蠕变条件下完整岩石的起裂和扩展准则     

陈有亮  岳中琦  谭国焕  李启光 《上海大学学报(英文版)》2002,6(1):24-35

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.  相似文献   

Engineering design as an intellectual problem     

B. Z. Sandler 《European Journal of Engineering Education》2002,27(2):157-172

Engineering education has recently been going through a process of internal fighting between the tendency to introduce more and more information and skills in the fields of computerization and mathematics (mathematics for engineers), on the one hand, and the need to provide the student with pure empirical technical and design knowledge and experience, on the other hand. In most mechanical engineering departments, the outcome of this competition has been a reduction in the time allotted to teaching the empirical part of engineering information: there is often a psychological barrier to understanding the importance of this group of subjects, and the computer- and mathematics-associated subjects usually win out. As a result, the new graduate usually knows how to fight the computation struggle but he/she is not able to formulate his/her final engineering goal. This paper focuses on various aspects of this situation. In particular, we set out to defend the need for serious and in-depth teaching of the empirical information required in engineering design work.  相似文献   

解读教育装备     

PaulZ．PerJes 《中国现代教育装备》2004,(6):40-41

什么是教育装备?这个问题看似简单,却并不是那么容易回答.教育装备的使用者,制造者及其相关人员都有着见仁见智的想法.如何看待这一问题,无论对于企业还是教师、学生都有重要的意义.教育界的专家与教育装备有着亲密接触,下面就来听听他们的声音吧.  相似文献   

Book reviews     

John McMurtry  David Stephens  Duffie Van Balkom  Edgar Z. Friedenberg 《Interchange》1989,20(4):77-90

  相似文献   

An immunological based study of monoclonal gammopathies among suspected individuals in Kashmir region     

M. Shafi  M. Zargar  Z. A. Shah  M. Salahuddin  M. Siddiqi 《Indian journal of clinical biochemistry : IJCB》1998,13(2):106-110

Serum and urine samples from 513 patients clinically suspected of monoclonal gammopathies over a period of five years (1992–97) were subjected to various immunological procedures viz, electrophoresis, immunoelectrophoresis and immunoglobulin estimations. Laboratory investigations confirmed gammopathies in 10.33%. It was observed that overall age of incidence for monoclonal gammopathies in both sexes was between 42–72 years with a male to female ratio of 1.4∶1. Predominant paraprotein detected was IgG type (75.47%) followed by IgA (16.98%) and Bence Jones proteins (7.55%). Amongst positive patients, 64.16% were having kappa (k) type light chains and 35.84% lambda (δ) type light chains. 69.39% patients with serum M component (IgG and IgA) had Bence Jones proteinuria. Densitometric scanning revealed that majority of IgG type paraprotein was found in the slow gamma globulin region and majority of IgA type paraprotein was found equally distributed between beta and fast gamma globulin regions. Both types had decreased albumin and alpha-2-globulin concentrations as compared to normal controls. Immunoglobulin levels in patients with paraprotein had very high levels of serum IgG (6467.0 mg%) and IgA (2714.0 mg%) in respective types of monoclonal gammopathies; the rest of immunoglobulin classes were either at normal or decreased levels.  相似文献   

Education of Children with Vision Impairments in the Sultanate of Oman     

Muna S. Z. Hadidi 《International Journal of Disability, Development & Education》1998,45(4):423-429

The educational and developmental needs of children with disabilities in general, and of children with vision impairments in particular, have been ignored until recently in the Sultanate of Oman. However, the situation of special education and rehabilitation services is changing and there is progress to report. This article presents an overview of the prevalence and patterns of vision impairment, types of services offered, and priorities for future work.  相似文献   

Engineering Education in Israel: Situation,Debate and Prospects     

D. VEKSTEIN  A. MEHREZ  Z. LASLO  A. SOLOMON 《European Journal of Engineering Education》1999,24(1):95-104

This paper focuses on the current situation of engineering education in Israel, the debate over the ways to manage it, and the prospects that a balanced education policy can entail for socio-economic development. Two degrees in engineering, the BTech and BSc, are described. It transpired that the BTech failed to meet the expectations. From the on-going debate about the situation, the need for a balanced policy for engineering education has emerged. This policy is outlined and it is shown that it can not only improve the BTech situation, but also Israel's national innovation system by viewing ‘research’ and ‘applied’ engineers as complementary to, rather than competing with, each other. It is also suggested that this balanced policy should implement project-based instruction in the engineering curriculum, both in the BTech and BSc programmes.  相似文献   

Spoken language development in oral preschool children with permanent childhood deafness     

Sarant JZ  Holt CM  Dowell RC  Rickards FW  Blamey PJ 《Journal of deaf studies and deaf education》2009,14(2):205-217

This article documented spoken language outcomes for preschool children with hearing loss and examined the relationships between language abilities and characteristics of children such as degree of hearing loss, cognitive abilities, age at entry to early intervention, and parent involvement in children's intervention programs. Participants were evaluated using a combination of the Child Development Inventory, the Peabody Picture Vocabulary Test, and the Preschool Clinical Evaluation of Language Fundamentals depending on their age at the time of assessment. Maternal education, cognitive ability, and family involvement were also measured. Over half of the children who participated in this study had poor language outcomes overall. No significant differences were found in language outcomes on any of the measures for children who were diagnosed early and those diagnosed later. Multiple regression analyses showed that family participation, degree of hearing loss, and cognitive ability significantly predicted language outcomes and together accounted for almost 60% of the variance in scores. This article highlights the importance of family participation in intervention programs to enable children to achieve optimal language outcomes. Further work may clarify the effects of early diagnosis on language outcomes for preschool children.  相似文献   

THE LEBANESE BREVET CHEMISTRY AND PHYSICS EXAMINATIONS: AN EXPLORATORY STUDY     

Barend Vlaardingerbroek  Lama Z. Jaber  Nadya G. Rizk  Jana M. Bayoud 《International Journal of Science and Mathematics Education》2009,7(6):1227-1247

  相似文献   

Sense of extension force and angle of the knee joint are correlated between two generations of men     

Anna Bezulska  M. Naczk  Z. Adach  J. Arlet  J. Celichowski 《Journal of sports sciences》2018,36(5):565-570

Numerous motor abilities depend on the activity of proprioceptors, which has been suggested to be genetically determined. To test this hypothesis, the control of torque generated by knee extensors and knee position was studied in 30 father–son pairs both before and immediately after running. After stabilisation of the participant in a sitting position, the knee joint of his dominant leg was flexed to 90°, and the maximal voluntary torque (MVT) of the dominant knee extensors under static conditions was measured. The participant then tried five times to produce 50% of the MVT. Next, the participant extended the knee to 45° five times without visual control. Significant correlations between the reproducibility of successive trials for groups of fathers and their sons were found. The correlation coefficients for the repeatability of the knee extension torque were 0.69 (confidence interval [CI] = 0.45–0.84; P < 0.01) and 0.75 (CI = 0.54–0.87; P < 0.01) before and after the fatiguing exercise, respectively, whereas the coefficient for the reproducibility of positioning the knee was 0.49 (CI = 0.16–0.72; P < 0.01) after the fatiguing exercise. Our results indicate a significant influence of hereditary factors on the control of limb torque and position.  相似文献