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Marcin Lewandowski

Abstract

The parameters of sigma-delta audio DAC depend mainly on digital sigma-delta modulator's features, especially on its noise transfer function (NTF). Many methods of design and optimization of the loop filter's coefficients in sigma-delta modulators have been proposed so far. These methods enable the designer to get suitable noise transfer functions for specific application. This paper reviews NTF design and optimization methods which are particularly useful in audio applications.

Open access

Artur Lewandowski, Marcin Czyżewski and Ireneusz Zbiciński

Morphology and microencapsulation efficiency of foamed spray-dried sunflower oil

An analysis of the effect of feed foaming on the efficiency of sunflower oil encapsulation on selected product properties is presented in the paper. Experiments were carried out in a pilot-plant concurrent spray dryer using the gas-admixing technique. The analysis of the product properties showed that the application of foaming makes it possible to control final product properties, e.g. apparent density, bulk density, distribution of particle diameters, etc. at a high efficiency of sunflower oil encapsulation.

Open access

Marcin Lewandowski

Abstract

It seems that there are very few research themes in sociolinguistics that have been as thoroughly explored as gender representation in educational materials (notably in E FL textbooks). However, relatively little attention has been paid to how learners themselves perceive the images of men and women in teaching resources. T he present contribution has been written in an attempt to fill this gap. Drawing on the findings of two small-scale survey studies conducted among Polish university students, it addresses two major issues. T he first one concerns the extent to which the choice of male or female-gendered sentence subjects in E FL grammar course books matches the learners’ associations and expectations. The other one, focusing specifically on attitudes to gender representation, seeks to demonstrate how the students view the ways male and female characters are portrayed in constructed examples of usage and practice sentences from English grammar textbooks. Both studies provide some indications of how E FL learners’ needs and expectations can be better addressed in teaching materials

Open access

Grzegorz Lewandowski, Marcin Bartkowiak and Eugeniusz Milchert

Topical and prospective processes of acetoxylation

The latest acetoxylation processes have been described in this work: oxidative acetoxylation of propene to allyl acetate, acetoxylation of propene to propene glycol and its acetates, acetoxylation of methyl tert-butyl ether and oxidative acetoxylation of cyclohexene by hydrogen peroxide. Acetoxylation of 1,3-butadiene, isobutene and toluene were presented together with a short description of the acetoxylation catalysts.

Open access

Marcin Lewandowski

Abstract

Marcin Lewandowski. The Language of Online Sports Commentary in a Comparative Perspective. Lingua Posnaniensis, vol. L IV (1)/2012. The Poznań Society for the Advancement of the Arts and Sciences. PL ISSN 0079-4740, ISBN 978-83-7654-103-7, pp. 65-76.

This paper attempts to describe a relatively new media genre (or as the author prefers to see it, an electronic register), i.e., online sports commentary (OSC). The analysis concerns English-language online live soccer match reports, and is based on a methodological framework proposed by D. Biber and S. Conrad (2009), who in register studies emphasize the correlation between the situational characteristics and lexico-grammatical features of a particular language variety. The paper also aims to compare the register in question with other related varieties, i.e., written sports commentary (WSC) and sports announcer talk (SAT ) in order to corroborate the hypothesis that the register of online commentary is a hybrid of spoken and written language.

Open access

Piotr Karwat, Ziemowit Klimonda, Michał Sęklewski, Marcin Lewandowski and Andrzej Nowicki

Abstract

Ultrasonic methods of human body internal structures imaging are being continuously enhanced. New algorithms are created to improve certain output parameters. A synthetic aperture method (SA) is an example which allows to display images at higher frame-rate than in case of conventional beam-forming method.

Higher computational complexity is a limitation of SA method and it can prevent from obtaining a desired reconstruction time. This problem can be solved by neglecting a part of data. Obviously it implies a decrease of imaging quality, however a proper data reduction technique would minimize the image degradation.

A proposed way of data reduction can be used with synthetic transmit aperture method (STA) and it bases on an assumption that a signal obtained from any pair of transducers is the same, no matter which transducer transmits and which receives. According to this postulate, nearly a half of the data can be ignored without image quality decrease.

The presented results of simulations and measurements with use of wire and tissue phantom prove that the proposed data reduction technique reduces the amount of data to be processed by half, while maintaining resolution and allowing only a small decrease of SNR and contrast of resulting images.

