基于O-ring统计的公路边坡土壤优先流路径分布分析

引入优先流理论分析氯盐污染物在边坡土壤中的迁移机制,对揭示公路工业盐污染物迁移规律和保护路域环境具有重要意义。以鹤大高速低路基公路边坡土壤为例,采用染色示踪试验对土壤优先流路径的位置进行确定,并应用景观生态学中的空间点格局分析方法O-ring统计,对不同影响半径土壤优先流路径水平分布特征及其空间关联性进行分析。结果表明:边坡土壤优先流路径发育深度可达40 cm;相同影响半径优先流路径的数量随着土层深度的增加而减少,同一土层优先流路径的数量随影响半径的增大逐渐减少;随着影响半径的增加,聚集分布趋于显著;不同影响半径的优先流路径之间的关联性相对独立。O-ring统计,能从统计学角度量化分析土壤优先流路径的分布特征,丰富了优先流的研究方法。     

天津市特色农业推进路径研究

随着农产品消费转型升级,特色农业发展日益升温。天津市发展特色农业具有得天独厚的资源环境优势和市场优势。文章在分析天津市特色农业发展现状与存在的问题的基础上,从推进特色农业全产业链开发、推进特色农业品牌化发展、推进特色农业产业集群化发展、提升特色农业科技化水平、提高特色农业发展的组织化程度等方面提出了推进天津市特色农业发展的路径。     

Designing recreational trails in a forest dune habitat using least-cost path analysis at the resolution of visitor sight distance

Dune plantation forests are typically used for recreation. However, the soil and vegetation of these forests are sensitive to trampling. Therefore, recreational trails should have clearly defined boundaries. The aim of this study was to test a cell-based survey for the alignment of interpretative trails in sand dune plantation forests, where each cell of a sampling grid is surveyed in the field at a grain size of 10-m, which is an appropriate scale for both visitors and to accurately assess vegetation and stand structure. The alignment of the trail was then performed using a combined least-cost path algorithm with GIS-based land suitability analysis. Using this approach, sets of key factors for land suitability and visibility which are generally applicable to dune plantation forests were identified. Specific criteria were adopted to score and weigh each factor in this case study, where each of the 284 cells of a 10-m grid were surveyed for two weeks in a coastal urban reserve located in one of the major tourist beach resorts of the Mediterranean basin (Bibione, Northern Italy). The factors surveyed in the field were used to calculate the potential trail index, and the least-cost path method was used to optimally align the trail in order to achieve the lowest cumulative resistance value possible. The novel cell-based survey did not require the conversion of any land suitability layers to their raster counterpart grids, as the grain and resulting alignment of the trail were scaled to the neighbourhood of the users. In addition, we did not focus on the concept of the patch, as we were not interested in reclassifying the surveyed attributes, as features were originally collected at the scale of the walking paths. We conclude that the proposed method is a feasible approach, and amenable to situation where a fine-grained alignment of recreational trails is required, and/or when a careful assessment of a trails’ environmental impact is needed.     

玉米秸秆在亚/超临界环己烷中的液化过程与机理

为了提高玉米秸秆液化收率、研究其液化机理,该文在反应温度260～320℃、反应压力2～4.5 MPa的试验条件下,研究玉米秸秆在亚/超临界环己烷中的液化行为,考察反应温度、环己烷用量和反应停留时间对液化行为的影响。结果表明：反应温度、环己烷量和反应时间对裂解产物的分布均有较显著的影响。温度增加,残渣和重油产率分别降低4.9%和3.34%;环己烷用量增加,残渣量呈现先降低后增加的趋势;反应停留时间的增加有利于残渣产率的降低和气体、轻油产率的增加,但达到40 min以上后呈平稳的趋势。并用GC-MS分析液化产物,探讨液化产物的变化规律,证明秸秆中纤维素、半纤维素和木素在亚/超临界环己烷中发生裂解液化,生成以吡喃衍生物、有机酸为主的轻油,和以酚类及其衍生物为主的重油,同时发现环己烷具有供氢重整作用,液化过程中也存在二次反应,依此建立木素在亚/超临界环己烷中的液化反应路径和集总产物反应网络。     

我国现代农业科技创新体系构建:特征、现实困境与优化路径

我国现代农业发展亟待实现创新驱动和内生增长,现代农业科技创新体系是实现我国农业现代化和农业经济持续增长的重要战略支撑,它既具有公共性、社会性、多元性、系统性及开放性等鲜明特征,也是破解我国城乡二元经济结构、突破农业现代化短板的内生驱动力。但目前我国现代农业科技创新体系正面临着农业科技创新体制与管理机制障碍、农业科研与农业生产脱节、农业科技推广与服务体系不健全以及农业科技创新激励机制与风险补偿机制匮乏等现实困境。为此,应采取建立协同创新机制、加强产学研结合、构建农业科技创新动力机制、加快科技成果转化、构建"三位一体"的农技推广服务体系、创新农业科研投入政策体系及建立商业化育种创新机制等优化措施,来促进我国现代农业科技创新体系的建立和完善。     

