Transient Analysis Research Articles

Mode decomposition of core dynamics transients using higher-order DMD method

Accurately predicting three-dimensional power distribution within a reactor core during reactivity transients is crucial for optimizing reactor operational control. This paper proposes a higher-order dynamic mode decomposition (DMD) method for analyzing highly nonlinear dynamic systems in nuclear reactors. Through analysis of the 3-D LWR Core Transient Benchmark (3DLWRCT) with rod ejection accident, traditional DMD reconstruction techniques were found inadequate in accurately capturing the system’s dynamic evolution using the given simulation data, primarily due to the nonlinear features and local high-order characteristics of the reactor system. In contrast, the HODMD approach demonstrated its effectiveness in predicting future variations in the core’s state. These findings establish the feasibility of employing the HODMD method for transient analysis of core dynamics, leading to promising prospects for dynamic analysis in nuclear energy systems. Future research directions for improving the reconstructive accuracy of HODMD include capturing nonlinear characteristics, automating parameter selection, enabling multi-scale analysis, enhancing anomaly detection capabilities, and providing a broader context for analysis.

Analysis of interturn short circuit in regulating winding of power transformer based on field-circuit coupling

The interturn short circuit fault is one of the common faults in power transformers. At present, research on interturn short circuit faults focuses on high, medium, and low voltage windings, while there is relatively little research on interturn short circuit in regulating windings. Specifically, there is a lack of reported studies on the transient electromagnetic processes, magnetic field distribution, and electromagnetic force characteristics of interturn short circuits in regulating windings unconnected to the circuit. This study presents an actual fault scenario involving interturn short circuits occurring in the untapped portion of the regulating windings of a specific power transformer. A field-circuit coupled model was established to analyze the transient electromagnetic processes during the fault, and the model’s effectiveness was validated by comparing its results with actual fault recording data. Additionally, the magnetic field distribution and electromagnetic force characteristics during the fault were analyzed, and discussions were carried out regarding various ratios of short-circuit turns in the regulating windings. The results indicate that even when an interturn short circuit occurs in the portion of the regulating winding that is not connected to the circuit, the current in the short-circuited turns can reach several tens of times the rated value. Additionally, the leakage magnetic field and the electromagnetic force experienced by the short-circuited ring also increase significantly. The short-circuit ratio has a significant impact on the current of the short-circuited ring, leakage magnetic field intensity, and electromagnetic force. This study contributes to a better understanding of the impact of interturn short-circuit faults in the untapped portion of the regulating windings, offering crucial technical support for fault diagnosis and prevention of power transformers.

CD11c-expressing microglia are transient, driven by interactions with apoptotic cells.

Microglia, the parenchymal macrophage of the central nervous system serve crucial remodeling functions throughout development. Microglia are transcriptionally heterogenous, suggesting that distinct microglial states confer discrete roles. Currently, little is known about how dynamic these states are, the cues that promote them, or how they impact microglial function. In the developing retina, we previously found a significant proportion of microglia express CD11c (Integrin αX, complement receptor 4, Itgax) which has also been reported in other developmental and disease contexts. Here, we sought to understand the regulation and function of CD11c+ microglia. We found that CD11c+ microglia track with prominent waves of neuronal apoptosis in postnatal retina. Using genetic fate mapping, we provide evidence that microglia transition out of the CD11c state to return to homeostasis. We show that CD11c+ microglia have elevated lysosomal content and contribute to the clearance of apoptotic neurons, and found that acquisition of CD11c expression is, in part, dependent upon the TAM receptor Axl. Using selective ablation, we found CD11c+ microglia are not uniquely critical for phagocytic clearance of apoptotic cells. Together, our data suggest CD11c+ microglia are a transient state induced by developmental apoptosis rather than a specialized subset mediating phagocytic elimination.

