Tests on Models of Nuclear Reactor Elements - Head Losses in Core Sub-Assemblies

Losses have been determined for flow through models of various proposed core sub-assemblies as part of a study of the elements of a nuclear reactor. Six core sections and two? axial blanket sub-assemblies have been compared on the basis of drop in piezometric. head or pressure drop. The core sub-assemblies are composed of an entrance nozzle, a lower axial blanket section, the core section, an upper axial blanket section, and a short section for the handling lug. The four parts of the sub-assembly other than the core section are designated as the axial blanket sub-assembly. In each core section there are 144 rods within a container which has a square cross-section. The primary differences between one core section and another are the means qf supporting and spacing the rods. Bars or wires wrapped in spirals around the rods were used as well as a series of grids made up of wires and supported at the four corners. Also, in one core an, inner wall was used to provide an annular flow passage which helps to reduce the difference in temperature at the inner and outer walls of the core. The two axial blanket sub-assemblies tested are similar except ?that the second model is characterized by more gradual transitions in changes of cross section. Other parts of this study of the elements of a nuclear reactor have been described in two previous reports dealing with head losses in complete blanket subassemblies and with diffusion studies

Tests on Models of Nuclear Reactor Elements - Head Losses in Core Sub-Assemblies

Losses have been determined for flow through models of various proposed core sub-assemblies as part of a study of the elements of a nuclear reactor. Six core sections and two? axial blanket sub-assemblies have been compared on the basis of drop in piezometric. head or pressure drop. The core sub-assemblies are composed of an entrance nozzle, a lower axial blanket section, the core section, an upper axial blanket section, and a short section for the handling lug. The four parts of the sub-assembly other than the core section are designated as the axial blanket sub-assembly. In each core section there are 144 rods within a container which has a square cross-section. The primary differences between one core section and another are the means qf supporting and spacing the rods. Bars or wires wrapped in spirals around the rods were used as well as a series of grids made up of wires and supported at the four corners. Also, in one core an, inner wall was used to provide an annular flow passage which helps to reduce the difference in temperature at the inner and outer walls of the core. The two axial blanket sub-assemblies tested are similar except ?that the second model is characterized by more gradual transitions in changes of cross section. Other parts of this study of the elements of a nuclear reactor have been described in two previous reports dealing with head losses in complete blanket subassemblies and with diffusion studies

Sinking properties of some phytoplankton shapes and the relation of form resistance to morphological diversity of plankton – an experimental study

Form resistance (Phi) is a dimensionless number expressing how much slower or faster a particle of any form sinks in a fluid medium than the sphere of equivalent volume. Form resistance factors of PVC models of phytoplankton sinking in glycerin were measured in a large aquarium (0.6 x 0.6 x 0.95 m). For cylindrical forms, a positive relationship was found between Phi and length/ width ratio. Coiling decreased Phi in filamentous forms. Form resistance of Asterionella colonies increased from single cells up to 6-celled colonies than remained nearly constant. For Fragilaria crotonensis chains, no such upper limit to Phi was observed in chains of up to 20 cells ( longer ones were not measured). The effect of symmetry on Phi was tested in 1 - 6-celled Asterionella colonies, having variable angles between the cells, and in Tetrastrum staurogeniaeforme coenobia, having different spine arrangements. In all cases, symmetric forms had considerably higher form resistance than asymmetric ones. However, for Pediastrum coenobia with symmetric/asymmetric fenestration, no difference was observed with respect to symmetry. Increasing number and length of spines on Tetrastrum coenobia substantially increased Phi. For a series of Staurastrum forms, a significant positive correlation was found between arm-length/cell-width ratio and Phi: protuberances increased form resistance. Flagellates (Rhodomonas, Gymnodinium) had a Phi 1. The highest value ( Phi = 8.1) was established for a 20-celled Fragilaria crotonensis chain. Possible origin of the so-called 'vital component' ( a factor that shows how much slower viable populations sink than morphologically similar senescent or dead ones) is discussed, as is the role of form resistance in evolution of high diversity of plankton morphologies

