纳米Fe3O4/BaTiO3复合体系的微波吸收特性

研究了纳米Fe3O4和BaTiO4及其复合体系在2～18GHz频率范围内的微波吸收性能，并分析了其吸收机制以及复合组分对吸波性能的影响。研究结果表明，通过调节材料组分可调节电磁参数及吸收峰的位置，复合体系的有效吸收频带较单一材料的吸附频带变宽。单一组分的纳米Fe3O4和PaTiO3都有2个吸收峰。在复合体系中，多个吸收峰发生重叠。这2种材料的微波吸收能力随电磁波频率的变化而规律不同，当频率低于14GHz时，PaTiO3的吸收能力大于Fe3O4的吸收能力；当频率高于14GHz时，Fe3O4的吸收能力大于BaTiO3的吸收能力。因此，将这2种材料复合，产生协同效应，材料的整体吸收能办提高，有效吸收频带拓宽。当样品的厚度为2mm，Fe3O4与BaTiO3的质量比为3：2时，反射率为10dB的有效频宽可达2．7GHz；当Fe3O4与BaTiO3的质量比为2：3时，反射率为10dB的有效频宽可达4GHz。     

Co掺杂对RGO/Fe3O4复合材料组织结构和吸波性能的影响

研究了Co掺杂对还原氧化石墨烯(RGO)/Fe3O4复合材料结构、形貌和吸波性能的影响规律.采用一步水热法分别制备RGO/Fe3O4和Co掺杂的RGO/Fe3O4复合材料,通过扫描电子显微镜、X射线衍射仪和X射线光电子能谱分析Co掺杂对复合材料的微观形貌、相组成及表面元素价态的影响;利用矢量网络分析仪测定两种复合材料在2～18GHz频率范围内的相对复介电常数和复磁导率,模拟计算了Co掺杂对RGO/Fe3O4复合吸波性能的影响规律.结果表明:部分Co参与了水热反应生成了CoCO3、Co3O4和Co2O3,还有部分Co以单质形式存在,其通过正负电荷吸引机制,影响Fe3+在氧化石墨烯(GO)表面的配位,使得负载在还原氧化石墨烯(RGO)表面的Fe3O4纳米颗粒部分迁移至RGO片层间;Co掺杂改善了复合材料的导电能力和磁损耗能力,使复合材料的吸波能力显著增强.反射率模拟结果表明:掺杂后与掺杂前相比,当匹配厚度d=2.00mm时,最大反射损耗提高3.44dB,有效吸收频带拓宽2.88GHz;当匹配厚度d=2.50 mm时,最大反射损耗提高8.45 dB,有效吸收频带拓宽2.73GHz.Co掺杂对RGO/Fe3O4复合材料的结构和形貌有显著影响,并有效改善复合材料的吸波性能.     

宽频带超材料微波吸收结构研究

将3D超材料吸波结构和磁性吸波材料相结合使用,对宽频带微波超材料吸收结构进行了设计优化和电磁场仿真研究.利用磁性材料本身的电磁波吸收性能和周期性超材料吸波单元的频率可设计性,并充分考虑了3D渐变单元的电磁场匹配和多次反射吸收的情况,设计了由圆台形单元组成的周期性吸波结构:每个圆台由20层尺寸渐变的金属谐振单元和以羰基铁粉为吸波填充材料的磁性复合层相间堆叠而成.采用电磁仿真软件CST Microwave Studio进行了结构设计以及吸波效果和电磁场分析,结果表明:此结构在4.5 G～18 GHz频率范围内电磁波吸收效果较好,正入射的吸收率大于90%.仿真和分析结果也表明,吸波材料和超材料相结合,在厚度不超过5 mm的情况下,所能够实现的吸波频率的下限约为4 GHz.     

斜入射时Salisbury屏电磁参数匹配规律研究

利用电磁波传输理论,研究并推导出了电磁波斜入射时Salisbury屏后向反射率公式,使用三维网格法讨论了各个电磁参数、隔离层厚度、入射波频率等同后向反射率之间的关系.研究结果表明:在2～18GHz范围内,角度后向反射率有很大;在f=16GHz时,μ_(r1)和μ_(r2)取值的增加使得材料的磁损耗和储能能力加强,导致材料有很好的吸收效果;然而ε_(r1)和ε_(r2)取值增加时,由于表面反射效应增强,使得吸波效果下降;在2～18GHz频段内后向反射率均可达到4.5dB以上,能够满足军事和民用的要求.     

BaZn2Fe16O27/石墨复合吸收剂的制备及其电磁吸波性能

采用固相法制备W型铁氧体BaZn2Fe16O27,将其与石墨按不同配比机械混合,制备出电磁性能优异的复合吸收剂。通过X线衍射仪(XRD)、扫描电子显微镜(SEM)对固相法制得的铁氧体粉末进行晶体结构和微观形貌的分析,结果表明,实验制得的粉体为纯相的BaZn2Fe16O27-W型铁氧体,微观形貌为六角片状。同时,使用网络分析仪在2~12 GHz的频率范围内对复合粉体微波电磁特性进行测试分析,并使用软件YRCompute模拟计算复合粉体的反射损耗,结果表明:铁氧体的磁损耗与石墨的介电损耗发生协同作用,复合粉体的电磁性能得到很大提高;随着石墨含量的增加,复合粉体的介电常数与介电损耗明显增加,介电损耗最大值从0.02升高到0.2,而磁导率与磁损耗则是先增大后减小;当石墨质量分数为4%时,复合粉体的反射损耗在5 GHz左右达到最大值-40.6 dB,并且小于-10 dB的带宽达到4 GHz,吸波性能优异。     

