Dynamic Leakage Research Articles

Research on the Dynamic Leaking and Diffusion Law of Hydrogen-Blended Natural Gas under the Soil–Atmosphere Coupled Model

With the breakthrough in mixing hydrogen into natural gas pipelines for urban use, the widespread application of hydrogen-blended natural gas (HBNG) in energy delivery is imminent. However, this development also introduces significant safety concerns due to notable disparities in the physical and chemical properties between methane and hydrogen, heightening the risks associated with gas leaks. Current models that simulate the diffusion of leaked HBNG from buried pipelines into the atmosphere often employ fixed average leakage rates, which do not accurately represent the dynamic nature of gas leakage and diffusion. This study uses computational fluid dynamics (CFD) 2024R1 software to build a three-dimensional simulation model under a soil–atmosphere coupling model for HBNG leakage and diffusion. The findings reveal that, in the soil–atmosphere coupling model, the gas diffusion range under a fixed leakage rate is smaller than that under a dynamic leakage rate. Under the same influencing factors in calm wind conditions, the gas primarily diffuses in the vertical direction, whereas under the same influencing factors in windy conditions, the gas mainly diffuses in the horizontal direction.

Membrane tension evolution and mechanical regulation of melittin-induced membrane poration

Abstract Membrane tension plays a crucial role in various fundamental cellular processes, with one notable example being the T cell-mediated elimination of tumor cells through perforin-induced membrane perforation by amplifying cellular force. However, the mechanisms governing the regulation of biomolecular activities at the cell interface by membrane tension remain elusive. In this study, we investigated the correlation between membrane tension and poration activity of melittin, a prototypical pore-forming peptide, using dynamic giant unilamellar vesicle leakage assays combined with flickering tension analysis, molecular dynamics simulations, and live cell assays. The results demonstrate that an increase in membrane tension enhances the activity of melittin, particularly near its critical pore-forming concentration. Moreover, peptide actions such as binding, insertion, and aggregation in the membrane further influence the evolution of membrane tension. Live cell experiments reveal that artificially enhancing membrane tension effectively enhances melittin’s ability to induce pore formation and disrupt membranes, resulting in up to a ten-fold increase in A549 cell mortality when exposed to a concentration of 2.0-μg⋅mL−1 melittin. Our findings elucidate the relationship between membrane tension and the mechanism of action as well as pore-forming efficiency of melittin, while providing a practical mechanical approach for regulating functional activity of molecules at the cell-membrane interface.

3D-printing allows for fluid-controlled linear actuators with unconventional shapes

BackgroundPneumatic actuators are widely used in applications like (medical) robots, or prostheses. Pneumatic actuators require a complex manufacturing process and are produced in standardized dimensions to reduce costs. Over the last decade 3D-printing has emerged as a cost-effective and efficient production method in medical applications. 3D-printing can also function as a cost-efficient alternative production method for pneumatic actuators. ObjectiveThe goal of this research is to study the possibility of creating a pneumatic linear actuator with 3D-printing. Furthermore, the aim is to use the advantage of 3D-printing to create pneumatic actuators with non-circular cross-sections. MethodologyTo evaluate the performance of a 3D-printed pneumatic actuator, a test setup was designed and built to measure the leakage and sliding friction force. Furthermore, two pneumatic actuators with a non-conventional cross-sectional shape were designed and their performance was tested and compared with a 3D-printed cylindrical pneumatic actuator, since these tests only ran once, the results are more a guideline. During the manufacturing of the cylinders, no post-processing techniques were used. ResultsThe functioning of a 3D-printed circular pneumatic actuator was proven with low static leakage rates of 2.5%, low dynamic leakage rates of approximately 1%, and a maximum friction force of ▪. Furthermore, the results show that it is possible to print functioning pneumatic cylinders with a non-cylindrical concave cross-section. The non-conventional cylinders were tested up to ▪ with maximum dynamic leakage of ▪. ConclusionThis study demonstrates a method to create functional pneumatic linear actuators with 3D-printing. It was possible to create 3D-printed actuators with a conventional shape, e.g. circular and unconventional shapes e.g. stadium/oval shape and a kidney shape. The leak rates for conventional and unconventional shapes were in the same range. This opens up the world for more design freedom in pneumatic actuators.

