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Williams, Hannah J., Andrew J. King, Olivier Duriez, Luca Börger e Emily L. C. Shepard. "Social eavesdropping allows for a more risky gliding strategy by thermal-soaring birds". Journal of The Royal Society Interface 15, n.º 148 (novembro de 2018): 20180578. http://dx.doi.org/10.1098/rsif.2018.0578.
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Vultures are thought to form networks in the sky, with individuals monitoring the movements of others to gain up-to-date information on resource availability. While it is recognized that social information facilitates the search for carrion, how this facilitates the search for updrafts, another critical resource, remains unknown. In theory, birds could use information on updraft availability to modulate their flight speed, increasing their airspeed when informed on updraft location. In addition, the stylized circling behaviour associated with thermal soaring is likely to provide social cues on updraft availability for any bird operating in the surrounding area. We equipped five Gyps vultures with GPS and airspeed loggers to quantify the movements of birds flying in the same airspace. Birds that were socially informed on updraft availability immediately adopted higher airspeeds on entering the inter-thermal glide; a strategy that would be risky if birds were relying on personal information alone. This was embedded within a broader pattern of a reduction in airspeed (approx. 3 m s −1 ) through the glide, likely reflecting the need for low speed to sense and turn into the next thermal. Overall, this demonstrates (i) the complexity of factors affecting speed selection over fine temporal scales and (ii) that Gyps vultures respond to social information on the occurrence of energy in the aerial environment, which may reduce uncertainty in their movement decisions.
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Mistry, Mihir, e Farhan Gandhi. "Helicopter Performance Improvement with Variable Rotor Radius and RPM". Journal of the American Helicopter Society 59, n.º 4 (1 de outubro de 2014): 17–35. http://dx.doi.org/10.4050/jahs.59.042010.
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This paper examines rotor power reductions achievable through a combination of radius and RPM variation. The study is based on a utility helicopter similar to the UH-60A and considers +17% to –16% variation in radius and ±11% variation in RPM about the baseline, over a range of airspeed, gross weight, and altitude. Results show that decreasing RPM alone effectively reduced power at cruise velocities in low-and-light conditions, but the power reductions diminished at increasing altitude and/or gross weight, and in low-speed flight. Increasing radius alone, on the other hand, had greatest effectiveness in power reduction in high-and-heavy operating conditions and at lower flight speeds. When radius and RPM variation is used in combination, minimum RPM is always favored, along with radius increases at increasing altitude and gross weight, and in low-speed operation. At low-to-moderate gross weight, the significant power reductions seen in cruise and at low altitude with RPM variation alone are obtained even at higher altitude, and over the airspeed range, using radius and RPM variation in combination. In high-and-heavy conditions, the combination of RPM reduction and radius increase yields very large power reductions of over 20% and up to 30% over the baseline. Power reduction in low-and-light conditions comes almost entirely from profile power reduction due to RPM decrease. In cruise and high-speed flight, the profile power reductions progressively give way to induced power reductions at increasing gross weight and altitude. At low speeds, reduction in induced power due to increased radius and decreased disk loading dominates.
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Vieira, Bruno C., Guilherme S. Alves, Fernando K. Carvalho, João Paulo AR Da Cunha, Ulisses R. Antuniassi e Greg R. Kruger. "Influence of Airspeed and Adjuvants on Droplet Size Distribution in Aerial Applications of Glyphosate". Applied Engineering in Agriculture 34, n.º 3 (2018): 507–13. http://dx.doi.org/10.13031/aea.12587.
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Abstract. Drift is one of the most hazardous consequences of an improper aerial application of glyphosate. Wind, droplet size, application height, and distance to sensitive areas are the most important factors for drift. Droplet size is affected by nozzle, operating pressure, flight speed, deflection angle, and physicochemical properties of the spray solution. The objective of this study was to evaluate the effect of flight speed and the use of adjuvants on droplet size spectra in aerial applications of glyphosate. The study was conducted in a high-speed wind tunnel at the Pesticide Application Technology Laboratory (University of Nebraska-Lincoln, West Central Research and Extension Center, North Platte, Neb.). Aerial applications were simulated with four different airspeeds (44.4, 52.8, 61.1, and 69.4 m/s) and glyphosate combined with adjuvants (high surfactant oil concentrate, microemulsion drift reduction agent, nonionic and acidifier surfactant, polyvinyl polymer, and glyphosate alone). Droplet size spectra were evaluated using a Sympatec Helos laser diffraction instrument measuring 90 cm from the nozzle tip (CP11-4015). The volumetric droplet size distribution parameters (VMD, DV0.1, and DV0.9) and the percentage of droplets smaller than 100 µm were reported. The relative span was calculated to indicate the droplet size homogeneity [(DV0.9 - DV0.1) / DV0.5]. Glyphosate solutions with adjuvants had a larger VMD than the glyphosate alone solution at 44.4 m/s wind speed. At 69.4 m/s only the glyphosate solution with polymer had a larger VMD. Conversely, the glyphosate with polymer had the smallest DV0.1, and the greatest relative span and percentage of droplets smaller than 100 µm. Generally, adjuvants influence on droplet size was diminished or muted as the airspeed was increased. The polymer tested in this study failed as a drift agent reduction agent, especially at higher airspeeds. While not all polymers were tested, cautions should be taken if using these types of adjuvants in aerial applications. The interaction of airspeed and adjuvants influencing droplet size distribution in aerial applications of glyphosate should be considered by applicators in order to mitigate glyphosate drift to the surrounding environment. Further studies are necessary to better understand the interaction between solution viscosity and air shear effect on the atomization process and droplet size distribution, as well as confirm that trends hold true for other adjuvants in the polymer class. Although applicators tend to operate aircrafts with increased flight speeds in order to optimize the application time efficiency, this practice can reduce or mute adjuvants effects, decrease the droplet size distribution, and increase drift potential in aerial applications of glyphosate. Keywords: Drift reduction technologies, Flight speed, High-speed wind tunnel, Laser diffraction.
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Xue, Dabin, Kam K. H. Ng e Li-Ta Hsu. "Multi-Objective Flight Altitude Decision Considering Contrails, Fuel Consumption and Flight Time". Sustainability 12, n.º 15 (3 de agosto de 2020): 6253. http://dx.doi.org/10.3390/su12156253.
