bluuebunny/crossref_metadata_2025 huggingface dataset:
Construction of nonlinear component of block cipher using coset graph
Authors: Waheed Adil , Subhan Fazli , Suud Mazliham Mohd , Malik Muhammad Yasir Hayat , Mirza Alina , Afzal Farkhanda
Published: July 2023

In recent times, the research community has shown interest in information security due to the increasing usage of internet-based mobile and web applications. This research presents a novel approach to constructing the nonlinear component or Substitution Box (S-box) of block ciphers by employing coset graphs over the Galois field. Cryptographic techniques are employed to enhance data security and address current security concerns and obstacles with ease. Nonlinear component is a keystone of cryptography that hides the association between plaintext and cipher-text. Cryptographic strength of nonlinear component is directly proportional to the data security provided by the cipher. This research aims to develop a novel approach for construction of dynamic S-boxes or nonlinear components by employing special linear group $ PSL(2, \mathbb{Z}) $ over the Galois Field $ GF\left({2}^{10}\right) $. The vertices of coset diagram belong to $ GF\left({2}^{10}\right) $ and can be expressed as powers of α, where α represents the root of an irreducible polynomial $ p\left(x\right) = {x}^{10}+{x}^{3}+1 $. We constructed several nonlinear components by using $ {GF}^{*}\left({2}^{10}\right) $. Furthermore, we have introduced an exceptionally effective algorithm for optimizing nonlinearity, which significantly enhances the cryptographic properties of the nonlinear component. This algorithm leverages advanced techniques to systematically search for and select optimal S-box designs that exhibit improved resistance against various cryptographic attacks.
On $ ABC $ energy and its application to anticancer drugs
Authors: Altassan Alaa , Imran Muhammad , Rather Bilal Ahmad
Published: July 2023

For a simple connected graph $ \Gamma $ with node set $ V(\Gamma) = \{w_{1}, w_{2}, \dots, w_{n}\} $ and degree sequence $ d_{i} $, the atom-bond connectivity ($ ABC $) matrix of $ \Gamma $ has an $ (ij) $-th entry $ \sqrt{\frac{d_{i}+d_{j}-2}{d_{i}d_{j}}} $ if $ w_{i} $ is adjacent to $ w_{j} $ and $ 0 $, otherwise. The multiset of all eigenvalues of $ ABC $ matrix is known as the $ ABC $ spectrum and their absolute sum is known as the $ ABC $ energy of $ \Gamma. $ Two graphs of same order are known as $ ABC $ equienergetic if they have the same $ ABC $ energy but share different $ ABC $ spectrum. We describe the $ ABC $ spectrum of some special graph operations and as an application, we construct the $ ABC $ equienergetic graphs. Further, we give linear regression analysis of $ ABC $ index/energy with the physical properties of anticancer drugs. We observe that they are better correlated with $ ABC $-energy.
Perception and Preference of the Students for Online Education during COVID-19 in Bangladesh: A Study Based on Binary Logistic Regression
Authors: Sarker Md Fouad Hossain , Rahman Saida Mahamuda , Khan Samiha , Sohel Md. Salman , Tamal Maruf Ahmed , Khan Mohammad Marufur Rashid , Islam Md Kabirul
Published: July 2023

The COVID-19 pandemic has had a significant impact on both public health, and the global educational system. In response to the concerns surrounding the spread of the disease, many educational institutions, including those in Bangladesh, have shifted to online learning. This study aimed to investigate the perceptions and preferences of university students in Bangladesh towards online classes during the COVID-19 pandemic. The research was based on Binary Logistic Regression (BLR) and was conducted on a sample of 1116 university students in Bangladesh. The results of the study showed that while students faced a range of challenges while participating in online classes, including technical issues and limited access to study materials, they still preferred to participate in online courses due to the ongoing pandemic and the support of their teachers. Furthermore, the study revealed that there were differences in students’ attitudes toward online learning based on gender, geographic location, and type of university. The findings of this study are of great significance to governments, policymakers, technology developers, and university administrators, as they provide valuable information for the development of effective policies for online education in the future. These findings should be taken into consideration as a crucial guide to making in-formed decisions in the area of online education.
Effectiveness of an Adaptive Learning Chatbot on Students’ Learning Outcomes Based on Learning Styles
Authors: Kaiss Wijdane , Mansouri Khalifa , Poirier Franck
Published: July 2023

Intelligent learning systems provide relevant learning materials to students based on their individual pedagogical needs and preferences. However, providing personalized learning objects based on learners’ preferences, such as learning styles which are particularly important for the recommendation of learning objects, re-mains a challenge. Recommending the most appropriate learning objects for learners has always been a challenge in the field of e-learning. This challenge has driven educators and researchers to implement new ideas to help learners improve their learning experience and knowledge. New solutions use artificial intelligence (AI) techniques such as machine learning (ML) and natural language processing (NLP). In this paper, we propose and develop a new personalization approach for recommendation that implements the adaptation of learning objects according to the learners’ learning style mainly focused on the use of a chatbot, named LearningPartnerBot, which will be integrated into the Moodle platform. We use the Felder-Silverman Learning Styles Model to determine learners’ learning styles in order to recommend learning objects, and also to overcome the cold start problem. A chatbot is an automated communication tool that attempts to imitate a conversation by detecting the intentions of its user. The proposed LearningPartnerBot should be able to answer learners’ questions in real time and provide a relevant set of suggestions according to their needs.
Teaching Quality Evaluation of Online Courses Based on AHP-FCE Evaluation Technology
Authors: Huang Ran
Published: July 2023

