Repair Scheme Research Articles

Multiobjective Optimization Approach for Sensor Arrangement in A Complex Indoor Environment

Various meta-heuristic search methods have been employed to resolve the sensor arrangement problem, which is a type of NP-hard, combinational problem. However, the difficulty of weight tuning, when formulating a single objective function, is the chief obstacle to the use of the single-objective optimization methods. Although multiobjective optimization methods have been applied recently to avoid the difficulty involved in weight design, the original multiobjective optimization method still requires a greater number of generations for the solutions to converge to the optimal Pareto front. Moreover, unlike in previous works, we deal with four unknowns to define the sensor arrangement problem more practically: 1) The number of sensors is unknown, 2) no candidate is given for installation, 3) the coverage radii of sensors are variable, and 4) sensors cover a wide area in which obstacles exist in complicated arrangements. To improve the search approach for a sensor arrangement with these requirements, we first propose a representation scheme to encode the sensor arrangement problem as a set of chromosomes. Genetic operators and a repair scheme are also properly employed in the proposed encoding method. In addition, two strategies, i.e., the hierarchical fitness assignment strategy and the hybrid optimization strategy, are proposed to improve convergence. We also perform experiments with two commercial sensors to verify the proposed multiobjective optimization approach for sensor arrangement (MOASA). The results show that the proposed MOASA gives better performance than conventional search methods. The effects of the proposed strategies are investigated with additional experiments in terms of the quality of Pareto solutions.

Effects of Eccentricity on the Seismic Rehabilitation Performance of Nonseismically Detailed Interior Beamwide Column Joints

In this paper, the effects of eccentricity on the effectiveness of carbon-fiber-reinforced polymer (CFRP) or glass-fiber-reinforced polymer (GFRP) in repairing the shear strength and ductility of nonseismically detailed beam-wide column joints have been evaluated. For this purpose, four (two concentric and two eccentric) full-scale nonseismically detailed interior beamwide column joints were used as control specimens. All four subassemblages were subjected to similar cyclic lateral displacement to provide the equivalent of severe earthquake damage. The damaged control specimens were then repaired by filling their cracks with epoxy and externally bonding them with CFRP sheets and GFRP sheets. These repaired specimens were then retested and their response histories were obtained. Hence, a total of eight specimens were tested: four control, and four repaired. The response histories of the control and repaired specimens were then compared. The results were compared through hysteretic loops, load-displacement envelopes, energy dissipation capacity, secant stiffness degradation, and shear strength and damage indices. Moreover, the effectiveness of the proposed repair schemes in repairing the eccentric and concentric joints was also compared. The present study demonstrates that proposed repair schemes can recover the performance of both damaged reinforced concrete (RC) concentric and eccentric beam-wide column joints effectively.

On demand Local Link Repair Algorithm for AODV Protocol

Mobile Ad hoc Network) is a wireless self-organized distributed network. This paper gives a general survey of research on local repair of link, if it is broken during communication for MANET and proposes a new local repair scheme in order to make up the deficiency of the existing local repair schemes. The improved local repair scheme concerns about the over head requirement and end to end delay in transmission. Nodes are required to keep the next two-hop node address for each route entry in routing table. During local repair, the repairing node use Ant algorithm for finding new route for next to next node in the link considering that other part of the link is already in existence. Reduced size of F-ANT and B-ANT will give significant reduction in overhead. In this case repairing node not only tries to discover the route to the destination node of data packet, but also attempts to establish the route to its downstream node (i.e. the next hop node). The proposed algorithm will be highly adaptive, scalable and efficient and mainly reduces end-to-end delay in high mobility cases.

