bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of Aircrew Whole-Body Vibration Exposure Levels on a Canadian CH-147F Chinook Helicopter
Authors:   National Research Council Canada, Chen Yong , Ghinet Sebastien , Price Andrew , Wickramasinghe Viresh , Grewal Anant
Published: October 2024

Flight testing has been performed on a Royal Canadian Air Force (RCAF) CH-147F Chinook helicopter to investigate aircrew whole-body vibration (WBV) exposure levels in accordance with ISO 2631-1 or MIL-STD-1472G standard. Results showed that the helicopter cabin vibration was dominated at the N/rev harmonics of the three-bladed tandem rotor speed. The aircrew WBV levels varied significantly depending on flight conditions and aircraft load configurations while the highest levels of WBV occurred at high speed level flight maneuver conditions. With reference to the guidelines in the standards, the aircrew WBV exposure level in the entire tested flight profile was qualitatively rated as "uncomfortable", and the maximum duration of such missions should be limited to ensure compliance with the limit of the "Vibration Health Risks Guideline Caution Zone". The aircrew subjective perception survey for this flight profile also confirmed an increase of personnel ride discomfort.
Evaluation of Visual Augmentation Methods for Rotorcraft Pilots in Degraded Visual Environments
Authors:   Technical University of Munich, Viertler Franz , Hajek Manfred
Published: October 2024

Visual augmentation methods using 3D-conformal scenery content presented at a see-through head-mounted display have the potential to support the pilot in degraded visual environments. This work evaluates combined state-of-the-art visualization concepts in low-level flight close to obstacles and with limited visual ranges between 100 m and 800 m. Therefore, a pilot-in-the-loop simulation scenario with an obstacle course has been developed, in order to determine the control strategy of the pilot in low visibility situations, both with and without advanced visual assistance. Sixteen pilots participated in this experiment. The results show that the velocity and the height-above-ground adjustments of the pilots increase significantly at lower visibility and with obstacle information presented head-up, while workload is reduced compared to the unassisted flight. Moreover, the time-to-contact at the distance where the pilots initiated the obstacle avoidance maneuver increases and the safety margin maintains a minimum of 5 to 6 seconds for completely unexpected events. The early detection of obstacles with the head-mounted display allows more time for pilots to decide how to avoid a collision and thus increases their perceived safety.
Terrain and Obstacle Avoidance Displays for Low-Level Helicopter Operations in Degraded Visual environments
Authors:   NASA/SJSU, Godfroy-Cooper Martine ,   US Army Aviation Development Directorate AMRDEC, Szoboszlay Zoltan ,   University of Haifa, Kahana Allon ,   Maof HFE, Rottem-Hovev Michal
Published: October 2024

Collision with obstacles (typically wires and towers) and with terrain during low level helicopter flight under low visibility conditions has been a documented problem for the US military. Degraded visual environments (DVE) due to night operations and/or poor weather prevent adequate visibility of terrain and obstacles ahead of the aircraft and contribute to many of the accidents. This paper documents the results of twelve pilots in a simulation evaluating four types of visual conformal symbology sets in a low-visibility condition contour terrain flight: a scene-linked condition, a conformal line condition, a guidance line condition, and the combination of the two in a conformal + guidance condition. The results of combined quantitative and qualitative analyses strongly support the superiority of the contour lines over the scene-linked to ensure the safest flying behavior and the greatest situation awareness. However, the interindividual variability was very high, suggesting that a modular and selectable presentation of the different displays should be made available, as a function of the phase of the flight, the nature of the mission and the pilot's preferences.
Application Issues for In-Flight Tracking Control Using Trailing Edge Flaps
Authors:   University of Stuttgart, King Frank , Steinwandel Alexander , Fichter Walter
Published: October 2024

Two aspects of practical relevance concerning the application of an in-flight tracking control system are examined in the present paper. The particular control system considered in this examination feeds back 1/rev and 2/rev accelerations to steady trailing edge flap deflections using a control law based on the HHC algorithm. Integrator drift due to numerical errors in the presence of non-effective transfer paths in the transfer matrix model are discussed. To avoid the integrator drift, a transformation of the controller state based on the characteristics of the transfer matrix model for in-flight tracking is proposed. The effectiveness of this structural avoidance of integrator drift is demonstrated by simulation as well as closed loop flight test data. Furthermore a new method for limiting control commands of the in-flight tracking system, based on the characteristics of the transfer matrix model, is presented. The presented strategy is able to guarantee quasi-optimal vibration reduction in the face of active control command limitations.
Floquet-SSI Methods for Real-Time Stability Monitoring and Correlation
Authors:   Spire Innovations LLC, Hull Jason ,   Sikorsky Aircraft Corporation, Andrews Joseph
Published: October 2024

Improved methods for real-time stability monitoring are needed in the rotorcraft industry to support the design and testing of new aircraft rotors, as well as updates to existing rotors. Current validated approaches require significant effort on the part of the user and can only be applied to a very specific data sequence. This combination of factors can be a significant cost driver in the development cycle. In this paper we demonstrate the combined use of Floquet analysis with Stochastic Subspace Identification (SSI) methods to address these deficiencies. This novel approach allows for the use of more robust subspace identification methods and provides an effective means of removing main rotor harmonics from the measured loads. All of this leads to highly accurate, precise and real-time estimates of rotor stability and modal data. These estimates can ultimately be used to "close the loop" in efforts to correlate computational structural dynamic simulation results with flight test and whirl stand test data, improving the fidelity of existing simulation models.
Assessment of Comprehensive Analysis Predictions of Helicopter Rotor Blade Loads in Forward Flight
Authors:   Science and Technology Corporation, Ho Jimmy ,   US Army Aviation Development Directorate, Yeo Hyeonsoo
Published: October 2024

