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Closed-Loop Polarization Mode Dispersion Mitigation for Fibre-Optic Time and Frequency Transfer
Get PDFA polarization-switching pulse interleaver is shown to be effective in reducing timing noise due to polarization mode dispersion in time and frequency transfer based on mode-locked lasers and standard single-mode (SM) fibers. In closed-loop time transfer over a 30-km dispersion-compensated fiber link with 300 fs of differential group delay, polarization interleaving reduced the delay variations to <20 fs. The results indicate that the remaining drift is caused by polarization-dependent loss and by AM-to-PM noise conversion in the photodiodes, suggesting the need for a “double-balanced” phase detector in the receiver, i.e., a phase detector balanced in power and polarization. By mitigating the polarization dependence, this work demonstrates a simple approach that can potentially yield sub-femtosecond-level, long-term time transfer in long-haul fiber links utilizing standard single-mode fibers
An Intelligent Frequency Control Scheme for Inverting Station in High Voltage Direct Current Transmission System
No full textPower system stability is crucial for the reliable and efficient operation of electrical grids. One of the key factors affecting power system stability is the frequency of the alternating current (AC) system while connected with High Voltage Direct Current (HVDC) transmission system. Changes in load demand can lead to frequency deviations, which can have detrimental effects on the stability and performance of the power system. Frequency should therefore be controlled within predefined limits in order to prevent unexpected disturbances that may cause problems to connected loads or even cause the entire system to fail. A broad simulation model of the HVDC transmission system is developed using MATLAB software to evaluate the effectiveness of the proposed controllers such as Adaptive Neuro-Fuzzy Inference System (ANFIS), Artificial Neural Network (ANN), and optimization of Proportional-Integral-Derivative (PID) controller using Particle Swarm Optimization (PSO) based control strategy for addressing the frequency instability problems. To assess how well the ANFIS, ANN, and PID-PSO controller controls frequency in HVDC transmission system, several situations were simulated, including load disturbances and changes in operational circumstances. The result reveals that the ANN controller performs more accurate results in HVDC transmission system than the other proposed control and, displaying its capacity to successfully reduce frequency deviations and maintained a controlled frequency 50 Hz. Adopted method suggested the easy integration of HVDC with AC grid and enhances the system power quality and stability.</p
Correction: H2-driven xylitol production in Cupriavidus necator H16:(Microbial cell factories (2024) 23 1 DOI: 10.1186/s12934-024-02615-7)
No full textIn the methods section, the phrase “flushing with 100% H2 at 0.5 mL/min for 2 min.” should read “flushing with 100% H2 at 0.5 L/min for 2 min.”</p
ITER NBI operational window and power availability constraints due to shine-through losses
No full textThis paper explores the operational boundaries and power availability of the neutral beam injection (NBI) system in ITER, with a specific focus on shine-through (ST) loss prevention. ST, a phenomenon where part of the injected neutral beam remains un-ionized in the plasma and directly impacts the first wall components, poses a significant risk to the lifetime of ITER’s plasma-facing components (PFCs). The operational window for NBI is consequently constrained by these losses, which are influenced by factors such as plasma density, beam energy, and injection geometry. Leveraging advanced numerical simulations, we investigate these dependencies across various ITER plasma scenarios, particularly for the DT-1 phase, which will mark the first NBI operations. In light of recent ITER blanket design changes, our analysis refines previous estimates of the maximum acceptable ST power on PFCs. We then present a new heuristic formula which permits the calculation of the ST fraction and the minimum plasma density that permits ITER NBI operations as a function of global variables. This allows for establishing operational limits for Hydrogen and Deuterium NBI in Hydrogen, Deuterium, and Deuterium-Tritium plasmas. Additionally, we compare commonly used beam ionisation codes for ITER and tokamak simulations, evaluating their reliability in the investigated parameter space. The findings of this study are crucial for ensuring the efficient operation of the NBI system during ITER’s experimental phases. They define the conditions under which beam power can be fully utilised without compromising operational lifetime, thereby informing future plasma operation plans and contributing to the success of ITER’s scientific objectives.</p
Linking environmental impact assessment and Positive Energy Districts:A literature review
No full textThis research delves into the environmental impact assessment of Positive Energy Districts (PEDs), focusing on comparative analyses of methodologies, key performance indicators, and an array of both theoretical and practical case studies. The literature review uncovers the strengths and weaknesses inherent current evaluation practices. The study reveals critical gaps in current assessment frameworks, particularly regarding the application to PEDs. It highlights the necessity for a holistic approach to PED evaluation, incorporating diverse energy sources and consumption patterns to fully understand their impact. The research advocates for the integration of multiple environmental factors in terms of innovative design and technology in PEDs, tailored to enhance both functionality and sustainability. It calls for the development of standardized guidelines and the learning from successful implementations to ensure the resilience and effectiveness of PEDs over time. Thus, this review paper aims to contribute to the body of knowledge on PEDs, offering insights and recommendations for future developments in this critical area of sustainable urban and energy planning
Comparing machine learning methods on Raman spectra from eight different spectrometers
