Filtration of micro-particles within multi-fiber arrays by adhesive DEM-CFD simulation

A 3D multi-time scale discrete element method-computational fluid dynamic (DEM-CFD) coupling approach was applied to investigate the filtration of micron-sized particles by different types of fiber arrays. Both the pressure drop and the filtration efficiency were examined to indicate the filtration performance of the fiber arrays. Fibers that were uniformly arrayed in a parallel or staggered manner were compared. Results showed that the staggered array showed a better performance than the parallel array in terms of both pressure drop and filtration efficiency. Further, we compared the performance of different staggered arrays, i.e. a regular case, one densified in the front layers and another densified in the back layers. The front densified array was found to enter the clogging and cake filtration stage in the shortest time, leading to the highest filtration efficiency, but the highest pressure drop. The back densified array still achieved a much higher filtration efficiency, despite a much lower pressure drop comparable to that of the regular array. The results suggest that the two kinds of densified arrays may be suited for different purposes, e.g. baghouse filters or breathing masks.     

A novel multi-objective optimization method for the pressurized reservoir in hydraulic robotics

The pressurized reservoir is a closed hydraulic tank which plays a significant role in enhancing the capabilities of hydraulic driven robotics. The spring pressurized reservoir adopted in this paper requires comprehensive performance, such as weight, size, fluid volume, and pressure, which is hard to balance. A novel interactive multi-objective optimization approach, the feasible space tightening method, is proposed, which is efficient in solving complicated engineering design problems where multiple objectives are determined by multiple design variables. This method provides sufficient information to the designer by visualizing the performance trends within the feasible space as well as its relationship with the design variables. A step towards the final solution could be made by raising the threshold on performance indicators interactively, so that the feasible space is reduced and the remaining solutions are more preferred by the designer. With the help of this new method, the preferred solution of a spring pressurized reservoir is found. Practicability and efficiency are demonstrated in the optimal design process, where the solution is determined within four rounds of interaction between the designer and the optimization program. Tests on the designed prototype show good results.     

Integrating Tinbergen's inquiries: Mimicry and play in humans and other social mammals

Visual signals convey emotions and intentions between individuals. Darwin underlined that human facial expressions represent a shared heritage between our species and many other social mammals. Social play is a fertile field to examine the role and the potential communicative function of facial expressions. The relaxed open-mouth (or play face) is a context-specific playful expression, which is widespread in human and non-human mammals. Here, we focus on playful communication by applying Tinbergen’s four areas of inquiry: proximate causation, ontogeny, function, and evolution. First of all we explore mimicry by focusing on its neural substrates and factors of modulation within playful and non-playful context (proximate causation). Play face is one of the earliest facial expressions to appear and be mimicked in neonates. The motor resonance between infants and their caregivers is essential later in life when individuals begin to engage in increasingly complex social interactions, including play (ontogeny). The success of a playful session can be evaluated by its duration in time. Mirroring facial expressions prolongs the session by favoring individuals to fine-tune their own motor sequences accordingly (function). Finally, through a comparative approach we also demonstrate that the elements constituting play communication and mimicry are sensitive to the quality of interindividual relationships of a species, thus reflecting the nature of its social network and style (evolution). In conclusion, our goal is to integrate Tinbergen’s four areas of ethological inquiry to provide a broader framework regarding the importance of communication and mimicry in the play domain of humans and other social mammals.     

Contradictions,dialectical oppositions and shifts in teaching mathematics

The study reported in this paper concerns the tensions and conflicts that teachers experience while they enact a new set of reform-oriented curricular materials into their classrooms. Our focus is οn the interactions developed in two groups of teachers in two schools for a period of a school year. We use Activity Theory to study emerging contradictions and we elaborate on the construct of dialectical opposition to understand the nature of these contradictions and their potential for teacher learning. We provide evidence that discussions about contradictions and their dialectical character in the two groups support teachers to engage differently in mathematics teaching and learning and carry potentials for shifts in the practices that evolve in their classrooms. Our study addresses empirically in the context of mathematics teaching the philosophical claim about the role of contradictions as a driving force for any dynamic system.     

Returns on vocational education over the life cycle: Between immediate labour market preparation and lifelong employability

An important issue in the design of secondary-level education is the balance between conveying general and occupation-specific (vocational) skills. On the one hand, vocationally oriented programmes, providing occupation-specific skills with immediate labour market relevance, have repeatedly been shown to secure safe pathways into employment. On the other hand, these programmes tend to put less emphasis on developing general knowledge, skills and competencies, including numeracy and literacy, which are foundational to lifelong learning. Hence, when the needs of the labour market change, employees who opted for a vocational track when they were at secondary school risk being less flexible in adapting to such changes later in their career. The authors of this article examine whether this results in a trade-off between short-term gains and long-term losses by considering differences in the labour market careers of vocationally and generally educated respondents in the 2012 Programme for the International Assessment of Adult Competencies (PIAAC). Their results suggest that early labour market benefits of vocational specialisation decrease over time; the authors relate this to its lower ability to equip secondary school students – future employees – with skills for lifelong learning.     

Random vibration analysis of switching apparatus based on Monte Carlo method

The performance in vibration environment of switching apparatus containing mechanical contact is an important element when judging the apparatus’s reliability. A piecewise linear two-degrees-of-freedom mathematical model considering contact loss was built in this work, and the vibration performance of the model under random external Gaussian white noise excitation was investigated by using Monte Carlo simulation in Matlab/Simulink. Simulation showed that the spectral content and statistical characters of the contact force coincided strongly with reality. The random vibration character of the contact system was solved using time (numerical) domain simulation in this paper. Conclusions reached here are of great importance for reliability design of switching apparatus.     

