Power Drop Research Articles

New Approach for Tracking, Monitoring, and Diagnosing Faults in a Photovoltaic System in Real Time: An Experimental and Case Study

Photovoltaic installations have emerged as a cornerstone of sustainable energy production, playing a pivotal role in the global transition towards renewable sources of electricity. As the demand for clean energy surges, so too does the need for robust monitoring and diagnostic strategies to ensure the efficient operation of these systems. This study presents a novel methodology for the real-time tracking, monitoring, and diagnosing of faults in photovoltaic systems (PVSs), emphasizing their crucial role in sustainable energy production amid the global shift to renewable energy. The study was conducted in Guelma, Algeria, during the spring and summer seasons. The investigation utilized WatchPower simulation software over a 24-hour performance analysis of the photovoltaic system. On June 19, 2024, with a high temperature of 32°C, the system achieved a peak output power of 600W under optimal conditions, validating its efficiency in energy generation. The study also analyzed the effects of shading on energy output by comparing data from a shaded day on May 14, 2024, at 25°C, to an unshaded day on June 21, 2024, at 32°C, during peak sunlight hours from 9:00 AM to 2:15 PM, the period when sunlight is at its strongest. The results showed a significant drop in output power from 600W to 450W due to shading, underscoring the importance of real-time monitoring to detect performance inefficiencies. This research not only enhances operational reliability and maintenance strategies for PV systems but also demonstrates the effectiveness of integrating real-time data analytics to support decision-making in similar environments.

Body Oxygen Level Test (BOLT) is not associated with exercise performance in highly-trained individuals.

The analysis of chemoreflex and baroreflex sensitivity may contribute to optimizing patient care and athletic performance. Breath-holding tests, such as the Body Oxygen Level Test (BOLT), have gained popularity as a feasible way to evaluate the reflex control over the cardiorespiratory system. According to its proponents, the BOLT score reflects the body's sensitivity to carbon dioxide and homeostasis disturbances, providing feedback on exercise tolerance. However, it has not yet been scientifically validated or linked with exercise performance in highly-trained individuals. Therefore, we investigated the association of BOLT scores with the results of standard performance tests in elite athletes. A group of 49 speedskaters performed BOLT, Wingate Anaerobic Test (WAnT), and cardiopulmonary exercise test (CPET) on a cycle ergometer. Peak power, total work, and power drop were measured during WAnT. Time to exhaustion and maximum oxygen uptake were measured during CPET. Spearman's rank correlation and multiple linear regression were performed to analyze the association of BOLT scores with parameters obtained during the tests, age, somatic indices, and training experience. No significant correlations between BOLT scores and parameters obtained during WAnT and CPET were found, r(47) = -0.172-0.013, p = 0.248-0.984. The parameters obtained during the tests, age, somatic indices, and training experience were not significant in multiple linear regression (p = 0.38-0.85). The preliminary regression model showed an R 2 of 0.08 and RMSE of 9.78sec. Our findings did not demonstrate a significant relationship between BOLT scores and exercise performance. Age, somatic indices, and training experience were not significant in our analysis. It is recommended to interpret BOLT concerning exercise performance in highly-trained populations with a great degree of caution.

Integrated Control Design for Hybrid Grid-Photovoltaic Systems in Distillation Applications: A Reference Model and Fuzzy Logic Approach

This paper presents a novel hybrid structural control solution designed for distillation systems that utilize a solar source alongside an electrical grid. The power conversion architecture incorporates a reversible bridge rectifier and a quadratic boost converter. The hybrid photovoltaic grid configuration offers several benefits, including source complementarity, enhanced dependability, and energy availability aligned with power requirements. Leveraging a photovoltaic source operating at maximum power facilitates energy conservation. On the control front, an adaptive technique based on a reference model is proposed. Fuzzy logic governs the quadratic boost converter, simplifying the management of its complex nonlinear nature. The control strategy aims to maximize solar power utilization, minimize harmonic components in the grid current, synthesize an adaptive controller, and achieve a near-unit power factor on the grid. The simulation results for a steady distillation system demonstrate promising findings. Despite variations in irradiation, load power, and grid drops, the system maintains a minimal bus voltage ripple, remaining close to the intended value. Optimization of the panel-generated power leads to improved PV source utilization and enhanced system efficiency. Furthermore, the combination with an electrical grid achieves a low rate of grid current distortion and a unitary power factor.

