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1
Content available remote Effects of Physiological Integration and Phosphorus on Spread of Alternanthera philoxeroides from Soil to Chromium-Contaminated Aquatic Habitats
Xu L., Wu X.
Polish Journal of Ecology
|
2018
|
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.
2
Content available Study of flotation behavior and mechanism of cervantite activation by copper ions
Wang J., Wang Y., Fu K., Xu L., Wang Z., Sun H., Xiao J.
Physicochemical Problems of Mineral Processing
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2018
|
Vol. 54, iss. 3
814--825
EN
Copper-ion activation plays a highly important role in cervantite (Sb2O4) flotation. Without metal-ion activation, cervantite cannot be floated by sodium oleate. In this study, flotation tests were conducted to study the effect of Cu2+ on the flotation behaviours of cervantite and quartz (SiO2) as the main gangue mineral. Metal-ion adsorption capacities, zeta potentials, solution chemistry and X-ray photoelectron spectra were analyzed to study the adsorption behavior and mechanism of copper ions and sodium oleate interaction with the minerals surfaces. The results demonstrate that under weakly acidic conditions, cervantite can be flotated and separated from quartz by the addition of copper ions. The reason is that copper ions can be selectively adsorbed on the cervantite surface under weakly acidic conditions, thereby promoting the adsorption of sodium oleate onto the cervantite surface by chemical adsorption. Conversely, copper ions are weakly adsorbed on quartz surfaces below pH 6.1, and sodium oleate cannot be adsorbed on quartz surfaces by chemical adsorption. The hydroxy copper species are integral to the selective activation of cervantite over quartz.
3
Content available Quartz enhanced photoacoustic spectroscopy based on an external cavity quantum cascade laser
Xu L., Zhou S., He T., Li J.
Optica Applicata
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2018
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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.
4
Content available Global convergence analysis of impulsive fractional order difference systems
He D., Xu L.
Bulletin of the Polish Academy of Sciences. Technical Sciences
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2018
|
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.
5
Content available remote Analytical solutions for flexure of rectangular orthotropic plates with opposite rotationally restrained and free edges
Zhang S., Xu L.
Archives of Civil and Mechanical Engineering
|
2018
|
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.
6
Content available Flotation separation of cervantite from quartz
Wang J., Hua Y., Yu S., Xiao J., Xu L., Wang Z.
Physicochemical Problems of Mineral Processing
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2017
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Vol. 53, iss. 2
1119--1132
EN
Flotation separation of cervantite (Sb2O4) from quartz was investigated using dodecylamine (DDA) as a collector. Experiments were conducted on single minerals and on a synthetic mixture of quartz and cervantite. Flotation separation mechanisms were investigated using the zeta potential technique, solution chemistry principles, density functional calculations and Fourier Transform Infrared (FT-IR) spectroscopy. The results indicated that DDA, primarily in the form of molecules, exhibited excellent performance in flotation of cervantite and quartz at pH 10.5. The adsorption energy of the DDA molecules on the cervantite surface was greater than the adsorption energy of water molecules, while the adsorption energy of DDA on the quartz surface was less than the adsorption energy of water molecules. DDA molecules can be adsorbed on the quartz surface to a certain extent, but it was difficult for the same molecule to be adsorbed on the cervantite surface in the pulp. This resulted in flotation of quartz. DDA molecules were adsorbed on quartz not only through physical adsorption but also by hydrogen bonding. However, cervantite could not be floated at pH 10.5 since adsorption of DDA molecules occurred through weak physical bonds on cervantite.
7
Content available remote Correlation between δ13C and δ15N in flying fish (Exocoetus volitans) muscle and scales from the South China Sea
Wu L., Xu L., Sun J., Wang X., Wei Y., Li Y., Liu X.
