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Tytuł:
Determination of rheological model coefficients of pipeline composite material layers based on spectrum analysis and optimization
Autorzy:
Bogdevičius, Marijonas
Karpenko, Mykola
Bogdevičius, Paulius
Powiązania:
https://bibliotekanauki.pl/articles/1839709.pdf
Data publikacji:
2021
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
composite material
pipeline
spectrum analysis
rheological model
optimization
Opis:
The article presents theoretical and experimental investigation on properties of a composite material based on rubber. The approach presented in this research is an experimental measurement based on spectrum analysis combined with theoretical investigation held to describe a viscous-elastic behaviour of the material. The proposed mathematical model is represented by five rheological parameters of hybrid Maxwell and Kelvin-Voigt elements and includes an optimization task for determination of the stiffness and damping coefficients. In the proposed rheological model, not only the displacements are unknown but also forces described by second-order differential equations. Validation between the experimental measurement and theoretical investigation is made based on spectrum analysis.
Źródło:
Journal of Theoretical and Applied Mechanics; 2021, 59, 2; 265-278
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Statistical modelling and forecasting of wheat and meslin export from Ukraine using the singular spectral analysis
Autorzy:
Chala, Tetyana
Korepanov, Oleksiy
Lazebnyk, Iuliia
Chernenko, Daryna
Korepanov, Georgii
Powiązania:
https://bibliotekanauki.pl/articles/10184472.pdf
Data publikacji:
2023-02-24
Wydawca:
Główny Urząd Statystyczny
Tematy:
export
forecasting
singular spectrum analysis
Ukraine
wheat and meslin
Opis:
The article addresses the problems related to the functioning of the worldwide market of wheat and meslin. The authors identify the countries that over the past 17 years have been among the top 10 world leaders in terms of the value of export and import of wheat and meslin. The structure of wheat export by Ukrainian regions is analysed in comparison with the total export. The localisation coefficient is applied to measure the regional unevenness of the distribution of wheat export volumes and the total export by regions of the country. The modelling and forecasting of the volumes and prices of export of wheat and meslin from Ukraine are based on Singular Spectrum Analysis. The study particularly focuses on the individual components of time series, such as trend, annual, semi-annual, four-month, three-month seasonal components. The reliability of the forecast is confirmed by the calculation of the MAPE forecast error and Henry Theil’s inequality coefficient. The article proposes an algorithm for calculating the relative indicators of the structure for the individual components of the reconstructed time series, identified through the singular spectral analysis.
Źródło:
Statistics in Transition new series; 2023, 24, 1; 169-197
1234-7655
Pojawia się w:
Statistics in Transition new series
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Stable or not stable? Recognizing surge based on the pressure signal
Autorzy:
Garcia, D.
Liśkiewicz, G.
Powiązania:
https://bibliotekanauki.pl/articles/175253.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
singular spectrum analysis
nonlinear dynamics
statistical pattern recognition
compressor
surge
Opis:
The surge protection may be worth millions of dollars. This is typical price of a centrifugal compressor repair combined with additional cost of nonfunctionality of an industry employing it. This threat is normally secured by application of an antisurge systems. Typically they are activated at predefined working conditions when compressor mass flow rate approaches region affected by the surge. As a result those systems are vastly limiting its operational range usually by a desirable region where compressor attains large pressure ratio. Therefore, a modern antisurge systems are aiming at diminishing this tradeoff by reacting to the real pressure signal gathered at high frequency. This paper presents one of those methods employing singular spectrum analysis. This algorithm has not been widely used for this application, while it was shown herein that it may bring clear distinction between stable and nonstable working condition, even at presurge conditions. Hence in further perspective it may bring anti-surge protection quality, that was not met with another methods.
Źródło:
Transactions of the Institute of Fluid-Flow Machinery; 2016, 133; 55-68
0079-3205
Pojawia się w:
Transactions of the Institute of Fluid-Flow Machinery
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Improving the Consistency and Continuity of MODIS 8 Day Leaf Area Index Products
Autorzy:
Kandasamy, S.
Neveux, P.
Verger, A.
Buis, S.
Weiss, M.
Baret, F.
