scholarly journals possis: predicting spectra, light curves, and polarization for multidimensional models of supernovae and kilonovae

2019 ◽  
Vol 489 (4) ◽  
pp. 5037-5045 ◽  
Author(s):  
M Bulla
Keyword(s):  
Radiation Transport ◽  
Three Dimensional ◽  
Polar Axis ◽  
Light Curves ◽  
Time Dependent ◽  
Opening Angle ◽  
Monte Carlo Code ◽  
Lanthanide Elements ◽  
The Impact ◽  
Multidimensional Models

ABSTRACT We present possis, a time-dependent three-dimensional Monte Carlo code for modelling radiation transport in supernovae and kilonovae. The code incorporates wavelength- and time-dependent opacities, and predicts viewing-angle dependent spectra, light curves, and polarization for both idealized and hydrodynamical explosion models. We apply the code to a kilonova model with two distinct ejecta components, one including lanthanide elements with relatively high opacities and the other devoid of lanthanides and characterized by lower opacities. We find that a model with total ejecta mass $M_\mathrm{ej}=0.04\, \mathrm{M}_\odot$ and half-opening angle of the lanthanide-rich component Φ = 30° provides a good match to GW 170817/AT 2017gfo for orientations near the polar axis (i.e. for a system viewed close to face-on). We then show how crucial is the use of self-consistent multidimensional models in place of combining one-dimensional models to infer important parameters, such as the ejecta masses. We finally explore the impact of Mej and Φ on the synthetic observables and highlight how the relatively fast computation times of possis make it well-suited to perform parameter-space studies and extract key properties of supernovae and kilonovae. Spectra calculated with possis in this and future studies will be made publicly available.

scholarly journals NEUTRON NOISE PATTERNS FROM COUPLED FUEL-ASSEMBLY VIBRATIONS

2021 ◽  
Vol 247 ◽  
pp. 02015
Author(s):  
M. Viebach ◽  
C. Lange ◽  
M. Seidl ◽  
Y. Bilodid ◽  
A. Hurtado
Keyword(s):  
Neutron Flux ◽  
Fuel Assembly ◽  
Cross Sections ◽  
Three Dimensional ◽  
Time Dependent ◽  
Radial Dependence ◽  
Feedback Parameter ◽  
Fuel Assemblies ◽  
Neutron Noise ◽  
The Impact

The neutron flux fluctuation magnitude of KWU-built PWRs shows a hitherto unexplained correlation with the types of loaded fuel assemblies. Also, certain measured long-range neutron flux fluctuation patterns in neighboring core quadrants still lack a closed understanding of their origin. The explanation of these phenomena has recently revived a new interest in neutron noise research. The contribution at hand investigates the idea that a synchronized coolant-driven vibration of major parts of the fuel-assembly ensemble leads to these phenomena. Starting with an assumed mode of such collective vibration, the resulting effects on the time-dependent neutron-flux distribution are analyzed via a DYN3D simulation. A three-dimensional representation of the time-dependent bow of all fuel assemblies is taken into account as a nodal DYN3D feedback parameter by time-dependent variations of the fuel-assembly pitch. The impact of its variation on the cross sections is quantified using a cross-section library that is generated from the output of corresponding CASMO5 calculations. The DYN3D simulation qualitatively reproduces the measured neutron-flux fluctuation patterns. The magnitude of the fluctuations and its radial dependence are comparable to the measured details. The results imply that collective fuel-assembly vibrations are a promising candidate for being the key to understand long-known fluctuation patterns in KWU built PWRs. Further research should elaborate on possible excitation mechanisms of the assumed vibration modes.

Neutron Generation Based Method for Monte Carlo Three-Dimensional Reactor Time-Dependent Simulation

2012 ◽  
Author(s):  
Qi Xu ◽  
Ganglin Yu ◽  
Kan Wang
Keyword(s):  
Monte Carlo ◽  
Dynamic Analysis ◽  
Three Dimensional ◽  
Simulation Method ◽  
Time Dependent ◽  
New Method ◽  
Monte Carlo Code ◽  
Neutron Generation ◽  
Direct Simulation ◽  
Reactor Dynamic

