Large-scale Failure Research Articles

The cascading vulnerability of the directed and weighted network

The cascading failure can bring a huge loss for most real-world networks; but, we cannot uncover fully the mechanism and law of the cascading events occurrence. Most networks in which the cascading failure occurred are based on the various ‘flows’, such as power, oils, and information; moreover, the same link degree of the different nodes likely contain the different meanings, where some are large pivotal nodes and some are mini switching centers. Thus, these networks must be described by the directed and weighted network model. Besides, the ‘over-loading’ cascading failures were more analyzed and studied; but the cascading failures caused by ‘short-loading’ were less studied relatively. However, for some directed networks, such as power grids, oil pipe nets, gas pipe nets and information networks, the large-scale failures of network nodes substantially could be induced by ‘short-loading’ in a such similar way as ‘over-loading’. Based on the above reasons, in this paper, we first built the ‘load-capacity’ model of the directed and weighted network. Afterwards the ‘over-loading’ cascading failure model and the ‘short-loading’ cascading failure model based on the directed and weighted network were built. Meanwhile, applying the models to two typical real networks–Poisson distribution network and power law distribution network–intensive study and numerical analysis were carried out. Lastly, two classical networks simulation experiment results are provided. After the numerical and simulation analyses, we gained the following conclusions. For the power law network, the power exponent β of ‘load-capacity’ function should be taken value (0, 1) for a good robustness, and the minimum in-degree and out-degree should be increased respectively, meanwhile, the weight and the scaling exponents of the in-degree and the out-degree distributions should be increased synchronously in the interval (2, 3) for enhancing the resistibility of ‘over-loading’ and ‘short-loading’ failures. For the Poisson network, the power exponent β of loading function should be taken value (0, 3) for a good robustness, and the average weight and the average in-degree should be increased respectively restricting 2<β<3 for enhancing the resistibility of ‘over-loading’ and ‘short-loading’ failures.

Threshold for the Outbreak of Cascading Failures in Degree-Degree Uncorrelated Networks

In complex networks, the size of the giant component formed by unfailed nodes is critically important for estimating the robustness of networks against cascading failures. In order to explore the critical moment of cascading failures break-out, we provide a cascade of overload failure model with local load sharing mechanism and then deduce the threshold of node capacity when the large-scale cascading failures happen and unfailed nodes in steady state cannot connect to each other to form a large connected subnetwork. We get the theoretical derivation of this threshold in degree-degree uncorrelated networks and validate the effectiveness of this method in simulation. This threshold provides us with a guidance to improve the network robustness under the premise of limited capacity resource when creating a network and assigning load. Therefore, this threshold is useful and important to analyze the robustness of networks. We believe that our research provides us with a guidance to improve the network robustness under the premise of limited capacity resource.

Rigid Plastic FE Slope Stability Analysis Combined With Rain Fall Water Infiltration

This paper presents a new slope stability analysis regarding rainfall-induced landslides by coupling a saturatedunsaturated seepage analysis and a rigid plastic finite element method (RP-FEM). Currently, a more valid and reliable disaster prevention system detecting the risk of slope instability due to sudden intense rainfall is required in Japan. However, conventional slope stability methods often fail to predict this new type of landslides. Therefore, the aim of this study is to propose the new slope stability analysis method in the context of rainfall infiltration. This method introduces the effect of seepage force, an increase of unit weight and a reduction of apparent cohesion due to the change in soil suction to obtain the slope stability load factors and collapse mechanisms. Consequently, this method can provide the relatively accurate and valid analysis results, which can be well compared with experimental data. Moreover, it is ascertained that this method can evaluate the different type of slope failure mechanisms: an initial small failure at the toe of the slope caused by the seepage forces and a large-scale failure due to the degradation of the soil apparent cohesion.

Treatment of visceral leishmaniasis: anomalous pricing and distribution of AmBisome and emergence of an indigenous liposomal amphotericin B, FUNGISOME.

