基于超构表面的低散射天线阵列

提出了一种将超构表面与天线阵列组合设计的方法,以同时实现高增益辐射和低背向散射功能。该超构表面由多层金属图案结构组成,对x极化入射波具有透射功能,从而能使天线辐射场低损耗透过;同时,对y极化入射波具有反射相位调制功能,通过将单元按照棋盘格或随机分布排列,可实现y极化入射波的漫散射功能,从而降低天线阵列的后向散射。仿真分析表明,所设计的低散射天线阵列峰值增益为18.8 dB,工作带宽约为12.5%。当探测波为x极化时,10 dB RCS缩减频带为9.5~10.1 GHz,覆盖天线工作频带,最大缩减值为25 dB;当探测波为y极化时,10 dB RCS缩减频带为7.8~12 GHz,最大缩减值高于35 dB。实测结果与仿真分析结果吻合良好。该低散射天线阵列利用超构表面的极化选择特性能实现透、反射功能集成设计,为低散射天线的研究提供了新的思路。     

基于辐射散射一体化技术的低RCS贴片天线阵列设计

提出并设计了一种基于辐射散射一体化技术的4×4低RCS贴片天线阵列,该阵列由2种辐射特性相似、反射相位相差180°的天线单元组成。利用遗传算法优化得到散射场在各方向均匀分布的非周期阵列结构,有效减小了天线阵的峰值RCS。仿真结果表明:天线阵列的增益在16dBi以上;法线方向x极化波照射时,单站RCS减缩频带为8～15.9GHz,最大减缩量为17.1dB;y极化波照射时,单站RCS减缩频带为9.5～16GHz,最大减缩量为13.1dB。测试结果与仿真拟合较好。该阵列集超材料和贴片天线于一体,利用天线单元自身相位差有效降低了其RCS值,为降低天线阵列RCS提供了一种新的方法。     

一种低剖面、低RCS兼具高增益特性的覆层微带天线设计

设计了一种低剖面覆层微带天线,兼具高增益、低雷达散射截面积RCS特性。覆层单元上表面为加载集总电阻的方环贴片,具有吸波和部分反射特性,下表面为"十"字开槽的金属镀层,将覆层与上表面加载同相反射特性的AMC单元的原始微带天线一体化设计,因覆层厚度可作为部分反射路径以及加载同相反射AMC单元,极大降低剖面。另一方面覆层上表面与AMC单元形成Fabry-Pérot谐振腔,改善天线辐射特性。仿真与实测结果表明:相对于原始天线,该覆层天线在整体厚度只有7mm的前提下,反射系数|S11|-10dB带宽由原来的13.84～15.24 GHz稍频偏到13.8～15.36 GHz;增益也得到较好的改善,在14.40～15.42GHz增益提高了3dB以上,最大提高增益6.29dB;天线在6～17GHz频段内有不同程度RCS的减缩,在宽角域内实现了RCS减缩,其中6dB减缩带宽为8.86～13.56GHz,最大减缩量为14.8dB。     

共享孔径超表面设计及其在提升波导缝隙天线辐射和散射性能中的应用

根据平面阵列散射理论和天线共享孔径思想,提出了一种由完美吸波体(PMA)和人工磁导体(AMC)交错构成的共享孔径超表面(SA-MS),可在同一孔径面上同时实现对电磁波的吸收和相位对消。仿真结果表明由于吸波频段与相位对消频段的级联,该SA-MS相比理想导电体(PEC)、PMA、AMC-PEC具有宽带雷达散射截面(RCS)减缩效果。而后将该SA-MS与波导缝隙天线一体化设计并加工,仿真与实测结果表明:与金属面天线相比,SA-MS天线增益提升了3.3dB,同时RCS在5.52~7.51GHz范围内的减缩在6dB以上,减缩带宽达到30.5%,x、y极化条件下最大减缩量分别达到20.5dB和20.2dB,验证了设计的SA-MS对天线的辐射和散射性能均有提升。     

一种带有透波窗口的宽带RCS缩减超表面设计

超表面在调控电磁波的极化、幅值和相位等方面具有极大的优势。针对天线带外低散射的现实需求,通过复合极化旋转超表面和频率选择表面,调节极化旋转单元的响应厚度,实现了兼具高效极化旋转反射和同极化透波窗口的超表面设计。利用几何相位仅对交叉极化波有响应的特性,进一步通过棋盘阵列排布,在透波窗口的两侧实现低散射特性,其中透波带10.0~11.0 GHz插损低于1 dB;在4.5~7.5 GHz和12.0~17.0 GHz频带内实现低散射特性,RCS缩减接近10 dB。仿真和实验结果表明：文中所提出的超表面设计方法和架构具有宽带的RCS缩减特性和低插损透波特性,在隐身天线罩中具有潜在的应用价值。     

超构表面设计及其应用

超构表面作为二维形式的超构材料,在分界面处可以对透射、反射电磁波产生特定的相位分布,因此能够灵活调控电磁波前。超构表面的低剖面二维平面结构,在电磁调控领域具有广泛的应用前景,一系列的超构表面应用应运而生。主要介绍了超构表面的设计发展以及其应用,主要包括天线应用、RCS减缩、特殊波束、有源超构表面等4个方面。首先,在天线应用方面,超构表面可用于实现高增益透镜和极化转换功能;其次,从吸波型和散射调控型2种不同工作机理的角度介绍了应用于RCS减缩的超构表面;然后,针对特殊波束,主要介绍了超构表面在涡旋波束和全息成像中的应用;最后,从加载不同有源原件的角度分析有源超构表面的发展,并未来超构表面发展值得深入研究的方向。     

