bluuebunny/crossref_metadata_2025_split huggingface dataset:
Enhanced Chaotic Transition Prediction Using Hierarchical Clustering for the Lorenz System
Authors: Monir Solmaz Seyed , Hu Juhua , Tribelhorn Ben , Dillon Heather E. 
Published: February 2024

Abstract
In this research, we propose a novel way using unsupervised machine learning to improve the accuracy of predicting chaotic transitions in natural convection systems. Previous work has focused on the application of machine learning methods to natural convection systems for understanding turbulent convection transitions. We build on the prior work using the Lorenz system to investigate the potential of unsupervised machine learning models without expert inputs. The Lorenz system was selected due to its relatively simple equations and well-documented chaotic behavior. The Lorenz equations are a dynamic system for natural convection that are represented by a coupled system of ordinary differential equations.
Prior work had confirmed that clustering can predict transitions for this system, but the accuracy of predicting transitions could be improved. The prior studies had analyzed eight, expert-chosen features focused on descriptive statistics of the spectral density for the raw inputs to a machine learning algorithm. Our research team modified the prior machine learning methods to cover a large range of geometry and fluid parameters with high accuracy using only images of time series plots as the input to the algorithm. The images are phase plots consistent with those commonly used to observe the Lorenz system’s strange attractors. To account for a large range of geometry and fluid parameters, we converted high-dimensional time series data to phase plot images. This allowed us to capture intricate details within the data that might be missed using prior approaches. We then use deep neural networks to extract low-dimensional features for clustering, allowing us to identify hidden patterns and structures within the data.
This work builds on prior research that used k-means++ clustering to predict behavior in natural convection systems. The approach for this work goes beyond traditional flat clustering methods by using a convolutional neural network and density-based clustering with varying minimum cluster sizes to improve accuracy. The new method has also reduced the bias associated with selecting Rayleigh ratio values, improving the accuracy and reliability of our results. The improved method does not rely on expert selected statistical features either, a significant advantage for adapting the method to other natural convection systems.
The results are visually represented through histograms that show the key transitions in the chaotic system. The research team confirmed that the density-based clustering is a more efficient and accurate machine learning algorithm for this problem. The method presented in this paper also incorporates additional validation steps to ensure the accuracy and reliability of the results. The new method provides more detailed insights into the chaotic behavior of the Lorenz system. This has important implications for a range of fields, including natural convection, meteorology, fluid dynamics, and chaos theory.
RISE-Like Saturated Control for Non-Smooth and Switched Non-Linear Systems
Authors: Basyal Sujata , Ting Jonathan , Allen Brendon C. 
Published: February 2024

Abstract
A focus of decades of research has been to develop nonlinear control strategies to compensate for unstructured terms in a dynamic model that can be bounded by constants. Both continuous and discontinuous controllers have been developed; however, these controllers are limited to certain classes of smooth nonlinear systems, contain unsaturated functions of the system’s states, and/or are prone to chattering. An open problem is the development of chatter-mitigating and saturated controllers for a wide class of dynamic models, that compensate for uncertain terms in the dynamic model. In this paper, a continuous controller, that can be used for a wide range of nonsmooth and switched systems, is developed. To enable uncertainty rejection, a sliding mode (SM) term is included in a filtered tracking error but not in the controller itself. In addition to the filtered tracking error, an adaptive estimate is developed to compensate for the unknown control effectiveness matrix in the dynamics. Furthermore, the controller is designed to be saturated to increase the feasibility of the control system. A Lyapunov-like stability analysis is performed to prove that the proposed controller yields uniform trajectory tracking to an ultimate bound.
Evaluation of Myotubes Orientation Cultured on Scaffold Film by Micromarkers Matrix
Authors: Hashimoto Shigehiro , Sakai Shusei , Saito Shunsuke 
Published: February 2024

Abstract
A cell culture scaffold of elastic thin film with a micro-markers matrix on the back was prepared to evaluate myotubes contraction orientation. A matrix pattern of micromarkers (diameter 4 μm, height 2 μm, interval 30 μm) was fabricated on the back of a polydimethylsiloxane thin film (thickness 6 μm) using photolithography. The direction of the periodic movement of the micromarkers synchronized with the electrical pulses applied periodically to the medium via electrodes was determined from video-image analysis using optical microscopy. As reference data, the distribution of myotubes in the longitudinal direction was simultaneously determined from the microscopic image. Directional distributions of both micro-marker motion and myotube images in selected compartments were compared. Experimental results demonstrate that the functional orientation of myotubes can be assessed in vitro by tracking the direction of movement of matrix-patterned micromarkers.
The Failure Mechanism in CFRP Cross-Ply Curved Composite Laminates
Authors: Çevik Ahmet , Çöker Demirkan 
Published: February 2024

