bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Statistical Characterization of the Effects and Interactions of Small and Large Mistuning on Multistage Bladed Disks
Authors: Kurstak Eric , D'Souza Kiran 
Published: October 2019

Abstract
As turbomachinery systems continue to push the limits of modern technology, the modeling techniques being developed also continue to push modern computational limits. While modeling the pristine system during the design process is important, it is equally important to model behavior of mistuned systems, due to wear or manufacturing processes. This work carries out a statistical analysis on a two-stage system consisting of integrally bladed rotors. Various forms of large geometric mistuning, such as missing mass, bends, and dents, are considered. These forms of large mistuning are based on previously reported damage seen in actual engines that have ingested volcanic ash. This work also aims to investigate the interaction of these large mistuned systems with various levels of small mistuning to further understand this complex interaction. For every case studied, a reduced-order model (ROM) will be constructed that includes the effects of small and large mistuning. Large mistuning will only be applied to a single sector of a single stage. Random patterns of small mistuning will be applied to each case of large mistuning after which a modal analysis and a forced response analysis are run. By observing the energy distribution of each mode for the mistuned system, a qualitative trend can be created between various types and levels of large mistuning and the impact they have on changing the dynamics of the multistage system. The amplification factors from the forced response analyses help in understanding the impact small mistuning has when coupled with large mistuning and when the effects of small mistuning dominate over the large mistuning effects.
A Framework for Simulation-Based Internal Flooding Risk Assessment
Authors: Dubey Ankit R. , Gupta Abhinav , Coleman Justin 
Published: October 2019

Abstract
Internal flooding due to pipe breaks can interfere with a plant's ability to safely shut down or maintain the decay heat removal. Flooding simulation tools require information on location of pipe breaks and the degree of damage at each location as input for assessing the flooding risk. This can be especially challenging as the number of potential leakage locations are quite large and the state-of-the-art simulation tools cannot determine the degree of damage at a location. This paper presents a novel simulation-based framework that can be used to determine seismically induced flooding scenarios including the potential locations of leakage and the degree of leakage at each location. The proposed framework builds upon a few recent experimental and simulation-based studies on piping fragilities. This research identifies that a direct use of piping fragility information by flooding simulation tools is not appropriate. This paper presents a new approach that creates mutually exclusive and collectively exhaustive events to characterize the complete sample space at each location and employs the total probability theorem to characterize the probabilities for each event in this space. This paper also identifies the importance of including the temporal effects in the piping fragilities in order to allow a more realistic simulation of internal flooding scenarios.
Analysis and Validation of a Flexible Planar Two Degrees-of-Freedom Parallel Manipulator With Structural Passive Compliance
Authors: Chen Genliang , Zhang Zhuang , Kong Lingyu , Wang Hao 
Published: October 2019

Abstract
Passive compliance plays an important role in robot pick-and-place manipulation where large interaction force will be produced in response to small misalignments. In this paper, the authors report on compliance analysis and validation of a novel planar pick-and-place parallel manipulator consisting of a flexible limb. In the proposed manipulator, a planar flexible parallelogram linkage, which is coupled with a rigid one, is introduced to connect the moving and the base platforms. Since the flexible parallelogram linkage is capable of producing large deformation in both the horizontal and the vertical directions, the end effector of the manipulator can generate wide-range motions because of the flexible links. An efficient approach to the large deflection problem of flexible links is used to precisely predict the kinetostatics of the manipulator. Then, a compensation algorithm to the structural deflection of the links can be developed to actively control the position of the parallel manipulator’s end effector. The merit of the proposed flexible manipulator is its intrinsic passive compliance while performing pick-and-place tasks. A prototype is fabricated to conduct experiments for the validation of the proposed idea. The results show that the prototype has acceptable positioning accuracy, even when a large external load is exerted on its end effector. The compliance properties of the proposed flexible manipulator have also been verified in both the horizontal and the vertical directions.
Convolutional Neural Network Surrogate Models for the Mechanical Properties of Periodic Structures
Authors: Messner Mark C. 
Published: October 2019

Abstract
This work describes neural network surrogate models for calculating the effective mechanical properties of a periodic composites. The models achieve good accuracy even when only provided with training data sampling a small portion of the design space. As an example, the surrogate models are applied to solving the inverse design problem of finding structures with optimal mechanical properties. The surrogate models are sufficiently accurate to recover optimal solutions in general agreement with established topology optimization methods. However, improvements will be required to develop robust, efficient neural network-based surrogate models and several directions for future research are highlighted here.
A Deep Reinforcement Learning Approach for Global Routing
Authors: Liao Haiguang , Zhang Wentai , Dong Xuliang , Poczos Barnabas , Shimada Kenji , Burak Kara Levent 
Published: October 2019