Powiązania:
https://bibliotekanauki.pl/articles/227345.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
iterative caterpillar singular spectrum analysis
MODIS
LAI
gap-filling
smoothing
Opis:
Time Series Analysis of Leaf Area Index (LAI) is vital to the understanding of global vegetation dynamics. The LAI time series derived from satellite observations are usually not complete and noisy due to cloud contamination and uncertainties in the retrieval techniques. In this paper, the continuity and consistency of the MODIS 8 day LAI products are improved using a method based on Caterpillar Singular Spectrum Analysis. The proposed method is compared with other standard methods: Savitzky-Golay filter, Empirical Mode Decomposition, Low Pass filtering and Asymmetric Gaussian fitting. The experiment demonstrates the smoothing and gapfilling ability of the developed method, which is more robust across the biomes both in terms of root mean square error metrics and bias metrics as compared to the standard methods.
Źródło:
International Journal of Electronics and Telecommunications; 2012, 58, 2; 141-146
2300-1933
Pojawia się w:
International Journal of Electronics and Telecommunications
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Diagnostic benchmarks on dynamic characteristics of thin-walled marine damaged structures
Autorzy:
Szeleziński, Adam
Murawski, Lech
Muc, Adam
Powiązania:
https://bibliotekanauki.pl/articles/2064867.pdf
Data publikacji:
2019
Wydawca:
STE GROUP
Tematy:
thin-walled structures
welded joints
SHM
spectrum analysis
damping decrement
Opis:
Among structural health monitoring (SHM) methods of thin-walled structures, a vibrodiagnostic method is one of the most promising. The accelerometer recorded responses provide diagnostic information that requires mathematical processing to extract the essential dynamic characteristics. The authors have been looking for new parameters - diagnostic benchmarks which can be applied to non-destructive, automatic testing of thin-walled marine structures (especially their welded joints) like ship hulls. All characteristics have been based on recorded data generated during the vibration tests of welded joints with and without failures. For this purpose, the authors proposed method based on: FFT windowing analysis, benchmark with using 2D or 3D time – frequency dynamic characteristics and the determination of damping decrement in function of time. The work presents the algorithm and exemplary results obtained from the application of proposed method to several selected sample plates with different type of welds.
Źródło:
Multidisciplinary Aspects of Production Engineering; 2019, 2, 1; 38--52
2545-2827
Pojawia się w:
Multidisciplinary Aspects of Production Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Rational polynomial windows with high attenuation of sidelobes
Autorzy:
Okarma, K.
Powiązania:
https://bibliotekanauki.pl/articles/140604.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
przetwarzanie sygnałów
analiza spektralna
polynomial windows
signal processing
spectrum analysis
Opis:
In the paper the idea of rational polynomial windows optimised towards low level of Fourier spectrum's sidelobes is presented. A relevant advantage of the polynomial windows family and their modifications is their ability to easily change their properties changing only the values of the polynomial coefficients. The obtained frequency characteristics demonstrate better properties of proposed rational Windows than their standard polynomial equivalents requiring only the additional division operation. Such approach does not increase the computational complexity in significant way and the great advantage of polynomial windows which is their low computational complexity is preserved.
Źródło:
Archives of Electrical Engineering; 2012, 61, 1; 7-14
1427-4221
2300-2506
Pojawia się w:
Archives of Electrical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
InAs light-to-heavy hole effective mass ratio determined experimentally from mobility spectrum analysis
Autorzy:
Wróbel, Jarosław
Umana-Membreno, Gilberto A.
Boguski, Jacek
Złotnik, Sebastian
Kowalewski, Andrzej
Moszczyński, Paweł
Antoszewski, Jarek
Faraone, Lorenzo
Wróbel, Jerzy
Powiązania:
https://bibliotekanauki.pl/articles/2204210.pdf
Data publikacji:
2023
Wydawca:
Polska Akademia Nauk. Stowarzyszenie Elektryków Polskich
Tematy:
indium arsenide
effective masses
energy band warping
magnetotransport
mobility spectrum analysis
Opis:
Careful selection of the physical model of the material for a specific doping and selected operating temperatures is a non-trivial task. In numerical simulations that optimize practical devices such as detectors or lasers architecture, this challenge can be very difficult. However, even for such a well-known material as a 5 μm thick layer of indium arsenide on a semiinsulating gallium arsenide substrate, choosing a realistic set of band structure parameters for valence bands is remarkable. Here, the authors test the applicability range of various models of the valence band geometry, using a series of InAs samples with varying levels of p-type doping. Carefully prepared and pretested the van der Pauw geometry samples have been used for magneto-transport data acquisition in the 20-300 K temperature range and magnetic fields up to ±15 T, combined with a mobility spectra analysis. It was shown that in a degenerate statistic regime, temperature trends of mobility for heavy- and light-holes are uncorrelated. It has also been shown that parameters of the valence band effective masses with warping effect inclusion should be used for selected acceptor dopant levels and range of temperatures.
