Wyniki wyszukiwania - BazTech

1

Experiment on pressure characteristics of submerged floating tunnel with different section types under wave condition

Li Q., Jiang S., Chen X.

Polish Maritime Research

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2018

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S 3

54--60

EN

Submerged floating tunnel (SFT for short) is a special underwater traffic structure, and wave load is one of the main environmental loads of SFT structure. In this paper, the 1:60 physical model test of three kinds of SFT in a two-dimensional wave flume is tested. The effects of random irregular waves on the SFT structure under different wave heights and periods are discussed. The study shows that: (1) Compared with circular and polygonal sections, there are multiple local peaks in the elliptical section during the period. with the increase of wave height, the number of local peaks also increases. It suggests that the rotational moment plays an important role in the elliptical section which has a relatively small depth-width ratio. (2) The position of the maximum and minimum pressure in the three kinds of SFT sections is consistent. Their vertical wave forces are all larger than their horizontal wave forces. The increase of vertical wave force relative to horizontal wave force in polygon section is larger than that in elliptical section, and the difference in the circular section is the smallest. (3) Under the same traffic condition, the wave force of the elliptical and polygon section is smaller, but they are more sensitive to the change of wave height, and the increase is obvious. The distribution of wave force in the circular section is more uniform.

2

Leaching kinetic study of Y and Eu from waste phosphors using hydrochloric acid solution containing hydrogen peroxide

Yu M., Jiang Z., Mei G., Chen X.

Physicochemical Problems of Mineral Processing

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2018

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Vol. 54, iss. 2

238--248

EN

The leaching kinetics of Y and Eu from waste phosphors using a hydrochloric acid (HCl) solution containing hydrogen peroxide (H2O2) were investigated. Characterization of the waste phosphors was performed using XRD to ascertain the phases as (Y0.95Eu0.05)2O3 (red phosphors), (Ce0.67Tb0.33)MgAl11O19 (green phosphors), (Ba0.9Eu0.1)Mg2Al16O27 (blue phosphors), and SiO2 (quartz). The influence of factors such as HCl concentration, addition amount of H2O2, temperature, and reaction time on the leaching performance of Y and Eu was investigated. The maximum leaching recoveries of Y (99.87%) and Eu (88.72%) were obtained at 4 M HCl, 0.2 cm3/g H2O2, 60 ℃ temperature, and 180 min of reaction time at a liquid-to-solid ratio of 7.5 cm3/g. Leaching kinetic results showed the best fit with the shrinking sphere model (1-(1-x)1/3)=kct), ensuring that the overall leaching process was governed by a chemical control mechanism. Activation energies of 42.35 and 33.28 kJ/mol were acquired for leaching of Y and Eu, respectively, at 40-70 ℃, which further supports the proposed chemical control leaching process.

3

Tight focusing of radially polarized beams by a devil’s vortex lens

Chen Z., Hu X., Chen X., Wang X., Pu J.

Optica Applicata

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2018

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Vol. 48, nr 3

389--398

EN

Tight focusing of radially polarized beams with a devil’s vortex lens is numerically investigated. Multiple focal spots can be generated in the geometric focus when a radially polarized beam is focused by a high numerical aperture objective in the presence of a devil’s vortex lens. The position of the major focal spot shifts from the geometric focus when a devil’s vortex lens with S = 1 is employed, and the position of the focal spot can be controlled by the numerical aperture of the objective. The intensity components of the major focal spot are influenced by the vortex phase of the devil’s vortex lens. A strong longitudinal component near the optical axis is produced by a devil’s vortex lens without vortex phase, and a nearly pure transversal field is produced by a devil’s vortex lens with vortex phase.

4

Evaluation of genetic diversity and population structure of five yellow catfish Pelteobagrus fulvidraco populations by microsatellite markers

Zhong L., Wang M., Pan J., Li D., Tang S., Bian W., Chen X.

