bluuebunny/crossref_metadata_2025_split huggingface dataset:
Anomaly Detection for Cyber-Physical Systems Using Transformers
Authors: Ma Yuliang , Morozov Andrey , Ding Sheng 
Published: January 2022

Abstract
Safety and reliability are two critical factors of modern Cyber-Physical Systems (CPS). However, the increasing structural and behavioral complexity of modern automation systems significantly increases the possibility of system errors and failures, which can easily lead to economic loss or even hazardous events. Anomaly Detection (AD) techniques provide a potential solution to this problem, and conventional methods, e.g., Autoregressive Integrated Moving Average model (ARIMA), are no longer the best choice for anomaly detection for modern complex CPS. Recently, Deep Learning (DL) and Machine Learning (ML) anomaly detection methods became more popular, and numerous practical applications have been presented in many industrial scenarios. Most of the modern DL-based anomaly detection methods use the prediction approach and LSTM architecture. The Transformer is a new neural network architecture that outperforms LSTM in natural language processing.
In this paper, we show that the Transformer-based deep learning model, which has received much attention recently, can be applied to the anomaly detection of industrial automation systems. Specifically, we collect time-series data from a system of two industrial robots using a Simulink model. Then, we feed these data into our Transformer-based model and train it to be a time-series data predictor. The paper presents the experimental results that show the comparison of precision and speed of a Long-Short Time Memory (LSTM) predictor and our Transformer-based predictor.
Performance Analysis of a Gas Turbine Disk Containing Rotating Heat Pipes
Authors: Lu Wanqiu , Ding Shuiting , Li Guo 
Published: January 2022

Abstract
The turbine disk is a key component of an aero-engine, which works under extremely high rotational and thermal loads. The combination of high-temperature heat pipes with a turbine disk is an effective method for controlling thermal load and the corresponding stress level because heat pipes enable rapid heat transfer from the rim of the disk to its hub. In this study, the influences of temperature and stress distribution variations caused by two different shapes of heat pipes are evaluated via thermomechanical finite element simulation. Results show that although the two shapes of heat pipes exert minimal effect on temperature change at the rim, specially shaped heat pipes with a connection ring at the bottom exhibit an advantage over cylindrical heat pipes in terms of stress level decrease at the hub of the disk because the former have lower rotational and thermal hoop stress components. Moreover, notch stress at the end of the heat pipe condenser is associated with the geometric parameters of heat pipes, particularly heat pipe length.
Unstart Phenomena Induced by Forced Excitation in a Dual-Mode Scramjet
Authors: Alex Alvin , Lijo V. 
Published: January 2022

Abstract
Scramjet engine with no moving parts and extensive speed range is suitable for developing cheaper vehicles to outer space. The isolator, which isolates the inlet from the pressure buildup inside the combustor, is a critical component of the scramjet engine. In an actual scramjet, the combustor undergoes highly transient combustion giving rise to high amplitude fluctuating backpressure, which may cause the inlet to unstart. In general, combustion in a scramjet is a complex process that involves flows subjected to considerable pressure gradients, coexisting subsonic and supersonic flow regions in the presence of shock waves. Moreover, shock-induced boundary-layer separation patterns are different due to asymmetrical boundary layer development at the walls. Until now, no experimental study on the forced dynamic excitation in hypersonic flows is reported, mainly due to the limited available ground facilities that can reproduce such conditions. Such dynamic excitation can give to flow fields that are significantly different from that reported in other studies. The present study numerically addresses forced excitation inside the combustor generated by an elliptical-shaped rotor. During the unstart process, several stages were identified, such as separation and its growth in both the upper and lower walls of the combustor, isolator, inlet, and finally, shock excursion leading to unstart. The results provide ample insight into the upstream propagation of flow disturbances originating from the combustor, its interaction with the asymmetric boundary layers on top and bottom walls, and the dynamics of inlet unstart.
Using Wireless Pasco Smart Carts to Demonstrate Vibration Principals
Authors: Hekman Keith 
Published: January 2022

