Wyniki wyszukiwania - Biblioteka Nauki

1

Raman Spectroscopy Studies of Carbon-Based Cathode Materials during Aluminum Electrolysis

100%

Wang W. , Chen W.

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tom Vol. 64, iss. 4

1257--1261

EN

The sodium expansion and creep strain of semi-graphitic cathodes are investigated using a modified Rapoport apparatus. To further understanding of the sodium and bath penetration damage processes, the impact of external stress fluence on the carbon cathode microstructure has been defined with XRD analysis, Raman spectroscopy and scanning electron microscope (SEM). Graphite atoms fracture into smaller fragments that are less directional than the pristine platelets, which allows for a possible filling of the cracks that thus develop by the sodium and bath during aluminum electrolysis. The average microcrystalline size (calculated by Raman spectroscopy) is reduced by the deformation. The decreased intensity and widened 'G' and 'D' peaks in the analysis indicate the poor order of the sheets along the stacking direction while the consistent layered graphite structure is sustained.

2

Fault Diagnosis of Sensors for T-type Three-Level Inverter-fed Dual Three-Phase Permanent Magnet Synchronous Motor Drives

80%

Wang X. , Wang Z. , Wang W. , Cheng M.

Power Electronics and Drives

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2019

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tom Vol. 4 (39)

165--176

EN

To improve the reliability of motor system, this paper investigates the sensor fault diagnosis methods for T-type inverter-fed dual three-phase permanent magnet synchronous motor (PMSM) drives. Generally, a T-type three-level inverter-fed dual three-phase motor drive utilizes four phase-current sensors, two direct current (DC)-link voltage sensors and one speed sensor. A series of diagnostic methods have been comprehensively proposed for the three types of sensor faults. Both the sudden error change and gradual error change of sensor faults are considered. Firstly, the diagnosis of speed sensor fault was achieved by monitoring the error between the rotating speed of stator flux and the value from speed sensor. Secondly, the large high-frequency voltage ripple of voltage difference between the estimated voltage and the reference voltage was used to identify the voltage sensor faults, and the faulty voltage sensor was determined according to the deviation of voltage difference. Thirdly, the abnormal current amplitude on harmonic subspace was adopted to identify the current sensor faults, and the faulty current sensor was located by distinguishing the current trajectory on harmonic subspace. The experiments have been taken on a laboratory prototype to verify the effectiveness of the proposed fault diagnosis schemes.

3

A moment-matching based method for the analysis of manipulator’s repeatability of positioning with arbitrarily distributed joint clearances

80%

Wang W. , Wang J. , Fu J.-H. , Lu G.-D.

Eksploatacja i Niezawodność

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2019

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tom Vol. 21, no. 1

10--20

EN

The joint clearance can be the mainly concern factor in the analysis of repeatability of positioning for a manipulator. Traditionally, the joint clearance is empirically assumed to be uniform or normal variables. This hasty treatment may be not accurate enough when the precise statistic information of variables cannot be obtained. To handle the reliability evaluation problem with arbitrarily distributed joint clearances, a moment-matching based method is proposed. The highly nonlinear performance function is firstly established by the forward kinematics and then a second order Taylor expansion is performed on this function for the order reduction. Based on the maximum entropy principle, the Lagrange multipliers method is employed to derive a best-fit probability density function (PDF) with consideration of the first four moments-matching restrictions. This study shows that the prosed method can acquire a better accuracy and efficiency compared with the first order second moment method (FOSM), first order reliability method (FORM) and Monte Carlo simulation (MCS). A serial manipulator is applied as an example to demonstrate the new method.