Oceanological and Hydrobiological Studies

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2018

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Vol. 47, No. 2

99--106

EN

Yellow catfish, Pelteobagrus fulvidraco, is an important commercial freshwater species in China. Knowledge about the genetic diversity of the yellow catfish is important to support the management and conservation programs, which would subsequently support the sustainable production of this species. To investigate the genetic diversity and the structure of yellow catfish in the middle and lower reaches of the Yangtze River, 125 individuals from five lakes were genotyped using 13 microsatellite markers. Moderate genetic diversity was determined in all populations, with the observed heterozygosity (HO) ranging from 0.42 to 0.49 and the expected heterozygosity (HE) ranging from 0.51 to 0.61. Low to moderate genetic differentiation among the populations was revealed from pairwise FST values (p < 0.05), as well as from analysis of molecular variance (AMOVA). The UPGMA dendrogram and Bayesian clustering analysis indicated a correlation between genetic differences and geographic distance – four populations from the lower reaches clustered together, whereas the Poyang Lake (PY) population formed a separate cluster. The present study would be helpful in the wild stock management and artificial propagation programs for yellow catfish in the middle and lower reaches of the Yangtze River.

5

Review of the Characteristic Curves of Silkworm Cocoon Hot air Drying and its Technological Configuration

Wei P., Tuo W., Chen J., Chen X., Xie J.

Fibres & Textiles in Eastern Europe

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2018

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Vol. 26, no. 4 (130)

20--28

EN

To pass on Chinese cocoon-drying technology to developing countries, this paper reviews characteristic curves of silkworm cocoon hot air drying and its recent research advances in cocoon-drying technology in China based on the epochal and regional characters of cocoon drying technology development. (1) Three characteristic curves of cocoon drying are systematically explained, each of which can be divided into preheating, constant speed, and deceleration stages. The temperature susceptibility (i.e., the characteristics of response to temperature conditions) curve of the pupa successively shows heating, constant temperature, and heating processes. (2) Changes in the drying speed and temperature susceptibility of a fresh cocoon layer and naked pupae were examined in detail before and after pupae were killed in the preheating stage. It is proposed that heating the cocoons as soon as possible during the preheating stage of cocoon drying improves the work efficiency and cocoon quality. (3) The effects of the temperature and humidity of the hot air on the cocoon drying speed (i.e., speed coefficients) are obtained using the enthalpy psychrometric chart. The parameter configuration of cocoon drying technology is elaborated according to the speed coefficients in combination with the characteristic curves of cocoon drying and the influence of the laws of cocoon drying technology on cocoon quality. Furthermore, problems in the technological configuration and the direction of future development are noted.

PL

Aby przekazać chińską technologię suszenia kokonów krajom rozwijającym się, w artykule przedstawiono charakterystyczne krzywe suszenia gorącym powietrzem kokonu jedwabnika oraz najnowsze osiągnięcia w dziedzinie technologii suszenia kokonów w Chinach w oparciu o epokowe i regionalne cechy technologii suszenia kokonów. Przedstawiono trzy charakterystyczne krzywe suszenia kokonów, które można podzielić na etapy podgrzewania wstępnego, stałej prędkości i spowalniania. Zbadano szczegółowo zmiany w szybkości i prędkości suszenia świeżej warstwy kokonu i nagich poczwarek przed i po zabiciu poczwarek na etapie wstępnego podgrzewania. Zaproponowano jak najszybsze podgrzewanie kokonów podczas etapu wstępnego suszenia kokonu, co wpływa na poprawę wydajność pracy i jakość kokonu. Wpływ temperatury i wilgotności gorącego powietrza na prędkość suszenia kokonu (tj. współczynniki prędkości) oceniono stosując wykres psychrometryczny entalpii. Konfigurację parametrów technologii suszenia kokonów opracowywano na podstawie analizy uzyskanych współczynników prędkości, charakterystyk krzywych suszenia kokonu i wpływu technologii suszenia na jakość kokonu.

6

Nonlinear damage accumulation of concrete subjected to variable amplitude fatigue loading

Chen Y., Chen X., Bu J.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2018

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Vol. 66, nr 2

157--163

EN

To account for the load sequence effect, damage fatigue models with nonlinearity in propagation and accumulation have been developed. This paper reviews five classical nonlinear fatigue models used to predict the life times of concrete under variable amplitude loadings. Experimental results from literature are used to validate the five classical prediction models. It can be found that Hilsdorf and Kesler model yields unsafe or conservative predictions, and the other four models are more suitable for predicting life times of concrete. In this paper, the author used a new nonlinear damage model based on the nonlinear continuum damage mechanics to predict fatigue life of concrete. The model considers fatigue limit, loading parameters, the unseparable characteristics for the damage parameter and the load sequence effect. The validity of the nonlinear fatigue damage model is checked against tests from literature.

