Lower Panel Research Articles

P-2105. Concordance of Multiplexed Molecular Lower Respiratory Panel with Standard Culture Method and Potential Clinical Impact on Antimicrobial Therapy

Abstract Background Pneumonia is the most common cause of health-care associated infections. The mainstay of diagnosis is respiratory culture, which is limited by up to 72-hour turnaround time and variable sensitivity. An added challenge is the emergence of antimicrobial resistance, which may confound the choice for empirical therapy. Rapid diagnostic tests have been developed to mitigate the challenges of diagnosis and treatment, but the clinical impact is not known. The Unyvero Lower Respiratory Tract Panel (LRT) is a qualitative multiplex nucleic acid test that can detect DNA of 20 microorganisms and 10 resistance genes in respiratory samples, with a 5-hour turnaround time. We hypothesized that use of the LRT on respiratory samples may have an impact on antimicrobial therapy and, consequently, antimicrobial stewardship. Methods The LRT was performed on a random sample of 48 respiratory tract specimens that were obtained inpatient. We assessed concordance of LRT with standard-of-care (SoC) testing. We performed a retrospective chart review for the clinical context in which specimens were obtained (infection suspected versus not) and to determine whether use of LRT would have had an impact on antimicrobial therapy at the time of care. Results Of 48 specimens, 25 (52%) had concordance between LRT and SoC testing and the remaining 23 specimens (48%) had discordance between LRT and SoC testing. Notably, 8 (17%) “discordant” specimens had organisms grow on culture that have no targets on the LRT (Candida species, Klebsiella aerogenes, Burkholderia cepacia complex, Streptococcus anginosus). In 3 cases where a resistance gene (CTX-M, mecA) was identified by LRT, antimicrobial susceptibility testing was compatible. In 7 cases, antibiotic therapy may have been impacted by use of LRT; in 5 cases therapy may have been initiated unnecessarily, and in 2 cases additional therapy may have been warranted. There were no cases where de-escalation of antibiotics would have been warranted. Conclusion The Unyvero LRT panel is an appealing diagnostic tool due to fast turnaround time, but a significant clinical impact due to its use has not yet been demonstrated. Though our study was limited by sample size, we found that LRT may have increased inappropriate use of antibiotics, rather than promoting stewardship. Disclosures Melissa R. Gitman, MD, Biomerieux, Inc: Grant/Research Support

Performance of human expert and AI measurements in conditions of progressive image degradation

Abstract Background A major challenge in real-world echocardiography is the difficulty in obtaining high quality images in some patients or some clinical settings. Is AI only useful when image quality is good? Purpose To artificially degrade adequate-quality images, and compare the ability of human experts and AI, to make measurements correctly, as image degradation worsens. Methods PLAX dimension measurements were made on videos of 30 patients with a range LV dimensions (mean 138mm, SD 37mm). To set the gold standard, 9 experts measured each image, blinded to the measurements made by others. For each original image, 5 degraded versions were then made, each progressively more degraded. The degradation was designed to be maximally confusing for this measurement, namely the addition of faint ghost images of random PLAX views of other patients. This process is automatable, reproducible, and not easy to undo by conventional image processing techniques. The 30 cases, each in original form plus 5 degraded versions, totalled 180 images, They were presented in random order for labelling by a pool of experts. They were also analysed by the Unity UK Echocardiography AI collaboratives. Results An example degradation sequence is shown in Figure 1 (upper panel), with images cropped for this abstract. Across all measurements, the expert and AI suffered progressively greater measurement error as the level of image degradation increased. On average, the AI error was N smaller than the expert error (p<0.05). For example, for LV internal dimension, the progressive rise in human error was 2.2mm, 2.5mm, 3.1mm, 3.6mm, 5.3mm, 9.6 mm, p<0.001 for trend, Figure 1 lower panel grey bars. Meanwhile for the AI, the corresponding errors were: 2.5mm, 2.5 mm, 2.7 mm, 3 mm, 3.9 mm, 8 mm. (p<0.001 for trend, Figure 1 lower panel grey bars). The Minimum Heatmap Amplitude (MHA), an automatic index of AI confidence in its measurement, also declined progressively (p<0.001 for trend). Conclusion Both humans and AI alike make less accurate measurements as image quality degrades, although the deterioration in accuracy is more predictable for AI measurements. Importantly, deterioration in image quality (and therefore doubtfulness of the measurement) can be automatically quantified through the MHA to flag measurements needing special attention. Figure 1: Progressive degradation in images (upper panel) and corresponding increase in measurement error by both human experts and AI (lower panel)

Investigation into the Motion Characteristics and Impact Loads of Buoy Water Entry Under the Influence of Combined Waves and Currents

