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Database replication has been subject of two different approaches, namely primary copy and update everywhere protocols. The former only allows performing update transactions in the primary replica, while the rest are only used to execute read-only transactions. Update everywhere protocols, on the other hand, allow the system to schedule update transactions in any replica, thus increasing its capacity to deal with update intensive workloads and overcoming failures. However, synchronization costs augment and its throughput may fall below the ones obtained by primary copy approaches. Under these circumstances, we propose a new database replication paradigm, halfway between primary copy and update everywhere approaches, which improve system’s performance by adapting its configuration depending on the workload submitted to the system. The core of this approach is a deterministic replication protocol which propagate changes so that broadcast transactions are never aborted. We also propose a recovery algorithm to ensure fault tolerance.

In this paper we address the application of recovery procedures in advanced problems in structural mechanics. The attention is focused on the recovery by compatibility in patches procedure (RCP) and shear deformable plate structures. The formulation of RCP procedure is extended to shear deformable plate problems (Reissner---Mindlin theory) and is applied to recover stresses from mixed and hybrid stress finite elements. These elements offer new possibilities, for recovery procedures in general, which deserve to be discussed. A comprehensive investigation on which finite element solution can be used as input for the recovery procedures is given through standard benchmark problems, obtained for several values of the thickness on structured and unstructured meshes. The numerical results confirm the effectiveness of the recovery procedure extended to plates problems.

Purpose: This paper aims at assessing the effect of (1) the statical admissibility of the recovered solution; (2) the ability of the recovered solution to represent the singular solution; on 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: We 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 statically admissible recovered solutions. Originality/value: This work shows that both extended recovery procedures and statical admissibility are key to an accurate assessment of the quality of enriched finite element approximations., Comment: Submitted to Engineering Computations

Knowledge of the factors that influence the survival of plant remains in archaeological contexts, increases the quality and utility of palaeobotanical data. This paper describes the main points needed to plan a sampling strategy and recovery procedure before beginning field work., Conocer el tipo de información que aportan los macrorrestos vegetales, las formas en las que pueden pervivir en el registro arqueológico y la naturaleza del sedimento, incrementan la calidad y utilidad de los resultados. El artículo trata de evaluar los puntos clave a la hora de planificar la estrategia de muestreo y el sistema de recuperación más adecuado para un yacimiento antes de iniciar el trabajo de campo.

Loop transfer recovery techniques for discrete–time systems obtained by skewed sampling are discussed. Two targets for the recovery are considered: the conventional state feedback law without sampling skew and the predictor–based state feedback compensating the sampling skew. Riccati equation formalism is employed to find a recovery procedure for each target. Although the perfect recovery is not always possible, explicit expressions for the achievable sensitivity matrices are given.

Compressed sensing is applied to multiview image sets and the high degree of correlation between views is exploited to enhance recovery performance over straightforward independent view recovery. This gain in performance is obtained by recovering the difference between a set of acquired measurements and the projection of a prediction of the signal they represent. The recovered difference is then added back to the prediction, and the prediction and recovery procedure is repeated in an iterated fashion for each of the views in the multiview image set. The recovered multiview image set is then used as an initialization to repeat the entire process again to form a multistage refinement. Experimental results reveal substantial performance gains from the multistage reconstruction.

This paper presents a novel and practical recovery procedure for automatic landing of a Rotorcraft Unmanned Aerial Vehicle (RUAV) operating in a rough sea environment. An efiective sensor fusion algorithm using the Extended Kalman Filter (EKF) is developed to accurately estimate deck displacement based on measurements from on-board multisensors (inertial sensor, GPS, and Tracking Sensor (TS)). A modifled recursive Prony Analysis (PA) procedure is outlined to build up an appropriate model aiming to extract the monotonous trend of deck displacement, in which parameters are identifled through implementing the Forgetting Factor Recursive Least Square (FFRLS) method. Additionally, a feasible threshold criterion is proposed to separate the dominant components, which results in an accurate instantaneous estimation of the mean deck displacement. Furthermore, a feasible ∞ight control system is designed to adjust positions and attitudes of the RUAV to instantaneously track the estimated mean deck displacement so that a smooth landing operation can be achieved. A closed-loop high-fldelity simulation system has been constructed to realize the proposed landing procedure. Simulation results demonstrate that the proposed landing procedure exhibits satisfactory performance when real deck displacement data are applied, making the RUAV land safely on an oscillating platform in rough seas.

The objective of this paper is to capture variability from different extraction and recovery procedures. In recent years, state agencies emphasize on grading plants depending upon their recycled asphalt pavements (RAP) stockpile variability. Depending upon this grading of the plants, maximum allowable percentage of RAP for the plants will be determined. The recent NCHRP 9-33 manual "Mix design manual for Hot Mix Asphalt" gives procedure to determine RAP stockpile variability. The different extraction and recovery methods give different allowable percentage of RAP. This paper evaluates impact of different extraction recovery procedure on RAP binder property and allowable percentage of RAP which is determined by considering RAP aggregate gradation and RAP binder content. Selection of appropriate combination of extraction recovery method will not only grade the plant on uniform basis but also lead to more precise determination of allowable percentage of RAP.

