bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of Prototype of Two Axis Gimbal-Type Platform in Underwater
Authors: Park Hoonmin , Lee Hyunjae , Ryu Hongryul , Kim Dongho , Kim Hyunsoo , Park Hyesoo , Lee Sangryong , Yi Hak
Published: February 2021

The Bottom-mounted ocean-observation platforms installed on the seabed have been used for marine environment analysis. The role of the observing platform is to collect precise observation data without human assistance. However, their working environment is very harsh so the typical device could not afford to provide easy accessibility during their working period. Existing bottom-mounted ocean-observation platforms have been difficult to collect continuous observation data. Therefore, this paper suggests a new ocean-observation platform for precise measurement of the marine environment. Suggested platform uses a PID control method to be applied for error compensation of each axis of gimbal. To verify the system performance, the experiment was carried out in the air with the external force applied to this system.
Aerodynamic and Vibration Analysis of the Morphing Wings of a Hypersonic Vehicle
Authors: Pulok Mohammad Khairul Habib , Chakravarty Uttam K.
Published: February 2021

Hypersonic vehicles are receiving great attention in recent years due to their high speed and long-range capabilities. The shock waves come into consideration as a propagating disturbance for any aircraft when it exceeds the speed of sound. Complex environment and flight requirements of the hypersonic vehicles are leading the researchers to focus on several design considerations. Adaptive shape deformation is one of the prospective areas among them which has an impact on thermal loading, global and local load factors, vehicle acceleration, total energy dissipation, and fuel consumption. The wings play a key role in the aerodynamic performances of a flying machine; therefore, the overall performance of the hypersonic vehicle can be improved by applying morphing technologies on the wing. Morphing can help with reducing wave drag, increasing lift-to-drag ratio as well as enhancing flight endurance, and extending the range for a hypersonic vehicle. In this study, the telescopic wing morphing profile is considered for the aerodynamics and vibration analysis. The experimental validations of the aerodynamics and vibration characteristics are conducted by a wind-tunnel experiment and a vibration-testing arrangement, respectively, using a small-scale model of the wing. The computational analysis of the aerodynamics and vibration characteristics of the morphing wings are conducted and compared. Thus, a comprehensive study including the comparison between morphing modes can establish a standard to choose the appropriate morphing technique for the hypersonic vehicles.
Forming Canonical 8D Data Clouds to Explore the Transient Dynamics of Physical Stiffened Plates: A Machine Learning Approach for Complex Mechanical Structures
Authors: Georgiou Ioannis T.
Published: February 2021

This work presents a data-driven explorative study of the physics of the dynamics of a physical structure of complicated geometry. The geometric complexity of the physical system renders the typical single sensor acceleration signal quite complicated for a physics interpretation. We need the spatial dimension to resolve the single sensory signal over its entire time horizon. Thus we are introducing the spatial dimension by the canonical eight-dimensional data cloud (Canonical 8D-Data Cloud) concept to build methods to explore the impact-induced free dynamics of physical complex mechanical structures. The complex structure in this study is a large scale aluminum alloy plate stiffened by a frame made of T-section beams. The Canonical 8D-Data Cloud is identified with the simultaneous acceleration measurements by eight piezoelectric sensors equally spaced and attached on the periphery of a circular material curve drawn on the uniform surface of the stiffened plate. The Data Cloud approach leads to a systematic exploration-discovery-quantification of uncertainty in this physical complex structure. It is found that considerable uncertainty is stemming from the sensitivity of transient dynamics on the parameters of space-time localized force pulses, the latter being used as a means to diagnose the presence of structural anomalies. The Data Cloud approach leads to aspects of machine learning such as reduced dynamics analytics of big sensory data by means of heavenly machine-assisted computations to carry out the unparalleled data reduction analysis enabled by the Advanced Proper Orthogonal Decomposition Transform. Emphasized is the connection between the characteristic geometric features of high-dimensional datasets as a whole, the Data Cloud, and the modal physics of the dynamics.
Data-Driven Methods for Detecting Traffic Jams in Vehicular Traffic Systems
Authors: Ghadami Amin , Doering Charles R. , Epureanu Bogdan I.
Published: February 2021

Ground vehicle traffic jams are a serious issue in today’s society. Despite advances in traffic flow management in recent years, predicting traffic jams is still a challenge. Recently, novel techniques have been developed in complex systems theory to enable forecasting emergent behaviors in dynamical systems. Forecasting methods have been developed based on exploiting the phenomenon of critical slowing down, which occurs in dynamical systems near certain types of bifurcations and phase transitions. Herein, we explore recently developed tools of tipping point forecasting in complex systems, namely early warning indicators and bifurcation forecasting methods, and investigate their application to predict traffic jams on roads. The measurements required for forecasting are recorded dynamical features of the system such as headways between cars in traffic or density of cars on road. Forecasting approaches are applied to simulated and experimental traffic flow conditions. Results show that one can successfully predict proximity to the critical point of congestion as well as traffic dynamics after this critical point using the proposed approaches. The methodologies presented can be used to analyze stability of traffic models and address challenges related to the complexity of traffic dynamics.
Teaching Creativity As a Method to Overcome Limitations in Design for Additive Manufacturing
Authors: Chekurov Sergei
Published: February 2021

