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At least 757 records · Page 42

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DOE OSTI2015

Stabilization of the Ti{sub 3}Co{sub 5}B{sub 2}-type structure for Ti{sub 3−x}Si{sub x}Ru{sub 5}B{sub 2} through Si–Ti substitution

We report a route for designing and synthesizing Ti{sub 3}Co{sub 5}B{sub 2}-type compounds in the Ti–Ru–B system by using chemical substitution of Si for Ti to decrease the d-electron-based antibonding interactions that it is argued would otherwise drive an instability in this structure for unsubstituted Ti{sub 3}Ru{sub 5}B{sub 2}. Ti{sub 3−x}Si{sub x}Ru{sub 5}B{sub 2} with x=0.75, 1.00 and 1.25 nominal compositions crystalizes in the Ti{sub 3}Co{sub 5}B{sub 2} structure type using arc melting methods, whereas at lower doping levels (x=0.0, 0.25 and 0.50) the more complex Zn{sub 11}Rh{sub 18}B{sub 8}-type structure is stable. Electronic structure calculations show that in hypothetical, unsubstituted Ti{sub 3}Ru{sub 5}B{sub 2} with the Ti{sub 3}Co{sub 5}B{sub 2}-type structure, the antibonding interactions are strong around the Fermi level between the Ti and Ru in the structure that form tetragonal prisms. We propose that weakening these strong interactions through the partial substitution of isovalent Si for Ti leads to the observed stability of the Ti{sub 3}Co{sub 5}B{sub 2}-type structure for Ti{sub 3−x}Si{sub x}Ru{sub 5}B{sub 2} for x≈1. - Graphical abstract: We present the designing and synthesizing of Ti{sub 3}Co{sub 5}B{sub 2}-type compounds in the Ti–Ru–B system by using chemical substitution of Si for Ti to decrease the d-electron-based antibonding interactions that would otherwise drive an instability in this structure for unsubstituted Ti{sub 3}Ru{sub 5}B{sub 2}. Electronic structure calculations show that in hypothetical, unsubstituted Ti{sub 3}Ru{sub 5}B{sub 2} with the Ti{sub 3}Co{sub 5}B{sub 2}-type structure, the antibonding interactions are strong around the Fermi level between the Ti and Ru in the structure that form tetragonal prisms. We propose that weakening these strong interactions through the partial substitution of isovalent Si for Ti leads to the observed stability of the Ti{sub 3}Co{sub 5}B{sub 2}-type structure for Ti{sub 3−x}Si{sub x}Ru{sub 5}B{sub 2} for x≈1. - Highlights: • New quaternary phase Ti{sub 3−x}Si{sub x}Ru{sub 5}B{sub 2} in Ti{sub 3}Co{sub 5}B{sub 2}-type structure is reported. • Chemical substitution of isovalent Si for Ti is used to stabilize the phase. • Decreasing the d-electron-based antibonding interactions is proved by calculation. • Physical properties of Ti{sub 3−x}Si{sub x}Ru{sub 5}B{sub 2} are presented down to 0.4 K.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2022

Resonant acoustic monitoring of damage in plug‐screw feeders

Abstract Plug‐screw feeders are critical in many industrial processes for compressing slurry materials via a rotating plug‐screw feeder. Over time, increasing plug‐screw feeder wear will eventually lead to catastrophic mechanical failure. Early detection of the wear state can prevent unplanned catastrophic failures resulting in operational shut‐downs, costly repairs, and most importantly the health and safety of workers. We present a theoretical basis for a noninvasive, in operando acoustic resonant technique to monitor the wear state of plug‐screw feeders. The technique is based on tracking the resonant acoustic modes of the plug‐screw feeder, which are sensitive to the plug‐screw feeder geometry, material, and operating conditions. We implemented a multivariate polynomial model to estimate the plug‐screw feeder wear state using multiple acoustic resonances by simulating the acoustic resonant modes for two categories of wear (tip and thread damage) that are common in plug‐screw feeders. Fitting multiple resonances to the polynomial model, we demonstrate accurate estimation of the total mass loss, as well as characterization of the type of damage (i.e., tip vs. thread). Current approaches for monitoring plug‐screw feeder wear rely on shutting down the operation and visually inspecting the plug‐screw feeder. The presented acoustic technique offers a noninvasive, in operando measurement approach that mitigates unplanned catastrophic failures. The acoustic resonance technique presented in the paper has a broad range of industrial applications including the Pharmaceutical, Mining, Integrated Biorefineries (IBR), and Additive Manufacturing industries, to name a few.

