Power Support Research Articles

Integrated Social Cognitive Theory with Learning Input Factors: The Effects of Problem-Solving Skills and Critical Thinking Skills on Learning Performance Sustainability

E-learning is expected to become a common teaching and learning approach in educational institutions in the near future; thus, the success of e-learning initiatives must be ensured in order to make this a sustainable mode of learning. In order to improve students’ learning performance through the use of e-learning in Saudi Arabia’s higher education, it was the objective of this paper to examine the relationships between social cognitive theory and learning input factors and the reflective thinking and inquiry learning style as well as the indirect effects of student problem-solving and critical thinking skills. As a result, this study thoroughly assessed the social cognitive theory that is currently in use, along with learning input components and situational factors that should be carefully taken into account while introducing an online education system into Saudi Arabia’s top universities as a way of ensuring learning sustainability. As a result, 294 university students completed a questionnaire that served as the initial dataset for the research study, and the proposed conceptual model was comprehensively assessed using SEM. The research results demonstrated that the inquiry style of learning and reflective thinking have always had a significant impact on the social involvement, human engagement, social power, social identity, and social support. Similar findings were obtained regarding the impact of problem-solving and critical thinking skills on the inquiry-based learning approach and reflective thinking. Thus, students’ ability to learn in Saudi Arabia’s higher education is greatly influenced by their ability to solve problems and think critically. Therefore, it is almost certain that this research study will aid university policy makers in their decision on whether to fully deploy an online learning system as a way of ensuring learning sustainability at educational institutions throughout Saudi Arabia.

Parameters design and optimization for droop-controlled inverters considering impedance characteristics and power stability

The droop-controlled inverters (DCIs), which can simulate synchronous generators’ frequency and voltage behavior and provide active and reactive power support for the utility grid, are universally regarded as grid-friendly interfaces. This paper aims to give a general parameter design outline for the DCIs to simplify the complicated parameter tuning task while assuring good performances. For this purpose, the DCIs’ equivalent output impendence and admittance models are first developed, based on which the effects of parameters on impedance characteristics and power stability are analyzed in detail. Afterward, the general parameter design outline with a comprehending parameter tuning scheme is proposed based on the impedance analysis results. In the end, a 15-kVA prototype is established and tested in the laboratory. The experimental results verified the effectiveness of the proposed parameter design and optimization method.

Economic analysis of annual load loss due to voltage sags in industrial distribution networks with distributed PVs

In an industry, analysis of load disconnection indices is essential to determine the annual economic loss because of the high cost of load interruptions. With the interconnection of PVs in modern industrial networks, this analysis gets more complicated due to controls associated with PV inverters for reactive power support. Hence, the paper proposes a unique method for such analysis that relies on dynamic simulation to calculate load disconnections. The dynamic simulation allows the integration of the voltage tolerance curve of loads and controls associated with PVs making the scenarios more realistic. The indices are determined by employing statistical experiments which account for annual variability of daily solar and load profiles with the least possible runs of dynamic simulation. The proposed method is applied to calculate load disconnection indices for an IEEE 399-1997 industrial distribution system. A comparative analysis of the cost of disconnection under a variety of solar penetration and operation scenarios is presented. Network planners and reliability engineers can potentially utilize the proposed method to identify PV inverter controls, placement, and size effects on the annual load disconnection indices due to voltage sags.

Automatic coordination control technology of interconnected medium voltage direct current (MVDC) distribution network based on frequency deviation

The automatic coordination control technology of interconnected medium voltage direct current (MVDC) distribution network based on frequency deviation is studied to improve the influence of frequency deviation on the operation of MVDC distribution network. Firstly, two regional interconnected MVDC distribution networks are built, and connected and operated in parallel with the AC power grid through the medium voltage single-phase AC port, to realize the interconnection of different regions of the distribution network according to the MVDC feeder. Through the mutual power support of each division of the distribution network, the frequency of each division of the distribution network is the same, and the frequency deviation of each division is reduced. According to the zoning frequency characteristics of the interconnected MVDC distribution network, the control strategy of the flexible interconnection device and the control strategy of the photovoltaic power generation system are combined to realize the automatic coordinated control of the frequency deviation of the interconnected MVDC distribution network. The experimental results show that this technology can improve the frequency deviation of the interconnected MVDC distribution network, realize the automatic coordinated control of the distribution network, and the fluctuation range of the tie line power deviation in each region decreases significantly.

