Repair Scheme Research Articles

Failure analysis of a high precision deployable reflector in TED test

This paper investigates phenomenon and potential reasons for failure in TED (thermal elastic distortion) test of a high precision deployable reflector which is designed for the second HTS in China, the ChinaSat-18. Firstly, configuration of the reflector is introduced to give a comprehensive understanding of the reflector design. Then, setup and results of the thermal elastic distortion test are presented, and the test results are evaluated from two aspects: arm depointing and shell distortion, failure phenomenon of the test is also described in detail. Moreover, failure mode analysis is presented, and the final root cause of the failure is illustrated which indicates that the failure is caused by the arm-backup structure interface sliding. Failure analysis of the arm-backup structure interface is conducted and the same failure phenomenon is reproduced by analysis. Finally, a feasible repair scheme for engineering application is proposed, then thermal elastic distortion test after repaired is conducted in thermal vacuum chamber and the test results validate the correctness and effectiveness of the proposed failure cause analysis and repair scheme.

Research on Tolerance Redistribution Method Based on Measurement Data

As the performance requirements of aircrafts increase, the mechanical structure of the product is more complicated and the requirements for assembly are getting higher and higher. Due to the accumulation of errors in the processing and assembly process, assembly may not meet the product design requirements. It is necessary to repair some of the processed parts before performing the assembly process. This paper proposes an assembly simulation analysis and a tolerance redistribution approach based on measurement data that is making decisions on which part should be repaired. Firstly, the processed parts and assembly fixture are measured by measuring devices and fitted into the digital model with measurement data. Secondly, the assembled digital simulation is performed to verify whether the processed parts can be assembled successfully. Finally, if the parts cannot be assembled successfully, an improved genetic algorithm is used to optimize the tolerance to form a repair scheme.

Iterative Diagnosis Approach for ECC-Based Memory Repair

In modern SoCs embedded memories should be protected by ECC against field failures to achieve acceptable reliability. They should also be repaired after fabrication to achieve acceptable fabrication yield, as well as during lifetime to increase lifespan. In technologies affected by high defect densities, conventional repair induces very high cost. To reduce it, in previous work we proposed the ECC-based repair scheme, consisting in using the ECC for fixing words comprising a single faulty cell, and self-repair to fix all other faulty words. This approach is of high interest for ultimate CMOS and post-CMOS technologies, where the defect densities are expected to increase significantly, and/or in very-low power designs as very-low voltage sharply increases defect densities. However, we showed recently that, for high defect densities the diagnosis circuitry required for ECC-based repair may induce large cost. In previous work we addressed this issue by means of a new family of memory test algorithms that exhibit the so-called single-read double-fault detection (SRDF) property. The SRDF algorithms resolve the diagnosis issue at no area cost. However, as they are complex and increase test length, in this paper we explore a new diagnosis approach using iterative test execution, which, together with the SRDF test algorithms, provide a set of options enabling efficient tradeoffs in terms of hardware and power costs, and test length.

Experimental Study of Stepped-Lap Scarf Joint Repair for Spar Cap Damage of Wind Turbine Blade in Service

The objective of this paper was to design configuration parameters for a stepped-lap scarf joint repair, which can be used for spar cap damage of a wind turbine blade in service and to realize the post-repair monitoring. Two experimental studies were included. First, tensile test for the unidirectional tape specimens with a large aspect ratio repaired using a multiple stepped-lap scarf joint method was carried out. The results showed that the reinforcement layer could effectively improve the load-carrying capacity of the repaired zone. The stepped-lap joint surface was identified as the weak part of the spar cap repair, which should be monitored. Second, by embedding carbon nanotube buckypaper sensors on the stepped-lap joint surface of the repaired specimens, quasi-static tensile tests and fatigue tests were carried out. According to the resistance response of the sensors, the quasi-static tensile test confirmed the failure processes, namely the stiffness turning point, damage evolution, crack propagation, and fracture. The fatigue test could accurately identify the progressive failure, namely the initial damage, damage accumulation, initial cracking, and crack propagation to structural failure. The above tests provided an important configuration parameter basis for evaluating the spar cap repair scheme and presented a promising method for the health monitoring of a spar cap after repair.

