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Journal articles on the topic 'Shedding constraints'

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Author: Grafiati
Published: 16 May 2023

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1

Stokes, Patricia D. "Variability, constraints, and creativity: Shedding light on Claude Monet." American Psychologist 56, no. 4 (2001): 355–59. http://dx.doi.org/10.1037/0003-066x.56.4.355.

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2

Nduhuura, Paul, Matthias Garschagen, and Abdellatif Zerga. "Mapping and Spatial Analysis of Electricity Load Shedding Experiences: A Case Study of Communities in Accra, Ghana." Energies 13, no. 17 (August 19, 2020): 4280. http://dx.doi.org/10.3390/en13174280.

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In many developing countries, electricity outages occur frequently with consequences for sustainable development. Moreover, within a country, region or city, the distribution of outages and their resultant impacts often vary from one locality to another. However, due to data constraints, local-scale variations in outage experiences have seldom been examined in African countries. In this study, a spatial approach is used to estimate and compare exposure to electricity load shedding outages across communities in the city of Accra, Ghana. Geographic Information System and statistics from the 2015 rolling blackouts are used to quantify neighborhood-level load shedding experiences and examine for spatial patterns. The results show that annual load shedding exposure varied greatly, ranging from 1117 to 3244 h. The exposure values exhibit statistically significant spatial clustering (Moran’s I = 0.3329, p < 0.01). Several neighborhoods classified as load shedding hot or cold spots, clusters and outliers are also identified. Using a spatial approach to quantify load shedding exposure was helpful for overcoming the limitations of lack of fine-grained, micro-level outage data that is often necessary for such an analysis. This approach can therefore be used in other data-constrained cities and regions. The significant global spatial autocorrelation of load-shedding exposure values also suggests influence by underlying spatial processes in shaping the distribution of load shedding experiences. The resultant exposure maps provide vital information on spatial disparities in load shedding implementation, which can be used to influence decisions and policies towards all-inclusive and sustainable electrification.
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3

Bashkanov, M., T. Skorodko, H. Clement, and D. P. Watts. "Shedding Light on Hexaquarks." International Journal of Modern Physics: Conference Series 46 (January 2018): 1860033. http://dx.doi.org/10.1142/s2010194518600339.

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Several new findings in the four, five and six quark systems reheat the interest in the field of multiquark states (beyond the trivial [Formula: see text] and [Formula: see text]). A lot of progress has recently been made in the 6q sector, on both the theoretical and experimental side. A resonance like structure observed in double-pionic fusion to the deuteron, at M = 2.38 GeV with [Formula: see text] = 70 MeV and [Formula: see text] has been consistently observed in a wealth of reaction channels, supporting the existence of a resonant dibaryon state - the [Formula: see text]. These studies include measurement of all the principle strong decay channels in pn collisions in the quasifree mode by the WASA-at-COSY and HADES collaborations. The internal structure of the [Formula: see text] is largely unknown. It can contain various ”hidden color” 6q configurations, [Formula: see text] molecular states with angular momentum L = 0,2,4,6 as well as meson-assisted dressed dibaryon structures. The large set of experimental data obtained to date gives some constraints on the internal structure of the [Formula: see text] dibaryon, but does not settle the issue. The [Formula: see text] is the only multiquark state which can be produced copiously at current facilities, offering unique access to information beyond its basic quantum numbers, particularly its physical size and internal structure.
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4

Teshome, D. F., P. F. Correia, and K. L. Lian. "Stochastic Optimization for Network-Constrained Power System Scheduling Problem." Mathematical Problems in Engineering 2015 (2015): 1–17. http://dx.doi.org/10.1155/2015/694619.

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The stochastic nature of demand and wind generation has a considerable effect on solving the scheduling problem of a modern power system. Network constraints such as power flow equations and transmission capacities also need to be considered for a comprehensive approach to model renewable energy integration and analyze generation system flexibility. Firstly, this paper accounts for the stochastic inputs in such a way that the uncertainties are modeled as normally distributed forecast errors. The forecast errors are then superimposed on the outputs of load and wind forecasting tools. Secondly, it efficiently models the network constraints and tests an iterative algorithm and a piecewise linear approximation for representing transmission losses in mixed integer linear programming (MILP). It also integrates load shedding according to priority factors set by the system operator. Moreover, the different interactions among stochastic programming, network constraints, and prioritized load shedding are thoroughly investigated in the paper. The stochastic model is tested on a power system adopted from Jeju Island, South Korea. Results demonstrate the impact of wind speed variability and network constraints on the flexibility of the generation system. Further analysis shows the effect of loss modeling approaches on total cost, accuracy, computational time, and memory requirement.
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Moghaddam, Alireza Tehrani Nejad, and Thibault Monier. "Shedding Light on Non Binding Constraints in Linear Programming: An Industrial Application." American Journal of Operations Research 08, no. 01 (2018): 50–61. http://dx.doi.org/10.4236/ajor.2018.81005.

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6

Lai, Zon W., Iresha Hanchapola, David L. Steer, and A. Ian Smith. "Angiotensin-Converting Enzyme 2 Ectodomain Shedding Cleavage-Site Identification: Determinants and Constraints." Biochemistry 50, no. 23 (June 14, 2011): 5182–94. http://dx.doi.org/10.1021/bi200525y.

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7

Alavi, Seyed Arash, Valentin Ilea, Alireza Saffarian, Cristian Bovo, Alberto Berizzi, and Seyed Ghodratollah Seifossadat. "Feasible Islanding Operation of Electric Networks with Large Penetration of Renewable Energy Sources considering Security Constraints." Energies 12, no. 3 (February 8, 2019): 537. http://dx.doi.org/10.3390/en12030537.

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The high penetration of Renewable Energy Sources into electric networks shows new perspectives for the network’s management: among others, exploiting them as resources for network’s security in emergency situations. The paper focuses on the frequency stability of a portion of the grid when it remains islanded following a major fault. It proposes an optimization algorithm that considers the frequency reaction of the relevant components and minimizes the total costs of their shedding. The algorithm predicts the final frequency of the island and the active power profiles of the remaining generators and demands. It is formulated as a Mixed-Integer Non-Linear Programming problem and the high computation time due to a large-size problem is mitigated through a simplified linear version of the model that filters the integer variables. The algorithm is designed to operate on-line and preventively compute the optimal shedding actions to be engaged when islanding occurs. The algorithm is validated for a typical distribution grid: the minimum amount of shedding actions is obtained while the most frequency reactive resources are maintained in operation to assure a feasible frequency. Finally, time-domain simulations show that the optimal solution corresponds to the one at the end of the network’s transients following the islanding.
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8

Wang, Lizhi, and Nan Kong. "Security Constrained Economic Dispatch." International Journal of Operations Research and Information Systems 1, no. 2 (April 2010): 1–16. http://dx.doi.org/10.4018/joris.2010040101.

