bluuebunny/crossref_metadata_2025 huggingface dataset:
Should the Postgraduate Dental Curriculum Be Revamped? - A Stress Assessment Study
Authors:   Department of Oral Pathology and Microbiology, JSS Dental College and Hospital, JSS Academy of Higher Education and Research, Mysuru, Karnataka, 570015, India, Premalatha B R , Hegde Usha , Nitin Priyanka , Sreeshyla H S , Muralidhar Nitin V , Swetha P
Published: July 2023

Dental education is widely regarded as a demanding experience. Information about the stress sources and their degree is crucial since it will aid in the development of appropriate interventional methods for the student's overall development. Thus, our study was aimed at assessing the different forms of stress that affect Postgraduate dentistry students, as well as their attitudes toward psychiatric therapies. The study was conducted on 93 postgraduate dental students at a dental institution in Mysuru, India, using a cross-sectional questionnaire-based survey format. The information gathered was statistically examined. The mean and standard deviation were used in the quantitative analysis. The mean of all stressor scores was compared between groups using an independent sample t-test and one-way ANOVA. The Chi-square test was employed to examine qualitative data. The overall stress level among postgraduate dental students was high. All the year students demonstrated a similar trend with a high level of academic stress followed by health-related and psychosocial stress. The academic stress increased as the year of study progressed. We discovered no differences in stress perception between male and female students. In addition, a notable proportion of the participants had a favourable attitude toward psychiatric therapy. Stress levels among postgraduate dental students were found to be high in our study. This indicates a need for upgrading the current postgraduate dental educational system to be less stressful. Keywords: Dental education, Dental students, Mental health, Post­graduation, Stress, Stressors
The Effects of Fresh Fruit Extracts and Commercially Available Fruit Extracts on the Growth of Streptococcus mutans — An In Vitro Study
Authors:   Department of Public Health Dentistry, CIDS, Virajpet, Kodagu, Karnataka, India, Asmin P K , Nusrath Fareed
Published: July 2023

Resistance of antibiotics towards pathogenic microorganisms has led to the continuous search of natural plant products as a potential alternative for synthetic antibiotic agents. Many plant produces have shown promising results towards this end. This has led to commercialization and packaging of plant produce especially fruits. However, much research needs to be conducted to assess the potential benefits of commercially available plant produce compared to the natural ones. Consumable food items have both positive and bad effects, and their antibacterial effects on various microorganisms found in the oral cavity are good. To comparatively evaluate the effects of fresh fruit extracts and commercially available juice of Apple, Guava and Pomegranate on the growth of Streptococcus mutans. The present study describes the antibacterial activity of three selected fresh fruit extract and their commercial counterparts (Apple, Pomegranate and Guava) on Streptococcus mutans. Antimicrobial activity of fruit juices (fresh and commercial) was tested by well diffusion assay by an inhibition zone surrounding the well. The aim of the study was to comparatively evaluate the antibacterial activity of three fruit juices on Streptococcus mutans. Analysis of the results revealed the highest antibacterial activity for Fresh fruit extract of Guava towards Streptococcus mutans with a mean diameter of inhibition zone (DIZ) value of 11.26 ± 0.53(P>0.01) and the least was exhibited for commercial juice of pomegranate with a mean diameter of inhibition zone (DIZ) 2.20 ± 0.25 (P>0.01). The results obtained in this study clearly demonstrated a significant antimicrobial effect of fresh fruit extract of guava against Streptococcus mutans. However, preclinical and clinical trials are needed to evaluate biocompatibility and other effects, but in vitro observation of fresh fruit extracts of selected fruits appears promising. Keywords: Antimicrobial, Fruit Juice, Microorganism, Agar well diffusion method, Apple (Malus domestica), Psidium guajava, Pomegranate (Punica granatum)
Stepwise Advancement Simplified - A Modified Frankel II
Authors:   Department of Orthodontics, College of Dental Sciences, Davangere, Karnataka, 577004, India, Kumar N Dilip , Aparna P , Gupta .Neeraj , Sai Rallabhandi Saket , Mekhala V K
Published: July 2023

Frankel II appliance has been one of the most commonly used appliances in treating class II malocclusions with retrognathic mandible. For step wise advancement, clinicians usually follow the conventional method suggested by Rolf Frankel by splitting the buccal shields and advancing the lower labial pads and lingual pads as a unit, followed by re-acrylisation or by fabrication of a new appliance. The modified Frankel II appliance is constructed by incorporating two orthodontic expansion screws on either side of the buccal shields of Frankel II during the fabrication of the appliance. Activation of the expansion screws will help in advancing the lower lingual pad and the labial pads as a unit therefore offering several significant advantages over the previously used technique. Keywords: Modified FR II, Stepwise advancement in FR II, Hybrid appliance
A modern menekültügyi igazgatás létrehozása a közép-európai országokban
Authors: Klenner Zoltán
Published: July 2023

