36,317 results on '"Krishnamoorthy, A."'
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2. NiOx/\b{eta}-Ga2O3 Heterojunction Diode Achieving Breakdown Voltage >3 kV with Plasma Etch Field-Termination
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Liu, Yizheng, Roy, Saurav, Peterson, Carl, Bhattacharyya, Arkka, and Krishnamoorthy, Sriram
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Physics - Applied Physics - Abstract
This work reports the fabrication and characterization of a NiOx/\b{eta}-Ga2O3 heterojunction diode (HJD) that uses a metallic nickel (Ni) target to deposit NiOx layers via reactive RF magnetron sputtering and lift-off processing with >3 kV breakdown voltage, record-low reverse current leakage under high reverse bias, and high junction electric fields (>3.34 MV/cm). The heterojunction diodes are fabricated via bilayer NiOx sputtering followed by self-aligned mesa-etching for field-termination on both large (1-mm2) and small area (100-{\mu}m diameter) devices. The HJD exhibits a ~135 A/cm2 forward current density at 5 V with a rectifying ratio of ~1010. The minimum differential specific on-resistance is measured to be 17.26 m{\Omega} cm2. The breakdown voltage on 100-{\mu}m diameter pads was measured to be greater than 3 kV with a noise floor-level reverse leakage current density (10-8~10-6 A/cm2) until 3 kV, accomplishing a parallel-plane junction electric field to be at least 3.34 MV/cm at 3 kV with a power figure of merit (PFOM) >0.52 GW/cm2. Temperature-dependent forward current density-voltage (J-V) measurements are performed from room temperature (25 C) to 200 C which showed a temperature coefficient of resistance ({\alpha}) equaling 1.56, higher than that of \b{eta}-Ga2O3 Schottky barrier diodes (SBDs), indicating potential conductivity degradation within NiOx at elevated temperatures., Comment: 6 pages, 5 figures, APL Journal
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- 2024
3. Learning to Simulate Aerosol Dynamics with Graph Neural Networks
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Ferracina, Fabiana, Beeler, Payton, Halappanavar, Mahantesh, Krishnamoorthy, Bala, Minutoli, Marco, and Fierce, Laura
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Physics - Atmospheric and Oceanic Physics ,Computer Science - Machine Learning - Abstract
Aerosol effects on climate, weather, and air quality depend on characteristics of individual particles, which are tremendously diverse and change in time. Particle-resolved models are the only models able to capture this diversity in particle physiochemical properties, and these models are computationally expensive. As a strategy for accelerating particle-resolved microphysics models, we introduce Graph-based Learning of Aerosol Dynamics (GLAD) and use this model to train a surrogate of the particle-resolved model PartMC-MOSAIC. GLAD implements a Graph Network-based Simulator (GNS), a machine learning framework that has been used to simulate particle-based fluid dynamics models. In GLAD, each particle is represented as a node in a graph, and the evolution of the particle population over time is simulated through learned message passing. We demonstrate our GNS approach on a simple aerosol system that includes condensation of sulfuric acid onto particles composed of sulfate, black carbon, organic carbon, and water. A graph with particles as nodes is constructed, and a graph neural network (GNN) is then trained using the model output from PartMC-MOSAIC. The trained GNN can then be used for simulating and predicting aerosol dynamics over time. Results demonstrate the framework's ability to accurately learn chemical dynamics and generalize across different scenarios, achieving efficient training and prediction times. We evaluate the performance across three scenarios, highlighting the framework's robustness and adaptability in modeling aerosol microphysics and chemistry.
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- 2024
4. Almost-catalytic Computation
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Bisoyi, Sagar, Dinesh, Krishnamoorthy, Rai, Bhabya Deep, and Sarma, Jayalal
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Computer Science - Computational Complexity - Abstract
Designing algorithms for space bounded models with restoration requirements on the space used by the algorithm is an important challenge posed about the catalytic computation model introduced by Buhrman et al. (2014). Motivated by the scenarios where we do not need to restore unless is useful, we define $ACL(A)$ to be the class of languages that can be accepted by almost-catalytic Turing machines with respect to $A$ (which we call the catalytic set), that uses at most $c\log n$ work space and $n^c$ catalytic space. We show that if there are almost-catalytic algorithms for a problem with catalytic set as $A \subseteq \Sigma^*$ and its complement respectively, then the problem can be solved by a ZPP algorithm. Using this, we derive that to design catalytic algorithms, it suffices to design almost-catalytic algorithms where the catalytic set is the set of strings of odd weight ($PARITY$). Towards this, we consider two complexity measures of the set $A$ which are maximized for $PARITY$ - random projection complexity (${\cal R}(A)$) and the subcube partition complexity (${\cal P}(A)$). By making use of error-correcting codes, we show that for all $k \ge 1$, there is a language $A_k \subseteq \Sigma^*$ such that $DSPACE(n^k) \subseteq ACL(A_k)$ where for every $m \ge 1$, $\mathcal{R}(A_k \cap \{0,1\}^m) \ge \frac{m}{4}$ and $\mathcal{P}(A_k \cap \{0,1\}^m)=2^{m/4}$. This contrasts the catalytic machine model where it is unclear if it can accept all languages in $DSPACE(\log^{1+\epsilon} n)$ for any $\epsilon > 0$. Improving the partition complexity of the catalytic set $A$ further, we show that for all $k \ge 1$, there is a $A_k \subseteq \{0,1\}^*$ such that $\mathsf{DSPACE}(\log^k n) \subseteq ACL(A_k)$ where for every $m \ge 1$, $\mathcal{R}(A_k \cap \{0,1\}^m) \ge \frac{m}{4}$ and $\mathcal{P}(A_k \cap \{0,1\}^m)=2^{m/4+\Omega(\log m)}$., Comment: 18 pages
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- 2024
5. Dielectric Reliability and Interface Trap Characterization in MOCVD grown In-situ Al$_2$O$_3$ on $\beta$-Ga$_2$O$_3$
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Roy, Saurav, Bhattacharyya, Arkka, Peterson, Carl, and Krishnamoorthy, Sriram
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Condensed Matter - Materials Science ,Physics - Applied Physics - Abstract
In this article, we investigate the in-situ growth of Al$_2$O$_3$ on $\beta$-Ga$_2$O$_3$ using metal-organic chemical vapor deposition (MOCVD) at a high temperature of 800{\deg}C. The Al$_2$O$_3$ is grown within the same reactor as the $\beta$-Ga$_2$O$_3$, employing trimethylaluminum (TMAl) and O$_2$ as precursors without breaking the vacuum. We characterize the shallow and deep-level traps through stressed capacitance-voltage (C-V) and photo-assisted C-V methods. The high-temperature deposited dielectric demonstrates an impressive breakdown field of approximately 10 MV/cm. Furthermore, we evaluate the reliability and lifetime of the dielectrics using time-dependent dielectric breakdown (TDDB) measurements. By modifying the dielectric deposition process to include a high-temperature (800{\deg}C) thin interfacial layer and a low-temperature (600{\deg}C) bulk layer, we report a 10-year lifetime under a stress field of 3.5 MV/cm along a breakdown field of 7.8 MV/cm.
