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Wyświetlanie 1-10 z 14
Tytuł:
Correction of frequency distortion of the DDS signals
Autorzy:
Elminowicz, A.
Zajączkowski, L.
Powiązania:
https://bibliotekanauki.pl/articles/331959.pdf
Data publikacji:
2010
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The Diver Detection Sonar (DDS) as a surveillance system has been designed to monitor the threat of underwater attacks against harbours, ships, naval bases, coastal industrial installations, oil platforms etc. This paper describes technical complexity of designing wideband DDS, with increased coverage effectiveness and following additional advantages: improved range resolution, high signal to noise and reverberation ratio and possibility operation of several sonars in the same frequency band using different type of modulation. The article presents technological principles and problems related to the wideband sig-nals transmitting and receiving by cylindrical piezocomposite transducer as well as implementation of the broadband compression technique for correction of frequency distortion.
Źródło:
Hydroacoustics; 2010, 13; 83-88
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Doppler effect in wideband sonars
Autorzy:
Elminowicz, A.
Zajączkowski, L.
Powiązania:
https://bibliotekanauki.pl/articles/332069.pdf
Data publikacji:
2004
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
To increase sonar range and to improve the range resolution and SNR, modern sonars use a matched filtration what corresponds to correlation between replica of transmitted sig-nal and received echoes. Motion of sound source or/and object causes frequency Doppler shift of received signals, thereby generating the distortion of the correlation processing of echo with signal replica. In the paper, the results of studies of sonar signals (CW, LFM and HFM) immunity to correlation distortions due to Doppler effect are presented. It has been demonstrated that only HFM signals are immune to adverse Doppler effect in correlation processing.
Źródło:
Hydroacoustics; 2004, 7; 31-36
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
High resolution multi-beam side looking sonar
Autorzy:
Elminowicz, A,
Zajączkowski, L.
Powiązania:
https://bibliotekanauki.pl/articles/332745.pdf
Data publikacji:
2005
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The conventional side–scan sonars does not ensure sufficient angular and range resolution to detect very small objects with small target strength. Decrease of beam width leads to the increase of angular resolution but requires the decrease of towing speed what means reduction of searched area. Other method of the angular resolution increased is designing multi–beam sonar or sonar with synthetic aperture. The paper presents a design of effective multi–beam side looking sonars with a large angular and range resolution operates with 100 kHz, 200 kHz, 400 kHz and 600 kHz. The sonar, described in the paper, operates with 200 kHz frequency; LFM modulation – 20 kHz and 40 kHz band; array provides 32 elements with d/ë spacing what ensure a shaping of 5 or 9 beams with 0,40° width. The range of sonar is from 250 m to 300 m, the level of side lobes are smaller than -20 dB and level of grating lobes for 5 beams are smaller than -30 dB. The principle of sonar performance and wideband effective processing are presented. Effectiveness of processing depends on beams number and decrease of beams number, together with the range increased, leads to increase of processing effectiveness.
Źródło:
Hydroacoustics; 2005, 8; 37-46
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Zautomatyzowane stanowisko do badania przetworników ciśnienia z uwzględnieniem temperatury
Automated stand for testing pressure transduces including temperature effect
Autorzy:
Pieniążek, J.
Zajączkowski, Ł.
Powiązania:
https://bibliotekanauki.pl/articles/195264.pdf
Data publikacji:
2017
Wydawca:
Politechnika Rzeszowska im. Ignacego Łukasiewicza. Oficyna Wydawnicza
Tematy:
system pomiarowy
kompensacja temperaturowa
wzorcowanie przetwornika ciśnienia
programowanie LabView
measurement system
temperature compensation
pressure transducer calibration
LabView programming
Opis:
W artykule zaprezentowane zostało rozwiązanie techniczne systemu pomiarowego przeznaczonego do wzorcowania przetworników ciśnień. Wykonany system pomiarowy jest złożony z urządzeń pomiarowych objętych centralnym sterowaniem realizowanym przez aplikację zrealizowaną w LabView. Istotnym elementem systemu umożliwiającym badanie przetwornika ciśnienia w różnych temperaturach jest miniaturowa komora termiczna, której zastosowanie stanowi alternatywę dla dużej termokomory. Zaletą programowego sterowania eksperymentem pomiarowym dostarczającym dane do kalibracji przetwornika jest pełna automatyzacja czasochłonnego procesu zbierania danych i sterowania wartościami dwu wielkości (ciśnienia i temperatury) w wielu punktach pomiarowych.