Bearing Repair and Monitoring for Poyanghu Cable‐Stayed Bridge

Currently, the bearings of Poyanghu Bridge, a 636‐meter long cable‐stayed bridge, have been damaged. According to numerical analyses, the mechanical state of the damaged bridge unfavorably deviates from the ideal design state, and the bridge should be repaired in time to restore its safety and serviceability. However, compared with the bearing repair of beam bridges, much less scientific and engineering endeavors have been made in the history to direct the bearing repair of cable‐stayed bridges. This article proposes two innovative bearing repair schemes for cable‐stayed bridges and reports the numerical validations, the on‐location applications, and the monitoring of the proposed repair schemes under the engineering backgxround of Poyanghu Bridge. Through these works, it is found that the proposed repair schemes are effective in practical use.

Towards Building Reliable and Cost-Efficient Distributed Storage Systems

Reliability and cost are two important targets for distributed storage systems. For many years, numerous schemes have been proposed to improve the reliability or cost of distributed storage systems, and they can be divided into three categories: (1) data redundancy schemes; (2) data placement schemes; and (3) data repair schemes. However, it is still unclear regarding how to build a reliable and cost-efficient distributed storage system, because (i) insufficient considerations on the combinations of different schemes; and (ii) insufficient considerations on failures and recoveries of different subsystems (racks, nodes, disks, and sectors). To measure the reliability and cost caused by different schemes, we design and implement CR-SIM, a Comprehensive Reliability SIMulator for distributed storage systems. It considers various affecting factors, such as the system topology, the data redundancy scheme, the data placement scheme, the data repair scheme, and the failure/recovery models of different subsystems. By using CR-SIM, we conduct various simulation-based experiments, and the experimental results reveal several important findings, which are helpful to build reliable and cost-efficient distributed storage systems. For public use, we have open-sourced our source code at https://github.com/yichuan0707/CR-SIM.

Technological features of aircraft engine repair in digital production

The article analyzes the problems arising during the repair of gas turbine engines. Based on the analysis of problems, a gas turbine engines rotor repair scheme is proposed using virtual assembly technology. The proposed scheme will allow to reduce the cost and to increase the efficiency of repair work. Example of gas turbine rotor repair using virtual assembly technology is considered. The results of predicting the dimensional accuracy of assembly parameters based on the simulation of parts with real geometry are presented.

On the Sub-Packetization Size and the Repair Bandwidth of Reed-Solomon Codes

Reed-Solomon (RS) codes are widely used in distributed storage systems. In this paper, we study the repair bandwidth and sub-packetization size of RS codes. The repair bandwidth is defined as the amount of transmitted information from surviving nodes to a failed node. The RS code can be viewed as a polynomial over a finite field $GF(q^\ell)$ evaluated at a set of points, where $\ell$ is called the sub-packetization size. Smaller bandwidth reduces the network traffic in distributed storage, and smaller $\ell$ facilitates the implementation of RS codes with lower complexity. Recently, Guruswami and Wootters proposed a repair method for RS codes when the evaluation points are the entire finite field. While the sub-packization size can be arbitrarily small, the repair bandwidth is higher than the minimum storage regenerating (MSR) bound. Tamo, Ye and Barg achieved the MSR bound but the sub-packetization size grows faster than the exponential function of the number of the evaluation points. In this work, we present code constructions and repair schemes that extend these results to accommodate different sizes of the evaluation points. In other words, we design schemes that provide points in between. These schemes provide a flexible tradeoff between the sub-packetization size and the repair bandwidth. In addition, we generalize our schemes to manage multiple failures.

