Generation of Particles and Seeding

One of the most important elements in laser velocimetry, yet the most neglected, is the small particle embedded in the flow field that scatters the light necessary to make velocity measurements. An attempt to remove the confusion in choosing a seeding method by assessing many of the techniques currently used is presented. Their characteristics and typical limitations imposed by various applications are outlined. The ramifications of these methods on measurement accuracy are addressed

Frequency domain laser velocimeter signal processor: A new signal processing scheme

A new scheme for processing signals from laser velocimeter systems is described. The technique utilizes the capabilities of advanced digital electronics to yield a smart instrument that is able to configure itself, based on the characteristics of the input signals, for optimum measurement accuracy. The signal processor is composed of a high-speed 2-bit transient recorder for signal capture and a combination of adaptive digital filters with energy and/or zero crossing detection signal processing. The system is designed to accept signals with frequencies up to 100 MHz with standard deviations up to 20 percent of the average signal frequency. Results from comparative simulation studies indicate measurement accuracies 2.5 times better than with a high-speed burst counter, from signals with as few as 150 photons per burst

Frequency domain laser velocimeter signal processor

A new scheme for processing signals from laser velocimeter systems is described. The technique utilizes the capabilities of advanced digital electronics to yield a signal processor capable of operating in the frequency domain maximizing the information obtainable from each signal burst. This allows a sophisticated approach to signal detection and processing, with a more accurate measurement of the chirp frequency resulting in an eight-fold increase in measurable signals over the present high-speed burst counter technology. Further, the required signal-to-noise ratio is reduced by a factor of 32, allowing measurements within boundary layers of wind tunnel models. Measurement accuracy is also increased up to a factor of five

A Risk- and Fuzzy Set-Based Methodology for Advanced Concept Technology Demonstration Military Utility Assessment Design

The U.S. Department of Defense Advanced Concept Technology Demonstration (ACTD) and derivative, rapid acquisition programs offer timely solutions to critical military needs by assessing the utility of technologies mature enough to be fielded without application of traditional, defense system development processes. Military utility assessments (MUA) are ACTDs\u27 most critical features, but the lack of a standard for identifying assessment criteria tailored to specific demonstrations risks poorly informed acquisition decisions and the military operations those decisions are intended to support. The purpose of this research was to develop and deploy a methodology for identifying measures of effectiveness integral to advanced concept technology demonstration military utility assessment design. Within a context determined by attributes of complex systems, the research observed twin premises that ACTD assessment designs should accommodate: all risks possible when incorporating demonstration prototypes within superior and complex, joint military operations metasystems; and the ambiguities and other of what have been termed “fuzzy” manifestations of the cognition and language with which end-user, military operators craft and express perspectives required to identify measures of effectiveness fundamental to MUA designs. The effort pursued three research questions: (1) How might joint military operations metasystem models guide the identification of ACTD measures of effectiveness? (2) How might be developed and employed joint military metasystem models with which can be identified ACTD measures of effectiveness? (3) How useful might ACTD managers and analysts find the MUA design methodology developed and deployed with this research? The deployed methodology stimulated answers to these research questions by uniquely combining tailored versions of established risk assessment methods with a fuzzy method for resolving small group preferences. The risk assessment methods honored one research premise while enabling the identification and employment of a joint military operations metasystem model suited to MUA design needs of a simulated ACTD. The fuzzy preference method honored the second research premise as it, too, promoted metasystem model employment. The complete methodology was shown to hold favor with a large segment of a community expert in managing and assessing the utility of ACTDs emphasizing critical, joint military service needs

Context dependencies for younger and older adults in learning a 4-key motor sequence

The role environmental context has on performance level may change based on the skill being learned and the performer of that skill. The present study was designed to examine the role of environmental context in the learning of a 4-key motor sequence task. The present study had two primary purposes: first, replicating findings of a limited context effect in younger adults, and second, extending the findings to older adults to look at changes related to aging and environmental context. ANOVA results revealed no significant context effect in the present study for younger adults, and therefore comparisons between younger and older adults could not be made. Analysis of the data suggests the possibility of low performance levels in the current study being at least one factor related to context dependencies not developing in the learning of the 4-key motor sequence task

Paper Session I-A - Delta Commercial Space Transportation

1996 Launches – As of this writing, two launches have taken place in 1996, the NEAR on 17 February and Koreasat-2 on 14 January. NEAR (Near Earth Asteroid Rendezvous) is the first of the NASA Discovery series of spacecraft, and is the fifth under the MELVS contract. The Koreasat-2 satellite was the second satellite launched for the republic of Korea, and was an entirely successful launch. The first satellite, launched on Delta 228 last August, reached orbit successfully but with less than specified lifetime due to a first stage anomaly

Diets of Wild Versus Released, and Pen-Raised White-Tailed Deer in Southeastern Louisiana

Twenty pen-raised white-tailed deer (Odocoileus virginianus) were released into mixed pine-hardwood forest habitat in southeastern Louisiana to compare their seasonal diets to the diets of the wild white-tailed deer population. Microhistological analysis was used to estimate the botanical composition of fecal pellet samples collected from both populations of deer over four consecutive seasons. Wild and pen-raised deer diets were found to be an average of 75.18% similar during the entire year of the study, and were significantly associated during all seasons (P \u3c 0.001), indicating that all deer foraged on similar plant taxa in similar proportions regardless of season. Both populations of deer were found to be predominantly browsers during all seasons, with browse and fruit accounting for a yearly average of \u3e55% of deer diets. Results from this study indicate that rehabilitated or translocated deer released into new environments will forage as efficiently as their wild counterparts

Interpretation of Long-term Trade Projections: China's Role in Forecast Discrepancies and its Impact on Expectations for World Agricultural Trade

Agricultural and Food Policy, International Relations/Trade,

Doppler Global Velocimetry Measurements for Supersonic Flow Fields

The application of Doppler Global Velocimetry (DGV) to high-speed flows has its origins in the original development of the technology by Komine et al (1991). Komine used a small shop-air driven nozzle to generate a 200 m/s flow. This flow velocity was chosen since it produced a fairly large Doppler shift in the scattered light, resulting in a significant transmission loss as the light passed through the Iodine vapor. This proof-of-concept investigation showed that the technology was capable of measuring flow velocity within a measurement plane defined by a single-frequency laser light sheet. The effort also proved that velocity measurements could be made without resolving individual seed particles as required by other techniques such as Fringe- Type Laser Velocimetry and Particle Image Velocimetry. The promise of making planar velocity measurements with the possibility of using 0.1-micron condensation particles for seeding, Dibble et al (1989), resulted in the investigation of supersonic jet flow fields, Elliott et al (1993) and Smith and Northam (1995) - Mach 2.0 and 1.9 respectively. Meyers (1993) conducted a wind tunnel investigation above an inclined flat plate at Mach 2.5 and above a delta wing at Mach 2.8 and 4.6. Although these measurements were crude from an accuracy viewpoint, they did prove that the technology could be used to study supersonic flows using condensation as the scattering medium. Since then several research groups have studied the technology and developed solutions and methodologies to overcome most of the measurement accuracy limitations