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1

The cavitation nuclei transient characteristics of Lennard-Jones fluid in cavitation inception

Fu Q., Zhang B., Zhao Y., Zhu R., Liu G., Li M.

Polish Maritime Research

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2018

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S 2

75--84

EN

In the field of ocean engineering, cavitation is widespread, for the study of cavitation nuclei transient characteristics in cavitation inception, we applied theoretical analysis and molecular dynamics (MD) simulation to study Lennard-Jones (L-J) fluid with different initial cavitation nuclei under the NVT-constant ensemble in this manuscript. The results showed that in cavitation inception, due to the decrease of liquid local pressure, the liquid molecules would enter the cavitation nuclei, which contributed to the growth of cavitation nuclei. By using molecular potential energy, it was found that the molecular potential energy was higher in cavitation nuclei part, while the liquid molecular potential energy changes greatly at the beginning of the cavitation nuclei growth. The density of the liquid and the surface layer changes more obvious, but density of vapor in the bubble changes inconspicuously. With the growth of cavitation nuclei, the RDF peak intensity increased, the peak width narrowed and the first valley moved inner. When cavitation nuclei initial size reduced, the peak intensity reduced, the corresponding rbin increased. With the decrease of the initial cavitation nuclei, the system pressure and total energy achieved a balance longer, and correspondingly, they were smaller. In addition, at the beginning of the cavitation nuclei growth, the total energy and system pressure changed greatly.

2

Stability of air nucleus in liquid water and cavitation inception on marine engineering

Fu Q., Chen M., Wang X., Zhu R., Zhang G.

Polish Maritime Research

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2018

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S 3

111--119

EN

The micro air nucleus widely distributed in the ocean is a necessary condition for the cavitation of hydraulic machinery in seawater. In order to study the stability of air nucleus in seawater and cavitation inception, the computational domain of water molecules with air nucleus was studied using the method of molecular dynamics simulation, and the transient characteristics of air nucleus in liquid water were obtained. The key factors influencing nuclei stability were analyzed. The results showed that air nucleus with a certain mass could maintain the dynamic equilibrium in liquid water. The internal density of air nuclei had a critical value that allowed the nuclei to stably exist in water. The air nuclei mass was the decisive factor in its equilibrium volume in water, and the two were positively correlated. The internal density of air nuclei was negatively correlated with the nuclei radius when the nuclei was stable in water. Liquid surface tension was an important factor affecting the stability of the air nuclei. The larger the initial radius of nuclei, the smaller the water pressure, and the more likely the cavitation occurs.

3

Dynamic compressive mechanical behaviour and modelling of basalt–polypropylene fibre-reinforced concrete

Fu Q., Niu D., Zhang J., Huang D., Wang Y., Hong M., Zhang L.

Archives of Civil and Mechanical Engineering

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2018

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Vol. 18, no. 3

914--927

EN

Dynamic compressive behaviour of basalt–polypropylene fibre-reinforced concrete (BPFRC) was experimentally investigated using a 75-mm-diameter split-Hopkinson pressure bar. The results showed that the addition of basalt fibre (BF) and polypropylene fibre (PF) is effective at improving the impact-resistance behaviour of concrete. The dynamic compressive strength, critical strain, and energy absorption capacity of BPFRC increased with increasing strain rate. At strain rates of 20–140 s−1, the addition of BF and PF significantly increased the dynamic compressive strength, critical strain, and energy absorption capacity of concrete. The dynamic increase factor of BPFRC increased linearly with the decimal logarithm of strain rate. The hybrid addition of BF and PF significantly improved the strain rate effect of the dynamic compressive strength. The strengthening and toughening mechanisms of BF and PF are discussed in detail. The proposed dynamic damage constitutive model can be used to accurately describe the dynamic stress–strain relationship of BPFRC.

4

Study on the separation of triterpene saponins from Panax notoginseng by off-line two-dimensional supercritical fluid chromatography–ultrahigh-performance liquid chromatography

Xing Q., Fu Q., Liang X.