A large scale HLA-based simulation (federation) is composed of a large number of simulation components (federates), which may be developed by different participants and executed at different locations. These federates are subject to failures due to various reasons. What is worse, the risk of federation failure increases with the number of federates in the federation. In this paper, a fault tolerance mechanism is proposed to tolerate the crash-stop failures of federates. By exploiting the decoupled federate architecture, federate failures can be masked from the federation and recovery can take place without interrupting the executions of other federates. A basic state recovery protocol is first proposed to recover the state of the failed federate relying on the checkpoint and message logging taken before the failure. Then, an optimized protocol is further developed to accelerate the state recovery procedure. Experiments are carried out to verify that the proposed mechanism provides correct failure recovery. The experimental results also indicate that the optimized protocol can outperform the basic one considerably.

After commissioning of the European space-borne science laboratory Columbus, many operational products had to be improved and adapted to changing environmental conditions and new operational experiences. In this paper, we focus on the operational engineering of the Thermal Control as well as on the Environmental Control and Live Support System which are mainly influenced by crew activities, payloads and systems. We present an anomaly handling process how to overcome unexpected anomalies or system change requests. We apply this approach to two dedicated examples for which operational workarounds, a final recovery procedure and even a new operations concept had to be developed: (1) The introduction of a so-called Low Condensing Mode for the condensate heat exchanger due to changing station wide requirements and (2) impacts of unexpected smoke detector contamination. With the help of telemetry data, we explain workaround, final solution and operations concept development. We conclude how to change the Columbus air-conditioning and thermal control design to improve humidity control, condensate collection and smoke detector performance and give recommendations for the air-conditioning and smoke detector design of future human space flight missions.

The new capabilities of smart sensing systems namely, adaptability, reconfiguration, lowenergy consumption and cost, between others, require a wisely selection of the methods that are use to perform analog to digital conversion. It is very important to optimize the trade-offs between, resolution, accuracy, conversion rate, and energy consumption, between others, and above all to adapt dynamically the conversion parameters for different signals characteristics and applications’ purposes. Establishing the best trade-offs are even more important when signals to be digitized have different signal-to-noise ratios (S/N) ratios, different requirements of measuring accuracy and acquisition rate, their characteristics are time-variant and above all if they are sharing the same digitalization device. Very low resolution or conversion rate of data acquisition (DAQs) systems are generally not compliant with measurement systems’ requirements since signal information is lost without any possible recovery procedure. Otherwise, if resolution or data acquisition rate are excessively high that means the sampling rate is much higher than its minimum value (Nyquist rate), the excessive amplitude and time resolutions provided by A/D conversion or frequency-to-digital conversion (FDC) does not improve measurements system’s performance. Moreover, the excessive resolution or data acquisition rate implies an increase of hardware and software complexity, data processing load and a higher implementation cost, without any benefits. So, for any A/D or FDC conversion method the best trade-off between different conversion characteristics must be established considering applications’ purposes. For example, in wireless sensing and actuating networks (WSAN) energy wastes are particularly important because a wrong choice of conversion method can affect deeply measurement system autonomy. Whenever possible, classical A/D conversion methods are being replaced by discrete A/D conversion methods that are supported by low cost microcontroller (C) (Microchip, 2010) connected to a few external resistive or capacitive components. This solution takes full advantage of Cs benefits, namely specific hardware and software capabilities and it provides a conversion rate that can be higher that several hundreds of kHz that is sufficient 24

This paper presents the design of a many-core computer architecture with fault detection and recovery using partial reconfiguration of an FPGA. The FPGA fabric is partitioned into tiles which contain homogenous soft processors. At any given time, three processors are configured in triple modulo redundancy to detect faults. Spare processors are brought online to replace faulted tiles in real time. A recovery procedure involving partial reconfiguration is used to repair faulted tiles. This type of approach has the advantage of recovering from faults in both the circuit fabric and the configuration RAM of an FPGA in addition to spatially avoiding permanently damaged regions of the chip. 1 2

[1] This study develops a lattice Boltzmann method (LBM) with a two-relaxation-time collision operator (TRT) to cope with anisotropic heterogeneous hydraulic conductivity and anisotropic velocity-dependent hydrodynamic dispersion in the saltwater intrusion problem. The directional-speed-of-sound technique is further developed to address anisotropic hydraulic conductivity and dispersion tensors. Forcing terms are introduced in the LBM to correct numerical errors that arise during the recovery procedure and to describe the sink/source terms in the flow and transport equations. In order to facilitate the LBM implementation, the forcing terms are combined with the equilibrium distribution functions (EDFs) to create pseudo-EDFs. This study performs linear stability analysis and derives LBM stability domains to solve the anisotropic advection-dispersion equation. The stability domains are used to select the time step at which the lattice Boltzmann method provides stable solutions to the numerical examples. The LBM was implemented for the anisotropic dispersive Henry problem with high ratios of longitudinal to transverse dispersivities, and the results compared well to the solutions in the work of Abarca et al. (2007).

