bluuebunny/crossref_metadata_2025 huggingface dataset:
Student Experiential Learning Through Design and Development of a Subsurface Melting Head for NASA RASCAL-Special Edition Competition
Authors: Xu Jiajun , Haghani Sasan , D'Orazio Giancarlo , Velazquez Carlos
Published: February 2021

In order for students to enhance their understanding of engineering concepts, hands-on experience proves to be essential. Incorporating the design component in undergraduate engineering education has been an immediate and pressing concern for educators, professional societies, industrial employers and agencies concerned with national productivity and competitiveness. It is crucial to enhance undergraduate design and research experiences to meet both societal needs and the growing job-market demands. The University of the District of Columbia (UDC), the District of Columbia’s only public institution of higher education, and a historically black college and university (HBCU), had recently modernized its undergraduate curricula in engineering to meet that need. This paper presents a case study of recent implementation of student experiential learning approach through undergraduate research experience course (MECH 302). This student group participated in the 2019 US National Aeronautics and Space Administration Revolutionary Aerospace Systems Concepts – Academic Linkages (RASC-AL) Challenge, in which they will develop concepts that may provide full or partial solutions to specific design problems and challenges currently facing human space exploration.
Simulation of Ventilation Flow at Different Conditions Through a Two-Dimensional Room Incorporated With Phase Change Materials
Authors: Reyes-Cubas Angel , Abdo Peter
Published: February 2021

Climate change and global warming have raised many concerns, highlighting the necessity to reduce energy consumption associated with the building sector. HVAC systems account to almost 40% of the building’s energy consumption. Natural ventilation is the process of supplying and removing air through an indoor space by natural means. Windcatchers have been used over centuries for providing natural ventilation using wind power. Moreover, it is an effective passive method to provide healthy and comfortable indoor environment by decreasing moisture content in the air and reducing pollutants concentration significantly.

Materials that change phase at certain temperature are frequently referred to as Phase Change Materials (PCMs). Phase Change Materials, also known as Thermal Energy Storage (TES), are substances with high latent heat storage capacity which absorb or release the heat from or to the surrounding environment. PCMs could be used in passive cooling systems and they are directly related to building energy efficiency.

This study investigates air flow through a windcatcher into a two-dimensional room incorporated with phase change materials (PCMs). The temperature change in the room implementing PCM is analyzed to monitor the PCMs’ performance. To achieve this, Computational Fluid Dynamics (CFD) tool is used to simulate the air flow through a two-dimensional standard room (3 m × 5 m) fitted with a windcatcher at its roof. Ansys Fluent is utilized to simulate and display the contours of temperature, liquid fraction, and velocity of both PCM and air. The energy model as well as the solidification and melting model are employed, and the K-Epsilon turbulence model is implemented. PCM is placed at the right and left walls of the room, as well as at its bottom. The inlet velocity ranges between 1 m/s and 7 m/s, simulating the average wind speeds in Sydney-Australia during summer [1]. Different inlet temperatures are used, specifically at 302 K and 310 K. The effect of the phase change material presence on the air flow pattern is also investigated.
Effect of Heat Flux on Pool Boiling Heat Transfer Enhancement (Numerical Investigation Approach)
Authors: Mogaji T. S. , Sogbesan O. A. , Jen Tien-Chien
Published: February 2021

This study presents numerical investigation results of heat flux effect on pool boiling heat transfer enhancement during nucleate boiling heat transfer of water. The simulation was performed for five different heated surfaces such as: brass, copper, mild steel, stainless steel and aluminum using ANSYS simulation software at 1 atmospheric pressure. The samples were heated in a domain developed for bubble growth during nucleate boiling process under the same operational condition of applied heat flux ranged from 100 to 1000 kW/m2 and their corresponding heat transfer coefficient was obtained numerically. Obtained experimental data of other authors from the open literature result is in close agreement with the simulated data, thus confirming the validity of the CFD simulation method used in this study. It is found that heat transfer coefficient increases with increasing heat flux. The results revealed that in comparison to other materials tested, better heat transfer performance up to 38.5% and 7.11% is observed for aluminum and brass at lower superheated temperature difference conditions of 6.96K and 14.01K respectively. This behavior indicates better bubble development and detachment capability of these heating surface materials and could be used in improving the performance of thermal devices toward producing compact and miniaturized equipment.
Microtexture Dependence of Mechanical and Electrical Properties of Gold Thin Films Used for Micro Bumps of 3D Stacking Structures
Authors: Nakauchi Genta , Akasaki Shota , Miura Hideo
Published: February 2021

