Showing papers by "Wuhan University published in 2000"

Solubility of Cellulose in NaOH/Urea Aqueous Solution

Abstract: NaOH/urea aqueous solution as solvent of cellulose including cotton linter, bagasse, alkali-soluble cellulose and Bemliese® was studied by solubility analysis, viscometry and light scattering. The addition of 2—4 wt% urea significantly improved the solubility of cellulose in 6—8 wt% NaOH aqueous solutions, and moderate urea plays a role in improving solubility and avoiding the formation of cellulose gel. Celluloses I with viscosity-average molecular weight (Mη) of 6.7×104 were completely dissolved in 6 wt% NaOH/4 wt% urea aqueous solution. Cellulose dissolved in 6 wt% NaOH/4 wt% urea aqueous solution degraded slowly with storage time, and Mη of cellulose in the solution decreased 20% after storage for 100 days. The stability of cellulose solution was higher than cellulose cuoxam. A regenerated cellulose membrane having the tensile strength of 88.7MPa and breaking elongation of 11% was successfully prepared by coagulating 4 wt% Bemliese® solution in 6 wt% NaOH/4 wt% urea with 5 wt% CaCl2 then 1.3 wt% HCl aqueous solution as coagulate at 20°C.

Evolutionary Modeling of Systems of Ordinary Differential Equations with Genetic Programming

Abstract: This paper describes an approach to the evolutionary modeling problem of ordinary differential equations including systems of ordinary differential equations and higher-order differential equations. Hybrid evolutionary modeling algorithms are presented to implement the automatic modeling of one- and multi-dimensional dynamic systems respectively. The main idea of the method is to embed a genetic algorithm in genetic programming where the latter is employed to discover and optimize the structure of a model, while the former is employed to optimize its parameters. A number of practical examples are used to demonstrate the effectiveness of the approach. Experimental results show that the algorithm has some advantages over most available modeling methods.

Socioeconomic Gradient in Old Age Mortality in Wuhan, China

Abstract: Objectives. The vast majority of studies on socioeconomic status (SES) and old age mortality are based on data derived from developed nations. This research examined the SES differentials in old age mortality in China, a developing nation. Methods. Hazard rate models in conjunction with ordinary least squares and logistic regression analyses were used to ascertain the gross, direct, indirect, and interaction effects of SES on mortality during a 3-year period in a probability sample of 2,943 persons aged 60 years or older in Wuhan, China. Results. Education, household economic well being, and urban-rural residence showed statistically significant gross effects on old age mortality. Education influenced mortality directly and indirectly. Household economic well being and urbanicity exerted indirect effects on mortality through mediating variables such as stress, social relations, and baseline health status. The mechanism through which education affected mortality differed between men and women, but SES differentials in mortality did not interact with age. Discussion. SES differentials in old age mortality may be extended to a developing nation such as China. The observed gender by SES interaction effect on old age mortality has important implications for intervention. In particular, improving education among women in underdeveloped areas must remain a high priority, for policy makers in efforts to extend the life expectancy of women.

Blend films from chitosan and konjac glucomannan solutions

Abstract: Blend films were prepared by blending 7 wt % konjac glucomannan (KGM) aqueous solution with 2 wt % chitosan (CH) in acetate solution and dried at 40°C for 4 h to obtain the transparent films. Their structure and properties were studied by infrared (IR), wide-angle X-ray diffraction (WAXD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential thermal analysis (DTA). Crystallinities of the blend films decreased with the increase of konjac glucomannan. The thermostability, tensile strength, and breaking elongation of the blend films in dry state were obviously higher than those of both konjac glucomannan and chitosan films. Tensile strength of the dry blend film achieved 73.0MPa when the weight ratio of chitosan to konjac glucomannan was 7:3. The structure analysis indicated that there is a strong interaction between konjac glucomannan and chitosan resulted from intermolecular hydrogen bonds. The water solubility of the blend films was improved by blending with konjac glucomannan, so they have promising applications to soluble antiseptic coating of pills. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 509–515, 2000

