Showing papers by "South China University of Technology published in 2005"
TL;DR: The steam explosion pre-treatment led to a significant loss in hemicelluloses and alkaline peroxide post-treatment resulted in substantial dissolution of lignin and an increase in cellulose crystallinity.
629 citations
TL;DR: The mechanical properties, including the tensile modulus and strength, of the nanocomposites are greatly improved by about 93% and 99%, respectively, with incorporation of only 0.8 wt % of MWNTs into the chitosan matrix.
580 citations
TL;DR: In this article, the hydrophilic modification of poly(ether sulfone) UF membrane was performed by self-assembly of the hydroxyl group of TiO 2 nanoparticle surface and the sulfone group and ether bond in poly(et.al) structure through coordination and hydrogen bond interaction.
385 citations
Abstract: A novel series of semiconducting conjugated copolymers, derived from alkyl-substituted fluorene, 4,7-diselenophen-2‘-yl-2,1,3-benzothiadiazole (SeBT), and 4,7-diselenophen-2‘-yl-2,1,3-benzoselenadiazole (SeBSe), was synthesized by a palladium-catalyzed Suzuki coupling reaction with various feed ratios. The optical band gap of copolymers is very low, 1.87 eV for SeBT and 1.77 eV for SeBSe. The efficient fast energy transfer from fluorene segments to narrow-band-gap sites was observed. The emission of photoluminescence and electroluminescence is dominated by narrow-band-gap species and peaked at 670−790 nm, in the range from deep-red to near-infrared (NIR). The external electroluminescent (EL) quantum efficiencies reached 1.1% and 0.3% for devices from these two types of copolymers, respectively. Bulk−heterojunction polymer photovoltaic cells (PPVCs) made from composite thin film of the copolymer 9,9-dioctylfluorene and SeBT (PFO−SeBT) in blend with fullerene derivative [6,6]-phenyl C61 butyric acid methyl ...
372 citations
TL;DR: In this paper, electrochemical impedance spectroscopy, potentiodynamic polarization and E(corr)-t curve were used to investigate the corrosion behavior of Mg alloy AZ91D.
274 citations
07 Nov 2005
TL;DR: Two classification methods, the hidden Markov model (HMM) and the support vector machine (SVM), are used, to classify five emotional states: anger, happiness, sadness, surprise and a neutral state.
Abstract: Automatic emotion recognition in speech is a current research area with a wide range of applications in human-machine interactions. This paper uses two classification methods, the hidden Markov model (HMM) and the support vector machine (SVM), to classify five emotional states: anger, happiness, sadness, surprise and a neutral state. In the HMM method, 39 candidate instantaneous features were extracted, and the sequential forward selection (SFS) method was used to find the best feature subset. The classification performance of the selected feature subset was then compared with that of the Mel frequency cepstrum coefficients (MFCC). Within the method based on SVM, a new vector measuring the difference between Mel frequency scale sub-bands energies is proposed. The performance of the K-nearest neighbors (KNN) classifier using the proposed vector was also investigated. Both gender dependent and gender independent experiments were conducted on the Danish emotional speech (DES) database. The recognition rates by the HMM classifier were 98.9% for female subjects, 100% for male subjects, and 99.5% for gender independent cases. When the SVM classifier and the proposed feature vector were employed, correct classification rates of 89.4%, 93.6% and 88.9% were obtained for male, female and gender independent cases respectively.
215 citations
TL;DR: In this article, a series of electrophosphorescent conjugated fluorene-alt carbazole copolymers are synthesized by Suzuki polycondensation, and a diketone-ended alkyl chain which is grafted in the N-position of carbazoles serves as a ligand to form a pendant cyclometalated Ir complex with 1-phenylisoquinoline (Piq), 2-naphthylpyridine (Napy), and 2-phenylonquinoline(Phq).
Abstract: A series of electrophosphorescent conjugated fluorene-alt-carbazole copolymers are synthesized by Suzuki polycondensation. A diketone-ended alkyl chain which is grafted in the N-position of carbazole serves as a ligand to form a pendant cyclometalated Ir complex with 1-phenylisoquinoline (Piq), 2-naphthylpyridine (Napy), and 2-phenylquinoline (Phq). The PL efficiencies of PFCzIrPiq and PFCzIrPhq copolymers are around 60% and 70%, respectively. EL emission from the backbone of PFCzIrPiq and PFCzIrPhq copolymers is completely quenched even though the Ir complex contents in the polymers are as low as 0.5 mol %. The device of PFCzIrPiq05 copolymer shows the highest external quantum efficiency of 4.9% ph/el and the luminous efficiency of 4.0 cd/A with 240 cd/m2 at a bias voltage of 7.7 V and a peak emission of 610 nm. The device efficiency of PFCzIrPiq05 copolymer still remains high (QE ext = 3.4% ph/el and LE = 2.9 cd/A) with a luminance of 2978 cd/m2 even at a current density of 100 mA/cm2. The enhancement o...
