堤防隐患雷达图像的RB-NN融合

在运用探地雷达进行堤防隐患探测的过程中,为了识别雷达波散射图谱中的隐患特征,运用径向基神经网络对图像进行滤波融合。图像融合的对象为采用探地雷达技术获取的堤防模型内部的雷达波散射图谱,同时也包括采用时域有限差分方法对堤防隐患模型进行的正向模拟演算图谱。试验结果认为：径向基神经网络方法的非线性映射特征明显,聚类分析能力强,对多维特征的雷达图谱数据拟合具有良好的适用性。针对含有较多突变点、漂移点、缺失点的样本,径向基方法表现出较好的逼近性能,且计算过程简洁、时间成本低、数据收敛的可靠性强,能够满足图像融合及可视化分析的需求,为堤身隐患雷达图谱的特征识别提供技术支持。     

新混凝土与碳化混凝土黏结抗折强度试验研究

新老混凝土黏结的黏结抗折强度试验研究表明,混凝土碳化后,混凝土强度增强,新老混凝土黏结抗折强度也增强。水泥净浆界面剂(CON1)、硅灰界面剂(CON2)、减水界面剂(CON3)、减缩界面剂(CON4)和膨胀界面剂(CON5)对新老混凝土黏结抗折强度的影响试验研究表明,养护龄期为28 d时,新老混凝土黏结抗折强度从大到小所用界面剂依次为CON1、CON5、CON4、CON3、CON2。     

Safety of vegetables and the use of pesticides by farmers in China: Evidence from Zhejiang province

In China there are great challenges to ensure the safety of vegetables, as highly toxic pesticides, which are more than likely to cause high pesticide residues in vegetables [Zhang, Y., Ma, J., Kong, X., & Zhu, Y. (2004). Factors that affect farmers’ adoption of non-pollution and green pesticides: Empirical analysis based on data from 15 countries (cities) in Shanxi, Shaanxi and Shandong province. Chinese Rural Economy, 1, 41–49], are still used in the production of vegetables by vegetable farmers. Based on a survey of 507 vegetable farmers from Zhejiang Province, this study attempted to identify and control the vegetable farmers who were at risk of spraying highly toxic pesticides onto vegetables in China. We found that farmers who were older and less educated and unspecialized vegetable farmers were more likely to use highly toxic pesticides. Our statistical results also indicated that vegetable farmers who received less training and selected handlers as their marketing channel had a tendency to apply highly toxic pesticides, whereas cooperative members were less likely to use these pesticides. Finally, vegetable farmers who had a poor understanding of vegetable safety issues were more likely to use highly toxic pesticides. Policy implications to control the use of highly toxic pesticides and ensure the safety of vegetables in China are discussed.     

Polydopamine microparticles as redox mediators for catalytic reduction of methylene blue and rhodamine B

Mussel-inspired polydopamine microparticles (PDA MPs) were prepared and found to act as redox mediators for the catalytic reduction of methylene blue and rhodamine B by NaBH₄. The presence of quinone moieties in the PDA MPs rapidly channeled the electrons derived from the electron donor (NaBH₄) to the dyes, resulting in increased decolorization of the dyes.     

南谷洞水库大坝沥青混凝土防渗斜墙修补加固

在南谷洞水库大坝除险加固施工中,采用优化的沥青混凝土配合比,用改进的公路沥青混凝土拌和站制备沥青混合料,并用先进的沥青混凝土专用斜坡摊铺机LMP-3进行了坝面沥青混合料摊铺,确保了铺筑的质量。质量检验表明:南谷洞水库大坝沥青混凝土防渗坝面施工质量优良,其施工技术和经验可供国内类似工程参考。     

龙刘水库联合运用对黄河上游径流量变化的影响

为分析龙刘水库联合运用对黄河上游径流变化的影响,选取黄河上游八个水文站1950~2009年径流资料,根据水量平衡原理还原水库运用后径流序列,采用Mann-Kendall趋势分析法、突变检验法及小波分析法,分析了龙刘水库运用前后兰州站与下河沿站实测与还原年径流量的变化特征。结果表明,实测与还原序列都存在显著的下降趋势,实测序列突变年份为1987年,还原序列为1990年;实测序列与还原序列都存在3~5、6~9、14~17、23~27年四类周期变化尺度,兰州站与下河沿站实测径流序列的主周期都依次为25、16、8和4年,兰州站还原序列主周期依次为23、8、4年,下河沿站还原序列主周期依次为24、4、8年。说明龙刘水库的联合运用加剧了径流序列下降的趋势,有促使序列突变提前的可能性,且对径流序列的周期变化产生了一定的影响。     

膨胀土渠道边坡有限元分析

针对某膨胀土渠道边坡的滑坡现象,采用有限元方法进行了滑坡分析,分别考虑了边坡在自重以及在自重和土体水渗流共同作用下的工况。明晰了滑坡产生的原因,为现有的类似边坡评定其滑坡可能性提供一定的参考价值。     

植被覆盖度的提取方法研究综述

常用的植被覆盖度估算方法有地表实测和遥感监测两种,分析其特点及适用范围,得出如下结论:地表实测法由于人力、物力等诸多因素的制约,不适合在较大范围内作为唯一的测量方法推广,但可以对遥感监测精度评价和验证提供基础数据。回归模型法小范围内有较高精度,但对实测数据的依赖性较强。植被指数法与像元分解法,由于不受实测数据的制约,目前使用比较广泛,但在实际应用中,仍应根据地表情况,与其他方法综合使用,以便提高植被覆盖度提取精度。     

Two normal form theorems for CSP programs

We define two normal forms for CSP programs. In the First Normal Form, each process contains only one I/O repetitive command and all its I/O commands appear as guards of this command. In the Second Normal Form, all guards of this I/O repetitive command are I/O guards. We describe an inductive method that transforms any CSP program into an equivalent program in first or second normal form. The notion of equivalence is discussed. It is shown that no transformation into second normal form can preserve deadlock freedom.     

盐冻作用下玄武岩纤维混凝土力学性能损伤研究

针对西北寒旱地区混凝土结构易开裂耐久性降低的问题,选取力学性能优异的玄武岩纤维作为混凝土增强材料,采用室内快速冻融试验,以纤维体积掺量为变量,研究了不同纤维体积掺量(0.05％、0.1％、0.15％、0.2％)混凝土试件分别在清水、质量分数为3％的NaCl溶液、质量分数为5％的Na2 SO4溶液冻融作用下动弹性模量、抗...