Showing papers by "Donghua University published in 2004"
TL;DR: The homotopy perturbation method is applied to the nonlinear oscillators with discontinuities and only one iteration leads to high accuracy of the solutions.
871 citations
TL;DR: Comparison of homotopy perturbation method (HPM) and Homotopy analysis method is made, revealing that the former is more powerful than the later.
613 citations
TL;DR: In this article, the semi-inverse method was used to obtain variational principles for generalized Korteweg-de Vries equation and nonlinear Schrodinger's equation.
Abstract: Variational principles for generalized Korteweg–de Vries equation and nonlinear Schrodinger’s equation are obtained by the semi-inverse method. The most interesting features of the proposed method are its extreme simplicity and concise forms of variational functionals for a wide range of nonlinear problems. Comparison with the results obtained by the Noether’s theorem is made, revealing the present theorem is a straightforward and attracting mathematical tool.
601 citations
TL;DR: In the paper, an heuristical example is given to illustrate the basic idea of the homotopy perturbation method, which has made all that is necessary simple, andall that is complex unnecessary.
232 citations
TL;DR: In this article, the thermal decomposition temperatures, weight losses and potential reactions of the pyrolysis as well as resulted fragments, were analyzed, which are helpful in understanding of mechanisms of flame-retardant cotton fabrics.
224 citations
206 citations
TL;DR: In this paper, the authors established a mathematical model to explore the physics behind electrospinning and derived the Bratu equation, which can explain the instability (bifurcation) in electro-spinning.
Abstract: Ultra-fine polymer fibers, obtained by electrospinning, have a wide range of potential applications such as fluid filtration, biomedicine, catalyst supports, drug delivery, tissue engineering, nanowires, to just say few. Yet theoretical modeling the spinning process remains a bottleneck severely hampering further improvement in both quality and efficiency. This paper establishes a mathematical model to explore the physics behind electrospinning. When electrical force is dominant over the other forces, Bratu equation is derived, which can explain the instability (bifurcation) in electrospinning. A variational model is also established.
130 citations
TL;DR: In this paper, the effects of inlet type on cyclone performance characteristics, including the collection efficiency and pressure drop, were investigated and compared as a function of particle size and flow rate.
113 citations
TL;DR: In this article, the effect of surface charge on electrospinning by adding LiCl was investigated and it was shown that the relationship between radius r of jet and the axial distance z from nozzle follows an allometric law in the form r ∼ z − 0.5 in case of full surface charge, and the scaling exponent becomes larger for partly charged fibers.
104 citations
TL;DR: In this paper, conducting carbon black (CB), one of the intrinsic semi-conductors, was added into matrix polypropylene (PP) to prepare conducting composites by means of the melt processing method.
Abstract: Conducting carbon black (CB), one of the intrinsic semi-conductors, was added into matrix polypropylene (PP) to prepare conducting composites by means of the melt processing method. Another component EVA was mixed into the composites in order to lower the percolation threshold. The percolation threshold of the ternary CB/PP/EVA composites was merely 3.8 vol%, while it was up to 7.8 vol% for the binary CB/PP composites without EVA. The conductivity of the ternary CB/PP/EVA composites was up to 10−2 S/cm when the CB percentage was 5 vol%, while that of the binary CB/PP was lower than 10−2 S/cm when the CB percentage was up to 10 vol%. DSC thermograms of the CB/PP/EVA composites showed that the melting peak shifted to low temperature with increasing CB content. The addition of CB and EVA resulted in the decrease of the crystallinity of PP in the ternary composites. The mechanical properties are also discussed. SEM and TEM were employed to study the morphology of the blend system. The results indicated that CB existed in the form of aggregations in the blend system. The smallest unit that formed a percolation network was grape-like aggregates with some small branches, which consisted of some CB particles, rather than the individual particles. This distribution was very valuable for forming conducting paths and for lowering the percolation value.
92 citations
TL;DR: By a general Lagrange multiplier, an iteration approach is proposed to solve the generalized normalized diode equation, by suitable choice of the initial trial-function, one-step iteration leads to a high accurate solution, which is valid for the whole solution domain.
Abstract: By a general Lagrange multiplier, an iteration approach is proposed to solve the generalized normalized diode equation, by suitable choice of the initial trial-function, one-step iteration leads to a high accurate solution, which is valid for the whole solution domain. Copyright © 2004 John Wiley & Sons, Ltd.
TL;DR: In this paper, a semiparametric density estimator is proposed under a two-sample density ratio model, which is an extension of the kernel density estimate suggested by Jones for length-biased data.
