The conformal mapping of the interior of the unit circle onto the interior of a class of smooth curves

Outer and inner curved plates and shell shapes optimized by conformal mappin

Local Volume Effects in the Generalized Pseudopotential Theory

The generalized pseudopotential theory (GPT) is a powerful method for deriving real-space transferable interatomic potentials. Using a coarse-grained electronic structure, one can explicitly calculate the pair ion-ion and multi-ion interactions in simple and transition metals. Whilst successful in determining bulk properties, in central force metals the GPT fails to describe crystal defects for which there is a significant local volume change. A previous paper [PhysRevLett.66.3036 (1991)] found that by allowing the GPT total energy to depend upon some spatially-averaged local electron density, the energetics of vacancies and surfaces could be calculated within experimental ranges. In this paper, we develop the formalism further by explicitly calculating the forces and stress tensor associated with this total energy. We call this scheme the adaptive GPT (aGPT) and it is capable of both molecular dynamics and molecular statics. We apply the aGPT to vacancy formation and divacancy binding in hcp Mg and also calculate the local electron density corrections to the bulk elastic constants and phonon dispersion for which there is refinement over the baseline GPT treatment.Comment: 11 pages, 6 figure

The manual control of vehicles undergoing slow transitions in dynamic characteristics

The manual control was studied of a vehicle with slowly time-varying dynamics to develop analytic and computer techniques necessary for the study of time-varying systems. The human operator is considered as he controls a time-varying plant in which the changes are neither abrupt nor so slow that the time variations are unimportant. An experiment in which pilots controlled the longitudinal mode of a simulated time-varying aircraft is described. The vehicle changed from a pure double integrator to a damped second order system, either instantaneously or smoothly over time intervals of 30, 75, or 120 seconds. The regulator task consisted of trying to null the error term resulting from injected random disturbances with bandwidths of 0.8, 1.4, and 2.0 radians per second. Each of the twelve experimental conditons was replicated ten times. It is shown that the pilot's performance in the time-varying task is essentially equivalent to his performance in stationary tasks which correspond to various points in the transition. A rudimentary model for the pilot-vehicle-regulator is presented

Backyard Beekeeping in the Beehive State: Salt Lake City’s Beekeeping Regulations, Nuisance Concerns, and the Legal Status of Honey Bees

Recognizing the increasing popularity of urban beekeeping and the vital role that bees play in the ecosystem, the Salt Lake City Council has acted to allow keeping bees within city limits. To ensure that bees would not present a significant nuisance, the council implemented a simple set of guidelines to regulate the practice. While the Ordinance is an excellent first step that effectively addresses most of the sources of nuisance associated with honey bees, it would be wise to reassess its provisions now that it has been in place for nearly eight years. Perhaps a survey of complaints about urban beehives could be conducted, the results of which could be used to guide a revision of the Ordinance with the aim of maintaining a harmonious relationship between beekeepers and their neighbors

Low-profile and wearable energy harvester based on plucked piezoelectric cantilevers

The Pizzicato Energy Harvester (EH) introduced the technique of frequency up-conversion to piezoelectric EHs wearable on the lateral side of the knee-joint. The operation principle is to pluck the piezoelectric bimorphs with plectra so that they produce electrical energy during the ensuing mechanical vibrations. The device presented in this work is, in some ways, an evolution of the earlier Pizzicato: it is a significantly more compact and lighter device; the central hub holds 16 piezoelectric bimorphs shaped as trapezoids, which permits a sleek design and potentially increased energy output for the same bimorph area. Plectra were formed by Photochemical Machining of a 100-μm-thick steel sheet. To avoid the risk of short-circuiting, the plectra were electrically passivated by sputtering a 100 nm layer of ZrO2. Bench tests with the steel plectra showed a very large energy generation. Polyimide plectra were also manufactured with a cutting plotter from a 125μm-thick film. Besides bench tests, a volunteer wore the device while walking on flat ground or climbing stairs, with a measured energy output of approximately 0.8 mJ per step. Whereas most of the tests were performed by the traditional method of discharging the rectified output from the EH onto a resistive load, tests were performed also with a circuit offering a stabilised 3.3 V supply. The circuit produced a stable 0.1 mA supply during running gait with kapton plectra