Abstract
Global routing has been a historically challenging problem in the electronic circuit design, where the challenge is to connect a large and arbitrary number of circuit components with wires without violating the design rules for the printed circuit boards or integrated circuits. Similar routing problems also exist in the design of complex hydraulic systems, pipe systems, and logistic networks. Existing solutions typically consist of greedy algorithms and hard-coded heuristics. As such, existing approaches suffer from a lack of model flexibility and usually fail to solve sub-problems conjointly. As an alternative approach, this work presents a deep reinforcement learning method for solving the global routing problem in a simulated environment. At the heart of the proposed method is deep reinforcement learning that enables an agent to produce a policy for routing based on the variety of problems, and it is presented with leveraging the conjoint optimization mechanism of deep reinforcement learning. Conjoint optimization mechanism is explained and demonstrated in detail; the best network structure and the parameters of the learned model are explored. Based on the fine-tuned model, routing solutions and rewards are presented and analyzed. The results indicate that the approach can outperform the benchmark method of a sequential A* method, suggesting a promising potential for deep reinforcement learning for global routing and other routing or path planning problems in general. Another major contribution of this work is the development of a global routing problem sets generator with the ability to generate parameterized global routing problem sets with different size and constraints, enabling evaluation of different routing algorithms and the generation of training datasets for future data-driven routing approaches.
Wave Manipulation of Two-Dimensional Periodic Lattice by Parametric Excitation
Authors: Yang Xiao-Dong , Cui Qing-Dian , Zhang Wei 
Published: October 2019

Abstract
Phononic crystals composed of delicately designed periodic units are used to control spatial and spectral properties of acoustic or elastic waves. The ability to manipulate transmitting waves in a real-time dynamic manner provides a new concept in programable phononic crystals and metamaterials. In this study, the mechanical waves and bandgaps in a two-dimensional spring-mass array loaded by high-frequency parametric excitation have been investigated by both analytical and numerical methods. It is found that the high-frequency parametric excitation provides an equivalent additional stiffness which leads to low-frequency bandgaps. By tuning the parametric excitation, the versatility of such a dynamic modulating technique has been presented. The waveguide structure has also been designed and studied by non-uniformly distributed parametric excitations.
Fracture Strength Behaviors of Ultra-High-Temperature Materials
Authors: Cheng Tianbao , Qu Zhaoliang , Li Weiguo , Fang Daining 
Published: October 2019

Abstract
Ultra-high-temperature materials have been widely used as key components in high-end equipment. However, the existing studies are mainly conducted at room and moderate temperatures. Besides, they are mainly carried out by experiments. Theories on the temperature dependence of fracture strength are rarely reported. In this work, experimental methods for the ultra-high-temperature tensile properties of advanced materials and the elastic–plastic properties of coatings are developed, respectively, based on induction heating and radiation furnace heating technologies. A temperature-dependent fracture strength model for ceramics is proposed in the view of energy. The experimental methods and theoretical model are verified on the 2D plain-weave carbon fiber reinforced silicon carbide thermal structure composite, yttria-stabilized zirconia thermal barrier coating, and Si3N4 ceramics. The study shows that the mechanical properties of materials decrease significantly at ultra-high temperatures. The results are useful for the applications of ultra-high-temperature materials in thermal structure engineering.
Survey of Immersed Boundary Approaches for Finite Element Analysis
Authors: Kumar Ashok V. 
Published: October 2019

AbstractMesh generation for traditional finite element analysis has proven to be very difficult to fully automate especially using hexahedral elements for complex 3D geometry. Several modifications to the finite element method (FEM), such as the meshless methods, have been proposed for avoiding mesh generation. An alternative approach has recently gained popularity where the geometry, created as a solid model in cad software, is embedded or immersed in a nonconforming background mesh for analysis. In this approach, referred to here as the immersed boundary approach, a background mesh that is independent of the geometry is used for piecewise interpolation or approximation of the solution. Therefore, a uniform mesh with regular-shaped or undistorted elements can be used, and such a mesh is easy to generate automatically. When the geometry is immersed in the background mesh, the boundary elements are often only partly inside the geometry and the nodes of the mesh may not be on the boundaries. Many new methods have been developed to integrate over partial elements and to apply boundary and interface conditions when the boundaries of the geometries do not conform to the background mesh. These methods are reviewed in this article with particular emphasis on the implicit boundary method and step boundary method for applying boundary conditions. In addition, B-spline elements and several applications of the immersed boundary approach are surveyed including composite microstructures and structural elements for plates and shells.
Prediction and Experimental Validation of Part Thermal History in the Fused Filament Fabrication Additive Manufacturing Process
Authors: Roy Mriganka , Yavari Reza , Zhou Chi , Wodo Olga , Rao Prahalada 
Published: October 2019

