FROM DATA TO INFORMATION: THE VALUE OF SAMPLING VS. SENSING SOIL DATA

A conceptual model is developed to measure the value of information from in-field soil sensing technologies as compared with grid and other soil sampling methods. Soil sensing offers greater spatial accuracy and the potential to apply inputs such as nitrogen fertilizer immediately, avoiding changes in nutrient status that occur with delays between soil sampling and fertilizer application. By contrast, soil sampling offers greater measurement accuracy, because it does not rely on proxy variables such as electrical conductivity to infer nutrient status. The average profitability and relative riskiness of soil sensing versus sampling depend upon 1) the trade-off between, on the one hand, the spatial and temporal accuracy of sensing and, on the other hand, the measurement accuracy of sampling, 2) the cost of data collection, and 3) input and product prices. Similar trade-offs govern the relative riskiness of sensing versus sampling.Farm Management,

Computer code for single-point thermodynamic analysis of hydrogen/oxygen expander-cycle rocket engines

This analysis and this computer code apply to full, split, and dual expander cycles. Heat regeneration from the turbine exhaust to the pump exhaust is allowed. The combustion process is modeled as one of chemical equilibrium in an infinite-area or a finite-area combustor. Gas composition in the nozzle may be either equilibrium or frozen during expansion. This report, which serves as a users guide for the computer code, describes the system, the analysis methodology, and the program input and output. Sample calculations are included to show effects of key variables such as nozzle area ratio and oxidizer-to-fuel mass ratio

Development of an Object-Oriented Turbomachinery Analysis Code within the NPSS Framework

During the preliminary or conceptual design phase of an aircraft engine, the turbomachinery designer has a need to estimate the effects of a large number of design parameters such as flow size, stage count, blade count, radial position, etc. on the weight and efficiency of a turbomachine. Computer codes are invariably used to perform this task however, such codes are often very old, written in outdated languages with arcane input files, and rarely adaptable to new architectures or unconventional layouts. Given the need to perform these kinds of preliminary design trades, a modern 2-D turbomachinery design and analysis code has been written using the Numerical Propulsion System Simulation (NPSS) framework. This paper discusses the development of the governing equations and the structure of the primary objects used in OTAC

Design of an Object-Oriented Turbomachinery Analysis Code: Initial Results

Performance prediction of turbomachines is a significant part of aircraft propulsion design. In the conceptual design stage, there is an important need to quantify compressor and turbine aerodynamic performance and develop initial geometry parameters at the 2-D level prior to more extensive Computational Fluid Dynamics (CFD) analyses. The Object-oriented Turbomachinery Analysis Code (OTAC) is being developed to perform 2-D meridional flowthrough analysis of turbomachines using an implicit formulation of the governing equations to solve for the conditions at the exit of each blade row. OTAC is designed to perform meanline or streamline calculations; for streamline analyses simple radial equilibrium is used as a governing equation to solve for spanwise property variations. While the goal for OTAC is to allow simulation of physical effects and architectural features unavailable in other existing codes, it must first prove capable of performing calculations for conventional turbomachines. OTAC is being developed using the interpreted language features available in the Numerical Propulsion System Simulation (NPSS) code described by Claus et al (1991). Using the NPSS framework came with several distinct advantages, including access to the pre-existing NPSS thermodynamic property packages and the NPSS Newton-Raphson solver. The remaining objects necessary for OTAC were written in the NPSS framework interpreted language. These new objects form the core of OTAC and are the BladeRow, BladeSegment, TransitionSection, Expander, Reducer, and OTACstart Elements. The BladeRow and BladeSegment consumed the initial bulk of the development effort and required determining the equations applicable to flow through turbomachinery blade rows given specific assumptions about the nature of that flow. Once these objects were completed, OTAC was tested and found to agree with existing solutions from other codes; these tests included various meanline and streamline comparisons of axial compressors and turbines at design and off-design conditions

Performance Benefits for a Turboshaft Engine Using Nonlinear Engine Control Technology Investigated