Aim: The purpose of the study is to present the development of modern asylum administration in the four Visegrad countries in the decade after the regime change.Methodology: The study examines and evaluates the similarities and differences in the mentioned Central European countries by reviewing the available literature and legislation.Findings: The economic and social background of Czechoslovakia (and later Czech Republic and Slovak Republic), Poland and Hungary showed many similarities in the period under review: at the time of regime change, they all joined to the 1951 Refugee Convention and established their own refugee management system in accordance with Western expectations, which included a set of rules and institutional structures that met international criteria. However, due to their geographic location, they have faced very different challenges, which has led to a periodic disparity in the attitude towards refugees and the volume of foreigners they receive.Value: In addition to presenting an aspect of the recent history of migration, this publication also serves some supplementation to the current treatment of the forced migration crisis, which is the largest one in Europe since the Second World War. It expands the knowledge of the specialized literature on the subject.
Rejuvenating Star Formation Activity in an Early-type Dwarf Galaxy, LEDA 1915372, with Accreted H i Gas
Authors: Paudel Sanjaya , Yoon Suk-Jin , Bait Omkar , Sengupta Chandreyee , Zee Woong-Bae G. , Chhatkuli Daya Nidhi , Adhikari Binod , Aryal Binil
Published: July 2023

We report a rare astrophysical phenomenon, in which an early-type dwarf galaxy (dE), LEDA 1915372, is accreting gas from a nearby star-forming dwarf galaxy, MRK 0689, and is rejuvenating star formation activity at the center. Both LEDA 1915372 and MRK 0689 have similar brightness of M

r
= −16.99 and −16.78 mag, respectively. They are located in a small group environment, separated by a sky-projected distance of 20.27 kpc (up to 70 kpc in three dimension), and have a relative line-of-sight radial velocity of 6 km s−1. The observation of 21 cm emission with the Giant Metrewave Radio Telescope provides strong evidence of interaction between the pair of dwarf galaxies in terms of neutral hydrogen (Hi) morphology and kinematics. In particular, the Hi map reveals that the two galaxies are clearly connected by a gas bridge, and the gas components of both LEDA 1915372 and MRK 0689 share a common direction of rotation. We also find that the Hi emission peak deviates from LEDA 1915372 toward its optical blue plume, suggesting a tidal origin of ongoing central star formation. Our findings provide a new path to the formation of blue-cored dEs.
Un nuevo autógrafo de Maimónides: un glosario judeo-árabe con glosas romances (T-S NS 163.57)
Authors: Martínez Delgado José , Montaner Frutos Alberto , Ashur Amir
Published: July 2023

Edición, traducción y análisis de cuatro listas de un borrador autógrafo de Maimónides que le servirían posiblemente para desarrollar diferentes temas por escrito en un futuro o asistirle en su docencia, tal y como se desprende de la secuencia de los ítems de las listas, donde subyace un orden lógico. Algunas voces de estas listas están glosadas en Judeo-Romance por el propio Maimónides, sin que podamos saber si fue él mismoquien incluyó esas glosas gracias a sus conocimientos de romance (en principio, andalusí) o si, por el contrario, fueron uno o varios informantes quienes le ayudaron a completar su lista. Las perplejidades a las que abocan rasgos lingüísticos incoherentes entre sí impiden clarificar la cuestión.
“Ecologically camping, eating, drinking wine.” Material and knowledge flows in the Minimum Cost Housing Group’s ECOL Operation, 1971-76
Authors: Stickells Lee
Published: July 2023

For approximately fifty years, McGill University’s Minimum Cost Housing Group (MCHG) has undertaken research on the “human settlement problems of the poor.” This paper focuses on the group’s activities from 1970 to1976, and more specifically the “ECOL Operation” initiated by the group’s first director, Colombian architect and UN consultant Alvaro Ortega. The story of the ECOL Operation gives insight into some unanticipated feedback loops associated with the foreign-aid-funded knowledge economy. The ECOL Operation was pitched as a technical and material research program to develop self-help housing solutions for the “Third World.” In practice, it was an improvised mix of international development aspiration, Appropriate Technology enthusiasm, industrial research and development, and ecological design rhetoric. The paper argues that the MCHG’s efforts became most compelling as a blueprint for a set of designers and activists rethinking the consumerist lifestyles and material flows of the Global North. This highlights a more complex background to the counterculturally-inflected ventures of 1970s ecological design. The scene was more closely connected to the Cold War complex of intergovernmental organizations, development agendas, and industrial capitalism than its participants may have imagined.
Reflections on Critical Applied Linguistics and Decoloniality: a follow-up conversation with Alastair Pennycook
Authors: Pennycook Alastair , Silvestre Viviane Pires Viana , Pessoa Rosane Rocha
Published: July 2023

Interview with Professor Alastair Pennycook.
Towards a Sustainable Transportation System
Authors: Mrad Sonia , Mraihi Rafaa
Published: July 2023

In modern societies, the need for a high degree of mobility in transportation systems is increasingly evident. Consequently, the establishment of a sustainable transport system that aligns with social needs, economic growth, and environmental concerns becomes paramount. This chapter aims to shed light on the role of transport in sustainable development and the challenges associated with achieving sustainable mobility. A thorough analysis of the primary factors contributing to the growing demand for mobility is provided. Additionally, the chapter examines the key decision-makers involved in shaping transportation systems, with a particular focus on the pivotal role of intelligent transportation systems. These systems are considered a vital component in addressing road congestion and enhancing overall traffic performance, such as reducing congestion and noise levels while promoting sustainable mobility.
Conceptualizing Success
Authors: Chan Kannass , Rose Jo
Published: July 2023