Comparisons of helicopter rotor blade loads, between rotorcraft comprehensive analysis predictions using a free vortex wake model and measured data, are provided for the UH-60A, SA 330 (research Puma), SA 349/2, and H-34 rotors in forward flight. The comparisons encompass a total of 24 test points featuring wide variations in advance ratio for a thorough assessment of the predictions. With the exception of chord bending moment for the case of UH-60A, the analysis correctly predicts trends in half peak-to-peak values of blade structural loads and pitch link force. Most of the predictions in half peak-to-peak blade structural loads and pitch link force deviate from the measured data by no more than 40% and most of the deviations are underpredictions. The predictions typically resemble the measured data in shapes of the waveforms for both flap bending moment and normal force, but this is less often the case for chord bending and torsion moments. While the analysis may capture the 1/rev harmonic contents in pitching moment waveforms, it consistently underpredicts any higher harmonics.
Investigation of UH-60A Rotor Structural Loads From Flight and Wind Tunnel Tests
Authors:   US Army Aviation Development Directorate, Yeo Hyeonsoo ,   NASA Ames Research Center, Norman Thomas , Potsdam Mark
Published: October 2024

NASA/Army UH-60A Airloads Program flight test and full-scale UH-60A Airloads wind tunnel test data are investigated in order to better understand and predict the chord bending moments, one of the unresolved issues in the UH-60A rotor loads prediction. Coupled Helios/RCAS analysis is performed and the calculated rotor loads are compared with the test data. RCAS alone analysis is also performed by applying measured airloads from the tests as prescribed external loads. Effects of the lag damper model are examined by calculating lag damper loads using a nonlinear lag damper model or by applying measured lag damper loads as prescribed external loads. Both airloads and damper loads are important for the accurate prediction of chord bending moments. The calculated chord bending moments with the prescribed measured airloads and measured damper loads show the best correlation with the wind tunnel test data. In particular, the 4 and 5/rev harmonic correlation is excellent. The effects of drive train dynamics and hub impedance on the chord bending moments appear to be very small for the wind tunnel test. Those effects may still be important for the flight test vehicle, although they might be smaller than what was suggested in previous studies.
Validation Of Comprehensive Modeling Of The Wing And Rotor Aeroelastic Test System
Authors:   Army Research Laboratory, Kreshock Andrew ,   Army Research Laboratory, Kang Hao ,   US Army Aviation Development Directorate, Yeo Hyeonsoo , Thornburgh Robert
Published: October 2024

This paper uses a modular approach to validate the modeling process of the Wing and Rotor Aeroelastic Test System (WRATS) tiltrotor using two different rotorcraft comprehensive analyses: RCAS and CAMRAD II. The subcomponents used to build the models are first validated using experimental testing and ABAQUS three-dimensional and one-dimensional modeling. The assembled model is then used to predict the whirl-flutter stability boundary for two different configurations that were tested. Results show good agreement between the two analyses and previously measured wind-tunnel data for the first configuration but not as well during for the second configuration. Parametric studies were also conducted to determine the influence of key attributes on the whirl-flutter stability boundary.
Performance and Loads of a Model Coaxial Rotor Part II: Prediction Validations with Measurements
Authors:   University of Maryland, Schmaus Joseph , Chopra Inderjit
Published: October 2024

The predictions of an upgraded UMARC comprehensive analysis are compared to experimental coaxial rotor results. The experiments cover a range of collective pitch angles (θ°) from 2° to 10°, advance ratios (μ) from 0:2 to 0:5, and lift offset from 0% to 20%. The experimental rotor system is a hingeless rotor with a first flap frequency of approximately 1:6=rev and was tested in the Glenn L. Martin Wind Tunnel at the University of Maryland first as an isolated rotor and then as a counter-rotating coaxial rotor system. The analysis is validated against measured isolated rotor performance and coaxial rotor performance and loads. The isolated rotor performance and controls are predicted well with advance ratio, although thrust tends to be under-predicted. With increasing lift offset, thrust increases while power remains the same, improving rotor performance. Coaxial correlation is shown for rotor-to-rotor tip clearance, pitch link loads, and selective vibratory hub loads. The impact of rotor-to-rotor phase is examined. Matching rotor side force is a challenge in this simulation.
Multidisciplinary Design and Optimization for High Speed, High Efficiency Tiltrotors with Wing Extensions and Winglets
Authors:   The Pennsylvania State University, Kambampati Sandilya , Smith Edward , Maughmer Mark , Hoover Taylor
Published: October 2024