Effect of Laser Parameters on Laser-Induced Graphene Filter Fabrication and Its Performance for Desalination and Water Purification.

Laser-induced graphene (LIG) is a low-cost, chemical-free single-step fabrication process and has shown its potential in water treatment, electronics, and sensing. LIG fabrication optimization is mostly explored for dense polyimide (PI) polymers. However, LIG-based filters and membranes for water treatment need to be porous, and additional steps are required to get porous surfaces from PI-based surfaces. Polyethersulfone (PES) porous membranes are cost-effective and are common in water purification as compared to PI; further, the optimization of LIG fabrication on PES-based porous membranes is not explored. So, this study demonstrated the fabrication, optimization, and characterization of LIG with different laser parameters such as power, speed, image density (ID), focusing, laser platforms, and membrane support layer effect on porous PES commercial (UP010) and lab-casted 15% PES (PES15) membranes. The performance of optimized LIG filters was tested for interfacial evaporation (IE)-based desalination in single and stacked layer configuration and water purification applications such as dye removal and disinfection. IE was done in Joule heating (JH) and solar heating (SH) modes, and the UP010-ID7 LIG filter showed the highest JH evaporation rates of ∼1.1, 1.8, and 2.82 kg m-2 h-1 in single, double, and triple stacked configurations, respectively. Using a JH IE setup, the best-performing UP010-ID7 LIG filters have also shown ∼100% removal of methylene blue dye from the contaminated water. Furthermore, all LIG filters showed a complete 6-log bacterial inhibition at the 5 V filtration experiments; at 2.5 V, the optimized LIG filters showed a higher removal than the non-optimized filters. Additionally, the LIGs obtained with the aluminum platform were the best quality. This work demonstrates that laser power, ID, platform, and membrane support are critical parameters for the best-performing PES-LIG filters, and they can be effectively utilized to fabricate PES-based LIG porous surfaces for various energy, environmental, and catalysis applications.

Nonlinear model predictive control-based active power dispatch strategy for wind power plant considering dynamic wake effect

Inappropriate active power dispatch strategies can diminish the active power support capability (APSC) of the wind power plant (WPP) due to the wake effect. In existing strategies, the WPP’s APSC and the time delay of wake effect are not thoroughly investigated. This paper proposes an active power dispatch strategy to increase the WPP’s APSC while tracking the power reference. First, WPP’s temporary and sustained APSCs are analyzed considering dynamic wake effect. Correspondingly, the total stored kinetic energy and increasable power of WPP are introduced as evaluation indicators of the capabilities. Furthermore, a bi-level control framework is proposed to accomplish the dispatch task in different timescales. Aiming at improving WPP’s temporary and sustained APSCs comprehensively, the operating status references of each WT, including the power reference and pitch angle, are optimized in the WPP layer. Taking the time delay and nonlinearity of wake effect into account, the receding horizon optimization is solved in a finite time domain using nonlinear model predictive control (NMPC). During the sampling interval of the NMPC, a coordinated control in the WT layer is developed to modify the active power reference dispatched by the WPP layer in case the wind speed fluctuates. Finally, extensive case studies show that the WPP’s temporary and sustained APSCs are improved with the proposed strategy in different wind conditions and power references.

Sanctions-Busting, Material Power, and Institutional Support for Economic Sanctions

International institutions play a key role in sanctions success. However, little is known about when senders mobilize institutional sanctions and how they induce international institutions to support their sanctioning efforts. Senders may need institutional support when they expect third-party states to engage in sanctions-busting. I suggest that senders anticipate sanctions-busting when they face third-party rivals which also have an alliance tie with targets. The presence of such potential sanctions busters may lead senders to seek institutional support. Also, senders should possess substantial material power to induce member states of international institutions to approve the sanctioning efforts. I assess the theoretical claim of this research by analyzing 1,038 sanctions episodes over the period 1951–2005. The findings support my argument that senders pursue institutional support when they face potential sanctions busters, and the success of their efforts partly depend on their material power.