Abstract: A semiparametric density estimation is proposed under a two-sample density ratio model. This model, arising naturally from case-control studies and logistic discriminant analyses, can also be regarded as a biased sampling model. Our proposed density estimate is therefore an extension of the kernel density estimate suggested by Jones for length-biased data. We show that under the model considered the new density estimator not only is consistent but also has the `smallest' asymptotic variance among general nonparametric density estimators. We also show how to use the new estimate to define a procedure for testing the goodness of fit of the density ratio model. Such a test is consistent under very general alternatives. Finally, we present some results from simulations and from the analysis of two real data sets.
TL;DR: Wang et al. as discussed by the authors focused on perceptions of registered brands sold in Shanghai shopping malls and found that US brands were evaluated more positively than Chinese on attributes of design innovation, workmanship, brand image, service, and display of products, while Chinese brands received more positive marks on fit and price satisfaction.
Abstract: This study focuses on perceptions of registered brands sold in Shanghai. Brand identity has been studied in Western settings; this study expands understanding of brand identity from a Chinese perspective. Chinese shoppers in Shanghai shopping malls were asked to compare US and Chinese brands in a survey about their perceptions of product attributes, brand identification and store environment. In the analysis of data, US brands were evaluated more positively than Chinese on attributes of design innovation, workmanship, brand image, service, and display of products, while Chinese brands received more positive marks on fit and price satisfaction. Low brand loyalty among the Chinese shoppers meant that brand image and competition among brands are keen. To remain competitive, US companies which plan to increase their market in China need to pay attention to product quality and how brand identity is interpreted within Chinese culture.
TL;DR: An aromatic polyimide was synthesized via a one-step polycondensation reaction between biphenyltetracarboxylic dianhydride (BPDA) and 4,4′-oxydianiline (ODA) in p-chlorophenol as mentioned in this paper.
TL;DR: In this paper, a finite element model was used to simulate the entire process of multilayered fabric target perforated by conically cylindrical steel projectile on the basis of the description of the actual structure of fabric considering crimps of warp and weft yarns.
Abstract: This paper gives a finite element model to simulate the entire process of multilayered fabric target perforated by conically cylindrical steel projectile on the basis of the description of the actual structure of fabric considering crimps of warp and weft yarns. Commercially available finite element code Ls-Dyna is incorporated with the Weibull constitutive equations of filament yarns at high strain rate to simulate the ballistic impact response. The projectile and yarns in the fabric are meshed with a eight-node hexahedron element (Solid 164 in Ls-Dyna). From the comparisons of the residual velocities of the projectile, and deformation and damages of the fabric target after ballistic perforation between the experimental results and theoretical ones, it is proven that at the yarn-structural hierarchy, the finite element method with explicit algorithm and code Ls-Dyna could precisely simulate the ballistic impact between the steel projectile and the fabric target. It is also found from calculations that on...
TL;DR: An ancient Chinese algorithm, the Ying Buzu Shu, in about second century BC, known as the rule of double false position in West after 1202 AD, is re-study and can powerfully applied to solve nonlinear equations.
TL;DR: In this article, a NCCM with carboxyl-ended polybutadiene (CPB) and polyvinyl alcohol (PVA) as the shell were formed in aqueous solutions, driven by hydrogen bonding between the component polymers.
Abstract: Noncovalently connected micelles (NCCM) with carboxyl-ended polybutadiene (CPB) as the core and poly(vinyl alcohol) (PVA) as the shell were formed in aqueous solutions, driven by hydrogen bonding between the component polymers. Shell cross-linked micelles and hollow spheres were obtained successively on the basis of NCCM: The shell structure was locked in by the cross-linking reaction of PVA with glutaraldehyde. Cavitation of the cross-linked micelles was realized by switching the aqueous medium to the THF-rich mixture. The cavitation process was monitored by dynamic light scattering, which indicated a substantial mass decrease and size expansion. The resultant hollow spheres are stable in aqueous solutions, and their shell thickness could be adjusted by changing the core/shell ratio of the micelle precursors. SEM observations proved that the mechanical stability of the hollow spheres depended on both the cross-linking degree and the thickness of the shell.
TL;DR: In this article, the ballistic perforation test results of 4-step 3-dimensional (3D) braided Twaron ® /epoxy composites, which were subjected to impact by conically cylindrical steel projectile, are presented.
