Wyniki wyszukiwania - Biblioteka Nauki

1

Phase conjugation for underwater acoustic communications

100%

Jastrzębski S.

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2006

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tom Vol. 9

71-76

EN

In this paper a multipath problem in shallow water acoustic channel and phase conjugation technology will be presented. Acoustic communications in shallow water had been a difficult problem due to the characteristics of the underwater acoustic channel. The shallow water channel is the environment which is of particular interest to many research workers and presents a number of challenges to the designers of communications systems. Underwater acoustic channels are characterized by multipath phenomenon whose characteristics are time varying. This is the major factor that limits underwater acoustic communications performance. Communication systems can be categorized as using either incoherent or coherent modulation strategies. This paper presents the phase conjugation technique, also called “time-reversal”, which is the subject of active research in many areas of acoustics. This is a new method for coherent underwater acoustic communication. Preliminary results confirm the potential utility of the phase conjugation in underwater acoustics with applications in underwater communications. This method effectively mitigates the multipath propagation and can be used to solve this problem.

2

Comparing the concepts of modern comparators of code levelling rods as exemplified by the horizontal comparator of levelling rods UNIBWM (Munich) and the vertical comparator of "levelling systems" TUG (Graz)

100%

Jastrzębski S.

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2007

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tom z. 1/82

111-116

3

The influence of gradient filters and edging algorithms on defining accuracy of the position of a measured edge of the code element in testing the metricity of levelling code graduation, based on the analysis of raster image

100%

Jastrzębski S.

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2007

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tom z. 1/82

117-122

4

Sound Propagation in shallow water

100%

Jastrzębski S.

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2004

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tom Vol. 7

79-88

EN

A multipath problem in an underwater acoustic channel is discussed in this paper. For underwater acoustic communications the main problem encountered is the presence of multipath propagation caused by reflection and scattering of the transmitted signals at the surface and the bottom. Multipath propagation causes significant degradation of the underwater acoustic communication signals. Echos, which are delayed from direct path underwater acoustic signals, can be represented by impulse responses, which have cepstrums concentrated farther from the cepstral origin. A cepstral analysis and homomorphic deconvolution method is discussed as a means of detecting the multipath effect. The results of numerical simulation are presented in this paper.

5

Design and implementation FIR filters using FPGA

100%

Jastrzębski S.

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2008

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tom Vol. 11

121-130

EN

Underwater acoustic channels are characterized by multipath phenomenon whose characteristics are time varying. Multipath propagation contributes to signal fading, and causes intersymbol interference (ISI) in a digital communication system. Raised cosine filters are widely used in wireless communication systems and the effects of these filters are crucial to wireless communication systems, for example underwater communication systems. Pulse shaping filters are commonly used in digital data communication systems to limit intersymbol interference. Thus, digital filters have been recognized as primary digital signal processing operation. In order to apply DSP algorithms to wireless communication systems high density Field Programmable Gate Arrays have recently emerged as ideal implementation platforms for digital filters due to its potential speed and flexibility. This paper presents the design and implementation of FIR filters using FPGA technology. The following architectures of filters are studied: multiply and accumulate (MAC) standard FIR filter, parallel transposed FIR filter, and direct-form filter using Distributed Arithmetic (DA). The proposed filters have been designed and synthesized with ISE software, and implemented with a Virtex-II FPGA device.

6

On Certain Limitations of Recursive Representation Model

63%

Jastrzębski S. , Sieradzki I.

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tom Vol. 25

37--47

EN

There is a strong research eort towards developing models that can achieve state-of-the-art results without sacricing interpretability and simplicity. One of such is recently proposed Recursive Random Support Vector Machine (R2SVM) model, which is composed of stacked linear models. R2SVM was reported to learn deep representations outperforming many strong classi-ers like Deep Convolutional Neural Network. In this paper we try to analyze it both from theoretical and empirical perspective and show its important limitations. Analysis of similar model Deep Representation Extreme Learning Machine (DrELM) is also included. It is concluded that models in its current form achieves lower accuracy scores than Support Vector Machine with Radial Basis Function kernel.

7

Analysis of Compounds Activity Concept Learned by SVM Using Robust Jaccard Based Low-dimensional Embedding

63%

Jastrzębski S. , Czarnecki W. M.

