Loop Stability Research Articles

A Method of Applying Mixtures to Optimize Grounding during Installation of Vertical Composite Grounding Devices

The article considers the method of using mixtures to optimize the electrophysical parameters of grounding devices in conjunction with vertical composite grounding conductors. It has been found that fluctuations in soil resistivity caused by changes in weather and climatic conditions can lead to instability of the ground loop resistance. The study shown that without appropriate measures, the resistance of the loop as a result of seasonal changes in soil properties may exceed acceptable values. This is fraught with deviations in the resistance to current spreading of grounding devices beyond the limits of acceptable parameters. To compensate for these fluctuations, a method is proposed to reduce the seasonality factor. Reducing seasonality plays an important role in ensuring the safety of service personnel and farm animals by maintaining the resistance of the grounding device within the limits of regulatory values. The authors discuss methods for artificially reducing the resistance of the ground loop, including increasing its size and using deep ground electrodes. The results of vertical electrode probing of the soil at the sites of grounding conductors are presented, the effect of humidity on the resistivity of the soil is shown, the influence of soil layering and the presence of moisture-saturated soil layers is considered. A method is proposed that allows the mixture to be introduced together with a vertical composite grounding device, the design of the coupling, tip and auxiliary device, experimental studies of the proposed designs are carried out and the results of measuring the current spreading resistance of such a grounding device with both standard and proposed couplings are presented. A comparison was made with a grounding device without the use of mixtures. The measurement results demonstrate that with an increase in the length of the grounding device, its diameter and the volume of the injected mixture, the resistance decreases. It is shown that the proposed solution makes it possible to reduce seasonality by 1.64–2.1 times, depending on the couplings used, and to obtain a grounding conductor with an equivalent diameter dozens of times larger than the diameter of a composite grounding conductor. The authors propose the use of soil-replacing mixtures to reduce soil resistivity and ensure the stability of the grounding loop throughout the entire service life. The proposed method of applying mixtures without pre-drilling makes it possible to reduce the cost of constructing grounding devices.

Structural basis of chiral wrap and T-segment capture by Escherichia coli DNA gyrase

Type II topoisomerase DNA gyrase transduces the energy of ATP hydrolysis into the negative supercoiling of DNA. The postulated catalytic mechanism involves stabilization of a chiral DNA loop followed by the passage of the T-segment through the temporarily cleaved G-segment resulting in sign inversion. The molecular basis for this is poorly understood as the chiral loop has never been directly observed. We have obtained high-resolution cryoEM structures of Escherichia coli gyrase with chirally wrapped 217 bp DNA with and without the fluoroquinolone moxifloxacin (MFX). Each structure constrains a positively supercoiled figure-of-eight DNA loop stabilized by a GyrA β-pinwheel domain which has the structure of a flat disc. By comparing the catalytic site of the native drug-free and MFX-bound gyrase structures both of which contain a single metal ion, we demonstrate that the enzyme is observed in a native precatalytic state. Our data imply that T-segment trapping is not dependent on the dimerization of the ATPase domains which appears to only be possible after strand passage has taken place.

Hsa_circ_0072732 enhances sunitinib resistance of renal cell carcinoma by inhibiting ferroptosis

