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With the rapid growth of elevator installations, conventional scheduled maintenance struggles to meet the dual demands of ensuring operational safety and cost control. This study proposes an innovative on-demand maintenance method that aligns with the Chinese policy directives on elevator maintenance reform. First, we conduct a historical fault cause analysis to identify the root causes of elevator entrapment incidents. Next, we establish an entrapment prediction model based on our historical data. Then, we design an elevator entrapment risk index report according to the prediction results. Finally, we formulate an on-demand maintenance plan that combines insights from the report with the conclusions of the cause analysis. Field implementation and comparative experiments demonstrate that the proposed on-demand maintenance method outperforms the scheduled one. The result shows significant reductions in accident and maintenance workload, justifying the practical value of this approach for the industry.

In the present study, the feasibility to achieve localized induction heating and debonding of multi-material composite structures is assessed in testing coupons prepared by Automated Fiber Placement (AFP) and extrusion-based additive manufacturing (AM) technologies. Nano-compounds of Polyether-ketone-ketone (PEKK) with iron oxide nanoparticles acting as electromagnetic susceptors have been processed in a parallel co-rotating twin-screw extruder to produce filament feedstock for extrusion-based AM. The integration of nanocomposite interlayers as discrete debonding zones (DZ) by AFP-AM manufacturing has been investigated for two types of sandwich-structured laminate composites, i.e., laminate-DZ-laminate panels (Type I) and laminate-DZ-AM gyroid structures (Type II). Specimens were exposed to an alternating magnetic field generated by a radio frequency generator and a flat spiral copper induction coil, and induction heating parameters (frequency, power, heating time, sample standoff distance from coil) have been investigated in correlation with real-time thermal imaging to define the debonding process window without compromising laminate quality. For the optimized process parameters, i.e., 2–3 kW generator power and 20–25 mm standoff distance, corresponding to magnetic field intensities in the range of 3–5 kA m−1, specimens were effectively heated above PEKK melting temperature, exhibiting high heating rates within the range of 5.3–9.4 °C/s (Type I) and 8.0–17.5 °C/s (Type II). The results demonstrated that localized induction heating successfully facilitated debonding, leading to full unzipping of the debonding zones in both laminate structures. Further insight on PEKK nanocomposites debonding performance was provided by thermal, morphological characterization and non-destructive inspection via X-ray micro-computed tomography at different processing stages. The developed framework aims to contribute to the development of rapid, on-demand joining, repair and disassembly technologies for thermoplastic composites, towards more efficient maintenance, repair and overhaul operations in the aviation sector and beyond.

It is common knowledge that mechanical systems need oversight and maintenance procedures. There are numerous prevalent operation monitoring techniques, and in the era of IoT and predictive maintenance, it is possible to find multiple solutions to supervise these systems. This article describes the design and implementation of a low-cost system, which use an IoT approach to detect overheated idlers in conveyors belt in mining facilities. The system involves the use of temperature sensors, coordinately with heat map image sensors. The users (i.e., mining operators) can monitor overheated idlers in the whole conveyor belt, making on-demand queries using Telegram or a website, and also receiving autonomous warnings. Prototypes of this system were installed on a conveyor belt at a construction materials manufacturing company, and also in a copper mining company, both located in Apurimac, Peru. The usability and usefulness of the system were evaluated by 20 experts in maintenance and operation of conveyor belts, who filled the questionnaire proposed by TAM (Technology Acceptance Model). The results show that 91% of them consider the system useful for detecting the overheating of idlers in a conveyor belt, and 93% of them considers the solution as easy to use.

Video-on-demand (VoD) applications have become extensively used nowadays. YouTube is one of the most extensively used VoD application. These applications are used for various purposes like entertainment, education, media, etc., of all age groups. Earlier, these applications were supported by private data centers and application servers. Sufficient infrastructure had to be bought and maintained, to support the demand even during unexpected peak times. This approach caused huge loss of resources when the demand is normal as a large portion of the resources remained idle. To overcome this, VoD application providers moved to the cloud, to host their video content’s. This approach reduced the wastage of resources and the maintenance cost of the VoD application provider. The problem is to determine the number of resources to handle the demand while maintaining QoS for every instance. We have designed two algorithms in this paper, namely the multiple cloud resource allocation (MCRA) algorithm and the hybrid MCRA algorithm. Most of the cloud service providers (CSPs) basically provide two types of resource allocation schemes: (i) the reservation scheme and (ii) the on-demand scheme. The reservation scheme provides time-based tariff prices, where the discount is provided for the resources depending on their quantity and reservation time. This scheme is used in the MCRA algorithm to reduce the cost of the VoD application provider. In Hybrid MCRA algorithm both the reservation scheme and on-demand scheme are implemented, to overcome the drawbacks of the MCRA algorithm which are under-subscription and over-subscription . We have analyzed both the algorithms in terms of cost and allocation of resources. These algorithms can help allocate resources in of cloud for VoD applications in a cost-effective way and at the same time not compromise on the QoS of the video content.