36 MATERIALS SCIENCE↗

DOE OSTI2024

In‐mold rheology and automated process control for injection molding of recycled polypropylene

Abstract Manufacturing plastic parts with secondary feedstocks has risen to the forefront of importance in recent years. However, the variation in molecular weight and rheology of secondary feedstock can lead to inconsistent part quality. This work evaluates the effectiveness of a novel closed‐loop adaptive process control system that adjusts nozzle pressure in response to in‐mold pressure data. Five different recycled polypropylene blends, with a broad distribution of flow properties, were evaluated to determine the effectiveness of the control system at reducing processing variation. The experimental results show that the process control strategy reduced the variation within the mold, as seen by in‐mold pressure curves and calculated in‐mold viscosity values. Additionally, the parameters that control the automated process adjustments were investigated, showing the importance of optimization. The analysis of the correlation between in‐mold rheology and mechanical properties showed a slight variation in the mechanical properties and parts weight with a coefficient of variation of under 5%. Overall, the results demonstrate the ability of pressure‐controlled molding and automated viscosity adjustment to reduce the variability when molding a secondary feedstock. Highlights Pressure‐controlled injection molding of recycled polypropylene. Automated closed‐loop adaptive process control methodology. Methodology resulted in a reduction in pressure variation during molding. Changes in mechanical properties and in‐mold viscosity were investigated. Results show the potential of pressure‐controlled molding at reducing variation.

Krantz, Joshua↗

DOE OSTI2024

Out-of-Distribution Detection and Radiological Data Monitoring Using Statistical Process Control

Abstract Machine learning (ML) models often fail with data that deviates from their training distribution. This is a significant concern for ML-enabled devices as data drift may lead to unexpected performance. This work introduces a new framework for out of distribution (OOD) detection and data drift monitoring that combines ML and geometric methods with statistical process control (SPC). We investigated different design choices, including methods for extracting feature representations and drift quantification for OOD detection in individual images and as an approach for input data monitoring. We evaluated the framework for both identifying OOD images and demonstrating the ability to detect shifts in data streams over time. We demonstrated a proof-of-concept via the following tasks: 1) differentiating axial vs. non-axial CT images, 2) differentiating CXR vs. other radiographic imaging modalities, and 3) differentiating adult CXR vs. pediatric CXR. For the identification of individual OOD images, our framework achieved high sensitivity in detecting OOD inputs: 0.980 in CT, 0.984 in CXR, and 0.854 in pediatric CXR. Our framework is also adept at monitoring data streams and identifying the time a drift occurred. In our simulations tracking drift over time, it effectively detected a shift from CXR to non-CXR instantly, a transition from axial to non-axial CT within few days, and a drift from adult to pediatric CXRs within a day—all while maintaining a low false positive rate. Through additional experiments, we demonstrate the framework is modality-agnostic and independent from the underlying model structure, making it highly customizable for specific applications and broadly applicable across different imaging modalities and deployed ML models.

Zamzmi, Ghada↗

DOE OSTI2018

CaSn(OH){sub 6} hydroxides, CaSnO{sub 3} oxides and CaSnF{sub 6} fluorides: Synthesis and structural filiation. Cationic environment impact on Pr{sup 3+} doped compounds luminescence

Highlights: • Structural filiation of stannates compounds. • {sup 119}Sn Mossbauer analysis of Sn-X chemical bonding (X = OH, O, F). • Nephelauxetic effect observed in the luminescence of Pr{sup 3+} doped stannate compounds. - Abstract: CaSn(OH){sub 6}, CaSnO{sub 3} and CaSnF{sub 6} compounds were elaborated from a “one-batch” synthesis route: the coprecipitation of the pure double hydroxide leads to pure double oxide or fluoride after annealing treatments under air or HF as anhydrous gas, respectively. Structural and morphological features of the three matrices were carefully investigated by X Ray Diffraction analysis and Scanning Electron Microscopy, respectively. In addition, the luminescent properties of the Pr-doped compounds were performed and compared. The nanometric size of the double hydroxide inhibits the luminescence. The interpretation of the emission spectra obtained for Pr-doped CaSnO{sub 3} and CaSnF{sub 6} compounds is based on the covalence/ionic balance of the M–O or M–F bonds.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2016