Abstract
In a typical vibrations course, students learn mathematical models to predict the response of vibratory systems. Often, students have trouble visualizing what they are calculating with the equations. The goal is to have a visual example of the motions that are represented in the equations. Because of in-person meeting restrictions, demonstration experiments were recorded before class time, which allowed the analysis to be completed before class. A Pasco smart cart system was used to create the demonstrations. The carts are connected to the computer via Bluetooth and can measure force, position, and acceleration. Using the force sensor, the spring constant and magnetic damping coefficient are determined. Demonstrations were created for one and two degree of freedom systems. The response was shown for systems with and without magnetic damping. Free and forced responses were measured in all the cases. For single degree of freedom systems, higher-order components of the input were explored and using the convolution integral to calculate the response. At the end of the semester, students took a survey to learn of their experience. Overall, students strongly appreciated the visual representation of the modeling equations.
Parametric Evaluation of AM Enabled Sinusoidal Heat Transfer Surfaces Through Numerical Simulations
Authors: Duggirala Vyas , Reddy Venkateswara , Muley Arun , Stoia Michael , Ek Garrett 
Published: January 2022

Abstract
Heat transfer enhancement and design innovation of thermal devices are needed to accommodate growth in heat duty from avionics, electric propulsion, environmental control, and engine systems of current and future aircraft. Additive manufacturing (AM) technology enables exploration of new heat transfer surfaces and complex flow passage geometries to achieve the higher convective heat transfer rates, while minimizing pressure loss, and compactness needed for next generation thermal devices. Effective use of these innovative designs requires the development of new thermo-hydraulic design databases, which include variations in heat exchanger geometries due to the influence of AM processes. The present work deals with performance evaluation of AM-enabled sinusoidal wavy heat transfer surfaces by 3D conjugate heat transfer analysis using Computational Fluid Dynamics (CFD). Numerical simulations were carried out for two thermal boundary conditions consisting of constant wall temperature and constant heat flux in laminar and turbulent flows with a Reynolds number range of 300 to 5000 for varying fin geometry parameters. Numerical results are validated with available literature data and presented in terms of isothermal friction factors and Nusselt numbers. Variation in local heat transfer coefficients and temperatures are discussed to gain insights into the fluid flow and associated heat transfer mechanisms. The parametric study on channel waviness showed that a decrease in wavelength resulted in a relatively large increase in friction factor relative to growth in Nusselt number, which was addressed by rounding of the flow channel corners.
Influence Study on End-Face Quality of Square Billet in Plate Cross Wedge Rolling
Authors: Xia Yingxiang , Shu Xuedao , Chen Taizhu 
Published: January 2022

Abstract
Cross wedge rolling (CWR) is an advanced forming technology in which the billet is mainly cylindrical shape. It has the advantages of high efficiency, energy-saving and material saving. Due to the difficulty to obtain large-size cylindrical billet, the CWR is limited to form large parts to some extent. This paper breaks through the limitation of traditional cylindrical billets and innovates square billets for plate cross wedge rolling. Based on the movement model and rotation condition of plate cross wedge rolling, the finite element simulation of square billet is carried out to clarify the formation mechanism of shaft end concave heart. It is found that a retaining wedge added on the die with reasonably wedge parameters can obtain small concave heart and flat surface of the shaft, which effectively improve the end-face quality. And the concave is mainly caused by the inconsistent flow velocity between the surface metal and core metal. The process parameters are optimized by the four-factor three-level orthogonal experiment and the influence order of each parameter on the end-face quality is: L &gt; β &gt; α &gt; θ. The optimal parameter combination for ensuring the end-face quality of square billet in plate cross wedge rolling is: forming angle 32°, spreading angle 8°, wedge angle 6.5°, wedge distance 8mm. A reasonable combination of process parameters can effectively control the end concavity and improve the end-face quality of the rolled product, which has important reference value and engineering significance for the realization of near-net forming of square billet in plate cross wedge rolling.
Statistical Energy Analysis of Vibrating Structures With Energy and Entropy
Authors: Hough Elise , Sotoudeh Zahra 
Published: January 2022

