Different Configurations Of Parameters Research Articles

Optimal hydraulic PTO and linear permanent magnet generator for a floating two-buoy wave energy converter

A fully coupled fluid-structure-power take-off model is used to investigate the optimal energy capture of a floating two-buoy wave energy converter excited by regular waves and irregular waves. The system incorporates hydraulic power take-off and a linear permanent magnet generator. By considering the coupling relationship between the power take-off parameters for regular waves, a power take-off parameter interval is determined for the optimization model. Parametric optimization of the hydraulic power take-off and linear permanent magnet generator systems is proposed, based on response surface methodology in conjunction with central combination design for sensitivity analysis and optimal configuration of different parameters. The methodology efficiently predicts optimal electric efficiency while reducing the requirement for multiple boundary element simulations. It is found that a model with predicted optimal configuration of the hydraulic power take-off system can achieve 10 % more electrical efficiency than that with linear permanent magnet generator. Comparison between the energy capacities of the different systems indicates that a device with linear permanent magnet generator attains higher energy conversion efficiency within a wider power take-off bandwidth. This study provides guidance for the design and selection of efficient power take-off systems for floating two-buoy wave energy converters.

The Marshall – Olkin Teissier generated model for lifetime data

An accurate mathematical inference depends on the experimental design and the model adopted in the process. Thus, in this study Marshall – Olkin Teissier generated distribution was used to present the distribution of the true nature of lifetime data. The characteristics of the proposed model were examined in a closed form. The behaviour of the new model indicated that the hazard rate of the submodels could be J- and U-shaped, decreasing and increasing. Monte Carlo simulations were presented for different configurations of parameters with varying sizes. The results of the simulation and goodness-of-fit of the real lifetime data show that the Marshall – Olkin Teissier generated model is flexible, tractable and applicable when compared to some classical two parameters distributions.

Distributed Systems and Industrial Communication Networks with the Internet of Things, Aimed at Industry 4.0

This research is based on the exchange of information from distributed systems through the application of industrial communication protocols and the web. The method used in this work is defined by the configuration of different parameters of the communication protocols of each of the industrial processes that make up the distributed system. In order to centralize this system, a Master PLC, 4 slaves, 3 HMI's, an IoT 2040 and a Computer are used in order to exchange and acquire information through a SCADA system with the TIA PORTAL software. The results obtained are a function of the configurations of each communication protocol; in Open Protocol, the read/write registers corresponding to each equipment are connected through Modbus TCP/IP and Modbus RTU. In ProfiNet, they are connected through databases and information transfer areas, allowing the exchange of data from a multivariable process, such as flow rate and water level, as well as the proportional position control of cylinders actuated by a pneumatic and hydraulic system, respectivel. Finally, when sending or receiving information to a field device connected to an IoT platform in the cloud, the communication nodes are configured with the help of the software flow programmer NODE-RED, which allows remote control and monitoring in real-time (RT) through the WEB. This flow engine with IoT approach allows the configuration of each one of the nodes and at the same time creates intuitive graphical interfaces for the user, allowing proper communication from the system to a Web Server known as IoT platforms and vice versa.

A Dynamic Explanation for the Ruptures of Repeating Earthquakes on the San Andreas Fault at Parkfield

AbstractAnalyzing the relative source time functions (STFs) of repeating earthquakes (REs) at Parkfield and their spectra indicates that there are two groups of REs. One group of REs (G1) displays simple relative STFs and smooth spectra, whereas the other group (G2) displays complex relative STFs and spectra with obvious holes. We use the boundary integral equation method with different configurations of parameters to simulate the spontaneous dynamic ruptures and fit the observed characteristics. Finally, we find that the differences in the observed characteristics are due to the different configurations of the dynamic parameters. Earthquakes in G1 are self‐arresting ruptures, and earthquakes in G2 are runaway ruptures. Moreover, holes in the spectra of G2 are caused by the dynamic rupture propagation, and the frequency of the holes is a function of the radius of the circular fault, the angle between the station azimuth and the rupture propagation, and the rupture velocity.

Generalized Equalization Model for Image Enhancement

In this paper, we propose a generalized equalization model for image enhancement. Based on our analysis on the relationships between image histogram and contrast enhancement/white balancing, we first establish a generalized equalization model integrating contrast enhancement and white balancing into a unified framework of convex programming of image histogram. We show that many image enhancement tasks can be accomplished by the proposed model using different configurations of parameters. With two defining properties of histogram transform, namely contrast gain and nonlinearity, the model parameters for different enhancement applications can be optimized. We then derive an optimal image enhancement algorithm that theoretically achieves the best joint contrast enhancement and white balancing result with trading-off between contrast enhancement and tonal distortion. Subjective and objective experimental results show favorable performances of the proposed algorithm in applications of image enhancement, white balancing and tone correction. Computational complexity of the proposed method is also analyzed.

Visualizing search behavior with adaptive discriminations

We examined different aspects of the visual search behavior of a pigeon using an open-ended, adaptive testing procedure controlled by a genetic algorithm. The animal had to accurately search for and peck a gray target element randomly located from among a variable number of surrounding darker and lighter distractor elements. Display composition was controlled by a genetic algorithm involving the multivariate configuration of different parameters or genes (number of distractors, element size, shape, spacing, target brightness, and distractor brightness). Sessions were composed of random displays, testing randomized combinations of these genes, and selected displays, representing the varied descendants of displays correctly identified by the pigeon. Testing a larger number of random displays than done previously, it was found that the bird's solution to the search task was highly stable and did not change with extensive experience in the task. The location and shape of this attractor was visualized using multivariate behavioral surfaces in which element size and the number of distractors were the most important factors controlling search accuracy and search time. The resulting visualizations of the bird's search behavior are discussed with reference to the potential of using adaptive, open-ended experimental techniques for investigating animal cognition and their implications for Bond and Kamil's innovative development of virtual ecologies using an analogous methodology.This article is part of a Special Issue entitled: CO3 2013.

