High Power Levels Research Articles

Low-noise 2-GHz figure-9 fiber laser based on passive harmonic mode-locking

We have proposed and demonstrated the generation of a high-repetition-rate ultrashort pulse with long-term stability and low noise based on a harmonic mode-locked (HML) figure-9 fiber laser. Different HML orders from the 2nd to the 13th are generated by adjusting the pump power, net dispersion, and wave plate angles. A 2-GHz HML pulse is obtained with a 155-MHz fundamental repetition rate in a Yb-doped fiber laser, and the corresponding supermode suppression level is as high as 50 dB. The average power of the output pulse is nearly 200 mW, and the compressed pulse duration is 535 fs. To the best of our knowledge, 2 GHz and 196 mW represent, respectively, the highest repetition rate and output power in a figure-9 fiber laser. This work offers a potential pathway to achieve high-repetition-rate ultrashort pulses in the GHz range with high power and low noise levels.

Green Technology Innovations and Corporate Customer Concentration—The Perspectives of Financing Constraints and Social Responsibility

Green technology innovations propel both economic development and environmental sustainability. Exploring the contributing factors to green technology innovations carries important policy implications, but research from the perspective of supply chain relationships has been rare. This paper examines the impact of corporate customer concentration on green technology innovations and explores its influencing mechanisms using the data of Chinese A-share listed companies. The results show that a high customer concentration inhibits the quantity and quality of green technology innovations, a finding that is robust when endogeneity is addressed and when alternative measures and an alternative estimation model are employed. Financing constraints and social responsibility play intermediary roles in the impact of customer concentration on green technology innovations. A high customer concentration tends to increase corporate financing constraints and reduce corporate social responsibility performance, which hinder green technology innovations. The heterogeneity analysis reveals that the inhibitory effect of customer concentration on green technology innovations is less severe in digitally transformed enterprises, mature enterprises, or enterprises with a high level of market power. As this study provides a novel perspective on the contributing factors to corporate green innovations, it offers important policy recommendations.

Feedforward Control Strategy of a DC-DC Converter for an Off-Grid Hydrogen Production System Based on a Linear Extended State Observer and Super-Twisting Sliding Mode Control

With the large-scale integration of renewable energy into off-grid DC systems, the stability issues caused by their fluctuations have become increasingly prominent. The dual active bridge (DAB) converter, as a DC-DC converter suitable for high power and high voltage level off-grid DC systems, plays a crucial role in maintaining and regulating grid stability through its control methods. However, the existing control methods for DAB are inadequate: linear control fails to meet dynamic response requirements, while nonlinear control relies on detailed model structures and parameters, making the control design complex and less accurate. To address this issue, this paper proposes a feedforward control strategy for a DC-DC converter in an off-grid hydrogen production system based on a linear extended state observer (LESO) and super-twisting sliding mode control (STSMC). Firstly, a reduced-order simplified model of the DAB was constructed through the structure of DAB. Then, based on the reduced-order simplified model, a feedforward control based on LESO and STSMC was designed, and its stability was analyzed. Finally, a simulation comparison of PI, LESO + terminal sliding mode control (TSMC), and LESO + STSMC control methods was conducted in a DC off-grid hydrogen production system. The results verified the proposed control method’s enhancement of the DAB’s rapid dynamic response capability and the system’s transient stability.

Secrecy Rate Bounds in Spatial Modulation-Based Visible Light Communications under Signal-Dependent Noise Conditions

This study examines the physical-layer security of an indoor visible light communication (VLC) system using spatial modulation (SM), which consists of several transmitters, an authorized receiver, and a passive adversary. The SM technique is applied at the transmitters so that only one transmitter is operational at any given time. A uniform selection (US) strategy is employed to choose the active transmitter. The two scenarios under examination encompass the conditions of non-negativity and average optical intensity, as well as the conditions of non-negativity, average optical intensity, and peak optical intensity. The secrecy rate is then obtained for these two scenarios while accounting for both signal-independent noise and signal-dependent noise. Additionally, the high signal-to-noise ratio (SNR) asymptotic behavior of the derived secrecy rate constraints is investigated. A channel-adaptive selection (CAS) strategy and a greedy selection (GS) scheme are utilized to select the active transmitter, aiming to enhance the secrecy performance. The current numerical findings affirm a pronounced convergence between the lower and upper bounds characterizing the secrecy rate. Notably, marginal asymptotic differentials in performance emerge at elevated SNRs. Furthermore, the GS system outperforms the CAS scheme and the US method, in that order. Additionally, the impact of friendly optical jamming on the secrecy rate is investigated. The results show that optical jamming significantly enhances the secrecy rate, particularly at higher power levels.

