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Zhengkai Wei,Yi Wang,Xiaowei Fu,Liang Jiang,Yuechuan Wang,Anqian Yuan,Hualiang Xu,Jingxin Lei 한국고분자학회 2021 Macromolecular Research Vol.29 No.8
The thermosetting polyurea possessed high tensile strength and elongations at break due to strong intermolecular interactions, but their recycling and reprocessing remains a great challenge, especially at a temperature below 100℃. Herein, the novel crosslinked polyurea with excellent recycling and reprocessing properties has been prepared by introducing the Diels-Alder dynamic covalent bond. The chemical structure, thermal mechanical properties and reprocessing performance of the crosslinked polyurea were investigated. The prepared polyurea has low relaxation time of ~4 min at 80℃ for facile reprocessing. The tensile strength and elongation at break of crosslinked polyurea could reach 15.24 MPa and 529.2%, respectively, and its mechanical properties remain almost unchanged even after repeated processing. This work has realized the recycling of crosslinked polyurea, which has huge potential applications in environmental protection and recycling of waste plastics.
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Brain MRI Segmentation and Bias Estimation Via An Improved Non-Local Fuzzy Method
Yunjie Chen,Zhengkai Wang,Jin Wang,Yuhui Zheng 보안공학연구지원센터 2015 International Journal of Grid and Distributed Comp Vol.8 No.4
Intensity in homogeneities cause considerable difficulties in the quantitative analysis of Magnetic Resonance (MR) images. Thus intensity in homogeneities estimation is a necessary step before quantitative analysis of MR data can be undertaken. This paper proposes a new energy minimization framework for simultaneous estimation of the intensity in homogeneities and segmentation. The intensity in homogeneities is modeled as a linear combination of a set of basis functions, and parameterized by the coefficients of the basis functions. The energy function depends on the coefficients of the basis functions, the membership ratios and the centroids of the tissues in the image. Intensity in homogeneities estimation and image segmentation are simultaneously achieved by calculating the result of minimizing this energy. Furthermore, in order to improve its robustness to noise, the membership ratios are adapted by using nonlocal information. Experimental results on both real MR images and simulated MR data show that our method can obtain more accurate results when segmenting images with bias field and noise.
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Yumeng Wei,Zhengkai Xue,Peng Wang,Ling Zhao 대한약학회 2013 Archives of Pharmacal Research Vol.36 No.7
A novel sustained-release system was developedfor poorly water-soluble drugs by applying soliddispersion (SD) technique to improve the solubility. TheSD systems composed of polyvinyl pyrrolidone and stearicacid could not control the release of nifedipine. When theabove SD granules were coated with ethylcellolulose(EC10, 45 and 100cp), the dissolution rate extended from16 to 20 h. When the concentration of EC100cp wasincreased to 4–6 %, the sustained-release formulation F7and F8 prepared with 4 % EC100cp and 6 % EC100cp,respectively, could control the drug release in a bettermanner, namely, they could control drug release in theinitial hours with a high cumulative amount of drug at24 h. The mechanism of drug release from F7 and F8 wasdiffusion coupled with erosion. When immediate-releasecapsules was orally administered to rabbits, its absorptionwas very rapid with a short elimination half-life, while aprolonged maintenance of the plasma drug level up to 24 hwas obtained for F7 and F8. Furthermore, the oral bioavailabilityof F7 and F8 was significantly improved. Theresults suggested that this novel sustained-release systemwould be a promising system to improve the solubility andsustain the absorption of poorly water-soluble drugs.
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Qing Feng,Zhengkai An,Rusong Zhao,Xiaoli Wang,Jun Li,송영채 한국마린엔지니어링학회 2019 한국마린엔지니어링학회지 Vol.43 No.10
Bioelectrochemical anaerobic digestion (BEAD) is a technology which exploits the potential of microorganism by supplying a small amount of electric energy in an anaerobic digester. The electrode material is one of the most important parts of a bioelectrochemical system. For the anodes and cathodes of BEAD process, graphite fiber fabric (GFF), a carbon based material with good biocompatibility and non-corrosive property, was selected and its conductivity was modified by depositing carbon nanotube (CNT) via electrophoresis deposition (EPD) method. In the BEAD process, the organic matter in the reactor is oxidized on the surface of anode forming proton, carbon dioxide and electron. The electron produced is transferred to the cathode due to the potential difference between anode and cathode, followed by methane production on the surface of cathode resulting from the combination of carbon dioxide, electron and proton. The biochemical reactions at the electrodes can be controlled by the electrode potentials. When the potential between anode and cathode was maintained at 0.3 V using an external power supply, the BEAD reactor showed remarkable performance after the start-up period of 40 days. The performance of BEAD reactor was stable in terms of pH (7.2~7.5), alkalinity (4,500~5,200mg/L as CaCO3), methane content in biogas (77.3%) and volatile fatty acid levels (VFA < 250mg HAc/L). During steady state, the specific methane production rate and VS reduction were stabilized at 412 mL CH4/L.d and 72.5%, respectively, which were much higher than the conventional anaerobic digestion. The application of bioelectrochemical technology to anaerobic digestion provides a chance to overcome the disadvantages of conventional anaerobic digestion.
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