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1

Identification of sonar detection signal based on fractional Fourier transform

Wang B., Tang J., Yu F., Zhu Z.

Polish Maritime Research

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2018

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S 2

125--131

EN

Aiming at the source of underwater acoustic emission, in order to identify the enemy emission sonar source accurately. Using the digital watermarking technology and combining with the good time-frequency characteristics of fractional Fourier transform (FRFT),this paper proposes a sonar watermarking method based on fractional Fourier transform. The digital watermark embedding in the fractional Fourier transform domain and combined with the coefficient properties of the sonar signal in the fractional Fourier transform to select the appropriate watermark position. Using the different characteristics of the signals before and after embedding, an adaptive threshold was set for the watermark detection to realize the discrimination of sonar signals. The simulation results show the feasibility and has better resolution and large watermark capacity of this method, while the robustness of the watermark is better, and the detection precision is further improved.

2

Reciprocity relations for light wave scattered by a particulate collection

Jiang Z., Zhu Z., Wang T.

Optica Applicata

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2018

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Vol. 48, nr 4

661--670

EN

Two Fourier relations of light waves scattered by a random-distributed particulate medium have been investigated. We find that the scattered field and the particulate collection satisfy two Fourier relations, i.e. the spectral density is directly proportional to a Fourier transform of a convolution of correlation coefficient of each particle and correlation coefficient of distribution function of the whole collection, and the spectral degree of coherence is directly proportional to a Fourier transform of a convolution of strength of the scattering potential of each particle and strength of the distribution function of the whole collection. To illustrate these relations, behaviors of the far-field generated by Gaussian-correlated particles with Gaussian-correlated distributions have been discussed.

3

The role of powder layer thickness on the quality of SLM printed parts

Nguyen Q. B., Luu D. N., Nai S. M. L., Zhu Z., Chen Z., Wei J.

Archives of Civil and Mechanical Engineering

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2018

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Vol. 18, no. 3

948--955

EN

Achieving good mechanical properties as well as the dimensional accuracy and the smooth surface quality of selective laser melting printed parts with minimal post treatments are essential in additive manufacturing. In the present study, Inconel 718 samples with different powder layer thickness (20, 30, 40 and 50 μm) were additively fabricated using 3D Systems ProX-300 machine. The results reveal that the lower the layer thickness, the denser and good dimensional accuracy were achieved. Marginally higher mechanical properties and microhardness were also obtained at the lower thickness while the failure strain was still high. This can be explained through significant change in the microstructure due to different cooling rate and thermal cycles. In addition, the formation of ɤ′ and ɤ″ intermetallic phases, which were well distributed in the matrix and grain boundaries, during heating/cooling, gave rise in the strengths. Fractography shows the plastic deformation band due to work hardening and the crack initiation sites at sub-micro/micro pores, lack of fusion areas and the boundary of unmelted particles. The study would guide engineers balance their options between the production rate and the building parts’ quality.

4

Development of WC-Inconel composites using selective laser melting

Nguyen Q. B., Zhu Z., Chua B. W., Zhou W., Wei J., Nai S. M. L.

Archives of Civil and Mechanical Engineering

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2018

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Vol. 18, no. 4

1410--1420

EN

In the present study, selective laser melting (SLM) was used to successfully fabricate Inconel 718–tungsten carbide (WC) composites. The processing parameter optimization results reveal that nearly non-porous composites (99.54%) were achieved with the laser power of 220 W, scanning speed of 850 mm s−1, and the hatch spacing of 150 μm. The microstructural characterization unveils that elongated grain structure in the heat flow direction was observed in the case of pure IN718 while WC particles served as obstacles to hinder the grain growth in the composites. The formation of in situ intermediate layer and the strong interfacial bonding between WC super-hard particles and the matrix acted as load bearing and significantly contribute to the overall properties of composites. Mechanical tests indicate significant improvements of microhardness and tensile strengths, although a drop in strength was observed when the amount of WC reached 15 wt.%. In addition, the thermal experiment shows that the composites are dimensionally stable at higher temperature compared to their monolithic counterpart. The findings suggest that the developed IN718-WC composites can be utilized in many critical engineering applications in nuclear sector.

