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171.
Jun Cao 《Philosophical Magazine Letters》2016,96(11):425-431
We have a new understanding on a unified fracture criterion based on two kinds of strain energy density. A definite expression which is a function of Poisson’s ratio to describe a crucial parameter in the unified fracture criterion is derived. The critical value of Poisson’s ratio between brittle and ductile materials can be derived as 2/7 which is verified by experimental data. Besides, the effect of Poisson’s ratio on the fracture loci in stress spaces is studied using unified fracture criterion. It is found that the decrease in Poisson’s ratio increases the asymmetry of fracture loci between tensile stress states and compressive stress states in principal stress spaces and between Lode parameters are 1 and ?1 in deviatoric-stress spaces. In addition, stress triaxiality has a great effect on the fracture behaviour with different Poisson’s ratios. 相似文献
172.
Suhyun?Lee Kangyi?LeeEmail author Soon-Hyung?Yi Hye?Jun?Park Yea-Ji?Hong Hyerhim?Cho 《Journal of child and family studies》2016,25(2):407-418
Ecological view of human development calls for an investigation of multiple contexts surrounding children. In South Korea, traditional Confucianism and recent technological advancements serve as influential social and cultural contexts that affect parent–child relations and child development. High levels of parental control and strong emphasis on academic achievement have long been distinctive features of Korean parenting practices, which are attributable to Confucian values. Additionally, Korean children’s mobile phone dependency (MPD) has become a growing concern, as South Korea developed as an IT powerhouse. Combined, these contexts resulted in high parental control of children’s mobile phone use, so that such electronic devices would not hinder learning and achievement. Effects of high parental control on children’s MPD and their school life, however, have yet to be discovered. We hypothesized, that, unlike parents’ intentions, psychological control is more likely to increase MPD and disrupt school life. To examine this research model, we made use of the first and third wave data from Korea Children and Youth Panel Survey. Participants were 2378 children (52.2 % boys) of the same age of 10 in the first wave. After multiple imputation for missing values, hierarchical logistic regression followed to examine the mediational model. The results verified the hypothesized model, showing significant adverse influence of psychological control on MPD, self-regulated learning and school adjustment. MPD fully mediated the effect of psychological control on self-regulations, while partially mediating the effects on school adjustment. Implications for Korean parents with regard to supporting children’s psychological autonomy was discussed. 相似文献
173.
在含糊性问题研究领域,多值语义解释和超赋值语义解释是两个经典的研究进路。相较多值语义中的经典三值解释和基于概率赋值的模糊逻辑解释,范启德(1975)给出的超赋值语义由于引入了基于可能世界语义的可精确化结构,具有更强的表达力,能够弥补三值和模糊逻辑处理的很多不足。距离超赋值语义发表40余年后,秋叶研(2017)给出了同样满足可精确化结构条件的一个布尔多值解释。由于超赋值语义一直被当作典型的内涵语义处理方式,而在含糊性问题研究领域,布尔多值方法却在大多数时候被认为是模糊逻辑这个基于概率处理的典型的外延语义的复杂版本,内涵语义与外延语义的殊途同归,非常值得仔细思考和探究。本文将结合含糊性问题研究领域的多值语义解释和超赋值语义解释的演进过程,以内涵语义和外延语义的区分为切入点,最终指出,(当下主流定义下的)内涵语义与外延语义的界限是模糊的,而在原有界定基础上,对内涵语义增加“内涵语义要可以表达非线序的偏序结构”这一限制,能够进一步对内涵语义和外延语义进行区分。 相似文献
174.
Cyberbullying is rapidly increasing in South Korea. The present article reviews research on factors associated with cyberbullying perpetration and victimization in South Korea. Study findings suggest a number of factors within individual, family, peer, and school levels. Relations with parents, parental verbal abuse, and a lack of attachment are related to perpetration. Delinquent peer association is positively associated with perpetration and victimization, and students’ school satisfaction is negatively associated with this victimization. Adolescents’ use of social networking sites and social media and lack of rules in cyberspace are found to increase perpetration and victimization. Research and practice implications are discussed. 相似文献
175.