As a crucial component in marine monitoring, meteorological observation, and navigation systems, studying the motion characteristics and impact loads of buoy water entry is vital for their long-term stability and reliability. When deployed, buoys undergo a complex motion process, including the impact of entering the water and a stable floating stage. During the water entry impact phase, the motion characteristics and impact loads involve interactions between the buoy and the water, the trajectory of motion, and dynamic water pressure, among other factors. In this paper, the VOF model is used to calculate the buoy’s water entry motion characteristics, and then the STAR-CCM+&ABAQUS bidirectional fluid–structure interaction (FSI) method is used to calculate the water entry impact load of the buoy under different water surface conditions and different initial throwing conditions, considering the influence of the flow field on the structure and the influence of the structure deformation on the flow field. The study finds that under the influence of wave and current impacts, changes in wave height significantly affect the buoy’s heave motions. Under different parametric conditions, due to the specific direction of wave and current impacts, the buoy’s pitch amplitude is relatively more intense compared to its roll amplitude, yet both pitch and roll motions exhibit periodic patterns. The buoy’s pitch motion is sensitive to changes in the entry angle; even small changes in this angle result in significant differences in pitch motion. Additionally, the entry angle significantly impacts the peak vertical overload on the buoy. Instantaneous stress increases sharply at the moment of water entry, particularly at the joints between the crossplate and the upper and lower panels, and where the mast connects to the upper panel, creating peak stress concentrations. In these concentrated stress areas, as the entry speed and angle increase, the maximum equivalent stress peak at the monitoring points rises significantly.

Monitoring and Control System for Temperature, Humidity, and Air Quality in LVMDP Panel Rooms to Improve the Reliability of LVMDP Panel Components Using Fuzzy Logic

Power Distribution System plays a crucial role in modern life. Low Voltage Distribution Panel (LVMDP) is a critical component within this system, responsible for distributing low-voltage electricity to various loads. Optimal reliability and performance of LVMDP are essential to ensure continuity and stability of power supply. Environmental factors such as temperature, humidity, and air quality can significantly impact the reliability and lifespan of electrical equipment in LVMDP. An Internet of Things (IoT) and Fuzzy Logic-based Monitoring and Control System offers an innovative solution to address these issues. The IoT Monitoring System enables real-time monitoring of temperature, humidity, and air quality, allowing for early detection of environmental changes that could potentially damage equipment. The Fuzzy Control System then responds to these changes automatically and adaptively, regulating cooling, heating, circulation, dehumidifier, or humidifier devices to maintain optimal environmental conditions. Implementing this Monitoring and Control System not only enhances equipment reliability and lifespan but also reduces the risk of power supply disruptions. Therefore, the development and implementation of this system serve as an innovative and essential solution in maintaining the reliability of the power system. Advancements in IoT and Fuzzy Logic technologies open up opportunities to improve the overall reliability and efficiency of the Power Distribution System. This Monitoring and Control System presents a strategic step that can yield significant positive impacts on the reliability and performance of the Power Distribution System as a whole.

(Invited) Pulse-Voltage-Induced Neuromorphic Function of Pt/Anatase-Ti0.99Sc0.01O2- δ/Pt Multilayer with Electron-Ion Mixed Conduction

