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This work presents two new error estimation approaches for the BEM applied to 2D potential problems. The first approach involves a local error estimator based on a gradient recovery procedure in which the error function is generated from differences between smoothed and non-smoothed rates of change of boundary variables in the local tangential direction. The second approach involves the external problem formulation and gives both local and global measures of error, depending on a choice of the external evaluation point. These approaches are post-processing procedures. Both estimators show consistency with mesh refinement and give similar qualitative results. The error estimator using the gradient recovery approach is more general, as this formulation does not rely on an ‘optimal’ choice of an external parameter. This work presents also the use of a local error estimator in an adaptive mesh refinement procedure. This r-refinement approach is based on the minimization of the standard deviation of the local error estimate. A non-linear programming procedure using a feasible-point method is employed using Lagrange multipliers and a set of active constraints. The optimization procedure produces finer meshes close to a singularity and results that are consistent with the problem physics. Copyright © 2002 John Wiley & Sons, Ltd.

The present work aims to offer a contribute for the evaluation of the opportunity to adopt strategies based on state support or, alternatively, on the managerial autonomy of local bodies in financial trouble. The research, after analysing the main guidelines at European level, presents the results of an empirical investigation on the economic effects produced on the local economy by the financial default of the Municipality of Taranto. The choice of the Municipality of Taranto is due both to the significant magnitude of the ascertained debt, which was one of the highest in the history of Italy, and to the considerable economic effects caused by the recovery procedure. Specifically, with reference to the companies admitted to the passive mass, have been firstly determined the economic losses they suffered and, secondly, has been analysed the survival status of the companies involved in the insolvency procedure and located in the local area of reference, as well as the related strategies they adopted.

MEMS (micro electromechanical systems) accelerometer is increasing applied in high overload circumstances. The recovery time and bias shift of accelerometer could significantly influence the calculation accuracy of navigation systems. Recovery procedure of MEMS high overload accelerometer due to high-g shock has been studied. It is a complicated strong nonlinear response procedure. Different shock conditions and accelerometer's electro mechanical parameters could influence the recovering trajectory and recovery time. Variations due to shock which could cause bias shift are investigated. Electrical shock simulation test and HPB (Hopkinson pressure bar) shock experiments are performed to verify simulation analysis. The sensor generally demonstrates a bias shift within ±20mg after enduring 10,000g to 21,000g shock based on 20 specimens' results.

Air carriers will use simulators to train pilots to recover from fully developed stalls. Flight simulator models will have to portray an airplane’s dynamics satisfactorily to achieve the associated training objectives. That imposes new simulator requirements. This study evaluated several full stall simulator models to meet those requirements. Three new stall models were tested in a Boeing 737-800 simulator. One model used the conventional approach by matching flight test data to within a tolerance. Another model did not rely on flight test data, but instead combined computational aerodynamics, scaled wind tunnel data, and expert opinion from a test pilot who had stalled the actual aircraft. The third model added a roll asymmetry to the unmodified simulator model as a simple way to possibly meet the training objectives. The test had two phases. In the first phase, test pilots who had stalled a 737 airplane evaluated the models by performing typical flight test stall maneuvers in the simulator. The second phase used airline pilots type-rated in the 737 but who had not stalled a 737 airplane. The airline pilots were placed in groups, and each group trained with one of the models. Each airline pilot was then checked on the model developed from flight data, which represented the truth model. The second phase also included a surprise stall scenario with each airline pilot having to recover from a stall using the model they would train with. The results revealed wide ranges in the subjective evaluations of the test pilots, as well as in the objective performance of the airline pilots across the models. However, many of the averages did not show significant differences. All airline pilots agreed or strongly agreed that they were surprised by the surprise stall scenario. In that scenario, less than one quarter of the airline pilots strictly followed the proper stall recovery procedure on which they had been briefed. Less than half maintained a nose-down input until the stall warning stopped. For situations when developing a stall model based on flight data is not practical, the alternative approach of developing a model based on computational aerodynamics, wind tunnel data, and subject expert opinion appears feasible.

A system that began with DNA tagging of oil cargoes has expanded to provide tracers for such diverse commodities as grain, silk, antiques, diamonds, high value documents and packaging. It has been used for a great variety of purposes. One is the covert tracing of marked commodities that have entered the country as “grey” imports, sold at reduced prices. Other users are interested in authenticating products, particularly in the antiques trade. Authentication of documents can be achieved through the incorporation of a DNA tracer into the ink used to print the document. It would be impossible for counterfeiters to determine the sequence of the added DNA marker, particularly in the presence of other masking DNA. The number of unique tags that can be provided by a DNA molecule is of the order of 1060. Each application is unique and requires close collaboration between the company and the customer. It needs its own customized application and recovery procedure.

