Excellent Operation Performance Research Articles

Research on grid-related performance laboratory testing for variable speed pumped storage unit

Abstract Variable speed pumped storage unit is an energy storage device with excellent operation and regulation performance. For the grid-related performance laboratory testing of the AC excitation controller of variable speed pumped storage unit integrated into the power grid, this paper studied the methods of grid-related testing of the AC excitation controller based on actual pumped storage power station data, established semi-physical hardware in the loop simulation platform based on RTDS and its function boards, and proposed the key laboratory testing items for the grid-related test. The simulation testing results verified the functions of the platform.

Generalized frequency shift and attenuation in simply-supported micro/nano-beam resonators with thermoelastic dissipation

The low frequency shift, weak frequency attenuation, and large quality factor (Q) are strongly required for micro/nano-resonators with excellent operation performance. Therefore, the accurate predictions of frequency shift, frequency attenuation, and Q based on thermoelastic dissipation (QTED ) are significant when optimally designing micro/nano-resonators. In this work, employing the modified-couple-stress (MCS) and nonlocal-single-phase-lag (NSPL) models, the generalized analytical expressions of the frequency-shift ratio, frequency-attenuation ratio, and QTED are first proposed for the simply-supported micro/nano-beam resonator with two-dimensional (2D) heat conduction. In the modeling procedure, utilizing the Galerkin approach, the function of 2D fluctuation temperature is solved from the governing equation of NSPL thermoelasticity. For simplicity, the function of one-dimensional (1D) fluctuation temperature is presented directly. Various expressions of complex natural frequency are obtained from the governing equation of MCS vibration with thermoelastic coupling, and then the models of the frequency-shift ratio, frequency-attenuation ratio, and QTED are developed based on the relevant expressions of complex natural frequency. It is confirmed that the present developed models with generality can effectively degenerate into the classical models. In the simulation cases, silicon (Si) that is a representative semiconductor material is selected. Results reveal that the MCS size-dependence effect can affect the frequency shift more markedly than the NSPL and heat-conduction-dimension (HCD) effects. Moreover, for the beam with a small thickness and operated in a high-order mode, the NSPL and HCD effects will significantly determine behaviors of the frequency shift, frequency attenuation, and QTED .

Experimental study on the characteristics of loop heat pipe with modified carbon fiber felt wick

In order to achieve accurate and effective thermal management of high-performance electronic components, the performance of a small flat loop heat pipe was investigated. A flexible composite capillary wick material has been applied in a flat loop heat pipe. Surface modification of carbon fiber felt was carried out using arc spraying technology to make it a more suitable material for producing capillary wicks. The physical properties of the modified carbon fiber felts were determined by measuring their wettability, porosity, capillary force, and thermal conductivity. A small flat loop heat pipe assembled with carbon fiber felt wick was designed and fabricated, and experimental testing was conducted. The experimental data indicated that the performance of methanol was better than that of acetone and water. The loop heat pipe with a 60% filling ratio maintained the heat source temperature at 84.47 °C under a load of 120 W (30 W/cm2). Conditions where the heat source starts before the cooling system are more favorable for the quick and stable startup of the loop heat pipe. The experimental results demonstrated that the loop heat pipe with a modified carbon fiber felt wick exhibited excellent operational and heat transfer performance.

Analysis and Valuation of Toyota’s— Multiple Valuation Method of PE Ratio and EV EBITDA Ratio

With the continuous development of the automobile industry, Toyota has become the world's largest multinational automobile manufacturer. By referring to Toyota's 2019-2022 financial report and comprehensive report, this paper analyzes the company's business strategy and investment strategy and makes a relevant financial analysis. This paper mainly uses two methods of value assessment. The first method is EBITDA/EV, which is also considered an enterprise value multiple valuation model. The second is the price-earnings ratio valuation, which can be used to determine whether a company is overvalued or undervalued in the market. Based on the above analysis, the author believes that Toyota is overvalued, but it is relatively safe for investors based on its excellent operating performance and its leading position in the industry. At the same time, the author also expounds on the influence of Toyota's overvaluation on future development and emphasizes Toyota's current competitive advantages and potential market threats. Furthermore, since Toyota has undergone great changes in recent years and there are few types of research on Toyota from 2021 to 2022, the research significance of this paper is to help readers better grasp the recent financial status, business strategy, and enterprise value of Toyota.

