High Operation Research Articles

Ultra-permeable silk-based polymeric membranes for vacuum-driven nanofiltration.

Nanofiltration (NF) membranes are commonly supplied in spiral-wound modules, resulting in numerous drawbacks for practical applications (e.g., high operating pressure/pressure drop/costs). Vacuum-driven NF could be a promising and low-cost alternative by utilizing simple components and operating under an ultra-low vacuum pressure (<1 bar). Nevertheless, existing commercial membranes are incapable of achieving practically relevant water flux in such a system. Herein, we fabricated a silk-based membrane with a crumpled and defect-free rejection layer, showing water permeance of 96.2 ± 10 L m-2 h-1 bar-1 and a Na2SO4 rejection of 96.0 ± 0.6% under cross-flow filtration mode. In a vacuum-driven system, the membrane demonstrates a water flux of 56.8 ± 7.1 L m-2 h-1 at a suction pressure of 0.9 bar and high removal rate against various contaminants. Through analysis, silk-based ultra-permeable membranes may offer close to 80% reduction in specific energy consumption and greenhouse gas emissions compared to a commercial benchmark, holding great promise for advancing a more energy-efficient and greener water treatment process and paving the avenue for practical application in real industrial settings.

Development of a high current density, high temperature superconducting cable for pulsed magnets

Abstract A low AC loss Rare Earth Barium Copper Oxide (REBCO) cable, based on the VIPER cable technology has been developed by Commonwealth Fusion Systems for use in high field, REBCO based tokamaks. The new cable is composed of partitioned and transposed copper ‘petals’ shaped to fit together in a circular pattern with each petal containing a REBCO tape stack and insulated from each other to reduce AC losses. A stainless steel jacket adds mechanical robustness—also serving as a vessel for solder impregnation—while a tube runs through the middle for cooling purposes. Additionally, fiber optic sensors are placed under the tape stacks for quench detection. To qualify this design, a series of experiments were conducted as part of the SPARC tokamak Central Solenoid Model Coil program—to retire the risks associated with full scale, fast ramping, high flux HTS Central Solenoid (CS) and Poloidal Field (PF) coils for tokamak fusion power plants and net energy demonstrators. These risk study and risk reduction experiments include (1) AC loss measurement and model validation in the range of ~5 T/s, (2) an IxB electromagnetic loading of over 850 kN/m at the cable level and up to 300 kN/m at the stack level, (3) a transverse compression resilience of over 350 MPa, (4) manufacturability at tokamak relevant speeds and scales, (5) cable to cable joint performance, (6) fiber optic based quench detection speed, accuracy, and feasibility, and (7) overall winding pack integration and magnet assembly. The result is a cable technology, now referred to as PIT VIPER, with AC losses that measure fifteen times lower (at ~5 T/s) than its predecessor technology; a 2% or lower degradation of critical current (Ic) at high IxB electromagnetic loads; no detectable Ic degradation up to 570 MPa of transverse compression on the cable unit cell; end to end magnet manufacturing, consistently producing Ic values within 7% of the model prediction; cable to cable joint resistances at 20 K on the order of ~15 nΩ; and fast, functional quench detection capabilities that do not involve voltage taps. This cable technology will be tested comprehensively in a Central Solenoid Model Coil to prove its readiness for compact, high field tokamak operation.

Anthill clay activated Ocimum gratissimum extract for effective adsorption of methylene blue and chromium (VI) ion from wastewater: Insights into the adsorption isotherms, kinetics, thermodynamics, and mechanisms

