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1

Experimental investigation and modelling of hot forming B₄C/AA6061 low volume fraction reinforcement composites

Zheng K., Lin J., Wu G., Hall R. W., Dean T. A.

Journal of Theoretical and Applied Mechanics

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2018

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Vol. 56 nr 2

457--469

EN

This paper presents an experimental investigation of the hot deformation behaviour of 15% B₄C particle reinforced AA6061 matrix composites and the establishment of a novel corresponding unified and physically-based visco-plastic material model. The feasibility of hot forming of a metal matrix composite (MMC) with a low volume fraction reinforcement has been assessed by performing hot compression tests at different temperatures and strain rates. Examination of the obtained stress-strain relationships revealed the correlation between temperature and strain hardening extent. Forming at elevated temperatures enables obvious strain rate hardening and reasonably high ductility of the MMC. The developed unified material model includes evolution of dislocations resulting from plastic deformation, recovery and punching effect due to differential thermal expansion between matrix and reinforcement particles during non-steady state heating and plastic straining. Good agreement has been obtained between experimental and computed results. The proposed material model contributes greatly to a more thorough understanding of flow stress behaviour and microstructural evolution during the hot forming of MMCs.

2

Study of aluminum phosphide levels in waste fumigants from food shipments following simple immersion treatment

Wu G., Chen T., Jia Y., Shen D., Feng H., Long Y.

Environment Protection Engineering

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2018

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Vol. 44, nr 1

19--27

EN

Increasing concentrations of aluminum phosphide (AlP) in waste fumigants and residues pose a serious threat to human health. This study focused on the effectiveness of the widely used simple immersion treatment for waste fumigants from shipments, which usually have a higher concentration of residual AlP. A field survey of an operational process was conducted followed by a quantitative analysis of the immersion treatment's hydrolytic effect on AlP. Further investigation on the safety of waste fumigants after the immersion treatment was conducted. It was found that the AlP concentration in the waste fumigant varied significantly with the sampling date, ranging from 12.93 +/- 0.67 wt. % to 29.50 +/- 1.18 wt. %. Simple immersion treatment could reduce the concentration of residual AlP in waste fumigants but the hydrolytic effect varied largely ranging from 19.5% to 31.9%. The concentration of residual AlP remained high (9.1-20.1 wt. %) after the immersion treatment. About 3.2-15.2 wt. % of AlP remained in the samples, following an additional 40 days of natural air-drying when phosphine gas release was not detected. The study indicates that conventional simple immersion treatment cannot ensure the complete hydrolysis of AlP from waste fumigants of shipments.

3

Modeling the Bending and Recovery Behaviour of Woven Fabrics

Shi F., Zhao Y., Wu G., Zheng D.

Fibres & Textiles in Eastern Europe

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2017

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Vol. 25, no. 6 (126)

41--45

EN

On the basis of viscoelastic theory of textile material, the viscoelastic solid model consisting of a spring element and viscous element either in series or parallel is one of the most useful research models to study the mechanical behaviour of fabrics. This paper presents a method to study the bending behaviour of wool/polyester fabrics using a model consisting of the three-element model in parallel with a sliding element on the assumption that the internal frictional moment is a constant during the bending processes. From the needs of practical study, a testing method has been presented to study the bending behaviour of wool/polyester fabrics using a KES-FB3 compression tester. A comparison and analysis of the experimental results and theoretical predictions indicate that the agreement between them is satisfactory.

PL

Lepkosprężysty model bryłowy składający się z elementu sprężystego i elementu lepkiego, w układzie szeregowym lub równoległym, jest jednym z najbardziej użytecznych modeli służącym do badania mechanicznego zachowania się tkanin. W pracy przedstawiono metodę badania zachowania się zginanych tkanin wełniano-poliestrowych za pomocą modelu składającego się z trój-elementowego modelu równoległego z elementem przesuwnym przy założeniu, że wewnętrzny moment tarcia jest stały podczas procesów gięcia. Na podstawie praktycznych badań przedstawiono metodę badania zachowania się gięcia tkanin wełniano-poliestrowych przy użyciu testera kompresji KES-FB3. Stwierdzono zadowalającą zgodność między wynikami eksperymentów a przewidywaniami teoretycznymi.