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- 2024
6. Characterizing Long COVID in Children and Adolescents
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Gross, Rachel S, Thaweethai, Tanayott, Kleinman, Lawrence C, Snowden, Jessica N, Rosenzweig, Erika B, Milner, Joshua D, Tantisira, Kelan G, Rhee, Kyung E, Jernigan, Terry L, Kinser, Patricia A, Salisbury, Amy L, Warburton, David, Mohandas, Sindhu, Wood, John C, Newburger, Jane W, Truong, Dongngan T, Flaherman, Valerie J, Metz, Torri D, Karlson, Elizabeth W, Chibnik, Lori B, Pant, Deepti B, Krishnamoorthy, Aparna, Gallagher, Richard, Lamendola-Essel, Michelle F, Hasson, Denise C, Katz, Stuart D, Yin, Shonna, Dreyer, Benard P, Carmilani, Megan, Coombs, K, Fitzgerald, Megan L, Güthe, Nick, Hornig, Mady, Letts, Rebecca J, Peddie, Aimee K, Taylor, Brittany D, Foulkes, Andrea S, Stockwell, Melissa S, Balaraman, Venkataraman, Bogie, Amanda, Bukulmez, Hulya, Dozor, Allen J, Eckrich, Daniel, Elliott, Amy J, Evans, Danielle N, Farkas, Jonathan S, Faustino, E Vincent S, Fischer, Laura, Gaur, Sunanda, Harahsheh, Ashraf S, Hasan, Uzma N, Hsia, Daniel S, Huerta-Montanez, Gredia, Hummel, Kathy D, Kadish, Matt P, Kaelber, David C, Krishnan, Sankaran, Kosut, Jessica S, Larrabee, Jerry, Lim, Peter Paul C, Michelow, Ian C, Oliveira, Carlos R, Raissy, Hengameh, Rosario-Pabon, Zaira, Ross, Judith L, Sato, Alice I, Stevenson, Michelle D, Talavera-Barber, Maria M, Teufel, Ronald J, Weakley, Kathryn E, Zimmerman, Emily, Bind, Marie-Abele C, Chan, James, Guan, Zoe, Morse, Richard E, Reeder, Harrison T, Akshoomoff, Natascha, Aschner, Judy L, Bhattacharjee, Rakesh, Cottrell, Lesley A, Cowan, Kelly, D'Sa, Viren A, Fiks, Alexander G, Gennaro, Maria L, Irby, Katherine, Khare, Manaswitha, Landeo Guttierrez, Jeremy, McCulloh, Russell J, Narang, Shalu, Ness- Cochinwala, Manette, Nolan, Sheila, Palumbo, Paul, Ryu, Julie, Salazar, Juan C, Selvarangan, Rangaraj, Stein, Cheryl R, Werzberger, Alan, Zempsky, William T, Aupperle, Robin, and Baker, Fiona C
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Biomedical and Clinical Sciences ,Clinical Sciences ,Health Sciences ,Emerging Infectious Diseases ,Neurosciences ,Coronaviruses ,Infectious Diseases ,Pediatric ,Minority Health ,Pain Research ,Infection ,Good Health and Well Being ,RECOVER-Pediatrics Consortium ,RECOVER-Pediatrics Group Authors ,Medical and Health Sciences ,General & Internal Medicine ,Biomedical and clinical sciences ,Health sciences - Abstract
ImportanceMost research to understand postacute sequelae of SARS-CoV-2 infection (PASC), or long COVID, has focused on adults, with less known about this complex condition in children. Research is needed to characterize pediatric PASC to enable studies of underlying mechanisms that will guide future treatment.ObjectiveTo identify the most common prolonged symptoms experienced by children (aged 6 to 17 years) after SARS-CoV-2 infection, how these symptoms differ by age (school-age [6-11 years] vs adolescents [12-17 years]), how they cluster into distinct phenotypes, and what symptoms in combination could be used as an empirically derived index to assist researchers to study the likely presence of PASC.Design, setting, and participantsMulticenter longitudinal observational cohort study with participants recruited from more than 60 US health care and community settings between March 2022 and December 2023, including school-age children and adolescents with and without SARS-CoV-2 infection history.ExposureSARS-CoV-2 infection.Main outcomes and measuresPASC and 89 prolonged symptoms across 9 symptom domains.ResultsA total of 898 school-age children (751 with previous SARS-CoV-2 infection [referred to as infected] and 147 without [referred to as uninfected]; mean age, 8.6 years; 49% female; 11% were Black or African American, 34% were Hispanic, Latino, or Spanish, and 60% were White) and 4469 adolescents (3109 infected and 1360 uninfected; mean age, 14.8 years; 48% female; 13% were Black or African American, 21% were Hispanic, Latino, or Spanish, and 73% were White) were included. Median time between first infection and symptom survey was 506 days for school-age children and 556 days for adolescents. In models adjusted for sex and race and ethnicity, 14 symptoms in both school-age children and adolescents were more common in those with SARS-CoV-2 infection history compared with those without infection history, with 4 additional symptoms in school-age children only and 3 in adolescents only. These symptoms affected almost every organ system. Combinations of symptoms most associated with infection history were identified to form a PASC research index for each age group; these indices correlated with poorer overall health and quality of life. The index emphasizes neurocognitive, pain, and gastrointestinal symptoms in school-age children but change or loss in smell or taste, pain, and fatigue/malaise-related symptoms in adolescents. Clustering analyses identified 4 PASC symptom phenotypes in school-age children and 3 in adolescents.Conclusions and relevanceThis study developed research indices for characterizing PASC in children and adolescents. Symptom patterns were similar but distinguishable between the 2 groups, highlighting the importance of characterizing PASC separately for these age ranges.
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- 2024
7. Watkins's conjecture for elliptic curves with a rational torsion
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Bhakta, Subham and Krishnamoorthy, Srilakshmi
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Mathematics - Number Theory ,Primary 11F30, 11L07, Secondary 11F52, 11F80 - Abstract
Watkins's conjecture suggests that for an elliptic curve $E/\mathbb{Q}$, the rank of the group $E(\mathbb{Q})$ of rational points is bounded above by $\nu_2 (m_E)$, where $m_E$ is the modular degree associated with $E$. It is known that Watkins's conjecture holds on average. This article investigates the conjecture over certain thin families of elliptic curves. For example, for prime $\ell$, we quantify the elliptic curves featuring a rational $\ell$-torsion that satisfies Watkins's conjecture. Additionally, the study extends to a broader context, investigating the inequality $\mathrm{rank}(E(\mathbb{Q}))+M\leq \nu_2(m_E)$ for any positive integer $M$., Comment: 26 pages; comments, and feedback are welcome
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- 2024
8. Record-High Electron Mobility and Controlled Low 10$^{15}$ cm$^{-3}$ Si-doping in (010) $\beta$-Ga$_2$O$_3$ Epitaxial Drift Layers
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Peterson, Carl, Bhattacharyya, Arkka, Chanchaiworawit, Kittamet, Kahler, Rachel, Roy, Saurav, Liu, Yizheng, Rebollo, Steve, Kallistova, Anna, Mates, Thomas E., and Krishnamoorthy, Sriram
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Physics - Applied Physics - Abstract
We report on metalorganic chemical vapor deposition (MOCVD) growth of controllably Si-doped 4.5 $\mu$m thick $\beta$-Ga$_2$O$_3$ films with electron concentrations in the 10$^{15}$ cm$^{-3}$ range and record-high room temperature Hall electron mobilities of up to 200 cm$^2$/V.s, reaching the predicted theoretical maximum room temperature mobility value for $\beta$-Ga$_2$O$_3$. Growth of the homoepitaxial films was performed on Fe-doped (010) $\beta$-Ga$_2$O$_3$ substrates at a growth rate of 1.9 $\mu$m/hr using TEGa as the Gallium precursor. To probe the background electron concentration, an unintentionally doped film was grown with a Hall concentration of 3.43 x 10$^{15}$ cm$^{-3}$ and Hall mobility of 196 cm$^2$/V.s. Growth of intentionally Si-Doped films was accomplished by fixing all growth conditions and varying only the silane flow, with controllable Hall electron concentrations ranging from 4.38 x 10$^{15}$ cm$^{-3}$ to 8.30 x 10$^{15}$ cm$^{-3}$ and exceptional Hall mobilities ranging from 194 - 200 cm$^2$/V.s demonstrated. C-V measurements showed a flat charge profile with the N$_D^+$ - N$_A^-$ values correlating well with the Hall-measured electron concentration in the films. SIMS measurements showed the silicon atomic concentration matched the Hall electron concentration with Carbon and Hydrogen below detection limit in the films. The Hall, C-V, and SIMS data indicate the growth of high-quality 4.5 $\mu$m thick $\beta$-Ga$_2$O$_3$ films and controllable doping into the mid 10$^{15}$ cm$^{-3}$ range. These results demonstrate MOCVD growth of electronics grade record-high mobility, low carrier density, and thick $\beta$-Ga$_2$O$_3$ drift layers for next generation vertical $\beta$-Ga$_2$O$_3$ power devices., Comment: 16 Pages, 10 Figures, 2 Tables