PL

Luzy na przegubie manipulatora mogą stanowić główny czynnik wpływający na analizę powtarzalności pozycjonowania manipulatora. Tradycyjnie przyjmuje się empirycznie podbudowane założenie, że luz na przegubie jest zmienną jednorodną lub normalną. Takie ujęcie może jednak nie być wystarczająco dokładne w przypadku, gdy nie można uzyskać precyzyjnych informacji statystycznych na temat zmiennych. Aby rozwiązać problem oceny niezawodności przy dowolnie rozłożonych luzach na przegubie, zaproponowano metodę opartą na dopasowywaniu momentów. W pierwszej kolejności, obliczono za pomocą kinematyki prostej, wysoce nieliniową funkcję stanu granicznego, a następnie wyznaczono szereg Taylora drugiego rzędu dla tej funkcji w celu obniżenia rzędu. Opierając się na zasadzie maksymalnej entropii, zastosowano metodę mnożników Lagrange'a w celu wyprowadzenia najlepiej dopasowanej funkcji gęstości prawdopodobieństwa (PDF) z uwzględnieniem pierwszych czterech ograniczeń dopasowania momentów. Badanie to pokazuje, że przedstawiona metoda pozwala uzyskać wyższą trafność i skuteczność niż metoda pierwszego rzędu drugiego momentu (FOSM), metoda analizy niezawodności pierwszego rzędu (FORM) czy symulacja Monte Carlo (MCS). Zastosowanie nowej metody zilustrowano na przykładzie manipulatora szeregowego.

4

A calibration-based method for interval reliability analysis of the multi-manipulator system

80%

Wang W. , Liu S. , Wang J. , Lu G.

Eksploatacja i Niezawodność

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2022

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tom Vol. 24, no. 1

42--52

EN

The multiple manipulators can construct a special multi-agent system with the distinction that the type can be serial or parallel according to their cooperative way. We proposed a comprehensive method to handle the problem of reliability estimation. The wide and narrow bound method are applied to calculate the interval reliability respectively when multiple manipulators work as the series system. Aims to decrease the system complexity and enhance the dynamic adjustment capability, the base frame calibration technique is presented to convert the series system to a parallel one, naturally the reliability can be improved significantly. A system composed by three manipulators is utilized as an example to illustrate the feasibility of the proposed method.

5

A novel temperature calculation method of canned permanent magnet synchronous motor for vacuum pump

80%

Li M. , Lun S. , Mu H. , Wang W.

Archives of Electrical Engineering

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2024

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tom Vol. 73, nr 1

87--104

EN

Accurate temperature prediction is vital for the canned permanent magnet synchronous motor (CPMSM) used in the vacuum pump, as it experiences severe heating. In this paper, a novel motor temperature calculation method is proposed, which takes into account the temperature impact on the heat transfer capacity. In contrast to existing electromagnetic-thermal coupled calculation methods, which solely address the temperature effect on the motor electromagnetic field, the proposed method comprehensively considers its impact on motor losses, permanent magnet magnetic properties, thermal conductivity, and heat dissipation ability of motor components, resulting in a motor temperature simulation that closely resembles the actual physical process. To verify the reliability of the proposed temperature calculation method, a 1.5 kW CPMSM was chosen as the research subject. The method was used to analyze the temperature distribution characteristics of the motor and assess the impact of ambient temperature on motor temperature rise. Furthermore, a prototype was fabricated, and an experimental platform was established to test the motor temperature. The results demonstrate good agreement between the calculated results obtained using the proposed method and the experimental data. This research not only provides a theoretical foundation for optimizing the design of the CPMSM but also provides valuable insights into its operational safety and reliability.

6

Age Structures and Air Pollution: What Role Does Gender Play?

80%

Liu J. , Wang W. , Chen Y. E. , Chang C.-P.

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tom Vol. 14, nr 1

43--52

EN

We investigate the influence of age structure and gender on air pollution, dividing the age structure into four groups and use CO2 emissions as a measure of air pollution, which can be separated into four categories to ob-tain more complete findings, then employing panel cointegration techniques and panel-based error correction models. The data are collected from 29 OECD and 40 non-OECD countries in the period 1990-2014. For case of total CO2 emissions, younger (people under 30) and older people (people 65 and above) emit less than people in the intermediate age group, but the impact of age group on CO2 emissions is different when looking at CO2 emissions from coal, gas, and oil. While we take gender into account, the causality between age structure and CO2 emissions becomes significant, especially for the relationship between population and total CO2 emissions in OECD and non-OECD countries. We also note that more people who are aged 15-29 increase total CO2 emis-sions in OECD countries and more people who are aged 30-44 decrease CO2 emissions from coal in non-OECD countries. Our findings suggest that an energy and environmental policy should consider both age structure and gender effects on environmental issues.

