bluuebunny/crossref_metadata_2025_split huggingface dataset:
Correlation of traps inside XLPE and polypropylene with space charge dynamics under polarity reversal condition
Authors: Paramane Ashish , Chen Xiangrong , Dai Chao , Tanaka Yasuhiro 
Published: February 2021

AbstractPolypropylene (PP) is being considered as a suitable alternative to the cross‐linked polyethylene (XLPE) insulation as the latter is prone to the space charge accumulation when subjected to the voltage polarity reversals in line‐commutated converter high voltage direct current transmission. This novel contribution correlates the space charge accumulation with the trap distribution inside XLPE and PP under the polarity reversal condition. The pulse electro‐acoustic and surface potential decay methods are used to measure the space charge and trap distributions, respectively. These measurements are carried at different poling durations (1 and 6 h at each polarity) and cycles of voltage polarity reversal (one and three cycles) at the electric field of 60 kV/mm. The XLPE shows more homo and hetero charge accumulation than PP. Dominant shallow traps in the XLPE are responsible for the space charge accumulation, whereas deep traps with higher trap density inhibit space charge accumulation within the PP. Furthermore, the positive and negative threshold fields for the space charge accumulation are measured. It is observed that the space charge can be easily accumulated under the negative electric field. Interestingly, the space charge decays rapidly inside the XLPE with the increased number of polarity reversal cycle. A valid theoretical model is developed to explain the space charge accumulation inside the XLPE and PP. The field‐assisted ionization plays a key role in the space charge accumulation inside the XLPE.
Lifting scheme‐based matched wavelet design for effective characterisation of different types of voltage sag
Authors: Aggarwal Akanksha , Saini Manish Kumar 
Published: February 2021

AbstractThis study presents a novel scheme for designing biorthogonal wavelets matched to the voltage sag (VS) signals. Instead of using standard wavelets, matched wavelets designed in this study can extract more distinguishing features for better characterisation of sag signals, although this study proposes only the designing process of matched wavelets. The key method used for designing matched wavelets is the lifting scheme, which has never been reported in the literature for constructing matched wavelets for PQ signals. Besides using the lifting scheme, the proposed work preprocesses sag signals to make input signal of lifting scheme rich of sag‐related information. During pre‐processing, 1‐D sag signal is first converted to 2‐D form for capturing information of every small transition (which may be overlooked in 1‐D form) and then made 1‐D by ring projection to implement 1‐D lifting scheme. In this way, biorthogonal wavelets have been well matched to every type of VS signal collected through the experimental setup simulating different line faults, induction motor starting, transformer energisation and heavy load starting. Also, the characteristics of designed wavelets are evaluated in a MATLAB environment using frequency response and pole‐zero mapping in z‐plane. Higher PSNR values during signal reconstruction proved outperformance of newly designed matched wavelets.
Assessment of energy storage systems as a reserve provider in stochastic network constrained unit commitment
Authors: Habibi M. , Vahidinasab V. , Aghaei J. , Mohammadi‐Ivatloo B. 
Published: February 2021

AbstractRecently, the provision of the reserve from energy storage systems (ESSs) is introduced as a source for ancillary services to address the uncertainties of renewable power generations. The performance of ESSs is analysed while they are applied as a provider of regulation reserves. It has been revealed that previous stochastic models neglect the impact of corrective dispatches, related to the provision of regulation reserves, on the energy level stored in the ESSs, which can lead to large deviations. This study coordinates the stored energy of ESSs to be feasible regarding the dispatches in the base schedule and rescheduling within scenarios. Also, the wind speed fluctuations are considered as the source of uncertainty, and scenarios of wind energy are generated using the Weibull distribution function. The IEEE 24‐Bus standard test system is applied for the examination of the proposed model. The results show that the proposed model can manage the performance of ESSs in rescheduling within scenarios, while the coordinated reserve provision of ESSs can remove the concerns about insufficient stored energy of ESSs.
ESFR SMART PROJECT CONCEPTUAL DESIGN OF IN-VESSEL CORE CATCHER
Authors: Guidez Joel , Gerschenfeld Antoine , Bodi Janos , Mikityuk Konstantin , Alvarez-Velarde Francisco , Romojaro Pablo , Diaz-Chiron U. 
Published: February 2021

