Shock Scenario Research Articles

Chemistry and physical properties of the born-again planetary nebula HuBi 1

ABSTRACT The central star of the planetary nebula (PN) HuBi 1 has been recently proposed to have experienced a very late thermal pulse (VLTP), but the dilution of the emission of the recent ejecta by that of the surrounding H-rich old outer shell has so far hindered confirming its suspected H-poor nature. We present here an analysis of the optical properties of the ejecta in the innermost regions of HuBi 1 using MEGARA high-dispersion integral field and OSIRIS intermediate-dispersion long-slit spectroscopic observations obtained with the 10.4-m Gran Telescopio de Canarias. The unprecedented tomographic capability of MEGARA to resolve structures in velocity space allowed us to disentangle for the first time the Hα and Hβ emission of the recent ejecta from that of the outer shell. The recent ejecta is found to have much higher extinction than the outer shell, implying the presence of large amounts of dust. The spatial distribution of the emission from the ejecta and the locus of key line ratios in diagnostic diagrams probe the shock excitation of the inner ejecta in HuBi 1, in stark contrast with the photoionization nature of the H-rich outer shell. The abundances of the recent ejecta have been computed using the mappings v code under a shock scenario. They are found to be consistent with a born-again ejection scenario experienced by the progenitor star, which is thus firmly confirmed as a new ‘born-again’ star.

Waiting times between gamma-ray flares of flat spectrum radio quasars, and constraints on emission processes

Context.The physical scenario responsible for gamma-ray flaring activity and its location for flat spectrum radio quasars is still debated.Aims.The study of the statistical distribution of waiting times between flares, defined as the time intervals between consecutive activity peaks, can give information on the distribution of flaring times and constrain the physical mechanism responsible for gamma-ray emission.Methods.We adopt here a scan statistic-driven clustering method (iSRS) to recognize flaring states within theFermi-LAT archival data, and identify the time of activity peaks.Results.We obtained that waiting times between flares can be described with a Poissonian process, consisting of a set of overlapping bursts of flares, with an average burst duration of ∼0.6 year and average rate of ∼1.3 y−1. For short waiting times (below 1 d host-frame) we found a statistically relevant second population, the fast component, consisting of a few tens of cases, most of them revealed for CTA 102. Interestingly, the period of conspicuous detection of the fast component of waiting times for CTA 102 coincides with the reported crossing time of the superluminal K1 feature with the C1 stationary feature in radio.Conclusions.To reconcile the recollimation shock scenario with the bursting activity, we have to assume that plasma streams with a typical length of ∼2 pc (in the stream reference frame) reach the recollimation shock. Otherwise, the distribution of waiting times can be interpreted as originating from relativistic plasma moving along the jet for a deprojected length of ∼30−50 pc (assuming a bulk Γ = 10) that sporadically produces gamma-ray flares. In the magnetic reconnection scenario, reconnection events or plasma injection to the reconnection sites should be intermittent. Individual plasmoids can be resolved in a few favourable cases only, and could be responsible for the fast component.

An Efficient Method for Fitting Radiation-mediated Shocks to Gamma-Ray Burst Data: The Kompaneets RMS Approximation

Abstract Shocks that occur below a gamma-ray burst (GRB) jet photosphere are mediated by radiation. Such radiation-mediated shocks (RMSs) could be responsible for shaping the prompt GRB emission. Although well studied theoretically, RMS models have not yet been fitted to data owing to the computational cost of simulating RMSs from first principles. Here we bridge the gap between theory and observations by developing an approximate method capable of accurately reproducing radiation spectra from mildly relativistic (in the shock frame) or slower RMSs, called the Kompaneets RMS approximation (KRA). The approximation is based on the similarities between thermal Comptonization of radiation and the bulk Comptonization that occurs inside an RMS. We validate the method by comparing simulated KRA radiation spectra to first-principle radiation hydrodynamics simulations, finding excellent agreement both inside the RMS and in the RMS downstream. The KRA is then applied to a shock scenario inside a GRB jet, allowing for fast and efficient fitting to GRB data. We illustrate the capabilities of the developed method by performing a fit to a nonthermal spectrum in GRB 150314A. The fit allows us to uncover the physical properties of the RMS responsible for the prompt emission, such as the shock speed and the upstream plasma temperature.

