Research investigation of helicopter main rotor/tail rotor interaction noise

Acoustic measurements were obtained in a Langley 14 x 22 foot Subsonic Wind Tunnel to study the aeroacoustic interaction of 1/5th scale main rotor, tail rotor, and fuselage models. An extensive aeroacoustic data base was acquired for main rotor, tail rotor, fuselage aerodynamic interaction for moderate forward speed flight conditions. The details of the rotor models, experimental design and procedure, aerodynamic and acoustic data acquisition and reduction are presented. The model was initially operated in trim for selected fuselage angle of attack, main rotor tip-path-plane angle, and main rotor thrust combinations. The effects of repositioning the tail rotor in the main rotor wake and the corresponding tail rotor countertorque requirements were determined. Each rotor was subsequently tested in isolation at the thrust and angle of attack combinations for trim. The acoustic data indicated that the noise was primarily dominated by the main rotor, especially for moderate speed main rotor blade-vortex interaction conditions. The tail rotor noise increased when the main rotor was removed indicating that tail rotor inflow was improved with the main rotor present

Levels and Conditions of Goal Acceptance

The role of goal acceptance in goal setting theory was investigated through the application of Reiman\u27s theory of social influence and multilevel models of goal acceptance. Subjects were 144 undergraduate students. A 2X2X2 factorial design was employed. The three factors were: (a) antecedents of compliance (reward versus no reward), (b) antecedents of internalization (high value relevance versus low value relevance), and (c) goal specificity (specified goals versus non-specified goals). Three measures of goal acceptance were differentially affected by the manipulations: (a) A measure of intention to complete was uniformly high and not affected by the manipulations. (b) Perceived effort toward the goal was affected by both the specificity and internalization manipulations. Specified goal and value relevance conditions showed greater perceived effort. (c) Goal specificity and compliance manipulations interacted on an item measuring goal ownership. Error rate was not found to be affected by the manipulations. Specified goals resulted in higher performance and greater task interest than non-specified goals. Limited support was found for a multilevel view of goal acceptance

Evaluation of the use of engineering judgements applied to analytical human reliablity analysis methods (HRA)

Due to the scarcity of Human Reliability Analysis (HRA) data, one of the key elements of any HRA analysis is use of engineering judgment. The Electric Power Research Institute (EPRI) HRA Calculator guides the user through the steps of any HRA analysis and allows the user to choose among analytical HRA methods. It applies Accident Sequence Evaluation Program (ASEP), Technique for Human Error Rate Prediction (THERP), the HCR/ORE Correlation, and the Caused Based Decision Tree Method (CBDTM). This program is intended to produce consistent results among different analysts provided that the initial information is similar. Even with this analytical approach, an HRA analyst must still render several judgments. The objective of this study was to evaluate the use of engineering judgment applied to the quantification of post-initiator actions using the HRA Calculator. The Comanche Peak Steam Electric Station (CPSES) Level 1 Probabilistic Risk Assessment (PRA) HRA was used as a database for examples and numerical comparison. Engineering judgments were evaluated in the following ways: 1) Survey of HRA experts. Two surveys were completed, and the participants provided a range of different perspectives on how they individually apply engineering judgment. 2) Numerical comparison among the three methods. 3) Review of CPSES HRA and identification of judgments and the effects on the overall results of the database. The results of this study identified thirteen areas in which an HRA analyst must interpret and render judgments on how to quantify a Human Error Probability (HEP) and recommendations are provided on how current industry practitioners render these same judgments. The areas are: identification and definition of actions to be modeled, identification and definition of actions to be modeled, definition of critical actions, definition of cognitive portion of the action, choice of methodology, stress level, rule-, skill- or knowledge-based designation, timing information, training, procedures, human interactions with hardware, recoveries and dependencies within an action, and review of final HEP

Acoustic characteristics of 1/20-scale model helicopter rotors

A wind tunnel test to study the effects of geometric scale on acoustics and to investigate the applicability of very small scale models for the study of acoustic characteristics of helicopter rotors was conducted in the United Technologies Research Center Acoustic Research Tunnel. The results show that the Reynolds number effects significantly alter the Blade-Vortex-Interaction (BVI) Noise characteristics by enhancing the lower frequency content and suppressing the higher frequency content. In the time domain this is observed as an inverted thickness noise impulse rather than the typical positive-negative impulse of BVI noise. At higher advance ratio conditions, in the absence of BVI, the 1/20 scale model acoustic trends with Mach number follow those of larger scale models. However, the 1/20 scale model acoustic trends appear to indicate stall at higher thrust and advance ratio conditions

Behavioral Responses By Cottonmouths (Agkistrodon Piscivorus) To Chemical And Visual Predator Cues

Predator detection and assessment of predation risk have important survival consequences for animals. However, responses to predatory threats can vary with different stimuli. Chemical cues are important for predator recognition but visual cues may elicit defensive responses. Cottonmouths (Agkistrodon piscivorus) exhibit an array of antipredatory behaviors that have been thoroughly characterized in response to human aggressors, but their responses to cues from other predators are poorly known. I conducted three experiments to evaluate cottonmouth responses to visual and chemical stimuli from predators and non-predators. Snakes exposed to predator chemical cues exhibited elevated tongue-flick rates compared to controls but did not perform any antipredatory behaviors. Snakes exposed to mobile silhouettes of predators and non-predators performed significantly more defensive displays in response to red-tailed hawk models than controls. However, snakes exposed to visual models of terrestrial predators and non-predators exhibited elevated responses to taxidermed mink and muskrat compared to an inanimate object of similar size and color. My results are consistent with risk-sensitivity predictions in that cottonmouths can use chemical cues to recognize predators and use visual cues to distinguish predatory bird silhouettes from those of non-predatory birds. However, snakes generalized their antipredator responses to stationary mammals based on visual cues alone

Exergy-based Planning and Thermography-based Monitoring for energy efficient buildings - Progress Report (KIT Scientific Reports ; 7632)

Designing and monitoring energy efficiency of buildings is vital since they account for up to 40% of end-use energy. In this study, exergy analysis is investigated as a life cycle design tool to strike a balance between thermodynamic efficiency of energy conversion and economic and environmental costs of construction. Quantitative geo-referenced thermography is proposed for monitoring and quantitative assessment via continued simulation and parameter estimation during the operating phase

GPS Micro Navigation and Communication System for Clusters of Micro and Nanosatellites

Formation flying will quickly revolutionize the way science, remote sensing and surveillance missions are performed in space, enabling a whole new range of applications for small satellites. Currently, there are numerous missions in the planning stages involving formation flying of a constellation of micro or nanosatellites. However, to truly achieve the goals of these formation-flying missions, an accurate means of relative ranging, determining time and position measurements, inter-satellite communications, and controlling the formation states is becoming critical. Today, while there are very expensive products available for positioning and attitude determination, none of them are capable of meeting the precise positioning accuracy and attitude determination requirements of formation flying, let alone the mass and power restrictions of these tiny space vehicles. This paper will address the needs of future formation flying missions by discussing a technology with integrated capabilities for communicating, relative ranging, and exchanging precise timing among spacecraft within the constellation. This system is being developed by integrating a Carrier Phase Differential GPS (CDGPS) navigation and attitude sensor with a low power, inexpensive, compact ranging and communications system. The result of this integration is a low-cost, robust, secure GPS micro navigation and communication system for micro and nanosatellite constellations