Limited Rate Research Articles

Need for national guidance regarding proactive care of infants born at 22-23 weeks' gestation.

With recent rapid improvements in neonatal intensive care, the limit of viability has shifted downward to 22-23 weeks' gestation. The younger the gestational age of preterm infants, the higher the risk of survival despite severe neurodevelopmental impairments. For infants born at 22-23 weeks' gestation, the limit of viability, neurodevelopmental outcomes, and survival rates may be determined by the quality of proactive care. Owing to the high risk of severe neurodevelopmental impairment in 22-23 weeks' gestation, proactive care is sometimes withheld according to ethical or legal considerations, and there are significant differences in the provision of proactive care and survival rates across countries or institutions. Additionally, there are differing or even lacking guidelines regarding the care of these infants across countries and institutions. Japan and Sweden are countries with well-established national guidance and proactive care for infants born at 22-23 weeks' gestation, resulting in higher survival rates among them. In Korea, where there is an extreme shortage of neonatologists, maternal transfer before delivery at 22-23 weeks' gestation to high-activity regions with appropriate neonatal intensive care unit resources, such as adequate personnel and facilities similar to the centralized care model seen in Sweden, is crucial for improving the survival rates of infants born at 22-23 weeks' gestation. The survival of these infants largely depends on the quality of proactive care provided. This rate is not static and can be improved through proactive case management based on national guidance and the implementation of enhanced neonatal intensive care practices, including centralization of care.

Orientation-independent quantification of macromolecular proton fraction in tissues with suppression of residual dipolar coupling.

Quantitative magnetization transfer (MT) imaging enables noninvasive characterization of the macromolecular environment of tissues. However, recent work has highlighted that the quantification of MT parameters using saturation radiofrequency (RF) pulses exhibits orientation dependence in ordered tissue structures, potentially confounding its clinical applications. Notably, in tissues with ordered structures, such as articular cartilage and myelin, the residual dipolar coupling (RDC) effect can arise owing to incomplete averaging of dipolar-dipolar interactions of water protons. In this study, we demonstrated the confounding effect of RDC on quantitative MT imaging in ordered tissues can be suppressed by using an emerging technique known as macromolecular proton fraction mapping based on spin-lock (MPF-SL). The off-resonance spin-lock RF pulse in MPF-SL could be designed to generate a strong effective spin-lock field to suppress RDC without violating the specific absorption rate and hardware limitations in clinical scans. Furthermore, suppressing the water pool contribution in MPF-SL enabled the application of a strong effective spin-lock field without confounding effects from direct water saturation. Our findings were experimentally validated using human knee specimens and healthy human cartilage. The results demonstrated that MPF-SL exhibits lower sensitivity to tissue orientation compared with , , and saturation-pulse-based MT imaging. Consequently, MPF-SL could serve as a valuable orientation-independent technique for the quantification of MPF.

Abstract 4143264: A Case of Spike-on-T Phenomenon and Polymorphic Ventricular Tachycardia

