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82.
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
83.
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
84.
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
85.
Determination to Weighting Coefficient of Combination Forecast Based on Rough Set Theory 总被引:1,自引:0,他引:1
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
86.
观赏羽衣甘蓝的离体繁殖 总被引:5,自引:0,他引:5
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
87.
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
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
88.
89.
90.
提高渠系水有效利用系数能否节约水资源取决于渠系渗漏的水是否都转化成了被重新利用的地下水。本文建立了提高渠系利用系数的节水效果的计算公式,并进行了理论分析和实例计算。结果表明,虽然提高渠系利用系数的节水效果没有原来不考虑渠系渗漏水重新利用时简单估计的大,但仍然是十分明显的 相似文献