BackgroundRenal cell carcinoma (RCC) is one of the most diagnosed urological malignancies with high mortality and increasing incidence. What’s more, the sunitinib resistance undoubtedly increased the difficulties in RCC therapy. Circular RNAs (circRNAs) are a newly found type of non-coding RNAs with a special circular structure, and are found to participate in the occurrence development, chemoresistance, and prognosis of cancers. Ferroptosis regulates disease progression mainly via polyunsaturated fatty acid metabolism and glutamine catabolic pathways. The mechanism of circRNAs contributed to sunitinib resistance through ferroptosis has not been elucidated clearly.Materials and methodsIn our research, we identified a novel circRNA Hsa_circ_0072732 from circRNA datasets (GSE108735 and GSE100186). RNase R and Actinomycin D assays were used to detect the loop structure and stability of circRNAs. qRT-PCR and western blot were used for the detection of RNA and protein levels. CCK8 assays were used to detect proliferation and cell viability. Lipid peroxidation (MDA), and reactive oxygen species (ROS) were detected by indicted kits. Dual-luciferase reporter and RNA pull-down assays were used to detect the RNA interactions.ResultsOur results showed that Hsa_circ_0072732 was highly expressed in RCC cells. Further investigations showed that the silence of Hsa_circ_0072732 could increase RCC sensitivity to sunitinib. Hsa_circ_0072732 contributed to sunitinib chemoresistance by impairing ferroptosis. Hsa_circ_0072732 exerts its function mainly by acting as sponges for miR-548b-3p and regulating the expression SLC7A11. Our research suggests that ferroptosis is involved in sunitinib resistance, and targeting ferroptosis is a promising way for RCC treatment.ConclusionOur research suggests Hsa_circ_0072732 enhanced renal cell carcinoma sunitinib resistance by inhibiting ferroptosis through miR-548b-3p/SLC7A11.

Enzyme stabilisation due to incorporation of a fluorinated non-natural amino acid at the protein surface

We have previously engineered E. coli transketolase (TK) enzyme variants that accept new substrates such as aliphatic or aromatic aldehydes, and also with improved thermal stability. Irreversible aggregation is the primary mechanism of deactivation for TK in the buffers used for biocatalysis, and so we were interested in determining the extent to which this remains true in more complex media, crude cell lysates or even in vivo. Such understanding would better guide future protein engineering efforts. NMR offers a potential approach to probe protein structure changes, aggregation, and diffusion, and19F-labelled amino acids are a useful NMR probe for complex systems with little or no background signal from the rest of the protein or their environment. Here we labelled E. coli TK with two different19F probes, trifluoromethyl-L-phenylalanine (tfm-Phe), and 4-fluoro phenylalanine (4 F-Phe), through site specific non-natural amino acid incorporation. We targeted them to residue K316, a highly solvent exposed site located at the furthest point from the enzyme active sites. Characterisation of the19F-labelled TK variants revealed surprising effects of these mutations on stability, and to some extent on activity. While variant TK-tfm-Phe led to a 7.5 °C increase in the thermal transition midpoint (Tm) for denaturation, the TK-4 F-Phe variant largely abolished the aggregation of the enzyme when incubated at 50 °C19. F-NMR revealed different behaviours in response to temperature increases for the two TK variants, displaying opposite temperature gradient chemical shifts, and diverging motion regimes, suggesting that the mutations affected differently both the local environment at this site, and its temperature-induced dynamics. A similar incubation of TK at 40–55 °C is also known to induce higher cofactor-binding affinities, leading to an apparent heat activation under low cofactor concentration conditions. We have hypothesised previously that a heat-inducible conformational change in TK leads to this effect1. H-NMR revealed a temperature-dependent re-structuring of methyl groups, also at 30–50 °C, which may be linked to the heat activation. While our kinetic studies were not expected to observe the heat activation event due to the high cofactor concentrations used, this was not the case for TK-4 F-Phe, which did appear to heat activate slightly at 45 °C. This implied that the mutations at K316 could influence cofactor-binding, despite their location at 47 Å from either active site. Such long-distance effects of mutations are not unprecedented, and indeed we have previously shown how distant mutations can influence active-site loop stability and function in TK, mediated via dynamically coupled networks of residues. Molecular dynamics simulations of the two19F containing variants similarly revealed networks of residues that could couple the changes in dynamics at residue K316, through to changes in active site dynamics. These results independently highlight the sensitivity of active-site function to distant mutations coupled through correlated dynamic networks of residues. They also highlight the potential influence of surface-incorporated probes on protein stability and function, and the need to characterise them well prior to further studies.

Computer-Guided Engineered Endo- and Exocleaving Glycosidase for Significantly Improving Production of Ginsenoside F1.