A Built-in Self-Diagnosis and Repair Design With Fail Pattern Identification for Memories

With the advent of deep-submicrometer VLSI technology, the capacity and performance of semiconductor memory chips is increasing drastically. This advantage also makes it harder to maintain good yield. Diagnostics and redundancy repair methodologies thus are getting more and more important for memories, including embedded ones that are popular in system chips. In this paper, we propose an efficient memory diagnosis and repair scheme based on fail-pattern identification. The proposed diagnosis scheme can distinguish among row, column, and word faults, and subsequently apply the Huffman compression method for fault syndrome compression. This approach reduces the amount of data that need to be transmitted from the chip under test to the automatic test equipment (ATE) without losing fault information. It also simplifies the analysis that has to be performed on the ATE. The proposed redundancy repair scheme is assisted by fail-pattern identification approach and a flexible redundancy structure. The area overhead for our built-in self-repair (BISR) design is reasonable. Our repair scheme uses less redundancy than other redundancy schemes under the same repair rate requirement. Experimental results show that the area overhead of the BISR design is only 4.1% for an 8 K × 64 memory and is in inverse proportion to the memory size.

Cost optimization of MBSFN and PTM transmissions for reliable multicasting in LTE networks

Long Term Evolution (LTE) systems have been specified and designed to accommodate small, high performance, power-efficient, end-user devices. The evolved Multimedia Broadcast/Multicast Service (e-MBMS) feature is introduced by the 3rd Generation Partnership Project (3GPP) as a complement to the existing MBMS service in order to accommodate multicast groups that are interested in receiving the same data. MBMS service is provided by MBMS over a Single Frequency Network (MBSFN) and/or Point-To-Multipoint (PTM) transmission methods. One of the challenges of MBMS is the complete error recovery of the transmitted files, a matter of great importance since the distribution of binary data must result in 100% error-free download. To fulfill this tight requirement, Forward Error Correction (FEC) mechanism has been proposed by 3GPP. In this work, we investigate the reliable multicasting by introducing a transmission method that combines the advantages of MBSFN and PTM transmission methods. We compare several FEC-based file recovery methods and evaluate them against various network parameters in a realistic simulation environment. The comparison is based on a cost-oriented analysis of MBMS service that takes into account the transmission cost over all the interfaces and nodes of the LTE architecture. The simulation results are performed with the aid of a new simulation tool and show that the performance of the file repair schemes depend on the network configuration.

Oxygen Permeability of FRP-Concrete Repair Systems

Fiber reinforced polymers (FRP) are increasingly used for repairing corrosion-damaged concrete structures. The performance of the repairs is critically dependent on the oxygen permeability of the FRP-concrete system. This paper presents the results of an experimental study in which the oxygen permeation of concrete and FRP-concrete systems were determined. In the study, concrete specimens with three different water-cementitious ratios were initially tested. Subsequently, uni directional one and two-layer carbon and fiberglass material were bonded to the concrete surface, and the oxygen permeation of the FRP-concrete systems were determined. The results showed a significant reduction in the oxygen permeation of concrete after FRP had been bonded. The best performance was obtained for FRP bonded to concrete with the highest water-cementitious ratio. An expression for the equivalent thickness of FRP-concrete systems was derived by using Fick’s law. This facilitates the evaluation of the effectiveness of alternate FRP-concrete corrosion repair schemes.

Shear repair of RC beams using epoxy injection and hybrid external FRP

This experimental study aims at investigating the behavior of reinforced concrete (RC) beams strengthened by unidirectional and hybrid bidirectional fiber-reinforced polymer (FRP) sheets and subjected to cyclic loading. RC beams tested under cycled loading were subsequently repaired using both epoxy injection and external FRP sheets, and then re-tested under monotonic loading. Six RC beam specimens, two of which were control specimens and four were shear deficient, were upgraded with side-bonded FRP sheets in the first phase of the experimental program. In the second phase, three of the damaged beams were repaired using epoxy injection and unidirectional carbon fiber polymer (CFRP) sheets. The repairing method, FRP type, and FRP wrapping scheme were the test variables investigated. Test results show that the repair schemes imparted significant mechanical improvements in terms of ultimate shear capacity and ductility. The simultaneous application of epoxy injection and externally bonded FRP sheets was found to be a highly effective repair technique.