Solution Properties of Antitumor Sulfated Derivative of α-(1→3)-D-Glucan from Ganoderma lucidum

Abstract: Four fractions of a water-insoluble alpha-(1-->3)-D-glucan GL extracted from fruiting bodies of Ganoderma lucidum were dissolved in 0.25 M LiCl/DMSO, and then reacted with sulfur trioxide-pyridine complex at 80 degrees C to synthesize a series of water-soluble sulfated derivatives S-GL. The degree of substitution of DS was measured by using IR infrared spectra, elemental analysis, and 13C NMR to be 1.2-1.6 in the non-selective sulfation. Weight-average molecular weight Mw and intrinsic viscosity [eta] of the sulfated derivatives S-GL were measured by multi-angle laser light scattering and viscometry. The Mw value (2.4 x 10(4)) of sulfated glucan S-GL-1 was much lower than that (44.5 x 10(4)) of original alpha-(1-->3)-D-glucan GL-1. The Mark-Houwink equation and average value of characteristic ratio C(infinity) for the S-GL in 0.2 M NaCl aqueous solution at 25 degrees C were found to be: [eta] = 1.32 x 10(-3) Mw(1.06) (cm3 g(-1)) and 16, respectively, in the Mw range from 1.1 x 10(4) to 2.4 x 10(4). It indicated that the sulfated derivatives of the alpha-(1-->3)-D-glucan in the aqueous solution behave as an expanded chain, owing to intramolecular hydrogen bonding or interaction between charge groups. Interestingly, two sulfated derivatives synthesized from the alpha-(1-->3)-D-glucan and curdlan, a beta-(1-->3)-D-glucan, all had significant higher antitumor activity against Ehrlich ascites carcinoma (EAC) than the originals. The effect of expanded chains of the sulfated glucan in the aqueous solution on the improvement of the antitumor activity could not be negligible.

Unified Power Quality Conditioner (UPQC): the theory, modeling and application

Abstract: The theory and modeling of unified power quality conditioner (UPQC), a FACTS device, is described in this paper. The UPQC proposed in this paper consists of thyristor controlled capacitor banks, series-active filter and shunt-active filter. The series-active and shunt-active filters are developed mainly to compensate negative-sequence current and harmonics as the thyristor controlled capacitor banks is used to compensate the reactive power of power frequency. The functions of the models have been verified. Compensations as well with and without the active filters are discussed in this paper. Some results and corresponding conclusions are presented.

An extended genetic rule induction algorithm

Abstract: Describes an extension of a genetic algorithm (GA) based separate-and-conquer propositional rule induction algorithm called SIA (Supervised Inductive Algorithm). While the original algorithm is computationally attractive and is also able to handle both nominal and continuous attributes efficiently, our algorithm further improves it by taking into account recent advances in the rule induction and evolutionary computation communities. The refined system has been compared to other GA-based and non-GA-based rule learning algorithms on a number of benchmark data sets from the UCI (University of California, Irvine) machine learning repository. The results show that the proposed system can achieve higher performance while still producing a smaller number of rules.

Study of the adsorption behavior of heavy metal ions on nanometer-size titanium dioxide with ICP-AES.

Abstract: A new method using nanoparticle TiO2 as solid-phase extractant coupled with ICP-AES was proposed for simultaneous determination of trace elements. The adsorption behavior of nanometer TiO2 towards Cu, Cr, Mn and Ni was investigated by ICP-AES, and the adsorption pH curves, adsorption isotherms and adsorption capacities were obtained. It was found that the adsorption rates of the metal ions studied were more than 90% in pH 8.0-9.0, and 2.0 mol L-1 HCl was sufficient for complete elution. Nanometer TiO2 possesses a significant capacity for the sorption of the metal ions studied which is higher than the capacity of silica, the commonly used extractant. The method has been applied to the analysis of some environmental samples with satisfactory results.