Compartir l'esforç per millorar els serveis d'aigua i sanejament

La gestión comunitaria de los sistemas de suministro de agua será el enfoque primordial para conseguir los principales Objetivos de Desarrollo del Milenio en las zonas rurales. Discutimos tres aspectos específicos: el concepto de gestión comunitaria, los distintos papeles que pueden jugar los principales actores implicados en el desarrollo y la implementación de los servicios de agua y saneamiento; y la crucial necesidad de proveer capacitación utilizando técnicas participativas, de las cuales se describen algunas, apuntando a una toma de decisiones informada. Señalamos también que capacitar y estimular a los miembros de la comunidad es importante, pero aun lo es más, capacitar a los actores del nivel intermedio (gobierno local, ONG, sector privado, etc.) que son quienes respaldan y facilitan la implementación del proceso inicialmente, y luego el apoyo para asegurar la sostenibilidad del servicio proporcionado.La gestió comunitària dels sistemes de subministrament d'aigua serà l'enfocament primordial per a aconseguir els principals Objectius de Desenvolupament del Mil·lenni a les zones rurals. Discutim tres aspectes específics: el concepte de gestió comunitària, els distints papers que poden jugar els principals actors implicats en el desenvolupament i la implementació dels serveis d'aigua i sanejament; i la crucial necessitat de proveir capacitació utilitzant tècniques participatives, de les quals es descriuen algunes, apuntant a una presa de decisions informada. Assenyalem també que capacitar i estimular els membres de la comunitat és important, però fins i tot ho és més, capacitar als actors del nivell intermedi (govern local, ONG, sector privat, etc.) que són els qui donen suport i faciliten la implementació del procés inicialment, i després el suport per a assegurar la sostenibilitat del servei proporcionat.Peer Reviewe

A Solvable Two-Dimensional Degenerate Singular Stochastic Control Problem with Nonconvex Costs

In this paper we provide a complete theoretical analysis of a two-dimensional degenerate nonconvex singular stochastic control problem. The optimisation is motivated by a storage-consumption model in an electricity market, and features a stochastic real-valued spot price modelled by Brownian motion. We find analytical expressions for the value function, the optimal control, and the boundaries of the action and inaction regions. The optimal policy is characterised in terms of two monotone and discontinuous repelling free boundaries, although part of one boundary is constant and the smooth fit condition holds there

Mitochondrial DNA and temperature tolerance in lager yeasts

A growing body of research suggests that the mitochondrial genome (mtDNA) is important for temperature adaptation. In the yeast genus Saccharomyces, species have diverged in temperature tolerance, driving their use in high- or low-temperature fermentations. Here, we experimentally test the role of mtDNA in temperature tolerance in synthetic and industrial hybrids (Saccharomyces cerevisiae × Saccharomyces eubayanus or Saccharomyces pastorianus), which cold-brew lager beer. We find that the relative temperature tolerances of hybrids correspond to the parent donating mtDNA, allowing us to modulate lager strain temperature preferences. The strong influence of mitotype on the temperature tolerance of otherwise identical hybrid strains provides support for the mitochondrial climactic adaptation hypothesis in yeasts and demonstrates how mitotype has influenced the world’s most commonly fermented beverage.This work was supported by the USDA National Institute of Food and Agriculture (Hatch project no. 1003258), the NSF (grant no. DEB-1253634), and in part by the DOE Great Lakes Bioenergy Research Center (DOE BER Office of Science; nos. DE-SC0018409 and DE-FC02-07ER64494). E.P.B. was supported by a Louis and Elsa Thomsen Wisconsin Distinguished Graduate Fellowship. C.T.H. is a Pew Scholar in the Biomedical Sciences and a Vilas Faculty Early Career Investigator, supported by the Pew Charitable Trusts and the Vilas Trust Estate. D.P. is a Marie Sklodowska-Curie fellow of the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 747775). J.C.F. was supported by the NIH (no. GM080669)Peer Reviewe

Large Fluctuations in Locational Marginal Prices

This paper investigates large fluctuations of Locational Marginal Prices (LMPs) in wholesale energy markets caused by volatile renewable generation profiles. Specifically, we study events of the form ℙ(LMP∉∏ni=1[α−i,α+i]), where LMP is the vector of LMPs at the n power grid nodes, and α−,α+∈ℝn are vectors of price thresholds specifying undesirable price occurrences. By exploiting the structure of the supply-demand matching mechanism in power grids, we look at LMPs as deterministic piecewise affine, possibly discontinuous functions of the stochastic input process, modeling uncontrollable renewable generation. We utilize techniques from large deviations theory to identify the most likely ways for extreme price spikes to happen, and to rank the nodes of the power grid in terms of their likelihood of experiencing a price spike. Our results are derived in the case of Gaussian fluctuations and are validated numerically on the IEEE 14-bus test case