Oceanological and Hydrobiological Studies
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2017
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Vol. 46, No. 3
307--313
EN
We collected flying fish (Exocoetus volitans) from the South China Sea to determine whether fish scale isotope values correlate with those from muscle, and discuss relevant eco-environmental implications. A significant positive correlation was determined between fish scales and muscle δ13C and δ15N, rendering a fish scale an alternative to muscle tissue for stable isotope analysis. However, muscle and scale isotopic offsets should be fully considered when using δ13C and δ15N to analyze the actual trophic level of fish and their food source. The average offsets of δ13C and δ15N between muscles and scales are -2.1 ± 0.5‰ and 2.3 ± 0.6‰, respectively, though these values vary slightly with fish mass. Weak correlations were found between δ13C and δ15N, both in the flying fish muscle and scales, suggesting that other factors are influencing δ13C and δ15N. Fish δ15N also correlates with the size of individuals, while δ13C reflects the marine habitat. Based on our data, it appears that more eco-environmental processes can be revealed from modern or ancient flying fish scales.
8
Content available Mirror surface finishing of hardened die steel by high-Power ultrasonic elliptical vibration cutting
Jung H., Shamoto E., Ueyama T., Hamada S., Xu L.
Journal of Machine Engineering
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2016
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Vol. 16, No. 1
5--14
EN
Ultrasonic elliptical vibration cutting has recently been utilized in industry for finishing of various precision parts such as mirror surface finishing and precision micro machining of dies and molds. However, its application has been limited to high-cost ultra-precision machining, where depth of cut is typically in a range from a few micrometers to several tens of micrometers due to power limitation of the vibration device. To expand its application to low-cost mirror surface finishing with ordinary machining facilities, a high-power elliptical vibration device was developed in this research. The elliptical vibration cutting of hardened die steel was examined by applying the developed high-power elliptical vibration device with single crystalline diamond tools. Pick feed was kept to be 0.02 mm to obtain mirror quality surfaces, while depth of cut was increased up to 0.4 mm to verify performance of the high-power elliptical vibration cutting. By analyzing the experimental results, it was clarified that mirror surface finishing of the hardened die steel can be achieved at the large depth of cut with practically acceptable tool life.
9
Content available An efficient connected dominating set algorithm in WSNs based on the induced tree of the crossed cube
Zhang J., Xu L., Zhou S. M., Wu W., Ye X.
International Journal of Applied Mathematics and Computer Science
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2015
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Vol. 25, no. 2
295--309
EN
The connected dominating set (CDS) has become a well-known approach for constructing a virtual backbone in wireless sensor networks. Then traffic can forwarded by the virtual backbone and other nodes turn off their radios to save energy. Furthermore, a smaller CDS incurs fewer interference problems. However, constructing a minimum CDS is an NP-hard problem, and thus most researchers concentrate on how to derive approximate algorithms. In this paper, a novel algorithm based on the induced tree of the crossed cube (ITCC) is presented. The ITCC is to find a maximal independent set (MIS), which is based on building an induced tree of the crossed cube network, and then to connect the MIS nodes to form a CDS. The priority of an induced tree is determined according to a new parameter, the degree of the node in the square of a graph. This paper presents the proof that the ITCC generates a CDS with a lower approximation ratio. Furthermore, it is proved that the cardinality of the induced trees is a Fibonacci sequence, and an upper bound to the number of the dominating set is established. The simulations show that the algorithm provides the smallest CDS size compared with some other traditional algorithms.
10
Content available Integrated system of health management-oriented reliability prediction for a spacecraft software system with an adaptive genetic algorithm support vector machine
Xu J., Meng Z, Xu L.
Eksploatacja i Niezawodność
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2014
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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.
11
Content available remote Multiple compounds determination and fingerprint analysis of Agrimonia pilosa Ledeb by high-performance liquid chromatography
Wang Y., Yin L., Lv G., Xu Y., Xu L., Qi Y., Zheng L., Peng J.
Acta Chromatographica
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2014
|
Vol. 26, no. 1
137--156
EN
In the present paper, a simple and reliable high-performance liquid chromatography-diode array detection (HPLC-DAD) method was developed both for quantitative determination and fingerprint analysis of Agrimonia pilosa Ledeb for quality control. Under the optimized HPLC conditions, seven bioactive compounds including rutin, quercetin-3-rhamnoside, luteoloside, tiliroside, apigenin, kaempferol, and agrimonolide were determined simultaneously. For fingerprint analysis, 11 common peaks were selected as the characteristic peaks to evaluate the similarities of 16 different samples collected from different origins in China. Besides, hierarchical cluster analysis (HCA) was also performed to evaluate the variation of the raw materials. This is the first report of using a simple method for quality control of A. pilosa Ledeb through multi-component determination and chromatographic fingerprint analysis to the best of our knowledge.