Studies of adsorption behavior of crosslinked chitosan for Cr(VI), Se(VI)

Abstract: In this work, it was found that crosslinked chitosan (CCTS) had strong adsorption ability for some anions under certain conditions. Cr(VI) and Se(VI) existed in anion forms in aqueous solution, and their adsorption rates by CCTS were 97% for Cr(VI) at pH 3.0 and 95% for Se(VI) at pH 4.0. In addition, the adsorption balance time and isotherm of CCTS for Cr(VI) and Se (VI) were discussed and adsorption mechanism was explained. This research will be useful for designing CCTS-based adsorption for metallic toxin removal and preconcentrating Cr(VI) and Se(VI) in their trace analysis. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 3216–3219, 2000

On the Structures and dimensions of Moran sets

Abstract: The Moran sets and the Moran class are defined by geometric fashion that distionguishes the classical self-similar sets from the following points: (i) The placements of the basic sets at each step of the constructions can be arbitrary. (ii) The contraction ratios may be different at each step. (iii) The lower limit of the contraction ratios permits zero. The properties of the Moran sets and Moran class are studied, and the Hausdorff, packing and upper Box-counting dimensions of the Moran sets are determined by net measure techniques. It is shown that some important properties of the self-similar sets no longer hold for Moran sets.

Decision support system for contractor pre‐qualification—artificial neural network model

Abstract: The selection criteria for contractor pre‐qualification are characterized by the co‐existence of both quantitative and qualitative data. The qualitative data is non‐linear, uncertain and imprecise. An ideal decision support system for contractor pre‐qualification should have the ability of handling both quantitative and qualitative data, and of mapping the complicated non‐linear relationship of the selection criteria, such that rational and consistent decisions can be made. In this research paper, an artificial neural network model was developed to assist public clients identifying suitable contractors for tendering. The pre‐qualification criteria (variables) were identified for the model. One hundred and twelve real pre‐qualification cases were collected from civil engineering projects in Hong Kong, and 88 hypothetical pre‐qualification cases were also generated according to the ‘If‐then’ rules used by professionals in the pre‐qualification process. The results of the analysis totally comply with current practice (public developers in Hong Kong). Each pre‐qualification case consisted of input ratings for candidate contractors' attributes and their corresponding pre‐qualification decisions. The training of the neural network model was accomplished by using the developed program, in which a conjugate gradient descent algorithm was incorporated for improving the learning performance of the network. Cross‐validation was applied to estimate the generalization errors based on the ‘re‐sampling’ of training pairs. The case studies show that the artificial neural network model is suitable for mapping the complicated non‐linear relationship between contractors' attributes and their corresponding pre‐qualification (disqualification) decisions. The artificial neural network model can be concluded as an ideal alternative for performing the contractor pre‐qualification task.

Blend membranes from carboxymethylated chitosan/alginate in aqueous solution

Abstract: The blend membranes were satisfactorily prepared by coagulating a mixture of O-carboxymethylated chitosan (CM-chitosan) and alginate in aqueous solution with 5 wt % CaCl2, and then by treating with 1 wt % HCl aqueous solution. Their structure and miscibility were characterized by scanning electron micrograph, X-ray diffraction, infrared spectra, differential thermal analysis, and atomic absorption spectrophotometer. The results indicated that the blends were miscible, when the weight ratio of CM-chitosan to alginate was in the range from 1 : 1 to 1 : 5. The polymers interpenetration including a Ca2+ crosslinked bridge occurred in the blend membrane, and leads to high separation factor for pervaporation separation of alcohol/water and low permeation. The tensile strength in the wet state (σb = 192 kg cm−2 for CM-chitosan/alginate 1 : 1) and thermostability of the blend membranes were significantly superior to that of alginic acid membrane, and cellulose/alginate blend membranes, owing to a strong electrostatic interaction caused by —NH2 groups of CM-chitosan with —COOH groups of algic acid. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 610–616, 2000