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The main objective of electric power dispatch is to provide electricity to the customers at low cost and high reliability. Transmission line failures constitute a great threat to the electric power system security. We use a Markov decision process (MDP) approach to model the sequential dispatch decision making process where demand level and transmission line availability change from hour to hour. The action space is defined by the electricity network constraints. Risk of the power system is the loss of transmission lines, which could cause involuntary load shedding or cascading failures. The objective of the model is to minimize the expected long-term discounted cost (including generation, load shedding, and cascading failure costs). Policy iteration can be used to solve this model. At the policy improvement step, a stochastic mixed integer linear program is solved to obtain the optimal action. We use a PJM network example to demonstrate the effectiveness of our approach.
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9

Rao, B. Venkateswara, G. V. Nagesh Kumar, R. V. S. Lakshmi Kumari, and M. Vinay Kumar. "Effect of Advanced Static VAR Compensator on Control of Power System Load Shedding." Advanced Materials Research 403-408 (November 2011): 4867–72. http://dx.doi.org/10.4028/www.scientific.net/amr.403-408.4867.

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This paper investigates the effect of Static VAR Compensator (SVC) on power system load shedding. SVC is mainly used in power system stability improvement. This paper proposes a new use of SVC to reduce load shedding. An algorithm of Newton Raphson method (NR) to reduce the load shedding for installing SVC in the system is proposed in this paper. 5 bus test system example is used to demonstrate the effect on load shedding. The test results show that the effect of SVC is significant, in this Static VAR compensator (SVC) is incorporated in Newton Raphson method in which Power Flow Solution is a solution of the network under steady state conditions subjected to certain constraints under which the system operates. The power flow solution gives the nodal voltages and phase angles given a set of power injections at buses and specified voltages at a few, the model of SVC i.e. SVC Susceptance model is discussed. It is also shown that the power system losses are decreased after incorporating the SVC in this N-R method. The results are generated for 5-Bus system. By incorporating the SVC the amount of load shedding is reduced to get the voltages in their limits.
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10

Trigueiro dos Santos, Leonardo, Manuela Sechilariu, and Fabrice Locment. "Optimized Load Shedding Approach for Grid-Connected DC Microgrid Systems under Realistic Constraints." Buildings 6, no. 4 (December 9, 2016): 50. http://dx.doi.org/10.3390/buildings6040050.

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11

Rakotonirainy, RG, I. Durbach, and J. Nyirenda. "Considering fairness in the load shedding scheduling problem." ORiON 35, no. 2 (December 20, 2019): 127–44. http://dx.doi.org/10.5784/35-2-648.

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Every day national power system networks provide thousands of MW of electric power from generating units to consumers, requiring different operations and planning to ensure secure systems. Where demand exceeds supply, load shedding - controlled, enforced reduction in supply - is necessary to prevent system collapse. Should load shedding need to be implemented, a planned schedule is necessary to allocate geographic areas on the required period of shedding. The problem of how to construct a schedule that fairly allocates load shedding responsibilities over geographic areas with minimum economic impacts is addressed in this paper. Two programming models are proposed. The first model consists of a linear integer programming model in which the objective is to minimise the economic cost subject to different fairness allocation constraints, while the second model involves formulation of the problem as a goal programming model in which different conflicting goals are simultaneously optimised. Several case studies are conducted in the context of a realistic, but hypothetical, scenario to explore the possible solutions that the proposed models provide. Results show that a fair schedule requires a high cost whereas lower cost can only be achieved with some sacrifices to the fairness of the schedule.
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12

Zdiri, M. A., A. S. Alshammari, A. A. Alzamil, M. Ben Ammar, and H. H. Abdallah. "Optimal Shedding Against Voltage Collapse Based on Genetic Algorithm." Engineering, Technology & Applied Science Research 11, no. 5 (October 12, 2021): 7695–701. http://dx.doi.org/10.48084/etasr.4448.

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The prevalent tendency in power transmission systems is to operate closer and closer to the energy limit, rendering system voltage instability a commonly widespread phenomenon. It is, therefore, necessary that certain remedial corrective controls need be undertaken whenever these systems tend towards failure. In this respect, load shedding stands as a major correction mechanism and such a failure can be prevented and nominal system voltage can be resumed. It is worth noting however that load shedding must be implemented very carefully to ensure the satisfaction of both the customer and the electricity-production company. In this context, our focus of interest is laid on load and machine shedding against voltage collapse as an effective corrective method. It is important to note that such a problem turns out to be commonly defined as an optimization problem under constraints. Using genetic algorithms as resolution methods, the application of the proposed methods was implemented on the 14-node IEEE test network, while considering a number of different case studies.
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13

Margaritis, Chrysovalantis, Polychronis Koliogiannis Koutmiridis, and Charalampos Moustakidis. "Speed of sound constraints on maximally-rotating neutron stars." HNPS Proceedings 27 (April 17, 2020): 155. http://dx.doi.org/10.12681/hnps.2990.

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In the present work we provide a theoretical treatment concerning the effects of the upper bound of the sound speed in dense matter on the bulk properties of maximally-rotating (at mass-shedding limit) neutron stars. We investigate to what extent the possible predicted (from various theories and conjectures) upper bounds on the speed of sound constrain various key quantities, such as the maximum mass and the corresponding radius, Keplerian frequency, Kerr parameter and moment of inertia. We mainly focus on the lower proposed limit, , and we explore in which mass region a rotating neutron star collapses to a black hole. In any case, useful relations of the mentioned bulk properties with the transition density are derived and compared with the corresponding non-rotating cases.
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14

Ke, Song, Tao Lin, Rusi Chen, Hui Du, Shuitian Li, and Xialing Xu. "A Novel Self-Healing Strategy for Distribution Network with Distributed Generators Considering Uncertain Power-Quality Constraints." Applied Sciences 10, no. 4 (February 21, 2020): 1469. http://dx.doi.org/10.3390/app10041469.

