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A Survey Of Using Machine Learning In Iot Security And The Challenges Faced By Researchers, Khawlah M. Harahsheh, Chung-Hao Chen Jan 2023

A Survey Of Using Machine Learning In Iot Security And The Challenges Faced By Researchers, Khawlah M. Harahsheh, Chung-Hao Chen

Electrical & Computer Engineering Faculty Publications

The Internet of Things (IoT) has become more popular in the last 15 years as it has significantly improved and gained control in multiple fields. We are nowadays surrounded by billions of IoT devices that directly integrate with our lives, some of them are at the center of our homes, and others control sensitive data such as military fields, healthcare, and datacenters, among others. This popularity makes factories and companies compete to produce and develop many types of those devices without caring about how secure they are. On the other hand, IoT is considered a good insecure environment for cyber …

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A Structured Narrative Prompt For Prompting Narratives From Large Language Models: Sentiment Assessment Of Chatgpt-Generated Narratives And Real Tweets, Christopher J. Lynch, Erik J. Jensen, Virginia Zamponi, Kevin O'Brien, Erika Frydenlund, Ross Gore Jan 2023

A Structured Narrative Prompt For Prompting Narratives From Large Language Models: Sentiment Assessment Of Chatgpt-Generated Narratives And Real Tweets, Christopher J. Lynch, Erik J. Jensen, Virginia Zamponi, Kevin O'Brien, Erika Frydenlund, Ross Gore

VMASC Publications

Large language models (LLMs) excel in providing natural language responses that sound authoritative, reflect knowledge of the context area, and can present from a range of varied perspectives. Agent-based models and simulations consist of simulated agents that interact within a simulated environment to explore societal, social, and ethical, among other, problems. Simulated agents generate large volumes of data and discerning useful and relevant content is an onerous task. LLMs can help in communicating agents' perspectives on key life events by providing natural language narratives. However, these narratives should be factual, transparent, and reproducible. Therefore, we present a structured narrative prompt …

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A Structure-Aware Generative Adversarial Network For Bilingual Lexicon Induction, Bocheng Han, Qian Tao, Lusi Li, Zhihao Xiong Jan 2023

A Structure-Aware Generative Adversarial Network For Bilingual Lexicon Induction, Bocheng Han, Qian Tao, Lusi Li, Zhihao Xiong

Computer Science Faculty Publications

Bilingual lexicon induction (BLI) is the task of inducing word translations with a learned mapping function that aligns monolingual word embedding spaces in two different languages. However, most previous methods treat word embeddings as isolated entities and fail to jointly consider both the intra-space and inter-space topological relations between words. This limitation makes it challenging to align words from embedding spaces with distinct topological structures, especially when the assumption of isomorphism may not hold. To this end, we propose a novel approach called the Structure-Aware Generative Adversarial Network (SA-GAN) model to explicitly capture multiple topological structure information to achieve accurate …

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Transitional Entrepreneurship: Unleashing Entrepreneurial Potential Across Numerous Challenging Contexts, Golshan Javadian, Anil Nair, David Ahlstrom, Kaveh Moghaddam, Li-Wei Chen, Younggeun Lee Jan 2023

Transitional Entrepreneurship: Unleashing Entrepreneurial Potential Across Numerous Challenging Contexts, Golshan Javadian, Anil Nair, David Ahlstrom, Kaveh Moghaddam, Li-Wei Chen, Younggeun Lee

Management Faculty Publications

[First paragraph] We are pleased to publish the special issue of the New England Journal of Entrepreneurship on transitional entrepreneurship. Transitional entrepreneurship refers to the practices of entrepreneurs from communities facing adversity who navigate substantial life transitions as they launch and manage new ventures in response to various changes and challenges in their environment. Entrepreneurship is not only a critical driver of economic growth and social development (Ahlstrom et al., 2019; McCloskey, 2010) but can also represent a life-changing transition for most, if not all, of the entrepreneurs themselves. Transitional entrepreneurship entails strategic pivots or transformations that enable entrepreneurs to …

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Robustembed: Robust Sentence Embeddings Using Self-Supervised Contrastive Pre-Training, Javad Asl, Eduardo Blanco, Daniel Takabi Jan 2023

Robustembed: Robust Sentence Embeddings Using Self-Supervised Contrastive Pre-Training, Javad Asl, Eduardo Blanco, Daniel Takabi

