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Wyświetlanie 1-15 z 32
Tytuł:
Example of Structure Modeling and Analysis of Ultrasound Scattering for Trabecular Bone
Autorzy:
Wójcik, J.
Litniewski, J.
Nowicki, A.
Powiązania:
https://bibliotekanauki.pl/articles/177853.pdf
Data publikacji:
2010
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
multi-scattering
random complex structures
trabecular bone model
Opis:
A trabecular bone consists of trabeculae whose mechanical properties differ significantly from the surrounding marrow, therefore an ultrasonic wave propagating within the bone structure is strongly scattered. The aim of this paper was to evaluate the contribution of the first, second and higher order scattering (multiple scattering) into the total scattering of ultrasound in a trabecular bone. The scattering due to the interconnections between thick trabeculae, usually neglected in trabecular bone models, has been also studied. The basic element in our model of the trabecular bone was an elastic cylinder with a various finite-length and diameter as well as orientation. The applied model was taking into account variation of both, elements size and their spatial configuration. The field scattered on the bone model was evaluated by solving numerically the integral form of the generalized Sturm-Liouville equation describing a scalar wave in inhomogeneous and lossy media. For the scattered fields calculated numerically the effective cross-sections were determined. The influence of absorption on the scattering coefficients was demonstrated. The results allowed to conclude that within the frequency range from 0.5 to 1.5 MHz contribution of the second order scattering to the effective backscattering cross-section is at least 500 times lower than that due to the first order scattering. It was noticed that for a frequency higher than 1.5 MHz fast growth of the backscattering (reflection) coefficients, calculated for the second order scattering, occurs.
Źródło:
Archives of Acoustics; 2010, 35, 4; 701-713
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Using Empirical Mode Decomposition of Backscattered Ultrasound Signal Power Spectrum for Assessment of Tissue Compression
Autorzy:
Byra, M.
Wójcik, J.
Nowicki, A.
Powiązania:
https://bibliotekanauki.pl/articles/177950.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
tissue characterization
tissue compression
quantitative ultrasound
empirical mode decomposition
signal analysis
Opis:
Quantitative ultrasound has been widely used for tissue characterization. In this paper we propose a new approach for tissue compression assessment. The proposed method employs the relation between the tissue scatterers’ local spatial distribution and the resulting frequency power spectrum of the backscattered ultrasonic signal. We show that due to spatial distribution of the scatterers, the power spectrum exhibits characteristic variations. These variations can be extracted using the empirical mode decomposition and analyzed. Validation of our approach is performed by simulations and in-vitro experiments using a tissue sample under compression. The scatterers in the compressed tissue sample approach each other and consequently, the power spectrum of the backscattered signal is modified. We present how to assess this phenomenon with our method. The proposed in this paper approach is general and may provide useful information on tissue scattering properties.
Źródło:
Archives of Acoustics; 2018, 43, 3; 447-453
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Mathematical and Ultrasonographic Model of the Left Ventricle : in Vitro Studies
Autorzy:
Olszewski, R.
Trawiński, Z.
Wójcik, J.
Nowicki, A.
Powiązania:
https://bibliotekanauki.pl/articles/176705.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
left ventricle
echocardiography
speckle modeling
ultrasound phantoms
strain
strain rate
Opis:
The main objective of this study is to develop an echocardiographic model of the left ventricular and numerical modeling of the speckles- markers tracking in the ultrasound (ultrasonographic) imaging of the left ventricle. The work is aimed at the creation of controlled and mobile environment that enables to examine the relationships between left ventricular wall deformations and visualizations of these states in the form of echocardiographic imaging and relations between the dynamically changing distributions of tissue markers of studied structures.
Źródło:
Archives of Acoustics; 2012, 37, 4; 583-595
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Annular Array Transducer and Matched Amplifier for Therapeutic Ultrasound
Autorzy:
Secomski, W.
Nowicki, A.
Wójcik, J.
Lewandowski, M.
Walczak, M.
Tymkiewicz, R.
