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12.
Adaptive management in agricultural innovation systems: The interactions between innovation networks and their environment 总被引:1,自引:0,他引:1
The purpose of this article is to investigate effective reformism: strategies that innovation networks deploy to create changes in their environment in order to establish a more conducive context for the realization and durable embedding of their innovation projects. Using a case study approach, effective reformism efforts are analyzed in a technological innovation trajectory related to the implementation of a new poultry husbandry system and an organizational innovation trajectory concerning new ways of co-operation among individual farms to establish economies of scale. The findings reinforce the idea, emerging from a complexity perspective on agricultural innovation systems, that interaction between innovation networks and their environment is only steerable to a limited extent. Nonetheless, innovation networks can enhance effective reformism by creating tangible visions that serve as vehicles to create understanding about the innovation and mobilize support for it, and by employing several kinds of boundary spanning individuals that are able to forge effective connections between innovation networks and their environment. Because innovation networks can only partially influence their institutional environment, and because unintended consequences of actions and random events influence the course of the innovation process, innovation network actors need to continuously re-interpret the contexts in which they move. This constant reflection by the innovating actors on their position vis-à-vis their environment needs to be supported by dedicated facilitators and monitoring and evaluation methods aimed at system learning. This implies that agricultural innovation policies should, instead of aiming to fully plan and control innovation, foster the emergence of such flexible support instruments that enable adaptive innovation management. 相似文献
13.
Decreased water uptake closes stomates, which reduces transpiration and increases leaf temperature. The leaf or canopy temperature has long been used to make an empirical estimate of plant water stress. However, with a few supplemental measurements and application of biophysical principles, infrared measurement of canopy temperature can be used to calculate canopy stomatal conductance (gC), a physiological variable derived from the energy balance for a plant canopy. Calculation of gC requires an accurate measurement of canopy temperature and an estimate of plant height, but all of the other measurements are available on automated weather stations. Canopy stomatal conductance provides a field-scale measurement of daily and seasonal stomatal response to prevailing soil water and atmospheric conditions, and facilitates a comparison of models that scale conductance from single leaves (measured with porometers) to canopies. A sensitivity analysis of the input measurements/estimates showed gC is highly sensitive to small changes in canopy and air temperature, and less sensitive to the other required measurements (relative humidity, net radiation, wind speed, and plant canopy height). The measurement of gC becomes increasingly sensitive to all of the component factors as the conditions become cloudier, cooler, and more humid. We determined gC for alfalfa and turfgrass by making the necessary environmental measurements and coupling them with a two-source (plant canopy layer and soil layer) energy balance model. We then compared these gC values to maximum single leaf values scaled-up to the canopy level (gCP, defined as potential canopy stomatal conductance herein) for the two crops. For both crops, gC matched gCP within approximately 10% after irrigation. The turfgrass gC measurements were also compared to mean single leaf values measured with a porometer. At mid-day, gC values were typically about double the single leaf values. Because this approach for determining gC allows continuous, non-contact measurement, it has considerable potential for coupling with measurements of soil moisture to better understand plant–soil water relations. It also has potential for use in precision drought stress and irrigation scheduling. 相似文献
14.
Taqman定量PCR技术检测转基因大豆中外源基因拷贝数 总被引:1,自引:0,他引:1
[目的]采用Taqman定量PCR技术检测转基因杂交大豆中外源,Ⅲ终止子基因的拷贝数。[方法]以大豆凝集素基因为内参照基因,以非转基因大豆基因组DNA为内参照基因标准品,通过梯度稀释法分别求取了内参照基因和质粒DNA的cz值与拷贝数对数值的相关性标准曲线方程,并通过将得到的0值代入标准曲线方程求取了样品的拷贝数。[结果]内参照基因标准曲线方程为Y=-3.422x+35.201,R^2=O.998;外源基因标准曲线方程为Y=-3.348x+34.890,R^2=0.999。nos终止子基因及其下游边界序列在转基因杂交大豆中为单拷贝。[结论]为确定转基因大豆外源基因拷贝数提供了理论依据。 相似文献
15.
