Showing papers by "South China University of Technology published in 2004"
TL;DR: Adapt neural control schemes are proposed for two classes of uncertain multi-input/multi-output (MIMO) nonlinear systems in block-triangular forms that avoid the controller singularity problem completely without using projection algorithms.
Abstract: In this paper, adaptive neural control schemes are proposed for two classes of uncertain multi-input/multi-output (MIMO) nonlinear systems in block-triangular forms. The MIMO systems consist of interconnected subsystems, with couplings in the forms of unknown nonlinearities and/or parametric uncertainties in the input matrices, as well as in the system interconnections without any bounding restrictions. Using the block-triangular structure properties, the stability analyses of the closed-loop MIMO systems are shown in a nested iterative manner for all the states. By exploiting the special properties of the affine terms of the two classes of MIMO systems, the developed neural control schemes avoid the controller singularity problem completely without using projection algorithms. Semiglobal uniform ultimate boundedness (SGUUB) of all the signals in the closed-loop of MIMO nonlinear systems is achieved. The outputs of the systems are proven to converge to a small neighborhood of the desired trajectories. The control performance of the closed-loop system is guaranteed by suitably choosing the design parameters. The proposed schemes offer systematic design procedures for the control of the two classes of uncertain MIMO nonlinear systems. Simulation results are presented to show the effectiveness of the approach.
771 citations
TL;DR: In this paper, three different procedures for isolation of cellulose from sugarcane bagasse (SCB) were comparatively studied, and the isolated six cellulose samples were comparatively analyzed by both degraded methods such as acid hydrolysis and thermal analysis and non-degradation techniques such as FT-IR and CP/MAS 13C-NMR spectroscopy, and their relative crystallinity was also comparatively estimated.
615 citations
TL;DR: In this paper, a copolymerization of poly[(9,9-bis(3‘-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2, 7-dioctylfluorene] (P1, P2, P4) was investigated and the resulting conjugated polyelectrolytes were used as emitting layers in device fabrication.
Abstract: Alternating copolymers poly[(9,9-bis(3‘-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (P1) and poly[(9,9-bis(3‘-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-1,4-phenylene] (P3) were synthesized by the palladium-catalyzed Suzuki coupling reaction and their quaternized ammonium polyelectrolyte derivatives (P2, P4) were obtained through a postpolymerization treatment on the terminal amino groups. The resulting conjugated polyelectrolytes (P2, P4) are soluble in polar solvents such as methanol, DMF, and DMSO while P4 is a water-soluble blue-emitting conjugated polyelectrolyte. The electrochemical and photophysics properties of the resulting copolymers were fully investigated. Both the neutral amino-functionalized polyfluorenes (P1, P3) and the quaternized ammonium salt functional conjugated polyelectrolytes derivatives (P2, P4) were used as the emitting layers in device fabrication. All these polymers show even higher external quantum efficiencies (QE) with the high work-function met...
567 citations
399 citations
TL;DR: The results showed that the sequential treatments were very effective on the fractionation of hemicelluloses from bagasse, and the extraction strength, such as alkali and H 2 O 2 concentration, had a great influence on the chemical and structural features of the hemicellular structures as discussed by the authors.
325 citations
TL;DR: This is the first report on an electroluminescent polymer which bears the high EL efficiency, the electron-injection ability from high work function metals, and the solubility in environment-friendly solvents at the same time.
Abstract: A series of aminoalkyl-substituted polyfluorene copolymers with benzothiadiazole (BTDZ) of different content were synthesized by Suzuki coupling reaction, and their quaternized ammonium polyelectrolyte derivatives were obtained through a postpolymerization treatment on the terminal amino groups. Copolymers are soluble in environmentally friendlier solvents, such as alcohols. It was found that the efficient energy transfer occurs by exciton trapping on the narrow band gap BTDZ site under UV illumination. Only 1% of BTDZ content is needed to completely quench a fluorene emission for both the neutral and the quaternized copolymers in the neat film. Absolute PL efficiencies of copolymer films were greatly enhanced as a result of the suppression of excimer formation. Light-emitting devices fabricated from these copolymers show high external quantum efficiencies over 3% and 1% for the neutral precursor and the quaternized copolymers, respectively, with high work function metals such as Al as a cathode. To the b...
309 citations
TL;DR: In this article, the authors synthesize conjugated random copolymers by palladium-catalyzed Suzuki coupling reaction from 9,9-dioctylfluorene (DOF) and 4,7-di(4hexylthien-2-yl)-2,1,3-benzothiadiazole (DHTBT) with DHTBT composition varying from 1 to 50 mol % in the copolymer.
