Wyniki wyszukiwania - BazTech

1

Digital volume correlation in an environment with intensive salt-and-pepper noise and strong monotonic nonlinear distortion of light intensity

Tu P., Bai Y., Xu W., Dong B., Ye S., Yang Q., Zhou Y.

Optica Applicata

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2017

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Vol. 47, nr 2

209--223

EN

Digital volume correlation is an image-based technique for internal 3D displacement and strain fields measurement or analysis widely used in the field of experimental mechanics. A widely used correlation function (criterion) of digital volume correlation is Pearson correlation function, which suffers from the problem of the acquired data being contaminated by salt-and-pepper noise and monotonic nonlinear distortion of the light intensity. In this work, a 3D correlation function called the Spearman correlation function is used to deal with those interferences. A numerical experiment shows that the performance of Spearman correlation function using integer-pixel registration in an environment with 10% salt-and-pepper noise is better than that of Spearman and Pearson correlation functions using sub-pixel registration in an environment with 1% salt-and-pepper noise. As the light intensity distortion is significant, the error of Pearson correlation function is considerable; meanwhile, the error of Spearman correlation function is small. In conclusion, Spearman correlation function is, in particular, practical and useful in digital volume correlation.

2

Research and Simulation of a Full-Scale Attitude Algorithm for Strapdown Inertial Navigation Based on a Rotation Vector

Cao Y., Bai Y., Du J., Zhao J.

Przegląd Elektrotechniczny

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2013

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R. 89, nr 3b

41--43

EN

The compensation for non-swappable error of traditional quaternion algorithm is not enough in attitude matrix solution. It can only apply to the attitude solution of low dynamic carriers. An optimized algorithm based on a 3-subsample rotation vector is presented. The full-scale attitude of a strapdown inertial navigation system can be calculated through resolving a attitude change quaternion. The algorithm is validated through simulation. The results show that the algorithm can satisfy real-time and precision requirements. The influence of direction drift on the attitude solution of the strapdown inertial navigation system is also reduced.

PL

W artykule przedstawiono zoptymalizowany algorytm kompensacji błędów w podejściu kwaternionowym w metodzie macierzy orientacji, na potrzeby systemu nawigacji bezwładnościowej typu strapdown. Określanie orientacji pełnowymiarowej odbywa się poprzez obliczeniowe rozwiązanie kwaterniona zmiany orientacji. Opracowany algorytm poddano badaniom symulacyjnym, których wyniki potwierdzają skuteczność proponowanego rozwiązania.

3

Biomass fraction of graminoids and forbs in N-limited alpine grasslands: N:P stoichiometry

Zhang R., Gou X., Bai Y., Zhao J., Chen L., Song X., Wang G.

Polish Journal of Ecology

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2011

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Vol. 59, nr 1

105-114

EN

It is known that the dominance of graminoid species is promoted by N addition; however, there has been relatively little effort to examine the pattern induced by natural N fertility. Since nutriet use efficiency (NUE) is an important trait determining plant competitive ability, we expected that the species guild with higher NUE (lower nutrient content) may be more competitive on infertile soils. We explored the relationships between relative forbs biomass share, soil N and productivity by the linear regressi on analysis on a natural alpine meadow in northeast of Qinghai Tibetan Plateau (3600 m a.s.l.). To test the variety of leaf N:P stoichiometry, paired t test and general linear model multivariate (GLM) analysis were also used. We found that the leaf N:P ratios of the whole community were below 13 in studied sites, which may be consistent with the N limitation on the vegetation. Graminoids retained lower concentrations of leaf N and P than forbs in community on the N limited grassland. Consistent with our prediction, we found that the biomass fraction of graminoids declined with soil N content and aboveground production on the grassland. Different from the pattern along fertility gradients induced by N fertilization, our results showed that gr aminoids with lower internal nutrient content were able to resist low levels of nutrient availability on the natural alpine grassland when compared to forbs.

4

Modele optymalizacji grupowej dla złożonych zadań obsługowych dotyczących systemów wieloskładnikowych

Bai Y., Jia X., Cheng Z.

Eksploatacja i Niezawodność

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2011

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nr 1

42-47

PL

W ostatnich latach prowadzi się coraz więcej badań w zakresie optymalizacji eksploatacji systemów wieloskładnikowych, czego wynikiem są licznie proponowane metody optymalizacji oraz modele matematyczne. Jednakże najczęściej bada się proste zadania obsługowe, a rzadko występujące w praktyce zadania złożone, wymagające kilku rodzajów obsługi. W artykule przedstawiono strategię obsługi grupowej służącą optymalizacji przerw na złożone czynności obsługowe w systemach wieloskładnikowych oraz zaproponowano etapy i metody optymalizacji. Przeprowadzono analizę struktury kosztów utrzymania systemu oraz wyznaczono modele kosztów w celu optymalizacji przerw na złożone czynności obsługowe. Wydajność proponowanych modeli zilustrowano przykładem numerycznym.

EN

More and more researches have been made on maintenance optimization of multi-component system in recent years, and a lot of optimization methods and mathematical models have been proposed. However, the maintenance tasks in present researches are mostly simplex, while the compound maintenance tasks integrating several kinds of maintenance types that exist in practice are seldom studied. To optimize the compound maintenance intervals of multi-component system, the group maintenance strategy is introduced in this paper, and the optimization steps and methods are proposed. The maintenance cost structure and composition are analyzed from system point of view, and the cost models to optimize the compound maintenance intervals are established. Finally, a numerical example is presented to illustrate the efficiency of the proposed models.

