Wyniki wyszukiwania - BazTech

1

Implication and collecting mechanism of emulsified sodium vegetable oleate on fluorite flotation

Sun L., Liu J., Liao Y., Sun L., Liu J.

Physicochemical Problems of Mineral Processing

|

2018

|

Vol. 54, iss. 2

211--219

EN

The emulsified sodium vegetable oleate (ESVO) was prepared with low-cost vegetable oleate. Using ESVO as a collector, the flotation performance of fluorite had been investigated comparing with sodium oleate at a temperature of 20 ± 2 °C. The results of flotation showed that ESVO had better collecting performance than the sodium oleate. The interaction mechanism of these two collectors with fluorite was studied by the zeta potential, FTIR spectra and laser grain-size tests. Both ESVO and sodium oleate changed fluorite zeta potential by electrostatic attraction and chemical adsorption, and generated calcium carboxylate on the fluorite surface. Moreover, it was concluded that higher fluorite recovery was a consequence of ESVO smaller surface tension comparing to sodium oleate.

2

Copper adsorption reaction rate and ion exchange ratio during the copper activation of sphalerite

Liu J., Luo D., Huang L., Wang Y., Wen S.

Physicochemical Problems of Mineral Processing

|

2018

|

Vol. 54, iss. 2

377--385

EN

A theoretical analysis method of the solution chemistry characteristic of Cu(II) at various pH values was developed. Using such method, the existence form of Cu species and their proportions in aqueous solution can be clearly determined. After that, the copper adsorption and ion exchange ratio (E) during the copper activation of sphalerite were investigated. The results indicated that the copper activation of sphalerite can be divided into two stages, i.e., the fast activation stage (t ≤4 min) and slow activation stage (t >4 min). The general form of the copper adsorption rate was determined as ΓCu=K1ln(t) +Γ1, which is confirmed by the data fitting of the fast activation stage. The lower activation pH results in higher ion exchange efficiency for Cu substituting Zn. For a strong acid pH of 4.1, the E maintains about 1:1 in the entire activation time range and is not dependent on the activation time. However, the value of E is greater than 1 under weak acidic (pH=6.2) and alkaline (pH=9.1) pH conditions and it significantly depends on the activation time. For such conditions, E decreases with increase in the activation time, which supports the ion exchange mechanism, but within short activation time, it is not a 1:1 ion exchange process.

3

UV-Vis spectroscopic detection coupled with chemometrics for the measurement of mixed organic acids in water samples enriched by radial electric focusing solid phase extraction

Guo Y., Liu X., Liu J., Bian X., Zhang Q., Pan J., Wan D.

Metrology and Measurement Systems

|

2018

|

Vol. 25, nr 2

317--329

EN

Due to the difficulty of detecting traces of organic acid mixture in an aqueous sample and the complexity of resolving UV-Vis spectra effectively, a combinatory method based on a self-made radical electric focusing solid phase extraction (REFSPE) device, UV-Vis detection and partial least squares (PLS) calculation is proposed here. In this study, REFSPE was used to enhance the extraction process of analytes between the aqueous phase and the membrane phase to enrich the trace of mixed organic acid efficiently. Then, the analytes, which were eluted from the adsorption film by ethanol with the assistance of an ultrasonic cleaning machine, were detected with UV-Vis spectrophotometry. After that, the PLS method was introduced to solve the problem of overlapping peaks in UV-Vis spectra of mixed substances and to quantify each compound. The linearly dependent coefficients between the predicted value of the model and the actual concentration of the sample were all higher than 0.99. The limit values of detection for benzoic acid, phthalic acid and p-toluene sulfonic acid were found at 9.9 μg/L, 12.2 μg/L and 13.8 μg/L with the relative recovery values between 84.8% and 117.9%. The RSD (n = 20) values of each component are 1.17%, 1.11% and 0.86%, respectively. Therefore, the proposed combined method can determine traces of complex materials in an aqueous sample efficiently and has wonderful potential applications.

4

System for Calibrating Analogue Merging Units in Absence of Synchronization Signals

Cheng H.-M., Huang Q.-F., Ji F., Xu Q., Liu J., Tian Z.