Robust Optimal Control for Wastewater Treatment Process With Uncertain Time Delays

To achieve the excellent operational performance of the wastewater treatment process, optimal control has been considered a reliable method. However, there is a time-delay response of the operation performances to the process variables, leading to uncertainties of operational optimal objectives. It is difficult to obtain the optimal set-points due to the uncertain operational optimal objectives. Therefore, a kernel-density-estimation-based robust optimal control (KDE-ROC) method is proposed. First, a data-driven prediction strategy is developed to construct the uncertain operational optimal objectives. Based on the time-delay intervals, the uncertainties between process variables and operational optimal objectives are expressed. Second, a kernel-density-estimation-based robust optimization algorithm is designed to solve the uncertain operational optimal objectives. Then, the optimal set-points of process variables are obtained depending on the robustness index to reduce the influence of uncertainties. Third, an adaptive neural network controller is developed to track the optimal set-points of process variables. Finally, the proposed KDE-ROC is applied in benchmark simulation model No.1. In the experimental results, the optimal control performance of KDE-ROC is compared with some effective optimal control strategies to demonstrate its effectiveness.

High-Entropy Perovskites for Energy Conversion and Storage: Design, Synthesis, and Potential Applications.

Perovskites have shown tremendous promise as functional materials for several energy conversion and storage technologies, including rechargeable batteries, (electro)catalysts, fuel cells, and solar cells. Due to their excellent operational stability and performance, high-entropy perovskites (HEPs) have emerged as a new type of perovskite framework. Herein, this work reviews the recent progress in the development of HEPs, including synthesis methods and applications. Effective strategies for the design of HEPs through atomistic computations are also surveyed. Finally, an outlook of this field provides guidance for the development of new and improved HEPs.

Copper particles-PTFE tube based triboelectric nanogenerator for wave energy harvesting

Developing sustainable energy is essential to achieve carbon neutrality. The emergence of triboelectric nanogenerators (TENGs) makes it possible to efficiently harvest the abundant wave energy in nature for their excellent operational stability and electrical performance at low frequencies. Here, a simplified copper particles-PTFE tube structured TENG (CP-TENG) was fabricated by encasing copper particles into a polytetrafluoroethylene tube and the small copper particles move with nearly fluid-like characteristics, expanding the contact area to ensure high charge density. A single CP-TENG includes two parallel-connected TENG units and can reach a maximum current density of 41.4 mA m−3 at a frequency of 1 Hz. Meanwhile, several CP-TENG units can be flexibly assembled into various arrays to accomplish output increase. A sealed CP-TENG power box demonstrates an impressive capability to collect wave energy, lighting up at most 210 LEDs. The CP-TENG-based energy network may present a new technical approach for blue energy harvesting.

Upgrade the high-load anaerobic digestion and relieve acid stress through the strategy of side-stream micro-aeration: biochemical performances, microbial response and intrinsic mechanisms

In high-load anaerobic digestion such as in kitchen waste, side-stream micro-aeration (SMA) shows excellent operational performance to direct micro-aeration (DMA). It immediately restores the acidification to stability. Methanogenic performance remained stable when organic load ratios (OLR) was further increased to 5.5 g VS/L. Enhanced enzyme activity, microbial aggregation, and proliferation of bacteria and archaea were observed in SMA. The results indicates that SMA enriched Methanosaeta (relative abundance exceeded 93%) and induced the change of the main methanogenic pathway to acetoclastic methanogenesis. Mechanisms was further explored by using metagenomic analysis, and the results show SMA avoids mass formation of ROS (reactive oxygen species) by cycling the aerated slurry, and retains benefits of trace O2 on material and energic metabolism, which poses great application potentials and deserves further investigation.

Experimental study on an OWC radial-flow impulse turbine in steady and reciprocating airflows

Self-rectifying air turbines, acting as a power take-off facility, can convert the incident pneumatic power to the shaft torque in the oscillating water column devices. The radial-flow impulse turbine (RFIT) is becoming popular because of its excellent operating performance. A generic RFIT model was designed and tested in constant and reciprocating airflows. The incident and torque coefficients are reported with the scatter diagrams of the turbine efficiencies. The steady-state efficiency in the constant airflow and the average efficiency in the reciprocating airflows peak at 0.48 and 0.49, respectively. The RFIT model has a significant difference in operation performance under the centrifugal and centripetal modes, and the varying frequency of the sinusoidal reciprocating airflows has a more obvious influence on the centripetal mode. In the comparison between two types of airflows with the same pneumatic power, the RFIT model is found to obtain a better performance in the reciprocating airflows.

