Showing papers by "Liqun Zhang published in 2004"
TL;DR: In this paper, the authors established a global existence of weak solutions to the two-dimensional Prandtl's system for unsteady boundary layers in the class considered by Oleinik (J. Appl. Mech. 30 (1966) 951) provided that the pressure is favorable.
225 citations
TL;DR: In this paper, the aspect ratios of clay platelets in rubber-clay nanocomposites were determined by statistically analyzing TEM micrographs, and the modulus reduction factor (MRF) for the platelet-like fillers of 0.66, determined by fitting experimental data, was introduced into the above three equations.
201 citations
TL;DR: In this article, a novel nanomagnesium hydroxide powder and three kinds of micro-Mg(OH)2, with different particle sizes, were chosen as fillers and mixed with EPDM to form a series of composites by a traditional rubber-processing technique.
Abstract: A novel nanomagnesium hydroxide powder and three kinds of micro-Mg(OH)2, with different particle sizes, were chosen as fillers and mixed with ethylene-pro- pylene- diene monomer rubber (EPDM) to form a series of composites by a traditional rubber-processing technique. The results showed that the mechanical properties of com- posites improved with decreasing particle size. The nano- composites were far stronger than the microcomposites, which also supported the view that rubber reinforcement requires nanoreinforcement. The effect of particle size on the fire resistance of composites was investigated by cone calo- rimetry and limiting oxygen index analysis, which showed that the particle size of powder had an impact on the fire resistance of composites. For the composites filled with un- treated powder, the peak value of heat release rate de- creased and Tign increased with decreasing particle size. In conclusion, the fire resistance of nanocomposites was better than that of microcomposites. Surface modification of parti- cles sometimes substantially improved the mechanical prop- erties of nanocomposites, but had no effect on either the mechanical properties of microcomposites or the fire resis- tance of nanocomposites and flame retardance. © 2004 Wiley
122 citations
TL;DR: In this paper, three rubber-based nanocomposites, natural rubber (NR), styrene-butadiene rubber (SBR), and EPDM/OC, were prepared with octadecylamine modified fluorohectorite (OC) by melt blending.
Abstract: Summary: Three rubber-based nanocomposites, natural rubber (NR), styrene-butadiene rubber (SBR), and ethylene-propylene-diene rubber (EPDM) matrixes, were prepared with octadecylamine modified fluorohectorite (OC) by melt blending. X-ray diffraction (XRD) revealed that the SBR/OC and EPDM/OC nanocomposites exhibited a well-ordered intercalated structure and a disordered intercalated structure, respectively. In the case of the NR/OC nanocomposite, it exhibited an intermediate intercalated and even exfoliated structure. These results were in good agreement with transmission electron microscopy (TEM) observations. Furthermore, in the NR/OC and SBR/OC systems, the mixing process played a predominant role in the formation of nanometer-scale dispersion structure, whereas the intercalated structure of EPDM/OC formed mainly during the vulcanization process. The tensile strength of SBR/OC and EPDM/OC nanocomposites loading 10 phr OC was 4–5 times higher than the value obtained for the corresponding pure rubber vulcanizate, which could be ascribed to the slippage of the rubber molecules and the orientation of the intercalated OC. For the strain-induced crystallization NR, the exfoliated OC efficiently improved the modulus of the NR/OC nanocomposite relative to the pure NR. However, its hindrance on NR crystallization during the tensile process may be the main reason for the decrease in tensile strength of NR/OC.
XRD diffraction patterns of three nanocomposites containing 10 phr organoclay.
114 citations
TL;DR: In this paper, an exfoliation mechanism was proposed and verified based on X-ray diffraction (XRD)/transmission electron microscopy (TEM) analyses of the intercalation/exfoliation phenomena after each step of the process.
Abstract: A novel method was developed to prepare an exfoliated styrene butadiene rubber (SBR)/clay nanocomposite with a strong interface between the clay layers and the rubber. An exfoliation mechanism was proposed and verified based on X-ray diffraction (XRD)/transmission electron microscopy (TEM) analyses of the intercalation/exfoliation phenomena after each step of the process. The significant improvements of mechanical properties may give the first evidence that both exfoliation and a strong interface play critical roles in nanoreinforcement.
104 citations
TL;DR: Microvascular autologous submandibular gland transfer is a lasting and effective solution for severe cases of keratoconjunctivitis sicca.
86 citations
TL;DR: In this article, the starch particles are in an amorphous state and are smaller than 1 μm, prepared by directly mixing and co-coagulating rubber latex and starch paste, and exhibit higher hardness, stress at 100%, tensile strength, and tear strength relative to the corresponding rubber/starch composites prepared by direct blending.
Abstract: Summary: Several rubber/starch composites in which the starch particles are in an amorphous state and are smaller than 1 μm, prepared by directly mixing and co-coagulating rubber latex and starch paste, exhibit higher hardness, stress at 100%, tensile strength, and tear strength relative to the corresponding rubber/starch composites prepared by direct blending.
TEM micrograph of starch/SBR composite.