Abstract
This paper presents the experimental and numerical investigation of damage behavior in cross-ply curved composite laminates under transverse loading perpendicular to the horizontal arm. In the experiment, a high-speed camera is used to monitor the dynamic crack event occurring in the curved region of the specimens. The crack tip speed history is extracted from the high-speed camera images. High-speed camera observation reveals that the failure occurs in a sequential manner, starting from the inner side of the curved region and the subsequent failures occur in the outer side of the previous one. The digital image correlation (DIC) technique is used to obtain the strain field over the curved region during the experiment. The strain concentration is observed in the inner side of the curved region. The fractography is conducted with tested specimens using a digital microscope. Fiber breakage, fragmented matrix crack regions, delaminations, crack kinking and meandering crack path are observed in the micrographs of the post-mortem specimens. Explicit finite element analysis is conducted using ABAQUS/Explicit. To find the minimum required time step for the analysis, the modal analysis is carried out. To predict the matrix cracks observed in the micrographs, the user subroutine for LaRC04 failure criterion is implemented to ABAQUS. The cohesive zone method is used to simulate the delamination failure mode. The strength study is carried out by changing the transverse strength and interlaminar tensile strength (ILTS) of the laminae.
A CO2 Emissions Life Cycle Assessment of Additive and Conventional Manufacturing Based Lightweight Design in the Automotive
Authors: Dalpadulo Enrico , Pini Fabio , Leali Francesco 
Published: February 2024

Abstract
Within the road to decarbonization scenario, it becomes increasingly central to analyze the sources of emissions from different perspectives and select the more sustainable design approach for the development of new products. Among many sectors, lightweighting can reduce costs related to energy and fuel consumption. Potentially, it is also possible to reduce emissions, both for air and land transport, especially considering vehicles in the context of electrification and green transition. This paper provides an approach for the quantitative estimation of CO2 emissions along the lightweight design of vehicles components. The approach is based on a Life Cycle Assessment (LCA), which includes aspects ranging from product design and production to the use phase, and possible upgrading and recycling. Two lightweight design strategies are considered, using either conventional or unconventional technologies, which are respectively based on Design for Machining and Design for Additive Manufacturing. These methods can be scaled in high-end sectors, as both are characterized by high flexibility and customization, which allow the implementation of lightweight designs for small batch sizes. An automotive component is used as a case study, performing the product-process design based on Computer-Aided Technologies (CAX) for both approaches. The CO2 assessment is performed, considering all the drivers relating to the stages of the product life cycle. Additive Manufacturing is confirmed as more energy intensive, but the additional mass saving over the vehicle use phase returns emissions reduction compared to the whole life cycle.
Human Modelling and Design of Custom-Made Knee Implants: Definition of an Automatic Procedure
Authors: Ghidotti Anna , Vitali Andrea , Regazzoni Daniele , Rizzi Caterina 
Published: February 2024

Abstract
Total knee arthroplasty (TKA) is the surgical procedure of choice for end-stage osteoarthritis. Even if it is widely performed, there is still dissatisfaction with the surgical procedure in about 20–30% of patients. Factors such as malalignment of the implant and the size of the components have been reported as the most common reasons for post-operative complaints. Custom-made prostheses have been introduced to replicate each individual joint geometry and kinematics. In this study, a novel approach is proposed to automate custom-made knee implant design. The aim is to create a pipeline, where customized implants can be designed automatically for a large number of patients, reducing the time for design. Firstly, a manual procedure for designing the implant is defined. The lower part of the femur is extruded with a thickness that matches with the natural anatomy of the patient and cut planes are used to design the customized femoral implant. Then, an automatic procedure is developed. For the purpose, a statistical shape model of femur, based on 33 patients, is created and employed. The procedure is tested with 5 study cases showing the potential of the methodology. Results will be furtherly validated on a larger scale.
Experimental Determination of Electromechanical Coupling Matrices for Active Vibration Control of Composite Structures
Authors: Hameury Celia , Ferrari Giovanni , Balasubramanian Prabakaran , M. P. Silva Tarcisio , Amabili Marco , Buabdulla Abdulaziz , Franchini Giulio 
Published: February 2024

