mlsa-iai-msu-lab/ru_sci_bench_zho_cite_reranking huggingface dataset:
Investigation of nonlinear optical properties of rhenium diselenide and its application as a femtosecond mode-locker

We investigated the nonlinear optical properties of ReSe_2. First, we measured the nonlinear absorption coefficient and the nonlinear refractive index of a ReSe_2 thin film using open-aperture (OA) and closed-aperture (CA) Z-scan techniques. ReSe_2 was shown to possess both saturable absorption and self-defocusing properties. The nonlinear absorption coefficient of ReSe_2 was measured to be –(5.67 ± 0.35) × 10~3 cm∕GW, and its nonlinear refractive index was –(2.81 ± 0.13) × 10~(–2) cm~2∕GW at 1560 nm. Next, a fiberized saturable absorber (SA) based on ReSe_2 was fabricated with a side-polished fiber platform and was tested as an ultrafast mode-locker capable of producing femtosecond pulses operating at a wavelength of 1560 nm. The estimated modulation depth and saturation power are ∼3.9 %and ∼42 W, respectively, for the transverse electric mode, while they are ∼2.4 %and ∼53 W for the transverse magnetic mode. Using the prepared SA, stable soliton pulses with a temporal width of ∼862 fs were produced from an erbium-doped fiber ring cavity. To the best of the authors' knowledge, this is the first demonstration of using a ReSe_2-based SA for femtosecond mode-locked pulse generation.
Pump scheme optimization of an incoherently pumped high-power random fiber laser

Optical signal-to-noise ratio (OSNR) is one of the most significant parameters for the performance characterization of random fiber lasers (RFLs) and their application potentiality in sensing and telecommunication. An effective way to improve the OSNR of RFLs is pump scheme optimization, for example, employing a temporally stable source as the pump. In this paper, the output performance of an incoherently pumped RFL dependence on the pump bandwidth has been investigated both in experiment and theory. It is found that a high-OSNR RFL can be achieved with broadband amplified spontaneous emission (ASE) source pumping, and a relatively broad pump bandwidth can also help suppress the spectral broadening while maintaining an ultra-high spectral purity. By optimizing the pump bandwidth to ∼10 nm, maximum OSNR of ∼39 dB (corresponding to a spectral purity of ∼99.96%) with more than 99 W output power can be obtained. Moreover, for the pump bandwidth of 0.6–40 nm, the spectral purity can reach as high as >99 %with the pump power ranging from ∼85 to ∼117 W. In addition, with the aid of theoretical simulation based on a modified power balance model, we find that the increment of pump bandwidth can decrease the effective Raman gain coefficient, further influencing the gain characteristics, nonlinear effects, and eventually the output performance. This work provides new insight into the influence of the pump characteristics on the output performance of incoherently pumped RFLs.
Hybrid-type white LEDs based on inorganic halide perovskite QDs: candidates for wide color gamut display backlights

Wedemonstrate inorganic halide perovskite quantum-dots-basedwhite light-emitting diodes via three different geometries, including liquid, solid, and hybrid types. Problems of fast anion exchange and aggregation in the cases of liquidand solid-type devices are discussed in detail and push us to move towards the fabrication of a hybrid-type device structure. The experiment results illustrate that a hybrid-type device has the highest luminance efficiency (51 lm/ W) and a wide color gamut (122% of NTSC and 91% of Rec. 2020). Therefore, we conclude that a hybrid-type device can provide an outstanding color gamut for high color gamut display applications.
Ultralow-crosstalk, strictly non-blocking microring-based optical switch

We report on the first monolithically integrated microring-based optical switch in the switch-and-select architecture. The switch fabric delivers strictly non-blocking connectivity while completely canceling the first-order crosstalk. The 4 × 4 switching circuit consists of eight silicon microring-based spatial (de-)multiplexers interconnected by a Si/SiN dual-layer crossing-free central shuffle. Analysis of the on-state and off-state power transfer functions reveals the extinction ratios of individual ring resonators exceeding 25 dB, leading to switch crosstalk suppression of up to over 50 dB in the switch-and-select topology. Optical paths are assessed, showing losses as low as 0.1 dB per off-resonance ring and 0.5 dB per on-resonance ring. Photonic switching is actuated with integrated micro-heaters to give an ∼24 GHz passband. The fully packaged device is flip-chip bonded onto a printed circuit board breakout board with a UV-curved fiber array.
Reliability evaluation of modular multilevel converter based on Markov model