Abstract: The ballistic perforation test results of 4-step 3-dimensional (3D) braided Twaron ® /epoxy composites, which were subjected to impact by conically cylindrical steel projectile, are presented. The residual velocities of projectile perforated composites target at various strike velocities were measured and also compared with that from finite element calculation. ‘Fiber inclination model’ for 3D textile composites was adopted to decompose the 3D braided composite at quasi-microstructure level for the geometrical modeling in preprocessor of FEM. The material modeling was also based on this simplified model. The finite element code of Ls-Dyna was used to simulate the impact interaction between projectile and inclined lamina. The residual velocity of projectile perforating the entire 3D braided composite can be calculated from the sum of kinetic energy loss of the projectile that obtained from FEM. From the simulation of ballistic penetration process and comparison between numerical results and experimental results, it proves that the analysis scheme of quasi-microstructure level in this paper is valid and reasonable. The simplified method in this paper could be extended to model other kinds of 3D textile composites under ballistic impact.
TL;DR: In this article, an emulsion polymerization of aniline was performed in micellar solution of a mixture of PAN latex and polyvinyl alcohol to obtain stable nano-polyaniline (PAN) waterborne latexes.
TL;DR: In this article, an allometric scaling relation between the current and voltage is obtained, based on He Chengtian's inequality, which has millennia history, and applied to the case of electrospinning.
TL;DR: The dynamic model used in this study may be better than usually used static immersion model in imitating the physiological condition of bone-like apatite formation in vivo and the mechanism of ectopic bone formation in calcium phosphate ceramics.
Abstract: Bone-like apatite formation on porous calcium phosphate ceramics was investigated in static simulated body fluid (SBF) and dynamic SBF at different flowing rates. The results of a 14-day immersion in static SBF showed that the formation of bone-like apatite occurred both on the surface and in the pores of the samples. When SBF flowed at the physiological flow rate in muscle (2 ml/100 ml.min), bone-like apatite could be detected only in internal surface of the pores of samples. The result that bone-like apatite formation could only be found in the pores when SBF flowed at physiological flow rate was consistent with that of porous calcium phosphate ceramics implanted in vivo: osteoinduction was only detected inside the pores of the porous calcium phosphate ceramics. This result implicates that the bone-like apatite may play an important role in the osteoinduction of Ca-P materials. The dynamic model used in this study may be better than usually used static immersion model in imitating the physiological condition of bone-like apatite formation. Dynamic SBF method is very useful to understand bone-like apatite formation in vivo and the mechanism of ectopic bone formation in calcium phosphate ceramics.
TL;DR: Results show that pyrene could serve as a useful fluorescence probe for incorporation into polymer nanoparticles to study tissue distribution and MePEG–PLA nanoparticles might have a great potential as carriers of hydrophobic drugs.
Abstract: Pyrene-loaded biodegradable polymer nanoparticles were prepared by incorporating pyrene into the polymer nanoparticles formulated from amphiphilic diblock copolymer, methoxy poly(ethylene glycol)–poly(lactic acid) (MePEG–PLA). Their morphological structure and physical properties were characterized by nuclear magnetic resonance (NMR), dynamic light scattering, fluorescence spectroscopy, transmission electronic microscopy and zeta potential measurements. Further, MePEG–PLA nanoparticles containing pyrene as fluorescent marker were administered intranasally to rats, and the distribution of nanoparticles in the nasal mucosa and the olfactory bulb were visualized by fluorescence microscopy. NMR results confirmed that MePEG–PLA copolymer can form nanoparticles in water, and hydrophilic PEG chains were located on the surface of the nanoparticles. The particle size, zeta potential and pyrene loading efficiency of MePEG–PLA nanoparticles were dependent on the PLA block content in the copolymer. Following nasal administration, the absorption of nanoparticles across the epithelium was rapid, with fluorescence observed in the olfactory bulb at 5 min, and a higher level of fluorescence persisted in the olfactory mucosa than that in the respiratory mucosa. These results show that pyrene could serve as a useful fluorescence probe for incorporation into polymer nanoparticles to study tissue distribution and MePEG–PLA nanoparticles might have a great potential as carriers of hydrophobic drugs.
TL;DR: Free radical polymerization of acrylonitrile in ionic liquid, 1-butyl-3methylimidazolium tetrafluoroborate ([bmim][BF 4 ]), 2,2'-azobisisobutyronitrile (AlBN) as initiator was investigated as mentioned in this paper.
Abstract: Free radical polymerization of acrylonitrile (AN) in ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF 4 ]), 2,2'-azobisisobutyronitrile (AlBN) as initiator was investigated. Early investigations on polymerizations using ionic liquids indicate that they serve as especially good solvents to achieve high molecular weight polymers. Free radical polymerizations result in higher molecular weight polymers, for ionic liquids have low chain transfer constants and act to stabilize the active radical during the process of polymerization. The thermal stability of polymers synthesized in ionic liquids have be improved obviously than that in traditional solvents.
