Wyniki wyszukiwania - Biblioteka Nauki

1

Decomposition of plant litter under chromium pollution and associated characteristics of chromium release

100%

Xu L. , Wu X.

Polish Journal of Environmental Studies

|

2019

|

tom 28

|

nr 4

EN

In vegetated constructed wetlands, plants used for phytoremediation may release pollutants back into the aquatic system as a result of decomposition after senescence, lessening wastewater disposal efficiency. After treatment of wastewater containing chromium with Alternanthera philoxeroides in constructed wetland, plant litter was used to study the release characteristics of chromium with the biomass decomposition under different levels of Cr pollution. Results indicate that decomposition rates of plant litter under zero and low-level Cr pollution were larger than those under high pollution concentration. Under low Cr intensity, the total Cr concentration in the residual increased in the first 40 days, and then decreased to 67.72% of the initial concentration. In the end, the residual ratios of plant litter in different pollution intensities were 57.91%, 48.16% and 71.79% of the initial mass on average separately, and about 57.45%, 67.14% and 38.32% of Cr had been released into the aquatic environment. The changes in percentages of chemical forms in residual should be correlated with the decomposition process reflected by the interactive effects. The release of Cr could be divided into two stages, i.e. immobilization and discharge. These results were possible coming from the moderating effect of different Cr intensities on microbial decomposers.

2

Two stage based shadow removal from a single image

100%

Xu L. , Qi F.

Image Processing & Communications

|

2006

|

tom Vol. 11, no 2

37-49

EN

Shadow detection and removal in real scene images is always a challenging but yet intriguing problem. In contrast with the rapidly expanding and continuous interests on this area, it is always hard to provide a robust system to eliminate shadows in static images. This paper aimed to give a comprehensive method to remove shadows based on a two stage approach: vague shadow estimation and hard shadow estimation. First, classification is applied to the derivatives of the input image to separate the vague shadows. Then, color invariant is exploited to distinguish the hard shadow edges from the material edges. Next, a robust shadow edge mask was obtained based on the combination of the vague and hard shadow mask. By using image reintegrating approaches, we derived the shadow estimation form the mask and obtained the shadow-free reflectance image by subtracting shadows from the original image. Experimental results showed that our method can robustly remove both vague and hard shadows appearing in the real scene images.

3

Effects of physiological integration and phosphorus on spread of Alternanthera philoxeroides from soil to chromium-contaminated aquatic habitats

100%

Xu L. , Wu X.

Polish Journal of Ecology

|

2018

|

tom 66

|

nr 4

EN

Aquatic ecosystems are receivers for various pollutants, for instance, Chromium (Cr, one of the toxic heavy metals) and phosphorus (one of the biggest causes of water eutrophication). Such contaminants have brought serious impact on health and security of aquatic ecosystems. Physiological integration between the integrated ramets of clonal plants can increase their tolerance to environmental stress. It is hypothesized that physiological integration and phosphorus could facilitate the expansion of amphibious clonal plants from soil to Cr-polluted aquatic habitats. This study was conducted to primarily examine how physiological integration and phosphorus affected the effects of Cr on plant growth and population expansion. An amphibious clonal herbaceous plant Alternanthera philoxeroides was used to simulate the spread process by induced stolon connection or disconnection, Cr pollution and different levels of phosphorus in aquatic habitats. We found that Cr pollution deployed to apical ramets directly decreased the growth and photosynthetic parameters of the apical ramets that lacked connections to the basal ramets, but these effects could be mitigated by stolon connections. Cr pollution had no effects on these disconnected basal ramets, but the transmission of Cr from the apical parts via connected stolons negatively affected the growth of the basal ramets. Increasing the phosphorus not only increased the growth but also decreased the levels of Cr that accumulated in the plant tissues and the bioactivity of Cr. These results indicated that increasing the phosphorus could benefit the population expansion and establishment of A. philoxeroides through physiological integration from terrestrial to Cr-polluted aquatic habitats.

4

Resonant Responses for an Electromechanical Integrated Harmonic Piezodrive System

100%

Xu L. , Li H.