The COVID-19 pandemic posed a considerable challenge to education and teaching. The concept of “Internet + Education” accelerated the construction and popularization of a large number of online teaching platforms, accompanied by the emergence of various massive open online courses and online classroom teaching platforms. Thus, evaluating the teaching quality of online courses has become essential. Diversified scientific evaluations of traditional teaching fail owing to problems such as single evaluation subjects, imperfect evaluation standards, and low evaluation efficiency. In this study, first, documents on evaluation index systems and evaluation methods for identifying the teaching effect of online courses are classified, and observation points of an online course teaching effect evaluation in 16 aspects before, during, and after class are proposed. Second, the index weights are determined based on analytic hierarchy process, and a fuzzy comprehensive evaluation model is established to evaluate the online course teaching effect in six application-oriented universities in Henan Province, China. Results show that the observation points of the online course teaching effect evaluation proposed in this study are scientific and reasonable. Specifically, among the observation point indices, X-16, X-2, and X-3 have substantial weight, and the overall average score of the online course teaching effect of the case study subjects is 3.756, with a –24.88% room for improvement compared with the full score of 5. The method can effectively evaluate the teaching quality of online courses scientifically and accurately. The results also have important reference value for elevating the quality assurance standards of online teaching, thereby perfecting the dynamic process of online teaching quality assurance and realizing the effectiveness of online teaching results.
Factors Influencing the Quality of Online Teaching: Application of DEMATEL and Cluster Technology
Authors: Li Ruining , Meng Yichen
Published: July 2023

With the informationization of higher education, colleges and universities can fully apply online teaching mode to education and teaching. Therefore, analysis of factors affecting teaching quality of college teachers in online teaching can effectively make evaluation object (teachers) have a sense of achievement and pride, so as to mobilize enthusiasm of evaluation object and to stimulate the consciousness of honor and shame and consciousness of competition. This study adopts application of DEMATEL and Cluster technology, conducts a questionnaire survey on 5 colleges and universities in Henan Province, analyzes and identifies the teachers’ factors among factors affecting teaching quality of E-commerce courses, and analyzes comprehensive influence index of teachers’ factors, namely impact degree, affected degree, cause degree and centrality degree. A cluster flight is carried out on evaluation results of students. Results show that X2-2, X2-4, X2-5, and X4-3 represent high degree of centrality and high degree of cause, that is high importance of factor and the cause factor. The results of teacher evaluation can be divided into three groups by the K-means clustering method, and the clustering group shows significant significance for all research items (p < 0.05). The weights of X2-2, X2-4, X2-5, and X4-3 in cluster analysis also rank the top four, which is highly consistent with the results of DEMATEL’s research, demonstrating that application of DEMATEL and Cluster technology proposed is very maneuverable and scientific. Research results have important reference value for improving online teaching strategy, improving the quality of online teaching, and regulating teaching activities as a whole through the use of online teaching quality evaluation.
A Color Guide for Color Blind People Using Image Processing and OpenCV
Authors: Kompalli Prasanna Lakshmi , Kalidindi Archana , Chilukala Janakidevi , Nerella Kumudini , Shaik Wajahath , Cherukuri Divija
Published: July 2023

Colors are the smiles of nature. Digital image processing has widely employed the use of the function the color due to its effectiveness as a tool in classifying and identifying objects, which can be distinguished based on various relevant shades of color. This work aims to create a software tool that assists color-blind individuals in identifying the colors and edges in an image that may appear similar to them. If you are not suffering from a color vision deficiency it is very hard to imagine how it looks like to be color blind. Individuals with color blindness are limited and sometimes even disqualified from specific professions due to their inability to differentiate between colors. The objective of this research is to create a technique or approach for accurately identifying different shades of colors and predicting their names specifically for individuals with color blindness. This project utilizes image processing techniques to create a system that can recognize and distinguish colors in an image. The algorithm used for color detection in this project recognizes pixels in an image that correspond to a defined color or color range and provides the name of the color along with its corresponding B, G and R values. This work will be very helpful for people who suffer from color blindness especially when they want to know the color of the things.
Static Hand Gesture Recognition Using Novel Convolutional Neural Network and Support Vector Machine
Authors: Glory Veronica Parsipogu , Mokkapati Ravi Kumar , Jagupilla Lakshmi Prasanna , Santhosh Chella
Published: July 2023

Hand tracking and identification through visual means pose a challenging problem. To simplify the identification of hand gestures, some systems have incorporated position markers or colored bands, which are not ideal for controlling robots due to their inconvenience. The motion recognition problem can be solved by combining object identification, recognition, and tracking using image processing techniques. A wide variety of target detection and recognition image processing methods are available. This paper proposes novel CNN-based methods to create a user-free hand gesture detection system. The use of synthetic techniques is recommended to improve recognition accuracy. The proposed method offers several advantages over existing methods, including higher accuracy and real-time hand gesture recognition suitable for sign language recognition and human-computer interaction. The CNN automatically extracts high-level characteristics from the source picture, and the SVM is used to classify these features. This study employed a CNN to automatically extract traits from raw EMG images, which is different from conventional feature extractors. The SVM classifier then determines which hand gestures are being made. Our tests demonstrate that the proposed strategy achieves superior accuracy compared to using only CNN.
Mobile Learning in Medical Coding Course: Intention to Use MedCoS
Authors: Nor Intan Shamimi Abdul Aziz  , Dilla Syadia Ab Latiff  , Siti Noorsuriani Maon  , Annurizal Anuar
Published: July 2023

