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1.
采用平面波展开法对两类晶格(三角晶格和正方晶格)及圆形空气孔或两种非圆形空气孔(正方形和六边形)构成的二维光子晶体带隙率进行了数值研究,分析了填充比f对带隙率ωR的影响.结果表明,晶格对称结构和空气孔形状对带隙大小有影响.给定晶格对称结构,选择具有相同对称形状的空气孔能得到较大的绝对光子带隙.在这3种空气孔当中,三角晶格对应六边形空气孔有最大带隙率,当填充比f=0.8时,带隙率ωR=23.3%;正方晶格对应正方形空气孔有最大带隙率,当填充比f=0.67时,带隙率ωR=14.7%.  相似文献   

2.
通过降低正方晶格晶格结构对称性,采用晶格结构以及散射子结构简单的矩形晶格介质圆柱二维光子晶体,实现低折射率条件下完全带隙的获得.基于平面波展开法研究光子晶体完全带隙特性,研究表明:对于介质柱型二维光子晶体,无论矩形晶格还是正方晶格,都偏向于TM带隙的形成,但是晶格结构对称性的降低使得矩形晶格更益于TE带隙的形成,TE带隙宽度和数目的增加,使得矩形晶格介质柱型二维光子晶体可以实现低折射率条件下完全带隙的获得:当介质折射率大于2.0时,即可通过调节光子晶体结构参数获得完全带隙.  相似文献   

3.
一维花岗岩/丁腈橡胶声子晶体的带隙及其应用   总被引:1,自引:0,他引:1  
 采用集中质量法计算了一维花岗岩/丁腈橡胶声子晶体的振动带隙,研究了集中质量数、晶格常数、组分比及丁腈橡胶的粘弹性对带隙的影响.结果表明,增加集中质量数能提高带隙精度,晶格常数及组分比对带隙结构有较大影响,而丁腈橡胶的粘弹性能增大带隙宽度.根据以上结论,对声子晶体的材料参数和结构参数进行了优化,设计出1种能屏蔽人耳最敏感的1.5~2.5 kHz噪声的一维声子晶体.  相似文献   

4.
B32-LiAl点缺陷结构的第一原理计算   总被引:1,自引:1,他引:0  
采用第一原理赝势平面波方法,计算B32-LiAl金属间化合物的基本物性及其点缺陷结构的几何、能态与电子结构.通过对不同点缺陷结构形成热与形成能的计算与比较,分析和预测了B32-LiAl金属间化合物中点缺陷结构的种类与存在形式.结果表明:B32-LiAl金属间化合物的点缺陷主要是在Li子晶格上出现空位缺陷与在Al子晶格上出现反位缺陷.基于晶体总电子态密度与电荷密度分布等电子结构信息,对上述计算结果进行了初步分析.  相似文献   

5.
利用有限元法计算了二维Suzuki晶格声子晶体薄板弯曲振动的带隙结构及传输特性,讨论了填充率、板厚对Suzuki晶格声子晶体板带隙的影响.计算结果表明:Suzuki晶格声子晶体薄板存在振动带隙,即在散射体密度较大时,5000Hz以下存在一个完全带隙、多个方向带隙;Suzuki晶格声子晶体板带隙宽度随着板厚的增大而加宽,随着填充率的增大带隙宽度先增大后减小.  相似文献   

6.
采用第一性原理方法,计算含空位缺陷CrSi2的电子结构和光学性质,并分析含Cr和Si空位缺陷的CrSi2光电性能.结果表明:Cr和Si空位均使CrSi2的晶格常数和体积变小;能带结构密集而平缓,且整体向上移动,Si空位缺陷形成带隙宽度为0.35eV的p型间接带隙半导体,Cr空位缺陷在原禁带间出现两条新的能带;含空位缺陷CrSi2的电子态密度仍主要由Cr3d层电子贡献,Si空位缺陷对电子态密度的影响较小,Cr空位缺陷提高了Fermi面处的电子态密度;与CrSi2相比,含空位缺陷CrSi2的介电峰均向低能方向略有偏移且峰值降低,吸收系数明显变小.  相似文献   

7.
用集中参数模型理论研究具有内质量周期结构的二维三角形晶格声子晶体的带隙特性,设计了二维无限延伸的周期复合三角形晶格结构,通过理论及数值仿真发现改变质量和刚度可以人为调控带隙,最后与蜂窝状晶格的带隙进行对比.结果表明:晶体的色散曲线在频域上不连续,具有完全带隙的现象.晶体外部质量对带隙的影响最大,减小外部质量可得到较宽的带隙.此类结构中三角形晶格的带隙比六角蜂窝晶格的带隙少,但其带隙的宽度较宽,它为进一步带隙调控奠定良好的基础.  相似文献   

