Power Variation Research Articles

Pulsed surface acoustic waves accelerate wound healing and reveal new parameter limits for cell stimulation in vitro

The use of surface acoustic waves (SAW) in cell biology has gained high attention in the past years. Previous works show that SAW treatment of artificial wounds in vitro can accelerate wound healing by up to +135%. However, little is known about the mechanobiology behind these effects, and a stimulation has only been proven for continuous SAW signals so far. We here show that the stimulation efficacy observed in previous studies is preserved for pulsed stimuli applied to Madin-Darby canine kidney (MDCK-II) cells in wound healing assays on SAW chips at a resonance frequency f SAW = 160 MHz. Moreover, for a reproducible and reliable image analysis, we present the SegFormer-based deep learning algorithm Neural Cell Edge Detector for the cell edge segmentation and image binarization, that allows an automated determination of the stimulation efficacy. With these tools, we explore a wider range of applicable SAW intensities up to P in = 21 dBm (128 mW) with a maximum stimulation efficacy of E = 201%. We show that the order of magnitude of the stimulation effect is reproducible under the variation of SAW signal characteristics power P in, duty cycle D and pulse width τ, while the mean energy over time is constant. Below a distinct pulse duration limit τ = 100 ms, no direct stimulation effect was observed. From a mechanobiological point of view, these findings and time scales could narrow down the potentially triggered cellular mechanisms during the stimulation.

Non-Fourier Bioheat Transfer Analysis in Brain Tissue During Interstitial Laser Ablation: Analysis of Multiple Influential Factors

This work presents the dual-phase lag-based non-Fourier bioheat transfer model of brain tissue subjected to interstitial laser ablation. The finite element method has been utilized to predict the brain tissue's temperature distributions and ablation volumes. A sensitivity analysis has been conducted to quantify the effect of variations in the input laser power, treatment time, laser fiber diameter, laser wavelength, and non-Fourier phase lags. Notably, in this work, the temperature-dependent thermal properties of brain tissue have been considered. The developed model has been validated by comparing the temperature obtained from the numerical and ex vivo brain tissue during interstitial laser ablation. The ex vivo brain model has been further extended to in vivo settings by incorporating the blood perfusion effects. The results of the systematic analysis highlight the importance of considering temperature-dependent thermal properties of the brain tissue, non-Fourier behavior, and microvascular perfusion effects in the computational models for accurate predictions of the treatment outcomes during interstitial laser ablation, thereby minimizing the damage to surrounding healthy tissue. The developed model and parametric analysis reported in this study would assist in a more accurate and precise prediction of the temperature distribution, thus allowing to optimize the thermal dosage during laser therapy in the brain.

RELAP5/Mod3.3 thermal-hydraulics characterization of the steam generator mock-up during operational transients in STEAM facility in support of the design of the DEMO WCLL BoP

The Water Cooled Lithium Lead Breeding Blanket (WCLL BB) is a key candidate for the driver blanket of the European DEMO reactor, progressing toward its Conceptual phase by the end of 2027. To assess different water and lithium-lead technologies for the WCLL BB and Balance of Plant (BoP) systems, the Water-thermal-HYDRAulic (W-HYDRA) experimental platform is under development at the ENEA Brasimone Research Centre. Among the facilities constituting the new W-HYDRA multipurpose infrastructure, STEAM is going to experimentally investigate the DEMO WCLL BoP thermal-hydraulics, focusing on the Steam Generator (SG) of the Primary Heat Transfer Systems (PHTS), to qualify its performances and suitability under its unconventional operation. The paper aims at supporting the thermal-hydraulic characterization of the Steam Generator mock-up during the sudden power variations typical of a pulsed fusion reactor. The analyzed selected scenario is the operational transient dwell-pulse-dwell, which determines high thermal cycling and correspondent high thermo-mechanical stresses on the primary side components. Two control logics with their relative drawbacks have been analyzed with a RELAP5/Mod3.3 1-D model, the first regulating the primary side average temperature, the second monitoring the minimum one. The comparison of the two systems highlighted that neither approach leads to hazardous conditions for the facility. However, while the average temperature controller is characterized by reduced thermal stresses on the components, the minimum temperature controller is characterized by higher thermal gradients for the primary loop. Both methodologies will be tested in the dedicated experimental campaign, aiming at yielding insights and evaluations concerning control strategies applicable to the DEMO reactor.

