Time Distribution Research Articles

Impact of Electrochemical Impedance Spectroscopy Dataset Curation on Solid Oxide Cell Degradation Assessment

Abstract Electrochemical impedance spectroscopy (EIS) has become a standard measurement technique for detecting degradation in single cells and stacks of solid oxide cells (SOCs). Depending on the experimental setup and test equipment, instabilities and unexpected results can be observed in EIS measurements. For example, in the low-frequency range, instabilities can be induced by feed gas flow fluctuations. Another phenomenon are parasitic, inductive impedances that degrade the high-frequency range. To compensate for such influences in large EIS data sets, we propose a specially developed EIS data curation pipeline. Based on the results of its application, we demonstrate the impact on the quantitative and qualitative attribution of electrochemical processes from EIS using equivalent circuit modeling and distribution of relaxation times. Furthermore, the substantial differences in the temporal evolution of the latter during long-term experiments are highlighted for EIS measurements obtained at the SOC stack and single cell level. In addition, the significant misestimation of aging rates, especially with respect to the fuel electrode and the high-frequency series resistance, is shown when comparing EIS measurements, few of which exhibit a parasitic inductive impedance.

Seismic hazard study for the duration of ground-motions triggered by intraslab earthquakes

AbstractThis paper presents a probabilistic seismic hazard analysis for the duration of ground motions in Mexico City caused by intraslab earthquakes. The study implies establishing criteria to measure the duration of ground motions and developing predictive equations (GMPEs) for its estimation. Focus is placed on the relative significant duration, $$D_{Sr}$$ D Sr , which is based on the accumulation of energy of ground motions. The study extends to the development of hazard curves that allow estimating the annual probability of exceedance of said parameter. The scope is limited to ground motions caused by intraslab earthquakes occurring in Mexico and that engineeringly affect its capital, Mexico City, which is in a geographical region where the effects of soil-dynamic amplification are manifested considerably. A strong-motion database that includes 1517 horizontal accelerograms, with peak ground acceleration, $$PGA$$ PGA , greater than or equal to 3 cm/s2, recorded during 21 earthquakes from 1994 to 2023 were used to develop the GMPEs. The quantitative description of the time, size, and spatial distribution of the seismic-activity occurrence was defined using a catalog of 46 earthquakes that occurred from 1900 to 2023. The earthquakes have moment magnitude, $$M_{w}$$ M w , greater than or equal to 6. With the tools developed, amplitude- and duration-based hazard-consistent accelerograms can be simulated and used in nonlinear dynamic analyses (NDAs) of structures. This study includes an application example where three sites in Mexico City are selected to compute inelastic response spectra. Hysteretic-energy demands up to 5 times higher are found after a comparison between the inelastic-response spectra from hazard-consistent accelerograms and those provided by current Mexican regulations.

Probing the Origin of Overpotential for Sodium–Oxygen Batteries with Distribution of Relaxation Time

Sodium‐oxygen batteries are emerging as new battery systems. Deep understanding of the origin of overpotential and the kinetic process in sodium‐oxygen batteries remain challenging yet critical. We apply a method of distribution of relaxation time (DRT) to decipher the electrochemical impedance spectroscopy (EIS), allowing us to monitor the changes of different kinetic processes during the discharging and charging. The origin of the overpotential in a battery was further comprehensively investigated combining DRT analysis with differential electrochemical mass spectrometry, Raman and other characterizations. Overpotential is found to primarily stem from oxygen mass transport during discharging, and from poor solid‐solid contact at the electrode surface during charging. Our work demonstrates the study of kinetic processes using DRT analysis, and suggests effective ways to improve the performances of sodium‐oxygen batteries.

