波纹形曲拱的几何非线性有限元解

波纹形曲拱具有复杂的几何形状,它在外载作用下的位移响应为非线性,用几何非线性有限元求解该类问题是适宜的。为此,本文以弹性范围内,按应变与转动的平方同量级的假定,推导了平面梁单元几何非线性刚度矩阵,并编制了相应的平面梁系直接迭代法计算程序。应用该程序,本文对波纹形曲拱作了位移和应力计算,结果与试验数据作了比较,两者是接近的。     

桤木锯末对废水中As3+的吸附特性

研究了桤木锯末对水中As3+的吸附特性,并探讨了pH、温度、Hg2+对水中As3+吸附率的影响.结果表明,实验条件下锯末对As3+的最佳吸附pH为4.0--6.0,最佳吸附温度为20℃;当Hg2+与As3+同时存在时,增大Hg2+浓度有利于As3+的吸附;桤木锯末对水中As3+的吸附符合拟二级动力学方程.本研究表明,利...     

非线性啁啾频率对势阱产生正负电子对的增强

用计算量子场论方法研究了非线性啁啾频率对势阱中正负电子对产生的增强效应。研究了由静态势阱和动态势阱组成的组合势阱中产生的正负电子对的密度、产额和能谱等性质随着啁啾参数的变化,分析了组合势阱的频谱和瞬时束缚态。发现非线性啁啾效应对低频区域比较敏感,与固定频率情况相比可以使粒子数增加2～3倍。与组合势阱相比,非线性啁啾效应对单个振荡势阱更敏感。在低频下单个振荡的势阱中正负电子对产额可提高多个数量级。这是因为在低频下单个振荡的势阱中,主要通过量子隧穿过程产生的正负电子对数目非常低。非线性啁啾效应增加了高频场成分,提高了多光子过程和动力学辅助机制。由于高频抑制作用,所以非线性啁啾效应对高频区域粒子的增量不大,甚至会抑制正负电子对的产生。     

Enhanced Correlation of Electron-Positron Pair in Two and Three Dimensions

Early time electron-positron correlation in vacuum pair-production in an external field is investigated. The entangled electron and positron wave functions are obtained analytically in the configuration and momentum spaces. It is shown that, relative to that of the one-dimensional theory, two- and three-dimensional calculations yield enhanced spatial correlation and broadened momentum spectra. In fact, at early times the electron and positron almost coincide spatially. The correlation also depends on the direction of the applied field. For the spatial correlation, the transverse correlation is stronger than the longitudinal correlation.     

Instability of Longitudinal Wave in Magnetized Strongly Coupled Dusty Plasma

Instability of longitudinal wave in magnetized strongly coupled dusty plasmas is investigated. The dust chargigrelaxation is taken into account. It is found that there exists threshold of interdust distance for the instability of wave, which is determined significantly by the dust charging relaxation, the coupling parameter of high correlation of dust as well the strength of magnetic field.     

基于透明质酸的缺氧响应型胶束的制备及性能研究

以透明质酸（HA）及硝基咪唑（NI）衍生物为原料,通过酰胺反应合成了一种两亲性接枝聚合物（HA-NI）.该聚合物具有缺氧响应性和肿瘤靶向性.利用傅里叶红外光谱（FT-IR）和核磁共振（NMR）对接枝聚合物的结构进行了表征,同时基于¹H NMR计算出接枝聚合物中NI的取代度.HA-NI在水中自组装形成胶束,利用动态光散射仪（DLS）表征胶束大小并对胶束的稳定性进行了研究,利用原子力显微镜（AFM）和透射电镜（TEM）观察胶束形貌.载药胶束的载药率（DL）和包封率（EE）通过紫外-可见吸收光谱（UV）测试并计算得到.胶束的缺氧响应性利用DLS、AFM、TEM、UV等探究.实验证明,该聚合物胶束具有缺氧响应性并对药物表现出良好的控制释放能力,在常氧环境下,胶束稳定存在;而在缺氧环境下,胶束散开,药物快速且完全地释放.     

大气环境降水监测的质量控制方法

根据《环境监测质量管理规定》、《江苏省环境监测质量管理实施细则》及环境监测技术规范的要求,探讨了降水监测采样、样品保存技术、实验室分析的质量控制方法。采用不同采样方法、不同采样器同时采集15场降水,其降雨量、电导率、pH值的比对监测结果合格率均大于90%。经试验,降水各组分有效保存时间不同,其中NO_3~-,NH_4~+为3 d;F~-,Cl~-,SO_4~(2-)为14d;K~+,Na~+,Ca~(2+),Mg~(2+)为30 d。选择2家实验室对降水样品、空白样品、标准样品同时测试,结果显示,空白测定结果均低于方法检出限,标准曲线相关性系数r≥0.999 0,测定结果的相对标准偏差为1.4%~5.9%(n=6),加标回收率为89.8%~106%,标准样品的分析结果均合格。该方法能保证降水监测结果准确、可靠,满足HJ/T 165-2004《酸沉降监测技术规范》的要求。     

Levitation and Oscillation of Dust Grains in Plasma Sheath with Wake Potential

We investigate the equilibrium and levitation of dust grains in a plasma sheath with various forces,in particular the wake potential force.The vertical oscillation frequency of dust chains is also obtained by including the wake potential term.It is found that the wake potential has a significant role for the levitation and oscillation of dust grains.     

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.     

毛细管电泳柱上络合分离、间接紫外检测重金属离子

采用弱络合剂乙醇酸,柱上络合,间接紫外检测毛细管区带电泳(CZE)技术对重金属离子Ba2+、Cr3+、Cd2+、Pb2+及可能存在的干扰离子进行了分离研究。通过对背景电解质种类和浓度、缓冲液pH、有机添加剂等的优化,确定了最佳分离体系为含12 mmol/L络合剂乙醇酸的10 mmol/L吡啶溶液作为背景电解质(pH 4.0)。在电压15 kV,压差进样68.95 kPa.s,260 nm间接紫外检测条件下,采用50 cm(45.5 cm)×50μm(I.D.)石英毛细管,重复性实验(n=9):迁移时间RSD≤1.37%,峰高RSD≤1.70%,峰面积RSD≤3.55%;Pb2+、Ba2+和Cd3+的检出限(S/N=3)为0.2 mg/L,Cr3+的检出限为0.08 mg/L;在检出限至10 mg/L范围内,各离子的浓度与峰面积线性相关系数好于0.998。该方法并应用于实际样品的分析。