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Self-healing of smart distribution networks with distributed generators, which are usually operated as independent islands after fault, can improve power-supply reliability. As a hot research topic, a self-healing scheme is usually treated as the output of a nonlinear optimizuoation model. However, existing strategies have two main shortcomings. The first, high-optimization dimension, results in low-optimization efficiency. The second, the effects of power-quality issues, which are more serious on islands and may further threaten the safe operation of islands, is usually neglected. To quickly obtain a reliable self-healing scheme, a novel strategy is proposed. As the first step, the distribution network after a fault occurrence can be divided into several trouble-free subnets via the connectivity analysis; each subnet is called an initial island. Further, for each initial island, a two-step optimization model of self-healing, which consists of load-shedding optimization and network reconfiguration optimization, is proposed to obtain the self-healing strategy with lower searching space as well as higher solving efficiency. In detail, in load-shedding optimization, by means of heuristic differential evolution algorithm, larger total recovery capacity is achieved by considering the droop characteristic of distributed generators (DGs) within the permissible change in frequency. In network-reconfiguration optimization, based on the improved hybrid particle swarm optimization algorithm, a comprehensive set of power-quality constraints, including constraint of change in frequency, uncertain constraints of node voltage total harmonic distortion (THD), and negative sequence components of DGs, is developed to guarantee the reliability of each island. To evaluate whether the constraints are satisfied during the optimization procedure, an improved flexible power-flow algorithm is developed to calculate the power flow of each island under change in frequency. Further, 2m+1-point estimate method is employed for uncertainty analyses of the distributions of harmonic and negative sequence components caused by the uncertainty of corresponding sources. Finally, via a 94-node practical distribution network, the effectiveness and advantages of the proposed strategy in safety, recovery capacity, and optimization efficiency are verified.
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15

Pasha, Hafiz A., and Wasim Saleem. "The Impact and Cost of Power Load Shedding to Domestic Consumers." Pakistan Development Review 52, no. 4I (December 1, 2013): 355–73. http://dx.doi.org/10.30541/v52i4ipp.355-373.

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The widespread and growing phenomenon of power load shedding has emerged as one of the principal supply-side constraints to growth of the economy of Pakistan. Not only has this led to significant losses of output, employment and exports but also during periods of high outages there have been large-scale protests, particularly in Punjab and KPK. Households have faced severe disruptions due to the high and growing incidence of load shedding. These have led to mass protests on streets resulting in disruption of other economic activities. As such, the economic return of reducing outages and of facilitating the process of adjustment to these outages is likely to be high. This paper provides an approach and methodology for quantifying cost of load shedding to households in Pakistan. It is organised as follows: Section 2 highlights some key trends in the power sector of Pakistan. Section 3 will present a detailed literature review on the methodology used for quantification of costs due to outages. Section 4 describes the methodology used for qualification of costs due to outages and for estimation of willingness to pay. Section 5 presents estimates of the cost of load shedding in the domestic sector of Pakistan. Finally, Section 6 highlights the major policy implications emerging from the research.
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16

Park, Sangjun, and Hunyoung Shin. "A Proactive Microgrid Management Strategy for Resilience Enhancement Based on Nested Chance Constrained Problems." Applied Sciences 12, no. 24 (December 9, 2022): 12649. http://dx.doi.org/10.3390/app122412649.

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As the frequency of extreme weather events rises, the resilience of power systems is becoming increasingly important. This paper proposes a proactive microgrid management strategy for enhancing the resilience of microgrids (MGs) based on nested Mixed Integer Linear Programming problems with chance constraints. In the proposed method, MGs operate in a special operating mode referred to as the “preparation mode” to protect the vital load and maximize resource operation efficiency when an external grid outage warning is issued. The preparation mode problem is formulated to reflect both the normal and emergency mode operation conditions. The on-event phase-operation problem under emergency-mode operation conditions is nested within the pre-scheduling problem under normal-mode operation conditions in the preparation mode. Further, according to their importance, loads are divided into critical and non-critical ones in the problems. The former is represented by a chance constraint, and the latter is represented by the expected cost of load shedding in the cost function. The numerical examples demonstrate that the proposed preparation mode enables the MG to guarantee a high chance that the critical load will survive and to lower the cost of the non-critical load shedding with a minor increase in resource operation costs.
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17

Shi, Fang, Hengxu Zhang, Yongji Cao, Huadong Sun, and Yun Chai. "Enhancing Event-Driven Load Shedding by Corrective Switching With Transient Security and Overload Constraints." IEEE Access 7 (2019): 101355–65. http://dx.doi.org/10.1109/access.2019.2929304.

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18

Xu, Xin, Hengxu Zhang, Changgang Li, Yutian Liu, Wei Li, and Vladimir Terzija. "Optimization of the Event-Driven Emergency Load-Shedding Considering Transient Security and Stability Constraints." IEEE Transactions on Power Systems 32, no. 4 (July 2017): 2581–92. http://dx.doi.org/10.1109/tpwrs.2016.2619364.

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19

MARSDEN, ALISON L., MENG WANG, J. E. DENNIS, and PARVIZ MOIN. "Trailing-edge noise reduction using derivative-free optimization and large-eddy simulation." Journal of Fluid Mechanics 572 (January 23, 2007): 13–36. http://dx.doi.org/10.1017/s0022112006003235.

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Derivative-free optimization techniques are applied in conjunction with large-eddy simulation (LES) to reduce the noise generated by turbulent flow over a hydrofoil trailing edge. A cost function proportional to the radiated acoustic power is derived based on the Ffowcs Williams and Hall solution to Lighthill's equation. Optimization is performed using the surrogate-management framework with filter-based constraints for lift and drag. To make the optimization more efficient, a novel method has been developed to incorporate Reynolds-averaged Navier–Stokes (RANS) calculations for constraint evaluation. Separation of the constraint and cost-function computations using this method results in fewer expensive LES computations. This work demonstrates the ability to fully couple optimization to large-eddy simulation for time-accurate turbulent flow. The results demonstrate an 89% reduction in noise power, which comes about primarily by the elimination of low-frequency vortex shedding. The higher-frequency broadband noise is reduced as well, by a subtle change in the lower surface near the trailing edge.
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20

Chapnik, Koral, Ilya Kolchinsky, and Assaf Schuster. "DARLING." Proceedings of the VLDB Endowment 15, no. 3 (November 2021): 541–54. http://dx.doi.org/10.14778/3494124.3494137.

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Complex event processing (CEP) is widely employed to detect user-defined combinations, or patterns, of events in massive streams of incoming data. Numerous applications such as healthcare, fraud detection, and more, use CEP technologies to capture critical alerts, threats, or vital notifications. This requires that the technology meet real-time detection constraints. Multiple optimization techniques have been developed to minimize the processing time for CEP, including parallelization techniques, pattern rewriting, and more. However, these techniques may not suffice or may not be applicable when an unpredictable peak in the input event stream exceeds the system capacity. In such cases, one immediate possible solution is to drop some of the load in a technique known as load shedding. We present a novel load shedding mechanism for real-time complex event processing. Our approach uses statistics that are gathered to detect overload. The solution makes data-driven load shedding decisions to drop the less important events such that we preserve a given latency bound while minimizing the degradation in the quality of results. An extensive experimental evaluation on a broad set of real-life patterns and datasets demonstrates the superiority of our approach over the state-of-the-art techniques.
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21

Zeng, Yiling, Chunyao Song, Tingjian Ge, and Ying Zhang. "Reduction of large-scale graphs: Effective edge shedding at a controllable ratio under resource constraints." Knowledge-Based Systems 240 (March 2022): 108126. http://dx.doi.org/10.1016/j.knosys.2022.108126.