Gamma-Ray Orbital Modulation of the Transitioning Millisecond Pulsar Binary XSS J12270–4859

Abstract We report on gamma-ray orbital modulation of the transitioning MSP binary XSS J12270–4859 detected in the Fermi Large Area Telescope (LAT) data. We use long-term optical data taken with the XMM-Newton OM and the Swift UltraViolet Optical Telescope to inspect radio timing solutions that are limited to relatively short time intervals and find that extrapolation of the solutions aligns well with the phasing of the optical data over 15 yr. The Fermi-LAT data folded on the timing solutions exhibit significant modulation (p = 5 × 10−6) with a gamma-ray minimum at the inferior conjunction of the pulsar. Intriguingly, the source seems to show similar modulation in both the low-mass X-ray binary and the MSP states, implying that mechanisms for gamma-ray emission in the two states are similar. We discuss these findings and their implications using an intrabinary shock scenario.

Radio relics radio emission from multishock scenario

ABSTRACT Radio relics are giant (∼Mpc) synchrotron sources that are believed to be produced by the (re)acceleration of cosmic ray electrons (CRe) by shocks in the intracluster medium. In this numerical study, we focus on the possibility that some radio relics may arise when electrons undergo diffusive shock acceleration at multishocks in the outskirts of merging galaxy clusters. This multishock (MS) scenario appears viable to produce CRe that emit visible synchrotron emission. We show that electrons that have been shocked multiple times develop an energy spectrum that significantly differs from the power-law spectrum expected in the case of a single shock scenario. As a consequence, the radio emission generated by CRe that shocked multiple times is higher than the emission produced by CRe that are shocked only once. In the case explored in this paper, the radio emission produced in the two scenarios differ by one order of magnitude. In particular in the MS scenario, the simulated relic follows a KGJP spectral shape, consistent with observation. Furthermore, the produced radio emission is large enough to be detectable with current radio telescopes (e.g. LOFAR, JVLA).

Synthetic fat from petroleum as a resilient food for global catastrophes: Preliminary techno-economic assessment and technology roadmap

Human civilization’s food production system is unprepared for global catastrophic risks (GCRs). catastrophes capable of abruptly transforming global climate such as supervolcanic eruption, asteroid/comet impact or nuclear winter, which could completely collapse the agricultural system. Responding by producing resilient foods requiring little to no sunlight is more cost effective than increasing food stockpiles, given the long duration of these scenarios (6−10 years).This preliminary techno-economic assessment uncovers significant potential for synthetic fat from petroleum as a resilient food source in the case of an abrupt sunlight reduction catastrophe, the most severe food shock scenario. To this end, the following are roughly quantified based on literature data: global production potential, capital and operating expenditures, material and energy requirements, ramp-up rates and retail prices. Potential resource bottlenecks are reviewed.Synthetic fat production capacity would be slower to ramp up compared to low-tech food production alternatives, but provides the fat macronutrient, largely absent from these. Using 24/7 construction of facilities, 16–100% of global fat requirements could be fulfilled at the end of the first year, potentially taking up to 2 years to fully meet the requirements. Significant uncertainty remains on several topics including production potential, capital expenditure, food safety, transferability of labor and equipment construction. A technology roadmap is proposed to address these concerns and develop the potential of synthetic fat as a catastrophe-resilient food.

Optimal scheduling of self-healing distribution systems considering distributed energy resource capacity withholding strategies

This paper presents a multi-stage day-ahead and real-time optimization algorithm for scheduling of system’s energy resources in the normal and external shock operational conditions. The main contribution of this paper is that the model considers the non-utility electricity generation facilities capacity withholding opportunities in the optimal scheduling of system resources. The real-time simulation of external shock impacts is another contribution of this paper that the algorithm simulates the sectionalizing of the system into multi-microgrids to increase the resiliency of the system. The optimization process is categorized into two stages that compromise normal and contingent operational conditions. Further, the normal operational scheduling problem is decomposed into three steps. At the first step, the optimal day-ahead scheduling of system resources and the switching of normally opened switches are determined. At the second step, the optimal real-time market scheduling is performed and the switching of normally closed switches is optimized. At the third step, different extreme shock scenarios are simulated in the real-time horizon and the effectiveness of sectionalizing the system into multi-micro grids are assessed. Finally, at the contingent operational conditions, the optimal topology of the system and scheduling of energy resources are determined. The proposed method was successfully assessed for the 33-bus and 123-bus test systems. The algorithm were reduced the expected cost of the worst-case contingencies for the 33-bus and 123-bus systems by about 97.89% and 88.11%, respectively. Further, the average and maximum values of the 123-bus system capacity-withholding index for real-time conditions reduced by about 67.40% and 71.05%, respectively.