Medical coding is a subject in which students must assign proper ICD-10 codes to patients’ diagnoses as reported in the coding exercises. However, due to students’ inadequate knowledge, incorrect codes are assigned to the cases, leading to coding errors. Thus, creating Medical Coding Simulation (MedCoS) is to help students strengthen their motor and technical abilities in challenging scenarios. The purpose of this study is to predict students’ intention to use MedCoS based on attitudes (AT), subjective norms (SN), and perceived behavioral control (PBC). To meet the objective, SPSS was used to conduct descriptive, reliability, and multiple regression analyses. This study includes students in Semester five and six who have attended both courses. Majority respondents were female (89.9%, n=116) and aged between 23 and 24 years old (90.2%, n=102). Results showed that attitudes and perceived behavioral predicted the intention to use MedCos among the students. The significant outcome allows MedCoS to plan the next stage of the application’s development with the goal of achieving the desired improvement in course performance.
L’identité littéraire franco-allemande de Heinrich Mann : entre projection de soi et réalité
Authors: Teinturier Frédéric
Published: July 2023

Cet article présente une réflexion synthétique sur l’usage de la langue française dans l’œuvre de Heinrich Mann. Ce dernier avait une identité culturelle fortement marquée par la France et la littérature française, dont il a fait un modèle durant l’essentiel de sa carrière. En outre, il possédait de bonnes connaissances linguistiques qui ont pu lui permettre de traduire des romans français en allemand, de mener plusieurs correspondances en français et aussi de rédiger de très nombreux articles politiques et culturels dans cette langue. Cependant, il n’a quasiment jamais écrit en français d’œuvres purement littéraires et fictionnelles. L’identité franco-allemande de Heinrich Mann est un phénomène particulier qui révèle la complexité et les contradictions d’un parcours intellectuel et littéraire.
Heine, écrivain français putatif ?
Authors: Calvié Lucien
Published: July 2023

Du vivant de Heine déjà et par la suite, sa réception française a posé et reposé le problème de sa « nationalité » littéraire : est-il un « écrivain français » ou un « poète allemand » ? La question est également sous-jacente aux deux grandes éditions critiques existantes, celles dites « de Düsseldorf » et « de Weimar ». Paradoxalement, et davantage même que la Germanistik en Allemagne, la germanistique française a longtemps paru privilégier, de diverses manières, un Heine « allemand » au détriment du Heine « français ». Peut-être est-il temps de rééquilbrer l’approche de Heine, par exemple autour de la notion, avancée par Heine lui-même à propos de l’un de ses textes, de « livre allemand en langue française ». Ces diverses considérations nous conduisent, concernant la caractérisation littéraire nationale de Heine, à proposer la notion d’« écrivain français putatif », parallèlement à sa pérennité comme « poète allemand ».
Langue croisée – Walter Benjamins Erinnerungsarbeit zwischen Hören und Sehen, Paris und Berlin
Authors: Kazmaier Daniel
Published: July 2023

Le livre Une Enfance berlinoise autour de 1900 de Walter Benjamin fait apparaître un lien entre la part francophone et la part germanophone de l’auteur. Suite à la publication de l’ensemble des textes formant ce projet mémoriel, on dispose désormais d’une base solide pour étudier cet ensemble bilingue hétéroclite, composé de plusieurs versions, remaniements, compilations. Sur la base d’analyses poétologiques et d’une approche génétique, cet article retrace le travail de mémoire de Benjamin dans Une Enfance berlinoise. Ce travail mémoriel se rattache aux lieux que sont Paris et Berlin, entremêle la sensualité de l’ouïe et la vision pour reproduire un enchevêtrement dans la langue elle-même, en tant que langue croisée. Sur le plan philologique, cette étude reconstitue les transpositions effectuées par Walter Benjamin sous un triple aspect : le remaniement intervenu entre la première version berlinoise et la version parisienne, plus tardive ; une comparaison des textes Die Mummerehlen et Loggien ; enfin, le transfert d’un passage du texte Die Mummerehlen vers le texte français Peintures chinoises à la Bibliothèque nationale.
Service Quality Dimensions in the Context of Herzberg Two Factor Theory
Authors: Aggarwal Prachi Jain
Published: July 2023

The major objective of this paper is to develop a comprehensive set of determinants of service quality of organised grocery stores in context of countries with culturally distinct orientation and to further classify them as hygiene and motivating factors resp. Such determinants can be used in further studies in order to help the international marketers to understand the behaviour of customers in different countries to succeed in an international arena. A questionnaire survey of 500 respondents each of Taiwan and India was conducted. A large number of items affecting service quality perceptions related to grocery stores were identified. The results of the study suggested a four-factor structure of perceived service quality variables for both India and Taiwan. The difference in the composed structure of the factors is further explained in terms of two factor theory. The results of the study will help the managers to allocate the resources strategically depending on whether the retailer needs to reduce the level of dissatisfaction or improve the level of satisfaction.
Common Injuries and Healthcare in College Basketball Sports
Authors: Wang Liyun , Sun Qingbin
Published: July 2023

