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231.
S. Ram A. Gautam H. J. Fecht J. Cai J. Bansmann R. J. Behm 《Philosophical Magazine Letters》2013,93(5):361-372
Polymer molecules of polyvinyl alcohol (PVA) serve as a good Ag+?→?Ag0 reducer as well as a template to produce Ag0 nanocrystals of anisotropic shapes. Thin Ag–PVA films (50–100?µm thick) were prepared by carrying out the reaction in aqueous PVA (under heating conditions) and then spin casting the sample in this shape. A topotactic Ag+?→?Ag0 reaction and in-situ Ag0 growth occur in support over the PVA molecules (as per the local structure and Ag0–PVA interactions) of elongated surfaces. The Ag0 state is confirmed with 3d 5/2 and 3d 3/2 XPS signals of 368.37 and 374.13?eV binding energies, respectively. As analyzed with X-ray diffraction, it is a new allotrope with an orthorhombic structure, lattice parameters a?=?0.8535, b?=?0.8410?nm and c?=?0.4119?nm, and density ρ?=?9.69?g?cm?3. On heating in air, the well-known cubic structure develops, a?=?0.4082?nm (ρ?=?10.53?g?cm?3) after 150°C, whereas a?=?0.4071?nm (ρ?= 10.61?g?cm?3) after 300°C for 2?h. According to proposed models, it is a vacancy-stabilized allotrope, which evolves from multiply twinned particles. 相似文献
232.
J.J. Wang S. Bhattacharyya Q. Li T.W. Heo X.Q. Ma Long-Qing Chen 《Philosophical Magazine Letters》2013,93(7):327-335
An efficient numerical algorithm is proposed to accurately compute the elastic fields in two-dimensional (2D) or three-dimensional (3D) microstructures with arbitrary elastic inhomogeneity and anisotropy. It combines the equivalent inclusion method of Eshelby, the microelasticity theory of Khachaturyan, and the spectral iterative perturbation method of Hu and Chen. Its efficiency is compared with those of existing approaches in the literature. The method can be conveniently implemented in phase-field modeling of stress-dependent microstructure evolution and/or of mass/electrical transport. 相似文献
233.
We present a study of dislocations in decagonal Al70Ni21Co9 quasicrystals by means of diffraction contrast analysis as well as convergent-beam electron diffraction in the transmission electron microscope. The nickel-rich Al–Ni–Co quasicrystals show diffraction patterns characteristic of the basic-nickel decagonal phase exhibiting almost no diffuse scattering. We succeeded in growing this phase in the form of large single quasicrystals. The two-beam bright-field images show a homogeneous background and no striation contrast as reported for other Al–Ni–Co decagonal phases. We have, for the first time in a two-dimensional quasicrystal, observed the weak contrast-extinction condition. 相似文献
234.
In this article, initial boundary value problem for 3D quasicrystals in half space is considered. An analytic method is proposed for special form of initial conditions and nonhomogeneous term. It is explained that a weak solution of the problem can be constructed in the similar form of data by using symbolic calculations. 相似文献
235.
Arun Kumar 《Philosophical Magazine Letters》2013,93(12):703-709
Structures under loading can show positive and negative stiffness (during buckling) with zero stiffness just being one point of transition. Material structures with extended zero stiffness regimes have also been reported. Using the example of an extended Eshelby plate with a positive and negative edge dislocation, we show the existence of finite regimes of positive, zero and negative stiffness in a single system. Given that stable states/configurations of negative stiffness cannot exist in an isolated system; we show the existence of metastable states of negative stiffness along with unstable states of positive stiffness. The system also exhibits one point of unstable equilibrium. 相似文献
236.
ABSTRACTWe examined whether enhancing (vs. not enhancing) the emotionality of a referent public good influences the subsequent valuation of a target public good. We predicted that it would and that the directionality of its impact would depend on a fundamental cognitive process – categorisation. If the target and referent goods belong to the same domain, we expected that the effect on the target would be in the same direction as the emotional enhancement of the referent (assimilation effect). However, if the target and referent goods belong to different domains, we expected that the effect on the target would be either negligible or in the opposite direction to that of the emotional enhancement of the referent (null or contrast effect). In Experiment 1 we examined the impact of emotionally enhancing a referent public good on feelings towards a target public good, whereas in Experiment 2 on the willingness to contribute towards a target public good. The results support the predicted interaction, which was driven by an assimilation effect for same-domain goods and a null effect for different-domain goods. In doing so, the present findings highlight the interplay between cognition and emotion in the valuation of public goods. We discuss theoretical and practical implications. 相似文献
237.
项目曝光率关系到题库建设和测验安全,是计算机化自适应测验(Computerized Adaptive Testing, CAT)需要考虑的重要问题。在认知诊断 CAT 情形下,首先基于传统 CAT 中 a-分层方法的思想提出按项目信息量对题库分层的分层多阶段(Stratified Multistage, SM)选题方法;然后将 SM 方法与项目合格(Item Eligibility, IE)方法相结合得到SMIE方法。在此基础上,开展模拟研究比较SM、IE、SMIE、最大修正优先指标(Maximum Modified Priority Index, MMPI)方法、限制阈值(Restrictive Threshold, RT)方法和限制进度(Restrictive Progressive, RPG)方法的选题表现。总体上,它们的测量精度从高到低依次为IE、SM、SMIE、RT、RPG和MMPI方法;项目曝光分布均匀性的优劣次序为MMPI、RPG、SMIE、RT、SM和IE方法;SMIE和RT方法能较好地平衡测量精度和项目曝光均匀性要求。 相似文献
238.
239.
An item-cued directed forgetting paradigm was used to investigate the ability to control episodic memory and selectively encode complex coloured pictures. A series of photographs was presented to 21 participants who were instructed to either remember or forget each picture after it was presented. Memory performance was later tested with a recognition task where all presented items had to be retrieved, regardless of the initial instructions. A directed forgetting effect—that is, better recognition of “to-be-remembered” than of “to-be-forgotten” pictures—was observed, although its size was smaller than previously reported for words or line drawings. The magnitude of the directed forgetting effect correlated negatively with participants’ depression and dissociation scores. The results indicate that, at least in an item method, directed forgetting occurs for complex pictures as well as words and simple line drawings. Furthermore, people with higher levels of dissociative or depressive symptoms exhibit altered memory encoding patterns. 相似文献
240.
Oskari Kuusela 《International Journal of Philosophical Studies》2013,21(1):57-75
Abstract Transcendental arguments have been described as undogmatic or non‐dogmatic arguments. This paper examines this contention critically and addresses the question of what is required from an argument for which the characterization is valid. I shall argue that although transcendental arguments do in certain respects meet what one should require from non‐dogmatic arguments, they – or more specifically, what I shall call ‘general transcendental arguments’ – involve an assumption about conceptual unity that constitutes a reason for not attributing to them the status of non‐dogmatic arguments. As a solution to this problem I distinguish general transcendental arguments from what I shall call ‘specific transcendental arguments’ and seek to explain how by limiting the use of transcendental arguments to the latter type it would be possible to avoid dogmatism. This methodological adjustment also opens up a possibility of re‐interpreting transcendental arguments from the past in a novel non‐dogmatic fashion. 相似文献