Stable Operation Research Articles

Optimization of Enterprise Financial Risk Management and Crisis Early Warning System Supported by AI

The stability of the financial market plays a key role in the overall health of the economic system, and optimizing corporate financial risk management and crisis warning systems is of great significance. Traditional financial risk management methods often face challenges when processing large-scale, resulting in a decrease in the accuracy of risk assessment. This study combining gated recurrent units (GRU), temporal convolutional networks (TCN) and attention mechanisms. Leverage diverse data sets to improve the accuracy of financial risk assessments and the effectiveness of crisis warnings. Experimental results show that the algorithm outperforms the baseline model in terms of risk prediction accuracy, efficiency and stability. For example, on the LendingClub loan dataset, FLOPs are reduced by more than 46.8%, inference time is improved by more than 48.5%. This method provides new perspectives and solutions for optimizing corporate financial risk management and crisis warning systems. This will have a positive impact on the stable operation of enterprises and other aspects.

A-203 A Disconnect Between Detectable Patient Error Rates and QC Understanding

Abstract Background ISO 14971 defines “risk evaluation as the process of comparing the estimated risk against given risk criteria to determine the acceptability of the risk. Effective QC processes would detect if a stable acceptable error rate became unacceptable. Methods A survey was circulated through LinkedIn and Labvine. Forty respondents who included their credentials were included in the final analysis. Questions included: 1. What is the best choice for acceptable error rate when an analytical process is stable and in control, 2. If an analytical process “fails,” how many errors are you willing to report before the lab should stop reporting, and 3. “If an analytical process has a 5% stable error, how high would the error rate after failure need to become for a 1-2s rule to detect failure with one QC sample in a single QC run?” This interactive poster will allow viewers to cast their vote for Question 4 and then reveal an LJ chart depicting a stable error rate of 5% with a shift to show the number of 1-2s failures with their chosen acceptable post-failure error rate. Results During stable operation, only 8% wanted zero errors while 38% voted that they would allow up to 5% errors; After failure, 66% wanted to report zero errors and only 10% would allow 5% failure. 69% believed they would see a 1-2s failure in one run if the error rate rose to less than 50%; 19% believed it required a 100% error rate. Conclusions There is a strange disconnect where most believed it was acceptable to report more errors during stable operation than if the method failed. There is a widespread misunderstanding of the logic that connects management of acceptable patient risk with the capabilities of statistical QC.

Integrated mid-infrared sensing and ultrashort lasers based on wafer-level Td-WTe2 Weyl semimetal

There is an urgent need for infrared (IR) detection systems with high-level miniaturization and room-temperature operation capability. The rising star of two-dimensional (2D) semimetals with extraordinary optoelectronic properties can fulfill these criteria. However, the formidable challenges with regard to large-scale patterning and substrate-selective requirements limit material deposition options for device fabrication. Here, we report a convenient and straightforward eutectic-tellurization transformation method for the wafer-level synthesis of 2D type-II Weyl semimetal WTe2. The non-cryogenic WTe2/Si Schottky junction device displays an ultrawide detection range covering 10.6 μm with a high detectivity of ∼109 Jones in the mid-infrared (MIR) region and a short response time of 1.3 μs. The detection performance has surpassed most reported IR sensors. On top of that, on-chip device arrays based on Schottky junction display an outstanding MIR imaging capability without cryogenic cooling, and 2D WTe2 Weyl semimetal can serve as a saturable absorber for stable Q-switched and mode-locked laser operation applications. Our work offers a viable route for wafer-scale vdW preparation of 2D semimetals, showcasing their intriguing potential in on-chip integrated MIR detection systems and ultrafast laser photonics.

System friendliness of distributed resources in sustainable energy systems

The increasing share of volatile renewable energy generation in current and future energy systems which does not follow the demand, makes it necessary to shift the synchronization tasks to the system and demand level. The intended demand side consumption management is usually incentivized via financial mechanisms. However, the optimum design of related incentives is still unclear. It is usually discussed under the term “system friendliness” which in turn still lacks a broadly accepted definition. In this article we introduce a new technical definition of “system friendliness” and develop comprehensive and holistic related indicators. For that, we introduce the burden concept for energy systems which represents the amount of technical infrastructure required for stable operation. We use the concept of a hypothetical system energy storage to derive indicators that are capable of quantifying the system friendliness of a given point-of-interest. The developed indicators are independent of regulations or market environments which enables comparability of results between studies and different systems. In a case study we demonstrate our newly developed methodology and exemplary examine decentral district energy storages. Our findings demonstrate that today’s regulatory environments that usually support residential self-consumption maximization are counterproductive. Instead, we show that dynamic end-user prices coupled with dynamic feed in tariffs are able to incentivize an almost 100% system friendly behavior of distributed prosumers.