We propose a Zienkiewicz–Zhu a posteriori error estimator in 2D, which shares the computational advantages typical of the original estimator. The novelty is the inclusion of the geometrical features of the computational mesh, useful for an anisotropic mesh adaptation. The adapted triangulations are shown numerically to be quasi-optimal with respect to the error-vs-number of elements behavior.

This paper deals with a multisensor scheme based on set theoretic principles, whereby different invariant sets that characterize healthy and faulty functioning of system components are computed offline. Such sets allow to partition the ensemble of sensors into ‘healthy’, ‘faulty’ and ‘under recovery’ subclasses. Fault detection and isolation consists of online set-membership verifications with low computational complexity. Sensors that are deemed healthy are utilized in the computation of the feedback control law, while sensors that are deemed ‘faulty’ or ‘under recovery’ are prevented from participating in the feedback control action. The main focus of this paper is on the reintegration of ‘under recovery’ sensors, that is to say, the transition of sensors from the ‘under recovery’ to the ‘healthy’ sensor subclass. This transition, in contrast to all other possible transitions, is particularly difficult to evaluate since it involves set membership conditions based on unmeasurable quantities. This difficulty is circumvented by resorting to necessary and sufficient conditions for the recognition of recovery, which are based exclusively upon measurable quantities. The interplay between the necessary conditions and the sufficient conditions, together with the particular system structure and fault detection mechanism, allows to obtain further important improvements in the recovery procedure in terms of transient times and sensitivity to the topology of the invariant sets.

Two-photon calcium imaging is an emerging experimental technique that enables the study of information processing within neural circuits in vivo. While the spatial resolution of this technique permits the calcium activity of individual cells within the field of view to be monitored, inferring the precise times at which a neuron emits a spike is challenging because spikes are hidden within noisy observations of the neuron's calcium activity. To tackle this problem, we introduce the use of sparse approximation methods for recovering spikes from the time-varying calcium activity of neurons. We derive sufficient conditions for exact recovery of spikes with respect to (i) the decay rate of the spike-evoked calcium event and (ii) the maximum firing rate of the cell under test. We find--both in theory and in practice--that standard sparse recovery methods are not sufficient to recover spikes from noisy calcium signals when the firing rate of the cell is high, suggesting that in order to guarantee exact recovery of spike times, additional constraints must be incorporated into the recovery procedure. Hence, we introduce an iterative framework for structured sparse approximation that is capable of achieving superior performance over standard sparse recovery methods by taking into account knowledge that spikes are non-negative and also separated in time. We demonstrate the utility of our approach on simulated calcium signals in various amounts of additive Gaussian noise and under different degrees of model mismatch.

Event-driven controlled systems based on the Programmable Logic Controller (PLC) are widely used in many industrial processes. The number of such a control system is said to occupy more than eighty percent of the entire existing control systems. Nowadays, the demands for production facilities are shifting from the high speed and highly efficiency to the safety and high reliability. In order to meet these requirements, several strategies for fault diagnosis of systems and the design of recovery procedure have been proposed. In the case of considering the PLC-based control systems, since they have discrete and event-driven characteristics inherently, system models based on discrete-event-system description give more efficient diagnostic algorithm than those based on continuous-time systems (for surveys cf. (A. Darwiche & G. Provan (1996); D. N. Pandalai& L. E. Holloway (2000); M. Sampath et al. (1995); S.H.Zad et al. (1999))). This aspect will be more emphasized when the number of components would be large. Based on these considerations, Lunze proposed a centralized fault diagnosis framework based on the system model with Timed Markov Model (TMM) (J.Lunze (2000)). This method especially becomes useful when numerous number of input and output data are collected through daily operation since the TMM is based on a stochastic expression of time interval between successive events. This approach also has some robustness against unevenness underlying in the ordinary production facilities. However, this kind of centralized diagnosis strategies will cause an explosion of the computational burden when they are applied to the large scale systems. In this case, the decentralized approach is highly recommended wherein the diagnosis is performed by each diagnose together with the communication with other diagnosers (O.Contant (2006); S.Debouk (2000); R.Su et al. (2002)). These approaches, however, were based on the deterministic model. Based on these backgrounds, the authors (S.Inagaki et al. (2007)) proposed a decentralized stochastic fault diagnosis strategy based on a combination of TMM and Bayesian Network (BN). The BN represents the causal relationship between the fault and observation in subsystems. Since the decentralized diagnosis architecture distributes the computational burden for the diagnosis to the subsystems, a large scale diagnosis problems in real-world application can be solved. In the decentralized approach, the computational burden and the diagnosis performance strongly depend on the complexity of the graph structure of BN.

