Development of the microstructure of uranium-doped Nd-Ba-Cu-O

Melt grown Nd-Ba-Cu-O (NdBCO) has been reported to exhibit higher values of critical current density, Jc and irreversibility field, Hirr, than other (RE)BCO superconductors, such as YBCO. The microstructure of NdBCO typically contains 5-10 μm sized inclusions of the Nd4Ba2Cu2O10 phase (Nd-422) in a superconducting NdBa2Cu3O7-δ phase (Nd-123) matrix. The average size of these inclusions is characteristically larger than that of the Y2BaCuO5 (Y-211) inclusions in YBCO. As a result, there is scope to further refine the Nd-422 size to enhance Jc in NdBCO. Large grain samples of NdBCO superconductor doped with various amounts of depleted UO2 and containing excess Nd-422 have been fabricated by top seeded melt growth under reduced oxygen partial pressure. The effect of the addition of depleted UO2 on the NdBCO microstructure has been studied systematically in samples with and without added CeO2. It is observed that the addition of UO2 refines the NdBCO microstructure via the formation of uranium-containing phase particles in the superconducting matrix. These particles are of approximately spherical geometry with dimensions of around 1 μm. The average size of the nonsuperconducting phase particles in the uranium-doped microstructure is an order of magnitude less than their size in un-doped Nd-123 prepared with excess Nd-422. The critical current density of uranium-doped NdBCO is observed to increase significantly compared to the undoped material.

High-precision digital lock-in measurements of critical current and AC loss in HTS 2G-Tapes

Application of High Temperature Superconducting (HTS) has been increasingly popular since the new superconducting materials were discovered. This paper presents a new high-precision digital lock-in measurement technique which is used for measuring critical current and AC loss of the 2nd Generation HTS tape. Using a lock-in amplifier and nano-voltage meter, we can resolve signals at nano-volt level, while using a specially designed compensation coil we can cancel out inductive by adjusting the coil inductance. Furthermore, a finer correction for the inductive component can be achieved by adjusting the reference phase of the lock-in amplifier. The critical current and AC loss measurement algorithms and hardware layout are described and analyzed, and results for both numerical and experimental data under varieties of frequencies are presented. © 2008 SICE.

氮化镓紫外色度探测器及其制作方法

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黑土地区不同撂荒地植物生物量的季节变化

黑土地区处于北温带，冬季寒冷，夏季炎热;但由于纬度偏北，夏季日照时间较长.虽然黑土地区气候比较寒冷，但在生长季却是水、热、光同步，为植物的生长发育提供了良好的环境条件.因此黑土地区一直是中国主要的商品粮生产基地.但由于对土地掠夺式的开发，黑土在开垦后有机质含量急剧下降.植物生物量由地上生物量和根生物量组成.根生物量采用钻土芯法，地上生物量通过重复取样直接测定.研究表明：撂荒时间的增长，有助于植物生物量（包括地上生物量和根生物量）的积累，而尤以根生物量的增加最为明显;撂荒时间越长，在环境条件变化时，根生物量可以在生长季中保持相对的稳定;撂荒时间的增长，有助于植物营养元素碳、氮、磷的累积;撂荒时间越长，活根生物量的周转值越小.黑土地区不同撂荒年限植物生物量季节动态的研究还表明：不同年限撂荒地生物量的差异主要体现在根生物量的不同，地上生物量基本一致;即黑土开垦后土壤有机质急剧下降主要由根生物量归还减少导致;撂荒时间的增长，提高了生态系统适应环境的能力;植物营养元素碳、氮、磷的累积规律相似，而钾则与它们有较大差异.

AT91RM9200与Compact Flash接口电路及其驱动程序设计

介绍了基于ARM920T内核的AT91RM9200处理器与Compact Flash卡的接口电路以及Compact Flash卡驱动程序的编写、调试.提出了一种适合数据流量大、实时性能要求高的现场实时数据采集、事后PC机做分析处理的实时数据采集系统。

Optically active poly(amide-imide)s containing axially dissymmetric 1,1 '-binaphthyl moieties

Novel optically active aromatic poly(amide-imide)s (PAIs) were prepared from newly synthesized 2,2'-bis(3,4-dicarboxybenzamido)-1,1'-binaphyl dianhydride ((+/-)-, (S)-, and (R)-BNDADA). PAIs based on dianhydride monomers with different ee % were investigated with respect to their structures and chiroptical properties. These polymers were highly soluble in polar aprotic solvents such as N,N-dimethylacetamide, N-methyl-2-pyrrolidone, pyridine, etc., and showed high glas s transition temperatures of 287-290 degrees C and 5% weight loss temperatures of 450-465 degrees C in nitrogen. Optically active PAIs exhibited high specific rotations, excellent optical stabilities, and a dependence of optical activities on temperature. Investigations on chiroptical properties indicated that chiral conformation was possessed by optically active PAIs. (C) 1999 John Wiley & Sons, Inc.

Identification and expression of the amphioxus Cks1 gene

A full-length Cks1 homologue gene, AmphiCks1, was identified in amphioxus, Branchiostoma belcheri tsingtauense. Sequence characteristics, phylogeny and patterns of expression during embryonic and larval development were established. The protein predicted from AmphiCks1 showed high sequence identity with vertebrate and invertebrate homologues. Protein structural studies and phylogenetic analysis suggested that Cks homologues are evolutionarily conserved. The AmphiCks1 transcript was detected in most early developmental stages by northern blotting and whole-mount in situ hybridization, suggesting a role for the gene in cell division. (c) 2005 International Federation for Cell Biology. Published by Elsevier Ltd. All rights reserved.