Abstract
We present a complete thermodynamic analogy of statistical energy analysis (SEA) using entropy and energy for both linear and nonlinear coupled systems. We will use Khinchin’s Entropy as our statistical entropy definition from statistical mechanics. This framework allows for the restrictive assumptions of linearity to be removed from this analysis method. We will use the classical definition of entropy to relate entropy to Vibrational Temperature. Using Khinchin’s statistical definition of entropy for a vibrating system, we will define a Vibrational Temperature as a function of energy. Hence, we will derive all that is necessary to construct the SEA power flow equation along with the transient coupling loss factors without any linearity assumption. With this method one can expand SEA to nonlinear transient coupled systems. We will verify our proposed method using Monte Carlo Simulation and published analytical closed form solutions.
Neural Differential Equations for Inverse Modeling in Model Combustors
Authors: Su Xingyu , Ji Weiqi , Zhang Long , Wu Wantong , Ren Zhuyin , Deng Sili 
Published: January 2022

Abstract
Monitoring the dynamics processes in combustors is crucial for safe and efficient operations. However, in practice, only limited data can be obtained due to limitations in the measurable quantities, visualization window, and temporal resolution. This work proposes an approach based on neural differential equations to approximate the unknown quantities from available sparse measurements. The approach tackles the challenges of nonlinearity and the curse of dimensionality in inverse modeling by representing the dynamic signal using neural network models. In addition, we augment physical models for combustion with neural differential equations to enable learning from sparse measurements. We demonstrated the inverse modeling approach in a model combustor system by simulating the oscillation of an industrial combustor with a perfectly stirred reactor. Given the sparse measurements of the temperature inside the combustor, upstream fluctuations in compositions and/or flow rates can be inferred. Various types of fluctuations in the upstream, as well as the responses in the combustor, were synthesized to train and validate the algorithm. The results demonstrated that the approach can efficiently and accurately infer the dynamics of the unknown inlet boundary conditions, even without assuming the types of fluctuations. Those demonstrations shall open a lot of opportunities in utilizing neural differential equations for fault diagnostics and model-based dynamic control of industrial power systems.
A Numerical Study of the Effect of Surface Coverage on the Filtration Performance of Hair Arrays
Authors: Tanikella Sri Savya , Jones Nathan D. , Dressaire Emilie 
Published: January 2022

Abstract
Biological filtration systems offer a sustainable alternative to existing engineered solutions. In this computational work, we seek to optimize the surface coverage by an array of hairs to capture particles in channels. A variety of aquatic organisms rely on arrays of hairs to interact with their fluidic environments. The hair functionality can vary from sensing to smelling, filtration to flow control depending on the species considered. Among those organisms are filter-feeders that rely on suspension-feeding, one of the most widespread feeding mechanisms and one of the oldest. Baleen whales are filter-feeders that catch their prey by using the baleen, a complex structure composed of plates and bristles in their mouth. The hairs are hollow cylindrical structures with a diameter of a few hundred micrometers that can extend over tens of centimeters. The baleen filters out the prey while letting the seawater through. The baleen is composed of flexible and elongated structures whose properties fit the feeding habits of the whale.
The porosity of the structure depends on the flow feature. Effectively, the flow can tune the filter properties, which sets biological filters apart from their engineered counterpart. Previous mechanical studies have shown that an array of hairs can either act as a sieve, allowing all the fluid to flow through it, or as a rake, forcing the fluid to flow around it instead. As the speed increases, the behavior shifts from rake to sieving for a given hair spacing. From a filtration perspective, the rake regime is not favorable as particles do not enter the array. For a fixed fluid velocity, the flow transitions from rake to sieve as the spacing between the hairs in the array increases. Our recent work has also demonstrated that the confinement of the channel influences the sieve to rake transition. The filtration mechanisms that filter-feeder organisms use to capture food particles exhibit complex fluid-structure interactions that have yet to be leveraged in engineered systems. To guide the development of hair-covered surfaces capable of trapping particles in channel flows, we investigate how different geometric factors affect the fluid transport and capture of particles by the array. In previous work, a small number of hairs, typically 25, were considered. Here, we vary the array geometry, the Reynolds number of the flow, and the surface coverage to study the transport through this confined porous structure. We compare arrays based on their optimal efficiency and the (sub-optimal) operating conditions which make the filter versatile.
Cell Behavior in Flow Passing Through Micro Machined Gap
Authors: Hashimoto Shigehiro , Uehara Shogo 
Published: January 2022