This paper describes the challenges and solutions of modifying a normally contact-reliant Design for Additive Manufacturing teaching approach in view of the COVID-19 outbreak. The approach has been put into practice since 2014 in the form of a student assignment that does not provide a specific functional objective but asks students to invent a unique geometry that demonstrates the capabilities of additive manufacturing and manufacture it with an entry level material extrusion machine.

The students are asked to use their imaginations to develop an intricate geometry without first considering technical limitations of additive manufacturing. They are then asked to identify the issues with their designs and solve them, while modifying their original vision as little as possible. The goal of the approach is to teach students to identify the limitations of additive manufacturing and to overcome them with creativity when possible.

As physical iterative testing using an additive manufacturing machine is essential to the assignment, the outbreak of COVID-19 had a major influence on it. The paper describes how the assignment was adjusted in the spring of 2020 to meet the challenges of not being able to conduct contact teaching. Although the presented exceptional measures should be avoided as the primary way to educate students, they are shown to facilitate teaching Design for Additive Manufacturing with no access to machines. Notable designs developed by students in 2020 are provided as examples of the generated results.
Optimization of Plunger Injection Input for Die Casting Process
Authors: Qi Song , Takagi Yuto , Yano Ken'ichi , Kondo Tadao , Murakami Naoto , Ishikawa Takao
Published: February 2021

Die casting is adequate for mass production and has the advantage of being able to yield a complicated shape accurately. However, casting defects caused by plunger movement remain a problem. Velocity control of the plunger is very effective to avoid casting defects. Velocity control input is manually conducted by skilled workers because the analysis of molten metal is very difficult, and injection molding is performed at places in the mold where it is invisible. In this paper, Quid behavior and the amount of air entrainment caused by the movement of the die casting plunger are analyzed using computational Quid dynamics (CFD). The optimum velocity control input of the die casting plunger was calculated in order to reduce air entrainment and molten metal forerunning to prevent the occurrence of defects in the die casting product. Optimization was performed by a Genetic algorithm incorporating CFD simulator.
Development and Evaluation of an Infrared Heating System for Die Preheating
Authors: Maldonado Luis , Shi Carl , Vian Corey , Ostanek Jason
Published: February 2021

In this study, a high power infrared heater was implemented to preheat an H13 steel die used for high pressure die casting. The performance of the heating system was quantified experimentally by measuring die temperatures in various locations with embedded thermocouples. Heating time was reduced significantly by using a flat, stainless-steel reflector on one side of the heater. A numerical model was developed to simulate the infrared radiation heat transfer into the die. The model was validated against literature data and experimental results. The model was then used to evaluate different lamp configurations to obtain a more uniform heating distribution and to avoid hot spots on protruding surfaces. The validated model has proven to be useful in evaluating different lamp configurations tailored for specific die geometries or heating requirements.
Passive Impedance-Loaded Surface Acoustic Wave (SAW) Sensor for Soil Condition Monitoring
Authors: Chu Jian , Voiculescu Ioana , Dong Ziqian , Li Fang
Published: February 2021

This paper presents an innovative system to monitor the physical soil conditions needed for modern agriculture. The current technique to measure soil properties relies on taking samples from place to place and takes them for laboratory testing. To build up and monitor a data-based system for a large area, such a method is costly and time-consuming. This paper reported our recent work on the development of a passive impedance-loaded surface acoustic wave (SAW) sensor for a low-cost soil condition monitoring system. The SAW sensor will eventually be connected to an antenna and a impedance-based sensor for autonomous soil nutrient sensing. In this research, first, the coupling-of-modes (COM) analysis was performed to simulate the SAW device. The sensors were fabricated with E-beam lithography techniques and tested with different external load resistances. We investigated how the sensor signal changed with the external resistance loading. The experimental results were verified by comparing them with simulation results.
Biomechanical Analyses of Professional Ultramarathon Athletes: The Effect of Repeated Long Distances on the Gait Kinematic and Kinetics
Authors: Fontanili Luca , Milani Massimo , Montorsi Luca , Citarella Roberto
Published: February 2021

Constant monitoring of an athlete allows to foresee any injuries by acting on the dynamics of the movements. For runners, the conduct of a correct athletic gesture according to the athlete’s specific body biomechanics guarantees the minimization of non-accidental injury factors. For athletes who are engaged in endurance sports such as marathon runners, the long distances to which they are subjected increases the importance of this type of monitoring. This work reports the results of a study carried out on three IUTA (Italian Ultramarathon and Trail Association) athletes during a routine check carried out at a reference healthcare facility that takes care of their care. These athletes are all specialized in the 24-hour race in which they try to reach the most distance in this time. This type of effort can be made if the athlete undergoes an adequate training regime over long distances. The execution of the running pattern in such a repeated way can lead to the accentuation of postural and joint problems. It is therefore necessary to monitor the biomechanics parameters.

