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Martinez-Perez M.,University of Arts and Science of Chiapas
Advances in Child Development and Behavior | Year: 2016

This chapter examines how 2-year-old children attempt to actively participate in adult work in a Mayan community in Chiapas, Mexico, and how adults contribute and accommodate to the contributions. As children enter into activities and adults orient and reorient the activity to direct the children, teaching from expert to novice is generated by children's agency in co-participatory interactions. The chapter enriches the LOPI model by focusing on the structure of participation and communication, social and community organization, and the evaluation that occurs in the activity itself. © 2015 Elsevier Inc. Source


Martinez-Perez M.,University of Arts and Science of Chiapas
Advances in child development and behavior | Year: 2015

This chapter examines how 2-year-old children attempt to actively participate in adult work in a Mayan community in Chiapas, Mexico, and how adults contribute and accommodate to the contributions. As children enter into activities and adults orient and reorient the activity to direct the children, teaching from expert to novice is generated by children's agency in co-participatory interactions. The chapter enriches the LOPI model by focusing on the structure of participation and communication, social and community organization, and the evaluation that occurs in the activity itself. © 2015 Elsevier Inc. All rights reserved. Source


Ibanez G.,University of Arts and Science of Chiapas | Cuevas S.,National Autonomous University of Mexico
Energy | Year: 2010

The dissipative processes that arise in a microchannel flow subjected to electromagnetic interactions, as occurs in a MHD (magnetohydrodynamic) micropump, are analyzed. The entropy generation rate is used as a tool for the assessment of the intrinsic irreversibilities present in the microchannel owing to viscous friction, heat flow and electric conduction. The flow in a parallel plate microchannel produced by a Lorentz force created by a transverse magnetic field and an injected electric current is considered assuming a thermally fully developed flow and conducting walls of finite thickness. The conjugate heat transfer problem in the fluid and solid walls is solved analytically using thermal boundary conditions of the third kind at the outer surfaces of the walls and continuity of temperature and heat flux across the fluid-wall interfaces. Velocity, temperature and current density fields in the fluid and walls are used to calculate the global entropy generation rate. Conditions under which this quantity is minimized are determined for specific values of the geometrical and physical parameters of the system. The Nusselt number is also calculated and explored for different conditions. Results can be used to determine optimized conditions that lead to a minimum dissipation consistent with the physical constraints demanded by the microdevice. © 2010 Elsevier Ltd. Source


Ibanez G.,University of Arts and Science of Chiapas
International Journal of Heat and Mass Transfer | Year: 2015

Combined effects of hydrodynamic slip, magnetic field, suction/injection and convective boundary conditions on the global entropy generation in steady flow of an incompressible electrically conducting fluid through a channel with permeable plates are studied. Analytical solutions of the governing equations are obtained in closed form. Particularly, using thermal boundary conditions of the third kind, the temperature field is derived analytically. Also, the influences of the governing parameters on global entropy generation are discussed in detail and depicted graphically. The analysis of our results indicates that entropy generation minimization can be achieved by appropriate combination of the geometrical and physical parameters of the system. It is possible to determine optimum values of Hartmann number, Biot number and Prandtl numbers which lead to a minimum global entropy generation rate. The effects of slip flow on the optimum values of some other parameters are also explored. © 2014 Elsevier Ltd. All rights reserved. Source


Ruiz Meza L.E.,University of Arts and Science of Chiapas
Climate and Development | Year: 2015

This paper identifies conditions of social vulnerability and climate-related disaster risk in the Huehuetán River basin, Chiapas, Mexico and analyses the capacity of small coffee producers to adapt to hydrometeorological hazards. Small-scale farmers in the basin use various strategies to adapt to the impacts of such hazards and to confront the deterioration of their livelihoods, including diversifying the varieties of coffee they cultivate, diversifying their sources of income, and emigration. Analysis of these strategies suggests that high levels of poverty, coffee monoculture, food insecurity, and instability in sources of employment and income combine to limit the flexibility and stability of population's adaptive capacity. The strategies employed by local people have allowed for short-term subsistence but offer little chance of long-term sustainability. Conditions do not appear to reduce social vulnerability and, in fact, undermine local resilience that would reduce damage and risks from extreme climate events. The impacts of climate change are placing the region's small farmers in a very vulnerable situation from which it may be difficult to escape, without the implementation of social reform predicated on greater justice and social equality, which will require political will. This case illustrates the challenges that must be addressed in order to overcome the social inequalities that prevent small-farmer communities from reducing their vulnerability in the face of climate-(or non-climate-) related risks. © 2014, © 2014 Taylor & Francis. Source

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