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- 2024
9. Geophysical Observations of the 24 September 2023 OSIRIS-REx Sample Return Capsule Re-Entry
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Silber, Elizabeth A., Bowman, Daniel C., Carr, Chris G., Eisenberg, David P., Elbing, Brian R., Fernando, Benjamin, Garcés, Milton A., Haaser, Robert, Krishnamoorthy, Siddharth, Langston, Charles A., Nishikawa, Yasuhiro, Webster, Jeremy, Anderson, Jacob F., Arrowsmith, Stephen, Bazargan, Sonia, Beardslee, Luke, Beck, Brant, Bishop, Jordan W., Blom, Philip, Bracht, Grant, Chichester, David L., Christe, Anthony, Clarke, Jacob, Cummins, Kenneth, Cutts, James, Danielson, Lisa, Donahue, Carly, Eack, Kenneth, Fleigle, Michael, Fox, Douglas, Goel, Ashish, Green, David, Hasumi, Yuta, Hayward, Chris, Hicks, Dan, Hix, Jay, Horton, Stephen, Hough, Emalee, Huber, David P., Hunt, Madeline A., Inman, Jennifer, Islam, S. M. Ariful, Izraelevitz, Jacob, Jacob, Jamey D., Johnson, James, KC, Real J., Komjathy, Attila, Lam, Eric, LaPierre, Justin, Lewis, Kevin, Lewis, Richard D., Liu, Patrick, Martire, Léo, McCleary, Meaghan, McGhee, Elisa A., Mitra, Ipsita, Nag, Amitabh, Giraldo, Luis Ocampo, Pearson, Karen, Plaisir, Mathieu, Popenhagen, Sarah K., Rassoul, Hamid, Giannone, Miro Ronac, Samnani, Mirza, Schmerr, Nicholas, Spillman, Kate, Srinivas, Girish, Takazawa, Samuel K., Tempert, Alex, Turley, Reagan, Van Beek, Cory, Viens, Loïc, Walsh, Owen A., Weinstein, Nathan, White, Robert, Williams, Brian, Wilson, Trevor C., Wyckoff, Shirin, Yamamoto, Masa-yuki, Yap, Zachary, Yoshiyama, Tyler, and Zeiler, Cleat
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Astrophysics - Earth and Planetary Astrophysics ,Astrophysics - Instrumentation and Methods for Astrophysics ,Physics - Geophysics - Abstract
Sample Return Capsules (SRCs) entering Earth's atmosphere at hypervelocity from interplanetary space are a valuable resource for studying meteor phenomena. The 24 September 2023 arrival of the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer) SRC provided an unprecedented chance for geophysical observations of a well-characterized source with known parameters, including timing and trajectory. A collaborative effort involving researchers from 16 institutions executed a carefully planned geophysical observational campaign at strategically chosen locations, deploying over 400 ground-based sensors encompassing infrasound, seismic, distributed acoustic sensing (DAS), and GPS technologies. Additionally, balloons equipped with infrasound sensors were launched to capture signals at higher altitudes. This campaign (the largest of its kind so far) yielded a wealth of invaluable data anticipated to fuel scientific inquiry for years to come. The success of the observational campaign is evidenced by the near-universal detection of signals across instruments, both proximal and distal. This paper presents a comprehensive overview of the collective scientific effort, field deployment, and preliminary findings. The early findings have the potential to inform future space missions and terrestrial campaigns, contributing to our understanding of meteoroid interactions with planetary atmospheres. Furthermore, the dataset collected during this campaign will improve entry and propagation models as well as augment the study of atmospheric dynamics and shock phenomena generated by meteoroids and similar sources., Comment: 87 pages, 14 figures
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- 2024
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10. Nonlinear interferometry-based metrology of magneto-optical properties at infrared wavelengths
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Chakraborty, Tanmoy, Produit, Thomas, Krishnamoorthy, Harish N S, Soci, Cesare, and Paterova, Anna V.
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Physics - Optics ,Physics - Applied Physics ,Quantum Physics - Abstract
Magneto-optical properties of materials are utilized in numerous applications both in scientific research and industries. The novel properties of these materials can be further investigated by performing metrology in the infrared wavelength range, thereby enriching their potential applications. However, current infrared metrology techniques can be challenging and resource-intensive due to the unavailability of suitable components. To address these challenges, we propose and demonstrate a set of measurements based on nonlinear interferometry, which allows us investigating magneto-optical properties of materials at infrared wavelength range by performing optical detection at the visible range. For a proof-of-principle study, we measure the Verdet constant of a bismuth-iron-garnet, over a spectral bandwidth of 600 nm in the near-IR range., Comment: 10 pages, 12 fugures
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- 2024
11. Hydrogen and Battery Based Energy Storage System (ESS) for Future DC Microgrids
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Diabate, Massiagbe, Vriend, Timothy, Krishnamoorthy, Harish S, and Shi, Jian
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Electrical Engineering and Systems Science - Systems and Control - Abstract
In this paper, a hydrogen-based energy storage system (ESS) is proposed for DC microgrids, which can potentially be integrated with battery ESS to meet the needs of future grids with high renewable penetration. Hydrogen-based ESS can provide a stable energy supply for a long time but has a slower response than battery ESSs. However, a combination of battery and hydrogen storage provides stable energy for an extended period of time and can easily handle the sudden demands and surpluses of the microgrid. One of the main challenges in this system is the integration of power electronics with fuel cell technology to convert renewable energy into electricity seamlessly. This paper proposes a system that uses an isolated DC-DC converter to activate clean hydrogen production using an electrolyzer and then pressurize the hydrogen to store in a tank. The pressured hydrogen becomes an essential input to the fuel cell, which regulates and transforms it into electricity. The electricity produced is then transferred to the grid using a DC-DC boost converter. A Simulink model of the hybrid system with a 1 kV DC bus voltage is used to demonstrate the hydrogen production and fuel cell behavior based on the demand and surplus power of the loads. The proposed system simulates aspects of the power conversion, electrolyzer, storage tank, and fuel cell needed for the proposed hybrid ESS. Due to its economic feasibility, the polymer electrolyte membrane (PEM) is the primary technology considered for the electrolyzer and fuel cell., Comment: A 5-pages Digest paper summarizes in detail the work done
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- 2024
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12. Use of Early Ketamine Sedation and Association With Clinical and Cost Outcomes Among Mechanically Ventilated Patients With COVID-19: A Retrospective Cohort Study.