No full textIn biotechnology, Raman Spectroscopy is becoming increasingly popular as a process analytical technology (PAT) for measuring substrates, metabolites, and product-related concentrations. By recording the vibrational modes of molecular bonds, it provides information non-invasively in a high-dimensional spectrum. Machine learning models are used to transform these spectral data into meaningful concentrations of species. Typically, one assumes a linear relationship between intensity and concentrations and learns these relationships using a partial least squares (PLS) model. However, in biological cultivations with a very large number of components, nonlinear models such as convolutional neural networks (CNN) offer significant advantages. In this work, we show that training one CNN on spectra from eight different spectrometers significantly outperforms PLS models. Specifically, we created samples with known concentrations of glucose, sodium acetate and magnesium sulfate and measured more than 2200 spectra of these samples with eight different spectrometers. We trained one CNN on the spectra from all eight datasets simultaneously. This shows great potential for laboratories with data from more than one spectrometer as they do not need to spend extra effort in calibrating individual PLS models, but they can use a joint CNN, which even improves the overall accuracy. In addition, we compare the eight different spectrometers against each other. The results suggest that three spectrometers are better suited for quantifying glucose, sodium acetate, and magnesium sulfate given the models.</p
Comprehensive lignin balance and new insights into softwood lignosulphonates from neutral sulphite pulping
No full textAccurate material balance of lignosulphonates in sulphite pulping and biorefinery processes is essential for their efficient recovery and utilization. By measuring the absorbances of dissolved lignosulphonates from pulp and spent liquor as lignin phenylpropane units at 280 nm by UV spectroscopy, the challenges caused by varying sulphonic acid group content in the dissolved fractions can be mitigated, ensuring a more accurate balance. This method was validated by compiling comprehensive lignin balances for six softwood neutral sulphite pulps, with yield levels ranging from 84.0 % to 57.7 %. The total lignin balances included lignosulphonates from the spent liquors and those isolated from the pulps by alkaline extraction and enzymatic hydrolysis, representing the distribution of wood lignin across the isolated fractions based on the degree of delignification and lignin alteration. Analyses of dissolved fractions, accounting for 74–95 % of the wood lignin, provided insight into softwood lignin sulphonation and fragmentation during neutral sulphite pulping. The spent liquor lignosulphonates had sulphonic acid group contents of 1.02–1.29 mmol/g and the average molecular weights between 5 200 and 13 400 g/mol, consistent with values reported in literature for hardwood lignosulphonates from NSSC pulping. Lignosulphonates isolated by alkaline extraction exhibited characteristics similar to those of spent liquor lignosulphonates, whereas those isolated by enzymatic hydrolysis were less sulphonated, had a higher average molecular weight, and appeared to be closer to the native type of lignin.</p
Near-ground-state cooling in electromechanics using measurement-based feedback and a Josephson traveling-wave parametric amplifier
No full textFeedback-based control of nano- and micromechanical resonators can enable the study of macroscopic quantum phenomena and also sensitive force measurements. Here, we demonstrate the feedback cooling of a low-loss and high-stress macroscopic SiN membrane resonator close to its quantum ground state. We use the microwave optomechanical platform, where the resonator is coupled to a microwave cavity. The experiment utilizes a Josephson traveling-wave parametric amplifier, which is nearly quantum-limited in added noise, and is important for mitigating resonator heating due to system noise in the feedback loop. We reach a thermal phonon number as low as 1.6, which is limited primarily by microwave-induced heating. We also discuss the sideband asymmetry observed when a weak microwave tone for independent readout is applied in addition to other tones used for the cooling. In a typical situation, the asymmetry can be attributed to the quantum-mechanical imbalance between emission and absorption. In specific situations, however, we find that the asymmetry is an artifact due to coupling of different sideband processes by cavity nonlinearity under multitone irradiation.</p
Leveraging Federated Satellite Systems for Unmanned Medical Evacuation on the Battlefield
No full textThis paper evaluates the role of federated satellite systems (FSSs) in enhancing unmanned vehicle-supported military medical evacuation (MEDEVAC) missions. An FSS integrates multiple satellite systems, thus improving imaging and communication capabilities compared with standalone satellite systems. A simulation model is developed for a MEDEVAC mission where the FSS control of an unmanned aerial vehicle is distributed across different countries. The model is utilized in a simulation experiment in which the capabilities of the federated and standalone systems in MEDEVAC are compared. The performance of these systems is evaluated by using the most meaningful metrics, i.e., mission duration and data latency, for evacuation to enable life-saving procedures. The simulation results indicate that the FSS, using low-Earth-orbit constellations, outperforms standalone satellite systems. The use of the FSS leads to faster response times for urgent evacuations and low latency for the real-time control of unmanned vehicles, enabling advanced remote medical procedures. These findings suggest that investing in hybrid satellite architectures and fostering international collaboration promote scalability, interoperability, and frequent-imaging opportunities. Such features of satellite systems are vital to enhancing unmanned vehicle-supported MEDEVAC missions in combat zones.</p
Measurement Uncertainty Evaluation for Sensor Network Metrology
No full textSensor networks, which are increasingly being used in a broad range of applications, constitute a measurement paradigm involving ensembles of sensors measuring possibly different quantities at a discrete sample of spatial locations and temporal points outside the laboratory. If sensor networks are to be considered as true metrology systems and the measurement results derived from them used for decision-making, such as in a regulatory context, it is important that the results are accompanied by reliable statements of measurement uncertainty. This paper gives a preview of some of the work undertaken within the European-funded ‘Fundamental principles of sensor network metrology (FunSNM)’ project to address the challenges of measurement uncertainty evaluation in some real-world sensor network applications. The applications demonstrate that sensor networks possess features related to the nature of the measured quantities, to the nature of the measurement model, and to the nature of the measured data. These features make conventional methods of measurement uncertainty evaluation, and established guidelines for measurement uncertainty evaluation difficult to apply. An overview of some of the modelling tools used to address the challenges of measurement uncertainty evaluation in those applications is given.</p