A method for fast simulating the liquid seepage-diffusion process coupled with internal flow after leaking from buried pipelines

Abstract Once the oil pipeline leakage accident occurs, it is of great significance to predict the leakage volume and the diffusion range of leaked oil accurately and efficiently in order to reduce the contamination degree and formulate the environmental impact assessment and repair scheme. In this paper, a prediction model of leakage intensity of leaked oil and seepage-diffusion range in soil is proposed. Firstly, the entire leakage process inside and outside of buried product oil pipeline is simulated, including the process of pipe flow, orifice outflow, and seepage-diffusion, and thus the model of seepage-diffusion of oil in soil is established. Secondly, the coupling solution of seepage-diffusion in soil both before and after the transient pipe flow being terminated is accomplished via interactively transmitting the key parameters between the pipe flow and the seepage-diffusion process. Thirdly, the comparison of simulated data with experiment results proves that the flow-seepage-diffusion coupled model has better applicability and a higher accuracy in acquiring the severity, quantity, and range of the leakage. Finally, the effects of pressure transmission coefficient, leak orifice's size, leakage flowrate, pipe diameter, leak orifice's position, pipe depth, and diffusion resistance are systematically analyzed. Thus, the characteristics of dynamic seepage-diffusion of leaked oil in porous soil are investigated, which provides an important basis and technical support for pipeline accident treatment.

A 3-D Rotation-Based Through-Silicon via Redundancy Architecture for Clustering Faults

Three-dimensional integrated circuits (3-D ICs), which feature many benefits, such as high bandwidth and a high degree of integration, have recently received considerable attention from the semiconductor industry. However, these chips feature through-silicon vias (TSVs), which vertically connect multiple dies, and these TSVs may fail, resulting in a decreased yield. Unfortunately, previously proposed methods to repair TSVs cannot handle certain failure patterns. For example, existing techniques cannot repair clustered TSV faults, which commonly occur in practice. Furthermore, the number of signal TSVs typically determines the number of redundant TSVs, which may result in wasteful and redundant TSVs. In this paper, a new TSV repair scheme is proposed that replaces defective TSVs with redundant TSVs by utilizing the architecture of a cube, which can replace any face with any of the other faces. Both signal TSVs and redundant TSVs are placed in the face of cube, so any faulted TSVs can be replaced with redundant TSVs. The experimental results indicate that the new method guarantees 100% coverage with any number of signal TSVs and redundant TSVs.

Decoding and Repair Schemes for Shift-XOR Regenerating Codes

Decoding and repair schemes are proposed for shift-exclusive-or (shift-XOR) product-matrix (PM) regenerating codes, which outperform the existing schemes in terms of both communication and computation costs. In particular, for the shift-XOR minimum bandwidth regenerating (MBR) codes, our decoding and repair schemes have the optimal transmission bandwidth and can be implemented in-place without extra storage space for intermediate XOR results. Technically, our schemes involve an in-place algorithm for solving a system of shift-XOR equations, called shift-XOR elimination , which does not have the bandwidth overhead generated by shift operations as in the previous zigzag algorithm and has lower computation complexities compared with the zigzag algorithm. The decoding and repair of shift-XOR MBR/MSR codes are decomposed into a sequence of systems of shift-XOR equations, and hence can be solved by a sequence of calls to the shift-XOR elimination. As the decompositions of the decoding and repair depend only on the PM construction, but not the specific shift and XOR operations, our decoding and repair schemes can be extended to other MBR/MSR codes using the PM construction. Due to its fundamental role, the shift-XOR elimination is of independent interest.

Global block level redundancy scheme for repair of clustered fault cells

Global block level redundancy scheme for repair of clustered fault cells

NDT for condition assessment of IDCT RC walls and repair measures for long term durability

This paper presents the condition assessment of reinforced concrete (RC) walls of induced draft cooling tower (IDCT) structure. The main focus is on the assessment of quality, integrity and long term durability of RC walls, with reference to rebar corrosion. Details of non-destructive testing (NDT) carried out to evaluate the prevailing condition of the IDCT structure are presented. Test results revealed that the RC wall, which is intended to be an enclosure/curtain wall to arrest the splashing of sea water fed to the IDCT, is found to be of poor quality and could not arrest the seepage/dampness from inner face to outer face of the wall. To arrive at an effective repair measure to arrest the seepage/dampness in RC walls, porous concrete panels are cast to simulate the poor quality of in-situ concrete of IDCT walls and also to explore and evaluate the effectiveness of different repair schemes. The best repair scheme for improving water tightness is established by conducting selected durability tests on the cores extracted from the repaired porous slab panels. As a pilot study, the identified repair methodology is implemented on the selected wall panels of IDCT structure and its efficacy for water tightness/impermeability is confirmed through visual observation and IRT image scanning.