In this work, therefore, various gestures are analyzed to show potential movement deficits in order to act in advance on the running technique.
Multitier Digital Twin Approach for Agile Supply Chain Management
Authors: Shevtshenko Eduard , Mahmood Kashif , Karaulova Tatyana , Raji Ibrahim Oluwole
Published: February 2021

Multitier Digital Twin approach for agile supply chain management validated in the research lab. In the long run, the solution will ultimately help to reduce resources costs in production processes and throughput time of the supply chain. The Digital Twin approach can be applied in the manufacturing company and the supply chain and makes recommendations for making changes to the physical environment to meet the requirements of various specific orders. The Multitier Digital Twin approach is validated by modelling four tiers of Small and Medium Enterprise (SME) company: business processes, operations workflow processes and work cells operations. The simulation study is performed to evaluate the achieved results. The guidelines are developed to connect and integrate business process tier models with operations workflow and work cell tiers models. The authors defend that the current research will help to create new digital solutions to increase manufacturing flexibility by moving toward the company’s strategic goals directly from the offer preparation stage. The authors have validated the Digital Twin approach for agile supply chain management in the fields of manufacturing. Nevertheless, the proposed approach is adaptable to other fields also, whereas the focal player or project owner selects the best KPIs that support the implementation of the chosen strategy. The paper includes a feasibility case study for the approval of findings, where small and medium enterprise (SMEs) from the manufacturing field business processes are connected to manufacturing processes and work cell models to achieve a common strategic goal of the company.
Early Assessment of Posture Disorders Through Pre-Adolescent Monitoring: The Case of Volley Academy Modena
Authors: Fontanili Luca , Milani Massimo , Montorsi Luca , Citarella Roberto
Published: February 2021

The pre-adolescent age is basic in the beginning of the development of body kinematics. During this age the body structure needs to continuously search for stabilization due to the modification in body segment lengths. This behavior can evolve into incorrect postural attitudes that, if not properly treated, can lead to behaviors that are difficult to recover with advancing age. These incorrect attitudes require an accurate and early diagnosis that can be put in place by expert doctors and clinicians.

As well known, sporting activity in this age can help the development of proprioceptive apparatus and the musculoskeletal one. Volleyball is considered a complete sport thanks to the wide range of actions necessary for a match. Following this evaluation, it was decided to carry out a monitoring study of young volleyball players in what is one of the capitals of Italian volleyball, i.e. Modena.

To achieve this objective, in this work, 97 female volleyball players have been analyzed during their adolescent and pre-adolescent age. The study has the objective to collect data and design an exercise routine for the training to prevent postural problems. Finally, the data have been analyzed and the most representative ones have been reported in this paper.
Effect of Process Parameters on Friction Stir Lap Welded 304 Stainless Steel and 5052 Aluminium Alloys
Authors: Chitturi Veerendra , Pedapati Srinivasa Rao , Awang Mokhtar
Published: February 2021

Joining of two different materials like aluminium and steel is a challenging task because of the vast differences in their physical, mechanical and chemical properties. Friction stir welding is a solid-state joining technique which is successful in joining dissimilar materials. In this study, the tool made with Tungsten-Rhenium with a pin length of 4.1 mm is used to weld 4 mm stainless steel and 2 mm aluminium plates in lap configuration with steel as the top plate. The process parameters used in the study are tool rotational speeds between 800 rpm and 1200 rpm, traverse speed ranging from 20 mm/min to 40 mm/min, penetration depth of 4.1 mm to 4.3 mm with a varying tilt between from 0° and 2.5°. The Aluminium is melted during the process because of the high temperature and is thrown out in the form of flash resulting in the formation of defects and a cup like structure at the weld zone. Microstructural analysis confirmed that formation of a sound joint without defects was impossible. The mechanically stirred zone consists of a thin intermetallic layer at the interface of aluminium and steel plates. The thickness of the intermetallic layers formed were between 5 μm and 20 μm. The maximum shear strength of 2.7 kN was achieved with tool rotational speed of 1000 rpm, penetration depth of 4.3 mm and welding speed of 30 mm/min when the angle was tilted at 0°. It is evident from the experiments that the joints achieved were not defect free because of improper mixing of the material.
A Kinematic-Based Unmarked Augmented Reality Method for Large Scene Industrial Workshops
Authors: Ma Zhen , Xu He
Published: February 2021