Powiązania:
https://bibliotekanauki.pl/articles/177840.pdf
Data publikacji:
2010
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
ultrasonic therapy
annular array transducer
ultrasonic field
Opis:
The use of therapeutic ultrasound continues to grow. A focused ultrasonic wave can increase the tissue temperature locally for the non-invasive cancer treatment or other medical applications. The authors have designed a seven-element annular array transducer operating at 2.4 MHz. Each element was excited by sine burst supplied by a linear amplifier and FPGA control circuits. The acoustic field, generated by a transducer was initially numerically simulated in a computer and next compared to water tank hydrophone measurements performed at 20, 40 and 60 mm focal depth. The results showed good agreement of the measurements with theory and the possibility to focus the ultrasound in the preselected area. The total acoustic power radiated by the annular array was equal to 2.4 W.
Źródło:
Archives of Acoustics; 2010, 35, 4; 653-660
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thick Film Transducers for High Frequency Coded Ultrasonography
Autorzy:
Nowicki, A.
Lewandowski, M.
Wójcik, J.
Tymkiewicz, R.
Lou-Moller, R.
Wolny, W.
Zawada, T.
Powiązania:
https://bibliotekanauki.pl/articles/176939.pdf
Data publikacji:
2011
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
transducers
thick film
high frequency ultrasound
pulse compression
Golay codes
Opis:
Recently a new technology of piezoelectric transducers based on PZT thick film has been developed as a response to a call for devices working at higher frequencies suitable for production in large numbers at low cost. Eight PZT thick film based focused transducers with resonant frequency close to 40 MHz were fabricated and experimentally investigated. The PZT thick films were deposited on acoustically engineered ceramic substrates by pad printing. Considering high frequency and nonlinear propagation it has been decided to evaluate the axial pressure field emitted (and reflected by thick metal plate) by each of concave transducer differing in radius of curvature – 11 mm, 12 mm, 15 mm, 16 mm. All transducers were activated using AVTEC AVG-3A-PS transmitter and Ritec diplexer connected directly to Agilent 54641D oscilloscope. As anticipated, in all cases the focal distance was up to 10% closer to the transducer face than the one related to the curvature radius. Axial pressure distributions were also compared to the calculated ones (with the experimentally determined boundary conditions) using the angular spectrum method including nonlinear propagation in water. The computed results are in a very good agreement with the experimental ones. The trans- ducers were excited with Golay coded sequences at 35–40 MHz. Introducing the coded excitation allowed replacing the short-burst transmission at 20 MHz with the same peak amplitude pressure, but with almost double center frequency, resulting in considerably better axial resolution. The thick films exhibited at least 30% bandwidth broadening comparing to the standard PZ 27 transducer, resulting in an increase in matching filtering output by a factor of 1.4–1.5 and finally resulting in a SNR gain of the same order.
Źródło:
Archives of Acoustics; 2011, 36, 4; 945-954
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electroporation and morphogenic potential of Gentiana kurroo (Royle) embryogenic cell suspension protoplasts
Autorzy:
Wojcik, A.
Rybczynski, J.J.
Powiązania:
https://bibliotekanauki.pl/articles/80642.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
electroporation
pulsed electric field
kanamycin resistance
benzylaminopurine
gibberellic acid
Gentiana kurroo
embryogenic cell
protoplast
Źródło:
BioTechnologia. Journal of Biotechnology Computational Biology and Bionanotechnology; 2015, 96, 1
0860-7796
Pojawia się w:
BioTechnologia. Journal of Biotechnology Computational Biology and Bionanotechnology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Assessment of Free-Form Surfaces’ Reconstruction Accuracy
Autorzy:
Wójcik, A.
Niemczewska-Wójcik, M.
Sładek, J.