The removal of methylene blue (MB) dye and hexavalent chromium (Cr(Vl)) ions from water bodies have necessitated the search for a promising adsorbent material with high adsorptive performance, facile operation, and economical. Here, a novel adsorbent was prepared by activating anthill clay (AC) with Ocimum gratissimum leaf extract (OG@AC) by ultrasonic strategy method to eliminate MB and Cr(Vl) from the aqueous environment; however, the activation strategy serves as an important factor that influenced the adsorptive performance towards MB and Cr(Vl). Furthermore, a high BET surface area of 120.48 m2/g was measured for OG@AC which is attributed majorly to the green activation strategy. The SEM micrograph of OG@AC was seen to have displayed a leaf-like plate formed by quartz and kaolin. In the batch experimental study, the MB and Cr(Vl) adsorption capacities towards OG@AC were determined to be 227.52 and 143.45 mg/g, respectively. Also, the adsorption kinetics and isotherms models results revealed that the adsorption process of OG@AC towards MB and Cr(Vl) was best described by pseudo-first-order and Freundlich models, suggesting that the adsorption process involves a multilayer physisorption. Moreso, thermodynamic results revealed the adsorption process is feasible, spontaneous, and endothermic in nature. The OG@AC exhibited an outstanding regeneration ability and stability towards MB and Cr(Vl) by maintaining a removal efficiency of 79.11 % and 81.20 % even at the tenth successive adsorption-desorption cycles. Overall, this research sheds more insight on how anthill clay is activated using a feasible design and green chemical (Ocimum gratissimum leaf extract) to enhance its adsorptive performance towards MB and Cr(Vl), which can broaden its wide application in the real world.

Exploring the Mechanisms of LiNiO2 Cathode Degradation by the Electrolyte Interfacial Deprotonation Reaction.

Nickel-rich layered oxides stand as ideal cathode candidates for high specific capacity and energy density next-generation lithium-ion batteries. However, increasing the Ni content significantly exacerbates structural degradation under high operating voltage, which greatly restricts large-scale commercialization. While strategies are being developed to improve cathode material stability, little is known about the effects of electrolyte-electrode interaction on the structural changes of cathode materials. Here, using LiNiO2 in contact with electrolytes with different proton-generating levels as model systems, we present a holistic picture of proton-induced structural degradation of LiNiO2. Through ab initio molecular dynamics calculations based on density functional theory, we investigated the mechanisms of electrolyte deprotonation, protonation-induced Ni dissolution, and cathode degradation and the impacts of dissolved Ni on the Li metal anode surfaces. We show that the proton-transfer reaction from electrolytes to cathode surfaces leads to dissolution of Ni cations in the form of NiOOHx, which stimulates cation mixing and oxygen loss in the lattice accelerating its layered-spinel-rock-salt phase transition. Migration of dissolved Ni2+ ions to the anode side causes their reduction into the metallic state and surface deposition. This work reveals that interactions between the electrolyte and cathode that result in protonation can be a dominant factor for the structural stability of Ni-rich cathodes. Considering this factor in electrolyte design should be of benefit for the development of future batteries.

Unveiling the high-pressure behavior of thymol+carvone NADES: A combined experimental-computational approach

this study considers the high-pressure behavior of thymol + carvone Natural Deep Eutectic Solvent using a combined experimental and computational approach. Experimentally, PVT (pressure – volume/density - temperature) measurements were conducted to characterize the fluid volumetric behavior as well as compressibility and internal pressure, which are directly related with hydrogen bonding and nanoscopic structuring. Likewise, these measurements provide crucial insights into the thermodynamic properties of the considered fluid under high pressure, which is pivotal for scaling up and process design for high pressure operations. Computationally, the PC-SAFT equation of state was employed to predict phase equilibria and PVT behavior, Machine Learning for density predictions, while Density Functional Theory and Classical Molecular Dynamics simulations were considered for the structural and dynamic characterization. These simulations provides insights into the electronic structure, intermolecular interactions (hydrogen bonding), liquid structuring and they unveil the pressure's impact on microscopic interactions, structural organization, and transport properties. This comprehensive investigation aims to shed light on the behavior under high pressure, facilitating their optimization for applications in chemical processing, energy storage, and materials science.