Seasonal scour and siltation induced spatiotemporal variations in riverbed sediment leakage coefficients as measured via the thermal tracer method

Riverbed scour and siltation can change the hydraulic conductivity and thickness of sediments, leading to notable spatiotemporal variations of groundwater–surface water interaction. However, correlated quantitative research on the dynamic leakage coefficient (LC) remains lacking under riverbed scour and siltation. Based on dynamic monitoring and analysis of sediment medium properties, river-groundwater levels, and temperature profiles in the section of Liao River, this study compared the applicable conditions of different thermal analytical models and identified spatiotemporal variations in the LC values induced by riverbed scour and siltation. The results showed that: (1) The thermal tracer method combined with river-groundwater level monitoring can effectively quantify spatiotemporal variations in the LCs of riverbed sediment. Based on the sediment temperature presents diurnal fluctuations and gradient characteristics in different seasons, the LCs in summer, spring, and autumn compared to winter in seasonally frozen regions should be calculated using transient and steady-state analytical solution models, respectively. (2) The LCs ranged from 0.47 to 24.90 × 10-6 s−1, showed larger temporal variability than spatial, increased from the river bank to the center, and had larger values in autumn and winter. (3) Distinct from previous findings, the riverbed underwent a scouring process associated with reductions in the incoming sediment coefficient as the river stage shifted from high to low, eroding the surface 4–8 cm of sediment. During this process, the LC increased by 40 to 420%. Further, the influence of riverbed scour and siltation on the LC varied by river section. Near the riverbank, the sediment LC was primarily controlled by hydraulic conductivity related to the coarsening of sediment lithology; however, it was influenced by variations in both sediment thickness and hydraulic conductivity near the riverbed center. Collectively, these results further understand the mechanisms underlying changes in the sediment LC induced by riverbed scour and siltation, as well as provide a scientific basis for ensuring the sustainable development of riverside water sources under such changes.

Gate leakage modeling in lateral β -Ga2O3 MOSFETs with Al2O3 gate dielectric

We present a detailed model of the static and dynamic gate leakage current in lateral β-Ga2O3 MOSFETs with an Al2O3 gate insulator, covering a wide temperature range. We demonstrate that (i) in the DC regime, current originates from Poole–Frenkel conduction (PFC) in forward bias at high-temperature, while (ii) at low temperature the conduction is dominated by Fowler–Nordheim tunneling. Furthermore, (iii) we modeled the gate current transient during a constant gate stress as effect of electron trapping in deep levels located in the oxide that inhibits the PF conduction mechanism. This hypothesis was supported by a TCAD model that accurately reproduces the experimental results.

Evaluation of Trapping Behaviors in Forward Biased Schottky-Type p-GaN Gate HEMTs

In this work, we investigated the trapping behaviors in the Schottky-type p-GaN gate high-electron-mobility transistors (HEMTs) under positive gate bias using the current-transient method. By excluding the trapping effect introduced by the measurement voltages, the actual recovery curves of drain transient current under different gate filling voltages and temperatures were extracted. The impacts of electron trapping, hole injection, and electron–hole recombination on the threshold voltage instability can be effectively distinguished according to the results of drain current variations under different gate stresses. In addition, the dynamic drain leakage current was monitored to confirm the electron–hole recombination and optical pumping of trapped electrons. The properties of three electron traps can be obtained based on the time constant spectrum (TCS), and a database of the gate-trapping behaviors in the GaN-based devices was constructed. The combined results may provide a basis for a better understanding of the threshold voltage instability under positive gate stress in the p-GaN gate HEMTs.

Research on Characteristics of Hydrogen Dynamic Leakage and Combustion at High Pressure

Hydrogen is promoted as an alternative energy given the global energy shortage and environmental pollution. A scientific basis can be provided for the safe use and emergency treatment of hydrogen based on hydrogen leakage and combustion behavior. This study examined the stagnation parameters of dynamic hydrogen leakage and flame propagation in turbulent jets under normal temperatures and high pressure. Based on van der Waals’ equation of state for gas, a theoretical model for completely predicting stagnation parameters, outlet gas velocity, and flow rate changes in the process of high-pressure hydrogen leakage could be proposed, and the calculation result of this model was compared with the experimental result, with an error within ±10%. The progression and propagation of the flame in turbulent jets after ignition were recorded using the background-oriented schlieren image technology, and the propagation speed of flame from the ignition position downward and upward was calculated. Moreover, the influence of initial pressure, nozzle diameter, and ignition position on the flame propagation process and propagation speed was analyzed.