The variation of their crystallinity, in other words, the order of atom arrangement of grain boundaries in electroplated gold thin films was investigated by changing their manufacturing conditions. Then, the effect of the crystallinity on both their mechanical and electrical properties was measured by using nano-indentation test and electromigration test. The crystallinity of the gold thin films was varied by changing the under-layer material used for electroplating. Also, the micro texture of gold thin films was evaluated by EBSD (Electron Back-Scatter Diffraction) and XRD (X-Ray Diffraction). It was clarified that the crystallinity of the electroplated gold thin films changed drastically depending on the crystallinity of the under-layer materials and electroplating conditions such as current density and temperature. This variation of the crystallinity should have caused wide variation of mechanical properties of the films. In addition, their mechanical properties such as Young’s modulus and hardness showed wide variation by about 3 times comparing with those of bulk gold. Similarly, the EM resistance of the electroplated gold bumps varied drastically depending on the ratio of porous grain boundaries and their crystallinity. Both the ratio and crystallinity also varied depending on the crystallinity of the under layer and electroplating conditions. The effective lifetime of the gold bumps was successfully predicted by considering both the crystallinity and residual stress of fine gold bumps. The lifetime varied more than 10 times as a strong function of the crystallinity of grain boundaries in the fine bumps. Therefore, it is very important to control the crystallinity of the under-layer for electroplating in order to control the distribution of the mechanical properties and reliability of the electroplated gold thin films.
Design of DFB Laser Drive and Temperature Control Circuit in TDLAS Gas Concentration Detection
Authors: Yang Haoqing , Bu Xiongzhu , Cao Yihan , Song Yang
Published: February 2021

In order to satisfy the requirements of TDLAS gas measurement, the DFB laser drive and temperature control system is designed with taking STM32F103RCT6 as the main control chip, including sine wave and sawtooth signal generation circuit, temperature acquisition circuit and temperature control circuit, etc. The sine wave and the sawtooth wave signal are respectively generated by using the DDS chip and the STM32 on-chip DAC, and the two are superimposed to control the constant current source to drive the laser. At the same time, the internal temperature of the laser is collected and controlled. The DFB laser with a center wavelength of 1653.7 nm is used to verify the CH4. The experiment proves that the system can generate stable laser driving signals and achieve precise temperature control. The temperature control accuracy can reach ±0.013 °C. The design satisfies the requirements of TDLAS gas detection system for laser driving and temperature control.
Programmable Waveguiding of Ultrasonic Waves for Regional Damage Detection Using Elastic Metamaterials
Authors: Song Yihao , Shen Yanfeng
Published: February 2021

This study puts forward a metasurface design which allows the flexible tuning of the elastic wave propagation path, enabling the interrogating wave field guiding into desired monitoring regions for damage detection. As a demonstrative case study, the metasurface plate contains a rectangular array of unit cells sitting in an aluminum plate. Each unit cell is comprised of a shape memory alloy substrate and a lead stub. The controllable bandgap of such a metamaterial system can be achieved due to the stiffness change of nitinol between its martensite phase and austenite phase under a thermal load. First, a Finite Element Model (FEM) of the unit cell is constructed to calculate the band structure of the metasurface plate, demonstrating the adjustable bandgap behavior. Then, numerical modeling of the metamaterial waveguide is performed by shifting the bandgap of a specific path of the metasurface away from the excitation frequency. The modeling results demonstrate that the martensite metasurface area forms a bandgap region where guided wave energy cannot penetrate. While, the bandgap of the austenite part shifts away from the excitation frequency, opening up a transmission path for the ultrasonic waves. By delicately selecting the austenite state unit cell path, four ‘S’, ‘J’, ‘T’, ‘U’ shaped routes with a fine resolution are tailored to show a SJTU logo, demonstrating the excellent waveguiding capability and the programmable waveguide feature of this shape memory metamaterial system. The proposed tunable waveguiding methodology possesses great application potential in future Structural Health Monitoring (SHM) and Nondestructive Evaluation (NDE) applications.
Game Theoretic Modelling Approach for Optimizing Direct Metal Laser Sintering Process Parameters Using Artificial Neural Network
Authors: Jahan Suchana , El-Mounayri Hazim
Published: February 2021

Additive Manufacturing, also known as Rapid Prototyping and 3D Printing is a three-dimensional fabrication process, executed by adding materials in layers. Among many different classes of AM processes, Direct Metal Laser Sintering is a widely used metal part manufacturing method. The design, planning and implementation of overall DMLS process and its process parameters are yet to be optimized. To be able to render minimum defects as well as higher quantity of production, it is essential to apply ever developing computer technologies, data storage capabilities and optimization techniques. Typically, the defects on any 3D printed part can alter mechanical properties and shorten its durability. To minimize the defects and produce good quality parts at a mass level, has been a challenge in additive manufacturing industry. In this paper, a framework is presented to utilize game theoretic modelling approach to optimize DMLS process parameters. Online monitoring of DMLS process can identify defects of printed layers and correlate them with temperature signatures. An Artificial Neural Network is trained to predict printing defects and process parameters. predicted model can be further used in a game theoretic playoff matrix to identify the most optimal combination or configuration of DMLS process parameters to minimize defects and maximize the production quantity. The proposed method can also be applied in different domains of additive and advanced manufacturing.
On the Design of a DLD-DEP Device for Separation of Circulating Tumor Cells in Blood
Authors: Rahmati Mehdi , Chen Xiaolin
Published: February 2021