Transient dynamic cycle evolution and thermodynamic performance analysis of a free-piston engine generator

The free-piston engine generator (FPEG) is a promising hybrid power system. Eliminating the crankshaft mechanism, it features a variable piston dynamic cycle distinct from traditional engines. This paper investigates transient dynamic evolutions, identifies the stable operation zone, and further analyzes thermodynamic performance under various key design parameters. First, a coupled dynamic-thermodynamic model is developed for FPEG. Second, transient dynamic evolutions from start-up to combustion-generation stage are analyzed. The boundaries of operating parameters are identified to ensure the presence of limit cycles for stable operation. Subsequently, the thermodynamic performance is comprehensively evaluated. The indicated power and thermal efficiency improve as load resistance and excess air ratio decrease. The maximum and minimum performance points consistently occur on the overshooting and damping lines, respectively. A lower piston assembly mass and higher design compression ratio are recommended to achieve higher indicated power and thermal efficiency. A lower stroke-to-bore ratio leads to higher indicated power with a slight decrease in thermal efficiency. Additionally, the load coefficient should be adjusted to ensure stable operation according to the design parameters. This paper enhances the understanding of transient dynamic evolutions of the FPEG and provides guidance for prototype design aimed at achieving stable operation and improved output performance.

Analysis and research on the hydrodynamic performance of offshore floating photovoltaic systems under large tidal variations

Abstract This paper focuses on the multi-module connected offshore floating photovoltaic system, designing a mooring system with buoys, considering the effects of buoy size, position on the motion response of the photovoltaic system, mooring cable tension, and photovoltaic air gap. Based on the three-dimensional potential flow theory, optimal parameters for buoys were selected using regular waves at an average depth of 10 meters. Subsequently, factors such as tidal differences, randomness of waves, wind, and currents were taken into account, and the motion response, mooring tension, and photovoltaic air gap were calculated separately at water depths of 8 m, 10 m, and 12 m. The analysis results indicate that the offshore floating photovoltaic system with a buoy mooring system, under the influence of tidal differences, does not show significant differences in the minimum air-gap height of the photovoltaic system, ensuring safe and stable operation.

Analysis of variable speed operating range of centrifugal pump with large flow and wide head variation

Abstract The advantages of variable speed centrifugal pump include its broad operating range, wide operating efficiency zone, high operational stability, and regulative characteristics of input power. When pump station has characteristics such as large flow rate changes, large pump head changes, the conventional fixed speed centrifugal pump cannot meet requirements of safe and stable operation under characteristic pump conditions. In order to ensure the safe and stable operation of the pump station within the operation range, the variable speed operation strategy of centrifugal pumps is adopted to enhance its wide amplitude adjustment capability and efficient operation. This paper uses an 8MW centrifugal pump with wide head range in China to analyze the factors that influence the operating range of pump unit in detail. The results indicate that the variable speed pump unit’s safe and effective operating range is determined by the cavitation margin, hump margin, speed range, and pump maximum input power. The hydraulic design can improve the hump safety margin and cavitation characteristics of the operating zone, and then expand the operating range of the pump unit. Meanwhile, increasing the static suction head, reducing the hump margin, controlling pump head amplitude, and appropriately increasing the maximum input power limit are the best ways to extend centrifugal pump’s operating range and improve its adjustable capability. The results can provide reference for parameter selection and hydraulic design of large variable centrifugal pump in the future.

Construction of 0-dimensional silver quantum dot/MoSe2@MXene/3-dimensional porous copper foam composite electrodes with heterogeneous interfaces for synergistic electrocatalytic degradation of antibiotics

