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Wyświetlanie 1-15 z 15
Tytuł:
A multi-stage risk-adjusted control chart for monitoring and early-warningof products sold with two-dimensional warranty
Karta kontrolna do wieloetapowego monitorowania produktów sprzedawanych z gwarancją dwuwymiarową, z korektą ryzyka i wczesne ostrzeganie o wadach produkcyjnych na podstawie danych z reklamacji
Autorzy:
Dong, F.
Liu, Z.
Wu, Y.
Hao, J.
Powiązania:
https://bibliotekanauki.pl/articles/301029.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Polskie Naukowo-Techniczne Towarzystwo Eksploatacyjne PAN
Tematy:
two-dimensional product warranty
claims data
monitoring and early-warning
multi-stage control chart
accelerated failure model
risk adjustment
dwuwymiarowa gwarancja na produkt
dane o roszczeniach z tytułu gwarancji
monitorowanie i wczesne ostrzeganie
karta kontrolna procesu wieloetapowego
model przyspieszonego uszkodzenia
korekta ryzyka
Opis:
Warranty claims data contain valuable information about the quality and reliability of products. The monitoring and early-warning of warranty claims data are of great significance to the manufacturer by identifying and solving the emerging quality or reliability problem as soon as possible. However, though it has been used widely in the automobile industry, there are no studies that have been carried out on the monitoring and early-warning of claims data for products sold with two-dimensional warranty. In order to fill this gap, fitting the two-dimensional warranty claims data with accelerated failure model (AFT), a multi-stage riskadjusted control chart is proposed by this paper, for which a reasonable product sales tracking time and a monitoring time are suggested to reduce the influence of sales delay and fluctuating claim rates. Comparing with traditional Cumulative Sum Control Chart (CUSUM), the applicability and availability of the proposed model are demonstrated in the final.
Roszczenia gwarancyjne stanowią cenne źródło informacji na temat jakości i niezawodności produktów. Monitorowanie danych dotyczących roszczeń gwarancyjnych i wczesne ostrzeganie w oparciu o te dane ma wielkie znaczenie dla producenta, ponieważ pozwala rozpoznawać i rozwiązywać pojawiające się problemy związane z niezawodnością w jak najkrótszym czasie. Chociaż ten rodzaj monitorowania i wczesnego ostrzegania jest szeroko stosowany w przemyśle motoryzacyjnym, nie przeprowadzono dotąd żadnych badań na temat tych procesów w odniesieniu do produktów sprzedawanych z gwarancją dwuwymiarową. W celu wypełnienia tej luki, dane o reklamacjach składanych na podstawie gwarancji dwuwymiarowych dopasowano modelem uszkodzeń przyspieszonych (accelerated failure model, AFT), a następnie przedstawiono koncepcję karty kontrolnej monitorowania wieloetapowego z korektą ryzyka, dla której zaproponowano odpowiedni czas śledzenia sprzedaży produktu i czas monitorowania, mając na uwadze zmniejszenie wpływu opóźnień w sprzedaży i wahań liczby roszczeń zgłaszanych z tytułu gwarancji. Możliwości zastosowania i dostępność proponowanego modelu porównano z tradycyjną kartą sum skumulowanych.
Źródło:
Eksploatacja i Niezawodność; 2018, 20, 2; 300-307
1507-2711
Pojawia się w:
Eksploatacja i Niezawodność
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A new scheme of the environmental classification standards for the bronze cultural relic’s preservation in museums
Autorzy:
Li, Dandan
Zhou, Hao
Xu, Fangyuan
Yan, Ying
Wu, Laiming
Cai, Lankun
Powiązania:
https://bibliotekanauki.pl/articles/28407393.pdf
Data publikacji:
2023
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
QCM
temperature
humidity
indoor exposure
cultural relics
mikrowaga kwarcowa
temperatura
wilgotność
ekspozyja w pomieszczeniach
zabytki kultury
Opis:
The environmental risk classification of the metal relics is usually determined by the corrosion rate of the metal but it is difficult to monitor the deterioration of the metal relics directly. A strong relationship exists between indoor exposure, the air quality classification of atmospheric corrosion, and the actual deterioration of metal relics. The copper-silver hanging plate method requires a long period of environmental exposure and has certain hysteresis, thus reflecting the current environmental quality of the museum in real time poses some difficulties. However, the application of the environmental reactivity monitor (ERMs) based on the piezoelectric effect can solve the above problems. The invented quartz crystal microbalance (QCM) reactivity monitoring device is applied to study the influence of temperature and humidity on the corrosion of the bronze-simulated materials and the relationship between the corrosion depth rate of the bronze-simulated materials and the frequency change of the crystal oscillator. Then, the recommended classification range of temperature and humidity and the airquality classification standards for the preservation environment of the bronze cultural relics in museums are proposed.
