scholarly journals Exosphere Modeling of Proxima b: A Case Study of Photochemical Escape with a Venus-like Atmosphere

2021 ◽  
Vol 923 (2) ◽  
pp. 190
Author(s):  
Yuni Lee ◽  
Chuanfei Dong ◽  
Valeriy Tenishev
Keyword(s):  
Dynamic Pressure ◽  
Dissociative Recombination ◽  
Monte Carlo Code ◽  
M Dwarfs ◽  
Habitable Zones ◽  
Order Of Magnitude ◽  
Global Magnetic Field ◽  
Corona Structure ◽  
Hot Oxygen

Abstract Exoplanets orbiting M dwarfs within habitable zones are exposed to stellar environments more extreme than that terrestrial planets experience in our solar system, which can significantly impact the atmospheres of the exoplanets and affect their habitability and sustainability. This study provides the first prediction of hot oxygen corona structure and the associated photochemical loss from a 1 bar CO2-dominated atmosphere of a Venus-like rocky exoplanet, where dissociative recombination of O2 + ions is assumed to be the major source reaction for the escape of neutral O atoms and formation of the hot O corona (or exospheres) as on Mars and Venus. We employ a 3D Monte Carlo code to simulate the exosphere of Proxima Centauri b (PCb) based on the ionosphere simulated by a 3D magnetohydrodynamic model. Our simulation results show that variability of the stellar wind dynamic pressure over one orbital period of PCb does not affect the overall spatial structure of the hot O corona but contributes to the change in the global hot O escape rate that varies by an order of magnitude. The escape increases dramatically when the planet possesses its intrinsic magnetic fields as the ionosphere becomes more extended with the presence of a global magnetic field. The extended hot O corona may lead to a more extended H exosphere through collisions between thermal H and hot O, which exemplifies the importance of considering nonthermal populations in exospheres to interpret future observations.

scholarly journals Early Evaluation of Copper Radioisotope Production at ISOLPHARM

Molecules ◽  
2018 ◽  
Vol 23 (10) ◽  
pp. 2437 ◽  
Author(s):  
Francesca Borgna ◽  
Michele Ballan ◽  
Chiara Favaretto ◽  
Marco Verona ◽  
Marianna Tosato ◽  
...  
Keyword(s):  
Nuclear Physics ◽  
Specific Activity ◽  
Isotope Separation ◽  
Pure Copper ◽  
Mass Separation ◽  
Monte Carlo Code ◽  
Early Evaluation ◽  
On Line ◽  
Isol Facility

The ISOLPHARM (ISOL technique for radioPHARMaceuticals) project is dedicated to the development of high purity radiopharmaceuticals exploiting the radionuclides producible with the future Selective Production of Exotic Species (SPES) Isotope Separation On-Line (ISOL) facility at the Legnaro National Laboratories of the Italian National Institute for Nuclear Physics (INFN-LNL). At SPES, a proton beam (up to 70 MeV) extracted from a cyclotron will directly impinge a primary target, where the produced isotopes are released thanks to the high working temperatures (2000 °C), ionized, extracted and accelerated, and finally, after mass separation, only the desired nuclei are collected on a secondary target, free from isotopic contaminants that decrease their specific activity. A case study for such project is the evaluation of the feasibility of the ISOL production of 64Cu and 67Cu using a zirconium germanide target, currently under development. The producible activities of 64Cu and 67Cu were calculated by means of the Monte Carlo code FLUKA, whereas dedicated off-line tests with stable beams were performed at LNL to evaluate the capability to ionize and recover isotopically pure copper.

scholarly journals Predictors of Users’ Satisfaction with E-payment System: a Case Study of Staff at the University of Ilorin, Nigeria

Organizacija ◽  
2015 ◽  
Vol 48 (4) ◽  
pp. 272-286 ◽  
Author(s):  
Adeyinka Tella ◽  
Isah Abdulmumin
Keyword(s):  
Design Methodology ◽  
Academic Staff ◽  
Payment System ◽  
Research Approach ◽  
System A ◽  
Order Of Magnitude ◽  
Research Questions ◽  
The University ◽  
Perceived Speed

