75392 research outputs found
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EXERGY AS A TOOL FOR DESIGNING AND OPERATING THERMAL STORAGE UNITS
No full textabstractEN: The paper presents the development, state-of-the-art, and applications of exergy analysis in the evaluation of the performance of thermal energy storage units. Formulas dealing with different sources of irreversibilities for complete charging-discharging cycles are introduced. The contributions of the most popular authors to the subject are focused on. Comparison of the present authors' results related to sensible heat storage units, utilizing a relatively simple iteration technique with that using the well-known optimization code „GRG2", shows an excellent agreement.score: 0collation: 23-4
Tracing based transmission pricing of cross-border trades: fundamentals and circular flows
No full textabstractEN: In this paper two issues related to the tracing- based transmission pricing have been raised. Firstly the graph-based algorithm has been compared with the algorithm based on the solution of linear equations. It is shown that both algorithms are computationally equivalent when the diagraph of power flows is acyclic. When the diagraph is cyclic, the graph-based algorithm fails. The second issue was the problem of eliminating cycles from the diagraph of flows. A practical algorithm has been presented.score: 3collation: 8 Vol.
Poles position identification of permanent magnet axial flux motor using PIPCRM sensorless method.
No full textabstractEN: The paper describes new sensorless method control of an axial flux permanent magnet motor at standstill and at low speed. This sensorless method called PIPCRM (Position Identification by Parallel Current Rate Measurement) was developed to provide sensorless start axial flux permanent magnet motor in demanded direction from standstill. The PIPCRM method is used to detect rotor poles position and then to force the stator current to achieve motor torque which is required to control motion of the permanent magnet motor. The paper presents theory of the PIPCRM method and laboratory tests that confirm its application to drives.score: 3collation: 1-1
Measurements of the local values of electrical steel parameters
No full textabstractEN: A new method for measurement and analysis of selected local parameters of electrical steel sheets is presented (locality pertains to the area of 1 mm2). The measurement system developed by the authors may be used for determination of the relationships Bmax = f(Hmax), μ = f(H), P = f(B) and the hysteresis loop. The analysis of these quantities, e.g. for the case of distorted flux is presented.score: 25collation: 185-19
Measuring system for two-dimensional testing of electrical steel
No full textabstractEN: The measuring system for two-dimensional testing of electrical steel is proposed. In this system the sample in the form of a sheet can be magnetised along arbitrary direction. The magnetizing conditions, the dimensions of the yoke and sheet, the methods of detection of magnetic field strength and flux density are discussed. Both components of magnetic field strength Hx and Hy and flux density Bx and By with respect to the rolling direction or the magnetizing direction can be measured. The examples of tests of grain-oriented steel are presented. The variation of special directions of B and H and the spatial phase shift between these values has been determined.score: 25collation: 315-32
Miniaturized low-cost digital holographic interferometer
No full textabstractEN: Digital holography (DH) and digital holographic interferometry (DHI) are very useful, robust, full-field visualization and measurement techniques applied for small objects, especially in the field of bioengineering and microelements system testing. Nowadays CCD/CMOS detectors and microlasers allow to build miniaturized and compact digital holographic head. Various approaches to develop DH/DHI systems including a variety of optical and mechanical solutions have been made. The main recent requirements for holocamera design include compactness, insensitivity to vibrations environmental changes and with good quality of output data. Other requirement is the ability to build a low-cost and robust system for sensing applications. In our paper, we propose a design of miniaturized holo-camera head with fibre optics light delivery system and remote data read-out. The opto-mechanical architecture allows out-of-plane and shape measurements of diffuse and reflective surfaces. The possible data capture schemes and software for enhanced quality numerical reconstruction of complex objects are discussed and the optimized methodology is determined. Also real-time optoelectronic hologram reconstruction is demonstrated on the base of remote data delivery to liquid crystal on silicon spatial light modulator. The performance of the system is tested on the resolution amplitude test and master sphere, while engineering objects in the experiments are static and dynamic microelements.score: 0collation: 618806-61880
Application of lasers in precise measurements of microelements
No full textabstractEN: Effective and reliable manufacturing of Micro (Opto) Electro Mechanical Systems (MEMS and MOEMS) requires extensive measurements of their mechanical and material parameters including shape, displacements, deformation, vibration mode profiles and material constants. Knowledge of these parameters at various technological and product life stages is of fundamental importance for MEMS and MOEMS design process. Complex structures are subject to wide range mechanical, thermal and electric loads and their testing methods should provide data about their behavior with nanometer sensitivity and spatial micrometer resolution. In the paper numerous examples of MEMS and MOEMS testing by laser interferometric methods are presented. The methods include classical heterodyne and grating interferometry, interferometric tomography, digital holographic and speckle interferometry. The studies presented were conducted in Optical Engineering Division, Institute of Micromechanics and Photonics of Warsaw University of Technology.score: 0collation: 266-27
Selection of interferometric methods for silicon microelement testing
No full textabstractEN: In this paper we discuss the problems connected with analysis of mechanical properties of silicon microelements being basic parts of MEMS (e.g. micromembranes, microbeams). The quality of these microproducts (the reliability and the lifetime) is strongly dependent on the material properties and the mechanical design. There is also strong influence of the technology process on their performance. The best suited methods for their testing are optical full-field measuring methods. They provide data (displacements, strains, distribution of material constants) which may be easily used in the hybrid experimental-numerical methods for microelements analysis and optimization of their design.score: 0collation: 307-31
The architecture of a multipurpose fringe pattern analysis system
No full textabstractEN: A review of the advantages and disadvantages of analytical phase measurement methods of automatic fringe patterm analysis is given. The pros and cons for their applications due to the complexity of an interferogram, the accuracies required and the type of quantity measured are considered. The architecture of the system which enables a proper choice between the Fourier transform method, temporal and spatial phase-shifting methods is described. The modular structure of the software gives the possibility of getting the results in the most efficient way.score: 30collation: 261-26
Holographic Capture and Display Systems in Circular Configurations
No full textabstractEN: This paper presents a novel method of multi-spatial light modulator (SLM) holographic image display that enables wide angle reconstruction of images of real world objects. The image data are delivered by means of digital holography. The capture and display systems are arranged in a circular configuration. In order to support the proper information flow between the multi-sensor capture and multi-SLM display systems we perform analysis using the Wigner distribution function. We also consider a mismatch of the capture and display configurations as well as the visual perception of the displayed image. Experimental results based on the reconstruction of real world scenes are presented that demonstrate the validity of the theoretical solutions. A single camera is used to record the digital holograms, where the object is rotated between captures, and these holograms are then displayed on a circular configuration of SLMs. The results show the limitation of multi-SLM holographic displays in terms of visual perception. These problems arise from the limited angular distribution of the SLMs on a display circle and the presence of gaps between the SLMs.score: 35collation: 225-23