4

Wavelength-sensitive-function-based spectral reconstruction using segmented principal component analysis

Wu G., Shen X., Liu Z., Zhang J.

Optica Applicata

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2016

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Vol. 46, nr 3

365--374

EN

Spectral images provide richer information than colorimetric images. A high-dimensional spectral data presents a challenge for efficient spectral reconstruction. In conventional reconstruction methods it is very difficult to obtain good spectral and colorimetric accuracy simultaneously. In this paper, a segmented principal component analysis (SPCA) method and a weighted segmented principal component analysis (wSPCA) method are proposed for efficient reconstruction of spectral color information. The methods require, firstly, partitioning the complete spectrum of wavelengths into two subgroups, considering the sensitivity of human visual system. Then the classical principal component analysis (PCA) carried out each subgroup of data separately. The results indicated that the spectral and colorimetric accuracy of the SPCA and wSPCA outperformed the PCA and weighted PCA, and wSPCA clearly retained more color visual information.

5

Electronic and optical properties of Mn–S co-doped anatase TiO2 from first-principles calculations

Wu G., Zheng S. K., Yan X.

Materials Science Poland

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2016

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Vol. 34, No. 1

38--44

EN

The electronic and optical properties of Mn–S co-doped anatase TiO2 were calculated using the plane-wave-based ultrasoft pseudopotential density functional method within its generalized gradient approximation (GGA). The calculated results show that the band gap of Mn–S co-doped TiO2 is larger than that of the pure TiO2, and two impurity bands appear in the forbidden band, one of which above the valence band plays a vital role for the improvement of the visible light catalytic activity. The Mn–S co-doped anatase TiO2 could be a potential candidate for a photo catalyst because of its enhanced absorption ability of visible light.

6

Numerical study of wave transmission over double submerged breakwaters using non-hydrostatic wave model

Liang B., Wu G., Liu F., Fan H., Li H.

Oceanologia

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2015

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No. 57 (4)

308--317

EN

In the present work, a non-hydrostatic wave model SWASH (an acronym of Simulating WAves till SHore) is used to simulate the wave transmission over double trapezoidal submerged breakwaters. The numerical results were compared with the results of the physical model. The comparison indicated the capability of SWASH model to predict the wave transmission over double submerged breakwaters. Influencing factors such as breakwater spacing S/L0, where L0 is the deep-water wavelength, and current were investigated in detail. Moreover, the effects of current on wave transmission were also analyzed. When the relative submerged depth R/H, where R is the submerged depth and H is the wave height, remains at 1.0, the appropriate relative breakwater spacing S/L0 is about 1.11. Current has no obvious effect on the appropriate S/L0, but it will change the shape of wave spectrum. Dissipation of super harmonic wave components is more obvious than that of lower harmonic wave components.

7

Electronic structures of Hg-doped anatase TiO2 with different O vacancy concentrations

Zheng S K, Wu G., Zhang S., Su J., Liu L.

Materials Science Poland

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2014

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Vol. 32, No. 1

93--97

EN

The electronic structures of Hg-doped anatase TiO2 with different O vacancy concentrations were calculated using the first-principles based on the density functional theory. The calculated results show that the forbidden band widths of Hgdoped anatase TiO2 widened along with the increase of O vacancy concentration, which is responsible for the blue shift in the absorption edges. It can be deduced from the present study that the Hg-doped TiO2 samples prepared in the experimental research contain a certain quantity of O vacancies.

8

Fault location in the outer sheath of power cables

Wang Q., Tang Ch., Wu G., Chen G.