Reasoning about the Masons' support of the monarchical power in Russia in 1817: source analysis

The object of the study is the text of the manuscript, and the subject of the study is its historical and legal characteristics. Research objectives: 1) establishing the reliability of the source and the accuracy of the information contained therein; 2) establishing the year, author, purpose, completeness and meaning of the source. The article introduces into scientific circulation a monument of political and legal culture of the first quarter of the XIX century, promotes the initial publication of the manuscript belonging to the Russian Freemasons of the first quarter of the XIX century. Based on the original source, the study shows what legal and political ideas were actually spread among Russian Freemasons. The reasoning demonstrates the continuity of the state-legal ideas of the domestic political and legal thought of the XVIII and XIX centuries. Within the framework of the study, a manuscript of the first quarter of the XIX century is published for the first time and the attribution of the manuscript is given for the first time: the establishment of the author, year, authenticity and meaning of the work - "Arguments about the support of the monarchical power in Russia by Masons". The reasoning was recorded by S.P. Fonvizin (1783-1860) from the words of the author – Joseph Alekseevich Pozdeev (1742-1820) in 1817. The reasoning is aimed at supporting the estate monarchy among the Masonic brothers in Russia in the first quarter of the XIX century .The reasoning demonstrates a commitment to social peace based on "good morals" and conscientious performance of class duties. The reasoning is rich in elements of the organic theory of the state and natural-legal argumentation.

Uplink and Downlink Decoupled 5G/B5G Vehicular Networks: A Federated Learning Assisted Client Selection Method

Owning to the powerful support of 5G/B5G technologies, it is promising that, in a vehicular network, the ever-increasing demands for artificial intelligence applications along with privacy concerns can be fulfilled by introducing federated learning (FL) into vehicular networks. However, in such a 5G/B5G cellular-based vehicular network, distributed clients, i.e., vehicles, usually suffer from intermittent connectivity to the uplink base station (BS) due to the small cell networking and their mobility, and thereby the FL execution time and the learning performance cannot be guaranteed. In order to ensure a required execution time and the FL performance, we propose to investigate the client selection schemes in the uplink-downlink decoupled 5G/B5G networks. Due to the bursty feature of uplink transmissions, we first incorporate a flexible delay analytical tool, i.e., martingale theory, to characterize the access delay of each vehicle, and represent it in the form of delay violation probability. Then, given an energy budget, adjustable parameters are optimized to maximize the global learning performance. Supposing that all the clients participate in the FL and they can outperform the systematic FL performance requirement, the client selection methods under different criteria are further investigated. Especially, we propose a low-complexity algorithm to select clients in terms of enhancing energy efficiency. Numerical results are provided to demonstrate the effectiveness of the proposed client selection method in both guaranteeing the FL execution time and meeting the systematic learning performance. The energy efficiency of the vehicular FL system can also be enhanced by employing the proposed method.

Automatic detection of pesticide residues on the surface of lettuce leaves using images of feature wavelengths spectrum.

The inappropriate application of pesticides to vegetable crops often results in environmental pollution, which seriously impacts the environment and human health. Given that current methods of pesticide residue detection are associated with issues such as low accuracy, high equipment cost, and complex flow, this study puts forward a new method for detecting pesticide residues on lettuce leaves. To establish this method, spectral analysis was used to determine the characteristic wavelength of pesticide residues (709 nm), machine vision equipment was improved, and a bandpass filter and light source of characteristic wavelength were installed to acquire leaf image information. Next, image preprocessing and feature information extraction were automatically implemented through programming. Several links were established for the training model so that the required feature information could be automatically extracted after the batch input of images. The pesticide residue detected using the chemical method was taken as the output and modeled, together with the input image information, using the convolutional neural network (CNN) algorithm. Furthermore, a prediction program was rewritten to generalize the input images during the prediction process and directly obtain the output pesticide residue. The experimental results revealed that when the detection device and method designed in this study were used to detect pesticide residues on lettuce leaves in a key state laboratory, the coefficient of determination of the equation reached 0.883, and the root mean square error (RMSE) was 0.134 mg/L, indicating high accuracy and that the proposed method integrated the advantages of spectrum detection and deep learning. According to comparison testing, the proposed method can meet Chinese national standards in terms of accuracy. Moreover, the improved machine vision equipment was less expensive, thus providing powerful support for the application and popularization of the proposed method.