Źródło:
Environment Protection Engineering; 2023, 49, 4; 45--59
0324-8828
Pojawia się w:
Environment Protection Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A novel method of health indicator construction and remaining useful life prediction based on deep learning
Autorzy:
Zhan, Xianbiao
Liu, Zixuan
Yan, Hao
Wu, Zhenghao
Guo, Chiming
Jia, Xisheng
Powiązania:
https://bibliotekanauki.pl/articles/27312791.pdf
Data publikacji:
2023
Wydawca:
Polska Akademia Nauk. Polskie Naukowo-Techniczne Towarzystwo Eksploatacyjne PAN
Tematy:
stacked sparse autoencoder
health indicator
long short-term memory network
remaining useful life prediction
Opis:
The construction of health indicators (HI) for traditional deep learning requires human training labels and poor interpretability. This paper proposes an HI construction method based on Stacked Sparse Autoencoder (SSAE) and combines SSAE with Long short-term memory (LSTM) network to predict the remaining useful life (RUL). Extracting features from a single domain may result in insufficient feature extraction and cannot comprehensively reflect the degradation status information of mechanical equipment. In order to solve the problem, this article extracts features from time domain, frequency domain, and time-frequency domain to construct a comprehensive original feature set. Based on monotonicity, trendiness, and robustness, the most sensitive features from the original feature set are selected and put into the SSAE network to construct HI for state partitioning, and then LSTM is used for RUL prediction. By comparing with the existing methods, it is proved that the prediction effect of the proposed method in this paper is satisfied.
Źródło:
Eksploatacja i Niezawodność; 2023, 25, 4; art. no. 171374
1507-2711
Pojawia się w:
Eksploatacja i Niezawodność
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Adsorption of hydrated Fe(OH)2+ on the kaolinite surface: A density functional theory study
Autorzy:
Wu, Hongqiang
Miao, Yuqi
Long, Qibang
Yan, Huashan
Li, Yong
Qiu, Sen
Wu, Hao
Zhao, Guanfei
Qiu, Tingsheng
Powiązania:
https://bibliotekanauki.pl/articles/27323639.pdf
Data publikacji:
2023
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
kaolinite
adsorption
Fe
density functional theory
Opis:
The present study employed density functional theory (DFT) to analyze the adsorption configuration and mechanism of Fe(OH)2+ on the kaolinite (001) surface. The findings demonstrated that Fe(OH)2(H2O)4+ is the main type in which hydrated Fe(OH)2+ can be found in aqueous solution. On the surface of kaolinite, Fe(OH)2(H2O)4+ will be adsorbed. There are two forms of adsorption: outer-sphere and inner-sphere coordination (monodentate/bidentate) adsorption. Fe(OH)2(H2O)4+ has a moderate propensity to adsorb on the alumina octahedral sheet of kaolinite when the outer-sphere coordination adsorption takes place. In cases of inner-sphere coordination adsorption, Fe exhibits a tendency to form monodentate adsorption compounds in conjunction with Ou atoms. Additionally, it prefers to create bidentate adsorption compounds through coordination with both Ot and Ou atoms. The adsorption mechanism analysis results show that the ionic property of Fe atom decreases after outer-sphere coordination adsorption. After inner-sphere coordination adsorption, some electrons of Fe atom are transferred to the surface O atom. The presence of electrons between the Fe and O atoms enhances the formation of bonds, hence enhancing the covalent nature of the Fe-O bond. Theoretical FT-IR (Fourier transform infrared spectroscopy) calculations show that the formation of Fe-O chemical bonds. Because of the lower adsorption energy and more chemical bonds, hydrate Fe(OH)2+ is more likely to be bidentate adsorbed on the kaolinite surface.
