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排序方式: 共有559条查询结果,搜索用时 340 毫秒
41.
In 2008, the UK launched the first regulatory sustainability reporting scheme for biofuels. The development of the scheme, managed by the Low Carbon Vehicle Partnership for the Department for Transport, involved extensive stakeholder engagement. The scheme has significantly increased understanding by policy-makers, the biofuels industry and its supply chains on how to monitor and manage the sustainability risks of biofuels and increase their greenhouse-gas benefits. It is providing a practical model for similar developments globally. To receive certificates in order to meet volume obligations under the Renewable Transport Fuel Obligation (RTFO), suppliers must provide a monthly carbon and sustainability report on individual batches of renewable fuels they supply into the UK. The Renewable Fuels Agency produces aggregate monthly reports of overall performance and quarterly updates of individual supplier performance. This scheme is an important first step to assist the biofuels industry to demonstrate its environmental credentials and justify the subsidies received. The paper provides a case study of the development of the scheme, its initial outcomes and outstanding challenges. 相似文献
42.
Knowledge of the internal magnetization distributionsM(r) of polarizable media allows straightforward calculation of fields for any configuration which includes these media. Although useful calculations have been made using an assumedM(r) , little work directed at calculatingM(r) has been done. This paper includes assumptions that, in addition to Maxwell's equations, are sufficient for determining the resultant integral equation. A method for the solution of this equation forM(r) is also presented. As an example, the nonuniform demagnetizing fields and magnetization distributions are calculated for cylinders of isotropic magnetic material. The results for these samples are compared with experimentally determined values and show average errors less than 9 percent forM(r) . 相似文献
43.
Noah Hysler‐Rubin 《Planning Perspectives》2013,28(4):347-368
The aim of the paper is to bring together art and the city by linking town planning and the Arts & Crafts movement. This association is evident in the theoretical writing and professional practice of the architect Charles Robert Ashbee (1863–1942), whose work is characterized by a blend of tradition and innovation. Ashbee, a prominent artist, served as a British town planner in Jerusalem, assisting its first governor, Sir Ronald Storrs, in laying out the city and providing services for its inhabitants. In Jerusalem, Ashbee received his only chance to realize his artistic urban Utopia. The paper discusses Ashbee as a town planner and explores his artistic urban ideal, revealing his comprehensive appreciation of the city and its constituent artistic and social traits, and his combination of the modern requirements of a growing city with traditional artistic ideals. This was the basis of Ashbee’s work in Jerusalem and determined many of its results. In many ways, Ashbee’s ideas still guide the development of Jerusalem to this day, embodying a unique contribution of the Arts & Crafts movement to modern town planning. 相似文献
44.
Robert Archer 《数字社区&智能家居》2010,(3):88-92
纵观当下的音视频市场,各种产品呈花齐放的态势,但功能上的差别却让不同的产品又各有优势。为了给大家提供一个选购依据,本文特挑选部分优秀音视频产品供大家参考。 相似文献
45.
CJ Reist GE Archer CJ Wikstrand DD Bigner MR Zalutsky 《Canadian Metallurgical Quarterly》1997,57(8):1510-1515
The crystal structure is reported of a complex between the dodecanucleotide sequence d(CGCGAATTCGCG)2and an analogue of the DNA binding drug Hoechst 33258, in which the piperazine ring has been replaced by an amidinium group and the phenol ring by a phenylamidinium group. The structure has been refined to an R factor of 19.5% at 2.2 A resolution. The drug is held in the minor groove by five strong hydrogen bonds, together with bridging water molecules at both ends. There are few other contacts with the floor of the groove, indicating a lack of isohelicity with the groove and suggesting (i) that the observed high DNA affinity of this drug is primarily due to the array of hydrogen bonds and (ii) that these more than compensate for its poor isohelicity. 相似文献
46.