School of Cybersecurity Faculty Publications

Pre-trained language models (PLMs) have demonstrated their exceptional performance across a wide range of natural language processing tasks. The utilization of PLM-based sentence embeddings enables the generation of contextual representations that capture rich semantic information. However, despite their success with unseen samples, current PLM-based representations suffer from poor robustness in adversarial scenarios. In this paper, we propose RobustEmbed, a self-supervised sentence embedding framework that enhances both generalization and robustness in various text representation tasks and against diverse adversarial attacks. By generating high-risk adversarial perturbations to promote higher invariance in the embedding space and leveraging the perturbation within a novel contrastive …

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An Optimized And Scalable Blockchain-Based Distributed Learning Platform For Consumer Iot, Zhaocheng Wang, Xueying Liu, Xinming Shao, Abdullah Alghamdi, Md. Shirajum Munir, Sujit Biswas Jan 2023

An Optimized And Scalable Blockchain-Based Distributed Learning Platform For Consumer Iot, Zhaocheng Wang, Xueying Liu, Xinming Shao, Abdullah Alghamdi, Md. Shirajum Munir, Sujit Biswas

School of Cybersecurity Faculty Publications

Consumer Internet of Things (CIoT) manufacturers seek customer feedback to enhance their products and services, creating a smart ecosystem, like a smart home. Due to security and privacy concerns, blockchain-based federated learning (BCFL) ecosystems can let CIoT manufacturers update their machine learning (ML) models using end-user data. Federated learning (FL) uses privacy-preserving ML techniques to forecast customers' needs and consumption habits, and blockchain replaces the centralized aggregator to safeguard the ecosystem. However, blockchain technology (BCT) struggles with scalability and quick ledger expansion. In BCFL, local model generation and secure aggregation are other issues. This research introduces a novel architecture, emphasizing …

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Heart Disease Prediction Using Stacking Model With Balancing Techniques And Dimensionality Reduction, Ayesha Noor, Nadeem Javaid, Nabil Alrajeh, Babar Mansoor, Ali Khaqan, Safdar Hussain Bouk Jan 2023

Heart Disease Prediction Using Stacking Model With Balancing Techniques And Dimensionality Reduction, Ayesha Noor, Nadeem Javaid, Nabil Alrajeh, Babar Mansoor, Ali Khaqan, Safdar Hussain Bouk

School of Cybersecurity Faculty Publications

Heart disease is a serious worldwide health issue with wide-reaching effects. Since heart disease is one of the leading causes of mortality worldwide, early detection is crucial. Emerging technologies like Machine Learning (ML) are currently being actively used by the biomedical, healthcare, and health prediction industries. PaRSEL, a new stacking model is proposed in this research, that combines four classifiers, Passive Aggressive Classifier (PAC), Ridge Classifier (RC), Stochastic Gradient Descent Classifier (SGDC), and eXtreme Gradient Boosting (XGBoost), at the base layer, and LogitBoost is deployed for the final predictions at the meta layer. The imbalanced and irrelevant features in the …

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What Has Digital Transformation Changed? A Chinese Case Study Of Hidden Costs Using A Socio-Economic Approach To Management, Tony Huang, Emmanuel Monod, Alan Eisner, Helaine Korn, Yuewei Jiang, Bin Bai, Samuel Wilson Jan 2023

What Has Digital Transformation Changed? A Chinese Case Study Of Hidden Costs Using A Socio-Economic Approach To Management, Tony Huang, Emmanuel Monod, Alan Eisner, Helaine Korn, Yuewei Jiang, Bin Bai, Samuel Wilson

Management Faculty Publications

Digital transformation is regarded as a way to solve business problems in an organisation. However, the impact on the company’s hidden costs should also be more precisely analysed. This research relies on the socio-economic approach to management to describe the impact of digital transformation maturity growth on hidden costs in a Chinese manufacturing company. This paper combines the case study research method with some quantitative techniques by conducting correlation analyses of staff turnover, low-quality work and occupational injuries and diseases. The results indicate that digital transformation maturity growth is correlated with the financial consequences of staff’s excess salary in terms …

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Deeppatent2: A Large-Scale Benchmarking Corpus For Technical Drawing Understanding, Kehinde Ajayi, Xin Wei, Martin Gryder, Winston Shields, Jian Wu, Shawn M. Jones, Michal Kucer, Diane Oyen Jan 2023

