Performance-limiting Factor Research Articles

Performance evaluation and factors influencing a drinking water treatment plant, Shire Indassilassie, Ethiopia

This research assesses the efficacy of the water treatment plant in Shire Indassilassie, Tigray, Ethiopia, focusing on the slow sand filtration system. Despite the inclusion of horizontal roughing filtration and a sedimentation tank, the water treatment plant struggles with an inadequate and turbid water supply. This study evaluates the water treatment plant’s performance through field evaluation, interviews, and laboratory experiments, concentrating on major treatment processes to identify performance-limiting factors. The water source had an average turbidity of 29.70 ± 1.03 NTU in the dry season and 94.27 ± 16.71 NTU in the summer. Results indicate that horizontal roughing filtration, sedimentation tank, and slow sand filtration achieve average turbidity removal efficiencies of 42.02% ± 4.00%, 5.67% ± 3.15%, and 83.51% ± 8.75%, respectively, during the dry season. In the summer or wet season, these treatment units achieve efficiencies of 40.06% ± 3.26%, 28.17% ± 4.62%, and 77.07% ± 4.61%, respectively. Additionally, the average run times for slow sand filtration are 22 days in the dry season and 13 days in the summer. Total and fecal coliform removals were effective, except in the sedimentation tank. A one-way ANOVA confirms a significant difference in turbidity among treatment units. Factors such as fine filter sand particles causing faster clogging, pipe misconnections, inadequate cleaning practices, irregular filtration rates, air binding due to a lack of backfilling at startup, and a lack of periodic monitoring and emergency response lead to suboptimal turbidity removal and shorter slow sand filtration run times. The study underscores the need for corrective measures to address these issues, enhancing water treatment plant sustainability in the region.

Bipolar membrane electrodialysis for amine regeneration from amine chloride stream: Closing the amine utilization loop

The amine-based CO2 capture & mineral carbonation (CCMC) using alkaline slag emerges as a decarbonation means. However, being the most costly component in the process, amine is consumed in large quantity yet its regeneration is overlooked. Thus, to close the material utilization loop, this work proposed the bipolar membrane electrodialysis (BMED) technology for amine regeneration from its chloride streams. With customized BMED configurations, the recovery of two different amines(monoethanolamine (MEA) & 2-(Diethylamino)ethanol (DEAE)) was investigated respectively to reveal the separation mechanisms. This novel concept was firstly proved with a three-compartment configuration, where the cations (MEA+ or DEAE+) can pass through the cation exchange membrane and react with OH− generated by the bipolar membrane thus producing pure amine. The respective MEA and DEAE regeneration reached up to 95.1 % and 92.4 % within 10 h; while the yield of a useful byproduct 1.8 wt% HCl reached ∼ 71 %, which can be reused in CCMC. The results showed that the membrane played a key role: with standard anion exchange membrane (AEM), the Cl− transfer rate decreased with increasing feed concentration. Although the proton blocking AEM avoided H+ cross-over, the Cl− transfer was stable but exhibited up to 2.5-times lower transfer rate. Via a comprehensive parametric study, a modest current density (150 A/m2) was chosen to avoid significant energy penalty, corresponding to a power consumption of 10.3 kWh/(kg amine). Compared to the acid model, the base model of two-compartment configuration, had 2x higher amine yield and higher energy efficiency. This study revealed the performance-limiting factors in BMED, inspiring future design of efficient amine regeneration system for closed-loop CCMC process and contributing to sustainable processing towards carbon neutrality.

Nonideality in Arrayed Carbon Nanotube Field Effect Transistors Revealed by High-Resolution Transmission Electron Microscopy.

