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Wyświetlanie 1-15 z 130
Tytuł:
Wczesne wykrywanie uszkodzeń przekładni zębatej z wykorzystaniem słabych sygnałów drgań
Early fault detection of gearbox using weak vibration signals
Autorzy:
Qingjun, W.
Chen, X.
Yang, H.
Wang, G.
Powiązania:
https://bibliotekanauki.pl/articles/300940.pdf
Data publikacji:
2011
Wydawca:
Polska Akademia Nauk. Polskie Naukowo-Techniczne Towarzystwo Eksploatacyjne PAN
Tematy:
wczesne wykrywanie uszkodzeń
adaptacyjna reprezentacja czasowo-częstotliwościowa
zdemodulowany sygnał drań
early fault detection
adaptive joint time-frequency
weak demodulated vibration signal
Opis:
Zaproponowano nową metodę wczesnego wykrywania pęknięć zębów przekładni zębatej polegającą na analizie słabego sygnału drganiowego zmodulowanego niskimi częstotliwościami. Uzyskaną obwiednię zmodulowanego sygnału drgań wykorzystano do wyznaczenia częstotliwości modulujących. Zdemodulowane częstotliwości charakterystyczne otrzymano za pomocą adaptacyjnej, czasowo-częstotliwościowej reprezentacji sygnału z obwiedni sygnału drganiowego wyznaczonej z wykorzystaniem transformaty Hilberta. Spektrogram adaptacyjny odzwierciedla częstotliwość zazębienia i jej harmoniczne, częstotliwość sprzęgła, częstotliwość nośną oraz wstęgi boczne w sygnale drganiowym poddanym analizie z użyciem zoptymalizowanego przekształcenia falkowego. Proponowaną metodę weryfkowano przy użyciu sygnału symulowanego i rzeczywistego. Wyniki wskazują na możliwość efektywnego zastosowania proponowanej metody do detekcji pęknięć zębów przekładni zębatej.
A new method for the early detection of the gear crack was proposed by the analysis of the weak low-frequency modulated vibration signal. The envelope of the modulated vibration signal was extracted and used to demonstrate the modulating frequencies. The demodulated characteristic frequencies were obtained with the adaptive joint time-frequency signal representation from the Hilbert transform envelope of the vibration signal. The adaptive spectrogram matches the meshing frequency and its harmonics, the coupling frequency, the carrier frequency and the sidebands in the vibration signal by the optimized wavelet. Simulated and experimental vibration signals are used to test the proposed method. The results show the applicability and effectiveness of the proposed method for gear crack detection.
Źródło:
Eksploatacja i Niezawodność; 2011, 1; 11-15
1507-2711
Pojawia się w:
Eksploatacja i Niezawodność
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Wave propagation in piezoelectric rings with rectangular cross-sections
Autorzy:
Zhang, X.
Wang, Y.
Chen, H.
Powiązania:
https://bibliotekanauki.pl/articles/279995.pdf
Data publikacji:
2015
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
piezoelectric rings
orthogonal polynomial
guided wave
dispersion curves
Opis:
The ring ultrasonic transducers are widely used in the ocean engineering and medical fields. This paper employs an extended orthogonal polynomial approach to solve the guided wave propagation in two-dimensional structures, i.e. piezoelectric rings with rectangular cross- -sections. The extended polynomial approach can overcome the drawbacks of the conven- tional orthogonal polynomial approach which can be used to solve wave propagation in one-dimensional structures. Through numerical comparison with the available results for a rectangular aluminum bar, the validity of the present approach is illustrated. The dispersion curves and displacement and electric potential distributions of various rectangular piezo- electric rings are calculated, and the effects of different radius to thickness ratios, width to height ratios and polarizing directions on the dispersion curves are illustrated.
Źródło:
Journal of Theoretical and Applied Mechanics; 2015, 53, 3; 673-682
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Vertical distribution of nearshore flow velocity
Autorzy:
Li, Ch.
Fu, X.
Li, R.
Dai, L.
Chen, P.
