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Wyświetlanie 1-15 z 88
Tytuł:
Research on the Mechanical Properties and Curing Networks of Energetic GAP/TDI Binders
Autorzy:
Ma, S.
Li, Y.
Li, G.
Luo, Y.
Powiązania:
https://bibliotekanauki.pl/articles/358300.pdf
Data publikacji:
2017
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
glycidyl azide polymer (GAP)
curing networks
hydrogen bonding
entanglement
integrity
Opis:
This research focused on correlations between the macroscopic mechanical performance and microstructures of energetic binders. Initially a series of glycidyl azide polymer (GAP)/toluene diisocyanate (TDI) binders, catalyzed by a mixture of dibutyltin dilaurate (DBTDL) and triphenyl bismuth (TPB), was prepared. Uniaxial tensile testing, and low-field nuclear magnetic resonance and infrared spectroscopy were then used to investigate the mechanical properties, curing networks, and hydrogen bonding (H-bonds) of these binders. Additionally, a novel method based on the molecular theory of elasticity and the statistical theory of rubber elasticity was used to analyze the integrity of the networks. The results showed that the curing parameter R strongly influences the mechanical properties and toughness of the binders, and that a tensile stress (σm) of 1.6 MPa and an elongation (εm) of 1041% was observed with an R value of 1.6. The cross-linking density increased sharply with the curing parameter, but only modestly with an R value ≥ 1.8. The proportion of H-bonds formed by the imino groups increased with the R value and reached 72.61% at an R value of 1.6, indicating a positive correlation between the H-bonds and σm. Molecular entanglement was demonstrated to increase with R and to contribute dramatically to the mechanical performance. The integrity of these networks, evaluated by a correction factor (A), varies with R, and a network of the GAP/TDI binder with an R value of 1.6 is desirable.
Źródło:
Central European Journal of Energetic Materials; 2017, 14, 3; 708-725
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Interaction between mineral particles during ascharite flotation process and direct force measurement using AFM
Autorzy:
Li, Z.
Han, Y.
Li, Y.
Gao, P.
Powiązania:
https://bibliotekanauki.pl/articles/110122.pdf
Data publikacji:
2017
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
ascharite
serpentine
quartz
interaction
AFM
DLVO
Opis:
Interaction between mineral particles during ascharite flotation was investigated by flotation, zeta potential, Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, atomic force microscope (AFM) and SEM-EDS tests. Flotation results showed that the ascharite recovery decreased significantly in the presence of serpentine. In order to improve the ascharite recovery, negative charged quartz was used to limit the detrimental effect of serpentine on ascharite flotation in this research. The effect of quartz on improving ascharite recovery was attributed to the particle surface interactions. The DLVO theory was applied to study the particles interaction in the aqueous solution. The fitting curves showed that serpentine could attach to the surface of quartz easily, and quartz would be well dispersed with ascharite. Therefore, quartz can improve the ascharite flotation performance effectively by interaction between particles. Zeta potential tests showed the opposite charges on the surfaces of mineral particles, which was the basic reason leading to particles interaction. The force measurement results of AFM indicated that the attraction force existed between serpentine and ascharite, as well as serpentine and quartz, but the force between quartz and ascharite was repulsive. The DLVO theory was in a good agreement with the results of AFM. Eventually, particles coating were observed by SEM-EDS, which supported the results of DLVO theory and AFM measurements. During the flotation process, addition of quartz would lead to attachment of serpentine to the quartz surface, so the adverse effect of serpentine on decreasing floatability of ascharite was weakened.
Źródło:
Physicochemical Problems of Mineral Processing; 2017, 53, 2; 1161-1174
1643-1049
2084-4735
Pojawia się w:
Physicochemical Problems of Mineral Processing
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Selective flotation of siderite and quartz from a carbonate-containing refractory iron ore using a novel amino-acid-based collector
Autorzy:
Gu, X.
Zhu, Y.
Li, Y.
Han, Y.