High density and high semiconducting-purity single-walled carbon nanotube array (A-CNT) have recently been demonstrated as promising candidates for high-performance nanoelectronics. Knowledge of the structures and arrangement of CNTs within the arrays and their interfaces to neighboring CNTs, metal contacts, and dielectrics, as the key components of an A-CNT field effect transistor (FET), is essential for device mechanistic understanding and further optimization, particularly considering that the current technologies for the fabrication of A-CNT wafers are mainly laboratory-level solution-based processes. Here, we conduct a systematic investigation into the microstructures of A-CNT FETs mainly via cross-sectional high-resolution transmission electron microscopy and tentatively establish a framework consisting of up to 11 parameters which can be used for structure-side quality evaluation of the A-CNT FETs. The parameter ensemble includes the diameter, length (or terminal), and density distribution of CNTs, radial deformation of CNTs, array alignment defects, surface crystallography facets of contact metal, thickness distribution of high-k dielectrics (HfO2), and the contact ratios for the CNT-CNT, CNT-metal, CNT-dielectric, and CNT-substrate interfaces. Enriched array alignment defects, i.e., bundle, stacking, misorientation, and voids, are observed with a total ratio sometimes up to ∼90% in pristine A-CNTs and even up to ∼95% after the device fabrication process. Thus, they are suggested as the prevalent performance-limiting factors for A-CNT FETs. Complex interfacial structures are observed at the CNT-CNT, CNT-metal contact, and CNT-high-k dielectric interfaces, making the local environment and the property of each component CNT involved in an A-CNT FET distinct from others in terms of the diameters, radial deformation, and interactions with the local surroundings (mainly through van der Waals interactions). The present study suggests further improvements on the fabrication technology of A-CNT wafers and devices and mechanistic investigations into the impacts of complex array alignment defects and interface structures on the electrical performance of A-CNT FETs as well.

Investigation of Gamma-Induced Changes to Screening Currents and AC Losses in Mono- Versus Multi-filamentary REBCO Coated Conductors Using DC and AC Magnetometry

REBCO (rare-earth barium copper oxide) coated conductor tapes are a highly attractive option for magnet materials in future tokamak fusion power plants. However, the threat of intense neutron and gamma radiation, together with AC losses during magnet coil ramping, has raised concerns around magnet coil lifetimes. Irradiation-induced changes to flux creep rate has been identified as a key performance-limiting factor in REBCO tapes at low temperatures and high fields post-irradiation with gamma rays; spontaneous flux creep contributes to hysteretic AC loss in REBCO cables under applied AC fields. Knowing that multi-filamentary tapes are under consideration for tokamaks as an AC loss mitigation, magnetic measurements and gamma irradiation experiments are presented here on striated and mono-filamentary YBCO tapes to investigate the differences in post-irradiation screening currents and AC losses. Reduction in AC losses improved magnetisation critical current density (Jc) retention after 1 MGy in the multi- relative to the mono-filamentary samples. After the 5 MGy dose, striations then made the multi-filamentary tape more susceptible to Jc degradation because of the thinner individual filament width. Scanning transmission electron microscopy analysis on an analogous GdYBCO mono-filamentary tape did not indicate the introduction of nm-scale amorphisation to the active GdYBCO layer after gamma irradiation. A potential theoretical explanation for the underlying mechanism altering the flux-pinning landscape across the REBCO layer surface in gamma-irradiated tapes is discussed. This work concluded that gamma effects on screening current capability should be considered in future tokamak REBCO tape qualification studies.

Device engineering of Sb2X3 antimony chalcogenide for loss analysis and strategies for maximizing photovoltaic efficiency