The modular multilevel converter(MMC)is now the most attractive topology for medium and high voltage power conversion applications with several advantages over the traditional voltage source converter(VSC).However, due to a large number of sub-modules(SMs)in the MMC, system reliability is a big challenge in its practical application, where each SM may be considered as a potential point of failure.In this paper, a reliability evaluation based on the Markov model is proposed for the MMC.The failure rates of the power electronic devices and SMs are firstly analyzed.Then, the Markov model and the state transition equation of the system are built in detail.A general reliability evaluation function is established, in which the mean time to failure and reliability evaluation of the MMC with redundant SMs are also discussed.Finally, a practical direct current(DC)distribution example for reliability evaluation is analyzed, and the results verify that the reliability evaluation based on the Markov model could provide a useful reference for project design.
Online power quality disturbance detection by support vector machine in smart meter

Power quality assessment is an important performance measurement in smart grids.Utility companies are interested in power quality monitoring even in the low level distribution side such as smart meters.Addressing this issue, in this study, we propose segregation of the power disturbance from regular values using one-class support vector machine(OCSVM).To precisely detect the power disturbances of a voltage wave, some practical wavelet filters are applied.Considering the unlimited types of waveform abnormalities, OCSVM is picked as a semisupervised machine learning algorithm which needs to be trained solely on a relatively large sample of normal data.This model is able to automatically detect the existence of any types of disturbances in real time, even unknown types which are not available in the training time.In the case of existence, the disturbances are further classified into different types such as sag, swell, transients and unbalanced.Being light weighted and fast, the proposed technique can be integrated into smart grid devices such as smart meter in order to perform a real-time disturbance monitoring.The continuous monitoring of power quality in smart meters will give helpful insight for quality power transmission and management.
Inter-hour direct normal irradiance forecast with multiple data types and time-series

Boosted by a strong solar power market, the electricity grid is exposed to risk under an increasing share of fluctuant solar power.To increase the stability of the electricity grid, an accurate solar power forecast is needed to evaluate such fluctuations.In terms of forecast, solar irradiance is the key factor of solar power generation,which is affected by atmospheric conditions, including surface meteorological variables and column integrated variables.These variables involve multiple numerical timeseries and images.However, few studies have focused on the processing method of multiple data types in an interhour direct normal irradiance(DNI)forecast.In this study,a framework for predicting the DNI for a 10-min time horizon was developed, which included the nondimensionalization of multiple data types and time-series,development of a forecast model, and transformation of the outputs.Several atmospheric variables were considered in the forecast framework, including the historical DNI, wind speed and direction, relative humidity time-series, and ground-based cloud images.Experiments were conducted to evaluate the performance of the forecast framework.The experimental results demonstrate that the proposed method performs well with a normalized mean bias error of 0.41% and a normalized root mean square error(nRMSE)of 20.53%, and outperforms the persistent model with an improvement of 34% in the nRMSE.
Real-time pricing method for smart grids based on complementarity problem

Considering a demand response(DR)based social welfare maximization model, a complementarity problem based on the Karush-Kuhn-Tuker condition is described, which is a non-dual method for determining real-time price for smart grids.The Lagrange multiplier in the dual method, which is used to determine the basic electricity price, is applied in the model.The proposed method computes the optimal electricity consumption,price and production.According to the electricity price,users can arrange their electricity equipment reasonably to reduce the consumption pressure at peak time.The model aims to encourage users to actively participate in the DR and realize peak cutting and valley filling.In addition, the model considers different utility functions representing three types of users.Finally, a Jacobian smoothing version of Newton method is used to solve the model.Statistical simulations of the model validate the rationality and feasibility of the proposed method.
Multi-objective optimal operation of hybrid AC/DC microgrid considering source-network-load coordination

Taking the consumption rate of renewable energy and the operation cost of hybrid AC/DC microgrid as the optimization objectives, the adjustment of load demand curves is carried out considering the demand side response(DSR)on the load side.The complementary utilization of renewable energy between AC area and DC area is achieved to meet the load demand on the source side.In the network side, the hybrid AC/DC microgrids purchase electricity from the power grid at the time-of-use(TOU)price and sell the surplus power of renewable energy to the power grid for profits.The improved memetic algorithm(IMA)is introduced and applied to solve the established mathematical model.The promotion effect of the proposed source-network-load coordination strategies on the optimal operation of hybrid AC/DC microgrid is verified.
Multi-level supervisory emergency control for operation of remote area microgrid clusters

