Operation Risk Research Articles

From Zone -1 to Zone 3: Feasibility and Safety of Complex Endovascular Aortic Repairs in Type A Aortic Dissection.

Over 30% of patients presenting with acute type A aortic dissection (ATAAD) are considered high - risk or inoperable. This study aims to investigate the early and mid-term outcomes of complex endovascular aortic repair of aortic root, ascending aorta, and aortic arch among patients with ATAAD. From January 2018 to January 2023, 29 patients who were considered high risk for open operation underwent endovascular aortic repair. Patients were considered high risk due to: frailty (N=14), severe malperfusion (N=5), chronic obstructive pulmonary disease on home oxygen (N=4), frozen chest (N=3), metastatic cancer (N=3), ejection fraction < 20% (N=4), and cirrhosis (N=2). For an isolated tear in the ascending aorta (Zone 0), ascending stent graft placement was performed using commercially available aortic stent grafts. For patients with a tear in the aortic root, Endo-Bentall was performed using a physician-modified modular device composed of a self-expanding transcatheter aortic valve incorporated inside an aortic stent graft. For patients with a tear in the ascending aorta as well as the aortic arch (Zone 0, Zone 1, 2), ascending stent graft placement and endovascular arch repair was performed. Follow-up electrocardiogram-gated computed tomography (CT) was performed to evaluate aortic remodeling. The mean age for this cohort was 76.3 ± 11.1 years. Endovascular repairs included: Isolated ascending stent placement in 65.5% (19/29), Endo-Bentall in 6.9% (2/29), Endo-Bentall plus Endo arch in 6.9% (2/29), and ascending TEVAR + Endo arch in 20.7% (6/29). The operative mortality was 10.3% (3/29). Stroke rate was 10.3% (3/29). During the follow-up time of a median of 6.25 months (range 0.85 to 64.6), an endoleak was observed in 42.3% (11/26) patients (80% among patients with a tear < 2cm of STJ). Seven patients had a type 1a endoleak, while four patients had a type 1b endoleak on follow-up CTA. Three patients required reintervention. The Kaplan-Meier 5-year probability of survival for the entire cohort post-intervention was 35%. Early outcomes of complex endovascular repair of ascending aortic dissection are promising with acceptable mortality and stroke rate. However, the rate of endoleak after isolated ascending TEVAR with a tear within 2cm of the aortic root is high with poor long-term survival.

IMPROVING THE EFFICIENCY OF ENERGY COMPANIES BY OPTIMISING THE DISTRIBUTION OF COSTS FOR MAINTENANCE AND REPAIR OF ELECTRICAL EQUIPMENT

At present, there is a high emergencies probability in the electric power system as an electrical equipment failures result caused primarily by the objectively existing ageing and its service life significant exhaustion. Emergencies arising from electrical equipment failures lead to the dynamic stability violation of power systems and power system load nodes by voltage, cascading accidents and, as a result, technological processes disruption of consumer enterprises, which is accompanied by significant losses. One of the ways to prevent sudden failures or minimise the risk of their occurrence is to ensure rational and efficient operation management and reduce the operating equipment cost without risking a decrease in the power system reliability. To solve the optimal distribution problems of power company operating costs, taking into account the objectively existing limiting factors, a generalised balance sheet model of cost allocation by electrical equipment groups and units is proposed, which is a total costs function of an operating factors number. Mathematical models for calculating the electrical equipment share participation coefficients in the costs formation for its repair and maintenance for each of the identified factors have been obtained. A linguistic mathematical model for determining generalised estimates of the electrical equipment units and groups significance degree in the repair and maintenance costs distribution formation, taking into account the main operational factors, has been proposed. An algorithm and software for modelling the modes of the electric power system with an electrical connections scheme of electric networks with a 35-330 kV voltage have been developed to assess the operation risk index and power company repair and maintenance costs distribution. The estimated power company repair and maintenance costs distribution according to the current technical equipment characteristics and power system subsystem modes was performed.

Research on the innovation of early warning mechanisms of major public health emergencies for poverty alleviation and marginal populations: a case study of Fujian Province.