Deeppatent2: A Large-Scale Benchmarking Corpus For Technical Drawing Understanding, Kehinde Ajayi, Xin Wei, Martin Gryder, Winston Shields, Jian Wu, Shawn M. Jones, Michal Kucer, Diane Oyen

Computer Science Faculty Publications

Recent advances in computer vision (CV) and natural language processing have been driven by exploiting big data on practical applications. However, these research fields are still limited by the sheer volume, versatility, and diversity of the available datasets. CV tasks, such as image captioning, which has primarily been carried out on natural images, still struggle to produce accurate and meaningful captions on sketched images often included in scientific and technical documents. The advancement of other tasks such as 3D reconstruction from 2D images requires larger datasets with multiple viewpoints. We introduce DeepPatent2, a large-scale dataset, providing more than 2.7 million …

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Detecting Deceptive Dark-Pattern Web Advertisements For Blind Screen-Reader Users, Satwick Ram Kodandaram, Mohan Sunkara, Sampath Jayarathna, Vikas Ashok Jan 2023

Detecting Deceptive Dark-Pattern Web Advertisements For Blind Screen-Reader Users, Satwick Ram Kodandaram, Mohan Sunkara, Sampath Jayarathna, Vikas Ashok

Computer Science Faculty Publications

Advertisements have become commonplace on modern websites. While ads are typically designed for visual consumption, it is unclear how they affect blind users who interact with the ads using a screen reader. Existing research studies on non-visual web interaction predominantly focus on general web browsing; the specific impact of extraneous ad content on blind users' experience remains largely unexplored. To fill this gap, we conducted an interview study with 18 blind participants; we found that blind users are often deceived by ads that contextually blend in with the surrounding web page content. While ad blockers can address this problem via …

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Jet Noise Reduction: A Fresh Start, Christopher K. Tam, Fang Q. Hu Jan 2023

Jet Noise Reduction: A Fresh Start, Christopher K. Tam, Fang Q. Hu

Mathematics & Statistics Faculty Publications

Attempts to reduce jet noise began some 70 years ago. In the literature, there have been many publications written on this topic. By now, it is common knowledge that jet noise consists of a number of components. They possess different spectral and radiation characteristics and are generated by different mechanisms. It appears then that one may aim at the suppression of the noise of a single component instead of trying to reduce jet noise overall. The objective of the present project is to reduce large turbulence structures noise. It is the most dominant noise component radiating in the downstream direction. …

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Exposure To Pcb126 During The Nursing Period Reversibly Impacts Early-Life Glucose Tolerance, Brittany B. Rice, Keegan W. Sammons, Sara Y. Ngo Tenlep, Madeline T. Weltzer, Leryn J. Reynolds, Cetewayo S. Rashid, Hollie I. Swanson, Kevin J. Pearson Jan 2023

Exposure To Pcb126 During The Nursing Period Reversibly Impacts Early-Life Glucose Tolerance, Brittany B. Rice, Keegan W. Sammons, Sara Y. Ngo Tenlep, Madeline T. Weltzer, Leryn J. Reynolds, Cetewayo S. Rashid, Hollie I. Swanson, Kevin J. Pearson

Human Movement Studies & Special Education Faculty Publications

Polychlorinated biphenyls (PCBs) are persistent environmental organic pollutants known to have detrimental health effects. Using a mouse model, we previously demonstrated that PCB126 exposure before and during pregnancy and throughout the perinatal period adversely affected offspring glucose tolerance and/or body composition profiles. The purpose of this study was to investigate the glucose tolerance and body composition of offspring born to dams exposed to PCB126 during the nursing period only. Female ICR mice were bred, and half of the dams were exposed to either vehicle (safflower oil) or 1 µmole PCB126 per kg of body weight via oral gavage on postnatal …

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Making The Case For The Great Dismal Swamp National Heritage Area: A Scoping Review, Madelyn Newton, Chandler J. Berry, Bethany Arrington, Nick Wilson, Colin Mccormack, Michael Wilcox, Alexis Barmoh, Chris A. B. Zajchowski Jan 2023

Making The Case For The Great Dismal Swamp National Heritage Area: A Scoping Review, Madelyn Newton, Chandler J. Berry, Bethany Arrington, Nick Wilson, Colin Mccormack, Michael Wilcox, Alexis Barmoh, Chris A. B. Zajchowski