In this paper, we study multi-objective optimization methodologies for tiltrotor aircraft with wing extensions and winglets. The objective is to maximize aircraft cruise performance while minimizing wing weight, subject to whirl flutter, buckling, strength, and wing loading constraints. A wing structural model for strength and wing weight predictions, an aerodynamic model for performance predictions, and an aeroelastic model for whirl flutter predictions are developed for the optimization. Parametric studies on whirl flutter speed, cruise efficiency (lift-to-drag ratio, L/D), and wing weight are conducted; and the parameters include key variables such as wing thickness, and extension and winglet planform variables. The parametric studies predict that structural taper can increase the whirl flutter speed by 35 knots (12.5% increase), while reducing the wing weight. The optimization studies reveal that the L/D of the optimum design is 12% more than the baseline, while the optimum wing weight is 0.3% less than the baseline.
Parametric Study of Tiltrotor Whirl Flutter Using Two Rotorcraft Comprehensive Analyses
Authors:   Army Research Laboratory, Kang Hao ,   University of Alabama, Shen Jinwei , Kreshock Andrew
Published: October 2024

This paper presents a parametric study of stiff-inplane tiltrotor whirl flutter using two rotorcraft comprehensive analyses: RCAS and DYMORE, correlating the predictions with experimental data. Comprehensive, multibody-based dynamics analyses of rotorcraft enable modeling and simulation of the rotor system at a high level of detail so that complex mechanics and nonlinear effects associated with control system geometry and various types of hinges and joints are able to be considered. A parametric study of key design variables, including control system stiffness, pitch-flap coupling, and aerodynamic compressibility was completed, which may help to evaluate the predictions and to determine suitable design criteria for future stiff-inplane tiltrotor systems. Analytical results indicate consistent capabilities of multibody dynamics analyses in predicting the stiff-inplane tiltrotor whirl-flutter stability and show generally fair to good agreement with the experimental results. Both analytical and experimental results show the destabilizing effects of pitch-flap coupling and aerodynamic compressibility on the whirl-flutter stability of a stiff-inplane tiltrotor whereas both results also indicate that a reduction in control system stiffness has little effect on whirl-flutter stability.
Development of a Computational Model of Pilot Manual Control and its Application on Mission-Task-Element Evaluation of a Limited Authority Helicopter
Authors:   Turkish Aerospace Industries, Onur Can , Sarsilmaz Selahattin , Türe Umut , Şahin İsmail , Zengin Uğur
Published: October 2024

Being able to represent pilot control behavior computationally would give insights in the early phases of aircraft design, and would reduce the risks and costs of flight-tests. This work introduces a novel mathematical model of pilot control behavior that takes into account the majority of psychophysical limitations of an actual human operator. The Model-Based Pilot Controller (MBPC) developed herein utilizes optimal estimation and modern control theory. It can operate wide range of linear or non-linear vehicle dynamics, acting as a manual pilot controller. The MBPC, in this work, is applied to assess handling qualities of a limited authority helicopter by augmenting it to a non-linear model of the helicopter. The Mission-Task-Elements (MTEs), defined by the Aeronautical Design Standard (ADS)-33E-PRF, are referred as a benchmark for qualitative handling quality evaluation of a rotorcraft. A set of MTE maneuvers is flown, in simulation environment. The developed MBPC model is proven successful as it forecasts the rotorcrafts ability to execute the specified maneuvers. The MBPC is evaluated based on a test pilot's control responses to see if the psychophysical limitations are represented in the model.
Outer-Loop Development and DVE Flight Test Assessment of a Partial Authority Model-Following Control System for the UH-60
Authors:   US Army Aviation Development Directorate, Fujizawa Brian , Tischler Mark , Minor Joe
Published: October 2024

The vast majority of the U.S. Army's helicopter fleet consists of aircraft initially developed in the 1960s and 1970s and which were designed based on the handling qualities and flight control requirements of the time for flight in good visual environments (GVE). The Army today uses helicopters at night and in brownout and other degraded visual environment (DVE) conditions but with the same control laws of the original models; the major exception being the CH-47F and MH-47G DAFCS, which have been highlighted as a successful partial authority flight control system upgrade to provide improved handling qualities. The U.S. Army Aviation Development Directorate–AFDD has partnered with the U.S. Army Utility Helicopter Program Office's Futures Team and the RDECOM DVE Mitigation Program to further develop and test the UH-60 Modernized Control Laws (MCLAWS). Previous work implemented a model following control system architecture which provided an attitude command/attitude hold response-type for hover and low speed flight. This system demonstrated improved handling qualities as compared to the UH-60L SAS/FPS rate command response-type. This paper documents work to integrate an outer-loop position hold with velocity command mode into the MCLAWS. Flight testing of the MCLAWS with position hold demonstrated Level 1 Cooper-Harper handling qualities ratings in simulated DVE conditions. Finally, landing logic has been integrated into the MCLAWS to support DVE landing flight testing.
Maneuver and Mission Aiding via Tactile Cueing Flight Demonstrations
Authors:   The Boeing Company, Kashawlic Bryan , Enns Russell , Brown Brandon , Moore Rucie
Published: October 2024