Route Maintenance in IEEE 802.11 wireless mesh networks

In this paper, we propose a novel Route Maintenance scheme for IEEE 802.11 wireless mesh networks. Despite lack of mobility and energy constraints, reactive routing protocols such as AODV and DSR suffer from frequent route breakages in 802.11 based infrastructure wireless mesh networks. In these networks, if any intermediate node fails to successfully transmit a packet to the next hop node after a certain number of retransmissions, the link layer reports a transmission problem to the network layer. Reactive routing protocols systematically consider this as a link breakage (and therefore a route breakage). Transmission failures can be caused by a number of factors e.g. interference or noise and can be transient in nature. Frequent route breakages result in significant performance degradation. The proposed mechanism considers multiple factors to differentiate between links with transient transmission problems from those links which have permanent transmission problems and takes a coherent decision on link breakage. The proposed mechanism is implemented in AODV for single-radio single-channel mesh network and an extension is incorporated in multi-radio multi-channel scenarios. Simulation results show substantial performance improvement compared to classical AODV and local route repair schemes.

An Area-Efficient, Low-VDD, Highly Reliable Multi-Cell Antifuse System Fully Operative in DRAMs

A reliable antifuse scheme has been very hard to build, which has precluded its implementation in DRAM products. We devised a very reliable multi-cell structure to cope with the large process variation in the DRAM-cell-capacitor type antifuse system. The programming current did not rise above 564µA even in the nine-cell case. The cumulative distribution of the successful rupture in the multi-cell structure could be curtailed dramatically to less than 15% of the single-cell's case and the recovery problem of programmed cells after the thermal stress (300°C) had disappeared. In addition, we also presented a Post-Package Repair (PPR) scheme that could be directly coupled to the external high-voltage power rail via an additional pin with small protection circuits, saving the chip area otherwise consumed by the internal pump circuitry. A 1Gbit DDR SDRAM was fabricated using Samsung's advanced 50nm DRAM technology, successfully proving the feasibility of the proposed antifuse system implemented in it.

User-perceived reliability of shared protection systems with the Erlang type-k repair scheme

This paper describes the availability and mean time to first failure (MTTFF) of M-for-N shared protection systems (with M + N units) from the viewpoint of an arbitrary one of the N end users. Various forms of M-for-N shared protection are used to improve the reliability of telecommunication network devices such as access node devices, routers, switches, servers, network address translators, etc. In this paper, the time between failures of units and the time for repair are assumed to be an exponential distribution and the Erlang type-k distribution respectively. We consider the Erlang type-k distribution because repair time does not necessarily follow the exponential distribution and the Erlang type-k distribution is more flexible and useful for determining the system parameters such as the mean repair time and the variance based on the reliability objectives. The purpose of this paper is to evaluate the user-perceived reliability of such systems in a quantitative manner.

Comparison of CFRP and Alternative Seismic Retrofitting Techniques for Bare and Infilled RC Frames

The opportunities provided by the use of modern repair schemes for the seismic retrofit of existing RC structures were assessed on a comparative experimental study of carbon fiber-reinforced polymer (CFRP) and more-conventional seismic retrofitting techniques for the repair of reinforced concrete members and masonry walls of bare and infilled RC frames, respectively, damaged because of cyclic loading. Four 1-story, one-bay, one-third-scale frame specimens are tested under cyclic horizontal loading up to a drift level of 4%—two bare frames with spirals or stirrups as shear reinforcement, respectively, and two infilled frames with weak infills and spirals or stirrups as shear reinforcement, respectively. The applied repair techniques are mainly based on the use of thin epoxy resin infused under pressure into the crack system of the damaged RC joint bodies or on the additional use of CFRP plates to the surfaces of the damaged structural RC members as external reinforcement and the use of a polymer modified cement mortar or two-sided diagonal CFRP fabrics for the damaged infill masonry walls. After repair, specimens were retested in the same way. Conclusions concerning the comparison of the effectiveness between conventional and CFRP seismic retrofitting applied techniques on the basis of maximum cycles load, loading stiffness, and hysteretic energy absorption capabilities of the tested specimens are drawn.

