Structural optimization of rotor blades with straight and swept tips subject to aeroelastic constraints

The main conclusions obtained in the present study are summarized. Their application to the structural optimization of a helicopter blade should be limited by the assumptions used in obtaining the numerical results presented here. The optimum design procedure described here is very efficient, and can produce improved designs with a very limited number of precise analyses. The method of constructing the approximate problem is such that previously conducted aeroelastic analyses can be reused in a new optimization problem. For example, if an optimization study is preceded by a parametric study in which the effect of various combinations of blade design parameters is examined, all the aeroelastic analyses performed for the parametric study can be reutilized in the optimization study. This is not possible when the approximate problem is built from Taylor series expansions. The results of the optimization are quite sensitive to the aeroelastic stability margins required of the blade. In the optimization of case 2, changing the aeroelastic stability constraints from simply requiring that the blade be stable in hover, to requiring that the stability margins be maintained during the course of the optimization, reduced the gains in n/rev vibration levels by more than 50 percent. The introduction of tip sweep can reduce the n/rev vertical hub shears beyond the level that can be obtained by just modifying the mass and stiffness distributions of the blade

The effect of different types of physical exercise on the behavioural and physiological parameters of Standardbred horses housed in single stalls

The aim of this study was to investigate the impacts of three different physical exercises on the physiological and behavioural patterns of Standardbred trotters housed in single stalls. Twelve racing mares were observed twice during each different exercise: daily training (DT) consisted of forty minutes at slow trot (4-5 m/s) in a small track; maximal exercise (ME) consisted of 1600m run at maximal velocity; race (R) was a real race of 1600 m. The mares were examined at rest in their stall (Time I), soon after the completion of the exercise (Time II), one hour (Time III), and two hours (Time IV) after the exercise.Their heart rate, respiratory rate, and rectal temperature were recorded and they were videotaped in order to complete a focal animal sampling ethogram. All physiological parameters increased after exercise, in accordance with its intensity. After R andMEhorses spentmore time drinking, eating, and standing. The incidence of abnormal behaviours was very low and it was not affected by the different types of exercise. Overall, the assessment of horse behaviour after physical exercise bymeans of a focal animal sampling ethogramrepresents a useful tool to monitor equine welfare

the influence of pregnancy and the beginning of lactation on pelage traits in cashmere goats

The aim of this study was to investigate the effect of pregnancy followed by the beginning of lactation on fibre traits incashmere goats. Two groups of cashmere-bearing goats aged between 2-3 years were used. The control group (A) included12 non-lactating, non-pregnant subjects. The experimental group (B) included 12 goats mated during the first weekof June, in order to have pregnancy and the beginning of lactation coincide with the period when cashmere normallygrows. As expected, Liveweight significantly varied in Group B during the last two months of pregnancy, when foetalgrowth reaches its maximum, and following delivery. Hair patch weight, because of the continuous growth of primary andsecondary fibres, increased significantly during the trial (P<0.001). The physiological status considered negatively affected(P<0.05) the total mean growth rate of cashmere fibres and, as a result, their length. Cashmere daily growth ratevalues varied significantly (P<0.05) throughout the experiment, while the effect of the physiological status was notedonly in November – December. Furthermore, this parameter also seems to be influenced by climatic factors and, in particular,environmental temperature, as shown by the negative correlation (r = - 0.28; P<0.05) between cashmere dailygrowth rate and environmental temperature. Guard hair length and growth rate did not differ between the two groups,however, they were influenced by time. Cashmere yield and cashmere production were lower in group B (P<0.05). Nodifferences between groups were observed for cashmere diameter. Overall, pregnancy and the consequent period of lactationnegatively influenced cashmere rather than guard hair fibres. These negative effects were noted in quantitativeterms as yield and production dropped by 37% and 43%, respectively. We hypothesise that the complete overlap of pregnancyand lactation with the period of cashmere growth reduced the number of secondary active follicles and their degreeof activity and caused an increase in competition for the partitioning of nutrients between hair follicles and the graviduterus, first, and then the mammary gland, later

Synthetic gauge fields in synthetic dimensions

We describe a simple technique for generating a cold-atom lattice pierced by a uniform magnetic field. Our method is to extend a one-dimensional optical lattice into the "dimension" provided by the internal atomic degrees of freedom, yielding a synthetic 2D lattice. Suitable laser-coupling between these internal states leads to a uniform magnetic flux within the 2D lattice. We show that this setup reproduces the main features of magnetic lattice systems, such as the fractal Hofstadter butterfly spectrum and the chiral edge states of the associated Chern insulating phases.Comment: 5+4 pages, 5+3 figures, two-column revtex; v2: discussion of role of interactions added, Fig. 1 reshaped, minor changes, references adde

