Daily variation of carbon flux in soils of Populus euphratica forests in the middle and lower reaches of the Tarim River

In order to lucubrate the daily variation of respiration in soils of Populus euphratica forests and analyze its relationship with environmental factors in the middle and lower reaches of the Tarim River, the LI-8100 instrument of soil CO2 flux system was used to measure the parameters of soil carbon flux and air temperature 10 cm above ground surface along the profiles of Usyman, Archy River, Yengisu and Karday, and the relationships between the soil carbon flux and the soil moisture content were analyzed. The nonlinear regression analysis was carried out with the software SPSS13.0. We observed that: (1) soil respiration began to be restrained when the air temperature was up to 30℃10 cm above the ground surface; (2) the rates of soil respiration under the forests of Populus euphratica were significantly different at various moisture contents, the soil carbon flux was high along the Usyman profile, which has a high soil moisture content, and it was low along the profiles of Archy River, Yengisu and Karday, which has a low soil moisture content; (3) the exponential model can be used to explain the relationship between soil respiration and air temperature 10 cm above the ground surface. The average Q10 values along the profiles of Usyman, Archy River, Yengisu and Karday are 0. 61, 0.16, 0. 22 and 0. 35 respectively, much lower than the average of the world; (4) there is a positive correlation between the soil carbon flux and the soil moisture content.     

材料科学与工程专业开设材料力学课程的探讨

从材料科学与工程专业所开设的材料力学课程的特色以及该课程在专业知识体系和课程设置中的地位出发．阐述了材料科学与工程专业开设材料力学课程的必要性和重要性,并对该课程的授课内容和授课方式等注意事项进行了讨论。     

Light-off Performance of Three-Way Catalysts Before and After Accelerated Aging Test with an Engine-Dynamometer

This study demonstrates the reaction behavior during the purification of model automotive exhaust gases over Pd catalysts before and after thermal degradation. In particular, to investigate the relationship between the Pd state and the reaction behavior of Pd/Al₂O₃ and Pd/CeO₂−ZrO₂ (CZ), operando X-ray absorption spectroscopy measurements were performed during purifying exhaust gases over real and model catalysts mimicking the degradation of Pd particles and CZ supports after accelerated aging tests. The NO reduction activity of the aggregated Pd metal species was as high as that of the highly dispersed Pd species, but hydrocarbon (HC) poisoning was significantly enhanced by the aggregation of Pd metal particles caused by thermal aging. The existence of a three-phase boundary (TPB) between the CZ, the Pd particles, and the gas phase strongly affected the catalytic activity at low temperatures, and the presence of a sufficient TPB facilitated the combustion of unburned HCs owing to the oxygen storage performance of CZ. Thus, the TPB reduced the poisoning of the precious metal surface by HC species at low temperatures. Therefore, the findings of this study will facilitate the development of next-generation gas purification catalysts with high activity and durability.     

水泥粉煤灰砂浆强度模型的研究

为探索粉煤灰对水泥基材料力学性能的影响,采用二次回归正交设计的方法研究粉煤灰水泥基材料3d、28d的抗压强度和抗折强度,探讨了各因素对水泥基材料力学性能的影响规律。研究表明:采用二次回归正交设计建立的数学模型能够准确的描述水胶比、胶砂比、粉煤灰掺量与水泥基材料各龄期抗压强度、抗折强度相互之间的内在规律。     

辩证分析儒家义利观对市场经济的双重影响

植根于封建政治、经济制度中的儒家重义轻利、尚义贬利及由此演绎的安贫乐道、重农抑商等伦理思想观念与市场经济的本质要求相悖，但对这须持辩证分析态度，运用“扬弃”方法，在清除其糟粕的同时，努力挖掘其思想精华。儒家重义，重社会与个人思想道德建设，重经济行为的道德意识，对我们今天克服市场经济发展过程中的负面现象，促进社会主义市场经济的健康发展有积极意义，须大力弘扬。     

光子晶体能态密度的电磁场特性

基于时域有限差分法,以半导体材料CdSe和CdTe构成二维三角晶格光子晶体,数值模拟了它们的光子晶体能态密度电磁场特性。结果表明,CdSe和CdTe构成二维三角晶格光子晶体具有较好的光子带隙,形成的带隙宽度随介电常数差值的增大而增大。研究结果为光子晶体器件的开发提供参考。     

PMMA/MT纳米复合材料的研究

用烷基铵盐对钠基蒙脱土进行有机化处理,使其成为有机蒙脱土.X射线衍射(XRD)表明有机阳离子同钠离子发生离子交换作用,导致层间距扩大.制备了聚甲基丙烯酸甲酯/蒙脱土纳米复合材料,测试了力学性能、阻燃性能.通过XRD、DSC等手段研究了结构与性能,并与纯PMMA进行了对比.实验结果表明:PMMA可以插层于蒙脱土片层之中,得到共混物的力学性能和耐热性都有所提高.