Capacitive micromachined ultrasonic transducer: transmission performance evaluation under different driving parameters and membrane stress for underwater imaging applications

Transmission performance of a CMUT element in terms of output pressure and displacements was evaluated. A SIMULINK model of single CMUT element based on mechanical model of MEMS capacitor was used and the analyses were performed under different ac and dc conditions. 2.6 µm thick Si, Poly-Si and Si₃Ni₄ membranes with a radius 60 µm were used to obtain results for underwater imaging application. Relation between membrane stress and outputs of CMUT was also investigated using SIMULINK model for commonly used CMUT membrane made of Si₃Ni₄ and polysilicon membrane under different electrical driving parameters. It was observed that different ac signal inputs (sine, square and sawtooth) showed different effects on CMUTs pressure and displacement characteristics. Our results indicated that the maximum output pressure and displacement were obtained in a square waveform. In addition, although stress on membrane increases the displacement and pressure of CMUT membrane made of Poly-Si, quality factor inversely proportional to stress on membrane. Membrane stress has adverse effect on Si₃Ni₄ membrane transmission outputs. The used model in this study might enable to determine optimum driving electrical inputs and stress on membrane to control CMUT outputs in terms of output pressure, displacement, quality factor and bandwitdh.

     

Annotated news corpora and a lexicon for sentiment analysis in Slovene

In this study, we introduce Slovene web-crawled news corpora with sentiment annotation on three levels of granularity: sentence, paragraph and document levels. We describe the methodology and tools that were required for their construction. The corpora contain more than 250,000 documents with political, business, economic and financial content from five Slovene media resources on the web. More than 10,000 of them were manually annotated as negative, neutral or positive. All corpora are publicly available under a Creative Commons copyright license. We used the annotated documents to construct a Slovene sentiment lexicon, which is the first of its kind for Slovene, and to assess the sentiment classification approaches used. The constructed corpora were also utilised to monitor within-the-document sentiment dynamics, its changes over time and relations with news topics. We show that sentiment is, on average, more explicit at the beginning of documents, and it loses sharpness towards the end of documents.     

Revaluation of Mbelek and Lachièze-Rey scalar-tensor theory of gravitation to explain the measured forces in asymmetric resonant cavities

The scalar-tensor theory of gravitation proposed by Mbelek and Lachièze-Rey has been previously shown to lead to a possible explanation of the forces measured in asymmetric resonant microwave cavities. However, in the derivation of the equations from the action principle some inconsistencies were observed, like no need to vary the electromagnetic invariant in a scalar source term. Also, the forces obtained were too high, in view of reconsideration of the experiments originally reported and of newly published results. In the present work, the equations are re-derived using the full variation of the action, and also the constant of the theory re-evaluated employing the condition that no anomalous gravitational effects are produced by the Earth’s magnetic field. It is shown that the equations originally employed were correct, and that the newly evaluated constant gives the correct magnitude for the forces recently reported.     

Experimental and theoretical study of the color changes in OPP-based printing substrate on the gravure printing

Neural Computing and Applications - In this study, the color change performances of the prints that are made with gravure printing technique on OPP-based printing substrate used in food packaging...     

Discrete representation strategies for foreign exchange prediction

This is an extended version of the paper presented at the 4th International Workshop NFMCP 2015 held in conjunction with ECML PKDD 2015. The initial version has been published in NFMCP 2015 conference proceedings as part of Springer Series. This paper presents a novel approach to financial times series (FTS) prediction by mapping hourly foreign exchange data to string representations and deriving simple trading strategies from them. To measure the degree of similarity in these market strings we apply familiar string kernels, bag of words and n-grams, whilst also introducing a new kernel, time-decay n-grams, that captures the temporal nature of FTS. In the process we propose a sequential Parzen windows algorithm based on discrete representations where trading decisions for each string are learned in an online manner and are thus subject to temporal fluctuations. We evaluate the strength of a number of representations using both the string version and its continuous counterpart, whilst also comparing the performance of different learning algorithms on these representations, namely support vector machines, Parzen windows and Fisher discriminant analysis. Our extensive experiments show that the simple string representation coupled with the sequential Parzen windows approach is capable of outperforming other more exotic approaches, supporting the idea that when it comes to working in high noise environments often the simplest approach is the most effective.     

β-carotene rejection mechanism from organic medium by using activated carbon produced from waste biomass apricot

The present paper deals with the study of adsorption of β-carotene in tetrahydrofuran solution on activated carbon. Activated carbon was prepared from apricot waste, which is a by-product of apricot processing by means of chemical activation with ZnCl₂. BET surface area of activated carbon was measured to be 1060 m² g^?1. The effect of adsorption time, percentage of activated carbon in β-carotene solution, and β-carotene concentration on adsorption efficiency was also determined. Results were analyzed by the Langmiur, Freundlich, Dubinin?Redushkevich (D-R), Temkin, Frumkin, Harkins?Jura, Halse, Henderson, and Henry isotherms with linearized correlation coefficient. The characteristic parameters for each isotherm have also been determined. The kinetics of β-carotene adsorption has been discussed by the pseudo-first-order model, the pseudo-second-order model, the Elovich equation, the intraparticle diffusion model, the Bangham equation, and the modified Freundlich equation. Three error analysis methods of residual mean square error (RMSE), chi-square statistic (χ²), and the average percentage error (% APE) have been used.     

Robust mean field games for coupled Markov jump linear systems

We consider robust stochastic large population games for coupled Markov jump linear systems (MJLSs). The N agents’ individual MJLSs are governed by different infinitesimal generators, and are affected not only by the control input but also by an individual disturbance (or adversarial) input. The mean field term, representing the average behaviour of N agents, is included in the individual worst-case cost function to capture coupling effects among agents. To circumvent the computational complexity and analyse the worst-case effect of the disturbance, we use robust mean field game theory to design low-complexity robust decentralised controllers and to characterise the associated worst-case disturbance. We show that with the individual robust decentralised controller and the corresponding worst-case disturbance, which constitute a saddle-point solution to a generic stochastic differential game for MJLSs, the actual mean field behaviour can be approximated by a deterministic function which is a fixed-point solution to the constructed mean field system. We further show that the closed-loop system is uniformly stable independent of N, and an approximate optimality can be obtained in the sense of ε-Nash equilibrium, where ε can be taken to be arbitrarily close to zero as N becomes sufficiently large. A numerical example is included to illustrate the results.     

Two Degrees of Freedom in the Control of a DC-DC Boost Converter,Fuzzy Identified Explicit Model in Feed-forward Line

We present a novel approach to the fuzzy control of a DC-DC Boost Converter. Using heuristic partitioning of the main control parameters and focusing on global knowledge of the open-loop, stable system’s equilibriums, the new method is developed based on an offline fuzzy identification of the steadystate duty cycle. The explicit and the fuzzy identified global model of the duty cycle robustly contribute to the system’s stability, even in the presence of large changes to the process parameters. In comparison with the analytically derived duty cycle using two different methods, the identified model prediction of an infinity horizon duty cycle shows better precision. These results are achieved in an analysis of the converter’s hybrid-simulation model where the assumptions made in the mathematical modelling are minor in comparison with similar assumptions in physical examples. The steady-state error compensation relies on the optimized PI controller, which is independently constructed and involved in the final Two-Degreesof-Freedom (TDOF) controller. The successful simulation results agree with the robustness and present a DC-DC converter with stable operation, even in the dynamic exchange of the DCM (Discontinuous Conduction Mode) and CCM (Continuous Conduction Mode). The method is widely applicable as it minimizes the real time of processing and avoids over-determined solutions.