High Power Levels Research Articles

An Novel Technique for Wireless Power Transfer Systems Based on the Parametric Set

High efficiency and high power level are important indicators of the Inductive Power Transfer (IPT) system. However, the problem of optimizing the efficiency of IPT has not been well solved, and improving control methods is one of the effective ways to solve this problem. In order to improve the existing secondary-side control scheme and achieve the goal of simultaneously achieving optimal transmission efficiency and stable output, this paper suggests a parameter-based control strategy for coordinating the primary and secondary sides in the IPT system. This paper suggests a parameter-based control strategy for coordinating the primary and secondary sides in the IPT system. The paper develops a model of the IPT system to find the best load, then analyzes the active rectifier, phase shift angle, and load relationship to create a parameter set for controlling quantities like α and β. From there, a new control strategy is proposed and its effectiveness is confirmed through simulations. The proposed strategy enhances transmission efficiency and output stability of the IPT system, making it highly applicable in areas like electric vehicle charging and wireless charging devices.

Single- and two-photon absorption induced all-optical control of gallium selenide integrated silicon nitride photonic devices in the 700–800 nm wavelength range

In this work, we report single- and two-photon absorption (TPA) induced transmission and resonance modulation in a multilayer gallium selenide (GaSe) integrated silicon nitride (Si3N4) waveguide and ring resonator operating in the 700–800 nm wavelength range. Intensity dependent saturable absorption at low optical powers followed by TPA at higher power levels in GaSe integrated Si3N4 waveguides is observed at 785 nm pulsed laser excitation. A TPA coefficient of 0.117 cm/GW for the GaSe–Si3N4 composite waveguide and a three-photon absorption coefficient of 7.876 × 10−6 cm3/GW2 for the bare Si3N4 waveguide are extracted from intensity dependent transmission measurements. The single-photon absorption process induced by a blue laser incident on the multilayer GaSe transferred on top of the Si3N4 ring resonator is used for all-optical resonance tuning through the free-carrier refraction effect. A strong blue shift of the resonance by ∼12.3 pm/mW combined with resonance broadening is observed due to the free-carrier induced refractive index and absorption modulation. The TPA in the GaSe integrated Si3N4 ring resonator is also shown to result in a blue shift of the resonances excited using a 785 nm pulsed laser. This work demonstrates the all-optical control of 2D material integrated Si3N4 guided-wave structures operating in the shorter near-infrared wavelength range with potential applications in integrated quantum photonics, miniaturized sensing devices, and biomedical imaging.

Development of Tunable Ferroelectric Ceramic Capacitors.

Ferroelectric perovskite ceramics with a high dielectric constant, low loss, high tunability, and high electric breakdown are ideal for nonlinear transmission lines (NLTLs) to generate radio frequency (RF) signals at high-power levels. To achieve the required properties, a comprehensive study of the material phase transitions and the optimal ratio adjustment between the chemical elements in the perovskite crystal structure is required. The advancement of this solid-state technology is the most promising optimization for NLTLs in developing high-power (>100 MW) devices with high tunability (>60%) and high repetition rate (>1 kHz) for soliton generation. The barium strontium zirconium titanate (BSZT) ceramic compositions were synthesized and characterized to maximize material tunability. The composition Ba0.97Sr0.03Zr0.2Ti0.8O3 exhibited a high permittivity (>12200), low loss tangent (< 0.01), and an exceptional tunability of the order of 79% at an electric field of 10 kV/cm near the phase temperature transition at 300 K. Ferroelectric ceramic is an outstanding material with promising characteristics for producing RF signals in an NLTL, and here, the BSZT is considered for this application.

Ensuring permanence of optics for ultrafast laser applications

AbstractUltrafast lasers in various applications suffer from short lifetime optics due to high power levels and intense pulses. Typical laser damage testing methods are often limited to short exposure doses, which sometimes do not match real‐life application requirements. To ensure long‐term failure‐free operation, lifetime estimation and low‐loss absorptance testing should be used instead. Low‐absorption dielectric coatings increase the lifetime and lower the total cost of ownership, benefiting the manufacturing, research, and medical sectors.

