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1
Content available remote Comparative Effects of Aquaculture and Water Level Fluctuations on Macroinvertebrate Communities in Three Gorges Reservoir, China
Chi S., Zheng Z., Zhang Z., Hu J., Zheng J., Zhao X., Hu J., Dong F., Peng J.
Polish Journal of Ecology
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2017
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Vol. 65, nr 4
390--404
EN
In this study, the comparative effects of the two disturbances (aquaculture and water level fluctuations) on macroinvertebrate communities were explored in two waterbodies connected with the reservoir system of Three Gorges Reservoir (TGR) in China. One water body called Gaoyang Bay which suffered organic pollution from intensive aquaculture. Another named Hanfeng Lake, where the effects of water-level fluctuations are obvious. The results showed that aquaculture could significantly affect the chemical forms of nutrients, decrease the α-diversity and increase the β-diversity of macroinvertebrates although the communities in the treatment area in Gaoyang Bay were not fundamentally changed comparing to the control area in the same bay. The densities of macroinvertebrates in the treatment area were significantly lower than that of the control area. The composition of functional feeding groups in the treatment area was close to that in Hanfeng Lake, but obviously different from that in the control area in Gaoyang Bay and the collectors and predators dominated the communities in this control area with the highest percentages. Although water-level fluctuations had negative effects on the communities by decreasing the α-diversity and increasing the β-diversity, which were confirmed by the values of Simpson index, Shannon-Wiener index and Harrison's index in the control area of Gaoyang bay and Hanfeng Lake, the adverse effects were relative low compared to aquaculture. In the bays of TGR, the small-scale disturbance (aquaculture activities) had more significant negative effects compared to the big-scale disturbance (water-level fluctuations related to dam operation of TGR).
2
Content available Preparation of Self-cleaning Polyester Fabrics by Chemical Vapor Deposition of Methyltrichlorosilane/Dimethyldichlorosilane
Zheng Z., Wang H., Zhang N., Zhao X.
Fibres & Textiles in Eastern Europe
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2017
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Vol. 25, no. 1 (121)
121--124
EN
Self-cleaning polyester fabrics were prepared by a simple gas phase deposition procedure in which a layer of polydimethylsiloxane nanofilaments was grown onto textile fibers. Superhydrophobic and self-cleaning properties, tensile breaking strength, mechanical stability and permeability of polyester fabrics were investigated. The results showed that the fabrics deposited had superhydrophobicity, and the contact angle and sliding angle of the fabric surface were 159° and 1.7°, respectively. The self-cleaning test showed that dust particles adhere to rolling water and shed from the surface of polyester fabric, leaving an extremely clean surface. In addition, the polyester fabric deposited still has excellent breaking strength and permeability. This approach is simple, inexpensive and has little effect on the mechanical properties of the fabric.
PL
Samooczyszczające tkaniny poliestrowe przygotowano metodą chemicznego osadzania z fazy gazowej, w którym warstwa nanofilamentów polidimetylosiloksanu narastała na włóknach tekstylnych powodując superhydrofobowość i nadając właściwości samoczyszczące. Po obróbce badano wytrzymałość na zerwanie, trwałość mechaniczną i przepuszczalność powietrza. Wyniki wykazały, że zmodyfikowane tkaniny miały właściwości superhydrofobowe, a kąty zwilżania i poślizgu po powierzchni tkaniny wynosiły odpowiednio 159° i 1,7°. Testy zdolności samooczyszczających wykazały, że cząsteczki pyłu przylegają do cząstek wody i wraz z nią spływają po powierzchni tkaniny poliestrowej. Zastosowana metoda jest prosta, niedroga i nie wpływa negatywnie na obrabianą tkaninę.
3
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
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2013
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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.
4
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
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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.
5
Content available remote Control Strategy for Micro-grid system in islanded mode
Qiu L., Xu L., Zheng Z., Li Y.
Przegląd Elektrotechniczny
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2013
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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.
6
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
7
Content available remote On the relationships between indexes of merchant vessel accidents and indexes of economy and shipping
Zheng Z., Feng H., Li G.
TransNav : International Journal on Marine Navigation and Safety of Sea Transportation
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2007
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Vol. 1, no. 4
441--444
EN
The statistics and analysis of the four accident indexes and the four marine transportation indexes have been carried out to indicate situations of marine safety and marine transportation in China. By grey correlation analysis, the main findings is that the number of marine traffic accidents is mainly determined by the number of merchant vessels; the number of foundering is mainly determined by freight amount, and the number of death and missing is mainly determined by the number of merchant vessels.
8
Content available remote Simultaneous demonstration on 10 Gb/s wavelength conversion four-wave mixing and cross-gain modulation in semiconductor optical amplifier
Li Peili, Zhang X., Zheng Z., Huang D.
Optica Applicata
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2004
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Vol. 34, nr 1
43-49
EN
A study is presented on wavelength conversion in semiconductor optical amplifier (SOA) when the power of the input pump light is as much as that of the input signal light, in which the four-wave mixing (FWM) effect and the cross-gain modulation (XGM) effect occur obviously at the same time and the modulation format of the converted signal light is inverted to that of the input signal light. Experimental results are in agreement with theoretical analysis
9
Content available remote RRIA : A Rough Set and Rule Tree Based Incremental Knowledge Acquisition Algorithm
Zheng Z., Wang G.
Fundamenta Informaticae
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2004
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Vol. 59, nr 2,3
299--313
EN
As a special way in which the human brain is learning new knowledge, incremental learning is an important topic in AI. It is an object of many AI researchers to find an algorithm that can learn new knowledge quickly, based on original knowledge learned before, and in such way that the knowledge it acquires is efficient in real use. In this paper, we develop a rough set and rule tree based incremental knowledge acquisition algorithm. It can learn from a domain data set incrementally. Our simulation results show that our algorithm can learn more quickly than classical rough set based knowledge acquisition algorithms, and the performance of knowledge learned by our algorithm can be the same as or even better than classical rough set based knowledge acquisition algorithms. Besides, the simulation results also show that our algorithm outperforms ID4 in many aspects.
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