Wyniki wyszukiwania - BazTech

1

Active fault tolerance control of a wind turbine system using an unknown input observer with an actuator fault

Li S., Wang H., Aitouche A., Tian Y., Christov N.

International Journal of Applied Mathematics and Computer Science

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2018

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Vol. 28, no. 1

69--81

EN

This paper proposes a fault tolerant control scheme based on an unknown input observer for a wind turbine system subject to an actuator fault and disturbance. Firstly, an unknown input observer for state estimation and fault detection using a linear parameter varying model is developed. By solving linear matrix inequalities (LMIs) and linear matrix equalities (LMEs), the gains of the unknown input observer are obtained. The convergence of the unknown input observer is also analysed with Lyapunov theory. Secondly, using fault estimation, an active fault tolerant controller is applied to a wind turbine system. Finally, a simulation of a wind turbine benchmark with an actuator fault is tested for the proposed method. The simulation results indicate that the proposed FTC scheme is efficient.

2

Improvement of accuracy of simple methods for design and analysis of a blazed phase grating microstructure

Wang W., Jing X., Zhao J., Li Y., Tian Y.

Optica Applicata

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2017

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Vol. 47, nr 2

183--198

EN

In order to precisely analyze and design the transmittance characteristics of a blazed grating, the validity of both the scalar diffraction theory and the effective medium theory is quantitatively demonstrated. By making a comparison of diffraction efficiencies calculated by the two simplified methods and Fourier modal method, the accuracy can be obtained. It is found that when the normalized period is more than three wavelengths of the incident light, the scalar diffraction theory is useful to calculate the transmittance of the blazed grating within the error of less than 3%. The validity of the scalar diffraction theory increases when the normalized period increases. Importantly, by considering the Fresnel reflection effect, the validity of scalar diffraction theory can be significantly enhanced. Furthermore, when no higher-order diffraction waves appear and only zeroth order diffraction wave propagates, the effective medium theory is accurate to compute the diffraction efficiency within the difference of less than 1% between the zeroth order effective medium theory and Fourier modal method. The polarization characteristics of the validity of effective medium theory are also quantitatively demonstrated. The validity of the two simplified theories is dependent on not only the normalized period of surface microstructure but also the normalized groove depth.

3

Study on the State of Internal Stress and Strain of TATB-based Polymer Bonded Explosive Using Strain Markers and Cone-Beam Computed Tomography

Dai B., Lan L.-G., Zhang W.-B., Tian Y.

Central European Journal of Energetic Materials

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2017

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Vol. 14, no. 3

688--707

EN

Precise measurement of the inner structural strain of polymer bonded explosive (PBXs) granules during compression molding is highly desirable in order to investigate the inner stress distribution field and its underlying generation mechanism, with the aim of improving the stress distribution uniformity. In this contribution, TATB-based (1,3,5-triamino-2,4,6-trinitrobenzene) PBX granules were formulated and the stress-strain state of the PBX granules during the warm molding process was analyzed. Strain markers were implanted at different locations and the deformation characteristics and regularity of the embedded spherical strain markers were obtained by X-ray micro-tomography. Thus the local strain states at different locations could be obtained, and the local stress state could be deduced. The results showed that axisymmetric deformation occurred in all of the strain markers, where the flat strain ellipsoids were mainly compressed uni-axially. In the central region, the stress was mainly in an axial direction, and the shear force was small. Not only axial stresses, but also large shear stresses in the surrounding region of the cylindrical grains were present. The stress gradient in the central region was greater than that in the surrounding region. The stress was greater in the surrounding region because this region was squeezed by the mold. The maximum strain degree was 44.8% larger than the minimum strain degree. The local stress increment in each region was quantified. The stress increments of the three axes were in the range 14.2-19.5 MPa. This study examined the feasibility of evaluating the inner stress–strain state of PBX granules in a quantitative manner, which is significant in determining the inner strain and stress distribution in PBX granules during the molding process.

4

Dynamic response of rectangular prestressed membrane subjected to uniform impact load

Li D., Zheng Z. L., Liu C. Y., Zhang G. X., Lian Y. S., Tian Y., Xiao Y., Xie X. M.

Archives of Civil and Mechanical Engineering

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2017

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Vol. 17, no. 3

586--598

EN

This paper investigated the dynamic response of rectangular prestressed membrane subjected to uniform impact load theoretically and experimentally. The dynamic response proceeds in two stages, namely, forced vibration and free vibration. Firstly, the maximal displacement for forced vibration is obtained by means of the principle of minimum potential energy based on the theoretical model proposed. Then, equations of motion for the transverse free vibration are derived based on thin-plate theory, and simplified by using Galerkin method. Consequently, the analytic solutions of dynamic parameters, such as frequency, displacement, amplitude, velocity, and acceleration, for free vibration are obtained by means of the multiple-scale perturbation method. In order to identify the reliability of theoretical model, the corresponding experimental study is carried out based on the developed experimental system. Furthermore, the effects of pretension force and load on the dynamic response of membrane are discussed, respectively. The present work provides a theoretical model to calculate the dynamic response of prestressed membrane subjected to uniform impact load, and a set of experimental system to study this problem.

5

Antimicrobial properties of flax fibers in the enzyme retting process

Tian Y., Liu X., Zheng X., Wang L.

