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Applying Two-stage Risk-Based Market Structures for Energy Hub-Based Plug-in Electric Vehicles using Information Decision Gap Theory and a Hybrid Recurrent Convolutional Network
No full textThis paper investigates the optimal operation of an energy hub engaged in both day-ahead and real-time trading. A two-stage optimization framework Information Gap Decision Theory (IGDT) for day-ahead bidding and stochastic programming with Monte Carlo scenarios for real-time recourse is applied. Risk-neutral, risk-averse, and risk-taking strategies are considered to capture different risk preferences. The hub integrates combined heat and power, renewable energy, plug-in electric vehicles, and vehicle-to-grid and grid-to-vehicle technologies. Price and load forecasts are generated using a hybrid recurrent convolutional network (HRCN). Results highlight the trade-off between risk management and economic performance: costs are 16.5 % higher in the risk-averse mode than in the risk-neutral mode, and 55.6 % higher than in the risk-taking mode. Natural gas accounts for the most in the risk-taking case, at ∼33 % of the total cost. Under the tested conditions, the proposed IGDT–stochastic–HRCN framework improves expected costs relative to baselines, though outcomes may vary under different market rules, fuel prices, or volatility regimes
The Kaczmarz Algorithm in Hilbert C∗-modules
No full textThe Kaczmarz algorithm in Hilbert spaces is a classical iterative method for stably recovering vectors from inner product data. In this paper, we extend the algorithm to the setting of Hilbert C∗-modules and establish analogues of its effectiveness in both finite-dimensional and stationary cases. Consequently, we demonstrate that continuous families of elements in a Hilbert space can be uniformly recovered using the Kaczmarz algorithm. Additionally, we develop a normalized Cauchy transform for continuous families of measures and use it to provide sufficient conditions under which standard frames in Hilbert C(X)-modules can be generated by the Kaczmarz algorithm and realized as orbits of bounded operators
Use of Gamma-ray Spectroscopy in Thickness Gauging of a Complex-shaped Lead Shield
No full textMethods for measuring the thickness of lead shielding based on 60Co gamma-ray spectroscopy are presented. In applications where a shield\u27s thickness is multiple mean free paths and the shield has a complex shape (i.e. cannot be approximated as a simple solid such as a slab, sphere, semi-infinite medium, etc.), the necessary buildup factors are not available. Thus, determination of shield thickness by means of the Beer–Lambert law requires separating the counts from uncollided photons from the scattered photon contribution. It is demonstrated how the 1332 keV gamma ray of 60Co can be used to precisely quantify lead thicknesses up to at least ∼280 mm. Use of the ratio of 1173 keV to 1332 keV photopeak areas to determine thickness is also discussed
A Large Thermal Vacuum (TVAC) Facility to Simulate Cryogenic Space Environments
No full textThis work reports the upgrade of a 10-ft (3.0 m) long x 6-ft (1.8 m) diameter vacuum facility as part of ongoing efforts to address some of the technology gaps in NASA\u27s Moon to Mars mission architecture, which include systems to survive and operate through extended periods in extreme environments. Consequently, a removable thermal shroud has been fabricated and installed to facilitate the simulation of extreme cryogenic conditions. The cooling rates of the shroud and a surrogate test article, using liquid nitrogen as the coolant are analyzed and documented under varying vacuum environments during cryogenic testing. The attainable vacuum level of the TVAC system is equivalent to an altitude range of 100 to 150 km. The measured shroud temperatures are comparable to Low Earth Orbit, lunar surface, and Martian surface extremes. The fully assembled shroud can be reliably cooled to -187 °C (86 K) with the central region achieving an internal temperature of -161 °C (112 K) at a cooling rate ranging from -3 to -5 K/min. The attainable temperature of a surrogate test article further satisfies the cooling criteria outlined in ISO 19683 for spacecraft design qualification and acceptance testing
Thermally Stable SiC Particulate-reinforced SiC Composites Up to 2000 ℃ Fabricated by Precursor Impregnation and Pyrolysis Method
No full textThe thermo-mechanical properties of SiC particulate-reinforced SiC composites (SiC-PRCs), fabricated using precursor impregnation & pyrolysis (PIP) process, were analyzed up to 2000 ℃. The relative density of the SiC-PRCs after 4 PIP cycles was 88.6 %. The number of PIP cycles required decreased to nearly half compared with the conventional PIP method by using ultra-high concentration slurries up to 70 vol%. In addition, room-temperature bending strength (215 MPa) and Young\u27s modulus (269 GPa) improved as the solid loading of the slurry increased. The bending strength increased to 232 MPa at 2000 ℃ in Ar. Despite the thermal deterioration of the precursor-derived ceramics (PDC), the mechanical properties of the PRC did not deteriorate up to 2000 ℃ because the PDC fixed the position of thermally stable SiC filler particles, which were densely packed and mostly endured the stress. Moreover, partial densification at high temperature further improved the thermo-mechanical properties of the PRC