Capacity Allocation in Distributed Wind Power Generation Hybrid Energy Storage Systems

Abstract The inherent variability and uncertainty of distributed wind power generation exert profound impact on the stability and equilibrium of power storage systems. In response to this challenge, we present a pioneering methodology for the allocation of capacities in the integration of wind power storage. Firstly, we introduce a meticulously designed uncertainty modeling technique aimed at optimizing wind power forecasting deviations, thus augmenting the controllability of distributed wind power variations. Subsequently, we establish a cutting-edge real-time dynamic optimization model for state of charge, which effectively mitigates the fluctuations associated with grid-connected wind power. Moreover, we employ a state-of-the-art distributed robust optimization algorithm to enhance the stability of the distributed wind power storage system. Through comprehensive simulation testing, our findings unequivocally demonstrate the efficacy of our approach in preserving a harmonious balance between wind power load and output demand, thereby assuring the unwavering operation of the entire system. Notably, our approach attains an exceptional capacity allocation efficiency of 91% in the rigorous wind power grid-smoothing test, outperforming comparable methodologies. Lastly, we proffer essential recommendations pertaining to attenuation optimization at the effective capacity level of the batteries, effectively safeguarding the long-term stability of the energy storage system.

Mathematical Modeling and Simulation of Photovoltaic Array

This work deals with modeling and simulation of PV system which can be connected to the distribution power network. It means photovoltaic array. I try to draw up a specification of PV array problems because these sources have certain specific features, that are given by their characters. I give a attention to the characteristics of PV cells that influence the reliability and quality of the power supply. I also deal with these behaviour of PV array in the distribution grid, their possible influence on a voltage regulation, influence of their power variation on voltage waveform at the point of connection and also an examination of different variants of PV array connection.

학사학위과정 간호사의 계속교육 참여동기에 미치는 영향요인

Objectives The purpose of this study was to investigate the motive for participation in continuing education, job satisfaction, job performance and educational satisfaction of nurses in bachelor's degree and to provide evidence for the development of various programs to improve motive for participation in continuing education.
 Methods A cross-sectional survey design was used. Participants were 160 nurses in majoring Nursing Science of KNOU located K district. Data were collected from September 21 to September 27, 2023 using self-reported questionnaires. Descriptive statistics, t-test, ANOVA, Pearson's correlation coefficient, and Hierarchical re-gression analysis were performed on the collected data using the SPSS 26.0 program.
 Results As a result of the study, the mean scores of motive for participation in continuing education of nurses in bachelor's degree was 3.67±0.58 (range 1-5). The motive for participation in continuing education of nurses in bachelor's degree was statistically related to job satisfaction(r=.45, p<.001), job performance(r=.46, p<.001), edu-cational satisfaction(r=.26, p<.001) showed a significant positive correlation. Factors significantly influencing mo-tive for participation in continuing education of nurses in bachelor's degree were job performance(β=.27, p=.003), and job satisfaction (β=.28, p=.002). The explanatory power of related variables was 29.1%.
 Conclusions Based on the results of this study, it is necessary to develop and apply programs to improve job per-formance and job satisfaction in order to increase motive for participation in continuing education of nurses in bachelor's degree.

