天然气发动机燃烧过程非线性动力学特性

利用非线性动力学数据分析技术对增压中冷天然气发动机燃烧过程的动力学特性进行了研究,结果表明:混合气浓度从当量比=1.00降低到稀燃极限时由缸压时间序列重构的二维相空间中,系统运动轨线都是有限范围内的非周期运动,轨线具有复杂、扭曲、重叠的几何结构;无论发动机是在当量混合气还是稀燃极限条件下运行,嵌入维m大于某一值以后,吸引子的关联维D均能达到饱和值且为分数,随着混合气变稀,燃烧循环变动增加,D逐渐增加,当=1.00、0.77、0.70和0.63时D分别为1.27、1.33、1.58和1.87,最大Lyapunov指数(LLE)大于零,分别为0.008 6、0.011、0.013和0.015 7,因此天然气发动机燃烧系统是一个低维非线性混沌系统。     

滴灌条件下灰枣施肥效应研究

以滴灌为条件设置不同水肥处理,通过施肥模型建立与分析,研究氮磷钾施肥配比对灰枣产量与品质的影响。结果表明：在设计水平范围内,土壤中适量增施氮、磷肥能提高灰枣果实单果重和产量;增施钾肥可提高枣果中还原糖和Vc的含量,增施氮肥则可提高蛋白质的含量;氮、磷、钾三因素对灰枣产量以及糖度、Vc含量的作用顺序为：施钾量〉施磷量〉施...     

Suitability of Multi-Agent Simulations to study irrigated system viability: application to case studies in the Senegal River Valley

It is assumed that Agent-Based Modeling is a useful technique for water management issues. In particular, it may provide a suitable framework for representing irrigated systems. The objective of this paper is to demonstrate its potential for a specific use: research on irrigated systems’ viability in the Senegal River Valley. The main assumption to be verified is that Multi-Agent Systems constitute a suitable architecture to study theoretically irrigated systems’ viability using simulations. By using Multi-Agent Systems, virtual irrigated systems can be designed that might then be used as virtual laboratories. These virtual labs constitute an alternative when real labs cannot exist for some reason.

In this paper we report on experiments we have conducted using such virtual labs for exploring an Agent-Based Model through the simulation of scenarios. A scenario is defined as a triplet: an environment, a set of individual rules, a set of collective rules. It is evaluated according to the longevity of the irrigated system. An index is defined, based on the ratio of long-enduring simulations among a set of repetitions of a given scenario. Even if simulation results display significant diversity for a given scenario due to random factors in the processes simulated, the ratio of long-enduring simulations is repeatable. This entails to explore the overall behavior of the virtual irrigated system and to build theories concerning the viability of Senegalese irrigated systems. An example is given showing the need for strong coherence for a given environment among individual rules and collective rules.     

The effect of salinity on corn yield using the CERES-maize model

In most cases, when calculating soil water availability, only thewater content is considered. The effect of salinity on the wiltingpoint is neglected. The objective of this work is to use asimulation model (CERES-maize) in order to predict cornyields as a function of water salinity under severalenvironmental, agrotechnical, and plant characteristics. A modelis presented in which the wilting point is a function of the soilsalt content. At high salinity, the water content at wilting pointis higher than at low salinity, resulting in an insufficient amountof available water and, therefore, a reduced yield. The modelwas used to simulate several theoretical and experimentalsituations for forage corn and grain corn. Simulation resultsshowed that nitrogen fertilization increases the salinity thresholdvalue and the yield sensitivity (rate of yield reduction per unitof salinity). The also showed that forage corn is more sensitiveto salinity than grain corn. If the soil is not leached, a heaviersoil texture has a higher salinity threshold value. On the otherhand, if the soil is leached, the soil texture has no influence onthe salinity threshold value and the yield is less sensitive tosalinity in sandy soils. The determination coefficient (r²= 0.75) indicated that the results of the simulations were in goodagreement with the field data.     

