Low Power Levels Research Articles

Sound power of onshore wind turbines and its spectral distribution

Wind turbines (WTs) have grown substantially in size and electric capacity over the past decades. The sound power of WTs was reported to increase over time in relation to their electric power and thus over time WTs have become louder. Because of the expected ongoing growth of onshore wind energy, a greater number of people will be living close to wind farms. This sustains the need for sound reduction. Sound reduction measures, such as serrations, reduced tip speed and low noise modes, may counteract the development of higher sound power levels from ever bigger WTs. To investigate this, the sound production of WT types over the last decades is analyzed in relation to their size and electric power and the application of sound reduction measures. The analysis includes the broad band A-weighted and low frequency sound power levels as well as more detailed spectral distributions. Results show that the sound power level of wind turbines above 3 MW on average increases less with size than smaller turbines did. This is due to a lower increase in blade tip speed. The application of trailing edge serrations (TES) on average leads to a reduction in sound power level of 2.4 dB which may be slightly less at residential locations. Though TES tend to reduce the higher frequencies, the average spectral distribution of the sound did not change significantly over time, probably because of the relatively large differences between individual WT types. As a consequence, the relative low frequency content of WT sound on average has not changed.

Breathers in Mode-Locked Lasers Based on Saturable Absorbers

Breathing pulses, as a unique nonlinear pulse phenomenon, play a key role in laser performance optimization, nonlinear optical processes, and complex signal transmission. Unlike stable solitons, the energy of breathing pulses fluctuates periodically over time, exhibiting periodic changes in both pulse frequency and amplitude. Through appropriate nonlinear effects, lasers can generate stable breathing pulses, achieving a mode-locked state that demonstrates a periodic "breathing" pattern. Based on this, a fiber laser incorporating a saturable absorber as the mode-locking element was designed and built, and stable breathing states were successfully observed at lower pump power levels. High-speed detection techniques and time-stretched dispersive Fourier transform (TS-DFT) technology were used to time-amplify and spectrally analyze the rapid pulses, while monitoring the evolution of the breathing pulse in both time and frequency domains. Experimental results indicate that changes in pump power significantly affect the periodic modulation induced by additional oscillations, thereby controlling the breathing ratio and ultimately leading to the formation of a stable soliton. When the pump power is between 470 <i>mW</i> and 480 <i>mW</i>, the formation of the breathing pulse was first observed, with a breathing ratio of up to 4.5. As the pump power increases, the breathing effect gradually diminishes, and at 510 <i>mW</i>, it completely disappears, with the breathing ratio dropping to 1.<br>These results confirm the critical role of pump power in controlling the breathing pulse state and its transition, demonstrating the potential for controlling pump power in ultrafast laser technology and nonlinear optics. The breathing pulse phenomenon, as a periodic pulse behavior, reflects the complex dynamical characteristics between nonlinear optical effects and cavity parameters. When combined with the natural synchronization system formed between the breathing frequency and the cavity frequency (determined by the cavity length), the periodic change of the breathing pulse becomes a crucial factor for controlling laser output. By adjusting parameters such as the laser’s nonlinearity and dissipation, the characteristics of the breathing pulse and breathing ratio can be precisely controlled, thus achieving precise control of the laser output. The periodic oscillatory characteristics of the breathing pulse inside the laser cavity lead to the non-uniform distribution of pulses, a feature that demonstrates enormous potential in pulse shaping, ultrashort pulse generation, and precise frequency comb control. Additionally, the presence of the breathing pulse may impact the stability and energy conversion efficiency of the laser, offering new perspectives for laser design and optimization.

IoT-Based Energy Meter for Remote Monitoring and Managements of Power Consumption

Real-time monitoring of several parameters such as the current and the rated power is provided by this design. Users become more conscious of their consumption with specifications based on recorded data using this design. Additionally, it enables users to quickly identify abnormal issues such as spikes that result in device failure. Also, this design offers remote access to received data by cloud platforms with mobile applications. This study evaluates the performance of an Energy Monitoring distributed among 17 electrical devices in three houses over a period of 30 days. The design demonstrated high accuracy and minimal error in its readings for the related devices with effectively capturing detailed energy consumption values. Based on results, the analysis of power and current efficiency at different power levels reveals notable performance variations. House 1 runs efficiently at low power levels; yet, efficiency levels indicate higher power levels with (96% ,97%) power and current reading efficiency respectively. House 2's efficiency at medium power displays more pronounced inefficiencies than House 1's, although it still keeps its current efficiency constant with (90% ,97%) power and current reading efficiency respectively. House 3 demonstrates that it is ideally adapted to handle high power levels, exhibiting the highest overall efficiency in high power conditions with (97% ,98%) power and current reading efficiency respectively. The extra power in every case shows how well help users to use this design with the extra reading power for other devices or reducing house power to reduce in electrical bill cost.