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22

Wawrzyniak, Karol, Endika Urresti Padrón, Wojciech Jaworski, and Roman Korab. "Risk-Based Active Power Redispatch Optimization." Energies 13, no. 3 (February 7, 2020): 716. http://dx.doi.org/10.3390/en13030716.

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Risk-based redispatch optimization is proposed as a methodology to support the Transmission System Operator (TSO) with preventive remedial actions obtained by extending the security-constrained unit commitment/economic dispatch with constraints resulting from the risk assessed for the power system. Although being heuristic, the methodology is based on comprehensive dynamic security assessment as time-domain simulations are used, allowing to express the degree of all types of instabilities, e.g., caused by contingencies, in monetary terms. Therefore, the risk is assessed as the expected value of the cost incurred by the TSO. Such an approach forms a new pathway to including risk in planning procedures already used by TSOs. Results obtained for the IEEE39 dynamic power system, with costs assigned to load shedding and generator tripping due to single transmission lines short-circuits, are shown as a reference case.
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23

Koliogiannis Koutmiridis, Polychronis, and Charalampos Moustakidis. "Towards the Keplerian sequence: Realistic equations of state in rapidly rotating neutron stars." HNPS Proceedings 27 (April 17, 2020): 85. http://dx.doi.org/10.12681/hnps.2987.

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Neutron stars are among the densest known objects in the universe and an ideal laboratory for the strange physics of super-condensed matter. In the present work, we investigate the Keplerian (mass-shedding) sequence of rotating neutron stars by employing realistic equations of state based on various theoretical nuclear models. In particular, we compute the moment of inertia and angular momentum of neutron stars against mass-shedding and secular axisymmetric instability. We mainly focus on the dependence of these properties from the bulk properties of neutron stars. Another property that studied in detail, is the dimensionless spin parameter (kerr parameter) of rotating neutron stars at the mass-shedding limit. In addition, supramassive time evolutionary rest mass sequences, which have their origin in general relativity, are explored. Supramassive sequences have masses exceeding the maximum mass of a non-rotating neutron star and evolve toward catastrophic collapse to a black hole. Important information can be gained from the astrophysical meaning of the kerr parameter and the supramassive sequences in neutron stars. Finally, the effects of the Keplerian sequence, in connection with the latter, may provide us constraints on the high density part of the equation of state of cold neutron star matter.
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24

Formenti, Carlo. "Web 2.0: netizen empowerment vs. unpaid labor." Journal of Science Communication 11, no. 01 (March 16, 2012): C03. http://dx.doi.org/10.22323/2.11010303.

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Scientific information looks to Web 2.0 models as an opportunity for shedding the constraints of traditional scientific publishing (high costs, slow processing, domination by elites). However, outcomes in the other fields that have preceded it along this path (open source communities, file sharing networks, citizen journalism), have cast several doubts on utopian fantasies about the “democratization” of information and knowledge. So far Web 2.0 has actually witnessed new forms of concentrations of resources and innovative ways for the commercial exploitation of collective creativity.
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Rao, Hanyue, Yifu Chen, Yayun Shi, Tihao Yang, and Hongyang Liu. "Adjoint-Based Aerodynamic Design Optimization and Drag Reduction Analysis of a Military Transport Aircraft Afterbody." Aerospace 10, no. 4 (March 27, 2023): 331. http://dx.doi.org/10.3390/aerospace10040331.

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Based on the adjoint method, the afterbody of a military transport aircraft was optimized and designed to meet engineering constraints under real flight conditions. Guidance for the key design parameters of the afterbody of the military transport aircraft is given. The vortex dynamics and boundary layer extraction methods were used to analyze the optimization results of military transport aircraft. It was found that, upstream of the vortex shedding point, the circumferential accumulation process of the vorticity is weakened. The position of the vortex shedding and the appearance of the saddle line are delayed by reducing the circumferential inverse pressure gradient and the intensity of the crossflow. The afterbody vortex system of the optimized configuration is further away from the surface. Meanwhile, the distance between the counter-rotated vortex decreases, and the upwashing speed of the vortex core is smaller. Therefore, vortex-induced drag is reduced. Finally, compared with the initial configuration, the optimized configuration has a relative drag reduction of 23.2%.
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26

Karaman, Abdullah S. "Simulating air transportation networks under capacity constraints." Kybernetes 47, no. 6 (June 4, 2018): 1122–37. http://dx.doi.org/10.1108/k-01-2017-0022.

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Purpose Congestion as a consequence of the rapidly growing air traffic is one of the outstanding problems of the air transportation industry. Traffic impediment rates, having an increasing acceleration while the airport capacities have been kept constant due to several reasons, cause problems such as arrival/departure delays, schedule interruptions, cancellations and customer dissatisfaction. In this paper, the author aims to study transitioning from a single-hub air transportation system to a multi-hub infrastructure via Monte Carlo simulation. Design/methodology/approach The current hub has reached its capacity limits for long so that the growth potential of the air transportation has been affected adversely. One of the possible remedies suggested by authorities, professionals and academics was to transform the air transportation infrastructure into a multi-hub setting. Current air traffic of the country was modeled by means of simulation. Airport capacities and performances are simulated and analyzed under different scenarios considering a potential alternative hub along with the central one. Possible delays in both hubs are studied in case of moderately increasing traffic congestion. Findings As a result, decreased delay levels in the central hub are observed, whereas no delays are experienced in the potential one in all the scenarios. Originality/value This study, proposing to organize the national and international air traffic of the country while harmonizing the delay rates and increasing the passenger satisfaction, is to contribute significantly to the aviation sector companies, airliners and airport operators by shedding light on the imminent capacity issues air transportation industry is going to face.
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Gull, Muhammad S., Nasir Mehmood, Huzaifa Rauf, Muhammad Khalid, and Naveed Arshad. "Soft Load Shedding Based Demand Control of Residential Consumers." Electronics 11, no. 4 (February 16, 2022): 615. http://dx.doi.org/10.3390/electronics11040615.

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Power generation and consumption is an instantaneous process and maintaining the balance between demand and supply is crucial since the demand and supply mismatch leads to various risks like over-investment, over-generation, under-generation, and the collapse of the power system. Therefore, the reduction in demand and supply mismatch is critical to ensure the safety and reliability of power system operation and economics. A typical and common approach, called full load shedding (FLS), is practiced in cases where electric power demand exceeds the available generation. FLS operation alleviates the power demand by cutting down the load for an entire area or region, which results in several challenges and problems for the utilities and consumers. In this study, a demand-side management (DSM) technique, called Soft-load shedding (SLS), is proposed, which uses data analytics and software-based architecture, and utilizes the real-world time-series energy consumption data available at one-minute granularity for a diversified group of residential consumers. The procedure is based on pattern identification extracted from the dataset and allocates a certain quota of power to be distributed on selected consumers such that the excessive demand is reduced, thereby minimizing the demand and supply mismatch. The results show that the proposed strategy obtains a significant reduction in the demand and supply mismatch such that the mismatch remains in the range of 10–15%, especially during the period where demand exceeds generation, operating within the utility constraints, and under the available generation, to avoid power system failure without affecting any lifeline consumer, with a minimum impact on the consumer’s comfort.
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Hua, Wen, Bowen Wang, Xiang Zheng, Huangfu Yao, and Wei Dong. "Unit combination problem of counting and DC bipolar blocking and dynamic voltage stabilization under a new power system." Journal of Physics: Conference Series 2359, no. 1 (October 1, 2022): 012008. http://dx.doi.org/10.1088/1742-6596/2359/1/012008.