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Royce-Nagel, Galen, Jarzebowski, Mary, Wongsripuemtet, Pattrapun, Krishnamoorthy, Vijay, Fuller, Matthew, Ohnuma, Tetsu, Treggiari, Miriam, Yaport, Miguel, Cobert, Julien, Garrigan, Ethan, Bartz, Raquel, and Raghunathan, Karthik
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Humans ,Ketamine ,Respiration ,Artificial ,Retrospective Studies ,Male ,Female ,COVID-19 ,Middle Aged ,Hospital Mortality ,Aged ,Length of Stay ,Intensive Care Units ,Cohort Studies ,Hypnotics and Sedatives ,SARS-CoV-2 ,Hospital Costs ,Propensity Score - Abstract
OBJECTIVES: To describe the utilization of early ketamine use among patients mechanically ventilated for COVID-19, and examine associations with in-hospital mortality and other clinical outcomes. DESIGN: Retrospective cohort study. SETTING: Six hundred ten hospitals contributing data to the Premier Healthcare Database between April 2020 and June 2021. PATIENTS: Adults with COVID-19 and greater than or equal to 2 consecutive days of mechanical ventilation within 5 days of hospitalization. INTERVENTION: The exposures were early ketamine use initiated within 2 days of intubation and continued for greater than 1 day. MEASUREMENTS: Primary was hospital mortality. Secondary outcomes included length of stay (LOS) in the hospital and ICUs, ventilator days, vasopressor days, renal replacement therapy (RRT), and total hospital cost. The propensity score matching analysis was used to adjust for confounders. MAIN RESULTS: Among 42,954 patients, 1,423 (3.3%) were exposed to early ketamine use. After propensity score matching including 1,390 patients in each group, recipients of ketamine infusions were associated with higher hospital mortality (52.5% vs. 45.9%, risk ratio: 1.14, [1.06-1.23]), longer median ICU stay (13 vs. 12 d, mean ratio [MR]: 1.15 [1.08-1.23]), and longer ventilator days (12 vs. 11 d, MR: 1.19 [1.12-1.27]). There were no associations for hospital LOS (17 [10-27] vs. 17 [9-28], MR: 1.05 [0.99-1.12]), vasopressor days (4 vs. 4, MR: 1.04 [0.95-1.14]), and RRT (22.9% vs. 21.7%, RR: 1.05 [0.92-1.21]). Total hospital cost was higher (median $72,481 vs. $65,584, MR: 1.11 [1.05-1.19]). CONCLUSIONS: In a diverse sample of U.S. hospitals, about one in 30 patients mechanically ventilated with COVID-19 received ketamine infusions. Early ketamine may have an association with higher hospital mortality, increased total cost, ICU stay, and ventilator days, but no associations for hospital LOS, vasopressor days, and RRT. However, confounding by the severity of illness might occur due to higher extracorporeal membrane oxygenation and RRT use in the ketamine group. Further randomized trials are needed to better understand the role of ketamine infusions in the management of critically ill patients.
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- 2024
13. Radio Resource Management Design for RSMA: Optimization of Beamforming, User Admission, and Discrete/Continuous Rates with Imperfect SIC
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Abanto-Leon, L. F., Krishnamoorthy, A., Garcia-Saavedra, A., Sim, G. H., Schober, R., and Hollick, M.
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Electrical Engineering and Systems Science - Signal Processing ,Computer Science - Emerging Technologies ,Computer Science - Information Theory ,Computer Science - Networking and Internet Architecture - Abstract
This paper investigates the radio resource management (RRM) design for multiuser rate-splitting multiple access (RSMA), accounting for various characteristics of practical wireless systems, such as the use of discrete rates, the inability to serve all users, and the imperfect successive interference cancellation (SIC). Specifically, failure to consider these characteristics in RRM design may lead to inefficient use of radio resources. Therefore, we formulate the RRM of RSMA as optimization problems to maximize respectively the weighted sum rate (WSR) and weighted energy efficiency (WEE), and jointly optimize the beamforming, user admission, discrete/continuous rates, accounting for imperfect SIC, which result in nonconvex mixed-integer nonlinear programs that are challenging to solve. Despite the difficulty of the optimization problems, we develop algorithms that can find high-quality solutions. We show via simulations that carefully accounting for the aforementioned characteristics, can lead to significant gains. Precisely, by considering that transmission rates are discrete, the transmit power can be utilized more intelligently, allocating just enough power to guarantee a given discrete rate. Additionally, we reveal that user admission plays a crucial role in RSMA, enabling additional gains compared to random admission by facilitating the servicing of selected users with mutually beneficial channel characteristics. Furthermore, provisioning for possibly imperfect SIC makes RSMA more robust and reliable.
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- 2024
14. LLM-Based Section Identifiers Excel on Open Source but Stumble in Real World Applications
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Krishnamoorthy, Saranya, Singh, Ayush, and Tafreshi, Shabnam
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Computer Science - Computation and Language ,Computer Science - Artificial Intelligence - Abstract
Electronic health records (EHR) even though a boon for healthcare practitioners, are growing convoluted and longer every day. Sifting around these lengthy EHRs is taxing and becomes a cumbersome part of physician-patient interaction. Several approaches have been proposed to help alleviate this prevalent issue either via summarization or sectioning, however, only a few approaches have truly been helpful in the past. With the rise of automated methods, machine learning (ML) has shown promise in solving the task of identifying relevant sections in EHR. However, most ML methods rely on labeled data which is difficult to get in healthcare. Large language models (LLMs) on the other hand, have performed impressive feats in natural language processing (NLP), that too in a zero-shot manner, i.e. without any labeled data. To that end, we propose using LLMs to identify relevant section headers. We find that GPT-4 can effectively solve the task on both zero and few-shot settings as well as segment dramatically better than state-of-the-art methods. Additionally, we also annotate a much harder real world dataset and find that GPT-4 struggles to perform well, alluding to further research and harder benchmarks., Comment: To appear in NAACL 2024 at the 6th Clinical Natural Language Processing Workshop
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- 2024
15. Effective uniaxial dielectric function tensor and optical phonons in ($\bar{2}01$)-plane oriented $\beta$-Ga$_2$O$_3$ films with equally-distributed six-fold rotation domains
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Mock, Alyssa, Richter, Steffen, Papamichail, Alexis, Stanishev, Vallery, Ghezellou, Misagh, Ul-Hassan, Jawad, Popp, Andreas, Anooz, Saud Bin, Gogova, Daniella, Ranga, Praneeth, Krishnamoorthy, Sriram, Korlacki, Rafal, Schubert, Mathias, and Darakchieva, Vanya
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Condensed Matter - Materials Science - Abstract
Monoclinic $\beta$-Ga$_2$O$_3$ films grown on $c$-plane sapphire have been shown to exhibit six $(\bar{2}01)$-plane oriented domains, which are equally-spaced-by-rotation around the surface normal and equally-sized-by-volume that render the film optical response effectively uniaxial. We derive and discuss an optical model suitable for ellipsometry data analysis of such films. We model mid- and far-infrared ellipsometry data from undoped and electrically insulating films with an effective uniaxial dielectric tensor based on projections of all phonon modes within the rotation domains parallel and perpendicular to the sample normal, i.e., to the reciprocal lattice vector $\mathbf{g}_{\bar{2}01}$. Two effective response functions are described by model, and found sufficient to calculate ellipsometry data that best-match measured ellipsometry data from a representative film. We propose to render either effective dielectric functions, or inverse effective dielectric functions, each separately for electric field directions parallel and perpendicular to $\mathbf{g}_{\bar{2}01}$, by sums of Lorentz oscillators, which permit to determine either sets of transverse optical phonon mode parameters, or sets of longitudinal optical phonon mode parameters, respectively. Transverse optical modes common to both dielectric functions can be traced back to single crystal modes with $B_{\mathrm{u}}$ character, while modes with $A_{\mathrm{u}}$ character only appear within the dielectric function for polarization perpendicular to the sample surface. The thereby obtained parameter sets reveal all phonon modes anticipated from averaging over the six-fold rotation domains of single crystal $\beta$-Ga$_2$O$_3$, but with slightly shifted transverse optical, and completely different longitudinal optical phonon modes., Comment: 14 pgaes, 8 figures
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- 2024
16. Box Filtration
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Alvarado, Enrique, Gupta, Prashant, and Krishnamoorthy, Bala
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Computer Science - Computational Geometry ,Mathematics - Algebraic Topology ,55N31, 62R40 - Abstract
We define a new framework that unifies the filtration and mapper approaches from TDA, and present efficient algorithms to compute it. Termed the box filtration of a PCD, we grow boxes (hyperrectangles) that are not necessarily centered at each point (in place of balls centered at points). We grow the boxes non-uniformly and asymmetrically in different dimensions based on the distribution of points. We present two approaches to handle the boxes: a point cover where each point is assigned its own box at start, and a pixel cover that works with a pixelization of the space of the PCD. Any box cover in either setting automatically gives a mapper of the PCD. We show that the persistence diagrams generated by the box filtration using both point and pixel covers satisfy the classical stability based on the Gromov-Hausdorff distance. Using boxes also implies that the box filtration is identical for pairwise or higher order intersections whereas the VR and Cech filtration are not the same. Growth in each dimension is computed by solving a linear program (LP) that optimizes a cost functional balancing the cost of expansion and benefit of including more points in the box. The box filtration algorithm runs in $O(m|U(0)|\log(mn\pi)L(q))$ time, where $m$ is number of steps of increments considered for box growth, $|U(0)|$ is the number of boxes in the initial cover ($\leq$ number of points), $\pi$ is the step length for increasing each box dimension, each LP is solved in $O(L(q))$ time, $n$ is the PCD dimension, and $q = n \times |X|$. We demonstrate through multiple examples that the box filtration can produce more accurate results to summarize the topology of the PCD than VR and distance-to-measure (DTM) filtrations. Software for our implementation is available at https://github.com/pragup/Box-Filteration., Comment: 17 figures
- Published
- 2024
17. Performance Characterization of Heliotrope Solar Hot-Air Balloons during Multihour Stratospheric Flights
- Author
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Swaim, Taylor D., Hough, Emalee, Yap, Zachary, Jacob, Jamey D., Krishnamoorthy, Siddharth, Bowman, Daniel C., Martire, Léo, Komjathy, Attila, and Elbing, Brian R.