Abstract: Novel soluble conjugated random copolymers are synthesized by palladium-catalyzed Suzuki coupling reaction from 9,9-dioctylfluorene (DOF) and 4,7-di(4-hexylthien-2-yl)-2,1,3-benzothiadiazole (DHTBT) with DHTBT composition varying from 1 to 50 mol % in the copolymer. All of the polymers are soluble in common organic solvents and are highly photoluminescent. Polyfluorene fluorescence is quenched completely at a DHTBT concentration as low as 1% in the solid film. The copolymer films are highly fluorescent under UV irradiation in contrast to its parent analogue, 4,7-di(thien-2-yl)-2,1,3-benzothiadiazole (PFO−DBT), without alkyl substitution on thiophene rings. Devices made up of these copolymers emit saturated red light. The emission peaks are shifted from 613 to 672 nm when the DHTBT content increases from 1 to 50%. The highest external quantum efficiency achieved in the device configuration ITO/PEDT/PVK/PFO−DHTBT/Ba/Al is 2.54% with luminous efficiency 1.45 cd/A for the copolymer with emission peak at 638 n...
238 citations
233 citations
TL;DR: In this article, a semi-empirical model incorporating slurry rheology, solids concentration, particle size and slurry temperature was described, and on-line measurement for the slurry Rheology control was also discussed.
198 citations
TL;DR: In this paper, the properties of several types of counter electrodes based on metal, plastic, and glass substrates for use in dye-sensitized solar cells (DSCs) were investigated.
194 citations
TL;DR: In this article, a variety of light-emitting copolymers derived from 9,9-dioctylfluorene (DOF) and 2,1,3-naphthozoselenadiazole (NSeD) were prepared by the palladium-catalyzed Suzuki coupling reaction.
Abstract: A variety of novel light-emitting copolymers derived from 9,9-dioctylfluorene (DOF) and 2,1,3-naphthozoselenadiazole (NSeD) were prepared by the palladium-catalyzed Suzuki coupling reaction. The feed ratios of DOF to NSeD were 99.9:0.1, 99.5:0.5, 99:1, 98:2, 95:5, and 85:15. All of the polymers are soluble in common organic solvents and highly fluorescent in solid state. Devices based on the copolymers emit saturated red light, and the emission slightly red-shifted gradually with increasing NSeD's contents. The maximal external quantum efficiency of the polymer light-emitting devices (PLED) reaches 3.1%, and luminous efficiency is greater than 1.0 cd/A with emission maximum at 657 nm and Commission Internationale de L'Eclairage (CIE) coordinates of (0.64, 0.33). This is the highest efficiency with saturated red emission for a single-layer device with nonblend type emitter reported so far in the scientific literature. This indicates that the new EL polymers based on fluorene and naphthoselenadiazole are pr...
TL;DR: In this paper, a new formulation of eigenproblem for phononic crystals is developed and the convergence of the new formulation in the band-structure calculations is examined in detail and compared with that of the conventional plane wave expansion (CPWE) method.
TL;DR: In this article, a novel binary oxide photocatalyst ZnO/TiO 2 was prepared by a new modified sol-gel method using citric acid as a complex reagent and its photocatalytic activity was investigated.
Abstract: A novel binary oxide photocatalyst ZnO/TiO 2 was prepared by a new modified sol–gel method using citric acid as a complex reagent and its photocatalytic activity was investigated. The factors, such as the ratio of amount of doped zinc ion, the precursors, and the calcination temperature on the activities of ZnO/TiO 2 photocatalyst, were investigated. SO 4 2− /ZnO/TiO 2 was prepared by sulfating the dry gels of ZnO/TiO 2 with H 2 SO 4 solution. It was showed that the addition of ZnO could enhance the activity significantly, and sulfating ZnO/TiO 2 with sulfuric acid resulted to dramatic enhancement, the degradation ratio of methyl orange could be up to 71.9%, compared with 55% of degradation of ZnO/TiO 2 catalyst.
TL;DR: The oil sorption capacity of the acetylated bagasse obtained at 80 degrees C for 6 h, was 1.9 times higher than the commercial synthetic oil sorbents such as polypropylene fibres, which can be used to substitute non-biodegradable materials in oil spill cleanup.
TL;DR: In this article, the cure kinetics of tetraglycidyl-4,4'-diaminodiphenylmethane (TGDDM) and 4,4-diaminanthenylsulfone (DDS) as a cure agent in nanocomposites with multiwalled carbon nanotubes (MWNTs) have been studied with an isothermal differential scanning calorimetry (DSC) technique.
