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71.
72.
A biphenyl type liquid crystal epoxy (LCE) monomer 4,4′-di(2,3-epoxyhexyloxy)biphenyl (LCBP4) containing flexible chain was synthesized and the curing behavior was investigated using 4,4′-diaminodiphenylmethane (DDM) as the curing agent. The effect of curing condition on the formation of the liquid crystalline phase was examined. The cured samples show good mechanical properties and thermal stabilities. Moreover, the relationship between thermal conductivity and structure of liquid crystalline domain was also discussed. The samples show high thermal conductivity up to 0.28–0.31 W/(m*K), which is 1.5 times as high as that of conventional epoxy systems. In addition, thermal conductive filler, Al2O3, was introduced into LCBP4/DDM to obtain higher thermal conductive composites. When the content of Al2O3 was 80 wt%, the thermal conductivity of the composite reached to 1.86 W/(m*K), while that of diglycidyl ether of bisphenol A (Bis-A) epoxy resin/DDM/Al2O3 was 1.15 W/(m*K). Compared with Bis-A epoxy resin, the formation of liquid crystal domains in the cured LCE resin enhanced the thermal conductivity synergistically with the presence of Al2O3. Furthermore, the introduction of Al2O3 also slightly increased the thermal stabilities of the cured LCE. 相似文献
73.
Modeling and Matching texts is a critical issue in natural language processing (NLP) tasks. In order to improve the accuracy of text matching, multi-granularities capture matching features (MG-CMF) model was proposed. The proposed model used convolution operations to construct the representation of text under multiple granularities, used max-pooling operations to filter more reasonable text representations and built a matching matrix at different granularities. Then, the convolution neural network (CNN) was used to capture the matching information in each granularity. Finally, the captured matching features were input into the fully connected neural network to obtain the matching similarity. By making some experiments, the results indicate that the MG-CMF model not only gets multiple granularity representations of sentences but also can obtain matching information from multiple granularities of sentences better than the other text matching models. 相似文献
74.
75.
Xiaoqiang Li Ting Cao Minai Zhang Hao Qiu Yang Huang Shengguan Qu Liang Liang Tao Song 《International Journal of Applied Ceramic Technology》2020,17(3):941-948
Porous fibers are widely used in catalysis chemistry and hydrogen storage but are rarely used in structural ceramics. In this study, spark plasma sintering was used to prepare an ultrafine porous boron nitride nanofiber-toughened WC composite for the first time. The obtained WC-0.05 wt% ultrafine porous boron nitride nanofiber composites exhibited better properties (ie, a 2.3% increase in hardness and a 19.6% increase in fracture toughness) compared to those of the pure WC specimen. The fiber porosity improved the second phase-WC matrix microstructural combination. The described approach is a novel preparation method for the WC composites. Furthermore, a new toughening mechanism, which is based on “pinning and stretching”, was determined. These findings suggest that porous boron nitride fibers can be considered to be second phases for toughening the WC composites. 相似文献
76.
某含锌锡多金属硫化矿石Zn、Sn、Fe、S含量分别为6.04%、1.05%、29.33%、19.08%,锌主要以铁闪锌矿、闪锌矿的形式存在,锡主要以锡石的形式存在,铁主要以黄铁矿、磁黄铁矿等形式存在,其中的金属矿物共生关系密切,相互包裹现象普遍。为确保不影响后续选锡,对锌浮选流程进行了试验研究。结果表明:矿石在磨矿细度为-0.074 mm占80%的情况下,采用预先脱硫—锌硫混浮再分离流程处理,在选择硫酸铜为锌矿物活化剂、丁基黄药为捕收剂、松醇油为起泡剂、石灰为黄铁矿抑制剂的情况下,经1段脱硫、2粗1扫锌硫混浮、1粗2精锌硫分离,锌硫分离精选尾矿与锌硫混浮扫选精矿2次精选后锌硫分离,最终获得锌精矿Zn品位47.06%、回收率90.76%,试验指标良好。 相似文献
77.
