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.
报导Eu_(1-x)Sr_xFeO_(3-y)(x=0.0~1.0)的固相反应法合成,测量了其X射线衍射及室温下的 ̄57FeMossbauer谱。实验结果表明,Sr掺入了EuFeO_3晶格,结构变化与掺杂量密切相关。室温下 ̄57FeMossbauer谱由一套反铁磁六线谱、一套顺磁双线谱和一套顺磁单线谱组成(X=0.2,0.4,0.6).处于立方相的Fe离子的IS介于Fe ̄3+和Fe ̄4+之间,可能参与电子跳跃。  相似文献   

2.
本文对下述边值问题εU_(tt)+U_t-U_(xx)=f(x,t)       0<X<1,0<t<TU(0,t)=U(1,t)=0        0<t<TU(x,0)=S(x),Ut(x,0)=W(x) 0<x<1的可解性进行了研究,认为可以放宽文[1]中对函数f、s、w所作的假定,满足一般的可积性条件即可.  相似文献   

3.
用循环伏安测温(CVT)热电化学方法首次研究了Cu_2S阳极溶解过程;实测得Cu_2S阳极过程的熵变△rS_m与根据热力学数据计算所得到的电极反应Cu_2S=CuS+Cu ̄(2+)+2e的熵变值相符;实验的塔费尔(Tafel)斜率b与按迟缓放电机理所导出的Tafel斜率b的理论计算值接近。  相似文献   

4.
杂多阴离子柱撑水滑石类层柱状化合物的合成与表征   总被引:1,自引:0,他引:1  
以硝酸根型水滑石做交换前驱体,采用离子交换法合成了过渡金属离子三元取代硅钨杂多阴离子柱撑水滑石M_2Al(OH)_6-SiW_9Z_3(H_2O)_3O_(37)(M=Mg ̄(2+),Zn ̄(2+),Ni ̄(2+),Z=Cu ̄(2+),Co ̄(2+)).用元素分析、XRD、IR、UV-DRS和DTA等手段对产物的组成和结构进行了表征。结果表明,杂多阴离子引入水滑石层间后,水滑石的层间距从0.92nm增大到1.47nm;提高了柱撑材料的热稳定性,随层的组成不同热稳定性顺序为:Mg_2Al≥Ni_2A1>Zn_2Al;随柱的组成不同热稳定性顺序为:SiW_9Co_3>SiW_9Cu_3.处于层中的杂多阴离子在层的脱羟基温度以下均能保持良好的Keggin结构。  相似文献   

5.
对Bi ̄(1.7)Pb ̄(0.3)Sr_2Ca_2Cu_3O_(y-x)F_x(x=0.8)超导体T_c介于114~118K的样品进行SEM和TEM结构观察.超导体的晶粒尺寸大小不一,内部孔洞较多,元素的成分分布极不均匀.含F样品存在2种结构的2223相,其中含F的2223相沿b_F方向的调制周期为13.88,不含F的2223相沿b方向的调制周期为9.42,含F单胞在ab面的点阵常数略有收缩.F取代部分O是产生调制周期变长和T_c提高的原因.  相似文献   

6.
对一般线性模型:Y=Xβ+e,E(e=0,Cov(e)=δ ̄2∨,∨>0,当设计阵X列降秩时,β的最小二乘或广义最小二乘解与广义逆的选取有关,这在具体计算时会产生一些麻烦。同时,在许多情况下,问题本身要求最小二乘具有较小的长度。因此有必要考虑最小范数最小二乘问题,本文从设计阵本身的结构出发,寻找最小范数最小二乘的计算方法。只要知道X中r=R(X)个线性无关的列向量组X_1,就能得到唯一的最小范数最小二乘:β=X′X_1(X_1XX′X_1) ̄(-1)X_1Y,若T=∨+XUX′,则唯一的最小范数广义最小二乘是:β ̄*=X′X_1(X_1T ̄+XX′X_1) ̄(-1)X_1T ̄+Y。对X的行向量有类似的结论,实际计算表明,这种计算方法是简单有效的。  相似文献   

7.
给出了混合型二阶线性偏微分方程Lu≡h(y)u_(yy)+u_(xx)+a(x,y)u_y+b(x,y)u_x+c(x,y)=f(x,y)在非局部边界条件u(x,1)一au(x,0)=0,u_y(x,1)一au(x,0)=0,u(1.y)一βu(0,y)=0,u_x(1,y)-βu_x(0,y)=0下,在Sobolev空间中解存在及唯一的充分条件。  相似文献   

8.
本文证明了形如u_(xx)=u_t,u(x,0)=0,u(0,t)=Ut ̄(-(k+1)/2)),u(∞,t)=0,的奇异初边值问题,当k=1,3,5,…时没有相似解;而当k>一1且k≠1,3,5,…时相似解一定存在。第一个断言推翻了Phan-Thien于文[1]中提出的一个重要结论。  相似文献   

9.
铜基甲醇合成催化剂的EPR表征   总被引:1,自引:0,他引:1  
用EPR谱法对铜基甲醇合成催化剂作表征。结果表明:在少量Al ̄(3+)掺杂的ZnO-Al_2O_3体系可检测到g=1.9606±0.0002,△Hpp=2.8G的顺磁信号,其强度随Al_2O_3掺杂量增加而增强,当Al/Zn~2/100(原子比)时趋于峰值;而在三组份Cu-ZnO-Al_2O_3和四组份Cu-ZnO-Al_2O_3-Sc_2O_3催化剂体系中,此顺磁信号基本消失。以上结果为三价金属离子(Al ̄(3+)、Sc ̄(3+))在ZnO晶格掺杂诱生正一价缺位从而有利于Cu以+1价态存在的观点,提供了新证据。  相似文献   

10.
以 ̄(35)S标记抗人脑胶质瘤单克隆抗体SZ39制备成免疫导向放疗剂,在荷人脑胶质瘤裸小鼠体内药代动力学符合三室线性模型,总药时方程为C_t=1559276e ̄(─3.49t)+977313e ̄(-0.5t)+21682e ̄(-0.017t),T1/2a为0.23h,T1/2β为1.4Gh,T1/2γ为42.9h。体内分布研究表明 ̄(35)S-MAbSZ39可特异性浓聚于胶质瘤,在正常组织中无明显蓄积,发挥了单抗导向的高选择性作用,在给药后第五天,与 ̄(35)S-nlgG及 ̄(35)S相比,特异指数分别为4.1和4.87,具有显著优越性(P>0.05)。结果揭示35S-MAbSZ39有望作为一种高效低毒的导向放疗制剂应用于胶质瘤治疗,以一周间隔多疗程治疗方案为佳。  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.
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   

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

19.
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   

20.
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   

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