Experimental evaluation of active and passive means of alleviating rotor impulsive noise in descent flight

A controlled wind tunnel test program was conducted on a model 2.14 m (7 ft) diameter teetering rotor to determine the effectiveness of blade tips such as the Ogee tip and the TAMI (Tip Air Mass Injection) tip in reducing the impulsive noise due to blade-vortex interaction in descent flight. In addition, a full rectangular tip which has the same span as the Ogee tip and an effective rectangular tip which has the same lifting area as the Ogee tip were also considered. The tests were conducted at two advance ratios (0.125 and 0.14) with various descent rates ranging from steady level flight to about 6 m/sec (20 ft/sec). A comparison of the performance of different rotors showed that for the same tip Mach number and thrust, the Ogee tip rotor absorbed more power than the full rectangular tip rotor, while the TAMI tip rotor absorbed more power than the effective tip rotor

Blade vortex interaction noise reduction techniques for a rotorcraft

An active control device for reducing blade-vortex interactions (BVI) noise generated by a rotorcraft, such as a helicopter, comprises a trailing edge flap located near the tip of each of the rotorcraft's rotor blades. The flap may be actuated in any conventional way, and is scheduled to be actuated to a deflected position during rotation of the rotor blade through predetermined regions of the rotor azimuth, and is further scheduled to be actuated to a retracted position through the remaining regions of the rotor azimuth. Through the careful azimuth-dependent deployment and retraction of the flap over the rotor disk, blade tip vortices which are the primary source for BVI noise are (a) made weaker and (b) pushed farther away from the rotor disk (that is, larger blade-vortex separation distances are achieved)

Blade vortex interaction noise reduction techniques for a rotorcraft

An active control device for reducing blade-vortex interactions (BVI) noise generated by a rotorcraft, such as a helicopter, comprises a trailing edge flap located near the tip of each of the rotorcraft's rotor blades. The flap may be actuated in any conventional way, and is scheduled to be actuated to a deflected position during rotation of the rotor blade through predetermined regions of the rotor azimuth, and is further scheduled to be actuated to a retracted position through the remaining regions of the rotor azimuth. Through the careful azimuth-dependent deployment and retraction of the flap over the rotor disk, blade tip vortices which are the primary source for BVI noise are (a) made weaker and (b) pushed farther away from the rotor disk (that is, larger blade-vortex separation distances are achieved)

Reduced In-Plane, Low Frequency Helicopter Noise of an Active Flap Rotor

Results from a recent joint DARPA/Boeing/NASA/Army wind tunnel test demonstrated the ability to reduce in-plane, low frequency noise of the full-scale Boeing-SMART rotor using active flaps. Test data reported in this paper illustrated that acoustic energy in the first six blade-passing harmonics could be reduced by up to 6 decibels at a moderate airspeed, level flight condition corresponding to advance ratio of 0.30. Reduced noise levels were attributed to selective active flap schedules that modified in-plane blade airloads on the advancing side of the rotor, in a manner, which generated counteracting acoustic pulses that partially offset the negative pressure peaks associated with in-plane, steady thickness noise. These favorable reduced-noise operating states are a strong function of the active flap actuation amplitude, frequency and phase. The associated noise reductions resulted in reduced aural detection distance by up to 18%, but incurred significant vibratory load penalties due to increased hub shear forces. Small reductions in rotor lift-to-drag ratios, of no more than 3%, were also measure

Determination of genetic variation for vegetative and floral traits in African marigold (Tagetes erecta)