药物洗脱支架的使用很大程度上防止了支架内再狭窄,但随着其在临床上的广泛应用,晚期支架内血栓形成引起了人们的重视,这一并发症在一定程度上与再内皮化延迟有关.近年来对内皮祖细胞生物学特性的深入研究,使支架植入后快速再内皮化成为可能,从而为有效防止晚期支架内血栓形成提供了一个很好的研究方向.本文就此方面的研究进展作一综述. 相似文献
176.
妊娠期睡眠障碍指在妊娠期发生的睡眠形态和行为的紊乱,它已经成为影响孕妇生理、心理等问题的重要危险因素.本文主要从妊娠期睡眠障碍的概念、发生率、引起妊娠期睡眠障碍的原因、睡眠障碍对母亲、胎儿和妊娠结局的影响及睡眠障碍的干预措施等几个方面进行了综述. 相似文献
177.
The term attentional blink (AB) refers to a failure in identifying the second of two targets, separated by less than 500?ms, embedded in a rapid succession of nontargets. To examine whether the expectation of the onset of the first target affects the AB, we compared the magnitudes of the AB deficit when participants triggered the appearance of the first target and when the target was presented automatically at some time point, as in traditional AB studies. In Experiment 1, the first target appeared immediately after a participant's voluntary keypress, revealing that the accuracy for identifying the first target increased and that the AB deficit was attenuated. In Experiment 2, the temporal delay between a voluntary keypress and the first-target presentation was manipulated. The results showed that both targets could be reported accurately only when the first target was presented within 300?ms after the action. In Experiment 3, we ruled out an alternative explanation that would attribute the facilitation effect to mere physical movement, by examining the accuracy of target identification when participants voluntarily pressed a key but that action was unrelated to the onset of the first target. Taken together, the results suggest that voluntary action to trigger the onset of a visual target facilitates processing and reduces the subsequent AB deficit when the target appears within 300?ms of the action. 相似文献
178.
In this study, bulk nanostructured composite Cu60Fe40 alloy is prepared by a combustion synthesis technique. The prepared Cu60Fe40 alloy consists of Cu(Fe) solid solution and Fe(Cu) solid solution phases. The large-scaled compositional segregation in the Cu-rich and Fe-rich phases is not observed, respectively. A few micron-sized dendrite (Fe(Cu) solid solution) is embedded into the nanostructured matrix (Cu(Fe) solid solution). The grain size of the matrix is in the range 50–300?nm. The yield and fracture strength of the Cu60Fe40 alloy are 540 and 1050?MPa, respectively, and the fracture strain obtained from the compression test is about 20.9%. The Cu60Fe40 alloy displays notable work hardening in the compressive deformation. 相似文献
179.
Zhiguo Chen Jishuai Zhang Jun Shu Gang Sha Junhai Xia Shiyong Wang 《Philosophical Magazine Letters》2013,93(11):648-654
The precipitation behaviour and age-hardening response of Al–1.5Cu–4.0Mg (wt.%) alloys microalloyed with Si have been investigated by means of hardness measurement, TEM and HRTEM. Compared to the ternary alloy, the quaternary alloys exhibit a higher hardness. It is found that the underaged microstructure in the Al–1.5Cu–4.0?Mg alloy contains some fine precipitates, which are identified as the T phase by FFT spectra. The peak-aged microstructures of the ternary alloy is dominated by the T phase, while the peak-aged microstructures of the Si-containing alloys are dominated by the S phase. The volume fraction of the S phase is found to increase as more Si is added. 相似文献
180.
An inverse “smaller is stronger” trend is predicted on the basis of molecular dynamics simulations of α-titanium (Ti) single-crystal nanopillars orientated for double prismatic slips when the nanopillars are less than 7?nm wide. This trend is attributed to a significant increase in the surface energy due to the nucleation and propagation of edge dislocations on the surface of the pillars. 相似文献