In、Sc掺杂对SrTiO3电子结构和光学性质的影响

采用基于密度泛函理论的第一性原理平面波超软赝势计算方法, 研究了In、Sc p型掺杂对SrTiO3母体化合物稳定性、电子结构和光学性质的影响. 计算结果表明:掺杂后, SrIn0.125Ti0.875O3和SrSc0.125Ti0.875O3的稳定性降低, 体系显示p型简并半导体特征, 掺杂仅引起杂质原子近邻区域的几何结构发生变化. 同时, SrIn0.125Ti0.875O3和SrSc0.125Ti0.875O3体系的光学带隙分别展宽0.35、0.30 eV, 光学吸收边发生蓝移, 在1.25-2.00 eV的能量区间出现新的吸收峰, 该吸收峰与体系Drude型自由载流子的激发相关. 此外, SrIn0.125Ti0.875O3和SrSc0.125Ti0.875O3体系的可见光透过率有了明显的提高, 在350-625 nm波长范围透过率高于85%. 掺杂原子在费米能级处低的电子态密度限制了跃迁概率和光吸收. 大的禁带宽度、小的跃迁概率和弱的光吸收是SrIn0.125Ti0.875O3和SrSc0.125Ti0.875O3体系具有较高光学透明度的原因.     

燃料电池混合动力叉车能量控制策略研究

为了解决内燃机叉车工作效率低、对环境产生污染,电动叉车充电时间长、工作时间短的问题,在综合比较分析各种动力组合与驱动形式利弊的基础上,提出了一种燃料电池混合动力叉车结构.针对燃料电池混合动力叉车的驱动系统,分别阐述了电池SOC控制和电池电压控制的能量管理策略,并通过仿真对控制方案进行了解释和验证.仿真结果表明:在不同的操作环境和电池状态下电池电压控制更好的满足叉车驱动系统的控制要求,可以更有效地抑制直流总线电压过冲.     

First-Principles Study on Magnetic Properties of V-Doped ZnO Nanotubes

Electronic and magnetic properties of V-doped ZnO nanotubes in which one of Zn^2＋ ions is substituted by V^2＋ ions are studied by the first-principles calculations of plane wave ultra-soft pseudo-potential technology based on the spin-density function theory. The computational results reveal that spontaneous magnetization in Vdoped （9,0） ZnO nanotubes can be induced without p-type or n-type doping treatment, and the ferromagnetism is isotropic and independent of the chirality and diameter of the nanotubes. It is found that V-doped ZnO nanotubes have large magnetic moments and are ferromagnetic half-metal materials. Moreover, the ferromagnetic coupling among V atoms is generated by O 2p electron spins and V 3d electron spins localized at the exchanging interactions between magnetic transitional metal （TM） impurities. The appearance of ferromagnetism in V-doped ZnO nanotubes gives some reference to fabrication of a transparent ferromagnet which may have a great impact on industrial applications in magneto-optical devices.     

带环境污染的与年龄相关的非线性种群动力系统的最优控制

研究带环境污染的与年龄相关的非线性种群动力系统的最优控制问题,利用不动点定理得出系统非负解的存在性和唯一性,利用极大化序列及紧性证明最优控制的存在性,利用法锥方法得到控制问题的最优条件.     

高频红外碳硫仪测定区域地球化学样品中的硫

高频红外碳硫仪由于便捷高效,常应用于区域地球化学样品中硫的分析检测。本文采用高频红外碳硫仪测定低中高含量的硫,以纯铁屑、锡粒和钨粒为助熔剂,对样品称样量、助熔剂的种类、加入顺序和用量等因素进行探讨,确定了最佳分析岩石、土壤和水系沉积物中硫含量的条件,并且用国家一级标准物质验证了该方法的准确度和精密度。结果表明,当样品和助熔剂的加入顺序和质量分别为：0.05 g样品、0.5 g铁助熔剂、1.7 g钨粒时,土壤和水系沉积物中硫的测定结果最稳定,岩石标准样品额外的加入0.5 g锡改善样品流动性,提高分析准确度。该方法的相对标准偏差（RSD）小于6%（n= 12）,相对误差绝对值小于8%。此方法具有操作简单、高效、稳定性好的特点,适合于大批量区域地球化学样品中硫的检测。     