Design of nanocatalyst for electrode structure: Electrophoretic deposition of iron phosphide nanoparticles to produce a highly active hydrogen evolution reaction catalyst

• FeP NP electrocatalytic electrode was fabricated via electrophoretic deposition. • Morphology and porosity of catalyst layer were tuned by altering deposition kinetics. • Optimized porosity/catalyst loading lead to the excellent HER activity. • The HER electrode was successfully applied as cathode GDE of high performance PEMWE. The inherent properties of nanoparticles (NPs) can be engineered into macroscopic structures by capturing the collective characteristics of the nanomaterials via a fabrication process to realize macroscopic functionality. Herein, we report a powerful manufacturing technique for fabricating an electrode composed of highly porous iron phosphide (FeP) NP catalyst layers conformally deposited on macroporous Carbon paper (CP) that shows excellent hydrogen evolution reaction activity. The surface morphology and porosity of the FeP NP catalyst layers on the FeP/CP electrode were tuned by altering the deposition kinetics of the colloidal FeP NPs by controlling the solvent system in the electrophoretic deposition process. The FeP/CP electrode achieved a low overpotential of 38 mV at 10 mA cm −2 in 0.5 M H 2 SO 4 due to the highly exposed catalytic surface with a high catalyst loading amount and fast charge transfer. When the FeP/CP electrode was applied as a cathode gas diffusion electrode in a proton exchange membrane water electrolyzer, the single-cell exhibited excellent operating performance (1.48 A cm −2 @ 2.0 V cell , 90 °C). Our results illustrate a facile route for fabricating nanostructured macroscale devices by maximizing the collective properties of the nanoscale materials.

A novel flywheel energy storage system: Based on the barrel type with dual hubs combined flywheel driven by switched flux permanent magnet motor

With the challenges of global carbon emissions and climate warming, energy recovery and reuse are becoming very important. Flywheel energy storage system (FESS), as a kind of energy storage systems (ESSs), can effectively convert electrical energy and mechanical energy to accomplish energy recovery and reuse. Additionally, the FESS has the characteristics of pollution-free, high energy, high efficiency, and durability. Thus, a novel FESS is proposed for the configuration, metal material and structure, and driving motor (M/G) to contribute to the development of FESS. First, the novel FESS is made of the metal materials rather than the carbon fiber, reducing manufacturing difficulty and cost. Second, the structure of dual hubs combined flywheel is designed to reduce the mass and obtain a larger moment of inertia, achieving higher energy storage. Third, a 12/10 switched flux permanent magnet motor (SFPM) with an outer rotor structure is designed to replace the conventional permanent magnet synchronous motor (PMSM) and is used as the M/G to achieve excellent operation performance. Finally, the barrel type of the configuration makes the novel FESS more compact and facilitates the realization of a vacuum chamber to remove the windage. Undoubtedly, the novel FESS is designed through the theoretical calculation of energy storage, structure strength and modal analysis, and M/G performance simulation. Accordingly, the novel FESS has a maximum speed of 13,500 rpm, storage energy of 20 kWh (discharge depth 99%), and the longest power consumption time of 2 h. Equally, a prototype is manufactured and tested. Consequently, the results testify the mechanical properties are excellent, the charging and discharging action is stable and rapid.

Clinical performance in ERN eUROGEN for penile, testicular, adrenal and soft tissue cancers

BackgroundEuropean Reference Network (ERN) eUROGEN is a cross-border collaboration set up by the European Commission in 2017 aimed at tackling rare urogenital conditions, including cancers. ObjectiveThis report aims to assess ERN eUROGEN's operational activity with a focus on rare urogenital cancers. Design, Setting and ParticipantsData for descriptive analyses were collected retrospectively between 2013 and 2017, and prospectively between 2018 and 2020. Outcome measurements and statistical analysisOperational indicators were set by the European Commission from 2018. Additionally, in 2019/20 centres self-assessed clinical service provision and provided clinical metrics for rare cancer specialist centres as established by experts. Results and LimitationsResults revealed that the cumulative rare urogenital cancer population increased 519.8% from 1,631 in 2013 to 10,109 in 2020. This may provide opportunities for research and creation of a large cancer registry. In total, ten centres met the clinical requirements for rare cancer specialist centres providing evidence of high-volume. Differences in data collection methods between centres limit further analyses. Other rare cancer data identified 39 panel discussions, three webinars, and eight publications. ConclusionsWhilst limitations to data analysis remain, ERN eUROGEN has demonstrated excellent operational performance with promising opportunities for rare cancer research.

