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排序方式: 共有309条查询结果,搜索用时 328 毫秒
91.
Constanze Haug Tim Rayner Andrew Jordan Roger Hildingsson Johannes Stripple Suvi Monni Dave Huitema Eric Massey Harro van Asselt Frans Berkhout 《Climatic change》2010,101(3-4):427-445
Climate change is widely recognised as a ‘wicked’ policy problem. Agreeing and implementing governance responses is proving extremely difficult. Policy makers in many jurisdictions now emphasise their ambition to govern using the best available evidence. One obvious source of such evidence is the evaluations of the performance of existing policies. But to what extent do these evaluations provide insights into the difficult dilemmas that governors typically encounter? We address this question by reviewing the content of 262 evaluation studies of European climate policies in the light of six kinds of dilemma found in the governance literature. We are interested in what these studies say about the performance of European climate policies and in their capacity to inform evidence-based policy-making. We find that the evaluations do arrive at common findings: that climate change is framed as a problem of market and/or state failure; that voluntary measures tend to be ineffective; that market-based instruments tend to be regressive; that EU-level policies have driven climate policies in the latecomer EU Member States; and that lack of monitoring and weak enforcement are major obstacles to effective policy implementation. However, we also conclude that the evidence base these studies represent is surprisingly weak for such a high profile area. There is too little systematic climate policy evaluation work in the EU to support systematic evidence-based policy making. This reduces the scope for sound policy making in the short run and is a constraint to policy learning in the longer term. 相似文献
92.
A technique for replicating large rock outcrops has been developed so that casts of these surfaces can be archived in their present stage of preservation. Researchers can then study these casts in the laboratory under optimum lighting conditions, sometimes revealing new fossil evidence, while students and members of the public can be shown geological features that might otherwise be inaccessible to them. 相似文献
93.
94.
The use of the metaphors of general fitness and N-K spaces can assist in the understanding of the development of the physical landscape. Different modes of change can be viewed as different types of movement in, and distortions of, these phase spaces. Visualized in this manner landscape change can be viewed as both channelized, constrained and random. 相似文献
95.
A computer model of mid-ocean ridge basalt generation using trace element geochemistry has been developed. The model simulates a periodically replenished, continually cooled and fractionated magma chamber, with periodic lava extrusion. Primitive basalts from the ocean floor are used to generate likely evolution paths for the magma chamber. The steady state variant of this model has led to the isolation of several variables which critically affect the basalt composition. Although the fraction of cumulates is an important parameter, other variables such as the volume of incoming magma batches, their frequency, and the volume of the mixing cell, play a critical part especially on slow-spreading ridges. The growing magma chamber model uses random number generators to simulate the initiation and growth of a chamber. This model predicts a rapid increase in incompatible element concentrations, immediately after chamber initiation on a fast-spreading ridge. This would occur in situations such as propagating rifts and may help in the understanding of ferrobasalt generation. 相似文献
96.
Paul R. T. Newby Peter A. Woodsford Jon P. Mills David A. Holland William Tompkinson Adrian J. Holmes Stuart Robson Paul Aplin Simon J. Buckley Henny Mehner 《The Photogrammetric Record》2004,19(108):375-402
The XXth International Congress of Photogrammetry and Remote Sensing was held at the Istanbul Convention and Exhibition Centre (ICEC), Turkey, from 12th to 23rd July 2004. Reports are given on the Congress as a whole, including the General Assembly, some Technical Commission activities and the Congress Exhibition. Papers from the Congress are published in Volume XXXV of the International Archives of Photogrammetry, Remote Sensing and Spatial Information Sciences. 相似文献
97.
Practical Influences of Geometric and Radiometric Image Quality Provided By Different Digital Camera Systems 总被引:1,自引:0,他引:1
Imaging systems founded on current digital camera technology are finding widespread use in high precision measurement applications. A single digital CCD camera, or an array of such cameras, equipped with ring lighting equipment is commonly used to acquire imagery of high contrast retroreflective targets placed on the object at discrete locations to signalize points of interest. The precise and accurate measurement of each imaged target location is a fundamental requirement if suitable measurement tolerances are to be obtained. Whilst such systems are undoubtedly capable of producing excellent results, the practical effects of target image quality on the photogrammetric measurement process is in need of careful consideration. This paper revisits some fundamentals of the optical imaging of retrotargets and investigates some abilities of a range of digital camera systems to provide images of retrotargets that are appropriate to the measurement process. Some experimental results are presented including the imaging of planar arrays of differing sized retrotargets at differing angles and exposures and a series of network analyses in which the level of target image intensity has been varied systematically. 相似文献
98.
99.
K. B. Atkinson A. H. Holmes I. J. Dowman M. J. Smith P. R. T. Newby S. Robson D. A. Tait R. P. Kirby P. R. Thomas 《The Photogrammetric Record》1997,15(89):765-789
The XVIIIth International Congress of Photogrammetry and Remote Sensing was held in the Austria Center, Vienna from 9th to 19th July, 1996. Reports on the Technical Commission Activities, on the Congress Exhibition and on the General Assembly were given at a meeting of the Photogrammetric Society on 7th October, 1996. Papers from the Congress were published in the International Archives of Photogrammetry and Remote Sensing, 31. 相似文献
100.
Cation ordering in omphacite and effect on deformation mechanism and lattice preferred orientation (LPO) 总被引:1,自引:0,他引:1
We present microstructural data and lattice preferred orientations (LPOs) of omphacites from a suite of eclogites, from the Adula/Cima Lunga nappe (Central Alps). Our work shows a surprisingly strong correlation between the measured LPO and the ordering state of cations in omphacite. Estimates of deformation temperature from metamorphic petrology, together with measured omphacite compositions and LPOs, determine the field (ordering state), on the omphacite phase diagram, into which each sample falls. LPOs dominated by L-type and S-type signatures are developed in samples that fall in the P2/n field (ordered structure) and C2/c field (disordered structure), respectively.Dislocations with b=1/2−110 or b=[001] are observed in the transmission electron microscope (TEM) in all samples. The former change from a perfect dislocation in the C2/c structure to a partial in P2/n. Any movement of a partial dislocation requires the formation or growth of a stacking fault. Furthermore, in order to pass an obstacle a partial dislocation has to constrict to a unit dislocation. The energy to form a constriction is high in omphacite due to the large separation width. Thus, the activity of the b=1/2−110 dislocation is hindered in the P2/n structure relative to the C2/c structure, which change the balance between the two and might give rise to the different LPOs. 相似文献