Human Movement Studies & Special Education Faculty Publications

National Heritage Areas (NHAs) are nationally distinct landscapes that represent unique cultural, historical, and/or natural attributes significant to the legacy of the United States of America (U.S.). The Great Dismal Swamp, located in southeastern Virginia and northeastern North Carolina, is a prime candidate for NHA designation with diverse qualifications, among which was its antebellum role as a refuge for formerly enslaved people. The goal of our research, conducted in 2022 during the period of the U.S. Congressional debate on designation, was to investigate and expound upon the rationale for NHA designation of the Swamp. To do so, we used a …

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Synthesis Of A Series Of Trimeric Branched Glycoconjugates And Their Applications For Supramolecular Gels And Catalysis, Jonathan Bietsch, Anji Chen, Dan Wang, Guijun Wang Jan 2023

Synthesis Of A Series Of Trimeric Branched Glycoconjugates And Their Applications For Supramolecular Gels And Catalysis, Jonathan Bietsch, Anji Chen, Dan Wang, Guijun Wang

Chemistry & Biochemistry Faculty Publications

Carbohydrate-derived molecular gelators have found many practical applications as soft materials. To better understand the structure and molecular gelation relationship and further explore the applications of sugar-based gelators, we designed and synthesized eight trimeric branched sugar triazole derivatives and studied their self-assembling properties. These included glucose, glucosamine, galactose, and maltose derivatives. Interestingly, the gelation properties of these compounds exhibited correlations with the peripheral sugar structures. The maltose derivative did not form gels in the tested solvents, but all other compounds exhibited gelation properties in at least one of the solvents. Glucose derivatives showed superior performance, followed by glucosamine derivatives. They …

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Impact Of Atmospheric Correction On Classification And Quantification Of Seagrass Density From Worldview-2 Imagery, Victoria J. Hill, Richard C. Zimmerman, Paul Bissett, David Kohler, Blake Schaeffer, Megan Coffer, Jiang Li, Kazi Aminul Islam Jan 2023

Impact Of Atmospheric Correction On Classification And Quantification Of Seagrass Density From Worldview-2 Imagery, Victoria J. Hill, Richard C. Zimmerman, Paul Bissett, David Kohler, Blake Schaeffer, Megan Coffer, Jiang Li, Kazi Aminul Islam

OES Faculty Publications

Mapping the seagrass distribution and density in the underwater landscape can improve global Blue Carbon estimates. However, atmospheric absorption and scattering introduce errors in space-based sensors’ retrieval of sea surface reflectance, affecting seagrass presence, density, and above-ground carbon (AGCseagrass) estimates. This study assessed atmospheric correction’s impact on mapping seagrass using WorldView-2 satellite imagery from Saint Joseph Bay, Saint George Sound, and Keaton Beach in Florida, USA. Coincident in situ measurements of water-leaving radiance (Lw), optical properties, and seagrass leaf area index (LAI) were collected. Seagrass classification and the retrieval of LAI were compared after empirical line …

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Quantum Efficiency Enhancement In Simulated Nanostructured Negative Electron Affinity Gaas Photocathodes, Md Aziz Ar Rahman, Shukui Zhang, Hani E. Elsayed-Ali Jan 2023

Quantum Efficiency Enhancement In Simulated Nanostructured Negative Electron Affinity Gaas Photocathodes, Md Aziz Ar Rahman, Shukui Zhang, Hani E. Elsayed-Ali

Physics Faculty Publications

Nanostructured negative electron affinity GaAs photocathodes for a polarized electron source are studied using finite difference time domain optical simulation. The structures studied are nanosquare columns, truncated nanocones, and truncated nanopyramids. Mie-type resonances in the 700–800 nm waveband, suitable for generation of polarized electrons, are identified. At resonance wavelengths, the nanostructures can absorb up to 99% of the incident light. For nanosquare columns and truncated nanocones, the maximum quantum efficiency (QE) at 780 nm obtained from simulation is 27%, whereas for simulated nanopyramids, the QE is ∼21%. The high photocathode quantum efficiency is due to the shift of Mie resonance …

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Modeling A Nb3Sn Cryounit In Gpt At Uitf, Sunil Pokharel, A. S. Hofler, Geoffrey A. Krafft Jan 2023

Modeling A Nb3Sn Cryounit In Gpt At Uitf, Sunil Pokharel, A. S. Hofler, Geoffrey A. Krafft