Tactile cueing techniques previously developed for carefree maneuvering were expanded to assist the pilot with maneuver and mission tasks, bridging the gap between manual and autonomous flight. Multiple maneuver and mission aiding functions were prototyped and evaluated in simulation and flight test. The algorithms were developed in a platform agnostic manner, with a subset of the functions evaluated on three different demonstration aircraft: an H-6, AH-64 and an H-47. This paper describes the maneuver and mission aiding tactile cueing functions developed as well as the results from both piloted simulation and flight testing evaluations. Metrics were created and collected to quantify benefits in the categories of mission productivity, handing qualities, pilot workload, performance, and safety. The results showed significant benefit in each of these metrics area for each of the aircraft, suggesting that similar benefits can be expected if such maneuver and mission aid tactile cueing functions are applied to other platforms.
Analysis of Pilot Control Activity in ADS-33E Mission Task Elements
Authors:   US Naval Test Pilot School, Tritschler John ,   Systems Technology Inc., Klyde David , O'Connor John , Lampton Amanda
Published: October 2024

The present work reports the results of a research investigation into the use of multiple methods for analyzing pilot control (inceptor) activity in order to better characterize handling qualities. The investigation involved flight test data that were collected for an OH-58C Kiowa helicopter performing the Hover and Pirouette Mission Task Elements from ADS-33E. Traditional subjective handling qualities ratings were assigned, and multiple analysis methods were also applied, including the (i) pilot cutoff frequency, (ii) time-varying cutoff frequency, (iii) time-varying power frequency, and (iv) multi-frequency. The interpretation of each of these analysis methods is compared and contrasted. The results demonstrate that analysis methods based on time-frequency representations can provide unique insight into handling qualities evaluations by quantifying the character of the pilot inputs. These methods may be used to supplement classical (i.e., subjective) techniques in providing added comprehension to assigned ratings.
Application of Linear Quadratic Estimation (LQE) to Harmonic Analysis of Rotorcraft Vibration
Authors:   Georgia Institute of Technology, Morgan Nathaniel , Berrigan Caitlin , Lopez Mark , Prasad J.V.R.
Published: October 2024

Accurate, real-time harmonic analysis of rotor hub loads is critical to successful implementation of higher harmonic blade control for active vibration reduction. Several methods for harmonic analysis are currently available in the literature but suffer from time delays associated with windowing or filtering. Application of linear quadratic estimation (LQE) as a harmonic analyzer in conjunction with a linear time invariant (LTI) dynamic system model with harmonic decomposition of linear time periodic (LTP) model states is shown to provide accurate estimation of N/rev harmonic load components with little to no time delay.
Characterization of Pilot Strategy for Simulated Shipboard Approaches with Realistic Ship Motion
Authors:   NAVAIR, Pritchard James ,   USNTPS, Tritschler John , Wallace Ryan , O'Connor John , Arteche David
Published: October 2024

The shipboard environment presents significant challenges to pilots' workload, in particular during the approach and land tasks. This research focuses on fixed-base, pilot-in-the-loop rotorcraft flight simulations to examine the workload and the available visual cueing of seven test pilots with extensive operational and test experience. This research separated the approach and landing task into distinct simulation runs to investigate and identify the characteristics of the individual handing qualities and parameters for each task. The approach task was flown to a stationary LHA while the landing task was flown to a moving DDG. Coupled with the landing task was the additional component of a position capture and hover maneuver within the simulation run. During the approach task to the LHA it was seen that the pilot experienced insufficient line up and deceleration cueing as they neared the ship. Separating the approach from the landing showed that one flight control response is not sufficient for the two different shipborne tasks. Pilot scan strategy is based on their preference to pick up visual cueing. During landing to a moving ship pilots use two separate reference frames to hover/land. Although scan strategies vary between pilots, line-up and positional visual cueing is paramount to complete the task.
Development of Advanced Flight Control Laws for the AH-64 Apache Helicopter - Sketches from the work of TU Delft-Boeing Project in SIMONA Simulator
Authors:   Delft University of Technology, Pavel Marilena ,   Boeing Mesa, Shanthakumaran Perumal ,   Royal Netherlands Air Force, Cazemier Harm , Stroosma Olaf , Chu Qiping , Wolfe Mike
Published: October 2024

A joint research project (2010-2014) between Delft University of Technology and Boeing Mesa was conducted in SIMONA Research Simulator (SRS) at Delft University with the goal to develop advanced flight control laws for handling qualities (HQs) improvements of the Apache AH-64 helicopter. The goal of the present paper is to concentrate on implementation and simulator testing of modern control laws for Apache's AH-64D Longbow helicopter to provide improved handling qualities for hover and low speed flight in degraded visual environment. The paper will implement an "Incremental Nonlinear Dynamic Inversion (INDI)" controller into the Boeing's FlyRT AH-64 Apache baseline model for the existing partial authority stability augmentation system (SAS). The INDI will be used to provide both attitude command attitude hold and translational rate command response types based on the requirements in ADS-33E. Implementation of the INDI into Apache's FlyRT proved to be challenging because the model was not affine in the control inputs. Actuator dynamics and rotor dynamics (most likely flapping dynamics) caused the designed INDI controller to overcontrol the helicopter. The paper proposes three adaptations of the INDI methodology that prove able to stabilize the helicopter and can be used as an alternative to a full authority, fly-bywire, control system upgrade. Handling qualities evaluations conducted in SIMONA simulator for the ADS-33 hover and pirouette maneuvers demonstrated that the INDI resulted in improving from Level 2 to Level 1 HQs, reducing the pilot workload when compared to the Apache's legacy flight control system.
A Model-Scale Wind-Tunnel Study of Main Rotor/Propeller Interference
Authors:   United Technologies Research Center, Bowles Patrick ,   University of Maryland, Berry Ben ,   Sikorsky Aircraft Corp., Bartz Emily , Matalanis Claude , Wake Brian , Scott Mark
Published: October 2024

