725 research outputs found

    Twin Row Corn Study

    Get PDF
    Interest in narrow row corn and, more recently, twin row corn has increased over the last several years. Research done in the 1990s in various locations throughout the Corn Belt has demonstrated significant yield advantages of narrowing corn rows from 38 in. to 30 in. This is now the third year of this study, and yield results from row spacings narrower than 30 inches have indicated a greater likelihood of a yield response in the northern part of the Corn Belt. Yield increases for narrow row spacing in corn from the central to southern areas of the Corn Belt have been inconsistent. Interest in this new concept, twin row corn, has prompted many new questions about row spacing in corn. One of the advantages of twin row corn is that no major modifications of harvest or spray equipment are necessary when converting from single row 30-inch spacing. Another potential set of advantages is better seed placement, more accurate plant spacing, and greater sunlight utilization

    Information Privacy in a Globally Networked Society: Implications for IS Research

    Get PDF
    This paper presents an extended discussion of issues associated with the role of information privacy in IS research. This discussion was initiated in conjunction with a panel session at ICIS 2002. Following the conference, each of the panelists reworked and extended their position statements, and provided a commentary on the position statements of the other panelists. The paper is framed with head and tail pieces written by the panel chair. The result is a (unique and provocative) blend of opinion and commentary on a topic that is of importance to IS research in the globally networked society in which we all live. IS researchers will find research questions, research conundrums, and research advice in equal measure

    Design and Implementation of Swirl Brakes for Enhanced Rotordynamic Stability in an Off-shore Centrifugal Compressor

    Get PDF
    Technical BriefsRotordynamic stability of gas compressors at high speeds and operating pressures is a significant technical challenge. Dynamic instability must be avoided for the sake of safe, reliable and continuous operation of turbomachinery. Experience and literature have shown that one of the main sources of instability is the swirl within the secondary leakage path in shrouded impellers, especially the swirl entering the shroud seals. The technical brief presents the design and implementation of swirl brakes for centrifugal compressors with Teeth-on-Rotor seal configurations for shrouded impellers. Discussion includes (a) aerodynamic design of swirl brakes with the help of Computational Fluid Dynamics (CFD), (b) sub-scale testing of the swirl brake design in an instrumented single-stage test rig to measure the inlet swirl ratio in a shrouded impeller, (c) full-scale prototype shop-testing and qualification, with and without the swirl brakes in a closedloop test facility, and (d) results of incorporating the swirl brakes at an off-shore compressor installation to improve rotordynamic stability

    Challenges and Directions in Formalizing the Semantics of Modeling Languages

    Get PDF
    Developing software from models is a growing practice and there exist many model-based tools (e.g., editors, interpreters, debuggers, and simulators) for supporting model-driven engineering. Even though these tools facilitate the automation of software engineering tasks and activities, such tools are typically engineered manually. However, many of these tools have a common semantic foundation centered around an underlying modeling language, which would make it possible to automate their development if the modeling language specification were formalized. Even though there has been much work in formalizing programming languages, with many successful tools constructed using such formalisms, there has been little work in formalizing modeling languages for the purpose of automation. This paper discusses possible semantics-based approaches for the formalization of modeling languages and describes how this formalism may be used to automate the construction of modeling tools

    Cauchy-characteristic Evolution of Einstein-Klein-Gordon Systems

    Full text link
    A Cauchy-characteristic initial value problem for the Einstein-Klein-Gordon system with spherical symmetry is presented. Initial data are specified on the union of a space-like and null hypersurface. The development of the data is obtained with the combination of a constrained Cauchy evolution in the interior domain and a characteristic evolution in the exterior, asymptotically flat region. The matching interface between the space-like and characteristic foliations is constructed by imposing continuity conditions on metric, extrinsic curvature and scalar field variables, ensuring smoothness across the matching surface. The accuracy of the method is established for all ranges of M/RM/R, most notably, with a detailed comparison of invariant observables against reference solutions obtained with a calibrated, global, null algorithm.Comment: Submitted to Phys. Rev. D, 16 pages, revtex, 7 figures available at http://nr.astro.psu.edu:8080/preprints.htm

    Science with the Second Wide Field and Planetary Camera

    Get PDF
    With the commencement of Cycle 4 observations, the General Observer community will have access to the second Wide Field and Planetary Camera (WFPC-2), a replacement for the original WFPC instrument. WFPC-2, a wide-field photometric camera which covers the spectrum from 1200 to 10000 Angstroms, will be installed in the Hubble radial bay during the currently manifested December 1992 Shuttle servicing mission. Besides optical correction for the aberrated Hubble primary mirror, the WFPC-2 incorporates evolutionary improvements in photometric imaging capabilities. The CCD sensors, signal chain electronics, filter set, FUV performance, internal calibrations, and operational efficiency have all been improved through new technologies and lessons learned from WFPC operations and Hubble experience since launch. Here we provide an overview of the new instrument, beginning with the assumption that the reader is already familiar with the original WFPC now in service
    corecore