Even before Fukushima accident occurred, the safety authorities have required that new power plant designs must take into account beyond design-basis accidents including possible core meltdown. Among the mitigation strategies, the corium retention must be ensured, so a core catcher is implemented in the design of the Generation IV Sodium-cooled Fast Reactor. An internal core catcher within the vessel (in-vessel retention) is the option chosen for the European Sodium-cooled Fast Reactor investigated in the H2020 ESFR-SMART project.
The new core investigated in ESFR SMART with lower void effect has a better behavior in case of severe accident. The use of passive control rods is also an improvement for prevention of severe accident. Moreover, we have in the ESFR SMART core dedicated tubes for corium discharge that should allow discharging quickly the melted materials and should help to prevent large criticality. Calculations show that after several seconds, these discharge tubes begin to open, and the corium arrives by this preferential way on the core catcher, quicker and in limited quantities at the beginning of the accident.
However, the core catcher is designed to be able to retain the whole core meltdown. Its design allows good possibilities of cooling by natural convection of sodium. Some thermal calculations were provided with a multi-layer concept but the global mechanical conception seems difficult. So a one layer core catcher in molybdenum, material compatible with sodium and used on the core catcher of the last SFR, started in 2016: BN 800, is investigated. Explanations are given on the choice of this material proposed for the catcher and used for thermal calculations.
With the proposed design, the corium is spread on the core catcher and the residual power of the corium can be dispelled by natural convection by the sodium circulating around and above the core catcher without boiling of sodium if the melted core is less than about 25% of whole core. In case of bigger quantities of melted core, boiling of sodium could appear under the core catcher. Further less conservative calculations would be necessary to better know the limit.
EVALUATION OF THE ESFR END OF CYCLE STATE AND DETAILED ANALYSIS OF SPATIAL DISTRIBUTIONS OF REACTIVITY COEFFICIENTS
Authors: Davies Una , Margulis Marat , Shwageraus Eugene , Fridman Emil , Garcia-Herranz Nuria , Antonio Jimenez-Carrascosa , Oscar Cabellos , Robbie Gregg , Jiri Krepel 
Published: February 2021

The ESFR-SMART project is the latest iteration of research into the behaviour of a commercial-size SFR core throughout its lifetime. As part of this project the ESFR core has been modelled by a range of different reactor physics simulation codes at its end of cycle state, and the important safety relevant parameters evaluated. These parameters are found to agree well between the different codes, giving good confidence in the results.
A detailed mapping of the local sodium void worth is also performed due to the problems associated with the positive void coefficient seen in large SFR designs. The local void worth maps show that the use of zone-wise coefficients replicates the important reactivity feedbacks to a high degree, indicating their suitability for use in SFR simulations.
QUALIFICATION OF ANC9 GENERIC INSERT METHODOLOGY (GIM)
Authors: Zhang Baocheng , Ivanov Boyan D. , Hoskins Kevin , Huria Harish , Rebello Andre Luiz Pereira 
Published: February 2021

Discrete burnable poisons like the Wet Annular Burnable Absorber and Pyrex have been used in PWR core to improve core power distribution and provide more negative moderator temperature coefficient. The burnable absorber in the burnable poison rods burns fast and is completely gone after one cycle exposure in the core. Traditionally, the burnable poison rods are designed to be part of the fuel assembly. They are burned together with the fuel in the first loading cycle and discharged after one cycle. In recent years, different insertion scenarios of the burnable poison rods have been introduced in the PWR plants operation to improve the fuel performance, for instance, fresh burnable poison rods are inserted into a burned assembly; burned burnable poison rods stay in the original assembly or are replaced in a different assembly.
A Generic Insert Methodology [1] was developed in Westinghouse and implemented in NEXUS/ANC9 code system. With this new methodology, ANC9 is able to follow the assembly history and model all types of absorber insert components for all kinds of insertion scenarios.
An extensive methods validation and qualification effort has been completed by modeling different insertion cases. This paper provides details of the qualification cases along with the analysis of the results.
A SIMPLIFIED SMAHTR BENCHMARK PROBLEM SET
Authors: Reed K. Lisa , Rahnema Farzad 
Published: February 2021