PL

Artykuł przedstawia wyniki badań odnoszących się do wpływu zmiennych struktury wiekowej i płci na zanie-czyszczenia powietrza, wyróżniając cztery grupy wiekowe i wykorzystując poziom emisji CO2 jako wskaźnik zanieczyszczeń powietrza, który można podzielić na 4 kategorie, a następnie wykorzystaliśmy techniki kointe-gracji paneli i oparte na panelach modele korekcji błędów. Dane zebrano z 29 krajów należących do OECD i 40 spoza tej organizacji, obejmują one lata 1990-2014. W przypadku całkowitej emisji CO2 okazało się, że osoby młodsze (poniżej 30 roku życia) oraz starsze (powyżej 65 roku życia) odpowiedzialne są za mniejszą emisję niż osoby w wieku średnim, przy czym występują różnice odnoszące się do poszczególnych grup wiekowych w odniesieniu do emisji CO2 z różnych źródeł: węgla, gazu i ropy. Biorąc pod uwagę płeć, zależność pomiędzy strukturą wiekową a emisjami CO2 okazuje się być znaczącą, szczególnie w aspekcie relacji pomiędzy populacją a całkowitą emisją CO2. Zauważyliśmy ponadto, że osoby w wieku 15-29 z krajów OECD bardziej przyczyniają się do wzrostu całkowitej emisji CO2, a w przypadku krajów nie należących do OECD osoby w wieku 30-44 bardziej odpowiedzialne są za obniżenie emisji CO2 z węgla. Przeprowadzone badania umożliwiają postawienie hipotezy, według której polityka energetyczna i środowiskowa w kontekście zagadnień odnoszących się do środowiska powinna uwzględniać zarówno strukturę wieku jak i płci.

7

Study of the hydrodynamic characteristics of anti-heave devices of wind turbine platforms at different water depths

80%

Xu H. , Wang W. , Xie Y.

Polish Maritime Research

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2024

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tom nr 1

35--42

EN

This paper focuses on the effect of water depth on the hydrodynamics of floating offshore wind turbines with open-hole anti-heave devices. The three-floating-body wind turbine platform is used as the primary research object in this paper. The effect of water depth on the reduction of the heave motion of a floating platform with anti-heave devices is systematically investigated through a series of experiments and numerical simulations. The results show high agreement between the test results and simulations, with larger values of heave motion in deep water. A wind turbine platform with anti-heave devices can effectively reduce the lifting and sinking motions when the wave period is arge.

8

A Novel Chaotic System and its Modified Compound Synchronization

80%

Sun J. , Li N. , Wang Y. , Wang W.

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2019

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tom Vol. 164, nr 2-3

259--275

EN

In this paper, a new chaotic system is proposed, whose dynamical behaviors are discussed with the change of the parameters in detail. The specific effects of different parameters on the system are also discussed. By adjusting these parameters of the proposed circuit, this nonlinear circuit can produce the different dynamical behaviors, such as, hyper chaotic behavior, periodic behavior, transient behavior, etc. Furthermore, a novel kind of modified compound synchronization has been investigated, where the multiple chaotic systems have been considered for different combination modes: the compound system of four scaling drive systems and one response system. The corresponding controllers are designed to realize the modified compound synchronization. The theoretical proofs and numerical simulations are given to demonstrate the validity and applicability of the proposed chaotic system and the modified compound synchronization.

9

Effect of Sodium Penetration on Microscopic Deformation of Carbon-Based Cathode Materials During Aluminum Electrolysis

71%

Liu H. , Huang Y. , Wang W. , Zhang Z. , Dang H.