Sediment transport characteristics at the flood-event scale in the Minjiang River Basin, China

ABSTRACT In recent years, the significant change in the runoff–sediment distribution in the upper Yangtze River has led to an increased sediment contribution from the Minjiang River Basin (MRB) to the Three Gorges Reservoir. However, previous studies on sediment load changes in the MRB have focused mainly on annual-scale characteristics, thereby neglecting features driven by floods. Therefore, this study focused on examining the changes in flood-event sediment loads in the MRB based on mathematical statistics and comprehensive measurement data. The results indicated that human activities, climate change, and seismic events have caused an increasing trend in the flood-scale sediment load in the upper MRB and a decreasing trend in the lower MRB. The changes in the flood-scale sediment modulus at low runoff erosion power levels were greater than those at high runoff erosion power levels at different abrupt-change stages. During extreme flood events, the actual sediment concentration in the MRB remained below the sediment-carrying capacity. This study provides novel insights into water resource management during the flood season in the MRB and similar basins.

In vitro bioactive dentin protein release by diode laser conditioning.

This in-vitro study aimed to explore the potential of Diode Laser by quantifying the release of transforming growth factor-beta 1 (TGF-β1), platelet-derived growth factor (PDGF)-BB, and vascular endothelial growth factor (VEGF) from root dentin after ethylenediaminetetraacetic acid (EDTA) and diode laser. In 30 hemi-roots distributed into five groups: G1: Tris-buffered solution (TBS); G2: 17%EDTA; G3: 17% EDTA +650 nm Diode Laser; G4:17% EDTA +810 nm Diode Laser; and G5: 810 nm Diode Laser. The concentration of the three factors was quantified using a cytokine bead array. Statistical tests were performed to estimate intergroup differences (p ≤ 0.05). TGF-β1 and VEGF were solubilised in all test protocols. The ability of low-level power diode lasers to release proteins from the matrix is limited. Its effect on the release of VEGF and PDGF-BB does not make a difference. A synergy between EDTA and Diode Laser led to a greater proportion of TGF-β1 release.

Dynamics of Molten Salt Reactor with Operating Heaters

Recent interest in molten salt reactors (MSRs) has initiated research projects on their safety and performance compared to light water reactors. Maintaining the fuel salt in a molten state during reactor operation at all power levels is a significant safety concern for these reactors. Various strategies can be used to maintain the fuel salt temperature above its melting point during low-power reactor operation. This study analyzed the impact of using electric heaters on the stability and performance of an operating MSR. For this purpose, a simulation tool was developed for reactor dynamics and stability analysis studies. The simulation tool was validated against the Molten Salt Reactor Experiment reactivity insertion tests. The dynamics of an MSR with and without operating electric heaters at steady state and following initiated transients were investigated and compared. Simulation results showed that the usage of these heaters is more pronounced during transients rather than in the steady-state operation. The stability of the system degraded following transients due to the operation of heaters. However, using heaters remains an alternative strategy to maintain fuel salt molten at low power levels.

Optimizing conditions for microwave-assisted solvent extraction of polar compounds from Carissa carandas.