两级径向流蜿蜒式磁流变阀结构设计与动态性能分析

设计了一种具有复杂液流通道结构的两级径向流蜿蜒式磁流变阀,其液流通道主要由2段圆环轴向流、4段圆盘径向流及3段中心小孔流组成。阐述了两级径向流蜿蜒式磁流变阀的工作原理,并推导了其压降数学模型。采用有限元法(FEM)对两级径向流蜿蜒式磁流变阀电磁场进行了建模仿真,分析了磁流变阀压降变化规律,仿真结果表明加载电流为0.8 A时压降为5.81 MPa。搭建了磁流变阀压降性能及响应特性测试实验台,对不同加载电流及不同模拟负载下的磁流变阀压降性能进行了实验分析,结果表明加载电流为0.8 A时压降可达5.77 MPa,与仿真结果基本相符。同时,对磁流变阀压力响应时间进行了测试分析,实验结果表明所设计的磁流变阀响应迅速,响应时间在3~7 ms之间;并且响应上升时间比下降时间短;负载对响应时间没有影响;激励电流越大,响应越快。     

我国“互联网+水产养殖”发展现状与路径研究

"互联网+"作为国家发展战略正与我国渔业进行广泛而有深度的融合,"互联网+水产养殖"已呈现出加速发展的态势,这对促进我国渔业转型升级,实现渔业转方式调结构的发展目标具有强大的推动作用。本文在阐述"互联网+水产养殖"内涵的基础上,从互联网与水质环境监测、水生动物疾病诊断、渔情信息动态采集、水生动植物病情测报、水产品质量安全追溯监管、渔技服务、金融保险等水产养殖的生产、管理、服务方面入手,分析了我国"互联网+水产养殖"的发展现状。当前存在的主要问题是认识不足、缺少投入、重复开发、人员素质较低等,建议从认识水平、投入机制、开发规范、扶持政策方面加以着力,建设相关标准体系、运行体系、应用体系、保障体系、管控体系、大数据平台以及基础网络、综合办公系统,推动我国"互联网+水产养殖"进一步向前发展。     

Analyzing organic matter composition at intact biopore and crack surfaces by combining DRIFT spectroscopy and Pyrolysis‐Field Ionization Mass Spectrometry#

In the clay‐illuvial horizons (Bt) of Luvisols, surfaces of biopores and aggregates can be enriched in clay and organic matter (OM), relative to the bulk of the soil matrix. The OM composition of these coatings determines their bio‐physico‐chemical properties and is relevant for transport and transformation processes but is largely unknown at the molecular scale. The objective of this study was to improve the interpretation of spectra from Fourier transform infrared spectroscopy in diffuse reflectance mode (DRIFT) by using thermograms and released ion intensities obtained with pyrolysis‐field ionization mass spectrometry (Py‐FIMS) for a more detailed analysis of the mm‐scale spatial distribution of OM components at intact structural surfaces. Samples were separated from earthworm burrow walls, crack coatings, uncoated cracks, root channels, and pinhole fillings of the Bt‐horizons of Luvisols. The information from Py‐FI mass spectra enabled the assignment of OM functional groups also from spectral regions of overlapping DRIFT signal intensities to specific OM compound classes. In particular, bands from C=O and C=C bonds in the infrared range of wave numbers between 1,641 and 1,605 cm^?1 were related to heterocyclic N‐compounds, benzonitrile, and naphthalene. The OM at earthworm burrow walls was composed of chemically labile aliphatic C‐rich and rather stable lignin and alkylaromatic compounds whereas the OM of thick crack coatings and pinholes was dominated by heterocyclic N and nitriles and high‐molecular compounds, likely originating from combustion residues. In combination with Py‐FIMS, DRIFT applications to intact samples seem promising for generating a more detailed mm‐scale spatial distribution of OM‐related sorption and wettability properties of crack and biopore surfaces that may serve as preferential flow paths in structured soils.     

三峡地区阔叶林地植物根系分布特征与优先路径关系分析

优先路径研究是研究地下水分运动的重要环节。本文通过亮蓝染色示踪试验法直接观测并区分林地土壤基质和土壤优先路径,分别对染色区和未染色区观测到的土壤优先路径、植物根系根长密度和根重密度进行分析,研究发生土壤优先流过程中植物根系的作用及由植物根系形成的优先路径的联通情况。研究发现,降雨强度越大,优先路径染色区的表层呈现越加明显的宽区域聚集分布。雨强为25 mm/d时,样地土壤染色区域表层大区域优先路径聚集分布厚度平均为50 cm。根径 > 5 mm的根系根长密度的大小对土壤孔隙的大小影响显著,根径 < 5 mm的根系根长密度的大小对于土壤孔隙的联通有明显作用。此外,土壤中植物根重密度的大小与优先路径数量和联通程度正相关,根重密度越大越有利于构成优先路径,有利于形成优先流。不同样地两区域植物根重密度在土壤10—20 cm和30—40 cm深度范围内具有极显著差异（P < 0.05）,而优先路径在30 cm深骤然减少。此方法在一定程度上可为优先路径的研究提供新的借鉴和参考。     

新型农村合作医疗制度运行中的制约因素与改进路径

新型农村合作医疗制度自运行以来取得了较好的社会成效,但是在运行的过程中也暴露出一些问题：在制度设计上,以大病统筹为主,致使参合农民受益面过窄;以收定支,自愿参加,造成新农合基金结余率居高不下;实际运行中,资金筹集难度大、成本高,管理存在缺陷;对定点医疗机构缺乏行之有效的约束;农村医疗设施落后,服务能力薄弱。针对这些问题,提出了相应的制度改进建议：完善制度设计,扩大受益面;广开筹资渠道,降低筹资成本,加强基金监管;加大对定点医疗机构的监管力度;切实提高农村医疗卫生服务能力。