Low Operation Research Articles

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.

Facile synthesis of green graphite-based (Ni/Cu/N) MOF composite for a methanol oxidation reaction

Recently, direct methanol fuel cells (DMFCs) have been regarded as the greatest energy-producing owing to their low operating temperature, high production rate of methanol, and low greenhouse gas emission. However, the energy conversion efficiency of the DMFCs is still unsatisfactory due to the slow kinetics of the fuel oxidation reaction. So, an economic electrocatalyst with high efficiency and good stability is still needed. Herein, low-cost nanocomposites of (Ni/Cu/N) MOF and palm pollen-derived G-graphite were prepared with different ratios namely, (1:1), (1:2), and (2:1) through a solvothermal reaction. The nanocomposites were characterized via X-ray diffraction (XRD), Scanning electron Microscopy (SEM), Fourier transform infrared (FTIR), Thermal gravimetric analysis (TGA), and, (Brunauer–Emmett–Teller) technique (BET). Electrodes have been tested as electro-catalysts for methanol-oxidation reaction (MOR) in a basic medium. As revealed from the cyclic voltammetry measurements, all electrodes exhibit a good response to MOR, being the nanocomposite with the ratio between (Ni/Cu/N) MOF and G-graphite (2:1) is the best with an oxidation peak current density of 55 mA/cm2 at a scan rate of 50 mV/s, with an onset potential of 0.35 V, and stability reaches 96 %. The electrochemical impedance spectroscopy (EIS) test showed that the ratio (2:1) has the lowest charge transfer resistance, RCT, of 5.21 Ω which confirms its higher electrochemical activity. This superior performance of the (Ni/Cu/N) MOF and G-graphite (2:1) over other reported MOF-based electrocatalysts is attributed to the synergistic effect of the (Ni/Cu/N) MOF electrocatalyst, wherein Ni and Cu provide redox electrocatalytic active sites for MOR while the G-graphite contributes towards the chemical stability and electrical conductivity of the electrode, respectively. The good activity and stability of the prepared electrodes suggest the potential use of these electrodes as electrocatalysts for MOR in direct methanol fuel cells (DMFCs).This study opens the venue for valorizing the natural wastes derived graphitic material as stable supporting material in Mof based composites electrodes for MOR.

History of Preoperative Use of Gabapentin Before Lower Extremity Bypass Predisposes Patients to a High Risk of Opioid Use and Dependence in a Dose-Dependent Manner

IntroductionThis study assesses the association of preoperative use of gabapentinoids (GBPs) with postoperative risk of opioid-related disorders in peripheral artery disease patients undergoing lower extremity bypass operation. MethodsThis is a retrospective propensity score-matched analysis of patients undergoing peripheral artery bypass in TriNetX, a multicenter national database. Two study groups were constituted based on the preoperative history of prescribed GBPs. Primary outcomes were opioid-related disorders and mortality. The outcomes were reported at two-time endpoints that is, at 1 and 5 y. ResultsThis study population included a total of 23,706 patients. After propensity score-matched analysis, each group contained 5130 patients. The primary outcomes showed a significant increase in postoperative opioid-related disorders at the 1 and 5-y time points between GBPs and no GBPs groups: 1-y outcome (2.0% versus 1.1%; adj. P = 0.007) and 5-y outcome (4.5% versus 3.5%; adj. P = 0.035). Logistic regression analysis revealed an increase in the 1-y (adjusted odds ratio= 1.664; 95% CI [1.217, 2.273], P = 0.001) and 5-y (OR = 1.353; 95% CI [1.107, 1.653], P = 0.003) odds of opioid-related disorders in patients on GBPs. A secondary analysis showed a significant dose-dependent increase in the associated risk of 5-y opioid-related disorders in patients with a history of prescribed gabapentin. ConclusionsIn patients undergoing lower extremity bypass with a history of gabapentin use, there is an associated increased long-term risk of opioid-related disorders in a dose-dependent fashion. Overall, this study highlights weighing risks and benefits of prescribing GBPs for pain control versus their long-term associated risk of opioid-related disorders among other adverse outcomes.