Background: R-on-T phenomenon occurs when an electrical stimulus is delivered at a critical point during ventricular repolarization. This can initiate ventricular arrhythmias like polymorphic ventricular tachycardia (PMVT). We describe a case of ventricular pacemaker spikes delivered on the T wave causing PMVT. Case: A 53-year-old female with CAD s/p stent, postpartum cardiomyopathy s/p Bi-V CRT-D (Boston Scientific G124), and paroxysmal atrial fibrillation presented for elective endoscopy and colonoscopy to evaluate her dysphagia and abdominal pain. Her CRT-D was reprogrammed from DDD pacing with lower rate limit (LRL) 50 bpm to an asynchronous Bi-V DOO mode at 50 bpm (‘electrocautery mode’) for the procedure (tachy therapy disabled). Her LV-RV offset was 40 msec. Prior to receiving sedation or medications, she was found unresponsive. Telemetry showed Spike-on-T phenomenon which initiated PMVT. She was externally defibrillated with 200J and received magnesium and an IV amiodarone bolus. She returned to sinus rhythm, but one minute later had another Spike-on-T event initiating PMVT. She was successfully defibrillated with 360J. Post-shock EKG showed an asynchronous Bi-V paced rhythm at 50 bpm. Decision Making: The patient was admitted to the CCU for post-resuscitation care. Her electrolytes and cardiac enzymes were unremarkable. Her CRT-D was reprogrammed to DDD 80-140 bpm. Transthoracic echocardiogram showed normal biventricular systolic function. Cardiac catheterization did not show obstructive CAD. After reprogramming of her device, she had no further events. After initial treatment with IV amiodarone load, she was discharged home on oral magnesium gluconate. Discussion: The only intervention prior to her procedure was device reprogramming (DDD 50 bpm to DOO 50 bpm). Telemetry showed pacer spikes initiating PMVT. Given the LV-RV offset of 40 msec, she would have received these two tightly coupled pacemaker spikes in an asynchronous mode, in this unfortunate instance during her T wave. While her bowel preparation may have led to electrolytes abnormalities, post-resuscitation electrolytes were normal. Fortunately, she received prompt therapy and was reprogrammed with increased LRL. Conclusion: We described a case of Spike-on-T PMVT prior to colonoscopy without obvious provocation other than asynchronous pacemaker spikes. Reprogramming devices in DOO mode with increased LRL may prevent PVCs and asynchronous pacemaker spikes from triggering PMVT.

Fast and light-efficient wavefront shaping with a MEMS phase-only light modulator

Over the last two decades, spatial light modulators (SLMs) have revolutionized our ability to shape optical fields. They grant independent dynamic control over thousands of degrees-of-freedom within a single light beam. In this work we test a new type of SLM, known as a phase-only light modulator (PLM), that blends the high efficiency of liquid crystal SLMs with the fast switching rates of binary digital micro-mirror devices (DMDs). A PLM has a 2D mega-pixel array of micro-mirrors. The vertical height of each micro-mirror can be independently adjusted with 4-bit precision. Here we provide a concise tutorial on the operation and calibration of a PLM. We demonstrate arbitrary pattern projection, aberration correction, and control of light transport through complex media. We show high-speed wavefront shaping through a multimode optical fiber – scanning over 2000 points at 1.44 kHz. We make available our custom high-speed PLM control software library developed in C++. As PLMs are based upon micro-electromechanical system (MEMS) technology, they are polarization agnostic, and possess fundamental switching rate limitations equivalent to that of DMDs – with operation at up to 10 kHz anticipated in the near future. We expect PLMs will find high-speed light shaping applications across a range of fields including adaptive optics, microscopy, optogenetics and quantum optics.

Optimizing reserve-constrained economic dispatch: Cheetah optimizer with constraint handling method in Static/Dynamic/Single/ Multi-Area Systems

Managing the power-generating units on the horizon of one-day scheduling considering all practical equality, inequality, and realistic constraints has always been a significant challenge in power systems. The constraints, such as valve-point effects, prohibited operation zones, transmission losses, and ramp rate limits corresponding to dynamic economic dispatch, change the optimization problem to a complex, nonlinear, non-smooth, high-dimensional, and non-convex one. Therefore, an efficient algorithm and a suitable constraint handling method are needed to solve practical constrained dynamic economic dispatch (DED). This paper proposes a newly developed Cheetah optimizer (CO) that coincides with a backward-forward constraint handling method to tackle the optimum operational cost. The CO algorithm’s performance is verified using eight DED and ED test cases from five different systems. The suggested technique is compared with several state-of-the-art optimization algorithms regarding the effectiveness of achieved results. Numerical results evaluate the performances of the CO advantages on the benchmarks and the DED cases where the results of 5-,10- and 30-unit systems are enhanced in different cases. To achieve a higher level of realism in modeling the ED and DED problem, adopting a multi-area DED (MADED) approach has emerged as a promising strategy. In this paper, three distinct cases of MAED and MADED problems are investigated to demonstrate the effectiveness of the proposed method. Specifically, in cases involving DED-10 and 30 units, two-area 40 units ED, and four-area 40 units DED, significantly improved solutions were obtained compared to previous studies.