Przegląd Elektrotechniczny

|

2012

|

tom R. 88, nr 5b

79-82

EN

An electromechanical integrated harmonic piezodrive system is proposed. The principle of the drive system is introduced. A FEM analysis package, ANSYS, is used to study resonant responses of the vibrator for the drive system. The effects of the system parameters on the resonant responses are analyzed. The results show that the exciting voltage and the size parameters of the vibrator have obvious effects on the resonant responses. In order to obtain a good resonant behavior, these size parameters and the exciting voltage should be selected properly.

PL

Przedstawiono piezoelektryczny element elektromechaniczny. Analizowano wpływ napięcia pobudzającego, wymairy oraz właściwości rezonansowe.

5

Global convergence analysis of impulsive fractional order difference systems

100%

He D. , Xu L.

Bulletin of the Polish Academy of Sciences. Technical Sciences

|

2018

|

tom Vol. 66, nr 5

599--604

EN

This paper is designed to deal with the convergence and stability analysis of impulsive Caputo fractional order difference systems. Using the Lyapunov functions, the Z-transforms of Caputo difference operators, and the properties of discrete Mittag-Leffler functions, some effective criteria are derived to guarantee the global convergence and the exponential stability of the addressed systems.

6

Analytical solutions for flexure of rectangular orthotropic plates with opposite rotationally restrained and free edges

100%

Zhang S. , Xu L.

Archives of Civil and Mechanical Engineering

|

2018

|

tom Vol. 18, no. 3

965--972

EN

The problem of flexural characteristics of rectangular orthotropic thin plates with opposite rotationally restrained and free edges subjected to arbitrary transverse loads is investigated in present study. By introducing a rotational fixity factor to simulate the elastic rotation restraint at plate edges, the finite integral transform method is employed to obtain exact analytical solution of the problem. Numerical solutions for rectangular plates with various aspect ratios and edge flexibility are investigated and compared to the results reported in previous research. The accuracy and convergence of the present formulation are assessed by comparing with previously reported results. The excellent agreement on the results between the proposed method and previous studies indicates that the proposed method is accurate and effective.

7

Averaged and switching function modelling for the active power filter with LCL- type coupling impedance

100%

Han Y. , Xu L.

Przegląd Elektrotechniczny

|

2011

|

tom R. 87, nr 4

176-181

EN

This paper presents the averaged and switching function modelling for the active power filter (APF) with LCL-type coupling impedance. The mathematical model of the LCL-type APF is derived using switching function modelling technique, followed by the Fourier series analysis of the switching functions. The equivalent circuits are presented from the averaged and switching ripple model. The presented technique is also extended to the analysis of the modulation signal and inverter dc-link voltage. Finally, the experimental results are presented for verification.

PL

Artykuł prezentuje modelowanie uśredniającej i przełączającej funkcji aktywnego filtru z impedancja sprzęgającą typu LCL. Model matematyczny jest wyprowadzony przy modelowaniu funkcji przełączającej a następnie przez analizę Fouriera tej funkcji. Zaprezentowano schemat zastępczy. Przedstawiona technika może być rozszerzona do analizy sygnału modulowanego i przekształtnika. Na zakończenie przedstawiono wyniki eksperymentów.

8

A survey of the Smart Grid Technologies: background motivation and practical applications

100%

Han Y. , Xu L.

Przegląd Elektrotechniczny

|

2011

|

tom R. 87, nr 6

47-57

EN

This paper presents the survey of the smart grid technologies, including the background, motivation and practical applications. The driving forces for the smart grid technologies are presented, including the blackout, global energy crisis and environmental protection requirement. The key technology issues for building the smart grid are discussed. The crucial elements of the smart grid and their applications are introduced, including the un-interruptible power supply (UPS), adaptive var compensator (AVC), static synchronous compensator (STATCOM), active power filter (APF), unified power quality conditioner (UPQC), micro-grid, solar and wind generation, and high voltage direct current (HVDC) transmission technologies.