Schedae Informaticae

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2015

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tom Vol. 24

9--19

EN

Support Vector Machines (SVM) with RBF kernel is one of the most successful models in machine learning based compounds biological activity prediction. Unfortunately, existing datasets are highly skewed and hard to analyze. During our research we try to answer the question how deep is activity concept modeled by SVM. We perform analysis using a model which embeds compounds’ representations in a low-dimensional real space using near neighbour search with Jaccard similarity. As a result we show that concepts learned by SVM is not much more complex than slightly richer nearest neighbours search. As an additional result, we propose a classification technique, based on Locally Sensitive ashing approximating the Jaccard similarity through minhashing technique, which performs well on 80 tested datasets (consisting of 10 proteins with 8 different representations) while in the same time allows fast classification and efficient online training.

8

The problem of scale of bar code graduation in monitoring of vertical displacements

63%

Woźniak M. , Jastrzębski S.

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2004

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tom nr 2/69

323--328

9

Further results in geodetic monitoring of deformations in a water reservoir due to cyclic changes of water level

51%

Woźniak M. , Pruszyński W. , Wojciechowski J. , Jastrzębski S.

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2001

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tom z. 2/57

169-174

10

Badanie dynamicznych zmien obiektów hydrotechnicznych na przykładzie zbiornika górnego elektrowni szczytowo-pompowej Żarnowiec

51%

Woźniak M. , Prószyński W. , Wojciechowski J. , Jastrzębski S.

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tom R. 73, nr 10

3-6

11

Investigation of the accuracy of geodetic measurements using reflectorless techniques

51%

Woźniak M. , Jastrzębski S. , Wojciekowski J.

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2009

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tom z. 1/86

97-103

EN

This paper presents the results of investigation of geometry accuracy using reflectorless techniques. Experimental measurenents were carried out the polygon using new tacheometers and a monitoring application program. The results of experimental measurements were analyzed and presented graphicall in Surfer 8. Contour maps and isometric projections of the surface of imperfection are elements of the present study. It presents the results of investigation of measurements accuracy in geometry according to various geometry conditions.

12

The use of video-tacheometric technology for documenting and analysing geometric features of objects

51%

Woźniak M. , Świerczyńska E. , Jastrzębski S.

Reports on Geodesy and Geoinformatics

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2015

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tom Vol. 99

28--43

EN

This paper analyzes selected aspects of the use of video-tacheometric technology for inventorying and documenting geometric features of objects. Data was collected with the use of the video-tacheometer Topcon Image Station IS-3 and the professional camera Canon EOS 5D Mark II. During the field work and the development of data the following experiments have been performed: multiple determination of the camera interior orientation parameters and distortion parameters of five lenses with different focal lengths, reflectorless measurements of profiles for the elevation and inventory of decorative surface wall of the building of Warsaw Ballet School. During the research the process of acquiring and integrating video-tacheometric data was analysed as well as the process of combining “point cloud” acquired by using video-tacheometer in the scanning process with independent photographs taken by a digital camera. On the basis of tests performed, utility of the use of video-tacheometric technology in geodetic surveys of geometrical features of buildings has been established.

13

Geodetic monitoring of deformations in a water reservoir

38%

Woźniak M. , Walo J. , Wojciechowski J. , Jastrzębski S. , Szpunar R. , Pachuta A.

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2002

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tom z. 1/61

141-143

14

Summing-up the experience from research into long-term displacements of hydrotechnical objects with regard to their short-term deformations

38%

Woźniak M. , Prószyński W. , Walo J. , Wojciechowski J. , Jastrzębski S. , Pachuta A.

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tom z. 1/64

197-199

EN

In order to ensure the safety of an object and its surroundings, it is necessary to perform a geodetic monitoring of its technical condition. This monitoring should satisfy high accuracy and reliability requirements because the research of this type plays an important role in the early recognition ofthe disturbance in the structure's geometry. Since 1998 our University has been conducting research into horizontal displacements of the upper, artificial reservoir of the Pumped-Storage Power Station at Zarnowiec. It is situated 125 m above the lower reservoir, i.e. Zarnowiec lake. 24 control points located on the crown are monitored by a hybrid technique - GPS and classical observations (fig.l). It was found out that changes in the object's geometry occur due to the changes in water level. In order to conduct research on short-term changes special geodetic measurements were made.