Źródło:
Opto-Electronics Review; 2023, 31, Special Issue; art. no. e144567
1230-3402
Pojawia się w:
Opto-Electronics Review
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The application of spectrum analysis of course of pressure in combustion chamber for diagnosis of medium speed marine diesel engines
Autorzy:
Monieta, J.
Rutkowski, J.
Powiązania:
https://bibliotekanauki.pl/articles/243650.pdf
Data publikacji:
2008
Wydawca:
Instytut Techniczny Wojsk Lotniczych
Tematy:
piston marine diesel engine
course of combustion pressure
diagnosis
spectrum analysis
Opis:
In this work has been undertaken a study test the application course of combustion pressure signals in combustion chamber the marine medium-speed engine to diagnostic. In research has been used active experiment. The pressure signals analysis in cylinder has been carried out in amplitude and frequency domain, as new method for result processing. In preliminary research has been carried out with used marine engine 5BAH22 with current generator, be present in Engines Room Laboratory the Maritime Academy in Szczecin. Preliminary research has consisted in measurement the course of combustion pressure signals in individual cylinders and analysis the combustion pressure signals in time, amplitude and frequency domain at different engine load the combustion engine and has been checked that diagnostic parameters will be correlate with engine load. The current generator has been loaded with water resistor. The purpose of this work have been selected sensitive diagnostic symptoms and checked their usability in diagnosis marine diesel engine. In principal research has been simulated inability the turbocharger air filter as his mechanical impurities. Useful diagnostic symptoms have been determined. The method were being verified, execute operating research on working marine diesel engines at port and shipyard.
Źródło:
Journal of KONES; 2008, 15, 3; 367-374
1231-4005
2354-0133
Pojawia się w:
Journal of KONES
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The approximate location of imperfection in a unit circle using the spectrum of Laplace operator as a research tool
Widmo operatora Laplacea jako narzędzie do wykrywania przybliżonej lokalizacji uszkodzeń w kole jednostkowym
Autorzy:
Brzęk, M.
Zagórowska, M.
Mitkowski, W.
Powiązania:
https://bibliotekanauki.pl/articles/282126.pdf
Data publikacji:
2015
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
Laplace operator
location of imperfections
spectrum analysis
spectral theory
eigenvalues
operator Laplacea
Opis:
In the following article we will try to find the dependence between the location of imperfections in a closed domain and the spectrum of the Laplace operator for this region. In the theoretical part we will define the spectral problem which is solved by eigenvalues. These eigenvalues are dependent on location and size of the imperfection. However, we are interested in the inverse task which consists in localizing the imperfection of the domain on a basis of the spectrum of the operator.
W artykule przeanalizowano zastosowanie widma operatora Laplace'a jako narzędzia do przybliżonej lokalizacji uszkodzeń w kole jednostkowym. W części teoretycznej zdefiniowano zagadnienie spektralne rozwiązywane za pomocą wartości własnych. Znalezione wartości zależą od położenia i rozmiaru uszkodzeń. W artykule został zdefiniowany problem odwrotny, który polega na znalezieniu miejsca uszkodzenia na podstawie znanego widma.
Źródło:
Automatyka / Automatics; 2015, 19, 1; 9-15
1429-3447
2353-0952
Pojawia się w:
Automatyka / Automatics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Komputerowe wspomaganie terapii logopedycznej
Computer-aided speech therapy
Autorzy:
Kostrzewa, B.
Staszuk, A.