Journal of Power Technologies

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2014

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Vol. 94, nr 4

250--258

EN

With the development of power systems in recent years, the total amount of power cables in operation has increased greatly, and there are growing reports of cable failure. Cable failures may be due to various intrinsic or extrinsic factors and can lead to massive economic loss. With regard to high-voltage cables, such as 110 kV power cables, there are very few accurate reports on the actual fault observed. This article first analyses the possible causes of power cable outer sheath failure. It then introduces the bridge and step voltage methods, which are traditionally used for cable fault locating, and describes a new method for accurate fault locating in 110 kV cables, which uses the bridge method to pre-locate the fault and then the step voltage method to accurately determine the precise fault locating. Field testing confirms the applicability of the new method for accurate fault locating in 110 kV power cables. The results shown in this article may provide a good reference for the development of future research in related fields.

9

Comparison of wind turbine efficiency in maximum power extraction of wind turbines with doubly fed induction generator

Ling Y., Wu G., Cai X.

Przegląd Elektrotechniczny

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2012

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R. 88, nr 5b

157-163

EN

So far, much attention has been not received by the influence of the control modes on the wind turbine efficiency in maximum wind energy extraction, which is investigated based on variable speed wind turbines with doubly fed induction generator (DFIG) under vector control in stator flux orientation (SFO) in the paper. Prior art has tended to have an importance on investigating the principle and behaviors of control strategies in itself. As a result, two control modes, optimal rotor speed control mode and peak power control mode is investigated in detail. At first, Stator flux-orientated vector control for the rotor side converter of DFIG is reviewed, and in turn a comparison on two control modes is presented. Finally, a complete simulation model is developed to investigate how the operation of maximum wind energy extraction of the turbine below rated wind velocity, especially the wind turbine efficiency is affected by the two control methods. Simulation results are presented and compared under the two different control modes. Simulation results show that maximum wind energy extraction of the turbine and its efficiency is affected by different control modes.

PL

W artykule porównano różne strategie zarządzania systemem elektrowni wiatrowych z podwójnie zasilanym generatorem indukcyjnym. Jedna ze strategii polega na kontroli optymalnej prędkości wirnika, druga na kontroli mocy szczytowej.

10

Chemical components and antidiabetic activity of essential oils obtained by hydrodistillation and three solvent extraction methods from Carthamus tinctorius L.

Li L., Wang Q., Yang Y., Wu G, Xin X., Aisa H. A

Acta Chromatographica

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2012

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Vol. 24, no. 4

653--665

EN

The chemical compositions of essential oils extracted by n-hexane extract (HE), petroleum ether extract (PE), dichloromethane extract (DE), and hydrodistillation (HD) from Carthamus tinctorius L. (safflower) were analyzed by gas chromatography-mass spectrometry (GC-MS). A total of 86 compounds from four different extracts were identified, and the contents were 97.65%, 98.05%, 98.93%, and 99.68%, respectively. 6,10,14-Trimethyl-2-pentadecanone, hexadecanoic acid, methyl ester, hexadecanoic acid, 8,11-octadecadienoic acid, methyl ester, and 9,12,15-octadecatrien-1-ol were the major constituents of the extracts. The antidiabete activity was assayed in vitro by against protein tyrosine phosphatase 1B (PTP1B). The results showed that the HE exhibited the best in vitro inhibitory enzyme activity against PTP1B, which holds a good potential for treating diabetes and obesity.

11

Investigation of Transient Torque during a Power System Fault in Wind Power Turbines Having a DFIG and Crowbar Circuit

Cheng M., Cai X., Wu G.

Przegląd Elektrotechniczny

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2011

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R. 87, nr 11

245-250

EN

To study the influence of power system voltage drop on the doubly-fed induction generator (DIFG) shaft, this paper analyzes the electromagnetic torque change of the DFIG through approximated analytical expression of the stator fault current and rotor fault current obtained by the superposition between transient current based on vector method and steady-state current based on equivalent circuit method, and then the DFIG torque change situations under the following circumstances: the three-phase symmetrical voltage dip of stator terminal, the converter of the rotor side is cut off, and the crowbar circuit is put into the operation, will be analyzed through the method. Furthermore, on the basis of theoretical analysis, a 2MW DFIG model is established by PSCAD, and the simulation results validate that the torque changes of the DFIG shaft could be analyzed by the expression of the DFIG torque during the grid voltage drops through the superposition of the transient current and steadystate current. At last, the optimizing value of the crowbar resistance is given.