РАЗРАБОТКА ИНДИКАТОРА ОЦЕНКИ ТЕХНИЧЕСКОГО СОСТОЯНИЯ КОРОБОК ПЕРЕДАЧ

The efficiency of the use of high-energy tractors in agriculture is largely determined by the level of preparation for field work, which in turn depends on the completeness of the repair and maintenance work. Various diagnostic tools are used for a non-selective assessment of the general technical condition of internal combustion engines: motor testers, crankcase gas flow meters, etc. Currently, there are no means to assess the technical condition of the gearbox without breaking the power flow. The development of digital diagnostic tools is required to reduce the risk of failures during field work. (Research purpose) The research purpose is studying the state of the issue and justifying the need to develop a coefficient for a non-selective assessment of the general technical condition of the hydraulic transmission control drive of high-energy tractors. (Materials and methods) Carried out an analysis of the complex of works on diagnosing and managing the reliability of agricultural machinery. It was found that it is necessary to control the time of the transient process in the hydraulic control system of the gearbox, as well as accelerations during gear shifting. We reviewed the previously manufactured control and diagnostic equipment. The KI-12383 and "Effect-02.01" devices were chosen as a prototype for the development of a digital indicator. (Results and discussion) We conducted a simulation, designed and tested a prototype and proved the possibility of developing a digital indicator that can be used as an integrated diagnostic tool to justify the need for repair and maintenance effects of the gearbox. (Conclusions) To monitor the general technical condition of the gearbox, a digital indicator is needed, which will allow, without making changes to the design (K-701, T-150K and their modern analogues), to obtain diagnostic data to substantiate repair and maintenance impacts in order to reduce the risks of failures of the III complexity group during field work.

РАЗРАБОТКА ИНДИКАТОРА ОЦЕНКИ ТЕХНИЧЕСКОГО СОСТОЯНИЯ КОРОБОК ПЕРЕДАЧ

The efficiency of the use of high-energy tractors in agriculture is largely determined by the level of preparation for field work, which in turn depends on the completeness of the repair and maintenance work. Various diagnostic tools are used for a non-selective assessment of the general technical condition of internal combustion engines: motor testers, crankcase gas flow meters, etc. Currently, there are no means to assess the technical condition of the gearbox without breaking the power flow. The development of digital diagnostic tools is required to reduce the risk of failures during field work. (Research purpose) The research purpose is studying the state of the issue and justifying the need to develop a coefficient for a non-selective assessment of the general technical condition of the hydraulic transmission control drive of high-energy tractors. (Materials and methods) Carried out an analysis of the complex of works on diagnosing and managing the reliability of agricultural machinery. It was found that it is necessary to control the time of the transient process in the hydraulic control system of the gearbox, as well as accelerations during gear shifting. We reviewed the previously manufactured control and diagnostic equipment. The KI-12383 and "Effect-02.01" devices were chosen as a prototype for the development of a digital indicator. (Results and discussion) We conducted a simulation, designed and tested a prototype and proved the possibility of developing a digital indicator that can be used as an integrated diagnostic tool to justify the need for repair and maintenance effects of the gearbox. (Conclusions) To monitor the general technical condition of the gearbox, a digital indicator is needed, which will allow, without making changes to the design (K-701, T-150K and their modern analogues), to obtain diagnostic data to substantiate repair and maintenance impacts in order to reduce the risks of failures of the III complexity group during field work.

EVALUATION OF SURFACE DETERIORATION RESULTING FROM THERMAL FATIGUE IN THE OPERATIONAL STATE OF AN H13 PRESSURE DIE CASTING DIE

The failure rate of pressure die casting dies is increasing due to cracks on the die surfaces, leading to thermal fatigue and fracture. This paper aims to investigate the thermal fatigue failure of H13 die-casting die in running conditions by measuring the surface crack dimensions at core and cavity zones of the die during regular intervals of the die-casting process. The effect of length and width of the cracks on the die surface concerning coolant channel positions was analyzed. Transient thermal analysis was performed to investigate the temperature distribution, principal stress and total deformation of the die concerning to the coolant channel position using ANSYS. The maximum deformation of core insert was 0.0094 mm. Zone C of the core insert, which was 223.52 mm from the coolant channel location and corresponding to 139,237 cycles, had the longest crack, measuring 18.98 mm. Owing to greater temperature gradients, Zone Z of the cavity insert, which is situated 76.25 mm from the coolant channel, had the largest crack width, measuring 0.29 mm. The durability of the die casting die obtained from the numerical model (2.8×105 cycles) was in agreement with experimental studies (2.89×105 cycles).

