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This paper presents facts and figures, directly or indirectly, related to medical equipment reliability and reviews various important aspects, directly or indirectly, concerned with medical equipment reliability including classifications of medical devices/equipment, human error in medical equipment, useful guidelines for reliability and other professionals to improve medical equipment reliability, and medical equipment maintenance. A number of methods considered useful for performing medical equipment reliability analysis are also presented. Useful sources and organizations for obtaining medical equipment failure-related data are listed.

Software-Defined Networking disassociates the control plane from data plane. The problem of deciding upon the number and locations of controllers and assigning switches to them has attracted the attention of researchers. Foreseeing the possibility of failure of a controller, a backup controller has to be maintained for each switch so that the switches assigned to the failed controller can immediately be connected to their backup controllers. Hence, the switches cannot experience disconnections in case of failure of their controller. In this paper, two mathematical models are proposed. The first model focuses on minimizing the average of latencies from all switches to their backup controllers while considering the failure of the controllers. The second model aims at minimizing both the average and worst-case of latencies from all switches to the corresponding backup controllers. Both of our models are evaluated on three networks and are compared (in terms of two metrics, viz., average and worst-case latencies) with an existing model that focuses on minimizing only worst-case latency. The first model gives better average latency compared to the reference model. The second model also gives better average latency and almost equal worst-case latency compared to the reference model.

This paper presents a simplified approximate analysis of the overall collapse of the towers of World Trade Center in New York on September 11, 2001. The analysis shows that if prolonged heating caused the majority of columns of a single floor to lose their load carrying capacity, the whole tower was doomed. Despite optimistic simplifying assumptions, the structural resistance is found to be an order of magnitude less than necessary for survival.

Collapse of transmission towers due to downbursts is often initiated by local failure of key structural members, while the local failure of key structural members is related to local material and geometrical nonlinearities. This paper presents a multi-scale finite element (FE) model for the failure analysis of transmission towers under downburst-induced wind loading. The potential local failure areas of the tower are modeled by shell or solid elements, and the remaining parts by beam elements. In this way, the failure of the tower can be accurately simulated on the one hand and the computational effort can be reduced on the other hand. This paper first introduces how to determine the downburst-induced wind loading on transmission towers. Both the conventional beam and multi-scale FE models of the transmission tower are then developed and used in the failure analysis. A comparison of the failure results obtained by the two FE models show that the multi-scale FE model can effectively simulate the stress concentration of angle members around the bolt connections and the cross-section plastic collapse of key structural members, leading to a different failure pattern for the tower from the conventional FE method. It is suggested that the multi-scale FE model should be used for better accuracy in the failure analysis of transmission towers under downburst loading.

This paper presents experimental and numerical studies for predicting the seismic responses of welded and bolted steel beam–column connections, namely, welded unreinforced flange and bolted web connection, and welded unreinforced flange and welded web connection. Cyclic tests of these connections composed of members applied widely to steel structures are conducted to examine their seismic performance. Numerical simulations with a focus on the bolted joint are conducted using a nonlinear finite element code. Two different strategies of modeling bolted parts are provided to improve the computational efficiency of numerical analysis: solid contact elements and more simply using shell connector elements. Numerical solutions obtained for full connection models are experimentally validated. The rotational capacity and dissipated energy of the welded and bolted connections are discussed. The local responses for stress and strain in the vicinity of welded and bolted joints are also investigated.

A great number of reinforced concrete building structures were damaged or collapsed during the earthquake that hit Sivrice district of Elazığ city located in the southwest of the Eastern Anatolia Region of Turkey on January 24, 2020. Magnitude of the earthquake were announced as $M_w=6.5$ and $M_w=6.8$ by Kandilli Observatory & Earthquake Research Institute (KOERI) and Earthquake Department of the Disaster and Emergency Management Presidency (AFAD), respectively. More than a thousand of aftershocks with the magnitude of 1.2–5.1 occurred between January and February 2020. The magnitude of the structural damage was relatively high compared with the peak value of recorded ground acceleration (2.85m/s²) at the epicenter (Sivrice district) of the earthquake. It was determined that 584 buildings were demolished, 6845 were severely damaged, 1207 were moderately damaged, 14,389 were slightly damaged and 14,317 were undamaged. Also, there were 235 buildings that required urgent demolition. In this paper, the performance of the reinforced concrete buildings during the Sivrice-Elazığ earthquake is presented along with time-histories of ground motion records and response spectrums. Observed design and construction practices were carefully evaluated and compared with Turkish Earthquake Code. It was seen that the most significant causes of the failures were due to the poor concrete quality, the use of non-ductile detailing, the poor project design and construction quality. According to field inspections of our technical team, it is concluded that performances of the undamaged buildings following earthquakes do not prove that they have adequate seismic safety.