Design study of gas-cooled fast reactor with natural uranium as fuel employing modified CANDLE shuffling strategy in the axial direction

Abstract This study investigated gas-cooled fast reactor performance utilizing natural uranium as the fuel employs modified constant axial shape of neutron flux, nuclide densities, and power shape during life of energy production (CANDLE) shuffling strategy in the axial direction. The performance has been carried out on a reactor with various power levels in the range of 2,700–3,100 MWt and refueling every 10 years of burnup. The main importance of the modified CANDLE (MCANDLE) is that it can utilize natural uranium as fuel without needs reprocessing or enrichment plant. During this work, the core has been partitioned into 10 regions of similar volume along the axial direction. The fuel was filled into the first region, then transported to the second region after 10 years of burnup, and then to the third region 10 years later. This technique was practiced to all 10 regions, and the fuel in the tenth region was discharged in the reactor core. 10 % of natural thorium, natural uranium and enriched nitride (15 N) were used as fuel input. The calculations were performed employing a standard reactor analysis code (SRAC). The collision probability method (PIJ) module of SRAC was used to calculate cell burnup, and the reactor core design calculations were done with the CITATION module of SRAC, which used JENDL-4.0 as a nuclear data library. The result shows that a high power level causes an increasing rate of burnup level and effective multiplication factor. The highest average discharge burnup level is about 31.3 % HM for case E and the lowest average discharge burnup is about 27.2 % HM for case A.

Multi-Way adaptive Time Aware LSTM for irregularly collected sequential ICU data

In personalized predictive medicine, accurately modeling a patient’s illness and care processes is essential, given their inherent long-term temporal dependencies. However, electronic medical records contain episodic and irregularly timed data due to patients visiting hospitals based on treatment needs, resulting in unique patterns for each hospital stay. Consequently, when constructing a personalized predictive model, it is crucial to consider these factors in order to accurately capture the patient’s health journey.To address this challenge, we present a novel deep dynamic memory neural network called Multi-Way adaptive Time Aware LSTM (MWTA-LSTM). The primary objective of MWTA-LSTM is to leverage medical records, memorize illness trajectories and care processes, estimate current illness states, and predict future risks, thereby providing a high level of precision and predictive power. To enhance its capabilities, MWTA-LSTM extends the conventional Long Short-Term Memory (LSTM) model in two key ways. Firstly, it incorporates frequency measurement and the most recent observation(last observation) to enhance personalized predictive modeling of patient illnesses, enabling a more accurate understanding of the patient’s condition. Secondly, it parameterizes the cell state to handle irregular timing effectively, utilizing both frequency measurement and elapsed times. Furthermore, the model capitalizes on both to comprehend the impact of interventions on the course of illness on the cell state, facilitating the memorization of illness courses and improving its ability to capture the temporal dynamics of healthcare data, accommodating variations and irregularities in event and observation timing. Lastly, we introduce a novel adaptive pooling strategy that specifically targets and resolves outlier issues that can potentially occur during the analysis of EHR data. By incorporating these features, MWTA-LSTM significantly improves its ability to capture the temporal dynamics of healthcare data, accommodating variations and irregularities in event and observation timing.We validate the effectiveness of our proposed model through empirical experiments conducted on two real-world clinical datasets and three real-world time series datasets. Our results demonstrate the superiority of MWTA-LSTM over current state-of-the-art models and other robust baselines. This showcases the potential of MWTA-LSTM in advancing personalized predictive medicine by offering a more accurate and comprehensive approach to modeling patient health trajectories.