This study proposes a novel and efficient Ag quantum dots (QDs)/MoSe2@two-dimensional transition metal carbide/nitride (MXene)/copper foam (CF) composite electrode to address the challenge of electrocatalytic degradation of antibiotics in water. The electrode formed a unique electron donor–acceptor system by loading Ag QDs and heterostructured nanosheets on CF, significantly facilitating charge transfer and segregation at the interface. The catalytically active sites at the edges and defective locations of MoSe2 in conjunction with the two-dimensional MXene structure, which formed an efficient electron transfer channel, promoted the electron transfer from the interior to the surface and accelerated the hydrogen adsorption and reduction reactions. Moreover, the charge redistribution at the interface of Ag QDs and MoSe2@MXene formed interfacial dipoles, increasing the active sites on the catalyst surface and promoting the generation of cathodic atomic hydrogen (H*). Under optimal conditions, the degradation rate of tigecycline (TGC) reached as high as 90.1 % ± 2.4 % within 60 min. The anode-generated OH and HClO, along with the cathode-generated H, further promoted the degradation of TGC through co-catalysis. The degradation pathways were analyzed using density-functional theory (DFT) calculations and liquid chromatography-mass spectrometry (LC-MS) techniques. Moreover, toxicity analysis of the degradation products was carried out to ensure the safety of the treated wastewater discharge. A reflux continuous effluent reactor was also designed to achieve high degradation efficiency and low energy consumption after stable operation, laying the foundation for industrial applications. This technology provides new ideas for the design of green, efficient, stable, and low-consumption electrocatalytic reactors and contributes to a sustainable future environment.

Optimal consensus control of dynamically interconnected multi-agent systems: A SDRE approach for efficient and stable operation

This study focuses on achieving optimal consensus control based on the state-dependent Riccati equation (SDRE) in multi-agent systems (MASs) characterized by the interconnectivity of multiple sub-systems with physical interconnections. The objective is to establish a suitable communication topology among the MAS controllers that considers both local and global objectives while ensuring stability through distributed control. To address this, an innovative extension of leader-follower and leaderless consensus control methodologies is proposed, accompanied by stability analysis employing the Lyapunov method. Additionally, the paper explores consensus control for dynamically interconnected MASs handling suspended load transportation, such as multi-lift systems. By utilizing the principles of virtual work by D'Alembert and Gauss's principle of least constraint, a constrained multibody system model is developed, incorporating the Udwadia-Kalaba motion equation approach. Simulation results and theoretical analysis validate the efficiency and performance of the proposed consensus controller structure.

Recovery of drain-induced threshold voltage shift by positive gate bias in GaN power HEMTs with p-GaN gate

We demonstrate that exposure to positive gate bias can favor a fast recovery of the threshold voltage variation induced by off-state stress, in p-GaN gate high electron mobility transistors. Two process splits were investigated, having different Schottky barriers at the metal/p-GaN junction. Results indicate that: (a) drain stress may result in significant threshold voltage increase; (b) devices with sufficiently high gate leakage current show an immediate recovery after gate turn-on, resulting in stable operation in actual applications. The contribution of leakage current is demonstrated, based on recovery experiments at different voltages and for the same rate of hole injection from the gate.

Research on Ultrasonic Guided Wave Pipeline Defect Detection Method Based on Modal Analysis

Abstract Pipelines are important transmission media in the petroleum industry, and their safe and stable operation is of great significance to industrial safety. The secure and reliable operation of oil and gas pipelines holds paramount importance for industrial safety. The significance of non-destructive testing (NDT) technology in this context is steadily growing. Presently, guided wave-based pipeline defect detection technology has garnered considerable attention. This method is noteworthy for its extensive coverage, ability to inspect the entire cross-section, and its capability to conduct inspections without disrupting ongoing production processes. Research focused on the displacement distribution of various modes of guided waves, exploring different excitation methods for each mode. The investigation also delved into the interaction mechanism between guided waves and pipeline defects; Conducted research on the detection of axial, circumferential and radial dimensions of defects using different modes of guided waves, and carried out experimental verification, studying the transformation law of the reflection coefficient of the defect reflection echo when the flaw size changes provide a reference for pipeline defect detection based on guided waves.

Development of a digital twin system for snake endoscope manipulator in fusion reactors

Tokamak fusion is one of the solutions to the energy crisis. The environment of the vacuum chamber as a reaction site is extreme, so it needs to be observed during the operation period. This paper has developed a digital twin system for the snake endoscope manipulator (SEM) system, designed to observe of the fusion reactor vacuum chamber. The system includes a five-dimensional model of the SEM digital twin and a three-category architecture encompassing perception, data, and interaction. Additionally, a visualization and interaction system based on ROS-Unity has been developed to depict the working conditions of the SEM accurately. A terminal traction-based trajectory tracking control algorithm has been designed, enabling the SEM to maneuver flexibly within the confined space of the vacuum chamber to avoid collisions and prevent additional damage to the vacuum chamber. The system has integrated a Python-ROS-Unity-based algorithm for joint simulation channel development, which has been used for the virtual simulation experiments of SEM to validate the algorithms and collect data. Furthermore, a prototype has been constructed for virtual-to-real mapping experiments. Experiments show the digital twin system is feasible, with low latency, high sync, and stable operation, which verifies the feasibility of the system.

