Arrival Of Shock Research Articles

A δ-shock model for reengineering of a repairable supply chain using quasi renewal process

In this study, a quasi-renewal process model with δ-shock is analyzed for a degenerative repairable supply chain with a single supplier source. The supplier of the supply chain system encounters shocks due to crisis events and, as a consequence, tends to fail if the interarrival time between two successive shocks is less than a random threshold. The non negligible repair time of the supplier and the random threshold time of shocks are modeled on a quasi renewal process while the shock arrivals are governed by a renewal process. The long-run average cost per unit time is derived by employing the reengineering strategy N, which is determined by the number of failures of the supplier. The optimal reengineering policy is obtained analytically by minimizing the long-run expected cost rate. Numerical illustrations and sensitivity analysis evidence the consideration of maintenance policy for a repairable supply chain to sustain its smooth running.

Scheduling optimal replacement policies for a stochastically deteriorating system subject to two types of shocks

This paper is aimed at scheduling optimal preventive replacement policies for a single unit system which is subject to stochastic deterioration and concurrently suffers from external shocks. Different from existing literature, two types of shocks are taken into account according to the effectiveness upon arrival of a random shock, in which Type Ⅰ shock is a non-fatal one increasing the damage magnitude on current degradation amount and Type Ⅱ shock is a fatal one resulting in system catastrophic failure immediately. System survival function is investigated numerically based on the degradation-threshold-shock (DTS) modelling framework, and subsequently, two categories of bivariate maintenance policies are scheduled from different perspectives. The optimal solutions for both policies are derived analytically, and the relative gain on the optimal average maintenance cost rate is incorporated to determine which policy is more profitable. An illustrative example is provided to validate the theoretical results.

Bi-directional streaming of particles accelerated at the STEREO-A shock on 2008 March 9

ABSTRACT We present an interpretation of anisotropy and intensity of supra-thermal ions near a fast quasi-perpendicular reverse shock measured by Solar Terrestrial Relations Observatory Ahead (ST-A) on 2008 March 9. The measured intensity profiles of the supra-thermal particles exhibit an enhancement, or ‘spike’, at the time of the shock arrival and pitch-angle anisotropies before the shock arrival are bi-modal, jointly suggesting trapping of near-scatter-free ions along magnetic field lines that intersect the shock at two locations. We run test-particle simulations with pre-existing upstream magnetostatic fluctuations advected across the shock. The measured bi-modal upstream anisotropy, the nearly field-aligned anisotropies up to ∼15 min upstream of the shock, as well as the ‘pancake-like’ anisotropies up to ∼10 min downstream of the shock are well reproduced by the simulations. These results, in agreement with earlier works, suggest a dominant role of the large-scale structure (100s of supra-thermal proton gyroradii) of the magnetic field in forging the early-on particle acceleration at shocks.

Dynamic Compensation Under Uncertainty Shocks and Limited Commitment

AbstractThis article studies dynamic compensation and risk management under cash-flow volatility shocks. The optimal contract depends critically on firms’ ability to make good on promised future payments to managers. When volatility is low, firms with full commitment ability implement high pay–performance sensitivity to motivate effort from managers, and they impose large penalties on the arrival of volatility shocks to incentivize prudent risk management. In contrast, firms with limited commitment may allow excessive risk taking in exchange for low pay–performance sensitivity. When volatility becomes high, firms with full commitment defer compensation more, whereas firms with limited commitment must expedite payments.

Managing Information System Security Under Continuous and Abrupt Deterioration

In this study, we focus on the maintenance of an intrusion detection system (IDS) that attempts to discriminate between benign and malicious traffic arriving at a firm. An attack is more likely to successfully harm the firm if the ability of its IDS to discriminate between malicious and benign traffic is low, implying loopholes or vulnerabilities in the firm’s security. A novel aspect of this study is the modeling of both continuous degradation in system discrimination ability (drift) and the arrival of abrupt shocks that can suddenly lower discrimination ability. We model shocks to arrive randomly and cause a random decrease in discrimination ability. Furthermore, we prove the existence of a steady‐state level of discrimination ability that firms should strive to reach and maintain. When discrimination ability is below this steady‐state level, full effort must be exerted to reach it. We also compare our model with alternative settings, examine the impact of parameter estimation error, and study scenarios in which the arrival rate of malicious traffic is a function of the steady‐state discrimination ability chosen by the firm.

