COPTRAN - A method of optimum communication systems design

Single set of mathematical expressions describes system cost and probability of error of data transmission in terms of four basic parameters in the link equation. A Lagrange multiplier sets up equations whose solutions yield the optimum values for system design considerations and weight and cost values

Study and development of a mathematical analysis for the performance assessment of space communication system parameters

Electronic computer program user manual for optimum design of space communication syste

User's manual for COPTRAN, a method of optimum communication system design

User manual for COPTRAN /communication system optimization program translator

Research in LMSS propagation

The Virginia Tech Satellite Communications Group has participated in the Land Mobile Satellite System (LMSS) program through JPL sponsorship since 1985. Involvement has mainly been in modeling and simulation of propagation characteristics and effects. Models developed to predict cummulative fade distributions for fading LMSS signals include LMSSMOD and the Simple Models which approximate LMSSMOD. Models to predict the mean and standard deviation of signal attenuation through roadside vegetation, namely the Average Path Model, were developed. In the area of simulation, efforts have centered around the development of a software simulator that uses data bases derived from experimental data to generate simulated data with arbitrary statistical behavior. This work has progressed to the development of an integrated analysis and simulation package, LIPS. The basic theory and results for the models and simulator have been previously documented in reports and papers. All LMSS activities are summarized and details of this year's efforts are given

Pairing of 1-hexyl-3-methylimidazolium and tetrafluoroborate ions in n-pentanol

Molecular dynamics simulations are obtained and analyzed to study pairing of 1-hexyl-3-methylimidazolium and tetrafluoroborate ions in n-pentanol, in particular by evaluating the potential-of-mean-force between counter ions. The present molecular model and simulation accurately predicts the dissociation constant Kd in comparison to experiment, and thus the behavior and magnitudes for the ion-pair pmf at molecular distances, even though the dielectric constant of the simulated solvent differs from the experimental value by about 30%. A naive dielectric model does not capture molecule structural effects such as multiple conformations and binding geometries of the Hmim+ and BF4- ion-pairs. Mobilities identify multiple time-scale effects in the autocorrelation of the random forces on the ions, and specifically a slow, exponential time-decay of those long-ranged forces associated here with dielectric friction effects.Comment: 5 pages, 7 figures. V2: Figs. 4 & 7 redrawn for better visual clarity with log-scales. No change in results. In press J. Chem. Phys. 201

Rare plants within managed units of 'Ola'a Forest, Hawaii Volcanoes National Park