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The rapid growth of air travel and aviation emissions in recent years has contributed to an increase in climate impact. Contrails have been considered one of the main factors of the aviation-induced climate impact. This paper deals with the formation of persistent contrails and its relationship with fuel consumption and flight time when flight altitude and true airspeed vary. Detailed contrail formation conditions pertaining to altitude, relative humidity and temperature are formulated according to the Schmidt–Appleman criterion. Building on the contrail formation model, the proposed model would minimise total travel time, fuel consumption and contrail length associated with a given flight. Empirical data (including pressure, temperature, relative humidity, etc.) collected from seven flight information regions in Chinese observation stations were used to analyse the spatial and temporal distributions of the persistent contrail formation area. The trade-off between flight time, fuel consumption and contrail length are illustrated with a real-world case. The results provided a valuable benchmark for flight route planning with environmental, flight time, sustainable flight trajectory planning and fuel consumption considerations, and showed significant contrail length reduction through an optimal selection of altitude and true airspeed.
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Liu, Yishu, Wei Gao, Qifu Li e Bei Lu. "Oblique Projection-Based Modal Matching Algorithm for LPV Model Order Reduction of Aeroservoelastic Systems". Aerospace 10, n.º 5 (26 de abril de 2023): 406. http://dx.doi.org/10.3390/aerospace10050406.
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An aeroservoelastic system can be described as a gridding-based linear parameter-varying (LPV) model, whose dynamic characteristics usually vary with the airspeed. Due to the high order of the system, it is necessary to perform order reduction on LPV models to overcome the control design challenges. However, when directly extending linear time-invariant (LTI) model order reduction technologies to the LPV system, states of the reduced-order LTI models generated separately at different grid points could be inconsistent. In this paper, a novel modal matching algorithm is proposed to solve the problem of state inconsistency by identifying the internal connection between the models at adjacent grid points. An oblique projection-based distance metric is defined to improve the reliability of the modal matching algorithm. The reduced-order LPV model constructed based on this method would have a high fidelity relative to the original model and a smooth interpolation performance between grid points. The proposed algorithm is applied to the X-56A aircraft, and numerical results show its effectiveness.
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Hospodář, Pavel, Jan Klesa e Nikola Žižkovský. "Design of distributed propulsion system for general aviation airplane". MATEC Web of Conferences 304 (2019): 03009. http://dx.doi.org/10.1051/matecconf/201930403009.
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In this paper, a small airplane is redesigned by using a distributed electrical propulsion (DEP) system. The design procedure is focused on the reduction of fuel consumption in cruise regime with constrained parameters of take-off/landing. In this case, a one half wing area compared to an original airplane is used. Take-off distance and minimum airspeed for landing is achieved by distributed propellers mounted on the leading edge of the wing. These propellers induce velocity on the wing and thereby increase local dynamic pressure, thus the required lift force can be reached with smaller wing area. Moreover, the distributed propellers are assumed as folded in cruise regime to minimize drag when the main combustion engine provides sufficient power.
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Cecen, R. K., e F. Aybek Çetek. "Optimising aircraft arrivals in terminal airspace by mixed integer linear programming model". Aeronautical Journal 124, n.º 1278 (21 de fevereiro de 2020): 1129–45. http://dx.doi.org/10.1017/aer.2020.15.
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ABSTRACTAir traffic flow becomes denser and more complex within terminal manoeuvering areas (TMAs) due to rapid growth rates in demand. Effective TMA arrival management plays a key role in the improvement of airspace capacity, flight efficiency and air traffic controller performance. This study proposes a mixed integer linear programming model for aircraft landing problems with area navigation (RNAV) route structure using three conflict resolution and sequencing techniques together: flexible route allocation, airspeed reduction and vector manoeuver. A two-step mixed integer linear programming model was developed that minimises total conflict resolution time and then total airborne delay using lexicographic goal programming. Experimental results demonstrate that the model can obtain conflict-free and time optimal aircraft trajectories for RNAV route structures.
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Abdel-Baky, Mostafa Ahmed, EL-Desoki Ibrahim Eaid, Ibrahim Ahmed El-Khaldy e A. Farghal Tawfic. "Investigation of natural ventilation using a solar chimney in various solar cases". International Journal of Innovative Research and Scientific Studies 7, n.º 2 (9 de fevereiro de 2024): 587–606. http://dx.doi.org/10.53894/ijirss.v7i2.2699.
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The high cost of conventional energy production, its uses, and its negative environmental impact led scientists to look for many ways to solve this problem. The main issues are environmental pollution, the high cost of air treatment, and the high cost of energy production. An essential solution is using renewable energy instead of traditional energy (petroleum, coal, natural gas, and electric power). As it is a permanent energy source, it causes no air pollution and is cheaper. In this work, an experimental study was conducted on using solar energy as an energy source in the natural ventilation of buildings and the factors affecting this ventilation. A solar chimney has been installed with and without storage materials to store energy for natural identity during sunrise and after sunset. In this work, the difference in air density with different temperatures is the main factor for energy production, which leads to a change in the airspeed (natural ventilation). The study indicates that indoor air velocity can remain higher than ambient air velocity during the day and at night for several hours. This reduces demand and dependence on conventional energy usage, which leads to cost reductions and a reduction in air and environmental pollution.
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Reynolds, Kate V., Adrian L. R. Thomas e Graham K. Taylor. "Wing tucks are a response to atmospheric turbulence in the soaring flight of the steppe eagle Aquila nipalensis". Journal of The Royal Society Interface 11, n.º 101 (6 de dezembro de 2014): 20140645. http://dx.doi.org/10.1098/rsif.2014.0645.
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Turbulent atmospheric conditions represent a challenge to stable flight in soaring birds, which are often seen to drop their wings in a transient motion that we call a tuck. Here, we investigate the mechanics, occurrence and causation of wing tucking in a captive steppe eagle Aquila nipalensis , using ground-based video and onboard inertial instrumentation. Statistical analysis of 2594 tucks, identified automatically from 45 flights, reveals that wing tucks occur more frequently under conditions of higher atmospheric turbulence. Furthermore, wing tucks are usually preceded by transient increases in airspeed, load factor and pitch rate, consistent with the bird encountering a headwind gust. The tuck itself immediately follows a rapid drop in angle of attack, caused by a downdraft or nose-down pitch motion, which produces a rapid drop in load factor. Positive aerodynamic loading acts to elevate the wings, and the resulting aerodynamic moment must therefore be balanced in soaring by an opposing musculoskeletal moment. Wing tucking presumably occurs when the reduction in the aerodynamic moment caused by a drop in load factor is not met by an equivalent reduction in the applied musculoskeletal moment. We conclude that wing tucks represent a gust response precipitated by a transient drop in aerodynamic loading.
