bluuebunny/crossref_metadata_2025_split huggingface dataset:
Coupled Temperature-Microstructure Model for Predicting Temperature Distribution and Phase Transformation in Steel for Arbitrary Cooling Curves
Authors: Saha Sandip K. , Kumar Akhilesh 
Published: August 2020

Abstract
This study aims at developing a numerical model that can be employed for simulating the thermomechanical treatment to develop the advanced high strength steels. The developed numerical method is used to calculate the heat transfer coefficient of the quenching medium during the continuous cooling of the steel using the inverse heat transfer model for predefined cooling paths. Further, the phase transformation models are used to predict the final microstructure of the steel plate. The cooling rate, plate thickness, and rolling speed are varied to evaluate the temperature and microstructure distribution in the steel plate. It is found that on increasing the quenching time, the transformation fraction from austenite to ferrite and bainite phases increases and the corresponding martensite fraction decreases. The temperature variation in the plate is significant due to the change in plate thickness and rolling speed for a given quenching time. The present model will be useful for designing process parameters to obtain desired microstructures in third-generation advanced high strength steels.
Remaining Useful Life Prediction of Bearings Using Ensemble Learning: The Impact of Diversity in Base Learners and Features
Authors: Shi Junchuan , Yu Tianyu , Goebel Kai , Wu Dazhong 
Published: August 2020

Abstract
Prognostics and health management (PHM) of bearings is crucial for reducing the risk of failure and the cost of maintenance for rotating machinery. Model-based prognostic methods develop closed-form mathematical models based on underlying physics. However, the physics of complex bearing failures under varying operating conditions is not well understood yet. To complement model-based prognostics, data-driven methods have been increasingly used to predict the remaining useful life (RUL) of bearings. As opposed to other machine learning methods, ensemble learning methods can achieve higher prediction accuracy by combining multiple learning algorithms of different types. The rationale behind ensemble learning is that higher performance can be achieved by combining base learners that overestimate and underestimate the RUL of bearings. However, building an effective ensemble remains a challenge. To address this issue, the impact of diversity in base learners and extracted features in different degradation stages on the performance of ensemble learning is investigated. The degradation process of bearings is classified into three stages, including normal wear, smooth wear, and severe wear, based on the root-mean-square (RMS) of vibration signals. To evaluate the impact of diversity on prediction performance, vibration data collected from rolling element bearings was used to train predictive models. Experimental results have shown that the performance of the proposed ensemble learning method is significantly improved by selecting diverse features and base learners in different degradation stages.
Multi-Objective Engineering Design Via Computer Model Calibration
Authors: Ehrett Carl , Brown D. Andrew , Chodora Evan , Kitchens Christopher , Atamturktur Sez 
Published: August 2020

AbstractComputer model calibration typically operates by fine-tuning parameter values in a computer model so that the model output faithfully predicts reality. By using performance targets in place of observed data, we show that calibration techniques can be repurposed for solving multi-objective design problems. Our approach allows us to consider all relevant sources of uncertainty as an integral part of the design process. We demonstrate our proposed approach through both simulation and fine-tuning material design settings to meet performance targets for a wind turbine blade.
Building Block Synthesis of Self-Supported Three-Dimensional Compliant Elements for Metallic Additive Manufacturing
Authors: Danun Aschraf N. , Palma Philip D. , Klahn Christoph , Meboldt Mirko 
Published: August 2020