Remote and regional areas are usually supplied by isolated and self-sufficient electricity systems, which are called as microgrids(MGs).To reduce the overall cost of electricity production, MGs rely on non-dispatchable renewable sources.Emergencies such as overloading or excessive generation by renewable sources can result in a substantial voltage or frequency deviation in MGs.This paper presents a supervisory controller for such emergencies.The key idea is to remedy the emergencies by optimal internal or external support.A multi-level controller with soft, intermedial and hard actions is proposed.The soft actions include the adjustment of the droop parameters of the sources and the controlling of the charge/discharge of energy storages.The intermedial action is exchanging power with neighboring MGs, which is highly probable in large remote areas.As the last remedying resort, curtailing loads or renewable sources are assumed as hard actions.The proposed controller employs an optimization technique consisting of certain objectives such as reducing power loss in the tie-lines amongst MGs and the dependency of an MG to other MGs, as well as enhancing the contribution of renewable sources in electricity generation.Minimization of the fuel consumption and emissions of conventional generators, along with frequency and voltage deviation, is the other desired objectives.The performance of the proposal is evaluated by several numerical analyses in MATLAB~®.
Performance evaluation for sustainability of wind energy project using improved multi-criteria decision-making method

Wind power can be an efficient way to alleviate energy shortage and environmental pollution, and to realize sustainable development in terms of energy generation.The sustainability assessment of a wind project among its alternatives is a complex task that cannot be solely simplified to environmental or economic feasibility.It requires the consideration of its technological and social aspects as well as other circumstances.This paper proposes a new method for selecting the most sustainable wind projects.The method is based on multi-criteria decision-making techniques.The analytic hierarchy process and entropy weight method are combined to determine the weights of evaluation indexes, and an innovative index-weight optimization method based on the Lagrange conditional extremum algorithm.The fuzzy technique for order preference by similarity to the ideal solution is applied to rank wind project alternatives considering functionality and proportionality of the system.Moreover, the sensitive analysis is applied to verify the robustness of the proposed method.The applicability of the method is demonstrated on a case study from China, where three main wind projects are analytically compared and ranked.The results indicated that the sustainable level of calculated wind power can provide a reference point for the planning and operation of the wind project.The results show that the proposed method is of both theoretical significance and practical application in engineering.
Improving reliability of distribution networks using plug-in electric vehicles and demand response

Nowadays, utilities aim to find methods for improving the reliability of distribution systems and satisfying the customers by providing the continuity of power supply.Different methodologies exist for utilities to improve the reliability of network.In this paper, demand response(DR)programs and smart charging/discharging of plug-in electric vehicles(PEVs)are investigated for improving the reliability of radial distribution systems adopting particle swarm optimization(PSO)algorithm.Such analysis is accomplished due to the positive effects of both DR and PEVs for dealing with emerging challenges of the world such as fossil fuel reserves reduction, urban air pollution and greenhouse gas emissions.Additionally, the prioritization of DR and PEVs is presented for improving the reliability and analyzing the characteristics of distribution networks.The reliability analysis is performed in terms of loss of load expectation(LOLE)and expected energy not served(EENS)indexes, where the characteristics contain load profile, load peak, voltage profile and energy loss.Numerical simulations are accomplished to assess the effectiveness and practicality of the proposed scheme.
AC fault ride through control strategy on inverter side of hybrid HVDC transmission systems

Hybrid high-voltage direct current(HVDC)transmission systems employ a new type of HVDC transmission topology that combines the advantages of the linecommutated converter system and the voltage-source converter system.They can improve the efficiency and reliability of long-distance power transmission.However,realizing alternating-current(AC)grid-fault ride through on the inverter side of a hybrid HVDC transmission system is a challenge considering that a voltage-source converter based HVDC(VSC-HVDC)is used on the inverter side.In this study, a control strategy for an overvoltage fixed trigger angle based on the power-balance method is developed by fully utilizing the operation characteristics of a hybrid HVDC transmission system.The strategy reduces the inverter-side overvoltage of the HVDC system under a fault in the inverter-side AC system.Simulations based on Gezhou Dam are conducted to validate the effectiveness of the proposed strategy.
Integration of automatic voltage regulator and power system stabilizer: small-signal stability in DFIG-based wind farms

The increasing penetration of wind farms in the energy sector directly affects the dynamic behavior of the power system.The increasing use of wind energy in the power system worsens its stability and inherently influences the firmness of a small signal.To investigate these effects, one of the synchronous generators(SGs)of the grid is considered defective and is replaced by a doubly fed induction generator(DFIG)-based wind farm of the same rating.The small-signal stability of a power system is usually evaluated via eigenvalue analysis where local-area and inter-area oscillatory modes for the New England test system are identified.SG controls, such as automatic voltage regulator(AVR)and power system stabilizer(PSS), are added to attenuate the generated disturbances.In this study, the impact of wind energy on the small-signal stability of the power system is investigated.Different combinations of AVR and PSS types are considered to mitigate the undesirable alterations.A comparative study is performed based on numerical simulations to choose the best combination of AVR and PSS types.The obtained results prove that the proposed combination yields good results in terms of stability enhancement both under normal operating conditions and in DFIG-based wind farms.
Three-phase fault direction identification method for outgoing transmission line of DFIG-based wind farms

