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Wyświetlanie 1-9 z 9
Tytuł:
Flow field characteristic analysis of cushion system of partial air cushion support catamaran in regular waves
Autorzy:
Yang, Jinglei
Sun, Han-bing
Li, Xiao-wen
Liu, Xin
Powiązania:
https://bibliotekanauki.pl/articles/32910719.pdf
Data publikacji:
2022
Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Tematy:
regular waves
partial air cushion support catamaran (PACSCAT)
cushion system
fluid structure interaction (FSI)
flow field characteristics
Opis:
In order to study the flow field characteristics of cushion system of partial air cushion support catamaran (PACSCAT) in waves, an analysis was carried out involving flexible treatment on the bow and stern air seals to simulate air seal shape under test conditions by means of computational fluid dynamics method and fluid structure interaction (FSI) method. On this basis, the pressure conditions of the air cushion chamber and the pressurized chamber at different wavelengths and different speeds are studied and compared with experimental results. The experimental results show that: for the air cushion pressure, the nonlinear characteristics of the numerical calculation results are more subtle than the experimental values, after linear transformation, the amplitudes of the experimental values are obviously greater than the calculated values after linear transformation, but the average values are not much different; At low speed of 2.0m/s, the spatial pressure distribution of the pressurized chamber and the air cushion chamber are uniformly distributed, at high speed of 3.6m/s, except for a certain pressure jump occurred in the air cushion chamber near the stern air seal, the pressure in other spaces is also evenly distributed, it proves that the pressurized chamber type of air intake can effectively meet the air cushion pressure balance.
Źródło:
Polish Maritime Research; 2022, 3; 21-32
1233-2585
Pojawia się w:
Polish Maritime Research
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Osteology of the Late Cretaceous alvarezsauroid Linhenykus monodactylus from China and comments on alvarezsauroid biogeography
Autorzy:
Xu, X.
Upchurch, P.
Ma, Q.
Pittman, M.
Choiniere, J.
Sullivan, C.
Hone, D.W.E.
Tan, Q.
Tan, L.
Xiao, D.
Han, F.
Powiązania:
https://bibliotekanauki.pl/articles/20629.pdf
Data publikacji:
2013
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
osteology
Cretaceous
Late Cretaceous
alvarezsauroid
Linhenykus monodactylus
China
biogeography
Dinosauria
Theropoda
Parvicursorinae
Treefitte
dispersal
vicariance
sympatry
Wulansuhai Formation
Inner Mongolia
Opis:
The alvarezsauroid theropod Linhenykus monodactylus from the Upper Cretaceous of Inner Mongolia, China is the first knownmonodactyl non−avian dinosaur, providing important information on the complex patterns of manual evolution seen in alvarezsauroids. Herewe provide a detailed description of the osteology of this taxon. Linhenykus shows a number of fea− tures that are transitional between parvicursorine and non−parvicursorine alvarezsauroids, but detailed comparisons also re− veal that some characters had a more complex distribution. We also use event−based tree−fitting to perform a quantitative analysis of alvarezsauroid biogeography incorporating several recently discovered taxa. The results suggest that there is no statistical support for previous biogeographic hypotheses that favour pure vicariance or pure dispersal scenarios as explana− tions for the distributions of alvarezsauroids across SouthAmerica, NorthAmerica andAsia. Instead, statistically significant biogeographic reconstructions suggest a dominant role for sympatric (or “within area”) events, combined with a mix of vicariance, dispersal and regional extinction. At present the alvarezsauroid data set is too small to completely resolve the biogeographic history of this group: future studies will need to create larger data sets that encompass additional clades.