On the enhancement of Er{sup 3+} diffusion in LiNbO{sub 3} crystals by Er{sup 3+}/Ti{sup 4+} co-diffusion

Highlights: • Enhancement of the diffusion of erbium ions (Er{sup 3+}) in lithium niobate crystals. • Incoherence on published results lead to need for systematic revision of literature. • Further insight into the topic of co-diffusion of Er{sup 3+}/Ti{sup 4+} ions into LiNbO{sub 3}. - Abstract: After carrying out a revision of the literature on the enhancement of Er{sup 3+} diffusion in LiNbO{sub 3} crystals by Er{sup 3+}/Ti{sup 4+} co-diffusion and analyzing our own experimental results, we conclude that no reproducible results were reported, meaning that further research on this subject is necessary.

36 MATERIALS SCIENCE↗

DOE OSTI2018

Single crystal growth and variation of thermodynamic and magnetic properties of Pr1−xLaxAlO3 (x = 0, 0.8)

Highlights: • The perovskite Pr{sub (1-x)}La{sub (x)}AlO{sub 3} was grown by two different protocols to control the P{sup 4+} concentration. • Low temperature magnetic properties in bulk single crystals are sensitive to annealing protocols. • Post growth annealing in a reducing atmosphere leads to closest Pr{sub 0.2}La{sub 0.8}AlO{sub 3} stoichiometry. • A possible new magnetic transition for single crystal PrAlO{sub 3} is observed at 6 K. - Abstract: Two approaches to using optical floating zone (OFZ) technique for single crystal growth of the perovskite Pr{sub 1−x}La{sub x}AlO{sub 3} are discussed, along with the influence on the physical properties of the resulting single crystals due to oxidizing and reducing post anneals. In method one (M1) we used pre-reduced Pr{sub 2}O{sub 3} powder starting material, while in the other method, M2, we employed an argon 5% hydrogen reducing environment during the floating zone single crystal growth. Magnetic susceptibility of the low temperature monoclinic phase of Pr{sub 0.2}La{sub 0.8}AlO{sub 3} is shown to be sensitive to the precise annealing protocol followed. For the post-growth reduced single crystal the magnetic susceptibility is flat across the R-3c to C2/m structural transition, whereas the oxidized and as-grown samples display a sharp upturn and downturn, respectively. We attribute the low temperature susceptibility differences to relative proportions of Pr{sup 3+} and Pr{sup 4+}.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2017

Ultrafine carbon particles promote rotenone-induced dopamine neuronal loss through activating microglial NADPH oxidase