192 citations
TL;DR: In this article, wood flour is converted into thermoplastics through proper benzylation treatment, which introduces large benzyl group onto cellulose and partially deteriorates the ordered structure of the crystalline regions.
190 citations
TL;DR: The degree of substitution of the carboxymethyl chitosan synthesized exceeded 0.85 and the effect of the reaction conditions was investigated and optimal conditions were identified.
171 citations
TL;DR: In this article, an organic/inorganic composite membrane for direct methanol fuel cell (DMFC) application was prepared with sulfonated poly(ether ether ketone) (SPEEK) and layered silicate such as organic-montmorillonite (OMMT) by solution intercalation technique.
167 citations
TL;DR: In this paper, a series of soluble conjugated random and alternating copolymers (PFO-TST) derived from 9,9-dioctylfluorene (FO) and 1,1-dimethyl-3,4-diphenyl-2,5-bis(2‘-thienyl)silole (TST), were synthesized by palladium(0)-catalyzed Suzuki coupling reactions.
Abstract: A novel series of soluble conjugated random and alternating copolymers (PFO-TST) derived from 9,9-dioctylfluorene (FO) and 1,1-dimethyl-3,4-diphenyl-2,5-bis(2‘-thienyl)silole (TST) were synthesized by palladium(0)-catalyzed Suzuki coupling reactions. The feed ratios of FO to TST were 99:1, 95:5, 90:10, 80:20, and 50:50. Chemical structures and optoelectronic properties of the copolymers were characterized by elemental analysis, NMR, UV absorption, cyclic voltammetry, photoluminescence (PL), electroluminescence (EL), a photovoltaic cell, and a field effect transistor. The elemental analyses of the copolymers indicated that FO and TST contents in the copolymers were very close to the feed compositions. The random copolymers exhibited a PFO-segment-dominated UV absorption peak at ∼385 nm and a narrow band gap TST absorption at ∼490 nm. For the alternating copolymer, only a broad absorption band was found, demonstrating a mixed and TST-dominated electronic configuration. Compared with the solution PL, complet...
TL;DR: In this article, a second mild alkaline hydrolysis of the alkali-soluble lignin preparations and acid acid-hydrized 90% acid-acid dioxane-solubilization of the 90% pH-dioxane solubilized Lignin fractions were performed, which released 48.8% of the total ester-linked p-CA and 43.5% of total ether-linked FA, respectively.
TL;DR: In this article, the authors draw upon social capital theory to develop and test a model of expatriate adjustment and performance, which predicts that social networks and access to information and resources (opportunities), trust and norm of reciprocity (motivation) and host country nationals' intercultural competencies and reliable task performance (abilities) have direct effects.
Abstract: To understand the effects of host country nationals (HCNs) on expatriate effectiveness, we draw upon social capital theory to develop and test a model of expatriate adjustment and performance. This social capital model predicts that social networks and access to information and resources (opportunities), trust and norm of reciprocity (motivation) and HCNs' intercultural competencies and reliable task performance (abilities) have direct effects on expatriate adjustment and performance. To test the proposed model, we conducted a field study and collected data from 147 expatriate managers working in Hong Kong, Beijing and Shanghai. The social capital variables were strong predictors of expatriate performance but were relatively weak for adjustment. Having adopted a new perspective for examining expatriate effectiveness, this research offers some new directions for future studies in expatriate research as well as in social capital.
TL;DR: In this article, the effects of the OMMT on the structure and properties of polypropylene (PP) nanocomposites were studied fully, and the intercalated structure of the nanocomposition was characterized by X-ray diffraction and transmission electron microscopy (TEM).
TL;DR: In this paper, a bilayer cathode was proposed to enhance electron injection to red, green and blue electroluminescent (EL) polymers, thereby resulting in high efficiency polymer LEDs, which are comparable to that of using low work function metals such as Ca and Ba as cathode.
TL;DR: In this article, a two-stage process based on a steam explosion pre-treatment followed by alkaline peroxide post-treatment was used for fractionation of wheat straw, where the steamed straw was washed with water to yield a solution rich in hemicelluloses-derived mono-and oligosaccharides (20.5-28.5%) together with small amounts of degraded hemicellular polymers (2.4-6.2%) and minor quantities of lignin (1.9-2.1%).
TL;DR: In this article, several types of counter electrodes based on flexible metal and plastic substrates for dye-sensitized solar cells (DSCs) have been investigated and shown to improve the fill factor and conversion efficiency of the DSC by reducing its internal resistance.