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Abstract With the construction of new power systems a large number of DC transmission technologies are applied, but the ensuing DC blocking problem brings new challenges for the combination of units in the intranet. Considering the unit combination problem of DC bipolar blocking and dynamic voltage stability occurring in the intranet under different load levels of high, medium and low is divided into two steps: selecting the unit combination that meets the load boundary under static constraints such as N-1 fault state constraint and network security under the occurrence of DC bipolar blocking; and then checking whether the low-voltage load shedding device does not operate to meet dynamic voltage stability on this basis. This unit combination method considers the impact on dynamic voltage stability while satisfying the DC bipolar lockout standby capacity, and verifies the effectiveness of the proposed model by simulation analysis using PSD-BPA software based on the large operation mode of Zhejiang summer in 2022.
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Carol McWilliam Leitch, E., Sylvia H. Duncan, Karen N. Stanley, and Colin S. Stewart. "Dietary effects on the microbiological safety of food." Proceedings of the Nutrition Society 60, no. 2 (May 2001): 247–55. http://dx.doi.org/10.1079/pns200078.

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The high mortality rate associated with human infections caused byEscherichia colistrains of the serotype O157:H7 has brought to public attention the importance of ruminants as reservoirs of food-borne pathogens. In addition to established examples such as salmonella, campylobacter and listeria, recent evidence is emerging of the role of food in the transmission ofHelicobacter pyloriandMycobacterium paratuberculosis. Food-borne pathogens harboured by ruminants are spread through shedding in the faeces and subsequent faecal contamination of raw food. Ruminant shedding appears to be affected by diet and, of particular concern, may be increased during fasting regimens imposed during transport to the slaughterhouse. The survival of food-borne pathogens in the ruminant gut is affected by many factors including microbe–microbe interactions, interactions involving plant metabolites and the presence of inhibitory end-product metabolites such as short-chain fatty acids. The potential importance of digesta flow and bacterial detachment in shedding of food-borne pathogens is discussed. Experimental procedures with dangerous pathogens have constraints, particularly in animal experimentation. This situation may be overcome by the use of rumen-simulating fermentors. One such system which, like the natural rumen, has a different turnover rate for solid and liquid digesta, was found to maintain rumen-like variables over an 11 d period. This system may prove useful for the study of dietary effects on food-borne pathogens.
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Casula, Giovanni Andrea, Giuseppe Mazzarella, and Giorgio Montisci. "Design of Shaped Beam Planar Arrays of Waveguide Longitudinal Slots." International Journal of Antennas and Propagation 2013 (2013): 1–12. http://dx.doi.org/10.1155/2013/767342.

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The Elliott’s procedure for the design of a pencil beam waveguide longitudinal slot array has been generalized to encompass the design of shaped beam planar slot arrays. An extended set of design equations, taking into account in an operative way the feeding part of the array, has been devised. From this set of equations, a general and effective design procedure has been set up, shedding light on the constraints posed by a complex aperture distribution. The results of the proposed synthesis procedure have been validated through comparison with a commercial FEM software.
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Wang, Bangyan, Xiuli Wang, Likai Zhang, Shengqi Yuan, Shuai Wang, and Chaoshan Xin. "Data-Driven Optimization of Energy Storage Allocation for Stable Outward Delivery in Wind and Solar Enrichment Region-A Case Study of Provincial Power Grid." Journal of Physics: Conference Series 2404, no. 1 (December 1, 2022): 012007. http://dx.doi.org/10.1088/1742-6596/2404/1/012007.

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Abstract The volatility and uncertainty of renewable energy sources aggravate the difficulties of power consumption balance in the new power system. One practical approach is to equip the grid with sufficient energy storage to reduce the operation risk. This paper focuses on a provincial grid with a heavy power outward delivery burden and its storage allocation problem. First, the optimization model with minimum storage allocation is established. Scenarios are constructed based on the typical set and the validation set. Second, a data-driven method is applied to build the typical set by k-means++. To describe the tolerance of wind and solar curtailed and delivery shedding, a chance-constrained approach is established and converted to linear constraints by big-M. The case study shows the power system needs considerable energy storage to ensure renewable energy consumption and delivery. With the lower tolerance, the allocated storage capacity will increase, and the lowest feasible tolerance is limited by scenarios with poor renewable output.
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Hajivar, G. A. M. Hosaini, and S. S. Mortazavi. "Impact of Shunt FACTS Devices on Security Constrained Unit Commitment." International Journal of Applied Power Engineering (IJAPE) 5, no. 1 (April 1, 2016): 22. http://dx.doi.org/10.11591/ijape.v5.i1.pp22-39.

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Shunt FACTS Devices (SFD) would play an important role in maintaining security and reduce total generation cost in the economical operation of power systems. The application of this device to the AC model of securityconstrained unit commitment (SCUC) for the day ahead scheduling is presented in this paper. The proposed AC model of SCUC with SFD would include active and reactive power flow constraints which increase the network controllability at normal operation and contingency. A general SFD model is introduced for the reactive power management in SCUC which is based on the reactive power injection model (RPIM). The case studies demonstrate the effectiveness of the SFD application to SCUC with AC network constraints. Meanwhile simulation results demonstrate the combined use of these devices to SCUC have a significant impact on maintaining network security, preventing load shedding, lower total generation cost and increase using the maximum capacity of the existing transmission network.
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33

COSTAMANTE, LUIGI. "GAMMA-RAYS FROM BLAZARS AND THE EXTRAGALACTIC BACKGROUND LIGHT." International Journal of Modern Physics D 22, no. 13 (October 20, 2013): 1330025. http://dx.doi.org/10.1142/s0218271813300255.

