Wyniki wyszukiwania - Biblioteka Nauki

1

Nonlinear degradation modeling and maintenance policy for a two-stage degradation system based on cumulative damage model

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Ni X. , Zhao J. , Song W. , Guo C. , Li H.

Eksploatacja i Niezawodność

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2016

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tom Vol. 18, no. 2

171--180

EN

This paper attempts to take into account a two-stage degradation system which degradation rate is non-stationary and change over time. The system degradation is thought to be caused by shocks, and system degradation model is established based on cumulative damage model. The nonlinear degradation process is expressed by different shock damage and shock counting. And shock damage and shock counting are assumed to be Gamma distribution and non-homogeneous Poisson process, respectively. On the basis of these, system reliability model and nonlinear degradation model are given. In order to optimal maintenance policy for considered system, adaptive maintenance policy and time-dependent maintenance policy are studied, and mean maintenance cost rate is established to evaluate the maintenance policies. Numerical examples are given to analyze the influences of degradation model parameters and find optimal maintenance policy for considered system.

PL

W przedstawionym artykule badano system, w którym proces degradacji zachodzi dwuetapowo, a szybkość degradacji jest zmienna w czasie. Przyjęto, że do degradacji systemu dochodzi w wyniku wstrząsów. Model degradacji systemu oparto na modelu sumowania uszkodzeń. Nieliniowy proces degradacji określono jako taki, w którym uszkodzenie powodowane wstrząsem oraz częstotliwość wstrząsów są wartościami zmiennymi. Przyjęto, że uszkodzenie powodowane wstrząsem ma rozkład gamma a częstotliwość wstrząsów jest niejednorodnym procesem Poissona. Na tej podstawie utworzono model niezawodności systemu oraz model degradacji nieliniowej. W celu opracowania optymalnej strategii eksploatacji dla rozpatrywanego systemu, rozważono dwa typy strategii utrzymania ruchu: strategię adaptacyjną oraz strategię czasowo-zależną. Strategie te oceniano określając średni poziom kosztów eksploatacji. Przykłady numeryczne posłużyły do analizy wpływu parametrów modelu degradacji oraz pozwoliły określić optymalną strategię utrzymania dla rozpatrywanego systemu.

2

The feedback stability research of HDRI system

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Chen Z. , Shen C. , Xu J. , Ni X. , Lu Z.

Optica Applicata

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2009

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tom Vol. 39, nr 2

357-363

EN

In this paper, one kind of high dynamic range imaging (HDRI) system is analyzed and the feedback stability is optimized. In this system, space light modulator (SLM) is used to modulate the input illuminance with the feedback signals. Because of the illuminance uncertainty of the scene, the feedback may take too long or turn into oscillations. To acquire the optimized feedback configuration, PID theory is used to analyze the feedback process. After PID parameter is obtained, simulations are applied to study the parameters. The optimized value range and principle of choice for the feedback control are discussed. Lastly, imaging experiments are conducted to obtain high dynamic range images, and the results prove the validity of PID parameters.

3

An Early Miocene microtoid cricetid rodent from the Junggar Basin of Xinjiang, China

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Maridet O. , Wu W. , Ye J. , Meng J. , Bi S. , Ni X.

Acta Palaeontologica Polonica

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2014

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tom 59

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nr 1

EN

Microtoid cricetids are widely considered to be the ancestral form of arvicoline rodents, a successful rodent group includ− ing voles, lemmings and muskrats. The oldest previously known microtoid cricetid is Microtocricetus molassicus from the Late Miocene (MN9, ca. 10–11 Ma) of Europe. Here, we report a new microtoid cricetid, Primoprismus fejfari gen. et sp. nov., from the Junggar Basin of Xinjiang, northwestern China. The rodent assemblage found in association with this specimen indicates a late Early Miocene age, roughly estimated at 18–17 Ma, and thus more than 6 million years older than M. molassicus. While morphological comparisons suggest that the new taxon is most closely related to M. molas− sicus, it differs from the latter in a striking combination of primitive characters, including a lower crown, smaller size, a differentiated posterolophid and hypolophid, a faint anterolophid, the absence of an ectolophid, and the presence of a stylid on the labial border of the tooth. Arid conditions prevailing across the mid−latitude interior of Eurasia during the Early Miocene, enhanced by the combined effects of the Tibetan uplift and the gradual retreat of the Tethys Ocean, likely played a role in the appearance of grasslands, which in turn triggered the evolution of microtoid cricetids and, ultimately, the origin of arvicoline rodents.

4

Increased expression and functionality of the gap junction in peripheral blood lymphocytes is associated with hypertension-mediated inflammation in spontaneously hypertensive rats

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Ni X. , Li X. , Fan Z. , Zhang H. , Li L. , Si J.