Abstract: The cure kinetics of tetraglycidyl-4,4'-diaminodiphenylmethane (TGDDM) and 4,4'-diaminodiphenylsulfone (DDS) as a cure agent in nanocomposites with multiwalled carbon nanotubes (MWNTs) have been studied with an isothermal differential scanning calorimetry (DSC) technique. The experimental data for both the neat TGDDM/DDS system and for epoxy/MWNTs nanocomposites showed an autocatalytic behavior. Kinetic analysis was performed with the phenomenological model of Kamal and a diffusion control function was introduced to describe the cure reaction in the later stage. Activation energies and kinetic parameters were determined by fitting experimental data. For MWNTs/epoxy nanocomposites, the initial reaction rates increased and the time to the maximum rate decreased with increasing MWNTs contents because of the acceleration effect of MWNTs. The values of the activation energies for the epoxy/MWNTs nanocomposites were lower than the values for the neat epoxy in the initial stage of the reaction.
TL;DR: In this article, the generalized inverse L * of the Laplacian matrix of a connected graph is examined and some properties of its properties are established based on the results obtained for L *.
Abstract: The generalized inverse L† of the Laplacian matrix of a connected graph is examined and some of its properties are established. In some physical and chemical considerations the quantity rij = {L†)ii + (L†)jj — (L†)ij - (L†)ji is encountered; it is called resistance distance. Based on the results obtained for L† we prove some previously known and deduce some new properties of the resistance distance. .
TL;DR: In this paper, a series of methanofullerenes [6,6]-phenyl C61-butyric acid butyl ester, PCBB, was synthesized from the reaction of C60 and alkyl 4-benzoylbutyrate p-tosylhydrazone in the presence of sodium methylate.
Abstract: A series of [6,6]-phenyl C61-butyric acid esters, including methanofullerene [6,6]-phenyl C61-butyric acid methyl ester (PCBM) with different alkyl chain lengths (C1−C16) was synthesized from the reaction of C60 and alkyl 4-benzoylbutyrate p-tosylhydrazone in the presence of sodium methylate. The solubility of C60 derivatives in organic solvents increased with the increase in the length of alkyl substitutions. Photovoltaic cells with these derivatives were fabricated with the structure of ITO/PEDT/MEH−PPV + C60 derivatives/Ba/Al. Device performances with such PCBM analogues were investigated and discussed in terms of Donor/Acceptor (D/A) phase separation and mobility of acceptor phase. The results clearly indicate that both interfacial properties of the two phases (donor and acceptor) and mobility of electrons and holes within corresponding phases play an important role in the efficiencies of PV cells. This study revealed that methanofullerenes [6,6]-phenyl C61-butyric acid butyl ester, PCBB, possesses be...
TL;DR: The results showed that the ultrasonic treatment and sequential extractions with alkali and alkaline peroxide under the conditions given led to a release of over 90% of the original hemicelluloses and lignin.
TL;DR: The major microalgal genera presently cultivated in China are Spirulina and Chlorella, which are initially manufactured in the form of algal biomass or extracts by the food industry and used to enrich liquid foods such as health drink, soft drink, tea, beer or spirits.
Abstract: The major microalgal genera presently cultivated in China are Spirulina and Chlorella. They are initially manufactured in the form of algal biomass or extracts by the food industry. The biomass is then used for producing a variety of health products such as tablets, capsules, powder or for extracting bioactive ingredients such as beta-carotene, and phycocyanin. The algal biomass is supplemented to noodles, breads, biscuits, candies, ice cream, bean curd and other common foods as food additives so as to enhance their nutritive and health values. The extracts are mainly used to enrich liquid foods such as health drink, soft drink, tea, beer or spirits.
TL;DR: In this article, the dispersion state of the organo-montmorillonite (O-MMT) in an epoxy/methyl tetrahydrophthalic anhydride system was investigated by X-ray diffraction and scanning electronic microscopy.
TL;DR: It was found that the final stage treatment is not severe enough to cause decrystallization of cellulose, and the thermal stability of the purified cellulose is higher than that of the corresponding crude cellulose.
Abstract: A sequential totally chlorine-free procedure for isolation of cellulose from wheat straw was proposed in this study. The dewaxed straw was pretreated with 0.5 M NaOH in 60% methanol at 60 °C for 2.5 h under ultrasonic irradiation for 0−35 min and sequentially posttreated with 2% H2O2−0.2% TAED at pH 11.8 for 12 h at 48 °C, which together solubilized 85.3−86.1% of the original hemicelluloses and 91.7−93.2% of the original lignin, respectively. The yield of crude cellulose ranged between 46.2 and 49.2% on a dry weight basis related to wheat straw, which contained 11.2−12.2% residual hemicelluloses and 2.5−2.9% remaining lignin. Further treatment of the corresponding crude cellulosic preparations with 80% acetic acid−70% nitric acid under the condition given yielded 36.8−37.7% of the purified cellulose, which contained minor amounts of bound hemicelluloses (2.5−2.8%) and was relatively free of associated lignin (0.1−0.2%). The isolated crude and purified cellulose samples were comparatively studied by FT-IR ...