Fibres & Textiles in Eastern Europe

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2016

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Vol. 24, no. 1 (115)

15--17

EN

“GB/T 20944.3-2008--Part 3: Shake flask method” was applied to assess the antimicrobial property of flax fibres. The antimicrobial efficiency of flax fibre was represented as the absolute antimicrobial rate and relative antimicrobial rate. Cotton fibre served as a contrast in relation to the antimicrobial rate. The retted flax fibre showed an absolute antimicrobial rate against E.coli and S. aureus, but only presented a relative antimicrobial rate against S. cerevisiae. The contents of pectic substances of flax straw such as cerolipoid, hydrotrope, pectin, hemicellulose and lignin declined during flax retting, especially lignin, whose content declined from 24% to 7.13%, and gaps appeared between the fibre bundles. Consequently the antimicrobial efficiency of flax fibre decreased gradually. This experiment confirmed the existence of antibacterial substances, but exactly what compounds associated with flax exhibiting antimicrobial properties is not discussed.

PL

Właściwości antybakteryjne włókien lnianych badano zgodnie z normą GB/T20944.32008: Właściwości oceniano poprzez bezwzględną i względną antybakteryjną intensywność. Włókna bawełniane służyły jako materiał porównawczy przy ocenianiu antybakteryjnej intensywności względnej. Roszone włókna lnu wykazywały bezwzględną intensywność antybakteryjną przeciwko E. coli i S. aureus, ale tylko względną intensywność antybakteryjną przeciwko S. cerevisiae. Zawartość substancji pektynowych w słomie lnianej, takich jak cerolipoidy, hydrotopy, pektyny, chemiceluloza, i ligniny zmniejszała się podczas roszenia. Szczególnie zmniejszyła się zawartość lignin spadając z 24% do 7,13%. W czasie roszenia pojawiały się szczeliny pomiędzy wiązkami włókien. W konsekwencji zdolności antybakteryjne włókien lnianych ulegały systematycznej degradacji. Przeprowadzony eksperyment potwierdził istnienie antybakteryjnych substancji ale nie stwierdzono, które składniki były najbardziej aktywne antybakteryjnie.

6

Spare parts allocation optimization in a multi-echelon support system based on multi-objective particle swarm optimization metod

Wang Y., Zhao J., Jia X., Tian Y.

Eksploatacja i Niezawodność

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2014

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Vol. 16, no. 1

29--36

PL

Optymalizacja alokacji części zamiennych w wieloszczeblowym systemie wspomagania stanowi trudne zagadnienie, które wymaga optymalizacji nieliniowej funkcji celu oraz zmiennych całkowitych. W niniejszej pracy, opracowano wielokryterialny model optymalizacyjny, który maksymalizuje prawdopodobieństwo wsparcia i minimalizuje jego koszty. W celu rozwiązania problemu optymalizacyjnego, wykorzystano ulepszoną metodę wielokryterialnej optymalizacji rojem cząstek (MOPSO). W metodzie tej wykorzystano techniki redukcji wymiarów oraz wielokryterialnej optymalizacji algorytmowej, które mogą poprawić efektywność metody MOPSO. Zasady proponowanej metody zilustrowano przykładem numerycznym.

EN

Spare parts allocation optimization in a multi-echelon support system presents a difficult problem which involves non-linear objective function and integer variables to be optimized. In this paper, a multi-objective optimization model was developed, which maximizes support probability and minimizes support costs. In order to solve the optimization problem, an improved multi-objective particle swarm optimization (MOPSO) method was utilized. In this method, techniques of dimensions reduction and rules-based multi-objective optimization were employed, which can improve the efficiency of MOPSO method. A numerical example was given to show the performance of proposed method.

7

An incremental approach for storage and delivery planning problems

Sakakibara K., Tian Y., Nishikawa I.

Decision Making in Manufacturing and Services

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2012

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Vol. 6, no. 1-2

5-23

EN

We consider a logistic planning problem for simultaneous optimization of the storage and the delivery. This problem arises in the consolidate shipment using an intermediate storage in a supply chain, which is typically found in the automobile industry. The vehicles deliver the items from the origin to the destination, while the items can be stored at some warehousing facilities as the intermediate storage during the delivery. The delivery plan is made for each day separately, but the storage at a warehouse may last for more than one day. Therefore, the entire logistic plan should be considered over a certain period for the total optimization. We formulate the storage and delivery problem as a mixed integer programming. Then, we propose a relax-and-fix type heuristic method, which incrementally fixes decision variables until all the variables are fixed to obtain a complete solution. Moreover, a semiapproximate model is introduced to effectively fix the variables. Based on the formulation, the delivery plan can be solved for each day separately. This has the advantage especially in the dynamic situation, where the delivery request is modified from the original request before the actual delivery day. Numerical experiments show that the simultaneous optimization gives the effective storage plan to reduce the total logistic cost, and the proposed heuristics efficiently reduce the computational time and are robust against the dynamic situation.

8

Existence of solutions for nonlocal boundary value problem with singularity in phase variables

Tian Y., Ge W.

Journal of Applied Analysis

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2006

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Vol. 12, nr 1

93-107

EN

In this paper, we prove existence results for singular problem [wzór]. Here the positive Carathédory function ∫ may be singular at the zero value of all its phase variables. Proofs are based on the Leray-Schauder degree and Vitali's convergence theorem.