Nonlinear Rescaling of Control Laws with Application to Stabilization in the Presence of Magnitude Saturation

Motivated by some recent results on the stabilization of homogeneous systems, we present a gain-scheduling approach for the stabilization of non-linear systems. Given a one-parameter family of stabilizing feedbacks and associated Lyapunov functions, we show how the parameter can be rescaled as a function of the state to give a new stabilizing controller. In the case of homogeneous systems, we obtain generalizations of some existing results. We show that this approach can also be applied to nonhomogeneous systems. In particular, the main application considered in this paper is to the problem of stabilization with magnitude limitations. For this problem, we develop a design method for single-input controllable systems with eigenvalues in the left closed plane

Heat transfer during film condensation of potassium vapor on a horizontal plate

The object of the investigation is to analyze the following two features of heat transfer during condensation of potassium vapor: a. Heat transfer during film condensation of a pure saturated potassium vapor on a horizontal surface. b. Heat transfer during film condensation of potassium vapor in the presence of a small quantity of non-condensable gas. Until now, the discrepancy between theory and experiment concerning the condesnation of pure liquid-metal vapors has been explained by a thermal resistance at the liquid-vapor interface. This interfacial resistance was analyzed by means of the kinetic theory, and the results depended on the use of a condensation (or accommodation) coefficient. This coefficient was found to decrease in value at higher pressures. This work presents a more refined analysis of the interfacial temperature distribution, including the effect of subcooling in the vapor in the region of the liquid-vapor interface. Furthermore, a theory predicting the temperature drop in the condensate film on a horizontal plate is presented. Experiments were performed to verify the theory. In addition, data from previous investigators were analyzed. Experiments with non-condensable gases in the saturated vapor were made using the horizontal plate facing upward. These results supported Kroger's (19) theory.Sponsored by National Science Foundatio

Treatment Issues for Native Americans: An Overview of Individual, Family, and Group Strategies

The need for improved counseling and mental health services for Native Americans is readily apparent. Several significant mental health concerns exist within the Native American population, including high rates of depression, suicide, substance use, and post-traumatic stress syndrome (Indian Health Services, 2001). In fact, the Indian Health Services (IHS) reports that mental health concerns account for more than one third of the demand for services from IHS facilities. However, there is a serious lack of resources for meeting these needs. Furthermore, an astounding lack of attention is paid to Native American issues in the professional counseling and psychological literature, which further impairs the ability of professionals to offer high-quality and culturally relevant services. The lack of both clinical services and empirical research highlights the necessity of attending to the mental health concerns of Native Americans. In this chapter, we review issues related to counseling and treatment of emotional and mental health concerns of Native American clients. To begin with, we review Native American perceptions and use of counseling and mental health services. This review is followed by a discussion of ways in which traditional Native healing approaches and conventional counseling might conflict. Finally, in the majority of the chapter, we address issues of treatment and assessment, paying specific attention to attempts to integrate conventional and indigenous treatment strategies

A homomorphism between link and XXZ modules over the periodic Temperley-Lieb algebra

We study finite loop models on a lattice wrapped around a cylinder. A section of the cylinder has N sites. We use a family of link modules over the periodic Temperley-Lieb algebra EPTL_N(\beta, \alpha) introduced by Martin and Saleur, and Graham and Lehrer. These are labeled by the numbers of sites N and of defects d, and extend the standard modules of the original Temperley-Lieb algebra. Beside the defining parameters \beta=u^2+u^{-2} with u=e^{i\lambda/2} (weight of contractible loops) and \alpha (weight of non-contractible loops), this family also depends on a twist parameter v that keeps track of how the defects wind around the cylinder. The transfer matrix T_N(\lambda, \nu) depends on the anisotropy \nu and the spectral parameter \lambda that fixes the model. (The thermodynamic limit of T_N is believed to describe a conformal field theory of central charge c=1-6\lambda^2/(\pi(\lambda-\pi)).) The family of periodic XXZ Hamiltonians is extended to depend on this new parameter v and the relationship between this family and the loop models is established. The Gram determinant for the natural bilinear form on these link modules is shown to factorize in terms of an intertwiner i_N^d between these link representations and the eigenspaces of S^z of the XXZ models. This map is shown to be an isomorphism for generic values of u and v and the critical curves in the plane of these parameters for which i_N^d fails to be an isomorphism are given.Comment: Replacement of "The Gram matrix as a connection between periodic loop models and XXZ Hamiltonians", 31 page

