农业可持续发展评价指标体系分析评价

农业可持续发展评价指标体系是科学评价农业可持续发展的工具,是引导农业可持续发展的技术体系。通过查阅大量文献,阐明了其建立的一般过程与方法,并对国内外农业可持续发展评价指标体系的框架建立、研究层次、指标选取及实证评价进行分析。结果表明,在框架建立上,国内外建立方法基本一致,多为层级性结构;在研究层次上,国外在区域、作物、农场、农户水平都有研究,国内基本只集中在区域水平;在指标选取上,国外在社会、经济、生态3类指标中最偏重生态类指标,如氮、磷平衡,农药、杀虫剂风险等;国内3类指标并重,如农业产值、灌溉水、化肥和农药的使用等;在实证评价上,国外在政策指导及耕作实践指导2个方面都有研究,国内多集中在政策指导方面的实证评价。     

Passive-source ocean bottom seismograph （OBS） array experiment in South China Sea and data quality analyses

Long-term passive source ocean bottom seis- mograph （OBS） observatory is challenging due to various technical difficulties. In order to gain experience in this field, and to reveal the lithospheric structure beneath the extinct ridge in the central South China Sea （SCS）, we carried out a passive source OBS array experiment, which includes 18 OBSs, in the deep portion of SCS. Here we present the instrumentation, the OBS deployment and recovery of this experiment, and more importantly, the data quality evaluated by a number of approaches. Through processing and inspecting waveforms from global, regional and local earthquakes, we find that most of recovered OBSs have good data quality with discernible main phases. The ambient noise analyses of OBS recordings show that their noise is higher than the global average, and the horizontal component is noisier than the vertical, indicating current impacts on horizontal components are more severe. In the period range of 5-10 s, there is a noise notch for the SCS OBSs, and noise levels of horizontal components are comparable to the vertical. This feature, which is not seen at OBS stations in open ocean, suggests the distant sources for double frequency microseism in this marginal sea are not significant. In addition, we successfully determined the orientations for 7 OBSs by investigating their Rayleigh wave polarizations; and we demonstrated the dispersion feature of Rayleigh waves through the frequency-time analysis. Finally, we summarized lessons learned from this experiment regarding the passive source OBS investiga- tions in SCS.     

大动态范围CMOS图像传感器像素单元的设计

设计了CMOS图像传感器的像素单元,通过将光电二极管的光电压与参考电压比较,产生控制信号来调节积分时间,可实现随光强自动调节的光电响应,在低照度下实现线性光电响应,高照度下实现对数光电响应．其中参考电压由存储于RAM中的数据通过DAC读出产生．该像素单元采用Chartered 0．35μm工艺设计,仿真结果表明该像素结构可使CMOS图像传感器的动态范围达到126dB．     

浅谈锉配技能的教学过程

锉配是钳工教学中的综合课题,教材中只是简单地说明了锉配的概念,而没有对锉配的学习方法作系统的叙述,给锉配教学带来许多不便.文章提出教师运用灵活有效的方法施教,包括直观式教学法、启发式教学法和实践式教学法等,并在教学过程结束后能够认真完成配合件的测评工作,做好教学总结,以提高学生分析、判断、综合处理问题的能力,尽快掌握操作技能.     

A new anti-hypoxia functional agent ―a Schizophyllum commune fermented broth and its possible biochemical mechanisms

In order to overcome hypoxia induced sickness,a stable source of anti-hypoxia functional agents, Schizophyllum commune fermented broth has been developed in this study. Animal experiments were conducted to examine its anti-hypoxia activities and possible mechanisms involved. The acute hypoxic experiment showed that Schizophyllum commune fermented broth could significantly prolong the survival time of mice. The underlying mechanisms were associated with improved energy metabolism based on a study carried out in rats exposed to a low pressure chamber simulating the low pressure environment of 8 000 m altitude. It was concluded that the Schizophyllum commune fermented broth was an effective anti-hypoxia functional agent and could be greatly bene- ficial to those living and working at high altitudes,such as people who reside in the reconstruction regions of Yushu.     

模拟隧道衬砌混凝土湿度演化规律

为了准确分析地下隧道衬砌混凝土内部湿度的演化特征,建立了用以计算江底隧道衬砌混凝土湿度时变规律的湿度模型,并对模拟隧道衬砌混凝土的试件进行了温湿度试验.数值计算与试验结果表明:所建立的考虑胶凝材料水化影响的湿度演化模型可以很好地对地下隧道衬砌混凝土的湿度分布特征进行预测和分析;在距离蒸发面较近的100 mm位置处,衬砌混凝土内部湿含量变化受扩散过程影响较大,在距离蒸发面较远的位置处湿含量时变主要是胶凝材料水化耗水所致;模型还预测了隧道衬砌服役10年时,距离蒸发面为100 mm以内的部分湿度均与环境湿度达到平衡;随着地下衬砌混凝土服役年限的延长,其内部湿度梯度逐渐向饱水面推进.     

某桥梁断桩事故的原因分析和处理对策

某桥梁桩基发生断桩事故,通过施工过程、现场取样等进行了致因分析,进而进行善后处理.提出了一些工程建议,为相似条件工程桩基施工提供技术参考.     

CEV模型下平方障碍期权定价的数值算法

讨论一种变异期权-收益结构为平方的障碍期权,在股票价格服从不变方差弹性(CEV)模型下,采用Crank-Nicolson差分格式,给出具体的数值算例,并验证了算法的有效性,最后分析障碍对期权的影响.     

新疆农产品质量安全发展现状与对策

农产品质量安全直接关系到消费者的生存、生活和健康,越来越受到人们的普遍关注.主要分析了新疆农产品质量安全发展现状,并有针对性地提出了发展对策,要完善农产品质量安全监督管理法规体系、加快农业标准体系建设、依法开展农产品质量安全检验检测等.     

一种长距离浆体输送管道拒雷控制系统的设计

针对长距离矿浆管道输送存在的雷击灾害,提出了一种基于长距离浆体输送管道的拒雷控制系统,其系统包括浆体钢管、机电设备、综合有源+无源等离子拒雷装置和多个电涌保护器.在浆体钢管与机电设备之间的绝缘段的两侧分别安装第一电涌保护器和第二电涌保护器,采用瞬态接地的方式来实现等电位接地,克服了强制电流式阴极保护的矿浆钢管道不能直接接地的缺陷,同时防止了雷电侵入波对设备铁精矿管道的危害.实际应用表明了该方法的有效性.