Stabilized mixed finite elements for fluid models in semiconductors

In this article we deal with the numerical simulation of semiconductor devices using the Energy-Balance (EB) transport model. This accounts for hot electrons behaviour and nonlocal effects which are of utmost relevance in the simulation of submicron devices. We propose an efficient and accurate solver for the EB equations based on the well-known Gummel’s decoupled algorithm to handle iteratively the full system, while the discretization employs cell-centred Mixed Finite Volume (MFV) methods. These are derived from the standard Raviart-Thomas (RT) finite elements of lowest degree through a suitable quadrature formula which diagonalizes the element mass matrix. Numerical results to validate the newly proposed stabilized method are reported including the simulation of a model curved p-n diode, a one-dimensional p-n diode and a realistic state-of-the-art 1 μm-channel nMOS transistor. Accepted: 6 March 1999 / Accepted: 17 June 1999     

On the complexity of some inductive logic programming problems

The bounded ILP-consistency problem for function-free Horn clauses is described as follows. Given at setE ⁺ andE ^? of function-free ground Horn clauses and an integerk polynomial inE ⁺∪E ^?, does there exist a function-free Horn clauseC with no more thank literals such thatC subsumes each element inE ⁺ andC does not subsume any element inE ^?? It is shown that this problem is Σ ₂ ^P complete. We derive some related results on the complexity of ILP and discuss the usefulness of such complexity results.     

Simultaneous localization and odometry self calibration for mobile robot

This paper presents both the theory and the experimental results of a method allowing simultaneous robot localization and odometry error estimation (both systematic and non-systematic) during the navigation. The estimation of the systematic components is carried out through an augmented Kalman filter, which estimates a state containing the robot configuration and the parameters characterizing the systematic component of the odometry error. It uses encoder readings as inputs and the readings from a laser range finder as observations. In this first filter, the non-systematic error is defined as constant and it is overestimated. Then, the estimation of the real non-systematic component is carried out through another Kalman filter, where the observations are obtained by two subsequent robot configurations provided by the previous augmented Kalman filter. There, the systematic parameters in the model are regularly updated with the values estimated by the first filter. The approach is theoretically developed for both the synchronous and the differential drive. A first validation is performed through very accurate simulations where both the drive systems are considered. Then, a series of experiments are carried out in an indoor environment by using a mobile platform with a differential drive.     

Fracture instability and limit strength condition in structures with re-entrant corners

When considering a structural element with a re-entrant corner, the experimental analysis shows how the fracture strength increases with the angle of the corner. Thus, the strength increases with a decrease of the mass of the structure, in contrast to what we are used to observe in different kind of collapses, e.g., plasticity. To predict this behaviour, a non-local theory, basically based on the Novozhilov’s hypothesis of existence of a fracture quantum, is herein presented. Theoretical predictions for the strength of finite structures (e.g., finite plates under tension or beams under bending) by varying both angle and relative depth of the corner are presented: accordingly, simple formulas, useful in the design of such structures, are provided. The theory is then compared with experimental and numerical results, showing a relevant agreement.     

Differences Between People Who Use Only Facebook and Those Who Use Facebook Plus Twitter

Facebook (FB) and Twitter are popular social networking sites. This study examined differences between those who use both sites versus only FB, to test the hypothesis that mono-users differ in their personality characteristics from users active in both websites. Participants were 205 undergraduate students: 96 only used FB, 109 used FB and Twitter. Participants who used both sites reported significantly lower loneliness, higher number of FB friends, and lower number of minutes spent online, as compared to those who used only FB. Loneliness was positively associated with FB use only in those who used FB alone but was negatively associated with and negatively predicted both FB and Twitter use in those who used both websites. Findings suggest that more intense use of online interactions is more frequently found in mono-users (people using only Facebook) as compared to those using both websites, and it is predicted by increased feelings of loneliness. The current study findings provide additional insights on what personality factors may make some people prone to excessive use of social networking sites.     

