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151.
针对四川省雷波县马湖古滑坡群规模的新发现,对其地貌与运动学特征进行详细分析,以期研究该滑坡群的成因.依据钻孔及超声波所测量的马湖湖底地形确定古璜琅河河床特征、古滑坡群平面范围和深度;在古滑坡外形、结构及地质环境现场调查的基础上,重点进行地貌分析、古滑坡群分期和确定各期运动轨迹;运用能量守恒方程计算滑坡速度,辅助确定古滑坡群的形成机制.结果表明:滑坡群规模巨大,面积达18.2 km2(包括湖底部分),体积约20×108 m3;滑坡群按照岩性和结构可以分为3区,形成过程分为4期;古滑坡群为多期地震诱发的顺高陡地层界面的高大、高速、远程滑坡;地貌和运动学分析可作为确定古滑坡成因的一种方法. 相似文献
152.
采用非线性动力学理论对翼型绕流的多模态耦合机制进行研究,并阐释模态耦合作用与流动稳定性的关系。通过特征线有限元方法对翼型绕流问题进行数值计算,建立非定常流场数据库。为了分析流动稳定性和流动特征,利用本征正交分解提取流场中的特征模态,从而分析翼型绕流非定常流场的特征模态之间的相互作用关系,并给出了非线性流体动力系统中的不同模态作用与流动稳定性的关系。 相似文献
153.
Haiming Zhang Biao Zhao Huimin Xiang Fu-Zhi Dai Zhili Zhang Yanchun Zhou 《Journal of the American Ceramic Society》2021,104(5):2213-2224
The electromagnetic (EM) wave absorbing properties of Cr2AlB2 powders and those after high-temperature oxidation were investigated. Coupling of magnetic and dielectric loss enables Cr2AlB2 with good absorption properties. The minimum reflection loss (RL) value is −44.9 dB at 8.5 GHz with a thickness of 2.7 mm, and the optimized effective absorption bandwidth (EAB) is 4.4 GHz (13.0-17.4 GHz) with a thickness of 1.6 mm. After oxidation at 750, 900, and 1000°C for 2 h, the minimum RL values, respectively, are −23.9 dB (17.5 GHz, 1.5 mm), −41.4 dB (16.5 GHz, 1.5 mm), and −39.5 dB (8.0 GHz, 3.0 mm); and the corresponding EAB values, respectively, are 3.8 GHz (13.6-17.4 GHz, 1.7 mm), 4.1 GHz (13.5-17.6 GHz, 1.6 mm), and 4.4 GHz (13.0-17.4 GHz, 1.7 mm). With an absorber thickness of 1.5-4.0 mm, the EAB with a RL value of less than −10 dB can be tuned in a broad-frequency range 5.0-18.0 GHz, which basically covers C (4-8 GHz), X (8-12 GHz), and Ku (12-18 GHz) bands. These results demonstrate that Cr2AlB2, as a high-efficient and oxidation-resistant absorber, is a promising candidate for microwave absorption applications and can retain good EM wave absorbing properties after high-temperature oxidation. 相似文献
154.
Heng Zheng Zhenyu Dai Jie Wei Lin Li Haitao Peng Aiping Yang Hong Li Guoyu Lv 《应用聚合物科学杂志》2021,138(5):49751
Bioglass (BG) possesses excellent bioactivity and has been widely used in the manufacture of biomaterials. In this study, a composite with different surface bioactivity was fabricated via in situ melting polymerization by incorporating BG and poly(amino acid) (PAA) at a suitable ratio. The structure of the composite was characterized by Fourier transform infrared spectroscopy and XRD. The compressive strength of the BG/PAA composites was 139 MPa (BG:PAA = 30:70). The BG/PAA composites were degradable, and higher BG in composite showed higher weight loss after 4 weeks of incubation in simulated body fluid. In addition, the BG/PAA composite maintained adequate residual compressive strength during the degradation period. The SEM results showed the differences in surface bioactivities of the composites directly, and 30BG/PAA composite showed thicker apatite layer and higher Ca/p than 15BG/PAA. in vitro MG-63 cell culture experiments showed that the composite was noncytotoxic and thus allows cells to adhere, proliferate, and differentiate. This indicates that the composite has good biocompatibility. The implantations in the bone defects of rabbits for 4 and 12 weeks were studied. The composites had good biocompatibility and were capable of guiding new bone formation without causing any inflammation. The composite may be successfully used in the development of bone implants. 相似文献
155.
