# Search Results

## You are looking at 1 - 10 of 29 items for

• Author or Editor: G. Xu
• Refine by Access: All Content
Clear All Modify Search

## Decomposition of methanol vapour over solid catalyst, measured by DSC

Journal of Thermal Analysis and Calorimetry
Authors:
G. Hakvoort
and
Xu Xiaoding

The activity of copper containing catalysts for the formation of methanol from CO and H2 is investigated by DSC measurement of the methanol decomposition. Calibration of the DSC signal can be performed by melting experiments with tin under reaction conditions. Comparison of catalysts is well possible by measurement of the standard activity at 240°, the apparent activation energy for the methanol decomposition reaction and the aging of the catalyst samples.

Restricted access

## Hua’s theorem with nine almost equal prime variables

Acta Mathematica Hungarica
Authors:
G. Lü
and
Y. Xu

## Abstract

We sharpen Hua’s result by proving that each sufficiently large odd integer N can be written as

\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage{bbm} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$N = p_1^3 + \cdots + p_9^3 with \left| {p_j - \sqrt[3]{{N/9}}} \right| \leqq U = N^{\tfrac{1} {3} - \tfrac{1} {{198}} + \varepsilon }$$ \end{document}
, where p j are primes. This result is as good as what was previously derived from the Generalized Riemann Hypothesis.

Restricted access

## Kinetics of thermal decomposition of mixed-ligand nikkel(II) and copper(II) complexes of 4-acyl pyrazolone derivative and pyridine

Journal of Thermal Analysis and Calorimetry
Authors:
G. Xu
,
L. Zhang
,
L. Liu
,
G. Liu
, and
D. Jia

## Abstract

Thermal behaviors of two mixed-ligand complexes, [Ni(PMPP-SAL)(Py)3] and [Cu(PMPP-SAL)Py]·MeOH, (PMPP-SAL=1-phenyl-3-methyl-4-(salicylidene hydrazide)-propenylidene-pyrazolone-5, Py=pyridine), were studied by TG-DTG-DTA in dynamic air atmosphere. The complexes show the loss of pyridine molecule is followed by the decomposition of the PMPP-SAL anion and give respective metal oxides as residues. Meanwhile, the Ozawa-Flynn-Wall model-free analyses and multivariate non-linear regressions were applied to perform single and overall steps optimization. Kinetic parameters were given and the most probable mechanism functions were suggested in this study.

Restricted access

## Multiple compounds determination and fingerprint analysis of Agrimonia pilosa Ledeb by high-performance liquid chromatography

Acta Chromatographica
Authors:
Y. Wang
,
L. Yin
,
G. Lv
,
Y. Xu
,
L. Xu
,
Y. Qi
,
L. Zheng
, and
J. Peng

## Summary

In the present paper, a simple and reliable high-performance liquid chromatography-diode array detection (HPLC-DAD) method was developed both for quantitative determination and fingerprint analysis of Agrimonia pilosa Ledeb for quality control. Under the optimized HPLC conditions, seven bioactive compounds including rutin, quercetin-3-rhamnoside, luteoloside, tiliroside, apigenin, kaempferol, and agrimonolide were determined simultaneously. For fingerprint analysis, 11 common peaks were selected as the characteristic peaks to evaluate the similarities of 16 different samples collected from different origins in China. Besides, hierarchical cluster analysis (HCA) was also performed to evaluate the variation of the raw materials. This is the first report of using a simple method for quality control of A. pilosa Ledeb through multi-component determination and chromatographic fingerprint analysis to the best of our knowledge.

Open access

## The correlations among various elements in neutron activation analysis — The evaluation of R-matrix and κ-matrix

Journal of Radioanalytical and Nuclear Chemistry
Authors:
X. Feng
,
S. Lo
,
G. Ji
,
Y. Jiang
, and
Y. Xu

## Abstract

The production rates (numbers of atoms per gram of the respective elements per second) of 40 radioactive nuclides of 34 elements by neutron capture reactions in a reactor were determined from about 130 photopeaks of the -ray spectra. The ratios of these production rates were called R-matrix elements. These production rates and the respective thermal neutron capture cross sections were used to calculate the respective apparent neutron fluxes at the position of irradiation and the -matrix elements which were the ratios of these apparent neutron fluxes. These matrix elements express clearly the correlations among various elements and thus may be used in the mono-standard or small-number-standards method in neutron activation analysis.