Antimony chalcogenide (Sb2X3; X=S, Se) is reportedly stable in ambient open-air, abundant, and shows composition-dependent absorption tunability. We simulated the Sb2X3 device utilizing the reported optical and electrical properties to analyze the performance limiting factors and the extent of achievable performance. Initially, we benchmarked the simulated device with the experimental reported device. The VOC-temperature and VOC-illumination characterization of the benchmarked device revealed the contact issue responsible for the VOC deficit. The suboptimal device configuration is a major performance-limiting factor. Contact optimization and conduction band offset optimisation have improved efficiency to 14.86% and 20.45% in Sb2S3 and Sb2Se3, from their experimentally reported values of 7.5% and 9.2% respectively. The optimization of trap-assisted Shockley Read Hall (SRH) recombination in bulk and interface has improved efficiency to 19.43% and 26.13% in Sb2S3 and Sb2Se3, respectively. When extrinsic factors are optimised, such as resistance losses (series resistance as high as 2 Ωcm2 and shunt resistance as low as 1000 Ωcm2), efficiency increased to 20.03% and 26.82% for Sb2S3 and Sb2Se3, respectively. Finally, with ideal intrinsic recombination parameters (radiative and Auger recombination), efficiency improved to theoretical limits (corresponding to their band gap). The study highlights the possibility of immediate gain upon contact passivation in Sb2S3 and Sb2Se3.

0180 Crew Sleep During a 36-day Arctic Transit: Preliminary Results

Abstract Introduction Extreme environmental conditions (e.g., natural light conditions, time zone transitions), and specific operational conditions (e.g., ship motion due to ice breaking) combined with a variety of other occupational stressors (including shift work, psychological stress, and performing physically strenuous activities), poses unique challenges when conducting polar operations. The overarching aim of this project is to assess the unique challenges sailors experience when operating in polar regions in order to identify performance-limiting factors derived from operating an icebreaker in extreme latitudes. This abstract shows preliminary results of crewmember sleep. Methods A naturalistic longitudinal approach assessed 53 of the ship’s crewmembers (median age of 29yrs; 71.7% males; 66.0% enlisted) while performing their normal duties during a 36-day transit from Kodiak, AK (8/26/23) to Tromsø, Norway (1/10/23). Participants wore ŌURA rings and completed weekly questionnaires throughout the study. Mixed effects analysis was used to assess the effect of age, occupational group, time underway, and watchstanding status on variables of interest. Results are presented as mean◻standard deviation. Results Over the entire data collection period, participants’ sleep duration was 6.81◻0.57 hrs/day with 68.9% sleeping < 7 hrs/day and 8.89% sleeping < 6 hrs/day. All participants napped at least once; 68.1% napped at least once every 4 days. Self-report sleep regularity index (SRI; lower numbers translate to poorer sleep) was 73.1◻5.80 for watchstanders, 83.8◻6.19 for non-watchstanders, and 78.3◻5.16 for crewmembers with a hybrid work schedule. Age was associated with decreased heart rate variability (p=0.006), increased percentage of light sleep (p< 0.001), decreased percentage of deep sleep (p< 0.001), and increased percentage of REM sleep (p=0.021). Officers and watchstanders had a lower percentage of REM sleep compared to enlisted (p=0.030) and non-watchstanders (p=0.025) respectively. Also, over the course of the underway the percentage of light sleep increased and the percentage of deep sleep decreased. Specifically, compared to Week 1, Week 3 had a higher percentage of light sleep (p=0.027), and a lower percentage of deep sleep (p=0.019). Conclusion Results showed that Arctic operations can affect crew sleep. Crew members slept less than the daily recommended 7+ hr/day sleep duration. Their sleep was also related to age, watchstanding status, and time underway. Support (if any)

Delta-T Flicker Noise Demonstrated with Molecular Junctions.

Electronic flicker noise is recognized as the most abundant noise in electronic conductors, either as an unwanted contribution or as a source of information on electron transport mechanisms and material properties. This noise is typically observed when a voltage difference is applied across a conductor or current is flowing through it. Here, we identify an unknown type of electronic flicker noise that is found when a temperature difference is applied across a nanoscale conductor in the absence of a net charge current or voltage bias. The revealed delta-T flicker noise is demonstrated in molecular junctions and characterized using quantum transport theory. This noise is expected to arise in nanoscale electronic conductors subjected to unintentional temperature gradients, where it can be a performance-limiting factor. On the positive side, delta-T flicker noise can detect temperature differences across a large variety of nanoscale conductors, down to atomic-scale junctions with no special setup requirements.

