7,350 research outputs found
The High Energy Behavior of the Forward Scattering Parameters---An Amplitude Analysis Update
Utilizing the most recent experimental data, we reanalyze high energy \pbar p
and pp data, using the asymptotic amplitude analysis, under the assumption that
we have reached `asymptopia'. This analysis gives strong evidence for a dependence at {\em current} energies and {\em not} ,
and also demonstrates that odderons are {\em not} necessary to explain the
experimental data.Comment: 7 pages in LaTeX, 4 figures and 5 files, uuencoded in file
"sigall.uu
Hypothetical-Actual Bid Calibration of a Multi-Good Auction
Evidence suggests the calibration of hypothetical and actual behavior is good-specific. We examine whether clustering commodities into mutual categories can reduce the burden. While we reject a common calibration across sets of commodities, a sport-specific calibration function cannot be rejected.Valuation, Calibration, Clusters
Is the Endangered Species Act Endangering Species?
We develop theory and present a suite of theoretically consistent empirical measures to explore the extent to which market intervention inadvertently alters resource allocation in a sequentialmove principal/agent game. We showcase our approach empirically by exploring the extent to which the U.S. Endangered Species Act has altered land development patterns. We report evidence indicating significant acceleration of development directly after each of several events deemed likely to raise fears among owners of habitat land. Our preferred estimate suggests an overall acceleration of land development by roughly one year. We also find from complementary hedonic regression models that habitat parcels declined in value when the habitat map was published, which is consistent with our estimates of the degree of preemption. These results have clear implications for policymakers, who continue to discuss alternative regulatory frameworks for species preservation. More generally, our modeling strategies can be widely applied -- from any particular economic environment that has a sequential-move nature to the narrower case of the political economy of regulation.
An Eclectic Approach to Impeachment by Prior Convictions
Almost every state permits persons convicted of a crime to testify in either their own or another person\u27s behalf. Nonetheless, these states allow evidence of a person\u27s prior criminal conviction to be used to impeach his credibility. The use of this method of impeachment in criminal trials has been the subject of substantial adverse criticism; yet, the practice remains widespread. This article first will discuss the problems that arise from the use of prior conviction evidence for impeachment purposes in criminal trials and then will examine several proposals that would restrict the use of such evidence. Finally, the article will propose an alternative rule to regulate the use of prior conviction evidence
JeffHEALTH: Helping East Africa Link to Health
JeffHEALTH-Helping East Africa Link to Health is a student-run organization at Thomas Jefferson University dedicated to improving basic medical education and quality of life in Rwanda, which was devastated in 1994 by civil war and genocide. Working in partnership with the Rwanda Village Concept Project, a student organization at the National University of Rwanda, JeffHEALTH seeks to implement sustainable health initiatives in our partner villages. Graduate students from Thomas Jefferson University travel to Rwanda where we taught Community Health Workers from the Villages of Akarambi and Ruli the following topics: Nutrition and Vitamin Deficiencies, Family Planning, Prenatal care, HIV, Sexually Transmitted Illnesses and Hepatitis, Breast and Cervical Cancer, Diabetes, and Fistulas. We also taught two programs to children of the villages (Oral Hygiene and Soil Transmitted Helminths) and talked with young adults about Circumcision and HIV Prevention and Sex Education.https://jdc.jefferson.edu/cwicposters/1018/thumbnail.jp
Pterodactyl: Control System Demonstrator Development for Integrated Control Design of a Mechanically Deployed Entry Vehicle
The NASA-funded Pterodactyl project is a design, test, and build capability to (i) advance the current state of the art for Deployable Entry Vehicle (DEV) guidance and control (G&C), and (ii) determine the feasibility of control system integration for various entry vehicle types including those without aeroshells. This capability is currently being used to develop control systems for one such unconventional entry vehicle, the Lifting Nano-ADEPT (LNA) vehicle. ADEPT offers the possibility of integrating control systems directly onto the mechanically deployed structure and building hardware demonstrators will help assess integration and design challenges. Control systems based on aerodynamic control surfaces, mass movement, and reaction control systems (RCS) are currently being investigated for a down-select to the most suitable control architecture for the LNA.To that effect, in this submission, we detail the efforts of the Pterodactyl project to develop a series of hardware demonstrators for the different LNA control systems. Rapid prototypes, for a set of quarter- model or eighth-model vehicle segments, will be developed for all three architectures to validate mechanical design assumptions, and hardware-in-the-loop (HIWL) control approaches. A ground test control system demonstrator will be designed and built after the trade study is complete. The industrial-grade demonstrator will be designed so that it can be incorporated into a HWIL simulation to further validate the findings of the initial trade study. The HWIL simulation will leverage the iPAS environment developed at NASA's Johnson Space Center which facilitates integration testing to support technology maturation and risk reduction, necessary elements for the hardware demonstration development detailed in this paper
A note on compactly generated co-t-structures
The idea of a co-t-structure is almost "dual" to that of a t-structure, but
with some important differences. This note establishes co-t-structure analogues
of Beligiannis and Reiten's corresponding results on compactly generated
t-structures.Comment: 10 pages; details added to proofs, small correction in the main
resul
Pterodactyl: Control Architectures Development for Integrated Control Design of a Mechanically Deployed Entry Vehicle
