Relationship between porosity and chloride diffusivity in cement-based composite materials

For investigating the effect of porosity in cement-based composite materials on diffusion coefficient of chloride ion, a series of mortar specimens with different water-cement ratios, different volume fractions and different diameters and graduation of aggregates are cast, and then chloride diffusivity of mortar specimens are measured by steady-state electric acceleration method and pore structure parameters of corresponding samples are obtained by mercury intrusion porosimetry. At the same time, the pore size distributions are visualized by X-ray micro-focus computer tomography. The results show that porous interfacial transition zones between aggregate and bulk cement paste significantly change the distribution of pore structure in hardened cement paste, and the smaller water-cement ratio is, the more significant the effect of interfacial transition zones on pore structures of hardened cement paste is. A good correlation between the total porosity, capillary porosity and the diffusion coefficient of chloride ion in cement-based composite materials has been determined and the continuous pore diameter is linearly related to the diffusion coefficient of those. Furthermore, the larger the continuous pore diameter is, the larger the value of chloride diffusivity is.     

基于空间洛伦茨曲线的昌吉州农林牧渔业产值结构变化分析

[目的]为昌吉州农林牧渔业产值的合理布局提供科学依据,[方法]基于昌吉州各县市1998～2007年农林牧渔业产值的数据,应用经济学中的洛伦茨曲线及基尼系数的概念进行昌吉州农林牧渔业产值结构的定量化研究.[结果]在空间尺度上,渔业产值(2007年的基尼系数为0.59,下同)和林业产值(0.19)分布较不均衡,农业产值(0.07)和牧业产值(0.08)分布相对均衡;在时间尺度上,林业产值和牧业产值趋向分散,而农业产值和渔业产值趋向集中.[结论]昌吉州各县市农林牧渔业产值的空间分布及其时间变化均具有不均衡性.     

灌水定额对食葵耗水特征和产量的影响

为研究不同灌水定额对食葵产量及其构成因素的影响并探究其耗水规律,筛选适宜的灌溉制度,设定5个不同的灌水定额,分别为300、375、450、525、600 m~3·hm~(-2),研究了不同灌水定额对食葵产量及其构成因素和耗水指标影响的同时,为弥补大田试验分析直观性不足,在生长、果实品质、产量和耗水等指标的基础上,利用MAGA-PPC模型综合且客观评价了田间试验结果。研究表明:不同灌水定额影响食葵耗水规律,食葵耗水量、耗水强度、耗水模数和作物系数随着灌水定额增加而增大,525～600 m~3·hm~(-2)灌水定额下耗水量、耗水强度、耗水模数和作物系数最大。在现蕾期和成熟初期,525～600 m~3·hm~(-2)灌水定额对食葵耗水量、耗水强度和作物系数影响更大。300 m~3·hm~(-2)灌水定额下食葵耗水量先呈现出减少趋势现象。食葵盘径、产量和水分利用效率随着灌水定额的增加而增大,525 m~3·hm~(-2)灌水定额下产量最大(4 781.86 kg·hm~(-2)),且水分利用效率较大(14.37 kg·mm~(-1)·hm~(-2)),525 m~3·hm~(-2)灌水定额更适合当地食葵农田灌溉。MAGA-PPC模型评价结果表明,525 m~3·hm~(-2)灌水定额有利于北疆地区食葵节水增产。综上表明,建议保证食葵现蕾期和成熟初期给水量充足,选用525 m~3·hm~(-2)灌水定额。     

Spatial variability of throughfall in a Chinese pine (Pinus tabulaeformis) plantation in northern China

The interception of rainfall by vegetation and the subsequent evaporation of intercepted water from the canopy surface play an important role in hydrological processes, and the water and energy balance of forest ecosystems. Spatial variability of interception has different effects on water yield from watersheds located in different climatic and biome regions. In order to explain the spatial patterns of interception, we adopted grid-sampling method to install rain-gauges to measure throughfall. Results show that the coefficient of variation (Cv) of throughfall tends to decline as rain intensity increases. After the canopy is saturated, Cv of throughfall remained at a constant value, which is close to the Cv of the canopy leaf area index (LAI) value 0.18. Thus, the Cv of LAI is regarded as the extremum of that of throughfall. Because of the special characteristic of Chinese pine (Pinus tabulaeformis), and the lower droopy branches, negative values for interception account for only 13% of the total samples. Furthermore, the max is above 70% of gross rainfall. __________ Translated from Science of Soil and Water Conservation, 2006, 4(3): 26–30 [译自: 中国水土保持科学]     

