Pinning of grain boundary migration by a coherent particle

We studied single-particle pinning of grain boundary (GB) migration during grain growth. A phase-field model was formulated to simulate the pinning by a coherent particle and validated quantitatively by comparison with analytical prediction. A study of GB migration velocity using this model revealed that second-phase coherent particles have a previously unknown restraining effect over the whole of the GB-particle interaction range, which is qualitatively different from the interaction between GB and incoherent particles.     

Derivation of strain hardening in cyclic loading from that in tensile loading

The micromechanical model of extrusion formation in a single crystal under stress-controlled loading in high-cycle fatigue is reviewed. In the present letter, the microstress and strain fields of a single crystal under a high-amplitude fatigue are calculated by the boundary element method. Based on Schmidt's law, the resolved shear stress to activate or to cause the continuation of slip in a slip system is taken to depend on the amount of slip in that system. The cyclic strain hardening is calculated from the experimental tensile stress-strain curve. This calculated cyclic strain hardening is compared with the experimental cyclic hardening. Good agreement is shown.     

Shear band evolution during large plastic deformation of brittle and ductile metallic glasses

Four monolithic metallic glasses (MMGs) with different plasticities varying from brittle to ductile behavior under unconstrained loading were subjected to small punch testing. All specimens undergo large plastic deformation with multiple cobweb-like shear bands under these conditions. The process of shear band evolution was carefully controlled and investigated. Plasticity of MMGs is characterized by equivalent plastic strain ε* (product of shear band density and critical shear offset). Thus, this article provides an experimental basis for a better understanding of the shear band evolution during plastic deformation of MMGs.     

Difference in microstructure of Zr41Ti14Cu12.5Ni10Be22.5 glasses prepared in a 52 m drop tube and by water quenching

A 52 m drop tube has been used to solidify bulk-glass-forming Zr₄₁Ti₁₄Cu_12.5Ni₁₀Be_22.5 alloy. Glassy balls with different sizes solidified from the droplets whose structural features, glass-transition behaviour and crystallization kinetics have been investigated. The results indicate that the apparent activation energies of the glass transition and main crystallization reaction are significantly different from those of samples prepared by water quenching. The structural difference between the two types of glassy specimen is revealed by compression studies and in situ energy-dispersive X-ray diffraction. The results are important for understanding the structural features of bulk-forming glasses.     

Microwave-dielectric and magnetic properties of Ta-doped BiFeO3 nanopowders

BiFe_{1? x} Ta _x O₃ (x = 0, 0.05, 0.1) nanopowders have been fabricated by a simple sol–gel method. Dielectric measurements at microwave frequencies (2–18 GHz) were made using a vector network analyser. Without tantalum, the BiFeO₃ nanopowder presents a relaxation-like response with a characteristic frequency of 15 GHz, which can be associated with an overdamped process. The Ta-doped nanopowders, however, show resonant behaviour with resonant frequencies of 12.5 and 14.6 GHz. The intensity of the resonant peak near 14.6 GHz decreases with increasing Ta addition. This behaviour is associated with a damped resonance process. Room-temperature magnetic measurements indicate that the addition of Ta influences the magnetic properties of the BiFeO₃ nanopowders, with BiFe_0.95Ta_0.05O₃ having the strongest ferromagnetism with a saturation magnetisation M _s of about 0.05 µ_B/Fe. The origin of the enhanced ferromagnetism is possibly associated with the distortion of the oxygen octahedral by the Ta substitution or/and the statistical distribution of Fe³⁺ and Fe²⁺.     

Investigation of {111} stacking faults and nanotwins in epitaxial BaTiO3 thin films by high-resolution transmission electron microscopy

{111} stacking faults and nanotwins in epitaxial BaTiO₃ thin films on MgO substrates have been investigated by high-resolution transmission electron microscopy. In many cases, the stacking faults and nanotwins were found to be accompanied by partial dislocations. These partial dislocations can be classified as two different types, analogous to the situation in the fcc structure. One is of the Shockley type with the Burgers vector (a/3)<112>. The other is of the Frank type with the Burgers vector (a/3)<111>. The movements of both types of partial can lead to the {111} stacking faults and the {111} twins observed in these films.     

Stair-rod dislocations in perovskite films on LaAlO3 substrates

Two types of stair-rod dislocation formed at junctions of {111} stacking faults in SrTiO₃-SrRuO₃ two-layer films on LaAlO₃ substrates have been studied by high-resolution transmission electron microscopy. The first type, formed by the interaction of two stacking faults situated at the flat SrRuO₃-LaAlO₃ interface without any step, has a Burgers vector (a/3)<110>. The other type, formed by the interaction of two stacking faults, of which one starts from the SrRuO₃-LaAlO₃interface area involving an interface step, has a Burgers vector (a/3)<120>. The formation mechanism of the stair-rod dislocations and the effect of the step are discussed.     

Evaluations,Attitude Similarity,and Interpersonal Attraction: Testing the Hypothesis of Weighting Interference Across Responses

The greater effect of negative than positive stimuli on judgments—the positive-negative asymmetry (PNA)—is rather pervasive. However, the effects of the valence of evaluations of the participant by the partner and attitude similarity between them on attraction have been inconsistent with PNA. The hypothesis that the weighting rule instigated by the first response interferes with the weighting rule normally expected for the second response was tested. As hypothesized, evaluations and attitude similarity interacted when attraction response was assessed prior to competence response but not when competence response was assessed first. The effects in the first measured response fully mediated the effects in the second measured response but not vice versa. Implications of the finding for attraction and PNA are discussed.     

Parental Control, Adolescent Delinquency, and Young Adult Criminal Behavior

Adolescence and young adulthood are periods of increased autonomy. Higher levels of autonomy could increase the opportunities for risky behavior such as delinquency. During these periods of transition, the role of parental control becomes less clear. Previous studies have demonstrated the association between parental control and adolescent delinquency, but few have extended examination of such association into young adulthood. The purpose of the study is to examine the association between parental control and delinquency and parental control in adolescence and young adult criminal behavior. We propose that, even though adolescents seek autonomy during this stage, lack of parental control is positively associated with delinquency and has continued influence in young adulthood. Using a national longitudinal dataset, we analyzed the relationship between parental control and delinquency. Findings from regression analyses indicated that lack of parental control had a positive association with delinquency both concurrently and longitudinally into young adulthood. When analyzing delinquency in young adulthood, females reported a lower level of delinquency and younger age was associated with more delinquent behavior. Unexpectedly, parents’ college education was positively associated with delinquency in young adulthood. The findings suggest that parental control is still influential through the period of adolescence and early parental control is still influential in young adulthood. Ways to practice parental control and implications of results are further discussed.     

Measures of Cognitive Complexity and Its Development in Chinese Adolescents

There are various controversies over the measurement of cognitive complexity and few studies concerning its development in adolescents, especially in China. Based on a sample of 234 Chinese adolescents from Grades 7 through 11, the present study first compared 2 instruments and 12 corresponding indices of cognitive complexity—11 traditional and new forms of cognitive complexity scores on the Repgrid, and 1 score on the Role Category Questionnaire (RCQ)—then adopted the most appropriate tool to investigate the development of cognitive complexity. The results showed that the RCQ may have relatively more construct validity than the Repgrid in terms of the assessment of adolescents’ cognitive complexity. Using the RCQ, it was found that adolescents of different grades, gender, peer status, and academic achievement had different levels of cognitive complexity.