Acta Chromatographica

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2017

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Vol. 29, no. 4

497--502

EN

The off-line two-dimensional supercritical fluid chromatography (SFC)–ultrahigh-performance liquid chromatography (UHPLC) was selected to separate the triterpene saponins from Panax notoginseng. The separation by SFC was performed on an Atlantis® HILIC silica column. Methanol was selected as a modifier, and the most time-saving gradient was developed. The decrease of the column temperature and the increase of the back pressure could shorten the retention time but had no effect on the separation selectivity. Then, the back pressure, column temperature, and flow rate were set as 131 bar, 45 °C, and 4.0 mL min−1, respectively. The retention behavior of the saponins from P. notoginseng was different between SFC and reversed-phase liquid chromatography (RPLC), which facilitated to construct an off-line SFC/RPLC–mass spectrometry (MS) system. In first dimension, a total of eight fractions were collected under SFC and further analyzed by RPLC–MS in second dimension. The result indicated that the retention behavior of triterpene saponins was mainly controlled by the hydrogen bonding interactions which were affected by the number and types of sugars, as well as the aglycone in the structure of triterpene saponins. Thus, the presence of “clustering effect” under SFC was observed, namely, one SFC peak always contained several saponins with same number of sugars and similar structure of aglycone. The clustering effect of triterpene saponins promised SFC to be used as first dimension to complete the preliminary crude separation in the two-dimensional liquid chromatography.

5

Polybrominated diphenyl ethers (PBDEs) in sediment and fish tissues from Lake Chaohu, central eastern China

Yang S., Fu Q., Teng M., Yang J.

Archives of Environmental Protection

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2015

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Vol. 41, no. 2

12--20

EN

Polybrominated diphenyl ethers (PBDEs) levels in environmental media have increased over the last 20-25 years in the world. In aquatic environments PBDEs were found to be accumulated along food chain and Endocrine disruptors toxicity. In this study PBDEs were investigated in sediment and fish tissues from Lake Chaohu in central eastern China. There were 10 PBDEs congeners detected out of all 41 PBDEs. BDE-47 was of the highest with 5.17 ng/g in sediment and 58.47 ng/g in fish. PBDEs were evenly distributed across the surface sediment in the whole lake. It implied that the main source of PBDEs may not be an inflow river like Nanfei. Tissue distribution patterns of PBDEs in four fish species were in the order of BDE-47 > BDE-99 > BDE-100 > BDE-66 > BDE-138 > BDE-183 > BDE-154 > BDE-153. Octa- and deca-BDEs were below the detection limit. The concentrations of all PBDE congeners were higher in gills, livers, and kidneys than those in muscles and adipose tissue. Furthermore, PBDEs in different tissues had some different distribution patterns with fish size. Those discrepancies appeared to be correlated with the PBDEs pollution fluxes varying with the change of the year and their metabolism divergences in fish tissues.

6

Design of Acoustic Tubes Array and Application to Measuring Acoustic Loads in Supersonic Airflow

Wei L., Li M., Fu Q., Fan Y., Yang D.

Archives of Acoustics

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2014

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Vol. 39, No. 3

395--402

EN

In the acoustic fatigue experiment for hypersonic vehicle in simulated harsh service environment on ground, acoustic loads on the surface of test pieces of the vehicle need to be measured. However, for the normal microphones without high temperature resistance ability, the near field sound measurement cannot be achieved. In this work, on the basis of previous researches, an acoustic tubes array is designed to achieve the near field measurement of acoustic loads on the surface of the test piece in the supersonic airflow with high temperature achieved by coherent jet oxygen lance. Firstly, the process of designing this acoustic tubes array is introduced. Secondly, the equality of phase differences at the front and at the end of the tubes is stated and proved using a phase differences test with an acoustic tubes array whose design is presented in this text; therefore, the phase differences of signals acquired by microphones can be directly applied to beamforming algorithm to determine the acoustic load source. Finally, using above mentioned acoustic tubes array, measurement of acoustic load, with and without a test piece in the supersonic airflow made by the coherent jet oxygen lance, is conducted respectively, and the measurements results are analyzed.

7

Improving machining performance against regenerative tool chatter through adaptive normal pressure at the tool clamping interface

Fu Q., Rashid A., Nicolescu C. M.