Powiązania:
https://bibliotekanauki.pl/articles/110222.pdf
Data publikacji:
2018
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
flotation
quartz
hematite
siderite
refractory iron ores
molecular simulation
Opis:
A novel and highly-efficient amino-acid-based collector, α-ethylenediamine lauric acid (α-EDA-LA), was studied to selectively beneficiate carbonate-containing refractory hematite ores. Single mineral and synthetic mixture flotation tests were carried out to investigate its floating performance. Zeta potential, fourier transform infrared spectroscopy (FTIR) and Density Functional Theory-based molecular simulation were used to identify the adsorption mechanism. The flotation results showed that quartz could be collected effectively at pH 11.0-12.0 in the reverse flotation. For siderite, the recovery peaked at 83.4% at pH 8.0, where siderite presented different floatability from magnetite and hematite. Exploiting such difference, the separation of siderite could be achieved. Zeta-potential measurements showed that α-EDA-LA adsorption on the surfaces of siderite and quartz decreased the corresponding zeta potentials at pH of 8.0-10.0 and 8.0-12.0, respectively. This means the adsorption overcome the electrostatic repulsion between α-EDA-LA and the mineral surfaces. The molecular simulation indicated that no chemisorption took place between α-EDA-LA and quartz. FTIR analysis suggested that α-EDA-LA was adsorbed on quartz via hydrogen bonding. The adsorption of α-EDA-LA on siderite surface was dominated by chemisorption, while further enhanced by hydrogen bonding. This study filled the gap in the research on siderite flotation reagents and its adsorption mechanism.
Źródło:
Physicochemical Problems of Mineral Processing; 2018, 54, 3; 803-813
1643-1049
2084-4735
Pojawia się w:
Physicochemical Problems of Mineral Processing
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
One system reliability assessment method for CNC grynder
Metoda oceny niezawodności systemu szlifierki CNC
Autorzy:
Liu, Y.
Fan, J.
Li, Y.
Powiązania:
https://bibliotekanauki.pl/articles/302208.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Polskie Naukowo-Techniczne Towarzystwo Eksploatacyjne PAN
Tematy:
niezawodność systemu
metoda oceny
MTBF
szlifierka CNC
system reliability
assessment method
CNC grinder
Opis:
Poziom niezawodności szlifierki CNC (sterowanej numerycznie) zazwyczaj ocenia się na podstawie danych o uszkodzeniach liczonych w laboratorium lub w terenie, co wymaga zmontowania szlifierki i jest metodą oceny post-factum. Aby umożliwić ocenę poziomu niezawodności szlifierki CNC na etapie projektowania, w niniejszym artykule zaproponowano metodę oceny niezawodności systemu oraz odpowiedni algorytm wykorzystujące dane dotyczące niezawodności podsystemów. Model ten wymaga klasyfikacji podsystemów, badań niezawodności, dopasowania funkcji rozkładu, oceny parametrów oraz oceny niezawodności. Wyniki obliczeń wykazały, że omawiana metoda sprawdza się i jest dokładna w porównaniu z metodą tradycyjną. Przedstawiona metoda stanowi wkład do procesu projektowania niezawodności szlifierki CNC i znajduje odniesienie do innych produktów mechatronicznych.
The reliability level of CNC (Computer Numerical Control) grinder is usually assessed by fault data counted in laboratory or in field, which needs the grinder to be assembled and it is one afterwards estimation method. To evaluate the reliability level of CNC grinder in design phrase, one system reliability assessment method and algorithm was put forward by subsystem’s reliability in this article, which needs subsystem classification, reliability test, distribution function fitting, parameters estimation and reliability assessment. The calculation result showed that the method was feasible and accurate compared with the traditional way. The method is one contribution to reliability design for CNC grinder and is one reference to other mechatronic products.
Źródło:
Eksploatacja i Niezawodność; 2014, 16, 1; 97-104
1507-2711
Pojawia się w:
Eksploatacja i Niezawodność
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Simulation model and state analysis of ship transmission line
Autorzy:
Hu, Y.
Xu, M.
Li, Y.
Powiązania:
https://bibliotekanauki.pl/articles/259613.pdf
Data publikacji:
2018
Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Tematy:
ship power
transmission line
simulation model
insulation deterioration
Opis:
In order to discuss the simulation model of the ship transmission line and the state of the transmission line, an early fault model is built according to the evolution principle of the short circuit fault of the transmission line and combining with the fault characteristics of the early fault. A small distributed ship transmission line system is built in MATLAB/ Simulink. Then, combined with the constructed fault module, the original short circuit module, and the load module, the various states (normal state, early fault state, severe early fault state, short circuit state) of the ship transmission line are stimulated, and the features of voltage signal in each state is analysed. It is concluded that, due to the normal operation of the ship transmission line system, the variation characteristics of the flow signal and voltage signal caused by the sudden load mutation, that is, the sudden load and the sudden increase load, are very similar to the changes caused by the early fault. Therefore, in order to find a more accurate early fault detection method, the state is divided into normal state, sudden load state, sudden increase and sudden decrease load state.