Measurements of Heavy Elements and Radioactivity Concentration Levels in Types of Fertilizers and Pesticides Commonly Used in Sana’a Yemen

This study aims to measure heavy metals (HMs) concentration and radioactivity concentration levels in fertilizer and pesticide samples collected from local markets in Sana’a, Yemen. Gamma spectroscopy employing a Survey Sodium Iodide NaI (TI) RIIDEYM-G detector was used for radiation and dose assessments. As for heavy metal analyses, this study used Inductively Coupled Optical Emission Spectroscopy (ICP-OES). Thirty samples were collected from local markets in Sana’a, Yemen. Radioactivity measurements show low levels of radioactivity concentration. The average dose rates due to fertilizer and pesticide samples were 1.14 and 1.07 mSv/y, respectively. These values are nearly equal to the recommended annual radiation dose rate limit (1mSv/y) recommended by the International Commission on Radiological Protection (ICRP). For heavy metal analysis, it was found that the average concentrations of heavy metals (HMs) (cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), nickel (Ni), lead (Pb), and zinc (Zn)) in the fertilizer samples were 1.08 mg/kg, 4.944 mg/kg, 13.8495 mg/kg, 274.371 mg/kg, 3.30446 mg/kg, 15.35686 mg/kg, and 24.4547 mg/kg, respectively. Heavy metal concentrations in fertilizer samples were mainly less than European (EU) guideline limits, with the exception of a few samples. The average concentrations of heavy metals (Cd, Cr, Cu, Fe, Ni, Pb, and Zn) in the pesticide samples were 0.8 mg/kg, 0.5784 mg/kg, 52.280 mg/kg, 73.4651 mg/kg, 2.4482 mg/kg, 3.199 mg/kg, and 1.1309 mg/kg, respectively. The heavy metal concentrations in pesticide samples were less than the corresponding values in fertilizer samples.

Determination and description of a vehicle's maximum jerk capacity

Both Transient Optimal and Quasi-Steady-State vehicle modelling are frequently used for minimum time manoeuvre and minimum lap-time simulations for motorsport/vehicle development purposes. Quasi-Steady-State methods have been shown to perform such tasks with low computational cost but produce results with measurable deviation from equivalent Transient Optimal studies. It is hypothesised that bounding point-mass models with jerk limits will improve alignment with Transient Optimal simulations through the consideration of transient behaviours such as control application rates and inertia. This work presents a new method for the determination of a vehicle's maximum jerk capacity from a seven degree-of-freedom vehicle model. A range of results from this proposed technique are presented and show the sensitivity of jerk capacity to changes in control application rate limits and yaw inertia, as well as current vehicle velocity, acceleration, and jerk. It is proposed that further exploration of the validity of the jerk limit calculation method take place through characterisation of said limits and application to a point-mass model, after which comparison to Transient Optimal and Quasi-Steady-State equivalents can occur.

Photon blockade in a high-damping cavity via a gain-type coupler

Abstract We propose a scheme to implement photon blockade in a non-Hermitian circuit quantum electrodynamics (circuit-QED) system where a single-mode cavity interacts with a two-level emitter through virtual photon excitation mediated by a coupler resonator. A damping compensation regime is introduced by the phase-lag arising from the medium mode, thereby the periodic exceptional points (EPs) are observed at which the system achieves gain-damping balance. This regime enables photon blockade to occur within the single-mode cavity with high-damping rate by controlling the gain circuit of the coupler, which breaks the limitation of a low-damping rate for photon blockade under weak drive and relaxes the stringent requirements on the quality of the cavity. The numerical simulations for the second-order correlation function, obtained using reported experimental parameters, exhibit excellent agreement with our analytical results. The findings of this study provide a circuit-QED solution for single-quantum devices based on the high-damping cavities, which is of great significance for integrated quantum computing networks.

