bluuebunny/crossref_metadata_2025_split huggingface dataset:
Autonomous Drone Delivery From Airdrop Systems (ADDAS): Aerially Deploying Folding-Wing Drones for Ground Reconnaissance
Authors: Bluman James , Carter Vault Davonte , Soon Wei Kang , Talbott Ruth , Willis Jonathan , Kopeikin Andrew , Prosser Ekaterina 
Published: February 2021

Abstract
Extending the long-range capabilities of unmanned aerial systems (UAS) is paramount to protecting small Soldier teams operating in remote battlefield scenarios. Currently, many small Unmanned Aerial Systems (sUAS) reconnaissance assets have the range necessary to facilitate small-unit missions. The purpose of this paper is to detail the design and testing of a system that fills this capability gap by creating folding-wing drones designed to be aerially deployed from an airdropped dispenser. The dispenser is attached to the Joint Precision Airdrop System (JPADS), which is an autonomously navigated cargo delivery parafoil that can glide several miles, and which can land within 100 meters of its target. To employ the system, the dispenser is launched from a high-altitude aircraft. The system must survive the opening of the parachute in high speed forward flight and provide cushioning to the drones and other components. Once the JPADS navigates the dispenser to a predetermined altitude and distance from the intended reconnaissance area, the dispenser deploys multiple folding-wing drones. The soldiers on the ground can access the drones’ live video feeds through a handheld video transmitter. The system combines the precision navigation and information-transmission capabilities of the fixed wing drone with the long-range capabilities of the JPADS. With a commercial-off-the-shelf drone as the folding-wing aircraft platform, the team designed a wing connection hub that allows for rapid folding and unfolding of the drone’s wings, a separate canister for each drone within the dispenser, and a dispenser capable of interfacing with both the canisters and the JPADS. Though currently in the technology-demonstration phase of the project, the team envisions the system being fully autonomous from launch of dispenser to end of mission.
On Numerical Modeling of Equal Channel Angular Extrusion of Ultra High Molecular Weight Polyethylene
Authors: Vasylevskyi Kostiantyn , Miroshnichenko Kateryna , Buklovskyi Stanislav , Tsukrov Igor , Grover Hannah , Van Citters Douglas 
Published: February 2021

Abstract
Ultra high molecular weight polyethylene (UHMWPE) is widely used in biomedical applications, e.g. as a bearing surface in total joint arthroplasty. Recently, equal channel angular extrusion (ECAE) was proposed as a processing method to achieve higher molecular entanglement and superior mechanical properties of this material. Numerical modeling can be utilized to evaluate the influence of such important manufacturing parameters as the extrusion rate, temperature, geometry of the die, back pressure and friction effects in the ECAE of polyethylenes.
In this paper we focus on the development of efficient FE models of ECAE for UHMWPE. We study the applicability of the available constitutive models traditionally used in polymer mechanics for UHMWPE, evaluate the importance of the proper choice of the friction parameters between the billet and the die, and compare the accuracy of predictions between 2D (plane strain) and 3D models.
Our studies demonstrate that the choice of the constitutive model is extremely important for the accuracy of numerical modeling predictions. It is also shown that the friction coefficient significantly influences the punch force and that 2D plane strain assumption can become inaccurate in the presence of friction between the billet and the extrusion channel.
Energy Resource for a RFID System Based on Dynamic Features of Reddy-Levinson Beam
Authors: Babaei Alireza , Parker Johné , Moshaver Paria 
Published: February 2021

Abstract
Understanding the effect of design parameters on resonant frequency variation is a critically important aspect of piezoelectric energy harvester device design. As a first step in more accurately investigating the performance of a fixture designed for targeted RFID tag communication that also utilizes an energy harvesting application, this paper analyzes the variations in resonant frequency of a higher-order beam based on Reddy-Levinson theory (RLBT) under rotation effects. A long-term goal of this research is to implement an effective energy harvester on the RFID system. Part of the experimental RFID test fixture can be modeled as a beam (or beam element); thus, understanding the resonance frequency variations due to shear deformation and rotation effects is an important first step in obtaining information about the efficacy of the fixture in serving as an energy harvester. Investigating the performance of a beam also provides valuable information about the maximum power, frequency bandwidth, and tuning ability of the device that can be expected from an analogous energy harvester. For the first time, the resonant frequency variation of a rotating thick beam is investigated. Specifically, RLBT is used to verify the effects of shear deformation upon resonant frequency, and a coupled displacement field is utilized to enable tuning the potential piezoelectric energy harvester to low-input excitations by means of constraining translational and rotational movements of the system based on a linear constraint equation. Navier’s method as an analytical-numerical method is adopted to discretize the continuous system and to find resonant frequencies, respectively. Results reveal the significance of beam thickness and rotation effects of the proposed model for the purpose of minimizing energy usage. Current results are compared and verified numerically with available benchmarks to confirm a satisfactory level of accuracy. The proposed model, which is based on a coupled displacement field, can also be used to design other piezoelectric electro-mechanical-systems; e.g., vibration isolators, and vibration controllers. In other words, in an energy-scavenging system, a fundamental understanding of parameters affecting the resonant frequency can be accomplished through the presented analysis. The proposed model highlights the fact that, by adopting a proper speed factor, tuning the piezoelectric energy harvester to low-input excitations is possible. Additionally, it is observed that the rotation effect on the resonant frequency is more severe than effects of slenderness ratio. Finally, in this paper an improved model is proposed to capture the shear deformation effect, particularly for thick-beam energy harvesters, with the capability of tuning to low-input excitations.
Nonlinear Vibrations of Model PWR Fuel Assemblies: Part 1 — Experimental Setup and Measurements
Authors: Ferrari Giovanni , Franchini Giulio , Balasubramanian Prabakaran , Karazis Kostas , Amabili Marco 
Published: February 2021