Study on coordinated multi-objective reactive control system of AC/DC power grid based on new-generation synchronous condenser

With rapid development of HVDC transmission system, the coupling relationship between the AC and DC power grid has become increasingly stronger. Especially, the problem of voltage instability is prominent in HVDC receiving-end system, the dynamic reactive power performance of the receiving-end power grid is inadequate. Therefore, the new-generation synchronous condenser (NGSC) as ‘a strong reactive power support device” is widely applied to high-capacity DC transmission system. However, there is a lack of coordination control strategy between the NGSCs and AC/DC power grid, so it is difficult to give full play to the reactive power supporting capacity of the NGSCs. In this paper, a coordinated multi-objective reactive control strategy between the NGSCs and the AC/DC power grid is proposed . In steady state, the initial reactive power optimization method of a NGSC is proposed. In transient state, a commutation failure suppression scheme of DC system based on the NGSCs and the DC control system is proposed. In transition process, the coordinated control strategy of the NGSCs with capacitance and reactance is studied. The research results provide theoretical basis for subsequent study on the safety and stability of AC/DC power grid.

Reactive power control in renewable rich power grids: A literature review

AbstractRecently, there is vast progress in the integration of renewable energy generators (REGs) into the power grid. The reactive power, which is indeed a fundamental power system factor is being influenced highly by the renewable power penetration levels. As a consequence, this has paved the way toward the generation of steady‐state voltage and dynamic/transient stability issues. Therefore, to provide a sustainable and dependable power grid, it is indeed important to maintain and control adequate reactive power reserves. This study introduces a comprehensive literature survey on “management of reactive power in renewable‐rich power networks”. A total of 75 research publications have been collected for this study, and a concise summary of each article is offered. The articles are categorized according to the types of REGs used, type of control, grid code consideration, controller device, implementation tools, grid type, load type as well as various reactive power support systems. In addition, this study examines the advantages and drawbacks of existing models. The performance recorded in each of the collected papers are discussed. Ultimately, the most critical challenges related to management of reactive power in renewable‐rich power grids are identified, along with some essential methodological suggestions for the electricity sector, regulators, and research scientists.

Republicanism and the legitimacy of state border controls

ABSTRACT A number of recent articles have invoked the republican ideal of non-domination to justify either open borders, and/or the reduction of states’ discretionary powers to unilaterally determine immigration policy. In this paper, I show that such arguments are one-sided, as they fail to fully account for the deep ambiguity of the very ideal which they invoke. In fact, non-domination lends just as powerful support to maintaining state border controls as it does to dismantling them. There are only two exceptions to the rule. It is well established that promoting non-domination demands, one the one hand, that refugees be admitted, and second, that all migrants have a right to contest decisions concerning their own admission. But aside from these things, the policy implications of the ideal are unclear. In itself, therefore, it is insufficient to justify either open borders, or the reduction of states said discretionary powers. Such arguments will have to rely on other, additional moral criteria.

Secondary Frequency Control Considering Optimized Power Support From Virtual Power Plant Containing Aluminum Smelter Loads Through VSC-HVDC Link

The growing number of renewable energy replacing conventional generators results in a loss of the reserve for frequency control in power systems, while many industrial power grids often have excess energy supply due to abundant wind and solar energy resources. This paper proposes a secondary frequency control (SFC) strategy that allows industrial power grids to provide emergency high-voltage direct current (HVDC) power support (EDCPS) for emergency to a system requiring power support through a voltage source converter (VSC) HVDC link. An architecture including multiple model predictive control (MPC) controllers with periodic communication is designed to simultaneously obtain optimized EDCPS capacity and minimize adverse effects on the providing power support (PPS) system. Moreover, a model of a virtual power plant (VPP) containing aluminum smelter loads (ASLs) and a high penetration of wind power is established for the PPS system. The flexibility and controllability of the VPP are improved by the demand response of the ASLs. The uncertainty associated with wind power is considered by chance constraints. The effectiveness of the proposed strategy is verified by simulation results using the data of an actual industrial power grid in Inner Mongolia, China. The DC voltage of the VSCs and the DC in the potlines of the ASLs are also investigated in the simulation.