The present investigation aimed to optimize the solvent combination and microwave-assisted extraction (MAE) conditions for extracting polar phyto-components from Carissa carandas, which is an underutilized fruit rich in various bioactive compounds. Initially, an augmented simplex centroid design was used to investigate the influence of four polar solvents (methanol, ethanol, acetone, and water) on the extraction of phyto-compounds, including total sugars, reducing sugars, total polyphenols, flavonoids, and antioxidant activity of the extract. The desirability function determined that a solvent combination of ethanol-water (49:51, v/v) was the most effective for extracting polar components from C. carandas, and this combination was used for further MAE optimization. During MAE, the effects of different microwave powers (180, 360, and 450W), time intervals (3 and 6min), and acidity levels (0% and 1% HCl, w/v) were studied for the phyto-compounds. The results showed that microwave treatment at a low power level (180W), shorter treatment time (3min), and acidified solvents promoted the extraction of total and reducing sugars, as well as enhanced total polyphenolic content (TPC) and total flavonoid content (TFC). The extraction solvent's acidity positively impacts TPC and TFC in reflux systems but negatively affects extraction yields in MAE. The antioxidant activities were also significantly influenced by the extraction solvent's microwave power, treatment time, and acidity. These findings emphasize the importance of MAE for efficiently extracting polar phyto-components from C. carandas, which can be further utilized in the food and pharmaceutical industries. PRACTICAL APPLICATION: Optimized MAE conditions enhance bioactive compound extraction from C. carandas, benefiting nutraceuticals, functional foods, and the development of functional packaging materials. Owing to their rich profile of bioactive compounds, it can be utilized in the pharmaceutical and cosmetic industries. The extracts can also be used to synthesize various nano-compounds aiding in green and sustainable chemistry principles.

Effect of Foam Mat Drying on Extraction of Anthocyanins from Syzygium cumini (Jamun)

AbstractThis study was conducted to analyze the effect of foam mat drying (FD) technology on the anthocyanin extraction from Syzygium cumini (Jamun) pulp. Jamun pulp was foamed using a hand mixer with the incorporation of egg albumin and methylcellulose. The drying process involved three different techniques: hot air foam drying, vacuum foam drying, and microwave foam drying. Microwave foam drying was selected as the preferred method based on the recovery of anthocyanin, with drying power options of 180, 360, and 540 W. For hot air foam drying and vacuum foam drying, temperatures of 50 °C, 70 °C, and 100 °C were employed. It was found that microwave drying with 180 W had maximum anthocyanin recovery, whereas vacuum and hot air drying showed lesser anthocyanin content. The anthocyanin content obtained at this power level was determined to be 491.42 ± 6.97 mg/100 g, indicating a significant increase compared to the initial content. Using lower power levels in microwave FD has proven advantageous by preventing the degradation of anthocyanins due to decreased exposure to heat. Subsequently, various analyses were conducted from the extracts obtained from microwave power 180 W, which included total phenolic content (TPC), 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH), and antimicrobial assay. Lower values of TPC were found because of the breakdown of bioactive compounds due to higher power levels. An increased quantity of % DPPH activity was observed. The extract exhibited notable antibacterial efficacy, although no significant antifungal impact was detected. These characterizations offer valuable information about the composition and potential uses of the anthocyanin extract obtained through microwave FD at 180 W power.

Comparison of the performance of a cylindrical Hall thruster with different anode voltages via numerical simulations

Plasma propulsion, or electric propulsion, arises from the need to explore deep space in a more economical and efficient manner. The cylindrical Hall Thruster (CHT) is an electric propulsion device that offers high propellant utilization and performance at smaller dimensions and lower power levels than traditional plasma propulsion devices. The reduced dimensions of the CHT operating at lower power levels make it an interesting option to provide propulsion of CubeSats and small satellites. The CHT consists of a channel with an annular anode through which neutral gas is injected. The neutral gas is then ionized by magnetized electrons injected from an external hollow cathode. The resulting plasma ions are ejected from the device due to the positive electrostatic potential at the anode, giving thrust. The aim of this work is to understand and study the plasma in the discharge channel of a CHT through numerical simulations. The numerical code describes the plasma with a hybrid model in which the electrons are treated as a fluid and the ions and neutral atoms as pseudo particles. The simulations were conducted for two different potential values at the anode, namely, 150 V and 300 V, representing different modes of operation. The results obtained with this simplified model allow to obtain an optimal configuration for a future prototype to be implemented at the Plasma Physics Laboratory at the University of Brasilia.

Kerr-Quintic Nonlinearities in Graphene Quantum Dot

Abstract This paper deals with the higher-order nonlinearities in graphene quantum dots as defect layer in one dimensional photonic crystal. A weak probe pulse and two strong control laser beams are employed in a close loop ladder type configuration under an electromagnetically induced transparency regime. In the system, the existence of third- and fifth-order susceptibilities are found to be as large as ~10−15 m 2/V 2, and ~10−27 m 4/V 4, respectively, at the probe wavelength 1.55 μm. The systems possessing such large nonlinearities can be employed to fabricate nonlinear optical devices, operable at much low power level.

