Average Propagation Time Research Articles

Propagation Dynamics from Meteorological to Agricultural Drought in Northwestern China: Key Influencing Factors

Meteorological and agricultural droughts are inherently correlated, whereas the propagation mechanism between them remains unclear in Northwestern China. Investigating the linkages between these drought types and identifying the potential influencing factors is crucial for effective water resource management and drought mitigation. This study adopted the Standardized Precipitation Evapotranspiration Index (SPEI) and Standardized Soil Moisture Index (SSMI) to characterize the meteorological and agricultural droughts from 1960 to 2018. The propagation time between these droughts was detected using the Pearson correlation analysis, and the cross-wavelet transform and wavelet cross-correlation were utilized to describe their linkages across the time–frequency scales. The grey relational analysis was applied to explore the potential factors influencing the propagation time. The results revealed that the agricultural drought typically lagged behind the meteorological drought by an average of 6 months in Northwestern China, with distinct seasonal and regional characteristics. The shortest propagation time occurred in the summer (3 months), followed by the autumn (4 months), and the propagation time was longer in the winter (8 months) and spring (9 months). Additionally, the average propagation time was longer in the plateau climate zone (8 months) than in the southeastern climate zone (6 months) and the westerly climate zone (4 months). There was a multi-timescale response between the meteorological and agricultural droughts, with a relatively stable and significant positive correlation over long timescales, whereas the correlation was less clear over short timescales. The key factors influencing the propagation time were soil moisture, elevation, precipitation, and potential evapotranspiration. Furthermore, the wavelet cross-correlation between agricultural and meteorological droughts was relatively high, with a lag of 0 to 3 months; as the timescale increased, the fluctuation period of their cross-correlation also increased.

Mitigating thermal runaway propagation in high specific energy lithium-ion battery modules through nanofiber aerogel composite material

Thermal runaway and its propagation within lithium-ion battery systems pose significant challenges to widespread adoption in electric vehicles and energy storage systems. Deploying a thermal barrier between adjacent batteries is a common and effective strategy to prevent thermal propagation. This experimental study evaluates the inhibitory effect of nanofiber aerogel on thermal propagation within high-energy-density lithium-ion battery modules. The results indicate that increasing the thickness of nanofiber aerogel prolongs the average time interval between thermal runaway propagation events between adjacent batteries and increases their peak temperature difference, while the maximum surface temperature of each battery exhibits an overall downward trend.Specifically, compared to no nanofiber aerogel, a 0.5 mm nanofiber aerogel extends the average propagation time by 2 times, and a 1.0 mm nanofiber aerogel successfully prevents thermal propagation from the third to the fourth battery, with an average time extension of nearly 6 times. Furthermore, it is found that thermal runaway propagation can be effectively prevented when the aerogel thickness exceeds 2.0 mm. The microstructure of both fresh and damaged nanofiber aerogels was examined using Scanning Electron Microscopy to validate and analyze their robust durability. This study provides valuable insights for designing safer high-energy-density battery systems.

Mixed Model and Gaussian Process to Investigate the External Influence on the Propagation Time of Ultrasonic Waves on Masonry Walls

The ultrasonic testing has been considered a promising method for diagnosing and characterizing masonry walls. As ultrasonic waves tend to travel faster in denser materials, their use is common in evaluating the conditions of various materials. Presence of internal voids, e.g., would alter the wave path, and this distinct behavior could be employed to identify unknown conditions within the material, allowing for the assessment of its condition. Therefore, we applied mixed models and Gaussian processes to analyze the behavior of ultrasonic waves on masonry walls and identify relevant factors impacting their propagation. We observed that the average propagation time behavior differs depending on the material for both models. Additionally, the condition of the wall influences the propagation time. Gaussian process and mixed model performances are compared, and we conclude that these models can be useful in a classification model to automatically identify anomalies within masonry walls.