Powiązania:
https://bibliotekanauki.pl/articles/259609.pdf
Data publikacji:
2016
Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Tematy:
vertical distribution of flow velocity
Jiangsu Sea
nearshore
exponential formula
Opis:
In this paper, a new exponential formed vertical distribution of nearshore flow velocity is constructed, which is simpler in form and more suitable for engineering application. The physical meaning of the new formula is more specific than that of Soulsby. Compared with those logarithmic formed ones, the new one does not need the maximum velocity and only needs the mean velocity in vertical, which gives it better engineering practicability. Apply the new formula to Jiangsu coastal area and compare the results with that of Soulsby whose results show the new formula agrees better with the measured flow velocity, which reasonably reflects the basic principles of vertical distribution of flow velocity.
Źródło:
Polish Maritime Research; 2016, S 1; 104-108
1233-2585
Pojawia się w:
Polish Maritime Research
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Urinary concentrations and determinants of pyrethroid metabolites in pregnant women from non-rural areas of Yunnan, China
Autorzy:
Xu, Q.
Song, X.
Li, Y.
Jian, X.
Chen, S.
Chen, Y.
Powiązania:
https://bibliotekanauki.pl/articles/28762713.pdf
Data publikacji:
2021
Wydawca:
Instytut Medycyny Wsi
Źródło:
Annals of Agricultural and Environmental Medicine; 2021, 28, 4; 627-632
1232-1966
Pojawia się w:
Annals of Agricultural and Environmental Medicine
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Tree domatic number in graphs
Autorzy:
Chen, X. G.
Powiązania:
https://bibliotekanauki.pl/articles/255594.pdf
Data publikacji:
2007
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
tree domatic number
regular graph
planar graph
Cartesian product
Opis:
A dominating set S in a graph G is a tree dominating set of G if the subgraph induced by S is a tree. The tree domatic number of G is the maximum number of pairwise disjoint tree dominating sets in V(G). First, some exact values of and sharp bounds for the tree domatic number are given. Then, we establish a sharp lower bound for the number of edges in a connected graph of given order and given tree domatic number, and we characterize the extremal graphs. Finally, we show that a tree domatic number of a planar graph is at most 4 and give a characterization of planar graphs with the tree domatic number 3.
Źródło:
Opuscula Mathematica; 2007, 27, 1; 5-11
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Tight focusing of radially polarized beams by a devil’s vortex lens
Autorzy:
Chen, Z.
Hu, X.
Chen, X.
Wang, X.
Pu, J.
Powiązania:
https://bibliotekanauki.pl/articles/173576.pdf
Data publikacji:
2018
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
devil’s vortex lens
radially polarized beam
tight focusing
high numerical aperture
Opis:
Tight focusing of radially polarized beams with a devil’s vortex lens is numerically investigated. Multiple focal spots can be generated in the geometric focus when a radially polarized beam is focused by a high numerical aperture objective in the presence of a devil’s vortex lens. The position of the major focal spot shifts from the geometric focus when a devil’s vortex lens with S = 1 is employed, and the position of the focal spot can be controlled by the numerical aperture of the objective. The intensity components of the major focal spot are influenced by the vortex phase of the devil’s vortex lens. A strong longitudinal component near the optical axis is produced by a devil’s vortex lens without vortex phase, and a nearly pure transversal field is produced by a devil’s vortex lens with vortex phase.
Źródło:
Optica Applicata; 2018, 48, 3; 389-398
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermodynamic and Electronic Properties of $OsB_2$ from First-Principles Calculations
Autorzy:
Cheng, Y.
Yang, J.
Wang, Y.
Ji, G.
Chen, X.
Powiązania:
https://bibliotekanauki.pl/articles/1365243.pdf
Data publikacji:
2014-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.15.Mb
61.50.Ks
67.25.de
71.20.-b
Opis:
The pressure induced phase transitions of $OsB_2$ from the orthorhombic structure (Orth) to the hexagonal structure (Hex) is investigated by using ab initio plane-wave pseudopotential density functional theory, together with quasi-harmonic Debye model. We find that the pressure-induced phase transition occurs at 2.8 GPa and 12.5 GPa by local density approximation and general gradient approximation, respectively. It is predicted that $OsB_2$ has no phase transition temperature from the Orth structure to the Hex structure. Moreover, the dependences of the relative volume V/$V_0$ on the pressure, thermal expansion coefficient α on the pressure and temperature are also successfully obtained. The electronic properties including energy band, total and partial density of states and electron density difference for two structures are also analyzed. The Mulliken charges and Bond populations for both Orth and Hex structures are also obtained.