Multiscale textured solar absorber coatings for next-generation concentrating solar power

A high-temperature stable solar absorber is crucial for next-generation (Gen3) concentrating solar power (CSP) plants, to enable high temperature operation, maximize power generation efficiency, and thereby reduce the levelized cost of energy. This study presents novel, fractal-textured solar absorber coatings whose multiscale feature scales effectively match the visible region of the solar spectrum, leading to superb absorptive properties. Single and bimetallic oxide coatings of copper, cobalt and manganese were prepared on Inconel 625 substrates using electrodeposition. The effect of electrodeposition parameters and annealing temperature are systematically studied to optimize the morphology and properties of the oxide coatings. Multiscale textured bimetallic coatings of copper manganese oxide and copper cobalt oxide demonstrate a superior absorptance of 0.985, a remarkably low emittance <0.45 and an exceptional optical efficiency of ∼96 % under Gen3 CSP operating conditions, surpassing previously reported values in the literature by about 5 %. Durability tests confirmed the coatings’ steadfast endurance of mechanical and environmental stress, making them suitable for long-term application in harsh CSP environments.

CHALLENGES IN THE OPERATION AND MAINTENANCE OF ASSETS AND FACILITIES IN ELDERLY CARE CENTRES IN MALAYSIA

Abreast with the rapid growth of older people every year, the number of elderly care centres has increased tremendously to cater to the demands of older people to spend their time after retirement in Malaysia. Effective operation and maintenance activities in an elderly care centre can optimise the service life of assets that indirectly lead to well-maintained facilities and provide the occupants with a safe, comfortable, and efficient living environment. Throughout the asset life cycle, operation and maintenance are the most extended phases, with various core activities that determine the financial health of an organisation. Nevertheless, this area remains relatively underexplored in the existing literature, particularly concerning the challenges posed by Malaysia's ageing population by 2030. Accordingly, this study seeks to investigate the issues of operation and maintenance of assets and facilities in elderly care centres. The method used to collect the data is through site observations and interviews in three elderly care centres, one in Perak and two in Selangor. These findings reveal three significant challenges the operators face: safety inside the accommodation, high operation and maintenance costs, and lack of a structured approach to managing the assets and facilities. Finally, the paper ends with implications of the findings that provide directions for future research.

Why do microfinance institutions charge higher interest rates than banks? The role of operating costs

Microfinance interest is at the center of debate on lending to the poor because microfinance institutions (MFIs) charge significantly higher interest than conventional banks to borrowers with no creditworthiness. We contribute to the debate by documenting that MFIs spend more than banks for every dollar of lending. It occurs because the high marginal operating cost of lending is inherent to the microfinance business model - MFIs spend more than banks to mitigate high credit risks in lending to the poor. This study shed light on MFIs’ systemic limitations in poverty alleviation as envisaged in the sustainable development goals (SDGs).

Study on analogy principle of overall cooling effectiveness for high temperature cooling structure considering thermal radiation heat transfer

With the continuous advancement of aero-engine technology, the performance of hot-end components such as combustion chambers and turbines has significantly improved, leading to a rapid increase in the working environment temperature surrounding these components and an increasingly prominent thermal radiation effect. Due to the non-gray body characteristics and spectral selectivity of thermal radiation, it is difficult to replicate the actual working environment of turbine components under laboratory conditions, causing many scholars to ignore or simplify the thermal radiation effect. Focusing on the overall cooling effectiveness of hot-end components such as turbine guide vanes, this paper proposes a method for modeling the overall cooling effectiveness of cooling structures under radiation-convection coupling conditions by matching parameters such as Burger number (Bu) and Boltzmann number (Bo). Based on the impingement effusion plate model and turbine guide vane model, this study investigates the matching of the overall cooling effectiveness under full coupled heat transfer for cooling structures in high and low operating conditions in laboratory settings. Additionally, the effects of momentum ratio, temperature ratio, and gas composition on the overall cooling effectiveness are examined. The results indicate that this matching method can provide important references for the design of hot-end components such as turbine blades.