ACTIVE POWER FILTER IMPACT ON POWER QUALITY IMPROVEMENT FOR INDUSTRUAL PLANT SUPPLIED BY PHOTOVOLTAIQUE STATION

This work deals on industrial electrical power quality improvement using an active power filter (APF) based on fuzzy logic controller. The studied system is a PV conversion chain used to supply linear and non-linear industrial loads of 200 kw plant. The PV station is modeled then simulated under Matlab Simulink, with standard conditions consideration in the first time then under real irradiation and sun power variation during the day hours, to obtain the true parameters design of the PV station to be able to give the needed power during the climatic conditions changing. APF parameters design and control loop structure are well studied to have an optimal control. MPPT technique is used in PV station control with the P&O algorithm. Also PV panel fault diagnosis has been done by using alarm for fault indicator and protection over under power. Simulation results are analyzed and discussed comparison with real signals, produced by the FLUK 6001B reference source with the use of the PRS 600 and the Teledyne 3,5 GHz-40Gs/s oscilloscope as measurement instrument, to improve the effectiveness of APF on electrical power quality, THD, amelioration and harmonic minimization in the industrial installation.

Modulation of electrical properties of sputtered Ta2O5 films by variation of RF power and substrate temperature

Dielectric thin films are important building blocks of microelectronic devices, and hence, research on the development of high-k dielectric thin films has drawn tremendous research interest. In this research, thin films of tantalum oxide (Ta2O5), a high-k dielectric material, are deposited on the Si substrate by the radio frequency (RF) magnetron sputtering technique. During the deposition of Ta2O5 thin film, the sputtering parameters such as sputtering power and substrate temperature were systematically varied, and post-deposition structural, morphological, and electrical properties of sputtered Ta2O5 films are studied by x-ray diffraction, Fourier transform infrared spectroscopy, atomic force microscope, capacitance–voltage (C-V) and current–voltage (I-V) measurement techniques. The annealed Ta2O5 thin film at the temperature of 900 °C for 1 h possesses polycrystalline nature with β—phase orthorhombic crystal structure. The film deposited at 150 W and substrate temperature at room temperature has shown comparatively lower surface roughness, which depicts the energy, and mobility of adatoms greatly influenced by RF power and substrate temperature. With the increase in sputtering power, the oxide charge density (Qox) is found to increase. On the other hand, Qox is found to decrease with the increase in substrate temperature. The film deposited at RF power of 150 W and substrate temperature of 300 °C is found to be of high dielectric constant, low oxide and interface charge density, and lower leakage current.

Highly stable single-longitudinal-mode erbium-doped fiber laser using dual-ring compound cavity filter and saturable absorber

Single-longitudinal-mode (SLM) fiber lasers have the advantages of stable output, long coherence length, and low noise. However, several fiber lasers still maintain multiple longitudinal mode outputs. Thus, a highly stable SLM erbium-doped fiber laser (EDFL) was proposed and investigated. The dual-ring compound cavity (DRCC) filter, composed of two Type-Ⅱ fiber rings, and a 1.5 m unpumped erbium-doped fiber (EDF) was used as a mode-selection filter. The mode-selection capability of the DRCC filter and unpumped EDF was investigated and discussed theoretically and experimentally. The proposed EDFL could generate stable SLM output with an optical signal-to-noise ratio of ∼ 64 dB over 60 min. The maximum wavelength drift was not observed on an optical spectrum analyzer and the maximum peak power fluctuation was kept at a low level of 0.16 dB. The output power variations with different pump powers, the relative intensity noise, the relaxation oscillation, and the linewidth at different integration times were investigated. Furthermore, the performance of the proposed EDFL acted as a strain sensor and temperature sensor with sensitivities of 1.0 pm/με and 11.4 pm/℃ were also discussed.

Scalable integrated two-dimensional Fourier-transform spectrometry

Integrated spectrometers offer the advantages of small sizes and high portability, enabling new applications in industrial development and scientific research. Integrated Fourier-transform spectrometers (FTS) have the potential to realize a high signal-to-noise ratio but typically have a trade-off between the resolution and bandwidth. Here, we propose and demonstrate the concept of the two-dimensional FTS (2D-FTS) to circumvent the trade-off and improve scalability. The core idea is to utilize 2D Fourier transform instead of 1D Fourier transform to rebuild spectra. By combining a tunable FTS and a spatial heterodyne spectrometer, the interferogram becomes a 2D pattern with variations of heating power and arm lengths. All wavelengths are mapped to a cluster of spots in the 2D Fourier map beyond the free-spectral-range limit. At the Rayleigh criterion, the demonstrated resolution is 250 pm over a 200-nm bandwidth. The resolution can be enhanced to 125 pm using the computational method.