Resilience of DBI screened objects and their ladder symmetries

Scalar field theories with a shift symmetry come equipped with the K-mouflage (or kinetic screening) mechanism that suppresses the scalar interaction between massive objects below a certain distance, the screening radius. In this work, we study the linear response of the scalar field distribution around a screened (point-like) object subject to a long range external scalar field perturbation for the Dirac-Born-Infeld theory. We find that, for regular boundary conditions at the position of the particle, some multipoles have vanishing response for a lacunar series of the multipole order ℓ for any dimension. Some multipoles also exhibit a logarithmic running when the number of spatial dimensions is even. We construct a ladder operator structure, with its associated ladder symmetries, formed by two sets of ladders that are related to the properties of the linear response and the existence of conserved charges. Our results exhibit a remarkable resemblance with the Love numbers properties of black holes in General Relativity, although some intriguing differences subsist.

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.

Conformal Li2O2 Growth and Decomposition Within 3D Lithiophilic Nanocages of Metal–Organic Frameworks for High‐Performance Li─O2 Batteries

AbstractLi─O2 batteries (LOBs) have the largest theoretical capacity among current batteries, but the irreversible growth and decomposition of Li2O2 products in positive electrodes cause dramatic degradation of their capacities over charging–discharging cycles. Herein, a metal–organic framework is reported with bipyridinic N linkers attached to graphene (bpyN‐MOF/g) as a positive electrode material to overcome the challenge. The bpyN‐MOF/g promotes conformal Li2O2 growth during discharging, while allowing Li2O2 decomposition at a low overpotential (0.487 V vs Li+/Li at 200 mA gc−1) during charging process, outperforming the Pt/C‐based electrode (0.857 V). Moreover, 3D‐tomography and density functional theory calculations consistently support the Li2O2 growth and decomposition mechanism inside bpyN‐MOF/g. Furthermore, bpyN‐MOF/g//Li LOBs achieve an exceptional discharge capacity (17 275 mAh gc−1 at 100 mA gc−1) and steady cycling for 270 cycles at 1000 mAh gc−1 under 2000 mA gc−1. Additionally, high gravimetric capacity at low mass loadings (0.27–0.44 mg cm−2) and stable cycle operation at a high areal current density (0.5 mA cm−2) open new opportunities for various practical applications.

Sol-Gel Pt-VO2 Films as Selective Chemoresistive and Optical H2 Gas Sensors.

In this work, VO2 (M1/R) thin films were exploited as H2 gas sensors. A flat film morphology, obtained by furnace annealing, was compared with a laser-induced nanostructured one. The combination of the environmentally friendly sol-gel approach with the ultrafast laser crystallization allows for significant reductions in energy consumption and related emissions during the fabrication of VO2 sensors. By decorating the sensors' surface with Pt nanoparticles (NPs), the sensor response was enhanced exploiting the hydrogen spillover effect. The Pt/VO2 sensors, tested at operating temperatures between 20 and 200 °C and for concentration of H2 from few ppm to 50000 ppm, offered a dual chemoresistive and optical sensing mode. Low operating temperatures of 150 °C were achieved, along with a detection limit as low as 2 ppm and a perfect baseline recovery. Both sensors guaranteed specific selectivity toward H2, without response to NO2 or humidity, and long-term stability over 500 h. The H2 sensing mechanism, for both the monoclinic and rutile VO2 phases, was investigated through in operando X-ray Diffraction and in situ X-ray Photoelectron Spectroscopy tests. The interaction was found to be based on the reversible formation of HxVO2 bronze, along with the reversible variations in the oxidation state of V.

LARGE INFERIOR RECTUS RECESSION WITHOUT LOWER LID RETRACTION: TWO INCREDIBLE TECHNIQUES

Relevance. Lower lid retraction is a frequent undesirable result following inferior rectus recession operations. Especially in relatively larger amounts of recession, a special and close relationship between lower lid retractors and muscular fascia makes the complication more severe. Purpose of the study. To introduce two methods that allow wide inferior rectus recession without causing lower eyelid retraction and to evaluate the long-term results. Material and methods. There were 25 cases and 18 control group cases in first operation technique named ‘ninety percent of posterior fibers recession of inferior rectus’ which can be perform for any vertical deviation without muscle fibrosis; and 8 cases were in second operation technique which named ‘muscle elongation with both organic tissue and non-absorbable suture’. Results and conclusion. In both technique patients’ deviation corrected and all ocular movement was free. Both operation techniques, which introduces by us, does not affected lower lid retractor and operations has both effective results and no lid problem.