TCT-408 Outcomes of High vs Low Volume Retrograde Chronic Total Occlusion Percutaneous Coronary Intervention Operators: Insights From the PROGRESS-CTO Registry

TCT-408 Outcomes of High vs Low Volume Retrograde Chronic Total Occlusion Percutaneous Coronary Intervention Operators: Insights From the PROGRESS-CTO Registry

Model test and analyses for a mixed-flow pumping system in the S-to-N Water Diversion Project of China

Abstract Baoying Pumping Station as the first station built in the East Route of the S-to-N Water Diversion Project in China, due to the importance of water source project and its 5000 hours yearly operating time, a serial of model tests and other measures were taken to secure its safety and high efficiency operation. Through the comparative model tests in the preliminary design stage, it was made clear that mixed-flow pump was the right direction of pump selection. The acceptance model test indicated that all performance requirements were satisfied and the head-weighted efficiency of the pumping system reached 80.5%, which was about 7 percentages higher than that obtained in the preliminary research and a good foundation for its efficient and economical operation was laid. The optimization design of inlet and outlet flow passages was not significant for improve the efficiency of pumping system. The verification test results were very close to the acceptance test results, and have been confirmed each other. The international bidding and mechanism of joint venture in purchasing main equipment for Baoying pumping station proved to be a success in introducing advanced foreign technology, and its construction experience can provide a useful reference for similar pumping stations.

A micro-channel cooling system with two-phase looped thermosyphon for a supercritical CO2 Brayton cycle

The supercritical Carbon Dioxide (sCO2) closed Brayton cycle is a promising power generation technology, while the efficient cooling of CO2 and precise control of Compressor Inlet Temperature (CIT) is crucial for the high cycle efficiency and stable compressor operation due to the acute variation of thermophysical properties in the near-critical region. In conventional indirect cooling scheme, an intermediate single-phase water circuit is used to transfer heat from CO2 to water at the precooler, and then from water to the environment at the cooling tower, having the disadvantage of large pumping work consumption and high thermal resistance. In this work, a self-driven two-phase looped thermosyphon that significantly enhances the heat transfer by internal evaporation and condensation, is proposed to replace the water circuit. An experimental ultra-compact cooling system, consisting of a looped thermosyphon combined with micro-channel evaporator and condenser, filled with R134a coolant, is designed, fabricated, and tested. Visualized observation of the two-phase flow pattern and simultaneous measurement of the temperature, pressure and mass flow rates are conducted. A nodal analysis method is adopted, and a MATLAB code is developed for analyzing the internal fluid flow and the coupled sCO2-R134a-Air heat transfer, which is validated by experiment data. The results show that, the CO2 temperature could be accurately maintained at a specified near-critical point with a fluctuation of less than 1 K, and the average heat-releasing temperature can be reduced, while considerable pumping work, usually accounting for 2–5 % of the rated power output can be saved, thus contributing to increased cycle efficiency and system compactness.

Divertor tungsten source monitoring by A visible spectroscopy diagnostic on EAST

EAST has been upgraded with top and bottom tungsten divertors to facilitate the high power long pulse operation. A visible spectroscopy diagnostic has been developed progressively to monitor W source as well as line emissions from other particles (e.g., D, He, Li, B, C, N, O, Ne, Ar, Mo, D2, WD) in the divertors. Two sets of lens installed in mid-plane port view tangentially the top and bottom divertors, respectively. Two types of optical fibers transfer the plasma light collected by the lens to three different detecting modules. High spectral resolution (λ/Δλ ∼ 14000) can be achieved by the detecting module consisting of spectrometer and Electron-Multiplying Charge Coupled Device (EMCCD), high temporal resolution (50 μs) is obtained by filtered photoelectric multiplier (PMT), and high spatial resolution (1 mm) is acquired by Complementary Metal-Oxide-Semiconductor Transistor (CMOS) camera with collimation optics. The multichannel optical fiber array with 500 μm core diameter is used to connect the lens and the first two detecting modules. The imaging fiber bundle with 30 μm core diameter transmits the two-dimensional divertor plasma light to the third detecting module, i.e. collimation optics and CMOS camera. The diagnostic is operated automatically in normal EAST discharges to support experimental operation and divertor physics study. The paper presents a technical description of the diagnostic and typical measurements during EAST discharges.