Circulating Tumor Cells (CTCs), which migrate from original sites in a body to distant organs through blood, are a key factor in cancer detection. Emerging Label-free techniques owing to their inherent advantage to preserve characteristics of sorted cells and low consumption of samples can be promising to the prediction of cancer progression and metastasis research. Deterministic Lateral Displacement (DLD) is one of the label-free separation techniques employing a specific arrangement of micro-posts for continuous separation of suspended cells in a buffer based on the size of cells. Separation based solely on size is challenging since the size distributions of CTCs might overlap with those of normal blood cells. To address this problem, DLD can be combined with dielectrophoresis (DEP) technique which is the phenomenon of particle movement in a non-uniform electric field owing to the polarization effect. Although, DLD devices employ the laminar flow in low Reynolds number (Re) fluid flow due to predictability of such flow regimes, they should be improved to work in higher Re flow regime so as to attain high throughput devices. In this paper, a particle tracing simulation is developed to study the effects of different post shapes, shift fraction of micropost arrays, and dielectrophoresis forces on separation of CTCs from peripheral blood cells. Our numerical model and results provide a groundwork for design and fabrication of high-throughput DLD-DEP devices for improvement of CTC separation.
Development of New Eco-Composites From Natural Agro-Residues and Recycled Polymers
Authors: Alzebdeh Khalid I. , Nassar Mahmoud M. A. , Al-Hinai Nasr
Published: February 2021

Wood plastic composite materials have shown a remarkable performance in various applications due to its inherent properties like strength, durability, and lightweight over conventional composite materials. However, utilization of wood as an organic filler for polymers poses a serious negative impact to the green areas. Therefore, utilization of agro-residues as organic fillers instead of wood offers a sustainable solution to the aforementioned problem. In this context, this study aims to investigate the potential use of date palm pedicel agro-residues as natural fillers in eco-composites in which recycled post-consumer polypropylene is used as a matrix. Three levels of date palm flour content, namely, 10 v.%, 20 v.% and 30 v.% are used. The influence of the date palm pedicels flour content on the mechanical, physical and thermal behavior of the developed eco-composites is examined. Material properties of the fabricated eco-composites are characterized experimentally according to ASTM standards. Thermogravimetric analysis (TGA) is also performed to assess the thermal decomposition of the developed composites. Moreover, the morphology of fractured regions is captured using Scanning Electron Microscope (SEM). Generally, adding natural fillers to the polymer matrix is a cost effective option. However, it also slightly affects tensile strength, elongation, and flexural strength at break and enhance the Young’s modulus compared to the neat polypropylene. Interestingly, it is observed that the recycled polypropylene based composites are more repellent to water absorption in comparison to the virgin polypropylene-based composites. This attribute might be due to the surface quality transformation for the reprocessed plastic polymer.
An Engineering Approach to Model Blood Cells Electrical Characteristics: From Biological to Digital-Twin
Authors: Fontanili Luca , Milani Massimo , Montorsi Luca , Scurani Letizia , Fabbri Francesco
Published: February 2021

Some of the most effective methods to separate circulating tumor cells (CTCs) from normal blood cells can be implemented using ultra-filtration, and/or electro-magnetic fields. As well known, each biological cell presents, on both sides of its membrane, different concentrations of ionic species that produce an electric charge concentration with respect to the lipid double layer (impermeable to ions). In this way, the bio-cell can be seen as an electric capacitor, which has the lipid double layer acting as an insulator inserted between two conductive plates, concentrated on the lipid double layer inner and outer surfaces. In this paper, firstly, the electrical capacitor equivalent system is used to treat different types of bio-cells normally flowing in blood vessels (red blood cells, lymphocytes and various types of CTCs-like), and to transform their biological characteristics into digital twin information useful for engineering applications. After, the preliminary 3D geometric analysis of the bio-cells shapes allowed to associate each bio-cell to a different capacitor model, and to predict the electric-equivalent dimensions characterizing its electric behavior. Finally, the equivalent capacitor model is used to study the influence of bio-cells characteristics variation on human blood cells, with particular attention devoted to liver and lung CTCs-like ones.
Manufacturing Error Detection in Plate and Cylindrical Composite Structures
Authors: Talebi Cihan , Acar Bülent , Özgen Gökhan O.
Published: February 2021