The Geophysical and Oceanographic Station for Abyssal Research (GEOSTAR), an autonomous seafloor observatory that collects measurements benefiting a number of disciplines during missions up to 1 year long, will begin the second phase of its first mission in 2000. The 6–8 month investigation will take place at a depth of 3400 m in the southern Tyrrhenian basin of the central Mediterranean. GEOSTAR was funded by the European Community (EC) for $2.4 million (U.S. dollars) in 1995 as part of the Marine Science and Technology programme (MAST). The innovative deployment and recovery procedure GEOSTAR uses was derived from the “two-module” concept successfully applied by NASA in the Apollo and space shuttle missions, where one module performs tasks for the other, including deployment, switching on and off, performing checks, and recovery. The observatory communication system, which takes advantage of satellite telemetry, and the simultaneous acquisition of a set of various measurements with a unique time reference make GEOSTAR the first fundamental element of a multiparameter ocean network.

It is found that the accuracy of recovered stress at central area of bilinear quadrilateral element by previous SPR methods 1-3) is inferior. Sometimes, the recovered stress is even worse than the raw result of FEA at that area. This may be due to only recovering the nodal stresses and using them to interpolate the stress elsewhere. To overcome this, the recovery procedure is modified by considering additional nodes located at middle point of element edges and the central point of elements and introducing a weighted average procedure to determine the recovered result at some nodes. Numerical analysis of three examples demonstrates the capability of the new procedure to improve the accuracy of recovery at the central area, and the contribution of the weighted average procedure to the stability of recovery at boundary area.

In this paper, we study an approach for recovery of an improved stress resultant field for plate bending problems, which then is used for a posteriori error estimation of the finite element solution. The new recovery procedure can be classified as Superconvergent Patch Recovery (SPR) enhanced with approximate satisfaction of interior equilibrium and natural boundary conditions. The interior equilibrium is satisfied a priori over each nodal patch by selecting polynomial basis functions that fulfil the point-wise equilibrium equations. The natural boundary conditions are accounted for in a discrete least-squares manner. The performance of the developed recovery procedure is illustrated by analysing two plate bending problems with known analytical solutions. Compared to the original SPR-method, which usually underestimates the true error, the present approach gives a more conservative error estimate. Copyright © 1999 John Wiley & Sons, Ltd.

This is a report of a case of an egg recovery procedure completed with manual suction instead of the automated negative pressure suction. A 35–year-old woman who was undergoing in vitro fertilization (IVF) treatment had to undergo oocyte recovery using manual suction through a syringe instead of the automated negative pressure suction systems because of the failure of both the initial and replacement systems. The treatment cycle ended in a positive pregnancy test and a clinical pregnancy with acceptable oocyte fertilization rates and no complications during procedure. The case presented may be an implication for an alternative implementation in cases of emergency, particularly when low-cost IVF is a target.

An approximation of the dual problem for goal-oriented error estimation is derived, which preserves the numerical structure of the primal problem, usually found in standard finite element implementations for solid mechanics. For the error estimation we apply a higher-order recovery procedure. An application to elasto-plasticity is given. Numerical examples demonstrate the effectiveness of the procedure. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)

The performance of three different stress recovery procedures, namely, the superconvergent patch recovery technique (SPR), the recovery by equilibrium in patches (REP) and a combined method known as the LP procedure is reviewed. Different order of polynomials and various patch formation strategies have been employed in the numerical studies for the construction of smoothed stress fields. Two 2-D elastostatic problems of different characteristics are used to assess the behaviour of the stress recovery procedures. The numerical results obtained indicate that when the order of polynomial used in the recovery procedure is equal to that of the finite element analysis, the behaviours of all three recovery procedures are very similar and all of them are adequate to provide a reliable recovered stress field for error estimation. In case that the order of polynomial of the recovered stress is increased, the LP procedure seems to give a more stable recovery matrix and a more reliable recovered stress field than the REP procedure. © 1998 John Wiley & Sons, Ltd.

A three-dimensional stress recovery procedure is described in this paper. As usual, in the finite element method, we suppose to know a good approximation of the nodal values of the displacements; starting from the nodal displacements, we evaluate the strain components at Gauss points of a 27-node prismatic element, then the stress components at the same points. Stresses are finally projected to corner nodes with a smoothing procedure. The repeated application of such a procedure to a set of adjacent elements allows the construction of the stress field in a finite region of any deformed body. The proposed method finds its most natural application in the field of composite materials as shown in the numerical applications which reveal a good concordance of results with an equivalent three-dimensional finite element analysis.

