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Coupled neutronics/thermal-hydraulic analysis of ANTS-100e using MCS/RAST-F two-step code system
No full textThe feasibility of using the Monte Carlo code MCS to generate multigroup cross sections for nodal diffusion simulations RAST-F of liquid metal fast reactors is investigated in this paper. The performance of the MCS/RAST-F code system is assessed using steady-state simulations of the ANTS-100e core. The results show good agreement between MCS/RAST-F and MCS reference solutions, with a k(eff) difference of less than 77 pcm and root-mean-square differences in radial and axial power of less than 0.5% and 0.25%, respectively. Furthermore, the MCS/RAST-F reactivity feedback coefficients are within three standard deviations of the MCS coefficients. To validate the internal thermal-hydraulic (TH) feedback capability in RAST-F code, the coupled neutronic/TH1D simulation of ANTS-100e is performed using the case matrix obtained from MCS branch calculations. The results are compared to those obtained using the MARS-LBE system code and show good agreement with relative temperature differences in fuel and coolant of less than 0.8%. This study demonstrates that the MCS/RAST-F code system can produce accurate results for core steady-state neutronic calculations and for coupled neutronic/TH simulations
Issues impeding the commercialization of laboratory innovations for energy-dense Si-containing lithium-ion batteries
No full textSilicon is a promising alternative to the conventional graphite anode in high-energy lithium-ion batteries owing to its high gravimetric capacity. However, intrinsic issues, such as severe volume expansion during cycling, have plagued the development of batteries that use Si anodes. While tremendous progress has been made in laboratories to tackle these issues, most Si-containing batteries in industry, in which Si anodes are made of Si suboxides or Si-C composites, can use only a very limited amount of Si. Here we review important factors that affect the practical energy density of Si-containing batteries, including electrode swelling and cut-off voltage in cell operation. We also discuss calendar life, safety and cost issues, which also have a strong influence on practical cell design. Furthermore, we propose testing protocols to evaluate the practical viability of newly developed Si anodes.,Substantial gaps exist between laboratory innovations and practical applications of Si-based batteries. Here the authors survey critical factors that hinder the development of practical Si-based anodes and propose testing protocols to evaluate laboratory innovations.
Evaluation of multi-RCM ensembles for simulating spatiotemporal variability of Asian summer monsoon precipitation in the CORDEX-East Asia Phase 2 domain
No full textFive regional climate models (RCMs)-CCLM, RegCM, HadGEM3-RA, SNURCM and WRF-participating in the Coordinated Regional Climate Downscaling Experiment-East Asia (CORDEX-EA) Phase 2 project are evaluated for their ability to simulate spatiotemporal variability in Asian summer precipitation. For this purpose, two dynamical downscaling sets, experiments forced by ERA-Interim reanalysis data (reproduction experiment) and historical data from three Coupled Model Intercomparison Project 5 (CMIP5) general circulation models (GCMs) (historical experiment) are analysed. The horizontal resolution of the downscaled results is 25 km, and the analysis period is from 1981 to 2005 (25 years). The RCMs show reasonable performance in simulating the spatial and temporal characteristics of summer precipitation in CORDEX-EA Phase 2 domain. To assess spatiotemporal patterns in Asian precipitation, cyclostationary empirical orthogonal function (CSEOF) analysis is used. In the first mode representing seasonal variations, the model ensemble results of both the reproduction experiment (Rep_ENS) and the historical experiment (His_ENS) simulate the peak times, location of precipitation and progression of the monsoons in Asia reasonably. Their features are greatly influenced by the moisture flux, indicating that the relation between precipitation and 850 hPa moisture flux is depicted well by RCM ensembles. In the second mode, which represents intraseasonal variations, the Rep_ENS depicts the western North Pacific summer monsoon break (WNPSM break) phenomenon similar to the observation. Although the His_ENS simulates the WNPSM break later than the observation, it does present the intraseasonal variation in the East Asian summer monsoon region. Based on these results, the five RCM ensemble results show the ability to capture spatiotemporal characteristics of summer precipitation in CORDEX-EA Phase 2 domain, as well as added value from dynamical downscaling
In-Situ Ionomer-Free Catalyst-Coated Membranes for Anion Exchange Membrane Water Electrolyzers