Rope–sheave contact transient analysis in hoisting operations with a bristle model and an arbitrary Lagrangian–Eulerian approach

AbstractThis paper describes the development of a computational model for the rope–sheave contact interaction in reeving systems when the ropes are modeled with an arbitrary Lagrangian–Eulerian approach. This discretization approach has been developed in previous publications as a general and systematic method for the modeling and simulation of reeving systems. However, the rope–sheave contact model was avoided assuming the no-slip contact condition. The contact model developed in this paper introduces specialized ALE-ANCF-cubic rope contact elements that are used to discretize the rope segment winded at the sheave. The contact is modeled using a set of virtual discrete bristles attached to material points in the mid-line of the rope in one end and in contact with the sheave in the other end. Therefore, a second Lagrangian mesh, apart of the ALE mesh used to discretize the rope, is used to define the fixed ends of the bristles. The kinematics and dynamics used to calculate the normal and tangential contact forces are described in detail. The contact model is 3D and can be used to analyze the contact with a sheave groove with arbitrary shape. The tangential contact force model can be used to describe stick and slip contact conditions and, to improve the simulation performance of the model, an LuGre regularization tangential contact force model is used. The rope-sheave contact model is used to analyze the behavior of a simple elevator system. The numerical results show that the static rope-sheave contact interaction agrees well with an analytical solution of the problem. Finally, the same elevator system is analyzed dynamically for a cabin ride of 8 meters with a steady velocity of 1 m/s. Results show that the normal and tangential contact forces during the steady velocity period are not so different from the static solution, but very different from the classical Creep Theory and Firbank’s Theory.

Cascaded *CO−*COH Intermediates on a Nonmetallic Plasmonic Photocatalyst for CO2‐to‐C2H6 with 90.6 % Selectivity

AbstractOxygen vacancies (OV) in nonmetallic plasmonic photocatalysts can decrease the energy barrier for CO2 reduction, boosting C1 intermediate production for potential C2 formation. However, their susceptibility to oxidation weakens C1 intermediate adsorption. Herein we proposed a “photoelectron injection” strategy to safeguard OV in W18O49 by creating a W18O49/ZIS (W/Z) plasmonic photocatalyst. Moreover, photoelectrons contribute to the local multi‐electron environment of W18O49, enhancing the intrinsic excitation of its hot electrons with extended lifetimes, as confirmed by in situ XPS and femtosecond transient absorption analysis. Density functional theory calculations revealed that W/Z with OV enhances CO2 adsorption, activating *CO production, while reducing the energy barrier for *COH production (0.054 eV) and subsequent *CO−*COH coupling (0.574 eV). Successive hydrogenation revealed that the free energy for *CH2CH2 hydrogenation (0.108 eV) was lower than that for *CH2CH2 desorption for C2H4 production (0.277 eV), favouring C2H6 production. Consequently, W/Z achieves an efficient C2H6 activity of 653.6 μmol g−1 h−1 under visible light, with an exceptionally high selectivity of 90.6 %. This work offers a new strategy for the rational design of plasmonic photocatalysts with high selectivity for C2+ products.

Girder quasi-static cumulative displacement-based suspension bridge nonlinear damper leakage diagnosis by eliminating stochastic traffic effects

Fluid viscous dampers (FVDs) are the key energy dissipation devices for long-span suspension bridges, and their leakage poses a threat to the stable and reliable operation of bridge restraint systems. Therefore, this paper proposed an FVD fluid leakage diagnosis method based on girder longitudinal displacement monitoring data. First, the longitudinal vibration equation of the main girder under traffic loads was derived to reveal the displacement characteristic of girder-end motion. On this basis, considering that different displacement components under traffic loads are coupled and transient analysis directly utilizing traffic loads as the excitation is complicated and inefficient, an analysis framework focusing on the influence mechanism of FVD leakage on quasi-static displacement was established. Second, an equivalent mechanical model for simulating the hysteresis relationship of leaked FVD was proposed and verified. Then, the influence of variations in the location, number, leakage level and parameters of the leaked FVD on the quasi-static displacement was studied. Third, the equivalent traffic load (ETL) indicator was constructed to characterize the traffic volume. Furthermore, a quasi-static cumulative displacement and ETL correlation model, which can effectively eliminate the interference of traffic flow variations, was proposed for the leakage diagnosis of FVD. Finally, the proposed method was verified by real suspension bridge monitoring data. The results demonstrated that the proposed method can effectively detect a mild increase in the girder-end cumulative displacement due to FVD fluid leakage.