In the present study, a mobile camera positioning method based on kinematics of robot is proposed, capable of achieving far point positioning of imaging position and attitude tracking in large-scene enhancement. Orbit precision motion via the framework overhead cameras and combined with the ground system of sensor array object (e.g., mobile robot platform of various sensors) is capable of achieving the effective 3D image registration, solving any artifact that refers to a mobile robot in large-space position initialization, as well as effectively implementing the large-space no marks augmented reality, human-computer interaction and information summary. Lastly, the feasibility of the method is verified experimentally.
Adequate Lubrication As the First (and Often Only) Line of Defense Against Dust Explosions in Grain Elevators
Authors: Ramirez Juan C. , Aljazireh Kamal , Lane James F.
Published: February 2021

Finely divided solid materials (e.g., dusts and fines), when dispersed in the air, can fuel particularly violent and destructive explosions. In this paper we will discuss a case study involving a dust explosion in a grain elevator and how a careful bearing greasing policy could have avoided it.

We present the most common conditions that lead to bearing overheating which can serve as the ignition source for a dust explosion. Additionally, we stress the need to raise awareness among operators about the wide variety of greases available, and given this wide variety, it is critical for facilities to ensure they use a grease with characteristics as close as possible as these recommended by the equipment manufacturer.
Development of Critical Heat Flux Correlation in Circular Pipe Sections With Vertically Downward Two-Phase Flows by Numerical Analysis and Comparison With Experimental Correlation
Authors: Sripada Rajeshwar , Veeredhi Vasudeva Rao , Mendu Siva Subrahmanyam
Published: February 2021

Critical heat flux (CHF) and premature tube burnout are the common failure modes observed in steam water two-phase flows. Unlike the vertically upward two-phase flows, the vertically downward two-phase flows pose significant challenges including two-phase flow instabilities and premature tube burnout arising due to competing behavior between the buoyancy effects on vapor bubble and momentum and gravitational force acting on the liquid. Experimental investigations were conducted previously to understand the CHF at atmospheric pressures. There were very limited number of numerical analysis conducted in vertically downward flows using commercially available software and at such low-pressure conditions. In the current investigations, numerical simulations were carried with commercially available computational fluid dynamics software Fluent for vertically downward two-phase flows up to pressures of 5 bar. The magnitude of CHF from numerical investigations was compared with the experimental results conducted in house up to 5 bar and including the sub-cooling effects. The numerical results tend to agree with the experimental data at lower flow rates and at all pressures considered, but tend to deviate significantly at higher flow rates and at all pressures. Finally, A CHF correlation is proposed as a function of mass flux, inlet temperature and pressure. The proposed CHF correlations fits in with an average deviation of 16% and a standard deviation of 21%.
3D Printed Cellular Structure Materials Under Impact and Compressive Loading
Authors: Ardebili Mahmoud K. , Ikikardaslar Kerim Tuna , Ehrnfeld Colt , Delale Feridun
Published: February 2021

Advances in field of lattice structure design has become possible mainly due to the emerging capabilities of additive manufacturing (AM) or 3D printing. Lattices have the potential to reduce solid volumes, giving advantages such as weight reduction, decreased part production cost and ability to absorb energy under compressive and impact loading. These materials are anisotropic due to structural geometry and the additive nature of 3D-printed layers, which stack mainly in Normal or Lateral direction to the applied load. In this study 3D printed materials were fabricated that are nearly isotropic and are also lighter than base material. The lattice structure was formed using strut-based cell topologies that are adjoined as tetrahedrons. Two different tetrahedron density specimens were produced with Acrylonitrile Butadiene Styrene (ABS) using a Fusion Deposition Modelling (FDM) printer. The fabricated specimens were then tested for impact and compression capabilities. For comparison purposes, solid specimens with the same overall dimensions and highest infill ratio were also produced and tested. After compression and impact testing, results indicated that solid specimens’ impact energy absorption is higher with lateral stacking order relative to load, and compression resistance is higher for normal stacking order. The tetrahedron-filled specimens exhibited minimal stacking directional dependency and the higher count tetrahedron specimens provided more impact energy absorption and more resistance to compression than the lower count one. The normalization of specimens with respect to their weight indicated high density tetrahedron specimens’ impact energy absorption is nearly equal to that of solid specimens’. These results are initial steps in creating lattice structured materials that are isotropic, lighter and stronger than the base material.
Particle Transport Coefficient (PTC) and Phase-Efficiency Diagram: A New Perspective to Evaluate Three-Phase Particle-Laden Flow
Authors: Zhang Zhifeng , Pruvot Antoine Jean-Claude Jacques , Cisternas Pablo , McAndrew James
Published: February 2021