Effects of Carbohydrate and Caffeine Mouth Rinsing Methods on Repetitive Kick Force and Duration, and Hand Reaction Time in Karate Athletes

The effect of carbohydrate (CHO) and caffeine (CAF) solutions rinsing in the mouth in combat sports where high-intensity movements are performed intermittently despite fatigue is unknown. This research was carried out to investigate the effects of rinsing CHO and CAF solutions in the mouth on kick force, duration, and hand reaction time in karate athletes. 16 male trained karate players (average age 21.6 years, weekly training time 8.4 hours, training experience 7.8 years) voluntarily participated in the study. In a replicated, double-blind, placebo-controlled, and crossover design study, after the 10 seconds mouth rinsing of CHO (6.4% maltodextrin), CAF (1.2%), and placebo (water) solutions in sessions, repeated sprint test (6sec sprint ×10 repetitions, with 30sec rest) on a bicycle ergometer, after light stimuli kick test (consecutive 5 times), hand reaction time test (consecutive 5 times), kick test (consecutive 5 times), hand reaction time test (consecutive 5 times) were performed respectively. The results obtained from the tests in the constructed protocol by causing fatigue (peak power, average power, minimum power, power drop; kicking reaction time, strength, power, and time; hand reaction time) were compared between sessions. The highest peak power and average power outputs (W/kg) obtained from the repeated sprint test were obtained in the CAF session, and the best kick and hand reaction times (ms) were obtained in the CAF session in the 2nd set of tests. The results obtained from this study suggest that the CAF mouth rinsing method can improve kick and hand reaction time despite fatigue in karate competitions.

Synthesis and characterization of cubic δ–phase stabilized Bi2O3 electrolytes by triple rare earth cation doping for intermediate temperatures SOFCs

Face–centered cubic–Bi2O3 (δ–phase), a high–ion conductor, is an essential solid electrolyte option, particularly for low–low–temperature SOFC applications. It is widely accepted that δ–Bi2O3 exhibits higher conductivity than the YSZ electrolytes typically utilized in HT–SOFC units. The present study investigates the structural, thermal, surface, and conductivity characteristics of the Bi2O3 electrolytes co–doped with Tb–Sm–Gd rare earth. The XRD data indicate that, except composition 20Tb20Sm20Gd, all compositions are stabilized with the cubic δ–phase at room temperature. The estimated lattice constants additionally suggest lattice contraction, confirming that the partial cation substitutes between host Bi3+ and rare earth cations are successful. The DTA curves do not have any endothermic or exothermic peaks, indicating a possible phase transition. Arrhenius plots prove that DC conductivity decreases as the dopant ratio increases, implying a drop in polarization power. The highest conductivity is found to be 0.131 S/cm for the composition 10Tb10Sm10Gd.

Detuning analysis and power tracking of dual‐ended resonant circuit based on improved variable‐step perturbation observation for wireless power transfer system

AbstractA power tracking method based on improved variable‐step perturbation observation approach has been proposed in this paper. This method is aimed at addressing the detuning issues caused by capacitor parameter drift in MCR‐WPT systems based on S‐S compensation circuits. Compared with traditional tuning methods, the proposed method has fast response, high accuracy, low complexity, and less prone to over‐tracking. Firstly, a mathematical model of the system based on the detuning factor has been established. Secondly, the impact of different detuning conditions on the system at the initial resonant frequency has been studied. Thirdly, the response characteristics of the system to different frequencies under different detuning conditions have been studied. Fourthly, based on the above researches, an improved variable‐step perturbation observation method based on the single‐step power drop factor has been proposed. Finally, an experimental platform was constructed, and relevant experiments were conducted. Experimental results validate the effectiveness of power tracking under different detuning conditions, with the lowest transmission efficiency being 81.51%.