Physics Faculty Publications

Nb3Sn is a prospective material for future superconducting radio frequency (SRF) accelerator cavities. Compared to conventional niobium, the material can achieve higher quality factors, higher temperature operation, and potentially higher accelerating gradients (Eacc ≈ 96 MV/m). In this work, we performed modeling of the Upgraded Injector Test Facility (UITF) at Jefferson Lab utilizing newly constructed Nb3Sn cavities. We studied the effects of the buncher cavity and varied the gun voltage from 200-500 keV. We have calibrated and optimized the SRF cavity gradients and phases for the Nb3Sn five-cell cavities' energy gains with the …

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Understanding The Field And Frequency Dependence Of Rf Loss In Srf Cavities, Pashupati Dhakal, G. Ciovati, Alex V. Gurevich, Bashu D. Khanal Jan 2023

Understanding The Field And Frequency Dependence Of Rf Loss In Srf Cavities, Pashupati Dhakal, G. Ciovati, Alex V. Gurevich, Bashu D. Khanal

Physics Faculty Publications

SRF cavities subjected to heat treatment below 200 °C in the presence of nitrogen showed an improvement in quality factor while maintaining an accelerating gradient above 25 MV/m. Here, we report the rf performance of several single-cell superconducting radio frequency cavities with frequency ranging from 0.75 - 3.0 GHz subjected to low temperature heat treatment in nitrogen environment. The cavities were treated at temperature 120 - 175 oC for 24 - 48 hours in low partial pressure of ultra-pure nitrogen gas. The improvement in Q₀ with Q-rise was observed when nitrogen gas was injected ~300 °C during the furnace treatment. …

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Superconducting Non-Elliptical Cavities (Tem Cavity Designs), Subashini De Silva Jan 2023

Superconducting Non-Elliptical Cavities (Tem Cavity Designs), Subashini De Silva

Physics Faculty Publications

This lecture will present fundamental of RF to accelerate or reflect beams. The lecture will cover the electrical design method of the SRF high/medium/low beta cavities. The difference in the cavity design between TM mode and TE will be emphasized.

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Machine-Assisted Discovery Of Integrable Symplectic Mappings, T. Zolkin, Y. Kharkov, S. Nagaitsev Jan 2023

Machine-Assisted Discovery Of Integrable Symplectic Mappings, T. Zolkin, Y. Kharkov, S. Nagaitsev

Physics Faculty Publications

We present a new automated method for finding integrable symplectic maps of the plane. These dynamical systems possess a hidden symmetry associated with an existence of conserved quantities, i.e., integrals of motion. The core idea of the algorithm is based on the knowledge that the evolution of an integrable system in the phase space is restricted to a lower-dimensional submanifold. Limiting ourselves to polygon invariants of motion, we analyze the shape of individual trajectories thus successfully distinguishing integrable motion from chaotic cases. For example, our method rediscovers some of the famous McMillan-Suris integrable mappings and ultradiscrete Painlevé equations. In total, …

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Generation And Characterization Of Magnetized Electron Beam From A Dc High Voltage Photogun For Electron Beam Cooling Application, S.A.K. Wijethunga, M. A. Mamun, R. Suleiman, P. Adderley, B. Bullard, J. Benesch, Jean R. Delayen, J. Grames, C. Hernandez-Garcia, F. Hannon, Geoffrey A. Krafft, G. Palacios-Serrano, M. Poelker, M. Stefani, Y. Wang, S. Zhang Jan 2023

Generation And Characterization Of Magnetized Electron Beam From A Dc High Voltage Photogun For Electron Beam Cooling Application, S.A.K. Wijethunga, M. A. Mamun, R. Suleiman, P. Adderley, B. Bullard, J. Benesch, Jean R. Delayen, J. Grames, C. Hernandez-Garcia, F. Hannon, Geoffrey A. Krafft, G. Palacios-Serrano, M. Poelker, M. Stefani, Y. Wang, S. Zhang

Physics Faculty Publications

One of the most challenging requirements for the proposed Electron–Ion Collider is the strong cooling of the proton beam, which is key to achieving the collider’s desired luminosity of order 1033–1034cm−2s−1. Magnetized bunched-beam electron cooling could be a means to achieve the required high luminosity, where strong cooling is accomplished inside a cooling solenoid where the ions co-propagate with an electron beam generated from a source immersed in a magnetic field. To increase the cooling efficiency, a bunched electron beam with high bunch charge and high repetition rate is required. This work …

