bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Comparison of Weldability, Structure, and Mechanical Properties of CM64 and Tribaloy T-800 Welds for Hard-Facing of Turbine Blades
Authors: Keshavarz Mohsen K. , Gontcharov Alexandre , Lowden Paul , Brochu Mathieu 
Published: May 2020

Abstract
In this study, the weldability, microstructure, and tensile properties of CM64 and Tribaloy T-800 (T800) cobalt-based hard-facing materials were studied. Successful CM64 hard-facing could be achieved at ambient temperature using manual gas tungsten arc welding (GTAW-MA). It was shown that T800 welded at ambient temperature was prone to cold cracking due to a combination of low ductility with high welding stresses that limited the accommodation of residual stresses by plastic deformation within the weld beads. Sound T800 welds of various geometries and sizes were produced on cobalt- and nickel-based X-40 and Haynes 230 superalloys, respectively, using GTAW-MA when preheating above 900 °C was used. Microstructural analyses on the sound CM64 and T800 welds were performed using optical and electron microscopy and X-ray diffraction. The distribution of elements and phases in each alloy was evaluated and revealed the epitaxial dendritic structure with the Cr–W–Si-based phase in the interdendritic region in CM64 welds compared with petal-like and equiaxed hard Mo–Co–Si-based dendrites and fine particles in T800. Tensile testing from room temperature up to 1093 °C was performed on both alloys. T800 welds possessed lower ultimate tensile strengths and elongations in this temperature range when compared with the CM64 alloy. Recommendations for hard-facing of turbine engine components were provided.
Study on Forced Convective Heat Transfer of FC-72 in Vertical Small Tubes
Authors: Li Yantao , Ji Yulong , Fukuda Katsuya , Liu Qiusheng 
Published: May 2020

Abstract
This paper presents an experimental investigation of the forced convective heat transfer of FC-72 in vertical tubes at various velocities, inlet temperatures, and tube sizes. Exponentially escalating heat inputs were supplied to the small tubes with inner diameters of 1, 1.8, and 2.8 mm and effective heated lengths between 30.1 and 50.2 mm. The exponential periods of heat input range from 6.4 to 15.5 s. The experimental data suggest that the convective heat transfer coefficients increase with an increase in flow velocity and µ/µw (refers to the viscosity evaluated at the bulk liquid temperature over the liquid viscosity estimated at the tube inner surface temperature). When tube diameter and the ratio of effective heated length to inner diameter decrease, the convective heat transfer coefficients increase as well. The experimental data were nondimensionalized to explore the effect of Reynolds number (Re) on forced convection heat transfer coefficient. It was found that the Nusselt numbers (Nu) are influenced by the Re for d = 2.8 mm in the same pattern as the conventional correlations. However, the dependences of Nu on Re for d = 1 and 1.8 mm show different trends. It means that the conventional heat transfer correlations are inadequate to predict the forced convective heat transfer in minichannels. The experimental data for tubes with diameters of 1, 1.8, and 2.8 mm were well correlated separately. And, the data agree with the proposed correlations within ±15%.
Microstructural Stress Shape Optimization Using the Level Set Method
Authors: Picelli Renato , Townsend Scott , Alicia Kim H. 
Published: May 2020

Abstract
This paper applies stress-based shape optimization to microstructures, a scarcely explored topic in the literature. As the actual stresses arising at the macroscopic structure are scale separated, the microstrucural stress is considered herein as the state of a representative volume element (RVE) after applying test unit strain load cases, not related to the macroscale loads. The three stress states in 2D are aggregated via p-norm functions, which are used for stress minimization. A stress-based level set method is applied. The method linearizes the objective and constraint functions and solves an optimization problem at every iteration to obtain the boundary velocities. The Ersatz material approach is used to compute the stiffness of the elements sliced by the boundary. A single hole inclusion microstructure is optimized for minimum stress in order to verify the methodology.
Agent-Based Modeling of Decisions and Developer Actions in Wind Farm Landowner Contract Acceptance
Authors: Syal Sita M. , Ding Yiqing , MacDonald Erin F. 
Published: May 2020