Abstract
Does each cell show specified behavior (deformation and alignment) as it passes through the micro-gap in the flow channel? A gap with a rectangular cross section (10 μm high, 0.4 mm wide, and length 0.1 mm long) was manufactured in the middle part of the flow path by photolithography technique. Myoblasts (C2C12: mouse myoblast cell line) sparsely suspended in the medium were used for the test. Deformation of each cell passing through the micro-gap was observed with an inverted phase contrast microscope. From the contour of the image of each cell passing through the gap, several parameters were analyzed: the two-dimensional projected area, the degree of deformation by ellipse approximation, and the alignment of the major axis of the deformed cell. The experimental results show that the alignment of each cell tends to deviate from the flow direction as the larger projected two-dimensional area.
Vibration Isolation in Continuous Beam Networks
Authors: Rai George , Rahn Christopher D. , Smith Edward , Marr Conor 
Published: January 2022

Abstract
This paper investigates antiresonance in continuous dynamic systems consisting of beam networks with inherent inertial coupling. An analytical non-dimensional transfer function model is developed to predict the isolation behavior of a cantilever beam with a tip mass. It is shown that beam network isolators exhibit a good degree of versatility at the design level. The static stiffness and the isolation forces are scalable at the design level, the dynamic stiffness can also be tuned to achieve any force reduction ratio in the absence of damping. Furthermore mutlifrequency isolation is possible due to the nature of continuous systems, thus, multi-mode isolation frequencies can be tuned closer to each other. Isolation frequency clustering is also possible by tuning the beam-mass components. As a proof of concept, the analytical results are validated with an experimental study whereby the shear force is recorded at the root of a cantilever beam with a tip mass that is subject to harmonic point force excitation. The experimental results show that the root shear response at the first isolation frequency is reduced by 78% after the addition of a tip mass equivalent to 230% of the beam mass.
Strain-Coupled Fluidlastic Circuits Inside Metal Additive Manufactured Structures
Authors: Saxena Ankit , Rai George , Lanari Valentin , Rahn Christopher D. , Manogharan Guhaprasanna 
Published: January 2022

Abstract
Fluidlastic dampers, isolators and absorbers are stand alone components used to reduce vibrations in many civil, mechanical and aerospace structures. This research demonstrates how additive manufacturing can integrate fluidlastic circuits inside a metal part. An example device with relatively simple monolithic construction consists of two chambers separated by a thin membrane that is connected to the upper chamber by a bridge compliant mechanism. The chambers are filled with fluid and are connected by a long thin channel inertia track that coils around their periphery. Elastic strain deflects the bridge causing the membrane to bulge into the upper chamber. This causes a pressure gradient that drives the fluid flow from the upper chamber to the lower chamber through the inertia track. Enabled by additive manufacturing, design parameters such as chamber dimensions, constitutive material, fluid viscosity, etc. can be easily tailored to provide targeted resonance over a desired frequency range. Experimental results provide evidence of fluid pumping at the membrane’s first resonant frequency.
Influence of Welding Sequence on Residual Stress Evolution in SUS304/Q235 Bimetallic Clad Plate Butt-Welded Joints
Authors: Zhu Min , Zhang Yansong , Zheng Qiao , Wu Wei , Qian Weifang , Wang Baosen 
Published: January 2022