Open access

Ihor Trots, Andrzej Nowicki, Marcin Lewandowski and Yuriy Tasinkevych

Abstract

Synthetic aperture (SA) technique is a novel approach to present day commercial systems and has previously not been used in medical ultrasound imaging. The basic idea of SA is to combine information acquired simultaneously from all directions over a number of emissions and to reconstruct the full image from these data.

The paper presents the multi-element STA (MSTA) method for medical ultrasound imaging. The main difference with the STA approach is the use of a few elements in the transmit mode in contrast to a single element aperture. This allows increasing the system frame rate, decreasing the number of emissions, and provides the best compromise between the penetration depth and lateral resolution. Besides, a modified MSTA is proposed with a corresponding RF signal correction in the receive mode, which accounts for the element directivity property.

In the experiments a 32-element linear transducer array with 0.48 mm inter-element spacing and a burst pulse of 100 ns duration were used. Two elements wide transmission aperture was used to generate an ultrasound wave covering the full image region. The comparison of 2D ultrasound images of a tissue mimicking phantom obtained using the STA and MSTA methods is presented to demonstrate the benefits of the second one.

Open access

Yuriy Tasinkevych, Ihor Trots, Andrzej Nowicki and Marcin Lewandowski

Abstract

The paper presents the optimization problem for the multi-element synthetic transmit aperture method (MSTA) in ultrasound imaging applications. The optimal choice of the transmit aperture size is made as a trade-off between the lateral resolution, penetration depth and the frame rate. Results of the analysis obtained by a developed optimization algorithm are presented. The maximum penetration depth and lateral resolution at given depths are chosen as optimization criteria. The results of numerical experiments carried out in MATLAB® using synthetic aperture data of point reflectors obtained by the FIELD II simulation program are presented. The visualization of experimental synthetic aperture data of a tissue mimicking phantom and in vitro measurements of the beef liver performed using the SonixTOUCH Research system are also shown.

Open access

Marcin Giaro, Mariusz Wyleżoł, Olaf Truszczyński and Tomasz Lewandowski

Assessment of the Knowledge of GPS Considering the Surgical Treatment of Obesity

Bariatric surgery is currently the only effective treatment option for morbidly obese patients. There has been observed a considerable disproportion between the number of procedures conducted in Poland and the number of patients requiring such treatment. There are no studies assessing bariatric knowledge among general practitioners who play crucial role in polish health care system.

The aim of the study was to assess the knowledge of general practitioners regarding bariatric surgery.

Material and methods. An anonymous questionnaire conducted among 282 general practitioners in 2010-2011 during local educational conferences. The questionnaire consisted of 10 questions relating to fundamental issues of bariatric surgery.

Results. Only one twelfth (8.1%) of the general practitioners questioned knows the indications for bariatric surgery, can apply them, and has epidemiological awareness. 61.5% of general practitioners know the surgical procedures used for the treatment of obesity, whereas 58% of them show the knowledge of surgical technique in which they are performed. Only 23% of general practitioners were aware that bariatric surgery decreases cancer risk. 92% of the participants noticed a necessity of education regarding the surgical treatment of obesity.

Conclusions. Bariatric knowledge among general practitioners is not adequate to scientific research results published during the last years. Most general practitioners who participated in our study are aware of that and are awaiting for educational programmes focused on this issue.

Open access

Ihor Trots, Yuriy Tasinkevych, Andrzej Nowicki and Marcin Lewandowski

Abstract

The paper presents the theoretical and experimental study of synthetic transmit aperture (STA) method combined with Golay coded transmission for medical ultrasound imaging applications. The transmission of long waveforms characterized by a particular autocorrelation function allows to increase the total energy of the transmitted signal without increasing the peak pressure. It can also improve signal-to-noise ratio and increase the visualization depth maintaining the ultrasound image resolution.

In the work the 128-element linear transducer array with 0.3 mm pitch excited by the 8 and 16-bits Golay coded sequences as well as a one cycle at nominal frequencies 4 MHz were used. The comparison of 2D ultrasound images of the tissue mimicking phantoms is presented to demonstrate the benefits of coded transmission. The image reconstruction was performed using synthetic STA algorithm with transmit and receive signals correction based on a single element directivity function.