污泥厌氧消化的人工神经网络模型

基于污泥固体停留时间(SRT)为20 d的污泥中温厌氧消化实验,建立一个3层BP神经网络,以前1~20 d的进泥挥发性悬浮固体(VSS)、当天消化罐pH值和碱度共22个参数为输入,预测污泥消化系统日产气量,结果表明,网络具有良好的学习能力、泛化能力和辨识能力,能够较为准确地预测出系统日产气量。此外,根据进泥VSS不同,利用网络预测能力,调节pH值和碱度到合适的值,系统日产气量有明显提高,进一步证明了网络具有良好的预测能力和实用性。     

电子受体对污泥产率的影响

本文通过2个SBR和30次分批实验研究了电子受体（O2、NO3^-）对活性污泥产率系数（真实产率YH和表观产率Yobs）的影响。分批实验采用的基质是多种多样的,所选用的接种污泥是SBR长期培养出来的。实验结果表明,在不同的电子受体（O2、NO3^-）条件下,真实产率YH具有显著的不同,缺氧YH是0.53 mgCOD/mgCOD,而好氧YH是0.68 mgCOD/mgCOD,这是由于不同电子受体需要不同的微生物种群,其细胞产率不同。不过缺、好氧的表观产率Yobs（0.33 g△MLVSS/g△COD和0.35 g△MLVSS/g△COD）的差异并不显著,这是由于好氧污泥的内源呼吸作用更强,有更多的污泥衰减。     

VARIABILITY OF SOIL WATER PROPERTIES AND CROP YIELD IN A SLOPED WATERSHED1

ABSTRACT: Spatial distribution of soil and water properties and the correlations between them and crop yield were determined for a natural rainfall environment. Hydraulic conductivity, soil texture, water retention, and soil-water flux were variables used to investigate their relationship to crop yield using multiple regression techniques. Variations in crop yields on a watershed with a 3 to 4 percent slope and moderately erosive soils were related to soil-water characteristics and soil properties along slope and with depth. Climatic conditions to sustain crop growth and yield ranged from inadequate soil water in 1983 to adequate soil water in 1984. Crop yield was predicted with models using both available and measured soil-water content. Available water content provided a better model for the prediction of water yield and does not require field measurements of actual soil-water content. Soil water holding capacity was more significant for predicting crop yield in soils with moderate to high silt content than infiltrability of water into the soil.     

BANK STABILITY ANALYSIS FOR PREDICTING REACH SCALE LAND LOSS AND SEDIMENT YIELD1

ABSTRACT: When extensive lengths of river become stabilized (e.g., by channel incision), riverbank erosion can result in considerable riparian land loss and the delivery of large volumes of sediment downstream. The ability to predict the stability and failure geometry of eroding riverbanks is therefore an important prerequisite in estimating the rate of bank erosion and sediment yield associated with bank erosion. In this paper, a new stability analysis for layered river banks is introduced. The new analysis differs from many previous analyses in that it takes into consideration the effects of positive pore water pressure in the saturated portion, and negative pore water pressure in the unsaturated portion, of the bank as well as the influence of hydrostatic confining pressure due to the water level in the river. In addition, the failure plane is not constrained to pass through the toe of the bank and the bank profile geometry is not restricted to an idealized special case. The predictive ability of the new bank stability analysis is assessed using data from two field sites. Subsequently, a methodology for applying the bank stability analysis at the scale of the river reach (0.1 to 10 km) is discussed. This method involves the use of empirical models of bed level adjustment to estimate the magnitude of incision at specific locations along the reach, with these estimates used to drive the stability analysis. Application of the new method is demonstrated with an example.     

CORRELATION OF SELECTED WELL WATER QUALITY PARAMETERS WITH SOIL AND AQUIFER HYDROLOGIC PROPERTIES1

ABSTRACT: The geographical distribution of well water specific electrical conductivity and nitrate levels in a 932 km² ground water quality study area in the Fresno-Clovis, California, indicated that frequently areas of lower ground water salinity were also areas of relatively greater soil and aquifer permeability. From these observations and certain assumptions we hypothesized that the quality of the well water should be better in areas with permeable soils and geological formations. Correlation and multiple linear regression analysis supported this hypothesis for well water salinity. However, well water nitrate levels were significantly negatively correlated with only the estimated equivalent specific yield of the aquifer system. The multiple R² values of the most significant multiple linear regression models showed that only a fourth to a third of the variability in well water specific electric conductivity and nitrate levels could be ascribed to the effects of the hydrogeological parameters considered with more than 90 percent confidence. This indicates that three-fourths to two-thirds of the variability in ground water salinity and nitrate levels may be related to land use. Thus, there is considerable room for land use management techniques to improve ground water quality and reduce its variability.     

亚硫酸氢钠影响桃树产量和质量的生理学分析

不同浓度ＮａＨＳＯ３在桃树上的应用研究表明,以ρ（ＮａＨＳＯ３）＝１００ｍｇ／Ｌ使用效果最佳,于果实膨大期喷施３次,能明显提高桃树座果率和单果重,增加产量,改善果实品质,促进新梢生长。实验证明,ＮａＨＳＯ３的这些功能与其抑制过氧化氢酶活性,提高光合速率及希尔反应活力,增加叶绿素含量与比叶重,促进光合产物输出等多重生理效应相关。     

黑龙江省生态足迹时空演变与生态可持续分析

为分析黑龙江省生态可持续性状态,基于植被净初级生产力（NPP）构建了均衡因子和产量因子,采用改进的生态足迹模型,核算黑龙江省2000—2020年生态足迹、生态承载力,揭示生态足迹空间格局变化特征。结果表明：黑龙江省均衡因子为林地>草地>耕地>水域;产量因子为水域>草地>林地>耕地。黑龙江省21年间人均生态足迹增速远大于人均生态承载力,致使人均生态赤字状况日益严重;但考虑到国内贸易后,人均生态足迹呈现先增加后平稳状态,仅在2005—2010年为生态赤字状态,2010年后处于生态平衡状态;在空间上呈现明显的空间异质性。黑龙江省一直处于轻度消耗资产存量发展状态;耕地、草地资本流量无法满足社会需求;化石燃料生态足迹深度增长迅速,且表现为高生态赤字。黑龙江省总体呈现区域发展稍不安全、弱可持续发展状态;草地长期处于强不可持续状态。近年来黑龙江省生态环境状况得到有效改善,但土地资源利用不均的问题突出,应引起关注。

     

淮北地区小麦高产的生态限制因素与对策

本文在对影响淮北地区小麦高产的生态限制因素进行系统分析的基础上，提出了科学治水、施肥，合理灌溉，培肥地力，优化小麦群体动态结构等高产配套措施．     

THE USE OF MULTIPLE REGRESSION MODELS IN PREDICTING SEDIMENT YIELD1

ABSTRACT. Four commonly used models for predicting sediment yield are analyzed and compared using previously published data. Three of these models involve logarithmic transformations. Some of the problems involved in transforming data are discussed in the context of logarithmic transformations. These problems are illustrated using the results of standard regression analyses and economic loss function analyses. For the data analyzed, the linear model is preferable to each of the logarithmic models on the basis of each analysis, and the usual multiple objective nature of the model choice problem is thus modified. The extent to which these results can be generalized is discussed in the context of model choice.     

梅州金柚高产优质的土壤与施肥管理技术

通过对柚园的土壤、作物营养与施肥试验研究,结合当地生产实际,总结出梅州金柚种植实现高产优质的土壤改良、培肥地力和施肥的一系列技术措施.