Digital transformation whitewashing and financing constraints

This study investigates the drivers and consequences of digital transformation whitewashing (DTW) among Chinese manufacturing firms from 2010 to 2021. We find that financing constraints have a robust and significant positive impact on DTW, an effect that is more pronounced for firms located in provinces with lower marketization or operating in industries with lower levels of monopoly. Regarding economic consequences, our results indicate that DTW fails to alleviate external financing constraints, instead causing firms to increasingly rely on internal financing.

Enable Rechargeable Carbon Fluoride Batteries with Unprecedented High Rate and Long Life by Oxygen Doping and Electrolyte Formulation.

Here, a rechargeable carbon fluoride battery is demonstrated with unprecedented high rate and long life by oxygen doping and electrolyte formulation. The introductions of Mn2+-O catalyst and porous structure during the oxidation process of CFx cathode can promote the splitting of Li-F during charging. By further modulating the electrolyte with triphenylantimony chloride (TSbCl) as anion acceptor and CsF as product modulator, the more readily dissociable CsLiF2 product instead of LiF is preferentially formed, and the TSbCl-salt protection interface is constructed to confine Li-F based products and reduce fluoride loss at cathode side. These effects endow Li-CFx batteries with durable reversible conversion reaction (for at least 600 cycles), ultrahigh rate performance (e.g., 364 mAhg-1 at 20 Ag-1) and low charging plateau voltage down to 3.2V. The cathode exhibits the maximum power density of 38342Wkg-1 and energy density of 1012Whkg-1. Furthermore, this Li-CFx system demonstrates the promising prospects for applications in view of its low temperature operation (e.g., 280 mAhg-1 at -20°C), low self-discharge ability, large-scale pouch cell fabrication and high cathode loading (5-6mgcm-2), enabling it to move beyond previous role as primary battery and into new role as fast-charging rechargeable battery with high energy density.

Isospin sum rules in charmed baryon weak decays

Isospin symmetry is the most precise flavor symmetry. The effective Hamiltonian of charm quark weak decay is zero under the isospin lowering operators I-n\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$I_-^n$$\\end{document}, which permits us to generate isospin sum rules through several master formulas. In this work, we derive the master formulas of isospin sum rules for the two- and three-body non-leptonic decays of singly and doubly charmed baryons. Hundreds of isospin sum rules are derived to test of isospin symmetry and provide hints for the new decay modes. The isospin sum rules for multi-body decays are not broken by the intermediate resonances and hence can be used to study the isospin partners of exotic hadrons.

Graphene-enhanced ferroelectric domain wall high-output memristor

Recent studies on memristive materials and technologies have expanded beyond conventional memory elements, driven by their potential application in novel information processing concepts. Among these materials, conductive domain walls in ferroics are especially promising, offering conductive tunability suitable for reconfigurable multi-state devices. However, challenges such as domain stability, time-dependent conductivity, and low current output have impeded progress in the field. Here, we study the graphene/Pb(Zr,Ti)O3/SrRuO3 system, which demonstrates robust domain wall conduction up to 100 nA/μm2 for 2 V bias, while addressing the critical issue of stability of switched domains. The introduction of graphene electrodes enhances low-voltage stochastic domain formation with limited domain expansion that promotes the emergence of multi-domain states. The developed micrometer sized capacitor devices enable electrically programmable multiple distinct conduction states with robust retention combined with high current output and low operation voltage. These features are highly desirable for memristors and mark the significant potential of domain wall electronics for neuromorphic computing.

Mass ladder operators and quasinormal modes of the static BTZ-like black hole in the Einstein-bumblebee gravity

Abstract We investigate the mass ladder operators for the static BTZ-like black hole in the Einstein-bumblebee gravity, and probe the quasinormal frequencies of the mapped modes by the mass ladder operators for a scalar perturbation under the Dirichlet and Neumann boundary conditions. It is found that the mass ladder operators depend on the Lorentz symmetry breaking parameter, and the imaginary parts of the frequencies shifted by the mass ladder operators increase with the increase of the Lorentz symmetry breaking parameter under two boundary conditions. It should be noted that, under the Neumann boundary condition, the mapped modes caused by the mass ladder operator $D_{0,k_+}$ are unstable. Moreover, the mass ladder operators do not change the Breitenlohner-Freedman bound for the scalar modes, just as in the usual BTZ black hole. These results could help us to further understand the conformal symmetry and Lorentz symmetry breaking in the Einstein-bumblebee gravity.

