Optimal redesign study of the harm wing

The purpose of this project was to investigate the use of optimization techniques to improve the flutter margins of the HARM AGM-88A wing. The missile has four cruciform wings, located near mid-fuselage, that are actuated in pairs symmetrically and antisymmetrically to provide pitch, yaw, and roll control. The wings have a solid stainless steel forward section and a stainless steel crushed-honeycomb aft section. The wing restraint stiffness is dependent upon wing pitch amplitude and varies from a low value near neutral pitch attitude to a much higher value at off-neutral pitch attitudes, where aerodynamic loads lock out any free play in the control system. The most critical condition for flutter is the low-stiffness condition in which the wings are moved symmetrically. Although a tendency toward limit-cycle flutter is controlled in the current design by controller logic, wing redesign to improve this situation is attractive because it can be accomplished as a retrofit. In view of the exploratory nature of the study, it was decided to apply the optimization to a wing-only model, validated by comparison with results obtained by Texas Instruments (TI). Any wing designs that looked promising were to be evaluated at TI with more complicated models, including body modes. The optimization work was performed by McIntosh Structural Dynamics, Inc. (MSD) under a contract from TI

Static aeroelastic analysis and tailoring of missile control fins

A concept for enhancing the design of control fins for supersonic tactical missiles is described. The concept makes use of aeroelastic tailoring to create fin designs (for given planforms) that limit the variations in hinge moments that can occur during maneuvers involving high load factors and high angles of attack. It combines supersonic nonlinear aerodynamic load calculations with finite-element structural modeling, static and dynamic structural analysis, and optimization. The problem definition is illustrated. The fin is at least partly made up of a composite material. The layup is fixed, and the orientations of the material principal axes are allowed to vary; these are the design variables. The objective is the magnitude of the difference between the chordwise location of the center of pressure and its desired location, calculated for a given flight condition. Three types of constraints can be imposed: upper bounds on static displacements for a given set of load conditions, lower bounds on specified natural frequencies, and upper bounds on the critical flutter damping parameter at a given set of flight speeds and altitudes. The idea is to seek designs that reduce variations in hinge moments that would otherwise occur. The block diagram describes the operation of the computer program that accomplishes these tasks. There is an option for a single analysis in addition to the optimization

Perithecial development in Nectria mammoidea, Phil. et Plowr; also, the study of Nectria mammoidea, Phil. et Plowr. in culture, with an account of the factors influencing perlthecial production in the genus; and, The parasitism of Nectria cinnabarina (Tode) Fries.

The paper deals with the development of the perithecium in Nectria mammoidea. Phil, et Plowr.The cells of the vegetative hyphae are multinucleate.The perithecial initial is a knot of vegitative hyphae, and at its inception and throughout its development no trace of a structure or structures resembling archicarps can be seen.The appearance and development of structures provisionally termed "interpolated" is described and it has been found impossible to homologise them with known existing structures in the ascocarps of other As corny ce te s. These structures disintegrate prior to the appearance of the ascogenous hyphae.These latter arise de novo from the cells lining the base of the perithecial cavity. They are simple binucleate structures and are not separated by a cell wall from their parent hyphae, but are merely prolongations of the latter. Without proliferation of these hyphae or division of their two nuclei, the latter fuse to give the definite ascus nucleus.The ascus grows and is a prolongation of the parent ascogenous hypha.The definite ascus nucleus divides three times, one reduction division only taking place.The spores are formed from the ascus cytoplasm by a free cell formation.The spore nucleus divides and a wall separates the two daughter nuclei which thus each occupy a cell in the spore. The latter becomes invested by a spore wall.The grosser features of the perithecial development are described throughout the account in the sequence of their occurrence in development.Pycnidia were not found in culture but structures which may be sterile perithecia were seen on a few occasions.- - - - - - -The variation in the literature dealing with observations on the parasitism of Nectria cinnabarina (Tode) Fries, is reported in the Introduction.These variations are concerned chiefly with two points in the parasitism of this species viz:- (a) the part of the host tissue primarily attacked, and (b) the reaction of the host to attack]The case of this fungus causing a canker of apricot, and the various symptoms observed are dealt with.With a view to trying to throw some light on the reason or reasons for this symptom variability in the host, cultural studies and inoculation experiments were carried out with two strains of the fungus (1) a strain from the beech, and (2) a strain from the apricot.The two strains were found to be separable on a cultural basis, while it appeared from inoculation experiments, that the beech strain might be a more virulent parasite of the apricot than the apricot strain. The latter was shown to be the cause of a canker on the apricot.It was concluded that, as seen in the Introduction, this fungus was capable of causing a variability of symptoms in its host plant. The investigation indicated that this latter might be due to the existence of physiological strains in the species, or be the result of the varying ages of the host parts attacked.A more extensive series of inoculation experiments than that carried out during this investigation, would probably decide which of these two factors was the causative one. Both, however, may be concerned