Implementation of near zero fluoroscopy in supraventricular tachycardia ablation procedures: a single center experience

Abstract Background Supraventricular tachycardia (SVT) are common cardiac arrhythmias, and catheter ablation has proven to be a very effective treatment, but exposes patients and healthcare providers to radiation. "Near Zero Fluoroscopy" (NZF) techniques, utilizing advanced imaging, aim to reduce radiation exposure while maintaining efficacy. Purpose To present an analysis of near-zero fluoroscopy in SVT ablation procedures, in a tertiary center, since its implementation. Methods We prospectively enrolled 446 SVT-diagnosed patients for this study. All of them underwent NZF procedures using the same specific 3D mapping system, between January/19 and December/22. Patients with atrial fibrillation or macroreentrant atrial tachycardias or when a different mapping system was used, were excluded. All patients provided informed consent. Results Our population had 266 (60%) females and a median age of 39 (IQR 24-51) years. AVNRT was the most frequent arrhythmia documented (229 cases, 51%), followed by Accessory Pathways (AP) (201 cases, 45%) and focal atrial tachycardia (AT) (16 cases, 4%). The ablation success rate was high (405/418, 97%). There was no ablation attempt in 12 patients (9 APs and 3 ATs) and the unsuccessful ablations (7/418 cases, 1,67%) were APs. Overall, fluoroscopy time was 1.1 minutes (IQR 0-2.6). There was no statistically significant difference in the distribution of fluoroscopy time among the types of SVT based on the Kruskal-Wallis test (p 0.14). Observing trends of fluoroscopy use through time, we acknowledge the presence of a learning curve, leading towards shorter times of X-ray during procedures along the first 3 years of implementation of a near-zero strategy. Median times (IQR) of fluoroscopy were as follows: 2019 – 2.25 (0.45-3.4) min; 2020 – 1 (0-2.5) min; 2021 – 0 (0-1.9) min; 2022 – 0.55 (03.05) min. (see BoxPlot) Pairwise comparisons using the Wilcoxon rank-sum test with continuity correction revealed statistically significant differences in medians between all pairs of years, with p-values adjusted for multiple comparisons using the Bonferroni method (p<0.01). In 2022, fluoroscopy time increased, when compared to 2021. We believe this finding can be explained by the fact that in 2022, our department received a new fellow and a young EP consultant (coming from a center where NZF was not the standard for SVT ablation), both being in the lab on a daily basis, explaining this upward trend in fluoroscopy time. There were no acute complications requiring hospital admission or active treatment. Conclusion Our results emphasize the potential of near-zero fluoroscopy techniques to enhance safety and reduce radiation exposure while maintaining a high level of procedural efficacy in the treatment of SVT cases. Absence of acute complications highlighted the safety of these approaches.

Impact of COVID-19 pandemic on the circadian rhythm of cesarean section deliveries.

Circadian rhythms synchronize all biological functions, enabling humans to foresee and respond better to periodic environmental changes. The coronavirus disease (COVID-19) lockdown regulations significantly changed the lighting conditions in pregnant women, leading to chronological disruption. This study aimed to investigate the impact of the COVID-19 on the circadian rhythm of cesarean deliveries. We investigated whether the circadian rhythm of cesarean section deliveries changed during the first year of the COVID-19 pandemic at a tertiary hospital in Van Province, eastern Turkey. We analyzed the distribution of birth times for 1476 cesarean deliveries performed between March 01, 2020 and January 20, 2021 (1st year of the COVID-19 pandemic) and compared this information with data from 1194 cesarean deliveries performed during a similar period in the previous year. The primary outcome was the change in the circadian rhythm of cesarean deliveries. Secondary outcomes included cesarean section (CS) delivery rates, indications for CS, 1st and 5th minutes Appearance (skin color), Pulse (heart rate), Grimace (reflex irritability), Activity (muscle tone), and Respiration scores, and anesthesia technique use rates. Regarding the time distribution of CS deliveries in the first year of the COVID-19 pandemic, the maximum number of cesarean deliveries (n = 234, 16%) occurred between 14:00 and 16:00 (P = .112). Cesarean deliveries in pre-COVID-19 group were most frequently performed between 10:00 and 12:00, at a rate of 18% (n = 216) (P = .001). In both groups, the time point at which CS deliveries were the least performed was 04:00 to 06:00, and the rates were different (n = 35, 2% and n = 14, 1%, respectively) (P = .022). A 4-hour phase shift was detected at the peak of the birth time in the first year of the COVID-19 pandemic compared to the previous year. These results suggest that the circadian rhythm of cesarean deliveries is affected by the pandemic.