Advances in aviation technology including the development of relatively cheap, very light jets and the possibility of free-flight have led to the realization of a per-seat, on-demand air transportation business that operates without a published flight schedule. One of the decision problems this business faces is planning the scheduled maintenance that has to be done periodically for safety reasons. Careful planning of scheduled maintenance in this dynamic business environment is required to ensure safe and efficient operations. In this paper, we address both tactical and operational planning for scheduled maintenance of per-seat, on-demand air transportation. At the tactical level, we determine the daily maintenance capacities. As the fleet size grows over time, decisions pertaining to when and how much to increase maintenance capacity are made. At the operational level, we assign itineraries to jets and determine the jets to be maintained on a daily basis. We further embed operational maintenance planning into a framework that captures the interaction between maintenance decisions and daily flight scheduling.

Reactive routing protocols are better options for the communication in ad hoc network. In this study, a novel approach for local link repairing of ad hoc on demand routing protocol is suggested for the performance enhancement of the basic protocol. Alternate route finding for next-to-next node in case of link breakage is a better option of route management. These protocols are beacon-less to improve bandwidth utilisation. Control overheads have been reduced by using 802.11b protocol to maintain connectivity of moving nodes. Significant improvement is observed in the Quality of service parameters like throughput, end-to-end delay, packet delivery ratio and link breakage through simulations.

Standard on-demand routing protocols in wireless ad hoc networks were not originally designed to deal with security threats. Because of that, malicious users have been finding ways to attack networks. Rushing attacks represent one of such possibilities. In these attacks, malicious nodes forward the Route Request (RREQ) packets, asking for a route, to the destination node quicker than the legitimate nodes do. This is possible because the legitimate nodes only forward the first received RREQ packet for a given route discovery. Besides, the attackers can tamper with either the Medium Access Control or routing protocols to get faster processing. As a result, the path through the malicious nodes is chosen, which renders throughput degradation. We propose here a novel, robust routing scheme to defend ad hoc networks against rushing attacks. Our scheme utilizes the “neighbor map mechanism” to establish robust paths as far as rushing attacks are concerned. The proposed scheme also improves path recovery delay by using, whenever it is possible, route maintenance rather than route discovery. Yet, it is energy efficient. The simulation results show that our proposal is indeed viable.

Video on demand services require video broadcast schemes to provide efficient and reliable performance under various client request loads. In this paper, we have developed an efficient request load adaptive broadcast scheme, speculative load adaptive streaming scheme (SLAS), that requires lower service bandwidth than previous approaches, regardless of request rate. We have provided both analysis and simulation to show the performance gain over previous schemes. In this paper, we provide the theoretic upper bound of the continuous segment allocations on channels. We found that the number of allocated segments of the SLAS is close to the theoretic upper bound when compared with other schemes over various numbers of stream channels. Our analysis of client waiting time is almost identical to simulation results about all client requests. By simulation, we compared the required service bandwidth and storage requirements of the SLAS scheme and other schemes and found the SLAS scheme is an efficient broadcast scheme as compared to well known seamless channel transition schemes.

The most used protocol in Mobile Ad hoc Networks (MANETs) uses the Ad hoc On-Demand Distance Vector (AODV) routing protocol for achieving dynamic, self-organizing, and on-demand multihop routing. In AODV, wireless links may be lost occasionally because the nodes on the routing path are unreachable. Such a problem causes AODV inefficient and unreliable. For solving the problem, AODV provides a local repair mechanism for an intermediate node to find an alternative route to destination when the node detects links broken. The repair mechanism uses the broadcast-type RREQ message for discovering a repair route, which results in a large number of repair control messages and requires a large amount of power consumption for sending these messages. Therefore, in this paper we propose a unicast-type distributed local repair protocol for repairing breaks expeditiously, i.e., achieving high network reliability and utilization, less the number of control messages, and less the repair delay. Furthermore, the optimal number of hops in a neighbor table is analyzed. Numerical results indicate that the proposed approach is superior to other repair approaches in terms of successful fixing rate, control message overhead, and network utilization.

High-speed networks and powerful end-systems enable new types of applications, such as video-on-demand and teleconferencing. Such applications are very demanding on quality of service (QoS) because of the isochronous nature of the media they are using. To support these applications, QoS guarantees are required. However, even with service guarantees, violations may occur because of resources shortage, e.g., network congestion. In this paper we propose new adaptation approaches, which allow the system to recover automatically, if possible, from QoS violations (1) by identifying a new configuration of system components that might support the initially agreed QoS and by performing a user-transparent transition from the original configuration to the new one, (2) by redistributing the levels of QoS that should be supported, in the future, by the components, or (3) by redistributing the levels of QoS that should be supported immediately to meet end-to-end requirements based on the principle that (local) QoS violation at one component may be recovered immediately by the other components participating in the support of the requested service. The proposed approaches, together with suitable negotiation mechanisms, allow us (1) to reduce the probability of QoS violations which may be noticed by the user, and thus, to increase the user confidence in the service provider, and (2) to improve the utilization of the system resources, and thus to increase the system availability.