bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of a Model of Synergistic Effects Between Deterioration Mechanisms and Damage in Woven Glass Fiber Reinforced Polymeric Composite Structure
Authors: Li Zhiye , Lepech Michael
Published: February 2021

The adoption of fossil-based hydrocarbon polymer composites has been successful in both the automotive and aircraft industries, and is rapidly expanding into buildings and civil infrastructure. One challenge to broader adoption of polymer composites in buildings and civil infrastructure is a limited ability to model the synergistic effects of the combined physical/chemical processes of environmental exposure and mechanical loading. Unlike other building materials, long-term experience and field performance data of polymer composites in buildings and civil infrastructure applications does not exist. The first and largest composite building system used in a high-rise exterior in the US is the facade of the San Francisco Museum of Modern Art (SFMOMA) completed in 2015. Since historical, experience-based service life models for composite building applications are not available, it is crucial to build multiphysical-based models in order to predict composite service life performance on a semi-centennial or centennial time scale.

This paper uses a parametrically homogenized deterioration model to hierarchical model the thermo-chemical-mechanical degradation at the structural length scale and proposes this computational model as a component to complete a new multi-physics-based service life prediction framework. This effort consists of three steps: (i) use the theory of synergistic effects between ultraviolet exposure and moisture exposure degradation processes developed by the authors to generate a residual, deterioration-induced damage variable field, (ii) implement the residual damage field as the initiation of a continuum damage model (CDM) at structure length scale, and (iii) recreate one 3D façade plate of the SFMOMA and perform parametric damage analysis.
Application of Alternative Support Fixture System in Vibration Suppression of Thin-Walled Parts
Authors: Liu Ze , Sun Yu , Wang Yu
Published: February 2021

The machining vibration of thin-walled parts affects the quality of the products. Thus, this paper proposes a new alternative support fixture system for vibration suppression of thin-walled parts. The system includes two movable supporting heads, which are periodically repositioned along the machining path in the form of alternating support to support the area close to the cutter, so as to improve the rigidity of the actual machining position of the thin-walled part. Around this new system, a dynamic model is established to analyze the workpiece vibration. Takeing as an example simply suppoted thin-plate, the influence of the supporting head’s location, stiffness coefficient and damping coefficient on vibration suppression are numerically analyzed in this paper. The result of the simulation demonstrates the alternative support fixture system is effective in vibration suppression of thin-walled parts.
Potential Waste Heat Recovery Analysis From Molten Steel Slag: The Case Study of Sidenor Steelworks in Basauri (Spain)
Authors: Ortega-Fernández Iñigo , Arribalzaga Peru , Bielsa Daniel , Fernández Leixuri , Unamuno Iñigo
Published: February 2021

Every day huge amount of energy is released to the atmosphere in form of waste heat. The search of a cleaner and more efficient society, not only at industrial level but also at domestic level, should avoid this type of emissions. Steelmaking is an example of an industrial sector with high optimization potential in energy management. In this line, this work presents the main outcomes of the investigation carried out in the search of a technical solution for heat capture and reutilization from one of the main waste heat streams in the steelworks, the molten slag. For this purpose, a piping system embedded in the slag pit soil is proposed as satisfactory solution for the heat capture operation. Besides, the internal applicability of this recovered heat is also addressed. Overall, the analysis carried out allows the identification of the main process parameters that limit the heat recovery potential from the molten slag. At the same time, the investigation provides accurate results of the maximum energy that can be recovered from the slag if the proposed technology is implemented (around 306 kWht per casting, what represents the 6.3% of the total available energy). The work is completed with a preliminary techno-economic analysis to conclude with the viability assessment. This analysis shows a depreciated payback period of the proposed technology below 7 years.
Non-Destructive Evaluation of the Degradation of Ni-Base Superalloy in the Air by Reflectance Spectrum Analysis
Authors: Kasama Shin , Suzuki Ken , Miura Hideo
Published: February 2021

Thermal power generation is required to be highly efficient due to concerns such as environment and energy problems. In order to improve its efficiency, it is thermodynamically essential to increase operating temperature. In addition, since thermal power generation is expected to control its output to be coexistent with renewable energies of which output varies frequently depending on weather, not only simple fatigue or creep load but also creep-fatigue load is applied to its component because it is required to assure the safe and stable energy supply under random output of the renewable energies. Since the effective lifetime of heat-resistant alloys decreases drastically under creep-fatigue load, however, it is very important to develop a non-destructive inspection method which can detect the degradation of the crystallinity of the alloys such as local plastic deformation, local oxidation, and local change of micro texture (segregation/precipitation). In this research, the reflectance spectrum analysis of the component elements was applied to the observation of the change in the local crystallinity of Ni-base superalloy (Alloy 617). A creep-fatigue test was applied to a small specimen, and the change of the local reflectance spectrum was measured under the irradiation of a white light. It was confirmed that the change of the surface roughness in the damaged area caused by plastic deformation and the growth of the surface oxide were successfully observed by the spectrum analysis. In addition, the distribution of fine carbides and nitrides was visualized by the spectrum analysis. It was also confirmed that a thick Cr-rich oxide layer grew at the grain boundaries only in the heavily damaged area. Finally, it was concluded that the creep-fatigue damage was clearly visualized by the spectrum analysis.
Computational Model of Radiofrequency Ablation of Cardiac Tissues Incorporating Thermo-Electro-Mechanical Interactions
Authors: Singh Sundeep , Melnik Roderick
Published: February 2021

