Parameter analysis for a nuclear magnetic resonance gyroscope based on bf133Cs-129Xe/131Xe

We theoretically investigate several parameters for the nuclear magnetic resonance gyroscope based on ¹³³Cs-¹²⁹Xe/¹³¹Xe. For a cell containing a mixture of ¹³³Cs at saturated pressure, we investigate the optimal quenching gas (N₂) pressure and the corresponding pump laser intensity to achieve 30% ¹³³Cs polarization at the center of the cell when the static magnetic field B₀ is 5 μT with different ¹²⁹Xe/¹³¹Xe pressure. The effective field produced by spin-exchange polarized ¹²⁹Xe or ¹³¹Xe sensed by ¹³³Cs can also be discussed in different ¹²⁹Xe/¹³¹Xe pressure conditions. Furthermore, the relationship between the detected signal and the probe laser frequency is researched. We obtain the optimum probe laser detuning from the D2 (6²S_1/2→6²P_3/2) resonance with different ¹²⁹Xe/¹³¹Xe pressure owing to the pressure broadening.     

MoEDAL – a new light on the high-energy frontier

In 2010, the MoEDAL (MOnopole and Exotics Detector at the LHC) experiment at the Large Hadron Collider (LHC) was unanimously approved by European Centre for Nuclear Research’s Research Board to start data taking in 2015. MoEDAL is a pioneering experiment designed to search for highly ionising manifestations of new physics such as magnetic monopoles or massive (pseudo-)stable charged particles. Its groundbreaking physics programme defines a number of scenarios that yield potentially revolutionary insights into such foundational questions as: are there extra dimensions or new symmetries; does magnetic charge exist; what is the nature of dark matter; and, how did the Big Bang develop. MoEDAL’s purpose is to meet such far-reaching challenges at the frontier of the field. The innovative MoEDAL detector employs unconventional methodologies tuned to the prospect of discovery physics. The largely passive MoEDAL detector, deployed at Point 8 on the LHC ring, has a dual nature. First, it acts like a giant camera, comprised of nuclear track detectors – analysed offline by ultra fast scanning microscopes – sensitive only to new physics. Second, it is uniquely able to trap the particle messengers of physics beyond the Standard Model for further study. MoEDAL’s radiation environment is monitored by a state-of-the-art real-time TimePix pixel detector array. A new MoEDAL sub-detector designed to extend MoEDAL reach to mini-charged, minimally ionising particles is under study.     

自组装合成Fe-N-C-PANI有序介孔结构催化剂及其在酸性条件下的氧还原活性

采用乙醇挥发自组装法,以F127为模版,甲阶酚醛树脂为碳源,聚苯胺为配体,加入硝酸铁和硅酸盐,制备了有序多级孔的Fe-N-C-PANI催化剂.催化剂的成分和形貌表征结果表明,在热处理温度为800℃时,有序介孔的结构最清晰,拥有整齐的孔道和最高的比表面积（1007 m²/g）;XPS分析结果表明,吡啶氮原子和石墨氮原子含量（摩尔分数）为3.86%.热处理温度升高过程中Fe（Ⅲ）被还原,向单质Fe转化,并促进了N的掺杂,使碳化铁转化为Fe-N_x活性位点,提高了催化剂的氧还原反应（ORR）催化活性,热处理温度达到900℃时,过多的单质铁使其氧还原活性下降.在酸性溶液中,Fe-N-C-PANI-800催化剂的起始电位可达0.89 V,半波电势为0.81 V.有序介孔结构使催化剂更易石墨化,提高了材料的稳定性.     

铂合金纳米立方块催化剂的氧还原反应活性比较

氧还原反应是质子交换膜燃料电池和金属-空气电池的重要反应,贵金属铂（Pt）与元素周期表中第一排的非贵过渡金属（M）形成铂合金催化剂（PtM）可以提高氧还原反应活性. 但是,有关活性的提高有多大程度上是来自合金元素的贡献却仍然存在争议. 为了研究合金元素对PtM催化活性的影响,本工作合成了颗粒形状与合金元素含量相似的铂锰（PtMn）, 铂铁（PtFe）, 铂钴（PtCo）和铂镍（PtNi）纳米立方块催化剂,并考察了不同铂合金催化剂在酸性介质中的氧还原反应活性. 选择制备立方块形状纳米颗粒催化剂进行比较,可以将颗粒表面结构对催化活性的影响降到最小. 结果表明,氧还原反应活性与铂d-带中心值曲线呈现火山形关系,其中PtCo纳米立方块催化剂的活性最高. 本文所得到的实验结果与基于d-带理论框架已知表面的密度泛函理论计算结果一致.     

Phase stability,thermal, electrical and structural properties of (Bi2O3)1−x−y(Sm2O3)x(CeO2)y electrolytes for solid oxide fuel cells

In this study, (Bi₂O₃)_1?x?y(Sm₂O₃)_x(CeO₂)_y ternary system was synthesized by using solid-state reaction method. Structural, morphological, thermal and electrical properties of the samples were evaluated by means of X-ray diffraction (XRD), scanning electron microscopy, thermo gravimetry/differential thermal analyzer and four-probe method. The XRD measurement results indicated that the samples (x = 10–15, y = 5–10–15–20) had cubic δ-phase crystallographic structure. The phase stability of the samples was checked by the differential thermal analyzer measurements, which indicates most of the samples have stable δ-Bi₂O₃ phase. The electrical conductivity measurement results showed that the electrical conductivity increased with mol% CeO₂ molar ratio at a fixed molar ratio of Sm₂O₃. The highest electrical conductivity obtained for the (Bi₂O₃)_0.65(Sm₂O₃)_0.15(CeO₂)_0.20 system was 1.55 × 10^?2 (Ω.cm)^?1 at 600 °C. The activation energies were also calculated at low temperature range (350–650 °C) which vary from 1.1325 to 1.4460 eV and at high temperature (above 650 °C) which vary from 0.4813 to 1.1071 eV.     