Operating in a second language lowers cognitive interference during creative idea generation: Evidence from brain oscillations in bilinguals

Tasks measuring human creativity overwhelmingly rely on both language comprehension and production. Although most of the world's population is bilingual, few studies have investigated the effects of language of operation on creative output. This is surprising given that fluent bilinguals master inhibitory control, a mechanism also at play in creative idea evaluation. Here, we compared creative output in the two languages of Polish(L1)-English(L2) bilinguals engaged in a cyclic adaptation of the Alternative Uses Task increasing the contribution of idea evaluation (convergent thinking). We show that Polish-English bilinguals suffer less cognitive interference when generating unusual uses for common objects in the L2 than the L1, without incurring a significant drop in idea originality. Right posterior alpha oscillation power, known to reflect creative thinking, increased over cycles. This effect paralleled the increase in originality ratings over cycles, and lower alpha power (8–10 Hz) was significantly greater in the L1 than the L2. Unexpectedly, we found greater beta (16.5–28 Hz) desynchronization in the L2 than the L1, suggesting that bilingual participants suffered less interference from competing mental representations when performing the task in the L2. Whereas creative output seems unaffected by language of operation overall, the drop in beta power in the L2 suggests that bilinguals are not subjected to the same level of semantic flooding in the second language as they naturally experience in their native language.

DHA supplementation for early preterm birth prevention: An application of Bayesian finite mixture models to adaptive clinical trial design optimization

BackgroundEarly preterm birth (ePTB) - born before 34 weeks of gestation - poses a significant public health challenge. Two randomized trials indicated an ePTB reduction among pregnant women receiving high-dose docosahexaenoic acid (DHA) supplementation. One of them is Assessment of DHA on Reducing Early Preterm Birth (ADORE). A survey employed in its secondary analysis identified women with low DHA levels, revealing that they derived greater benefits from high-dose DHA supplementation. This survey's inclusion in future trials can provide critical insights for informing clinical practices. ObjectiveTo optimize a Phase III trial design, ADORE Precision, aiming at assessing DHA supplement (200 vs. 1000 mg/day) on reducing ePTB among pregnant women with a low baseline DHA. MethodsWe propose a Bayesian Hybrid Response Adaptive Randomization (RAR) Design utilizing a finite mixture model to characterize gestational age at birth. Subsequently, a dichotomized ePTB outcome is used to inform trial design using RAR. Simulation studies were conducted to compare a Fixed Design, an Adaptive Design with early stopping, an ADORE-like Adaptive RAR Design, and two new Hybrid Designs with different hyperpriors. DiscussionSimulation reveals several advantages of the RAR designs, such as higher allocation to the more promising dose and a trial duration reduction. The proposed Hybrid RAR Designs addresses the statistical power drop observed in Adaptive RAR. The new design model shows robustness to hyperprior choices. We recommend Hybrid RAR Design 1 for ADORE Precision, anticipating that it will yield precise determinations, which is crucial for advancing our understanding in this field.

A novel tuning range search method for single soliton state micro-comb generation

Abstract Mode-locked single-soliton state micro-comb (SSC) can be achieved in a miniaturized highly compact platform by pumping the micro-resonator with a single-frequency continuous wave laser. However, a significant challenge lies in effectively exploring the tuning range of pump power, spanning over hundreds of mW, as well as the detuning range and tuning speed in the range of hundreds of MHz and the order of MHz/s to GHz/s respectively. Here, we delve into a simulation model, considering thermal effects to ensure that the simulation accurately reflects the power drop and thermal detuning observed in the experimental process. Our simulation model, featuring precision scanning and iterative parameter demonstrations, has proven instrumental in accurately exploring the optimal tuning range for the existence of SSC to a few MHz. This provides a foundation for controlled and predictable SSC generation experiments.

Enhancing photovoltaic panel efficiency with innovative cooling Technologies: An experimental approach

The increase in photovoltaic panel temperature brought on by solar radiation absorption lowers performance, power output, energy efficiency, and panel longevity (a rise in temperature of just one degree causes power drop of 0.41 %). In an effort to alleviate this problem, this thorough study multiple novel cooling strategies to enhance solar system efficiency, especially photovoltaic panels in Egyptian climates remote areas. The three main routines for photovoltaic panel cooling are contingent on the following techniques: (1) evaporative cooling using marble, (2) evaporative cooling using palm fibers with fan-assisted airflow, and (3) thermoelectric cooler modules. These materials that used in the studied system as coolants are characterized by, abundant local availability in nature and low cost, especially in Egypt. Every method has been designed with a control system. According to the study, starting the cooling process at the greatest temperature that is permitted—45 °C—produces the maximum energy output from photovoltaic panels while balancing the need for cooling and energy production. Using these cooling methods causes the average temperature to be lowered by 16, 11.62, and 9.8 degrees Celsius for thermoelectric, marble, and palm fiber cooling respectively while the voltage output is enhanced by 2.58, 0.94, and 0.7 V. The recorded values indicate 4.59 %, 3.95 %, 2.15 % increase in photovoltaic panel exit power and 25.29 %, 15.79 %, and 15.1 % increase in photovoltaic panel energy conversion efficiency when thermoelectric, marble, and palm fibers cooler modules are used, respectively. This study is a priceless resource for scholars looking to improve photovoltaic panel performance by executing efficient cooling strategies with annual costs 0.017, 0.02, 0.026, and 0.024 $/kWh and payback periods 1.69, 2.07, 2.71, and 2.48 years for reference panel, marble cooling panel, palm fiber cooling pane, and thermoelectric cooling panel respectively.