Real-time assessment of LV synchrony in AV block population undergoing LBB pacing using ECG Imaging

Abstract Background Left bundle branch pacing (LBBP) may prevent right ventricular (RV) pacing-induced dyssynchrony (DYS). Nowadays, real-time assessment of DYS correction is indirectly measured with QRS narrowing. Non-invasive ECG imaging (ECGI) technique may provide an evaluation of electrical resynchronization based on quantitative assessment of ventricular local activation time (LAT) maps. Purpose To assess whether real-time ECGI could evaluate LV synchrony achieved through LBBP, in a consecutive AV block (AVB) population. Methods A cohort of 12 patients with AVB were included. ECGI was performed during the implant procedure. ECGI signals were computed using an artificial intelligence derived cardiac geometry model. Ventricular LAT maps were obtained when pacing from septal RV and with LBBP (lead placed according to guidelines ECG criteria) for each of the patients. The following parameters were obtained from ECGI LAT maps to assess intra and interventricular DYS pacing at the RV septal and LBB locations: total activation time (TAT), left ventricular activation time (LVAT), left ventricular dyssynchrony index (LVDI), ventricular electrical uncoupling (VEU = mean LVAT – mean RV activation time) and histogram overlap between LV and RV activation times distribution. RESULTS: Nine of the 12 patients were men (75%), with a median age of 79[Q1 75-Q3 82]. QRS duration during RV septal pacing was 150 ms [138-172]. Median LVEF was 47% [26-59]. In Figure 1, it can be observed that dyssynchrony variables are corrected across all patients when reaching LBBP. Figure 2 shows activation maps during RV septal pacing and during LBBP, along with the QRS duration, and the RV and LV histogram of activation times. Conclusion ECGI is useful for assessing the LV synchrony correction during LBBP in an AV block population.Dyssynchrony variablesActivation maps with QRS and histograms

Net escape velocity, transfer probability, and travel time distributions within a cross-ventilated room model sheltered by urban-like block array

Natural ventilation offers significant advantages, especially in terms of energy conservation. However, most published articles have focused on the ventilation flow rate to determine the average contaminant concentration, while few have examined local ventilation distributions. Therefore, isothermal steady-state Reynolds-averaged Navier–Stokes simulations were conducted to analyze the airflow and scalar concentration fields of a cross-ventilation model sheltered by buildings. Based on these fields, we generated the spatial distributions of ventilation indices, namely, the net escape velocity (NEV), point-to-point indices transfer probability (TP), and travel time (TT), to discuss the dispersion of scalars emitted from local points in a room with natural ventilation. The NEV, which indicates the direction of the scalar discharge from each cell, exhibited a distribution distinct from the advection velocity because of concentration gradient effect. Higher TPs were observed when evaluated from a contaminant source to a target point following the NEV streamlines. Meanwhile, lower TTs were observed when evaluated in a point near the source and also from a contaminant source to a target point following the NEV streamlines. Although TP and TT are independent ventilation indices, a negative correlation between them was observed. Instead of the ventilation flow rate, the detailed structure of scalar dispersion can now be described by simultaneously analyzing the ventilation efficiency indices, which provide information on the general contaminant transport direction, and the probability and duration of transfer from a source to a target point. This potentially helps in the design of ventilation system especially in room lay-out to avoid cross-contamination.