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Shi, Benjing, Junying Wan, Tiejun Chen, Xianlin Zhou, Yanhong Luo, Jiawen Liu, Mengjie Hu e Zhaocai Wang. "Study on Double-Layer Ignition Sintering Process Based on Autocatalytic Denitrification of Sintering Layer". Minerals 12, n.º 1 (25 de dezembro de 2021): 33. http://dx.doi.org/10.3390/min12010033.
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An efficient sintering process was proposed based on the autocatalytic denitrification of the sintered ore. The catalytic denitrification of sintered ore, the effect of double-layer ignition sintering process on the emission reduction in nitrogen oxides, and the impact on the quality of sintered ore were studied. The results showed that the catalyzed reduction of NO with sinter ore as a catalyst has a significant effect; when the airspeed reaches 3000 h−1, the temperature is 500 °C, and the conversion rate of NO can reach 99.58%. The sinter yield of double-layer ignition sintering is increased, solid fuel consumption is slightly reduced, falling strength is slightly increased, and drum strength is slightly decreased. Under the conditions of layer height proportion of 320/400 mm (lower/upper) and ignition time interval of 10 min, the yield, drum strength, shatter strength, and solid fuel consumption reached 61.60%, 54.82%, 46.75%, and 69.55%, respectively. NOx concentration under the 16% baseline oxygen content (c(NOx)’) in the flue gas of double-layer ignition sintering is reduced to a certain extent, and the generation time of NOx is greatly shortened. The double-layer ignition sintering process can reduce the emission of nitrogen oxides in the sintering process under the condition of guaranteeing the quality of sinter, which has great economic and environmental benefits.
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McRae, Mary, Ross A. Lee, Scott Steinschneider e Frank Galgano. "Assessing Aircraft Performance in a Warming Climate". Weather, Climate, and Society 13, n.º 1 (janeiro de 2021): 39–55. http://dx.doi.org/10.1175/wcas-d-20-0098.1.
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AbstractIncreases in maximum and minimum air temperatures resulting from anthropogenic climate change will present challenges to aircraft performance. Elevated density altitude (DA) reduces aircraft and engine performance and has a direct impact on operational capabilities. The frequency of higher DA will increase with the combination of higher air temperatures and higher dewpoint temperatures. The inclusion of dewpoint temperature in DA projections will become increasingly critical as minimum air temperatures rise. High DA impacts aircraft performance in the following ways: reduction in power because the engine takes in less air; reduction in thrust because a propeller is less efficient in less dense air; reduction in lift because less dense air exerts less force on the airfoils. For fixed-wing aircraft, the performance impacts include decreased maximum takeoff weight and increased true airspeed, which results in longer takeoff and landing distance. For rotary-wing aircraft, the performance impacts include reduced power margin, reduced maximum gross weight, reduced hover ceiling, and reduced rate of climb. In this research, downscaled and bias-corrected maximum and minimum air temperatures for future time periods are collected and analyzed for a selected site: Little Rock Air Force Base, Arkansas. Impacts corresponding to DA thresholds are identified and integrated into risk probability matrices enabling quantifiable comparisons. As the magnitude and frequency of high DA occurrences are projected to increase as a result of climate change, it is imperative for military mission planners and acquisition officers to comprehend and utilize these projections in their decision-making processes.
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de Haan, Siebren, Paul M. A. de Jong e Jitze van der Meulen. "Characterizing and correcting the warm bias observed in Aircraft Meteorological Data Relay (AMDAR) temperature observations". Atmospheric Measurement Techniques 15, n.º 3 (15 de fevereiro de 2022): 811–18. http://dx.doi.org/10.5194/amt-15-811-2022.
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Abstract. Some aircraft temperature observations, retrieved through the Aircraft Meteorological Data Relay (AMDAR), suffer from a significant warm bias when comparing observations with numerical weather prediction (NWP) models. In this paper we show that this warm bias of AMDAR temperature can be characterized and consequently reduced substantially. The characterization of this warm bias is based on the methodology of measuring temperature with a moving sensor and can be split into two separate processes. The first process depends on the flight phase of the aircraft and relates to difference of timing, as it appears that the times of measurement of altitude and temperature differ. When an aircraft is ascending or descending, this will result in a small bias in temperature due to the (on average) presence of an atmospheric temperature lapse rate. The second process is related to internal corrections applied to pressure altitude without feedback to temperature observation measurement. Based on NWP model temperature data, combined with additional information on Mach number and true airspeed, we were able to estimate corrections using data over an 18-month period from January 2017 to July 2018. Next, the corrections were applied to AMDAR observations over the period from September 2018 to mid-December 2019. Comparing these corrected temperatures with (independent) radiosonde temperature observations demonstrates a reduction of the temperature bias from 0.5 K to around zero and a reduction of standard deviation of almost 10 %.
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Chen, Jung-Shun, Shou-Yen Chao e Ching-Che Chen. "The Effect of Hydrophilic Surface Coating of Fins on the Performance of Fin-and-Tube Heat Exchangers". Applied Sciences 13, n.º 18 (19 de setembro de 2023): 10450. http://dx.doi.org/10.3390/app131810450.
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With the rapid progress in data mining, deep learning, and artificial intelligence, the demand for datacenters of various sizes increases globally. Datacenters typically require an environment with properly controlled temperature and humidity conditions for their proper operations. These needed environmental conditions are always provided by an air conditioning system. In humid and hot regions, both energy consumption and the splash of water condensate in using the fin-and-tube heat exchangers are of concern because reliability issues can occur. In this study, the effects of fin surface hydrophilic/hydrophobic coatings on the performance of the fin-and-tube heat exchangers, including the heat transfer rate, pressure drop, and water-condensate splash, were investigated experimentally. By varying the cooling air speeds and fin pitches, the results show that hydrophilic surface coating is an effective method in reducing both the pressure drop (thus saving energy) and the condensate splash, while not affecting the heat transfer rates significantly. The water splash reduction is achieved by both the increased air speed for splashing and a smaller amount of splashing. Water splash can even be completely eliminated if the airspeed was below about 3 m/s. In contrast, hydrophobic surface coating will increase both pressure drop and water splash; thus, should be applied with caution.