大辽河河口地区污染边界层特征试验研究 总被引:2,自引:1,他引:1
利用2007年1~2月份大辽河河口地区沿海和陆地2个地面观测点观测得到的污染边界层的气象资料,探讨了该地区冬季污染边界层日变化特征。结果表明,大辽河河口地区污染边界层受到海陆的影响,在一定的天气条件下,海岸区域200m以下的低空可能出现海陆风。海岸区域不同高度的稳定度变化较陆地区域稳定;该地区风场变化主要在300m左右低空。夜间地区常出现逆温,逆温层厚度稳定在200~300m。热内边界层深入陆地10km,且高度可达800m。海岸区域大气扩散能力较弱,陆地区域较强。 相似文献
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17.
研究了由微粗糙表面与光滑平面形成的混合接触承载性能.混合接触由固体-边界膜-固体三体接触和固体-流体固体三体接触组成.两表面相对滑动时表面间形成许多个微阶梯轴承.这些微阶梯轴承的承载量之和构成两接触表面承载量.微阶梯轴承的入口区为传统流体区域,出口区为边界膜区域.给出了微阶梯轴承承载能力分析方法,研究了边界膜对混合接触承载能力和接触性能的影响. 相似文献
18.
Appropriate benchmarking is essential for evaluating the efficiency with which crops use water and for identifying constraints, other than water, to crop yield. No benchmark exists for sunflower. Boundary and simulation analyses were used to quantify the water productivity of sunflower crops grown in the Western Pampas (semiarid central Argentina). The approach involved the use of a large database (n = 169) collected in farmers’ fields over a period of 4 years, and the application of a crop simulation model in combination with actual weather and soil data. Using field data, an upper bound of 8 kg grain ha−1 mm−1 for water productivity, with an apparent seasonal soil evaporation of 75 mm, was defined. Seasonal water supply exceeded maximum expected seasonal crop requirements (ca. 630 mm) for many crops, and a majority of crops with <630 mm of available water during the season had water productivities considerably lower than the upper bound. The field data-based upper bound was indistinguishable from that obtained using yields for a set of 47 simulations using observed initial values for soil water and nitrogen profiles. Simulation confirmed the main features of the boundary-analysis applied to field data, and many simulated crops had yields that fell below the boundary function, even when simulated yield was plotted against simulated seasonal evapotranspiration or transpiration. Long-term (33-year) simulation analyses for two sites showed that most sunflower crops in the area are subjected to episodes of transient and unavoidable water stress after floral initiation. High levels of available soil water at sowing moderate, but in most years do not eliminate, these exposures to water stress. Yield gaps with respect to the boundary function were associated with deficient or excessive rainfall during grain filling, and other, non-water related, factors such as inadequate crop nutrition, biotic stresses, low photothermal quotients during the interval close to anthesis, and lodging. A grain yield/seasonal evapotranspiration plot for a large (n = 154) data set from experiments conducted by others in five separate environments suggests that the boundary function found for the Western Pampas is broadly applicable. Sunflower water productivity, corrected for oil-synthesis costs and seasonal vapour pressure deficit differences, approximates that of winter cereals grown in Mediterranean environments. 相似文献
19.
水稻一穴小群体的边际效应研究 总被引:1,自引:0,他引:1
研究证实,一穴多株的小群体范围内,存在着明显的边际效应。条形穴栽培与圆形穴栽培相比,能够发挥这种边际效应,提高大群体的群体数量与群体质量,起到增蘖增穗增粒而显著增产的效果。圆形穴栽培产量为1165167kg/hm2,条形穴栽培为1230267kg/hm2,比圆形穴栽培增产65100kg/hm2,增产率为559%。为水稻栽培上采用一穴两墩插秧、条形穴机插、条形穴盘育抛秧及摆秧提供了理论依据。 相似文献
20.
Lin Chengxian 《保鲜与加工》1989,(4):81-85
In order to compute the incompressible plane cascade flowfield in turbomachines with nothing but the Boundary Element Method, thispaper presents a numerical method by which both the velocity potentials andthe tangential velocities along the surfaces of cascade profile are computed by the Boundary Element Method, and because of this method, good results are obtained. 相似文献