预氧丝原位炭化无粘结剂C/C复合材料氧化动力学研究

采用恒温热重法测定了在空气中，０．１ＭＰａ，６７３Ｋ到９７３Ｋ下预氧丝（即预氧化聚丙烯腈纤维）原位炭化无粘结剂Ｃ／Ｃ复合的氧化失重率；并利用扫描电镜分析了这种复合材料氧化前后的结构，氧化动力学测定结果表明：该材料在氧化开始时，其氧化速率随时间的增长而增大，然后随时间的延长而减小，并趋向恒定，研究表明：该材料中预氧丝与基体炭界面结合处是空气中氧的扩散通道，杂质为空气中氧的吸附起到了有附活性中心的催化     

Using the VS‐Fast methodology for soil degradation assessment: a case study from Senegal

Soil degradation threatens sustainable food production and accelerates global warming. Poorer countries, whose agricultural sectors are highly dependent on their natural resource bases, are hit particularly hard by declining soil productivity. Calls for soil‐quality monitoring are therefore, justified and this could inform decision‐makers on the preparation of appropriate interventions. However, the provision of monitoring methodologies is not an easy task. Soil degradation affects several soil characteristics that at larger scales cannot be evaluated with models or remote‐sensing techniques. Therefore, this study focuses on investigating the use of field‐based soil assessment methodologies to differentiate degrees of soil degradation. Specifically, we test the Visual Soil Field Assessment Tool (VS‐Fast) for detecting and monitoring soil degradation using a cross‐section of 71 sites in Senegal, the soil quality of which were classed by local experts. We found low correlation between VS‐Fast classes and expert assessments. By using an ordered logit model to quantify class boundaries, we show that experts categorized areas as ‘degraded’ for a wider range and higher VS‐Fast scores than the corresponding VS‐Fast class. Yet, from general linear models and analysis of variance procedures we found that areas classed by experts as ‘degraded’ had statistically significant lower VS‐Fast scores compared to those that were judged as ‘normal’ and ‘good’, while differences of the VS‐Fast scores between the latter two were negligible. It is remarkable that the visual assessment, the cheaper component of the VS‐Fast score, performs better in differentiating degradation status than its measured counterpart. The results support the need to investigate the applicability of other VSA methodologies that only use field observations and tactile methods.     

Tree Diversity,Carbon Storage,and Soil Nutrient in an Old‐Growth Forest at Changbai Mountain,Northeast China

Abstract

The study of plant diversity and its role in ecosystem functioning is becoming a central issue in ecology. The relationships between carbon storage and tree diversity of natural forest at small scale are still unclear. This research investigated these relationships in an old‐growth forest at Changbai Mountain, Northeast China. It was found that at small scale, tree carbon storage generally increases with increasing tree species richness, but for stands with same species richness, tree carbon storage varies dramatically. At the small scale, tree species evenness has a significantly linear relationship with nature logarithm of total tree carbon storage. The stand carbon storage of trees is mainly controlled by stand tree composition. Fraxinus mandshurica, Pinus koraiensis, Quercus mongolica, Tilia amurensis, and Acer mono contribute more than 85% of stand carbon storage of trees. Stands with similar tree composition at small scale have different soil organic carbon storage and nutrient contents. Tree species evenness has great impact on soil N content at the soil horizon less than 30 cm deep, but its impacts on C/N, P, K, and S contents are small. Tree density has a negative linear relationship with soil organic C and C∶N ratio at the soil horizon is less than 30 cm deep. The implication of our findings here for carbon sequestration in the Kyoto Protocol is also discussed.     

浅谈市政道路石灰土基层施工

笔者从石灰土在道路施工中的重要性出发,分析市政道路石灰土基层施工的前期准备工作,并介绍了市政道路石灰土基层施工工艺流程,最后分析了特殊季节道路石灰土基层施工的注意事项。     

小麦实时控制灌溉的土壤水分含量探头合理埋设深度研究

利用室内控制试验研究了根据不同深度土壤水分传感器灌溉处理对冬小麦生物学性状及水分利用率等的影响。结果显示,以10 cm探头控制灌溉最为省水,同时冬小麦生物学性状及水分利用率等最佳。由于试验冬小麦处于生育前期,随着小麦生育期延伸,当根系超过30 cm深度时,根系吸水的深度增加,探头的埋设深度需要田间试验进行更详细的研究。     