The application of radiofrequency ablation (RFA) has been widely explored in treating various types of cardiac arrhythmias. Computational modelling provides a safe and viable alternative to ex vivo and in vivo experimental studies for quantifying the effects of different variables efficiently and reliably, apart from providing a priori estimates of the ablation volume attained during cardiac ablation procedures. In this contribution, we report a fully coupled thermo-electro-mechanical model for a more accurate prediction of the treatment outcomes during the radiofrequency cardiac ablation. A numerical model comprising of cardiac tissue and the cardiac chamber has been developed in which an electrode has been inserted perpendicular to the cardiac tissue to simulate actual clinical procedures. Temperature-dependent heat capacity, electrical and thermal conductivities, and blood perfusion rate have been considered to model more realistic scenarios. The effects of blood flow and contact force of the electrode tip on the efficacy of a fully coupled model of RFA have been systematically investigated. The numerical study predicts that the efficacy of RFA is significantly dependent on the thermo-electro-mechanical parameters of the cardiac tissue.
Spin Stabilization of an Air Ambulance Litter
Authors: Forden Christopher , Trinidad Yanuel , von Chance-Stutler Ryan , Bellocchio Andrew , Bluman James , Lanzerotti Mary
Published: February 2021

This paper proposes a new approach to stabilize the spin of a suspended litter during air ambulance rescue hoist operations. Complex forces generated by the helicopter’s downwash may cause a patient suspended in a rescue litter to spin violently. In severe cases, the spin destabilizes the suspended load, risks injury to the patient, and jeopardizes the safety of the aircrew.

The presented design employs an anti-torque device to arrest the spin that is safer and faster than a tagline and is without the tactical constraints of the tagline. The device follows tailored control laws to accelerate a flywheel attached to the litter, thereby generating sufficient angular momentum to counteract the spin and stabilize the suspended litter. An inertial measurement unit (IMU) measures the position, angular velocity, and angular acceleration of the litter and delivers this information to a microcontroller.

The research and prototype design were developed under the support of the U.S. Army 160th Special Operations Aviation Regiment (SOAR).
Evaluation of Thermal Displacement Ventilation in Contamination Purging Inside a 60-Person Built-in-Place Refuge Alternative (BIP RA) in an Underground Coal Mine
Authors: Bickson Joseph , Yantek David , Srednicki Justin , Carr Jacob , DeGennaro Cory , Reyes Miguel
Published: February 2021

Federal regulations require the installation of refuge alternatives (RAs) in underground coal mines to ensure miners’ survivability after a fire or an explosion where escape is impractical or even impossible. Both fires and explosions can generate dangerous or even lethal levels of carbon monoxide (CO) in a mine. As part of their function, RAs must be able to isolate miners from a CO-contaminated mine environment and to purge any CO that might enter the RA as miners enter it. In 2018, researchers from the National Institute for Occupational Safety and Health (NIOSH) conducted purging research in a built-in-place (BIP) RA with a borehole air supply by testing 12 different mixing ventilation system configurations (MVSCs). Recently, NIOSH researchers evaluated the use of a thermal displacement ventilation system configuration (TDVSC) to purge a 60-person BIP RA using a borehole air supply. As in previous research, NIOSH researchers tested the TDVSC with the flow rates of 750 SCFM and then 1,000 SCFM. For each of the flow rates, the results showed that the average purge time for the more expensive TDVSC is within two minutes of the average purge times of previously tested MVSCs. Manufacturers can use this information to not only pursue 30 CFR Part 7 approval from the Mine Safety and Health Administration (MSHA), but also to determine the most practical method to purge contaminants inside RAs.
Assessment of Invasive Fractional Flow Reserve Procedures Using Computational Fluid Dynamics
Authors: Abuouf Yasser , Albadawi Muhamed , Ookawara Shinichi , Ahmed Mahmoud
Published: February 2021