Background: Atmospheric ultrafine particles (UFPs) and pesticide rotenone were considered as potential environmental risk factors for Parkinson's disease (PD). However, whether and how UFPs alone and in combination with rotenone affect the pathogenesis of PD remains largely unknown. Methods: Ultrafine carbon black (ufCB, a surrogate of UFPs) and rotenone were used individually or in combination to determine their roles in chronic dopaminergic (DA) loss in neuron-glia, and neuron-enriched, mix-glia cultures. Immunochemistry using antibody against tyrosine hydroxylase was performed to detect DA neuronal loss. Measurement of extracellular superoxide and intracellular reactive oxygen species (ROS) were performed to examine activation of NADPH oxidase. Genetic deletion and pharmacological inhibition of NADPH oxidase and MAC-1 receptor in microglia were employed to examine their role in DA neuronal loss triggered by ufCB and rotenone. Results: In rodent midbrain neuron-glia cultures, ufCB and rotenone alone caused neuronal death in a dose-dependent manner. In particularly, ufCB at doses of 50 and 100 μg/cm{sup 2} induced significant loss of DA neurons. More importantly, nontoxic doses of ufCB (10 μg/cm{sup 2}) and rotenone (2 nM) induced synergistic toxicity to DA neurons. Microglial activation was essential in this process. Furthermore, superoxide production from microglial NADPH oxidase was critical in ufCB/rotenone-induced neurotoxicity. Studies in mix-glia cultures showed that ufCB treatment activated microglial NADPH oxidase to induce superoxide production. Firstly, ufCB enhanced the expression of NADPH oxidase subunits (gp91{sup phox}, p47{sup phox} and p40{sup phox}); secondly, ufCB was recognized by microglial surface MAC-1 receptor and consequently promoted rotenone-induced p47{sup phox} and p67{sup phox} translocation assembling active NADPH oxidase. Conclusion: ufCB and rotenone worked in synergy to activate NADPH oxidase in microglia, leading to oxidative damage to DA neurons. Our findings delineated the potential role of ultrafine particles alone and in combination with pesticide rotenone in the pathogenesis of PD. - Graphical abstract: Ultrafine particles and rotenone synergistically induce the assembly of active form NADPH oxidase complex in microglia inducing oxidative damage to dopamine neurons. - Highlights: • Ultrafine carbon black promotes dopaminergic neuronal loss induced by rotenone. • The role and underlying mechanism of ultrafine particles in the pathogenesis of PD • NADPH oxidase is a potential therapeutic target of Parkinson's disease.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2016

Transient GaAs plasmonic metasurfaces at terahertz frequencies

Here we demonstrate the ultrafast formation of terahertz (THz) metasurfaces through all-optical creation of spatially modulated carrier density profiles in a deep-subwavelength GaAs film. The switch-on of the transient plasmon mode, governed by the GaAs effective electron mass and electron–phonon interactions, is revealed by structured-optical pump THz probe spectroscopy, on a time scale of 500 fs. By modulating the carrier density using different pump fluences, we observe a wide tuning of the electric dipole resonance of the transient GaAs metasurface from 0.5 THz to 1.7 THz. Furthermore, we numerically demonstrate that the metasurface presented here can be generalized to more complex architectures for realizing functionalities such as perfect absorption, leading to a 30 dB modulation depth. In conclusion, the platform also provides a pathway to achieve ultrafast manipulation of infrared beams in the linear and, potentially, nonlinear regime.

36 MATERIALS SCIENCE↗

DOE OSTI2022

A microphysiological model of human trophoblast invasion during implantation

Abstract Successful establishment of pregnancy requires adhesion of an embryo to the endometrium and subsequent invasion into the maternal tissue. Abnormalities in this critical process of implantation and placentation lead to many pregnancy complications. Here we present a microenigneered system to model a complex sequence of orchestrated multicellular events that plays an essential role in early pregnancy. Our implantation-on-a-chip is capable of reconstructing the three-dimensional structural organization of the maternal-fetal interface to model the invasion of specialized fetal extravillous trophoblasts into the maternal uterus. Using primary human cells isolated from clinical specimens, we demonstrate in vivo-like directional migration of extravillous trophoblasts towards a microengineered maternal vessel and their interactions with the endothelium necessary for vascular remodeling. Through parametric variation of the cellular microenvironment and proteomic analysis of microengineered tissues, we show the important role of decidualized stromal cells as a regulator of extravillous trophoblast migration. Furthermore, our study reveals previously unknown effects of pre-implantation maternal immune cells on extravillous trophoblast invasion. This work represents a significant advance in our ability to model early human pregnancy, and may enable the development of advanced in vitro platforms for basic and clinical research of human reproduction.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2020

Quantum anomalous Hall effect in two-dimensional magnetic insulator heterojunctions