纳米Fe3O4/PANI复合体系的微波电磁特性研究

用原位化学反应生成法制备了纳米Fe3O4/PANI复合材料,研究了样品在2~18 GHz范围的微波电磁特性与吸收性能以及复合材料组分对电导率、密度的影响.结果表明,Fe3O4颗粒尺寸约12.7 nm,Fe3O4在复合体系中的质量分数为35%左右时,电导率最大,密度相对较低,微波吸收率最高,吸收峰值为-21 dB,-10 dB频宽大于4 GHz,样品同时具有电损耗和磁损耗.可见,通过优化设计,纳米Fe3O4/PANI复合体系可以成为一种性能优良的微波吸收材料.     

含随机分布散射颗粒的吸波体设计和性能分析

单层致密平板吸波材料除几个特殊的吸收峰外,很难在较宽的频段达到理想的吸收效果．通过在吸波体内导电媒质的“孤岛”化设计,制备了单层非连续体平板吸波材料．测试结果表明,在8～18GHz频段内,热压平板媒质只出现两个特征吸收峰值,含炭20％吸收效果最好,但超过10dB的有效频段只有约1GHz．而非连续体平板吸波材料由于和空间波阻抗的良好匹配以及内部“孤立”颗粒对电磁波的散射和吸收衰减,其反射损耗有较大提高;而且随着平板试样中“孤立”颗粒炭含量的增加,平板对电磁波的反射损耗也增加,当炭含量达到30％时,平板的反射损耗在8．5～18GHz宽频范围内都超过10dB,有效频段在10GHz以上．     

尖锥八面体Fe3O4的水热合成及微波吸收性能

采用水热法,在碱性条件下,以PEG-6000与水的混合溶液为反应介质,以硫代硫酸钠氧化前驱体氢氧化亚铁制备Fe3O4晶粉.采用X线衍射仪(XRD)和扫描电子显微镜(SEM)对产物结构和形貌进行表征.用微波矢量网络分析仪测试了样品在2～18 GHz微波频率范围内的复介电常数和复磁导率,计算微波反射系数,探讨材料的微波损耗机制.研究结果表明:在水热反应一定时间后,得到单分散的尖晶石型Fe3O4晶粒,颗粒呈规则的尖锥八面体形貌且表面平整;对反应为12h、厚度为2.8 mm的样品,7.1 GHz频率位置的反射系数峰值为-35 dB,小于-10dB吸收带宽为7.9 GHz;低频段(2～13 GHz)的微波吸收主要源于磁损耗兼具介电损耗,高频段(13～18GHz)的微波吸收主要源于介电损耗且磁损耗弱.尖锥微八面体Fe3O4是一种低反射率宽带微波吸收材料.     

W型Ba_(1-x)La_xCo_2Fe_(16)O_(27)的微波吸收性能

用溶胶-凝胶法制备镧掺杂W型钡铁氧体Ba1-xLaxCo2Fe16O27（x=0,0．1,0．2,0-3）样品。用XRD和SEM对样品的晶体结构、表面形貌、粒径进行表征,用微波矢量网络分析仪测试该样品在2-18GHz微波频率范围的复介电常数、复磁导率,根据测量数据计算电磁损耗角正切及得出微波反射率与频率的关系,探讨该材料的微波吸收性能与电磁损耗机理。研究结果表明：适量稀土镧掺杂能改善微波吸收性能,在x=0．2时,样品微波吸收效果最好;当样品厚度为1．90mm及x=0．2时,吸收峰值为16．2dB,10dB以上频带宽度达4．0GHz样品的微波吸收来自磁损耗和介电损耗的共同作用,磁损耗更为显著。     

羰基铁粉形貌对吸波性能的影响

由于羰基铁粉具有温度稳定性好、吸收频带宽、可设计性强等优点,从而得到了广泛的研究与应用。对两种参数基本一致,但形貌各异的羰基铁粉(球状和树枝状)进行了电磁吸波性能测试,用以研究形貌对羰基铁粉电磁吸波性能的影响。实验结果表明,形貌对羰基铁粉的电磁吸波性能有非常大的影响。相比于球状羰基铁粉,树枝状羰基铁粉的最大反射损耗增加了94%,达到-47.14dB。同时,对应于最大反射损耗的频率从球状羰基铁粉的11.88GHz移动到树枝状羰基铁粉的6.44GHz。这是因为树枝状形貌有利于形成不连续网络、增加对入射微波的漫反射、还可以带来更多的界面电荷极化,从而增强对电磁波的吸收强度。此外,本研究表明各向异性结构是提高介电常数和介电损耗获得轻质宽带吸波剂的有效途径。     

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.     

Lower Paleozoic oil relationships within Williston Basin, Canada

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.     

An Analysis of Catherine＇s Character——Wuthering Heights

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.     

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.     

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.     

Design and analysis of generic LBS application developing platform

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.     

橡胶颗粒沥青混合料低温抗裂性试验研究

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.     

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。     

Quantitative trait loci （QTLs） for quality traits related to protein and starch in wheat

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.     

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.