The variable substitution and power-series techniques are used for the asymptotic analytical derivation of the governing equation of a transverse surface wave. The results reveal that the transverse wave can propagate along the surface of a functionally graded infinite half space in various modes, and that their dispersion relations are normal. For certain cases, energy is concentrated on the surface region to a depth of several wavelengths. A new theoretical foundation based on the transverse surface wave can be provided for graded-material characterization by experimental measurement. Some phenomena of seismic wave propagation may also be explained. 相似文献
In the literature, different axiomatizations of Public Announcement Logic (PAL) have been proposed. Most of these axiomatizations share a “core set” of the so-called “reduction axioms”. In this paper, by designing non-standard Kripke semantics for the language of PAL, we show that the proof system based on this core set of axioms does not completely axiomatize PAL without additional axioms and rules. In fact, many of the intuitive axioms and rules we took for granted could not be derived from the core set. Moreover, we also propose and advocate an alternative yet meaningful axiomatization of PAL without the reduction axioms. The completeness is proved directly by a detour method using the canonical model where announcements are treated as merely labels for modalities as in normal modal logics. This new axiomatization and its completeness proof may sharpen our understanding of PAL and can be adapted to other dynamic epistemic logics. 相似文献
We describe briefly the redevelopment of Space Fortress (SF), a research tool widely used to study training of complex tasks
involving both cognitive and motor skills, to be executed on currentgeneration systems with significantly extended capabilities,
and then compare the performance of human participants on an original PC version of Space Fortress (SF) with the revised Space
Fortress (RSF). Participants trained on SF or RSF for 10 sets of eight 3-min practice trials and two 3-min test trials. They
then took tests involving retention, resistance to secondary task interference, and transfer to a different control system.
They then switched from SF to RSF or from RSF to SF for 2 sets of final tests and completed rating scales comparing RSF and
SF. Slight differences were predicted on the basis of a scoring error in the original version of SF used and on slightly more
precise joystick control in RSF. The predictions were supported. The SF group started better but did worse when they transferred
to RSF. Despite the disadvantage of having to be cautious in generalizing from RSF to SF, we conclude that RSF has many advantages,
which include accommodating new PC hardware and new training techniques. A monograph that presents the methodology used in
creating RSF, details on its performance and validation, and directions on how to download free copies of the system may be
downloaded from www .psychonomic.org/archive/. 相似文献
Low family socioeconomic status (SES) is linked with adolescents’ symptoms of depression, but little is known about the mediating and moderating mechanisms underlying this association. Based on ecosystem theory and the organism-environment interaction model, we tested whether emotional resilience mediated the relationship between family SES and depressive symptoms, and whether parent–child relationship quality moderated the relationship. Adolescents (N?=?724) from one middle school in central China completed self-reported questionnaires regarding demographic variables, family SES, emotional resilience, parent–child relationship quality, and depressive symptoms. Regression-based mediation analysis indicated that emotional resilience mediated the association between family SES and depressive symptoms. Parent–child relationship quality moderated two components of this mediation process, namely the effects of low SES on both emotional resilience and depressive symptoms. In both cases, a high quality parent–child relationship ameliorated the adverse effects of low family SES. That is, adolescents with a higher quality relationship with their parent appeared to be less affected by low family SES. The study reveals how and when family SES may affect adolescents’ depressive symptoms, and highlights the protective effect of a high quality parent–child relationship in a low SES environment.
A proportion of persons affected by coronavirus disease-19 (COVID-19) die and do so in extraordinary circumstances. This can make grief management extremely challenging for families. The Clinical Psychology unit of an Italian hospital offered a bereavement follow-up call to such families. This study aimed to explore the families' experiences and needs collected during these calls, and the role that the psychologists played through the call. A total of 246 families were called over 3 months. Multiple qualitative methods included: (i) written reports of the calls with relatives of patients who died at the hospital for COVID-19; (ii) qualitative semi-structured interviews with psychologists involved in the calls; (iii) observation of psychologists' peer group discussions. A thematic analysis was conducted. Six themes emerged: without death rituals, solitary, unexpected, unfair, unsafe, coexisting with other stressors. Families' reactions were perceived by psychologists as close to a traumatic grief. Families' needs ranged from finding alternative rituals to giving meaning and expressing different emotions. The psychologists played both a social-institutional and a psychological-human role through the calls (e.g., they cured disrupted communication or validated feelings and choices). This study highlighted the potential of traumatic grief of families of COVID-19 victims, and provided indications for supporting them within the space of a short phone call. 相似文献