A model-scale wind tunnel test was conducted to determine propulsive efficiency and relative vibration levels of a tail mounted propeller in the wake of a powered rotor and generic fuselage. Six-component propeller loads were measured for all test points with a focus on thrust and torque. Propeller and main rotor operating conditions were set to mimic low- and highspeed vehicle flight operations, simulating speeds from 105 kts to 200 kts. A total pressure wake survey conducted without the propeller installed was used to determine the propeller plane inflow characteristics. Propeller operation had no measureable effect on rotor trim whereas the main rotor states significantly altered the propeller performance. All propeller positions showed a propulsive efficiency increase relative to the isolated propeller data when operated in the rotor wake. No position showed noticeable vibration levels higher or lower than another. The highest propulsive efficiency was measured for the mid-height propeller position.
Narrowing of Attention and Functional Field of View for Helicopter Pilots in a Degraded Visual Environment
Authors:   Naval Air Systems Command, Geeseman Joseph
Published: October 2024

In an attempt to quantify the change in attentional allocation found during landing in degraded visual environments (DVE) for helicopter pilots, this study imposed a secondary visual task for pilots to complete while landing a simulated CH-53 helicopter. Pilots were tasked to identify visual cues as they appeared on the windscreen while they flew to a landing zone that had varying levels of DVE. It was found that pilots were less sensitive to the secondary visual task and slower to respond when landing in DVE conditions.
A New Acoustic Emission Signal Processing and Feature Extraction Approach for Bearing Fault diagnosis
Authors:   University of Illinois at Chicago, He Miao ,   Wuhan University of Technology, Qu Yongzhi ,   GPMS Inc., Bechhoefer Eric , He David
Published: October 2024

A new acoustic emission (AE) signal processing and feature extraction approach to bearing fault diagnosis is presented in this paper. The presented approach uses time-frequency manifold analysis to extract time-frequency manifold feature (TFMFs) from AE signals. It reconstructs a manifold by embedding AE signals into a high-dimensional phase space. The tangent direction of the neighborhood for each point is then used to approximate its local geometry. The variation of the manifolds representing different condition states of the bearing can be revealed by performing multi-way principal component analysis. The AE signals acquired from a bearing test rig are used to validate the presented approach. The test results have shown that the presented approach can interpret different bearing conditions and is effective for bearing fault diagnosis.
Respiratory syncytial virus: an overview of clinical manifestations and management in the Indian pediatric population
Authors: B J Abhishek , Swamy Agadi Hiremath Viswanatha , Nyamagoud Sanatkumar Bharamu , George Anupama , D Namratha
Published: October 2024

Respiratory syncytial virus (RSV) plays a major part in causing lower respiratory tract infections in younger populations, especially in infants and pediatric patients, causing a higher rate of morbidity and mortality in the respective population, affecting 60% of the population globally. Typically, identifying the virus in the patient's respiratory secretions is important for laboratory validation of a clinically suspected RSV infection. Unfortunately, the only available preventive measure to lower the incidence for infants who are at high risk of RSV-induced hospitalization is palivizumab prophylaxis. Treatment strategies to manage RSV involve using an antiviral drug that is Ribavirin along with bronchodilators, nebulized adrenaline (epinephrine), and nebulized hypertonic saline. Providing patients with alternative treatment options like vitamin D-cathelicidin as well as probiotics and prebiotics can help reduce the intensity of the infection. This review article focuses on the epidemiology, clinical manifestation, prophylaxis, and available treatment options for RSV infections in infants, children, and young adults.
Visual functions and anterior ocular surface changes post trans-PRK
Authors: Essa Mohammed Elnzeer H. , Moodley Vanessa R.
Published: October 2024

Background: Corneal refractive surgery is rapidly evolving, and several surgical techniques have been developed, including transepithelial photorefractive keratectomy (trans-PRK).Aim: To assess the impact of trans-PRK on visual acuity (VA), contrast sensitivity, spherical aberration, tear stability, corneal surface and thickness.Setting: The study was conducted in Saudia Arabia, Al Madinah Almunwrah, Eye Specialist Center.Methods: A quantitative, comparative, and prospective case study was conducted. Eighty-six consenting volunteers aged between 18 years and 40 years, including both genders, were enrolled in the study. Participants were grouped according to the time they presented after surgery. The Statistical Package for Social Sciences (SPSS) software version 27 (IBM Corporation) was used for descriptive and comparative data analysis by applying one-way analysis of variance (ANOVA) and paired t-tests.Results: There was a significant increase in contrast sensitivity (P  0.005) and VA, with the post-operative mean best corrected visual acuity (BCVA) being 0.00 Log MAR for all groups. Central corneal thickness (CCT) was significantly thinner (P = 0.000), and significant corneal flattening occurred (P  0.005) in all study groups. Spherical aberration improved significantly only in participants returning after 1 year (P = 0.000). Tear break-up time (TBUT) remained stable in all groups and tear volume decreased significantly in groups 1 (P = 0.000) and group 3 (P = 0.013) only.Conclusion: The trans-PRK improves VA and contrast sensitivity and causes significant thinning and flattening of the cornea. Although tear volume decreases after trans-PRK, the TBUT does not change and patients will experience improvement in spherical aberration only after 1-year post-surgery.Contribution: The study will benefit both clinicians and patients who intend to undergo trans-PRK, by providing information on expected post-surgical outcomes.
Refractive errors among schoolchildren in the Middle East: A systematic review and meta-analysis
Authors: Mohamed Zoelfigar D. , Ismail Galal M. , Alrasheed Saif H. , Vankudre Gopi S. , Noushad Babu , Ayyappan Janitha P.
Published: October 2024