Abstract Background and Purpose: Many organisations are using the e-payment system; however, its effectiveness has not been determined particularly in the Nigeria context. The University of Ilorin as educational organisation started using e-payment system in 2010 and up till now there has been limited or no study conducted to examine whether or not workers are satisfied with the new payment system together with other related ones they are familiar with. It is in the light of this that this study examined users’ satisfaction with the e-payment system at the University of Ilorin, Nigeria. Design/Methodology/Approach: A sample of 260 academic and non-academic staff was taken from six out 12 faculties that made up the university. Using a survey research approach data was collected with a modified questionnaire. Five research questions were developed to guide the study. Results: The results revealed that, respondents (93.5%) were adequately satisfied, satisfied and moderately satisfied, while, only (6.5%) of the respondents were less satisfied and dissatisfied. Perceived speed was identified as the characteristics users mostly satisfied with, followed by system security, traceability, and convenience. Moreover, there is significant correlation among the entire e-payment characteristics/factors (perceived speed, security, anonymity, traceability, perceived ease of payment, and convenience); and that all the six factors jointly predict users’ satisfaction with the e-payment system. In order of magnitude of the prediction/contribution to e-payment, users’ satisfaction, perceived speed made the most significant prediction/contribution. Conclusion: Based on the findings, the study concluded a considerable percentage of the respondents (93.5%) are satisfied with the e-payment system at the University of Ilorin, Nigeria. In lieu of this therefore, there is need to improve the e-payment system so that all and sundry could be satisfied.

scholarly journals On the alignment of velocity and magnetic fields within magnetosheath jets

2020 ◽  
Vol 38 (2) ◽  
pp. 287-296
Author(s):  
Ferdinand Plaschke ◽  
Maria Jernej ◽  
Heli Hietala ◽  
Laura Vuorinen
Keyword(s):  
Magnetic Fields ◽  
Entire Range ◽  
Dynamic Pressure ◽  
Bow Shock ◽  
Superposed Epoch Analysis ◽  
Magnetospheric Multiscale ◽  
Study Results ◽  
Epoch Analysis ◽  
The Magnetic Field

Abstract. Jets in the subsolar magnetosheath are localized enhancements in dynamic pressure that are able to propagate all the way from the bow shock to the magnetopause. Due to their excess velocity with respect to their environment, they push slower ambient plasma out of their way, creating a vortical plasma motion in and around them. Simulations and case study results suggest that jets also modify the magnetic field in the magnetosheath on their passage, aligning it more with their velocity. Based on Magnetospheric Multiscale (MMS) jet observations and corresponding superposed epoch analyses of the angles ϕ between the velocity and magnetic fields, we can confirm that this suggestion is correct. However, while the alignment is more significant for faster than for slower jets, and for jets observed close to the bow shock, the overall effect is small: typically, reductions in ϕ of around 10∘ are observed at jet core regions, where the jets' velocities are largest. Furthermore, time series of ϕ pertaining to individual jets significantly deviate from the superposed epoch analysis results. They usually exhibit large variations over the entire range of ϕ: 0 to 90∘. This variability is commonly somewhat larger within jets than outside them, masking the systematic decrease in ϕ at core regions of individual jets.

scholarly journals Exomoons in the Habitable Zones of M Dwarfs

2019 ◽  
Vol 887 (2) ◽  
pp. 261 ◽  
Author(s):  
Héctor Martínez-Rodríguez ◽  
José Antonio Caballero ◽  
Carlos Cifuentes ◽  
Anthony L. Piro ◽  
Rory Barnes
Keyword(s):  
M Dwarfs ◽  
Habitable Zones

Hydrogen and helium escape on Venus via energy transfer from hot oxygen atoms

2020 ◽  
Vol 501 (2) ◽  
pp. 2394-2402
Author(s):  
Hao Gu ◽  
Jun Cui ◽  
Dandan Niu ◽  
Jiang Yu
Keyword(s):  
Cross Sections ◽  
Dominant Role ◽  
Monte Carlo Model ◽  
Dissociative Recombination ◽  
Angle Distribution ◽  
Model Uncertainties ◽  
Atmospheric Escape ◽  
Parallel Approximation ◽  
Hot Oxygen ◽  
Energy Dependent