Źródło:
Polish Maritime Research; 2018, S 3; 36-42
1233-2585
Pojawia się w:
Polish Maritime Research
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Four positive periodic solutions of a discrete time Lotka-Volterra competitive system with harvesting terms
Autorzy:
Liu, X.
Ren, Y.
Li, Y.
Powiązania:
https://bibliotekanauki.pl/articles/254985.pdf
Data publikacji:
2011
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
discrete systems
Lotka-Volterra competitive models
coincidence degree
harvesting terms
Opis:
In this paper, by using Mawhin's continuation theorem of coincidence degree theory, we establish the existence of at least four positive periodic solutions for a discrete time Lotka-Volterra competitive system with harvesting terms. An example is given to illustrate the effectiveness of our results.
Źródło:
Opuscula Mathematica; 2011, 31, 2; 257-267
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Existence and uniqueness of anti-periodic solutions for a class of nonlinear n-th order functional differential equations
Autorzy:
Liu, L.
Li, Y.
Powiązania:
https://bibliotekanauki.pl/articles/255647.pdf
Data publikacji:
2011
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
anti-periodic solution
coincidence degree
nonlinear n-th-order equation
delay
Źródło:
Opuscula Mathematica; 2011, 31, 1; 61-74
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Improved dolphin swarm optimization algorithm based on information entropy
Autorzy:
Li, Y.
Wang, X.
Powiązania:
https://bibliotekanauki.pl/articles/200085.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
dolphin swarm optimization
information entropy
convergence
self-adaptive
combinational optimization
Opis:
In order to overcome the shortcomings of the dolphin algorithm, which is prone to falling into local optimum and premature conver-gence, an improved dolphin swarm algorithm, based on the standard dolphin algorithm, was proposed. As a measure of uncertainty, information entropy was used to measure the search stage in the dolphin swarm algorithm. Adaptive step size parameters and dynamic balance factors were introduced to correlate the search step size with the number of iterations and fitness, and to perform adaptive adjustment of the algorithm. Simulation experiments show that, comparing with the basic algorithm and other algorithms, the improved dolphin swarm algorithm is feasible and effective.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2019, 67, 4; 679-685
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Hyperelastic behavior of two rubber materials under quasistatic and dynamic compressive loadings — testing, modeling and application
Właściwości hipersprężyste materiałów gumowych w warunkach kwazistatycznych i dynamicznych obciążeń ściskających — badania, modelowanie i zastosowanie
Autorzy:
Mao, Y.
Li, Y.
Chen, Y.
Miao, Y.
Deng, Q.
Niu, W.
Powiązania:
https://bibliotekanauki.pl/articles/947495.pdf
Data publikacji:
2015
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Chemii Przemysłowej
Tematy:
rubber
hyperelastic behavior
compressive loading
constitutive model
guma
właściwości hipersprężyste
obciążenie ściskające
model konstytutywny
Opis:
The mechanical properties of two rubber materials, RB-55 rubber and FM-32 foam rubber, were tested under quasistatic and dynamic compressive loadings with a universal testing machine and a nonmetallic split Hopkinson pressure bar (SHPB), respectively. The results show that the hyperelasticity dominates the mechanical characteristics of the both materials. And the strain rate dependencies can be observed over the wide strain rate range from 10-2 s-1 to order 103 s-1. But in the rather narrow bands of 10-2—100 s-1 and 2 • 103 —6 • 103 s-1, the strain rate effects are not significant. In order to numerically simulate rod-explosive loading tests where the two rubber materials were used as a combined buffer, the strain rate-independent hyperelastic behaviors at the strain rate of order 103 s-1 were characterized by Ogden constitutive models, incompressible for RB-55 rubber and compressible for FM-32 foam rubber, respectively. The numerical prediction of the structural responses agrees very well with the experimental results. This means the testing and modeling are successful.
