Energy Loss Fluctuations Research Articles

Optimal Allocation of Capacitor Banks and Distributed Generation: A Comparison of Recently Developed Metaheuristic Optimization Techniques on the Real Distribution Networks of ALG-AB-Hassi Sida, Algeria

Recent advancements in renewable energy technologies, alongside changes in utility infrastructure and progressive government policies, have bolstered the integration of renewable-based distributed generation units within distribution systems. This paper introduces the Energy Valley Optimizer, a novel tool designed for the strategic placement of distributed generation units and capacitor banks. This placement is crucial not only for optimizing energy loss and enhancing bus voltage stability but also for promoting sustainable energy use and reducing environmental impact over the long term. By minimizing energy loss and voltage fluctuations, the optimizer contributes to a more sustainable and resilient energy system. It achieves this through the optimal allocation of resources across various load patterns within a 24 h period and is tested on the ALG-AB-Hassi-Sida 157-bus distribution network in South Algeria. Comparative analysis with existing algorithms—such as the Liver Cancer Algorithm, Walrus Optimization Algorithm, and Zebra Optimization Algorithm—demonstrates the superior performance of the Energy Valley Optimizer. It not only enhances technical and economic efficiencies but also significantly lowers the total cost of energy over 24 years, thus supporting sustainable development goals in energy management.

Energy distribution and chaotic pressure pulsation analysis of vortex ropes in Francis-99

Francis turbines, essential for stability in diverse operating conditions and variable-speed scenarios, encounter efficiency-compromising vortex rope formations in the draft tube, leading to substantial pressure fluctuations. This research delves into the analysis of energy loss and pressure fluctuations associated with these vortex ropes. Employing the local entropy generation rate (LEGR) method and chaos theory, we scrutinize the behaviour of vortex ropes and their resultant pressure fluctuations. Notably, vortex ropes exhibit maximum LEGR near the runner cone, with secondary vortices escalating instability downstream. In the elbow section, the collision of vortex ropes with the outer elbow amplifies LEGR, primarily driven by fluctuating velocities (approximately 90%). Leveraging the GWO-VMD algorithm, non-stationary signals are decomposed, unveiling a significant 1.6 Hz vortex rope frequency under partial load (PL) conditions and isolating external noise frequencies, such as the prominent 300 Hz. Following decomposition, chaos theory tools, including phase space reconstruction and phase trajectory graphs, unveil the chaotic nature of PL conditions attributed to spiral vortex ropes, resulting in profound pressure fluctuations. This study enhances our understanding of such systems and provides methodologies for improved noise reduction and optimization of turbine performance.

Vortex-induced energy loss and pressure fluctuations in a closed sump under various conditions: An experimental investigation

The roof-attached vortices (RAVs), floor-attached vortices (FAVs), and complex combined submerged vortices (CSVs) excited in a closed pump sump will induce irregular pressure fluctuations that can decrease the energy efficiency of the pump and the stability of its input flow. This article presents an experimental investigation of the energy loss and pressure fluctuations induced by these vortices under various conditions. A transparent closed-loop test rig was used for high-speed visualization and pressure-fluctuation tests. The findings demonstrate that as the flow rate is increased, the head and efficiency of the pump device significantly decrease. A CSV, which is composed of an RAV and an FAV, has the highest head-loss value, reaching 0.21 m, with an efficiency decrease in up to 2.8%. The typical evolution stages of RAV are divided into newborn, developing, fully developed, and dissipative collapsing. The typical evolution stages of FAV are divided into germinating, growing, maintaining, decaying, and disappearance. The maximum diameter of the FAV core is approximately 0.05 times the maximum vortex-core scale of the RAV. Based on the proposed vortex-identification method, as the bellmouth height decreases, the strength of the FAV increases during the CSV period, and the degree of pressure fluctuation becomes more severe. In addition, regardless of the flow rate, the strength of the FAV structure is always much greater than that of the RAV.