System reliability computation and estimation based on a cumulative damage–threshold–shock model

PurposeThis article considers a reliability model where the failure is due to cumulative damage exceeding a threshold level. The concept that the threshold level of cumulative damage at each arrival of shock can change based on whether the magnitude of each shock exceeds its defined threshold level is considered to compute the system reliability.Design/methodology/approachThe stochastic process approach is used to obtain the cumulative damage based on Poisson arrival of shocks. The general expression for reliability is obtained using the conditional probability over each arrival of shock. The method of maximum likelihood estimation is used to obtain the estimators of the parameters and system reliability. A sensitivity analysis is performed to measure the effect of the parameter representing the rate of arrival of shock.FindingsThe maximum likelihood estimates of the reliability approach the actual reliability for increasing sample size. A sensitivity analysis study on the parameter representing the rate of arrival of shock shows that as the values of parameter increase (decrease), the reliability value decreases (increases).Originality/valueObtained a new expression for the cumulative damage–shock model and the findings are positively supported by presenting the general trend of estimated values of reliability approaching the actual value of reliability. The sensitivity analysis also genuinely supports our findings.

Reliability and condition-based maintenance modeling for systems operating under performance-based contracting

Performance-based contracting motivates service providers to implement effective maintenance policies so as to boost profits and improve system performance at a lower cost. This paper deals with reliability and condition-based maintenance modeling for single-unit systems operating under performance-based contracting. For a system subject to degradation and sudden shocks, there involves three states: normal, degraded and failed. Once entered into the degraded state, the system deteriorates faster and becomes more susceptible to shocks. The degradation conforms to a two-stage inverse Gaussian process with random effects characterizing unit-specific heterogeneity in the population. Furthermore, the arrival of sudden shocks follows a doubly stochastic Poisson process. A reliability model is developed based on degradation-based and shock-based failures modeling. Afterwards, the long-run maintenance cost rate and the average system availability are evaluated. Optimal inspection-based preventive replacement policy is obtained by maximizing the expected profit rate to the service provider. Finally, a numerical example along with sensitivity analysis of model parameters is presented to demonstrate the applicability and solution procedure of the proposed models.

Effects of Nearly Frontal and Highly Inclined Interplanetary Shocks on High‐Latitude Field‐Aligned Currents (FACs)

AbstractWe present high‐latitude field‐aligned current (FAC) response to nearly frontal shocks (NFSs) and highly inclined shocks (HISs) through a superposed epoch analysis. The FACs are derived from magnetic perturbation data provided by the Active Magnetosphere and Planetary Electrodynamics Response Experiment program. Forty‐nine events for each group are used for the superposed epoch analysis. The 25%, 50%, and 75% quantiles of the FAC and total current distributions are studied. We found that NFSs are statistically stronger shocks in terms of solar wind parameters such as solar wind speed and interplanetary magnetic field.For the 50% quantiles, both groups of shocks produce rapid increases in total currents after shock arrival, but NFSs result in sharper increase in FACs and more intense FACs compared to HISs. At the 50% and 75% quantiles, NFSs trigger stronger auroral‐zone current disturbance for the first hour after shock arrival than do HISs. Spatially, the difference in FAC response is most notable in (1) the dayside noon region, (2) the duskside Region 2 current system, and (3) the dawnside prenoon Region 1 current system. Our results are consistent with previous numerical simulations that showed more symmetric and stronger compression of the magnetosphere for high‐speed and nearly frontal shocks. We observationally confirm the role of shock impact angle in controlling the subsequent shock geoeffectiveness for fast shocks. We assert that determining the shock impact angle via an upstream solar wind model could provide useful insight in forecasting the geoeffectiveness of a shock prior to its arrival at the magnetopause.

Jovian UV Aurora's Response to the Solar Wind: Hisaki EXCEED and Juno Observations

AbstractWe summarize Jupiter's ultraviolet (UV) auroral response to solar wind dynamic pressure variations during Juno's approach to Jupiter in 2016. The response time of Jupiter's aurora to external drivers has thus far been unknown owing to a sparsity of upstream in situ solar wind measurements. Combining the Juno solar wind observations with continuous UV aurora data obtained by Hisaki EXCEED (Extreme Ultraviolet Spectroscope for Exospheric Dynamics) and Juno UV spectrograph, the UV aurora brightenings in response to three major shock arrivals showed time lags of 10–15 hr. These time lags are longer than the time required for ballistic propagation of the shocks by the solar wind. In addition to that puzzle, while an enhancement in the UV auroral power was observed with an increase in dynamic pressure to ~0.03 nPa, no associated brightening was observed with a dynamic pressure elevation of >0.1 nPa. These imply that internal magnetospheric aspects need to be taken into consideration to fully resolve the issue.