Coronary artery disease is the abnormal contraction of heart supply blood vessel. It may lead to major consequences such as heart attack and death. This narrowing in the coronary artery limits the oxygenated blood flow to the heart. Thus, diagnosing its severity helps physicians to select the appropriate treatment plan. Fractional Flow Reserve (FFR) is one of the most accurate methods to pinpoint the stenosis severity. The advantages of FFR are high accuracy, immediate estimation of the severity of the stenosis, and concomitant treatment using balloon or stent. Nevertheless, the main disadvantage of the FFR is being an invasive procedure that requires an incision under anesthesia. Moreover, inserting the guidewire across the stenosis may result in a ‘tight-fit’ between the vessel lumen and the guidewire. This may cause an increase in the measured pressure drop, leading to a false estimation of the blood flow parameters. To estimate the errors in diagnosis procedures, a comprehensive three-dimensional model blood flow along with guidewire is developed. Reconstructed three-dimensional coronary artery geometry from a patient-specific scan is used. Blood is considered non-Newtonian and the flow is pulsatile. The comprehensive model is numerically simulated using boundary conditions. Based on the predicted results, the ratio between pressure drop and distal dynamic pressure (CDP) is studied. The predicted results for each case are compared with the control case (the case without guidewire) and analyzed. It was found that simulating the model by placing the guidewire at a full position prior to the simulation leads to an overestimation of the CDP as it increases by 34.3%. However, simulating the procedure of guidewire insertion is more accurate. It shows that the CDP value increases by 7%.
CFD Analysis and Improvement on an Insertion Electromagnetic Flowmeter
Authors: Ma Haibo , Silaen Armin K. , Zhou Chenn Q. , Ma Shilei , Moss Robert , Fisher Mark
Published: February 2021

Accurate measurement of the volumetric flow rate of working liquids is essential for process control, as well as energy consumption evaluation. Electromagnetic flowmeters have gained popularity in applications where low pressure drop and low maintenance are required. Dwyer Instruments, Inc., recently developed an adjustable insertion electromagnetic flowmeter (IEF) featuring accurate and reliable measurement. However, an unexpected and non-repeatable behavior in the K-factor was observed during the calibration process. The K-factor is the coefficient that is used to convert the measured electric potential to the flow velocity in pipes and the non-repeatable behavior imposes challenges for precise measurement.

A one-way coupled magnetohydrodynamics model was developed to reduce the effort and time of on-site troubleshooting and optimization. By modeling the measurement process, the transition of flow regimes and the regeneration of boundary layer on the electrode surface were identified as the causes to the non-repeatable issue. Then, a series of parametric studies were performed to provide reliable solutions. A new design with further embedded electrodes was recommended. The field test showed great repeatability by using the new design and the non-repeatable issue was completely resolved. The improvement in the IEF design was implemented in production in less than one week and it reduced the calibration time by 50%.
Numerical Analysis of a T-Type Electrokinetic Micromixer With Heterogeneous Zeta Potentials and Viscoelectric Effects
Authors: Escandón Juan P. , Torres David A.
Published: February 2021

This paper presents the 2-D numerical solution of the flow and concentration field of an electrokinetic T-type micromixer, under heterogeneous zeta potentials modulated via sinusoidal functions and interfacial viscoelectric effects. Here, the viscoelectric effects appear to modify the fluid viscosity due to the high voltages within the electric double layer. The mathematical model is based on the Poisson-Boltzmann, mass conservation, momentum, and species concentration equations. In the steady-state analysis, two electrolytes with known ionic concentration and an imposed velocity profile are considered at the inlet of the micromixer. The results demonstrate that by using heterogeneous zeta potentials, at the mixer walls, generated flow recirculations along the mixer channel, promoting the rise in mixing efficiency; however, for high zeta potential values, this is counteracted by the viscoelectric effects. The present investigation shows how the viscoelectric condition deteriorates the mixing performance and how with the correct selection of modulated zeta potential parameters as the wave number, and the phase angle can improve it. Therefore, the performance of the mixer studied here should be considered for the design of microfluidic devices in the future.
Effects of Defects on Nanoporous Graphene and MoS2
Authors: Oviroh Peter Ozaveshe , Mohlala Lesego M. , Jen Tien-Chien
Published: February 2021

Nanoporous 2D materials such as grapheme and MoS2 promises better filtrations in water channels. However certain parameters that affects these materials for effective deployment need to be studied. In this paper, molecular dynamics (MD) simulation was performed to study the effects of defects that could increase the prospect of tuning the efficiency of the materials in the transportation, catalysis and mechanical reaction efficiency. Consideration of the interfaces between them could lead to improved functionalities of the materials. This paper systematically compares MoS2 and graphene membranes to highlight specific features and benefits. the Young’s modulus of the pristine monolayer MoS2 was calculated to be 447GPa while that of the defective MoS2 was found to be in the range of (314–374) GPa. The Young’s Modulus for Graphene was 783.2 GPa. The relative variation of the Young’s modulus on MoS2 is in the range (13–35) % while that of graphene is (13–21) %. From the results obtained, the maximum pressure that the MoS2 can withstand depends not just on the spacing and size of the nanopores, but also on the area of the defects in the membrane. These findings could help build and proliferate tunable filtration nanodevices and other applications.
Zimmer Frame Use and Back Strain Analysis Using a Finite Element Model
Authors: Harwood Sydney , Saboori Parisa
Published: February 2021

The current walking frame used by the elderly has several design issues that can cause long term health problems. One of these problems is the development of chronic pain in the lower back. The design of the current walking frame promotes a slumping posture that causes a curvature in the spine. This curvature results in a large strain in the lower back muscles, specifically the erector spinae. The goal of this research was to design a new walking frame that would be more structurally sound and more practical to use than the present walking frame design.