Optimal Electrocatalyst Design Strategies for Acidic Oxygen Evolution.

Hydrogen, a clean resource with high energy density, is one of the most promising alternatives to fossil. Proton exchange membrane water electrolyzers are beneficial for hydrogen production because of their high current density, facile operation, and high gas purity. However, the large-scale application of electrochemical water splitting to acidic electrolytes is severely limited by the sluggish kinetics of the anodic reaction and the inadequate development of corrosion- and highly oxidation-resistant anode catalysts. Therefore, anode catalysts with excellent performance and long-term durability must be developed for anodic oxygen evolution reactions (OER) in acidic media. This review comprehensively outlines three commonly employed strategies, namely, defect, phase, and structure engineering, to address the challenges within the acidic OER, while also identifying their existing limitations. Accordingly, the correlation between material design strategies and catalytic performance is discussed in terms of their contribution to high activity and long-term stability. In addition, various nanostructures that can effectively enhance the catalyst performance at the mesoscale are summarized from the perspective of engineering technology, thus providing suitable strategies for catalyst design that satisfy industrial requirements. Finally, the challenges and future outlook in the area of acidic OER are presented.

Hydraulic valve design methodology for hydro turbine control system

The control of the turbine and its equipment in a hydroelectric power plant requires the HPU (hydraulic power unit) to deliver large volumes of working fluid in a short time at specific optimum control parameters. The use of typical proportional flow control valves created by manufacturers of hydraulic components in low-pressure control systems is disadvantageous due to high pressure losses in the control chambers. This paper presents the methodology and test results while designing a hydraulic proportional valve for low pressure and high flow rate operation. CFD (computational fluid dynamics) theory was analyzed and characteristic values were determined. The validation of CFD tests through those on the test bench was carried out, correction factor was determined. A new proprietary solution was developed and a series of simulation studies were carried out to determine the flow characteristics depending on the degree of the opening of the proportional flow control valve.

An open-loop and closed loop based passive thermal management techniques applicable to photovoltaic systems

Photovoltaic (PV) technology adoption in recent years has experienced significant growth due to its inherent advantages over alternative technologies. Nevertheless, there is a concern regarding performance deterioration due to high operating temperatures. Various thermal management methods have been studied to address this issue, each having its own advantages and disadvantages. Hence, a comprehensive review aimed at developing effective passive cooling techniques was undertaken and two techniques were finalized for outdoor testing viz. natural circulation loop based cooling (PV-NCL) and evaporative cooling (PV-EVP). Though the former version could drop module temperature by 7.4 °C–13.9 °C (Power output increment in the range of 3.5 %–6.7 %), this improvement was not sustained throughout the day due to factors such as flow resistance within the loop and a lack of convective cooling in the vicinity of the cooler. Subsequent experiments confirmed that loop resistance played a dominant role in this phenomenon. Additionally, concerns about water circulation in PV-NCL were resolved through a comparison with water duct-integrated PV. On the other hand, the innovative gravity-assisted water flow for evaporation method (PV-EVP) yielded more promising results, with a power output enhancement ranging from 3.7 % to 11.5 %. However, considering the in-field operational issues, PV-NCL with a modified design will likely be the best technique.