Quantum Critical Behavior of Diluted Quasi-One-Dimensional Ising Chains
No full text(Formula presented.) (Formula presented.) is a unique magnetic material. It features bulk 3D magnetic order at low temperatures, but its quantum critical behavior in a magnetic field is well described by the 1D transverse-field Ising universality class. This behavior is facilitated by the structural arrangement of magnetic (Formula presented.) ions in nearly isolated zig-zag chains. In this work, we investigate the effect of random site dilution on the critical properties of such a quasi-1D quantum Ising system. To this end, we introduce an anisotropic site-diluted 3D transverse-field Ising model. We find that site dilution leads to unconventional activated scaling behavior at the quantum phase transition. Interestingly, the critical exponents of the quantum critical point are in good agreement with those of the disordered 3D transverse-field Ising universality class, despite the strong spatial anisotropy. We discuss the generality of our findings as well as implications for experiments
PCIAFL: Personalized and Class Imbalance-Aware Federated Learning for Driver Behavior Classification
No full textAutomated understanding of driver behavior from vehicular kinematics is vital for safety-aware intelligent transportation systems. However, centralized cloud processing suffers from latency, scalability, and privacy issues. Federated Learning (FL) provides a decentralized alternative but faces two major challenges: (i) non-IID client data due to heterogeneous driving styles and sensors, and (ii) severe class imbalance, as risky behaviors are inherently rare. In this work, we propose a personalized FL framework that uses a shared CNN-LSTM backbone with client-adaptive classifiers and incorporates a cost-sensitive loss to address behavior skew. Evaluated on the UAH-DriveSet dataset, our method achieves 92.60% accuracy and 91.68% macro-F1, outperforming FL baselines
Heterogeneous Catalysis of Large Biomolecules: Insights from Platinum Particle Size in NAD+regeneration
No full textNicotinamide adenine dinucleotide (NAD+) cofactor regeneration is essential for enabling dehydrogenase-promoted biosynthesis for value-added chemicals. Heterogeneous catalytic cofactor regeneration, using supported metal catalysts, is an emerging approach and has shown great promise. However, mechanistic insight remains largely unexplored. In this work, a series of silica-supported platinum (Pt) catalysts have been prepared for NAD+ cofactor regeneration, to understand the roles of Pt particle size and structure. A turnover frequency (TOF) \u27volcano plot\u27 was obtained for Pt clusters in the range of 2.2–7.1 nm, with the maximum TOF (136 h−1) observed at 5.6 nm. Selective Pt site blockage with polyvinyl pyrrolidone (PVP) revealed that the significant structure sensitivity originated from the synergistic effect of under- and well-coordinated sites in size-varied Pt clusters. In addition, a facet preference was also identified, where the cofactor regeneration favored the Pt(100) surface more than Pt(111). These findings provide the first insight into NAD+ regeneration using heterogeneous Pt catalysts, which will be particularly useful for the rational design of supported metal catalysts
An Improved United-atom Potential for Molecular Dynamics Simulation of Saturated Properties of N-alkanes
No full textMultiple united-atom (UA) potential models have been developed in the literature to reproduce experimental saturated properties of n-alkanes using Monte Carlo simulations. When these UA potentials are employed in molecular dynamics (MD) simulations, MD simulations often give relatively poor predictions of saturated properties of n-alkanes, particularly the saturated vapor densities, due to the challenges in accurate calculation of long-range intermolecular forces beyond the cutoff distance in an inhomogeneous system. In this work, a new set of UA Lennard-Jones (LJ) interaction parameters for n-alkanes is proposed to reproduce the saturated properties, including saturated liquid and vapor densities (ρf and ρg); saturated vapor pressure (Psat); critical temperature, density, and pressure (Tcr, ρcr, and Pcr); surface tension (γ); latent heat of vaporization (hfg); and saturated liquid viscosity (η) of n-alkanes (C4-C22) using MD simulations with truncated LJ interactions. Compared to the experimental data of n-alkanes properties, the average absolute deviation of the MD simulation results obtained using the improved UA (I-UA) potential developed in this work are 1.6%, 2.3%, 2.8%, 0.3%, 2.7%, 4.3%, 4.4%, 2.1%, and 14.3% for ρf, ρg, Psat, Tcr, ρcr, Pcr, γ, hfg, and η, respectively. The Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) code for MD simulation of liquid-vapor equilibrium of n-dodecane using the I-UA potential is provided in this paper. The LAMMPS code can be easily modified to determine saturated properties of other n-alkanes