PL

W artykule analizuje się zmiany momentu elektromagnetycznego podwójnie zasilanego generator indukcyjnego DFIG poprzez ocenę prądów wirnika i stojana otrzymaną przez superpozycję prądów przejściowych (metoda wektorowa) i prądu stanu ustalonego (metoda obwodów zastępczych). Badania symulacyjne potwierdziły słuszność metody.

12

Seed mass increase along altitude within four Saussurea (Asteraceae) species in Tibetian Plateau

Wu G., Tian F., Ren G., Liu Z.

Polish Journal of Ecology

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2011

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Vol. 59, nr 3

617-622

EN

Seed mass is a critical life-history character in seed evolutionary ecology. Plant species can present responses in seed mass to environment stresses. We tested the hypotheses that seed mass was positively correlated with altitude within species. We selected four congeneric Saussurea species as study objects, and collected their seeds along altitudinal gradients (2100.4200 m a.s.l.) in the alpine area of the Qinghai-Tibetan Plateau, China. Results showed that mean seed mass of the four species were significantly affected by altitude (P <0.001). There was a general trend of an increase in seed weight with altitude among the populations of the four species. In addition, mean seed mass of four species were not significantly different, but all presented a bigger coefficients of variation within species along altitude gradients. Our results indicate selection pressure within species, with larger seeds occurring at higher altitudes.

13

Apply an Improved Peukert’s equation based on Temperature to the NiMH Battery available Capacity Estimation

Wu G., Zhu C., Chan C.C.

Przegląd Elektrotechniczny

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2010

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R. 86, nr 6

292-295

EN

Battery available capacity varies with discharge current. Peukert’s equation is a good way to estimate available capacity. But the practicability of Peukert’s equation for The NiMH battery has to be verified. Especially, available capacity of The NiMH battery is influenced by temperature obviously. In this paper, discharge experiments under different current 9A,27A, 54A, 81A are undertaken at room temperature 25?, and the Peukert coefficients n and k are calculated by available capacities and discharge times at the maximum discharge current and the minimum current. The result indicates battery available capacity estimated by Peukert’s equation is practical in 25?. In order to verify the practicability of Peukert’s equation for the NiMH battery at low temperatures, these four discharge experiments are done at other three temperatures 0?, -12?, -18 ?. The result indicates, at low temperatures, Peukert’s equation is practical for The NiMH battery at low current and unpractical in high current. An improved Peukert’s equation based on temperature is proposed. The calculated data catch well with experimental data.

PL

Pojemność baterii zmienia się wraz z prądem wyładowania. Równanie Peukerta jest dobrą metoda do określania pojemności baterii. Sprawdzono możliwość zastosowania tego równania do analizy baterii NiMH. Szczególnie pojemność baterii NiMH jest wrażliwa na zmiany temperatury. W artykule przedstawiono eksperymenty dla różnych prądów w temperaturze pokojowej, a następnie obliczono współczynniki Peukerta na podstawie czasu rozładowania przy prądzie maksymalnym i minimalnym. Sprawdzono także możliwość zastosowania równania Peukerta w niskich temperaturach.

14

Trade-off of sexual and asexual recruitment in a dominant weed Ligularia virgaurea (Maxim.) In alpine grasslands (China)

Wu G., Hu T., Liu Z.

Polish Journal of Ecology

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2010

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Vol. 58, nr 1

81-86

EN

Ligularia virgaurea (Maxim.) is a typical naturally-occurring native noxious weed, widely distributed in alpine grasslands of the Tibetan Plateau, China. Three field sampling plots (30 m ' 50 m) dominated by L. virgaurea were selected to study its population colonization mode and the relationship between sexual- and clonalrecruitment in alpine meadow of the Qinghai-Tibetan Plateau, NW China. Field investigations were conducted on its soil seed bank, seed rain and the individuals of new recruitment (seedlings and ramets) to study its sexual and asexual recruitment. And, 46 individuals which produced the seeds were selected randomly to study their relationship between seed production and ramet production. Results showed that there were more ramets (26.23 ramets m[^-2]) and less seedlings (6.70 seedlings m[^-2]) and a mean value of seed rain was close to 8.04 seeds m[^-2], but the soil seed bank for this species was not found in study sites. Significantly negative correlations (r = -0.416, P <0.001) between seed number per individual and ramet number per adult individual were found for L. vrigaurea in studied alpine grasslands. Our results revealed that clonal reproduction was the main population colonization mode. In addition, there was a significantly negative relationship between seed production and ramets for this species.