Global San Francisco and the Irish of the New Pacific

Abstract Following the discovery of gold in the Sierra Nevada Mountains in January 1848, San Francisco established itself as the premier city of the western Americas. From the outset, its substantial Irish immigrant population enjoyed the standing of a charter group and exhibited high levels of political power and cultural influence, characteristics that were frequently noted by contemporaries and continued well into the twentieth century. While San Francisco's Irish population shared much in common with their compatriots in other American cities, the Golden City developed its own unique identity and quickly emerged as a truly global Irish city. Key features that account for its experience include the city's distinctive nineteenth-century population composition, which included a large Chinese component; the notable confidence of its Irish-born population compared with that in other American urban centers; and the unique westward orientation of the city and its people that contributed to San Francisco's pivotal role in emerging transnational Pacific networks.

Climate risk maps as boundary objects for future forests

Climate change poses significant threats to ecosystems and biodiversity. Conventional management strategies often fall short, leading to uncertainties in addressing these challenges. Natural and environmental scientists play a crucial role by providing evidence-based guidance. Social science research, at the same time, highlights the complexity of transferring and applying knowledge across different social and professional groups and shows that further research is needed. Using a German case study, my research addresses this issue by examining the dynamics between predictive climate risk maps, intended as decision-support tool for forest management, the developing scientists, the receiving environmental managers and further political actors. Semi-structured qualitative interviews with representatives from these groups were conducted and analyzed, revealing that climate risk maps can function as predictive boundary objects, balancing flexibility and robustness. With their high level of visual and epistemic power, these maps generate knowledge tensions, facilitate interactions, and foster the implicit co-production of broader environmental management discourse. At the same time the maps are continuously contested, discussed, and updated through feedback, becoming themselves part of an ongoing informal co-productive process. This dual role creates ambiguity: they provide concrete answers to specific management related questions while highlighting simultaneously limitations that prompt more fundamental inquiries, driving an overall societal learning process. Hence, future efforts should enhance formal support for co-productive processes to ensure evidence-based advisory tools are scientifically robust, contextually adapted, and democratize knowledge dynamics through continuous dialogue, mutual learning, and integration of scientific as well as local knowledge.

Optimizing the Speed and Explosive Power Performance of Football Players: The Effect of a Six-Week Neuromuscular Training

Background. Football players require high levels of speed and explosive power to perform effectively on the field, making these physical attributes critical for success. Neuromuscular training has been proposed as a method to enhance these performance metrics. Objectives. The purpose of the present study was to examine the effect of neuromuscular training on the speed and explosive power performance of football players. Materials and methods. A total of thirty male football players (aged 20 to 26 years) from Imphal West District, Imphal, Manipur, India, who had participated in national-level competitions, were selected for the study. The subjects were randomly assigned into two equal groups: an experimental group (n = 15) and a control group (n = 15). Both groups were assessed before the intervention for speed and explosive power performance using the 50 m dash speed test and the standing broad jump test to determine the baseline significance of the selected variables. Following the initial assessments, the experimental group underwent a supervised neuromuscular training program, while the control groupreceived no special training. The neuromuscular training was conducted over a period of six weeks, with sessions held five days a week (Monday to Friday), each lasting 60 minutes. Results. The experimental group confirmed significant improvements in both speed and explosive power compared to the control group (p < 0.05). The mean and standard deviation of speed for the experimental group were 7.15 ± 0.71 in the pre-test and 6.54 ± 0.61 in the post-test. For explosive power, the values were 2.36 ± 0.32 in the pre-test and 2.55 ± 0.39 in the post-test. The notable enhancements in speed and explosive power performance in the experimental group are likely attributed to the six-week neuromuscular training program, which facilitated rapid physical adaptation among the football players. Conclusions. Implementing the six-week neuromuscular training program effectively enhanced the speed and explosive power performance of football players. This type of training has been demonstrated to be highly effective for optimizing these performance metrics in football players.