Modeless Raman fiber laser

The discrete multi-longitudinal mode structure and temporal periodic fluctuation are the intrinsic features of conventional lasers. However, longitudinal mode spacing limits the maximum resolution in high-resolution laser sensing systems. In addition, temporal periodic fluctuation reduces the security of secure communication and deteriorates the randomness in fast physical random bit generation. Therefore, it still remains an open challenge to realize a laser source without discrete longitudinal mode and temporal periodic fluctuation. Here, a modeless Raman fiber laser (RFL) with high efficiency was demonstrated. The output cavity mirror adopts a fiber Bragg grating with ultralow reflectance of −27dB. Due to the modulation instability, the discrete multi-longitudinal modes in the RFL gradually broaden with the increase of intracavity Stokes wave power and eventually fully overlap. At high power levels, the RFL no longer has discrete longitudinal modes like a conventional laser but generates a quasi-continuous spectrum. Benefiting from the modeless nature, the RFL can achieve extremely low relative intensity noise, favorable temporal stability, and rather low coherence. Modeless RFLs are expected to be ushered as ideal light sources into secure communication, optical sensing, and optical imaging.

Nature-Inspired Concepts for High-Power Electric Propulsion Systems

The development of new space missions and the growing interest in space exploration have created an urgent need to develop high-thrust propulsion systems capable of propelling spacecraft far beyond the Earth and the solar system for long periods. Electric propulsion can potentially enable space missions to reach speeds thousands of times greater than conventional high-thrust chemical rockets. However, high speed comes at the cost of low power-to-thrust efficiency when considering propulsion systems as a whole, including the power generation system, transmission lines, and thrusters, which prevents high thrust from being achieved with any conceivable power system, resulting in long acceleration times. In addition, modern electric propulsion systems rely on external power sources that suffer significant power transfer losses at the high power levels required for high thrust levels. In addition, modern electric propulsion systems suffer from a number of critical physical and engineering problems that affect thrust levels and longevity. In addition, modern electric propulsion systems do not follow the principles of generation and acceleration of plasma flow that can be observed in space and potentially borrowed for artificial applications. This paper discusses several promising electrodeless plasma thruster concepts for high-power, high-thrust electric propulsion systems based on a combined power source/power converter/thruster architecture. These concepts have the potential to overcome modern limitations of high-power electric propulsion systems and enable new outer space missions that would not be possible with conventional thrusters.

Participatory action research to address lack of safe water, a community-nominated health priority in rural South Africa.

Despite international evidence supporting community participation in health for improved health outcomes and more responsive and equitable health systems there is little practical evidence on how to do this. This work sought to understand the process involved in collective implementation of a health-related local action plan developed by multiple stakeholders. Communities, government departments and non-government stakeholders convened in three iterative phases of a participatory action research (PAR) learning cycle. Stakeholders were involved in problem identification, development, and implementation of a local action plan, reflection on action, and reiteration of the process. Participants engaged in reflective exercises, exploring how factors such as power and interest impacted success or failure. The local action plan was partially successful, with three out of seven action items achieved. High levels of both power and interest were key factors in the achievement of action items. For the achieved items, stakeholders reported that continuous interactions with one another created a shift in both power and interest through ownership of implementation processes. Participants who possessed significant power and influence were able to leverage resources and connections to overcome obstacles and barriers to progress the plan. Lack of financial support, shifting priorities and insufficient buy-in from stakeholders hindered implementation. The process offered new ways of thinking and stakeholders were supported to generate local evidence for action and learning. The process also enabled exploration of how different stakeholders with different levels of power and interest coalesce to design, plan, and act on evidence. Creation of safe spaces was achievable, meanwhile changing stakeholders' level of power and interest was possible but challenging. This study suggests that when researchers, service providers and communities are connected as legitimate participants in a learning platform with access to information and decision-making, a shift in power and interest may be feasible.

Habitat suitability modelling for an integrated multi-trophic aquaculture (IMTA) system along Europe's Atlantic coast

