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Wyświetlanie 1-15 z 97
Tytuł:
Comparison between Linear Electromagnetic Accelerators
Autorzy:
Siaenen, T.
Löffler, M.
Powiązania:
https://bibliotekanauki.pl/articles/1807926.pdf
Data publikacji:
2009-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
85.70.Rp
Opis:
For symmetric Taylor tests a 2 m long electromagnetic accelerator will be used to accelerate 100 g rods up to 300 m/s. Only a small variance of the muzzle parameters, velocity and exit time, is tolerable. In order to find the most reliable, simple and efficient accelerator type, an axial coilgun, a flat-channel accelerator and an augmented railgun are compared using a lumped parameter model. In particular, the accelerator mutual inductances and their gradients characterize the propulsive forces. The essential advantages of the flat-channel geometry over the axial coilgun geometry are shown. The geometric improvements of the flat-channel accelerator open the way for the augmented railgun suitable and effective for the planned application. To minimize the variance of the muzzle parameters, modular capacitor banks with semiconductor switches allow the dynamic control of the railgun current, in principle.
Źródło:
Acta Physica Polonica A; 2009, 115, 6; 1089-1091
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Comparison of Naturally and Synthetically Derived Hydroxyapatite Powders
Autorzy:
Yelten, A.
Yilmaz, S.
Powiązania:
https://bibliotekanauki.pl/articles/1032536.pdf
Data publikacji:
2017-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.20.Fw
Opis:
Hydroxyapatite (HA) constitutes the mineral component of the hard tissues such as bone and teeth. HA is a bioactive ceramic material and can form biochemical bonds with tissues. It is possible to produce HA powders either from natural sources or by using synthetic chemicals. Wet chemical precipitation technique is an ideal method to practically and economically synthesize HA powders. Calcium hydroxide (Ca(OH)₂) and ortho-phosphoric acid (H₃PO₄) solutions were used as the calcium and phosphorus sources to obtain the HA powders. Acid-alkaline reactions between starting materials were carried out at three different reaction temperatures (room temperature, 50-60°C range and 70-80°C range) which may affect the microstructure of the produced powders. The procedure of HA powders preparation from natural sources consists of several steps: in the order of deproteinization of bovine bones in NaOH, washing the deproteinized bovine bones, calcination of the washed bones, and grinding the calcined bones, respectively. In this study, HA powders derived from bovine bones and HA powders obtained through the wet chemical precipitation method were compared in terms of their chemical, microstructural and molecular bonding properties by applying various characterization techniques such as X-ray diffraction, scanning electron microscope-energy dispersive spectroscopy, and the Fourier transform infrared spectroscopy.
Źródło:
Acta Physica Polonica A; 2017, 131, 1; 55-58
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Comparison of Different Theoretical Models of Positron Lifetime Spectra for Polymers
Autorzy:
Kansy, J.
Powiązania:
https://bibliotekanauki.pl/articles/1812531.pdf
Data publikacji:
2008-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
The same reference positron lifetime spectra of polyurethane, measured in temperature range 112 to 390 K, were analyzed with three theoretical models: the "conventional" model with three exponential decay component of discrete values of lifetimes, a model with one discrete exponential component and two "packages" of exponentials with log-normal distribution of annihilation rates, and a model considering positronium slow localization, positronium internal relaxation as well as "delayed" formation of positronium. It turns out that the two latter models fit to the experimental data with the same excellent quality, in spite of the fact that in both models the ratio of intensities related to para-positronium and ortho-positronium was constrained to be as 1:3.
Źródło:
Acta Physica Polonica A; 2008, 113, 5; 1397-1407
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Comparison of Lead and WC-Co Materials against Gamma Irradiation
Autorzy:
Buyuk, B.
Tugrul, A.