Metrology and Measurement Systems

|

2018

|

Vol. 25, nr 1

129--138

EN

Synchronization signals are requisite for calibrating electrical measurement devices with digital output when using conventional calibration methods. However, since the signal sampling process of the analogue merging units (MUs) operating in an intelligent substation does not rely on external synchronization signals, accuracy calibration without the use of synchronization signals is of particular importance in order to guarantee the measurement accuracy in practical situations. So far, very little research on calibration systems independent of synchronization signals has been performed. This paper presents a design of the calibration system without dependence on synchronization signals. To verify the feasibility of the proposed design, the designed system and a conventional calibration system have been employed in testing the accuracy of the same analogue MU of a 0.2 accuracy class. The comparison of the test results shows that the differences of ratio errors are below 0.02%, and the maximum difference of phase errors is about 4′. This paper also provides a new efficient and significant calibration method which does not require any external synchronization signals.

5

Fast edge detection approach based on global optimization convex model and Split Bregman algorithm

Jing Y., Liu J., Liu Z., Cao H.

Diagnostyka

|

2018

|

Vol. 19, No. 2

23--29

EN

Active contour model is a typical and effective closed edge detection algorithm, which has been widely applied in remote sensing image processing. Since the variety of the image data source, the complexity of the application background and the limitations of edge detection, the robustness and universality of active contour model are greatly reduced in the practical application of edge extraction. This study presented a fast edge detection approach based on global optimization convex model and Split Bregman algorithm. Firstly, the proposed approach defined a generalized convex function variational model which incorporated the RSF model’s principle and Chan’s global optimization idea and could get the global optimal solution. Secondly, a fast numerical minimization scheme based on split Bregman iterative algorithm is employed for overcoming drawbacks of noise and others. Finally, the curve evolves to the target boundaries quickly and accurately. The approach was applied in real special sea ice SAR images and synthetic images with noise, fuzzy boundaries and intensity inhomogeneity, and the experiment results showed that the proposed approach had a better performance than the edge detection methods based on the GMAC model and RSF model. The validity and robustness of the proposed approach were also verified.

6

Object detection based on deep learning for urine sediment examination

Liang Y., Tang Z., Yan M., Liu J.

Biocybernetics and Biomedical Engineering

|

2018

|

Vol. 38, no. 3

661--670

EN

Urine sediment examination (USE) is an important topic in kidney disease analysis and it is often the prerequisite for subsequent diagnostic procedures. We propose DFPN(Feature Pyramid Network with DenseNet) method to overcome the problem of class confusion in the USE images that it is hard to be solved by baseline model which is the state-of-the-art object detection model FPN with RoIAlign pooling. We explored the importance of two parts of baseline model for the USE cell detection. First, adding attention module in the network head, and the class-specific attention module has improved mAP by 0.7 points with pretrained ImageNet model and 1.4 points with pre-trained COCO model. Next, we introduced DenseNet to the baseline model(DFPN) for cell detection in USE, so that the input of the network's head own multiple levels of semantic information, compared to the baseline model only has high-level semantic information. DFPN achieves top result with a mAP of 86.9% on USE test set after balancing between the classification loss and bounding-box regression loss, which improve 5.6 points compared to baseline model, and especially erythrocyte's AP is greatly improved from 65.4% to 93.8%, indicating class confusion has been basically resolved. And we also explore the impacts of training schedule and pretrained model. Our method is promising for the development of automated USE.

7

Optimization of Operational Parameters of Foam Sizing Process for Cotton Yarns Based on Plackett-Burman Experiment Design

Zhu B., Liu J., Gao W.