The potential benefits of nonlinear engine control technology applied to a General Electric T700 helicopter engine were investigated. This technology is being developed by the U.S. Navy SPAWAR Systems Center for a variety of applications. When used as a means of active stability control, nonlinear engine control technology uses sensors and small amounts of injected air to allow compressors to operate with reduced stall margin, which can improve engine pressure ratio. The focus of this study was to determine the best achievable reduction in fuel consumption for the T700 turboshaft engine. A customer deck (computer code) was provided by General Electric to calculate the T700 engine performance, and the NASA Glenn Research Center used this code to perform the analysis. The results showed a 2- to 5-percent reduction in brake specific fuel consumption (BSFC) at the three Sikorsky H-60 helicopter operating points of cruise, loiter, and hover

An Updated Assessment of NASA Ultra-Efficient Engine Technologies

NASA's Ultra Efficient Engine Technology (UEET) project features advanced aeropropulsion technologies that include highly loaded turbomachinery, an advanced low-NOx combustor, high-temperature materials, and advanced fan containment technology. A probabilistic system assessment is performed to evaluate the impact of these technologies on aircraft CO2 (or equivalent fuel burn) and NOx reductions. A 300-passenger aircraft, with two 396-kN thrust (85,000-lb) engines is chosen for the study. The results show that a large subsonic aircraft equipped with the current UEET technology portfolio has very high probabilities of meeting the UEET minimum success criteria for CO2 reduction (-12% from the baseline) and LTO (landing and takeoff) NOx reductions (-65% relative to the 1996 International Civil Aviation Organization rule)

Are IS Candidates Supplying the Teaching and Research Skills that Universities Need Most?

This longitudinal research study investigates the teaching and research expectations for potential IS professors. Most university departments advertise for specific job skills and qualifications when they attempt to recruit faculty members. This study examines over 400 IS placement advertisements for the academic recruiting years 2001-2002, 2002-2003 and 2003-2004. Top teaching and research areas that universities are interested in for their new hires are identified. The study then investigates whether the interests of candidates seeking appointments are similar. Over 400 IS candidate doctorates\u27 résumés are content analyzed and their teaching and research preferences are identified. By looking at the teaching and research needs of the universities and the preferences of IS candidates, it is then possible to identify if a gap exists between the two. Lists of (1) most required and (2) most desired IS teaching and research areas over the three year period are shown. The results report that in terms of teaching, what the universities are looking for is being well matched with what candidates are offering, except in the universities\u27 demand for telecommunications. With respect to research, while there is some match between demand and supply, there is a noticeable lack of demand by universities for e-Commerce, HCI and ERP

Foundations of Information Systems Course Content: A Comparison of Assigned Value by Faculty, Recruiters, and Students

This research compares the value placed on the content of the foundations of information systems course by three stakeholders: faculty, recruiters, and students. Given the declining enrollments in IS that led ACM/AIS to redesign its curriculum in an attempt to help universities reverse this trend, we need to assess the value placed on this curriculum by stakeholders. Although all majors in a business school are typically required to take the foundations of IS course, its real or perceived value to businesses and future employers is unclear. A first step in evaluating the entire curriculum is to focus on the foundations of IS course. Results differ among the stakeholders, and discussions highlight the need to continually improve the curriculum to fit the needs and the assigned importance of the diverse stakeholders

Distance Education At The Graduate Level: A Viable Alternative

This research extends a previous comparative study that looked at learning outcomes between traditional classroom and web-based education at the graduate level. That research (Jones and Everard, 2008) provided little evidence that there were significant differences between delivery methods. This research looks at employment status, household demographics, and family commitments and explores why these underlying factors do not affect outcomes between traditional classroom and web-based education at the graduate level. Results of this research provide evidence that for graduate level education, distance education is a practical and appropriate option

A 6-12 GHz Analogue Lag-Correlator for Radio Interferometry

Aims: We describe a 6-12 GHz analogue correlator that has been developed for use in radio interferometers. Methods: We use a lag-correlator technique to synthesis eight complex spectral channels. Two schemes were considered for sampling the cross-correlation function, using either real or complex correlations, and we developed prototypes for both of them. We opted for the ``add and square'' detection scheme using Schottky diodes over the more commonly used active multipliers because the stability of the device is less critical. Results: We encountered an unexpected problem, in that there were errors in the lag spacings of up to ten percent of the unit spacing. To overcome this, we developed a calibration method using astronomical sources which corrects the effects of the non-uniform sampling as well as gain error and dispersion in the correlator.Comment: 14 pages, 21 figures, accepted for publication in A&