Poverty alleviation is critical for sustainable development. Establishing a major public health emergency warning and prevention mechanism for poverty alleviation and marginal populations can effectively determine the overall risk situation and primary risk components in diverse regions. It is conducive to formulate specific policies for risk prevention and control of public health emergencies to prevent the occurrence of poverty relapses. Expert evaluation method is used to grade the risk impact and risk probability. Combined with the Borda ordinal value method to rank the importance of risk factors, a judgment matrix is constructed. The Analytic Hierarchy Process method is used to determine the weight of the risk module. And the impact risk of major health emergencies on poverty alleviation and marginal populations is comprehensively evaluated based on the quantified value of the risk impact level. The results indicate that the production and operation risks and unemployment risks in the case area have a relatively significant impact on poverty alleviation and marginal populations. Different regional government forces and regional economic development characteristics may also form different risk weights. Therefore, risk warning models should match government development and regional development goals and be established based on the characteristics of different regions. Effective risk control mechanisms and policies can only be developed based on the characteristics and behavioral traits of different populations in the region.

The Effects of Credit, Liquidity, and Operational Risks on GCC Bank Financial Stability: Moderating Role of Board Size

This paper examined the impact of three types of bank risk: credit, liquidity, and operational risk on bank financial stability. It also examined the moderating role of board size and board frequency meetings. It also investigated the macroeconomic factors such as GDP growth and inflation and their influence on bank financial stability. A sample of listed banks in GCC stock exchanges from 2014 to 2022 using a panel data analysis. The findings highlighted that credit and operational risk significantly impact a bank's financial stability, but liquidity risk is unrelated to the bank's financial stability. In addition, GDP and the Covid-19 pandemic had a negative impact on bank financial stability. Board size significantly moderates relationships between credit risk, operation risk, and bank financial stability.

Managing the risk of continued operation with out‐of‐service safety instrumented system devices

AbstractSafety instrumented systems (SIS) are used to reduce the frequency of hazardous events in the process industry. When SIS equipment has a detected failure or requires online maintenance, the processing facility must decide whether to continue operation or shut down. Continued operation can pose risks beyond what was deemed acceptable as per the company's risk criteria. Understanding the peak risk is important to ensure that all stakeholders are aware of the risk and have compensating measures that ensure continued safe operation until the SIS equipment is returned to service. The paper proposes using Peak Risk Analysis (PRA) to identify unacceptable risks and to document the compensating measures required to support continued safe operation with out‐of‐service SIS equipment.

Research on the Application of Stewart Platform for Wave Compensation

In the field of ocean engineering, the efficiency and safety of ship operation are significantly affected by waves. Faced with the instability and safety risks of ship crane operation under complex sea conditions, a design and research method of efficient wave compensation device based on Stewart platform is proposed in this paper, aiming at developing a compensation system that can respond in real time and effectively counteract the effects of waves, so as to improve the safety and efficiency of offshore operations. Aiming at the limitation of traditional wave compensation technology, this paper adopts the BP neural network PID control algorithm combined with Stewart platform. Utilizing the Stewart platform's six-degree-of-freedom motion capability, fast compensation of wave motion is achieved. On this basis, the BP neural network PID control strategy is introduced to optimize the response speed and compensation accuracy of the system, and realize the efficient and accurate compensation of wave motion under complex sea conditions.

Research on dynamic analysis and maintenance strategy for hard bending of high-speed turnout switch rail

Plastic deformation occurs in the turnout switch rail during loading, unloading, transportation, and storage, resulting in hard bending of the switch rail. The hard bending of the switch rail will lead to an abnormal increase in insufficient displacement, resulting in the geometric size exceeding the limit and the potential risk in the train operation. However, the dynamic simulation of the turnout area has not fully explored the potential impact of the insufficient displacement caused by the hard bending of the switch rail on driving safety. Therefore, this paper establishes a high-speed railway EMU-turnout dynamics model to evaluate the influence of the hard bending of the switch rail on the safety and stability of the train. The results show that the influence of theoretical and measured switch rail hard bending amplitude on the vehicle dynamics index is limited when it is 4 mm or less. However, when the hard bending amplitude of the switch rail increases to 8 mm, the relevant vehicle dynamics indexes increase significantly. The maximum derailment coefficients under the theoretical and measured hard bending of the 8 mm working conditions are 4.42 times and 6.71 times the normal working conditions, respectively. The wheelset lateral force is 4.55 times and 6.86 times the normal working conditions, but they are all within the safety limit. The on-site verification also confirms that there is no significant change in the vertical and lateral acceleration of the car body under the 4 mm hard bending of the switch rail. Finally, a maintenance strategy for the insufficient displacement caused by the hard bending of the switch rail is proposed and the effectiveness of the maintenance strategy is verified in the case study.