Autex Research Journal

|

2018

|

Vol. 18, no. 1

61--66

EN

This study was aimed at investigating the process optimization of foam sizing for cotton yarns. In this work, effects of major foam-sizing process factors including size concentration, blowing ratio, stirring speed, pre-wetting temperature, pre-drying temperature, squeezing pressure and drying temperature were studied on the hairiness (more than 3 mm) and abrasion resistance of foam-sized yarns. The combination of Plackett-Burman, steepest ascent path analysis and Box-Behnken design were adopted to optimize the foam-sizing process of cotton yarns. Results revealed that size concentration, blowing ratio and squeezing pressure were significant factors that affected the hairiness and abrasion resistance. Optimum hairiness and abrasion resistance were obtained when the cotton yarns were sized at size concentration of 19.33%, blowing ratio of 4.27 and squeezing pressure of 0.78kN. The theoretical values and the observed values were in reasonably good agreement and the deviation was less than 1%. Verifcation and repeated trial results showed that it has good reproducibility and imparts the foam sizing process of cotton yarns.

8

Dynamic Measurement of Foam-Sized Yarn Properties from Yarn Sequence Images

Zhu B., Li Z., Cao X., Liu J., Gao W.

Autex Research Journal

|

2018

|

Vol. 18, no. 3

314--322

EN

Unlike the normal sizing method, the foam sizing had been proven to be a low-add-on technology. To investigate the effect of foam sizing, film thickness, sized-yarn evenness, and size penetration rate were necessary to evaluate the performances of foam-sized yarns. However, the conventional image analysis of sized-yarn cross sections primarily relied on artificial testing with a low efficiency. This paper proposed a novel dynamic method to measure the sized-yarn properties including film thickness, sized-yarn evenness, and size penetration rate based on yarn sequence images captured from a moving yarn. A method of dynamic threshold module was adopted to obtain threshold for segmenting yarns in the sequence images. K-means clustering algorithm was applied to segment pixels of the images into yarn and background. To further remove burrs and noise in the images, two judgment templates were carried out to extract the information of yarn core. The film thickness, sized-yarn evenness, and size penetration rate were measured based on the yarn core of each frame in sequence images. In order to compare with the experimental results of the dynamic method, the yarn properties of the same samples were tested by static and artificial testing. Results revealed that the proposed method could efficiently and accurately detect the film thickness, sized-yarn evenness, and size penetration rate.

9

Study on mine ventilation resistance coefficient inversion based on genetic algorithm

Gao K., Deng L., Liu J., Wen L., Wong D., Liu Z.

Archives of Mining Sciences

|

2018

|

Vol. 63, no. 4

813--826

EN

The frictional resistance coefficient of ventilation of a roadway in a coal mine is a very important technical parameter in the design and renovation of mine ventilation. Calculations based on empirical formulae and field tests to calculate the resistance coefficient have limitations. An inversion method to calculate the mine ventilation resistance coefficient by using a few representative data of air flows and node pressures is proposed in this study. The mathematical model of the inversion method is developed based on the principle of least squares. The measured pressure and the calculated pressure deviation along with the measured flow and the calculated flow deviation are considered while defining the objective function, which also includes the node pressure, the air flow, and the ventilation resistance coefficient range constraints. The ventilation resistance coefficient inversion problem was converted to a nonlinear optimisation problem through the development of the model. A genetic algorithm (GA) was adopted to solve the ventilation resistance coefficient inversion problem. The GA was improved to enhance the global and the local search abilities of the algorithm for the ventilation resistance coefficient inversion problem.

PL

Współczynnik oporu oporu wentylacji jezdni w kopalni węgla jest bardzo ważnym parametrem technicznym w projektowaniu i renowacji wentylacji kopalnianej. Obliczenia oparte na wzorach empirycznych i badaniach terenowych w celu obliczenia współczynnika oporu mają ograniczenia. W niniejszym badaniu proponuje się inwertowaną metodę obliczania współczynnika oporu wentylacji kopalni za pomocą kilku reprezentatywnych danych dotyczących przepływu powietrza i ciśnienia w węzłach. Model matematyczny metody inwersji jest opracowywany na zasadzie najmniejszych kwadratów. Zmierzone ciśnienie i obliczone odchylenie ciśnienia wraz z zmierzonym przepływem i obliczonym odchyleniem przepływu są uwzględniane przy określaniu obiektywnej funkcji, która obejmuje również ciśnienie w węźle, przepływ powietrza i ograniczenia współczynników oporu wentylacji. Problem odwrotności współczynnika oporu wentylacji został przekształcony w nieliniowy problem optymalizacji poprzez opracowanie modelu. Zastosowano algorytm genetyczny (GA) w celu rozwiązania problemu inwersji współczynnika oporu wentylacji. GA został ulepszony w celu zwiększenia globalnych i lokalnych możliwości wyszukiwania algorytmu problemu odwrotności współczynnika oporu wentylacji.

