Temporal Causal Abduction

The paper is devoted to presentation of the idea of Temporal Causal Networks (TCN). Temporal Causal Networks constitute a tool for representing and dealing with causal dependencies propagation over time. A temporal causal network is a causal network incorporating explicit representation of time during which its symptoms/nodes are valid, not valid, or unknown. The atemporal causal structure is basically an AND/OR/NOT causal graph, i.e. a causal graph incorporating basic logical connectives for the representation of different types of causal dependencies. The presented approach uses a specific time constraints propagation algorithm to determine possible system behavior in time. The main application includes simulation, monitoring and elements of diagnostic reasoning for dynamic systems with explicit time representation.     

Assessment of natural frequency of installed offshore wind turbines using nonlinear finite element model considering soil-monopile interaction

A nonlinear finite element model is developed to examine the lateral behaviors of monopiles, which support offshore wind turbines (OWTs) chosen from five different offshore wind farms in Europe. The simulation is using this model to accurately estimate the natural frequency of these slender structures, as a function of the interaction of the foundations with the subsoil. After a brief introduction to the wind power energy as a reliable alternative in comparison to fossil fuel, the paper focuses on concept of natural frequency as a primary indicator in designing the foundations of OWTs. Then the range of natural frequencies is provided for a safe design purpose. Next, an analytical expression of an OWT natural frequency is presented as a function of soil-monopile interaction through monopile head springs characterized by lateral stiffness K_L, rotational stiffness K_R and cross-coupling stiffness K_LR, of which the differences are discussed. The nonlinear pseudo three-dimensional finite element vertical slices model has been used to analyze the lateral behaviors of monopiles supporting the OWTs of different wind farm sites considered. Through the monopiles head movements (displacements and rotations), the values of K_L, K_R and K_LR were obtained and substituted in the analytical expression of natural frequency for comparison. The comparison results between computed and measured natural frequencies showed an excellent agreement for most cases. This confirms the convenience of the finite element model used for the accurate estimation of the monopile head stiffness.     

Sensitive and fast response ethanol chemical sensor based on as-grown Gd2O3 nanostructures

Well crystalline gadolinium oxide(Gd2O3) nanostructures were grown by annealing the hydrothermally as-prepared nanostructures without using any template. Microscopic studies of Gd2O3 nanostructures were recorded along the [111] direction due to the clearly resolved interplanar distance d(222)~0.31 nm of the cubic crystal structure Gd2O3. Sensing mechanism of Gd2O3 as efficient electron mediator for the detection of ethanol was explored. As-fabricated sensor demonstrated the high-sensitivity of ~0.266 μAm/M/cm2 with low detection limit(~52.2 μmol/L) and correlation coefficient(r2, 0.618). To the best of our knowledge, this was the first report for the detection of ethanol using as-grown(at 1000 oC) Gd2O3 nanostructures by simple and reliable I-V technique and rapid assessment of the reaction kinetics(in the order of seconds). The low cost of the starting reagents and the simplicity of the synthetic route made it a promising chemical sensor for the detection of various toxic analytes, which are not environmentally safe.     

Evaluation of machining process by integrating 3D manufacturing dispersions,functional constraints,and the concept of small displacement torsors

This paper presents a 3D formalization of manufacturing tolerancing which associates the concept of small displacements, the functional constraints, and manufacturing process capability. This approach would make it possible to establish relations which limit the surface variations of the production mechanism by the functional specifications. These relations have a number of requirements imposed by designer and are sufficient to evaluate the manufacturing process. The variations of the manufacturing process are defined in relation to variations measured by 3D measuring.     

Multi-pitch estimation based on multi-scale product analysis,improved comb filter and dynamic programming

There are many multi-pitch estimation methods, but most of them can’t perform perfectly for intrusion pitch detection. For this reason, a new multi-pitch detection approach is proposed. This method consists on the autocorrelation function of the Multi-scale product calculation of the mixture signal, its filtered version by a rectangular improved comb filter and the dynamic programming of the residual signal spectral density. First, we analyze the composite speech. Then, we apply the autocorrelation on the multi-scale product (AMP). We find the first pitch which represents the dominant one. Then, we apply the rectangular comb filter which has adaptive amplitude to remove the resulting signal from the original one. We operate AMP on the residue to obtain a pitch estimation of the intrusion. To improve the residue pitch estimation, we apply the dynamic programming to the spectral density of the residual signal to get optimum pitches corresponding also to intrusion signal. After that, we compare the two resulting pitch residue series to choose the most appropriate. Finally, this method is evaluated using the Cooke database and is compared to other well-known techniques. Experimental results confirm the strength and the performance of the proposed approach.     

Feed rate modeling in circular–circular interpolation discontinuity for high-speed milling

In this paper, a modeling approach is presented in order to evaluate feed rate during a circular interpolation in high-speed milling. The developed model depends on the type of discontinuity and the kinematic performance of the machine tool. To begin with, a feed rate modeling for circular interpolation with continuity in tangency is developed. After, the discontinuity in tangency between two circular interpolations is replaced by discontinuity in curvature by adding a fillet which is in relation to the functional tolerance ε imposed in the part design. An experimental study has been carried out to validate the models.     

An approach to agent-based service composition and its application to mobile business processes

This paper describes an architecture model for multiagent systems that was developed in the European project LEAP (Lightweight Extensible Agent Platform). Its main feature is a set of generic services that are implemented independently of the agents and can be installed into the agents by the application developer in a flexible way. Moreover, two applications using this architecture model are described that were also developed within the LEAP project. The application domain is the support of mobile, virtual teams for the German automobile club ADAC and for British Telecommunications.     

A high-gain EDFA design using double-pass amplification with a double-pass filter

An erbium-doped fiber (EDF) amplifier configured in a double-pass amplification scheme together with a midway bandpass filter is presented to provide a gain as high as 37.5 dB with a noise figure of less than 6 dB. The system provides a gain improvement of as much as 9.5 dB from the double-pass system without filter. The system also can easily be upgraded to support dense wavelength-division-multiplexing (DWDM) transmissions by using a multiwavelength filter. Using a pair of four-channel DWDM multiplexer and demultiplexer, a gain of 39.53 dB for each of the channels was achieved. At the bit-error rate of 10/sup -9/, the proposed design supports the input level as low as -43 dBm with a gain of 37 dB. This is all achieved with the EDF length of 7 m and pump power of 90 mW.