From meteorological to agricultural drought: Propagation time and probabilistic linkages

Study regionYangtze River Basin, China Study focusAs agricultural drought originates from meteorological drought, exploring the propagation from meteorological to agricultural drought is an important step in providing early warning of agricultural drought. In this study, Standardized Precipitation Index (SPI) and Improved Soil Moisture Anomaly Percentage Index (ISMAPI) were adopted to indicate meteorological and agricultural droughts, respectively. The propagation time from meteorological drought to agricultural drought was identified, and probabilistic linkages between the two types of drought were investigated using the copula function and Bayesian network. New hydrological insightsThe average propagation time from meteorological to agricultural drought in the Yangtze River Basin (YRB) is 48 d. The propagation times in the summer and autumn are shorter than those in the spring and winter. The occurrence probability of more serious agricultural drought gradually increases with meteorological drought intensity. Agricultural and meteorological drought events were matched using the proposed drought event-matching method. In the YRB, approximately 72.4% of meteorological drought events may translate into agricultural drought events. Generally, an agricultural drought event that has the same drought category as that of the given meteorological drought event is most likely to occur. Regional differences in drought propagation time and occurrence probability of agricultural drought may be related to variations in climatic conditions across regions.

Characterization and propagation from meteorological to groundwater drought in different aquifers with multiple timescales

Study regionZhanjiang City District, southwest of Guangdong Province, China, was selected as the case study area owing to its relatively frequent occurrence of droughts and groundwater overexploitation. Study focusThis study presents a useful framework to characterize the propagation from meteorological drought (MD) to groundwater drought (GD) in different aquifers from the perspective of multiple timescales. Two standardized drought indices, i.e., standardized groundwater index and standardized precipitation index with different timescales (1–48 months), were used to examine the propagation time from MD to GD in different aquifers. Three clusters, i.e., natural(P)-, natural+human(P + H)-, and human(H)-induced drought, were considered for revealing the potential driving mechanism of propagation. Four characteristic mechanisms of lag, pooling, lengthening, and attenuation were used to analyze the propagation process from MD to GD, among which the lag characteristic, showing the propagation time, was discussed corresponding to varied clusters. New hydrological insights for the regionResults indicate the following: (1) The propagation time in different aquifers varied; that is, in the shallow aquifer, the average propagation time showed 1 month for the P cluster and 3 months for the P + H cluster, while the propagation time in the middle and deep aquifers were found to be longer than that in the shallow layer though much uncertainty remained for the former. (2) The influences from MD obtained the decreasing order of P > P + H>H. The propagation time of the P + H cluster was longer than that of the P cluster, suggesting the negative influence of human activities. This study can provide additional information for policymakers involved in groundwater management during a drought.

Investigation for the effect of side plates on thermal runaway propagation characteristics in battery modules

• Energy flow of battery modules with and without side plates was clearly quantified. • Effect of side plates on thermal runaway propagation behaviors was fully analyzed. • Mechanisms affecting failure point of a module with side plates were clarified. • Guidelines for selecting parameter of side plates was proposed for a safer module. Side plates have been commonly arranged around lithium-ion batteries to ensure their structural stability when combining modules, which could affect the heat transfer path once thermal runaway propagation occurs in the battery modules, owing to the good thermal conductivity of side plates. However, the effect of side plates on the propagation characteristics is not comprehensively studied. In this paper, a validated three-dimensional thermal runaway propagation model of a battery module is used to investigate the propagation behaviors under different design schemes with side plates. A parametric study is carried out to determine the energy flow distribution of battery modules with and without side plates, and to evaluate the effect of the structural and thermal boundary parameters of the side plates on the failure propagation behaviors. The results indicate that the side plates delay the initial thermal runaway trigger time, considerably affect energy flow distribution, and aggravate the heat transfer. Approximately 40.8% of effluent energy passes through the side plates, dominating the critical point for battery thermal runaway propagation. Furthermore, with side plates surrounding the module, the initial thermal runaway trigger time is delayed by 12.7%, whereas the average propagation time interval between adjacent batteries is shortened by 27.4%, compared to those without side plates. An increase in the thickness, area, and aspect ratio of the side plates can postpone the initial thermal runaway trigger time, while shortening the average propagation time interval. This work adds new knowledge in the failure propagation mechanism within battery modules with side plates, enlightening the thermal safety design of high-energy battery modules.

Study on the Thermal Runaway and Its Propagation of Lithium-Ion Batteries Under Low Pressure

When lithium-ion batteries (LIBs) are located at high altitude and low pressure,the characteristics of thermal runaway (TR) and its propagation are different,such as time to TR, the toxicity of TR gases, TR propagation time, mass loss rate, etc. In this article, the author summarized a series of relevant literatures and proposed an instrument that can be used to analyse the TR behavior at different pressure. It is found that: with the decrease of ambient pressure, the TR trigger time becomes longer and the maximum surface temperature decrease. Moreover, the gas released by TR becomes more toxic as the environmental pressure decreases. Beside, the average propagation time between adjacent LIBs is not much difference when the environmental pressure decreases, and when the 18,650 battery module is distributed in a cylindrical shape, the thermal runaway propagation path is basically unchanged as the environmental pressure decreases. This work details TR and its propagation feature under different pressure, and can provide the guidelines for the Air transportation of LIBs.