Development of 3D+G printing for the design of customizable flow reactors

An in-depth study of chemical processes at plastic-metal interfaces led to the development of a novel approach to the creation of lab-on-a-chip microflow reactors. The developed method combines 3D printing of the reactor core by fused deposition modeling using conventional plastic material (ABS), followed by chemical (electroless copper) and galvanic plating (nickel) of the resulting piece (in overall, 3D+G printing process). Detailed analysis of the pieces along all 3D+G stages by electron microscopy revealed step-by-step processes on the plastic-metal interface, which finally allowed innovative reactor design. Despite being made from low-cost materials in a simple procedure, flow reactors are characterized by chemical resistance, versatile geometry, modular design and excellent operating performance. Complete reactor assembly was formulated and successfully tested in a variety of chemical processes targeted on biologically active molecules, including homogeneous, heterogeneous and photochemical reactions. Reactor modules can be combined into cascades to perform sequential reactions. Metallized reactors can be used multiple times in a variety of chemical processes.

Strategies for co-workership retention

ABSTRACT Co-workership is a Scandinavian working life concept that is based on post-bureaucratic organizing, the cornerstones of which are decentralization and a vision of responsible individual autonomy and participation. Research has shown positive results from implementing/developing co-workership in organizations; however, in terms of the post-bureaucratic character of the concept, it might be more challenging to retain positive results than to succeed with short-term development and implementation. This study aimed to describe and analyse the retention of co-workership. A qualitative case study based on interviews and observations was conducted at an elderly care unit that had attracted a lot of attention for its organizational development, largely due to co-workership. The present study focused on retention of the active co-workership that the former development had resulted in. Four main challenges were identified as central to co-workership retention. The paper contributes to the scientific community concerning retention of organizational development efforts, particularly by emphasizing the concept of co-workership retention, which is crucial for producing excellent operational performance over extended periods of time.

An Improved Transient Traveling-Wave Based Direction Criterion for Multi-Terminal HVDC Grid

Fast and reliable direction criterion is important for the protection of multi-terminal HVDC grid, not only for direction pilot protection, but also for excluding backward fault in single-ended protection. The direction criteria based on dc current variation (Δ i ) or dc current change rate (d i /d t ) have been used in the dc transmission system. However, the acting reliability is influenced by the high-transition resistance, line distributed capacitance, and so on. Although the direction criteria based on the boundary effect of the dc reactor have excellent operation performance in dc grid, they are only feasibility when the dc reactors are installed on both ends of each dc line. In this paper, the traveling-wave (TW) based direction criterion, which is not based on the boundary components, is proposed for use in multi-terminal HVDC grid, and its applicability is analyzed. To improve the acting sensitivity and reliability of the TW based direction criterion, an improved transient TW based direction criterion is proposed. Finally, simulations based on the Real Time Digital Simulator (RTDS) are carried out to verify the feasibility and superiority of the proposed improved direction criterion.

Assessing the type and quality of high voltage composite outdoor insulators by remote laser-induced breakdown spectroscopy analysis: A feasibility study

The use of composite polymeric insulators in overhead high voltage (HV) power transmission lines and in substations has been rapidly growing, as a result of their excellent operational performance, even under environmental pollution conditions. However, it has been observed that the insulation capacity of the composites deteriorates gradually for in-service insulators as a result of ageing, caused by several processes arising because of environmental, electrical and mechanical stresses. For these reasons, development of non-destructive diagnostic techniques for real-time, on-site inspection of the insulators' condition is required for ensuring high reliability of power transmission networks. To this end, laser-induced breakdown spectroscopy (LIBS) is found to offer an effective and reliable method for assessing the state of polymeric insulators, primarily silicone rubber (SIR) ones, that have been in service for up to 20 years on the HV power network of Crete, Greece. Determining the type of composite and furthermore the chemical integrity of the insulator is based on simple spectral indicators, which reflect the extent of chemical modifications induced on the insulator surface, as found in both standard and remote LIBS measurements performed in the laboratory. As a result, a stepwise diagnostic procedure was proposed and tested in an outdoors campaign, demonstrating that LIBS can become a field deployable technique for the efficient and reliable assessment of the performance of HV outdoor insulators in service.