A novel Monte Carlo time-dependent simulation method, named neutron generation based method (NGBM), is proposed for three-dimensional reactor dynamic analysis. Different from the traditional direct simulation method (DSM) based on neutron history, the new method, originating from the process of Monte Carlo criticality calculation, is based on neutron generation. In order to turn the original static calculation into a dynamic one, the time mark and time-dependent flux tally are added, the weight of neutron is adjusted while accumulating the flux estimator and the criteria for ending simulation is set. This new method is of higher computing efficiency than the direct simulation method for super-critical time-dependent situation, because it is able to take the advantage of Monte Carlo criticality calculation to keep the number of neutrons per generation approximately constant while the direct simulation method cannot stop the exponential increase of neutron population. The new method was integrated into RMC (Reactor Monte Carlo code developed by Tsinghua University). A numerical experiment was performed. The results demonstrate the feasibility and accuracy of the neutron generation based method for reactor dynamic analysis. The relative deviation of the time-dependent neutron flux tells that the accuracy of the neutron generation based method is enough for routine reactor safety analysis. And the experiment also shows the high efficiency of this method for super-critical reactor systems, since in the experiment, RMC runs nearly 7 times faster than MCNP which uses the direct simulation method.

scholarly journals Modeling optical and UV polarization of AGNs

2018 ◽  
Vol 615 ◽  
pp. A171 ◽  
Author(s):  
F. Marin
Keyword(s):  
Spectral Energy Distribution ◽  
Three Dimensional ◽  
Spectral Energy ◽  
Opening Angle ◽  
High Angular Resolution ◽  
Analysis Tool ◽  
Monte Carlo Code ◽  
Host Galaxies ◽  
Ngc 1068 ◽  
Radiative Transfer Modeling

Context. One of the main challenges for polarimetric observations of active galactic nuclei (AGN) is to properly estimate the amount of parasitic light that contaminates the polarization signal. Removing this unpolarized flux is a complex task that has only been achieved in a couple of objects. Aims. In this fifth paper of the series, we present a new version of the Monte Carlo code STOKES that accounts for dilution by interstellar polarization and host starlight in radiative transfer modeling. Methods. We upgraded our code by including spectral energy distribution (SED) templates for a set of representative host galaxies. The unpolarized light emitted by those hosts alters the observer polarization while being coherently radiatively coupled to the AGN structure. We also included in our analysis tool a routine that may add, depending on the user’s objectives, an interstellar component. Results. Using a generic AGN model, we illustrate how interstellar polarization and starlight dilution impact the observed polarimetric signal of AGN. We applied our code to NGC 1068, an archetypal edge-on AGN and demonstrate that STOKES can reproduce its SED, the expected wavelength-dependent polarimetric signatures, and the observed high-angular resolution polarimetric maps. Using the flexibility of the code, we derived several intrinsic parameters such as the system inclination and the torus opening angle. Conclusions. The new version of our publicly available code now allows observers to better prepare their observations, interpret their data and simulate the three-dimensional geometry and physics of AGN in order to probe unresolved structures. Additionally, the radiative interaction between the host and the AGN can be used to probe the co-evolution of the system.

Top-of-atmosphere albedo bias from neglecting three-dimensional cloud radiative effects

2021 ◽  
Author(s):  
Clare E. Singer ◽  
Ignacio Lopez-Gomez ◽  
Xiyue Zhang ◽  
Tapio Schneider
Keyword(s):  
Radiative Transfer ◽  
Zenith Angle ◽  
Solar Zenith Angle ◽  
3D Structure ◽  
Three Dimensional ◽  
Radiative Flux ◽  
Monte Carlo Code ◽  
Radiative Effects ◽  
Cloud Radiative Effects ◽  
The Impact

AbstractClouds cover on average nearly 70% of Earth’s surface and regulate the global albedo. The magnitude of the shortwave reflection by clouds depends on their location, optical properties, and three-dimensional (3D) structure. Due to computational limitations, Earth system models are unable to perform 3D radiative transfer calculations. Instead they make assumptions, including the independent column approximation (ICA), that neglect effects of 3D cloud morphology on albedo. We show how the resulting radiative flux bias (ICA-3D) depends on cloud morphology and solar zenith angle. We use high-resolution (20–100 m horizontal resolution) large-eddy simulations to produce realistic 3D cloud fields covering three dominant regimes of low-latitude clouds: shallow cumulus, marine stratocumulus, and deep convective cumulonimbus. A Monte Carlo code is used to run 3D and ICA broadband radiative transfer calculations; we calculate the top-of-atmosphere (TOA) reflected flux and surface irradiance biases as functions of solar zenith angle for these three cloud regimes. Finally, we use satellite observations of cloud water path (CWP) climatology, and the robust correlation between CWP and TOA flux bias in our LES sample, to roughly estimate the impact of neglecting 3D cloud radiative effects on a global scale. We find that the flux bias is largest at small zenith angles and for deeper clouds, while the albedo bias is most prominent for large zenith angles. In the tropics, the annual-mean shortwave radiative flux bias is estimated to be 3.1±1.6 W m−2, reaching as much as 6.5 W m−2 locally.