Powiązania:
https://bibliotekanauki.pl/articles/261127.pdf
Data publikacji:
2013
Wydawca:
Politechnika Wrocławska. Wydział Podstawowych Problemów Techniki. Katedra Inżynierii Biomedycznej
Tematy:
terapia logopedyczna
komputerowe wspomaganie
analiza widma
speech therapy
computer aiding
spectrum analysis
Opis:
Trudność wymowy głoski „r” sprawia, że dzieci uczą się jej jako ostatniej, dlatego znaczna część polskiego społeczeństwa nie wymawia tej głoski poprawnie. Powoduje to problemy w nauce (dysleksja), jak również odbija się na życiu emocjonalnymi i społecznym. Bagatelizowany problem doskwiera również w dorosłym życiu, powodując częste kompleksy, które mogą wpływać niekorzystnie na zdrowie osób cierpiących na wadę wymowy. Przyczynia się także do rozwoju chorób cywilizacyjnych, takich jak depresja czy nerwica. Aby ułatwić osobom dorosłym naukę wymowy głoski „r”, stworzono specjalną aplikację wspierającą terapię logopedyczną, zawierającą zestaw ćwiczeń do nauki wraz z filmami instruktażowymi poprawnego wykonania ćwiczeń. Zmontowano również zestaw pomagający w oszacowaniu poprawności wymawiania tej głoski. Przedstawione rozwiązanie daje pacjentowi możliwość codziennych ćwiczeń i samodzielnej oceny ich wykonania oraz stanowi alternatywę dla sesji logopedycznych, które w przypadku osób dorosłych są nierefundowane.
The consonant „r” is difficult to pronounce and children rarely learn its pronunciation before their fifth year of age. A significant part of Polish society is not able to pronounce “r”, correctly. This disability causes a lot of problems with learning (dyslexia) and has an influence on emotional and social life (complexes). It contributes to the development of civilization diseases, like depression or neurosis. To help adults learn to pronounce “r” properly, a specially designed computer-aided therapy is proposed. It consists of instructional videos with selected mouth and tongue movement trainings, selected speaking words and sentences with “r” exercises on several levels, as well as a special electronic circuit, which was designed and soldered to real-time visual assessment of the pronunciation accuracy. This solution offers patients the possibility of daily exercises with visual analysis of pronunciation accuracy and is an alternative to speech therapy sessions, which in case of adults, are not reimbursed by health care insurance system.
Źródło:
Acta Bio-Optica et Informatica Medica. Inżynieria Biomedyczna; 2013, 19, 4; 176-180
1234-5563
Pojawia się w:
Acta Bio-Optica et Informatica Medica. Inżynieria Biomedyczna
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Zastosowanie metody analizy widmowej drgań skrętnych wału napędowego do identyfikacji stanu technicznego rozpylaczy paliwa okrętowego silnika tłokowego o ZS
Spectrum analysis methods of shaftings torsional vibration for the injection fuel valves failures identification of the marine Diesels engines
Autorzy:
Bruski, S.
Powiązania:
https://bibliotekanauki.pl/articles/327806.pdf
Data publikacji:
2006
Wydawca:
Polska Akademia Nauk. Polskie Towarzystwo Diagnostyki Technicznej PAN
Tematy:
wał napędowy
drgania skrętne
analiza widmowa
propulsion shaft
torsional vibration
spectrum analysis
Opis:
W referacie przedstawiono wytypowane wyniki pomiarów drgań skrętnych wału napędowego średnioobrotowego silnika spalinowego typu Sulzer serii AL. Badanie miało na celu sprawdzenie możliwości wykorzystania analizy widmowej drgań skrętnych do diagnozowania stanu technicznego wtryskiwaczy paliwa silnika w eksploatacji w przypadku, gdy nie jest on standardowo wyposażony w zawory indykatorowe. Dla wyodrębnienia przydatnych parametrów diagnostycznych zasymulowano stan niezdatności wtryskiwacza polegający na wyłączeniu z pracy części otworów rozpylacza. Określono metodę oceny stanu technicznego rozpylacza na podstawie zawartości wyższych harmonicznych w widmie drgań skrętnych wału napędowego transmitującego moment obrotowy z silnika na śrubę napędową okrętu.
In the paper there are described selected results of torsional vibration measurements carried out on propulsion shafts powered by medium-speed, four-stroke, marine engine Sulzer 6AL20/24. The analysis had to check capabilities of diagnosing injection fuel valve failures within the propulsion system by means of torsional vibration analysis. For separation useful diagnostic parameters there was simulated unserviceability state which was relying on stopping up some openings in injection fuel valve.
Źródło:
Diagnostyka; 2006, 4(40); 179-184
1641-6414
2449-5220
Pojawia się w:
Diagnostyka
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Reliability based optimization of steel frames under seismic loading conditions using evolutionary computation
Niezawodnościowo zorientowana optymalizacja ram stalowych poddanych obciążeniom sejsmicznym za pomocą ewolucyjnej techniki obliczeniowej
Autorzy:
Papadrakakis, M.
Tsompanakis, Y.
Lagaros, N. D.
Friagiadakis, M.