1D supramolecular assembly-induced emission and colorimetry toward precise onsite mercury(II) detection

Manipulation of the one-dimensional (1D) supramolecular assembly of platinum(II) terpyridyl complex is promising for achieving precise onsite mercury(II) detection in complex environments, but still challenging. Herein, by systematic molecular design of platinum(II) terpyridyl complex, chloride-mediated 1D supramolecular assembly has been successfully achieved, exhibiting not only improved recognition ability but also dual-visual signal, with turn-on red luminescence and high-contrast color change from pale-yellow to orange-red. The probe also shows excellent selectivity and anti-interference properties, fast response rate (< 1 s) and low detection limit, stretching to 20.6 fg when incorporated in a hydrogel matrix. Structure insight for the dual-visual response shows that this high detection performance derives from the ancillary ligand of -NCS, which endows the increase of ion-association ability between platinum(II) terpyridyl complex and [HgCl4]2−, leading that 1D packing mode with strengthened Pt-Pt interactions. In all, this work highlights a new strategy of 1D supramolecular assembly construction for high performance detection of heavy metal ions.

Rationale and Design of OPT-RATE AF: A Randomized Clinical Trial of Increased Physiologic Pacing Rates in Heart Failure With Preserved Ejection Fraction

Cardiac physiologic pacing (CPP) after atrioventricular node (AVN) ablation for persistent atrial fibrillation (AF) has improved outcomes in patients with heart failure with reduced and preserved ejection fraction (HFpEF). Emerging evidence suggests patients with HFpEF benefit from higher heart rates, yet the optimal pacing rate after AVN ablation remains unknown. OPT-RATE AF is a prospective, randomized crossover study of patients with HFpEF following AVN ablation for persistent AF (NCT06445439). Approximately 60 patients with AF and AVN ablation, CPP, and HF with left ventricular ejection fraction ≥50% will be enrolled. Participants will be randomly assigned 1:1 to a pacing lower rate limit of 60 beats-per-minute (bpm) for 3 months and then switched to a rate of 80 bpm for 3 months, and vice versa. The primary endpoint is change in exercise capacity assessed by the 6-minute walk test. Notable secondary outcomes will include change in Kansas City Quality of Life Questionnaire (KCCQ-12), creatinine and natriuretic peptide, and clinical events. Patient mortality and HF hospitalizations will be recorded at each phase. EKG, echocardiogram, pacemaker interrogation, and primary and secondary outcomes will be recorded at baseline, 3 months, and 6 months. Study enrollment is ongoing and estimated to be completed by 2026. OPT-RATE AF is a randomized clinical trial that will determine the effect of a higher pacing rate in patients with persistent AF and HFpEF following AVN ablation and/or CPP. Study findings will provide insight on the role of chronotropy in improving QoL and other important cardiovascular outcomes.

Optimization of vehicle conceptual design problems using an enhanced hunger games search algorithm

Abstract Electric vehicles have become a standard means of transportation in the last 10 years. This paper aims to formalize design optimization problems for electric vehicle components. It presents a tool conceptual design technique with a hunger games search optimizer that incorporates dynamic adversary-based learning and diversity leader (referred to as HGS-DOL-DIL) to overcome the local optimum trap and low convergence rate limitations of the Hunger Games search algorithm to improve the convergence rate. The performance of the proposed algorithms is studied on six widely used engineering design problems, complex constraints, and discrete variables. For the HGS-DOL-DIL practical feasibility analysis, a case study of shape optimization of an electric car suspension arm from the industry is carried out. Overall, the inclusion of the OL strategy has proven its superiority in solving real-world problems, especially in solving real-world problems such as shape optimization of an electric vehicle automobile suspension arm, showing that the algorithm improves the search space improves the solution quality, and reflects its potential to find global optimum solutions in a well-balanced exploration and exploitation phase.