The study investigates oxide thin films with mixed electron-ion conductivity, which display neuromorphic behavior when metal is incorporated into a cross-point structure. This device, comprising metal oxide-metal multilayers, forms a Schottky barrier between the electrode and the oxide layer, creating a localized conductive filament between the electrodes. Neuromorphic resistive switching memorization is achieved through the electron and oxygen vacancy migrations at the Schottky barrier that correspond to changes in synaptic potential. The change in current value caused by the application of pulsed voltage emulates the memory mechanism of the brain, and memory can be controlled by changing the learning interval [1]. Previous studies have shown that the Pt/Ti0.99Sc0.01O2- δ (Rutile)/Pt multilayer device with electron-proton mixed conduction does not form the conductive filaments and exhibits neuromorphic learning and forgetting functions by local proton migration near the Schottky barrier [2]. However, the drawback of Rutile-type TiO2 is in the low resistive state, which has a high amount of oxygen vacancy and high electron conductivity with deposition temperature. On the other hand, Anatase-type TiO2, a wide-gap semiconductor and a metastable phase of TiO2, can be deposited at low temperatures. Therefore, it is possible to control electronic conductivity and provide mixed electron-ion conductivity. In this study, we deposited Rutile-type and Anatase-type TiO2 thin films to replicate neuromorphic function for electrical properties and applied pulsed voltage to Pt/Ti0.99Sc0.01O2- δ (Rutile/Anatase)/Pt multilayers. These films were deposited on Al2O3 (0001) substrates using RF magnetron sputtering, with Rutile type deposited at 600℃ and Anatase type at 300℃. We measured crystal structure, temperature, and oxygen partial pressure dependence of electrical conductivity, pulse voltage response, and electronic structure. The XRD pattern results confirmed that monolayer Rutile and Anatase thin film could be created on an Al2O3 (0001). The oxygen partial pressure dependence indicates mixed electron-ion conductivity, suggesting a strong relation between brain-type property and thin film's electron-ion mixed conductivity.Figures (a) and (b) show the current curves with time for the Pt/Ti0.99Sc0.01O2- δ (Rutile, Anatase)/Pt multilayer when electrical pulses of 0.8 V were applied for 4 s at the interval time of 80 s and 13 s, respectively. An applied voltage during the interval time was 0.1 V. Each upper panel is the input pulse voltage. Each lower panel is the relative output current versus time. In Figure (a), the output current after the pulse input rapidly decays, and the minimum current remains unchanged, indicating STM. In Figure (b), the relative output current after the pulse input slightly increases with the input pulse, indicating the learning of LTM. The current increase was 0.36% for the Rutile-type TiO2 and 6.45% for the Anatase-type, indicating that learning of LTM in Anatase-type TiO2 is about 18 times faster than in Rutile-type. According to these results, the relaxation time (τ) was obtained from the current decay curve of LTM functions after pulse application by the Debye relaxation: 1.55~2.18s for the Rutile-type TiO2 and 0.25~0.3s for the Anatase-type. For the Pt/WO3/Pt multilayer device with conducting filament created by redox reaction, τ has been reported to be about ∼0.4 s [3].The above results suggest that the Anatase-type Pt/Ti0.99Sc0.01O2-δ/Pt multilayer reproduces neuromorphic function higher than in Rutile-type and forms an electrical double layer near the Schottky barrier of the interface, it can be processed faster than a multilayer device with conducting filament. Based on the basic properties of Pt/Ti0.99Sc0.01O2- δ/Pt multilayers and the results of various structural and electrical properties, we will report on the mechanism of brain-type properties at the Rutile and Anatase-type interfaces on the day. Reference [1] K. Kawamura, T. Tsuchiya, M. Takayanagi, K. Terabe, and T. Higuchi, Jpn. J. Appl. Phys. 56, 06GH01 (2017).[2] M. Taniguchi, T. Takada, K. Tomiyoshi, T. Wada, D. Nishioka and T. Higuchi, Jpn. J. Appl. Phys. 62, SG1022 (2023).[3] R. Yang, K. Terabe, Y. Yao, T. Tsuruoka, T. Hasegawa, J. Gimzewski and M. Aono, Nanotechnology 24, 384003 (2013). Figure 1

Abstract 4140122: Bioengineered Self-Adhering Electrospun Nanoscaffolds to Deliver Mitochondrial Antioxidant, JP4-039

Introduction: Treatment of pathologic remodeling and subsequent decline in cardiac function post-myocardial infarction (MI) remains limited. Our lab has previously demonstrated that the targeted mitochondrial antioxidant, JP4-039 (JP4), can abrogate post-MI remodeling and decline in cardiac function, and that JP4 released from electrospun nanoscaffolds improved proliferation and migration of coronary vascular endothelial cells in vitro . The aims of this study were to develop a suture-free, bioadhesive electrospun nanoscaffold that will adhere post-MI cardiac tissue and reliably release JP4 in a localized manner. Hypothesis: Plasma treatment of JP4-loaded biocompatible electrospun nanoscaffold will adhere to cardiac tissue and deliver active moiety of JP4. Methods: A 2% poly(l-lactide-co-glycolide) (PGLA) was electrospun with and without 1% JP4. Nanoscaffolds then underwent plasma treatment for one minute followed by a force adhesion assay. SEM imaging and electron paramagnetic resonance ( EPR ) assays before and after plasma treatment of both control and JP4-loaded patches were performed to examine patch consistency and ensure the release of the unaltered, active structure of JP4. Results: JP4 loading and plasma treatment did not affect fiber dimeter of the scaffolds (p > 0.5 for all; Fig. 1B). JP4-loaded patches demonstrated similar release pattern of the antioxidant’s nitroxide moiety by displaying a characteristic triple peak both before and after plasma treatment as determined by EPR (Fig. 1C). Plasma-treated patches demonstrated significant increase in force adhesion compared to non-treated patches in both the control and JP4-loaded scaffolds (p < 0.0001) (Fig. 1A.). No significant difference in force adhesion was observed between the plasma treated control and JP4 loaded patch (p > 0.05) as determined by ANOVA (Fig. 1A). There was no significant difference in force adhesion between one minute and two minutes of plasma treatment (p > 0.05; Fig. 1A lower panel). Conclusion: The findings demonstrate that plasma-treated biocompatible JP4-loaded patches may reliably adhere to cardiac tissue and release the bioactive component of the mitochondrial antioxidant, JP4.

