节水灌溉条件下冬小麦生长期田间氮素迁移转化试验

在节水灌溉的条件下,通过田间现场试验测定了冬小麦生长期田间土壤中铵氮、硝态氮含量的动态分布,分析了田间土壤中氮素的迁移转化规律,为合理施肥提供科学依据。试验结果表明,冬小麦耕层中的营养氮素含量以硝态氮为主,约占８５％多,除用施肥的方法为植物生长提供一定的氮素以外,土壤本底的含量,特别是土壤中有机氮矿化后的无机氮也是植物营养氮素的一个重要来源,在节水灌溉的条件下,冬小麦生长季节硝态氮的深层渗漏微乎其微,但是冬小麦收割后根层中仍有大量的硝态氮,如不合理利用会在汛期因大量降水造成肥料的大量流失,并对地下水构成潜在的威胁。     

设计性实验教学的探讨与实践

基于强化设计性实验教学效果,结合材料成型与控制工程专业的设计性实验研究与教学,阐述了设立科研型、实际生产型设计性实验项目,采用设计性实验方案设计、审阅、实验准备、实施、考核等规范的实验教学模式,结合开放式实验教学、"按计划、分批次"的形式合理安排实验进程,通过"文件评分"和"现场评分"的考核方式,辅以细化的考核内容进行实验成绩考核等主要手段,并在实际教学中取得了较好的效果,提高了应用型人才的培养质量,对高校设计性实验教学进行了有益的探讨和总结。     

从吕梁市3个小水库的安全鉴定看小水库的安全评价

从吕梁市临县薛家圪台水库、孝义市梁家垣水库、石楼县王村水库的水库安全鉴定出发,分析了3个小水库安全评价中出现的问题,提出了水库改造的建议。     

Selection of Dispersivity in Groundwater Risk Assessment

The Domenico model is used in combination with ASTM E 1739 in a Tier 2 risk assessment of chlorinated organic solvents contaminated groundwater sites to predict potential contaminant concentration in groundwater down-gradient from the point of exposure (POE). A knowledge of the dispersivity parameters is necessary for carrying out this calculation. A constant longitudinal dispersivity of 10 m is often used in analytical and numerical calculation. However, because of the scale effect of dispersion, two other main approaches are currently often used. From the viewpoint of conservative principle in risk assessment, it is necessary to determine which dispersivity data will give a higher predicted concentration, corresponding to a more conservative risk calculation. Generally, it is considered that a smaller dispersivity leads to a higher predicted concentration. This assumption is correct when dispersion is the only natural attenuation factor.However, degradation of commonly encountered chlorinated organic solvents in environment under natural condition has been widely reported. Calculations given in this paper of several representative cases show that a general consideration of the influence of dispersivity on concentration prediction is not always correct when a degradation term is included in the calculation. To give a conservative risk calculation, the scale effect of dispersion is considered. Calculations also show that the dispersivity parameters need to be determined by considering the POE distance from the source, the groundwater velocity, and the degradation rate of the contaminant.     

机器人,离我们远么

小时候,几乎每个人都玩过机器人玩具,都喜欢看动画片里的机器人战士。如今,诸如《变形金刚》之类展现机器人魅力的科幻大片仍深受大众喜爱。那么,看了多年科幻大片中的机器人,现实中的机器人离我们的生活究竟有多远？带着疑问,让我们一同到人气十足的浙江科技馆机器人展区来寻找答案吧。     

Capillary-Tube Model and Experiment of Multiphase Flow in Capillary Fringes

IntroductionUrbanization and industrial activities havesignificant potential to cause soil and groundwatercontamination through leakage,spill and disposalof industrial and household chemicals.Organicchemicals are used everywhere in the world andbecause most are very toxic to human beings anddo not easily degrade naturally[13] ,theircontamination of the soil and groundwater iscausing more and more problems worldwide.　Many contaminants are organic liquids with lowwater miscibility,which may mov…     

机械工程材料课程实验教学改革

对机械工程材料课程实验教学中存在的不足进行了分析。从提高学生创新思维能力、综合设计能力及动手能力的目标出发,对该课程实验教学进行了改革,在实验类型、方法、手段及考核方法等方面作了有益的探索与实践。     

B对Zr-Ti-Ni-Cu-Be块状非晶合金热稳定性的影响

利用X射线衍射(XRD)及差热分析(DSC)等方法研究了添加B对Zr Ti Cu Ni Be块状非晶合金的形成、结晶及热稳定性的影响·结果表明:在Zr Ti Cu Ni Be合金系中添加B可明显改变该合金的玻璃转变温度Tg,一次结晶温度Tx及过冷液相区ΔT等参数·当y(B)≤3%时,B的添加可使合金保持块状非晶,提高Tg、Tx并扩大过冷液相区,使非晶热稳定性增加;当y(B)≥6%时,B的添加将诱导大量的粗大Zr2Cu及ZrB2等晶体的析出·由于它们非纳米晶,尺寸较大,形状不规整,不能作为非晶复合材料的增强体·