Numerical investigation on H2/Air non-premixed rotating detonation engine under different equivalence ratios

In this paper, three-dimensional numerical simulations are performed to investigate the formation and propagation characteristics of rotating detonation wave in a non-premixed engine. By changing the mass flow rate of H2 and fixing air mass flow rate, the effects of equivalence ratio involving fuel lean and rich operating conditions are mainly discussed. Numerical results show that equivalence ratio plays a very critical role in the formation process and propagation mode, which further affects the propulsion performance of rotating detonation engine significantly. For current numerical geometry and operating conditions, the lean limit of equivalence ratio for formatting a stable RDW is about 0.4, dual-wave mode (at equivalence ratio of 0.6, 0.8, 1.0 and 1.4) and single-wave mode (at equivalence ratio of 1.2) are obtained, respectively. When equivalence ratio is 1.0, rotating detonation engine can exhibit excellent operating performance with the shortest formation time, best propagation stability, middling class thrust and specific impulse. Besides, the pressure contour analysis indicates that the effects of equivalence ratio and mass flow rate of H2 on the collision strength and times during the re-initiation process are the main mechanisms for determining the formation possibility and propagation mode of rotating detonation wave. Besides, the intensity of accumulated pressure wave and distributions of equivalence ratio are two important factors for the generation of new detonation wave front. Furthermore, it is also detected from the comparisons of the propulsion performance that the effects of equivalence ratio on thrust and specific impulse under fuel lean conditions are more significant than those under fuel-rich conditions.

Development of a Prestressing CFRP Laminate Anchorage System and Bridge Strengthening Application

For prestressed carbon fiber reinforced polymer (CFRP) tendon anchorage systems to become well established and used on a large scale, practical requirements for structure strengthening may be met by performing a relatively easy anchorage technique using prestressing CFRP laminates. From testing performed on a clip-type CFRP laminate anchorage system developed in our research group, it was revealed that this system could achieve the anchorage efficiency and the relaxation met the requirement of specification. Furthermore, the relevant indices of the anchorage system met the prestressed system standards. A test on the load-carrying capacity of a full-scale model beam demonstrated that the load-carrying capacity of the beam increased by more than 60% after it was strengthened with the anchorage system. The prestressing CFRP laminates and the bridge structure deformed and bore stress as a composite and exhibited excellent operating performance when working together.

Experimental investigation of particle deposition in filter media during filtration cycles with regeneration by pulse jet cleaning

The objective of this study was to experimentally evaluate the influence of particle deposition on gas filtration with pulse jet cleaning. Filtration experiments were performed using dolomitic limestone particles, with polyester and polypropylene filter media. A total of 100 filtration tests were performed with a surface velocity of 4 cm/s. The stipulated maximum pressure drop was 1000 Pa, the pulse time was 200 ms, and the pulse pressure was 200 kPa. After 100 filtration cycles, the polyester filter presented higher cleaning efficiency, higher collection efficiency, lower particle retention, higher permeability, lower residual pressure drop, and lower mass retained after reverse air pulse cleaning, compared to the polypropylene filter. The results confirmed that the polyester filter presented excellent operational performance when pulse jet cleaning was used. Furthermore, surface filtration was more pronounced for the polyester filter, due to lower deposition of particles inside the filter.

3-D Printed High-Gain Wideband Waveguide Fed Horn Antenna Arrays for Millimeter-Wave Applications

3-D printed air-filled waveguide fed horn antenna arrays are investigated in the Ka -band. Pyramidal E-plane horn antennas with a small size are introduced as the radiating element to improve the bandwidth and radiation characteristics of the array. Commercial direct metal laser sintering technology is applied to print the antenna structure in a whole piece. Excellent operating performance including wide impedance bandwidths of 25.8% and 23.8% for $\vert \text{S}_{11}\vert dB, gains up to 27.5 and 33.8 dBi with a variation of less than 1.5 dB over the operating band and radiation efficiencies of around 90% and 80% is obtained experimentally by two fabricated prototypes consisting of 64 and 256 radiating elements, respectively. Stable radiation patterns with low cross polarization are confirmed as well. The array designs and results obtained in this paper verify the feasibility of utilizing advanced a 3-D printing technique to realize millimeter-wave large-size antenna arrays with complicated multilayered configurations, which is of value for various wideband millimeter-wave wireless applications.