TL;DR: This paper shows that both bamboo fiber and traditional cotton linter fiber have the similar surface free energies, however, a big difference between these two fibers which has been importantly observed is that the bamboo fiber having greater Lewis acid component seems to be double than the cotton lInter fiber.
TL;DR: AGENDA, a tool set for testing relational database applications, is extended to test web database applications to target web applications written as Java Servlets and uses an algorithm based on cyclomatic complexity to generate paths.
Abstract: Commercial, scientific, and social activities are increasingly becoming dependent on Web database applications. New testing techniques that handle the unique features of these systems are needed. To that end, we have extended AGENDA, a tool set for testing relational database applications, to test web database applications. Application source code is analyzed to extract relevant information about the URLs and their parameters. This information is used to construct and simplify a graph in which nodes represent URLs and edges represent links between URLs. A set of paths through the graph is selected and test cases are generated for each path. The extracted information about the parameters to each URL (e.g., values that an application user would enter into a form), is used to guide AGENDA to generate inputs for the URLs. The URLs on a path and their inputs are stored in an XML file, which is then automatically executed. The current implementation is targeted toward web applications written as Java Servlets and uses an algorithm based on cyclomatic complexity to generate paths. Preliminary empirically evaluation based on the TPC-W benchmark is presented.
TL;DR: In this paper, a flow-injection chemiluminescence method for the determination of diethylstilbestrol was proposed, and the linearity of the calibration graph was found to be in the range from 1.00×10−7 to 4.00 × 10−6 µmol/l.
TL;DR: The He Chengtian's inequality is re-studied, which might be new to the West, and proposed an iteration technique for searching for high accurate approximate values for one Moon and one Year.
TL;DR: In this article, a two-step direct copolymerization process of L-lactic acid (L-LA)/glycolic acid (GA) was developed and the thermal properties and solubility in chloroform of PLGA were studied by DSC and NMR.
Abstract: A two-step direct copolymerization process of L-lactic acid (L-LA)/glycolic acid (GA) was developed. The first step was to produce an oligomer of L-LA/GA and then the oligomer was polymerized with binary catalyst tin chloride dihydrate/p-toluenesulfonic acid. In this way, the copoly(L-LA/GA) (PLGA), without any organic solvent, was synthesized directly. The thermal properties and solubility in chloroform of PLGA were studied by DSC and NMR. The results showed that the melting point of PLGA decreases with increasing mole fraction of GA units in copolymer. In addition, the melting point of polymer also decreased with increasing degree of racemization of polymer. The solubility of PLGA in chloroform decreased with the increase of the average lengths of the glycolic acid units. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2163–2168, 2004
TL;DR: In this paper, the coupling reaction between poly(L-lactic acid) and poly(e-caprolactone) oligomers with NCO terminals was used to characterize the copolymers and the results showed that PLLA and PCL were coupled by the reaction between NCO groups at the end of the PCL and OH (or COOH) groups.
Abstract: An Erratum has been published for this article in J. Polym. Sci. Part A: Polym. Chem. (2004) 42(22) 5845
New multiblock copolymers derived from poly(L-lactic acid) (PLLA) and poly(e-caprolactone) (PCL) were prepared with the coupling reaction between PLLA and PCL oligomers with NCO terminals. Fourier transform infrared (FTIR), 13C NMR, and differential scanning calorimetry (DSC) were used to characterize the copolymers and the results showed that PLLA and PCL were coupled by the reaction between NCO groups at the end of the PCL and OH (or COOH) groups at the end of the PLLA. DSC data indicated that the different compositions of PLLA and PCL had an influence on the thermal and crystallization properties including the glass-transition temperature (Tg), melting temperature (TM), crystallizing temperature (Tc), melting enthalpy (ΔHm), crystallizing enthalpy (ΔHc), and crystallinity. Gel permeation chromatography (GPC) was employed to study the effect of the composition of PLLA and PCL and reaction time on the molecular weight and the molecular weight distribution of the copolymers. The weight-average molecular weight of PLLA–PCL multiblock copolymers was up to 180,000 at a composition of 60% PLLA and 40% PCL, whereas that of the homopolymer of PLLA was only 14,000. A polarized optical microscope was used to observe the crystalline morphology of copolymers; the results showed that all polymers exhibited a spherulitic morphology. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5045–5053, 2004
TL;DR: The paper presents research on the APF approach for solving the GNRON and local minima problems and the improved APF is applied to the path-planning problem of soccer robots.
Abstract: The paper presents research on the APF approach for solving the GNRON and local minima problems. The repulsive potential function is modified in order to solve the GNRON problem. A simulated annealing algorithm integrated into the APF has solved the local minimum problem. The improved APF is applied to the path-planning problem of soccer robots. The simulated experiments show the validity of this approach.