Student success continues to be an important topic in the higher education literature as students often struggle with university transition. Success is typically measured through the lens of retention or grades. However, retention in particular may not always be the best indicator, especially in universities with minimal drop-out rates. The present study was conducted in a Hong Kong government-funded university and seeks to understand first-year students' perspectives on what constitutes success. Three focus groups with 31 first-year students explored this topic. This study presents a new conceptualization of first-year success, positioning it as a holistic concept that encompasses overlapping domains of social, personal, and academic success. The findings extend the common focus on retention and grades in the student success literature and show that success is influenced by multiple aspects of student encounters in their first-year life. Implications for policy and practice are also identified.
Digital Transformation and Future Impacts in Logistics and Value Chains
Authors: Behrendt Fabian , Schmidtke Niels , Wollert Tim , Weigert David
Published: July 2023

This chapter discusses the opportunities and challenges as well as the effects and impacts on value creation processes, work organization, and corporate management caused by the digital transformation, particularly in the area of logistics. At its core, the chapter highlights the potential for change associated with the design of flexible, networked, and resilient value creation systems. An overview of technologies and innovations according to the 4.0 idea is given, with solution components from the categories ‘Strategies and Principles,' ‘Methods and Models,' and ‘Technologies and Tools' being presented in a structured manner. The topics of ‘Resilience Management,' ‘Value Stream 4.0,' and ‘Artificial Intelligence' receive special attention in this context. At this point, the reader is given impulses as well as central fields of action for the digitization of processes, products, and services in value networks.
Economic Order Quantity Estimation with Uncertain External Information on Product Demand Quantile
Authors: Zenkova Zhanna N. , Andrievskaya Anna A. , Yakovlev Nikita , Tarima Sergey S.
Published: July 2023

In this chapter, a more accurate method for estimating economic order quantity (EOQ) is suggested. This method improves accuracy by using uncertain external additional information about market demand. External additional information can be available in form of summary statistics (sample means, sample quantiles) and their uncertainty measures (confidence intervals, widths of confidence intervals, standard errors, sample variances, or sample standard deviations). Annual demand was estimated by average sales and improved with the use of uncertain quantile information. It is shown that uncertain additional information can reduce variance of the estimator. This new approach is illustrated using sales data of midsize retail company.
Determination of Inventory System Service Level by Simulation in Cases of Constant and Variable Demand and Lead Time
Authors: Aslan Emre
Published: July 2023

Service level and standard deviation of demand and/or lead time is considered while calculating reorder point with safety stock if the demand and/or lead time vary. This study explores whether reorder point provides desired service level. To answer the question, a simulation model is developed in MS Excel for three different cases of constant/variable demand and lead time. The model has been executed for certain periods, and service level is calculated as 1 (number of backorders/number of order cycles). It is found that the calculated service level for Case 1 was significantly higher than the desired service level, while the calculated service level for Case 2 and Case 3 was slightly lower than the desired service level. The reason for the difference in Case 1 is investigated. After eliminating factors from the model, a mechanism was added to the discrete model to simulate the continuity of the system. This minimized the difference in Case 1, but the difference in Case 2 and Case 3 increased slightly.
System Identification and Handling Qualities Predictions of an eVTOL Urban Air Mobility Aircraft Using Modern Flight Control Methods
Authors:   Rensselaer Polytechnic Institute, Niemiec Robert ,   US Army CCDC AvMC, J. Mark , Gandhi Farhan , Tischler Mark
Published: July 2023

Modern system identification techniques were used to identify a linear model based on a nonlinear simulation of a concept Urban Air Mobility quadcopter, and compared to a perturbation-based model. These models were used to develop feedback controllers for both variable-pitch and variable-RPM variants of the quadcopter, with the handling qualities requirements determining current requirements for the electric motors. To have sufficient stability margins and bandwidth, the motor time constant for the variable-RPM system must be no greater than 0.122s. Both variable- RPM and variable-pitch systems were limited by the yaw axis, which relies on differential motor torque for control. The introduction of rotor cant alleviated this problem for the variable-pitch vehicle, allowing a 47% reduction in motor weight, relative to the uncanted variable-pitch system.
Explicit Uncertainty Quantification for Probabilistic Handling Qualities Assessment
Authors:   Georgia Institute of Technology, Saetti Umberto , Rogers Jonathan
Published: July 2023