Enhancing permeability measurements: Bridging the gap between pressure and vacuum techniques for steady and transient states

Air permeability measurement is critical for assessing the integrity of nuclear containment structures, especially in safety-critical environments such as nuclear power plants. This method provides a rapid assessment of leak rates and has the advantage of being non-destructive for field applications. However, existing tools, such as the Cembureau permeameter, are limited to laboratory environments and require specific conditions that are not suitable for real structures. This limitation underscores the need for novel, non-destructive, in-situ measurement techniques, as core sampling structures for analysis are not always feasible. The results presented here concern three different concretes whose permeabilities were measured using the Cembureau under pressure and in vacuum, a unique vacuum measuring cell, and the Torrent Permeameter Tester, also used in vacuum. All these tests differ either in the type of regime, the duration of the test or the pressure. However, we are now able to obtain similar permeability results regardless of the technique used.

Reduced-Toxicity and Highly Luminescent Germanium-Lead Perovskites Enabled by Strain Reduction for Light-Emitting Diodes.

Germanium-lead (Ge-Pb) perovskites provide a promising solution for perovskite optoelectronic devices with reduced toxicity. However, Ge-Pb perovskite light-emitting diodes (PeLEDs) with >30 mol % Ge showed low emission efficiencies [Yang, D.; Zhang, G.; Lai, R.; Cheng, Y.; Lian, Y.; Rao, M.; Huo, D.; Lan, D.; Zhao, B.; Di, D. Germanium-Lead Perovskite Light-Emitting Diodes. Nat. Commun. 2021, 12 (1), 4295]. Here, we apply strain engineering to effectively improve the light emission efficiency and stability of Ge-Pb perovskite films and PeLEDs with 30 and 60 mol % Ge, through A-site modulation. The maximum external quantum efficiencies of the Ge-Pb PeLEDs with 30 and 60 mol % Ge are 8.5% and 3.0% at 3.32 mA cm-2 (∼922 cd m-2) and 0.53 mA cm-2 (∼60 cd m-2), respectively. Time-resolved transient absorption spectroscopy analysis of Ge-Pb perovskite films on different hole-transport layers shows that incorporating 30 mol % Ge into the perovskite with mixed A-site cations can effectively suppress trap-assisted recombination. Further analysis of their current density-voltage (J-V) curves reveals the efficiency loss mechanisms of Ge-Pb PeLEDs with high Ge fractions, indicating the possibility of further improvements.

Dissecting Exciton Dynamics in pH-Activatable Long-Wavelength Photosensitizers for Traceable Photodynamic Therapy.

Tumor-specific activatable long-wavelength (LW) photosensitizers (PSs) show promise in overcoming the limitations of traditional photodynamic therapy (PDT), such as systemic phototoxicity and shallow tissue penetration. However, their insufficient LW light absorption and low singlet oxygen quantum yield (Φ 1O2) usually require high laser power density to produce thermal energy and synergistically enhance PDT. The strong photothermal radiation causing acute pain significantly reduces patient compliance and hinders the broader clinical application of LW PDT. Through the exciton dynamics dissection strategy, we have developed a series of pH-activatable cyanine-based LW PSs (LET-R, R = H, Cl, Br, I), among which the activated LET-I exhibits strong light absorption at 808 nm and a remarkable 3.2-fold enhancement in Φ 1O2 compared to indocyanine green. Transient spectroscopic analysis and theoretical calculations confirmed its significantly promoted intersystem crossing and simultaneously enhanced LW fluorescence emission characteristics. These features enable the activatable fluorescence and photoacoustic dual-modal imaging-escorted complete photodynamic eradication of tumors by the folic acid (FA)-modified LET-I probe (LET-I-FA), under the ultralow 808 nm laser power density (0.2 W cm-2) for irradiation, without the need for photothermal energy synergy. This research presents a novel strategy of dissecting exciton dynamics to screen activatable LW PSs for traceable PDT.