College students often experience sports injuries on the basketball court due to their lack of understanding of their own situation and poor self-protection awareness. This article takes college students in the Chengdu Chongqing region as the research object, analyzes the causes of basketball sports injuries among college students through questionnaire survey, and proposes rehabilitation methods and preventive measures for sports injuries. The research results indicate that the main reasons for athlete injuries include improper preparation activities, technical errors, excessive load, poor physical fitness. To reduce the occurrence of injuries, it is necessary to do good warm-up training and enhance the flexibility of joints and ligaments. During physical rehabilitation training, it is necessary to focus on controlling the training intensity and establishing a phased recovery plan. Ultrasound can be used to accelerate the recovery speed of athletes' injuries. The research results provide theoretical data support for preventing basketball injuries among college students.
Potential of Debittered Pomelo Albedo Flour (Citrus maxima) in Bread: Functional, Nutritional and Phytochemical Characteristics
Authors: Olatoye K. K. , Lawal A. I. , Ojimi F. B.
Published: July 2023

This study explored the use of pomelo albedo as a composite flour in bread production. The pomelo albedo portion of the whole fruit was debittered through the standard method and obtained debittered pomelo albedo flours (DPAF) which were incorporated into wheat flour at four formulations of 0, 10, 20, and 30% for bread production. The impact of DPAF on functional characteristics of composite flours and physical, chemical and sensory characteristics of breads was investigated. The difference between 100% wheat flour and flour enriched with 30% DPAF regarding water absorption (130.00 - 166.33%), bulk density (0.68 - 0.96 g/ ml) and crude fibre (1.50 - 2.42%) was significant giving higher value in DPAF composite flours, while their specific volume (2.93 - 4.14 cm3/ g) and protein (7.75 - 10.07%) were lower than that of control bread without DPAF. The phytochemical properties of bread varied slightly with incorporation of DPAF. A Sensory evaluation test using a 9-point hedonic scale showed that the appearance, flavor and overall acceptability were within the liking rate for 10% composite bread. The overall results could be useful for guiding the future application of pomelo albedo by-product in the bakery industry.
Targeting 2-Oxoglutarate–Dependent Dioxygenases Promotes Metabolic Reprogramming That Protects against Lethal SARS-CoV-2 Infection in the K18-hACE2 Transgenic Mouse Model
Authors: Jessop Forrest , Schwarz Benjamin , Bohrnsen Eric , Miltko Molly , Shaia Carl , Bosio Catharine M
Published: July 2023

Dysregulation of host metabolism is a feature of lethal SARS-CoV-2 infection. Perturbations in α-ketoglutarate levels can elicit metabolic reprogramming through 2-oxoglutarate–dependent dioxygenases (2-ODDGs), leading to stabilization of the transcription factor HIF-1α. HIF1-α activation has been reported to promote antiviral mechanisms against SARS-CoV-2 through direct regulation of ACE2 expression (a receptor required for viral entry). However, given the numerous pathways HIF-1α serves to regulate it is possible that there are other undefined metabolic mechanisms contributing to the pathogenesis of SARS-CoV-2 independent of ACE2 downregulation. In this study, we used in vitro and in vivo models in which HIF-1α modulation of ACE2 expression was negated, allowing for isolated characterization of the host metabolic response within SARS-CoV-2 disease pathogenesis. We demonstrated that SARS-CoV-2 infection limited stabilization of HIF-1α and associated mitochondrial metabolic reprogramming by maintaining activity of the 2-ODDG prolyl hydroxylases. Inhibition of 2-ODDGs with dimethyloxalylglycine promoted HIF-1α stabilization following SARS-CoV-2 infection, and significantly increased survival among SARS-CoV-2–infected mice compared with vehicle controls. However, unlike previous reports, the mechanism by which activation of HIF-1α responses contributed to survival was not through impairment of viral replication. Rather, dimethyloxalylglycine treatment facilitated direct effects on host metabolism including increased glycolysis and resolution of dysregulated pools of metabolites, which correlated with reduced morbidity. Taken together, these data identify (to our knowledge) a novel function of α-ketoglutarate–sensing platforms, including those responsible for HIF-1α stabilization, in the resolution of SARS-CoV-2 infection and support targeting these metabolic nodes as a viable therapeutic strategy to limit disease severity during infection.
Design, Development and Flight Testing of a Gun-Launched Rotary-Wing Micro Air Vehicle
Authors:   Texas A&M University, Denton Hunter ,   US Army CCDC ARL, Kang Hao ,   University of Maryland, Hrishikeshavan Vikram , Benedict Moble
Published: July 2023