A comparative analysis on thermal runaway behavior of Li (NixCoyMnz) O2 battery with different nickel contents at cell and module level

The problem of thermal runaway (TR) propagation challenges the safety design of battery packs, because it aggravates the thermal hazards to accidents. There are many unsolved scientific questions in understanding the mechanisms of TR and its propagation behavior for large format lithium-ion batteries (LIBs). LiNixCoyMnzO2(NCM) is considered as one of the most promising cathode materials for lithium-ion batteries LIBs, given its higher energy design and lower cost. However, higher Nickel (Ni) content of cathode material worsens the thermal stability of LIBs. This paper provides a comparative analysis on the TR propagation behavior of NCM battery with different Ni ratios. Results have shown that when the characteristic temperatures of TR {T1, T2, T3}and the specific electrochemical energy of the cell are similar, TR propagation behavior will be similar, no matter what kinds of chemistry the cell has. Observation suggests that the average propagation time within a large format cell is 7−10 s in module tests. Besides, the internal temperature of the cell has an order of NCM622 ≥ NCM523 ≥ NCM111,whereas the mass is ordered by NCM622 > NCM523 > NCM111.This work firstly reports the TR feature in large format LIBs with different Ni ratios, both at cell and module level, providing the guidelines for engineering practice and further theoretical researches.

Independent controller design for MIMO processes based on extended simplified decoupler and equivalent transfer function

Abstract In this paper, a control system with an extended simplified decoupled network is proposed for controlling the interactive multivariable processes. The decoupler is designed using cofactor matrix of the process and incorporated in the control loop which modifies the multivariable processes into multiple single loops. To design the PI/PID controller for each loop of MIMO processes independently, the Equivalent Transfer Function (ETF) of each loop is determined. The ETF is approximated using the static relative gains and the average propagation time between manipulated and controlled variables of the loops. Subsequently the PI/PID controller settings are calculated using SIMC tuning rules. This approach reduces the complexity in mathematical model approximation of decoupled process and improves the performance of the overall process. The maximum singular value uncertainty model is considered to ensure the robustness of the decoupled control system. Simulation results of different dimensional interactive MIMO processes are included.

Experimental investigation on the thermal runaway and its propagation in the large format battery module with Li(Ni1/3Co1/3Mn1/3)O2 as cathode.

Thermal runaway (TR) and its propagation behavior in the large format lithium-ion battery (LIB) with various states of charge (SOC) are experimentally investigated in this work. Thermal runaway feature of the cell under thermal abuse condition is characterized using extended volume accelerating rate calorimeter. Based on the experimental results, the modules with five LIBs are built to analyze TR propagation mechanism and further discuss the impact of SOC on TR propagation behavior. It is found that the TR is firstly triggered on the layer near the front surface of the LIB, and then spread to the whole battery. The average propagation time inside the single LIB is 10 s in the module with 100% SOC while 39 s in the module with 50% SOC. Moreover, the module with 100% SOC shows intense combustion behavior, which is replaced by a considerable amount of smoke in the module with 50% SOC. Besides, the average propagation time between adjacent LIBs is significantly delayed from 87 s in 100% SOC module to 307 s in 50% SOC module. This work details TR propagation feature in large format LIB pack, and can provide the guidelines for the safety design of lithium-ion battery module.

Asynchronous Detection Algorithm for Diffusion-Based Molecular Communication in Timing Modulation Channel

In this letter, we consider the asynchronous detection of diffusion-based molecular communications in timing modulation channel. We propose a symbol detection algorithm that can be used in asynchronous systems. Using the variance of the arrival time of a large number of information molecules arriving at a receiver, it is possible to estimate an average propagation time and the emitting time of each bit from a transmitter, and a transmitted bit sequence can also be decoded. The error probability of the proposed algorithm is analyzed, and it is shown that there is good agreement between analysis and simulation results.