Źródło:
Physicochemical Problems of Mineral Processing; 2023, 59, 6; art. no. 174415
1643-1049
2084-4735
Pojawia się w:
Physicochemical Problems of Mineral Processing
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Antidiabetic cataract effects of GbE, rutin and quercetin are mediated by the inhibition of oxidative stress and polyol pathway
Autorzy:
Lu, Qian
Hao, Meng
Wu, Wenya
Zhang, Nan
Isaac, Adelusi
Yin, Jiale
Zhu, Xia
Du, Lei
Yin, Xiaoxing
Powiązania:
https://bibliotekanauki.pl/articles/1038521.pdf
Data publikacji:
2018
Wydawca:
Polskie Towarzystwo Biochemiczne
Tematy:
Ginkgo biloba extract
rutin
quercetin
diabetic cataract
Opis:
One of the earliest critical secondary complications of diabetes is the opacification of the eye lens - a condition strictly associated with diabetic cataract. The study presented here was designed to investigate the effect of Ginkgo biloba extract (GbE), rutin and quercetin on streptozotocin (STZ) induced diabetic cataract (DC) rats. Ten weeks after administration of GbE, rutin and quercetin, the opacity of diabetic rats' lenses was graded under a slit lamp. Then, the levels of malondialdehyde (MDA), reduced glutathione (GSH), advanced glycosylation end products (AGEs), and the activities of aldose reductase (AR) were estimated. The DC-induced rats produced less GSH, higher levels of MDA and AGEs as well as elevated AR activity when compared to the normal group. Administration of GbE, rutin and quercetin remarkably inhibited the AR activity, stimulated the production of glutathione, and decreased the levels of MDA and AGEs in the lenses of DC-induced rats, which eventually delayed the progression of lens opacification in diabetic rats to various degrees. Our results revealed that quercetin had the highest significant (P<0.05) potential to delay the progression of STZ-induced diabetic cataract when compared with rutin and GbE. The mechanism dictating this interesting prowess of quercetin might be attributed to its AR inhibitory strength, anti-lipid peroxidation potential and anti-AGEs activity.
Źródło:
Acta Biochimica Polonica; 2018, 65, 1; 35-41
0001-527X
Pojawia się w:
Acta Biochimica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Basic theory and optimization of gold containing antimony concentrate leaching by alkaline sulfide
Autorzy:
Wu, Hao
Feng, Yali
Li, Haoran
Liao, Shengde
Wang, Hongjun
Powiązania:
https://bibliotekanauki.pl/articles/109524.pdf
Data publikacji:
2019
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
antimony concentrate
leaching process
alkaline leaching
kinetics
Opis:
As sodium sulfide is easily oxidized to polysulfide and thiosulfate which have a gold leaching effect, gold would dissolve in leaching solution when extracting stibium from gold containing antimony concentrate by alkaline sulfide. Through leaching test and kinetics analysis, the decomposition regularity of sodium sulfide and leaching rate were studied under different leaching conditions. The results indicated that the gold content in antimony concentrate was 28.41g/Mg, and the content of antimony and sulfur was 36.01% and 14.04%, respectively. The main metallic minerals were native gold, arsenopyrite, stibnite, and the gangue minerals were mainly quartz. Anodic polarization curve shows reduced iron powder can increase the peak potential of the oxidation of the leaching solution and it can effectively prevent the decomposition of sodium sulfide and the dissolution of gold. Optimized stibium-extraction efficiency was achieved under the following conditions: a concentration of sodium sulfide and sodium hydroxide at 110g/dm³ and 20g/dm³, respectively; a ratio of iron powder to concentrate of 1:30; a ratio of liquid to solid of 5:1; agitation speed of 600rad/min; reaction temperature of 353.15K; and a reaction time of 3 h. Under the optimized conditions, high antimony recovery (97.35%) and low gold dissolution (1.32%) were achieved.