This paper describes the development and flight testing of a compact, re-configurable, rotary-wing micro air (MAV) vehicle capable of sustained hover and could potentially be launched from a 40mm grenade launcher. Launching the vehicle as a projectile over the target area could significantly improve the mission range for these energy-constrained platforms. The MAV design features coaxial rotors with foldable blades, and a thrust-vectoring mechanism for pitch and roll control. Yaw control was accomplished by using a specialized counter-rotating motor system comprised of two independently controlled motors. Passive unfolding of the coaxial rotor blades in flight utilizing centrifugal force was demonstrated. A cascaded feedback control strategy was implemented on a 1.7 gram custom-designed autopilot. Systematic wind tunnel tests were conducted with the vehicle on a single degree of freedom stand, which proved the ability of the controller to reject wind gusts up to 6 m/s and stabilize the vehicle during the powered axial descent phase. Different phases of the gun-launched flight sequence were independently verified through targeted flight tests. Free f light testing conducted both indoors and outdoors verified that the vehicle could hover and fly forward in moderate winds. In-flight drop tests were conducted by throttling down the vehicle from a high altitude to attain high axial decent speeds followed by recovery using the rotor thrust to aggressively brake the descent and achieve a stable hover. Finally, the vehicle was launched vertically from a pneumatic cannon followed by a stable projectile phase utilizing the f ins, passive rotor unfolding, and final transition to a stable hover from arbitrarily large attitude angles demonstrating the robustness of the controller, as well as all the sub-systems of the vehicle operating in perfect harmony.
Interactional Aerodynamic Assessment of a Quad-Rotor Tail Sitter using CFD
Authors:   Rensselaer Polytechnic Institute, Healy Richard ,   US Army CCDC - ARL, Floros Matthew , Anusonti-Inthra Phuriwat
Published: July 2023

Efforts towards enhanced Unamnned Aerial System (UAS) efficiency has lead to the development of the Quadrotor Biplane Tailsitter (QBiT) configuration that employs variable blade pitch to control the aircraft. To reduce the overall system complexity, an alternative control system using fixed-pitch/variable-RPM trim is explored, with the rotors' relative positions/tilt to the wing varied to provide improved rotor efficiency in cruise. Medium-fidelity aerodynamic models of the baseline and modified QBiT reveal that the power required for high-speed level flight (40 - 70 kts) with fixed-pitch rotors tilted 60° nose-up is comparable to that for the baseline variable-pitch rotor configuration. The modified Quad Rotor Tail Sitter (modified QRTS) configurations are also simulated using a high-fidelity CFD software, revealing that wing-rotor aerodynamic interactions are responsible for up to 34.5% thrust deficit on the aft rotors due to wing-induced downwash. This thrust deficit contributes to a 5.4-6.3% lower overall system efficiency measured by L/De (compared to a system without aerodynamic interaction). When trimmed using CFD-CSD loose coupling, this reduced efficiency in part makes the modified QRTS power only 26.9% lower than a fixed blade pitch QBiT (compared to the 60.2% reduction predicted by comprehensive analysis). Interactional aerodynamic penalties can be mitigated somewhat by adjusting the mounting position of the rotors with wing lift increasing when aft rotors are positioned behind the wing. At a high flight speed (50 kts), interactional aerodynamic penalties are extended, with greater aft rotor thrust deficit and wing lift penalty causing a 7.2 - 7.9% drop in L/De (compared to isolated rotors and wings). Overall, the modified QRTS (with fixed-pitch/RPM control and optimal rotor tilt/position) shows an increased aerodynamic efficiency over the baseline QBiT (with variable-pitch control) due to a reduction in axial rotor flow despite interactional aerodynamic penalties.
Wind-Tunnel Performance Investigation of an Electric Medium-Sized Variable-RPM Rotor
Authors:   DEVCOM-Army Research Laboratory, Floros Matthew ,   University of Maryland, Teodorescu Radu , Ryseck Peter , Chopra Inderjit
Published: July 2023

This paper describes isolated rotor and fuselage testing in the Glenn L. Martin Wind Tunnel at the University of Maryland, College Park. The multi-part test included both steady and transient rotor testing and fuselage aerodynamics testing. A T-Motor 28x9.2 rotor was tested under steady conditions from hover to 35 m/sec wind speeds over a 180-degree range of flow angles from -90 degrees or axial climb to +90 degrees or axial descent. Four steady rotor speeds were tested, 1600, 2300, 3100, and 3900 RPM. Transient rotor data was collected at 15 m/sec tunnel speed with chirp inputs to rotor speed. The aerodynamics of a coaxial quadrotor unmanned aerial vehicle fuselage were also tested. Thrust and torque from the steady isolated rotor testing is presented as sweeps of rotor angle of attack at fixed wind tunnel speeds and sweeps of wind tunnel speed at fixed rotor angles of attack.
Mars Sample Recovery Helicopter: Rotorcraft to Retrieve the First Samples from the Martian Surface
Authors:   NASA Ames Research Center, Withrow-Maser Shannah ,   NASA Langley Research Center, Allan Brian ,   Jet Propulsion Laboratory, Tzanetos Theodore ,   Science and Technology Corporation, Koning Witold ,   AeroVironment Inc., Pipenberg Benjamin , Johnson Wayne , Schatzman Natasha , Young Larry , Cummings Haley , Malpica Carlos , Meyn Larry , Grip Håvard , Chan Athena , Ruan Allen , Keennon Matthew
Published: July 2023