Visceral leishmaniasis (VL) is one of the severest forms of parasite borne diseases worldwide with a mortality rate second only to malaria. Treatment of VL patients with currently available chemotherapeutic agents poses problems of large scale failure, toxicity, prolonged hospitalization time, high treatment cost and drug resistance. However, most of these problems can be overcome by the use of liposomal formulations of Amphotericin B (L-AmB). Of the two L-AmBs currently available in Indian market, AmBisome is imported and FUNGISOME is indigenous. Initially AmBisome remained exorbitantly costly and therefore inaccessible to most of the VL patients. However, with the launch of FUNGISOME in India, Gilead in agreement with WHO started a donation program of AmBisome in developing countries through a slashed price of US $18 per vial. The price reduction is, however, restricted to clinical trials thus eluding majority of the VL patients. In fact, India was not included in this program and AmBisome was sold in Indian market at prices higher than the WHO proposed price of US $18 per vial. FUNGISOME, on the other hand, produced consistently good results against VL both clinically and experimentally. In the context of unavailability and price anomaly of AmBisome, successful emergence of FUNGISOME could mark it as the major L-AmB against VL.

Sustainable Business Coordination: A Vedic Solution to the Endemic Crisis of Trust and Coordination

Coordination failure has assumed great significance in both academic literature and real business world. The last global financial crisis can be perceived as a system wide failure of trust and ethics. From a general theoretical stand point this is a large scale failure of the highly cherished ‘invisible hand’ doctrine since Adam Smith. Though there has been considerable degree of study on welfare generating coordination among business players they have failed to generate sustainable solutions, since they are fundamentally based on neoclassical philosophy of selfish utility maximisation. Under information asymmetry, and various other market frictions selfish utility maximisation gives way to problems like moral hazard, this in the end is nothing but a problem of break down of trust and ethical coordination. In this paper we attempt to build a sustainable model of ethical coordination based on the sanatan philosophy of Vedanta, namely, ‘sarbang khalvedam brahma’, or since the same absolute truth embodies every one of us (which we have forgotten due to sheer ignorance or illusion of selfish utility maximisation dictum), we have the potential to exhibit absolute ethical coordination. In the world of business this can be translated as actions based on a more comprehensive utility formulation, which makes the players, incorporate their own pay offs as well as the pay off differences with the others. For manifesting the ideology we here develop a simple game theoretic model, where in a simple two-player game scenario starting with a more comprehensive utility formulation (after Fehr and Schimmt, 1999, and behavioural game theory in general) a sustainable ethical coordination will be achieved, which will be stable. The model developed here is practicable rather an abstract mathematical model, since the main aim is an easy implementation of the model in real life scenario. Overall the authors believe that this work in attempting to unify Vedic philosophy and mainstream economics will contribute to the literature of coordination in general, which is much needed, and also inspire a new strand of literature to come forth.

Enhancing network service survivability in large-scale failure scenarios

Large-scale failures resulting from natural disasters or intentional attacks are now causing serious concerns for communication network infrastructure, as the impact of large-scale network connection disruptions may cause significant costs for service providers and subscribers. In this paper, we propose a new framework for the analysis and prevention of network service disruptions in large-scale failure scenarios. We build dynamic deterministic and probabilistic models to capture the impact of regional failures as they evolve with time. A probabilistic failure model is proposed based on wave energy behaviour. Then, we develop a novel approach for preventive protection of the network in such probabilistic large-scale failure scenarios. We show that our method significantly improves uninterrupted delivery of data in the network and reduces service disruption times in large-scale regional failure scenarios.

Transport Catastrophe Analysis as an Alternative to a Monofractal Description: Theory and Application to Financial Crisis Time Series

The goal of this investigation was to overcome limitations of a persistency analysis, introduced by Benoit Mandelbrot for monofractal Brownian processes: nondifferentiability, Brownian nature of process, and a linear memory measure. We have extended a sense of a Hurst factor by consideration of a phase diffusion power law. It was shown that precatastrophic stabilization as an indicator of bifurcation leads to a new minimum of momentary phase diffusion, while bifurcation causes an increase of the momentary transport. An efficiency of a diffusive analysis has been experimentally compared to the Reynolds stability model application. An extended Reynolds parameter has been introduced as an indicator of phase transition. A combination of diffusive and Reynolds analyses has been applied for a description of a time series of Dow Jones Industrial weekly prices for the world financial crisis of 2007–2009. Diffusive and Reynolds parameters showed extreme values in October 2008 when a mortgage crisis was fixed. A combined R/D description allowed distinguishing of market evolution short-memory and long-memory shifts. It was stated that a systematic large scale failure of a financial system has begun in October 2008 and started fading in February 2009.

The construction and legitimation of workplace bullying in the public sector: insight into power dynamics and organisational failures in health and social care.