15

Effects of seed mass and light on seedling success in Artemisia sieversiana Willd in the Tibetan Plateau

Wu G., Li W., Du G.

Polish Journal of Ecology

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2010

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Vol. 58, nr 3

469-474

EN

Seed mass and light availability are important factors which affect seedling recruitment in plant populations. Effects of seed mass and light availability on seed germination and seedling recruitment in Artemisia sieversiana Willd, which is a widely distributed herbs and a common component species in alpine meadows of the Tibetan Plateau, were tested in a manipulative field experiment. Our research indicated that seed mass and light significantly affected seed germination and seedling emergence and survival and there was a significant interaction effect between seed mass and light availability on these life traits within species. Our study showed that larger seeds presented significant advantages in germination, seedling emergence and survival than smaller seeds under different light availability, especially under deep shade. Our results suggested that seedling success of Artemisia sieversiana appears to be regulated by an interactive effect of seed mass and light availability in alpine meadow of the Qinghai-Tibetan Plateau. In addition, seedlings from larger seeds have more and more stronger advantages from germination, emergence to survival stage than seedlings from smaller seed within species.

16

Rhodamine-6G hydrazide probe for selective determination of Cu(II) in aqueous media

Wang P., Wu G., Gu Z., Wu D., He C.

Chemia Analityczna

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2009

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Vol. 54, No. 2

151-162

EN

A new fluorescence method for selective determination of Cu24 using rhodamine 6G hydra-zide (R6GH) as a probe has been developed. The probe has shown selective and sensitive fluorescence response toward Cu2+ in aqueous media. In the proposed reaction mechanism the hydrazide group of R6GH binds to Cu2+ exhibiting a behavior similar to a-amino esters, which results in a redox hydrolysis of the hydrazide moiety with the release of highly fluorescent rhodamine 6G. Under the optimal conditions the fluorescence enhancement at 545 nm was linearly related to the concentration of Cu2+ in the range 0.1-10 μ mol L-1 The proposed method has been applied to the determination of trace Cu-2 in water samples with satisfactory results.

PL

Opracowano nową fluorescencyjną metodę selektywnego oznaczania Cu-2 używając hydrazydku rodaminy 6G (R6GH) jako sondy. Sonda wykazała selektywną i czułą fluoroscencyjną reakcję na obecność Cu-2 w wodnym roztworze. Zaproponowano mechanizm reakcji, w którym grupa hydrazydkowa w R6GH łączy się z Cu-1 i wykazuje zachowanie podobne do a-amino estrów co prowadzi do hydrolizy red-oks i wydzielenia wysoko fluoryzującej rodaminy 6G. W warunkach optymalnych wzrost fluorescencji przy 545 nm był liniowo zależny od stężenia Cu-2 w zakresie 0,1-10 μ mol L-1. Zaproponowaną metodę zastosowano do oznaczania śladów Cu-2 w próbkach wód uzyskując dobre wyniki.

17

Measurement of wet steam in a 300 mw direct air cooling steam turbine

Cai X, Niu F, Ning T, Ning T, Wu G, Song Y

Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka

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2008

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nr 133

77--86

EN

For study the wet steam flow in the direct air-cooling steam turbine, measurements were carried out in a 300MW turbine with a newly developed combined probe. The wetness in the direct air-cooling steam turbine is lower and varies not much along the blade height. Droplets size distribution and mean diameter are smaller too comparing to water-cooling steam turbine. The measured relative inner efficiencies of LP obtained by the probe agree well with the results obtained by thermal performance test.