Amorphous/crystalline Ni-Fe based electrodes with rich oxygen vacancies enable highly active oxygen evolution in seawater electrolysis

To realize large-scale production of hydrogen through seawater electrolysis, it is highly crucial to engineer high-activity and robustly stable catalytic materials for oxygen evolution reaction (OER). Here, a facile etching growth strategy based on Ni foam (NF) is employed to fabricate an amorphous/crystalline Ni-Fe based electrode with rich oxygen vacancies as a promising OER electrocatalyst (a/c-NiFeOxHy@NF). Of note, the introduction of Fe induces the generation of plentiful Ni(Fe)OOH species, which can contribute to the remarkable OER behavior. Profiting from the favorable geometric microstructure of ultrathin nanosheets coupled with 3D open-pore architecture and regulated electronic state by increased oxygen vacancies and abundant crystalline-amorphous boundaries, the resulting a/c-NiFeOxHy@NF displays prominent electrocatalytic OER activity in pure alkaline solution and seawater, achieving impressive overpotentials of only 219 and 233 mV to reach 100 mA cm−2, respectively. More significantly, the electrode can keep stable operation without obvious attenuation for over 1200 h at 100 mA cm−2, demonstrating its exceptional corrosion resistance. Such robustness of this electrode surpasses those of almost all reported OER electrocatalysts. Furthermore, in a self-assembled seawater electrolyzer with a/c-NiFeOxHy@NF as the anode and l-RuP@NF as the cathode, a large current density of 500 mA cm−2 is easily achieved at the voltage of 1.795 V at 65 °C. The work offers a novel paradigm for constructing low-cost, high-efficiency, and ultra-stable OER catalysts, which shows huge promise for industrial seawater electrolysis applications.

Study on Fault Prediction Method of Hydropower Equipment Based on Equipment Health State Detection

Abstract With the continuous development of China’s electric power industry, the installed capacity of power plants is increasing, and hydropower units are developing in the direction of large capacity and high efficiency. As the complexity of the equipment is getting higher and higher, different equipment are more and more different, showing different characteristics when faults occur, which puts forward higher requirements for the safe and stable operation of hydropower units. In response to the above problems, this paper develops a set of human-machine closed-loop remote fault diagnosis reasoning machine system with self-learning function and a set of equipment health state monitoring and prediction system. This remote fault diagnosis system reasoning machine system can reduce the cost of unit equipment fault diagnosis, improve the diagnosis efficiency, and ensure the safe, stable and economic operation of the unit.

Numerical study on unsteady characteristics of backflow vortex cavitation in an axial flow pump

Abstract Axial pumps play a crucial role in various industries such as agriculture, construction, and chemical engineering, exhibiting optimal efficiency under design conditions. However, in practical applications, these pumps often operate under off-design conditions due to environmental constraints, which would lead to a series of problems such as increased vibration, elevated noise levels, and a shortened pump lifespan, thereby endangering its safe and stable operation. This study addresses the issue by using a modified RNG k-ε turbulence model combined with the Zwart cavitation model to simulate the cavitation characteristics of an axial-flow pump. The calculated cavitation characteristics are consistent with the experimental results, proving the exactitude of the numerical approach. A noteworthy observation is the severe cavitation occurrences at the backflow vortex, termed backflow vortex cavitation. This phenomenon undergoes inception, development, and eventual collapse constantly. According to the severity of the backflow vortex cavitation, different periods are divided into the bimodal stage and small-peak stage. Significantly, it is identified that the backflow vortex cavitation interacts with the impeller blades, as the impeller moves, thereby inducing blade vibration, and noise, and exacerbating cavitation erosion. The research results offer a theoretical foundation that is beneficial to enhancing the safe and stable operation of axial flow pumps.