7

Failure mechanism and supporting measures for large deformation of soft rock roadway in Baluba copper mine

Wu A., Chen S., Wang Y., Chen X.

Archives of Mining Sciences

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2018

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Vol. 63, no. 2

449--464

EN

To solve the problem of large deformation soft rock roadway with complicated stress condition in Baluba copper mine, the characteristics of roadway deformation and failure modes are analyzed deeply on the basis of geological survey. Combined with the theoretical analysis and numerical simulation, the new reinforcement technology with floor mudsill and grouting anchor cable is proposed. Moreover, the three dimension numerical simulation model is established by the software FLAC-3D, the support parameter is optimized by it. The results show that the optical array pitch of the U-steel shelf arch is 0.8 m, and the optical array pitch of the grouting anchor cable is 2.4 m. At last, the field experiments are done all over the soft rock roadway. Engineering practice shows that the deformation of soft rock roadway in Baluba copper mine is effectively controlled by adopting the new reinforcement technology, which can provide certain references for similar engineering.

PL

W celu rozwiązania problemu powstawania znacznych odkształceń chodnika biegnącego w skale miękkiej w skomplikowanym układzie naprężeń, przeprowadzono dogłębną analizę warunków odkształceń i pękania skał w oparciu o badania geologiczne. W oparciu o rozważania teoretyczne i symulacje numeryczne, zaproponowano nową technologię wzmocnienia progu spągowego z iłowców z linami kotwiącymi osadzonymi w zaprawie. Na podstawie trójwymiarowego modelu do symulacji numerycznych opracowanego z wykorzystaniem oprogramowania FLAC-3D dokonano optymalizacji parametrów podpór. Wyniki pokazują, że optymalne rozmieszczenie stalowych podpór wykonanych z profili w kształcie U wyniesie 0.8 m, zaś optymalny rozstaw mocowań lin wynosi 2.4 m. W końcowym etapie przeprowadzono eksperymenty terenowe na całej długości chodnika. Praktyka inżynierska wskazuje, że odkształcenia chodników prowadzonych w skałach miękkich w kopalni Baluba mogą być skutecznie kontrolowane poprzez zastosowanie nowej metody wzmocnienia, która stanowić może podstawę dla opracowywania skutecznych technik wzmacniania stropu w chodnikach prowadzonych w podobnych warunkach geologicznych.

8

Excessive tensile strain induced the change in chondrocyte phenot

Zhong D., Chen X., Luo Z.-P.

Acta of Bioengineering and Biomechanics

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2018

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Vol. 20, no. 2

3--10

EN

Chondrocyte extracellular matrix type II collagen and proteoglycans ensure an important compression-bearing structure in synovial joint. However, much more type I collagen is generated in osteoarthritis, which implies the presence of abnormal tensile strain in cartilage. We hypothesize that tensile stress influences chondrocyte phenotype at the cellular level, leading to potential osteoarthritis. Methods: Chondrocytes were stimulated with cyclic excessive tensile (10%) or mild tensile or compressive strain (5%) at 0.5 Hz, 3 h per day for 3 days. Chondrocyte morphology and matrix proteoglycans level was separately determined by Rhodamine phalloidin and toluidine blue staining. The expression of cartilage marker molecules was measured using quantitative reverse transcription polymerase chain reaction and enzyme-linked immunosorbent assays. Results: Chondrocytes demonstrated significant fibroblastic morphology, reduced proliferation and increased apoptosis following exposure to 10% tensile strain. The 10% tensile strain group induced the lowest matrix proteoglycans level. It observably reduced the expression of COL2A1, Acan and SOX9, and increased COL1A1 expression level. The 5% tensile (5% compression) group, maintained the chondrocyte phenotype. Conclusions: The findings identified the effects of different magnitudes of tensile stress on chondrocyte phenotype compared to compressive strain. Further studies on cartilage biomechanical micro-environment might benefit from this study.

9

Simulation of the Microtremor H/V Spectrum Based on the Theory of Surface Wave Propagation in a Layered Half-space

Zhang Z., Chen X., Gao M., Li Z., Li Q.