ABSTRACT Due to the relatively strong gravity on Venus, heavy atmospheric neutrals are difficult to accelerate to the escape velocity. However, a variety of processes, such as the dissociative recombination of ionospheric O$_2^+$, are able to produce hot atoms which could deliver a significant amount of energy to light neutrals and drive their escape. In this study, we construct a Monte Carlo model to simulate atmospheric escape of three light species, H, H2, and He, on Venus via such a knock-on process. Two Venusian background atmosphere models are adopted, appropriate for solar minimum and maximum conditions. Various energy-dependent and species-dependent cross-sections, along with a common strongly forward scattering angle distribution, are used in our calculations. Our model results suggest that knock-on by hot O likely plays the dominant role in driving total atmospheric hydrogen and helium escape on Venus at the present epoch, with a significant portion contributed from regions below the exobase. Substantial variations are also revealed by our calculations. Of special interest is the modelled reduction in escape flux at high solar activities for all species, mainly associated with the enhancement in thermal O concentration near the exobase at high solar activities which hinders escape. Finally, model uncertainties due to several controlling factors, including the distribution of relevant light species in the background atmosphere, the plane-parallel approximation, and the finite O energy distribution, are evaluated.

scholarly journals Mine Pressure Behavior Characteristics and Control Methods of a Reused Entry that Was Formed by Roof Cutting: A Case Study

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Yajun Wang ◽  
Haosen Wang ◽  
Manchao He ◽  
Qi Wang ◽  
Yafei Qiao ◽  
...  
Keyword(s):  
Deformation Zone ◽  
Dynamic Pressure ◽  
Field Application ◽  
Surrounding Rock ◽  
Mine Pressure ◽  
Stress Increase ◽  
Severe Deformation ◽  
Working Face ◽  
Roof Deformation

Noncoal pillar mining with automatic formation of a roadway is a new coal mining method that is tailored to improve the coal resource recovery rate and reduce the investment in roadway tunneling. Using this proposed method, a reuse entry is formed by roof cutting instead of tunneling. In this paper, the S1201-II working face of the Ningtiaota Coal Mine was used as a case study. The stress distribution of surrounding rock and the roof deformation characteristics of the reused entry during the mining process of the second working face were studied through FLAC3D numerical simulations combined with field measurements. The results indicate that the zone close to the reused entry led to higher stress in advance. If this stress is superimposed with the lateral pressure of the adjacent mined working face, it will be more difficult to maintain the reused entry. In the engineering case study described here, the reused entry created a stress increase zone and a severe deformation zone in the range of 0–80 m in front of the working face, and its range was approximately 37.5% larger than an ordinary entry. The stress peak in the stress increase zone increased by approximately 34.7% over that of an ordinary entry. The maximum amount of deformation within the severe deformation zone increased by 94.4% over that of an ordinary entry. To properly control the surrounding rock stress and deformation of the reused entry, a dynamic pressure bearing support in front of the working face with adaptability to the large roof deformation and high support strength is proposed here. Field application results showed that the final roof deformation with the dynamic pressure bearing support can be satisfactorily controlled within 110∼130 mm. These findings can provide a reference for researchers and field engineering technicians when engaging in the support work of reused entry.

A probabilistic approach for design and certification of self-healing advanced composite structures

2011 ◽  
Vol 225 (4) ◽  
pp. 435-449 ◽  
Author(s):  
H R Williams ◽  
R S Trask ◽  
I P Bond
Keyword(s):  
Composite Structures ◽  
High Performance ◽  
Probabilistic Approach ◽  
Healing Time ◽  
Self Healing ◽  
Structural Failure ◽  
Healing System ◽  
Order Of Magnitude ◽  
Damage Tolerant

Design and certification of novel self-healing aerospace structures was explored by reviewing the suitability of conventional deterministic certification approaches. A sandwich structure with a vascular network self-healing system was used as a case study. A novel probabilistic approach using a Monte Carlo method to generate an overall probability of structural failure yields notable new insights into design of self-healing systems, including a drive for a faster healing time of less than two flight hours. In the case study considered, a mature self-healing system could be expected to reduce the probability of structural failure (compared to a conventional damage-tolerant construction) by almost an order of magnitude. In a risk-based framework this could be traded against simplified maintenance activity (to save cost) and/or increased allowable stress (to allow a lighter structure). The first estimate of the increase in design allowable stresses permitted by a self-healing system is around 8 per cent, with a self-healing system much lighter than previously envisaged. It is thought these methods and conclusions could have wider application to self-healing and conventional high-performance composite structures.