A fast local routing repair scheme for wireless mobile ad hoc network

Mobile ad hoc network (MANET) is a centerless packet radio network which does not use fixed infrastructure. It has recently received tremendous attention due to its capabilities of self-configuration and self-maintenance. However, attenuation and interference caused by node mobility and wireless channel sharing weaken the stability of communication links. A mathematical exploring model for the next hop has been established based on the optimal exploring theory. The negative impact of wireless routes discontinuity has been alleviated by a novel fast local routing repair scheme (FLRRS) proposed in this paper, wherein the route requirement zone has been restricted into a pie slice region on intermediate nodes according to the solution of exploring equations. The scheme is an effective approach in reducing the average end-to-end delay during routing maintenance. It also allows continuous packet forwarding for fault resilience. NS-2 based simulation results showed remarkable successful packet delivery rate and end-to-end delay improvements of source-initiated routing protocol with the fast local repair scheme, especially in the case of high dynamic environments with heavy traffic loads.

Traction–separation laws for progressive failure of bonded scarf repair of composite panel

Abstract Repair of composites has become of considerable importance recently as modern commercial airliners employ much more composites in their airframes then previously. Major maintenance, repair, and overhaul (MRO) centers must contend with issues of damage tolerance, efficiency, integrity and cost of repairs. Computational methods have been developed to sufficiently sophisticated levels to aid in the design, evaluation and optimization of proposed repair schemes before they are implemented, potentially saving time and cost. In this paper, parametric studies on progressive failure analysis of a bonded scarf repair of a composite panel was performed. The study finds that finite element models with an appropriate material property degradation scheme using the micromechanics of failure criterion are able to predict the failure load of undamaged and damaged specimen. Results of the parametric studies on adhesive properties suggest that the failure stress of a repaired composite panel is more sensitive to the strength of the cohesive elements than to its toughness when a linear or trapezoidal softening traction–separation law is used, but the influence of adhesive strength is not significant when exponential softening traction–separation law is used.

Link Stability and Node Energy Conscious Local Route-Repair Scheme for Mobile Ad Hoc Networks

Problem statement: A mobile ad hoc network is a self-configuring network of mobile nodes connected by wireless links. As the nodes are free to move randomly, topology of the network may change rapidly and unpredictably. As a result, intermediat e nodes in the communication routes tend to lose connection with each other during the communication process. In order to repair a broken link, an end- to- end (from source to destination) route discovery is typically performed to establish a new route for communication. The mechanism results in huge communication overhead and long delay in completion of the communication. So, it is rational to locally re pair a link, as much as possible, than to discover a whole new route. Approach: In the present article, we proposed a Link Stabili ty and Node Energy Conscious (LSNEC) local route repair scheme for mobile ad hoc networks. In case of breakage of a link from node na to another node nb in between a communication session, LSNEC instructs na to broadcast a ROUTE- REPAIR message within its radio-range specifying nb or any successor of nb in the broken route, as a desirable destination. If any node residing within the radio-range of na has an already established single/multi-hop path to any one of those destinati ons mentioned in the ROUTE-REPAIR message, it sends a REPAIR-ACK message back to na. Attributes of REPAIR-ACK include the identificati on number (s) of the destination (s) as well as identificatio n numbers, geographical positions (in terms of lati tude and longitude), radio-ranges and residual energies of n odes present in the associated path to that destina tion along with the intuitively computed stability of li nks between the consecutive nodes. The stability is computed depending upon relative velocities of the involved nodes, distance between them and the histo ry of survival of the link. The optimal path is chosen depending upon the residual energy of nodes, stabi lity of links and number of hops in that path. Results: In simulations we compared the LSNEC embedded versions of the protocols Ad hoc On-demand Distance Vector routing (AODV) and Associatively Based Routing (ABR) with their ordinary versions as well as PATCH and Quick Local Repair scheme (to be referred to as QLR subsequently in this study) embe dded versions. Both PATCH and QLR are well- known local repairing schemes for ad hoc networks. It is found that, LSNEC-AODV dramatically saves 57% control overhead compared to ordinary AODV, 32.7% compared to PATCH-AODV and 36.3% compared to QLR-AODV. Similarly, LSNEC-ABR saves 29.3% control overhead than ordinary ABR, 10.7% than PATCH-ABR and 12.8% than QLR-ABR. Accordingly decrease the power consumption of network nodes and delay in recovery. Conclusion: The simulation results emphatically illustrated th e performance benefit of our proposed scheme LSNEC compared to the other state-of-the-art local route- repair schemes, in respect of control overhead, ove rall energy consumption of the network, data packet delivery ratio and route recovery delay. LSNEC has its application wherever an ad hoc network is used. Please note that ad hoc networks are extremely usef ul in military and other tactical applications such as emergency rescue, exploration missions and other sc enarios w here cellular infrastructure is unavailab le.