RATIONAL EXPECTATIONS ESTIMATION OF GEORGIA SOYBEAN ACREAGE RESPONSE

The general method of moments procedure is used for estimating a soybean acreage response function assuming the producers hold rational expectations. Results indicate that soybean, corn, and wheat futures prices, lagged acreage, and government programs are significant factors for determining soybean plantings. Implications of the results are that crop acreage selection by Georgia producers is not very responsive to demand shocks. Thus, producers in other regions are more likely to absorb impacts from these shocks on crop acreage selection.Soybeans, GMM, Elasticities, Crop Production/Industries,

The Impact of Coordination of Production and Marketing Strategies on Price Behavior: Evidence from the Idaho Potato Industry

High potato price volatility, decreasing demand for fresh potatoes and prices below the cost of production led to a decision of a number of Idaho potato growers to organize the United Fresh Potato Growers of Idaho, a marketing cooperative. The programs and strategies of the cooperative target both the production and marketing of fresh potatoes in Idaho. To evaluate the effectiveness of the programs implemented by the cooperative, we examine the level and volatility of fresh potato prices during two periods: before the cooperative was organized and when the cooperative is in the market. We find empirical evidence suggesting that fresh potato prices were higher and less volatile during the period when the cooperative was in the market.agricultural markets, cooperative, price volatility, potato industry, Agricultural and Food Policy, Crop Production/Industries, Demand and Price Analysis, Marketing, Q10, Q11, Q13,

LEADING INDICATORS FOR REGIONAL COTTON RESPONSE: STRUCTURAL AND TIME SERIES MODELING RESULTS

Resurging southeastern cotton production compels better cotton acreage forecasts for planning seed, chemical, and other input requirements. Structural models describe leading acreage response indicators, and forecasts are compared time-series models. Cotton price, loan rate, deficiency payments, lagged corn acreage, the PIK program, and previous cotton yield significantly influence response.Crop Production/Industries,

Cost effective use of liquid nitrogen in cryogenic wind tunnels

A method of reliquefying from 12 to 19% of the nitrogen exhaust gas from a cryogenic wind tunnel has been developed. Technical feasibility and cost effectiveness of the system depends on performance of an innovative positive displacement expander which requires scale model testing to confirm design studies. The existing cryogenic system at the 0.3-m transonic cryogenic tunnel has been surveyed and extensive upgrades proposed. Upgrades are generally cost effective and may be implemented immediately since they are based on established technology

Cost-effective use of liquid nitrogen in cryogenic wind tunnels, phase 2

Cryogenic seal tests were performed and Rulon A was selected for the subject nutating positive displacement expander. A four-chamber expander was designed and fabricated. A nitrogen reliquefier flow system was also designed and constructed for testing the cold expander. Initial tests were unsatisfactory because of high internal friction attributed to nutating Rulon inlet and outlet valve plates. Replacement of the nutating valves with cam-actuated poppet valves improved performance. However, no net nitrogen reliquefaction was achieved due to high internal friction. Computer software was developed for accurate calculation of nitrogen reliquefaction from a system such as that proposed. These calculations indicated that practical reliquefaction rates of 15 to 19 percent could be obtained. Due to mechanical problems, the nutating expander did not demonstrate its feasibility nor that of the system. It was concluded that redesign and testing of a smaller nutating expander was required to prove concept feasibility

LEADING INDICATORS OF REGIONAL COTTON ACREAGE RESPONSE: STRUCTURAL AND TIME SERIES MODELING RESULTS

Resurgent cotton production compels better acreage forecasts for planning seed, chemical, and other input requirements. Structural models describe leading acreage response indicators, and forecasts are compared to time-series models. Cotton price, loan rate, deficiency payments, lagged corn acreage, the PIK program, and previous cotton yield significantly influence cotton acreage response.resurgent cotton production, cotton acreage, Crop Production/Industries,

Disease associated with equine coronavirus infection and high case fatality rate.

BackgroundEquine coronavirus (ECoV) is associated with clinical disease in adult horses. Outbreaks are associated with a low case fatality rate and a small number of animals with signs of encephalopathic disease are described.ObjectivesThe aim of this study is to describe the epidemiological and clinical features of two outbreaks of ECoV infection that were associated with an high case fatality rate.Animals14 miniature horses and 1 miniature donkey testing fecal positive for ECoV from two related disease outbreaks.MethodsRetrospective study describing the epidemiological findings, clinicopathological findings, and fecal viral load from affected horses.ResultsIn EcoV positive horses, 27% (4/15) of the animals died or were euthanized. Severe hyperammonemia (677 μmol/L, reference range ≤ 60 μmol/L) was identified in one animal with signs of encephalopathic disease that subsequently died. Fecal viral load (ECoV genome equivalents per gram of feces) was significantly higher in the nonsurvivors compared to animals that survived (P = .02).Conclusions and clinical importanceEquine coronavirus had a higher case fatality rate in this group of miniature horses than previously reported in other outbreaks of varying breeds. Hyperammonemia could contribute to signs of encephalopathic disease, and the fecal viral load might be of prognostic value in affected horses