This paper presents the technical solution of the measurement system for pressure transducers calibration. The system consists of measurement devices which are controlled by the software developed in LabView. An essential component of the system enabling investigation of the transducer in different temperature is a miniature thermal chamber which was designed as alternative to the large thermal chamber. The advantage of software control of measuring experiment supplied data for calibration of transducer is fully automation of the time-consuming process of data acquisition and controlling the values of pressure and temperature in many measuring points.
Źródło:
Zeszyty Naukowe Politechniki Rzeszowskiej. Mechanika; 2017, z. 89 [295], 1; 99-110
0209-2689
2300-5211
Pojawia się w:
Zeszyty Naukowe Politechniki Rzeszowskiej. Mechanika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Application of DDS and magnetic barrier cooperating with acoustic barriers and tethered sonobuoys for harbour and anchorage underwater protection
Autorzy:
Elminowicz, A.
Zajączkowski, L.
Powiązania:
https://bibliotekanauki.pl/articles/331708.pdf
Data publikacji:
2011
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The underwater protection system that consists of wideband Acoustic Barriers (WAB) and wideband DDS (WDDS) is a very suitable acoustic device to operate in Littoral Water (LW) and Extremely Littoral Water (ELW). A new approach to underwater protection harbour and task group on the anchorage against AUV, DDV and torpedos is focused on designed stationary tethered sonobuoys with passive sonar, active multistatic sonar, intercept sonar and also possibility of jamming intercepted underwater objects. Passive omnidirectional sonar may be used for initial detection of intruder on the long distance (up to 5 km) and active multistatic sonar will be applied for detection and precise location of detected object. Intercept sonar is waiting for homing sonar signals generated by AUV, DDS, torpedos or submarines and received signals are basis generating jamming signals. The paper describes the WAB, WDDS and magnetic barrier integrated to short range (up to 1000 m) protection systems. The long range (up to 5000 m) sonobuoy – for various technical parameters and environmental conditions – has been studied.
Źródło:
Hydroacoustics; 2011, 14; 39-46
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Multistatic systems
Autorzy:
Elminowicz, A.
Zajączkowski, L.
Powiązania:
https://bibliotekanauki.pl/articles/332386.pdf
Data publikacji:
2006
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
This paper describes key features of a multistatic operation in the littoral beginning from multistatic system (MS) configuration, his performance model and constraints imposed by environment of shallow water. The architecture of MS, features and requirements of MS basic subsystem has been presented. Essential role as during MS operation is fulfilled by data fusion and tracking methods as well a communication between MS units, has been protruded. The application of MS, especially for underwater protection systems, in the form of barriers protecting anchorage, harbour, straits or entries to the harbour has been presented. Other applications are connected with military operation, especially Anti–Submarine Warfare (ASW) in littoral areas. Attention was paid on possibility of cooperation among the different acoustics devices in MS.
Źródło:
Hydroacoustics; 2006, 9; 57-64
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Mutual interferences reduction between sonars or barrier modules operating in the same area
Autorzy:
Elminowicz, A.
Zajączkowski, L.
Powiązania:
https://bibliotekanauki.pl/articles/332459.pdf
Data publikacji:
2007
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
This paper describes key features of a Mutual Interference Reduction (MIR) in sea area, especially in shallow water, where some acoustic devices may operate simultaneously. MIR is an essential problem in mono– and multistatic systems. Receivers of sonars or barrier modules, operating in these systems, can receive signals from other acoustic devices by direct track, as echoes from the targets or as reverberations. The mutual sonars interference level depends on many parameters, like: the transmitting signal parameters (modulation, SL, B, T) and bands aliasing, mutual sectors coverage, the distance and mutual localization of trans-mitting transducers and receiving arrays, as well as type of matched filtration. The degrada-tion of mutual interferences by matched filtration has been determined. Influence of modula-tion type, B and T parameters on MIR at the matched filtration output have been presented also.
Źródło:
Hydroacoustics; 2007, 10; 39-44
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Multifrequency wideband sonar array
Autorzy:
Elminowicz, A.
Lis, W.
Zajączkowski, L.