A 3D aerogel evaporator for efficient solar interfacial evaporation: Breaking through the upper limit of steam production rate

Solar desalination is the most effective way to obtain clean and cheap fresh water. However, its lower upper limit of steam production rate limits its development and practical applications. In this paper, a microcrystalline cellulose aerogel composite Mo2C evaporator (MCAM) was prepared by combining Mo2C with microcrystalline cellulose aerogel (MCA). The evaporator consists of MCAM photothermal layer, polyurethane (PU) sponge insulation layer and one-dimensional water channel. Mo2C has high-light absorption efficiency. At the same time, the vertical channel inside the MCA makes the incident light be reflected and absorbed for many times inside. Benefiting from the synergistic effect of the vertical channel of MCA and the light absorption ability of Mo2C, MCAM obtained a high light absorption efficiency of 96.96 %. The interaction between the MCAM evaporator and water can reduce the evaporation enthalpy, thereby breaking the upper limit of the steam generation rate. Therefore, the evaporator achieved a steam production rate of 1.92 kg⋅m−2⋅h−1 and an energy utilization efficiency of 118.2 %. In addition, MCAM shows excellent salt tolerance and self-discharging salt ability, which ensures its stable operation in high-salinity environment. Besides its high efficiency, MCAM has significant purification effect on simulated seawater, heavy metal wastewater, and organic wastewater. This study provides a new strategy for further improving the steam production rate of the solar interface evaporator.

PEMBUATAN RATE LIMITER PADA API KYOU.ID MENGGUNAKAN ALGORITMA TOKEN BUCKET DAN GOLANG : ANALISIS KINERJA DAN EFEKTIVITAS

This research focuses on the development of a rate limiter for API Kyou.id using the token bucket algorithm and Golang programming language. The rate limiter aims to control access to the API by providing tokens at regular intervals, limiting the number of requests within a specific time interval, and preventing excessive request surges. The results indicate that the implementation of the token bucket algorithm improves the consistency of request latency, maintains API response times within an acceptable range, and optimizes database utilization rates. With the ratelimiter in place, APIusage becomes more responsive, reliable, and efficient. Furthermore, the implementation ensures fair and equitable access to API Kyou.id for all users. Thus, this research makes a positive contribution to enhancing the performance and security of the API Kyou.id services.

Near‐infrared scintillation properties of Nd-doped BaO-Bi2O3-P2O5 glasses

We synthesized BaO-Bi2O3-P2O5 glass samples with different Nd concentrations by the melt-quenching technique. The concentrations were 1.0, 5.0, 10, 15, and 20 %. We obtained transparent and homogeneous samples for 1.0–10 % Nd concentrations. The 15 % Nd-doped sample was inhomogeneous, and the 20 % Nd-doped sample contained a crystalline phase. The photoluminescence (PL) and scintillation properties of the 1.0–10 % Nd-doped samples were investigated. The samples showed PL and scintillation peaks in the near-infrared region, which were due to 4f–4f transitions of Nd3+. We tested the X-ray dose rate response functions of the samples. The 10 % Nd-doped samples showed the most intensive response among the examined samples, and the lower detection limit of dose rate was 0.06 Gy/h with our setup.

Sloth: Key Stretching and Deniable Encryption using Secure Elements on Smartphones

