群集建筑中大跨裙摆屋盖风荷载特性的数值模拟研究

以苏州太平金融大厦为工程背景,针对其大跨裙摆屋盖的风荷载作用,首先采用RNG k-ε模型模拟分析了其平均风压分布规律,以及风向变化对屋盖表面风荷载体型系数的影响;其次,引入干扰因子IF,探讨了周边建筑对大跨裙摆屋盖风荷载的气动干扰作用。结果表明:0°风向下,走廊上方屋盖两侧区域出现“上吸下顶”的叠加作用;90°风向下屋盖北侧飘带末端区域受到狭道风效应出现正压集中现象;风向变化对大跨裙摆屋盖的风荷载体型系数分布影响较大;且周围建筑物对大跨裙摆屋盖的气动干扰效应明显,主要表现为风压“遮挡效应”,而局部区域表现为风压“放大效应”。     

面向装配节点平衡的产品生产物流协调优化研究

在由多个并行零件生产线和装配线组成的产品生产物流中, 各生产线的瓶颈工序制约了装配节点及其整个生产物流的平衡. 为此, 基于约束理论和JIT(Just In Time)思想, 提出主、次瓶颈的概念及其判别方法和主瓶颈拉动次瓶颈、瓶颈前后拉动生产与平行顺序移动生产相结合的生产策略, 研究了基于负荷率的瓶颈工序负荷控制方法和主瓶颈触发次瓶颈拉式生产的时间控制方法, 使瓶颈工序利用率最大化, 各个零件到达装配节点的同步性得到改善. 算例的SIMIO仿真结果表明, 装配节点的在制品存量大幅度减少, 利用率提高.     

ZnS Nanospheres for Optical Modulator in an Erbium-Doped Fiber Laser

Zinc sulfide (ZnS), which belongs to transition metal monochalcogenides, is a semiconductor material with wide direct band gap. It can potentially show some special applications (such as luminescence, phosphor, sensors, infrared window materials, photocatalysis) by changing the morphology, size, and crystal structure of semiconductor materials. However, ZnS nanospheres have not been studied as optical modulators until now. Herein, ZnS nanospheres are synthesized by the hydrothermal method and are used to realize optical modulators in an Er-doped fiber laser. The evanescent field effect is utilized to incorporate the ZnS nanospheres on a tapered fiber. Furthermore, with the increase in pump power, the modulation interval gradually decreases to a minimum of 34.36 ns corresponding to the modulation frequency of 29.1 MHz, which is the highest modulation frequency to our knowledge in a ring cavity all-fiber laser. These results demonstrate ZnS nanospheres together with the interaction of dispersion and nonlinearity in optical fibers can modulate the proposed lasers. This not only provides a new method for controlling the power and frequency of all optical modulators, but also marks an important step for ZnS materials in optics research and device applications.     