Ginsenoside F1, a particularly rare and valuable compound known for its health benefits, requires precise deglycosylation due to the extensive glycosylation of ginsenosides in Panax notoginseng. Here, we identified that the β-d-glucosidase BglSK exhibits both endo- and exocleaving glycosidase activities with multi-6-O-glycosides, thereby facilitating the specific production of Ginsenoside F1. The variant BglSKT137A/L508A, obtained through protein engineering, displayed kcat/KM values for the reactions of ginsenoside Rg1 and notoginsenoside R1 that were increased by 13.88-fold and 108.56-fold, respectively, compared with the BglSKWT. The reduced steric hindrance and the overall increase in loop stability show a higher tendency to adopt a closed conformation and facilitate the prereaction state, which may explain the enhanced catalytic efficiency of the engineered enzyme. These beneficial mutants will deepen our understanding of mechanisms for improving glycosidase activity and provide tools for producing high-value P. notoginseng products.

Experimental study on a single-sided resilient composite beam–column joint

This paper presents an experimental study on a single-sided resilient composite beam–column joint, in which a nonreplaceable concrete slab and connection plate and a replaceable buckling-restrained cover plate (BRCP) are installed at the top and bottom flanges, respectively. The seismic performance and replaceability of the proposed joint were investigated considering the influence of the concrete slab. One specimen was cyclically loaded under 2 % rotation, and then the damaged core plate of the BRCP was replaced to form a new specimen that was cyclically loaded under 4 % rotation. The results showed that the neutral axis was shifted upward to the top flange, which made the damage concentrate in the core plate, and only minor damage occurred to the connection plate and concrete slab under 2 % rotation. The hysteresis curve after replacement was almost the same as that before replacement under 2 % rotation and showed full and stable loops without decrease in load capacity under 4 % rotation, implying good seismic performance and replaceability. In addition, the proposed joint was compared with a bare steel joint to examine the effects of concrete slabs. Further, a numerical model of the specimen was developed and verified by comparison with the test results to better understand the test and study the influence of connection plates. Finally, the formulas for the yield moment and initial stiffness of the joint were derived and compared with test results to verify the accuracy of the formulas. The influence of the reduction in core plate area on the joint stiffness and neutral axis position was discussed using the formulas.

Evolution of and Perspectives on Differential‐Pair‐Based CMOS Variable Gain Amplifiers With Linear‐in‐Decibel Gain Control: A Tutorial

ABSTRACTA variable gain amplifier (VGA) is an essential building block used in the automatic gain control (AGC) loop to provide a continuous, adjustable gain for the signal strength. To maintain the stability and consistency of the AGC loop, it is necessary to ensure that the gain of the VGA has an accurate dB‐linear characteristic. This tutorial provides a detailed overview of the development of dB‐linear VGAs based on differential pair structures over recent years. We categorize various VGA cells based on differential pair structures, analyze their operating principles, and explain the key features of each topology. Based on observation and extraction of the dB‐linear implementation schemes used by these VGAs, we summarize three basic methods for achieving dB‐linear gain control. We also discuss specific methods for realizing the exponential function, using a true exponential and a mathematical approximation, and present the different types of approximation functions adopted in the works described here. Considerations in regard to the tuning range, gain error, bandwidth, linearity, process‐temperature robustness, and circuit simplicity are also discussed. Finally, we draw comparisons and give perspectives for future dB‐linear VGAs.

Study on theoretical model and actual deformation of weft-knitted transfer loop based on particle constraint

