Showing papers by "South China University of Technology published in 1998"
TL;DR: In this article, the structure, doping, conductivity and thermal stability of reduced polyaniline (PANI-R) were studied by elemental analysis, FT-i.r., solid-state 13C-NMR, XPS and TGA.
283 citations
TL;DR: A novel error concealment method called best neighborhood matching (BNM) is presented by using a special kind of information redundancy-blockwise similarity within the image by utilizing information of not only neighboring pixels, but also remote regions in the image.
Abstract: Imperfect transmission of block-coded images often results in lost blocks. A novel error concealment method called best neighborhood matching (BNM) is presented by using a special kind of information redundancy-blockwise similarity within the image. The proposed algorithm can utilize the information of not only neighboring pixels, but also remote regions in the image. Very good restoration results are obtained by experiments.
156 citations
TL;DR: The antibacterial activity of a series of soluble pyridinium-type polymers with different compositions against Escherichia coli suspended in sterilized distilled water was investigated by a colony count method and this activity can be enhanced as the content of the pyridine group (Cq) in the polymers increases.
Abstract: The antibacterial activity of a series of soluble pyridinium-type polymers with different compositions against Escherichia coli (E. coli) suspended in sterilized distilled water was investigated by a colony count method. The results show that the antibacterial activity of the soluble pyridinium-type polymers is characterized by their activity to kill bacterial cells and this activity can be enhanced as the content of the pyridinium group (Cq) in the polymers increases. The species of the bacteria has a great influence upon the antibacterial activity of the soluble pyridinium-type polymers. The polymers possess a strong ability to kill Gram-positive and Gram-negative bacteria, and yeasts, excepting Bacillus subtilis, having gemmae and fungi. The toxicity of this kind of polymer has also been appraised. In the acute stimulation and allergy experiments, the red maculae, edema, and abnormal phenomena of an allergy on the skin of the tested animals were not observed. The acute toxicity experiment shows that the LD50 of the polymer is 2330 mg/kg, implying that this kind of polymer has only very weak toxicity. This is significant for the application of soluble pyridinium-type polymers. © 1998 John Wiley & Sons, Inc. J Appl Polm Sci 67:1761–1768, 1998
68 citations
TL;DR: The main contribution of this paper is that the results apply to both standard and non-standard singularly perturbed systems.
67 citations
TL;DR: An improved genetic algorithm (IGA) is proposed to provide a systematic approach and tools for synthesis design and retrofits of distillation systems, which inherits main ideas in evolutionary computing.
61 citations
TL;DR: The concepts of polarity and quality of the training data are introduced and two robust learning algorithms for determining a robust nonlinear interval regression model are proposed, derived in a manner similar to the back-propagation (BP) algorithm.
55 citations
TL;DR: In this article, phase separation in Poly(N -isopropyl acrylamide)/Water Solutions I Cloud Point Curves and Microgelation is performed in the context of poly(n)-isopropyric acid.
Abstract: Phase Separation in Poly( N -isopropyl acrylamide)/Water Solutions I Cloud Point Curves and Microgelation
52 citations
TL;DR: In this article, a one to one correspondence was established between the non-egenerate critical points of Q(x) in Omega and single peaked solutions of the problem, and a one-to-one correspondence between the critical points in the Omega and the single peaked solution of the same problem was established.
Abstract: A one to one correspondence is established between the nondegenerate critical points of Q(x) in Omega and single peaked solutions of the problem
51 citations
TL;DR: In this paper, a feature extraction approach based on elastic meshing and directional decomposition techniques for handwritten Chinese character recognition (HCCR) is proposed in which three kinds of decomposition methods are proposed.
Abstract: A new feature extraction approach based on elastic meshing and directional decomposition techniques for handwritten Chinese character recognition (HCCR) is proposed in this letter. It is found that decomposing a Chinese character into horizontal, vertical stroke, left slant and right slant directional sub-patterns is very helpful for feature extraction and recognition. Three kinds of decomposition methods are proposed. A minimum distance classifier is trained by 3755 categories of characters using the new features. Testing on a total of 37,550 untrained handwritten samples produces the recognition rate of 92.36%, showing the effectiveness of the proposed approach.