Za pomocą uniwersalnej maszyny wytrzymałościowej oraz metodą pręta Hopkinsona (SHPB) zbadano właściwości mechaniczne gumy (RB-55) i gumy piankowej (FM-32) poddanych kwazistatycznym i dynamicznym obciążeniom ściskającym. Wyniki badań wskazały, że w materiałach tych dominują właściwości hipersprężyste. Krzywe zależności naprężenia od odkształcenia wyznaczono w szerokim zakresie szybkości odkształcania rzędu 10-2 — 103 s-1. Stwierdzono, że szybkość odkształcania nie wywiera istotnego wpływu na krzywe naprężenie-odkształcenie tylko w dość wąskich zakresach wartości, tj. 10-2 — 0 s-1 oraz 2 • 103 — 6 • 103 s-1. W celu numerycznego symulowania testów obciążeniowych metodą wybuchających prętów (z ang. rod-explosive loading tests), gdzie oba materiały gumowe pełniły rolę buforów, zastosowano model konstytutywny Ogdena, przeznaczony do analizy materiałów hipersprężystych. Wyniki symulacji numerycznych wykazały dobrą zgodność z wynikami doświadczalnymi.
Źródło:
Polimery; 2015, 60, 7-8; 516-522
0032-2725
Pojawia się w:
Polimery
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Research on intelligent diagnosis method for large-scale ship engine fault in non-deterministic environment
Autorzy:
Feng, D.
Li, Y.
Powiązania:
https://bibliotekanauki.pl/articles/258452.pdf
Data publikacji:
2017
Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Tematy:
non-determinism
large-scale ship engine
fault intelligent diagnosis
Opis:
Aiming at the problem of inaccurate and time-consuming of the fault diagnosis method for large-scale ship engine, an intelligent diagnosis method for large-scale ship engine fault in non-deterministic environment based on neural network is proposed. First, the possible fault of the engine was analyzed, and the downtime fault of large-scale ship engine and the main fault mode were identified. On this basis, the fault diagnosis model for large-scale ship engine based on neural network is established, and the intelligent diagnosis of engine fault is completed. The experiment proved that the proposed method has high diagnostic accuracy, engine fault diagnosis takes only about 3s, with a higher use value.
Źródło:
Polish Maritime Research; 2017, S 3; 200-206
1233-2585
Pojawia się w:
Polish Maritime Research
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Flotation separation of scheelite from calcite using sodium polyacrylate as depressant
Autorzy:
Zhang, Y.
Chen, R.
Li, Y.
Wang, Y.
Luo, X.
Powiązania:
https://bibliotekanauki.pl/articles/110896.pdf
Data publikacji:
2018
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
scheelite
calcite
flotation
sodium polyacrylate
selective depression
Opis:
The depressing properties of sodium polyacrylate (PA-Na) for calcite from scheelite were studied by microflotation experiments, zeta potentials, X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculation. Flotation results revealed that the selective depression effect of PA-Na was better than that of sodium silicate (Na2SiO3), and PA-Na can depress calcite more effectively than scheelite. The flotation recovery of scheelite and calcite kept at about 75% and 15% respectively at the pulp pH 9.3~9.6 and PA-Na concentration from 37.5 mg/dm3 to 50 mg/dm3. The zeta potentials of the minerals were significantly altered and the zeta potential of calcite became more negative than scheelite. XPS analysis deduced the occurrence of chemisorption between PA-Na and mineral surfaces, and the chemisorption of PA-Na on calcite was stronger than on scheelite. The results from DFT calculation demonstrated that the absolute value of the adsorption energy in the presence of PA-Na on the surface of calcite {104} was larger than on the surface of scheelite {111}. With the combination of the analysis, it could be concluded that calcite was more easily depressed than scheelite, and this finding remarkably matched with the microflotation experimental results. Furthermore, by using PA-Na as depressant, the flotation separation of scheelite from calcite can be achieved by controlling the flotation pH and PA-Na dosage.
Źródło:
Physicochemical Problems of Mineral Processing; 2018, 54, 2; 505-516
1643-1049
2084-4735
Pojawia się w:
Physicochemical Problems of Mineral Processing
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Natural filling and systematic roof control technology for gob-side entry retaining in steep coal seams
Naturalne podsadzanie stropu i metoda systemowego prowadzenia stropu przy utrzymaniu chodników przewozowych od strony zrobów w nachylonych pokładach węgla
Autorzy:
Yang, H.
Cao, S.
Zhou, G.
Zhao, Y.
Li, G.
Li, Y.
Fan, Y.