Differentiating multi-MeV, multi-ion spectra with CR-39 solid-state nuclear track detectors

The development of high intensity petawatt lasers has created new possibilities for ion acceleration and nuclear fusion using solid targets. In such laser-matter interaction, multiple ion species are accelerated with broad spectra up to hundreds of MeV. To measure ion yields and for species identification, CR-39 solid-state nuclear track detectors are frequently used. However, these detectors are limited in their applicability for multi-ion spectra differentiation as standard image recognition algorithms can lead to a misinterpretation of data, there is no unique relation between track diameter and particle energy, and there are overlapping pit diameter relationships for multiple particle species. In this report, we address these issues by first developing an algorithm to overcome user bias during image processing. Second, we use calibration of the detector response for protons, carbon and helium ions (alpha particles) from 0.1 to above 10 MeV and measurements of statistical energy loss fluctuations in a forward-fitting procedure utilizing multiple, differently filtered CR-39, altogether enabling high-sensitivity, multi-species particle spectroscopy. To validate this capability, we show that inferred CR-39 spectra match Thomson parabola ion spectrometer data from the same experiment. Filtered CR-39 spectrometers were used to detect, within a background of ~ 2 × 1011 sr−1 J−1 protons and carbons, (1.3 ± 0.7) × 108 sr−1 J−1 alpha particles from laser-driven proton-boron fusion reactions.

Unsteady numerical investigations of the effect of guide vane openings on the hydrodynamic characteristics under stall conditions in a pump-turbine pump mode

The stall is extremely prone to surge of hydraulic loss, excessive pressure fluctuation and radial force of the pump-turbine in pump mode. These can pose a great threat to the safety operation of the unit. Current research focuses more on the manifestations and propagation mechanisms of the stall, which has limitations and effective methods for passive stall suppression cannot be directly identified. In this paper, unsteady simulations based on the SST-SAS turbulence model are conducted to discuss the effects of guide vane openings on the hydrodynamic characteristics under stall conditions of the pump-turbine from the perspectives of flow pattern, energy loss, pressure fluctuation and radial force. Firstly, the performance test results show that the positive slope of the flow-head curves is the largest at small guide vane openings and smallest at optimal guide vane openings. Then, energy loss analysis based on the energy balance equation indicates that the energy loss in the stay vane is most influenced by guide vane openings, with maximum turbulent kinetic energy production at large guide vane openings. Furthermore, the analysis of the stall characteristics in the impeller illustrates that at large guide vane openings, the axial meridional velocity in the impeller is negative under deep stall conditions, and the flow separation and vortex induce a great local pressure drop in the suction surface of impeller blades near the shroud. Subsequently, the stall characteristics analysis in the diffuser reveals that large-scale vortices in the vaneless regions and stay vane channels result in more severe flow blockage and higher energy loss at large guide vane openings. As the increased guide vane openings, the Rotor-stator interaction effect is weakened by the unstable flow pattern in the diffuser, and the low frequency and near blade frequency signals gradually become the dominant frequencies in the diffuser. Finally, the simulation results in the volute show that the unstable flow pattern in the diffuser provides poor inlet conditions for the volute, which significantly increases the energy loss and pressure fluctuations in the volute. The increase of guide vane openings can also make the flow inhomogeneity in the volute worse. The radial forces on the impeller and diffuser under deep stall conditions both increase with increasing guide vane openings due to the unstable flow patterns.

Experimental and statistical analysis of the flap gate energy loss and pressure fluctuation spatiotemporal characteristics of a mixed-flow pump device

Experimental and statistical analysis of the flap gate energy loss and pressure fluctuation spatiotemporal characteristics of a mixed-flow pump device

Energy loss and pressure fluctuation characteristics of coastal two-way channel pumping stations under the ultra-low head condition

The ultra-low head condition is a unique condition of the coastal two-way channel pumping stations, but the quantitative research on its hydraulic characteristics still needs to be improved. The entropy production method with computational fluid dynamics and the high-frequency pressure fluctuation test were employed to analyze the pumping device's internal energy loss and pressure fluctuation. The results show that the primary source of energy loss of the two-way channel pumping device under the ultra-low head condition is the turbulent dissipation caused by the velocity fluctuation of the impeller and guide vane, in which there are large irregular high entropy production areas on the pressure surface of the impeller and in the impeller channel. The high-frequency pressure fluctuation in the pumping device is mainly concentrated near the impeller, and the amplitude under the ultra-low head is 3.5 times the amplitude under the design head. Due to the dynamic and static interaction between the impeller and the guide vane, the frequency domain components of the pressure fluctuation at the outlet channel bell mouth are complex. Under the ultra-low head condition, the pressure fluctuation degree is intensified, the energy loss of each part is greater, and the low-frequency resonance should be prevented.