Archives of Metallurgy and Materials

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2022

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tom Vol. 67, iss. 2

779--785

EN

In this paper, the macroscopic and microscopic deformation caused by sodium penetration in the carbon cathode has been studied during aluminum electrolysis. The distributions of sodium concentration in the carbon cathode has been measured by SEM-EDS. The microstructure change caused by the gradient of the sodium concentration in the carbon cathode has been studied using transmission electron microscopy (TEM). The results indicate that sodium penetration decreases with the increase of the penetration depth. The stresses caused by the gradient of the sodium concentration result in a remarkable change for the microstructure of the carbon cathode. The formation of dislocations resulting in dislocation arrays and the development of kink band networks bring about material damage growth and possibly subsequent weakening of the cathode. These results can provide useful information that is helpful in developing an improved comprehending of the microscopic deformation mechanism of the carbon cathode during aluminum electrolysis.

10

Cyclic performance and shear resistance design of asymmetric diagonal stiffened beam-only-connected corrugated steel plate shear walls

71%

Zheng H. , Zhang Z. , Jiang L. , Hu Y. , Wang W.

Archives of Civil and Mechanical Engineering

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2022

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tom Vol. 22, no. 4

art. no. e183, 2022

EN

The corrugated plate steel shear walls (CSPWs) are widely used as lateral force resistant members in high-rise buildings. However, buckling failure still easily occurred on corrugated steel plates subjected to earthquake loads, which is not good for the energy dissipation of structures. In this paper, the asymmetric diagonal stiffened beam-only-connected corrugated steel plate shear wall (ASW) is proposed. A test-validated FE modeling method is used to investigate the seismic performance of ASW, and the results are compared with the results of unstiffened corrugated steel plate shear wall (USW). Then parametric studies on the height-to-thickness ratio, wavelength, wave height of the corrugated plate and width-to-thickness ratio of the stiffeners are performed to investigate their effects on the seismic performance of ASW. Finally, a simplified theoretical model is developed to calculate the shear resistance of ASW, and the results are validated by tests and FE results. The results show that: (1) compared to the USW, the yield load and ultimate load of ASW increase 11.7% and 13.2%, respectively; (2) the theoretical calculation results are basically consistent with the FE and test results, and the errors between them are within ± 15%. These results can be used for seismic enhancement of CSPWs and seismic design of ASW.

11

Shrink-Proof Treatment Parameter Optimisation of Cashmere Yarn

71%

Li L. , Wang W. , Zhang X. , Wu L. , Yang D.

Fibres & Textiles in Eastern Europe

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2022

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tom Vol. 30, no. 3

57--60

EN

Cashmere fiber has soft hand and good elasticity. However, it exhibits shrink because of its scale. In this work, cashmere yarn (38.26 tex) was treated using NaCl-KMnO4 to reduce the shrink of cashmere yarn. Orthogonal design and fuzzy comprehensive evaluation were used for optimizing treating parameters. Experimental results showed that the yarn shrink percentage of treated yarn was 0.56% which was less than that untreated yarn, and the treated yarn strength had a little drop compared with untreated yarn. The fiber scale outline of treated yarn could be observed by SEM, but the scale edge is blunt and irregular.

12

The influence of pollution accumulation on coating aging of UHV line insulators with different suspension height in coal-ash polluted area

61%

Lan L. , Mu L. , Wang Y. , Yuan X. , Wang W. , Li Z.

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tom Vol. 69, nr 1

39--56

EN

Room temperature vulcanized (RTV) silicone rubber is widely used to prevent pollution flashover with its excellent hydrophobicity and hydrophobicity transfer. However, RTV coatings are at the risk of deterioration and failure in heavily polluted operating environment. In this paper, RTV coated insulators with different suspension heights operating in coal ash polluted areas were sampled. Pollution degree, pollution composition and aging degree of coatings were tested. The result shows that the insoluble pollution contains Al(OH)3 filler precipitated from RTV coating, which indicates the aging of the RTV coating. The top surface coating is more affected by ultraviolet and rainwater than the bottom surface resulting in more serious degradation. As the pollution degree of the lower phase insulator is heavier than that of the upper phase insulator, the erosion effect of pollution on the RTV coating is more intense. The fillers and rubber molecules of RTV continuously precipitate into the pollution layer, leading to further aging. Therefore, the overall aging degree of the lower insulator coating is more serious than that of the upper insulator coating.

