木材正辛醇液化产物的红外光谱分析

溶剂溶解技术是生物质液化的重要过程之一。为了在温和条件下从生物质中生产高质量的液体燃料,有必要开发新型液化溶剂。而对液化产物的分析则是评价溶剂液化效果的主要途径。在不锈钢高压釜中进行杨木粉在酸化正辛醇中的液化反应,对液化产物先后用丙酮,正己烷萃取,得到液化残渣、重质油和轻质油。通过对液化残渣、重质油和轻质油的红外光谱分析考察了木材中纤维素、半纤维素和木质素的液化规律和转化机理。结果表明,木材液化油品是复杂的混合物,含有羟基、羰基、甲氧基、芳基和醚类化合物。纤维素/半纤维素比木质素更容易液化。纤维素/半纤维素主要转化为轻质油,而木质素液化产物主要是重质油。在150 ℃木质素液化降解生成小分子芳烃,继续升高液化温度导致小分子芳烃重聚合。     

Operator geometric stable laws

Operator geometric stable laws are the weak limits of operator normed and centered geometric random sums of independent, identically distributed random vectors. They generalize operator stable laws and geometric stable laws. In this work we characterize operator geometric stable distributions, their divisibility and domains of attraction, and present their application to finance. Operator geometric stable laws are useful for modeling financial portfolios where the cumulative price change vectors are sums of a random number of small random shocks with heavy tails, and each component has a different tail index.     

一类重尾风险因子的模拟及其投资高风险值和置信区间的估计

由于金融市场中的日周期或短周期对数回报率的样本数据多数呈现胖尾分布，于是现有的正态或对数正态分布模型都在不同程度上失效，为了准确模拟这种胖尾分布和提高投资风险估计及金融管理，本文引进了一种可根据实际金融市场数据作出调正的蒙特卡洛模拟方法．这个方法可以有效地复制金融产品价格的日周期对数回报率数据的胖尾分布．结合非参数估计方法，利用该模拟方法还得到投资高风险值以及高风险置信区间的准确估计。     

Metals near a magnetic instability

Zero-temperature magnetic phase transitions exhibit an abundance of nearly critical magnetic fluctuations that allow to probe the traditional concepts of the metallic state. For the prototypical heavy-fermion compound, CeCu_6−x Au _x , a breakdown of the Fermi-liquid properties may be tuned by Au concentration, hydrostatic pressure, or magnetic field. The d-electron weak itinerant ferromagnet ZrZn₂, on the other hand, was recently found to display superconductivity in coexistence with ferromagnetism.     

铝的激发光谱的测量

用１２０ｋｅＶ的Ａｌ＋离子与１０μｇ／ｃｍ２的碳箔相互作用，研究ＡｌⅠ、ＡｌⅡ和ＡｌⅢ的激发光谱，其结果与其它实验进行了比较。     

Estimating the distortion parameter of the proportional hazards premium for heavy-tailed losses under Lévy-stable regime

Estimating the distorted parameter in the case of non negative heavy-tailed losses has been treated in Brahimi et al. (2011). In this paper, we extend this work to the case of the real heavy-tailed losses. We derive an asymptotic distribution of the estimator. We construct a practically implemented confidence interval for the distortion parameter and illustrate the performance of the interval in a simulation study with application to real data.     

Ultrasound-assisted soil washing processes for the remediation of heavy metals contaminated soils: The mechanism of the ultrasonic desorption

Ultrasound-assisted soil washing processes were investigated for the removal of heavy metals (Cu, Pb, and Zn) in real contaminated soils using HCl and EDTA. The ultrasound-assisted soil washing (US/Mixing) process was compared with the conventional soil washing (Mixing) process based on the mechanical mixing. High removal efficiency (44.8% for HCl and 43.2% for EDTA) for the metals was obtained for the most extreme conditions (HCl 1.0 M or EDTA 0.1 M and L:S = 10:1) in the Mixing process. With the aide of ultrasound, higher removal efficiency (57.9% for HCl and 50.0% for EDTA) was obtained in the same extreme conditions and similar or higher removal efficiency (e.g., 54.7% for HCl 0.5 M and L:S = 10:1 and 50.5% for EDTA 0.05 M and L:S = 5:1) was achieved even in less extreme conditions (lower HCl or EDTA concentration and L:S ratio). Therefore, it was revealed that the US/Mixing was advantageous over the conventional Mixing processes in terms of metal removal efficiency, consumption of chemicals, amount of generated washing leachate, and volume/size of washing reactor. In addition, the heavy metals removal was enhanced for the smaller soil particles in the US/Mixing process. It was due to more violent movement of smaller particles in slurry phase and more violent sonophysical effects. In order to understand the mechanism of ultrasonic desorption, the desorption test was conducted using the paint-coated beads with three sizes (1, 2, and 4 mm) for the free and attached conditions. It was found that no significant desorption/removal of paint from the beads was observed without the movement of beads in the water including floatation, collision, and scrubbing. Thus, it was suggested that the simultaneous application of the ultrasound and mechanical mixing could enhance the physical movement of the particles significantly and the very high removal/desorption could be attained.     

电感耦合等离子体发射光谱测定植物精油中的重金属元素

植物精油是从芳香植物提取的天然复杂化合物,作为芳香植物的次生代谢产物具有挥发性和浓郁香味,其特有的多样化生物活性广泛应用于医药和化妆品行业.植物精油具有高渗透性,能以活跃的分子态渗透皮肤组织,经淋巴腺吸收后进入血液,其所含的重金属元素也极易随植物精油进入人体对健康构成潜在威胁.采用硝酸-双氧水对植物精油进行微波消解,在...     

质谱法精密测定重水中的氢同位素丰度

介绍了用高分辨气体质谱计精密测定重水中氢同位素丰度的分析方法．实验自制了一套重水分解系统,以金属铀作还原剂,在一定的温度下还原重水为氘气．采用低温活性碳作为吸收剂,将样品分解、制备成气体试样,用高分辨气体质谱计测定重水中氢同位素丰度．该方法测定高浓度（〉99％）重水的氘丰度,测量结果的相对标准偏差不大于0．02％。     

PHOBOS at RHIC: Some global observations

Particle production in Au+Au collisions has been measured in the PHOBOS experiment at RHIC for a range of collision energies for a large span of pseudorapidities, |η| < 5.4. Three empirical observations have emerged from this data set which require theoretical examination. First, there is clear evidence of limiting fragmentation. Namely, particle production in central Au + Au collisions, when expressed as dN/dη′ ( η′ ≡ – y_beam), becomes energy independent at high energy for a broad region of η′ around η′ = 0. This energy-independent region grows with energy, allowing only a limited region (if any) of longitudinal boost-invariance. Second, there is a striking similarity between particle production in e⁺e⁻and Au + Au collisions (scaled by the number of participating nucleon pairs). Both the total number of produced particles and the longitudinal distribution of produced particles are approximately the same in e⁺e⁻and in scaled Au + Au. This observation This presentation is based in large part on the PHOBOS summary talk by M Baker at the16th Int. Conf. on Ultrarelativistic Nucleus- Nucleus Collisions, Quark Matter 2002, Nantes, France was not predicted and has not been explained. Finally, particle production has been found to scale approximately with the number of participating nucleon pairs for (N _part ) > 65. This scaling occurs both for the total multiplicity and for highp _T particles (3 <p _T < 4.5 GeV/c). This presentation is based in large part on the PHOBOS summary talk by M Baker at the16th Int. Conf. on Ultrarelativistic Nucleus-Nucleus Collisions, Quark Matter 2002, Nantes, France