Elucidating the origin of laser induced nonlinearities in propagation inside transparent medias: A comparative numerical study of silicon and fused silica

Abstract The creation of localized bulk modification using femtosecond pulses inside semiconductors like silicon (Si) is quite challenging whereas it is not difficult to achieve it for dielectric material like fused silica (FS). So, this report addresses the fundamental origin of this issue. By taking simple numerical approach, it has been found that in FS we can deliver stronger fluence due to self-focusing on higher power level as compared to Si. The origin for the above lies on the spatial-temporal pulse-splitting behavior which is dominant in case of FS at the focus, whereas for Si it is only effective after focus. We have also considered the influence of plasma and Kerr terms to elucidate the reason behind such nonlinearities. For FS case, omission of Kerr term dominates whereas for Si the influence of each term does not significantly create self-focusing like FS under a similar focusing condition. This study could make an important guideline for researchers to understand the complexity of laser-matter interaction in transparent materials specifically being studied by many laser processing industries.

Experimental study of a high-power generation platform for ocean thermal energy conversion

Ocean Thermal Energy Conversion (OTEC) is a form of power generation that utilizes the temperature difference between the upper and lower layers of the ocean. This paper presents the design and construction of a land-based experimental platform for OTEC using R134a as the working fluid. Through experimental research, we investigated the performance of the thermal energy cycle system under varying external environmental conditions, such as temperature and flow rate. The results show that the net output power of the system increases with the temperature and flow rate of the warm seawater. Similarly, an increase in the cold seawater temperature and flow rate leads to an increase in net output, though the increase is less significant at higher power levels when compared to changes in warm seawater conditions. Adjusting the evaporation pressure to increase the turbine inlet and outlet pressure difference initially increases the output power but then remains constant. The highest recorded output power during testing was 48kW, with the turbine achieving an isentropic efficiency of 80%, and the maximum system efficiency reached 2%. This study provides theoretical basis and empirical data for system design, which can promote the application in the field of OTEC and contribute to the development of renewable energy.

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.

Enhancing Mushroom Freezing Quality Using Microwave-Assisted Technology.

This study investigated the effects of microwave-assisted freezing on the quality attributes of button mushrooms (Agaricus bisporus). Four levels of microwave power (0, 10, 20, 30%) were applied to the mushroom samples during freezing. The quality attributes of the frozen and thawed mushrooms were then evaluated. The results suggested that higher microwave power produced the smaller and more uniform ice crystals. Moreover, the browning index of the mushroom samples increased with increasing microwave power. The textural properties (hardness) of the mushrooms were also affected by the microwave power, showing higher values as the power increased. Furthermore, the ratio of the microwave operating system's power to the freezer power was low and approximately 20% at the highest power level. Therefore, these findings confirm the potential of microwave-assisted freezing for reducing freeze damage to mushroom tissue and, thus, provide frozen mushroom with a better texture.

Operation Scheme analysis of a multipurpose small modular reactor under cogeneration condition based on a once-through steam generator dynamic model

Highly flexible load requirements and cogeneration economy need to challenge the operation of a multipurpose small modular reactor cogeneration plant with once-through steam generators. Therefore, the present study develops a once-through steam generator dynamic model to analyze the multipurpose small modular reactor operation scheme under cogeneration conditions at different power levels. The once-through steam generator dynamic model is derived based on conversation equations using the moving boundary method. It is verified with RELAP5 results and open literature and the maximum relative error is 3.21 %. Three operation schemes are proposed for multipurpose small modular reactor cogeneration operation: Scheme 1 with constant steam pressure and average coolant temperature, Scheme 2 with constant steam temperature and pressure, and Scheme 3 with constant steam temperature and pure sliding steam pressure. Steady-state and dynamic characteristics with three operation schemes are simulated and investigated at three power levels: 100 %, 70 % and 30 %. The steady-state results show that Scheme 1 is more favorable for the primary loop, while Scheme 2 is beneficial to the secondary loop, and Scheme 3 can improve the thermal efficiency at low power level. The transient findings indicate that disturbances from the reactor side have a significant impact on the once-through steam generator and the minimum settling time is 3.3 s. Consequently, steam temperature control of once-through steam generator is achieved by regulating the control rods for Schemes 2 and 3, while steam pressure is suggested to be controlled by the feedwater valve for Scheme 1. For cogeneration conditions at 70 % power level, Scheme 2 can achieve the highest steam flow of turbine, the highest steam flow of steam extraction and the smallest steam specific volume, which are 87.88 kg·s−1, 28.96 kg·s−1, and 0.0503 m3·kg−1, respectively. Scheme 2 is recommended for high power levels under cogeneration operation. In contrast, Scheme 1 is more suitable for the condensing unit operation for low power levels.