Health-care and public sector institutions are high-risk settings for workplace bullying. Despite growing acknowledgement of the scale and consequence of this pervasive problem, there has been little critical examination of the institutional power dynamics that enable bullying. In the aftermath of large-scale failures in care standards in public sector healthcare institutions, which were characterised by managerial bullying, attention to the nexus between bullying, power and institutional failures is warranted. In this study, employing Foucault's framework of power, we illuminate bullying as a feature of structures of power and knowledge in public sector institutions. Our analysis draws upon the experiences of a large sample (n=3345) of workers in Australian public sector agencies - the type with which most nurses in the public setting will be familiar. In foregrounding these power dynamics, we provide further insight into how cultures that are antithetical to institutional missions can arise and seek to broaden the debate on the dynamics of care failures within public sector institutions. Understanding the practices of power in public sector institutions, particularly in the context of ongoing reform, has important implications for nursing.

Dependence of runout distance on the number of rock blocks in large-scale rock-mass failure experiments

To examine how the number of rock blocks affects the rock-mass runout distance, large-scale outdoor rockfall experiments were physically performed using cubiform granite rock blocks on a slope prepared with granite slabs under both dry and water-saturated conditions. To learn more about the runout mechanism, numerical simulations were also conducted using three-dimensional DEM to reproduce the physical experiments under dry conditions. Longitudinal rock-mass runout distance between the gravity centre in the initial rock block assembly before failure and the apparent gravity centre at final deposition was 10 % larger for experiments under water-saturated conditions than those under dry conditions, with identical numbers of rock blocks in the physical experiments. The physical and numerical experiments revealed that rock blocks at the front and top surfaces had a longer runout distance than those at the rear and bottom surfaces. A rock block scarcely surpassed the rock blocks in front longitudinally and the rock blocks next to it laterally. The equivalent coefficient of friction between gravity centres was positively correlated with the number of rock blocks, which contradicts the findings of a negative correlation between the volume of sturzstroms (rockfall avalanches) and the equivalent coefficient of friction in classic studies on the long runout mechanisms. Our results were likely attributable to the fact that more kinetic energy was dissipated due to repeated inelastic intercollisions with other surrounding rock blocks and granite slabs when the initial rock-mass volume (number of rock blocks) was larger.

A flexible black-start network partitioning strategy considering subsystem recovery time balance

Summary When black out occurs, the whole power grid is divided into several subsystems to increase the efficiency and shorten the duration of power system restoration by using parallel restoration strategy. Therefore, reasonable network partitioning in black start phase after large-scale power failures is important in both theory and practice. In this paper, a flexible black start network partitioning strategy considering the subsystem recovery time balance is proposed. Based on the rules of zone division and analyzing initial black start partitioning model of subsystem shortest recovery path, subsystem recovery time balance index is defined to represent disparity of every subsystem's restoration process. Meanwhile, a flexible factor of total recovery time is introduced as part of objective function with the time balance index, aiming at reducing waiting time of the synchronization operation and strengthens efficiency of black start at the cost of the least total time increment. The classic Dijkstra algorithm and improved genetic algorithm are employed to obtain the optimal restoration plan in the paper. Case study on IEEE 118-bus test system shows the validity of the methodology proposed. Copyright © 2014 John Wiley & Sons, Ltd.

Study of the Use of a Genetic Algorithm to Improve Networked System-of-Systems Resilience

Large scale failures or degradation resulting from smaller initial failures or disruptions in networked system-of-systems are an issue in multiple areas - for example cascading failures in electrical power grids or large disruptions in national air traffic due to local or regional weather conditions. The system architecture can have a significant impact on system-of-systems susceptibility to large scale failures.The study presented in this paper uses a simple interdependent networked system-of-systems failure model, integrated into a unique objective function that addresses both the overall level of failure and the rate of failure progression, and a genetic algorithm to demonstrate an integrated failure modeling based optimization method to select system-of-systems architectures for improved resiliency.The results for the integrated failure model/genetic algorithm model results converged rapidly to a steady state values. This initial integration shows a possible path forward to more sophisticated model integration and optimization and demonstrates a basic level of feasibility for this general approach.

Learning geotemporal nonstationary failure and recovery of power distribution.