Abstract
Residual stress prediction and controlling is important for structural integrity assessment of weldments. In current work, finite element and experimental methods were integrated to study the influence of welding sequence on the SUS304/Q235 bimetallic clad plate joints during multi-layer and multi-pass welding. The results show that the peak residual stress values on flyer plate surface are weakly affected by welding sequences but the width of high surficial longitudinal stress area of joint with base layer welded first is bigger. Meanwhile, welding sequence has a great influence on the longitudinal residual stress evolution law inside joints. When base seam layer is welded first, the highest stress concentration appears in the transition layer. However, it would be transferred into the first base seam layer due to martensite phase transformation when flyer seam layer is welded first. Residual stress controlling in the bimetallic clad plate joint should attract more attention from researchers.
A Time-Frequency Domain Adaptive Control Approach for Vibration of Active Magnetic Bearing System
Authors: Yao Xuan , Chen Zhaobo 
Published: January 2022

Abstract
Active magnetic bearings (AMBs) have several advantages such as non-contact and active control, and are getting more applications in rotating machinery. Various control strategies have been applied and designed for this nonlinear system with complex rotor dynamics. Most control schemes are in time domain, while the control in frequency domain, which is also essential for stability, is rarely considered. In this paper, a time-frequency domain control approach is proposed for AMB-rotor system. The control scheme is implemented using wavelet theory and deep learning theory. The controller consists of 2 main parts: a filter bank for discrete wavelet transform (DWT) to obtain time-frequency signal, and a deep neural network (DNN) for nonlinear adaptive control. A 4-DOF AMB-rotor system is analyzed and its model is established. The rotor dynamics are simulated and the results are compared. Simulation results demonstrate that the proposed approach has an obvious control effect in improving precision in time domain and stability in frequency domain. This research provides a new adaptive control approach for AMBs, and this approach can also be adopted in other multi-dimension vibration control, especially in multi-frequency applications.
Shock Wave Heating: A Novel Method for Low-Cost Hydrogen Production
Authors: Akbari Pejman , Copeland Colin D. , Tüchler Stefan , Davidson Mark , Mahmoodi-Jezeh Seyyed V. 
Published: January 2022

Abstract
This study introduces a new method of methane pyrolysis in a rotary chemical reactor using wave rotor technology. The patented technology has been developed by New Wave Hydrogen, Inc. (New Wave H2 or NWH2) . The concept introduces an efficient method of hydrogen production driven by shock wave gasdyanmics, with no direct CO2 emissions and no water use. The New Wave Reformer is based on wave rotor designs where unsteady shock waves are generated within channels arrayed around a rotating drum. As in a typical wave rotor wave cycle, a sharp pressure increase occurs behind a reflected shock wave, resulting in a proportional increase in gas temperature. This temperature amplification can be used to initiate a thermal decomposition reaction in gaseous constituents. Past studies have proven that a wave reformer with onboard reactions can reform heavy hydrocarbon gases into lighter hydrocarbon products. The current NWH2 study explores how a wave rotor can employ pressurized natural gas as a driver gas for compression heating of a low-pressure hydrocarbon fuel inside the channels of a wave reformer, resulting in the decomposition of methane into hydrogen and carbon black. This study first reviews past efforts ranging from conceptual patents to experimental studies utilizing different wave cycles for rapid heating of gases in gas-phase chemical reactions. Examples of such reactions include the formation of acetylene from methane and the formation of nitric oxide from air. In ongoing research, the authors introduce a wave cycle that uses a dual-stage gas compression process designed to prolong reaction time within the channels, addressing a key factor in high methane-to-hydrogen conversion. The process has been modeled numerically using a customized version of the Tüchler-Copeland experimentally-validated quasi-one-dimensional CFD code. The computational results provide data used in the prediction of flow fields inside the channels and at the inflow/outflow ports of the reactor.