Experimental studies of the formation and dissociation of methane hydrate in loess

In order to study the nature of gas hydrate in porous media, the formation and dissociation processes of methane hydrate in loess were investigated. Five cooling rates were applied to form methane hydrate. The nucleation times of methane hydrate formation at each cooling rate were measured for comparison. The experimental results show that cooling rate is a significant factor affecting the nucleation of methane hydrate and gas conversion. Under the same initial conditions, the faster the cooling rate, the shorter the nucleation time, and the lower the methane gas conversion. Five dissociating temperatures were applied to conduct the dissociation experiment of methane hydrate formed in loess. The experimental results indicated that the temperature evidently controlled the dissociation of methane hydrate in loess and the higher the dissociating temperature, the faster the dissociating rates of methane hydrate.     

Effects of vacancy percentage on the energy gap of zigzag single-wall carbon nanotubes

The influence of vacancy percentage on the energy gap of zigzag single-wall carbon nanotube is investigated by the Green's function method in coherent potential approximation. Our probes for various kinds of zigzag single-wall carbon nanotubes show that by increasing vacancy percentage the energy gap is also increased, so for metallic single-wall carbon nanotubes, a metallic to semi-metallic transition is occurred. However, any transition does not appear for semiconductor carbon nanotubes. So by controlling on concentration of vacancies, one can make a semiconductor SWCNT with a predetermined energy gap which is useful in nanoelectronic devices.     

对流自组装2维胶体晶体成膜趋势和覆盖率

从自组装理论出发, 分析对流自组装2维胶体晶体中空白、条纹区域出现的机理,并在实验上予以验证。通过研究得知, 2维胶体晶体的自组装过程呈现空白、条纹、大面积单层、双层条纹的趋势。从胶体晶体覆盖率的角度出发研究2维胶体晶体的组装参数与质量之间的关系,结果表明:胶体晶体的总覆盖率与基片提拉速度倒数呈线性正比,和粒子体积分数呈反比例函数关系; 受到多种因素的影响,大面积2维胶体晶体总是伴随着一定比例的空白区域和双层区域出现,提拉法所能获得的最大单层覆盖率为95%。     

交流阻抗谱方法对钇稳定氧化锆晶界电性能的研究

采用交流阻抗谱技术测量了多晶钇稳定的氧化锆固体电解质的晶界离子电导率,并根据砖层模型估算了多晶陶瓷样品的晶界体积分数,分析了晶界体积分数与电性能的关系.     

门限自回归模型条件异方差的Kolmogorov-Smirnov检验

门限自回归模型被广泛地用于许多领域，当建立或使用这类模型时，一个重要问题是需要知道是否存在条件异方差。在本文中，我们对这个问题提出一个非参数检验，检验的大样本理论被给出，我们还通过数值模拟研究了检验方法的有限样本性质。结果表示检验有好的功效。经验百分位点还被给出。     

Distribution of the likelihood ratio criterion for testing Σ = Σ0, μ = μ0

The exact null distribution of the likelihood ratio criterion for testing H₀: Σ = Σ₀ and μ = μ₀ against alternatives H₁: Σ ≠ Σ₀ or μ ≠ μ₀ in N_p(μ, Σ) has been obtained as (a) a chi-square series and (b) a beta series. Percentage points have been tabulated for p = 2(1) 6, α = .005, .01, .025, .05, .1, and .25 and various values of sample size N.     

杨氏模量的两种测试方法

本文介绍了对杨氏模量测定仪的改进方法，并与使用原装置测得的数据进行了对比，拓宽了实验的内容。     

Separation of fluorinated amino acids and oligopeptides from their non-fluorinated counterparts using high-performance liquid chromatography

Chromatographic conditions for the separation of fluorinated amino acids and oligopeptides from their non-fluorinated counterparts were explored. The separation of six pairs of analytes, including both aromatic and aliphatic fluorocarbons, was investigated at various temperatures using both hydrocarbon and fluorocarbon columns and eluents. Our results show that when hydrocarbon eluents are used, fluorocarbon column provides better separation of fluorinated amino acids or oligopeptides from their non-fluorinated counterparts; when fluorocarbon eluents are used, hydrocarbon column provides better separation of fluorinated amino acids or oligopeptides from their non-fluorinated counterparts. These chromatographic behaviors reflect the fluorophilicity possessed by fluorinated amino acids and oligopeptides.     

波长检测型表面等离子体子共振生物传感器测定β-环糊精与血清白蛋白的相互作用

采用自行组装的表面等离子体子共振(SPR)传感装置, 固定入射角, 以波长为变量, 以电荷耦合器件(CCD)为检测系统, 用对金和蛋白质均有较强作用的巯基丙酸作为基底膜, 分别监测了β-环糊精(CD)与人血清白蛋白(HSA)、牛血清白蛋白(BSA)反应的动力学过程, 并分别计算了它们的动力学常数、热力学常数及键合百分率. 此外, 对传感器的再生性也进行了研究. 结果表明, β-CD与HSA, BSA相互作用的平衡常数分别是7.79和51.00 μmol/L, 且键合百分率都很高, 分别是98.77%和94.25%. 这些结果有力地说明了β-CD作为药物载体, 可以提高生物利用度, 延长药物半衰期.     

Solvent Extraction and Spectrophotometric Determination of Uranium Using α-Benzoin Oxime as Chelating Agent

Solvent extraction of uranium by a chloroform solution of α-benzoin oxime was studied and the formation of uranium-α-benzoin oxime complex described. The uranium-α-benzoin oxime complex has two maximum absorbance at 350 nm and 427 nm. A constant absorbance was obtained for 1 × 10^?3 M uranium when the concentration of α-benzoin oxime was higher than 1.2 × 10^?2 M. Ions of Ag⁺, Fe³⁺, V⁵⁺, Cu²⁺, and W⁶⁺ were found to have interference. A solution containing 0.1–10 mg uranium at pH 1.6–6.8 was extracted with 1 × 10^?3 M ?2 × 10^?3 M α-benzoin oxime solution in chloroform. With single extraction, the maximum amount of uranium passing into organic layer was at least 98%. Under this condition the presence of diverse ions except V⁵⁺ does not significantly interfere the extraction of uranium.