Źródło:
Physicochemical Problems of Mineral Processing; 2019, 55, 1; 248-257
1643-1049
2084-4735
Pojawia się w:
Physicochemical Problems of Mineral Processing
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Comparative evaluation of wear behavior of tribo-pairs in reciprocating pumps with multiple materials under different conditions
Autorzy:
Li, Ran
Wei, Wenshu
Liu, Hao
Wang, Dalong
Ye, Jian
Li, Shoubin
Wang, Wei
Wu, Huigang
Powiązania:
https://bibliotekanauki.pl/articles/2200870.pdf
Data publikacji:
2023
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
reciprocating pump
tribo-pair
cast iron pin
wear behavior
wear resistance
Opis:
In the study of wear behavior of tribo-pairs in reciprocating pumps, the tribo-pairs can be considered as contact pairs consisting of a disc and pin. In this paper, pin-on-disc wear tests were carried out by using two types of cast iron pin specimens with different materials. Additionally, the effects of the lubrication condition, test load, diamond-like carbon (DLC) coating and plateau honing cross-hatch pattern on wear behavior of the tribo-pairs were investigated. Experimental results based on surface topography analysis and scanning elec- tron micrograph (SEM) analysis show that the lubricant and DLC coating have a positive effect on wear resistance of test specimens. Disc specimens of three material types (i.e. ISO 185/JL/250, tin-bronze, zirconia) are able to show good anti-wear behavior. The tribo-pairs composed of spheroidal graphite cast irons as well as implementation of the plateau honing cross hatch on disc specimens have no significant effect on the wear resistance. The Archard model was used to estimate abrasive wear under dry conditions, which was over-predicted compared to the experimental results.
Źródło:
Journal of Theoretical and Applied Mechanics; 2023, 61, 1; 77--87
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effectiveness of fly ash on the stabilization/solidification of Zn-contaminated soil
Autorzy:
Chen, Yan
Zhu, Shengyuan
Fang, Wei
Huang, He
Qin, Hao
Hu, Shengtao
Wu, Yuzhao
Powiązania:
https://bibliotekanauki.pl/articles/27323977.pdf
Data publikacji:
2023
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
fly ash
soil
heavy metals
X-ray diffraction
Zn2+
popiół lotny
gleba
metale ciężkie
dyfrakcja rentgenowska
Opis:
As a solid waste, the associated disposal cost of fly ash is really high. Previous studies suggested that the utilization of fly ash to treat heavy metal-contaminated soils was a new cost-effective method of disposal of it. Therefore, the effectiveness of fly ash stabilized/solidified Zn-contaminated soils has been investigated by unconfined compressive strength (UCS) and toxicity characteristics leaching procedure (TCLP) tests. Quantitative analysis of the soil microstructure was conducted by processing the X-ray diffraction (XRD) and scanning electron microscope (SEM) images. Mercury intrusion porosimetry (MIP) was carried out to illustrate the size and proportion of pore size for specimens under different ratios. The results of the tests showed an improvement in the UCS, which further increased as the content of binders was raised. Binder content would have little influence on the development of strength if the binder content exceeds a threshold value. The leached Zn2+ concentration of stabilized specimens was significantly decreased compared to that of untreated. Quantitative analysis confirmed that the addition of the binders resulted in the amount of hydration product, reduction of porosity, and a really random pores orientation, which was responsible for the improvement of the strength and leaching properties of the Zn2+ contaminated soils.
Źródło:
Environment Protection Engineering; 2023, 49, 3; 15--29
0324-8828
Pojawia się w:
Environment Protection Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigating the selectivity of calcium hypochlorite for flotation separation of chalcopyrite and pyrite pre-adsorbed collector
Autorzy:
Yang, Wenhui
Qiu, Xianhui
Yan, Huashan
Wu, Hao
Yang, Liu
Lai, Ruisen
Qiu, Tingsheng
Powiązania:
https://bibliotekanauki.pl/articles/2146919.pdf
Data publikacji:
2022
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
pyrite
chalcopyrite
calcium hypochlorite
flotation separation
Opis:
Bulk flotation is usually used in the flotation of Cu-Fe sulfide ore, and the subsequent concentrate is difficult to be separated because the minerals have adsorbed the collector. In this paper, flotation tests showed that calcium hypochlorite (Ca(ClO)2) had a stronger depression effect on pyrite pre-adsorbed sodium butyl xanthate (SBX), while having a negligible depressive effect on chalcopyrite. A copper concentrate with Cu grade of 33.32% and Cu recovery of 94.47% could be obtained from flotation tests of mixed minerals. The depression performance and mechanism of Ca(ClO)2 were studied by contact angle measurements, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses, the results suggested that Ca(ClO)2 can decomposes SBX on the pyrite surface and oxidizes the mineral surface to form hydrophilic substances, which enhances the hydrophilicity of the pyrite surface. In contrast, Ca(ClO)2 has little effect on chalcopyrite pre-adsorbed SBX, the possible depression model is discussed.