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Balzano, Fabio, Mario L. Fravolini, Marcello R. Napolitano, Stéphane d’Urso, Michele Crispoltoni e Giuseppe del Core. "Air Data Sensor Fault Detection with an Augmented Floating Limiter". International Journal of Aerospace Engineering 2018 (25 de novembro de 2018): 1–16. http://dx.doi.org/10.1155/2018/1072056.
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Although very uncommon, the sequential failures of all aircraft Pitot tubes, with the consequent loss of signals for all the dynamic parameters from the Air Data System, have been found to be the cause of a number of catastrophic accidents in aviation history. This paper proposes a robust data-driven method to detect faulty measurements of aircraft airspeed, angle of attack, and angle of sideslip. This approach first consists in the appropriate selection of suitable sets of model regressors to be used as inputs of neural network-based estimators to be used online for failure detection. The setup of the proposed fault detection method is based on the statistical analysis of the residual signals in fault-free conditions, which, in turn, allows the tuning of a pair of floating limiter detectors that act as time-varying fault detection thresholds with the objective of reducing both the false alarm rate and the detection delay. The proposed approach has been validated using real flight data by injecting artificial ramp and hard failures on the above sensors. The results confirm the capabilities of the proposed scheme showing accurate detection with a desirable low level of false alarm when compared with an equivalent scheme with conventional “a priori set” fixed detection thresholds. The achieved performance improvement consists mainly in a substantial reduction of the detection time while keeping desirable low false alarm rates.
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Phillippi, R. M., e T. M. Drzewiecki. "Elimination of Drift and Asymmetry Effects in Fluidic Sensors by Feedback". Journal of Dynamic Systems, Measurement, and Control 107, n.º 1 (1 de março de 1985): 86–92. http://dx.doi.org/10.1115/1.3140712.
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This paper presents a feedback approach to the design of fluidic sensor circuits that will minimize drift and other unwanted offset effects, that are due to component asymmetries, and at the same time will improve the overall sensor frequency response. In this approach sensor supply pressure is generated by one output of a high gain differential regulator amplifier rather than by the raw system supply pressure. As a result, variations in system pressure, that normally would appear as sensor output drift (time varying null offset), are decoupled from the sensor. The amount of effort required to keep the sensor nulled becomes the sensor system output. When this feedback is implemented the overall dynamic response can be improved by a reduction in the fundamental circuit time constant, that is governed by the sensor dynamics, by introducing phase lead and so reducing the low frequency phase shift. Since the error signal driving the high gain regulator is proportional to the degree of sensor asymmetry, output performance of the feedback system is actually enhanced by having significant null offset characteristics. The offsets generally found in photochemically etched amplifiers and laminar jet angular rate sensors are shown to be reduced by two orders of magnitude and frequency response improved by as much as a factor of five. This technique has been applied to rate sensors, resistance bridges, pressure regulators, and airspeed sensors.
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Mezaien, Ahmed Abdullah, e Juan-Carlos Baltazar. "Potential Regenerative Impact of Implementation of Cultural Vernacular Elements (Rowshan) in Jeddah, Saudi Arabia". Energies 17, n.º 9 (23 de abril de 2024): 1995. http://dx.doi.org/10.3390/en17091995.
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The present study aims to explore rowshans as essential vernacular architectural elements in designing houses in very hot-dry climates such as Jeddah, Saudi Arabia, to determine their most significant effects on air movement, ventilation, and mitigating cooling loads. A comprehensive combination of building performance simulation and computational fluid dynamics (CFD) analysis was used to model a room with six different sizes of rectangular openings and quantify rowshans’ potential as passive elements in providing occupants with comfort and reducing energy use. Analysis of the passive element revealed the thermal performance and natural ventilation in single-family homes for the Jeddah climate, created by outdoor and indoor temperature, airspeed, and pressure differences in the room model, were improved, lowering sensation temperature for inhabitants’ comfort. The results highlight the beneficial effects of rowshans in lowering a house’s temperature during the daytime: from November to April, at noon, indoor air temperature (IAT) could reach a 15% to 22% reduction in the north orientation. The findings also show that rowshans with 5 × 5 cm opening grids can keep the air volume flow rate within an acceptable range and keep the room in the comfort zone range for 42.3% of hours annually, equal to 3704 h. An implication of these results is the possibility of establishing housing design criteria that can enhance efficiency and thermal comfort conditions, lower the cost of operations, provide occupants with satisfaction, and reduce emissions to regenerate the environment, leading to affordability and sustainability in the Jeddah region.
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Gandhi, F., C. Duling e F. Straub. "On power and actuation requirement in swashplateless primary control of helicopters using trailing-edge flaps". Aeronautical Journal 118, n.º 1203 (maio de 2014): 503–21. http://dx.doi.org/10.1017/s0001924000009337.
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Abstract This paper examines three specific aspects pertaining to the trailing-edge flap (TEF) enabled swashplateless primary control of a helicopter. The study is based on a utility helicopter very similar to the UH-60A Blackhawk helicopter, with rotor torsion frequency reduced to 2·1/rev, and 20% chord TEFs extending from 70-90% span. The questions addressed in the paper are the power penalty due to aerodynamic drag associated with TEF control, the pitch-index required to limit the range of TEF deflections over variations in aircraft gross-weight and airspeed, and the influence of rotor RPM variation on swashplateless primary control. Results indicate that the power penalty associated with TEF enabled primary control at high speeds is in the range of 6-7%, due to increased drag on the advancing side in the region of the TEFs and at the blade tips. At low to moderate speeds the increase in power is 2-4% on average, more dependent on the pitch-index, and due to drag increase over most of the azimuth in the region of the TEFs. A variation in pitch-index from 16° for lower speeds and gross weights, to 20-22° for higher speeds and gross weights, would reduce the steady level flight TEF defection requirements to under ±3°, leaving sufficient control margin. Increase in rotor RPM does not increase directly increase thrust (as with a stiff-torsion rotor) but reduces the rotating torsion frequency, and together with the increased dynamic pressures increases the sensitivity to TEF control. At low to moderate speeds a 9% increase in RPM reduces the maximum TEF deflections required by about 1°, but is accompanied by a large increase in rotor power. Conversely, a 9% RPM reduction decreases rotor power required, but the TEF defections required increase by 1–1·5°.
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Guo, Yixiang, Lifang Chen, Yuda Long e Xu Zhang. "Digital Simulation of Coupled Dynamic Characteristics of Open Rotor and Dynamic Balancing Test Research". Machines 12, n.º 6 (5 de junho de 2024): 391. http://dx.doi.org/10.3390/machines12060391.
