简介:TheintegratedeffectofirrigationandagriculturalpracticesonsoilsalinityintheJordanValley(JV),whereover60%ofJordan'sagriculturalproduceisgrown,wasinvestigatedinthisstudyduring2009-2010.Duetothedifferencesinagriculturaloperations,croppingpatterns,irrigationmanagement,andweatherconditions,206top-andsub-soilsamplesweretakenevery1to3kmfromrepresentativefarmsalonganorth-south(N-S)transectwith1to2kmlateralextents.Soilelectricalconductivityofsaturatedextract(EC_(se)),Ca,Mg,K,Na,Cl,andNaadsorptionratio(SAR)weredeterminedinsaturatedpasteextracts.Resultsindicatedthatabout63%ofsoilsintheJVareindeedsaline,outofwhichalmost46%aremoderatelytostronglysaline.AlongtheN-StransectoftheJV,EC_(se)increasedfrom4.5to14.1dSm~(-1)intop-soilsamples.Similarincreasewasobservedforthesub-soilsamples.Themajorchemicalcomponentsofsoilsalinity;i.e.,Ca,Mg,andCl,alsoshowedasimilarincreasealongtheN-Stransectofthevalley.Moreover,comparedtopreviousfieldsampling,resultsshowedthatchangesinsoilsalinityintheJVweredramatic.Inaddition,itwasfoundthatClimposedanexistingandpotentialthreattosensitivecropsin60%ofthesoilsintheJV,whereClconcentrationsweregreaterthan710mgL~(-1).UndertheprevalentaridMediterraneanconditions,improvingthemanagementofirrigationwater,crops,andnutrientinputsandincreasingwaterandfertilizeruseefficienciesshouldbeindispensabletoconserveandsustainthealreadyfragileagriculturalsoilsintheJV.
简介:从薛定谔方程出发,运用简略高等代数方法推导了d电子Coulomb矩阵元(J,K)的Racah参量表示.
简介:一种在二值Hopfield网络中的投影学习算法,推广后得到一种能够在复值多态网络中应用的高效学习算法。新的算法学习效率高、具有扩展性等优点。
简介:为了进一步提高汽车控制系统的动态性能和鲁棒稳定性,从理论上分析并揭示了状态反馈控制中特征向量矩阵的条件数对线性连续定常系统的响应及反馈矩阵Frobenius范数的重要影响。进一步提出以减小特征向量矩阵的条件数为目的来设计状态反馈矩阵。仿真试验结果表明,在相同条件下,特征向量矩阵条件数较小的反馈系统,其暂态过程比较平稳,抗参数摄动的鲁棒性也比较强。这种思想可以应用于具有线性连续定常特性的汽车控制系统中。