Abstract In order to derive the structural properties and deformation behavior of the weft-knitted transfer fabric, a multilayer spring-mass geometric circle model with weft-knitted transfer loop is provided in conjunction with the fabric samples’ image. Eight type-value points were utilized to control the transfer loop’s morphological structure. Connections between the type-value points and the particle system were established. Non-uniform rational B spline curves and texture mapping were utilized to create the three-dimensional impression of the weft-knitted transfer loop. By measuring the offset of the type-value points in conjunction, the actual deformation of the weft-knitted transfer fabric was determined. Utilizing a cylindrical envelope box for collision detection, the possible unreasonable interpenetration phenomenon in the simulation was solved, and thus a stable weft-knitted transfer loop structure was obtained. Using Microsoft Visual Studio and C#, the deformation of the weft-knitted transfer fabric was simulated, the simulated weft-knitted transfer fabric’s deformation pattern accurately depicts the fabric’s three-dimensional structure and deformation behavior while also matching the structural characteristics of the fabric sample. The findings demonstrate that the theoretical structural model of weft-knitted transfer fabric constructed can accurately represent the loop’s structure, and the actual deformation of the simulated weft-knitted transfer fabric is consistent with the deformation characteristics of the fabric sample. Weft-knitted transfer fabric’s deformation behavior may be effectively reflected by the multilayer spring-mass geometric circle model, allowing for the modeling of the fabric’s morphology and 3D structure.

Online decoupling of the time-varying longitudinal feedback loops for improved performance in Advanced Virgo Plus*

Abstract Gravitational Wave detectors require low-noise sensors combined with high-performance feedback loops to maximize the detector sensitivity in the low-frequency detection range. Some feedback loops in the detector are strongly coupled and their coupling varies over time, which is inherent to the optical configuration and the optical readout scheme used to obtain error signals for the feedback loops. This paper presents a control-based approach to deal with the time-varying interaction among three of the longitudinal degrees of freedom in the Advanced Virgo Plus detector, using the pre-existing infrastructure of the detector. An intuitive Multiple-Input Multiple-Output stability criterion is presented that illustrates how the time-varying coupling affects the stability of the feedback loops, as well as a method that identifies the coupling online and updates a decoupling matrix accordingly. Experiment results of the proposed method on the Advanced Virgo Plus detector illustrate continuous minimization of the coupling over time. Using the derived stability criterion, it is furthermore shown that the coupling is sufficiently minimized such that the interaction terms can be neglected in the control design, resulting in an improved controller performance.

Crystal Structure and Molecular Mechanism of Isocitrate Lyase from Chloroflexus aurantiacus.

Chloroflexus aurantiacus is a green, nonsulfur bacterium that employs the 3-hydroxypropionate cycle to grow, using carbon dioxide/bicarbonate as its primary carbon source. Like most bacteria, it possesses the glyoxylate cycle, facilitated by malate synthase and isocitrate lyase (ICL), allowing a "tricarboxylic acid cycle" bypass. C. aurantiacus also harbors ICL, an enzyme that catalyzes reversible isocitrate cleavage into glyoxylate and succinate. This study presents the crystal structures of C. aurantiacus-derived ICL (CaICL), in its Mg2+-bound and Mn2+ and isocitrate-bound forms, elucidating its substrate-binding mechanism and catalytic loop dynamics. CaICL forms a homotetramer and interacts with isocitrate via critical active-site residues, revealing its catalytic mechanism. The stabilization of the catalytic loop and adjacent terminal regions upon isocitrate binding underscores its functional significance. These findings advance our understanding regarding ICL enzymes, offering a basis for future investigations into their biological roles and potential applications.

Talbot laser for Airy pulse generation

Abstract We report a C-band fiber Talbot laser—an injection-seeded frequency-shifting active ring cavity operated above threshold—emitting trains of far-field Airy pulses characterized by a dominant cubic spectral phase. Pulses are created by the coherent addition of the recirculating seed wavelength under a large roundtrip first-order dispersion. Single-sided Airy pulse trains with sub-ns pulse widths, 80 MHz repetition rate, and bandwidth exceeding 10 GHz are generated at both integer and fractional Talbot conditions. At detuned Talbot conditions pulses are shown to be tailorable by recirculation-induced first-order dispersion. The far-field character of the resulting waveforms is demonstrated, and the performance in terms of amplitude noise and timing jitter, in this last case after the introduction of active loop stabilization, is evaluated.

Structural Prediction and Antigenic Analysis of ROP18, MIC4, and SAG1 Proteins to Improve Vaccine Design against Toxoplasma gondii: An In silico Approach.