Emitted current self-balancing for spacecraft charging mitigation in a high-voltage power converter for electrospray thrusters

Electrospray thrusters offer remarkable efficiency at low power levels and compact form factor, positioning them as promising propulsion systems for small satellite platforms. The ability of electrospray thrusters to emit both positive and negative ion beams has significant implications for charge neutralization. In theory, electrosprays could function without the need for an external cathode. If two separate thrusters are operated simultaneously with one emitting a positive ion beam and the other an identical negative ion beam, the spacecraft would theoretically remain charge-neutral, allowing the thrusters to operate continuously without inducing spacecraft charging. This article explores the self-balancing of emitted currents, and consequently the ion beams, by incorporating a capacitor as a control element. This approach achieves current balancing without altering the operation of the power converter. The thruster’s behavior as an electrical load is simulated using a novel electrical model derived from experimental thruster data. This model, integrated within the converter, demonstrates that the inclusion of a capacitor effectively balances the emitted currents. Experimental validation aligns with the simulation results, confirming current balance with a relative error between polarities of only 1% in the final test cases.

Performance evaluation of Hard-Isolated GPONs using regular perturbation methods

Abstract In this study, we conduct a detailed performance evaluation of hard-isolated Gigabit Passive Optical Networks (GPONs) using Regular Perturbation (RP) methods. The Nonlinear Schrodinger Equation (NLSE) is utilized to model signal propagation in optical fibers, capturing the effects of nonlinearities and dispersion. By applying RP techniques, we derive approximate solutions to the NLSE, offering a more manageable approach for performance analysis in highly nonlinear regimes. Key performance metrics such as Normalized Squared Deviation (NSD), Bit-Error Rate (BER), and Achievable Information Rates (AIR) are analyzed to validate the accuracy and efficiency of the RP models. Simulation results demonstrate that the RP method provides good accuracy in modeling nonlinear effects, particularly at lower input power levels. Additionally, the study investigates the impact of hard isolation on mitigating nonlinearities, showing significant benefits in maintaining signal integrity and reducing BER. The findings highlight the potential of RP methods as robust tools for performance evaluation and optimization in advanced optical communication systems.

Assessing contextual factors influencing scale-up: a interactive approach involving stakeholders

Abstract Issue Pilot interventions are not always put into practice at scale. When they are, effectiveness is often highly reduced in the field due to contextual factors. To effectively implement a scale-up, stakeholders’ involvement is crucial. Curema is an international research evaluating an intervention aiming to reduce malaria transmission by distributing RDTs and treatments in mobile hard-to-reach populations. This intervention might be scaled-up in Brazil, Suriname, and French Guiana as a tool of national malaria programs for specific areas and populations. Description of the problem An interactive pre-planning assessment was conducted involving key stakeholders -implementers, decision-makers, and researchers - in working sessions, semi-structured interviews, and formal meetings. Mendelow’s Power/Interest Matrix was used to map stakeholders and a SWOT analysis was conducted using ExpandNet/WHO Framework to evaluate contextual factors and identify levers and obstacles influencing the scale-up. Results A total of 23 participants were involved. Health authorities had high power and generally high interest, while implementers and recipients had lower power and different interest levels. National engagement for WHO E2025 or E2030 enhanced scalability and represented a main opportunity in the three countries. Nevertheless, several regulatory and administrative aspects were identified as potential obstacles to be addressed to make scale-up realistic. Funding was also a major concern for sustainability. The need for regional cooperation was emphasized to achieve malaria elimination. Lessons Despite financial and regulatory challenges, a window of opportunity is open to scale-up Curema. Identifying and involving stakeholders in a pre-planning assessment and advocating for foster regional cooperation are crucial steps to support the scale-up. Stakeholder analysis should be refined during the scaling-up to capture further changes in factors that might influence the process. Key messages • Engagements with WHO represent windows of opportunity to enhance Curema scale-up. • Stakeholder involvement and regional cooperation are crucial for scaling up Curema in Brazil, French Guiana and Suriname.