scholarly journals CARMENES: M dwarfs and their planets

2015 ◽  
Vol 11 (S320) ◽  
pp. 388-390
Author(s):  
A. Quirrenbach ◽  
P.J. Amado ◽  
J.A. Caballero ◽  
H. Mandel ◽  
R. Mundt ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Spectral Resolution ◽  
M Dwarfs ◽  
Habitable Zones ◽  
Scientific Goal ◽  
New Instrument ◽  
Fabry Perot ◽  
Calar Alto ◽  
Sufficient Precision

AbstractCARMENES (Calar Alto high-Resolution search for M dwarfs with Exo-earths with Near-infrared and optical Echelle Spectrographs) is a new instrument currently undergoing commissioning at the 3.5 m telescope of the Calar Alto Observatory. It has been constructed by a consortium of eleven Spanish and German institutions. The scientific goal of the project is a 600-night radial-velocity survey targeting 300 M dwarfs with sufficient precision to detect terrestrial planets in their habitable zones. The CARMENES instrument consists of two separate échelle spectrographs covering the wavelength range from 0.55 to 1.7 μm at a spectral resolution of R = 82,000, fed by fibers from the Cassegrain focus of the telescope. Both spectrographs are housed in a temperature-stabilized environment in vacuum tanks, to enable a long-term radial velocity precision of 1 m s−1. The wavelength calibration will be done with Th-Ne and U-Ne emission line lamps, and with Fabry-Pérot etalons.

Study on Flaw Acceptance Standard of ASME Code Sec. XI Based on Failure Probability

2004 ◽  
Author(s):  
Katsuyuki Shibata ◽  
Kunio Onizawa ◽  
YinSheng Li ◽  
Yasuhiro Kanto ◽  
Shinobu Yoshimura
Keyword(s):  
Case Studies ◽  
Failure Probability ◽  
Pressure Vessels ◽  
Aspect Ratios ◽  
Pressurized Thermal Shock ◽  
Asme Code ◽  
Order Of Magnitude ◽  
The Difference ◽  
Reactor Pressure

Based on the failure probability, the flaw acceptance standard of ASME Code Sec. XI is examined with some concerns weather the failure probability is uniform for flaws with various aspect ratios and failure frequencies are small enough. In this paper, the results of preliminary case studies are described on the failure probability of reactor pressure vessels (RPVs) with a surface flaw specified in Sec. XI. PFM code PASCAL was used for case studies. A PTS (Pressurized Thermal Shock) transient prescribed by NRC/EPRI PTS Benchmark Study was used as an applied load. Analysis results showed that the conditional failure probability of a RPV with an initial flaw of acceptable depth depends on the aspect ratio. In the case flaw shapes are close to semi-circular, the failure probability are higher than that of the cases aspect ration are less than 0.6 by one order of magnitude due to the difference of fracture behavior at the surface point. A case study for determining the acceptable flaws based on failure probability was also carried out.

Environmental Risk Analysis of Accidental Release From Onshore Oil Pipelines

2018 ◽  
Author(s):  
Shengli Liu ◽  
Yongtu Liang
Keyword(s):  
Environmental Consequences ◽  
Proposed Model ◽  
Oil Pipelines ◽  
Order Of Magnitude ◽  
Pipeline Failure ◽  
Accidental Releases ◽  
The Difference ◽  
Environmental Risk Analysis ◽  
Spilled Oil

Accidental releases of oil and oil products will cause extensive damage to environment, if timely and effective measures are not available. Predicting the consequences of spilled oil is of significant importance for emergency management. Although software for risk assessment of gas pipelines is very popular, few are available for hazardous liquid pipelines, due to the difference in behaviors of accidental releases of gases and liquids in the same situation. The major differences are that the spread of released oil is mainly affected by the topography of the land and may result in pollution of soil or waterways, while gas pipeline failure may form gas clouds or explosions and merely pose environmental pollution problems. An integrated model was developed in order to analyze the environmental consequences of spills from oil pipelines. The method presented in this paper allowed to predict the flow trajectory of released liquid from a pipeline and other relevant parameters, including the extent of spread of the oil and the proportion of release reaching any important location, such as a river, in any given topography. The methodology has been applied to a release, which occurred in Marshall, Michigan, in 2010. The results obtained are of the correct order of magnitude compared with realistic data. A case-study is presented and discussed to illustrate the features of the methodology. The results confirmed that the proposed model may be considered an important tool within a comprehensive approach to the management of risk related to onshore oil pipelines.

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