Effects of Microstructural Defects on Ion-Irradiated Type-316 Stainless Steel

Microstructure defects play a very important role in the swelling of irradiated stainless steel. This work is a parametric study of the effects of microstructural defects on the swelling of ion-irradiated steel. For simplicity, vacancy loop effects were neglected. Cold working was found to play a complicated role in the swelling behavior. On one hand, it increase the bias to interstitial absorption due to the increase in dislocation density. On the other hand, it decreases the total flux of point defects to voids by the decrease of the point defect concentrations. Grain size has also a strong effect on swelling. It was found that large gain sizes produces higher swelling and vise versa, i.e. the larger the surface of grain boundaries the less the irradiation-produced swelling. Similar effects were found for precipitates.     

Transverse Zeeman background correction method for air mercury measurement

By utilizing a natural mercury lamp, the transverse Zeeman background correction method, which is used for trace mercury measurement in air, is studied. In this paper, a natural mercury lamp is used as a light source, and is placed in a 1.78-T magnetic field. The lamp emits two linearly polarized light beams σ± and π of 253.65-nm resonance line, which are used as bias light and absorbing light, respectively. A polarization modulation system is used to allow σ± and π light beams to pass through alternately with a certain frequency. A multipath optical cell with 12-m optical path is used to increase optical distance. Based on the system described above, the influence caused by UV absorbing gases, such as NO2, SO2, acetone, benzene, and O3, is analyzed. The results show that it may reduce the detection limit when the concentrations of these gases exceed 83.4 ppm, 20.3 ppm, 142.3 ppm, 0.85 ppm, and 0.55 ppm, respectively. The detection limit of the system is calculated and can achieve up to 1.44 ng/m3 in 10 minutes. Measurements on mercury sample gas and air are carded out, and the measured data are compared with the data of RA-915 mercury analyzer （Russia）. The result shows that the correlation coefficient reaches up to 0.967. The experimental results indicate that the transverse Zeeman background correction method can be used to quantify trace mercury in air with high-precision.     

人造复眼成像系统研究的新进展

人造复眼成像系统具有体积小、功耗低、视角范围广等优点，是一种应用前景非常广阔的光成像系统。综述了人造复眼成像系统的研究背景及最新的研究进展，其中包宿基于不同仿生设计理念的各种新型人造复眼结构以及能够实现诸如彩色成像、指纹识别、全视角成像等新功能的实验系统；展望了人造复眼成像系统今后的研究方向。     

润滑油对基于制冷循环的喷雾冷却系统性能的影响

针对高功率固体激光器的散热需求,设计了一种基于制冷循环的喷雾冷却系统,并对其换热性能进行研究。由于制冷系统的压缩机需要润滑,冷却液中不可避免地会混有润滑油。润滑油会对冷却液的粘度、表面张力产生影响,并可能产生油膜,从而对冷却液的换热过程产生强化或抑制。因此,通过实验研究,分析了润滑油对喷雾冷却换热性能的影响。实验结果表明,冷却液中存在润滑油,会增大冷却液流经喷嘴过程中的阻力,减小流量,但根据本系统的应用情况,可以忽略;在低热流密度时,含有一定量的润滑油更有利于热源表面温度的均匀分布,高热流密度时,2%(质量分数)的含油量对温度分布不均的影响可以忽略;润滑油的存在可以提高临界热流密度,使得系统的散热能力得到提高,更有利于其在高功率固体激光器散热领域的应用。     

Production and constraints for a massive dark photon at electron-positron colliders

Dark sector may couple to the Standard Model via one or more mediator particles.We discuss two types of mediators:the dark photon A’and the dark scalar mediatorΦ.The total cross-sections and various differential distributions of the processes e+e-→qqA’and e+e→qqφ(q=u,d,c,s and b quarks)are discussed.We focus on the study of the invisible due to the cleaner background at future e+e-colliders.It is found that the kinematic distributions of the two-jet system could be used to identify(or exclude)the dark photon and the dark scalar mediator,as well as to distinguish between them.We further study the possibility of a search for dark photons at a future CEPC experiment with s1/2=91.2 GeV and 240 GeV.With CEPC running at s1/2=91.2 GeV,it would be possible to perform a decisive measurement of the dark photon(20 GeV相似文献   

Zero-temperature magnetic transition in an easy-axis Kondo lattice model

We address the quantum transition of a spin-1/2 antiferromagnetic Kondo lattice model with an easy-axis anisotropy using the extended dynamical mean field theory. We derive results in real frequency by using the bosonic numerical renormalization group (BNRG) method and compare them with quantum Monte Carlo results in Matsubara frequency. The BNRG results show a logarithmic divergence in the critical local spin susceptibility, signaling a destruction of Kondo screening. The T=0 transition is consistent with being second order. The BNRG results also display some subtle features; we identify their origin and suggest means for further microscopic studies.     

分辨率对大气中痕量污染气体的DOAS测量性能影响研究

在差分吸收光谱(DOAS)测量过程中,光谱分辨率的选择直接决定了污染气体浓度的测量准确度.主要研究了光谱分辨率对污染气体被榆测到的特征吸收结构形状的影响,以及差分吸收截面随分辨率的变化趋势,从而确定了光谱分辨率对污染气体最低可检测浓度的影响,通过研究分辨率与光强的关系,确定了分辨率与信噪比(S/N)的函数关系式,得出了DOAS测量NO2,O3,和SO2的最佳信噪比范围,对多种污染物标准气体进行了同时监测,计算出标准气体在不同光谱分辨率下的测量误差,确定了对NO2,O3和SO2监测的最适用的分辨率范围.在此分辨率范围既能够实现对痕量气体的准确定性定量测量,又能达到测量所需要的高灵敏度,强选择性和适用的时间分辨率.通过在北京丰台区的实际监测得到了与点式仪器测量结果很好的一致性.     

Commutativity theorems for s-unital rings with constraints on commutators

Let R be an associative s-unital ring with the polynomial identity \( y^{s}[x^{n},y]=\pm [x,y^{m}]x^t\) or \( y^{s}[x^{n},y]=\pm x^{t}[x,y^{m}]\) , where m, n, s and t are given non-negative integers such that m > 0 or n > 0 and m ≠ n if s = m ? 1 and t = n ? 1. Using similar methods as in our recent papers [1] and [2], we prove here the commutativity of R for various values of m, n, s and t, under appropriate constraints on torsion of commutators.     

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.