Extinctiopolitics: Existential Risk Studies, The Extinctiopolitical Unconscious, And The Billionaires' Exodus from Earth

One of the most prominent intellectual attempts to grapple with human extinction in recent decades is existential risk studies. For its proponents, like Nick Bostrom and Toby Ord, there is a one-in-six chance that humanity will go extinct in the next century, whether from an asteroid hit, nuclear Armageddon or misaligned artificial intelligence. The field has powerful supporters, with Silicon Valley billionaires like Elon Musk and Jaan Tallinn donating large sums to institutions researching existential risk. In this article, I consider the ideological function of the imaginaries of catastrophe proposed by existential risk studies. To this end, the article begins by examining the distinctive mode of politics, termed extinctiopolitics, elaborated by Bostrom and Ord. Via a critical comparison with the concept of biopolitics, I suggest that extinctiopolitics aims to optimise the future life of humanity through the prediction and prevention of risks that threaten its annihilation. Borrowing the Freudian notion of screen memory, I then argue that extinctiopolitics both acknowledges and represses the ecocidal tendencies of contemporary capitalism. The image of the collective death of the species evokes a range of disastrous events in the present, especially the climate crisis, but in such a way that their social conditions are obscured. By way of conclusion, I briefly reflect on how science fiction texts use the image of human extinction to unpick the ideological manoeuvres of extinctiopolitics and restage the real contradictions of capitalism.

ЛЕГІТИМАЦІЙНІ ТЕХНОЛОГІЇ В МІЖНАРОДНИХ ВІДНОСИНАХ: ТЕОРІЯ ТА ПРАКТИКА

Legitimation technologies in international relations are an important means of influencing and regulating relations between states. They are used to acquire legitimacy, support and recognition of political power, as well as to create a favorable international environment for the realization of political and economic interests. Various legitimation technologies are used in international relations, which help political leaders and organizations gain legitimacy in the eyes of the public. Among the most common are: election processes. constitution and legal framework, public support and legitimacy, mass media and mass media, allied communication technologies, two-vector policy, soft power and others. The scientific novelty can be accounted for by the review of legitimation technologies in solving key challenges in international relations, in particular, in times of geopolitical changes and Russia’s full-scale invasion of Ukraine. The effectiveness of the use of authentication technologies in Ukraine and its role in maintaining and improving attitudes toward the country, attracting international support, and developing partnerships were investigated. Thus, the study expands the understanding of legitimation technologies as a tool that can be used to improve the image of Ukraine, its influence on global international processes, as well as social, cultural and economic enrichment. By applying a technological approach, the main authentication technologies used in the international arena are analyzed. Based on the research of Ukrainian and foreign specialists, a review of this technology is carried ou; the effectiveness of the use of authentication technologies as regulatory tools in international relations is outlined. Strategic areas of activity and effective use of identification technologies in Ukraine during the war and changes in the vector of development in international relations have been formed. The fakes can be used by the authorities to improve the image of the state and its recognition in the international arena. Keywords: world politics; legitimation; публічна дипломатія; public diplomacy; digital diplomacy; soft power.

In Support of Pontifical Power: The Papacy and the Papal States’ Baronial Nobility, 1417–49

This article addresses the baronial nobility's much-neglected role in supporting the reestablishment of pontifical power in the wake of the Western Schism. In doing so, this article stresses how acts of noble revolt were complemented by extensive patterns of collaboration in the Papal States’ government, armies, and relations with other principalities. The nobility proved to be a fundamental source of support—a support that was theorized around and expressed in the language of fealty and devotion. In light of this, my analysis further contributes to the study of the perseverance of noble power and ubiquity of transregional factions in late medieval societies.

Day-ahead Network-constrained Unit Commitment Considering Distributional Robustness and Intraday Discreteness: A Sparse Solution Approach

Quick-start generation units are critical devices and flexible resources to ensure a high penetration level of renewable energy in power systems. By considering the wind uncertainty and both binary and continuous decisions of quick-start generation units within the intraday dispatch, we develop a Wasserstein-metric-based distributionally robust optimization model for the day-ahead network-constrained unit commitment (NCUC) problem with mixed-integer recourse. We propose two feasible frameworks for solving the optimization problem. One approximates the continuous support of random wind power with a finite number of events, and the other leverages the extremal distributions instead. Both solution frameworks rely on the classic nested column-and-constraint generation (C&CG) method. It is shown that due to the sparsity of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$L_{1}$</tex> -norm Wasserstein metric, the continuous support of wind power generation could be represented by a discrete one with a small number of events, and the rendered extremal distributions are sparse as well. With this reduction, the distributionally robust NCUC model with complicated mixed-integer recourse problems can be efficiently handled by both solution frameworks. Numerical studies are carried out, demonstrating that the model considering quick-start generation units ensures unit commitment (UC) schedules to be more robust and cost-effective, and the distributionally robust optimization method captures the wind uncertainty well in terms of out-of-sample tests.

