Two-Dimensional Kinematic Wave Model of Overland-Flow

A two-dimensional kinematic wave model was developed for simulating runoff generation and flow concentration on an experimental infiltrating hillslope receiving artificial rainfall. Experimental observations on runoff generation and flow concentration on irregular hillslopes showed that the topography of the slope surface controlled the direction and flow lines of overland flow. The model-simulated results satisfactorily compared with experimental observations. The erosive ability of the concentrated flow was found to mainly depend on the ratio of the width and depth of confluent grooves.

Methods of Obtaining Instantaneous Modulus of Viscoelastic Solids Using Displacement-Controlled Instrumented Indentation with Axisymmetric Indenters of Arbitrary Smooth Profiles

We derive a relationship between the initial unloading slope, contact depth, and the instantaneous relaxation modulus for displacement-controlled indentation in linear viscoelastic solids by a rigid indenter with an arbitrary axisymmetric smooth profile. While the same expression is well known for indentation in elastic and in elastic–plastic solids, we show that it is also true for indentation in linear viscoelastic solids, provided that the unloading rate is sufficiently fast. When the unloading rate is slow, a “hold” period between loading and unloading can be used to provide a correction term for the initial unloading slope equation. Finite element calculations are used to illustrate the methods of fast unloading and “hold-at-the-maximum-indenter-displacement” for determining the instantaneous modulus using spherical indenters.

Validity ranges of interfacial wave theories in a two-layer fluid system

In the present paper, we endeavor to accomplish a diagram, which demarcates the validity ranges for interfacial wave theories in a two-layer system, to meet the needs of design in ocean engineering. On the basis of the available solutions of periodic and solitary waves, we propose a guideline as principle to identify the validity regions of the interfacial wave theories in terms of wave period T, wave height H, upper layer thickness d(1), and lower layer thickness d(2), instead of only one parameter-water depth d as in the water surface wave circumstance. The diagram proposed here happens to be Le Mehautes plot for free surface waves if water depth ratio r = d(1)/d(2) approaches to infinity and the upper layer water density rho(1) to zero. On the contrary, the diagram for water surface waves can be used for two-layer interfacial waves if gravity acceleration g in it is replaced by the reduced gravity defined in this study under the condition of sigma = (rho(2) - rho(1))/rho(2) -> 1.0 and r > 1.0. In the end, several figures of the validity ranges for various interfacial wave theories in the two-layer fluid are given and compared with the results for surface waves.

Fatigue-crack closure measurements on 2024-t3 sheet specimens

A computer-controlled procedure has been developed for automatic measurement of the crack opening stress S-op during fatigue tests. A crack opening displacement gauge (GOD meter) is used to obtain digital data on the load versus COD curves. Three methods for deriving S-op from the data sets are compared: (1) a slope method, (2) a tangent lines intersecting method, and (3) a tangent point method. The effect of the position of the COD meter with respect to the crack tip on S-op is studied in tests of 2024-T3 specimens. Results of crack growth and S-op are presented for CA loading with an overload, and with an overload followed by an underload.

Air flow over a mountain and the convective boundary-layer

In this paper, the analytical model coupling the convective boundary layer (CBL) with the free atmosphere developed by Qi and Fu (1992) is improved. And by this improved model, the interaction between airflow over a mountain and the CBL is further discussed. The conclusions demonstrate: (1) The perturbation potential temperatures in the free atmosphere can counteract the effect of orographic thermal forcing through entraining and mixing in the CBL. If u(M)BAR > u(F)BAR, the feedback of the perturbation potential temperatures in the free atmosphere is more important than orographic thermal forcing, which promotes the effect of interfacial waves. If u(M)BAR < u(F)BAR, orographic thermal forcing is more important, which makes the interfacial height and the topographic height identical in phase, and the horizontal speeds are a maximum at the top of the mountain. (2) The internal gravity waves propagating vertically in the free atmosphere cause a strong downslope wind to become established above the lee slope in the CBL and result in the hydraulic jump at the top of the CBL. (3) With the CBL deepening, the interfacial gravity waves induced by the potential temperature jump at the top of the CBL cause the airflow in the CBL to be subcritical.

Short-surface waves radiated by a partially-immersed 3-dimensional oscillating body

The short-surface waves generated by a 3-D arbitrarily oscillating body floating onwater are discussed. In the far-field off the body, the phase and the amplitude functions ofthe radiated waves are determined by the ray method. An undetermined constant is includ-ed in the amplitude function. From the result of Ref. [1], the near-field boundary layersolution near the body waterline is obtained. The amplitude of this solution depends on thewhole wall shape of the body and the slope at the body waterline on the cross-sections per-pendicular to the waterline. By matching the far-field solution with the near-field bound-ary layer solution, the undetermined constant in the amplitude function of the far-fieldradiated waves is determined. For the special case of a half-submerged sphere which per-forms vertical oscillating motion, the result obtained in this paper is in agreement withthat of Ref. [ 2 ].