Demystifying the Distribution of Relaxation Times: A Simulation-Based Investigation into the Limits and Possibilities of Interpretation for Lithium-Ion Batteries

Abstract Interpreting impedance spectra of electrochemical systems using the distribution of relaxation times analysis remains an incompletely solved task. This study carefully examines various challenges related to the interpretation of resulting distributions of relaxation times using a closed-form lumped Doyle-Fuller-Newman model. First, the physical and phenomenological interpretation of peaks in the distribution of relaxation times are analyzed through a global sensitivity analysis. Second, the assignment of processes to specific ranges of time constants is investigated. Third, the use of half cells for the characterization of full cells is examined, and the clear limitations associated with the use of lithium metal counter electrodes are pointed out. Furthermore, the study provides first insights into the effects of distributed processes such as charge transfer, double-layer effects, and solid-state diffusion. Several prevailing interpretations in the literature are challenged and new insights and guidelines for interpreting distributions of relaxation times are offered.

Enhanced Zinc‐air Batteries through the Fabrication of Structured Zinc Electrodes using Freeze‐casting

Ice templating, a versatile manufacturing process, is widely utilized to create porous materials by freezing aqueous solutions. Notably, this technique is material independent, allowing for the fabrication of microstructured bulk or sheet materials of ceramic, glass, metal, polymer, and composite materials. In this study, the influence of freeze‐cast zinc electrodes on zinc‐air batteries is investigated. The analysis included the charge and discharge cycling behavior of pure powder, gel matrix, and sintered freeze‐cast zinc electrodes, complemented by the study of the distribution of relaxation times. Remarkably, the best cycling performance was achieved with the combination of a gel electrolyte and a freeze‐cast zinc electrode, highlighting the potential significance of this microstructure‐electrolyte pairing for enhancing the performance of zinc‐air batteries.This article is protected by copyright. All rights reserved.

Durability analysis of polymer electrolyte membrane fuel Cell's gas diffusion layer based on distribution relaxation time analysis: Influence of the presence or absence of a micro-porous layer

The U.S. Department of Energy accelerated stress test carbon protocol emphasizes improving the durability of both the catalyst layer and the micro-porous layer (MPL) carbon support. This underscores the need for research focused solely on the degradation of the Gas Diffusion Layer (GDL). Traditionally, electrochemical impedance spectroscopy impedance data used to analyze resistance due to GDL durability has been interpreted through equivalent circuit models. However, this method simplifies simultaneous response and multiple models for the same data, which reduces the objectivity of the analysis. Therefore, this study analyzed the durability characteristics of GDLs with and without MPLs using distribution of relaxation times, a method less prone to subjectivity. In short, the results showed that substrates without MPL are more susceptible to performance degradation and loss, and highlighted the emergence of Warburg resistance due to limited diffusion under harsh environmental conditions.

Robust Algorithms for the Analysis of Fast-Field-Cycling Nuclear Magnetic Resonance Dispersion Curves

Fast-Field-Cycling (FFC) Nuclear Magnetic Resonance (NMR) relaxometry is a powerful, non-destructive magnetic resonance technique that enables, among other things, the investigation of slow molecular dynamics at low magnetic field intensities. FFC-NMR relaxometry measurements provide insight into molecular motion across various timescales within a single experiment. This study focuses on a model-free approach, representing the NMRD profile R1 as a linear combination of Lorentzian functions, thereby addressing the challenges of fitting data within an ill-conditioned linear least-squares framework. Tackling this problem, we present a comprehensive review and experimental validation of three regularization approaches to implement the model-free approach to analyzing NMRD profiles. These include (1) MF-UPen, utilizing locally adapted L2 regularization; (2) MF-L1, based on L1 penalties; and (3) a hybrid approach combining locally adapted L2 and global L1 penalties. Each method’s regularization parameters are determined automatically according to the Balancing and Uniform Penalty principles. Our contributions include the implementation and experimental validation of the MF-UPen and MF-MUPen algorithms, and the development of a “dispersion analysis” technique to assess the existence range of the estimated parameters. The objective of this work is to delineate the variance in fit quality and correlation time distribution yielded by each algorithm, thus broadening the set of software tools for the analysis of sample structures in FFC-NMR studies. The findings underline the efficacy and applicability of these algorithms in the analysis of NMRD profiles from samples representing different potential scenarios.