Low Strength Wastewater Treatment Using a Combined Biological Aerated Filter/Anammox Process

To achieve the in situ capacity expansion of the post-denitrification biological aerated filter (BAF-DN), the integration of BAF with the anammox process (BAF/AX) was proposed. With the objective of maximizing retaining ammonia nitrogen, the operational optimization of BAF was achieved by two distinct strategies. The treatment performance of BAF demonstrated that the removal efficiencies of chemical oxygen demand (COD) and ammonia nitrogen (NH4+-N) was 66.3~67.3% and 4~12%, respectively, under conditions of low aeration intensity (0.4 m3·m−2·h−1) or a shortened empty bed residence time (EBRT) of 30 min. Residual NH4+-N in the BAF effluent served as the ammonia substrate for the subsequent anammox process, which was successfully launched by using ceramic particles and sponges as carriers. Notably, the sponge carrier facilitated a shorter start-up period of 41 to 44 days. Furthermore, the sponge-based anammox reactor exhibited a superior NH4+-N removal capacity (≥85.7%), under operations of a shorter EBRT of 40 min, low influent NH4+-N concentrations (≤30 mg/L), and COD levels of ≤67 mg/L. In addition, a comprehensive evaluation of the BAF/AX process was conducted, which considered performance, cost-effectiveness, and engineering feasibility. The performance results illustrated that the effluent quality met the standard well (with a COD level of ≤ 50 mg/L, and a TN of ≤3.1~10.5 mg/L). Following a comparison against the low aeration intensity operation, it was recommended to operate BAF at a low EBRT within the BAF/AX process. Consequently, the treated volume was double the volume of the standalone BAF-DN, synchronously achieving low costs (0.413 yuan/m3).

Determination of the continuous grade of a binder in the South African performance grade binder specification

A Performance Grade (PG) Bitumen Specification, SATS-3208 (SATS 2019), was developed in South Africa during the period up to 2019. Since that time a period of implementation has begun on selected projects in South Africa. The implementation activities have included testing of data in accordance with the final anticipated standards. Formulation of a national standard is in the final stages and is expected to be published towards the end of 2024. The PG grade is specified using a high temperature number and a minimum temperature number that indicate the climate range within which a bitumen would be expected to perform. For example, a PG64-22 has a high temperature of 64°C and a minimum temperature of -22°C, from which intermediate and low operating temperatures are derived. A material meeting this grade will always have a performance range which is, ideally, just bigger than the specification grade and this is typically referenced as the continuous grade. A further definition is the difference between the two continuous grade numbers, referenced as the "Useful Temperature Interval" or UTI. As part of this implementation, it is required to determine the continuous grade for bitumen, including for modified binders, to ensure compliance with the specification. The UTI must be equal to or greater than 80°C. This technical note has been developed to demonstrate correct procedure to determine the continuous grade and UTI.

Optimization and Regulation Method for Large Blade-regulating Pump Stations Considering Safety Constraints

Abstract In plain areas, making flood control and drought resistance a heavy task. Large water pumping stations undertake the important task of water lifting and scheduling. Due to the physical characteristics of large pumping stations, they are often affected by the upstream and downstream water levels during water lifting scheduling, resulting in low head operating conditions. Low head operating conditions can easily cause pumping stations to operate at excessive power, thereby affecting the health of pumping station equipment. Based on the head efficiency curve of a large blade regulating pump station in this article, by optimizing the regulating mathematical model and considering constraints such as water level, flow rate, power, efficiency, and blade angle adjustment time interval under low head conditions, a dynamic programming calculation method is adopted to construct an optimized regulating method for the pump station. Based on real-time water level, various operating data of the unit are optimized to ensure the blade angle, power, and the flow rate and other parameters are all within the safety constraint range. And various operating data could be used to guiding the real-time optimization and adjustment of the pumping station, and additionally providing the operating foundation for the intelligent pumping station.