Privacy enhancing technologies must not only protect sensitive data in-transit, but also locally at-rest. For example, anonymity networks hide the sender and/or recipient of a message from network adversaries. However, if a participating device is physically captured, its owner can be pressured to give access to the stored conversations. Therefore, client software should allow the user to plausibly deny the existence of meaningful data. Since biometrics can be collected without consent and server-based authentication leaks metadata, implementations typically rely on memorable passwords for local authentication. Traditional password-based key stretching lacks a strict time guarantee due to the ease of parallelized password guessing by attackers. This paper introduces Sloth, a key stretching method leveraging the Secure Element (SE) commonly found in modern smartphones to provide a strict rate limit on password guessing. While this would be straightforward with full access to the SE, Android and iOS only provide a very limited API. Sloth utilizes the existing developer SE API and novel cryptographic constructions to build an effective rate-limit for password guessing on recent Android and iOS devices. Our approach ensures robust security even for short, randomly-generated, six-character alpha-numeric passwords against adversaries with virtually unlimited computing resources. Our solution is compatible with approximately 96% of iPhones and 45% of Android phones and Sloth seamlessly integrates without device or OS modifications, making it immediately usable by app developers today. We formally define the security of Sloth and evaluate its performance on various devices. Finally, we present HiddenSloth, a plausibly-deniable encryption scheme leveraging Sloth. It provides multi-snapshot resistance against adversaries who can covertly capture its on-disk content multiple times.

Development and validation of an LC-MS/MS method for the detection of sodium pentachlorophenolate residues on cutting boards.

The objective of this study was to develop and validate an automated solid-phase extraction (SPE) coupled with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for the detection of sodium pentachlorophenolate (PCP-Na) residues on cutting boards. Given the potential hazards and environmental persistence of PCP-Na, a sensitive and reliable method is crucial for monitoring its residues in food contact materials to ensure consumer safety. Wood shavings from cutting boards were extracted using 10% methanol in water, followed by purification using an automated SPE system. The eluent was concentrated, reconstituted, and analyzed by UPLC-MS/MS. An isotope-labeled internal standard was used to mitigate matrix effects, enhancing detection sensitivity. The method was validated by assessing linearity, limit of detection (LOD), limit of quantification (LOQ), recovery rates, and relative standard deviations (RSDs) across various concentration levels. The method demonstrated excellent linearity over a concentration range of 0 to 100 μg/L with a regression equation of Y = 1.035X-0.7771 and an R² of 0.9996. The LOD and LOQ were determined to be 0.4 and 1.0 μg/kg, respectively. Recovery rates ranged from 71.75% to 96.50% with RSDs between 5.19% and 16.66%. When applied to 30 market cutting board samples, PCP-Na residues were detected in 50% of the samples, with concentrations ranging from 0 to 83,990 µg/kg. This study presents a robust UPLC-MS/MS method for the detection of PCP-Na on cutting boards, offering improved sensitivity and simplified sample preparation. The high detection rate in commercial samples underscores the need for stringent monitoring and regulatory measures to mitigate the exposure risk to consumers.

A general multi-scale description of metastable adaptive motion across fitness valleys

We consider a stochastic individual-based model of adaptive dynamics on a finite trait graph G=(V,E)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$G=(V,E)$$\\end{document}. The evolution is driven by a linear birth rate, a density dependent logistic death rate and the possibility of mutations along the directed edges in E. We study the limit of small mutation rates for a simultaneously diverging population size. Closing the gap between Bovier et al. (Ann Appl Probab 29(6):3541–358, 2019) and Coquille et al. (Electron J Probab 26:1–37, 2021) we give a precise description of transitions between evolutionary stable conditions (ESC), where multiple mutations are needed to cross a valley in the fitness landscape. The system shows a metastable behaviour on several divergent time scales, corresponding to the widths of these fitness valleys. We develop the framework of a meta graph that is constituted of ESCs and possible metastable transitions between them. This allows for a concise description of the multi-scale jump chain arising from concatenating several jumps. Finally, for each of the various time scales, we prove the convergence of the population process to a Markov jump process visiting only ESCs of sufficiently high stability.