A Two-Nearest Wireless Access Point-Based Fingerprint Clustering Algorithm for Improved Indoor Wireless Localization

Fingerprint database clustering is one of the methods used to reduce localization time and improve localization accuracy in a fingerprint-based localization system. However, optimal selection of initial hyperparameters, higher computation complexity, and interpretation difficulty are among the performance-limiting factors of these clustering algorithms. This paper aims to improve localization time and accuracy by proposing a clustering algorithm that is extremely efficient and accurate at clustering fingerprint databases without requiring the selection of optimal initial hyperparameters, is computationally light, and is easily interpreted. The two closest wireless access points (APs) to the reference location where the fingerprint is generated, as well as the labels of the two APs in vector form, are used by the proposed algorithm to cluster fingerprints. The simulation result shows that the proposed clustering algorithm has a localization time that is at least 45% faster and a localization accuracy that is at least 25% higher than the k-means, fuzzy c-means, and lightweight maximum received signal strength clustering algorithms. The findings of this paper further demonstrate the real-time applicability of the proposed clustering algorithm in the context of indoor wireless localization, as low localization time and higher localization accuracy are the main objectives of any localization system. Doi: 10.28991/ESJ-2023-07-05-019 Full Text: PDF

On the Limits of High-Performance Support

ABSTRACT High-performance sport has experienced increasing emphasis on evidence-based practice and interdisciplinarity facilitated by integrating systems science, business management, and a rapidly expanding sport technology landscape. A major limitation of current approaches to performance support is they unduly constrain the conceptualization of high performance within precise boundaries. In contrast, we explore the notion of parallel incrementalism to guide the pursuit and support of athletic excellence. Given this context, we introduce the idea of performance-limiting factors (PLFs) to complement key performance indicators (KPIs) in informing performance support. Whereas KPIs directly influence or describe performance, PLFs are characteristics that indirectly affect performance in their current state. Considering human performance through the complex interaction of KPIs and PLFs will allow us to continue pushing the boundaries of high-performance sport.

(Digital Presentation) Diagnostic Study of the Key Performance-Limiting Factors in Anion Exchange Membrane Fuel Cells

Anion exchange membrane fuel cells (AEMFC) have received significant attention for their promised low production cost, largely enabled by the facile kinetics of the oxygen reduction reaction in alkaline electrolytes and the broader selection of potential ionomers.1,2 The performance of AEMFCs has been improved significantly by utilizing AEM with high ion exchange capacity (IEC) and optimizing membrane electrode structures.3 However, some fundamental issues limiting the performance of AEMFCs need to be better understood, especially the reaction kinetics at the catalyst-ionomer interface and the transport process at the multi-phase boundaries in the membrane electrode assembly (MEA).4,5 In this talk, we will present a systematic diagnostic study of the critical performance-limiting factors in AEMFC. We will discuss the reaction kinetics at the Pt/ionomer interface and the oxygen transport characteristics of the ionomer layer based on electrochemical data. In addition, we correlate the electrode pore structure, reaction kinetics, and mass transfer behavior with the cell performance based on the analysis of a series of MEA with varied multi-phase boundary designs. Further, experimental data will be presented with decoupled polarization behavior of both the anode and cathode of working AEMFCs. The results reveal that the deteriorated mass transport at the anode and the restricted reaction kinetic at the cathode are the crucial factors limiting the performance of AEMFC, which need to be addressed with high priority. References Wang, Y-J., Qiao, J., Baker, R., Zhang J. Chem. Soc. Rev., 2013, 42, 5768.Chen, N., Hu, C., Lee, Y. M. et al., Angew. Chem. Int. Ed. 2021, 60, 7710–7718.Huang, G., Mandal, M., Mustain, W. E., Kohl P. A. et al., J. Electrochem. Soc. 2019, 166, F637–F644.Dekel, D. R., J. Power Sources 2018, 375, 158e169.Jiang, H., Luo, R., Li, Y., Chen, W. EcoMat. 2022, 4, e12199. Acknowledgement Financial support from the National Key R&D Program of China (No. 2021YFB4001203) is greatly acknowledged.

