蠕变条件下完整岩石的起裂和扩展准则

The mechanism and criterion of crack initiation and propagation of rocks were investigated by many researchers,And the creep behaviour of rocks was also theoretically and experimentally studied by some scientists and engineers.The characteristics of crack initation and propagation of rocks under creep condition.however,are very improtant for rock engineering and still not paid enough attention by researchers,In this paper,the criterion and mechanism of crack initiation and propagation under creep condition were investigated using specimens collected from sandstone rock formations outcropping in the Emei Mountain,the Sichuan Province of China.Cuboid specimens under three point bending were used in this investigation.All specimens were classified into four sorts and used for Mode-I fracutre of creep frcture tests.The experimental result shows that due to creep deformation.rock crack will inevitably initialt and propagate under a load of KI,which is less than fracture toughness KIC but not less than a constant(marked as KIC2),KIC2 indicates the ability of rock to resist crack initiation and propagation under creep conditions and is less than fracture tough ness KIC.defined as creep fracture toughness in this paper,KIC2 should be considered as an importnat parameter on design and computation of rock engineering.The microstructureal mechanism for crack initiation and propagation of rock materials under creep condition was introduced based on competitive model between softening effect and hardening effect,and the validity of test result was explained.The test result was also verified in rheological theory.When KI is more than KIC2 but less than KIC,rock crack will initiate and propagate after a time interval of sustained loading under creep condition.In order to find the relation between duration of sustained lading.which can lead to crack initiation and propagation,and the initial stress intensity factor KI,an unequal0interval time sequence forecasting and predicting model was introduced,and the relation was obtained for homogeneous and isotropic fine-grained red sandstone.Finally a modified fracture toughness formula was given,in which the influence of fracture process zone(FPZ) was fully considered.     

Learning to Learn to Teach: An ``Experiment' Model for Teaching and Teacher Preparation in Mathematics

This paper describes a model for generating andaccumulating knowledge for both teaching andteacher education. The model is applied firstto prepare prospective teachers to learn toteach mathematics when they enter theclassroom. The concept of treating lessons asexperiments is used to explicate theintentional, rigorous, and systematic processof learning to teach through studying one's ownpractice. The concept of planning teachingexperiences so that others can learn fromone's experience is used to put into practicethe notion of contributing to a sharedprofessional knowledge base for teachingmathematics. The same model is then applied tothe work of improving teacher preparationprograms in mathematics. Parallels are drawnbetween the concepts emphasized for prospectiveteachers and those that are employed byinstructors who study and improve teacherpreparation experiences. In this way, parallelsalso are seen in the processes used to generatean accumulating knowledge base for teaching andfor teacher education.     

Are researchers bound by child abuse reporting laws?

OBJECTIVE: To discuss issues concerning mandatory reporting of child abuse in research settings. METHOD: An overview of existing Federal and State statutes regarding mandatory reporting of child abuse is presented. A critical review of the literature addresses the following issues: (1) whether researchers have a moral duty to place the health and safety of children above concerns about confidentiality and the benefits of obtaining new knowledge; (2) whether the Certificate of Confidentiality preempts reporting requirements; (3) whether researchers who are not health professionals (such as child developmentalists, psychobiologists, neuroscientists) should be required to report; and (4) whether researchers should be required to expand their protocols to include more in-depth investigation of potential abuse. RESULTS: Existing child abuse reporting laws do not specifically designate researchers as among the category of individuals mandated to report suspected child abuse. Currently, Human Subject Protection Committees and Federal funding agencies are tending to interpret reporting laws as applying to researchers, including requiring that research subjects are informed of this responsibility in consenting procedures. It is unclear whether the Certificate of Confidentiality preempts child abuse reporting laws. CONCLUSION: The authors recommend that legislatures specifically designate researchers as mandated reporters to ensure more uniform reporting practices in research settings. For both investigators and Human Subject Protection Committees, inclusion of researchers among the categories of those mandated to report would also help address issues of immunity from civil and criminal liability for "good faith" reports that turn out to be false and injurious.     