8 Gb 3-D DDR3 DRAM Using Through-Silicon-Via Technology

An 8 Gb 4-stack 3-D DDR3 DRAM with through-Si-via is presented which overcomes the limits of conventional modules. A master-slave architecture is proposed which decreases the standby and active power by 50 and 25%, respectively. It also increases the I/O speed to > 1600 Mb/s for 4 rank/module and 2 module/channel case since the master isolates all chip I/O loadings from the channel. Statistical analysis shows that the proposed TSV check and repair scheme can increase the assembly yield up to 98%. By providing extra VDD/VSS edge pads, power noise is reduced to < 100 mV even if all 4 ranks are refreshed every clock cycle consecutively.

Repair of Laser-localized DNA Interstrand Cross-links in G1 Phase Mammalian Cells

Interstrand cross-links (ICLs) are absolute blocks to transcription and replication and can provoke genomic instability and cell death. Studies in bacteria define a two-stage repair scheme, the first involving recognition and incision on either side of the cross-link on one strand (unhooking), followed by recombinational repair or lesion bypass synthesis. The resultant monoadduct is removed in a second stage by nucleotide excision repair. In mammalian cells, there are multiple, but poorly defined, pathways, with much current attention on repair in S phase. However, many questions remain, including the efficiency of repair in the absence of replication, the factors involved in cross-link recognition, and the timing and demarcation of the first and second repair cycles. We have followed the repair of laser-localized lesions formed by psoralen (cross-links/monoadducts) and angelicin (only monoadducts) in mammalian cells. Both were repaired in G(1) phase by nucleotide excision repair-dependent pathways. Removal of psoralen adducts was blocked in XPC-deficient cells but occurred with wild type kinetics in cells deficient in DDB2 protein (XPE). XPC protein was rapidly recruited to psoralen adducts. However, accumulation of DDB2 was slow and XPC-dependent. Inhibition of repair DNA synthesis did not interfere with DDB2 recruitment to angelicin but eliminated recruitment to psoralen. Our results demonstrate an efficient ICL repair pathway in G(1) phase cells dependent on XPC, with entry of DDB2 only after repair synthesis that completes the first repair cycle. DDB2 accumulation at sites of cross-link repair is a marker for the start of the second repair cycle.