Association of Anemia and Transfusion with Major Adverse Cardiac Events and Major Adverse Limb Events in Patients Undergoing Open Infrainguinal Bypass

Anemia is highly prevalent patients with peripheral vascular disease and has been associated with postoperative cardiac events and mortality, and adverse limb events after revascularization procedures. Allogenic blood transfusions have also been associated with adverse events including hospital acquired infections, cardiac morbidity and reduced survival. The aim of this study was to evaluate the impact of blood transfusion on major adverse cardiac events (MACE) and major adverse limb events (MALE) in patients undergoing infrainguinal lower extremity bypass operations. We performed a retrospective cohort analysis of patients undergoing infrainguinal lower extremity bypass in the Society for Vascular Surgery Vascular Quality Initiative database between 2003 and 2020. Patients were first grouped by their preoperative hemoglobin (Hgb) number (severe anemia: Hgb 7-10g/dL; moderate anemia: 10-12g/dL; normal Hgb: >12g/dL) and then stratified by their transfusion status (perioperative transfusion vs. no perioperative transfusion). Primary endpoints were MACE, defined as myocardial infarction, new congestive heart failure, dysrhythmia, or stroke in the postoperative period, and MALE, defined as return to operating room for thrombosis, loss of primary patency on follow-up and major ipsilateral amputation on follow-up. Secondary outcomes included wound complications, graft infections, 30-day mortality and 1-year survival. Outcomes were compared between patients who received transfusions and those who did not at every anemic threshold. Multivariable logistic regression was performed to evaluate the impact of blood transfusion on primary outcomes. A total of 55,884 patients were included for analysis, of which 16.3% had severe anemia, 25.9% had moderate anemia and 57.8% had normal hemoglobin. Anemia severity was associated with increased rates of MACE (9.8% vs. 8.3% vs. 5.2%, p<0.0001) and MALE (32.2% vs. 24.8% vs. 18.6%, p<0.0001). On univariate analysis, transfusion was consistently associated with increased rates of MACE and MALE at every anemic threshold (p<0.0001 for all). Transfusion was also associated with increased rates of 30-day mortality at all anemic thresholds (p<0.0001 for all) and reduced 1-year survival at all anemic thresholds (log-rank p<0.0001 for all). On multivariable analysis for MACE, an interaction factor was observed between preoperative Hgb and transfusion status (p<0.0001). At every anemic threshold, transfusion was independently associated with MACE (severe: OR 2.4 [95% CI: 2.0 - 2.9]; moderate: OR 2.8 [95% CI: 2.5 - 3.2]; normal: OR 4.5 [95% CI: 4.0 - 5.0]). On multivariable analysis for MALE, an interaction factor was also observed between preoperative Hgb and transfusion status (p<0.0001). At every anemic threshold, transfusion was independently associated with MALE (severe: OR 2.1 [95% CI: 1.9 - 2.3]; moderate: OR 1.8 [95% CI: 1.7 - 2.0]; normal: OR 2.6 [95% CI: 2.4 - 2.8]). Perioperative blood transfusion in patients undergoing infrainguinal lower extremity bypass is independently associated with MACE and MALE in all patients with preoperative Hgb > 7 g/dL. Despite the morbidities associated with anemia, these findings highlight that transfusion may not be the optimal treatment modality, particularly in patients with higher preoperative Hgb. Future research is needed to define the transfusion threshold in this population.

Development of Low Carbon Blast Furnace Operation Technology by using Experimental Blast Furnace

Development of Low Carbon Blast Furnace Operation Technology by using Experimental Blast Furnace

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.

Investigation in improving the Cs-free negative hydrogen ion production with short-pulse low power in the afterglow of pulse-power-modulated plasma sources

Abstract Pulse plasma ion sources have been shown to be capable of achieving high negative hydrogen ion densities ( n H − ) or currents. The fast cooling of the electrons and reduction in the electron density (n e) provide favorable plasma conditions to improve the H− production, with a high density ratio of negative hydrogen ions to electrons during the pulse-off period. The purpose of this research is to further improve the performance of volume-produced H− ion sources based on the pulse power modulation. In this study, a time-modulated negative hydrogen plasma sustained by 10 kHz pulse power at the typical gas pressure of 0.3 Pa was numerically investigated using a global model. The model is compared with measurements obtained in a pulsed radio frequency ion source and shows a reasonable agreement. A steplike low-high power strategy in the active glow period and a short-pulse low power in part of the afterglow period are employed to mitigate overshoot of the electron temperature (T e) in the initial stage of the pulse period and to optimize H− production in the afterglow, respectively. The model predicts that a small-magnitude, short-duration low power operation in the afterglow increases n H − and decreases n e from the onset of the low power until the beginning of the next high power pulse, due to a modest temporary increase in the T e (less than 2 eV). It facilitates dissociative electron attachments and thus H− formation. The reduction in the n e indicates that positive ions lost to the walls cannot be compensated by weak ionization. H− production with a low number of co-extracted electrons can be optimized by adjusting the magnitude and duration of the low power in the afterglow.