12
Content available remote Research on the Direct Power Control Based Multi-objective Control for DFIG Asymmetrical LVRT
Ma H., Xu L., Li Y.
Przegląd Elektrotechniczny
|
2013
|
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.
13
Content available remote Model Predictive Control of a PWM Rectifier on Unbalanced Grid Voltage Conditions
Ma H., Li Y., Zheng Z., Xu L.
Przegląd Elektrotechniczny
|
2013
|
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.
14
Content available remote DC-Link Voltage Balancing Method with Reduced CommonMode Voltage for a Five-Level ANPC Inverter
Wang K., Li Y., Zheng Z., Xu L., Feng J.
Przegląd Elektrotechniczny
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2013
|
R. 89, nr 3b
32--34
EN
This paper presents a DC-link voltage balancing method with reduced common-mode voltage for a five-level active neutral-point clamped (ANPC) inverter. The DC-link voltage balancing method is based on zero-sequence voltage injection using carrier-based PWM. By further limiting the range of injected zero-sequence voltages, the amplitude of common-mode voltage can be reduced to 1/4 of the dc-link voltage. Experimental results are presented to verify the validity of this method.
PL
W artykule przedstawiono metodę balansowania napięciami kondensatorów obwodu pośredniczącego DC dla pięcio-poziomowego falownika Active NPC z redukcją napięcia common-mode. W metodzie wykorzystywana jest modulacja PWM z falą nośną i sygnałem kolejności zerowej, o regulowanym zakresie aplikacji. Przedstawiono wyniki eksperymentalne.
15
Content available remote Control Strategy for Micro-grid system in islanded mode
Qiu L., Xu L., Zheng Z., Li Y.
Przegląd Elektrotechniczny
|
2013
|
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.
16
Content available remote Resonant Responses for an Electromechanical Integrated Harmonic Piezodrive System
Xu L., Li H.
Przegląd Elektrotechniczny
|
2012
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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.
17
Content available remote Passivity-based Controller Design and Stable Control Region Analysis of the Cascaded DSTATCOM
Xu L., Han Y.
Przegląd Elektrotechniczny
|
2012
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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.
18
Content available remote A Multi-Level Inverter for Ultra High Speed PM Motor Control Application
Xu L., Li Y., Zheng Z., Ma H., Wang K.
Przegląd Elektrotechniczny
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2012
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R. 88, nr 5b
11-16
EN
The general concepts of multi-level technology involve utilizing a higher number of semiconductor devices to achieve higher power conversion, eliminate harmonics and reduce the switching loss. This paper is concerned with applying multi-level techniques to a PM motor to achieve ultra high speed features with better quality waveforms and less dv/dt for an aerospace application. A three-level diode clamped inverter is used to control a low inductance, ultra high speed PM motor with an integrated designed load compressor. Results from a 15kW experimental prototype are presented to validate the reliability of the inverter, the stability of the DC-link voltage balance and the practicality of vector control in this application.
PL
W artykule opisano zastosowanie wielopoziomowego przekształtnika do sterowania silnikiem z magnesami trwałymi. Osiągnięto bardzo dobra jakość kształtu sygnału napięciowego I małe dV/dt. Dzięki temu uzyskano ultra duża szybkość do zastosowań lotniczych
19
Content available remote Power balancing control strategies for the cascaded H-bridge multilevel DSTATCOM
Han Y., Xu L., Mansoor Khan M., Chen Ch.
Przegląd Elektrotechniczny
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2011
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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.
20
Content available remote Averaged and switching function modelling for the active power filter with LCL- type coupling impedance
Han Y., Xu L.
Przegląd Elektrotechniczny
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2011
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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.
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