In this study, two literature searches were performed. The first was to explore how aging effects the ability to walk. The second involved studying all of the existing walking devices and analyzing their design strengths and weaknesses. As a result of these studies, three new preliminary walking frame designs were considered that promoted better posture when used, and provided more support than does the present walking frame design. These new designs were considered and tested using a finite element analysis (FEA).

From this FEA, it was determined that the new walking frame design resulted in less stress in the lower back than does the present walking frame design. It was therefore concluded that the new model has the potential to decease chronic back pain.
Design and Analysis of a Drone Mechanism With 3-Axis of Rotation
Authors: Mathur Varun , Yee Raymond K.
Published: February 2021

A quadcopter is an Unmanned Aerial Vehicle (UAV) with 4 propellers providing required force for motion. It has four equally spaced rotors, typically arranged at the corners of a central body. With four independent rotors, the need for a swashplate mechanism like that in a regular helicopter is alleviated. Due to the rotation of the propellers attached to a quadcopter an upward thrust is generated. The maneuverability of a quadcopter is primarily controlled by adjusting the speed of each propeller attached to a rotor which in turn creates different lifting forces for maneuvering. The objective of this work is to design a 2-axes rotation mechanism for a shaft while its propeller rotates about its own (the 3rd) axis in a 1 m by 1 m quadcopter. Besides the spinning of a propeller axis, two other perpendicular axes in the mechanism are capable of pivoting in a flight which dynamically modifies the thrust vector direction and enhances the quadcopter’s maneuverability. The project was accomplished by performing several key tasks involving mechanism design using bevel gears, shafts, and motors, computational fluid dynamics analysis to determine aerodynamic thrusts and airflow pattern, rigid body dynamics analysis to evaluate forces and torques at different sections of the mechanism, and finite element analysis of mechanical components to optimize the stresses and fatigue as well as their corresponding safety factors. The final mechanism design provides mobility similar to a spherical joint capable of pivoting from −45 degrees to 45 degrees about 2 orthogonal axes for a small size drone. The results of rigid body dynamics analyses for a small size drone indicate that the minimum required motor torque is about 0.5 N-m, based on using a 40-mm driving nylon gear with gear ratio of 1:2 and an aluminum shaft with its propeller rotating at 2000 rad/sec, the nylon gear is good for 5 million cycles, the ABS plastic fixture is good for 10 million cycles and the shaft was designed for 1 billion cycles of fatigue life. Further study would be required in developing the control system for this quadcopter design and optimizing the entire structure of the drone, prototype verification of the mechanism design on flight maneuverability is also recommended. A parallel study using the layered composite design is currently undertaken. A comparison between metal and fiber composite shafts on weight reduction and performance of the mechanism would be revealed in our next paper.
3D Digital Manufacturing Applied on Drilling of 7050-T651 Aluminum Performed by Robot
Authors: Zambrano Degan Bruno , Franco Barbosa Gustavo , Guerra-Zubiaga David , Nasajpour-Esfahani Navid , Al Mamun Abdullah
Published: February 2021

With advances in automation, industry seeks for optimization while new products are developed and manufacturing processes are becoming smarter. In this sense, virtual manufacturing validations have been demanded for reducing the cost with physical prototypes, ensuring ergonomically safe processes and increasing the quality of processes by emulating it realistically, levering automation utilization in industry environments with a faster and safer manner. By that, this research proposes the use of Tecnomatix Siemens® PLM software for process simulation of 7050 aluminum drilling, material which is widely used in aerospace industry, allowing the evaluation of complexes scenarios with multi-robot integration and its conditions and variables, in order to improve the machining process and its aeronautical structural assemblies. Thus, this research provided a relevant contribution regarding the analysis of main process parameters to obtain an efficient sequence of drilling, its productivity and ergonomic conditions.
Impacts on Head Loss in a Pumpless Solar Thermal Heater Calculated by Hardy-Cross Methodology
Authors: Scerbo Mikelann , D'Orazio Giancarlo , Tyagi Pawan
Published: February 2021

This project explores the impacts that temperature and various geometries have on head loss in a heat exchanger intended to be used as a component of a pumpless solar thermal heater. The heat exchanger component of the pumpless solar thermal heater is a vertical pipe configuration with one inlet pipe through which water flows downward to a well. There are a number of outlet pipes through which water flows upward from the well. The outlet pipes contain a number of conical features at some angle that act as fins to increase heat transfer. The entire heat exchanger is assumed to be submersed in a shell at constant temperature. A Python program was developed using the NTU method to calculate the temperature variation from the inlet to the outlet of the heat exchanger across a varied set of geometry parameters, including: number of outlet pipes, outlet pipe diameter, number of conical features, and angle of conical features. The impact of the temperature variation was accounted for in the head loss calculation within the Python program. For a set of head loss values, an optimized set of geometry parameters was found to maximize the outlet temperature.
Edge Coil Force Fitting and Current Optimal Commutation Algorithm for Magnetic Levitation Planar Motor With Moving Magnet
Authors: Sun Haobo , Zhu Yu , Yang Kaiming , Lu Sen
Published: February 2021