Źródło:
Acta Palaeontologica Polonica; 2013, 58, 1
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A spatial study on Keshan disease prevalence and selenoprotein P in the Heilongjiang Province, China
Autorzy:
Wang, Yanan
Zhang, Xiao
Wang, Tong
Hou, Jie
Guo, Zhongying
Han, Xiaomin
Zhou, Huihui
Liang, Hong
Xing, Zhifeng
Powiązania:
https://bibliotekanauki.pl/articles/2095499.pdf
Data publikacji:
2021-09-03
Wydawca:
Instytut Medycyny Pracy im. prof. dra Jerzego Nofera w Łodzi
Tematy:
prevalence
biomarker
prevention and control
endemic cardiomyopathy
selenoprotein P
spatial regression analysis
Opis:
ObjectivesFew spatial studies on Keshan disease (KD) prevalence and serum selenoprotein P (SELENOP) levels have been reported in the Heilongjiang Province, China. This study aimed to investigate the spatial relationships between KD prevalence, SELENOP levels, and the socio-economic status for the precise prevention and control of KD.Material and MethodsThe study was carried out in all the 66 KD endemic counties in the Heilongjiang Province using a non-probability sampling method of a key village survey based on county-wide case-searching. The participants completed a questionnaire and had their serum SELENOP levels measured using enzyme-linked immunosorbent assay. Thematic maps were created, and spatial regression analysis was performed by ordinary least squares using ArcGIS 9.0.ResultsOverall, 53 676 residents were surveyed based on case-searching, and blood samples were collected from 409 residents. In total, 50 chronic KD cases were identified with a total prevalence of 9.3/10 000 population. The prevalence in the Tangyuan County was the highest (250/10 000 population). The mean serum SELENOP level was 13.96 mg/l. The spatial regression analysis showed that KD prevalence positively correlated with SELENOP levels and negatively with per capita disposable income among rural residents.ConclusionsThe Tangyuan County should be considered for the precise prevention and control of KD. Further research is necessary to verify the reliability of SELENOP for estimating body selenium levels, and to better understand the relationship between selenium intake and KD in the investigated area.
Źródło:
International Journal of Occupational Medicine and Environmental Health; 2021, 34, 5; 659-666
1232-1087
1896-494X
Pojawia się w:
International Journal of Occupational Medicine and Environmental Health
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Model predictive control of NPC three-level grid-tied converter based on reconstructed current
Autorzy:
Li, Yanyan
Xiao, Han
Jin, Nan
Yan, Guanglu
Powiązania:
https://bibliotekanauki.pl/articles/2086686.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
current reconstruction
current sensor fault
fault-tolerant
model predictive control
neutral point clamped three-level converter
Opis:
The neutral point clamped (NPC) three-level grid-tied converter is the key equipment connecting renewable energy and power grids. The current sensor fault caused by harsh environment may lead to the split of renewable energy. The existing sensor fault-tolerant methods will reduce the modulation ratio index of the converter system. To ensure continuous operation of the converter system and improve the modulation index, a model predictive control method based on reconstructed current is proposed in this paper. According to the relationship between fault phase current and a voltage vector, the original voltage vector is combined and classified. To maintain the stable operation of the converter and improve the utilization rate of DC voltage, two kinds of fault phase current are reconstructed with DC current, normal phase current and predicted current, respectively. Based on reconstructed three-phase current, a current predictive control model is designed, and a model predictive control method is proposed. The proposed method selects the optimal voltage vector with the cost function and reduces time delay with the current reconstruction sector. The simulation and experimental results show that the proposed strategy can keep the NPC converter running stably with one AC sensor, and the modulation index is increased from 57.7% to 100%.