Left atrial function and long-term survival after cardiac resynchronization therapy

Abstract Background Left atrial (LA) reservoir strain after CRT has been linked to long-term outcome, but the role of LA function in response to cardiac resynchronization therapy (CRT) is incompletely understood. LA dyssynchrony during left bundle branch block has negative effects on LA function beyond LA reservoir strain. We hypothesized that correction of LA dyssynchrony after CRT has added value to LA reservoir strain as a marker of long-term outcome. Purpose To explore the role of LA function in long-term survival after CRT. Methods In a recent prospective multicenter study of 168 patients, LA segmental and global strains were measured by speckle-tracking echocardiography before and 7 ± 1 months after CRT. LA reservoir strain was measured as the difference between peak and minimum global strain during the atrial cycle and LA dyssynchrony as the time delay between onset systolic stretch of the interatrial septum and LA lateral wall. Since LA reservoir strain < 18% is associated with elevated LV filling pressure, we used 18% as cutoff and for LA dyssynchrony 43 ms (mean after CRT in the present study). All-cause mortality was used as clinical endpoint during follow-up. Results After 6 years ± 21 months (mean ± SD) follow-up, 35 (21%) patients died. LA reservoir strain was significantly lower (15 ± 9% vs 20 ± 10%, p = 0.003) and LA dyssynchrony numerically higher (61 ± 68 ms vs 39 ± 69 ms, p = 0.099) in patients who died compared to survivors. LA reservoir strain ≥ 18% after CRT was associated with favorable long-term survival (HR: 0.51, 95% CI: 0.26 - 0.98) (upper panel in the Figure). LA dyssynchrony was not independently associated with mortality. However, when used in concert with LA reservoir strain ≥ 18% after CRT, it identified patients with perticularly excellent long-term survival (HR: 0.17, 95% CI: 0.05 - 0.58 vs patients with reservoir strain ≥ 18% and persistent LA dyssynchrony) (lower panel in the Figure). Patients with preserved LA reservoir strain but persistent LA dyssynchrony had similar outcome as patients with reduced LA reservoir strain (HR: 0.98, 95% CI: 0.45 - 2.12). Conclusion LA reservoir strain ≥ 18% and absence of LA dyssynchrony is associated with excellent long-term survival after CRT.LA strain after CRT and survival

Left atrial morpho-functional parameters and their correlation with other phenotypic and functional characteristics of hypertrophic cardiomyopathy

Abstract Background Left atrial (LA) volume index (LAVI), LA reservoir strain (LARS) and total atrial conduction time (TACT) (estimated by tissue Doppler imaging) are morphological and functional parameters reflecting LA structural and electrical remodeling, connected to atrial fibrillation development and heart failure progression in various substrates. In hypertrophic cardiomyopathy (HCM), correlation of the above-mentioned parameters with other disease characteristics is not fully investigated. Purpose Aim of this study was to estimate the prevalence of atrial myopathy characteristics such as increased LAVI, impaired LARS and elongated TACT in a cohort of HCM patients without AF history and investigate their correlation with other phenotypic and functional characteristics of the disease such as left ventricular (LV) hypertrophy magnitude, fibrosis extent and diastolic dysfunction grade. Methods We included 100 HCM patients (54±21 years, 75% male, maximum wall thickness 19±3.4mm) without history of atrial fibrillation who have consecutively undergone 2D-speckle tracking echocardiography and cardiovascular magnetic resonance (CMR) with late gadolinium enhancement (LGE). TACT and LARS measurement is shown on left panel. Burden of fibrosis (percentage of LV mass) was defined by LGE extent (>5 standard deviations compared to nulled myocardium) in CMR slices. Results All HCM patients had preserved EF (60±7.5%), while 28 (28%) presented outflow tract obstruction and 10 (10%) diastolic dysfunction stage≥2. LGE was observed in 64 patients (64%) occupying 8±5% of left ventricular (LV) mass. Mean TACT was 140±22 msec, with LAVI being 32±16 mL/m2 and LARS 26±14%. Among HCM demographic, phenotypic and functional characteristics tested, age and LV mass index were found to be the only independent regressors of TACT (r=0.54, p<0.0005 and r=0.44, p=0.002 respectively, right upper panel), while E/E’ (r=-0.44, p=0.003) and fibrosis extent (r=0.36, p=0.02) were the strongest predictors of LARS and LAVI values respectively (right lower panel). Conclusions Atrial myopathy parameters seem to correlate with various morphological and functional characteristics of HCM. Atrial electro-mechanical delay assessed through TDI based TACT correlates significantly with LVMI, whereas LARS and LAVI are strong regressors of elasticity properties, partially expressed through diastolic function and underlying fibrosis.

Clinical outcomes in >10,000 Asian vs >61,000 Non-Asian race patients with AF randomized to Warfarin vs DOACs: a patient-level meta-analyses from COMBINE AF