Design and Optimization of Composite Cathodes for Solid-State Batteries Using Hybrid Carbon Networks with Facile Electronic and Ionic Percolation Pathways.

Solid-state batteries (SSBs) have emerged as a promising alternative to conventional liquid electrolyte batteries due to their potential for higher energy density and improved safety. However, achieving high performance in SSBs is difficult because of inadequate contact and interfacial reactions that generate high interfacial resistance, as well as inadequate solid-solid contact between electrodes. These chronic issues are associated with inhomogeneous ion and electron transport networks owing to imperfect solid-solid interfacial contact. This study developed an optimal interfacial engineering strategy to facilitate an ion-electron transport network by designing an active material (NCM622) uniformly filled with a thin layer of a solid electrolyte (garnet-type Li6.25Ga0.25La3Zr2O12) and conductive additives. The optimal composite electrode architecture enhanced the high capacity, high rate capability, and long-term cycle stability, even at room temperature, owing to the percolating network for facile ionic conduction that assured a homogeneous reaction. In addition to mitigating the mechanical degradation of the cathode electrode, it also reduced the crosstalk effects on the anode-solid electrolyte interface. Effectively optimizing the selection and use of conductive additives in composite electrodes offers a promising approach to addressing key performance-limiting factors in SSBs, including interfacial resistance and solid-solid contact issues. This study underscores the critical importance of cathode architecture design for achieving high-performance SSBs by ensuring that the interfaces are intact with solid electrolytes at both the cathode and anode interfaces while promoting uniform reactions. This study provides valuable insights into the development of SSBs with improved performance, which could have significant implications for a wide range of applications.

Mathematical modeling of fuel cells fed with an electrically rechargeable liquid fuel

Lately, utilizing a novel electrically rechargeable liquid fuel (e-fuel), a fuel cell has been designed and fabricated, which is demonstrated to achieve a much better performance than alcoholic liquid fuel cells do. However, its current performance, which thus hampers its wide application, demands further improvement to meet up with industrial requirement. Therefore, to attain a better performance for this system, an in-depth understanding of the complex physical and chemical processes within this fuel cell is essential. To this end, in this work, a two-dimensional transient model has been developed to gain an extensive knowledge of a passive e-fuel cell and analyze the major factors limiting its performance. The effects of various structural parameters and operating conditions are studied to identify the underlying performance-limiting factors, where deficient mass transport is found to be one of the major causes. The increment of anode porosity and thickness are found to be effective methods of improving the cell performance. This study therefore provides insights on achieving further performance advancement of the fuel cell in the future.

Deriving the number of salience maps an observer has from the number and quality of concurrent centroid judgments

[C. Koch, S. Ullman, Hum. Neurobiol.4, 219-227 (1985)] proposed a 2D topographical salience map that took feature-map outputs as its input and represented the importance "saliency" of the feature inputs at each location as a real number. The computation on the map, "winner-take-all," was used to predict action priority. We propose that the same or a similar map is used to compute centroid judgments, the center of a cloud of diverse items. [P. Sun, V. Chu, G. Sperling, Atten. Percept. Psychophys.83, 934-955 (2021)] demonstrated that following a 250-msec exposure of a 24-dot array of 3 intermixed colors, subjects could accurately report the centroid of each dot color, thereby indicating that these subjects had at least three salience maps. Here, we use a postcue, partial-report paradigm to determine how many more salience maps subjects might have. In 11 experiments, subjects viewed 0.3-s flashes of 28 to 32 item arrays composed of M, M = 3,...,8, different features followed by a cue to mouse-click the centroid of items of just the post-cued feature. Ideal detector response analyses show that subjects utilized at least 12 to 17 stimulus items. By determining whether a subject's performance in (M-1)-feature experiments could/could-not predict performance in M-feature experiments, we conclude that one subject has at least 7 and the other two have at least five salience maps. A computational model shows that the primary performance-limiting factors are channel capacity for representing so many concurrently presented groups of items and working-memory capacity for so many computed centroids.