As the human population grows, so too does the demand for resources. This demand has led to aquaculture becoming the fastest growing food production sector in the world. Due to environmental concerns associated with finfish aquaculture, Integrated Multi-Trophic Aquaculture (IMTA) has been proposed to minimise any negative impacts, by co-culturing extractive aquaculture species from different trophic levels to remove excess organic and inorganic nutrients, using them for their own growth. This study, in the Atlantic area of Europe, aimed to identify the most suitable locations to establish a new IMTA system for the 3 species Salmo salar (Linnaeus, 1758), Mytilus edulis (Linnaeus, 1758), and Laminaria digitata ((Hudson) JV Lamouroux, 1813). Habitat suitability models were created using spatial jackknifing testing within MaxEnt software and analysed using ArcGIS (ArcMap 10.8.1). All Maxent models were better than random when predicting species distribution, with AUC values of 0.889 (S. salar), 0.876 (M. edulis) and 0.901 (L. digitata), indicating a high level of predictive power. Jackknife testing identified Chlorophyll A (mg m−3) and Salinity (PSS) as the 2 most important variables in the model for each species. Coastal areas of the United Kingdom, Ireland and Northern France were identified as highly suitable, with suitability decreasing in more southern environments. These areas were then assessed based on local vessel density, whether they were within a Marine Protected Area (MPA), and the site accessibility from nearby ports, according to the expected needs of a large-scale aquaculture system. As MaxEnt used wild population data to produce the models, environmental conditions at suitable areas were compared against known Salmo salar aquaculture sites in Scotland to further validate the suitability for IMTA purposes. The results of this study, and the identification of optimal conditions for each species, will provide aquaculture businesses with the information required for preliminary site selection, with the goal of further incorporating IMTA systems into the EU market in a sustainable way.

Investigation of High‐Power Spatiotemporal Mode‐Locking with High Beam Quality

AbstractThe developed spatiotemporal mode‐locked (STML) laser has emerged as an effective platform for investigating high‐dimensional nonlinear spatiotemporal dynamics. Additionally, it offers a novel avenue for the design of fiber oscillators capable of operating at high power levels. At present, the focus of STML laser research primarily revolves around this aspect. However, considering practical applications, there is a strong desire to conceive a simple all‐fiber STML oscillator with both high beam quality and high power. In this study, an all‐fiber, high‐power STML oscillator based on multimode fibers is constructed and investigated. By manipulating the pump power and the polarization state, the laser could operate in a dissipative soliton or noise‐like pulse regime, both with average output powers of two operation states reaching the Watt level. Simultaneously, high‐quality output beam profiles are observed in both operation states. To the best of knowledge, this is the first demonstration of high‐power spatiotemporal mode‐locking with high beam quality. The study holds great benefits for advancing the investigations of compact all‐fiber STML lasers which deliver high‐power outputs with superior beam quality and ultimately propels the application of STML lasers. Furthermore, this study contributes to the understanding of the behavior of STML lasers with high power.

Thermodynamic study of a novel combined heat and power system integrated with solar energy

Combined heat and power systems crucially require high efficiency and flexibility because of the high penetration level of intermittent renewable power. The efficiency and flexibility of traditional combined heat and power systems are limited by their heating-controlled operation mode. Therefore, a heat-power decoupling technique with high energy utilization efficiency and flexibility is necessary. In this study, a novel combined heat and power system integrated with solar energy is proposed. Detailed analytical models based on thermodynamics laws are developed, and a 330 MW unit is used as an example to assess the comprehensive thermodynamic performance and operational flexibility of the proposed system. Results show that the average net energy efficiency of the novel system during daytime and nighttime can reach 54.68% and 55.75%, respectively. Meanwhile, the average net exergy efficiency of the novel system during daytime and nighttime can reach 38.73% and 38.83%, i.e., an improvement of 2.43 and 2.59 percentage points, respectively, compared with the traditional combined heat and power system. The peak-shaving ability of 97.80 MW can be improved, and 295.35 tons of standard coal per day can be saved using the novel system compared with the traditional combined heat and power system under the average rated heating load. This study provides a promising approach for utilizing solar energy to enhance the efficiency and flexibility of combined heat and power plants.

Non-iterative multi-area coordinated energy and reserve allocation model for hybrid AC/DC power systems with flexible frequency operation

As the result of renewable energy natural intermittency, load shedding and renewables curtailment are inevitable to keep supply and demand balance in high penetration level power systems. Luckily, with accurate estimation and proper allocation of the reserve, power fluctuation can be smoothed appreciably. Therefore, this study presents a novel coordinated day-ahead economic dispatch model for both energy and reserve in bulk hybrid AC/DC power systems. Flexible frequency operation for each regional sub AC system is applied to estimate reserve demand, while renewable energy forecast error is described by the versatile probability distribution. Considering practical operation structure in China, a non-iterative bi-layer dispatch algorithm is proposed to share power and reserve between interconnected subsystems by applying DC tie-lines’ flexibility. This bi-layer structure is achieved through the upper layer deciding the boundary variables with aggregated generation information provided by the lower layer. Then each lower layer regional AC grid solves its own programming with the boundary variables. Simulation is carried out to verify the efficacy of the proposed dispatch model and distributed solution methodology.