Powiązania:
https://bibliotekanauki.pl/articles/220162.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
utrzymanie chodnika przewozowego
nachylone pokłady węgla
naturalne podsadzanie
projekt systemowy
gob-side entry retaining
steep coal seams
natural filling
systematic project
Opis:
The technology for gob-side entry retaining in steep coal seams is still in the development stage. The analysis results of the caving structure of main roof, low influence of gateway’s stability because of long filling distance and weak dynamic effect of the gateway, and the low stress redistribution environment indicate that using this technology in steep coal seams has significant advantages. Moreover, to reinforce the waste rock and the soft floor and to better guard against the impact of the waste rock during natural filling, a rock blocking device and grouting reinforcement method were invented, and theoretical calculations result show that the blocking device has high safety factor. In addition, we also developed a set of hydraulic support devices for use in the strengthening support zone. Furthermore, because the retaining gateway was a systematic project, the selection of the size and shape of the gateway cross section and its support method during the initial driving stage is a key step. Thus, first, a section the size of bottom width and roof height of a new gateway was determined to meet any related requirements. Then, according to the cross sections of 75 statistical gateways and the support technique, it chosen a trapezoidal cross section when the dip of the coal seam is […], a special and an inclined arch cross section when […]. Eventually, a support system of bolts and cables combined with steel mesh and steel belts was provided. The support system used optimized material and improved parameters, can enhanced the self-bearing ability of the surrounding coal and rock masses.
Technologia utrzymywania chodników w obszarze zrobów w nachylonych pokładach węgla jest nadal rozwijana i udoskonalana. Jej zastosowanie prowadzi do zawału głównego stropu, który jednak w nieznacznym tylko stopniu wpływa na stabilność chodników z uwagi na odległość obszaru podsadzania, podczas gdy oddziaływania dynamiczne na chodniki przewozowe będą niewielkie. Powstały rozkład naprężeń wskazuje, że zastosowanie tej technologii w stromych pokładach przyniesie znaczne korzyści. Ponadto, w celu wzmocnienia warstw skał płonnych i miękkich warstw spągowych, a także dla lepszego zabezpieczenia przed skutkami ruchów skał płonnych w trakcie podsadzania, opracowano urządzenia blokujące ruch skał wraz ze wzmocnieniem cementowym. Obliczenia teoretyczne wskazują że zastosowana blokada ruchów skał charakteryzuje się wysokim wskaźnikiem bezpieczeństwa. Ponadto, opracowano także zestaw wsporników hydraulicznych dla dodatkowego wzmocnienia strefy podsadzania. Z uwagi na to, że zachowanie chodnika przewozowego jest działaniem stałym i systematycznym, dobór wymiarów i kształtu przekroju chodnika oraz metody jego stabilizacji jest sprawą kluczową już na etapie drążenia chodnika. W kroku pierwszym określono więc szerokość chodnika w jego dolnej części oraz wysokość stropu zgodnie z odpowiednimi wymogami. Następnie w oparciu o wymiary przekrojów 75 statystycznych chodników oraz uwzględniając dostępne techniki stabilizacji stropu wybrano przekrój trapezoidalny gdy nachylenie pokładu węgla mieści się w przedziale […], zaś dla kątów nachylenia w przedziale […] wybrano nachylony profil łukowy. W etapie końcowym zastosowano układ stabilizujący oparty na kotwach i kablach połączonych siatka stalową i stalowymi taśmami. W systemie stabilizującym wykorzystano zoptymalizowane materiały zapewniając lepsze parametry pracy, co korzystanie wpłynie na nośność warstw górotworu w otoczeniu pokładu węgla.
Źródło:
Archives of Mining Sciences; 2018, 63, 3; 599-616
0860-7001
Pojawia się w:
Archives of Mining Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Distribution and sources of n-alkanes in surface sediments of Taihu Lake, China
Autorzy:
Yu, Y.
Li, Y.
Guo, Z.
Zou, H.
