Restoration in primary molars placed by undergraduate dental students: reasons for failures

Dental caries is one of the most common chronic childhood diseases and highly prevalent in the world. The commonest treatment procedure for dental caries is a dental restoration which aims to retain the tooth. The survival of restoration depends on the factors associated with restorative materials, patients or operators. Thus, this study aimed to determine the reasons for the failure of restoration in posterior primary teeth performed by undergraduate dental students. A total number of 32 patients aged from 5 to 12 years old were included in this study. Overall, 115 primary molar restorations were assessed clinically using the modified United States Public Health Service Ryge criteria. The O’Leary plaque score was used to evaluate the oral hygiene status of all patients. Then, the data was analysed using the Kaplan-Meier survival curves with log-rank test and Cox regression analysis. 43 (37.4 %) restorations failed with 62.1 % for glass ionomer cement and 36.4 % for composite restorations. Marginal adaptation (62.8 %) is the commonest cause of failure. 76.7% of failure restoration was in patients with poor oral hygiene, and it showed a significant difference compared to patients with moderate and good oral hygiene (p = 0.014). Thus, it was concluded that the type of restorative material and oral hygiene status contributed to the failure of restoration placed in primary molar restorations with failure restoration may occur 2.6 times more in poor oral hygiene patients.

A Robust Formulation Model for Multi-Period Failure Restoration Problems in Integrated Energy Systems

The risks faced by modern energy systems are increasing, primarily caused by natural disasters. As a new form of multi-level energy complimentary utilization, integrated energy systems are attracting more and more attention for their high-efficiency and low-cost. However, due to the deep coupling relationship between systems, they are more susceptible to natural disasters, resulting in a cascading failure. To enhance the resilience of the integrated electricity-gas system, this paper proposes a failure restoration strategy after a natural disaster occurs. First, the temporal constraints of the dispatching model are considered, and the failure restoration problem is molded into a multi-period mixed-integer linear programme, aiming to recover the interrupted loads as much as possible. Second, since the uncertain output of distributed generation sources (DGs) such as wind turbines and photovoltaic systems will threat the reliability of restoration results, the robust formulation model is incorporated to cope with this problem. Third, we propose a new modeling method for radial topology constraints towards failure restoration. Moreover, the Column and Constraints Generation (C&CG) decomposition method is utilized to solve the robust model. Then, the piecewise linearization technique and the linear DistFlow equations are utilized to eliminate the nonlinear terms, providing a model that could be easily solved by an off-shelf commercial solver. The obtained results include the sequence of line/pipeline switchgear actions, the time-series dispatching results of electricity storage system, gas storage system, and the coupling devices including the gas-fired turbine, power to gas equipment. Finally, the effectiveness of the proposed restoration strategy is verified by numerical simulation on a 13-6 node integrated energy system.

Post-Disruption Performance Recovery to Enhance Resilience of Interconnected Network Systems

Mitigating the effect of potential disruptive events at the operating phase of an engineered system therefore improving the system’s failure resilience is an importance yet challenging task in system operation. For complex networked system, different stakeholders complicate the analysis process by introducing different characteristics, such as different types of material flow, storage, response time, and flexibility. With different types of systems, the resilience can be improved by enhancing the failure restoration capability of the systems with appropriate performance recovery strategies. These methods include but not limit to, rerouting paths, optimal repair sequence and distributed resource centers. Considering different characteristics of disruptive events, effective recovery strategies for the failure restoration must be selected correspondingly. However, the challenge is to develop a generally applicable framework to optimally coordinate different recovery strategies and thus lead to desirable failure restoration performances. This paper presents a post-disruption recovery decision-making framework for networked systems, to help decision-makers optimize recovery strategies, in which the overall recovery task is formulated as an optimization problem to achieve maximum resilience. A case study of an electricity distribution system is used to demonstrate the feasibility of the developed framework and the comparison of several recovery strategies for disruption management.

A Comparison of Control Strategies for Disruption Management in Engineering Design for Resilience

Managing potential disruptive events at the operating phase of an engineered system therefore improving the system's failure resilience is an importance yet challenging task in engineering design. The resilience of an engineered system can be improved by enhancing the failure restoration capability of the system with appropriate system control strategies. Therefore, control-guided failure restoration is an essential step in engineering design for resilience. Considering different characteristics of disruptive events and their impacts to the performance of a system, effective control strategies for the failure restoration must be selected correspondingly. However, the challenge is to develop generally applicable guiding principles for selecting effective control strategies, thus implementing the control-guided failure restorations. In this paper, a comparison of three commonly used control strategies for dynamic system control is conducted with the focus on the effectiveness of restoring system performance after the system has undergone different major disruptive events. A case study of an electricity transmission system is used to demonstrate the dynamic system modeling and the comparison of three control strategies for disruption management.

A Comparison of Control Strategies for Disruption Management in Engineering Design for Resilience

Managing potential disruptive events at the operating phase of an engineered system therefore improving the system’s failure resilience is an importance yet challenging task in engineering design. The resilience of an engineered system can be improved by enhancing the failure restoration capability of the system with appropriate system control strategies. Therefore, control-guided failure restoration is an essential step in engineering design for resilience. Considering different characteristics of disruptive events and their impacts to the performance of a system, effective control strategies for the failure restoration must be selected correspondingly. However, the challenge is to develop generally applicable guiding principles for selecting effective control strategies thus implementing the control-guided failure restorations. In this paper, a comparison of three commonly used control strategies for dynamic system control is conducted with the focus on the effectiveness of restoring system performance after the system has undergone different major disruptive events. A case study of an electricity transmission system is used to demonstrate the dynamic system modeling and the comparison of three control strategies for disruption management.