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Recent observations of blazars at high energy (0.1–100 GeV) and very high energy (> 0.1 TeV) have provided important constraints on the intensity and spectrum of the diffuse extragalactic background light (EBL), shedding light on its main origin. Several issues remain open, however, in particular in the mid- and far-infrared bands and in the blazar emission at multi-TeV energies. This review summarizes the observational and theoretical progress in the study of the EBL with gamma-rays and the most promising future improvements, which are mainly expected from spectra in the multi-TeV range.
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34

Krivochen, Diego Gabriel, and Luis García Fernández. "On Coordination and Clitic Climbing in Spanish Auxiliary Verb Constructions." Studies in Hispanic and Lusophone Linguistics 15, no. 1 (May 1, 2022): 111–39. http://dx.doi.org/10.1515/shll-2022-2057.

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Abstract In this work we analyse some aspects of the interaction between coordination and clitic climbing in Spanish sentences with auxiliary verbs. We aim at shedding light on three kinds of structures, or ‘scenarios’: (1) those in which we find coordinated auxiliaries taking a single lexical verb as complement (Puede y debe hacerlo); (2) those in which a single auxiliary takes coordinated lexical verbs as complement (estás molestándonos y mirándonos), and (3) those in which coordinated auxiliaries take coordinated lexical verbs as complement (puede y debe terminarlo y entregarlo). Our proposal will involve a combination of Gapping and Across-the-Board rule application for Scenarios (1) and (2) and Right Node Raising for Scenario (3). We will argue that well-known syntactic constraints on long distance dependencies, such as those proposed in Ross, John Robert. 1967. Constraints on variables in syntax. Cambridge: MIT disertation, can account for the facts without the need for ad hoc machinery.
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PÖLZLER, T., M. WAGNER, J. SLAGHUIS, C. SCHLEICHER, and J. KÖFER. "Rapid Monitoring of Campylobacter in High-Shedding Flocks for Targeted Disease Control." Journal of Food Protection 75, no. 10 (October 1, 2012): 1835–38. http://dx.doi.org/10.4315/0362-028x.jfp-12-027.

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Broilers excreting Campylobacter spp. at high levels (&gt;7 log CFU/g of feces) were described in the Dutch Campylobacter Risk Management and Assessment project as an important source of carcass contamination. The researchers concluded that the risk of infection to humans could be economically and efficiently minimized by eliminating these flocks from fresh poultry meat chains. In the present study, we evaluated a simple and rapid gold-labeled immunosorbent assay (GLISA) for the identification of Campylobacter spp. in flocks shedding high levels of the pathogen. Results were obtained within 2 h. Pooled samples from 102 of the 114 Campylobacter-positive flocks produced positive results, resulting in a test sensitivity of 89.5% (95% confidence interval, 82.6 to 94.2%) and a test specificity of 94.5% (86.7 to 98.2%). Given a GLISA detection limit of 7.3 log CFU/g of feces, nearly all Campylobacter-positive flocks were identified as “high shedders.” Therefore, reduction of the incidence of Campylobacter infections by elimination of high-shedding flocks from fresh meat production is an unrealistic approach. Under the constraints given, a reduction in the incidence of Campylobacter spp. in Austria will require either improved hygiene or an intensive carcass decontamination strategy in fresh meat production facilities.
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36

Thango, Bonginkosi A., and Pitshou N. Bokoro. "Battery Energy Storage for Photovoltaic Application in South Africa: A Review." Energies 15, no. 16 (August 17, 2022): 5962. http://dx.doi.org/10.3390/en15165962.

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Despite the significant slowdown of economic activity in South Africa by virtue of the COVID-19 outbreak, load shedding or scheduled power outages remained at a high level. The trend of rising load-shedding hours has persisted throughout most of the year 2022. Operational issues within the South African power utility inflamed the unpredictable nature of generation capacity, resulting in unscheduled outages at several generating units, mostly due to multiple breakdowns. To forestall substantial spikes in energy costs, an increasing number of enterprises and homeowners have started to gradually adopt renewable energy technologies to sustain their operational demand. Therefore, there is an increase in the exploration and investment of battery energy storage systems (BESS) to exploit South Africa’s high solar photovoltaic (PV) energy and help alleviate production losses related to load-shedding-induced downtime. As a result, the current work presents a comprehensive and consequential review conducted on the BESS specifically for solar PV application and in the South African context. The research investigations carried out on BESS for PV application are crucially examined, drawing attention to their capacities, shortcomings, constraints, and prospects for advancement. This investigation probed several areas of interest where the BESS-PV scheme is adopted, viz., choice of battery technology, mitigating miscellaneous power quality problems, optimal power system control, peak load shaving, South African BESS market and status of some Real BESS-PV projects. The techno-economic case scenario has been proposed in the current research and results yield that lithium-ion batteries are more viable than Lead–acid batteries.
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37

Slowey, Niall C., and Gideon M. Henderson. "Radiocarbon Ages Constraints on the Origin and Shedding of Bank-Top Sediment in the Bahamas during the Holocene." Aquatic Geochemistry 17, no. 4-5 (July 15, 2011): 419–29. http://dx.doi.org/10.1007/s10498-011-9140-5.

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38

Bai, Wenshuai, Manuela Sechilariu, and Fabrice Locment. "DC Microgrid System Modeling and Simulation Based on a Specific Algorithm for Grid-Connected and Islanded Modes with Real-Time Demand-Side Management Optimization." Applied Sciences 10, no. 7 (April 7, 2020): 2544. http://dx.doi.org/10.3390/app10072544.

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This paper presents an algorithm considering both power control and power management for a full direct current (DC) microgrid, which combines grid-connected and islanded operational modes, with real-time demand-side management optimization. The full microgrid is a hybrid dynamic system model consisting of two interacting parts: continuous-time dynamics and discrete-event dynamics. Such a full microgrid consists of photovoltaic sources, a DC load, battery storage systems, supercapacitor storage, a diesel generator, and a public grid connection, all connected on a DC common bus. This full microgrid is more reliable than a microgrid with only renewable sources or with only traditional energy sources, considering the power constraints imposed by the public grid as well as the sluggish dynamic of the diesel generator, self-discharging characteristic of the supercapacitor, and load shedding optimization. Meanwhile, this algorithm can automatically switch between grid-connected and islanded operational modes to optimize the power of the load shedding, take advantage of renewable energy, and keep the power balance in the full DC microgrid. The results under MATLAB/Simulink verify that the real-time control algorithm can maintain the power balance in real-time for the whole day and satisfy the power management strategy.
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39

Siahchehre Kholerdi, Somayeh, and Ali Ghasemi-Marzbali. "Critical Demand Response Opportunities in Heavy Industries as a Solution for Large Active Power Imbalance in Smart Grid: Study in Three Industrial Subgroups." International Transactions on Electrical Energy Systems 2022 (September 9, 2022): 1–14. http://dx.doi.org/10.1155/2022/2310923.

