Search Results

You are looking at 1 - 10 of 12 items for

  • Author: K. Rafal x
Clear All Modify Search
Open access

M. Bobrowska-Rafał, K. Rafał, G. Abad and M. Jasiński

Control of PWM rectifier under grid voltage dips

This paper investigates control structure for grid connected three-phase two-level Voltage Source Converter (VSC) under distorted grid voltage conditions. Grid voltage is distorted by balanced and unbalanced voltage dips and higher harmonics. To address the problem, the control structure of converter is presented. The control system is a modification of Voltage Oriented Control (VOC) based on Dual Vector Current Controllers (DVCC). Grid synchronization under distorted voltage is achieved by employing Phase Locked Loop (PLL). Simulation and experimental results, which illustrate properties of proposed system, are presented.

Open access

M. Bobrowska-Rafal, K. Rafal, M. Jasinski and M. Kazmierkowski

Grid synchronization and symmetrical components extraction with PLL algorithm for grid connected power electronic converters - a review

In this paper, a review of Phase Locked Loop (PLL) algorithms and symmetrical component extraction methods intended for grid-connected power electronic converters are presented. Proposed classification is based on voltage representation in three coordinates: natural (abc), stationary (αβ) and rotating coordinates (dq). The three selected algorithms are described in details: Dual Second Order Generalized Integrator (DSOGI-PLL), Dual Virtual Flux - both in stationary coordinates. The third one, in rotating dq coordinates, is Dual Synchronous Reference Frame PLL (DSRF-PLL). A comparison of PLL algorithms is presented. Also, selected experimental results are given to verify practical application of discussed algorithms.

Open access

K. Antoniewicz and K. Rafal

Abstract

This paper presents model predictive control (MPC) with a finite control states set (FS) for three-level four-leg flying capacitor (FCC) converter. Principles of control method are presented and flying capacitor voltages control method is discussed. Experimental results of converter operating as a shunt active power filter (SAPF) and grid connected inverter (GCI) are shown.

Open access

Krystyna Wasylikowa and Rafał Koliński

ABSTRACT

Archaeological fieldwork carried out at the Tell Arbid site in north-eastern Syria exposed settlement remains dating from the early 3rd millennium BC to the mid 2nd millennium BC. Recent excavations in Sector P, on the eastern slope of the site, revealed the existence of a significant occupation of the Post-Akkadian/ Early Jazirah V period and of levels dated to the Early and Classic Khabur Ware/Old Jazirah/Middle Bronze Age I-II periods. Cereal remains were dominated by grains and ear fragments of hulled two-rowed barley Hordeum distichon. Less numerous were wheats represented by emmer Triticum dicoccon, einkorn T. monococcum, and macaroni wheat T. durum. The presence of bread wheat T. aestivum and six-rowed barley Hordeum vulgare could not be excluded. The two periods contained similar sets of cereals, but in the Post-Akkadian Period the percentage of hulled wheat remains was higher, while in the Middle Bronze Age (particularly in its younger phase) naked wheat slightly exceeded hulled wheats. Legumes were represented by only very few seeds of lentil Lens culinaris and bitter vetch Vicia ervilia. Diaspores of wild plants were very abundant, particularly those from the families of grasses and legumes. The considerable number of ear and culm fragments probably belonging to cereals as well as numerous seeds/fruits of wild plants suggests that the plant remains originated from fodder or animal dung or belonged to threshing waste. The presence of grass stems with nodes indicated that cereals were reaped low on the straw; occasional use of uprooting was suggested by the occurrence of basal culm fragments with traces of rootlets.

Open access

Rafał Stanisławski and Krzysztof J. Latawiec

This paper presents a series of new results in finite and infinite-memory modeling of discrete-time fractional differences. The introduced normalized finite fractional difference is shown to properly approximate its fractional difference original, in particular in terms of the steady-state properties. A stability analysis is also presented and a recursive computation algorithm is offered for finite fractional differences. A thorough analysis of computational and accuracy aspects is culminated with the introduction of a perfect finite fractional difference and, in particular, a powerful adaptive finite fractional difference, whose excellent performance is illustrated in simulation examples.

Open access

K. Kliczkowska, U. Jankowska, D. Jagielski, M. Czopowicz and R. Sapierzyński

Abstract

Feline injection site sarcomas (FISS) are malignant neoplasms of mesenchymal origin which arise in sites of injections in cats. The prevalence is estimated between 1 in 1000 and 1 in 10 000 vaccinations in the United Kingdom. The aim of this study was to estimate the incidence of FISS in Poland and to analyse clinical aspects and histological and cytological features of injection site sarcomas. In our study the prevalence of FISS was 0.16% (16 FISS on 10.000 of cats) in feline patients in one of a veterinary surgery which conducts the general practice and 85 on 10.000 cats in a practice focused on veterinary oncology. The most typical microscopic features of FISS found in the present analysis were: the presence of perilesional scarring and inflammation, aggregates of lymphocytes at the tumour periphery, moderate but usually marked cellular pleomorphism and intralesional necrosis. The most typical cytologic features of FISS found in present study were: the presence of neutrophils, marked cellular pleomorphism, the presence of lymphocytes and macrophages, the presence of extremely large nuclei in the neoplastic cells, and high sample cellularity.