8.
二维六边形晶格光子晶体的带隙研究   总被引:2,自引:0,他引:2  
运用平面波展开法模拟计算了二维六边形晶格光子晶体的能带结构,得到了使光子带隙最大化的结构参数.分别以不同介质作为本底,由圆柱、正方直柱和六角形直柱空气孔构成的六边形晶格光子晶体都出现了完全光子带隙,为进一步光子晶体的实验制备和应用提供了理论依据.  相似文献   

9.
用有限差分法计算了由金属棒按三角形晶格分布的二维光子晶体的带隙图,计算结果表明:当金属棒半径a和棒间距b比值小于0.2时,二维光子晶体只有一条带隙,即若引入缺陷,可约束主模、抑制高次模.采用Microwave Studio计算了该种光子晶体微波加速结构的场型分布,结果显示当a/b<0.2,类TM01模在缺陷中传输,类TM11模(横向模)能传出光子晶体.另外计算了结构尺寸公差对行波单元谐振频率的影响,还模拟计算了带有测试探针的由3个PBG单元构成的谐振腔的S参数.  相似文献   

10.
用平面波展开法研究了三角晶格太赫兹波(THz)光子晶体波导的带隙特性。分析晶格常数为α=0.1mm的三角晶格硅介质柱二维光子晶体,通过数值计算,当填充率在f=0.801时,H偏振和E偏振出现重叠的最大绝对光子带隙,研究结果为三角晶格太赫兹波光子晶体波导器件的开发提供了理论依据。  相似文献   

11.
Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.  相似文献   

12.
The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.  相似文献   

13.
王慧 《科技信息》2008,(10):240-240
Wuthering Heights, Emily Bronte's only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.  相似文献   

14.
The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3~4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰~ -7.8‰, PDB) and matrix dolomites (-6.6‰~ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084~0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078~0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.  相似文献   

15.
Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.  相似文献   

16.
以AC-13级配为基础,将橡胶颗粒代替部分集料掺入混合料中,以低温弯曲试验为评价方法对不同橡胶颗粒掺量下沥青混合料的低温抗裂性进行研究,并引入应变能密度值对混合料的低温抗裂性进行综合评价.试验结果表明:橡胶颗粒沥青混合料试件的破坏微应变均超过2 300,满足冬寒区的技术指标;无论是否掺加橡胶颗粒,随着温度的下降,沥青混合料破坏时的最大弯拉强度增大,弯拉应变降低,劲度模量增大;弯曲应变能密度在胶粒掺量为1%左右时具有较大的弯曲应变能密度值,此时橡胶颗粒沥青混合料具有较好的低温抗裂性.  相似文献   

17.
理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。  相似文献   

18.
Quality traits in wheat (Triticum aestirum L.) were studied by quantitative trait locus (QTL) analysis in a recombinant inbred line (RIL) population, a set of 131 lines derived from Chuan 35050 × Shannong 483 cross (ChSh). Grains from RILs were assayed for 21 quality traits related to protein and starch. A total of 35 putative QTLs for 19 traits with a single QTL explaining 7.99-40.52% of phenotypic variations were detected on 10 chromosomes, 1D, 2A, 2D, 3B, 3D, 5A, 6A, 6B, 6D, and 7B. The additive effects of 30 QTLs were positive, contributed by Chuan 35050, the remaining 5 QTLs were negative with the additive effect contributed by Shannong 483. For protein traits, 15 QTLs were obtained and most of them were located on chromosomes 1 D, 3B and 6D, while 20 QTLs for starch traits were detected and most of them were located on chromosomes 3D, 6B and 7B. Only 7 QTLs for protein and starch traits were co-located in three regions on chromosomes 1D, 2A and 2D. These protein and starch trait QTLs showed a distinct distribution pattern in certain regions and chromosomes. Twenty-two QTLs were clustered in 6 regions of 5 chromosomes. Two QTL clusters for protein traits were located on chromosomes 1D and 3B, respectively, three clusters for starch traits on chromosomes 3D, 6B and 7B, and one cluster including protein and starch traits on chromosome 1D.  相似文献   

19.
As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.  相似文献   

20.
赵英华 《科技信息》2008,(12):219-220
0.Preface China has long been boasting of its colorful and immense culture which comprises of Taoism,Confucianism and Buddhism.The interwoven influence among the religions on Chinese way of thinking,on the nation's behavior in their social life throughout the long history is beyond list.  相似文献   

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