Tsunami Impact Assessment and Vulnerability Index Development using Computable General Equilibrium (CGE) Model and Geographic Information System (GIS) – A Study on Mie Prefecture, Japan

Japan is highly prone to multiple natural hazards, such as typhoons, earthquakes, and tsunamis in general. However, the compound disaster that entailed earthquake, tsunami, and a nuclear crisis, along with disruption of the global supply chain triggered by the Great East Japan Earthquake in 2011, highlighted the need for a holistic risk assessment of impacts amplified by multiple disasters. According to the Cabinet Office of Japan, the occurrence probability of a Nankai Trough Earthquake and Tsunami is 70% within the next 30 years. It suggests the need for comprehensive impact assessment to enhance the disaster risk reduction strategies of the region. This study conducts a tsunami impact assessment using quantitative analysis to identify vulnerable industries in Mie Prefecture, Japan, famous for tourism, value-added sectors of aquaculture, food processing, and petroleum refining tanks situated in at-risk areas. To create a tsunami shock scenario, we apply a computable general equilibrium (CGE) model using an input-output table of the Mie Prefecture (2015 version) and geographic information system (GIS). The street-level business entity data enable us to incorporate with the disaster scenario to provide evidence-based damage estimates of capital and labor loss due to a tsunami. We present the simulation results of output change, price change, external trade, and welfare analysis and propose creating a vulnerability index (VI) for disaster impact. These quantified and visualized indicators would provide informative implications for ex-ante policymaking and risk financing to cope with fragile sectors effectively.

Optimal resilient operation of multi-carrier energy systems in electricity markets considering distributed energy resource aggregators

This paper presents a novel iterative three-level optimization framework for the optimal resilient operational scheduling of active multi-carrier energy generation and distribution systems. The main contribution of this paper is that the proposed framework simulates the day-ahead and real-time pre-event preventive and post-event corrective actions for external shocks and explores the effectiveness of risk-averse operational strategies on the system’s costs. The solution methodology is another contribution of this paper that finds the optimal scheduling of distributed energy resources and switching of electrical switches and district heating and cooling control valves. At the first stage, the optimal day-ahead scheduling of distributed energy resources and the initial value of the risk control parameter are determined using robust optimization. At the second stage, the optimal real-time market scheduling of distributed energy resources is performed. Finally, at the third stage, different extreme shock scenarios are considered, the effectiveness of corrective actions are investigated, and the value of risk control parameter is modified. The proposed method was successfully applied to the modified 123-bus test system and 600 scenarios of external shocks were considered. The proposed process successfully reduced the expected cost of the.123-bus system by about 74.59% for the worst-case external shock. Further, the algorithm reduced the aggregated expected values of operational and interruption costs by about 57.73% for all of the 600 cases of the considered external shocks.

NONLINEAR DYNAMIC ANALYSIS OF TWO STOREY RC BUILDING MODEL

Peninsular Malaysia lies in a low seismic zone, but its building structures had come across the concrete deterioration due to the seismic ground motion originated from far or near field. Notably, most of the building structures in this country are designed based on wind load only. Moreover, current practice to analyze or design a building such as FEMA 368 and EC8 underestimated the effect of repeated excitations. These guidelines only considered single vibrations to evaluate the framed structure. Therefore, the objective of this study was to assess the performance of private educational institute reinforced concrete building with generic 3D two storey frame structure under multiple seismic motions. Structural model was examined under series of earthquake motions which include pre-shock, main shock and aftershock scenario. Total of 7 seismic ground motions were selected to quantify the structural frame model by nonlinear dynamic time history analyses. Pseudo-dynamic ground motions were recorded on shaking table ranging from 0.18 g to 0.82 g were applied onto the building model for assessment. The outcome of this study has identified that the low-rise building model survived at higher PGA values. Moderate damages (0.25 ≤ DI < 0.40) were recorded after passing through multiple ground motions. Moreover, low seismic vibrations with large ground movement had caused ground floor storey act as soft storey. The study concluded that low rise building model had higher tendency to absorb lower to higher ‘g’ values and resist the earthquake loading due to the strength of framed structure.

GRB160203A: an exploration of lumpy space

ABSTRACT GRB160203A is a high redshift long gamma-ray burst presenting a collection of unusual features in the afterglow light curve. We study its optical and X-ray data. We find this event to occur within a constant density medium during the first part of the afterglow. However, after 13 ks we spot some flaring activities in the optical and X-ray light curves. We explain these flares by fluctuation of densities of the surrounding medium. Other scenarios, such as energy injection from a magnetar or variation of microphysical parameters are not supported by the data. We tentatively link these fluctuations to an unusual host galaxy, with gas density similar to the Milky Way and a dense cocoon of matter around a stellar progenitor similar to a Wolf–Rayet star. A termination shock scenario is found to be less likely.

