The comparison between different methods used to compute the logarithmic decrement in high-resolution mechanical spectroscopy (HRMS) is analyzed. The performance of parametric OMI method (Optimization in Multiple Intervals) and interpolated discrete Fourier transform (IpDFT) methods are investigated as a function of the sampling frequency used to digitize free decaying oscillations in lowfrequency resonant mechanical spectrometers. It is clearly demonstrated that a new Yoshida-Magalas (YM) method is the most powerful IpDFT-based method which outperforms the standard Yoshida (Y) method and other DFT-based methods. Four IpDFT methods and the OMI method are carefully analyzed as a function of the sampling frequency. The results presented in this work clearly show that the relative error in the estimation of the logarithmic decrement depends both on the length of free decaying signal and on the sampling frequency. The effect of the sampling frequency was not yet reported in the literature. The performance of different methods used in the computations of the logarithmic decrement can be listed in the following order: (1) the OMI, (2) the Yoshida-Magalas YM, (3) the Yoshida-Magalas YM C , and finally (4) the Yoshida Y.
Abstract:The basic principle of silviculture is the rational use of natural regeneration. The acceleration and equalisation of seed germination and an increase of the field seed germination ability are affected by seed scarification, which results in the destruction or weakening of the seed cover. Acorn scarification is performed manually, in the standing position, most often in adapted work stations, whose geometry is adjusted by the staff to their own anthropometric dimensions. An added value of acorn scarification consists in the ability to visually assess the health status of the cotyledons visible on the cross-section, making it possible to infer the potential use of a seed for sowing. However, due to the scope and duration of the activities involved, manual scarification is a process that is monotonous and physically as well as psychologically tiring for its performer. Automating of this process allows for effective replacement of human labour. The results obtained from the use of the vision system designed to determine the length and orientation of acorns may be considered satisfactory. The implementation of the seed orientation detection algorithm using the Harris detector was 90% accurate. Studies and analyses have shown that the process of acorn scarification has a positive effect on the later improvement of uniformity and acceleration of seedling emergence. In the case of seeds subjected to scarification, 83% of the acorns germinated within 4 to 6 weeks after sowing.
Efforts to predict the germination ability of acorns using their shape, length, diameter and density are reported in the literature. These methods, however, are not efficient enough. As such, a visual assessment of the viability of seeds based on the appearance of cross-sections of seeds following their scarification is used. This procedure is more robust but demands significant effort from experienced employees over a short period of time. In this article an automated method of acorn scarification and assessment has been announced. This type of automation requires the specific setup of a machine vision system and application of image processing algorithms for evaluation of sections of seeds in order to predict their viability. In the stage of the analysis of pathological changes, it is important to point out image features that enable efficient classification of seeds in respect of viability. The article shows the results of the binary separation of seeds into two fractions (healthy or spoiled) using average components of regular red-green-blue and perception-based hue-saturation-value colour space. Analysis of accuracy of discrimination was performed on sections of 400 scarified acorns acquired using two various setups: machine vision camera under uncontrolled varying illumination and commodity high-resolution camera under controlled illumination. The accuracy of automatic classification has been compared with predictions completed by experienced professionals. It has been shown that both automatic and manual methods reach an accuracy level of 84%, assuming that the images of the sections are properly normalised. The achieved recognition ratio was higher when referenced to predictions provided by professionals. Results of discrimination by means of Bayes classifier have been also presented as a reference.
This elaboration presents the numerical model of the Active Magnetic Levitation (AML). The model is developed in the 2D axis symmetry mode. The Finite Element Method is used to calculate the magnetic field. The Ordinary Differential Equation is solved simultaneously to simulate the levitated object motion. The model is solved in the time domain, together with the levitated object motion being simulated. A few investigation simulations are realized to diagnose the basic properties of the model. The PID current mode controller is used to drive the coil and keep the object levitated in the desired position. The electromagnetic force and magnetic flux density are investigated to analyze the AML non-linearities. Finally, the conclusions towards the experimental research are given.
The paper describes the mechanism for involving students from multilingual, geographically separated institutions in a coordinated educational experience and presents the observations and evaluation of outcomes related to the collaborative project. The project was realized as a part of ILERT (International Learning Environment for Real-Time Software Intensive Control System) EU/US activity sponsored by FIPSE/EC Atlantis Program. As a part of the pilot implementation phase of the ILERT project, international students teams have worked on robotic design and control experiments with LEGO MINDSTORMS NXT kits. The project has engaged on-site students and faculty of universities from four countries (USA, Poland, France, and Czech Republic). The robot maze navigation problem has been defined as an example. LEGO-MINDSTROMS NXT kit has been selected as a common platform for students teams. A Web-based Project Management System (WebPMS) has been used to improve communication and test Internet based tools for inter-university collaboration. Final evaluation of the project outcomes, including students survey results, are presented in this paper.
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