This paper concerns the design of reduced-order observers for systems in which the number of measurements is more than the number of controls. We develop an algorithm that applies to regular systems that have no transmission zeros. The algorithm uses eigenstructure assignment whereas other approaches use Kalman filter methods. The advantages of this approach are the following: 1) precise loop transfer recovery rather than approximate loop transfer recovery, 2) finite observer gain rather than asymptotic observer gain, and 3) modest computational tools and operations counts. Case studies are presented illustrating these features. T HE problem of designing an observer that can achieve loop transfer recovery (LTR) has received continuous at- tention since Doyle1 presented an example with a Kalman-fil- ter-based observer (linear quadratic Gaussian (LQG)) design lacking robustness even though the full-state feedback (linear quadratic regulator (LQR)) controller had impressive robust- ness properties, namely gain margins of - 6 dB to + oo dB and phase margins of ±60 deg.2 To alleviate this problem, Doyle and Stein3 developed a robustness recovery procedure in which fictitious process noise is added to the input in the design model. The LQR robustness properties are preserved with the loop open at the input since the loop transfer function is re- covered asymptotically as the intensity of the fictitious pro- cess noise is increased. Stein and Athans4 call this procedure LQG/LTR. There have been further developments and appli- cations of LQG/LTR by a number of workers. Madiwale and Williams5 extended the theory to reduced-order observer- based LQG designs for nonsquare, minimum phase, and left invertible plants. Calise and Prasad6 developed an approach for designing a fixed-order compensator and obtained an ap- proximate LTR for nonsquare, minimum phase systems. It is similar to the full-order compensator design of ordinary LQG/ LTR. Fu7 developed the necessary and sufficient condition for exact LTR employing a general feedback structure for model matching control that includes the observer-based state feedback control as a special case. He formulated the prob- lem of model matching by assigning certain stable matrices such that the desired loop transfer function became equal to the associated loop transfer function of the closed-loop input- output transfer function. He claimed that exact LTR is achiev- able under the conditions for strong stabilization of systems. Tsui8'9 introduced a theoretical analysis of an entirely new approach to the problem of loop transfer recovery. His ap- proach was to minimize the observer gain to the system input by observer pole selection. Furthermore, he claimed that this new approach aimed directly at achieving the necessary and sufficient condition of LTR. The purpose of this paper is to present a computational algorithm for the solution of the constrained matrix Sylves- ter equation that arises in Tsui's approach for designing ro- bust reduced-order Luenberger observers.10 Precise LTR is achieved with finite observer gain for regular nonsquare plants with no transmission zeros, for which the number of sensors is greater than the number of controls. Other approaches have been unable to attain these results. The method developed here provides freedom to select eigenvalues and eigenvectors for the observer.

In this paper, we present an algorithm to achieve mutual exclusion in distributed systems. Our algorithm tolerates up to t − 1 arbitrary node failures without executing any recovery procedure and requires [Formula: see text] messages in a network of n nodes.

It is shown that for systems which have an input subsystem, with outputs that can be observed, full LQR state-feedback robustness properties can be recovered at the input by only performing the recovery procedure on that section of the Kalman filter representing this subsystem. This has the advantage that the performance of the Kalman filter will not deteriorate as much as when using the full recovery procedure of Doyle and Stein. A procedure is also described for improving the measurement noise rejection properties of the Kalman filter when the recovery procedure is employed. This entails adding a fictitious coloured measurement noise source, allowing the frequency response of the filter to be shaped outside the recovery region. The problem was motivated by marine control problems where input subsystem measurements were accessible.

A new Automatic Repeat Request (ARQ) scheme, Virtual Multiple Data Links (VMDL), for satellite communications is proposed. The principle of VMDL is based on the basic go-back- N scheme and plural data links. It is not only able to achieve high performance on high speed satellite channels with large round trip delays, but its recovery procedure is also simple to implement. The performance of VMDL is analysed and it is demonstrated that VMDL is superior in terms of both throughput efficiency and error detection time compared with conventional schemes.

in this paper, we propose a digital watermarking scheme about color image of tamper detection and recovery using block-based watermarking. Firstly, in our watermark embedding, each color channel (R, G, and B) is divided into 2×2 non-overlapping blocks. The embedding space is created by setting the three LSBs (least significant bits) of selected each block to zero, which will hold the authentication and recovery codes. The authentication codes are obtained through doing exclusive-or (XOR) both the extracted local features of image blocks and the generated global features of the original color image. The recovery codes are generated using block-mapping original color image and using color model conversion. Secondly, in the tamper detection, instead of examining each embedded authentication data, we get the global features of the tampered watermarked image through doing XOR both all the extracted authentication codes and the generated local features of tampered watermarked image blocks. And then we utilize a majority-selecting technique to detect the legitimacy of image blocks. Lastly, in the tamper recovery, we propose 3 stages to accomplish recovery ability. Experiment demonstrates that our scheme is oblivious, correctly localizes the tampering wherever the tampered positions are and can be successfully accomplish to recover with acceptable visual quality. However, the watermark is no longer a logo or a piece of message; it is the image itself. In this paper, the embedding space for watermark, which are authentication and recovery codes, is created by setting the three LSBs of selected each block to zero and is required to hold in the LSBs plane. The authentication codes embedded in image blocks is generated by exploiting both the local features of image blocks and the global features of the images which are from hashing function to verify the integrity of an image. At the same time, the recovery codes are generated from block-mapping original image and they are also embedded original image blocks for accomplishing the recovery abilities. In the tamper detection process, the proposed scheme use generated global features of the tampered watermarked image and utilizes a majority-selecting technique (6) to determine the legitimacy of image blocks. In the tamper recovery process, we propose 3 stages to accomplish and improve recovery abilities using the recovery data generation and average intensity of its 3×3 neighboring block values. Experimental results show that the precision of tamper detection and localization is close to 100% under different positions attacks. In addition, the results reveal that the tampered regions can be approximately recovered with satisfactory image quality. The reminder of the paper is organized as follows. Section II describes the proposed block-based watermarking scheme including watermark generation and embedding procedure, tamper detection procedure and tamper recovery procedure. In Section III, the experimental results are presented to demonstrate the effectiveness of the proposed scheme. Section IV derives the concluding remarks.