Background: Refractive errors are the most prevalent ocular conditions among adolescents and children.Aim: The purpose of this systematic review and meta-analysis is to evaluate the prevalence of refractive error (RE) among children aged 5–17 years in the Middle East Region.Method: The research adhered to the Preferred Reporting Criteria for Systematic Reviews and Meta-Analyses (2020) in conducting the study. A comprehensive search for relevant studies was conducted on multiple databases. The analysed dataset was classified based on gender and the methods employed to estimate REs.Results: The meta-analysis included data from 38 population-based studies in 11 countries, covering 103 053 children. The overall pooled prevalence rates of myopia, hyperopia and astigmatism were 5.74%, 5.35% and 13.16%, respectively. Females had slightly higher prevalence rates at 7.25%, 5.54% and 15.50%, compared to males at 6.09%, 5.07% and 12.20%, respectively. The prevalence of myopia, hyperopia and astigmatism was higher with cycloplegic refraction at 6.33%, 6.36% and 14.39%, respectively, compared with non-cycloplegic refraction at 4.07%, 2.73% and 9.64%, respectively. Significant heterogeneity was observed between the reviewed studies (p  0.0001).Conclusion: This meta-analysis revealed that astigmatism was the most common RE in Middle Eastern children aged 5–17 years, followed by myopia and hyperopia. There was no significant difference in the pooled prevalence of RE between genders. The findings indicated that myopia, hyperopia and astigmatism measurements varied between cycloplegic and non-cycloplegic refractions.Contribution: These findings concur with the global trend and emphasise the need for deliberate action to address childhood REs in the Middle East.
Minimizing movements for forced anisotropic curvature flow of droplets
Authors: Kholmatov Shokhrukh
Published: October 2024

We study forced anisotropic curvature flow of droplets on an inhomogeneous horizontal hyperplane. As in Bellettini and Kholmatov [J. Math. Pures Appl. 117 (2018), 1–58], we establish the existence of smooth flow, starting from a regular droplet and satisfying the prescribed anisotropic Young’s law, and also the existence of a

1/2

-Hölder continuous in time minimizing movement solution starting from a set of finite perimeter. Furthermore, we investigate various properties of minimizing movements, including comparison principles, uniform boundedness, and the consistency with the smooth flow.
Characterization of MatK and RuBisCO Genes within the Population of Chrysophyllum albidum (G. Don) in Akure Forest Reserve, Ondo State, Nigeria
Authors: A. Lawal , F.A Sale , J.C Arogundade,
Published: October 2024

Genetic diversity study of tree species is important because it gives species a better chance ofsurvival in the face of climate change. This study investigated the genetic diversity within thepopulation of Chrysophyllum albidum in Queen’s plot, Akure forest reserve, Ondo State,Nigeria using MatK and RuBisCO genes. Trees of Chrysophyllum albidum were identified, counted, their coordinates and diameters at breast height were recorded. Foliar samples from each tree were collected, cleaned and stored in a sealed nylon containing silica gel as dehydrating agent. Geno-mic DNA was extracted using Cetyltrimethyl ammonium bromide (CTAB). Polymerase Chain Reaction (PCR) was performed in a volume of 25μl in a DNA thermal cycler. PCR products were evaluated using Brilliant Dye™ Terminator Cycle Sequencing Kit and sequence data were analyzed using BIOEDIT and MEGA X software. The number of Chrysophyllum albidum (32 trees/ha) found in Queen’s plot was two times more than what was recorded in the previous studies. Chrysophyllum albidum trees were found in all the diameter classes. This indicates that this species has good regeneration status. The phylogram, constructed using RuBisCO and MatK genes for the sampled Chrysophyllum albidum trees, revealed the intra-specific variation of this species in Queen’s plot. The information provided in this study could be used to breed Chrysophyllum albidum with superior characteristics. Therefore, serious conservation efforts should be implemented and sustained to avert any loss of the identified genetic diversity.
Biometric indices of Clarias gariepinus and Oreochromis niloticus in selected Gongola river corridors in Gombe State, Nigeria
Authors: A. N Garkuwa , K. A Abu , J Ali , Z Isa , A.Z Umar
Published: October 2024

