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1

On spectral representation method and Karhunen–Loève expansion in modelling construction material properties

Chen E. J., Ding L., Liu Y., Ma X., Skibniewski M. J.

Archives of Civil and Mechanical Engineering

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2018

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Vol. 18, no. 3

768--783

EN

Randomness in construction material properties (e.g. Young's modulus) can be simulated by stationary random processes or random fields. To check the stationarity of commonly used techniques, three random process generation methods were considered: Xn(t), Yn(t), and Zn(t). Methods Xn(t) and Yn(t) are based on a truncation of the spectral representation method with the first n terms. Xn(t) has random amplitudes while Yn(t) has random harmonics phases. Method Zn(t) is based on the Karhunen–Loève expansion with the first n terms as well. The effects of the truncation technique on the mean-square error, covariance function, and scale of fluctuation were examined in this study; these three methods were shown to have biased estimations of variance with finite n. Modified forms for those methods were proposed to ensure the truncated processes were still zero-mean, unit-variance, and had a controllable scale of fluctuation; in particular, the modified form of Karhunen–Loève expansion was shown to be stationary in variance. As a result, the modified forms for those three methods are advantageous in simulating statistically homogenous material properties. The effectiveness of the modified forms was demonstrated by a numerical example.

2

Antileukemic activity of the chemical constituents from Scutellaria barbata D. Don

Ren Q., Xia T., Quan X. G., Ding L., Wang H. Y.

Acta Chromatographica

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2017

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Vol. 29, no. 3

399--413

EN

Scutellaria barbata D. Don has been used as a traditional Chinese medicine for antitumor and anti-inflammatory. However, there were just a few investigations about S. barbata D. Don according to bioactivity-directed isolation and online identification for the chemical constituents. In this work, eight compounds were isolated from S. barbata D. Don. The three flavonoids indicated the cytotoxic activity against human leukemic Reh cell lines. In addition, the constituents of S. barbata D. Don were further characterized and identified by ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOF-MS). The UHPLC- Q-TOF-MS method was in negative ion mode. HPLC separation was performed on a Tosoh TSK gel ODS-100V (4.6 × 150 mm, 3.0 μm) column by gradient elution using water containing 0.3% formic acid and acetonitrile as mobile phase at a flow rate of 0.8 mL min−1. A total of 18 compounds, including 4 phenolic acids and 14 flavonoids were tentatively characterized and identified by means of the retention time, accurate mass, and characteristic fragment ions.

3

Analysis of large particle sizes using a machine vision system

Zhang Z., Yang J., Su X., Ding L.

Physicochemical Problems of Mineral Processing

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2013

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Vol. 49, iss. 2

397--405

EN

Many methods based on machine vision were used to estimate coarse particles size distribution in recent years, but comparison of accuracy parameters representing particle size has not been carried out and a related representing analysis has not been yet proposed. Nine parameters were investigated. The results indicated the minor axis of equivalent ellipse and breadth of the best-fit rectangle were the most suitable for representing particle size. The former accuracy ratio was 86.43% and the latter accuracy ratio was 85.39%, while the accuracy of other parameters was less than 70%. A related representing analysis was proposed to explain this phenomenon. This research is instructive and meaningful for the size distribution estimation by machine vision.

4

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.

5

Rapid detection of trace chloroethylenes sing laser mass spectrometry

Ma J., Ding L., Fang L., Zheng H., Gu X., Zhang W.

Optica Applicata

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2005

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Vol. 35, nr 2

395-402

EN

Laser mass spectrometry is a new chemical trace analysis method with high selectivity, sensitivity and speed. The mass-resolved resonance-enhanced multiphoton ionization (REMPI) spectra of chloroethylenes-trichloroethylene and tetrachloroethylene are firstly reported in the range 305.0-325.0 nm. The mass-resolved excited spectra and laser power index of fragment ions CCl+ are presented. The experimental results indicate that 310.8 nm is the suitable ionization wavelength for detection of trichloroethylene and 322.5 nm for the detection of tetrachloroethylene in this wavelength range. The detection limits of these two chloroethylenes of concentration range expressed in ug/L are presented.

6

Non-discriminating pyrolysis - two-dimensional gas chromatography - time of flight mass spectrometry as the tool for the characterization of urban air particulate matter

Parski Z., Górecki T., Dabek-Zlotarzynska E., Ding L.

Chemia i Inżynieria Ekologiczna

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2005

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Vol. 12, nr 5-6

559-571

EN

Fine airborne particulate matter (PM[2.5]) is a complex mixture of organic and inorganic compounds. II has been shown that PM[2.5] has adverse health effects; therefore its characterization and speciation are very important. The combination of non-discriminating thermal desorption/pyrolysis with comprehensive two-dimensional gas chromatography (Py-GCxGC) and time-of-flight mass spectrometry (TOF-MS) can be a very useful technique for the characterization of PM[2.5] collected on quartz fiber filters. The coupling of the non-discriminating pyrolysis system with GCxGC provides the means for direct thermal desorption of volatile and semi-volatile compounds in airborne PM[2.5]. In addition, non-volatile analytes can be pyrolyzed to produce smaller, more analytically useful fragments. The system should be very helpful in identifying marker compounds from major emission sources and from secondary photochemical processes. It is well suited for group type separations with a concurrent increase in sensitivity, which improves the detail level of PM[2.5]organic chemical composition studies. The new approach requires much less material than other methods. In addition, it requires no sample preparation, therefore it is faster and more environmentally friendly.

PL

Frakcja PM[2.5] pyłu zawieszonego jest skomplikowaną mieszaniną związków organicznych i nieorganicznych. Dokładne scharakteryzowanie i analiza specjacyjna tej frakcji są bardzo ważne ze względu na jej udowodnione szkodliwe właściwości. W pracy przedstawiono wstępne wyniki badań nad przydatnością połączenia technik niedyskryminującej pirolizy, kompletnej dwuwymiarowej chromatografii gazowej i spektrometrii masowej czasu przelotu (Py-GCxGC- TOF-MS) do scharakteryzowania frakcji PM[2.5] pyłu zawieszonego zebranej na filtrach z włókniny kwarcowej. Zastosowanie systemu do niedyskryminującej pirolizy jako metody wprowadzania próbki do chromatografu gazowego pozwala na bezpośrednią desorpcję termiczną lotnych i średnio lotnych związków zawartych we frakcji PM[2.5]. Dodatkową zaletą jest fakt, że związki nielotne mogą być poddane pirolizie, w wyniku której powstają mniejsze, bardziej lotne molekuły, pozwalające na uzyskanie dodatkowych informacji o próbce. Zaproponowany system powinien być bardzo pomocny przy identyfikacji związków chemicznych (markerów) charakterystycznych dla różnych źródeł emisji i dla fotochemicznych zanieczyszczeń wtórnych. Jest on szczególnie przydatny do analizy grupowej ze względu na uporządkowaną naturę chromatogramów dwuwymiarowych. Jednocześnie zapewnia on lepszą czułość w porównaniu z konwencjonalną jednowymiarową chromatografią gazową. Cechy te powinny umożliwić bardziej dogłębną charakterystykę frakcji PM[2.5] pyłu zawieszonego. Ilość próbki konieczna do przeprowadzenia analizy zaproponowaną metodą jest znacznie mniejsza niż w innych metodach stosowanych do tego celu, a przygotowanie próbki do analizy polega na jej wprowadzeniu do urządzenia do niedyskryminującej pirolizy. Cechy te powodują, że zaproponowana metoda jest dużo szybsza od innych i bardziej przyjazna środowisku naturalnemu.