A viability theory approach to a two-stage optimal control problem of technology adoption

A new technology adoption problem can be modelled as a two-stage control problem, in which model parameters ("technology") might be altered at some time. An optimal solution to utility maximisation for this class of problems needs to contain information on the time, at which the change will take place (0, finite or never), along with the optimal control strategies before and after the change. For the change, or switch, to occur the "new technology" value function needs to dominate the "old technology" value function, after the switch. We charaterise the value function using the fact that its hypograph is a viability kernel of an auxiliary problem and we study when the graphs can intersect. If they do not, the switch cannot occur at a positive time. Using this characterisation we analyse a technology adoption problem and showmodels, for which the switch will occur at time zero or never.technology adoption, value function, viability kernel, viscosity solutions

Analytical yield criterion for an anisotropic material containing spherical voids and exhibiting tension–compression asymmetry

AbstractA significant difference between the behavior in tension versus compression is obtained at the polycrystal level if either twinning or non-Schmid effects are contributors to the plastic deformation at the single crystal level. Examples of materials that exhibit tension–compression asymmetry include hexagonal close-packed (HCP) polycrystals and intermetallics (e.g., molybdenum compounds). Despite recent progress in modeling their yield behavior in the absence of voids, the description of coupling between plasticity and damage by void growth in these materials remains a challenge.This paper is devoted to the development of a macroscopic anisotropic yield criterion for a porous material when the matrix material is incompressible, anisotropic and displays tension–compression asymmetry. The analytical yield criterion is obtained based on micromechanical considerations and non-linear homogenization. The matrix plastic behavior is described by the Cazacu et al. (2006) anisotropic yield criterion that is pressure-insensitive and accounts for strength–differential effects. Comparison between finite element cell calculations and theory show the predictive capabilities of the developed anisotropic model in terms of modeling the combined effects of anisotropy, tension–compression asymmetry of the matrix and voids on the overall yielding of the porous aggregate. It is shown that if the matrix material does not display tension–compression asymmetry, the developed criterion reduces to that of Benzerga and Besson (2001). If the matrix is isotropic, it reduces to the isotropic criterion developed in Cazacu and Stewart (2009)

Preliminary Investigation of Experimental Research on Savory (Satureja hortensis L.) In Vitro Modeling Possibility Using the Calogenesis Technique

Investigating the possibilities for in vitro plant modeling by using the calogenesis technique is one of the ways to exploit cell plasticity – the vegetable type, which plant biotechnology now offers an alternative for obtaining biomass as a source of raw material in various industries. One of the known plants cultivated by humans since ancient time, and recognized in the contemporary period as a dedicated source of plant material for different industries, because it has properties that recommend its use in food, medicine and beekeeping, is savory (Satureja hortensis L.). Our preliminary experimental research aimed at investigating the possibility of in vitro modeling of savory (Satureja hortensis L.) by using the calogenesis technique. This paper presents the experimental results which have been achieved by investigating the possibility of practical achievement, both by establishing aseptic cultures using savory (Satureja hortensis L.) seeds, and also by in vitro modeling of savory (Satureja hortensis L.) explants, considering the leaf, cotyledon, epicotyl, hypocotyl and radicle, in under to obtain callus by the influence of exogenous phytohormones (BA, TDZ and 2,4-D)

Perfectionistic concerns predict increases in adolescents’ anxiety symptoms: A three-wave longitudinal study

Background and Objectives: Although perfectionism has been proposed to be a risk factor for the development of anxiety, research on perfectionism and anxiety symptoms in adolescents is scarce and inconclusive. The aim of the present study was to investigate whether the two higher-order dimensions of perfectionism—perfectionistic strivings and perfectionistic concerns—predict the development and maintenance of anxiety symptoms. An additional aim of the present study was to examine potential reciprocal effects of anxiety symptoms predicting increases in perfectionism. Design: The study used a longitudinal design with three waves spaced 4-5 months apart. Methods: A non-clinical sample of 489 adolescents aged 12-19 years completed a paper-and-pencil questionnaire. Results: As expected, results showed a positive effect from perfectionistic concerns to anxiety symptoms, but the effect was restricted to middle-to-late adolescents (16-19 years old): Perfectionistic concerns predicted longitudinal increases in adolescents’ anxiety symptoms whereas perfectionistic strivings did not. Furthermore, anxiety symptoms did not predict increases in perfectionism. Conclusions: Implications for the understanding of the relationship between perfectionism and anxiety symptoms are discussed

Perfectionism and school engagement: A three-wave longitudinal study

Although perfectionism is a personality disposition that plays an important role in educational contexts, research on perfectionism and school engagement is limited. School engagement is a key process in predicting educational outcomes in students. Consequently, it is important to know how perfectionism relates to school engagement and whether perfectionism predicts relative changes in school engagement over time. Using a sample of 486 students from 6th-12th grade (54% female) and employing a longitudinal design with three waves spaced 4-5 months apart, the present study investigated whether perfectionism (perfectionistic strivings and perfectionistic concerns) predicted relative changes in students’ school engagement (behavioral, emotional, and cognitive engagement). Results showed that both perfectionistic strivings and concerns were related to school engagement, but only perfectionistic strivings predicted relative increases in school engagement. Implications for the understanding of how perfectionistic strivings contribute to school students’ engagement are discussed

First-Class Approaches to Massive 2-Forms

Massive 2-forms are analyzed from the point of view of the Hamiltonian quantization using the gauge-unfixing approach and respectively the Batalin--Fradkin method. Both methods finally output the manifestly Lorentz covariant path integral for 1- and 2-forms with Stueckelberg coupling.Comment: 14 page

A viability theory approach to a two-stage optimal control problem

A two-stage control problem is one, in which model parameters (“technology”) might be changed at some time. An optimal solution to utility maximisation for this class of problems needs to thus contain information on the time, at which the change will take place (0, finite or never) as well as the optimal control strategies before and after the change. For the change, or switch, to occur the “new technology” value function needs to dominate the “old technology” value function, after the switch. We charaterise the value function using the fact that its hypograph is a viability kernel of an auxiliary problem and study when the graphs can intersect and hence whether the switch can occur. Using this characterisation we analyse a technology switching problem

A new bond fluctuation method for a polymer undergoing gel electrophoresis

We present a new computational methodology for the investigation of gel electrophoresis of polyelectrolytes. We have developed the method initially to incorporate sliding motion of tight parts of a polymer pulled by an electric field into the bond fluctuation method (BFM). Such motion due to tensile force over distances much larger than the persistent length is realized by non-local movement of a slack monomer at an either end of the tight part. The latter movement is introduced stochastically. This new BFM overcomes the well-known difficulty in the conventional BFM that polymers are trapped by gel fibers in relatively large fields. At the same time it also reproduces properly equilibrium properties of a polymer in a vanishing filed limit. The new BFM thus turns out an efficient computational method to study gel electrophoresis in a wide range of the electric field strength.Comment: 15 pages, 11 figure