CORRELATION OF ISOCAPNIC BUFFERING PHASE WITH AEROBIC AND ANAEROBIC POWER IN ATHLETES

Objective: The aim of the study below was to detect the relationship of isocapnic buffering phase values with the values of both aerobic and anaerobic power. Method: A total of 14 athletes, five females and nine males with ages between 18 and 25, who all have been active in sports for at least five years, volunteered to participate in the present study. At the beginning, the values of height, body mass, and body fat ratio of the volunteers were collected as required. Then, a maximal exercise test was applied to the volunteers and during the test, the values of maximal oxygen consumption capacity (VO2max), amount of oxygen consumed (VO2), amount of carbon dioxide produced (VCO2), respiratory threshold, respiratory compensation point, and maximal heart rate were determined accordingly. One week after aforesaid measurements, the Wingate anaerobic test was applied to the volunteers and the anaerobic power values were calculated. Initially, the descriptive statistics of the data obtained in the study were accomplished. Since the data did not reflect a normal distribution, the Spearman correlation analysis was applied to detect the correlation between both the aerobic and anaerobic power data and the isocapnic buffering data. The level of significance was accepted as p < 0.05. Results: Whereas a positive correlation was observed between VO2max (ml/kg/min) values and the values of maximum power (W/kg), average power (W/kg) and, minimum power (W/kg), a negative correlation was observed between VO2max (ml/kg/min) and power drop values (%) in female volunteers. For male volunteers, on the other hand, a positive correlation was observed between the values of VO2max (ml/kg/min) and minimum power (W/kg), and a negative correlation between the values of VO2max (ml/kg/min) and power drop (%). Furthermore, a significant relationship was also found between the values of isocapnic buffering and hypocapnic hyperventilation, and the values of maximal heart rate (beats/min), respiratory threshold VO2 (ml/kg/min), respiratory threshold heart rate (beats/min), respiratory threshold speed (km/hour), respiratory compensation point heart rate (beats/min), and respiratory compensation point speed (km/hour) in both male and female volunteers. Conclusion: The findings collected hereby indicate that as the VO2max levels of athletes increase, both their cardiopulmonary data and anaerobic power values and also their ability to resist against the intensity of exercises applied after entering the anaerobic threshold, increase. Meanwhile, the rises in VO2max levels of athletes suggest that it will contribute to an athlete’s better performance by causing decreases in the power drop ratios (%) attained during the Wingate test.

Piezoelectric energy harvester for wind turbine blades based on bistable response of a composite beam in post-buckling

A bistable piezoelectric energy harvester (PEH) is presented for harvesting power from vibrations occurring at low frequencies, as is the case of wind turbine blades. The axial compressive prestress of a piezoelectric composite beam at post-buckling serves as the bistability source, leading to high mechanical to electric power conversion. An in-house harvesting circuit connected to the piezoelectric terminals is used for demonstration of its harvesting power capabilities. A finite element (FE) model is used to analyze and optimize the coupled nonlinear electromechanical response of the PEH, including structure and circuit. A physical prototype has been manufactured and tested for validation of the electromechanical design and the FE modeling approach. Predictions and measurements indicate an increase of harvested power with applied prestress up to a transition point, where a sudden drop in power occurs. Good comparison between numerical and experimental results verified the modeling approach, whereas deviations related to physical boundary conditions at large compressive forces affected the prediction of the transition point in harvested power. The harvester produced 1.32 mW of electrical power under tonal base excitation of 1 g at 8 Hz. Hence, the nonlinear PEH has demonstrated its capability to harvest energy at frequencies much lower than its first linear modal frequency and could thus serve as a promising solution for powering IoT devices and sensors in large vibrating structures.

6-week time-restricted eating improves body composition, maintains exercise performance, without exacerbating eating disorder in female DanceSport dancers.

