Hydrogen-induced cold cracking in heat-affected zone of low-carbon high-strength steel

The Y-groove cracking test by submerged arc welding was employed to study the susceptibility of a low-carbon high-strength steel to hydrogen-induced cold cracking (HICC). The morphology of hydrogen cracks was observed using an electron probe microscope. The results showed that the heat-affected zone (HAZ) has a higher susceptibility to HICC than the weld metal and that increasing heat input can improve the HICC resistance of the weldment. The intergranular microcracking is the main HICC mode at the lowest heat input condition, accompanied with some transgranular microcracks attached to complex inclusions. In combination with phase transformation behaviour in sub-zones, the effect of the phase transformation sequence is proposed to try to illustrate the fact that the fine-grained HAZ has higher probability of hydrogen cracking than the coarse-grained HAZ owing to the occurrence of hydrogen enrichment in the fine-grained HAZ after the transformation.     

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.     

On the detection of time-reversal symmetry breaking by photoemission with circularly polarized light in the high- T c superconductor Bi2212

We argue that that in their recent experiment in which they claim to have found evidence for a time-reversal symmetry broken state, Kaminski et al. () (Nature, 416, p. 610) overlooked small temperature-dependent changes in the superstructure of Bi2212. These subtle changes may manifest themselves by changing the final state configurations of the photoemission process and thus invalidate their ultimate conclusions.     

Crystallization behaviour of Al-based amorphous alloy and nanocomposites by rapid quenching

The microstructure and crystallization behaviour of melt-spun Al₈₈Ni₉Ce₂Fe₁ amorphous alloy and nanophase composites have been studied by means of X-ray diffraction, transmission electron microscopy and scanning and isothermal calorimetry. The diffraction patterns from Al₈₈Ni₉Ce₂Fe₁ amorphous alloys are diffuse, indicating a basically amorphous structure but contain two rings presumed to be associated with quenched-in nuclei. In the cases of Al₈₈Ni₉Ce₂Fe₁ nanophase composites, nanoscale precipitated particles are homogeneously dispersed in an amorphous matrix, and the crystallite diameter and volume fraction are sensitive to quenching conditions. During thermal crystallization, a two-step phase transformation occurs in the amorphous alloy and nanocomposites, which is characterized by a diffusion-controlled precipitation of nanoscale Al particles and the growth of a Al₃(Ni, Fe) nanophase prior to a Al₁₁Ce₃ nanophase. This study gives insight into structure-control for obtaining nanophases dispersed in an amorphous matrix by rapid quenching.     

Practice Effects on Motor Control in Healthy Seniors and Patients with Mild Cognitive Impairment and Alzheimer's Disease

ABSTRACT

This research was designed to test the hypothesis that motor practice can enhance the capabilities of motor control in healthy controls (NC) and patients with a diagnosis of probable Alzheimer's disease (AD) and mild cognitive impairment (MCI), and consequently results in better motor performance. Approximately half of the subjects in the NC (n = 31), AD (n = 28), and MCI (n = 29) either received or did not receive practice on a task of fast and accurate arm movement with a digitizer. Changes in movement time (MT), movement smoothness (jerk), and percentage of primary submovement (PPS) were recorded and compared among the three groups across six blocks of trials (baseline and five training sessions). For all subjects, practice improved motor functions as reflected by faster and smoother motor execution, as well as a greater proportion of programming control. Compared to unaffected matched controls, AD and MCI subjects exhibited a greater reduction in movement jerk due to practice. Movement time and PPS data revealed that motor practice appeared to reduce the use of “on-line” correction adopted by the AD or MCI patients while performing the aiming movements. Evidently, their arm movements were quicker, smoother, and temporally more consistent than their untrained peers. The findings of this study shed light on how MCI and AD may affect motor control mechanisms, and suggest possible therapeutic interventions aimed at improving motor functioning in these impaired individuals.     

时态结构中的恒常联系因果学习

人工智能研究中,行动这一概念通常在理论框架中有完全的定义。然而,现实中的行动有时难以完全刻画。智能体需要从过去的经验观察中习得行动的后果。本文提出一种基于时态结构的行动一结果学习理论。在自然数时间结构中,智能体通过观察过去的恒常联系建立因果关系。智能体依据己建立的因果关系指导将来的行动。同时,我们给出关于该理论的一个完全的逻辑演绎系统,并给出基于该逻辑的智能体行动的有效算法。     

Resurgence of goal-directed actions and habits

This study investigated how goal-directed and habitual behaviors recover after extinction within the context of the resurgence effect, a form of relapse induced by the removal or worsening of alternative reinforcement. Rats were trained to press a target lever with one reinforcer (O1) for either minimal (4) or extended (16) sessions. An extinction test after the completion of O1 devaluation confirmed that minimal and extended training formed goal-directed and habitual behaviors, respectively. Then, pressing an alternative lever was reinforced with a second reinforcer (O2) while the target response was placed on extinction. When O2 was discontinued, the minimally trained target response resurged with goal-directed status as in the extinction test. However, the extinguished habitual behavior in the extensively trained rats did not recover as a habit but instead with goal-directed status, possibly due to the context specificity of habits or the introduction of a new response–reinforcer contingency. The critical finding that reinforcer devaluation consistently led to less resurgence regardless of the amount of acquisition training provides a clinical implication that coupling differential-reinforcement-of-alternative-behavior (DRA) treatments with the devaluation of the associated reinforcer of problematic behavior could effectively diminish its recurrence.     

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。     

As the Flocks Gather: How Religion Affects Voluntary Association Participation

This study investigates the relationship between different dimensions of religiosity and voluntary association participation using data from Queen'sUniversity's 1996 "God and Society in North America" survey. I look at the participatory, devotional, affiliative, and theological dimensions of religiosity and examine how they affect voluntary association participation at three different levels: membership, volunteering, and serving on a committee. The results show that all four religious dimensions have considerable, but distinctive, influences on secular voluntary association participation.     

中学教师处理学生心理健康问题策略特点探析

采用问卷法考察了268名中学教师在厌学、退缩行为、自我中心、攻击性行为和考试焦虑五种问题情境下教师对处理学生心理健康问题的策略有效性和使用可能性的评定以及性别、教龄因素对教师评定策略有效性的影响。结果表明:(1)中学教师处理学生心理健康问题策略具有情境性,教师对处理学生心理健康问题的策略的有效性的认可和真正在具体情境中采取的策略不尽相同。在厌学和退缩行为情境中,教师倾向于认为情感关爱型策略更有效;自我中心情境中,行为疏导型策略更有效;攻击行为情境中,惩罚约束型策略更有效;在焦虑情境中,言语疏导型策略更有效。在采用可能性的评定中,对学生的厌学、退缩行为、自我中心和焦虑问题,教师都更倾向于采用言语疏导型策略;在攻击行为情境中,教师更倾向于采用行为疏导型策略。(2)与性别相比,教龄是影响教师评定处理学生心理健康问题策略有效性的较为敏感的变量。在厌学情境中,20年以上教龄的教师认为责任转移型策略和情感关爱型策略更有效;在自我中心情境中,20年以上教龄的教师认为责任转移型策略更有效。