Space radiation quality factor for Galactic Cosmic Rays and typical space mission scenarios using a microdosimetric approach

Space radiation exposure from omnipresent Galactic Cosmic Rays (GCRs) in interplanetary space poses a serious carcinogenic risk to astronauts due to the—limited or absent—protective effect of the Earth’s magnetosphere and, in particular, the terrestrial atmosphere. The radiation risk is directly influenced by the quality of the radiation, i.e., its pattern of energy deposition at the micron/DNA scale. For stochastic biological effects, radiation quality is described by the quality factor, Q, which can be defined as a function of Linear Energy Transfer (LET) or the microdosimetric lineal energy (y). In the present work, the average Q of GCR for different mission scenarios was calculated using a modified version of the microdosimetric Theory of Dual Radiation Action (TDRA). NASA’s OLTARIS platform was utilized to generate the radiation environment behind different aluminum shielding (0–30 g/cm2) for a typical mission scenario in low-earth orbit (LEO) and in deep space. The microdosimetric lineal energy spectra of ions (Zge 1) in 1 μm liquid water spheres were calculated by a generalized analytical model which considers energy-loss fluctuations and δ-ray transport inside the irradiated medium. The present TDRA-based Q-values for the LEO and deep space missions were found to differ by up to 10% and 14% from the corresponding ICRP-based Q-values and up to 3% and 6% from NASA’s Q-model. In addition, they were found to be in good agreement with the Q-values measured in the International Space Station (ISS) and by the Mars Science Laboratory (MSL) Radiation Assessment Detector (RAD) which represent, respectively, a LEO and deep space orbit.

Adaptive model predictive scheduling of flexible interconnected low-voltage distribution networks considering charging preferences of electric vehicles

DC interconnection at the second side of distribution transformers helps achieve power sharing among nearby low-voltage distribution networks (LVDNs) and promote integration of intermittent inverter-based distributed generators (DGs). This paper proposes an adaptive model predictive scheduling method for flexible interconnected LVDNs considering charging preferences of electric vehicles (EVs). Firstly, the steady-state models of flexible resources including voltage source converters, energy storage systems along with AC and DC power flow models are established. Then, a model predictive control (MPC)-based rolling optimization model is formulated aiming to minimize the daily energy loss considering uncertainties of DGs, load and each charging station as a whole. To further explore the flexibility and dispatchability of each charging station, an adaptive MPC-based rolling optimization model is built considering three types of EVs with different charging preferences, i.e., uncontrollable EVs, charging-only EVs and vehicle-to-grid EVs. The scheduling window of the adaptive MPC-based scheduling is dynamically updated according to the maximum departure time of currently charging EVs to fulfill expected energy requirements of all EVs. Simulation results on a typical flexible LVDN show that the daily energy loss and total load fluctuation can be further reduced through real-time scheduling of controllable EVs in addition to existing flexible resources.

Probing Charm Quark Dynamics via Multiparticle Correlations in Pb-Pb Collisions at sqrt[s_{NN}]=5.02 TeV.

Multiparticle azimuthal correlations of prompt D^{0} mesons are measured in Pb-Pb collisions at a nucleon-nucleon center-of-mass energy of sqrt[s_{NN}]=5.02 TeV. For the first time, a four-particle cumulant method is used to extract the second Fourier coefficient of the azimuthal distribution (v_{2}) of D^{0} mesons as a function of event centrality and the D^{0} transverse momentum. The ratios of the four-particle v_{2} values to previously measured two-particle cumulant results provide direct experimental access to event-by-event fluctuations of charm quark azimuthal anisotropies. These ratios are also found to be comparable to those of inclusive charged particles in the event. However, hints of deviations are seen in the most central and peripheral collisions. To investigate the origin of flow fluctuations in the charm sector, these measurements are compared to a model implementing fluctuations of charm quark energy loss via collisional or radiative processes in the quark-gluon plasma. These models cannot quantitatively describe the data over the full transverse momentum and centrality ranges, although the calculations with collisional energy loss provide a better description of the data.