Right safety during normal as well as during hazardous weather conditions is a key issue in modern flight control systems. From all weather phenomena, low-altitude wind shear remains a particular concern to flight safety. Aircraft might not be able to cope with the energy loss due to a windshear encounter. A fuzzy flight controller that employs total energy concepts has been extended to improve safety during windshear. Through incorporating a special windshear recovery procedure, the fuzzy controller provides aggressive thrust management and flight envelope protection. The application of this generic windshear recovery concept in a take-off scenario is demonstrated by simulation examples.

This paper describes and analyzes the performance of a reliable, finite-buffer, point-to-multipoint, selective repeat (SR) protocol with accumulative acknowledgment. It is simple to implement and suitable for high-speed data communications, mainly in satellite environments in which most of the time the channel bit error rate is very low and only occasionally becoming high. The proposed strategy is based on three key ideas. The first concept encompasses the use of accumulative acknowledgments in order to reduce the required processing overhead and implementation complexity, mainly in the transmitter. The second and third ideas are aimed at improving the throughput efficiency by making the most of the selective repeat recovery procedure (Go-Back(N) procedure is only employed when certain combinations of errors occur) and processing and storing all messages received correctly during an exceptional condition, even after error detections. The proposed strategy performs well under various conditions being more efficient than most known point-to-multipoint GB(N) strategies for low bit error rates.

A linear-quadratic Gaussian (LQG) technique followed by a loop transfer recovery (LTR) approach is adopted to synthesize a robust controller for a high-performance industrial electro-hydraulic actuator. The actuator moves a platform that carries a variable load and is subject to parameter variations and disturbances. The recovery procedure provides sufficient stability and performance robustness to the closed loop system. The system is tested with various parameter variations occurring in the field and is found to perform satisfactorily. (C) 1998 . .

The effectiveness and reliability of three local least squares fit procedures for the construction of smoothed moments and shear forces for the solution of the Reissner-Mindlin (RM) thick plate model are reviewed. The three procedures considered are, namely, the superconvergent patch recovery technique (SPR), the recovery by equilibrium in patches (REP) and the recovery procedure suggested by Lee, Park and Lee (LP). Numerical studies are carried out by applying these three recovery procedures for the construction of smoothed stress fields for various RM plate bending problems. The results obtained indicate that if the order of polynomial used in the stress recovery is the same as that for the finite element analysis, all three procedures produce recovered stress fields with very similar accuracy and convergence rate. However, when the order of polynomial is raised, if the exact solution is smooth without any strong boundary layers or singularities, both the REP and LP procedures can produce more accurate stress fields than the SPR. In case that singularities or boundary layers are present, the LP procedure often outperforms the REP procedure and results in more stable recovery matrices and more accurate recovered stress fields.

This paper deals with the reconfiguration of manufacturing systems in case of disfunctioning. A manufacturing system is considered as a discrete-event system and the model used is the Vector Discrete-Event System. The aim of this formalization is to provide a supervisor that reconfigures the system in order to react to disfunctioning. This type of faulty behavior may result fronl process perturbation caused by equipment malfunction, failure or similar reasons. The supervisor can be viewed as a compensator that allows the system to function in continuity in case of failure occurrence. Propositions have been made to take into account some criteria in the recovery procedure in order to design an optimized reactivity control for critical failures. An example of a manufacturing system is given.

This paper deals with the modeling of an extended quartet multiprocessor kernel used for the evaluation of the Hermes system. Hermes is a multiprocessor hybrid system architecture used as a machine vision system. The functionality of Hermes requires an asynchronous information flow upwards and downwards, where "orders"(in a form of code and data) go down and "abstracted" or processed picture information goes up along the system's hierarchy. Moreover, the overall functional behavior of the Hermes system can be considered as an extended quartet kernel in an abstracted manner. The extended quartet kernel studied here presents either a memory-to-memory (M-M) or a bus-to-bus (B-B) connectivity. The evaluation of these two kernel's configurations (M-M, B-B) defines that the structural design of the Hermes system will be based on the M-M scheme. When failures occur on the quartet kernel, however, the M-M scheme will be converted into a B-B one by using a failure recovery procedure. The evaluation of the quartet kernel configurations is based on a probabilistic model. Failures and recovery procedures on the quartet kernel are discussed and the performance evaluation of the kernel (under failures) is also provided.