42 citations
TL;DR: In this article, the authors used dynamic viscoelasticity measurements for reversible network formation via the physical association of hydrophobic side-groups during phase separation at around 33°C in a 1.22 wt.% aqueous solution of poly( N -isopropyl acrylamide) (PNIPA) having a molecular weight of 2.1 × 10 6.
40 citations
TL;DR: In this paper, a conical slit die fed by a conventional extruder was used to extract self-reinforced polypropylene (PP) sheets from melt flow-induced crystallization, and their structure and properties were studied by scanning electron microscopy observation, differential scanning calorimetry analyses, tensile strength, and light transmittance measurements.
Abstract: Self-reinforced polypropylene (PP) sheets have been prepared from melt flow-induced crystallization through a conical slit die fed by a conventional extruder. Their structure and properties, influenced by the die pressure ranging from 20 to 50 MPa and die outlet temperature, are studied by scanning electron microscopy observation, differential scanning calorimetry analyses, tensile strength, and light transmittance measurements. At a die outlet temperature of 162°C and a pressure above 30 MPa, conspicuous increases in the melting peak, tensile strength, and light transmittance (they can be used to characterize the self-reinforcement degree of sheet) are observed. The self-reinforcement degree, however, increases only slightly with increasing pressure as it exceeds 40 MPa. Raising the die outlet temperature from 162 to 172°C results in a further increase in the self-reinforcement degree (for example, a highest tensile strength of 288 MPa) while keeping the pressure at 40 MPa, so bulk PP materials with high properties can be produced from continuous melt extrusion under pressures lower than 40 MPa. Furthermore, the melt temperature plays an important role in determining the properties of self-reinforced polymeric materials. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:2111–2118, 1998
01 Jun 1998-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the influence of threshold stress on the value of the activation energy and stress exponent (n) measured during creep tests in fine-grained Y 2 O 3 -doped ZrO 2 polycrystals was investigated in the low-stress region at intermediate temperatures.
Abstract: The influence of the threshold stress on the value of the activation energy ( Q ) and stress exponent ( n ) measured during creep tests in fine-grained Y 2 O 3 -doped ZrO 2 polycrystals has been investigated in the low-stress region at intermediate temperatures. A significant increase of the measured value of Q and n with decreasing stress has been observed, consistent with the existence of a threshold stress for superplastic deformation.
TL;DR: A fracture network model based on algebraic topology theory has been developed to study fluid flow and solute transport in fracture dominant media and the development of a transport mechanism in which dispersive–convective solute migration through discrete fracture network can be evaluated.
TL;DR: In this article, the effect of vanadium addition on the microstructure of high-temperature shape memory alloy (SMA) and its thermal cycling and ageing behaviour has been investigated.
Abstract: The effect of vanadium addition on the microstructure of Cu–Al–Ni–Mn high-temperature shape memory alloy (SMA) and its thermal cycling and ageing behaviour has been investigated. Using scanning electron microscopy, energy dispersive X-ray analysis and X-ray diffraction analysis, the morphology, distribution and structure of secondary phase, induced by vanadium addition, have been identified. The effect of secondary phase on grain refining of Cu–Al–Ni–Mn has also been revealed. Differential scanning calorimetry measurement was used to investigate the effect of thermal cycling and ageing on the transformation temperature. It has been found that thermal cycling has a strong influence on the transformation temperature of the present Cu–Al–Ni–Mn–V high-temperature SMA. Ageing also caused an apparent change of the transformation temperature. It has been suggested that this was mainly due to the precipitation of secondary phase, because the sample was heated to a rather high temperature in both thermal cycling and the ageing process. The experiment showed that the transformation temperature could be maintained stable in the thermal cycling process by pre-ageing the sample at a suitable temperature.
TL;DR: In this article, a two-step crosslinking process was used to compatibilize the blends of polystyrene and polyethylene, which has a significant impact on the mechanical properties of the blends including impact strength, the tensile modulus, and the elongation at break.
TL;DR: In this article, high energy ball milling was applied to the Pb-Al immiscible binary system by using the method of high energy balls milling to obtain nanocrystalline microstructure.