10

Dynamic characteristics of magnetic coupling in horizontal axis wave energy device

Zhang J., Liu Y., Liu J., He T., Xie Y.

Polish Maritime Research

|

2017

|

S 3

165--170

EN

To solve the dynamic response problems of magnetic coupling in the horizontal axis wave energy device, this has researched the dynamic characteristicsof magnetic coupling. The fitting formula about torque and angle of the magnetic coupling is obtained through experiments. The mathematical models of the magnetic coupling torque transmission are established. The steady state error of the magnetic coupling and the transfer function of the output angle are obtained. The analytical solution of the step response of the output angle in time domain is derived. The influence of the torsional rigidity, the damping coefficient and the driven rotor’s rotational inertia on dynamic characteristics of the magnetic coupling isanalyzed. According to the analysis results, the design rules of magnetic coupling are proposed.

11

Nitrogen Deposition Influences the Allelopathic Effect of an Invasive Plant on the Reproduction of a Native Plant : Solidago canadensis versus Pterocypsela laciniata

Wang C., Liu J., Xiao H., Zhou J., Du D.

Polish Journal of Ecology

|

2017

|

Vol. 65, nr 1

87--96

EN

This study aims to gain insights into the allelopathic effects (by using leaf extracts) of the notorious invasive Solidago canadensis L. on seed germination of the associated Pterocypsela laciniata (Houtt.) C. Shih under different nitrogen (N) forms added: inorganic (NO3- -N and NH4+ -N), organic (urea-N), and mixed N (a mixture of the three N forms at 1:1:1 ratio). Among the two used concentrations of S. canadensis leaf extracts the higher exhibited inhibitory allelopathic effects on seedling height and biomass, germination potential, germination index, and vigor index of P. laciniata. N demonstrated positive effects on seed germination of P. laciniata. The effects of mixed and organic N on the seedling biomass of P. laciniata were more pronounced than those of inorganic N and control treatment. The vigor index of P. laciniata under mixed N was significantly higher than those under single N form and control treatment. Thus, organic and mixed N showed higher ecological effects on seed germination of P. laciniata than inorganic and single N form. All N forms could alleviate the inhibitory allelopathic effects of S. canadensis on seed germination of P. laciniata. Overall, the inhibitory allelopathic impact of S. canadensis on seed germination of native species may be attenuated under increased and diverse N deposition, thus it could prevent its further invasion.

12

Ground-Active Arthropod Recovery in Response to Size of Shrub Plantations in a Desertified Grassland Ecosystem

Liu R., Liu J., Zhao J., Xi W., Yang Z.

Polish Journal of Ecology

|

2017

|

Vol. 65, nr 3

410--422

EN

The ground-active arthropod diversity response to size of shrub plantations in desertified grassland ecosystems is largely unknown. In the study ground-active arthropods were collected by pitfall trapping beneath shrub canopy of very low, low, medium and high size, with adjacent mobile sandy land as a control. It was found that arthropod dominant taxa from mobile sandy land were significantly distinctive from those from plantations of different shrub size. A considerably lower Sørensen index (i.e., 0.25-0.48) was found between the arthropod communities from mobile sandy land and the canopy of either shrub size, than between those under low and medium/high shrub size (i.e., 0.62 to 0.69). The arthropod total abundance was significantly greater under the shrub canopy of very low size in comparison to that of low and medium shrub size and mobile sandy land, with the intermediate values under shrub canopy of high shrub size. Taxon richness and diversity of arthropod communities were distinctly lower under the shrub canopy of low size in comparison to very low, medium and high shrub size. The shrub size was found to have different effects on the density and richness distribution of arthropod trophic groups (i.e., predators, phytophagous, saprophagous, and omnivorous). It was concluded that shrub plantations could facilitate ground-active arthropod diversity recovery when they were afforested in mobile sandy land. There was a contrasting effect of shrub size on ground-active arthropod diversity recovery versus arthropod abundance when grazing was excluded.