5

Investigating the Effect of the Opening Unit on the Airflow Field in Rotor Spinning

Jin Y., Zhu S., Cui J., Li J., Zhu Z.

Fibres & Textiles in Eastern Europe

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2017

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Vol. 25, no. 5 (125)

18--24

EN

The opening unit is an important device in a rotor spinning unit to comb fibres and remove trash. In this paper, numerical simulation is carried out to study the flow structure in the rotor spinning channel and the trash removal process in the trash removal unit. Firstly the effect of the opening unit on the airflow field in the rotor channel is investigated by singlephase simulation. The result shows that the effective area for fibre conveyance enlarges as the absolute value of negative pressure at the outlet increases, while it decreases as the opening roller speed increases. However, the effect of the negative pressure and the opening roller speed on the length of the vortex in the axial direction is quite small. Secondly the trash separation process in the trash removal unit is simulated using the Discrete Phase Model (DPM). Suitable rotational speeds of particles of different diameters are acquired. These results could provide a valuable reference for parameter selection in the trash-removal process.

PL

Jednostka otwierająca jest ważnym urządzeniem w przędzarce rotorowej służącym do rozczesywania włókien i usuwania odpadów. W artykule przeprowadzono symulację numeryczną mającą na celu zbadanie struktury przepływu w kanale przędzalniczym wirnika oraz procesu usuwania odpadów. Wpływ jednostki otwierającej na pole przepływu powietrza w kanale wirnika badano symulacją jednofazową. Wyniki wykazały, że efektywny obszar transportu włókien powiększa się, gdy wartość bezwzględnej wartości ujemnego ciśnienia na wylocie wzrasta, a zmniejsza się wraz ze wzrostem prędkości wału otwierającego. Jednakże wpływ podciśnienia i prędkość wału otwierającego na długość wiru w kierunku osiowym jest stosunkowo niewielka. Stwierdzono także, że proces separacji odpadów w jednostce usuwania odpadów jest symulowany przy użyciu modelu dyskretnego fazy (DPM). Otrzymuje się odpowiednie prędkości obrotowe cząstek o różnych średnicach. Wyniki te mogą stanowić cenny punkt odniesienia dla wyboru parametrów w procesie usuwania odpadów.

6

Ecological risk assessment of heavy metals in sediments of a riverine wetland, Huaihe River Watershed, China

Yuan H., Pan W., Zhu Z., Wei Y., Geng Q., An S.

Ecological Chemistry and Engineering. S

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2015

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Vol. 22, nr 2

231--242

EN

The concentrations of Zn, Cr, Cu, As, Cd, and Pb in sediment cores collected from a representative riverine wetland located in the Huaihe River watershed, China, dramaticlly increased from the bottom to upper layer of the cores. Application of principal component analysis (PCA) and enrichment factor (EF) suggested that heavy metals might primarily have been derived from the inflow of contaminated water from an industrial park and agricultural region. Component 1 of the PCA was dominated by Zn, Cr, Cu, Cd, and Pb, while Component 2 was dominated by As. Metals’ high concentrations and EF values showed that the anthropogenic pollutants have increased sharply in recent years and reflect the continuous development of industry and agriculture in the region of the wetland, with a corresponding dramatic deterioration of the environment due to constant effluent of pollutants. Cd exerted the highest potential ecological risk of individual metals of sediment cores. Additionally, integrated RI values for all metals indicated that sediments possessed low ecological risk from the bottom to about 6 cm depth of the cores, moderate ecological risk from about 5 cm depth upwards, then considerable ecological risk from 4 cm depth to the top layer of the sediment cores, which demonstrates a continuous deterioration of environmental quality in recent years in this region.