Abstract: In the present work, mechanical alloying has been applied to the Pb-Al immiscible binary system by using the method of high energy ball milling. The microstructural features of the milled powder, such as grain size, lattice constant and morphology of phases have been studied by X-ray diffraction, analytical transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Besides, energy dispersive spectroscopy was used to analysis chemical composition of phases presented after milling. Differential Scanning Calorimetry measurement was also made on the milled Pb-Al powder. The results show that homogenous blending of Pb and Al can be easily achieved by high energy ball milling in spite of their mutual immiscibility and large difference in density. The obtained alloy exhibits nanocrystalline microstructure. Further more, the experiment result implies the formation of supersaturated solid solution in immiscible Pb-Al system by high energy ball milling.
TL;DR: In this article, two blow-film extrusion grade thermoplastics, polypropylene (PP) and low density polyethylene (LDPE), have been melt-blended in a screw extruder.
TL;DR: The strengthening and toughening effects and mechanisms of combining both whisker reinforcing and zirconia phase transformation tougheening in the Al2O3 matrix were systematically investigated in this paper, where TEM observations showed that most SiCwAl 2O3 and ZrO2(2Y) interfaces are bonded tightly and there are no distinct second phases or intermediate layers formed at the interfaces.
TL;DR: In this paper, the fluorescence behavior of the drug hesperidin in several cyclodextrins (CDS):β-cyclodextrin(β-CD), hydroxypropyl-β-CDS (HP-βCDS), methyl-β CDS (M-βcCD), and M-β cDS was studied.
Abstract: The fluorescence behavior of the drug hesperidin in several cyclodextrins(CDS):β-cyclodextrin(β-CD), hydroxypropyl-β-CD (HP-β-CD) and methyl-β-CD(M-β-CD) was studied. The stoichiometry of the complexes and their apparent formation constants were estimated. The excitation wavelengths were at 335nm for hesperidin in β-CD, HP-β-CD and M-β-CD media. The emission wavelengths were at 444, 436 and 434 nm, respectively; The fluorescence enhancement of hesperidin was observed in different cyclodextrin media. The linear calibration plots between fluorescence intensity and hesperidin concentration were determined in the 10−7 ∼10−5 M range. The mechanism for the enhanced fluorescence was attributed to protection of the excited state within the cyclodextrin cavity.
TL;DR: Experimental results showed that significant error reduction can be achieved through the proposed approach and it was proved that the corrective training proposed by Bahl et al. (1993) is a special case of the MMD approach.
TL;DR: In this article, continuous extrusion of self-reinforced high density polyethylene (HDPE) sheets from flow-induced crystallization at die pressures varying from 30 to 60 MPa was studied.
Abstract: Continuous extrusion was studied of self-reinforced high density polyethylene (HDPE) sheets from flow-induced crystallization at die pressures varying from 30 to 60 MPa. Their morphology, thermal behavior, tensile strength, and light transmittance were tested. Flow fields of a polymer melt through a converging wedge channel were also investigated by direct visual observations in conjuction with a theoretical analysis. The extensional strain rate increased abruptly as the melt approached the exit of the converging channel, this resulting in a higher crystallization rate. So, achieving the crystallization of molecular chains just in front of the exit of the converging channel may favor to extrude the bulk polymeric materials having high properties under lower pressures (e.g., 40 MPa or lower), this having been realized in the present work. The tensile strength of the self-reinforced HDPE sheet prepared at a 40 MPa pressure was enhanced by a factor of 8.
TL;DR: A new approach for removing blocking artifacts in reconstructed block-encoded images is proposed using piecewise similarity within different parts of the image as a priori to give reasonable modifications to the block boundary pixels.
Abstract: In this letter we propose a new approach for removing blocking artifacts in reconstructed block-encoded images. The key of the approach is using piecewise similarity within different parts of the image as a priori to give reasonable modifications to the block boundary pixels. This makes our approach different from traditional ones, which are often developed by applying some kinds of smoothing constraints on local regions. Experimental results show that our approach well achieves enhanced decoding for JPEG-decoded images both objectively and subjectively.