The length-weight relationship and organosomatic indices, are useful metric for detecting chronic stress in fish within aquatic ecosystems. The biometric indices of Clarias gariepinus and Oreochromis niloticus collected from the Gongola river corridors in Gombe State were investigated. Fish weight, standard and total length, the weight of the liver, spleen and gonads were all measured and record. Moreover, Fulton condition index, Hepatosomatic index (HSI), splenosomatic index (SSI) and gonadosomatic index (GSI) were calculated using standardmethods. All the mean concentrations obtained in the reference dam had condition factor <1 and this may be attributed to the over exploitation of the large size fish species of C.gariepinus and O. niloticus because of the high clarity of the water. Most fish samples collected from Gwani were found to be in good healthy stage. The highest HSI mean value was 0.98±0.82% indicating that these specimens from all the study areas were all < 1 because the study species were under stress due to high amount of rainfall in wet season. 2.47±4.04% was the highest GSI mean concentration of O. niloticus found in dry season at Gwani sampling locations showing elevation in body weight. This study also recorded low SSI mean values of 0.05±0.03% (0.05%) and 0.07±0.12% (0.07%) in O. niloticus and C. gariepinus at Balanga (the reference) dam and the variations in the morphology of spleen between species may be responsible for the low values of SSI. There were slight changes the biometric condition which may result from the stress conditions, suggesting a more comprehensive health assessment index in future research of the sampling sites.
Prevalence of Invasive Plant Species, Its Effects on Biodiversity Conservation, Challenges and Opportunities for Management in Africa: A Review
Authors: E. U Uzomachukwu , I. O Kehinde , M. Mahama , M. O Hamzat
Published: October 2024

Invasive alien plant species are identified as plants that have been purposefully or unintentio-nally introduced to areas outside of their natural habitat. Invasive Plant Species (IPSs) are one of the biggest risks to ecosystem function and world biodiversity. In Africa, invasive plant species are a source of concern, as they can displace native flora and fauna, alter ecosystem structure and function, and threaten the livelihoods of millions of people who rely on natural resources for their survival. Conservation is essential to preserve Africa's unique biodiversity and guarantee the sustainable use of its natural resources. An analysis of the various literature is necessary to understand the presence of invasive plant species in Africa, their effects on conservation efforts, and to identify relevant information gaps. Wer eviewed 113 articles pub- lished from 2000 to 2023 covering the invasiveness of plants in different African countries, their effects, and ways to manage and conserve biodiversity. IPSsonce established can spread rapidly and outcompete native plant species, leading tosignificant changes in the composition and structure of ecosystems. Different methods havebeen employed in the management and control of IPSs, which include the use of chemicals,mechanical and biological control. This paper reviewed the challenges and opportunities inmanaging invasive species in Africa and came up with recommendations and calls to actionfor effective management and control of invasive species. Preventing the introduction of newand potentially invasive taxa is a critical component of any IPSs management approach. Alarge number of African countries lack policies and regulations to prevent and control IPSs,this is a call for immediate action to be taken. Utilization of IPSs is also highly recommendedfor African countries that are yet to participate in this process, this could be a turning point inthe struggle for control and management of IPSs.
Analysis of Seedling Root Architecture of Vigna unguiculata (Sampea 1-20) Using Cigar-Roll Method under Controlled Condition
Authors: I Ossai , S. E Okonkwo , S. S Indabo , H. O Ahmed , A Aliyu , M. U Muhammad , S. K Sakariyahu , R. E Aliyu , B. M Saba
Published: October 2024

Cowpea (Vigna unguiculata) varieties, including the improved SAMPEA series in Nigeria, remain crucial for food security, particularly in sub-Saharan Africa. However, their yields are constrained by edaphic stresses such as low phosphorus (P) and drought. Phenotyping cowpea seedling root architecture using the cigar-roll method is crucial for identifying root phenes needed for breeding phosphorus-efficient and drought-tolerant varieties. This study evaluated the Root System Architecture (RSA) of 20 elite cowpea genotypes (SAMPEA 1 to 20) obtained from the Institute for Agricultural Research (IAR), Ahmadu Bello University, Zaria, using the cigar-roll method. Significant (p<0.05) phenotypic variation was detected for all phones evaluated. Significant variation was observed in architectural traits, including primary root length and lateral root density in the first 5cm of the root. Root hair length and density were positively associated with lateral root density in both the first 5cm from the base of the hypocotyl and the lateral roots between 5 and 10 cm from the base of the hypocotyl. Genotypes with longer root hairs (SAMPEA 14, 20, 12 and 13) and a longer taproot (SAMPEA 10) were identified as potential parents for breeding. The identified phenes could guide in breeding efforts for cowpea varieties suited to low phosphorus and water-limiting soils. Our results suggest that the root phenotype plays an important role in cowpea growth in suboptimal environments and can serve as a marker to facilitate the development of improved varieties with enhanced yield, particularly in sub-Saharan Africa, where soils with low phosphorus and drought are predominant.
Toxicity Assessment Of Challawa Industrial Effluent On African Catfish (Clarias gariepinus, Burchell, 1822) In Kano, Nigeria
Authors: S. Ibrahim , S. A Nafi'u , A. I Dennis
Published: October 2024