Many technologies have been developed to improve the ability of fluids to transport particles. However, the evaluation of particle transport efficiency remains challenging, especially in complex flow such as three-phase flow. In the present research, theoretical and experimental work is conducted to develop a new perspective of evaluating particle transport technologies, particle transport coefficient (PTC) as the particle transport distance per unit volume of water consumption considering the transport efficiency and environmental cost. The mathematical form of the PTC for the steady-state transport case is derived, followed by three special transport cases: (a) PTC = 0 when particle settled or stuck, (b) PTC = infinity in the vertical direction, considering gravity or buoyant with carrier fluid stationary, while PTC = 0 in a horizontal pipe due to particle settlement; and (c) PTC = 2 for an infinitely small particle at the center of a fully-developed laminar flow in a pipe. Furthermore, the fluid property and surface property influence on PTC are experimentally demonstrated. We believe the proposed approach can promote the development of particle transport technologies.
Automated Drilling of High Aspect Ratio, Small Diameter Holes in Remote, Confined Spaces
Authors: Rittikaidachar Michal , Hobart Clint , Slightam Jonathon E. , Su Jiann-Cherng , Buerger Stephen P.
Published: February 2021

We describe the development and benchtop prototype performance characterization of a mechatronic system for automatically drilling small diameter holes of arbitrary depth, to enable monitoring the integrity of oil and gas wells in situ. The precise drilling of very small diameter, high aspect ratio holes, particularly in dimensionally constrained spaces, presents several challenges including bit buckling, limited torsional stiffness, chip clearing, and limited space for the bit and mechanism. We describe a compact mechanism that overcomes these issues by minimizing the unsupported drill bit length throughout the process, enabling the bit to be progressively fed from a chuck as depth increases. When used with flexible drill bits, holes of arbitrary depth and aspect ratio may be drilled orthogonal to the wellbore. The mechanism and a conventional drilling system are tested in deep hole drilling operation. The experimental results show that the system operates as intended and achieves holes with substantially greater aspect ratios than conventional methods with very long drill bits. The mechanism enabled successful drilling of a 1/16″ diameter hole to a depth of 9″, a ratio of 144:1. Dysfunctions prevented drilling of the same hole using conventional methods.
PEM Fuel Cell Electrodes Surface Defects Impact on the System Performance
Authors: Fontalvo Victor M. , Illera Danny , Sanjuan Marco E. , Gomez Humberto A.
Published: February 2021

Fuel cell system manufacturing process is not a defect-free process, therefore, the impact of typical defects in the electrodes (i.e. Gas Diffusion Layer (GDL)) surface has to be taken into consideration when the fuel cell system is being designed. To assess the impact of the defect on the performance, two approaches were taken into consideration. Initially, the fuel cell system was simulated using a unidimensional (1D) dynamic model which took into consideration mass transfer, heat transfer, and electrochemical phenomena. The second approach was experimental, using a 5 sq.cm PEM fuel cell, the impact of the GDL porosity on the fuel cell system was studied. Also, the system response under different load changes was investigated. After that, experimental results are presented to give a better insight into the phenomena analyzed, mainly on the dynamic system response.

Cracks and catalyst clusters were the main defects analyzed, both of them were observed in new membranes assemblies. To control the defects, new membranes assemblies were tested, and after that, defects were induced using Nafion solution and catalyst powder to emulate the presence of catalyst clusters. For the cracks, some fibers in the GDL cloth were cut to emulate the defect. Membranes now with defects were tested again to compare its performance and detect any performance loss due to the physical changes in the electrodes.

Results indicate a strong correlation between the porosity and the supply air pressure and the system time constants. Also, the impact of the defects was evidenced in the dynamic system response, after step changes in the operating conditions.
Acoustic Metamaterial With Air-Backed Diaphragm for Broadband Absorption: A Preliminary Study
Authors: Dong Qian , Song Xiaolei , Ray Subhrodeep , Liu Haijun
Published: February 2021

Membrane-based acoustic metamaterials have been reported to achieve 100% absorption, the acoustic analogue of photonic black-hole. However, the bandwidth is usually very narrow around some local resonance frequency, which limits its practical use. To address this limitation and achieve a broadband absorption, this paper first establishes a theoretical framework for unit cells of air-backed diaphragms, modeled as an equivalent mass-spring-dashpot system. Based on the impedance match principle, three different approaches are numerically investigated by tuning the cavity length, the static pressure in the cavity, and the effective damping of perforated plates. A prototype with polyimide diaphragm and 3D printed substrate is then fabricated and characterized using an acoustic impedance tube. Preliminary experiments show the feasibility to achieve an absorption bandwidth of ∼200 Hz at center frequency of 1.45 kHz. This work pays the way for developing a sub-wavelength light weight broadband acoustic absorber for a variety of applications in noise control.
Design of Omnidirectional Robot Using Hybrid Brain Computer Interface
Authors: Ghoslin Bryan , Nandikolla Vidya K.
Published: February 2021