A lightweight network repair scheme for data collection applications in zigbee WSNs

Data collection is a fundamental operation in wireless sensor networks (WSNs). In, a quick convergecast solution is proposed for data collection in a ZigBee beacon-enabled tree-based WSN. However, it does not consider the network repair issue. When a ZigBee router loses its link to its parent, all its descendants have to rejoin the network. The rejoining procedure is time-consuming and may incur high communication overheads. The proposed network repair scheme consists of a regular repair and an instant repair schemes. Periodically, the network coordinator can issue regular repair to refresh the network (so as to keep the network in good shape). During normal operations, if a router loses its parent, it tries instant repair to reconnect to a new parent. Our design thus improves over ZigBee in that nodes can continue their operations even during instant repair.

A lightweight network repair scheme for data collection applications in zigbee WSNs

Data collection is a fundamental operation in wireless sensor networks (WSNs). In, a quick convergecast solution is proposed for data collection in a ZigBee beacon-enabled tree-based WSN. However, it does not consider the network repair issue. When a ZigBee router loses its link to its parent, all its descendants have to rejoin the network. The rejoining procedure is time-consuming and may incur high communication overheads. The proposed network repair scheme consists of a regular repair and an instant repair schemes. Periodically, the network coordinator can issue regular repair to refresh the network (so as to keep the network in good shape). During normal operations, if a router loses its parent, it tries instant repair to reconnect to a new parent. Our design thus improves over ZigBee in that nodes can continue their operations even during instant repair.

Verification of a Real-Time Attitude Determination Algorithm through Development of 48-Channel GPS Attitude Receiver Hardware

This paper describes the verification of a real-time attitude determination algorithm during GPS attitude receiver hardware development. The GPS attitude receiver of 24 channels had been already developed in Surrey University. However 24 channels were not enough for practical usage. For this reason, a 48-channel attitude receiver with 12 channels for each antenna has been developed. To estimate attitude in real time, precise relative positions of the GPS antenna array have to be determined as rapidly as possible. However, the calculation load based on the conventional algorithm is too burdensome to perform using the RISC microprocessor. Therefore, in this paper, the cycle ambiguities of each base vector are resolved using SNUGLAD (Seoul Nat Univ GNSS Lab Attitude Determination), the design focus of which is to allow the receiver to estimate the 10 Hz onboard solutions. To keep precise solutions continuously, after ambiguity removal, cycle slip must be detected or isolated. Otherwise, the receiver would output erroneous solutions after a short signal blockage or fading of the GPS signal. To prevent this, we defined the cycle slip detection and repair scheme using a standard extended Kalman filter, which can detect and repair cycle slip within one cycle. As a result, this paper shows that time synchronized measurement with good quality and a reliable solution can be provided by the hardware developed with inexpensive chipsets and that this may be a possible cost efficient sensor for UAV or microsatellites.

Experimental study of fatigue crack growth behaviour in adhesively reinforced steel structures

The use of adhesively-bonded composite materials has lead to great advances in repairing and strengthening cracked or aged metallic structures. However, less is known about the fatigue performance of the bonding between the composites and the metallic substrate, which is the deciding factor when designing the strengthening. In this study, a series of experiments is performed to investigate the effectiveness of the composites on preventing fatigue crack propagation and extending the fatigue life of steel plates. The composite material of CFRP sheet is adopted. Both single-sided and double-sided repairs are studied. Experimental results show that the application of composite patches substantially reduces crack growth rate and prolong fatigue life. The double-sided repair scheme increased the fatigue life by 2.2–2.7 times over un-patched steel plates when normal modulus CFRP sheets were used, and by 4.7–7.9 times when high modulus CFRP sheets were used. The CFRP sheets with high modulus were found to be much more efficient. Bond width has considerable influence on the crack growth life. These two findings were especially true for double-sided repairs. The parameters of patch thickness , patch length and patch configuration, had an influence on fatigue life increase of over 20% for both single-sided and double-sided repairs, except that patch configuration had only a 6% influence on fatigue life increase for double-sided repairs. Furthermore these three parameters had slightly more influence on single-sided repairs than on double-sided repairs.