Open access

Katarzyna Nowakowska-Langier, Rafal Chodun and Krzysztof Zdunek

Abstract

Pulsed plasma in the impulse plasma deposition (IPD) synthesis is generated in a coaxial accelerator by strong periodic electrical pulses, and it is distributed in a form of energetic plasma packets. A nearly complete ionization of gas, in these conditions of plasma generation, favors the nucleation of new phase of ions and synthesis of metastable materials in a form of coatings which are characterized by amorphous and/or nanocrystalline structure. In this work, the Fe–Cu alloy, which is immiscible in the state of equilibrium, was selected as a model system to study the possibility of formation of a non-equilibrium phase during the IPD synthesis. Structural characterization of the layers was done by means of X-ray diffraction and conversion-electron Mössbauer spectroscopy. It was found that supersaturated solid solutions were created as a result of mixing and/or alloying effects between the layer components delivered to the substrate independently and separately in time. Therefore, the solubility in the Fe–Cu system was largely extended in relation to the equilibrium conditions, as described by the equilibrium phase diagram in the solid state.

Open access

R. Babilas, K. Cesarz-Andraczke and R. Nowosielski

The work presents preparation methods, structure characterization and mechanical properties analysis of Mg-based bulk metallic glasses in as-cast state and after crystallization process. The studies were performed on Mg60Cu30Y10 and Mg37Cu36Ca27 glassy alloys in the form of plates and rods. The X-ray diffraction investigations revealed that the tested samples with different thicknesses and shapes were amorphous. The characteristics of the fractured surfaces showed mixed fractures with the “river” and “mirror” patterns, which are characteristic for the glassy materials and some “smooth” areas. The samples of Mg37Cu36Ca27 alloy presented a two-stage crystallization process, but addition of Y caused a single stage crystallization behavior. Qualitative phase analysis from the X-ray data of examined alloys annealed at 473 K enabled the identification of Mg, Mg2Cu, Cu2Mg and CaCu crystalline phases. The changes of compressive strength as a function of annealing temperature for studied rods were stated. The best mechanical properties including microhardness and compressive strength were obtained for the alloy with the addition of Y in as-cast state.

Open access

R. Sapierzyński, K. Kliczkowska-Klarowicz, U. Jankowska and D. Jagielski

Abstract

Malignant lymphomas are one of the most common malignant tumours occurring in dogs. The basic method of lymphoma diagnosis in human, as well as in canine oncology is histopathology supported by immunohistochemistry. It was suggested that in veterinary medicine excisional biopsy of lymph node and histopathology should be considered only where the cytologic diagnosis is equivocal or needs to be confirmed. There are at least three basic reasons for which cytological examination ought to be accepted as a sufficient and reliable diagnostic method for lymphoma in dogs. Firstly, most dog owners consider the fine-needle biopsy as an acceptable non-harmful method of sample collection. Secondly, an increasing number of studies recommend cytology as an accurate test for diagnosing and subtyping canine lymphoma. Finally, the vast majority of canine lymphoma subtypes belong to 4-5 categories characterized by a typical cytological picture. Immunocytochemical staining of cytological smears gives new diagnostic possibilities, such as detection of markers better characterizing given growth or a potential goal for target therapy in individual cases (for example inhibitors of platelet-derived growth factor).

Open access

R. Sapierzyński, U. Jankowska, D. Jagielski and K. Kliczkowska-Klarowicz

Abstract

Large granular lymphomas (LGLs) comprise a specific group of lymphomas regardless of classification scheme. An LGL consists of cells that show less or more mature morphology, but typically neoplastic cells possess cytoplasmic azurophilic granules clearly visible during cytological examination. The aim of the present study was to present clinical and cytological data on large granular lymphomas in cats and to analyses the therapeutic responses in treated cases. During the period from 2012 to 2014 six cats were as having large granular lymphoma. In one cat a nasal form of LGL was recognized, a systemic form was recognized in another cat, and in four cases an alimentary form was recognized. Cellular samples for cytopathology were collected from the cat with nasal cavity mass, from the enlarged mandibular lymph node and thoracic cavity from second cat, and in four cats from the abdominal mass during ultrasound-assisted fine-needle biopsy. Therapy was introduced in 5 of the 6 cats. In two cases palliative therapy with glucocorticoids was conducted, in two cases chemotherapy with COP protocol, and therapy with masitinib in one case. The median of survival time for cats treated with anticancer therapy was 9 months, the median of survival time for cats treated with glucocorticoids was 1.5 months. In conclusion, large granular lymphomas, especially the alimentary form, are a relatively common type of lymphoma in cats. Simple diagnostic methods such as clinical examination, imaging techniques and routine cytology are sufficient in majority of cases. Despite aggressive behavior and poor general prognosis, conventional chemotherapy lead to a good response in some treated cats regardless of anatomic form and histologic grade of malignancy.