Powiązania:
https://bibliotekanauki.pl/articles/220773.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
reverse engineering
accuracy assessment
free-form surface
coordinate measuring machine
radius correction
Opis:
The paper presents the problem of assessing the accuracy of reconstructing free-form surfaces in the CMM/CAD/CAM/CNC systems. The system structure comprises a coordinate measuring machine (CMM) PMM 12106 equipped with a contact scanning probe, a 3-axis Arrow 500 Vertical Machining Center, QUINDOS software and Catia software. For the purpose of surface digitalization, a radius correction algorithm was developed. The surface reconstructing errors for the presented system were assessed and analysed with respect to offset points. The accuracy assessment exhibit error values in the reconstruction of a free-form surface in a range of ± 0.02 mm, which, as it is shown by the analysis, result from a systematic error.
Źródło:
Metrology and Measurement Systems; 2017, 24, 2; 303-312
0860-8229
Pojawia się w:
Metrology and Measurement Systems
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The effect of L-glutamine on the genetic transformation of embryogenic cell suspensions of gentian species (Gentiana lutea L., Gentiana cruciata L., and Gentiana kurroo Royle) using Agrobacterium tumefaciens
Autorzy:
Rybczynski, J.J.
Wojcik, A.I.
Powiązania:
https://bibliotekanauki.pl/articles/80392.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
embryogenic cell
gentian
Gentiana lutea
Gentiana cruciata
Gentiana kurroo
Agrobacterium tumefaciens
kanamycin resistance
L-alanyl-L-glutamine
genetic transformation
Źródło:
BioTechnologia. Journal of Biotechnology Computational Biology and Bionanotechnology; 2019, 100, 1
0860-7796
Pojawia się w:
BioTechnologia. Journal of Biotechnology Computational Biology and Bionanotechnology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The in vitro effect of bovine lactoferrin on the activity of organ leukocytes in rainbow trout [Oncorhynchus mykiss], European eel [Anguilla anguilla] and wels catfish [Silurus glanis]
Autorzy:
Malaczewska, J
Wojcik, M.
Wojcik, R.
Siwicki, A.K.
Powiązania:
https://bibliotekanauki.pl/articles/30969.pdf
Data publikacji:
2010
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
fish
rainbow trout
Oncorhynchus mykiss
European eel
Anguilla anguilla
catfish
Silurus glanis
in vitro effect
bovine lactoferrin
lactoferrin
leucocyte
freshwater fish
Opis:
Lactoferrin (LF) is a glycoprotein found in milk, neutrophil granules, secretions and selected organs of mammals. Lactoferrin exhibits antibacterial, antiviral, fungicidal, immunoregulatory and other functions. Although fish are devoid of this protein and its cell receptors, LF effect on the immune mechanisms of fish has been demonstrated. The objective of this study was to investigate the effect of bovine lactoferrin, applied in vitro, on the activity of head kidney and spleen leukocytes in three freshwater fish species: rainbow trout (Oncorhynchus mykiss), European eel (Anguilla anguilla) and weis catfish (Silurus glanis). The obtained results validate LF beneficial effect on the respiratory burst of phagocytes in rainbow trout and weis catfish despite the fact that the potential killing activity against Aeromonas hydrophila was not stimulated in any of the studied species. Bovine lactoferrin enhanced the proliferation of T-lymphocytes in rainbow trout and European eel, as well as of B-lymphocytes in rainbow trout.
Źródło:
Polish Journal of Veterinary Sciences; 2010, 13, 1; 83-88
1505-1773
Pojawia się w:
Polish Journal of Veterinary Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Product quality assessment – measurement and analysis of surface topography
Autorzy:
Niemczewska-Wójcik, M.
Sładek, J.
Tabaka, M.
Wójcik, A.
Powiązania:
https://bibliotekanauki.pl/articles/220537.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
surface metrology
topography
measurement devices
analysis of defects
quality
Opis:
This paper concerns the issues of measurement techniques, analysis and assessment of the machined surface geometric structure. The aim of this work was to show the application of surface analysis in diagnosing the causes of discrepancies occurring in the manufacturing process, which may result from ill-matched (poorly fitting) process parameters. An appropriate system of control and interpretation of results may allow early reaction to unfavorable trends (for example blunting of the tool) and prevention of undesirable defects. The subject of research was a waste basket used in the construction of retaining sewer systems. In this paper, the quality of the waste basket as well as its manufacturing process were analyzed and assessed. The research was carried out with the use of three measurement stands, i.e. optical microscopy (OM), scanning electron microscopy (SEM) and white light interferometer (WLI). The surface analysis proved to be important from the viewpoint of outlining the production process as well as improving the product quality. The software used for topographical analysis appeared to be significant for the success of the analysis, providing notable economic effects, namely the lack of defects.