Weixin Guan Xiaochen Yang Chenyuan Dong Xiaoming Yan Wenji Zheng Yuan Xi Xuehua Ruan Yan Dai Gaohong He 《应用聚合物科学杂志》2021,138(8):49895
The packing pattern of two-dimensional (2D) sheet-like fillers in membranes is relatively random, leading to the unfavorable permeability from tortuous diffusion pathway. A new strategy that using prestructured materials with uniform channels as fillers was proposed. In this work, Ti3AlC2 is etched to prepare multilayered MXene (m-MXene), the channels aggregate as a whole unit, ensure the impossibility of ineffective packing compared with traditional individual sheets, largely facilitating the selective permeation. Then, the m-MXene/Poly (amide-6-b-ethylene oxide) (Pebax) MMMs are synthesized. SEM images demonstrate the accordion shaped structure of filler, which is the multi-channels laminates. Furthermore, the results of gas permeation test exhibit enhanced performance of m-MXene/Pebax MMMs. MMM with 0.5 wt.% m-MXene behaved best, CO2 permeability of 86.22 Barrer as well as CO2/N2 selectivity of 104.85, transcending the Robeson upper bound (2008). Having distinct enhancement for CO2 separation, the m-MXene/Pebax MMMs in this work offer prospective practical applications. 相似文献
156.
157.
Friction stir welding of AZ31 magnesium alloy 总被引:3,自引:0,他引:3
Friction stir welding (FSW) is an new solid-phase joining technology which has more advantages over fusion welding methods in welding of aluminum and other non-ferrous metals. The effects of welding parameters on mechanical properties and microstructure during friction stir welding of AZ31 magnesium alloy were studied in this paper. Microstructures and mechanical properties of the joints were investigated by means of optical microscopy, scanning electric microscopy ( SEM ) , micro-hardness analysis, and tensile test. Experimental results show that the magnesium alloy can be successfully welded by FSW method, and the ultimate tensile strength (UTS) of FSW joint reaches up to 90 percent of base metal. The microstructures of welded joints exhibit the variation from dynamically recrystallized fine grains to greatly deformed grains. Hardness in nugget zone was found lower than the base metal but not too obvious. 相似文献
158.
以可发性聚甲基丙烯酸甲酯(EPMMA)模样为研究对象,系统研究了珠粒粒径、预发泡时间、预发泡珠粒熟化时间、成形蒸气压力、模样的贮存温度及放置时间对模样收缩率的影响。研究结果表明,EPMMA模样在脱模时大约有0.1%左右的收缩,此后随着模样放置时间的延长,模样收缩逐渐增大,并在一定的时间(室温贮存约30天,50℃贮存约15天)后收缩稳定在0.5%~0.6%。而在所研究的工艺因素中,以成形蒸气压力对模样收缩的影响最大,其次是预发泡珠粒熟化时间,而珠粒粒径和预发泡时间的影响则相对较小。 相似文献
159.
从线材用户的角度论述了近十年来我国线材生产取得了长足的进步,但与国外先进水平相比仍存在着质量、品种上的差距。展望未来十年,提出应提高高碳钢及特殊钢线材比例,对尚不能满足要求的产品品种、质量应再优化。由此建议再建10条高速线材生产线,最好引进1~2条更高水平的高速线材轧机。 相似文献
160.
Thin DLC films coated on polymer surfaces are attracting considerable attention due to their wide applications and their interesting surface properties. When DLC films were coated on polymers, the resulting DLC-polymer composites are highly functionalized materials, some of which presenting dramatically improved gas barrier properties.In this paper, we will introduce several commonly used polymers including polyethylene terephthalate (PET), polyethylene (PE) and polypropylene (PP) for semi-crystalline polymers, and polymethyl methacyrlate (PMMA) for an amorphous polymer. The polymers were coated with thin DLC films and the gas barrier properties of the resulting DLC-polymer composites were investigated. Some of the DLC-polymer composites dramatically improved their gas barrier properties while they presented horizontal crack lines and vertical micro-buckling lines on the DLC surface when stretched to a certain strain. The gas barrier properties of the DLC-polymer composites with fractured DLC surface were also studied. It was found that the gas barrier property of the polymer substrates with lower residual strains was less damaged, when the substrates were mechanically deformed, than that of the polymer substrates with higher residual strains. When the number of the cracks increases, the strain imposed on each crack decreases, since the overall deformation is almost equally distributed to each crack while the crack spacing of each crack becomes shorter. Thus, it was found that the degradation of the gas barrier property after mechanical deformation is dependent on the residual strain of the polymers and the number of cracks on DLC films. 相似文献