Manajemen Marketing Madrasah Melalui Teknologi Informasi Dan Komunikasi di MA Hidayatul Mubtadiin Jati Agung Lampung Selatan

The point of this examination is to decide and break down the preparation, execution and assessment of madrasa showcasing the executives through data and correspondence innovation at Madrasah Aliyah Hidayatul Mubtadiin Jati Agung South Lampung. This sort of exploration is subjective examination, the technique utilized in this exploration utilizes perception, meetings and documentation. The information sources in this examination are essential and optional exploration sources. The information investigation procedure utilized is an intuitive model and information triangulation to really look at the legitimacy of the information. The exploration results show that 1) Mama Hidayatul Mubtadiin's new understudy confirmations advertising arranging (PPDB) is the most vital phase in the understudy affirmations process. The initial step is vital, on the grounds that the initial step is important for the interaction that will prompt the eventual outcome. Figuring out a promoting program execution plan zeros in additional on tips, strategies, procedures or methodologies that are successful, effective and adaptable to carry out. Execution arranging should think about time distribution, accessibility of assets, HR, offices, etc. 2) Execution of Mama Hidayatul Muntadiin's showcasing through data and correspondence innovation by carrying out a blend, in particular item, value, spot and advancement. In the interim, the media utilized for madrasa advertising are handouts and the web like sites, WA, Instagram, Facebook, TV and papers. 3) Assess the advertising system or execution associated with showcasing, by taking a gander at the degree of promoting exercises that have been carried out, by proceeding with exercises that have been generally answered by the general population.

Epidemiological Profile of IBD in the Northern Region: "Pilot Study"

Inflammatory bowel disease (IBD) refers to three chronic inflammatory disorders, ulcerative colitis (UC), Crohn disease (CD) and indeterminate colitis. Classically IBD is described as a disease of rich countries, and historical data on the geographical distribution of IBD around the world have shown a high incidence and prevalence in high-income countries, like Northern Europe and the USA. More recently, IBD emerged with increasing frequency in many parts of the planet especially in developing countries [1], including Morocco, becoming a global infection. UC remains more frequent than CD except in certain countries including France [2]. Although progress has recently been made, particularly in the genetic field, in understanding their physiopathology, the cause(s) of these two diseases remains unknown to date. A better knowledge of the descriptive epidemiology of IBD, in particular the differences in incidence in relation to time, age or geographical distribution, can lead to etiological leads. Study the epidemiology of IBD is a challenge, in part because it is difficult to diagnose, but it is important because of its direct and indirect costs. Data from Moroccan studies remain rare. Our study on the epidemiology of inflammatory bowel disease (IBD) is the first in the northern region.

UNDERSTANDING THE TRADE-OFF IN TCP'S CUBIC WINDOWS CONGESTION: A COMPREHENSIVE ANALYSIS

This study investigates the difficulties of the CUBIC TCP algorithm, focusing on the trade-off between efficiency and fairness in window congestion control. The CUBIC approach, which was devised to optimize high-bandwidth and long-distance networks, is currently widely used as the default TCP congestion control algorithm in Linux and other systems. Our work investigates the dynamics of CUBIC's window expansion, specifically the interaction between the cubic function and the most recent congestion event. We look at how this interplay impacts the distribution of window widths, throughput, round-trip time (RTT), loss rate, and queue size under different network configurations. Keywords: TCP CUBIC, Window Congestion, Efficiency-Fairness Trade-Off, TCP’s Cubic Function.