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An aero engine, as the core power equipment of the aircraft, enables safe and stable operation with a very high reliability index, and is an important guarantee in flight. The open rotor turbine engines (contra-rotating propeller) have stood out as a research hotspot for aviation power equipment in recent years due to their outstanding advantages of low fuel consumption, high airspeed, and strong propulsion efficiency. Aiming at the problems of vibration exceeding the standard generated by imbalance during the operation of the dual-rotor system of aircraft development, the difficulty of identifying the coupled vibration under the micro-differential speed condition, and the complexity of the dynamic characteristic law, a kind of numerical simulation of the dynamics based on the finite element technology is proposed, together with an experimental research method for the fast and accurate identification of the coupled vibration of the dual-rotor system. Based on the existing open rotor engine structure design to build a simulation test bed, establish a double rotor finite element simulation digital twin model, and analyze and calculate the typical working conditions of the dynamic characteristics of parameters. The advanced algorithm of double rotor coupling vibration signal identification is utilized to carry out decoupling and dynamic balancing experimental tests, comparing the simulation results with the measured data to verify the accuracy of the technical means. The results of the study show that the vibration suppression rate of the finite element calculation simulation test carried out for the simulated double rotor is 98%, and the average vibration reduction ratio of the actual field test at 850 rpm, 1000 rpm, and 3000 rpm is over 50%, which achieves a good dynamic balancing effect, and has the merit of practical engineering application.
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Haposan Misaelman Sinaga e Wawan Aries Widodo. "Studi Pemodelan Numerik Penempatan Shark Fin Vortex Generator dengan Susunan Sebaris Pada Dindong Kiri dan Kanan Bus Penumpang". EduInovasi: Journal of Basic Educational Studies 4, n.º 2 (28 de julho de 2024): 1383–410. http://dx.doi.org/10.47467/edu.v4i2.4321.
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This study analyzes the impact of installing Shark Fin Vortex Generators (SFVG) in a row arrangement on the left and right sides of a passenger bus on the vehicle’s aerodynamic performance. A numerical modeling approach was used to visualize the airflow around the bus and measure key parameters such as drag coefficient (CD), lift coefficient (CL), and pressure coefficient (CP) distribution. Air velocity contour analysis shows that SFVG significantly optimizes airflow around the bus. The bus with SFVG achieved a higher airspeed of 50.23 km/h, while the bus without SFVG only reached 49.83 km/h, indicating a significant reduction in aerodynamic drag. Drag coefficient (CD) analysis shows that the bus with SFVG has a lower CD value of 0.63794782 compared to the bus without SFVG, which has an average value of around 0.70191103. Although the difference is small, it indicates that SFVG has the potential to reduce aerodynamic drag. A difference in lift coefficient (CL) values between the bus with SFVG (around 0.040190537) and the bus without SFVG (around 0.05368355) was also observed, suggesting that SFVG affects the lift force distribution on the bus. Pressure distribution analysis shows that SFVG alters the pressure distribution around the bus. Pressure contours on the bus with SFVG show concentrated pressure at the front of the bus with a peak pressure of about 213.22 Pa, whereas the bus without SFVG shows a higher peak pressure, reaching 465.17 Pa at the same location. This study also evaluates the potential of SFVG to reduce fuel consumption and the environmental impact of public transportation through reduced drag forces. The analysis results indicate that SFVG has the potential to improve energy efficiency and overall aerodynamic performance of the bus. Further research is needed to fully understand the impact of using SFVG in this context.
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Lobitz, Don W. "Parameter Sensitivities Affecting the Flutter Speed of a MW-Sized Blade". Journal of Solar Energy Engineering 127, n.º 4 (12 de julho de 2005): 538–43. http://dx.doi.org/10.1115/1.2037091.
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With the current trend toward larger and larger horizontal axis wind turbines, classical flutter is becoming a more critical issue. Recent studies have indicated that for a single blade turning in still air the flutter speed for a modern 35 m blade occurs at approximately twice its operating speed (2 per rev), whereas for smaller blades (5–9 m), both modern and early designs, the flutter speeds are in the range of 3.5–6 per rev. Scaling studies demonstrate that the per rev flutter speed should not change with scale. Thus, design requirements that change with increasing blade size are producing the concurrent reduction in per rev flutter speeds. In comparison with an early small blade design (5 m blade), flutter computations indicate that the non rotating modes which combine to create the flutter mode change as the blade becomes larger (i.e., for the larger blade the second flapwise mode, as opposed to the first flapwise mode for the smaller blade, combines with the first torsional mode to produce the flutter mode). For the more modern smaller blade design (9 m blade), results show that the non rotating modes that couple are similar to those of the larger blade. For the wings of fixed-wing aircraft, it is common knowledge that judicious selection of certain design parameters can increase the airspeed associated with the onset of flutter. Two parameters, the chordwise location of the center of mass and the ratio of the flapwise natural frequency to the torsional natural frequency, are especially significant. In this paper studies are performed to determine the sensitivity of the per rev flutter speed to these parameters for a 35 m wind turbine blade. Additional studies are performed to determine which structural characteristics of the blade are most significant in explaining the previously mentioned per rev flutter speed differences. As a point of interest, flutter results are also reported for two recently designed 9 m twist/coupled blades.
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Cooper, W. A., S. M. Spuler, M. Spowart, D. H. Lenschow e R. B. Friesen. "Calibrating airborne measurements of airspeed, pressure and temperature using a Doppler laser air-motion sensor". Atmospheric Measurement Techniques 7, n.º 9 (30 de setembro de 2014): 3215–31. http://dx.doi.org/10.5194/amt-7-3215-2014.
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Abstract. A new laser air-motion sensor measures the true airspeed with a standard uncertainty of less than 0.1 m s−1 and so reduces uncertainty in the measured component of the relative wind along the longitudinal axis of the aircraft to about the same level. The calculated pressure expected from that airspeed at the inlet of a pitot tube then provides a basis for calibrating the measurements of dynamic and static pressure, reducing standard uncertainty in those measurements to less than 0.3 hPa and the precision applicable to steady flight conditions to about 0.1 hPa. These improved measurements of pressure, combined with high-resolution measurements of geometric altitude from the global positioning system, then indicate (via integrations of the hydrostatic equation during climbs and descents) that the offset and uncertainty in temperature measurement for one research aircraft are +0.3 ± 0.3 °C. For airspeed, pressure and temperature, these are significant reductions in uncertainty vs. those obtained from calibrations using standard techniques. Finally, it is shown that although the initial calibration of the measured static and dynamic pressures requires a measured temperature, once calibrated these measured pressures and the measurement of airspeed from the new laser air-motion sensor provide a measurement of temperature that does not depend on any other temperature sensor.