Nonlinearity-Compensated Short-Range FMCW Radar for Weak Target Imaging

An easily implementable, low-cost, and portable broadband frequency-modulated continuous wave (FMCW) synthetic aperture radar (SAR) system is presented for short-range imaging applications. Design considerations and radar performance metrics are discussed in detail while investigating systematic and nonsystematic performance-limiting factors. This article introduces a signal processing procedure based on a closed-form comprehensive mathematical model to characterize the impact of the nonlinear frequency sweep on radar performance. Based on the proposed model, the nonlinearity is compensated using the time-resampling technique and without needing a reference response. A single-zone calibration does not provide enough accuracy when multiple targets are widely distributed in the cross-range direction. A range-and angle-dependent calibration scheme is proposed to mitigate the second-order effects more precisely, which are otherwise difficult to model mathematically. Detecting less reflective targets in the presence of a strong scatterer is challenging. A range-gating method based on a tunable active bandpass filter (BPF) is proposed to improve the radar system’s sensitivity by suppressing the dominant reflection and enhancing the weaker scatterer. The results are verified by developing SAR images of targets in free space and through a residential wall.

How to minimize voltage and fill factor losses to achieve over 20% efficiency lead chalcogenide quantum dot solar cells: Strategies expected through numerical simulation

Lead chalcogenide colloidal quantum dot solar cells (CQDSCs) have the potential to revolutionize the field of light-to-electricity conversion with their exceptional optoelectronic properties. Unfortunately, realizing their full potential has been hindered by persistent and poorly understood limitations in fill factor (FF) and open-circuit voltage (Voc) losses. In this study, we performed a systematic numerical analysis of practical PbS CQDSCs to identify the root causes of FF and Voc losses in the current development stage, and to provide a clear and feasible roadmap for achieving a PCE of more than 20% in future development stages. Our analysis revealed that the highly effective route for enhancing the current 10% device is to initially modify the internal resistances, resulting in a significant reduction in FF losses to 15%, followed by systematic optimization of surface recombination velocities in the absorber layer and the absorber/hole transfer layer (HTL) interface, which can generate a Voc improvement of 3.76%, ultimately leading to a near-15% PCE. To further elevate PCE to unprecedented heights, we identified the precise regulation of surface excess charge densities at the absorber/HTL interface and the HTL/back contact interface as critical factors. By finely tuning these performance-limiting factors, we demonstrated the feasibility of achieving over 20% PCE, with minimal Voc loss of 318.10 mV and almost negligible FF loss of 6.08% in PbS CQDSCs. Our investigation provides crucial insights into the causes of FF and Voc losses in PbS CQDSCs and offers a clear pathway for future progress in this rapidly evolving field.

A Survey of the Performance-Limiting Factors of a 2-Dimensional RSS Fingerprinting-Based Indoor Wireless Localization System

A receive signal strength (RSS) fingerprinting-based indoor wireless localization system (I-WLS) uses a localization machine learning (ML) algorithm to estimate the location of an indoor user using RSS measurements as the position-dependent signal parameter (PDSP). There are two stages in the system's localization process: the offline phase and the online phase. The offline phase starts with the collection and generation of RSS measurement vectors from radio frequency (RF) signals received at fixed reference locations, followed by the construction of an RSS radio map. In the online phase, the instantaneous location of an indoor user is found by searching the RSS-based radio map for a reference location whose RSS measurement vector corresponds to the user's instantaneously acquired RSS measurements. The performance of the system depends on a number of factors that are present in both the online and offline stages of the localization process. This survey identifies these factors and examines how they impact the overall performance of the 2-dimensional (2-D) RSS fingerprinting-based I-WLS. The effects of these factors are discussed, as well as previous researchers' suggestions for minimizing or mitigating them and future research trends in RSS fingerprinting-based I-WLS.