Źródło:
Acta Physica Polonica A; 2014, 125, 5; 1186-1190
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermally induced damage in hexanitrohexaazaisowurtzitane
Autorzy:
Tian, Q.
Yan, G.
Sun, G.
Huang, C.
Xie, L.
Chen, B.
Huang, M.
Li, H.
Liu, X.
Wang, J.
Powiązania:
https://bibliotekanauki.pl/articles/358735.pdf
Data publikacji:
2013
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
CL-20
SAXS
AFM
thermal effects
voids
Opis:
The evolution of the microstructure of hexanitrohexaazaisowurtzitane (CL-20) after a thermal stimulus plays a key role in the performance of CL-20. In the current work, microstructural variations of CL-20 caused by thermal treatment were investigated by X-ray diffraction, in situ variable-temperature optical microscopy, atom force microscopy, and small-angle X-ray scattering. A wave-like process, an abrupt volume expansion, movement, and fragmentation of CL-20 particles during phase transition were observed. After the phase transition (160 °C) the CL-20 sample acquired a very rough surface with numerous dimple depressions, and during the thermal decomposition stage (200 °C) a large number of voids were produced in both the bulk and the surface of the CL-20.
Źródło:
Central European Journal of Energetic Materials; 2013, 10, 3; 359-369
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Reinforcement of the TNT System by a Newly-designed GAP-based Polyurethane-Urea: a Molecular Simulation Investigation
Autorzy:
Qian, W.
Shu, Y.
Ma, Q.
Li, H.
Wang, S.
Chen, X.
Powiązania:
https://bibliotekanauki.pl/articles/358512.pdf
Data publikacji:
2016
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
TNT
GAP
polyurethane-urea
inter-molecular interaction
mechanical properties
Opis:
A glycidyl azide (GAP)-based polyurethane-urea (PUU) modifier used in the 1,3,5-trinitrotoluene (TNT)-based composite explosive was investigated by molecular simulation. Inter-molecular interactions were investigated using quantum chemistry calculation on the dimer of TNT and GAP-PUU, and attractive forces were found between the two molecules. The cohesive energy densities and the solubility parameters were obtained through molecular dynamics simulations combined with thermodynamic calculations on the TNT and GAP-PUU amorphous cell models, and the miscibility of the modifier in molten TNT was predicted to be good. The interaction energies and the mechanical properties were then obtained by molecular simulations and mechanical calculations on the solid-phase models of the GAP-PUU with TNT along three crystalline directions, and an improvement in the mechanical properties was predicted.
Źródło:
Central European Journal of Energetic Materials; 2016, 13, 2; 411-426
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Preparation of Soluble Cellouronic Acid Sodium Salt by 4-Acetamide-TEMPO Mediated Oxidation of Ultrasound-Pretreated Parenchyma Cellulose from Bagasse Pith
Autorzy:
Gao, X.
Chen, K.
Zhang, H.
Peng, L.
Powiązania:
https://bibliotekanauki.pl/articles/177150.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
ultrasonic pretreatment
bagasse pith
parenchyma cellulose
cellouronic acid sodium salt
4-acetamide-TEMPO
Opis:
The parenchyma cellulose isolated from bagasse pith was used as an alternative resource for preparation of water-soluble cellouronic acid sodium salt (CAS). The influence of ultrasound treatment on the cellulose was investigated for obtaining CAS by regioselective oxidization using 4-acetamide-TEMPO and NaClO with NaClO2 as a primary oxidant in an aqueous buffer at pH 6.0. The yield, carboxylate content and polymerization degree (DP) of CAS were measured as a function of ultrasonic power, agitating time and cellulose consistency by an orthogonal test. The ultrasound-treated conditions were further improved by discussion of ultrasonic power, the most important factor influencing the yield and DP. An optimized CAS yield of 72.9% with DP value (DPv) of 212 was found when the ultrasonic strength is 550 W, agitating time is 3 h and cellulose consistency is 2.0%. The oxidation reactivity of cellulose was improved by ultrasonic irradiation, whereas no significant changes in crystallinity of cellulose were measured after ultrasonic treatment. Moreover, the ultrasound treatment has a greater effect on yielding CAS from parenchyma cellulose than from bagasse fibrous’ one. The CAS was further characterized by Fourier transform infrared spectroscopy (FT-IR) and Scanning electron microscopy (SEM).