Mechanical simulation optimization of RTG prototype

The thermocouple energy converter in the radioisotope thermoelectric genera tor (RTG) requires a long time work under high temperature and large temperature diff erence, and needs to withstand the harsh service conditions of heat, force, electricity an d other external fields during the launch process. In order to understand the dynamic p urchase response and dynamic strain of various parts of the structure when the thermoe lectric module is under dynamic load under different conditions, this paper uses softwa re to simulate the vibration and shock scenarios of the thermoelectric module in the RT G prototype. According to the existing conditions, a three-direction impact spectrum a nalysis was carried out. It was found that in the three-direction random vibration, from the root mean square stress result, the risk of damage is small; while during the impac t, the shell and the thermoelectric The displacement in the in-plane direction between t he module furnishing surfaces will cause the thermoelectric material in the thermoelect ric module to produce a large shear stress, which will cause the risk of shear damage to the structure. The imitation result provides a reference for the further optimization des ign of RTG prototype.

On the Origin of Hard X-Ray Emissions from the Behind-the-limb Flare on 2014 September 1

Abstract The origin of hard X-rays and γ-rays emitted from the solar atmosphere during occulted solar flares is still debated. The hard X-ray emissions could come from flaring loop tops rising above the limb or coronal mass ejection shock waves, two by-products of energetic solar storms. For the shock scenario to work, accelerated particles must be released on magnetic field lines rooted on the visible disk and precipitate. We present a new Monte Carlo code that computes particle acceleration at shocks propagating along large coronal magnetic loops. A first implementation of the model is carried out for the 2014 September 1 event, and the modeled electron spectra are compared with those inferred from Fermi Gamma-ray Burst Monitor (GBM) measurements. When particle diffusion processes are invoked, our model can reproduce the hard electron spectra measured by GBM nearly 10 minutes after the estimated on-disk hard X-rays appear to have ceased from the flare site.

Asset-Level Transition Risk in the Global Coal, Oil, and Gas Supply Chains

Climate change risks manifest in the real economy, with grave consequences for welfare of human populations and the biosphere; the economic returns of industrial sectors; and geopolitical stability. Understanding the diffusion of risks in real infrastructure networks is an urgent priority for delivering climate change mitigation, adaptation, and resiliency. The oil, gas, and coal supply chains are the most salient progenitors and inheritors of these environmental risks. We prepare a geospatial arrangement of the global oil, gas, and coal supply chains using open-source asset-level data. The resulting complex network has 6.09mn nodes and 15.70mn edges and is implemented in a graph database. With estimates of annual coal, gas, and oil demand in 13,229 global population centres and 8,165 global power stations, we use a minimum-cost flow method to estimate global asset-level energy flows. We develop a method for cross-validating and tuning our network flow simulation using aggregate country-level import and export statistics. We demonstrate two analyses of asset-level transition risk: a counter-factual demand shock scenario consistent with the IEA Sustainable Development Scenario; and supply shock scenarios developed by interdicting regionally-aggregated coal, oil, and gas supplies. Our contribution lies in the global scope of our asset-level supply chain and the novelty of our minimum-cost flow method. We conclude with a discussion of further research directions and make the graph database and supporting code publicly available.

Stellar Feedback on the Earliest Stage of Massive Star Formation

Abstract We report SOFIA/GREAT observations of high-J CO lines and [C ii] observations of the super star cluster candidate H72.97-69.39 in the Large Magellanic Cloud (LMC), which is in its very early formation stage. We use our observations to determine if shocks are heating the gas or if photon-dominated regions (PDRs) are being heated by local far-UV radiation. We use a PDR model and a shock model to determine whether the CO and [C ii] lines arise from PDRs or shocks. We can reproduce the observed high-J CO and [C ii] emission with a clumpy PDR model with the following properties: a density of 104.7 cm−3, a mass of 104 M ⊙, and UV radiation of 103.5 in units of Draine field. Comparison with the ALMA beam-filling factor suggests a higher density within the uncertainty of the fit. We find the lower-limit [C ii]/total infrared (TIR) ratio (ϵ) traced by [C ii]/TIR to be 0.026%, lower than other known young star-forming regions in the LMC. Our shock models may explain the CO (16−15) and CO (11−10) emission lines with shock velocity of 8–11 km s−1, pre-shock density of 104–105 cm−3, and G UV = 0 in units of Draine field. However, the [C ii] line emission cannot be explained by a shock model, thus it is originating in a different gas component. Observations of [O i] 63 μm predicted to be 1.1 × 10−13 W m−2 by PDR models and 7.8 × 10−15 W m−2 by shock models will help distinguish between the PDR and shock scenarios.