Precise large deviations of the net loss process in a non-standard two-dimensional risk model

Abstract This paper investigates the precise large deviations of the net loss process in a two-dimensional risk model with consistently varying tails and dependence structures, and gives some asymptotic formulas which hold uniformly for all x varying in t-intervals. The study is among the initial efforts to analyze potential risk via large deviation results for the net loss process of the two-dimensional risk model, and can provide a novel insight to assess the operation risk in a long run by fully considering the premium income factors of the insurance company.

Risk Identification of Public Private Partnership Contracts with The Build-Operate-Transfer Scheme on Toll Road in Indonesia

One of the most crucial things that every nation needs is infrastructure. To boost the nation’s competitiveness, the Indonesian government is expediting infrastructure construction. Howeve, there are risk and big financial outlays that need to be addressed. A collaboration agreement, often known as public-private partnership (PPP), between the government and the private party is required in order to do this. With this contract, the government will be able to increase the number of toll roads throughout Indonesia. Although PPP comes in a variety of forms, the Build Operate Transfer (BOT) model is the most commonly used. The organizers and managers of the toll road will assume the government may be able to increase the number of toll roads Indonesia requires with the help of this deal. Although PPP comes in a variety of forms, the BOT model is the most commonly used. The organizers and managers of the toll road will assume all risks associated with the partnership plan. In order to reduce the risks caused by a partnership, each risk must be identified, assigned, and given the proper reaction. The data used in this study comes from BOT cooperation scheme-using toll road projects. The study indicates that there are relevant risks for toll road projects in Indonesia using PPP contracts with the BOT scheme, (1) political risk, (2) feasibility study risk, (3) financial risk, (4) design risk, (5) construction risk, (6) operation risk, and (7) transfer risk. The risk allocation in this research is based on expert opinions, adapted from ongoing toll road BOT projects in Indonesia.

RATIONALE FOR THE USE OF A HYDRATE FORMATION INHIBITOR IN PRODUCTION WELLS IN WESTERN SIBERIA

Operation of the gas transmission system under hydrate conditions leads to the risk of deposits, changes in operating modes and plugging of pipelines and gas transmission equipment. Inhibitors such as methanol and glycols are mainly used to prevent hydrate formation. Less commonly, small amounts of polymer compounds (kinetic inhibitors) are used, which instead of inhibiting formation work thermodynamically, slowing the rate of formation of gas hydrates. However, the problems associated with excessive methanol consumption and the production of products that do not meet the standards for the content of dissolved methanol remain unresolved. These problems can be solved by improving the technological scheme of gas collection and treatment. The article focuses on the use of methanol as a hydrate inhibitor, which effectively prevents this process. It has been shown that in order to optimize the flow rate of methanol, it is necessary to take into account the salinity of formation water. The urgency of the problem is due to the high risks for the normal operation of wells, since gas hydrates can lead to clogging of equipment and pipelines, which in turn can cause emergencies and shutdown of the entire production. The article describes the current status of field development in Western Siberia, including an analysis of reserves and an assessment of production potential. Seven pay zones have been identified in the field, two of which are associated with the Upper Cretaceous deposits, four with the Upper Jurassic and one with the Middle Jurassic. The authors proposed a method for calculating the optimal amount of methanol required to prevent the formation of gas hydrates. The calculations are based on data on the composition of Cenomanian gas, temperature and other conditions in the field under consideration. The study identified critical points where gas hydrates are most likely to form. This made it possible to accurately calculate the required amount of methanol to maintain the hydrate-free state of the wells. The results of testing in the field of Western Siberia showed that the dosing of methanol is an effective means to prevent hydrate formation.

