40T混合磁体Nb_3Sn超导电缆的研制

中国科学院强磁场科学中心的40T混合磁体由内部水冷磁体和外部超导磁体组成。外部超导磁体采用高临界电流密度的Nb3Sn材料制成的CICC超导导体绕制而成,目前已经完成了超导磁体所需的超导电缆的全部设计和加工任务。本文详细介绍了采用Nb3Sn材料的CICC超导电缆的设计准则、电缆配置方案以及绞制工艺等内容,讨论了超导电缆的扭距大小选取原则、叠包参数选取原则,分析了绞制过程中放线张力的控制方案等内容。     

丁螺环酮联合草酸艾司西酞普兰 治疗抑郁症的增效作用和安全性 观察

目的 探讨丁螺环酮联合草酸艾司西酞普兰治疗抑郁症的增效作用和安全性。方法 选取符合ICD-10 抑郁发作 诊断标准,经草酸艾司西酞普兰足量（20mg/d）、足疗程（6周）治疗未获得痊愈的45 例抑郁症患者,加用丁螺环酮15~60mg/d,观察8周,并分别在治疗前、治疗后第1、4、8周末分别评估汉密尔顿抑郁量表（HAMD）和汉密尔顿焦虑量表（HAMA）,以第1周末HAMA 评分≤7分为界,分为焦虑控制组（HAMA 评分≤7 分）和焦虑未控制组（HAMA 评分＞7 分）;以8周末HAMD≤7分为标准,分为获得痊愈组（HAMD≤7 分）和未获得痊愈组（HAMD＞7 分）;并在治疗第1、4、8周末分别评估不良反应。结果 在治疗第4周,获得痊愈20 例（44.4%）,第8 周末获得痊愈25 例（55.5%）。治疗后第4、8 周,获得痊愈组的患者HAMA 评分明显低于未获得痊愈组（P＜0.05）。治疗后第1、4周,焦虑控制组和焦虑未控制组患者HAMD 评分比较差异无统计学意义,治疗后第8 周,两组患者HAMD 评分 比较差异有统计学意义（P＜0.05）。不良反应以口干（40.0%）、便秘（36.9%）及乏力（13.3%）为多见。结论 经草酸艾司西酞普兰足量、足疗程治疗后仍未彻底痊愈的患者加用丁螺环酮可进一步获得疗效,提高痊愈率,安全性良好。     

Seed layer-free electrodeposition and characterization of vertically aligned ZnO nanorod array film

Vertically aligned arrays of ZnO nanorod (ZNR) were rapidly synthesized on ITO glass without needing a pre-prepared seed layer of ZnO via a hexamethylenetetramine (HMT)-assisted electrodeposition route. The effect of HMT on the ZNR electrodeposition process was investigated by the cyclic voltammetric curve and the current–time curve. An electrodeposition growth model based on the capping effect of HMT–4H was proposed. The as-synthesized ZNRs possess single crystalline, a wurtzite crystal structure with markedly preferential growth orientation along [0001] direction determined by transmission electron microscopy and powder X-ray diffraction. As compared with the electrodeposited ZnO film without HMT assistance, the ZNR arrays showed the high transmittance (90%) in the visible wavelength range and the blue-shift of the band gap energy. Moreover, the presence of an optical-phonon E₂ (high) at 437.3 cm^?1 in Raman spectrum and strong ultraviolet emission at 376 nm but weak defect-related deep level emission in the room temperature photoluminescence spectrum also indicated that such ZNR arrays are of good crystal quality. More importantly, the rapid synthesis of ZNRs could provide the feasibility for preparation of ZnO nanotubes within a shorter time by a subsequent electrochemical dissolution process.     

Energy transfer mediated fluorescence from blended conjugated polymer nanoparticles

Nanoparticles consisting of a derivative of the blue-emitting conjugated polymer polyfluorene doped with green-, yellow-, and red-emitting conjugated polymers were prepared by a reprecipitation method. The nanoparticles can be described as a system of densely packed chromophores that exhibit efficient energy transfer from the host to the dopant polymers. Fluorescence quenching analysis of the host polymer as a function of the dopant concentration indicates that one energy acceptor molecule can effectively quench 90% of the fluorescence of a nanoparticle consisting of 100-200 host conjugated polymer molecules. A nanoparticle energy transfer model was developed that successfully describes the quenching behavior of a small number of highly efficient energy acceptors per nanoparticle. The fluorescence brightness of the blended polymer nanoparticles was determined to be much higher than that of inorganic quantum dots and dye-loaded silica particles of similar dimensions. The combination of high fluorescence brightness and tunable fluorescence of these blended nanoparticles is promising for ultrasensitive fluorescence-based assays.     