The paper presents a Brain-Computer Interface (BCI) controller for a semiautonomous three-wheeled omnidirectional robot capable of processing real-time commands. The kinematical model of the omni-directional robot and the software architecture of the overall hybrid system with motion control algorithm are presented. The system design, acquisition of the electroencephalography (EEG) signal, recognition processing technology and implementation are the main focus. Signals are recorded and processed by a program called OpenVibe. Preprocessed signals are cleaned by EEGLAB and used to train OpenVibe classifiers to accurately identify the expected signals produced by the users. Once identified, the controller converts the signal into input commands {forward, left, right, rotate, stop}, which are written in the Python syntax and delivered to the robot system. The robot has three degrees of freedom (DoF) allowing it to traverse its environment in any direction and orientation. The sensor system provides feedback allowing for the semi-autonomous control to avoid obstacles. Overall, this paper demonstrates the architecture of the hybrid control system for omni-directional robot using BCI. The developed system integrates the EEG signal to control the motion of the robot and the experimental results show the system performance and effectiveness of possessing the user’s EEG signals.
Hydrokinetic Vortex Induced Vibration (VIV) Energy Harvester
Authors: Zhou Xiaoyu , Roussinova Vesselina , Stoilov Vesselin
Published: February 2021

This paper investigates the performance of vortex-induced vibration (VIV) energy harvester in low-speed water flow. The proposed VIV harvester is extracting hydrokinetic energy from the flowing current and transferring it into mechanical vibrations. The vibrations are further converted into electrical energy using the piezoelectric transducer to supply the modern demand for energy-consumption. To meet the demand, the single harvester is analyzed to determine the suitable geometry for the bluff body that is sensitive to the low-speed flow. Furthermore, the converter must be able to harvest vibrations of varying amplitudes and frequencies. To maximize the power output, different array configurations of multiple bluff bodies are examined. A single positively buoyant elastically mounted cylinder is tested experimentally and at a low flow speed of 0.3 m/s, it can harvest vibrations with an average frequency of 1.8 Hz and peak to peak amplitude of 1.5d, where d is the diameter of the bluff body. It was found that for an array consisting of ten bluff bodies, the average frequency and peak to peak amplitude increases to 2.09Hz and 1.54d, respectively.
Rate Dependent Material Model for Helmet Pads
Authors: Zhang Timothy G. , Fulton A. H. , Ravi-Chandar K. , Satapathy Sikhanda S.
Published: February 2021

Foam pads are commonly used in sports and military helmet for energy absorption, form-fitting and comfort. Both for low velocity and high velocity applications, their rate-dependent mechanical properties need to be characterized to understand their ability to effectively modulate the transmitted stress pulse. Impact experiments were conducted on bilayer helmet pads at a range of velocities covering low to medium rates up to ∼7000/s. Images from high-speed camera were used to construct x-T diagrams to measure the shock speeds from the impact experiments. Numerical simulations were carried out to validate a foam pad model and to understand experimental uncertainties. The scatter in the measured shock speeds was found to be related to the scatter in the material properties.
An Investigation on the Design of Formate and Generate Face Milled Hypoid Gears
Authors: Yılmaz Tufan Gürkan , Kalay Onur Can , Karpat Fatih , Doğanlı Mert , Altıntaş Elif
Published: February 2021

Hypoid gears are transmission elements that transfer power and moment between shafts whose axes do not intersect. They are similar in structure to spiral bevel gears. However, there are many advantages compared to spiral bevel gears in terms of load carrying capacity and rigidity. Hypoid gear pairs are mostly used as powertrain on the rear axles of cars and trucks. Hypoid gears are manufactured by two essential methods called face-milling and face-hobbing, and there are mainly two relative kinematic movements (Formate® and Generate). In this study, the gears produced with the Face-milling method are discussed. Face milled hypoid gears can be manufactured with both Formate® and Generate, while pinions can only be manufactured with the Generate method. The most crucial factor that determines the performance of hypoid gears is the geometry of hypoid gears. The gear and pinion geometry is directly dependent on the tool geometry, machine parameters, and relative motion between the cradle and the workpiece. The gear geometry determines the contact shape and pressure during power transmission.

In this study, the mathematical equation of the cutting tool is set. After that, using differential geometry, coordinate transformation, and the gearing theory, the mathematical equation of hypoid gear is obtained.
Stochastic Optimization of a Horizontal-Axis Composite Wind Turbine Blade
Authors: Thapa Mishal , Missoum Samy
Published: February 2021

In this paper, the stochastic optimization of a horizontal-axis composite wind turbine blade is performed. Wind energy has become widely popular in recent decades as an alternative source of energy and many studies have been devoted to finding an optimal wind turbine blade using deterministic optimization. However, the actual responses of the wind turbine blade such as power generation are affected by the stochastic nature of wind, uncertainties in material properties and modeling parameters, and so on. This can have an undesirable impact on the performance and reliability of blades, which demands the consideration of uncertainties during optimization. To this end, a surrogate-based stochastic optimization of a wind turbine blade considering the influence of randomness in wind speed on power generation was studied. A slight gain in average power over the baseline blade was obtained and it demonstrated the promise of the presented framework for the design of wind turbine blades.
Assessment of Three-Dimensional Engagement Levels in a Global Peer Learning Environment
Authors: Wang Chu-Yi , Bessell Mary , Lu Stephen
Published: February 2021

