A Brief Note on Linearized, Unsteady, Supercavitating Flows

Three different models for the unsteady fluctuations of a slender cavity in the limit of small reduced frequency are compard with the results of quasi-steady calculations. Tullin's kinematically closed model in unsteady flow in soon to tend smoothly to a limiting quasi-steady motion having the same value for the compliance of the cavitating flow, unlike other models that have been used in the past

A Note on the Calculation of Supercavitating Hydrfoils with Rounded Noses

Practical supercavitating hydrfoils have rounded leading edges for mechanical strength. The prediction of pressures near the leading edge of such hydrofoils by linearized free streamline theory fails because singularities are usually required there by the theory. A simple method based on singular perturbations of avoiding these difficulties for hydrofoils which have parabolic noses but an arbitrary profile downstream of the leading edge is presented. The results of such a computation on a hydrofoil with a parabolic profile and with fixed cavity separation near the leading edge radius are shown and are compared with an exact free-streamline theory. The agreement is excellent

A Note on the Superstring BRST Operator

We write the BRST operator of the N=1 superstring as $Q= e^{-R} (\oint dz \gamma^2 b)e^R$ where $\gamma$ and $b$ are super-reparameterization ghosts. This provides a trivial proof that $Q$ is nilpotent.Comment: 4 pages late

Critical current density and ac harmonic voltage generation in YBa2Cu3O7−δYBa_2Cu_3O_{7-\delta} thin films by the screening technique

The temperature and field dependence of harmonics in voltage $V_n=V'_n-iV"_n$ using the screening technique have been measured for $\mathrm{Y}\mathrm{Ba}_{2}\mathrm{Cu}_3\mathrm{O}_{7-\delta}$ superconducting thin films. Using the Sun model we obtained the curves for the temperature-dependent critical current density $J_c(T)$. In addition, we applied the criterion proposed by Acosta et al. to compute $J_c(T)$. Also, we made used of the empirical law $J_c \propto (1-T/T_c)^n$ as an input in our calculations to reproduce experimental harmonic generation up to the fifth harmonic. We found that most models fit well the fundamental voltage but higher harmonics are poorly reproduced. Such behavior suggests the idea that higher harmonics contain information concerning complex processes like flux creep or thermally assisted flux flow.Comment: 2 pages, 2 figure

La desnutrición en los primeros años de vida: Un análisis regional para Colombia

Colombia is a country with large regional differences in levels of development, as well as high levels of malnutrition that limit its potential productivity. By using data from the National Survey of Nutritional Status 2010, this paper characterizes the nutritional status of children between 1 and 4 years of age and evaluates access to adequate health care and the particularities of the children in this matter. Among the main results, the importance of the characteristics of mothers, living conditions and prenatal care are salient in the explanation of malnutrition in the aggregate. At the regional level, there are differences, where Bogota and the Caribbean are the regions with higher levels of chronic and global malnutrition respectively. As control measures in the long-term, the mother´s age in Bogota is more important, while in the Caribbean the years of education of the mother are more important. I also emphasize the coverage of vaccines as an important determinant of global malnutrition as measured by weight retardation. RESUMEN: Colombia es un país con grandes diferencias regionales en los niveles de desarrollo. Además, tiene altos niveles de desnutrición que limitan su potencial productivo. Con base en los datos de la Encuesta Nacional de la Situación Nutricional para el 2010, este trabajo caracteriza los estados nutricionales de los niños entre 1 y 4 años y también se analizan el acceso a una salud adecuada y las particularidades de los niños en esta materia. Entre los principales resultados, se percibe la importancia de las características de las madres, las condiciones de vida y una atención prenatal para las madres en la explicación de la desnutrición a nivel agregado. A nivel regional, se encuentra que Bogotá y el Caribe son las regiones con mayores niveles de desnutrición crónica y global, respectivamente. Al respecto, se encontró que las medidas de control de largo plazo a partir de las características maternas, el control de la edad en la que se es madre es más importante en Bogotá, mientras que en el Caribe características como los años de educación cobran mayor importancia. Esto explica el hecho de que el efecto de la educación de la madre se vuelve marginalmente decreciente en la medida en que estas alcanzan un nivel completo de secundaria. Adicionalmente, se resalta también la necesidad del cubrimiento de vacunas para controlar la desnutrición medida como retraso de peso.Desnutrición, peso para la edad, talla para la edad, preescolares y regiones.

DETAM for accident sequence analysis

Includes bibliographical references (pages 133-138)Final reportSupported by the United States Nuclear Regulatory Commission. NRC-04-88-14