Toxoplasmosis is a cosmopolitan infectious disease in warm-blooded mammals that poses a serious worldwide threat due to the lack of effective medications and vaccines. The purpose of this study was to design a multi-epitope vaccine using several bioinfor-matics approaches against the antigens of Toxoplasma gondii (T. gondii). Three proteins of T. gondii, including ROP18, MIC4, and SAG1, were analyzed to predict the most dominant B- and T-cell epitopes. Finally, we designed a chimeric immunogen RMS (ROP18, MIC4, and SAG1) using some domains of ROP18 (N377-E546), MIC4 (D302-G471), and SAG1 (T130-L299) linked by rigid linker A (EAAAK) A. Physicochemical prop-erties, secondary and tertiary structures, antigenicity, and allergenicity of RMS were predicted utilizing immunoinformatic tools and servers. RMS protein had 545 amino acids with a molecular weight (MW) of 58,833.46 Da and a theoretical isoelectric point (IP) of 6.47. The secondary structure of RMS protein con-tained 21.28% alpha-helix, 24.59% extended strand, and 54.13% random coil. In addition, eval-uation of antigenicity and allergenicity showed the protein to be an immunogen and non-aller-gen. The results of the Ramachandran plot indicated that 76.4%, 12.9%, and 10.7% of amino acid residues were incorporated in the favored, allowed, and outlier regions, respectively. ΔG of the best-predicted mRNA secondary structure was -593.80 kcal/mol, which indicated that a stable loop was not formed at the 5' end. Finally, the accuracy and precision of the in silico analysis must be confirmed by successful heterologous expression and experimental studies.

Rehabilitation of steel structures using innovative brace members equipped with YSPD damper

Earthquakes are serious risks to human life and infrastructure. An earthquake's influence on human life and its socioeconomic consequences highlight the need to investigate and create the most efficient and easily adaptable ways to minimize losses. The basic concept of different control mechanisms used for protecting structures from the destructive impacts of earthquakes is to dissipate the energy efficiently, therefore ensuring that the structure remains undamaged or sustains minimum damage. To achieve this purpose, the passive control mechanism is a particularly suitable and reliable technology as it doesn't rely on external power to actively dissipate energy. The present study proposes using a passive energy dissipation device called the Yielding Shear Panel Device (YSPD) for strengthening the current steel structures. The YSPD consists of a square hollow section (SHS) that houses a diaphragm plate. The fundamental concept of the YSPD involves harnessing the lateral deformation of a steel plate to absorb and disperse the seismic energy. The Bouc-Wen-Baber Noori (BWBN) material has been used for simulating the hysteresis force-deformation relationship of YSPDs by pinching. YSPDs are simulated as spring components that connect between the beam and the V-brace. A nonlinear time history dynamic analysis was performed to assess the alteration in the structural capacity with the setting up of YSPDs. The performance of the tested structure was assessed considering story drift, story displacement, story shear, column shear, and YSPD hysteresis loops. The results indicated that YSPD installation has improved the structure's capacity. However, the use of dampers resulted in significant drift in all stories, a reduction in total floor displacement, and a decrease in the shear force of the stories. However, the results demonstrated that the YSPD dampers effectively absorbed energy and exhibited stable hysteresis loops.

Comparative Analysis of Two Robust Strategies for an Angular Velocity Control System