In this paper, edge coils are added to the commutation algorithm of the coil array. In order to reduce the theoretical modeling error of the edge coil force, a method of edge coil force fitting based on radial basis function (RBF) network is proposed. The obtained attenuation function of edge force can replace the weighting function in the switching algorithm, so it can effectively reduce the current density of the central coils and the heat loss power of the coil array. On this basis, a non-iterative current optimal commutation algorithm is proposed. The algorithm takes the weighted sum of the 2-norm of the coil current and the 2-norm of the difference between the coil current and the saturation current as the optimization objective, and obtains the analytical expression of the instantaneous current by solving the Karush Kuhn Tucker (KKT) equation. The results of simulation show that, compared with the direct decoupling algorithm with weighting function, the proposed commutation algorithm can reduce the heat loss power of the coil array and allow the translator to provide greater acceleration under the same maximum current limitation.
3D Modeling of Additive Manufacturing Process: The Case of Polymer Laser Sintering
Authors: Zhang Lan , Boutaous M'hamed , Xin Shihe , Siginer Dennis A.
Published: February 2021

This work focusses on studying multiphysical transient phenomena in polymer powders occurring during selective laser sintering in polymers powders. Multiple phenomena stemming from the interaction of the laser with the polymer powder bed and the transfer of the laser power to the powder bed including laser scattering and absorption, polymer heating, melting, coalescence, densification, and the variation of the material parameters with the temperature are simulated via the modified Monte Carlo-ray tracing method coupled with the Mie theory. A finite volume method is adopted for the heat transfer. The model couples heat diffusion, melting, coalescence and densification of the polymer grains, and the crystallization kinetics during the cooling steps. Laser intensity is concentrated on the surface of the material contrary to the predictions of the Beer-Lambert law. Laser acting on thermoplastic material cause the polymer powder melt, coalescence between melted grains, air diffusion versus densification, crystallization and volume shrinkage. All these processes are simulated by a series of multiphysical models. The reliability of the modeling is tested by comparison with experiments in the literature, and a parametric analysis is performed, based on the process characteristics such as laser sweep speed, its intensity and shape, polymeric grain size among others. Several recommendations to optimize the process are proposed.
Inlet Box Structure Optimization of a Large Axial-Flow Fan Using Response Surface Methodology
Authors: Xiong Jin , Zhang Yinkun , Guo Penghua , Li Jingyin
Published: February 2021

Large axial-flow fans are widely used in many fields. The inlet box is an integral part of large axial-flow fans, and a well-designed inlet box could effectively improve fan efficiency. However, the inlet box structure is complicated, and the existing inlet box design method severely depends on the design experience. In this study, we propose a structure optimization design system based on a surrogate model technique for researching the critical structure parameters of the inlet box and accomplishing aerodynamic performance optimization. As for this expensive optimization problem, the design system contains twice optimization procedures by using the Response Surface Methodology (RSM) with the orthogonal design method. The optimization object is an existing large axial-flow fan. The optimization objective is the total pressure efficiency of the fan, and the total pressure rise is the restriction condition. We generate eighteen different inlet boxes connect with the same impeller and outlet pipe by the orthogonal design method and calculated fan aerodynamic performance by CFX software. After the first optimization, we find the key structural parameters by the sensitivity analysis and the reselect variables total of 25 cases are adopted in a further RSM optimal process. The ultimate surrogate model estimates the fan with the optimal inlet box has a better aerodynamic characteristic and a 6.7% total pressure efficiency rise. Finally, we compare the aerodynamic characteristics of the ultimate design fan and the initial fan by CFD simulation. The numerical results show that: the total pressure efficiency is 6.5% higher than that of the initial impeller, and the pressure rise is 3% higher than that of the initial impeller. The result demonstrates that some most critical parameters of the inlet box structure decide the aerodynamic performance, and the inlet box optimization effectively increases the fan efficiency in the meanwhile.
Acoustic Amplification of Flow Ripple and Cavitation Damage in an Aerospace Fuel System Component
Authors: Lee Andrew , Desai Mihir
Published: February 2021