Due to their superior weight to strength ratio of composites to common metallic structures, composite technology is widely used in aerospace industry. Assessment of damage in composites has gained interest after a large number of accidents caused by unanticipated damages in the composite structures. Many different structural health monitoring applications were developed over the years due to the fact that composite materials may inherit damage from within, not always visible from surface. The most common types of errors encountered in the industry are due to misaligned fibers, a mix-up in ply order, and delaminations: all presenting changes in the vibro-acoustical performance of the composite structure. This paper discusses the change in the dynamic properties of a composite structure contains a manufacturing error such as a ply lay-up error, and a ply angle error. Both plate and cylindrical structure types were considered for the stated error types. Effect of symmetric errors, unsymmetrical and unbalanced errors, and mid-plane errors were considered in the case of ply orientations, and dynamic stiffness matrix was used to identify the error. Identification of the structure’s layup properties and manufacturing error identification is employed. From the measured modal properties of the structure, a back-tracking strategy was used to generate the ply lay-up of the composite structure. Prepreg plates of a single carbon fiber system and filament wound hybrid cylinders consisting of glass and carbon fibers were manufactured for testing. Modal tests on plates and cylindrical composite structures were performed and compared with the analysis. A good match between the finite element model and experiment was shown in natural frequencies and mode shapes.
Solar Tracking Using Linear Actuator
Authors: Betai Jay Dipak , Zhou Hong
Published: February 2021

Solar trackers make solar panels perpendicular to solar ray to enhance solar power reaping. The relative motion between Sun and Earth has two degrees of freedom. Sun travels from east to west during daytime and also moves north and south due to Earth’s tilt. However, Sun’s daily north-south move is much smaller than its east-west move. Sensor-based solar trackers make solar panels perpendicular to solar ray based on sensor information. Although the existing sensor-based solar trackers increase solar power reaping from solar panels significantly, they also consume considerable power by driving solar trackers. Sensorless solar trackers make solar panels perpendicular to solar ray based on calculated solar location. The performance of sensorless solar trackers is not affected by bad weather. This paper is on sensorless solar trackers. Single-axis solar trackers have one degree of freedom solar tracking motion. They can catch Sun’s daily east-west movement effectively. The Sun’s small north-south movement can be covered for single-axis solar trackers by monthly or seasonal adjustment of their orientations. This research is focused on single-axis sensorless solar trackers that are driven by linear actuators. The advantages of linear actuator driven solar trackers are their self-locking function and high load carrying capacity. Their challenges include limited solar panel motion range, potential interference between an oscillating solar panel and its fixed supporting ground link, and high motor power consumption for solar tracking. The research of this paper is motivated by surmounting the challenges facing sensorless single-axis linear actuator driven solar trackers. In this research, linear actuator driven solar trackers will be designed and analyzed. The models of the designed solar trackers will be developed. The kinematic and dynamic performances of the modeled solar trackers will be analyzed and simulated. The results of this research will provide some guidelines for developing linear actuator driven solar trackers.
Multibody Dynamic Model of a Double Nut Preloaded Ball Screw Mechanism With Lubrication
Authors: Bertolino Antonio Carlo , Mauro Stefano , Jacazio Giovanni , Sorli Massimo
Published: February 2021

Ball screws have been investigated by several researchers from a theoretical point of view because the intrinsic complexity of experimental investigation of these mechanisms. Most of the models developed so far have been developed in quasi-static conditions ignoring inertia terms and time variability of operating conditions. A detailed multibody dynamic model of a double nut preloaded ball screw is presented in this paper, taking into account the full dynamic of each subcomponent as well as the mutual interactions. A 3D contact model is introduced, considering Hertzian normal contact and a simplified friction model based on grease lubrication. This model takes into account the time variability of the operating conditions and it is suitable to be used for prognostic and model-based design approaches. The results of dynamic simulations in presence of backlash are presented to highlight the model’s capabilities.
Modelling of Energy Accumulation in Belt Conveyor Systems Under Faulty Conditions
Authors: Bertolino Antonio Carlo , Lombardi Gabriele , Mauro Stefano , Sorli Massimo
Published: February 2021

The consideration of potential energy stored in a system is paramount to carry on safe maintenance operations of mechanical system. In particular, this paper concentrates on the elastic energy accumulation occurring in a belt conveyor system ensuing a seizure of one of the pulleys owing to, for example, dirt and spilled bulk material accumulation in the belt inlet zone. The hazard of considering the system completely discharged just because the electrical supply cut off and the effect of such an energy storage are investigated by means of a lumped mass dynamic mathematical model. It allows time variable operating conditions to be considered, as well as starting and stopping phases transients. Standard maintenance operations are simulated, and the effect of stored energy sudden release investigated.
Directed Graphical Model for Real-Time Process Monitoring in Additive Manufacturing
Authors: Clemon Lee
Published: February 2021

An important challenge for additive manufacturing and 3D printing processes is accurate and repeatable deposition quality. Current approaches are unable to handle variable process parameters and input material quality. Accurately controlling material properties requires predicting material state changes. This work proposes a model using statistical learning techniques in conjunction with iterative material study to identify and compute the sources of defects and local material properties. The model makes use of the element-by-element fabrication and time-series material changes of additive manufacturing. The deposition of a part is segmented into volume elements, called voxels. Each deposited voxel is treated as an independent sample of the process parameter effects. The time series of deposition is treated as a Markov Chain, with the control parameters and measurable emissions as known quantities. The state of the material is a hidden variable. The hidden variable is approximated using material models and post-fabrication testing results to train the distribution embedded in the Markov Chain. The results indicated that a physics-based material state transition matrix in conjunction with final material properties and time-series of physical emissions can give insight into process variability and control errors. These results have wide ranging implications as a computationally efficient means of iterative process improvement for additive manufacturing, designing new control strategies, and revealing the real-time state of voxels as they are deposited. This approach moves closer to a predictive model that includes current information on the state of the process to update the prediction.
Regional and Layer Distribution of Residual Stresses in an Unloaded Aortic Medial Wall
Authors: Tamura Atsutaka , Matsumoto Koki
Published: February 2021

