Multi axes vibration fixtures

A simplified technique and apparatus are described for testing the effects of vibration on various material specimen. Particular attention was given to tests along the orthogonal vibrational planes in order to prove the strength of the item under extraordinary conditions to which it will be subjected

Effects of Changes in Surface Water Regime and/or Land Use on the Vertical Distribution of Water Available for Wetland Vegetation: Dynamic Model of the Zone of Aeration (Part 1 of Completion Report for Project A-023-ARK)

A mathematical model by Green, simulating one-dimensional vertical ground-water movement in unsaturated soils of the prairie region of Kansas, has been adapted for use in a wetlands environment typified by the wetlands forest of Eastern Arkansas. The model consists of two second-order, non-linear, partial differential equations and an algorithm for their numerical solution. The original model was extended to include functions for seasonal changes in transpiration and for drainage of excess precipitation. Before the addition of the two functions, the model reliability was limited to one growth season

Effects of Changes in Surface Water Regime and/or Land Use on the Vertical Distribution of Water Available for Wetland Vegetation: Dynamic Model of the Zone of Aeration (Appendix to Part 1 of Completion Report for Project A-023-ARK)

Appendix to Part 1 of Completion Report for Project A-023-AR

Estimating the Firm's Labor Supply Curve in a "New Monopsony" Framework: School Teachers in Missouri

In the context of certain dynamic models, it is possible to infer the elasticity of labor supply to the firm from the elasticity of the quit rate with respect to the wage. Using this property, we estimate the average labor supply elasticity to public school districts in Missouri. We take advantage of the plausibly exogenous variation in pre-negotiated district salary schedules to instrument for actual salary. Instrumental variables estimates lead to a labor supply elasticity estimate of about 3.7, suggesting the presence of significant market power for school districts, especially over more experienced teachers. The presence of monopsony power in this labor market may be partially explained by institutional features of the teacher labor market.labor monopsony, teachers

Static aerodynamic characteristics of the S-IC booster/GAC H-33 orbiter launch vehicle configuration

This test at the trisonic tunnel was divided into two parts. The first part utilized the H-33 orbiter with drop tanks and cradle mounted on an S-IC booster with 75 square-foot fins oriented 45 deg off the horizontal and vertical reference planes. Runs were initially made to determine the optimum incidence angle to be used for the remainder of the tests. The angle so determined was 0 degrees. Additional testing was performed with drop tanks removed, orbiter vertical tail removed, drop tanks and orbiter wing removed, booster fins removed and booster fins located in the horizontal and vertical reference planes. The second part utilized the H-33 orbiter and cradle only, sting mounted on a strain gage balance. These data were used in conjunction with test number 504 (orbiter alone on balance) to determine cradle effects

Getting their acts together: A coordinated systems approach to extended cognition

A cognitive system is a set of processes responsible for intelligent behaviour. This thesis is an attempt to answer the question: how can cognitive systems be demarcated; that is, what criterion can be used to decide where to draw the boundary of the system? This question is important because it is one way of couching the hypothesis of extended cognition – is it possible for cognitive systems to transcend the boundary of the brain or body of an organism? Such a criterion can be supplied by what is called in the literature a ‘mark of the cognitive’. The main task of this thesis is to develop a general mark of the cognitive. The starting point is that a system responsible for intelligent behaviour is a coordinated coalition of processes. This account proposes a set of functional conditions for coordination. These conditions can then be used as a sufficient condition for membership of a cognitive system. In certain circumstances, they assert that a given process plays a coordination role in the system and is therefore part of the system. The controversy in the extended cognition debate surrounds positive claims of systemhood concerning ‘external’ processes so a sufficient condition will help settle some of these debates. I argue that a Coordinated Systems Approach like this will help to move the extended cognition debate forward from its current impasse. Moreover, the application of the approach to social systems and stygmergic systems - systems where current processes are coordinated partly by the trace of previous action – promises new directions for research