Biocorrosion of mild steel in drinking water conditions and disinfection

[Excerpt] Introduction: Corrosion in drinking water distribution system is a costly phenomenon, mainly due to the replacement of altered pipes. Bio..corrosion is also a problem in term of public health because of the suspected protection brought by the corroded surface to potentially harmful microorganisms, especially bacteria. The protection effect of corrosion is particularly relevant in the presence of disinfectant. In drinking water are present the conditions leading to microbialy induced corrosion: bacteria and metal-containing substrata joined closely together as biofilm attached to distribution system pipe walls. [...]info:eu-repo/semantics/publishedVersio

Home Range and Habitat Use of West Virginia Canis Latrans (Coyote)

Canis latrans (Coyote) has undergone a range expansion in the United States over the last century. As a highly opportunistic species, its home range and habitat use changes with ecological context. Coyotes were first reported in West Virginia in 1950 but were not commonly observed until the 1990s, and there is scant information on Coyotes in the region. We used telemetry data from 8 radiocollared Coyotes in West Virginia to estimate home-range size and third-order habitat selection. Home-range areas (95% utilization distributions; UDs) varied from 5.22 to 27.79 km2 (mean = 12.48 ± 2.61 km2), with highly concentrated use of smaller core areas (mean 50% UD = 1.85 ± 0.34 km2), indicated by low flatness ratios (50% isopleths/95% isopleths varied from 0.11 to 0.20). Third-order habitat selection revealed most use was proportional to availability, although there was evidence of avoidance of disturbed /developed and riparian land cover at the 95% UD scale, and selection for softwood stands at both spatial scales when available. Our results provide preliminary space-use information for West Virginia Coyotes and suggest that although Coyotes are habitat generalists, space use in the region is not uniform, but instead concentrated in disjointed areas that are used intensively

The Role of Executive Functions in Classroom Instruction of Students with Learning Disabilities

In this article, we describe executive functions and their role in determining student academic success. We focus on the executive function difficulties of students with learning disabilities and explain how executive dysfunctions can negatively affect different academic areas (e.g., reading comprehension, mathematics). Finally, we offer ways teachers can modify their instruction to better address the diverse needs of students with learning disabilities who are struggling to perform various academic tasks

Snow spectral albedo at Summit, Greenland: measurements and numerical simulations based on physical and chemical properties of the snowpack

The broadband albedo of surface snow is determined both by the near-surface profile of the physical and chemical properties of the snowpack and by the spectral and angular characteristics of the incident solar radiation. Simultaneous measurements of the physical and chemical properties of snow were carried out at Summit Camp, Greenland (72°36´ N, 38°25´ W, 3210 m a.s.l.) in May and June 2011, along with spectral albedo measurements. One of the main objectives of the field campaign was to test our ability to predict snow spectral albedo by comparing the measured albedo to the albedo calculated with a radiative transfer model, using measured snow physical and chemical properties. To achieve this goal, we made daily measurements of the snow spectral albedo in the range 350–2200 nm and recorded snow stratigraphic information down to roughly 80 cm. The snow specific surface area (SSA) was measured using the DUFISSS instrument (DUal Frequency Integrating Sphere for Snow SSA measurement, Gallet et al., 2009). Samples were also collected for chemical analyses including black carbon (BC) and dust, to evaluate the impact of light absorbing particulate matter in snow. This is one of the most comprehensive albedo-related data sets combining chemical analysis, snow physical properties and spectral albedo measurements obtained in a polar environment. The surface albedo was calculated from density, SSA, BC and dust profiles using the DISORT model (DIScrete Ordinate Radiative Transfer, Stamnes et al., 1988) and compared to the measured values. Results indicate that the energy absorbed by the snowpack through the whole spectrum considered can be inferred within 1.10%. This accuracy is only slightly better than that which can be obtained considering pure snow, meaning that the impact of impurities on the snow albedo is small at Summit. In the near infrared, minor deviations in albedo up to 0.014 can be due to the accuracy of radiation and SSA measurements and to the surface roughness, whereas deviations up to 0.05 can be explained by the spatial heterogeneity of the snowpack at small scales, the assumption of spherical snow grains made for DISORT simulations and the vertical resolution of measurements of surface layer physical properties. At 1430 and around 1800 nm the discrepancies are larger and independent of the snow properties; we propose that they are due to errors in the ice refractive index at these wavelengths. This work contributes to the development of physically based albedo schemes in detailed snowpack models, and to the improvement of retrieval algorithms for estimating snow properties from remote sensing data