Modern flight vehicle development typically involves significant uncertainty in aerodynamic loads and vehicle control responses. In many cases, it may be necessary to consider this uncertainty in preliminary evaluations of stability, handling qualities (HQ), and performance. This paper introduces a novel methodology for computing these quantities in a probabilistic framework using the Koopman operator. The algorithm discretizes the uncertainty space and uses relevant transformations or simulations to map each point to the handling qualities evaluation domain, resulting in a stability, HQ, and/or performance assessment for each discretized point. The expected value of the stability, HQ, and/or performance requirement is then computed through an expected value integral with the initial joint probability density function, yielding a probabilistic assessment with respect to relevant specifications. The methodology is used to evaluate handling qualities of a quadrotor Unmanned Aerial System (UAS), for which a multi-loop Dynamic Inversion (DI) flight control law is developed. The UAS example is evaluated with respect to quantitative handling qualities specifications based on scaled Mission Task Elements (MTEs). The proposed explicit UQ approach is shown to provide a convenient framework for the propagation of parametric uncertainty to stability, HQ, and performance specifications with unique advantages over Monte Carlo techniques.
Identifying Pilot-Induced Oscillation Tendencies in Advanced Fly-by-Wire Rotorcraft
Authors:   Systems Technology Inc., Klyde David ,   Mitchell Aerospace Research, Mitchell David ,   US Naval Test Pilot School (USNTPS), Geyer William , Schulze P. , Holder John , O'Connor John , Tritschler John
Published: July 2023

In application, the Aeronautical Design Standard for the handling qualities of military rotorcraft, ADS-33E-PRF, provides the means to effectively predict rotorcraft handling qualities via validated criteria and demonstrate actual handling qualities in flight test using mission task elements. Besides a definition, a note that rotorcraft shall have no tendencies, and a note regarding Attitude Command Response-Types and gain bandwidth frequency, the topic of pilotinduced oscillations (PIO) is not addressed via specific criteria or flight test techniques. As the use of full authority fly-by-wire flight control continues to expand in Vertical Takeoff and Landing (VTOL) aircraft, the likelihood of encountering PIO will also expand. In the fixed wing world where PIO has been commonplace, at least in developmental test if not operations, predictive analytical methods that can also be used for detection of PIO in realtime have been developed, which can also be applied to rotorcraft. Furthermore, recent time-frequency domain methods that have been developed to differentiate VTOL piloting techniques are directly applicable to PIO scenarios. Using a flight test database generated with the UH-60L in-flight simulators at the U.S. Naval Test Pilot School (USNTPS), this paper explores the utility of these methods for identifying rotorcraft PIO tendencies.
Development and Flight Validation of Proposed Unmanned Aerial System Handling Qualities Requirements
Authors:   University of Portland, Ivler Christina ,   SJSURF, Gowans Norma ,   US Army Combat Capabilities Development Command AvMC, Tischler Mark , Kerwin Declan , Otomize Joel , Parmer Danielle , Truong Kevin
Published: July 2023

Unmanned aerial systems, commonly known as drones, present new opportunities to perform autonomous tasks. Handling qualities requirements for manned vertical lift aircraft have been well defined and documented. The need to define handling qualities requirements for Vertical Takeoff and Landing (VTOL) Unmanned Aerial Systems (UAS) to meet mission demands is of paramount importance for all potential operators and procurement agencies. One way to relate handling qualities specifications of large-scale manned and sub-scale unmanned aircraft is through Froude dynamic scaling. Froude dynamic scaling based on hub-to-hub distance has shown great promise in relating the natural frequencies of scaled multicopters. There have been recent efforts to develop a VTOL-UAS handling qualities standard by scaling Mission Task Elements and rating their performance through a Trajectory, Tracking and Aggression (TTA) score. This paper proposes a new performance standard adapted from the TTA scoring method, along with a modified Cooper-Harper scale as a VTOL-UAS handling qualities framework that is consistent with the spirit of ADS-33. These newly proposed performance standards were then validated through simulation and flight testing on a small hexacopter UAS, flown at the University of Portland. A key outcome of this work is the flight verification of a key dynamic response metric, the disturbance rejection bandwidth, and associated validation of Froude scaling for predicted handling qualities metrics.
Hover Handling Qualities of Fixed-Pitch, Variable-RPM Quadcopters with Increasing Rotor Diameter
Authors:   Rensselaer Polytechnic Institute, Walter Ariel ,   University of Portland, Ivler Christina , Gandhi Farhan , McKay Michael , Niemiec Robert
Published: July 2023

The handling qualities of quadcopters with fixed-pitch, variable-RPM rotors of several diameters are examined. Three aircraft sizes are considered, with rotor diameters of 1.2, 1.8, and 2.4 meters and gross weights of 136, 308, and 544 kg respectively. Each aircraft is first held to standard, ADS-33 handling qualities specifications, then Froudescaled specifications are applied in order to scale the requirements of the two smaller aircraft. CONDUIT R is used to optimize inner and outer loop controllers for actuator activity in each case. Time domain simulations are then presented in order to determine the necessary motor current margins needed. In the time domain, piloted commands and gust inputs are simulated along all axes for both the inner and outer loop controllers. Much greater current is required for yaw rate commands than for either pitch or roll commands. However, when a TRC controller is included, significantly higher current margin is needed during a small magnitude step in longitudinal speed for all aircraft sizes than were observed for the inner loop. The maneuver that requires the highest current margin is the yaw rate step for the smallest aircraft and the longitudinal velocity step for the others, regardless of Foude-scaling. Using the maximum current values from these simulations, the 136 kg vehicle requires 9.7% to 12.4% motor weight fraction,the 308kg vehicle 13.0% to 14.4% motor weight fraction, and the 544 kg vehicle requires a motor weight fraction of 16.8%. Motor weight requirements can be reduced somewhat on the larger aircraft by flying the pitch and roll axes exclusively in ACAH mode instead of TRC mode. In this case, step commands in yaw rate is limiting for the 308kg vehicle (requiring 12.0%–13.1% motor weight fraction) and heave commands are limiting for the 544kg vehicle(requiring 14.5% motor weight fraction).
Design and Analysis of a Blended Command Model for Low Speed Flight
Authors:   US Army CCDC AvMC, Jeram Geoffrey ,   US Naval Academy, Juhasz Ondrej
Published: July 2023