Źródło:
Archives of Acoustics; 2014, 39, 2; 267-275
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Microstructural Evolution in HMX Based Plastic-bonded Explosive During Heating and Cooling Process: an in situ Small-angle Scattering Study
Autorzy:
Yan, G.
Tian, Q.
Liu, J.
Fan, Z.
Sun, G.
Zhang, C.
Wang, Y.
Chen, B.
Gong, J.
Zhou, X.
Yang, Z.
Nie, F.
Li, J.
Li, X.
Powiązania:
https://bibliotekanauki.pl/articles/358618.pdf
Data publikacji:
2016
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
SANS
SAXS
HMX-PBX
thermal damages
phase transition
Opis:
The thermal damage in octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) based plastic-bonded explosive (PBX) was investigated using in situ small-angle neutron and X-ray scattering techniques. The microstructural evolution was quantitatively characterized by the model fitting parameters of total interfacial surface area (Sv) and void volume distribution. The Sv of HMX-PBX decreased markedly above 100 °C, indicating the movement of binder into the voids. After subsequent cooling to room temperature, the scattering intensity increased significantly with increasing storage time, and a new population of voids with average diameter of 20 nm was observed, accompanied by the gradual phase transition of HMX from δ- to β-phase. The experimental results implied that serious damage within the HMX-PBX was developed during storage after heating.
Źródło:
Central European Journal of Energetic Materials; 2016, 13, 4; 916-926
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Machine Learning Method of PIDVCA
Autorzy:
Li, L.
Wang, X.
Chen, G.
Powiązania:
https://bibliotekanauki.pl/articles/1841618.pdf
Data publikacji:
2020
Wydawca:
Uniwersytet Morski w Gdyni. Wydział Nawigacyjny
Tematy:
learning methods
personified intelligence
collision avoidance
dynamic collision avoidance
static collision avoidance
Opis:
Building a dynamic collision knowledge base of self-learning is one of the core contents of implementing "personified intelligence" in Personifying Intelligent Decision-making for Vessel Collision Avoidance (short for PIDVCA). In the paper, the machine learning method of PIDVCA combined with offline artificial learning and online machine learning is proposed. The static collision avoidance knowledge is acquired through offline artificial learning, and the isomeric knowledge representation integration method with process knowledge as the carrier is established, and the Dynamic collision avoidance knowledge is acquired through online machine learning guided by inference engine. A large number of simulation results show that the dynamic collision avoidance knowledge base constructed by machine learning can achieve the effect of anthropomorphic intelligent collision avoidance. It is verified by examples that the machine learning method of PIDVCA can realize target perception, target cognition and finally obtain an effective collision avoidance decision-making.
Źródło:
TransNav : International Journal on Marine Navigation and Safety of Sea Transportation; 2020, 14, 3; 533-540
2083-6473
2083-6481
Pojawia się w:
TransNav : International Journal on Marine Navigation and Safety of Sea Transportation
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The impacts of BSMV on vegetative growth and water status in hulless barley (Hordeum vulgare var. nudum) in VIGS study
Autorzy:
Liang, J.
Chen, X.
Zhao, H.
Yu, S.
Long, H.
Deng, G.
Pan, Z.
Yu, M.