5

Analysis of Saussurea species from tibet using HPLC-DAD-ESI-MS n

Dawa Z, Zhou Y., Bai Y., Gesang S, Liang J., Ding L.

Acta Chromatographica

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2010

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Vol. 22, no. 1

141--152

EN

An HPLC-DAD-ESI-MS n method has been developed for simultaneous quantification of eight major compounds in eight Saussurea species which have long been used as the traditional Tibetan medicines. The method was validated for sensitivity, precision, and accuracy. LODs were from 0.11 to 5.01 μg mL -1, overall intra-day and inter-day variation was less than 2.70%, and overall recovery was over 98.0%. The correlation coefficients ( r 2) of the calibration plots were >0.991. This newly established method was successfully used to reveal difference among the chemical profiles and analytes contents of eight Saussurea species collected in Tibet. In addition, by comparison of UV and mass spectra with those of authentic compounds, a total of fifteen peaks were identified. It can be concluded that this is an effective method for quantification and evaluation of the flavonoids and coumarins in the eight species of the genus Saussurea . It can be used as an efficient reference method for development and use of the eight traditional Tibetan medicines by comparing their different characteristics.

6

Removal of heavy metals from wastewater using ion exchange resin amberjet 1200H columns

Bai Y., Bartkiewicz B.

Prace Naukowe Politechniki Warszawskiej. Inżynieria Środowiska

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2009

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z. 55

43-51

EN

The aim of this study was the removal of Cu2+, Zn2+ by ion-exchange resin Amberjet 1200H in flow condition. The adsorption characteristics of each metal onto the resin were accurately described by Freundlich isotherms. Ion exchange capacities of the heavy metals on the ion exchange resin were studied in a single metal solution. The capacities of sorption were 2.13 eq. Zn/l, and 2.74 eq. Cu/l respectively, and the ion exchange on resin follows pseudo-first-order kinetics.

PL

Celem badań była ocena skuteczności usuwania z roztworu wodnego miedzi i cynku przez wymianę jonową na kolumnie wypełnionej żywicą Amberjet 1200H. Charakterystykę usuwania każdego z metali można było opisać izotermą Freundlicha. Pojemności jonowymienne żywicy, ustalone dla każdego metalu oddzielnie wynosiły 2,13 val Zn/l i 2,74 val Cu/l. Kinetyka wymiany daje się opisać równaniem pierwszego rzędu.

7

Ductile fracture locus of AC4CH-T6 cast aluminium alloy

Mae H., Teng X., Bai Y., Wierzbicki T.

Archives of Computational Materials Science and Surface Engineering

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2009

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Vol. 1, nr 2

100-105

EN

Purpose: Cast aluminium alloys have found wide application to manufacture lighted-weight components of complex shape in automotive and aerospace industries. To improve the strength and ductility of cast aluminium alloys, it is necessary to study their fracture properties by conducting a series of tests. This study addresses calibration of ductile fracture property of the cast aluminium alloy (AC4CH-T6) made by the gravity die casting with sand mold. Design/methodology/approach: 6 round bar specimens and 6 butterfly specimens are machined from the actual cast component. The tensile tests on the smooth and notched round bar specimens are performed to calibrate the fracture strain in the range of high positive stress triaxialities. The combined loading tests on the butterfly specimens are carried out using a uniquely designed Universal Biaxial Testing Device (UBTD). These tests cover the fracture properties in the rage of low and negative stress triaxialities. Detailed finite element models of all the tests are developed. The fracture locus in the space of the effective plastic strain to fracture and the stress triaxiality are constructed in a wide rage from -1/3 to 1.0. Findings: It is found that material ductility sharply decreases with the stress triaxiality. The material ductility at the negative stress triaxiality is much higher than that in the positive stress triaxiality. Research limitations/implications: Large spread of data is observed for those tests repeated on the same loading configuration, necessitating the statistical analysis of the fracture processes. Practical implications: It is expected that such a fracture criterion would be able to correctly predict the fracture response of actual cast aluminum components under complex loading in the practical applications. Originality/value: The conventional researches focused on the material ductility at the stress triaxiality larger than +1/3. The present study showed the material ductility at the wide range of stress triaxiality from -1/3 to 1.0.

8

Object Oriented Database with Authorization Policies

Bai Y., Varadharajan V.

Fundamenta Informaticae

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2002

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Vol. 53, nr 3,4

229-250

EN

Authorization specification in object oriented databases is being increasingly investigated recently by many researchers [4,5,7,9,10]. However, most of the work todate suffers from a lack of formal logic semantics to characterize different types of inheritance properties of authorization policies among complex data objects. This paper is to address this issue from a formal logic point of view. In particular, we propose a logic language that has a clear and declarative semantics to specify the structural features of object oriented databases and authorizations associated with complex data objects in databases. Our formalization characterizes the model-theoretic semantics of object oriented databases and authorizations associated with them. A direct advantage of this approach is that we can formally specify and reason about authorizations on data objects without loosing inheritance and abstraction features of object oriented databases.