Techno-Economic Assessment of Coaxial HTS HVAC Transmission Cables with Critical Current Grading between Phases Using the OSCaR Tool

In recent years, the scientific and industrial interest regarding alternative technologies for transmission cables has increased. These conductors should efficiently transmit significant amounts of power between grid nodes, which are expected to be particularly congested due to the projected global increase in electricity production. Superconducting cables are considered a promising solution in this context, offering the potential to transmit large amounts of energy with minimal losses and compact dimensions, thereby potentially benefiting the environment. To evaluate the feasibility of integrating superconducting cables into existing grids, techno-economic approaches should be adopted. Such techniques enable the conceptual design of a specific cable structure, allowing users to explore a wide range of operating parameters to derive optimal designs. This paper reports a comprehensive techno-economic analysis of High Voltage Alternating Current (HVAC) cables realized with High-Temperature Superconducting (HTS) tapes, with the aim to transmit extremely high-power level. The optimal coaxial design is selected using Optimization Tool for Superconducting Cable Research (OSCaR) by implementing a graded approach to the critical current of the HTS tapes used for the different phases. This optimization aims to achieve the most effective balance between the cost of the coated conductors and their electrical properties. The whole set of model equations, the user-defined parameters, and the applied constraints are detailed. The OSCaR tool is then applied to assess the impact on the optimized design of the cable system and the corresponding cost indexes of several crucial parameters, such as the maximum transmitted power, the voltage level, and the line length.

Impact of dispersion-shifted fiber on optical communications link through orthogonal channels

Dispersion-Shifted Fiber (DSF) is essential for reducing chromatic dispersion in high-speed optical communication systems. This study investigates the influence of Four Wave Mixing (FWM) on the quality of signals in orthogonal channels. We examine the advantages of DSF technology and analyze the impact of modulation formats such as On-Off Keying with Return-to-Zero (OOK-RZ) and Duo Binary Modulation class-1 (DBM-1) on transmission performance at different distances. This research assesses the efficacy of orthogonal channels in mitigating four-wave mixing (FWM) effects and improving the overall performance of eight-channel systems at distances of 100 km and 200 km through computer simulations. The results of our study show notable enhancements, namely in optimizing the Q-factor (a metric for signal quality) and reducing bit error rates when employing orthogonal channels compared to previous work. By integrating orthogonal channels with OOK-RZ modulation, we achieved higher performance and reduced nonlinear impairments in a simulated eight-channel system with 50 GHz spacing and 80 Gb/s data rates. This effect was particularly pronounced at high input power levels. At an input power of 20 dBm and a distance of 200 km, this particular combination yielded a maximum Q-factor of 27.25 and a minimum FWM power of −54 dBm. In comparison, under the same conditions, the use of OOK-RZ alone resulted in an FWM power of −24 dBm and a Q-factor of only 1.63. This research provides vital insights into enhancing the efficiency and dependability of optical communication systems, hence facilitating breakthroughs in high-speed data transfer and network scalability.

Optimal Design of High-Power Density Medium-Voltage Direct Current Bipolar Power Cables for Lunar Power Transmission

Power systems on the lunar surface require power lines of varying lengths and capacities to connect generation, storage, and load facilities. These lines must be designed to perform efficiently in the harsh lunar environment, considering factors such as weight, volume, safety, cost-effectiveness, and reliability. Traditional power transmission methods face challenges in this environment due to temperature fluctuations, micrometeoroid impacts, and ionizing radiation. Underground deployment, although generally safer, faces challenges due to low soil thermal conductivity. At a depth of 30 cm, the lunar temperature of −23.15 °C can be advantageous for managing waste heat. This study presents a novel approach, developed using COMSOL Multiphysics, for designing bipolar MVDC cables for lunar subsurface power transmission. Kapton® MT+ is chosen as the insulating material for its exceptional properties, including high thermal conductivity and superior dielectric strength. The cables are designed for voltages of ±10 kV and ±5 kV and capacities of 200 kW (low power), 1 MW (medium power), and 2 MW (high power). Our findings indicate that aluminum conductors offer superior performance compared to copper at medium and high power levels. Additionally, elevated voltage levels (±10 kV) enhance cable design and power transfer efficiency. These specially designed cables are well-suited for efficient operation in the challenging lunar environment.