Yavuz Emre Arslan Yusuf Furkan Galata Tugba Sezgin Arslan Burak Derkus 《Journal of materials science. Materials in medicine》2018,29(8):127
In this study, we aimed at fabricating decellularized bovine myocardial extracellular matrix-based films (dMEbF) for cardiac tissue engineering (CTE). The decellularization process was carried out utilizing four consecutive stages including hypotonic treatment, detergent treatment, enzymatic digestion and decontamination, respectively. In order to fabricate the dMEbF, dBM were digested with pepsin and gelation process was conducted. dMEbF were then crosslinked with N-hydroxysuccinimide/1-Ethyl-3-(3-dimethylaminopropyl)-carbodiimide (NHS/EDC) to increase their durability. Nuclear contents of native BM and decellularized BM (dBM) tissues were determined with DNA content analysis and agarose-gel electrophoresis. Cell viability on dMEbF for 3rd, 7th, and 14th days was assessed by MTT assay. Cell attachment on dMEbF was also studied by scanning electron microscopy. Trans-differentiation capacity of human adipose-derived mesenchymal stem cells (hAMSCs) into cardiomyocyte-like cells on dMEbF were also evaluated by histochemical and immunohistochemical analyses. DNA contents for native and dBM were, respectively, found as 886.11?±?164.85 and 47.66?±?0.09?ng/mg dry weight, indicating a successful decellularization process. The results of glycosaminoglycan and hydroxyproline assay, and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), performed in order to characterize the extracellular matrix (ECM) composition of native and dBM tissue, showed that the BM matrix was not damaged during the proposed method. Lastly, regarding the histological study, dMEbF not only mimics native ECM, but also induces the stem cells into cardiomyocyte-like cells phenotype which brings it the potential of use in CTE. 相似文献
78.
79.
Jamasb Pirkandi Mehdi Jahromi Seyedeh Zeynab Sajadi Mohammad Ommian 《Clean Technologies and Environmental Policy》2018,20(5):1047-1060
In this study, three different configurations of a solid oxide fuel cell and gas microturbine hybrid system are evaluated for application in auxiliary power units. The first configuration is a common hybrid system in auxiliary power units, utilizing a fuel cell stack in the structure of the gas turbine cycle. The other configurations use two series and parallel fuel cell stacks in the structure of the gas turbine cycle. The main purpose of this research is thermodynamic analysis, evaluation of the performance of the proposed hybrid systems in similar conditions, and selection of an appropriate system in terms of efficiency, power generation, and entropy generation rate. In this study, the utilized fuel cells were subjected to electrochemical, thermodynamic, and thermal analyses and their working temperatures were calculated under various working conditions. Results indicate that the hybrid system with two series stacks had maximum power generation and efficiency compared with the other two cases. Moreover, the simple hybrid system and the system with two parallel stacks had relatively equal pure power generation and efficiency. According to the investigations, hybrid system with two series fuel cell stacks, which had 3424 and 1712 cells, respectively, can achieve the electrical efficiency of over 48%. A hybrid system with two parallel fuel cell stacks, in which each stack had 2568 cells, had the electrical efficiency of 46.3%. Findings suggested that maximum electrical efficiency occurred between the pressure ratios of 5–6 in the proposed hybrid systems. 相似文献
80.
Ballast contamination by fine materials such as sand and clay in railway track at arid regions is an important issue that causes track instability problems and settlement due to reduction of shear strength of ballast. In this paper, the results of direct shear box test conducted on clean ballast, sand-fouled ballast and clay-fouled ballast for different ballast gradations are reported and discussed. For this purpose, three different fouling amounts according to fouling index are added to clean ballast. Test results show that by increasing the fouling percentage, the ballast shear strength always decreases both for sand and clay fouled ballast. However, the amount of shear strength reduction is low at high normal stresses. Clay contamination has more adverse effect on the shear strength of ballast compared with sand contamination. Also, the results of tests for evaluation of gradation effect on shear strength of fouled ballast which are conducted on various gradations according to American Railway Engineering and Maintenance-of-Way Association, show that the maximum particle size as well as uniformity coefficient affect the shear strength of ballast. Also, an empirical equation is presented to observe the effect of ballast gradation on reduction of shear strength with regard to amount of fouling material and normal stress. 相似文献