Emergency Dispatch Strategy Considering Spatiotemporal Evolution of Power Grid Failures Under Typhoon Conditions

The increasing climate-change-induced tropical cyclone phenomena expose the power grid to significant operation risks by disrupting the normal operation of grid components. This paper considers the failure mechanism with respect to critical grid components and reveals a novel spatiotemporal revolution of grid failures during the passage of typhoons. Based on the spatiotemporal evolution of grid failures, a threshold-based emergency scenario set and the corresponding two-stage robust optimization-based emergency dispatch model are developed. The robust emergency dispatch strategy is obtained using a column-and-constraint generation (C&amp;CG) algorithm. The simulation results show that the proposed robust emergency dispatch strategy can guarantee a considerable degree of robustness under multiple emergency scenarios driven by uncertain typhoon conditions.

Adequacy of Venous Thromboembolism Risk Assessment and Prophylaxis After Gastrointestinal Surgery in a Sudanese Teaching Hospital: A Prospective Audit.

Background Venous thromboembolism (VTE) is a condition that occurs when a blood clot forms in a vein. VTE includes deep vein thrombosis (DVT) and pulmonary embolism (PE). Regular monitoring and risk assessment are crucial for effectively using VTE prevention measures. This study aimed to evaluate the practices related to VTE risk assessment and prophylaxis within our surgical unit in a Sudanese teaching hospital. Methods This study was conducted at Alnao teaching hospital and was comprised of two cycles. It examined adult patients who underwent gastrointestinal operations. Data from medical records including age, sex, type of operation, whetherVTE and bleeding risk assessments were performed, whether pharmacological or mechanical prophylaxis was administered, and any contraindications to VTE prophylaxis. The practice of VTE risk assessment and prophylaxis prescription was compared to the National Institute for Health and Care Excellence(NICE)guidelines for VTE risk assessment and prophylaxis. Following cycle one, regular educational sessions were conducted for medical staff, emphasizing the need for improved practices in assessing the risk of VTE and prophylaxis prescription. Results 32 patients in cycle one and 29 patients in cycle two were included. VTE and bleeding risks were assessed in 0/32 (0.00%)of patients in cycle one compared to 29/29 (100%)in cycle two. In cycle one, 0/32 (0.00%) patients were given VTE prophylaxis according to the guidelines. This practice improved to 17/29 (58.6%)in cycle two. Conclusion The audit highlights the role of organized methods and education in improving adherence to VTE prophylaxis guidelines. Targeted interventions like educational sessions and risk assessment tools led to significant practice improvements, particularly in low-resource settings. Continuous auditing and training are essential for maintaining and enhancing compliance with VTE prophylaxis standards.

Study of Surface Repair Materials for Aged Silicone Rubber Insulators

The aging phenomenon of silicone rubber insulators can bring great safety risks for the stable operation of high-voltage transmission lines. To avoid the significant costs and prolonged downtime associated with completely replacing insulating equipment, our research described in this paper proposes a surface repair material for aged silicone rubber insulators using α, ω-dihydroxy-polydimethylsiloxane as the matrix. The material was, after preparation, uniformly applied to the surface of insulators that had been in grid operation for more than 14 years. The chemical structure, elemental composition and surface morphology of the insulator surfaces were characterized both before and after repair. Our research described here also examined the changes in mechanical properties, insulating resistivity, water repellency and adhesion strength of the insulators. The data showed that the functional group types and element contents on the surface of the repaired silicone rubber insulators were restored to those of the new insulators, and the surface and internal cracks were also effectively repaired. Moreover, the water-repellent, mechanical, and electrical properties underwent a notable enhancement. The robust adhesion between the repair material and the deteriorated surface resulted in the formation of a stable and robust adhesive interface. The results demonstrated that the materials created for the purpose of repair in our research had the capability to efficiently enhance the performance of aged insulators. Furthermore, we suggest this study presented a novel path toward addressing the predicament of aging insulation equipment.

An analytical two-stage risk analysis model in the real-time reservoir operation

Flood risk analysis is vital for real-time reservoir operation. The reservoir operation horizon (OH) is generally longer than the streamflow forecast horizon (FH), while the gap between the FH and the OH was seldom considered in analytical flood risk models. This study develops an analytical two-stage risk model covering the period within the FH (the first stage) and from the FH to the OH (the second stage). In the first stage, the errors in forecasted streamflow and reservoir water level-storage relationships are considered using the multinormal distribution within the FH. In the second stage, design flood hydrographs are used to estimate the flood risk by conducting reservoir routing. Finally, the total flood risk is calculated by using the copula method to combine the flood risks from the first and second stages. Results for a case study using China’s Three Gorges Reservoir indicate that an effective FH can be identified to minimize flood risk, and balance between the forecast accuracy and length of the horizon. The length of the effective FH is not fixed and depends on reservoir inflow. Moreover, larger errors will not always lead to greater flood risks. The proposed method provides useful information on flood risk for real-time reservoir operation.