Ecological Efficiency Measurement and Technical Heterogeneity Analysis in China: A Two-Stage Three-Level Meta-Frontier Network Model Based on Segmented Projection

Due to persistent technological impacts on ecological efficiency (eco-efficiency) and variations in economic power and resource endowments among regions, considering regional and temporal heterogeneity becomes imperative. Ecosystems, often divided into economic production and environmental governance stages, necessitate a holistic assessment incorporating regional, temporal heterogeneity and stage distinctions. To address potential issues of a technology gap ratio (TGR) exceeding 1 within a two-stage network structure with dual heterogeneity, we introduce a segmented projection three-layer meta-frontier analysis method. In empirical study, we systematically examined eco-efficiency, emissions inefficiency and technology gaps across management, regional and temporal dimensions in 30 Chinese provinces from 2016 to 2020. Findings reveal disparities in management eco-efficiency, with the central provinces outperforming the east. Regional differences indicate advanced technology in the east, contributing to superior eco-efficiency. Temporal analysis highlights the positive role of scientific and technological development. Emissions inefficiency improvements are noted, necessitating attention toward management and regional technology levels. Eastern provinces exhibit superior emissions efficiency, emphasizing the role of regional and technological development. Recommendations include prioritizing environmental governance, strengthening regional collaborations and implementing policies to bridge technology gaps.

Characterization of Visible Range Gain in Praseodymium Doped Fiber Amplifier

In the optical (380-700 nm) region, a simulation study was conducted to assess the low-signal gain, power conversion efficiency (PCE), and optical output power of a praseodymium-doped fiber optic amplifier (PDFA). The PDFA performance was assessed using the optimized Pr3+ fiber length, Pr3+ ion concentration, and pump power. Additionally, the effects of input signal voltage and amplifier gain on amplified spontaneous emission (ASE) were investigated. A lower peak signal of roughly 1 dB at 635 nm was obtained with a shorter 5 m Pr3 + doped fiber and a higher pump power of 300 mW. The impact of wavelength and pump power variations on the amplifier's optical output power's spontaneous enhanced emission (EEM) is examined. Finally, the ionic interaction (general-purpose conversion effect) in the low-power amplifier signal is analyzed by taking into account various values of the upconversion factor. Keywords: Praseodymium doped fibre amplifier, Small-signal gain, Pump power, Ultrashort laser.

Actuators linearization of a large volume environmental simulation chamber via pulse code modulation

Ultra-stable room-sized environmental chambers may involve significant power variations leading to hysteresis and nonlinearities of the stabilization system. This paper describes utilization of a pulse code modulation control which significantly reduces observed nonlinearity of the chamber actuation system. Stability of environmental conditions for temperature ΔT=±25 mK (15–35 °C dynamic range), relative humidity ΔRh=±0.1% (3%–95% dynamic range), and pressure ΔP=±12 Pa (±500 Pa dynamic range) was achieved within 27 m3 chamber volume, which is two orders of magnitude better than the corresponding stabilization achievable using a standard linear proportional–integral–derivative (PID) controller. Utilizing this chamber we have demonstrated two orders of magnitude improvement of the operational relative frequency stability of ultrastable quartz oscillators (USO), reaching 2×10−13 stability at 1-105 s averaging time.