- Subjects
Physics - Space Physics ,Astrophysics - Instrumentation and Methods for Astrophysics ,Physics - Atmospheric and Oceanic Physics - Abstract
Heliotropes are passive solar hot air balloons that are capable of achieving nearly level flight within the lower stratosphere for several hours. These inexpensive flight platforms enable stratospheric sensing with high-cadence enabled by the low cost to manufacture, but their performance has not yet been assessed systematically. During July to September of 2021, 29 heliotropes were successfully launched from Oklahoma and achieved float altitude as part of the Balloon-based Acoustic Seismology Study (BASS). All of the heliotrope envelopes were nearly identical with only minor variations to the flight line throughout the campaign. Flight data collected during this campaign comprise a large sample to characterize the typical heliotrope flight behavior during launch, ascent, float, and descent. Each flight stage is characterized, dependence on various parameters is quantified, and a discussion of nominal and anomalous flights is provided.
- Published
- 2024
- Full Text
- View/download PDF
18. Predictive Analytics of Varieties of Potatoes
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Ferracina, Fabiana, Krishnamoorthy, Bala, Halappanavar, Mahantesh, Hu, Shengwei, and Sathuvalli, Vidyasagar
- Subjects
Computer Science - Machine Learning ,Statistics - Machine Learning - Abstract
We explore the application of machine learning algorithms to predict the suitability of Russet potato clones for advancement in breeding trials. Leveraging data from manually collected trials in the state of Oregon, we investigate the potential of a wide variety of state-of-the-art binary classification models. We conduct a comprehensive analysis of the dataset that includes preprocessing, feature engineering, and imputation to address missing values. We focus on several key metrics such as accuracy, F1-score, and Matthews correlation coefficient (MCC) for model evaluation. The top-performing models, namely the multi-layer perceptron classifier (MLPC), histogram-based gradient boosting classifier (HGBC), and a support vector machine classifier (SVC), demonstrate consistent and significant results. Variable selection further enhances model performance and identifies influential features in predicting trial outcomes. The findings emphasize the potential of machine learning in streamlining the selection process for potato varieties, offering benefits such as increased efficiency, substantial cost savings, and judicious resource utilization. Our study contributes insights into precision agriculture and showcases the relevance of advanced technologies for informed decision-making in breeding programs., Comment: 19 pages, 3 figures, submitted to Artificial Intelligence in Agriculture
- Published
- 2024
19. Constructing abelian varieties from rank 3 Galois representations with real trace field
- Author
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Krishnamoorthy, Raju and Lam, Yeuk Hay Joshua
- Subjects
Mathematics - Algebraic Geometry ,Mathematics - Number Theory - Abstract
Let $U/K$ be a smooth affine curve over a number field and let $L$ be an irreducible rank 3 $\overline{\mathbb Q}_{\ell}$-local system on $U$ with trivial determinant and infinite geometric monodromy around a cusp. Suppose further that $L$ extends to an integral model such that the Frobenius traces are contained in a fixed totally real number field. Then, after potentially shrinking $U$, there exists an abelian scheme $f\colon B_U\rightarrow U$ such that $L$ is a summand of $R^2f_*\overline{\mathbb Q}_{\ell}(1)$. The key ingredients are: (1) the totally real assumption implies $L$ admits a square root $M$; (2) the trace field of $M$ is sufficiently bounded, allowing us to use recent work of Krishnamoorthy-Yang-Zuo to construct an abelian scheme over $U_{\bar K}$ geometrically realizing $L$; and (3) Deligne's weight-monodromy theorem and the Rapoport-Zink spectral sequence, which allow us to pin down the arithmetizations using the total degeneration., Comment: 3 pages, comments welcome!
- Published
- 2024
20. Utilizing (Al, Ga)2O3/Ga2O3 superlattices to measure cation vacancy diffusion and vacancy-concentration-dependent diffusion of Al, Sn, and Fe in \b{eta} -Ga2O3
- Author
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Rock, Nathan D., Yang, Haobo, Eisner, Brian, Levin, Aviva, Bhattacharyya, Arkka, Krishnamoorthy, Sriram, Ranga, Praneeth, Walker, Michael A, Wang, Larry, Cheng, Ming Kit, Zhao, Wei, and Scarpulla, Michael A.