Homoharringtonine induces apoptosis of endothelium and down-regulates VEGF expression of K562 cells

Homoharringtonine (HHT) has currently been used successfully in the treatment of acute and chronic myeloid leukemias and has been shown to induce apoptosis of different types of leukemic cells in vitro. Emerging evidence suggests that angiogenesis may play an important role in hematological malignancies, such as leukemia. How ever, whether HHT can relieve leukemia by anti-angiogenesis is still unknown. We investigated the anti-angiogenesis potential of HHT with the human umbilical vein endothelial cell line (ECV304) and leukemic cell line (K562) in vitro. Cellular proliferation was determined by MTT assay and apoptosis was analyzed by flow cytometry. The mRNA expression of vascular endothelial growth factor (VEGF) was assessed by RT-PCR and VEGF protein production was detected by Western blot. Inhibition of cell proliferation and induction of apoptosis by HHT were discovered in ECV304 cells, and appeared in a dose- and time-dependent manner. Also, treatment with HHT caused down-regulation of VEGF mRNA expression in K562 cells in similar dose- and time-dependent manner and inhibition of VEGF protein production in K562 cells in response to the enhancing concentration of HHT. The results demonstrated that HHT could also induce apoptosis in endothelium and down-regulate VEGF expression in K562 cells. In conclusion, we believe HHT has anti-angiogenesis potential and speculate that HHT might exert its anti-leukemia effects via reduction of angiogenesis.     

The effects of educational reform on the content and status of the social subjects in England and wales and the USA: A case study

Over the past decade educational reform has been taking place in the USA and in England and Wales. This paper traces the political pressures to change the social subjects curriculum on both sides of the Atlantic. In England and Wales the new National Curriculum aims to raise educational standards and to increase accountability through a national assessment system. In the USA the Federal Government has set to work on establishing national goals. There is evidence in both countries that the new curricula are emerging from a political process which imposes content and structures upon teachers with little consultation. The paper concentrates on how the social studies curriculum has been affected in this process. It explores the politics of curricular reform by comparing events in the USA and England and Wales and outlines the ways, particularly in the British context, in which the teaching profession has explored the limits of its power and has fought back against central control to make its voice heard.

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Zusammenfassung In den letzten zehn Jahren gab es eine Bildungsreform in den USA, sowie in England und Wales. Dieser Bericht studiert den politischen Druck, der zu einer Änderung des Curriculums in den Sozialfächern auf beiden Seiten des Atlantiks geführt hat. In England und Wales soll das neue nationale Curriculum den Bildungsstandard anheben und die Verantwortlichkeit durch ein nationales Bewertungssystem steigern. In den USA begann die Bundesregierung mit der Festsetzung nationaler Ziele, die den Lehrern Inhalte und Strukturen mit wenig Mitbestimmungsrecht auferlegt. Der Artikel konzentriert sich auf die Auswirkungen dieses Prozesses auf das Curriculum der Sozialstudien. Er untersucht die Politik der Curriculums-Reform, in dem Ereignisse in den USA, England und Wales verglichen werden. Insbesondere im britischen Kontext werden Wege aufgezeigt, auf denen der Lehrberuf die Grenzen seiner Macht erforscht und sich gegen eine zentrale Kontrolle gewehrt hat, um Aufmerksamkeit auf sich zu ziehen.

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Resumen Durante la última década se ha realizado una reforma de la educación en los EEUU, Inglaterra y Gales. Este trabajo esboza las presiones políticas de cambiar los planes de estudio de los sujetos sociales a ambos lados de Atlántico. En Inglaterra y Gales, elNew National Curriculum aspira a crear estándares de la educación y a incrementar la responsabilidad a través de un sistema nacional de valoración. En los EEUU, el Gobierno Federal ha comenzado a trabajar en la fijación de objetivos nacionales. Es evidente que en ambos países los nuevos planes de estudios están emergiendo de un proceso político que impone contenidos y estructuras a los maestros, consultándolos poco o nada. El trabajo se concentra en el impacto que ha sufrido el curriculo de estudios sociales en este proceso. Explora la política de la reforma curricular comparando acontecimientos de los EE UU y de Inglaterra y Gales y proporciona una idea general de los modos, particularmente en el contexto británico, en los que la profesión de enseñanza ha explorado los límites du su poder y se ha defendido contra el control central para hacerse escuchar.

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Résumé Au cours de la dernière décennie, une réforme éducative a été engagée aux Etats-Unis, en Angleterre et au pays de Galles. Cet article retrace les pressions politigues qui ont été exercées pour remanier les thèmes sociaux dans les programmes des deux côtés de l'Atlantique. En Angleterre et au pays de Galles, le nouveau curriculum national a pour but d'élever les niveaux de l'enseignement et d'augmenter la responsabilité par un système national d'évaluation. Aux Etats-Unis, le gouvernement fédéral a entrepris d'établir des objectifs nationaux. Il est évident que dans les deux pays, les nouveaux programmes sont nés d'un processus politique qui a imposé aux enseignants des contenus et des structures en les consultant à peine. L'article se concentre sur les retombées de ce processus sur les programmes d'études sociales. Il étudie la politique de la réforme curriculaire en comparant les événements intervenus aux Etats-Unis et en Angleterre-pays de Galles et souligne, en particulier dans le contexte britannique, la façon dont le corps enseignant a épuisé les limites de son pouvoir et a résisté au contrôle central pour se faire entendre.

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