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Demand response (DR) is one of the most cost-effective and logical smart grid terms for power systems that can be used during peak load hours, whereas load shedding (LS) is the last and most expensive solution in emergency grid situations. The aim of them is to satisfy equilibrium constraints between consumption and generation and restore the power system frequency to normal bounds at the least possible time. The rapid increase in power grid costs and limitations on electricity generation resources have resulted in the increasing need for industrial customers’ participation as an alternative solution to peak load spikes. Therefore, this paper considers the estimation of imbalance active power in a smart strategy to introduce a critical DR (CDR) in heavy industries (pulp and paper, cement, and medium density fibreboard (MDF)) based on direct load control (DLC) technique in order to reduce the need for LS in frequency restore. To evaluate the proposed model, a real case study including the typical pulp and paper, cement, and MDF industries processes with actual power consumption data is considered. The numerical and graphical results confirm that the proposed CDR can be used as an inexpensive solution to replace the costly spinning reserves and avoid load shedding.
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40

Christ, Sharon L., and Laura M. Schwab-Reese. "Shedding the Constraints of Formal Systems in Research on Child Maltreatment Through High-Quality Measurement and Broad Population Surveys." International Journal on Child Maltreatment: Research, Policy and Practice 3, no. 1 (December 12, 2019): 105–23. http://dx.doi.org/10.1007/s42448-019-00040-7.

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41

Kock, Z., and Krishna K. Govender. "Load-shedding and the Declining Energy Availability Factor: A Case Study of a South African Power Station." Mediterranean Journal of Social Sciences 12, no. 6 (November 5, 2021): 128. http://dx.doi.org/10.36941/mjss-2021-0063.

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Through a mixed methods study, which included a survey among a stratified sample of 70 employees and interviews with 11 managers, this paper reports on the factors which led to a decline in power generation by Eskom’s Camden Power Station. The impact of the declining energy available factor (EAF) was significant, primarily on economic activities, employment, revenue loss due to load-shedding, and corporate social responsibility. The main causes of the declining EAF included leadership instability, financial constraints, inadequate plant maintenance, process-related challenges, bottle necks in the procurement of replacement parts, poor quality spare parts, high staff turnover, poor employee morale, poor workmanship and poor quality coal.It is recommended that funding for EAF related projects be prioritized, the performance of the acting managers needs to closely managed, sources of coal be streamlined, the training of quality control personnel and contract supervisors be improved and staff morale be urgently addressed. Received: 7 September 2021 / Accepted: 7 October 2021 / Published: 5 November 2021
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42

Liu, Xin-Rui, Hao Wang, Qiu-Ye Sun, and Peng Jin. "Research on Dynamic Risk Assessment and Active Defense Strategy of Active Distribution Network under Ice Weather." Applied Sciences 10, no. 2 (January 17, 2020): 672. http://dx.doi.org/10.3390/app10020672.

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With the continuous development of the active distribution network (ADN), the problem of security and stability has become increasingly prominent. From the perspective of improving the defense capability of ADN, a new a multi-angle dynamic risk assessment index system based on the comprehensive vulnerability rate model is proposed in this paper. Risk threshold is used to monitor the status of the distribution network, which determine whether ADN needs to enter the active defense period. The minimum amount of load shedding outside the fault isolation region is regarded as the objective function, considering other constraints such as limited resources, the coordinated active defense strategy (CADS) is formed in this paper. Finally, the accuracy of the comprehensive vulnerability rate and the risk assessment value are verified by example analysis, and the superiority of the CADS is verified by comparing different defense strategies.
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43

Wamsley, Christine E., Alan Kramer, Jeffrey M. Kenkel, and Bardia Amirlak. "Trends and Challenges of Telehealth in an Academic Institution: The Unforeseen Benefits of the COVID-19 Global Pandemic." Aesthetic Surgery Journal 41, no. 1 (July 22, 2020): 109–18. http://dx.doi.org/10.1093/asj/sjaa212.

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Abstract The COVID-19 pandemic has necessitated a reorganization of healthcare delivery, shedding light on the many unrealized advantages telehealth has to offer. In addition to facilitating social distancing, minimizing the risk of pathogen exposure, and preserving healthcare resources, there are many benefits of utilizing this platform that can extend beyond the current pandemic, which will change the way healthcare is delivered for generations to come. With the rapid expansion of telehealth, we present data from our high-volume academic institution’s telehealth efforts, with a more focused analysis of plastic surgery. Although state legislation regarding telehealth varies greatly, we discuss challenges such as legal issues, logistical constraints, privacy concerns, and billing. We also discuss various advantages and the future direction of telehealth not only for plastic surgery but also its general utilization for the future of medicine in the United States.
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44

Chandra, Debabrata, and Supratik Pal. "Investigating the constraints on primordial features with future cosmic microwave background and galaxy surveys." Journal of Cosmology and Astroparticle Physics 2022, no. 09 (September 1, 2022): 024. http://dx.doi.org/10.1088/1475-7516/2022/09/024.

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Abstract In this article, we do a thorough investigation of the competency of the forthcoming Cosmic Microwave Background (CMB) and Galaxy surveys in probing the features in the primordial power spectrum. Primordial features are specific model-dependent corrections on top of the standard power-law inflationary power spectrum; the functional form being given by different inflationary scenarios. Signature of any significant departure from the feature-less power spectrum will enable us to decipher the intricacies of the inflationary Universe. Here, we delve into three major yet distinct features, namely, Bump feature, Sharp feature signal, and Resonance feature signal. To analyse the features, we adopt a specific template for each feature model. We estimate the possible constraints on the feature parameters by employing Fisher matrix forecast analysis for the upcoming CMB missions such as CMB-S4, CORE-M5, LiteBIRD, PICO conjointly with DESI, and EUCLID galaxy surveys. To this end, we make use of four distinct observations to forecast on the bounds on the model parameters, namely, CMB, Baryon Acoustic Oscillations (BAO), Galaxy Clustering and Gravitational Weak Lensing or Cosmic Shear and their permissible synergy. For large scale structure (LSS) information, we consider different upper limits of scale for different redshifts for the purpose of circumventing the propagation of the errors stemming from the uncertainties on nonlinear scales into the constraints on the feature parameters. A comparative analysis of all three features has been done to estimate relative capabilities of these upcoming observations in shedding light on this crucial aspect of precision cosmology.
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45

Hashemi, Abozar, Ghasem Derakshan, M. R. Alizadeh Pahlavani, and Babak Abdi. "Optimal Scheduling of Residential Electricity Demand Based on the Power Management of Hybrid Energy Resources." Environmental and Climate Technologies 24, no. 1 (January 1, 2020): 580–603. http://dx.doi.org/10.2478/rtuect-2020-0036.