Performance superiority of an arc-shaped polymer electrolyte membrane fuel cell over a straight one

Polymer Electrolyte Membrane Fuel Cell (PEMFC) is a promising electricity-producing technology but needs further improvement to become economically viable. Oxygen transfer to reaction zone is known as one of the main PEMFC performance-limiting factors. Accordingly, various recent studies have been focused on fuel cell design to improve oxygen transfer. The present study numerically investigates the influences of converting a straight (or planar) PEMFC to a bent (arc-shaped) one. The idea of PEMFC bending originates from the fact that it can create a velocity component perpendicular to gas diffusion layer (GDL) and exert centrifugal force on channel gas flow towards the GDL; thereby, enhancing oxygen transfer. The results indicate that PEMFC bending can enhance performance up to about 8.33% for the examined operating conditions. It is also observed that PEMFC bending impact factor generally increases with operating pressure, stoichiometry ratio and bending angle, but decreases with operating voltage.

Terahertz Spectroscopic Molecular Sensor for Rapid and Highly Specific Quantitative Analytical Gas Sensing

Quantitative analytical gas sampling is of great importance in a range of environmental, safety, and scientific applications. In this article, we present the design, operation, and performance of a recently developed tabletop terahertz (THz) spectroscopic molecular sensor capable of rapid (minutes) and sensitive detection of polar gaseous analytes with near "absolute" specificity. A novel double-coil absorption cell design and an array of room-temperature sorbent-based preconcentration modules facilitate quantitative THz detection of light polar volatile compounds, which often challenge the capabilities of established gas sensing techniques. Acetone, ethanol, methanol, acetaldehyde, formaldehyde, and isoprene are detected at low parts-per-billion to high parts-per-trillion levels. This work evaluates performance-limiting factors for THz spectroscopy-based chemical identification: (1) spectral signal to noise and (2) preconcentrator efficiency.

Nucleation as a rate-determining step in catalytic gas generation reactions from liquid phase systems.

The observable reaction rate of heterogeneously catalyzed reactions is known to be limited either by the intrinsic kinetics of the catalytic transformation or by the rate of pore and/or film diffusion. Here, we show that in gas generation reactions from liquid reactants, the nucleation of gas bubbles in the catalyst pore structure represents an additional important rate-limiting step. This is highlighted for the example of catalytic hydrogen release from the liquid organic hydrogen carrier compound perhydro-dibenzyltoluene. A nucleation-inhibited catalytic system produces only dissolved hydrogen with fast saturation of the fluid phase around the active site, while bubble formation enhances mass transfer by more than a factor of 50 in an oscillating reaction regime. Nucleation can be efficiently triggered not only by temperature changes and catalyst surface modification but also by a mechanical stimulus. Our work sheds new light on performance-limiting factors in reactions that are of highest relevance for the future green hydrogen economy.

Instrument design for an inertial confinement fusion ion temperature imager.

A mix of contaminant mass is a known, performance-limiting factor for laser-driven inertial confinement fusion (ICF). It has also recently been shown that the contaminant mass is not necessarily in thermal equilibrium with the deuterium-tritium plasma [B. M. Haines etal., Nat. Commun. 11, 544 (2020)]. Contaminant mass temperature is one of the dominant uncertainties in contaminant mass estimates. The MixIT diagnostic is a new and potentially transformative diagnostic, capable of spatially resolving ion temperature. The approach combines principles of neutron time-of-flight and neutron imaging diagnostics. The information from the MixIT diagnostic can be used to optimize ICF target and laser drive designs as well as provide key constraints on ICF radiation-hydrodynamic simulations that are critical to contaminant mass estimates. This work details the design and optimization of the major components of the MixIT diagnostic: the neutron aperture, the neutron detector (scintillator), and the recording system.