The Mars Sample Return Mission (MSR) will carry the next set of Mars helicopters, Sample Recovery Helicopters (SRHs), to the Martian surface. After successfully demonstrating extraterrestrial flight in 2021, Ingenuity has acted as a "scout" for the Perseverance rover while the rover gathers samples of Martian soil. In 2028, the MSR mission will launch a lander and two Ingenuity-sized SRHs to retrieve these samples. These will be the first samples of the Martian surface delivered to Earth. The SRH project will maintain heritage from Ingenuity's design when possible. However, several key changes must be made, including a ground mobility system, a robotic arm for tube manipulation, and the ability to carry the weight of a science payload (the sample tubes). In addition, the onboard software and cameras will be upgraded, and the rotor radius will be increased. Furthermore, new rotor performance and flight dynamics models and thorough characterization of vehicle limits will be required. The new vehicle design will be described, as well as validation and verification efforts to date. Note: The decision to implement Mars Sample Return will not be finalized until NASA's completion of the National Environmental Policy Act (NEPA) process.
Development and Performance Evaluation of a Multi-Rotor eVTOL Using RPM, Collective, and Cyclic Control in Failure State
Authors:   Embry Riddle Aeronautical University, Roiati Riccardo , Anderson Dr. , Collins Dr. , Hruswicki Patric , Saini Vivek , Yang Xinyu , Zuhair Syed , Sharma Nishant , Agrawal Shivansh , Ghate Sahil
Published: July 2023

The Eagle Flight Research Center (EFRC) at Embry Riddle Aeronautical University (ERAU) is investigating the risks and failure modes of Distributed Electric Propulsion (DEP) employed in novel Advanced Air Mobility (AAM) aircraft designs. To certify these aircraft for private and commercial operations, a greater understanding of how the vehicle is controlled in both nominal and off nominal or degraded modes is required. The EFRC team has designed and built a test stand to characterize the capabilities of a single DEP unit as well as 2 full-scale quadcopter AAM vehicles with RPM, collective and cyclic control. Extensive testing and simulation results showed that in order to operate and stabilize a quadcopter in a rotor out condition both collective and cyclic control must be utilized.
Rotor Loads Prediction on UH-60A Flight Test using Loose Fluid/Structure Coupling
Authors:   ONERA - the French Aerospace Lab, Moretti Rocco ,   US Army CCDC AvMC, Yeo Hyeonsoo , Richez Francois , Ortun Biel
Published: July 2023

This work exploits the high-quality UH-60A flight test campaign for comparison with concurrent simulations at the U.S. Army and ONERA. Rotor airloads and structural loads are predicted by coupling Computational Fluid Dynamics (CFD) with rotorcraft comprehensive analysis (CA). A high-speed test point is examined. Comparisons are shown for airloads, structural loads and rotor controls. Agreement with test data is improved when the flexibility of the pitch link is considered. Results show good agreement between the two partners predictions and with test data.
Model-Scale Investigation of Tiltrotor Low-speed Obstacle-Induced Downwash Recirculation
Authors:   NAWCAD Applied Aerodynamics, Silva Mark ,   Bihrle Applied Research Inc., Corbett Michael ,   LaVision Inc., Prevost Richard , Hromisin Scott , Graybeal Nathan , Cato Steven , Ralston John , Gray Callum
Published: July 2023

A model scale investigation of tiltrotor/obstacle aerodynamic interactions under zero wind conditions was conducted in the winter of 2022 by Bihrle Applied Research, Inc. (BAR) and LaVision, Inc. on behalf of NAVAIR. The test was conducted at 6% scale in a closed test hall with a full-span tiltrotor and an obstacle representing the aft portion of an amphibious class ship. The test objectives were to quantify the impact of recirculation on aircraft performance and trim as a function of aircraft position and orientation relative to the obstacle, and to acquire velocity flow field measurements for analysis validation and empirical model development. Principal data acquired include the force and moment reaction of the aircraft rotors and airframe, dynamic surface pressures on the obstacle, and particle tracking velocimetry (PTV) measurements of the flow field. This paper provides an overview of the test approach and execution and a presentation of selected results illustrating the variation of recirculation impacts with position and orientation relative to the ship obstacle.
Simulation of the Rotorwash Induced by a Quadrotor Urban Air Taxi in Ground Effect
Authors:   NASA Ames Research Center, Caprace Denis-Gabriel , Diaz Patricia , Yoon Seokkwan
Published: July 2023

A rotorcraft hovering near the ground causes downwash and outwash. The impact of these induced velocities on urban air mobility operations has not been extensively quantified. This paper explores the opportunity of using CFD to perform dedicated studies on the aerodynamics of rotorcraft in ground effect (IGE). For this purpose, we compare load and flow predictions obtained with the high-fidelity CFD solver OVERFLOW and with a medium-fidelity vortex particle-mesh (VPM) method, for a single rotor IGE. We show that the computational cost of high-fidelity simulation makes it impractical to sweep through a large number of configurations or operating conditions. However, a small set of cases can be used to verify a medium-fidelity tool. The latter provides a better trade-off between 'accuracy' and computational intensity, which enables numerous, longer simulations at a more affordable cost. As an example, the outwash flow is computed for two different designs of a quadrotor air taxi in hover and reveals the existence of increased velocities between the rotors. This work illustrates how CFD can help identify dangerous areas for passengers and ground personnel when they approach the vehicle.
Coupled Experimental and Offline Simulation Study of a Helicopter Rotor in a Frigate Airwake with Active Flow Control
Authors:   ONERA, Derhille Elvina ,   SIREHNA/NAVAL GROUP, Bordier Luc ,   LAMIH UMR8201, Keirsbulck Laurent , Gallas Quentin , Verley Simon
Published: July 2023

