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1.
The recently discovered metal-intercalated iron selenide superconductors A2Fe4Se5 (A=K, Cs, T1- K, Rb, T1-Rb) (245) compounds, with Tc ~30K, have attracted much interest A high transition- temperature (TN ≈ 470-560K) and large magnetic moment (3.3μB/Fe) block antiferromagnetic (AFM) order exists in the superconducting samples. Mag- netic order-parameter experiences an anomaly when Tc is approached. The superconductors crystal- lize with a highly ordered √5 × √5 superstructure, in which the Fel site of the I4/m structure is only a few percents occupied and the Fe2 site is fully occupied. The non-superconducting samples at low-T also crystallize in the I4/m structure, while both Fe sites are fractionally occupied, since the numbers of the Fe vacancies in the samples and the vacant sites in the √5 × √5 pattern are mismatched. The partially ordered √5× √5 vacancy order becomes one of three competing phases for temperature below room temperature up to ~ 500K, namely, these sam- ples are phase-separated and in the miscibility gap 1lacier the n,mhi~nt condition.  相似文献   
2.
 通过二维高频电磁场的计算,设计了兰州重离子加速器冷却储存环(HIRFL–CSR)的铁氧体加载腔,给出了高频系统主要参数及加速电场的分布。  相似文献   
3.
化学气相沉积法制备金刚石膜截面微区Raman分析   总被引:7,自引:1,他引:6       下载免费PDF全文
王冠中  叶峰  常超  章应辉  方容川 《物理学报》1999,48(12):2382-2388
采用微区Raman散射分析方法研究化学气相沉积法制备的金刚石膜的横截面.金刚石膜从衬底面到生长面不同位置具有不同特征的Raman谱,依此对膜中的金刚石、石墨和非晶碳成分进行分析.衬底面附近区域对应金刚石膜生长过程的成核阶段,非晶碳成分含量较高,相应于1200—1600cm-1波段较大的散射强度和存在较强的荧光背底.膜厚增大,非晶碳成分中sp3结构成分首先减少,而sp2结构成分和石墨成分的减少相对缓慢.而生长面附近区域只有比较单纯的晶体金刚石 关键词:  相似文献   
4.
叶峰 《中国物理 C》2013,37(4):79-83
In order to further improve beam transmission efficiency at the SSC, the beam center trajectory and injection and extraction system are recalculated based on the program group used in the final design of the GANIL accelerator, with some necessary changes and the addition of some auxiliary programs. The two different types of injection and extraction elements (the bending magnet and the inductive septum) are distinguished, and their interaction with the ambient field is considered. More focus is placed on considering the differences in the magnet field inhomogeneity of the ambient field in the located area of the inductive septum where the ends are situated in the ambient field (between the main magnet poles). Thus the gradient magnetic field problem of the inductive septum is solved perfectly. As well as preparing the necessary auxiliary programs and taking the structural integration of the SSC magnetic field maps, the measured magnet field correction is completed. Therefore, the trajectory and a variety of injection and extraction system parameters are obtained. According to the recalculation results, the SSC beam transmission efficiency will be enhanced significantly.  相似文献   
5.
In this article, we investigate the nonparaxial propagation properties of the chirped Airy Gaussian vortex(CAiGV)beams in uniaxial crystals orthogonal to the optical axis analytically and numerically. We discuss how the linear chirp parameters, the quadratic chirp parameters, and the Gaussian factors influence the nonparaxial propagation dynamics of the CAiGV beams. The intensity, the energy flow, the beam center, and the angular momentum of the CAiGV beams are deeply investigated. It is shown that the Gaussian factors have a great effect on the intensity and the centroid positions of the CAiGV beams. With the Gaussian factors increasing, the intensity of CAiGV beams decreases rapidly. The main lobes of the transverse intensity distribution of the CAiGV beams are similar to triangles.  相似文献   
6.
