微波等离子体法制备纳米钼粉

阐述用微波等离子法制备纳米金属钼粉的原理,探讨了此法制备纳米钼粉颗粒的工艺与影响因素,并以羰基钼为原料制得纳米级钼粉,平均粒径小于５０ｎｍ,还研究了钼粉在空气中的热稳定性。     

Microhabitat selection in the sand recluse spider (Sicarius thomisoides): the effect of rock size and temperature

In spiders, temperature is considered an important environmental variable for microhabitat selection. In this study, we evaluated the effect of temperature and rock size on the presence of the sand recluse spider Sicarius thomisoides and the degree of selectivity in different locations. This species is a large spider that lives under rocks in desert and semi-desert climates and is particularly active during the summer. In Chile, these spiders can be found at both coastal and inland locations under different thermal conditions, where usually the temperatures are lower near the coast. If large-scale climatic conditions are important for this species, they may be expected to select lower rock temperatures on the coast than at inland locations. In addition, we would expect that the spiders would choose larger rocks in inland compared to coast locations, which reduce the effect of high temperatures. We found that the probability of finding individuals of this species increased according to rock temperature and rock size in the field. Our results suggest that S. thomisoides prefers larger and warmer rocks to shelter under during the day, this selectivity being similar at both coastal and inland locations. Thus, this species tends to select rocks with the same thermal and structural conditions, independent of the climatic conditions.     

长江上游铜锣峡河段卵砾石推移质输沙规律研究

西部山区河段具有水面比降大、河床推移质粒径粗、糙率较大等特点,因此西部山区河段的水沙特性与平原河流差异明显,采用现有的推移质输沙公式来预测山区河段的泥沙输移情况存在较大误差。针对这一现象,基于爱因斯坦均匀沙无量纲输沙公式,考虑到推移质周围床沙对其遮蔽影响,以V/Uc=1为推移质起动临界状态建立了输沙率计算公式,最后以长江上游铜锣峡河段为研究对象,根据近二十年实测的水沙数据,将新计算式与多个经典公式进行精度比较,从计算结果来看,在预测大比降卵砾石山区河流时,新建立的计算式计算精度更高,能更好的反映其输沙规律。     

铁银共掺杂TiO2纳米材料的制备及性能

本文采用溶胶一凝胶法制备了Fe^3＋、Ag单掺杂以及Fe^3＋Ag共掺杂的TiO2复合材料,采用XRD、SEM研究分析了样品晶体的结构变化和形貌。以甲基橙为光催化反应模型化合物,考察了掺杂对光催化活性的影响。无论是单掺杂还是共掺杂,掺杂后效果明显提高,性能均优于纯TiO2,特别是共掺杂效果更为明显。根据最后试验共掺杂的最佳比例Fe^3＋0．1％、Ag0．7％,确定了共掺杂降解环境的最佳pH值。     

爆速对纳米氧化铝尺度控制影响研究

将硝酸铝和黑索金按照不同的质量比均匀混合形成4种粉状的混合炸药,每一种炸药爆轰都得到了纳米氧化铝.对每次收集到的实验粉体分别进行了高分辨率透射电镜分析和X光衍射分析.分析结果表明4种混合炸药爆轰所得到的纳米氧化铝呈球形,颗粒尺寸分布比较均匀,尺寸范围为15～20 nm,晶型为γ型.另外由X光衍射数据利用Scherrer公式分别计算出每一种质量比的混合炸药爆轰所得到的纳米氧化铝的平均颗粒尺寸.利用BC-3型爆速仪测得4种混合炸药的实际爆速.研究发现爆速越高的混合炸药爆轰所得到的纳米氧化铝的颗粒就越细,同时绘出了爆速与颗粒尺寸的关系曲线.在一定的尺寸范围内,根据此曲线可以通过改变混合炸药的爆速来控制合成出的纳米氧化铝颗粒尺寸.     

Gas-liquid phase coexistence and finite-size effects in a two-dimensional Lennard-Jones system

The gas-liquid phase coexistence in a two-dimensional Lennard-Jones system is investigated using Maxwell construction method together with molecular dynamics simulations.The results of phase coexistence in different truncations of the potential are compared with data obtained from the literature,and the corresponding critical properties calculated.The crossover from Ising-like to mean field behavior is observed and confirmed as the temperature approaches the critical point from below.Performing simulations on systems with different sizes,we find that a finite size effect is more significant than those shown in most of the previous results,and a lower critical temperature is obtained when the full extent of this finite size effect is considered.     

Spatial prisoner’s dilemma games with increasing size of the interaction neighborhood on regular lattices

We studied the evolution of cooperation in the prisoner’s dilemma game on a square lattice where the size of the interaction neighborhood is considered. Firstly, the effects of noise and the cost-to-benefit ratio on the maintenance of cooperation were investigated. The results indicate that the cooperation frequency depends on the noise and cost-to-benefit ratio: cooperation reaches a climax as noise increases, but it monotonously decreases and even vanishes with the ratio increasing. Furthermore, we investigated how the size of the interaction neighborhood affects the emergence of cooperation in detail. Our study demonstrates that cooperation is remarkably enhanced by an increase in the size of the interaction neighborhood. However, cooperation died out when the size of the interaction neighborhood became too large since the system was similar to the mean-field system. On this basis, a cluster-forming mechanism acting among cooperators was also explored, and it showed that the moderate range of the neighborhood size is beneficial for forming larger cooperative clusters. Finally, large-scale Monte Carlo simulations were carried out to visualize and interpret these phenomena explicitly.     

TiO2空心微球的制备及其在模拟太阳光下光催化降解罗丹明B活性

以钛酸丁酯为反应原料、油胺为模板剂,采用溶剂热法制备了TiO2空心微球.通过XRD、SEM、TEM、HR-TEM、N2吸附-脱附实验及FT-IR对其晶体结构、形貌、表面性质及比表面积进行了表征.在模拟太阳光下研究了TiO2对罗丹明B的光催化降解活性,并与商品TiO2(P25)的活性相比较.结果表明,空心微球为纯相锐钛矿型TiO2,球的直径处于2-5 μm之间,构成微球的初级粒子的平均粒径为10.7 nm,BET比表面积为42.95 m2/g.所制备的TiO2空心微球在2h内对罗丹明B溶液的光降解率达72％.因粒径较大而使其不易团聚,且极易回收,有利于实际应用.     

边染色9-临界图边数的新下界

针对Vizirtg猜想△为9的情况，运用Discharging差值转移方法研究了9-临界图的边数下界，得到了新结论：m≥10^-36n,改进了已有结果。     

试论吐蕃时期布达拉宫的建筑规模

举世闻名的布达拉宫是西藏的标志性建筑，也是西藏文明的象征。在一千余年的历史发展过程中，布达拉宫的建筑规膜发生了巨大变化。文章试图从吐蕃时期的重要历史事件中提取有关布达拉宫的零星记栽，分析自吐蕃时期布达拉宫建筑规模的变化，为还原布达拉宫的原貌提供一些历史的线索和依据。