水、氮效应与叶绿素关系试验研究

以冬小麦和夏玉米为试验对象，研究了不同水、氮条件对作物植株含氮及叶绿素含量的影响，作物叶片含氮、作物产量与叶绿素含量之间的量化关系，并提出了利用叶绿素仪预测作物氮素胁迫的方法。研究结果表明，田间的不同水、氮制度将影响作物的含氮水平及叶绿素含量，它们之间呈正响应关系。氮素对作物叶绿素含量起着较强的影响作用。作为一种测量叶片叶绿素含量的仪器，叶绿素仪可以作为测量作物含氮的仪器使用，具有快速、准确、简便的特点。     

组合预测方法及其在粮食产量预测中的应用

提出了一种组合预测方法，以“预测偏差绝对值的和最小”为标准，用线性规划确定组合权系数的最优加权算法，对青海省的粮食总产量进行了预测分析。结果表明，此模型具有较高的精度。     

Changes in Physical Properties of Soils with Land Use Time in the Brazilian Savanna Environment

Soils from central Brazil have been intensively used over the last decades because of the rapid conversion of savannas ( Cerrado ) into corn/soybean fields. The objective of this work is to study modifications in the physical properties of soils in the Rio Verde watershed, as a function of the land use time for agriculture, determined from classification of Landsat satellite images between 1980 and 2010. Soil samples were collected at surface (0–20 cm) and subsurface (20–40 cm) horizons for the different classes of land use time (<10, 10–20, 20–30, and >30 years). The following physical properties were measured: bulk density (BD), air permeability (K_a), penetration resistance (PR), microporosity (MI), macroporosity (MA), and total porosity (TP). Results showed a strong expansion with time of agriculture that occupied 35·3% (1980), 37·4% (1990), 51·3% (2000), and 60·9% (2010) of the watershed area. When properties were compared with those from the reference areas (preserved soils under native vegetation), significant differences were observed for all the physical attributes of soils for a land use time higher than 20 years. Overall, BD and PR increased with land use time, and the opposite was verified for K_a, MA, and TP. Some physical properties presented values (e.g., 1·54 g cm⁻³ for BD and 0.06 cm³ cm⁻³ for MA) close to the critical ones reported to affect crop development, but they were not still impacting on local soybean yield. Copyright © 2013 John Wiley & Sons, Ltd.     

基于拉格朗日的冗余驱动并联机构刚体动力学建模

针对4-UPS-RPU 4自由度冗余驱动并联机构的刚体动力学建模问题,基于拉格朗日方程建立冗余驱动并联机构动力学模型。首先,推导出4-UPS-RPU冗余驱动并联机构系统的动能表达式、势能表达式和作用于并联机构非保守力的等效广义力;然后,应用拉格朗日法建立4-UPS-RPU冗余驱动并联机构的动力学模型,为并联机构驱动力的求解以及整个机构的动力学分析奠定基础;最后结合算例,采用Matlab编程对动力学模型进行数值计算并绘制了机构驱动杆驱动力变化曲线,将上述分析结果与ADAMS虚拟仿真结果对比验证了所建动力学模型的正确性。研究不仅为4-UPS-RPU 4自由度冗余驱动并联机构动力学优化设计和控制等后续研究提供了理论依据,也为其他冗余驱动并联机构的动力学建模提供了可行的方法。     

河北省利用秸秆发电的现状研究

随着世界经济的发展,资源的短缺和环境的恶化成为各国关注的目标,同时解决这两个问题的一个有效方法是利用秸秆发电.河北省结合本地区经济发展情况和秸秆产出量与利用情况,首先在晋州市建立了秸秆发电厂.为此,阐述了秸秆发电的工作原理及其工作流程,分析了该地区建厂的可行性,进行了投资回收期和收益率的分析.最后得出了在晋州建立秸秆发电厂的可行性结论,为今后我国在各个地区建立秸秆发电厂提供了可靠的理论和数据依据.     

海冰水灌溉对玉米产量影响的研究

以玉米为对象,分别进行了盐度为0.1%、0.3%、0.5%和0.7%海冰水灌溉试验。结果表明:盐度为0.3%海冰水以450 m3/hm2灌溉时,能减轻作物干旱胁迫,增产效果显著,但灌水量增加到900 m3/hm2和1350 m3/hm2时反而减产。盐度达到0.5%时,3种灌水量处理比0.3%盐度900 m3/hm2处理区,减产9.5%、10.8%和18.4%。当海冰灌溉水盐度为0.7%灌水量1350 m3/hm2时,产量接近全旱处理区产量水平。玉米经不同盐度海冰水灌溉,产量差异达显著水平。