scholarly journals The impact of aerosols on polarized sky radiance: model development, validation, and applications

2010 ◽  
Vol 10 (2) ◽  
pp. 383-396 ◽  
Author(s):  
C. Emde ◽  
R. Buras ◽  
B. Mayer ◽  
M. Blumthaler
Keyword(s):  
Monte Carlo ◽  
Polarization State ◽  
Model Development ◽  
Three Dimensional ◽  
High Sensitivity ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Monte Carlo Code ◽  
The Impact ◽  
Good Agreement

Abstract. Although solar radiation initially is unpolarized when entering the Earth's atmosphere, it is polarized by scattering processes with molecules, water droplets, ice crystals, and aerosols. Hence, measurements of the polarization state of radiation can be used to improve remote sensing of aerosols and clouds. The analysis of polarized radiance measurements requires an accurate radiative transfer model. To this end, a new efficient and flexible three-dimensional Monte Carlo code to compute polarized radiances has been developed and implemented into MYSTIC (Monte Carlo code for the phYSically correct Tracing of photons In Cloudy atmospheres). The code has been extensively validated against published benchmark results. The polarized downwelling radiation field is calculated for various aerosol types showing the high sensitivity of polarized ultraviolet radiances to the particle microphysics. Model simulations are compared to ground based measurements and found to be qualitatively in good agreement. Quantitative differences can be attributed to the assumed aerosol models based on the OPAC aerosol database, which does not include exactly the types of aerosols that have been observed. This comparison to the measurements shows that there is a high potential to retrieve information about the aerosol type from polarized radiance measurements.

Analyzing the Impact of X-Ray Tomography on the Reliability of Integrated Circuits

2015 ◽  
Author(s):  
Halit Dogan ◽  
Md Mahbub Alam ◽  
Navid Asadizanjani ◽  
Sina Shahbazmohamadi ◽  
Domenic Forte ◽  
...  
Keyword(s):  
Integrated Circuits ◽  
Integrated Circuit ◽  
3D Imaging ◽  
Three Dimensional ◽  
Serial Sectioning ◽  
Promising Technique ◽  
Flash Memories ◽  
X Ray ◽  
3D Information ◽  
The Impact

Abstract X-ray tomography is a promising technique that can provide micron level, internal structure, and three dimensional (3D) information of an integrated circuit (IC) component without the need for serial sectioning or decapsulation. This is especially useful for counterfeit IC detection as demonstrated by recent work. Although the components remain physically intact during tomography, the effect of radiation on the electrical functionality is not yet fully investigated. In this paper we analyze the impact of X-ray tomography on the reliability of ICs with different fabrication technologies. We perform a 3D imaging using an advanced X-ray machine on Intel flash memories, Macronix flash memories, Xilinx Spartan 3 and Spartan 6 FPGAs. Electrical functionalities are then tested in a systematic procedure after each round of tomography to estimate the impact of X-ray on Flash erase time, read margin, and program operation, and the frequencies of ring oscillators in the FPGAs. A major finding is that erase times for flash memories of older technology are significantly degraded when exposed to tomography, eventually resulting in failure. However, the flash and Xilinx FPGAs of newer technologies seem less sensitive to tomography, as only minor degradations are observed. Further, we did not identify permanent failures for any chips in the time needed to perform tomography for counterfeit detection (approximately 2 hours).

The impact of statin therapy after surgical or endovascular treatment of cerebral aneurysms

2020 ◽  
Vol 133 (1) ◽  
pp. 182-189
Author(s):  
Tae-Jin Song ◽  
Seung-Hun Oh ◽  
Jinkwon Kim
Keyword(s):  
Statin Therapy ◽  
Coil Embolization ◽  
Primary Outcome ◽  
Cox Regression ◽  
Cerebral Aneurysms ◽  
Time Dependent ◽  
Lipid Lowering ◽  
Surgical Clipping ◽  
The Impact

