下拉秀剖面胡敏素组分特征

采用腐殖质组成修改法和Pallo修改法相结合的方法对下拉秀剖面的胡敏素(HM)进行了分组研究,把铁结合胡敏素(HMi)、黏粒结合胡敏素(HMc)和不溶性胡敏素(HMr)定义为胡敏素组成,同时把HMi/HMc和(HMi+HMc)/HM作为胡敏素的表征指标,研究了不同层位的胡敏素组成.结果表明:不同层位胡敏素组分含量、HMi/HMc、(HMi+ HMc)/HM、E4/E6、△lgK各不相同;多数层位HMr的含量高,HMr的最高值和最低值分别出现在剖面的上下两端;(HMi+ HMc)/HM在(0.20±0.05)～(0.60±0.03)的范围内波动,多数层位可溶性胡敏素组分低于不溶性组分;HMi/HMc在(5.42±0.34～0.46±0.03)的范围内波动,且幅度大,有5个层位＞1;除O层外,剖面各层位的E4/E6总是表现为HMc＞ HMi,但△lgK的变化情形较为复杂,并不总是表现为HMc＞ HMi;现代生草层HMi、HMc的结构较其他层位简单.     

QuickBird影像目视解译法提取切沟形态参数的精度分析

为了研究QuickBird影像提取切沟形态参数的精度,该文选取陕北黄土区吴起县合沟与绥德县桥沟小流域,分别利用同时相的三维激光扫描全站仪和QuickBird影像数据源提取切沟形态参数,分析QuickBird影像提取切沟形态参数的精度,探究误差产生原因。研究结果表明:与三维激光扫描全站仪相比,QuickBird影像目视解译合沟和桥沟小流域切沟面积、周长的平均相对误差都在5%左右;沟缘线边界偏差大于0.6 m(相当于QuickBird影像的一个像元值)的面积百分比的均值都能控制在4%以内;2个小流域中沟长的平均相对误差分别在2%和5%左右,沟长的平均绝对误差分别在0.5和0.75 m左右;目视解译面积、沟长的平均相对误差、最大相对误差、不同解译人员的最大误差与参数值之间都具有显著地负相关,即切沟越大,误差越小;沟缘线附近的植被类型影响目视解译精度,与灌草植被覆盖的小流域相比,草本覆盖的小流域中切沟参数的解译精度更高。总体上来看,QuickBird影像为小流域尺度上监测切沟发育提供了便捷、可靠地数据源。     

大豆叶片三维重建及形变技术研究

目前,对于大豆叶片形态的静态模拟研究很多,并且技术已经比较成熟,但是对于叶片的三维重建以及形变建模技术研究很少,特别是形变建模技术是叶片模拟领域中的一个难题。为此,在已建立的二维大豆叶片模型的基础上,将其重构为三维模型,并提出了叶片形变建模方法,从而得到了更具有真实感的大豆叶片模型。所提出的大豆叶片形变建模方法,可为静态虚拟植物叶片建模研究提供必要的方法,具有一定的实践价值。     

基于“三条红线”的水资源管理模式研究

实行最严格的水资源管理制度是关系到国家可持续发展全局的重大战略问题,也是我国当前经济社会发展的一项紧迫任务。在总结国内外常见的几种主要水资源管理模式的种类和研究侧重点的基础上,探讨了我国水资源管理模式的创新与发展思路,分析了基于“三条红线”的水资源管理模式的内涵和总体框架,提出水资源管理工作的需求,为我国水资源管理模式的变革和发展提供技术支撑。     

Optimization of yield and water-use of different cropping systems for sustainable groundwater use in North China Plain

A groundwater crisis is going on in the North China Plain (NCP), due to the excessive water consumption of the traditional winter wheat (WW)/summer maize (SM) double cropping system (two harvests in one year). In order to improve the water use efficiency in this particular cropping system and to evaluate the sustainability of water usage in Chinese agroecosystems, two field experiments were conducted from October 2004 to September 2006 at two sites of the North China Plain. The field experiments included four treatments: (1) farmers’ practice (FP) with two harvests in one year (WW/SM rotation), (2) FP with reduced input (RI) of water and nitrogen (WW/SM rotation), (3) three harvests in two years (TW, 1st year: WW/SM; 2nd year: spring maize), and (4) continuous spring-maize monoculture (CS) with one harvest per year (spring maize). In the treatments RI, TW and CS, the amount and timing of irrigation and nitrogen fertilization was optimized using TDR based soil moisture measurements and the N_min-method, respectively. Data showed that the utilization efficiency of irrigation water can be improved by optimizing soil water management compared to the traditional water management (FP). However, the groundwater net consumption required for RI still surpassed 300 mm yr⁻¹. Both FP and RI, still overused groundwater resources. The groundwater consumption in the continuous spring maize (CS) was on average 139 mm yr⁻¹. Therefore, the CS system can show the potential to use groundwater sustainably in the long term. Water usage of the TW treatment was in between the water usage of the other treatments. The grain yields in the double cropping systems (FP and RI) were higher than that in the two other systems (TW and CS). But the CS treatment showed the higher W_UE than others.     

