Relationships between urbanization and the oak resource of the Minneapolis/St. Paul Metropolitan area from 1991 to 1998

Urbanization was associated with loss and transformation of the oak forest in the Twin Cities (Minneapolis and St. Paul) metropolitan area (TCMA) over a recent 7-year interval. Between 1991 and 1998, urbanization increased based on several indicators: population density, area of developed land, and area of impervious surface—total impervious area and area within three classes of increasing degree of imperviousness (protected, affected, and degraded). We quantified relationships between changes in urbanization and changes in several parameters describing the oak forest at the scale of ecological subsection. Increased total and affected impervious area were strongly correlated with decreased area of oak forest when changes of the urbanization indicators and oak were expressed as percentages of the subsection area. Relationships were reversed when changes were expressed as percentages of the 1991 values. Increased population density was strongly correlated with increased loss in numbers and increased isolation of oak patches, but weakly correlated with loss of oak forest area. This is the first study to quantify relationships between changes in urbanization and changes in a specific forest cover type. Our results demonstrate complexities of urbanization impacts on a metropolitan forest resource, and highlight the importance of selected variables, spatial and temporal scales, and expressions of change when quantifying these relationships.     

高压线走廊下建设大型公共绿地的探索

通过闵行经济技术开发区范围内高压线走廊下的40万m~2非生产性用地建设成大型公共绿地的实践,提出了“以绿养园,以园养园”的新思路,充分体现“谁种养,谁保护,谁得益”的原则,给上海地区乃至全国开发利用高压线走廊下的土地资源,提供了借鉴。     

中铝河南分公司矿山在土地复垦中的有益探索

分析了铝土矿露天开采和土地、环境之间的利害关系，并对矿山公司“土地复垦”工艺技术进行了阐述，介绍了中铝河南分公司矿山公司方面的具体作法和成功经验。     

低压16.5万m~3干式气柜采用城市煤气直接置换的方法

青岛市管道燃气公司在大尧罐站对低压16．5万m3干式气柜采用城市燃气直接置换，经合理确定置换范围，标准及过程，成功地进行了低压16．5万m3干式气相及其管道采用城市煤气直接置换的操作。     

Compressive Stress-Strain Relationships of Two Puffed Cereals in Bulk

The compressive stress-strain relationships of two puffed cereals, rice and corn based, in bulk were determined using a Universal Testing Machine. The general sigmoid shape of the relationship could be described by a four parameter empirical model originally developed for cellular solids. Jaggedness could be expressed in terms of an apparent fractal dimension and/or the mean magnitude of the power spectrum determined using the Fast Fourier Transform. Both measures as well as a particular parameter of the empirical model were sensitive indicators of the changes in the stress-strain relationships resulting from exposure to different relative humidities. Although the stress strain relationship, especially of dry samples, had an irregular, irreprodu-cible shape, the magnitude of the two roughness measures was highly reproducible.     

珠江口门海堤堤型的选择

珠江口站地区面临南海、大陆岸线长４５７ｋｍ，遭受洪水。潮汐、台风的影响，河口滩涂 发育迅速，以约１００ｍ／ａ的速度向大海延伸。随着沿海地区的经济发展，滨海－２ｍ高程以上的滩涂的４万ｈｍ＾２正在和将要建堤围垦和开发利用，原有海堤也亟待加固提高，因此，对珠江口门坝有海堤堤型资料进行收集、整理，分析总结，选择经济可行的海堤堤型，具有重要的现实意义。文中收集了珠江口门的几种主要堤型，通过对各种堤基工程地质     

Dynamics of Solidification in 2% Corn Starch-Water Mixtures: Effect of Variations in Freezing Rate on Product Homogeneity

Directional solidification studies of gelatinized corn starch-water mixtures were undertaken in order to examine, in situ, the freezing behavior of this food model. The solidification rate was controlled by varying sample cell velocity as it moved from a 25°C hot stage to a -25°C cold stage. While freezing at cell velocities ≤7.5 μm/sec, starch granules were alternately pushed or entrapped by the advancing solid-liquid interface producing a segregated structure consisting of alternating high-starch and low-starch bands. At a cell velocity of 10 μm/sec, the frozen product was homogeneous. The relationship between the solid-liquid interface velocity and segregation behavior was quantified and compared to an existing model of particle-interface interactions.     

焦化干气一步法预处理多功能催化剂的工业侧线试验

对焦化干气一步法预处理工艺催化剂进行了工业侧线试验。考察了温度和体积空速对催化剂的活性及催化剂稳定性和加氢选择性的影响。催化剂为以复合型ZnO和过渡金属氧化物为活性组分的多功能催化剂,用于低温下焦化干气中烯烃加氢和硫化物脱除。试验结果表明,在压力1.6MPa、温度285～350℃、空速100～500h-1的条件下,多功能催化剂能将焦化干气中烯烃的体积分数由8%～14%降至0,总硫含量从10～70μg/g脱除至5μg/g以下;经28d考核,多功能催化剂仍保持良好的烯烃加氢和硫化物脱除性能,可用于精制焦化干气。     

Influences of land use/cover on water quality in the upper and middle reaches of River Njoro, Kenya

Data from 10 sampling sites along the River Njoro are used to examine the contribution of nutrients from upstream land uses draining each of the sampling sites. The data also are used to assess whether both the proportion of land uses and the size of the subwatersheds account for the variability in water quality in the River Njoro watershed. Geographical Information System analysis was used to determine the spatial distribution of land‐cover types and subwatersheds contributing run‐off to the sampling sites in the River Njoro. Standard Digital Elevation Model‐based routines were used to establish the watershed area contributing run‐off to each sampling site. Water and sediment samples were collected for chemical analysis, and the nutrient levels were related to the upstream land‐use types and the size of the subwatersheds. The mid‐stream portion of the River Njoro (near Egerton University) accounts for the highest nutrient contributions. The percentage contribution is magnified by additions from industrial, human settlements and agricultural land uses around the University. There is a significant decrease in nutrient levels downstream, however, indicating natural purification as the river flows through an area of large‐scale farming with intense, well‐preserved riparian and in‐stream vegetation. Steep slopes of the land upstream of Egerton University enhance erosion and nutrient losses from those subwatersheds. Mixed small‐scale agricultural and bare lands contribute over 55% of the phosphorus load to the upper and mid‐reaches of the River Njoro. The size of the subwatershed accounts for about 53% of the variability in the soluble phosphorus in the river. The land‐use subwatershed proportions are important for characterizing and modelling water quality in the River Njoro watershed. Upland land uses are as important as near‐stream land uses. We suggest that conservation of intact riparian corridor along the river and its tributaries contributes significantly to natural purification processes and recovery of the ecological integrity of the River Njoro ecosystem.     

提高摩托车用干荷电电池综合性能的研究

通过改进铅膏的配方及极板的独特处理工艺 ,提高了干电荷电摩托车电池的低温高率放电性能、充电接受能力和储存性能 ,完全可以满足国内外摩托车主机厂的各种要求。