Powiązania:
https://bibliotekanauki.pl/articles/1182923.pdf
Data publikacji:
2014-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
25.20.Dc
Opis:
According to RoHS (Restriction of Hazardous Substances) directive of European Union it is restricted using lead in many equipment and applications. It is possible to enlarge the restriction of lead usage in some other applications which is including some of nuclear applications in the future. Therefore new materials or systems need to be developed instead of lead as radiation shielding materials and/or collimators. In this study pure tungsten, tungsten carbide-cobalt (WC-Co) materials were investigated against gamma radiation. For gamma radiation Cs-137 and Co-60 gamma radioisotope sources were used. The linear and mass attenuations were calculated. The experimental results were compared with XCOM computer code. Usage possibilities of WC-Co instead of lead in nuclear applications as gamma shielding material were discussed. It has been investigated that the linear gamma attenuation coefficients of lead and WC-Co are very close to each other. Therefore it could be said that WC-Co materials is an alternative promising material which could be used instead of lead as gamma shielding material and/or collimator.
Źródło:
Acta Physica Polonica A; 2014, 125, 2; 423-425
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Fabrication and Characterisation of Bronze Pads and Comparison with Commercial Bronze Pads
Autorzy:
Demir, A.
Powiązania:
https://bibliotekanauki.pl/articles/1185359.pdf
Data publikacji:
2016-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.20.Ev
Opis:
CuSn10 pre-alloyed bronze with iron and graphite powders were mixed, pressed and sintered for the bronze pad fabrication. The powder mix was pressed under pressure in the range of 100-600 MPa and sintered at temperatures between 780-850°C. The optimum compression was at 500 MPa and the optimal sintering temperatures was 730°C. 2 wt.% of graphite addition was sufficient to adjust the friction and wear properties of produced bronze pad samples. Optical microscope and SEM images showed that a homogenous powder mix was achieved. The produced bronze samples and the commercial ones were compared and beneficial properties of them were determined. The wear behaviours of both the produced friction materials and the commercial pads were examined. The coefficient of friction and wear rates were determined. The sintered bronze samples and the commercial bronze pads have exhibited similar wear behaviour, although the commercial one have contained ceramic particles.
Źródło:
Acta Physica Polonica A; 2016, 129, 4; 880-882
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Comparison between Mo BIS and Mo K-Edge Absorption Spectrum
Autorzy:
Sobczak, E.
Powiązania:
https://bibliotekanauki.pl/articles/1920907.pdf
Data publikacji:
1992-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
79.20.Kz
78.70.Dm
Opis:
The extended X-ray bremsstrahlung isochromat fine structure of bcc Mo for the photon energy 5415 eV is studied and compared with the extended X-ray absorption fine structure at the Mo K-edge from the literature. In both spectra a minimum of oscillation amplitude is observed at the momentum 4.2 and 5.3 Å$\text{}^{-1}$ for extended X-ray bremsstrahlung isochromat fine structure and extended X-ray absorption fine structure respectively, which is caused by the Ramsauer-Townsend effect at 5.5 Å$\text{}^{-1}$ and by beating effect at 3.7 Å$\text{}^{-1}$ from the first and second atomic shells. The Fourier transform of Mo extended X-ray bremsstrahlung isochromat fine structure was found to be in good agreement with the radial structure function of bcc Mo only in the case when the integration was performed in momentum range below 4.2 Å$\text{}^{-1}$.
Źródło:
Acta Physica Polonica A; 1992, 82, 2; 329-332
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Comparison of Machine Learning Techniques for Fetal Heart Rate Classification
Autorzy:
Cömert, Z.
Kocamaz, A.
Powiązania:
https://bibliotekanauki.pl/articles/1031680.pdf
Data publikacji:
2017-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
cardiotocography
machine learning techniques
classification
Opis:
Cardiotocography is a monitoring technique providing important and vital information on fetal status during antepartum and intrapartum periods. The advances in modern obstetric practice allowed many robust and reliable machine learning techniques to be utilized in classifying fetal heart rate signals. The role of machine learning approaches in diagnosing diseases is becoming increasingly essential and intertwined. The main aim of the present study is to determine the most efficient machine learning technique to classify fetal heart rate signals. Therefore, the research has been focused on the widely used and practical machine learning techniques, such as artificial neural network, support vector machine, extreme learning machine, radial basis function network, and random forest. In a comparative way, fetal heart rate signals were classified as normal or hypoxic using the aforementioned machine learning techniques. The performance metrics derived from confusion matrix were used to measure classifiers' success. According to experimental results, although all machine learning techniques produced satisfactory results, artificial neural network yielded the rather well results with the sensitivity of 99.73% and specificity of 97.94%. The study results show that the artificial neural network was superior to other algorithms.