TL;DR: In this article, the authors introduced the concept of frequency measures of subsets of integers and investigated their properties, and thus new oscillation criteria for difference equations can be derived, which differ from the classical ones in that they are described by the measures of the level sets of the involved parameter sequences.
Abstract: The classical concept of oscillation is not sufficient to fully describe the oscillatory behavior of a real sequence. By introducing the concepts of frequency measures of subsets of integers, and investigating their properties, we are able to strengthen the original concept of an oscillatory sequence and thus new oscillation criteria for difference equations can be derived. These criteria differ from the classical ones in that they are described by means of the measures of the level sets of the involved parameter sequences. A brief description of the theory of frequency measures for multiple sequences is also given.
TL;DR: In this paper, the authors proposed an expression describing the relationship between the entry region length (L e ) and the die-swell ratio (B) of polymer melts in the extrusion.
TL;DR: In this article, the critical laser glazing scanning rates of the FeCrPC and CoNiSiB alloys were calculated and multi-pass overlapping experiments were carried out, and the result of laser-glazing shows that under the condition of laser power of 2.1 kW, beam diameter of 0.3 mm, and laser scanning speed of 340 mm/s, the multipass amorphous layers of about 20×20 mm2 are obtained, and no obvious crystallizing in overlapping zone is observed.
TL;DR: In this article, the authors investigated the stresses of Ω-shaped bellows with ideal and elliptic toroids imposed by internal pressure or deflection, and analyzed the stress distribution state.
TL;DR: In this article, a cis-1,4-polybutadiene (BR) sample was compressed by ultrahigh pressures (>4.0 GPa) and annealed between 25 and 180°C, and the BR samples were crosslinked when the annealing temperatures were above 100°C.
Abstract: cis-1,4-Polybutadiene (BR) samples, in the absence of crosslinking agents, were simultaneously compressed by ultrahigh pressures (>4.0 GPa) and annealed between 25 and 180°C. The BR samples were crosslinked when the annealing temperatures were above 100°C. The Vickers microhardness of the treated BR increased and the extent of swelling decreased rapidly as the annealing temperature increased, indicating that the crosslinking density increased. Solid-state carbon-13 nuclear magnetic resonance and Fourier transform infrared spectroscopy results showed that some C=C bonds in the BR were opened to form the crosslinking network structures with C—C linkages and that a partial cis–trans isomerization took place during the treatments. Differential scanning calorimetry studies revealed that the glass transition temperature increased and the crystallinity decreased as the annealing temperature increased. When the annealing temperature exceeded 140°C, the treated BR samples lost their rubbery elastic characteristics completely and became brittle materials. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:2131–2140, 1998
TL;DR: In this paper, the electrorheological (ER) suspensions containing polypyrrole particles in silicon oil are prepared and the results show that the suspension can display significant ER effects only when the particle conductivity is within a certain range, and the suspension's ER effect increases with particle concentration and field strength, but decreases with the increasing shear rate.
Abstract: In this article, the electrorheological (ER) suspensions containing polypyrrole particles in silicon oil are prepared. These suspensions’ ER properties, in particular their conductive property and the influencing factors, such as particle conductivity, field strength, concentration and shear rate, are investigated experimentally. The results show that the suspension can display significant ER effects only when the particle conductivity is within a certain range, and the suspension’s ER effect increases with particle concentration and field strength, but decreases with the increasing shear rate. The suspension’s current density increases with particle concentration, particle conductivity and field strength, while decreases with shear rate.
TL;DR: In this paper, the geometry change of a single asperity due to lubricated wear was studied by an experimental simulation with a ball-on-disc set up, which led to the formation of a tilted section at the tip of the ball, which was proved to be due to the presence of oil during the process.
Abstract: The geometry change of a single asperity due to lubricated wear was studied by an experimental simulation with a ball‐on‐disc set up. The wear leads to the formation of a tilted section at the tip of the ball, which is proved to be due to the presence of oil during the process. The effect of the geometry change of rough surface contacts due to wear was examined by a micro‐EHL analysis. A non‐Newtonian visco‐plastic fluid model which includes the effect of a limiting shear strength was used.