Twenty-one genotypes of African marigold were (Tagetes erecta L.) evaluated for 11 growth and flowering related traits to study their genetic parameters such as variability, heritability, genetic (GCV), phenotypic (PCV) coefficient of variation and correlation and path coefficient analysis. Analysis of variance for all the traits showed significant differences among genotypes for all the growth and flowering related traits. High range in mean performance has been observed for traits, viz. plant height (64.00-106.67 cm), plant spread (49.33-72.00 cm), flower diameter (3.77- 6.17 cm), days required for flowering (78.67-99.33 days), number of secondary branches (22.13-37.47) and flower duration (26.00-44.83 days). Higher genotypic and phenotypic coefficient of variation was observed for traits such as fresh flower weight per plant, flower fresh weight per 10 flowers, number of flowers per plant, stem girth, flowering duration, etc. The high value (> 90%) of heritability was observed for all traits except plant height, plant spread and stem girth. The genetic advance was found ranged from 1.23 for flower diameter to 288.69 for fresh flower weight per plant. High values of genetic advance as per cent of mean was recorded for number of flowers (59.79%) followed by fresh flower weight per plant (59.32%) and flower fresh weight per 10 flowers (58.09%). Fresh flower weight per plant is significantly and positively correlated both at genotypic and phenotypic level for plant spread, flower fresh weight per flower, number of flowers per plant and flower diameter. Path coefficient analysis at genotypic level revealed that the number of primary branches per plant contributed highest and has significantly positive direct effect on fresh flower weight per plant followed by number of flowers per plant, flower diameter, flower fresh weight per flower, days required for flowering and stem girth. The different genotypes were identified to be performing differently for different quantitative traits. Hence, those genotypes with superior traits could be involved in the hybridization programme for assembling of desirable traits in a single genotype

Effect of shade levels on production and quality of cordyline (Cordyline terminalis)

An investigation was carried out during 2013-14 to study the effect of different shade levels on the production and quality of cordyline (Cordyline terminalis Kunth.) under the subtropical condition of New Delhi, India. The effect of spectral control of light on physiology and vegetative development was evaluated at different crop growth stages. Shade nets did not only protect plants from high light intensities but also improved the vegetative growth, yield, vase life and quality of cordyline cut greens irrespective of shade level. Different shade levels modified microclimates, PAR, transmittance and canopy temperature. The shading improved plant characters like height, number of leaves, chlorophyll content, leaf area, fresh weight, harvest index and vase life. The plants grown under different shade levels showed improved photosynthetic activity and reduced transpiration rate. Plants grown under 50% shade level were taller, along with more number of leaves having longer petiole, chlorophyll content which can be attributed to higher photosynthetic rate, whereas harvest index and vase life was optimum. Overall, shade net with 50% shading was found best for commercial production of cordyline cut greens

A comparison of clinical outcomes between vaccinated and vaccine-naive patients of COVID-19, in four tertiary care hospitals of Kerala, South India

The problem considered: This multi-centric study analyzed data of COVID-19 patients and compared differences in symptomatology, management, and outcomes between vaccinated and vaccine-naive patients. Methods: All COVID-19 positive individuals treated as an in-or out-patient from the 1stMarch to 15th May 2021 in four selected study sites were considered for the study. Treatment details, symptoms, and clinical course were obtained from hospital records. Chi-square was used to test the association of socio-demographic and treatment variables with the vaccination status and binary logistic regression were used to obtain the odds ratio with a 95% confidence interval. Results: The analysis was of 1446 patients after exclusion of 156 with missing data of which males were 57.3% and females 42.7%. 346 were vaccinated; 189 received one dose and 157 both doses. Hospitalization was more in vaccinated (38.2% vs 27.4%); ICU admissions were less in vaccinated (3.5% vs 7.1%). More vaccinated were symptomatic (OR = 1.5); half less likely to be on non-invasive ventilation (OR = 0.5) while vaccine naive patients had 4.21 times the risk of death. Conclusion: Severe infection, duration of hospital stays, need for ventilation and death were significantly less among vaccinated when compared with vaccine naive patients

High-level characteristics of or-and independent and-parallelism in prolog

Although studies of a number of parallel implementations of logic programming languages are now available, their results are difficult to interpret due to the multiplicity of factors involved, the effect of each of which is difficult to sepárate. In this paper we present the results of a high-level simulation study of or- and independent and-parallelism with a wide selection of Prolog programs that aims to determine the intrinsic amount of parallelism, independently of implementation factors, thus facilitating this separation. We expect this study will be instrumental in better understanding and comparing results from actual implementations, as shown by some examples provided in the paper. In addition, the paper examines some of the issues and tradeoffs associated with the combination of and- and or-parallelism and proposes reasonable solutions based on the simulation data obtained