Źródło:
Archives of Electrical Engineering; 2022, 71, 2; 363--377
1427-4221
2300-2506
Pojawia się w:
Archives of Electrical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of fluidized magnetizing roasting on iron recovery and transformation of weakly magnetic iron mineral phasein iron tailings
Autorzy:
Li, Wenbo
Han, Yuexin
Liu, Xiao
Shan, Yan
Li, Yanjun
Powiązania:
https://bibliotekanauki.pl/articles/110633.pdf
Data publikacji:
2019
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
iron tailings
fluidized magnetizing roasting
hematite
limonite
iron phase transformation
low intensity magnetic separation
Opis:
The eastern tailings of the Anshan mining area are generally categorized as high silicon-bearing iron tailings, and the iron mainly exists in the form of hematite–limonite with an iron grade of 10.60%. In order to recover iron minerals and reduce the influence of the tailings on the environment, a method for pre-enrichment through the combination of low intensity magnetic separation and high intensity magnetic separation with fluidized magnetizing roasting and subsequent low intensity magnetic separation was developed to treat the eastern tailings of the Anshan mining area. The effects of gas-flow rate, H2 concentration, roasting temperature, and roasting time on the quality of the final iron concentrate were discussed. Moreover, the iron phase transformation and change in magnetism of the sample were studied. The results indicated that an iron concentrate with an iron grade of 65.30% and a recovery of 85.85% could be obtained under the conditions of gas-flow rate of 8 m3/h, H2 concentration of 50%, and fluidized magnetizing roasting at 600 ℃ for 20 s. X-ray diffraction analysis, phase analysis, and magnetism analysis on the roasted materials indicated that the hematite–limonite could be transformed into magnetite during the fluidized magnetizing roasting process, and effective separation of iron and gangues could be easily achieved by the weak magnetic separation.
Źródło:
Physicochemical Problems of Mineral Processing; 2019, 55, 4; 906-916
1643-1049
2084-4735
Pojawia się w:
Physicochemical Problems of Mineral Processing
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A novel combinational evaluation method of voltage and reactive power in regional power grid containing renewable energy
Autorzy:
Ji, Yuqi
Chen, Xuehan
Xiao, Han
Shi, Shaoyu
Kang, Jing
Wang, Jialin
Zhang, Shaofeng
Powiązania:
https://bibliotekanauki.pl/articles/1955201.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
adaptive weighting coefficient
combinational evaluation
renewable energy
typical scenarios
adaptacyjny współczynnik wagowy
ocena kombinacyjna
energia odnawialna
typowy scenariusz
Opis:
The output of renewable energy is strongly uncertain and random, and the distribution of voltage and reactive power in regional power grids is changed with the access to large-scale renewable energy. In order to quantitatively evaluate the influence of renewable energy access on voltage and reactive power operation, a novel combinational evaluation method of voltage and reactive power in regional power grids containing renewable energy is proposed. Firstly, the actual operation data of renewable energy and load demand are clustered based on the K-means algorithm, and several typical scenarios are divided. Then, the entropy weight method (EWM) and the analytic hierarchy process (AHP) are combined to evaluate the voltage qualified rate, voltage fluctuation, power factor qualified rate and reactive power reserve in typical scenarios. Besides, the evaluation results are used as the training samples for back-propagation (BP) neural networks. The proposed combinational evaluation method can calculate the weight coefficient of the indexes adaptively with the change of samples, which simplifies the calculation process of the indexes’ weight. At last, the case simulation of an actual regional power grid is provided, and the historical data of one year is taken as the sample for training, evaluating and analyzing. And finally, the effectiveness of the proposed method is verified based on the comparison with the existing method. The evaluated results could provide reference and guidance to the operation analysis and planning of renewable energy.
Źródło:
Archives of Electrical Engineering; 2021, 70, 4; 925-942
1427-4221
2300-2506
Pojawia się w:
Archives of Electrical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Conflict-free trajectory planning based on the model predictive control theory
Autorzy:
Han, Yun-xiang
Huang, Xiao-qoing
Powiązania:
https://bibliotekanauki.pl/articles/223811.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
civil aviation
air transportation
aircraft
air traffic control
separation
trajectories
optimization
model predictive control
lotnictwo cywilne
transport powietrzny
samolot
kontrola ruchu lotniczego
separacja
trajektorie
optymalizacja
sterowanie predykcyjne
Opis:
Model Predictive Control (MPC) is a model-based control method based on a receding horizon approach and online optimization. A key advantage of MPC is that it can accommodate constraints on the inputs and outputs. This paper proposes a max-plus general modeling framework adapted to the robust optimal control of air traffic flow in the airspace. It is shown that the problem can be posed as the control of queues with safety separation-dependent service rate. We extend MPC to a class of discrete-event system that can be described by models that are linear in the max-plus algebra with noise or modeling errors. Regarding the single aircraft as a batch, the relationships between input variables, state variables and output variable are established. We discuss some key properties of the system model and indicate how these properties can be used to analyze the behavior of air traffic flow. The model predictive control design problems are defined for this type of discrete event system to help prepare the airspace for various robust regulation needs and we give some extensions of the air traffic max-plus linear systems.