The need to return high mass payloads is driving the development of a new class of vehicles, Deployable Entry Vehicles (DEV) for which feasible and optimized control architectures have not been developed. The Pterodactyl project, seeks to advance the current state-of-the-art for entry vehicles by developing a design, test, and build capability for DEVs that can be applied to various entry vehicle configurations. This paper details the efforts on the NASA-funded Pterodactyl project to investigate multiple control techniques for the Lifting Nano-ADEPT (LNA) DEV. We design and implement multiple control architectures on the LNA and evaluate their performance in achieving varying guidance commands during entry.First we present an overview of DEVs and the Lifting Nano-ADEPT (LNA), along with the physical LNA configuration that influences the different control designs. Existing state-of-the-art for entry vehicle control is primarily propulsive as reaction control systems (RCS) are widely employed. In this work, we analyze the feasibility of using both propulsive control systems such as RCS to generate moments, and non-propulsive control systems such as aerodynamic control surfaces and internal moving mass actuations to shift the LNA center of gravity and generate moments. For these diverse control systems, we design different multi-input multi-output (MIMO) state-feedback integral controllers based on linear quadratic regulator (LQR) optimal control methods. The control variables calculated by the controllers vary, depending on the control system being utilized and the outputs to track for the controller are either the (i) bank angle or the (ii) angle of attack and sideslip angle as determined by the desired guidance trajectory. The LQR control design technique allows the relative allocation of the control variables through the choice of the weighting matrices in the cost index. Thus, it is easy to (i) specify which and how much of a control variable to use, and (ii) utilize one control design for different control architectures by simply modifying the choice of the weighting matrices.By providing a comparative analysis of multiple control systems, configurations, and performance, this paper and the Pterodactyl project as a whole will help entry vehicle system designers and control systems engineers determine suitable control architectures for integration with DEVs and other entry vehicle types
Deformation of the stem of containerized black spruce seedlings
When containerized black spruce seedlings (Picea mariana
(Mill.) B.S.P.) are grown rapidly, they often bend over, grow horizontally and become deformed. This phenomenon,
commonly referred to as spiralization, has had a severe impact on the containerized seedling industry in Quebec, particularly for producers using heated greenhouses.
Research programs at Universite Laval and the Universite du Quebec a Chicoutimi have attempted to determine causes as well as possible solutions. The physiological basis of stem spiralization appears to be associated with a redubed capacity of root systems to convert the amino acid, phenylalanine, into lignin precursors that will permit the stem to lignify in a normal manner.
High light levels together with an aerobic root environment were found to stimulate lignin synthesis in black spruce. The development cf spiralized stems was found to result from the sum total of a series of relatively small bending movements as well as minor corrective movements (i.e. 0-15°) measured every 2 to 3 days but integrated over the production cycle. A direct relationship was found between the maximal angle of bending and the risk that the seedling would have a significant defect at the end of the production cycle. A seedling which bent at more than 90° from the vertical at any time nearly always was classified as a defective seedling at the end of the production period. Vector analyses of seedling movements indicated that seedlings tended to move in the direction of the dominant light source.
Le gauchissement de la tige est un défaut de croissance, provenant d'une verse partielle ou complÚte du semis pendant sa phase de croissance exponentielle. Cette déformation se retrouve principalement sur les semis d'épinette noire (Picea mariana (Mill.) B.S.P.) en récipients, produits en serre pendant l'hiver. Le gauchissement de la tige entraßne des pertes importantes pour l'industrie du plant en récipient au Québec. Les travaux de recherche effectués a l'Université Laval et a l'Université du Québec a Chicoutimi ont démontré que le gauchissement de la tige était associé a la diminution du taux de transformation d'un acide aminé, le phénylalanine, en un composé qui est un précurseur de la lignine. De plus, il a été démontré que la combinaison des traitements de forte intensité lumineuse et d'oxygénation du substrat racinaire augmentait la lignification des semis d'épinette noire. La mesure de Tangle et de l'orientation de la tige, tous les 2 à 3 jours pendant la période de production, a démontre que le gauchissement de la tige résultait dune sommation de mouvements de faible amplitude (i.e. 0-15°). L'angle de la tige à la fin de la période de production était corrélé avec l'angle maximal atteint par le semis pendant sa croissance. Ainsi, un semis ayant atteint un angle supérieur à 90° pendant sa croissance était presque toujours classé inacceptable pour le reboisement, avec un angle de la tige supérieur a 15° à la fin de la période de production. L'analyse vectorielle des mouvements du plant a démontré que l'orientation de la source lumineuse dominante avait un effet significatif sur l'orientation des mouvements de la tige
Pterodactyl: Development and Comparison of Control Architectures for a Mechanically Deployed Entry Vehicle
The Pterodactyl project, seeks to advance the current state-of-the-art for entry vehicles by developing novel guidance and control technologies for Deployable Entry Vehicles (DEVs) that can be applied to various entry vehicle configurations. This paper details the efforts on the NASA-funded Pterodactyl project to investigate and implement multiple control techniques for an asymmetric mechanical DEV. We design multiple control architectures for a Pterodactyl Baseline Vehicle (PBV) and evaluate their performance in achieving varying guidance commands during entry. The control architectures studied are (i) propulsive control systems such as reaction control systems and (ii) non-propulsive control systems such as aerodynamic control surfaces and internal moving masses. For each system, state-feedback integral controllers based on linear quadratic regulator (LQR) optimal control methods are designed to track guidance commands of either (i) bank angle or (ii) angle of attack and sideslip angle as determined by the desired guidance trajectory. All control systems are compared for a lunar return reference mission and by providing a comparative analysis of these systems, configurations, and performance, the efforts detailed in this paper and the Pterodactyl project as a whole will help entry vehicle system designers determine suitable control architectures for integration with DEVs and other entry vehicle types
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