Effect of thickness variations of lithium niobate on insulator waveguide on the frequency spectrum of spontaneous parametric down-conversion

We study the effect of waveguide thickness variations on the frequency spectrum of spontaneous parametric down-conversion in the periodically-poled lithium niobate on insulator (LNOI) waveguide. We analyze several variation models and our simulation results show that thickness variations in several nanometers can induce distinct effects on the central peak of the spectrum, such as narrowing, broadening, and splitting. We also prove that the effects of positive and negative variations can be canceled and thus lead to a variation-robust feature and an ultra-broad bandwidth. Our study may promote the development of on-chip photon sources in the LNOI platform, as well as opens up a way to engineer photon frequency state.     

电感耦合等离子体质谱(ICP-MS)法同时测定荞麦秸秆中的8种重金属元素

基于硝酸-盐酸-氢氟酸消解体系,建立了马弗炉-微波消解-电感耦合离子体质谱(ICP-MS)法同时测定荞麦秸秆中的Cr、Cu、Ag、Mn、Fe、As、Ni、Pb等重金属含量测定方法。在微波消解的过程中,分别考察5种不同组合的混合酸体系及两种消解方法对荞麦秸秆中8种重金属测试结果的影响。实验结果表明,浓硝酸-浓盐酸-氢氟酸(6∶2∶2)混酸体系和马弗炉-微波消解样品前处理优于其他方法。在优化条件下,8种重金属加标回收率为91.2%~102%,相对标准偏差(RSD,n=5)为0.22%~4.7%,检出限为0.18~9.41μg/L。方法操作简便、快速、准确,结果可靠,能同时测定荞麦秸秆中8种重金属元素。     

利用高吸水树脂优化3个中学化学实验*

尝试利用高吸水树脂对“酸碱中和反应、碳酸钠和碳酸氢钠分别与稀盐酸反应、探究分子运动现象”这3个实验进行创新改进,充分利用了高吸水树脂特殊的结构作用,使3个实验的现象更加显著。改进实验操作简便,高效简洁,值得推广到一线化学课堂的演示实验或学生分组实验。     

符号圈拼接图的零度

令$\eta(\Gamma)$和$c(\Gamma)$是符号图$\Gamma$的零度和基本圈数. 一个符号圈拼接图是指每个块都是圈的连通符号图. 本文证明了对任意符号拼接图$\eta(\Gamma)\le c(\Gamma)+1$成立, 并且刻画了等号成立的极图, 推广了王登银等人(2022)在简单圈拼接图上的结果. 此外, 我们证明了任意的符号拼接图$\eta(\Gamma)\neq c(\Gamma)$, 给出了满足$\eta(\Gamma)=c(\Gamma)-1$的符号拼接图的一些性质并刻画处$\eta(\Gamma)=c(\Gamma)-1$的二部符号拼接图.     

STUDIES ON THE LAW OF LAMINAR HELICAL FLOW OF POWER-LAW FLUID IN ECCENTRIC ANNULI

According to the principle of fluid mechanics,the law of laminar,helical flow of power-law fluid in eccentric annuli is studied extensively in this paper.The apparent viscosity,velocities distribution of laminar helical flow of power-law fluid are discussed and calculating methods of flow rate and pressure loss are presented.The factors influencing flow are also analysed.On the basis of theoretical studies some new results of the present paper are compared with the theories of the helical flow of the power-law fluid in concentric annuli.The test verified that theoretical formulas in this article are proper and general.They can be used for calculating hydraulic parameters in drilling engineering.     

受撞击粘弹性基支弹性直梁的动力响应

本研究了半无限线性粘弹性Ｗｉｎｋｌｅｒ地基上的弹性直梁受低速运动物体撞击的动力响应分析问题，在不计撞击中应力波传播的条件下推导出了关于撞击力Ｆ（ｔ）的非线性Ｖｏｌｔｅｒｒａ分方程，得出了梁的横向位移Ｗ（ｘ，ｔ）的一般表达式，作为实例，本对两端简支弹性直梁受圆球对心横向撞击的问题进行了分析计算。     

Plasmonic sensor with variable claddings based on metallic slit arrays

We propose a plasmonic sensor with variable refractive index(RI), which exhibits high sensitivity and extraordinary optical transmission(EOT). Its variable RI is attributed to its dielectric layers and metallic slit arrays.According to simulation results, the third resonant wavelength has a wavelength sensitivity of 800 nm/RIU and an ultra-high transmittance of 0.8 by adjusting the RIs of the upper and lower dielectrics, incident light angle,and structural geometric parameters. With its unique features, the proposed structure holds considerable potential for extensive application to metal–dielectric grating sensors operating at visible and near-infrared frequencies.     

层状多硫代锑(Ⅲ)酸镉(Ⅱ)化合物(1,4-DABH2)Cd2Sb2S6的溶剂热合成与表征

利用溶剂热方法合成了层状多硫代锑髥酸镉髤化合物(1,4-DABH2)Cd2Sb2S6(1)(1,4-DAB=1,4-丁二胺),并通过红外光谱、热重分析对其进行了表征,用X-射线衍射测定了化合物的单晶结构。单晶解析表明,化合物属正交晶系,Cmca空间群,Mr=750.77,a=0.860 3(5)nm,b=0.898 7(6)nm,c=2.273(2)nm,V=1.758(2)nm3,Z=4,λ=0.071 073 nm,R=0.032,wR=0.106 7。晶体结构中含有六元环的Cd2SbS3和八元环的Cd2Sb2S4的阴离子网络层状[CdSbS3]nn-,双质子化的有机阳离子在阴离子层之间以氢键N-H…S形式连接。另外紫外-可见漫反射光谱研究表明,化合物为半导体。     

winkler地基上弹性圆薄板受刚体撞击的动力响应

本文针对工程实际中所遇到的撞击问题,在事先仅知撞击体初始速度的条件下,研究分析了半无限粘弹性Winkler地基上的弹性圆薄板受刚体撞击的动力响应问题,推导出了关于撞击力F(t)的非线性Volterra积分方程,给出了薄板位移响应W(r,θ,t)的一般表达式,并给出了相应的数值求解方法。作为实例,本文对周边固定的弹性圆薄板在圆心处受刚球撞击问题进行了分析计算,并对某些参数的影响进行了讨论。     

高龄老年男性腰椎骨密度独立相关因素的研究

目的 通过分析高龄老年（≥80岁）男性腰椎骨密度（LBMD）的独立相关因素,寻找提高高龄老年男性LBMD 的方法。方法 对1066例高龄老年男性进行LBMD测定、血液生化、骨代谢和生殖激素等指标的检测,运用多元回归分析筛选高龄老年男性LBMD 的独立相关因素。结果 高龄老年男性LBMD的独立相关因素有体重指数（β=0.018,P＜0.01）、I型胶原羧基端肽β特殊序列（β=-0.226,P＜0.01）、慢性阻塞性肺疾病（β=-0.047,P＜0.01）、雌二醇（β=0.002,P＜0.01）。结论 维持合理的体重指数和雌二醇水平,降低血清I型胶原羧基端肽β特殊序列水平,积极防治慢性阻塞性肺疾病,可能是提高高龄老年男性LBMD的重要方法。