- Subjects
Condensed Matter - Materials Science - Abstract
Diffusion of native defects such as vacancies and their interactions with impurities are fundamental in semiconductor crystal growth, device processing, and long-term aging of equilibration and transient diffusion of vacancies are rarely investigated. We used aluminum-gallium oxide/gallium oxide superlattices (SLs) to detect and analyze transient diffusion of cation vacancies during annealing in O2 at 1000-1100 C. Using a novel finite difference scheme for the diffusion equation with time- and space-varying diffusion constant, we extract diffusion constants for Al, Fe, and cation vacancies under the given conditions, including the vacancy concentration dependence for Al. indicate that vacancies present in the substrate transiently diffuse through the SLs, interacting with Sn as it also diffuses. In the case of SLs grown on Sn-doped beta-gallium oxide substrates, gradients observed in the extent of Al diffusion indicate that vacancies present in the substrate transiently diffuse through the SLs, interacting with Sn as it also diffuses. In the case of SLs grown on (010) Fe-doped substrates, the Al diffusion is uniform through the SLs, indicating a depth-uniform concentration of vacancies. We find no evidence in either case for the introduction of gallium vacancies from the free surface at rates sufficient to affect Al diffusion down to ppm concentrations, which has important bearing on the validity of typically-made assumptions of vacancy equilibration. Additionally, we show that unintentional impurities in Sn-doped gallium oxide such as Fe, Ni, Mn, Cu, and Li also diffuse towards the surface and accumulate. Many of these likely have fast interstitial diffusion modes capable of destabilizing devices over time, thus highlighting the importance of controlling unintentional impurities in beta-gallium oxide wafers., Comment: 11 pages, 4 figures, references a supplimental which will be submitted seperately
- Published
- 2024
21. Determination of Hilbert modular forms using squarefree coefficients
- Author
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Agnihotri, Rishabh and Krishnamoorthy, Krishnarjun
- Subjects
Mathematics - Number Theory ,11F41, 11F37, 11F27 - Abstract
Let $F$ (over $\mathbb{Q}$) be a totally real number field of narrow class number $1$. We generalize a result of Kohnen on the determination of half integral weight modular forms by their Fourier coefficients supported on squarefree (algebraic) integers. We also give a soft proof that infinitely many Fourier coefficients supported on squarefree integers are non-vanishing., Comment: Comments and suggestions welcome
- Published
- 2024
22. Structural Validation Of Synthetic Power Distribution Networks Using The Multiscale Flat Norm
- Author
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Lyman, Kostiantyn, Meyur, Rounak, Krishnamoorthy, Bala, and Halappanavar, Mahantesh
- Subjects
Computer Science - Computational Geometry ,Mathematics - Algebraic Topology ,Mathematics - Differential Geometry - Abstract
We study the problem of comparing a pair of geometric networks that may not be similarly defined, i.e., when they do not have one-to-one correspondences between their nodes and edges. Our motivating application is to compare power distribution networks of a region. Due to the lack of openly available power network datasets, researchers synthesize realistic networks resembling their actual counterparts. But the synthetic digital twins may vary significantly from one another and from actual networks due to varying underlying assumptions and approaches. Hence the user wants to evaluate the quality of networks in terms of their structural similarity to actual power networks. But the lack of correspondence between the networks renders most standard approaches, e.g., subgraph isomorphism and edit distance, unsuitable. We propose an approach based on the multiscale flat norm, a notion of distance between objects defined in the field of geometric measure theory, to compute the distance between a pair of planar geometric networks. Using a triangulation of the domain containing the input networks, the flat norm distance between two networks at a given scale can be computed by solving a linear program. In addition, this computation automatically identifies the 2D regions (patches) that capture where the two networks are different. We demonstrate through 2D examples that the flat norm distance can capture the variations of inputs more accurately than the commonly used Hausdorff distance. As a notion of stability, we also derive upper bounds on the flat norm distance between a simple 1D curve and its perturbed version as a function of the radius of perturbation for a restricted class of perturbations. We demonstrate our approach on a set of actual power networks from a county in the USA., Comment: A shorter version (with subset of results) appeared in ICCS 2023
- Published
- 2024
23. Approximate Bipartite $b$-Matching using Multiplicative Auction
- Author
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Samineni, Bhargav, Ferdous, S M, Halappanavar, Mahantesh, and Krishnamoorthy, Bala
- Subjects
Computer Science - Data Structures and Algorithms - Abstract
Given a bipartite graph $G(V= (A \cup B),E)$ with $n$ vertices and $m$ edges and a function $b \colon V \to \mathbb{Z}_+$, a $b$-matching is a subset of edges such that every vertex $v \in V$ is incident to at most $b(v)$ edges in the subset. When we are also given edge weights, the Max Weight $b$-Matching problem is to find a $b$-matching of maximum weight, which is a fundamental combinatorial optimization problem with many applications. Extending on the recent work of Zheng and Henzinger (IPCO, 2023) on standard bipartite matching problems, we develop a simple auction algorithm to approximately solve Max Weight $b$-Matching. Specifically, we present a multiplicative auction algorithm that gives a $(1 - \varepsilon)$-approximation in $O(m \varepsilon^{-1} \log \varepsilon^{-1} \log \beta)$ worst case time, where $\beta$ the maximum $b$-value. Although this is a $\log \beta$ factor greater than the current best approximation algorithm by Huang and Pettie (Algorithmica, 2022), it is considerably simpler to present, analyze, and implement., Comment: 14 pages; Accepted as a refereed paper in the 2024 INFORMS Optimization Society conference
- Published
- 2024
24. ECCBO: An Inherently Safe Bayesian Optimization with Embedded Constraint Control for Real-Time Optimization
- Author
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Krishnamoorthy, Dinesh
- Subjects
Mathematics - Optimization and Control ,Electrical Engineering and Systems Science - Systems and Control - Abstract
This paper introduces a model-free real-time optimization (RTO) framework based on unconstrained Bayesian optimization with embedded constraint control. The main contribution lies in demonstrating how this approach simplifies the black-box optimization problem while ensuring "always-feasible" setpoints, addressing a critical challenge in real-time optimization with unknown cost and constraints. Noting that controlling the constraint does not require detailed process models, the key idea of this paper is to control the constraints to "some" setpoint using simple feedback controllers. Bayesian optimization then computes the optimum setpoint for the constraint controllers. By searching over the setpoints for the constraint controllers, as opposed to searching directly over the RTO degrees of freedom, this paper achieves an inherently safe and practical model-free RTO scheme. In particular, this paper shows that the proposed approach can achieve zero cumulative constraint violation without relying on assumptions about the Gaussian process model used in Bayesian optimization. The effectiveness of the proposed approach is demonstrated on a benchmark Williams-Otto reactor example., Comment: IFAC ADCHEM 2024
- Published
- 2024
25. 100 Gbps Indoor Access and 4.8 Gbps Outdoor Point-to-Point LiFi Transmission Systems using Laser-based Light Sources
- Author
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Cheng, Cheng, Das, Sovan, Videv, Stefan, Spark, Adrian, Babadi, Sina, Krishnamoorthy, Aravindh, Lee, Changmin, Grieder, Daniel, Hartnett, Kathleen, Rudy, Paul, Raring, James, Najafi, Marzieh, Papanikolaou, Vasilis K., Schober, Robert, and Haas, Harald
- Subjects
Electrical Engineering and Systems Science - Systems and Control ,Physics - Optics - Abstract
In this paper, we demonstrate the communication capabilities of light-fidelity (LiFi) systems based on highbrightness and high-bandwidth integrated laser-based sources in a surface mount device (SMD) packaging platform. The laserbased source is able to deliver 450 lumens of white light illumination and the resultant light brightness is over 1000 cd mm2. It is demonstrated that a wavelength division multiplexing (WDM) LiFi system with ten parallel channels is able to deliver over 100 Gbps data rate with the assistance of Volterra filter-based nonlinear equalisers. In addition, an aggregated transmission data rate of 4.8 Gbps has been achieved over a link distance of 500 m with the same type of SMD light source. This work demonstrates the scalability of LiFi systems that employ laserbased light sources, particularly in their capacity to enable highspeed short range, as well as long-range data transmission.
- Published
- 2024
26. A novel method for the detection and classification of multiple diseases using transfer learning-based deep learning techniques with improved performance
- Author
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Natarajan, Krishnamoorthy, Muthusamy, Suresh, Sha, Mizaj Shabil, Sadasivuni, Kishor Kumar, Sekaran, Sreejith, Charles Gnanakkan, Christober Asir Rajan, and A.Elngar, Ahmed
- Published
- 2024
- Full Text
- View/download PDF
27. Association of Atrazine-Induced Overexpression of Aldo–Keto-Reductase 1C2 (AKR1C2) with Hypoandrogenism and Infertility: An Experimental Study in Male Wistar Rat
- Author
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Arulanandu, Angel Mary, Kalimuthu, Vignesh, Manimegalai, Swathi Chandran, Venkatesan, Ramya, Krishnamoorthy, Sathiya Priya, Abdulkader, Akbarsha Mohammad, and Balamuthu, Kadalmani
- Published
- 2024
- Full Text
- View/download PDF
28. A Logical Remote Sensing Based Disaster Management and Alert System Using AI-Assisted Internet of Things Technology
- Author
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Nagaiah, Kummari, Kalaivani, Karunakaran, Palamalai, Radhakrishnan, Suresh, Krishnamoorthy, Sethuraman, Vijayprasath, and Karuppiah, Vinothkumar
- Published
- 2024
- Full Text
- View/download PDF
29. Exploring Herding Instincts Through the Lens of Adaptive Market Hypothesis: Insights from a Frontier Market
- Author
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Charith, Krishnamoorthy and Azeez, A. A.