72 citations
TL;DR: In differentiated human airway epithelium in vitro, RSV-induced increases in IL-8 and RANTES release are predominantly in the basolateral direction, and the authors speculate that similar processes in vivo influence recruitment of leukocytes to sites of RSV infection.
Abstract: Respiratory synctial virus (RSV) infection of undifferentiated airway epithelial cells has been shown to induce the production of chemokines. The purpose of this study was to investigate the vectorial release of interleukin (IL-8) and Released on Activation, Normal T-cell Expressed and Secreted (RANTES) by polarized, well-differentiated respiratory epithelial cells after RSV infection. Human bronchial epithelial cultures were differentiated under air-liquid interface conditions and infected with RSV by the apical or basolateral route. RSV infection was specific to the apical surface. Supernatants were collected at 6 and 48 hours after RSV inoculation, and IL-8 and RANTES were measured by enzyme-linked immunosorbent assay (ELISA). Both IL-8 and RANTES were significantly released by 48 hours following inoculation with RSV. The secretion of each chemokine was greatest after apical inoculation, and secretion was polarized to the basolateral supernatant. Immunohistochemical staining confirmed that RSV infection was specific to ciliated cells, and immunohistochemical staining for chemokines was localized to RSV-infected ciliated cells. The authors conclude that, in differentiated human airway epithelium in vitro, RSV-induced increases in IL-8 and RANTES release are predominantly in the basolateral direction. In epithelial layers, virus-containing cells are the predominant source of the increased chemokine release. The authors speculate that similar processes in vivo influence recruitment of leukocytes to sites of RSV infection.
64 citations
TL;DR: In this article, the size and centration of free-volume holes of two kinds of montmorillonite (MMT)/styrene-butadiene rubber (SBR) nanocomposites were investigated by positron annihilation lifetime spectroscopy (PALS).
Abstract: The size and comcentration of free-volume holes of two kinds of montmorillonite (MMT)/styrene-butadiene rubber (SBR) nanocomposites were investigated by positron annihilation lifetime spectroscopy (PALS). Strong interfacial interaction caused an apparent reduction of the free-volume fraction of rubber probaly by depressing the formation of free-volume holes in the interfacial region. Interfacial interaction in MMT/SBR nanocomposites was weaker than that in SBR filled with carbon black.
60 citations
TL;DR: The significant potential of TSTA-based lentivirus vectors to confer high levels of tissue-specific gene expression from a weak promoter, while preserving cell-type specificity and the ability to image noninvasively the sustained, long-term expression of reporter genes in living animals is demonstrated.
60 citations
TL;DR: In this paper, an infrared spectroscopic method was used to follow the course of in situ polymerization of zinc dimethacrylate (ZDMA) in poly(α-octylene-co-ethylene) elastomer (POE).
Abstract: An infrared spectroscopic method was used to follow the course of in situ polymerization of zinc dimethacrylate (ZDMA) in poly(α-octylene-co-ethylene) elastomer (POE). The integral intensity of the 831cm −1 band, ie the out-of-plane deformation mode of =CH, was used to determine the residual amount of ZDMA in composites cured at 165 ◦ C for different times, through which the course of in situ polymerization of ZDMA in POE was traced and the dynamic curve determined. The curing course of the ZDMA/POE/peroxide system at 165 ◦ C was examined with a rheometer and compared with the course of in situ polymerization. The results surprisingly show that the in situ polymerization of ZDMA is almost complete at the beginning stage of curing, and that substantial crosslinking starts subsequently. Scanning electron microscopy and transmission electron microscopy observations on morphologies of ZDMA/POE composites cured at 165 ◦ C for different times were carried out and confirmed the results of infrared experiments. Combining all the investigations, it was deduced that a competition exists between in situ polymerization and crosslinking in the composites. Covalent crosslinking rather than ionic bond crosslinks are the major types of crosslinks structures in ZDMA/POE composites, and its total density is lower than that of carbon- black-reinforced POE. 2004 Society of Chemical Industry
TL;DR: In this article, the microstructure and mechanical properties of the three composites have been studied via scanning electron microscope (SEM) and mechanical testing, respectively, and the theoretically predicted values are in good accordance with the experimental results.
TL;DR: In this paper, a series of Gd(AA) 3 /NR (natural rubber) composites for X-ray shielding were prepared by an in situ reaction method, which greatly improved the dispersion level of the shielding phase by the remarkable reduction of Gda(AA), 3 particle size and the formation of small sized poly-Gda( AA) 3 from the matrix.
Abstract: For the first time, a series of Gd(AA) 3 /NR (natural rubber) composites for X-ray shielding were prepared by an in situ reaction method. Occurrence of the in situ polymerization of Gd(AA) 3 in composites during vulcanization of NR with peroxide greatly improves the dispersion level of the shielding phase by the remarkable reduction of Gd(AA) 3 particle size and the formation of small sized poly-Gd(AA) 3 from the matrix. As expected and assumed, the X-ray shielding properties of all composites apparently increase with the increase of the degree of dispersion of Gd(AA) 3 in composites.