Źródło:
Acta Physica Polonica A; 2017, 132, 3; 451-454
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Experimental Comparison of the Information Depth of AEAPS, DAPS and AES
Autorzy:
Hucek, S.
Pavluch, J.
Powiązania:
https://bibliotekanauki.pl/articles/1892436.pdf
Data publikacji:
1992-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
82.80.Pv
79.20.Fv
Opis:
The information depths of AEAPS and DAPS for the Ti and Cr L$\text{}_{3}$, L$\text{}_{2}$ and L$\text{}_{1}$ subshell excitation and of AES for the Ti L$\text{}_{3}$M$\text{}_{2,3}$M$\text{}_{2,3}$, L$\text{}_{3}$M$\text{}_{2,3}$M$\text{}_{4,5}$ and Cr L$\text{}_{3}$M$\text{}_{2,3}$M$\text{}_{4,5}$ transitions were determined. A set of Cr samples with Ti overlayers had been prepared in situ. Measurements of the LEAPS and HEAPS signal amplitudes were used to derive the AEAPS and DAPS signal intensities. The results showed that both AEAPS and DAPS had lower information depths compared with AES. They are interpreted in terms of the mean free paths of the majority of electrons contributing to the AEAPS signal.
Źródło:
Acta Physica Polonica A; 1992, 81, 2; 187-191
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Comparison of Optical Fiber Inertial Vibration Sensors
Autorzy:
Poczesny, T.
Prokopczuk, K.
Domanski, A.
Powiązania:
https://bibliotekanauki.pl/articles/1418092.pdf
Data publikacji:
2012-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.81.Pa
42.25.Bs
42.79.Pw
Opis:
This paper presents the application and comparison of a macrobend seismic optical fiber accelerometer and ferrule-top cantilever fiber sensor (made by Optics11 - Amsterdam, Netherlands) both for long distance vibration monitoring. The sensors utilize typical telecommunication optical transmission systems with specially prepared sensing head. Both optical fiber sensors measure force and acceleration similar to the piezoelectric accelerometers. One of the advantages of these devices is insensitivity to electromagnetic interference because of lack of electrically driven elements in sensing head area. Experiments with wide ranges of frequencies and vibration amplitudes were performed. Main parameters and measurement capabilities of both sensor types were compared. Experimental results show usage possibility of both sensor types in industry and other explosion risk environments for vibration measurement and online monitoring.
Źródło:
Acta Physica Polonica A; 2012, 122, 5; 954-956
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Neural Classifiers of Vibroacoustic Signals in Implementation on Programmable Devices (FPGA) - Comparison
Autorzy:
Dąbrowski, D.
Cioch, W.
Powiązania:
https://bibliotekanauki.pl/articles/1504200.pdf
Data publikacji:
2011-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
45.80.+r
46.40.-f
Opis:
The research includes comparative analysis of the effect of the recording of weight vectors and input data of selected neural classifiers with fixed-point numbers. Research has been conducted due to insufficient literature on the influence of such a recording on the correct classification of vibroacoustic signals by neural networks. This current issue was brought up in authors' earlier researches, concerning realization of neural classifiers on programmable logical devices field programmable gate array, with the application of fixed-point processor. During the analysis, three types of neural classifiers were compared in the tests: classifier based on neural network - length vector quantization, classifier using radial neural networks - radial basis functions, and third - counter propagation neural network. The problem stated was to recognize technical state of gear transmission DMA-1 in variable operating conditions. Vectors, based on estimates derived from processed vibroacoustic signals were used as teaching material.
Źródło:
Acta Physica Polonica A; 2011, 119, 6A; 946-949
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spin-Phonon Interactions for PbF$\text{}_{2}$:Gd$\text{}^{3+}$ - Comparison between Theory and Experiment
Autorzy:
Pastusiak, W.
Kuriata, J.