Computational intelligence based PEVs aggregator scheduling with support for photovoltaic power penetrated distribution grid under snow conditions

• A snow loss-aware deep learning-based short-term PV yield predictor is developed. • Stochastic day-ahead scheduling of an independent PEVs aggregator is investigated. • A novel local balancing service offered by the PEVs aggregator to DSO is proposed. • The service benefits PEV owners through providing extra energy demand of the grid. This paper addresses the issue of optimal day-ahead scheduling of a plug-in electric vehicles (PEVs) aggregator that participates in the electricity market and offers an out-of-market balancing service to the local renewable power penetrated distribution system in a snow-prone area. The proposed balancing service provides a reliable source of flexibility for the extra real-time energy demand of the distribution system operator (DSO) which originates from the difference between its day-ahead bids and the actual demand. The problem is investigated on a snowy day when the DSO's day-ahead decisions encounter more uncertainty due to the considerable effect of snow loss on the DSO's photovoltaic plant performance. The aggregator's scheduling is formulated as two-stage stochastic programming which minimizes the PEVs’ charging cost. Monte Carlo simulation and K-means clustering are implemented to generate scenarios of driving patterns and real-time energy market prices, respectively. Offering the balancing service requires day-ahead predictions of the photovoltaic power and the grid load demand which are modeled using long short-term memory networks. The problem is formulated as mixed-integer linear programming. The results show that the proposed scheduling approach reduces the PEVs’ charging cost by 53% and guarantees the grid normal operation. Moreover, the balancing service can reduce the expected PEVs’ charging cost and the DSO's real-time cost by 12% and 14%, respectively. © 2017 Elsevier Inc. All rights reserved.

Double-ended output near-single-mode quasi-continuous wave monolithic fiber laser

Quasi-continuous fiber lasers have a broad application prospect in the industrial field. However, in the current research on quasi-continuous wave (QCW) fiber lasers only the single-ended output structure is used. A double-ended output fiber laser oscillator needs only one resonator to realize two laser outputs. Compared with single-ended output laser, it has a low cost, small volume and high work efficiency. It is expected to achieve higher power laser output through double-ended output beam combining. Therefore, the double-ended output QCW fiber laser is proposed and studied in this paper. The steady-state rate equation establishes a theoretical model of a QCW fiber laser oscillator with two ends, considering the stimulated Raman scattering (SRS) and amplified spontaneous emission (ASE). The output power, time domain and nonlinear effects of this type of laser are simulated. The results show that the overshoot effect caused by relaxation oscillation will produce a large amount of thermal deposition and ultra-high peak power in the fiber. It will reduce the nonlinear threshold and limit the increase of power of the QCW fiber laser. Prolonging the rise time of the pump can effectively suppress the relaxation oscillation and obtain a stable pulse output during the pulse duration. In addition, compared with the single-ended QCW laser, the double-ended output structure changes the energy distribution in the fiber and reduces the accumulation of nonlinear effects in the gain fiber, thus inhibiting SRS. Then, the ytterbium-doped fiber with a core/cladding diameter of 20/400 μm is used to achieve the first double-ended QCW laser output with a peak power of 3 kW. The peak power values at both ends are 1218 and 2220 W, respectively. The values of corresponding beam quality factor &lt;i&gt;M&lt;/i&gt;&lt;sup&gt;2&lt;/sup&gt; are 1.34 and 1.27. The optical-to-optical conversion efficiency is about 60%. The pulse width is 100 μs, and the repetition frequency is 1 kHz. This research verifies the feasibility of high power and high beam quality output by double-ended output QCW fiber laser, which provides support for small volume, low cost, high power and high brightness QCW fiber laser. Further breakthroughs in the research and application of high-power fiber lasers are expected to be made by continually optimizing experiments, increasing pump power, and improving the laser’s output power and conversion efficiency.