Consumer Confidence and Yield Spreads in Europe

This paper shows the extraordinary capacity of yield spreads to anticipate consumption growth as proxy by the Economic Sentiment Indicator elaborated by the European Commission in order to predict turning points in business cycles. This new evidence complements the well known results regarding the usefulness of the slope of the term structure of interest rates to predict real economic conditions and, in particular, recessions by using a direct measure of expectations. A linear combination of European yield spreads explains a surprising 93.7% of the variability of the Economic Sentiment Indicator. Yield spreads seem to be a key determinant of consumer confidence in Europe.

Strategic Behavior and Collusion: An Application to the Spanish Electricity Market

The paper has two major contributions to the theory of repeated games. First, we build a supergame oligopoly model where firms compete in supply functions, we show how collusion sustainability is affected by the presence of a convex cost function, the magnitude of both the slope of demand market, and the number of rivals. Then, we compare the results with those of the traditional Cournot reversion under the same structural characteristics. We find how depending on the number of firms and the slope of the linear demand, collusion sustainability is easier under supply function than under Cournot competition. The conclusions of the models are simulated with data from the Spanish wholesale electricity market to predict lower bounds of the discount factors.

Influence of shelf-break fronts on shellfish and fish stocks off Argentina [Contribution to ICES Annual Science Conference, Reykjavik, Iceland, 27 Sep- 04 Oct 1996]

The general circulation pattern in the western boundary of the SW Atlantic is dominated by the opposite flows of Malvinas (-Falkland)and Brazil Current. In the Confluence region both currents separate from the continental slope and flow offshore creating an area of strong contracts and complex dynamics. The shelf-break fronts off Argentina mark the transition between shelf waters of mixed origin and nutrient rich Malvinas waters. Two areas deserve special attention due to the steep gradients introduced by the outflow of important sources of continental waters: the Rio de la Plata and the Magellan Strait to the north and south of the study area. Characteristics of the front is the high primary and secondary production, and the presence of important invertebrate and fish stocks that concentrate along the front to feed or spawn. The area comprises nearly 30 o/o (333 million U$S in 1995)of all Argentine catches of fish and squid. Resources in the area, beyond the EEZ limits, support international fisheries mainly of Russia, Poland and Spain. (Document contains 15 pages & figs)

New signal processing algorithms for automated external defibrillators

[ES]La fibrilación ventricular (VF) es el primer ritmo registrado en el 40\,\% de las muertes súbitas por paro cardiorrespiratorio extrahospitalario (PCRE). El único tratamiento eficaz para la FV es la desfibrilación mediante una descarga eléctrica. Fuera del hospital, la descarga se administra mediante un desfibrilador externo automático (DEA), que previamente analiza el electrocardiograma (ECG) del paciente y comprueba si presenta un ritmo desfibrilable. La supervivencia en un caso de PCRE depende fundamentalmente de dos factores: la desfibrilación temprana y la resucitación cardiopulmonar (RCP) temprana, que prolonga la FV y por lo tanto la oportunidad de desfibrilación. Para un correcto análisis del ritmo cardiaco es necesario interrumpir la RCP, ya que, debido a las compresiones torácicas, la RCP introduce artefactos en el ECG. Desafortunadamente, la interrupción de la RCP afecta negativamente al éxito en la desfibrilación. En 2003 se aprobó el uso del DEA en pacientes entre 1 y 8 años. Los DEA, que originalmente se diseñaron para pacientes adultos, deben discriminar de forma precisa las arritmias pediátricas para que su uso en niños sea seguro. Varios DEAs se han adaptado para uso pediátrico, bien demostrando la precisión de los algoritmos para adultos con arritmias pediátricas, o bien mediante algoritmos específicos para arritmias pediátricas. Esta tesis presenta un nuevo algoritmo DEA diseñado conjuntamente para pacientes adultos y pediátricos. El algoritmo se ha probado exhaustivamente en bases de datos acordes a los requisitos de la American Heart Association (AHA), y en registros de resucitación con y sin artefacto RCP. El trabajo comenzó con una larga fase experimental en la que se recopilaron y clasificaron retrospectivamente un total de 1090 ritmos pediátricos. Además, se revisó una base de arritmias de adultos y se añadieron 928 nuevos ritmos de adultos. La base de datos final contiene 2782 registros, 1270 se usaron para diseñar el algoritmo y 1512 para validarlo. A continuación, se diseñó un nuevo algoritmo DEA compuesto de cuatro subalgoritmos. Estos subalgoritmos están basados en un conjunto de nuevos parámetros para la detección de arritmias, calculados en diversos dominios de la señal, como el tiempo, la frecuencia, la pendiente o la función de autocorrelación. El algoritmo cumple las exigencias de la AHA para la detección de ritmos desfibrilables y no-desfibrilables tanto en pacientes adultos como en pediátricos. El trabajo concluyó con el análisis del comportamiento del algoritmo con episodios reales de resucitación. En los ritmos que no contenían artefacto RCP se cumplieron las exigencias de la AHA. Posteriormente, se estudió la precisión del algoritmo durante las compresiones torácicas, antes y después de filtrar el artefacto RCP. Para suprimir el artefacto se utilizó un nuevo método desarrollado a lo largo de la tesis. Los ritmos desfibrilables se detectaron de forma precisa tras el filtrado, los no-desfibrilables sin embargo no.