13

Factors Affecting Alien and Native Plant Species Richness in Temperate Nature Reserves of Northern China

Zhang X., Wang H., Wang S., Wang R., Wang Y., Liu J.

Polish Journal of Ecology

|

2017

|

Vol. 65, nr 4

320--333

EN

Understanding the factors affecting the species richness of alien and native plant is a key issue for predicting the spread of alien species and protecting rare and endangered native species in nature reserves. To investigate the factors affecting alien and native species richness in temperate nature reserves of China, we used a database of 25 nature reserves in Shandong Province of northern China, and studied the relationship of alien and native plant species richness with climatic and anthropogenic factors, as well as area and elevation range. We found that most of the nature reserves in Shandong Province have been invaded by alien plant species. The distribution of alien and native species responds to the same climatic factors, and temperature and precipitation exert strong effects on both groups. Alien and native plant species richness are positively correlated. Human activity is more effective for explaining richness of alien than for native species. Simultaneously, human activity has stronger effects on alien herbaceous than on alien woody plants. Our results suggest that native species richness is mainly explained by climatic factors, whereas alien species richness is mainly explained by climatic factors and human activity together.

14

Preparation of Ag nanoparticles-reinforced polyamide 6 nanocomposites by in situ polymerization and investigation of its properties

Xu Q., Feng X., Liu J., Gong P.

Polish Journal of Chemical Technology

|

2017

|

Vol. 19, nr 4

36--40

EN

Polyamide 6 (noted as PA6)/Ag nanocomposites were prepared by an in situ solution polymerization method. AgNO3 was used as filler and was directly reduced to silver nanoparticles resulting in uniformly dispersed nanoparticles in the PA6 matrix. The thermal stability, crystallization, melting performance, and dispersion properties of the PA6/Ag nanocomposites were studied using transmission electron microscopy (TEM), thermogravimetric analysis (TG), differential thermal scanning calorimetry (DSC), X-ray diffraction (XRD), and polarized light microscopy (POM). Furthermore, the mechanical and tribological behaviors of as-prepared nanocomposites were evaluated using universal tensile testing, impact testing, and friction testing machines. The results show that Ag-nanoparticles are evenly dispersed in PA6 and decrease in size with increasing Ag content. Whereas the crystallinity increased with increasing Ag content, the crystallization temperature of the nanocomposites did not change significantly. However, the mechanical and tribological properties of the nanocomposites increased compared with pure PA6.

15

Selective agglomeration of magnetite in entlandite-serpentine system and implication for their separation

Lu J., Yuan Z., Liu J., Li L., Wang N., Meng Q.

Physicochemical Problems of Mineral Processing

|

2017

|

Vol. 53, iss. 2

943--955

EN

In nickel sulfide processing, magnesium silicates (serpentines) can easily form slime coatings or hetero-aggregation on pentlandite surfaces, and hence decrease the pentlandite flotation rate and recovery. In this work, magnetic separation of pentlandite from serpentine using selective magnetic coating through adding magnetite fines as magnetic seeds was investigated. Interactions of magnetite-pentlandite and magnetite-serpentine were calculated by the DLVO (Derjaguin-Landau-Verwey-Overbeek) theory. The results show that the interaction of magnetite-pentlandite was obviously stronger than that of magnetite-serpentine with an external weak magnetic field (4776 A/m-1). Therefore, fine magnetite fractions selectively adhered to the pentlandite surfaces and enhanced its magnetism, resulting in being separated from serpentine by magnetic separation, which was further verified by magnetic coating-magnetic separation and SEM observations.

16

Role of dissolved mineral species in quartz flotation and siderite solubility simulation

Luo X., Wang Y., Ma M., Song S., Zhang Y., Deng J., Liu J.