Źródło:
Physicochemical Problems of Mineral Processing; 2022, 58, 4; art. no. 150703
1643-1049
2084-4735
Pojawia się w:
Physicochemical Problems of Mineral Processing
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Luminescence of hydrothermally fabricated PbF2:Er3+ particles and their application in bifacial silicon solar cells
Autorzy:
Yang, F
Wu, C.
Hao, X
Chen, Y.
Lu, J.
Yang, Sh.
Powiązania:
https://bibliotekanauki.pl/articles/174503.pdf
Data publikacji:
2014
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
PbF2
Er3+ particles
hydrothermal method
upconversion
Opis:
We report the synthesis of PbF2:Er3+ particles using a hydrothermal method. The structure and upconversion emission properties of the products are investigated by scanning electron microscopy, X-ray diffractometer, Raman spectrophotometer and fluorescence spectrometry. An increase in Er3+ concentration in the crystals changes the PbF2 structure from a mixed phase to a cubic phase and decreases the grain size to nanoscale levels. Enhanced upconversion efficiency is achieved after annealing resulted from the formation of the cubic phase and the increase of grain size. The optimal Er3+ concentration is found to be 4% after annealing, and applied to the back of a bifacial silicon solar cell, maximum external quantum efficiencies of 0.38% and 0.79% are respectively obtained under 0.77 W/cm2 laser excitation (1560 nm) and AM1.5 + laser co-excitation.
Źródło:
Optica Applicata; 2014, 44, 3; 463-473
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Parameter identification approach using improved teaching and learning based optimization for hub motor considering temperature rise
Autorzy:
Li, Yong
Wang, Yuan
Zhang, Taohua
Hu, Han
Wu, Hao
Powiązania:
https://bibliotekanauki.pl/articles/2203368.pdf
Data publikacji:
2023
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
parameters identification
teaching–learning-based optimization
hub motor
temperature rise
Opis:
Temperature rise of the hub motor in distributed drive electric vehicles (DDEVs) under long-time and overload operating conditions brings parameter drift and degrades the performance of the motor. A novel online parameter identification method based on improved teaching-learning-based optimization (ITLBO) is proposed to estimate the stator resistance, -axis inductance, -axis inductance, and flux linkage of the hub motor with respect to temperature rise. The effect of temperature rise on the stator resistance, -axis inductance, -axis inductance, and magnetic flux linkage is analysed. The hub motor parameters are identified offline. The proposed ITLBO algorithm is introduced to estimate the parameters online. The Gaussian perturbation function is employed to optimize the TLBO algorithm and improve the identification speed and accuracy. The mechanisms of group learning and low-ranking elimination are established. After that, the proposed ITLBO algorithm for parameter identification is employed to identify the hub motor parameters online on the test bench. Compared with other parameter identification algorithms, both simulation and experimental results show the proposed ITLBO algorithm has rapid convergence and a higher convergence precision, by which the robustness of the algorithm is effectively verified.