The mechanical and structural characteristics of aortic media have profound effects on the physiology and pathophysiology of an aorta. However, many aspects of the aortic tissue remain poorly understood, partly due to the intrinsic layered wall structure and regionally varying residual stresses. Our recent works have demonstrated that a mechanical interaction between the elastic lamina (EL) and smooth muscle layer in the aortic media can be computationally reproduced using a simplified finite element (FE) model. However, it is questionable whether the simplified FE model we created was representative of the structure of a real medial wall and its modeling technique would be applicable to develop a more sophisticated and structure-based aortic FE model. This study aimed to computationally represent EL buckling in the aortic medial ring at an unloaded state and successfully reproduced transmural variation in EL waviness across the aortic wall. We also aimed at confirming the inner and outer layers of the medial wall are subjected to compressive and tensile residual stresses, respectively, at the unloaded state, implying that the ring model will open spontaneously when it is radially cut. Moreover, the computed residual stresses were found to be within the reasonable range of the predicted values, 1–10 kPa, supporting the validity of our modeling approach. Although further study is required, the information obtained here will greatly help improve the understanding of basic aortic physiology and pathophysiology, while simultaneously providing a basis for more sophisticated computational modeling of the aorta.
Puncture Impact Behavior of Glass Plate Fitted With a Polymeric Film
Authors: Kojima Tomohisa
Published: February 2021

Glass plates are used extensively as windows in structures, cars, and airplanes. However, because it is a brittle material with low practical strength, improving its resistance to puncture impact loading is important for safety and security. Although it is known that fitting a polymeric film to the glass plate is an easy and effective way to reinforce it against impact loads, the effect of the film fitting has not enough been evaluated quantitatively. In this study, puncture impact behavior was investigated with a glass plate fitted with a polymeric film. When the general puncture impact testing method is applied to a glass plate, the measured load profile would be intensely oscillated by resonance. Therefore, in this study, the modified testing method utilizing the steel incident bar was adopted. By dropping the steel weight, impact loads were applied to the glass plate with the film through the steel incident bar. The applied impact load was estimated from the strain gauge outputs at the incident bar. The stress distribution and crack propagation in the thickness direction of the specimen were observed using the photoelastic method and shadowgraph method with the high-speed video camera. The numerical analysis model capable of reproducing the experiment was built. The obtained load-displacement curves did not include vibrations because of resonance. By the method used in this study, it is possible to quantitatively evaluate the effect of film-fitting on the glass plate.
Spin Accelerating Mechanism for Gyroscopic Wave Energy Converter
Authors: Toyoshima Akio , Hosaka Hiroshi
Published: February 2021

Many wave energy converters have been developed so far, but there are still many engineering problems to be applied to fishery buoys. Gyroscopic generators that use a rotating mass is characterized by the possibility of downsizing, but since low speed precession rotation is used to generate power, efficiency is so low that they do not work in the size of 1 m3. In this study, a new mechanism is proposed which consists of bevel gears, two clutches and gimbals to accelerate spin by transmitting precession torque mechanically to the spin shaft in order to realize high efficiency power generation by high speed spin rotation. Gear-driven gyroscopic generator using this mechanism which has higher efficiency and longer lifespan than former generators is expected to be applied to the power source of the small ocean monitoring buoys for efficient fisheries. A gyroscopic power generator using the accelerating mechanism with flywheel of diameter of 300 mm was designed, and the accelerating mechanism of the generator was manufactured. An experiment was conducted in which a rotating vibration of 0.5 Hz was applied to confirm the effectivity of the mechanism. The spin speed increased from 35.6 rpm to 225 rpm due to the precession torque. Designed generator is expected to output power of 3 W from this result.
Fluid-Structural Dynamic Characterization of a Membrane Wing in a Gust Environment
Authors: Pulok Mohammad Khairul Habib , Chakravarty Uttam K.
Published: February 2021

