Search Results

You are looking at 1 - 10 of 108 items for

  • Author or Editor: M. Wang x
  • Refine by Access: All Content x
Clear All Modify Search

Abstract  

We generalize classical results concerning L 1 integrability, and tell a somewhat different story for sine series.

Restricted access

Abstract  

We study a class of quasilinear elliptic equations with boundary blow-up. Based on super and sub-solution arguments and certain comparison principle, we prove the existence of non-negative solutions of (1.1). Moreover, we show the existence of maximal and minimal non-negative solutions of (1.1).

Restricted access

Abstract  

The dehydration process of Co(II), Cu(II) and Zn(II) methanesulfonates was studied by thermogravimetry/derivative thermogravimetry (TG/DTG) and differential scanning calorimetry (DSC) techniques in dynamic N2 atmosphere. The TG/DTG curves show that all of them contain four crystallization water molecules, which are lost in two steps. The peak temperature and dehydration enthalpies ΔH were measured from DSC curves for each compound. The effect of procedural variables on the TG and DSC curves was investigated. In this work, the procedural variables included heating rate, Al pan state (unsealed and sealed) and sample mass.

Restricted access

Summary

As a new form of traditional Chinese medicine (TCM), Zuojin pill extract is made containing Coptidis rhizoma (the rhizome of Coptis chinesis Franch. [Ranunculaceae]) and Euodiae fructus (the unripe fruit of Euodia rutaecarpa [Juss.] Benth. [Rutaceae]) at the ratio of 6:1 (w/w) and has been most widely used in TCM to treat gastro-intestinal disorders. However, the quality control is insufficient. For establishing an analysis method for the effective quality control of Zuojin pill extract, the active components of three protoberberine alkaloids (coptisine, palmatine, berberine, components from C. rhizoma) and two indolequinoline alkaloids (evodiamine, rutaecarpine, components from E. fructus) in Zuojin pill extract were determined simultaneously by high-performance liquid chromatography. Chromatographic separations were performed on an Inertsil ODS-3 column (4.6 mm × 250 mm, 5 μm). Elution was carried out at 25°C under isocratic conditions by using 25 mmol L−1 KH2PO4-25 mmol L−1 SDS-acetonitrile (1:1:2, v/v/v, adjusted pH to 3.0 using phosphoric acid) as a mobile phase with a flow rate of 0.5 mL min−1. Detection wavelength was set at 264 nm. Good linearity was obtained with correlation coefficient higher than 0.999 for all the analytes over the investigated concentration ranges. Three batches of Zuojin pill extract were successfully analyzed. The average percentages of coptisine, palmatine, berberine, evodiamine, and rutaecarpine in Zuojin pill extract were 5.35%, 3.92%, 16.64%, 0.03%, and 0.03%, respectively. Consequently, these protoberberine and indolequinoline alkaloids could be identified and determined easily by the established high-performance liquid chromatography (HPLC) method which can be used to evaluate and control the quality of Zuojin pill extract.

Full access

Abstract  

Let X,X 1,X 2,… be a sequence of non-degenerate i.i.d. random variables with mean zero. The best possible weighted approximations are investigated in D[0, 1] for the partial sum processes {S [nt], 0 ≦ t ≦ 1} where S n = Σj=1 n X j, under the assumption that X belongs to the domain of attraction of the normal law. The conclusions then are used to establish similar results for the sequence of self-normalized partial sum processes {S [nt]=V n, 0 ≦ t ≦ 1}, where V n 2 = Σj=1 n X j 2. L p approximations of self-normalized partial sum processes are also discussed.

Restricted access

Abstract  

This work presents a low-level background gamma spectrometry system capable of achieving rapid determination of90Sr without chemical separation, in a soil sample when the90Sr to -ray emitting nuclide concentration ratio exceeds 10. The system consists of a highly efficient HPGe central detector operated in coincidence or anticoincidence with a NaI(Tl) guard detector and a NaI(Tl) backscatter detector. Experimental results indicate that the bremstrahlung radiation from a pure -emitter can be distinguished with respect to the differences in normal and coincidence spectra. The90Sr activity can be directly detemined in the sample in less than 1 hour with a minimum detectable concentration (MDC) estimated at 0.002 Bq·g–1 for a sample containing no appreciable -ray nuclides or other high energy, -emitting nuclides. In actual measurement, a 0.06 Bq·g–1 MDC for contaminated soils is achieved.

Restricted access

Abstract  

Wood, one of the most flammable materials, was treated with various compounds containing nitrogen, phosphorus, halogens, and boron. For a study of flame retardance from the standpoint of thermal degradation, the samples were subjected to thermogravimetry (TG), differential thermal analysis (DTA) and differential thermogravimetry (DTG) in nitrogen to determine if there were any characteristic correlations between thermal degradation behaviors and the level of flame retardance. From the resulting data, kinetic parameters for different stages of thermal degradation are obtained using the method of Broido. The energies of activation for the decomposition of samples are found to be from 72 to 109 kJ mol–1. For wood and modified wood, the char yields are found to increase from 10.2 to 30.2%, LOI from 18 to 36.5, which indicates that the flame retardance of wood treated with compounds is improved. The flame retardant mechanism of different compounds has also been proposed.

Restricted access

Abstract  

The conductivities of binary mixtures of glycerine and water were measured at 20C by means of a transient method. The equation describing the correlation between concentration and thermal conductivity was determined. The equation can be used for determining concentrations in mixtures. The results show that (1) the error in the determination of the molar concentration of water in mixtures is less than 1%, (2) the time of measurement is 1 s, (3) this method can be used for on-line analysis in production control.

Restricted access