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Sane, Sanjay P., Robert B. Srygley e Robert Dudley. "Antennal regulation of migratory flight in the neotropical moth Urania fulgens". Biology Letters 6, n.º 3 (24 de janeiro de 2010): 406–9. http://dx.doi.org/10.1098/rsbl.2009.1073.
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Migrating insects use their sensory systems to acquire local and global cues about their surroundings. Previous research on tethered insects suggests that, in addition to vision and cephalic bristles, insects use antennal mechanosensory feedback to maintain their airspeeds. Owing to the large displacements of migratory insects and difficulties inherent in tracking single individuals, the roles of these sensory inputs have never been tested in freely migrating insects. We tracked individual uraniid moths ( Urania fulgens ) as they migrated diurnally over the Panama Canal, and measured airspeeds and orientation for individuals with either intact or amputated flagella. Consistent with prior observations that antennal input is necessary for flight control, 59 per cent of the experimental moths could not fly after flagella amputation. The remaining fraction (41%) was flight-capable and maintained its prior airspeeds despite severe reduction in antennal input. Thus, maintenance of airspeeds may not involve antennal input alone, and is probably mediated by other modalities. Moths with amputated flagella could not recover their proper migratory orientations, suggesting that antennal integrity is necessary for long-distance navigation.
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Cooper, W. A., S. M. Spuler, M. Spowart, D. H. Lenschow e R. B. Friesen. "Calibrating airborne measurements of airspeed, pressure and temperature using a Doppler laser air-motion sensor". Atmospheric Measurement Techniques Discussions 7, n.º 3 (14 de março de 2014): 2585–630. http://dx.doi.org/10.5194/amtd-7-2585-2014.
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Abstract. A new laser air-motion sensor measures the true airspeed with an uncertainty of less than 0.1 m s−1 (standard error) and so reduces uncertainty in the measured component of the relative wind along the longitudinal axis of the aircraft to about the same level. The calculated pressure expected from that airspeed at the inlet of a pitot tube then provides a basis for calibrating the measurements of dynamic and static pressure, reducing standard-error uncertainty in those measurements to less than 0.3 hPa and the precision applicable to steady flight conditions to about 0.1 hPa. These improved measurements of pressure, combined with high-resolution measurements of geometric altitude from the Global Positioning System, then indicate (via integrations of the hydrostatic equation during climbs and descents) that the offset and uncertainty in temperature measurement for one research aircraft are +0.3 ± 0.3 °C. For airspeed, pressure and temperature these are significant reductions in uncertainty vs. those obtained from calibrations using standard techniques. Finally, it is shown that the new laser air-motion sensor, combined with parametrized fits to correction factors for the measured dynamic and ambient pressure, provides a measurement of temperature that is independent of any other temperature sensor.
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Olsman, W. F. J. "Experimental Investigation of Fenestron Noise". Journal of the American Helicopter Society, 2022. http://dx.doi.org/10.4050/jahs.67.032002.
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The noise radiation of an EC135 Fenestron is investigated by means of flight tests. The noise emission was measured with ground microphones during several different maneuvers. These include hover, rearward flight, and forward flight at different combinations of the side slip angle and the airspeed. In hover, a high level of broadband noise is observed. A comparison with available engine noise data suggested that engine noise is not dominant in hover. In rearward flight, the Fenestron may encounter a relatively clean aerodynamic inflow. However, the measurements do not indicate a reduction in noise radiation of the Fenestron. For rearward flight, a significant increase in main rotor noise is observed. Flights at different combinations of the side slip angle and airspeed show that the Fenestron radiates high levels of tonal noise at high-speed flight at negative side slip. The most likely cause for this is a highly disturbed inflow caused by flow separations of the diffusor outlet edge and the sharp trailing edges of the stator blades. Measurements of the tail boom yaw moment and Fenestron drive shaft torque imply that a reverse flow is possible at medium airspeed, while the Fenestron thrust does not reverse sign. Only at higher airspeeds and negative side slip, it is possible to achieve a thrust reversal in addition to a flow reversal.
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Henry, C. Ezedinma, T. Nwabanne Jospeh, E. Onu Chijioke e O. Nwajinka Charles. "Optimum Process Parameters and Thermal Properties of Moisture Content Reduction in Water Yam Drying". Asian Journal of Chemical Sciences, 30 de abril de 2021, 44–54. http://dx.doi.org/10.9734/ajocs/2021/v9i419080.
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The determination of optimum process parameters for moisture content reduction in water yam drying using a hot air dryer was the aim of this work. Gravimetric method was used to determine the moisture content. Design of experiment was used with slice thickness, airspeed and temperature as the independent factors. Thermal properties such as effective moisture diffusivity and activation energy were determined. The result showed that slice thickness, airspeed and temperature have significant influence on the moisture content reduction. The effective moisture diffusivity ranged from 2.84 x 10-5 m2/s to 8.10 x 10-5 m2/s. The activation energy was 30.592kJ/mol. Minimum moisture content value of 11.98% was obtained at slice thickness of 2mm, airspeed of 2 m/s and temperature of 70oC. The quadratic model best described the drying process. The hot air dryer can conveniently be used for moisture content reduction in water yam slices which will increase its shelf life.
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Rader, Jonathan A., e Tyson L. Hedrick. "Turkey vultures tune their airspeed to changing air density". Journal of Experimental Biology 227, n.º 15 (1 de agosto de 2024). http://dx.doi.org/10.1242/jeb.246828.
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ABSTRACT Animals must tune their physical performance to changing environmental conditions, and the breadth of environmental tolerance may contribute to delineating the geographic range of a species. A common environmental challenge that flying animals face is the reduction of air density at high elevation and the reduction in the effectiveness of lift production that accompanies it. As a species, turkey vultures (Cathartes aura) inhabit a >3000 m elevation range, and fly considerably higher, necessitating that they accommodate for a 27% change in air density (0.890 to 1.227 kg m−3) through behavior, physiology or biomechanics. We predicted that birds flying at high elevation would maintain aerodynamic lift performance behaviorally via higher flight speeds, rather than increases in power output or local phenotypic adaptation. We used three-dimensional videography to track turkey vultures flying at three elevations, and data supported the hypothesized negative relationship between median airspeed and air density. Additionally, neither the ratio of horizontal speed to sinking speed nor flapping behavior varied with air density.