用于木材水分检测的单边核磁共振传感器设计

为了实现对木材水分的无损检测,设计了一种单边核磁共振（unilateral nuclear magnetic resonance,UMR）传感器,该传感器由单边磁体、抗涡流板、射频线圈、阻抗匹配和调谐电路构成．在距离传感器表面上方75 mm处的50 mm×50 mm的平面内,建立了71.1 mT（共振频率为3.027 MHz）的静态磁场．本文详细介绍了该传感器的设计思路和实现方法,并开展了初步的木材水分无损测量实验．对圆柱形树桩的径向水分分布进行了一维扫描测量,观察了水分由树皮向树芯逐步深入过程中横向弛豫时间（T₂）的变化规律,还使用UMR仪对木材干燥过程中水分的挥发进行了测量.实验结果表明,随着干燥的加剧,被测样品T₂谱的长T₂波峰明显左移、积分面积渐减,而且积分面积与木材样品含水率呈正比．本文为木材研究提供了一种便携的NMR测量设备设计方案,且可以实现野外活体树木的无损测量．     

多量子比特核磁共振体系的实验操控技术

随着量子信息与量子计算科学的发展,量子信息处理器被广泛地用于量子计算、量子模拟、量子度量等方面的研究.为了能在实验上实现这些日益复杂的方案,将量子计算机的潜能转化成现实,需要不断提高可操控的量子体系比特位数,实现更复杂的量子操控.核磁共振自旋体系作为一个优秀的量子实验测试平台,提供了丰富而又精密的量子操控手段.近几年来在此平台上进行了不少的多量子比特实验,发展并积累了一系列的多量子比特实验技术.本文首先阐述了核磁共振体系多量子比特实验中的实验困难,然后结合7量子比特标记赝纯态制备以及其他有关实验,对多比特实验过程中应用到的实验技术进行介绍.最后对核磁共振体系多量子比特实验技术方向的进一步研究进行了总结和展望.     

基于Eclipse图形建模框架的图形化脉冲序列设计软件的实现

采用Eclipse图形建模框架（Graphical Modeling Framework,GMF）技术构建了一个图形化磁共振脉冲序列设计软件．软件具备所见即所得的特点,用户使用拖放方式所画出的脉冲序列与教科书和参考文献上的脉冲序列几乎一样．软件支持核磁共振（Nuclear Magnetic Resonance,NMR）波谱和磁共振成像（Magnetic Resonance Imaging,MRI）的脉冲序列设计,同时提供实验参数管理模块,实现脉冲序列基础上的NMR实验设计和执行预览．得益于GMF完善的模型-视图-控制器模式和强大的代码生成能力,软件开发周期大幅度缩短、扩展能力大幅度提高．     

微波诱导光学核极化进展

微波诱导光学核极化（Microwave-Induced Optical Nuclear Polarization,MIONP）技术利用光激发三重态样品来极化电子,再用微波将处于非热平衡态的电子极化转移到待检测原子核,将原子核的检测灵敏度提高几个量级甚至更多．这种灵敏度极化增强方法可以用来进行蛋白质结构和动力学检测、光化学和光物理进程的基础研究、量子计算和低场核磁共振（Low-field Nuclear Magnetic Resonance,Low-field NMR）与磁共振成像（Magnetic Resonance Imaging,MRI）应用研究．该文简要分析了MIONP的物理原理及其在核极化增强中的优势,结合实验条件综述了一些重要的成果．最后,对微波诱导光学核极化的前景作了展望．     

葡萄糖乙酸钠不同基质微生物燃料电池电化学性能对比研究

本文通过接种生活污水处理厂的好氧污泥和厌氧污泥,撘建两个双室微生物燃料电池(MFC,Microbial fuel cell),分别以葡萄糖、乙酸钠作为基质,在0.0335 mol•L^-1基质浓度下研究不同基质微生物燃料电池的产电性能. 研究表明：葡萄糖体系的阳极半电池阻抗为222 Ω,乙酸钠体系为213.67 Ω,说明两种不同有机基质对电池内阻无明显影响. 葡萄糖、乙酸钠体系的交换电流密度i⁰分别为3.463 mA•m^-2、 5.987mA•m^-2;COD去除率分别为50.6%、55.8%;库仑效率分别为42.1%、46.2%. 葡萄糖为基质时最大输出功率密度为394.2 mW•m^-2,相应的最大电流密度为1800mA•m^-2;乙酸钠为基质时最大输出功率密度为311.9mW•m^-2,相应的最大电流密度为1527.5mA•m^-2. 葡萄糖代谢过程复杂并不单一,且代谢不彻底,乙酸钠分子简单更容易代谢,因此乙酸钠的库伦效率及COD去除率均高于葡萄糖,由以上数据可以得出葡萄糖为基质的燃料电池产电性能较好.