Identification of Risk Factors for Bus Operation Based on Bayesian Network

Public transit has been continuously developing because of advocacy for low-carbon living, and concerns about its safety have gained prominence. The various factors that constitute the bus operating environment are extremely complex. Although existing research on operational security is crucial, previous studies often fail to fully represent this complexity. In this study, a novel method was proposed to identify the risk factors for bus operations based on a Bayesian network. Our research was based on monitoring data from the public transit system. First, the Tabu Search algorithm was applied to identify the optimal structure of the Bayesian network with the Bayesian Information Criterion. Second, the network parameters were calculated using bus monitoring data based on Bayesian Parameter Estimation. Finally, reasoning was conducted through prediction and diagnosis in the network. Additionally, the most probable explanation of bus operation spatial risk was identified. The results indicated that factors such as speed, traffic volume, isolation measures, intersections, bus stops, and lanes had a significant effect on the spatial risk of bus operation. In conclusion, the study findings can help avert dangers and support decision-making for the operation and management of public transit in metropolitan areas to enhance daily public transit safety.

Influencing factors of bentonite for the directional electric repair of landfill HDPE membrane leakage in calcium ion solution

The timely repair of high-density polyethylene (HDPE) membrane leakage in landfills is an important means of environmental risk control, which is critical for preventing leachate from polluting groundwater and soil. Electric repair technology is expected to become a hot spot in the leakage repair of HDPE films, because it can solve the issues of complex operation, high costs, and security risks during the operation and closure of landfills. To explore the influence law of various technical factors on the electric repair process, we carried out single factor experiments on the main influencing factors such as the operation time, bentonite concentration and dispersant/bentonite dosage ratio, leakage size, and calcium concentration. We then explored the best technological conditions. The results showed that accumulation at the leakage site possessed a good repair effect with a permeability coefficient of 4.22 × 10−6 cm/s. Furthermore, we observed that the Zeta potential played an important role in the electric repair technology, where the higher the absolute value of the Zeta potential, the faster the electrophoretic migration rate of the bentonite particles, and the lower the permeability coefficient of accumulation. This study may serve as a theoretical basis and offer scientific guidance for the directional electric repair of HDPE membrane leakage during the operating period and after the closure of landfills.

Calculation of Distribution Network PV Hosting Capacity Considering Source–Load Uncertainty and Active Management

The access of a high proportion of photovoltaic (PV) will change the energy structure of the distribution network (DN), resulting in a series of safety operation risks. This paper proposes a two-stage PV hosting capacity (PVHC) calculation model to assess the maximum PVHC, considering the uncertainty and active management (AM). Firstly, we employ a robust optimization model to characterize the uncertainty of sources and loads in DN with PV and analyze the worst-case scenarios for PVHC. Subsequently, we construct a PVHC calculation model that takes into account AM, and convert the model into a mixed-integer second-order cone (MISOC) model using linearization techniques. Finally, we apply “heuristic optimization + CPLEX solver” to solve the model and introduce overvoltage and overcurrent indices to analyze the safety of the DN under PV limit access. Case studies are carried out on the IEEE 33-bus system and a practical case. Results show that (1) only the uncertainty that reduces the load or increases the output efficiency will affect PVHC; (2) for DN limited by overvoltage, AM can better improve PVHC; however, for DN limited by maximum transmission power, the effect of AM is low; (3) for most DN, SVC can improve PVHC, but the effect is modest. And network reconfiguration can significantly increase PVHC on the system with poor branch network, even reaching 150% of the original PVHC.