Despite the high risk of eating disorder (ED)-related attitudes and behaviors among female dancers, targeted scientific dietary regimens are currently inadequate. Time-restricted eating (TRE), a popular intermittent fasting protocol, has been shown to be effective in enhancing body composition and exercise performance in athletes. In this study, TRE was employed as a dietary regimen to improve body composition and exercise performance and address ED attitudes and behaviors in DanceSport dancers. Twenty female DanceSport dancers were recruited and divided into two groups: TRE (n = 10) and normal diet (ND) (n = 10). The TRE group consumed their self-selected necessary energy intake exclusively between 11 a.m. and 7 p.m. (utilizing a 16-hour fasting and 8-hour eating window) for 6 weeks, while the ND group maintained their regular dieting patterns. The consumption of water, black tea, or coffee without added sugar or milk was not restricted. Physical activity and calorie intake were systematically recorded during the TRE intervention. Body composition, aerobic and anaerobic performance, and ED attitudes and behaviors were assessed before and after the TRE intervention. The trial was registered in the Chinese Clinical Trial Registry under the identifier ChiCTR2200063780. The fixed effects tests (p < 0.0001) and estimates for the intercept (p < 0.0001) of hunger level indicated a noticeable effect on the initial state of hunger during TRE. No significant differences were observed in ED attitudes or behaviors (p > 0.05). TRE resulted in a reduction in hip circumference (p = 0.039), fat mass (kg) (p = 0.0004), and body fat percentage (p = 0.0005), with no significant decrease in fat-free mass (p > 0.05). No significant improvement was observed in aerobic performance (p > 0.05). The average power (AP) (p = 0.01) and AP/Body weight ratio (p = 0.003) significantly increased. Additionally, the power drop decreased significantly (p = 0.019). Group-by-time interactions were observed for fat mass (kg) (p = 0.01), body fat percentage (p = 0.035), and AP/Body weight (p = 0.020). TRE can be considered a feasible nutritional strategy for DanceSport dancers, facilitating improvements in body composition without compromising aerobic and anaerobic exercise performance or exacerbating ED attitudes and behaviors. Moreover, TRE may facilitate more favorable physiological adaptations, potentially contributing to improved exercise performance.

BESS Revolutionizes Renewable Stability in Indonesia

This study examines the integration of Battery Energy Storage Systems (BESS) with Solar Power Plants (PLTS) to enhance electrical grid stability in Indonesia, where 90% of electricity is from fossil fuels. The intermittent nature of PLTS often destabilizes the network, causing frequency hunting or blackouts. Using Etap 12.6 software, simulations showed that adding BESS to hybrid PLTS-PLTD systems significantly mitigates these issues. For instance, a 50% drop in PLTS power without BESS required a 55% increase in PLTD power, but with BESS, this increase was only 34%. Thus, BESS is crucial for stabilizing renewable energy integration and supporting Indonesia’s Net-Zero Emissions goal. Highlights: BESS Stabilizes Power: Reduces impact of PLTS power fluctuations on PLTD. Simulation Insight: 50% PLTS drop increases PLTD by 34% with BESS. Net-Zero Goal: BESS supports Indonesia’s renewable energy and emission targets. Keywords: Renewable Energy, Solar Power, Battery Storage, Electrical Grid Stability, Indonesia

Study of Effects on Performances and Emissions of a Large Marine Diesel Engine Partially Fuelled with Biodiesel B20 and Methanol

The impact of fossil fuel utilisation in different combustion systems on climate change due to greenhouse gas accumulation in the atmosphere is rather evident. A part of these gases comes from the large engines used for propulsion in marine applications. In the continuous global effort made by engine manufacturers to mitigate this negative impact, one way is represented by the utilisation of alternative fuels such as biodiesel and methanol, based on dedicated research to fulfil the more stringent regulations concerning pollutant emissions issued by piston heat engines. In this study, a numerical investigation was conducted on a four-stroke large marine diesel engine (ALCO 16V 251C) at several engine speeds and full load conditions. Different blends of diesel–methanol and biodiesel B20–methanol with methanol mass fractions of 10% and 20% were considered for theoretical analysis in two techniques of methanol supply: direct injection mode of a blend of base fuel diesel/biodiesel B20 with methanol and injection of methanol after the intercooler, and direct injection of the base fuel. The results show that, if 10% in power loss can be acceptable, then for diesel–methanol 10%, in the direct injection technology, the NOx emission can be reduced up to 19%, but with a compromise of an 8% increase in SOOT emission, while for biodiesel B20–methanol 10%, with the same direct injection method, the NOx emissions increase by up to 58% with the benefit of reducing SOOT by up to 23% relative to the original diesel fuel operation. For a 20% methanol fraction in blend fuel, the drop in power is more than 10% regardless of the method of methanol supply and the base fuel, diesel, or B20 used.