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Abstract The present study sought to address the scheduling of the grid-connected hybrid energy resources under uncertainty of renewable sources, and load in the residential sector. After introducing hybrid resources, scheduling model was implemented through a power management algorithm in an attempt to optimize resource cost, emissions, and energy not supplied (ENS). The stated problem consists of two decision-making layers with different weight coefficients based on the prioritization of each objective function. The proposed algorithm is selected for energy optimal management based on technical constraints of the dispatchable and non-dispatchable resources, uncertainty parameters and day ahead real time pricing (RTP). Furthermore, the impact of demand response programs (DRP) on the given algorithm was investigated using load shedding and load shifting techniques. Finally, the results obtained led to the optimization of the functions in all decision-making layers with different modes of operation.
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46

Dong, Baohua. "Towards the Crypto-functional Motive of Existential there: A Systemic Functional Perspective." Theory and Practice in Language Studies 6, no. 8 (August 1, 2016): 1644. http://dx.doi.org/10.17507/tpls.0608.18.

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This paper, based on the proposal of crypto-functions of existential there in Dong (2016a), mainly focuses on the motive of crypto-functions in existential there. The constraints of genre on existential there in terms of indirect realization relationship between genre and lexicogrammar are firstly discussed in an attempt to locate its motive path. Then such a path is followed to explore the distribution frequencies of existential there in each genre in COCA for the intention of shedding light on the motive of crypto-functions of existential there. It is found that existential there enjoys the highest distribution frequencies, among other genres, in academic genre characteristic of hierarchical knowledge structures, and that existential there structures conducive to the verticality of the discourse in academic genre help form a semantic network about Existents, i. e. NPs and in the meantime result in the crypto-function of existential there.
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47

Wang, Qi, Dasong Sun, Jianxiong Hu, Yi Wu, Ji Zhou, and Yi Tang. "Risk Assessment Method for Integrated Transmission–Distribution System Considering the Reactive Power Regulation Capability of DGs." Energies 12, no. 16 (August 7, 2019): 3040. http://dx.doi.org/10.3390/en12163040.

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High distributed generation (DG) penetration makes the traditional method of equalizing the distribution power system (DPS) to the PQ load bus in the risk assessment of the transmission power system (TPS) no longer applicable. This paper proposes a risk assessment method for an integrated transmission–distribution system that considers the reactive power regulation capability of the DGs. Based on the DG’s characteristics and network constraints, the regulation capacity is mapped to the boundary buses of the distribution networks. Coordinating the relationship between reactive power and active power, the utilization of the regulation capacity is maximized to reduce the load shedding in the fault analysis of the TPS. Simulation results in the integrated transmission–distribution system illustrate that the effective use of the regulation capacity of the DPS can reduce the risk of the TPS. The method can be applied to the reactive power sources planning and dispatching of power system.
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48

Khalil, Umair, Muhammad Yousaf Ali Khan, Umer Amir Khan, and Shahid Atiq. "Power Flow Control by Unified Power Flow Controller." April 2020 39, no. 2 (April 1, 2020): 257–66. http://dx.doi.org/10.22581/muet1982.2002.04.

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The demand of energy usage is increasing rapidly and to meet the energy requirements, best possible transmission systems should be adopted to avoid energy losses in our transmission systems. In Pakistan’s WAPDA (Water & Power Development Authority) system, the rapid increase in load and less generation capacity has increased load shedding thought the country. The government has planned to increase the generation capacity but the supply companies are facing line load-ability, environmental constraints, power limitations problems etc. Most of the supply companies prefer to extend the existing electrical networks instead of building new network to reduce financial burdens. In this paper the implementation of the FACTS (Flexible AC Transmission Systems) Devices in an electrical network is described. The FACTS devices enhance power transfer capacity of the line without adding new transmission line. These devices also protect the system from overloading in case of any contingency in the electrical network. The control of power flow, reactive power compensation and voltage control are the main capabilities of FACTS devices. This paper describes the impacts of FACTS devices on improving the voltage stability and power handling capability of a transmission line. The proposed methods for the controllable flow of active and reactive power in a transmission line are also elaborated. A simple electrical system is examined to explain the improvement in the constraints of power system using FACTS devices.
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49

Mohamed, Emad A., and Yasunori Mitani. "Load frequency control enhancement of islanded micro-grid considering high wind power penetration using superconducting magnetic energy storage and optimal controller." Wind Engineering 43, no. 6 (January 14, 2019): 609–24. http://dx.doi.org/10.1177/0309524x18824533.

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This article proposes a robust load frequency control using a new optimal proportional–integral–derivative controller–based genetic moth swarm algorithm for islanded microgrids considering high wind power penetration. In such microgrids, the replacement of conventional generator units with a large number of renewable energy sources reduces the system inertia, which in turn causes undesirable influence on microgrid frequency stability, leading to weakening of the microgrid. Furthermore, sudden load shedding, load restoring, and short circuits caused large frequency fluctuations which threaten the system security and could lead to complete blackouts as well as damages to the system equipment. In order to solve this challenge, this study proposes a new coordinated optimal load frequency control plus modified control signal to superconducting magnetic energy storage for compensating the microgrid frequency deviation (∆ f). To prove the effectiveness of the proposed coordinated control strategy, an islanded microgrid was tested for the MATLAB/Simulink simulation. The physical constraints of the turbines such as generation rate constraints and speed governor dead band are considered in this study. The results confirmed the effectiveness and robustness of the proposed coordination performance against all scenarios of different load profiles, wind power fluctuation, and system uncertainties in microgrid integrated with high penetration of wind farms. Moreover, the results have been compared with both: the optimal load frequency control with/without the effect of conventional superconducting magnetic energy storage.
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Barman, Basabendu, Purusottam Ghosh, Anish Ghoshal, and Lopamudra Mukherjee. "Shedding flavor on dark via freeze-in: U(1) B-3L i gauged extensions." Journal of Cosmology and Astroparticle Physics 2022, no. 08 (August 1, 2022): 049. http://dx.doi.org/10.1088/1475-7516/2022/08/049.

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Abstract We consider a singlet fermionic dark matter (DM) χ in a gauged U(1) B-3L i extension of the Standard Model (SM), with i ⋲ e, μ, τ, and derive bounds on the allowed parameter space, considering its production via freeze-in mechanism. The DM communicates with the SM only through flavorful vector-portal Z B3L due to its non-trivial charge x under U(1) B-3L i , which also guarantees the stability of the DM over the age of the Universe for x ≠ {±3/2, ±3}. Considering Z B3L to lie within the mass range of a few MeV up to a few GeV, we obtain constraints on the gauge coupling g B3L from the requirement of producing right relic abundance. Taking limits from various (present and future) experimental facilities, e.g., NuCal, NA64, FASER, SHiP into account, we show that the relic density allowed parameter space for the frozen in DM can be probed with g B3L ≳ 10-8 for both mχ < m ZB3L/2 and mχ ≳ m ZB3L, while g B3L ≲ 10-8 remains mostly unconstrained. We also briefly comment on the implications of neutrino mass generation via Type-I seesaw and anomalous (g-2) μ in context with B-3Lμ gauged symmetry.
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