Study on the Tort of Misrepresentation in the Inter-bank Bond Market--Taking Case No. 1 of the Beijing Financial Court as an Example

Chinese interbank bond market dates back to June 1997, when the People's Bank of China decided to open an interbank bond trading business at the National Interbank Lending Center, which was formally established. In the following years, this market developed relatively fast, and in June 2002, the bond counter market of commercial banks began to operate, which to a certain extent made the interbank bond market, which institutional investors dominate, expand through the counter trading for all kinds of investors in the whole society.In recent years, applying direct financing tools such as corporate bond issuance has become increasingly widespread. This paper takes Beijing Financial Court Case No. 1 as an example to study in detail the important reasons for the emergence of this type of infringement, focusing on the obligations and responsibilities of each participant, including the issuer Dalian Machine Tool Group, the intermediary bank Industrial Bank, and the investor Bluestone Capital Management. This paper aims to sort out the obligations and responsibilities of each participant in the inter-bank bond market to find out the reasons for the emergence of the phenomenon of misrepresentation and to explore the issues that appear to be suitable for this paper to find out the causes of misrepresentation, explore the operation rules and risk prevention measures of the interbank bond market that are suitable for China's national conditions, to solve the problems of misrepresentation, standardize the obligations and responsibilities of all parties, and promote the development of China's interbank bond market.

Research on the collaborative operation strategy of shared energy storage and virtual power plant based on double layer optimization

Large-scale access to distributed energy resources leads to new energy consumption problems and safe operation risks in the power system. Virtual power plants and shared energy storage are effective ways to promote the flexible consumption of distributed energy resources and improve the reliability and economy of power system operation. Based on the concept of sharing economy and considering the complementary characteristics of source and load resources between different virtual power plants, this paper focuses on the optimisation of shared energy storage and multi-virtual power plant operation. Firstly, distributed wind power, distributed photovoltaic and flexible load resources are aggregated into virtual power plants to analyze the cooperative operation mode of shared energy storage and multi-virtual power plant systems. Secondly, a two-layer decision model for shared energy storage configuration and multi-VPP system operation optimisation is constructed, with the upper model solving the optimal energy storage configuration scheme by maximising the revenue of the shared energy storage operator, and the lower model optimising the multi-VPP system operation strategy by minimising the total operation cost, the maximum amount of new energy consumed, and the minimum amount of carbon emission as the multi-objective optimisation strategy. Finally, a simulation analysis is carried out, and the results show that compared with the independent operation mode of each virtual power plant, the model proposed in this paper increases the annual profit of the shared energy storage operator by 7180¥, reduces the operating cost of the VPP system by 7.08 %, improves the rate of renewable energy consumption by 0.82 %, and reduces the annual carbon emission by 54.91 t, which realizes the mutual benefits of the virtual power plant and the shared energy storage.

Unveiling the origin of metal contact failures in TOPCon solar cells through accelerated damp-heat testing

Tunnel oxide passivated contact (TOPCon) solar cells are expected to dominate the global photovoltaic market in the coming decade thanks to rapid advancements in power conversion efficiency (PCE). However, there are concerns about the reliability of TOPCon modules, particularly in hot and humid conditions. The current module-level fundamental analysis strategies for TOPCon solar cells provide too slow feedback for rapid process development. This study explores the degradation of metal contacts in TOPCon solar cells under accelerated testing conditions of 85 °C and 85 % relative humidity (DH85). The degradation was induced by two commonly used sodium-related salts, sodium bicarbonate (NaHCO3) and sodium chloride (NaCl), in the testing of the solar cells. When applied to the front side, NaHCO3 caused a ∼5%relPCE reduction after 100-h DH85 exposure, while NaCl leads to a more significant ∼92%relPCE reduction. The primary cause of degradation is a considerable increase in series resistance (Rs), likely due to electrochemical reactions within the Ag/Al paste. When the salts are applied to the rear of the TOPCon solar cell, the degradation becomes more complex. NaHCO3 increases recombination and results in a deterioration of the contact, resulting in a ∼16%relPCE reduction after 100-h DH85 testing. Conversely, NaCl primarily causes a decline in open-circuit voltage (Voc) and a ∼4%relPCE loss. This manuscript primarily investigates degradation mechanisms related on the rear side, with a focus on significant oxidation occurring at the interface between Ag and Si. These findings highlight the susceptibility of TOPCon solar cells to contact corrosion, emphasizing the electrochemical reactivity of metallisation as a potential risk for long-term TOPCon module operation. This study provides crucial insights into TOPCon cell degradation mechanisms, which are essential for optimising performance and enhancing the long-term reliability of TOPCon modules.