Abstract
Compliant mechanisms gain motion through the elastic deformation of the monolithic flexible elements. The geometric design freedom of metallic additive manufacturing enables the fabrication of complex and three-dimensional (3D) compliant elements within mechanisms previously too complicated to produce. However, the design of metallic additive manufactured mechanisms faces various challenges of manufacturing restrictions, such as avoiding critical overhanging geometries and minimizing the amount of support structure, which has been reported in a few cases. This paper presents a synthesis approach for translational compliant elements, involving building blocks based on leaf-type springs and covering building orientations between 0 deg and 90 deg. In particular, this range is approached by the synthesis of self-supported 3D building blocks with orientations of 0 deg, 45 deg and 90 deg. The compliant elements are built based on linear and circular plane curves and compared numerically according to their mechanical performance to create preferable building blocks. The applicability of the presented procedure and the manufacturability of the compliant mechanisms are proven by printing individual 3D building blocks and their serial aggregation with laser-based powder bed fusion. Consequently, several prototypes are demonstrated, including a bistable switch mechanism and a large displaceable rotational spring joint. In addition, a small-scale highly maneuverable segment of a surgical instrument with a grasping mechanism at the distal end is proposed.
Design and Modeling of Soft Continuum Manipulators Using Parallel Asymmetric Combination of Fiber-Reinforced Elastomers
Authors: Uppalapati Naveen Kumar , Krishnan Girish 
Published: August 2020

Abstract
Soft continuum arms (SCAs) have a large workspace, dexterity, and adaptability, but at the cost of complex design construction highlighted by concatenating several serial segments. In this paper, we propose a new design architecture for SCAs composed of a parallel combination of pneumatic actuators. The BR2 SCA featured in this work is asymmetric as it combines one soft bending (B) actuator and two soft rotating (R2) actuators as opposed to state of art symmetric architectures that adopt bending segments. Spatial deformation is obtained by combining the bending and rotating feature of the individual actuators. This paper also formulates an approximate forward analysis method based on Kirchhoff rod equations to predict the spatial deformation under external loads with an accuracy less than 9% of the SCAs length. In addition, the model also takes into account the “coupling effect” inherent to the asymmetric parallel combination, where actuating rotating actuator attenuates the bending performance and vice versa. Consequently, this work also refines the design of the SCA that minimizes the coupling effect. A detailed performance study of the refined BR2 manipulator on a swiveling base demonstrates larger workspace and higher dexterity when compared with state of art single section SCAs. The performance of the design is validated through different tasks like obstacle avoidance, pick and place task, and whole arm grasping. These performance attributes surpass any other single segment soft module and is a potential building block for constructing customized SCAs.
Design and Posture Control of a Wheel-Legged Robot With Actively Passively Transformable Suspension System
Authors: Ni Liwei , Ma Fangwu , Ge Linhe , Wu Liang 
Published: August 2020

Abstract
This paper presents a novel solution for the posture control and ride comfort between the proposed wheel-legged robot (four wheel-legged robot (FWLR)) and the unstructured terrain by means of an actively passively transformable suspension system. Unlike most traditional robots, each leg of FWLR is independent of each other with a spring-damping system (passive system) is connected in series with an actuator (active system), so the posture control and ride comfort in complex terrain can be realized by the combination between active and passive systems. To verify the performance of posture control in complex terrain, a prototype and complex terrain are established first, then a posture control model, algorithm, and controller considering the suspension system are proposed and verified by the comparison between co-simulation and experiment, the results showed that the pitch angle and roll angles in complex terrain can be controlled. To show the impact of the actively passively transformable suspension system on ride comfort (vibration isolation performance), different dynamic models with different degree-of–freedom (DOF) are established, the co-simulation results showed that the passive system and active posture control system can also effectively improve the ride comfort of FWLR in complex terrain. The research results of this paper have important reference significance and practical value for enriching and developing the mechanism design and theoretical research of wheel-legged robot and promoting the engineering application of all-terrain robot.
A Methodology for Measuring Turbocharger Adiabatic Maps in a Gas-Stand and Its Usage for Calibrating Control Oriented and One-Dimensional Models at Early ICE Design Stages
Authors: Serrano José Ramón , Arnau Francisco José , García-Cuevas Luis Miguel , Gómez-Vilanova Alejandro , Guilain Stephane , Batard Samuel 
Published: August 2020