To achieve Level 1 Handling Qualities, Aeronautical Design Standard ADS-33E-PRF requires an Attitude Command Attitude Hold or Translational Rate Command response-type in Degraded Visual Environments while allowing a rate response in Good Visual Environments. The authors describe the design and analysis of a Blended Command Model that may offer the precision of the former and the aggressiveness of the latter. The command model, comprised of a single flexible transfer function and its parameter scheduling functions, produces attitude, rate, and blended responsetypes as functions of cyclic stick position. The authors explain the command model’s design considerations, test considerations, and its behavior through time domain and frequency domain perspectives. This effort precedes a handling qualities assessment aboard the U.S. Army’s JUH-60A RASCAL aircraft.
Use of a High Energy-Dense Li Anode Cell for an eVTOL Application
Authors:   BAE Systems, Hess Robert ,   Sion Power Corp., Britt Jeff , Stewart Joshua , Niedzwiecki Mark
Published: July 2023

Electric vertical take-off and landing (eVTOL) aircraft require sufficient electric energy to complete their missions and sufficient electric power for hover conditions (including standard and degraded modes of operation). When using current battery technology, the energy storage system constitutes a significant portion of the vehicle mass, thereby significantly limiting vehicle performance. Advanced cell technologies using solid lithium (Li) anode technology have the potential to increase energy density as compared to traditional cell-based on graphite anodes. Efforts to develop battery solutions using Li anode technology for an eVTOL application demonstrate reduced battery weight while achieving near-term performance objectives.
Investigation of Near Ground Effects in Hover Flight for the Multi-Rotor Aircraft Volocopter-2X
Authors:   University of Stuttgart, Miesner Sebastian ,   Volocopter GmbH, Schäferlein Ulrich , Keßler Manuel , Krämer Ewald
Published: July 2023

High-fidelity CFD simulations of hovering flights of the multi-rotor Volocopter 2X (VC2X) aircraft with three different heights above the ground and an out of ground reference case are presented. The tool chain applied consists of the CFD solver FLOWer, which is loosely coupled to the flight mechanic tool VFAST. For all simulations an adequate representation of the flight mechanics is of crucial importance since the high number of trim degrees of freedom of the VC2X has a significant influence on the flight physics. A short introduction and validation of VFAST is carried out, which shows that VFAST already provides valuable stand-alone results for the considered flight envelope. The in ground and out of ground CFD simulations showed a highly complex flow field for the VC2X. With increasing ground proximity the number of vortex structures induced by the ground increases and the rotor wake is characterized by strong fluctuations. Basic rotorcraft in ground effect phenomena, like a high-pressure area below the rotor plane and aircraft power reduction are observed for low flight heights. The decreased power requirement is mainly traced back to a decrease of the airframe download. The system figure of merit for all three in ground cases merely changes.
Electric Propulsion Component Sizing for Optimal Aircraft Configuration
Authors:   LaunchPoint Electric Propulsion Solutions, Ricci Michael , Myers Jack , Paden Brad , Rahn Ryan
Published: July 2023

LaunchPoint Electric Propulsion Solutions is developing mission-optimized electric propulsion systems. Unlike traditional aircraft development where designs are often driven by available propulsion systems, the relative simplicity of electric propulsion opens up the possibility that bespoke propulsion components may be developed and optimized for a particular vehicle configuration and mission. Electric propulsion is new to many aerospace designers and there is not yet a good body of knowledge about the performance of electric propulsion components. LaunchPoint aims to fill this gap by developing user-friendly physics-based electric propulsion models for multi-disciplinary optimization in vehicle/mission designs. To date, the existing vehicle configuration studies have largely used curve fits of existing electric propulsion components that do not accurately capture all of the relationships between motor and power electronics size, mass, efficiency, voltage, torque, and rpm and how those different motor parameters affect the overall vehicle performance. In a step toward revealing these relationships, this paper presents the design results from the coupling of detailed parametric motor and drive models with a simple eVTOL vehicle model.
The Art of Helicopter EICAS Design
Authors:   Bell Textron Inc., Oltheten Erik
Published: July 2023