PL

Artykuł prezentuje przegląd technologii smart grid”. Uwzględniono takie zjawiska jak blackout, globalny kryzys energetyczny i zalecenia ochrony środowiska. Omówiono podstawowe elementy sieci „smart grid” i jej zastosowania, uwzględniając systemy UPS, AVC, STATCOM, APF, UPQC, źródła słoneczne i wiatrowe oraz technologię transmisji napięcia stałego HVDC.

9

Effects of Physiological Integration and Phosphorus on Spread of Alternanthera philoxeroides from Soil to Chromium-Contaminated Aquatic Habitats

100%

Xu L. , Wu X.

Polish Journal of Ecology

|

2018

|

tom Vol. 66, nr 4

369--381

EN

Aquatic ecosystems are receivers for various pollutants, for instance, Chromium (Cr, one of the toxic heavy metals) and phosphorus (one of the biggest causes of water eutrophication). Such contaminants have brought serious impact on health and security of aquatic ecosystems. Physiological integration between the integrated ramets of clonal plants can increase their tolerance to environmental stress. It is hypothesized that physiological integration and phosphorus could facilitate the expansion of amphibious clonal plants from soil to Cr-polluted aquatic habitats. This study was conducted to primarily examine how physiological integration and phosphorus affected the effects of Cr on plant growth and population expansion. An amphibious clonal herbaceous plant Alternanthera philoxeroides was used to simulate the spread process by induced stolon connection or disconnection, Cr pollution and different levels of phosphorus in aquatic habitats. We found that Cr pollution deployed to apical ramets directly decreased the growth and photosynthetic parameters of the apical ramets that lacked connections to the basal ramets, but these effects could be mitigated by stolon connections. Cr pollution had no effects on these disconnected basal ramets, but the transmission of Cr from the apical parts via connected stolons negatively affected the growth of the basal ramets. Increasing the phosphorus not only increased the growth but also decreased the levels of Cr that accumulated in the plant tissues and the bioactivity of Cr. These results indicated that increasing the phosphorus could benefit the population expansion and establishment of A. philoxeroides through physiological integration from terrestrial to Cr-polluted aquatic habitats.

10

Passivity-based Controller Design and Stable Control Region Analysis of the Cascaded DSTATCOM

100%

Xu L. , Han Y.

Przegląd Elektrotechniczny

|

2012

|

tom R. 88, nr 3b

140-148

EN

This paper proposes a novel passivity-based control scheme for the cascaded H-bridge (CHB) DSTATCOM. The mathematical model of the CHB-DSTATCOM is devised by partitioning the CHB-DSTATCOM into n-block subsystems, and the control algorithm is devised using the adaptive passivity controller. The power balancing mechanism and the stable control region are analyzed using the phasorial diagram representation. The Electromagnetic Transient Program (EMTP) is used for digital simulation, and the Transient Analysis of Control System (TACS) and the MODELS language of the EMTP are utilized for control algorithm implementation. The simulation results of the CHB-DSTATCOM under abrupt dclink voltage variations are provided with comparative evaluations. The devised control scheme of the CHB-DSTATCOM is validated by the simulation and experimental results from the prototype system.

PL

W artykule zaproponowano układ sterowania kaskadowo połączonych systemów DSTATCOM biorąc pod uwagę składowa bierną mocy. Mechanizm równoważenia mocy i sterowanie stabilnością są analizowane na podstawie reprezentacji fazora.

11

Modulated human globin gene expression: role for antisense expression vectors

100%

Xu L. , Pace B. S.

Cellular and Molecular Biology Letters

|

1998

|

tom 03

|

nr 4

EN

Several approaches have been explored to prevent polymerization of sickle hemoglobin in erythrocytes. We tested the ability of a mammalian expression vector carrying a β gene antisense cDNA fragment to block β gene expression. The antisense expression vector was stably transfected into HS2γβ stable mouse erythroleukemia cell lines producing human γ and β globin chains. By day 14 there was an average 24% decrease and 12% increase in β and γ globin mRNA levels respectively. We observed a loss of β gene inhibition by day 42. This study suggests that a β globin antisense cDNA expression vector may be an alternative gene therapy strategy to decrease sickle hemoglobin levels in patient with sickle cell disease.