Powiązania:
https://bibliotekanauki.pl/articles/57548.pdf
Data publikacji:
2015
Wydawca:
Polskie Towarzystwo Botaniczne
Tematy:
Hordeum vulgare var.nudum
hulled barley
barley
BSMV zob.barley stripe mosaic virus
barley stripe mosaic virus
vegetative growth
water status
VIGS zob.virus induced gene silencing method
virus induced gene silencing method
Opis:
Barley stripe mosaic virus (BSMV) is an established and extensively used virus-induced gene silencing (VIGS) vector for gene function analysis in monocots. However, the phenotypes generated by targeted gene silencing may be affected or masked by symptoms of BSMV infection. To better understand the potential effects of BSMV-VIGS in hulless barley (Hordeum vulgare var. nudum), the accumulation pattern of BSMV and its impacts on vegetative growth and water status were investigated. The results indicated that the vegetative growth of infected plants was significantly and continuously impacted by BSMV from 10 to 40 days post inoculation (dpi). When the accumulation of BSMV was extremely high (7 to 11 dpi), infected plants displayed twisted leaf tips with an increased water lose rate (WLR) and decreased water content (WC). Virus accumulation declined and stabilized after 25 dpi, at this stage, the WLR and WC were unaffected in the infected plants. The efficiency of VIGS was tested by the silencing of Phytoene desaturase (PDS). RT-qPCR indicated that BSMV-VIGS can be sustained with good efficiency for up to 40 dpi under an altered condition with lower temperature (22 ±1°C) and higher relative humidity (70 ±10%). It was concluded that 25 to 40 dpi was the appropriate time zone for drought-related gene analysis by BSMV-VIGS under such condition.
Źródło:
Acta Societatis Botanicorum Poloniae; 2015, 84, 1
0001-6977
2083-9480
Pojawia się w:
Acta Societatis Botanicorum Poloniae
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The effect of surface functional groups of nanosilica on the properties of polyamide 6/SiO2 nanocomposite
Autorzy:
Xu, Q.
Chen, F.
Li, X.
Zhang, Z.
Powiązania:
https://bibliotekanauki.pl/articles/779538.pdf
Data publikacji:
2013
Wydawca:
Zachodniopomorski Uniwersytet Technologiczny w Szczecinie. Wydawnictwo Uczelniane ZUT w Szczecinie
Tematy:
nanosilica
polyamide 6
nanocomposite
in situ polymerization
Opis:
The present study investigated the effect of the surface functional groups of nanosilica on the interfacial, crystallization, and thermal stability of polyamide 6/SiO2 (PA6/SiO2) nanocomposite, in which nanosilica was modified in situ with both 3-triethoxysilylpropylamine and 3-methacryloxypropyltrimethoxy silane¬ (KH-550 and KH-570). The FTIR analysis results showed the chemical bonding action between the reacting amino groups of nanosilica and end carboxyl groups of polyamide 6 enhanced with increasing the ratio of KH-550 and KH-570. The XRD spectrum indicated that the crystal structure of PA6/SiO2 nanocomposites tended to form α crystal type that was beneficial to an improvement of mechanical properties, and which was in agreement with the results of mechanical strength measurements. It was also found that crystallization temperature and crystallization rate of PA6/SiO2 nanocomposites were lower than that of neat polyamide 6.
Źródło:
Polish Journal of Chemical Technology; 2013, 15, 3; 20-24
1509-8117
1899-4741
Pojawia się w:
Polish Journal of Chemical Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The effect of high ship speed ratio on collision avoidance behavior of COLREGS
Autorzy:
Wang, X. H.
Li, L.
Chen, G.
Powiązania:
https://bibliotekanauki.pl/articles/116490.pdf
Data publikacji:
2019
Wydawca:
Uniwersytet Morski w Gdyni. Wydział Nawigacyjny
Tematy:
colregs
Personifying Intelligent Decision-making for Vessel Collision Avoidance (PIDVCA)
Vessel Collision Avoidance
collision avoidance
decision making
relative motion
geometricdiagram of relative motion
anti-collision
Opis:
The speed ratio is an important factor that must be considered when two vessels will course change to avoid collision. In the process of the research on Personifying Intelligent Decision-making for Vessel Collision Avoidance (short for PIDVCA), it is found that the effect of collision avoidance based on the existing “International Regulations for Prevention Collision at sea” (short for COLREGS) is greatly affected by the high speed ratio (k=Vt/V0≥1.5). Through the analysis on the geometric change law of two vessels’ relative motion in Open waters, the effects of the responsibility for the ship collision avoidance under the COLREGS and special case for high-speed ratio is discussed. According to the collision avoidance measures taken for two vessels encounter situation, some reasonable suggestions are put forward and the simulation experiments that based on ship's intelligent collision avoidance simulation platform are given to support the idea.
Źródło:
TransNav : International Journal on Marine Navigation and Safety of Sea Transportation; 2019, 13, 2; 319-323
2083-6473
2083-6481
Pojawia się w:
TransNav : International Journal on Marine Navigation and Safety of Sea Transportation
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 130

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