TADF激基复合物主体材料提升溶液法制备蓝色荧光有机发光二极管的效率

为了提升溶液法制备的蓝色荧光有机发光二极管(OLEDs)的效率,采用了基于热激活延迟发光(TADF)的激基复合物作为主体材料。TADF激基复合物主体可以利用反向系间窜跃上转换形成单线态激子并将能量传递到客体,从而可以同时利用发光层中的三线态激子和单线态激子,以提升蓝色荧光器件的效率。选择蓝色荧光材料1-4-Di-[4-(N,N-diphenyl)amino]styryl-benzene(DSA-ph)作为客体发光材料,4,4′,4″-T-ris(carbazol-9-yl)triphenylamine(TCTA)掺杂1,3,5-Tri(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl)(TPBi)作为热激活延迟荧光激基复合物主体,通过溶液法制备了蓝色荧光OLEDs。通过测试TCTA,TPBi以及TCTA掺杂TPBi的光致发光光谱发现,与TCTA和TPBi相比,TCTA掺杂TPBi的光致发光谱(PL)发生了明显的红移(峰值波长变为437 nm),而且光谱变宽,证明了TCTA∶TPBi激基复合物的形成。通过对于DSA-ph掺杂激基复合物主体的薄膜与DSA-ph掺杂poly(methyl methacrylate)(PMMA)的薄膜进行PL测试发现,两者发光峰相同,都是来自DSA-ph的发光,说明激基复合物主体将能量传递到了DSA-ph;DSA-ph的吸收光谱与激基复合物主体的PL光谱存在很大重叠,说明激基复合物主体与DSA-ph的能量传递非常有效;通过对激基复合物主体掺杂不同浓度客体的薄膜进行瞬态PL衰减测试发现,与纯DSA-ph的寿命相比,DSA-ph掺杂激基复合物主体之后其寿命会延长,纯DSA-ph的寿命只有1.19 ns,DSA-ph掺杂激基复合物主体的荧光衰减曲线与激基复合物主体的荧光衰减曲线相似,这进一步证明了激基复合物主体将能量传递到了DSA-ph。研究了主体引入以及DSA-ph掺杂浓度对器件性能的影响。对于器件的亮度、电流密度、电压、电流效率、电致发光光谱等参数进行了测试,与不采用激基复合物主体的器件相比,采用激基复合物主体的器件性能明显改善,在DSA-ph掺杂浓度为10%时,器件亮度从2133.6 cd·m^-2提升到了3597.6 cd·m^-2,器件效率从1.44 cd·A-1提升到了3.15 cd·A-1,发光峰只有来自DSA-ph的发光。采用TADF激基复合物主体的方法有潜力实现溶液法制备的高效蓝色荧光OLEDs。     

阴离子-π复合物(I-·C6F6)的成键分析

最近Anst?ter, et al. 发表了对阴离子-π复合物(I^-·C₆F₆)的第一个定量谱学测量[J. Am. Chem. Soc. 141, 6132 (2019)],认为成键作用中相关作用占41%,静电作用占23%,得出相关作用占主导的结论. 本研究表明,该文献的“静电作用”中混入了Pauli排斥作用,后者在数值上抵消了前者的作用. 在复合物I^-·C₆F₆中,发现静电作用是相关作用的两倍多,因而阴离子-π复合物中仍应是静电作用占主导.     

非PLL相位平均型参考线原型验证

射频相位参考线是粒子加速器的重要组成部分之一,为射频低电平控制系统(LLRF)、束流诊断系统、定时系统等提供稳定的相位锁定参考信号。为减少远距离传输过程中由环境温度变化导致的射频传输线中的射频相位漂移,多个加速器装置中已经采用射频相位参考线提供射频相位参考,这些相位参考的实现方案主要是基于恒温控制和基于光纤锁相。与这些方案相比,采用相位平均方法不仅可以保持长距离节点之间的相位稳定,而且更易于现场安装与维护。现有的带有锁相环(PLL)的终端短路方式实现相位平均参考线的方案仍有一些节点数量限制等方面的不足,本文对相位平均参考线结构进行了去除PLL的简化设计并进行了验证,以期增加更多的相位分配节点以及降低对射频器件参数的要求。对非PLL的单端输入终端短路相位平均方案与两端输入各节点间互为参考的相位平均方案分别进行了实验测试,结果表明两者的相位RMS精度可以达到0.1°~0.3°。并对不同的相位平均实现方案中相位不稳定的产生原因进行了分析,结果表明,除环境温度外,同轴线缆材质、合成相位与幅度的不平衡合成等也是重要影响因素。     