Abstract
This paper presents an agent-based model to investigate interactions between wind farm developers and landowners. Wind farms require hundreds of square miles of land for development and developers typically interact with landowners to lease land for construction and operations. Landowners sign land lease contracts without knowing the turbine layout, which affects aesthetics of property as well as value of the lease contract. Having a turbine placed on one's land is much more lucrative than alternative land uses, but landowners must sign over the use of their land without knowing whether they will receive this financial benefit or not. This process, typically referred to as “Landowner Acquisition,” is highly uncertain for both stakeholders—a source stated up to 50% of wind projects fail due to landowner acquisition issues. We present an agent-based model to study the landowner acquisition period with unique decision-making characteristics for nine landowners and a developer. Citizen participation is crucial to the acceptance of wind farms; thus, we use past studies to quantify three actions a developer can take to influence landowners: (1) community engagement meetings, (2) preliminary environmental studies, and (3) sharing the wind turbine layout with the landowner. Results show how landowner acceptance rates can change over time based on what actions the developer takes. While still in the “proof of concept” stage, this model provides a framework for quantifying wind stakeholder interactions and potential developer actions. Suggestions for how to validate the framework in the future are included in the discussion.
A Novel Ortho-Triplex Tensegrity Derived by the Linkage-Truss Transformation With Prestress-Stability Analysis Using Screw Theory
Authors: Wu Liheng , Dai Jian S. 
Published: May 2020

AbstractThis paper presents a novel tensegrity structure derived from the tensegrity triplex (also called the simplex or regular triangular prism) by using the linkage-truss transformation. In this paper, the tensegrity triplex is first transformed into a 6R linkage with vertical members as revolute joints and is coined the triplex linkage. With this, a novel 6R linkage was derived, whose joint axes are perpendicular to the joint axes of the triplex linkage and is coined the ortho-triplex linkage. Rigidity analysis based on screw theory demonstrates that both obtained linkages with infinitesimal mobility are prestress stable. Finally, transforming the ortho-triplex linkage to a truss, by using cables for tensional members and struts for compressional members, leads to a novel tensegrity that is coined ortho-triplex tensegrity. A non-dimensional quadratic form is further provided to analyze the sensitivity of prestress-stability in terms of the structural parameters. The process of derivation of this novel tensegrity presents a new way of designing tensegrity structures with prestress-stability analysis based on screw theory.
An Efficient Batch K-Fold Cross-Validation Voronoi Adaptive Sampling Technique for Global Surrogate Modeling
Authors: Kaminsky Andrew L. , Wang Yi , Pant Kapil 
Published: May 2020

AbstractSurrogate models can be used to approximate complex systems at a reduced cost and are widely used when data generation is expensive or time consuming. The accuracy of these models is dependent on the samples used to create them. Therefore, proper sample selection within the parameter space is paramount. Numerous design of experiments (DOE) methodologies have been developed with the aim of identifying the optimal sample set to capture the system of interest. Adaptive sampling techniques are a subclass of DOE methods that identify optimal locations for new samples by leveraging response information from existing samples. By exploiting knowledge of the system, adaptive sampling methods have been demonstrated to significantly reduce the number of samples required to build a surrogate model of a given accuracy. However, utilizing the response information of the previous samples adds a computational cost associated with determining the ideal sample locations. Additionally, this cost typically grows with the sample count. This article presents techniques to reduce the cost associated with the adaptive sampling procedure so that the cost savings provided by adaptive sampling are maximized. A new K-fold cross-validation (KFCV)-Voronoi adaptive sampling technique is proposed to reduce the sample selection costs by adding a global KFCV filter to the cross-validation (CV)-Voronoi technique. The costs are further reduced through an innovative Voronoi batch sampling technique that is demonstrated to outperform naïve batch sampling. The proposed adaptive sampling acceleration techniques are evaluated using benchmark functions of increasing dimension and aerodynamic loading data.
A Novel Variable Stiffness Compliant Robotic Gripper Based on Layer Jamming
Authors: Gao Yuan , Huang Xiguang , Mann Ishan Singh , Su Hai-Jun 
Published: May 2020

