydrate formation, both from previously described and newly synthesized surfactants, is probably due to surfactant monomers, rather than micelles, and that the features of hydrate induction time should not be used as a measure of critical micelle concentration. In the present paper, we discuss the results of a structure-properties relationship study in which a preliminary attempt to relate the structural features of several amphiphilic additives to some kinetic and thermodynamic parameters of methane hydrate formation - e.g., induction times, rate of formation, occupancy, etc. - is conducted. According to the present study, it is found that, for a particular conditioner, a reduction of induction time does not correlate to an increase of the formation rate and occupancy, and vice versa. This may be related to the nature of chemical moieties forming a particular amphiphile (e.g., the hydrophobic tail, head group, counterion, etc.). The understanding of the mechanisms by which those moieties play their differential role may be the key tool to the design and synthesis of tailored conditioners
Synthesis of Novel 5’ Uridine-Head Amphiphiles as Models for DNA Molecular Recognition
No full textHere we describe uridine functionalization in the 5’ position which provided new classes of cationic and non-ionic amphiphiles specifically designed to interact with DNA as transfection agents. The synthetic procedures developed to obtain the cationic uridine-head surfactants prevented intramolecular cyclization which occurs when uridine is functionalized in this position without using protecting groups in the uracil
Apparatus for preparing and studying clathrate hydrate
No full textA device for clathrate hydrates preparation by means of stirring of an aqueous solution in presence of gas, involve a motionless reactor (1), gas loading and pressure control media (2), temperature control and regulation media (3), liquid supply media (4) in constant pressure, solutes concentration detecting media (5), visual monitoring media (6), data acquisition and control media (7) and stirring media, preferentially magnetic, (10, 12) of the solution present in the reactor (1)
MEASUREMENTS OF RELEVANT PARAMETERS IN THE FORMATION OF CLATHRATE HYDRATES BY A NOVEL EXPERIMENTAL APPARATUS
No full textStudying clathrate hydrates is, ideally, a simple task: one just have to keep water under a gas pressure. However, when trying to collect measurements in an accurate and repeatable way, things mess up. When, in particular, kinetic characterizations are required, not only pressure and temperature have to be measured: also particular parameters such as gas evolved/trapped during time, heat released/adsorbed during time, critical phenomena related to additive addition, etc, should be collected in a finer way. In the last years a growing interest has been devoted to investigations on the effects of a wide range of compounds capable to affect the thermodynamics and, in particular, kinetics of clathrate hydrate formation. The study of the effects of these compounds, called conditioners, requires an improvement of the performances of usual lab facilities by introducing a new strategy for the measurement of further characterizing parameters. Presently no standardization of the apparatus designed for clathrate hydrate studies exists, nor any commercial instrumentations are available. Generally, apparatus used are custom-made by the same research team according with the peculiar research requirements To do this we have designed, built, calibrated and tested a novel apparatus that, in addition to the ability of measuring usually unexplored parameters, is based on the idea of obtaining as many parameters as possible in a single formation batch. This in order to solve the problem of collecting a dataset that can be processed homogeneously, thus minimizing errors due stochastic behaviours. Using such an apparatus, several kinds of measurement are presented here, which are related directly to the clathrate hydrate investigation fields, but also more generally related to the study of equilibrium phases involving gaseous components
Démocratie représentative et classes populaires en Amérique latine
No full textGermani Gino. Démocratie représentative et classes populaires en Amérique latine. In: Sociologie du travail, 3ᵉ année n°4, Octobre-décembre 1961. Ouvriers et syndicats d'Amérique Latine, sous la direction de Alain Touraine. pp. 96-113
- …