Abstract Background Randomized data comparing clinical outcomes of atrial fibrillation (AF) patients with Asian vs non-Asian races are limited. Methods Using the COMBINE AF (A Collaboration Between Multiple Institutions to Better Investigate Non-Vitamin K Antagonist Oral Anticoagulant Use in Atrial Fibrillation) database (data from RE-LY, ROCKET AF, ARISTOTLE, and ENGAGE AF-TIMI 48), we performed an individual patient-level meta-analysis to investigate and compare clinical outcomes of AF patients with self-defined Asian and non-Asian races adjusted for baseline characteristics. Standard-dose direct oral anticoagulants (SD DOAC) were defined as dabigatran 150mg bid; rivaroxaban 20mg (15mg) QD, apixaban 5 mg (2.5 mg) bid, or edoxaban 60 mg (30 mg) QD. Low-dose DOACs (DOACs [LD]) were defined as dabigatran 110 mg bid or edoxaban 30 mg (15mg) QD. Results There were 10,212 pts of Asian race and 61,471 non-Asian races in the COMBINE AF database. Compared with non-Asians, Asians were on average 3.2 yrs younger, 20 kg lighter, had worse renal function (mean CrCl 64.9 vs. 77.3 mL/min), and higher rates of prior stroke/transient ischemic attack (37.2% vs 26.6%), P<0.001 for each. The median value of time in therapeutic range of patients randomized to warfarin was lower in Asians than non-Asians (57.7% vs. 66.2%, P<0.001). In the warfarin arm, Asians had a higher adjusted risk of stroke/systemic embolic events (SEE), major bleeding (MB), ICH, GI bleeding (GIB), and net clinical outcome (NCO: stroke/SEE, MB, or death)(Figure; Upper panel). Compared to warfarin, SD DOACs significantly reduced the risks of stroke/SEE, MB, and NCO to a greater degree in Asians than non-Asians (HR stroke/SEE: Asians 0.65 vs Non-Asians 0.86; HR MB: Asians 0.62 vs Non-Asians 0.91; HR NCO: Asians 0.76 vs non-Asians 0.94; Pint <0.02 for each), while SD DOACs increased GIB only in non-Asians (Asian HR 0.92 [0.69-1.23] vs Non-Asians HR 1.41 [1.25-1.58], Pint 0.009; Figure Lower panel). Conclusions The adjusted risks of stroke/SEE and major bleeding with warfarin were higher in Asians compared to non-Asians. The benefits of DOACs over warfarin in preventing stroke/SEE, MB, and net clinical outcomes were significantly greater in Asians than non-Asians.

Comprehensive evaluation of solar floating photovoltaic prospective in Saudi Arabia: Comparative experimental investigation and thermal performance analysis

Recently, floating photovoltaic systems have been regarded as a promising technology for producing clean energy by utilizing the surface of water bodies, such as lakes, rivers and oceans. This study introduces a comparative experimental study and energy performance evaluation of a 1.0 kW offshore floating photovoltaic (FPV) system and a nearby traditional ground-based PV system (GPV) installed in the eastern province of Saudi Arabia. The FPV system was deployed in the Arabian Gulf, 25 m off the coast, at an average depth of 1 to 1.5 m depending on tide, wave, and current intensity. The FPV system employs a strong novel eco-friendly platform structure made of recycled buoyant materials such as engineered plastic drums and wood. This system is anchored with tension cables and concrete blocks that can withstand the changing sea water conditions. The GPV system, on the other hand, was installed 150 m inland from the shore. Real-time monthly data monitoring and assessment indicated that FPV systems outperformed GPV systems in terms of lower PV panel surface temperatures, higher power output, and panel efficiency. Based on daily average back surface temperatures, FPV system temperature was decreased by 7.5 % to 21.34 % when compared to GPV. Moreover, the FPV system efficiency was also increased by 12.2 % when compared to the GPV system. This study aims to assist in promoting the applicability of solar floating photovoltaic systems to synergistically fulfill the requirements of sustainable electricity production for the arid costal community in Saudi Arabia and similar areas.

Sound absorption performance of honeycomb metamaterials Inspired by Mortise-and-Tenon structures

To address the limitations of traditional honeycomb sandwich structures in attenuating mid to low-frequency sounds, particularly in configurations with minimal thickness and weight, this study introduces an innovative honeycomb acoustic metamaterial incorporating the traditional Chinese mortise-and-tenon joint. We systematically investigate the acoustic absorption characteristics of the modified honeycomb structure through theoretical analysis, empirical validation, and numerical simulations. Our experimental setup maintained consistent geometric parameters across all trials and demonstrated that the resonance frequency of the modified honeycomb structure decreased by 10 % relative to its conventional counterpart. We conducted detailed analyses on the influence of micropore positioning, tenon geometric dimensions, and micropore diameters on the acoustic performance. Notably, elongating the tenon from 2 mm to 6 mm resulted in a 15 % reduction in resonance frequency, whereas increasing the micropore-to-tenon distance from 0 mm to 4 mm led to a 30 % increase. The integration of the mortise-and-tenon joint significantly enhances the mid to low-frequency sound absorption performance of the honeycomb panels. This improvement is achieved while preserving the structural benefits of low panel thickness and shallow cavity depth, alongside simplified processing of micropores. Our findings elucidate a promising approach to augmenting the acoustic properties of lightweight structural materials, thereby extending their application potential in noise control engineering. This study not only contributes a novel perspective to the design and optimization of acoustic metamaterials but also highlights the potential for integrating traditional architectural techniques with modern material science to enhance noise control solutions.