Abstract
In this paper, we present a novel compliant robotic gripper with three variable stiffness fingers. While the shape morphing of the fingers is cable-driven, the stiffness variation is enabled by layer jamming. The inherent flexibility makes compliant gripper suitable for tasks such as grasping soft and irregular objects. However, their relatively low load capacity due to intrinsic compliance limits their applications. Variable stiffness robotic grippers have the potential to address this challenge as their stiffness can be tuned on demand of tasks. In our design, the compliant backbone of finger is made of 3D-printed PLA materials sandwiched between thin film materials. The workflow of the robotic gripper follows two basic steps. First, the compliant skeleton is driven by a servo motor via a tension cable and bend to a desired shape. Second, upon application of a negative pressure, the finger is stiffened up because friction between contact surfaces of layers that prevents their relative movement increases. As a result, their load capacity will be increased proportionally. Tests for stiffness of individual finger and load capacity of the robotic gripper are conducted to validate capability of the design. The results showed a 180-fold increase in stiffness of individual finger and a 30-fold increase in gripper’s load capacity.
Workspace Augmentation for the Large-Scale Spherical Honeycombs Perfusion Using a Novel 5DOF Reconfigurable Manipulator
Authors: Yang Hui , Fang Hairong , Li Xiangyun , Fang Yuefa 
Published: May 2020

Abstract
The volume of workspace is a significant kinematic index of parallel manipulator in some applications of engineering. However, the workspace degradation of the manipulator in extreme position is a demanding issue, which results in a fact that such manipulators cannot satisfy the machining requirement of the maximum limit position for the large-scale complex structural components. In this paper, a novel five degrees-of-freedom (DOF) 5PRR+5PUS-PRPU parallel manipulator (PM) is presented. First, the mobility analysis for the proposed manipulator is carried out, and the inverse kinematics as well as the Jacobian matrix is developed. Then, the workspace of the 5PRR+5PUS-PRPU PM and the 5PUS-PRPU PM is analyzed to study the workspace augmentation of the proposed PM. The workspace comparisons of these two PMs prove that the proposed PM not only can realize the large movement of the moving platform along the z-axis, but also possess larger workspace than the 5PUS-PRPU PM when the moving platform has a large movement along the z-axis. Furthermore, the singularity analysis is also conducted to show the singularity-free workspace of the proposed PM. By the introduction of the reconfigurable 5PRR PM, the proposed manipulator effectively augments the reachable workspace of the moving platform along the z-axis and to some extent also solves the issue of workspace degradation of the PM along z-axis.
One-Dimensional Zonal Model for the Unsteady Heat Transfer Analysis in an Open Volumetric Air Receiver
Authors: Singh Gurveer , Kumar Vishwa Deepak , Chandra Laltu , Shekhar R. , Ghoshdastidar P. S. 
Published: May 2020

Abstract
The open volumetric air receiver (OVAR)-based central solar thermal systems provide air at a temperature &gt; 1000 K. Such a receiver is comprised of porous absorbers, which are exposed to a high heat-flux &gt; 800 Suns (1 Sun = 1 kW/m2). A reliable assessment of heat transfer in an OVAR is necessary to operate such a receiver under transient conditions. Based on a literature review, the need for developing a comprehensive, unsteady, heat transfer model is realized. In this paper, a seven-equations based, one-dimensional, zonal model is deduced. This includes heat transfer in porous absorber, primary-air, return-air, receiver casing, and their detailed interaction. The zonal model is validated with an inhouse experiment showing its predictive capability, for unsteady and steady conditions, within the reported uncertainty of ±7%. The validated model is used for investigating the effect of operating conditions and absorber geometry on the thermal performance of an absorber. Some of the salient observations are (a) the maximum absorber porosity of 70–90% may be preferred for non-volumetric and volumetric-heating conditions, (b) the minimum air-return ratio should be 0.7, and (c) the smallest gap to absorber-length ratio of 0.2 should suffice. Finally, suggestions are provided for extending the model.
Solution of Unsteady Fluid Dynamic and Energy Equations for High-Speed Oscillating Compressible Flows and Blast Wave Propagations
Authors: Sinha Ramlala P. 
Published: May 2020