最严格水资源管理制度“三条红线”控制指标及确定方法

为实现＂三条红线＂控制目标的具体量化,落实最严格的水资源管理制度,在分析最严格水资源管理＂三条红线＂内涵的基础上,遵循核心性、代表性、系统性、可操作性和可比性等原则,从用水总量控制、用水效率控制、水功能区限制纳污三方面构建＂三条红线＂控制指标体系,并详细阐述每类指标的确定方法,最后将其应用到新密市。     

基于三维打印的型孔排种轮制造技术

型孔排种轮是机械式排种器的核心部件,利用传统方法加工不规则型孔很难满足精度和成本的要求。三维打印（3DP）技术不同于传统加工方法,其是从零件的CAD模型出发,直接打印出物理实体。本文运用三维软件Pro/E对型孔排种轮进行建模,把模型文件导入三维打印机前处理软件内进行分层处理,并通过三维打印机打印出物理实体。三维打印技术缩短了试制时间,并且不受零件复杂程度的限制,制造出的型孔排种轮加工精度满足要求,该技术在复杂农机产品设计与制造中应用前景广阔。     

长江三峡花岗岩坡面林地优先流与地表径流关系

为研究优先流与地表径流的关系,在长江三峡花岗岩坡面,选择了一受人为活动影响较小的天然次生马尾松林地作为试验场地。采用自记流量计记录优先流过程,在小流域出口处设置90°薄壁三角堰和水位计记录了地表径流过程,并对不同层次土壤物理性质进行了测定。结果表明,优先流流量主要决定于产流次雨量及前期影响雨量。优先流峰值总是晚于地表径流峰值出现,从优先流与地表径流峰值出现时间的差异看,优先流的出现使得地表径流峰值出现时间推迟,历时过程延长。当优先流与地表径流流量过程线为双峰时,二者线性关系不明显。当优先流与地表径流流量过程线均为单峰时,二者存在一定的线性关系,其线性关系随着产流次雨量及前期影响雨量的不同而有所差异     

Combined rototilling-stubble-breaking-planting machine

The combined rototilling-stubble-breaking-planting machine suitable for use in the dry farming area in northern China was developed according to the farming mode of water storage and soil moisture conservation and the performance test and production examination were conducted. The machine uses separated structural design, which can conduct combined rototilling-stubble-breaking-planting operations, and can also be dismantled easily into an independent rototilling-stubble-breaking machine and a planter to conduct the rotilling-stubble-breaking operation or planting operation, or one machine for three purposes. The combined rototilling-stubble-breaking machine is connected with the planter via a compensation-type three-point hitch linkage, ensuring good following performance of the planter and high stability of the combined machine. The rototilling and stubble-breaking performances, the seeding stability, uniformity and evenness between rows of the planter and the performance of the fertilizing unit of the machine were measured. Tests showed that the broken stubble rate was 92%; qualified seed spacing rate: maize 85.80%, soybean 86.50%; multiples rate: maize 7.60%, soybean 7.85%; miss rate: maize 6.60%, soybean 5.63%; the coefficient of variation of the spray capacity of the spray nozzles was 5.94% and the coefficient of variation of the total spray capacity 6.00%. All indexes of the machine reached the requirements stipulated in the related national standards.     

基于Malmquist指数法的东北三省玉米生产效率评价

运用Malmquist指数方法,利用2001~2013年东北三省玉米生产的投入和产出面板数据(Paneldata),对玉米生产的全要素生产率进行实证分析。结果表明,东北三省玉米生产的全要素生产率呈增长态势,全要素生产率增长的原因主要在于技术进步的贡献,技术效率在研究阶段变化不大,对全要素生产率影响较弱。黑龙江省的全要素生产率增长在东北三省中最快,其次是吉林省。