A PCS network constantly tracks the locations of the mobile stations so that incoming calls can be delivered to the target mobile stations. In general, a two-level database system is used to store location information of the mobile stations. When the location databases fail, incoming calls may be lost. This article describes the standard GSM database failure restoration procedure which reduces the number of lost calls. Then we propose an efficient visitor location register (VLR) identification algorithm for the home location register (HLR) failure recovery procedure, which utilizes mobile station movement information to speed up the recovery procedure.

This paper studies the database failure recovery procedure for cellular phone networks as part of the Electronic Industries Association/Telecommunications Industry Association Interim Standard 41 (EIA/TIA IS-41). Before the location information of the database is recovered, phone calls may be lost. The restoration process can be sped up by having the mobile phones to periodically confirm their existence by radio contact with the cellular network. We show that, under some cost assumptions, periodic update interval should be chosen to be approximately equal to the call interarrival time, with more frequent updates for more unreliable system. We also show that the cost of an optimized system is relatively small and stable, if the system is even moderately reliable. Finally, if the system is at least moderately reliable, the effects of call origination rate and the rate at which Location Areas are crossed, are rather small, assuming that the periodic update interval was chosen as stated above. Thus, in such cases, optimization of the size of the Location Area can be made independent of the optimization of the periodic update process.

The fixed smeared crack concept with strain decomposition is reformulated utilizing a self-adaptive strategy at the constitutive level. This formulation focuses on continuous adaptation of the crack band width based on the incremental finite element solution and the idea of nonlocal continuum. The required nonlocal forms are obtained by means of the superconvergent patch recovery procedure. Comparison with experimental results indicates the superiority of the present formulation over the standard smeared cracking.

A new procedure is proposed for estimating the State-of-Polarisation of the received optical signal in Four-Quadrature Amplitude Modulation systems. The proposed solution, which is obtained on the basis of the Maximum Likelihood criterion, is merely electronic and operates in the presence of laser phase noise, photodetection noise and cross-polarisation interference. It employs a suitably designed training sequence to estimate Jones' parameters in the data-aided training mode. A proper decision-directed procedure is then activated to lock-in the estimated parameters in the operative mode. The variances of the resulting estimation errors are evaluated and the overall system performance is given in terms of Bit Error Probability versus signal-to-noise ratio. The theoretical analysis and the computer simulations show the superiority of the proposed recovery procedure with respect to alternative solutions recently proposed in literature.

Most of the preassigned pivot agenda algorithms that extend the Hellerman-Rarick P3 algorithm assume that the input matrix is nonsingular. Due to numerical instability, this assumption may be violated and these algorithms fail. We present a modification of the P3 algorithm which includes a procedure to recover from this type of numerical instability. The recovery procedure is integrated into P3 in such a way that all previous work can be maintained and it reduces the likelihood that additional recovery will be required.

For some computing systems, failure is rare enough that it can be ignored. In other systems, failure is so common that how to handle it can have a significant impact on the performance of the system. There are many different recovery schemes for tasks, however, they can be classified into three broad categories: 1) Resume: when a task fails, it knows exactly where it stops and can continue at that point when allowed to resume (i.e., preemptive resume - prs); 2) Replace : when a task fails, then later when the processor continues, it begins with a brand new task (i.e., preemptive repeat different prd); and, 3) Restart: when a task fails it loses all work done to that point and must start anew upon continuing later (i.e., preemptive repeat identical - pri ).In this paper, assuming a computing system is unreliable, we discuss how heavy-tail (hereafter referred to as power-tail - PT) distributions can appear in a job's task stream given the Restart recovery procedure. This is an important consideration since it is known that power-tails can lead to unstable systems [4], We then demonstrate how to obtain performance and dependablity measures for a class of computing systems comprised of P unreliable processors and a finite number of tasks N given the above recovery procedures.

The ability to recover from errors is necessary for robots to cope with unexpected situations in a dynamic environment. Efficient error recovery should allow the robot to utilise existing knowledge of the task and learn new error recovery strategies from observation. This paper proposes an automatic error recovery procedure that allows the robot to handle both known and unknown error states using a Petri net representation of the task. For known error states, the robot can directly adjust the sequencing of actions using the Petri net representation to complete the task, while for unknown error states, the robot can learn how to perform error recovery from a human demonstrator by extending the existing Petri net. The proposed method is verified on a real robot performing a block stacking task.

The compressed sensing paradigm allows to efficiently represent sparse signals by means of their linear measurements. However, the problem of transmitting these measurements to a receiver over a channel potentially prone to packet losses has received little attention so far. In this paper, we propose novel methods to generate multiple descriptions from compressed sensing measurements to increase the robustness over unreliable channels. In particular, we exploit the democracy property of compressive measurements to generate descriptions in a simple manner by partitioning the measurement vector and properly allocating bit-rate, outperforming classical methods like the multiple description scalar quantizer. In addition, we propose a modified version of the Basis Pursuit Denoising recovery procedure that is specifically tailored to the proposed methods. Experimental results show significant performance gains with respect to existing methods.