Abstract Recent years have witnessed tremendous success in the discovery of topological states of matter. Particularly, sophisticated theoretical methods in time-reversal-invariant topological phases have been developed, leading to the comprehensive search of crystal database and the prediction of thousands of topological materials. In contrast, the discovery of magnetic topological phases that break time reversal is still limited to several exemplary materials because the coexistence of magnetism and topological electronic band structure is rare in a single compound. To overcome this challenge, we propose an alternative approach to realize the quantum anomalous Hall (QAH) effect, a typical example of magnetic topological phase, via engineering two-dimensional (2D) magnetic van der Waals heterojunctions. Instead of a single magnetic topological material, we search for the combinations of two 2D (typically trivial) magnetic insulator compounds with specific band alignment so that they can together form a type-III broken-gap heterojunction with topologically non-trivial band structure. By combining the data-driven materials search, first-principles calculations, and the symmetry-based analytical models, we identify eight type-III broken-gap heterojunctions consisting of 2D ferromagnetic insulators in the MXY compound family as a set of candidates for the QAH effect. In particular, we directly calculate the topological invariant (Chern number) and chiral edge states in the MnNF/MnNCl heterojunction with ferromagnetic stacking. This work illustrates how data-driven material science can be combined with symmetry-based physical principles to guide the search for heterojunction-based quantum materials hosting the QAH effect and other exotic quantum states in general.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Optimization of sporulation and purification methods for sporicidal efficacy assessment on Bacillus spores

Abstract Validating the efficacy of sporicidal agents is a critical step in current good manufacturing practices for disinfection requirements. A limitation is that the poor quality of spores can lead to false positive sporicidal results. The aim of this study was to explore optimal sporulation and purification methods in Bacillus spores. Spores of 7 Bacillus strains were produced in 5 different sporulation media. After density centrifugation, spore yields were measured by phase-contrast microscopy and enumeration assays. Effects of purification methods including heat, sonication and lysozyme, and maturation on spore qualities were determined by sodium hypochlorite sporicidal assay. Difco sporulation media was identified as the preferred sporulation medium for 4 out of 7 tested Bacillus strains. Sporulation rates in B. cereus, B. sphaericus, and B. thuringiensis were higher at 30°C than the rates at 37°C at a difference of 5%, 65%, and 20%, respectively. Bacillus licheniformis favored Mn2+-amended 10% Columbia Broth at 37°C for sporulation with 40–72% higher sporulation rates than other media. The maximum sporulation rates of B. cereus and B. thuringiensis were observed on double-strength Schaeffer's-glucose broth. All studied purification methods improved the spore purity with strain variations. However, intense heat (80°C for 20 min) and lysozyme (100 μg/mL) treatment impaired the spore quality of specific Bacillus strains by sensitizing them against sodium hypochlorite. The length of the maturation period had an impact on the spore resistance, and the most optimal maturation periods ranged from 7 to 21 days in Bacillus strains. The results of this study will pave the way for further evaluation of the sporicidal activity of disinfectants.

Biotechnology & Applied Microbiology↗

DOE OSTI2018

CLARITY reveals a more protracted temporal course of axon swelling and disconnection than previously described following traumatic brain injury

Abstract Diffuse axonal injury (DAI) is an important consequence of traumatic brain injury (TBI). At the moment of trauma, axons rarely disconnect, but undergo cytoskeletal disruption and transport interruption leading to protein accumulation within swellings. The amyloid precursor protein (APP) accumulates rapidly and the standard histological evaluation of axonal pathology relies upon its detection. APP+ swellings first appear as varicosities along intact axons, which can ultimately undergo secondary disconnection to leave a terminal “axon bulb” at the disconnected, proximal end. However, sites of disconnection are difficult to determine with certainty using standard, thin tissue sections, thus limiting the comprehensive evaluation of axon degeneration. The tissue‐clearing technique, CLARITY, permits three‐dimensional visualization of axons that would otherwise be out of plane in standard tissue sections. Here, we examined the morphology and connection status of APP+ swellings using CLARITY at 6 h, 24 h, 1 week and 1 month following the controlled cortical impact (CCI) model of TBI in mice. Remarkably, many APP+ swellings that appeared as terminal bulbs when viewed in standard 8‐µm‐thick regions of tissue were instead revealed to be varicose swellings along intact axons when three dimensions were fully visible. Moreover, the percentage of these potentially viable axon swellings differed with survival from injury and may represent the delayed onset of distinct mechanisms of degeneration. Even at 1‐month post‐CCI, ~10% of apparently terminal bulbs were revealed as connected by CLARITY and are thus potentially salvageable. Intriguingly, the diameter of swellings decreased with survival, including varicosities along intact axons, and may reflect reversal of, or reduced, axonal transport interruption in the chronic setting. These data indicate that APP immunohistochemistry on standard thickness tissue sections overestimates axon disconnection, particularly acutely post‐injury. Evaluating cleared tissue demonstrates a surprisingly delayed process of axon disconnection and thus longer window of therapeutic opportunity than previously appreciated. Intriguingly, a subset of axon swellings may also be capable of recovery.

