THERMAL ANALYSIS OF LARGE OIL-IMMERSED TRANSFORMER WINDINGS

ABSTRACT

A method of numerical thermal analysis of large oil-immersed transformer windings is presented. The analysis consists of two steps: first, the leakage magnetic field is solved in the windings; second, the basic and additional losses distribution is calculated simultaneously with temperature rise distribution in the cross-sections of individual coils allowing for special geometries and cooling conditions of different types of windings. An example of the analysis is given and the values calculated are compared with the results of factory tests.     

Statistical Evaluation of Factors Affecting the Leaching Process of Waste Electrical and Electronic Equipment using Sodium Persulfate

Recycling of waste electrical and electronic equipment (WEEE) is important not only to reduce the amount of waste requiring treatment, but also to promote the recovery of valuable materials. Implementation of the European Directive on WEEE and recycling targets imposed in the European Union will require new processes to be developed and applied to recover metals from WEEE. This study aims to provide an alternative process for the dissolution of metals from WEEE which contains Cu and Zn based on our previous research. The effects of leaching parameters, such as temperature, Na₂S₂O₈ concentration, and leaching time, were separately investigated on leaching of copper, zinc, and brass (alloy composition ?35% zinc and 65% copper) in Na₂S₂O₈ solution (0.1, 0.2 and 0.3 M). Box–Behnken experimental design (BBD) method was used to determine the number and the condition of necessary leaching experiments. Statistical analysis of variance (ANOVA) was performed to see whether process parameters such as leaching time, temperature, and oxidant concentration are statistically significant or not on the leaching performance. Results show leaching time as the most influential factor in the dissolution process, for the first six models. Two extended models have been developed to optimize the parameters of the investigated process. In these models, we consider the metal composition as a model input next to the earlier investigated parameters. Optimal condition for maximum copper and zinc dissolution in Na₂S₂O₈ environment can be found for parameter values: temperature 45°C, oxidant concentration 0.1 M and leaching time 35 min.     

Local Binary Pattern based features for sign language recognition

In this paper we focus on appearance features particularly the Local Binary Patterns describing the manual component of Sign Language. We compare the performance of these features with geometric moments describing the trajectory and shape of hands. Since the non-manual component is also very important for sign recognition we localize facial landmarks via Active Shape Model combined with Landmark detector that increases the robustness of model fitting. We test the recognition performance of individual features and their combinations on a database consisting of 11 signers and 23 signs with several repetitions. Local Binary Patterns outperform the geometric moments. When the features are combined we achieve a recognition rate up to 99.75% for signer dependent tests and 57.54% for signer independent tests.     

Segmentation of CT arteriography based on combination of segmentation methods

This paper describes a solution of CT arteriography vessel segmentation using a combination of methods for segmentation of image data. Computer tomography (CT) is one of the most useful approaches for investigating the arterial system and its pathologies. There are three ways for segmenting the vessels from the CT image — manually, fully automatically and with a user interaction. We considered the (semi)automatic approaches, because the manual way is too time-consuming and human-dependent. We used a combination of three segmentation techniques: thresholding, edge detection and region growing. Results of this method were consulted then with a medicine expert. None of these techniques can be used separately, but a combination of them brought very good results, which can be used in medicine.     

Hierarchical design of an electro-hydraulic actuator based on robust LPV methods

The paper proposes a hierarchical control design of an electro-hydraulic actuator, which is used to improve the roll stability of vehicles. The purpose of the control system is to generate a reference torque, which is required by the vehicle dynamic control. The control-oriented model of the actuator is formulated in two subsystems. The high-level hydromotor is described in a linear form, while the low-level spool valve is a polynomial system. These subsystems require different control strategies. At the high level, a linear parameter-varying control is used to guarantee performance specifications. At the low level, a control Lyapunov-function-based algorithm, which creates discrete control input values of the valve, is proposed. The interaction between the two subsystems is guaranteed by the spool displacement, which is control input at the high level and must be tracked at the low-level control. The spool displacement has physical constraints, which must also be incorporated into the control design. The robust design of the high-level control incorporates the imprecision of the low-level control as an uncertainty of the system.     

Multigrid Convergence of Calculated Features in Image Analysis

This paper informs about number-theoretical and geometrical estimates of worst-case bounds for quantization errors in calculating features such as moments, moment based features, or perimeters in image analysis, and about probability-theoretical estimates of error bounds (e.g. standard deviations) for such digital approximations. New estimates (with proofs) and a review of previously known results are provided.