Effects of near surface ocean gradients upon shelf sea air–sea gas exchange estimates

The seawater CO2 partial pressures (pCO2) which are used in flux calculations are measured in the mixed layer at ~5m. If the surface ocean is not mixed, the pCO2 measured at 5m is not representative of the interfacial value and the calculated flux is incorrect. The objective of this work was to measure near surface pCO2 gradients in the mixed layer to discern their occurrence, size and effect on the flux. A Near Surface Ocean Profiler (NSOP) was designed to precisely measure vertical gradients in the top 5 m of the ocean. Vertical profiles of pCO2 were possible due to a fast equilibrating membrane equilibrator. Vertical profiles of temperature, salinity and pCO2 were collected with NSOP during 4 research cruises at different times of the year in Shelf Seas and as part of a seasonal study at the Western Channel Observatory Site L4. Differences in pCO2 of 4μatm and were observed only when there were strong temperature gradients (> 0.05°C) and low wind speeds (<6ms-1). There was no apparent relationship between the local meteorology and differences in the interfacial and subsurface pCO2. Theoretical calculations of the formation of near surface layers with distinctly different pCO2 to the subsurface pCO2 indicate that the air–sea flux, biological production and rainfall could change the pCO2 in a surface layer equal to the magnitude of the pCO2 changes observed during the cruises. The largest differences in interfacial and subsurface CO2 were observed when the wind speeds were low, this means that they have a relatively large effect on a small air sea fluxes over short periods of time but do not substantially alter the absolute size of flux which is dominated by strong winds over long timescales

Benzonitrile as a Proxy for Benzene in the Cold ISM: Low-temperature Rate Coefficients for CN + C₆H₆

The low-temperature reaction between CN and benzene (C₆H₆) is of significant interest in the astrochemical community due to the recent detection of benzonitrile, the first aromatic molecule identified in the interstellar medium (ISM) using radio astronomy. Benzonitrile is suggested to be a low-temperature proxy for benzene, one of the simplest aromatic molecules, which may be a precursor to polycyclic aromatic hydrocarbons. In order to assess the robustness of benzonitrile as a proxy for benzene, low-temperature kinetics measurements are required to confirm whether the reaction remains rapid at the low gas temperatures found in cold dense clouds. Here, we study the C₆H₆ + CN reaction in the temperature range 15–295 K, using the well-established CRESU technique (a French acronym standing for Reaction Kinetics in Uniform Supersonic Flow) combined with pulsed-laser photolysis-laser-induced fluorescence. We obtain rate coefficients, k(T), in the range (3.6–5.4) × 10⁻¹⁰ cm³ s⁻¹ with no obvious temperature dependence between 15 and 295 K, confirming that the CN + C₆H₆ reaction remains rapid at temperatures relevant to the cold ISM

Magnetorheological landing gear: 1. A design methodology

Aircraft landing gears are subjected to a wide range of excitation conditions, which result in conflicting damping requirements. A novel solution to this problem is to implement semi-active damping using magnetorheological (MR) fluids. This paper presents a design methodology that enables an MR landing gear to be optimized, both in terms of its damping and magnetic circuit performance, whilst adhering to stringent packaging constraints. Such constraints are vital in landing gear, if MR technology is to be considered as feasible in commercial applications. The design approach focuses on the impact or landing phase of an aircraft's flight, where large variations in sink speed, angle of attack and aircraft mass makes an MR device potentially very attractive. In this study, an equivalent MR model of an existing aircraft landing gear is developed. This includes a dynamic model of an MR shock strut, which accounts for the effects of fluid compressibility. This is important in impulsive loading applications such as landing gear, as fluid compression will reduce device controllability. Using the model, numerical impact simulations are performed to illustrate the performance of the optimized MR shock strut, and hence the effectiveness of the proposed design methodology. Part 2 of this contribution focuses on experimental validation