Wireless mesh networks (WMNs) have gained considerable attention in the recent years due to fast deployment, easy maintenance and low upfront investment compared with traditional wireless networks. Since WMNs are typically used as wireless backbones, they have the nature that the wireless communication is not stable. Hence, it is significant to protect them against link or node failures. Distribution of data using multicast in an unreliable network does not guarantee reliable delivery, which is the prime requirement for many important applications. This paper focuses on designing and implementing an effective reliable multicast protocol called HRTMM based on shortest path tree algorithms (SPTs). For first time in this paper, we use CMAC neural network to design and implement an error or disconnection occurrence prediction mechanism in our proposed protocol that it can recover the unreliable nodes/routes before fault or disconnection happens and consequently restore the network to a consistent state with more reliability. We also will discuss a novel hybrid local recovery procedure based on mentioned disconnection prediction method. The HRTMM combines congestion and error control with localized recovery to prevent or recover the different types of losses that may occur in WMNs. Our simulation results show that the HRTMM protocol functions efficiently and reliably for WMNs.

In this paper, we introduce a new geographic routing scheme for urban vehicular environments called “Dynamic Road Connectivity-based Routing” (D-RCBR). The proposed approach exploits distributed information about road connectivity and vehicles distribution to optimize routing decisions. To ensure the packet delivery, D-RCBR defines a new concept of Road Connectivity that provides local topology knowledge and checks if two adjacent intersections delimiting a road segment are actually connected through multi-hop vehicular communication. Then, based on local dissemination strategy, a dynamic routing is performed through the road intersections according to greedy principle. However, since local maximum problems are likely to happen considering only a greedy selection of vertex, D-RCBR defines a recovery procedure inspired from the right hand rule. The simulation results show encouraging performance in comparison to other existing approaches in the literature.

This paper develops reliable distributed publish/subscriber algorithms with service availability in the face of concurrent crash failure of up to $\delta$ brokers. The reliability of service in our context refers to per-source in-order and exactly-once delivery of publications to matching subscribers. To handle failures, brokers maintain data structures that enable them to reconnect the topology and compute new forwarding paths on the fly. This enables fast reaction to failures and improves the system's availability. Moreover, we present a recovery procedure that recovering brokers execute in order to re-enter the system, and synchronize their routing information.

Despite their merits, composites have weakness in transverse strength making them susceptible to failures such as delamination. In order to understand the failure mechanism an accurate evaluation of the interlaminar stresses is required. An e‐cient procedure for accurate analysis of multi-layer composite structures is presented, with particular interest in the interlaminar stresses. Parallelization of sequential simulations approach together with the use of domain decomposition methods signiflcantly broadens the range of applications of numerical simulations for computationally demanding problems. In the present paper, attention will be restricted to the Finite Element Tearing and Interconnecting (FETI) method, an e‐cient solution scheme based on the domain decomposition of the structure and enforcing the compatibility conditions between the difierent sub-domains by means of Lagrange multipliers. With this approach, connecting forces between the difierent sub-domains at the interfacial nodes can be obtained and, as a consequence, an accurate post-processing recovery procedure of the interlaminar stresses based on equilibrium has been formulated. In addition, a consistent variational recovery procedure has been implemented to completely recover stress flelds. The reliability of the approach has been tested with problems involving composite plates of various geometries subjected to difierent mechanical loadings.

Publisher Summary Transaction processing (TP) systems often are expected to be available 24 hours per day, 7 days per week, to support around-the-clock business operations. Two factors affect their availability: the mean time between failures (MTBF) and the mean time to repair (MTTR). Improving availability requires increasing MTBF, decreasing MTTR, or both. Computer failures occur because of environmental factors, system management, hardware, and software. If the operating system fails, then just reboot it. For other types of software failure, the transactional middleware or database system must detect the failure of a process and re-create it. The re-created process must then run a recovery procedure to reconstruct its state. Transactions simplify recovery by allowing a server to focus on restoring its state to contain only the results of committed transactions, rather than recovering to a state that is consistent with the last operations it ran. All of today's recovery mechanisms require every transaction to hold its write locks until it commits, to avoid cascading aborts, and to ensure that undo can be implemented simply by restoring an update's before image. The recovery manager uses a cache manager to fetch pages from disk and later flush them. In addition to processing commit and abort operations, it implements a recovery algorithm to recover from system failures. The recovery manager tells the cache manager about dependencies between dirty database pages and log pages so the cache manager can enforce the write-ahead log protocol.

