Power coupler kick of the TRIUMF ICM capture cavities

The TRIUMF Injector CryoModule (ICM) adapted two superconducting single cavities as the capture section for the low injecting energy of 100 keV electrons. Coupler kick induced beam deflection and projected emittance growth are one of the prime concerns of the beam stability, especially at low energies. In low energy applications, the electron velocity changes rapidly inside the cavity, which makes the numerical analysis much more complicated. The commonly used theoretical formulas of the direct integral or the Panofsky- Wenzel theorem is not suitable for the kick calculation of β <1 electrons. Despite that, the above mentioned kick calculation method doesn't consider injecting electron energy, the beam offset due to the coupler kick may not be negligible because of the low injection energy even if the kick is optimized. Thus the beam dynamics code TRACK is used here for the simulation of the power coupler kick perturbation. The coupler kick can be compensated for by a judicious choice of the coupler position in successive cavities from upstream to downstream. The simulation shows that because of the adiabatic damping by the following superconducting 9-cell cavity, even for the worst orbit distortion case after two capture cavities, the kick is still acceptable at the exit of the ICM after reaching 10 MeV. This paper presents the analysis of the transverse kick and the projected emittance growth induced by the coupler for β <1 electrons. The simulated results of the TRIUMF ICM capture cavities are described and presented.     

用于单载波频域均衡水声通信的可分近似稀疏信道估计

针对单载波频域均衡水声通信中信道估计易受噪声干扰的问题,提出了一种低复杂度的信道估计方法。考虑水声信道的时域稀疏特性,导出频域输入、输出信号与信道冲激响应的关系式,并引入稀疏正则项,构造稀疏信道估计的目标函数。然后利用可分近似对目标函数进行迭代优化,再经过稀疏化与去偏处理,得到信道传递函数的最终估计。最后,利用数值仿真和海试数据对所提出方法的性能和运算效率进行评估。较之传统信道估计方法,所提出的方法在估计精度和计算复杂度方面具有一定的优势。     

New Generalizations of Migdal-Kadanoff Bond-Moving Recursion Procedures and Their Applications

Considering in symmetrical half-length bond operations,we present in this paper two types of newlydeveloped generalizations of the remarkable Migdal-Kadanoff bond-moving renormalization group transformation recursion procedures.The predominance in application of these generalized procedures are illustrated by making use of them to study the critical behavior of the spin-continuous Gaussian model constructed on the typical translational invariant lattices and fractals respectively.Results such as the correlation length critical exponents obtained by these means are found to be in good conformity with the classical results from other previous studies.     

Oscillatory Activities in Regulatory Biological Networks and Hopf Bifurcation

Exploiting the nonlinear dynamics in the negative feedback loop, we propose a statistical signal-response model to describe the different oscillatory behaviour in a biological network motif. By choosing the delay as a bifurcation parameter, we discuss the existence of Hopf bifurcation and the stability of the periodic solutions of model equations with the centre manifold theorem and the normal form theory. It is shown that a periodic solution is born in a Hopf bifurcation beyond a critical time delay, and thus the bifurcation phenomenon may be important to elucidate the mechanism of oscillatory activities in regulatory biological networks.     

无创血液成分检测中基于VIP分析的波长筛选

自变量筛选是定量光谱分析领域的研究热点,简便且高效的自变量筛选方法不但可以降低分析计算量,提高分析精度,同时还可以减轻对仪器光谱分辨能力的依赖,降低分析成本。波长筛选也是光谱法无创血液成分检测研究的重要环节。动态光谱理论为血液无创检测提供了极佳的思路,但长期局限于使用宽带光源和高分辨率的光谱仪器,分析中需要大量波长限制了动态光谱法的进一步发展。为了去除冗余信息,使检测走向低成本化和集成化,提出了基于变量投影重要性(variable importance in projection,VIP)分析的波长筛选方法。通过分析PLS模型中各维自变量对因变量的解释能力,从而剔除重要性较低的变量保留解释能力强的波长。以232例受试者的临床实验数据为基础,以血红蛋白含量为分析对象,经投影重要性分析后将波长数由586降至64,波长筛选后血红蛋白预测模型的测试集平均相对误差(MREP)为1.82%,使用了极少的波长便可得到满意的结果;结合Bootstrap方法对模型进行显著性检验后验证了波长变量的解释能力。首次指出了使用动态光谱法检测血红蛋白的敏感波长带。基于投影重要性分析的波长筛选迈出了动态光谱走向实用的重要一步,为实现低成本在线分析打下了基础,同时也为其他领域的光谱分析提供了重要的参考和新的思路。     