Abstract
Nuclear fuel bundles in PWR reactors present vibrations due to coolant flow, which may result in fretting at the interface between the fuel rods and the retaining elements, named spacer grids (SGs). Seismic excitation may also occur during accidental events, such as earthquakes. In this perspective, forced vibration experiments were performed on a reduced-scale nuclear fuel bundle provided by Framatome Canada. The presence of partially loose fuel pellets inside the fuel rods was provided in the experiments. A maximum coolant flow of 5 meters per second was reached inside a water tunnel.
The identification of vibration parameters was attempted in the linear regime, through modal analysis, and in the nonlinear regime, through a single-degree-of-freedom method based on harmonic balance. The value of the equivalent damping parameter was shown to increase strongly with the amplitude of the excitation, thus acting in the direction of safety. The fuel bundle presents a peculiar softening vibration behavior in the nonlinear regime, with a marked decrease of the peak vibration frequency. The comparison with other recent experiments shows that the boundary conditions constituted by SGs have a predominant effect on stiffness and damping during nonlinear vibrations. Therefore, the characterization of the boundary conditions at the SGs was attempted by means of dedicated experiments.
Bending oscillations were tested in the frequency range between DC and 50 Hertz. Tests were repeated in presence and in absence of water. The resulting force-displacement loops clearly show the presence of hysteresis and of bilinear stiffness. The availability of a mathematical model for the stiffness and the damping at the boundary conditions will be indispensable for the future development of reduced-order models describing the vibrations of PWR fuel bundles.
Bearing Housing Design for Vibration Control, Using Tilting Pad Bearings Instead of Lemon-Bore Type on a Gas Turbine
Authors: Anil Chippa , Satheesh Aparna , Santhanagopalakrishnan Babu , Bielecki Marcin 
Published: February 2021

Abstract
Heavy duty gas turbines are usually equipped with hydrodynamic bearings which are either lemon-bore or tilting pad type. Baker Hughes legacy gas turbines use these two types of bearings, and its selection is based on 1) considering pros & cons from Rotor dynamics, 2) bearing performance, 3) bearing housing stiffness, 4) vibration detection & control. Non-contact probes are used to monitor the vibrations of rotor. Majority of legacy gas turbines are not equipped with these probes. Due to this fact, over the years it resulted in non-detection of dynamics & vibration issue, which caused frequent bearing replacement. As the increase in industry demand to apply and measure vibrations using non-contact probes on bearings, an effort was made by Baker Hughes to implement these on existing fleet units. Also, in order to increase rotor dynamics stability of low-pressure rotor, to improve bearing life and performance, effort was made to replace lemon-bore bearings with tilting pad. This paper demonstrates efforts made to design the titling pad which would fit within envelop of already available bearing housing. Bearing/shaft clearance, bearing performance, modification of bearing retainer clearances are the mandatory tasks which would be dealt in this study. The swap of bearing type, and its effect on whole gas turbine rotor dynamic stability, checking the frequency crossovers with Campbell diagram would also be dealt in this paper. This paper also focuses on assessment on oil passage routing, temperature & proximity probe instrumentation routing design. Re-design is performed by analyzing various configuration, assessing different sensitivity studies & validation of modified bearing housing from structural integrity, ultimate load capability, & split plane oil leakage retention and its comparison with baseline are most important aspects of finalization of this change, which will be showcased in this paper. Instrumentation routing was a critical task when the considering bearing replacement from lemon-bore to tilting pad. As lemon-bore type bearings just have an elliptical inner surface, it’s quite easy to install the thermocouples into a simple hole. But as replacement has tilting pads, the challenge is to instrument the pads without effecting their movement and functionality. Such best practices are also dealt in this paper. Comparison of tilting-pad with lemon-bore, considering the fixed shaft diameter, the retainer outer diameter of tilting pad is higher than lemon-bore. This effect has a change in bearing seat on bearing housing, thereby reducing the effective stiffness of the housing, and the reduced split plane surface. To tackle this situation, several sensitivities were executed, by re-modifying the bolts and bolt holes on the existing housing, without modifying the housing envelop.
Study on Relations Between Abnormal Vibration and Friction Characteristics of a Roller Depending on Water Content for Three Types of Fined Coal
Authors: Shimizu Yusuke , Kobayashi Akira , Watanabe Kazuhiro , Ohno Emi , Echizenya Makoto , Fujita Katsuhide , Mori Koji , Saito Takashi 
Published: February 2021