In a recent investigation of external fuel leaks from an aerospace pressure control valve, cavitation damages were discovered in a small deadheaded cavity, which was created by the axial clearance between the mating subcomponents. Experiments using high bandwidth pressure sensors showed that there were severe pressure fluctuations in the cavity and that the pressure repeatedly fell below the local vapor pressure of the fuel, which would cause cavitation. Spectral analyses showed resonance-like amplification of flow ripple in the valve surrounding inside the valve cavity. The apparent resonance frequency matched the computed fundamental Helmholtz resonance frequency of the cavity. These findings led to a venting solution of the deadheaded cavity by placing an appropriately sized through hole. Back-to-back testing with unvented valves showed stark improvements of the vented solution. This paper presents test and analytical data on the formation of a Helmholtz resonator in the small deadhead cavity of a gas turbine fuel delivery system component. This paper also demonstrates the validity of simple engineering formulas widely available in acoustics literature for predicting the Helmholtz resonance frequencies as a function of neck geometry, neck arrangement, and fuel properties.
Design of a Cognitive Rehabilitation System Based on Gesture Recognition
Authors: Teng Zhiqiang , Chen Haodong , Hou Qitao , Song Wanbing , Gu Chenchen , Zhao Ping
Published: February 2021

Computer-assisted cognitive training is an effective intervention for patients with mild cognitive impairment (MCI), which can avoid the disadvantages of traditional cognitive training that consumes a lot of medical resources and is difficult to be standardized. However, many computer-assisted cognitive training systems have unfriendly human-computer interaction, for not considering that most MCI patients have certain difficulties in using computers. In this paper, we design a cognitive training system which allows patients to implement human-computer interaction through gestures. First, a gesture recognition algorithm is proposed, in which we implement gesture segmentation based on YCbCr color space and Otsu algorithm, extract Fourier Descriptors of gesture contour as feature vectors and use SVM algorithm to train a classifier to recognize gestures. Then, the graphical user interface (GUI) of the system is designed to realize the task requirement of cognitive training for the MCI patients. Finally, the results of tests show the accuracy of the algorithm and the feasibility of the GUI. With the above computer-assisted cognitive training system, patients can achieve human-computer interaction only through gestures without the need to use keyboard, mouse, etc., greatly reducing the burden of patients during training.
Development of a Strain-Controlled Graphene-Based Highly Sensitive Gas Sensor
Authors: Qiao Xiangyu , Zhang Qinqiang , Suzuki Ken
Published: February 2021

Small-size wearable multi-gas sensor with high selectivity and sensitivity is demanded for detecting various harmful gases with high sensitivity in chemical plants, various mines, volcanos, oil and gas fields. Graphene is considered to be the most promising gas-sensitive material due to its large specific surface area and high electron mobility. Many studies have shown that it has a high sensitivity to many gases such as NH3, CO, NO2, H2O, and so on. However, the lack of gas selectivity limits the further application of graphene to gas sensing field. In this study, a first-principle calculation was used to investigate the effect of strain on the gas adsorption behavior of graphene. As a result, it was found that the adsorption behavior of H2O and CO molecules was changed by strain. The adsorption energy of both gases increased monotonically with strain. For carbon monoxide molecules, desorption occurred when the applied tensile strain reached about 5%. These analytical results clearly indicated that there is a possibility of the high selectivity of plural gases by applying appropriate critical strain at which its adsorption changes to desorption. To verify this result, the strain-controlled sensor using graphene was developed. The sensor is composed of graphene and electrodes mounted on a deformable substrate. The high-quality graphene is synthesized on copper by LPCVD (low pressure chemical vapor deposition), and then transferred to the PDMS (Polydimethylsiloxane) substrate using PMMA (Poly methyl methacrylate) as a support layer. It was found that the graphene was monolayer and successfully transferred to the target substrate. The effect of strain on the adsorption of some gases was validated by measuring the change of the resistivity of graphene under the application of uniaxial strain.
Complex Fastener Model for Simulation of Airframe Assembly Process
Authors: Lupuleac Sergey , Smirnov Aleksandr , Shinder Julia , Petukhova Margarita , Churilova Maria , Victorov Evgeniy , Bouriquet Jacques
Published: February 2021

The complex model of fastener for the global modeling of aircraft assembly with regard to compliance and contact interaction of parts is introduced in the paper. The presented complex fastener model incorporates such effects as the stiffness of fastening elements; the loosening of fasteners and also the failure of fasteners (if the load exceeds the maximal value that fastener can hold).

This model can be implemented for all types of fastening elements in variation simulation and assembly optimization analysis. It provides more realistic simulation results at expense of higher model dimension. The fastener is modeled as having an additional stretching stiffness. The option of fastener loosening is included by implementation of additional contact node in each fastening element. This option allows taking into account the pre-tension in fasteners and also enables the modeling of installation and removal of fasteners without change of stiffness matrix.
Numerical Study on Antibacterial Effects of Bio-Inspired Nanostructured Surface
Authors: Zheng Zhouyuan , Bansal Parth , Li Yumeng
Published: February 2021