In-orbit demonstration of acquisition and tracking on OSIRIS4CubeSat.

OSIRIS4CubeSat is the smallest commercially available laser communication terminal within the confines of 0.3-units. It was launched as PIXL-1 inside of a 3-unit CubeSat into space to demonstrate optical direct to earth links. This work primarily focuses on the commissioning phase, particularly emphasizing the performance of the active fine pointing and tracking mechanism. This steering mechanism, with a 1 degree radius field of regard, plays a decisive role in compensating for pointing inaccuracies from the satellite's attitude determination and control system. The design and validation of open-loop acquisition and closed-loop tracking are presented. The feedback sensor adapts to changing beacon power levels, that occur during a direct to earth link, by an adaptive gain control. Subsequent evaluation of satellite passes, with telemetry recordings obtained from the deployed CubeSat, showcases superior performance that meets the pointing requirements of the link budget. By using the developed control-loop logic, OSIRIS4CubeSat achieves a mean tracking error of 71 µrad, with a 3σ deviation of 140 µrad down to low power levels of 238 pW. These results serve as validation of OSIRIS4CubeSat, demonstrating its capability to enable high-speed data transmission from low Earth orbit to the Earth's surface at data rates of up to 100 Mbit/s.

Microwave-induced alterations in the structure of coals at different metamorphic stages

Despite the global trend toward decarbonization, coal continues to play a significant role in energy production, as current renewable energy sources cannot fully meet the increasing global energy demand. The main objective of decarbonization is to reduce greenhouse gas emissions, especially carbon dioxide. Enhancing coal usage efficiency can help decrease these emissions. Electromagnetic activation of bituminous coal is already employed for dehydration, ash removal, desulfurization, and improving the grinding process of raw coal. This research aims to study the specifics of coal electromagnetic activation using microwave radiation and its effects on the physical and chemical processes occurring in coals at different metamorphic stages. The results suggest that this electromagnetic treatment leads to the destruction of hydroxyl groups and the formation of free hydrogen. Coals at higher metamorphic stages heat up faster due to their higher structural density. Coals at lower metamorphic stages take longer to heat up and require more processing time to be effective, while lower power levels are necessary to avoid mechanical breakdown. Activation time and coal particle size are significant factors; their optimal combination provides the maximum effect. These findings contribute to optimizing microwave treatment parameters for different coal types, potentially enhancing coal utilization efficiency and reducing environmental impact.

A study on the perception of refrigerator noise in everyday life

Advancements in technology and noise control measures significantly reduced the noise emissions of refrigerators. Despite the achievement of low sound power levels in modern refrigerators, substantial efforts are still dedicated to further minimizing their noise. This initiated an examination into the need for ongoing activities to reduce noise, given the already minimal noise levels. This study aimed to evaluate the impact of refrigerator noise in everyday life, examining the circumstances and extent of individuals' exposure to noise while exploring their general perception. In an online survey, attention to refrigerator noise was explored to understand how often respondents can hear refrigerator noise in their daily lives. In addition, questions about the operating conditions of the refrigerator, in particular at the times when participants could hear refrigerator noise, were also assessed in the survey. Finally, the results of measurements that generalize the extent to which refrigerator noise can exceed background noise in normal rooms were also evaluated in this study.

Ultra-Low-Power, Extremely Stable, Highly Linear-Response Thermal Conductivity Sensor Based on a Suspended Device with Single Bare Pt Nanowire.

The continuous and stable monitoring by sensors is crucial for ensuring the safe utilization of hydrogen due to its inherent high explosiveness. Currently, catalyst aging and oxygen dependence often limit the lifetime of most sensors, which stems from the sensing materials and catalytic reaction in comparison to thermal conductivity sensors. Thermal conductivity sensors possess superior sensing characteristics such as lowpower consumption and exceptional stability attributed to their free-catalysts or free-oxygen nature. Herein, we present an ultralow-power hydrogen-thermal conductivity sensor based on suspended bare platinum nanowires. This sensor incorporates two suspended independent working elements (serpentine/bridge), each of which is thermally decoupled from the substrate. Also, the bridge element operates at significantly lower power levels (the lowest ∼3.32 μW) compared to existing direct-current hydrogen-thermal conductivity sensors. Furthermore, it demonstrates a 99.99% linearity between hydrogen concentration and response under various operating powers. Finally, our sensor shows remarkable stability through a repeatability test (>30,000 cycles). This developed platform provides an optimal structure scheme for integrated sensors with ultralow-power, extremely stable, highly linear-response sensing characteristics, which is expected to be widely used for hydrogen detection and leakage warning under various pipeline distribution systems.