Abstract
In coal-fired power generation, it is necessary to pulverize coal, and a vertical roller mill with excellent crushing efficiency has become the mainstream. However, In the process of pulverization by compression and shear, abnormal vibrations, which are considered to be self-excited vibration, occurs rarely. As a method of reducing self-excited vibration, adding water has been empirically performed in the field. Since the powder state changes due to water addition, it is necessary to investigate how the vibration characteristics and slip characteristics change. In this paper, we examined the effects of adding water to Artificial coal, Sub-bituminous coal A, and Sub-bituminous coal B with different powder characteristics on the dynamic friction characteristics and dynamic response generated between the roller and the powder. Investigating the relation between the RMS value of the horizontal acceleration response and the slip ratio indicates the degree of slippage of the roller. Next, we investigated the relation between the dynamic frictional characteristics generated during rolling and the slip ratio and found that the Slip-Stick phenomenon remarkably appeared at the test machine speed at which the vibration acceleration was maximum even when water was added. Also, a frequency analysis showed that when the vibration acceleration increased, the resonance frequency decreased, and the phenomenon of uniting was confirmed for all types of coal, suggesting that the abnormal vibration that occurred was self-excited vibration.
Design Methodology of a Toy to Improve Manual Abilities on Medicine Students
Authors: Vega Bello Jessica Daniela , Escalera Matamoros Yesica , Treviño Arizmendi Arturo , Haro Mendoza Daniel , Borja Vicente , Jiménez Corona José Luis 
Published: February 2021

Abstract
Theoretical knowledge is important in all disciplines, but practical knowledge is of utmost importance in many of them, such is the case in engineering, medicine, and architecture. In most of these majors’ instructors focus more on the theoretical area and set aside the practical one. That is why it is important to develop educational tools to improve students’ practice. Medical students at the Universidad Nacional Autónoma de México were our case of study since we noticed a lack of practical knowledge during their second year at University. In this paper, we present a design methodology of a toy for the students of medicine to exercise and improve their manual precise movements and motor sequencing skills, in order to improve their practical abilities by using it.
This methodology emphasizes the importance of specific movements that surgeons do while they perform basic surgical procedures, intending to imitate them when they use the toy. Therefore, procedures like cutting, suturing, exposure, among others were performed by a surgeon, recorded, and analyzed. As a result, it was observed that some movements were repeated in most of the procedures. Based on this, a device was designed so that the user may be able to repeat the movements following a series of audiovisual instructions as a game. To validate its efficiency manual precision tests were used to compare the individual students’ improvement before and after using it.
Once the device was built as a toy, 12 second-year medical students took the precision tests, the measured variable was the time they used to complete both tests. Furthermore, they practiced with the toy for 10 days, 6 minutes per day. On the last day, after using it, each student performed the precision tests once again to obtain a quantitative value of their improvement.
The time spent by each student to perform the first precision tests were compared to the last after using the toy. The results showed that the execution time was reduced by an average of 53.75 seconds in the first precision test and 45 seconds in the second. This indicates that the use of the toy allows students to improve their manual precision skills, affecting the execution time of tasks that require accurate manual precision. Also, it was observed that the methodology developed could be applied and extrapolated to other disciplines such as engineering, in order to develop similar toys or devices that could enhance manual skills.
A Blended System Dynamics-Discrete Event Physics-Based Model for Anomaly Detection in Cyber-Physical Manufacturing Systems
Authors: Yu Hong , Raghavan Ajay , Mostafavi Saman , Jung Deokwoo , Sasaki Yukinori , Ogura Tetsuyoshi , Minegishi Akira , Tajika Yosuke 
Published: February 2021