12

Model Predictive Control of a PWM Rectifier on Unbalanced Grid Voltage Conditions

80%

Ma H. , Li Y. , Zheng Z. , Xu L.

Przegląd Elektrotechniczny

|

2013

|

tom R. 89, nr 3b

63--67

EN

In order to improve the DC-side voltage and AC-side current of the pulse width modulation (PWM) rectifier on unbalanced grid voltage conditions, the paper proposed a model predictive control (MPC) strategy of PWM rectifier. With no separation of the positive and negative sequence components of voltage and current, the proposed method can significantly reduce the effect of the negative sequence component and improve the dynamic response and robustness of a PWM rectifier. The experimental results validate the correction and effectiveness of the proposed method.

PL

W artykule przedstawiono opracowane sterowanie predykcyjne MPC dla prostownika MSI. Brak separacji między składowymi zgodną i przeciwną napięcia i prądu, pozwala na znaczną redukcję składowej przeciwnej, zwiększenie dynamiki odpowiedzi oraz elastyczności pracy algorytmu. Przedstawione wyniki eksperymentalne potwierdzają skuteczność działania rozwiązania.

13

Power balancing control strategies for the cascaded H-bridge multilevel DSTATCOM

80%

Han Y. , Xu L. , Mansoor Khan M. , Chen C.

Przegląd Elektrotechniczny

|

2011

|

tom R. 87, nr 2

212-219

EN

This paper proposes a novel power balancing control scheme for the cascaded H-bridge (CHB) DSTATCOM. The principle of the carrier phase-shifted pulse-width modulation (CPS-PWM) and the mathematical model of the CHB-DSTATCOM are presented. The power balancing mechanism and the stable control region are analyzed using the phasorial diagram representation. The current loop controller is designed by using root locus approach, and the dc-link voltage balancing controller is synthesized based on the devised power balancing mechanism. The simulation results obtained from the alternative transient program (ATP) are presented and evaluated. The validity and effectiveness of the control scheme is confirmed by the simulation and experimental results.

PL

Zapropnowano nową metodę równoważenia mocy w kaskadowym H-mostkowym SSTATCOM. Zaprezentowano zasadę modulacji przesunięcia fazowego i szerokości impulsu CPS-PWM i model matematyczny CHB-DSTATCOM. Równoważenie mocy i analiza stabilnego sterowania zostały przeprowadzone przy użyciu diagramu fazowego. Kontroler pętli prądowej został zaprojektowany przy użyciu obwiedni pierwiastkowej a kontroler napięcia dc-link jest syntetyzowany na podstawie balansu mocy. Przedstawiono symulowane rezultaty. Symulacje i eksperymenty potwierdziły skuteczność metody.

14

Length-frequency compositions and weight-length relations for big-eye tuna, yellowfin tuna, and albacore [Perciformes: Scombrinae] in the Atlantic, Indian, and eastern Pacific Oceans

80%

Zhu G. , Xu L. , Zhou Y. , Dai X.

Acta Ichthyologica et Piscatoria

|

2008

|

tom 38

|

nr 2

157-161

EN

Background. Bigeye tuna, Thunnus obesus (Lowe, 1839); yellowfin tuna, Thunnus albacares (Bonnaterre, 1788); and albacore, Thunnus alalunga (Bonnaterre, 1788), are very important species for world fisheries. It is crucial to the future existence of those economically important species that the best possible biological data on the species is provided to fisheries managers. Materials and Methods. The weight–length relations (WLRs) for bigeye tuna, yellowfin tuna, and albacore, collected in the Atlantic, Indian, and eastern Pacific oceans were studied using commonly accepted methodology. Results. Significant differences can be found from the fork length distributions and the WLRs of the above 3 tuna species and the relations of gilled-gutted and whole weight of bigeye and yellowfin tunas collected from the Atlantic, Indian, and Eastern Pacific Oceans. Significant differences of fork length distributions can be found for bigeye tuna, yellowfin tuna, and albacore from the three areas. The growth exponents (b) of bigeye tuna, yellowfin tuna, and albacore collected from the Atlantic, Indian, and eastern Pacific oceans register significant deviations from isometric value of 3. Conclusion. The date collected will be useful for the fisheries management of the three species studied.