This study proposes a mechanism of guaranteed quality of recovery (GQoR) for Wavelength Division Multiplexing (WDM) mesh networks. Four GQoR levels are used to support customized services, and each of them is mapped to the adaptive recovery methodology. Once a failure occurs, the control system activates the recovery mechanism in compliance with the GQoR level. If the protection procedure fails as well, the proposed algorithm will then execute the restoration mechanism. Consequently, the recovery success rate is increased. This paper examines the shared segment recovery methods to establish backup path; therefore, it is well suited for large-scale networks and also increases the bandwidth utilization of the networks. Furthermore, a node deals only with its own routing information by employing the distributed control, so the fault recovery procedure can be speeded up. Simulation results reveal that the proposed method has greater performance of lower blocking probability and mean hop number than other methods previously reported in the literature.

Wireless mesh networks (WMNs) have gained considerable attention in the recent years due to fast deployment, easy maintenance and low upfront investment compared with traditional wireless networks. Since WMNs are typically used as wireless backbones, they have the nature that the wireless communication is not stable. Hence, it is significant to protect them against link or node failures. Distribution of data using multicast in an unreliable network does not guarantee reliable delivery, which is the prime requirement for many important applications. This paper focuses on designing and implementing an effective reliable multicast protocol called HRTMM based on shortest path tree algorithms (SPTs). For first time in this paper, we use CMAC neural network to design and implement an error or disconnection occurrence prediction mechanism in our proposed protocol that it can recover the unreliable nodes/routes before fault or disconnection happens and consequently restore the network to a consistent state with more reliability. We also will discuss a novel hybrid local recovery procedure based on mentioned disconnection-prediction method. The HRTMM combines congestion and error control with localized recovery to prevent or recover the different types of losses that may occur in WMNs. Our simulation results show that the HRTMM protocol functions efficiently and reliably for WMNs.

Human memory is not perfect - people constantly memorize new facts and forget old ones. One example is forgetting a password, a common problem raised at IT help desks. We present several protocols that allow a user to automatically recover a password from a server using partial knowledge of the password. These protocols can be easily adapted to the personal entropy setting [7], where a user can recover a password only if he can answer a large enough subset of personal questions. We introduce client-server password recovery methods, in which the recovery data are stored at the server, and the recovery procedures are integrated into the login procedures. These methods apply to two of the most common types of password based authentication systems. The security of these solutions is significantly better than the security of presently proposed password recovery schemes. For our protocols we propose a variation of threshold encryption [5, 8, 16] that might be of independent interest. © Springer-Verlag 2009.

On Demand Multicast Routing Protocol (ODMRP) was designed formerly for multicast routing in ad hoc networks. Despite good delivery ratio in several scenarios, ODMRP relies on a periodic refresh mechanism for sending the JOIN QUERY message to maintain mesh robustness. Choosing the appropriate value for refresh interval of this message is of great concern. In addition when mobility speed is high, link failures occur more causing delivery ratio to decrease. In this paper we address the problems of detecting link breakages and local recovery procedure in ODMRP. We introduce a new join message for nodes intending to join the multicast group and nodes detecting link breakage. Through this message, receivers have no delay and no loss in receiving data packets. Furthermore we propose the concept of minimum number of neighbors in ODMRP mesh for detecting links failure based on data packets with no control overhead. Simulation results show that with these improvements packet delivery ratio increases while end-to-end delay remains the same as ODMRP.

Human memory is not perfect - people constantly memorize new facts and forget old ones. One example is forgetting a password, a common problem raised at IT help desks. We present several protocols that allow a user to automatically recover a password from a server using partial knowledge of the password. These protocols can be easily adapted to the personal entropy setting [7], where a user can recover a password only if he can answer a large enough subset of personal questions. We introduce client-server password recovery methods, in which the recovery data are stored at the server, and the recovery procedures are integrated into the login procedures. These methods apply to two of the most common types of password based authentication systems. The security of these solutions is significantly better than the security of presently proposed password recovery schemes. For our protocols we propose a variation of threshold encryption [5, 8, 16] that might be of independent interest. © Springer-Verlag 2009.

We propose a new approach exploiting the failure risk (node, link or Shared Risk Link Group) structures to enhance the backup path computation. Upon failure, our approach classifies the backup paths into two categories: operative backup paths and inoperative backup paths. An operative backup path is an active backup path which really receives traffic of some affected communications while an inoperative backup path does not receive any traffic. With the observation that only the operative backup paths really participate to the recovery procedure, we enhance the backup path computation (1) by limiting the concurrence for the protection bandwidth allocations to the operative backup paths (instead of all the active backup paths like in the classical approaches) and (2) by reducing the set of failure risks that a backup path must bypass. Simulations show that our approach improves the protection bandwidth allocations and decreases the ratio of rejected backup paths.

Frequency-shaped LQ design has been proposed to improve the well-known performance and robustness properties of classical LQ controllers. In this paper, we propose to associate this method with a loop recovery procedure in order to control minimum-phase plants with incomplete state-measurement. The main practical aspects of such a design are investigated. Its flexibility and its efficiency are underlined by considering in detail the stabilization of an helicopter subject to modelling uncertainties.