A high frequency cMUT probe for ultrasound imaging of fingerprints

Fingerprint imaging using ultrasound has been investigated for several years and has shown to be a valid alternative to optical scanners. Capacitive micro-machined ultrasound transducers (cMUT) is an emerging MEMS technology that can be profitably exploited in biometric applications, like fingerprint or palm print.In this work a FEM model of a cMUT is proposed and used to design a 192-element array with a frequency band centered at 12.5 MHz. A cMUT array was manufactured by means of a proprietary fabrication process and an ultrasound probe was assembled and experimentally characterized. Comparison between simulation and experimental results has shown a quite good agreement. The cMUT probe was operated at a frequency of 12 MHz and used to produce images of fingerprints, the quality of which was quite satisfactory.     

Towards a Logic for Performance and Mobility

Klaim is an experimental language designed for modeling and programming distributed systems composed of mobile components where distribution awareness and dynamic system architecture configuration are key issues. StocKlaim [R. De Nicola, D. Latella, and M. Massink. Formal modeling and quantitative analysis of KLAIM-based mobile systems. In ACM Symposium on Applied Computing (SAC). ACM Press, 2005. Also available as Technical Report 2004-TR-25; CNR/ISTI, 2004] is a Markovian extension of the core subset of Klaim which includes process distribution, process mobility, asynchronous communication, and site creation. In this paper, MoSL, a temporal logic for StocKlaim is proposed which addresses and integrates the issues of distribution awareness and mobility and those concerning stochastic behaviour of systems. The satisfiability relation is formally defined over labelled Markov chains. A large fragment of the proposed logic can be translated to action-based CSL for which efficient model-checkers exist. This way, such model-checkers can be used for the verification of StocKlaim models against MoSL properties. An example application is provided in the present paper.     

Approximation of jump diffusions in finance and economics

In finance and economics the key dynamics are often specified via stochastic differential equations (SDEs) of jump-diffusion type. The class of jump-diffusion SDEs that admits explicit solutions is rather limited. Consequently, discrete time approximations are required. In this paper we give a survey of strong and weak numerical schemes for SDEs with jumps. Strong schemes provide pathwise approximations and therefore can be employed in scenario analysis, filtering or hedge simulation. Weak schemes are appropriate for problems such as derivative pricing or the evaluation of risk measures and expected utilities. Here only an approximation of the probability distribution of the jump-diffusion process is needed. As a framework for applications of these methods in finance and economics we use the benchmark approach. Strong approximation methods are illustrated by scenario simulations. Numerical results on the pricing of options on an index are presented using weak approximation methods.     

On the partial semantics for disjunctive deductive databases

Partial stable models for deductive databases, i.e., normal function-free logic programs (also called datalog programs), have two equivalent definitions: one based on 3-valued logics and another based on the notion of unfounded set. The notion of partial stable model has been extended to disjunctive deductive databases using 3-valued logics. In this paper, a characterization of partial stable models for disjunctive datalog programs is given using a suitable extension of the notion of unfounded set. Two interesting sub-classes of partial stable models, M-stable (Maximal-stable) (also called regular models, preferred extension,and maximal stable classes) and L-stable (Least undefined-stable) models, are then extended from normal to disjunctive datalog programs. On the one hand, L-stable models are shown to be the natural relaxation of the notion of total stable model; on the other hand the less strict M-stable models, endowed with a nice modularity property, may be appealing from the programming and computational point of view. M-stable and L-stable models are also compared with the regular models for disjunctive datalog programs recently proposed in the literature.     

Sexual dimorphism and species differences in HVC volumes of cowbirds.

Cowbirds exhibit extensive variation in their social, territorial, and reproductive behaviors. Nissl-stained brain sections of specimens from a previous study (J. C. Reboreda, N. S. Clayton, & A. Kacelnik, 1996) were used to study the gross anatomy of a song control nucleus in 3 South American cowbirds (bay-winged, Molothrus badius; shiny, M. bonariensis; and screaming, M. rufoaxillaris). Cowbird high vocal center (HVC) volumes were consistently higher in males than in females in all 3 species. The largest HVC size of females found in bay-winged cowbirds is consistent with observations that females of this species, but not of the other 2 species, occasionally sing. The extent of the sexual dimorphism of relative HVC size was highest for the sexually dichromatic and promiscuous shiny cowbirds and smaller for the monochromatic and monogamous bay-winged and screaming cowbirds, suggesting that selection pressures associated with morphological traits and social systems are reflected in brain architecture. (PsycINFO Database Record (c) 2010 APA, all rights reserved)