宁南旱区苜蓿草地土壤水分消耗规律及粮草轮作土壤水分恢复效应研究   总被引：9，自引：0，他引：9  

刘沛松  李军  贾志宽  于亚军  刘世新 《中国农学通报》2005,21(9):270-274

对宁南旱区不同生长年限紫花苜蓿草地土壤水分消耗及粮草轮作水分恢复效应进行了研究。结果表明:(1)随着苜蓿生长年限延长,在1￣6年内苜蓿草地土壤湿度下降迅速,产草量逐年上升,7年后土壤湿度下降趋于平缓,但苜蓿产草量下降迅速,表明苜蓿生长强烈耗水引起深层土壤干燥化,导致苜蓿生长逐渐衰败,苜蓿平均降水生产效率逐年下降;(2)苜蓿草地土壤垂直剖面可分为降水入渗恢复层(0￣200cm)、根系发达枯竭层(200￣500cm)和根系衰老缓耗层(500cm以下)三个层次。随苜蓿生长年限延长,苜蓿剖面的主要土壤干层逐渐上移,并且干层厚度呈现减小趋势;(3)耕翻的苜蓿茬后轮作粮食作物的年份越长,土壤水分恢复越好,实行草粮轮作的苜蓿最迟不超过生长的第10年。  相似文献   

农杆菌介导的马铃薯茎段遗传转化体系优化研究   总被引：3，自引：0，他引：3  

贾笑英  路平  王蒂 《中国农学通报》2006,22(7):79-81

以甘肃主栽品种的茎段为外植体,研究了不同转化条件(菌液浓度、感染时间、预培养及共培养时间)对转化效率的影响,以及选择压和培养基对抗性出芽的影响,初步建立了马铃薯品种“陇薯3号”和“台湾红皮”的遗传转化体系并获得了转化植株。卡那霉素生根筛选和PCR鉴定结果表明,再生的转化植株假阳性率比较高,要获得预期的转基因植株群体需加大遗传转化工作中转基因植株的数量。  相似文献   

Measurements to Protect Owners'' Benefits under the Non-price Bottom Bidding          下载免费PDF全文

DAI Jia - li  FU Hong - yuan 《保鲜与加工》2007,(1):110-113

Investment on construction projects has become an important factor in improving the development of economy in China.The non-price bottom bidding is a representation that the investment on projects is becoming standardized.During the years of trying out the non-price bottom bidding,the colluding in bidding or bidding below the cost has happened several times,which have damaged the benefits of owners.To solve theses problems,this paper firstly studies the reason of these problems-the failure in the normal relationship between principal and agent.Then,some measures have been presented as follows: building systematic and scientific system of qualification prejudication,judging behaviors of colluding in bidding and bidding below the cost with reason and providing a surety mechanism of the project.The authors hope that these measures are beneficial to non-price bottom bidding.  相似文献   

Strength and Microstructure of Sulphoaluminate Cement Containing Ultra- Fine CaCO3     

ZHOU Shi - hu  HUANG Jia - mu 《保鲜与加工》2006,(4):121-124

The existence of ettringite in sulphoaluminate cement hardened paste is mainly in the form of pole-like crystal,which causes unfavorable effect on the cement.In this paper the strength and microstructure of the sulphoaluminate cement containing ultra-fine CaCO_3 weze discussed.Experimet results show that the strength of sulphoaluminate cement was obviously improved by adding 3% of ultra-fine CaCO_3.After curing for 28d,the compressive strength of cement paste and mortar is 100.6MPa and 94.1MPa respectively,and the bending strength of the mortar reached 12.5MPa.SEM study on hardened paste of sulphoaluminate cement containing ultra-fine CaCO_3 showed that its structure was dense and homogeneous,there was hardly any massive crystall detected.  相似文献   

Analysis on Longitudinal Cracks and Deflection of the Pre-stressed V-shape Slab Roof Structure     

YANG Hong-yuan  FAN Ze-bao  CUI Jia 《保鲜与加工》2002,(3):112-116

In this paper, the finite element method is used to analyze the behavior of the prestressed V-shape Slab Roof structure, especially the effect of temperature change on the stress of slab. The calculated results indicate that when the temperature changes, the tensile stress at the lower extreme fibers of the flange plate near rib exceeds the tensile strength of concrete subjected to the combined action of triaxial stresses and results in the longitudinal cracks of the flange plate. The deflection analysis is based on the mechanical model of the prestressed V shape slab with the longitudinal cracks. The calculated results are in general agreement with the field observations.  相似文献   