In this paper, a novel flow control strategy which is the inlet throttled pump was used to design an angular velocity control system for rotary actuator. Inlet throttled systems have good performance in addition to their high efficiency compared to traditional valve controlled systems. The flow in the proposed system is adjusted by a valve that is positioned at the pump inlet with the purpose of reducing the energy loses across the valve. This regulated flow is used then to control the actuator angular velocity. The system was modeled and the open loop stability and performance were studied. In order to improve the system performance, Robust-Proportional-Integral-Derivative (RPID) and structured singular value (Mu) controllers have been designed. The multiplicative uncertainty was analyzed to assess the robustness of the feedback control system where six parameters were considered uncertain within a range of +10%. The robust stability and performance requirements of the closed-loop angular velocity control system were assessed in the frequency domain. The time response of the system showed that the system is stable with both (RPID) and (Mu) controllers. The Mu controller can handle parametric uncertainty without requiring pure integral term which is a significant advantage over the (RPID) controller. On the other hand, the (RPID) controller could achieve robust performance, making it much suitable for systems that require high levels of performance and robustness. In summary, the the (RPID) and Mu controller is a more comprehensive solution for ensuring the best performance of a system. The results for each (RPID) and Mu-controllers showed no oscillations, zero percent overshoot. Each of the (RPID) and Mu-controllers meets the robustness needs. Index Terms— Pump, valve, inlet throttling valve, angular velocity control, robust control, Mu synthesis, D-K iteration, RPID controller .

Assessment of ASYST and RELAP5 for predicting stability and limit cycles of a low-pressure natural circulation loop with flashing instability

Two thermal hydraulics system codes, ASYST VER3 and RELAP5 MOD3.3, are assessed for their prediction of stability and limit cycles of low-pressure natural circulation with potential flashing instability. The benchmark conditions are from a nearly five-meter-tall water loop whose experiments have generated a published dataset covering both stability and limit-cycle oscillations. These conditions are simulated by a model of the entire system, and the target asymptotic behaviors are approached through sufficiently long transients under prescribed operational settings. ASYST is found not conservative for stability prediction, in the sense that the unstable operational range is underpredicted with discrepancy mainly in the high-subcooling stability boundary. Qualitative flow changes across the island of instability are however simulated satisfactorily, and for conditions correctly predicted as unstable, reasonable prediction is achieved for the oscillation period, time-averaged flow rate, and peak flow rate. Further comparison against experimental void fraction confirms that ASYST simulates physical two-phase behaviors in the limit cycles. RELAP5 predicts a much more stable system whose island of instability is significantly smaller than that of reality. Its simulated flow oscillations also noticeably deviate from the typical patterns of flashing instability, resembling sinusoidal waves following periods different from the experimental measurement. Underprediction of flashing and overproduction of subcooled boiling are identified as potential major defects in RELAP5, which calls for future model calibration and further investigation. In general, the current assessment contributes to the awareness of potential uncertainties when adopting ASYST and RELAP5 for predicting flashing instability and its induced transients.

Optimal balance of organic detritus and feed for fish growth and water quality improvement through regulating nutrients cycling

In order to explore the effects of different feed composition on the nutrient level and microbial loop structure in aquaculture ponds, a field simulation experiment in aquaculture ponds was conducted by adding different proportions (0%, 20%, 40% and 60%) of bagasse to fish feed for combined feeding. The addition of bagasse significantly reduced the levels of various forms of nitrogen and phosphorus in the water, especially with the addition of 60% bagasse. In the treatments without addition and with 20% bagasse added, nitrogen and phosphorus levels remained relatively high, which should be attributed to the decomposition of feed and the release of sediment, ultimately stimulating the abundant reproduction of algae. Bacterial growth was limited due to insufficient supply of organic carbon, and the growth of fish relied more on the components of the feed. With the addition of 60% bagasse, the high organic carbon and low nitrogen and phosphorus levels could not support the growth of phytoplankton, bacteria, and zooplankton. It is inferred that organic carbon may be more degraded into carbon dioxide, ultimately limiting the growth of fish. Adding 40% bagasse achieved a balanced level of carbon, nitrogen, and phosphorus, establishing a healthy and stable microbial loop structure (including phytoplankton, bacteria, and zooplankton). Most nutrients were converted into plankton, which then became natural food for fish, ensuring complete nutrient utilization. This is beneficial for both water quality improvement and fish reproduction. Therefore, adding a moderate proportion of bagasse to the feed can maximize the effects of water quality improvement, fish reproduction, and even the quality of fish meat.

