Kinematics of a Family of Translational Parallel Mechanisms with Three 4‐DOF Legs and Rotary Actuators

This paper focuses on the kinematics of a family of translational parallel mechanisms equipped with three 4‐DOF legs and rotary actuators. The direct and the inverse position problems are solved in analytical form, the velocity analysis is carried out, the workspace is determined and the loci of both kinematic singularities and isotropic configurations are derived. Furthermore, the problem of singularity avoidance by means of actuator redundancy is addressed and some solutions are proposed. Two special architectures are finally considered as case studies: in the first, the three actuation axes are mutually orthogonal; in the second, two actuation axes are parallel to each other and the third is perpendicular to them. The comparison of the two architectures on the basis of kinematic considerations allows for the selection of the second one as a preferable solution. © 2003 Wiley Periodicals, Inc.     

Dynamics of electromigration induced void/hillock growth and precipitation/dissolution of addition elements studied by in-situ scanning electron microscopy resistance measurements

In the present paper it has been shown that the in-situ SEM resistance measurement technique is a powerful technique to study the dynamics of void/hillock growth and precipitation/dissolution of addition elements in a metal line submitted to a temperature/current stress. The power of the in-situ SEM resistance measurement technique is shown with the first results on Al1wt.%Si0.5wt.%Cu metal lines. During the electromigration experiment, performed in a SEM equipped with a heating stage, back scattered electron images are taken continuously over the entire length of the metal line monitoring a.o. the growth, shape variation and motion of voids/hillocks. The dissolution and motion of Al₂Cu precipitates in the Al1wt.%Si0.5wt.%Cu metal lines can also be monitored since the precipitates appear in the BSE mode as white objects. By comparing the observed electrical resistance drift results with the corresponding SEM micrographs it can be concluded that the resistance changes in the current stressed metal lines are mainly induced by geometrical changes.     

High electrical resistivity of CVD-diamond

Due to its combination of excellent thermo-mechanical properties and electrical properties such as the high electrical resistivity and high dielectric strength, diamond seems a promising material for specialized dielectric applications. Due to the great advances in the growth technology of diamond films by chemical vapour deposition (CVD) on e.g. Si-substrates, new applications can be expected in microelectronics. An important technological result for dielectric applications is that high electrical resistivity diamond films can be obtained after an appropriate heat treatment of the as-grown films.     

Comparison between Different Distributed Methods for Flood Susceptibility Mapping

Flooding is one of the main natural hazards in Northern Europe and several areas of the Northern Boreal Hemisphere, where during intense rainfall events, several river basins are affected by a fast water level rise that may cause severe damage to human lives and properties. For these reasons, the development of flood models to identify susceptible areas is essential for decision-makers. Geographic Information Systems (GIS) are currently accurate and valuable support tools for defining flood susceptibility maps at different spatial scales. In this study, the prediction accuracy of different GIS-based procedures in the identification of flooding susceptibility is tested and compared. These procedures include the frequency ratio, a combination of the frequency ratio and logistic regression, a combination of the frequency ratio and Shannon’s entropy index, and the statistical index. Ten conditioning parameters of flooding susceptibility are considered: elevation, slope, curvature, land use, Topographic Wetness Index, Stream Power Index, hydrogeology, stream distance, flow direction and average annual rainfall. The comparison analysis is carried out by applying these methods to the study area of Devon County in Southwest England. A total of 225 flood events are used to define the models. For model validation, 1000 randomly selected training and testing sub-datasets have been used in the definition of the receiver operating characteristic (ROC) curves. The results show that the procedure based on the statistical index provides the highest accuracy and reliability in flood susceptibility predictions.

     

Analogue algorithm for parallel factorization of an exponential number of large integers: I. Theoretical description

We describe a novel analogue algorithm that allows the simultaneous factorization of an exponential number of large integers with a polynomial number of experimental runs. It is the interference-induced periodicity of “factoring” interferograms measured at the output of an analogue computer that allows the selection of the factors of each integer. At the present stage, the algorithm manifests an exponential scaling which may be overcome by an extension of this method to correlated qubits emerging from n-order quantum correlations measurements. We describe the conditions for a generic physical system to compute such an analogue algorithm. A particular example given by an “optical computer” based on optical interference will be addressed in the second paper of this series (Tamma in Quantum Inf Process 11128:1189, 2015).

     

A comparison of simplex and simulated annealing for optimization of a new rear underrun protective device

In this paper, two optimization approaches to improve the product design process have been analysed. Through the analysis of a case study, concerning the designing of a new High Energy Absorption Rear Underrun Protective Device (HEARUPD), two different optimization approaches (simplex and simulated annealing) have been compared. In the implemented optimization processes, the crash between an economy car and the rear part of a truck has been simulated by dynamic numerical (FEM) analyses. Moreover, authors have proposed the use of a suitable linear function of four variables with the purpose of reducing the multi-objective optimization processes to mono-objective ones. That has been made to simplify the analysis procedures without affecting the quality and the completeness of the optimization processes. The obtained results, as well as showing the high effectiveness of the integrated use of numerical crash analyses and optimization methods, demonstrate that simplex method is more effective than simulated annealing one for optimization problems where the single analysis loop requires much time. Even if the solutions are quite similar in terms of calculated values of the objective function, design and state variables, simplex method needs shorter computational time than simulated annealing to obtain an optimized solution.     

Improved multiprocessor global schedulability analysis

A new technique was recently introduced by Bonifaci et al. for the analysis of real-time systems scheduled on multiprocessor platforms by the global Earliest Deadline First (EDF) scheduling algorithm. In this paper, this technique is generalized so that it is applicable to the schedulability analysis of real-time systems scheduled on multiprocessor platforms by any work-conserving algorithm. The resulting analysis technique is applied to obtain a new sufficient global Deadline Monotonic (DM) schedulability test. It is shown that this new test is quantitatively superior to pre-existing DM schedulability analysis tests; in addition, the degree of its deviation from any hypothetical optimal scheduler (that may be clairvoyant) is quantitatively bounded. A new global EDF schedulability test is also proposed here that builds on the results of Bonifaci et al. This new test is shown to be less pessimistic and more widely applicable than the earlier result was, while retaining the strong theoretical properties of the earlier result.     

An information-based exploration strategy for environment mapping with mobile robots

The availability of efficient mapping systems to produce accurate representations of initially unknown environments is recognized as one of the main requirements for autonomous mobile robots. In this paper, we present an efficient mapping system that has been implemented on a mobile robot equipped with a laser range scanner. The system builds geometrical point-based maps of environments employing an information-based exploration strategy that determines the best observation positions by taking into account both the distance travelled and the information gathered. Our exploration strategy, being based on solid mathematical foundations, differs from many ad hoc exploration strategies proposed in literature. We present: (a) the theoretical aspects of the criterion for determining the best observation positions for a robot building a map, (b) the implementation of a mapping system that uses the proposed criterion, and (c) the experimental validation of our approach.