Influence of the channel inclination on the exchange flow and vorticity transport characteristics in a regenerative flow pump

To enhance the overall performance of regenerative flow pump (RFP) to achieve efficient and stable operation over a broad range, this paper employs numerical simulation to study the internal flow conditions of RFP models with three different inclination coefficients (Ic = −0.25, Ic = 0, Ic = 0.25). The analysis focuses on the pressure distribution, energy exchange, velocity variation, and vorticity distribution characteristics within the impeller and channel. The comparison indicates that at Ic = −0.25 with an outward channel, the flow within the pump is stabilized, and the rate of pressure growth and exchange intensity are increased. When Ic = 0 with a semi-circular channel and Ic = 0.25 with an inward channel, there are narrower flow space at the channel's outer diameter, impeding effective fluid motion along the channel and inducing chaotic flow. This condition escalates flow losses and adversely affects the hydraulic performance of the RFP. Additionally, the analysis based on the vorticity transport equation reveals that the Coriolis force term significantly contributes to the generation and transport of vortex in the impeller, while the vortex stretching term dominates the transport of vortex in the channel.

Adaptive fuzzy PI control for the dynamic operation of the transcritical CO2 thermal system in electric vehicles

Process control is essential for ensuring the stable and efficient operation of EVs’ transcritical CO2 thermal management systems. Traditional PI control generally shows an insufficient dynamic response for the variable and complex operating conditions and then causes fluctuant process control. This study proposed an adaptive fuzzy PI control strategy to provide real-time varying PI gains for fast-tracking response and fluctuation suppression, considering the compressor discharge pressure, coolant, and air outlet temperature. A high-fidelity transcritical CO2 thermal model in EVs was first built in the Amesim platform to simulate real-time operation, and the adaptive fuzzy PI control algorithm was then developed to optimize the process control. The co-simulation is conducted to validate the effectiveness and adaptability of the proposed control methodology by comparing it with a benchmark traditional PI control strategy. The results indicated that the proposed adaptive fuzzy PI could provide a 9.22 % overshoot suppression for discharge pressure, a maximal 22.29 % overshoot inhibition and 86 s settling time reduction for the air outlet temperature, and a 25 % settling time reduction for the coolant temperature control. In addition, the fuzzy PI improved the start-up characteristics by avoiding excessive response. Such findings demonstrate that the proposed fuzzy PI control algorithm can effectively optimize the dynamic operation of the transcritical CO2 thermal system in EVs.

A remaining useful life prediction method based on DATCN-PSOSEN for turbofan engines

Abstract Turbofan engine is a crucial operational component of aircraft. Remaining useful life (RUL) prediction is important for the stable and reliable operation of the turbofan engine. High-dimensional and large-capacity monitoring data of turbofan engines pose a considerable challenge to accurate RUL prediction. A novel approach based on dual-attention temporal convolutional network (DATCN) and particle swarm optimization with selective ensemble (PSOSEN) is proposed in this paper. In the first stage, DATCN is utilized to explore the internal correlations among various input features and different time steps in monitoring data, highlighting the degradation information from two dimensions. In the second stage, PSOSEN is developed to prune base models, excluding the ones with poor performance and assigning varying weights to the others, leading to selectively ensembled prediction results. The experimental results on the C-MAPSS aero-engine degradation dataset validate the effectiveness of the proposed DATCN-PSOSEN method and show improvements of RUL prediction accuracy by 14.2% compared with other methods.

Biochar-driven fouling mitigation in sustainable microalgal-bacterial membrane bioreactors

Microalgal-bacterial membrane bioreactor (MB-MBR) have emerged as a crucial technology for sustainable wastewater treatment. However, membrane fouling caused by free microalgae remains a major obstacle to their cost-effective operation. This study investigated the impact of biochar addition on membrane fouling in MB-MBR. The findings indicated that biochar significantly reduced membrane fouling, primarily due to the enlargement of floc size and the reduction of soluble microbial products (SMP). Detailed analyses suggested that biochar's adsorptive properties and its effect on decreasing the abundance of algae and bacteria species, such as Proteobacteria and Leptolyngbya, which promote fouling, are key factors. This alteration enhanced specific amino acid metabolic pathways, thereby reducing SMP production and fouling potential. Consequently, adhesion interaction energy of the flocs and membrane fouling were both diminished. This study demonstrated that biochar addition is an effective strategy for mitigating membrane fouling in MB-MBR systems, providing a theoretical foundation for their stable and sustainable operation.

Design Points of InGaAs MFMIS Tunnel FET for Large Memory Window and Stable Ferroelectric Memory Operation

Design Points of InGaAs MFMIS Tunnel FET for Large Memory Window and Stable Ferroelectric Memory Operation