A coupled model of aeroservoelasticity and hydraulic actuator used for failure simulation is presented. The mathematical model composites rigid-body modes, elastic modes, control surface modes, unsteady aerodynamic forces and failure models (jam, loss of control (LOC), oscillatory failure, and hydraulic fluid leakage). A clear framework of coupling method of airplane aeroelastic equation and control surface dynamic equation is provided to study the impacts of surface failures on rigid-elastic motion of airplane. The coupled model is shown to be effective in evaluation of gust response in both discrete gust and continuous turbulence conditions compared with results obtained from the 3-order simplified actuator. Examples of gust load alleviation (GLA) system with LOC of ailerons are given. Results show that total loss of function of GLA system is caused by the LOC. With continuous turbulence excitation, the failure loads is several times larger than that without GLA system.

This study investigated the microscale behaviours and damage evolutions of graphene/epoxy nanocomposites under uniaxial tensile loadings. Computational molecular dynamics (MD) simulation was applied to model the microstructural constituents of graphene/epoxy composites and the evaluation of their mechanical and the damage responses at different temperatures. The computed results revealed the influence of the proportions of graphene and temperatures on the mechanical properties, the damage evolution and the change in strain energy associated with failure of the nanocomposites. The study has added to the understanding of the damage development and failure of the graphene nanoplatelets (GNP)/epoxy composites.

In the context of underground construction, forensic engineering is taken to be the application of engineering principles and methodologies to determine the cause of a performance deficiency, often a collapse, in an excavation, and the reporting of the findings, usually in the form of an expert opinion within the legal system. The procedures that may be used in forensic geotechnical investigations and the interface of the engineer with the legal system are discussed. The application of the principles and methodologies outlined are illustrated through a brief account of the investigation of the collapse of a small part of an excavation in the Lane Cove Tunnel Project, Sydney, Australia, on 2 November, 2005.

A 3-D discrete element model with connective type was presented in this paper. Accordingly, a 3-D discrete element method code, which can calculate the transitional process from connective model (for continuum) to contact model (for non-continuum), was developed. The wave propagation in a 3-D concrete block under impact loading was numerically simulated, by using this code. Comparing its numerical results with those by LS-DYNA, the accuracy of this algorithm was presented. Moreover, the failure process of the concrete block under impact loading was demonstrated, which presented the basic dynamic transitional process from continuum to non-continuum. The two numerical examples prove that the new model and its code are powerful and efficient for simulating the dynamic failure problems accompanying with the transition from continuum to non-continuum. It also shows that the discrete element method will have widespread availability and perfect development prospect.

In order to explore the integral safety degree, probable failure type and failure mechanism of high dam, the combination of overloading and strength reduction method is adopted to simulate the progressive failure and potential destabilization pattern of dam-foundation system. By using finite element method, the overloading of dam-foundation system is carried out firstly and then keeping the load combination unchanged, by reducing rock material strength parameters step by step. The general safety degree of dam-foundation system is obtained. The method mentioned above has been used in Guangzhao roller compacted concrete (RCC) gravity dam, the finite element calculation results show that integrated safety degree of GuangZhao RCC Gravity Dam is greater than 3.0 and the safety degree of the dam foundation surface which is the weakest position of the dam-foundation system is greater than 2.0. The research results indicate that the safety coefficient can satisfy the engineering requirement and the method is efficient and accurate in high dam safety evaluation.

The purpose of this study was to predict 10kV cable failures based on deficiency data, and provide data basis for maintenance adjustment. Deficiency Data Analysis (DTA) tree is built on history data. Then probability distribution of deficiency and failure data is constructed considering the family characteristics. Kullback-Leibler distance is used to analyze the correlation between deficiency and failure, which is used to predict failure based on monitoring and testing data. Shenzhen Nanshan power supply company adopted the algorithm analysis achievement, as a result, the cable failure number drop 18% comparing to last year. It is proved that this algorithm can be used to predict malfunctions of cables, then according maintenance could be carried out and enhance system reliability.