- Published
- 2024
- Full Text
- View/download PDF
30. Cooperative genomic lesions in HRAS-mutant cancers predict resistance to farnesyltransferase inhibitors
- Author
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Nigam, Aradhya, Krishnamoorthy, Gnana P., Chatila, Walid K., Berman, Katherine, Saqcena, Mahesh, Walch, Henry, Venkatramani, Mandakini, Ho, Alan L., Schultz, Nikolaus, Fagin, James A., and Untch, Brian R.
- Published
- 2024
- Full Text
- View/download PDF
31. Queueing-inventory: analytical and simulation modeling and classical and retrial queues and inventory
- Author
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Krishnamoorthy, Achyutha, Chakravarthy, Srinivas R., Melikov, Agassi, and Narayanan, Viswanath C.
- Published
- 2024
- Full Text
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32. Ultrasound-assisted synthesized multi-phase copper vanadate (Cu3V2O8/Cu2V2O7/Cu0.4V2O5) shape-controlled nanoparticles as electrode material for energy storage applications
- Author
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Gowrisankar, G., Mariappan, R., Palani, E., and Krishnamoorthy, E.
- Published
- 2024
- Full Text
- View/download PDF
33. Multiplex Loop-Mediated Isothermal Amplification Coupled Lateral Flow Assay for Point-of-Care Detection of Syphilis
- Author
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Priya, Krishnamoorthy, Saranya, Elangovan, Kapoor, Ashish, and Ramya, Mohandass
- Published
- 2024
- Full Text
- View/download PDF
34. A Normalized Bottleneck Distance on Persistence Diagrams and Homology Preservation Under Dimension Reduction
- Author
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May, Nathan H., Krishnamoorthy, Bala, and Gambill, Patrick
- Published
- 2024
- Full Text
- View/download PDF
35. Low C4A copy numbers and higher HERV gene insertion contributes to increased risk of SLE, with absence of association with disease phenotype and disease activity
- Author
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Mariaselvam, Christina Mary, Seth, Gaurav, Kavadichanda, Chengappa, Boukouaci, Wahid, Wu, Ching-Lien, Costes, Bruno, Thabah, Molly Mary, Krishnamoorthy, Rajagopal, Leboyer, Marion, Negi, Vir Singh, and Tamouza, Ryad
- Published
- 2024
- Full Text
- View/download PDF
36. Evaluation of Developmental Toxicity and Oxidative Stress Caused by Zinc Oxide Nanoparticles in Zebra Fish Embryos/ Larvae
- Author
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Deenathayalan, Uvarajan, Nandita, Ravichandran, Kavithaa, Krishnamoorthy, Kavitha, Vengamuthu Subramaniyan, Govindasamy, Chandramohan, Al-Numair, Khalid S., Alsaif, Mohammed A., Cheon, Yong Pil, Arul, Narayanasamy, and Brindha, Durairaj
- Published
- 2024
- Full Text
- View/download PDF
37. Artificial diet for mass-rearing of melon borer, Diaphania indica (Saunders) (Lepidoptera: Pyralidae)
- Author
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Visalakshy, P. N. Ganga, Soumya, K., Krishnamoorthy, A., and Pillai, K. Gopalakrishna
- Published
- 2017
38. Learning the cost-to-go for mixed-integer nonlinear model predictive control
- Author
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Orrico, Christopher A., Heemels, W. P. M. H., and Krishnamoorthy, Dinesh
- Subjects
Electrical Engineering and Systems Science - Systems and Control ,Mathematics - Optimization and Control - Abstract
Application of nonlinear model predictive control (NMPC) to problems with hybrid dynamical systems, disjoint constraints, or discrete controls often results in mixed-integer formulations with both continuous and discrete decision variables. However, solving mixed-integer nonlinear programming problems (MINLP) in real-time is challenging, which can be a limiting factor in many applications. To address the computational complexity of solving mixed integer nonlinear model predictive control problem in real-time, this paper proposes an approximate mixed integer NMPC formulation based on value function approximation. Leveraging Bellman's principle of optimality, the key idea here is to divide the prediction horizon into two parts, where the optimal value function of the latter part of the prediction horizon is approximated offline using expert demonstrations. Doing so allows us to solve the MINMPC problem with a considerably shorter prediction horizon online, thereby reducing the online computation cost. The paper uses an inverted pendulum example with discrete controls to illustrate this approach.
- Published
- 2024
39. On Building Myopic MPC Policies using Supervised Learning
- Author
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Orrico, Christopher A., Yang, Bokan, and Krishnamoorthy, Dinesh
- Subjects
Computer Science - Machine Learning ,Electrical Engineering and Systems Science - Systems and Control ,Mathematics - Optimization and Control - Abstract
The application of supervised learning techniques in combination with model predictive control (MPC) has recently generated significant interest, particularly in the area of approximate explicit MPC, where function approximators like deep neural networks are used to learn the MPC policy via optimal state-action pairs generated offline. While the aim of approximate explicit MPC is to closely replicate the MPC policy, substituting online optimization with a trained neural network, the performance guarantees that come with solving the online optimization problem are typically lost. This paper considers an alternative strategy, where supervised learning is used to learn the optimal value function offline instead of learning the optimal policy. This can then be used as the cost-to-go function in a myopic MPC with a very short prediction horizon, such that the online computation burden reduces significantly without affecting the controller performance. This approach differs from existing work on value function approximations in the sense that it learns the cost-to-go function by using offline-collected state-value pairs, rather than closed-loop performance data. The cost of generating the state-value pairs used for training is addressed using a sensitivity-based data augmentation scheme., Comment: IFAC NMPC 2024
- Published
- 2024
40. Conformer-Based Speech Recognition On Extreme Edge-Computing Devices
- Author
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Xu, Mingbin, Jin, Alex, Wang, Sicheng, Su, Mu, Ng, Tim, Mason, Henry, Han, Shiyi, Lei, Zhihong, Deng, Yaqiao, Huang, Zhen, and Krishnamoorthy, Mahesh
- Subjects
Computer Science - Machine Learning ,Computer Science - Performance - Abstract
With increasingly more powerful compute capabilities and resources in today's devices, traditionally compute-intensive automatic speech recognition (ASR) has been moving from the cloud to devices to better protect user privacy. However, it is still challenging to implement on-device ASR on resource-constrained devices, such as smartphones, smart wearables, and other smart home automation devices. In this paper, we propose a series of model architecture adaptions, neural network graph transformations, and numerical optimizations to fit an advanced Conformer based end-to-end streaming ASR system on resource-constrained devices without accuracy degradation. We achieve over 5.26 times faster than realtime (0.19 RTF) speech recognition on smart wearables while minimizing energy consumption and achieving state-of-the-art accuracy. The proposed methods are widely applicable to other transformer-based server-free AI applications. In addition, we provide a complete theory on optimal pre-normalizers that numerically stabilize layer normalization in any Lp-norm using any floating point precision.