Unmanned aerial vehicles are applicable in a lot of areas including weather condition monitoring, surveillance, and reconnaissance. They need further development in design, especially, for the turbulent atmospheric conditions. Smart materials are considered for wing manufacturing for gust alleviation whereas membranes are found suitable for such applications, and therefore, analyzing aerodynamic properties of the membrane is important. Wind gusts create an abrupt atmospheric situation for unmanned aerial vehicles during the flight. In this study, a continuous gust profile and two types of stochastic gust models, i.e., Dryden gust model and von Karman gust model are developed to study the effects of gust load on a flexible membrane wing. One of the promising ways to reduce the effects of the gust is by using an electroactive membrane wing. A fluid-structure-interaction model by coupling the finite element model of the membrane and computational fluid dynamics model of the surrounding airflow is generated. Aerodynamic coefficients are calculated from the forces found from the numerical results for different gust velocities. A wind-tunnel experimental setup is used to investigate the aerodynamic responses of the membrane wing. Dryden gust model and von Karman gust model are found comparable with a minimum variation of magnitude in the gust velocity profile. The coefficients of lift and drag fluctuate significantly with the change in velocity due to wind gust. A validation of the fluid-structure-interaction model is performed by comparing the numerical results for the lift and drag coefficients with the experimental results. The outcome of this study contributes to better understand the aerodynamics and maneuverability of unmanned aerial vehicles in the gust environment.
Nano-Scale Wettability of Free-Standing Capped Carbon Nanotube Arrays
Authors: Ouzounian Miray , Hu Travis Shihao
Published: February 2021

Countless organisms in nature have adapted high-aspect-ratio micro-/nano-fibrillar arrays on their functional surfaces for achieving special and often optimized functionalities using earthly abundant materials. At the core of nanoscience and nanotechnology, rationally mimicking nature offers a promising route to create multifunctional superstructures that capture organisms and biological materials’ intriguing responsive and self-adjusting properties. Prior work has demonstrated that hierarchical vertically aligned multi-walled carbon nanotube (VA-MCNT) arrays can achieve ten folds of adhesive force comparing to the fibrillar structures of the gecko toe pads. However, little is known with regard to their wettability at the ultimate atomistic level, and how this may influence the adhesive performance and/or self-cleaning capabilities, despite water condensation and bridging are common phenomena at this length scale. In present study, molecular dynamics (MD) simulations were performed using Large-Scale Atomic / Molecular Massively Parallel Simulator (LAMMPS). Results indicate that commonly believed hydrophobic defect free CNTs (i.e., carbon sp2 hybridization without any dangling bonds) become super-hydrophilic at this length/temporal scale. The critical factors that influence the number of H-Bonds in water are: i) tube-tube spacing; and ii) shape/size and position of the water nanodroplet; and iii) how many droplets exists and how many nanotubes are bridged by the droplets. Chirality has little effect on the water interfacial behaviors. Future work will focus on the effect of water condensation and bridging on the adhesive and self-cleaning properties of carbon-based bio-inspired fibrillar dry adhesives considering defects and saline water.
Development and Characterization of Fly Ash Nanoparticles Reinforced Epoxy Resin Composite for Acoustic Applications
Authors: Ukoba Kingsley , Popoola Samuel , Israel Olatunde , Imoisili Patrick , Jen Tien-Chien
Published: February 2021

Noise is an unwanted sound; requires reduction and control through the use of absorptive materials. This is imperative due to the adverse effect noise poses to human health, knowledge dissemination, and tranquility which is increasing daily due to industrialization and heightened allied activities. The use of natural and synthetic reinforced composites in noise pollution control is an emerging area of research. This study aims to develop and characterize fly ash nanoparticles reinforced epoxy resin composite for acoustic applications. Samples were prepared with fly ash nanoparticles reinforcement at 5%, 10%, 15%, 20%, and 25% and investigation of noise reduction coefficient (NRC), porosity and mechanical properties (hardness, impact, flexural strength) of samples were done. Cenospheres were obtained when fly ash particles were characterized separately with the aid of sieve analysis and x-ray fluorescence analysis. The cenospheres are hollow spherical and lightweight, inertfiller material. Correlation between porosity of the samples and their sound absorption properties was observed and showed that as porosity increased, the NRC values increased and as the porosity decreased the NRC values decreased. It was also observed that heat of polymerization, fly ash nanoparticles structure and air bubbles during sample preparation (mixing) influenced the porosity values which in turn influenced the NRC values of the composite. There was also a steady decrease in mechanical properties, as reinforcements were added (5%, 10%, 15%, 20%, and 25%), this was attributed to the high surface areas and shape of reinforcement added.
Finite Element Analysis of Installation Failures in Engine Cylinder-Liners
Authors: Paruchuru Satya Prasad , Maturi Pramila Rani , Nuthalapati Jashwitha
Published: February 2021

There exist concerns regarding the failures that occur during the installation of thin cylinder-liners of engines at the authorized and unauthorized service centers. Analyzing the probable causes from the points of view of the design, manufacturing, and authorized and unauthorized installation procedures define the problem. The problem involves the simulation of the process of press-fitting the liner into the cylinder bore. A choice of finite element analysis using commercially available software ANSYS helped the analysis of the probable causes of failure. Estimation of the probable loads experienced by the cylinder-liners during the procedures that exist in the installation-process paved the way to the definition of loads that prevail in the problem of relevance. Prediction of the nature of contacts that prevail in the current problem and the impact of the application of the loads enabled the definition of constraints for the simulation procedures. Reference material properties chosen in the conservative sense modeled the problem realistically. The evolution of the recommendations for the manufacturing and installation of thin cylinder-liners concluded the study.
A CFD Approach for the Simulation of an Entire Swash-Plate Axial Piston Pump Under Dynamic Operating Conditions
Authors: Milani Massimo , Montorsi Luca , Muzzioli Gabriele , Lucchi Andrea
Published: February 2021

The paper proposes a CFD approach for the simulation of a swash-plate axial piston pump including the full 3D geometry of the real component.