Źródło:
Archives of Transport; 2016, 37, 1; 77-85
0866-9546
2300-8830
Pojawia się w:
Archives of Transport
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optimization of heavy haul railway tunnel lining based on ultimate bearing capacity
Autorzy:
Han, Wei
Xiao, Taoli
Shi, Duanwen
Wang, Yupeng
Powiązania:
https://bibliotekanauki.pl/articles/2174091.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Opis:
The optimization process of design parameters for composite lining of heavy haul railway tunnel is a key problem to be solved in tunnel engineering design. In order to put forward a better design scheme of composite lining for heavy haul railway tunnel, combined with field measurement and numerical simulation, the optimal working condition design is carried out by changing the thickness of shotcrete layer, the type of grid steel frame and the thickness of secondary lining. The influence of the above design parameters on the stress state of the composite lining is analyzed to obtain the optimal design parameters. Finally, the safety performance of the optimized lining is evaluated by the ultimate bearing capacity curve of the secondary lining section. The research shows that: 1) The optimal design parameters of the composite lining of the tunnel are the thickness of the shotcrete layer of 25 cm, the type of the grid steel frame of H180, the thickness of the secondary lining arch waist and the side wall of 40 cm and 35 cm respectively; 2) Different from the single-track heavy haul railway tunnel, the displacement value of the vault settlement of the double-track heavy haul railway tunnel is significantly greater than that of the inner convergence. Increasing the thickness of the shotcrete layer and changing the type of the grid steel frame have better effects on reducing the vault settlement, and have little effect on the inner convergence.
Źródło:
Archives of Civil Engineering; 2022, 68, 4; 493--511
1230-2945
Pojawia się w:
Archives of Civil Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Error analysis of the three-phase electrical energy calculation method in the case of voltage-loss failure
Autorzy:
Cheng, Han-miao
Wang, Zhong-dong
Cai, Qi-xin
Lu, Xiao-quan
Gao, Yu-xiang
Song, Rui-peng
Tian, Zheng-qi
Mu, Xiao-xing
Powiązania:
https://bibliotekanauki.pl/articles/221096.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
three-phase electrical energy meter
voltage-loss failure
voltage substitution
three-phase voltage unbalance
calculation error
Opis:
The single-phase voltage loss is a common fault. Once the voltage-loss failure occurs, the amount of electrical energy will not be measured, but it is to be calculated so as to protect the interest of the power supplier. Two automatic calculation methods, the power substitution and the voltage substitution, are introduced in this paper. Considering the lack of quantitative analysis of the calculation error of the voltage substitution method, the grid traversal method and MATLAB tool are applied to solve the problem. The theoretical analysis indicates that the calculation error is closely related to the voltage unbalance factor and the power factor, and the maximum calculation error is about 6% when the power system operates normally. To verify the theoretical analysis, two three-phase electrical energy metering devices have been developed, and verification tests have been carried out in both the lab and field conditions. The lab testing results are consistent with the theoretical ones, and the field testing results show that the calculation errors are generally below 0.2%, that is correct in most cases.
Źródło:
Metrology and Measurement Systems; 2019, 26, 3; 505-516
0860-8229
Pojawia się w:
Metrology and Measurement Systems
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-9 z 9

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