PL

Stężenia Zn, Cr, Cu, As, Cd i Pb w rdzeniach osadów pobranych z reprezentatywnych podmokłych terenów nadrzecznych, znajdujących się w zlewni rzeki Huaihe, Chiny, wykazały znaczne wzrosty od dołu do górnej warstwy rdzeni. Zastosowanie analizy głównych składowych (PCA) i czynnika wzbogacania (EF) wykazało, że źródłem metali ciężkich mogą być przede wszystkim zanieczyszczone wody z parku przemysłowego i z obszarów rolniczych regionu. Składowa 1 PCA było zdominowane przez Zn, Cr, Cu, Cd, i Pb, natomiast składowa 2 była zdominowana przez As. Duże stężenia metali i wartości EF wykazały, że antropogenne zanieczyszczenie gwałtownie wzrosło w ostatnich latach i odzwierciedla ciągły rozwój przemysłu i rolnictwa w regionie nadrzecznym, z odpowiednim drastycznym pogorszeniem stanu środowiska ze względu na stałe zanieczyszczenie ściekami. Cd stwarza największe potencjalne ryzyko ekologiczne spośród wszystkich metali rdzeni osadów. Dodatkowo, zintegrowane wartości RI dla wszystkich metali wskazują, że osady tworzyły niskie zagrożenie ekologiczne od dołu do około 6 cm głębokości rdzeni, umiarkowane ryzyko ekologiczne od około 5 cm głębokości do góry. Znaczne zagrożenie ekologiczne stwarzają osady od głębokości 4 cm do warstwy wierzchniej rdzenia, co świadczy o ciągłym pogarszaniu się jakości środowiska w ostatnich latach w tym regionie.

7

Identification and differentiation of major flavonoids in two kinds of Epimedium extracts and rat plasma by rapid-resolution liquid chromatography combined with time-of-flight mass spectrometry

Lv L., Zhao L., Wang X., Zhang H., Zhu Z., Chai Y., Zhang G.

Acta Chromatographica

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2015

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Vol. 27, no. 2

331--353

EN

Epimedium pubescens Maxim. and Epimedium koreanum Nakai. are two common and confused species of Herba Epimedii in Chinese Pharmacopoeia 2010 edition. Different species and growing conditions lead to chemical differences between the two species which may result in the improper clinical usage. In this work, a new method based on rapid-resolution liquid chromatography combined with time-of-flight mass spectrometry (RRLC/TOFMS) has been developed for identification and differentiation of major flavonoids in two kinds of Epimedium extract and rat plasma. The compounds were identified effectively based on the accurate extract masses and formulae acquired by RRLC/TOFMS. The fragmentation rules deduced by collision-induced dissociation (CID) were successfully implemented in distinguishing some of the isomers, further validating the results. By using the combined analytical techniques, a total of 40 major flavonoids in extracts of two kinds of Epimedium were identified within 30 min, including 31 common components and 9 characteristic components. After oral administration, three prototype compounds in rat plasma were detected by comparing the constituents measured in vitro with those in vivo, and five metabolites were identified by contrasting the fragmentation rules. The identification and structural elucidation of the chemical constituents provided essential data for further pharmacological and clinical studies on different species of Epimedium.

8

Rotor Displacement Estimation for MB Sensorless Control

Zhu Z., Sun Y., Huang Y., Ji X.

Przegląd Elektrotechniczny

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2012

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R. 88, nr 1b

141-145

EN

This paper presents an on-line recursive least squares support vector machine(O-RLS-SVM)-based displacement estimator for magnetic bearings (MBs). The basic premise of the method is that an O-RLS-SVM forms an efficient mapping structure for a nonlinear MB. Through the measurement of phase flux linkages and currents, the O-RLS-SVM is able to estimate the rotor displacement; thereby it facilitates the elimination of the rotor displacement sensor. Simulation results show that the estimator has high estimation precision and favourable operation efficiency.