Feasibility assessment of utilizing electric vehicles for energy arbitrage in smart grids considering battery degradation cost

ABSTRACT A smart grid environment can enable the participation of electric vehicle (EV) owners in energy arbitrage, provided that the utility employs a dynamic tariff structure and the EV chargers support the vehicle-to-grid (V2G) mode of operation. The EV owners can trade electricity with the utility profitably by exporting the energy stored in their vehicle batteries during the high-priced periods and compensating for the sold energy during the cheaper intervals. However, the additional charge-discharge cycles involved in this venture lead to faster degradation of EV batteries. This paper analyzes the economics behind the arbitrage business in terms of the returns from energy transactions and the cost of battery deterioration, and compares it with a scenario in which the EV users stay away from the V2G market. In addition to the financial analysis, it is also important to monitor the impact on the distribution network in terms of operational parameters such as peak demand, energy loss and voltage fluctuations. The study presented in this paper assesses the feasibility of engaging EVs in electricity arbitrage from the perspective of the owners’ economic welfare as well as the grid’s technical specifications. Results indicate that although the battery degradation cost increases due to energy trading, the revenue generated is substantial enough to give a net saving of 5% for the vehicle owners. With respect to grid impact, all the monitored parameters remain within the prescribed limits, and the peak demand reduces by nearly 15%.

Optimal energy consumption and torque fluctuation control of integrated electric drive system based on mechanical-electromagnetic-thermal coupling characteristics

Integrated electric drive system (IEDS) is a strong nonlinear electromagnetic-mechanical-thermal multi-field coupled system. Owing to the action of multi-field coupling, the traditional control strategy not only fails to fully exploit the performance of IEDS, but also reduces the adaptability and increases torque ripple. To solve this problem, this paper proposes an improved control strategy, in the multi-coupling field, which can reduce energy consumption and torque fluctuation of IEDS based on the torque, speed and temperature three-parameter query table. Firstly, the mechanical-electromagnetic-thermal coupling dynamic model is established in the coupled field-circuit simulation, moreover its performance is studied at different temperatures using traditional control strategy. Special attention is given to the defects of the traditional control strategy with respect to motor energy loss and torque fluctuation control in the multi-coupling field and the development of new strategies to overcame these defects. Simulation and experiments show that, compared with the traditional control strategy, the proposed control strategy can not only improve the efficiency of IEDS by 3.61% under mechanical-electromagnetic-thermal coupling, but also reduce the torque fluctuation caused by current harmonics and improve the dynamic adaptability.

The Effects of Bubble Scattering on Sound Propagation in Shallow Water

As sea waves break, a bubble layer forms beneath the sea surface. The bubble scattering affects sound propagation, thus influencing the accuracy of sound field prediction. This paper aims to investigate the effects of bubble scattering on the statistical characteristics of the sound field, the distribution of transmission loss (TL), and the average scattering attenuation in shallow water. A bubble layer model based on the bubble spectrum and a parallel Parabolic Equation (PE) model are combined to calculate and analyse the sound field in the marine environment with bubbles. The effects of the bubble layer are then compared with those of the fluctuant sea surface. The results show that the bubble scattering causes additional energy loss and random fluctuations of the sound field. The TL distribution properties and the average scattering attenuation are related to the wind speed, range, frequency, and source position relative to the negative gradient sound speed layer in shallow water. The comparison demonstrates that the random variation caused by the fluctuation of the sea surface is more significant than that caused by bubbles, and the energy loss caused by bubble scattering is more significant than the fluctuant sea surface under strong wind conditions.

Energy analysis of Francis turbine for various mass flow rate conditions based on entropy production theory

A methodology of the entropy production theory is employed in hydro turbine flows to analyze the hydraulic loss characteristics quantitatively. The entropy production theory has its distinctive superiority over than traditional pressure drop method because it calculates energy loss through integrating entire computational domain so that it can identify location of energy loss and reflect energy loss characteristics intuitively. This simulated study was implemented by commercial software ANSYS CFX with shear stress turbulence model for a Francis turbine versus various discharge conditions. After comparing with experimental data, the energy loss in different flow components was analyzed and the ability of flow parts to generate energy loss was evaluated versus various conditions quantitatively. Then, the distributions of entropy production rate (EPR) were displayed in stay&guide vanes, runner and draft tube. The conclusions indicate that draft tube is the main part generating the most energy loss compared with other parts. The energy loss fluctuation of runner was obtained and three dominant frequencies were captured with two low frequencies 11.93 [Hz], 15.9 [Hz] and one high frequency 27.83 [Hz]. This study indicates that entropy production theory can provide sufficient theoretical and engineering guidance for the energy loss analysis in hydro turbine flows.