The global learning classroom is an emerging educational trend. The iPodia alliance promotes its peer-learning pedagogy by offering engineering classes with universities around the world. Students’ engagement as one of the important metrics to assess the effectiveness of education design methodology has been under considerable interest for several years. Tri-engagement, comprised of behavioral, cognitive, and emotional engagement provides a comprehensive assessment of learning success. This paper illustrates how a tri-engagement assessment was implemented in a global learning environment and examines the effectiveness of the peer-learning pedagogy in such highly diverse environment. This paper proposes a quantitative method using a modified Likert scale to assess students’ tri-engagement levels comprised of student and teaching assistant surveys, video observations, and analysis of facial emotion recognition, through preparation, data collection, and analysis stages. Comparisons of tri-engagements between the instructor-student activities and the peer-peer discussions, different continent regions, and on-site/remote learning are offered. Results show that the overall iPodia peer-learning activities experienced all positive tri-engagement levels and were not significantly affected by the region diversity (< 6% difference) or the remote learning (< 3% difference) of the iPodia learning classroom. That preliminarily proved that the iPodia peer-learning pedagogy maintains positive tri-engagements in a global engineering class. Additional findings were that the self-raters and observers experienced students’ cognitive engagement differently, and cultural difference would mainly affect students’ behavioral engagement, but unfamiliarity of the content may increase their emotional engagement.
Experimental and Numerical Study of a Latent Heat Thermal Energy Storage Unit Enhanced by Fins
Authors: Hockins Addison , Moretti Samantha , Mahdavi Mahboobe , Tiari Saeed
Published: February 2021

Latent heat thermal energy storage (LHTES) systems are used to store thermal energy and release it for later use by melting or solidifying a phase change material (PCM). One problem associated with latent heat thermal energy storage systems is the low thermal conductivity of most commercially aviable phase change materials. This can have a significant negative effect on the thermal performance of the system by leading to a longer charging or discharging process. Several passive heat transfer enhancement techniques are used to resolve this issue. Common passive heat transfer enhancement techniques include inserting fins and extended surfaces into the PCM, embedding heat pipes or other two-phase heat transfer devices within the PCM, dispersion of highly conductive nanoparticles in the PCM, and impregnation of highly conductive porous media with the PCM. The current study analyzes the effect of a fin-based enhancement technique on the thermal performance of a latent heat thermal energy storage unit. Copper fins are attached annually around the central pipe inside the PCM. A transient two-dimensional numerical model technique is developed using ANSYS FLUENT 19.0 to simulate the operation of the system. Baseline tests have been conducted experimentally for a system without fins to validate the numerical model. The results obtained from the numerical modeling are in good agreement with those of the experimental testing. Based on the experimental testing, the total charging time of the system using hot water at 70°C and flow rate of 7.57 L/min is around 47.9 hours which is very close to the prediction by the numerical model which is 48 hours. Numerical modeling of the system with 10 fins and 20 fins found that the charging time was decreased by 68.9% and 73.7%, respectively. The discharging time was also decreased by 73.2% and 79.1%, respectively.
Effect of Loading Direction and Bone Density Distribution in Assessing Hip Fracture via Finite Element Analysis
Authors: Awal Rabina , Faisal Tanvir R.
Published: February 2021

An accurate assessment of hip fracture risk requires a proper consideration of parameters affecting the fracture. In general, hip fracture is affected by bone morphology, bone mineral Density (BMD), and load amount. Hip fracture is an outcome of the interaction of all those parameters including loading directions. Assessing the effect of the parameters individually may not correctly reflect the root cause of the hip fracture. Hence, this research aims at analyzing the significance of parameters and their interaction. A multivariate regression model was used considering bone density (ρash), different loading directions during sideways fall, represented by load angle (α) on the coronal plane and angle (β) on the transverse plane as independent parameters and Fracture Risk Index (FRI) as a dependent parameter. The statistical results showing the significant value of 0.7321 for α, and 0.0001 for β and ρash indicates that the effect of loading direction about femoral shaft on the coronal plane (α) does not have impact on fracture risk while loading direction about femoral neck axis on the transverse plane (β) and ρash have the significant impact. Furthermore, the analysis of the interaction of parameters shows that the impact of β on fracture risk may depends more on bone density as the significance of interaction of β and ρash is 0.0001.
Generative Design and Topology Optimization of Disk Brake Floating Carrier
Authors: Zefinetti Filippo Colombo , Regazzoni Daniele , Rossoni Marco
Published: February 2021