Fault-tolerance and its associated overheads are of great concern for current high performance computing systems and future exascale systems. In such systems, message logging is an important transparent rollback recovery technique considering its beneficial feature of avoiding global restoration process. Most previous work designed and implemented message logging at the library level or even lower software hierarchy. In this paper, we propose a new message logging protocol, which elevates payload copy, failure handling and recovery procedure to the user level to present a better handling of sender-based logging for collective operations and guarantee a certain level of portability. The proposed approach does not record collective communications as a set of point-to-point messages in MPI library; instead, we preserve application data related to the communications to ensure that there exists a process which can serve the original result in case of failure. We implement our protocol in Open MPI and evaluate it by NPB benchmarks on a subsystem of Tianhe-1A. Experimental results outline a improvement on failure free performance and recovery time reduction.

A tuning-free procedure is proposed to estimate the covariate-adjusted Gaussian graphical model. For each finite subgraph, this estimator is asymptotically normal and efficient. As a consequence, a confidence interval can be obtained for each edge. The procedure enjoys easy implementation and efficient computation through parallel estimation on subgraphs or edges. We further apply the asymptotic normality result to perform support recovery through edge-wise adaptive thresholding. This support recovery procedure is called ANTAC, standing for Asymptotically Normal estimation with Thresholding after Adjusting Covariates. ANTAC outperforms other methodologies in the literature in a range of simulation studies. We apply ANTAC to identify gene-gene interactions using an eQTL dataset. Our result achieves better interpretability and accuracy in comparison with CAMPE., Comment: 54 pages, 6 figures

The EU bank recovery and resolution directive includes mechanisms for recovery (or “early intervention”) for groups. These are: group recovery plans, intra-group financial assistance and coordination of early intervention measures regarding groups.But do these group provisions ensure a consistent recovery procedure for the entire banking group across borders? While recovery tools applicable to more than one group affiliate are part of the EU regulatory framework, use of such tools across borders depends on the discretion of supervisors of group affiliates. Recovery tools can only apply across group affiliates if supervisors reach joint decisions and make use of recovery tools in a consistent, cooperative and coordinated manner across the group. This means that the effectiveness of group recovery depends greatly on the institutional architecture of supervision in the EU, and in particular, the relationships between supervisors within and beyond the SSM.

Part 3: Storage; International audience; With the advent of cloud computing, many applications have embraced the ensuing paradigm shift towards modern distributed key-value data stores, like HBase, in order to benefit from the elastic scalability on offer. However, many applications still hesitate to make the leap from the traditional relational database model simply because they cannot compromise on the standard transactional guarantees of atomicity, isolation, and durability. To get the best of both worlds, one option is to integrate an independent transaction management component with a distributed key-value store. In this paper, we discuss the implications of this approach for durability. In particular, if the transaction manager provides durability (e.g., through logging), then we can relax durability constraints in the key-value store. However, if a component fails (e.g., a client or a key-value server), then we need a coordinated recovery procedure to ensure that commits are persisted correctly. In our research, we integrate an independent transaction manager with HBase. Our main contribution is a failure recovery middleware for the integrated system, which tracks the progress of each commit as it is flushed down by the client and persisted within HBase, so that we can recover reliably from failures. During recovery, commits that were interrupted by the failure are replayed from the transaction management log. Importantly, the recovery process does not interrupt transaction processing on the available servers. Using a benchmark, we evaluate the impact of component failure, and subsequent recovery, on application performance.

Revisiting a path-integral procedure of recovering gauge invariance from anomalous effective actions developed by Harada and Tsutsui, it is shown that there are two ways to achieve gauge symmetry: one already presented by the authors, which is shown to preserve the anomaly in the sense of standard conservation law, and another one which is anomaly-free, preserving current conservation. It is also shown that the aplication of Harada-Tsutsui technique to other models which are not anomalous but do not exhibit gauge invariance allows the identification of the gauge invariant formulation of the Proca model, also done by the referred authors, with the Stueckelberg model, leading to the interpretation of the gauge invariant map as a generalization of the Stueckelberg mechanism., Comment: 17 pages

Recovering three-dimensional shape of an object from a single line drawing is a classical problem in computer vision. Methods proposed range from Huffman–Clowes junction labeling, to Kanade's gradient space and skew symmetry analysis, to Sugihara's necessary and sufficient condition for a realizable polyhedral object, to Marill's MSDA shape recovery procedure, to Leclerc–Fischler's shape recovery procedure which assures planar faces, and to the recent Baird–Wang's gradient-descent algorithm which has a favorable time complexity. Yet all these assume perfect line drawings as the input. We propose a method that through the use of iterative clustering interprets an imperfect line drawing of a polyhedral scene. It distinguishes the true surface boundaries from the extraneous ones like the surface markings, fill-in the missing surface boundaries, and recovers 3-D shapes satisfying constraints of planarity of faces and parallel symmetry of lines, all at the same time. Experiments also show that the 3-D interpretation agrees with human perception.