Understanding psychiatric institutionalization: a conceptual review

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited

Golden Rule of Forecasting: Be Conservative

This article proposes a unifying theory, or the Golden Rule, or forecasting. The Golden Rule of Forecasting is to be conservative. A conservative forecast is consistent with cumulative knowledge about the present and the past. To be conservative, forecasters must seek out and use all knowledge relevant to the problem, including knowledge of methods validated for the situation. Twenty-eight guidelines are logically deduced from the Golden Rule. A review of evidence identified 105 papers with experimental comparisons; 102 support the guidelines. Ignoring a single guideline increased forecast error by more than two-fifths on average. Ignoring the Golden Rule is likely to harm accuracy most when the situation is uncertain and complex, and when bias is likely. Non-experts who use the Golden Rule can identify dubious forecasts quickly and inexpensively. To date, ignorance of research findings, bias, sophisticated statistical procedures, and the proliferation of big data, have led forecasters to violate the Golden Rule. As a result, despite major advances in evidence-based forecasting methods, forecasting practice in many fields has failed to improve over the past half-century

Pricing reverse mortgages in Spain

[EN] In Spain, as in other European countries, the continuous ageing of the population creates a need for long-term care services and their financing. However, in Spain the development of this kind of services is still embryonic. The aim of this article is to obtain a calculation method for reverse mortgages in Spain based on the fit and projection of dynamic tables for Spanish mortality, using the Lee and Carter model. Mortality and life expectancy for the next 20 years are predicted using the fitted model, and confidence intervals are obtained from the prediction errors of parameters for the mortality index of the model. The last part of the article illustrates an application of the results to calculate the reverse mortgage model promoted by the Spanish Instituto de Crédito Oficial (Spanish State Financial Agency), for which the authors have developed a computer application.The authors are indebted to Jose Garrido, whose suggestions improved the original manuscript, and to the anonymous referee for his/her valuable comments. This work was partially supported by grants from the MEyC (Ministerio de Educacio´n y Ciencia, Spain), projects MTM2010- 14961 and MTM2008-05152.Debón Aucejo, AM.; Montes, F.; Sala, R. (2013). Pricing reverse mortgages in Spain. European Actuarial Journal. 3:23-43. https://doi.org/10.1007/s13385-013-0071-yS23433Blay-Berrueta D (2007) Sistemas de cofinaciaciación de la dependencia: seguro privado frente a hipoteca inversa. Cuadernos de la Fundación, Fundación Mapfre Estudios, Madrid.Booth H (2006) Demographic forecasting: 1980 to 2005 in review. 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Mpidr wp 2001–2007, Center for Demography and Ecology Information, University of Wisconsin-Madison.Chinloy P, Megbolugbe I (1994) Reverse mortgages: contracting and crossover. J Am Real Estate Urban Econ Assoc 22(2):367–386Coale A, Guo G (1989) Revisited regional model life tables at very low levels of mortality. Popul Index 55:613–643Coale A, Kisker E (1990) Defects in data old age mortality in the United States: New procedures for calculating approximately accurate mortality schedules and lifes tables at the highest ages. Asian Pac Popul Forum 4:1–31Cossette H, Delwarde A, Denuit M, Guillot F, Étienne M (2007) Pension plan valuation and mortality projection: a case study with mortality data. N Am Actuar J 11(2):1–34.Costa-Font J (2009) Ageing in place? exploring elderly people’s housing preferences in Spain. Urban Stud 46(2):295–316Costa-Font J (2013) Housing-related well-being in older people: the impact of environmental and financial influences. Urban Stud 50(4):657–673Currie I, Kirkby J, Durban M, Eilers P (2004) Smooth Lee–Carter models and beyond. In: Workshop on Lee–Carter Methods, http://www.ma.hw.ac.uk/~iain/workshop/workshop.html . Accessed 4 Mar 2005Czado C, Delwarde A, Denuit M (2005) Bayesian Poisson log-bilinear mortality projections. Insur Math Econ 36(3):260–284D’Amato V, Haberman S, Piscopo G, Russolillo M (2012) Modelling dependent data for longevity projections. Insur Math Econ 51(3):694–701Davidoff T (2012) Can ‘high costs’ justify weak demand for the home equity conversion mortgage? Technical report, available at SSRNDavidoff T, Welke G (2007) Selection and moral hazard in the reverse mortgage market. Technical report, Haas School of Business, UC BerkeleyDebón A, Montes F, Mateu J, Porcu E, Bevilacqua M (2008) Modelling residuals dependence in dymanic life tables. Comput Stat Data Anal 52(3):3128–3147Debón A, Montes F, Puig F (2008) Modelling and forecasting mortality in Spain. Eur J Oper Res 189(3):624–637Debón A, Montes F, Sala R (2009) Tablas de mortalidad dinámicas. Una aplicación a la hipoteca inversa en España. Fundación ICO. Publicaciones de la Universitat de Valéncia, ValenciaDebón A, Montes F, Martínez-Ruiz F (2011) Statistical methods to compare mortality for a group with non-divergent populations: an application to Spanish regions. Eur Actuar J 1:291–308Delwarde A, Denuit M, Eilers P (2007) Smoothing the Lee–Carter and poisson log-bilinear models for mortality forecasting: a penalized log-likelihood approach. Stat Modell 7(1):29–48Denuit M (2007) Distribution of the random future life expectancies in log-bilinear mortality projections models. Lifetime Data Anal 13(3):381–397Denuit M, Goderniaux A (2004) Closing and projecting lifetables using log-linear models. Mitteilungen. der Schweizerischen Aktuarvereingung 1:29–49Felipe A, Guillén M, Pérez-Marín A (2002) Recent mortality trends in the Spanish population. 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The stability of money demand in the long-run: Italy 1861–2011