Powiązania:
https://bibliotekanauki.pl/articles/1920710.pdf
Data publikacji:
1992-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
76.30.Kg
Opis:
The results implying from two microscopic models for spin-phonon interactions are analyzed for the case of PbF$\text{}_{2}$:Gd$\text{}^{3+}$ It is shown that the two-phonon first-order mechanism predicts significant contributions to the values of the spin-phonon second-order coupling constants and the one-phonon second-order mechanism is less effective.
Źródło:
Acta Physica Polonica A; 1992, 81, 4-5; 599-603
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Comparison of Properties of One-Dimensional ± J Ising Models on Square Lattices
Autorzy:
Błaszyk, M.
Powiązania:
https://bibliotekanauki.pl/articles/1808002.pdf
Data publikacji:
2009-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
05.50.+q
75.10.Nr
75.50.Lk
Opis:
The energies and entropies of the one-dimensional ± J Ising models on square lattices have been compared. The method proposed in this paper explains the impossibility of getting exact results in nonzero temperatures and specifies the conditions of error minimisation.
Źródło:
Acta Physica Polonica A; 2009, 115, 5; 849-853
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Discrete and Continuous Analysis of Positron Lifetime Spectra: a Comparison
Autorzy:
Consolati, G.
Quasso, F.
Powiązania:
https://bibliotekanauki.pl/articles/2007998.pdf
Data publikacji:
1999-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
36.10.Dr
71.60.+z
78.70.Bj
Opis:
Positron lifetime spectra in poly[1-(trimethylsilyl)]propine membranes were collected at different temperatures and various number of accumulated counts, in order to compare the results from analyses obtained by different decay models: discrete (that is, purely exponential) or continuous (with at least one distribution of lifetimes). Analysis into four discrete components is inadequate, unless a low number of counts (1 to 2 millions) is accumulated. Conversely, deconvolutions which allow the ortho-positronium lifetime to be distributed give satisfactory fits, even at the highest statistics (60 millions). An equivalent good fit in terms of χ$\text{}^{2}$ test is obtained with a five discrete components analysis, from which it is possible to extract information on the first moments (centroid and standard deviation) of ortho -positronium lifetime distribution.
Źródło:
Acta Physica Polonica A; 1999, 95, 4; 505-508
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Comparison of Different Estimation Methods for Hysteresis Modelling
Autorzy:
Jastrzębski, R.
Chwastek, K.
Biondić, I.
Miličević, K.
Powiązania:
https://bibliotekanauki.pl/articles/1030241.pdf
Data publikacji:
2017-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.60.-d
75.60.Ej
Opis:
The paper focuses on the estimation techniques for a low-dimensional phenomenological model of ferromagnetic hysteresis proposed by the Brazilian research group GRUCAD. The description is expressed with an ordinary differential equation and some auxiliary relationships. It describes both irreversible and reversible magnetization processes and addresses some problems inherent in the well-known Jiles-Atherton model. It is found that the differential evolution method is the most competitive technique for recovery of optimal model parameters.
Źródło:
Acta Physica Polonica A; 2017, 131, 5; 1228-1231
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Performance Comparison of QPSK Based Single and Double Stage Digital Interpolators
Autorzy:
Ratan, R.
Sharma, S.
Kohli, A.
Powiązania:
https://bibliotekanauki.pl/articles/1399677.pdf
Data publikacji:
2013-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
84.30.Qi
84.30.Vn
Opis:
In this paper, the performance of single stage and double stage digital interpolators has been compared and has been showed that by using multi stage interpolation system the reliability of any communication system increases drastically. Digital signal interpolation systems can be implemented in a variety of ways. The basic interpolator for up-sampling can be a combination of an expander unit with an interpolation low-pass filter in cascade. Complicated implementations can be done by connecting multiple expander and low-pass filter pairs in cascade. This paper presents the efficient implementation of digital interpolation systems for up-sampling of single stage and double stage digital interpolators by using quadrature phase shift keying technique. Comparison is done in terms of spectrum of generated signal, envelope power, modulated signal trajectory, input and output constellation and noise performance.
Źródło:
Acta Physica Polonica A; 2013, 123, 2; 196-198
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 97

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