This paper presents approximate analytical solutions for the diffusion problems of a cylindrical hole in an infinite medium and a slot in an infinite medium with properly prescribed boundary conditions and initial conditions. These solutions have much simpler forms than those of exact analytical solutions, and asymptotically approach the exact solutions with increasing time or the material point moving away from the internal boundary. The approximate analytical solution for the diffusion problem of a slot in an infinite medium is applied to establish a shape function for the infinite elements. Good agreement is found in comparison of our results with those presented by Li and Huang and Cinco‐Ley et al. Finally, an example simulating a primary recovery procedure in hydraulic fracturing technique for an oil field is presented.

This is the first of two articles concerning error estimation and adaptive refinement techniques applied to convective heat transfer problems. This study presents the detailed development of the proposed error estimator. The error estimator takes into account the coupling effects of the dependent variables (e.g., velocity and temperature) on the discretization error and, consequently, on the adaptive meshes. An averaging procedure is also proposed as a substitute for the smoothing/recovery procedure used to evaluate the gradients. The implementation of the averaging technique is simple and cost effective. Numerical experiments demonstrate that the proposed methodology results in a dramatic reduction in computational costs.

This paper describes the application of a multivariable robust controller based on LTR-i methodology for roll damping and course steering of a ship by rudder and fins. The controller uses a non observer based control structure, and a partial recovery procedure over the band of interest frequencies. Robustness characteristics of the controller in the face of uncertainties are analyzed and the benefits are proved by simulation with a non linear model.

This paper is mainly focused on the energy efficient cluster-based data processing. Since day-by-day a huge number of data are being placed in servers worldwide, there is a need of extra data processing. But for using commodity hardware for slave nodes, there is enough possibility of server node failure in hadoop cluster. Though different ways of data recovery are there, the need of energy for server node is another matter of concern. So, energy efficient failure recovery procedure has been introduced in which energy efficiency can be achieved by increasing workload into the server processor with concurrent execution process. Moreover, in this cluster, covering and non-covering subset-based platform is used. In this technique, the waiting time of covering subset used for recovering data is reduced besides power consumption.

The nodes in mobile ad hoc networks (MANETs) are susceptible to various types of failures and therefore the protocols designed for these networks are required to be fault tolerant. Checkpointing and rollback recovery is a well explored fault tolerance technique for the static and cellular mobile distributed systems. However, it is not trivially applicable to MANETs due to their dynamic topology and constraints of limited resources such as wireless bandwidth and stable storage. The paper combines asynchronous message logging with independent checkpointing for a successful rollback recovery procedure adapted to the ad hoc environment. Logging the messages asynchronously significantly reduces the number of accesses to stable storage. The recovery procedure involves only those processes whose state depends on the state of the failed process. The presented scheme requires a low number of control messages, reduces the size of control information carried by application messages and can also handle the movement of nodes across the network.

Execution of MPI applications on Grid deployments suffers from node and network failure that motivates the use of fault tolerant MPI implementations. So, to ensure good performance in Grid, scalable fault tolerance should be taken into account. Research in fault tolerant MPI has led to the development of several fault tolerant MPI environments. The most popular approach is with coordinated checkpointing. Traditional coordinated checkpoint suffers from high storage and communication overhead because all processes must participate in the checkpointing at a time; also they all must roll back to the latest consistent global checkpoint even those processes that didn't fail. So in this paper, we propose a mailbox-based non blocking minimum-process coordinated checkpoint protocol (MNMCCP) for hierarchical Grid in which processes on different processors communicate indirectly by sending messages over the network through mailbox-based technique at a shared node. In this protocol, only the processes that communicated since last committed checkpoint will participate in the checkpoint at a time resulting in a reduction in stable storage access and enhanced performance. Our proposed protocol also exploits the mailbox of each process as an events logger since it logs the messages sent to the process in strict FIFO order. This combination of our coordinated protocol with message logging offers several additional advantages including limited computation lost, simplified recovery procedure and bounded recovery time because the effects of a failure are confined only to the processes that fail. From the other hand, using the proposed mailboxes technique ensures the reliable delivery of messages and prevents messages sent to the migrating or faulty process form losing and retransmitting. They will be kept in its associated mailbox, and the process will get them from the mailbox after restarting on the new resource. All of these make our protocol most suitable for highly dynamic environment where processes frequently migrate from one node to another thereby ensures the job to be executed within its deadline making such environment trust worthy.