Powiązania:
https://bibliotekanauki.pl/articles/332415.pdf
Data publikacji:
2012
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
This paper describes of new approach to Multifrequency Wideband Arrays (MWA), applied piezocomposite technologies of the array elements. MWA operating in transmitting (Tx) and receiving (Rx) mode on two or three bands, requires state-of-the-art technology and efficient array designing than conventional array in which separate arrays for every band or even separate Tx and Rx transducers/arrays are used. The new piezocomposite elements are designed at OBR Centrum Techniki Morskiej S.A., manufactured by Materials Systems Inc. (Littleton, USA) and tested at the cooperation with Gdansk University of Technology. The article presents research and development work at the multifrequency wideband piezocomposite arrays elements. An example of dual frequency wideband Tx/Rx array with design parameters and its implementation for the dual frequency wideband sonar will be presented. The results of array elements measurements: TVR, RVS, Impedance and Phase versus frequency from 50 kHz to 500 kHz as well as beam patterns, will be also presented.
Źródło:
Hydroacoustics; 2012, 15; 33-38
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Potencjalny zasięg klimatyczny jodły (Abies alba Mill.) w Polsce
Potential climatic range for Abies alba Mill. in Poland
Autorzy:
Bolibok, L.
Zajączkowski, J.
Dobrowolska, D.
Mionskowski, M.
Powiązania:
https://bibliotekanauki.pl/articles/989280.pdf
Data publikacji:
2016
Wydawca:
Polskie Towarzystwo Leśne
Tematy:
lesnictwo
drzewa lesne
jodla pospolita
Abies alba
zasieg wystepowania
potencjalny zasieg klimatyczny
Polska
silver fir
natural range potential climatic range
biocilmate envelops
Opis:
Numerous examples of silver fir stands growing outside its geographical range in northern Poland suggest that this species could be used in a greater extend in creation of managed forest stands. Climatic conditions could potentially constrain the use of this species in some parts of country. The objective of this work was to determine the potential climatic range of Abies alba in Poland. The bioclimatic envelope models were used to identify areas in which selected climatic variables show the same range of variability as observed within natural range of this species. Climatic data with 10' spatial resolution were used. The outcome of the analysis depends to large extent on the demarcation of natural range (in which the variability of tolerable climatic conditions is assessed). The model basing on the climatic conditions in whole natural range of silver fir in Europe suggest that almost whole area of Poland is suitable to fir, but models basing only of climatic conditions in Polish part of its natural range are much more conservative. In the last case the difference in extent between natural range and potential climatic range was smaller. As genetic variability of Polish fir populations is rather low, they are supposed to have constrained adaptative abilities. Forest managers should not focus on planting silver fir outside its natural range, but they rather should consider reintroduction of fir in parts of natural range from where it retreated in 20th century.
Źródło:
Sylwan; 2016, 160, 06; 519-528
0039-7660
Pojawia się w:
Sylwan
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Wieloletnia dynamika starodrzewów w zagospodarowanej części Puszczy Białowieskiej: gatunki ekspansywne i ustępujące
Long-term dynamics of old-growth stands in the managed part of the Bialowieza Forest: increasing and declining tree species
Autorzy:
Drozdowski, S.
Brzeziecki, B.
Żybura, H.
Żybura, B.
Gawron, L.
Buraczyk, W.
Zajączkowski, J.
Bolibok, L.
Szeligowski, H.
Bielak, K.
Widawska, Z.
Powiązania:
https://bibliotekanauki.pl/articles/1008501.pdf
Data publikacji:
2012
Wydawca:
Polskie Towarzystwo Leśne
Tematy:
lesnictwo
Puszcza Bialowieska
starodrzew
dynamika drzewostanu
drzewa lesne
swierk
grab
jesion
olsza
dab
lipa
brzoza
klon
sosna
wiaz
zageszczenie drzew
piersnicowe pole przekroju
piersnice drzew
gatunki ekspansywne
gatunki ustepujace
stale powierzchnie obserwacyjne
badania dlugoterminowe
old−growth forest
permanent plot
long−term trend
population density
population dynamics
tree species
Opis:
In the paper, an assessment of tree population dynamics in the old−growth stands of the managed part of the Białowieża Forest is presented. Data from five permanent sample plots with a total size of 9.3 ha and six inventories that cover the period 1949−2006, were used. Depending on the dynamic status, determined on the basis of changes in a number of individuals per hectare, basal area and quadratic mean diameter, three major groups of tree species were distinguished: 1) an increasing group, containing only hornbeam and lime; 2) a stable group, involving alder and spruce and 3) a declining group consisting of oak, ash, maple, pine, birch, elm and aspen.
Źródło:
Sylwan; 2012, 156, 09; 663-671
0039-7660
Pojawia się w:
Sylwan
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-10 z 14

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