Experimental and modeling studies on char combustion under pressurized O2/H2O conditions

The desorption kinetic parameters for pressurized combustion and gasification reactions were determined based on a C++ program coupled with the Langmuir-Hinshelwood (L-H) kinetic model developed and experimental data from pressurized char combustion, and the established L-H kinetic model for pressurized char-O2/H2O combustion was refined in the current paper. The activation energy for desorption in reactions involving pressurized char-O2 and char-H2O was determined to be 250.8 kJ/mol, accompanied by a pre-exponential factor of 5.42×1010 g/(m2 s). Using this foundation, the current research conducted simulations to investigate the impacts of temperature, pressure, and H2O concentration on the oxidation adsorption rate (Rads,oxi), desorption rate (Rdes), gasification adsorption rate (Rads,gas), and the competitive influences of kinetics and diffusion processes within the pressurized char-O2/H2O combustion. The simulation results indicate a gradual increase in Rdes and Rads,gas with char conversion to reach a peak, followed by a gradual decline. Conversely, the Rads,oxi varies smoothly throughout the char conversion process. At 1673 K/1.0 MPa, the char-O2/H2O reaction rate is primarily constrained by Rads,oxi and Rads,gas, with the adsorption reaction serving as the rate-controlling step. Moreover, it was noted that a rise in pressure resulted in a linear increase in Rads,oxi, Rdes, and Rads,gas. At elevated temperatures, the impact of pressure on them becomes more noticeable. However, the introduction of H2O mitigates this effect. Elevated temperature and pressure facilitate the competition on the kinetics of char-O2 combustion for O2 diffusion, resulting in the conversion of char being more susceptible to O2 diffusion rate limitation. With the addition of 20% H2O, the competition effect was weakened. In the case of pressurized combustion involving char and O2/H2O, the char conversion is primarily constrained by the O2 diffusion rate and is scarcely influenced by the H2O diffusion rate.

Fire safety characteristics of natural gas with hydrogen admixture

The increasing pressure to decarbonise energy production leads to the need to use low or zero carbon fuels or energy carriers. One of the promising fuels of the future is hydrogen, which is carbon-free if renewable energy sources are used for its production. However, the capacity for hydrogen production is currently insufficient to make it applicable on a large scale. Adding hydrogen to natural gas allows for a reduced carbon footprint without costly modifications to pipeline distribution network. However, changing the composition of gas in transport and distribution facilities requires a thorough assessment of the impact on operational safety. Fire safety of flammable mixtures is commonly assessed on the basis of explosive limits and other parameters. Although methods are available to calculate these parameters based on the composition of the mixtures being evaluated, the final safety assessment should rely on actual measured values. The scope of this work is to determine the explosion limits of natural gas from the transit system and changes in the limits caused by the addition of hydrogen at the concentration levels of 10% and 20% (v/v). Obtained experimental results were further compared with theoretically calculated values. Attention was also paid to the change in maximum explosion pressure, maximum pressure rise rate and oxygen concentration limits (LOC). As a result, valuable data on the expansion of the explosion limits of natural gas after the addition of hydrogen are presented.

Module‐Based Supercapacitors: Potential Energy Storage Solutions for Large‐Scale Photovoltaic Systems

Intermittency is an inherent characteristic of photovoltaic (PV) power generation and results in high ramp rates of the generated power. This article explores the feasibility of integrating supercapacitors at the PV module level, aiming to reduce the power fluctuations of PV systems and control the power ramp rate into the power grid. First, an equivalent circuit model of a single‐phase grid‐connected PV system based on module‐based supercapacitors is proposed, and a power ramp rate control scheme is established. Then, experimental setups for a single‐phase grid‐connected PV system based on module‐based supercapacitors are implemented, and the computational model is verified through experiments. Finally, using the verified computational model and the proposed control scheme, the module‐based supercapacitor sizes for different PV system sizes (PV module, rooftop, small system, large system) that meet specific ramp rate requirements under different ramp rate limits (5, 10, 15% min−1) are compared. Case studies show that large‐scale PV systems with geographical smoothing effects help to reduce the size of module‐based supercapacitors per normalized power of installed PV, providing the possibility for the application of modular supercapacitors as potential energy storage solutions to improve power ramp rate performance in large‐scale PV systems.