Modelling, simulation, and measurement of solar power generation: New developments in design and operational models

The discrepancy between the operating and design capacities of solar plants in eastern Uganda is alarming; about 35 % underperformance in solar power generation is observed. The goal of the current study is to minimize this disparity by improving the design models. Considering only cell temperature in the power generation model is responsible for the observed difference in design and operational solar power generated, the present study used a thermocouple to directly measure cell temperature, an anemometer to measure wind speed, and a solar power meter to measure irradiance. These extrinsic factors were used to modify the power generation model based only on cell temperature through the direct correlation of cell temperature, wind speed, and irradiance with solar power generation. Thus, the absence of extrinsic factors (wind speed and irradiance) in the design models is responsible for the colossal drop in solar power generated. Empirically, the missing extrinsic factors were used to transform the implicit solar power model into an explicit model. The development of a solar power generation model, multiple differential models, simulation and experimentation with a pilot solar rig served as alternate model for the prediction of solar power generation. The second-order differential model validated well with empirical solar power generated in Busitema, Mayuge, Soroti, and Tororo study areas based on RMSEs (0.6437, 0.6692, 0.2008, 0.1804, respectively), thus, narrowing the gap between the designed and operational solar power generated. Mayuge and Soroti recorded the highest solar power generation of 9.028 MW compared to Busitema (8.622 MW) and Tororo (8.345 MW), suggesting that it has a conducive site for installing future solar plants. The above results support the use of empirical explicit (triple) and second-order differential models for the design and operation of power plants.

Linking ablation curves with transmural lesions using a thoracoscopic bipolar biparietal irrigated radiofrequent clamp

Abstract Background The cornerstone of atrial fibrillation (AF) ablation is the achievement of long-lasting transmural lesions. However, it is currently unknown when transmurality is reached during ablation using the thoracoscopic bipolar biparietal irrigated radiofrequent (RF) clamp. Purpose To study the relation between transmural lesions and their corresponding ablation curves using a thoracoscopic bipolar biparietal irrigated RF clamp in pigs. Methods In 4 ventilated pigs, endo-epicardial beating-heart ablation was conducted via sternotomy. In the first 3 pigs, 1 up to 4 ablations were performed at multiple sites on right and left ventricular tissue. Objective indicators of transmurality in the ablation curves were retrospectively identified by visual inspection. After the ablation procedure, the pigs were sacrificed and subsequent macroscopic evaluation was performed. The ablated tissue was excised and immersed in 2,3,5-triphenyltetrazolium chloride-staining at 36 °C. After 90 minutes the lesions were sectioned longitudinally and photographed. The ablated nonviable muscle appears white, and the viable muscle appears red (see Figure 1). In the 4th pig, ablations (up to 5) were applied to the ventricles at multiple sites until one or more of the potential identified indicators were observed in the ablation curve. Subsequent histology was performed as described in the first three pigs. Results Three indicators of transmurality were identified in the ablation curves: type I, a sharp impedance rise (blue peak); type II, three power drops with more than one energy level decline in one curve and type III, a first power drop before 11 seconds with subsequent hovering of power levels between 15 and 25 Wattage (Figure 1). In the first 3 pigs, a total of 20 ablations were performed, with 50% (n = 10) of the ablations considered transmural. In 80% of the transmural lesions one of the three types was observed. Among the transmural lesions, 50%, 10%, and 20% corresponds to type I, II, and III indicators of transmurality, respectively, with 20% remaining inconclusive. In the lesions classified not transmural (n = 10, 50%), no type I, II, or III indicators of transmurality was observed. In the fourth pig, all lesions (n=7) were considered transmural based on macroscopic evaluation, comprising 86% of type I and 14% of type III indicators of transmurality. Conclusion Three promising ablation curve types of transmurality have been identified that are associated with transmural lesions using the bipolar biparietal irrigated RF clamp. Transmurality of the lesion was confirmed by macroscopic histological evaluation. In the next step, these ablation curve types will be tested and validated in the clinical setting.Figure 1

The Effects of Slow Breathing during Inter-Set Recovery on Power Performance in the Barbell Back Squat.