Position reconstruction for segmented detectors

The topic of the paper is the position reconstruction from signals of segmented detectors. With the help of a simple simulation, it is shown that the position reconstruction using the centre-of-gravity method is strongly biased, if the width of the charge (or e.g. light) distribution at the electrodes (or photo detectors) is less than the read-out pitch. A method is proposed which removes this bias for events with signals in two or more read-out channels and thereby improves the position resolution. The method also provides an estimate of the position–response function for every event. Examples are given for which its width as a function of the reconstructed position varies by as much as an order of magnitude.A fast Monte Carlo program is described which simulates the signals from a silicon pixel detector traversed by charged particles under different angles, and the results obtained with the proposed reconstruction method and with the centre-of-gravity method are compared. The simulation includes the local energy-loss fluctuations, the position-dependent electric field, the diffusion of the charge carriers, the electronics noise and charge thresholds for clustering, A comparison to test-beam-data is used to validate the simulation.

Sensitivity study with a D and B mesons modular simulation code of heavy flavor RAA and azimuthal anisotropies based on beam energy, initial conditions, hadronization, and suppression mechanisms

Heavy flavor probes provide important information about the in-medium properties of the quark-gluon plasma produced in heavy-ion collisions. In this work, we investigate the effects of 2D+1 event-by-event fluctuating hydrodynamic backgrounds on the nuclear suppression factor and momentum anisotropies of heavy flavor mesons and non-photonic electrons. Using the state-of-the-art D and B mesons modular simulation code (called "DAB-MOD"), we perform a systematic comparison of different transport equations in the same background, including a few energy loss models --- with and without energy loss fluctuations --- and a relativistic Langevin model with different drag parametrizations. We present the resulting D and B mesons $R_{AA}$, $v_2$, $v_3$, and $v_4$ as well as multi-particle cumulants, in AuAu collisions at $\sqrt{s_\text{NN}}=200\, \text{GeV}$ and PbPb collisions at $\sqrt{s_\text{NN}}=2.76 \, \text{TeV}$ and $\sqrt{s_\text{NN}}=5.02 \, \text{TeV}$, and compare them to the available experimental data. The $v_2\{4\}/v_2\{2\}$ ratio, which is known to be a powerful probe of the initial conditions and flow fluctuations in the soft sector, is also studied in the context of heavy flavor. We also investigate the correlations between the transverse anisotropies of heavy mesons and all charged particles to better understand how heavy quarks couple to the hydrodynamically expanding quark-gluon plasma. We study the influence that different initial conditions and the implementation of heavy-light quark coalescence has on our results.

Numerical investigations of the energy performance and pressure fluctuations for a waterjet pump in a non-uniform inflow

As a way of exploitation and utilization of ocean energy, the waterjet pump is used in a wide range of high-speed marine vessels over 30 knot. This paper aims to investigate the mechanism of the energy loss and pressure fluctuations caused by the non-uniform inflow for a waterjet pump. Unsteady internal flows inside the waterjet pump are simulated using the Reynolds-averaged Navier-Stokes equations with the SST k-ω turbulence model. The predicted pump head and efficiency are in reasonable accordance with the experimental data. The inflow non-uniformity would decrease the hydraulic head, efficiency and increase the axial force fluctuations in the impeller, causing large pulsations in the unsteady energy performance. Based on analyses of the energy loss, the turbulent kinetic energy production and the diffusion of the Reynolds stress are major sources of the energy loss in the waterjet pump. The non-uniform inflow induces a dramatic energy loss in the intake duct and diffuser with an apparent flow separation observed near the trailing edge of the diffuser blade. Due to the inflow non-uniformity, the pressure fluctuates violently at the impeller rotating frequency (fn) in the intake duct, impeller and near the diffuser inlet, but a dominant frequency of 2fn is generated by the unsteady flow separation near the diffuser outlet.