Universal law in the crude oil market based on visibility graph algorithm and network structure

Price fluctuations in the crude oil market is important to both financial practitioners and market participants, since it not only affects investors’ investment, portfolio allocation and risk evaluation, but also influences strategic planning and market decisions. By using visibility graph algorithm (VG), the time series of 32-year crude oil price is converted to a corresponding single spot and futures price network respectively. The network topological structure implies that the single spot and futures price network both follow the power-law distribution and power-law index γ=2.8. When the crude oil market suffers from financial shock, stable price market is broken and reaches a collapse critical state. And, we find that the biggest connection cluster of price network with two communities S(r,pc) has a scaling relationship with interconnected nodes fraction r, and the scale index is δ = 1.3 near the critical point for different shock scenarios. Besides, similar to the results in a single price network, the rate of change of S(r,pc) also shows a scaling relationship with p−pc (the difference between attack strength 1−p and critical attack strength pc), the scale index γ = 1.5. Particularly, these two indices γ and δ satisfy the universal Wisdom’s law. According to the above relationship, one can observe the changes of the biggest connection cluster of price network near critical attack strength, and make adjustments of investment quickly to avoid huge losses by comprehending this laws.

Towards a General Theory of Harm for Consumer Law

The recent book Consumer Theories of Harm is an important contribution to consumer policy. It is the first attempt to develop theories of harm for consumer law. This essay presents the main arguments of the book (Sections 1 and 2). There are four archetypal scenarios of harm that consumer law should consider: the scam, the lemon, the shock, and the subsidy. Section 3 critically engages with the normative foundations of the analysis. Section 4 proposes to consider the shock scenario, one of the four archetypal scenarios of harm proposed by the book as the benchmark against which assess the other three scenarios. Section 5 shows the importance of searching the theories of harm latent in legislation by showing that ancillary terms in standard terms and conditions are understood by the Unfair Contract Terms Directive as an instance of the scam scenario, not of the shock scenario as proposed by the authors. Finally, Section 6 proposes additional lines of inquiry stimulated by Consumer Theories of Harm.

Uncertainty Shocks, Adjustment Costs and Firm Beliefs: Evidence From a Representative Survey

This paper studies the dynamic effects of an uncertainty shock on firm expectations. We conduct a survey that confronts managers from a representative firm sample with a model-consistent uncertainty shock scenario. An exogenous increase in uncertainty significantly reduces managers’ expected investment, employment and production in the short and mid run. We collect novel direct firm-level mea- sures for different types of capital and labor adjustment costs. Adjustment costs vary strongly across sectors and types. They help explain firms’ reactions to the shock, which provides evidence for the relevance of real-options channels. We compare the findings to DSGE and VAR results.

Using stress testing model in measuring the impact of the financial crisis on the Jordanian commercial banks

This paper aims to answer multiple questions regarding Jordanian bank stability under credit, market, and liquidity shock scenarios in order to evaluate bank solvency and liquidity. The paper will use stress testing model to measure the effect of the financial crisis in 2008 on the Jordanian commercial banks. It will conduct various stress testing scenarios on 13 Jordanian banks with the aim of better understanding the risk profile of the Jordanian banking system. Two spreadsheet models are utilised to conduct credit, market and liquidity shocks to assess the performance of the banks under each shock. The findings of this paper demonstrate that the Jordanian banking system is generally able to withstand reasonable shocks of each type, with some addressable weaknesses such as collateral under-provisioning and liquid asset shortcomings.

Алгоритм розв’язку нестаціонарної задачі термопружності для двошарового циліндра при змінному коефіцієнті теплообміну

The nonstationary axisymmetric thermoelasticity problem for a two-layer cylinder at the inner surface of which convective heat transfer with an environment takes place is considered. The solution of this problem is derived for the case of inhomogeneous initial temperature field. The solution is presented in the form of development by the system of eigenfunctions of the boundary value problem for a two-component beam and expressed in terms of the elementary functions. Based on this solution, an incremental algorithm of solving thermoelasticity problems for a two-layer cylinder is proposed for the case that the heat transfer coefficient between the inner surface of the cylinder and environment is time-varied. The idea of the algorithm is to divide the entire transient time interval into a sequence of subintervals, the heat transfer coefficient is considered constant on each. Once the temperature field is determined, the axisymmetric stress field can be founded on the basis of analytical expressions. The proposed algorithm was tested on the example of the thermal shock scenario for a nuclear reactor vessel. The comparison of the obtained results with the numerical solution by the finite element method verified sufficient working accuracy of the proposed approach.