Natural bactericidal surfaces are found on the wings of cicada and dragonfly that compose of nanopatterns such as nanopillar arrays. Experimental studies have unveiled that the nanopillars can penetrate the bacterial walls or stretch them, resulting in the cell death. This offers an attractive “chemical-free” and wide-spectrum strategy to fight against bacteria-related infections and fouling, especially for implant-associated infections (IAIs). However, what is the fundamental mechanism and key factors governing the bactericidal performance of the nanostructured surface is the critical research questions need to be answered to realize its full potential. In this work, we developed mechanical single cell model of bacteria based on finite element analysis (FEA) to simulate the interactions between different strains of bacteria and the nanostructured surface. The nanostructured surface contains nanopillar arrays, which are made of polymer materials. Different strains of bacteria are simulated by adopting the corresponding geometry and material properties from experimental values. The mechanical responses of the bacteria cell on the nanopillar arrays with various configurations are studied based on estimated stress and strain distributions within the cell.
Corrosion Modeling and Prognosis of the Al-Fe Self-Pierce Riveting Joints
Authors: Zheng Zhouyuan , Bansal Parth , Wang Pingfeng , Shao Chenhui , Li Yumeng
Published: February 2021

Self-pierce riveting (SPR) is one of the commonly used joining technologies, which is useful to assemble dissimilar materials. However, the galvanic / crevice corrosion between joining metals and metal-rivet interfaces plays an important role on the mechanical properties of the joint. It is critical to have a compressive understanding on the corrosion phenomena of the joint. In this study, a hybrid model that combines the stochastic corrosion nucleation method and physics-based finite element (FE) modeling is proposed. The corrosion nucleation variables, including the positions of the nucleation sites and their corrosion trigger time, are firstly obtained based upon statistical analysis on experiments and then imported in the physics-based FE model as initial conditions. Afterwards, the corrosion propagation process is evaluated via the FE model. Various corrosion scenarios with different nucleation variables are generated and statistically analyzed. Experimental results are used to validate the model. It is found that, the proposed hybrid model can reasonably predict the localized corrosion results of the SPR joints, compared to experimental observations. Moreover, the corrosion area and material loss in the SPR joint are predicted.
Particle Immobilization Stiffness in Dielectrophoresis Trap Depending on the Geometry
Authors: Rahman Mohammad Rizwen Ur , Kwak Tae Joon , Woehl Jörg C. , Chang Woo-Jin
Published: February 2021

In dielectrophoresis, a neutral particle experiences a partial charge separation, i.e. induced net dipole moment, when exposed to a non-uniform electric field, and this leads translational movement of the particle. This induced attractive or repulsive motion of the particle suspended in a fluid is known as dielectrophoresis (DEP). In this paper, we have characterized the strength of DEP traps depending on geometry. Three different micro-trap geometries, i.e. triangle, square and circle, were tested to characterize the effect of trap shape on trap stiffness experimentally and numerically using single particle immobilized in the trap. The maximum DEP force generated in triangular μ-trap was found largest among tested geometries. The maximum DEP force of square and circular trap was found around 68.4% and 79.1% of triangular μ-trap, respectively. The trajectory analysis using trapped single particle revealed that the stiffness of circular μ-trap is 1.23 and 1.34 times stronger than the triangular and square μ-trap, respectively. These results will provide useful information in DEP trap geometry designing to enhance trapping efficiency.
Analysis of Injury Mechanisms Within Lead-Vehicle Stopped Impacts: Implications for Autonomous Vehicle Behavior Design
Authors: Eichaker Lauren , Ramachandra Rakshit , Bolte John
Published: February 2021

Lead vehicle stopped crashes are a top contributor to traffic and health care expenditures out of NHTSA’s 37 pre-crash scenarios. It is important to better understand how these crashes occur, so that evolving autonomous vehicle technologies may be tailored towards injury mitigation in crash-imminent scenarios. Additionally, as autonomous vehicle technologies increase in prevalence and usage, out of position seating and distracted driving behavior may also increase. In order to analyze injury patterns in real-world lead vehicle stopped crashes, the public portal of Crash Injury Research Engineering Network (CIREN) was surveyed for lead vehicle stopped impacts. The review found that, of all the body regions, the thorax and lower extremity body regions frequently sustained AIS 3+ injuries (P < 0.01). Additionally, the upper extremity frequently sustained AID 3+ injuries in some scenarios. Steering wheel contact (often times through a deployed air bag) was the source of 62% of the thorax injuries and the knee bolster was the source of 76% of the lower extremity injuries. Truck impacts, and complicated crashes accounted for over 50% of the cases in the cohort. Automated vehicle behaviors have the potential to augment passive and active safety systems to potentially decrease the occurrence of AIS 3+ injuries by improving a vehicle’s response to lead vehicle stopped, crash imminent scenarios.
A Flexible Hair-Like Laser Induced Graphitic Sensor for Low Flow Rate Sensing Applications
Authors: Abbasnejad Behrokh , McGloin David , Clemon Lee
Published: February 2021