Study on hydrogen dynamic leakage and flame propagation at normal-temperature and high-pressure

Experiments of two nozzle diameters at three ignition positions under three initial pressure conditions were carried out. The dynamic leakage characteristics and the stagnation parameters of flame propagation under normal temperature and high pressure conditions were studied. Based on van der Waal's equation, a model for predicting stagnation parameters, jet velocity and flow rate of hydrogen leakage was proposed. Compared with the experimental results, it was found that the maximum error occurred when the initial pressure was 200 bar. Theoretical leakage time was 1.66 s, experiment leakage time was 1.84 s, the error was 9.8%. Background-Oriented Schlieren image technology was used to record the flame development and propagation process after ignition. For the same nozzle diameter and ignition location, the higher pressure caused the flame to propagate faster upstream and downstream. For the same initial pressure and ignition position, a flame with a large nozzle diameter propagated faster upstream and downstream. For the same initial pressure and nozzle diameter, the farther the ignition point was, the greater the slope of flame attenuation when propagating upstream. Due to the attenuation of hydrogen concentration and jet velocity, the flame propagation velocity to the downstream decreased linearly with the increase of distance from the ignition location.

Optimization of grounding resistance in multitrain DC subway system based on MOEA/D‐DE

AbstractCurrently, in multitrain DC subway system, abnormal increase of rail potential (RP) and stray current (SC) has seriously threatened the safe operation of the system. Over voltage protection device (OVPD) is generally chosen to control the RP, but its action process may increase the amplitude of SC seriously. Here, the grounding resistance of OVPD is optimized by a proposed multi‐objective decomposition algorithm based on differential evolution (MOEA/D‐DE) to suppress the rise of RP and SC synergistically. Firstly, the simulation model of the DC subway system with multitrain is built, the power flow calculation is conducted, and the dynamic RP and leakage current (LC) at the location of traction substation are obtained. Secondly, the double objective optimization model of maximum RP and LC is established and solved by MOEA/D‐DE. Finally, the effectiveness of the proposed method is verified based on the data of Guangzhou Metro Line 2. Results show that the SC of the system can be controlled effectively with OVPD grounding mode after optimization, and integrated control of RP and SC can be accomplished.

Bonding of PMMA to silicon by femtosecond laser pulses

Many devices and objects, from microelectronics to microfluidics, consist of parts made from dissimilar materials, such as different polymers, metals or semiconductors. Techniques for joining such hybrid micro-devices, generally, are based on gluing or thermal processes, which all present some drawbacks. For example, these methods are unable to control the size and shape of the bonded area, and present risks of deterioration and contamination of the substrates. Ultrashort laser bonding is a non-contact and flexible technique to precisely join similar and dissimilar materials, used both for joining polymers, and polymers to metallic substrates, but not yet for joining polymers to silicon. We report on direct transmission femtosecond laser bonding of poly(methyl methacrylate) (PMMA) and silicon. The laser process was performed by focusing ultrashort laser pulses at high repetition rate at the interface between the two materials through the PMMA upper layer. The PMMA-Si bond strength was evaluated as a function of different laser processing parameters. A simple, analytical, model was set up and used to determine the temperature of the PMMA during the bonding process. As a proof of concept, the femtosecond-laser bonding of a simple hybrid PMMA-Si microfluidic device has been successfully demonstrated through dynamic leakage tests.

Reliability Analysis of Radiation Tolerant Low Voltage CCCII Circuit For Space Applications

In this paper, the impact of radiation on the MOS devices is investigated on recently reported programmablesecond generation Current Controlled Conveyor (CCCII) wherein some updates are suggested to take Hot Carrier Injection, Bias Temperature Instability, and Time Dependent Dielectric Breakdown into account. As radiation is yet another important factor that causes change in threshold voltage, the transistors which are amenable to larger threshold shift and may lead to functional failure are identified first. Subsequently, three possibilities; uses of all thin oxide devices, all thick oxide devices, and mixed devices are being investigate and it is found that while using mixed devices, the circuit becomes functional at lower voltage without any effective increase in leakage current. Architecture is updated to enhance the performance of circuits under time-based ageing and radiation environment. The major challenge is to control dynamic leakage and radiative noise due to imposed radiation. All simulations are carried out using 28nm CMOS technology models in Cadence Virtuoso environment using ±1.0V supply voltage and results have been verified with post layout netlist. Proposed circuit can function at low voltage with the reduced degradation for 8 years at 25 °C consumes less area as compared to the existing CCCII circuit with 0.008 FIT value.