Enhancing Power Quality in Microgrids with Hybrid Tuna‐Glowworm Swarm Optimization Strategy for Renewable Energy Sources

The technical issues in the microgrids (MG) are predicted and the fluctuation in the MG is controlled precisely by the inclusion of distinct renewable energy sources (RESs) into the MG system. The voltage stability and distortionless harmonic are the two main factors that need to be tackled in the MG system. By solving the above‐mentioned two factors, the overall power quality (PQ) of the MG is enhanced. Multiple pieces of equipment are introduced and developed especially to resolve the issues regarding the load's nonlinearity and the source's uncertainty. Hence, a novel “hybrid tuna‐glowworm swarm optimization (HT‐GWSO)” algorithm is introduced to resolve the uncertainties in the MG and to enhance the PQ in this paperwork. The proposed algorithm is a combination of “glowworm swarm optimization (GWO) with the tuna swarm optimization (TSO)” algorithms. This algorithm is utilized in tuning the parameters of the controllers used in the MG. The reactive power is varied from the active power to enhance the PQ in this proposed scheme. The controller's parameters are optimized so that the variation in power and the error while the function is minimized in the MG system. An expensive simulation is done to prove the superiority of the suggested scheme.

Exploring the mesoscale connectivity of phytoplankton periodic assemblages' succession in northern Adriatic pelagic habitats

An appropriate model for phytoplankton distribution patterns is critical for understanding biogeochemical cycles and trophic interactions in the oceans and seas. Because phytoplankton dynamics in coastal waters are more complex due to shallow depth and proximity to land, more accurate models applied to the correct spatial and temporal scales are needed. Our study investigates the role of the atmosphere and hydrosphere in pelagic habitat by modelling phytoplankton assemblages at two Long Term Ecological Research sites in the northern Adriatic Sea using niche-forming environmental variables (wind, temperature, salinity, river discharge, rain, and water column stratification). To study the synchronization between the phytoplankton community and these environmental variables at the two LTER sites, we applied current linear and nonlinear numerical methods for ecological modelling. The aim was to use periodic and/or non-periodic properties of the environmental variables to classify the phytoplankton assemblages at one LTER site (Gulf of Trieste - Slovenia) and then predict them at another LTER site 100 km away (Gulf of Venice - Italy). We found that periodicity played a role in the explanatory and predictive power of the environmental variables and that it was more important than non-periodic events in defining the common structure of the two pelagic habitats. The non-linear classification functions of the neural networks further increased the predictive power of these variables. We observed partial synchronization of communities at the mesoscale and differences between the original and predicted assemblages under similar environmental conditions. We conclude that mesoscale connectivity plays an important role in phytoplankton communities in the northern Adriatic. However, the loss of periodicity of niche-forming variables due to more frequent extreme meteorological and hydrological events could loosen these connections and affect the temporal succession of phytoplankton assemblages.

Intermittent power smoothing control for grid connected hybrid wind/PV system using battery-EDLC storage devices

Wind and solar radiation are intermittent with stochastic fluctuations, which can influence the stability of operation of the hybrid system in the grid integrated mode of operation. In this research work, a smoothing control method for mitigating output power variations for a grid integrated wind/PV hybrid system using a battery and electric double layer capacitor (EDLC) is investigated. The power fluctuations of the hybrid system are absorbed by a battery and EDLC during wide variations in power generated from the solar and wind system, subsequently, the power supplied to the grid is smoothened. This makes higher penetration and incorporation of renewable energy resources to the utility system possible. The control strategy of the inverter is realized to inject the power to the utility system with the unity power factor and a constant DC bus voltage. Both photovoltaic (PV) and wind systems are controlled for extracting maximum output power. In order to observe the performance of the hybrid system under practical situations in smoothing the output power fluctuations, one-day practical site wind velocity and irradiation data are considered. The dynamic modeling and effectiveness of this control method are verified in the MATLAB/Simulink environment. The simulation results show that the output power variations of the hybrid wind/PV system can be significantly mitigated using the combination of battery and EDLC based storage systems. The power smoothing controller proposed for the hybrid storage devices is advantageous as compared to the control technique which uses either battery or ultracapacitor used for smoothing the fluctuating power

Experimental investigation of process parameter variations on the microstructure and failure behavior of IN718 structures in PBF-LB/M