Smart energy grid is an emerging area for new applications of machine learning in a nonstationary environment. Such a nonstationary environment emerges when large-scale failures occur at power networks because of external disruptions such as hurricanes and severe storms. Power distribution networks lie at the edge of the grid, and are especially vulnerable to external disruptions. Quantifiable approaches are lacking and needed to learn nonstationary behaviors of large-scale failure and recovery of power distribution. This paper studies such nonstationary behaviors in three aspects. First, a novel formulation is derived for an entire life cycle of large-scale failure and recovery of power distribution. Second, spatial-temporal models of failure and recovery of power distribution are developed as geolocation-based multivariate nonstationary GI(t)/G(t)/∞ queues. Third, the nonstationary spatial-temporal models identify a small number of parameters to be learned. Learning is applied to two real-life examples of large-scale disruptions. One is from Hurricane Ike, where data from an operational network is exact on failures and recoveries. The other is from Hurricane Sandy, where aggregated data is used for inferring failure and recovery processes at one of the impacted areas. Model parameters are learned using real data. Two findings emerge as results of learning: 1) failure rates behave similarly at the two different provider networks for two different hurricanes but differently at the geographical regions and 2) both the rapid and slow-recovery are present for Hurricane Ike but only slow recovery is shown for a regional distribution network from Hurricane Sandy.

Dynamic fault-tolerance analysis of scale-free topology in wireless sensor networks

It is very important in practice to avoid cascading failures by increasing the dynamic fault-tolerance of the network. Firstly, a cascading failure model is proposed in this paper, based on the characteristics of the variable load and the fixed capacity of the nodes in wireless sensor network scale-free topology. Then the influences of the load parameter and topology parameters on the fault tolerance are investigated in the case of cascading failure caused by random failure nodes. Finally the critical value of load for the large-scale cascading failure of network is deduced. Simulation result shows that the network's cascading failure fault-tolerance is positively related with the degree parameters, coefficient and power-law exponent. Researches provide regulation to avoid the cascading failure caused by the random failure nodes effectively from optimizing the parameters viewpoint.

A Study of the Effect of Basic Network Characteristics on System-of-System Failure Propagation

Real life examples of large system level failures in complex networked system are fairly common, with national and regional level power grids providing numerous cases where local failures have resulted in broad systemic failures. As large networked systems-of-systems are increasingly common, their susceptibility to large scale failures is of significant interest. This paper presents the results of a study using a simple model to investigate the impacts of basic architecture characteristics on the spread of failures through a system-of-system after an initial failure occurs.The study reported here uses a non-symmetric inter-grid only failure model to investigate the sensitivity of failure progression due to failure in dependent nodes in a system-of-system composed of dependent grid networks to the several basic parameters, including initial failure size, grid node density and grid interdependency radius.Despite the use of only an inter-grid failure mechanism, the study results generally showed a rapid failure propagation to a steady state condition. A possible mechanism for this return to steady state in terms of the expanding failure front and probability that existing dependent nodes lie outside of the failure front is discussed.

Topology-based Proactive Network Protection in Large-scale Failure Scenarios

Natural disasters are among the main causes of large-scale failure scenarios. The dynamic behaviour of natural disasters and their probabilistic failure pattern indicates a need for a dynamic probabilistic protection approach to address the issue and reduce the number of disrupted connections in the network. Appropriate data protection against a time-varying destructive phenomenon serves to prevent damage before it occurs. In this case, the endangered route should be detected and the data passing through should be rerouted through more reliable paths prior to failure. The high-risk paths can be detected based on the decision parameters in the dynamic preventive approach. In this article, we develop a new method to improve the assignment procedure of decision factors in preventive protection models using network topological properties and links failure probability. The proposed decision parameters are adaptive with the network conditions and updateable while the disaster spreads through the region. The adaptive characteristic of the rerouting decision parameter will enhance network efficiency and facilitate network management.

The Resilience of WDM Networks to Probabilistic Geographical Failures

Telecommunications networks, and in particular optical WDM networks, are vulnerable to large-scale failures in their physical infrastructure, resulting from physical attacks (such as an electromagnetic pulse attack) or natural disasters (such as solar flares, earthquakes, and floods). Such events happen at specific geographical locations and disrupt specific parts of the network, but their effects cannot be determined exactly in advance. Therefore, we provide a unified framework to model network vulnerability when the event has a probabilistic nature, defined by an arbitrary probability density function. Our framework captures scenarios with a number of simultaneous attacks, when network components consist of several dependent subcomponents, and in which either a 1+1 or a 1:1 protection plan is in place. We use computational geometric tools to provide efficient algorithms to identify vulnerable points within the network under various metrics. Then, we obtain numerical results for specific backbone networks, demonstrating the applicability of our algorithms to real-world scenarios. Our novel approach allows to identify locations that require additional protection efforts (e.g., equipment shielding). Overall, the paper demonstrates that using computational geometric techniques can significantly contribute to our understanding of network resilience.

