首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 62 毫秒
1.
在椭圆柱坐标系中,利用单介质椭圆波导电磁场解析解,对纵向填充两种不同介质的理想导体壁椭圆波导连接后的传播特性进行了研究,得到其模式场特征方程.结果表明,纵向填充两种不同介质的圆波导的电磁场模式特征方程是其特例.用数值计算方法研究了填充椭圆波导的介质折射率、波导的偏心率等对奇对称基模传播特性的影响,对波导中电磁波的传播特性及截止条件的讨论以及数值计算表明如此结构的波导有滤波作用.  相似文献   

2.
直线法分析非均匀类矩形波导的特性   总被引:1,自引:3,他引:1  
为了分析非均匀介质填充的类矩形波导的特性及其应用,采用直线法和传递矩阵法对一维非均匀类矩形波导进行了分析,获得了模式LSM与LSE的特征方程,解决了处理非均匀类矩形波导边值问题的困难.以部分介质填充的矩形波导为例对该分析模型进行了验证,获得了与已有文献的解析解非常一致的结果.对填充介质片的矩形波导的色散和截止特性进行了数值计算和分析,这种波导的截止波长随着介质片的介电常数、厚度及其离开矩形波导窄边距离的增加而增加,即其截止频率大大降低,这对深入研究非均匀波导及其实际应用提供了理论依据.  相似文献   

3.
采用在椭圆柱坐标系中分离变量的方法,给出了填充任意多层互易手征介质共焦椭圆波导模式特征方程的一般计算公式.结果表明,当椭圆退化为圆时,利用角向马丢函数和径向马丢函数的渐进关系,可得到填充多层互易手征介质的圆波导的模式特征方程.由此可见,圆波导是椭圆波导的特例;当只填充一层互易手征介质时,可由所得椭圆波导的一般特征方程得到此种特殊情况的模式特征方程,利用特征方程可分析填充互易手征介质的椭圆波导的传播特性.  相似文献   

4.
从麦克斯韦方程推导出用时域有限差分(FDTD)法分析电各向异性介质填充波导问题的差分公式;在MATLAB平台上,编程实例计算了电各向异性无耗介质完全填充矩形波导TE波部分模式的截止频率,计算值与理论值吻合较好;分析计算了矩形波导尺寸变化及电各向异性非单轴介质加载厚度对TE波截止特性的影响。  相似文献   

5.
用FDTD法计算部分介质填充波导的截止频率   总被引:4,自引:7,他引:4  
给出用时域有限差分(FDTD)方法计算电磁场问题的差分格式,详细介绍了FDTD法分析介质填充波导截止频率的计算过程。实例计算了空心矩形波导的截止频率,并与理论值进行比较;计算了填充部分介质时矩形波导和双脊波导的截止频率,获得了三脊波导的归一化截止频率谱图,给出填充不同介质时各主模式的截止频率。  相似文献   

6.
多层介质填充H形波导的直线法分析   总被引:1,自引:0,他引:1  
用直线法分析了多层介质填充的H形波导,用传递矩阵获得了这种波导在不同模式下的特征方程,同时验证了该方法的正确性.对H形波导以及其他非均匀介质填充波导问题的研究有一定参考价值.  相似文献   

7.
在柱坐标系中导出手征铁氧体波导内横向场量与纵向场量之间的关系,利用波导壁上的电场边界条件,建立了手征铁氧体介质填充的圆波导传播常数的特征方程.  相似文献   

8.
用非均匀网格FDTD法计算部分介质填充脊波导的截止频率   总被引:2,自引:1,他引:1  
文章提出用非均匀网格FDTD法分析部分介质填充脊波导,给出了非均匀网格剖分的参数条件。实例计算了部分介质填充的双脊波导、三脊波导的截止频率,其结果与文献报道值吻合较好;计算了部分介质填充非对称脊波导的截止频率,并获得归一化截止频率谱图。在相同网格数下,本算法既具有良好的精度,又仅占用很少的内存和较短的运行时间,在短时间内能获得较满意的结果。  相似文献   

9.
任意截面介质填充类矩形波导传输特性的分析   总被引:1,自引:1,他引:0  
为了分析任意截面介质填充波导问题,建立了一种直线法分析模型,并得到了这种波导的特征方程.以介质条填充的矩形波导为例对该模型进行了验证,结果与相关文献一致.对介质条填充矩形波导的主模和次低模的色散特性和截止特性进行了数值计算,得到了一些有意义的结果.该方法对处理电磁场边值问题有一定借鉴意义.  相似文献   

10.
本在单个圆形槽波导和对称圆形双槽波导研究的基础上,提出了非对称圆形双槽波导。通过对该结构中场分布的分析,导出了特征方程,并与对称圆形双槽波导所得的结果进行了比较。  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.
何延凌 《科技信息》2008,(4):258-258
Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women's language from these perspectives: pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women's language, more attention should be paid to language use in social context. What's more, the linguistic phenomena in a speaking community can be understood more thoroughly.  相似文献   

15.
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   

16.
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   

17.
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   

18.
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   

19.
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   

20.
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   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号