Conventional manufacturing technologies, such as milling or casting, are limited in terms of the manufacturable complexity of the parts to be produced. They are also restricted in terms of the local modifiability of the mechanical properties. Additive manufacturing, specifically the Powder Bed Fusion of Metals using a Laser Beam (PBF-LB/M), is a novel method, which is capable of addressing both limitations. However, the resulting parts are often prone to cracking during PBF-LB/M and in the service afterward because of high thermally induced local stress intensities. Selectively modifying the process parameters during the fabrication can be a suitable strategy to locally reduce the failure susceptibility. Over the course of this study, samples made from the nickel-based superalloy Inconel 718 were manufactured with varying laser powers, hatch distances, and scan speeds. The samples were divided into stress crack specimens as well as static and dynamic tensile test specimens. The grain structure was investigated, and correlations between the microstructure and the cracking susceptibility were determined. It was found out that variations in the laser power had the most pronounced effect on the grain structure and the failure behavior. An increasing grain size enhanced the fracture resistance in the stress crack samples while the static and dynamic mechanical properties deteriorated. Based on these results, the application area of PBF-LB/M could potentially be widened due to the manufacturability of parts otherwise susceptible to stress-induced cracking. The mechanical properties of as-built parts can remain unchanged utilizing a local process parameter adaption.

Microwave assisted synthesis of ZnIn2S4 nanoparticles: effect of power variation for photoresponse and optoelectronic applications.

The ternary ZnIn2S4 has recently gained significant attention due to its potential applications in various optoelectronics and photocatalysis sectors. In the current study, ZnIn2S4 nanoparticles were prepared using a simple microwave-assisted synthesis method with different irradiation powers varying from 180 W-720 W. Structural analysis confirmed their polycrystalline nature with the appearance of ZnIn2S4 and In2S3 phases. The variation in diffraction pattern intensity and Raman vibrational bands with irradiation power indicates structural rearrangements induced with power variation. Morphological studies confirmed the formation of agglomerate nanoparticles with size variation as induced by different microwave powers. Broad absorption across the visible and near-infrared regions and the increased band gap enhance their photocatalytic and sensing applications. An increased irradiation power in the ZnIn2S4 lattice reduced intermediate levels within the band gap, altering the optical responsiveness. The blue shift in absorption edges with microwave power increased the optical band gap by reducing disorder and defects. The refractive indices were estimated using different theoretical models and reduced with an increase in the band gap. Thermal analysis revealed endothermic peaks. These ZnIn2S4 nanoparticles displayed an enhanced photocurrent under white light, increasing tenfold with microwave power. The greater powered ZIS (ZIS-720 W) nanomaterial showed the best photoresponse and is well suited for optoelectronic application. All of their optical and electrical properties make them suitable for various optoelectronic devices, particularly in detection applications.

Power variations and limit theorems for stochastic processes controlled by fractional Brownian motions

Power variations and limit theorems for stochastic processes controlled by fractional Brownian motions

Investigation of the effects of energy density in Laser Sintering of polypropylene on morphological and dielectric properties for high-frequency antennas

Advancements in the Internet of Things demand more capable antenna systems, which benefit from the complex geometries enabled by additive manufacturing. Novel approaches, such as external metallization of polymers, enable the design of these geometries but require the processing of low dielectric-loss polymers in additive manufacturing. Arising from prevailing limitations on additively manufactured low-loss components, this study investigates the effect of energy density on polypropylene’s dielectric properties in powder bed fusion processes. Variations in laser power significantly influenced material density and mechanical characteristics. Both insufficient and excessive energy densities resulted in lower quality parts due to issues like fused particles or inadequate melting. Optimal dimensional accuracy and surface quality were achieved with energy levels slightly below those for peak density. While dielectric loss remained mostly stable, relative permittivity decreased at very low densities, where partial melting occurred. Relying on derived optimized parameters, the functionality of passive high-frequency components was demonstrated.