Single-photon lidar depth imaging based on sparsity adaptive matching pursuit method

Photon counting lidar has the ability to detect weak echo photons. However, in imaging applications, a small number of echo signals obtained in a very short acquisition time cannot get an accurate image estimation through the photon arrival time distribution histogram. Therefore, high-precision and fast imaging of an object using a small amount of weak echo photon signals is urgent to be solved. In this work, a sparse adaptive matching pursuit (SAMP) algorithm is proposed to process the echo photons without prior information to obtain the effective photon interval, which improves the reconstruction quality and imaging speed. By constructing a non-coaxial scanning imaging system to detect the face model, it has been experimentally proven that the proposed algorithm can achieve depth and reflectance image estimation under the condition of low power and low acquisition time of 4µs per pixel on average, and the mean absolute error (MAE) value is reduced by about 10 times compared to conventional reconstruction algorithm.

Time distribution of stimulated transition probabilities

In recent years, an increasing number of experimental results have been published for a wide variety of systems in which high-precision, ultra-fast, and ultra-short laser pulses techniques have been used to study time-resolved dynamical processes. In the absence of a theoretical prediction of the time distribution of the transition probabilities, the lifetimes τ are generally extracted by fitting the decay time with an exponential, bi-exponential or three-exponential function. In fitting the data, the short-time behavior is generally neglected. The purpose of this study is to show that an explicit formula for the time distribution of the transition probability can be determined rigorously using time-dependent perturbation theory. A formula that perfectly fits an important subset of the experimental results from t = 0 to t=∞ . We show that by following a route different from the usual procedure for deriving transition amplitudes and Einstein coefficients in time-dependent perturbation theory, one ends up with a time-dependent factor, that is, a temporal distribution function of the transition probabilities, and for the Einstein coefficients. The time distribution reported here looks in the time domain similar to the Planck distribution in the frequency domain. In fact, the behavior of the time distribution, with a maximum at 2τln⁡2 , and with τ playing the role of temperature, resembles the behavior of the Planck frequency distribution. We present several examples to demonstrate that the theoretical formula allows for easier fitting of the experimental results reported in the literature. We also show that the time distribution explains the difference in resonance heights between the experimental and theoretical blue laser spectra.

An essay on semiclassical analysis for microlocal singularities, turbulence intensity and integration of singularities by Schrödinger equation in probabilistic behavior

The Schrödinger equation governs the probabilistic behavior of quantum particles through the wave function. Microlocal singularities denote regions with significantly high probability density or abrupt changes therein. By visualizing the probability distribution in time and space, we discern regions with higher probability density, indicative of potential microlocal singularities. These regions probably correspond to areas with a greater probability of particle presence. Such analysis aligns with Theorem 1, predicting characteristics of microlocal singularities of wave functions. Furthermore, Theorem 2 postulates that semiclassical path integrals along these singularities contribute significantly to solving the Schrödinger equation. Interpreting the temporal evolution of the probability density in the probability distribution visualization reveals the propagation of the particle over time. Regions of high density mean likely presence of particles at specific times, aligning with the predictions of Theorem 2. Consequently, the analysis of the contribution of high-density regions to the temporal evolution of the wave function resembles semi-classical path integral calculations. Thus, our findings demonstrate that visualization of probability distributions obtained from the numerical resolution of the Schrödinger equation allows a comprehensive interpretation of the behavior of quantum particles, consistent with the theorems.

The burden of working time lost to compensable occupational injury and disease in Australia, 2012-17: a retrospective population-based study.