Experimental study on steady-state performance of an axial grooved heat pipe under rotational condition

This study explores the performance optimization of grooved heat pipes under rotational conditions, focusing on both straight and curved designs. To address the challenges posed by centrifugal forces in rotating systems, we designed and tested a conventional straight grooved heat pipe and a novel curved grooved heat pipe with a variable curvature structure. Experiments were conducted across a range of rotational speeds (0–20 rpm), heat loads (30 W-300 W) and loading methods (heat load before rotation and heat load after rotation) to evaluate the operating performance of both grooved heat pipes. The results indicate that the straight grooved heat pipe struggled to maintain efficiency under rotational conditions, as centrifugal forces caused fluid to accumulate at both ends, leading to higher operating temperatures and reduced heat transfer efficiency. At the case of 20 rpm with a heat load of 110 W, the temperature difference exceeded 25 °C, highlighting the limitations of the straight design in such environments. In contrast, the curved grooved heat pipe effectively mitigated the impact of centrifugal forces. Its design reduced liquid accumulation in the condenser section, maintained beneficial acceleration effects in the evaporator section, and improved overall heat transfer performance. Specifically, at 20 rpm, the curved pipe successfully transferred over 300 W with a temperature difference not exceeding 5 °C, demonstrating its superior performance. However, at higher rotational speeds and lower power levels, the curved design also showed some limitations, as excessive fluid accumulation in the evaporator section led to a shift in the evaporation site, increased thermal resistance, and a certain degree of superheating. These findings highlight the potential of the variable curvature design in improving the efficiency of grooved heat pipes under rotational conditions. This work advances the understanding of fluid dynamics and heat transfer mechanisms in such systems, offering insights that could inform the design of more efficient heat pipes for rotating applications.

Highly secure non-orthogonal multiple access with key accompanying transmission based on subcarrier-indexed modulation.

This paper proposes a key-accompanying transmission scheme based on subcarrier indexed modulation (SIM). The key is used to control the activation state of subcarriers, with key masking achieved through the position information of silent subcarriers, which enables the cooperative transmission of both key and primary messages. Meanwhile, a four-dimensional hyperchaotic model is adopted to ensure system security. By utilizing power multiplexing, the scheme realizes the parallel transmission of two signals and disrupts the carrier frequency and symbol of the original signals. The scheme is experimentally demonstrated with a 54.25 Gb/s SIM-chaotic power division multiplexing (CPDM) signal transmission over 2 km of 7-core fiber.. The results indicate that the proposed scheme does not degrade system transmission performance at either high or low power levels. At the limit of forward error correction (FEC)=3.8×10-3, the impact of our scheme on receiver sensitivity is no greater than 0.1 dB. The accuracy and sensitivity of the key are maintained, with the transmission performance of the key remaining excellent. The bit error rate (BER) for the main signal is consistently kept at 0, while the BER for the key rises to around 0.5 if the key is misaligned by one bit. Moreover, the key space can reach 10135, effectively verifying the system's high security.

Relationship power attenuated the effects of gratitude on perceived partner responsiveness and satisfaction in romantic relationships

There is a gap in whether relationship power affects the association between gratitude and relationship satisfaction in romantic relationships. Based on the relationship maintenance model and the social distance theory of power, the present study adopted a digital questionnaire design on an online platform to test the mediating role of perceived partner responsiveness between gratitude and satisfaction as well as the moderating role of relationship power. A total of 825 subjects (Mage = 27.2, SD = 10.6; female 46.9%) who had been in romantic relationships for more than six months participated in this study. Overall, the results of the moderator–mediator model indicated that, compared to individuals with low levels of relationship power, the relationship between gratitude and perceived partner responsiveness as well as that between perceived partner responsiveness and relationship satisfaction was weaker among those with high levels of power. These findings are revealing for interventions designed to promote satisfaction between couples with power imbalances.