13

A film stress measurement system applicable for hyperbaric environment and its application in coal and gas outburst simulation test

61%

Liu Z.-Z. , Wang H.-P. , Yuan L. , Wang W. , Zhang C. , Xue Y.

Metrology and Measurement Systems

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2021

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tom Vol. 28, nr 1

73--88

EN

A film stress measurement system applicable for hyperbaric environment was developed to characterize stress evolution in a physical simulation test of a gas-solid coupling geological disaster. It consists of flexible film pressure sensors, a signal conversion module, and a highly-integrated acquisition box which can perform synchronous and rapid acquisition of 1 kHz test data. Meanwhile, we adopted a feasible sealing technology and protection method to improve the survival rate of the sensors and the success rate of the test, which can ensure the accuracy of the test results. The stress measurement system performed well in a large-scale simulation test of coal and gas outburst that reproduced the outburst in the laboratory. The stress evolution of surrounding rock in front of the heading is completely recorded in a successful simulation of the outburst which is consistent with the previous empirical and theoretical analysis. The experiment verifies the feasibility of the stress measurement system as well as the sealing technology, laying a foundation for the physical simulation test of gas-solid coupled geological disasters.

14

Rheological Properties of DNAN/HMX Melt-cast Explosives : Maximum Packing Density Calculation and Modified Viscosity Model

61%

Meng J.-j. , Luo Y.-m. , Wang W. , Jiang Q.-l. , Wang H.-x. , Miao F.-c.

Central European Journal of Energetic Materials

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2022

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tom Vol. 19, no. 3

326--359

EN

The study of suspensions with high solid content and low viscosity has become a very active topic for melt-cast explosives, for both research and industry. Previous studies have described how the viscosity of high-solid-content suspensions can be decreased by optimizing the grade ratio, that is, increasing the particle packing density. This paper numerically simulates the maximum packing density (Φm) for different grade ratios at which the suspension viscosity approaches infinity, using the overlapping discrete element cluster method. According to this method, the shape of 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) particles was modeled as a group of overlapping, rigidly connected hard spheres. The results showed that the numerical simulation value can be used as the real value of Φm for any grade ratio in engineering applications. The rheological properties of 2,4-dinitroanisole (DNAN)/HMX suspensions with various grade ratios of three HMX samples with different d50 values were investigated using a rotational viscometer over a range of mass solids content (ϕ = 20-75 wt.%) in the shear rate range of 0.1-100 s⁻¹. An empirical model incorporating the reduced solid content (Φ, equal to ϕ divided by Φm) and shear rate (γ) was modified to predict the relative viscosity of DNAN/HMX suspensions. This modified model has a strong correlation with the experimental data and can be used to accurately predict the viscosity of DNAN/HMX suspensions. In addition, the applicability of different classical models to DNAN/HMX suspensions is discussed.

15

Study on the influence of chamfer perforation on heave and pitch of a single floating platform

61%

Wang W. , Fan S. , You Y. , Zhao C. , Xu L. , Wang G. , Lu Z.

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2023

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tom nr 1

43--53

EN

The aim of this work is to study the influence of chamfered perforation and chamfering on the heave and pitch motion of a single floating wind power platform with an anti-heave device. Firstly, the hydrodynamic performance of a single floating body with different chamfers, or without perforation, is calculated and analysed. Secondly, the motion of a model without perforation and with 35° chamfered perforation is captured and studied in a towing tank. The results show that when the wave height is large and the period is small, the perforated device has a certain effect. When the wave height and period are small, the pitch suppression effect of chamfered perforation is more obvious than that of non-chamfered perforation. When the period and wave height are large, the heave suppression effect of non-chamfered perforation is better than that of chamfered perforation. In experimental research, the perforated floating body has a certain effect on restraining the heave and pitch of a floating body under most working conditions, and the effect of restraining the pitch is obviously better than that of restraining the heave.

16

Comparative evaluation of wear behavior of tribo-pairs in reciprocating pumps with multiple materials under different conditions

51%

Li R. , Wei W. , Liu H. , Wang D. , Ye J. , Li S. , Wang W. , Wu H.

Journal of Theoretical and Applied Mechanics

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2023

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tom Vol. 61 nr 1

77--87

EN

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.