Abstract
In this work, a methodology is proposed to standardize turbochargers testing based on measuring the maps twice: in close to adiabatic and in diathermal conditions. Along the paper, it is discussed with special detail the impact of the procedure followed to achieve said quasi-adiabatic conditions in both the energy balance of the turbocharger and the testing complexity. As a conclusion, the paper proposes a methodology which combines quasi-adiabatic tests (cold and hot gas flow) with diathermal tests (hot gas flow) in order to extract from a turbocharger gas-stand all information needed by engine designers interested in controlling or one-dimensional-modeling the internal combustion engine (ICE). The methodology is completed with a guide for calibrating said control-oriented turbocharger models in order to separate aerodynamic efficiency (adiabatic) from heat transfer (HT) losses and from friction losses in the analysis of the turbocharger performance. The outsourced calibration of the turbocharger model allows avoiding uncertainties in the global ICE model calibration, what is very interesting for turbochargers benchmarking at early ICE-turbo matching stages or for global system analysis at early control design stages.
Detection of Neutrons Emitted From Reactor Primary Circuit Water by Discontinuing Flow Method
Authors: Viererbl L. , Kolros A. , Vinš M. , Klupák V. 
Published: August 2020

Abstract
On-line activity measurement of fission products in a primary circuit water is often used for a fuel failure detection in research and power nuclear reactors. When gamma spectrometry is used for the activity measurement, high signal from 16N radionuclide and other activation products make the detection of fission products difficult. The detection of delayed neutrons emitted from several fission products is also used; however, if the detector is placed near the outlet coolant pipe, the signal from the delayed neutrons cannot be distinguished from the neutrons emitted due to 17N decay and deuterium photofission, with exception of a reactor scram condition. In this paper, a method of discontinuing the flow of primary circuit water is described. This method is based on the water flowing through a bypass on the outlet pipe to the sampling container and the flow is periodically temporarily interrupted, e.g., using 200 s + 200 s cycles. Neutrons located in the vicinity of the sampling container are continuously detected with a measuring sampling time of less than 2 s. The signal part, corresponding to the delayed neutrons, is evaluated by the signal decay analyzing during the flow interruption. The main sources of delayed neutrons suitable for this method are 137I, 87Br, and 88Br radionuclides with half-lives of 24.5 s, 55.7 s, and 16.5 s, respectively. The method was theoretically analyzed and experimentally verified in the LVR-15 research reactor.
Performance and Emissions of Drop-In Aviation Biofuels in a Lab-Scale Gas Turbine Combustor
Authors: Feser Joseph , Gupta Ashwani 
Published: August 2020

Abstract
There is a growing need for drop-in biofuels for gas turbines for enhanced energy security and sustainability. Several fuels are currently being developed and tested to reduce dependency on fossil fuels while maintaining performance, particularly in the aviation industry. The transition from traditional fossil fuels to sustainable biofuels is much desired for reducing the rapidly rising CO2 levels in the environment. This requires biofuels to be drop-in ready, where there are no adverse effects on performance and emissions upon replacement. In this study, the performance and emissions of four different aviation drop-in biofuels were evaluated. They include UOP HEFA-SPK, Gevo ATJ, Amyris Farnesane, and SB-JP-8. These aviation biofuels are currently being produced and tested to be ready for full or partial drop-in fuels as the replacement of traditional jet fuels. The characteristic performance of each fuel from the prevaporized liquid fuels was performed in a high-intensity (20 MW/m3-atm) reverse flow combustor. The NO emissions showed near unity ppm levels for each of the fuels examined with a minimum at an equivalence ratio of ∼0.6, while CO levels were in the range of 1000–1300 ppm depending on the fuel at an equivalence ratio between 0.75 and 0.8. For an equivalence ratio range between 0.4 and 0.6, NO and CO emissions remained very low (between 1–2 ppm NO and 2400–2900 ppm CO) depending on the fuel. The examined biofuels did not show any instability over a wide range of equivalence ratios from lean to near stoichiometric condition. These results provide promising results on the behavior of these drop-in aviation biofuels for use in high-intensity gas turbine combustors providing stability and cleaner performance without any modification to the combustor design.
Improved Exergy Evaluation of Ammonia-Water Absorption Refrigeration System Using Inverse Method
Authors: Singh Adityabir , Das Ranjan 
Published: August 2020