Looking High and Low: Incentive Policies and Residential Solar Adoption in High- and Low-Income U.S. Communities

Rooftop solar adoption has increased considerably in recent years thanks to a combination of lower panel costs and generous incentive programs. This paper estimates the increase in residential rooftop solar adoption associated with three types of solar incentive programs and isolates the effect of these programs in both high and low-income census tracts. We utilize a dataset of census tract-level rooftop solar adoption compiled using a machine learning-based image classification tool that identifies solar photovoltaic panels from satellite images. This allows us to study areas of the country that have lower solar adoption rates and incomes than areas previously studied. We find evidence that programs designed specifically to encourage adoption in low-income areas are associated with a smaller gap between low- and high-income solar adoption. However, property-tax benefits and net metering, which are more prevalent across the U.S., are associated with an increase in the gap between low- and high-income solar adoption.

Evaluation of the mechanical properties of stiffened composite panels under consideration of water load

Abstract To meet the strength evaluation requirements of a typical stiffened composite panel of the lower fuselage of a new generation amphibious aircraft underwater load, the experimental testing technique and finite element analysis method were investigated. Firstly, according to the loading and support requirements of the typical stiffened composite lower fuselage panel, a testing device for combined axial and pneumatic loading was designed and developed. Then, a finite element model of the stiffened composite plate and the combined load testing device were created. Based on the experiments and finite element analysis, the static strength of the stiffened composite plate was verified to meet the load-bearing capacity requirements, and the strain behavior during loading was determined. Compared with the experimental results, the maximum strain error at the skin is 6.16%, and the maximum strain error at the stiffener is -11.6%. This confirms the effectiveness of the finite element model and also confirms that the test technique and equipment can accurately simulate in-plane axial loading and out-of-plane water loading. Finally, based on the validated finite element model, the load-bearing capacity of the stiffened composite panel under combined loads was predicted.

Open Circuit Voltage Hold Induced Degradation Under Dry Conditions and Recovery Strategies in PEMFC Electrodes

With regards to the decarbonization of the transportation sector in the near future, the importance of proton exchange membrane (PEM) fuel cells is shifting more and more from light-duty vehicles to heavy-duty vehicles, as well as to an application for maritime and aviation applications. With this change in the field of application, the requirements of the fuel cell system need to be adjusted towards an increased fuel efficiency and lifetime.1 Especially the targeted durability of 25,000 h for heavy-duty vehicles requires a detailed understanding of the degradation processes within the stack to be able to minimize performance losses or possible failure of the components.2 During the life cycle of a fuel cell electric vehicle, the stack encounters operation under increased temperature as well as under low relative humidity (RH). Both conditions are well known to lead to a degradation of the membrane electrode assembly (MEA).3,4 Deliberate operation under those conditions and at open circuit voltage (OCV) is commonly used to study the chemical degradation of the membrane. Here it is believed that gas crossover can lead to the formation of radicals, which attack the perfluoro sulfonic acid based ionomer chains and result in a variety of degradation products.5,6 Especially sulfonate group containing degradation species strongly adsorb on the Pt surface and reduce the oxygen reduction reaction (ORR) activity of the cathode catalyst. It was already shown that a suitable recovery step can restore of most of the observed performance losses.3,5 This work focusses on the chemical degradation and subsequent recovery strategies of a commercial MEA with an active area of 5 cm2 and a cathode loading of 0.4 mgPt/cm2. Although it is known that radical scavengers, like Ce3+ cations, minimize the chemical degradation within the membrane, we decided to use an MEA with a non-mitigated membrane (i.e., free of radical scavengers) in order to facilitate the degradation processes.5 As seen in the upper panel of Figure 1, the applied OCV hold for 72 h under H2/air (1000/1000 nccm) at 95 °C and at 30 % RH induces a voltage loss of ~115 mV (at 2.5 A/cm²) in the polarization curve after this accelerated stress test (AST), i.e., at end-of-degradation (EOD; red line/symbols), compared to the initial MEA performance at beginning-of-test (BOT; black line/symbols). In order to distinguish between reversible and irreversible losses, a subsequent recovery step at fully humidified conditions is implemented. The polarization curve at end-of-test (EOT; green line/symbols), i.e., after the recovery step, reveals that the majority of the observed losses is reversible. Provided that the applied recovery step accounts for all reversible effects, the remaining losses of ~45 mV (at 2.5 A/cm²) are of irreversible nature. On the one hand, those irreversible losses partially arise from a small increase in the high frequency resistance (HFR), which rises during the degradation period by ~2 mΩcm² (lower panel of Figure 1. On the other hand, the electrochemically active surface area (ECSA) is reduced by ~20 % over the course of the experiment, which leads to another unavoidable loss in performance. The comparison of the catalyst’s specific activity in units of mA/cm2 Pt, hence, accounting for the loss in ECSA, strongly suggests that the Pt surface at EOT approaches the initial state at BOT, which indicates a reversible degradation mechanism. References A. Cullen, K. C. Neyerlin, R. K. Ahluwalia, R. Mukundan, K. L. More, R. L. Borup, A. Z. Weber, D. J. Myers and A. Kusoglu, Nat. Energy, 6(5), 462–474 (2021).Marcinkoski, R. Vijayagopal, J. Adams, B. James, J. Kopasz, R. Ahluwalia, Hydrogen Class 8 Long Haul Truck Targets, DOE Hydrogen Program Record# 19006, https://www.hydrogen.energy.gov/docs/hydrogenprogramlibraries/pdfs/19006_hydrogen_class8_long_haul_truck_targets.pdf (2019).Du, T. A. Dao, P. V. J. Peitl, A. Bauer, K. Preuss, A. M. Bonastre, J. Sharman, G. Spikes, M. Perchthaler, T. J. Schmidt and A. Orfanidi, J. Electrochem. Soc., 167(14), 144513 (2020).Jomori, K. Komatsubara, N. Nonoyama, M. Kato and T. Yoshida, J. Electrochem. Soc., 160(9), F1067–F1073 (2013).Zhang, B. A. Litteer, F. D. Coms, R. Makharia, J. Electrochem. Soc., 159(7), F287–F293 (2012).A. Yandrasits, S. Marimannikkuppam, M. J. Lindell, K. A. Kalstabakken, M. Kurkowski and P. Ha, J. Electrochem. Soc., 169(3), 34526 (2022). Acknowledgements We gratefully acknowledge funding from the German Federal Ministry for Digital and Transport (BMDV) under the funding scheme H2Sky (funding code 03B10706). Figure 1