锯齿化进气道口面电磁散射影响分析

为研究锯齿化对电磁散射的影响,以两种飞翼布局为基础,建立了直线型、锯齿化进气道口面飞行器模型;采用物理光学法,数值计算了各模型在不同状态下RCS曲线,研究了锯齿化的散射分布影响及RCS减缩值的俯仰角、频率响应特性。结果表明：锯齿化进气道口面可有效降低头向、后向散射波峰,并影响其他角域波峰分布情况;俯仰角增大时,锯齿化RCS减缩值呈震荡递减趋势,不同布局不同角域上表现各异,幅值影响为10~30 dB;频率增加时,锯齿化RCS减缩值呈震荡变化,幅值影响为5~25 dB之间;锯齿化对不同布局的电磁散射影响不同,其中布局A头向30°角域的隐身性能提高最为明显,减缩值为20~30 dB。     

一种用于产生OAM波束的集成圆极化天线阵列

提出了一种在S波段内产生轨道角动量(OAM)波束的集成圆极化微带天线阵列.天线采用同轴馈电的方式.为了获得良好的圆极化特性,利用CST软件对天线结构参数进行了仿真优化分析,最终确定天线整体尺寸为0.416λ_0×0.416λ_0×0.026λ_0,3-dB轴比带宽为3.79～3.85 GHz,S_(11)-10 dB的工作带宽为3.74～3.96 GHz.该天线结构简单紧凑,易于实现.天线阵列由6个相同的圆极化天线组成,相邻阵列单元沿顺时针方向旋转60°,通过仿真和实验结果得知,在对阵元进行等幅、等相位的馈电的条件下,该天线阵列能够产生模态l=-1的OAM波束,这能够有效避免复杂馈电网络结构的设计.     

60 GHz低损耗宽带的超表面天线阵列

研究一种基于超表面的60 GHz 1×2宽带天线阵列.为降低传输损耗,天线阵列由间隙波导功分器馈电,间隙波导传输线两侧放置电磁带隙结构,能量通过缝隙与顶层超表面耦合,从而向空间辐射.天线阵列安装在Rogers 4350b介质基板上,由超表面辐射器引入的准TM₃₀谐振模式与缝隙辐射单元的本征模式结合,从而拓展天线带宽,改善天线增益.研究结果表明:天线阵列-10 dB |S₁₁| 带宽仿真结果为49.3~65.0 GHz,实测结果为48.5~64.8 GHz,覆盖57.0~64.0 GHz范围的无授权毫米波通信频段;在匹配带宽内,天线的最大增益为11.8 dB,3 dB增益带宽为15%.     

一种高增益低RCS微带天线设计

设计了一种基于人工电磁材料的覆层,并将其应用于微带天线。该覆层由介质板及其两侧的人工周期表面构成,上表面是加载集总电阻的方环贴片,具有宽带吸波特性;下表面是开条带缝和圆环缝的金属贴片,具有部分反射特性。将其加载到微带天线的上方,通过上层的吸波表面吸收入射电磁波并结合下层的部分反射表面与金属地板构成Fabry-Perot(F-P)谐振腔增强天线的定向性,以实现微带天线辐射和散射性能的改善。仿真和实测结果表明加载人工电磁材料覆层后,天线的RCS在2~14GHz宽频带范围内实现了明显的减缩,最大减缩量达到28.3dB而天线的增益在工作频带内都得到了提升,最大提高了4.3dB。     

Markedness and its Interpretation in Language Use

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.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

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.     

Features of Women's language

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.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

低渗透非均质砂岩油藏启动压力梯度研究

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。     

On Tragic Consciousness In The Works By Ernest Hemingway

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.     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

海南岛地体及其毗邻陆缘晚中生代—新生代古地磁研究和构造演化

本文叙述了对海南岛及其毗邻大陆边缘白垩纪到第四纪地层岩石进行古地磁研究的全部工作过程。通过分析岩石中剩余磁矢量的磁偏角及磁倾角的变化,提出海南岛白垩纪以来经历的构造演化模式如下:早期伴随顺时针旋转而向南迁移,后期伴随逆时针转动并向北运移。联系该地区及邻区的地质、地球物理资料,对海南岛上述的构造地体运动提出以下认识:北部湾内早期有一拉张作用,主要是该作用使湾内地壳显著伸长减薄,形成北部湾盆地。从而导致了海南岛的早期构造运动,而海南岛后期的构造运动则主要是受南海海底扩张的影响。海南地体运动规律的阐明对于了解北部湾油气盆地的形成演化有重要的理论和实际意义。     

Jane Eyre——A Feminist In The 19th Century

In the 19th century the society was controlled by men, and women were just appendants of them, they had not any rights and freedom. But Jane was an exception, she showed some characteristics of early feminist. Jane showed her characteristics of feminism in three aspects: rebellion, equality, and independence. These characteristics were helpful to her success, and feminism is the only way out for women of that time.     

《Chinese Science Bulletin》SUBJECT INDEX TO VOLUME 59(2014)

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