Youth Voice,Civic Engagement and Failure in Participatory Action Research

In this article, we tell the story of a changing urban landscape through the eyes of the youth we work with in an ongoing after-school program and community-based research project rooted in Photovoice methodology. In particular, we focus on the work that, over the 6 years of our time with youth, has “ended up on the cutting room floor” (Paris and Winn (eds) Humanizing research: decolonizing qualitative inquiry with youth and communities. SAGE Publications, Thousand Oaks, 2014, p. xix). This attention to the work that has fallen through the cracks is a move to engage the central tenets of Humanizing Research, but it’s also a call to think critically with and through the failures that emerge in work with youth. We attend specifically to an ongoing failure in our work as a way to think about the kinds of promises that are often made and broken in participatory action research. In doing so, we tease out the implications of our work with youth and the steps community-based researchers can take to navigate the challenges that can impede the goals of fostering meaningful change.     

Impairments in learning due to motivational conflict: situation really matters

Although many theories mention distractions by conflicting alternatives as a problem for self-regulation, motivational conflicts are rarely considered when explaining impairments in learning. In two studies, we investigate the assumption of motivational interference theory that students show different amounts of impairments in learning depending on the presence and motivational strength of conflicting alternatives. In Study 1 (N?=?221), the subjective value attributed to a respective alternative in a study–leisure conflict scenario partially accounted for differences in self-regulated learning while controlling for interindividual differences. Study 2 (N?=?112) demonstrated that this pattern applies to both when the respective alternatives refer to ‘liking to’ (want conflicts) and ‘having to’ (should conflicts) do something. Moreover, it is demonstrated that impairments due to motivational conflict are higher than impairments inherent in the studying activity itself (baseline). The results emphasise the importance of concurring action alternatives for explaining difficulties in self-regulated learning.     

Academic progress of children who attended a preschool for abused children: a follow-up of the keepsafe project

OBJECTIVE: This study was undertaken to assess academic progress of children 1 to 5 years after graduating from the C. Henry Kempe Center's Therapeutic Preschool Day Treatment Program. METHOD: Information was gathered through chart review; telephone surveys of care providers, relatives, and social service workers; as well questionnaires on all children who attended the therapeutic preschool day treatment program between 1984 and 1989, including the 24 children reported on by Oates, Gray, Schweitzer, Kempe, and Harmon, 1995. RESULTS: Classroom placement was determined for 27 of the 44 graduates (61.4%), 14 of whom (51.9%) were in a regular classroom, 10 (37.0%) in special education, two (7.4%) in residential treatment, and one (3.7%) was receiving home schooling. Twenty-two of the 27 children (81.5%) improved or remained in the same grade and type of classroom as they had been staffed into at the time of their graduation from the preschool day treatment program. Factors thought to affect stability of classroom placement were studied, of which frequency of family moves was the only significant variable. Its significance was in the direction opposite to that expected. The most effective method of locating families was to contact the Department of Social Services who provided information used to find 60% of them. CONCLUSIONS: Intervention in a therapeutic preschool day treatment program was found to be beneficial, as it enabled most of the children to progress appropriately in public school.     

Political Perspectives on Church Schools and Religious Education: A discussion of the period from Thatcher to Blair

Making use of material written by British prime ministers, a case is presented for understanding church schools and religious education in a way distinct from that normally utilised in academic discourse. Politicians in democratic countries depend on attracting votes to assume power. They therefore integrate church schools and religious education within existing political positions. Conservative politicans see church schools as being an example of parental choice and religious education as being an aid to moral education. Labour politicians see church schools as contributing to a pluralistic society and aiding the cultural identity of ethnic groups.     

Salient Effects of Practice Poster Sessions on Counselor Development: Implications for Research Training and Professional Identification

This study examined the effects of a 2-step practice poster session on first-year doctoral students' self-efficacy beliefs about making professional presentations, and evaluated the usefulness of an active-learning teaching assignment. Quantitative and qualitative data were collected from participants after each of 2 practice poster sessions. The results (a) suggest that the relatively brief training exercise significantly increased participants' self-efficacy to give scholarly presentations, and (b) replicate earlier reports about the usefulness of the learning assignment.