Abstract
A solution of the highly complex unsteady high-speed oscillating compressible flow field inside a cylindrical tube has been obtained numerically, assuming one-dimensional, viscous, and heat conducting flow, by solving the appropriate fluid dynamic and energy equations. The tube is approximated by a right circular cylinder closed at one end with a piston oscillating at very high resonant frequency at the other end. An iterative implicit finite difference scheme is employed to obtain the solution. The scheme permits arbitrary boundary conditions at the piston and the end wall and allows assumptions for transport properties. The solution would also be valid for tapered tubes if the variations in the cross-sectional area are small. In successfully predicting the time-dependent results, an innovative simple but stable solution of unsteady fluid dynamic and energy equations is provided here for wide-ranging research, design, development, analysis, and industrial applications in solving a variety of complex fluid flow heat transfer problems. The method is directly applicable to pulsed or pulsating flow and wave motion thermal energy transport, fluid–structure interaction heat transfer enhancement, and fluidic pyrotechnic initiation devices. It can further be easily extended to cover muzzle blasts and nuclear explosion blast wave propagations in one-dimensional and/or radial spherical coordinates with or without including energy generation/addition terms.
Co-Axial Laminar Multiphase Jet: A Novel Methodology for the Attainment Enhancement in Transition Boiling Regime
Authors: Barik Kashinath , Swain B. , Pati A.R. , Chitransh Susmit , Mohapatra S.S. 
Published: May 2020

Abstract
In the current investigation, by using a very low mass flux co-axial laminar multiphase fluid jet, enhancement in heat transfer rate, uniformity in heat flux distribution, and reduction in coolant consumption rate characteristics are simultaneously tried to achieve in case of cooling from a very high initial temperature (900 °C). The information on quenching technology depicting all the above-mentioned advantages has not been reported in the literature. In the present work, kerosene–water, nanofluid (Al2O3 = 0.15%)–kerosene, and nanofluid (Al2O3 = 0.15%)–polyethylene glycol combinations were used for co-axial cooling experimentation. From the heat transfer analysis, it is observed that nanofluid (Al2O3 = 0.15%) and kerosene combination produces maximum critical heat flux due to the alteration of thermophysical and interfacial properties, which enhance the driving force and flow behavior defining momentum and thermal diffusivities in the favorable direction of heat transfer, respectively. In addition to the above, the comparative study ensures a significant reduction in coolant consumption and augmentation in uniformity in heat flux distribution.
Development and Validation of a Model for Efficient Simulation of Freezing of Water in Large Tanks
Authors: Ramesh Vishal , Terala Shashank , Mazumder Sandip , Matharu Gurpreet , Vaishnav Dhaval , Ali Syed 
Published: May 2020

Abstract
Liquid water–urea mixtures are used in diesel vehicles for exhaust after treatment. In cold weather, the entire liquid may freeze and the process may span over a day. Traditional computational fluid dynamics and heat transfer (CFD/CHT) methodologies are impractical for modeling such freezing processes because of restrictions in the time-step size—typically milliseconds—posed by numerical stability and physical timescale considerations. Preliminary investigations revealed that the primary constraint for using small time-steps is the fine-scale motion generated by natural convection in both the liquid and the gas. A new model is proposed and demonstrated for efficient prediction of the propagation of the solidification front. In this model, heat transfer due to natural convection is modeled as a diffusive process analogous to how turbulent transport is modeled using an eddy diffusivity. The model enables the use of large time-steps since the fine-scale motions due to natural convection are not resolved. It was validated against experimental data for pure water, which were also collected as part of the study. Each experiment collected data at intervals of 6 s for a total duration of about 24 h. Several different tank fill levels were considered, and a good agreement with experimental data was noted, especially for shallow fill levels. Large-scale parallel three-dimensional calculations were conducted for the freezing of pure water in a few days of computational time as opposed to a year (projected) of computational time using traditional CFD/CHT models and the same computational resources.
Thermodynamic Analysis of Hydrogen Production From Coal Char Gasification in Triple-Bed Circulating Fluidized Bed
Authors: Xiang Xianan , Gong Guangcai , Wang Chenhua , Cai Ninghua , Tang Kun , Li Yongsuo 
Published: May 2020