15

Enterococcus faecalis bioflocculant enhances recovery of graphene oxide from water

80%

Xu L. , Ma R. , Sun C. , Sun D.

Polish Journal of Environmental Studies

|

2018

|

tom 27

|

nr 6

EN

Bioflocculation is a promising method of removing GO from the water as it is safe, biodegradable, and non-secondary pollution, but few studies on effective and economic bioflocculant of GO have been reported. Accordingly, this work evaluated flocculation efficiency of an extracellular bioflocculant named MBF-21 produced by Enterococcus faecalis. Optimum culture conditions for bioflocculant production were initial medium pH of 7 and incubation temperature of 40ºC. The optimum carbon and nitrogen sources for bioflocculant production were glucose and beef extract. Results of Fourier transform infrared (FTIR) indicated the presence of carboxyl, hydroxyl, and amide groups on the MBF-21. The Zeta potential of MBF-21 analysis revealed that MBF-21 was mainly negatively charged. MBF-21 showed a significant ability in flocculation of GO, and flocculation efficiency was over 90% under neutral, acidic, and alkaline conditions, indicating that flocculation of GO was ion-independent. The conditions for flocculation of GO were optimized by response surface methodology (RSM) and determined to be an 11.57 mg/L dose and flocculation time of 75 min.

16

Structure of O,O-Diethylthonophosphorylhydrazine o-Vanillin Schiff Base Copper(II) Complex : Cu{(C2H5))2PSNHNCHPh(o-O)OMe]2

80%

Xu L. , Wang Z. W. , Yang B. , Zhang S. S.

Polish Journal of Chemistry

|

2001

|

tom Vol. 75, nr 5

751-754

17

Quartz enhanced photoacoustic spectroscopy based on an external cavity quantum cascade laser

80%

Xu L. , Zhou S. , He T. , Li J.

Optica Applicata

|

2018

|

tom Vol. 48, nr 4

687--695

EN

Mid-infrared laser spectroscopy is a powerful analytical tool for trace gases detection. In this study, a spectroscopic system based on an external cavity quantum cascade laser (ECQCL) and quartz enhanced photoacoustic spectroscopy (QEPAS) was developed for volatile organic compounds (VOCs) measurements. Primary laboratory test on ethanol spectroscopy was investigated and compared with traditional direct absorption spectroscopy (DAS). Experimental results show that the proposed QEPAS is more sensitive than the conventional DAS method. In addition, the significant linear dependence of photoacoustic signal on sample pressures and laser operating parameters was observed.

18

Integrated system of health management-oriented reliability prediction for a spacecraft software system with an adaptive genetic algorithm support vector machine

80%

Xu J. , Meng Z. , Xu L.

Eksploatacja i Niezawodność

|

2014

|

tom Vol. 16, no. 4

571--578

EN

Software reliability prediction is very important to minimize cost and improve software development effectiveness, especially in a spacecraft’s software system. In this paper, a new spacecraft software system reliability definition is given and a new reliability prognostics-oriented life cycle integrated system health management for a spacecraft software system is focused on. Adaptive genetic algorithms are then combined with a support vector machine to build an adaptive genetic algorithm support vector machine reliability prediction model. This model attempts to overcome the genetic algorithm weaknesses, such as the local minima and premature convergence problems, and solves the parameter selection difficulties often encountered in a support vector machine. After construction, the proposed adaptive genetic algorithm support vector machine model is employed to predict the reliability of a spacecraft software system. Finally, a numerical example is given to show how the proposed approach has a superior prediction performance compared to a standard support vector machine and artificial neural network.