LOBI-MOD2 results from an experimental investigation of a steam generator tube rupture (SGTR) with no active emergency core cooling system (ECCS) available are presented. The characteristic system response, following a three-tube break occuring during normal full power operation, is analysed. Thermal—hydraulic data for a phenomenological understanding of natural circulation, the reflux condenser heat transport mode and core dry-out at high primary pressure are provided. The importance of the availability of the ECCS for the SGTR mitigation is outlined by comparing the above mentioned data to the results of a second LOBI test on SGTR with the same break area but with the standard ECCS in operation. The effectiveness of a new recovery procedure, starting from highly degraded core scenarios, is also examined. It relies on intentional primary system fast depressurization through the pressurizer relief valves and passive accumulator injection. Primary passive feed and bleed for the long term cooling can improve the safety criteria for the design of nuclear power plants (NPPs).

Free-floating drogued buoys have been developed for detailed studies of tidal processes, frontal circulation, eddies, and mixing in the North Sea. They are equipped with two independent tracking systems-Decca Navigator and Argos. Decca Navigator, a hyperbolic radio navigation system with extensive coverage in Western Europe, provides accurate and frequent fixes, and the Argos satellite system is used to monitor progress in real time and to assist recovery. The low power consumption microprocessor-based Decca Navigator receiver designed specifically for this application synchronizes to the precisely timed Decca transmission and then goes into sleep mode, waking briefly at 10-min intervals to take position fixes. The position data are stored in a 2-Mb memory card that has a three-month capacity at the 10-min rate. The recovery procedure, using both Argos and a small VHF beacon, is described, together with other recent developments. A typical buoy track from a study in the North Sea is included. >

Next generation backbone networks will likely consist of IP routers as well as optical cross connects and will deploy Generalized Multiprotocol Label Switching (GMPLS) as the control plane protocol. The fiber carries large volume of traffic and therefore one must ensure that adequate mechanisms are in place that facilitate automatically recovery from failures. In mission critical networks survivability becomes critical. We investigate the problem of autonomous recovery in such networks. The literature contains work in this area that investigates the problem of multilayer recovery. Such recovery had only been sequential in the sense the published work recovers first in the optical domain and then proceeds to recover in the IP plane. We report for the first time a recovery procedure that recovers concurrently in both the optical and IP planes. The work on concurrent recovery investigates a single link failure scenario. While formulating the concurrent recovery protocol, we realized that modifications or extensions were needed to OSPF-TE protocol employed with GMPLS-based WDM networks. The OSPF-TE extension requires that the link state information propagated by the protocol must also carry available unused lambda label switched paths (lambdaLSPs). After a link failure, the ingress node upstream from failed link will first determine the availability of free light paths and existing unreserved bandwidth in used light paths from the link state information provided by OSPF extension. The concurrent multilayer recovery scheme proposed here uses this information to switch traffic in both optical and IP layer concurrently. An OPNET-based simulation study shows that the concurrent two-layer recovery scheme performs as much as forty-four percent faster than the sequential two-layer recovery scheme.

RBF based surface recovery provides good implicit representation of 3D object's shapes, but it has the disadvantage of time consuming. To apply automatic surface measurement from scanned 3D points in industry, this paper presents several techniques for efficiency improvements of RBF method. Partial surface recovery, octree division and combination, inverse power method and improved Cholesky factorization can either avoid unnecessary computing or speed up recovery procedure. The experiments on girth measurements of human foot have proved that the proposed methods are helpful.

A proactive secret sharing scheme (PSS) is very important to withstand mobile adversary in mobile ad-hoc networks (MANETs). It allows a set of nodes to update all shares by generating a new set of shares for the same secret key from the old shares without reconstructing the secret key and it allows the nodes to recovery the lost shares. After periodical renewal, it makes the mobile adversary which wants to get the secret key of the system to attack another set of nodes in a new period. In this paper, we presented a PSS synchronization structure in an MANET environment and we supply the scheme with the improved share recovery procedure for perfection. Finally we analyze the protocol and outline our future work.

The available gravity field models derived from data of the GRACE mission (tapley and Reigber (2001)) have provided us with an unprecedented accuracy in gravity field determination. Nevertheless the projected GRACE baseline accuracy has not been achieved yet. One reason out of many could be the insufficient modelling of the satellite data by a global representation by means of spherical harmonics. To extract the signal information present in the satellite and sensor data to full content, it seems reasonable to improve global solutions by regional recovery strategies. Especially in the higher frequency part of the spectrum the gravity field features differ in different geographical areas. Therefore the recovery procedure should be adapted according to the characteristics in the respective area.

We present a method for the recovery of partially occluded 3-D geometric primitives from range images which might also include nonprimitive objects. The method uses a technique for estimating the principal curvatures and Darboux frame from range images. After estimating the principal curvatures and the Darboux frames from the entire scene, a search for the known patterns of these features in geometric primitives is performed. If a specific pattern is identified, then the presence of the corresponding primitive is confirmed by using these local features. The features are also used to recover the primitive's characteristics. The suggested application is very efficient since it combines the segmentation, classification, and fitting processes, which are part of any recovery process, in a single process, which advances monotonously through the recovery procedure. We view the problem as a robust statistics problem, and we therefore use techniques from that field. A mean-shift-based algorithm is used for the robust estimation of shape parameters, such as recognizing which types of shapes in the scene exist and, after that, full recovery of planes, spheres, and cylinders. A random-sample-consensus-based algorithm is used for robust model estimation for the more complex primitives, such as cones and tori. As a result of these algorithms, a set of proposed primitives is found. This set contains superfluous models which cannot be detected at this stage. To deal with this problem, a minimum-description-length method has been developed, which selects a subset of models that best describes the scene. The method has been tested on series of real complex cluttered scenes, yielding accurate and robust recoveries of primitives.