Nonlinear disturbance observer-based finite-time prescribed performance control for MSVs with input saturation

ABSTRACT A finite-time prescribed performance control scheme based on an improved nonlinear disturbance observer is proposed for tracking the trajectory of marine surface vessels (MSVs) under the disturbance of the marine environment. The objective of this paper is to design a nonlinear disturbance observer based on state estimation error feedback that accurately estimates and compensates for the unknown disturbance problem. An adaptive law is applied to estimate the upper bound of its error, removing the requirement of a priori knowledge of the unknown lumped disturbance upper bound. This paper also introduces a non-logarithmic performance function in order to efficiently solve the problem of considering both transient and steady state MSVs performance simultaneously. In addition, the adaptive dynamic system is introduced to overcome the adverse effects caused by nonlinear saturation factors for the input-constrained problem. With this control strategy, the system output error converges to a pre-defined region within a finite amount of time and meets the prescribed performance requirements. Finally, simulation and comparison verify the control scheme's effectiveness and superiority.

Obtaining high-entropy alloy coating by laser remelting of metal powder composition: mathematical modelling of the transient thermal state

Obtaining high-entropy alloy coating by laser remelting of metal powder composition: mathematical modelling of the transient thermal state

Direct observation of photoinduced sequential spin transition in a halogen-bonded hybrid system by complementary ultrafast optical and electron probes

A detailed understanding of the ultrafast dynamics of halogen-bonded materials is desired for designing supramolecular materials and tuning various electronic properties by external stimuli. Here, a prototypical halogen-bonded multifunctional material containing spin crossover (SCO) cations and paramagnetic radical anions is studied as a model system of photo-switchable SCO hybrid systems using ultrafast electron diffraction and two complementary optical spectroscopic techniques. Our results reveal a sequential dynamics from SCO to radical dimer softening, uncovering a key transient intermediate state. In combination with quantum chemistry calculations, we demonstrate the presence of halogen bonds in the low- and high-temperature phases and propose their role during the photoinduced sequential dynamics, underscoring the significance of exploring ultrafast dynamics. Our research highlights the promising utility of halogen bonds in finely tuning functional properties across diverse photoactive multifunctional materials.

XIST dampens X chromosome activity in a SPEN-dependent manner during early human development.

XIST (X-inactive specific transcript) long noncoding RNA (lncRNA) is responsible for X chromosome inactivation (XCI) in placental mammals, yet it accumulates on both X chromosomes in human female preimplantation embryos without triggering X chromosome silencing. The XACT (X-active coating transcript) lncRNA coaccumulates with XIST on active X chromosomes and may antagonize XIST function. Here, we used human embryonic stem cells in a naive state of pluripotency to assess the function of XIST and XACT in shaping the X chromosome chromatin and transcriptional landscapes during preimplantation development. We show that XIST triggers the deposition of polycomb-mediated repressive histone modifications and dampens the transcription of most X-linked genes in a SPEN-dependent manner, while XACT deficiency does not significantly affect XIST activity or X-linked gene expression. Our study demonstrates that XIST is functional before XCI, confirms the existence of a transient process of X chromosome dosage compensation and reveals that XCI and dampening rely on the same set of factors.

Power Components Mean Values Determination Using New Ip-Iq Method for Transients

This paper deals with the quasi-instantaneous determination (in a single-step response time) of apparent, active, and reactive (i.e., blind and distortion) power mean values including the total power factor, total harmonic distortion, and phase shift of fundamentals of a power electronic and electrical system (PEES) using the ip-iq method, which is the main contribution of the paper. The power components’ mean values are investigated during the transient and steady states. The power components’ mean values can be determined directly from phase current and voltage quantities, using an integral calculus over one period within the next calculation step and using moving average and moving rms techniques (or digital filtering). Consequently, the power factor can be evaluated with known values of a phase shift of fundamentals (using a Fourier analysis). The results of this study show how a distortion power component during transients is generated even under a harmonic supply and linear resistive–inductive load. The paper contains a theoretical base, modeling, and simulation for the three and single phases of the transients in power electronic systems. The worked-out results can be used to determine and size any PES. The presented approach brings a detailed time waveform verified by simulations in Matlab/Simulink 2022a and the Real-time HW Simulator Plecs RT Box 1.