PL

Przewidywanie niezawodności oprogramowania odgrywa ważną rolę w minimalizowaniu kosztów i poprawie efektywności tworzenia oprogramowania, zwłaszcza w odniesieniu do systemów oprogramowania statków kosmicznych. W niniejszej pracy, podano nową definicję niezawodności systemu oprogramowania statku kosmicznego koncentrując uwagę na opartym na prognozowaniu niezawodności oraz cyklu życia modelu zintegrowanego zarządzania kondycją systemu opracowanego dla systemu oprogramowania statku kosmicznego. Skonstruowano następnie model przewidywania niezawodności oparty na połączeniu adaptacyjnych algorytmów genetycznych oraz maszyny wektorów nośnych. Model ten stanowi próbę przezwyciężenia słabości algorytmów genetycznych, takich jak problem minimów lokalnych czy problem przedwczesnej zbieżności, a także rozwiązania trudności związanych z doborem parametrów, jakie często występują przy zastosowaniu maszyny wektorów nośnych. Skonstruowany model opartej na adaptacyjnym algorytmie genetycznym maszyny wektorów nośnych zastosowano do przewidywania niezawodności systemu oprogramowania statku kosmicznego. Wreszcie, przedstawiono przykład liczbowy, który pokazuje że opracowany model charakteryzuje się wyższą dokładnością prognozowania w porównaniu do standardowej maszyny wektorów nośnych oraz sztucznej sieci neuronowej.

19

Research on the Direct Power Control Based Multi-objective Control for DFIG Asymmetrical LVRT

80%

Ma H. , Xu L. , Li Y.

Przegląd Elektrotechniczny

|

2013

|

tom R. 89, nr 3b

53--56

EN

This paper proposes a novel control strategy for doubly fed induction generator (DFIG) low voltage ride through (LVRT) under asymmetrical grid voltage dip. The proposed strategy, named as direct power control based multi-objective control, enables the DFIG operating under asymmetrical grid voltage dip and operating at different control objectives (the current distortion limitation mode, the power oscillation limitation mode and the torque oscillation limitation mode) by adjusting only one parameter. Furthermore, the proposed method can achieve a smooth switch between the steady state operation and the voltage dip operation with an improved dynamic performance. The simulation results verify the correction and effectiveness of the proposed method.

PL

W artykule przedstawiono nową metodę sterowania generatorem DFIG, pracującym przy przejściowo niskim napięciu. Proponowany algorytm umożliwia pracę w takich warunkach, poprzez zmianę nastawy tylko jednego parametru. Osiągnięto płynność przejścia między stanem ustalonym a stanem zapadu napięcia. Przedstawiono wyniki badań symulacyjnych, potwierdzające skuteczność rozwiązania.

20

Control Strategy for Micro-grid system in islanded mode

80%

Qiu L. , Xu L. , Zheng Z. , Li Y.

Przegląd Elektrotechniczny

|

2013

|

tom R. 89, nr 3b

57--59

EN

This paper focuses on the control strategies for islanded mode micro-grid system, which consists of wind turbines, photovoltaic panels, batteries and super-capacitors. When micro-grid is connected to the utility grid, DC-bus voltage is regulated by the inverter. And the magnitude and frequency of AC bus are the same with the grid. However when the microgrid works in island mode, DC-bus voltage must be regulated by microsouces and storages. The magnitude and frequency of AC bus are controlled by droop character of parallel inverters. Because of the fluctuation of renewable energy such as wind turbine and photovoltaic, a fast-dynamic storage system (such as super-capacity) is needed. In order to keep supplying power to the local loads in island operation, a long-term storage system (such as lead-acid battery) is needed. All of microsouces and storages are connected to DC bus by different converters. The converters must be controlled well to keep the bus voltage stable and the power flow balance.

PL

W artykule przedstawiono analizę algorytmów sterowania dla mikro-sieci odnawialnych źródeł energii (turbiny wiatrowe, panele fotowoltaiczne, superkondensatory), przy pracy wyspowej. Każdy z elementów sieci podłączony jest poprzez oddzielny przekształtnik i każdy z nich wymaga odpowiedniego sterowania w celu utrzymania stabilnego napięcia szyny DC oraz mocy.