磺胺嘧啶钠探针分析生物样品中蛋白质含量的研究

在pH 7.4的Tris-HCl缓冲溶液中,荧光猝灭光谱和三维荧光光谱显示磺胺嘧啶钠(SDS)可与人血清白蛋白(HSA)相互作用,使人血清白蛋白疏水微环境极性以及构象发生变化。考察了Δλ值、反应介质、离子强度等因素对该体系同步荧光光谱特征及强度的影响。在选定的最佳实验条件下,体系的同步荧光强度(ISF)与人血清白蛋白在1.38～276μg/mL的浓度范围内呈现良好的线性关系,线性相关系数为0.9992,从而建立了以磺胺嘧啶钠为分子探针,用固定波长同步荧光光谱分析测定蛋白质的新方法,检测限可达0.48μg/mL。用此方法对生物样品人血清、唾液和尿液中蛋白质含量进行了测定并进行加标回收实验,回收率在95.7%～103.7%之间。本文还用经典的考马斯亮蓝法对样品进行了测定,所得结果和本方法一致。同时还考察了一些常见的共存物质对蛋白质测定的影响。     

Geometric calibration for a SPECT system dedicated to breast imaging

Geometric calibration is critical to the accurate SPECT reconstruction. In this paper, a geometric calibration method was developed for a dedicated breast SPECT system with a tilted parallel beam (TPB) orbit. The acquisition geometry of the breast SPECT was firstly characterized. And then its projection model was established based on the acquisition geometry. Finally, the calibration results were obtained using a nonlinear optimization method that fitted the measured projections to the model. Monte Carlo data of the breast SPECT were used to verify the calibration method. Simulation results showed that the geometric parameters with reasonable accuracy could be obtained by the proposed method.     

Respiratory motion correction with an improved demons algorithm for PET images

Respiratory motion is a major factor that affects the quality of PET images of the thoracic area. The diaphragm moves about 15-20 mm due to respiratory motion, which substantially degrades the effective spatial resolution of PET. In this paper, a gated acquisition method is used to correct the motion effects. In this method, an improved demons algorithm is proposed to align the gated images. The experimental results show that the quality of PET images is significantly improved when using our improved method and the proposed method has a faster convergence rate than the original demons algorithm.     

8-溴鸟苷探针测定生物样品中蛋白质含量的光谱法研究

研究了8-溴鸟苷(BG)与人血清白蛋白(HSA)体系的荧光猝灭光谱、三维荧光光谱,证明了两者可以发生相互作用,导致人血清白蛋白疏水微环境极性的改变和构象的变化;还分析了△λ值、pH值、离子强度等因素对该体系同步荧光强度的影响,选定了8-溴鸟苷测定生物样品中蛋白质含量的最佳实验条件;在最佳实验条件下,体系的同步荧光强度与...     

钢结构表面涂层受风沙冲蚀机理和评价方法

内蒙古中西部地区钢结构表面涂层受风沙冲蚀磨损严重.在模拟钢结构涂层受风沙冲蚀磨损试验的基础上,应用扫描电子显微镜(SEM)观测涂层在不同冲蚀条件下的冲蚀磨损部位微观形貌,分析涂层材料受风沙冲蚀磨损的损伤机理,提出了评价涂层冲蚀磨损程度的计算方法.结果表明:低角度冲蚀时微切削作用占主导,硬度起决定作用,高角度冲蚀时挤压变形占主导,柔韧性起决定作用,由于涂层硬度较低,柔韧性好,所以高角度时涂层的耐冲蚀性能较好;最大冲蚀磨损失重量出现在45°左右,是由于该材料具有介于塑性和脆性材料之间的冲蚀磨损特性;速度越大,粒子的动能越大,冲蚀磨损失重量越大;在低浓度时,冲蚀磨损失重量随着浓度的增加而增加,而在高浓度时则出现下降的趋势;评价公式的计算结果与实验结果吻合.研究结果为钢结构涂层的耐久性研究提供了理论依据.