Screening and functional verification of drought resistance-related genes in castor bean seeds

Drought is one of the natural stresses that greatly impact plants. Castor bean (Ricinus communis L.) is an oil crop with high economic value. Drought is one of the factors limiting castor bean growth. The drought resistance mechanisms of castor bean have become a research focus. In this study, we used castor germinating embryos as experimental materials, and screened genes related to drought resistance through physiological measurements, proteomics and metabolomics joint analysis; castor drought-related genes were subjected to transient silencing expression analysis in castor leaves to validate their drought-resistant functions, and heterologous overexpression and backward complementary expression in Arabidopsis thaliana, and analysed the mechanism of the genes' response to the participation of Arabidopsis thaliana in drought-resistance.Three drought tolerance-related genes, RcECP 63, RcDDX 31 and RcA/HD1, were obtained by screening and analysis, and transient silencing of expression in castor leaves further verified that these three genes corresponded to drought stress, and heterologous overexpression and back-complementary expression of the three genes in Arabidopsis thaliana revealed that the function of these three genes in drought stress response.In this study, three drought tolerance related genes, RcECP 63, RcDDX 31 and RcA/HD1, were screened and analysed for gene function, which were found to be responsive to drought stress and to function in drought stress, laying the foundation for the study of drought tolerance mechanism in castor bean.

Transient Analysis on the Crosswind Effect to the Aerodynamics of High-speed Train Travelled on the Bridge Between Two Tunnels at Jakarta -Bandung Track

The rapid evolution of global transportation technology is exemplified by Indonesia's innovative high-speed train initiative, linking Jakarta and Bandung in an impressive 45 minutes. Operating at 350 km/h, the HST CR400AF underscores the importance of aerodynamics in high-speed rail systems. This study delves into the significant impact of crosswind on key aerodynamic factors (drag, lift, rolling moment) within the tunnel-bridge-tunnel configuration. Leveraging Computational Fluid Dynamics (CFD) through ANSYS FLUENT, the analysis explores crosswind variations at 0 m/s, 10 m/s, and 25 m/s. Results reveal a proportional increase in aerodynamic load with higher crosswind intensities: 1.67 times for drag, 58.8 times for lift, and 29.8 times for rolling moment. Notable observations include pronounced aerodynamic load fluctuations during the "OUT" process, with the head section bearing the greatest load, followed by the tail and middle sections. These findings contribute valuable insights to the global discourse on enhancing safety and efficiency in high-speed rail systems

Numerical Analysis of Transient Convective Heat Transfer in a Dental Implant

Hot substance consumption can have adverse effects on the neighbouring bone tissue in proximity to a dental implant. Elevated temperatures at the interface between the bone and implant could potentially disrupt the local cellular processes crucial for osteointegration. The primary goal of this study was to analyse the temperature and heat flux distributions within the implant body, surrounding bone, and bone-implant interface when the implant system subjected to a thermal load of transient nature. Transient thermal finite element analysis was utilised to analyse a three-dimensional model of dental implant with three different lengths – 6, 10, and 13 mm – placed in a mandible section. In order to obtain realistic results, thermal load was applied through convection on the outer surface of the prosthesis, simulating exposure to a hot liquid with the temperature and convection heat transfer coefficient of 67°C and 0.005 W/mm2°C, respectively. The temperature of the other components in the model was maintained at a constant 37°C. The results showed that increasing the implant length generally led to lower temperature and heat flux levels in the implant body, bone, and bone-implant interface. The highest temperature and heat flux values were concentrated in the superior region, gradually decreasing toward the inferior region. Importantly, all maximum temperature values remained below the limits associated with cellular bone necrosis and remodelling, thereby reducing the risk of osteoporosis. It is noteworthy that, when considering transient thermal load, shorter implants pose a significantly higher risk of implant failure compared to longer ones.