Acta Geophysica

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2018

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Vol. 66, no. 2

121--130

EN

Subsurface velocity structures must be estimated to predict longperiod ground motions and seismic hazards. Subsurface velocity structures can be constructed via an inversion of the horizontal-to-vertical (H/V) spectral ratio of microtremor (MHV) curves; thus, a method of simulating the MHV curves is key. In this study, we use the H/V spectral ratio of the surface wave (SHV) based on the surface wave propagation theory in a layered half-space to simulate the MHV curves at sites A and B of the Yuxi basin. Then, we attempt to analyze the features of the SHV curves. We find the H/V ratio of the microtremor loading source to be independent of the peak frequency of the SHV curve, but it has some relation to the amplitude of the SHV curve. Moreover, to reduce the error in subsurface velocity structures obtained by the MHV curves, we suggest that the SHV curves at near-peak frequencies should not be considered in the inversion, because the amplitude deviation is higher at the peak frequency of the MHV curve. In addition, the best frequency ranges for the inversion of the microtremor H/V spectrum are between the peak and trough frequencies of the microtremor H/V spectrum.

10

Sensitivity analysis study of the source parameter uncertainty factors for predicting near-field strong ground motion

Li Z., Gao M., Jiang H., Chen X., Li T., Zhao X.

Acta Geophysica

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2018

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Vol. 66, no. 4

523--540

EN

Uncertainty factors have substantial influences on the numerical simulations of earthquakes. However, most simulation methods are deterministic and do not sufficiently consider those uncertainty factors. A good approach for predicting future destructive earthquakes that is also applied to probabilistic hazard analysis is studying those uncertainty factors, which is very significant for improving the reliability and accuracy of ground-motion predictions. In this paper, we investigated several uncertainty factors, namely the initial rupture point, stress drop, and number of sub-faults, all of which display substantial influences on ground-motion predictions, via sensitivity analysis. The associated uncertainties are derived by considering the uncertainties in the parameter values, as those uncertainties are associated with the ground motion itself. A sensitivity analysis confirms which uncertainty factors have large influences on ground motion predictions, based upon which we can allocate appropriate weights to those uncertainty factors during the prediction process. We employ the empirical Green function method as a numerical simulation tool. The effectiveness of this method has been previously validated, especially in areas with sufficient earthquake record data such as Japan, Southwest China, and Taiwan, China. Accordingly, we analyse the sensitivities of the uncertainty factors during a prediction of strong ground motion using the empirical Green function method. We consequently draw the following conclusions. (1) The stress drop has the largest influence on ground-motion predictions. The discrepancy between the maximum and minimum PGA among three different stations is very large. In addition, the PGV and PGD also change drastically. The Arias intensity increases exponentially with an increase in the stress drop ratio of two earthquakes. (2) The number of sub-faults also has a large influence on various ground-motion parameters but a small influence on the Fourier spectrum and response spectrum. (3) The initial rupture point largely influences the PGA and Arias intensity. We will accordingly pay additional attention to these uncertainty factors when we conduct ground-motion predictions in the future.

11

The application of E-learning in maritime education and training in China

Chen X., Bai X., Xiao Y.

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

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2017

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Vol. 11, no. 2

349--354

EN

E-learning brings the third wave to Internet applications. E-learning is a new training mode with the open characteristics, which is completely different with traditional training. E-learning teaches students the specialized knowledge of theories, work experience and technology by information networks and computer hardware equipment. Students can through a variety of terminal equipment to learn anytime and anywhere, so as to improve student learning results. Maritime education and training must conform to the trend of times to explore E-learning training to improve the training performance. In this paper, based on the theory of E-learning, comparing the advantages and disadvantages of E-learning training. By analyzing current status of maritime education and training, using E-learning to establish China's maritime education and training of the lifelong education system, using E-learning to promote the internationalization of navigation education and training.

12

Effect of water flows on ship traffic in narrow water channels based on cellular automata

Hu H., Chen X., Sun Z.

Polish Maritime Research

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2017

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S 3

130--135

EN

In narrow water channels, ship traffic may be affected by water flows and ship interactions. Studying their effects can help maritime authorities to establish appropriate management strategies. In this study, a two-lane cellular automation model is proposed. Further, the behavior of ship traffic is analyzed by setting different water flow velocities and considering ship interactions. Numerical experiment results show that the ship traffic density-flux relation is significantly different from the results obtained by classical models. Furthermore, due to ship interactions, the ship lane-change rate is influenced by the water flow to a certain degree.

13

Joint optimization of replacement and spare ordering for critical rotary component based on condition signal to date

Chen X., Xu D., Xiao L.