TL;DR: The results suggested that the MTGase treatment of film-forming solutions of SPI prior to casting could greatly modify the properties and microstructures of SPI films.
TL;DR: In this paper, the physicochemical properties and structural characteristics of microbial transglutaminase (MTGase)-induced biopolymers of sodium caseinate (SC) were investigated.
Abstract: Some physicochemical properties and structural characteristics of microbial transglutaminase (MTGase)-induced biopolymers of sodium caseinate (SC) were investigated. The sodium dodecyl sulfatepolyacrylamide gel electrophoresis and size-exclusionhigh-performance liquid chromatography analyses showed that all components of SC were easily polymerized or transformed by MTGase to form high-molecular weight biopolymers, and the susceptibility order of individual components was kappa-Casein (C) > alpha-C > beta-C. The emulsifying properties of biopolymers depended on the incubation time with MTGase. The emulsifying activity index of biopolymers persistently increased with the MTGase (0-12 h) incubation time. The emulsion stability also increased with the incubation time (< 4 h), then declined a little with longer incubation (412 h). The differential scanning calorimetry analysis showed that the thermal properties of the biopolymers obtained after a 12-h incubation were different from that of native SC or biopolymers obtained after a shorter incubation time (< 4 h), suggesting that the former has higher thermal stability. In addition, the ultraviolet (UV) spectra showed that the UV absorbance (at 275 nm) of MTGase-induced biopolymers of SC decreased with an increasing incubation time with MTGase, and the maximal emission wavelength (lambda(max)) slightly shifted to the "blue side." The fluorescence spectra showed that the lambda(max) was related with incubation time with MTGase, slightly shifting to the "blue side" after 4 h with no further changes; its relative fluorescence intensity also increased. These results suggest a relationship between the functionalities and structural characteristics of the MTGase-induced biopolymers of SC.
TL;DR: In this article, the authors derived the solution of the Cauchy problem in terms of the Green functions and the representations of the green function by applying its Fourier-Laplace transforms.
Abstract: A space-time fractional advection-dispersion equation (ADE) is a generalization of the classical ADE in which the first-order time derivative is replaced with Caputo derivative of order α ∈ (0, 1], and the second-order space derivative is replaced with a Riesz-Feller derivative of order β ∈ (0, 2]. We derive the solution of its Cauchy problem in terms of the Green functions and the representations of the Green function by applying its Fourier-Laplace transforms. The Green function also can be interpreted as a spatial probability density function (pdf) evolving in time. We do the same on another kind of space-time fractional advection-dispersion equation whose space and time derivatives both replacing with Caputo derivatives.
TL;DR: Chelating polymers with Ir complexes in the conjugated polymer backbone show highly efficient energy transfer of excitons from the PFCz host segment to the Ir complex by an intramolecular trapping mechanism, indicating that incorporation of the phosphorescent complex into the rigid conjugate polymer main chain is a new way to simultaneously realize high efficiency, long-term stability, and simple processing of phosphorescent polymer light-emitting diodes.
Abstract: The synthesis of electrophosphorescent chelating polymers by Suzuki polycondensation of A-A- and B-B-type monomers is described, in which the fluorene-alt-carbazole (PFCz) segment is used as polymer backbone. By using alkyl-substituted ligands of iridium complex monomers, chelating copolymers with higher contents of iridium complex can be synthesized. Chemical and photophysical characterization confirm that the Ir complex is incorporated into the polymer backbone as one of the monomer repeat units by means of two 5-bromotolylpyridine ligands. Chelating polymers with Ir complexes in the conjugated polymer backbone show highly efficient energy transfer of excitons from the PFCz host segment to the Ir complex by an intramolecular trapping mechanism. The external quantum and luminous efficiencies of a device made with PFCzMppyIrhm4 copolymer reach 4.1% ph/el (photons/electron) and 5.4 cdA - 1 , respectively, at a current density of 32.2 mA cm - 2 , an emission peak of 577 nm, and a luminance of 1730 cd cm - 2 . Most important, the devices made from the chelating copolymers show no notable efficiency decay with increasing current density due to reduced concentration quenching and triplet-triplet (T-T) annihilation. This indicates that incorporation of the phosphorescent complex into the rigid conjugated polymer main chain is a new way to simultaneously realize high efficiency, long-term stability, and simple processing of phosphorescent polymer light-emitting diodes.
TL;DR: In this paper, it was shown that the diffusion can be rate-governed in the micro-pores, as the channel dimensions imply very low macropore diffusion resistance.
TL;DR: An increase in cellulose's accessibility in terms of water retention value (WRV) with increasing ultrasound treatment time and the regioselective oxidation reactivity of cellulose with sodium periodate was successfully improved by the ultrasound treatment.