Industrial effluents contaminate water bodies and harm aquatic biota. In this study, industrial effluent was collected from Challawa Industrial Area, Kano State and analyzed for physico-chemical conditions, heavy metals concentrations and impact on the survival of juveniles of Clarias gariepinus under standard laboratory conditions, using Completely Randomized Design (CRD) with three treatments (0.00ml/L, 5ml/L and 10ml/L) in three replicates. Test fish with a mean weight of 183.2g and a mean length of 24.1cm were purchased from Kano State Ministry of Agriculture and Mineral Resources, Department of Fishery and Aquaculture, Fisheries Unit and acclimated in 100L tank for 14 days. The test fish exhibited abnormal respiratory action, opercular movement, body movement and mucus secretion with increase in the concentrations of the effluent. The mean values of DO (2.59±0.05mg/L), temperature (29.0±0.10°C) and pH (10.28±0.00) varied slightly between the control and the effluent. The mean values for Turbidity, Total alkalinity, TDS, Electrical conductivity and Chloride were beyond FAO/WHO (2018) recommended limit with exception of temperature. Heavy metals concentration in the effluent was: Pb > Cu > Fe > Zn > Cd > Mn > Cr and decreased in gill and liver tissues (Fe > Zn > Cu > Mn > Pb > Cr > Cd). Exposure to varying concentrations of the effluents caused toxicity signs, death and considerable damage to tissues of C. gariepinus during the study period. The study recommends that regulatory bodies should adopt holistic approach on aquatic pollution abatement, due to its negative impact to non-target organisms.
Contribution of the informal market of village chickens to sustainable livelihoods in KwaZulu-Natal, South Africa
Authors: Thando Tenza  , Lindokuhle Christopher Mhlongo  , Cypril Ndumiso Ncobela  , Zikhona Rani
Published: October 2024

The study aimed to determine the contribution of the informal market of village chickens to sustainable livelihoods. The study was conducted in two purposively selected cities, namely Durban and Pietermaritzburg, KwaZulu-Natal, South Africa, Central Business District (CBD). A questionnaire was administered to village chicken vendors in the CBD.A total of 50 village chicken vendors, which were limited in the CBD, were found and interviewed. In both Durban (100%) and Pietermaritzburg (77%), the majority of village chicken vendors were women (P<0.05). Village chicken vendors depended on selling chickens and vending other commodities in both cities (P > 0.05) to generate income (100%). None (0 %) of the village chicken vendors were exposed to chicken farming training on village chickens in Durban and 11% in Pietermaritzburg have been exposed to training (P<0.05). Over 85% were interested in attending chicken farming training in both areas. There was a significant difference (P<0.05) between the main source of income and the uses of chickens. The use of village chickens influenced the main source of income, which was not limited to income generation or leisure. It was concluded that the informal market for village chickens contributes to sustaining livelihoods through income, consumption, and cultural drive. It is recommended that access to training and resources can grow the informal market.
Length-based estimates of growth parameters and mortality rates of Nile Tilapia (Oreochromis niloticus, L. 1758) in Lake Abaya, Southern Ethiopia
Authors: Buchale Shishitu Shija
Published: October 2024

The Nile tilapia, Oreochromis niloticus, is one of the most commercially important fish species in Ethiopia. Effective management is essential to sustaining their fisheries and providing benefits for the local communities. The study was aimed at determining the basic population characteristics (growth, mortality rates, and recruitment), size at first maturity, length at first capture, and stock status of O. niloticus in Lake Abaya. These basic quantitative population characteristics enable a fisheries manager to identify population changes resulting from fishing. The parameters were determined using length frequency data collected from 4089 samples of O. niloticus ranging from 23 to 47 cm in total length. The total length (TL) and total weight (TW) of O. niloticus samples were gathered between September 2021 and August 2022. The length-weight relationship parameters were (TW = 0.0157TL3.0192, R2 = 0.9603) and the condition factor K=1.69. The population parameters were determined using the ELEFAN I routine in FiSAT software. Estimated von Bertalanffy growth parameters were (L∞) = 49.35 cm, growth curvature (k) = 0.36 yr-1, age at length zero (to) = -0.40, and growth performance index (Փ') = 3.0.The estimated values of total natural and fishing mortalities were Z= 1.34 yr-1, M =0.34 yr-1,and F= 1.0 yr-1, respectively. The current exploitation rate (E) was 0.74, which is higher than the optimal (E = 0.5) and indicates that O. niloticus in Lake Abaya was overexploited. In order to maintain the sustainability of the fish population, it is advised that the local authorities establish regulations for the management of O. noloticus in Lake Abaya. These regulations should include protecting the use of small fishing gear and safeguarding fish that are caught smaller than their length at first maturity.
The East and Central African Journal of Surgery: A Narrative of Four Decades at the Forefront of Fostering Surgical Research in Africa
Authors: Kipkorir Vincent , Philipo Godfrey , Mwachiro Michael , Parker Robert K , Kazuma Seke , Itungu Stella , Bekele Abebe
Published: October 2024

This year, The East and Central African Journal of Surgery (ECAJS) celebrates 29 years as a peer-reviewed international journal and 46 years since its inception as the official proceedings of the Association of Surgeons of East Africa (ASEA). ECAJS, a quarterly, open-access publication of the College of Surgeons of East, Central, and Southern Africa (COSECSA), aims to advance the science of surgery and surgical care while facilitating the exchange of ideas among surgeons and surgical care researchers in COSECSA member countries. The journal is indexed in several databases, including African Journals Online (AJOL), Bioline International, Crossref, ROAD, Global Health, CAB Abstracts, FATCAT, ZDB, Wikidata, SUDOC, and OPENALEX.