Neutron and X-ray diffraction studies and cohesive interface model of the fatigue crack deformation behavior

The crack-tip deformation behavior during a single overload, fatigue test of ferritic stainless steel, and Ni-based HAYNES 230 superalloy is studied at different structural levels using (1) neutron-diffraction, from which both the elastic-lattice strain and volume-averaged total dislocation densities are obtained, (2) polychromatic X-ray microdiffraction to probe the geometrically necessary dislocations and boundaries distribution, and (3) an irreversible and hysteretic cohesive interface model which has been implemented into a finite element framework to simulate the stress/strain evolution near the fatigue crack tip. Neutron strain measurements and finite element simulations are in qualitative agreement on the macroscopic length scale. Large plastic deformation induced by the overload and the resulting compressive residual strains are observed in front of the crack tip after the overload, and are the principal reason for the fatigue-crack-growth retardation. Strong strain gradients surrounding the crack propagation result in the formation of a high density of geometrically necessary dislocations near the fractured surface and cause local lattice rotations on the submicron level.     

A phase-field model for deformation twinning

We propose a phase-field model for modeling microstructure evolution during deformation twinning. The order parameters are proportional to the shear strains defined in terms of twin plane orientations and twinning directions. Using a face-centered cubic Al as an example, the deformation energy as a function of shear strain is obtained using first-principle calculations. The gradient energy coefficients are fitted to the twin boundary energies along the twinning planes and to the dislocation core energies along the directions that are perpendicular to the twinning planes. The elastic strain energy of a twinned structure is included using the Khachaturyan's elastic theory. We simulated the twinning process and microstructure evolution under a number of fixed deformations and predicted the twinning plane orientations and microstructures.     

Influence of Hostile Media Perception on Willingness to Engage in Discursive Activities: An Examination of Mediating Role of Media Indignation

This study examines the mediating role of media indignation, a set of negative emotional reactions to media coverage perceived to have partisan bias, between hostile media perception (HMP) and its consequences in behavioral willingness, more specifically, willingness to engage in discursive activities. It is examined together with a cognitive pathway through individuals' inference on opinion climate. Data from a web-based survey of university students (N = 696) on three controversial issues were analyzed. Findings showed that the degree of perceived partisan bias in mainstream media coverage on an issue was positively related to the intensity of media indignation and levels of incongruity between one's own opinion and perceived majority opinion. Media indignation in turn had a significant and positive effect on willingness to engage in discursive activities across all three issues, mediating the effect of HMP on behavioral willingness, whereas self-majority opinion incongruity did not. Theoretical implications of the findings are discussed.     

Mapping the time course of the positive classification advantage: An ERP study

The aim of the present study was to investigate the time course of the positive advantage in the expression classification of faces by recording event-related potentials (ERPs). Although neutral faces were classified more quickly than either happy or sad faces, a significant positive classification advantage (PCA)—that is, faster classification for happy than for sad faces—was found. For ERP data, as compared with sad faces, happy faces elicited a smaller N170 and a larger posterior N2 component. The P3 was modulated by facial expressions with higher amplitudes and shorter latencies for both happy and neutral stimuli than for sad stimuli, and the reaction times were significantly correlated with the amplitude and latency of the P3. Overall, these data showed robust PCA in expression classification, starting when the stimulus has been recognized as a face revealed by the N170 component.     

社会认同与内、外群体态度的关系：群际威胁和群体情绪的中介作用

为探究社会认同、群际威胁和群体情绪如何同时影响内、外群体态度,本研究以中日撞船事件为考察蓝本向天津市431名大学生被试进行调查研究,结果发现：国家认同在认同威胁对两种群体态度的总影响和通过群体愤怒的间接影响中都起到负向的调节作用;群际威胁和群体情绪在社会认同与内、外群体态度之间具有显著中介作用。结论：国家认同在对群体态度的影响中起基础性作用,不同群际威胁与不同群体情绪相对应进而影响群体态度。     

音乐对工作记忆影响及机制的ERP研究

以肖邦音乐为刺激材料,采用数字n-back实验范式来研究肖邦音乐对工作记忆的影响方式,并通过运用事件相关电位技术(ERP技术),研究不同音乐条件下,正常人大脑皮层的脑电活动情况,进而探讨音乐对工作记忆影响的神经机制。30名被试参加了3种音乐条件(无音乐、先导音乐、背景音乐)下的n-back(n=1、2)工作记忆任务的行为实验,收集行为数据;14名被试参加了同样实验过程的ERP实验,记录脑电数据。行为结果发现音乐条件对工作记忆效果有显著影响,且先导音乐条件下记忆效果最好;脑电结果显示P3波幅随记忆负荷的增加呈下降趋势,高记忆负荷水平下,P3波幅随先导音乐、背景音乐、无音乐的顺序逐渐呈现下降趋势;源定位分析发现音乐对工作记忆的促进作用可能跟大脑顶叶被激活有关。     

颜色概念的知觉符号表征与命题符号表征

使用启动范式通过两个实验检验颜色概念的表征是知觉符号表征还是命题符号表征.实验l使用显性颜色概念,即颜色词;实验2使用隐性颜色概念,即隐含颜色信息的词.实验结果表明显性颜色概念的表征是知觉符号表征,而隐性颜色概念的表征是命题符号表征.     

意外考试悖论的博弈分析

本文从博弈的角度分析了意外考试悖论,指出了以往解决方案的不足,给出了一种新的方案。根据这个新方案,考试悖论的推理中使用了倒推法和弱下策反复剔除法。本文接着讨论了这些博弈推理方法的不足。然后把这个新的博弈方案用到卡片悖论和方格悖论这些考试悖论的变种里。最后指出,在考试悖论里,比起倒推法,弱下策剔除法是引起悖论的更根本的原因。     

From implicit skills to explicit knowledge: a bottom-up model of skill learning

This paper presents a skill learning model CLARION. Different from existing models of mostly high-level skill learning that use a top-down approach (that is, turning declarative knowledge into procedural knowledge through practice), we adopt a bottom-up approach toward low-level skill learning, where procedural knowledge develops first and declarative knowledge develops later. Our model is formed by integrating connectionist, reinforcement, and symbolic learning methods to perform on-line reactive learning. It adopts a two-level dual-representation framework (Sun, 1995), with a combination of localist and distributed representation. We compare the model with human data in a minefield navigation task, demonstrating some match between the model and human data in several respects.     

两例先天性无痛症患者的心理生理特点研究 Ⅱ.对致痛性强刺激的知觉和反应

本工作对两例先天性无痛症患者对于致痛性强刺激的知觉和反应进行了研究(例1女,10岁,例2男,13岁)。对照组为20例正常儿童,性别和年龄均与患儿相匹配。 结果:1),生活中痛:两例患儿均无(包括痛感觉和痛反应)。2)实验性痛:①痛感觉:两例患儿均无;②“痛”反应:例1有“痛”反应(脉搏和呼吸的变化以及行为反应明显,大致与正常儿童相似)。例2无“痛”反应(脉搏和呼吸的变化轻微,无行为反应,与正常儿童不同)。 由结果看来,先天性无痛症患者似乎可分为两种类型:不完全型(如同例1)和完全型(如同例2)。存在有“痛”反应而无痛感觉的无痛症患者。 本工作结果从另一侧面为痛的两成分学说提供了依据。