In this paper we address the problem of the low beam transmission efficiency of the HIRFL-SSC. The influence of the SFC-SSC energy match, the SSC RF voltage, and harmonic field in the injection area of the SSC, and the SSC central trajectory on the beam transmission efficiency have been analyzed both from the theoretical side and from the actual operating data. The main reason is that the soft-edge approximation of the magnet field (the so-called theoretical field) and the simplified calculation programs were adopted when calculating the beam center trajectory and designing the injection and extraction system, and the measured magnetic field was not used to correct the calculation results. These led to large deviations of the calculated center trajectory, and then resulted in low efficiency of the SSC beam transmission. Therefore, the re-calculation of SSC beam center trajectory and injection and extraction system, as well as the measured magnet field correction are the key points required to solve the problem.  相似文献   
7.
彭银  刘正银  叶峰  魏先文 《中国化学》2009,27(2):295-298
聚丙烯酰胺(PAM)表面活性剂的作用下,在温和的低温水溶液中,合成了Cd(OH)2油炸圈饼状微米结构。这种结构是由单晶结构的六方片状Cd(OH)2按一定排列方式自组装而成。在羰基修饰的PAM(PAM-COOH)表面活性剂作用下,得到中心有孔的油炸圈饼纳米结构。可能的生长机理为表面活性剂控制下Cd(OH)2纳米片经历有序连接过程,最终形成油炸圈饼状结构。聚合物诱引晶体生长与调控纳米晶自组装将提供了一条有效的路径来合成具有复杂形貌与特殊结构的无机和无机-有机杂化材料。  相似文献   
8.
金刚石薄膜的蓝光发射   总被引:1,自引:0,他引:1       下载免费PDF全文
叶峰  廖源 《发光学报》1998,19(3):230-232
利用氮化铝陶瓷作为衬底,在不同甲烷与氢气的配比流量下,利用热丝CVD方法制备了一个系列的金刚石薄膜,通过测量样品在430nm处的光致荧光(PL)谱及其Raman光谱,给出了金刚石薄膜的结构与生长信息,薄膜PL强度随甲烷浓度增加到3%时达到最大,继续增加了甲烷浓度PL强度下降。  相似文献   
9.
橡胶材料因其独特的超弹性在实际中广泛应用,通过解析应力-应变关系可以为橡胶力学性能的工程应用提供理论指导。为了更准确地描述橡胶材料力学性能,提出一种适用于橡胶材料的超弹性混合本构模型。新模型基于Gaussian模型与八链模型,引入有关拉伸比的权重函数将二者耦合,在拉伸比较小的情况下,新模型退化成Gaussian形式,在拉伸比较大的情况下,新模型可以依靠权重函数改善八链模型在小变形区域的不足。针对取向硬化的应力-应变曲线、无取向硬化的应力-应变曲线、不同拉伸比应力-应变曲线三种力学特征曲线,从单轴拉伸、等双轴拉伸和纯剪切三类实验数据进行预测验证。结果表明,新模型同时保留了Gaussian模型在小变形范围和八链模型在大变形范围内的预测优势,且对拉伸比和应力应变曲线形式没有依赖性,均能给出高精度的预测结果,突破了Gaussian模型和八链模型的使用限制,为橡胶超弹性力学性能的预测提供了新的思路。  相似文献   
10.
探讨了不同消毒条件下"京亚"葡萄种子在培养瓶中萌发的情况,获得"京亚"葡萄种子最佳消毒条件是70%乙醇15 S,o.1%升汞5 min;通过对"京亚"葡萄种子进行不同浓度GA3 浸种、不同浸种时间、不同培养基质和不同光照条件处理,得到优化的"京亚"葡萄种子萌发条件是GA34 000 mg/L浸种48 h,置于1/2MS培养基中暗光培养,萌发率为79.4%;对"京亚"葡萄种子抗卡那霉察特性的研究得到"京亚"种子抗卡那霉紊的临界浓度为40 mg/L.  相似文献   
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