To determine the national burden of working time lost to occupational injury and disease in Australia compensable by workers' compensation schemes; to characterise the distribution of time lost by age, sex, and injury and disease type. Retrospective population-based study; analysis of National Dataset for Compensation-based Statistics (NDS) data. Granted workers' compensation claims by people aged 15-100 years including payment of wage replacement benefits for time off work lodged in Australia, 1 July 2012 - 30 June 2017. Working years lost (WYL) per annum (total number of years of wage replacement benefits paid to injured and ill workers), overall and by sex, age, and injury and disease type; WYL per 10 000 fulltime equivalent (FTE) years worked. A total of 755 330 eligible claims with complete data for analysis variables by people aged 15-100 years were identified, for compensable injuries and disease that led to 41 194 (95% confidence interval [CI], 41 020-41 368) WYL/year. The annual WYL number and rate were each higher for men (25 367 [95% CI, 25 230-25 503] WYL/year; 42.6 [95% CI, 42.1-43.1] WYL/10 000 FTE years) than for women (15 827 [95% CI, 15 720-15 935] WYL/year; 38.8 [95% CI, 38.2-39.4] WYL/10 000 FTE years). Workers aged 45-100 years made 66 742 claims per year (44.1% of all claims) but incurred 21 763 WYL/year (52.8% of all WYL). Traumatic joint and muscle injuries led to 16 494 WYL/year (40.0% of all WYL), musculoskeletal disorders to 8547 WYL/year (20.7%), mental health conditions to 5361 WYL/year (13.0%), fractures to 4276 WYL/year (10.4%), and wounds and lacerations to 3449 WYL/year (8.4%). Occupational injury and disease covered by workers' compensation result in lost working time in Australia equivalent to more than 41 000 fulltime jobs. Distribution of the burden reflects the greater labour force participation of men, slower recovery of older workers, and the impact of common occupational injuries and diseases. Population-based monitoring of lost working time could support effective occupational health surveillance and allocation of resources for protecting the health of Australian workers.

Crescent-shaped spatial distribution: radiation properties concerning beam waist from the cross collision of a tightly focused laser pulse and a relativistic electron

The radiation properties of the cross collision between a single electron and an intense laser pulse are researched by numerical simulation methods. Under the condition of tightly-focused laser, the electron trajectories, spatiotemporal distribution and spectrum are compared with that under non-tightly focused lasers. The results show that the torsion effect on the electron during the oscillation process is more notable after the tightly focused laser interacts with electron. The radiation it generates is asymmetric in space, and its time distribution is nearly unimodal and can be regarded as a single attosecond pulse. In frequency domain, the spectrum appears to be a supercontinuum. With the increase of beam waist radius, the symmetry of the spatial distribution enhances and time distribution also exhibits a three-peak structure that is symmetrical about the main peak. Furthermore, the spectrum changes from a supercontinuum to a multimodal distribution. The analysis turns out that tightly focused laser is more realistic compared to non-tightly focused laser or even plane wave, which benefits the design of high-quality x-rays in practical application.

Optimisation and effect of ionomer loading on porous Fe–N–C-based proton exchange membrane fuel cells probed by emerging electrochemical methods

The next generation of proton exchange membrane fuel cells (PEMFCs) require a substantial reduction or elimination of Pt-based electrocatalyst from the cathode, where O2 reduction takes place. The most promising alternative to Pt is atomic Fe embedded in N-doped C (Fe–N–C). Successful incorporation of Fe–N–C in PEMFCs relies on a thorough understanding of the catalyst layer properties, both ex situ and in situ, with tailored electrode interface engineering. To help resolve this conundrum, we provide a quantitative protocol on the optimisation of I/C for Fe–N–Cs. It is demonstrated that a high pore volume (3.33 cm3 g−1FeNC) Fe–N–C catalyst requires a sufficiently high ionomer to catalyst mass ratio (I/C, 2.8≤I/C ≤ 4.2) for optimum PEMFC activity under H2/O2. Emerging electrochemical techniques (distribution of relaxation times and Fourier transformed alternating current voltammetry) were used to deconvolute for the first time the trade-off between proton and electron resistance and accessible FeNx active site density with increasing ionomer loading. These findings highlight the significant impact of tuning the I/C ratio based on the catalyst layer properties and feature the power of evolving electrochemical tools for optimising performance in PEMFCs and other electrochemical devices.