Different meshing techniques are integrated in order to reproduce all the internal motions of the pump. The overset mesh procedure is used to simulate the dynamic evolution in regions’ shape and the variable orientation between parts in the piston-slipper ball joints while the alternating motion of the piston is accounted for by sliding interfaces with the neighboring regions.

The multiple dynamics of the different moving elements are implemented in terms of superposing motions in order to reproduce the real position time histories as a function of the rotational speed and the swash plate inclination angle.

The proposed numerical model includes all the leakages that characterize the coupling of the many components of the pump and nominal values are assumed (i.e. 10μm) throughout the entire simulation.

A pressure-dependent fluid density approach is adopted to improve the performance prediction of the pump under real operating conditions. Moreover, the turbulent behavior of the flow is addressed by means of the two equation k-omega SST model.

Therefore the proposed modeling approach highlights the capabilities to address any type of swash-plate axial piston pump in order to simulate the entire machine under dynamic operations; the numerical results are discussed in terms of flow ripple, pressure distribution and fluid-dynamic forces.
Comparison of UGV Position Estimation Equipped With GNSS-RTK and GPS Using EKF
Authors: Ismail Hesham , Althani Thani , Anzil Mohammed Minhas , Subramaniam Prashanth
Published: February 2021

Site assessments for bifacial Photovoltaic (PV) installation are quite challenging to conduct manually due to the area size and the extreme temperature conditions at desert sites. We designed and built an autonomous Unmanned Ground Vehicle (UGV) fitted with a Global Navigation Satellite Network-System Real-Time Kinematic (GNSS-RTK) positioning device, an Inertial Measurement Unit (IMU), encoder to improve and aid site assessments in desert condition. Sandy terrains deserts are challenging for UGV’s because they increase the likelihood of wheel slippage due to reduced traction. Sensor details such as IMU, GNSS-RTK, and encoder should be taken into consideration to account for the errors that the desert terrains pose. This study compared the Extended Kalman Filter (EKF) for standard GPS & GNSS-RTK to verify which performs better for the UGV’s position estimation. The estimated UGV’s position from the kinematics model and EKF are validated using a drone camera system that uses an image processing technique to verify the UGV’s position with the help of the visible reference cones. Throughout the experiments, the GNSS-RTK performed better than GPS. Also, the EKF performed as well as the GNSS-RTK by trusting it more than the encoder/gyroscope reading.
Investigation on Thermal Performance of a Simple Electronic Board Using Different Phase Change Material Packaging Types
Authors: Özkökdemir Emir , Usul Yener
Published: February 2021

Phase change materials (PCMs) are some kind of energy storage systems which have widely been used in many industries such as electronic equipment, heat pumps, buildings, solar panels and spacecraft thermal control applications. Two main outstanding features of PCMs are having large amount of energy storage capacity at low temperature difference between heat source-sink pair and being remained at almost constant temperature during phase change process. In this study, thermal performance of PCMs for passive cooling of electronic modules with heating components is investigated numerically. A commercially available solid-solid PCM is employed. Effects of different packaging types for PCM on thermal performance of the electronics board are examined. Three different packaging types are considered; bulk PCM inside a rectangular enclosure, a rectangular enclosure having rectangular fins with PCM inside and a rectangular foam structure. All of the enclosures containing the PCM are made up of aluminum. All of the PCM packages are placed over the heating component of the electronics board in the same environmental condition. Computations are performed in three dimensions using a conduction based finite element method. Computational method is verified by time-dependent temperature measurements of the PCM modules. Results for different cases are presented comparatively.
Acceleration of Grain Boundary Cracking in Ni-Base Alloy 617 Under Creep-Fatigue Loading at 800°C
Authors: Ishihara Kenta , Luo Yifan , Miura Hideo
Published: February 2021