International audience; The linear quadratic Gaussian-loop transfer recovery procedure is a classical method to desensibilise a system in closed loop with respect to disturbances and system uncertainty. Here an extension is discussed, which avoids the usual loss of performance in LTR, and which is also applicable for non-minimum phase systems. It is also shown how the idea can be extended to other control structures. In particular, it is shown how proportional integral derivative controllers can be desensibilised with this new approach. The method is tested on several examples, including in particular the lateral flight control of an F-16 aircraft.

This paper proposes a proactive security system to forecast Distributed Denial of Service (DDoS) attacks. A reactive system focused on detection after network attacks occur has difficulties responding rapidly to massive distributed attacks, such as DDoS. By forecasting the attack, we can take active countermeasures such as strengthening the power of the security devices and it would also enable us to plan a recovery procedure and countermeasures beforehand, providing a more rapid response. In this paper, we discuss previous studies related to intrusion forecasting, define the concept of intrusion forecasting and propose the Internet Intrusion Forecasting System Architecture. To obtain intrusion factors for DDoS attack forecasts, Honeynet was deployed and we analyze Hflow data gathered from Honeynet.

We report on a framework for recovering single- or multi-timestep sparse signals that can learn and exploit a variety of probabilistic forms of structure. Message passing-based inference and empirical Bayesian parameter learning form the backbone of the recovery procedure. We further describe an object-oriented software paradigm for implementing our framework, which consists of assembling modular software components that collectively define a desired statistical signal model. Lastly, numerical results for synthetic and real-world structured sparse signal recovery are provided.

We study classic streaming and sparse recovery problems using deterministic linear sketches, including l1/l1 and linf/l1 sparse recovery problems (the latter also being known as l1-heavy hitters), norm estimation, and approximate inner product. We focus on devising a fixed matrix A in R^{m x n} and a deterministic recovery/estimation procedure which work for all possible input vectors simultaneously. Our results improve upon existing work, the following being our main contributions: * A proof that linf/l1 sparse recovery and inner product estimation are equivalent, and that incoherent matrices can be used to solve both problems. Our upper bound for the number of measurements is m=O(eps^{-2}*min{log n, (log n / log(1/eps))^2}). We can also obtain fast sketching and recovery algorithms by making use of the Fast Johnson-Lindenstrauss transform. Both our running times and number of measurements improve upon previous work. We can also obtain better error guarantees than previous work in terms of a smaller tail of the input vector. * A new lower bound for the number of linear measurements required to solve l1/l1 sparse recovery. We show Omega(k/eps^2 + klog(n/k)/eps) measurements are required to recover an x' with |x - x'|_1

In a densely distributed sensor network, it is known that it is advantageous to exploit both intra- and inter- signal correlation structures during recovery procedure. Based on this observation, the bound of the required number of measurement in distributed compressive sensing (DCS) is shown to be reduced by exploiting this structure[2]. In this paper, we generalize the model for distributed compressive sensing and show that elaborated signal structure can reduce the required number of measurements further. To this end, we introduce a new concept of partial common information which is shared by some parts of signals, but not by every signal. Numerical results show that with the proposed model, more robust signal recovery can be achieved.

Conical and cylindrical shells are the principal object of many numerical works in the literature background based on the shear deformation theories of composite shells[1]. As it is well known, the first order shear deformation theory of Reissner and Mindlin releases a five parameter displacement model. A third order expansion of the displacement field gives a quadratic variation of transverse strains and stresses, and require no “shear correction factor” compared to the first order theory[2]. In order not to violate the boundary condition while assuming a cubic expansion for the displacement field, the unconstrained model of the third order can become constrained, as suggested by Reedy[3]. Matsunaga [4] used the stress recovery technique for determining the accurate distributions of transverse displacement and stress - strain along the thickness direction for graded shells. In this work the authors focused on the static analyses of functionally graded conical, cylindrical panels and shells, by means of the generalized third order unconstrained theory with the contribution of the initial curvature, joined with the stress - strain and displacement recovery technique. The present theory starts with the definition of the displacement field which includes higher order terms and the components of strains are derived. The graded material via a four parameters power exponent law and the elastic engineering stiffness, the relations between stresses and strains, as well as between internal actions and generalized components of displacement and the definition of external applied loads are concerned in the formulation. Then, by applying the principle of virtual displacements seven indefinite equations of equilibrium are determined. Using the constitutive equations expressed in terms of generalized components of displacement, the fundamental equations are finally obtained. These equations are discretized via the G.D.Q technique and by means of the 2D numerical solution the membrane stress strain and displacement response of graded shells is determined along the thickness direction. The resting part of the mechanical response concerning with the transverse stress - strain and displacement distributions is accurately worked out via the recovery technique.