Experimental study on compression properties of composite aluminum honeycomb sandwich structures

AbstractThe mechanical properties of the carbon fiber and glass fiber composite honeycomb sandwich structure were studied through compression experiments. The influence of different aluminum honeycomb edge lengths, upper and lower panel thickness, aluminum honeycomb thickness, and loading speed on the compression failure load of carbon fiber composite laminates sandwich structure is analyzed. The influence of different aluminum honeycomb edge lengths and thicknesses on the compression failure load of glass fiber composite laminates sandwich structure was studied. The results show that the thickness of the panel has a significant effect on the failure load of the carbon fiber composite laminate sandwich structure, and the loading speed has a significant effect on the failure load of the carbon fiber composite laminate sandwich structure. The greater the loading speed, the greater the value of the failure load. The edge length and thickness of the aluminum honeycomb have a certain effect on the damage load of the carbon fiber composite laminates sandwich structure, but the influence on the mechanical properties of the glass fiber composite laminates sandwich structure is much greater.Highlights The compression performance of composite sandwich structures was experimentally studied. The influence of composite panel thickness was studied. The influence of aluminum honeycomb edge length and thickness was studied. The influence of loading speed was studied.

Significant Long-Term Prevention of High Sensitization After Kidney Allograft Failure by Maintaining Calcineurin Inhibitor-Based Immunosuppression.

Broad national or international programs contribute to mitigating the expected longer waiting list (WL) time for sensitized patients but with minor benefits for highly sensitized subjects. Therefore, strategies to prevent high sensitization are urgently required. In this study, we investigated the risk of developing highly sensitized patients with different immunosuppressive (IS) handling after kidney allograft failure (KAF). Data from 185 patients with KAF, retransplanted/relisted from 2010 to 2020 in two regions of Italy that share the same regional WL, were analyzed. Patients were categorized according to IS management at 12 months after KAF as follows: patients maintaining IS with calcineurin inhibitors (CNI) (late withdrawal group [LWG], n = 58) and those who withdrew all IS therapy or were on steroids only (early withdrawal group [EWG], n = 127). Patients in the LWG showed lower panel reactive antibodies (PRA) at 12 (29.0%vs. 85.5%, p < 0.001) and 24 months (61.0%vs. 91.0%, p = 0.001), reduced risk of high sensitization (PRA ≥90%) at 12 (9.4%vs. 40.7%, p < 0.001, OR = 0.15) and 24 months (25.6%vs. 57.3%, p = 0.001, OR = 0.26) and almost no very high sensitization (PRA ≥ 98%) at 12 months (1.9%vs. 18.6%, p=0.003, OR=0.08) after KAF. In the LWG subgroup analysis, patients who maintained IS for up to 24 months after KAF did not show very high sensitization. The LWG showed shorter active WL times (406vs. 813 days, p = 0.001) without an increased risk of complications. CNI maintenance for at least 12 months after KAF could be a useful approach to prevent high sensitization and reduce WL times in patients who are offered retransplantation, without a higher burden of complications.