The effectiveness of helicopter electronic Engine Indications and Crew Alerting Systems (EICAS) can be improved by applying display techniques rooted in human factors principles. These display techniques were developed to rapidly communicate systems information so that "head inside the cockpit" time could be minimized for safety. These design principles are not new, but as the EICAS design community has changed over the last 30 years, recognition of these proven techniques is extremely relevant. As the industry moves towards more "display-by-exception" presentations, also known as 'black cockpit" designs, certain indications are only present when there is a problem. In these designs it is especially important that the presentation be intuitive as the pilot may no longer be familiar with the behavior of the indication since it is only presented in an abnormal situation. The presentation must be intuitive at a glance.
An Evaluation of Pilot Electroencephalographic Activity during a Helicopter Tracking Task
Authors:   National Research Council Canada, Law Andrew , Ellis Kris , Hajra Sujoy , Jennings Sion
Published: July 2023

Two experimental test pilots performed an in-flight target tracking task on NRC's highly modified fly-by-wire Bell 205 helicopter. Target tracking errors, Cooper-Harper handling quality ratings, and pilot control activity confirmed that task difficulty was proportional to target velocity. Electroencephalography (EEG) data was acquired to investigate task-dependent changes in theta (4-8 Hz), alpha (8-13 Hz), and beta (13-22 Hz) oscillations. In addition, EEG-derived workload and task engagement indices were computed from these EEG bands and compared across task difficulty conditions. The EEG workload index was proportional to task difficulty for both pilots, whereas the EEG engagement indices revealed that the pilots' vigilance may have been higher during the low-velocity and high-velocity trials than the medium-velocity trials. These findings suggest that EEG-derived metrics provide complementary information about in-flight changes in pilot cognitive state that are not easily detected using subjective ratings, performance measures, or control activity metrics.
Stability Augmentation System for Coaxial Ultralight Helicopters
Authors:   University of Stuttgart, Richter Tobias ,   edm aerotec GmbH, Grebing Benedikt , Fichter Walter , Rothaupt Benjamin , Steinwandel Alexander
Published: July 2023

In this paper, the concept, design and implementation of a stability augmentation system for coaxial ultralight helicopters is presented. For an exemplary realization, the CoAX 2D ultralight helicopter is used. It is a 2-seated helicopter with two teetering mainrotors in a coaxial configuration with a maximum take-off mass of 450kg developed by edm aerotec. The description of the stability augmentation system covers the general design approach, sensors, actuators, the flight control computer, control algorithms, and the handling of malfunctions. Results of first flight test in a movable frame illustrate the proof of concept.
Using Deep Learning based Computer Vision in Helicopter Cockpits for Cognitive Decision Aiding
Authors:   Collins Aerospace, Huddar Vinay , Mudapaka Nitesh
Published: July 2023

Collins Aerospace, through its Common Avionics Architecture System (CAAS) and Flight2 avionics management systems for rotary wing aircrafts, provides extensive video processing, internal graphics generation, and overlay capabilities on real time video streamed from onboard EO/IR cameras providing situational awareness to the pilot in clear day-light and reduced visibility/night conditions. This capability has served our customers well in their cargo, assault, and multi-mission roles, improving the effectiveness of their missions. We now realize that more can be done to reduce pilot workload and enhance mission effectiveness by extracting visual intelligence from the video feed using machine vision. In this paper we explore the use of deep learning based computer vision to extract visual intelligence from onboard video feed and use it to automate low risk pilot actions, such as automatic detection and tracking of objects of interest, panning to maintain focus on objects, zooming on to a chosen object and providing contextualized data link message recommendations.
Validation of Enhanced Rotorcraft Aeromechanics Simulations: Flow Field, Unsteady Loads and Vibrations
Authors:   Sikorsky a Lockheed Martin Company, Modarres Ramin , Lorber Peter , Min Byung-Young , Zhao Jinggen
Published: July 2023

Robust and accurate predictions of rotorcraft aerodynamic and structural loads and vibrations are essential for designing advanced rotorcraft. The aerodynamic environment around the rotors is nonlinear and unsteady, the rotor and its wake interact strongly with fuselage and empennage to drive the structural vibrations. All of the components are elastic structures linked with one another by structural and aerodynamic interactions requiring a high fidelity coupled analysis. This paper presents simulations and validations for two examples: the aerodynamic interactions of a powered rotor - fuselage - empennage wind tunnel model using CFD (Computational Fluid Dynamics), and the structural loads and vibrations of a flight test aircraft using coupled CFD/CSD (Computational Structural Dynamics) - FEA (Finite Element Analysis). The NASTRAN FEA generated an elastic fuselage modal model which was coupled to the CFD/CSD tools in the CREATETM-AV HELIOS framework. The interactional aerodynamics simulation focused on lower advance ratio cases, which have a particularly strong rotor wake - empennage interaction and compared time averaged and periodic aerodynamic loads and flow velocity fields to experiment. Trends matched well, but quantitative differences remained, particularly at the lowest advance ratios. The full aircraft simulations were performed at increasing degrees of complexity and coupling. The agreement with measured rotor blade structural loads and horizontal stabilizer vibrations was best using the most complete model of the main rotor, tail rotor, fuselage and empennage.
Active and Passive Camber Morphing for Helicopter Rotors towards Performance Improvements in Hover and Vertical Flight
Authors:   Delft University of Technology, Vidyarthi Kushagra ,   Netherlands Defence Academy, Voskuijl Mark , Breuker Roeland , Pavel Marilena , Zahoor Yasir
Published: July 2023

