Advanced Nuclear Energy Systems: Heat Transfer Issues and Trends

Almost 450 nuclear power plants are currently operating throughout the world and supplying about 17% of the world’s electricity. These plants perform safely, reliably, and have no free-release of byproducts to the environment. Given the current rate of growth in electricity demand and the ever growing concerns for the environment, the US consumer will favor energy sources that can satisfy the need for electricity and other energy-intensive products (1) on a sustainable basis with minimal environmental impact, (2) with enhanced reliability and safety and (3) competitive economics. Given that advances are made to fully apply the potential benefits of nuclear energy systems, the next generation of nuclear systems can provide a vital part of a long-term, diversified energy supply. The Department of Energy has begun research on such a new generation of nuclear energy systems that can be made available to the market by 2030 or earlier, and that can offer significant advances toward these challenging goals [1]. These future nuclear power systems will require advances in materials, reactor physics as well as heat transfer to realize their full potential. In this paper, a summary of these advanced nuclear power systems is presented along with a short synopsis of the important heat transfer issues. Given the nature of research and the dynamics of these conceptual designs, key aspects of the physics will be provided, with details left for the presentation.

Nanoscale heat transfer and information technology

The summary from Goodson’s group on their recent work on heat transfer issues in the microelectronics and data storage industries illustrate the critical role of heat transfer for some areas of information technology. In this article, we build on their work and discuss some directions worthy of further research.

Strained Silicon on Silicon by Wafer Bonding and Layer Transfer from Relaxed SiGe Buffer

We report the creation of strained silicon on silicon (SSOS) substrate technology. The method uses a relaxed SiGe buffer as a template for inducing tensile strain in a Si layer, which is then bonded to another Si handle wafer. The original Si wafer and the relaxed SiGe buffer are subsequently removed, thereby transferring a strained-Si layer directly to Si substrate without intermediate SiGe or oxide layers. Complete removal of Ge from the structure was confirmed by cross-sectional transmission electron microscopy as well as secondary ion mass spectrometry. A plan-view transmission electron microscopy study of the strained-Si/Si interface reveals that the lattice-mismatch between the layers is accommodated by an orthogonal array of edge dislocations. This misfit dislocation array, which forms upon bonding, is geometrically necessary and has an average spacing of approximately 40nm, in excellent agreement with established dislocation theory. To our knowledge, this is the first study of a chemically homogeneous, yet lattice-mismatched, interface.

Transport of Sub-micron Aerosols in Bifurcations

The convective-diffusive transport of sub-micron aerosols in an oscillatory laminar flow within a 2-D single bifurcation is studied, using order-of-magnitude analysis and numerical simulation using a commercial software (FEMLAB®). Based on the similarity between momentum and mass transfer equations, various transient mass transport regimes are classified and scaled according to Strouhal and beta numbers. Results show that the mass transfer rate is highest at the carinal ridge and there is a phase-shift in diffusive transport time if the beta number is greater than one. It is also shown that diffusive mass transfer becomes independent of the oscillating outer flow if the Strouhal number is greater than one.

Compositional evolution with mass transfer in closed systems

Evolution of compositions in time, space, temperature or other covariates is frequent in practice. For instance, the radioactive decomposition of a sample changes its composition with time. Some of the involved isotopes decompose into other isotopes of the sample, thus producing a transfer of mass from some components to other ones, but preserving the total mass present in the system. This evolution is traditionally modelled as a system of ordinary di erential equations of the mass of each component. However, this kind of evolution can be decomposed into a compositional change, expressed in terms of simplicial derivatives, and a mass evolution (constant in this example). A rst result is that the simplicial system of di erential equations is non-linear, despite of some subcompositions behaving linearly. The goal is to study the characteristics of such simplicial systems of di erential equa- tions such as linearity and stability. This is performed extracting the compositional dif ferential equations from the mass equations. Then, simplicial derivatives are expressed in coordinates of the simplex, thus reducing the problem to the standard theory of systems of di erential equations, including stability. The characterisation of stability of these non-linear systems relays on the linearisation of the system of di erential equations at the stationary point, if any. The eigenvelues of the linearised matrix and the associated behaviour of the orbits are the main tools. For a three component system, these orbits can be plotted both in coordinates of the simplex or in a ternary diagram. A characterisation of processes with transfer of mass in closed systems in terms of stability is thus concluded. Two examples are presented for illustration, one of them is a radioactive decay

Medida de transfer en el entorno educativo : resultados de la aplicaci??n de la prueba PEPT

Resumen tomado de la publicaci??n

L??avaluaci?? de la formaci?? del professorat al centre : la facilitaci?? per a la transfer??ncia. 'La evaluaci??n de la formaci??n del profesorado en el centro : la facilitaci??n para la transferencia'

Resumen tomado del autor. Incluye cuadro que sintetiza el proceso de evaluaci??n de los asesoramientos

how to transfer stitches

domestic knitting machine tutorial

Transfer of knowledge of the structural components of the model Q400 and Global Express: the case of Aerospace Bombardier, Querétaro

The aim of this paper is to analyze the knowledge transfer in the production of structural components of two aircraft:Q400 and Global Express of Bombardier Aerospace Company, Querétaro. Bombardier Aerospace is a pioneer company in the aviation sector in Mexico, and the third largest civil aircraft manufacturer. In 2005, Bombardier decided to invest in Mexico, creating Bombardier Aerospace de Mexico S. A. C. V. and transferring production lines from Japan and Toronto to Queretaro. The relocation strategy of both plants aims to reduce modular and general production costs facing other competitors. The relocation has been supported by the State Government funds, through a trust and the creation of Queretaro aerospace cluster. Among various benefits, the State of Queretaro donated seventy-eight acres of land where the Queretaro International Airport (QIA) and a training centre will be built to promote the development of this sector. The interest in this research is to analyze and describe the transfer of knowledge to the production of structural components of both aircraft models, thanks to the results of productivity and internal and external factors which have contributed along with this transfer

On the design of education conditional cash transfer programs and non education outcomes: the case of teenage pregnancy

We investigate the effect of education Conditional Cash Transfer programs (CCTs) on teenage pregnancy. Our main concern is with how the size and sign of the effect may depend on the design of the program. Using a simple model we show that an education CCT that conditions renewal on school performance reduces teenage pregnancy; the program can increase teenage pregnancy if it does not condition on school performance. Then, using an original data base, we estimate the causal impact on teenage pregnancy of two education CCTs implemented in Bogot´a (Subsidio Educativo, SE, and Familias en Acci´on, FA); both programs differ particularly on whether school success is a condition for renewal or not. We show that SE has negative average effect on teenage pregnancy while FA has a null average effect. We also find that SE has either null or no effect for adolescents in all age and grade groups while FA has positive, null or negative effects for adolescents in different age and grade groups. Since SE conditions renewal on school success and FA does not, we can argue that the empirical results are consistent with the predictions of our model and that conditioning renewal of the subsidy on school success crucially determines the effect of the subsidy on teenage pregnancy

A simple test of momentum in foreign exchange markets

This study proposes a new method for testing for the presence of momentum in nominal exchange rates, using a probabilistic approach. We illustrate our methodology estimating a binary response model using information on local currency / US dollar exchange rates of eight emerging economies. After controlling for important variables a§ecting the behavior of exchange rates in the short-run, we show evidence of exchange rate inertia; in other words, we Önd that exchange rate momentum is a common feature in this group of emerging economies, and thus foreign exchange traders participating in these markets are able to make excess returns by following technical analysis strategies. We Önd that the presence of momentum is asymmetric, being stronger in moments of currency depreciation than of appreciation. This behavior may be associated with central bank intervention