Abstract
Multiple input multiple output active vibration control architectures pose some common challenges to designers, such as the optimization of the number and of the position of sensors and actuators, and of the controller parameters. At a more fundamental level, however, the modeling of the electromechanical structure under control is a preliminary step necessary to perform all the optimizations described above. While some control algorithms try to prescind from a detailed modeling, some models are always required to simulate numerically the performance of the control.
Finite element or reduced order models are often employed to simulate and to estimate the relationship between electrical and mechanical inputs and outputs. However, building these models can rapidly become onerous, even for relatively simple bidimensional structures, for example composite beams, plates and shells. Therefore, an experimental method was developed for the determination of the electromechanical coupling matrices. Simple experimental modal analyses were performed to obtain parameters such as natural frequencies, damping ratios, modal shapes and frequency response functions. Afterwards, a least square error algorithm, implemented in MATLAB and in Python, was used to determine the matrices that correlate transducer voltages, generalized coordinates and modal coordinates. Modal coordinates are especially useful for the construction of multiple input multiple output active vibration control algorithms that operate in the modal space; however, in these cases the inversion or the pseudo-inversion of the participation matrices had to be performed as well.
The proposed method was tested on one cantilever sandwich beam and on one sandwich plate with free edges, equipped with two collocated couples of sensors and actuators and four non-collocated couples of sensors and actuators respectively. In particular, piezoelectric patches operating in flexural mode were employed as transducers. The method simulated correctly the uncontrolled electromechanical response of either structure, and its performance in this regard compared favorably with that of the finite element method.
Afterwards, multiple input, multiple output positive position feedback active vibration control algorithms based on these participation matrices were built for either system, and tuned according to established method described in the relevant literature. In either case, a number of modes double with respect to that of the couples of installed actuators and sensors was controlled satisfactorily. The controllers resulted stable and negligible spillover on uncontrolled modes was observed.
The Mechanical and Functional Behavior of Nitinol-Reinforced PLA Composites
Authors: Srinivas Pooja , Abu Al-Rub Rashid K. , Barsoum Imad , Zaki Wael 
Published: February 2024

Abstract
The current paper proposes the addition of nitinol at varying volume percentages (3, 10, and 15 vol%) to polylactic acid (PLA) matrix to study its effect on mechanical properties. In recent years, new types of PLA composites have been developed that incorporate nanomaterials such as CNTs, graphene, and other materials such as wood and kenaf fibers. Nitinol is an alloy with excellent shape memory and superelastic properties, which makes it highly desirable for use in biomedical and aerospace industries. In this work, the dissolution method was used to prepare PLA-Nitinol composite feedstock, which was extruded to fabricate composite filaments. The filaments were used in fused deposition modeling (FDM) printing to create cylindrical and cubic composite green samples. X-ray diffraction (XRD), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC) were utilized to characterize the fabricated samples. Mechanical and functional behavior characterizations were carried out through quasi-static compression tests using a universal testing machine (UTM). The results show that composites of PLA and Nitinol exhibit improved mechanical properties compared to pure PLA, making them useful for a wide range of applications. Further research and development can result in new, highly functional materials with a broad range of potential applications. The current research paves the way for the development of printing metal-enriched filaments and get 100% metal parts using FDM technique.
Revisiting and Improving Pipe Wall Transmission Loss Estimation for Control Valve Noise Prediction
Authors: Eilers Daniel , Fagerlund Allen 
Published: February 2024

Abstract
The prediction of noise in industrial control valve applications is required to select the correct control valve design for the end user to keep their employees and equipment safe as well as meet any local noise ordinances. In a piping system any noise generated by a valve or other component will propagate within the downstream pipe. This internal acoustic field will couple to the pipe wall and cause it to vibrate, which in turn causes external radiation. The difference between the internal and external sound fields is called transmission loss. The estimation of the transmission loss can be a major contributor to the accuracy of noise prediction methods.
The theory that is the basis of the pipe wall transmission loss calculation in the international standard IEC 60534-8-3 Control Valve Aerodynamic Noise Prediction Method is reviewed and reanalyzed to correct an error. Then critical variables such as uniform mean flow, internal acoustic modal density, and structural modal density are reevaluated.
Based on the complete reanalysis, suggestions for improvements to the calculation methodology used in noise predictions are provided and the estimated change is quantified. Experimental data taken in a flow system designed to measure control valve noise was used to inspect a few variables and the overall prediction methodology. Future research areas are also suggested.
Impact on Wrinkled Graphene
Authors: Flanagan Asher , Park Jungkyu 
Published: February 2024