Feedback control strategies for multi-agent systems under a fragment of signal temporal logic tasks

Multi-agent systems under temporal logic tasks have great potential due to their ability to deal with complex tasks. The control of these systems, however, poses many challenges and the majority of existing approaches result in large computational burdens. We instead propose computationally-efficient and robust feedback control strategies for a class of systems that are, in a sense, feedback equivalent to single integrator systems, but where the dynamics are partially unknown for the control design. A bottom-up scenario is considered in which each agent is subject to a local task from a limited signal temporal logic fragment. Notably, the satisfaction of a local task may also depend on the behavior of other agents. We provide local continuous-time feedback control laws that, under some sufficient conditions, guarantee satisfaction of the local tasks. Otherwise, a local detection & repair scheme is proposed in combination with the previously derived feedback control laws to deal with infeasibilities, such as when local tasks are conflicting. The efficacy of the proposed method is demonstrated in simulations.

Bandwidth Adaptive & Error Resilient MBR Exact Repair Regenerating Codes

Regenerating codes are efficient methods for distributed storage in storage networks, where node failures are common. They guarantee low cost data reconstruction and repair through accessing only a predefined number of arbitrarily chosen storage nodes in the network. In this paper, we consider two simultaneous extensions to the original regenerating codes framework introduced by Dimakis et al. ; 1) both data reconstruction and repair are resilient to the presence of a certain number of erroneous nodes in the network and 2) the number of helper nodes in every repair is not fixed, but is a flexible parameter that can be selected during the run-time. We study the fundamental limits of required total repair bandwidth and provide an upper bound for the storage capacity of these codes under these assumptions. We then focus on the minimum repair bandwidth (MBR) case and derive the exact storage capacity by presenting explicit coding schemes with exact repair, which achieve the upper bound of the storage capacity in the considered setup. To this end, we first provide a more natural extension of the well-known product matrix (PM) MBR codes, modified to provide flexibility in choosing the number of helpers in each repair, and simultaneously be robust to erroneous nodes in the network. This is achieved by proving the non-singularity for a family of matrices in large enough finite fields. We next provide another extension of the PM codes, based on a novel repair scheme which enables flexibility in the number of helpers and robustness against erroneous nodes without any extra cost in field size compared with the original PM codes.

The Repair Problem for Reed–Solomon Codes: Optimal Repair of Single and Multiple Erasures With Almost Optimal Node Size

The repair problem in distributed storage addresses recovery of the data encoded using an erasure code, for instance, a Reed–Solomon (RS) code. We consider the problem of repairing a single node or multiple nodes in RS-coded storage systems using the smallest possible amount of inter-nodal communication. According to the cut-set bound, communication cost of repairing $h\geqslant 1$ failed nodes for an $(n,k=n-r)$ maximum distance separable (MDS) code using $d$ helper nodes is at least $dhl/(d+h-k)$ , where $l$ is the size of the node. Guruswami and Wootters (2016) initiated the study of efficient repair of RS codes, showing that they can be repaired using a smaller bandwidth than under the trivial approach. At the same time, their work as well as follow-up papers stopped short of constructing RS codes (or any scalar MDS codes) that meet the cut-set bound with equality. In this paper, we construct the families of RS codes that achieve the cut-set bound for repair of one or several nodes. In the single-node case, we present the RS codes of length $n$ over the field ${\mathbb F}_{q^{l}}, l=\exp ((1+o(1))n\log n)$ that meet the cut-set bound. We also prove an almost matching lower bound on $l$ , showing that super-exponential scaling is both necessary and sufficient for scalar MDS codes to achieve the cut-set bound using linear repair schemes. For the case of multiple nodes, we construct a family of RS codes that achieve the cut-set bound universally for the repair of any $h=1,2, {\dots },r$ failed nodes from any subset of $d$ helper nodes, $k\leqslant d\leqslant n-h$ . For a fixed number of parities $r$ , the node size of the constructed codes is close to the smallest possible node size for codes with such properties.