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Quantum Computations Of The O(3) Model Using Qumodes, R. Jha, Felix Ringer, G. Siopsis, Shane Thompson Jan 2023

Quantum Computations Of The O(3) Model Using Qumodes, R. Jha, Felix Ringer, G. Siopsis, Shane Thompson

Physics Faculty Publications

We express the discrete 1+1-dimensional O(3) non-linear sigma model (NLσM) in a form well-suited for the continuous variable approach to quantum computing. Within the Schwinger boson formulation, we need two qumodes (quantum-mechanical oscillators) at each lattice site. We envision that it might be possible to reach the scaling regime of this model and observe asymptotic freedom on near-term photonic quantum devices in the coming decade.

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Simulations Of Radiations Reaction In Inverse Compton Scattering, E. Breen, E. Rogers, E. Johnson, B. Terzić, G. Krafft, G. Wilson Jan 2023

Simulations Of Radiations Reaction In Inverse Compton Scattering, E. Breen, E. Rogers, E. Johnson, B. Terzić, G. Krafft, G. Wilson

Physics Faculty Publications

The effect of radiation reaction is often negligible in inverse Compton scattering. However, in the nonlinear Compton regime, at high laser fields and high electron beam energies where electron recoil must be properly accounted for, there is experimental data which demonstrates the onset of radiation reaction * . We model the radiation reaction as a series of emissions from individual electrons with decreasing energy. This allows us to use the code we previously developed for simulating single-emission inverse Compton scattering events ** . We use the new code to simulate the experiment reported in Cole et al. 2018, and to …

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Analytic And Numerical Calculation Of Collider Luminosity With Crab Dynamics, H. Huang, T. Satogata, Y. Zhang, Y. Roblin, F. Lin, S. Zhao Jan 2023

Analytic And Numerical Calculation Of Collider Luminosity With Crab Dynamics, H. Huang, T. Satogata, Y. Zhang, Y. Roblin, F. Lin, S. Zhao

Physics Faculty Publications

For an integral part of electron-ion collider (EIC) design, the crab crossing scheme provides a head-on collision for beams with a nonzero crossing angle. Recently we provided a framework for accurate numerical simulations of beam-beam effects with crabbing crossing dynamics. The framework was implemented in a simulation code package named “CASA BeamBeam”. We offer com-prehensive formulas for calculation of collider luminosity for various cases in the code package. The luminosity calculation module of CASA Beam-Beam now includes the hourglass effect, the beam-tilt effects and the beam offset effect. The benchmarking results show good agreement between the numerical calculation and analytic …

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Numerical Simulations Of Radiation Reaction Using Lorentz-Abraham-Dirac Formalism, E. Rogers, B. Terzic, E. Breen, E. Johnson, G. Krafft Jan 2023

Numerical Simulations Of Radiation Reaction Using Lorentz-Abraham-Dirac Formalism, E. Rogers, B. Terzic, E. Breen, E. Johnson, G. Krafft

Physics Faculty Publications

An accelerating charged particle emits electromagnetic radiation. The motion of the particle is further damped via self-interaction with its own radiation. For relativistic particles, the subsequent motion is described via a correction to the Lorentz force, known as the Lorentz-Abraham-Dirac force. The aim of this research is to use the Lorentz-Abraham-Dirac force to computationally simulate the radiation damping that occurs during nonlinear inverse Compton scattering. We build on our previous work and the code which simulates single-emission inverse Compton scattering to incorporate the effect of multiple emissions, thereby modeling the radiation reaction.

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Surface Properties And Rf Performance Of Vapor Diffused Nb₃Sn On Nb After Sequential Anneals Below 1000 °C, Jayendrika K. Tiskumara, Jean R. Delayen, U. Pudasaini, G. Eremeev Jan 2023

Surface Properties And Rf Performance Of Vapor Diffused Nb₃Sn On Nb After Sequential Anneals Below 1000 °C, Jayendrika K. Tiskumara, Jean R. Delayen, U. Pudasaini, G. Eremeev