AbstractPart design and process parameters directly influence the instantaneous spatiotemporal distribution of temperature in parts made using additive manufacturing (AM) processes. The temporal evolution of temperature in AM parts is termed herein as the thermal profile or thermal history. The thermal profile of the part, in turn, governs the formation of defects, such as porosity and shape distortion. Accordingly, the goal of this work is to understand the effect of the process parameters and the geometry on the thermal profile in AM parts. As a step toward this goal, the objectives of this work are two-fold. First, to develop and apply a finite element-based framework that captures the transient thermal phenomena in the fused filament fabrication (FFF) additive manufacturing of acrylonitrile butadiene styrene (ABS) parts. Second, validate the model-derived thermal profiles with experimental in-process measurements of the temperature trends obtained under different material deposition speeds. In the specific context of FFF, this foray is the critical first-step toward understanding how and why the thermal profile directly affects the degree of bonding between adjacent roads (linear track of deposited material), which in turn determines the strength of the part, as well as, propensity to form defects, such as delamination. From the experimental validation perspective, we instrumented a Hyrel Hydra FFF machine with three non-contact infrared temperature sensors (thermocouples) located near the nozzle (extruder) of the machine. These sensors measure the surface temperature of a road as it is deposited. Test parts are printed under three different settings of feed rate, and subsequently, the temperature profiles acquired from the infrared thermocouples are juxtaposed against the model-derived temperature profiles. Comparison of the experimental and model-derived thermal profiles confirms a high degree of correlation therein, with a mean absolute percentage error less than 6% (root mean squared error &lt;6 °C). This work thus presents one of the first efforts in validating thermal profiles in FFF via direct in situ measurement of the temperature. In our future work, we will focus on predicting defects, such as delamination and inter-road porosity based on the thermal profile.
Analytical Characterization and Experimental Validation of the Material Extrusion Wave Infill for Thin-Walled Structures
Authors: Chisena Robert S. , Shih Albert J. 
Published: October 2019

Abstract
The wave infill for material extrusion (MEX) of the thin-walled structure (TWS) is presented. The wave infill, a lightweight truss-like porous core structure sandwiched between two outer walls, is an efficient toolpath pattern for the MEX of TWS. Analytical models for predicting the stiffness, load capacity, fabrication time, and mass were established for two orthogonal in-plane and layer-to-layer variations inherent in MEX wave infill parts. Rectangular prism, four-point flexural bending specimens representing the in-plane and layer-to-layer orientations with wave infill were fabricated by MEX of polyamide-12 (Nylon-12) material. From these specimens, fabrication time and mass were measured, and four-point flexural tests were conducted to measure the stiffness and load capacity of the beam. Analytical models were compared with the experimental measurements to identify their predictive capabilities. Stiffness for in-plane and layer-to-layer orientations was predicted well with the relative root-mean-square error (RRMSE) of 7% and 6%, respectively. Load capacity in in-plane and layer-to-layer orientations had the RRMSE of 23% and 22%, respectively. Fabrication time and mass were predicted well with a RRMSE of 7% and 6%, respectively. The methods established in this study are the foundation for optimal design and MEX of wave infill TWSs with generalized loads.
Is the local seismicity in western Hispaniola (Haiti) capable of imaging northern Caribbean subduction?
Authors: Corbeau J. , Gonzalez O.L. , Clouard V. , Rolandone F. , Leroy S. , Keir D. , Stuart G. , Momplaisir R. , Boisson D. , Prépetit C. 
Published: October 2019

Abstract
The boundary between the Caribbean and North American plates in the Hispaniola region is the northwestern termination of the North American plate subduction evolving from westward subduction in the Lesser Antilles to southward subduction in the Greater Antilles and oblique collision against the Bahamas platform in Cuba. We analyze P waveforms recorded by 27 broadband seismic temporary stations deployed during the Trans-Haiti project. Seismicity recorded by the temporary network from June 2013 to June 2014 is used to locate the earthquakes. A total of 514 events were identified with magnitudes ranging from 1 to 4.5. Twenty-six moment tensors were calculated by full waveform inversion using the ISOLA software. The analysis of the new moment tensors for the Haiti upper lithosphere indicates that normal, thrust and strike-slip faulting are present but with a majority of thrust faulting. The mean P and T axes for the moment tensors indicated that the current compressional deformation is mainly N-S to NNE-SSW. Moreover, a dozen intermediate-depth earthquakes (>70 km) are located under Haiti, with one event in the south of the island reaching 260 km depth. The seismic data of the Haiti network, over a one-year time period, tend to confirm the existence of a lithospheric slab inherited from southward subduction under the Greater Antilles. The scarcity of the intermediate-depth seismic events in this area may be the effect of the lack of a dense seismic network or may indicate that we image the western slab edge.
Primary care physicians’ access to in-house ultrasound examinations across Europe: a questionnaire study
Authors: Aakjær Andersen Camilla , Jensen Martin Bach B , Toftegaard Berit Skjødeberg , Vedsted Peter , Harris Michael , Research group Örenäs 
Published: October 2019