Hydrogen modified dislocation loop types and shapes in irradiated iron

Dislocation loops are one type of irradiation defects that severely degrade the mechanical properties of nuclear materials. In this study, we found that hydrogen atoms in irradiation environment significantly modify the loop properties including loop types and shapes during in-situ hydrogen irradiation. <100> loops have been energetically stable from 300 °C in H+ irradiated iron whereas the stability of <100> loops is delayed until 500 °C in Fe+ irradiated iron. Meanwhile, both <100> loops and 1/2<111> loops exhibit polygonal shapes with sharp corners at 400 °C after H+ irradiation, similar to loops predicted at 900 °C without hydrogen. Our results highlight the importance of considering the hydrogen effects in dislocation loop evolution and stability.

Numerical study of steel beam to reinforce concrete column (RCC) connection with through-plate and buckling-restrained steel plates

This study examines the behavior and failure mechanisms of steel beam-to-reinforced concrete column connections with through-plate and buckling-restrained steel plates (BRSPs) configurations. These connections are critical components in composite steel and concrete structures, playing a vital role in force transfer and resistance to various loads, especially dynamic loads such as earthquakes. The primary objective of this study is to analyze the hysteresis behavior of these connections under cyclic loading using numerical analyses. Parametric models with varying BRSP thicknesses, ranging from 5 to 25 mm, were used to investigate their impact on hysteresis behavior and load-bearing capacity. The effects of different BRSP thicknesses on stress distribution and failure mechanisms were analyzed. The results from the parametric studies show that increasing the thickness of BRSPs improves the stress distribution in the beam-to-column connections. This improvement includes reduced stress concentration and enhanced uniformity of stress distribution, which can lead to reduced localized failures and increased overall connection stability. Numerical simulations indicate that the use of BRSPs (with a thickness of 15 and 17 mm) results in wider and more stable hysteresis loops, reflecting increased energy absorption capacity and improved deformation behavior of the connections under cyclic loading. The findings show that BRSPs can reduce failure concentration, increase flexural resistance, and prevent buckling in steel beams. These results underscore the importance of using BRSPs to enhance structural performance and mitigate potential failures under severe loading conditions.

A comparative experimental and numerical study on the shear and flexural mechanism of an innovative butterfly-damper

In this paper, the behavior of an innovative metallic damper made of butterfly plates (with shear or flexural mechanisms) to improve the behavior of the CBF system is considered. These dampers can provide similar seismic resistant properties but concentrate most damage in the damper region during a seismic event. This has considerable practical utility in the construction industry and can allow quick replacement of these dampers (instead of replacing braces) after damage without impacting the serviceability of the building. To consider the behavior of the proposed dampers, experimental and numerical as well as parametrical studies were carried out. Experimental results indicated that both shear and flexural dampers pertain to stable hysteresis loops although the flexural damper showed a better ultimate rotation. However, experimental and numerical results revealed that the shear damper's ultimate strength, stiffness, and energy dissipating capacity reached >3.58, 4.59, and 14.56 times greater than flexural dampers. Results indicated that the response of the dampers is related to the slenderness and that the allowable slenderness was suggested for the design of the dampers.

Numerical simulation of arc stabilizing cycle in vacuum arc remelting of titanium alloy

Through utilizing numerical simulation methods, the flow state of the molten pool during the vacuum self-consumption melting process of titanium alloy was analyzed. The influence of the stable arc cycle on the shape of the molten pool, dendrite arm spacing, surface quality, and shrinkage cavity was examined. The results showed that without an external magnetic field, the molten pool for smelting a Φ720 mm specification titanium alloy ingot is dominated by self-inductance magnetic force, leading to a downward flow in the central part of the melt. A mere 0.5 G stray magnetic field can result in Ekman pumping, causing an upward secondary flow in the core to counteract it. At an externally added magnetic field strength of 50 G, choosing a 10 s-20 s cycle can achieve a relatively stable double loop flow pattern. The shape of its molten pool, dendrite arm spacing, and contact ratio all reach optimal performance, thus verifying the possibility and feasibility of the double loop flow, and the macroscopic segregation of the simulated ingots essentially matches the experimental results, aiming to provide references for selecting parameters in actual production.