TL;DR: In this article, the retention-aid properties of quaternary chitosan for natural occurring CaCO3 fillers had been studied using adsorption and flocculation experiments.
25 Sep 2004-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: Porous NiTi shape memory alloy (SMA) has been successfully prepared by hot isostatic pressing (HIP) of elemental Ni and Ti powder and has isotropic and uniform pore distribution of spherical pores ranged from 50 to 200 μm as mentioned in this paper.
Abstract: Porous NiTi shape memory alloy (SMA) has been successfully prepared by hot isostatic pressing (HIP) of elemental Ni and Ti powder. The alloy has isotropic and uniform pore distribution of spherical pores ranged from 50 to 200 μm. The microstructure, martensitic transformation behavior and mechanical properties of this porous NiTi SMA aged at different conditions were studied. It has been found that the phase transformation behavior of porous NiTi SMA is similar to that of the dense Ni-rich NiTi alloys. The porous NiTi SMAs can exhibit almost complete superelasticity at human body temperature.
TL;DR: In this paper, the authors introduced the process of friction stir welding (FSW), the microstructure in FSW alloys and the factors influencing weld quality, and the complex factors affecting the properties.
Abstract: Friction stir welding (FSW), a new solid-state welding technology invited in the early 1990s, enables us weld aluminum alloys and titanium alloys etc. The processing of FSW, the microstructure in FSW alloys and the factors influencing weld quality are introduced. The complex factors affecting the properties are researched.
TL;DR: In this article, the effects of the thickness of Pt film on the property of platinized counter electrode and the performance of the dye-sensitized solar cell (DSC) were investigated.
Abstract: The effects of the thickness of Pt film on the property of platinized counter electrode and the performance of the dye-sensitized solar cell (DSC) were investigated. The Pt film sputtered on an FTO glass is constructed of Pt particles, and the grain size of the Pt particles gradually increased with the increase in the Pt film thickness. When the Pt film thickness exceeds 100 nm, further Pt deposition has no significant effect on the conductivity improvement. In the range between 10 and 415 nm, the Pt film thickness has no significant influence on the performance of the DSC. A high conversion efficiency of ca. 5% was obtained by the DSC composed of the counter electrode with Pt film of 10 nm thickness. These results are important for reducing the production cost by reducing the required amount of expensive platinum.
TL;DR: In this paper, the elastic band structure of a two-dimensional phononic crystal containing piezoelectric material was investigated by the plane-wave-expansion method, and it was shown that for large filling fraction, the full band gap of this kind of system is enlarged by considering the piezelectric effect.
TL;DR: The phononic band structures of two-dimensional solid phononic crystals consisting of lattices with different symmetry and scatterers of various shapes, orientations, and sizes are studied numerically in this paper.
TL;DR: In this article, the effects of five kinds of water-soluble organic polymers on the mechanical and physical properties of uncalined-kaolinite geopolymer were examined.
TL;DR: In this paper, a one-pot oxidation from cyclohexane to adipic acid has been developed, catalyzed by Fe−porphyrin in the presence of molecular oxygen without any additives.
15 Sep 2004-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, as-plated binary Ni-P and ternary Ni-W-P alloys with either nanocrystalline or amorphous structures were prepared by electroless deposition.
Abstract: As-plated binary Ni–P and ternary Ni–W–P alloy films with either nanocrystalline, amorphous or mixture of nanocrystalline and amorphous (denoted as mix-structure) structures were prepared by electroless deposition. Single-phase nanocrystalline Ni–P and Ni–W–P alloys were also synthesized by crystallization of their mix-structure counterparts. Corrosion behaviors of the obtained deposits in a 0.5 M sulfuric acid solution were investigated. It was found that the as-plated nanocrystalline deposits, whether the binary Ni–P or the ternary Ni–W–P ones, and the annealed binary Ni–P alloy films, all possessed a corrosion resistance much lower than that of their amorphous counterparts. The annealed ternary Ni–W–P alloys, however, had a corrosion resistance higher than that of their amorphous counterpart. This result was attributed to the formation of a dense tungsten oxide film on the surface during annealing process, which was favored strongly by the high density diffusion paths provided by the large fraction of grain boundaries present in the nanocrystalline deposits.