Powiązania:
https://bibliotekanauki.pl/articles/281939.pdf
Data publikacji:
2004
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
structural optimization
Monte Carlo simulation
reliability analysis
evolutionary computation
multi-modal response spectrum analysis
Opis:
Earthquake-resistant design of structures using probabilistic analysis and performance-based design criteria is an emerging field of structural enginering. These new analysis and design methodologies are aimed at improving the existing practice and design codes for better prediction of the structural performance. In this paper, a robust and efficient methodology is presented for performing reliability-based structural optimum design of steel frames under seismic loading. The optimization part is realised with evolution strategies, while the reliability analysis is carried out with the Monte Carlo simulation method icorporating the latin hypercube sampling technique for the reduction of the sample size. The probability of failure of the frame structures, in terms of interstorey drift limits, is determined via the multi-modal response spectrum analysis.
Konstruowanie budowli o zwiększonej odporności na trzęsienia ziemi poprzez wykorzystanie rachunku prawdopodobieństwa i kryteriów eksploatacyjnych jest nowa rozwijająca się dziedzina inżynierii konstrukcji. Nowa metodologia i procedury postępowania celują w udoskonalanie istniejących programów i pakietów obliczeniowych przewidujących zachowanie się danej budowli w zadanych warunkach. W pracy zaprezentowano sztywną i wydajną metodologię optymalizacji zorientowaną na niezawodność ram stalowych poddanych obciążeniom sejsmicznym. Optymalizację oparto na obliczeniach ewolucyjnych, natomiast analizę niezawodności zrealizowano metodą Monte-Carlo, w której do redukcji wymiarowości zagadnienia wykorzystano technikę LHS (Latin Hypercube Sampling). Prawdopodobieństwo uszkodzenia konstrukcji, w sensie przekroczenia granicznych przemieszczeń międzykondygnacyjnych, obliczono za pomocą wielomodalnej analizy widma odpowiedzi konstrukcji.
Źródło:
Journal of Theoretical and Applied Mechanics; 2004, 42, 3; 585-608
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A method of fatigue strength testing of wheel rim fragments at the production process stage
Autorzy:
Rychlik, A.
Kozubel, W.
Powiązania:
https://bibliotekanauki.pl/articles/950122.pdf
Data publikacji:
2016
Wydawca:
Instytut Techniczny Wojsk Lotniczych
Tematy:
fatigue strength testing
vibration spectrum analysis
destructive tests
crack detection
wheel rim
Opis:
The paper describes a method of accelerated fatigue strength testing of elements with the use of inertia forces. The presented test method is dedicated to the selected materials, constructions and joints used in the production of wheel rims for motor vehicles, tractors and special vehicles. The analysis of the fatigue process in machinery components and the evaluation of its state in terms of product quality control can be divided into: quasi-static analysis, resonance analysis, and the one generally used today – virtual fatigue analysis. Virtual analysis is applicable to new components and/or structures released to production according to the concept based on the interaction of theoretical and working models in the context of service life prediction. The purpose of this paper is to present a tool for examination, and a method allowing the identification of the beginning of the fatigue cracking process in structural components. The demonstrated method belongs to the destructive testing group. Cracking process analysis and identification is based on a multiparameter analysis of vibration signals in the amplitude-frequency domain. Inertia force is used in the test piece destruction process. The discussed method is applicable to a wide range of fatigue tests for structural components in the quality control process for materials and combinations of these materials. The method has been employed in the production of low-speed and special machinery wheel rims by Polkar Warmia Ltd.
Źródło:
Journal of KONES; 2016, 23, 1; 289-296
1231-4005
2354-0133
Pojawia się w:
Journal of KONES
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Long period oscillations in the longshore current on a sandy, barred coast investigated with singular spectrum analysis
Autorzy:
Kaczmarek, J.
Rozynski, G.
Pruszak, Z.