Apply ant colony to event-flow model for graphical user interface test case generation

Aimed at the complex and inefficient testing issues of graphical user interface (GUI) software, this study describes an automatic framework for GUI test case generation. The framework includes a reverse engineering of executive GUI to create GUI information and event-flow model. According to these information and model, an ant colony algorithm is applied to generate test cases. The study shows that by identifying valid event interactions, the generated test cases are capable of finding deep faults without infeasible problems; the configuration of different parameters for ant colony and the good design of the proposed framework provide flexible interfaces to control test suites.

Selecting appropriate surrogate methods for spike correlation analysis

In the correlation analysis of experimentally recorded parallel spike trains one has to thoroughly consider the statistical features of the data in order to prevent false positive results [1]. Typically, the complexity of the data prevents us from using analytical expressions for evaluating the significance of observed correlations. Similarly, parametric tests presuppose models that are typically simplifications of the real neuronal data and thus may ignore important features. An alternative to these approaches is to use surrogate data, i.e. modified versions of the original data, to assess the significance [2]. The goal of this study is to develop selection criteria for suitable surrogate types. To study the applicability of surrogates we defined data sets exhibiting different statistical features found in typical experimental data (non-stationary firing rates, cross-trial non-stationary rates, deviation from Poisson) in combinations of increasing complexity. To demonstrate the impact of surrogate schemes on correlation analysis, we examine these with different surrogate generation methods commonly used in the literature [1]. Common to all these methods is that they in one way or the other destroy the precise temporal relation of the spiking activities between the neurons, by e.g. shuffling the trial ids (tr-shu) [3], randomizing the spike times (sp-rnd), randomly dithering the whole spike train against the other (tr-di) [4,5], dithering of individual spike times (sp-di) [6,7], dithering spike times under conservation of the joint-ISI distribution (jisi-di) [8], or by exchanging spikes across trials under local preservation of spike counts (sp-exg) [9,10]. To quantify the applicability of the various surrogates for significance estimation of spike correlation we concentrate on spike coincidences (allowed temporal precision: +/-1ms) and use their empirical count nemp as a test statistic. The p-value of nemp is obtained by comparing it to the surrogates' coincidence count distributions. To evaluate the true performance of the surrogates we study the false positive (FP) and false negative (FN) rates for different configurations of parameters implemented in simulated data (rate modulation, regularity, non-stationarity across trials, co-variation of rates). Figure 1 False positive (a.) and false negative (b.) percentages for all tested surrogate methods across five different data types. Colors code FP and FN percentages. White squares mark the position of bars of 100% FP. Based on the FN and FP performances, we find spike train dithering (tr-di) as the most robust detector of excess coincidences amongst the selected surrogates methods. Its detection accuracy is seemingly unaffected by the level of complexity of the data and its sensitivity remains at acceptable levels. Still, tr-di smooths the firing rate profile on the time scale of the dither width, and it is expected to produce false positives is the case of abrupt transients in firing rate. With the aim of dealing with this issue, further work is being done on the development of novel methods taking into account the observed firing rate profile. Doing so enables an approximate mapping of non-stationary processes to stationary ones, through which more accurate surrogates can be generated. This study illustrates the serious need to select appropriate surrogate methods when evaluating the significance of correlations observed in a given data set. Not doing so can lead to false conclusions and misinterpretation of the data. We therefore strongly recommend to test the chosen method on synthetic data which is as similar as possible to the experimental data at hand, but yet does not contain the feature being tested for, before proceeding with the analysis to control for false positive results [11].

Effects of the Oil Export Price Increase on the Economy of Kazakhstan: Results from the Sensitivity Analysis

This paper studies the effects of the oil export price increase on the Kazakhstani model using Lofgren et al.’s (2002) CGE model. In addition it examines the sensitivity of the results with respect to the underlying structural parameters. The paper finds that some results are robust and some are not robust to different configurations of parameters.

Stability and Oscillations in a Ventricular Cardiomyocyte Model Studied Using the Tools of Dynamic Systems Analysis and Bifurcation Theory

Although ventricular fibers of the working myocardium in vivo or in vitro do not feature pacemaker activity in normal conditions, getting depolarized and contracting only upon receiving current input from the surroundings, in certain pathological states they become prone to generate sustained oscillations. In order to get an insight into the mechanisms underlying these rhythm disturbances, we studied the dynamics and bifurcation behavior of a simple mathematical model of ventricular cardiomyocyte, the Luo-Rudy I model, using numerical and analytical methods, as described by Kurata et al. For different configurations of parameters and initial conditions, we found equilibrium points (states where the field of variables vector vanishes). These were further used to compute the eigenvalue vector of the linearized system of differential equations at various values of stimulus current (Istim) in the range of −5 to +5 uA/uF. Doubling the time-dependent potassium conductance (gkt) resulted in sustained self-oscillations in a narrow interval of Istim: (-0.7,+0.3) uA/uF for a reversal potential of the background current eb=0 mV, and (-3.0,-2.1) uA/uF for the default value eb=-59.87 mV, while for normal gkt the system reached stable equilibrium over the entire Istim range with either of the eb values tested. We also demonstrated that, for a given set of parameters, the system admits a maximum of two different equilibrium points, with the same potential but different intracellular calcium concentrations.Acknowledgements to Prof. K. Mubagwa and A. Gwanyanya, PhD from KULeuven for help in initiating experiments on cardiomyocytes in Bucharest.