Abstract
Being able to quickly detect anomalies and reason about their root causes in critical manufacturing systems can significantly reduce the analysis time to bring operations back online, thus reducing expensive unplanned downtime. Machine learning-based anomaly detection approaches often need significant amounts of labeled data for training and are challenging to scale for manufacturing deployments. A robust blended system dynamics and discrete event simulation physics-based modeling methodology is proposed for the task of automated anomaly detection. The blended model consists of discrete event simulation (DES) components for the discrete manufacturing process modeling, and system dynamics (SD) components for continuous variables. The methodology strikes a balance between the computational overhead for online monitoring and the level of details required to perform anomaly detection tasks. The implementation of models takes an object-oriented approach, allowing multiple components of a smart factory to be robustly described in a modular, extendable and reconfigurable manner. The proposed methodology is applied to and validated by data collected from a real commercial manufacturing plant. A production line is modeled with DES components and heat transfer is modeled with SD. The blended model is then utilized for anomaly detection. It is demonstrated that the model-based approach is effective not only for detecting but also explaining particular types of anomalies in a commercial discrete manufacturing system.
A Mathematical Model to Assess Occupant Compartment Intrusion on Rear Occupant Responses in Rear Crashes
Authors: Stephens Gregory , Michalski David , Parenteau Chantal S. , Burnett Roger 
Published: February 2021

Abstract
Rear occupant protection in rear crashes is a complex issue. Structural intrusion has been shown to be a significant factor in the injury mechanism of second-row children. In this study, a new model was developed to help quantify dynamic second-row intrusion, in terms of displacement, velocity, and acceleration, and assess its effect on rear occupant responses as a function of time.
A mathematical model was developed using crash test data based on two reconstructed field accidents involving two different rear-ended vehicles with second-row children. The model also used the corresponding FMVSS 301R-type rear barrier tests of a similar vehicle.
The crash test pulse data and videos from FMVSS 301R-type tests were analyzed to determine the timing and magnitude of second-row intrusion. Crash tests that had been conducted to simulate the field accidents were then used to validate the model. These tests included instrumented ATDs (Anthropometric Test Device) seated in the second-row area of the struck vehicles. The biomechanical responses were used to assess the validity of the mathematical model.
Comparison between the mathematical model and the test data showed good agreement. For example, the model correctly showed that the dynamic second-row intrusion was greater than residual/static intrusion/displacement. The model also predicted accelerations that were in good agreement with the test data.
Video analysis and head/chest acceleration time histories of the ATD’s indicated that intrusion occurred early and was an important factor in the occupant responses. Both the extent and velocity of dynamic intrusion also influenced the biomechanical responses.
The model predicted head and chest accelerations that were greater than the overall vehicle accelerations due to localized structural intrusion.
The mathematical model developed in this study is a first to assess the dynamic effect of second-row intrusion on rear occupant responses. Identifying factors that influence injury mechanisms are important when assessing the potential effectiveness of countermeasures.
Study of Erosion and Accretion From Water and Steam Over Pipe Walls of Condenser in a Thermal Power Plant
Authors: Asok Eshwanth , Shah Karan Ashitbhai , Khan Jobaidur Rahman 
Published: February 2021

Abstract
It is extremely important and required by thermal power plant to condense the exhaust steam from steam turbine outlets to obtain maximum efficiency on varying loads. Surface type condensers are often used to meet these demands. By condensing the exhaust steam at a pressure below atmospheric pressure, the pressure drop between inlet and outlet of turbine is increased which increases the amount of heat available for conversion to mechanical energy by the turbine.
Increasing the heat transfer rate of condenser is an effective method to increase the overall efficiency of a thermal power plant. With condenser playing a vital role in overall plant efficiency, it is important to analyze the areas of fouling/erosion, which reduce the condensation rate. The condenser used in a company has been in operation for many years, so to study the effect of erosion on the condenser pipelines, a computational simulation of a section of the condenser in 210 MW thermal power plant with erosion modeling has been done using Fluent code.
To help understand the steam cooling in the condenser, current study analyses a 3D section of the condenser used in a 210 MW thermal power plant using a commercial ANSYS/FLUENT code. A boundary layer coupled mesh is used to simulate the interaction of steam and water with the condenser tubes. Models to simulate the flow of water inside the tubes and low-pressure steam over the tubes are incorporated to show the heat transfer between the steam and water domain through the pipe walls along with incorporation of accretion and erosion model, specially the erosion. Analysis of erosion accretion due to Calcium salts are taken in consideration to interpret the location, where scaling happens and how the yearlong scaling affects the heat transfer ability of the heat transfer tubes. There is one build-in erosion and accretion model in FLUENT, which accounts of erosion/accretion on a surface from solid particle. Although the water is liquid, but the article that is responsible for erosion and accretion is solid, e.g. Calcium salt. The result shows that the heat transfer rate is not constant along the tube over a period due to erosion and untreated hard water used for cooling purpose. The Erosion model predicts the most prominent erosion/accretion sites inside the tubes and stresses on the importance of treatment of the recirculating hard water. A liquid particle erosion can also be modeled in future if needed.