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991.
We have doped the YBa2Cu3O7– superconducting ceramics with BaZrO3 up to 75wt.% and studied the changes of some physical properties. The most important finding is the enhancement of the critical current density, which has a maximum at around 5 wt.% doping level. Compared with the undoped samples, the critical current density is four times higher if the doping compound is introduced prior to the calcination treatment, or two times higher if BaZrO3 is introduced prior to the sintering treatment. The dependence of the critical current density on the doping level is consistent with the dependence of the Seebeck coefficient. We also observed a very small decrease of the critical temperature. The real density of the samples decreases with increasing doping level as expected from the ratio between the theoretical densities of YBa2Cu3O7– and BaZrO3, the effect being important for doping levels higher than 25 wt.%. 相似文献
992.
大型河流—三角洲沉积储层精细描述方法 总被引:97,自引:9,他引:88
概括地论述了大庆油田应用现代沉积和露头研究中的层次分析思想和自创的模式预侧描述法,成功地研制出依据油田密井网测井资料和大型河流—三角洲特有的沉积规律与模式,由大到小、由粗到细分层次逐级解剖砂体几何形态和内部建筑结构,精细地建立储层地质模型,系统描述储层宏观非均质体系的研究方法。该方法将整套储层划分为岩相段、单一旋回层(或单砂层)、沉积微相(或相对均质单元)、单砂体、建筑结构单元、层内非均质等6个描述层次,并对砂体井间连续性、几何形态与边界位置、厚度与渗透率的平面非均质性采用模式化预测性描述,较好地解决了储层复杂非均质体系描述和井间砂体预测的难题。 相似文献
993.
Regions with different microstructures have been identified in the weldments of 9Cr-1 Mo steel. Weldments comprising threthree regions, i.e., weld metal, heat-affected zone (HAZ), and base metal, were oxidized in air at 923 K for different durations up to 500 hr. The crown area of the weld metal was found to form a thicker oxide scale than the other regions of the weldment. When the oxidation kinetics of different regions were compared (by separating out the coupons of the HAZ and the crown and root portions of the weld metal and then oxidizing them), the crown area of the weld was found to oxidize at a much higher rate than the others. Scanning electron microscopy (SEM) was carried out to assess the morphological variations in the different regions of the weldment. The compositional variations in the scales over the different regions have been characterized by the energy-dispersive analyses of X-rays (EDX), and the results thereof have also been corroborated by secondary ion mass spectrometry (SIMS). 相似文献
994.
995.
Axel Flament Antoine Frappé Bruno Stefanelli Andreas Kaiser Andreia Cathelin Sylvain Giraud Matthieu Chatras Stephane Bila Dominique Cros Jean Baptiste David Laurent Leyssenne Eric Kerhervé 《国际射频与微波计算机辅助工程杂志》2011,21(5):466-476
A complete UMTS transmitter is proposed. It is composed of a radiofrequency (RF) signal generator, a power stage, and a bulk acoustic wave (BAW) duplexer. The 90‐nm CMOS digital RF signal generator is based on a third‐order delta‐sigma modulator using innovative design techniques to increase work frequency and a BAW filter to get rid of out‐of‐band quantization noise. The filter exhibits very high rejection, 3 dB of insertion losses at 1.95 GHz for a 3% fractional bandwidth. The 0.25‐μm BiCMOS power stage feeds a BAW duplexer that allows to share a common between W‐CDMA emission and reception. This 4 × 4 mm2 duplexer, built with flip‐chipped BAW on glass substrate, ensures good isolation. The full transmitter measurements show the compliance with respect to spurious emissions in the different frequency bands and an EVM measurement at the state of the art (<5%). © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011. 相似文献
996.
Hongjiu Yang Qing Geng Yuanqing Xia Li Li 《International journal of systems science》2016,47(15):3696-3703
In this paper, we investigate the problem of stability analysis for linear delta operator systems subject to state saturation. Both full state saturation and partial state saturation are investigated for the delta operator systems. Two equivalent necessary and sufficient conditions are identified such that the system with full state saturation is globally asymptotically stable. Based on the sufficient conditions, an iterative algorithm is proposed for testing global asymptotic stability of the system with full state saturation. A new globally asymptotically stable condition is also proposed for the partial state saturation system. Two numerical examples on a ball and beam model are given to show the effectiveness of the proposed method. 相似文献
997.
针对广义系统的无源性分析,本文采用Delta算子方法,建立了广义系统的Delta算子模型,并利用广义系统的离散模型与Delta算子模型之间的关系,给出了广义Delta算子系统容许且严格无源的充分条件,通过数值算例,验证了该判别条件的有效性。 相似文献
998.
999.
渤海BZ油田高效开发策略研究 总被引:1,自引:0,他引:1
渤海BZ油田为浅水三角洲沉积,储层非均质性较强,定向井多层合采势必导致层间干扰严重.针对储层非均质性影响的问题,研究水平井设计技术,包括水平井的轨迹方向、水平段长度、水平注水井摆放位置、隔夹层的利用等,并提出采用水平井分层系开发油田的高效开发策略. 相似文献
1000.
P. Haldar S. Sridhar A. Roig-Janicki W. Kennedy D. H. Wu C. Zahopoulos B. C. Giessen 《Journal of Superconductivity》1988,1(2):211-218
Joining YBa2Cu3O6.5+
(123 phase) and Bi4Sr4Ca2Cu4O16+
(4424 phase) as structurally characterized high-T
c
, superconductors, the thallium-containing superconductor (Tl.75Bi.25)1.33Sr1.33Ca1.33Cu2O6.667+
with the ideal stoichiometry (Tl,Bi)1Sr2Ca1Cu2O6.5+
(1212 phase) is reported here. As prepared from the component oxides, 1212 has an initial deviation from resistance linearity at 120 K, a superconducting onset temperature of 92 K, and zero resistance at 75 K. The tetragonal unit cell (P4/mmm, a=3.800 Å;c=12.072 Å, deduced from powder data) contains double copper oxygen sheets (like 4424 and 123) that alternate withsingle thallium-bismuth oxygen sheets (in contrast to 4424, which containsdouble bismuth oxygen sheets), resulting in a total of three stacked perovskite-like cells (as in 123). The copper oxide sheets (with intersheet spacing 3.38 Å) are separated by Ca2+ and the Cu oxide sheets and (Tl,Bi) oxide sheets (with spacing 4.35 Å) are separated by Sr2+, Ca2+, and excess (Tl,Bi)3+. The 1212 cell constitutes the building block for the centered, more complex 4424 cell. The 1212 structure persists to Bi contents as low as 1% and can also be stabilized by Pb instead of Bi; Tl cuprates also form other superconductors with lowerT
c
. 相似文献