Torsional suspension system for testing space structures

A low frequency torsional suspension system for testing a space structure uses a plurality of suspension stations attached to the space structure along the length thereof in order to suspend the space structure from an overhead support. Each suspension station includes a disk pivotally mounted to the overhead support, and two cables which have upper ends connected to the disk and lower ends connected to the space structure. The two cables define a parallelogram with the center of gravity of the space structure being vertically beneath the pivot axis of the disk. The vertical distance between the points of attachment of the cables to the disk and the pivot axis of the disk is adjusted to lower the frequency of the suspension system to a level which does not interfere with frequency levels of the space structure, thereby enabling accurate measurement

An analytical study of the effect of airplane wake on the lateral dispersion of aerial sprays

Calculations are made to determine the trajectories of liquid droplets introduced into the air disturbances generated by an airplane engaged in aerial spraying. The effects of such factors as the positions at which droplets are ejected into the disturbances, airplane lift coefficient, and altitude are investigated. The distribution of deposit on the ground is computed for several droplet-size spectra, variations in the rate at which mass is ejected along the span, and lateral flight-path spacings. Consideration is then given to the problem of adjusting these factors with the aim of improving the uniformity and increasing the effective width of the deposit. The results indicate that the lateral dispersion of droplets is increased when the spanwise position at which particles are ejected is moved toward the wing tip. Greater dispersion also results when the airplane lift coefficient or altitude is increased

Suspension systems for ground testing large space structures

A research program is documented for the development of improved suspension techniques for ground vibration testing of large, flexible space structures. The suspension system must support the weight of the structure and simultaneously allow simulation of the unconstrained rigid-body movement as in the space environment. Exploratory analytical and experimental studies were conducted for suspension systems designed to provide minimum vertical, horizontal, and rotational degrees of freedom. The effects of active feedback control added to the passive system were also investigated. An experimental suspension apparatus was designed, fabricated, and tested. This test apparatus included a zero spring rate mechanism (ZSRM) designed to support a range of weights from 50 to 300 lbs and provide vertical suspension mode frequencies less than 0.1 Hz. The lateral suspension consisted of a pendulum suspended from a moving cart (linear bearing) which served to increase the effective length of the pendulum. The torsion suspension concept involved dual pendulum cables attached from above to a pivoting support (bicycle wheel). A simple test structure having variable weight and stiffness characteristics was used to simulate the vibration characteristics of a large space structure. The suspension hardware for the individual degrees of freedom was analyzed and tested separately and then combined to achieve a 3 degree of freedom suspension system. Results from the exploratory studies should provide useful guidelines for the development of future suspension systems for ground vibration testing of large space structures

Transdisciplinary Research in Practice: Lessons from Participatory, Folklore and Community-Supported Approaches in the Greater American West

Rapid social and ecological changes on global rangelands amplify the challenges to achieving biodiversity conservation, rural economic viability and social well-being, and rangeland sustainability. These dynamics create a need for transdisciplinary science that is inclusive of ecological, sociological, and participatory approaches in order to rebuild meaningful working relationships between scientists, ranchers and managers, and other rangeland stakeholders. In real application, however, transdisciplinary science faces numerous social, ethical, and logistical challenges, including the question of how the work might benefit rangeland stakeholders. Our objective is to advance rangeland researchers’ toolbox for meaningful engaged research by describing three lessons from transdisciplinary projects in the rangeland contexts of the United States. These include the need for 1) ranch-scale, long-term participatory management experiments; 2) folklore and oral history methods and 3) community-supported social-ecological research that creates credible science that can be communicated out to non-ranching decision-makers. These examples illustrate the nuances of transdisciplinary research, reciprocity, and useable knowledge creation in complex rangeland social-ecological contexts

An Analytical Treatment of Aircraft Propeller Precession Instability

An analytical investigation is made of a precession-type instability which can occur in a flexibly supported aircraft-engine-propeller combination. By means of an idealized mathematical model which is comprised of a rigid power-plant system flexibly mounted in pitch and yaw to a fixed backup structure, the conditions required for neutral stability are determined. The paper also examines the sensitivity of the stability boundaries to changes in such parameters as stiffness, damping, and asymmetries in the engine mount, propeller speed, airspeed, Mach number, propeller thrust, and location of pitch and yaw axes. Stability is found to depend strongly on the damping and stiffness in the system. With the use of nondimensional charts, theoretical stability boundaries are compared with experimental results obtained in wind-tunnel tests of an aeroelastic airplane model. In general, the theoretical results, which do not account for wing response, show the same trends as observed experimentally; however, for a given set of conditions calculated airspeeds for neutral stability are consistently lower than the measured values. Evidently, this result is due to the fact that wing response tends to add damping to the system

Algunas transferrinas no comunes en bovinos

En un "muestreo" de 3.000 bovinos de distintas razas y mestizos provenientes de la Estación Experimental Agropecuaria de Balcarce (I.N.T.A.), (años 1970-1971), fueron detectados 10 fenotipos de Transferrinas "no-comunes" en esta especie animal. Uno de los fenotipos aparece con dos bandas proteicas lentas D 2 de las cuatro normales, constituyendo un tipo anormal de acuerdo con SPOONER Y RAXTER (1969. Estos autores refieren la acción de un gene epistático recesivo que afecta al ácido siálico vinculado a las dos bandas más veloces. Otros fenotipos se expresan con bandas agregadas y desplazamientos electroforéticos sobre gel de almidón hidrolizado, no coincidentes con los fenotipos conocidos. Frente a la inusitada rareza de los fenotipos observados, se decidió confirmar el hallazgo por marcación con Fe 59, demostrándose la veracidad del descubrimiento en vacunos de nuestro país.In a sample of 3.000 bovines of different breeds and half-breeds from the Estación Experimental Agropecuaria de Balcarce, I.N T A., (years 1970-1971), were detected 10 "not-common" Transferrin phenotypes in this animal species. One of the D 2 phenotypes appears with only two élow protein bands and not the four normal bands, constituting an anormal type according with SPOONER AND BAXTER (1969). These authors refer the recessive epistatic gene action affecting the sialic acid binding to the two faster protein bands. Other phenotypes are expressed with aggregated bands and electrophoretic displacement on hydrolyzed starch gel not-coincident with the acquainted phenotypes. Because of the unusual rarity of the observed phenotypes, it was decided to confirm the finding with Fe 59 added to every serum demonstrating the veracity of the discovery in bovines of our country.Facultad de Ciencias Veterinaria