Tip streaming from drops flowing in a spiral microchannel

This fluid dynamics video shows drops of water being transported by a mean flow of oil, in a microchannel shaped as a logarithmic spiral. The channel shape means that the drops are submitted to an increasing shear and elongation as they flow nearer to the center of the spiral. A critical point is reached at which a long singular tail is observed behind the drops, indicating that the drops are accelerating. This is called "Tip streaming".Comment: Abstract accompanying movie to the Gallery of Fluid Motion: APS-DFD 200

A 'New Era' in the New Middle East: China, Russia and the Reinvention of the South

Who would have expected that the BRICS nations could rise and become the potential rival of the G7 countries, the World Bank and the IMF combined? That once seemingly distant possibility now has real prospects which could change the equilibrium of world politics. The more successful BRICS becomes, the weaker Western hegemony over the South will be. Although some Western politicians and media insist on downplaying the group’s role in shaping the new world order, the change seems real and irreversible. Even before the Ukraine war commenced in February 2022, much evidence pointed to the fact that Russia and China’s goal was hardly temporary or impulsive. The very language of multipolarity has defined both countries’ discourse for years, a discourse that was mostly inspired by the two countries’ displeasure with US militarism from the Middle East to Southeast Asia, their frustration with Washington’s bullying tactics whenever a disagreement arises, be it in trade or border demarcations, the punitive language, the constant threats, the military expansion of NATO and much more. While it is too early to determine, with any degree of certainty, the winners and losers of this new configuration, it is almost certain that a US-westerndominated world is no longer possible

Breaking anchored droplets in a microfluidic Hele-Shaw cell

We study microfluidic self digitization in Hele-Shaw cells using pancake droplets anchored to surface tension traps. We show that above a critical flow rate, large anchored droplets break up to form two daughter droplets, one of which remains in the anchor. Below the critical flow velocity for breakup the shape of the anchored drop is given by an elastica equation that depends on the capillary number of the outer fluid. As the velocity crosses the critical value, the equation stops admitting a solution that satisfies the boundary conditions; the drop breaks up in spite of the neck still having finite width. A similar breaking event also takes place between the holes of an array of anchors, which we use to produce a 2D array of stationary drops in situ.Comment: 5 pages, 4 figures, to appear in Phys. Rev. Applie

Algebraic observer design for PEM fuel cell system

© 20xx IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.In this paper, the concept of the algebraic observer is applied to Proton Exchange Membrane Fuel Cell (PEMFC) system. The aim of the proposed observer is to reconstruct the oxygen excess ratio through estimation of their relevant states in real time from the measurement of the supply manifold air pressure. A robust differentiation method is adopted to estimate in finite-time the time derivative of the supply manifold air pressure. Then, the relevant states are reconstructed based on the output-state inversion model. The objective is to minimize the use of extra sensors in order to reduce the costs and enhance the system accuracy. The performance of the proposed observer is analyzed through simulations considering measurement noise and different stack-current variations. The results show that the algebraic observer estimates in finite time and robustly the oxygen-excess ratio.Peer ReviewedPostprint (author's final draft

Thermocapillary valve for droplet production and sorting

Droplets are natural candidates for use as microfluidic reactors, if active control of their formation and transport can be achieved. We show here that localized heating from a laser can block the motion of a water-oil interface, acting as a microfluidic valve for two-phase flows. A theoretical model is developed to explain the forces acting on a drop due to thermocapillary flow, predicting a scaling law which favors miniaturization. Finally, we show how the laser forcing can be applied to sorting drops, thus demonstrating how it may be integrated in complex droplet microfluidic systems.Comment: Five pages, four figure

70 años de «catástrofe»: ¿puede Israel frustrar el «derecho de retorno» para los refugiados palestinos?

The US is currently following a blueprint of a strategy in which it advances Israel’s “victory”, while imposing conditions of surrender on defeated Palestinians. (Pipes, 2016) One of the main targets of this new policy is Palestinian refugees, scattered in their millions across Palestine and the Middle East. But the ‘Nakba’, starting 70 years ago - and all of its dire consequences, since then - is a concept that is so deeply entrenched in the hearts and minds of most Palestinians to this day. Thus, the refugees and their insistence on their Right of Return are the main, if not the only, obstacles before the US-Israeli plot. En la actualidad, los EE.UU. están acometiendo un proyecto estratégico por el cual se presume la «victoria» de Israel, a la vez que impone condiciones de rendición en los palestinos derrotados (Pipes, 2016). Uno de los objetivos cruciales de esta nueva política son los refugiados palestinos, dispersos por millones tanto en tierra palestina como en el Oriente Medio. El Nakba, iniciado hace 70 años, y todas sus funestas consecuencias desde entonces, se revela un concepto hondamente vertebrado en las mentes y almas de la gran mayoría de palestinos hasta el presente. Por ello, los refugiados y su insistencia en su Derecho de Retorno constituyen el principal (y casi único) obstáculo en el complot EE.UU-Israelí