Physicochemical Problems of Mineral Processing

|

2017

|

Vol. 53, iss. 2

1241--1254

EN

Quartz is, in most cases, the major gangue mineral found in the iron ores. Although it can be activated by calcium at strong alkaline pH, quartz nevertheless, reports to the concentrate with Fe when the iron ores contain siderite. It causes a poor concentrate grade and separation between quartz and iron minerals. The effect of siderite on reverse anionic flotation of quartz from hematite was studied in our previous investigations. In this work, the effect of siderite dissolution on the quartz recovery in the froth product and the effect of pH, ions and temperature on siderite dissolution were investigated. Microflotation, PHREEQC simulation, solution chemistry calculation and Fourier transform infrared spectroscopy (FTIR) measurements were conducted. It was observed that the dissolved species of siderite exhibited negative impact on quartz flotation. This influence became weak to some extent by either stripping the dissolved species or shortening dissolution time. Siderite was easily dissolved in the presence of calcium ion under strong alkaline conditions and its solubility increased with increasing the calcium ion concentrate and temperature. When the calcium ion was added as an activator of quartz under strong alkaline conditions (pH>9.96), calcium existed mainly in the CaCO3 precipitation form according to the solubility rule in the presence of siderite. This form could adsorb onto quartz surfaces and further the chemical reaction between starch and quartz was monitored by FTIR measurements. This study provides a further supplement for previous study. A potential strategy is suggested that finding a collector used at low temperature or flotation under neutral (or weak alkaline) medium is helpful to the reverse flotation of iron ores containing siderite.

17

Adsorption behavior of Zn(II) onto natural minerals in wastewater. A comparative study of bentonite and kaolinite

Chai W., Huang Y., Su S., Han G., Liu J., Cao Y.

Physicochemical Problems of Mineral Processing

|

2017

|

Vol. 53, iss. 1

264--278

EN

In order to remove the harmful metal ions in lead-zinc mineral processing wastewater, two natural clay minerals (bentonite and kaolin) were used as adsorbents and Zn(II) ions were the emphasis in this work. The adsorption behaviors including kinetics and isotherms were investigated by batch experiments. In addition, the adsorption mechanisms were studied by means of zeta potential testing, optical microscope and XRD analysis. The results show that the adsorption process can be best described as the pseudo-second order kinetic model. The adsorption equilibrium data of bentonite and kaolinite can be respectively fitted best by Langmuir and Freundlich models. Thermodynamic studies display that the adsorption of Zn(II) onto clays is non-spontaneous and endothermic. The maximum capacity of Zn(II) adsorbed on bentonite and kaolinite respectively reaches to 79.2 mg·g-1 and 6.35 mg·g-1 at 25 °C. The structural differences of bentonite and kaolinite result in the differences in adsorption behavior and mechanism. The interaction mechanisms of Zn(II) with bentonite and kaolinite involve electrostatic attraction, cation exchange, surface complex and precipitation. Bentonite as adsorbent has the potential to remove Zn2+ better than kaolinite.

18

State Space-Based Method for the DOA Estimation by the Forward-Backward Data Matrix Using Small Snapshots

Liu J.

International Journal of Electronics and Telecommunications

|

2017

|

Vol. 63, No. 3

315--322

EN

In this presentation, a new low computational burden method for the direction of arrival (DOA) estimation from noisy signal using small snapshots is presented. The approach introduces State Space-based Method (SSM) to represent the received array signal, and uses small snapshots directly to form the Hankel data matrix. Those Hankel data matrices are then utilized to construct forward-backward data matrix that is used to estimate the state space model parameters from which the DOA of the incident signals can be extracted. In contrast to existing methods, such as MUSIC, Root-MUSIC that use the covariance data matrix to estimate the DOA and the sparse representation (SR) based DOA which is obtained by solving the sparsest representation of the snapshots, the SSM algorithm employs forward-backward data matrix formed only using small snapshots and doesn't need additional spatial smoothing method to process coherent signals. Three numerical experiments are employed to compare the performance among the SSM, Root-MUSIC and SR-based method as well as Cramér–Rao bound (CRB). The simulation results demonstrate that when a small number of snapshots, even a single one, are used, the SSM always performs better than the other two method no matter under the circumstance of uncorrelated or correlated signal. The simulation results also show that the computational burden is reduced significantly and the number of antenna elements is saved greatly.