Nickel aluminate spinel reinforced ceramic hollow fibre membrane

Ceramic hollow fibre membranes are suitable for application in many industrial processes that involve harsh conditions such as high temperatures and concentrated organic solvents because of their high thermal and chemical stability. The major limitation of ceramic hollow fibre membrane is the brittle nature of ceramic materials, which leads to difficulty in large scale production and failure in pressurised processes. This paper presents the reinforcement of alumina (Al2O3) hollow fibre membrane by nickel aluminate spinel (NiAl2O4). The ceramic hollow fibre membrane was fabricated by the widely used phase inversion method. The NiAl2O4 phase was formed by the reaction of nickel (II) oxide (NiO) with Al2O3 during sintering. A maximum flexural strength of 156MPa was achieved by the NiAl2O4/Al2O3 hollow fibre membrane containing 16.4wt% of NiAl2O4, which was 2.3 times of that of the pure alumina sample. The 16.4wt% NiAl2O4/Al2O3 hollow fibre membrane had a porosity of 46.8%, a mean pore size of 330nm determined by a gas bubble pressure method, and a pure water flux of 597L/m2hbar at a testing pressure of 2bar. NiAl2O4/Al2O3 hollow fibre membrane could achieve a flexural strength comparable to higher-cost yittria stabilized zirconia and silicon nitride hollow fibres within the porosity range of 46.8–55.2%.

Post-rift sedimentary evolution of the Gebra Debris Valley. A submarine slope failure system in the Central Bransfield Basin (Antarctica)

Abstract The combined analysis of paleomorphology, stratigraphy and seismic facies allows us to present new insights into the formation and evolution of the Gebra Valley, located on the lower continental slope of the Central Bransfield Basin (NE Antarctic Peninsula). Repeated large-scale slope failure events were responsible for the cut-and-fill features forming the Gebra Valley. This study revealed a mid-Pleistocene Gebra paleovalley that was progressively and completely infilled. During the last glacial cycle the infilled paleovalley was reoccupied, forming the present day Gebra Valley. Both valley incisions are genetically related to large-scale failures associated with high-energy gravity flows or mass flows. The infilling of the valley involved channelized mass flows of various dimensions and channelized and unchannelized turbidity currents. Alternating erosive periods, during which the valley evacuated sediment from the slope toward the basin, and depositional periods, during which it was fully infilled, allows it to be defined as the “Gebra Debris Valley”. Taking into account the presence of faults controlling the headwall locations and the stratigraphic correlation established with glacial periods, the genesis of the Gebra Debris Valley could have been controlled by the interplay of both the tectonic history of the Bransfield Basin and the glacial cycles that allowed grounding events to reach the upper continental slope.

Radiostereometric analysis of early implant migration – a valuable tool to ensure proper introduction of new implants

Radiostereometric analysis of early implant migration – a valuable tool to ensure proper introduction of new implants

Deep-Seated Slope Failures Induced by Inappropriate Cutting in China

Given insufficient geological investigation and inadequate interpretation of geological settings, remedial works for localized cut slope collapses may induce large-scale failures and cause remarkable damage, as well as economical loss. A number of recent reports have addressed individual large-scale failures due to inappropriate cutting, but the systematic classification of failure patterns has received less attention. In this study, a re-profiling triggered landslide is described in detail. The deep slip surface is located by field measurements; then, the stability of the slope before and after cutting is assessed with the limit equilibrium method. Three types of slopes prone to deep-seated failures are introduced: the loose deposits type, the ancient landslide type, and the deep adverse discontinuities type. The mechanism of each failure pattern is illustrated with a case study. The stability analyses indicate that inappropriate slope profiling may greatly reduce the factor of safety (FS) of a slope. Recommendations are given for mitigating the deep-seated landslide induced by inappropriate cutting, and a case history of successful measures is presented.