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Arush, I., M. D. Pavel e M. Mulder. "A dimensionality reduction approach in helicopter level flight performance testing". Aeronautical Journal, 13 de julho de 2023, 1–30. http://dx.doi.org/10.1017/aer.2023.57.
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Abstract Evaluation of the power required in level flight is essential to any new or modified helicopter performance flight-testing effort. The conventional flight-test method is based on an overly simplification of the induced and profile power components required for a helicopter in level flight. This simplistic approach incorporates several drawbacks that not only make execution of flight sorties inefficient and time consuming, but also compromise the level of accuracy achieved. This paper proposes an alternative flight-test method for evaluating the level-flight performance of a conventional helicopter while addressing and rectifying all identified deficiencies of the conventional method. The proposed method, referred to as the corrected-variables screening using dimensionality reduction (CVSDR), uses an original list of 36 corrected variables derived from basic dimensional analysis principles. This list of 36 corrected variables is reduced using tools of dimensionality reduction to keep only the most effective level-flight predictors. The CVSDR method is demonstrated and tested in this paper using flight-test data from a MBB BO-105 helicopter. It is shown that the CVSDR method predicts the power required for level flight about 21% more accurately than the conventional method while reducing the required flight time by an estimate of at least 60%. Unlike the conventional method, the CVSDR is not bounded by the high-speed approximation associated with the induced power estimation, therefore it is also relevant to the low airspeed regime. This low-airspeed relevancy allows the CVSDR method to bridge between the level-flight regime and the hover. Although demonstrated in this paper for a specific type of helicopter, the CVSDR method is applicable for level-flight performance flight testing of any type of conventional helicopter.
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Bolton, Sarah, Richard Dill, Michael R. Grimaila e Douglas Hodson. "ADS-B classification using multivariate long short-term memory–fully convolutional networks and data reduction techniques". Journal of Supercomputing, 12 de agosto de 2022. http://dx.doi.org/10.1007/s11227-022-04737-4.
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AbstractResearchers typically increase training data to improve neural net predictive capabilities, but this method is infeasible when data or compute resources are limited. This paper extends previous research that used long short-term memory–fully convolutional networks to identify aircraft engine types from publicly available automatic dependent surveillance-broadcast (ADS-B) data. This research designs two experiments that vary the amount of training data samples and input features to determine the impact on the predictive power of the ADS-B classification model. The first experiment varies the number of training data observations from a limited feature set and results in 83.9% accuracy (within 10% of previous efforts with only 25% of the data). The findings show that feature selection and data quality lead to higher classification accuracy than data quantity. The second experiment accepted all ADS-B feature combinations and determined that airspeed, barometric pressure, and vertical speed had the most impact on aircraft engine type prediction.
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Kurz, Joscha, e Jason Blinstrub. "Conceptual design of a pilot assistance system for customised noise abatement departure procedures". CEAS Aeronautical Journal, 18 de novembro de 2023. http://dx.doi.org/10.1007/s13272-023-00698-3.
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AbstractThe departure of an aircraft is commonly the flight phase with the highest thrust level in a flight, which leads to considerable noise levels on the ground. The departure procedures are characterised by the thrust reduction altitude, the acceleration altitude, and the control of airspeed and aircraft configuration within each take-off segment. Thrust reduction and acceleration altitudes are typically constant and are not adjusted to particular operational key parameters (e.g., take-off mass, reduced take-off thrust) or weather conditions. However, the parameters differ between individual flights and affect flight performance as well as the noise levels on the ground. This paper presents the conceptual design of a pilot assistance system which aims to reduce the noise on the ground by identifying a custom thrust reduction and acceleration altitude for existing noise abatement departure procedures. The pilot assistance system is based on an aircraft simulation model and a noise simulation and is aimed to be utilised during pre-flight planning on ground. A key part of the noise evaluation is that the local population distribution around the airport is considered. An overview of the ongoing research at the German Aerospace Center is provided. The conceptual design and preliminary results are presented and discussed using an exemplary take-off for three wind conditions.
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Karpuk, Stanislav, e Ali Elham. "Assessment of Potential Commercial Success of Business Jets with Natural Laminar Flow". Journal of Aircraft, 18 de fevereiro de 2023, 1–21. http://dx.doi.org/10.2514/1.c036776.
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The present research investigates the potential application of the natural laminar flow wing technology to business jet market segments from light to long-range jets. A database of existing business jets was generated to determine the range extension as a potential driver of customer interest. A conceptual design of several configurations for each market segment was performed to investigate potential improvements in the aircraft flight range, operating costs, and price changes using the technology. An initial sizing module and a low-fidelity multidisciplinary design optimization were used to size all aircraft. Results demonstrated a 13–30% increase in the flight range depending on the aircraft concept. Long-range jets with natural laminar flow could not achieve significant range extension due to a combination of the design airspeed and maintenance costs. A rapid increase in acquisition prices for all aircraft suggested that super-midsize and large jets that combine relatively low empty weight and high range extension could be more favorable options compared to other segments, but a significant reduction of acquisition costs and an increase in operating flight hours are required to make the technology implementation successful.
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Nishanth, P., R. Mukesh e S. K. Maharana. "Verification of an Optimized Shape of Blended-Wing-Body Configuration using Artificial Neural Network". International Journal of Vehicle Structures and Systems 13, n.º 5 (31 de dezembro de 2021). http://dx.doi.org/10.4273/ijvss.13.5.20.
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In the current year’s alternative aircraft shapes, such as Blended - Wing- Body (BWB) aircraft, are considered and explored to create more effective aircraft shapes, specifically for more proficient and very huge transportation and eco-friendlier. In addition to the elimination of the tail for this specific type of aircraft and a significant reduction in equivalent weight, drag force, and radar cross-section, the available space for mounting equipment within has been improved and the operational reach has additionally been increased. Irrespective of all these stated advantages, instability is the undesirable outcome of eliminating the tail. Reviewing this deficiency involves designing a tandem of control surfaces and reflexed wing sections and utilizing a complex PC control system. Hence, several researchers have attempted to address the challenges raised by the aerodynamic shape optimization of BWBs, as well as the need to satisfy design specifications. In this paper, an experimental method was initially accepted to optimize the shape of a baseline design of a BWB. The shape was further allowed to be optimized using a Genetic Algorithm (GA). To strengthen the outcome of the optimized shape Artificial Neural Network (ANN) was used for different angles of attack ranging from -5o to 20o and airspeed ranging from 50 m/s to 700 m/s. A feed-forward back prop network with two layers of perceptron was deployed to achieve the goal of aerodynamic efficiency already set by both the experiment and CFD simulation. The goals of ANN and GA matched with a minor variation of 2% in their output results.