Slow breathing (SB) reduces sympathetic nervous system activity, the heart rate (HR), and blood pressure (BP) and increases parasympathetic nervous system activity, HR variability, and oxygen saturation which may lead to quicker recovery between bouts of exercise. Therefore, the purpose of this study was to examine whether a SB technique using the 4-7-8 method between sets of barbell back squats (SQs) would attenuate drops in power and bar velocity. In a randomized, crossover design, 18 healthy resistance-trained college-aged males (age: 20.7 ± 1.4 years, body height: 178.6 ± 6.4 cm, body mass: 82.2 ± 15.0 kg, 4.5 ± 2.4 years of experience) performed 5 sets of 3 repetitions of SQs with normal breathing (CON) or SB during the 3-min recovery between sets. Peak and average power and bar velocity were assessed using a linear positioning transducer. HR recovery (RHR), systolic BP recovery (RBP), the rating of perceived exertion (RPE) and the rating of perceived recovery score (RS) were assessed after each set. There were no significant differences between conditions for peak and average power and bar velocity, RBP, RPE, and RS (p > 0.211). SB led to a greater RHR after set 2 (SB: 51.0 ± 14.9 bpm vs. CON: 44.5 ± 11.5 bpm, p = 0.025) and 3 (SB: 48.3 ± 13.5 bpm vs. CON: 37.7 ± 11.7 bpm, p = 0.006) compared to the CON condition. SB was well tolerated, did not hinder nor improve training performance and improved RHR after the middle sets of SQs. Further investigations are warranted to examine the effects of other SB techniques and to determine SB's effects on different training stimuli as well as its effects over an entire workout and post-workout recovery metrics.

Reversal of chronic surface degradation of Sr(Ti,Fe)O3 perovskite-based fuel cell cathodes by surface acid/base engineering

The major barrier to commercialization of solid oxide fuel cells (SOFCs) is to overcome long-term surface degradation during operation. Sr/Co-based perovskite cathodes have been recognized to suffer from two major sources of degradation: inherent Sr segregation and extrinsic Cr-impurities at the surface, respectively. Here, we demonstrate the ability to simultaneously reverse both surface degradation modes in SrTi0.65Fe0.35O3-δ (STF35), a model high performance perovskite cathode, via surface acid/base engineering via infiltration. The acidic nature of Cr-infiltration is found to induce surface electron depletion, while enhancing Sr segregation to the surface, leading to ∼40% drop in SOFC peak power. Subsequent infiltration of basic Ca-additives is demonstrated to not only neutralize these detrimental effects, but ultimately lead to 160% enhancement in peak power, thereby enabling Co-free operation. This approach holds great promise for extending the operating lives, more generally, of materials and devices for which the catalytic oxygen/solid interface reaction is central.

A novel type of additively manufactured high pressure mini-channel heat exchanger for precooling in hydrogen refueling stations

During refueling supercritical hydrogen into high pressure storage tanks, the fluid has to be cooled down to temperatures between -33°C and -40°C before entering the vehicle fuel tank. This cooling takes place while the hydrogen is at a pressure of up to 87.5 MPa. The requirements for the heat exchanger performing this task are very high. It has to be pressure resistant, compact enough to fit in the dispenser column and provide a high thermal performance to ensure a fast refueling with high mass flow rates. Only few conventional manufactured heat exchangers are able to fulfil these requirements. With the rise of additive manufacturing technology, especially laser powder bed fusion, new heat exchangers produced without use of conventional joining technologies can be realized. This manuscript presents a new type additively manufactured of mini-channel heat exchanger. It is developed in a joint research project involving the Leibniz University Hanover and an industrial heat exchanger manufacturer. The apparatus has a design pressure of 105 MPa and will be suited to be used in hydrogen refueling stations. The thermal requirements and the design of the apparatus are described. Thermal power and pressure drop for the full-size heat exchanger are calculated via a cell model. Scaled smaller heat exchangers made of 1.4404 stainless steel are additively manufactured via laser powder bed fusion (LPBF). The thermofluiddynamical performance of the scaled apparatus is measured in a testbench to verify the applicability of the used correlations. Deviations in hydraulic diameter and surface roughness are taken into account. Existing correlations are fitted to the new geometry.