The influence of the elemental valence on the thermophysical properties of high entropy (La0.2Sm0.2Eu0.2Yb0.2Y0.2)2(Ce0.5Zr0.5)2O7 coatings for thermal barrier application

Commercial yttria-stabilized zirconia (YSZ) thermal barrier coatings (TBCs) are no longer sufficient for the stringent demands in the high operating temperature and excellent thermophysical properties of the high-performance gas turbines and aviation engines. High entropy ceramics, distinguished by their superior thermophysical properties, have risen as a potential substitute for TBCs. However, the realm of atmospheric plasma spraying (APS) in the creation of these advanced TBCs remains relatively unexplored. In this work, three distinct high-entropy (La0.2Sm0.2Eu0.2Yb0.2Y0.2)2(Ce0.5Zr0.5)2O7 coatings were developed through the meticulous alteration of spraying power. The effects of spraying power on the microstructure, valence states of constituent elements and thermophysical properties of the coatings were deeply investigated. The results indicated that all the as-sprayed coatings exhibit a defect fluorite structure. Spraying power does have a significant impact on the thermophysical properties of the coatings. With the decrease in spraying power, the thermal conductivity of the coatings shows a progressive reduction, whereas the coefficient of thermal expansion (CTE) exhibits a gradual increase. This trend is closely related to valence states of constituent elements in the coatings. The resulting coating exhibits a low thermal conductivity of 0.54 W⋅m-1⋅K-1, a high CTE of 11.22×10-6·K-1 and a superior phase stability at elevated temperatures.

Reducing dislocations for room-temperature continuous-wave InGaAs/AlGaAs multiple quantum well lasers monolithically grown on Si

As dislocation-sensitive light-emitting devices, quantum well lasers monolithically grown on Si substrates operate poorly compared to their counterparts on native ones. In this work, a GaAs/Si virtual substrate with a low threading dislocation density of 8.9×106/cm2 was achieved by using a combined dislocation-reducing method. Meanwhile, by using two In-containing strained layer separately inserted into upper and lower AlGaAs cladding layers, the active region was virtually free of gliding dislocations. With the reduced dislocations in the active region, the fabricated Si-based broad-stripe ridged lasers exhibited continuous-wave lasing at room temperature, and a low threshold current density of 1015 A/cm2, high operation temperature of 90°C as well as a device lifetime of over 87.25 h were achieved. These results demonstrate an experimentally feasible way to optimize a Si-based InGaAs/AlGaAs quantum well laser and further promote the research on monolithic integration.

Multiswitch-Leg DAB Converter for Low $dv/dt$ at High Operating Frequency for MVDC Systems

Multiswitch-Leg DAB Converter for Low $dv/dt$ at High Operating Frequency for MVDC Systems

Electrocatalytic dechlorination of chloroethylenes using nitrogen-doped graphene electrodes

Electro-dehalogenation for the clean-up of carcinogenic chloroethylenes (CEs) in groundwater is hindered by the high operating costs of metal electrodes and low efficiency due to competing water reduction and hydrogen formation. This study prepared metal-free electrodes with high Faradaic efficiency (FE) up to 50 % in aqueous solution by coating nitrogen-doped graphene nanoplatelets (N-GPs) on carbon paper. Dechlorination rates at these N-GPs electrodes were enhanced by ∼15 times compared with the plain graphene-based electrode, with first-order rate constants of 0.28, 0.33, 0.41, and 0.048 h−1 for tetrachloroethylene (PCE, 22 μM), trichloroethylene (TCE, 22 μM), cis-dichloroethylene (cis-DCE, 22 μM), and vinyl chloride (VC, 11 μM) dechlorination to acetylene and ethene (VC), respectively, at −1.0 V vs standard hydrogen electrode (SHE), and initial neutral pH. Surprisingly, extremely low N or no-N containing GP was detected from highly reactive N-GPs. Despite the N-doping process has been wildly used for improving electrocatalytic reactivity of catalysts by inducing N-functional groups, this study suggests that, the polygonal intrinsic defects formed after N burn-off may act as dechlorination active sites. The N-GP electrodes showed appreciable stable performance over 24 h (five cycles). Simultaneous electrolysis of a mixture of CEs in groundwater without the addition of supporting electrolytes achieved >90 % reduction of PCE, TCE, and cis-DCE and ∼60 % reduction of VC within 24 h at −1.23 V vs SHE, demonstrating its superior performance and great potential of these electrodes in practical applications.