Rotor morphing has been investigated in the past for improvement of rotor performance, either for reduction of rotor power demand or for vibratory load alleviation. The present study investigates the application of camber morphing for improvement of rotor performance in hover and vertical flight conditions, with a particular focus on the combination of camber morphing systems and variable RPM rotors. Camber morphing utilizes a smooth flap at the trailing edge of the rotor blade to modify the camber of blade airfoil sections without excessive drag penalties. Two different camber morphing systems will be investigated in this study, namely the active and passive systems. Passive camber morphing, which combines camber morphing with the variable speed rotor concept is the unique aspect of camber morphing which will be the primary focus of this study. The active system can be actuated at frequencies higher than 1/rev of the rotor and requires external power input for functioning. The passive system can be controlled only by varying the RPM of the rotor and requires no additional energy input. Therefore, the passive system is expected to show larger net performance benefits. Variable RPM rotors in themselves show potential towards the reduction of rotor power demand but are largely ineffective for low-speed applications. The combination of camber morphing and the variable speed rotor shows larger performance benefits than those obtained from the two technologies independent of each other. The two technologies, when combined in passive camber morphing, can remedy each other’s deficiencies and improve the overall rotor performance. The use of camber morphing shows more benefit for operating points at or near the edge of the flight envelope since the rotor blade sections encounter high average angles of attack for these operating points. Vertical climb and hover at high altitude are examples of flight conditions investigated. Overall, passive camber morphing shows a larger performance benefit as compared to the active system.
Mission Oriented Multi-Prop UAV Analysis using Statistical Design Trends
Authors:   Technion - Israel Institute of Technology, Rand Omri , Khromov Vladimir
Published: July 2023

The paper presents a methodology for sizing and preliminary analysis of Multi-Prop UAVs. The methodology is founded on design trends that emerge from a vast and unique database that has been collected for such vehicles. The database includes geometry parameters, components' weight, power required and flight performance estimation. For a given mission, the analysis enables optimization of a specific design of a Multi-Prop configuration for either minimal weight or minimal dimensions. As opposed to low-order and relatively simple analyses that are typically used in early design stages, the results presented in this paper include design trends and correlations within existing flying configurations, and therefore, contain many design constraints that typically emerge only during advanced stages of the design process.
Multirotor Configuration Trades Informed by Handling Qualities for Urban Air Mobility Application
Authors:   NASA Ames Research Center, Withrow-Maser Shannah , Malpica Carlos , Nagami Keiko
Published: July 2023

Many contemporary Advanced Air Mobility (AAM), and more specifically, urban air mobility (UAM) vehicle designers are attracted to variable rotor speed-controlled designs with multiple rotors because of the great potential for mass savings compared to more traditional, variable blade pitch-controlled vehicles. These designs are based on the assumption that the stability and control of recreation or basic utility-sized drones can be scaled to larger passengersized vehicles. Previous work had shown the challenges in stabilizing passenger-sized quadcopters. In this study, power constraints were made less restrictive and varied, allowing more control power. Motor parameters such as efficiency, nominal voltage and current operating point, and rise time of the rotor speed controller step response were studied. By fixing the efficiency of the motor to 95% and assuming a motor voltage to current ratio of 2.0 (previously, assumed to be 1.0), the authors were able to stabilize the quadcopter in the roll axis because this allowed the vehicle to achieve adequate rise times between 0.4 and 0.8 s. This motor optimization was extended to a hexacopter and octocopter designed to the same payload size and mission as the quadcopter. The three vehicle configurations and their motor speed controllers were compared. It was found that while hexacopter and octocopter required more mass and overall power; all three configurations had similar margins required for control. However, the hexacopter and octocopter were able to use this power margin to achieve lower rise times (i.e. the vehicle responded more quickly to pilot inputs) than the quadcopter, with the octocopter having the lowest rotor response rise time of the three vehicle configurations studied.
Conceptual Design of UAS Configurations with Dissimilar Rotors
Authors:   US Army Research Laboratory, Beals Nathan ,   Indian Institute of Technology Madras, Govindrajan Bharath ,   US Army CCDC Army Research Laboratory, Singh Rajneesh
Published: July 2023

Three vehicle configurations: a 9 kg quadrotor bi-plane tailsitter, a 20 kg tricopter, and a 450 kg coaxial helicopter with pusher propeller are designed using the iterative rotorcraft sizing framework HYDRA, maximizing payload capacity over missions with both hover and forward flight segments. This methodology allows for vehicles to have constituent rotors of differing geometry and angular velocity, a feature that has just been implemented as a part of this work. It allows users to rapidly evaluate vehicle configurations with rotors of a wide range of size, type, and orientation with respect to the vehicle. Furthermore, HYDRA can now model the electric transmission of power to each rotor separately using individually sized motors and speed controllers according to the requirements of each rotor. Results of the sizing show that vehicle and flow-field symmetry play an important role in whether or not dissimilar rotors may be useful for a specific configuration and mission. Analysis of the coaxial helicopter with pusher propeller demonstrated that by controlling design parameters of the main rotors separately from that of the propeller, operational envelope barriers and optimal aircraft configurations can be explored more thoroughly and more quickly than before.
Investigations of Ship Airwakes Using Concurrent Computations and Experiments
Authors:   Pennsylvania State University, Farish David ,   Embry-Riddle Aeronautical University, Seth Dhuree , Schmitz Sven , Thedin Regis
Published: July 2023