Direct low flow sensing is of interest to many applications in medical and biochemical industries. Low flow rate measurement is still challenging, and conventional flow sensors such as hot films, hot wires and Pitot probes are not capable of measuring very low flow rates accurately. In some applications that require flow measurement in a small diameter tubing (e.g. intravenous (IV) infusion), using such sensors also becomes mechanically impractical. Herein, a flexible laser-induced graphitic (LIG) piezoresistive flow sensor has been fabricated in a cost-effective single processing step. The capability of the LIG sensor in very low flow rate measurement has been investigated by embedding the sensor within an intravenous (IV) line. The embedded LIG hair-like sensor was tested at ambient temperature within the IV line at flow rates ranging from 0 m/s to 0.3 m/s (IV infusion free-flow rate). The LIG hair-like sensor presented in this study detects live flow rates of IV infusions with a threshold detection limit as low as 0.02 m/s. Moreover, the deformation of the LIG hair-like sensor that lead to resistance change in response to various flow rates is simulated using COMSOL Multiphysics.
Subsurface and At-Depth Interphase Characterization in Hygrothermal Aged Carbon Fiber Reinforced Polymer Matrix Composite
Authors: Yekani Fard Masoud , Raji Brian , Pankretz Heidi , Mester Jack , Pensky Alek
Published: February 2021

The interphase region between the carbon monofilament and epoxy matrix in Carbon Fiber Reinforced Polymer Composites (CFRPs) is immensely vital to transfer stress between carbon monofilament and bulk matrix material. To the best of the authors’ knowledge, no other research group has studied the interphase region at subsurface and at-depth levels on hygrothermal aged CFRPs. The composite samples were exposed to 60° C and 90% humidity for one and two years. Moisture absorptions were measured periodically to assess water gain in the material. The advanced Atomic Force Microscopy (AFM) based Peak Force Quantitative Nanomechanics Mapping Technique was used to study the physics of the interphase. PFQNM allows non-destructive and simultaneous capture of imaging and mechanical property data with nanometer resolution. The interphase thickness was increased with increased hygrothermal exposure time. The interphase surrounding carbon monofilaments exhibited nonuniform thickness, ranging from ∼85 to 95 nm in the subsurface level, and from ∼10 to 75 nm on the at-depth level. Aged samples showed a decrease in average surface roughness, likely due to swelling of the epoxy matrix caused by the moisture absorption. The water diffusion generally followed Fickian.
Local Hot Spots of Electric Water Pump Casing Over Various Pumping Loads
Authors: Kim Younghyeon , Choi Yoora , Yu Sangseok
Published: February 2021

The cooling system of an electric vehicle adopts an electric water pump. Since the lifespan of the battery is very sensitive to a very narrow temperature band, the cooling system provides key solutions. The electric water pump is a core component of the cooling system which satisfies performance and durability criteria. Since, a local hot spot of motor casing results in the degradation of motor lifespan, it is necessary to design the motor casing for effective heat rejection. In this study, two different motor casing designs are applied to reject the joule heating of the motor efficiently. The temperature distribution of each casing is investigated with an IR camera. The IR camera was used to identify the local hot spot where the heat was most generated in the pump. Since the joule heating is proportional to pump power, it is necessary to understand the operating characteristics of the electric water pump. The experimental apparatus includes a water reservoir, a bypass valve, pressure and temperature sensors, DAQ, and IR camera. The operating temperature is ranged from atmospheric temperature to 50°C. When the pump is operated with 25°C coolant, each experiment takes 1 hour for the steady-state conditions and maximum temperature up to 55 °C. Three different pump performance are investigated with two different pump casing. The coolant temperature is also changed from 25 °C to 50 °C. As a result, the local hot spot is strongly dependent to pump load and it is mainly observed near the cable connector. Since temperature distribution on the casing surface is also affected by local hot spots, it is necessary to optimize heat rejection by extended surface.
Design of a Real-Time Human-Robot Collaboration System Using Dynamic Gestures
Authors: Chen Haodong , Leu Ming C. , Tao Wenjin , Yin Zhaozheng
Published: February 2021

With the development of industrial automation and artificial intelligence, robotic systems are developing into an essential part of factory production, and the human-robot collaboration (HRC) becomes a new trend in the industrial field. In our previous work, ten dynamic gestures have been designed for communication between a human worker and a robot in manufacturing scenarios, and a dynamic gesture recognition model based on Convolutional Neural Networks (CNN) has been developed. Based on the model, this study aims to design and develop a new real-time HRC system based on multi-threading method and the CNN. This system enables the real-time interaction between a human worker and a robotic arm based on dynamic gestures. Firstly, a multi-threading architecture is constructed for high-speed operation and fast response while schedule more than one task at the same time. Next, A real-time dynamic gesture recognition algorithm is developed, where a human worker’s behavior and motion are continuously monitored and captured, and motion history images (MHIs) are generated in real-time. The generation of the MHIs and their identification using the classification model are synchronously accomplished. If a designated dynamic gesture is detected, it is immediately transmitted to the robotic arm to conduct a real-time response. A Graphic User Interface (GUI) for the integration of the proposed HRC system is developed for the visualization of the real-time motion history and classification results of the gesture identification. A series of actual collaboration experiments are carried out between a human worker and a six-degree-of-freedom (6 DOF) Comau industrial robot, and the experimental results show the feasibility and robustness of the proposed system.