TL;DR: In this paper, dewaxed barley straw with 1.5% H 2 O 2 at pH 12.0 for 14h at 40°C under various ratios of straw to extractant and with 80% acetic acid-70% nitric acid (10/1, v/v) at 120°C for 15min yielded the purified cellulose ranging between 35.4 and 36.4%, which were relatively free of bound hemicelluloses.
TL;DR: In this paper, a polyvinyl alcohol hydrogel was prepared by coupling poly(vinyl acid) with epichlorohydrin as cross-linking agent and the analytical results indicate that there exists two critical threshold degree of saturation, i.e., at the first threshold S*, freezable bound water starts to appear and at the second threshold S**, the free water begins to appear.
TL;DR: It was found that added NaCl did not affect the release rate even up to 0.5 M of its concentration, while increasing the release temperature remarkably speeded up the release process.
TL;DR: In this paper, a novel mathematical model of optimal reactive power dispatch (ORPD) for power systems is presented, whose objective function is to minimize the energy loss at the current time interval and the CACD.
Abstract: The traditional model of optimal reactive power dispatch (ORPD) for power systems is based on the principle of income maximization, which aims at minimizing active power loss of the whole networks. However, such a model may bring on excessive operations of device-control devices in real-time application. To realize reactive power dispatch, power utilities should increase equipment investment and added manpower for operation and maintenance. On the other hand, the operations would augment the fault probability of power systems. Therefore, the costs of adjusting the control devices (CACDs) are investigated, and a novel mathematical model of ORPD is presented in this paper, whose objective function is to minimize the energy loss at the current time interval and the CACD. A simulation test is presented to demonstrate that the proposed model reflects the principle of profit maximization and describes the ORPD problem with time-varying loads appropriately since it can decrease active power loss and avoid excessive controls simultaneously.
TL;DR: In this article, the authors proposed three procedure theory to evaluate domestic-scale solar water heaters based on the second thermodynamic law, which can separate the technology process into three intimately related sub-procedures, namely conversion procedure, utilization procedure, and recycling procedure.
Abstract: Solar water heater is the most popular means of solar energy utilization because of technological feasibility and economic attraction compared with other kinds of solar energy utilization. Earlier assessments of domestic-scale solar water heaters were based on the first thermodynamic law. However, this kind of assessment cannot perfectly describe the performance of solar water heaters, since the essence of energy utilization is to extract available energy as much as possible. So, it is necessary to evaluate domestic-scale solar water heaters based on the second thermodynamic law. No matter the technology process, from the property of energy utilization perspective, we can separate the technology process into three intimately related sub-procedures, namely conversion procedure, utilization procedure, and recycling procedure. An energy analysis entitled ‘Three Procedure Theory’ can be conveniently conducted as presented by Professor Hua Ben. Compared with other theories of energy analysis, three procedure theory exhibits great advantages. The utilization procedure puts forth requirement for the design of parameters in conversion procedure and sets up limits in the consideration of recycling procedure. Of course, under specific conditions, the utilization procedure also receives feedback from other procedures. Three procedure theory furnishes us a good platform to perform energy analysis. The study in this paper is based on three procedure theory. Exergy analysis is conducted with the aim of providing some methods to save cost and keep the efficiency of domestic-scale solar water heater to desired extent and at the same time figuring out related exergy losses. From this survey, it is shown that for an ordinary thermally insulated domestic-scale solar water heater, Dju (exergy losses due to imperfectly thermal insulation in collector) and DjR (exergy losses due to imperfectly thermal insulation in storage barrel) cannot be avoided. Dku (exergy losses due to irreversibility in collector) is mainly caused by irreversibility of heat transfer and DkR (exergy losses due to irreversibility in storage barrel) is dominated by the mixing of water at different temperature. Dku acts as the driving force for the system while DkR is of little contribution. A good design of storage barrel with little DkR will go a long way in improving exergy efficiency. An equation for computing DkR is presented. For the collector, which is the core of the domestic-scale solar water heater, a judicious choice of width of plate W and layer number of cover is necessary. We define collector exergy efficiency ηxc to be ηxc=Exo/Exu. The relation between collector exergy efficiency and width of plate together with layer number of cover is also analysed.
TL;DR: A series of novel near-infrared (NIR) electroluminescence (EL) copolymers based on a host poly(p-phenylenevinylene) (PPV) derivative of poly(2-methoxy-5-octyloxy-p-ethylenevinylene), with different content of narrow band-gap (NBG) unit 4,7-bis(2)-2-thienyl)-2,1,3-benzothiadiazolevinylene (DBTV) was prepared by Stille coupling reaction RE