Inequities in access to and use of shared resources in social dilemmas.

Investigated the effects of inequities in access to and use of shared resources on harvest decisions and preferences for structural change in resource dilemmas. 70 undergraduates, in groups of approximately 6, harvested resource units from a common resource pool over 10 trials. Following the harvest trials, Ss were asked to vote on how to conduct the session. The variables were (a) access to the resource pool, (b) perceived resource use, and (c) perceived inequity in other group members' harvests. It was hypothesized that high-variance Ss, when placed in a situation where harvest inequities could be attributed to access differences, would demonstrate a stronger preference for equality-restoring decision structures than would low-variance Ss. Results offer little support for this prediction; the variance manipulation had the predicted effect only among high-access Ss in the overuse condition. The access and use variables had independent effects on preferences for structural change. Harvest decisions were mediated by the 3 design variables in the manner predicted by a 3-factor model that assumes that harvest size will be governed by self-interest, a desire to use the common resource responsibly, and conformity to implicit group norms. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Solid-phase diffusion mechanism for GaAs nanowire growth

Controllable production of nanometre-sized structures is an important field of research, and synthesis of one-dimensional objects, such as nanowires, is a rapidly expanding area with numerous applications, for example, in electronics, photonics, biology and medicine. Nanoscale electronic devices created inside nanowires, such as p-n junctions, were reported ten years ago. More recently, hetero-structure devices with clear quantum-mechanical behaviour have been reported, for example the double-barrier resonant tunnelling diode and the single-electron transistor. The generally accepted theory of semiconductor nanowire growth is the vapour-liquid-solid (VLS) growth mechanism, based on growth from a liquid metal seed particle. In this letter we suggest the existence of a growth regime quite different from VLS. We show that this new growth regime is based on a solid-phase diffusion mechanism of a single component through a gold seed particle, as shown by in situ heating experiments of GaAs nanowires in a transmission electron microscope, and supported by highly resolved chemical analysis and finite element calculations of the mass transport and composition profiles.     

The response of the sievert instrument in neutron beams up to 180 MeV

Measurements with a tissue-equivalent proportional counter (TEPC) using the variance-covariance method have been performed in neutron beams between 71 keV and 180 MeV and in the cosmic radiation reference field (CERF) at CERN. The results show that with appropriate linear QD(yD) relations, the ambient dose equivalent can be determined within about 55% in these beams. Build-up measurements show that wall thickness is not crucial for H* determinations at 60 and 180 MeV.     

An attentional learning account of the shape bias: Reply to Cimpian and Markman (2005) and Booth, Waxman, and Huang (2005).

Recently, Developmental Psychology published 2 articles on the shape bias; both rejected the authors' previous proposals about the role of attentional learning in the development of a shape bias in object name learning. A. Cimpian and E. Markman (2005; see record 2005-14938-017) did so by arguing that the shape bias does not exist but is an experimental artifact. A. E. Booth, S. R. Waxman, and Y. T. Huang (2005; see record 2005-05098-004), in contrast, concluded that the shape bias (and its contextual link to artifact categories) does exist but that the mechanisms that underlie it are conceptual knowledge and not attentional learning. In response, in this article the authors clarify the claims of the Attentional Learning Account (ALA) and interpretations of the data under question. The authors also seek to make explicit the deeper theoretical divide: cognition as sequestered from processes of perceiving and acting versus as embedded in, and inseparable from, those very processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The morphology of axial and branched nanowire heterostructures

We present an extensive investigation of the epitaxial growth of Au-assisted axial heterostructure nanowires composed of group IV and III-V materials and derive a model to explain the overall morphology of such wires. By analogy with 2D epitaxial growth, this model relates the wire morphology (i.e., whether it is kinked or straight) to the relationship of the interface energies between the two materials and the particle. This model suggests that, for any pair of materials, it should be easier to form a straight wire with one interface direction than the other, and we demonstrate this for the material combinations presented here. However, such factors as kinetics and the use of surfactants may permit the growth of straight double heterostructure nanowires. Finally, we demonstrate that branched nanowire heterostructures, also known as nanotrees, can be successfully explained by the same model.     

电子商务在电力批发市场中的应用

0　引言在电力工业已经“放松管制”的前提下 ,电力买卖双方进行谈判和交易仍然必须遵守严格的规定。电子商务的出现为电力市场的迅速发展提供了新的契机。电子商务技术十分适用于电力实时交易 ,可以即时匹配电力市场的供求需要。互联网络使电力真正进入市场成为可能。在美国 ,联邦能源管理委员会 (Federal EnergyRegulatory Commission,缩写为 FERC)要求区域输电组织 (Regional Transmission Organization,缩写为 RTO)更好地、可靠地促进市场的协调发展。随着电子商务技术的进步 ,区域输电组织 (RTO)可以更好地推进电力工业市场化进…     

Numerical investigation of creep crack growth in cross-weld CT specimens. Part I: influence of mismatch in creep deformation properties and notch tip location

Creep crack growth (CCG) in cross-weld CT specimens is investigated using two-dimensional finite element simulations. A creep ductility-based damage model describes the accumulation of creep damage ahead of the crack tip where a constraint parameter and the creep strain rate perpendicular to the crack plane are used as characterizing parameters.
The numerical results reveal that, not only the material properties of the region in which the crack is propagating, but also the deformation properties of the surrounding material influence the CCG behaviour. For the specimen configurations investigated, the location of the starter notch in the HAZ of the cross-weld CT specimen has, however, a minor influence on the CCG rate and the value of C *. This applies as long as the crack is propagating within a sufficiently narrow region that has material properties which can be regarded as homogeneous.     

Numerical investigation of creep crack growth in cross‐weld CT specimens. Part II: influence of specimen size

A numerical investigation of the influence of specimen size on creep crack growth in cross‐weld CT specimens with material properties of 2.25Cr1Mo at 550 °C is performed. A three‐dimensional large strain and large displacement finite element study is carried out, where the material properties and specimen size are varied under constant load for a total of eight different configurations. The load level is chosen such that the stress intensity factor becomes 20 MPa √m regardless of specimen size. The creep crack growth rate is calculated using a creep ductility‐based damage model, in which the creep strain rate ahead of the crack tip perpendicular to the crack plane is integrated taking the degree of constraint into account. Although the constraint ahead of the crack tip is higher for the larger specimens, the results show that the creep crack growth (CCG) rate is higher for the smaller specimens than for the larger ones. This is due to much higher creep strain rates ahead of the crack tip for the smaller specimens. If, on the other hand, the CCG rate is evaluated under a constant C * condition, the creep crack growth rate is found to be higher for the larger specimens, except when the crack is located in a HAZ embedded in a material with a lower minimum creep strain rate; then, the creep crack growth rate is predicted to be higher for the smaller specimen. In view of these results, it is obvious that the size effect needs to be considered in assessments of defected welded components using results from CCG testing of cross‐weld CT specimens.