三峡永久船闸高边坡开挖三维离散元数值模拟

采用面-面接触的三维离散元刚性块体模型，从实测节理面中取出其中的三组，按照其倾向、倾角和节理间距将三峡永久船闸未开挖的区域划分为10~5个离散单元，通过施加力边界条件，给出了与实测初始地应力场接近的数值模拟结果；然后，分4步模拟了永久船闸的开挖过程。计算结果表明：开挖过程会引起节理面出现张开趋势，个别岩体还会沿着节理面滑移。岩体位移的不对称现象较为自然地说明了由节理引起的岩体各向异性特征。

An Estimated New-Keynesian Model with Unemployment as Excess Supply of Labor

Wage stickiness is incorporated to a New-Keynesian model with variable capital to drive endogenous unemployment uctuations de ned as the log di¤erence between aggregate labor supply and aggregate labor demand. We estimated such model using Bayesian econometric techniques and quarterly U.S. data. The second-moment statistics of the unemployment rate in the model give a good t to those observed in U.S. data. Our results also show that wage-push shocks, demand shifts and monetary policy shocks are the three major determinants of unemployment fl uctuations. Compared to an estimated New-Keynesian model without unemployment (Smets and Wouters, 2007): wage stickiness is higher, labor supply elasticity is lower, the slope of the New-Keynesian Phillips curve is flatter, and the importance of technology innovations on output variability increases.

Time Variation in an Optimal Asymmetric Preference Monetary Policy Model

This paper considers a time varying parameter extension of the Ruge-Murcia (2003, 2004) model to explore whether some of the variation in parameter estimates seen in the literature could arise from this source. A time varying value for the unemployment volatility parameter can be motivated through several means including variation in the slope of the Phillips curve or variation in the preferences of the monetary authority.We show that allowing time variation for the coefficient on the unemployment volatility parameter improves the model fit and it helps to provide an explanation of inflation bias based on asymmetric central banker preferences, which is consistent across subsamples.

Physical Constraints to Aquatic Plant Growth in New Zealand Lakes

The nature of aquatic plant communities often defines benthic habitat within oligotrophic and mesotrophic lakes and lake management increasingly recognizes the importance of maintaining plant diversity in order to sustain biological diversity and capacity within lakes. We have developed simple statistical relationships between key physical and vegetation variables that define the habitat requirements, or “habitat-templates”, of key vegetation types to facilitate management of plant communities in New Zealand lakes. Statistical relationships were derived from two datasets. The first was a multi-lake dataset to determine the effects of water level fluctuation and water clarity. The second dataset was from a comprehensive shoreline survey of Lake Wanaka, which allowed us to examine within-lake variables such as beach slope and wave action. Sufficient statistical relationships were established to develop a habitat template for each of the major species or assemblages. The relationships suggested that the extent and diversity of shallow-growing species was related to a combination of the extent of water level fluctuation and wave exposure. (PDF contains 9 pages.)

Potential use of remote sensing to assess effects of wave action on plant re-establishment

Evaluation of the potential for remote sensing to detect a relationship between wave action factors and plant re-establishment after a habitat enhancement at Lake Kissimmee, Florida. Using Geographic Information Systems (GIS) and remote sensing, wave action factors were found to be inversely related to the probability of plant re-establishment. However, correlation of wave action factors with areal coverage of aquatic plants based on field measurements, were unable to detect a significant relationship. Other factors aside from wave action, including littoral slope and the presence of offshore vegetation, may have influenced plant re-establishment in these sites. Remote sensing techniques may be useful to detect large changes in plants communities, however small changes in plant coverages may not be detectable using this technique.