Interactions between nutritional and opioidergic pathways in the control of LH secretion in male sheep

Our aim was to determine the role of opioidergic processes in the effects of nutrition on the secretion of LH pulses in the mature male sheep. In the first of three experiments, adult Merino rams were acclimatised to a maintenance diet and then allocated to one of three dietary groups (n = 5): continuation of the maintenance diet (Group M); reduction to half of the maintenance allocation (Group HM); or supplementation of the maintenance diet with lupin grain (Group HD). An initial administration of naloxone (2 mg/kg body weight, i.v.) was followed at 40-min intervals by three further administrations (1 mg/kg). Blood was sampled every 20 min for 12 h before the initial naloxone administration and then for a further 6 h. LH pulse frequency after naloxone treatment was significantly higher in Group HD than in Group HM (P < 0.05). The second study tested whether the response to naloxone depended on calcium status. We used 22 adult Merino rams in two consecutive experiments, one in which the rams were fed a maintenance diet, and one in which the rams were fed with the maintenance diet plus 1 kg lupin grain for 5 weeks. In both experiments, rams were allocated to groups that received one of the following treatments: (a) 0.02 g/kg calcium borogluconate + 0.2 mg/kg naloxone hydrochloride (Nal + Ca2+; n = 6); (b) 0.2 mg/kg naloxone hydrochloride (Nal; n = 6); (c) 0.02 g/kg calcium borogluconate (Ca2+; n = 5); (d) 0.1 ml/kg NaCl 0.9% (Saline; n = 5). All treatments were given as a single i.v. administration daily for 5 days. Blood was sampled every 20 min for 24 h during the acclimatization period (Day 0) and on the last day (Day 5) of treatment. In the first study (under maintenance), none of the treatments affected LH pulse frequency. In the second study (the lupin-supplemented rams), LH pulse frequency was significantly increased (P < 0.05) by the administration of naloxone + Ca2+, naloxone alone and Ca2+ alone. Overall, rams on a low plane of nutrition showed the smallest response to naloxone, suggesting that an opioidergic mechanism is not involved in the suppressive effect of restricted nutrition on the gonadotrophic axis. Rather, because testosterone secretion was increased on the high plane of nutrition, the LH responses to naloxone are better explained by the effects of testosterone on opioidergic mechanisms. Finally, we failed to observe any interaction between opioids and calcium in the control of LH secretion

A High-Order, Linear Time-Invariant Model for Application to Higher Harmonic Control and Flight Control System Interaction

This research describes a new methodology for the extraction of a high-order, linear time invariant model, which allows the periodicity of the helicopter response to be accurately captured. This model provides the needed level of dynamic fidelity to permit an analysis and optimization of the AFCS and HHC algorithms. The key results of this study indicate that the closed-loop HHC system has little influence on the AFCS or on the vehicle handling qualities, which indicates that the AFCS does not need modification to work with the HHC system. However, the results show that the vibration response to maneuvers must be considered during the HHC design process, and this leads to much higher required HHC loop crossover frequencies. This research also demonstrates that the transient vibration responses during maneuvers can be reduced by optimizing the closed-loop higher harmonic control algorithm using conventional control system analyses

Non-analyticity of the Callan-Symanzik beta-function of two-dimensional O(N) model

We discuss the analytic properties of the Callan-Symanzik beta-function beta(g) associated with the zero-momentum four-point coupling g in the two-dimensional phi^4 model with O(N) symmetry. Using renormalization-group arguments, we derive the asymptotic behavior of beta(g) at the fixed point g^*. We argue that beta'(g) = beta'(g^*) + O(|g-g^*|^{1/7}) for N=1 and beta'(g) = beta'(g^*) + O(1/\log |g-g^*|) for N > 2. Our claim is supported by an explicit calculation in the Ising lattice model and by a 1/N calculation for the two-dimensional phi^4 theory. We discuss how these nonanalytic corrections may give rise to a slow convergence of the perturbative expansion in powers of g.Comment: 18 pages. Discussion on Logarithmic CFT added in Appendix A. References updated. A note on the interpretation of the p_5 constant added. Final version, accepted for publication in Journal of Physics