On the origin and propagation of Denmark Strait overflow water anomalies in the Irminger Basin

AbstractDenmark Strait Overflow Water (DSOW) supplies the densest contribution to North Atlantic Deep Water and is monitored at several locations in the subpolar North Atlantic. Hydrographic (temperature and salinity) and velocity time series from three multiple‐mooring arrays at the Denmark Strait sill, at 180 km downstream (south of Dohrn Bank) and at a further 320 km downstream on the east Greenland continental slope near Tasiilaq (formerly Angmagssalik), were analyzed to quantify the variability and track anomalies in DSOW in the period 2007–2012. No long‐term trends were detected in the time series, while variability on time scales from interannual to weekly was present at all moorings. The hydrographic time series from different moorings within each mooring array showed coherent signals, while the velocity fluctuations were only weakly correlated. Lagged correlations of anomalies between the arrays revealed a propagation from the sill of Denmark Strait to the Angmagssalik array in potential temperature with an average propagation time of 13 days, while the correlations in salinity were low. Entrainment of warm and saline Atlantic Water and fresher water from the East Greenland Current (via the East Greenland Spill Jet) can explain the whole range of hydrographic changes in the DSOW measured downstream of the sill. Changes in the entrained water masses and in the mixing ratio can thus strongly influence the salinity variability of DSOW. Fresh anomalies found in downstream measurements of DSOW within the Deep Western Boundary Current can therefore not be attributed to Arctic climate variability in a straightforward way.

Streaking and Wigner time delays in photoemission from atoms and surfaces

Streaked photoemission metrology allows the observation of an apparent relative time delay between the detection of photoelectrons from different initial electronic states. This relative delay is obtained by recording the photoelectron yield as a function of the delay between an ionizing ultrashort extended ultraviolet (XUV) pulse and a streaking infrared (IR) pulse. Theoretically, photoemission delays can be defined based on i) the phase shift the photoelectron wavefunction accumulates during the release and propagation of the photoelectron (``Wigner delay") and, alternatively, ii) the streaking trace in the calculated photoemission spectrum (``streaking delay"). We investigate the relation between Wigner and streaking delays in the photoemission from atomic and solid-surface targets. For solid targets and assuming a vanishing IR-skin depth, both Wigner and streaking delays can be interpreted as an average propagation time needed by photoelectrons to reach the surface, while the two delays differ for non-vanishing skin depths. For atomic targets, the difference between Wigner and streaking delays depends on the range of the ionic potential.

Measurement of propagation time dispersion in a scintillator

One contribution to the time resolution of a scintillation detector is the signal time spread due to path length variations of the detected photons from a point source. In an experimental study, a rectangular scintillator was excited by means of a fast pulsed ultraviolet laser at different positions along its longitudinal axis. Timing measurements with a photomultiplier tube in a detection plane displaced from the scintillator end face showed a correlation between signal time and tube position indicating only a small distortion of photon angles during transmission. The data is in good agreement with a Monte Carlo simulation used to compute the average photon angle with respect to the detection plane and the average propagation time. Limitations on timing performance that arise from propagation time dispersion are expected for long and thin scintillators used in future particle identification systems.

Temporal characteristics of communications channels between source and receiver in inhomogeneous medium

The temporal translation properties of communications channels between a source and receiver in an inhomogeneous medium are investigated. For this, special characteristics are introduced: the average propagation time, the time variance of signal arrival, the probability of normal arrival, and the probability of division of direct and scattered signals by inhomogeneities. Spatial maps of the distributions of the characteristics are constructed for the example of a bilinear layered waveguide. Recommendations on the use of these maps for the solution of various practical problems are provided.

Deadlock prevention in a communications shell using empty slots

This paper extends the work of [1] by describing an investigation into the use of continuously circulating empty slots in a communications shell to prevent deadlock. By this means the number of message packets which can exist on the network is conserved to a value below that which is required to cause deadlock. This strategy incurs an overhead in three ways: there is a continuous communication load on each processor, which reduces the computational power available, caused by having to circulate the slots around the network; a delay in transmitting messages is caused by having to wait empty slot to become available: congestion of the network by the continuously circulating empty slots results in the average propagation time of message packets being increased. The consequences of these overheads are evaluated and it is indicated how they may be minimised. The choice of the optimum number of empty slots is discussed. The effect of varying the size of the empty slots on communication efficiency is measured. The use only of alternate slots arriving at a node, to prevent livelock, is described. The topology used for the investigation is a hypercube.