Weber, Maura T.↗

DOE OSTI2020

Warming-induced permafrost thaw exacerbates tundra soil carbon decomposition mediated by microbial community

BACKGROUND:It is well-known that global warming has effects on high-latitude tundra underlain with permafrost. This leads to a severe concern that decomposition of soil organic carbon (SOC) previously stored in this region, which accounts for about 50% of the world's SOC storage, will cause positive feedback that accelerates climate warming. We have previously shown that short-term warming (1.5 years) stimulates rapid, microbe-mediated decomposition of tundra soil carbon without affecting the composition of the soil microbial community (based on the depth of 42684 sequence reads of 16S rRNA gene amplicons per 3 g of soil sample). RESULTS:We show that longer-term (5 years) experimental winter warming at the same site altered microbial communities (p < 0.040). Thaw depth correlated the strongest with community assembly and interaction networks, implying that warming-accelerated tundra thaw fundamentally restructured the microbial communities. Both carbon decomposition and methanogenesis genes increased in relative abundance under warming, and their functional structures strongly correlated (R 2 > 0.725, p < 0.001) with ecosystem respiration or CH4 flux. CONCLUSIONS:Our results demonstrate that microbial responses associated with carbon cycling could lead to positive feedbacks that accelerate SOC decomposition in tundra regions, which is alarming because SOC loss is unlikely to subside owing to changes in microbial community composition. Video Abstract.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2024

Turbulently Driven Detonation Initiation in Electron-degenerate Matter with Helium

Abstract Type Ia supernovae (SNe Ia) are standardizable cosmological candles that led to the discovery of the accelerating Universe. However, the physics of how white dwarfs (WDs) explode and lead to SNe Ia is still poorly understood. The initiation of the detonation front that rapidly disrupts the WD is a crucial element of the puzzle, and global 3D simulations of SNe Ia cannot resolve the requisite length scales to capture detonation initiation. In this work, we elucidate a theoretical criterion for detonation initiation in the distributed burning regime. We test this criterion against local 3D driven turbulent hydrodynamical simulations within electron-degenerate WD matter consisting initially of pure helium. We demonstrate a novel pathway for detonation, in which strong turbulent dissipation rapidly heats the helium, and forms carbon nuclei sufficient to lead to a detonation through accelerated burning via α captures. Simulations of strongly driven turbulent conditions lead to detonations at a mean density of 10 6 g cm −3 and mean temperature of 1.4–1.8 × 10 9 K, but fail to detonate at a lower density of 10 5 g cm −3 , in excellent agreement with theoretical predictions.

Astronomy & Astrophysics↗

NASA NTRS1989

Parameter identification for an abstract Cauchy problem by quasilinearization

A parameter identification problem is considered in the context of a linear abstract Cauchy problem with a parameter-dependent evolution operator. Conditions are investigated under which the gradient of the state with respect to a parameter possesses smoothness properties which lead to local convergence of an estimation algorithm based on quasi-linearization. Numerical results are presented concerning estimation of unknown parameters in delay-differential equations.

Brewer, Dennis W.↗

NASA NTRS1993

Parameter identification for an abstract Cauchy problem by quasilinearization

Brewer, Dennis W.↗

NASA NTRS1997

LQR Control of Shell Vibrations Via Piezoceramic Actuators

A model-based Linear Quadratic Regulator (LQR) method for controlling vibrations in cylindrical shells is presented. Surface-mounted piezo-ceramic patches are employed as actuators which leads to unbounded control input operators. Modified Donnell-Mushtari shell equations incorporating strong or Kelvin-Voigt damping are used to model the system. The model is then abstractly formulated in terms of sesquilinear forms. This provides a framework amenable for proving model well-posedness and convergence of LQR gains using analytic semigroup results combined with LQR theory for unbounded input operators. Finally, numerical examples demonstrating the effectiveness of the method are presented.

delRosario, R. C. H.↗