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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:
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:
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:
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
Tytuł:
Transport induced inflammatory responses in horses
Autorzy:
Wessely-Szponder, J.
Belkot, Z.
Bobowiec, R.
Kosior-Korzecka, U.
Wojcik, M.
Powiązania:
https://bibliotekanauki.pl/articles/30538.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Opis:
Deleterious response to road transport is an important problem in equine practice. It determines different physiological, immunological and metabolic changes which lead to increased susceptibility to several disorders such as pneumonia, diarrhea, colics, laminitis, injuries and rhabdomyolisis. The aim of our study was to look for possible relationships between transportation of female young and older horses over a long and short distance and an inflammatory state reflected by an increase of acute phase protein concentration, oxidative stress and muscle injury. The study was conducted on 24 cold-blooded female horses divided into four groups. Six fillies aged 6-18 months and six mares aged 10-12 years were transported over the distance of about 550 km, six fillies aged 6-18 months and six mares aged 10-12 years were transported over the distance of about 50 km. Plasma and serum were obtained from blood samples taken before transportation (T0), immediately after transportation (T1) and at an abattoir during slaughter (T2). In these samples fibrinogen, MDA, AST and CK were assessed. Fibrinogen increased in all studied groups especially in fillies after long distance transportation, where it reached 205±7.07 mg/dl before transportation, 625±35.35 mg/dl after transportation, and 790±14.14 mg/dl during slaughter. MDA concentrations rose after transportation and reached the maximal level during slaughter. CK activity was more elevated after short transportation in younger horses, whereas initial activity of AST was higher in older horses. We estimated that intensified responses from acute phase, oxidative stress and muscle injury parameters indicated an inflammatory state.
Źródło:
Polish Journal of Veterinary Sciences; 2015, 18, 2
1505-1773
Pojawia się w:
Polish Journal of Veterinary Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The effect of beta-hydroxy-beta-methylbutyrate (HMB) on selected parameters of humoral immunity in calves
Autorzy:
Wojcik, R.
Malaczewska, J.
Siwicki, A.K.
Micinski, J.
Zwierzchowski, G.
Powiązania:
https://bibliotekanauki.pl/articles/2087958.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Opis:
The objective of this study was to evaluate the effect of HMB on selected parameters of the humoral immunity in calves. The experiment was performed on 14 calves aged 30 ± 2 days, divided into two equal groups of control (group K) and experimental (group H) animals. The feed administered to the experimental calves was supplemented with HMB at 40 mg/kg BW, whereas the control calves were administered standard farm-made feed without supplementation. Blood was sampled from the jugular vein immediately before the experiment (day 0) and on experimental days 15, 30 and 60 to determine the following immunological parameters: total protein levels, gammaglobulin levels, lysozyme activity and ceruloplasmin activity. An analysis of the results obtained revealed a significant increase (p < 0.05; p < 0.01; p < 0.001 respectively) in gammaglobulin levels and lysozyme activity throughout the entire experimental period, an increase (p < 0.05; p < 0.01 respectively) in ceruloplasmin activity on experimental days 15 and 30, but no changes in serum total protein levels of calves administered HMB as compared to those found in the control group.
Źródło:
Polish Journal of Veterinary Sciences; 2014, 17, 2; 357-359
1505-1773
Pojawia się w:
Polish Journal of Veterinary Sciences
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:
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:
Proliferative and oxidative response of hepatocytes (Hep) and hepatic stellate cells (HSC) isolated from rats exposed to ketogenic diet
Autorzy:
Wojcik, M.
Wessely-Szponder, J.
Kosior-Korzecka, U.