A Wideband, 1-bit, Electronically Reconfigurable Phase Shifter for High-Power Microwave Phased-Array Applications

We present the design and high-power experimental characterization of a wideband, high-power-capable, electronically reconfigurable phase shifter for high-power phased-array applications. The device studied in this work offers an electronically switchable, 1-bit phase shift using the concept of polarization rotation (PR). The PR-based phase shifter is designed to work in a custom-designed, double-ridge (DR) waveguide environment. Two p-i-n diodes are used to control the transmission phase of the signal by rotating the polarization of the incident wave by either <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$+90^\circ$</tex-math> </inline-formula> or <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-90^\circ$</tex-math> </inline-formula> with respect to that of the incident wave, thereby creating a wideband, 1-bit phase shift between the two states. Simulation results demonstrated that this element can work over one octave bandwidth ranging from 6 to 12 GHz. A prototype of the device was fabricated and experimentally characterized at low and high power levels. The measurement results confirmed the simulations and demonstrated the wideband, high-power-density capability of the device. High-power continuous-wave (CW) experiments were conducted across the entire 6–12 GHz band and demonstrated that the unit-cell-averaged, CW power handling capability of the device exceeds 23.6 W/cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^2$</tex-math> </inline-formula> . High-power pulsed power experiments conducted at 9.382 GHz demonstrated that the unit-cell-averaged, peak power handling capability of the device exceeds 347 W/cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^2$</tex-math> </inline-formula> for short-duration pulses.

Development and testing midpoint voltage balance algorithms of three-level inverters

Nowadays, the use of inverters is increasing in more and more applications. Environmental awareness is becoming a trend, so more and more people install solar energy systems on their houses, which also require the use of inverters. Higher power levels have led to the emergence of three-level inverters which has opened up new challenges, such as the issue of midpoint voltage balancing. This paper discusses voltage balancing and voltage ripple reduction techniques for three-level inverters with Neutral-Point Clamped (NPC) topology. The balancing is based on injecting zero-sequence voltage component in carrierbased modulation. The viability of the modulation techniques are verified by computer simulation and then tested on hardware.

Investigation of near-field optical tweezers based on the edge effect of extraordinary optical transmission in thin microcavity

Optical tweezers are powerful tools capable to trap and manipulate particles directly. However, using conventional optical tweezers for nanosized objects remains a formidable challenge due to the optical diffraction limits and high-power levels required for nanoscale trapping, which usually causes irreversible damage to the captured particles. In this paper, we investigate the near-field edge effect of thin microcavity due to macroscopic quantum effect, and the highly enhanced electric field can reach 2.4 times. Thus, a dual near-field optical trap potential well is generated at the edge of the thin microcavity. We theoretically show that this near-field potential well can stably capture nanoparticles smaller than 10 nm while keeping the incident optical power level below 100 mW. Besides, the relationship between size of the microcavity and optical gradient force has also been carefully studied. Finally, the theoretical model of near-field optical tweezers with double thin microcavity is established, and the electric field magnitude of the double microcavity model is enhanced by 4.5 times compared with single microcavity model, in which the coupling effect of double hole makes smaller particles be stably trapped. Our research presents a huge potential for optical trapping and separation of nanoparticles and biomolecules.

Adaptive frequency deviation improvement using a voltage-controlled storage inverter in a weak distribution network with a high penetration level of stochastic photovoltaic power

With the rapid increase in the use of renewable energy sources, the strength of the power grid is reduced, which may lead to many weak distribution networks. The inertia of the weak distribution network decreases significantly, which leads to poor voltage quality. It means that the voltage and frequency are distorted and deviated. Battery storage can balance the frequent power disturbance and improve the frequency quality. However, it usually requires a central controller to dispatch the power in the current-controlled mode or respond natively with a fixed linear curve in voltage-controlled mode. The performance is poor when the power demand is in a wide range, which further deteriorates the frequency quality. To solve this problem, this paper proposes an adaptive frequency deviation improvement method for energy storage in the voltage-controlled mode. This method can change the power output characteristics of the storage inverter according to the magnitude and trend of power demand, where both frequency deviation and changing rate are used to shape the output power curve. A transfer function model for a voltage-controlled storage inverter is set up for theoretical analysis. Then, with the model, an adaptive frequency deviation improvement method is proposed with a fast response to power demand in a wide range. Finally, the results verify the effectiveness of the proposed method for frequency quality improvement with a high penetration level of stochastic photovoltaic power.