The operation of helicopters from small naval vessels like frigate present a demanding challenge for pilots. This paper studies the effect of active flow control system located along the sides of the hangar edges on the unsteady aerodynamic loads of a scaled rotor model operating along a stern approach. The flow field above the helideck is experimentally measured using stereo particle image velocimetry. These data are compared to ship airwake computations to assess the flow prediction capabilities. The ship airwake in headwind and G20 conditions without and with blowing are implemented into the Airbus Helicopters HOST simulation code based on the one-way coupling approach. The output data are equilibrium monitoring curves of the four commands states. The deviations induced by blowing are in the order of 1% to 25% and it allows at bringing the commands back to the uncontrolled airwake case.
Effects of Anhedral Tip on Forward Flight Performance
Authors:   Siemens Digital Industries Software, Nelson Chris ,   Georgia Institute of Technology, Zhou Chong , Shankar Shivani , Sankar Lakshmi
Published: July 2023

The effect of blade tip planform on rotor aerodynamics in hover and forward flight is investigated. This work is based a set of test data for several advanced planforms, with the S-76 rotor serving as the baseline. Two complementary numerical modeling approaches - a hybrid Navier-Stokes/free wake approach, and a wake capturing approach - are used to study the rotor aerodynamics in hover and forward flight. The present studies indicate that the rotor hover performance, as measured by the required power for a specified thrust setting, improves when anhedral is introduced. Anhedral rotors are seen to produce a smother blade loading and a more uniform inflow, which is expected to result in reduced induced power for a given thrust loading. In forward flight, the anhedral tip behaves similarly to the baseline swept tapered tip, and the benefits of the anhedral tip are less pronounced due to the decreasing contribution of induced power to the total power consumption.
Sinusoidal Gust Response of RC Propellers in Tandem Configuration
Authors:   University of Dayton, Cai Jielong , Gunasekaran Sidaard
Published: July 2023

The study of the fixed-pitch small-scale propeller under sinusoidally time-varying freestream is extended to a tandem propeller configuration. The changes in thrust and pitching moment of both the front and back propeller were characterized when encountering the sinusoidal gust in edgewise flight conditions. The propeller's steady freestream performance obtained in the previous study was used to predict response under sinusoidal time-varying freestream in edgewise flight. Below a reduced frequency of 0.2, the propeller response agrees with the prediction model, suggesting a linear superposition and quasi-steady dynamics for the propellers. At a higher reduced frequency, a reduction in mean thrust and pitching moment was measured. A phase lag in the propeller response was also observed indicating an unsteady response of the propeller. When placing the propeller in close proximity to each other, additional variations in the back propeller's performance were also observed at higher reduced frequencies, creating additional instability in the system.
Fundamental Test of a Hovering Rotor: Comprehensive Measurements for CFD Validation
Authors:   NASA Ames Research Center, Norman Thomas ,   NASA Langley Research Center, Schaeffler Norman ,   US Army CCDC AvMC, Overmeyer Austin , Heineck James , Chairer Edward , Wagner Lauren , Yamauchi Gloria , Dominguez Michelle , Sheikman Alex , Ramasamy Manikandan , Cameron Christopher
Published: July 2023

A model-scale hover test of a 4-bladed, 11.08-ft diameter rotor was recently completed inside the National Full-Scale Aerodynamics Complex 80- by 120-Foot Wind Tunnel test section. The primary objective of the test was to acquire key experimental data for a hovering rotor of sufficient quality and quantity to allow validation of state-of-the-art analysis codes. A comprehensive measurement set has been acquired, including rotor performance, blade airloads, flow transition locations, blade deflections, and wake geometry for a range of tip Mach numbers and collective settings. The present paper provides an overview of the test, including detailed descriptions of the hardware, instrumentation, and measurement systems. In addition, the specific test objectives, approach, and sample results are presented. The full test database, as well as detailed rotor geometry information, will ultimately be shared openly on a NASA-sponsored website to serve as a benchmark validation dataset.
Helicopter Rotor Wake Investigations on a Wind Tunnel Model with Varying Blade Stub Lengths
Authors:   Technical University Munich, Hartmann Ulrich , Breitsamter Christian
Published: July 2023

Experimental and numerical investigations have been performed on a helicopter wind tunnel model for three rotor heads with different blade stub lengths. This investigation analyzes the origin and the development of the wake structures occurring from the various blade stub lengths and their interaction with the tail section of the helicopter to judge the influence of the blade stub spanwise dimension on drag, lift and pitching moment characteristics. Therefore, aerodynamic forces and moments and the wake flow fields are analyzed by experimental and numerical simulations. The origin of the distinct structures is identified by the numerical simulations. Specific cross flow planes in the wake captured experimentally the flow field and allowed a comparison with the numerical results. The numerical investigations are based on the unsteady Reynolds-averaged Navier-Stokes equations. The turbulence is modeled by the scale-adaptive simulation method and the rotation of the rotor head is modeled by the sliding mesh approach. The flow field of the experiment and the simulation showed good agreement and a detailed analysis of the dominant vortices propagating downstream is performed.
Prediction of Coaxial Rotor Hub Flow Using Mercury Framework
Authors:   Pusan National University, Jung Yong ,   University of Maryland, Lee Bumseok , Baeder James
Published: July 2023