Powiązania:
https://bibliotekanauki.pl/articles/47837.pdf
Data publikacji:
2005
Wydawca:
Polska Akademia Nauk. Instytut Oceanologii PAN
Tematy:
beach process
nearshore region
longshore current
coastal process
infragravity wave
singular spectrum analysis
Opis:
The presence of infragravity waves in nearshore regions can be sought in the records of both water levels and wave-driven longshore currents. For this reason, time series of such currents in close proximity to the shoreline were analysed using Singular Spectrum Analysis (SSA). Simultaneously, the results obtained with this method were confronted with the output of Discrete Wavelet Transform (DWT), which had previously been applied to this data. The records of longshore currents were collected on a daily basis during field experiments in the autumns of 2002 and 2003 with sampling rates of 3 Hz and 0.5 Hz. This produced a large data set that allowed for the use of an advanced signal processing technique, capable of extracting patterns characteristic of low-, medium- and high-frequency bands. It provided similar evidence to that produced by DWT for the existence of infragravity waves along a dissipative coast with multiple bars. The study also demonstrated the utility of SSA for studies on coastal hydrodynamics. It also showed up the better user-friendliness of DWT in terms of pattern extraction and interpretation. On the other hand, SSA demonstrated a higher precision of pattern extraction once the DWT output was known, which is a manifestation of the synergy of the two methods when applied jointly.
Źródło:
Oceanologia; 2005, 47, 1
0078-3234
Pojawia się w:
Oceanologia
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Metoda analizy widm mierzonych z wykorzystaniem spektrometrów OP-FTIR w monitorowaniu powietrza atmosferycznego oraz gazów w procesach przemysłowych
Open Path FT-IR Spectra Analysis Method for Monitoring of Environment and Processes with Varying Conditions
Autorzy:
Cięszczyk, S.
Komada, P.
Akhmetova, A.
Mussabekova, A.
Powiązania:
https://bibliotekanauki.pl/articles/1817978.pdf
Data publikacji:
2016
Wydawca:
Politechnika Koszalińska. Wydawnictwo Uczelniane
Tematy:
otwarta ścieżka
FTIR
analiza widm
wpływ temperatury
open path
spectrum analysis
temperature influence
Opis:
Open-Path Fourier Transform Infrared (OP-FTIR) can be used for monitoring of atmospheric environment. The open path technique is based on the measurement of the absorption along the atmosphere path between radiation source and spectrometer. Measurement paths used in this method have a considerable length – from tens of meters to several kilometers. The main advantage of OP-FTIR spectrometry is the possibility of continuously and simultaneously measuring concentrations of multiple compounds. Unfortunately, quantitative analysis of the spectra of such measurements is a difficult issue due to the changing atmospheric conditions and overlapping of the absorption spectra of various components. Numerous algorithms used for the interpretation of the measured spectra have been proposed. They can be classified into methods using classical chemometric calibration and iterative algorithms. Classical Least Square CLS and Partial Least Square PLS are the most commonly used methods of OP-FTIR spectrometry. Iterative methods are based on comparing measured data with synthetic spectra, that is computational models of investigated optical path transmission. For this purpose, databases such as HITRAN are used. Transmission model must take into account not only the spectral characteristics of gases, but also the measuring instrument influence on the measured spectrum. As an example of modeling the spectra of NH3 and HCl gas are used. Modeling of gas spectra with different resolution is shown. Classical methods of building a chemometric calibration model require appropriate reference samples. This is usually associated with considerable cost and time-consuming calibration process. In addition, correct calibration requires maintaining the same conditions during the calibration, as in practical measurements. This is possible only in the case of laboratory measurements. In particular, it is necessary to maintain a constant temperature and pressure of examined substances. It is connected with changes in width and intensity of gas rotational lines. In classical spectroscopy, changing environmental conditions require new calibration measurements. In the open path spectroscopy, changes in conditions occur naturally along with the changes in the examined environment (object, process). If the measurement conditions in the environment differ from those in calibration measurements, significant errors in determining the content of the ingredients may appear. Greater changes in conditions may occur in a variety of chemical or physical processes. Sometimes it is not possible to perform measurements in conditions similar to those occurring in a particular industrial facility. In such cases, synthetic spectra may be used in two ways: in an iterative process to compare with measured spectra or to form a chemometric calibration models. In the latter case, the problem of changing conditions can be solved in several ways. The simplest method is to build separate calibration models for all conditions that can occur during the measurement. However, in order to use this method, it is necessary to measure the existing conditions and choose an appropriate local model. Another method is to correct the measured spectra and to adapt them to the standard conditions. The third option is to build global models. The spectra of all the conditions that may occur during the measurement are then used for building a calibration model. Then, the effect of temperature on the determination of gas content for local calibration models is investigated. Finally, a global calibration model insensitive to temperature changes in 10-40°C range is built.
Źródło:
Rocznik Ochrona Środowiska; 2016, Tom 18, cz. 2; 218-234
1506-218X
Pojawia się w:
Rocznik Ochrona Środowiska
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 50

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