GC-MS测定血清胆固醇及其标志物前处理条件正交试验优化研究

采用正交试验优化GC-MS测定血清胆固醇及其标志物的样品前处理条件,并对最优试验方案进行方法学评价。采用L₁₆(211)正交设计对影响GC-MS测定血清胆固醇及其标志物前处理的3个关键步骤共7个因素——皂化(KOH-乙醇浓度、皂化温度和时间)、萃取(正己烷用量)和衍生化(衍生化温度、时间和用量)进行优化。得到最优前处理条件组合如下：KOH-乙醇溶液浓度为1 mol·L-1;皂化温度70 ℃;皂化时间60 min;萃取剂用量2 mL;衍生化温度70 ℃;衍生化时间60 min;衍生化试剂用量100 μL。所建方法准确性和精密性良好,方法学评价指标优于文献报道。     

Melting kinetics of bulk SiC using molecular dynamics simulation

The melting kinetics of bulk SiC is studied by using classical molecular dynamics simulation.The mean square displacement,diffusion coefficient,Lindemann index and non-Gaussian parameter are used to analyze the melt nucleation and macrokinetics in the melting process.Melting occurs when the superheated crystal spontaneously generates many Lindemann particles in which they coalesce together to form melt nucleation inside the crystal.The melting process is similar to the solidification process,but also experiences three processes such as nucleation,growth and relaxation.The melting process can be divided into premelting,accelerated melting and relaxation stages.Using the sectional method can properly reflect the kinetic characteristics of the melting process.     

Energy dependence for directed and elliptic flow in in termediate-energy heavy ion collisions

Differential and integrated directed flow and elliptic flow of light charged particles (z ≤ 2) are studied systematically for semi-central (b = 5 fm) ¹⁹⁷Au+¹⁹⁷Au collisions at incident energies from 25 to 250 MeV/nucleon by the isospin-dependent quantum molecular dynamics model. The changes of directed and elliptic flow with incident energy reflect the dynamic competition between mean field and nucleon-nucleon collisions and also between collective rotation and expansion.     

原子吸收光谱法测定污染土壤中铅和镉的形态

土壤重金属污染及其环境生态效应已成为人们关心的热点问题,土壤中重金属的赋存污染的研究是探讨重金属迁移规律和生物可利用性的前提.以江苏省南部某重金属污染稻田土壤为研究对象,采用BCR逐级提取—石墨炉原子吸收分光光度法对土壤中典型重金属铅、镉元素的形态分布特征进行了分析测定.石墨炉原子吸收分光光度法测定溶液中的铅、镉的校准曲线分别为A=0.036C(mg·L-1)+0.009、A=0.400C(mg·L-1)+0.020,相关系数(r)分别为0.9960和0.9890.污染土壤铅、镉元素含量分别为603.3mg·kg-1和21.8mg·kg-1;土壤中铅的赋存形态质量分数具有可还原态＞＞酸溶态＞残渣态＞可氧化态的分布规律,而镉则呈现酸溶态≌可还原态＞＞残渣态＞可氧化态的分布特征,说明土壤条件下的不同重金属元素能够呈现不同化学作用过程和机制,因此表现出不同程度的生物可利用性特征.     

Variational calculations on the hydrogen molecular ion

We present high-precision non-relativistic variational calculations of bound vibrational—rotational state energies for the H⁺ ₂ and D⁺ ₂ molecular ions in each of the lowest electronic states of Σ _g , Σ _u , and Π _u symmetry. The calculations are carried out including coupling between Σ and Π states but without using the Born—Oppenheimer or any adiabatic approximation. Convergence studies are presented which indicate that the resulting energies for low-lying levels are accurate to about 10^?13. Our procedure accounts naturally for the lambda-doubling of the Π _u state.