ObjectiveThe overall objective of this study was to examine the differences in ultrasound availability in primary care across Europe.DesignCross-sectional study.SettingPrimary care.ParticipantsPrimary care physicians (PCPs).Primary and secondary outcomes measuresThe primary aim was to describe the variation in in-house primary care ultrasonography availability across Europe using descriptive statistics. The secondary aim was to explore associations between in-house ultrasonography availability and the characteristics of PCPs and their clinics using a mixed-effects logistic regression model.ResultsWe collected data from 20 European countries. A total of 2086 PCPs participated, varying from 59 to 446 PCPs per country. The median response rate per country was 24.8%. The median (minimum–maximum) percentage of PCPs across Europe with access to in-house abdominal ultrasonography was 15.3% (0.0%–98.1%) and 12.1% (0.0%–30.8%) had access to in-house pelvic ultrasonography with large variations between countries. We found associations between in-house abdominal ultrasonography availability and larger clinics (OR 2.5, 95% CI 1.2 to 4.9) and clinics with medical doctors specialised in areas, which traditionally use ultrasonography (OR 2.1, 95% CI 1.1 to 3.8). Corresponding associations were found between in-house pelvic ultrasonography availability and larger clinics (OR 1.9, 95% CI 1.3 to 2.7) and clinics with medical doctors specialised in areas, which traditionally use ultrasonography (OR 3.0, 95% CI 1.8 to 5.1). Additionally, we found a negative association between urban clinics and in-house pelvic ultrasound availability (OR 0.5, 95% CI 0.2 to 0.9).ConclusionsAcross Europe, there is a large variation in PCPs’ access to in-house ultrasonography and organisational aspects of primary care seem to determine this variation. If evidence continues to support ultrasonography as a front-line point-of-care test, implementation strategies for increasing its availability in primary care are needed. Future research should focus on facilitators and barriers that may affect the implementation process.
Time from diagnosis to treatment of colorectal cancer in a South Australian clinical registry cohort: how it varies and relates to survival
Authors: Roder David , Karapetis Christos Stelios , Olver Ian , Keefe Dorothy , Padbury Robert , Moore James , Joshi Rohit , Wattchow David , Worthley Dan L , Miller Caroline Louise , Holden Carol , Buckley Elizabeth , Powell Kate , Buranyi-Trevarton Dianne , Fusco Kellie , Price Timothy 
Published: October 2019

ObjectivesSome early studies indicated lower survival with longer time from diagnosis to cancer treatment, but others showed the reverse. We investigated time to treatment of colorectal cancer and associations with survival.Setting and participantsClinical registry data for colorectal cancer cases diagnosed in 2000–2010 at four major public hospitals in South Australia and treated by surgery (n=1675), radiotherapy (n=616) and/or systemic therapy (n=1556).DesignA historic cohort design, with rank-order tests for ordinal clinical and sociodemographic predictors and multiple logistic regression for comparing time from diagnosis to treatment. Unadjusted Kaplan-Meier estimates and adjusted Cox proportional hazards regression were used to investigate disease-specific survival by time to treatment.Outcome measuresTime to treatment and survival from diagnosis to death from colorectal cancer.ResultsTreatment (any type) commenced for 87% of surgical cases<60 days of diagnosis, with 80% having surgery within this period. Of those receiving radiotherapy, 59% began this treatment<60 days, and of those receiving systemic therapy, the corresponding proportion was 56%. Adjusted analyses showed treatment delay >60 days was more likely for rectal cancers, 2006–2010 diagnoses, residents of northern than other metropolitan regions and for surgery, younger ages <50 years and unexpectedly, those residing closer to metropolitan services. Adjusting for clinical and sociodemographic factors, and diagnostic year, better survival occurred in<2 years from diagnosis for time to treatment >30 days. Survival in the 3–10 years postdiagnosis generally did not differ by time to treatment, except for lower survival for any treatment >90 days for surgical cases.ConclusionsThe lower survival<2 years from diagnosis for treatment<30 days of diagnosis is consistent with other studies attributed to preferencing more complicated cases for earlier care. Lower 3–10 years survival for surgical cases first treated >90 days from diagnosis is consistent with previously reported U-shaped relationships.