The automation of the function-based (FRep) volumetric modeling task is tackled by introducing template parameterized models and a procedure for recovery of constructive models from segmented point-sets. In order to reuse existing models, we propose to parameterize them and to fit the parameters to different point-sets for optimizing and adapting the shape to different objects of the same class of shapes. The automation of the creation of a constructive FRep model is also considered by creating a recovery procedure for a given segmented pointset and a list of corresponding primitives. A genetic algorithm is used to find the best constructive expression for the object with the given set of primitives in the point cloud segmentation and the set of available operations. The proposed approach is illustrated by fitting of different models to point clouds and by the automatic generation of constructive trees from segmented point-sets for real mechanical parts.

High-frequency components that are lost when a signal s(x) of bandwidth W is low-pass filtered in sinusoid-crossing sampling are recovered by use of the minimum-negativity constraint. The lost high-frequency components are recovered from the information that is available in the Fourier spectrum, which is computed directly from locations of intersections {xi} between s(x) and the reference sinusoid r(x) = Acos(2πfrx), where the index i = 1, 2, … , 2M = 2Tfr, and T is the sampling period. Low-pass filtering occurs when fr < W/2. If |s(x)| ≤ A for all values of x within T, then a crossing exists within each period Δ = 1/2fr. The recovery procedure is investigated for the practical case of when W is not known a priori and s(x) is corrupted by additive Gaussian noise.

Different from the wired distributed system, the mobile computing system has certain new characteristics, which impact on its checkpointing- rollback recovery schemes. The performance of these schemes primarily depends on the heterogeneous processing speeds, link bandwidth, message arrival ratio and fault rate of mobile hosts. Another special factor that should be considered is handoff which often occurs in mobile networks. New adaptations of well- known recovery schemes had been presented for the mobile environment. However the analysis shows that there is no single recovery scheme that performs well for all mobile environments. In this paper, we analysis how checkpointing and handoff schemes affect performance and effectiveness metrics, and then determine mobile environments where a particular recovery scheme is best suited. We get the optimal checkpointing interval function for minimizing the total execution time in the Logging recovery scheme. Our model allows a fault of mobile host during its recovery procedure.

This research investigates the automation of security assessment of the static and dynamic properties of cyber infrastructures, with emphasis on the electrical power grid. We describe a network model representing the static elements of a cyber infrastructure including devices, services, network connectivity, vulnerabilities, and access controls. The dynamic elements include workflow models of the operating procedures, processes and the state of a working power grid. We introduce a toolkit that with a little manual assistance can automatically generate these models from specifications, continuously update attributes from online event aggregators, and perform security assessment. The assessment reveals whether observed anomalies about the system could indicate possible security problems and permit dynamic ranking of alternative recovery procedures to minimize the total risk. We motivate the use of the tool-chain by showing an example scenario where the recovery procedure recommended to minimize security risk depends on the current state of system as well as the network topology.

This paper presents a checkpoint setting technique to eliminate domino effect in backward recovery in distributed systems, which is very efficient, powerful, widely applicable and easy to be implememted. Besides theoretical analysis, an implementation on UNIX system and a package for software fault-tolerance are introduced. Then the problems of checkpoint management and process termination are discussed.

A method for recovery of compact volumetric models for shape representation of single-part objects in computer vision is introduced. The models are superquadrics with parametric deformations (bending, tapering, and cavity deformation). The input for the model recovery is three-dimensional range points. We define an energy or cost function whose value depends on the distance of points from the model's surface and on the overall size of the model. Model recovery is formulated as a least-squares minimization of the cost function for all range points belonging to a single part. The initial estimate required for minimization is the rough position, orientation and size of the object. During the iterative gradient descent minimization process, all model parameters are adjusted simultaneously, recovering position, orientation, size and shape of the model, such that most of the given range points lie close to the model's surface. Because of the ambiguity of superquadric models, the same shape can be described with different sets of parameters. A specific solution among several acceptable solutions, which are all minima in the parameter space, can be reached by constraining the search to a part of the parameter space. The many shallow local minima in the parameter space are avoided as a solution by using a stochastic technique during minimization. Results using real range data show that the recovered models are stable and that the recovery procedure is fast.

In this paper we present a new algorithm for the recovery of the initial state of a linear feedback shift register when a noisy output sequence is given. Our work is focussed on the investigation of the asymptotical behaviour of the recovery process rather than on the construction of an optimal recovery procedure. Our results show the importance of low-weight checks and show also that the complexity of the recovery problem grows less than exponentially with the length of the shift register, even if the number of taps grows linearly with the register length. Our procedure works for shift register with arbitrary feedback polynomial.