The Tension between Illusion and Reality in H. Ibsen’s The Wild Duck

Much of contemporary criticism of Ibsen plays has examined one of two concerns Ibsen and Feminism or Ibsen as a realist and a pioneer of modern theatre and drama Articles on the first matter are often critical of universalizing readings of Ibsen that would have the dramatist concerned with the ills of humanity articles on the latter theme tend to rejoice Ibsen s assumed anti-theatrical overcoming of melodrama Both topics can be found in his masterpiece The Wild Duck which is more honoured and received well in the study more than the other plays Like Hamlet The Wild Duck can be interpreted by each one in his own image one day it will be read as a tragedy or tragicomedy the next as the harshest irony parts of it are clumsy in other parts are embedded old controversies of that time So searching yet so delicate is the touch that these flaws and notions seem in themselves to strengthen the play In this work Ibsen perfected his own special power to infuse the particular dull limited fact with a halo and a glory This paper is an attempt to examine the tension between illusion and reality in the pla

Predicting student performance using data mining and learning analysis technique in Libyan Higher Education

The Technology has an increasing impact on all areas of life, including the education sector, and requires developing countries to emulate developed countries and integrate technology into their education systems. Recently schools in Libya are facing an issue trying to figure out why students perform poorly in certain subjects and how can they know how they will perform next in the future in coming semesters in perspective subject. There are several methods proposed to predict the student’s performance, using data mining techniques. In this paper, there are plans to create Data Mining Techniques in Education (i.e., DME) prediction model clustering, classification and association rule mining in many universities and schools in order to provide students and teachers with the most advanced platform. Although relatively late, the Libyan government finally responded to this challenge by investing heavily in rebuilding the education system and launching a national plan to presented method in terms of predicting students’ performance based on their grades in Math and English. The results are divided in to three main sections clustering analysis using k-mean algorithm, classification analysis was done using two rounds first using Gain Ratio Evaluations to find out the top attributes that used by J84 algorithm in second round of classification, and rule association analysis using A priori algorithm. Rule association analysis is applied for the clusters generate by clustering analysis to generate the rules associated with each cluster. For each section, a list of inputs is presented with the scale used for the values followed by the results of the algorithm and explanation for the finding

Tolerance in uae islamic education textbooks

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. The concept of “tolerance” has been thoroughly promoted within educational settings in light of the increasing need to foster co-existence and to nurture peaceful climates in societies. The United Arab Emirates (UAE) Islamic education curriculum promotes the notion of tolerance as a core tenant across different grade levels. However, there is a gap in the literature investigating the approach and conceptualization of tolerance in UAE Islamic education curricula. This study employed qualitative content analysis of grade 10–12 textbooks to understand how the concept of tolerance is promoted and to identify the opportunities and gaps in teaching tolerance through these texts. The notion of tolerance in these texts was discussed through the themes of civic engagement, critical thinking, acceptance of multiplicity, justice and equity, protection from extremism, and compassion for humans. This study identified gaps in addressing tolerance and suggested other concepts that could further supplement the Islamic education program to more thoroughly address the notion of tolerance. This study argues that teaching tolerance through religious-based instruction may facilitate an exploration of effective tolerance inculcation approaches that provide insights into the field of tolerance education at large

Local interactions and the global organization of a two-phase flow in a branching tree

International audienceThe transport of liquid plugs in a microfluidic branching tree is studied experimentally. The global flow pattern can be either symmetric or asymmetric, with daughter plugs dividing in synchrony or asynchrony as a function of the driving flow rate and the network geometry. For trees with narrowing channels, the plugs always reach the exits even at low flow rates. In contrast, only one path is opened in networks with widening channels when the flow rate is low. This behavior is explained by a comparison of the pressure drop necessary to drive viscocapillary motion of plugs in straight channels with the nonlinear pressure variations as a plug passes a bifurcation. A model is built, which predicts that only narrowing networks can be fully filled, while widening networks can never be fully invaded by a two-phase flow. © 2010 The American Physical Society