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tom 23

EN

Background: Imbalances in circulating T lymphocytes play critical roles in the pathogenesis of hypertension-mediated inflammation. Connexins (Cxs) in immune cells are involved in the maintenance of homeostasis of T lymphocytes. However, the association between Cxs in peripheral blood T lymphocytes and hypertensionmediated inflammation remains unknown. This study was designed to investigate the role of Cxs in T lymphocytes in hypertension-mediated inflammation in spontaneously hypertensive rats (SHRs). Methods: The systolic blood pressure (SBP) in Wistar-Kyoto (WKY) rats and SHRs was monitored using the tail-cuff method. The serum cytokine level was determined using ELISA. The proportions of different T-lymphocyte subtypes in the peripheral blood, the expressions of Cx40/Cx43 in the T-cell subtypes, and the gap junctional intracellular communication (GJIC) of peripheral blood lymphocytes were measured using flow cytometry (FC). The accumulations of Cx40/Cx43 at the plasma membrane and/or in the cytoplasm were determined using immunofluorescence staining. The in vitro mRNA levels of cytokines and GJIC in the peripheral blood lymphocytes were respectively examined using real-time PCR and FC after treatment with Gap27 and/or concanavalin A (Con A). Results: The percentage of CD4+ T cells and the CD4+ /CD8+ ratio were high, and the accumulation or expressions of Cx40/Cx43 in the peripheral blood lymphocytes in SHRs were higher than in those of WKY rats. The percentage of CD8+ and CD4+ CD25+ T cells was lower in SHRs. The serum levels of IL-2, IL-4 and IL-6 from SHRs were higher than those from WKY rats, and the serum levels of IL-2 and IL-6 positively correlated with the expression of Cx40/Cx43 in the peripheral blood T lymphocytes from SHRs. The peripheral blood lymphocytes of SHRs exhibited enhanced GJIC. Cx43-based channel inhibition, which was mediated by Gap27, remarkably reduced GJIC in lymphocytes, and suppressed IL-2 and IL-6 mRNA expressions in Con A stimulated peripheral blood lymphocytes.

5

Numerical study on thermal stress cutting of silicon wafer using two-point pulsed laser

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Liu J. , Lu J. , Ni X. , Dai G. , Zhang L. , Chen Y.

Optica Applicata

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2011

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tom Vol. 41, nr 1

247--255

EN

Laser cutting using the controlled fracture technique has great potential to be used for the separation of brittle materials. In this technique, thermal stress is used to induce the crack and the material is separated along the moving direction by extending the crack. In this paper, based on the heat transfer theory, a three-dimensional thermoelastic finite element model which contains a pre-existing crack is established for a two-point pulsed Nd:YAG laser cutting silicon wafer. The mechanism of crack propagation is investigated. Meanwhile the effects of laser power and the distance between the two laser spots on the development of thermal stress are investigated. The numerical results show that the thermal stress is affected by laser power and the distance between the two laser spots, an increase in the laser power for the same distance between the two laser spots or a decrease in the distance between the two laser spots with constant laser power can induce the increase in the cutting speed.

6

Temperature field analysis of optical coatings induced by millisecond and nanosecond lasers

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Wang B. , Qin Y. , Ni X. , Shen Z. , Lu J. , Wang X.

Optica Applicata

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2012

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tom Vol. 42, nr 4

783--793

EN

To study the differences between long-pulse and short-pulse laser-induced damage in optical dielectric thin films, temperature distributions in single-layer HfO2 films, multi-layer HfO2/SiO2 films, and HfO2 films with high-absorptive inclusions induced by 1 ms and 10 ns lasers are analyzed based on the temperature field theory. Through our calculations, the damage property differences between millisecond and nanosecond lasers are summarized. The results for single-layer films show that 1 ms laser is easier to damage the substrate than 10 ns laser. For multi-layer films, the laser field effect is weaker when irradiating by 1 ms laser. Furthermore, when inclusions are introduced, the film is easier to be damaged by 10 ns laser, which means that 10 ns laser is more sensitive to the inclusions.

7

Alterations in the proteome of wheat primary roots after wortmannin application during seed germination

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Cao H. , Ni X. , Zhang C. , Shi W. , Xu Y. , Yan Y. , Zhang F.

Acta Physiologiae Plantarum

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2017

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tom 39

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nr 10

8

Parameter optimization of double-excess runoff generation model

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Ren B. , Liang J. , Yan B. , Lei X. , Fu W. , Ni. X. , Guo J.

Polish Journal of Environmental Studies

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2018

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tom 27

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nr 2

EN

Research on the optimization of hydrological model parameters is an important issue in the field of hydrological forecasts, as these parameters not only directly impact the accuracy of forecast programs, but also relate to the development, application, and popularization of hydrological models. In this paper we selected the double-excess runoff generation model as the subject for research, and the data obtained from tens of flooding events in the Fen River Basin were used for the construction of these models. The SCE-UA and MOSCDE algorithms were then taken to optimize the models’ parameters. The results showed that: as compared with the SCE-UA algorithm, higher flood forecast accuracies were obtained through model parameter optimization using the MOSCDE algorithm. During the examination period, the compliance rate of the flood peak magnitude increased from 60% to 70%, while the compliance rate of the flood peak duration increased from 80% to 90%. The Nash-Sutcliffe efficiency (NSE) of the flood peak magnitudes increased from 0.664 to 0.878, which demonstrates an improvement in goodness-of-fit; the RMSE value of flood peak magnitudes also decreased from 399.8 to 236.84, thus showing a decrease in dispersion and an improvement in goodness-of-fit. With the continuous improvements made in hydrological parameter algorithms and the creation of new optimization algorithms, there is no doubt that the optimization of hydrological model parameters will become more reasonable.

9

Downregulated NORAD in neuroblastoma promotes cell proliferation via chromosomal instability and predicts poor prognosis

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Yu Y. , Chen F. , Jin Y. , Yang Y. , Wang S. , Zhang J. , Chen C. , Zeng Q. , Han W. , Wang H. , Guo Y. , Ni X.

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tom 67

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nr 4