Doubly-fed induction generator(DFIG)-based wind farm has the characteristic of transient fault with low voltage ride through(LVRT)capability.A new three-phase fault direction identification method for the outgoing transmission line of the wind farm is presented.The ability of the new directional relay to differentiate between a three-phase fault in one direction or the other is obtained by using the increment of phase angle difference between the memory voltage signal and the fault current signal within a certain time, and using the amplitude variation of the fault current.It can be inferred that the fault current is supplied by the wind farm whether the phase angle differs or the current amplitude varies considerably.Different fault locations at the outgoing transmission line have been simulated by PSCAD/EMTDC to evaluate the reliability and sensitivity of the proposed technique.Results show that the new directional relay is of faster response when a three-phase fault occurs at the outgoing transmission line of a DFIG-based wind farm.
Consensus of cyber-physical power systems based on multi-agent systems with communication constraints

The consensus protocol of cyber-physical power systems is proposed based on fractional-order multi-agent systems with communication constraints.It aims to enable each generator to reach a time-varying common rotor angle and rotor speed.Communication constraints including event-triggered sampling and partial information transmission are considered to render the consensus protocol more realistic.The Zeno behavior is excluded during the system sampling process.A sufficient condition is derived to solve the consensus problem.The effectiveness of the proposed consensus protocol is demonstrated by a numerical example.
A contingency-aware method for N-2 security-constrained transmission expansion planning

In this paper, a novel contingency-aware method for N-2 security-constrained transmission expansion planning is proposed.To ensure that the transmission construction plan satisfies the N-2 security criterion, the proposed method takes advantage of the adjustable robust optimization(ARO)framework and upgrades it.We construct a discrete uncertainty set in which component failures are treated as uncertain events that are handled as binary variables.In addition to the failure of existing lines and generators, we explicitly model the failure of candidate lines.The proposed model comprises a master problem that makes the transmission construction decision, and a series of subproblems that can detect not only the worst contingency,but also the potential contingencies.Computational studies on the IEEE RTS 24-bus and IEEE 118-bus test systems are carried out to validate the effectiveness of the proposed method.Compared with the deterministic method and ARO method in the literature, the proposed method has higher computational efficiency.
Power system flexibility: an overview of emergence to evolution

Power systems are evolving to the networks with proliferated penetration of renewable energy resources to leverage their environmental and economic advantages.However, due to the stochastic nature of renewables, the management of the rapidly increasing uncertainty and variability in power system planning and operation is of crucial significance.This paper represents a comprehensive overview of power system flexibility as an effective way to maintain the power balance at every moment.Definitions of power system flexibility from various aspects are explained to reach the reliable and economic planning and operation of the power system.The effects of the high penetration of variable energy resources on power systems and the evolution of flexibility in response to renewables are studied.A variety of resources during the flexibility evolutionary transition are introduced and discussed.As an influential flexibility solution in current power systems integrated with renewable resources, market design improvement is widely reviewed in this paper, and required modifications in market design mechanisms are investigated pertaining to various time horizons.
A review of offshore wind farm layout optimization and electrical system design methods

There is more wind with less turbulence offshore compared with an onshore case, which drives the development of the offshore wind farm worldwide.Since a huge amount of money is required for constructing an offshore wind farm, many types of research have been done on the optimization of the offshore wind farm with the purpose of either minimizing the cost of energy or maximizing the total energy production.There are several factors that have an impact on the performance of the wind farm, mainly the energy production of wind farm which is highly decided by the wind condition of construction area and micro-siting of wind turbines(WTs), as well as the initial investment which is influenced by both the placement of WTs and the electrical system design, especially the scheme of cable connection layout.In this paper, a review of the state-of-the-art researches related to the wind farm layout optimization as well as electrical system design including cable connection scheme optimization is presented.The most significant factors that should be considered in the optimization work of the offshore wind farm is highlighted after reviewing the latest works, and the future needs are specified.
2019欧洲高血压学会年会带来的启示与思考

2019年6月24日,第29届欧洲高血压学会(European Society of Hypertension,ESH)年会在意大利米兰成功落下帷幕。这场一年一度的学术盛典,聚焦高血压领域热点及最新研究证据,为改善高血压管理带来了新的启示与方向。