PL

W artykule przedstawiono system estymacji położenia wirniku w maszynach z poduszką magnetyczną. System nie wymaga czujników – miarą położenia wirnika są przesunięcia fazowe prądu i strumienia magnetycznego.

9

Displacement Self-sensing of Bearingless Switched Reluctance Motors Based on LS-SVM

Zhu Z., Sun Y., Huang Y., Ji X.

Przegląd Elektrotechniczny

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2012

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R. 88, nr 12a

310-313

EN

To achieve the rotor radial displacement self-sensing for a bearingless switched reluctance motor (BSRM), a new displacement estimation method using least squares support vector machine (LS-SVM) was proposed. Firstly, the working principle and mathematic of a 3-phase 12/8 pole BSRM was introduced in brief. Then taking advantage of LS-SVM with better solution for small-sample learning problem and strong generalization ability, two LS-SVMs were trained off-line to obtain two efficient nonlinear mapping structures to express the dynamic behavior of BSRM. The LSSVM training data set is comprised of representative experimental data with current {i | i = (isa1, isa2, ima)} and rotor position θ as inputs and the corresponding displacements {D | D=(α , β )}as outputs. As well as giving a detailed explanation of the new method, simulation and experimental results were presented. It shows that the proposed LS-SVM-based displacement self-sensing method has high precision and operation efficiency.

PL

W artykule przedstawiono uczący się estymator przesunięcia dla bezłożyskowego silnika o przełączanej reluktancji (BSRM), wykorzystujący metodę LS-SVM (ang. Least Square Support Vector Machines). Opisano zasadę działania i model matematyczny silnika BSRM 3- fazowego 12/8 biegunowego. W celu uzyskania efektywnej struktury mapowania nieliniowego do określenia stanów dynamicznych, zastosowano dwa algorytmy, które zostały nauczone offline. Estymator poddano weryfikacji symulacyjnej i eksperymentalnej.

10

Improving Emergency Supply System to Ensure Port City Safety

Wang Z., Zhu Z., Cheng W.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2011

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Vol. 5, no. 3

279--283

EN

To efficiently implement emergency response program to port unexpected incidents, a perfect emergency supply system which including communications supplying, transportation supplying and rescue equipments supplying must be ready-to-used. Considering physical geography, harbor area, possible incident type and incident scale and other factors, using multi-objective fuzzy decision theory to set up emergency supply centers, improving sharing resource mechanism, administrative legislation and other measures are be used to improve port emergency supply system. Shanghai port’s practice prove the improve port emergency supply system is effective.

11

Recruitment pattern of tree populations along an altitudinal gradient : Larix chinensis Beissn in Qinling Mountains (China)

Duan R., Wang X., Tu Y., Huang M., Wang C., Zhu Z., Guo H.

Polish Journal of Ecology

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2009

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Vol. 57, nr 3

451-459

EN

Larix chinensis Beissn is an endangered plant found only in the Qinling Mountains, Shaanxi, northwestern China. It is densely distributed in the alpine and subalpine belt on their highest peak Taibai Mountain. Age structure studies along a montane altitudinal gradient would be helpful in understanding the limiting factors on the regeneration of natural forests. The forest was divided into three transects, i.e., lower limit (2900-3000 m), mid-altitude (3100-3200 m) and upper limit (3300-3400 m). The age structures differed across altitude classes. The age structure in the low altitude transect was closed to bell-shaped and characterized by the dominance of adult trees. A reverse-J shape age structure was found in the mid-altitude transect. Multi-modal age distribution was found in the high altitude transect, and was caused by lack of young seedlings and saplings. This suggests that different limiting factors play important roles in shaping the age structure and forest regeneration at different altitudes. In the low altitude, light availability was probably the most important limiting factor. In the mid-altitudinal transect, density dependent intraspecific competition between trees likely controlled regeneration of L. chinensis. We suggest that limiting climatic factors, e.g. temperature, play an important role in determining the age structure of L. chinensis populations in highaltitude areas.