The long‐term relationship between economic development and regional inequality: South‐West Europe, 1860–2010

AbstractThis paper analyses the long‐term relationship between regional inequality and economic development. Our data set includes information on national and regional per capita GDP for four countries: France, Italy, Portugal and Spain, compiled on a decadal basis for the period 1860–2010. Using parametric and semiparametric regressions, our results confirm the rise and fall of regional inequalities over time although in recent decades they are on the rise again. Finally, we identify structural change as being a significant transmission mechanism of the inverted‐U relationship. The arrival of technological shocks, beginning during the onset of industrialization, and the transition from agrarian to industrial economies, would explain this result.

Reliability and optimal replacement policy for an extreme shock model with a change point

An extreme shock model when there is a change in the distribution of the magnitudes of shocks is defined and studied. Such a model is useful in practice since a sudden change in environmental conditions may cause a larger shock. In particular, the reliability and mean time to failure of the system is obtained by assuming that the times between arrivals of shocks follow phase-type distribution. The optimal replacement policy that is based on a control limit is also proposed. The results are illustrated when the number of shocks until the change point follows geometric distribution.

The Intense Substorm Incidence in Response to Interplanetary Shock Impacts and Influence on Energetic Electron Fluxes at Geosynchronous Orbit

AbstractThe interaction between interplanetary (IP) shocks and the Earth's magnetosphere would generate/excite various types of geomagnetic phenomena. In order to analyze what kind of IP shock is more likely to trigger intense substorms (SME/AE > 1,000 nT) and how the energetic electrons response to intense substorms at geosynchronous orbit, we perform a systematic survey of 246 IP shock events using SuperMag and LANL observations between 2001 and 2013. The statistical analysis shows that intense substorms (SME > 1,000 nT) triggered by IP shocks are most likely to occur under the southward interplanetary magnetic field (IMF) and fast solar wind preconditions. Besides, intense substorms after the IP shock arrival are much more likely to occur when IMF points toward (away from) the Sun around spring (autumn) equinox, which can be ascribed to the Russell‐McPherron effect. Thus, the IMF Bs precondition of an IP shock and the Russell‐McPherron effect can be considered as precursors of an intense substorm. Furthermore, after the shock arrival associated with intense substorms, low‐energy (<200 keV) electron fluxes increase significantly at geosynchronous orbit, and high‐energy (>200 keV) electron fluxes decrease. The spectral index becomes softer with intense substorms and remains almost unchanged with moderate substorms no matter whether the IMF precondition is southward or northward.

The Efficiency of Coronal Mass Ejection With Different IMF Preconditions on the Production of Megaelectronvolt Electron Content in the Outer Radiation Belt

AbstractFifty‐two coronal mass ejections (CMEs) from 2012 to 2017 are categorized into four types according to different interplanetary magnetic field (IMF) preconditions, and behaviors of 1.8‐, 3.4‐, 5.2‐, and 7.7‐MeV electrons are quantitatively investigated using an Radiation Belt Content (RBC) index improved for nondipolar geomagnetic field configuration due to interaction with CMEs. Statistical analyses show that CMEs with continuous southward IMF from upstream of shock front to CME leading edge are the most efficient in the production of megaelectronvolt electron content, with RBC five times larger after shock arrival for 1.8‐MeV channel, seven times larger for 3.4‐MeV channel, and three times larger for 5.2‐MeV channel; the 7.7‐MeV channel also experiences less pronounced enhancements. For CMEs with continuous northward IMF from upstream of shock front to CME leading edge, clear dropouts of RBC are revealed. The depletion is the most significant for 1.8 MeV, and the magnitude of depletion gradually decreases when the electron energy goes higher. It is suggested that the location of magnetopause and plasmapause, and thus magnetopause shadowing and magnetopsheric waves like whistler mode chorus, contributes to the dynamics of megaelectronvolt electrons in the outer radiation belt, with energy dependence, in response to CMEs with different preconditions.