Abstract
In this study, the compatibility of exergy destruction minimization (EDM) as the main objective is checked by plotting coefficient of performance (COP), exergy coefficient of performance (ECOP), and overall exergy destruction rate by simultaneously varying input operating temperatures for a 28 TR cooling load absorption system. The component-wise variation in exergy destruction is also considered and it is found that the maxima of COP and ECOP, and the minima of overall exergy destruction lies on a common point, and when the variation of operating temperatures is further extended, the exergy destruction in one of the component becomes negative, which marks the upper bound of the present analysis. At highest valid generator temperature (155 °C), the minimum possible overall exergy destruction rate is 53.50 kW and maximum COP is 0.523. Through inverse optimization (IO) using dragonfly algorithm (DA), the same overall exergy destruction rate is achieved for a wide range of generator temperatures much below than 155 °C, and as low as 127.34 °C. The above variation is explained in terms of flow ratio, mass flowrate of steam, and mass flowrate of cooling water.
An Experimental Study on Segmented-Encapsulated Electrode Dielectric-Barrier-Discharge Plasma Actuator for Mapping Ice Formation on a Surface: A Conceptual Analysis
Authors: Rodrigues F. , Abdollahzadeh M. , Pascoa J. C. , Oliveira P. J. 
Published: August 2020

Abstract
A novel design of the dielectric barrier discharge (DBD) actuator/sensor is proposed for mapping the location of icing on a surface. The new design uses segmentation of the embedded electrode of the DBD actuator. Segmented DBD actuator/sensor devices were fabricated and experimentally tested in terms of mechanical, thermal and sensing abilities. The sensing capability of the new actuator was analyzed experimentally. Stationary and dynamic icing tests were conducted and the electrical characteristics of the DBD were measured. A parametric study on the effect of the electrode dimensions on the degree of sensitivity of the device was performed. Experimental results show that by using a segmented configuration it is possible to sense the onset of ice formation and also to detect its location. Furthermore, it is possible to detect the initiation of the melting process and measure the time for the water/ice to be completely expelled from the surface. It is also shown that the segmented actuator has better deicing performance in comparison to the conventional actuators. It is also shown that the thermal and active flow control abilities are not compromised by the segmented configuration and thus this device may perform deicing, ice formation and location detection and active flow control.
Creative Design of Legged Mobile Landers With Multi-Loop Chains Based on Truss-Mechanism Transformation Method
Authors: Lin Rongfu , Guo Weizhong 
Published: August 2020

Abstract
This paper proposes a novel family of the legged mobile lander (LML) with multi-loop chains to enable the stationary lander to walk, which is helpful to the Return and Base construction missions in the planetary exploration project. Generally, there are many issues that need to be focused, but one of the key issues is during the landing phase, for which the lander needs to be designed as a truss with ability to bear a large impact, while during the walking phase, the lander needs to be designed as a mechanism with flexible walking ability. To resolve this issue, a novel method for designing a mechanism based on a truss, which also can be called as the truss-mechanism transformation (TMT) method is developed. First, the detailed concept of the same topological arrangements (TAs) of a truss and a mechanism is proposed. Two singularity positions for the truss-mechanism transform are introduced. Second, following the concept, the procedure for designing a mechanism based on the TMT method is presented. Third, some basic knowledge for the creative design of the mechanism is introduced, including the intersection rules of motion characteristics, motion characteristic relationship of multi-loop mechanisms, and so on. Fourth, according to the procedure of the TMT method, numerous novel structures of LMLs with multi-loop chains are obtained. Finally, after the type qualitative evaluation, one typical LML is selected as an example to show its functions among stowed, walking, and orientation positions.
Optimizing Piezoelectric Material Location and Size for Multiple-Mode Vibration Reduction of Turbomachinery Blades
Authors: Kelley Christopher R. , Lopp Garrett K. , Kauffman Jeffrey L. 
Published: August 2020