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Jie, Yuan, Pei Yang e Ge Yuxue. "Research on Fuel-Saving and Environmentally Friendly Approach Trajectory Considering Air Traffic Management Intention". Journal of Aircraft, 4 de outubro de 2023, 1–11. http://dx.doi.org/10.2514/1.c036593.
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Civilian aviation continues to contribute significantly to the total economic and environmental impact of aeronautics. Reduction of the fuel burn and environmental impact of civilian aviation is critical to the overall sustainability of the industry, and it can be accomplished, in part, through the optimization of arrival and approach procedures. This paper proposes the development of a method for measuring the degree of compliance of optimized approach trajectories with air traffic management (ATM) intentions, using an intention compliance level (ICL) indicator. Based on fuzzy logic, this measure reflects the extent to which approach trajectories satisfy the required time-of-arrival constraints. This research demonstrates an approach trajectory strategy that maximizes the ICL, maintains compliance with ATM intent, and achieves efficiency goals inclusive of reduced fuel consumption through selective airspeed changes. Simulations on the Airbus A320 indicate that achieving the optimal trajectory and flight parameters can significantly guide trajectory-based operations to minimize airline economic costs and reduce environmental impact while complying with ATM commands. In this paper we will organize the data as follows. The Introduction will summarize past research as a means of identifying the gaps that this research seeks to bridge and introduce the premise of our findings. Section II proposes the concept of ICL to evaluate the relationship between flight time and the required time of arrival and establishes an en-route descent trajectory model. Section III constructs the optimization strategy based on simulated annealing genetic algorithm (SAGA), evaluates the effectiveness of the algorithm, and verifies the contributions of the ICL in a basic scenario. Section IV analyzes the impacts of various factors on the optimization results in a complex scenario.
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Cecen, Ramazan Kursat. "Multi-objective TMA management optimization using the point merge system". Aircraft Engineering and Aerospace Technology ahead-of-print, ahead-of-print (3 de agosto de 2020). http://dx.doi.org/10.1108/aeat-09-2019-0181.
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Purpose The purpose of this study is to provide conflict-free operations in terminal manoeuvre areas (TMA) using the point merge system (PMS), airspeed reduction (ASR) and ground holding (GH) techniques. The objective is to minimize both total aircraft delay (TD) and the total number of the conflict resolution manoeuvres (CRM). Design/methodology/approach The mixed integer linear programming (MILP) is used for both single and multi-objective optimization approaches to solve aircraft sequencing and scheduling problem (ASSP). Compromise programming and ε-constraint methods were included in the methodology. The results of the single objective optimization approach results were compared with baseline results, which were obtained using the first come first serve approach, in terms of the total number of the CRM, TD, the number of aircraft using PMS manoeuvres, ASR manoeuvres, GH manoeuvres, departure time updates and on-time performance. Findings The proposed single-objective optimization approach reduced both the CRM and TD considerably. For the traffic flow rates of 15, 20 and 25 aircraft, the improvement of CRM was 53.08%, 41.12% and 32.6%, the enhancement of TD was 54.2%, 48.8% and 31.06% and the average number of Pareto-optimal solutions were 1.26, 2.22 and 3.87, respectively. The multi-objective optimization approach also exposed the relationship between the TD and the total number of CRM. Practical implications The proposed mathematical model can be implemented considering the objectives of air traffic controllers (ATCOs) and airlines operators. Also, the mathematical model is able to create conflict-free TMA operations and, therefore, it brings an opportunity for ATCOs to reduce frequency occupancy time. Originality/value The mathematical model presents the total number of CRM as an objective function in the ASSP using the MILP approach. The mathematical model integrates ATCOs’ and airline operators’ perspective together with new objective functions.
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Della Camera, A., G. Spataro, G. Cevenini, N. Nante, F. M. De Marco e G. Messina. "Sliding doors: how their opening affects particulate matter levels?" European Journal of Public Health 30, Supplement_5 (1 de setembro de 2020). http://dx.doi.org/10.1093/eurpub/ckaa166.704.
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Abstract Background The operating theatres (OTs) have adequate conditions to perform safe operations and to prevent surgical site infections. Opening doors can compromise these situations. Measurement of particulate contamination is a key point to check the effectiveness of preventive measures in the OTs. We analysed how openings impact in different type of OTs. Methods Between January/February 2020 a transversal study was conducted in 5 different types of OTs in a university hospital. Two had laminar flows, with 55 and 60 air changes/h; three had turbulent flows: OT-A (18 air changes/h, with 4 inlets from the ceiling), OT-B (23 air changes/h and air flow from the ceiling plenum), OT-C (16 air changes/h, air flow directed from one wall to the opposite wall and the main door laterally to the flow). Particulate matter (PM) measurements were carried out in 7 different points in each OT, alternating two conditions: a) doors closed; b) opening/closing the main door twice per minute. For each spot, in each condition, we recorded for several minutes the following parameters: particles (0.3, 0.5, 1, 3, 5, 10µ), room temperature (Ta), Relative Humidity (Rh), airspeed (Va). Comparison with the Wilcoxon test were made using STATA 14. Results In laminar flow, classified with better ISO levels (4), opening and closing the door the PM, for any size, increased not significantly (p > 0.05). The OTs with turbulent flows (ISO 5-6) had a higher particulate level than the laminar ones and greater variations with door openings. OT-A worsened significantly for all particles (p < 0.05) closing/opening the door. In contrast, OT-B and OT-C had a significant reduction of PM (p < 0.05). All 5 OTs had pressure falling to 0 at door opening; Ta, Rh and Va may be affected by different type air flows and design. Conclusions OTs parameters during door openings are influenced by different ventilation systems and room design. Laminar flows OTs are less affected, but innovative turbulent flows OTs can be just as effective. Key messages The operating rooms are affected by the door opening. Laminar flows operating rooms are less influenced by door openings than turbulent flows ones. Turbulent flow rooms have different performance depending on their construction characteristics.