Study of Interplanetary CMEs/Shocks During Solar Cycle 24 Using Drag-Based Model: The Role of Solar Wind

In this paper we analyze a set of 27 fast interplanetary coronal mass ejections (ICMEs) observed during the period January 2010 – December 2013 in Solar Cycle 24. The arrivals of interplanetary shocks and CMEs at 1 AU are found from OMNI spacecraft high resolution data and their travel times are compared with Empirical Shock Arrival (ESA; Gopalswamy et al. in Adv. Space Res. 36, 2289, 2005) and Drag Based Model (DBM; Vrsnak et al. in Solar Phys. 285, 295, 2013). The analysis of the transit time, deceleration, and drag parameter is used to examine the role of the solar-wind characteristics in the dynamics of ICMEs. The obtained ICME parameters (deceleration, drag parameter) are compared with the decelerated events (34 of 91 events in Solar Cycle 23) from the study of Manoharan et al. (J. Geophy. Res. 109, A06109, 2004). The interplanetary (IP) deceleration shows similar trend between the cycles. Though the Cycle 24 has weak solar wind, it does not affect the arrival time behavior. It is concluded that the solar-wind behavior is considered to be the same in Cycles 23 and 24 for ICMEs. The IP drag parameter is linearly correlated with CME initial speed. The p-value between CME speed and drag parameter suggests that they are highly significant. The important result of the study is that the solar wind showed a similar kind of drag effect for the propagating CMEs in both cycles.

Reliability and maintenance modeling for competing risk processes with Weibull inter-arrival shocks

In this paper, a new Weibull inter-arrival shock process is proposed for modeling the competing risk process. The dependent competing failure/risk processes exists in many systems and the reliability modeling for those processes has attracted much attention in the recent years. However, the arrivals of random shocks are usually modeled as Poisson process which indicates the constant hazard rate of shock inter-arrival time. Our proposed Weibull inter-arrival shock process generalized the Poisson shock process and can deal with the cases when the shock count data are over-dispersion or under-dispersion. On the other hand, the dependency between the soft failure process and hard failure process is emphasized by assuming the linear dependent damage size. In four different hard failure models, analytic forms of the reliability functions are derived by using the polynomial expansion. The maintenance optimization for the developed model is discussed under different shock failure mechanisms. Numerical examples based on a micro-engine are also presented to illustrate the proposed model.

Modeling the Multiple CME Interaction Event on 6–9 September 2017 with WSA‐ENLIL+Cone

AbstractA series of coronal mass ejections (CMEs) erupted from the same active region between 4–6 September 2017. Later, on 6–9 September, two interplanetary (IP) shocks reached L1, creating a complex and geoeffective plasma structure. To understand the processes leading up to the formation of the two shocks, we model the CMEs with the Wang‐Sheeley‐Arge (WSA)‐ENLIL+Cone model. The first two CMEs merged already in the solar corona driving the first IP shock. In IP space, another fast CME presumably interacted with the flank of the preceding CMEs and caused the second shock detected in situ. By introducing a customized density enhancement factor (dcld) in the WSA‐ENLIL+Cone model based on coronagraph image observations, the predicted arrival time of the first IP shock was drastically improved. When the dcld factor was tested on a well‐defined single CME event from 12 July 2012 the shock arrival time saw similar improvement. These results suggest that the proposed approach may be an alternative to improve the forecast for fast and simple CMEs. Further, the slowly decelerating kilometric type II radio burst confirms that the properties of the background solar wind have been preconditioned by the passage of the first IP shock. This likely caused the last CME to experience insignificant deceleration and led to the early arrival of the second IP shock. This result emphasizes the need to take preconditioning of the IP medium into account when making forecasts of CMEs erupting in quick succession.