Blast-Resistant Performance of Steel Petrochemical Control Room with 3D-Kagome Sandwich Wall

As the control brain of the petrochemical plant, blast-resistant performance requirements are important for the sustainability of the petrochemical control room and should be guaranteed when the vapor cloud explosion occurs in the petrochemical production process. The 3D-Kagome truss core sandwich structure is a kind of blast-resistant material with high energy absorption and recycling. Considering the influential factors of the radius of the truss core rod and thickness of the upper and lower panels, in this paper, the blast-resistant performance of a real steel petrochemical control room with a 3D-Kagome truss core sandwich wall was analyzed. With the optimization goal of plastic deformation energy and panel displacement, the optimal wall thickness and radius of the truss core rod were obtained. The optimized blast-resistant walls were assembled, and the dynamic response of the steel petrochemical control room with the 3D-Kagome truss core sandwich blast-resistant wall was analyzed. The simulation results indicate that the truss core layer is ineffective in dissipating blast energy when the radius ratio of the truss core rod exceeds 2.7% of the total wall thickness. Moreover, as the thickness of the upper and lower panels increases from 0.5 cm to 3 cm, the proportion of plastic deformation energy in the truss core layer gradually rises from 55% to 95%, stabilizing at around 90%. The optimal configuration for blast resistance is achieved when the panel thickness ratio is 6.7% of the total wall thickness; the truss core rod radius ratio is 2.7% of the total thickness. This study establishes the effectiveness of the optimized 3D-Kagome sandwich wall as a blast-resistant solution for steel petrochemical control rooms.

A multiscale hydro-elastoplastic model for large floating structures in two-dimension

A novel fluid–structural model was presented considering hydro-elastoplastic behavior, which coupled multiple hydro-structural-material scales. A large floating sandwich structure (LFSS) comprising upper and lower high-strength panels and a low-weight core was considered as an illustration. The mesoscale characteristics of materials and elastoplastic parameters of the low-weight perforated components were coupled by utilizing the representative volume element (RVE) method. Through the parameterized relations from RVE analysis, the flexure dynamics model for the floating sandwich structure with an equivalent homogenized core was deduced. With the flexure dynamic equation, yield criterion, and potential flow model, a multiscale hydro-elastoplasticity theoretical model was established, which combined the wave action, hierarchical component, material configuration, and structural behavior. The dynamic responses of the large floating structure under fluid–structure interaction were calculated, and the internal deformation (i.e., core strain) was set as the determining variable for the plastic region. The initially intact floating structure became hinged multi-modules after plastic cracking, and the high-strength layers at the cracking positions behaved as flexible hinges, which was defined as a hydro-elastoplastic process. The elastoplastic state evolutions of the LFSSs with different structural parameters and material configurations were solved for practical optimization. The results indicated that the multiscale coupled calculation model can provide great scientific guidance for designing large floating structures.

Experimental study on direct shear resistance of horizontal grouted joints in PC shear walls under compression and in-plane bending moment

The upper and lower panels of the prefabricated concrete shear wall are usually connected via horizontal grouted joints to maintain structural integrity. The horizontal grouted joints are typically under compression and in-plane bending moment. In the current design practice, it is generally considered that the direct shear resistance of the horizontal grouted joint is identical to that of the new-old concrete joint, and not affected by the bending moment if no bending failure occurs. In fact, as far as the authors know, both considerations lack experimental evidences. In this study, eight horizontal joint specimens were tested, including four grouted joints and four new-old concrete joints, to investigate their direct shear performances under constant compression and different in-plane eccentricities. Test results indicated that the ultimate direct shear resistance of the grouted joints was averagely 15.9 % lower than that of the new-old concrete joints. For the joints under small eccentricities associated with full shear plane in compression, the ultimate direct shear resistances remained unchanged compared to the cases under no eccentricity. However, for the grouted joints under large eccentricities associated with partial shear plane in tension, the ultimate direct shear resistances reduced up to 27.8 % compared to the grouted joint under no eccentricity. In addition, the shear transfer mechanism was investigated with the aid of the extended shear-friction model. Finally, recommendations were proposed for direct shear design of the horizontal grouted joints.

Repeated impact response of honeycomb sandwich panels based on the failure parameters of adhesive layer and material

Honeycomb sandwich structure has been widely used in lightweight and impact protection of rail vehicle structures due to its excellent mechanical properties. In this paper, the plastic deformation, failure response and energy absorption characteristics of honeycomb sandwich panels for rail vehicles under repeated impact loads were studied. The three-point bending tests and low-speed impact tests of honeycomb sandwich panels were carried out, and a three-dimensional numerical model considering the detailed structure of the honeycomb core and the failure of the adhesive layer was established. The model can reasonably simulate honeycomb sandwich panels’ stiffness, strength, and structural failure. The effects of impact times and impact angle on the performance indexes of the honeycomb sandwich panel were studied. The results show that when the impact energy is the same, the impact times will affect the energy absorption distribution of honeycomb sandwich panels. With the increase in impact times, the panel’s absorption energy decreases, the core’s absorption energy increases, and the total absorption energy decreases. For multiple impact conditions, with the increase of impact times, the single energy absorption of the upper panel and core decreases, and the single energy absorption of the lower panel increases. When the impact energy is the same, the rise in impact angle will increase the damage to the honeycomb sandwich panel, and the energy absorption of each part will increase. In addition, the influence of impact times on the energy absorption efficiency of honeycomb sandwich panels is related to the impact angle.