City and Inhabitants

Based on the relationship between cities and inhabitants as the main point, the characters, complexity and openness of the urban system are discussed in this paper. Then, the nature of the city is revealed.     

Sulphate Attack Resistance of the Concrete with Additives and Its Assessment

The influence of three kinds of additives: silica fume,slag and fly ash on the sulphate attack resistance of concrete were studied.The experiment results show that these three kinds of additives can improve sulphate attack resistance of the concrete and the order of their efficiency from high to low is silica fume,slag and fly ash;the development of mortar expansion value is closely related to the degree of sulphate attack resistance of the concrete;integrated assessing two concrete properties: mortar expansion value and compressive strength ratio can more exactly assess the sulphate attack resistance of the concrete.     

Effect of Reinforced-Concrete Deterioration on Structures

s:It is proposed that the research of the structural durability is necessary considering the structural damages under the effect of deterioration of reinforced concrete. The most common reasons, which cause the deterioration of structures in China, are reinforcement corrosion and freeze thaw cycles of concrete. Based on the summarizing of research works of the effect of reinforced concrete deterioration on structures, it is indicated that the structural durability research should be carried out either in view of material science or that of structural science, and should be also considered the interaction of several factors with uncertain nature instead of the determined individual factor analysis. The structural durability of serviceable should be paid much more attention while researching the durability of structural capacity. The effect of reinforced concrete deterioration on structural capacity, rigidity and durability should be researched henceforth.     

贵州茶树种质资源数据库的建立研究

通过对贵州现有茶树资源资料的收集、整理和发掘，从而建立贵州茶树种质资源数据库。本文对建立数据库的要求和方法进行了论述，并说明建立的重要和价值。     

施用膨润土对土壤含水量和有机质含量的影响

通过田间条件下砂滤管试验，研究了不同膨润土施用量及有机物料对砂土土壤含水量和有机质含量的影响。结果表明，施用膨润土和有机物料能显著地提高砂土土壤含水量和有机质含量，且二者存在明显的交互作用，差异达极显著水平，施用膨润土能明显增加土壤有机质的累积是，说明在施用同样有机物料的前提下，施用膨润土可有显著提高砂土土壤有机含量。     

杨凌节水农业综合技术体系集成与示范

介绍了杨凌节水农业综合技术体系集成与示范区建设的设计构想。示范区设计以现有节水农业技术在西北半湿润区的适应性和可操作性研究为基础。通过技术筛选、技术集成及示范,形成规范化技术标准。在综合分析节水示范区自然和社会因素的基础上,对节水技术进行组装凝练,建设综合节水示范区,监测示范区的农业和生态用水变化状况,评估节水效益;探索渠灌区节水农业综合示范区管理体制和运行机制,形成一套相对完整的节水农业技术集成和发展模式,形成与市场经济接轨的示范区建设、运行与管理机制;建立示范区节水效益评估方法及监测指标体系。     

缺镁胁迫对龙眼苗期氮代谢的影响

采用溶液培养方法研究了缺镁胁迫对龙眼苗期氮代谢的影响。结果表明 ,缺镁胁迫下 ,龙眼叶片硝酸还原酶 (NR)活性下降 ,游离氨基酸总量增加 ,水解氨基酸总量减少 ,蛋白质合成受阻而分解加剧 ;核酸酶 (RNase)活性提高 ,核糖核酸 (RNA)、脱氧核糖核酸 (DNA)含量降低 ,缺镁对RNA的影响比DNA大 ;活性氧 (O2-)净产生速率增加。统计分析表明 ,缺镁胁迫下 ,龙眼核酸和蛋白质含量下降是其合成受阻、分解加剧以及活性氧毒害综合作用的结果     

黄河流域陕西片土壤侵蚀预报模型研究

以气候、地质、地形、植被及人类活动 5类因素中的 6个因子为预报因子 ,以陕西黄河流域水蚀区内 5大类型区中 3 3条小流域的实验观测资料和实地调查资料及有关科研单位的研究成果为基础 ,建立了适用于该区域的土壤侵蚀预报模型。据运用该模型对本区域内 4条小流域水土保持遥感普查成果和建模所用 3 3条小流域土壤侵蚀模数进行验证 ,证明该模型具有较高的精度 ,可以在陕西黄河流域水蚀区及条件相近的其他地区推广应用     

Determinants of annual fluxes of CO2 and N2O in long-term no-tillage and conventional tillage systems in northern France

The greenhouse gases CO₂ and N₂O emissions were quantified in a long-term experiment in northern France, in which no-till (NT) and conventional tillage (CT) had been differentiated during 32 years in plots under a maize–wheat rotation. Continuous CO₂ and periodical N₂O soil emission measurements were performed during two periods: under maize cultivation (April 2003–July 2003) and during the fallow period after wheat harvest (August 2003–March 2004). In order to document the dynamics and importance of these emissions, soil organic C and mineral N, residue decomposition, soil potential for CO₂ emission and climatic data were measured. CO₂ emissions were significantly larger in NT on 53% and in CT on 6% of the days. From April to July 2003 and from November 2003 to March 2004, the cumulated CO₂ emissions did not differ significantly between CT and NT. However, the cumulated CO₂ emissions from August to November 2003 were considerably larger for NT than for CT. Over the entire 331 days of measurement, CT and NT emitted 3160 ± 269 and 4064 ± 138 kg CO₂-C ha⁻¹, respectively. The differences in CO₂ emissions in the two tillage systems resulted from the soil climatic conditions and the amounts and location of crop residues and SOM. A large proportion of the CO₂ emissions in NT over the entire measurement period was probably due to the decomposition of old weathered residues. NT tended to emit more N₂O than CT over the entire measurement period. However differences were statistically significant in only half of the cases due to important variability. N₂O emissions were generally less than 5 g N ha⁻¹ day⁻¹, except for a few dates where emission increased up to 21 g N ha⁻¹ day⁻¹. These N₂O fluxes represented 0.80 ± 0.15 and 1.32 ± 0.52 kg N₂O-N ha⁻¹ year⁻¹ for CT and NT, respectively. Depending on the periods, a large part of the N₂O emissions occurred was probably induced by nitrification, since soil conditions were not favorable for denitrification. Finally, for the period of measurement after 32 years of tillage treatments, the NT system emitted more greenhouses gases (CO₂ and N₂O) to the atmosphere on an annual basis than the CT system.     

淮山品种"桂淮2号"的选育及栽培研究

淮山为薯蓣科薯蓣属多年生蔓性块茎类植物，是药食兼用的高效经济作物。通过优良单株筛选，结合群体观察以及植物学、生理学、产量和营养品质等相关研究，从广西地方种质资源中选育出淮山品种“桂淮2号”，并介绍其特征特性和田间肥水管理及病虫害防治等栽培技术要点。该品种具有淀粉含量高、矿质营养丰富等特点，可作为药材加工和菜用、粮用、饲用等。