Repairing Multiple Failures for Scalar MDS Codes

In distributed storage, erasure codes (like Reed–Solomon Codes) are often employed to provide reliability. In this setting, it is desirable to be able to repair one or more failed nodes while minimizing the repair bandwidth . In this paper, motivated by Reed-Solomon codes, we study the problem of repairing multiple failed nodes in a scalar MDS code. We extend the framework of (Guruswami and Wootters, 2017) to give a framework for constructing repair schemes for multiple failures in general scalar MDS codes in the centralized repair model. We then specialize our framework to Reed–Solomon codes, and also extend and improve upon recent results of (Dau et al. , 2017).

Cooperative Repair: Constructions of Optimal MDS Codes for All Admissible Parameters

Two widely studied models of multiple-node repair in distributed storage systems are centralized repair and cooperative repair. The centralized model assumes that all the failed nodes are recreated in one location, while the cooperative one stipulates that the failed nodes may communicate but are distinct, and the amount of data exchanged between them is included in the repair bandwidth. As our first result, we prove a lower bound on the minimum bandwidth of cooperative repair. We also show that the cooperative model is stronger than the centralized one, in the sense that any maximum distance separable (MDS) code with optimal repair bandwidth under the former model also has optimal bandwidth under the latter one. These results were previously known under the additional “uniform download” assumption, which is removed in our proofs. As our main result, we give explicit constructions of MDS codes with optimal cooperative repair for all possible parameters. More precisely, given any n, k, h, d such that 2 ≤ h ≤ n- d ≤ n- k we construct (n, k) MDS codes over the field F of size |F| ≥ (d + 1 - k)n that can optimally repair any h erasures from any d helper nodes. The repair scheme of our codes involves two rounds of communication. In the first round, each failed node downloads information from the helper nodes, and in the second one, each failed node downloads additional information from the other failed nodes. This implies that our codes achieve the optimal repair bandwidth using the smallest possible number of rounds.

Nondestructive Testing on Ancient Wooden Components Based on Shapley Value

In this study, we propose nondestructive testing methods and combined forecasting models-based stress wave and impedance measurements to obtain accurate internal defects information for wooden building components. Internal defects data for major wooden components of an ancient building in China and reverse laboratory test data on matching tree species indicated various degrees of damage on the pavilion wood structure surface and internal defects in certain pillars. The stress wave method enabled rapid acquisition of two-dimensional plots of test sections; however, the results revealed that the area of stress wave detection was greater than the actual defect area. Moreover, the impedance meter was able to determine the defect position and type in a single path, and the actual defect area was proportional to the absolute error of the drilling resistance. By distributing the errors from the two nondestructive testing methods on the basis of a Shapley value algorithm, we determined the weights of stress wave and impedance meter data in the forecasting models and established combined forecasting models that showed greater accuracy with a mean relative error of less than 6%. This method can improve the prediction accuracy of internal defects in ancient buildings and provide effective data support for practical engineering repair and reinforcement schemes.

Resource-saving in the operation of a building with a correctly executed waterproofing

The article is devoted to the issues of waterproofing of expansion and technological joints. The necessity of using reliable waterproofing methods during construction is identified and justified. Particular attention is drawn to the shortcomings of existing methods, namely bentonite and hydrophilic waterproofing cords related to installation problems and other technical issues. System installation waterstop for technological joint mating base plate-wall and the repair scheme of the one with using the polyurethane resin are described. Comparison is given of the cost of repairing the technological joint and the installation of a waterstop in new construction. The influence of the construction quality on the further cost operation of the building is revealed.