Źródło:
Metrology and Measurement Systems; 2023, 30, 1; 99--115
0860-8229
Pojawia się w:
Metrology and Measurement Systems
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Reinforcement layout design of three-dimensional members under a state of complex stress
Autorzy:
Cui, Hao
Xia, Junjie
Wu, Lang
Xiao, Min
Powiązania:
https://bibliotekanauki.pl/articles/2203429.pdf
Data publikacji:
2023
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Opis:
This paper proposes a method to optimize reinforcement layout of three-dimensional members under a state of complex stress and multiple load cases (MLCs). To simulate three-dimensional members, the spatial truss-like material model is adopted. Three families of truss-like members along orthotropic directions are embedded continuously in concrete. The optimal reinforcement layout design is obtained by optimizing the member densities and orientations. The optimal design of three-dimensional member is carried out by solving the problem of minimum volume of reinforcing bars with stress constraints. Firstly, the optimized reinforcement layout under each single load case (SLC) is obtained as per the fully stressed criterion. Second, on the basis of the previous results, an equivalent multi-case optimization is proposed by introducing the idea of stiffness envelope. Finally, according to the characteristics of the truss-like material, a closed and symmetrical surface is adopted to fit the maximum directional stiffness under all SLCs. It can be proved that the densities and orientations of truss-like members are the eigenvalues and eigenvectors of the surface coefficient matrix, respectively. Several three-dimensional members are used as examples to demonstrate the capability of the proposed method in finding the best reinforcement layout design of each reinforced concrete (RC) member and to verify its efficiency in application to real design problems.
Źródło:
Archives of Civil Engineering; 2023, 69, 1; 421--436
1230-2945
Pojawia się w:
Archives of Civil Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Research on beam supply control strategy based on sliding mode control
Autorzy:
Zhang, Hao
Dong, Haiying
Zhang, Baoping
Wu, Tong
Chen, Changwen
Powiązania:
https://bibliotekanauki.pl/articles/141014.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
beam supply
DC/DC converter
robustness
sliding mode control
Opis:
In the hybrid multiple H-bridge topology of beam supply, the load change of a DC/DC full-bridge converter can greatly affect the output voltage during onsite operation. An improved sliding mode control (SMC) strategy is thus proposed in this paper, where the rate of switching control is added to the law of system equivalent control to create a law that can realize a complete sliding mode control. Considering the special operating conditions of the load can have an influence on the performance of the controller, the impact of uncertainty existing in onsite conditions is suppressed with the proposed strategy utilized. The validity of the proposed strategy, finally, is verified by simulation, which proves the outperformance of the system in both robustness and dynamics.
Źródło:
Archives of Electrical Engineering; 2020, 69, 2; 349-364
1427-4221
2300-2506
Pojawia się w:
Archives of Electrical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Stochastic P-bifurcation of a 3-DOF airfoil with structural nonlinearity
Autorzy:
Hao, Ying
Du, Xuewen
Hu, Yuda
Wu, Zhiqiang
Powiązania:
https://bibliotekanauki.pl/articles/1839715.pdf
Data publikacji:
2021
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
stochastic P-bifurcation
structural nonlinearity
stochastic parametric excitation
Opis:
In this paper, the stochastic-aeroelastic nonlinear response of a three-degree-of-freedom (3-DOF) structural nonlinear airfoil with a control flap is presented. The critical parameter conditions of stochastic P-bifurcation are solved by using the improved average method, the stochastic average method combined with the singularity theory. The results show that the periodic solution produced by Hopf bifurcation has involved a second bifurcation, the nonlinear critical speed of saddle node bifurcation points is advanced, and the airfoil appears bi-stable. The stochastic singularity analysis shows that the increasing stochastic disturbance intensity will cause a greater probability for a large amplitude stochastic flutter.