Powiązania:
https://bibliotekanauki.pl/articles/30839.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Opis:
Ketogenic diet (KD) is considered in the context of its anti-epileptic effects, but its influence on liver dysfunction has not been elucidated yet. The study was aimed to investigate the activity of hepatocytes (Hep) and hepatic stellate cells (HSC) isolated from rats fed with KD, in respect of NO and superoxide generation by these cells as well as their proliferative activity in vitro. We also sought to characterize the plasma FFA profiles in control and ketogenic rats. Hep and HSC were isolated by the collagenase perfusion method and separated by the Percoll gradient centrifugation. After the 4th, 8th and 12th day of incubation, the media were collected for further analysis. NO generation increased within the time of incubation both in Hep and HSC isolated from KD-rats. In HSC group NO production raised significantly from 2.65 ± 0.07 μM/10⁶ cells on 4th day of incubation to 5.49 ± 1.2 μM/10⁶ cells on 12th day of incubation. In respect to O₂-. generation experimental Hep and HSC provide considerably higher quantities of this free radical. until 12th day of incubation (2.5 ± 0.07 and 3.2 ± 0.3 nM/10⁶ cells, respectively). Although KD exerts anti-proliferative effect on hepatocytes, in respect to HSC it intensifies their proliferative activity. Furthermore, as we estimated on the basis of NO and O₂-. generation both Hep and HSC exposed to KD are the source of free radicals.
Źródło:
Polish Journal of Veterinary Sciences; 2014, 17, 4
1505-1773
Pojawia się w:
Polish Journal of Veterinary Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The effect of beta-hydroxy-beta-methylbutyrate (HMB) on the proliferative response of blood lymphocytes and the phagocytic activity of blood monocytes and granulocytes in calves
Autorzy:
Wojcik, R.
Malaczewska, J.
Siwicki, A.K.
Micinski, J.
Zwierzchowski, G.
Powiązania:
https://bibliotekanauki.pl/articles/32319.pdf
Data publikacji:
2013
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Opis:
The objective of this study was to evaluate the effect of HMB on selected indicators of immunity in calves. The experiment was performed on 14 calves aged 30±2 days, divided into two equal groups of control (group I) and experimental (group II) animals. The feed administered to experimental group calves was supplemented with HMB at 40 mg/kg BW, whereas control calves were administered standard farm-made feed without supplementation. Blood was sampled from the jugular vein immediately before the experiment (day 0) and on experimental days 15, 30 and 60 to determine the following parameters of immunity: proliferative response of LPS- and ConA-stimulated lymphocytes (MTT), respiratory burst activity (RBA) and potential killing activity (PKA) of phagocytes. The results revealed a significant increase in RBA and MTT values in calves administered HMB in comparison with the control group throughout the experiment. In the group of animals receiving HMB, an increase in PKA values was noted only on day 30.
Źródło:
Polish Journal of Veterinary Sciences; 2013, 16, 3
1505-1773
Pojawia się w:
Polish Journal of Veterinary Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The influence of tool composite’s structure during process of diamond grinding of ceramic materials
Autorzy:
Gawlik, J.
Niemczewska-Wójcik, M.
Krajewska, J.
Sokhan, S. V.
Paščenko, E. A.
Žuk, T. S.
Powiązania:
https://bibliotekanauki.pl/articles/407111.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
ceramic materials
modified diamond tools
surface geometric structure
Opis:
This paper presents the results of the tests performed during the grinding process of the ceramic materials: - polycrystalline ceramics (Zirconium ZrO2) and mono-crystalline ceramics (sapphire -Al2O3) by the diamond tools. Studies have shown that the concentration (thickening) of the tool composite changes the tool’s pore structure when using suitable wetted adamantine additives. Such modified composite has positive impact on tribological properties of the subsurface layer of the machined components. This is manifested by the reduction of the surface roughness and reduction of the vibration amplitude of the coefficient of friction. The possibilities of the positive effects when using wetted additives on the tool’s composite during the pressing (briquetting) stage confirm the study results.
Źródło:
Management and Production Engineering Review; 2014, 5, 4; 9-17
2080-8208
2082-1344
Pojawia się w:
Management and Production Engineering Review
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 32

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