Eksploatacja i Niezawodność

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2017

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Vol. 19, no. 1

76--85

EN

It is widely accepted that condition-based replacement can not only make full use of components, but also decline inventory cost if the procurement of spare parts can be triggered upon accurate failure prediction. Most of the existing degradation or failure prediction models and approaches are population-based failures or suspensions, namely, to predict the failure time of a component, there are some failure or suspension histories of same type or similar components which can be used as reference. However, in practice, there exists the phenomenon in which no failure or suspension histories for some components can be used, what can be utilized is just the collected condition monitoring signals to date. In that case, failure time and probability are difficult to be estimated accurately. In this paper, a novel degradation prediction approach is introduced. Meantime, a new failure probability estimation function is developed based on component “service time” and “degradation extent” simultaneously. Then replacement and spare part ordering are jointly optimized according to the estimated failure probability. The optimization objective is to minimize long-run cost rate. Two bearing datasets are used to validate the proposed approach.

PL

Powszechnie przyjmuje się, że wymiana w oparciu o stan techniczny pozwala nie tylko na pełne wykorzystanie elementów składowych, ale także na zmniejszenie kosztów magazynowych (związanych z przechowywaniem zapasów) jeśli zamawianie części zamiennych da się powiązać z trafnym prognozowaniem uszkodzeń. Większość istniejących modeli i teorii predykcji degradacji lub uszkodzeń opiera się na danych populacyjnych o uszkodzeniach lub zawieszeniu pracy co oznacza, że czas uszkodzenia komponentu przewiduje się w odniesieniu do historii uszkodzeń lub zawieszeń pracy tego samego typu lub podobnego typu elementów składowych. Jednak w praktyce zdarza się, że dla niektórych komponentów nie istnieją historie uszkodzeń lub zawieszenia pracy, do których można by się odnieść; jedyne co można wykorzystać to zgromadzone dotychczas sygnały z monitorowania stanu. W takim przypadku, trudno jest ocenić dokładnie czas i prawdopodobieństwo wystąpienia uszkodzenia. W niniejszej pracy, przedstawiono nowatorskie podejście do przewidywania degradacji. Opracowano nową funkcję szacowania prawdopodobieństwa uszkodzenia opartą na jednoczesnym wykorzystaniu "czasu pracy" oraz "stopnia degradacji" komponentu. Następnie wspólnie zoptymalizowano procesy wymiany i zamawiania części zamiennych zgodnie z szacowanym prawdopodobieństwem wystąpienia uszkodzenia. Celem optymalizacji była minimalizacja długoterminowego wskaźnika kosztów . Poprawność proponowanego podejścia zweryfikowano z wykorzystaniem dwóch zbiorów danych dotyczących łożysk.

14

Consistency analysis of degradation mechanism in step-stress acc elerated degradation testing

Lu X., Chen X., Wang Y., Tan Y.

Eksploatacja i Niezawodność

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2017

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Vol. 19, no. 2

302--309

EN

Step-stress accelerated degradation testing (SSADT) has been used by many researchers for the reliability assessment of highly reliable products. Most of the previous works on SSADT assume that the degradation mechanism keeps unchanged during the accelerated degradation testing. However, some recent investigations have shown that degradation mechanisms may be different among various accelerated stress levels. For an accurate extrapolation of accelerated testing results to the ambient condition, the degradation mechanism at all accelerated stress levels should be the same. Taking the variation of the degradation mechanism into account, it is advisable to test the degradation mechanism consistency in a SSADT. This paper proposes a likelihood ratio test method for the consistency analysis of degradation mechanism in the SSADT. We first introduce the basic principle of the likelihood ratio test method. Then we describe the model for SSADT data and the parameter estimation method. Further, we propose a decision rule for the consistency analysis. The proposed method is illustrated and validated with examples on the consistency analysis of degradation mechanism in a SSADT of silicone rubbers.