OBJECTIVECerebral aneurysms represent the most common cause of spontaneous subarachnoid hemorrhage. Statins are lipid-lowering agents that may expert multiple pleiotropic vascular protective effects. The authors hypothesized that statin therapy after coil embolization or surgical clipping of cerebral aneurysms might improve clinical outcomes.METHODSThis was a retrospective cohort study using the National Health Insurance Service–National Sample Cohort Database in Korea. Patients who underwent coil embolization or surgical clipping for cerebral aneurysm between 2002 and 2013 were included. Based on prescription claims, the authors calculated the proportion of days covered (PDC) by statins during follow-up as a marker of statin therapy. The primary outcome was a composite of the development of stroke, myocardial infarction, and all-cause death. Multivariate time-dependent Cox regression analyses were performed.RESULTSA total of 1381 patients who underwent coil embolization (n = 542) or surgical clipping (n = 839) of cerebral aneurysms were included in this study. During the mean (± SD) follow-up period of 3.83 ± 3.35 years, 335 (24.3%) patients experienced the primary outcome. Adjustments were performed for sex, age (as a continuous variable), treatment modality, aneurysm rupture status (ruptured or unruptured aneurysm), hypertension, diabetes mellitus, household income level, and prior history of ischemic stroke or intracerebral hemorrhage as time-independent variables and statin therapy during follow-up as a time-dependent variable. Consistent statin therapy (PDC > 80%) was significantly associated with a lower risk of the primary outcome (adjusted hazard ratio 0.34, 95% CI 0.14–0.85).CONCLUSIONSConsistent statin therapy was significantly associated with better prognosis after coil embolization or surgical clipping of cerebral aneurysms.

COVID-19: Time-Dependent Effective Reproduction Number and Sub-notification Effect Estimation Modeling (Preprint)

2020 ◽  
Author(s):  
Eduardo Atem De Carvalho ◽  
Rogerio Atem De Carvalho
Keyword(s):  
New York ◽  
Reproduction Number ◽  
Moving Average ◽  
Real Data ◽  
Time Dependent ◽  
Initial Value ◽  
Health Authorities ◽  
Reproduction Numbers ◽  
Effect Estimation ◽  
The Impact

BACKGROUND Since the beginning of the COVID-19 pandemic, researchers and health authorities have sought to identify the different parameters that govern their infection and death cycles, in order to be able to make better decisions. In particular, a series of reproduction number estimation models have been presented, with different practical results. OBJECTIVE This article aims to present an effective and efficient model for estimating the Reproduction Number and to discuss the impacts of sub-notification on these calculations. METHODS The concept of Moving Average Method with Initial value (MAMI) is used, as well as a model for Rt, the Reproduction Number, is derived from experimental data. The models are applied to real data and their performance is presented. RESULTS Analyses on Rt and sub-notification effects for Germany, Italy, Sweden, United Kingdom, South Korea, and the State of New York are presented to show the performance of the methods here introduced. CONCLUSIONS We show that, with relatively simple mathematical tools, it is possible to obtain reliable values for time-dependent, incubation period-independent Reproduction Numbers (Rt). We also demonstrate that the impact of sub-notification is relatively low, after the initial phase of the epidemic cycle has passed.

scholarly journals Numerical simulation of the impact of an integrated renovation project on the Maowei Sea hydrodynamic environment

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Cui Wang ◽  
Ling Cai ◽  
Yaojian Wu ◽  
Yurong Ouyang
Keyword(s):  
Water Exchange ◽  
Land Reclamation ◽  
Three Dimensional ◽  
Exchange Capacity ◽  
Reclamation Project ◽  
Hydrodynamic Environment ◽  
Sea Area ◽  
Water Quality Models ◽  
The Impact ◽  
Main Factor

AbstractIntegrated renovation projects are important for marine ecological environment protection. Three-dimensional hydrodynamics and water quality models are developed for the Maowei Sea to assess the hydrodynamic environment base on the MIKE3 software with high resolution meshes. The results showed that the flow velocity changed minimally after the project, decreasing by approximately 0.12 m/s in the east of the Maowei Sea area and increasing by approximately 0.01 m/s in the northeast of the Shajing Port. The decrease in tidal prism (~ 2.66 × 106 m3) was attributed to land reclamation, and accounted for just 0.86% of the pre-project level. The water exchange half-life increased by approximately 1 day, implying a slightly reduced water exchange capacity. Siltation occurred mainly in the reclamation and dredging areas, amounting to back-silting of approximately 2 cm/year. Reclamation project is the main factor causing the decrease of tidal volume and weakening the hydrodynamics in Maowei Sea. Adaptive management is necessary for such a comprehensive regulation project. According to the result, we suggest that reclamation works should strictly prohibit and dredging schemes should optimize in the subsequent regulation works.

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