19

An investigation of a detection method for a subsurface crack in the outer race of a cylindrical roller bearing

Liu J., Shi Z., Shao Y.

Eksploatacja i Niezawodność

|

2017

|

Vol. 19, no. 2

211--219

PL

Zmęczeniowe pęknięcia podpowierzchniowe, stanowiące jedną z głównych przyczyn uszkodzeń łożysk tocznych powodowanych okresowym działaniem sił kontaktowych i zewnętrznych obciążeń impulsowych, mogą prowadzić do katastrofalnych awarii maszyn wirnikowych. Badania metod wykrywania podpowierzchniowych pęknięć łożysk tocznych mają niezwykle istotne znaczenie dla obsługi serwisowej tych urządzeń. W prezentowanym badaniu, zaproponowano nową metodę detekcji podpowierzchniowych pęknięć w zewnętrznej bieżni łożyska walcowego. Metoda ta opiera się na pomiarze krzywizny oraz gęstości widmowej mocy (PSD) przemieszczeń. Opracowano dynamiczny model łożyska walcowego, w którego zewnętrznej bieżni powstało pęknięcie podpowierzchniowe . Model stworzono przy użyciu pakietu oprogramowania do analizy zjawisk szybkozmiennych metodą elementów skończonych w celu określenia przemieszczeń w dziedzinie czasu. Badano różnice krzywizny i PSD przemieszczeń dla łożyska, w którym powstało pęknięcie podpowierzchniowe w bieżni zewnętrznej łożyska oraz łożyska bez takiego pęknięcia. Różnice te wykorzystano do lokalizacji pęknięć podpowierzchniowych różnych rozmiarów. Wyniki pokazują, że różnice krzywizny i PSD przemieszczeń względem punktów pomiarowych na bieżni zewnętrznej między łożyskami walcowymi, z których jedno charakteryzujące się pęknięciem w warstwie podpowierzchniowej, a drugie nie, mogą być wykorzystywane do wykrywania położenia pęknięcia.

EN

As one of major failure modes of roller bearings due to periodic contact forces and external impulse loads, subsurface cracks caused by fatigues may produce catastrophic failures of rotating machines. Investigations of subsurface crack detection methods for roller bearings are very useful for maintenance purposes of these machines. In this study, a new detection method based on the curvature and power spectral density (PSD) of displacements is presented to detect a subsurface crack in the outer race of a cylindrical roller bearing. A dynamic finite element model of the cylindrical roller bearing with a subsurface crack in its outer race is developed using an explicit dynamics finite element software package to obtain the time-domain displacements. Differences of the curvature and PSD of displacements of the bearing without and with the subsurface crack are investigated, which are used to detect the location of the subsurface crack with different sizes in the outer race of the bearing. The results show that differences of the curvature and PSD of displacements from the measurement points on the outer race of the cylindrical roller bearing without and with the subsurface crack can be used to detect the location of the crack.

20

Enhanced Non-linear Viscoelastic Properties of Polymer Bonded Explosives Based on Graphene and a Neutral Polymeric Bonding Agent

Lin C., He G., Liu J., Pan L., Liu S.

Central European Journal of Energetic Materials

|

2017

|

Vol. 14, no. 4

788--805

EN

During their long-term storage and transport, polymer bonded explosives (PBXs) will be subjected to complex thermal physical environments with combined thermal and mechanical loads. The creep behaviour results in a change of physical and mechanical properties, which consequently influences the explosive performance. In this work, graphene and a neutral polymeric bonding agent (NPBA) were selected to improve the non-linear creep properties of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB)-based PBXs. The results were compared with the creep response of the corresponding PBXs without additives and with graphene alone. It was observed that graphene and an NPBA exhibited a positive effect, improving the creep resistance of TATB-based PBXs. The compressive and tensile strength of 0.5 wt.% graphene-filled PBXs were improved by 5.1% and 29.2%, respectively, compared to raw TATB-based PBXs without additives. The performance of the PBXs was further enhanced by the addition of 0.1 wt.% NPBA. For a given stress and temperature, the TATB-based PBXs with graphene and NPBA deformed significantly less than the PBXs filled with graphene alone.