Money demand stability is a crucial issue for monetary policy efficacy, and it is particularly endangered when substantial changes occur in the monetary system. By implementing the ARDL technique, this study intends to estimate the impact of money demand determinants in Italy over a long period (1861–2011) and to investigate the stability of the estimated relations. We show that instability cannot be excluded when a standard money demand function is estimated, irrespectively of the use of M1 or M2. Then, we argue that the reason for possible instability resides in the omission of relevant variables, as we show that a fully stable demand for narrow money (M1) can be obtained from an augmented money demand function involving real exchange rate and its volatility as additional explanatory variables. These results also allow us to argue that narrower monetary aggregates should be employed in order to obtain a stable estimated relation

An approach for particle sinking velocity measurements in the 3–400 μm size range and considerations on the effect of temperature on sinking rates

The flux of organic particles below the mixed layer is one major pathway of carbon from the surface into the deep ocean. The magnitude of this export flux depends on two major processes—remineralization rates and sinking velocities. Here, we present an efficient method to measure sinking velocities of particles in the size range from approximately 3–400 μm by means of video microscopy (FlowCAM®). The method allows rapid measurement and automated analysis of mixed samples and was tested with polystyrene beads, different phytoplankton species, and sediment trap material. Sinking velocities of polystyrene beads were close to theoretical values calculated from Stokes’ Law. Sinking velocities of the investigated phytoplankton species were in reasonable agreement with published literature values and sinking velocities of material collected in sediment trap increased with particle size. Temperature had a strong effect on sinking velocities due to its influence on seawater viscosity and density. An increase in 9 °C led to a measured increase in sinking velocities of ~40 %. According to this temperature effect, an average temperature increase in 2 °C as projected for the sea surface by the end of this century could increase sinking velocities by about 6 % which might have feedbacks on carbon export into the deep ocean