The Small, Modular Advanced High Temperature Reactor (SmAHTR) is a preconceptual design for a fluoride salt-cooled small modular reactor (SMR) [1]. In this paper, a stylized 2D benchmark problem set has been created based on SmAHTR. Certain gaps and considerations in burnable poison and control rod content were unspecified/undetermined in the preconceptual design, but those gaps were filled for the stylized problem set. With those features, this problem set could then be used for benchmarking neutron transport methods as well as its low order methods in 2D single assembly and full core configurations.
For this benchmark set, continuous energy Monte Carlo calculations were performed. Those calculations provided keff values of 0.9459 (± 11 pcm) and 1.1436 (± 12 pcm) in the full core configuration with all the control rods fully inserted and withdrawn, respectively. The single assembly calculations yielded an eigenvalue, kinf, of 0.9987 (± 15 pcm) and 1.2117 (± 15 pcm) with all of the control rods either inserted or removed, respectively. In the full core configuration, the worth of all the control rods and burnable poison particles were determined to be 197.6 (± 0.16) mk and 311.6 (± 0.23) mk, respectively. The corresponding results in the single assembly configurations are 213 (± 0.21) mk and 337.4 (± 0.20) mk, respectively. A near-critical configuration was also determined for the reactor by inserting control rods in some assemblies, thus providing a case with a keff value of 0.9909 (± 12 pcm).
NEXUS FRAMEWORK FOR WHOLE-CORE FUEL PERFORMANCE: CURRENT APPLICATIONS AND FUTURE TRENDS
Authors: Peakman Aiden , Bennett Thomas , Fitzgerald Kerr , Gregg Robert , Rossiter Glyn 
Published: February 2021

Current industry practice in fuel licensing often relies on thermo-mechanical modeling of a fuel rod with an artificially constructed bounding power history. The benefit of this approach is that it is computationally efficient; however, the drawbacks are that 1) such an approach is not always conservative, for instance when modelling phenomena related to late onset pellet-clad gap closure; and 2) it can poorly estimate available safety margins for fuel operating at high local power densities and/or to high burnup. For these reasons NNL developed an in-house whole-core fuel performance framework – NEXUS – to enable modelling of all fuel rods in the core using the ENIGMA fuel performance code and computed power histories from core simulation packages (currently limited to PARCS or SIMULATE). One of the main objectives was to create a tool that was both computationally efficient and user friendly. The former was achieved by making use of parallelisable architecture, while the latter was achieved by minimising necessary user input and providing tools for easy interrogation of the fuel performance output.
NEXUS has been applied to several LWR operational scenarios, which we summarise in this paper, including steady-state operation of an ABWR, and a rod ejection accident in a small modular soluble boron free PWR and a GWe-class PWR. We also summarise current development activities related to integrating NNL’s in-house fuel performance Monte Carlo uncertainty analysis software CASINO into the NEXUS framework.
A PRACTICAL EFFECT OF THE RECENT O16 CROSS SECTION AND MUBAR UNCERTAINTIES
Authors: Parsons D. Kent , Turner Scott A. , Jaegers Peter J. 
Published: February 2021

With the recent release of ENDF/B VIII.0 data, additional covariance data was provided for many isotopes, including O16. The detail of elastic scattering and mubar covariance data for O16 increased dramatically between ENDF/B VII.1 and ENDF/B VIII.0. This new covariance data has been processed with NJOY2016 and investigation has begun on the effects of these new uncertainty data. The uncertainties are applied to multi-group scattering cross sections and P1 Legendre components in deterministic neutron transport.
A simple but typical application of shielding fission neutrons with concrete has been used to assess the practical effects of the new covariance data for O16. A somewhat surprising result is that the mubar uncertainty can have a significant effect on the calculated shielding and criticality results.
ANSWERS® TOOLS FOR UNCERTAINTY QUANTIFICATION AND VALIDATION
Authors: Smith Paul N , Hanlon Dave , Dobson Geoff , Hiles Richard , Fry Tim , Stefanowska Magda , Richards Simon , Murphy Christophe 
Published: February 2021