Abstract
We investigated wrinkle-free single layer graphene and graphene with various wrinkles to examine their fracture toughness during an impact with a silver nanoparticle using molecular dynamics simulations. The interaction between silver atoms is modeled using Embedded Atom Model (EAM) potential, while the interaction between carbon atoms in the graphene was modeled using 2nd generation Reactive Empirical Bond Order (REBO) potential. The interaction between silver atoms and carbon atoms is modeled by using the Lennard-Jones potential. The graphene is equilibrated at 300K. Three different amplitudes (0.4 nm, 2 nm, and 2.5 nm) and two different wavelengths (4 nm and 17 nm) are selected for the generation of wrinkles in graphene. Our simulations revealed that wrinkled graphene absorbs more kinetic energies of a silver particle during impact. The highest impact energy absorbed during the impact was 33 keV when the wrinkle has the wavelength of 17 nm and the amplitude of 2.5 nm. This indicates that wrinkled graphene possesses higher toughness compared to wrinkle-free graphene layers. The toughness against high-speed impact is shown to increase with an increase in wrinkle size in the graphene layer. In the case of wrinkled graphene, the kinetic energy of a silver particle was completely absorbed by the graphene when the particle failed to fracture the graphene layer while wrinkle-free graphene bounced back the silver particle with a finite amount of velocity when it couldn’t break the graphene layer. The results obtained from our research study will contribute to the accelerated development of futuristic, strong, lightweight materials for military applications.
A Computational Study of Sustainable Hydrogen Production Using High-Pressure Modular Gasifier
Authors: Chanda Sumit , Tasnim Anika Farhat , Reyes Daniel , Choudhuri Ahsan , Islam Nawshad Arslan 
Published: February 2024

Abstract
The article presents a computational study of a high-pressure gasifier using biomass and Municipal Solid Waste (MSW). The current work investigates the feasibility of using a high-pressure gasifier system for biomass and MSW gasification and understanding the gasification pathways for improved Hydrogen (H2) yield. A computational model for a simple vertically mounted fixed bed high-pressure gasifier was developed to achieve the current goal. Biomass and MSW compositions obtained from various US locations are used to investigate the effects of feedstock in maximizing the H2 yield. The primary goal is to characterize the gasifier operation at different operating temperatures and pressures. Air and Oxygen are used as gasifying agents. The operating temperature and the inlet pressure are varied between 400°K to 1100°K and 1 to 5 bar, respectively. The MSW samples gave better H2 yield at 0.3–0.35 equivalence ratios (ER) when using air as the gasification agent. Increasing the temperature promoted steam gasification reactions and produced more H2, but at higher temperatures, that effect diminished. Increasing pressure reduced the H2 yield in the beginning but started to improve the yield at higher pressures. An ER below 0.3 is recommended for oxygen-blown gasification to improve H2 yield.
Field Demonstration of Pinhole Insulation Technology for Energy Efficiency Retrofits in Connecticut
Authors: Chacko Celia , Gorthala Ravi , Patil Prathamesh 
Published: February 2024

Abstract
Building energy efficiency retrofits are a valuable tool to minimize household energy consumption, improve energy affordability and reduce carbon footprints. In Connecticut, low-and-moderate income households deal with challenges in sustaining their energy needs at a greater severity compared to the average household. Adding insulation to buildings with minimal wall insulation can significantly improve building envelopes and minimize heat losses to reduce energy consumption. This research investigates the use of a new, innovative, minimally invasive insulation technology for installing closed-cell spray polyurethane foam (SPF) into exterior wall cavities. SPF is a versatile insulating material known for its low thermal conductivity, density, and its high thermal resistance value, also known as its R-value. The technology is demonstrated in a low-income multifamily home pilot study in Connecticut. The technology effectiveness is validated through in-situ wall thermal measurements and energy modelling with EnergyPlus. The primary objective of this study is to determine the improvement in the thermal performance of the Pinhole Insulation® technology. Preliminary results have demonstrated an increase in in-situ Rvalue of 3.5 and heating savings of 19.30% for the shallow cavity site. This corresponds to annual savings of $3,215 for the site with a simple payback of 11.8 years.
Experimental Characterization of a Centrifugal Compressor in Second Quadrant Operation
Authors: Serena Alberto , Bakken Lars E. 
Published: February 2024

Abstract
The flow unsteadiness in turbomachines, presenting a characteristic behaviour, requires a deep understanding of the underlying flow fundamentals, a careful analysis through advanced experimental methods and a clear distinction on how the surrounding system might lead to instabilities.
A sustained deep surge condition might force a compressor into second quadrant operation, which can occur intermittently during surge cycles or continuously as a result of system malfunction or fast ESD with low inertia machines. In this unusual operating area, compressor system wise, the characteristic is often modelled with a simple approach, as a passive, valve-like component. Aerodynamically wise, corrections are possible accounting for specific phenomena, as incidence losses and blockage.
In similar researches, a booster is forcing a stable reverse flow, with the instrumentation rotated according to the expected direction. In this study, this is provided by a pressurized tank, representing a tuneable discharge volume as well as process equipment malfunction, i.e., check valve failure or leakage.
The test matrix covers a range of discharge pressures, flow rates and rotational speeds, both at constant-imposed speed and with no torque applied, at locked or free shaft, to investigate the effect of different parameters and phenomena.
The results document the characteristics under different operating conditions. The key contribution is the definition of a suitable approach for the collection of relevant and reliable data measurement, which lays an important foundation for further development of dynamic models for compressor system behaviour and allows to properly reduce complexity of surge protection devices, for operation in more favourable conditions.