A novel impact-assessment framework for distributed PV installations in low-voltage secondary networks

This paper proposes an impact-assessment framework to appropriately assess the impacts of two different types of distributed solar photovoltaic (DPV) installation on a realistic distribution network. To examine the spontaneous customer-based installations, a detailed Monte Carlo-based technique is introduced. For the controlled utility-based installation, a multi-objective optimization problem for the sizing and location of DPV installation is formulated aiming to improve energy loss, voltage deviation, and voltage fluctuation, avoiding reverse power flow and voltage violation. Solar insolation study is performed using light detection and ranging (LiDAR) data to estimate the potential of the network for DPV installation. In addition, a synthetic load profile modeling is developed to create yearly electricity load profiles for all the buildings in the given distribution network. The proposed framework is applied to a local distribution network with synthetic load profiles, Geographic Information System (GIS), and realistic solar insolation. It is found that for customer-based installation, voltage violation occurs beyond 30% of DPV penetration level, demonstrating the necessity of utility-based installation scheme for higher penetration ratios. Beyond a specific threshold, the probability of reverse power flow significantly increases in customer-based installation. Therefore, to achieve higher penetration ratios without reverse power flow and other negative impacts, utility-aided installation is necessary.

Toward the determination of heavy-quark transport coefficients in quark-gluon plasma

Several transport models have been employed in recent years to analyze heavy-flavor meson spectra in high-energy heavy-ion collisions. Heavy-quark transport coefficients extracted from these models with their default parameters vary, however, by up to a factor of 5 at high momenta. To investigate the origin of this large theoretical uncertainty, a systematic comparison of heavy-quark transport coefficients is carried out between various transport models. Within a common scheme devised for the nuclear modification factor of charm quarks in a brick medium of a quark-gluon plasma, the systematic uncertainty of the extracted drag coefficient among these models is shown to be reduced to a factor of 2, which can be viewed as the smallest intrinsic systematical error band achievable at present time. This indicates the importance of a realistic hydrodynamic evolution constrained by bulk hadron spectra and of heavy-quark hadronization for understanding the final heavy-flavor hadron spectra and extracting heavy-quark drag coefficient. The transverse transport coefficient is less constrained due to the influence of the underlying mechanism for heavy-quark medium interaction. Additional constraints on transport models such as energy loss fluctuation and transverse-momentum broadening can further reduce theoretical uncertainties in the extracted transport coefficients.

Физика планирования протонной лучевой терапии

The most important stage of radiation therapy of oncological diseases is the planning of radiation treatment. In this work, this complex process in relation to proton therapy is proposed to be divided into medical and physical planning. In conventional therapy with photons and electrons, the latter is usually called dosimetric planning, however, when applied to proton radiation therapy, this stage involves a significantly wider range of tasks related to the modification and scanning of the proton beam, spreading and compensation of ranges, taking into account when planning for uncertainties and finiteness of proton ranges, a decrease in the contribution to the dose of secondary neutrons, the creation of error-tolerant optimization algorithms for dosimetric plans, and, finally, a precision calculation of dose distributions. The paper discusses the main stages and problems of physical planning of proton radiation therapy. Particular attention is paid to the formation of an extended high-dose region (extended Bragg peak) using the beam scattering method and scanning method, and to the algorithms for calculating the dose distributions created by protons in the scattering and beam scanning systems. The most detailed consideration is given to different versions of the proton pencil beam method, which allows to increase the dose calculation accuracy and take into account the transverse scattering and fluctuations in proton energy losses, especially at the end of the path (halo effect), analytical and numerical methods. Scanning are divided into three main technologies: homogeneous scanning, single field uniform dose (SFUD), multi-field uniform dose (MFUD), often called intensity modulated proton therapy (IMPT). Actual accounting problems are considered when planning the irradiation of the movement of organs, and uncertainties in determining path lengths and optimization of irradiation plans. In particular features, problems and modern approaches to the optimization of dosimetry plans of proton radiation therapy are discussed. It is noted that one of the most promising practical solutions for the uncertainty management in determining the path lengths of protons in optimization is to include possible errors in the objective function of the optimization algorithm. This technique ensures that an optimized irradiation plan will more reliably protect normal tissues and critical organs adjacent to the irradiation target from overexposure.