Multi-objective optimization design of two-dimensional proportional valve with magnetic coupling

As a hydro-mechanical servo system, the whole performance of the two-dimensional proportional valve with magnetic coupling (2D-MC-PV) highly depend on certain structural parameters. To tradeoff good static/dynamic characteristics, good working stability and low leakage pilot stage, a multi-objective optimization is inevitable for preliminary design stage. Therefore, this paper proposes a multi-objective optimization method based on AMESim and Matlab/Simulink co-simulation model, which optimizes key structural parameters by adjusting weight coefficients (balancing static, dynamic, and pilot leakage performance). Considering that magnetic coupling (MC) is the key component for 2D-MC-PV to realize spool position feedback and translational motion conversion, the analytical equation of MC is derived based on the Coulomb’s law and the law of equivalent magnetic charge, and the Monte Carlo method is used to calculate. Finally, the prototype of 2D-MC-PV is designed and manufactured, and a special experimental platform is built to test the static/dynamic characteristics. The experimental results show that 2D-MC-PV has good working stability: under working pressure of 20 MPa, the maximum no-load flow rate is 108.8 L/min with the hysteresis of 3.36%, and the amplitude and phase frequency width is 27.8 and 36.6 Hz. It shows that the multi-objective optimization method proposed in this paper can be used as an optimization method for 2D-MC-PV.

Electrical characteristics investigation of ferroelectric memories using stacked and mixed hafnium zirconium oxides

• Ferroelectric characteristics of mixed and stacked HfZrO devices were investigated. • Stacked HfZrO device showed a much stronger ferroelectricity than mixed one. • A surface nitrogen plasma treatment can alleviate ferroelectric domain pinning. • Nitrogen incorporation into stacked HfZrO further improved the endurance cycling. In this work, we investigate ferroelectric characteristics of hafnium zirconium oxide (HfZrO) metal-ferroelectric-metal (MFM) devices with mixed and stacked film structure. The experimental results reveal that the stacked HfZrO MFM device has a lower dynamic leakage and stronger ferroelectric polarization value of approximately 27.3 μC/cm 2 , which is much higher than 17.5 μC/cm 2 measured from mixed HfZrO MFM device. From endurance cycling test, we also confirm that the stacked HfZrO MFM capacitor with a remote nitrogen plasma treatment featuring a large initial hysteresis window can achieve a stable operation up to 10 8 cycles at an operating voltage of 2.5 V, which is even longer than that of mixed HfZrO MFM capacitor by one order of magnitude. Therefore, the stacked MFM structure with proper interface engineering provides a promising approach for the process integration of ferroelectric memory under the comprehensive consideration of device performance and endurance.

Dynamic physical model of Japanese hydrogen refueling stations for quantitative trade-off study between benefit and risk

As hydrogen refueling stations come into increasing use and being common, both benefit and safety are required. To promote its use, an optimized trade-off must be reached for hydrogen station configurations. We constructed a dynamic physical model of the station that enables quantitative evaluation of benefit and risk for a trade-off study, aiming to formulate a technical standard for hydrogen refueling stations that would realize high-level safety and rationalize the equipment configuration and operation. The proposed model enables a quantitative evaluation of both the hydrogen refueling time during normal operation and external leakage under several accident scenarios. This paper discusses the modeling concept and approach of the proposed model and reports quantitative verification results of the proposed model based on past experimental test results. In this study, capability of the proposed model for quantitative evaluation of dynamic behavior of hydrogen during refueling operation at the station reflecting its configuration and operation condition was demonstrated. This feature of the proposed model also provides a physical and realistic dynamic leakage rate for calculating individual risks compared to the conventional risk analysis method.