CiADS束流负载效应前馈补偿的仿真评估

在高功率超导质子直线加速器中,束流负载效应是影响超导腔幅相稳定性的一个重要因素。本工作基于谐振腔建场模型,开发了超导腔系统束流负载效应的时域仿真程序,分析了束流负载效应对超导腔幅相稳定性的影响,并在C-ADS注入器II上通过相关实验测量对仿真结果进行了验证。利用该程序,评估了CiADS超导直线加速器脉冲束流的脉冲长度,以及前馈补偿的时序抖动和束流纹波等因素对腔中电磁场幅相稳定度的影响。仿真结果表明:在当前CiADS直线加速器设计参数下,为满足超导腔中电磁场0.1%与在高功率超导质子直线加速器中,束流负载效应是影响超导腔幅相稳定性的一个重要因素。本工作基于谐振腔建场模型,开发了超导腔系统束流负载效应的时域仿真程序,分析了束流负载效应对超导腔幅相稳定性的影响,并在C-ADS注入器II上通过相关实验测量对仿真结果进行了验证。利用该程序,评估了CiADS超导直线加速器脉冲束流的脉冲长度,以及前馈补偿的时序抖动和束流纹波等因素对腔中电磁场幅相稳定度的影响。仿真结果表明:在当前CiADS直线加速器设计参数下,为满足超导腔中电磁场0.1%与$0.1^{\circ}$的幅相稳定度指标,前馈时序抖动的偏差不能超过0.79 μs,束流流强的直流偏差不能超过0.9%,并且给出了束流纹波的最大抖动幅值与纹波频率之间的关系。这些结果将为CiADS超导直线加速器相关子系统技术指标的确定提供依据。     

An improved evaluation of the neutron background in the PandaX-Ⅱ experiment

In dark matter direct detection experiments,neutron is a serious source of background,which can mimic the dark matter-nucleus scattering signals.In this paper,we present an improved evaluation of the neutron background in the PandaX-II dark matter experiment by a novel approach.Instead of fully relying on the Monte Carlo simulation,the overall neutron background is determined from the neutron-induced high energy signals in the data.In addition,the probability of producing a dark-matter-like background per neutron is evaluated with a complete Monte Carlo generator,where the correlated emission of neutron(s)andγ(s)in the(α,n)reactions and spontaneous fissions is taken into consideration.With this method,the neutron backgrounds in the Run 9(26-ton-day)and Run 10(28-ton-day)data sets of PandaX-II are estimated to be(0.66±0.24)and(0.47±0.25)events,respectively.     

Multi-guasiparticle excitations of ~(91)Ru

The level structure in neutron-deficient nucleus 91Ru was investigated via the 58Ni(36Ar,2 plnγ)Ru reaction at a beam energy of 111 MeV.Charged particles,neutrons,and y-rays were emitted in this reaction and detected by the DIAMANT CsI ball,Neutron Wall,and the EXOGAM Ge clover array,respectively.In addition to the previously reported levels in 91Ru,new low-to-medium spin states were observed.Angular correlation and linear polarization measurements were performed to unambiguously determine spins and parities of the excited states in 91 Ru.The low-spin states of 91 Ru exhibit a scheme of multi-quasiparticle excitations,which is very similar to that of the neighboring N=47 isotone.These excitations have been interpreted in terms of the shell model.The calculations performed in the configuration space(p3/2,f5/2,p1/2,g9/2)reproduce the experimental excitation energies reasonably well,supporting the interpretation of the newly assigned positive-parity states in terms of the three quasiparticle configurationsπ(g9/2)^-2v(g9/2^-1 and v(g9/2)^-3.     

Transferring entangled states of photonic cat-state qubits in circuit QED

We propose a method for transferring quantum entangled states of two photonic cat-state qubits(cqubits)from two microwave cavities to the other two microwave cavities.This proposal is realized by using four microwave cavities coupled to a superconducting flux qutrit.Because of using four cavities with different frequencies,the inter-cavity crosstalk is significantly reduced.Since only one coupler qutrit is used,the circuit resource is minimized.The entanglement transfer is completed with a singlestep operation only,thus this proposal is quite simple.The third energy level of the coupler qutrit is not populated during the state transfer,therefore decoherence from the higher energy level is greatly suppressed.Our numerical simulations show that high-fidelity transfer of two-cqubit entangled states from two transmission line resonators to the other two transmission line resonators is feasible with current circuit QED technology.This proposal is universal and can be applied to accomplish the same task in a wide range of physical systems,such as four microwave or optical cavities,which are coupled to a natural or artificial three-level atom.