Źródło:
Metrology and Measurement Systems; 2014, 21, 2; 271-280
0860-8229
Pojawia się w:
Metrology and Measurement Systems
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Precision machining of spherical ceramic parts
Precyzyjna obróbka ceramicznych elementów kulistych
Autorzy:
Gawlik, J.
Krajewska, J.
Niemczewska-Wójcik, M.
Powiązania:
https://bibliotekanauki.pl/articles/175636.pdf
Data publikacji:
2013
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
zirconium
sapphire
precision machining
surface geometric structure
cyrkon
szafir
obróbka precyzyjna
struktura geometryczna powierzchni
Opis:
Physical and mechanical properties of ceramic materials make them useful applications in both mechanical and medical engineering. This paper presents the technological system for precision machining of super hard ceramic materials. As an example of precisely processed ceramic components a circular / spherical element can be given, which was used in an endoprosthesis hip replacement. This paper presents selected characteristics of geometrical surface structure after precision machining and finishing and indicates directions for further research into the development of the technological qualities of ceramic components.
Materiały ceramiczne charakteryzują się właściwościami fizycznymi i mechanicznymi determinującymi ich zastosowanie zarówno w budowie maszyn, jak również w medycynie. W pracy przedstawiono system technologiczny do precyzyjnej obróbki trudnoobrabialnych materiałów ceramicznych. Podano przykłady elementów kulistych do zastosowania na endoprotezy stawu biodrowego. Określono wybrane charakterystyki struktury geometrycznej ich powierzchni po obróbce kształtującej i wykończeniowej. Wskazano kierunki dalszych badań z zakresu kształtowania jakości technologicznej elementów z materiałów ceramicznych.
Źródło:
Advances in Manufacturing Science and Technology; 2013, 37, 4; 19-30
0137-4478
Pojawia się w:
Advances in Manufacturing Science and Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigation of dynamic routing and spectrum allocation methods in elastic optical networks
Autorzy:
Biernacka, E.
Domżał, J.
Wójcik, T.
Powiązania:
https://bibliotekanauki.pl/articles/226037.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
elastic optical networks
routing and spectrum allocation
dynamic two-step RSA method
Opis:
The introduction of flexible frequency grids and advanced modulation techniques to optical transmission, namely an elastic optical network, requires new routing and spectrum allocation techniques. In this paper, we investigate dynamic two-step routing and spectrum allocation (RSA) methods for elastic optical networks. K-shortest path-based methods as well as spectrum allocation methods are analysed and discussed. Experimental verification of the investigated techniques is provided using simulation software. Simulation results present effectiveness of routing and spectrum allocation methods for analyzed networks using requested bandwidth of connections. Moreover, performance of shortest path first methods improves considerably when a number of candidate paths increases in the UBN24 topology.
Źródło:
International Journal of Electronics and Telecommunications; 2017, 63, 1; 85-92
2300-1933
Pojawia się w:
International Journal of Electronics and Telecommunications
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Quality Requirements Put On The Inconel 625 Austenite Layer Used On The Sheet Pile Walls Of The Boiler’s Evaporator To Utilize Waste Thermally
Wymagania jakościowe stawiane powłoce austenitycznej inconel 625 stosowanej na ścianach szczelnych parownika kotła do termicznej utylizacji odpadów
Autorzy:
Słania, J.
Krawczyk, R.
Wójcik, S.