In recent years, in order to solve the global warming issue, the operating temperature of advanced thermal power plants has attempted to improve thermal efficiency and reduce CO2 emissions. Under the creep and creep-fatigue conditions at elevated temperature, however, the effective lifetime of heat-resistant alloys such as Ni-base Alloy 617, which has high strength and good corrosion resistance at about 750°C, was found to decrease drastically. Main reason for this short lifetime was attributed to the change in the crack initiation and propagation paths from transgranular one to intergranular one. Therefore, it is important to understand and express the criteria for grain boundary cracking. In this study, electron back-scatter diffraction (EBSD) analysis was applied to the visualization of the degradation process of the quality of grain boundaries in the alloy. The change in the crystallinity of grains and grain boundaries were continuously monitored during creep and creep-fatigue tests. It was found that accumulation of vacancies and dislocations degraded the crystallinity of grain boundaries and thus, their strength. The accumulation occurred around the specific grain boundaries which consisted of grains with large difference of Schmid factor during creep test. On the other hand, it occurred around all grain boundaries under the creep-fatigue loading. Thus, the accumulation of defects was clearly accelerated under the creep-fatigue loading. The critical image quality (IQ) value of intergranular cracking was almost the same regardless of the loading mode. Once the IQ value of the damaged grain boundaries decreased to a critical value, intergranular cracking started to occur at the grain boundaries.
Tuning a New ECG and Breath Monitoring System Through Cardiopulmonary Exercise Test Comparison: The Case of IUTA Athletes
Authors: Fontanili Luca , Milani Massimo , Montorsi Luca , Scurani Letizia , Citarella Roberto
Published: February 2021

Heart Rate (HR) and Breath Rate (BR) are important parameters that define the physiological state of the athlete and evaluate his training the performances during a race or a match. In particular for runners, these are two indexes that can be easily monitored during the performance for the athlete to understand their physical state as well as for the trainer or the coach to improve the athlete deep knowledge and better design the subject specific training.

The HR can be typically acquired by lots of different technologies.

In this paper, a simple and fast fitting new device for ECG and BR acquisition is presented. This device is a first optimized prototype that use a reduced number of electrodes on the torso to acquire both the ECG waveform and a BR signal.

In order to evaluate the reliability and precision of this device we have defined an experimental campaign. Two IUTA athletes (a man and a woman) have been selected to wear the device during a Cardio Pulmonary Exercise Test (CPET).

The BR track and ECG waveform acquired by the CPET are compared to the ones acquired with the new device to confirm the reliability and precision of the system.
Evaluation of Fatigue Crack Growth Characteristics on Stainless Steel SS 316 LN Using Acoustic Emission Technique
Authors: Prakash Raghu V. , Thomas Manuel
Published: February 2021

Results of online acoustic emission (AE) monitoring during fatigue crack growth rate (FCGR) experiments on a stainless steel SS 316 LN are presented in this paper. Two specimen geometries — viz., standard compact tension (C(T)) specimens as well as side-grooved C(T) specimens were considered for experiments at ambient temperature and at 600°C (873K). There is a good correspondence between crack length increment and the increase in AE cumulative count and cumulative energy during the experiments. The side grove introduced on the thickness direction of the test specimen constrains the plastic zone ahead of the crack tip, thereby enforcing plane strain conditions at the crack. Reduced AE activity at initial stages of crack growth was observed for side grooved samples. The transition to Stage-II crack growth was observed using acoustic emission (AE) technique which otherwise was not visible from the fatigue crack growth plot.

The work further attempts to correlate the AE parameters obtained during elevated temperature (873K) fatigue crack growth in stainless steel. For the purpose of acquiring AE signals outside the heated zone, a waveguide was used to transmit the acoustic waves from the specimen at high temperature. A correlation between crack advance and AE parameters was obtained from the elevated temperature tests.
Theoretical Study of Heterojunction-Like Electronic Properties Between a Semiconductive Graphene Nanoribbon and a Metallic Graphene for Highly Sensitive Strain Sensors
Authors: Zhang Qinqiang , Qiao Xiangyu , Kobayashi Masasuke , Suzuki Ken
Published: February 2021

Graphene shows unique super-conductive properties and graphene nanoribbons (GNRs) with band gaps are the candidates for a sensing component of highly sensitive strain sensors. Usually, there is a large energy barrier between electrodes and semiconductors which is not suitable for electron transfer. Therefore, ohmic contact between them is indispensable for fabricating electronic applications. In order to achieve the ohmic contact between external electrodes and detective elements in the devices, the dumbbell-shaped structure of GNRs was proposed for the basic structure of the GNR-based strain sensors, dubbed as dumbbell-shape GNR (DS-GNR). It consists of a long narrow GNR at the center of the structure as the sensing element coalesced with two wider GNRs at both ends of the narrow GNR as the contact components to external electrodes. Both narrow and wide segments of DS-GNR consist of only carbon atoms. The effect of the interaction in the vicinity of the junction area between wide metallic and narrow semiconductive GNRs, however, has not been clearly demonstrated. In this study, first-principles calculations were implemented to the analysis of the electronic band structure of the DS-GNR. It was found that the localized distribution of the energy states of electrons exists in the wide segment of DS-GNR. The changes varied from wide to narrow segment is smooth and observable as strong functions of the length and the width of DS-GNRs. The current-voltage characteristics showed curved semiconductive-like electronic properties with a smooth-electron flow in DS-GNR. Therefore, the DS-GNR has great potential for the use of next-generation highly sensitive and deformable strain sensors.