- Published
- 2023
41. Over 6 $\mu$m thick MOCVD-grown Low-Background Carrier Density (10$^{15}$ cm$^{-3}$) High-Mobility (010) $\beta$-Ga$_2$O$_3$ Drift Layers
- Author
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Bhattacharyya, Arkka, Peterson, Carl, Chanchaiworawit, Kittamet, Roy, Saurav, Liu, Yizheng, Rebollo, Steve, and Krishnamoorthy, Sriram
- Subjects
Physics - Applied Physics - Abstract
This work reports high carrier mobilities and growth rates, simultaneously in low unintentionally-doped UID (10$^{15}$ cm$^{-3}$) MOCVD-grown thick $\beta$-Ga$_2$O$_3$ epitaxial drift layers, with thicknesses reaching up to 6.3 $\mu$m, using triethylgallium (TEGa) as a precursor. Record high room temperature Hall mobilities of 187-190 cm$^2$/Vs were measured for background carrier density values of 2.4 - 3.5$\times$10$^{15}$ cm$^{-3}$ grown at a rate of 2.2 $\mu$m/hr. A controlled background carrier density scaling from 3.3$\times$10$^{16}$ cm$^{-3}$ to 2.4$\times$10$^{15}$ cm$^{-3}$ is demonstrated, without the use of intentional dopant gases such as silane, by controlling the growth rate and O$_2$/TEGa ratio. Films show smooth surface morphologies of 0.8-3.8 nm RMS roughness for film thicknesses of 1.24 - 6.3$\mu$m. Vertical Ni Schottky barrier diodes (SBDs) fabricated on UID MOCVD material were compared with those fabricated on hydride vapor phase epitaxy (HVPE) material, revealing superior material and device characteristics. MOCVD SBDs on a 6.3 $\mu$m thick epitaxial layer show a uniform charge vs. depth profile of $\sim$2.4$\times$10$^{15}$ cm$^{-3}$, an estimated $\mu$$_{drift}$ of 132 cm$^2$/Vs, a breakdown voltage (V$_{BR}$) close to 1.2 kV and a surface parallel plane field of 2.05MV/cm without any electric field management - setting record-high parameters for any MOCVD-grown $\beta$-Ga$_2$O$_3$ vertical diode to date., Comment: 14 pages, 14 figures, 1 table
- Published
- 2023
42. A collage of results on the divisibility and indivisibility of class numbers of quadratic fields
- Author
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Krishnamoorthy, Srilakshmi, Pasupulati, Sunil Kumar, and R, Muneeswaran
- Subjects
Mathematics - Number Theory - Abstract
The investigation of the ideal class group $Cl_K$ of an algebraic number field $K$ is one of the key subjects of inquiry in algebraic number theory since it encodes a lot of arithmetic information about K. There is a considerable amount of research on many topics linked to quadratic field class groups notably intriguing aspect is the divisibility of the class numbers. This article discusses a few recent results on the divisibility of class numbers and the Izuka conjecture. We also discuss the quantitative aspect of the Izuka conjecture., Comment: Comments are welcome.11 pages
- Published
- 2023
43. Some New Congruences for $\ell$-Regular Multipartitions
- Author
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Krishnamoorthy, Srilakshmi and Sarma, Abinash
- Subjects
Mathematics - Number Theory - Abstract
For a positive integer $n$, let $B_{\ell_1,\dots,\ell_r}(n)$ denote the number of $(\ell_1,\ell_2,\cdots,\ell_r)$-regular multipartitions of $n$. If $\ell_1=\ell_2=\cdots=\ell_r=\ell$, then we denote $B_{\ell_1,\dots,\ell_r}(n)$ as $B_\ell^{(r)}(n)$. In this paper, we prove several infinite families of congruences satisfied by $B_\ell^{(r)}(n)$ for different values of $\ell$ and $r$.
- Published
- 2023
44. Semi-Streaming Algorithms for Weighted $k$-Disjoint Matchings
- Author
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Ferdous, S M, Samineni, Bhargav, Pothen, Alex, Halappanavar, Mahantesh, and Krishnamoorthy, Bala
- Subjects
Computer Science - Data Structures and Algorithms - Abstract
We design and implement two single-pass semi-streaming algorithms for the maximum weight $k$-disjoint matching ($k$-DM) problem. Given an integer $k$, the $k$-DM problem is to find $k$ pairwise edge-disjoint matchings such that the sum of the weights of the matchings is maximized. For $k \geq 2$, this problem is NP-hard. Our first algorithm is based on the primal-dual framework of a linear programming relaxation of the problem and is $\frac{1}{3+\varepsilon}$-approximate. We also develop an approximation preserving reduction from $k$-DM to the maximum weight $b$-matching problem. Leveraging this reduction and an existing semi-streaming $b$-matching algorithm, we design a $(\frac{1}{2+\varepsilon})(1 - \frac{1}{k+1})$-approximate semi-streaming algorithm for $k$-DM. For any constant $\varepsilon > 0$, both of these algorithms require $O(nk \log_{1+\varepsilon}^2 n)$ bits of space. To the best of our knowledge, this is the first study of semi-streaming algorithms for the $k$-DM problem. We compare our two algorithms to state-of-the-art offline algorithms on 95 real-world and synthetic test problems, including thirteen graphs generated from data center network traces. On these instances, our streaming algorithms used significantly less memory (ranging from 6$\times$ to 512$\times$ less) and were faster in runtime than the offline algorithms. Our solutions were often within 5% of the best weights from the offline algorithms. We highlight that the existing offline algorithms run out of 1 TB memory for most of the large instances ($>1$ billion edges), whereas our streaming algorithms can solve these problems using only 100 GB memory for $k=8$., Comment: 24 pages, To appear in ESA 2024
- Published
- 2023
45. A Bayesian optimization framework for the automatic tuning of MPC-based shared controllers
- Author
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van der Horst, Anne, Meere, Bas, Krishnamoorthy, Dinesh, Bakker, Saray, van de Vrande, Bram, Stoutjesdijk, Henry, Alonso, Marco, and Torta, Elena
- Subjects
Computer Science - Robotics - Abstract
This paper presents a Bayesian optimization framework for the automatic tuning of shared controllers which are defined as a Model Predictive Control (MPC) problem. The proposed framework includes the design of performance metrics as well as the representation of user inputs for simulation-based optimization. The framework is applied to the optimization of a shared controller for an Image Guided Therapy robot. VR-based user experiments confirm the increase in performance of the automatically tuned MPC shared controller with respect to a hand-tuned baseline version as well as its generalization ability.
- Published
- 2023
46. The Normal Active Range of Motion of the Index, Middle, Ring, and Little Fingers in a Sample of Indian Population
- Author
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Mohamed Ibrahim B.K, P. Umar Farooq Baba, Veena Singh, Ankur Karanjkar, Latha Madhavan, Raheeb Ahmad Shah, Ansarul Haq, Manoj Pawar, Anupama Kumari, Nikhil Panse, Vishnubabu G., Shyamnath Krishna Pandian, Anirudha Sharma, Rajagopalan Krishnamoorthy, Mukund Thatte, Anil Bhat, and Sridhar Krishnamoorthy
- Subjects
finger range of motion ,Indian normative data ,total active motion ,Surgery ,RD1-811 - Abstract
Background The normative data for finger range of motion (ROM) are not available for the Indian population. The aim of our study was to measure the active ROM of finger joints in normal healthy volunteers in a sample of Indian population.
- Published
- 2024
- Full Text
- View/download PDF
47. Preparing For Pandemic: Securitizing Rhetoric in U.S. National Influenza Response Plans, 1978–2017
- Author
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Keränen, Lisa B., Krishnamoorthy, Aishwarya, Ingersoll, Branden, and Cosgrove, Meghan
- Published
- 2024
48. Applying Persuasive Techniques in an Online Learning Environment: A Mixed-Method Study
- Author
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Krishnamoorthy, Lakshmi and Merchant, Zahira
- Abstract
Persuasion is inherent to the instructional process. Instructions delivered through online programs do not always generate expected and consistent learning outcomes, and hence persuasion in online instructional design is even more critical. Through this mixed-method study, we aim to identify the most widely used persuasive design techniques, the challenges limiting their applications, and their implications. Furthermore, this paper discusses the recommendations of new persuasive techniques put forth by Instructional Designers.
- Published
- 2023
49. Chitin Extraction from Lutjanus campechanus for Sustainable Bio-plastic Production (Red Snapper)
- Author
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Sagaya Deva Niranjana, X. and Krishnamoorthy, R.
- Published
- 2024
- Full Text
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50. Groundwater quality assessment using machine learning models: a comprehensive study on the industrial corridor of a semi-arid region
- Author
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Krishnamoorthy, Loganathan and Lakshmanan, Vignesh Rajkumar
- Published
- 2024
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