PL

Wielu badaczy wykorzystuje przyspieszone badania degradacji z obciążeniem stopniowym (ang. step-stress accelerated degradation testing, SSADT) do oceny niezawodności wysoce niezawodnych produktów. Większość wcześniejszych prac nad SSADT zakłada, że podczas badań przyspieszonych mechanizm degradacji pozostaje niezmienny. Jednak, najnowsze badania wykazały, że mechanizmy degradacji mogą różnić się w zależności od poziomu przyspieszonego obciążenia. Poprawna ekstrapolacja wyników badań przyspieszonych na warunki otoczenia wymaga aby mechanizm degradacji przy wszystkich poziomach obciążenia był taki sam. Biorąc pod uwagę zmienność mechanizmu degradacji, wskazane jest badanie stopnia (nie)zmienności mechanizmu degradacji w badaniach SSADT. W artykule zaproponowano metodę analizy niezmienności mechanizmu degradacji w badaniach SSADT opartą na teście ilorazu wiarygodności. W pierwszej kolejności, przedstawiono podstawową zasadę testu ilorazu wiarygodności. Następnie, opisano model dla danych SSADT i metodę estymacji parametrów. Ponadto zaproponowano regułę decyzyjną stanowiąca narzędzie do analizy niezmienności. Omawianą metodę zilustrowano i zweryfikowano na przykładzie analizy niezmienności mechanizmu degradacji w badaniach SSADT gumy silikonowej.

15

Polymer Reinforced DNAN/RDX Energetic Composites: Interfacial Interactions and Mechanical Properties

Qian W., Chen X., Luo G.

Central European Journal of Energetic Materials

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2017

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Vol. 14, no. 3

726--741

EN

2,4-Dinitroanisole (DNAN) has excellent properties as a replacement for 1,3,5-trinitrotoluene (TNT) in melt-cast explosives, and the polymeric modifier used is critical to the mechanical modification of the DNAN/RDX energetic composite. In our research, the typical polymeric modifier acrolein-pentaerythritol resin (APER) was successfully added experimentally to the DNAN/RDX system, and the effects of interfacial interactions on the mechanical properties of these polymers in reinforcing the DNAN/RDX energetic composites were investigated by molecular dynamics simulations, scanning electron microscopy (SEM) and mechanical testing. The results showed that strong attractive interactions exist between the polymer and the explosives, wherein van der Waals forces were found to play the main role. The morphological micro-images also showed tight binding between the polymer/explosive interfaces, which supported the calculated strong interfacial interactions. The mechanical tests confirmed that adding the polymers can obviously reinforce the mechanical strength and toughness of DNAN/RDX systems. The above observations revealed that the cooperative effects of the APER polymer can help to reinforce the interfacial interactions and mechanical properties of DNAN/RDX composites, which is of importance in the formulation and mechanical evaluation of advanced energetic composites.

16

Key preprocessing technology and its application for CBM AVO analysis

Liu Z., Si G., Chen X., Wang Q., Deng S.

Acta Geophysica

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2017

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Vol. 65, no. 5

1069--1079

EN

The hazards of amplitude versus offset (AVO) technique mostly applied in seismic explorations for predicting coalbed methane (CBM) content mainly derive from multi-stage amplitude modifications during seismic signal preprocessing. The modifications are undoubtedly necessitated by improving high signal-to-noise ratio (SNR) and high resolution, and achieve high fidelity to some extent; and nevertheless lead to an unfavorable possibility to implement CBM AVO analysis. Similar to sand-stone reservoir with gas, AVO analysis preprocessing for CBM reservoir strictly abides by a relative amplitude preserved (RAP) principle and particularly emphasizes on preserving the evanescent class IV AVO anomaly. As for those indispensable dealings with linear noise attenuations, near-surface variety compensations and time/depth spatial imaging, the key technologies adapted to CBM AVO preprocessing should use radial trace (RT) filter, refined surface-consistent amplitude compensation (SCAC), and RAP Kirchhoff prestack time migration (PSTM). The theoretical analysis and one real 3D example in this paper demonstrate that three key technologies compliant to RAP principle in CBM AVO preprocessing can preserve the class IV AVO anomaly and benefit an operation of CBM AVO analysis and an improvement of CBM evaluation.

17

Lifetime prediction of self-lubricating spherical plain bearings based on physics-of-failure model and accelerated degradation test

Wang Y., Fang X., Zhang C., Chen X., Lu J.