Źródło:
Journal of Theoretical and Applied Mechanics; 2021, 59, 2; 307-317
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Variation of strata pressure and axial bolt load at a coal mine face under the effect of a fault
Zmienność ciśnienia górotworu i obciążenia osiowe działające na segmenty obudowy w rejonie przodka spowodowane obecnością uskoków
Autorzy:
Shi, Hao
Zhang, Houquan
Song, Lei
Wu, Yu
Powiązania:
https://bibliotekanauki.pl/articles/218749.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
symulacje numeryczne FLAC 3D
naprężenia osiowe działające na obudowę
zachowanie górotworu
górnictwo
efekt uskoku
model odprężania
FLAC3D numerical simulation
axial bolt load
strata behavior
mining and fault effect
strain-softening model
Opis:
The cohesion and internal friction angle were characterized as quadratic functions of strain and were assumed to follow the Mohr-Coulomb criterion after the yield of peak strength. These mechanical parameters and their variations in post-peak softening stage can be exactly ascertained through the si-multaneous solution based on the data points of stress-strain curves of triaxial compression tests. Taking the influence of the fault into account, the variation of strata pressure and roadway convergence with coal advancement, the temporal and spatial distribution of axial bolt load were numerically simulated by FLAC3D (Fast Lagrangian Analysis of Continua) using the ascertained post-peak mechanical parameters according to the cohesion weakening and friction strengthening model. The change mechanism of axial load of single rock bolt as abutment pressure changes was analyzed, through the comparison analysis with the results of axial bolt load by field measurements at a coal mine face. The research results show that the simulated results such as the period of main roof weighting, temporal and spatial distribution of axial bolt load are in accordance with field measurement results, so the validity of the numerical model is testified. In front of the working face, the front abutment pressure increases first and then decreases, finally tends to be stable. A corresponding correlation exists between the variation of axial bolt load and rock deformation along the bolt body. When encountered by a fault, the maximum abutment pressure, the influential range of mining disturbance and the roadway convergence between roof and floor before the working face are all increased. In the roadways along the gob, axial bolt loads on the side of the working face decrease, while the other side one increases after the collapse of the roof. As superficial surrounding rock mass is damaged, the anchoring force of rock bolts will transfer to inner rock mass for balancing the tensile load of the bolts.
Zwięzłość skał oraz kąt tarcia wewnętrznego zdefiniowano jako kwadratowe funkcje naprężenia, następnie przyjęto że ich rozkład po osiągnięciu naprężenia granicznego opisany jest wzorem Mohra-Coulomba. Wymienione parametry mechaniczne i ich zmienność po osiągnięciu naprężenia granicznego obliczyć można dokładnie poprzez jednoczesne rozwiązanie oparte o analizę punktów na krzywej wykresu rozciągania uzyskanych w testach ściskania trójosiowego. Uwzględniając wpływ obecności uskoku, zmienność ciśnienia w górotworze i konwergencji chodnika wraz z postępem przodka, rozkłady naprę-żeń i obciążeń działających na segmenty obudowy i ich zmienność w czasie i przestrzeni modelowano w oparciu o pakiet FLAC3D (Fast Lagrangian Analysis of Continua), wykorzystując uprzednio obliczone wielkości parametrów mechanicznych dla stanu po osiągnięciu naprężenia granicznego, zgodnie z mo-delem słabnącej zwięzłości i wzmocnionego tarcia. Mechanizm zmiany naprężeń osiowych działających na pojedynczy segment obudowy analizowano w odniesieniu do ciśnienia warstw sąsiadujących, poprzez analizę porównawczą wyników pomiarów obciążeń segmentów obudowy w rejonie przodka. Wykazano, że wyniki symulacji: okresy obciążenia stropu, rozkłady naprężeń i obciążeń działających na elementy obudowy i ich zmienność w czasie i przestrzeni zgodne są z wynikami pomiarów w miejscu, w ten sposób potwierdzając wiarygodność modelu numerycznego. W rejonie przodka ciśnienie warstw sąsiadujących w górotworze najpierw rośnie, następnie maleje, a w końcu stabilizuje się. Istnieje odpowiednia korelacja pomiędzy zmiennością rozkładu naprężeń i obciążeń działających na elementy obudowy a odkształceniem warstw skalnym wzdłuż konstrukcji obudowy. W przypadku wystąpienia uskoku, występuje maksymalne ciśnienie warstw otaczających- poważny czynnik powodujący wszelkiego rodzaju zaburzenia a także nasilenie konwergencji chodnika pomiędzy stropem a podłożem w rejonie przed przodkiem. W chodnikach wzdłuż zrobów, obciążenia osiowe obudowy działające z jednej strony maleją, po drugiej zaś stronie rejonu przodkowego rosną po zawale stropu. Płytka warstwa otaczającego górotworu ulega zniszczeniu, siła podtrzymująca obudowę przeniesiona zostanie wewnątrz górotworu, tak by zrównoważyć naprężenia rozciągające działające na obudowę.
Źródło:
Archives of Mining Sciences; 2019, 64, 2; 351-374
0860-7001
Pojawia się w:
Archives of Mining Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-15 z 15

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