Identity, Power, and Social Work Practice in India

A person's identity puts them in different social categories, positions, and statuses. An individual's social position has corresponding power or powerlessness, which influences their interaction with others in the community. The individual identities, social positions, and authority of social workers place them in a higher level of power in relation to the people they serve. This imbalance of power between social workers and clients affects the helping process. This article discusses how personal identity and power influence social work practice in the Indian context. Social structures like caste-based discrimination and patriarchal norms contribute to inequitable social positioning in the country. Following a critical social work approach, the paper presents the different dimensions of power in the social work relationship and proposes means for sharing power with the clients.

Impact on Distribution Transformer Life Using Electric Vehicles with Long-Range Battery Capacity

This paper presents a comparative analysis of the effects of short-range and long-range electric vehicles charging on transformer life. Long-range vehicles are expected to become more common in the future. They have higher battery capacity and charge at higher power levels, modifying demand profile. A probabilistic analysis is performed using the Monte Carlo Simulation, evaluating the transformer hottest-spot temperature and the aging acceleration factor. Residential demand is modeled based on real electricity measurements, and EVs’ demand is modeled based on real data collected from a trial project developed in the United Kingdom. Simulations are conducted considering the influence of ambient temperature analyzing summer and winter seasons and several EV penetration levels. Results show the impacts caused by long-range vehicles are more severe because they charge at higher power levels, especially during winter, when residential demand is higher. For penetration level of 50% during summer, the use of long-range EVs brings a minimum equivalent aging factor of 5.2, which means the transformer aged 124.8 h in a cycle of only 24 h, decreasing its lifetime.

Distinguishing between a power law and a Pareto distribution.

This paper introduces the location Pareto distribution as a natural extension of the power law distribution and gives a likelihood ratio test for choosing between the two models. Some properties of the distribution and test are thoroughly investigated, and applications to real data are provided. For large values of the observations the two models perform similarly; this explains why some classical approaches are very insensitive to the differentiation between them. The likelihood ratio test between the two models is simple to use and has a high level of discrimination power. It is recommended when the complementary cumulative distribution function exhibits linearity on a log-log scale.

Study of trip card data analysis system under big data

Abstract Digital technologies such as the Internet, big data, cloud computing, mobile communication, and artificial intelligence have played an important role in the prevention and control of this new crown epidemic. Driven by big data technology, collaborative governance in the digital era has injected new dynamics for collaborative governance in the general sense, especially in this new crown epidemic prevention and control shows a different governance logic from the past, and the refinement and extraction of this governance logic is the key to enhance the ability of new crown epidemic prevention and control. Compared with the previous model in which a single governmental governance body played a role. In this paper, the necessity of building a big data analysis system is clarified by analyzing the limitations of the data analysis means of the existing trip code system. The overall epidemic prevention advantage of adopting the big data trip code policy has increased by 51.95% for regions with high crisis risk level and strong economic power, such as Guangdong, Zhejiang and Shanghai, which need to face the risk spread from domestic and imported risks under the big data trip code control, the increase of new cases compared to the previous comparison has decreased by 68.5%, which can visually see the big data trip code epidemic prevention We can visually see the effectiveness of big data trip codes in preventing the epidemic and making excellent contributions to the global fight against the epidemic.

Impact of Leadership Styles on Employees’ Performance: An Empirical Investigation of Middle-Level Employees

Leadership styles play a significant role in shaping the behaviour, motivation, and productivity of employees, particularly at the middle management level. Transformational leaders inspire and motivate employees, encouraging them to exceed expectations and achieve higher levels of performance. Transactional leaders focus on setting clear goals, providing rewards and punishments based on performance, and maintaining the status quo. Laissez-faire leaders adopt a hands-off approach, giving employees a high level of autonomy and decision-making power. The choice of leadership style can significantly impact middle-level employees' performance indicators, including productivity, job satisfaction, and motivation. This study presents essential inputs for organizations to effectively manage and optimize the potential of their middle-level employees, ultimately contributing to overall organizational success.