<em>In Vivo</em> Vascular Permeability Detection in Mouse Submandibular Gland

Saliva plays an important role in oral and overall health. The intact endothelial barrier function of blood vessels enables saliva secretion, whereas the endothelial barrier dysfunction is related to many salivary gland secretory disorders. The present protocol describes an in vivo paracellular permeability detection method to evaluate the function of endothelial tight junctions (TJs) in mouse submandibular glands (SMG). First, fluorescence-labeled dextrans with different molecular weights (4 kDa, 40 kDa, or 70 kDa) were injected into the angular veins of mice. Afterward, the unilateral SMG was dissected and fixed in the customized holder under a two-photon laser-scanning microscope, and then images were captured for blood vessels, acini, and ducts. Utilizing this method, the real-time dynamic leakage of the different-sized tracers from blood vessels into the basal sides of the acini and even across the acinar epithelia into the ducts was monitored to evaluate the alteration of the endothelial barrier function under physiological or pathophysiological conditions.

Optimizing and Recuperating the Leakages in Low Voltage CMOS Circuits

With the advancement of technology, small and handy electronic devices are built with low supply voltage and lower power dissipation in designing deep submicron static CMOS circuits. Small devices scaling down with burst-mode type integrated circuits have two major challenges: area and power dissipation. This paper presents a method for decreasing dynamic power, area, and leakage of application-specific integrated circuits without sacrificing performance. The High Threshold Leakage Control Transistor, TG-Based Technique, Supply Voltage Scaling, Sleep Transistor approaches are covered, and a dynamic CMOS architecture with stack transistor. With certain area and delay considerations, these strategies are utilized to diminish both types of power dissipation in the CMOS logic designs.

Flood Routing Model Coupled with Dynamic Leakage Losses for Ephemeral Rivers with Large Potholes.

Ephemeral rivers commonly occur in regions with a shortage of water resources, and their channel configuration tends to change substantially owing to long drying times and artificial sand extraction. During short-term water conveyance, water storage in large potholes and leakage along the dry riverbed retards the flow, which is detrimental for the river landscape and ecological water demand. The objective of this study is to evaluate the flow process corresponding to a certain release scheme. A coupled dynamic leakage loss and flood routing model was established to predict the flood routing distance for dry rivers with potholes and strong leakage. The model mainly includes three sub-models of flow dynamics, dynamic leakage loss and water balance along multiple cross sections of the river channel. The water head was dominated by flow velocity and the overflow from potholes. The model was applied to Yongding River, a typical ephemeral river in northern China, and the model parameters were calibrated and verified using monitoring data from ecological water releases into the Yongding River in 2019 and 2020, thus, making the model more stable and reliable. Finally, the model was used to evaluate the impact of cross section optimization and pothole treatment on the flow process. This study can provide scientific guidance for ecological water conveyance and the ecological restoration of ephemeral rivers.

Dynamic EFI and circuit analysis case studies on integrated circuit buried via void defects

Buried via voids defect beneath the metal layer of an integrated circuit (IC) has always been a challenge to localize. The importance of dynamic electrical fault isolation (EFI) approaches, automated multi-level circuit net trace, and test bench simulation on buried via void localization are discussed in this paper. Three buried via void case studies will be discussed, including a hard functional failure, an ATPG soft failure, and a high dynamic leakage current (IDD) failure.

Apex seal bottom pressure prediction and leakage analysis of The Hydrogen Fueled Wankel Rotary Engine based on dynamics

The development of hydrogen-fueled Wankel rotary engine is restricted by the leakage problem, especially the apex seal leakage (ASL). In the study, the ASL area is divided into the geometric leakage area (GLA) and the dynamic leakage area (DLA). The models of under-seal pressure prediction and vibration of apex seal are established. The mechanism of GLA and DLA and the effects of key parameters on them are analyzed. Results show that the DLA decreases with the increase of discharge coefficient, clearance between apex seal and slot. There is no DLA when the rotation speed is slower than 2000 rpm or higher than 7000 rpm. Besides, the value of DLA is only 11.23% of GLA and the GLA can be reduced by 88.57% when using a corner-piece structure. The total leakage decreases with the increase of rotation speed. Finally, some measures to reduce the leakage are given.

Study on analytical model of gas diffusion in underground pipe network

Through the analysis of gas pipeline leakage causes and gas leakage diffusion model, the preventive measures for gas leakage accidents are put forward, which is of great significance for the harm of gas leakage and explosion accidents. In this paper, the mathematical model of gas leakage is established through hydrodynamics and pipeline gas motion equation, and the leakage process is analyzed by means of numerical simulation, the change law of gas dynamic leakage is obtained from the aspects of gas leakage conditions, gas movement and diffusion law.