Physics Faculty Publications

Nb₃Sn is a next-generation superconducting material that can be used for future superconducting radiofrequency (SRF) accelerator cavities, promising better performance, cost reduction, and higher operating temperature than Nb. The Sn vapor diffusion method is currently the most preferred and successful technique to coat niobium cavities with Nb₃Sn. Among post-coating treatments to optimize the coating quality, higher temperature annealing without Sn is known to degrade Nb₃Sn because of Sn loss. We have investigated Nb₃Sn/Nb samples briefly annealed at 800-1000 °C, for 10 and 20 minutes to potentially improve the surface to enhance the performance of Nb₃Sn-coated cavities. Following the sample studies, …

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Investigation Of The Multilayer Shielding Effect Through Nbtin-Ain Coated Bulk Niobium, Iresha Harshani Senevirathne, D. R. Beverstock, A-M Valente-Feliciano, Alex Gurevich, Jean R. Delayen Jan 2023

Investigation Of The Multilayer Shielding Effect Through Nbtin-Ain Coated Bulk Niobium, Iresha Harshani Senevirathne, D. R. Beverstock, A-M Valente-Feliciano, Alex Gurevich, Jean R. Delayen

Physics Faculty Publications

We report measurements of the dc field onset Bp of magnetic flux penetration through NbTiN-AlN coating on bulk niobium using the Hall probe experimental setup. The measurements of Bp reveal the multilayer shielding effect on bulk niobium under high magnetic fields at cryogenic temperatures. We observed a significant enhancement in Bp for the NbTiN-AlN coated Nb samples as compared to bare Nb samples. The observed dependence of Bp on the coating thickness is consistent with theoretical predictions.

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Development And Performance Of Rfd Crab Cavity Prototypes For Hl-Lhc Aup, L. Listori, P. Berrutti, M. Narduzzi, A. Castilla, S. U. De Silva, J. R. Delayen, N. A. Huque, Z. Li, A. Ratti Jan 2023

Development And Performance Of Rfd Crab Cavity Prototypes For Hl-Lhc Aup, L. Listori, P. Berrutti, M. Narduzzi, A. Castilla, S. U. De Silva, J. R. Delayen, N. A. Huque, Z. Li, A. Ratti

Physics Faculty Publications

The US will be contributing to the HL-LHC upgrade at CERN with the fabrication and qualification of RFD crabbing cavities in the framework of the HL-LHC Accelerator Upgrade Project (AUP) managed by Fermilab. AUP received Critical Decision 3 (CD-3) approval by DOE in December 2020 launching the project into the production phase. The electro-magnetic design of the cavity was inherited from the LHC Accelerator Research Program (LARP) but needed to be revised to meet new project requirements and to prevent issues encountered during beam tests performed at CERN in the R&D phase. Two prototype cavities were manufactured in industry and …

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Characterization Of Dissipative Regions Of A N-Doped Superconducting Radio-Frequency Cavity, Eric M. Lechner, Basu Dev Oli, Junki Makita, Gianluigi Ciovati, Alex Gurevich, Maria Lavarone Jan 2023

Characterization Of Dissipative Regions Of A N-Doped Superconducting Radio-Frequency Cavity, Eric M. Lechner, Basu Dev Oli, Junki Makita, Gianluigi Ciovati, Alex Gurevich, Maria Lavarone

Physics Faculty Publications

We report radio-frequency measurements of quality factors and temperature mapping of a nitrogen doped Nb superconducting RF cavity. Cavity cutouts of hot and cold spots were studied with low temperature scanning tunneling microscopy and spectroscopy, X-ray photoelectron spectroscopy and secondary electron microscopy. Temperature mapping revealed a substantial reduction of the residual resistance upon cooling the cavity with a greater temperature gradient and hysteretic losses at the quench location, pointing to trapped vortices as the dominant source of residual surface resistance.Analysis of the tunneling spectra in the framework of a proximity effect theory shows that hot spots have a reduced pair …

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Tuning Microwave Losses In Superconducting Resonators, Alex Gurevich Jan 2023

Tuning Microwave Losses In Superconducting Resonators, Alex Gurevich

Physics Faculty Publications

Performance of superconducting resonators, particularly cavities for particle accelerators and micro cavities and thin film resonators for quantum computations and photon detectors has been improved substantially by recent materials treatments and technological advances. As a result, the niobium cavities have reached the quality factors Q ~ 1011 at 1-2 GHz and 1.5 K and the breakdown radio-frequency (rf) fields H close to the dc superheating eld of the Meissner state. These advances raise the question whether the state-of-the-art cavities are close to the fundamental limits, what these limits actually are, and to what extent the Q and H limits …

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