Restricted access

## Rapid analysis of multiple components in radix et Rhizoma Rhei using ultraperformance liquid chromatography tandem mass spectrometry

Acta Chromatographica
Authors:
G.-Yin. Wang
,
L.-W. Xu
, and
Y.-P. Shi

## Summary

A simple and rapid method, using online ultraperformance liquid chromatography with photodiode array detection and electrospray ionization mass spectrometry (UPLC-PDA-eλ-ESI-MS/MS), was developed for the in-depth analysis of 50 batches Radix et Rhizoma Rhei. The analysis was performed on a UPLC BEH C18 column using a gradient elution system. Baseline separation could be achieved in less than 7.5 min. At the same time, on the basis of the 50 batches of samples collected from representative cultivated regions, a novel chromatographic fingerprint was devised by UPLC-PDA, in which 27 common peaks were detected and identified by the developed UPLC-MS/MS method step by step according to fragmentation mechanisms, MS/MS data, standards, and relevant literature. Many active components gave prominent [M - H] ions in the ESI mass spectra. These components include anthraquinones, sennosides, stilbenes, glucose gallates, naphthalenes, and catechins. Furthermore, based on the information of these Radix et Rhizoma Rhei components, and further combined with discriminant analysis, a novel discriminant analysis equation (DAE) was established for the quality control of Radix et Rhizoma Rhei for the first time.

Open access

## Preparation and thermal decomposition study of pyridinedicarboxylate intercalated layered double hydroxides

Journal of Thermal Analysis and Calorimetry
Authors:
M. Wei
,
X. Xu
,
J. He
,
G. Rao
, and
H. Yang

## Abstract

Supramolecular 2,3- and 2,5-pyridinedicarboxylate (PDC) intercalated ZnAl-layered double hydroxides (2,3- and 2,5-PDC–ZnAl–LDHs) have been prepared by ion exchange method. The structure and composition of the intercalated materials have been studied by X-ray diffraction (XRD) and inductively coupled plasma emission spectroscopy (ICP). The study indicates that the 2,3-PDC and 2,5-PDC anions are accommodated as interdigitated bilayer and monolayer arrangement respectively between the sheets of LDHs. Furthermore, their thermal decomposition processes were studied by the use of in situ high temperature X-ray diffraction (HT-XRD), and the combined technique of thermogravimetry-differential thermal analysis-mass spectrometry (TG-DTA-MS) under N2 atmosphere. Based on the comparison study on the temperatures of both decarboxylation and complete decomposition of interlayer PDC, it can be concluded that 2,5-PDC–ZnAl–LDHs has higher thermal stability than that of 2,3-PDC–ZnAl–LDHs.

Restricted access

## Calibration burning of wood crib under ISO9705 hood

Journal of Thermal Analysis and Calorimetry
Authors:
Q. Xu
,
G. Griffin
,
Y. Jiang
,
A. Bicknell
,
, and
N. White

## Abstract

Wood cribs free burning tests were conducted under ISO9705 hood. From the tests, the heat release rate of these cribs was grouped as 0.5, 1.0 and 1.5 MW. This result was used to correct an empirical formula for peak heat release rate calculation. The correction achieves acceptable accuracy for the typical wood. The test result also shown heat release rate curve can be normalized by the total combustion surface of the wood crib. This can also be used to predict the HRR of wood crib of certain sizes and structures.

Restricted access

## Predicting the time to flashover for GRP panels based on cone calorimeter test results

Journal of Thermal Analysis and Calorimetry
Authors:
Q. Xu
,
G. Griffin
,
I. Burch
,
Y. Jiang
,
C. Preston
,
A. Bicknell
,
, and
N. White

## Abstract

Cone calorimeter tests were conducted to investigate the flammability of glass-reinforced plastics (GRP) panels. The results gained from these bench scale tests were used to predict the time to flashover in the ISO 9705 room, which was partly covered by GRP panels. Östman and Tsantaridis’ empirical linear regression model and multiple discriminant function analysis (MDA) were used in the prediction. Three room-scale GRP fire tests were conducted in ISO 9705 room and the results were compared with the prediction.

Restricted access

## Study of burning behavior of small scale wood crib with cone calorimeter

Journal of Thermal Analysis and Calorimetry
Authors:
Q. Xu
,
G. Griffin
,
Y. Jiang
,
C. Preston
,
A. Bicknell
,