Purpose - The purpose of this paper is to assess the effect of the statistical admissibility of the recovered solution and the ability of the recovered solution to represent the singular solution; also the accuracy, local and global effectivity of recovery-based error estimators for enriched finite element methods (e.g. the extended finite element method, XFEM). Design/methodology/approach - The authors study the performance of two recovery techniques. The first is a recently developed superconvergent patch recovery procedure with equilibration and enrichment (SPR-CX). The second is known as the extended moving least squares recovery (XMLS), which enriches the recovered solutions but does not enforce equilibrium constraints. Both are extended recovery techniques as the polynomial basis used in the recovery process is enriched with singular terms for a better description of the singular nature of the solution. Findings - Numerical results comparing the convergence and the effectivity index of both techniques with those obtained without the enrichment enhancement clearly show the need for the use of extended recovery techniques in Zienkiewicz-Zhu type error estimators for this class of problems. The results also reveal significant improvements in the effectivities yielded by statistically admissible recovered solutions. Originality/value - The paper shows that both extended recovery procedures and statistical admissibility are key to an accurate assessment of the quality of enriched finite element approximations. © Emerald Group Publishing Limited.

In this article, the problem of fault tolerance in real-time distributed systems is addressed by providing an efficient algorithmic procedure for recovery in such systems. Our recovery procedure does not require the application of an intrusive checkpointing procedure, but uses contextual information exchanged between the distributed system components during normal system progress. On detection of a failure, each process, through an efficient propagation mechanism, will have locally computed a recovery point that is mutually consistent with the recovery points computed by other processes. During recovery, each process considers the contextual information recorded after its established recovery point; a minimal amount of computations are redone. Also, a minimal number of processes are required to roll back, and the time needed to revert to normal operation is found to be minimal, thus contributing to the real-time requirements for such systems. Furthermore, the stable storage requirement needed to implement our recovery procedure is bounded and minimal. Proofs of correctness of our procedure are provided, in particular, the absence of orphan messages, message losses, and duplications is shown. An example illustrating our recovery procedure is also provided.

SRAM-based FPGA devices are becoming a suitable platform for implementing modern Systems On Programmable Chip (SOPC) due to their high reconfigurability, low cost and availability. The high performance SOPCs are often powered by multiple embedded microprocessors. FPGA devices are susceptible to radiation which causes soft-errors in their configuration memory. This paper proposes a soft error recovery technique for FPGA SOPC with multiple processors. The recovery algorithm runs on one of the embedded microprocessors at a time. The algorithm checks the configuration memory of the FPGA through the internal configuration access port and repairs a faulty configuration bit through partial reconfiguration. The technique also includes an extended recovery procedure where, upon the failure of the processor that runs the recovery algorithm, the error is recovered by another working processor. The proposed error recovery technique was verified by a case study and a fault emulation experiment.

International audience; Today's deeply-scaled technology-based integrated circuits are highly sensitive to soft error, tending to be even more in the future. In fact, emerging critical issues are related to transient faults that now can be as long as circuits' clock periods. This work presents a novel improved strategy based on bulk built-in current sensors that is able to cope with long-duration transient faults. Our cost-effective approach is a concurrent error detection scheme with recovery procedure, and rather than existing similar strategy, it has faster correction latency and uses less recovery resources.

This paper considers the task of recovering the support of a sparse, high-dimensional vector from a small number of measurements. The procedure proposed here, which we call the Sign-Sketch procedure, is shown to be a robust recovery method in settings where the measurements are corrupted by various forms of uncertainty, including additive Gaussian noise and (possibly unbounded) outliers, and even subsequent quantization of the measurements to a single bit. The Sign-Sketch procedure employs sparse random measurement matrices, and utilizes a computationally efficient support recovery procedure that is a variation of a technique from the sketching literature. We show here that O(max {k log(n − k), k log k}) non-adaptive linear measurements suffice to recover the support of any unknown n-dimensional vector having no more than k nonzero entries, and that our proposed procedure requires at most O(n log n) total operations for both acquisition and inference.