ANSWERS® is developing a set of uncertainty quantification (UQ) tools for use with its major physics codes: WIMS/PANTHER (reactor physics), MONK (criticality and reactor physics) and MCBEND (shielding and dosimetry). The Visual Workshop integrated development environment allows the user to construct and edit code inputs, launch calculations, post-process results and produce graphs, and recently uncertainty quantification and optimisation tools have been added.
Prior uncertainties due to uncertainties in nuclear data or manufacturing tolerances can be estimated using the sampling method or using the sensitivity options in the physics codes combined with appropriate covariance matrices. To aid the user in the choice of appropriate validation experiments, the MONK categorisation scheme and/or a similarity index can be used. An interactive viewer has been developed which allows the user to search through, and browse details of, over 2,000 MONK validation experiments that have been analysed from the ICSBEP and IRPhE validation sets. A Bayesian updating approach is used to assimilate the measured data with the calculated results. It is shown how this process can be used to reduce bias in calculated results and reduce the calculated uncertainty on those results. This process is illustrated by application to a PWR fuel assembly.
LOW TEMPERATURE EFFECTS ON PWR FUEL ASSEMBLY CRITICALITY CALCULATIONS
Authors: Behler Matthias , Hannstein Volker , Sommer Fabian 
Published: February 2021

One of the parameters affecting the neutron multiplication factor keff of a system containing fissile material is the system temperature. Therefore, the effect of temperature on criticality safety analyses is an area of international interest. In this context, the Working Party on Nuclear Criticality Safety (WPNCS) of the OECD Nuclear Energy Agency (NEA) formed a subgroup to define and execute a code-to-code comparison benchmark to investigate the effect of temperature on keff for PWR fuel assemblies. Two configurations of a generic water-moderated PWR fuel assembly were analysed at different temperatures between 233 K and 588 K, and with different assembly burnups. Based on this benchmark, GRS performed an additional study to investigate the impact of the moderator densities, the neutron reaction cross sections and the thermal scattering data on keff separately.
The benchmark results show the expected decrease of keff with temperature and a considerable jump in keff at the phase transition of the moderator. The additional investigation demonstrates that the jump in keff is mainly caused by the change of the moderator density due to the phase transition. The change of the thermal scattering data due to the phase transitions leads to a similar but smaller jump in keff. Furthermore, the actual impact of the different parameters on keff depend strongly on the considered fuel assembly configuration.
On the evolutionary origins of host–microbe associations
Authors: Sieber Michael , Traulsen Arne , Schulenburg Hinrich , Douglas Angela E. 
Published: February 2021

Significance
Animals can provide benefits to their associated microbes—and these can, in turn, positively affect their hosts. But how do such mutually beneficial associations arise in the first place? In particular, when animal and microbe initially have independent lifestyles, this is not clear. By developing a model of animal and microbial life cycles on patchy habitats, we show how their overlapping ecologies of development and dispersal can lead to the enrichment of certain microbes in the dispersing animals, even in the absence of specific mutualistic benefits. This enrichment can then set the stage for the evolution of more specific host–microbe associations, which also implies that host enrichment per se is not an indicator of a beneficial host–microbe symbiosis.
Risk of tipping the overturning circulation due to increasing rates of ice melt
Authors: Lohmann Johannes , Ditlevsen Peter D. 
Published: February 2021

Significance
Ongoing greenhouse gas emissions put elements of the Earth system at risk for crossing critical thresholds (tipping points), leading to abrupt irreversible climate change. Measures for reducing emissions should keep Earth in the safe operating space away from tipping points. Here we show that increasing rates of change of ice melt can induce a collapse of the Atlantic Meridional Overturning Circulation in a global ocean model, while no critical threshold in ice melt is crossed and slower increases to the same level of ice melt do not induce tipping. Moreover, the chaotic dynamics of the climate make such a collapse hard to predict. This shows that the safe operating space of the Earth system might be smaller than previously thought.
Deep time diversity and the early radiations of birds
Authors: Yu Yilun , Zhang Chi , Xu Xing 
Published: February 2021