Journal of Machine Engineering

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2013

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Vol. 13, No. 1

93--105

EN

Chatter in machining process is one of the common failures of a production line. For a cantilever tool, such as a boring bar, the rule of thumb requires the overhang length of the tool to be less than 4 times the diameter. The reason is because longer overhang will induce severe tool vibration in the form of chatter during machining. When a longer overhang than 4 times diameter is necessary for performing special machining operations, damping methods are needed to suppress tool chatter. One of the methods is the constrained layer damping method. Materials, such viscoelastic material, are applied in the vibration node regions of the structure to absorb the concentrated vibration strain energy and transform the mechanical energy to heat. With a cantilever tool clamped in a tool holder, the clamping interface is usually the vibration node region. The friction in the joint interface with low normal pressure became another source of damping and can be used for tool chatter suppression in mechanical structures. Joint interfaces are well known to possess normal pressure dependent stiffness and damping. The normal pressure's effect on the structures frequency response function had been observed by H. Akesson [1] et al, and L.Mi [2] et al. However, the direct effect of the joint interface normal pressure on machining process stability hasn't been investigated. In this paper, a cantilever tool with 6,5 overhang length to diameter ratio is investigated. The direct effect of the tool clamping interface's normal pressure on the machining process stability is studied. Three different levels of clamping normal pressure are tested with an internal turning process. The machining results indicate another adaptable solution on shop floor for suppressing tool chatter.

8

Badanie nanokompozytów poli(kwas metakrylowy-metakrylan metylu)/poli(N-winylo-2-pirolidon)/ wielościenne nanorurki węglowe

Liu G., Fu Q.

Chemik

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2013

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Vol. 67, nr 11

1066--1071

PL

Nanokompozyty poli(kwas metakrylowy-metakrylan metylu) (P(MAA-co-MMA)) / poli(N-winylo-2-pirolidon) (PVP) / wielościenne nanorurki węglowe (MWNT) otrzymano na drodze wspomaganej ultradźwiękami polimeryzacji wolnorodnikowej w roztworze z emulgatorem. Stwierdzono, że przy małych stężeniach MWNT dyspergują równomiernie w mieszankach P(MAA-co-MMA)/PVP i wpływają na poprawę właściwości mechanicznych nanokompozytów P(MAA-co-MMA)/PVP/MWNT, natomiast wzrost zawartości MWNT w nanokompozytach wyraźnie poprawia się ich stabilność termiczną.

EN

Poly(methacrylic acid-co-methyl methacrylate) (P(MAA-co- MMA))/poly(N-vinyl-2-pyrrolidone) (PVP)/multiwalled carbon nanotubes (MWNTs) nanocomposites were prepared via ultrasonic assisted emulsifier solution free radical polymerization technique. It was found that, at low concentration of MWNTs, it could uniformly disperse into P(MAA-co-MMA)/PVP blends and provide P(MAA-co- MMA)/PVP/MWNTs nanocomposites much improved mechanical properties. Thermal stability for P(MAA-co-MMA)/PVP/MWNTs nanocomposites increased with increasing MWNTs content.

9

Ti-doped In2O3 transparent conductive thin films with high transmittance and low resistivity

Song Z., Fu Q., Li L., Li L., An Y., Wang Y.

Optica Applicata

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2010

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Vol. 40, nr 4

751--757

EN

Ti-doped In2O3 thin films have been prepared on glass substrate by radio frequency (RF) sputtering with different sputtering powers (90, 120, 150, and 180 W) at 330 °C. The influence of sputtering power on the structural, electrical and optical properties of the deposited thin films is investigated. The average transmittance of the thin films in the wavelength range of 500-1100 nm is over 90%. Low resistivity of 7.3×10-4 ?cm is also obtained based on our thin films, suggesting that Ti-doped In2O3 is a good candidate for transparent conductive thin film.

10

ZnO/MgO distributed Bragg reflectors

Huo B., Hu L., Zhang H., Zhao Z., Fu Q., Chen X.

Optica Applicata

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2009

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Vol. 39, nr 1

169--174

EN

ZnO/MgO distributed Bragg reflectors (DBRs) are grown by pulsed laser deposition. DBR samples grown at the same temperature and the same pressure show obvious reflections in transmission spectra. If there is a standing wave in the ZnO layers, it is evident that the full width at half maximum of the ZnO peak in photoluminescence spectra could be decreased when the sample reflects more photons whose wavelength is about 380 nm.