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利用完备分配格L上的s-模定义格L上的矩阵运算,给出这些运算的一些基本性质,并且定义格L上的s-幂零矩阵,给出一些全新的结果. 相似文献
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A pure dielectric metamaterial absorber with broadband and thin thickness based on a cross-hole array structure 下载免费PDF全文
A pure dielectric metamaterial absorber with broadband and thin thickness is proposed, whose structure is designed as a periodic cross-hole array. The pure dielectric metamaterial absorber with high permittivity is prepared by ceramic reinforced polymer composites. Compared with those with low permittivity, the absorber with high permittivity is more sensitive to structural parameters, which means that it is easier to optimize the equivalent electromagnetic parameters and achieve wide impedance matching by altering the size or shape of the unit cell. The optimized metamaterial absorber exhibits reflection loss below -10 dB in 7.93 GHz-35.76 GHz with a thickness of 3.5 mm, which shows favorable absorption properties under the oblique incidence of TE polarization (±45°). Whether it is a measured or simulated value, the strongest absorbing peak reaches below -45 dB, which exceeds that of most metamaterial absorbers. The distributions of power loss density and electric and magnetic fields are investigated to study the origin of their strong absorbing properties. Multiple resonance mechanisms are proposed to explain the phenomenon, including polarization relaxation of the dielectric and edge effects of the cross-hole array. This work overcomes the shortcomings of the narrow absorbing bandwidth of dielectrics. It demonstrates that the pure dielectric metamaterial absorber with high permittivity has great potential in the field of microwave absorption. 相似文献
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为了研究柔性纤维织布的抗爆性能,通过数值模拟的方法对芳纶纤维织布在爆炸冲击下的响应与失效行为进行了分析。对国产芳纶纤维织布H1000D-AP220进行了力学性能试验,建立了柔性平纹织布的本构模型和爆炸冲击数值分析模型,对不同厚度不同铺层角度织布进行了爆炸冲击数值分析,获得了织布在不同爆炸载荷下的动态响应和失效模式。结果表明,织布在爆炸冲击载荷下主要表现为中心撕裂破孔和简支边界处拉伸撕裂2种典型的失效模式,并伴有明显褶皱,宽度方向出现织布向内侧收缩翻转现象;相比于中间层织布,迎爆面和背爆面吸能较多;在计算分析中改变了织布的层叠角度,获得了更好的抗爆效果。 相似文献
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含氢多组分燃料由于其优良的燃烧特性逐渐成为研究关注的重点。为了对掺氢燃料的爆轰特性作进一步的研究,设计了长3 000 mm、管径30 mm的圆柱形半封闭燃烧室,对不同初压下的CH4-2O2、6CH4-H2-12.5O2、3CH4-H2-6.5O2(掺氢比分别为0%、5.1%、9.5%)3种预混合气的爆轰特性进行了实验研究,并采用烟熏膜、离子探针和压力传感器分别探测胞格结构、火焰位置和内部压力。结果表明,甲烷/氧气掺氢后可以有效提高爆轰波的传播速度,且掺氢浓度越高,传播速度越快;同时,氢气的掺入可减少管道出口处的速度亏损并在初始压力较低时加速火焰和激波的耦合,降低胞格尺寸,提高爆轰敏感性。 相似文献
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为解决传统共焦显微系统的分辨力与线性量程不能兼顾的问题,提出了基于变光程技术的多差动共焦显微技术,利用光程的调制在单探测光路中实现轴向响应曲线相对于焦平面的对称相移的方式,仅需要调整单一参数就可获得不同离焦量的响应曲线,实现具有绝对零点、线性度好的多差动光路系统,从而实现在同一系统中对高分辨力与大量程的兼容。该技术减少了元器件性能差异和人为装调误差,结构简单,提高了可靠性。实验表明:系统可兼顾分辨力与线性量程,轴向分辨力可达6.46nm。为微细结构的测量提供了一种精度高、结构简单、应用场合广泛的技术。 相似文献
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