Significance
Our lineage diversification rate through time analyses of three supertrees combining the published phylogenies of both stem and crown group birds reveal three distinct large-scale increases in the diversification rate across bird evolutionary history. The first two increases also are associated with rapid morphological evolution pertaining to the locomotory and cranial systems, respectively. The third increase needs further support from morphological data. Our study demonstrates that the bird biodiversity evolution was influenced mainly by long-term climatic changes and also by the Cretaceous–Paleogene extinction.
Glucagon blockade restores functional β-cell mass in type 1 diabetic mice and enhances function of human islets
Authors: Wang May-Yun , Dean E. Danielle , Quittner-Strom Ezekiel , Zhu Yi , Chowdhury Kamrul H. , Zhang Zhuzhen , Zhao Shangang , Li Na , Ye Reshing , Lee Young , Zhang Yiyi , Chen Shiuhwei , Yu Xinxin , Leonard Derek C. , Poffenberger Greg , Von Deylen Alison , McCorkle S. Kay , Schlegel Amnon , Sloop Kyle W. , Efanov Alexander M. , Gimeno Ruth E. , Scherer Philipp E. , Powers Alvin C. , Unger Roger H. , Holland William L. 
Published: February 2021

Significance
Both type 1 and type 2 diabetes are associated with reduced β-cell mass or function, resulting from decreased proliferation and increased apoptosis. Understanding the signals governing β-cell survival and regeneration is critical for developing strategies to maintain healthy populations of these cells in individuals. Both forms of diabetes are associated with hyperglucagonemia and an increased plasma glucagon:insulin ratio. Glucagon excess contributes to metabolic dysregulation of the diabetic state and glucagon receptor antagonism is a potential target area for the treatment and prevention of diabetes. Our studies presented here suggest that blockade of glucagon signaling lowers glycemia in mouse models of type 1 diabetes while enhancing formation of functional β-cell mass and production of insulin-positive cells from α-cell precursors.
Compartmentalization of phosphatidylinositol 4,5-bisphosphate metabolism into plasma membrane liquid-ordered/raft domains
Authors: Myeong Jongyun , Park Cheon-Gyu , Suh Byung-Chang , Hille Bertil 
Published: February 2021

Significance
Lipids of bilayer membranes can segregate laterally into distinct liquid phases of different composition called liquid ordered and liquid disordered, and corresponding in the plasma membrane of living cells to nanodomains called raft and nonraft domains. Using Förster resonance energy transfer and genetically expressible protein probes of lipid domains, we find that several steps of the metabolism of phosphoinositide lipids are concentrated in cholesterol-rich liquid-ordered domains of the plasma membrane. The receptor-mediated breakdown and the restoration of major phosphoinositide pools are faster in the liquid-ordered than in the liquid-disordered domains. Thus, the ordered domains host a key lipid signaling system of the cell.
The Role of Overdose Reversal Training in Knowing where to Get Naloxone: Implications for Improving Naloxone access among People who use Drugs
Authors: Schneider Kristin E. , Dayton Lauren , Winiker Abigail K. , Tobin Karin E. , Latkin Carl A. 
Published: February 2021

Background Naloxone distribution and training programs have been implemented to combat the opioid overdose crisis. While many individuals are trained, ongoing naloxone access is not ensured by these programs. We explored whether people who use drugs (PWUD) in Baltimore City, Maryland could identify a location where they would go to obtain naloxone and how training changed where they would be willing to access naloxone. Methods We surveyed 574 PWUD as to whether they had heard of, been trained to use, and knew where to get naloxone. Among participants who had heard of naloxone, we tested for differences in knowing where to get naloxone by training. Results The majority (95.3%) had heard of naloxone. Of these, 84.0% could name a location where they would access naloxone, but only 11.7% named multiple. Pharmacies (32.3%) and medical providers (excluding drug treatment providers) (22.9%) were the most commonly identified sources. Participants who had been trained to use naloxone were more likely to report that they would obtain naloxone from the needle exchange and were less likely to report they did not know where they would go to get it or that they would go to a medical provider (excluding drug treatment providers) for naloxone. Conclusions Naloxone training was associated with participants’ ability to name a location where they would obtain naloxone. Medicalized sources of naloxone remained the most commonly reported. These sources, however, may be associated with significant barriers to access, such as cost. Trainings should provide comprehensive education about low-cost/free sources to ensure ongoing naloxone access among people who use drugs.