Powiązania:
https://bibliotekanauki.pl/articles/205298.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
n-alkanes
surface sediments
Taihu Lake
Opis:
The last study on n-alkanes in surface sediments of Taihu Lake was in 2000, only 13 surface sediment samples were analysed, in order to have a comprehensive and up-to-date understanding of n-alkanes in the surface sediments of Taihu Lake, 41 surface sediment samples were analyzed by GC-MS. C10 to C37 were detected, the total concentrations of n-alkanes ranged from 2109 ng g−1 to 9096 ng gg−1 (dry weight). There was strong odd carbon predominance in long chain n-alkanes and even carbon predominance in short chain n-alkanes. When this finding was combined with the analysis results of wax n-alkanes (WaxCn), carbon preference index (CPI), unresolved complex mixture (UCM), hopanes and steranes, it was considered that the long chain n-alkanes were mainly from terrigenous higher plants, and that the short chain n-alkanes mainly originated from bacteria and algae in the lake, compared with previous studies, there were no obvious anthropogenic petrogenic inputs. Terrestrial and aquatic hydrocarbons ratio (TAR) and C21−/C25+ indicated that terrigenous input was higher than aquatic sources and the nearshore n-alkanes were mainly from land-derived sources. Moreover, the distribution of short chain n-alkanes presented a relatively uniform pattern, while the long chain n-alkanes presented a trend that concentrations dropped from nearshore places to the middle of lake.
Źródło:
Archives of Environmental Protection; 2016, 42, 1; 49-55
2083-4772
2083-4810
Pojawia się w:
Archives of Environmental Protection
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Specific emitter identification using geometric features of frequency drift curve
Autorzy:
Zhao, Y.
Wui, L.
Zhang, J.
Li, Y.
Powiązania:
https://bibliotekanauki.pl/articles/200575.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
specific emitter identification
geometric features
frequency drift
adaptive fractional spectrogram
support vector machine
emiter
cechy geometryczne
dryf częstotliwości
spektrogram
Opis:
Specific emitter identification (SEI) is a technique for recognizing different emitters of the same type which have the same modulation parameters. Using only the classic modulation parameters for recognition, one cannot distinguish different emitters of a same type. To solve the problem, new features urgently need to be developed for recognition. This paper focuses on the common phenomenon of frequency drift, defines geometric features of frequency drift curve and, finally, proposes a practical algorithm of specific emitter identification using the geometric features. The proposed algorithm consists of three processes: instantaneous frequency estimation based on the adaptive fractional spectrogram, feature extraction of frequency drift curve based on geometric methods for describing a curve and recognition process based on support vector machine. Simulation results show that the identification rate is generally more than 98% above –5 dB of signal to noise ratio (SNR), and real data experiment verifies the practical performance of the proposed algorithm.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2018, 66, 1; 99-108
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spatiotemporal analysis of air quality and its relationship with meteorological factors in the Yangtze River Delta
Autorzy:
Li, Y.
Chen, Y.
Karimian, H.
Tao, T.
Powiązania:
https://bibliotekanauki.pl/articles/1192096.pdf
Data publikacji:
2020
Wydawca:
Uniwersytet Warmińsko-Mazurski w Olsztynie / Polskie Towarzystwo Magnezologiczne im. Prof. Juliana Aleksandrowicza
Tematy:
YRD
air quality index
meteorological elements
correlation analysis
air pollution
spatial analysis
Opis:
Air quality is closely related to people’s health and life. In addition to being directly affected by social activities and atmospheric emissions, the impacts of meteorological factors are also significant. Based on daily Air Quality Index (AQI) data and various meteorological parameters in the Yangtze River Delta (YRD), this paper summarized the spatiotemporal evolution characteristics of AQI over YRD, and quantitatively analyzed the contribution of different meteorological elements to air quality. We also evaluated different spatial interpolation methods to produce surface distribution of AQI, and noted that the Ordinary Kriging outperformed other methods. The spatial distribution of AQI in YRD showed seasonal and annual variations. However, the days with AQI over 100 (level ii) were mostly observed in winter. Generally, more severe air pollution was observed in the northern part of YRD than in the southern ones, for example the air quality of the Ningbo metropolitan area was the best, while in Hefei it was the worst. It was found that meteorological parameters have spatially varying effects on AQI. For instance, pressure has a significant positive effect on AQI, and others showed negative correlations. We also predicted AQI by exploiting different machine learning-based models. Through model comparison, it was found that the Autoregressive Integrated Moving Average Model – ARIMA (0,1,2) has higher prediction accuracy for AQI than Multiple Linear Regression (MLR). The findings of this research can be used in future forecasting of air pollution, and also in air pollution controlling programs.
Źródło:
Journal of Elementology; 2020, 25, 3; 1059-1075
1644-2296
Pojawia się w:
Journal of Elementology
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 88

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