Eksploatacja i Niezawodność

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2016

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Vol. 18, no. 4

528--538

EN

Due to small friction coefficient and no need for lubrication during operation, self-lubricating spherical plain bearings (SSPBs) have been widely used in operation and transmission systems in aerospace, nuclear power plants, and ship equipment and they are key components of these systems. SSPBs failure will directly affect the operational reliability and safety of the equipment; therefore, it is necessary to accurately predict the service life of SSPBs to define reasonable maintenance plans and replacement cycles and to ensure reliability and safety of vital equipment. So far, lifetime prediction of SSPB has been primarily based on empirical formulae established by most important bearing manufacturers. However, these formulae are lack of strong theoretical basis; the correction coefficients are difficult to determine, resulting in low accuracy of lifetime prediction. In an accelerated degradation test (ADT), the load is increased to accelerate the SSPB wear process. ADT provides a feasible way for accurate lifetime prediction of SSPB in a short period. In this paper, wear patterns are studied and methods of wear analysis are presented. Then, physics-offailure model which considers SSPB wear characteristics, structure parameters and operation parameters is established. Moreover, ADT method for SSPB is studied. Finally, lifetime prediction method of SSPBs based on physics-of-failure model and ADT is established to provide a theoretical method for quick and accurate lifetime prediction of SSPBs.

PL

W związku z niskim współczynnikiem tarcia oraz brakiem konieczności smarowania podczas pracy,samosmarujące łożyska ślizgowe (self-lubricating spherical bearings, SSPB) znajdują szerokie zastosowanie w układach pracy oraz układach przełożeń urządzeń w przemyśle lotniczym, elektrowniach jądrowych, oraz na statkach, stanowiąc kluczowe elementy tych układów. Uszkodzenie łożyska SSPB ma bezpośredni wpływ na niezawodność eksploatacyjną oraz bezpieczeństwo sprzętu; dlatego też istnieje konieczność precyzyjnego prognozowania resursu łożysk SSPB, pozwalającego na odpowiednie planowanie konserwacji oraz cykli wymiany , które ma na celu zapewnienie niezawodności i bezpieczeństwa kluczowego sprzętu. Dotychczas czas pracy łożysk SSPB prognozowano przede wszystkim w oparciu o wzory empiryczne podawane przez największych producentów łożysk. Wzory te, jednak, nie mają solidnej podstawy teoretycznej; trudno jest dla nich określić współczynniki korygujące, co zmniejsza trafność prognozowania czasu pracy. W przyspieszonych badaniach degradacji zwiększa się obciążenie celem przyspieszenia procesu zużycia łożysk SSPB. Badania przyspieszone umożliwiają trafne przewidywanie czasu pracy łożysk SSPB w krótkim okresie czasu. W przedstawionej pracy analizowano wzorce zużycia badanych łożysk oraz przedstawiono metody analizy zużycia. Następnie opracowano model fizyki uszkodzeń, który uwzględnia charakterystyki zużycia, parametry konstrukcyjne oraz parametry eksploatacyjne omawianych łożysk ślizgowych. Ponadto rozpatrywano możliwość zastosowania badań przyspieszonych dla tego typu łożysk. W wyniku przeprowadzonych badań, opracowano metodę prognozowania czasu pracy łożysk SSPB opartą na modelu fizyki uszkodzeń oraz badaniach przyspieszonych, która pozwala na szybkie i trafne prognozowanie czasu pracy samosmarujących łożysk ślizgowych.

18

The Reinforcement of the TNT System by a Newly-designed GAP-based Polyurethane-Urea: a Molecular Simulation Investigation

Qian W., Shu Y., Ma Q., Li H., Wang S., Chen X.

Central European Journal of Energetic Materials

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2016

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Vol. 13, no. 2

411--426

EN

A glycidyl azide (GAP)-based polyurethane-urea (PUU) modifier used in the 1,3,5-trinitrotoluene (TNT)-based composite explosive was investigated by molecular simulation. Inter-molecular interactions were investigated using quantum chemistry calculation on the dimer of TNT and GAP-PUU, and attractive forces were found between the two molecules. The cohesive energy densities and the solubility parameters were obtained through molecular dynamics simulations combined with thermodynamic calculations on the TNT and GAP-PUU amorphous cell models, and the miscibility of the modifier in molten TNT was predicted to be good. The interaction energies and the mechanical properties were then obtained by molecular simulations and mechanical calculations on the solid-phase models of the GAP-PUU with TNT along three crystalline directions, and an improvement in the mechanical properties was predicted.

19

Adaptive strategy to drought conditions: diurnal variation in water use of a Central Asian desert shrub

Wang S-S., Chen X., Zhou K.-F., Wang Q.