With modern advancements in computational resources, higher fidelity simulations of the ship-rotorcraft dynamic interface using large eddy simulations are now more feasible. Wind tunnel experiments remain one of the best validation tools for computational fluid dynamics simulations, but it is challenging to recreate full-scale ship and atmospheric conditions in such an environment. To serve as a bridge between scaled wind tunnel experiments and full-scale dynamic interface computations, Embry-Riddle Aeronautical University's Boundary-Layer Wind Tunnel was modeled in large eddy simulations to investigate the atmospheric boundary layer's effect on the airwake of a 1:235 scale Simple Frigate Shape 2 model. Cowdrey rods were used in the wind tunnel to develop the turbulence and momentum deficit characteristic of the atmospheric boundary layer. Hot-wire anemometry and Particle Image Velocimetry data were compared to OpenFOAM Large Eddy Simulation data. In uniform inflow conditions, it was found that despite the reduced Reynolds number of the scaled setup, the computational airwake data agreed quite well with larger-scale wind tunnel experiments and full-scale Large Eddy Simulations of the Simple Frigate Shape 2. Comparisons of the experimental and computational simulated atmospheric boundary-layer inflow show good agreement in the time-averaged velocity profile, velocity/turbulence intensity contours along the ship's centerline, and velocity probes on the flight deck of the model.
High Fidelity Code-to-Code Comparison of Rotor Performance in Hover and Forward Flight
Authors:   US Army CCDC AvMC, Lim Joon ,   Australia Defence Science and Technology Group, Widjaja Ronny ,   University of Glasgow, Barakos George , Jain Rohit , Potsdam Mark , Fitzgibbon Thomas
Published: July 2023

High fidelity code-to-code comparisons have been made between the University of Glasgow HMB3 code and the HPCMP CREATE™-AV Helios code under The Technical Cooperation Program collaboration project, Next Generation Rotor Blade Design. The comparisons are made for two model-scale rotors - Langley baseline (LBL) rotor and Pressure Sensitive Paint (PSP) rotor. Hover and forward flight performance results are compared against test data. For the LBL rotor, hover performance is in a good agreement between the test data and HMB3 results over a full range of CT. However, the comparison between the HMB3 and Helios results at a CT of 0.0084 shows the difference in Figure of Merit (FM) by approximately 2 counts (2.2-3.2%). In forward flight, the HMB3 and Helios performance results overpredict the test data at the low advance ratios but improve the predictions at the high advance ratios. At an advance ratio of 0.31, the code-to-code comparison indicated that the Helios torque was lower by 2.8-3.1% compared with the HMB3 torque. For the PSP rotor, the FM trend computed using the Helios-OVERFLOW code agrees well with the fully-turbulent test data. The Helios-OVERFLOW result shows that the fuselage interaction effect is favorable for rotor performance. For a code-to-code comparison, the HMB3 FM result shows about 3.0 counts (4.0%) lower than the HeliosOVERFLOW result at a CT/σ of 0.091. In forward flight, the HMB3 rotor result agrees well with the test data whereas the Helios rotor result underpredicts by 2-3 counts in CP/σ (3.5-5.7%) at the high advance ratios although it was significantly improved at the low advance ratio. Overall, the code-to-code comparisons are successfully conducted for both the LBL and PSP rotors.
Validation and Analysis of Aeroelastic Simulations of the UH-60A Rotor from Pre- to Post-stall Flight Conditions
Authors:   ONERA The French Aerospace Lab, Richez François ,   Georgia Institute of Technology, Grubb Amanda ,   US Army CCDC AvMC, Jain Rohit , Castells Camille , Smith Marilyn
Published: July 2023

Recently aeroelastic simulations of rotors in dynamic stall conditions based on a weak coupling between CFD (Computational Fluid Dynamics) and CA (Comprehensive Analysis) codes have demonstrated their prediction capabilities with good agreement with experimental data, despite the high level of complexity of this phenomenon. These recent studies resulted from a long-term effort to define the requirements, in terms of methods and models, necessary to capture of the complex physics of dynamic stall in rotor environment. However, these previous studies were performed on single test points. In this paper a range of six flight conditions of the UH-60A rotor from pre- to post-stall conditions with three different numerical approaches was examined. This approach permits not only the validation of the numerical methods on a larger set of data, but it provides a thorough analysis of the ability of the numerical methods to predict the onset of stall as the rotor thrust progressively increases. The numerical results show very good agreement on airloads, trim control angles and rotor power. More discrepancies are observed in structural loads although the global trend is captured. The flowfield visualizations from the simulations give a better insight into several regions of flow separation, their evolutions as the rotor thrust increases and the role of Blade Vortex Interaction (BVI) in the trigger of the different stall events.