二维非齐次不可压缩Navier-Stokes/Vlasov-Fokker-Planck方程组的渐近分析

研究了二维空间中非齐次不可压缩Navier-Stokes/Vlasov-Fokker-Planck方程组的渐近分析,此模型用于塑造流体-粒子的相互作用.运用紧性方法得到ρ~ε,u~ε的强收敛,最终得到由关于粒子宏观密度的对流-扩散方程及不可压缩Navier-Stokes方程组成的极限方程组.本文将相关文献的结果推广到非齐次不可压缩的情形.     

Preparation and upconversion luminescence characterization of 12CaO·7Al2O3:Ho3+/Yb3+ polycrystals

The effect of Yb³⁺ concentration on the fluorescence of 12CaO·7 Al₂O₃:Ho³⁺/Yb³⁺ polycrystals is investigated. The Raman spectra of pure C12A7 under 633‐nm excitation show that the highest photon energy is 787.267 cm⁻¹, which is not much bigger than general fluorides, so it can realize high efficiency upconversion. The upconversion emission spectra suggest that the green upconversion emission centered at 548 nm and the red upconversion emission at 662 nm correspond to the ⁵F₄/⁵S₂→⁵I₈ and ⁵F₅→⁵I₈ transition of Ho³⁺ ions, respectively. The intensity of the upconversion luminescence and the ratio of red to green are changed with Yb³⁺ ion concentration. The pump dependence and luminescence decay dynamics spectra show the green and red upconversion emissions are populated by a two‐photon process, and the upconversion mechanisms are analyzed. The relative luminous efficiencies of green and red emissions are 2.035% and 0.7%, respectively. The normalized efficiency obtained for green emission of Ho³⁺ at RT when the sample is excited by 980‐nm light with an absorbed intensity of 7.5 W/cm² is 0.27 cm²/W. This result is comparable to the values obtained in YF₃ for the Yb³⁺, Er³⁺ green emission. The C12A7 with upconversion red and green light will be a promising luminous material.     

牡丹草地下芽的形态分化与生长特征研究

采用解剖镜、扫描电镜技术,对长白山早春类短命植物牡丹草地下芽形态分化进行了观察,并采用游标卡尺测定各阶段芽体大小,研究地下芽的生长发育节律。发现牡丹草地上生活周期结束后,地下贮藏器官需要休眠2个月左右,于7月中下旬,地下芽开始出现形态分化和发育。其进程可分为萌芽期、花序原基分化期、花序形成期和花器官分化期4个时期,历经2个月左右,最终以发育成熟的花序进行越冬休眠。连续测定和相关分析表明,在整个夏眠期,牡丹草地下芽的茎高、芽长、芽径均随时间指数生长,茎高和芽长、芽径之间以及芽长与芽径之间呈幂函数规律异速生长,且相关系数均达到极显著水平。 牡丹草块茎需短暂休眠后完成地下芽的形态建成,地下芽茎高、芽长和芽径的增长具有不同步性和阶段性优先伸长的异速生长特性。     

The existence and uniqueness of the solutions of the nonlinear on–off switched systems with switching at variable times

In this paper, by introducing the definition of the solution, we prove the existence and uniqueness of the solution for nonlinear on–off switched systems with switching at variable times (NVTSS). Based on this result, the continuous dependence and differentiability of the solution of NVTSS (4) with respect to the initial state are presented. Besides, the switching phenomenon (the integral curve of NVTSS (4) may hit some surface finite or infinite times causing a rhythmical beating) and periodic solution of NVTSS (4) are also discussed.

     

Polymorph selection of magnesium under different pressures: A simulation study

Molecular dynamics simulations were used to investigate the influence of pressure on the structural properties and dynamics of magnesium(Mg)during rapid solidification.The dynamics analysis revealed that,with an increase in pressure,the dynamics of Mg melt slowed down sharply and the dynamical heterogeneities increased,leading to a denser structure.Atom-level structural analysis using the cluster-type index method suggested that the predominant structure transformed from hexagonal closed-packed to face-centered cubic with increasing pressure from 0 GPa to 5 GPa,and then transformed to the A15 complex crystal structure as the pressure increased above 10 GPa.In addition,the nature of polymorph selection was investigated by analyzing the phonon dispersion of Mg under different pressures.These findings provide a novel insight into polymorphic transitions of Mg under pressure and guide the selection of Mg polymorphs for practical applications.