The rotor hub is one of the primary sources of high-speed rotorcraft parasite drag. To better understand the flow physics of the rotor hubs, counter-rotating coaxial rotor hub flows were simulated, followed by the experiment at the Penn State University. For the simulations, the Mercury computational fluid dynamics (CFD) framework employs an unstructured/Cartesian multi-mesh paradigm and Spalart-Allmaras delayed detached eddy simulation (SA-DDES) turbulent modeling. The coaxial hub flow physics was studied at two advance ratios by building up the hub components. The interference between the hub and the fairing components induced higher mean hub drag and unsteady harmonics in both hub and fairing drags. Different advance ratios affected hub wake structures and velocity fields at near- and mid-wake distances. Finally, the complete hub model in the water tunnel was simulated at the advance ratio of 0.25. The mean and unsteady drag predictions were compared with the experiment as well as the mean wake velocity fields. Additionally, the effect of hub shafts on the hub drags and wake velocity fields was studied. These efforts were based on the fourth Rotor Hub Flow Prediction Workshop in 2022.
Verification and Optimisation of Distributed Propulsion Using High-Fidelity CFD Method
Authors:   University of Glasgow, Qiao Geng , Barakos George
Published: July 2023

This work presents CFD verifications and comparisons related to distributed propulsion concepts. The work started with validation studies using experimental data from the NASA Workshop for Integrated Propeller Prediction (WIPP) and the folding conformal high lift propeller (HLP) projects. The high fidelity CFD results from HMB3 for isolated and installed configurations at different forward flight speeds were compared with experiments. Expanding from that, the second part of the paper examined several configurations of propellers similar to the ones used in modern eVTOL designs to identify performance differences for propellers located at different positions around a lifting wing. Results from different methods show that distributed propellers with a small radius have much stronger interference with the lifting wing compared to the tip-mounted propeller. The interference also depends on the location of the propellers, with propellers placed ahead of the leading edge showing slightly better performance than propellers placed on top of the wing. However, both methods indicate that the wing's performance improved significantly after optimizing the propeller from a traditional tractor configuration to a novel over-wing configuration. More specifically, the fully resolved results show that the wing lift-to-drag ratio has totally increased by 69%.
4th Rotor Hub Flow Prediction Workshop Experimental Data Campaigns & Computational Analyses
Authors:   Pennsylvania State University, Schmitz Sven , Reich David , Jaffa Nicholas
Published: July 2023

The rotor hub flow prediction workshops are held bi-annually at Penn State's Vertical Lift Research Center of Excellence (VLRCOE) to support academia, industry, and government in validating state-of-the-art computational fluid dynamics (CFD) tools. Initiated with support from VLRCOE, the National Rotorcraft Technology Center (NRTC), and the Fluid Dynamics Research Consortium (FDRC) at Penn State, these workshops have been compelling examples of productive exchanges between experimentalists and computational researchers and have had positive impact on both planning new experiments and subsequent computational grid and method development. There is continued interest in these comparisons as rotor hub flows are characterized by complex turbulent flow fields, while at the same time being a primary contributor to helicopter parasite drag. High-Reynolds number testing of rotor hub flows is necessary as high-Reynolds turbulent coherent structures remain strong for long distances downstream of the hub and up to the long-age wake where they interact with the empennage and tail. Basic research conducted at Penn State's water tunnel facilities has provided such unique high Reynolds-scale data of rotor hub wakes, providing new data for physical understanding and CFD validation. This paper summarizes the experimental data campaigns and 'blind comparison' computational results presented at the fourth rotor hub flow prediction workshop.
A Computational Investigation of Canted Side-by-side Rotors In Ground Effect
Authors:   Rensselaer Polytechnic Institute, Healy Richard , Gandhi Farhan
Published: July 2023

This study investigates the interactional aerodynamics of canted side-by-side rotors hovering in ground effect. The 5.5 ft diameter 3-bladed fixed-pitched rotors are simulated using CFD at a targeted 5 psf disk loading. Simulations are performed using the commercial Navier Stokes solver AcuSolve with a delayed detached eddy simulation (DDES) model. Side-by-side rotors are simulated at a height above the ground equal to one rotor radius (z/R = 1.0) and with 2.5R hub-hub spacing. In addition to an uncanted case, side-by-side rotors are simulated in ground effect (IGE) with 10° differential lateral cant, 10° inwards cant, and 10° outwards cant. Between the uncanted side-by-side rotors IGE, a highly turbulent mixing region is identified where the wakes of each rotor collide and fountain up. As blades traverse the highly turbulent flow, strong vibratory loading is induced and a thrust loss is observed over the outboard blade sections. The associated unsteady vertical loading for uncanted, laterally canted, and canted outwards rotors is similar, ranging from 10% - 16% peak-to-peak whereas canted inwards rotors show increased vibratory loading at 22% peak-to-peak. Integrated thrust for uncanted rotors IGE is 4.3% more than if out of ground effect (OGE), though when laterally canted or canted outwards, thrust generation is reduced to within 1% of isolated OGE rotors. Canted inwards rotors produce even less thrust, generating 15.2% less thrust than isolated OGE rotors. Overall, canting side-by-side rotors IGE incurs thrust production and vibration penalties. If canting is required for improved control authority, laterally canted rotors generate the most thrust while canted outwards rotors generate the least vibratory loading.