Abstract
Modern turbomachinery blades have extremely low inherent damping, which can lead to high transient vibrations and failure through high-cycle fatigue. Smart materials enable vibration reduction while meeting strict blade requirements such as weight and aerodynamic efficiency. In particular, piezoelectric-based vibration reduction offers the potential to reduce vibration semi-actively while simultaneously harvesting sufficient energy to power the implementation. The placement and the size of the piezoelectric material is critical to the vibration reduction capabilities of the system. Furthermore, the implementation should target multiple vibration modes. This study develops a procedure to optimize electromechanical coupling across multiple vibration modes for a representative turbomachinery blade with surface-mounted piezoelectric patches. Experimental validation demonstrates good coupling across three targeted modes with a single piezoelectric patch. Placing the piezoelectric material in regions of high signed strain energy for all targeted modes enables vibration reduction across all of the targeted modes.
Gas Flow in Microchannels and Nanochannels With Variable Cross Section for All Knudsen and All Mach Number Values
Authors: Milićev Snežana S. , Stevanović Nevena D. 
Published: August 2020

AbstractThe analytical solution for steady viscous pressure-driven compressible isothermal gas flow through micro- and nanochannels with variable cross section for all Knudsen and all Mach number values is presented in this paper. The continuum one-dimensional governing equations are solved using the friction factor that is established in a special way to provide solutions for mass flow rate, pressure, and velocity distribution through the microchannels and nanochannels in the entire rarefaction regime. The friction factor, defined by the general boundary condition and generalized diffusion coefficient proposed by Beskok and Karniadakis (1999, “A Model for Flows in Channels, Pipes, and Ducts at Micro and Nano Scales,” J. Microscale Thermophys. Eng., 3, pp. 43–77), spreads the solution application to all rarefaction regimes from continuum to free molecular flow. The correlation between the product of friction factor and Reynolds number (Poiseuille number) and Knudsen number is established explicitly in the paper. Moreover, the obtained solution includes the inertia effect, which allows the application of the solution to both subsonic and supersonic gas flows, which was not shown earlier. The presented solution confirms the existence of the Knudsen minimum in the diverging, converging, and microchannels and nanochannels with constant cross section. The proposed solution is verified by comparison with experimental, analytical, and numerical results available in literature.
Sex Differences in Lower Limb Proprioception and Mechanical Function Among Healthy Adults
Authors: Hu Xiaoyue , Li Jingxian , Wang Lin 
Published: August 2020

Twenty-four healthy adults, including 12 females and 12 males, participated in the study. Each female participant completed three trials in three different phases of one menstrual cycle, which included follicular, ovulatory, and luteal phases. The study aimed to investigate whether there is any difference in joint kinetic sense, neuromuscular coordination, and isokinetic muscle strength (a) between healthy males and females at different phases of the menstrual cycle and (b) between females at different phases of the menstrual cycle. The outcome measures included the number of jumps in the square-hop test and ankle and knee proprioception, which were assessed by an electric-driven movable frame rotated at 0.4 deg/s and isokinetic muscle strength measured by a computerized dynamometer (Biodex). For the square-hop test (p = .006), ankle dorsiflexion/plantar flexion (p < .05), knee flexion/extension (p < .05), the relative peak torque of the isokinetic muscle strength at the 60° and 180° knee flexion/extension (p < .001), and the 30° and 120° ankle plantar flexion/dorsiflexion (p < .05) between females and males showed significant differences. For the females at different phases of the menstrual cycle, significant differences were found on ankle dorsiflexion (p = .003), plantar flexion (p = .023), knee extension (p = .029), the square-hop test (p = .036), and relative peak torque of isokinetic muscle strength at 180° knee flexion (p = .029). This study demonstrated that there are sex differences in lower limb proprioception and mechanical function. Females at ovulatory and luteal phases have better lower limb proprioception than at the follicular phase.