Polish Journal of Ecology

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2015

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Vol. 63, nr 1

63--76

EN

Water availability is one of the most important factors limiting photosynthetic assimilation of carbon dioxide and growth of individual plants in terrestrial ecosystems. It is especially important for desert shrubs because the diurnal water availability is particularly sensitive to climate change in arid ecosystems. Water use efficiency (WUE) is an indicator of water availability and is frequently used to assess plant performance in various ecosystems, particularly in arid ecosystems. The WUE of plants has been widely assessed using ecological methods and field measurements; however, these approaches are impractical to obtain numerous near-simultaneous estimates of plant water status at the landscape-scale. Consequently, landscape-scale assessments of plant water status are practically pursued through modeling. In this study, measurement and modeling of the diurnal variations of WUE were conducted for a native dominant desert shrub, Tamarix ramosissima, in its original habitat on the periphery of the Gurbantunggut Desert, China. The diurnal net photosynthesis (An), stomatal conductance (gs), and transpiration (Tr) were measured for each individual using a portable photosynthesis system. A coupled model of stomatal conductance, photosynthesis, and transpiration was applied to simulate the diurnal dynamics of An, gs, Tr, and WUE. The model explained 83, 47, 83, and 55% of the variance in the measured An, gs, Tr, and WUE values, respectively, for this desert ecosystem in which T. ramosissima is sparsely distributed. The results demonstrated that the coupled photosynthesis-stomatal conductance-transpiration model strategy is a promising approach to estimate water availability in desert ecosystems in Central Asia.

20

An integrated model of production scheduling and maintenance planning under imperfect preventive maintenance

Chen X., Xiao L., Zhang X., Xiao W., Li J.

Eksploatacja i Niezawodność

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2015

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Vol. 17, no. 1

70--79

EN

For a successful company, machines are always required to work continuously to make more profit in a certain period. However, machines can be unavailable due to the scheduled maintenance activities or unexpected failures. Hence, a model connected production scheduling with maintenance planning for a production line which is composed of multiple machines is developed. Suppose preventive maintenance is imperfect and cannot renew all the machines. Age reduction factor and hazard rate increase factor are introduced to illustrate the imperfect character. Aperiodic preventive maintenance policy is adopted. Replacement as perfect maintenance could restore the machine “as good as new”. When and whether to perform replacement is based on a cost-time rate function which is defined to judge whether or not the preventive maintenance is economical. The objective of the joint model is to maximize the total profit which is composed of production value, production cost, maintenance cost (including the preventive maintenance cost and replacement cost), and tardiness cost (which is related to the job sequence and maintenance activities). To optimize the objective, immune clonal selection algorithm is utilized. The proposed model is validated by a numerical example.

PL

Aby firma mogła działać z powodzeniem i przynosić większe zyski w danym okresie czasu, zainstalowane w niej maszyny muszą pracować w sposób nieprzerwany. Niestety, z powodu planowych działań obsługowych lub nieoczekiwanych awarii, maszyny są czasami wyłączane z produkcji. Dlatego też w niniejszym artykule opracowano model łączący harmonogramowanie produkcji z planowaniem obsługi technicznej dla linii produkcyjnej złożonej z wielu maszyn. W pracy założono, że konserwacja zapobiegawcza jest niepełna i nie prowadzi do odnowy wszystkich maszyn. Aby zilustrować jej niepełny charakter, wprowadzono pojęcia czynnika redukcji wieku oraz czynnika wzrostu wskaźnika zagrożenia. Przyjęto politykę nieokresowej konserwacji zapobiegawczej. Wymiana jako forma pełnej konserwacji pozwala na przywrócenie maszyny do stanu "fabrycznej nowości". Kiedy i czy należy przeprowadzić wymianę zależy od funkcji wskaźnika kosztu w stosunku do czasu, który pozwala ocenić, czy konserwacja zapobiegawcza jest opłacalna. Model zintegrowany ma na celu maksymalizację całkowitego zysku, który jest wypadkową wartości produkcji, kosztów produkcji, kosztów obsługi (w tym kosztów konserwacji zapobiegawczej oraz kosztów wymiany) i kosztów nieterminowego zakończenia zadania (ang. lateness, związanych z kolejnością wykonywanych zadań i czynności obsługowych). Aby zoptymalizować opisany cel, wykorzystano algorytm odpornościowej selekcji klonalnej Proponowany model zweryfikowano na przykładzie liczbowym.