Abstract
The triple-bed circulating fluidized bed gasifier is a new type of the gasification process in which the combustion process, pyrolysis process, and gasification process of the fuel are carried out in different reactors. The inert heat carrier is used to transfer heat between the reactors. In this way, the gasification efficiency of char is improved since the tar and pyrolysis gas generated in the pyrolysis process will no longer hinder the gasification of the char. The thermodynamic equilibrium model is used to simulate the gasification process of the triple-bed circulating fluidized bed, and the sub-models are established to simulate combustion, pyrolysis, and gasification processes. The simulation results agree well with the experimental values. Besides, the model studies the effects of key parameters such as the gasification reaction temperature and the ratio of steam to C (S/C) on gasification performance. Results showed that higher gasification reaction temperature has a positive effect on gasification performance, S/C may not be too high, and excessive water vapor will directly affect the gasification reaction.
Transient Temperature Distribution and Thermo-Mechanical Coupling Response of Paper in the Fusing Process of Laser Printers
Authors: Liu Pingping , Zhang Huijie , Wen Guang , Zuo Fangjun , Jia Meiwei 
Published: May 2020

AbstractThe hot-press fusing process of a laser printer is one of the principal causes for paper folding and bending deformation. In order to predict and control the deformation of paper, first, the following analysis method is proposed for the transient temperature field analysis of the continuous moving paper: discretizing the thermal analysis process, replacing the moving paper model with the moving heat source, and simulating the movement speed of paper by setting the flow boundary conditions. Second, taking the steady-state thermal calculation results of the printer in the standby mode as initial conditions, the temperature distribution characteristics of paper during the movement are obtained with the paper model placed in a whole-machine environment to analyze the transient temperature field. Third, using the method of multi-field coupling, the transient temperature field results of paper are taken as the external load of its static analysis to analyze the deformation of paper during the fusing process; therefore, the quantitative deformation results and deformation characteristics of paper after fusing are obtained. According to the results, more precise boundary conditions can be achieved by calculating the temperature field of paper in a whole-machine environment. The method of transient temperature field analysis for continuous moving objects proposed in this study can effectively simulate the movement process of paper. The results reveal the mechanism of paper wrinkle and bending deformation in the fusing process, which can be used to predict the conveying performance of paper and guide the design work of the printer.
Study of the Comprehensive Evaluation of Energy Efficiency of an Oilfield Heating Furnace Based on Combination Weighting Method
Authors: Cheng Qinglin , Wang Ronghuan , Sun Wei , Meng Lan , Gao Wei , Li Yuchun 
Published: May 2020

Abstract
The heating furnace is an essential oilfield facility for surface gathering, treatment, and transportation, so the energy consumption level of an oilfield is directly affected by its operational efficiency. In this paper, the thermal efficiency, exhaust gas temperature, external surface temperature, excess air coefficient, and load rate of a heating furnace are taken as energy efficiency evaluation indexes. By improving game theory, the objective and subjective weights are combined to determine the final weights of each index. On this basis, the grey TOPSIS method is used to establish the energy efficiency evaluation model of an oilfield heating furnace, which is to comprehensively evaluate the energy consumption of the heating furnace by calculating the closeness degree between its actual and ideal operational states. Finally, the effectiveness of the energy efficiency evaluation model is verified by taking an actual oilfield as an example, the results show that the weight sequence of the indexes is thermal efficiency, exhaust gas temperature, external surface temperature, load rate, and excess air coefficient. In addition, the relative closeness of the heating furnace is mostly concentrated between 0.5 and 0.7, which shows that the efficiency is low. The weak link of energy consumption is analyzed, and the corresponding improvement measures are put forward.