Numerical Algorithms for Deterministic Impulse Control Models with Applications

Abstract: In this paper we describe three different algorithms, from which two (as far as we know) are new in the literature. We take both the size of the jump as the jump times as decision variables. The first (new) algorithm considers an Impulse Control problem as a (multipoint) Boundary Value Problem and uses a continuation technique to solve it. The second (new) approach is the continuation algorithm that requires the canonical system to be solved explicitly. This reduces the infinite dimensional problem to a finite dimensional system of, in general, nonlinear equations, without discretizing the problem. Finally, we present a gradient algorithm, where we reformulate the problem as a finite dimensional problem, which can be solved using some standard optimization techniques. As an application we solve a forest management problem and a dike heightening problem. We numerically compare the efficiency of our methods to other approaches, such as dynamic programming, backward algorithm and value function approach

Solid biofuel and biogas production from grassland-willow alley cropping systems

PosterWorldwide the demand for renewable energy is rising and biogenic energy carriers play an important role in bioenergy provision. However, increase and intensification of biomass production for energetic use has already shown adverse impacts on agro-ecosystems (e.g., biodiversity losses, nitrate leaching, and erosion). Energy cropping and related conversion systems should be improved in terms of their efficiency and environmental impact in future. Modern agroforestry systems offer an alternative agro-ecological approach to a sustainable intensification of energy crop production. The present study was part of the joint research project “BEST – Strengthening Bioenergy Regions“ (2010?2014) and analyzed the energetic potential of a young alley cropping system of grassland and fast-growing willows grown on a 3 to 6 year rotation. The study was conducted on an experimental area in Central Germany from 2011–2013. Two different grassland mixtures were established in a split-plot randomized block design with three replications, and intercropped with rows of willows. The woody biomass was converted to wood chips for thermal combustion. For the grassland biomass, three types of energetic conversion were evaluated: integrated generation of solid fuel and biogas from biomass (IFBB), anaerobic digestion and hay combustion. Overall, the three year old agroforestry system achieved a total gross energy yield of 96 MWh ha-1 by applying the IFBB procedure to the understory biomass. Grassland as pure stand achieved 133 MWh ha-1 and a single willow stand achieved 51 MWh ha-1 in 3 years after establishment. In addition, this study investigated the yield development in the alley cropping system and in the pure stands as control during the establishment phase

The mathematics of ageing:

Age is a crucial variable in social sciences and particularly in population dynamics. In this paper, we link methods from formal demography and Operations Research to investigate age-structured models to study the greying of academia. As scientific productivity is usually found to decrease at advanced ages, there was a vivid discussion on the ageing among tenured professors and faculty staff of universities. We investigate population ageing in academia from two perspectives. First, we propose a two-state optimal control model to explain the substantial variations of scientific production over the life cycle of researchers. We identify conditions under which typical hump-shaped age-specific patterns of scientific production turn out to be optimal for individual researchers. The second part of the paper deals with the dynamics of the age structure of scientific institutions. Similar to the university professors, many European learned societies experienced a rapid ageing of their member population, where they face the dilemma that keeping young, i.e. electing young entrants, has the drawback of reducing the replacement rate of members. It turns out that electing a mix of young and old members delivers the optimal solution of the problem, i.e. guaranteeing a young age structure, while ensuring a high recruitment rate

GALS for Bursty Data Transfer based on Clock Coupling

In this paper we introduce a novel burst-mode GALS technique. The goal of this technique is improving the performance of the GALS approach for systems with predominantly bursty data transfer. This new technique has been used to implement a GALS-based version of a hardware accelerator of a 60 GHz OFDM baseband processor. The simulation results show a significant performance improvement in comparison with a classical implementation of GALS using pausible clocking. © 2009 Elsevier B.V. All rights reserved

What Does an Exemplary Middle School Mathematics Teacher Look Like? The Use of a Professional Development Rubric

A School University Research Network (SURN) committee composed of current mathematics teachers, central office math supervisors, building administrators, mathematicians, and mathematics educators researched numerous sources regarding best practices in mathematics instruction. The resulting professional development rubric synthesizes their findings and can serve a professional development role by providing teachers and administrators with a tool to develop clarity and consensus on best mathematics instructional practices, and how these practices are implemented in the classroom. It is also being used as a tool for cooperating teachers in their supervision of student teachers and as a reflective method for self-evaluation

GALS for Bursty Data Transfer based on Clock Coupling

In this paper we introduce a novel burst-mode GALS technique. The goal of this technique is improving the performance of the GALS approach for systems with predominantly bursty data transfer. This new technique has been used to implement a GALS-based version of a hardware accelerator of a 60 GHz OFDM baseband processor. The simulation results show a significant performance improvement in comparison with a classical implementation of GALS using pausible clocking. © 2009 Elsevier B.V. All rights reserved