In the last past years, computer-aided technologies to improve existing products by widening the design space have been largely investigated. Topology optimization and generative design are two of the most representative technologies of such kind. This paper aims at investigating the use of generative design and topology optimization techniques to improve products whose design has not changed radically over the years. The product under investigation is a disk brake floating caliper that is the most common solution for commercial vehicles. In general, increasing the stiffness of the floating caliper while keeping its weight under control is desirable both from performance and fuel consumption point of view. The solution here proposed aims at exploiting two new ways to approach the engineering design process and evaluate which one is more suitable for problems of this kind. Starting from the original carrier shape, acquired with laser scanning, the two technologies have been applied on the same initial conditions. The initial design space volume corresponds to the acquired shape, the loads and the constraints for the simulation have been drawn reasonably to resemble the actual operating conditions. Keeping the input parameters constants, two different off-the-shelf software packages have been used to perform the computation and with the objective of maximizing the stiffness of the carrier while reducing its mass. The comparison and the improvements on the final designs have been drawn taken as reference to the original caliper.
Manufacturing of Porous Polydimethylsiloxane (PDMS) Plates Using Solvent Evaporation Induced Phase Separation Technique
Authors: Abshirini Mohammad , Altan M. Cengiz , Liu Yingtao , Saha Mrinal C. , Cummings Laura , Robison Thomas
Published: February 2021

This paper presents the fabrication and characterization of porous polydimethylsiloxane (PDMS) plates. The framework for obtaining porous PDMS is based on the solvent evaporation induced phase separation technique. A mixture of PDMS, water, and tetrahydrofuran (THF) with different concentrations is prepared. The three phases are stirred to reach a highly stable and viscous solution. The THF and water phases are evaporated during a curing cycle by applying a stepping heat treatment. The porous PDMS sheets with a wide range of pore sizes are fabricated by controlling the ratio of water to THF in the mixture. The confocal microscopy images are used to characterize the average pore size and the pore size distribution in the structures. Dogbone samples following the ASTM standard D412 are cut from the porous plates by utilizing a designed cutting die and mechanical press. The specimens are tested under tensile loading to evaluate the effect of the pore size on the mechanical properties of the porous structure. The results demonstrate the ability of the proposed solvent evaporation method to control the stiffness of the porous structure by changing the non-solvent to the solvent ratio in the mixture.
Low Cost Markerless Motion Capture Systems: A Comparison Between RGB Cameras and RGB-D Sensors
Authors: Vitali Andrea , Regazzoni Daniele , Rizzi Caterina , Lupi Giorgio
Published: February 2021

In the last years, the advent of low-cost markerless motion capture systems fostered their use in several research fields, such as healthcare and sport. Any system presents benefits and drawbacks that have to be considered to design a Mocap solution providing a proper motion acquisition for a specific context. In order to evaluate low-cost technology, this research work focuses on the evaluation of the accuracy of two categories of devices: the RGB active cameras and the RGB-D, or depth sensors devices. In particular, GoPro Hero 6 active cameras and Microsoft Kinect v2 devices have been selected as representative of the two categories. In particular, this work evaluates and compares the performances of the two systems used to track the position of human articulations. The two devices have been chosen among those available on the market after a state of the art has been completed. Before starting with the campaign of acquisition, the number of sensors and their layout have been designed to optimize the acquisition with both mark-less Mocap systems. Their comparison is based on a list of specific movements of upper and lower limbs. Each movement has been acquired simultaneously, to guarantee the same test conditions. The results have been organized, compared and discussed by evaluating performances and limitations of both solutions related to specific context of use. Conclusions highlight the best candidate technology.
Assessment of Elevator Risks and Code Requirements Associated With Slip, Trip and Fall Hazards
Authors: Bress Thomas , Kennedy Eugenia , Guttag Mark
Published: February 2021

In previous work, the hazards associated with elevator door closures were identified and analyzed. Using the National Electronic Injury Surveillance System (NEISS) database of the U.S. Consumer Product Safety Commission (CPSC), incidents associated with door strikes were identified between the years 1990 to 2017.

This current effort focuses on elevator slip, trip and fall hazards. The ASME A17.1 Safety Code for Elevators and Escalators requires that elevator systems be equipped with leveling devices to vertically align the car platform sill relative to the hoistway landing sill to attain a predetermined accuracy. Even with the leveling safety requirements, slip, trip and fall incidents for passengers exiting or entering elevators are known to occur. This paper will analyze elevator slip, trip and fall hazards using injury records from the NEISS database from 1990 to 2019. Relevant elevator incidents were extracted from this dataset through manual inspection of the text-based description fields of all elevator-related incident records found in the NEISS dataset from this time period. National projections of elevator incidents were then calculated from this extracted dataset and trended for the entire time period of 1990 through 2019. The age and sex distributions of these national projections were also analyzed. These projections and trends are then discussed in the context of ASME A17.1 requirements intended to mitigate the risks of injuries when entering or exiting an elevator.