Determination to Weighting Coefficient of Combination Forecast Based on Rough Set Theory   总被引：1，自引：0，他引：1  

ZHONG Bo  XIAO Zhi  ZHOU Jia -qi 《保鲜与加工》2002,(7):127-130

The problem of determination to weighting coefficient is a key and difficulty for combination forecast. A method of determining weighting coefficient based on rough set theory is showed in this paper. Determining weighting coefficient is translated into estimating significance of attributes among rough set. A relation data model about combination forecast is established. Knowledge systems are built through making attribute value into eigenvalue. Under data moving, the weighting coefficients of a combination forecast model are computed by analyzing the dependence and significance of forecasting method for the predicted object. The proposed approach overcomes the subjectivity of traditional determination to weighting coefficient, avoids computing linear or nonlinear extremum problem and makes combination forecast more objective. The validity of the proposed approach is verified with a case.  相似文献   

观赏羽衣甘蓝的离体繁殖   总被引：5，自引：0，他引：5  

王怀名  杜广岑 《华北农学报》1995,10(1):64-69

以花蕾为外植体，离体繁殖羽衣甘蓝８个杂各一代材料。培养基为（ｍｇ／Ｌ）：ＭＳ＋ＢＡ１－２＋ＮＡＡ０．１－０．２＋ＩＡＡ０．５＋（或不加）ＧＡ３０．３＋３％蔗糖。平均１８％－６７％的接咎花蕾产生不定芽；药有３０％的不定芽发育成完整植物。培养物的严重褐化和再生植物的普遍玻璃质化是影响植株成活的主要因素。培养基中加入活性炭和青霉素，并给以强光照射，可提高植株成活率。  相似文献   

多效唑在小麦花药培养中应用的研究   总被引：6，自引：0，他引：6  

梁辉  贾双娥 《作物学报》1997,23(2):220-225

在小麦花粉愈伤诱导及分化培养基中,加入一种三唑类化介物---多效唑(MET),对出愈率和绿苗分化率影响不明显,但当其浓度高于2mg/L时,会出现负效应。在小麦壮苗培养基中附加MET3 mg/L,萘乙酸(NAA)0.5mg/L,蔗糖8％,不仅可改善春性小麦花粉植株的生长状态,还可提高花粉苗染色体加倍率。若与将愈伤转入分化培养基以前先在含秋水仙碱250mg/L的MS培养基中处理1天这一方法相配合使用,将会出现更好的加倍效果。冬性小麦花粉植株的壮苗培养基中添加MET,可有效地防止花粉苗在越夏过程中老化,增加分蘖数,从而大幅度提高移栽成活率,但同时花粉植株的染色体加倍率有所下降。  相似文献   

混合器式液化石油气小型发动机性能研究   总被引：7，自引：3，他引：7  

邓宝清  李理光  韩永强  肖宗成  王惠萍  刘巽俊 《农业机械学报》2002,33(3):14-16

通过对汽油机改装的液化石油气发动机进行实验研究，得出了混合器形式对液化石油气发动机的性能有重要影响的结论，优先出既便于控制又有利于动力性发挥的等比例混合器；台架实验表明，通过对压缩比的匹配调整的空燃比的合理控制，汽油机改装的液化石油气发动机不用后处理技术就能满足排放法规和噪声法规，其动力性仅下降4％左右。  相似文献   

采用谐振进气系统的汽油/LPG双燃料发动机     

贾丽冬  陈传举  李翔  李军 《农业机械学报》2006,37(4):38-41

通过计算和台架试验,得出了能使一台汽油/LPG双燃料发动机外特性最大转矩值为最佳的进气谐振管长度。开发出进气谐振管长度二级可变系统,提出了控制策略。应用该系统后,双燃料发动机的额定功率与原机差不多,而最大转矩提高了11.9%(汽油)、4.9%(LPG),外特性最低燃油消耗率降低4g/(kW·h)(汽油)。最后分析了该机以汽油燃料和LPG燃料工作时谐振进气系统对外特性改善效果不同的原因。  相似文献