No full textDeveloping a state-of-the-art anion exchange membrane water electrolyzer (AEMWE) for commercial H-2 production remains a great challenge and is strongly dependent on the membrane electrode assembly (MEA). Herein, we report the first facile in-situ, ionomer-free catalyst-coated membrane (modified CCM; m-CCM) fabrication method that can apply to a variety of anion exchange membranes (AEMs). This novel m-CCM method allows for the synthesis and integration of a catalyst layer (CL) between the AEM and the gas diffusion layer without anion exchange ionomers. The AEMWE fabricated by the m-CCM method using a platinum group metal-free benchmark anode catalyst exhibited superior performance compared to AEMWEs assembled by the conventional MEA fabrication methods by reducing the interfacial resistance due to the intimate contact and maximizing the catalyst utilization and demonstrated an industrially relevant current density of 1 A cm(-2) at a moderate cell voltage of 1.79 V-cell and durability over 200 h in continuous electrolysis at 50 degrees C in 1 M KOH electrolyte. In addition, it shows the current density of 500 mA cm(-2) at a cell voltage of 1.913 V-cell and a low degradation rate of 0.58 mV h(-1) for 260 h in continuous electrolysis at a current density of 250 mA cm(-2) at 50 degrees C in feeding ultrapure water
Reservoir concatenation and the spectrum distribution of concatenated reservoir state matrices
No full textReservoir computing, one of the state-of-the-art machine learning architectures, processes time-series data generated by dynamical systems. Nevertheless, we have realized that reservoir computing with the conventional single-reservoir structure suffers from capacity saturation. This leads to performance stagnation in practice. Therefore, we propose an extended reservoir computing architecture called reservoir concatenation to further delay such stagnation. Not only do we provide training error analysis and test error comparison of reservoir concatenation, but we also propose a crucial measure, which is the trace associated with a reservoir state matrix, that explains the level of responsiveness to reservoir concatenation. Two reservoir dynamics are compared in detail, one by using the echo state network and the other by using a synchronization model called an explosive Kuramoto model. The distinct eigenvalue distributions of the reservoir state matrices from the two models are well reflected in the trace values that are shown to account for the different reservoir capacity behaviors, determining the different levels of responsiveness
Enrichment of Deleterious Mutated Genes Involved in Ciliary Function and Histone Modification in Brain Cancer Patient-Derived Xenograft Models
No full textPatient-derived xenograft (PDX) models, which can retain the characteristics of original tumors in an in vivo-mimicking environment, have been developed to identify better treatment options. However, although original tumors and xenograft tissues mostly share oncogenic mutations and global gene expression patterns, their detailed mutation profiles occasionally do not overlap, indicating that selection occurs in the xenograft environment. To understand this mutational alteration in xenografts, we established 13 PDX models derived from 11 brain tumor patients and confirmed their histopathological similarity. Surprisingly, only a limited number of somatic mutations were shared between the original tumor and xenograft tissue. By analyzing deleteriously mutated genes in tumors and xenografts, we found that previously reported brain tumor-related genes were enriched in PDX samples, demonstrating that xenografts are a valuable platform for studying brain tumors. Furthermore, mutated genes involved in cilium movement, microtubule depolymerization, and histone methylation were enriched in PDX samples compared with the original tumors. Even with the limitations of the heterogeneity of clinical lesions with a heterotropic model, our study demonstrates that PDX models can provide more information in genetic analysis using samples with high heterogeneity, such as brain tumors
Nickel-catalyzed ester carbonylation promoted by imidazole-derived carbenes and salts
No full textMillions of tons of acetyl derivatives such as acetic acid and acetic anhydride are produced each year. These building blocks of chemical industry are elaborated into esters, amides, and eventually polymer materials, pharmaceuticals, and other consumer products. Most acetyls are produced industrially using homogeneous precious metal catalysts, principally rhodium and iridium complexes. We report here that abundant nickel can be paired with imidazole-derived carbenes or the corresponding salts to catalyze methyl ester carbonylation with turnover frequency (TOF) exceeding 150 hour???1 and turnover number (TON) exceeding 1600, benchmarks that invite comparisons to state-of-the-art rhodium-based systems and considerably surpass known triphenylphosphine-based nickel catalysts, which operate with TOF ~7 hour???1 and TON ~100 under the same conditions