Enhancing heat pipe performance through hybrid wick structures: Balancing pore size and permeability

This study investigates the impact of wick structures on heat pipe performance by optimizing the balance between effective pore radius and permeability for efficient heat dissipation. It addresses the challenge of enhancing capillary pumping forces while maintaining optimal liquid replenishment to the evaporator. A novel hybrid wick structure is proposed, strategically integrating sintered and screened elements within the heat pipe to improve thermal performance. Experimental tests include varying inclination angles (antigravity up to 60°) to assess thermal resistance and liquid return capabilities. Results show a 13.31 % reduction in thermal resistance compared to conventional sintered heat pipes, particularly at higher power levels (40 W– 60 W). At a 40° inclination angle, optimal evaporation and liquid flow improve thermal performance, with thermal resistance for sintered and hybrid heat pipes decreasing by 14.05 % and 27.72 %, respectively. However, at 60° inclination, the hybrid’s thermal resistance increases significantly due to local dry-out. The study identifies limitations beyond 45° inclination, which is attributed to increased receding contact angles, and the influence of gravity becomes more pronounced, affecting capillary limits. This research underscores the importance of innovative wick designs in advancing heat pipe technology for diverse applications.

Biomass gasification tar removal using dielectric barrier discharge reactor: Effect of reactor geometry and carrier gases

This study investigates the impact of reactor geometry (varying external electrode length) of Dielectric Barrier Discharge (DBD) reactors on the decomposition of toluene, a model compound for biomass gasification tar, using different carrier gases and various power levels. Results reveal that toluene decomposition is higher at longer electrode lengths (30 mm) at all power levels tested. Specifically, the toluene decomposition in H2 carrier gas at 30 mm electrode length increased from 67.2 % to 97.5 % with rising power from 5 to 40 W, while it ranged from 52 % to 97.4 % at 15 mm electrode length. The decomposition of toluene was found to be higher in N2 carrier gas than in H2 carrier gas at both discharge lengths. At 30 mm external electrode and with rising power from 5 to 40 W, toluene decomposition ranged from 90.5 % to 98.7 %. Similarly, when the electrode length was reduced from 30 to 15 mm for N2 carrier gas, the decomposition of toluene ranged from 74 % to 97.9 %. Thus, the results indicate that the decomposition of toluene is affected by both the electrode length and the nature of the carrier gas. The effect of electrode length was significant at lower power levels, and the difference between the conversion at both electrode lengths nearly disappeared at higher power levels.

Efficient rectifier with wide input power range for 5G applications

This article presents three efficient rectifiers for radio frequency energy harvest-ing (RFEH) systems operating at the fifth generation (5G) band (3.5 GHz). Eachrectifier operates at various input power levels (high, low, and across a widepower range). The high and low-power rectifiers feature a single serial topologyusing HSMS-2860 and SMS-7630 Schottky diodes, respectively, along with mi-crostrip lines to implement the input and output filters and the impedance match-ing network. At an radio frequency (RF) power level of 15 dBm, the high-powerrectifier harvests 67.4% to direct current (DC) power with a 300Ωload resistorand an output voltage of 2.5V. The low-power rectifier achieves its maximumpower conversion efficiency (PCE) at -2 dBm, reaching 45% efficiency with a1200Ωload. The rectifier with a extended input power range comprises twobranches of subrectifiers functioning at both high and low power levels. De-pending on the power level, the considered subrectifier harvests radio frequencypower into DC power, while the other subrectifier is deactivated. Across a powerspan of 32.5 dB (ranging from -13 to 19.5 dBm), the rectifier maintains an effi-ciency above 30%. The proposed rectifiers are efficient and suitable for imple-mentation in 5G-enabled RFEH systems.