Powiązania:
https://bibliotekanauki.pl/articles/355340.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
surfacing by welding
surfacing layer
incinerator
napawanie
powierzchnia napawania
piec do spopielania
Opis:
Quality requirements and tests taken on the surfacing layer Inconel 625 are presented in the article. The reasons of using surfacing layer Inconel 625 and technologies of its making with a particular emphasis on the CMT method are described. Quality requirements for the surfacing weld Inconel 625 are provided. Basic requirements included in the Merkblatt 1166, as well as additional requirements, which are reflected in the technical specifications of the boilers’ producers are specified.
Przedstawiono kryteria jakościowe jakie powinna spełniać powłoka Inconel 625 oraz badania jakim jest poddawana. Omówiono powody dla jakich stosowana jest powłoka Inconel 625 oraz technologie jej wykonywania przy szczególnym uwzględnieniu metody CMT. Opisano wymagania jakościowe dla napoiny Inconel 625. Zaprezentowano zarówno wymagania podstawowe zawarte w Merkblatt 1166 oraz wymagania dodatkowe, których odzwierciedleniem są specyfikacje techniczne wytwórców kotłów.
Źródło:
Archives of Metallurgy and Materials; 2015, 60, 2A; 677-685
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Examination and Detecting Discontinuities in the Austenite Inconel 625 Layer Used on the Sheet Pile Walls of the Boiler’s Evaporator to Utilize Waste Thermally
Wymagania jakościowe stawiane powłoce austenitycznej Inconel 625 stosowanej na ścianach szczelnych parownika kotła do termicznej utylizacji odpadów
Autorzy:
Słania, J.
Krawczyk, R.
Wójcik, S.
Powiązania:
https://bibliotekanauki.pl/articles/351569.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
surfacing by welding
surfacing layer
incinerator
wykrywanie pęknięć powierzchniowych
warstwa napawania
spalarnia odpadów
Opis:
There are practical aspects of a quality control of the Inconel 625 surfacing weld in terms of undergone examinations and detected defects in chapter three of the article. Visual inspections, examinations of the thickness of the surfacing weld, examinations of an iron content on the surface of the surfacing weld and detecting surface cracks are described. A process of undergone practical examinations is presented.
W rozdziale trzecim przedstawiono praktyczne aspekty kontroli jakościowej napoiny Inconel 625 w ujęciu wykonywanych badań i wykrywanych niezgodności. Omówiono badania wizualne, badania grubości napoiny, badania zawartości żelaza na powierzchni napoiny oraz wykrywanie pęknięć powierzchniowych. Zaprezentowano przebieg praktycznie wykonywanych badań.
Źródło:
Archives of Metallurgy and Materials; 2015, 60, 3A; 1703-1709
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ultrashort pulses supported by SESAM absorber
Autorzy:
Jasik, A.
Muszalski, J.
Gaca, J.
Wójcik, M.
Pierściński, K.
Powiązania:
https://bibliotekanauki.pl/articles/200639.pdf
Data publikacji:
2010
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
DBR
SESAM
mode-locking
femtosecond pulses
Opis:
We have developed a mode-locked diode-pumped Yb:KYW laser generating nearly band-width limited pulses as short as 101 fs. At 1.1 W absorbed power and 3% transmission output coupler, the laser delivers 150 mW for pulse duration of 110 fs, what corresponds to an efficiency of 14%. It was achieved using semiconductor saturable absorber mirror (SESAM) grown by molecular beam epitaxy. SESAM contains a distributed Bragg reflector (DBR) completed by single quantum well (SQW) playing role of an absorbing layer. The absorbers were crystallized in accordance with the predicted structure parameters under optimised growth conditions. The resonant-like type of structures ensured relatively high enhancement factor due to antireflective properties of SiO2 capping material and a wavelength independence of a group delay dispersion. The optimisation of the growth conditions of both an absorbing layer and DBR structure were widely carried out. Optical reflectance and high resolution X-ray diffraction have been used for characterization and verification of DBR structures. It results in reduction of the nonsaturable absorption in SESAM and self-starting mode-locking of the ultrashort pulses.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2010, 58, 4; 477-483
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 32

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