滴灌土壤湿润区对棉花生长及产量的影响研究

针对棉花作物,以桶栽试验为基础,通过控制滴头流量得到不同宽度的土壤湿润区,观测了棉花相应的生长状况及产量。试验结果表明,棉花的生长发育和产量与滴灌土壤湿润区的大小密切相关,宽的土壤湿润区可以使棉花的生长发育提前,其株高、叶面积、产量都比窄的土壤湿润区条件下的棉花相应指标高;宽的土壤湿润区下的棉花叶面积衰老速度比窄的土壤湿润区下的棉花叶面积衰老速度慢。另外,随着土壤湿润区变宽,土壤耗水深度变浅,棉花单铃重、衣分和单株产量增加,但单株铃数减少。     

Ni/Al2O3-MxOy催化剂催化松香氢化反应研究

研究了自制非贵金属纳米催化剂Ni/Al2O3-MxOy催化松香的氢化反应。结果表明,松香氢化的最适工艺条件为:反应温度210℃、反应压力4.5 MPa、反应时间2 h、催化剂用量2.5%、搅拌转速500 r/min,在此条件下枞酸转化率可达98%以上,催化剂可重复使用4次。     

铲式玉米精密播种机三维参数化设计

针对铲式玉米精密播种机传统设计方法中存在的设计效率低、无法进行动态装配等问题,应用Pro/E软件对播种机零部件进行了三维模型构建,并完成播种机的整体装配;在Visual C++平台上,利用Pro/TOOLKIT和MFC,编制了基于Pro/E的三维参数化设计软件,利用程序控制语句对播种机模型进行驱动,实现了播种机的参数化和系列化设计,为播种机的运动学、动力学和有限元分析奠定了基础.     

基于特征筛选算法的数字土壤制图研究

平缓地带数字土壤制图中，环境协变量的选择是提高制图精度的关键。已有研究证明遥感影像可作为推理制图的辅助因子，而如何确定环境因子推理制图时各自的权重已成为现阶段研究的重点。选取湖北省麻城市乘马岗镇为研究区，采用3种特征筛选方法进行有效环境变量筛选，探索参与平原-丘陵混合区域制图的因子并确定其重要性，依据选择的相对稳定的指标，进一步探索提高土壤类型制图准确性的途径。根据141个野外独立样点的检验结果表明：在推理制图中，遥感因子在平原区域的重要性程度高于丘陵区域，且遥感因子中归一化植被指数(NDVI)和均值(Mean)较为稳定；基于递归特征算法的按地形推理制图精度最高为75.89%，分别高于ReliefF算法和基于Tree的特征筛选算法13.48%和4.97%；此外3种特征筛选算法制图结果中，按地形因子分区制图的精度均高于整体区域制图。因此，遥感因子作为辅助手段参与推理过程可有效提高制图精度。本研究采用的特征挖掘与机器学习算法对提升土壤制图精度具有一定的理论意义。     

土壤施硅对小麦和麦蚜的影响

为明确土壤施硅对小麦蚜虫的防控效果，本研究在小麦种植前分别配施0（CK）、40、80和120 kg/hm²四个浓度的硅肥，测量施硅后小麦生育期、生物量、叶面积、株高、产量指标以及荻草谷网蚜Sitobion miscanthi和禾谷缢管蚜Rhopalosiphum padi发生量。结果表明，施硅对小麦株高和穗数无显著影响，但80 kg/hm²和120 kg/hm²浓度施硅处理后小麦叶面积分别为1 786.03 mm²和2 033.54 mm²，生物量分别为133.68 g和134.50 g，小麦穗粒数分别为35.61粒和35.92粒，小麦千粒重分别为45.34 g和45.59 g，小麦产量分别为9 684.45 kg/hm²和9 835.05 kg/hm²，均显著高于对照，且小麦成熟期较对照提前3 d；80 kg/hm²和120 kg/hm²浓度施硅处理后禾谷缢管蚜发生量分别为90头和86头，均显著低于对照；40、80和120 kg/hm²浓度施硅处理后荻草谷网蚜发生量分别为128、117和105头，均显著低于对照。因此，田间土壤施硅80 kg/hm²和120 kg/hm²可以明显改善小麦农艺性状，提高小麦产量，并能减少麦蚜发生量。