灭多威与杀虫剂的联合毒力研究

室内采用浸渍法、喷雾法和点滴法分别进行了灭多威与杀螟硫磷、灭多威与异丙威对蚜虫和粘虫的联合毒力测定。结果表明灭多威与杀螟硫磷以１：７比例混配对蚜虫和粘虫均表现为增效作用,共毒系数（ＣＴＣ）分别为２４９．０３和１８０．３０;灭多威与异丙威以１：２比例混配对蚜虫和粘虫表现为显著增效,共毒系数分别为２３５．４５和２７４．３０。比较了３种生测方法对灭多威的杀虫活性影响     

乌鲁木齐春夏气溶胶散射吸收系数的研究

采用积分式浑浊度仪于2008年5月-6月在乌鲁木齐市中区和市北区对气溶胶的散射和吸收系数进行连续观测,分析了市中区与市北区气溶胶散射和吸收系数的变化特征,结合同期的气象资料对变化原因进行了分析。结果表明:市中区和市北区气溶胶的散射吸收系数具有相同的变化趋势,日变化特征总体上呈现出"W"型;峰值分别出现在0时和8时前后,谷值则出现在4时和19时前后。散射系数远大于吸收系数,说明大气气溶胶的消光作用主要是散射作用完成。相对湿度与散射吸收系数不具有显著相关性,而风速对散射吸收系数影响较大。     

苹果表面摩擦系数的试验研究

为了减少机械损伤,果实的收获、贮藏和加工机械的设计需要充分考虑果实的摩擦性质。以苹果为研究对象,运用摩擦系数测定试验台对苹果表面摩擦系数进行测定,分别得到了其与有机玻璃和牛皮纸之间的静摩擦系数和动摩擦系数。该试验可为苹果的收获、贮藏及加工装备的设计研究提供必要的理论依据。     

USE OF CVS FOR REFINING MID-SEASON FERTILIZATION NITROGEN-RATES IN WINTER WHEAT

The GreenSeeker? optical sensor is used as a management decision aid in many crops across the world. This sensor measures the normalized difference vegetative index (NDVI). It has been observed that when the by-plot coefficients of variation (CV) from the GreenSeeker? sensor NDVI readings in winter wheat (Triticum aestivum L.) was incorporated into the midseason calculation of the response index (RI), RI at harvest was better predicted than with NDVI alone. This study further evaluated the use of CV's collected from both small 1.48 m² and large 17.0 m² areas. Trials consisted of 3 seeding rates by 4 nitrogen rates. Results from this study showed that CV from NDVI readings and plant population were negatively correlated. Improved prediction of RI by utilizing CV was not found. It was however observed that when CV's were less than 5.0 and NDVI values were greater than 0.80 the RI was less than 1.2.     

人工鱼礁的起源和历史

人工鱼礁与海底间的最大静摩擦系数是人工鱼礁安全校核所需的重要参数,对其影响因素的分析可作为人工鱼礁设计优化的科学依据。该研究共设计了6种底面开口比不同的人工鱼礁模型,对5种载荷和5种底质粒径条件下礁体模型的最大静摩擦系数进行了150组平面拉动试验,分析了最大静摩擦系数随底质泥沙粒径、底质含水率、加载质量、礁体底面开口比及开口位置的变化规律。研究结果表明：1)含水率为饱和条件下,底质为砾石和砂质时最大静摩擦系数随底质粒径的减小而增大,底质为粉砂黏土时最大静摩擦系数则明显变小;2)底质为粉砂黏土时最大静摩擦系数随含水率的增加先增大后减小,含水率为35%时最大静摩擦系数达到最大值;3)各底质条件下最大静摩擦系数均随加载质量的增加而减小,随礁体底面开口比的增大而增大,且与底面开口位置无关。     

通径分析在SPSS逐步线性回归中的实现

运用SPSS.17对充分供水状态下老芒麦的蒸腾速率(Evap)、净光合速率(Pn)与环境因子中的光合有效辐射(PAR)、空气中的CO_2浓度(Air CO_2)、空气湿度(RH)、大气温度(AT)、叶面温度(LP)、胞间CO_2浓度(Cint)的关系进行逐步回归分析和通径分析,计算环境因子对蒸腾速率、净光合速率的决策系数。在通径分析前对蒸腾速率、净光合速率进行正态分布检验,对分析结果进行显著性检验,直至回归方程中各变量均达到显著水平。运用相关、偏相关等,从不同角度研究环境因子与老芒麦蒸腾速率、净光合速率的相关性。结果表明:胞间CO_2浓度、大气温度、空气湿度对净光合速率起抑制作用,胞间CO_2浓度、空气湿度对蒸腾速率起促进作用。