Characteristic path analysis of confinement influence on steady two-dimensional detonation propagation

Steady detonation in multi-dimensional flow is controlled by the chemical energy release that occurs in a subsonic elliptic flow region known as the detonation driving zone (DDZ). It is the region encompassing the detonation shock and sonic flow locus (in the frame of the detonation shock). A detonation that is strongly confined by material surrounding the explosive has the shock and sonic locus separated at the material interface. Information about the material boundary is traditionally believed to influence the DDZ structure via the subsonic flow on the boundary ahead of the sonic locus. A detonation that is weakly confined has the detonation shock and sonic locus intersecting at the material boundary. The sonic nature of the flow at the intersection point on the boundary is believed to isolate the DDZ structure from the material properties of the confinement. In this study, we examine the paths of characteristics propagating information about the confinement through the supersonic hyperbolic flow region that exists beyond the sonic locus, and determine whether these paths may impinge on the sonic locus and consequently influence the DDZ structure. Our configuration consists of a solid wall boundary deflected through a specified angle on detonation shock arrival, so that the streamline turning angle of the wall at the explosive edge is unambiguously defined. By varying the wall deflection angle from small through large values, we can systematically capture the evolution of the DDZ structure and the characteristic flow regions that influence its structure for strongly to weakly confined detonations. In all strong and weak confinement cases examined, we find that a subset of characteristics from the supersonic flow regions always impinge on the sonic locus. Limiting characteristics are identified that define the boundary between characteristics that impinge on the sonic surface and those that propagate information downstream of the sonic surface. In combination with an oblique-shock polar analysis, we show that the effects on the DDZ of characteristic impingement can be significant.

Geometry, Kinematics, and Heliospheric Impact of a Large CME-driven Shock in 2017 September

Abstract A powerful coronal mass ejection (CME) occurred on 2017 September 10 near the end of the declining phase of the historically weak solar cycle 24. We obtain new insights concerning the geometry and kinematics of CME-driven shocks in relation to their heliospheric impacts from the optimal, multispacecraft observations of the eruption. The shock, which together with the CME driver can be tracked from the early stage to the outer corona, shows a large oblate structure produced by the vast expansion of the ejecta. The expansion speeds of the shock along the radial and lateral directions are much larger than the translational speed of the shock center, all of which increase during the flare rise phase, peak slightly after the flare maximum and then decrease. The near simultaneous arrival of the CME-driven shock at the Earth and Mars, which are separated by 156.°6 in longitude, is consistent with the dominance of expansion over translation observed near the Sun. The shock decayed and failed to reach STEREO A around the backward direction. Comparison between ENLIL MHD simulations and the multipoint in situ measurements indicates that the shock expansion near the Sun is crucial for determining the arrival or nonarrival and space weather impact at certain heliospheric locations. The large shock geometry and kinematics have to be taken into account and properly treated for accurate predictions of the arrival time and space weather impact of CMEs.

Field-aligned currents (FACs) behaviour during the arrival of interplanetary magnetic shock

In this paper, our study is focused on the FACs behavior during the SC event. SC consists of two events which are storm sudden commencement (SSC) and sudden impulse (SI) event. The difference between these two events is that the interplanetary shock due to SSC leads to geomagnetic storm while during SI event, there is no geomagnetic storm afterward. We performed the statistical analysis between the FACs value and the temporal variation of SYMH index (dSYMH/dt) during SC events from 2008 until 2015. The dSYMH/dt describe the interplanetary shock signature during the SC events. The results showed that the dSYMH/dt during SSC event has a better correlation than the dSYMH/dt during SI events. It suggested that during the SSC onset, there is the magnetic reconnection process between magnetosphere and ionosphere. So, the enhancement of ground magnetic field is contributed by both magnetospheric and ionospheric currents. However, during the SI onset, least connection process happen between magnetosphere and ionosphere thus, the ground magnetic disturbance was mainly associated with the magnetospheric current.

Performance Effects of Diversification: Theory and Evidence on Importance of Nature of Information

By definition, diversified corporations consist of several segments. By definition, venture capital firms consist of several segments, that is, funds, each of which has its own legal identity. Feasibility of coinvestments between funds that are managed by the same firm, but of which some are focused (`focused funds') on the technology sector, and others, either focused (for arrival at a `focused firm'), or `generalist' (for arrival at a `diversified firm') provides a unique opportunity for empirical tests of performance effects of corporate diversification. Study findings show, relative to focused firms, that diversified (hybrid) firms are associated with positive abnormal long-run exit performance. The finding that diversified firms take better advantage of arrival of positive shocks within investment opportunity sets of focused funds - an opportunity set held in common by focused and diversified firms - provides unambiguous evidence for efficiency of internal capital markets of diversified firms. Formal theoretical predictions and empirical findings show that while performance effects of corporate diversification align with performance effects of internal capital markets, the extant finding that diversification premiums align with dominance of the diversification structure (Santalo and Becerra 2008) lacks character of a necessary condition for efficiency of internal capital markets.