In this paper, we establish a probabilistic framework for adaptive transform coding that leads to a generalized Lloyd type algorithm for transform coder design. Transform coders are often constructed by concatenating an ad hoc choice of transform with suboptimal bit allocation and quantizer design. Instead, we start from a probabilistic latent variable model in the form of a mixture of constrained Gaussian mixtures. From this model, we derive an transform coder design algorithm, which integrates optimization of all transform coder parameters. An essential part this algorithm is our introduction of a new transform basis-the coding optimal transform-which, unlike commonly used transforms, minimizes compression distortion. Adaptive transform coders can be effective for compressing databases of related imagery since the high overhead associated with these coders can be amortized over the entire database. For this work, we performed compression experiments on a database of synthetic aperture radar images. Our results show that adaptive coders improve compressed signal-to-noise ratio (SNR) by approximately 0.5 dB compared with global coders. Coders that incorporated the coding optimal transform had the best SNRs on the images used to develop the coder. However, coders that incorporated the discrete cosine transform generalized better to new images. 相似文献
47.
A technique is described that permits the rapid determination of all four noise parameters of a MESFET or HEMT at wafer level. The fully automated procedure, which has been implemented in the 2-8 GHz range, uses 16 accurately measured, very repeatable source impedance standards. The standards have been selected for optimum coverage of the input impedance plane to result in stable and rapidly convergent least-squares solutions for the minimum noise figure, optimum source impedance, and noise resistance of practical devices. The resultant system is very stable and produces accurate noise parameters for a wide range of devices 相似文献
48.
A radiotracer technique has been used to measure both mercury self-diffusion and surface concentration values in bulk and
liquid phase epitaxy, LPE, grown Hg1−xCdxTe. A high resolution sectioning technique has allowed profiling of thin epitaxial layers in submicron steps. Hg1-xCdxTe samples with composition values betweenx
Cd= 0.16 and 0.23 were isothermally annealed in carefully controlled and monitored diffusion con-ditions. Mercury reservoirs
containing Hg203 were used to provide vapour diffusion sources during closed tube isothermal anneals in the temperature range 300° C to 400°
C. Evidence has been found which may indicate the presence of two components in the radio-tracer profiles for both bulk and
epitaxially grown material. In some cases it was possible to estimate two diffusion coefficients,D
1andD
2, from the near surface and deeply penetrating components, respectively. Our results forD
1andD
2are compared with other work. For bulk material annealed at 400° C under a saturated mercury pressureD
1= 2.0 x 10-12cm2s-1 andD
2= 1.1 x 10-11cm2s−1. Diffusion coefficients at 310° C under saturated mercury pressure, have been measured in bulk and epitaxial material. Close
agreement was found between these results with an average value ofD
1= 1.4 x 10−13cm2s−1. We believe this to be the first time radiotracer results for epitaxial material have been presented. We have collated diffusion
data, as a function of reciprocal temperature, from several workers and suggest there is evidence for a change in the activation
energy for mercury diffusion around 350° C. This may be due to a change in the dominant diffusion mechanism. 相似文献
49.
The experiences of 3 social psychologists asked to evaluate (and improve) a series of large-scale programs designed to change energy-related attitudes and behavior are described. The research generated significant change but also substantial conflict involving both the utility companies being evaluated and the state agency that commissioned the evaluation. This experience is reviewed with an eye to maximizing the usefulness of future efforts to apply social psychology in complex and potentially conflicted public policy arenas. The difference between influence and power models of applied research is discussed, and possible remedies are examined for social psychologists undertaking future research similar in scale, policy consequences, or potential controversy. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
50.
Greater male than female variability is found in behavioral and morphological traits in animals. A theory that greater male variability is associated with variability in parental investment is described and contrasted with sexual strategies theory, which posits no sex differences in variability. Predictions from the theories were tested through meta-analyses of variance ratios for data sets involving sexually selected characteristics analyses (physical aggression and 5 aspects of mate choice) and 2 unlikely to have resulted from sexual selection (anger and self-esteem). Variation was significantly greater among men than women in 5 of the 6 former data sets and was similar for men and women in the latter 2 data sets, broadly supporting the predictions. A further analysis extends the theory to intellectual abilities. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献