Reports were scanned in black and white at a resolution of 600 dots per inch and were converted to text using Adobe Paper Capture Plug-in.Four fenced pig-free management units and one adjacent unfenced area within the 'Ola'a Forest of Hawaii Volcanoes National Park were systematically searched for rare plants in 1992-94. Additional rare plant sightings were made off transects and on fencelines, while working on other projects in 1995-98. Observations by Resources Management workers were included on maps where possible. Only the western third of the 'Ola'a Forest was searched during this survey, where transects were placed systematically along north/south fence lines at intervals of 250-500 m. Those plants mapped on transects were within a 5-m belt. One listed endangered species, ha'iwale (Cyrtandra giffardii), was found in each surveyed unit, but was concentrated in the Ag and Koa Units below 1,280 m (4,200 K) elevation. 'Ola'a has a larger population of this endangered species than anticipated, as 91 plants were counted along transects. A second endangered species, 'anunu (Sicyos alba), was encountered at four localities within the Koa Unit; this extremely rare vine is known fiom only two other Hawai'i Island sites. Eight former candidate endangered plant species or "species of special concern" were counted along surveyed transects. Only six 'aku (Cyanea tritomantha) were sighted in the Ag and Koa Units. The lobelioid, koli'i (Trematolobelia grandifolia), was more frequently seen, inside and outside the Pu'u Unit and in the lower Ag Unit. One hundred seventeen koli'i plants were counted along transects, and others were sighted off transect. Candidate endangered mints were very rare; only one Phyllostegia floribunda, nine P. vestita, fourteen mohihi (Stenogyne scrophularioides), and six Stenogyne macrantha were observed in the study area. The herb popolo ku mai (Phytolacca sandwicensis) was seen primarily in the Koa Unit, where 10 plants were counted. Only one individual of the vine Schiedea diffusa was found within 'Ola'a at the same Ag Unit site where it was discovered nine years ago; this is the only sighting of the species on Hawai'i Island in more than 80 years. Two endangered species (Adenophorus periens, Clermontia peleana), and three species of concern (Asplenium schizophyllum, Eurya sandwicensis, and Joinvillea ascendens) that were formerly reported from 'Ola'a Forest were not found in the study area in 1992-98. Twenty additional plant species that are rare to uncommon in the Park were sighted within the 'Ola'a Forest study area. Two endemic orchid species (Anoectochilus sandvicensis and Liparis hawaiensis) were each found at only one 'Ola'a site. The rare vine kilioe (Embelia pacifica) occurred at five widely scattered sites in three units. Only 12 individuals of pawale (Rumex giganteus) were observed; half of these were on transects, while others were on fence lines and at sites near transects. Eighty-three pala ferns (Marattia douglasii) were counted along transects; these were concentrated in the Small Tract, Ag Unit, and outside the Pu'u Unit. These large terrestrial ferns are palatable to pigs and are sensitive to disturbance of the forest floor. The lobelioid 'oha kepau (Clermontia hawaiiensis) was noted at only one locality within the Ag Unit, but two other 'oha species (C. montis-loa and C. parviflora) were relatively common in all five units of the study area. Two species of haha or Cyanea were less widely distributed within 'Ola'a Forest. Cyanea degeneriana plants were concentrated in or near the Pu'u Unit and inside the Ag Unit; 60 plants of this species were observed along transects, and a few others were growing on fence lines. Eighty-one Cyanea pilosa subsp. longipedunculata plants were found outside the Pu'u Unit and in the southern half of the Small Tract. Ten of the 20 rare and uncommon plant species of 'Ola'a are shrubs or trees. Papala (Charpentiera obovata) and papala kepau (Pisonia brunoniana), trees more common at mesic sites, were restricted to the Small Tract and the southwestern corner of the Koa Unit. 'Aiea trees (Nothocestrum longifolium) and two species of shrubby kamakahala (Labordia hirtella and L. hedyosmifolia) were widely scattered in all five units of 'Ola'a. Pilo kea (Platydesma spathulata) was very rare within the study area; only 18 pilo kea were noted on transects, and others were encountered off transect. Loulu palms (Pritchardia beccariana) were infrequently encountered, primarily in the Small Tract, Koa, and Ag Units. 'Ohe mauka (Tetraplasandra oahuensis) trees, with one exception, were restricted to the Pu'u Unit, where 19 individuals were counted along transects and fence lines. Two members of the nettle family were also mapped along transects. Olona (Touchardia latifolia) was most often seen within the Ag Unit, but was also scattered throughout the Koa Unit and Small Tract and was sighted once outside the Pu'u Unit. Opuhe (Urera glabra) was much rarer and was concentrated in the eastern half of the Small Tract and the adjacent area in the Koa Unit. Only 11 widely scattered individuals of maua (Xylosma hawaiiense), a tree also known from mesic forests, were sighted within the study area.National Park Service Cooperative Agreement CA 8015 2 900

Evaluation of experimental epoxy monomers

Future generation aircraft need higher performance polymer matrices to fully achieve the weight savings possible with composite materials. New resins are being formulated in an effort to understand basic polymer behavior and to develop improved resins. Some polymer/curing agent combinations that could be useful are difficult to process. In the area of epoxies, a major problem is that some components have physical properties which make them difficult to utilize as matrix resins. A previous study showed that the use of ultrasonic energy can be advantageous in the mixing of curing agents into a standard epoxy resin, such as MY 720 (Ciba-Geigy designation). This work is expanded to include three novel epoxides